The connection method of oil casing pipe

　　1. External thickness direct connection method: one section of the pipe is thickened and has internal thread, while the other end is external thread. When connected together, the sleeve has a smooth internal surface.

　　2. Direct connection method: both ends of the pipe are internal and external screw threads, which are directly connected, and the internal and external smooth surfaces of the pipe are smooth.

　　3. Take over connection method: both ends of the pipe are internal thread buckles, which are connected with the take over. After connecting, the outside is smooth.

　　4. Coupling connection method: both ends of the pipe are externally screwed and connected with external coupling. In addition to the internal smooth surface in the later stage of connection, recently, API 5CT pipe fitting Tubing and Casing Couplings the internal surface of the pipe is smooth after welding with the method of welding sleeve joint.