Article

Characterization of fluvial and aeolian reservoirs: Problems and approaches

August 1993
Geological Society London Special Publications 73(1):1-6

DOI:10.1144/GSL.SP.1993.073.01.01

Authors:

Colin P North

University of Aberdeen

Jeremy Prosser

Task Fronterra Geoscience

Sedimentological research has traditionally produced geological models primarily relevant to hydrocarbon exploration, focusing predominantly on location and external geometry of sediment bodies and underplaying the importance of the internal reservoir framework. This failure inhibits the application of new technologies to improve recovery efficiencies. It is reservoir architecture that ultimately controls the paths of fluid migration during oil and gas emplacement and subsequent extraction. If an understanding of the origin of the reservoir is developed, reservoir architecture, and hence fluid-flow paths, become predictable. This volume assesses the current position of the predictive geoscience for fluvial and aeolian systems. The 24 contributions (abstracted separately) are arranged in four sections: fluvial reservoirs, aeolian reservoirs, structure and methods, and a subject index is provided. -from Editors

Sedimentology and Reservoir Characteristics of the Carboniferous Joggins Formation, Nova Scotia, Atlantic Canada

Thesis

Aug 2022

Trevor B. Kelly

Reservoir characterization has experienced significant changes within the energy industry due to technological innovation and computerization, but challenges remain, particularly with understanding reservoir compartmentalization and fluid flow. These challenges impact energy diversification and security on the pathway to achieving carbon neutrality through secondary recovery, CCS, geothermal, and geostorage. The SPE Research & Development Committee has identified five challenges the energy industry must resolve for further advancement. This dissertation investigates three of the five challenges through integration of outcrop and subsurface data from the Late Carboniferous Joggins Formation: (1) higher resolution subsurface imaging, (2) increasing recovery factors, and (3) carbon capture, utilization, and storage. This research defines stratigraphy, geobodies, architectural elements, and baffles and barriers to fluid flow, using shallow subsurface geophysical techniques (GPR and lidar) for reservoir outcrops at the well to seismic scale. Methodology developed from analogous studies in geoforensics using GPR and subsequent 3D renderings allows the delineation of shallow subsurface objects and is transferrable to the high-resolution delineation of architectural elements within geobodies. This dissertation documents for the first time Late Carboniferous tidal rhythmite intervals in the Joggins Formation, providing support for a mid-Euramerican seaway connecting to the Paleo-Tethys Ocean and demonstrating deposition in a semi-diurnal tidal model with a lunar monthly tidal cycle. The identification of these tidal processes and depositional environments through high-resolution Fourier transform analysis is an example that delineates the fine-scale baffles and barriers to fluid flow for reservoir characterization studies. Well-log data identified spectral peaks in an interval of the Joggins Formation corresponding to the four main orbital periods (400 kyr, 100 kyr, 40 kyr, and 20 kyr) of Milankovitch cyclicity with a ratio of 18.99:5.15:2.02:1. The identification of cyclic occurrences influencing deposition can facilitate stratigraphic correlation and high-resolution reservoir characterization.

Analysis of Factors Influencing the Interpretation of a Digitally Examined Fluvial Meanderbelt System: Joggins Formation, Nova Scotia

Article

Full-text available

Apr 2020
CAN J EARTH SCI

Clastic reservoir exploration, development, and exploitation are inherently complex with recovery depending largely on the understanding of sand body architecture and interlayered clayey/silty baffles and barriers. Numerous data collection techniques and methods are now widely available for helping to enrich reservoir outcrop analogue data extraction from the well-scale to the larger seismic-scale. This integrated study uses the inherited, combined data from a localized light detection and ranging survey, measurements taken from a portable handheld spectrometer and air permeameter, in addition to total (or absolute) porosity measurements from thin sections to assist with the analysis of components influencing the interpretation of a digitally analyzed fluvial meanderbelt system outcrop. The purpose is not to perform a detailed reservoir characterization or to model a potential reservoir, but rather to study a section of a reservoir analogue and apply reservoir geology with integrated data collection techniques to highlight potential benefits and shortcomings of this type of approach. A point cloud survey generated from light detection and ranging, coupled with other tools including a portable handheld spectrometer and permeameter, supplements data from the light detection and ranging scan and increases the confidence of interpretations. Spectrometer measurements recorded at the outcrop are used to generate a pseudo-gamma log. Handheld air permeameter measurements give a sense of the permeability of corresponding lithologies as well as the variability in permeability of the reservoir both laterally and vertically. Light detection and ranging also provides important information regarding rock properties.

Reservoir Heterogeneity in "Homogeneous" Sandstones

Preprint

Oct 2018

Clastic reservoir production is inherently complex with recovery depending largely on the understanding of sand body architecture and interlayered clayey/silty baffles and barriers. Numerous data collection techniques and methods are now widely available for helping to enrich reservoir outcrop analog data extraction from the well-scale to the larger seismic-scale. These methods include handheld X-ray fluorescent (XRF) analyzers, terrestrial light detection and ranging (lidar) scanners, ground-penetrating radar surveying, and portable handheld air permeameter analyzation. This study uses the combined data from a lidar survey, measurements taken from a portable handheld spectrometer and air permeameter, in addition to total (or absolute) porosity measurements from thin sections to aid with the characterization of an outcrop in terms of heterogeneity within a fluvial meanderbelt system. A point cloud survey generated from lidar scanning, coupled with other tools including a portable handheld spectrometer and permeameter, supplements data from the lidar scan and increases the confidence of interpretations. Spectrometer measurements recorded at the outcrop are used to generate a pseudo-gamma log. Handheld air permeameter measurements give a sense of the permeability of corresponding lithologies as well as the permeability of the reservoir both laterally and vertically. Lidar also provides important information regarding rock properties. The high detail of the outcrop images are used for the assessment of reservoir characteristics. The reservoir data leads to an increased understanding of subsurface reservoirs, particularly of the fluvial meanderbelt type.

Reservoir Heterogeneity in "Homogeneous" Sandstones

Preprint

Jan 2019

Implementación del lidar terrestre en la caracterización y modelización de análogos de análogos de reservorios fluviales: desarrollo y aplicación de nuevas metodologías en afloramientos del Abanico Fluvial de Huesca (Mioceno de la Cuenca del Ebro)

Thesis

Full-text available

Jan 2016

Rubén Calvo

In recent years, improvements in digital data collection techniques and processing software have led to significant advances in the field of outcrop characterization. This evolution is based on the premise that the greater the quantity, quality (accuracy), and speed of data collection, the better constrained the deterministic models derived from them. Terrestrial laser scanning (TLS) is based on lidar technology, which although developed in the early 1960s, has only recently been incorporated into the study of geological outcrops. Lidar typically uses the two-way travel time of a laser pulse to determine the distance to a target as sonar uses sound waves or as radar uses radio waves, but with a much higher resolution and accuracy. The main advantages of TLS over the rest of digital data collection techniques are the following: (1) very rapid collection of large amounts of 3D data (thousands of points per second); (2) high resolution (few centimeters) and accuracy; and (3) photorealistic 3D data visualization obviating the need to create a mesh from the point cloud, avoiding thereby the generation of extra geometries. Adequate characterization of depositional architecture is of great importance when studying fluvial outcrops as reservoir analogs. The complex three-dimensional (3D) distribution and lateral and vertical relationships of sandstone bodies require a high degree of stratigraphic control in order to make a proper assessment of the distribution and connectivity of the reservoir facies. Unfortunately, clear marker beds (e.g., ash layers, coal beds, and paleosols) are not always available in fluvial outcrops, and when present, they are often covered by vegetation or debris that prevents their tracking over long distances. Thus, the characteristics of facies in fluvial outcrops cause the uncertainty of the correlations to increase with the number of sandstone bodies and the distance between them. The main aim of this thesis is to take advantage of the potential of the TLS to provide new tools and methodologies focused on solving the main limitation found by the geologists when working in fluvial outcrops: acquire the stratigraphic control required to detect, understand and characterize the high degree of spatial and temporal heterogeneity of fluvial successions. TLS data from 8 outcrops of the Huesca Fluvial Fan (Early Miocene, northern Spain) were acquired to this purpose. The resulting point clouds were processed using commercially available software to obtain adequate Virtual Outcrops (VO’s), but most of the achievements accomplished from their study were possible thanks to in-house developed applications. In addition, several detailed stratigraphic columns were measured and lithological samples from different types of sandstone bodies were collected. Based on this, the most relevant results obtained are as follows:  A comprehensive characterization of the fluvial facies that includes the petrological and petrophysical properties of the sandstone bodies.  A simple method using the VO to correct the heights and thicknesses of the sedimentary bodies measured in the stratigraphic columns. The main factors that may have influenced the measurements made with the Jacob’s staff have been studied and discussed.  A new method to achieve highly accurate and semiautomatic correlations within fluvial VO’s is presented in response to the need for further correlation procedures, especially in the absence of suitable datums. The method is based on the hypothesis that the average depositional paleosurface of a sedimentary system can be represented by a plane at outcrop scale. If this assumption is met in the outcrop, this plane can be used as a virtual datum to identify along the VO the sediments that were deposited simultaneously. The method was tested and applied successfully within four kilometer-scale outcrops of the Huesca fluvial fan, where the virtual datum provided accurate correlations regardless of stratigraphic or topographical complexities. Moreover, all the sedimentary successions of the outcrops can be automatically subdivided into the desired stratigraphic intervals by only moving the virtual datum vertically. These intervals can be subsequently isolated to facilitate the detection of subtle variations and trends of their fluvial properties.  The virtual datums were also used to establish a new procedure that leads to infer the relative stratigraphic positions of distant outcrops (more than 10 Km apart) inside the entire fluvial sequence.  A facies modelling has been performed using a new method to extract in a semiautomatic way the surfaces of the outcrop that belong to paleochannel exposures. Typical modelling workflows use the data from stratigraphic logs in the form of pseudowells to constrain the facies proportions and distributions. With the method presented here, the entire surface of the outcrop can be considered to this purpose, raising significantly de adjustment of the model to the reality. In view of their numerous benefits regarding the characterization of fluvial outcrops, especially in those large and topographically complex that lack suitable marker horizons, the different methods established here from the study of TLS data have proved to be useful in building good models of reservoir analogs. Furthermore, it is considered that their application can definitely help to improve our understanding of the factors and mechanisms that influenced the evolution of ancient fluvial sedimentary systems.

Applications of digital outcrop models: Two fluvial case studies from the Triassic Wolfville Fm., Canada and Oukaimeden Sandstone Fm., Morocco

Article

Nov 2009
GEOL J

The application and benefits of employing digital outcrop models (DOMs) are discussed using two Triassic fluvial case studies to demonstrate data collection and integration methods. Developments in data analysis techniques are examined to demonstrate their utility for collecting meaningful and reliable statistical information needed to build realistic stochastic reservoir models. To establish a significant geostatistical dataset a large number of accurate observations are required. It is difficult to get the necessary statistics using subsurface data alone, due to the limited resolution and/or areal coverage of respectively seismic and well data. Outcrop studies are, therefore, commonly utilized to provide analogue statistical information (e.g. channel width, length, thickness and thickness vs. width ratio). Traditional data collection methods used in the field are however largely restricted to areas with (easy) physical access, or using remote observations with limited accuracy, such as photographic methods. Digital data collection techniques such as LiDAR (Light Detection and Ranging) and differential GPS allow more accurate measurements, as well as from previously inaccessible locations, to be taken of sedimentary architecture. The technique generates much larger volumes of measurements, as the area from which accurate data can be extracted is increased. This offers a more meaningful statistical dataset, hence reducing uncertainty in the final reservoir model. Both case studies, the Oukaimeden Sandstone Formation (OSF), Morocco and Wolfville Formation, Canada, are from Late Triassic braided fluvial systems. The OSF dataset has been used to illustrate how geometric information of channel width versus thickness relationships (W:T) are collected using a projection plane technique. The results show W:T variations between 3.49:1 in the Lower Oukaimeden member, 1.54:1 in the Middle Oukaimeden member and 3.75:1 in the Upper Oukaimeden member, demonstrating the observed architectural evolution of the fluvial system. The Wolfville Formation case study shows how DGPS in combination with LiDAR data has been used to more accurately map faults to obtain statistical information on fault orientation (NE–SW) and length (mean = 38.3 m and median = 18.2 m). Another applied analysis technique utilizes a facies classified point‐cloud to aid surface correlations between sedimentary logs and construct a log based correlation panel from which estimates of facies frequencies are derived. Copyright © 2009 John Wiley & Sons, Ltd.

