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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 7. (July)

First Page: 1363

Last Page: 1363

Title: Organic Geochemistry and Petroleum Exploration--Problems?: ABSTRACT

Author(s): Leigh C. Price

Article Type: Meeting abstract


Results of organic-geochemical studies of deep well bores contradict current concepts on the generation, maturation, and thermal destruction of hydrocarbons. Main-phase hydrocarbon generation (high bitumen coefficients) apparently occurs between 190 and 250°C in Lower Cretaceous to Devonian rocks in five separate well bores. In these same rocks, the kerogen still retains high values of pyrolyzable hydrocarbons normalized to organic carbon. All five well bores have had higher than 250°C paleotemperatures. These results indicate that much higher temperatures than those commonly accepted are required for the complete generation and thermal destruction of hydrocarbons. Other results from these studies contradict the following accepted organic-geochemical trends vers s depth: (1) maturation of saturated hydrocarbons; (2) the S1/S1 + S2 ratio (S1 = extractable bitumens and S2 = pyrolyzable hydrocarbons per thermal analysis); (3) the temperature at the maximum of the S2 peak; (4) the thermal phaseout of C15 + hydrocarbons; and (5) correlation of elemental kerogen composition and vitrinite reflectance with extractable and pyrolyzable hydrocarbons. Laboratory duplication of generation-maturation reactions in closed, pressurized, water-wet systems shows that the controlling parameters of these reactions are not as described in the accepted mathematical formulas modeling these reactions. Concepts concerning the generation and thermal destruction of hydrocarbons apparently have bee greatly oversimplified.

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