| Abstract |
Integrated reservoir modeling and simulation technology has been developed which will improve the quality of mathematical reservoir models by taking account of repeated geophysical survey data sets (andor continuous geophysical monitoring data) in addition to the conventional data sets usually employed in reservoir engineering studies. Various computational ìpostprocessorsî were developed in order to couple these geophysical survey data with numerical reservoir simulations. These geophysical survey data sets involve changes in surface microgravity, downhole microgravity profiling, self-potential, and electrical resistivity (monitored by repeated DC, MT and/or CSAMT surveys). A computational feasibility study of reservoir monitoring using geophysical survey techniques was performed based on a numerical model of the Oguni geothermal reservoir. Starting with the steadystate natural condition of the system, an exploitation strategy involving a 20MWe geothermal power station was devised and further numerical calculations were performed, which induced changes in underground pressure, temperature, steam saturation and the underground flow pattern. Then, various mathematical ìpostprocessorsî were applied to the computed reservoir history to appraise changes that could be observed using various surface geophysical measurement techniques. The results suggest that these techniques have considerable promise for monitoring of geothermal reservoir evolution. The ìpostprocessorsî can help develop more robust reservoir models, because more constraints (based on more field measurements) can be imposed upon the model during model calibration (history matching). The postprocessors are also useful for designing an appropriate reservoir-monitoring program. |