Petroleum Systems of Deepwater Settings
... Sediment distribution within deep basins (water depth > 1 km) is often controlled by proximity to large siliciclastic suppliers such as large river delta and shelf area, impacting the basin's depocenter, whereas channel-levees complexes and fan lobes control the local scale sediments distribution (e.g. Posamentier and Allen, 1999;Weimer and Slatt, 2004;Allen and Allen, 2013). Based on these principles we investigate the depositional history of the Levant basin and the mechanism by which basin filling occur since the Pliocene. ...
... In addition to the study of submarine sediment transportation, analysis and mapping of channel systems can provide crucial information for deep water hydrocarbon exploration and for geohazard studies. Deep-water channels have been recognized as a major conduit of coarse grain sediments with a potential to form hydrocarbon reservoirs (Abreu et al., 2003;Posamentier and Kolla, 2003;Mayall et al., 2006;Weimer and Slatt, 2004;McHargue et al., 2011) as well as causing instabilities at the shallow subsurface, leading to various geohazards (Bruschi et al., 2006;Thomas et al., 2010;Carter et al., 2014). In light of several gas discoveries from Pliocene reservoirs in the Israeli shelf area (Noa, Mari-B, Or and Nir fields), assessing the sediment's origin and transportation pattern to the deep basin is a primary step for hydrocarbon potential evaluation. ...
... While the channel systems described in this study likely acted as carriers of coarse-grained siliciclastic sediments, they are not considered as the only mechanism contributing to the accumulation of the Pliocene-to-Recent succession in the basin, and suspended load deposited in an unconfined setting has also prevailed. Channel flow direction however is assumed to be indicative of the overall depositional pattern and transport of coarse to fine grained terrigenous material from source areas surrounding the basin (Weimer and Slatt, 2004). ...
The Pliocene-to-Recent succession in the deep Levant basin is coeval to the development of the Nile River delta and to the progradation of the thick (∼1500 m) Sinai-Israel shelf. It hides a series of paleo-channels exhibiting transportation and sedimentation patterns revealing a world class source to sink system feeding a deep (>1500 m) siliciclastic basin. The general agreement that the Pliocene-to-Recent succession originates from the Nile Delta dispersing sediments via a system of counterclockwise currents does not reveal how the sediments were transported to the deep basin. Particularly, how sediments originating from the Nile Delta could have bypassed the ∼50 km wide Sinai-Israeli shelf. Here, we examine the various sources that contributed to the accumulation of the Pliocene-to-Recent succession in the deep Levant basin, and the temporal and spatial contribution of each source. Analysis of a unique seismic data set covering the shelf, slope and deep basin enable us to track submarine sediment transport systems; we map channel sets, analyze their morphological features and interpret their erosional and depositional patterns. We argue that sediments sources vary from eastward remnant Arabian drainage network at the onset of the Pliocene, to Nilotic origin during the Pliocene. Since the Late Pleistocene reworked sediments, deriving from the Israeli shelf and northern Sinai provide a major source to the deep basin. Furthermore, our results demonstrate an increase in channel's complexity since the Early Pliocene to Recent, suggesting a gradual transition from sporadic submarine flow events, carrying fewer sediments to the deep basin at the Early Pliocene, to more frequent events during the Late Pleistocene-to-Recent characterized by an increase in sediment load. The gradual increase of channel complexity from Pliocene-to-Recent is discordant to the general trend of sea-level fluctuation, suggesting that sea-level has a minor effect on sediment accumulation in the deep basin.
... The 13 lithofacies types previously described were grouped into seven general facies associations that were interpreted in terms of depositional systems. These spatially related facies were interpreted according to the depositional architectural element scheme of Normak (1987, 1991), modified and expanded by Chapin, Davies, Gibson, and Pettingill (1994), Mahaffie (1994), Richards, Bowman, and Reading (1998) and Elliot (1998), and summarized by Weimer and Slatt (2004). Here, we used the term frontal splay, instead of sheet sands for the deposits at the termini of the channels, to avoid confusion in the description of the depositional elements mentioned later in this work. ...
... Channel-fill deposits in well logs commonly exhibit a boxcar log motif, and channel margin deposits show a fining-upward pattern. An example of the interpretation of well log patterns and cores is shown in Figure 11; this example comes from well A, and the channel facies association is observed in Core 2. This facies association is mainly the result of high-density turbidity currents and generally occurs in a more proximal environmental setting (Weimer & Slatt, 2004). Layered sands are interbedded sand and mud packages, and (f) They are common between channels in the mid to upper fan and in more distal parts or lateral part of the fan (Weimer & Slatt, 2004). ...
... An example of the interpretation of well log patterns and cores is shown in Figure 11; this example comes from well A, and the channel facies association is observed in Core 2. This facies association is mainly the result of high-density turbidity currents and generally occurs in a more proximal environmental setting (Weimer & Slatt, 2004). Layered sands are interbedded sand and mud packages, and (f) They are common between channels in the mid to upper fan and in more distal parts or lateral part of the fan (Weimer & Slatt, 2004). This facies association is the result of low-density turbidity currents. ...
Detailed stratigraphic and facies analyses were conducted and combined with seismic facies and 3D seismic‐derived plan view images to interpret the depositional environments, processes and depositional elements during the Miocene for an area located in the southern Gulf of Mexico.
The results showed that deposition during the Miocene mainly occurred in a slope setting, with bathymetric changes associated with highs and mini‐basins related to salt features. From the sedimentological interpretation, 13 sedimentary facies were identified. The abundant lithofacies were structureless (massive) sandstone and massive mudstone. Ripple‐ , parallel and cross‐laminated sandstone and siltstone were found in minor proportions. The main depositional processes were related to turbidity currents, including high‐density and low‐density currents; debris flows (mud flows and grain flows) were of secondary importance, as was deposition from fallout of suspended hemipelagic mud particles.
The vertical and lateral distributions of facies revealed seven facies associations linked to depositional environments. These facies associations were the building blocks that were used to characterize the depositional elements recognized on seismic data. The main depositional elements identified were mass‐transport complexes, submarine channels, and frontal splays.
Finally, interpretations from different data sets enabled the conclusion that, during the Miocene in this area were submarine fans deposited on an irregular paleotopography, with topographic lows and highs controlled by salt tectonics .
... Modern submarine fans and ancient turbidite systems are a major focus of research and petroleum exploration (Bouma, 1985;Shanmugam and Moiola, 1988;Weimer and Link, 1991;Stow and Mayall, 2000;Weimer and Slatt, 2004). Two important advances in understanding these clastic deepwater deposits are architectural elements Normark, 1987, 1991;Pickering et al., 1995) and classification based on grain size and feeder system (Reading and Richards, 1994). ...
... Two important advances in understanding these clastic deepwater deposits are architectural elements Normark, 1987, 1991;Pickering et al., 1995) and classification based on grain size and feeder system (Reading and Richards, 1994). Architectural elements include erosional features (e.g., channel-fills and slides) and depositional features (e.g., overbank deposits, lobes/ sheets and channel-lobe transition deposits) Normark, 1987, 1991;Pickering et al., 1995;Stow and Mayall, 2000;Weimer and Slatt, 2004); and twelve classes of deepwater systems in unconstrained depositional settings (Reading and Richards, 1994;Weimer and Slatt, 1999) are differentiated on the basis of grain size (i.e., mud-rich, mud/sand-rich, sand-rich, and gravel-rich) and type of feeder system (i.e., point-source fan, multiplesource ramp, and linear-source apron). ...
... The 29 lithofacies types can be grouped into four lithofacies associations. These are spatially related lithofacies that are interpreted according to the depositional and erosional architectural element scheme of Normark (1987, 1991), modified and expanded by Chapin et al. (1994), Mahaffie (1994), Richards et al. (1998) and Elliot (1998), and recently summarized by Weimer and Slatt (2004). The architectural elements provide the basis for reconstructing the subdivisions of the turbidite system (i.e., upper, middle and lower) preserved in the Dezadeash Formation. ...
The Dezadeash Formation is a northwest trending belt of predominantly Jura–Cretaceous deep-marine siliciclastic rocks in southwestern Yukon, Canada. It is truncated to the southwest by the Denali Fault System, a major transcurrent fault along which ∼ 370 km of dextral slip occurred in post-Early Cretaceous time, and it is flanked to the northeast by the Kluane Schist, a mainly mica–quartz schist assemblage of unknown age and origin. This study provides a robust quantitative description of lithofacies comprising a point-source mud/sand-rich turbidite system: approximately 16 335 m of measured strata from 75 sections throughout the Dezadeash Formation indicate that up to 29 lithofacies types are present and these are dominated by thin- to thick-bedded sandstone–mudstone couplets and medium- to thick-bedded sandstone. The various lithofacies are grouped into conglomerate, sandstone, sandstone–mudstone, and siltstone–mudstone lithofacies associations, which are interpreted as slide, channel-lobe transition, lobe, and overbank architectural elements, respectively. Stacked channel-lobe transition and lobe elements predominate, but the depositional architecture displays no apparent, overall vertical trend. The Dezadeash Formation represents mainly the lower middle and lower subdivisions of a point-source, mud/sand-rich turbidite system that records a single stage of fan growth as it prograded transversely from a volcano-plutonic arc into the basin.
... Submarine canyons, channels and gullies are integral sediment conduits as parts of larger source-to-sink sedimentary systems (Allen, 2017). These systems are globally significant features at continental margins through which sediment, organic carbon, nutrients and pollutants are transported from shallow water to deep-sea environments (Field et al., 1999;Weimer and Slatt, 2004;Covault, 2011;Hughes et al., 2015;Kane et al., 2020). In the foreland Taranaki Basin, located inboard of the Australia-Pacific plate boundary (the Hikurangi subduction zone) ( Fig. 1), prior studies have documented a Miocene progradational slope margin (Bull et al., 2019) and sediment conduits across part of the paleo-shelf, and in particular the related slope (Strogen et al., 2011;Kroeger et al., 2019). ...
... The aim of this research is to gain insights into the sediment pathways that filled Taranaki Basin by understanding the morphometrics, evolution and distribution of canyon, channel and gully networks on the prograding slope margin as it steepened through the Miocene. In addition to understanding ancient sedimentary processes, the outcomes of this study provide numerical data that can be used for exploration and modelling of large-scale petroleum reservoirs typical of deep-water systems (Hewlett et al., 1993;Weimer and Slatt, 2004;Mayall and Kneller, 2021) or reservoirs for CO 2 and H 2 geostorage (Benson and Cook, 2005;Heinemann et al., 2018;Raza et al., 2018). ...
