Abstract: Indirect Prediction of Underlying Tertiary Marine Source-Rock Facies from Biomarkers in Oils, Condensates, and Seeps
HUIZINGA B. J., M. A. MCCAFFREY, D. E. NEDLAND, and S. ROTH
Prediction of relative oil versus gas potential is a critical component of exploration evaluation, due to the often differing economics for these hydrocarbon products. The gas/oil ratio in any accumulation is dependent on a number of geologic factors, including source-rock facies, thermal maturity and timing of trap filling, and secondary alteration.
To better evaluate source quality, we have developed a tool for predicting Tertiary marine source-rock facies indirectly from biomarkers in oils, gas condensates, or seeps. The source facies (i.e., average HIinitial) within the fetch area of a specific hydrocarbon occurrence can be predicted using: (a) the measured C35-hopane index of the hydrocarbon liquid and (b) a Tertiary marine source-rock calibration curve (plot of C35-hopane indices versus HIinitial) developed for Para-Tethyan basins (Carpathians, Black Sea) and the Pacific Far-East (Sakhalin Island). These indirect source-facies predictions from hydrocarbon liquids are complementary to conventional source-rock mapping, but have the added advantage of providing information in areas where the underlying source rocks are not available for direct characterization.
Based on our indirect predictions from hydrocarbon liquids in Para-Tethyan basins, excellent oil-prone source facies occur in the Carpathians (Romania), South Caspian (Azerbaijan-Turkmenistan), and offshore NW Black Sea (Romania); marginal mixed oil-gas to mostly gas-prone facies are present in the Taman Peninsula (Russia); and mostly gas-prone facies occur in the Thrace basin (Turkey). For Sakhalin Island, the predicted Tertiary marine source facies vary widely from oil-prone in the eastern offshore, changing progressively to mostly gas-prone in the far western onshore.
AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria