EERE Network News - 2/23/08

The first commercial attempt to create a commercial geothermal power plant using hot dry rock technology reached a crucial milestone on Tuesday, when a production well successfully reached its target depth. Hot dry rock technology was invented to draw energy from deep underground areas where geothermal heat is abundant, but no water exists to carry the heat to the surface. To tap the energy in this hot dry rock, a well is drilled into it and water is injected at high pressure, forming fissures in the rock to create a geothermal "reservoir" consisting of water-impregnated fractured rock. At least one "production" well is then drilled into the reservoir to draw the hot water back to the surface. A completed facility would direct the hot fluid from the production well to a power plant, which would extract the heat from it to produce power, after which the cooled fluid would be injected back into the ground.

Geodynamics has been trying for years to establish a geothermal reservoir deep below the surface of the Australian outback. The company successfully completed its first well, Habanero 1, back in 2003 and established a reservoir late that year, but suffered multiple problems drilling its first production well, Habanero 2, which was eventually abandoned. The company began drilling its new production well, Habanero 3, in mid-August, 2007, but encountered problems by late October and suspended drilling. Drilling resumed in late November and proceeded until the drilling was finished yesterday. The well first intersected the fracture zone at a depth of 13,716 feet, at which time a hydraulic connection was established between Habanero 1 and 3. Drilling then continued to the target depth of 13,850 feet.

The well should be completed within the next week, as all that remains to do is to insert a liner into the well to maintain its integrity, and then add the valves and piping needed to control the well. At that point, the company will be able to perform flow testing on the reservoir to confirm that the two wells can produce hot geothermal fluid at the temperature and flow rate needed to sustain a geothermal power plant.

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