Abstract
The Woodford–Mississippian “Commingled Production” is a prolific unconventional hydrocarbon play in Oklahoma, USA. The tight reservoirs feature variations in produced fluid chemistry usually explained by different possible source rocks. Such chemical variations are regularly obtained from bulk, molecular, and isotopic characteristics. In this study, we present a new geochemical investigation of gasoline range hydrocarbons, biomarkers, and diamondoids in oils from Mississippian carbonate and Woodford Shale. A set of oil/condensate samples were examined using high-performance gas chromatography and mass spectrometry. The result of the condensates from the Anadarko Basin shows a distinct geochemical fingerprint reflected in light hydrocarbon characterized by heptane star diagrams, convinced by biomarker characteristics and diamantane isomeric distributions. Two possible source rocks were identified, the Woodford Shale and Mississippian mudrocks, with a variable degree of mixing. Thermal maturity based on light hydrocarbon parameters indicates that condensates from the Anadarko Basin are of the highest maturity, followed by “Old” Woodford-sourced oils and central Oklahoma tight oils. These geochemical parameters shed light on petroleum migration within Devonian–Mississippian petroleum systems and mitigate geological risk in exploring and developing petroleum reservoirs.
Highlights
Woodford Shale has been proven to be an excellent source rock charging conventional reservoirs in Kansas and Oklahoma (Comer and Hinch 1987; Burruss and Hatch 1989; Philp et al 1989; Jones and Philp 1990; Comer 1992; Wang and Philp 1997), and a frontier for unconventional resource play exploration and production
Many studies suggest that the Woodford Shale accounts for more than 85% of commercial oil produced from conventional reservoirs in Oklahoma and Kansas (Welte et al 1975; Lewan et al 1979; Reber 1988; Burruss and Hatch 1989), but few publications have shown strong evidence to prove the oils were sourced from the Woodford Shale
Oil samples produced from multiple conventional reservoirs of different ages and extracts of possible source rocks indicated that most of the oils were primarily derived from the Woodford Shale in the Anadarko Basin (Jones and Philp 1990)
Summary
Woodford Shale has been proven to be an excellent source rock charging conventional reservoirs in Kansas and Oklahoma (Comer and Hinch 1987; Burruss and Hatch 1989; Philp et al 1989; Jones and Philp 1990; Comer 1992; Wang and Philp 1997), and a frontier for unconventional resource play exploration and production. Oil samples produced from multiple conventional reservoirs of different ages and extracts of possible source rocks indicated that most of the oils were primarily derived from the Woodford Shale in the Anadarko Basin (Jones and Philp 1990). Burruss and Hatch (1989) undertook a detailed geochemical investigation of 104 crude oils and 190 core samples of dark-colored shales from the Anadarko Basin They identified three oil end members, which generally correlated with the reservoir and source rock age. Data suggest different sources of hydrocarbons, with various thermal maturity stages These data shed light into factors affecting petroleum accumulation in Woodford–Mississippian tight reservoirs such as water-washing and petroleum mixing.
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