Submarine canyons, channels and gullies are conduits that transport sediments across shelf-slope margins to deep water. In South Taranaki Basin, an increase in sediment supply through the Miocene resulted in progradation and significant steepening of the slope system. Previous studies have identified numerous sediment conduits developed within this system, however their morphology and morphometric relationships with the depositional slope have not been considered. Here we apply seismic geomorphology to establish the statistical relationships between the metrics of sediment conduits at three stratigraphic intervals between which the slope gradient progressively increased. In the early-Middle Miocene, sinuous upper Moki Formation channel complexes with an average width of 1.1 km developed on a slope with an average gradient of 0.2o, routing sediment from south to north. By the late-Middle Miocene, the slope began to prograde rapidly, concurrent with a regional reorientation of the slope to the northwest, on which the lower Mount Messenger Formation canyon networks developed with a slope gradient of 0.4–1.0o. At shallow slopes of less than 0.5o, canyon morphometrics (mean width 6.6 km) are 1.8–4.7 times larger than on related upper slopes with gradients steeper than 0.5o (mean canyon width of 2.7 km). This significant shift in morphometrics occurs abruptly across the clinoform toe line. Rapid Late Miocene slope progradation resulted in the development of steep clinoform slope surfaces up to 9o, into which linear upper Mount Messenger Formation gully complexes incised. The mean gully width throughout the Middle to Late Miocene interval decreased from 1.3 km to 1.0 km as the slope gradient became steeper. This study documents how the morphology and morphometrics of sediment conduits on the South Taranaki Basin slope system changed through time in relation to changes in depositional slope gradients.
... Subaqueous mass-transport deposits (MTD) and mass-transport complexes (MTC) are generally mounded features comprising sediments and/or rocks that have been remobilized en masse by gravity (Weimer & Slatt, 2004;Posamentier & Martinsen, 2011), having been evacuated from an up-dip source area or scar (McAdoo et al., 2000;Posamentier & Martinsen, 2011). They are usually deposited either on or adjacent to slopes in seas, oceans (Camerlenghi et al., 2010;Moscardelli & Wood, 2015) and lakes (Wiemer et al., 2015;Zhang et al., 2016;Moernaut et al., 2017). ...
... The term MTD is used in outcrop studies to refer to the sedimentary product of one single depositional event, but which may contain more than one flow phase (Payros et al., 1999;Mart ın-Merino et al., 2014;Fallgatter et al., 2017). Conversely, the term MTC is commonly used in seismic interpretation when there is evidence of several MTDs but these cannot be clearly distinguished from one another (Weimer & Slatt, 2004). ...
Basal interaction beneath frontally-emergent mass-transport deposits has been widely documented in seismic data, but its effect on deposit heterogeneity not convincingly calibrated at outcrop. Several blocky mass-transport deposits occur as part of the Late Eocene Ventimiglia Flysch of north-west Italy, comprising slope-derived marlstones, representing the original slide, and turbidite material, entrained after erosion of substrate sediments; this study reports on the best exposed. Correlation of twenty-nine sedimentary logs tied to the hosting turbidite stratigraphy allows thickness and facies changes to be tracked over an area of ca 40 km², spanning the erosionally confined to emergent transition. A basal erosion >55 m deep and several kilometres wide confines a marlstone megabreccia containing megaclasts of up to 1 km across, interpreted as the product of a submarine slide originated from a sector collapse of the western basinal slope. Approaching the downstream limit of this erosional confinement the marlstone megabreccia is replaced by highly deformed turbidites that, more distally, are in turn superseded by a debrite composed dominantly of turbidite material. Structural and textural characteristics suggest that the distally-extending debrite was deposited by a forerunner debris flow formed as substrate sediments liquefied ahead of the advancing slide, whereas the deformed turbidites were accumulated at slide margins shortly before it came to a halt. Farther downstream, the debrite is a few metre-thick and sits onto the undisturbed basin floor, indicating that the mass flow became emergent distally, and was sufficiently mobile (with an estimated runout in excess of a few tens of kilometres) to redistribute the material evacuated from the basal erosion (>0.5 km³). The mass-transport deposit terminates upward into a graded marlstone conglomerate deposited by a late-stage multiphase flow. This study provides a rare insight into facies variation in a frontally-emergent mass-transport deposit, showing how basal interaction with poorly consolidated substrates can result in erosional confinement and significant transformation of the parental flow.
... Comprenant une surface sédimentaire d'environ 100,000 km 2 , le Bassin de Campos est considéré, à ce jour, comme le plus important système de pétrole en eaux profondes de la plate-forme continentale brésilienne en termes de production et de réserves de pétrole, et l'un des plus grands du monde (Weimer, 2004 (Johann et al., 2006) étaient présents sur la zone. L'objectif de cette campagne est principalement de contrôler les déplacements de fluides dans le réservoir correspondant donc à la réponse au régime /méthode de récupération des hydrocarbures, basé sur un mécanisme d'injection d'eau. ...
... With a sedimentary area about 100,000 km2, the Campos Basin is considered, to date, as the most important deepwater petroleum system of the Brazilian continental shelf in terms of oil production and reserves, and one of the biggest in the world (Weimer, 2004). ...
This thesis research aims at investigating seismic interpretation methodologies and techniques that will help on better characterizing time-lapse, or 4D, seismic signatures. These techniques and methodologies are used to evaluate the time-lapse repeatability and then to filter out undesirable artefacts that are non-related to the production, while enhancing the 4D signature. To achieve these goals, a methodology based on geostatistical tools, was developed. Typically, at least two time-interval windows are considered: one above and the other comprising the reservoir of interest. A statistical and variographic analysis, conducted on both windows and on all surveys, leads to an interpretation step where common or independent structures -in the variographic sense- can be pointed out. The structures interpreted as not related to the geology or to the production mechanism are filtered from the data by a multivariate factorial cokriging technique, based on the concept of Kriging Analysis developed by Matheron in 1982. Two real case time-lapse studies were used to test the methodology. The first case is a Canadian onshore heavy oil reservoir submitted to steam injection, where three different time-lapse surveys were shot to monitor the steam-chamber evolution. The noise present in the three surveys was first filtered using the technique described above; next, an unsupervised seismic facies analysis was conducted on both raw and filtered data in order to evaluate the filtering technique, and finally an interpretation, in terms of reservoir properties changes, of the time-shit observed between the campaigns was proposed. In the second case, the seismic data was acquired on a deepwater turbiditic oilfield from Brazil at two different times of reservoir life, before and after production and water injection. The two seismic surveys were filtered using the factorial kriging technique; the quality of the filtering was, in this case, evaluated by comparison with more common techniques
... This backfilling process is similar to channel backfilling in deepwater siliciclastic systems (e.g., Pickering et al., 2001;Weimer and Slatt, 2004;Clark et al., 2008), but occurs much further up the slope in the Capitan dataset due to 1) the high angle-of-repose of breccia deposits giving them the capacity to freeze along steep gradients, and 2) the lenticularity of the breccia deposits to produce substantial depositional topography along the slope profile. This architecture is observed at toe-of-slope positions where debris complexes pinch out as well as in more proximal, middle slope positions just downdip of the boundstone (Figs. ...
... The concept of backfilling is not new and has been utilized as a fundamental concept in how deep-water siliciclastic channel systems fill after phases of sediment bypass (e.g., Pickering et al., 2001;Weimer and Slatt, 2004;Clark et al., 2008). Gerber et al. (2008) present a suite of quantitative and laboratory experiments analyzing siliciclastic turbidity current processes and architectures that support the interpretations made here from the Upper Permian Capitan outcrops. ...
Steep, debris-rich, progradational carbonate slope systems have been well-documented around the world in a variety of settings and time periods. While the association of such slopes with deep microbial boundstone upper slope factories, the planar nature of their clinoform profiles, and their toe-of-slope trajectory patterns have been discussed thoroughly, the internal architecture and genesis of clinothems and the mechanics behind progradation remain poorly understood. Capitan Formation (Seven Rivers and Yates Formation equivalent) exposures in the southern Guadalupe Mountains of west Texas allow for examination of steep, prograding Upper Permian (Guadalupian) carbonate slope strata that are coeval with deep, skeletal-microbial boundstone reefs positioned on the upper slope (100–200 m water depth). Measured section data tied to interpreted photomosaics and hand samples were collected within a 7 square-kilometer study area in Pine Canyon and the Frijole wall to document the deposits and architecture of the Capitan slopes. A subset of a regional airborne Lidar dataset was utilized for mapping declivities and orientations of clinoform surfaces.
The outcrops reveal that Capitan middle to lower foreslopes are dominated by lenticular breccia deposits originating from the brittle failure of upper slope boundstone factories, with lesser intercalations of platform-derived carbonate grain-dominated deposits and bypassed siliciclastics. The observed lenticular carbonate breccia deposits stack hierarchically and exhibit lateral and upslope offsetting (compensational) architecture in response to the slope topography of previously deposited debris. Over time, this process constructed lower to middle slope conical sediment bodies that coalesced laterally to form strike-extensive, debris-dominated aprons. Once these debris aprons filled the slope profile up to the level of in situ microbial boundstone production, substrate became available for the upper slope reefs to prograde over. The advance of the boundstones overtop their own debris completed the development of a shelf-to-basin debris-dominated clinothem, and the process repeated resulting in boundstone margin and foreslope progradation.
These Capitan foreslope architectures indicate that sustained, small-scale gravitational failure of the upper slope boundstones was the dominant resedimentation process that contributed to slope development. Single collapse events that produced individual breccia beds occurred at a much greater frequency than relative sea level fluctuations recorded on the platform-top, and variability in breccia matrix sediment suggests that boundstones were shedding material downslope throughout all stages of the accommodation cycle. We propose that boundstone accretion, local instability and failure, and resulting slope breccia deposition were somewhat independent of allocyclic, high-frequency accommodation changes, and that an autogenic control associated with deep oligophotic microbial margins is dominant during the development and progradation of steep, debris-dominated slope systems.
... Once 3D data sets became commercially available, it quickly became apparent that plan-view images derived from 3D seismic volumes could be used to detect and map stratigraphic features (e.g., Brown et al., 1981). Time slices, horizon slices, proportional slices, and other types of plan-view images now are routinely used to generate paleogeographic images from 3D cubes (e.g., Brown, 2004;Weimer and Slatt, 2004). These images can be very useful for fundamental studies of depositional systems (e.g., Figure 3) and for qualitative rock property predictions based on relationships between depositional elements and properties of interest (see seismic facies discussion above). ...
... Vertical transects (e.g., 2D seismic data) continue to be used in exploration settings to help define lithologies and depositional histories in areas lacking well control (e.g., Bachtel et al., 2004;Gregersen and Skaarup, 2007). Diagnostic combinations of seismic facies and reflection terminations have been advanced for a variety of different depositional settings (e.g., Handford and Loucks, 1993;Weimer and Slatt, 2004; Figure 8). However, the approach has some pitfalls, including: (1) nonuniqueness of the seismic response due to resolution problems, interference effects Figure 6. ...
