Stratigraphic Trapping Mechanisms Research Articles

Integrated Sequence Stratigraphic and Seismic Facies Analysis for Hydrocarbon Prospectivity of the Taranaki Basin, New Zealand

This study analyses the hydrocarbon potential and basin characteristics of the Taranaki Basin in New Zealand, the country's primary petroleum-producing region. The research, which uses a robust methodology involving 2D seismic data, well logs, and other geological information, examines the basin's stratigraphy, structural features, and petroleum systems. Key findings include the identification of two genetic sequences with associated system tracts, multiple reservoir and source rock units, and both structural and stratigraphic trapping mechanisms. Seismic facies analysis revealed eight distinct facies types which characterize the depositional environments. Play fairway mapping identified sweet spots where all petroleum system elements overlap. Risk assessment highlighted factors like gas chimneys and fault-compromised seals. The study concludes by presenting the geologic chance of success for three identified plays and one prospect in different stratigraphic intervals. This comprehensive analysis provides new insights into the under-explored portions of the Taranaki Basin and its hydrocarbon potential. By enhancing the understanding of the basin's stratigraphic architecture and depositional history, this study aims to improve reservoir distribution and quality predictability. Moreover, integrating seismic facies analysis with sequence stratigraphy offers a robust tool for delineating potential hydrocarbon-bearing zones, thereby reducing exploration risk and aiding the efficient reassessment of existing prospective zones and future exploration efforts.

On the applicability of seismic attributes in the description and interpretation of mass-transport deposits

Mass transport deposits (MTDs) have gained economic importance in the last years because of their significance as seals or stratigraphic trapping mechanisms in deep water turbidite prospects. The analysis of MTDs in 3D seismic data provides a better understanding of their characteristics when compared to outcrop or 2D seismic data, as it is possible to capture both internal and external features over large areas in 3D. Moreover, this analysis can be further improved by applying seismic attributes, which have been employed only to describe specific aspects of these deposits. In this study, we applied several seismic attributes systematically in the characterization of an MTD, located in the northern Santos Basin (offshore southeastern Brazil), aiming to identify their applicability in the description and interpretation of 33 characteristics of this kind of deposit. As a result, it was possible to identify which features of the MTD the application of seismic attributes is indispensable, helpful, or redundant.

Carbon Dioxide Sequestration in Low Porosity and Permeability Deep Saline Aquifer: Numerical Simulation Method

Abstract The saline aquifer is the most reliable place where anthropogenic carbon dioxide gas storage has shown a promising future. This paper evaluates and predicts the capacities of different carbon dioxide storage trapping mechanisms in storing carbon dioxide gas in low porosity and permeability deep saline aquifers by using commercial reservoir simulator software i.e., Computer modeling group (CMG). Four carbon dioxide storage trapping modeled and simulated were structural or stratigraphic trapping mechanisms, residual trapping mechanisms, solubility trapping mechanisms, and mineral trapping mechanisms. Carbon dioxide gas was injected into a deep saline aquifer for 15 years, followed by 833 years of post-injection. To reflect the real field reality and have a reasonable approximation of the amount of carbon dioxide which can be stored in an aquifer, this paper included water vaporization effects that occur during carbon dioxide injection and water injection operations so as to optimize residual and solubility trapping mechanisms as the most important trapping mechanisms. Furthermore, the effects of different important parameters such as salinity, vertical-to-horizontal permeability ratio, injection rate, bottom hole pressure, and temperature on each carbon dioxide trapping mechanism were analyzed. Results revealed that each carbon dioxide trapping mechanism has a different capacity for storing carbon dioxide and could be either affected linearly or nonlinearly with various parameters. Higher aquifer temperatures are not recommended for carbon dioxide storage because most of the carbon dioxide gas is stored as free gas, which increases the risk of leakage in case of mechanical failure or imbalance. Excess salinity is the only factor that reduces aquifer storage capacity. Furthermore, it was found that an aquifer with a lower vertical-to-horizontal permeability ratio is recommended for carbon dioxide storage because it increases carbon dioxide stored in an immobile phase, which avoids risk leakages. There was an increase of 43.2% and a decrease of 16.84% for minimum and maximum vertical-to-horizontal permeability (kv/kh) ratios, respectively, compared to the base for residual trapping mechanisms. Also, there was a decrease of carbon dioxide dissolved by 19% at maximum kv/kh ratios and an increase of 58% at minimum kv/kh ratios, compared to the base case. Further, there was an increase of carbon dioxide trapped by 96.4% and dissolved by 97% when water was injected at a higher rate compared to the base case (no water injection). Thus, a high injection rate is suggested to enhance residual and solubility trapping mechanisms. It is recommended that the carbon dioxide injection rate and bottom hole pressure be kept at optimal levels to avoid mechanical failure due to aquifer pressures building up, which can increase the risk of leakages and must be monitored and controlled at the surface using pressure gauges or sensor technology.

