Optimization of the Numerical Simulation in a Giant Oil Field by Upscaling of Relative Permeability Curves

Abstract

Abstract This paper presents the methodology applied to optimise the dynamic simulation of the giant Bu Attifel oil field (Libya) producing for 21 years under water injection. When building the full field model of a giant field it is fundamental to limit the number of cells and CPU times without jeopardising the structural and sedimentological complexity of the reservoir. This will allow a correct simulation of future development phases, such as improvement in water injection (production-injection scheme optimisation, infill wells) and EOR processes (gas injection). The first step of the study was the construction of two-dimensional cross sections based on the geological and dynamical data of the most representative wells. Then different oil displacement processes (water injection and gas injection) were simulated, mainly varying vertical communication and anisotropy of layers. Groups of relative permeability pseudo functions, consistent with the different geological configurations, were used in the full field model to simplify and optimise the history match phase. Introduction The complete reservoir study was aimed at optimising the future phases of the exploitation of Bu Attifel oil field by using a 3-D simulation model. The numerical model had two ambitious targets:–to respect the main physical properties shown by the field production performance,–to simulate the behaviour of each single well as accurately as possible to obtain a reliable tool also for short term reservoir management. This would require too large a number of computational grid blocks with very long CPU times. The use of pseudo functions of relative permeability is a means of decreasing grid dimensions without compromising simulation accuracy. These functions scale up the results of laboratory core flooding experiments to macroscopic sand sections (full field model layering). Therefore, they take into account the effect of reservoir heterogeneity and gravity forces. P. 413