--> Abstract: Elevated Thermal Maturation in Pennsylvanian Rocks, Cherokee Basin, Southeastern Kansas: Importance of Regional Fluid Flow, by K. M. Wojcik, C. E. Barker, R. H. Goldstein, and A. W. Walton; #91004 (1991)
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Elevated Thermal Previous HitMaturationNext Hit in Pennsylvanian Rocks, Cherokee Basin, Southeastern Kansas: Importance of Regional Fluid Flow

WOJCIK, K. M., University of Kansas, Lawrence, KS, C. E. BARKER, U.S. Geological Survey, Denver, CO, and R. H. GOLDSTEIN and A. W. WALTON, University of Kansas, Lawrence, KS

Thermal history of sedimentary basins is commonly assumed to be dominated by burial heating. Marked contrast between reconstructed burial temperatures and other temperature determinations would suggest alternative processes. In the Cherokee basin of southeastern Kansas, reconstruction of burial and thermal history indicates that basal Pennsylvanian strata were not buried more than 1.8 km, and should have reached only about 90 degrees C. However, our study of Pennsylvanian rocks of the Cherokee basin indicates that higher temperatures were reached and that the pattern of thermal Previous HitmaturationNext Hit is inconsistent with simple burial heating.

Regional pattern of vitrinite reflectance reveals several "warm spots" where thermal Previous HitmaturationNext Hit is elevated above the regional background. Rvalues in warm spots reach 0.9-1.5%; background values average 0.7%. These values correspond to temperatures of 110 degrees C on a regional level to >150 degrees C in warm spots. Rock-Eval pyrolysis confirms the vitrinite data; average T(max) of 436 degrees C is equivalent to R(m) of 0.65%. Over a thickness of 600 m, vitrinite data show a very low vertical gradient. However, in individual wells, closely spaced values exhibit high spikes that may show an increase from 0.65 up to 1.36% R(m) over only a 6 m interval.

Primary fluid inclusions in late Ca-Mg-Fe carbonate cements yield homogenization-temperature modes or petrographically consistent populations ranging from 100 to 150 degrees C. These data suggest that the samples experienced at least those temperatures, hence fluid inclusions closely agree with vitrinite and Rock-Eval.

Elevated temperatures, warm spots, confined thermal spikes, and a low R(m) gradient argue against simple burial heating. These observations are consistent with regional invasion of warm fluids, probably from the Ouachita-Arkoma system, and their subsequent upward migration into Pennsylvanian strata through faults and fractures. Petroleum exploration should consider the possibility of regionally elevated thermal Previous HitmaturationTop levels with even more elevated local maxima. Consequences may include local generation of hydrocarbons or local changes in diagenetic patterns.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)