Electric Power Potential Estimates of High-Temperature Geothermal Fields in Indonesia and the Philippines (a Historic Review)

Abstract

Electric power potential estimates (Pe) have been used for the initial development phase of 7 geothermal fields in Indonesia and 8 fields in the Philippines during 1975 to 2000. Most of the estimates were based on stored (anomalous) heat assessments together with data from a few flow-tested discovery wells (proven reserves). The same data were used for predicting the potential of a few prospects by numerical modelling (using early simulation codes). Most estimates were upgraded after a significant response of the exploited reservoirs was noticed. However, only a few upgraded Pe estimates of developed fields were published.

It is assumed that beyond a production time of more than 10 years most plant optimisations involving enlargement or reduction of plant capacity have occurred. The present day running plant capacity can therefore be compared with initial and subsequent Pe estimates to assess whether the initial and later potential estimates did approach the presently producing capacity. Although single reservoir characteristics do vary, overall characteristics can be assumed to be similar since all 15 exploited fields occur in similar active tectonic arc settings.

Comparison between initial Pe values and recently published average running field capacity data (2009/10) shows that there is a tendency of overestimating somewhat the initial potentials, both in Indonesia and the Philippines, whereas underestimates are indicated for a few Philippines prospects. Significant differences are associated with predictions of the potential of reservoirs marked by large, concealed outflow structures (Palinpinon and Tiwi in the Philippines) and geothermal reservoirs containing some magmatic fluids (Dieng and Sibayak in Indonesia).