Damage location prediction of cement-sandstone combinations under axial force: Three-dimensional structure reconstruction and stress distribution simulation based on μ-CT

Abstract

Effective isolation between the cement sheath and the sandstone is crucial for the development and production of oil and gas wells in sandstone formations. In this study, a cement-sandstone composite (CSC) was prepared, and based on μ-CT three-dimensional reconstruction imaging and finite element analysis (FEA) techniques, the stress distribution and potential failure mechanism at the cement-sandstone bonding interface under axial loading were analyzed. The key findings are as follows: (1) stress concentrations are highly likely to form at the gap between the cement and sandstone interface and around interfacial voids, with Von Mises stress reaching critical levels of 18.0–20.0 MPa at these locations, significantly exceeding the stress magnitudes in well-bonded regions; (2) the phenomenon of local stress concentration driven by interfacial defects can be identified as the main basis for predicting damage location in interfacial debonding and continuous shear under axial load; (3) ensuring tight cementation at the cement-sandstone interface and minimizing interfacial voids are paramount for preventing stress-induced failure; (4) the critical Von Mises stress value of 20 MPa at the interface defect can be used as a benchmark for material selection and designed to ensure long-term integrity in oil and gas well applications subjected to similar axial loads. These findings contribute to a more accurate understanding of the failure mechanism of the cement-sandstone interface and to the precise design of material properties, thereby ensuring the long-term integrity of oil and gas well applications subjected to similar axial loads.