Bimetal composite coiled tubing for gas lift operation and manufacturing method thereof

Abstract

A bimetallic composite coiled tubing for gas lift operation comprises a base layer and a composite layer arranged outside the base layer, and the base layer and the composite layer are welded to form a tubing body. The outer diameter of the pipe body is phi 25.4 to 50.8 mm, and the length of the single pipe body is 1000 to 2000 m; the base layer is made of low-carbon steel, and the thickness of the base layer is 2-3mm; the composite layer is made of Inconel 625 nickel base alloy, and the thickness of the composite layer ranges from 1 mm to 1.5 mm. The bimetallic composite coiled tubing for gas lift operation is manufactured, the problem that an existing carbon steel coiled tubing is poor in corrosion resistance is solved, and therefore support is provided for development of acid oil and gas fields.

Description

Technical Field

[0001] The invention belongs to the technical field of coiled tubing and relates to a bimetallic composite coiled tubing for gas lift operation and a manufacturing method thereof. Background Art

[0002] Coiled tubing (CT) is a type of tubing ranging from several hundred to several thousand meters in length. Most are made of low-carbon microalloyed steel, either HFW or laser-welded, and are wound onto large-diameter reels for transportation and use. In the oil and gas industry, it is widely used in oilfield workover, drilling, completion, logging, and production stimulation. The tubing on the reel can be repeatedly retracted and deployed during operations. However, in the development of highly sour oil and gas fields containing corrosive media such as H2S, CO2, and Cl-, conventional CT not only suffers from high-rate weight loss corrosion and localized corrosion, but can also lead to operational failure, hindering the development of sour oil and gas fields.

[0003] In view of this, it is necessary to develop a continuous oil pipe that can solve the above problems. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method for manufacturing bimetallic composite coiled tubing for gas lift operations. The coiled tubing manufactured by this method solves the problem of poor corrosion resistance of existing carbon steel coiled tubing, thereby providing support for the development of sour oil and gas fields.

[0005] The present invention is achieved through the following technical solutions, providing a bimetallic composite coiled tubing for gas lift operations, comprising: a base layer, a cladding layer arranged outside the base layer, wherein the base layer and the cladding layer are welded to form a tubing body; The outer diameter of the pipe is Φ25.4-50.8mm, and the length of a single pipe is 1000-2000m; The base material is low carbon steel with a thickness of 2 to 3 mm; The composite layer is made of Inconel 625 nickel-based alloy and has a thickness of 1 to 1.5 mm.

[0006] In particular, the chemical composition of the base layer, calculated by mass percentage, includes the following components: C 0.08~0.10%, Si 0.10~0.24%, Mn 0.8~1.0%, P≦0.004%, S≦0.004%, Cr 0.80~1.2%, Mo 0.12~0.16%, Ni 0.18~0.22%, Ti 0.02~0.03%, Al 0.02~0.03%, and the rest are Fe and unavoidable impurities.

[0007] In particular, a plug and a one-way positive pressure valve are installed at the front end of the tube body, wherein the plug is made of Inconel 625 nickel-based alloy, and a threaded through hole is opened at one end of the plug toward the tube body, and the one-way positive pressure valve is threadedly connected to the plug through the threaded through hole.

[0008] Particularly, a union is welded to the tail end of the tube body.

[0009] The present invention also provides a method for manufacturing a bimetallic composite coiled tubing for gas lift operation, comprising the following steps: S1. Compounding the base layer and the cladding layer by explosive welding to obtain a bimetallic composite coil, wherein the base layer is made of low carbon steel and the cladding layer is made of Inconel 625 nickel-based alloy; S2: The bimetallic composite coil obtained in S1 is cut into steel strips using a slitting machine according to the coiled tubing specifications, and the steel strips are spliced ​​at the ends according to the required length; S3: Based on the outer diameter and wall thickness requirements of the final bimetallic composite coiled tubing, the end faces of the extended steel strip are milled into I-shaped grooves. The steel strip is then rolled into a tubular shape using a roller forming method. A laser welding process is then performed on the longitudinal weld seam using ERNiCrMo-3 nickel-based alloy welding wire. The resulting bimetallic composite coiled tubing is then wound onto a reel I of an appropriate core diameter. S4 transports the bimetallic composite coiled tubing made in S3 to the heat treatment unit, and uses a scraper to scrape a V-shaped scraping groove with a depth of 0.8 to 1 mm and an angle of 60° along the length direction on the surface of the longitudinal weld. Then, cladding welding is performed to realize the cladding of the bimetallic composite coiled tubing. In this invention, the depth of the V-shaped scraping groove is set to 0.8 to 1 mm, which can control the welding penetration of the cladding nickel-based alloy layer to be no greater than the thickness of the cladding nickel-based alloy layer, while ensuring that the chemical composition of the weld metal is closer to that of the cladding nickel-based alloy material, thereby improving the corrosion resistance of the weld joint. At the same time, the angle of the V-shaped groove of the present invention is set to 60°, so that the cladding layer is wider than the base weld after welding, so as to ensure that the base weld is not exposed on the outer surface of the pipe body and causes corrosion.

