Laser drills could relight geothermal energy dreams

FROM fossil fuels to geothermal heat, accessing the planet's energy riches usually involves boring deep into the Earth with giant metal drills. But could lasers do the same job?

Foro Energy, a start-up company in Littleton, Colorado, has developed what it claims is an inexpensive system of high-powered lasers that can rip through rock, potentially revolutionising drilling and hastening the adoption of greener forms of power.

Foro announced last month that a test system had sent a beam from a 20-kilowatt commercial laser through 1.5 kilometres of optical fibre. Development has been funded by the US Department of Energy's research arm, ARPA-E. Borehole drilling trials are planned for next year.

Mechanical drills can easily grind through soft rocks like sandstone to tap petroleum reserves, but they wear out quickly in hard crystalline rocks such as granite and basalt. It is these harder rocks that often hide the best sources of geothermal energy. Foro's intense laser beam heats hard rock surfaces so fast that thermal shock fractures the upper few millimetres, leaving a crumbled layer that a mechanical drill can scrape away quickly and with little wear. This approach could increase drilling rates, a major component in well cost, by up to a factor of 10, says ARPA-E.

But a flashy prototype is far from proof that the rig will hold up in the brutal environment found in the bottom of a borehole, which is filled with rock chips and churning water that lubricates the drill bit. The optics must deliver the beam directly to the rock, says Jared Potter of Potter Drilling in Redwood City, California, who is developing a drilling process that shatters rock with extremely hot water. If the beam hits fluid, it will heat the liquid instead of the rock face. "It's amazing how much energy it takes to boil water," Potter says, and even a powerful laser couldn't hope to zap both water and rock at once. He thinks Foro "has a long way to go to have a tool they can deploy in a geothermal or oil well".

Still, the cost of drilling has been a roadblock to expanding the adoption of geothermal energy. If Foro can prove its technology is ready for the grunt work of punching hundreds of holes through the hard igneous rocks, it would change the mathematics of low-carbon energy. In the meantime, Potter says Foro's lasers could be used instead of explosives to make holes in the steel casings of oil and gas wells, which are needed to drain fluid from the surrounding rock.

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