Casing is the steel pipe that supports the walls of oil and gas wells. Each well uses several layers of casing depending on the drilling depth and geology. Casing after the well to use cement to cement, casing and tubing, drill pipe is different, it can not be reused, belongs to a one-time consumption of materials. Therefore, casing consumption accounts for more than 70% of all oil well pipes. Casing can be divided into pipe, surface casing, technical casing and oil layer casing according to the use, and their structure in the oil well is shown in the figure.
Pipe: mainly used in ocean and desert drilling, to separate seawater and sand, to ensure the smooth drilling, the main specifications of this layer of casing are: ∮762mm(30in) ×25.4mm, ∮762mm(30in) ×19.06mm.
Surface casing: mainly used for the first drilling, drilling the soft ground to the bedrock, in order to seal this part of the ground without collapse, need to use the surface casing for sealing. Main specifications of surface casing: 508mm(20in), 406.4mm(16in), 339.73mm(13-3/8in), 273.05mm(10-3/4in), 244.48mm(9-5/8in), etc. The depth of the pipe depends on the depth of the soft formation, which is generally 80~1500m. Its external pressure and internal pressure are not large, generally using K55 steel grade or N80 steel grade.
Technical casing: is used in the drilling process of complex formation, when it encounters the collapse layer, oil layer, gas layer, water layer, lost layer, salt paste layer and other complex parts, it needs to be sealed, otherwise the drilling can not be carried out. Some Wells are deep and complex, and the depth of the well is thousands of meters, this deep well requires several layers of technical casing, its mechanical properties and sealing performance requirements are high, the use of steel grade is also higher, in addition to K55, more N80 and P110 steel grade, some deep Wells also use Q125 or higher non-API steel 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), etc.
Oil layer casing: When drilling into the target layer (the oil and gas bearing layer), it is necessary to seal the oil and gas layer and the upper exposed formation with oil casing, and the oil pipe is inside the oil casing. In all kinds of casing casing, the drilling depth is the deepest, and its mechanical properties and sealing performance requirements are also the highest. The steel grades are K55, N80, P110, Q125, V150 and so on. The main specifications of reservoir casing are: 177.8mm(7in),168.28mm(6-5/8in),139.7mm(5-1/2in),127mm(5in),114.3mm(4-1/2in), etc.
Post time: Oct-13-2023
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