<p>The failure of wellbore sealing is a major cause of leakage in gas storage salt caverns, but preventing wellbore leakage over the long term is very challenging. The presence of an annular transport channel in the wellbore does not necessarily result in large-scale leakage; it also requires assessment based on conditions such as pressure state. The axial leakage pathways in the wellbore are mainly due to the absence of the cement sheath interface, while radial leakage pathways are mainly due to matrix micro-cracks, both of which are caused by cyclic loads from intense injection and extraction activities. Random injection and extraction operations result in variable load amplitudes and loading frequencies, making it difficult to calculate the fatigue damage of the cement sheath. In this paper, a nonuniform amplitude fatigue damage model was developed to calculate wellbore leakage pathways and the permeability characteristics of the cement sheath. Various cyclic load tests on cement with different amplitudes were conducted, and permeability was measured. The model was validated using data from acoustic emission, permeability, and irreversible deformation. The paper also established a wellbore leakage model considering cement sheath damage and interface voids, and performed leakage calculations under different injection and extraction amplitudes and cycles. The following conclusions were drawn: Cyclic loads can induce crack propagation in the cement sheath, and radial cracks can lead to interlayer leakage in the wellbore. The axial leakage pathways in the wellbore are formed by irreversible deformation that causes micro-annular spaces to connect. The width and circumferential span of these micro-annular spaces are the main factors affecting leakage flow. However, at higher casing pressures, leakage pathways may experience local closure, so leakage calculations need to account for changes in transport pathways.</p>