Análise termo-poroelástica da integridade estrutural de bainhas de cimento em poços de petróleo

Abstract

This work investigates the influence of considering the porous behavior of the cement sheath and the adjacent rock formation on the stress distribution within the casing–cement–formation system, as well as on the structural integrity of the cement sheath itself. Responsible for anchoring the casing to the formation and ensuring hydraulic isolation between permeable zones, the cement sheath plays a crucial role in maintaining the structural integrity of oil wells, acting as one of the main safety barriers throughout the well’s lifecycle. To ensure its performance, proper mechanical design is essential. Traditionally, thermoelastic models have been widely used for cement sheath design. However, recent studies suggest that the porous nature of cement can significantly affect its mechanical response, especially under varying thermal conditions. To investigate this effect, the present study proposes a methodology structured in five steps: (i) mathematical modeling of the problem; (ii) derivation of analytical thermoelastic and thermo-poroelastic solutions; (iii) assessment of cement sheath integrity based on failure criteria; (iv) comparison of results from each approach; and (v) numerical modeling and validation against the analytical solutions. The results show that the thermoporoelastic approach more realistically captures the stress state within the cement sheath. Although the thermoelastic approach generally results in higher effective stresses, the thermoporoelastic analysis provides a more conservative evaluation of structural integrity. Numerical and analytical results show excellent agreement, with relative errors below 2% in most evaluated points. Despite its simplified configuration, the numerical model proves effective and can be extended to more complex scenarios where analytical solutions are not feasible. Therefore, this study offers relevant technical insights for cement sheath design, supporting the improvement of engineering practices in the oil and gas industry. The findings presented here establish a solid foundation for future research involving irregular geometries, nonlinear material behavior, and non-uniform loading conditions.