Experimental and numerical simulation of the injection of a CO2 saturated solution in a carbonate reservoir: application to the CO2-DISSOLVED concept combining CO2 geological storage and geothermal heat recovery

The CO2-DISSOLVED project explores the technical and economic feasibility of a promising concept combining CO2 storage and geothermal heat extraction. The CO2 released by low CO2 emitters is dissolved in the extracted brine via a doublet heat exchanger system. To study the effect to CO2-rich and thus acidic solution in the geothermal doublet, three reactive flow-through experiments mimicking the injection of a CO2 rich solution were performed. The chemical interactions in the near-injection well area between the reservoir rock, the cement phases and the acidic CO2-rich solution was investigated under geothermal reservoir conditions. The main results are i) the formation of a highly permeable network due to specific dissolution pattern called wormholes, and ii) the preservation of mechanical cohesion the cement/rock interface despite the cement carbonation. The experimental results are compared with those obtained by chemical-transport modelling with the coupled PHREEQC-MARTHE codes. (C) 2017 The Authors. Published by Elsevier Ltd.