Setbacks for Advanced Geothermal Technology in U.S., Australia

Two companies have announced setbacks to demonstration projects seeking to develop and commercialize enhanced geothermal systems (EGS) technology. California-based AltaRock Energy shelved a project for which it had secured $36 million from the U.S Energy Department and had the backing of several large venture capital firms, citing “geologic anomalies.” Geodynamics Ltd., meanwhile, encountered a new set of technical difficulties and is reevaluating a 1-MW pilot project in the Australian outback.

EGS technology makes use of available geothermal resources to heat engineered reservoirs, which can be tapped to produce electricity. It essentially involves pumping water into the earth, creating fractures in the hot dry rock. The water then flows into the fissures, creating a reservoir of very hot geothermal fluid that is continuously heated, and when it is returned to the surface, the pressure decrease produces steam, which is used to turn a turbine.

But drilling into hard rock at high temperatures presents an array of technical challenges. AltaRock Energy last week said it had encountered a “number of physical difficulties” in the drilling of the first well planned in The Geysers, which had resulted in “geologic anomalies particular to the formation underlying this well location.”

The company had come under scrutiny after The New York Times pointed out similarities between the demonstration and a Swiss geothermal prospecting project in Basel, which is believed to have triggered a massive earthquake on Dec. 8, 2006, after prospectors drilled 3 miles into a significant fault. AltaRock’s project proposed to fracture hard rock more than 2 miles deep in an area overlying two fault lines.

“We have suspended the drilling of this well as part of the Geysers Demonstration project. We are continuing with the development of our EGS technology and are currently evaluating a number of alternative well locations, at the Geysers and elsewhere for demonstrating this technology,” the company said last week.

Drilling problems were also the reason Geodynamics was considering reevaluating its EGS pilot project in Cooper Basin. The company had completed drilling wells for the project early last year after nearly five years of technical challenges. 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 reportedly 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 (PDF), which found that 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 sulfide in the reservoir fluid.

“The implications of the findings for future well design, material selection and any revision of operational procedures are complex, but are within the bounds of general operational experience in the geothermal industry,” Geodynamics said on Aug. 21.

“Available options will be critically examined and assessed resulting in a revised work program for the project. These activities will take at least eight weeks, and may lead to a revision of the previously indicated delay of six to nine months in the commissioning of the 1-MW Pilot Plant. The revised work program and project delivery timelines will be communicated as they are finalised.”

Sources: AltaRock, The New York Times, Geodynamics, EERE