Reservoir parameter estimates and water level predictions for the Laugarnes low-temperature system, SW-Iceland, by simple analytical and lumped parameter models

Abstract

The Laugarnes geothermal field is located near the centre of Reykjavík, SW-Iceland. It has been utilized since 1928. Currently, there are 12 production wells, producing geothermal fluids with an average temperature of 130°C and average total production rates of around 168 l/s. Monthly measured water level data exist from 1962 and indicate the reservoir’s response to long-term production. In this paper, the data were analysed using a simple analytical method and the lumped parameter method. The results of the study indicate that the Laugarnes geothermal field is an open system with a combination of confined and free surface effects. The permeability of the Laugarnes geothermal system is estimated to be around 11 mD, and the area of the reservoir is between 21 and 940 km2. The storativity is between 8.59×10-8 and 1.02×10-5 s2/m2. Both methods were used to predict water levels within the reservoir for 30 years into the future. The model's prediction of the reservoir's response, after 30 years of producing at a rate of 168 l/s, indicates a water level of between -51.10 and -32.60 m a.s.l. A comparison of the simple analytical method and the lumped parameter method highlights the different advantages of each method.