IAMG 2001--Cancún Technical Program--Session J

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Petroleum Systems Analysis: Algorithms, Special Procedures and Case Studies by Erwin E. Dufour*, and Melvyn M.R. Giles, Shell International Exploration & Production, The Netherlands, Kees C. Vuik, Guus A. Segal, and Koos J.A. Meijerink, University of Delft, The Netherlands In the past decennium, Shell has put much emphasis on developing mathematical techniques for petroleum systems analysis. The current program uses forward modelling techniques to calculate hydrocarbon accumulations, composition, geo-pressures and rock properties through geological time. In order to do so, it calculates the basin infill based on an assumption of vertical in-place deposition of sediments. The primary variables, temperature and pressure, are calculated by solving a set of non-linear differential equations (PDE's) completed with a number of algebraic equations accounting for variations in rock and fluid properties. This implies that the exact geometry of the basin is part of the solution, and a Newton type procedure is used to fit current day seismic interpreted, depth converted maps. A fit for purpose (DICCG) preconditioner has been derived to handle the ill-conditioned matrix equation resulting from finite element discretisation of the PDE's. Theory and practice of this method will be shown on small example cases. The primary variables will subsequently be used to calculate generation, expulsion, composition (PVT) and secondary migration pathways of hydrocarbons to predict their ultimate location, composition, volume and in-situ conditions. Using case studies from European and American basins it will be shown how this information is used to predict: Trap integrity and locations of protected traps, Relative timing of charge and trap integrity, Hydrocarbon fill and gas-oil ratios, Escape of hydrocarbons from overpressured reservoirs, Reservoir compartmentalisation by faults and lithology, Porosity and other reservoir properties, Aquifer support and continuity, and Source rock maturity.