Ulubelu, First Year Reservoir Monitoring

Abstract

Production of Ulubelu geothermal field in Lampung, Indonesia, has been commenced by Pertamina Geothermal Energy since mid-2012. 11 production wells supply steam to two PLN turbines of 55 MWe capacities each. Produced brine is re-injected to the reservoir through 4 wells while the condensate is re-injected through one well. Results of reservoir monitoring along first year of production are presented here. Changes have occurred in observed wellhead pressures which may indicate an early decrease in reservoir pressure, or may also be a transient response of reservoir due to early production. Production rate and enthalpy are monitored from daily data and changes are observed from tracer dilution test data. Injection tracer test was also conducted as a part of reservoir monitoring to determine the effects of reinjection wells.