A method for threaded connection of a bimetallic composite pipe

Abstract

The application discloses a threaded connection method of a bimetal composite pipe, and particularly relates to the field of oil and gas pipes for oil and gas, and specifically comprises the following steps: (1) preparing laser cladding powder; (2) preparing a composite pipe blank and a coupling blank; (3) pretreating the coupling blank; (4) laser cladding treatment of the coupling blank; (5) processing the female thread of the coupling blank; (6) cutting processing of the composite pipe blank; (7) laser cladding treatment of the nose end of the composite pipe blank; (8) copper plating of the finished composite pipe and the finished coupling; and (9) assembling the finished composite pipe and the finished coupling. The application improves the mechanical properties and corrosion resistance of the shoulder of the nose end of the bimetal composite pipe and the coupling by means of laser cladding technology without increasing additional cost, and is compatible with various specifications of bimetal composite pipes, couplings and thread types, and can be flexibly selected according to the requirements of field working conditions.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipeline technology, and more specifically to a threaded connection method for bimetallic composite pipes. Background Technology

[0002] With the advancement of oil and gas field exploration and development technologies, significant progress has been made in the exploration and development of high-sulfur natural gas reservoirs worldwide. High-sulfur natural gas reservoirs contain a large amount of H2S and also contain a certain concentration of CO2, which places higher demands on pipe materials and corrosion prevention technologies.

[0003] Bimetallic composite pipes possess both the excellent mechanical properties of the carbon steel base layer and the good corrosion resistance of the corrosion-resistant alloy lining layer, making them widely used in oil and gas extraction and transportation. The joints of oil and gas pipelines are the weakest points in the entire pipeline structure, and couplings are often used to connect the pipes. However, this connection method creates gaps at the sealing surfaces and shoulder areas of the oil and gas pipes and the shoulder areas of the couplings, making them susceptible to corrosion. To improve corrosion resistance in these areas, corrosion-resistant alloys are often applied through welding to the sealing surfaces and shoulder areas of the oil and gas pipes, with the couplings using the same corrosion-resistant alloy. However, welding can easily lead to element migration between the corrosion-resistant alloy layer and the carbon steel layer, reducing the corrosion resistance of the weld. Welding can also cause significant deformation in the welded area, affecting connection and sealing performance. Furthermore, couplings made entirely of corrosion-resistant alloys are relatively expensive.

[0004] Laser cladding uses a high-energy-density laser beam as a heat source, combined with inert gas protection. Following a preset scanning path, the laser beam irradiates a material that is simultaneously delivered or pre-coated onto the substrate surface, achieving rapid melting and solidification of both the cladding material and the substrate surface, ultimately forming a cladding layer with…

[0005] Functional coatings with metallurgical bonding properties belong to a type of additive manufacturing technology. Compared to traditional stacking...

[0006] Laser cladding, a type of additive manufacturing technology, offers higher density coatings with fewer defects such as pores and cracks, lower heat-affected zones and thermal deformation, and better metallurgical bonding. However, its application in improving the corrosion resistance of oil and gas pipe joints is still under development. Direct use of laser cladding technology faces challenges such as high cost, difficulty in determining cladding powders, and challenges in selecting process parameters. Summary of the Invention

[0007] In view of this, the present invention provides a threaded connection method for bimetallic composite pipes to solve the problem of reduced corrosion resistance caused by element migration and deformation of the welded portion during the welding process at the nose of the bimetallic composite pipe.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A threaded connection method for a bimetallic composite pipe specifically includes the following steps:

[0010] (1) Preparation of laser cladding powder

[0011] Carbon powder, silicon powder, chromium powder, molybdenum powder, niobium powder, copper powder, yttrium powder, manganese powder, and nickel powder are mixed evenly according to different mass percentages to obtain the laser cladding powder of the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end, as well as the laser cladding powder of the shoulder of the coupling and the total sealing surface of the coupling.

[0012] (2) Prepare composite pipe blanks and coupling blanks

[0013] Prepare a bimetallic composite pipe blank and a coupling blank that matches the specifications of the bimetallic composite pipe blank.

[0014] (3) Pretreatment of coupling blank

[0015] With the midpoint of the axis of the coupling blank as the center, cut off the surrounding part to form an annular plane, grind it smooth and clean the annular plane, and perform preheating treatment.

[0016] (4) Laser cladding treatment of coupling blanks

[0017] The laser cladding powder of the coupling shoulder and the total sealing surface of the coupling in step (1) is loaded into the powder feeder of the laser cladding equipment. The coupling blank is kept rotating. The powder feeding method is coaxial powder feeding. The cladding powder is clad on the annular plane by synchronous laser cladding method. After the coupling shoulder and the total sealing surface of the coupling are completely formed, the laser cladding equipment is turned off and the coupling shoulder and the total sealing surface of the coupling are polished to make the coupling shoulder and the total sealing surface of the coupling smooth and flat.

[0018] (5) Machining of the female thread of the coupling blank

[0019] The coupling blank after laser cladding in step (4) is machined from the outside to the inside with female threads until the starting position of the sealing surface of the coupling is formed into a finished coupling.

[0020] (6) Machining of composite pipe blank

[0021] The prepared composite pipe blank is machined to cut out the sealing surface three at the nose end of the composite pipe, and male threads are cut from the starting position of the sealing surface three at the nose end of the composite pipe along the axial direction away from the pipe opening.

[0022] (7) Laser cladding treatment of the nose end of the composite tube blank

[0023] Clean the composite tube blank after cutting and preheat it. Load the cladding powder of the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end from step (1) into the powder feeder of the laser cladding equipment. Keep the composite tube blank after cutting and rotating. The powder feeding method adopts coaxial powder feeding. The powder is clad on the composite tube nose end of the composite tube blank after cutting and using the synchronous laser cladding method. The cladding direction is from the inside to the outside. After the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end are formed, turn off the laser cladding equipment and polish the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end to make the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end smooth and flat, and obtain the finished composite tube.