[0010] S5: A union is welded to the tail end of the bimetallic composite coiled tubing and connected to the water injection pump, followed by quenching and tempering heat treatments. S6 inserts a plug equipped with a one-way positive pressure valve into the front end of the bimetallic composite coiled tubing and uses argon arc welding to weld it to the bimetallic composite coiled tubing end at the external groove, thus completing the processing of the bimetallic composite coiled tubing for gas lift operations.

[0011] In particular, when the ends of the steel strips in S2 are spliced ​​together, the ends of the two spliced ​​steel strips need to be sheared by a shearing machine into a 45° bevel with respect to the length direction of the steel strips. Subsequently, the two steel strips are welded by a plasma welding process, and the welding wire used is ERNiCrMo-3 nickel-based alloy. After welding is completed, the weld excess height is ground to be flush with the parent material. In the present invention, since the butt welds of the steel strips are spirally distributed on the pipe body after pipe forming, in S2, the ends of the two spliced ​​steel strips are sheared by a shearing machine into a 45° bevel with respect to the length direction of the steel strips. In this way, when the weld is subjected to stress during operation, the stress concentration at the weld can be effectively reduced, thereby improving the safety of the welding operation.

[0012] In particular, before the composite welding in S4, a pressure wheel is used to press the ERNiCrMo-3 nickel-based alloy welding wire with a diameter of 1 mm into the bottom of the V-shaped scraper groove. Subsequently, two plasma welding guns are distributed at 30° on both sides of the central axis of the V-shaped scraper groove and spaced 300 mm apart to weld the composite weld. The weld penetration is controlled at 0.8 to 1 mm. In this step, the welding current is 100 A, the voltage is 22 V, the welding speed is 480 mm / min, the ion gas flow rate is 2.8 L / min, the shielding gas rate is 15 L / min, the gas type is Ar+5% H2, and the weld cladding metal thickness is 1 to 1.5 mm.

[0013] In particular, the S5 is implemented in accordance with the following scheme: A medium frequency heat treatment furnace is used to heat the bimetallic composite coiled tubing to 950°C under the protection of an inert atmosphere. At the same time, water is injected into the tubing through a water injection pump for cooling, and the bimetallic composite coiled tubing is wound on reel II. After quenching, the heat treatment unit is operated in reverse, and the tubing body is heated to 550°C under the protection of an inert atmosphere, and air-cooled to achieve tempering heat treatment, and the bimetallic composite coiled tubing is wound on reel I. The medium frequency induction heating coil length of the medium frequency heat treatment furnace is 150 mm, and the internal circulating water flow rate when the water injection pump injects water into the tubing for cooling is 100 m 3 / h.

[0014] In particular, the welding processes of S5 and S6 are the same, both using ERNiCrMo-3 nickel-based alloy welding wire, welding current 75A, voltage 16V, welding speed 4.5cm / min, shielding gas argon, and gas flow rate 12L / min.

[0015] During operation of the bimetallic composite coiled tubing for gas lift operation manufactured by the present invention, the front end of the tubing is lowered into the water layer in the well, and the rear end of the tubing is connected to a nitrogen operation vehicle via a union; the nitrogen operation vehicle injects nitrogen into the tubing; when the nitrogen injection pressure reaches a certain value, the one-way positive pressure valve opens, and high-pressure nitrogen is injected into the well through the through hole in the plug; the nitrogen carries out the bottom hole liquid through the annulus between the bimetallic composite coiled tubing and the production tubing, thereby performing a gas lift operation.

