Repair method of coiled tubing

Abstract

The invention discloses a coiled tubing repairing method which comprises the following steps: step 1, polishing and cleaning a damaged area needing to be repaired on the surface of a coiled tubing, and recording information of a damaged position; 2, cladding powder is prepared; step 3, implementing laser cladding; and 4, implementing heat treatment, and completing the heat treatment operation of the cladding layer by adopting a laser induction normalizing process. The invention belongs to the technical field of petroleum and natural gas pipes and solves the problem that the service life of a coiled tubing is directly affected due to the fact that defects generated on the surface of the coiled tubing are difficult to repair in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas pipeline technology, and relates to a method for repairing coiled tubing. Background Technology

[0002] Coiled tubing, also known as flexible tubing, is highly flexible and can replace conventional tubing for many operations. It features pressurized operation, continuous lifting and lowering, small equipment size, fast operation cycle, and low cost, making it a powerful tool for reducing costs and increasing efficiency in oil and gas development.

[0003] However, as the operating conditions of coiled tubing become increasingly complex, surface defects frequently occur, leading to coiled tubing failures. This not only results in economic losses but, in severe cases, can also endanger personal safety. Currently, there are no reports specifically on the repair of coiled tubing. If a repair method could be developed to re-repair defective sections of the coiled tubing, the cost of oil and gas extraction could be minimized, facilitating a qualitative leap in oilfield development. Summary of the Invention

[0004] The purpose of this invention is to provide a repair method for coiled tubing, which solves the problem that existing technologies make it difficult to repair defects on the surface of coiled tubing, directly affecting the service life of the coiled tubing.

[0005] The technical solution adopted in this invention is a method for repairing coiled tubing, implemented according to the following steps:

[0006] Step 1: Grind and clean the damaged area on the surface of the coiled tubing that needs to be repaired, and record the location of the damage;

[0007] Step 2: Prepare the cladding powder;

[0008] Step 3: Perform laser cladding;

[0009] Step 4: Perform heat treatment.

[0010] Laser induction normalizing process is used to complete the heat treatment of the cladding layer.

[0011] The beneficial effects of the present invention include the following aspects: (1) The repair material powder used in the repair method adopts a specific ratio, which extends the service life of the coiled tubing after repairing the defective coiled tubing, and has higher corrosion resistance, toughness and compatibility with raw materials. (2) Laser cladding repair can repair any defect morphology, and the laser and alloy powder act synchronously on the metal surface, quickly melting to form a molten pool, and then quickly solidifying to form a dense, uniform and thickness-controllable metallurgical bonding layer. (3) The laser normalizing heat treatment process ensures that the repair area not only matches the substrate in chemical composition, but also achieves metallurgical bonding, and realizes the performance matching between the substrate and the repair area. Attached Figure Description

[0012] Figure 1 This is a photograph of the unrepaired tissue area in Example 3 of the present invention;

[0013] Figure 2 This is a photograph of the tissue area after repair in Embodiment 3 of the present invention. Detailed Implementation

[0014] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0015] The repair method of this invention employs a powder formulation combined with laser cladding and heat treatment processes to meet specific material performance requirements and process demands, ensuring high efficiency and quality in the repair and remanufacturing process, and achieving a high degree of compatibility with the original substrate. The powder formulation required for laser cladding comprises the following components by weight percentage: C 0.01-0.16, Mn 0.6-1.7, Si 0.1-0.7, Cr 0.4-23, Mo 0.05-4, Ni 0.05-5.2, Al 0.01-0.05, Cu 0.05-0.35, Nb 0.008-0.08, Ti 0.005-0.03, V 0.01-0.2, with the balance being Fe, and unavoidable, negligible trace impurities. The repaired coiled tubing, after undergoing laser normalizing heat treatment, exhibits mechanical properties superior to those of the original substrate.

[0016] The method for repairing coiled tubing of the present invention is implemented according to the following steps:

[0017] Step 1: Grind and clean the area of ​​the coiled tubing that needs repair.

