Assessment of the Hofsstadir geothermal field, W-Iceland, by lumped parameter modelling, Monte Carlo simulation and tracer test analysis

Abstract

The Hofsstadir geothermal system, which was discovered during an extensive regional reconnaissance survey in W-Iceland in 1995, is a typical liquid-dominated convective low-temperature system. The entire monitoring data available for the only production well, HO-1, were simulated by lumped parameter modelling. Due to insufficient recharge, a continuous water-level decline -1has been observed. Reinjection started in early 2007 by injecting the return water from the heating system into injection well HO-2. Through simulating various production scenarios, using the best fitting model based on data collected without reinjection, the connection between the two wells was studied. The future water-level changes in the production well were predicted, based on the assumption that a given percentage of the reinjected water could eventually be re-extracted through the production well, without causing additional pressure drop. The calculated results indicate that this system will be able to sustain a 20 l/s average production through 2032, without reinjection. This will require that the down-hole pump in HO-1 be lowered. If reinjection is applied in the long term, then the production capacity of the field can reach up to 30 l/s with minor cooling of the production well. Monte Carlo volumetric assessment was applied to the Hofsstadir field. The results predict ...