CO_2-水-岩相互作用对盖层渗透率影响的数值模拟

Numerical Simulation of CO_2-Water-Rock Interaction Impact on Caprock Permeability

针对我国江汉盆地深部含水层的基础地质和水文地质条件,运用国际先进的反应溶质运移数值模拟软件TOUGHRE-ACT建立垂向一维模型,探索研究了CO2进入盖层后,CO2-水-岩相互作用对盖层渗透率的影响。模拟结果表明,CO2进入盖层后,会使pH值降低,导致矿物组分和渗透率的变化。模拟5 000a后,盖层底部和顶部渗透率分别增加了10%和6.7%,主要是由石膏在该处的溶解以及菱镁矿未能沉淀造成的;盖层中部渗透率降低了约6.7%,主要是因为铁白云石和菱镁矿在后期发生了沉淀;绿泥石的溶解为铁白云石和菱镁矿的沉淀提供了必要的Mg2+和Fe2+离子来源,对盖层渗透率的变化起到了至关重要的作用。

This paper, based on the basical geological and hydrogeological conditions of deep aquifers in Jianghan Basin in China, established a one-dimensional Vertical model with the famous TOUGHREACT code to study the impact on permeability of caprocks induced by CO2-water-rock interaction after CO2 breaking into the eaprock. The simulation results showed that CO2 breaking into the caprock reduces the pH value, and changes the mineral composition and permeability. After 5000 years of simulation time, the permeability on the bottom and top of caproek increases by 10% and 6.7%, respectively, mainly clue to the dissolution of gypsum and no precipitation of magnesite in the area. At the central of caprock, the permea- bility decreases by about 6.7%, mainly due to ankerite and magnesite precipitate in the later period. The dissolution of chlorite provides Mg2＋ and Fe2＋ for precipitation of ankerite and magnesite, which plays a crucial role on permeability changes of the caprock.