Improving off-structure carbonate reservoir characterization using integrated Shared Earth Approach and Forward Stratigraphic Modelling: The Marrat Fm of southern Kuwait

A high-resolution reservoir characterization workflow is applied to assess the off-structure prospectivity of Lower Jurassic complex carbonate reservoirs of the Marrat Formation in the southern part of The State of Kuwait along the Dharif-Abduliyah fields. A detailed sedimentological and petrophysical assessment was integrated with 3D seismic interpretation and delineated vertical and lateral facies changes within the fields, which are affected by sets of complex fault patterns. Carbonate geo-bodies have been mapped using seismic stratigraphy, and 3D multi-seismic attribute and seismic acoustic inversion workflows. The Middle Marrat has been subdivided into 5 units (Middle Marrat 1-MM1 to Middle Marrat 5-MM5) that show vertical and lateral lithological and facies variability. The developed integrated sequence stratigraphic framework permitted to better assess the influence of accommodation variations as well as carbonate ecological settings on sedimentary facies development. This framework pointed to the influence of marine incursions and subsequent flooding surfaces, on the development of wackestone to mudstone textures interbedded within porous grainier inner ramp/shoal reservoir intervals. This integrated Shared Earth Approach that combined the various multi-disciplinary and multi-scale results was supported for the first-time by high resolution Forward Stratigraphic Modelling to provide a mapping and identification of petroleum systems elements including potential reservoir locations and baffles as well as stratigraphic trapping mechanisms. This workflow opens a new perspective to increasing hydrocarbon reserves along the Dharif and Abduliyah Fields as well as many other fields along the State of Kuwait.

Α study on the Gas-bearing Miocene Sediments of MESSARA Basin in Crete (Greece) by Using Seismic Reflection, Geochemical and Petrophysical Data

The focus on exploiting natural gas resources has been increased in the recent years since it was characterized as the transitional fuel to a net-zero era. Consequently, a reevaluation of the gas resources under a new perspective seems to be logical. Within this context, the gas-bearing Miocene sediments of the Messara basin in Crete (Greece) are discussed in this paper. The gas shows have been first reported during the 1990’s, without being thoroughly evaluated. This paper presents the interpretation of eight legacy onshore seismic reflection lines, which led to the construction of the 3D subsurface structural model of the Neogene Messara basin. The seismic data reveals the basin depocenter which accommodates approximately 1500 m of the Miocene sediments. The relationship of the Miocene deposits with the existence of shallow gas is also examined and discussed. New organic geochemical results combined with the published geochemical data are used to discuss the gas generation potential of the Miocene sediments. The porosity and permeability measurements on surface samples are also presented to describe the reservoir characteristics. The integration of the data mentioned above suggests that the Miocene sediments of the Messara basin comprise intervals with adequate organic matter to generate the observed gasses and good reservoir sandstones to accumulate the generated gas. The gas might have been trapped by lateral and vertical facies changes which provide efficient stratigraphic trapping mechanisms.

