Roger Slatt

• Ph,D.
• Chair at University of Oklahoma

Reservoir quality (RQ), commonly related to diagenesis, is important to predict formation porosity and permeability. The lack of studies to understand the role of diagenesis on tight reservoirs is a limiting factor for predicting petroleum accumulation in unconventional reservoirs. This study aims to determine the influence of diagenesis on RQ for...

The geological controlling factors of natural fracture distribution and density in the Woodford Shale Formation are quantitatively investigated in this study. The Upper Woodford Shale member in southern Oklahoma, is exceptionally brittle due to the abundance of recrystallized radiolaria chert beds that alternate with siliceous shale beds. Bed-bound...

La Luna Formation is an upper Cretaceous classic shale system that has been interpreted as the major source rock in the Middle Magdalena Valley Basin (MMVB), Colombia. The unit is divided in three members: upper, middle and lower and named respectively as Galembo (calcareous shales with limestone layers and nodules), Pujamana (claystone, mudstone,...

Petrographic analysis is based on the microscopic description and classification of rocks and is a crucial technique for sedimentary and diagenetic studies. When compared to hand specimens, thin sections provide better and more accurate means for analysis of mineral proportion, distribution, texture, pore space analysis, and cement composition. Mos...

Studying seismic responses of velocity and amplitude on wide/full azimuth seismic data is now common for unconventional reservoir characterization. The velocity variation with azimuth (VVAz) and amplitude variation with azimuth (AVAz) are two of the most popular tools to map not only the relative intensity and orientation of natural fractures but a...

Optimal upscaling of a high-resolution static geologic model that reflects the flow performance of the reservoir is important for reasons such as time and calculation efficiency. In this study, we demonstrate that honoring reservoir heterogeneity is critical in predicting accurate production and reducing the time and cost of running reservoir flow...

This paper presents an interpreted depositional environment, developed 2nd order sequence stratigraphy framework, and detailed lithofacies identification from two Mississippian Sycamore outcrops (I-35 Sycamore and Speake Ranch) and subsurface wells in the SCOOP (South Central Oklahoma Oil Province). Then these rocks calibrate the rock properties wi...

Although once considered as only hydrocarbon source rocks, organic-rich shales have become a major contributor to the global energy mix. Similarly, though once considered as uniform “black shales,” the recent “shale boom” has revealed several different properties that express their variability. These properties are described in terms of their measu...

A workflow has been developed to characterize unconventional resource shales (mudstones) which encompasses a variety of methodologies at a variety of scales for a particular outcrop or subsurface resource shale deposit. Critical screening criteria include permeability/porosity, brittleness (fracability), organic richness and maturity of the shale,...

We summarized threefold significance of karst unconformity boundary in this review study: 1) development of a sequence stratigraphic model for the Devonian Woodford Shale Formation is transferrable to the Upper Wolfcamp in the Permian Basin; 2) demonstration of the more general application of that model beyond the Woodford to other resource shales;...

Geologic models built from well logs and natural fracture (NF) parameters obtained at shale and carbonate outcrops/quarries were employed in understand artificial hydraulic fracture (HF) propagation and stimulated reservoir volume (SRV) geometries. We applied field HF treatment parameters from an Arkoma Basin well, located 20–25 miles (32–40 km) ea...

Reservoir characterization of unconventional reservoirs is challenging and highly time-consuming due to the detail needed to identify key features when evaluating the rocks. When using conventional methods to estimate porosity, there are always limitations related to the resolution of the tools to measure these parameters. This study proposes an in...

This paper presents detailed lithofacies identification from the I-35 Sycamore outcrop and predicts the rock properties from wireline logs to propose landing zones within the Mississippian Sycamore rocks in Southern Oklahoma. To achieve these objectives, three types of studies were conducted: (a) field studies (b) lab analysis, and (c) machine lear...

Measuring joint sizes in three dimensions is a challenge, as they are not concurrently exposed in all directions in the outcrops. More often than not, a single fracture's trace (vertical or horizontal or both) or face is partly obscured. Using limited observations to develop discrete fracture network (DFN) models is challenging because the estimati...