Here, I provide an historical summary of seismic stratigraphy and suggest some potential avenues for future collaborative work between sedimentary geologists and geophysicists. Stratigraphic interpretations based on reflection geometry- or shape-based approaches have been used to reconstruct depositional histories and to make qualitative and (sometimes) quantitative predictions of rock physical properties since at least the mid-1970s. This is the seismic stratigraphy that is usually practiced by geology-focused interpreters. First applied to 2D seismic data, interest in seismic stratigraphy was reinvigorated by the development of seismic geomorphology on 3D volumes. This type of reflection geometry/shape-based interpretation strategy is a fairly mature science that includes seismic sequence analysis, seismic facies analysis, reflection character analysis, and seismic geomorphology. Rock property predictions based on seismic stratigraphic interpretations usually are qualitative, and reflection geometries commonly may permit more than one interpretation. Two geophysics-based approaches, practiced for nearly the same length of time as seismic stratigraphy, have yet to gain widespread adoption by geologic interpreters even though they have much potential application. The first is the use of seismic attributes for "feature detection," i.e., helping interpreters to identify stratigraphic bodies that are not readily detected in conventional amplitude displays. The second involves rock property (lithology, porosity, etc.) predictions from various inversion methods or seismic attribute analyses. Stratigraphers can help quality check the results and learn about relationships between depositional features and lithologic properties of interest. Stratigraphers also can contribute to a better seismic analysis by helping to define the effects of "stratigraphy" (e.g., laminations, porosity, bedding) on rock properties and seismic responses. These and other seismic-related pursuits would benefit from enhanced collaboration between sedimentary geologists and geophysicists.
... Turbidite channels are recognised as very important hydrocarbon reservoir types in almost all areas and settings where deep-water facies are being explored, appraised or produced (Beydoun et al., 2002;Brami et al., 2000;Broucke et al., 2004;Clemenceau et al., 2000;Deptuck et al., 2003;Fonnesu, 2003;Fugitt et al., 2000;Humphreys et al., 1999;Kendrick, 2000;Kolla et al., 2001;Mayall and O'Byrne, 2002;Mayall and Stewart, 2000;Navarre et al., 2002;Posamentier, 2003;Posamentier and Kolla, 2003;Posamentier et al., 2000;Prather, 2003;Prather et al., 1998;Sikkema and Wojcik, 2000;Wonham et al., 2000;Weimer and Slatt, 2004). Over the last 5-10 years, in particular, the significance of turbidite channel reservoirs to the hydrocarbon industry has substantially driven forward our understanding of these depositional systems. ...
... Interpretation of the high-resolution seismic data is being supported by increasing well log and core data. Accompanying the subsurface data, outcrop analogue studies and studies of modern and Pleistocene channel systems have resulted in an extensive and mounting literature on the nature of turbidite channel reservoirs (Abreu et al., 2003;Adedayo et al., 2005;Babonneau et al., 2002;Beaubouef, 2004;Beaubouef et al., 1999;Browne and Slatt, 2002;Busby and Camacho, 1998;Campion et al., 2000;Clark and Gardiner, 2000;Clark and Pickering, 1996a, b;Cook et al., 1994;Cronin, 1995;Cronin and Kidd, 1998;Cronin et al., 2000Cronin et al., , 2002Damuth et al., 1983;DeVries and Lindholm, 1994;Elliott, 2000;Emmel and Curray, 1985;Eschard et al., 2003;Gardner and Borer, 2000;Gardner et al., 2003;Haughton, 2000;Hickson and Lowe, 2002;Johnson et al., 2001;Kenyon et al., 1995;Kirschner and Bouma, 2000;Kneller, 2003;Link and Stone, 1986;Lomas et al., 2000;May and Warme, 2000;Busby-Spera, 1988, 1990;Mulder et al., 2003;Peakall et al., 2000;Pirmez et al., 2000;Pirmez and Imran, 2003;Prather et al., 2000;Samuel et al., 2003;Slatt, 2000;Slatt et al., 1994Slatt et al., , 2000Spinell and Field, 2001;Walker, 1975;Weimer and Slatt, 2004). These numerous, detailed and comprehensive studies have focused on channel classification, specific aspects of channel morphology, depositional processes, detailed studies of individual channels or studies of regional systems. ...
Turbidite channels are important but frequently complex reservoirs in the exploration, appraisal and development of deep-water facies. Over the last 10 years in particular, high-resolution seismic data and extensive outcrop studies have increased our knowledge of the complexity of these sedimentary bodies. Such is their variability and complexity that developing and applying single or even multiple depositional models has limited applicability. Instead, we recognise an alternative approach to help rapidly evaluate turbidite channel reservoirs. The paper mainly concerns the evaluation of large erosionally confined 3rd-order channels, typically 1–3 km wide and 50–200 m thick.Each channel is unique but each generally has four recurring elements namely, the sinuosity, the facies, repeated cutting and filling and the stacking patterns.Several different styles of sinuosity can be identified, each having different implications for sand distribution. Four main facies can often be recognised on seismic, calibrated by cores and logs; a basal lag, slump/debris flows, high net:gross stacked channels and low N:G channel levees. Most channels contain all of these facies but in widely varying proportions.Repeated cutting and filling is a feature of just about every channel studied. The process has major implications for reservoir and non-reservoir distribution.The stacking patterns of the 4/5th-order channels within the 3rd-order channel can have a critical impact on facies and heterogeneity distribution and can strongly influence well design and even potentially the development concept.This paper discusses the impact of each of these elements on exploration, appraisal and development issues.
... The notion of an interplay between submarine failure deposits and hydrocarbon accumulations is not novel among explorationists (e.g., Fairbridge, 1946). Although these deposits were historically considered as a facies to avoid from a viewpoint of hydrocarbon exploration (Posamentier and Kolla, 2003;Weimer and Slatt, 2004), it has now been recognized that MTCs and MTDs can act as source (Johnson et al., 2015;Tanavsuu-Milkeviciene and Sarg, 2012), reservoir (Bhatnagar et al., 2019;Meckel, 2011;Shanmugam et al., 2009;Welbon et al., 2007), or seal (Algar et al., 2011;Amy, 2019;Cardona et al., 2016;Godo, 2006;Kessler and Jong, 2018). Moreover, the resultant relief created by the emplacement of MTCs and MTDs can influence the pathways of post-emplacement turbidite flows (e.g., Armitage et al., 2009;Jackson et al., 2009;Kneller et al., 2016;Kremer et al., 2018;Henry et al., 2018) and creates accommodation for "healing phase" top-fill reservoir targets [e.g., Ubit field with STOIIP (stock-tank oil initially in place) ~2 billion barrels of oil (BBO), offshore Nigeria (Clayton et al., 1998); Tarn field with STOIIP ~100 MMBO and Meltwater field with STOIIP ~50 MMBO in North Slope Alaska (Houseknecht, 2019;Houseknecht and Schenk, 2007)]. ...
Mass transport complexes and their associated mass transport deposits—both referred to here as submarine failure deposits—are virtually ubiquitous in the modern and ancient sedimentary record of many deepwater basins. As exploration expands to new frontiers, submarine failure deposits are being identified as components of the petroleum system in numerous prospects. Although such deposits were historically considered facies to avoid from a viewpoint of petroleum exploration, it is now recognized that they can act as source, reservoir, or seal elements. In this paper, we set out to investigate the role of submarine failure deposits as effective seals in the petroleum system using published data and propose a methodology to risk some first-order factors at a macro-, meso-, and micro-scale that influence the seal quality of these submarine failure deposits. We accomplish this by discussing the properties intrinsic to submarine failure deposits that affect the seal quality at different scales. Based on published literature, at least six offshore fields from the Gulf of Mexico and NW Borneo are reported to have a submarine failure deposit as an effective seal. These fields combined account for ∼0.9 billion barrels of oil equivalent of cumulative discovered reserves globally and prove the potential of submarine failure deposits as effective seals and a future undervalued play concept. We use three case studies to illustrate our methodology. Our methodology can be further customized using datasets from industry and public records. The seal risk matrix presented here is based on more than a decade of research and has been already used by several exploration companies with encouraging feedback. We acknowledge the limitations of the methodology, but future interdisciplinary research and integration of new datasets and results will improve the de-risking of submarine failure deposits in exploration. Additionally, this methodology can potentially be applied to assessing seal potential of submarine failure deposits for carbon capture sequestration and storage projects.
... Canyons are complex geomorphological features formed by erosion from gravity flows occurring near subaqueous slopes (Shepard, 1972;Canals et al., 2006;Harris & Whiteway, 2011). Canyons are often associated with sand-rich gravity flows which develop into submarine fans, which can act as high quality deepwater hydrocarbon reservoirs (Stow & Mayall, 2000;Weimer & Slatt, 2004;Steventon et al., 2021). Mass-transport complexes (MTCs) are gravity-driven shear failure deposits resulting from creep, spread, slide, slump and debris-flow processes (Posamentier & Martinsen, 2011;Wu et al., 2021). ...
The offshore area of the Otway Basin (south‐eastern Australia) is dominated by multibranched canyons where mass‐transport complexes are widely distributed. This study integrates high‐resolution multibeam and seismic data to investigate the importance of mass‐transport complexes in dictating the evolution of canyons. The study interprets three regionally distributed mass‐transport complexes that fail retrogressively and affect almost 70% of the study area. Within the mass‐transport complexes, seven canyons that initiated from the continental shelf edge and extended to the lower slope are observed. Although the canyons share common regional tectonics and oceanography, the scales, morphology and distribution are distinctly different. This is linked to the presence of failure‐related scarps that control the initiation and formation of the canyons. The retrogressive failure mechanisms of mass‐transport complexes have created a series of scarps on the continental shelf and slope. In the continental shelf, where terrestrial input is absent, the origin of the canyons is related to local failures and contour current activities, occurring near the pre‐existing larger headwall scarps (ca 120 m high, 3 km long). The occurrence of these local failures has provided the necessary sediment input for subsequent gravity‐driven, downslope sediment flows. In the continental slope, the widespread scarps can capture gravity flows initiated from the continental shelf, developing an area of flow convergence, which greatly widens and deepens the canyons. The gradual diversion and convergence through mass‐transport complex related scarps have facilitated the canyon confluence process, which has fundamentally changed the canyoning process. Thus, this study concludes that the retrogressive failure mechanism of mass‐transport complexes has a direct influence on the initiation, distribution and evolution of the canyons. The scarps associated with mass‐transport complexes have greatly facilitated the delivery of sediments and marine plastics from the shelf edge into the deep oceans, especially in areas where fluvial input is missing.
... The most widely recognized deposits stem from turbidity currents. Deepwater hydrocarbon-reservoirs can be located within channel-fill deposits, overbank deposits and sediment lobes (Weimer and Slatt, 2004;García et al., 2015). Sediment routing systems can be variable depending on margin morphology as controlled by structural deformation, faulting, basin subsidence, sedimentation and erosion (Clark and Pickering, 1996;Cross et al., 2009;Mayall et al., 2010;Pinter et al., 2018;Tillmans et al., 2021). ...
