Steel casing pipe is a piece of oilfield equipment used to place steel pipes in newly drilled open holes. The usual sequence of operations is to drill a section of open hole, run casing, then perform cementing operations to ensure the safety of the wellbore, and then proceed to the next section of drilling.
There are three types of casing, namely surface casing, technical casing and oil layer casing. Regarding the design of surface casing, technical casing and oil layer casing, each has its own design characteristics and design emphasis.
The surface casing is a layer of casing dropped to consolidate the loose layer on the surface and install a wellhead blowout prevention device. It also has to bear part of the weight of the lower layers of casing. Therefore, the design feature of the surface casing is to withstand the formation pressure during downhole gas invasion or blowout. The main consideration in casing design is to resist internal pressure to prevent the casing from bearing high pressure and bursting when the well is shut in.
There are three types of casing, namely surface casing, technical casing and oil layer casing. Regarding the design of surface casing, technical casing and oil layer casing, each has its own design characteristics and design emphasis.
1.Design features of surface casing
The surface casing is a layer of casing dropped to consolidate the loose layer on the surface and install a wellhead blowout prevention device. It also has to bear part of the weight of the lower layers of casing. Therefore, the design feature of the surface casing is to withstand the formation pressure during downhole gas invasion or blowout. The main consideration in casing design is to resist internal pressure to prevent the casing from bearing high pressure and bursting when the well is shut in.
2.Design features of technical casing
Technical casing is a layer of casing that is lowered to isolate complex formations. During subsequent drilling, it must withstand the internal pressure during a blowout and the collision and wear of drilling tools. The design feature of technical casing is that it must have high resistance to internal pressure and the ability to resist drilling tool impact wear.3.Design features of oil layer casing
The oil layer casing is the last layer of casing that is run into the oil and gas well, and the oil pipe is run into it for oil production. The depth of the casing in this layer is relatively large, and resistance to external extrusion is a key consideration for the lower casing. This layer of casing should be considered separately according to the problems it may encounter in production. If some are not used for water injection, some wells need to be fracturing or acidified during oil production, and the casing may also bear large internal pressure. The internal pressure resistance strength of the oil layer casing of such wells should be strictly checked. ; Some wells are mainly used for thermal mining by injecting hot steam, etc. The casing will expand under the action of heat for a long time, resulting in large compressive stress. The tensile safety factor when applying pre-tension stress should be considered in the design.
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