Burial and thermal history of the Paradox Basin, Utah and Colorado, and petroleum potential of the Middle Pennsylvanian Paradox Formation

Abstract

The Ismay-Desert Creek interval and Cane Creek cycle of the Alkali Gulch interval of the Middle Pennsylvanian Paradox Formation in the Paradox Basin of Utah and Colorado contain excellent organic-rich source rocks having total organic carbon contents ranging from 0.5 to 11.0 percent. The source rocks in both intervals contain types I, II, and III organic matter and are potential source rocks for both oil and gas. Organic matter in the Ismay-Desert Creek interval and Cane Creek cycle of the Alkali Gulch interval (hereinafter referred to in this report as the "Cane Creek cycle") probably is more terrestrial in origin in the eastern part of the basin and is interpreted to have contributed to some of the gas produced there. EVOLUTION OF SEDIMENTARY BASINS-PARADOX BASIN O2 The area around Hermosa, Colo., in the southeastern part of the basin, has experienced a shallower burial history than the other areas in the basin, yet it has one of the highest thermal maturities. Here, the Ismay-Desert Creek interval and Cane Creek cycle have vitrinite reflectance values of 1.58 and 1.63 percent and were buried to 13,700 ft and 15,500 ft, respectively. Due to Tertiary igneous activity in this part of the basin, a variable heat flow is proposed: from 600 to 30 Ma, 45 mWm-2 ; from 30 to 25 Ma, 63 mWm-2 ; and from 25 Ma to present, 50 mWm-2. Significant petroleum generation began at 72 Ma for the Ismay-Desert Creek interval and at 76 Ma for the Cane Creek cycle.