Thermo-poroelastic modelling of cement sheath: pore pressure response, thermal effect and thermo-osmotic effect

Cement sheath provides zonal isolation and structural support during oil/gas well exploitation. Mechanical behaviours of cement sheath are of increasing concern with the exploitation of shale gas. In order to overcome the drawbacks of continuum assumption of cement sheath, a comprehensive thermo-poroelastic model, accounting for the pore water pressure resulted from hydraulic pressure in casing, the thermal loading induced by the temperature difference between the injected water in casing and underground formation, and thermo-osmotic effect, is developed to determine the evolution of effective stress of cement sheath. Moreover, failure criteria for the cement sheath, whose parameters are temperature dependent, are proposed to assess failure modes of cement sheath. A case study is also carried out to assess the tendencies of the failure modes of cement sheath during loading. Application of the proposed model on a triaxial test of undrained heating of oil well cement paste shows the capability of the model with to well reproduce the experimental results.

Automated summary

A comprehensive thermo-poroelastic model was developed in this study to consider various factors affecting the mechanical behavior of cement sheath in oil/gas well exploitation. The model takes into account hydraulic pressure, thermal loading, and thermo-osmotic effect. Temperature-dependent failure criteria were proposed to assess the failure modes of the cement sheath. The model was applied to a triaxial test and successfully reproduced the experimental results.