A　microannulus　(MA)　is　the　primary　reason　for　sustained　casing　pressure　in　multi-stage　fractured-shale　gas　wells.　However,　the　effect　of　the　casing　eccentricity　on　the　long　horizontal　section　has　not　been　considered.　In　this　study,　a　full-scale　integrity　tester　for　cement　sheaths　is　adopted　to　measure　the　cumulative　plastic　deformation.　Numerical　models　are　applied　to　evaluate　the　development　of　the　cumulative　plastic　deformation　and　quantify　the　MA　width　considering　casing　centralization　and　eccentricity　in　the　context　of　multiple　loading　and　unloading　cycles.　Subsequently,　the　influences　of　the　eccentricity　distance　and　angle,　cement-sheath　mechanical　variables,　and　different　well　depths　on　the　cumulative　sheath　plastic　deformation　and　sheath　MA　development　are　explored.　The　research　results　demonstrate　that　casing　eccentricity　significantly　increases　the　cumulative　sheath　plastic　deformation　compared　with　that　of　the　casing-centered　condition.　Consequently,　the　risk　of　sealing　integrity　failure　increases.　The　accumulated　plastic　deformation　increases　when　the　eccentricity　distance　increases.　In　contrast,　the　initial　plastic　deformation　increases　as　the　eccentricity　angle　increases.　However,　the　cumulative　plastic　deformation　decreases　after　a　specific　loading　and　unloading　cycle　count.　Affected　by　the　coupled　influence　of　the　internal　casing　pressure　and　fracturing　stages,　the　width　of　the　MA　in　the　horizontal　section　increased　from　the　toe　to　the　heel,　and　the　casing　eccentricity　significantly　increased　the　MA　width　at　each　stage,　thus　increasing　the　risk　of　gas　channeling.　Finally,　an　engineering　case　is　considered　to　study　the　influence　of　casing　eccentricity.　The　results　show　that　cement　slurries　that　form　low　and　high　elastic　moduli　can　be　applied　to　form　a　cement　sheath　when　the　fracturing　stage　is　lower　or　higher　than　a　specific　value,　respectively.　The　results　of　this　study　offer　theoretical　references　and　engineering　support　for　the　integrity　control　of　cement　sheath　sealing.　©　2024　The　Authors