Abstract: In order to prevent damage of cement ring caused by casing deformation during large scale fracturing,block gas channeling path and prevent wellhead pressure,an outer casing anti-gas channeling device was developed based on the analysis of gas channeling causes in shale gas well.Through a numerical simulation test,a pressure deformation test and a pressure seal test,the pressure deformation law of the casing and the outer casing anti-gas channeling device was analyzed.Using that information,the pressure seal performance of the outer casing anti-gas channeling device was verified.Under a casing pressure of 70 MPa,the outer radical deformation of the device was only 0.007 mm,and the gas channeling path was formed.The outer casing anti-gas channeling device had strong anti-gas channeling performance,and could bear the differential pressure of 35 MPa in the case of compression and sealing.This device was tested in the pay zone cementing of Well Jiaoye 88-2HF and Well Jiaoye 93-2HF.No wellhead pressurizing occurred either well after fracturing.Both the performance test and the field test demonstrated that the outer casing anti-gas channeling device could reduce casing deformation damage to the cementation.The new technique could prevent micro gaps in the cement ring caused by large scale fracturing,so as to prevent gas channeling.This technique could provided a new technical means for anti-gas channeling in shale gas wells.