Facies and architectural element analysis of the Upper Bokabil Sandstone in the Bengal Basin

Article

Full-text available

Jul 2023
SEDIMENT GEOL

Early Pennsylvanian fluvial - aeolian interplay in the Amazonas Basin (Central-Western Gondwana) and its relation to marine transgression

Article

Sep 2020
J S AM EARTH SCI

The Monte Alegre Formation corresponds to the main reservoir rock in the Amazonas Basin petroleum system in Brazil and is correlated with the Pennsylvanian rocks of the Parnaíba and Solimões basins. Previous outcrop and well-based studies are concentrated on the southern edge of the basin and show that the Monte Alegre Formation basically represents an aeolian, deltaic and transitional marine succession. However, there is no published research that demonstrates the depositional system in the northern edge of Amazonas Basin. In this sense, outcrop-based facies and stratigraphic analysis is carried-out to understand the distal influence of marine incursion into the basin and its relationship with paleogeography in the Upper Carboniferous. The data show that the aeolian Monte Alegre system is represented by a braided fluvial system formed by five architectural elements: (i) sandy bedform, (ii) downstream-accretion macroform, (iii) gravel bars and bedforms, (iv) channel and (v) laminated sand sheets, pointing to a braided depositional system. The aeolian succession overlies the fluvial system and is represented by medium-scale trough cross-bedding and large-scale planar cross-bedded sandstones resulting from the accumulation and migration of transverse dunes toward the northwest that grade upward to dry interdunes and aeolian sand sheet deposits that are interbedded, consisting basically of translatent ripple cross-lamination and low-angle cross-stratified lamination sandstones related to water table raises. The stratigraphic record defines a wetting-upward stacking pattern of Monte Alegre Formation resulting from local sea level rise as a result the advance of the marine incursion that settled in the central-western region of Gondwana during the Late Carboniferous. Thus, in addition to corroborating the paleo wind directions predicted for the region during the Late Carboniferous, these deposits help to understand the paleoenvironmental relations between the northern and southern edges of the Amazonas Basin.

Characterization of complex fluvio–deltaic deposits in Northeast China using multi-modal machine learning fusion

Article

Full-text available

Aug 2020

Due to the lack of petroleum resources, stratigraphic reservoirs have become an important source of future discoveries. We describe a methodology for predicting reservoir sands from complex reservoir seismic data. Data analysis involves a bio-integrated framework called multi-modal machine learning fusion (MMMLF) based on neural networks. First, acoustic-related seismic attributes from post-stack seismic data were used to characterize the reservoirs. They enhanced the understanding of the structure and spatial distribution of petrophysical properties of lithostratigraphic reservoirs. The attributes were then classified as varied modal inputs into a central fusion engine for prediction. We applied the method to a dataset from Northeast China. Using seismic attributes and rock physics relationships as input data, MMMLF was performed to predict the spatial distribution of lithology in the Upper Guantao substrata. Despite the large scattering in the acoustic-related data properties, the proposed MMMLF methodology predicted the distribution of lithological properties through the gamma ray logs. Moreover, complex stratigraphic traps such as braided fluvial sandstones in the fluvio–deltaic deposits were delineated. These findings can have significant implications for future exploration and production in Northeast China and similar petroleum provinces around the world.

Intensifying aeolian activity following the end Permian mass extinction: Evidence from the Late Permian-Early Triassic terrestrial sedimentary record of the Ordos Basin, North China

Article

Full-text available

Feb 2020

Sedimentary successions provide direct evidence of climate and tectonics, and these give clues about the causes of the mass extinction around the Permian–Triassic boundary. Terrestrial Permian–Triassic boundary strata in the eastern Ordos Basin, North China, include the Late Permian Sunjiagou, Early Triassic Liujiagou and late Early Triassic Heshanggou formations in ascending order. The Sunjiagou Formation comprises cross-bedded sandstones overlaid by mudstones, indicating meandering rivers with channel, point bar and floodplain deposits. The Liujiagou Formation was formed in braided rivers of arid sand bars interacting with some aeolian dune deposits, distinguished by abundant sandstones where diverse trough and planar cross-bedding and aeolian structures (for example, inverse climbing-ripple, translatent-ripple lamination, grainfall and grainflow laminations) interchange vertically and laterally. The Heshanggou Formation is a rhythmic succession of mudstones interbedded with thin medium-grained sandstones mainly deposited in a shallow lacustrine environment. Overall, the sharp meandering to braided to shallow lake sedimentary transition documents palaeoenvironmental changes from semi-arid to arid and then to semi-humid conditions across the Permian–Triassic boundary. The die-off of tetrapods and plants, decreased bioturbation levels in the uppermost Sunjiagou Formation, and the bloom of microbially-induced sedimentary structures in the Liujiagou Formation marks the mass extinction around the Permian–Triassic boundary. The disappearance of microbially-induced sedimentary structures, increasingly intense bioturbation from bottom to top and the reoccurrence of reptile footprints in the Heshanggou Formation reveal gradual recovery of the ecosystem after the Permian–Triassic boundary extinction. This study is the first to identify the intensification of aeolian activity following the end-Permian mass extinction in North China. Moreover, while northern North China continued to be uplifted tectonically from the Late Palaeozoic to Late Mesozoic, the switch of sedimentary patterns across the Permian–Triassic boundary in Shanxi is largely linked to the development of an arid and subsequently semi-humid climate condition, which probably directly affected the collapse and delayed recovery in palaeoecosystems.

Analysis of the Factors that Influence Diagenesis in the Terminal Fan Reservoir of Fuyu Oil Layer in the Southern Songliao Basin, Northeast China

Article

Full-text available

Dec 2018

The diagenesis mechanism and the physical properties of a terminal fan reservoir are determined by nuclear magnetic resonance (NMR), X-ray diffraction and scanning electron microscopy. The main provenance directions are NE and SE, and the two oppositely directed fans converge to form a small catchment basin. The mudstone color is red or purplish red, which accounts for 60% of the total rock. The sandstones are lithic-feldspar sandstones and feldspar-lithic sandstones, with a smaller quartz component relative to the adjacent sandstone formations. The reservoir mainly consists of intergranular pores (51%), intragranular pores (22%), corrosion pores (20%), micro-fractures (5%) and clay matrix pores (2%). The porosity of the reservoir is only 13%, and the throats are fine with high displacement pressure. The diagenetic processes included compaction, cementation, replacement, and dissolution, and the most influential factor on the reservoir porosity was compaction. The detrital rock cement mainly consists of clay minerals (48%), quartz (23%), carbonate (19%), feldspar (7%) and dawsonite (3%). Among them, the mixed I/S layer has the most content and the most important cementation. In addition, a small amount of dawsonite is found in the pores of the sandstone, which is a unique mineral that is related to the background of inorganic CO 2 . The main diagenesis factors that affected this sandstone’s porosity were compaction, early quartz overgrowth and calcite cementation, which reduced the porosity from 40% to approximately 8%. Although dissolution and fracture increased the porosity (from 8% to 26%), clay- and carbonate-mineral cementation during the late diagenesis period had a dramatic effect, forming a typical low-porosity and low-permeability reservoir.

The uses of Virtual Outcrops in Reservoir Modelling of Fluvial Systems. A Case Study Review

Thesis

Full-text available

Aug 2017

Saad Bhatty

Fluvial sandstones have been long known as some of the most complex reservoirs to predict and model. Their labyrinth-like geometries and distributions make them extremely hard to model and while laterally extensive channel belts can be correlated at the well-scale, it's the fluvial systems within the interwell-scale that cause problems. Factors such as river avulsion, climate and crustal movement variations make determining the presence of reservoir-quality sands in the subsurface a challenging feat. Identifying and mapping the heterogeneities as a consequence of these factors is key to creating realistic reservoir models. A recognised way of refining subsurface fluvial reservoir predictability is with the use of geological outcrop analogues. By finding an analogous outcrop, sand body dimensions, facies distributions and stacking patterns can be quantified and used to create reservoir models. Fluvial modelling has significantly improved over the last two decades, primarily due to refinements in stochastic modelling techniques. This study presents an analysis of six fluvial systems with the aim of using the geometric data extracted to create and populate reservoir models. To evaluate the differences between object and pixel-based modelling, three outcrops are modelled using object and Sequential Indicator Simulation (SIS) while one outcrop is modelled using a combination of the two. The results show that object-based modelling performs better in fluvial environments with low accommodation and low net-to-gross values. The object-based methods produce well-confined channels in isolation amongst the background floodplain deposits. However, they fail to realistically represent overbank deposits such as crevasse splays, often being too amalgamated and not laterally discontinuous. SIS modelling, on-the-other hand, performs better in modelling high net-to-gross systems, where the major internal heterogeneities are discontinuous muds with limited lateral connectivity. Using a combination of the two modelling techniques (object-based

Heterogeneity analysis of reservoir porosity and permeability in the Late Ordovician glacio-fluvial Sarah Formation paleovalleys, central Saudi Arabia

Article

Full-text available

Sep 2017

The Late Ordovician glacio-fluvial Sarah Formation is an important tight gas reservoir target in Saudi Arabia. This study uses statistical methods to characterize the petrophysical heterogeneity of the paleovalleys of the Sarah Formation that crop out in central Saudi Arabia. Four paleovalleys were studied: Bukayriyah, Hanadir, Sarah, and Khanasir Sarah. Several lithofacies were identified in each that vary in texture, porosity, permeability, and facies abundance that reflect periods of ice advance and retreat. The heterogeneity analysis is based on three statistical measures, namely, the coefficient of variation, the Dykstra-Parsons coefficient, and the Lorenz coefficient. The coefficient of variation values is in the 0.62–1.94 range, indicating an extremely heterogeneous distribution. The Dykstra-Parsons coefficient values are in the 0.56–0.88 range, suggesting very high to extremely high heterogeneity in the reservoirs. The Lorenz coefficient correlates well with the Dykstra-Parsons coefficient for paleovalleys of the Sarah Formation. The heterogeneity parameters studied here indicate that the outcrops of Sarah Formation paleovalleys represent heterogeneous to very heterogeneous reservoirs, which may be attributed to complex depositional and diagenetic variations that have affected the porosity and permeability distribution.

Modelling Temporal and Spatial Sedimentary Architectural Complexity in Mixed Aeolian-Fluvial Reservoir Successions

Conference Paper

Apr 2017

Mohammed A Al-Masrahy

Studies of modern desert dune fields allow geologists to draw conclusions about the controls that govern the development of spatial patterns of arrangement of desert landforms. This knowledge can be applied to predict the likely arrangement of architectural elements in preserved ancient desert successions. This serves as the basis for the development of more sophisticated facies, architectural-element and sequence stratigraphic models that can be applied in reservoir geology. This study presents a series of ten bespoke facies models that demonstrate different types of aeolian-fluvial interaction documented from dune-field margin settings. These ten semi-quantitative models have been developed based on analysis of modern and ancient systems, and via comparison of literature-derived case-study examples of ancient successions using a meta-analysis approach. The presented facies models account for the nature and origin of stratigraphic complexity present in aeolian dune-field margin successions that arose in response to the combined interplay of a series of autogenic and allogenic controls. From an applied perspective, mixed aeolian and fluvial successions are known to form several major reservoirs for hydrocarbons, including the Permian Unayzah Formation of Saudi Arabia. However, quantitative stratigraphic prediction of the three-dimensional form of heterogeneities arising from aeolian and fluvial interaction is notoriously difficult: (i) interactions observed in one-dimensional core and well-log data typically do not yield information regarding the likely lateral extent of sand-bodies; (ii) stratigraphic heterogeneities of these types typically occur on a scale below seismic resolution and cannot be imaged using such techniques. Understanding the nature and surface expression of various types of aeolian and fluvial interaction, and considering their resultant sedimentological expression, is important for prediction and interpretation of preserved deposits of such interactions that might be recognized in the ancient stratigraphic record. Assessment can be made of the spatial scale over which such interactions are likely to occur and this has applied significance; the developed facies models facilitate the prediction of net reservoir sandbody dimensions from subsurface successions by constraining the geometry and lateral and vertical connectivity of sand bodies for specific desert system types. Assuming layer-cake correlations between neighbouring wells within stratigraphically complex reservoirs composed of mixed aeolian and fluvial facies is inappropriate; instead, a range of bespoke facies models should be utilized, each of which considers possible stratigraphic configurations and each of which has implications for likely reservoir performance.

A test of analog-based tools for quantitative prediction of Large-scale fluvial architecture

Article

Feb 2016

Outcrop analogs are routinely used to constrain models of subsurface fluvial sedimentary architecture built through stochastic modeling or interwell sand-body correlations. Correlability models are analog-based quantitative templates for guiding the well-to-well correlation of sand bodies, whereas indicator variograms used as input to reservoir models can be parameterized from data collected from analogs, using existing empirical relationships. This study tests the value and limitations of adopting analog-informed correlability models and indicator variogram models and assesses the effect and significance of analog choice in subsurface workflows for characterizing fluvial reservoirs. A 3.2-km (2-mi)-long architectural panel based on a virtual outcrop from the Cretaceous Blackhawk Formation (Wasatch Plateau, Utah) has been used to test the methodologies. Vertical dummy wells have been constructed across the panel, and the intervening fluvial architecture has been predicted using correlability models and sequential indicator simulations. The correlability and indicator variogram models employed to predict the outcrop architecture have been compiled using information drawn from an architectural database. These models relate to (1) analogs that partially match with the Blackhawk Formation in terms of depositional setting and (2) empirical relationships relating statistics on depositional element geometries and spatial relations to net-to-gross ratio, based on data from multiple fluvial systems of a variety of forms. The forecasting methods are assessed by quantifying the mismatch between predicted architecture and outcrop observations in terms of the correlability of channel complexes and static connectivity of channel deposits. Results highlight the effectiveness of correlability models as a check for the geologic realism of correlation panels and the value of analog-informed indicator variograms as a valid alternative to variogram model parameterization through geostatistical analysis of well data. This work has application in the definition of best-practice use of analogs in subsurface workflows; it provides insight into the typical degree of realism of analog-based predictions of reservoir architecture; as well as the effect of analog choice, and draws attention to associated pitfalls. © Copyright 2016. The American Association of Petroleum Geologists. All rights reserved.

