The main vector of oil and gas migration in the northern Gulf of Mexico Basin, and in other basin... more The main vector of oil and gas migration in the northern Gulf of Mexico Basin, and in other basins characterized by salt tectonics and growth faulting, is vertical or cross stratigraphic. Geochemistry of oils from Neogene reservoirs located in the deep shelf and shelf-edge areas of the northern part of the basin provides evidence of oil mixing. Oils in this area are compositionally intermediate between Jurassic-derived oils occurring basinward, and Cretaceous-derived oils occurring in shallower parts of the shelf. The existence of mixed oils indicates a complex migrationaccumulation history. Some of the mixed oils are bacterially altered, but possess a "fresh" gasoline range chemistry. This pattern is more complex involving oil-oil mixing, bacterial alteration, and introduction of condensate or light oil into the reservoir. The polyhistory compositional pattern helps recognition of complex migration-accumulation histories. The pattern can result from direct migration of fluids from the source or sources, or by remigration of fluids contained in older reservoir sections to younger reservoir sections. Multiple fluid migration-accumulation episodes are certainly more common than generally recognized, and probably, most common in densely faulted offshore areas. Also, many biodegraded oils are presently at reservoir temperatures that are too high for active biodegradation (>60 C or 140 F) suggesting the oil was biodegraded at shallower depths with remigration subsequent to intense Pleistocene sediment loading.
Proceedings of the 8th Unconventional Resources Technology Conference, 2020
The URTeC Technical Program Committee accepted this presentation on the basis of information cont... more The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of, and, is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk. The information herein does not necessarily reflect any position of URTeC. Any reproduction, distribution, or storage of any part of this paper by anyone other than the author without the written consent of URTeC is prohibited.
Summary Mesan Governorate in particular passes into two main basins; these are the Zagross Fold B... more Summary Mesan Governorate in particular passes into two main basins; these are the Zagross Fold Belt Basin to the east toward the Iranian Border with continuation northward toward Diyala and Sulaimaniyah Governorates and hence contain mainly structural reservoirs. On the other hand, the second main basin is the Mesopotamian Foredeep Basin to the west toward Nasiriyah Governorate with continuation southward toward Basrah Governorate and northward toward Baghdad the capital, this basin contains more stable and thick strata that contain stratigraphic as well as structural reservoirs.
Chemometric analyses of geochemical data for 165 crude oil samples from the San Joaquin Basin ide... more Chemometric analyses of geochemical data for 165 crude oil samples from the San Joaquin Basin identify genetically distinct oil families and their inferred source rocks and provide insight into migration pathways, reservoir compartments, and filling histories. In the first part of the study, 17 source-related biomarker and stable carbon-isotope ratios were evaluated using a chemometric decision tree (CDT) to identify families. In the second part, ascendant hierarchical clustering was applied to terpane mass chromatograms for the samples to compare with the CDT results. The results from the two methods are remarkably similar despite differing data input and assumptions. Recognized source rocks for the oil families include the (1) Eocene Kreyenhagen Formation, (2) Eocene Tumey Formation, (3-4) upper and lower parts of the Miocene Monterey Formation (Buttonwillow depocenter), and (5-6) upper and lower parts of the Miocene Monterey Formation (Tejon depocenter). Ascendant hierarchical clustering identifies 22 oil families in the basin as corroborated by independent data, such as carbon-isotope ratios, sample location, reservoir unit, and thermal maturity maps from a three-dimensional basin and petroleum system model. Five families originated from the Eocene Kreyenhagen Formation source rock, and three families came from the overlying Eocene Tumey Formation. Fourteen families migrated from the upper and lower parts of the Miocene Monterey Formation source rocks within the Buttonwillow and Tejon depocenters north and south of the Bakersfield arch. The Eocene and Miocene families show little cross-stratigraphic migration because of seals within and between the source rocks.
Predictions of source rock type, geologic age, and thermal maturity can be made based on biomarke... more Predictions of source rock type, geologic age, and thermal maturity can be made based on biomarkers from migrated crude oils whilst natural gas origin and maturity can be deduced from stable isotopic compositions. Various petroleum systems are mapped across northern Africa, based upon the predicted source rock type and age. The solid component of petroleum, asphaltenes, can be used as source rock kerogen surrogates to determine generation kinetic characteristics.
