Mathematical model of oil generation, degradation, and expulsion

The authors present a mathematical model (PYROL) for simulating oil generation, degradation, and other chemical reactions occurring during pyrolysis of petroleum source rocks over a specified history of temperature and hydrostatic pressure. The model also simulates compaction of the source rock and expulsion of a liquid water phase, a hydrocarbon-rich liquid phase, and a vapor phase. The governing equations for PYROL consist of the time derivatives of 150 variables: 32 vapor species, 32 liquid species, 19 solid species, and 67 other variables (including pore pressure, pore volume, and diagnostics). These ordinary differential equations are expressed in terms of 100 chemical reaction rates and 32 vaporization/condensation relations. A modified Redlich--Kwong--Soave equation of state is used in calculating the vapor/liquid equilibria and PVT behavior.