A test of analog-based tools for quantitative prediction of large-scale fluvial architecture

Article

Feb 2016
AAPG BULL

Outcrop analogs are routinely used to constrain models of subsurface fluvial sedimentary architecture built through stochastic modeling or inter-well sandbody correlations. Correlability models are analog-based quantitative templates for guiding the well-to-well correlation of sand-bodies, whereas indicator variograms used as input to reservoir models can be parameterized from data collected from analogs, using existing empirical relationships. This study tests the value and limitations of adopting analog-informed correlability models and indicator-variogram models, and assesses the impact and significance of analog choice in subsurface workflows for characterizing fluvial reservoirs. A 3.2 km long architectural panel based on a Virtual Outcrop from the Cretaceous Blackhawk Formation (Wasatch Plateau, Utah, USA) has been used to test the methodologies: vertical 'dummy' wells have been constructed across the panel, and the intervening fluvial architecture has been predicted using correlability models and sequential indicator simulations. The correlability and indicator-variogram models employed to predict the outcrop architecture have been compiled using information drawn from an architectural database. These models relate to: (i) analogs that partially match with the Blackhawk Formation in terms of depositional setting, and (ii) empirical relationships relating statistics on depositional-element geometries and spatial relations to net-to-gross ratio, based on data from multiple fluvial systems of a variety of forms. The forecasting methods are assessed by quantifying the mismatch between predicted architecture and outcrop observations in terms of the correlability of channel complexes and static connectivity of channel deposits. Results highlight the effectiveness of correlability models as a check for the geologic realism of correlation panels, and the value of analog-informed indicator variograms as a valid alternative to variogram-model parameterization through geostatistical analysis of well data. This work has application in the definition of best-practice use of analogs in subsurface workflows; it provides insight into the typical degree of realism of analog-based predictions of reservoir architecture, as well as on the impact of analog choice, and draws attention to associated pitfalls.

Sedimentary facies, correlation, and architecture of Rotliegend reservoirs at the Southern Permian basin margin: The P01-FA case study and the challenged myth of layer-cake stratigraphy

Article

Full-text available

Jan 2011

Andrea Moscariello

Sedimentology, log analysis, and high-resolution seismic data of the P01-FA structure, located in the western part of the Netherlands sector of the North Sea, were used to assess the correlatability and connectivity of the sand bodies, to unravel the complex internal reservoir architecture, and to demonstrate the impact that different conceptual geological models driven by different correlation methods can have on the correct understanding of the subsurface. Heterogeneity of reservoir architecture and internal reservoir facies was first assessed based on a well-to-well log-based correlation, and the results were compared with a correlation based on detailed examination of an inverted seismic cube. The overall resulting reservoir architecture based on detailed seismic-supported geological and stratigraphical analysis is significantly different from the one based only on well-to-well correlation, which may, at first glance, suggest a simple layercake architecture. The new model highlights how both, the internal structural and stratigraphical framework and the distribution of reservoir facies are most likely the result of a complex interplay of erosion, sedimentation, and tectonics. Tectonics was especially active during the lower and middle part of the Upper Rotliegend Group accumulation, thus influencing the lateral continuity of individual stratigraphic units. This study also demonstrates how unravelling the internal composition of mixed aeolian-fluvial reservoirs, by detailed seismic examination, is critical to describe the reservoir heterogeneity in order to assess and predict connectivity. This is especially important in sandy reservoir containing minor reservoir elements which can create large permeability contrasts (e.g., baffles and barriers) and ultimately influence hydrocarbon flow. This study demonstrates that an integrated evaluation using detailed sedimentary facies analysis and examination of seismic inversion data can allow a better understanding of reservoir geology by reducing the subsurface uncertainties and thus the risk associated with future appraisal and development activities.

A Quantitative Approach to the Characterization of Sedimentary Architecture in Mixed Aeolian-Fluvial Reservoir Successions

Conference Paper

Aug 2015

Mohammed A Al-Masrahy

Eolian and fluvial processes operate coevally in most desert-margin settings to generate a range of styles of sedimentary interaction that are documented from both modern arid systems and analogous ancient preserved outcrop and subsurface successions. Such styles of system interaction give rise to considerable complexity in terms of sedimentology and preserved stratigraphy. The physical boundary between geomorphic systems in hot deserts is dynamic such that facies belts undertake considerable lateral shift over time with the result that preserved sequence architectures exhibit complexity arising from system interactions that operate at a range of spatial and temporal scales from local to regional. An improved understanding of factors that govern these multiple scales of interaction is important for prediction of preserved stratigraphic architecture and therefore for assessment of fluid-flow properties and for development of well placement strategy in mixed eolianfluvial reservoir prospects. A database has been developed to record the temporal and spatial scales over which eolian and fluvial events operate and interact in a range of modern and ancient desert-margin settings. Data have been collated using high-resolution satellite imagery, field observation and subsurface data. Ten distinct styles of eolian-fluvial interaction are recognized: fluvial incursions aligned parallel to the trend of linear chains of eolian dune forms; fluvial incursions oriented perpendicular to the trend of eolian dunes; bifurcation of fluvial systems around eolian dunes; through-going fluvial channel networks that cross entire eolian dune-fields; flooding of dune-fields due to regionally elevated water-table levels associated with fluvial floods; fluvial incursions emanating from a single point source into dune-fields; incursions emanating from multiple sheet sources; cessation of the encroachment of entire eolian dune-fields by fluvial systems; termination of fluvial channel networks into playas within eolian dunefields; long-lived versus short-lived styles of fluvial incursion. The database of case-study examples is employed to develop a series of quantitative facies models with which to account for dynamic spatial and temporal aspects of eolian-fluvial system behavior. Models can be used to predict the arrangement of architectural elements that define gross-scale system architecture in a variety of mixed eolian-fluvial reservoirs. http://www.searchanddiscovery.com/documents/2015/41669almasrahy/ndx_almasrahy.pdf

Unlocking the correlation in fluvial outcrops by using a DOM-derived virtual datum: Method description and field tests in the Huesca fluvial fan, Ebro Basin (Spain)

Article

Full-text available

Jul 2015
GEOSPHERE

Adequate characterization of depositional architecture is of great importance when studying fluvial outcrops as reservoir analogs. The complex three-dimensional (3D) distribution and lateral and vertical relationships of sandstone bodies require a high degree of stratigraphic control in order to make a proper assessment of the distribution and connectivity of the reservoir facies. This assessment demands the use of reliable correlation datums. Unfortunately, clear marker beds (e.g., ash layers, coal beds, and paleosols) are not always available in fluvial outcrops, and when present, they are often covered by vegetation or debris that prevents their tracking over long distances. A new method to achieve highly accurate and semiautomatic correlations within fluvial digital outcrop models (DOMs) is presented in response to the need for further correlation procedures, especially in the absence of suitable datums. The method is based on the hypothesis that the average depositional paleosurface of a sedimentary system can be represented by a plane at outcrop scale. If this assumption is valid, this plane can be used as a virtual datum to identify along the DOM the sediments that were deposited simultaneously. The method was tested and applied successfully within two kilometer-scale outcrops of the Huesca fluvial fan (Early Miocene, northern Spain), where the virtual datum provided accurate correlations regardless of stratigraphic or topographical complexities. Moreover, all the sedimentary successions of the outcrops could be automatically subdivided into the desired stratigraphic intervals by only moving the virtual datum vertically. These intervals can be subsequently isolated to facilitate the detection of subtle variations and trends of their fluvial properties. Consequently, a virtual datum is the equivalent of having a marker bed crossing the stratigraphic succession of an outcrop at any desired position. The advantages provided by a virtual datum prove to be especially useful in large and topographically complex outcrops that previously could not have been studied with such a high degree of 3D stratigraphic control.

ARQUITETURA DE FÁCIES E EVOLUÇÃO ESTRATIGRÁFICA DOS DEPÓSITOS FLÚVIO-EÓLICOS DA FORMAÇÃO TOMBADOR, (MESOPROTEROZÓICO) CHAPADA DA DIAMANTINA -BA

Article

Porto Alegre

Approaches to Modeling Stratigraphic Heterogeneity in Mixed Fluvial and Aeolian Hydrocarbon Reservoirs,

Conference Paper

Apr 2014

Mohammed A Al-Masrahy

Dynamic relationships between coevally active fluvial and aeolian systems give rise to a range of styles of sedimentary interaction that are documented from both modern arid-climate systems and analogous ancient preserved outcrop and subsurface successions. Mixed fluvial and aeolian successions are known to form several major reservoirs for hydrocarbons, including the Permian Unayzah Formation of Saudi Arabia, the Permian Rotliegend Group of the North Sea, and the Jurassic Norphlet Sandstone of the Gulf of Mexico and typically give rise to stratigraphic heterogeneity at a number of scales. Quantitative stratigraphic prediction of the three-dimensional form of heterogeneities arising from fluvial and aeolian interaction is notoriously difficult: (i) the preserved products of system interactions observed in one-dimensional core and well-log data typically do not yield information regarding the likely lateral extent of sand bodies; (ii) stratigraphic heterogeneities typically occur on a scale below seismic resolution and cannot be imaged using such techniques. A database recording the temporal and spatial scales over which aeolian and fluvial events operate and interact in a range of present-day and ancient desert-margin settings has been collated using high-resolution satellite imagery, aerial photography and field observation. Together, these data have been used to develop a series of dynamic facies models to predict the arrangement of architectural elements that define gross-scale system architecture. Case-study examples have enabled the construction of a series of depositional models to account for the diversity of styles of fluvial and aeolian system interactions. Several styles of aeolian-fluvial interaction have been documented and the preserved deposits can now be predicted through quantitative geological models that account for spatial and temporal changes in system dominance. For example, the preserved architectural elements of fluvially flooded interdunes tend to expand laterally as successive flood deposits develop in front of advancing aeolian dunes. In non-climbing aeolian systems, such behavior favors the development of sheet-like bypass surpersurfaces. In aeolian systems that climb at low angles and for which fluvial incursions are episodic, thin and laterally impersistent fluvial elements tend to accumulate. The scale and connectivity of fluvial flood deposits tends to diminish with increasing distance toward the aeolian dune-field center.

Helicopter-based laser scanning: A method for quantitative analysis of large-scale sedimentary architecture

Article

Jun 2014

Studies of large-scale sedimentary architecture are mainly based on the interpretation of two-dimensional photomosaics. This method cannot account for the natural rugosity of outcrop exposures, introducing errors in the measurement of geobody sizes and orientations. In the past, three-dimensional outcrop studies have relied on time-intensive fieldwork, with irregular sampling and low geometric accuracy. More recently, terrestrial laser scanning, or LiDAR (Light Detection and Ranging), has been widely applied to small-scale outcrops, but range and accessibility preclude its usage on larger-scale outcrops. Oblique helicopter-based laser scanning, however, allows the collection of tens of kilometres of outcrop sections in a relatively short time frame. In this paper, a procedure for collecting and processing such virtual outcrop data is outlined, and the application of the technique for extracting dimensions of fluvial geobodies from two large and otherwise inaccessible outcrops from Utah is presented. The results are compared to interpretations from more conventional photomosaicking of the same outcrops. Results show that the use of helicopter-based laser scanning enables geoscientists to rapidly acquire georeferenced data that can then be used for sedimentological interpretation and analysis on reservoir scales. It is concluded that helicopter-based laser scanning promotes sedimentological research and is well suited to capturing quantitative geometrical data from large outcrops.

Mass and hyperconcentrated flow deposits record dune damming and catastrophic breakthrough of ephemeral rivers, Skeleton Coast Erg, Namibia

Article

Full-text available

Aug 2003
SEDIMENT GEOL

Channel-shaped deposits of well sorted sand with only 2–4% fine-grained material, being either massive and structureless or upward fining with basal lag, are found interbedded with aeolian sand in the Skeleton Coast Erg, Namibia. Detailed analyses of the channel-shaped deposits suggest that they are formed as hyperconcentrated flows within the erg. Grain-size analysis and whole rock geochemical modeling revealed that some of the fluvial sediments contain up to 70% aeolian sand, interpreted as a result of dune collapse into the fluvial system. In certain cases, this instantaneous supply of sand resulted in generation of sandy mass flows with laminar flow behaviour. The presence of smectite as dominant clay mineral proved to be of crucial importance in formation of mass flow deposits. These mass flows had no erosional capacity, and drape the palaeotopography. They are comparable to those generated by catastrophic collapse of dunes, described in the literature. This paper suggests that all these deposits should be termed intra-erg mass flows, as several of them carry little, if any debris. Based on their origin, intra-erg mass flows can be divided into two groups:(1)Attached intra-erg mass flows, which are formed and found attached to the dune that sourced the flow;(2)Detached intra-erg mass flows, which are not found adjacent to the dune sourcing the flow, and often carry material sourced outside the dune field.A five-stage model is proposed, involving dune damming to explain the observed deposits and the degree of reworking. When the flood basin behind the erg overtops the threshold area, water pours into the erg, giving rise to a complex fluvio-aeolian setting. The setting in the Skeleton Coast erg is comparable to recent as well as ancient settings, and reveals valuable information for reservoir characterization and hazard assessment.