[0024] (8) Copper plating of composite pipes and couplings

[0025] To prevent the finished composite pipes and couplings from sticking together, copper plating is performed on them. First, the finished composite pipes and couplings are placed in an alkaline degreasing solution containing sodium hydroxide, sodium carbonate, trisodium phosphate, and sodium silicate at 80-90℃ for 5-10 minutes. After alkaline washing, they are thoroughly rinsed with deionized water to ensure that the residual alkali is completely removed. Then, the finished composite pipes and couplings are placed in a mixed pickling solution of nitric acid and hydrofluoric acid at room temperature for 3-5 minutes. After pickling, the residual acid is removed with deionized water. Finally, the workpieces are immersed in a copper sulfate solution at 40-50℃ with a pH value maintained between 10 and 12 for 80-100 minutes to form a copper plating layer. After copper plating, they are rinsed with deionized water and immediately dried with hot air.

[0026] (9) Assembly of finished composite pipes and finished couplings

[0027] The male thread at one end of a single finished composite pipe is screwed onto the female thread of a finished coupling to complete the initial assembly. After being transported to the site, the male thread at the other end of the composite pipe is screwed onto the next finished coupling or a finished coupling that has already been installed in the wellhead, thereby connecting them in series to form a complete downhole tubing string.

[0028] Preferably, in step (1), the laser cladding powder of the shoulder of the coupling and the total sealing surface of the coupling, by mass percentage, includes: carbon powder: 0.01%~0.03%, silicon powder: 0.01%~0.02%, chromium powder: 20%~23%, molybdenum powder: 8%~9%, niobium powder: 2.5%~3.5%, copper powder: 1%~1.5%, yttrium powder: 0.2%~0.4%, manganese powder: 0.3%~0.4%, and nickel powder as the balance; the particle size of the laser cladding powder of the shoulder of the coupling and the total sealing surface of the coupling is 70um~120um, and the sphericity is 0.8~0.95.

[0029] Preferably, in step (1), the laser cladding powder for the sealing surface one, sealing surface two, outer transition fillet, and shoulder surface of the composite tube nose end, by mass percentage, includes: carbon powder: 0.02%~0.04%, silicon powder: 0.01%~0.02%, chromium powder: 22%~24%, molybdenum powder: 8%~9%, niobium powder: 3.5%~5%, copper powder: 1%~1.5%, yttrium powder: 0.3%~0.5%, manganese powder: 0.3%~0.4%, and nickel powder as the balance; the particle size of the laser cladding powder for the sealing surface one, sealing surface two, outer transition fillet, and shoulder surface of the composite tube nose end is 25um~65um, and the sphericity is 0.8~0.95.

[0030] Preferably, in step (3), the axial length L of the annular plane is 50mm~82mm.

[0031] Preferably, in steps (3) and (7), the preheating temperature is 150℃~300℃.

[0032] Preferably, in step (4), the laser cladding process parameters are: laser power: 1500W~3600W, powder feeding speed: 8g / min~15g / min, scanning speed: 8mm / s~12mm / s, spot diameter: 2mm~4mm, overlap rate: 45%~65%, and protective gas is argon.

[0033] Preferably, the positional relationship between the shoulder surface of the coupling, the inner transition fillet, the first sealing surface of the coupling, the second sealing surface of the coupling, and the female thread is as follows: the shoulder surface of the coupling is located above the inner transition fillet, the first sealing surface of the coupling, the second sealing surface of the coupling, and the female thread; along the axial direction away from the hammer line m in the coupling, the distances from the hammer line m in the coupling from near to far are as follows: inner transition fillet, first sealing surface of the coupling, second sealing surface of the coupling, and female thread;

[0034] The overall sealing surface of the composite pipe nose end consists of sealing surface one, sealing surface two, sealing surface three, and the outer transition fillet. The positional relationship between the shoulder surface, the outer transition fillet, sealing surface one, sealing surface two, sealing surface three, and the male thread of the composite pipe nose end is as follows: the shoulder surface of the composite pipe nose end is located above the outer transition fillet, sealing surface one, sealing surface two, sealing surface three, and the male thread; along the axial direction away from the composite pipe opening, the axial distances from the composite pipe opening from near to far are as follows: outer transition fillet, sealing surface one, sealing surface two, sealing surface three, and the male thread.

[0035] After the composite pipe and coupling are engaged and tightened, the shoulder surface of the coupling and the shoulder surface of the nose end of the composite pipe form a sealing pair one, the inner transition fillet and the outer transition fillet form a sealing pair two, the sealing surface one of the coupling and the sealing surface one of the nose end of the composite pipe form a sealing pair three, and the sealing surface two of the coupling, the sealing surface two of the nose end of the composite pipe and the sealing surface three of the nose end of the composite pipe form a sealing pair four.

