###### Abstract
Currently, an estimated 20,000 casing-damaged wells exist in China, with the number of such wells across different oil fields continuing to increase. The mechanism of casing damage varies according to the geological characteristics of the reservoir. Casing deterioration is a multifaceted process shaped by all phases from drilling to development, encompassing oil extraction. It involves rock mechanics, fluid dynamics, string mechanics, and the amalgamation of multiple disciplines, resulting in a wide array of intricate types and mechanisms of casing damage [22]. Understanding the induction mechanism of casing damage has been a recent focus and research challenge [23; 24]. In the 1970s and 1980s, scholars investigated the effect of non-uniform loads on the casing's outer wall, employing stress superposition to derive theoretical formulas for internal stress changes in the casing. Soviet researchers devised an experimental apparatus to simulate the compression impact of rock viscoelastic flow on the casing's outer wall, studying the forces exerted on it. This experiment yielded data on casing wall stress variations and rock viscoelastic expansion. [PERSON] et al. employed the modified Lade criterion to predict wellbore stability [25]. [PERSON] et al. qualitatively analyzed the effects of formation shear stress, formation dislocation, and reservoir stress on casing failure [7]. Scholars have employed finite element methods to investigate the mechanism of casing damage in water injection oilfields [26; 27; 28]. They have focused on studying the causes and patterns of casing damage during the high-pressure water injection stage. It has been observed that, with current cementing quality and development technology, high-pressure water injection penetrates weak mudstone interlayers, creating a submerged water area. This leads to changes in in-situ stress within the submerged water area and formation displacement, which is the primary cause of casing damage [29; 30; 31]. Scholars have proposed a calculation method for casing stress and strength under elliptical non-uniform external loads caused by rock creep, elucidating the mechanical factors behind casing compression damage [32; 33; 34; 35]. Extensive indoor research, wellbore corrosion coupon test analysis of the Luohe Formation in the Changqing Oilfield, and water quality analysis have highlighted the role of corrosion in exacerbating casing damage severity in different areas of the Changqing Oilfield. In summary, excessive development resulting in formation compaction and settlement is the predominant cause of casing damage in foreign oilfields, whereas water injection development and corrosion are the main inducing factors in domestic oilfields. This research focuses on the low permeability reservoir G155 in the Changing Oilfield as a representative area with concentrated casing damage. The study delves into the mechanical mechanisms underlying casing damage. It commences by offering an overview of the G155 block and detailing the present scenario of casing deterioration in this region. Subsequently, casing damage is classified from a mechanical standpoint. The distribution of impaired well segments and the longevity of these wells are then subject to statistical analysis. The research predominantly concentrates on casing deformation, specifically examining the surface stress conditions of the casing and cement sheath under non-uniform in-situ stress. A two-dimensional finite element mechanical model of the casing-cement sheath assembly is formulated to simulate variations in Von Mises stress due to differences in maximum and minimum horizontal principal stresses. It is observed that casing deformation in this area is influenced not only by non-uniform in-situ stress but also by other creep-related additional load factors. Additionally, a three-dimensional finite element model is established to analyze the impact of mudstone creep as an additional load on casing stress and examine the characteristics of casing damage.