Abstract: The inherent mechanism by which workover operations, as a type of intense transient engineering disturbance, disrupt the original dynamic equilibrium of the wellbore and induce subsequent pipe string damage remains unclear. Through comparative analysis of field data on pipe string damage under workover and non-workover conditions, the evolution of liquid–solid media in the wellbore caused by tripping the pipe string and well flushing is systematically investigated. The results show that mechanical disturbance during workover is the dominant factor leading to an increase in both the production and particle size range of coal fines. The deposition equilibrium of coal fines at the bottom hole and on the pipe wall is disrupted by instantaneous pressure fluctuations (surge pressure) and mechanical collisions during workover, resulting in a sharp increase in the particle size range and quantity of initially produced coal fines. Brittle vitrinite is preferentially exfoliated, which enlarges the particle size span of coal fines, and the concentrated release of large-sized coal fines ( > 50 μm) significantly increases the physical erosion on the pipe surface. The synergistic acceleration mechanism of “physical damage initiation – subsequent corrosion” induced by workover disturbance is elucidated. The passive film on the metal surface is completely destroyed by mechanical micro-damage such as scratches and pits generated during workover, and preferential invasion paths for corrosive media during subsequent drainage and production are thereby provided; meanwhile, the micro-roughness of the damaged surface is increased, and the nucleation difficulty of mineral crystallization is reduced. The combined effect of “initial instantaneous wear damage” and “local synergistic acceleration during long-term drainage and production” is identified as the root cause of abnormal thinning and perforation of the pipe string after workover. The feasibility of establishing a diagnostic indicator for wellbore disturbance intensity based on abnormal changes in coal fines composition is proposed. The short-term increase in chloride ion concentration in the initial flowback fluid after workover is mainly caused by the displacement and release of deep highly saline formation water driven by workover pressure. The disturbance degree of the workover operation to the reservoir can be effectively quantified by monitoring the fluctuation of the proportion of inorganic minerals (clay, quartz) to organic components (vitrinite) in the flowback coal fines. If an abnormal evolution of “decrease first and then increase” is observed in the proportion of inorganic minerals, it is indicated that the physical equilibrium of the wellbore is severely damaged. It is considered that the optimization of workover technology should focus on controlling operational surge pressure to reduce physical exfoliation of coal fines, thereby cutting off the inducement for subsequent synergistic damage. The results provide a theoretical reference for workover fluid regulation and long-term protection of the pipe string in coalbed methane wells.