Determination of Kinetic Parameters Specific for a Given Source Rock: Optim Method

Philippe Ungerer, Pierre-Yves Chenet

The OPTIM method consists of processing pyrolysis data in order to obtain an optimized set of kinetic parameters which account for the kinetics of hydrocarbon formation from the specific source rock considered. The basic principles of the underlying kinetic model are the same as the Tissot and Espitalie model, in which the number of parallel reactions has been increased. The first way to use the OPTIM program is to use Rock-Eval pyrolysis data from a unique immature kerogen sample at various heating rates. Additional data obtained from autoclave pyrolysis may be integrated optionally. This way is particularly adapted to early stages of basin exploration, when the source rock is already identified but not sampled in the oil formation zone. As shown in cases where the predi tions could be checked against well data, the model optimized by this way is applicable to natural conditions with a reasonable accuracy. The second way to use the program is to integrate pyrolysis data from several immature and mature samples of the type considered, together with the thermal history of each sample. Such a use of the program is possible only when the basin is already well explored and when the paleotemperatures do not suffer high uncertainties. The advantage of the method is then to account explicitly for the natural maturation process. Several application examples are presented which show very important differences of behavior between various source rocks, from a kinetic as well as from a quantitative viewpoint. Our method provides the industry with an operational and r latively rapid tool in order to account for these differences.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.