Key Performance Indicators for Pumped Well Geothermal Power Generation

Abstract

Line shaft or electrical submersible down-hole pumps can be used to pump hot fluid from geothermal aquifers to generate electricity. The potential geothermal settings for this development approach include hot sedimentary or naturally fractured aquifers in a range of non-volcanic settings and lateral outflows of higher temperature geothermal systems in volcanic terrains. Although technically feasible, and proven in a number of fields around the world, specific project commercial viability depends on a number of geothermal resource, economic, and project development factors. In addition the location of a geothermal resource relative to the off-taker can be a consideration when power transmission infrastructure and associated costs are taken into account. These key performance indicators are inter-related and a favourable combination can be attractive relative to the local off-take power price. They can be comparable to higher enthalpy conventional geothermal generation(deep self discharging wells supplying condensing steam turbine, binary, or combined cycle plant). Numerical models representing the reservoir characteristics, engineering processes of pumped flow in wells, fluid flow in surface gathering systems, and electrical power generation are presented. In conjunction with a financial analysis a probabilistic Monte Carlo approach is presented to illustrate the sensitivity of the key performance indicators on project return on investment. Project development risks and how these developments can be staged to reduce risk are discussed and compared to conventional geothermal generation in several regional settings. A prospective list of locations where these project developments may be economically viable is presented.