Compaction correction for burial history curves: application to Lopatin's method for source rock maturation determination

Source rock maturation is a critical parameter required when evaluating the ability to generate hydrocarbons. Vitrinite reflectance, TAI values, etc. are not always available, in which case time-temperature maturity models can be used for predicting both hydrocarbon generation and preservation. Lopatin's (1971) time-temperature method of calculating source rock maturation requires a reconstruction of the local depositional and tectonic history. Waples (1980) suggested plotting depth of burial versus geological age. However, the present day thickness should be corrected for compaction since each geological unit was thicker in the past and has been compressed by loading to its present thickness. A method, requiring knowledge of the lithologies overlying the source rock and utilizing a reverse calculation iterative matrix, has been developed that corrects the burial history curve for the effects of compaction through geological time. Corrected time-temperature index values (CTTI) are calibrated using known maturity data from a variety of wells. A number of uncorrected burial history curves have been compared to burial history curves that were corrected for compaction. The effect of correcting curve for compaction is that the source rock horizon subsides more rapidly; thus the calculating timing of oil and gas generation is consistently earlier when the correction ismore » applied to Lopatin's method.« less