Implications of Stratigraphic Variability of Source Rock

KATZ, BARRY J., et al., Texaco Inc., Houston, TX

There has been substantial progress in organic geochemistry over the past two decades in the realms of geochemical modeling and analytical methods. However, little attention has been paid by geochemists to the natural variability of the geologic system. An examination of several stratigraphic units from South America, North America, and southeast Asia reveal that variations in depositional conditions control how the source rock intervals are distributed as well as the character of the organic matter and the nature of the products generated upon thermal maturation.

The distribution of organic-rich sequences within a source unit impact the quantity of hydrocarbons generated as well as the expulsion efficiency. Variations within the organic-rich units directly impact both the quantity and character of the generated products. Variations in product can be substantial enough to question many proposed oil-to-source rock correlations. The available data clearly indicate the need for more geologically controlled geochemical sampling programs.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)