| Abstract |
I-I deep well, the last well of 2012-2013 Salak Drilling Campaign, was drilled at Pad I with two objectives, namely, (1) augment steam supply and (2) reduce the uncertainty of the base of reservoir (BoR) in the inferred upflow region southwest of Salak (also known as Awibengkok) Geothermal System. Although the well was completed about 20% shallower than planned to 10,402’ MD (3,170 m) only, it is now the deepest well drilled in the Salak reservoir. Interpretation of borehole image logs indicates that I-I deep well intersected predominantly pyroclastics (volcanics) with interbedded lavas and sedimentary rocks below 10,000’ MD. These units appear to be a member of the Marine Sediments and Volcaniclastics (MSV) Formation which is now deeper than what were previously interpreted as continuous sedimentary rocks. Before, it was believed that sedimentary rocks (called Continuous Sediments Formation) underlie the MSV Formation to form the basement of the Salak reservoir. I-I deep well successfully encountered the deepest permeable entry to date at ~6,350’ BSL at Salak. It confirmed the presence of deep permeability (likely related to the geothermal system’s upflow) in this part of the field and prompted a revision of the P10 BoR. Geology, geochemistry, and Pressure-Temperature (PT) data also support the interpretation of a high-temperature upflow in the Pad I area. However, both Qtz and NKC geothermometries don’t work very well because brine injection at Pad I since 1994 has impacted the reservoir and has camouflaged the original chemistry of Pad I wells. These favorable results at I-I deep well confirm previous interpretations that the upflow of the geothermal system is beneath the southwest area. The presence of the deep feed zone in the MSV Formation indicates that this formation is not the basement of the geothermal reservoir and supports further drilling of deep wells in this area. |