Geological Society, London, Special Publications, 2016
We describe an examination of two lines of evidence, tectono-structural evolution and hydrocarbon... more We describe an examination of two lines of evidence, tectono-structural evolution and hydrocarbon geochemistry, of asymmetric opening of the Atlantic Equatorial Margin. Our structural mapping used compilations of geophysical data and a review of both published literature and oil company public presentations. Geochemically, we accessed regional non-exclusive oil studies of the conjugate margins of Africa and South America, plus considerable published material. A group of non-exclusive oils was refined to 286, which clustered into five families, all represented along the NE Brazil margin but only one along the West African Transform (WAT) margin. Multiple lacustrine-sourced oils were seen around the South Atlantic, including NE Brazil, but a rich, oil-prone lacustrine source was not indicated offshore Ivory Coast and Ghana. Despite minor evidence of mixed source, possibly lacustrine stringers within an alluvial to marine setting, the predominant source is marine Cretaceous (Cenomanian–Turonian and possibly Albian). We find that opening asymmetry (a) biased the location of lacustrine (Early to mid-Cretaceous prerift to early synrift) source rocks to the NE Brazil margin and (b) locally narrowed the width of the optimal marine (Mid-Late Cretaceous postrift) WAT Margin source kitchens. Burial of the latter has aggravated the risk of late charge from light (condensate and gas) hydrocarbons.
Abstract The geochemistry of oils and gases, as well as sediments from which they are derived, is... more Abstract The geochemistry of oils and gases, as well as sediments from which they are derived, is fundamental knowledge. The current study produces a subregional to regional characterization of the geochemistry of Eagle Ford oils and sediments in the context of a meaningful stratigraphic framework. The study area includes the main and most important producing areas of the Eagle Ford shale oil play. The lower part of the Eagle Ford is shown to be the organically richest part of the group. This is demonstrated by the general literature, reference to work completed by colleagues of this volume, and presentation of data for a core from an important Eagle Ford producing area. This interval is lower-middle Cenomanian in age. It depositionally predates the Oceanic Anoxic Event 2 (OAE2) that occurs at the Cenomanian–Turonian boundary. Elevated organic richness in the lower Eagle Ford that varies along strike suggests organic accumulation is partly controlled by localized, semipermanent circulatory patterns. Multivariate statistical classification using biomarkers and carbon isotopes from a large number of oils in Cretaceous reservoirs closely related to the Eagle Ford resulted in the identification of eight compositionally distinct families, three of which occur in the main part of the Eagle Ford shale oil-producing area: Family 2, Family 3, and Family 7. Average data for each family are compared to a large set of global oils representing a variety of depositional environments and depositional times. Comparison of the south Texas oils to the cosmopolitan dataset indicates that Family 3 oils were derived from shales deposited in distal marine settings. Family 7 oils compare favorably with oils derived from carbonate-rich source rocks and Family 2 oils from compositionally intermediate marl-rich sediments. Maturity-sensitive data from the oil families were submitted to principal component analysis. Seventy-five to ninety-four percent of the variability in these datasets was contained in the first or primary principal component (Factor 1). The level of correlation suggested these Factor 1 values could be converted to equivalent vitrinite reflectance values (%VRE). This was accomplished and the VRE for the oils mapped. Oil maturities obtained by this process are consistent with maturity trends obtained from regional considerations. When assessing source rock thermal maturity using pyrolysis techniques (e.g., Rock-Eval), it is useful to measure pyrolysis parameters both before and after solvent extraction, especially at or near peak oil maturity levels. The certitude that oils in this study are derived from the Eagle Ford, as opposed to the Austin Chalk or some third source, comes from several observations. Some Family 2 oils come directly from completions in the Eagle Ford. Family 7 oils come from the First Shot field area and Family 3 oils from Giddings are derived from Eagle Ford/Boquillas Shales based on positive oil-source correlations. Several source scenarios can be imagined given two proven Eagle Ford sources (lower-middle Cenomanian and Turonian) and three organic facies represented by oils. It is possible that one or more organofacies are active sources within each chronostratigraphic interval.
