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Evaluation of Travis Peak gas reservoirs, west margin of the East Texas BasinLi, Yamin 15 May 2009 (has links)
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.
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