| Abstract |
This paper reports the results of initial exploration drilling of a 44,000 km2 geothermal concession associated with the large Tangkuban Parahu stratovolcano in Central West Java, Indonesia. The concession was awarded in November of 2009, to Tankuban Parahu Geothermal Power (TPGP). A geothermal reservoir with the potential to support two 55MW power plants could be associated with the broad Sunda – Tangkuban Parahu “TBP” volcano.. TBP has a summit height of 2066m asl. The young volcanic craters on TBP have experienced phreatic eruptions cyclically for about three weeks every 2 – 3 years since 1926. In November 2011 the summit crater experienced the input of magmatic gasses and fumarole temperatures of 286 oC were measured. Acidic hot springs occur both on the north and south flanks of TBP, less than 5 km from the summit crater. Neutral pH warm springs are found within 9 km S, SW, and N of the summit. Reconnaissance of the TBP field was initiated in 1970 by Pertamina. In 2010-2011, the Energy and Geoscience Institute “EGI”-USA, working under a USTDA grant awarded to PT Indonesia Power, conducted additional fluid geochemical sampling, a noble gas sampling survey, and an extensive magneto-telluric (MT) survey covering ± 80 sq km. Analyses suggest a high temperature liquid-dominated reservoir. Faults which may provide conduits for hydrothermal fluid transmission, were identified using various satellite imagry, aerial photography and a recent LiDAR survey. The interpretation of the MT survey suggests the main upflow zone occurs beneath the youthful main volcanic edifice, with hydrothermal outflow extending in several different directions for varying distances. The potential is not yet known, but reservoir temperatures of 250oC to 300oC are suggested by geothermometry calculations. The Kancah area, on the south flank of TBP, was identified as the priority location for drilling of the first 3 slim holes. These will be rotary drilled to about 630 m, then core drilled to target depths of about 1500 m TD. Data from the exploratory core holes will be used to target full-sized production test wells. The MT survey suggests the target depth for the reservoir zone may be 2500 – 3000 meters Results of the slim hole drilling, planned for 2014, is reported in this paper. TPGP is working with the local government and agencies in a time-consuming process to obtain required permits. These include permits for land clearing, environmental monitoring and management, and temporary retain and disposal permits for drilling fluids and cuttings. Among other challenging efforts, the company is not only working with local officials to facilitate permitting but also to afford employment opportunity for local unskilled labors and conduct community outreach about the project. |