Analysis of temperature and pressure and characteristics of the Hverahlíd geothermal field in the hengill geothermal system, SW-Iceland.

Abstract

The Hverahlíd geothermal field is a high-temperature field located in the southern part of the Hengill geothermal system. Interglacial lava series dominate the geological succession at Hverahlíd with subordinate sub glacial hyaloclastites. Very active northeast trending fissure swarms with northwest trending transform structures are believed to supply the main permeability for geothermal fluid flow in the area. Analysis of temperature and pressure profiles from four boreholes reveals the presence of three major feed zones at 800, 1000-1200 and 1800-2000 m depths. The reservoir at Hverahlíd geothermal field is characterised by formation temperatures of more than 300°C and pressures well over 85 bars at the best feed zones. The main up-flow zone is located in the middle of the area with a northwest directed lateral flow. A homogenous reservoir model with constant pressure boundaries fits best in simulating the injection well tests of three boreholes in Hverahlíd. The reservoir is characterised by high transmissivity and storativity values; injectivity index values comparable to the average values in the Hellisheidi area were obtained.