Basin and Petroleum System Modeling

Abstract

Since the early 1970s, basin and petroleum system modeling (BPSM ) has evolved from a simple tool, used mainly to predict regional source rock thermal maturity, to become a critical component in the worldwide exploration programs of many national and international oil companies for both conventional and unconventional resources. The selection of one-dimensional 1-D, 2-D or 3-D BPSM depends on available input data and project objectives. Organic richness and rock properties must be reconstructed to original values prior to burial. For example, in geohistory analysis each unit is decompacted to original thickness and corrected for paleobathymetry and eustasy. Boundary conditions for thermal evolution include heat flow and sediment-water interface temperature corrected for water depth through time. Default petroleum generation kinetics available in most software should be used only when suitable samples of the source rock organofacies are unavailable. Kinetic parameters are best measured using representative, thermally immature equivalents of the effective source rock. 3-D poroelastic and poroplastic rock stress modeling are significant advances over the 1-D Terzaghi method employed by most software. Calibration should start with the available pressure data, followed by thermal calibration (e. g., corrected borehole temperatures or vitrinite reflectance) and calibration to other measurements (e. g., petroleum composition). The dynamic petroleum system concept has proven to be a more reliable tool for exploration than static play fairway maps used in the past, partly because BPSM accounts for the timing of trap formation relative to generation-migration-accumulation. Tectonic activity and other processes can result in remigration or destruction of accumulations and more than one critical moment on the petroleum system event chart. Organoporosity within the kerogen and solid bitumen accounts for much of the petroleum in unconventional mudstone reservoirs, and secondary cracking of oil to gas is particularly important. Hybrid unconventional systems, which juxtapose ductile organic-rich and brittle, more permeable organic-lean intervals are typically the best producers.