Summary Through the analysis of the characteristics of the perforating barrel repair, it is proposed to cover the root of the perforating eye with a small blocking plate, and then carry out the new process of repair welding, which realizes the reuse of the barrel and provides valuable for the repair of similar products in the oil field. experience. In oil exploration, the perforating guns used in oil and gas fields have special characteristics not found in other metal structures during perforating operations: perforating bullets or explosives are detonated in a barrel of a certain depth downhole, producing instantaneous high temperature and strong impact, breakdown The perforating part of the barrel is then shot through the rock layer or the oil and gas layer to achieve the purpose of perforating the oil and gas well. Therefore, the relevant departments have strict requirements on the use of the barrel, and it is clearly stipulated that the use of the barrel is one-off. Once the perforating operation is carried out, the products are scrapped or degraded. At present, most of the domestic oil and gas field perforating guns use imported gun barrels from the United States and Japan, which are expensive and cost as much as 500 yuan per meter. The material has poor weldability, severe hardening tendency, and great crack sensitivity. So far, there are no precedents for repair, and there is no research report on the repair process. With the determination to actively try and explore boldly, we used manual arc welding to repair the scrapped barrel in the oil and gas field logging perforation industry, breaking through the restricted area of ​​barrel repair. The quality of the φ114 mm×7.72 mm×2 m barrel welded by the welding was approved by the China National Petroleum Corporation’s oil and gas field perforating equipment quality supervision and inspection center. 1 Repair features of perforating barrel 1.1 Perforation barrel overview Figure 1 Schematic diagram of barrel perforation 1.2 Analysis of welding characteristics of the barrel According to this, it is judged that the barrel has a large tendency of hardening and cold cracking, and the weldability is extremely poor. During the welding process, when the temperature of the quenching zone is >Ac3, due to the thermal cycling of the arc and the excessive cooling rate, the austenite is easily transformed into a brittle and hard high-carbon martensite structure with a great tendency to harden ( 600HB ~ 700HB), which increases the brittleness of the welded joint and aggravates the formation and generation of cracks in the HAZ (heat affected zone). At the same time, even with an alkaline low-hydrogen electrode, the hydrogen content in the weld metal is 6.8 ml/100 g, which is prone to hydrogen-induced cracking under welding stress. Therefore, corresponding control, adjustment and protective measures should be taken during the welding process and before and after welding to prevent cracks. 2 Preparation before welding 2.1 Design and processing of the groove Figure 2 Groove structure diagram In order to ensure the alignment ratio of the perforating eye of the gun body to the original hole ≥85% and the convenience of processing, Q235 (φ14 mm) round steel with lower strength grade is selected and processed into a truncated cone shape of φ10 mm×φ14 mm×3 mm on the lathe. The blocking plate (Fig. 3), placed at the root of the groove, intentionally prevents the root from penetrating and creates conditions for penetrating the perforation. Figure 3 Schematic diagram of the blocking plate Next page Celadon Round Edge Irregular Glass Mosaics
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Key words: perforating barrel repair process
0 Foreword
The Q102-16-90 perforating gun is a G41350 steel pipe imported from the United States with a specification of φ114 mm×7.72 mm×2 m. Its material is similar to that of China's 35CrMoA.
The barrel after perforating operation is shown in Fig. 1. The perforation is distributed on the surface of the entire barrel, and the arrangement is regular. The diameter of the perforation is not equal, but both are ≤10 mm. 
The material of the barrel is low-alloy high-strength structural steel (which can also be classified as chrome-molybdenum heat-resistant steel). The average carbon content in the steel is as high as 0.35%. The hardness of the steel is increased by the inclusion of Cr and Mo alloy elements. The carbon equivalent formula and calculation results recommended by the International Welding Society to reflect the hardening tendency of alloy structural steel are shown in equation (1). 
(1)
1.3 Design requirements for barrel repair
While ensuring the minimum chemical loss of the chemical composition of the barrel base while welding, it is required to perform hydraulic test under the condition of 30 MPa, constant pressure for 30 min, no leakage of the barrel, no deformation of the gun body; no cracks are allowed in the welded joint. There is no welding and welding on the inner wall of the barrel. During the perforating operation, the perforating hole must be penetrated from the original hole position, and the alignment ratio of the perforating hole of the gun body to the original hole is ≥85%.
In order to meet the design requirements and achieve the purpose of perforating, in the repair, a special structural form is adopted: firstly, all the holes with irregular shapes and sizes on the original barrel are uniformly processed on the drill bed into concentric and same diameter with the original hole ( For the hole of φ10 mm), drill the hole of concentric φ14 mm on the hole of φ10 mm. Do not drill through the drill bit. Finally, drill the large hole with concentricity of φ16 mm and drill depth of 4.72 mm. Thus, a truncated cone shape of φ10 mm × φ14 mm × 3 mm is formed at the root (Fig. 2). 