A review of recent research in fluvial sedimentology

Article

May 1993
SEDIMENT GEOL

Christopher R. Fielding

SEDIMENT ARCHITECTURE AND COMPOSITION OF THE WATERLOO MORAINE, SOUTHERN ONTARIO: EMERGING INSIGHTS

Article

Full-text available

Jan 2005

Many moraines in Ontario are important areas of groundwater recharge. Moraine topography and structure controls the transmission of water from surface to groundwater and regional aquifers. An improved understanding of moraines in southern Ontario is of particular interest due to increased concern over source water protection (TEC, 2004). The Waterloo Moraine provides ~60 % of the water supply to Waterloo region (Frind et al., 2002). It is the focus of short term artificial recharge and storage (Wootton et al., 1997), is the site of municipal landfills, has increasing urban encroachment (Sanderson, 1995), and is the headwaters for many stream in the area. Thus, improved information on sediment extent, composition and variability is needed to sustain these vital watershed activities. One, well developed, and little-applied research method in southern Ontario moraines, is sedimentological analogue studies of outcrop and subsurface core for improved understanding of reservoir-aquifer geometry and character (e. g. North and Prosser, 1993; Galloway and Hobday, 1996)

Mass and hyper-concentrated flow deposits record dune damming and catastrophic breakthrough of ephemeral rivers, Skeleton Coast Erg, Namibia.

Article

Jan 2003
SEDIMENT GEOL

Hoanib River flood deposits of Namib Desert interdunes asanalogues for thin permeability barrier mudstone layers inaeolianite reservoirs

Article

Full-text available

Aug 2002
SEDIMENTOLOGY

ABSTRACT The ephemeral braided Hoanib River of NW Namibia flows for a few days a year, and only high discharges enable the river to pass through interdunal depressions within the northern Namib Desert dune field to the Atlantic. The dune field comprises mainly large transverse dunes resulting from predominant SSW winds. River flood deposits between aeolian dunes are analogous to mudstone layers conformably interbedded with ancient aeolianite dune foresets. Deep floods pond laterally to considerable depths (metres to >10 m) in adjacent interdunes, depositing mud layers (1–50 cm) to considerable heights on avalanche and stoss faces of bounding dunes. Fairly passive flooding only disturbs aeolian stratification minimally. Floodwater clay infiltrates and settles as an impermeable seal, with a flood pond on top, perched, above regional groundwater. Flood ponds evaporate slowly for long periods (>3 years). Early emergence desiccates higher parts of a mud layer. Subsequent floods can refill a predecessor pond, benefiting from the existing impervious seal. Potential preservation of such mud layers is lower on the stoss face, but high on the avalanche face after burial by subsequent dune reactivation and migration. The leeward (right) Hoanib bank, a dune stoss face, is river and wind eroded to exhume fossil interdune pond mud layers of an earlier Hoanib channel. The highly inclined layers are interbedded with dune avalanche foresets and represent the edges of two successive fossil ponds exposed in plan. Ancient flood pond mudstones occur in the Permian–Triassic hydrocarbon reservoir, the Sherwood Sandstone Group of the Cheshire Basin (Kinnerton Formation) and Irish Sea Basin and were previously used erroneously to argue against the aeolian origin of cross-bed sets. Hoanib studies show that primary river interaction with a dune field might preserve only localized erosional omission surfaces in ancient aeolianites, with little sandy barform preservation, prone to aeolian reworking. Around the main fluvial channel locus, however, flood pond mudstone layers should form a predictable halo, within which fluid permeability will decrease.

High-resolution stratigraphy and depositional model of wind- and water-laid deposits in the Ordovician Guaritas Rift (southernmost Brazil)

Article

Full-text available

Dec 2007
SEDIMENT GEOL

The upper portion of the Pedra Pintada Alloformation includes about 100 m of mostly eolian deposits. This paper emphasizes the vertical succession and lateral association of sedimentary facies, based on analysis of outcrop data and aerial photographs, as well as the hierarchy and origin of bounding surfaces. It aims to propose a high-resolution stratigraphic and depositional model that may be useful to exploitation of eolian reservoirs. The succession has been preserved due to basin subsidence, and is described in terms of four facies associations that constitute three dominantly eolian units. These units are sharply bounded by major flooding surfaces (super surfaces) that, in turn, are overlain by 1 to 2 m thick, dominantly water-laid facies (lacustrine, fluvial, deltaic and eolian). Both their internal organization and boundaries were controlled by changes in the base level rise rate. The basal Eolian Unit is composed of crescentic eolian dunes and damp interdune deposits ascribed to a wet eolian system. On the other hand, eolian units II and III, also characterized by crescentic eolian dunes (simple and compound) deposits, were related to dry eolian systems, since they comprise dry (eventually wet) interdune facies. Eolian Unit III is truncated by basinwide unconformity, which is then overlain by the ephemeral fluvial deposits (Varzinha Alloformation). This second type of super surface is related to climate-induced wind erosion (deflation) down to the water table level (regional Stokes surface) followed by fluvial incision linked to tectonic activity.

Quantitative analysis of aeolian stratigraphic architectures preserved in different tectonic settings

Article

Full-text available

Dec 2022
EARTH-SCI REV

Despite a well-documented record of preserved sedimentary architectures of aeolian successions from a variety of different sedimentary basin types, relationships between tectonic setting and aeolian accumulation and preservation remain poorly constrained and largely unquantified. This study uses a database-informed approach to quantitatively document the variability in preserved sedimentary architecture of 56 globally distributed aeolian systems, and to relate these variations to differences in their basin settings. Three different tectonic settings are considered: intracratonic, foreland, and rift basins. Key finding are as follows. (1) Intracratonic basins are characterized by slow accommodation generation. They favour the accumulation and preservation of relatively thin aeolian genetic units; likely generated by dunes and interdunes that climbed at low angles, resulting in the accumulation and preservation of relatively thin dune and interdune elements. Depressed water tables – indicated by abundant dry interdune elements – left accumulated dune successions exposed above the erosional baseline, making them vulnerable to post-depositional reworking. This likely resulted in sporadic episodes of aeolian dune accumulation, between long episodes of sediment bypass or deflation, under conditions of low rates of net accommodation generation. (2) Rapid accommodation generation in the depocentres of foreland basins favours the preservation of thick dune-set and interdune elements, enabled by a rapid rate of rise of the accumulation surface that allowed bedform climb at relatively high angles. High rates of sediment supply associated with erosion of adjacent orogenic belts allowed the construction of large dunes. Elevated water tables – indicated by abundant wet interdune elements – may have allowed aeolian accumulations to be placed beneath the baseline of erosion shortly after deposition, thereby protecting them from potential post-depositional deflation. (3) Despite rift basins experiencing the highest rates of accommodation generation, their fills tend to be associated with the preservation of relatively thin dune and sandsheet elements. Elevated water tables, associated with rapid accommodation generation, create damp substrates and consequently restrict the availability of dry sand for dune construction. In the examples considered here, rapid accommodation generation outpaces sediment supply, favouring the construction and rapid migration of small dunes that consequently accumulate thin dune sets. Aeolian dunes in rift basins are also commonly reworked by fluvial and alluvial processes, in some cases likely related to orographic precipitation, associated with rift shoulder topography. Results of this analysis can be applied to improve predictions of the architecture of ancient aeolian successions at the basin scale, both in outcrop and in subsurface successions.

Aeolian Sand Dune Sedimentary Architecture Is Key in Determining the “Slow-Gas Effect” during Gas Field Production Performance

Article

Dec 2021

Aeolian deposits are typically considered to act as homogeneous “tanks” of sand, which do not contain significant heterogeneities that impact the production of hydrocarbons. However, a succession of deeply buried aeolian gas reservoirs from the Permian Rotliegend exhibit a characteristic production decline profile that is typified by high initial flow rates, followed by a rapid decline in bottomhole pressure and decline in flow rate, subsequently followed by stabilization at low flow rates for an extended period (over several decades). This effect has been termed here as the “slow-gas effect,” and this production phenomenon has previously been attributed to structural compartmentalization. This paper presents an alternative, sedimentological hypothesis for the cause of the slow-gas effect based upon facies-controlled permeability differences within aeolian dune trough architectures. To test this, three interwell (km) scale models from well-studied aeolian analogs from Utah and Arizona were modeled with standard geostatistical reservoir techniques and populated with petrophysical properties from producing Rotliegend reservoirs in Germany. These models were subsequently dynamically simulated to analyze production behavior and test whether a similar “slow-gas” production profile could be reproduced. This study finds that the slow-gas effect primarily results from heterogeneities created by the complex interaction of deposition, accumulation, and erosion within aeolian strata, as opposed to the structural compartmentalization of homogeneous tanks of sand as previously thought. Structural compartmentalization and baffling through faulting where present will have an impact on fluid flow; however, it is not considered here to be the primary cause of the slow-gas effect. Results of this work demonstrate the necessity of accurately characterizing and reproducing low permeability heterogeneity in aeolian systems. These heterogeneities can either be modeled explicitly through the use of geostatistical reservoir modeling techniques as done here, or implicitly through the use of characteristic length and transmissibility multipliers. These results have significant implications on our understanding of how tight aeolian systems produce; namely, after depletion of the near-wellbore volume, production from the surrounding reservoir is baffled by a hierarchy of low permeability bounding surfaces and associated transmissibility barriers. Application for enhancing reservoir depletion strategies include optimizing well trajectories to maximize the number of dune penetrations and percentage of net reservoir facies in communication to the well; maximizing the size of the primary reservoir compartment. Neighboring wells should be placed in separate compartments to maximize the amount of fast-flowing gas production during the early production stage. Pressure management can be used to cyclically produce, deplete, and recharge the primary reservoir compartment to manage and optimize recovery during the decline phase and production tail.

A Database of Aeolian Sedimentary Architecture for the characterization of modern and ancient sedimentary systems

Article

Feb 2021
MAR PETROL GEOL

The Database of Aeolian Sedimentary Architecture (DASA) records the architecture and spatio-temporal evolution of a broad range of modern and recently active aeolian systems, and of their preserved deposits in ancient successions. DASA currently stores data on >14,000 geologic and geomorphic entities (including bounding surfaces and transition relationships) extracted from >60 case-study examples documented in the published literature. DASA stores data on a variety of aeolian and associated non-aeolian entities of multiple scales, including attributes that characterize their type, geometry, spatial relations, hierarchical relations, temporal significance, and textural and petrophysical properties; associated metadata are also stored. Database output describes (1) stratigraphic relationships between aeolian and associated fluvial, lacustrine and paralic depositional systems; (2) the geometry of aeolian architectural elements, and hierarchical and spatial relationships between them; (3) the probabilities of vertical and lateral transition from one type of deposit or landform to another; (4) the presence and nature of aeolian bounding surfaces at different scales, and their nested, hierarchical relationships; (5) aeolian lithofacies types, proportions and distributions, and (6) grain-scale textural parameters. DASA is applied to quantitatively characterize and compare modern and ancient aeolian sedimentary systems. Examples of database outputs demonstrate how DASA outputs can be tailored for numerous applications, including: (1) the development of bespoke quantitative facies models, specifically tailored for particular sets of boundary conditions; (2) the empirical assessment of how aeolian systems, and associated preserved sedimentary architectures, represent a response to allogenic and autogenic forcings; and (3) the instruction of forward stratigraphic models and 3D geocellular subsurface models. DASA is a valuable tool for the characterization of subsurface aeolian successions, such that output can help to (1) predict three-dimensional lithological heterogeneity in subsurface successions that are resource targets, (2) constrain geocellular stochastic models, and (3) facilitate borehole correlations of aeolian dune sets or associated non-aeolian elements.

