A thermo-poroelastic model for dual steel casing−cement sheath−formation in deep earth environment

Based on thermo-poroelastic theory and accounting for the thermo-osmotic effect, this work investigates the poroelastic behavior of dual steel casing−cement sheath−formation subject to inner casing pressure and thermal loading. According to the model validation, the model well reproduces the experimental data in the existing literature. The model results show that compared with the drained cement sheath 2, the undrained cement sheath 1 is more susceptible to radial cracking and interface debonding; compared with the application of 50 MPa inner casing pressure, −100 ℃ thermal loading induce higher negative pore pressure at interface 1 of cement sheath 1, whose pore water pressure reach as much as −26.4 MPa, the high negative pore water pressure leads to high effective tensile stress at interface 1, resulting in the radial cracking and debonding of interface 1; when the thermo-osmotic coefficient of cement sheath is higher than 1×10⁻¹² m²/(℃∙s), the thermo-osmotic effect leads to higher negative pore water pressure and thus higher effective tensile stress at interface 1, resulting in radial cracking and interface debonding at interface 1.