3D forward stratigraphic modelling of the Lower Jurassic carbonate systems of Kuwait

This paper describes the architectural and texture/facies evolution of a complex carbonate system through the construction of a regional scale 3D stratigraphic forward model (252 × 152 km2, 4 km × 4 km grid size) encompassing onshore and offshore Kuwait. The model mimics the development of a Jurassic carbonate ramp system at a 2nd to 3rd sequence stratigraphic order (1–80 Myr duration; Schlager, 2010) by simulating sedimentary processes and ecological parameters such as carbonate production versus depth, time, wave energy, as well as erosional and gravitational transport. Multi-scale 1D, 2D, and 3D geological and geophysical constraints have been used to calibrate the Lower Jurassic Marrat stratigraphic model, which resulted in the identification of (1) a dominantly transgressive lower unit composed of onlapping packages of mudstone to wackestone textures, with anhydritic intercalations; (2) a dominantly regressive middle unit composed of prograding inner ramp shoal and lagoonal facies with wackestone to grainstone textures, and finally (3) a transgressive onlapping upper unit composed of mudstones to wackestones textures in a mid-ramp system. The identification of potential reservoir facies like oncolitic shoals located onshore Kuwait, as well as possible porous reworked material transported away from the shoal loci in a relatively deeper mid ramp settings provides a better insight on further model improvement needed to de-risk stratigraphic trapping mechanisms. The identification of porous features in 3D provides crucial insights on the influence of ecological constraints on the complex Jurassic carbonate ramp systems of Arabia.

SATURATION AND WATTABILITY EVOLUTION UNDER NON-ISOTHERMAL CARBON DIOXIDE INJECTION INTO SALINE AQUIFER

To reduce the cost of carbon capture, transportation and eventual geologic storage at potential geologic sites future sequestration plans envisage the locating of power plants at potential geologic sites. The implication is that the injection temperature of flue gas will be typically those encountered in combustion power plants. This, obviously has a geomechanical consequence considering the fact that heat transferred from the aquifer to the low permeability cap rock will cause excessive pore pressure build up due to poor pore pressure diffusion characteristics of these rocks. While these low permeability rocks are required to provide stratigraphic trapping mechanisms such excessive pore pressure build up can result in compromising the geomechanical integrity. This paper has used heat transfer theories and geomechanical concepts to obtain steady state temperature distribution in cap rocks for temperatures ranging from 50 to 800 degrees Celsius. In so doing, cap rock critical temperatures for tensile and shear failures have been established for a potential on-site gas injection into saline aquifers.

Stratigraphic Trapping Mechanisms in the Iles Formation, Piceance Basin, Colorado

Compartmentalization within shoreface and deltaic reservoirs is key to trapping gas in the Iles Formation of the southern Piceance Basin. There are two types of reservoirs: 1) compartmentalized gas-saturated Corcoran and Cozzette sandstones, and 2) continuous water-saturated Rollins sandstones. Compartmentalized sandstones are interpreted to have been deposited during a time of relatively low accommodation with relatively low sediment supply while more connected sandstones were deposited during a time of relatively high accommodation and a much higher sediment supply. The compartmentalization is due to 1) location within the overall parasequence stacking pattern; 2) facies variability within the deltaic and wave-dominated deposits; and 3) further partitioning due to the superposition of multiple types of erosion surfaces ultimately related to low accommodation rates. The continuous sandstones are more connected because they were apparently deposited during a period of time when rates of progradation were more regular and overall accommodation and sedimentation were higher.

CARBON DIOXIDE GEOSEQUESTRATION: OPTIMUM GAS INJECTION TEMPERATURE REQUIRED FOR CAP ROCK GEOMECHANICAL INTEGRITY

In the efforts to mitigate the unprecedented anthropogenic carbon dioxide presence in the atmosphere, the decision to store this greenhouse gas in geologic repositories has received global appreciation with assured technical and financial viability. The implication is that the injection temperature of flue gas in the potential geologic sites will be typically those encountered in combustion power plants. This, obviously has a geomechanical consequence considering the fact that heat transferred from the aquifer to the low permeability cap rock will cause excessive pore pressure build up due to poor pore pressure diffusion characteristics of these rocks. While these low permeability rocks are required to provide stratigraphic trapping mechanisms such excessive pore pressure build up can result in compromising the geomechanical integrity. This article has used heat transfer theories and geomechanical concepts to obtain steady state temperature distribution in cap rocks for temperatures ranging from 50 to 800 °C. In so doing, cap rock critical temperatures for tensile and shear failures have been established for a potential on-site gas injection into saline aquifers.

