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Characteristics of Mississippian Production in the Northwestern Anadarko Basin
Rocks of Mississippian age are important sources of oil and gas in the northwestern Anadarko basin. The most important reservoirs are limestones and dolomites of the St. Louis and Spergen-Warsaw formations, Meramecian in age, and limestones of the Chester. Lenticular sandstones in the lower part of the Chester and limestones in the Ste. Genevieve formation, youngest Meramecian, also afford minor production. Stratigraphic traps in a weathered cherty mantle at the top of the Osagean yield both oil and gas high on the flanks of the basin.
Production from Chesterian strata is principally gas and is widespread in the basin. Accumulation is generally found in stratigraphic traps where secondary porosity has been developed in proximity to the truncating post-Mississippian–pre-Pennsylvanian unconformity. Oil production from Meramecian strata is confined to the northern flank of the basin near the truncated wedge edges of the St. Louis and Spergen-Warsaw formations. However, good showings of both oil and gas have been reported from other portions of the basin. The Spergen-Warsaw yielded considerable oil in the discovery well in the Lips field, Roberts County, Texas, deep in the basin.
Although Meramecian production to date has been found on closed anticlinal structures, the development of secondary porosity through leaching by percolating ground waters and dolomitization during the long period of erosion in late Mississippian or early Pennsylvanian time plays an equally important role.
Prospects for additional profitable discoveries of both oil and gas in Chesterian, Meramecian and Osagean strata appear to be very good. Chesterian discoveries will undoubtedly be made in stratigraphic traps in many parts of the basin where favorable porosity and permeability are found near the truncated top of the series. Additional discoveries of oil and/or gas, not only in structural but in stratigraphic traps, will be made in the Meramecian St. Louis and Spergen-Warsaw formations. The cherty mantle at the top of the Osagean is expected to yield discoveries high on the flanks of the basin where the Keokuk-Burlington formations have been weathered.
In the past, drilling usually has been suspended after penetrating the Chester approximately 100 feet. Although the importance of production from the lower Chesterian and the Ste. Genevieve remains to be demonstrated, discovery of such production will result in more wells penetrating the entire Chesterian section into the Meramecian. Lenticular sandstones in the Kinderhookian, the only Mississippian series not yet productive, offer real promise for discovery in the northwestern Anadarko basin.
Considerable Mississippian production, particularly in the Meramecian, has been found on local closed structure as a result of seismic, surface or core hole mapping. However, careful, detailed subsurface studies of regional structure, stratigraphy, facies and geologic history are mandatory to assure that exploration is carried on in the most promising areas.
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