A concept of CO₂ Georeactor sequestration at the Ogachi HDR site, NE Japan

A field experimental study of CO₂ sequestration into the Ogachi hot dry rock (approximately 200 grad C, mainly consists of granitic rocks) have been conducted to explore safe and permanent CO₂ storage by creating carbonate minerals in the subsurface. In the CO₂-Injection Experiment by single well testing, CO₂ dissolved water with a tracer was injected by free flowing injection through a deep geothermal well (OGC-2) to the reservoir. And chemical monitoring with a wireline sampler in batch has been enforced for the estimation of the release of base cations from reservoir rock, reaction of CO₂ with cations. Resultant CO₂-Tracer balance suggests that carbonates might precipitate in a few days. In addition, the crystal-growth testing in the borehole using a newly developed chemical reactor sonde was implemented to ascertain CO₂ fixation as carbonates under in-situ conditions and it was indicated that a spiral growth rate of calcite was order of mm/year. Laboratory experiments and simulations for CO₂-water-rock interaction also have been executed to make long-term evaluation of the CO₂ storage process and optimization of reservoir modeling.