Seattle-based AltaRock Energy Inc.has announced that it is confident that it has created three geothermal reservoirs from a single well.

The importance of this is the high cost of drilling a deep well to reach hot rock deep underground is less significant if multiple reservoirs of hot fluid, possibly at diferent levels, can be created from a single well.

AltaRock engineers pumped cold water into the ground, cracking open fissures in the deep rock and forming a reservoir of hot water..They then sealed this reservoir by injecting ground-up recycled plastic bottles, which plugged up the cracks.

Millions more gallons of cold water were then pumped in to create more fissures and a second and third reservoir.

The company says that more analysis and testing are needed to determine whether the reservoirs are good enough for commercial power production, which would be achieved by using steam from the reservoirs to generate electricity.