[0036] The lengths of the total sealing surface of the coupling and the total sealing surface of the composite pipe nose are a and b, respectively. The sum of the axial length of the first sealing surface of the coupling and the axial length of the inner transition fillet is a1. The sum of the axial length of the first sealing surface of the composite pipe nose and the axial length of the outer transition fillet is b1. Both a1 and b1 are 6mm~10mm. The radii of the outer and inner transition fillets are both R: 0.5mm~1.5mm. The axial length b2 of the second sealing surface of the composite pipe nose is 4mm~8mm. The axial length b3 of the third sealing surface of the composite pipe nose is: 2mm~4mm, the axial length a2 of the sealing surface two of the coupling is equal to the sum of the axial length b2 of the sealing surface two of the composite pipe nose and the axial length b3 of the sealing surface three of the composite pipe nose, that is: a2=b2+b3, the shoulder width c of the coupling is twice the distance d from the intersection of the shoulder surface of the coupling and the inner transition fillet to the center hammer line m, that is: c=2d, the value range of d is: 12mm~25mm, and the sealing surface two of the composite pipe nose and the sealing surface three of the composite pipe nose are tangent, and the sealing surface three of the composite pipe nose and the sealing surface two of the coupling are both tangent to the inner surface of the coupling blank on the same side in step (2); the axial length a of the total sealing surface of the coupling, the axial length b of the total sealing surface of the composite pipe nose and the axial length c of the shoulder of the coupling have the following relationship: L=a+c, a=a1+a2+a3, b=b1+b2.

[0037] Preferably, in steps (4) and (7), the sealing method is a conical surface to conical surface sealing, the shoulder of the coupling is a negative angle shoulder, the included angle between the sealing surface one and the sealing surface two of the composite pipe nose end and the included angle between the sealing surface one and the sealing surface two of the coupling are both α: 4°~12°, the included angle between the shoulder surface of the composite pipe nose end and the shoulder surface of the coupling and the vertical line l are both β: 8°~15°, the shoulder surface of the coupling and the sealing surface one of the coupling are both tangent to the inner transition fillet, and the shoulder surface of the composite pipe nose end and the sealing surface one of the composite pipe nose end are both tangent to the outer transition fillet.

[0038] Preferably, in steps (5) and (6), the thread parameters are: number of threads per inch n: 4 to 7, taper T: 1:16 to 1:10, thread profile height h: 0.9 mm to 2.3 mm, bearing surface angle γ: -10° to 4°, and guide surface angle φ: -3° to 30°.

[0039] Preferably, in step (7), the laser cladding process parameters are: laser power: 1500W~3000W, powder feeding speed: 7g / min~14g / min, scanning speed: 6mm / s~10mm / s, spot diameter: 0.8mm~2.5mm, overlap rate: 45%~75%, and protective gas is argon.

[0040] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The use of laser cladding technology improves the metallurgical bonding ability of the alloy layer and carbon steel layer of the total sealing surface of the composite pipe nose and the shoulder surface of the composite pipe nose, as well as the shoulder and body of the coupling, effectively suppressing the structural deformation of the heat-affected zone and significantly improving the corrosion resistance of the contact area between the composite pipe nose and the shoulder of the coupling.

[0042] 2. A portion of the material is removed from the center of the coupling axis to form an annular plane. Then, laser cladding technology is used to clad the shoulder of the coupling and the total sealing surface of the coupling. This design not only significantly improves its resistance to localized corrosion, but also has excellent comprehensive mechanical properties, effectively resisting the effects of tensile, compressive, shear stress and torque.

[0043] 3. The design mainly focuses on the overall sealing surface of the composite pipe nose, the shoulder surface of the composite pipe nose, and the shoulder of the coupling, thereby improving the corrosion resistance in high sulfur-containing environments. Compared with couplings made of pure corrosion-resistant alloys, it not only reduces costs but also improves corrosion resistance in high sulfur-containing corrosive environments. It is widely applicable to various bimetallic composite pipes and couplings. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0045] Figure 1 The process flow of the coupling manufacturing process of this invention Figure 1 ;

[0046] Figure 2 The process flow of the coupling manufacturing process of this invention Figure 2 ;

[0047] Figure 3 The process flow of the coupling manufacturing process of this invention Figure 3 ;

[0048] Figure 4 The process flow of the coupling manufacturing process of this invention Figure 4 ;

[0049] Figure 5 The process flow of the composite pipe manufacturing process of this invention is as follows. Figure 1 ;

[0050] Figure 6 The process flow of the composite pipe manufacturing process of this invention is as follows. Figure 2 ;

[0051] Figure 7 The process flow of the composite pipe manufacturing process of this invention is as follows. Figure 3 ;

[0052] Figure 8 This is a cross-sectional view of the composite pipe and coupling connection of the present invention;

[0053] Figure 9 for Figure 8 Enlarged view at point A;

[0054] Figure 10 for Figure 8 Enlarged view at point B;

[0055] Figure 11 This is a magnified view of a portion of the thread.

[0056] In the diagram: 1. Coupling blank; 2. Annular plane; 3. Laser cladding portion of the coupling; 4. Shoulder of the coupling; 5. Shoulder surface of the coupling; 6. Overall sealing surface of the coupling; 6-1. Sealing surface one of the coupling; 6-2. Sealing surface two of the coupling; 7. Inner transition fillet; 8. Female thread; 9. Finished coupling; 10. Composite pipe blank; 10-1. Inner liner of the composite pipe; 10-2. Base pipe of the composite pipe; 11. Laser cladding portion of the composite pipe; 12. Shoulder surface of the nose end of the composite pipe; 13. Overall sealing surface of the nose end of the composite pipe; 13-1. Sealing surface one of the nose end of the composite pipe; 13-2. Sealing surface two of the nose end of the composite pipe; 13-3. Sealing surface three of the nose end of the composite pipe; 14. Outer transition fillet; 15. Male thread; 16. Finished composite pipe. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Example 1

[0059] A threaded connection method for a bimetallic composite pipe specifically includes the following steps:

[0060] (1) Preparation of laser cladding powder

[0061] To prepare laser cladding powder for the sealing surface 13-1, sealing surface 13-2, outer transition fillet 14, and shoulder surface 12 of the composite tube nose end: Weigh 0.25g carbon powder, 0.15g silicon powder, 191g chromium powder, 72g molybdenum powder, 36g niobium, 11.9g copper powder, 2.9g yttrium powder, 2.8g manganese powder, and 483g nickel powder, mix them evenly to obtain the cladding powder. The particle size is 45 μm and the sphericity is 0.85. Laser cladding powder for preparing the shoulder 4 and the total sealing surface 6 of the coupling: Weigh 0.18 g of carbon powder, 0.12 g of silicon powder, 179 g of chromium powder, 68.7 g of molybdenum powder, 32.8 g of niobium powder, 10 g of copper powder, 2.4 g of yttrium powder, 2.8 g of manganese powder and 504 g of nickel powder, mix them evenly to obtain cladding powder with a particle size of 100 μm and a sphericity of 0.85.

