Development of a detailed model of petroleum formation, destruction, and expulsion from lacustrine and marine source rocks

A variety of laboratory experiments, including programmed micropyrolysis, isothermal fluidized-bed pyrolysis, oil evolution from a self-purging reactor, pyrolysis-mass spectrometry, and hydrous pyrolysis are analyzed to derive chemical kinetic expressions for pyrolysis of lacustrine and marine kerogens. These kinetic parameters are incorporated into an improved, detailed chemical-kinetic model which includes oil and gas generation from kerogen, oil degradation by coking and cracking, gas generation from residual kerogen, and hydrogen consumption reactions. Oil is described by eleven boiling-point fractions of two chemical types. The model includes equation-of-state calculations of vapor/liquid equilibria and PVT behavior. The model can simulate closed, open and leaky systems, and the open system can include an inert-gas purge. The porosity is calculated for both unconstrained conditions as well as conditions simulating natural compaction and fracturing during sedimentary burial. Model calculations are compared to results from a variety of laboratory experiments, including hydrous pyrolysis. Oil expulsion efficiencies and properties are also calculated for a variety of geological conditions. The relative amounts of water and hydrocarbon phase(s) expelled are governed by saturation-dependent relative permeabilities. Gas/oil ratios in the expelled petroleum are related to organic content and geological heating rate.