DOE Plans Geothermal Drilling Safeguards

The New York Times has reported that the U.S. Department of Energy (DOE) plans to set up more stringent regulations governing enhanced geothermal projects. The new regulations follow the failures of a California geothermal project by AltaRock Energy, Inc. that was shut down because of fears that it might trigger an earthquake.

The DOE is planning to require that similar projects, called Enhanced Geothermal Systems (EGS), utilize ground-motion sensors and have an approved plan to shut down operations if the drilling initiates strong earthquakes. Companies must also do studies of expected earthquake activity and submit project proposals to outside experts for risk assessment.

AltaRock had planned to drill into bedrock underlying the Geysers steam reservoir, to a total depth of 12,000 feet, as part of a DOE-funded enhanced geothermal systems project to demonstrate the ability to create multiple fracture zones in one well. After several attempts, the drilling assembly got stuck when the drill hole collapsed and was never able to reach the necessary depth.

A finding by the DOE, reported by the New York Times, showed that any earthquakes would have been small and had little impact in the sparsely populated area. However, in the face of local opposition, AltaRock abandoned the project. The DOE has shown confidence in AltaRock, by subsequently awarding the company $25 million to try a similar project at the Newberry Volcanic Monument near Bend, Oregon.

The New York Times also quoted Ernie Majer, a seismologist and deputy director of the Earth Science Division at Lawrence Berkeley National Laboratory in California, as saying that the new standards show how the DOE “is being ultra-careful about any induced seismicity,” referring to earthquakes triggered by humans.

The EGS concept is to extract heat by creating a subsurface fracture system to which water can be added through injection wells. Creating an enhanced, or engineered, geothermal system requires improving the natural permeability of rock. Rocks are permeable due to minute fractures and pore spaces between mineral grains. Injected water is heated by contact with the rock and returns to the surface through production wells, as in naturally occurring hydrothermal systems. EGS are reservoirs created to improve the economics of resources without adequate water and/or permeability.