The Cotton Valley Group is an Upper Jurassic to Lower Cretaceous sequence of sandstone, shale, and limestone that underlies much of the northern Gulf of Mexico coastal plain from eastern Texas to Alabama.
From a regional perspective, two productive trends of Cotton Valley sandstones are recognized based on sandstone reservoir properties, gas-production rates, and necessity of hydraulic-fracturing treatments to achieve commercial production.
Across northernmost Louisiana, so-called Cotton Valley blanket sandstones have sufficiently high porosity and permeability that commercial rates of gas production can be obtained without artificial well stimulation. South of this area, in northern Louisiana, and extending westward across the Sabine uplift into northeastern Texas, sandstones in the Cotton Valley massive-sandstone trend have poorer reservoir properties and require hydraulic-fracture treatments to achieve commercial rates of gas production.
Because basin-centered, continuous gas accumulations characteristically occur within low-permeability reservoirs, the tight, Cotton Valley massive sandstone trend across northern Louisiana and northeastern Texas is an ideal setting in which to look for potential basin centered gas accumulations. Beginning in 1937 and continuing through the early 1960’s, commercial gas production was established from porous and permeable Cotton Valley Group blanket-sandstone reservoirs across northern Louisiana.
In the 1970’s, gas production from low-permeability, Cotton Valley massive sandstones became commercial as a result of technical advances in hydraulic-fracturing techniques together with significantly higher gas prices. At Bethany field on the Sabine uplift in eastern Texas in 1972, Texaco successfully increased the rate of production from tight Cotton Valley sandstones from 500 MCFD to a sustained rate of 2,500 MCFD and 30 BCPD (barrels of condensate per day) through hydraulic fracturing (Jennings and Sprawls, 1977).
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