| Title | Simulation of Reinjection at Cerro Prieto Using an Idealized Two-Reservoir Model |
|---|---|
| Authors | C. F. Tsang, D. C. Mangold, M. J. Lippmann |
| Year | 1979 |
| Conference | DOE-CFE Symposium on Cerro Prieto |
| Keywords | |
| Abstract | Most of the papers published on the hydrodynamic and thermal effects of reinjection in geothermal fields assume asingle reservoirwith uniform transmissivity and storativity. However, there is evidence that the Cerro Prieto geothermal field is a two-reservoir system and that each reservoir has different hydraulic properties (Abril and Noble, 1979). Because two-reservoir fields have not been adequately studied, we will analyze the thermohydrological response of this kind of geothermal system to various alternative schemes of reinjection. We use parameters relevant to the Cerro Prieto system so that the results will be useful in planning future reinjection operations at this field. In our present analysis, we use the LBL integrated finite-difference computer program CCC (Lippmann et aI.,1977), which is capable of model ing the complex geological and boundary conditions of a geothermal system. CCC also simulates the major physical factors involved in the movement of the injected waters: 1J forced convective flow between the production and injection areas; 2) heat exchange among injected water, rock matrix, and native waters; 3) density-buoyancy effects; and 4) influence of temperature·dependent viscosity on fluid flow. The problems associated with the chemistry of the fluids and the porous media -such as injectibility of the wells, injected/native groundwater compatibility, and water-rock interactions-will not be covered here. These matters are addressed in a number of other papers at this symposium. Instead, we show the results of computations for the response of a two-reservoir geothermal system to injection at various depths and positions within the field. The influence of differences in thermal, hydraulic, and geometric properties between the reservoirs are discussed. The results indicate that it is possible to stabilize or 'increase reservoir pressures and maintain production temperature in a two-reservoir geothermal field by using an appropriate fluid reinjection scheme. |