The increment in induced seismicity in North-Central Oklahoma has been related to saltwater disposal wells. Despite the many studies that have been completed to understand the main cause of the induced earthquakes related to disposal wells in the Arbuckle Formation, more studies are required to predict the areas and operational conditions where flu...

From reducing uncertainty in well correlations to identifying target zones with low and high reservoir quality, chemostratigraphy has demonstrated to be an excellent tool in geosciences. Chemofacies, an analog of lithofacies, are characterized by a signature composition of 30 elements obtained with X-Ray fluorescence (XRF) spectroscopy. However, a...

This study fully integrates multidisciplinary, multi-scalar subsurface and surface data for successful exploration and development programs in a fractured rock reservoir. Unconventional Sycamore/Meramec and conventional Hunton Carbonate plays in Oklahoma are the focus of this study. The following questions are addressed in this thesis: 1) what fact...

Identifying distinct facies shifts within mudrocks has made it difficult to build sequence stratigraphic frameworks within fine-grained lithologies. Three cores from Lincoln, Pottawatomie, and Pontotoc counties and two outcrops at the Hunton anticline quarry in Murray County cover proximal and distal regions of the Arkoma basin within southern Okla...

The Hunton Group on the carbonate ramp often exhibits highly variable porosity and lithology resulting in heterogenous production. The generation of an accurate geocellular model requires upscaling of sparse porosity logs followed by their integration with denser seismic impedance volumes. The integration of multi-scalar data consisting of core, lo...

Natural fractures likely have a significant role in the Hunton Group tight carbonate effective permeability due to its low matrix porosity/permeability. This paper presents a realistic, multidisciplinary approach to fracture characterization in the Hunton Group. Field and core measured fracture parameters constrained by seismic attributes were used...

Understanding and predicting the impact of lithofacies changes and structural effects on fracture distributions is vitally important to optimize a drilling location and orientation. To evaluate and model fracture intensity of the Late Ordovician-Silurian-Early Devonian Hunton Group carbonates in Oklahoma, natural fractures were studied at different...

This paper provides a comprehensive analysis and documentation of a popular outcrop (roadcut) of the Woodford Shale, known as the 'I-35 Outcrop'. At the bed scale, based on outcrop weathering responses, lithology of the Woodford Shale is cyclically represented by two distinctive, intercalated rock types: soft (incompetent, ductile) siliceous shales...

Subsurface natural fractures in shales are vital for fluid transport pre- and post-hydraulic fracturing in naturally fractured reservoirs such as the Woodford Shale. However, the dominant fracture sets that control the fluid flow in the subsurface are mostly unseen, and their intensity variation is unknown due to non-availability of image logs in m...

This paper provides a comprehensive analysis and documentation of a popular outcrop (roadcut) of the Woodford Shale, known as the I-35 outcrop. At the bed scale, based on outcrop weathering responses, the lithology of the Woodford Shale is cyclically represented by two distinctive, intercalated rock types: soft (incompetent, ductile) siliceous shal...

Highly variable porosity and lithology within Hunton Group Limestones contributes to highly heterogeneous production. Apart from depositional circumstances, variable rock and petrophysical properties may arise from diagenetic and structural phenomena related to karsting and resulting collapse breccia. To investigate this effect, two horizontally be...

Natural fracture aperture-size, spacing, and stratigraphic variation in fracture density are factors determining the fluid flow capacity of low permeability formations. In this study, several facies were identified in a Woodford Shale complete section. The section was divided into four broad stratigraphic zones based on interbedding of similar faci...

The SCOOP (South Central Oklahoma Oil Province), has been one of the most competitive lower 48 unconventional play areas in terms of persistent rig count. Oil and gas companies have significantly reduced operational costs and have become more efficient during drilling and completion activities. However, these efforts do not directly result in bette...

