Fatigue Damage of Wellbore Cement Sheath in Gas Storage Salt Cavern Under Alternating Internal Pressure

This paper investigates the fatigue damage of the wellbore cement sheath under different cyclic loading conditions. According to the irreversible principle of thermodynamics, a damage evolution model considering both tension and compression fatigue damage is established. With acoustic emission monitoring, uniaxial compression and Brazilian disc splitting cyclic loading failure tests were performed. Based on the test results, the damage theory is verified using the cumulative strain, Young's modulus and acoustic emission characteristics. The research gives a numerical algorithm of the fatigue damage theory to develop as a constitutive equation. With reference to the structural and operating parameters of a gas storage salt cavern in Jintan, a casing-cement sheath-stratum numerical model is established. By inserting the damage constitutive equation into the numerical model calculation, the damage characteristics of the cement sheath are shown. Finally, the gas storage operating parameters that meet the requirements of high injection-production efficiency and long service life are given.

Automated summary

This paper investigates the fatigue damage of the wellbore cement sheath under different cyclic loading conditions and develops a damage evolution model considering both tension and compression fatigue damage. The damage theory is verified through tests and numerical modeling, showing the damage characteristics and providing gas storage operating parameters that meet the requirements of high injection-production efficiency and long service life.