Integrated Numerical Reservoir Modeling Coupled with Geophysical Monitoring Techniques

Abstract

A new R & D project to develop novel techniques for monitoring and modeling reservoir mass and heat flows is described. Integrated reservoir modeling and simulation technology is being developed which will improve the quality of mathematical reservoir models by taking account of geophysical data sets such as changes in micro-gravity, selfpotential, resistivity and seismic properties in addition to the conventional data sets usually employed in reservoir engineering studies. Computational feasibility studies of reservoir monitoring using geophysical survey techniques were performed based on a steady-state three-dimensional model of a hypothetical (but realistic and typical) geothermal reservoir system which was developed using a numerical reservoir simulator. Starting with this steady-state system, an exploitation strategy involving a 50 MW geothermal power station was devised and further numerical calculations were performed, which induced the changes in underground pressure, temperature, steam saturation and the underground flow pattern caused by 27 years of field operation. Then, various mathematical ìpostprocessorsî were applied to this 27-year computed reservoir history to appraise changes that could be observed using various surface geophysical measurement techniques. Survey methods examined include surface microgravity, downhole microgravity profiling, electrical resistivity surveys, self-potential surveys and seismic surveys. The results suggest that these techniques have considerable promise. The development of various ìpostprocessorsî and a database system were planned based on these feasibility studies.