This paper presents a detailed rock-based documentation of a previously undescribed Woodford Shale outcrop in South Central Oklahoma. The complete exposed section provided the opportunity to investigate lithological attributes across the complete Woodford Shale thickness, as well as on its under- and overlying formational contacts. Within the Woodf...

The Mississippian carbonate mudrocks have been one of the best unconventional hydrocarbon reservoirs in Oklahoma, from the Mississippi lime in the north through the Meramec along the Anadarko basin, ending with the Sycamore lime in the Ardmore basin. Unfortunately, a poor understanding of the transition from Mississippian limestones in norther Okla...

The SCOOP (South Central Oklahoma Oil Province), has been one of the most competitive lower 48 unconventional play areas in terms of persistent rig count. Oil and gas companies have significantly reduced operational costs and have become more efficient during drilling and completion activities. However, these efforts do not directly result in bette...

Importance of Outcrops

The Woodford Shale (WDS) as many other self-source unconventional rocks is evidently anisotropic. However, anisotropy (lamination/bedding) is not commonly included on defining "fracability". FMI log, Core (Wyche-1), and thin section inspection illustrates that middle and lower WDS brittle intervals are characterized by more frequent and visible lam...

The North Carnarvon Basin in Australia is one of the most prolific basins developed for oil and gas potential in Australia in the last 10 years. This is a premier basin where important hydrocarbon fields have been found. While the 10 most significant oil and gas fields fall within the Triassic Brigadier formation in the Rankin Platform subbasin, th...

Karsting is a common feature of carbonate environments that causes topographic irregularities on an unconformity surface. In parts of the Cherokee platform, Central Oklahoma, the Hunton Limestone underlies the Woodford Shale and might have controlled Woodford deposition. The main objectives of this study are to 1) understand the impact of karsting...

The Devonian Woodford Shale is a prolific unconventional resource shale for oil and gas. Like many such shales, the Woodford sits atop an unconformity on the surface of underlying carbonate rocks (mainly the Hunton Group in this case). There is variable topographic relief on the unconformity surface due to incised valleys, cave collapse, and/or kar...

The Jackfork Group in Arkansas, U.S.A. is a major ‘training ground’ for academics, students, and petroleum industry geoscientists interested in deep water exploration and development. Several superb outcrop sections are exposed and over the years numerous papers have been published on these rocks. The Kirby sections in western Arkansas provide a un...

Comparing the concentration of molybdenum (Mo) (ppm) and total organic carbon (TOC) (wt%) within sediments allows interpretation of the relative degrees of bottom water restriction within the geologic record. The Woodford Shale is interpreted as transgressive systems tract (TST) grading into highstand systems tract (HST). The lowermost Woodford pre...

Analysis of a high resolution 3D seismic volume from Cenozoic strata in the offshore of North Carnarvon basin, Australia has revealed fine details of deep water architectural elements, including their dimensions and position on the slope. Four main groups of architectural elements were identified and measured within eight stratigraphic sequences in...

The Woodford Shale like many other self-source unconventional rocks is evidently anisotropic. However, anisotropy (lamination/bedding) is not commonly included when defining “fracability”. Micro-resistivity logs, Core (Wyche-1) and thin section inspection illustrates that middle and lower Woodford Shale brittle intervals are characterized by more f...

La Luna Formation is of crucial importance in the petroleum geology of northern South America, especially in Venezuela and Colombia. La Luna Formation has been considered for a long time the main focus of study for conventional oil production, since it is the most important source rock in the Maracaibo Basin and in Venezuela. However, recent works...

La Luna Formation is of crucial importance in the petroleum geology of northern South America, especially in Venezuela and Colombia. La Luna Formation has been considered for a long time the main focus of study for conventional oil production, since it is the most important source rock in the Maracaibo Basin and in Venezuela. However, recent works...

Integration of 3D seismic data, geological insights and well logs to predict TOC sweet spots

Application of sequence stratigraphy to fine-grained lithologies has previously been hindered by the difficulty of identifying distinct facies shifts within mudrocks. Three cores from Lincoln, Pottawatomie and Pontotoc Counties in Oklahoma and two outcrops at the Hunton Anticline Quarry in Murray County, OK record both proximal and distal regions o...