Sedimentology and isotope geochemistry of transitional evaporitic environments within arid continental settings: From erg to saline lakes

Article

Full-text available

Oct 2020

Arid continental basins typically contain a spectrum of coeval environments that coexist and interact from proximal to distal. Within the distal portion, aeolian ergs often border playa, or perennial, desert lakes, fed by fluvial incursions or elevated groundwaters. Evaporites are common features in these dryland, siliciclastic dominant settings. However, sedimentary controls upon evaporite deposition are not widely understood, especially within transitional zones between coeval clastic environments that are dominantly controlled by larger scale allocyclic processes, such as climate. The sulphur (δ³⁴S) and oxygen (δ¹⁸O, Δ¹⁷O) isotope systematics of evaporites can reveal cryptic aspects of sedimentary cycling and sulphate sources in dryland settings. However, due to the lack of sedimentological understanding of evaporitic systems, isotopic data can be easily misinterpreted. This work presents detailed sedimentological and petrographic observations, coupled with δ³⁴S, δ¹⁸O and Δ¹⁷O data, for the early Permian Cedar Mesa Sandstone Formation (western USA). Depositional models for mixed evaporitic / clastic sedimentation, which occurs either in erg‐marginal or lacustrine‐marginal settings, are presented to detail the sedimentary interactions present in terms of climate variations that control them. Sedimentological and petrographical analysis of the evaporites within the Cedar Mesa Sandstone Formation reveal a continental depositional environment and two end member depositional models have been developed: erg‐margin and lake‐margin. The δ³⁴S values of gypsum deposits within the Cedar Mesa Sandstone Formation are consistent with late Carboniferous to early Permian marine settings. However, a marine interpretation is inconsistent with sedimentological and petrographic evidence. Consequently, δ³⁴S, δ¹⁸O and Δ¹⁷O values are probably recycled and do not reflect ocean‐atmosphere values at the time of evaporite precipitation. They are most likely derived from the weathering of older marine evaporites in the hinterland. Thus, the results demonstrate the need for a combination of both sedimentological and geochemical analysis of evaporitic systems to better understand their depositional setting and conditions.

Heterogeneities of the fluvial-eolian reservoirs of the Sergi Formation, Recôncavo Basin

Article

Full-text available

May 2009

The Sergi Formation can be subdivided into three sequences, bounded by unconformities. The depositional and diagenetic heterogeneities that affect reservoir quality of sequences I and II were identified. The integration of sedimentologic, stratigraphic and petrologic data revealed significant differences in the depositional and diagenetic characteristics of these sequences, which have decisively influenced the definition of the reservoir heterogeneity patterns and porosity and permeability distribution. This integrated analysis supplied parameters to construct reservoir quality and heterogeneity models that can be applied to develop the fields producing from Sergi Formation, as well as predict the quality of Sergi reservoirs under exploration. Sequence I reservoirs are made up of fine to medium-grained sandstones, well to moderatelysorted, deposited by fluvial-eolian systems. Sequence II reservoirs, in their turn, are made up of fine to conglomeratic, predominantly coarse-grained sandstones, deposited by braided fluvial systems. In addition to the depositional differences, there are systematic differences in the dominant diagenetic processes. Sequence I sandstones are characterized by a more intense carbonate cementation and larger chlorite abundance, while Sequence II sandstones show mechanical clay infiltration as the dominant diagenetic process, which has inhibited further diagenetic events. Intraclastic lags at the base of ephemeral channel cycles of Sequence I are commonly pervasively cemented by calcite, constituting local flow barriers. The concentrations of mechanically infiltrated clays constitute flow barriers and deflectors, being the most important controls on reservoirs quality and heterogeneity within Sequence II.

Oil field production geology

Article

Jan 2009

M. Shepherd

Reconstruction of three-dimensional eolian dune architecture from one-dimensional core data through adoption of analog data from outcrop

Article

Jan 2014
AAPG BULL

Data derived from core and well-logs are essentially one-dimensional and determining eolian system type and likely dimensions and orientation of architectural elements present in subsurface eolian reservoir successions is typically not possible from direct observation alone. This is problematic because accurate predictions of the three-dimensional distribution of interdune and dune-plinth elements that commonly foam relatively low-permeability baffles to flow, of net:gross, and of the likely distribution of elements with common porosity-permeability properties at a variety of scales in eolian reservoirs is crucial for effective reservoir characterization. Direct measurement of a variety of parameters relating to aspects of the architecture of eolian elements preserved as ancient outcropping successions has enabled the establishment of a series of empirical relationships with which to make first-order predictions of a range of architectural parameters from subsurface successions that are not observable directly in core. In many preserved eolian dune successions, the distribution of primary lithofacies types tends to occur in a predictable manner for different types of dune sets, whereby the pattern of distribution of grain-flow, wind-ripple, and grain-fall strata can be related to set architecture, which itself can be related back to original bedform type. Detailed characterization of individual eolian dune sets and relationships between neighboring dune and interdune elements has been undertaken through outcrop studies of the Permian Cedar Mesa Sandstone and the Jurassic Navajo Sandstone in southern Utah. The style of transition between lithofacies types seen vertically in preserved sets, and therefore measurable in analogous core intervals, enables predictions to be made regarding the relationship between preserved set thickness, individual grain-flow thickness, original bedform dimensional properties (e.g., wavelength and height), the likely proportion of the original bedform that is preserved to form a set, the angle of climb of the system, and the likely along-crest variability of facies distributions in sets generated by the migration of sinuous-crested bedforms. A series of graphical models depict common facies arrangements in bedsets for a suite of dune types and these demonstrate inherent facies variability.

The application of outcrop analogues in geological modelling: a review, present status and future outlook

Article

Full-text available

Jun 2014

Analogues, especially outcrop analogues, have played a central role in improving understanding of subsurface reservoir architectures. Analogues provide important information on geobody size, geometry and potential connectivity. The historical application of outcrop analogues for understanding geobody distributions in reservoirs is reviewed, from the pioneering work of the 1960s to the high-tech virtual outcrop methodologies of today. Four key types of analogue data are identified: hard data, which describe the dimensions and geometry of the geobody; soft data, which describe the conceptual relationships between different geobody types; training images, which record the dimensions, proportions and spatial relationship; and analogue production data, which are taken from direct subsurface production analogues. The use of these different data types at different stages of the geomodelling workflow is discussed and the potential sources of error considered. Finally, a review of geobody and analogue studies in different clastic environments is discussed with reference to selected previous work and the range of papers in the current volume.

Alluvial-slope deposition of the Skull Ridge Member of the Tesuque Formation, Espanola Basin, New Mexico

Article

Jan 2001

Miocene sediment eroded from the Sangre de Cristo Mountains is well exposed in the Española Basin and provides the opportunity to describe deposition on a non-fan, alluvial slope. The study site, located approximately 40 km (25 mi) north of Santa Fe, New Mexico, consists of a 150-m (492-ft) thick section of the Skull Ridge Member of the Tesuque Formation. Eight depositional lithofacies were defined, and four vertically alternating and laterally continuous lithosomes were identified. The lithofacies are varied and range from massive, extensively bioturbated very fine sand and silt, to pebbly coarse bedded sand, to well-sorted fine sand. Internally massive lithofacies of fine sand and silt are most abundant, followed by fine sand channel deposits, then coarse pebbly sand channel deposits, and finally, well-sorted fine sand deposits. These lithofacies are interpreted to represent many small channels and adjacent floodplains on an alluvial slope. Persistence of channels across the piedmont is contrary to expectations for alluvial-fan deposition. The four lithosomes are tens of meters thick with abrupt vertical transitions. The first and third lithosomes consist predominantly of silt and very fine sand and are crudely bedded but internally massive due to extensive bioturbation. The second and fourth lithosomes consist of many channel-deposit lithofacies and well-sorted eolian sand in addition to internally massive beds of very fine sand and silt. Variability in alluvial-slope deposits is observed at two scales. Depositional processes produce facies alternations at a bedding scale. External forcing mechanisms such as tectonics and/or climate produce lithosomes on a scale of tens of meters, which serve as confining units and heterogeneous permeable units. We favor climate as the allogenic control for the larger-scale variations. Fundamental sedimentological differences exist between alluvial-fan and alluvial-slope deposits. These lateral and vertical distribution of facies. The distinction between terms of lateral and vertical variability.

Characterization Of Estuary-Shoreface Type Reservoir Using Outcrop Analogue And Modeling Of Flow Using A Nonuniform Coarsened Grid

Article

Full-text available

Apr 2002

A methodology for constructing an analogue 3D model for clastic reservoirs in an estuary-shoreface depositional environment using outcrop information is discussed. Such analogue models provide valuable information related to reservoir architecture and rock properties that can be used to model sedimentary structures in the subsurface. A new approach for upscaling high-resolution models using nonuniform coarsened grid is introduced. Simulation results for a viscous dominated flow process show that nonuniform grids yield better results compared to uniform grids.

Integration of digital outcrop models (DOMs) and high resolution sedimentology - workflow and implications for geological modelling: Oukaimeden Sandstone Formation, High Atlas (Morocco)

Article

Full-text available

Apr 2010

Outcrop analogue studies provide key information for reservoir modelling which is difficult to obtain from traditional subsurface datasets (i.e. seismic data, well data). Terrestrial laser scanners or LiDAR (light detection and ranging), combined with digital photography, provide a new technique to create high resolution 3D digital outcrop models (DOMs). These DOMs generate exhaustive information which is used to build more realistic three-dimensional facies-based geocellular models and populate the different model zones. This paper documents the use of an extensive dataset, which combines high resolution traditional field data and DOMs. We provide an accurate description of the workflow followed in the geocellular modelling of a fluvial-dominated continental formation. Geocellular facies association and connectivity models are well constrained by outcrop observations and a number of different techniques are used in the quality control of the final model. The study also qualitatively discusses the uncertainties identified during the workflow and proposes methods to reduce them. The workflow and results shown in this paper can be applied in similar analogue systems in order to help improve model building for subsurface reservoirs.

Imaging the subsurface stratigraphy in the Ubehebe hydrovolcanic field (Death Valley, California) using ground penetrating radar

Article

Full-text available

Feb 2000
J VOLCANOL GEOTH RES

Ground penetrating radar GPR surveys were carried out to collect subsurface images of the basaltic base surge deposits in the Ubehebe hydrovolcanic field, Death Valley National Park, California. Antennae with frequencies of 50, 100 and 200 MHz were used. This technique allowed the collection of useful geologic data, for example, the lower stratigraphic boundary of the pyroclastic deposits can be imaged and their thickness can be estimated. Different radar responses were also obtained from base surge deposits and underlying sedimentary rocks, which enable their recognition where no outcrops are available. Furthermore, GPR data confirmed the presence of small, eroded craters, which are partially filled by alluvium. In this case, an unconformity between the overlying, horizontally bedded alluvium and the underlying bowl-shaped base surge deposits Ž . can be recognized within the crater and the thickness of the alluvium estimated. Common mid-point CMP surveys suggested subsurface velocities of the electromagnetic waves in the upper part of these deposits between 0.095–0.1 mrns. q 2000 Elsevier Science B.V. All rights reserved.

Facies Discrimination in a Mixed Fluvio-Eolian Setting Using Elemental Whole-Rock Geochemistry--Applications for Reservoir Characterization

Article

Full-text available

Jan 2007

Fluvio-eolian successions are generally characterized by a high degree of complexity and internal heterogeneity. Quantifying the rapid facies changes in time and space is a major challenge to characterization of hydrocarbon reservoirs. We present a method for facies discrimination in fluvio-eolian successions. The method presented here is developed on the modern fluvio-eolian sediments from the Skeleton Coast dune field, Namibia. The examined sediments comprise eight different facies types: eolian dune sands, interdune fluvial channel sands, intraerg mass-flow deposits, intraerg hyperconcentrated-flow deposits, fluvial channel sands, fluvial mud, lacustrine heterolithic sand, and lacustrine heterolithic mud. The contrasting provenance of the fluvial and eolian sediments results in a distinct source fingerprint which can be discriminated using elemental whole-rock geochemistry. A multivariate statistical technique performed on the geochemical data has enabled discrimination of seven of the eight facies types. Furthermore, the facies discrimination method allowed a quantitative estimate of the degree of fluvial reworking of eolian sand. The Skeleton Coast dune field was chosen as a test area for geochemical facies discrimination, because of its remarkable difference between the immature fluvial source and the mature quartz-rich eolian source. We hope that the method presented here can be applied to subsurface data from geological settings with the same difference in fluvial and eolian sources. It is furthermore hoped that the method can be used in more complex sedimentological settings.

Bias in estimating fractal dimension with the rescaled-range ( R/S ) technique

Article

Jul 1994

Fractal geostatistics are being applied to subsurface geological data as a way of predicting the spatial distribution of hydrocarbon reservoir properties. The fractal dimension is the controlling parameter in stochastic methods to produce random fields of porosity and permeability. Rescaled range (R/S)analysis has become a popular way of estimating the fractal dimension, via determination of the Hurst exponent (H). A systematic investigation has been undertaken of the bias to be expected due to a range of factors commonly inherent in borehole data, particularly downhole wireline logs. The results are integrated with a review of previous work in this area. Small datasets. overlapping samples, drift and nonstationariry of means can produce a very large bias, and convergence of estimates of H around 0.85–0.90 regardless of original fractal dimension. Nonstationarity can also account for H>1, which has been reported in the literature but which is theoretically impossible for fractal time series. These results call into question the validity of fractal stochastic models built using fractal dimensions estimated with the R/Smethod.