[0018] 1.1) Use a grinder to grind the area to be repaired. Grinding not only removes surface oxides, but also removes rust, grease, paint and other impurities, laying the foundation for subsequent treatment. Heat is generated during the grinding process, which may affect the microstructure of the material. Therefore, allow the surface of the continuous tubing to cool naturally after grinding to restore the original properties of the material.

[0019] 1.2) After sanding, clean the surface with alcohol. Alcohol cleaning not only cleans the surface but also removes any remaining microparticles and grease, reducing the risk of corrosion caused by moisture. After cleaning, inspect the surface again to ensure no contaminants or defects are missed. This step is crucial for ensuring the quality of the repair work.

[0020] 1.3) After all processes are completed, the laser cladding equipment with built-in scanning device is used to scan the repair area to ensure the entry of information such as the shape and repair depth of the repair area.

[0021] Step 2: Prepare the cladding powder.

[0022] In accordance with the principle of matching with the substrate composition, an electronic balance is used to weigh each component of the required cladding powder to achieve precise proportioning and obtain a cladding mixture;

[0023] The cladding mixture is then placed in a vacuum ball mill jar to ensure ball milling in an oxygen-free environment to prevent powder oxidation. Grinding balls of varying diameters (e.g., equal numbers of balls with diameters of 2mm, 4mm, 6mm, and 8mm) are then placed in the jar, and vacuum ball milling begins. The milling speed is 300-450 R / min, and the ball-to-material ratio is 20-30:1. To prevent overheating during milling, a 5-7 minute break is made after every 15-20 minutes of continuous milling. Alternating forward and reverse rotation is used to ensure uniform force distribution. The entire milling process takes approximately 36-48 hours to ensure that the requirements of subsequent processes are met and a uniformly mixed cladding powder is obtained.

[0024] Step 3: Perform laser cladding.

[0025] Laser cladding technology is used to precisely repair defects after cleaning. The process parameters are as follows:

[0026] The laser power is 200-300W to ensure appropriate energy input.

[0027] Under the protection of an argon atmosphere, oxidation is prevented and the purity of the cladding area is maintained;

[0028] The cladding powder feed rate is 0.3-0.5 g / s to ensure the continuity and uniformity of the mixed powder replenishment;

[0029] The scanning speed is 4-6 mm / s to precisely control the formation rate of the cladding layer;

[0030] The laser beam has a diameter of 0.5mm, enabling high-precision cladding trajectory tracking;

[0031] The thickness of a single cladding layer is 0.2-0.5mm, ensuring the uniformity of the cladding layer and its perfect bonding with the substrate.

[0032] Step 4: Perform heat treatment.

[0033] After completing the laser cladding process, a laser induction normalizing process is used to further optimize the microstructure and macroscopic properties of the cladding layer material.

[0034] The normalizing heat treatment temperature is strictly set within the range of 920℃-1100℃ to ensure that the material undergoes uniform heat treatment at an appropriate temperature; the holding time is controlled at 5-10 minutes to ensure sufficient transformation of the material's internal structure. The main purpose of this treatment is to eliminate residual stress generated during the rapid heating and cooling process of the material in laser cladding, thereby improving the material's stability and service life, and enhancing its properties. It also improves the material's mechanical properties, such as hardness, toughness, and strength. During the treatment, the material's microstructure transforms, and the grains are refined. After heat treatment, the cladding layer is ensured to not only match the substrate chemically, achieving metallurgical bonding, but also significantly improving the overall performance and service life of the coiled tubing.

[0035] Example 1

[0036] The object of repair in this embodiment 1 is The implementation steps for using steel-grade low-carbon microalloyed coiled tubing are as follows:

[0037] Step 1: Grind and clean the area to be repaired.

[0038] For damaged sections of φ50.8×4.44mm-CT80 low-carbon microalloyed tubing, the first step is to grind them using an angle grinder. Grinding removes not only surface oxides but also rust, grease, paint, and other impurities. After grinding, the tubing surface should be allowed to cool naturally to restore the material's original properties. Following grinding, the tubing should be cleaned with alcohol to remove residual microparticles and grease, reducing the risk of corrosion from moisture. After cleaning, the surface should be inspected again to ensure no contaminants or defects are missed.

