The aim of the project is to use the observation of gravity field changes at the Earth's surface to better understand and quantify mass displacements in the subsurface and basic processes in geothermal reservoirs. For a better understanding of largely coupled processes (e.g., between fluid movements and stress changes), a more accurate estimation of reservoir parameters such as rock permeability and other structural and dynamic parameters should be obtained. In the long term, this should lead to more precise quantification of the sustainability of the use of a geothermal resource.
The project originally started in Indonesia but, due to changed boundary conditions, essential investigations had to be relocated to Iceland. This resulted in a unique database suitable for adapted evolution of the microgravimetric methodology for geothermal use applicable in Indonesia and worldwide. This is a contribution to the expansion of sustainable geothermal energy use.
The project demonstrated the feasibility of the methodology at a site in the far north of Iceland under difficult climatic and logistical conditions. Continuous gravity measurements in the injection and production area allowed to identify mass displacements in the underground. Quantification requires the consideration of local hydro meteorological parameters (such as precipitation, soil moisture, etc.) and the inclusion of operating parameters (e.g. injection and production rates). The first were recorded during the field campaign. The latter are provided by the industrial partner Landsvirkjun. This is an exemplary project for a good cooperation between Icelandic industry and international research institutions.
The experiences gained from the implementation in Iceland provides a framework for the successful use of the methodology. These relate in particular to infrastructure requirements for measurements with superconducting gravimeters, the procedure for drift correction as well as the observation of groundwater levels close to the gravity stations.
The combination of continuous microgravimetric and seismic measurements will lead to new possibilities in the large-scale observation and assessment of reservoir processes. However, a final interpretation including all the data from this project is still pending.