| Title | Effects of Diffusion Potential on Self-Potential Distribution in Geothermal Areas |
|---|---|
| Authors | Ishido, Tsuneo; Pritchett, John W. |
| Year | 2011 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Self-potential; electrokinetic coupling; diffusion potential; reservoir simulation; natural hydrothermal circulation; production-induced flow |
| Abstract | Our “EKP Postprocessor” calculates temporal changes in the distribution of electrokinetic self-potential (SP) caused by changes in underground conditions such as pressure, temperature, salinity and liquid-phase saturation as computed by numerical reservoir simulations. Recently, we have extended the EKP Postprocessor to incorporate electrochemical diffusion potential in addition to electrokinetic coupling as SP generation mechanisms. We applied the new postprocessor to computed results from reservoir simulations representing natural hydrothermal circulation and subsequent geothermal fluid production. The present preliminary simulations indicate that diffusion potential effects could account for a substantial part of the natural-state SP anomalies associated with natural hydrothermal circulation systems, especially if a large salinity contrast is present between the hot upflowing thermal fluid and surrounding fresh water. But diffusion potential effects will not play significant roles in production-induced SP changes since production-induced changes in the distributions of fluid chemistry will be minor compared to flow pattern changes, particularly in the early stages of exploitation. |