[0039] Step 2, the proportioning of laser cladding powder,

[0040] The chemical element composition of the powder required for laser cladding, by weight percentage, is as follows: C 0.12, Mn 0.9, Si 0.65, Cr 0.55, Mo 0.16, Ni 0.21, Al 0.03, Cu 0.22, Nb 0.023, Ti 0.015, V 0.03, with the balance being Fe and unavoidable impurities.

[0041] Weigh the above-mentioned component powders and place them in a vacuum ball mill jar. Then, take grinding balls of different diameters (select an equal number of grinding balls with diameters of 2 / 4 / 6 / 8 mm) and place them in the ball mill jar. Then, start vacuum ball milling at a speed of 350 R / min and a ball-to-material ratio of 20:1. To prevent the ball mill temperature from getting too high, the ball mill should be stopped for 5 minutes after every 15 minutes of continuous ball milling. Alternate forward and reverse rotation of the ball milling to ensure uniform force. The entire ball milling time is about 36 hours.

[0042] Step 3: Perform laser cladding.

[0043] Laser cladding technology is employed, with the laser power set at 200W. An argon atmosphere is used to prevent oxidation and maintain the purity of the cladding area. The powder feed rate is controlled at 0.5g / s to ensure continuous and uniform material replenishment. The scanning speed is 5mm / s to precisely control the formation rate of the cladding layer. A laser beam with a diameter of only 0.5mm is used to achieve high-precision cladding trajectory tracking. Furthermore, the thickness of a single cladding layer is reduced to 0.3mm, ensuring the uniformity of the cladding layer and its perfect bonding with the substrate.

[0044] Once the process parameters are set, turn on the laser cladding equipment and begin cladding.

[0045] Step 4: Perform heat treatment.

[0046] The normalizing heat treatment temperature is strictly set at 920℃, and the holding time is controlled at 10 minutes to ensure full transformation of the material's internal structure. This ensures that the cladding layer not only matches the substrate in chemical composition but also achieves a seamless bond in physical properties.

[0047] Step 5: Product performance testing:

[0048] The performance of the CT80 steel grade low carbon microalloy coiled tubing repaired in Example 1 was measured. As can be seen from Table 1, the coiled tubing repaired by the method of the present invention has better performance than the original substrate. While the strength and toughness are improved, the hardness is consistent with the substrate material, which extends the service life of the coiled tubing and improves the operational safety.

[0049] Table 1. Relevant properties of CT80 grade low-carbon microalloy coiled tubing repaired in Example 1

[0050] Serial Number project Performance parameters (repair area) Performance parameters (unrepaired areas) 1 Yield strength (MPa) 591 561 2 Tensile strength (MPa) 744 703 3 Elongation (%) 25.6 22.3 4 hardness 229 233

[0051] Example 2

[0052] The object to be repaired in this embodiment 2 is The implementation steps for low-carbon microalloyed coiled tubing are as follows:

[0053] Step 1: Grind and clean the area to be repaired.

[0054] For damaged sections of φ50.8×4.44mm-CT110 grade low-carbon microalloyed coiled tubing, the first step is to use an angle grinder to remove not only surface oxides but also rust, grease, paint, and other impurities. After grinding, the surface of the coiled tubing should be allowed to cool naturally to restore the original properties of the material. Following grinding, the tubing should be cleaned with alcohol to remove any remaining microparticles and grease, reducing the risk of corrosion caused by moisture. After cleaning, the surface should be inspected again to ensure no contaminants or defects are missed.

[0055] Step 2: Prepare laser cladding powder.

[0056] The chemical elemental composition of the powder required for laser cladding, by weight percentage, is as follows: C 0.11, Mn 1.6, Si 0.31, Cr 0.82, Mo 0.23, Ni 0.17, Al 0.05, Cu 0.33, Nb 0.06, Ti 0.021, V 0.04, with the balance being Fe and unavoidable impurities.

[0057] Weigh the above-mentioned component powders and place them in a vacuum ball mill jar. Then, take grinding balls of different diameters (select an equal number of grinding balls with diameters of 2 / 4 / 6 / 8 mm) and place them in the ball mill jar. Then, start vacuum ball milling at a speed of 400 R / min and a ball-to-material ratio of 20:1. To prevent the ball mill temperature from getting too high, the ball mill should be stopped for 6 minutes after every 18 minutes of continuous ball milling. Alternate forward and reverse ball milling should be used to ensure uniform force. The entire ball milling time is 42 hours.

