Analysis of rock microstructure after CO2 breakthrough based on CT scanning

The alteration of mudstone’s microscopic properties within the caprock in CO2 geological storage determines the effect of storage. One of the crucial evaluating aspects of storage security is the effect of caprock’s change. Micro-computed tomography (CT) and nano-CT with high accuracy and different resolutions are used to conduct our experiments on Shiqianfeng Formation rocks obtained from the Ordos CO2 capture and storage project. We scan the rock microstructures before and after the breakthrough, compare the changes before and after the breakthrough of CO2, and combine the CT image results after the breakthrough with a numerical simulation technology to analyze the changes in the pore characteristic parameters of the rocks after the breakthrough and evaluate the CO2 sealing capacity of the distribution laws. We present the following results. (1) Pore fluid pressure rises during CO2 breakthrough, opening the connection of some sheet pores and creating micro fractures. (2) The smaller the observation scale, the more substantial the heterogeneity of rock pores. (3) The connection between large pores is tighter and exhibits better connectivity. Meanwhile, the roar channel between small pores is thinner and demonstrates less connectivity. (4) Rock porosity is in the form of approximate normal distribution.