Chert reservoirs of the Lower Devonian Thirtyone Formation represent a substantial part of the hydrocarbon resource in the Permian Basin. More than 700 million barrels of oil has been produced from these rocks, and an equivalent amount of mobile oil remains.

Canyon sandstones form a prolific low-permeability gas play in the Val Verde Basin of southwest Texas. Exploration and development activity is at a high level, but little published information on Canyon geology is available. Although several geographically and stratigraphically distinct "Canyon" intervals (Upper Pennsylvanian-Lower Permian) are productive, our study focused on characterizing the stratigraphy, diagenesis, and natural fractures of Sonora Canyon sandstones in Sutton County and Ozona Canyon sandstones in Crockett County.