Peridynamics-Based Finite Element Analysis of Sealing Failure at Casing-Cement Sheath Interfaces in Ultra-Deep Wells

Area of Science:

• Geotechnical Engineering
• Petroleum Engineering
• Materials Science

Background:

• Ultradeep wells in China face increasing integrity risks due to the casing-cement bonding interface, the weakest point under high temperature, pressure, and stress.
• Failure of this interface compromises long-term wellbore safety and sealing capabilities.

Purpose of the Study:

• To develop a thermo-mechanical coupling model for ultradeep well composite systems using peridynamics.
• To quantitatively simulate casing-cement sheath interface fracture under service conditions.
• To identify key failure processes under multifield coupling and their influencing factors.

Main Methods:

• Development of a peridynamics-based thermo-mechanical coupling model for ultradeep well systems.
• Quantitative simulation of casing-cement sheath interface fracture under coupled high temperature, high pressure, and in situ stresses.
• Analysis of damage progression influenced by material properties and stress conditions.

Main Results:

• Interface damage primarily follows the path of minimum principal stress.
• Damage progression is significantly influenced by the nonuniform in situ stress coefficient, Poisson's ratio, and cement sheath elastic modulus.
• A nonuniform stress coefficient increase from 1.1 to 1.5 results in an 86.7% damage increase, leading to sealing failure above 1.3.

Conclusions:

• Optimizing material parameters, particularly the nonuniform stress coefficient, is critical for enhancing wellbore integrity and sealing dependability.
• The study provides engineering direction for designing safer and more reliable ultradeep wellbores.
• Understanding multifield coupling effects is essential for preventing interface failure in extreme environments.