The　casing　deformation　issues　have　occurred　widely　in　Changning-Weiyuan　National　Shale　Gas　Demonstration　Area.　During　multi-stage　volume　fracturing　process,　a　large　amount　of　fracturing　fluid　is　injected　into　the　formation,　leading　to　tremendous　change　of　stratum　property　and　formation　stress　field.　To　assess　the　influence　of　shale　formation　on　casing　deformation,　the　acoustic　velocity　is　measured　to　obtain　the　shale　rock　elastic　modulus　after　saturation　with　water　for　different　times.　Then,　the　three-dimensional　physical　and　finite　element　models　are　established　using　the　stage　finite　element　method　considering　transient　thermal-pressure　coupling.　Shale　anisotropy,　shale　stiffness　degradation,　and　formation　slip　are　taken　into　account　to　investigate　the　influences　on　casing　deformation.　Experiment　results　indicate　that　shale　stiffness　degrades　dramatically　after　saturation　with　water　for　24h.　Numerical　simulations　indicate　that　the　shale　modulus　degradation　mainly　leads　to　large　casing　stress.　Formation　slipping　not　only　causes　excessive　casing　stress,　but　also　causes　large　casing　displacement.　When　slipping　distance　is　larger　than　15mm,　casing　stress　can　reach　up　to　the　yield　stress　for　P110　grade　casing.　Meanwhile,　the　casing　deformation　will　be　14.95mm,　blocking　the　fracturing　tools　into　the　well　bottom.　Shale　anisotropy　has　a　minor　influence　on　casing　deformation.