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Thirty-five different samples from three different sulfur cycles were examined in this stratigraphically oriented study of the Shell 22x-1 well (U.S.G.S. C177 core) in the Piceance Basin, Colorado. Carbon isotopic compositions of constituents of Green River bitumens indicate mixing of three main components: products of primary photoautotrophs and their immediate consumers (? ?30? vs PDB), products of methanotrophic bacteria (? ?85?), and products of unknown bacteria (? ?40?). For individual compounds synthesized by primary producers, ?-values ranged from ?28 to ?32?. 13C contents of individual primary products (?-carotene, steranes, acyclic isoprenoids, tricyclic triterpenoids) were not closely correlated, suggesting...
This study compares kinetic parameters determined by open-system pyrolysis and hydrous pyrolysis using aliquots of source rocks containing different kerogen types. Kinetic parameters derived from these two pyrolysis methods not only differ in the conditions employed and products generated, but also in the derivation of the kinetic parameters (i.e., isothermal linear regression and non-isothermal nonlinear regression). Results of this comparative study show that there is no correlation between kinetic parameters derived from hydrous pyrolysis and open-system pyrolysis. Hydrous-pyrolysis kinetic parameters determine narrow oil windows that occur over a wide range of temperatures and depths depending in part on the...
Crude oils from the Laramide structures of Wyoming were studied with respect to their geochemical compositions. The sampling areas include the Greater Green River, Wind River and Big Horn basins, and the Casper Arch region. Based on pristane/phytane ratio and various hopane and sterane parameters, the Permian Phosphoria Formation derived oils can be readily differentiated from oils with different origins. Within the Phosphoria Formation derived oils, three subgroups can be identified using Ts/(Ts+Tm) and diasterane/regular sterane ratios, corresponding to sources with subtle variation in organic facies and/or thermal maturity of the Phosphoria Formation. Differences in source organic input, depositional environments,...
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Carbon isotopic compositions of saturated hydrocarbon, aromatic hydrocarbon, NSO (resin), and asphaltene fractions of vein-forming gilsonites (Cowboy, Bonanza, Independence, Wagonhound and Harrison veins) in the NE Uinta Basin, Utah, are all similar and isotopically resemble Mahogany Zone shale extracts of the Green River Formation (δ 13C −29 to −31%). Individual molecular fossils in the gilsonites show a wider variability in compositions indicative of their paleoecological origins within the Eocene Uinta/Greater Green River paleolake system. Carbon isotopic compositions of C28 and C29 steranes (δ 13C = −25 to −32%), pristance and phytane (−33 to —34%) and perhydroβ-carotene (carotane) (δ 13C = −33.2%) suggest that...
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Two members of the Green River Formation in the Washakie Basin have been analysed by organic geochemical and organic petrographic techniques and the results placed in a sequence stratigraphic framework. One of these members, the Laney Shale, was deposited in a hydrologically closed, alkaline lake under an arid climate and was characterized by high concentrations of alginite-rich organic matter whereas the other, the Luman Tongue, was deposited in a hydrologically open, freshwater lake under a humid climate and consisted of organic-poor profundal lake mudstones and coaly lake margin sediments. Potential source rocks in both lake types have the potential for generating high-wax oil at high subsurface temperatures...
Results of extraction experiments performed on immature Green River Formation source rock samples from the Black Shale Facies (Uinta Basin, Utah) demonstrate the potential of extracting high molecular weight hydrocarbons (HMWHC) with sequential dichloromethane:methanol/soxhlet and p-xylene/sonication techniques. The first soxhlet extraction step with DCM:MeOH removes lower molecular weight alkanes from the source rock while the HMWHC remain in the rock residue. Sonication of the rock residue with p-xylene recovers these HMWHC, showing distinct hydrocarbon distributions and preferences in high temperature gas chromatograms. Extracts obtained by using p-xylene/soxhlet with original source rocks and sequential soxhlet...
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We have analyzed the solvent extracts from three different types of native bitumens from the Uinta Basin in northeastern Utah by a variety of analytical techniques, including GC-IRMS, to evaluate variations in the paleodepositional environment during two periods of Lake Uinta deposition. The gilsonite and tabbyite bitumens are associated with Parachute Creek Member sediments deposited during a major expansion of ancient Lake Uinta. Compound specific isotopic analyses of ß-carotane and phytane (δ 13C = −32.6 to −32.1%0) from these bitumens reflect input from primary photosynthetic producers such as cyanobacteria. Sterane δ 13C values (−34.5 to −29.2%0) refflect contributions from lacustrine algae, while extremely...
    map background search result map search result map Carbon isotopic composition of individual biomarkers in gilsonites (Utah) Compound specific isotopic variability in Uinta Basin native bitumens: paleoenvironmental implications Organic geochemistry of freshwater and alkaline lacustrine sediments in the Green River Formation of the Washakie Basin, Wyoming, U.S.A. Carbon isotopic composition of individual biomarkers in gilsonites (Utah) Compound specific isotopic variability in Uinta Basin native bitumens: paleoenvironmental implications Organic geochemistry of freshwater and alkaline lacustrine sediments in the Green River Formation of the Washakie Basin, Wyoming, U.S.A.