Two geothermal projects shut down
Saturday, 12 December, 2009 — technological-failure environment unintended-consequences energy
The New York Times has two pieces, both by James Glanz, talking about geothermal projects in Switzerland and California being shutdown.
The Swiss project was shutdown over concerns that it would generate millions of dollars in earthquake damage annually.
The California project was getting Dept. of Energy funding. The company’s rationale isn’t known, but several issues are mentioned, including the earthquakes caused in Basel, Switzerland:
Geothermal enthusiasts asserted that drilling miles into hard rock, as required by the technique, could be done quickly and economically with small improvements in existing methods, Professor Schrag said. “What we’ve discovered is that it’s harder to make those improvements than some people believed,” he added.
In fact, AltaRock immediately ran into snags with its drilling, repeatedly snapping off bits in shallow formations called caprock. The project’s safety was also under review at the Energy Department after federal officials said the company had not been entirely forthcoming about the earthquakes produced in Basel in making the case for the Geysers project.
Other projects at the California site have also caused earthquakes. Back in June, Scientific American looked into why geothermal drilling causes earthquakes:
About a million years ago, there was a magmatic intrusion (protovolcano) that didn’t make it to the surface. Under the surface is a rock called felsite—you can think of it like granite; it’s the heat source for the sandstone.
The new project is going to exploit the felsite directly. But there’s no water in the felsite, so they drill, then they pipe water under strong pressure and flow rate, to fracture the rock. They’ll be using earthquake-monitoring equipment and will send cameras down the hole to see which direction the fractures were occurring. Then they drill a second hole to intersect the new fracture.
So the potential is to extract much more heat, but you have to create your own fractures and you have to introduce water.
That bit of creating fractures? That creates the earthquake.