Mega Compartment Complex in the Anadarko Basin: A Completely Sealed Overpressured Phenomenon

AL-SHAIEB, ZUHAIR, JAMES PUCKETTE, PATRICK ELY, and AZHARI ABDALLA, Oklahoma State University, Stillwater, OK

Integrated pressure, potentiometric, and geologic data demonstrate the existence of a basin-wide, completely sealed overpressured compartment in the Anadarko basin. All reservoirs within this complex exhibit pressure gradients ranging from 0.6 to 0.98 psi/ft, which exceeds the normal gradient of 0.465 psi/ft. These reservoirs have produced large quantities of natural gas, particularly from the Pennsylvanian Red Fork and Morrowan sandstones.

This mega compartment complex is enclosed by top, bottom, and lateral seals. The top seal, which is located between 8500 and 11,000 ft below the surface, is relatively horizontal, dips slightly to the southwest, and appears to cut across stratigraphy. However, the basal seal is stratigraphically controlled and seems to coincide with the Devonian Woodford Shale. The complex is laterally sealed to the south by the Wichita Mountain uplift frontal fault zone and by the convergence of the top and basal seals along the eastern, northern, and western boundaries.

Nested within this complex is a myriad of smaller compartments with their own distinct pressure gradients. In addition, local overpressured compartments are present outside the mega compartment complex in normal and near-normal pressured regions.

Significant gas fields producing from the Morrow and Red Fork horizons are considered nested compartments within the mega compartment complex. The Southwest Leedey field contains a stratigraphically and/or lithologically sealed Red Fork sandstone compartment. The Upper Morrowan chert conglomerate reservoirs in the Cheyenne field area comprise a compartment with a distinct lateral seal associated with the frontal fault zone of the Wichita Mountain uplift.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)