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为了解关键性矿物在“超临界CO2-水-岩石”系统中的地球化学作用,利用先进的数值模拟软件TOUGHREACT,结合我国鄂尔多斯盆地深部咸水含水层的基础地质条件,建立一维垂向模型,研究了盖层中绿泥石含量分别为3%、9%、15%时对CO2-水-岩石相互作用的影响.发现CO2进入盖层后,盖层的矿物成分和渗透率发生了较大变化.当绿泥石体积分数为3%时,盖层渗透率在5 000a期间一直处于增大状态,不适合CO2封存;当绿泥石体积分数为9%和15%时,盖层渗透率呈现先增大后减小的趋势,产生自封闭现象,有利于CO2封存.结果表明,绿泥石的溶解为盖层中钙蒙脱石、铁白云石、片钠铝石、菱镁矿的沉淀提供了必要的Mg2+、Fe2+、AlO2-等离子.绿泥石含量越多,CO2矿化捕集量越大,盖层的自封闭效应越明显,其渗透率最大减少10%.本研究结果可为CO2地质封存的长期性和稳定性评价提供理论依据.
In order to understand the geochemical effects of key minerals in the “supercritical CO2-water-rock” system, an advanced numerical simulation software named TOUGHREACT was used to establish a one-dimensional vertical profile based on the basic geological conditions of saline aquifers in the deep Ordos Basin. The influence of the chlorite content in the caprock at 3%, 9%, 15% on the CO2-water-rock interaction was studied, and the mineral composition and permeability of the caprock were found to occur after the CO2 entered the caprock When the volume fraction of chlorite is 3%, the permeability of caprock has been increasing during 5 000 a, which is not suitable for CO2 sequestration. When the chlorite volume fraction is 9% and 15% The permeability of the layer first increases and then decreases, resulting in a self-sealing phenomenon, which is favorable for the CO2 sequestration.The results show that the dissolution of chlorite is the main component of Ca-montmorillonite, iron dolomite, dawsonite, Magnesite precipitation provides the necessary Mg2 +, Fe2 +, AlO2- plasma.With more chlorite content, the greater the CO2 mineralization capture, the more self-sealing effect of the cover layer, the maximum reduction of permeability of 10% The results provide a theoretical basis for the long-term and stability evaluation of CO2 geological storage.