[0016] Compared with the prior art, the present invention provides a bimetallic composite coiled tubing for gas lift operations, which has the following beneficial effects: 1. The present invention places a composite nickel-based alloy layer on the outer layer of the pipe, effectively preventing the corrosion of corrosive media such as hydrogen sulfide in the working environment on the pipe string; the base low-carbon steel layer is placed on the inner layer of the pipe string, and a plug and a one-way positive pressure valve are installed at the front end, effectively preventing the corrosive media from entering the interior of the coiled tubing and corroding the internal low-carbon steel layer; 2. Adding 0.80-1.2% of Cr element by mass to the base low-carbon steel layer alloy can effectively improve the hardenability and ensure the mechanical properties of the pipe body. Adding 0.02-0.03% of Al element by mass can prevent the generation of pores during laser welding of nickel-based alloys. 3. The welding joint adopts a 60° V-shaped groove and a nickel-based alloy welding wire with a preset diameter of 1mm at the root. This solves the process problem of not being able to reduce the dilution rate of the weld alloy elements by welding a transition layer due to the thin thickness of the steel strip during the production process, effectively ensuring the corrosion resistance of the composite weld. 4. During the quenching heat treatment process of the pipe body, water injection cooling is adopted. Compared with the traditional external spray cooling, this solves the oxidation problem of the composite nickel-based alloy layer, and also improves the hardenability of the inner low-carbon steel layer, ensuring the mechanical properties of the base metal; 5. The laser wire-filling welding method is used for the formed bimetallic composite coiled tubing, which has the advantages of welding efficiency and small welding heat-affected zone, and prevents the problem of cracks caused by overheating during the welding process of nickel-based alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view of a bimetallic composite coiled tubing for gas lift operation according to the present invention; Figure 2 This is a schematic diagram of the structure of a bimetallic composite coiled tubing string for gas lift operations according to the present invention; Figure 3 This is a schematic diagram of a multi-layer welding and heat treatment unit during the manufacturing process of a bimetallic composite coiled tubing for gas lift operation according to the present invention; Figure 4 This is a structural diagram of the groove of the composite layer welding during the manufacturing process of a bimetallic composite coiled tubing for gas lift operation according to the present invention. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings.

[0019] In order to solve the problems of poor corrosion resistance of existing low-carbon micro-alloy steel coiled tubing and high price of corrosion-resistant alloy coiled tubing in gas lift operations in highly acidic oil and gas wells with high H2S, CO2 and Cl- corrosive media, the present invention provides a bimetallic composite coiled tubing for gas lift and a preparation method thereof.

[0020] See also Figure 1 , Figure 1 This is a cross-sectional view of a bimetallic composite coiled tubing for gas lift operations, which comprises a base layer 101 and a cladding layer 102 disposed outside the base layer 101. The base layer 101 and the cladding layer 102 are welded to form a tubing body (i.e., bimetallic composite coiled tubing 1). The outer diameter of the pipe is Φ25.4-50.8mm, and the length of a single pipe is 1000-2000m; The base layer 101 is made of low carbon steel with a thickness of 2 to 3 mm. Its chemical composition, calculated by mass percentage, includes the following components: C 0.08~0.10%, Si 0.10~0.24%, Mn 0.8~1.0%, P≦0.004%, S≦0.004%, Cr 0.80~1.2%, Mo 0.12~0.16%, Ni 0.18~0.22%, Ti 0.02~0.03%, Al 0.02~0.03%, the rest is Fe and unavoidable impurities; The composite layer 102 is made of Inconel 625 nickel-based alloy and has a thickness of 1 to 1.5 mm.

[0021] See also Figure 2 , Figure 2 This is a schematic diagram of the bimetallic composite coiled tubing string structure for gas lift operations. The bimetallic composite coiled tubing for gas lift operations includes: a plug 4 welded to the front end of the bimetallic composite coiled tubing 1. The upper end of the plug 4 is inserted into the bimetallic composite coiled tubing 1 and connected to the bimetallic composite coiled tubing 1 via a weld 3. The plug 4 has a through hole 5 formed therein and has an internal thread machined on its upper portion, which is connected to the one-way positive pressure valve 2 via the threads. A union 7 is welded to the rear end of the bimetallic composite coiled tubing 1. The entire bimetallic composite coiled tubing 1 is wound around a reel 6. Example 1

[0022] The present invention provides a bimetallic composite coiled tubing for gas lift operation, comprising the following steps: S1 Preparation of bimetallic composite coils The base layer and the composite layer are composited together by explosive welding and rolling to obtain a bimetallic composite coil.

[0023] S2 Bimetallic Composite Coil Slitting and Splicing The bimetallic composite coil prepared by S1 is cut into steel strips with a length of about 500m by a slitting machine according to the specifications of the continuous oil pipe. The steel strips are spliced ​​at the head and tail according to the required pipe string length. When splicing, the ends of the two steel strips to be spliced ​​together are sheared by a shearing machine to form a bevel at 45° to the length direction of the steel strips. Then, plasma welding is adopted for welding. The welding wire used is ERNiCrMo-3 nickel-based alloy. After welding, the weld reinforcement is ground to be flush with the base material.