The main vector of oil and gas migration in the northern Gulf of Mexico Basin, and in other basin... more The main vector of oil and gas migration in the northern Gulf of Mexico Basin, and in other basins characterized by salt tectonics and growth faulting, is vertical or cross stratigraphic. Geochemistry of oils from Neogene reservoirs located in the deep shelf and shelf-edge areas of the northern part of the basin provides evidence of oil mixing. Oils in this area are compositionally intermediate between Jurassic-derived oils occurring basinward, and Cretaceous-derived oils occurring in shallower parts of the shelf. The existence of mixed oils indicates a complex migrationaccumulation history. Some of the mixed oils are bacterially altered, but possess a "fresh" gasoline range chemistry. This pattern is more complex involving oil-oil mixing, bacterial alteration, and introduction of condensate or light oil into the reservoir. The polyhistory compositional pattern helps recognition of complex migration-accumulation histories. The pattern can result from direct migration of fluids from the source or sources, or by remigration of fluids contained in older reservoir sections to younger reservoir sections. Multiple fluid migration-accumulation episodes are certainly more common than generally recognized, and probably, most common in densely faulted offshore areas. Also, many biodegraded oils are presently at reservoir temperatures that are too high for active biodegradation (>60 C or 140 F) suggesting the oil was biodegraded at shallower depths with remigration subsequent to intense Pleistocene sediment loading.
Proceedings of the 8th Unconventional Resources Technology Conference, 2020
The URTeC Technical Program Committee accepted this presentation on the basis of information cont... more The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of, and, is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk. The information herein does not necessarily reflect any position of URTeC. Any reproduction, distribution, or storage of any part of this paper by anyone other than the author without the written consent of URTeC is prohibited.
Summary Mesan Governorate in particular passes into two main basins; these are the Zagross Fold B... more Summary Mesan Governorate in particular passes into two main basins; these are the Zagross Fold Belt Basin to the east toward the Iranian Border with continuation northward toward Diyala and Sulaimaniyah Governorates and hence contain mainly structural reservoirs. On the other hand, the second main basin is the Mesopotamian Foredeep Basin to the west toward Nasiriyah Governorate with continuation southward toward Basrah Governorate and northward toward Baghdad the capital, this basin contains more stable and thick strata that contain stratigraphic as well as structural reservoirs.
Chemometric analyses of geochemical data for 165 crude oil samples from the San Joaquin Basin ide... more Chemometric analyses of geochemical data for 165 crude oil samples from the San Joaquin Basin identify genetically distinct oil families and their inferred source rocks and provide insight into migration pathways, reservoir compartments, and filling histories. In the first part of the study, 17 source-related biomarker and stable carbon-isotope ratios were evaluated using a chemometric decision tree (CDT) to identify families. In the second part, ascendant hierarchical clustering was applied to terpane mass chromatograms for the samples to compare with the CDT results. The results from the two methods are remarkably similar despite differing data input and assumptions. Recognized source rocks for the oil families include the (1) Eocene Kreyenhagen Formation, (2) Eocene Tumey Formation, (3-4) upper and lower parts of the Miocene Monterey Formation (Buttonwillow depocenter), and (5-6) upper and lower parts of the Miocene Monterey Formation (Tejon depocenter). Ascendant hierarchical clustering identifies 22 oil families in the basin as corroborated by independent data, such as carbon-isotope ratios, sample location, reservoir unit, and thermal maturity maps from a three-dimensional basin and petroleum system model. Five families originated from the Eocene Kreyenhagen Formation source rock, and three families came from the overlying Eocene Tumey Formation. Fourteen families migrated from the upper and lower parts of the Miocene Monterey Formation source rocks within the Buttonwillow and Tejon depocenters north and south of the Bakersfield arch. The Eocene and Miocene families show little cross-stratigraphic migration because of seals within and between the source rocks.
Predictions of source rock type, geologic age, and thermal maturity can be made based on biomarke... more Predictions of source rock type, geologic age, and thermal maturity can be made based on biomarkers from migrated crude oils whilst natural gas origin and maturity can be deduced from stable isotopic compositions. Various petroleum systems are mapped across northern Africa, based upon the predicted source rock type and age. The solid component of petroleum, asphaltenes, can be used as source rock kerogen surrogates to determine generation kinetic characteristics.
