- Convection-Dominated Geothermal Systems
- Conduction-Dominated Geothermal Systems
CD-3: Crystalline Rock - Basement
Moeck-Beardsmore Geothermal Play Type:
The Fenton Hill Hot Dry Rock Project in New Mexico was the world's first geothermal heat extraction project to target a conductive geothermal play in crystalline basement rocks.
According to Moeck and Beardsmore, conductive geothermal plays in crystalline basement rocks are typically encountered where intrusive rocks occur in flat terrain. Such settings may feature gentle surface topography underlain by fractured, critically stressed hot crystalline rocks capped by a thermal insulating layer. Isotherms are dominantly conductive in this setting, with heat flows measuring much greater than the continental average. Plays of this type typically consist of a moderate temperature resource (150 - 250°C) at relatively deep levels between 4 and 6 km. ￼Stored heat in the system may originate from shallow mantle, bodies of hot rock in the upper crust, and/or from radiogenic heat produced by elements in the rock.
Reservoir rocks in basement geothermal plays consist of hot intrusive rocks with low natural porosity, permeability, or volume of contained fluid. The ideal reservoir rock hosts natural fractures that are amenable to hydraulic pressure stimulation, hydro-shearing, and/or thermal stimulation. Fractured granite is a typical reservoir rock fitting these criteria, and tends to host fracture-dominated permeability that is favorable to stimulation. The variability of the orientation of these fractures is controlled by the tectonic stress field - comprehensive understanding of the stress field is critical for achieving interconnection between reopened fractures and planned injection and production wells. The matrix of the primary reservoir rock must be strong in order to support open fractures created or opened during stimulation. Following stimulation, fracture controlled circulation of water along dominant flow paths from injection to production wells becomes the primary mechanism of heat transport used to recover energy from the reservoir. As a consequence, fluid access to the stored heat resource is limited by the continuity of reopened fractures and by the volume of reservoir rock that has been engineered via stimulation techniques.
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|Fenton Hill HDR Geothermal Area||Rio Grande Rift||Lithologically Controlled||Precambrian||Crystalline basement “pCu” (undifferentiated in map units); Biotite Granodiorite (Phase I Reservoir); Gneiss, Schist, Granodiorite, Granite, Metavolcanic Rocks (Phase II Reservoir)||20 MW|
|Innamincka SA||South Austrailia||1 MW|
- Inga S. Moeck,Graeme Beardsmore. 2014. A New 'Geothermal Play Type' Catalog: Streamlining Exploration Decision Making. In: Proceedings. Thirty-Ninth Workshop on Geothermal Reservoir Engineering; 2014/02/24; Stanford, California. Stanford, California: Stanford University; p. 8
- U.S. Department of Energy, Science Photo Library. Schematic Diagram of the Fenton Hill Geothermal Project [Internet]. unknown. Science Photo Library. [cited 2014/03/26]. Available from: http://www.sciencephoto.com/media/340444/view
- Inga Moeck. 2013. Geothermal Plays in Geologic Settings. In: IGA Workshop on Developing Best Practice for Geothermal Exploration and Resource/Reserve Classification; 2013/11/14; Essen, Germany. IGA website: International Geothermal Association; p. 19
- Graeme Beardsmore. 2013. Conductive Plays - Basement. In: IGA Workshop on Developing Best Practice for Geothermal Exploration and Resource/Reserve Classification; 2013/11/14; Essen, Germany. IGA website: International Geothermal Association; p.