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Demaison Gerard J

Bio: Demaison Gerard J is an academic researcher from Chevron Corporation. The author has contributed to research in topics: Source rock & Structural basin. The author has an hindex of 9, co-authored 15 publications receiving 1964 citations.

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Journal ArticleDOI
TL;DR: The anoxic aquatic environment is a mass of water so depleted in oxygen that virtually all aerobic biologic activity has ceased as discussed by the authors, where the demand for oxygen in the water column exceeds the supply.
Abstract: The anoxic aquatic environment is a mass of water so depleted in oxygen that virtually all aerobic biologic activity has ceased. Anoxic conditions occur where the demand for oxygen in the water column exceeds the supply. Oxygen demand relates to surface biologic productivity, whereas oxygen supply largely depends on water circulation, which is governed by global climatic patterns and the Coriolis force. Organic matter in sediments below anoxic water is commonly more abundant and more lipid-rich than under oxygenated water mainly because of the absence of benthonic scavenging. The specific cause for preferential lipid enrichment probably relates to the biochemistry of anaerobic bacterial activity. Geochemical-sedimentologic evidence suggests that potential oil source beds are and have been deposited in the geologic past in four main anoxic settings as follows. 1. Large anoxic lakes: Permanent stratification promotes development of anoxic bottom water, particularly in large lakes which are not subject to seasonal overturn, such as Lake Tanganyika. Warm equable climatic conditions favor lacustrine anoxia and nonmarine oil source bed deposition. Conversely, lakes in temperate climates tend to be well oxygenated. 2. Anoxic silled basins: Only those landlocked silled basins with positive water balance tend to become anoxic. Typical are the Baltic and Black Seas. In arid-region seas (Red and Mediterranean Seas), evaporation exceeds river inflow, causing negative water balance and well-oxygenated bottom waters. Anoxic conditions in silled basins on oceanic shelves also depend upon overall climatic and water-circulation patterns. Silled basins should be prone to oil source bed deposition at times of worldwide transgression, both at high and low paleolatitudes. Silled-basin geometry, however, does not automatically imply the presence of oil source beds. 3. Anoxic layers caused by upwelling: These develop only when the oxygen supply in deep water cannot match demand owing to high surface biologic productivity. Examples are the Benguela Current and Peru coastal upwelling. No systematic correlation exists between upwelling and anoxic conditions because deep oxygen supply is often sufficient to match strongest demand. Oil source beds and phosphorites resulting from upwelling are present preferentially at low paleolatitudes and at times of worldwide transgression. 4. Open-ocean anoxic layers: These are present in the oxygen-minimum layers of the northeastern Pacific and northern Indian Oceans, far from deep, oxygenated polar water sources. They are analogous, on a reduced scale, to worldwide "oceanic anoxic events" which occurred at global climatic warmups and major transgressions, as in Late Jurassic and middle Cretaceous times. Known marine oil source bed systems are not randomly distributed in time but tend to coincide with periods of worldwide transgression and oceanic anoxia. Geochemistry, assisted by paleogeography, can greatly help petroleum exploration by identifying paleoanoxic events and therefore widespread oil source bed systems in the stratigraphic record. Recognition of the proposed anoxic models in ancient sedimentary basins should help in regional stratigraphic mapping of oil shale and oil source beds.

1,361 citations

Journal ArticleDOI
TL;DR: In this paper, a case study involving a number of heavily biodegraded oil seeps from Greece is presented, where the surviving biomarker remnants can be utilized to accomplish source correlations.