Bounding surfaces in a mixed aeolian–fluvial system (Rotliegend, Wessex Basin, SW UK)

Article

Mar 2001
MAR PETROL GEOL

Andrew Newell

The Dawlish Sandstone Formation is a Late Permian succession of mixed aeolian and fluvial deposits in the Wessex Basin (SW England). It is used to illustrate two contrasting types of fluvial/aeolian bounding surface (planar and incised). Planar bounding surfaces separate tabular bodies of fluvial conglomerate and aeolian dune sandstone. They were produced primarily by wind scour to groundwater table, with the later emplacement of conglomerates resulting in local fluvial erosion of cemented aeolian dune sandstones. Incised bounding surfaces were produced by fluvial downcutting. The erosive relief was infilled with mixed aeolian/fluvial deposits. The Dawlish Sandstone Formation may provide the first outcrop example of these incised valley fills, which have recently been identified as a major component of the subsurface Rotliegend in the Southern North Sea Basin. The potential variability of aeolian/fluvial sedimentary architecture has important implications for well-to-well correlation and reservoir modelling.

Sedimentology and hydrogeology of two braided streams

Article

Dec 1999
SEDIMENT GEOL

Two approaches were used to quantify the spatial distribution of hydrofacies in braided stream deposits. One approach involved mapping a 50 by 60 by 3.3 m section of a proximal braided stream deposit. In a second study, we generated a 400 by 400 by 2.6 m section of a medial braided stream deposit using a computer model. In both cases we produced three-dimensional images showing connected hydrofacies with high permeabilities that form preferential flow paths. This information was input to a groundwater flow model and flow paths were analyzed by following the transport of imaginary particles. In both systems, particles that were uniformly distributed at the up-gradient end of the model clustered along preferential flow paths during transport, showing that connection among high-permeability facies is a critical factor in hydrogeological investigations involving assessment of contaminant movement and remediation.

Glacier surges as a control on the development of proglacial fluvial landforms and deposits.

Article

Jan 2002

Thaiënne A.G.P. Van Dijk

Thesis (Ph. D.)--University of Keele, 2002.

CONTRASTING ARCHITECTURE OF TWO ALLUVIAL SUITES IN DIFFERENT STRUCTURAL SETTINGS

Chapter

Full-text available

Jan 1987

The architecture of alluvial suites is governed by a variety of autocyclic and allocyclic mechanisms that work in concert. Careful evaluation of source lithologies, climatic conditions, and tectonic setting must be combined with sedimentologic analysis of three-dimensional exposures of fluvial rocks to rigorously determine controls on the architecture of individual sequences. Consequently, although study of alluvial architecture is a potentially effective and important means of elucidating the depositional and tectonic history of continental basins, there are few well documented field studies. The lower Eocene Willwood Formation of Wyoming and the Plio-Pleistocene Glenns Ferry Formation of Idaho offer contrasting examples of alluvial architecture even though both sequences were generated by meandering streams in tectonically active intermontane basins. Independent evidence for the chronostratigraphy, provenance, climate, and tectonic setting is documented for each unit. Evaluation of these parameters demonstrates that differences in tectonic framework, specifically differences in the rate of basin subsidence, were responsible for the contrasting architectures. Decreasing rates in the Bighorn Basin produced a sequence with a thick and strongly multistory sand body plus mature paleosols in the Willwood Formation. In contrast, single or weakly multistory channel deposits, encased by vast quantities of overbank sediments, characterize the Glenns Ferry Formation and reflect more rapid rates of subsidence and sediment accumulation in the Snake River Plain of Idaho.

Fluviodeltaic Reservoir, South Belridge Field, San Joaquin Valley, California

Chapter

Full-text available

Jan 1990

A high percentage of the oil produced from sandstone reservoirs comes from fluviodeltaic sandstones. The abundance of high-quality reservoir sand, the ideal location relative to downdip source beds, and the high potential for stratigraphie trap development all make this depositional setting a favored target for explorationists. However, the sand-body architecture and reservoir quality of fluviodeltaic sandstones commonly display extreme variability over short vertical and lateral distances due to depositional controls. The fluvial-dominated delta system described in this chapter displays a wide spectrum of depositional settings from sandy braided fluvial to muddy delta front. This case study presents an opportunity to compare and contrast the reservoir characteristics of distal-bar, mouth-bar, meandering fluvial, and braided fluvial sands from the same depositional system in a single field, with well spacing close enough to make correlations relatively certain.

Integration of Channel and Floodplain Suites, Developmental Sequence and Lateral Relations of Alluvial Paleosols

Article

Full-text available

Jul 1987
J Sediment Petrol

The lower Eocene Willwood Formation of the Bighorn Basin, northwest Wyoming, consists of about 770 m of alluvial rocks that exhibit extensive mechanical and geochemical modifications resulting from Eocene pedogenesis. Five arbitrary stages are proposed to distinguish these soils of different maturities in the Willwood Formation. An inverse relationship exists between soil maturity and short-term sediment accumulation rate. Illustrates several important principles of soil-sediment interrelationships in aggrading alluvial systems that have broad application to other deposits.-from Authors

Patterns of Permeability in Eolian Deposits: Page Sandstone (Jurassic), Northeastern Arizona

Article

Full-text available

Jun 1988

The eolian, Jurassic Page sandstone of northeastern Arizona is marked by a highly ordered heterogeneity. The heterogeneity is expressed by the intricate association of stratification types, which are a direct result of the depositional processes. The dominant stratification types in eolian reservoirs are grainflow, grainfall, and wind-ripple deposits, which form on the lee faces of migrating dunes; interdune deposits, which form between migrating dunes; and extra-erg deposits, which occur sporadically when other depositional environments encroach upon an eolian system. These stratification types each have a unique permeability range, which implies that the fluid migration routes in eolian reservoirs will be dictated by the geometry and types of stratification present. One of the most important aspects of this study is the correlation of qualitative geologic descriptions with quantitative variables such as permeability. About 2,000 measurements were made with a field minipermeameter on an outcrop of the Page sandstone. These data show that three distinct permeability modes directly relate to the different stratification types. Permeability exhibits two components of variation: a structural or systematic component and a random or noise component. In this context, the structural component may be correlated to identifiable geologic processes, whereas the random component covers all unexplained variations. These definitions, however, are entirely scale dependent. That is, by decreasing the scale of measurement, structure is revealed in the random variation. This scale dependence is evident in the subject outcrop and, using several statistical tools, we are able to illustrate the "nested" nature of the spatial variation in permeability.

Depositional architecture of Cenozoic Gulf Coastal Plain fluvial systems

Article

Full-text available

Jan 1981

William E. Galloway

The depositional architecture of aggrading coastal plain fluvial sequences includes both the three-dimensional interrelationships and geometries of component framework sand bodies and the distribution of bedding and internal structures within the framework facies. Examination of late Quaternary and Oligo-Miocene fluvial systems of the Texas Coastal Plain illustrates the architectural variety inherent in aggradational coastal plain sequences and indicates common depositional styles. Because fluvially deposited stratigraphic units peripheral to large marine sedimentary basins most likely consist of a mosaic of individual depositional systems and component elements, accurate description and interpretation of coastal plain paleogeography necessitates a hierarchical, three-dimensional approach to analysis of alluvial stratigraphy. -from Author

Inside Auk - The anatomy of an eolian oil reservoir

Conference Paper

Full-text available

Feb 1989

Alan Peter Heward

Auk field is located in the central North Sea UK sector, and produces from Permian Zechstein carbonates and the underlying Rotliegend sandstones. Thirty wells have been drilled at spacings between 70 m and 3.6 km. The Rotliegend is about 300 m thick and can be divided into five possibly distinct phases of desert sedimentation; the upper three of these are oil bearing with eolian slipface sands forming the main productive horizons. (1) The earliest deposits are localized fluviatile conglomerates which infill topography on the unconformity with the Devonian. (2) The overlying highly porous sands form a large wedge-shaped body onlapping the Devonian. They comprise predominantly eolian slipface sands with slipfaces oriented toward the southeast. (3) This interval represents a change in eolian deposition with a marked increase of tighter wind-ripple laminated sandsheet, dry interdune, and dune apron sands. This unit fluctuates in thickness by about one-third over the field area. Stacked dune slipface sands are oriented toward the east and cannot be correlated over a few hundreds of meters across wind. (4) An even greater proportion of wind-ripple laminated deposits are contained in this interval. Its geometry is that of a depositional mound 100 m thick and 7 km across wind. Dune and possibly dry slipface sands, oriented east, occur where it is thickest. Fine-grained eolian sands are banked up on its northern flank. (5) Finally, waterlain mass-flow sands partially infill depositional lows and appear to represent rainfall reworking of a largely abandoned erg. The marine Zechstein transgressed and draped remaining topography.

North Sea Oil & Gas Reservoirs-II

Book

Jan 1990

The first North Sea Oil and Gas Reservoirs Conference was held in Trondheim in 1985 as part of the Norwegian Institute of Technology's 75th anniversary celebrations. Favourable reactions from the delegates prompted the Committee to re-run the event some three and a half years later, and it is now intended that the Confe rence be held on a regular basis as long as there is a demand for this type of gathering. The objectives of the 1989 Conference, which were broadly similar to those of the previous one, were: (a) to bring together those engaged in various geoscientific and reservoir engineering aspects of North Sea Oil and gas reservoirs in one forum; (b) to demonstrate wherever poSsible the interdependence of the various disciplines and specializations; (c) to promote innovative, synergistic approaches to research and development programmes aimed at North Sea conditions; and (d) to reflect current trends in the reservoir sciences. Naturally there was no place for specialist parallel sessions in a Conference aimed at encouraging interdisciplinary integration and awareness.

Sandy fluvial system

Article

Jan 1979

Introduction to the Petroleum Geology of the North Sea

Article

Jan 1985

K.W. Glennie

SEDIMENTOLOGIC RESERVOIR STUDY OF A STEAM-DRIVE PROJECT IN DELTAIC RIVER SANDS, EAST TIA JUANA FIELD, VENEZUELA

Chapter

Jan 1987

A hexagon steam-flood pattern in the Middle Miocene Lower Lagunillas Sand Member was described geologically and petrophysically in anticipation of a fieldwide “M-6” steam drive in East Tia Juana field, Venezuela. Data were obtained in a seven-well hexagon centered on well 3054 and having an average spacing of 231 m (758 ft). Rubber-sleeve cores from five wells and sidewall samples from additional wells were examined. The sequence of productive sands is primarily fluvial deltaic and is overlain by a shallow marine interval. Lateral correlations emphasizing bases of channels and inundation planes were given preference over correlating log shapes. Log shapes were used in mapping local subfacies within the channels. Channel sand trends were found to be well defined on maps of Ø.So, where Ø.So values exceeded 0.3. Regional cross sections showing various classes of Ø.So were also used to illustrate the vertical and lateral sequences of active fill, abandoned fill, and interdistributary splay sands. The productive sands recognized in the pilot area were designated separately as D-1, D-2 and D-3. Since no permeability boundaries were interpreted to exist between these sands, vertical communication was predicted to be very good. Several wells contained only one fluvial sand subfacies. Additional oil produced from individual wells, as a result of steam injection in the D-1 sand, can be directly related to the type of channel subfacies encountered. In a well which was located primarily in the active channel fill, production of additional oil was 200,000 extra barrels; abandoned channel-fill wells produced from 0 to 50,000 extra barrels, and a well interpreted to produce primarily from a natural levee or flood basin produced only 20,000 extra barrels. These variations in production were predicted by construction of detailed geologic maps and cross sections.

Sand Body Dimensions and Infill Sequences of Stable, Humid-Climate Delta Plain Channels

Chapter

Jan 1990

T. Dreyer

Sediments deposited in delta plain settings are common in the Jurassic sequences of the Norwegian continental shelf (e.g. the Ness Formation). The most prominent reservoir units in this type of deposit are distributary channel sand bodies. These mainly appear to be laterally discontinuous in a direction normal to the palaeoslope, and probably reflect cut-and-fill processes in stable distributaries. Based on well-data alone, it is difficult to determine vital reservoir parameters such as the geometry and interconnectedness of these channel sand bodies. Studies of well-exposed possible analogues like the Saltwick Formation of Yorkshire (England) and the Aspelintoppen Formation of Spitsbergen were therefore undertaken. This study indicates that single-storey sand bodies deposited in stable cut-and-fill channels have ribbon-like geometries, whereas multistorey channel bodies of the same type tend to display more sheet-like dimensions. A curve relating the width and thickness of these sand bodies has been constructed. Humid climate cut-and-fill sand bodies deposited in stabilized distributaries can be recognized by an infill sequence that, when complete, reflects three stages of infilling (active, partly active and passive phase fills). Active phase infills frequently have the best reservoir quality at the top, owing to high-discharge events prior to (partial) abandonment. In addition to palaeo-river morphology, sandbody dimensions and the degree of interconnectedness are governed by the pattern of differential subsidence along depositional strike, and by the ratio between sediment supply and accommodation.