The northwest (NW) Borneo margin is one of the geologically most complex regions of Southeast Asia characterized by a steep slope gradient and an extensive deepwater fold and thrust belt. This area is economically important because of large-volume hydrocarbon accumulations in the deep-marine sandstones in fold and thrust anticlines. Although much attention has been paid to the distribution of deepwater reservoir rocks, the provenance of these rocks and compositional variations are yet not fully understood. In this study we present geomorphological and petrological analyses of Late Miocene deepwater channel deposits, which is one of the major reservoirs in the region. Our results reveal the presence of a northwest-trending deepwater channel system displaying morphological variations induced by syn-sedimentary structural developments. Petrological analyses of core samples show a predominant lithic-rich rock composition in the reservoir sandstones, suggesting sediment supply from a lithic-rich Crocker Formation hinterland, probably through a paleo-Padas River. This rock composition differs from the quartz-rich rock composition of an adjacent contemporaneous deepwater reservoir mainly comprising reworked quartz-rich Meligan sandstones. The observed petrological differences are interpreted to reflect a Late Miocene multi-source sediment supply system that drained offshore different NW Borneo hinterland areas. Offshore, sediment transport to and across the slope was dominantly margin-perpendicular, linear or of low sinuosity, in the deepwater locally affected by faulting and folding. This study provides new insights into the complexity of sediment routing systems along continental margins, highlighting the influences of the configuration of the sediment supply system and tectonics on deepwater sedimentation.
Download: https://doi.org/10.1016/j.jseaes.2022.105126
... Deep-water channel systems constitute many significant reservoirs (e.g., Beydoun et al., 2002;Chapin, 2002;Mayall and O'Byrne, 2002;Samuel et al., 2003;Broucke at al., 2004;Weimer and Slatt, 2004;Porter et al., 2006;Cobos et al., 2012, and many others). Several architectural models of deepwater channel systems have been published, derived from a range of data sets, with emphasis on different aspects. ...
... Offshore petroleum exploration accounts for nearly 30% of global oil production (EIA, 2016). Since the late 1970s, petroleum exploration and production in deepwater (water depth between 500 mand 2000 m) and ultra-deepwater (water depth > 2000 m) regions have been boosted with technology and scientific innovation (Pettingill and Weimer, 2002;Weimer and Slatt, 2004). Recently, changing economics and the exhaustion of hydrocarbon potential have significantly contributed to the shifting of petroleum exploration and production from the shallow offshore to deepwater and ultra-deepwater regions. ...
The Baiyun Sag plays a role as the most important, largest deepwater target in petroleum exploration across the northern side of the South China Sea. Three sets of primary source rocks are developed in the Baiyun Sag: Early Eocene middle-deep lacustrine source rock (EMD), Late Eocene-Early Oligocene inshore-shallow lacustrine source rock (OIS), and Late Oligocene transitional source rock (LOT). A quantitative 3D model of the Baiyun Sag was constructed by using a stratigraphic framework based on 3D seismic interpretations and lithology logging data of 66 wells. The geothermal parameters of the 3D model were determined and calibrated based on the measurements of seafloor temperature, formation temperature, and vitrinite reflectance from the wells. The source rock property parameters of the EMD, OIS, and LOT in the 3D model were set according to the results of the total organic carbon test and Rock-Eval pyrolysis analysis of the well samples. The thermal maturation, hydrocarbon generation and expulsion histories of the EMD, OIS, and LOT were reconstructed to study how the evolution of source rocks influenced the current oil accumulation. Modeling results show significant differences among evolutions of the EMD, OIS, and LOT in both vertical and plane directions. The majority of the EMD reached the threshold of hydrocarbon generation (Ro = 0.5 %) at about 45 Ma and kept in the oil window (Ro = 0.5-1.3 %) from 45 to 15 Ma. The majority of the OIS and LOT was not capable of generating hydrocarbon until 35 Ma and 20 Ma, respectively, and have not entirely passed the oil window at present. The EMD, OIS, and LOT in the south and east region of the Baiyun Sag matured faster than the ones in the north and west region. The total oil generation quantities of the EMD, OIS, and LOT are 3772.51 × 10⁸ t, 585.93 × 10⁸ t, and 517.83 × 10⁸ t, respectively; and the total oil expulsion quantities of the EMD, OIS, and LOT are 1246.04 × 10⁸ t, 47.85 × 10⁸ t, and 18.49 × 10⁸ t, respectively. The oil generated and expelled in the Sub-sag B1 accounts for 82 % of the total oil generation and 96 % of the total oil expulsion in the study area, respectively. However, only 4 % of the oil originated from the EMD, and 3 % of the oil generated in the Sub-sag B1, was expelled after the deposition of primary reservoir rocks (23.8-0 Ma). On the contrary, 69 % of the oil expulsion of the OIS and all of the oil expelled from the LOT took place after 23.8 Ma. The EMD in the Sub-sag B2, the OIS in the Sub-sag B1 and B4, and the LOT in the Sub-sag B1 are favorable to current oil accumulation due to their high proportions and large quantities of the oil expulsion after the deposition of primary reservoir rocks.
... Frequently occurring, at the base, are shoaling and/or coarsening upward carbonate and siliciclastic sequences. This lithofacies has no reservoir potential but may have an excellent source or seal potential (Weimer and Slatt, 2004). ...
Northeastern Egypt is one of the most important exposures in the Middle East and North Africa to study Jurassic facies. The present study analyzes 130 thin sections from a subsurface well (Well X) in the northern Gulf of Suez, and from two surface sections at Gebel Maghara (north Sinai) and Khashm Elgalala (North Eastern Desert), Egypt for petrographic and lithofacies analyses. In the present study, detailed petrographic analysis is used as a tool to better understand the diagenetic history of the Early to Late Jurassic siliciclastic sediments; the identified diagenetic elements are inferred concerning the reservoir quality. For this, sidewall cores, scanning electron microscopy and thin sections are used to detail detrital and authigenic mineralogy; these are then used to infer the depositional framework, factors controlling reservoir characteristics, and the operating diagenetic processes. The inferred depositional paleoenvironment is a prograding and retrograding linear siliciclastic shoreline within a shallow marine carbonate platform with coal swamps and occasional cross-cutting rivers. Diagenesis, petrographical characteristics and depositional conditions are the main factors controlling continental and marine reservoir architecture. The diagenetic processes affecting siliciclastic sedimentation are near the surface, shallow to intermediate burial, and deep burial cycles with different pore fluid filling at each stage. The siliciclastic sediments have been categorized into seven depositional lithofacies - calcareous claystone (S1a), carbonaceous claystone (S1b), siltstone (S2), planar and trough cross-bedded sandstone (S3), coarse, well rounded, large scale trough cross-bedded sandstone (S4), ooid sandstone (S5) and coal (C). Grain compaction, various phases of syntaxial quartz overgrowth, carbonate cementation and replacement, creation of dissolution porosity, and clay authigenesis are the most important diagenetic processes that have affected the siliciclastic continental and marine sediments. Many different diagenetic events, both destructive and constructive, have modified porosity. The destructive events include compaction and cementation (of silica, kaolinite, ferroan dolomite, Illite, and anhydrite). The constructive events include silica cementation, feldspar dissolution, and ferroan dolomite dissolution. Additionally, present data also suggest that the continental sandstones have excellent reservoir quality whereas the marine sandstones have good to very good reservoir potential. Despite the excellent reservoir quality of the continental sandstone lithofacies, the effective stratigraphic seal is leaking. The interbedded calcareous and carbonaceous claystone lithofacies may provide an excellent stratigraphic seal for these siliciclastic reservoirs. Based on these analyses, a model is proposed that can be used as a template for subsurface Jurassic reservoir characterization and reservoir discrimination.
... The depositional environment of the E1 and H9 reservoirs studied is interpreted as a confined submarine channels based on the Weimer and Slatt (2004) classification (Fig. 10). The channels show high net-to-gross values and a blocky log response in the channel axis, with lower net-to-gross values and a serrated log response towards the margins (c.f. ...
A high-resolution study involving the integration of cores, wireline logs and reflection seismic dataset was used to unravel the facies assemblages, reservoir quality and hydrocarbon potential of E1 and H9 reservoirs in the “PAC” field, Offshore Niger Delta. Facies analysis of the cored PAC-14 well shows six lithofacies: massive mudstone, parallel-laminated mudstones with sideritic bands, fine-grained parallel-laminated sandstone, medium-grained parallel-laminated sandstone, fine-grained ripple laminated sandstone, and coarse massive sandstone. These lithofacies were grouped into five facies associations: channel story axis (CSA), channel story margin (CSM), inter-channel thin beds (ICTB), mud-rich thin beds (MRTB) and injectites (INJ). These facies associations are typical of a confined channel and basin floor fan deposit of a deep-water turbidite depositional environment. Reservoir unit E1 was dominated by the facies association CSA while the H9 reservoir consists mainly of the facies associations MRTB and INJ. The observed sand injectites are suggested to have formed due to overloading of compacted sands leading to upward remobilization of sand into the overlying shale. Seismic horizons and faults were mapped to understand the structures, trend and reflections within the study area. Results from petrophysical volumetrics estimated the net hydrocarbon pore volume for the E1 and H9 reservoirs as 456 MMBBL and 378 MMBBL, respectively. Exploration for deep-water reservoir mainly targets high amplitude and bright seismic reflectors and ignores the low amplitude reflectors (dim loops) which are typically interpreted as non-reservoir units. However, this study shows a low-amplitude reflector containing medium-grained sand injectite unit, which has high porosity (31.7%) and permeability (4472 mD) values, and contains recoverable hydrocarbon.
... Canyons and channels were first noticed when echo sounders were introduced for deep-water surveys in the 1920s (Daly, 1936), which led to decades of extensive deep-water research (e.g. Walker, 1978) but aroused particular interest from the hydrocarbon industry when large volumes of sand were encountered down-dip of muddy slopes, e.g. in Angola and the northern Gulf of Mexico (Mutti, 1977;Weimer and Slatt, 2004). The dominant mechanisms of downslope sediment transport through canyons and channels are sediment gravity flows, which are driven by the action of gravity on their excess density with respect to the ambient seawater (Middleton and Hampton, 1973). ...
... Key to the interpretation of subsurface geohazards is a methodology to understand the depositional system and to make reliable predictions of lithology, typically in the absence of local log data. Deepwater seismic geomorphology concepts such as those described by Posamentier et al. (1992), Posamentier (2003), and Weimer and Slatt (2004) enable sand-rich facies to be identified, which can then be investigated through generation of horizon slices, coherency slices, and perspective images from 3-D seismic data. The potential occurrence of sand-rich units is be inferred from such images where geobodies with morphologies consistent with submarine channel or fan deposition can be mapped. ...
