Calculated separations of carbon isotopes between the normal alkane components of a natural gas have been related to source rock maturity by use of a single, continuous diagram, independent of source type. Actual data confirm this relationship and demonstrate applicability to the source rock Levels of Organic Metamorphism ranging from 8 to 13, covering the entire range of oil and wet-gas generation. At greater maturities, the wet-gas components undergo thermal degradation, losing their usefulness for correlation. These examples showing indigenous gas (West Texas), non-indigenous gas (Gippsland Basin, Australia), and gas mixtures from multiple sources (southeastern Alberta) illustrate exploration applications.--Modified journal abstract.

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