[0058] Step 3: Perform laser cladding.

[0059] Laser cladding technology is employed, with the laser power set at 300W. An argon atmosphere is used to prevent oxidation and maintain the purity of the cladding area. The powder feed rate is controlled at 0.5g / s to ensure continuous and uniform material replenishment. The scanning speed is adjusted to 5mm / s to precisely control the formation rate of the cladding layer. A laser beam with a diameter of only 0.5mm is used to achieve high-precision cladding trajectory tracking. Furthermore, the cladding layer thickness is limited to 0.3mm to ensure uniformity and perfect bonding with the substrate.

[0060] Once the process parameters are set, turn on the laser cladding equipment and begin cladding.

[0061] Step 4: Perform heat treatment.

[0062] The normalizing heat treatment temperature is strictly set at 930℃, and the holding time is controlled at 7 minutes to ensure full transformation of the material's internal structure. This ensures that the cladding layer not only matches the substrate in chemical composition but also achieves metallurgical bonding in terms of physical properties.

[0063] Step 5: Product performance testing:

[0064] The performance of the CT110 steel grade low carbon microalloy coiled tubing repaired in Example 2 was measured, and the results are shown in Table 2.

[0065] Table 2. Relevant properties of CT110 grade low-carbon microalloyed coiled tubing repaired in Example 2

[0066]

[0067]

[0068] As can be seen from Table 2, the coiled tubing repaired using the method of the present invention has better performance than the original substrate. While improving strength and toughness, the hardness remains consistent with the substrate material, thus extending the service life of the coiled tubing and improving operational safety.

[0069] Example 3

[0070] The object to be repaired in this embodiment 3 is The implementation steps for stainless steel continuous tubing are as follows:

[0071] Step 1: Grind and clean the area to be repaired.

[0072] for For damaged areas of stainless steel continuous tubing, the first step is to grind them using an angle grinder. Grinding removes not only surface oxides but also rust, grease, paint, and other impurities. After grinding, the surface of the tubing should be allowed to cool naturally to restore the material's original properties. Following grinding, the area should be cleaned with alcohol to remove residual microparticles and grease, reducing the risk of corrosion caused by moisture. After cleaning, the surface should be inspected again to ensure no contaminants or defects are missed. Photos of the tissue morphology of the damaged area before repair should be taken. Figure 1 As shown.

[0073] Step 2: Prepare laser cladding powder.

[0074] The chemical composition of the powder required for laser cladding, by weight percentage, is as follows: C 0.02, Mn 1.5, Si 0.55, Cr 22.85, Mo 3.52, Ni 5.15, Al 0.025, Cu 0.08, Nb 0.008, Ti 0.005, V 0.20, with the balance being Fe and unavoidable impurities.

[0075] Weigh the above-mentioned component powders and place them in a vacuum ball mill jar. Then, take grinding balls of different diameters (select an equal number of grinding balls with diameters of 2 / 4 / 6 / 8 mm) and place them in the ball mill jar. Then, start vacuum ball milling at a speed of 400 R / min and a ball-to-material ratio of 30:1. To prevent the ball mill temperature from getting too high, the ball mill should be stopped for 7 minutes after every 20 minutes of continuous ball milling. Alternate forward and reverse rotation of the ball mill should be used to ensure uniform force. The entire ball milling time is 42 hours.

[0076] Step 3: Perform laser cladding.

[0077] Laser cladding technology is employed, with the laser power set at 300W. An argon atmosphere is used to prevent oxidation and maintain the purity of the cladding area. The powder feed rate is controlled at 0.5g / s to ensure continuous and uniform material replenishment. The scanning speed is adjusted to 5mm / s to precisely control the formation rate of the cladding layer. A 0.5mm diameter laser beam is used to achieve high-precision cladding trajectory tracking. The cladding layer thickness is limited to 0.2mm to ensure uniformity and perfect bonding with the substrate.