[0024] S3 forming and first step welding Based on the final outer diameter and wall thickness requirements of the bimetallic composite coiled tubing, the end faces of the extended steel strip are milled to form I-shaped grooves. The steel strip is then rolled into a tubular shape using a roller forming method. The longitudinal welds are then laser-welded using ERNiCrMo-3 nickel-based alloy wire. The bimetallic composite coiled tubing is then wound onto a reel I of an appropriate core diameter during tubing fabrication.

[0025] S4 composite welding See also Figure 3 , Figure 3 Figure 1 is a schematic diagram of a composite welding and heat treatment unit, which includes: the heat treatment unit consists of a water injection pump 8, a reel I, a delivery roller 9, a scraper 10, a pressure roller 12, a plasma welding gun 13, a plasma welding gun 14, a medium-frequency heat treatment furnace 15, and a reel II; the bimetallic composite coiled tubing made of S3 is moved to the heat treatment unit and transported to the heat treatment unit via the delivery roller 9; the scraper 10 is used to scrape the surface of the longitudinal weld of S3 along the length direction to form a V-shaped scraping groove with a depth of 0.8 to 1 mm and an angle of 60°; then, a 1 mm diameter ERNiCrMo-3 nickel-based alloy welding wire 11 is pressed into the bottom of the V-scraping groove by the pressure roller 12; then, two plasma welding guns 13 and 14 are distributed at 30° on both sides of the central axis of the scraping groove and spaced 300 mm apart to weld the composite weld, and the weld penetration is controlled within the range of 1 to 1.5 mm.

[0026] S5 heat treatment A union is welded to the tail end of the bimetallic composite coiled tubing and connected to a water injection pump 1. The bimetallic composite coiled tubing is heated to 950°C in an inert atmosphere using a medium frequency heat treatment furnace 15. Simultaneously, water is injected into the bimetallic composite coiled tubing 1 via a water injection pump 8 for quenching heat treatment. Simultaneously, the quenched bimetallic composite coiled tubing is wound onto reel II. After the quenching heat treatment is completed, the heat treatment unit is reversed, and the tubing is heated to 550°C in an inert atmosphere using a medium frequency heating furnace and air-cooled for tempering heat treatment. The bimetallic composite coiled tubing is then wound onto reel I.

[0027] S6 Welding of bimetallic composite coiled tubing end plug and union A plug 4 equipped with a one-way positive pressure valve was inserted into the front end of the bimetallic composite coiled tubing and welded to the coiled tubing nozzle at the external groove using argon arc welding. The welding wire was ERNiCrMo-3 nickel-based alloy wire, the welding current was 75A, the voltage was 16V, the welding speed was 4.5cm / min, and the shielding gas was argon at a gas flow rate of 12L / min. A union was then welded to the tail end of the bimetallic composite coiled tubing using the same welding process as the plug.

[0028] During operation, the bimetallic composite coiled tubing provided by the present invention is lowered into the wellbore's liquid layer via a coiled tubing operation vehicle. The rear end of the tubing is connected to a nitrogen operation vehicle via a union, which then injects nitrogen at a predetermined pressure into the tubing string. When the nitrogen injection pressure reaches the opening pressure of a one-way positive pressure valve (e.g., 12 MPa), the valve opens, and high-pressure nitrogen is injected into the wellbore through a through-hole in the plug. The high-pressure nitrogen then drains the bottomhole liquid through the annulus between the bimetallic composite coiled tubing and the production tubing, achieving a gas lift operation.

Claims

1. A bimetallic composite coiled tubing for gas lift operation, characterized in that: include: A base layer and a composite layer arranged outside the base layer, wherein the base layer and the composite layer are welded to form a pipe body; The outer diameter of the pipe is Φ25.4-50.8mm, and the length of a single pipe is 1000-2000m; The base material is low carbon steel with a thickness of 2 to 3 mm; The composite layer is made of Inconel 625 nickel-based alloy and has a thickness of 1 to 1.5 mm.

2. The bimetallic composite coiled tubing for gas lift operation according to claim 1, characterized in that: The chemical composition of the base layer is calculated by mass percentage and includes the following components: C 0.08~0.10%, Si 0.10~0.24%, Mn 0.8~1.0%, P≦0.004%, S≦0.004%, Cr 0.80~1.2%, Mo 0.12~0.16%, Ni 0.18~0.22%, Ti 0.02~0.03%, Al 0.02~0.03%, and the rest are Fe and unavoidable impurities.

