Numerical Research of the Thermo-Mechanical Coupling Behavior of Cement Sheath in Deepwater Well Using COMSOL

The cement sheath functions as a critical load-bearing and sealing element between the casing and the formation, and its integrity is directly related to well safety and marine environmental protection. Under deepwater conditions of high hydrostatic pressure and pronounced vertical temperature gradients, periodic temperature and pressure fluctuations induced by continuous extraction of produced fluids can generate significant thermo-mechanical coupling effects, which may lead to stress concentration and progressive damage of the cement sheath, the formation of flow pathways, and degradation of sealing performance. To systematically investigate these evolution mechanisms, this study develops a three-dimensional axisymmetric finite-element model of the casing-cement sheath-formation system in COMSOL Multiphysics, coupling heat transfer with structural mechanics to solve for temperature and thermal stress fields. Boundary conditions account for thermal expansion, seawater temperature, and deepwater hydrostatic pressure. Both steady-state and transient analyses are conducted to characterize the spatiotemporal evolution of temperature and stress. Parametric studies are performed by varying temperature differential, cement sheath stiffness, and thickness to provide numerical insights and theoretical guidance for optimization of deepwater well cementing design, material selection, and long-term integrity assessment.