Perforation　operation　is　critical　in　bridging　completion　and　production　enhancement　operations.　At　the　same　time,　the　perforation　parameters　also　affect　the　structural　integrity　of　the　casing.　Still,　there　are　fewer　studies　on　the　stress　distribution　of　the　casing　under　the　blast　transient　impact　loading　of　multi-hole　perforation.　To　address　this,　considering　the　engineering　application　of　helical　perforation　in　unconventional　oil　and　gas　reservoirs,　a　three-dimensional　numerical　model　of　perforating　charge-casing-cement　sheath-formation　is　established,　and　the　Holmquist-Johnson-Cook　(HJC)　rock　dynamics　material　model,　as　well　as　the　fluid–solid　coupling　and　Arbitrary　Lagrange-Euler　(ALE)　algorithms.　On　this　basis,　the　variation　rule　and　distribution　characteristics　of　the　effective　stress　in　the　double-perforation　holes　stress　superposition　area　under　different　perforation　density,　phase　angle,　and　geostress　conditions　are　analyzed　with　the　casing　strength　safety　threshold　as　the　optimization　judgment　condition　of　perforation　parameters.　The　research　results　show　that　the　numerical　simulation　result　has　good　consistency　in　the　results　of　engineering　practice,　perforation　aperture　diameter　error　is　3.04%,　and　jet　head　velocity　error　is　6.85%.　The　variation　rule　of　perforation　density　and　phase　angle　has　a　significant　effect　on　the　effective　stress　distribution　in　the　stress　superposition　area　around　the　hole:　with　the　decreasing　perforation　density　or　increasing　phase　angle,　the　casing　stress　superposition　area　in　the　middle　part　of　the　neighboring　perforation　holes　is　gradually　narrowed　down,　and　when　the　perforation　density　is　more　than　9　P/m　and　51°,　the　casing　stress　in　the　stress　superposition　area　between　the　perforated　holes　is　lower　than　the　safety　threshold　value.　With　the　increasing　ground　stress,　the　stress　in　the　middle　of　the　neighboring　perforated　holes　increases　continuously,　showing　a　quadratic　function　change　trend.　The　perforation　density　should　be　appropriately　reduced,　and　the　phase　angle　should　be　increased　when　the　geostress　is　high　to　ensure　the　integrity　of　the　casing　structure　after　the　perforation　operation.　The　research　results　can　provide　a　practical　reference　for　conducting　perforation　engineering　operations　and　optimizing　perforation　parameters.　©　2023　Elsevier　Ltd