Christopher Laughrey FRIDay 2015 Oral Presentation Abstract

click Save on discount prescription drugs from Canada with our licensed online canadian pharmacy online or toll free. Canada Drugs is your online Canada pharmacy and online The Stable Isotope and Noble Gas Geochemistry of a Natural N2 Gas Reservoir, Northwestern Denver-Julesburg Basin, Goshen County, Wyoming

Christopher Laughrey, Dolan Integration Group

Natural gas produced from the Permian Hartville sandstone in the Samson Oil and Gas Bluff #1-11 well in Goshen County, Wyoming is composed of 97.58% N2, 2.05% CH4, 0.17% CO2, 0.151 to 0.152% He, and trace amounts of C2H6 through C6+ hydrocarbons and argon. The N2/Ar ratio is 7,933.3, a value that eliminates air contamination as a possible source of the N2. The δ15N of the produced nitrogen gas is +20.4‰, a value compatible with a crustal or magmatic source. The 3He/4He ratio of the Bluff #1-11 gas is 4.5 x 10-8 (R/Ra = 0.032), a value which eliminates a magmatic source from consideration and indicates a crustal origin for the N2. There are three possible crustal sources for the nitrogen: 1) N2 fixed as NH4+ in potassium-rich sediments; 2) N2 fixed in biotite and K-feldspar in crystalline rocks; and 3) denitrification of organic matter in hydrocarbon source rocks. The N2 concentration, δ15N of the gas, 4He/N2 and N2/20Ne ratios support an interpretation that the N2 produce d from the Bluff #1-11 well was generated by denitrification of post mature organic matter. The methane δ13C of the Bluff #1-11 gas is -32.87‰ and the δ2H of the methane is -173.7‰. These carbon and hydrogen isotopic values, in combination with the chemical composition of the Bluff gas, indicate that the CH4 is a thermogenic, post-mature gas. The respective C2H6 and C3H8 δ13C of the hydrocarbons are -27.9 and -32.3‰. The hydrocarbon gases exhibit a partial isotope reversal with respect to carbon number, i.e., δ13C1 < δ13C2 > δ13C3 which suggests mixing of wet and dry thermogenic gases in the Hartville sandstone and/or its source rocks (Pennsylvanian-age Desmoinesian black shales and marlstones) during progressive burial in the Paleogene. The CH4 and C2H6 in the Bluff well gas are co-genetic and were generated through moderate to extensive cracking of oil. The C3H8 is residual and was generated earlier from labile (oil-prone) kerogen within the late oil window. The δ13C of the CO2 in the gas is -1.6‰. The relative magnitude of isotopic offset between the CO2 and CH4 in the gas (αCO2-CH4) is 1.03215, a value consistent with a thermogenic origin. Thermal degradation of carbonate minerals in the source rocks is the likely source of CO2 in the gas. The 20Ne/22Ne ratio of 9.461 in the Bluff #1-11 well gas approximates the air ratio of 9.80. Respective 38Ar/36Ar and 21Ne/22Ne ratios of 0.190 and 0.0365 constrain an atmospheric source for the 20Ne and 36Ar components in the produced gas. R/Ra and 20Ne/4He ratios suggest mixing of radiogenic crustal-produced He and Ne with groundwater-transported radiogenic He and atmospheric Ne components. Regional groundwater degassing of 20Ne, 36Ar, and 84Kr is the source of the atmospheric noble gas components in the Bluff well gas.

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Front Range Isotope Group