198 citations

Journal ArticleDOI
TL;DR: In this article, a simple working nomenclature that consists of combining qualifiers from each of the following three categories: (1) charge factor (supercharged, normally charged, or undercharged), (2) migration drainage style (vertically drained or laterally drained), and (3) entrapment style (high impedance or low impedance).
Abstract: Our genetic classification of petroleum systems is founded on a simple working nomenclature that consists of combining qualifiers from each of the following three categories: (1) charge factor (supercharged, normally charged, or undercharged), (2) migration drainage style (vertically drained or laterally drained), and (3) entrapment style (high impedance or low impedance). The charge factor is estimated on the basis of the richness and volumetrics of mature source rocks. The source potential index (SPI), which combines source-rock richness and thickness into a single parameter, is a convenient shortcut for comparing the petroleum potential of diverse source rocks containing dissimilar kerogen types and for rapidly estimating regional charging capacity. In extensively explored basins, a positive correlation exists between the magnitude of SPI and basin-wide petroleum reserves. The migration drainage style is determined from the structural and stratigraphic framework of a basin. Vertical-migration drainage, which occurs mainly through faults and fracture systems breaching a seal, is characteristic of petroleum systems contained within rift basins, deltaic sequences, salt-dome provinces, wrench basins, and fold-and-thrust belts. In contrast, lateral-migration drainage is dominant wherever stratigraphically continuous seal-reservoir "doublets" extend over a very large area in a tectonically stable province (e.g., commonly foreland or intracratonic platform basins). Recognition of the dominant migration style helps to predict the location of zones of petroleum occurrence in relation to the "hydrocarbon kitchens." The entrapment style, which is also dependent on the structural framework and the presence and effectiveness of seals, describes the degree of resistance (i.e., impedance) working against dispersion of the petroleum charge. Application of these working concepts should help to significantly reduce geologic risk, particularly in new ventures-type exploration.

165 citations

Journal ArticleDOI
TL;DR: In this article, the authors identified the most favorable areas for the possible existence of very large "tar" sand-like accumulations, but are the areas that have the highest risk for their degradation.
Abstract: Sixteen very large "tar" deposits are estimated to contain about 2,100 billion bbl of oil in place. This is nearly as much heavy oil as the world's total discovered recoverable oil reserves. The seven largest "tar" deposits of the world contain 98% of the world's heavy oil; that is, these seven heavy-oil deposits contain about as much oil in place as the world's 264 giant oil fields. These accumulations are remarkable not only for their size, but also for their unconventional geologic settings--in traps that feature various degrees of stratigraphic control in combination with structure; in marginal marine or nonmarine sediments; and commonly in thermally immature sediments without associated local source beds. For very large tar-sand accumulations to be formed and localized, the following are geologic prerequisites: (1) a paleodelta system comprising organic-rich source beds and very far-reaching, efficiently interfingered carrier sandstones; (2) a widespread regional cap restraining vertical fluid escape from the underlying paleodelta and channeling fluid movements laterally to the edges of the basin; (3) a homocline with updip stratigraphic convergence and, preferably, low-amplitude arching plunging into the basin; and (4) degradation of oil to heavy sour "tars" by water washing and bacterial action. Most of the settings reviewed indicate moderately rich source beds widespread over large areas, excellent gathering and focused drainage systems in paleodeltas, very long migration distance, and the predominance of regional structural and stratigraphic factors over local structural factors in determining both size and sites of accumulations. Some authors already have suggested the possibility that supergiant accumulations of medium-gravity producible oil may lie undiscovered in settings similar to the very large "tar" sands. The writer concludes that foreland basins are the most favorable areas for the possible existence of very large "tar" sand-like accumulations, but are the areas that have the highest risk for their degradation. The central parts of large rift basins are better protected against oil degradation, but gathering areas and migration distances are considerably more restricted than in foreland basins. The possibilities of passive, Atlantic-type, margin settings are unpredictable. Small intermountain basins can offer possibilities, if thick and exceptionally rich source beds are present.

