WO2012034516A1

WO2012034516A1 - Bi-metal composite tube

Info

Publication number: WO2012034516A1
Application number: PCT/CN2011/079619
Authority: WO
Inventors: 谢凯意
Original assignee: 衡阳华菱钢管有限公司
Priority date: 2010-09-14
Filing date: 2011-09-14
Publication date: 2012-03-22

Abstract

A bi-metal composite tube comprising of an inner tube (10) and an outer tube (20). The inner tube (10) is placed within the outer tube (20) and is made of corrosion-resistant material. The bi-metal composite tube also has a connector (30) connected with the outer tube (20) by screw threads and connected with the inner tube (10) by welding. A bi-metal composite tube having a connector (30) and an outer tube (20) connected by screw threads can avoid deterioration of welds that may arise from the welding together of different metals, thereby ensuring the connectivity of oil well tubing. The inner tube (10) made of corrosion-resistant material ensures that corrosive material within the inner tube cannot contact the outer tube (20), thereby ensuring the safe usage of the bi-metal composite tube.

Description

TECHNICAL FIELD The present invention relates to the field of petrochemical plants, and more particularly to a bimetallic composite pipe. BACKGROUND OF THE INVENTION In the development of oil and gas fields in Tarim, Sichuan, Changqing and other regions, there are serious corrosion problems. Oil and gas wells contain corrosive media such as H ₂ S, C0 ₂ and CI. These media are highly corrosive to pipes, causing not only huge economic losses, but also catastrophic consequences such as casualties and shutdowns. Discontinued production and environmental pollution. The economic losses caused by corrosion to the petroleum industry are very high, so higher corrosion resistance requirements are imposed on the pipes used. The selection of pipes with excellent performance is the main measure to prevent corrosion accidents, but the carbon steel pipe or low alloy steel pipe of low price is generally poor in corrosion resistance, while the corrosion resistance is good, such as stainless steel, nickel-based alloy, titanium and titanium alloy. The price is high. In order to save the consumption of high-priced materials, people began to research, manufacture and select composite pipes, including bimetallic composite pipes. The existing bimetal composite pipe comprises two layers: the outer pipe is a low-cost carbon steel pipe or a low-alloy steel pipe, and has a large wall thickness, and is mainly subjected to external force or internal pressure; the inner pipe is made of stainless steel which is expensive but has excellent corrosion resistance. Or corrosion-resistant materials such as nickel-based alloys, or titanium and titanium alloys, with small wall thickness, mainly for corrosion resistance. The outer tube of the bimetal composite pipe guarantees various physical performance indexes in addition to corrosion resistance, and the inner pipe ensures corrosion resistance performance index, so that when the steel pipe is used for corroding environmental oil and gas wells, under the premise of ensuring various technical indexes, Achieve a significant cost reduction. The oil pipe string and the casing pipe string in the oil and gas well are connected by a plurality of oil pipes and a plurality of pipes through joints, but the connection between the plurality of pipes of the double metal composite pipe becomes a double metal composite pipe used for A problem in the field of oil and gas field mining. The prior art is to weld joints at both ends of the outer tube, the joint is the same corrosion resistant material as the inner tube, and the outer tube is carbon steel or low alloy steel. Although this technical solution solves the problem that the corrosive medium in the pipeline contacts the outer pipe, since the connection mode of the outer pipe and the joint is dissimilar metal welding, the welding performance is difficult to meet the connection strength requirement of the oil column, and the safety performance is poor. Therefore, there is almost no application in the downhole oil casing of oil and gas fields. SUMMARY OF THE INVENTION The present invention is directed to a bimetallic composite pipe which can ensure that the corrosive medium in the pipe does not contact the outer pipe and can ensure the connection performance of the oil pipe string. A bimetal composite pipe according to the present invention comprises an inner pipe and an outer pipe, the inner pipe is made of a corrosion resistant material, the inner pipe is located inside the outer pipe, and the bimetal composite pipe further comprises a connecting portion, and the connecting portion and the outer pipe pass The threads are connected and the inner tube is welded to the joint. Further, the connection is made of a corrosion resistant material. Further, the outer tube is made of carbon steel or low alloy steel. Further, the outer wall of both ends of the outer tube has a thread. Further, the connecting portion includes a first joint, the first joint is located at one end of the outer tube, the connecting portion further includes a first joint, and the second joint is located at the other end of the outer tube. Further, the connecting portion includes a first joint, the first joint is located at both ends of the outer tube, and the connecting portion further includes a second joint, and the second joint is connected to the first joint of one end of the outer tube by a thread. Further, the first joint is a tubular joint including a first section having a thread on the inner wall, and a second section of the first joint other than the first section, the outer wall of the second section having a thread. Further, the inner diameter of the second section of the first joint is equal to the inner diameter of the outer tube. Further, the inner tube extends across the seam between the first joint and the outer tube and is welded to the inner wall of the first joint having no threaded portion. Further, the second joint is a tubular joint having threads on the inner walls at both ends thereof. Further, the inner wall of the second joint has an annular protrusion, the inner diameter of the protrusion is equal to the inner diameter of the outer tube, and the protrusion is located between the threads on the inner wall of the two ends of the second joint. Further, the inner tube extends across the seam between the second joint and the outer tube and is welded to the inner wall of the protrusion. The bimetal composite pipe of the invention comprises an inner pipe and