黏土矿物含量对CO_2地质埋存体盖层封闭性的影响

Effect of Clay Mineral Contents on Sealing Capacity of Cap Rock of CO_2 Geological Storage

为了解CO_2地质储存过程中黏土矿物含量对盖层封闭性的影响,本文以鄂尔多斯盆地三叠系和尚沟组泥岩盖层为研究对象,利用TOUGHREACT软件研究了不同黏土矿物含量、储层厚度对盖层封闭性的影响。研究表明,当盖层黏土矿物含量达到50%时,渗透率最大可减降低36%,有效封存厚度可达70 m;当黏土矿物含量减少至10%时,盖层自封闭性大幅降低,有效封存厚度为4 m,且盖层中的蒙脱石也由沉淀转化为溶解。黏土矿物含量越高,盖层封闭性越强,有效封存厚度越大。储层厚度对盖层封闭性有直接影响,当储层厚度大于盖层有效封存厚度时,则会发生泄漏;当储层厚度达到100 m时,CO_2将在125年后穿透黏土矿物含量为50%的盖层。本研究可为CO_2地质储存的储盖层选择和安全性评价提供理论依据。

In order to investigate the effect of clay mineral on sealing capacity of cap rock,we have studied the sealing capacity of the Heshanggou Formation mudstone in the Ordos Basin with different mineral contents and reservoir thickness using TOUGHREACT software. The results show that when rocks contain high contents of clay mineral up to 50%,the permeability could decrease 36%,and the effective storage thickness can be as thick as 70 m. When clay mineral contents are reduced to 10%,the sealing capacity of cap rock is greatly lowered and the effective storage thickness is only 4 m. The smectite would experience the transfer from precipitation to dissolution under this condition. The higher the clay mineral content in the cap rock,the stronger sealing capacity of the cap rock,and the greater effective thickness of the cap rock.The reservoir thickness has a direct effect on the sealing capacity of cap rock. Once the reservoir thickness is greater than the effective thickness of the cap rock,CO2 leakage will occur. When the reservoir thickness is 100 m,CO2 can penetrate the cap rock with 50% clay minerals after 125 years. This study provides a theoretical basis for long-term safety evaluation of CO2 geological storage.