Final Report - National Energy Technology Laboratory - U.S. ...

GEOLOGIC SETTING
The Anadarko Basin extends from western Oklahoma to the eastern part of the Texas panhandle. Figure 1
shows the geomorphic or tectonic features that border the basin: the Amarillo Uplift to the southwest, the Wichita-
Criner Uplift to the south, the Arbuckle and Hunton-Pauls Valley Uplift to the southeast, the Nemaha Ridge and
Central Oklahoma Platform to the east, and the Northern Oklahoma Platform to the north. The Anadarko Basin is
asymmetric in profile and deepest along the steep southwestern flank near the Wichita Fault system. Displacement
along this fault exceeds 30,000 feet (Al-Shaieb, et al., 1997a).
One of the deepest basins in the United States, the Anadarko Basin contains over 40,000 feet of Paleozoic
sediments. Figure 2 shows a generalized stratigraphic column of the basin. Hill and Clark (1980) have divided the
deposits into five sequences: 1) a mid-Cambrian Arbuckle to post-Hunton-orogeny period (of mostly carbonate
deposition), with hydrocarbons found mainly in structural traps; 2) Mississippian deposition of carbonates that
formed stratigraphic traps for gas; 3) Pennsylvanian deposition of Morrow-Springer series clastic rocks (mostly in
the northern shelf areas where the sediments were unaffected by orogenic movements in the southern parts of the
basin); 4) post-Morrowan or Late Pennsylvanian deposition of segregated sand lenses; and 5) deposition of lower to
middle Permian dolomitized shelf carbonates and Pennsylvanian Granite Wash sediments.
Formation of the Anadarko Basin began during the collision of Gondwana with the southern continental margin
of Paleozoic North America. Structural inversion of the core of the southern Oklahoma aulacogen into the Wichita
thrust belt caused thrust loading of the region to the north, which subsided and became the Anadarko Basin. Late
Pennsylvanian transpression formed numerous thrust-cored, en-echelon anticlines within the southeastern part of the
basin that were later eroded and overlain unconformably by Permian carbonates. Subsidence of the basin continued
into middle Permian time. The basin has remained quiescent since late Permian time (Perry, 1989).
HYDROCARBON PRODUCTION
Major hydrocarbon production from the Anadarko basin includes gas and oil from multiple Pennsylvanian
reservoirs (Granite Wash, Atoka, Morrow, and Springer Formations). The largest Pennsylvanian Atoka field is the
Berlin in Beckham County, Oklahoma, with an estimated ultimate recovery of 362 BCFG at 15,000 ft depth (Lyday,
1990). Some deep production has occurred from Mississippian through Cambro-Ordovician strata: Washita Creek
field in Hemphill County, Texas, from the Cambro-Ordovician at 24,450 ft depth (single well reserves as high as 24
BCFG); and the Knox field (near the southeastern flank of the basin) from the Ordovician Bromide (Simpson) at
15,310 ft depth (single well reserves as high as 6.2 BCFG).
EVIDENCE FOR BASIN-CENTERED GAS
Strong evidence for a basin-centered gas accumulation is present in the form of thermally mature source rocks,
widespread production and shows of gas, and overpressuring (Figure 3) that cuts across stratigraphic boundaries.
The Woodford shale forms the base of the pressure cell (Figure 4); the top of the cell climbs stratigraphically into
the basin. Vitrinite reflectance values for the Woodford follow this same general trend. The Pennsylvanian Atokan
source rocks may exhibit these same maturation trends.
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