[0062] (2) Prepare composite pipe blanks and coupling blanks

[0063] like Figure 1 and Figure 5 As shown, prepare a bimetallic composite pipe blank 10. 219.1 The material of the composite pipe base pipe 10-2 is C110 with a wall thickness of 9mm. The material of the composite pipe inner liner pipe 10-1 is Incoloy 625 with a wall thickness of 2.5mm. Prepare a coupling blank 1 with the same specifications as the composite pipe blank 10 and the material is C110.

[0064] (3) Pretreatment of coupling blank

[0065] like Figure 2 As shown, with the midpoint of the axis of the coupling blank 1 as the center, the surrounding part is cut off to form an annular plane 2 with an axial length L of 62mm. The annular plane 2 is polished and cleaned, and then preheated at 150℃.

[0066] (4) Laser cladding treatment of coupling blanks

[0067] like Figure 3 As shown, the laser cladding powder of the shoulder 4 and the total sealing surface 6 of the coupling in step (1) is loaded into the powder feeder of the laser cladding equipment. The coupling blank 1 is kept rotating. The powder feeding method adopts coaxial powder feeding. The cladding powder is clad on the annular plane 2 by synchronous laser cladding method. After the total sealing surface 6 and the shoulder 4 of the coupling are completely formed, the laser cladding equipment is turned off, and the total sealing surface 6 and the shoulder 4 of the coupling are polished to make the total sealing surface 6 and the shoulder 4 of the coupling smooth and flat.

[0068] See Figure 9 The laser cladding process parameters are as follows: laser power is 2400W, powder feeding rate is 9g / min, spot diameter is 3mm, scanning speed is 10mm / s, overlap rate is 50%, protective gas is argon, the sum of the axial length of the sealing surface 1-6-1 and the axial length of the inner transition fillet 7 is a1, the axial length of the sealing surface 2-6-2 is a2, which are 7mm and 9mm respectively, the axial length c of the shoulder 4 of the coupling is 30mm, the radius of the inner transition fillet 7 is 1mm, the included angle α between the sealing surface 1-6-1 and the sealing surface 2-6-2 of the coupling is 7°, the shoulder 4 of the coupling is a negative angle shoulder, the included angle β between the shoulder surface 5 of the coupling and the vertical line l is 14°, the shoulder surface 5 of the coupling and the sealing surface 1-6-1 of the coupling are both tangent to the inner transition fillet 7, and the sealing surface 2-6-2 of the coupling is tangent to the inner surface of the coupling blank 1.

[0069] (5) Machining of the female thread of the coupling blank

[0070] like Figure 4 As shown, the coupling blank after laser cladding treatment in step (4) is machined from the outside to the inside with the female thread 8 to the starting position of the sealing surface 6-2 of the coupling;

[0071] See Figure 11The thread parameters are as follows: number of threads per inch n: 5, taper T: 1:16, thread height h: 1.6mm, bearing surface angle γ: -3°, and guide surface angle φ: -3°.

[0072] (6) Machining of composite pipe blank

[0073] like Figure 6 As shown, the prepared composite pipe blank 10 is machined to cut out the sealing surface 313-3 of the nose end of the composite pipe with an axial length b3 of 3mm, and the male thread 15 is cut out from the starting position of the sealing surface 313-3 of the nose end of the composite pipe blank 10 along the axial direction away from the pipe opening.

[0074] See Figure 11 The thread parameters are as follows: number of threads per inch n: 5, taper T: 1:16, thread height h: 1.6mm, bearing surface angle γ: -3°, and guide surface angle φ: -3°.

[0075] (7) Laser cladding treatment of the nose end of the composite tube blank

[0076] like Figure 7 As shown, the composite tube blank 10 after machining is cleaned and preheated. The laser cladding powder of the sealing surface 13-1, sealing surface 13-2, outer transition fillet 14, and shoulder surface 12 of the composite tube nose end from step (1) is loaded into the powder feeder of the laser cladding equipment. The composite tube blank 10 after machining is kept rotating. The powder feeding method adopts coaxial powder feeding. The powder is clad onto the nose end of the composite tube blank 10 after machining using a synchronous laser cladding method. The cladding direction is from the inside to the outside. After the sealing surface 13-1, sealing surface 13-2, outer transition fillet 14, and shoulder surface 12 of the composite tube nose end are formed, the laser cladding equipment is turned off, and the sealing surface 13-1, sealing surface 13-2, outer transition fillet 14, and shoulder surface 12 of the composite tube nose end are polished to make the sealing surface 13-1, sealing surface 13-2, outer transition fillet 14, and shoulder surface 12 of the composite tube nose end smooth and flat, thus obtaining the finished composite tube 16.

[0077] See Figure 10The axial length of the total sealing surface 13 at the nose of the composite pipe is 12 mm. The sum of the axial length of the sealing surface 13-1 and the axial length of the outer transition fillet, b1, and the axial length of the sealing surface 13-2, b2, are 6 mm and 6 mm respectively. The radius of the outer transition fillet 14 is 1 mm. The angle α between the sealing surface 13-1 and the sealing surface 13-2 is 7°. The angle β between the shoulder surface of the composite pipe nose and the vertical line l is 14°. The outer transition fillet 14 and the shoulder surface 12 of the composite pipe nose are both tangent to the sealing surface 13-1. The sealing surfaces 13-2 and 13-3 are tangent to the inner surface of the coupling blank 1.