Regional seismic interpretation of the hydrocarbon prospectivity of offshore Syria

ABSTRACT Analysis of 5,000 km of multi-client long-offset 2-D seismic data has led to the identification of three sedimentary basins, Levantine, Cyprus, and Latakia, located in offshore Syria. Each basin has a unique structural and stratigraphic history. They are separated from each other by the middle to Late Cretaceous aged Latakia Ridge System that initiated as a compressional fold-thrust belt and was re-activated under a sinistral strike-slip regime that developed during the Early Pliocene in response to a re-organisation of the plate-tectonic stresses. There is significant evidence for a working petroleum system in offshore Syria with numerous onshore oil and gas shows, DHIs (direct hydrocarbon indicators) observed on seismic, and oil seeps identified from satellite imagery. Prospective reservoirs range in age from Triassic to Pliocene – Quaternary and include Lower Miocene deep-water turbidite sands as encountered in recent discoveries in the offshore southern Levantine Basin. The complex structural evolution of each of the three sedimentary basins has produced an array of potential structural and stratigraphic trapping mechanisms.

The biogenic gas potential of the submarine canyon systems of Plio-Peistocene foreland Basin, southwestern Taiwan

Biogenic gas was accidentally discovered and produced from the Plio/Pleistocene formation of the Hsinying gas field in southwestern Taiwan in 1989. A stratigraphic trapping mechanism related to the evolution of submarine canyon systems in the Plio-Peistocene foreland basin has been proposed in a previous study which explained underestimated recoverable gas reserve before drilling. To verify this shallow gas exploration hypothesis and to systematically evaluate the biogenic gas generation and entrapment potential of the submarine canyon systems, seismic interpretation, high-resolution sequence stratigraphic interpretation, seismic attribute analysis and geochemical analysis were performed and integrated in this study. Twenty-nine submarine canyons mapped mainly trend in a NE direction, except the NW trending Eurchungchi submarine canyons located near the Chiali paleo-high. Bright seismic amplitudes were often observed at the incised valley heads of the canyon systems. The shales located near the incised valley heads and deposited during flooding stage possess the highest biogenic gas generation potential, as canyon fill reveals the second highest. Due to the high sediment accumulation rate in the foreland basin, organic matter in such a depositional environment tends to become diluted. A Class III AVO anomaly, inverted impedance lower than 4.7 e + 6 kg/M 3*M/S and A/ B (the ratio between the target horizon amplitude and the RMS amplitude from the background strata) greater than 1.78 were identified as valid direct gas indicators as sand is buried shallower than 1000 m. Class IV AVO anomaly and A/ B greater than 1.4 were concluded to be the indicators of gas sand in the case that sand is buried deeper than 1600 m. Based on the results of sequence stratigraphic interpretation and the consistency between spatial geometries of seismic attributes and those of the submarine canyons, a stratigraphic trap associated with the incised valley heads was concluded to be the original gas entrapment style of the Hsinying and the Kuantian gas fields. Biogenic gas migrated after being trapped startigraphically, hence contributing to the present-day gas field structure. Due to the prevalent erosional features of the submarine canyons on the time structural maps, different types of stratigraphic traps formed in combination with faults and submarine canyons can be recognized easily.

The Cement Packer: A Simple and Economic Method of Accessing Bypassed Reservoir Potential

