高温下CO2地中貯留を模擬したカラム試験における炭酸塩鉱物の付着速度評価

概要

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Two types of flow experiments using columns packed with rock fragment and glass beads were performed to examine the deposition and clogging phenomena at high temperatures (180°C at Ogachi HDR site and 70°C at Matsushiro hot spring, respectively) during calcium carbonate water injection. Flow rates of both column tests decreased gradually with decrease of permeability due to mineral precipitation. Deposition of carbonate mineral was found as calcite and aragonite on the surface of rock cuttings and glass beads respectively. In this paper, the numerical simulations using deposition rates provide good agreements with the observed flow rate changes. For the column test at Ogachi, the deposition rate is estimated to be almost constant during the experiment, whereas that at Matsushiro increases with duration time. This result shows that deposition mechanisms of carbonate minerals in both experiments differs each other. At Matsushiro, nucleation of carbonate must be occurred before the injection into the column. The formed fine crystals deposited on the surface of glass beads where precipitation rates were accelerated. This carbonate mineralization on CO2 sequestration will decrease the possibility of CO2 leakage risk at hydrothermal conditions and prevent buoyancy from moving upward.