ABSTRACT

Samples of Devonian-Mississippian age Woodford Shale from Western Oklahoma were studied in terms of the composition of the organic material present.

Geochemical analyses of two cores and six sets of rotary cuttings were performed in order to ascertain whether earlier defined palynological facies could be discerned chemically. Among the parameters examined were C¹³ values, pristane-to-phytane ratios, n-alkane distributions, saturate hydrocarbon distribution, the amount of extractable organic matter present, organic carbon content, and ratios of components of the n-alkanes.

A number of the variables considered exhibit systematic variations which can be attributed to changes in the composition of the organic source material. Four parameters; (1) the n-alkane distribution pattern, (2) the % of C₂₅-C₃₃ in the C₁₅₊ n-alkanes, (3) the ratio C₂₁+C₂₂/C₂₈+C₂₉, and (4) the C¹³ values indicate microfacies scale variation. The variation is from marine material of two groups with differing amounts of terrestrial input. These parameters and one other, the % of n-alkanes in the C₁₅₊ portion of the saturates, also exhibit a pattern of compositional variation. The second variation pattern is on a larger, macrofacies, scale similar to that seen in the earlier mentioned palynological study.

It is concluded that both macro- and microfacies variation exists within the Devonian-Mississippian age Woodford Shale of Oklahoma. Suggestion is made for further study combining both geochemical and palynological investigation.