Casing Pipe: Manufacturing Process

Date:2024-07-11Tags:Casing Pipe,well pipe casing

Oil casing pipe is a key oil extraction equipment, mainly used to support the wellbore wall, prevent wellbore collapse and mud loss. The production process of oil casing pipe includes a series of complex steps from steel selection to final product inspection to ensure that the produced casing pipe can play a role in the harsh oilfield environment. This article will introduce the production process of oil casing pipe and its various links in detail.


1. Raw material selection

The main materials of oil casing pipes are low alloy steel and high alloy steel. Before production, it is necessary to select suitable steel according to the specifications and design requirements of the casing. Generally speaking, the selection of high-quality steel is the basis for ensuring the performance of oil casing pipe. Commonly used steels include carbon steel and various grades of alloy steel. The chemical composition and mechanical properties of the steel must be strictly controlled during the material selection process to ensure that it meets the requirements of industry standards such as API5CT.


2. Heat treatment process

Heat treatment is an important step in the production process of steel pipes. Both seamless steel pipes and welded steel pipes need to undergo heat treatment. Through a series of heating and cooling processes, the mechanical and physical properties of the steel pipes can be significantly improved. Commonly used heat treatment methods include normalizing, quenching and tempering. During the normalizing process, the steel pipe is heated to an appropriate temperature and maintained for a period of time, and then cooled in the air; quenching is to quickly cool the steel pipe to increase its hardness and strength; tempering is to heat it again after quenching to eliminate the brittleness caused by quenching and improve toughness.


3. Pressing and perforation

The heat-treated steel needs to be pressed and perforated to form a tubular structure. Pressing is to press the steel into a cylindrical shape through mechanical equipment, and perforation is to punch holes in the cylindrical steel through mechanical or heat treatment methods. These two steps ensure the initial forming of the steel pipe and prepare for subsequent processes.


4. Diameter adjustment

After the tubular structure is formed, the diameter of the steel pipe needs to be adjusted to meet the technical requirements. This is usually done by drawing or rolling. Drawing is to adjust the outer and inner diameters of the steel pipe by stretching it, while rolling is adjusted by rotating rollers. The accuracy of diameter adjustment is crucial to ensure the final size and shape of the steel pipe.

Casing Pipe

5. Annealing process

The casing after diameter adjustment needs to be annealed to eliminate the stress generated during the processing and improve its internal structure. The annealing process is to heat the casing pipe to an appropriate temperature and then slowly cool it to soften the material, improve toughness and eliminate stress. This step helps to improve the overall performance of the casing pipe and make it perform better in actual use.


6. Trimming process

After annealing, the casing pipe needs to be trimmed to ensure that both ends are flat and meet technical requirements. The trimming process is usually carried out by mechanical processing to ensure that both ends of the casing pipe have good verticality and parallelism. In addition, it is necessary to check and correct defects on the surface of the steel pipe, such as pits, scratches, etc., to ensure its surface quality.


8. Material Preparation

Before the thickening process, material preparation is required. The thickening department issues a raw material requisition form based on the production plan and collects the raw materials from the raw material warehouse. After obtaining the raw materials, the loader must confirm the steel grade, specifications, length, and all measured dimensions of the thickening pipe material. Additionally, they must inspect the pipe body for dents, scratches, bends, concentricity, and other issues. Only raw materials that pass these rigorous inspections can proceed to the loading operation.


9. Heating Process

Heating is a crucial step in the thickening process of casing pipes. Before starting the machine, the operator must ensure that the power supply is normal, the cooling water tank has water, and the water pressure is greater than or equal to 0.2 MPa. Additionally, the guide columns of the thickening machine and the tracks of the heating trolley must be lubricated. During production, the pipe material is fed into the intermediate frequency furnace for heating via a stepping mechanism. When the machine is first started, the initial few pipes need to be heated three times, with the temperature controlled between 1050°C and 1100°C. The subsequent heating temperatures gradually decrease to between 950°C and 1050°C.


10. Thickening process

When thickening pipes of various specifications, it is necessary to select molds of corresponding sizes, check whether the specifications and integrity of the molds meet the production requirements, and install the molds correctly according to the operating procedures. In the thickening process, the length of the water spraying time directly affects the temperature of the mold and the punch, thereby affecting the quality of the pipe. When producing the first few pipes, the water spraying time should be controlled between 7-8 seconds to allow the punch and the mold to maintain a certain temperature, and then the water spraying time will be extended as the temperature of the mold and the punch increases, and the control range is generally between 10-12 seconds. The jet time is mainly determined by the size of the air flow rate, and it can be used to blow dry the cooling water in the lower mold, which is generally controlled between 1-3 seconds. To produce qualified pipes, the mold punch must maintain a certain temperature, and the temperature can generally be determined from the effect of graphite coating on the mold. When the graphite is applied to the mold and the punch and cannot immediately stick to the mold surface, it proves that the mold temperature is too low and the cooling time needs to be reduced. When blisters or graphite directly slides off when graphite is applied to the mold punch, the mold temperature is too high and the cooling time needs to be increased. The optimum temperature is when the graphite adheres to the die punch surface immediately after being applied and begins to dry.


11. Grinding treatment

The thickened pipe needs to be polished to trim the waste edge of the pipe end surface. During the grinding process, the outer surface of the pipe end should be beautiful, and the surface after grinding should have no protruding edges and corners, and the surface of the pipe end should be smooth and clean.


12. Normalizing and quenching and tempering treatment

When the products need normalizing treatment, they are inspected and polished and then transported to the material rack of the normalizing production line. Since the normalizing adopts the medium frequency heating furnace, the power of each device should be turned on before normalizing to ensure that each device can start normally, check whether there is water in the cooling water tank, whether there is water pressure (greater than or equal to 0.2Mpa) in the heating medium frequency furnace, and then start the heating medium frequency furnace to check whether it can start heating normally. Finally, start the auxiliary oil pump and check whether each sensor is normal. After the equipment is running normally, the thickened pipe material is transported to the medium frequency furnace by the auxiliary machine for heating. The heating time is generally set to 80 seconds and the heating temperature is generally set to 910±10℃. After the heating is completed, the auxiliary machine is transported to the cooling position of the material rack for air cooling. After the air cooling is completed, the auxiliary machine is transported to the material rack frame to complete the normalizing. If the thickened pipe needs to be tempered, it can be inspected and put into storage after the grinding process is completed, and then transferred to the heat treatment workshop for tempering process.


13. Finished product inspection and warehousing

After all processes are completed, the finished casing pipes need to be strictly inspected. After passing the inspection, they are packaged and stored according to the specifications, and marked to ensure that each casing pipe has clear information such as steel grade, specification, material, storage date, production team, weight and furnace batch number.


The production process of oil casing pipe is complex and strict, and every step is crucial. Only by selecting high-quality raw materials, adopting scientific heat treatment processes, precise size adjustment and perfect inspection methods can high-quality oil casing be produced to meet the needs of oil extraction.

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