Continuous High Resolution Gravity Measurements at a Geothermal Field in Northern Iceland: Setup and Instrumental Performance
Florian FORSTER, Philippe JOUSSET, Jacques HINDERER, Severine ROSAT, Christian VOIGT, Kemal ERBAS, Tilo SCHOENE, Richard WARBURTON, Andreas GUENTNER
[GFZ Potsdam, Germany]
For a better understanding of the sustainability of geothermal resources, we want to quantify subsurface mass changes caused by production and injection of fluids at the Þeistareykir geothermal field in Northeast Iceland. For this purpose, we installed three superconducting gravity meters (iGrav006, iGrav015 and iGrav032) in vicinity to the new geothermal power plant that started operation in October 2017. Prior to the Iceland installation, all gravity meters were setup at the gravimetric observatory J9 in Strasbourg for simultaneous side-by-side measurements. The obtained data were used for instrumental calibration, comparison of noise levels and tidal analysis. For determination of the iGrav drift behaviour, we included the measurements of the observatory gravity meter iOSG023 as a reference. In Þeistareykir and at a reference site outside the geothermal field, we constructed four monitoring stations, with decoupled concrete pillars for remote operation of the three iGravs. On a second pillar next to the relative gravity meters, we performed repeated absolute gravity measurements (FG5#206) for instrumental calibration and drift correction. At each station additional physical parameters, which influence the local gravity signal, are measured. This includes the continuous monitoring of GPS-positions, rainfall, soil moisture and snow thickness. Here, we present the results of the unique intercomparison of three superconducting gravity meters at Strasbourg and the time series obtained at the geothermal site in Iceland. We compare the stability of calibration, noise levels and drift behaviour at both sites. Based on our findings, we give a recommendation for the preparation of high-resolution gravity measurements in remote areas.
|        Topic: Geophysics||Paper Number: 13157|