Milliken's (2014) classification scheme for fine-grained sediments and sedimentary rocks is an attempt to provide an improved classification that relies on interpreted grain origin to replace existing nomenclature schemes based on sedimentary structures, grain size, and composition. Milliken posits that existing terminology is confusing and therefo...

Facies shifts within mudrocks are often too subtle to be documented through visual inspection alone. This may give rise to the false premise that fine-grained lithologies are homogenous and should contain relatively consistent mechanical and/or reservoir properties. Using well cores from the Woodford Shale as an example, it is possible to demonstra...

This chapter examines and interprets the vertical stratigraphy, and sometimes lateral attributes, of the Barnett Shale, Woodford Shale, New Albany Shale, Marcellus Shale, Haynesville Shale, Eagle Ford Shale, LaLuna Shale, and Brown Shale. All of these shales exhibit stratigraphic zonation indicating at least two scales of predictable relative sea-l...

Understanding mudrocks and shale reservoirs has become a significant area of interest within industry and academia in recent years. Of particular interest is understanding the pervasive variability present within these units. This variability became apparent when conventional approaches, such as lithostratigraphic analysis and well log correlation,...

The nanoscale porosities in shales have been widely studied by industry with emphasis on organo-porosity and its significant to migration (and generation) of hydrocarbons. However, not much attention is paid to the next scale up, which would include burrows to provide potential migration pathways. The original intent of the work was to evaluate whe...

Based on a sequence stratigraphic framework developed using gamma ray stacking patterns, we have identified brittle-ductile couplets, which allow us to better interpret the microseismic response recorded during a single-stage hydraulic fracture stimulation treatment monitored from three strategically located observation wells. We have analyzed and...

Understanding sequence stratigraphy architecture in the incised-valley is a crucial step to understanding the effect of relative sea level changes on reservoir characterization and architecture. This paper presents a sequence stratigraphic framework of the incised-valley strata within the late Messinian Abu Madi Formation based on seismic and boreh...

Reservoir quality controls the storage, distribution, and flow of fluids within a reservoir. Porosity and permeability are key parameters that are readily measured on rock samples and from well logs; with calibration, porosity can be mapped from 3D seismic surveys. If core material is obtained from a well and porosity and permeability measurements...

The focus of this chapter has been on eolian reservoirs, with only a secondary emphasis on description of outcrops. That is because the unique, fine-scale stratification characteristics of eolian deposits that affect their reservoir performance have been very well documented from the reservoirs themselves. Because of the likelihood of stratigraphic...

There are many tools and techniques for characterizing oil and gas reservoirs. Seismic-reflection techniques include conventional 2D and 3D seismic, 4D time-lapse seismic, multicomponent seismic, crosswell seismic, seismic inversion, and seismic attribute analysis, all designed to enhance stratigraphy/structure detection, resolution, and characteri...

Certain parts of this chapter have been taken directly from the publication Important geological properties of unconventional resource shales, by Roger M. Slatt, published in the fourth-quarter issue of the Central European Journal of Geosciences (2011). The journal’s permission to reproduce those parts of that paper here is gratefully acknowledged...

This chapter has summarized the concepts, techniques, and definitions of sequence stratigraphy. As in most subdivisions of geology, sequence stratigraphers have developed their own set of definitions and terminology, which have been outlined here for use in subsequent chapters. It is proposed that sequence stratigraphy form the basis for reservoir...

In summary, physical, biogenic, and chemical sedimentary structures are important to many aspects of reservoir characterization and should be included in every characterization, whether the analyst is using cores, borehole-image logs, or an analog outcrop. Sedimentary structures provide important information about the depositional environment of th...

This chapter has summarized the important characteristics of deepwater deposits and reservoirs. These reservoirs are quite complex and variable. An understanding of the different architectural elements and their interrelations is critical to hydrocarbon recovery, because the elements exhibit different external geometries, sizes, spatial orientation...