an outer pipe, the inner pipe is made of a corrosion resistant material, the bimetal composite pipe further comprises a connecting portion, the connecting portion is connected with the outer pipe by a thread, and the inner pipe and the connecting portion are connected welding. The connection between the connecting portion and the outer tube is a bimetallic composite tube in the form of a threaded connection, which avoids the possibility of a decrease in the welding strength caused by the heterogeneous metal welding, and ensures the connection performance of the oil well string, so that the bimetal composite tube of the present invention can be pressed At the same time, the inner tube made of corrosion-resistant material ensures that the corrosive medium in the tube does not contact the outer tube, which ensures the safety of the use of the bimetal composite tube. The drawings are intended to provide a further understanding of the invention, and are intended to be a part of the invention. In the drawings: FIG. 1 is a schematic structural view of an embodiment of a bimetal composite pipe according to the present invention; FIG. 2 is a schematic structural view of another embodiment of a bimetal composite pipe according to the present invention; Schematic diagram of the first joint of the bimetallic composite pipe; and FIG. 4 is a schematic structural view of the second joint of the bimetallic composite pipe according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings in conjunction with the embodiments. A bimetal composite pipe according to the present invention as shown in FIGS. 1 and 2 includes an inner pipe 10 made of a corrosion-resistant material and an outer pipe 20, the inner pipe 10 being located inside the outer pipe 20, double The metal composite pipe further includes a connecting portion 30 that is connected to the outer pipe 20 by threads, and the inner pipe 10 is welded to the connecting portion 30. The connection between the connecting portion 30 of the bimetal composite pipe and the outer pipe 20 is in the form of a screw connection, which avoids the weld strength drop caused by the heterogeneous metal welding which may occur, ensures the connection strength and the connection performance of the oil well pipe string, and makes the bimetal composite pipe At the same time, the inner tube 10 made of a corrosion-resistant material can ensure that the corrosive medium in the inner tube 10 does not contact the outer tube 20 when a corrosive medium exists in the oil and gas well. The safety of the use of bimetallic composite pipes is guaranteed. The inner tube 10 is welded to the connecting portion 30 such that the inner tube 10 and the connecting portion 30 are coupled together. The inner tube 10 is a thin-walled flat end tube. After the inner tube 10 is placed in the outer tube 20, the inner tube 10 is expanded and deformed by an external force and abuts against the outer tube 20 and the inner wall of the connecting portion 30. The inner walls of the connecting portions 30 at both ends of the tube 20 are hermetically welded to completely isolate the corrosive medium in the inner tube 10 from the outer tube 20 to prevent the outer tube 20 from being corroded. Preferably, the connecting portion 30 is made of a corrosion resistant material. The outer tube 20 is made of carbon steel or low alloy steel. The connecting portion 30 is formed of a thick-walled tube, and the connecting portion 30 is made of a corrosion-resistant material. Preferably, the connecting portion 30 and the inner tube 10 are made of the same material, have good corrosion resistance and welding performance matched with the inner tube 10, and avoid the dissimilar metal welding of the inner tube 10 and the connecting portion 30 during welding. The joint strength and weld sealing safety of the two are guaranteed. Alternatively, the connecting portion 30 may be made of a corrosion-resistant material similar to the inner tube 10 which can be welded to the inner tube 10. The outer tube 20 is carbon steel or low alloy steel, and its outer diameter is generally 60.3 mm to 508 mm. The thickness is 4mm to 20mm, and the wall thickness is large. It is mainly used to withstand external force or internal pressure during use. Correspondingly, the inner tube 10 is made of corrosion-resistant material, and the inner tube 10 is made of stainless steel or nickel-based alloy. Titanium and titanium alloys or other corrosion resistant materials with a thickness of 1 mm to 4 mm and a small wall thickness. The inner tube 10 abuts against the outer tube 20 and the inner wall of the joint 30, and is mainly resistant to corrosion. The outer tube 20 is made of ordinary carbon steel or low alloy steel, which ensures the low cost of the bimetal composite tube; the inner tube 10 and the connecting portion 30 are made of corrosion resistant materials, although the price of the material is high, but due to the inner tube 10 The wall thickness is small, the length of the connecting portion 30 is short, and the corrosion resistance is also prevented, and the cost of the bimetal composite pipe is also prevented from being excessive. Therefore, the bimetal composite pipe of the invention limits the cost within a reasonable range under the premise of ensuring various performance indexes, and is beneficial to the promotion and use of the bimetal composite pipe in the development of oil and gas fields. According to an embodiment of the present invention, as shown in Fig. 1, the outer walls of both ends of the outer tube 20 are threaded. The connecting portion 30 includes a first joint 31, the first joint 31 is located at one end of the outer tube 20, the connecting portion 30 further includes a second joint 32, and the second joint 32 is located at the other end of the outer tube 20. In the present embodiment, the outer tubes of the outer tubes 20 have threads on the outer walls, that is, the outer tubes 20 are designed to machine male threads at both ends, and the male threads at the ends of the outer tube 20 and the females on the first joint 31 and the second joint 32, respectively. The threads are connected. Through the first joint 31 and the second joint 32, a plurality of bimetallic composite pipes are connected together to reach the length of the pipe string required for oil and gas field exploitation. As shown in Fig. 3, the first joint 31 is a tubular joint including a first section having a thread on the inner wall, and a second section of the first joint 31 other than the first section, the outer wall of the second section