The oil casing is the lifeline that keeps the well running.Due to the different geological conditions, the downhole stress state is complex, and the comprehensive action of tensile, compressive, bending and torsional stresses on the pipe body, which puts forward higher requirements for the quality of the casing itself.If the casing itself is damaged for some reason, it can reduce production or even kill the entire well.
According to the strength of the steel itself, the casing can be divided into different steel grades, namely J55, K55, N80, L80, C90, T95, P110, Q125, V150 and so on.The main specifications are 139.77.72 r-2, 177.89. 19r-2, 244.58. 94r-2, 244.510.03r-2, 244.511.05r-2, etc.There are three lengths specified by API: r-1 is 4.88-7.62m, r-2 is 7.62-10.36m, and r-3 is 10.36m to longer well conditions and depths. Different steel grades are used.The casing itself is also required to have corrosion resistance under corrosive conditions.The casing is also required to have anti - crushing performance in the place of complicated geological conditions.Machining form of casing end: short round thread, long round thread, partial trapezoidal thread, special thread, etc.It is mainly used to support the borehole wall during drilling and after completion to ensure the drilling process and the normal operation of the whole well after completion.