The oil casing is a kind of steel pipe used to support the well wall of oil and gas wells, so as to ensure the normal operation of the whole oil well during the drilling process and after the completion of the well. According to different drilling depth and geological conditions, several layers of casing shall be used for each well. After casing running into the well, cement should be used for cementing. It is different from tubing and drill pipe, and can not be reused. It belongs to disposable consumption material. Therefore, the consumption of casing accounts for more than 70% of all oil well pipes.
Casing can be divided into: conduit, surface casing, technical casing and reservoir casing according to the usage.
Different well conditions and well depths lead to different steel grades. In corrosive environment, the casing itself is also required to have corrosion resistance ability. In the complex geological conditions, casing is also required to have collapse resistance ability.According to API 5CT,there are three kinds of casing lengths: R1 is 4.88-7.62m, R2 is 7.62-10.36m, and R3 is 10.36m and longer.
The oil casing is a kind of large-diameter pipe, which is used to fix the oil and natural gas wellbore or hole.The casing is inserted into the hole and held in place with cement to help the well block the rock and prevent the hole from collapsing, while allowing drilling mud to circulate for easy drilling.
Steel grades of oil casing: H40, J55, K55, N80, L80, C90, T95, P110, Q125, V150, etc.Thread types: short round thread casing(STC), long round thread casing(LC), buttress thread casing (BTC),partial trapezoidal thread casing and special buckle casings such as BT-1 thread casing,BT-2 thread casing,BT-3 thread casing,vam top thread casing,new vam thread casing and OTTM thread casing,etc.
API 5CT establishes requirements for three product specification levels (PSL-1, PSL-2, PSL-3). The requirements for PSL-1 are the basis of this standard.
Different types of casing used in the production of oil: surface casing protects the well from contamination by shallow water and gas, supports wellhead equipment and maintains the weight of other layers of casing.Technology oil casing separates the pressure at different levels so that the drilling fluid line can flow normally and protect the production casing.For installation of anti-blowout, leak preventer and liner in the well.The reservoir casing carries oil and gas out of the reservoir below the surface.Used to protect the well and to layer the drilling mud.The outer diameter of the casing is usually 114.3 mm to 508 mm.