Print this pageA New Regional Thermal Maturity and Burial History of the Ft. worth Basin Based from Gas Isotopic and Vitrinite Reflectance Studies
Vitrinite reflectance evaluation of a set of well cuttings over 10 counties of the Ft. Worth Basin demonstrate that the basin has experienced relatively uniform heat flow over the area studied, but that the basin has undergone differential burial and uplift, and it is this burial history that controls the maturity across the basin. Produced gas methane carbon isotopic signatures from a larger set of wells tell the same story of differential burial & differential uplift across the basin, and the methane isotopic signatures can be calibrated and used as a surrogate for measured vitrinite reflectance. This thermal maturation map for the Barnett shale differs from published maturation maps in both degree of maturation and maturation line contours. Moreover, gas composition, as measured by wetness / specific gravity / BTU does not correlate as closely to thermal maturity as the methane isotopic signatures. In parts of the basin, the gas is wetter than expected for its degree of maturation. In the western portion of the basin, this may be related to the absence of the underlying Viola “seal,” leading to methane “depletion” via water dissolution into the underlying Ellenberger aquifer.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009