Surface-downhole electrical resistivity tomography applied to monitoring of CO2 storage at Ketzin, Germany

ABSTRACTSurface-downhole electrical resistivity tomography (SD-ERT) surveys were repeatedly carried out to image CO2 injected at the pilot storage Ketzin, Germany. The experimental setup combines surface with downhole measurements by using a permanent electrode array that has been deployed in three wells. Two baseline experiments were performed during the site startup and three repeat experiments were performed during the first year of CO2 injection. By the time of the third repeat, approximately 13,500 tons of CO2 had been injected into the reservoir sandstones at about 650 m depth. Field data and inverted resistivity models showed a resistivity increase over time at the CO2 injector. The lateral extent of the related resistivity signature indicated a preferential CO2 migration toward the northwest. Using an experimental resistivity-saturation relationship, we mapped CO2 saturations by means of the resistivity index method. For the latest repeat, CO2 saturations show values of up to 70% near the injectio...