In Situ - Vaporisation of Geothermal Water in Low Permeability Rock and a Saline Environment

Abstract

A method is proposed to produce steam from hot but low permability rock in a saline environment without putting at risk the the bore-hole and plant. Mineral precipitates (scaling) could be avoided by injecting freshwater into the low permeability rock, thereby replacing saline brines within a defined rock district around the bore-hole. The injected freshwater will be shut in and heat up to rock temperature. Subsequently, in situ-vaporisation will be initiated by a sudden reduction in pressure. Steam will be generated and flowing to the surface, where it can be harnessed by turbogenerators. The sudden reduction in pressure will be provided by a specific patented equipment that has been described by Herr (2002). Once the slowly prograding vaporisation front has reached the brine-filled rock domain, the water content of the brine will be turned to steam. The dissolved mineral contents will precipitate and be left in the rock. Crystallisation of salts is kept away from the well-bore and adds more heat to the rock.