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 108973, "Multitype Application of Cement Packer: Simple and Economic Method of Accessing Bypassed Reservoir Potential," by Muhammad Idris, SPE, Martin Rylance, SPE, and Krisjahbana Joenoes, Vico Indonesia, and Nanang Firmansyah and Anton Supriyono, Halliburton Indonesia, originally prepared for the 2007 SPE Asia Pacific Oil and Gas Conference and Exhibition, Jakarta, 30 October- 1 November. The paper has not been peer reviewed. Cement-packer operations offer a potentially attractive economic opportunity for a rigless intervention to add additional hydrocarbon potential to a well. The full-length paper details the steps involved in this operation. The cement-packer process was first introduced in 1995; since then, a number of variants of the approach have been developed and applied. These variants have been driven in response to individual-well limitations, special requirements, and increased technical understanding and experience. Introduction The Sanga Sanga Production Sharing Contract (PSC) fields are in the onshore part of the Mahakam delta, East Kalimantan, Indonesia. Vico Indonesia has been actively exploring and developing fields within the Sanga Sanga PSC since 1968. The initial exploration drilling phases resulted in the discovery of the giant Badak and Nilam fields. Over the next decade, additional commercial discoveries were made to the west, along the Sanga Sanga anticline—namely, the Semberah and Mutiara fields. The hydrocarbon accumulations are located in the Middle Miocene sequence of numerous distributary-channel sandstone reservoirs, with mixed structural and stratigraphic trapping mechanisms. A combination of a highly complex fluvial-deltaic environment and increasing field maturity has resulted in a significant challenge for ensuring a continuous development strategy for the remaining reserves while maintaining economic conditions to meet commercial requirements. Completion Philosophy The completion philosophy, within the Vico developments, has evolved over the years. In the early field developments, between 1970 and 1994, the philosophy was to use multiple strings. Typically, a well was drilled with a 12 1/4-in. hole through the F Sands and a 9 5/8-in.-casing string was run. Subsequently, an 8 1/2-in. hole was drilled across the deeper G Sands, and a 7-in. liner was run to total depth. The wells then were completed with two separate produc-tion strings and selective completions (Fig. 1). The tubing strings were either both 3 1/2-in. or a combination of 3 1/2- and 2 3/8-in. strings. Only a single string would penetrate the 7-in. liner (referred to as the long string), with selective zones isolated between packers and behind sliding sleeves within the 7- and 9 5/8-in. sections, where the second string terminated (referred to as the short string).

Seismic stratigraphy of the Late Permian Tinowon Formation, Surat Basin, Australia : new opportunities in a mature basin

The Myall Creek and Riverside gas fields were recently discovered in the Surat Basin. The discoveries were only 2km apart, yet are contained in two separate sand units within the Late Permian Tinowon Formation: the Upper Tinowon Sandstone and Mid Wallabella Sandstone. The DST data of the discovery well of the Myall Creek Field suggest the reserves are greater than the mapped structure could hold invoking a strong stratigraphic trapping mechanism. A post-drill interpretation of the reprocessed seismic data has resolved each sand unit. The distribution of the channel sand, which hosts the Riverside Field, has been mapped and the extent of the stratigraphic trap of the Myall Creek Field is delineated. Both cases open new opportunities for prospects of their respective play types.

Three-dimensional sequence stratigraphy and subtle stratigraphic traps associated with systems tracts: West Cameron region, offshore Lousiana, Gulf of Mexico

Three-dimensional sequence stratigraphy is a potent exploration and development tool for the discovery of subtle stratigraphic traps. Reservoir morphology, heterogeneity and subtle stratigraphic trapping mechanisms can be better understood through systematic horizontal identification of sedimentary facies of systems tracts provided by three-dimensional attribute maps used as an important complement to the sequential analysis on the two-dimensional seismic lines and the well log data. On new prospects as well as on already-producing fields, the additional input of sequential analysis on three-dimensional data enables the identification, location and precise delimitation of new potentially productive zones. The first part of this paper presents four typical horizontal seismic facies assigned to the successive systems tracts of a third- or fourth-order sequence deposited in inner to outer neritic conditions on a clastic shelf. The constructiion of this synthetic representative sequence is based on the observed reproducibility of the horizontal seismic facies response to cyclic eustatic events on more than 35 sequences registered in the Gulf coast Plio-Pleistocene and Late Miocene, offshore Louisiana in the West Cameron region of the Gulf of Mexico. The second part shows how three-dimensional sequence stratigraphy can contribute in localizing and understanding sedimentary facies associated with productive zones. A case study in the early Middle Miocene Cibicides opima sands shows multiple stacked gas accumulations in the top slope fan, prograding wedge and basal transgressive systems tract of the third-order sequence between SB 15.5 and SB 13.8 Ma.

