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.