| Title | Two-Dimensional Inversion of Resistivity Monitoring Data from the Cerro Prieto Geothermal Field, Mexico |
|---|---|
| Authors | Goldstein, N. E.; Sasaki, Y.; Wilt, M. J. |
| Year | 1985 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Reservoir Engineering; Research Agencies; Mexico; Cerro Prieto; Fluid Flow; Brines; Reservoir Evaluation; Numerical Modeling; LBL |
| Abstract | Two dimensional iterative, least squares inversions were performed on dc resistivity data obtained over the Cerro Prieto geothermal field at five successive times during the 1979-1983 period. The data were taken on 20 km long control line centered over the production region. Inversions were performed on the apparent resistivities after they were converted to percent changes in apparent resistivity relative to the base year data of 1979. The resulting solutions gave the percent change in resistivity within each of 47 rectangular blocks representing the reservoir and recharge regions. These changes are compared to and found consistent with hydrological and recharge models proposed by other workers on the basis of geophysical well logs, well cutting, well production , geochemical and reservoir engineering data. The solution support the model of a reservoir that is being recharged mainly by cooler, less saline water, causing changes in both pore fluid resistivity and the extent of boiling near the wells. There may be a component of high temperature recharge from below and to the east, but flow may be impeded by a two phase zone. Notwithstanding the various sources of error and uncertainty in the data acquisition and 2 D inversions, repetitive, high precision dc resistivity monitoring seems to be a useful method for assessing reservoir conditions when used in conjunction with production and reservoir engineering data and analyses. |