Volume　fracturing　of　shale　gas　wells　has　been　observed　to　lead　to　the　failure　of　cement　sheath　and　to　sustained　casing　pressure　(SCP).　This　paper　presents　a　new　numerical　investigation　aimed　at　understanding　the　failure　mechanism　of　the　cement　sheath　during　volume　fracturing.　A　wellbore　temperature　model　was　established　to　obtain　the　required　input　parameters　for　the　dynamic　temperature　boundary.　The　numerical　model　considers　the　coupling　of　casing,　cement　sheath,　and　formation　rock　to　calculate　the　radial　and　tangential　stresses　in　the　cement　sheath.　In　addition　to　the　cement　mechanical　properties,　the　influencing　factors　considered　include　the　casing　pressure,　fracturing　fluid　displacement,　and　initial　temperature.　The　cement　sheath　integrity　was　evaluated　using　the　Mohr-Coulomb　failure　criterion.　The　results　show　that　the　temperature　of　cement　sheath　changes　drastically　during　fracturing.　The　radial　and　tangential　stresses　in　the　cement　sheath　change　continuously　with　time.　Lowering　the　internal　wellbore　pressure　can　effectively　reduce　the　radial　and　tangential　stresses　in　the　cement　sheath.　Reducing　the　fracturing　fluid　displacement　can　significantly　lower　the　radial　and　tangential　stresses　in　the　cement　sheath.　Increasing　the　initial　fracturing　fluid　temperature　will　cause　the　radial　stress　of　cement　sheath　to　increase　and　the　tangential　stress　to　decrease.　The　use　of　cements　with　low　Young＇s　modulus　values　can　significantly　reduce　the　radial　and　tangential　stresses　in　the　cement　sheath.　The　use　of　cements　with　low　Poisson＇s　ratio　values　can　lower　the　tangential　stress.　The　results　obtained　using　the　model　were　verified　by　field　data　that　demonstrated　no　occurrence　of　casing　pressure　when　using　a　cement　with　a　low　elastic　modulus,　as　suggested　by　the　model.