A Geochemical Correlation Study of Oklahoma Crude Oils Using a Multivariate Statistical Method

Scott W. Imbus, Michael H. Engel, John E. Zumberge

Despite significant production in the southern Mid-Continent, organic geochemical characterization of oils and potential source rocks has been limited and, with respect to correlation studies, somewhat inconclusive. In the present study, 46 Oklahoma oils of varying reservoir ages (Cambro-Ordovician to Pennsylvanian-Morrowan) from an extensive geographic area were analyzed for saturate and aromatic hydrocarbon distributions, percent S, and stable carbon isotopic compositions. Eighteen of the oils were analyzed by GC/MS for biological marker compound distributions. Similarities and differences between oils were assessed using multivariate statistical methods.

In general, the majority of oils were mature, of marine origin, and very similar with respect to chemical and stable carbon isotopic compositions. Some differences were, however, observed. In particular, oils from the Oklahoma Panhandle (Pennsylvanian-Morrowan) were enriched in ¹³C and had high Pr/Ph values. Oils from the Marietta basin and the southeast portion of the Anadarko basin (Ordovician) had high n-C₁₉/n-C₁₈ values. With few exceptions, the remaining oils from throughout the state appeared to be identical. Simultaneous R-mode, Q-mode factor analyses confirm these distinctions, and it is tentatively proposed that the Oklahoma oils that have been analyzed to date represent three distinct families. The geographic distributions of these families m y be useful for establishing their respective sources and migration pathways. While the Woodford formation is commonly recognized as the principal source for Oklahoma oils, with organic facies changes accounting for some of the slight differences in oil compositions, other possible local sources as well as the possibility of multiple sources, i.e., mixing, are currently being investigated.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.