End face with a gap, no boss butt is refers to the upper and lower casing left a certain gap between the upper and lower main chord rod end face at the same time contact.
端面有间隙、无凸台对接是指在上、下套管之间留有一定间隙，上、下主弦杆端面同时接触对接。
2
Pull-out failure is the main damage form of round thread casing connections.
连接接头滑脱失效是圆螺纹套管损坏的主要形式。
3
Cement sheath are the main composites for cementing well and isolating the pay zone together with casing pipes.