--> Geochemistry of Oil-Bearing Fluid Inclusions Insight Into Hydrocarbon Charge in Devonian-Mississippian Petroleum Systems, Anadarko Basin

AAPG ACE 2018

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Geochemistry of Oil-Bearing Fluid Inclusions Insight Into Hydrocarbon Charge in Devonian-Mississippian Petroleum Systems, Anadarko Basin

Abstract

Devonian-Mississippian unconventional reservoirs in Oklahoma comprise one of the most hydrocarbon prolific geologic formations. Variation in produced crude-oil geochemistry is commonly observed in hydrocarbons produced from Woodford Shale and Mississippian Mermac carbonates within the Anadarko Basin. In this study, we compare produced crude-oil composition with oil-bearing fluid inclusions with the aim to better constrain the history of petroleum migration timing and reservoir filling. The micron-sized oil inclusions provide valuable evidence of paleo-oil composition, source rock contributions and episodes of hydrocarbon charge. Such results are a valuable input to calibrate and constrain basin models simulating hydrocarbon generation and migration.

A collection of oil-inclusions and produced crude-oil were examined in this study. Oil-inclusion were observed in core samples from number of counties including, Canadian, Blaine, Kingfisher and Logan. They are primarily contained in calcite filling fractures within the Mississippian limestone. Oil-inclusions were extracted with organic solvents then analyzed along with crude-oil samples using Gas Chromatography-Flame Ionization Detector (GC-FID), Gas Chromatography–Mass Spectrometry (GC-MS) technique, together with Gas Chromatography–Triple Quadrupole Mass Spectrometry (GC-MSQQQ).

Geochemical composition of the oil-bearing fluid inclusions suggests different hydrocarbon sources, and most notably different thermal maturity level. Oil inclusions in Blaine Co. are the most mature with the methylphenanthrene index and triaromatic steroids ratios suggesting a late-oil to condensate level, which is equivalent to 0.9-1.1 %Ro. Whereas, inclusions in Logan Co. are marginally mature at the early-oil window stage. These observations suggests episodic hydrocarbon charge in areas within the Anadarko-Shelf. Additionally, distribution of biomarkers distribution varied through the fluid-inclusions. For example, a sample from Logan Co. is enriched in extended tricyclic terpaens, which is a geochemical signature known to be diagnostic of Mississippian carbonate source rock and associated crude-oil. [Office1] The knowledge gained from the fluid-inclusions geochemistry will be used to constrain hydrocarbon migration in a basin modeling workflow.