Shallow drilling hazard assessment consists of geological/geophysical review of drill sites to enable the avoidance or effective mitigation of problems that can affect the safe drilling of the “top-hole” section of wells. Primary seafloor hazards include infrastructure, hardgrounds, chemosynthetic communities, and areas of high slope or potential seafloor instability. Shallow subsurface hazards include strata that may contain overpressured water, free gas, or gas hydrate. Among these issues, the potential hazards posed by gas hydrate have historically been the most difficult to quantify and constrain. This paper reviews the history of gas hydrate shallow hazard assessment, much of which has been framed by difficulties in remote detection and quantification of typical low-saturation, mud-hosted hydrate occurrences. Recent drilling results indicate that such accumulations can be safely drilled using existing industry protocols. However, assessment of drilling hazards associated with high saturation, sand-hosted hydrates warrant further investigation, and therefore was a key focus of the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II (JIP Leg II) program conducted in 2009. Pre-drill site hazard assessment for JIP Leg II utilized standard industry methods in which geohazards associated with gas hydrate and free gas were identified in a primarily-qualitative manner using seismic amplitude analysis, seismic stratigraphic interpretation, and geo-pressure analysis. While these methods can reliably detect shallow hydrocarbons, including highly-concentrated gas hydrates, they are not sufficient to determine if free gas may exist below gas hydrate, particularly where they occur in close vertical succession. Such undetected free gas occurrences can pose potential drilling hazards that can be quantitatively assessed using advanced seismic methods.
... Future research will certainly extend the insights gained into the evolution of normal fault systems to the study of thrust and wrench fault systems (Fig. 6) (e.g. Hef-fernan et al., 2004;Scheidhauer et al., 2005), particularly since deep water fold and thrust belts are the locus for intense petroleum exploration at present (White et al., 2003;Fowler et al., 2004;Ingram et al., 2004;Morgan 2004;Weimer & Slatt, 2004). ...
The proliferation of three-dimensional (3D) seismic technology is one of the most exciting developments in the Earth Sciences over the past century. 3D reflection seismic data provide interpreters with the ability to map structures and stratigraphic features in 3D detail to a resolution of a few tens of metres over thousands of square kilometres. It is a geological ‘Hubble’, whose resolving power has already yielded some fascinating (and surprising) insights and will continue to provide a major stimulus for research into geological processes and products for many decades to come. Academic and other research institutions have a major role to play in the use of this data by exploiting the enormous volume of geological information contained in 3D seismic surveys. This paper reviews some of the recent advances in basin analysis made using the medium of 3D seismic data, focusing on the fields of structural and sedimentary geology, fluid–rock interactions and igneous geology. It is noted that the increased resolution of the 3D seismic method provided the essential catalyst necessary to stimulate novel observations and discover new geological structures such as mud diapir feeders, km-long gas blow-out pipes, giant pockmarks and sandstone intrusions, and to capture the spatial variability of diagenetic fronts. The UKs first impact crater was also discovered using 3D seismic data. The potential for future developments in this field of geophysical interpretation is considerable, and we anticipate that new discoveries will be made in many years to come.
... Over the last decade, a tremendous amount of deep-water depositional models have been formulated, primarily as a result of extensive exploration activities (e.g. Beaubouef and Friedmann, 2000;Posamentier and Kolla, 2003;Posamentier and Walker, 2006;Weimer and Slatt, 2004). These models are revealing more and more complexity with a number of deep-water reservoir elements at different scales, which are the basis for testing various plays. ...
Ichnofabrics are applied in concert with sedimentological data to discriminate sub-environments within a Campanian deep-sea fan system in the Norwegian Sea. Seven ichnofabric types are recognised in the studied cores, which correspond to specific architectural elements of the fan system, including amalgamated channels, lobate sand sheets, proximal and distal overbank, fan fringe, and hemipelagic basin plain environments. A unique observation is an ultra-deep Chondrites ichnofabric, interpreted to result from the activity of a chemosymbiotic tracemaker, possibly utilising hydrothermal vents or hydrocarbon seeps in the near vicinity of an active rift system. Mapping and inter-well correlation of ichnofabrics allow a better control of lateral and vertical facies changes, which are important to exploration and production strategies. This study demonstrates that ichnofabric analysis is proving to be a valuable tool for the characterisation and prediction of reservoir quality, the recognition of potential flow barriers and prediction of lateral depositional trends in deep-sea fan deposits.
The West Delta Deep Marine concession offshore Egypt’s Simian field was exposed to simultaneous pre-stack inversion to test its quantitative interpretation potential. In heterogeneous submarine channel reservoirs, characterising reservoir lithology and fluid distribution and isolating gas sand, brine sand, and background shale are the key Simian field challenges. Due to poor water sand mapping, numerous Simian field wells had surprising early water production rates. Therefore, this study may investigate if pre-stack seismic data and sophisticated inversion techniques can precisely pinpoint Simian field lithology, facies changes, and fluid distribution. Concurrent pre-stack inversion estimates rock parameters, including acoustic or P-wave impedance (Zp), shear impedance or S-wave impedance (Zs), and density (ρ), which are strongly related to lithology. Before the inversion procedure, two wells were analysed in a rock physics investigation, and three angle gathers (0–15°, 15–30°, and 30–45°) were pre-stacked inverted for Zp, Zs, P-wave velocity (Vp), S-wave velocity (Vs), Vp/Vs ratio, and ρ. Lambda-Mu-Rho (LMR) analysis involves obtaining Lamé parameters by inverting Zp and Zs simultaneously, resulting in Lamda-Rho (Incompressibility) (λρ) and Mu-Rho (Rigidity) (µρ) volumes. The training process involved pre-stack inversion analysis employing angle stack seismic data and well log data, cross-validation, and Vp, Vs, and Vp/Vs volumes. Vp/Vs and Zp volumes predicted Sw values that matched well gas-water contact. The study used a test well (Simian-Di) and validated the result at a blind well location (Simian-Dj) to evaluate a pre-stack inversion approach. It found accurate predictions, suggesting better output and economic efficiency.
A successful gas exploration/appraisal drilling campaign of the Pliocene-aged complex deep-water incised canyon reservoir in the Mediterranean Basin is achieved with outstanding results through applying an innovative integrated workflow that firmly assisted with the artificial intelligence (AI) algorithms and technologies. The convolutional neural network (CNN) algorithm is the core building block of the workflow, which enabled us to recognize and delineate the internal depositional architectural elements of the incised canyon reservoir (i.e. 4th/5th order channels) directly from the 3D seismic data with high-level of accuracy. Six 4th/5th order channels have been successfully delineated within the deep-water incised canyon of interest. Three discrete depositional facies have been robustly distinguished for each 4th/5th order channel through implementing Kohonen self-organizing mapping (Kohonen SOM) algorithm. This enabled for confident high-resolution assessment of the reservoir facies and properties heterogeneities. A robust 3D reservoir model has been built utilizing the outcomes of the AI-assisted workflow, which then used to optimize the subsurface locations of the exploration and appraisal wells targeting the reservoir sweet spots. An appraisal well has been optimized and successfully drilled that encountered 102 m of net pay thickness. The long production test of the well has been shown 38 MMscf/d production rate, which is a very good commercial rate. The workflow is a major step in maximizing the exploration success rate of the Mediterranean Basins through accurate delineation of the deep-water turbidite reservoir heterogeneities and complexities, as well as in other basins where similar settings exist. By applying the workflow, the subsurface complexities were revealed with the artificial intelligence algorithms, uncertaintie s were captured, risks were reduced and project commercial value was uplifted.
Accurate mapping of internal depositional architectural elements of a Pliocene-aged gas-bearing turbidite reservoir of the Mediterranean Basin into discrete 3D geobodies has been achieved through applying innovative workflow assisted by the convolutional neural network. The mapped reservoir depositional architectures have been integrated to the acoustic and elastic properties inverted form 3D seismic data to build robust multi-realizations reservoir static models. These models have been used to optimize the appraisal and development well locations and accurately assess the gas initial in-place of the discovery. Four wells have been sited utilizing the results of the constructed models. The wells have been successfully drilled and added 175 Million standard cubic feet in a day (MMscf/d) which obviously improve the commercial value of the project. The workflow is a major step in accurate delineation of the internal depositional architectural elements of the deep-water turbidite reservoirs of the Mediterranean Basins, as well as in other locations/basins where similar settings exist. By applying the workflow, the subsurface complexities were revealed with the artificial intelligence algorithms, uncertainties were captured, risks were reduced and project commercial value was uplifted.
Despite the rise in published evidence of deep‐marine bottom current processes and associated deposits there are still very few documented outcrop examples. Herein are reported results of a contourite channel system related to the late Miocene palaeo‐Mediterranean Outflow Water in the Rifian Corridor, Morocco. This work aims to unravel the sedimentary evolution and facies distribution based on the study of large morphological features related to contourite channels and their subsequent sandstone dominated infill sequences. It was found that the channel evolution and facies distribution are related to spatiotemporal changes in flow characteristics of the palaeo‐Mediterranean Outflow Water. The recognized channel facies distribution correlates well with previously established bedform stability diagrams. Erosion and upper‐stage flow regime bedforms are associated with the most vigorous bottom currents, generally related to its core. Laterally, following the decrease in flow velocity towards the adjacent drift, bedforms comprise dunes, lower‐stage plane bedforms and more heterolithic facies. Similar facies changes are also observed down‐channel, related to a decrease in flow velocities resulting from turbulent mixing of water masses, associated decreases in density gradients and the subsequent deceleration due to gravity. Results of this work have been used to propose a three‐dimensional facies model for channelized sandy contourites. This study contributes to understanding contourite systems, thus benefitting oceanographic and climatic reconstructions as well as aiding the predictability of contourite channel systems for industry geoscience applications.
Turbidity currents and mass transport are two principal processes in deepwater settings. However, their roles in shaping deepwater depositional systems and interpreting their deposits in seismic profiles have not been fully settled due to the lack of extensive well data and high-quality seismic data in comparison with onshore oil fields. Therefore, this study integrated stratigraphic forward modeling (SFM) and seismic forward modeling to differentiate between the contributions of turbidity currents and mass transport as well as their seismic expressions.
The workflow firstly compared three single-scenario SFM models, Model A (mass transport active), Model B (turbidity currents active), Model C (both active) to explore their contributions and interplay. Secondly, a multi-process and multi-scenario SFM model, Model D, is discussed with special emphasis on canyons. Thirdly, synthetic seismic profiles are generated via seismic forward modeling using the outcomes of the second step, then compared with actual seismic facies to verify the reliability.
Through the abovementioned three steps, this study reveals that mass transport plays a major role in initiating canyons whereas turbidity currents act mainly as the reworking process. Turbidites are usually confined to shelf-incised canyons and adjacent canyons fed by terrestrial systems. Mass transport deposits (MTDs) are mainly distributed on the bottom of canyons and deep basins, forming the base boundary of each depositional cycle. A total of 14 synthetic seismic facies are identified. The comparison with actual seismic data shows that modeling results are similar to equivalent actual seismic features. This study helps to predict the spatial emplacement of MTDs and turbidites and interpret deepwater seismic data.
Many oil and gas operators have challenges in deepwater turbidite gas asset's reservoir management plan (RMP) readiness due to lack of experience and very limited analog field data. The objective of this article is to demonstrate how data analytics workflow, comprising of data mining and machine learning-based global deepwater turbidite gas field benchmarking and lessons learned, to identify field performance and mitigate subsurface challenges in developing and managing deepwater turbidite gas assets.
