The Cotton Valley Group, which extends from South Texas to the Florida panhandle across the US Gulf Coast, could contain undiscovered mean volumes of 14 million bbl of oil, 430 bcf of conventional gas, 34,458 bcf of continuous gas, and a total of 391 million bbl of natural gas liquids, according to United States Geological Survey’s (USGS) most recent assessment.
The study identified four assessment units (AU) in the Cotton Valley Group in the Upper Jurassic-Cretaceous-Tertiary Composite total petroleum system for the onshore lands and state waters of the Gulf Coast. The potential reservoirs include fluvial-deltaic and shallow-marine sandstones of moderate-to-high porosity. The agency reported the Upper Jurassic Smackover, Haynesville, and Bossier formations were likely sources of oil and gas. The USGS defined the following AUs in its study:
• Cotton Valley Updip Oil (1 million bbl of oil).
• Cotton Valley Peripheral Fault System Oil and Gas (2 million bbl of oil).
• Cotton Valley Downdip Oil and Gas (11 million bbl of oil).
• Cotton Valley Tight Sanstones Gas (34,028 bcf).
Mean conventional and continuous gas resources are 430 bcf and 34,028 bcf, respectively. According to the USGS, seals are intraformational mudstone or thin limestone, and the Knowles Limestone is a regional seal. Traps are stratigraphic, structural, or in combination, but low-permeability reservoirs can retain petroleum in the absence of well-defined closures.