Name: China OCTG Casing Pipe Manufacturers Suppliers Factory - Cheap OCTG Casing Pipe for Sale - GNEE Pipe
Brand: GNEE
SKU: 233893208

Oil well casing is a steel pipe used to support the wellbore of oil and gas wells, ensuring the normal operation of the well during drilling and after completion. It is a disposable material and is generally not reused. Oil well casing can be classified according to its use into guide pipe, surface casing, technical casing, and reservoir casing.

Surface Casing

- Protects the well from contamination by shallow water and shallow gas layers.

- Supports wellhead equipment and maintains the weight of other casing layers.

Technical Casing

- Separates the pressure between different layers to ensure normal and smooth flow of drilling fluid and protects the production casing.

- Allows for the installation of anti-fracture devices, leak-proof devices, and tailpipes within the well.

Reservoir Casing

- Extracts oil and natural gas from the underground reservoir.

- Protects the well and separates drilling mud.

Oil well casing typically has an outer diameter ranging from 114.3 mm to 508 mm during production.

API 5CT Casing chemical composition

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API 5CT casing

API specifies three lengths: R-1 is 4.88~7.62m, R-2 is 7.62~10.36m, and R-3 is 10.36m or longer.

API 5CT oil casing is a piping system used in oil and gas wells. It is used for several important purposes:

Protecting the Wellbore: As a protective shell for the wellbore, the oil casing prevents wellhead collapse and external damage. It can withstand geological stresses and well pressures, maintaining the stability of the borehole.
Controlling Well Pressure: The oil casing controls pore pressure and drilling pressure, guiding them to the surface. This helps prevent blowouts and other safety incidents.
Guiding Oil and Gas: As a conduit within the wellbore, the oil casing brings oil and gas from the bottom of the well to the surface. It has high sealing performance, ensuring the smooth flow of fluids and gases within the well.
Isolating Formations: The oil casing isolates different fluids in different formations, preventing cross-contamination and mixing. This is crucial for the efficient extraction and production of oil and gas.
Supporting the Wellbore: The structural strength of the oil casing supports the wellbore, preventing wellbore collapse and wellhead sinking. It can withstand formation pressures and the weight of the fluids within the well.

Core Process Flow of API 5CT Casing Production

Raw Material Preparation
Select continuously cast round billets or hot-rolled steel billets, commonly made of carbon steel or alloy steel (such as 37Mn5). API 5CT standard specifies that J55 grade casing must have a carbon content ≤0.34%, and N80 grade requires the addition of alloying elements such as chromium and molybdenum.

The billet diameter is typically 180-350mm. Composition is analyzed using a spectrometer to ensure that sulfur and phosphorus content are ≤0.025% (refer to GB/T 222).

Hot Rolling Forming
The heating furnace heats the billet to 1200-1280℃ (excessive temperature can lead to grain coarsening), forming a hollow tube blank through a piercing mill.

The continuous rolling mill extends the tube blank to the target outer diameter, for example, a Φ139.7mm casing with a wall thickness of 6.2-12.7mm, at a rolling speed of approximately 0.8-1.5m/s.

Cold Working and Heat Treatment
Cold-rolled tubing is produced using two- or three-roll mills, with deformation controlled within 30-50%, resulting in higher precision (wall thickness tolerance ±10%).

Heat treatment is crucial: J55 requires normalizing (900℃±20℃, holding for 30 min), while N80 requires quenching and tempering (quenching + tempering) to achieve a hardness of HRC22-32.