[0078] The laser cladding process parameters are as follows: laser power is 2100W, powder feeding rate is 8g / min, spot diameter is 1.5mm, scanning speed is 8mm / s, overlap rate is 60%, and the protective gas is argon.

[0079] (8) Copper plating of finished composite pipes and finished couplings

[0080] First, place the finished composite pipe 16 and finished coupling 9 in an alkaline degreasing solution containing sodium hydroxide, sodium carbonate, trisodium phosphate and sodium silicate at 85°C and soak for 6 minutes to thoroughly remove grease and contaminants from their surfaces. After alkaline washing, rinse thoroughly with deionized water to ensure that residual alkaline solution is completely removed. Then, place the finished composite pipe 16 and finished coupling 9 in a mixed pickling solution of nitric acid and hydrofluoric acid at room temperature and soak for 3 minutes to dissolve rust on the surface. After pickling, remove residual acid with deionized water. Finally, immerse the workpiece in a copper sulfate solution at 50°C and pH 10 for 83 minutes to form a copper plating layer. After copper plating, rinse with deionized water and immediately dry with hot air.

[0081] (9) Assembly of finished composite pipes and finished couplings

[0082] like Figure 8 As shown, in the factory, the male thread of one end of a single finished composite pipe 16 is screwed onto the female thread 8 of the finished coupling 9 to complete the initial assembly. After being transported to the site, the male thread of the other end of the finished composite pipe 16 is screwed onto the next finished coupling 9 or the finished coupling 9 that has been installed in the wellhead, so as to form a complete downhole tubing string.

[0083] Example 2

[0084] A threaded connection method for a bimetallic composite pipe specifically includes the following steps:

[0085] (1) Preparation of laser cladding powder

[0086] To prepare laser cladding powder for the sealing surface 13-1, sealing surface 13-2, outer transition fillet 14, and shoulder surface 12 of the composite tube nose end: Weigh 0.19g carbon powder, 0.11g silicon powder, 187g chromium powder, 75.4g molybdenum powder, 35g niobium, 13.1g copper powder, 2.4g yttrium powder, 2.8g manganese powder, and 484g nickel powder, mix them evenly, and obtain the cladding powder. Finally, the particle size is 46 μm and the sphericity is 0.90; to prepare the cladding powder for the shoulder 4 and the total sealing surface 6 of the coupling: weigh 0.17 g of carbon powder, 0.13 g of silicon powder, 176.2 g of chromium powder, 72 g of molybdenum powder, 31.6 g of niobium, 9 g of copper powder, 2.5 g of yttrium powder, 2.4 g of manganese powder and 506 g of nickel powder, mix them evenly to obtain the cladding powder with a particle size of 110 μm and a sphericity of 0.85;

[0087] (2) Prepare composite pipe blanks and coupling blanks

[0088] like Figure 1 and Figure 5 As shown, prepare an unthreaded bimetallic composite pipe blank 10. 168.3, The material of the composite pipe base pipe 10-2 is P110SS, the wall thickness is 6.6mm, the material of the composite pipe inner lining pipe 10-1 is Hastelloy C276, the wall thickness is 2mm, and a coupling blank 1 corresponding to the specification of the composite pipe blank 10 is prepared, the material of which is P110SS.

[0089] (3) Pretreatment of coupling blank

[0090] like Figure 2 As shown, with the midpoint of the axis of the coupling blank 1 as the center, the surrounding area is cut off to form an annular plane 2 with an axial length L of 56mm. The annular plane 2 is polished and cleaned, and then preheated at 160℃.

[0091] (4) Laser cladding treatment of coupling blanks

[0092] like Figure 3 As shown, the laser cladding powder in step (1) is loaded into the powder feeder of the laser cladding equipment. The coupling blank 1 is kept rotating. The powder feeding method is coaxial powder feeding. The cladding powder is clad on the annular plane 2 by synchronous laser cladding method. After the total sealing surface 6 of the coupling and the shoulder 4 of the coupling are completely formed, the laser cladding equipment is turned off, and the total sealing surface 6 of the coupling and the shoulder 4 of the coupling are polished to make the total sealing surface 6 of the coupling and the shoulder 4 of the coupling smooth and flat.

[0093] See Figure 9The laser cladding process parameters are as follows: laser power is 2500W, powder feeding rate is 10g / min, spot diameter is 3mm, scanning speed is 11mm / s, overlap rate is 55%, protective gas is argon, the sum of the axial length of the sealing surface 6-1 and the axial length of the inner transition fillet 7, a1, and the axial length a2 of the sealing surface 6-2 are 6mm and 8mm respectively, the radius of the inner transition fillet 7 is 0.75mm, the axial length c of the shoulder 4 of the coupling is 28mm, the included angle α between the sealing surface 6-1 and the sealing surface 6-2 of the coupling is 7°, the shoulder 4 of the coupling is a negative angle shoulder, the included angle β between the shoulder surface 5 of the coupling and the vertical line l is 12°, the inner transition fillet 7 and the shoulder surface 5 of the coupling are both tangent to the sealing surface 6-1 of the coupling, and the sealing surface 6-2 of the coupling is tangent to the inner surface of the coupling blank 1.

[0094] (5) Machining of the female thread of the coupling blank

[0095] like Figure 4 As shown, the coupling blank after laser cladding treatment in step (4) is machined from the outside to the inside with the female thread 8 to the starting position of the sealing surface 6-2 of the coupling;

[0096] See Figure 11 The thread parameters are as follows: number of threads per inch n: 5, taper T: 1:16, thread height h: 1.4mm, bearing surface angle γ: -2°, and guide surface angle φ: 10°.