3. The bimetallic composite coiled tubing for gas lift operation according to claim 1, characterized in that: A plug and a one-way positive pressure valve are installed at the front end of the tube body, wherein the plug is made of Inconel 625 nickel-based alloy, and a threaded through hole is opened at one end of the plug toward the tube body, and the one-way positive pressure valve is threadedly connected to the plug through the threaded through hole.

4. The bimetallic composite coiled tubing for gas lift operation according to claim 1, characterized in that: A union is welded to the tail end of the tube body.

5. A method for manufacturing a bimetallic composite coiled tubing for gas lift operation according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1 The base layer and the composite layer are bonded together by explosive welding to obtain a bimetallic composite coil; S2 uses a slitting machine to cut the bimetallic composite coil into steel strips, and splices the ends of the steel strips according to the required length; S3: Rolling the steel strip into a tube using a roller forming method, welding the longitudinal weld using a laser wire filling process, and winding the resulting bimetallic composite coiled tubing onto a reel I; In step S4, the bimetallic composite coiled tubing produced in step S3 is transported to the heat treatment unit. A scraper is used to scrape the longitudinal weld surface to create a V-shaped groove with a depth of 0.8 to 1 mm and a 60° angle. Next, double-layer welding is performed to complete the re-welding of the bimetallic composite coiled tubing. S5: A union is welded to the tail end of the bimetallic composite coiled tubing and connected to the water injection pump, followed by quenching and tempering heat treatments. S6 inserts a plug equipped with a one-way positive pressure valve into the front end of the bimetallic composite coiled tubing and uses argon arc welding to weld it to the bimetallic composite coiled tubing end at the external groove, thus completing the processing of the bimetallic composite coiled tubing for gas lift operations.

6. The method for manufacturing a bimetallic composite coiled tubing for gas lift operation according to claim 5, characterized in that: When the ends of the steel strips in S2 are spliced ​​together, the ends of the two spliced ​​steel strips need to be sheared into a 45° bevel with the length direction of the steel strips by a shearing machine. Then, the two steel strips are welded by a plasma welding process. The welding wire used is ERNiCrMo-3 nickel-based alloy. After welding is completed, the weld excess height is ground to be flush with the base material.

7. The method for manufacturing a bimetallic composite coiled tubing for gas lift operation according to claim 5, characterized in that: In S2, before preparing the tubular member, for the steel strip that needs to be extended, the end faces on both sides of the steel strip need to be processed into I-shaped grooves by milling.

8. The method for manufacturing a bimetallic composite coiled tubing for gas lift operation according to claim 5, characterized in that: Before welding the composite layer in S4, a pressure wheel is used to press the ERNiCrMo-3 nickel-based alloy welding wire with a diameter of 1 mm into the bottom of the V-shaped scraper groove. Subsequently, two plasma welding guns are distributed at 30° on both sides of the central axis of the V-shaped scraper groove and spaced 300 mm apart to weld the composite weld. The weld penetration is controlled at 0.8 to 1 mm. In this step, the welding current is 100 A, the voltage is 22 V, the welding speed is 480 mm / min, the ion gas flow rate is 2.8 L / min, the shielding gas rate is 15 L / min, the gas type is Ar+5% H2, and the weld cladding metal thickness is 1 to 1.5 mm.

9. The method for manufacturing a bimetallic composite coiled tubing for gas lift operation according to claim 5, characterized in that: The S5 is specifically implemented according to the following scheme: A medium frequency heat treatment furnace is used to heat the bimetallic composite coiled tubing to 950°C under the protection of an inert atmosphere. At the same time, water is injected into the tubing through a water injection pump for cooling, and the bimetallic composite coiled tubing is wound on reel II. After quenching, the heat treatment unit is operated in reverse, and the tubing body is heated to 550°C under the protection of an inert atmosphere, and air-cooled to achieve tempering heat treatment, and the bimetallic composite coiled tubing is wound on reel I. The medium frequency induction heating coil length of the medium frequency heat treatment furnace is 150 mm, and the internal circulating water flow rate when the water injection pump injects water into the tubing for cooling is 100 m 3 / h.

10. The method for manufacturing a bimetallic composite coiled tubing for gas lift operation according to claim 5, characterized in that: The welding processes of S5 and S6 are the same, both using ERNiCrMo-3 nickel-based alloy welding wire, welding current 75A, voltage 16V, welding speed 4.5cm / min, shielding gas is argon, and gas flow rate is 12L / min.

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