Computation of initial well productivities in aeolian sandstones on the basis of geological model, Leman Gas Field, UK

Article

Jan 1987

K.J. Weber

Realistic well productivity calculations based on geologic models are an important aid in predicting field performance. For the Leman field, such models have been used to predict production potentials of untested wells and to judge the danger of water coning at an early stage (1973) of the field production history. The Leman field is situated in the southern North Sea 48 km offshore from the English coast. The original reserves were about 10.5 Tcf when production started in 1968. The western half of the field is operated by Shell/Esso and the eastern unit by Amoco. At the time of the study, there were 10 platforms with 130 producing wells. The Leman field reservoir rock is the Permian Rotliegendes Sandstone, which is 180–270 m thick and lies at a depth of about 2,000 m. The major and most productive part of the reservoir is composed of giant aeolian crossbed sets with an average thickness of 4.5 m. The orientation of the forset laminae is remarkably uniform. It is inferred that the laminae represent the lee slope of transverse dunes. The variation in permeability of the foreset laminae and the generally low permeability of the bottomset zones underlying these spoon-shaped crossbed sets cause a very heterogeneous permeability distribution. The heterogeneity is enhanced by variations in grain size and associated authigenic clay content and diagenesis. No literature data were available on the length/width/thickness ratio of giant aeolian crossbed sets formed by transverse dunes. Outcrop studies in the De Chelly Canyon (Arizona) were thus carried out to gather information on the geometry of this type of crossbed set. The large horizontal extent of the crossbed sets (length approximately 200 × thickness), combined with the low permeability of the associated bottomsets, indicates that water coning will be minimal, an interpretation that has been corroborated by 10 years of production data. Initial well behavior is probably controlled by the properties of the thickest more permeable crossbed sets. Furthermore, some pairs of wells may be interconnected via continuous, fairly permeable beds, because the average well spacing is smaller than the average crossbed set length (900 m). Log correlations tend to confirm this conclusion.

Sebkha-dune deposition in the Lyons Formation (Permian) Northern Front Range

Article

Jan 1979

An application of statistical modelling to the prediction of hydrocarbon recovery factors in fluvial reservoir sequences

Chapter

Jan 1987

Fluvial channel sandstones commonly form hydrocarbon reservoirs in oil- and gas-bearing basins. Where such sands were the product of deposition in broad, extensive channel systems, their lateral extent is often greater than the area of the producing oil or gas field. In such situations, lateral pinchout of reservoir sandstone bodies is unlikely to reduce the gross reservoir volume of the field. Where fluvial sands were deposited in more laterally restricted, perhaps meandering channel belts, however, lateral pinchouts are common. In the case of laterally restricted fluvial reservoirs, the spacing and distribution of producing wells becomes critical, particularly where numbers of laterally offset, “shoestring” sandstone bodies within a vertical sequence are isolated from each other by floodplain/floodbasin fines. A method has been developed for predicting the proportion of laterally discontinuous fluvial reservoir sandstones that can be accessed by specified development well patterns. The method is based on (1) relationships between channel belt width, channel depth and deposit thickness for various fluvial regimes; and (2) a statistical description of reservoir sandstone beds encountered in previously drilled wells, and is designed to be generally applicable. A Fortran IV computer program has been written to allow rapid and easy usage of the method.

Active tectonic control on alluvial architecture

Chapter

Jan 1987

Tectonic control of alluvial architecture is commonplace in extensional, transcurrent and compressional tectonic terrains. The primary influence of tectonic activity on floodplain behavior is tilting, which varies areally and temporally and is superimposed on the pre-existing channel gradient. These effects are considered theoretically and illustrated by Pleistocene and Holocene examples from southwest Montana and the Mississippi Valley. A transverse slope will cause the movement of channel belts toward the area of maximum subsidence either 1) by processes of downslope cutoff and preferential erosion, producing an abnormally wide and asymmetric sandstone body, or 2) in steps, by avulsion. Avulsion may be triggered by tilting or may occur subsequently through preferential flooding of the down-tilted side of the floodplain. Although the channel will move toward the position of maximum subsidence, it will often be offset by fans constructed from the footwall or it may flow into a lake occupying the floodplain low. Differential subsidence strongly affects deposition rates, groundwater behavior, pedogenesis and flood distribution, in addition to channel migration.

Architectural Controls on the Recovery of Hydrocarbons From Sandstone Reservoers

Chapter

Jan 1991

Development of the 330-billion-barrel oil resource remaining in United States reservoirs after conventional primary and secondary recovery will be dependent on the advanced understanding of facies relations and compartmentalization inherent in reservoir depositional systems. Style of deposition, as reflected in internal reservoir architecture, defines flow units that determine how a reservoir drains, where hydrocarbons remain unrecovered at the interwell (macroscopic) scale, and what approaches will be effective in accessing unrecovered oil. A substantial part of the unrecovered oil resource is nonresidual oil that, although mobile in the reservoir, remains unrecovered owing to poor contact by existing wells and vertical or areal bypassing by the waterflood front. Because heterogeneity style is a product of depositional system, it is predictable and can be characterized in terms from low to high in a lateral and vertical sense. For sandstones, the wave-dominated deltas, barrier cores, and sand-rich strand plains show a low degree of heterogeneity in both dimensions, whereas the highly aggradational backbarrier fans, fluvially dominated deltas, and fine-grained meander belts show a higher intensity of heterogeneity. Other systems can be similarly classified. The resulting matrix leads to delineation of targeted approaches to incremental oil recovery specifically tailored to the distribution of remaining oil saturation. Such approaches, optimized to the character of the depositional system, may include geologically targeted infill drilling, selective recompletion, horizontal drilling, and strategic cross-reservoir flooding involving flood redesign and profile modification. Such techniques are herein termed Advanced Secondary Recovery (ASR) and represent advancements in technology that will lead to near- and mid-term improvements in efficiency that set the stage for later approaches to Enhanced Oil Recovery (EOR).

Braidplain and Deltaic Reservoir, Prudhoe Bay Field, Alaska

Chapter

Jan 1990

This chapter illustrates, by means of a case study of a super giant field, the excellent reservoir characteristics of braidplain and associated deltaic facies. It also discusses some of the difficulties encountered in most efficiently producing hydrocarbons from this type of sequence.

Meander-Belt Reservoir Geology, Mid-Dip Tuscaloosa, Little Creek Field, Mississippi

Chapter

Jan 1990

Meander belts represent the first genetic sequences that were understood by geologists. Research on modern point bars in the Brazos River of South Texas in the period 1953 to 1960 led to the formulation of a facies model that was directly applicable to subsurface exploration (Bernard and Major, 1963). It is this model which, in the late 1950s and early 1960s, guided the exploration and development of Little Creek Field, the case study of this chapter. This chapter represents one of the first uses of facies models in the oil industry and is a documentation of the first point-bar reservoir to be explored and produced with geologic forethought. The success of the point-bar facies model in predicting reservoir distribution can be measured by the high success rate of drilling by the main operators as compared with that of the surrounding farmed-out acreage.

A Braided Fluvial Reservoir, Peco Field, Alberta, Canada

Chapter

Jan 1990

Although the deposits of braided fluvial systems commonly have excellent reservoir characteristics, as demonstrated by other chapters in this volume, diagenesis may nevertheless greatly impair their reservoir quality. The ability to predict reservoir quality successfully where diagenesis may have overprinted the depositional controls lies with understanding the diagenesis itself. This chapter concerning the Belly River Formation shows what is probably a very common case for reservoirs, in which diagenetic alterations that determine the final reservoir quality are directly controlled by depositional factors, principally grain size. The finer-grained sandstones have been compacted and cemented to the point of almost totally eliminating porosity, whereas the conglomeratic sandstones retained their depositional porosity and permeability and now are the main reservoir facies.

The Brent Field, Block 211/29, UK North Sea

Article

Jan 1991

The Brent Field was the first discovery in the northern part of the North Sea, and is one of the largest hydrocarbon accumulations in the United Kingdom licence area. There are two separate major accumulations: one in the Middle Jurassic (Brent Group reservoir) and one in the Lower Jurassic/Triassic (Statfjord Formation reservoir). The field lies entirely within UK licence Block 211/29 at latitude 61°N and longitude 2°E. The water depth is 460 ft. The discovery well was drilled in 1971, and six further exploration and appraisal wells were drilled. Seismic data over the Brent Field has been acquired in three separate vintages. The latest acquisition is a 3-D grid recorded in 1986. Reprocessing of the entire 1986 3-D seismic data set was initiated in 1989. The original oil/condensate-in-place, estimated on 1/1/89, is 3500 MMBBL, and the estimated original wet gas-in-place is 6700 TCF. Oil production is now in the decline phase. Average production in 1988 was 334,000 BOPD, with gas sales remaining at the plateau rate of 500 MMSCFD. The field is being developed from four fixed platforms, each providing production, water injection and gas injection facilities for both Brent and Statfjord Formation reservoirs. Gas injection is distributed to achieve an intermediate oil rim development in some reservoir units. The platforms were installed between 1975 and 1978. Production commenced in 1976. The slump faulted crestal areas of both reservoirs have yet to be developed. These crestal areas contain about 5% of the recoverable reserves. Appraisal drilling was carried out in the crest during 1988 and 1989. The Brent Field is located approximately 100 miles north-east of the Shetland Islands and 300 miles NNE of Aberdeen (Fig. 1). The discovery well location is at latitude 61°05'53.87" North longitude 1°41'30.H" East. The water depth is 460 ft The field comprises two distinct reservoirs, the Brent Group and the Statfjord Formation, which are of Middle Jurassic and Lower Jurassic/Triassic age respectively. The reservoirs occur in a westerly dipping tilted fault block in a fault controlled unconformity trap (Fig. 2). The size of the hydrocarbon bearing area is approximately 10 miles from north to south and 3 miles from east to west (Fig. 3). The reservoirs are in turn divided into seven separate reservoir units; four cycles in the Brent Group reservoir and three units in the Statfjord Formation reservoir. Laterally two major east-west orientated faults divide the field into three separate production areas. A fourth area is the north-south orientated crestal part of both reservoirs, which is faulted and has a series of down faulted slump blocks overlain by 'Reworked Sediment'. This area still has to be developed. The Shell/Esso joint venture North Sea oilfields are named after water and waterside birds. The Brent Field is named after the Brent goose.

The three-dimensional facies architecture of terrigenous clastic sediments, and its implications for hydrocarbon discovery and recovery, Concepts and Models in Sedimentology and paleontology

Book

Jan 1992

Sandy Fluvial Systems

Chapter

Jan 1984

The West Sole Field, Block 48/6, UK North Sea

Article

Jan 1991

West Sole is located in the Sole Pit area of the Southern North Sea Permian Basin in UK Block 48/6. The field was discovered in 1965 and was the first commercial discovery in the UK Continental Shelf. Gas Production commenced in 1967. Initial reserves are 1.873 TCF of which 1.335 TCF had been produced by the end of 1989. Gas is trapped in aeolian sandstones of the Permian Lower Leman Sandstone Formation. Three depositional facies are recognized, comprising aeolian dune, fluvial and sabkha. The aeolian dune facies form the principal reservoir sandstones, in units up to 40 m (131 ft) thick. However, permeability is reduced due to pervasive illite cementation, such that it averages 3 md in the dune sandstones. Productivity is enhanced in the southern part of the field by 'open' gas-filled fractures, generated during the Alpine inversion. The trap was also amplified at this stage and comprises a faulted inversion anticline trending NW-SE. The source rock is the Westphalian Coal Measures, lying directly beneath the reservoir.

The Forties Field, Block 21/10, 22/6a, UK North Sea

Article

Jan 1991

J. M. Wills

The Forties Field is located 180 km (112 miles) ENE of Aberdeen, predominantly in UK Licence Block 21/10. It was discovered in 1970, when an exploration well encountered hydrocarbons in Palaeocene sandstone within an anticlinal structure. Four appraisal wells confirmed the existence of a major oilfield, with an area of approximately 90 sq km (35 sq miles) at a depth of approximately 2000 m (6500 ft). The reservoir occurs in thick Late Palaeocene sandstones deposited in two major sand-rich submarine fan sequences. The field has been producing oil since September 1975. Stock Tank Oil Initially in Place (STOIIP) has been calculated as 4343 MMBBL, and original reserves estimated as 2470 MMBBL, representing an overall recovery of 57%. The field came off plateau production of 500 000 BOPD in 1981, and by mid-1989 production had declined to about 250 000 BOPD. After fourteen years production, the field has produced more than 2 billion STB. Remaining reserves are about 500 MMBBL which includes recovery via artificial lift. Field life has been projected to extend beyond the year 2000. Water injection into the aquifer commenced in 1976, and continues at the present day at an average rate of 390 000 BWPD. There is also a significant contribution to pressure support from the underlying aquifer. At present there are 103 available wells in the field, 81 producers and 22 injectors.