Geological Society, London, Special Publications, 2016
We describe an examination of two lines of evidence, tectono-structural evolution and hydrocarbon... more We describe an examination of two lines of evidence, tectono-structural evolution and hydrocarbon geochemistry, of asymmetric opening of the Atlantic Equatorial Margin. Our structural mapping used compilations of geophysical data and a review of both published literature and oil company public presentations. Geochemically, we accessed regional non-exclusive oil studies of the conjugate margins of Africa and South America, plus considerable published material. A group of non-exclusive oils was refined to 286, which clustered into five families, all represented along the NE Brazil margin but only one along the West African Transform (WAT) margin. Multiple lacustrine-sourced oils were seen around the South Atlantic, including NE Brazil, but a rich, oil-prone lacustrine source was not indicated offshore Ivory Coast and Ghana. Despite minor evidence of mixed source, possibly lacustrine stringers within an alluvial to marine setting, the predominant source is marine Cretaceous (Cenomanian–Turonian and possibly Albian). We find that opening asymmetry (a) biased the location of lacustrine (Early to mid-Cretaceous prerift to early synrift) source rocks to the NE Brazil margin and (b) locally narrowed the width of the optimal marine (Mid-Late Cretaceous postrift) WAT Margin source kitchens. Burial of the latter has aggravated the risk of late charge from light (condensate and gas) hydrocarbons.
Abstract The geochemistry of oils and gases, as well as sediments from which they are derived, is... more Abstract The geochemistry of oils and gases, as well as sediments from which they are derived, is fundamental knowledge. The current study produces a subregional to regional characterization of the geochemistry of Eagle Ford oils and sediments in the context of a meaningful stratigraphic framework. The study area includes the main and most important producing areas of the Eagle Ford shale oil play. The lower part of the Eagle Ford is shown to be the organically richest part of the group. This is demonstrated by the general literature, reference to work completed by colleagues of this volume, and presentation of data for a core from an important Eagle Ford producing area. This interval is lower-middle Cenomanian in age. It depositionally predates the Oceanic Anoxic Event 2 (OAE2) that occurs at the Cenomanian–Turonian boundary. Elevated organic richness in the lower Eagle Ford that varies along strike suggests organic accumulation is partly controlled by localized, semipermanent circulatory patterns. Multivariate statistical classification using biomarkers and carbon isotopes from a large number of oils in Cretaceous reservoirs closely related to the Eagle Ford resulted in the identification of eight compositionally distinct families, three of which occur in the main part of the Eagle Ford shale oil-producing area: Family 2, Family 3, and Family 7. Average data for each family are compared to a large set of global oils representing a variety of depositional environments and depositional times. Comparison of the south Texas oils to the cosmopolitan dataset indicates that Family 3 oils were derived from shales deposited in distal marine settings. Family 7 oils compare favorably with oils derived from carbonate-rich source rocks and Family 2 oils from compositionally intermediate marl-rich sediments. Maturity-sensitive data from the oil families were submitted to principal component analysis. Seventy-five to ninety-four percent of the variability in these datasets was contained in the first or primary principal component (Factor 1). The level of correlation suggested these Factor 1 values could be converted to equivalent vitrinite reflectance values (%VRE). This was accomplished and the VRE for the oils mapped. Oil maturities obtained by this process are consistent with maturity trends obtained from regional considerations. When assessing source rock thermal maturity using pyrolysis techniques (e.g., Rock-Eval), it is useful to measure pyrolysis parameters both before and after solvent extraction, especially at or near peak oil maturity levels. The certitude that oils in this study are derived from the Eagle Ford, as opposed to the Austin Chalk or some third source, comes from several observations. Some Family 2 oils come directly from completions in the Eagle Ford. Family 7 oils come from the First Shot field area and Family 3 oils from Giddings are derived from Eagle Ford/Boquillas Shales based on positive oil-source correlations. Several source scenarios can be imagined given two proven Eagle Ford sources (lower-middle Cenomanian and Turonian) and three organic facies represented by oils. It is possible that one or more organofacies are active sources within each chronostratigraphic interval.
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