The modelling of carbon isotope kinetics and its application to the evaluation of natural gas

The modelling of carbon isotope kinetics of natural gas is a leading research direction in oil and gas geochemistry at home and abroad. Combined with basin sedimentary burial and geothermal histories, the modelling of carbon isotope kinetics provides a new and effective means for evaluating the origin and accumulation history of natural gas pools. In this paper, we briefly introduce the modelling of carbon isotope kinetics of natural gas formation and its applications to the assessment of natural gas maturity, the determination of gas source, the history of gas migration and accumulation, and the oil-gas ratio. We show that this approach is of great value for those applications. The carbon isotopic characteristics of natural gas are not only affected by gas source and maturity, but also are related to accumulation conditions and the geothermal gradient in a basin. There are obvious differences in the characteristics of carbon isotope ratios between instantaneous gas and cumulative gas. The kinetic model of carbon isotope fractionation may be different for different basins, which depends on gas source condition, accumulation history and sedimentary-tectonic history. Since the origin of natural gas pools in the superposed basins of our country is very complicated, and because natural gas pools have features of multiphase and variable gas-sources, this paper may provide new thoughts for the study and evaluation of natural gas.