[0097] (6) Composite pipe cutting and machining

[0098] like Figure 6 As shown, the prepared composite pipe blank 10 is machined to cut out the sealing surface 313-3 of the nose end of the composite pipe with an axial length b3 of 2mm, and the male thread 15 is cut out from the starting position of the sealing surface 313-3 of the composite pipe blank 10 along the axial direction away from the pipe opening.

[0099] See Figure 11 The thread parameters are as follows: number of threads per inch n: 5, taper T: 1:16, thread height h: 1.4mm, bearing surface angle γ: -2°, and guide surface angle φ: 10°.

[0100] (7) Laser cladding treatment of the nose end of the composite tube blank

[0101] like Figure 7As shown, the composite tube blank 10 after cutting is cleaned and preheated. The laser cladding powder from step (1) is loaded into the powder feeder of the laser cladding equipment. The composite tube blank 10 after cutting is kept rotating. The powder feeding method adopts coaxial powder feeding. The powder is clad onto the nose end of the composite tube blank 10 after cutting using a synchronous laser cladding method. The cladding direction is from the inside to the outside. The powder is clad onto the sealing surface 13-1 of the nose end of the composite tube and the nose end of the composite tube. After the sealing surface 13-2, the outer transition fillet 14, and the shoulder surface 12 of the composite tube nose are formed, the laser cladding equipment is turned off, and the sealing surface 13-1, the sealing surface 13-2, the outer transition fillet 14, and the shoulder surface 12 of the composite tube nose are polished to make the sealing surface 13-1, the sealing surface 13-2, the outer transition fillet 14, and the shoulder surface 12 of the composite tube nose smooth and flat, thus obtaining the finished composite tube 16.

[0102] See Figure 10 The axial length of the total sealing surface 13 of the composite pipe nose end is 12mm. The sum of the axial length of the sealing surface 13-1 and the axial length of the outer transition fillet b1 and the axial length of the sealing surface 13-2 of the composite pipe nose end are 6mm and 6mm respectively. The radius of the outer transition fillet is 0.75mm. The angle α between the sealing surface 13-1 and the sealing surface 13-2 of the composite pipe nose end is 7°. The angle β between the shoulder surface of the composite pipe nose end and the vertical line l is 12°. The outer transition fillet 14 and the shoulder surface 12 of the composite pipe nose end are both tangent to the sealing surface 13-1 of the composite pipe nose end. The sealing surface 13-2 and the sealing surface 13-3 of the composite pipe nose end are tangent to the inner surface of the coupling blank 1.

[0103] The laser cladding process parameters are as follows: laser power of 2200W, powder feeding rate of 7g / min, spot diameter of 1mm, scanning speed of 8mm / s, overlap rate of 50%, and argon as the protective gas.

[0104] (8) Copper plating of finished composite pipes and finished couplings

[0105] First, place the finished composite pipe 16 and finished coupling 9 in an alkaline degreasing solution containing sodium hydroxide, sodium carbonate, trisodium phosphate and sodium silicate at 87°C and soak for 5 minutes to thoroughly remove grease and contaminants from their surfaces. After alkaline washing, rinse thoroughly with deionized water to ensure that residual alkaline solution is completely removed. Then, place the finished composite pipe 16 and finished coupling 9 in a mixed pickling solution of nitric acid and hydrofluoric acid at room temperature and soak for 4 minutes to dissolve rust on the surface. After pickling, remove residual acid with deionized water. Finally, immerse the workpiece in a copper sulfate solution at 45°C and pH 11 for 81 minutes to form a copper plating layer. After copper plating, rinse with deionized water and immediately dry with hot air.

[0106] (9) Assembly of finished composite pipes and finished couplings

[0107] like Figure 8 As shown, in the factory, the male thread of one end of a single finished composite pipe 16 is screwed onto the female thread 8 of the finished coupling 9 to complete the initial assembly. After being transported to the site, the male thread of the other end of the finished composite pipe 16 is screwed onto the next finished coupling 9 or the finished coupling 9 that has been installed in the wellhead, so as to form a complete downhole tubing string.

[0108] Performance testing

[0109] 1. Element detection

[0110] Elemental analysis was performed on samples taken from the laser-clad portion 11 of the composite tube and the laser-clad portion 3 of the coupling in Examples 1 and 2. The results are shown in Table 1.

[0111] Table 1 shows the elemental composition (wt.%) of the laser cladding portion 11 and the laser cladding portion 3 of the coupling in the composite pipe.

[0112] The above experiments demonstrate that the composite pipes and couplings formed by this method have excellent comprehensive mechanical properties, effectively resisting tensile, compressive, shear stresses and torques. They are more effective than conventional welding techniques and have high practical value.

[0113] 2. Corrosion resistance test

[0114] The composite pipes and couplings of Examples 1 and 2 were subjected to corrosion resistance tests in a high sulfur content environment, and the steps are as follows:

[0115] Three samples were taken from the weld seam of the bimetallic composite pipe liner, the shoulder surface of the bimetallic composite pipe nose end, and the shoulder surface of the coupling using cutting technology. All samples were arc-shaped. The sample from the weld seam of the bimetallic composite pipe liner was 16 mm long, 1.5 mm thick, and 20 mm long, ensuring that the weld seam of the bimetallic composite pipe liner was located at the symmetrical center of the sample. The sample from the shoulder surface of the bimetallic composite pipe nose end and the shoulder surface of the coupling was 8 mm long, 2 mm deep, and 12 mm long.

