超临界CO_2在地下盐水层内弥散现象的数值模拟

Numerical simulation of the dispersion of supercritical CO_2 storage in saline aquifers

在超临界CO2地质封存过程中,CO2在迁移过程中溶于盐水产生密度梯度,从而在盐水层中弥散并沉降,这对于减少盖层承受压力、降低CO2的泄露风险以及提高地下CO2的封存容量具有很重要的意义。该文研究了超临界CO2注入储层多孔结构后CO2在盐水中的弥散质量随时间的变化规律,分析了CO2地质封存工程应用中的关键参数盐度、温度、压强对一定时间内单位体积盐水层中CO2弥散质量的影响。研究表明:对于渗透率以及颗粒分布状况相同的储层结构,在CO2自由区气相饱和度相同时,盐水层盐度越大,指进现象越不明显,盐水层溶解CO2的质量也越少;盐水层温度越高,指进现象越明显,但是盐水层溶解CO2的质量减小;盐水层的压强越大,指进现象越明显,盐水层溶解CO2质量越大。

Supercritical COz storage in saline aquifers results in a density gradient which causes dispersion and sedimentation due to CO2 dissolving in the brine during the CO2 migration. This density gradient plays a significant role in promoting the geological storage capacity, reducing pressures on the caprock, and reducing the CO2 leakage risk. This paper describes numerical investigations of the influence of key parameters such as the salinity, temperature, and pressure on the amount of CO2 dissolved in brine per unit volume over time. The results show that, for the same permeability and porous structure of the saline aquifer, a higher salinity leads to weak fingering with small amounts of dissolved CO2. Higher temperatures contribute to strong fingering and small amounts of dissolved CO2. Higher pressures also produce fingering with large amounts of dissolved CO2.