Geologic Reservoir Model for the Triassic Doig Formation, Northeast British Columbia, Canada

A subsurface investigation of the mid-Triassic Doig formation in northeastern British Columbia documented two main reservoir facies. Both are a product of mass movement and sediment gravity flow processes on a progradational, tectonically active continental shelf margin. Substrate instability was likely a product of sediment loading, perhaps in concert with seismic activity. Sedimentary facies and reservoir parameters were determined from analysis of approximately 150 cores and 900 well logs. Laterally discontinuous Doig sandstones are up to 60 m thick and trend northeasterly within the study area. The main reservoir facies are incised density flow deposits and laterally extensive slump deposits. Reservoir quality within these sands is extremely variable with porosity ranging from less than 5% to 15%. In core, these deposits consist of moderately well sorted, very fine grained sandstones with no vertical grain size variation. The best production to date is in the Buick Creek field with initial flows of 346 BOPD. The slump deposits are thinner and tend to be more elongate parallel to paleoshoreline. These sands were subject to some wave or current reworking. Modern analogs where similar processes and products of deposition are known to occur include the Gulf of Alaska continental shelf and the Frasermore » River Delta slope. Doig sandstones usually are enclosed in fine-grained shelf deposits that provide a good stratigraphic trapping mechanism. Successful development of Doig reservoirs must incorporate geologic modes that assist in understanding the complex and highly variable reservoir quality of sandstones units.« less

Quantitative Analysis of Infill Performance: Robertson Clearfork Unit

Infill drilling has significantly increased the cumulative production, conventional remaining reserves, and EOR prospects in the Robertson Clearfork Unit, Gaines County, Texas. This paper documents the successful infill program and the techniques used to quantify reservoir performance under varying well spacings and injection patterns. Robertson is a highly stratified, lenticular dolomite reservoir. Continuity of pay between wells is unusually poor, and the reservoir was only partially drained by wells on 40-acre spacing. Ultimately 10-acre wells and 40-acre inverted ninespot patterns were required for an effective waterflood. Expected recovery from the unit has been increased about 24 million barrels by drilling 218 infill wells and increasing the number of water injection wells to form the 40-acre inverted nine-spot patterns. Three approaches were used to quantify reservoir continuity as a function of horizontal distance: geologic correlation, pressure transient behaviour, and regression analysis of infill performance. All three techniques indicate that 10-acre/well spacing can effectively drain 80%-85% of the reservoir volume by primary production (solution gas drive). However, on this spacing, reservoir discontinuities limit the floodable volume to only 60%-65% of the total reservoir. These studies have permitted the operator to quantitatively project the results of further infill drilling. They also permit amore » realistic assessment of EOR potential based on actual floodable reservoir volume calculations.« less

Facies Comparison and Regional Correlation of Tensleep and Minnelusa Formations, Northeastern Wyoming and South-Central Montana: ABSTRACT

Regional correlation of the Tensleep and Minnelusa Formations between the Powder River and Bighorn basins has been complicated by disagreement over age designations, variability in the geologic nomenclature, and lack of information concerning the paleogeographic and paleotectonic setting during Pennsylvanian time. An understanding of these factors discloses differences in intrabasinal tectonic histories, the effects of regional paleostructural features upon distribution and correlation of units, and potential similarities in stratigraphic trapping mechanisms. The Tensleep Formation includes strata of Desmoinesian, Missourian, and Virgilian age and is equivalent to the middle member (Leo sandstones) of the Minnelusa Formation. Both formations are characterized by open-marine carbonate and siliciclastic facies, transitional restricted-marine carbonate and evaporite facies, and terrestrial sabkha and dune facies. Similarity of paleogeographic setting and facies led to deposition of analogous sedimentary sequences exhibiting like vertical and lateral relationships in the two formations. This suggests that the stratigraphic trapping mechanisms well documented in the more densely drilled Minnelusa Formation may also function in the Tensleep Formation, which to date has been primarily a structural play.