having a thread. The inner diameter of the second section of the first joint 31 is equal to the inner diameter of the outer tube 20. The first joint 31 is a female thread and the other end is a male thread; the first joint 31 is a tubular joint, and a part of the inner hole has a thread on the inner wall, and the part is the first section of the first joint 31, and the rest is The second section of the first joint 31 has a threaded portion over a portion of the outer wall thereof, and the inner diameter of the inner bore of the second section of the first joint 31 is the same as the inner diameter of the inner bore of the outer tube 20. As shown in FIG. 1, the female thread of the first joint 31 is engaged with the male thread of the end of the outer tube 20, and the inner diameter of the portion of the inner wall having no thread is equal to the inner diameter of the outer tube 20. In addition, the female thread on the first section of the first joint 31 is mated with the male thread of the outer tube 20, the male thread on the second section of the first joint 31 and the second joint on the other end of the other bimetallic composite pipe. The 32-end female thread is mated, and so on, thereby joining a plurality of bimetallic composite tubes together. In the present embodiment, the inner tube 10 extends across the seam between the first joint 31 and the outer tube 20 and is welded to the inner wall of the first joint 31 having no threaded portion. Since the inner diameter of the portion of the inner wall of the first joint 31 which is not threaded is equal to the inner diameter of the outer tube 20, after the first joint 31 is connected to the outer tube 20, the inner wall of the pipe is smooth without protrusion. As shown in Figure 1, the inner tube 10 The seam spanning the first joint 31 and the outer tube 20 is extended and the seam is shielded from the corrosive medium in the inner tube 10 from entering the joint formed by the first joint 31 and the outer tube 20 and corroding the outer tube 20. The inner tube 10 is welded to the inner wall of the end of the first joint 31 which is not connected to the outer tube 20, and since it is welded to the same metal, the welding performance is good, and the connection strength between the inner tube 10 and the first joint 31 is ensured. Weld seal performance. Further, since the weld bead is located at the outer edge of the end portion of the first joint 31 which is not connected to the outer tube 20, even if the diameter of the inner diameter of the first joint 31 is small, the welding can be satisfied by the welding condition. As shown in Fig. 3, the portion of the inner wall of the first joint 31 having a thread is larger than the inner diameter of the portion having no thread, and the transition of the two portions has an annular shoulder. As shown in FIG. 1, when the outer tube 20 is connected to the first joint 31, the end of the outer tube 20 is placed at the annular shoulder of the first joint 31, and after the screw is tightened, the positioning function can be tightened to prevent the outer tube 20 from being tightened. The connection with the first joint 31 can be screwed through the "over-twisting phenomenon" of the predetermined position in the downhole operation, thereby preventing the weld of the inner tube 10 and the first joint 31 from cracking. As shown in Fig. 4, the second joint 32 is a tubular joint having threads on the inner walls at both ends. The inner wall of the second joint 32 has an annular projection 321 having an inner diameter equal to the inner diameter of the outer tube 20, and the projection 321 is located between the threads on the inner wall of the both ends of the second joint 32. The second joint 32 is a tubular joint having a thread on the inner wall at both ends thereof, that is, both ends thereof are female threads. The female thread of the second joint 32 is mated with the male thread at the end of the outer tube 20. As shown in FIG. 1, the female thread on the inner wall of the second joint 32 is mated with the male thread of the outer tube 20, and the second joint 32 is joined to the outer tube 20, and the other end of the inner wall of the second joint 32 is connected. The female thread is connected to the male thread of the first joint 31 on the other bimetal composite pipe by an interference fit, and the plurality of bimetal composite pipes are connected together. The inner wall of the second joint 32 has an annular protrusion 321 having an inner diameter equal to the inner diameter of the outer tube 20 to ensure smoothness of the inner walls of the plurality of bimetallic composite tubes after the connection. In the present embodiment, the inner tube 10 extends across the seam between the second joint 32 and the outer tube 20 and is welded to the inner wall of the projection 321 . Since the inner diameter of the protruding portion 321 is equal to the inner diameter of the outer tube 20, after the second joint 32 is connected to the outer tube 20, the inner wall of the pipe is smooth without protrusion. As shown in FIG. 1, the inner tube 10 extends across the joint between the second joint 32 and the outer tube 20, and blocks the joint to prevent the corrosive medium in the inner tube 10 from entering the second joint 32 and the outer tube 20. The seam is etched and the outer tube 20 is etched. The inner tube 10 is welded to the inner wall of the projection 321 of the second joint 32. Since it is welded to the same metal, the welding performance is good, and the joint strength and weld sealing performance of the inner tube 10 and the second joint 32 are ensured. As shown in FIG. 4, both sides of the annular projection 321 of the second joint 32 form an annular shoulder with the thread connected thereto. As shown in FIG. 1, when the outer tube 20 is connected to the second joint 32, the end of the outer tube 20 is placed on the second joint. At the annular shoulder of the 32, after the screwing is tightened, the positioning function can be tightened to prevent the connection of the outer tube 20 and the second joint 32 from being screwed through the predetermined position of the "over-screw phenomenon" in the downhole operation, thereby The weld of the inner tube 10 and the second joint 32 is prevented from cracking. The manufacturing technical solution of the embodiment is as follows: 1. The inner hole size of the outer tube 20 is the same as the inner hole size of the first joint 31 and the second joint 32, and is larger than the outer diameter of the inner tube 10 by 1 mm to 4 mm;

