Casing pipe is mainly composed of couplings and pipe bodies. In order to ensure the reliability of oil casing pipe in use and facilitate transportation, the separate pipe bodies and couplings are bolted together in the factory and then transported to the oil and gas field site. On site, the casing is connected end to end and used after the required length is reached with the pup joint. In order to enhance the compressive strength and tightening control of the bolted connection, electric welding is required after the coupling and pipe body are bolted together. Therefore, it is particularly important to analyze the electric welding characteristics of materials such as 37Mn5 and formulate a scientific and reasonable welding method.
Cementing and free section treatment of oil casing pipe
After each layer of technical casing pipe and oil layer casing is cemented, if the concrete is not returned to the ground, part of the oil casing pipe will float in the wellbore without support points and become free casing pipe. The weight of this part of free casing pipe presses on the sealed casing pipe. In actual operation, the free oil casing pipe may cause the stretching and internal stress changes of the oil casing pipe due to the influence of pressure and temperature, which may easily cause damage to the oil casing pipe. In order to avoid this situation, the casing head needs to be installed after the concrete is cured to seal the annulus between the multiple layers of oil casing pipe and suspend the weight of the free section of the oil casing pipe so that its force presses on the surface oil casing pipe.
Types and installation of casing heads
Casing heads are divided into slip type and screw type according to the structural form of hanging oil casing pipe, mainly including three-layer casing pipe structure of oil layer casing pipe, technical casing pipe and surface casing pipe. One layer of casing head is installed on the top of the surface oil casing pipe, connected with the surface oil casing pipe by thread, and the flange of the casing head is basically flush with the ground. After the technical oil casing pipe is solidified with concrete, part of the weight of the free section is suspended in the cone of the casing head, and the slip seat bears the weight in the cone and seals the annulus between the two layers of oil casing pipe , and then the joint can be removed.
Welding characteristics and methods of Thirty-seven Mn5 material
Thirty-seven Mn5 is a common material used to manufacture oil casing pipe. Its welding characteristics directly affect the connection strength and service life of oil casing pipe. In order to ensure the welding quality, it is necessary to analyze the welding characteristics of Thirty-seven Mn5 material in detail and formulate a scientific and reasonable welding method. First of all, it is necessary to have a comprehensive understanding of the chemical composition and physical properties of the material, including its carbon content, alloy elements, and the hardness and toughness of the material. Secondly, the selection of welding methods should take into account the site conditions and the feasibility of actual operation. Common welding methods include manual arc welding, gas shielded welding and submerged arc automatic welding.
During the welding process, welding parameters such as current, voltage, welding speed and preheating temperature need to be strictly controlled to ensure the quality of the welded joint. After welding, the weld needs to be subjected to non-destructive testing such as ultrasonic testing, radiographic testing and magnetic particle testing to find and eliminate defects in the weld. Finally, in order to improve the corrosion resistance of the welded joint, the weld can also be heat treated, such as normalizing, tempering and annealing.
Specific operation process of casing pipe installation
The installation of oil casing pipe is a complex process that requires multiple processes to be carried out in coordination. The following is a typical oil casing pipe installation process:
Preparation: Connect the pipe body and the coupling in the factory by bolts, and then transport them to the oil and gas field site.
On-site assembly: On site, connect the casing pipe end to end and use it after reaching the required length. During the assembly process, special tools are required to tighten and ensure the sealing of the threaded connection.
Electric welding reinforcement: In order to enhance the compressive strength of the bolted connection, it is necessary to weld the connection between the coupling and the pipe body. During the welding process, the welding parameters need to be strictly controlled to ensure the welding quality.
Cementing operation: After the casing pipe is lowered into the well, cementing operation is required. The casing pipe is fixed to the well wall by injecting cement slurry into the well. After the cementing operation is completed, it is necessary to wait for the cement slurry to solidify.
Installation of casing head: After the cement slurry solidifies, the casing head is installed. The installation of the casing pipe head needs to be carried out strictly in accordance with the design requirements to ensure the sealing and bearing capacity of the casing pipe.
Hanging free section: The weight of the free section is hung in the cone of the casing head, and the slip seat bears the weight in the cone and seals the annulus between the multiple layers of casing pipe.
Inspection and testing: After installation, the entire casing system needs to be inspected and tested to ensure that it meets the design requirements and usage standards.
Maintenance and care of oil casing pipe
During use, oil casing pipe is affected by the complex environment downhole and is prone to wear, corrosion and deformation. Therefore, it is very important to regularly maintain and care for oil casing pipe. Common maintenance measures include:
Regular inspection: Use advanced testing equipment to regularly inspect oil casing pipe to discover and promptly deal with potential problems.
Anti-corrosion treatment: Anti-corrosion treatment of casing pipe, such as coating with anti-corrosion coating, electroplating or using preservatives, to extend the service life of casing pipe.
Repair and replacement: Repair or replace damaged casing pipe to ensure the integrity and safety of the entire casing pipe system.
Summary
The installation of oil casing pipe is a very critical part of the oil production process, involving multiple technologies and processes. Through scientific and reasonable design, precise operating procedures and strict quality control, the installation quality and service life of oil casing pipe can be ensured, thereby improving the efficiency and safety of oil production. At the same time, regular maintenance and care are also important measures to ensure the long-term stable operation of oil casing pipe.
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