Thermal Energy Extraction by Reinjection from the Laugaland Geothermal System in N-Iceland

Abstract

A two-year reinjection experiment was completed in late 1999 in the Laugaland geothermal system in N-Iceland, the first such project undertaken in an Icelandic low-temperature area. The Laugaland system is embedded in low-permeability fractured basalt and its productivity is limited by insufficient recharge. More than sufficient thermal energy is, however, in-place in the 90 - 100 ?C hot rocks of the system, some of which may be extracted by injection. The purpose of the reinjection project was to demonstrate that energy production from fractured low-temperature geothermal systems might be increased by reinjection. The Laugaland reinjection test was a co-operative project involving a few companies and institutions in Iceland, Sweden and Denmark, partly supported by the European Commission. Between 6 and 21 kg/s were injected into two reinjection wells and a comprehensive monitoring program was implemented as part of the reinjection project. Also included were three tracertests, monitoring of associated micro-seismic activity, steprate injection tests and temperature logging of the injection wells. Results of the experiment indicate that reinjection will be a highly economical mode of increasing the production potential of the Laugaland system and reinjection is expected to be an important part of the management of the Laugaland reservoir for decades to come.