--> ABSTRACT: Western Tight Gas Carbonates: Comparison of Council Grove Group, Panoma Field, Southwest Kansas and Western Low Permeability Sandstones, by Alan P. Byrnes, Martin K. Dubois, and Michael Magnuson; #90906(2001)
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Alan P. Byrnes1, Martin K. Dubois1, Michael Magnuson1

(1) Kansas Geological Survey, Lawrence, KS

ABSTRACT: Western Tight Gas Carbonates: Comparison of Council Grove Group, Panoma Field, Southwest Kansas and Western Low Previous HitPermeabilityNext Hit Sandstones

The Hugoton natural gas area of southwest Kansas has produced over 27 Tcf of gas from the Hugoton, Panoma, Bradshaw, Greenwood, and Byerly fields. Of this total, over 2.7 Tcf have been produced since 1968 from low-Previous HitpermeabilityNext Hit carbonates of the Lower Permian Council Grove Group, Panoma Field. Previous research has documented low-Previous HitpermeabilityNext Hit gas sandstone properties. Council Grove low Previous HitpermeabilityNext Hit carbonates illustrate the universality of certain low-Previous HitpermeabilityNext Hit rock properties and provide insight into lithologic controls on reservoir properties.

Like Mesaverde Group and Frontier Formation low-Previous HitpermeabilityNext Hit sandstones and siltstones (medium to very fine grained, massive to flasier bedded, litharenite to sublitharenite), Council Grove limestone porosity and Previous HitpermeabilityNext Hit decrease with decreasing grain size (grainstone to mudstone) and increasing shalyness. In situ carbonate porosities average 0.5 porosity percent less than routine porosities compared with approximately 0.8 porosity percent less in sandstones. In both groups in situ Klinkenberg Previous HitpermeabilityNext Hit (ki) exhibits similar increasing difference from routine air Previous HitpermeabilityNext Hit (kair) with decreasing Previous HitpermeabilityNext Hit. For kair<1 millidarcy: log10ki=1.5(+0.1) log10kair - 0.3(+0.1). Both also exhibit the characteristic exponential or cube root core Previous HitpermeabilityNext Hit decrease with increasing confining stress from routine to in situ stress conditions.

Both groups of low-Previous HitpermeabilityNext Hit rocks exhibit decrease in "irreducible" water saturation (Swi) with increasing ki. Differences in the slope of a log Swi-logki correlation are consistent with differences in clay content and distribution. Comparison of carbonate and sandstone rocks indicate that many low-Previous HitpermeabilityTop petrophysical properties are "universal" and indicate the moniker "tight gas" isn't just for sandstones anymore.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado