--> Abstract: Organic Geochemistry of Black Shale and Associated Oils of the Pennsylvanian Hermosa Group, Paradox Basin, Utah and Colorado, by J. L. Clayton and C. Jianyu; #90993 (1993).
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CLAYTON, J. L., U.S. Geological Survey, Denver, CO, and CHEN JIANYU, China University of Geosciences, Wuhan, China

ABSTRACT: Organic Geochemistry of Previous HitBlackNext Hit Shale and Associated Oils of the Pennsylvanian Hermosa Group, Paradox Basin, Utah and Colorado

According to recent estimates, the Paradox basin may contain more than 700 million bbl and 1.3 tcf of producible Previous HitoilNext Hit and gas, respectively. Newly developed horizontal drilling methods may increase the potential for Previous HitoilNext Hit produced from fractured, organic-rich shale in the Paradox Formation of the Hermosa Group. The purpose of this study was to characterize the organic matter contained in the Previous HitblackNext Hit shale, interbedded lithologies, and oils produced from associated reservoir rocks. Total organic carbon (TOC) content of the rocks is from less than 0.2 wt.% in evaporites to as much as about 25 wt.% in some of the Previous HitblackNext Hit shales. TOC content generally increases in the order of evaporites < siltstones < carbonates < Previous HitblackNext Hit shale. Only the carbonate rock and Previous HitblackNext Hit shale contain sufficient OC to have generated and expelled petroleum. Varying proportions of organic matter types I, II, and III are present in the organic-rich Previous HitblackNext Hit shales according to Rock-Eval pyrolysis (hydrogen indexes from 700 to less than 100 mg/g), visual kerogen analyses (amorphous to structured kerogen), and carbon isotope ratios (-23 to -27 o/oo PDB). Analyses of 23 oils from the major producing intervals in the basin indicate variable maturity according to molecular distributions of aromatic hydrocarbons and organosulfur compounds. Source-related differences also are evident among the oils. For example, Cane Creek oils have relatively lower pristane/phytane and tricyclic/pentacyclic terpane ratios than Desert Creek and Barker Creek oils. Understanding the distribution and maturity of the organic sou ce facies, coupled with identification of Previous HitoilTop-source rock correlations, should help define new areas for exploration in the basin.

AAPG Search and Discovery Article #90993©1993 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah, September 12-15, 1993.