Automated Reconstruction of a Basin Thermal History with Integrated Paleothermometry and Genetic Algorithm

Abstract

Source-rock maturity and the timing and the yield of hydrocarbon generation are key risk factors in many exploration tasks. Therefore, an accurate thermal history model of a source-rock (and thereby the basin) becomes very critical for basins with complex geologic histories.

Traditionally, a basin thermal history has been predicted based on burial history constrained by present-day temperature and organic maturity indicators (e.g. vitrinite reflectance). Recently, new inorganic paleothermometers such as smectite/illite transformation, illite-age analysis, and apatite fission track analysis data provide additional information to further constrain the heating and cooling history. We formulated an automated method of determining the temperature history of source rocks from these organic and inorganic palethermometers. The method uses kinetic models that simulate the effect of thermal history on inorganic palethemometers and a genetic algorithm to search for acceptable thermal histories. The result is a family of thermal histories that are consistent with the paleothermometers and their uncertainty observed from sample rocks and other thermal and geologic indicators.

Patent granted: Patent No. 5,704,713, Jan. 6, 1998