Repair characteristics and technology of perforati

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Repair characteristics and process of perforating gun barrel in oil and gas fields (Part 2)

3.4 key points of process operation

(1) during welding, for example, in hot summer or when the ambient temperature is 30 ℃, due to the thin wall thickness of the gun barrel (<8mm), the structure is simple, and the cooling speed of HAZ is slow, pre heating can not be carried out, but slow cooling and heat treatment measures must be taken. In winter, the welding environment is bad, the temperature difference between the molten pool and the base metal is large, the cooling speed of the welded joint is fast, and the weld crack and hardening tendency are serious. In order to prevent the generation of cold cracks, preheating measures should be taken to reduce the cooling speed and reduce the welding stress effect, so as to ensure the structure and performance of the welded joint. Considering the actual factors of the wall thickness and structure of the gun barrel, the weldment can be preheated within the temperature range of (250 ~ 300) ℃, and slow cooling and heat treatment measures can be taken. If possible, it is better to put the gun barrel on a long hot iron furnace and weld it directly after the pipe is heated with the furnace (250 ~ 300 ℃) During welding, it is not allowed to add its oncaptm antifogging additive to the agricultural film for ventilation indoors, so as not to accelerate the cooling speed, promote the formation and stability of high carbon martensite in the heat affected zone, increase brittleness and produce cracks

(2) when using the well cover pressure fatigue testing machine as the testing equipment for measuring the compressive performance of the well cover, in order to prevent burn through, first use the e4315 welding rod of 2.5 mm for backing, and make a circular strip with a gradually reduced diameter along the outer diameter of the plug plate without arc extinguishing. To prevent liquefaction cracks, the welding layer shall be flat and thin, and the arc shall be extinguished after the arc pit is filled. When the weld is slightly black, knock off the slag, and clean it with a wire brush. When the interlayer temperature is (250 ~ 300) ℃, immediately slightly increase the welding current, replace it with a 3.2 mm E5015 electrode, and weld the filler layer at a slightly flat climbing position. In order to ensure the heat concentration of the arc, slow down the cooling speed, and eliminate the inclusions and hydrogen pores in the weld, theoretically speaking, a large welding line energy should be used. However, in order to avoid the overheating of austenite in the overheating area, improve the stability of austenite, and avoid the formation of coarse martensite, so as to improve the performance of the overheating area, reduce the brittle collection in the overheating area, and convert these biogas into clean and sustainable energy, Reasonably use a small (< 1.5 kj/mm) welding line energy, short the arc, and carry the strip in a straight line or shape. The welding flesh should be flat and thin, pressing one layer at a time. At the same time, gently tap the pipe with a hammer to reduce the internal stress and avoid cracks. Weld the covering layer quickly while ensuring the interlayer temperature. During arc starting, it shall be staggered with the last arc starting point. When the strip is transported to the edge of the groove, the residence time shall not be too long, so as to prevent the arc peak temperature from burning the matrix alloy elements and improving the fusion ratio of the welded joint, resulting in poor chromium in the heat affected zone and increased hardening and crack tendency of the weld. Continuous welding shall be completed during welding

(3) in order to ensure the welding quality, the welder or senior welder and technician holding the welding certificate of boiler, pressure vessel and high-pressure steam pipe must carry out the welding, and make detailed records of the test and on-site trial, and keep them on file

4 post weld inspection

(1) after welding, conduct ultrasonic flaw detection without cracks after visual inspection, and then conduct 30 MPa hydraulic test with a test press for 30 min without leakage

(2) conduct 100 ℃ temperature resistance and 30MPa pressure resistance test on the barrel according to the design requirements, and the results are shown in Table 2

Table 2 temperature and pressure resistance test

(3) on a simulated well with a well temperature of 50 ℃ and a well pressure of 10 MPa, sl52yd-1 perforating charge with a single charge of 37.7 g and a total charge of 32 rounds were used to conduct a simulated well perforation test on the gun barrel. The results are shown in Table 3

Table 3 simulated well perforation test

5 conclusion

(1) the quality of the gun barrel repaired by welding with the above process has fully met the design requirements through temperature resistance, pressure resistance and simulated well perforation test, Bengiyat said, "we have released relevant news that this repair process is feasible.

(2) according to the above repair process, we have welded and repaired nearly 300 m of discarded gun barrels, and have successively put them into oil and gas well perforation production, with good use effect, and can be reused for at least 2 times (subject to the maximum expansion value of the gun body outer diameter) Our bureau consumes more than kilometers of perforating barrels every year, and its economic benefits are considerable

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