盐水层中注水促进超临界CO2溶解的数值模拟

采用数值模拟的方法,通过考察不同注水模式、注水速率、注水位置、盐度和孔隙度下CO_2的分布特性和溶解行为,系统地分析了注水对CO_2溶解的影响。结果表明,超临界态CO_2呈倒锥形分布于注入井附近的盐水层顶部,并随时间延长缓慢向外扩展。注水虽不明显改变CO_2的分布,但能促进CO_2的溶解,降低超临界态CO_2的量。增大注水速率、靠近盐水层顶部注水、在注CO_2的过程中同时注水均可有效提高CO_2的溶解率。在一定范围内,CO_2的溶解量随盐水盐度降低而提高,但几乎不随岩石孔隙度变化。研究表明,通过优化注水条件可以显著促进CO_2的溶解封存。

Numerical study for enhancing the dissolution of the supercritical CO2 by water injection into the saline aquifer

This paper is to devote itself to a simulation study of the impact of injecting water into the saline aquifer on the supercritical dissolution of CO2 based on a self-developed program,that is,the so-called SoFaR_PM.For the purpose,we have also developed a two-dimensional cylindrical saline aquifer model 100 m thick with its radius beingl00 km around.We have also adopted the Newton-Raphson method to solve the equations of the flow and transfer of CO2 in the said saline aquifers.While taking into consideration an injection rate of water at a rate of 10 kg/s during a period of 30 years for CO2,it is necessary to make the injection rate and duration varied in a range of 3-50 kg/s and 30-70 years.The simulation results we have gained indicate that the injected supercritical gas of CO2 gathered at the top of the saline aquifer should crop up in a shape of an inverted cone.At the same time,it can also be made to expand radially with time and the increase.d degree of CO2 dissolution.However,the injection of water during or after the CO2 injection should not be able to change the CO2 distribution rate obviously,but rather enhance its dissolution significantly.What is more,as compared with the case of water injection following the CO2 injection,simultaneous injection of water and CO2are supposed to1 ead to pronounce a great more of CO2 dissolution.Thus,needless to say,a higher rate of water injection,plus a shorter distance of the water injection point to the top of the saline aquifers,may surely result in more CO2 dissolution.Thus,it can also be concluded that lower salinity of the saline injection is expected to be more beneficial for promoting higher amount of CO2 dissolution.In contrast,changing the rock porosity can hardly influence the CO2 dissolution.Therefore,the simulation results of this paper clearly shows that water injection can greatly help to enhance the CO2 dissolution in the saline aquifers,which helps to make the results of the present study a guide to the development of CO2 storage technology