Abstract: Use of Vitrinite Reflectance Data in Thermal Maturity Modeling

Mark A. Pasley, Brenda L. Claxton, Joseph C. Faulkerson, David S. Muller, Steve C. Behling

The validity of any thermal maturity and hydrocarbon generation model is best checked by calibration to measured thermal maturity. This process involves comparison of a calculated thermal maturity profile to measured values along that depth profile. Therefore, reliable thermal maturity data are of fundamental importance to the calibration of these models and vitrinite reflectance data are the most suitable form of thermal maturity data. Vitrinite reflectance data are not without problems, however. First, accurate thermal maturity assessment is dependent on high quality, representative sample material. Sample contamination can lead to erroneous data. Models that are calibrated to these data provide misleading results. This problem is best solved using caution in sample selection and pr paration and integration of vitrinite reflectance data with bottom hole temperatures and other thermal maturity data. A second more significant type of problem with vitrinite reflectance data is that these data are indicative of total thermal exposure and, therefore, offer a non-unique solution for modeling the timing of hydrocarbon generation. Models with complex burial histories are more susceptible to the adverse effects of this problem because unconformities often represent unknown amounts of missing section. Integration of various forms of thermal maturity data with regional geologic information is of significant help with this problem but it must ultimately be realized that multiple explanations for

the measured (present day) thermal maturity are plausible. Therefore, the sensitivity of a particular prospect or play to varying hydrocarbon generation history should be tested for proper risk analysis. Examples of both of these problems and their respective consequences will be presented.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994