This is an excerpt from EERE Network News, a weekly electronic newsletter.
U.S. and Australian Advanced Geothermal Projects Face Setbacks
Efforts to develop and commercialize a new type of geothermal energy, called Enhanced Geothermal Systems (EGS), are facing technical setbacks in both the United States and Australia. EGS involves injecting water at high pressure into deep, hot rock formations to fracture the rock, creating either a new geothermal reservoir of hot water embedded in hot rock or expanding an existing geothermal reservoir. But drilling into hard rock at high temperatures and pressures has always presented a technical challenge to EGS technology. As previously reported in the EERE Network News, Geodynamics, Ltd. of Australia finally completed drilling the wells for its EGS project early last year, after encountering drilling problems over the course of nearly 5 years. See the January 2008 article from the EERE Network News.
Last week, AltaRock Energy Inc. announced that it has suffered similar difficulties in drilling a well for a demonstration EGS project at The Geysers, an existing geothermal resource in northern California. Citing "geologic anomalies," AltaRock announced that it is giving up on the current well and is evaluating alternative well locations. In Australia, Petratherm, Ltd. appears to be having similar problems, as a drilling effort for a well that was supposed to take 2-3 months is now expected to take 3-4 months. Petratherm experienced slow penetration rates for its 17.5" hole in the hard rock, but the company is now drilling a narrower (12.25"), deeper section of the well and is making better progress. See the press releases from AltaRock (PDF 29 KB) and Petrotherm (PDF 274 KB). Download Adobe Reader.
Meanwhile, Geodynamics has moved on to a whole new set of technical problems at its demonstration project at Cooper Basin in the Australian outback. In late April, the company experienced a blowout at its Habanero 3 well, causing an uncontrolled release of steam and hot water at the wellhead. It took the company 28 days to get the well back under control with weighted mud, and the well was then capped with two cement plugs. In late August, the company released the results of its investigation, which found the fluid chemistry in the well caused hydrogen embrittlement in some of the high-strength steel used in the well, making it prone to cracking. The investigation blamed the embrittlement on dissolved carbon dioxide and hydrogen sulphide in the reservoir fluid. Because of those findings, the company installed cement plugs in two other wells, Habanero 2 and 3, and planned to also secure Habanero 1. Despite the setback, the company still intends to generate geothermal power in the Cooper Basin, but its near-term plans for a 1-megawatt pilot plant are currently being reevaluated. See the Geodynamics announcements on the well blowout (PDF 28 KB), the well capping (PDF 167 KB), and the results of the investigation (PDF 134 KB).