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Abstract: Abstract: Petroleum Source-Rock Potential of Arbuckle Group (Cambrian-Ordovician), Oklahoma

A. Lynn Cardwell

Oil and gas have been produced from the Cambrian-Ordovician Arbuckle Group in the Mid-Continent for more than 50 years, but to date no satisfactory answer has been offered for the question of whether or not petroleum source beds are present within the group. The answer is important in determining whether significant petroleum can be expected in this thick and relatively unexplored section of carbonate rocks.

Detailed studies of the composition of oils produced from Arbuckle reservoirs compared with those from Pennsylvanian reservoirs showed no discernible differences. These studies, which included determination of the composition of gasoline-range hydrocarbons and C+15 saturated hydrocarbons, and the gross composition of the whole oils, strongly suggest that very similar source beds generated all the oils. Additional studies of the composition of the bitumen present in nonreservoir Arbuckle rocks showed very distinct hydrocarbon differences between the oils and rock bitumens. The Arbuckle rocks apparently were not the source beds for any of the oils investigated in this study, however, Pennsylvanian shales could have been important.

Further studies of the thermal maturity and organic richness of the Arbuckle rocks by use of pyrolysis-gas chromatographic methods revealed that, in most of Oklahoma, the Arbuckle section is thermally mature but is deficient in organic matter. The sparsity of organic matter apparently is the reason that the Arbuckle Group has not acted as a significant petroleum source. The lack of adequate source beds within the Arbuckle section indicates that significant amounts of petroleum cannot be expected far below the top of that unit unless there are other source beds in favorable position (i.e., a fault contact can be demonstrated).

AAPG Search and Discovery Article #90969©1977 AAPG-SEPM Rocky Mountain Sections Meeting, Denver, Colorado