Research on the Relationship between Pore Structure and the Compressive Strength of Oil-Well Cement

The integrity of wellbore cement is an important guarantee for the long-term safety and effectiveness of carbon dioxide geological storage. During the process of CO 2 capture, utilization, and storage, construction factors will cause changes in temperature and pressure distribution, leading to changes in the pore structure of cement and a decline in compressive strength, which can easily cause the failure of cement ring integrity. To provide theoretical guidance and analysis methods for evaluating the mechanism of cement strength performance degradation and optimizing injection parameters, in this study, we conducted the following research based on relevant studies: (1) The fracture theory was revised based on the characteristic factors of oil-well cement; (2) a pore structure model was established to analyze the failure process of cement, clarifying the relationship between pore structure and the compressive strength of cement; (3) the parameters of the pore structure model were determined and analyzed, considering the influence of cement content and total porosity on the model, and finally, the regression parameter K value was determined to be 1600. This article can provide a useful reference for the research on the failure of cement rings in the CO 2 injection process and other related studies.