Fluid-Driven Debonding of Cement Interfaces of an Injector Well: A Coupled Thermo–Hydro–Mechanical Approach

• Published in: Rock mechanics and rock engineering 2024-07, Vol.57 (7), p.4513-4531
• Main Authors: Gu, Chenwang, Feng, Yongcun, Mosleh, Mojgan Hadi, Li, Xiaorong, Sanei, Manouchehr, Deng, Jingen
• Format: Article
• Language: English
• Subjects: Cement; Civil Engineering; Concrete; Content analysis; Crack initiation; Debonding; Earth and Environmental Science; Earth Sciences; Flow rates; Flow velocity; Fluid flow; Fluids; Fracture mechanics; Geophysics/Geodesy; Hydrology; Influence; Injection; Interfaces; Low temperature; Mathematical analysis; Mathematical models; Mechanical properties; Modulus of elasticity; Numerical models; Original Paper; Pore pressure; Pore water pressure; Pressure; Pressure effects; Propagation; Risk reduction; Sheaths; Viscosity
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-024-03786-w

Fluid leakage caused by debonding at the cement interfaces driven by low-temperature fluids is recognized as a significant challenge to wellbore integrity. Previous studies have primarily focused on casing/cement interface debonding, without thoroughly analyzing the simultaneous propagation of debonding fractures at the casing/cement interface and cement/formation interface. Furthermore, prior investigations have been conducted based on hydro-mechanical coupling analysis, neglecting the influence of injection fluid temperature on interface debonding. Therefore, this paper aims to reveal the debonding mechanism of the two cement interfaces using a coupled thermal–hydrological–mechanical (THM) modeling approach. Considering the effect of injected fluid temperature, a 3D numerical model of casing-cement-formation is developed for the simulation of the fluid-driven debonding based on the coupled pore pressure cohesive zone method. The influences of various factors including injection fluid temperature, flow rate, viscosity, casing pressure and cement Young's modulus on the cement sheath debonding are studied, and grey relational analysis is carried out on the influence degree of different factors. The results indicate that the fracture propagation pressure (FPP) is higher, and the fracture height is lower at the casing/cement interface compared to the cement/formation interface. When the fluid temperature is considered by the model, the FPP at the cement sheath interface is lower, and fracture initiation and propagation are more likely to occur. The results also demonstrate that higher fluid temperature, flow rate, viscosity and casing pressure increase the FPP and reduce the risk of cement sheath interface debonding. Casing pressure and fluid temperature exhibit a more prominent influence on FPP. The method can effectively predict the propagation of debonding failures at the cement sheath interface, and provide a foundation for the optimization of injection parameters. Highlights This paper investigates the simultaneous propagation of the fluid-driven debonding of two cement interfaces considering the injected fluid temperature. A novel numerical model considering the fully coupled thermal–hydrological–mechanical processes is developed. Effects of injection fluid temperature, flow rate, viscosity, casing pressure and cement Young's modulus on the interface debonding are examined. A grey relational analysis is conducted to rank the influence degree of differen