To mine turbidite field data from around the world, a customized R script was constructed using optical character recognition, regular expression (regex), rule-based logic to extract subsurface and surface data attributes from unstructured data sources. All extracted contents were transformed into a properly structured query language (SQL) database relational format for the cleansing process. Having established the turbidite assets repository, exploratory data analysis (EDA) was then employed to discover insight datasets. To analyze the field performance, the number of wells needed to deplete the field was identified using support vector regression, subsequently, K-means clustering was used to classify the reservoirs productivity.
The results of field benchmarking analysis from EDA are deployed in a fit-for-purpose dashboard application, which provides an elegant and powerful framework for data management and analytics purposes. The analytic dashboard which was developed to visualize EDA findings will be presented in this article. The productivity of deepwater turbidite gas reservoirs has been classified based on the maximum gas flow rate and estimated ultimate recovery per well. This result help in identifying the high-rate, high-ultimate-recovery (HRHU) reservoirs of a deepwater turbidite gas field. The regex pattern for subsurface challenges specifically as related to reservoir uncertainties and associated risks, including operational challenges in developing and managing deepwater turbidite gas fields were identified through word cloud recognition. Key subsurface challenges were then categorized and statistically ranked, finally, a decomposition tree was used to identify the issues, impacts, and mitigation plan for dealing with identified risks based on best practices from a global project point of view.
Deployment of this novel workflow provides insight for better decision-making and can be a prudent complementary tool for de-risking subsurface uncertainties in developing and managing deepwater turbidite gas assets. The findings from this study can be used to develop the framework that captures current best-practices in the formulation and execution of a RMP including monitoring and benchmark of asset performance in deepwater turbidite gas fields.
Distal slope and basin depositional systems in deep waters of the Pará-Maranhão Basin, Equatorial Brazil, are investigated using a high-resolution 3D seismic volume, borehole data and multispectral satellite imagery. A Neogene calciclastic submarine fan and a series of channel-levee systems are analysed at water depths of 100 m to 3,500 m. Channel-levee systems have sinuous and straight morphologies and are of different sizes. Their origin is related to turbidity flows sourced and funnelled from the carbonate shelf to submarine canyons and gullies, as well as from areas with marked slope instability. A mixed calciclastic-siliciclastic sediment input is recognised with autochthonous calcarenites and calcilutites comprising the bulk of sediment on the mid and outer continental shelf. Minor amounts of siliciclastic sediment sourced from small rivers occur on the inner shelf. Sedimentation processes of a distally steepened carbonate ramp are discussed considering a general depositional setting dominated by fluctuations in relative sea level. Cross-sectional and planar parameters of mixed calciclastic-siliciclastic channel-levee systems are compared to their siliciclastic counterparts. Morphological results show similarities between calciclastic and siliciclastic channel-levee systems. As a corollary, three types of channel-levee systems are described: (1) channels related to calciclastic submarine fans, (2) low-sinuosity, aggradational channels, and (3) high-sinuosity channels.
The shallow-marine turbidite fans in the Upper Miocene Huangliu Formation of the Yinggehai Basin in the northwestern South China Sea (SCS) provide an excellent opportunity to understand their sedimentary processes in a shelf depositional environment. The down-slope gravity flow processes and along-slope bottom-current reworking processes of shallow-marine turbidite fans were interpreted by using seismic, well logging, core, petrographic, geochemical, and petrophysical data. Several depositional elements were identified in the shallow-marine turbidite fans, namely, channel-fill high-density turbidites (HDTs), channel-fill low-density turbidites (LDTs) and associated frontal splays, sand-rich/mud-rich lobe deposits, and bottom-current reworked channel-fill/lobe deposits. Deep U-shaped (or V-shaped) seismic reflections and low root-mean-square (RMS) amplitudes characterize the channel-fill HDTs that consist of massive fine-grained sandstones with mud clasts. The channel-fill LDTs, characterized by V-shaped or worm-shaped reflections, mostly consist of normally graded, laminated and rippled, very fine-grained sandstones. Frontal splays are generally associated with channel-fill LDTs. The sand-rich lobe deposits show continuous high-amplitude sheet-like reflections and consist of HDTs and LDTs, whereas the mud-rich lobe deposits show continuous moderate-amplitude reflections and consist of muddy debrites. The bottom-current reworked sandstones (BCRSs), which comprise well-sorted, fine-grained sandstones with traction-current structures, are usually located in the upper parts of thick sandbodies. The variability of depositional elements from large-scale channel-fill HDTs with strong basal erosion in fan-1 to small-scale channel-fill LDTs in fan-2 is closely linked with sea-level fluctuations that result in variable gravity-flow energy and sediment input. However, the reoccurrence of large-scale channel-fill HDTs in fan-3 at sea-level highstands may possibly be attributed to enhanced sediment input from the source areas. Down-slope flow transformation from turbidity flows into muddy debris flows within an individual channel-lobe complex (CLC) resulted in a dramatic increase in clay content and resultant decreasing reservoir quality from the channel-fill HDTs to the mud-rich lobe deposits, because muddy sediments are incorporated into the precursor turbidity flows and turbulence is suppressed. Additionally, it is suggested that the widely developed traction-current structures and tidal signatures (double mud layers, mud-draped ripples, discrete wavy bedding, internal truncation surface, and convex-up laminae) are the products of reworking by internal waves and -tides. During periods of sea-level highstands, the upper parts of gravity-flow sandstones would undergo bottom-current reworking, thus resulting in the retransportation of muddy fines and the formation of reworked sandstones with traction-current structures and tidal signatures. In this study, a combination of traction-current structures, tidal signatures, vertical sequences showing sharp upper contacts and non-gradational upper contacts, and trace elements is considered to be convincing diagnostic criteria in distinguishing reworked sandstones from gravity-flow sandstones. The representative bottom-current reworked sandstones should be preferable hydrocarbon targets in further exploration because of their better reservoir properties compared with gravity-flow sandstones. This research offers some insight into gravity-flow processes and bottom-current reworking processes in a shallow marine environment.
The onshore and shallow marine conventional hydrocarbon resources around the world are mostly at the maturation phase and hence, exploration activity globally, showing increasing interest into progressively deeper water hydrocarbon prospects such as South China Sea basins. However, a comprehensive understanding of basin tectonics, depositional history, and petroleum systems of the basin is required to deduce the exploration prospectivity of these deeper reservoirs. The Sabah Basin is a prolific hydrocarbon province in southeast Asia and has a significant economic impact on this part. Recent discoveries in the deep-water hydrocarbon prospects in the NW Sabah Trough prompted a comprehensive investigation of the surrounding area, e.g., Dangerous Grounds for hydrocarbon prospectivity. Previous studies in the Dangerous Grounds mainly focused on the sparse 2D seismic and gravity-magnetic data analysis. A systematic review of stratigraphic evolution has not been presented thus far in the published literature. In this paper, recently acquired high-resolution 3D seismic data with the core and cuttings and conventional well log data from the adjacent areas have been combined to characterize the stratigraphic evolution of the Dangerous Grounds in the NW Sabah platform. Seven horizons interpreted from the 7570 sq. km 3D seismic data, calibrated with the global sea level and geological time scale, to establish the stratigraphic evolution in the study area. Based on distinct structural and seismic characteristics, and calibrated with the adjacent regions well data, two mega-sequences, namely, lower syn-rift and upper post-rift mega-sequences, have been identified and evaluated. The Paleocene to Early Oligocene syn-rift sequence consists of clastic sedimentary fill in grabens and half-grabens is overlain by Late Oligocene to recent post-rift sedimentary successions represented by siliciclastic and carbonates deposits. Major depositional units within these two mega-sequences, including carbonate, channel, mass transport deposits, and turbidites, have been identified and evaluated. During Late Oligocene to Middle Miocene, the area has witnessed the deposition of carbonate platforms and reefs on top of pre-existing structural highs. Late Oligocene to Middle Miocene channel-levee complexes with convex upward sand filling features is prominent in the seismic data. Mass Transport Deposits and turbidites have also been observed above the Middle Miocene Unconformity with distinct seismic characteristics. The pelagic and hemipelagic nature of the sedimentary succession deposited from Pliocene to recent in a passive margin condition have also been interpreted from their unique seismic features. Paleocene-Early Oligocene syn-rift siliciclastic hydrocarbon play, Late Oligocene-Middle Miocene carbonate play, and Late Miocene turbidite play within the study area have been interpreted.
Three-dimensional (3D) seismic data reveal the complex interplay between the surface topography of a c. 4405 km ³ mass transport deposit (MTD) and overlying sedimentary packages over approximately the last two million years. The data image part of the Pleistocene to recent shelf to slope to basin-floor Giant Foresets Formation in offshore western New Zealand. The MTD created substantive topographic relief and rugosity at the contemporaneous seabed, formed by the presence of a shallow basal detachment surface, and very large (up to 200 m high) intact slide blocks, respectively. Sediments were initially deflected away from high-relief MTD topography and confined in low areas. With time, the MTD was progressively healed by a series of broadly offset-stacked and increasingly unconfined packages comprised of many channel bodies and their distributary complexes. Positive topography formed by the channels and their distributary complexes further modified the seafloor and influenced the location of subsequent sediment deposition. Channel sinuosity increased over time, interpreted as the result of topographic healing and reduced seafloor gradients. The rate of sediment supply is likely to have been non-uniform, reflecting tectonic pulses across the region. Sediments were routed into deep water via slope-confined channels that originated shortly before emplacement of the MTD.
Early detection of subsea pipeline leaks is a very serious and ongoing issue for the oil and gas industry with limited successful cases reported. For example, aerial surveillance of pipelines can be applied only for relatively shallow and concentrated areas, and an advanced technology such as fiber-optic cable can be considered at the significant expense of time and cost for installation and equipment. The objective of this study is to evaluate a software-based leak-detection technique through complex multiphase flow mechanics. More specifically, this study investigates (i) how leak-detection problems can be formulated from a fluid-mechanics viewpoint and (ii) how reliable such a technique can be under conditions resembling the deepwater Gulf of Mexico (GOM). In examining a wide range of scenarios, this study proves that software-based techniques have a potential for playing a key role in the future.
First, this study defines a base case selected from the literature review of deepwater GOM flowlines in terms of pressure and temperature conditions, fluid properties, reservoir properties, and flowline characteristics that allows a steady-state flow in pipeline to be determined with no leak present. Next, leaks with certain opening sizes (dleak) at different longitudinal locations (xD = x/L) are positioned, and new steady states in the presence of leaks are calculated. By comparing the two steady-state responses (with and without leak), finally, the changes in two leak-detection indicators [i.e., change in upstream pressure (ΔPin) and change in downstream total flow rate (Δqt out)] can be calculated in a wide range of input parameters. This study presents the results in the form of contour plots for pressure and flow responses.
