Geochemical Characterization of Woodford Shale Oil and Potential Source Rock
ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, OK, USA
Organic Geochemical Characterization of the Woodford Shale Oil and Potential Source Rocks Recently shale oil has been produced from the immature-to-early-mature Woodford Formation in the Mid-North Cherokee Platform (Oklahoma). These oil samples are medium-to-light oils (40-45oAPI) with no evidence of biodegradation. The producing formation is the Woodford Shale, which is a well-known black shale widespread deposited in the southern mid-continent rich in organic matter (4~12% TOC) with very low porosity (< 1.25%) and low permeability (< 1mDa) leading to the presumption that these oils were generated in-situ. But based on the vitrinite reflectance measurement of the Woodford Shale by Brian Cardott, the thermal maturity of Woodford Shale in the study area is in the range of 0.52% to 0.58% VRo (vitrinite reflectance) corresponding to the immature-to-early-mature range of oil generation. In this study a detailed geochemical investigation of these oil samples and the Woodford core extracts have been carried to evaluate the possible sources of these oils.The C7 light compounds analysis for the oils and core extracts indicated these oils were correlated with the Woodford cores in-situ. The vitrinite reflectance of the Lower Woodford from one well in that area were measured as 0.77% Ro. Pre-oil bitumen and post-oil bitumen were found in the same core sample. The basin analysis indicated the Woodford in mid-north Cherokee platform went into the oil window around 310~305 Ma, which was before the Wichita-Marathon-Orogeny. All of these preliminary results lead to these sweet oils were generated in-situ.
AAPG Search and Discovery Article #90199 © 2014 AAPG Foundation 2014 Grants-in-Aid Projects