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.

The Tirrawarra Sandstone is the primary producing zone at Tirrawarra field in the Cooper Basin of South Australia, where it contains 146 million barrels (MMbbl) of unrecovered oil. Because previous reservoir models had failed to predict reservoir performance accurately and development drilling had yielded poor results, we undertook this study in order to construct a three-dimensional descriptive model of the Tirrawarra Sandstone reservoir, within which we calculated the volumes and residency of original and remaining oil in place.