The major finding of this study is that, theoretically, it is possible to estimate both size and longitudinal location of the leak with the two leak-detection indicators in the software-based leak-detection method. The results from various subsea flowline conditions [such as different gas/oil ratios (GORs) and fluid types, water depths, pressures at the receiving facilities, inclination angles, pipe diameters, water cuts, and so on] show that the reliability of this technique is improved when the sink term (i.e., amount of leaking fluid) is more dominant, which, in turn, means that leaks positioned farther upstream, with larger opening size, and occurring at higher pressure inside pipe are relatively easier to detect. In many of the scenarios considered, Δqt out as a leak-detection indicator shows more than a 10% change in the presence of a leak with dleak>1 in., allowing relatively easier activation of a leak-warning system, which demonstrates the robustness of this technique. Other scenarios in which the indicators are less than a few percent changes, however, may be challenging—in those cases, additional responses from other methods (hardware-based or transient simulation) will be helpful.
To make clear about the sedimentary facies types and distribution of deep water sandstone reservoirs in Campos basin of Brazil, this paper researches the characteristics of deep-water sedimentary system in Campos basin through the comprehensive analysis of drilling, logging and seismic data. There are 3 subfacies and 7 microfacies in the study area. There are 3 channels from south to north in Upper Cretaceous Maastrichtian, and the sedimentary incised valley and compound channels developed in micro-salt basin are the main deep water depositional types. The Paleocene to Eocene dominated by sedimentary incised valley and eroded compound channel deposits, also include 3 channel systems. From Oligocene to Miocene, the main deposition type is lobe, which is mainly distributed in central-north of the basin. Corresponding to deep water depositional stages, 3 kinds of depositional models are found. From Turonian to Maastrichtian of Upper Cretaceous, with tectonic uplift, strong source material supply, and the negative topography produced by salt rock movement providing favorable accommodation for sand deposition, the depositional model was terrigenous direct feed mechanism with sedimentary incised valley and compound channels in micro salt basin. From Paleocene to Eocene, as the amplitude of tectonic uplift reached the maximum and the accompanied erosion peaked, accommodation space offered by micro salt basin was leveled up; the depositional model was terrigenous direct feed mechanism with sedimentary valley and incised compound channels. From Oligocene to Miocene, because of sable tectonics, sea level fluctuation is the main controlling factor for deep water deposition, so the depositional model was wide shelf indirect feed mechanism with bypass incised valley and lobe. The analysis of the characteristics and controlling factors of the 3 types deep-water sedimentary systems during 3 different stages in Campos Basin can provide valuable reference for the oil exploration in deep-water deposits in the Campos Basin and across the world. © 2018 Research Institute of Petroleum Exploration & Development, PetroChina
Early detection of subsea pipeline leaks is a very serious, and still continuing, issue for the oil and gas industry with limited successful cases reported. For example, aerial surveillance of pipeline can only be applied for relatively shallow and concentrated areas, and an advanced technology such as fiber optic cable can be considered at the significant expense of time and cost for installation and equipment. The objective of this study is to evaluate a software-based leak-detection technique through the complex multiphase flow mechanics. More specifically, this study investigates (i) how leak-detection problems can be formulated from fluid-mechanics viewpoint and (ii) how reliable such a technique can be under the conditions similar to deepwater Gulf of Mexico. Examining a wide range of scenarios, this study proves that software-based techniques have potential in playing a key role in the future.
This study, first of all, defines a base case selected from theliterature review of deepwater GoM flowlines in terms of pressure and temperature conditions, fluid properties, reservoir properties, and flowline characteristicswhich allows a steady-state flow in pipeline to be determined with no leak present. Next, leaks with certain opening sizes (dleak) at different longitudinal locations(xD=x/L) are positioned, and new steady states in the presence of leaks are calculated. By comparing the two steady-state responses (with and without leak), finally the changes in two leak-detection indicators (i.e., change in upstream pressure (ΔPin) and change in downstream total flow rate (Δqt out) can be calculated in a wide range of input parameters. This study presents the results in aform of contour plots for pressure and flow responses.
The major finding of this study is that, theoretically, it is possible to estimate both size and longitudinal location of the leak, by using the two leak detection indicators in the software-based leak-detection method. The results from various subsea flowline conditions (such as different GORs and fluid types, water depths, pressures at the receiving facilities, inclination angles, pipe diameters, water cuts, and so on) show that the reliability of this technique is improved when the sink term (i.e., amount of leaking fluid) is more dominant, which in turn means, leaks positioned further upstream, with larger opening size, and occurring at higher pressure inside pipe are relatively easier to detect. In many of the scenarios considered, Δqt outas a leak detection indicator shows more than10% change in the presence of a leak with dleak>1-inch, allowing relatively easier activation of leak-warning system, which demonstrates the robustness of this technique. Other scenarios where the indicators are less than a few percent changes, however, may be challenging in those cases, additional responses from other methods (hardware-based or transient simulation) will be helpful.
This chapter focuses on optimizing some important geological and geophysical (G&;#38;G) activities and strategies for deepwater exploration. It aims to identify, assess, and improve the efficacy of some of the G&;#38;G activities. Due to high risk and exorbitant cost of deepwater exploration, exploration and production (E&;#38;P) companies are under pressure for minimizing cost, maximizing utilization of available resources and opportunities for discovery of precious oil and gas. The chapter aims to improve the efficacy of some G&;#38;G activities and optimize G&;#38;G strategies taking into consideration techno&;#x02010;economic factors. It takes into account G&;#38;G activities associated with formation evaluation such as wireline logging, coring, and well testing operations, which are required for completing a well and fulfilling the objective of assessing hydrocarbon (HC) potential of prospects. G&;#38;G evaluation time is generally the time spent on wireline logging, coring, and production testing (PT). The evaluation time in the chapter is mostly due to wireline logging.
Drilling into deepwater prospects of South East Asia have been very challenging especially in NW Borneo and subsurface hazards related to pore pressure and wellbore stability remain the greatest obstacle. A myriad of wellbore issues have led to failure of some wells to reach geological targets and the drilling cost as high as US$100 million (as of 2014) is not uncommon in the area. It is important to be able to understand the geological nature of pore pressure mechanism in deepwater Sundaland continental margin (DSCM) and thus redefine pore pressure prediction strategy in the area to better align with the regional characteristics.
The currently established empirical effective stress-based pore pressure prediction is dissected to reveal its pitfalls especially regarding its application to DSCM. Compaction mechanism assumptions are also revisited in depth. Three wells from a deepwater field in Northwest Borneo are used as a case study to demonstrate the distinct overpressure nature of the area.
This study confirms that DSCM not only exhibits overpressure profile typical to deepwater anywhere else, but also possesses distinct geopressure characteristics related to its unique geological setting, most notably the active compressional shortening of the mega thrust-fold belts accompanied by continuous rapid deltaic sediment deposition. As a result, unique geopressure-related challenges prevail in this area, such as: shallow top of overpressure, the failure of standard empirical compaction methods, and prominent centroid phenomenon.
It is successfully demonstrated that the shallow top of overpressure of DSCM is linked to rapid sedimentation of low permeability sediments; undrained tectonic shearing is the central cause of common underestimation of popular effective-stress based pore pressure prediction method; and that the dominance of compressional geological structures explains the high likelihood of centroid effect.
The Nelson Field has been in production since 1994 and is at the mid-mature stage of field life. The current management strategy has focussed on identifying infill well locations with the aim of recovering bypassed oil. An increasingly detailed reservoir description is required in order to locate these opportunities and to help screen them for their economic viability. A systematic workflow has been followed through to localize those areas of the Nelson Field where the target oil volumes are most likely to be found. This workflow is given the name 'locate the remaining oil' within Shell. The aim of this workflow is to understand the relationship between sweep and the geological framework of the reservoir. On this basis, drainage cells are defined within the reservoir. Rather than behaving as a single 'tank' of oil with a common rising oil-water contact, the Nelson Field produces from nine discrete drainage volumes, each with separate producing oil-water contacts. The drainage cells have been defined on the basis of sedimentology, oil and water geochemistry in combination with quantitative volumetric analysis. Screening of the nine drainage cells in the reservoir has identified four cells that contain significant remaining volumes of mobile oil. These have then been investigated in further detail with a view to locating any stranded oil volumes that are unlikely to be produced by the existing well stock, and to determine if these are large enough to justify infill well drilling. © Petroleum Geology Conferences Ltd. Published by the Geological Society, London.
Interpretation of 2D long-offset multi-client seismic data acquired by CGGVeritas in 2004-5 has allowed the distribution and composition of the Messinian salinity crisis (MSC) facies to be mapped across the offshore Sirt Basin, Libya. The results reveal that only the Lower and Upper Evaporites are present within the marginal offshore Sirt Basin, with the middle halite unit confined to the deeper basin. The Upper Evaporites, 'Lago Mare', are characterized by a period of fluctuating base level and strong water salinity changes controlled by astronomical precession. They consist of interbedded evaporites and clastics with a total of seven precessional cycles recognized, each associated with erosional sub-aerial channels interpreted to have been created by the Eosahabi rivers sourced from the flooding of Neogene Lake Chad. The Lower Evaporites display a high relief, irregular topography which strongly controls the distribution of the overlying Lago Mare facies. They have an overall chaotic high amplitude response with very little internal structure and are interpreted to represent mass transport complex deposits of the Re-sedimented Lower Gypsum unit. There is a strong correlation between the distribution and composition of the MSC facies and the quality of seismic imaging.
This paper performs comparative seismic investigations of reservoir responses in the main producing deepwater provinces of the world, i.e., Gulf of Mexico, offshore East Brazil and offshore West Africa. These fields occur in basins that have been shaped by salt tectonics overlying sub‐salt sequences predominantly located in the slope and rise. Exploration of these basins accelerated in the last decade, extending the drilling activity now to the continental‐oceanic crust (cob) boundaries. Hydrocarbon bearing reservoirs occur, both in the post‐salt and sub‐salt sequences, resulting in a combination of structural and stratigraphic traps in all of these basins. Most of the presently producing fields are in the post‐salt although, exploration of allochthonous sub‐salt reservoirs have clinched remarkable success recently in the GoM and West Africa, and in the sub‐salt offshore Brazil. Reservoirs of post‐salt in all of these basins are situated in basin floor fans, prograding wedges and slope fan systems tracts. Recently acquired 2D regional and 3D Q Marine seismic data show them to consist of high amplitude high continuity and hummocky lower continuity reflectors. The seismic examples from fields in the Gulf of Mexico are from mini‐basins surrounded by allochthonous salt canopies. By contrast, the Brazil and West Africa field seismic are all controlled by massive autochthonous salt… Hydrocarbon migration into the Brazil and West Africa pre‐salt fields is from a syn‐rift source via large faults. Migration to post‐salt reservoirs occurs when these faults breach the salt where it is welded. Migration into the mini‐basins of the Gulf of Mexico is more complex via salt‐welded mini‐basin floors.
In deepwater-reservoir modeling, it is important to properly represent the spatial distribution of architectural elements to account for pore-volume distribution and the connectivity of reservoir sand bodies. This is especially critical for rock and fluid-volume estimates, reservoir-performance predictions, and development-well planning.
