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

为了弥补储层中已存在和/或诱导裂缝造成的CO_2泄漏，我们研究了一种使用水溶液的概念。该溶液具有足够低的粘度，甚至可以通过很小的孔径，而且只要溶液保持原状，就不会影响地层渗透率。当溶液遇到溶解的CO_2时，由于化学反应会产生沉淀。因此，将沉积物充填在岩石的孔隙和裂缝中，会降低岩石的渗透率。我们首先通过模拟1000 m深（即10 MPa和40°c）地下条件的实验室实验证明了这一想法。结果表明，即使玻璃珠人造岩石的初始高渗透率很少达西，该方法也能使其渗透率降低99%。非等温反应地球化学输运程序TOUGHREACT成功地再现了这种渗透率的降低。在此基础上，将该方法应用于野外物理化学条件下的二维盖层-含水层系统的数值模拟。结果表明：析出相的产生充分地填充了泄漏通道出口附近的孔隙，阻断了CO_2的运移，并在较长时间内证实了这一条件是稳定的。

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.