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Estimates of Oil
Generation
Temperature Based on a Kinetic Recalibration of Heptane
Distributions
Requejo, A.G., Geochemical Solutions International, The Woodlands, TX
Thermal maturity
estimates of the generation temperature of oils and condensates based on the heptane (C7) ratio 2,4-dimethylpentane/2,3-dimethylpentane
(2,4-DMP/2,3-DMP) have become an industry standard. This ratio is thought to be
independent of source rock heating rates, age, kerogen
type and lithology. However, application to gas
condensates or fluids generated at high heating rates often yield anomalously
low temperatures, suggesting some dependence on source type as well as rate of
heating. A kinetic-based re-calibration of the 2,4-DMP/2,3-DMP
ratio is proposed that accounts for variations in heating rates and
incorporates source rock type based on fluid chemistry. Its application to
thermal classification of oils and condensates in various offshore hydrocarbon
basins is demonstrated, including