Development of the method to remedy leakage from geological CO2 reservoir using CO2 reactive grout

为了通过储集层原有的和/或诱发的裂缝修复二氧化碳泄漏，我们研究了使用水溶液的概念。该溶液具有足够低的粘度，即使是小孔径也可以通过，而且只要溶液保持不变，就不会影响地层渗透率。当溶液遇到溶解的CO_2时，会发生化学反应而发生沉淀。因此，通过用沉淀物填充岩石中的孔隙和裂隙，渗透率将会降低。我们首先通过实验室实验模拟了1000米深，即10兆帕和40度的地下条件，证明了这一想法。结果表明，该方法使玻璃微珠人造岩石的渗透率降低了99%，即使其最初的高渗透率也很少达西。这种渗透率的降低被非等温反应地球化学传输程序TOUGHREACT成功地重现。在此基础上，将该方法应用于野外物理和化学条件下的二维盖层-含水层系统的数值模拟。结果表明，在泄漏通道出口附近产生了大量的沉淀物，充填了气孔，阻碍了CO_2的迁移，且稳定了很长时间。

In order to remedy CO_2 leakage through pre-existing and/or induced fractures from storage reservoirs, we studied a concept to use an aqueous solution. The solution will have a sufficiently-low viscosity for passing through even small aperture, and it will not impact formation permeability as long as the solution is left as it is. When the solution encounters dissolved CO_2, precipitation will occur due to chemical reaction. As a result, the permeability will be reduced by filling the pores and fractures in the rocks with the precipitates. We demonstrated first this idea through laboratory experiments simulating subsurface condition at 1000 m deep, i. e. 10 MPa and 40 deg. C. The results show that the present method led to a 99 %permeability reduction in a glass-bead artificial rock even its initially-high permeability of few darcy. Such reduction of permeability was reproduced successfully by the non-isothermal reactive geochemical transport program TOUGHREACT. Based upon these success, the present method was applied by numerical modeling to a 2-D caprock-aquifer system under field physical and chemical conditions. The results show that the precipitates were produced and they filled up pores around outlet of the leakage path so sufficiently that the CO_2 migration was blocked, and the condition was confirmed stable over a long time.