This new integrated stochastic reservoir-modeling approach accounts for stratigraphic and geomorphic controls to generate the reservoir architecture. Information on stratal-package evolution and sediment provenance can be integrated into the reservoir-modeling process. A slope-area analytical approach is implemented to account for topographical constraints on channel and sheet-form reservoir architectures and their distribution. Inferred paleo-channel direction statistics (from outcrop and stratigraphic studies) and simulated high-frequency eustatic sea-level curves are also used to constrain the architectural-element statistics. Based on these geomorphic and sedimentological constraints, architectural elements (channels, lobes, sheets) are built into the model sequentially (in age order).
Integration of realistic geological and engineering attributes into numerical reservoir models is vital for optimal reservoir management. This approach is unique in that it is constrained more directly to geomorphic and sedimentological parameters than traditional object-based or surface-based techniques for stochastic deepwater reservoir modeling.
The narrow shelf and upper slope immediately above the Gonone canyon head off NE Sardinia represent areas of very low sedimentation rates. Along the sides of the canyon head (1,600 m water depth), the sediment deposits are homogeneous but show alternating light-grey intervals rich in carbonate and dark-grey ones rich in organic matter, possibly related to distal turbidite processes. Deposits older than 50,000 years are already encountered at core depths of 2.50 m, the sedimentation rates varying from 6-21 cm/10(3) years in the lower parts of two cores and from 1.5-3 cm/10(3) years in the upper parts. At about 35,000 years BP, both cores show a simultaneous drop in sedimentation rate by a factor of 3, probably in response to local mechanisms of channel avulsion. Lithological, mineralogical and geochemical properties reveal the environmental factors which are responsible for the extremely slow sediment accumulation. The southernmost sector of the coast, and partly also of the shelf, consists of Jurassic limestones which supply only small amounts of fine-grained material transported in suspension. During the last sea-level highstand, the accumulation of the Cedrino River pro-delta remained restricted to the coast, the low siliciclastic sediment yields resulting in poor shelf sediment trapping. The present morphology of the canyon head prevented the occurrence of gravity processes in the deeper part of the canyon system, including the coring sites. Accordingly, deposition was mainly fed by hemipelagic material of planktonic origin, together with only moderate terrigenous inputs. On a wider late Pleistocene timescale, seismic data indicate the occurrence of a coarse-grained, layered turbidite facies, implying a very different architecture of the canyon drainage system probably prior to 60,000 years BP.
Geological domains in northeastern India evolved though time after the rupture of the Gondwanaland. Collision of the Indian and the Burmese plates took place during the middle part of Cretaceous. Evolution of the Paleogene Barail trough, Neogene Surma and Tipam Groups took place gradually. The Barail trough originated at the active margin of the Indo-Burmese plate convergence. Previously, the Barail sedimentary wedge was interpreted to have been deposited in a deltaic to shallow-marine environment. Latter studies have proposed a new depositional model. The Barail Group, a part of the Assam-Arakan Orogen comprises the lowermost Laisong Formation, middle Jenam and upper Rinji Formation. Most of the Paleogene strata of the Barail Group carry imprints of a deep-water submarine fan near an active subduction zone. A deep-water proximal- to mid-fan depositional setting has been ascribed to the lower Laisong strata. Facies analysis of the extensive exposures of the Jenam Formation, near the Jenamghat, Assam, have enabled a detailed reconstruction of a proximal to mid-part of a submarine fan under an overall influence of turbidity currents and debris flow, ultimately evolving into turbidity currents. The Jenam sedimentary wedge bears tell-tale preservation of olistostromes (chaotic facies) with abundant volcaniclastics and basic rock fragments, massive sandstones, conglomeratic sandstone to sandstone-siltstone-shale and sandstone-siltstone-mudstones with profuse turbidites. Facies attributes amply signal the inherent instability of the Barail trough owing to its location near an active subduction zone. The Jenam suite of rocks containing a strong impress of volcanogenic materials along with quartzo-feldspathic rocks were mixed up by turbidity currents and shed into the submarine environment as the Jenam deep-water turbidites.
Gas hydrates have recently been recognised as a class of unconventional petroleum resource and the economic viability of gas production from hydrates is now being viewed as a realistic possibility within the next decade. Therefore, potential offshore hydrate accumulations in the world-class endowed gas hydrate province, the Hikurangi Margin, New Zealand, represent a significant medium- to long-term opportunity to meet the country's future energy requirements.In this paper we delineate a potential gas hydrate reservoir in the East Coast Basin, New Zealand and quantitatively estimate its gas hydrate concentrations from 2D seismic data with no well information available.The target is interesting for exploration since it shows evidence for gas-hydrate bearing sands, in particular, buried channel systems. We use a combined analysis of high-resolution velocity analysis, amplitude-versus-offset (AVO) attribute and AVO inversion to investigate whether we can identify regions that are likely to contain highly concentrated gas hydrates and whether they are likely to be sand-dominated. To estimate hydrate concentrations we apply a rock physics model.Our results indicate the presence of several – up to 200 m thick – zones that are likely to host gas hydrates, with one location predicted to consist of high-permeable channel sands and an inferred gas hydrate saturation of ∼25%. These findings suggest significant amounts of gas hydrates may be present in high-quality reservoirs on this part of the margin.
In the northern Calabrian margin offshore, the Paola Ridge, seaward from the 700 m deep Paola intraslope basin, tops at a depth of around 600 m. Multibeam bathymetry, seafloor reflectivity and seismic data are available. The Paola Ridge consists of circular or elongated ridges cored by a transparent seismic facies that are interpreted as mud diapirs. The diapirs have radius in the order of 5 km and elevate on average 200 m from the adjacent seafloor. The elongated shape of the diapirs is an evidence of a tectonic influence on the pathways exploited by the rising structures. The most recent seismic unit drapes the topographic relief associated with the diapirs showing that diapir rise is at present mainly quiescent. Pockmarks fields and evidence of gas charged sediments are due to degassing from the inactive diapirs. Two mud volcanoes, shown by high backscatter mud flows fed from circular high backscatter areas centred by a collapse feature, are also present on top of one of the dormant diapirs. The only diapir that is actively rising and deforming the seafloor is not associated with pockmarks. Thus, a relationship between fluid expulsion from the diapiric mass and the arrest of the diapir rise is apparent. The increased seafloor steepness due to diapir rise and the presence of gas within the sedimentary succession promotes sediment instability as shown by a thick slump deposit and numerous mass-wasting scars. Sometimes, the diapirs rise in coincidence with extensional faults that offset the Messinian evaporites. The mud remobilization structures are located along a NW–SE trending belt characterized by active extensional faulting. Hence, genetic processes similar to many of the mud diapir and volcano provinces of the Mediterranean, consisting of pre-Messinian source rocks mobilized along discrete belts of active tectonic deformation, is advanced as controlling the setting of the study area.
The Upper Cretaceous Cerro Toro Formation in the Silla Syncline, Parque Nacional Torres del Paine, Magallanes Basin, Chile, includes over 1100 m of mainly thin-bedded mud-rich turbidites containing three thick divisions of coarse conglomerate and sandstone. Facies distributions, stacking patterns and lateral relationships indicate that the coarse-grained sandstone and conglomerate units represent the fill of a series of large south to south-east trending deep-water channels or channel complexes. The middle coarse division, informally named the Paine member, represents the fill of at least three discrete channels or channel complexes, termed Paine A, B and C. The uppermost of these, Paine C, represents a channel belt about 3·5 km wide and its fill displays explicit details of channel geometry, channel margins, and the processes of channel development and evolution. Along its northern margin, Paine C consists of stacked, laterally offset channels, each eroded into fine-grained mudstone and thin-bedded sandy turbidites. Along its southern margin, the Paine C complex was bounded by a single, deeply incised but stepped erosional surface. The evolution of the Paine C channel occurred through multiple cycles of activity, each involving: (i) an initial period of channel erosion into underlying fine-grained sediments; (ii) deposition of coarse-grained pebble to cobble conglomerate and sandstone within the channel; and (iii) waning of coarse sediment deposition and accumulation of a widespread sheet of fine-grained, thin-bedded turbidites inside and outside the channel. The thin-bedded turbidites deposited within, and adjacent to, the channel along the northern margin of the Paine C complex do not appear to represent levée deposits but, rather, a separate fine-grained turbidite system that impinged on the Paine C channel from the north. The Cerro Toro channel complex in the Silla Syncline may mark either an early axial zone of the Magallanes Basin or a local slope mini-basin developed behind a zone of slope faulting and folding now present immediately east of the syncline. If the latter, flows moving downslope toward the basin axis further east were diverted to the south by this developing structural high, deposited part of their coarse sediment loads, and exited the mini-basin at a point located near the south-eastern edge of the present Silla Syncline.
The seafloor morphology and the subsurface of the continental slope of the Olbia intraslope basin located along the eastern,
passive Sardinian margin (Tyrrhenian Sea) has been mapped through the interpretation of high-resolution multibeam bathymetric
data, coupled with air-gun and sparker seismic profiles. Two areas, corresponding to different physiographic domains, have
been recognized along the Olbia continental slope. The upper slope domain, extending from 500 to 850m water depth, exhibits
a series of conical depressions, interpreted as pockmarks that are particularly frequent in seafloor sectors coincident with
buried slope channels. In one case, they are aligned along a linear gully most likely reflecting the course of one of the
abandoned channels. The location of the pockmarks thus highlights the importance of the distribution of lithologies within
different sedimentary bodies in the subsurface in controlling fluid migration plumbing systems. A linear train of pockmarks
is, however, present also away from the buried channels being related to a basement step, linked to a blind fault. Two bathymetric
highs, interpreted as possible carbonate mounds, are found in connection with some of the pockmark fields. Although the genetic
linkage of the carbonate mounds with seafloor fluid venting cannot be definitively substantiated by the lack of in situ measurements,
the possibility of a close relationship is here proposed. The lower slope domain, from 850m down to the base of the slope
at 1,200m water depth is characterized by a sudden gradient increase (from 2° to 6°) that is driven by the presence of the
basin master fault that separates the continental slope from the basin plain. Here, a series of km-wide headwall scars due
to mass wasting processes are evident. The landslides are characterized by rotated, relatively undeformed seismic strata,
which sometimes evolve upslope into shallow-seated (less than 10m), smaller scale failures and into headless chutes. Slope
gradient may act as a major controlling factor on the seafloor instability along the Olbia continental slope; however, the
association of landslides with pockmarks has been recognized in several continental slopes worldwide, thus the role of over-pressured
fluids in triggering sediment failure in the Olbia slope can not be discarded. In the absence of direct ground truthing, the
geological processes linked to subsurface structures and their seafloor expressions have been inferred through the comparison
with similar settings where the interpretation of seafloor features from multibeam data has been substantiated with seafloor
sampling and geochemical data.
KeywordsPockmark–Submarine channel–Carbonate mound–Submarine landslide–Multibeam–Seafloor morphology–Eastern Sardinian margin
Thesis (M.S.)--University of Oklahoma, 2007. Includes bibliographical references (leaves 78-80).
ResearchGate has not been able to resolve any references for this publication.