Aquifer Boiling May Be Normal in Exploited High-Temperature Geothermal Systems

Abstract

The Wairakei, New Zealand geothermal system has been extensively studied as the first major hot-water system to be exploited for the generation of electricity. There is a temptation to assume that other high-temperature geothermal systems will respond to exploitation in the same way; however, Wairakei is probably an atypical geothermal system. Although some shallow drillholes now produce only wet steam, unusually high fracture permeability at Wairakei allows most drillholes to tap large flows of liquid water which flash to steam-water mixtures only in the wellbores and cyclone separators. This high permeability is not found in vapor-dominated systems or in most wells of Cerro Prieto or Broadlands, the two other extensively studied hot-water geothermal systems.