Organic Thermal Maturity Applications to Source Rock Potential Analyses at Phillips Petroleum Company: ABSTRACT

Abstract

The importance of determining accurate organic thermal maturity levels in potential hydrocarbon source rocks cannot be overstated. As important as organic quantity and quality, sufficient thermal alteration of the host rock must occur to convert the organics to hydrocarbons. In the author's laboratories the two most important criteria for determining the thermal alteration level of a rock sample are measuring its mean random vitrinite reflectance and estimating the spore coloration index (i.e., thermal alteration index, TAI) of plant spores and pollen present. An additional thermal maturity indicator is the fluorescence intensity of the oil-prone kerogen present. These three maturity criteria are microscopically derived measurements made on the concentrated kerogen (i.e., insoluble organics) recovered from rock samples after acidification. Source rock analysts have generally accepted a scale force relating vitrinite R{sub 0} (reflectance in immersion oil) and TAI to four thermal maturity stages: (1) immature for oil generation, (2) early oil generation, (3) peak oil generation, and (4) dry gas to overmature for hydrocarbon generation. These maturity data, when combined with the kerogen type and relative abundance, and then merged with the quantitative TOC and pyrolysis results, constitute Phillips' basic hydrocarbon source rock potential technique. This procedure is considered to bemore » an accurate measure of source rock potential and is further enhanced when all the data (as many as 24 values) are evaluated by their licensed artificial intelligence program, Source Rock Advisor. This PC-driven computer program generates a totally standardized and reproducible source rock evaluation.« less