ABSTRACT: Red Oak and Fanshawe Sands: Two Submarine-Fan Channel Tight-Gas Reservoirs in a Complex Thrust Belt, Arkoma Basin, Oklahoma

Laura L. Wray

Pennsylvanian-Atokan-age sedimentation and subsequent structural development of a foreland thrust belt have created traps for large hydrocarbon accumulations in the Arkoma basin in eastern Oklahoma and western Arkansas. Red Oak field, located in Latimer and Leflore counties in Oklahoma, is the largest dry gas reservoir in the basin. The middle Atokan Fanshawe and Red Oak sands are the two dominant clastic reservoirs and have produced 800 bcf of gas to date.

The submarine-fan-channel depositional origin proposed for these two sands is supported by sedimentary structures visible in cores, petrologic evidence, and the three-dimensional distribution of sands. Variations in these criteria exist between the Red Oak and Fanshawe sands, representing the evolutionary development of the Arkoma basin that affected sediment discharge, transport mechanisms, and sea level fluctuations.

Convergent tectonism along the Ouachita orogenic belt resulted in the development of Atokan thrust imbricates in Red Oak field. Thrust repetition of Fanshawe and Red Oak sands increases reservoir thicknesses in a given well bore but necessitates the palinspastic restoration of these imbricates in order to reconstruct the original depositional trends of these sinuous, anastomosing fan channels.

Field-wide correlation of these stacked channels is impossible. Petrologic studies have failed to provide depositional or diagenetic criteria for distinguishing sedimentary episodes during fan development. Isopach maps of the total clean sand intervals have been utilized successfully to maximize reservoir thicknesses in 45 infill well locations.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990