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Geothermal start-up AltaRock suspends drilling

AltaRock Energy is one of a few companies pursuing enhanced geothermal systems, a technology that holds lots of promise but has raised concerns about safety.

A new company pursuing an advanced geothermal energy technology has had to suspend its first attempt to drill a deep well in Northern California.

AltaRock Energy on Wednesday said it ran into problems during drilling for a demonstration project, "resulting from geologic anomalies particular to the formation" at the Geysers Geothermal field.

The project, said to be budgeted at $17 million, was partially funded by a Department of Energy grant given to several companies to explore the viability of enhanced geothermal systems. Sausalito, Calif.-based AltaRock was funded by Googleand venture capital company Kleiner Perkins Caufield & Byers.

AltaRock Energy

Although technical difficulties are normal in drilling projects, the progress of AltaRock is significant because it is one of few companies pursuing enhanced, or engineered, geothermal systems. It's a technology that holds great promise but that has raised safety concerns.

Traditional geothermal power draws on naturally occurring underground hot-water reservoirs to make electricity. With enhanced geothermal systems, wells are dug a few miles underground, and rock formations are fractured. Then water is injected into the wells, heated by the rock, and pulled back up. That hot water is converted to steam to turn an electricity turbine.

A Massachusetts Institute of Technology study two years ago found that using this enhanced method of geothermal power generation could supply 10 percent of the electricity in the United States. It could also be done in a wide variety of locations, rather than just the limited number of locations that have traditional geothermal resources.

But an article in The New York Times in June raised questions over the safety of enhanced geothermal systems, due to the deep drilling. In one test in Switzerland, drilling from a geothermal project caused earthquake tremors, causing the project to shut down. The Department of Energy and the Department of the Interior's Bureau of Land Management will not allow AltaRock to fracture rock before a review which is still pending, according to the Times report.

In its statement, AltaRock didn't offer many details on why it suspended drilling but said it is evaluating other locations to build a demonstration facility, including other spots at the site where it had been working.