The oil casing is composed of a collar and a pipe body. In order to ensure the function and facilitate transportation, the separate pipe body and the collar are bolted together and transported to the oil and gas field, and are connected end to end in the field, and applied after the length is specified. In order to strengthen the compressive strength and fastening operation of the bolted connection of the structure, the collar and the bolt connection of the pipe should be welded, so it is particularly important to analyze the welding characteristics of 37 Mn5 and formulate a scientific and reasonable welding method.
After each technical oil casing and oil reservoir oil casing is fixed, if the concrete does not return to the road surface, a part of the oil casing floats in the hole without support point, which is free oil casing. The force of this part of the oil casing presses on the sealed oil casing. In the manufacturing process, the pressure and temperature of the free oil casing cause the extension of the oil casing and the internal stress change, which is easy to damage the oil casing. Therefore, the casing head should be modified after the concrete waiting for setting to seal the annulus between the double oil casing and suspend the force of a part of the free section of the oil casing so that the force is pressed on the surface oil casing.
The casing head is divided into slip type and screw type according to the structural form of suspension oil casing, including three layers of oil casing, technical oil casing and surface oil casing. A layer of casing head is installed on the top of the surface oil casing, connected with the pipe thread of the surface oil casing, and the flange level of the casing head is basically flush with the road surface. After the concrete is fixed in the technical oil casing, a part of the suspended weight in the free section is placed in the cone of the casing head with slips, so that the suspended weight is placed on the cone and the annulus between the double oil casing is sealed.
