ABSTRACT: Three Levels of Compartmentation within the Overpressured Interval of the Anadarko Basin

AL-SHAIEB, Z., J. PUCKETTE, A. ABDALLA, and P. ELY, Oklahoma State University, Stillwater, OK

Deep basin pressure compartments can be classified on the basis of their size, stratigraphy, and pressure regimes. Detailed investigations of the geologic setting and pressure gradients of numerous reservoirs in the Anadarko basin reveal the presence of three distinct levels of compartmentation.

Level 1 is a basin-wide feature known as the mega-compartment complex (MCC). This complex is an overpressured volume of rocks that is completely enclosed by seals. It is approximately 150 mi long and 70 mi wide and has a maximum thickness in excess of 16,000 ft. Gas reserves of the overpressured reservoirs within the MCC are speculated to be approximately 30 tcf. The other two compartmentation levels are further subdivisions of the internal volume of the MCC.

Level 2 compartmentation consists of multiple, field-sized configurations within a particular stratigraphic interval. These compartments are 20 to 30 mi long, 12 to 20 mi wide, and 400 to 600 ft thick. Their reserve estimates can exceed 2 tcf. An example of this type is the Upper Morrowan Chert Conglomerate reservoirs in the Cheyenne/Reydon field area.

Level 3 consists of a single, small field or a particular reservoir nested within Level 2. These compartments are generally 2 to 4 mi long, <1 to 3 mi wide, and 10 to 100 ft thick. Reserve estimates range from <1 to several hundred bcf. Examples include the Southwest Leedey Red Fork field and the individual channel-fill reservoirs of the "Pierce" chert conglomerate.

The integration of tectonic history, stratigraphic relationships, facies distribution, thermal history, and diagenetic patterns of seal zones suggests that the three levels of compartmentation evolved during the Pennsylvanian orogenic episode. This occurred during the rapid subsidence phase of the orogeny over a period of approximately 30 million years.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)