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A Geochemical Appraisal of the Potential Source(s) of Oils in the STACK and SCOOP Plays in the Anadarko Basin, Oklahoma


The SCOOP and STACK plays in the Anadarko Basin, Oklahoma, have developed rapidly over the past decade into significant oil producing regions. These areas have a long history of oil production for over 100 years from conventional wells and the majority of the oil produced over that time has been ascribed to having a Woodford source. As a result many operators have automatically assumed that the source of the oils in the SCOOP and STACK areas are also sourced primarily from the Woodford with little evidence to support such an origin. Previous work on the Woodford has shown that oils derived from this source have certain very characteristic geochemical features that appear to be absent from the STACK and SCOOP oils. For example conventional Woodford oils contain a series of arylisoprenoids, and depending on level of maturity, carotenoids, that can be associated with green sulfur bacteria prevalent during the deposition of the Woodford under euxinic conditions. In addition the Woodford sourced oils also contain a characteristic terpane signature with both tricyclic and pentacyclic terpanes present. However the STACK and SCOOP oils do not appear to contain the arylisoprenoids and many of the oils are dominated by tricyclic terpanes with an absence of the pentacyclic hopanes. This leads to the question as to whether the geochemical signature associated with oils could result from the maturation of a typical Woodford or represent a different source facies. Data will presented in this paper suggesting that it is unlikely that maturity is the only factor responsible for the characteristic fingerprints of the STACK and SCOOP oils. Various Mississippian source facies in the area have been shown to have similar geochemical characteristics to those observed in the oils. Extracts from certain cores have shown this characteristic fingerprints, dominated by the tricyclic terpanes, at depths between extracts that contain both the tricyclics and pentacyclic terpanes. If maturity was responsible one would expect with increasing depth that the hopanes would be absent in the deeper samples. In summary it is proposed that while in certain areas of the STACK and SCOOP plays the Woodford may be contributing to the source of the oils, in other areas there is probably a significant contribution from Mississippian sources.