Effects of source, thermal maturity, and biodegradation on the distribution and isomerization of homohopanes in petroleum

Rearranged hopanes in sediments and petroleum

Detailed biomarker and light hydrocarbon geochemistry confirm that the marine Mississippian Barnett Shale is the primary source rock for petroleum in the Fort Worth Basin, north-central Texas, although contributions from other sources are possible. Biomarker data indicate that the main oil-generating Barnett Shale facies is marine and was deposited under dysoxic, strong upwelling, normal salinity conditions. The analysis of two outcrop samples and cuttings from seven wells indicates variability in the Barnett Shale organic facies and a possibility of other oil subfamilies being present. Light hydrocarbon analyses reveal significant terrigenous-sourced condensate input to some reservoirs, resulting in terrigenous and mixed marine-terrigenous light hydrocarbon signatures for many oils. The light hydrocarbon data suggest a secondary, condensate-generating source facies containing terrigenous or mixed terrigenous-marine organic matter. This indication of a secondary source rock that is not revealed by biomarker analysis emphasizes the importance of integrating biomarker and light hydrocarbon data to define petroleum source rocks. Gases in the Fort Worth Basin are thermogenic in origin and appear to be cogenerated with oil from the Barnett Shale, although some gas may also originate by oil cracking. Isotope data indicate minor contribution of biogenic gas. Except for reservoirs in the Pennsylvanian Bend Group, which contain gases spanning the complete range of observed maturities, the gases appear to be stratigraphically segregated, younger reservoirs contain less mature gas, and older reservoirs contain more mature gas. We cannot rule out the possibility that other source units within the Fort Worth Basin, such as the Smithwick Shale, are locally important petroleum sources.

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Oil and gas geochemistry and petroleum systems of the Fort Worth Basin

https://deepblue.lib.umich.edu/bitstream/handle/2027.42/29445/0000527.pdf?sequence=1

Sulfur speciation in heavy petroleums: Information from X-ray absorption near-edge structure

Selective biodegradation of extended hopanes to 25-norhopanes in petroleum reservoirs. Insights from molecular mechanics

Etude de la composition chimique et de la maturation d'huiles provenant du Bassin Adriatique afin d'etablir des correlations entre la nature des huiles et les roches meres. L'etude experimentale est realisee en combinant l'utilisation de marqueurs biologiques et l'analyse des isotopes stables

C. Y. Lee

Papers

Source correlation and maturity assessment of select oils and rocks from the central Adriatic Basin (Italy and Yugoslavia)