1. Bushing: Mainly used for drilling in the sea and desert, to separate the seawater and sand and ensure the well drilling. The main specifications of this bushing are: ∮762mm (30in) × 25.4mm, ∮762mm (30in) × 19.06mm.
2. Surface casing: mainly used for the first time drilling, drilling soft surface ground to bedrock, in order to seal this part of the formation will not collapse, the need to use surface casing for sealing. The main specifications of the surface casing: 508mm (20in) 406.4mm (16in), 339.73mm (13-3 / 8in), 273.05mm (10-3 / 4in), 244.48mm (9-5 / 8in) and so on. Under the tube depth depends on the depth of the soft formation, usually 80 ~ 1500m. The external pressure and internal pressure are not large, generally use more K55 steel grade or N80 steel grade.
3. Technology casing: used in complex formation drilling process, when encountered in collapsed layer, oil layer, gas layer, water layer, leakage layer, salt paste layer and other complex parts, the need for technical casing sealing, otherwise drilling will not work. Some well deep and complex wells, and go down to a depth of several kilometers, this deep well requires several layers of technology casing, its mechanical properties and sealing performance requirements are high, the steel grade is also higher, in addition to K55, More is the use of N80 and P110 steel grade, some deep wells also use Q125 or even higher non-API grade such as V150. The main specifications of the technical casing are: 339.73mm (13-3 / 8in), 273.05mm (10-3 / 4in), 244.48mm (9-5 / 8in), 219.08mm (8-5 / 8in), 193.68mm (7- 5 / 8in), 177.8mm (7in) and so on.
4. Oil casing: when drilling the target layer (oil and gas layers), the need to use oil and gas casing casing layer bare exposed all of the upper seal, reservoir casing inside the tubing. Oil and gas casing in all types of casing depth down the deepest, its mechanical properties and sealing performance requirements are the highest.
