ABSTRACT: Crude Oil Geochemistry and Exploration: Constraints and Potential

ZUMBERGE, JOHN, and STEPHEN BROWN, GeoMark Research Inc., Houston, TX

In areas where substantial oil production has been established, regional crude oil geochemical studies are excellent ways of identifying, evaluating, and comparing the various petroleum systems that have contributed to reserves. The number of effective source units can be determined by establishing the number of compositionally distinct oil families. Source rock depositional environments or other characteristics for each family and thermal maturity can be deduced, with varying degrees of confidence, based upon bulk and molecular parameters. Information such as source lithology, anoxicity, salinity, and organic input (marine, lacustrine, terrigenous) can often be inferred. In areas of sparse production, geochemical analyses of DST or seep samples can quickly aid in appraising the petro eum potential of frontier basins. Multivariate statistical treatment of the geochemical data will become more common and necessary in oil studies where hundreds of oils are being compared, with a multitude of geochemical parameters like %S, stable carbon isotopes of saturate and aromatic hydrocarbon fractions, -paraffin and isoprenoid distributions, and various sterane and terpane biomarker ratios obtained for each oil. Some problems relate to the data input such as differential weighting, use of all or selected data, and normalizations of various biomarkers. New analytical techniques, such as combined capillary gas chromatography/isotope ratio mass spectrometry, will most likely add even more useful geochemical data that must be integrated with traditional parameters.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)