Reinjection of the separated brines back into the geothermal reservoir is very important to maintain the reservoir pressure and to avoid a rapid decline. The reinjection sector is best chosen when its temperature is slightly higher than the temperature of reinjection fluids. The relative distance from the reinjection to the production sectors is also important, not too close but not too far. The role of geochemistry is also taken into account in this matter. Once a certain technology is selected for the utilization of the reservoir, the reservoir management system is then developed that leads to a good steam field design. On the basis of heat and mass balance, hopefully the reservoir would receive a good treatment until the end of the utilization. A problem might occur when the initial reservoir management system is for condensing turbines, but years later lower pressure or multiple flash turbines are added to the current power plants. The reservoir management system needs a re-written. The additional investment could be high when the reinjection sectors need relocations in order to prevent reservoir damage.
Production decline in geothermal industries is very common. There are various causes, such of lack of recharge, well damage, mineral depositions in the vicinity of the wellbores, over exploitation, rapid cold liquid intrusions from far field, leakage from shallow cold aquifer downto the reservoir. The following graph shows an example of production decline from the parameters shown in the table. The values could be modified and the output is shown by clicking the Calculate button.