Water availability analysis for natural injection in geothermal reservoir water dominated

Water balance between production and injection in geothermal water dominated reservoir is essential to maintain the sustainability of steam power plant production. Thus in the planning of the steam production, a natural injection calculation must be completed first. This natural substance is infiltration water into a reservoir that comes from rainwater inside the reservoir of the Geothermal Electricity Power Plant (GEPP). The method of knowing natural injection is by analyzing the availability of water in the GEPP watershed, the area of the river flowing into the reservoir is 22,21 km2, with annual rainfall around 3802 mm. One of the calculation methods used is FJ. Mock method. This method transforms rainfall into run-off based on the concept of a hydrological model. Water availability analysis is in monthly rainfall. From the calculation results, the monthly average infiltration is about 650 kg/s, and the annual total is about 7,760 kg/s. Consequently, the total annually mass production must not exceed 7,760 kg/s, if mass production exceeds infiltration, need to do injection through injection wells.