Geology and Occurrence of Natural Gas in Laramie and Hanna Basins, Wyoming

Abstract

Abstract Eibht small anticlinal gas fields have been discovered in the Laramie and Hanna basins. During Paleozoic time carbonate, evaporite, and clastic sediments were deposited, but none of the Paleozoic rocks have yielded commercial gas. The Mesozoic was a time of repeated marine and continental transitions with predominantly clastic deposition. By the end of the Mesozoic Era recurrent basement uplift, followed by vigorous degradation, caused accumulation of thick sequences of nonmarine Upper Cretaceous rocks in the rapidly sinking Hanna and northern Laramie basins. Early Tertiary deposition followed a similar pattern. Extensive alluviation, periodically affected by regional uplift, tilting, and normal faulting, continued throughout the rest of the Tertiary. Major tectonic features of the Laramie-Hanna basins region are basement controlled; both basins are downwarped asymmetrically and have divergent structural elements. Natural gas has been found only in sandstone reservoirs. Hydrocarbon exploration has been focused on structural traps; stratigraphic drilling is just beginning. Proved natural gas reserves appear minor in comparison to the potential gas reserves in Upper Cretaceous and lower Tertiary rocks, particularly in the Hanna basin.