| Abstract |
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 on land. Modeling indicates that a well producing from a supercritical reservoir would have ten times the power output of a typical moderate-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 2015-16 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 spreading center. This well will penetrate the roots of a hydrothermal system similar to the heat source of black smokers on mid-ocean ridges. Plans for drilling to explore for deep potentially supercritical geothermal resources are already underway in other countries, such as the Taupo Volcanic Zone of New Zealand (Project HADES), and in northeast Japan. The “Japanese Beyond the Brittle Project” (Project JBBP) is an ambitious program attempting to create an EGS reservoir in ~500°C rocks. In North America there is a significant potential to develop similar supercritical geothermal systems in Alaska, Canada, Hawaii, the western USA, and the Trans-Mexican Volcanic Belt. However, although in the short term more difficult and expensive to develop as practical power source, the offshore geothermal resource base of Canada, USA, and Mexico far exceeds the equivalent potential on land. For example, a preliminary estimate for the energy resources of the Gorda, Explorer, and Juan de Fuca Ridges indicates the geothermal resources base exceeds many thousands of GWe. Similarly, off-shore Mexico very large potential high-enthalpy, and possibly supercritical, geothermal resources also exist, for example, on the Revillagegido Ridge and in the Sea of Cortez. The higher costs of offshore drilling, power production and electrical transmission, could be offset by developing production from the hottest, supercritical, submarine resources yielding higher productivity per well, by clustering the power plants, and possibly by using high-temperature electrolysis to produce hydrogen as a fuel. Another approach to mitigating the cost issue would be to form a consortium of industry, government and academia to share the costs and broaden the scope an investigation, as was done by the Iceland Deep Drilling Project. |