[0116] The sample surface was polished step by step with 800#-1800# sandpaper to remove oxide scale and physically uneven areas, then cleaned with deionized water, degreased with acetone, and dehydrated and dried with anhydrous ethanol.

[0117] A simulated formation aqueous solution with pH=3 was prepared and thoroughly deoxygenated. The ion content is shown in Table 2.

[0118] Table 2 Simulated Formation Water Ion Content

[0119] After the prepared simulated formation aqueous solution and sample were placed into the autoclave and sealed, the oxygen was removed with high-purity nitrogen for 2 hours, and then the temperature was raised to 142℃. H2S and CO2 gases were introduced. The partial pressure of H2S was 7MPa, the partial pressure of CO2 was 3MPa, the total pressure was 50MPa, and the corrosion duration was 30 days.

[0120] After the experiment, the samples were removed from the reaction vessel, and the dissolved salts on the sample surface were first washed off with distilled water, then dehydrated with anhydrous ethanol, dried with cold air, and finally the products and corrosion samples were analyzed. All reagents used in the experiment were chemically pure.

[0121] The results are shown in Table 3.

[0122] Table 3 Corrosion rate and surface condition of bimetallic composite pipe and coupling samples

[0123] As shown in the table, the corrosion rates of Examples 1 and 2 were lower than the mild corrosion standard, and no pores or cracks were found on the sample surface.

[0124] The above experiments demonstrate that the present invention has excellent corrosion resistance in high sulfur-containing corrosive environments and can meet application requirements.

[0125] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0126] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A threaded connection method for a bimetallic composite pipe, characterized in that, Specifically, the following steps are included: (1) Preparation of laser cladding powder Carbon powder, silicon powder, chromium powder, molybdenum powder, niobium powder, copper powder, yttrium powder, manganese powder, and nickel powder are mixed evenly according to different mass percentages to obtain the laser cladding powder of the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end, as well as the laser cladding powder of the shoulder of the coupling and the total sealing surface of the coupling. (2) Prepare composite pipe blanks and coupling blanks Prepare a bimetallic composite pipe blank and a coupling blank that matches the specifications of the bimetallic composite pipe blank. (3) Pretreatment of coupling blank With the midpoint of the axis of the coupling blank as the center, cut off the surrounding part to form an annular plane, grind it smooth and clean the annular plane, and perform preheating treatment. (4) Laser cladding treatment of coupling blanks The laser cladding powder of the shoulder and the total sealing surface of the coupling in step (1) is loaded into the powder feeder of the laser cladding equipment. The coupling blank is kept rotating. The powder feeding method is coaxial powder feeding. The cladding powder is clad on the annular plane by synchronous laser cladding method. After the shoulder and the total sealing surface of the coupling are completely formed, the laser cladding equipment is turned off and the shoulder and the total sealing surface of the coupling are polished to make the shoulder and the total sealing surface of the coupling smooth and flat. (5) Machining of the female thread of the coupling blank The coupling blank after laser cladding in step (4) is machined from the outside to the inside with female threads until the starting position of the sealing surface of the coupling is formed into a finished coupling. (6) Machining of composite pipe blank The prepared composite pipe blank is machined to cut out the sealing surface three at the nose end of the composite pipe, and male threads are cut from the starting position of the sealing surface three at the nose end of the composite pipe blank along the axial direction away from the pipe opening. (7) Laser cladding treatment of the nose end of the composite tube blank Clean the composite tube blank after cutting and preheat it. Load the laser cladding powder of the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end from step (1) into the powder feeder of the laser cladding equipment. Keep the composite tube blank after cutting and rotating. The powder feeding method adopts coaxial powder feeding. The powder is clad on the nose end of the composite tube blank after cutting and using the synchronous laser cladding method. The cladding direction is from the inside to the outside. After the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end are formed, turn off the laser cladding equipment and polish the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end to make the sealing surface 1, sealing surface 2, outer transition fillet, and shoulder surface of the composite tube nose end smooth and flat, and obtain the finished composite tube. (8) Copper plating of finished composite pipes and finished couplings To prevent the finished composite pipes and couplings from sticking together, copper plating is performed on them. First, the finished composite pipes and couplings are placed in an alkaline degreasing solution containing sodium hydroxide, sodium carbonate, trisodium phosphate, and sodium silicate at 80-90℃ for 5-10 minutes. After alkaline washing, they are thoroughly rinsed with deionized water to ensure that the residual alkali is completely removed. Then, the finished composite pipes and couplings are placed in a mixed pickling solution of nitric acid and hydrofluoric acid at room temperature for 3-5 minutes. After pickling, the residual acid is removed with deionized water. Finally, the workpieces are immersed in a copper sulfate solution at 40-50℃ with a pH value maintained between 10 and 12 for 80-100 minutes to form a copper plating layer. After copper plating, they are rinsed with deionized water and immediately dried with hot air. (9) Assembly of finished composite pipes and finished couplings The male thread at one end of a single finished composite pipe is screwed onto the female thread of a finished coupling to complete the initial assembly. After being transported to the site, the male thread at the other end of the composite pipe is screwed onto the next finished coupling or a finished coupling that has already been installed in the wellhead, thereby connecting them in series to form a complete downhole tubing string.

2. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, In step (1), the laser cladding powder of the shoulder and the total sealing surface of the coupling, by mass percentage, includes: carbon powder: 0.01%~0.03%, silicon powder: 0.01%~0.02%, chromium powder: 20%~23%, molybdenum powder: 8%~9%, niobium powder: 2.5%~3.5%, copper powder: 1%~1.5%, yttrium powder: 0.2%~0.4%, manganese powder: 0.3%~0.4%, and nickel powder as the balance; the particle size of the laser cladding powder of the shoulder and the total sealing surface of the coupling is 70um~120um, the sphericity is 0.8~0.95, and the total sealing surface of the coupling consists of an inner transition fillet, a first sealing surface of the coupling, and a second sealing surface of the coupling.

3. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, In step (1), the laser cladding powders for the sealing surface one, sealing surface two, outer transition fillet, and shoulder surface of the composite tube nose end, by mass percentage, include: carbon powder: 0.02%~0.04%, silicon powder: 0.01%~0.02%, chromium powder: 22%~24%, molybdenum powder: 8%~9%, niobium powder: 3.5%~5%, copper powder: 1%~1.5%, yttrium powder: 0.3%~0.5%, manganese powder: 0.3%~0.4%, and nickel powder as the balance; the particle size of the laser cladding powders for the sealing surface one, sealing surface two, outer transition fillet, and shoulder surface of the composite tube nose end is 25um~65um, and the sphericity is 0.8~0.

95.

4. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, In step (3), the axial length L of the annular plane is 50mm~82mm.

5. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, In steps (3) and (7), the preheating temperature is 150℃~300℃.

6. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, In step (4), the laser cladding process parameters are as follows: laser power: 1500W~3600W, powder feeding speed: 8g / min~15g / min, scanning speed: 8mm / s~12mm / s, spot diameter: 2mm~4mm, overlap rate: 45%~65%, and protective gas is argon.

7. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, The sealing surface three of the composite pipe nose end and the sealing surface two of the coupling are both tangent to the inner surface of the coupling blank on the same side in step (2); the positional relationship between the shoulder surface of the coupling, the inner transition fillet, the sealing surface one of the coupling, the sealing surface two of the coupling and the female thread is as follows: the shoulder surface of the coupling is located above the inner transition fillet, the sealing surface one of the coupling, the sealing surface two of the coupling and the female thread; along the axial direction away from the hammer line m in the coupling, the distance from the hammer line m in the coupling from near to far is as follows: inner transition fillet, sealing surface one of the coupling, sealing surface two of the coupling and the female thread; The overall sealing surface of the composite pipe nose end consists of sealing surface one, sealing surface two, sealing surface three, and the outer transition fillet. The positional relationship between the shoulder surface, the outer transition fillet, sealing surface one, sealing surface two, sealing surface three, and the male thread of the composite pipe nose end is as follows: the shoulder surface of the composite pipe nose end is located above the outer transition fillet, sealing surface one, sealing surface two, sealing surface three, and the male thread; along the axial direction away from the composite pipe opening, the axial distances from the composite pipe opening from near to far are as follows: outer transition fillet, sealing surface one, sealing surface two, sealing surface three, and the male thread. After the composite pipe and coupling are engaged and tightened, the shoulder surface of the coupling and the shoulder surface of the nose end of the composite pipe form a sealing pair one, the inner transition fillet and the outer transition fillet form a sealing pair two, the sealing surface one of the coupling and the sealing surface one of the nose end of the composite pipe form a sealing pair three, and the sealing surface two of the coupling, the sealing surface two of the nose end of the composite pipe and the sealing surface three of the nose end of the composite pipe form a sealing pair four. The lengths of the total sealing surface of the coupling and the total sealing surface of the composite pipe nose are a and b, respectively. The sum of the axial length of the first sealing surface of the coupling and the axial length of the inner transition fillet is a1. The sum of the axial length of the first sealing surface of the composite pipe nose and the axial length of the outer transition fillet is b1. Both a1 and b1 are 6mm~10mm. The radii of the outer and inner transition fillets are both R: 0.5mm~1.5mm. The axial length b2 of the second sealing surface of the composite pipe nose is 4mm~8mm. The axial length b3 of the third sealing surface of the composite pipe nose is: The axial length a2 of the second sealing surface of the coupling is equal to the sum of the axial length b2 of the second sealing surface of the composite pipe nose and the axial length b3 of the third sealing surface of the composite pipe nose, i.e., a2=b2+b3. The shoulder width c of the coupling is twice the distance d from the intersection of the shoulder surface of the coupling and the inner transition fillet to the center hammer line m, i.e., c=2d. The value range of d is 12mm~25mm. The second sealing surface and the third sealing surface of the composite pipe nose are tangent. The axial length a of the total sealing surface of the coupling, the axial length b of the total sealing surface of the composite pipe nose and the axial length c of the shoulder of the coupling have the following relationship: L=a+c, a=a1+a2+a3, b=b1+b2.

8. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, In steps (4) and (7), the sealing method is conical surface to conical surface sealing, the shoulder of the coupling is a negative angle shoulder, the included angle between the sealing surface one and the sealing surface two of the composite pipe nose end and the included angle between the sealing surface one and the sealing surface two of the coupling are both α: 4°~12°, the included angle between the shoulder surface of the composite pipe nose end and the shoulder surface of the coupling and the vertical line l are both β: 8°~15°, the shoulder surface of the coupling and the sealing surface one of the coupling are both tangent to the inner transition fillet, and the shoulder surface of the composite pipe nose end and the sealing surface one of the composite pipe nose end are both tangent to the outer transition fillet.

9. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, In steps (5) and (6), the thread parameters are as follows: number of threads per inch n: 4 to 7, taper T: 1:16 to 1:10, thread profile height h: 0.9 mm to 2.3 mm, bearing surface angle γ: -10° to 4°, and guide surface angle φ: -3° to 30°.

10. The threaded connection method for a bimetallic composite pipe according to claim 1, characterized in that, In step (7), the laser cladding process parameters are as follows: laser power: 1500W~3000W, powder feeding speed: 7g / min~14g / min, scanning speed: 6mm / s~10mm / s, spot diameter: 0.8mm~2.5mm, overlap rate: 45%~75%, and protective gas is argon.

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