地质封存中CO_2泄漏的非稳态扩散数值模拟研究

Numerical Study on Unsteady State Dispersion of Leakage CO_2 from Geological Sequestration

针对碳捕集与封存技术中泄漏监测的难点,利用数值模拟方法研究了地质封存中CO2泄漏的非稳态扩散,以及不同的垂直风廓线形式、大气、地形等因素对非稳态扩散模拟结果的影响,探索了地质封存中CO2泄漏扩散的分布规律.研究结果表明:不同风廓线下CO2泄漏的扩散规律基本一致,仅在垂直方向上CO2的体积分数略有差异;大气层结不稳定程度越高,越有利于泄漏气体的扩散;风速越大,扩散达到稳定所需要的时间越短,稳定的CO2的体积分数越小;大气温度越高,同一高度上稳定的CO2体积分数越大,越有利于泄漏气体的垂直扩散;地表面粗糙度越大,越有利于垂直湍流波动的形成,当水平扩散减慢时,CO2达到稳定所需要的时间延长.

An unsteady state dispersion of CO2 leakage from geological sequestration was investigated by using the computational fluid dynamics method for the CO2 leakage monitor in the carbon capture and sequestration technology. Three types of wind profiles and some atmosphere and terrain factors affecting the atmospheric gas dispersion were studied. The results show that the dispersion law is consistent under different wind profiles. The vertical variation of wind velocity is greater than that in uniform velocity and logarithm law, and thus the variation of vertical concentration in power law is larger. The stronger instability of atmosphere is more favorable for gas dispersion. Moreover, the influence of atmosphere stability is greater when the measurement location is closer to the leakage source. The time of leakage gas reaching the stable state is shorter with lower stable concentration when the wind speed is faster. The stable concentration increases with an increase in temperature at the same height, which is beneficial for vertical dispersion of the leakage gas. The heavier ground roughness is in favor of forming vertical turbulence and therefore impedes the horizontal dispersion.