BERNER, ULRICH, PETER GERLING, and ECKHARD FABER, Federal Institute of Geosciences and Natural Resources, Hannover, Germany

ABSTRACT: Kinetic Models of Carbon Isotope Variations in Methane, Ethane, and Propane in Comparison with Field Data of Europe

Kinetic models of gas generation from primary cracking are used to simulate isotope variations of methane, ethane, and propane during thermal decomposition of different kerogen types, assuming instantaneous Rayleigh fractionation processes. The results of these calculations are used to classify gases from type I, II, and III kerogens. Comparisons with measured data from reservoir gases of Europe are given, also showing possible deviations from the model, due to secondary effects.

Additionally, a mathematical simulation of maturities, using a modified version of the kinetic model of Burnham and Sweeney (1989), is combined with the kinetic isotope fractionation model, allowing the simultaneous calculation of isotope/maturity pairs. The results of this approach are compared to measured isotope data from gas fields of Europe, where the maturities of the source rocks are known. The calculated values excellently approximate the measured field data when secondary effects can be excluded. However, gases affected by secondary alteration deviate from the model.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.