ABSTRACT
The carbon isotopic compositions of the wet gas components, particularly propane, isobutane, and normal butane, have been found to be particularly valuable for correlating one reservoired gas with another. The usefulness of these components for correlation results from their carbon isotopic compositions reflecting both the nature of their source and their maturity. This source control is strongest for gases derived from the more highly structured types of kerogen (i.e., woody-coaly; type III), although the wet gas components’ carbon isotopic compositions of most gases are at least partly controlled by their source for levels of maturity below the point at which thermal destruction of the wet components occurs. As a result, the wet gas components are found to provide more positive correlations than is methane alone.
Three exploration examples illustrate the use of the carbon isotopic compositions of the wet gas components for correlation: the Leduc reef trend of Alberta, Canada; the Sleipner area in the North Sea; and the Lena field, offshore Louisiana, United States. The three examples also illustrate the need to integrate geochemical interpretations with regional geology to obtain a good understanding of the hydrocarbon source.
