Application of a Transpressive Tectonic Model to a Shallower Pool Development, Eola Field, Garvin County, Southern Oklahoma
KENDALL, JEROME J., Mobil Oil Corporation, Oklahoma City, OK
The Eola field was initially developed in the 1950s, producing from Ordovician Simpson sand at depths of 11,000 ft to 15,000 ft. Application of a new geologic model has aided the development of the fractured Mississippian Sycamore Limestone and the Devonian Hunton Limestone between 6000 ft and 8000 ft.
A detailed investigation of the field employing an interactive computer-based geologic interpretation system can document two phases of faulting. The most significant was a transpressive deformation, followed by west over east thin-skinned thrusting. The most prominent structure of the Eola field is an east-west-trending overturned syncline anticline pair with the Eola fault cutting through the crest of the anticline. There is 300-500 ft of apparent normal offset on this fault. The basal Oil Creek Formation is a 240-ft-thick oil sand north of the fault. South of the fault the equivalent section becomes a 200-ft-thick brown shale. The Hunton Formation is 250 ft thick north of the fault; south of the fault only the bottom 45 ft of the Hunton exists. These stratigraphic mismatches and th structural inconsistency of an apparently normal fault in a zone of extreme shortening are best explained by incorporating a lateral component of fault motion during compression. The lack of a stratigraphic match within the field implies at least 3-5 km of lateral motion.
Later, west over east thin-skinned thrusting offsets the Eola fault and the anticlinal axis. These late-stage shallow thrusts define the upper limits of producible Sycamore and Hunton reservoir.
AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)