An Overview of Selected Blanket-Geometry, Low-Permeability Gas Sandstones in Texas

Abstract

Major blanket-geometry, low-permeability gas sandstones in Texas include the Cotton Valley sandstone, the Travis Peak Formation, the Cleveland formation, and the Olmos Formation. The Cotton Valley (Upper Jurassic) and the Travis Peak (Lower Cretaceous) are widespread, sand-rich units within the East Texas basin that contain marginal marine deltaic, barrier-strandplain, and fan-delta facies. Gas production from the Cotton Valley is more extensively developed than from the Travis Peak, in part because today's hydraulic fracturing technology was either developed or improved during completion of Cotton Valley tight gas reservoirs. The Pennsylvanian Cleveland sandstone of the Anadarko basin is in a mixed gas and oil to somewhat gas-prone province wherein the Cleveland produces gas from thin, distal deltaic facies or prodelta sediments reworked by shelf processes. Clay is abundant in the fine to very fine sandstone of the Cleveland. The Upper Cretaceous Olmos Formation contains gas within broadly lenticular delta-front deposits of the Maverick basin. The Olmos contains fine-grained to very-fine-grained silty sandstones within massive shales. In 1980 tight gas sandstones accounted for 28% of gas wells completed in the 5,000- to 15,000-ft-depth range in Texas. Most of the completions in blanket-geometry hydro-pressured sandstones were within the formations reviewed herein.