Evaluation of Travis Peak gas reservoirs, west margin of the East Texas Basin

Gas production from low-permeability (tight) gas sandstones is increasingly important in the USA as conventional gas reservoirs are being depleted, and its importance will increase worldwide in future decades. Travis Peak tight sandstones have produced gas since the 1940s. In this study, well log, 2D seismic, core, and production data were used to evaluate the geologic setting and reservoir characteristics of the Travis Peak formation. The primary objective was to assess the potential for basinward extension of Travis Peak gas production along the west margin of the East Texas Basin. Along the west margin of the East Texas Basin, southeast-trending Travis Peak sandstones belts were deposited by the Ancestral Red River fluvial-deltaic system. The sandstones are fine-grained, moderately well sorted, subangular to subrounded, quartz arenites and subarkoses; reservoir quality decreases with depth, primarily due to diagenetic quartz overgrowths. Evaluation of drilling mud densities suggests that strata deeper than 12,500 ft may be overpressured. Assessment of the geothermal gradient (1.6 ?F/100 ft) indicates that overpressure may be relict, resulting from hydrocarbon generation by Smackover and Bossier formation potential source rocks. In the study area, Travis Peak cumulative gas production was 1.43 trillion cubic feet from January 1, 1961, through December 31, 2005. Mean daily gas production from 923 wells was 925,000 cubic ft/well/day, during the best year of production. The number of Travis Peak gas wells in ?high-cost? (tight sandstone) fields increased from 18 in the decade 1966-75 to 333 in the decade 1996-2005, when high-cost fields accounted for 33.2% of the Travis Peak gas production. However, 2005 gas production from high cost fields accounted for 63.2% of the Travis Peak total production, indicating that production from high-cost gas wells has increased markedly. Along the west margin of the East Texas Basin, hydrocarbon occurs in structural, stratigraphic, and combination traps associated with salt deformation. Downdip extension of Travis Peak production will depend on the (1) burial history and diagenesis, (2) reservoir sedimentary facies, and (3) structural setting. Potential Travis Peak hydrocarbon plays include: updip pinch-outs of sandstones; sandstone pinch-outs at margins of salt-withdrawal basins; domal traps above salt structures; and deepwater sands.