A GEOTHERMAL ENERGY FRONTIER: POTENTIAL OFFSHORE RESOURCES OF THE PACIFIC NORTHWEST

The Iceland Deep Drilling Project (IDDP) is a consortium of industry, government and academia collaborating to investigate the technical and the economic feasibility of producing electricity from supercritical geothermal resources. Modeling indicates that a well producing from a supercritical reservoir would have ten times the power output of a typical high-enthalpy, but not supercritical, well. In 2009 the IDDP planned to drill a deep supercritical well at Krafla in NE Iceland. However drilling had to be terminated at only 2.1 km depth when 900°C rhyolite magma flowed into the well. The resultant well was highly productive capable of generating >35 MWe from superheated steam at a well-head temperature of ~450°C. In 2015 the IDDP will drill a 4.5 km deep well in a high temperature geothermal field in SW Iceland on the Reykjanes peninsula, the landward extension of the Mid-Atlantic Ridge. This well will penetrate the roots of a hydrothermal system similar to those that supply black smokers on ocean ridges.

Plans for drilling to explore for deep supercritical geothermal resources are already underway in the Taupo Volcanic Zone of New Zealand (Project HADES), and in northeast Japan the “Beyond Brittle Project” (JBBP) is an ambitious program attempting to create an EGS reservoir in ~500^oC rocks. There is a significant potential to develop similar supercritical geothermal systems in Hawaii, the western USA, Canada, and Alaska. However the offshore geothermal resource base of western Canada and USA far exceeds the equivalent potential on land. A preliminary estimate for the Gorda, Explorer, and Juan de Fuca Ridges indicates the geothermal resources base exceeds many hundreds of GWe. By developing production from the hottest, supercritical, submarine resources the higher productivity per well should offset the higher costs of offshore drilling, power production and electrical transmission.