黏土矿物组合类型对盖层封闭性的影响

Influence of Assemblage Types of Clay Minerals on the Sealing Ability of Caprock

在CO2地质封存中,封存的安全性备受关注。本文根据我国主要含油气盆地盖层中黏土矿物的组合特征,总结了5种常见的盖层黏土矿物组合类型,并以鄂尔多斯盆地为例,运用Toughreact软件建立了一维储盖层模型,研究了不同黏土矿物组合类型对盖层的溶蚀与自封闭效应的影响。结果表明:黏土矿物组合类型不同,引起的CO2-水-岩石的地球化学反应不同,导致盖层渗透率发生不同程度的变化,从而影响盖层的封闭性;ISCK、ISK组合以自溶蚀作用为主,尤其是ISCK组合自溶蚀效应最严重,不利于CO2的地质封存;ISC、IKC、IC组合以自封闭作用为主,其中IC组合渗透率最大减小14%,对盖层的封闭性有积极的意义。在此基础上,对我国南方5个盆地盖层的封闭性进行了初步评价,以期为我国盆地CO2地质封存的适宜性评价提供参考。

During the process of geologic sequestration of CO2,the safety of storage is the focus of attention.Based on different assemblage types of clay minerals in China＇s main basins,this paper sums up five common assemblage types of clay minerals of caprock.For the purpose of studying the influence of different assemblage types on the sealing ability of caprock,the paper takes Ordos Basin as an example and establishes a one-dimensional model by using Toughreact.The results show that different assemblage types lead to different CO2-water-caprock geochemical processes,and changes of permeability of caprock at different degrees as a result,and thus the sealing ability of caprock is affected.The ISCK and ISK assemblages are mainly of dissolution,and the most serious corrosion effect occurs with ISCK assemblage type,which is not conducive to the sequestration of CO2.The ISC,IKC and IC assemblages are mainly of self-sealing effects,and the IC assemblage type reaches a 14 percent of reduction in permeability,which has a positive meaning to the sealing ability of caprock.Based on this,the paper makes a preliminary assessment on the sealing ability of caprock in five basins in South China to provide some references for the evaluation of CO2 geological storage.