Abstract: ø139.7 mm plug-drilling-free well cementing completion technology was studied to replace conventional ø139.7 mm screen top cementing technique which was deficient over an extended period of plug drilling,sticking,casing and screen damage,and impact on subsequent tripping-in of the string.Based on the screen-top-cementing well completion technique,the existing ø177.8 mm plug-drilling-free well cementing tool was redesigned by adding ball socket,upper rubber packer,and removable sealing mechanism and optimizing the pressure differential of shear pins,so as to develop the ø139.7 mm plug-drilling-free well cementing tool and supporting technology.Field tests in 3 wells showed that the ø139.7 mm plug-drilling-free well cementing tool could create piston effects for the circulation while running casing,well cementing assisted with the upper rubber packer,and fish releasing after landing,thus reducing the fishing force by more than 200 kN and the completion time by about 30%.The study also suggested that the ø139.7 mm plug-drilling-free well completion technology was devoid of such completion procedures as plug drilling,thus avoiding risks in completions.Therefore,the technology is suitable for screen-top-cementing operations in all kinds of oil reservoirs,and medium-deep,deep and large-hole wells.