Abstract: Spiculitic Chert Reservoir Rocks: Glick Field, Kiowa and Comanche Counties, Kansas
James P. Rogers, Mark W. Longman
Glick field, discovered in 1957, has produced more than 362 BCF of gas from Mississippian Osage chert commonly referred to as the "Chat." Other "Chat" reservoirs in Kansas and Oklahoma produce mainly from mixed chert and dolomite beneath the pre-Pennsylvanian unconformity, but Glick field's reservoir is dominated by spiculitic chert. Glick field is a stratigraphic trap with production ending where the spiculitic facies pinches out into tight limestone to the south and west. Updip, to the northeast, the productive spiculitic facies is truncated by the unconformity. Reworked chert conglomerates overlying the spiculitic reservoir at the unconformity also produce minor amounts of gas.
The spiculitic chert forming the reservoir was deposited below wavebase and grades laterally into echinoderm and brachiopod-rich skeletal wackestones and lime mudstones. Even where completely silicified, these associated limestones are tight. They form the lateral seal in the field. Thus, the reservoir is an in situ oval-shaped complex of internally brecciated sponge mats and bioherms capped in part by the chert conglomerate. The spiculitic chert contains up to 50% porosity in molds after sponge spicules, matrix micropores, and vugs coupled with fracture and breccia porosity.
Distribution of the sponge bioherms which form the reservoir facies was partly controlled by a subtle change on the shallow Mississippian carbonate shelf from clean skeletal limestones southward into shaly (and probably more anoxic) carbonates known locally as the "Cowley Facies." This lithologic boundary can be mapped across southern Kansas and provides a potential exploration tool that may help in finding other stratigraphically trapped spiculitic reservoirs in the area.
AAPG Search and Discovery Article #90957©1995 AAPG Mid-Continent Section Meeting, Tulsa, Oklahoma