Casing and tubing are steel pipes used to support the well walls of oil and gas wells to ensure the normal operation of the entire oil well during the drilling process and after completion. Each well requires several layers of casing and tubing based on different drilling depths and geological conditions. Cement must be used to cement the casing and tubing after it is lowered into the well. Unlike oil pipes and drill pipes, it cannot be reused and is a one-time consumable material. Therefore, the consumption of casing accounts for more than 70% of all oil well pipes. Casing and tubing can be divided into: conduit, surface casing, technical casing and oil layer casing according to usage conditions. Casing and tubing is used to create a good flow channel for oil or natural gas in underground reservoirs to flow to the surface. The important function of production casing is to protect the well wall and isolate fluids in each layer, so as to facilitate layered testing, layered mining and layered transformation of oil and gas wells.
Production process of oil casing and tubing:
In order to improve the quality of the oil well pipe body, the oil casing plant used imported technology and joint design to manufacture precision pipe rolling mills. Using continuous casting round tube billet, heating in an annular heating furnace, piercing by a tapered roller piercing machine, rolling by a precision tube mill, sizing, cooling bed cooling, forming a seamless steel tube short-flow production line, and its production process: EAF → furnace refining → vacuum degassing → continuous casting → heat transfer → tube heating → perforation → rolling pipe → sizing → cooling tempering (reserved) → online quenching (reserved) → tempering (reserved) → sizing (reserved) → cooling → straightening → flaw detecting → sawing → cutting head → inspection → rail straight pipe machining.
The pipes are inspected by the magnetic flux leakage detector, and the qualified products are processed by the CNC pipe thread lathe in turn. If they pass the inspection, they will be used for future use: the bad coupling materials are threaded by the CNC pipe thread lathe.
After the inspection, the flaw is detected by the magnetic flux leakage detector, and the pipe is marked after passing the inspection. Next, the coupling screwing machine connects the pipe to the coupling. After passing the inspection, the marking machine is used for marking, and the pressure is tested by the hydrostatic pressure tester (water pressure (0~70MPa, different pipe diameters and different pressures), measure the length and weigh, put protective rings on both ends of the pipe, use an automatic painting machine to evenly apply epoxy asphalt anti-corrosion paint on the outer wall of the pipe, then spray mark, and finally the finished product passes the inspection Then pack it and put it in the product storage area.
Casing and tubing Manufacturing Process
1. Material Selection
The first step in casing and tubing manufacturing is the selection of the appropriate material. Typically, special steels with specific mechanical properties are used, such as low alloy steel or stainless steel, depending on the operating conditions. These materials are selected based on their corrosion resistance, high temperature resistance and durability characteristics.
2. Raw Material Preparation
Once the materials have been selected, the raw materials are prepared. The steel coils undergo a cutting and forming process to obtain the desired shape. The steel used is checked to ensure that it meets quality standards before proceeding with manufacturing.
3. Rolling Process
At this stage, steel coils are heated and passed through a rolling process. This process transforms the coils into steel tubes. Depending on the type of tube, a welding or extrusion process may be used to close the tubes. The most common welding method is arc welding, which ensures the material is joined without compromising its mechanical properties.
4. Forming and Bending
After welding, the tubes are formed and bent to the specifications required for the application. Casing and tubing tubes must be adjusted to precise dimensions to ensure their ability to withstand the forces applied during use in the oil field. The forming process is carried out on specialized machines that allow the shape and dimensions of the tube to be modified.
5. Heat Treatment
To improve the strength and durability of the steel, casing and tubing tubes are subjected to heat treatment. This process involves heating the tubes to a controlled temperature and then cooling them rapidly. Heat treatment removes internal stresses and improves the structure of the material, ensuring that the pipes can withstand the extreme pressure and temperature conditions inside oil wells.
6. Quality Inspection
Before the pipes move on to the next stage, they undergo rigorous quality testing. These tests include visual inspections, hardness measurement, and tensile strength analysis. Non-destructive testing, such as ultrasound or X-rays, is also performed to verify the integrity of the material and the quality of the welds.
7. Coating and Corrosion Protection
To ensure that the pipes can withstand the corrosive conditions in oil well environments, protective coatings are applied. These coatings, such as zinc or epoxy coatings, are applied to the inside and outside of the pipes. This improves the life of the casing and tubing, protecting them against corrosion, especially in conditions of high humidity or salinity.
8. Manufacturing of Threads and Connections
Once the pipes are fully formed and treated, the threads and connections are manufactured. These pipes require special threads to connect the different pipe segments at the drilling site. The connections are manufactured according to international standards such as API (American Petroleum Institute) to ensure their performance and safety.
9. Final Testing
Before the pipes are shipped to the customer, final testing is performed. These tests include verification of dimensions, pressure resistance, and impact testing. In addition, the quality of the threads and connections is reviewed to ensure that they meet the established requirements.
10. Packaging and Shipping
The last step in the production process is the packaging and shipping of the pipes. The pipes are carefully packaged to prevent damage during transport. Appropriate packaging methods are used to maintain the quality of the product until it reaches the final customer.
Inspection and quality control: During the production process, various inspections are required on oil and casing, including dimensional inspection, chemical composition analysis, mechanical property testing, etc., to ensure that product quality meets the standard requirements of API5CT. At the same time, a complete quality control system is established to strictly control every link.
Performance: Solution to poor toughness of casing and tubing
One is to use rapid cooling after tempering to avoid high temperature brittleness and gain toughness.
The second is the sub-temperature quenching method, which effectively improves harmful elements and impurities and improves toughness through incomplete austenitization of steel. The first method has relatively strict requirements on heat treatment equipment and requires additional costs. The low-temperature fire is lower than the conventional temperature, which reduces the quenching stress and thereby reduces the quenching deformation. This ensures the smooth operation of heat treatment production and provides good raw materials for subsequent wire processing.
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