Globally, deltas often contain major oil and gas reservoirs. The geometry, size, and internal architecture of deltas are functions of many variables related to the delta's mode of formation. A tripartite classification of deltas, into river-, wave-, and tide-dominated deltas, has been a standard for many years. However, even within each of these de...

Shallow marine environments, from the shoreline to the shelf edge, are complex and result in complex deposits. In turn, complex deposits translate into complex reservoirs. To maximize reservoir performance, it is imperative that we understand the type of shallow marine deposit that makes up the reservoir. That is not an easy task, as is exemplified...

There are different types of fluvial deposits and reservoirs. The two end-member depositional types are braided-river and fluvial-river deposits. A third type, incised valley fill, can contain either or both of these end members within the confines of the valley. In addition, fluvial deposits near the mouths of the valleys may become reworked by es...

URTeC 1573336 Pores, spores, pollen and pellets are all important constituents of resource shales. Pores provide the storage place and, when connected, the transport route for hydrocarbon molecules. Conventional Scanning Electron Microscopy (SEM and FESEM) of pores from untreated surfaces from several resource shales reveal a common variety of pore...

The area of influence of the Magdalena submarine fan, offshore northern Colombia, is a global frontier basin with sparse well control and only publically available 2D seismic from which to conduct exploration surveys. We have conducted a 2D seismic stratigraphic study to advance knowledge of the tectonostratigraphic evolution of this area and, furt...

This chapter describes and illustrates features of shales and mudstones at the nanometer and micrometer scales using standard scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM) techniques. Microfabric observations at these scales not only provide insights into sedimentary and postdepositional processes but a...

Rivers are the sources of sediment for most depositional systems of the world's coasts. Marine deltas form where rivers discharge into the coastal ocean. Dispersal and deposition of sediment from delta distributaries is largely determined by river plume dynamics and whether conditions are hypopycnal or hyperpycnal. Delta type (river-dominated, wave...

Knowledge of reservoir saturation variation is vital for in-fill well drilling, while information on reservoir stress variation provides a useful guide for sand production management, casing design, injector placement and production management. Interpreting time-lapse difference is enhanced by decomposing time-lapse difference into saturation, pres...

Comparison of some Paleozoic and Mesozoic gas shales has revealed a generally common sequence stratigraphy, consisting of, from the base upward: combined sequence boundary/transgressive surface of erosion (SB/TSE) upon which sits a transgressive systems tract (TST) enriched in organic matter, then a somewhat ‘cleaner gamma-ray’ highstand or regress...

The lower Pennsylvanian Jackfork Group in Arkansas has been the subject of studies, field trips, and publications for many years because of excellent outcrop exposures of different deep-water architectural elements. This latest study is focused on the Baumgartner Quarry located near Kirby, Arkansas, which exposes a series of vertical walls in three...

This research uses data from well-exposed outcrops and published information to document static connectivity in Deepwater channelized systems. Two measures of static reservoir connectivity on outcrop analogs are proposed: margin connectivity and sand-on-sand connectivity. Margin connectivity (Cm) is the length between two stratigraphically adjacent...

This presentation illustrates and describes features of shales and mudstones observed at the nano-to micro-meter scale from freshly broken surfaces using standard scanning electronmicroscopy (SEM) and field emission scanning electron microscopy (FESEM) techniques. Microfabric observations at this scale provide insights into not only sedimentary and...

The Hollywood Quarry, located in Clark County (near to Hollywood, AR), Arkansas, has been studied using many techniques in order to characterize its stratigraphy, structural deformation and general geological features. The quarry exposes deepwater sediments of the Jackfork Group (Pennsylvanian) often utilized by petroleum companies as a potential 3...

This article uses data from well-exposed outcrops and published information to document static connectivity in deepwater channelized systems. Two measures of static reservoir connectivity on outcrop analogs are proposed: margin connectivity and sand-on-sand connectivity. Margin connectivity (C-m) is the length between two stratigraphically adjacent...