79 citations

01 Jan 1994
TL;DR: In this paper, a simple working nomenclature that consists of combining qualifiers from each of the following three categories: (1) charge factor (supercharged, normally charged, or undercharged), (2) migration drainage style (vertically drained or laterally drained), and (3) entrapment style (high impedance or low impedance).
Abstract: Our genetic classification of petroleum systems is founded on a simple working nomenclature that consists of combining qualifiers from each of the following three categories: (1) charge factor (supercharged, normally charged, or undercharged), (2) migration drainage style (vertically drained or laterally drained), and (3) entrapment style (high impedance or low impedance). The charge factor is estimated using the initial richness of the source rock and the volume of mature source rock. The source potential index (SPI), which combines source rock richness and net source rock thickness into a single parameter, is a convenient shortcut for comparing the petroleum potential of diverse source rocks containing dissimilar kerogen types and for rapidly estimating regional charging capacity. In extensively explored petroleum provinces that contain a single petroleum system, a positive correlation exists between the magnitude of the SPI and province-wide petroleum reserves. Migration drainage style is determined from the structural and stratigraphic framework of the basin fill. Vertical migration drainage, which occurs mainly through faults and fractures that breach a seal, is characteristic of petroleum systems in rift basins, deltaic sequences, salt dome provinces, wrench basins, and fold and thrust belts. In contrast, lateral migration drainage is dominant wherever stratigraphically continuous seal-reservoir "doublets" or carrier beds extend over a large area in a tectonically stable province (e.g., foreland or intracratonic platform basins). Recognition of the dominant migration style helps to predict the location of zones of petroleum occurrence in relation to the pod of mature source rock. Entrapment style, which is also dependent on the structural framework and the presence and effectiveness of seals, describes the degree of resistance (impedance) working against dispersion of the petroleum charge. Application of these working concepts should help to reduce geologic risk significantly, particularly in new ventures exploration.

75 citations


Cited by
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Journal ArticleDOI
TL;DR: For example, in a recent paper as discussed by the authors, the authors investigated the mechanisms governing sedimentary organic matter preservation in marine sediments and found that organic preservation in the marine environment is < 0.5% efficient, and that the factors which directly determine preservation vary with depositional regime, but have in common a critical interaction between organic and inorganic materials over locally variable time scales.

2,216 citations

MonographDOI
16 Dec 2004
TL;DR: The second edition of The Biomarker Guide as mentioned in this paper provides a comprehensive account of the role that biomarker technology plays both in petroleum exploration and in understanding Earth history and processes.
Abstract: The second edition of The Biomarker Guide is a fully updated and expanded version of this essential reference. Now in two volumes, it provides a comprehensive account of the role that biomarker technology plays both in petroleum exploration and in understanding Earth history and processes. Biomarkers and Isotopes in the Environment and Human History details the origins of biomarkers and introduces basic chemical principles relevant to their study. It discusses analytical techniques, and applications of biomarkers to environmental and archaeological problems. The Biomarker Guide is an invaluable resource for geologists, petroleum geochemists, biogeochemists, environmental scientists and archaeologists.

2,163 citations

Journal ArticleDOI
TL;DR: In this article, the organic matter content of sediments is inferred from bulk properties such as elemental compositions, carbon and nitrogen stable isotope ratios, Rock-Eval pyrolysis data, and organic petrography.

1,947 citations

Journal ArticleDOI
TL;DR: In this article, the authors examined the distribution of minor and trace elements in marine sediments and provided forensic tools for determining the redox conditions of the bottom waters at the time of deposition.

1,391 citations

MonographDOI
09 Jan 2020
TL;DR: The third edition of the reference book as discussed by the authors has been thoroughly updated while retaining its comprehensive coverage of the fundamental theory, concepts, and laboratory results, and highlights applications in unconventional reservoirs, including water, hydrocarbons, gases, minerals, rocks, ice, magma and methane hydrates.
Abstract: Responding to the latest developments in rock physics research, this popular reference book has been thoroughly updated while retaining its comprehensive coverage of the fundamental theory, concepts, and laboratory results. It brings together the vast literature from the field to address the relationships between geophysical observations and the underlying physical properties of Earth materials - including water, hydrocarbons, gases, minerals, rocks, ice, magma and methane hydrates. This third edition includes expanded coverage of topics such as effective medium models, viscoelasticity, attenuation, anisotropy, electrical-elastic cross relations, and highlights applications in unconventional reservoirs. Appendices have been enhanced with new materials and properties, while worked examples (supplemented by online datasets and MATLAB® codes) enable readers to implement the workflows and models in practice. This significantly revised edition will continue to be the go-to reference for students and researchers interested in rock physics, near-surface geophysics, seismology, and professionals in the oil and gas industries.

1,387 citations