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

Abstract

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 $k_{pT}=5\times {10}^{-12}{\mathrm{m}}^2/(°\mathrm{C.s})$ to well reproduce the experimental results.

Keywords:

• Cement sheath
• thermo-poroelastic model
• thermo-osmotic effect
• effective stress
• failure criteria

Acknowledgments

The authors are grateful to Professor E. Detournay at the University of Minnesota for his support during the course of this work. This study was supported by grants from the National Natural Science Foundation of China (NSFC) project (Grant no. 51708404).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by grant from the National Natural Science Foundation of China (NSFC) project (grant no. 51708404).