[0078] Once the process parameters are set, turn on the laser cladding equipment and begin cladding.

[0079] Step 4: Perform heat treatment.

[0080] The normalizing heat treatment temperature is strictly set at 1050℃, and the holding time is controlled at 7 minutes to ensure full transformation of the material's internal structure. This ensures that the cladding layer not only matches the substrate in chemical composition but also achieves a seamless bond in physical properties.

[0081] Step 5: Product performance testing:

[0082] Performance tests were conducted on the repaired CT80-2205 stainless steel coiled tubing, and the following conclusions were drawn:

[0083] 1) The repaired area exhibits good resistance to HIC, with no hydrogen bubbling or cracking. The hardness of the coiled tubing repaired using this method remains consistent with the base material, extending the service life of the coiled tubing and improving operational safety.

[0084] 2) The hardness value of the repaired area was 270 HV, and the hardness value of the unrepaired area was 275 HV. Its tissue morphology is as follows: Figure 2 As shown in the figure, the microstructure of the repaired area and the substrate are not significantly different, achieving performance matching between the substrate and the repaired area.

[0085] 3) Intergranular corrosion tests were conducted on the repaired area of ​​the 2205 stainless steel coiled tubing according to Method E in the national standard GB / T 4334-2008. Following the standard specifications, the samples in the repaired area were boiled in CuSO4 solution for 16 hours, and then bent 180°. After bending, no cracks were observed in the samples under a 10x magnifying glass, indicating that the repaired stainless steel coiled tubing has good resistance to intergranular corrosion.

Claims

1. A method of repairing coiled tubing, characterized by, The following steps are implemented: Step 1, polish and clean the damaged area of the coiled tubing surface that needs to be repaired, and record the information of the damaged location; Step 2, prepare the cladding powder; Step 3, implement laser cladding; Step 4, implement heat treatment, The heat treatment operation of the cladding layer is completed by using laser induction normalizing process.

2. The coiled tubing repair method of claim 1, wherein, In step 1, the specific process is, 1.1) Use a sander to polish the area to be repaired, remove surface oxides, rust, grease, paint and other impurities, and naturally cool the coiled tubing surface after polishing; 1.2) After polishing, clean with alcohol; 1.3) Scan the repair area and complete the information input of the topography and repair depth of the repair area.

3. The coiled tubing repair method of claim 1, wherein, In step 2, the specific process is, According to the principle of matching the composition of the base material, weigh the components of the cladding powder required to obtain the cladding mixture; Then put the cladding mixture into a vacuum ball mill jar, and then put different diameter grinding balls into the jar, and then start vacuum ball milling to obtain a uniformly mixed cladding powder.

4. The coiled tubing repair method of claim 3, wherein, The weight percentage of each component is: C 0.01-0.16, Mn 0.6-1.7, Si 0.1-0.7, Cr 0.4-23, Mo 0.05-4, Ni 0.05-5.2, Al 0.01-0.05, Cu 0.05-0.35, Nb 0.008-0.08, Ti 0.005-0.03, V 0.01-0.2, and the balance is Fe.

5. The coiled tubing repair method of claim 3, wherein, In step 2, an equal number of grinding balls with diameters of 2mm, 4mm, 6mm and 8mm are selected.

6. The coiled tubing repair method of claim 3, wherein, In step 2, the process parameters of the ball milling process are: The ball milling speed is 300-450R / min, the ball-to-material ratio is 20-30:1, the ball milling process is stopped for 5-7 minutes every 15-20 minutes of continuous ball milling, and the ball milling is alternately reversed, the whole ball milling time is 36-48h.

7. The coiled tubing repair method of claim 1, wherein, In step 3, the process parameters of laser cladding are: The laser power is 200-300W; under the protection of argon atmosphere, the purity of the cladding area is maintained; the cladding powder feeding rate is 0.3-0.5g / s; the scanning speed is 4-6mm / s; the laser beam diameter is 0.5mm; the single cladding layer thickness is 0.2-0.5mm.

8. The coiled tubing remediation method of claim 1, wherein, In step 4, the process parameters of normalizing treatment are: the heat treatment temperature is 920-1100℃, and the holding time is 5-10min.

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