Reservoir Sedimentology

Book

Jan 1987

Collection of papers focuses on sedimentology of siliclastic sandstone and carbonate reservoirs. Shows how detailed sedimentologic descriptions, when combined with engineering and other subsurface geologic techniques, yield reservoir models useful for reservoir management during field development and secondary and tertiary EOR. Sections cover marine sandstone and carbonate reservoirs; shoreline, deltaic, and fluvial reservoirs; and eolian reservoirs. References follow each paper.

Introduction to Petroleum Geology of the North Sea

Book

Jan 1984

K.W. Glennie

This book presents papers on North Sea oil and gas deposits. Topics considered include North Sea exploration from 1964-1983, the structural framework and the pre-Permian history of the North Sea area, the late Permian period, the Triassic period, the Jurasic period, the Cretaceous period, the Cenozoic era, source rocks of the North Sea, and North Sea hydrocarbon plays.

Reservoir Characterization

Book

Jan 1989

Larry Lake

Reservoir characterization is a scientific and mathematical discipline that seeks to define the input data needed to predict flow through permeable media. Although predictions can be of any type, numerical reservoir simulation is among the most important. Because both simulation and geology are very complicated, reservoir characterization has many aspects. The goal of this book is to illustrate these aspects. The papers address the central issue of data input.

Basic types of stratification in small eolian dunes

Article

Jun 1977
SEDIMENTOLOGY

RALPH E. HUNTER

The thinnest recognizable strata in modern eolian dune sands can be grouped into six classes. They are herein named planebed laminae, rippleform laminae, ripple-foreset crosslaminae, climbing translatent strata, grainfall laminae, and sandflow cross-strata. Planebed laminae are formed by tractional deposition on smooth surfaces at high wind velocities. They are very rare in the deposits studied. Grainfall laminae are also formed on smooth surfaces, largely by grainfall deposition in zones of flow separation. They are much more common than planebed laminae, which they closely resemble. Eolian climbing-ripple structures are composed primarily of climbing trans-latent strata, each of which is the depositional product of a single climbing ripple. Climbing translatent strata that formed at relatively high or supercritical angles of ripple climb are typically accompanied by rippleform laminae, which are wavy layers parallel to the rippled depositional surfaces. Ripple-foreset crosslaminae, which are incomplete rippleform laminae produced when the angle of ripple climb is relatively low or subcritical, are rarely visible in eolian sands. Sandflow cross-strata are formed by the avalanching of noncohesive sand on dune slipfaces. Their form varies with slipface height and with other factors.

Practical characterization of eolian reservoirs for development: Nugget Sandstone, Utah-Wyoming thrust belt

Article

Apr 1988
SEDIMENT GEOL

Sandra J. Lindquist

The Jurassic eolian Nugget Sandstone of the Utah-Wyoming thrust belt is a texturally heterogeneous formation with anisotropic reservoir inherited primarily from the depositional environment. Original reservoir quality has been reduced somewhat by cementation and slightly enhanced by dissolution. Low-permeability, gouge-filled micro-faults compartmentalize the formation, whereas intermittently open fractures provide effective permeability paths locally.Where productive, the Nugget Sandstone ranges from approximately 800 to 1050 ft (244–320 m) thick at subsurface depths of 7500 to 15,000 ft (2286–4572 m). Porosity ranges from several percent to 25%, and permeability covers five orders of magnitude from hundredths of milliDarcies to Darcies. Some Nugget reservoirs are fully charged with hydrocarbons.Different stratification types have unique depositional textures, primary and diagenetic mineralogies, and deformational fabrics resulting in characteristic porosity, permeability, permeability directionality, and pore geometry attributes. Such characteristics can be determined from core analysis, mercury injection, nuclear magnetic resonance, conventional log, dipmeter and production data.Nugget dune deposits (good reservoir facies) primarily consist of grainflow and wind-ripple cross-strata, the former of which have the better reservoir quality and the lesser heterogeneity in bedding texture. High-permeability facies are commonly affected by local quartz and nodular carbonate cementation, chlorite (and lesser illite) precipitation, and minor framework and cement dissolution. Gouge-filled micro-faults are the predominant deformational overprint.Interdune, sand-sheet, and other water-associated deposits (poor reservoir facies) are characterized by low-angle wind-ripple laminae and more irregular bedding, some of which is associated with damp or wet conditions. Water-associated Nugget stratification generally contains the finest grained depositional textures and has the poorest reservoir properties. These non-dune facies contain intergranular micritic carbonate and illite precipitates and are most affected by compaction and pressure solution phenomena. Open types of fractures are somewhat more likely in this lower permeability rock.Depositional models incorporating dune morphologies, facies distribution, permeability directionality, and theoretical concepts regarding dune migration through time are useful in delineating correlative intervals most likely to have continuity and potential communication of reservoir properties. Stratigraphic models can be adapted for reservoir simulation studies and also can be utilized in solving structural resolution problems if correlatable vertical sequences and relatively consistent cross-strata orientations exist.

North sea oil and gas reservoirs

Article

Jon Kleppe

Oil and gas have been produced from North Sea reservoirs for almost two decades. This book summarizes current knowledge of North Sea reservoirs, and brings future challenges into focus. Particular emphasis is placed on the interdependence of reservoir geoscientists and technologists engaged in reservoir development and innovative and synergistic approaches to reservoir research and development programmes for the North Sea. Topics covered in this volume include: field reviews; improved seismic methods; characterization of near-well environment; reservoir mechanics and recovery processes; reservoir heterogeneities; modelling and simulation.

Modern and ancient eolian deposits: petroleum exploration and production

S G Fryberger
L F Krystinik
C J Schenk

FRYBERGER, S. G., KRYSTINIK, L. F. & SCHENK, C. J. 1990. Modern and ancient eolian deposits: petroleum exploration and production. Rocky Mountain section, SEPM, Denver, USA.

Active tectonic control on alluvial architecture (eds) Recent developments in fluvial sedimentology

Jan 1987
243-252

J Leeder

ALEXANDER, J. & LEEDER, M. R. 1987. Active tectonic control on alluvial architecture. In: ETHRIDGE, F. G., FLORES, R. M. & HARVEY, M. D. (eds) Recent developments in fluvial sedimentology. SEPM Special Publications, 39, Tulsa, 243-252.

Reservoir characterization Reservoir characterization--II

Jan 1986

L W Carroll
H B Jr

LAKE, L. W. & CARROLL, H. B. Jr. (eds) 1986. Reservoir characterization. Academic Press, Orlando. & WASSON, T. C. (eds) 1991. Reservoir characterization--II. Academic Press, Orlando.

The Leman Field, blocks 49/26, 49/27, 49/28, 53/1, 53/2, UK North Sea

Jan 1991
451-458

A Hmlier
P Williams

HmLIER, A, P. & WILLIAMS, B. P. J. 1991. The Leman Field, blocks 49/26, 49/27, 49/28, 53/1, 53/2, UK North Sea. In: ABaOTTS, I. L. (ed.) United Kingdom Oil and Gas Fields, 25 Years Commemorative Volume. Geological Society, London, Memoirs, 14, 451-458.

Lower Permian-Rotliegend) Introduction to the petroleum geology of the North Sea

Jan 1990
120-152

GLENNIE, K. W. 1990. Lower Permian-Rotliegend. In: GLENNIE, K. W. (ed.) Introduction to the petroleum geology of the North Sea. 3rd edition. Blackwell Scientific Publications, Oxford, 120-152.

Sedimentology and subsurface geology of deltaic facies, Admire 650' Sandstone, El Dorado field, Kansas Reservoir sedimentology

Jan 1987

R W Jordan

TILLMAN, R. W. & JORDAN, D. W. 1987. Sedimentology and subsurface geology of deltaic facies, Admire 650' Sandstone, El Dorado field, Kansas. In: TILLMAN, R. W. @BULLET WEBER, K. J. (eds) Reservoir Sedimentology. SEPM Special Publications, 40, Tulsa, 221 291. ---& WEBER, K. J. (eds) 1987. Reservoir sedimentology. SEPM Special Publications, 40, Tulsa.

Braidplain and deltaic reservoir (eds) Sandstone Petroleum Reservoirs

Jan 1990
7-29

C D Mcgowen
J H Bloch
S Lun-Dell
L L Trumbly

ATKINSON, C. D., McGOWEN, J. H., BLOCH, S., LUN- DELL, L. L. & TRUMBLY, P. N. 1990. Braidplain and deltaic reservoir, Prudhoe Bay Field, Alaska. In: BARWIS, J. H., MCPHERSON, J. G. & STUDLICK, J. R. J. (eds) Sandstone Petroleum Reservoirs. Springer Verlag, New York, 7-29.

(eds) 1990. North Sea oil and gas reservoirs--lI. Graham and Trotman

M T Buller
E Berg
O Hjelmeland
J Kleppe
O Torsaeter

BULLER, m. T., BERG, E., HJELMELAND, O., KLEPPE, J., TORSAETER, O. & AASEN, J. O. (eds) 1990. North Sea oil and gas reservoirs--lI. Graham and Trotman, London.

(eds) Recent and ancient nonmarine depositional environments: models for exploration

Jan 1981
127-155

W E Galloway

GALLOWAY, W. E. 1981. Depositional architecture of Cenozoic Gulf Coast plain fluvial systems. In: ETHRIDGE, F. G. & FLORES, R. M. (eds) Recent and ancient nonmarine depositional environments: models for exploration. SEPM Special Publications, 31, Tulsa, 127-155.

The threedimensional facies architecture of terrigenous clastic sediments and its implications for hydrocarbon discovery and recovery

HEWARD, A. P. 1991. Inside Auk--the anatomy of an eolian oil reservoir. In: MIALL, A. D. & TYLER, N. (eds) The three-dimensional facies architecture of terrigenous clastic sediments and its implications for Hydrocarbon discovery and recovery. SEPM Concepts in Sedimentology and Palaeontology, 3, Tulsa, 44-56.

(eds) 1991. Reservoir characterization--II

Jan 1986

L W Lake
H B Carroll

LAKE, L. W. & CARROLL, H. B. Jr. (eds) 1986. Reservoir characterization. Academic Press, Orlando. & WASSON, T. C. (eds) 1991. Reservoir characterization--II. Academic Press, Orlando.

The threedimensional facies architecture of terrigenous clastic sediments and its implications for hydrocarbon r P. NORTH & D. J. PROSSER discovery and recovery

Jan 1990
109-130

Tulsa
D M Miller
J G Mcpherson
T E Covington

MIALL, A. D. & TYLER, N. (eds) 1991. The threedimensional facies architecture of terrigenous clastic sediments and its implications for hydrocarbon r P. NORTH & D. J. PROSSER discovery and recovery. SEPM Concepts in Sedimentology and Palaeontology, 3, Tulsa. MILLER, D. M., MCPHERSON, J. G. & COVINGTON, T. E. 1990. Fluviodeltaic reservoir, South Belridge Field, San Joaquin Valley, California. In: BARWlS, J. H., MCPHERSON, J. G. & STUDLICK, J. R. J. (eds) Sandstone petroleum reservoirs. Springer Verlag, New York, 109-130.

United Kingdom Oil and Gas Fields, 25 Years Commemorative Volume

Jan 1991
517-523

O A Winter
B King

WINTER, O. A. & KING, B. 1991. The West Sole Field, block 48/6, UK North Sea. In: ABBOTTS, I. L. (ed.) United Kingdom Oil and Gas Fields, 25 Years Commemorative Volume. Geological Society, London, Memoirs 14, 517-523.

Sedimentology and subsurface geology of deltaic facies, Admire 650′ Sandstone, El Dorado field, Kansas

Jan 1987
221

Tillman

TILLMAN, R. W. & JORDAN, D. W. 1987. Sedimentology and subsurface geology of deltaic facies, Admire 650' Sandstone, El Dorado field, Kansas. In: TILLMAN, R. W. • WEBER, K. J. (eds) Reservoir Sedimentology. SEPM Special Publications, 40, Tulsa, 221 291. ---& WEBER, K. J. (eds) 1987. Reservoir sedimentology. SEPM Special Publications, 40, Tulsa.

Sandstone Petroleum Reservoirs, A braided fluvial reservoir, Peco Field

Gardiner S Thomas
D V Bowering
E D Mcminn

Reservoir characterization

Jan 1986

L W Lake
H B Carroll
Lake L. W.

Sandstone petroleum reservoirs, Fluviodeltaic reservoir, South Belridge Field

D M Miller
J G Mcpherson
T E Covington

The Leman Field, blocks 49/26, 49/27, 49/28, 53/1, 53/2, UK North Sea United Kingdom Oil and Gas Fields, 25 Years Commemorative

Jan 1991
451

A P Hillier
B P J Williams
I L Abbotts
Hillier A. P.

The Brent Field, block 211/29, UK North Sea United Kingdom Oil and Gas Fields, 25 Years Commemorative

Jan 1991
63

A P Struijk
R T Green
I L Abbotts
Struijk A. P.

The West Sole Field, block 48/6, UK North Sea United Kingdom Oil and Gas Fields, 25 Years Commemorative

Jan 1991
517

D A Winter
B King
I L Abbotts
Winter D. A.

Characterization of fluvial and aeolian reservoirs: Problems and approaches

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