Carboniferous Clastic-Wedge Stratigraphy, Sedimentology, and Foreland Basin Evolution: Black Warrior Basin, Alabama and Mississippi: ABSTRACT

Carboniferous clastic-wedge stratigraphy and sedimentology in the Black Warrior basin of Alabama and Mississippi indicate deposition in an evolving foreland basin flanking the Appalachian-Ouachita fold-thrust belt. The strata reflect specific responses to foreland basin subsidence, orogenic activity, sediment supply, and dispersal systems. Definition of the regional stratigraphy of the clastic wedge provides for interpretation of the foreland basin subsidence history by enabling quantitative reconstruction of regional compaction and subsidence profiles. Comparison of the interpreted subsidence history with model profiles of foreland basin subsidence (predicted from loading and flexure of continental lithosphere) allows evaluation of mechanical models in terms of observed clastic-wedge sedimentology and stratigraphy. Mechanical modeling of foreland basin subsidence predicts formation of a flexural bulge that migrates cratonward ahead of the subsiding foreland basin during loading. In the Black Warrior basin, local stratigraphic thins, pinch-outs, and areas of marine-reworked sediments suggest migration of the flexural bulge. Comparison of flexural bulge migration with thermal maturation history allows evaluation of timing of stratigraphic trapping mechanisms with respect to onset of hydrocarbon generation.

Deep-Water Hydrocarbon Potential of Georges Bank Trough: ABSTRACT

Characterization of the petroleum potential for Georges Bank Trough has been based primarily on limited organic geochemical data that indicate the area of recent drilling activity behind the paleoshelf edge to be poor in organic carbon and C15+ extract values, with predominantly terrestrial kerogen types. Maturation data also suggest an inadequate thermal history for hydrocarbon generation in the area. It is possible that the effects of heat flow from the New England Seamount Chain may contribute to hydrocarbon generation in the Georges Bank Trough--a relationship that may also exist between the Newfoundland Seamount Chain and the Hibernia area of the Grand Banks. Also, comparisons can be drawn between the Atlantis Fracture Zone bordering the Georges Bank Troug and the Romanche-St. Paul Fracture Zone off the Ivory Coast. In the latter region, restricted anoxic environments with sediments rich in marine kerogen types have been identified, as have both structural and stratigraphic trapping mechanisms. Within this rhombochasm configuration, reservoir lithologies of sandstone and carbonate turbidites, fractured deep-water chalks, and reefal limestones should occur. The relationships of seamount to fracture zone, as applied to the rhombochasm model for the Georges Bank Trough, should enhance the hydrocarbon potential of the lower Mesozoic sediments seaward of the paleoshelf edge and thus classify this area as a future major hydrocarbon province. End_of_Article - Last_Page 278------------

Trapper Canyon Deposit, Eastern Big Horn Basin, Wyoming: Tar Sand or Heavy Oil?: ABSTRACT

The Trapper Canyon Deposit (Battle Creek Deposit in U.S. Bureau of Mines Monograph 12) is located on the western flank of the Bighorn Mountains approximately 30 mi (48 km) east of Greybull, Wyoming. The petroleum occurs in the upper eolian sequence of the Pennsylvanian Tensleep Sandstone which dips from 5° to 8° to the southwest. The deposit was initially reported by N. H. Darton in U.S. Geological Survey Professional Paper 51 in 1906. A characterization study was made on the deposit which included mapping the deposit and surrounding area, measuring three stratigraphic sections in the Tensleep Sandstone, and sampling 13 outcrop localities. Thickness of the deposit ranged from 0 to 22.5 ft (6.8 m) in the 13 sample localities. Preliminary analyses of outcrop sampl s indicate API gravities and viscosities consistent with the definition of a tar sand. Oil properties are similar to those published for Phosphoria-sourced oils produced from the Tensleep Sandstone in fields to the west. Lateral pinch-out of the deposit, tight characteristics of upper and lower bounding units, and the lack of any apparent structural controls in the area, are all evidence for a stratigraphic trapping mechanism. Recoverable reserves are estimated at 1.96 million bbl over a 67-acre (27 ha.) area. End_of_Article - Last_Page 1359------------