Abstract

Glick Field, located in Kiowa and Comanche counties of southern Kansas, was discovered in 1957 and has produced more than 362 BCF 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 chert containing abundant sponge spicules. Glick Field is partly a stratigraphic trap with production ending where the spiculitic facies pinches out into tight limestones to the south and west which provide a lateral seal. Updip, to the northeast, the productive facies is truncated by the unconformity. Reworked chert conglomerates overlying the spiculitic reservoir at the unconformity also produce some gas.

The spiculitic chert forming the reservoir was deposited below storm wavebase and grades laterally in all directions into echinoderm and brachiopod-rich skeletal wackestones and lime mudstones. Even where completely silicified, these associated limestones are tight. 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 connected in part by 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." The sponge bioherms formed most commonly just updip from this boundary which can be mapped across southern Kansas. Thus, lithologic mapping provides a potential exploration tool with which to find other stratigraphically trapped spiculitic reservoirs in the area.