2. cleaning the inner hole of the outer tube 20 and the outer surface of the inner tube 10 to remove oil and oxide;

3. The thread is processed at both ends of the outer tube 20;

4. The first joint 31 and the second joint 32 are machined with threads and treated with the thread surface; 5. The outer tube 20 and the connecting portion 30 are mechanically tightened, that is, the first joint 31 is tightened at the end of the outer tube 20, and the other end of the outer tube 20 is tightened. Second joint 32;

6. Insert the inner tube 10 into the outer tube 20 with joints at both ends;

7. The two ends of the inner tube 10 are sealed and welded to the inner walls of the two joints;

8. Sealing at the joints at both ends with a sealing ring, applying a hydraulic pressure to the inner tube 10, so that the outer wall of the inner tube 10 and the outer tube 20 and the inner wall of the joint are in close contact with each other, and the hydraulic pressure is according to the outer tube 20 and the inner tube 10 The outer diameter, thickness and strength rating of the material depend on it. According to another embodiment of the present invention, as shown in FIG. 2, the connecting portion 30 includes a first joint 31, the first joint 31 is located at both ends of the outer tube 20, and the connecting portion 30 further includes a second joint 32, and the second joint 32 The first joint 31 of one end of the outer tube 20 is connected by a thread. The structures of the first joint 31 and the second joint 32 in this embodiment are the same as those in the foregoing embodiment, and will not be described in detail herein. Since the inner tube 10 is welded to the protruding portion 321 of the second joint 32, both ends of the protruding portion 321 of the second joint 32 have an extended portion having an internal thread, and therefore, when engaged with the outer tube 20, the second portion When the inner diameter of the joint 32 is small (such as a tubing composite pipe), the welding of the inner tube 10 and the protrusion 321 cannot be completed by a conventional welding method. Therefore, when the diameter of the outer tube 20 is small, in the present embodiment, as shown in FIG. 2, both ends of the outer tube 20 are connected to the first joint 31, and the inner tube 10 is welded to the outer joint 20 of the first joint 31. One end of the connection is on the inner wall near the outer edge. Then, one end of the second joint 32 is screwed to the other end of the first joint 31, and the other end of the second joint 32 is connected to the first joint 31 of one end of the other bimetallic composite pipe, and so on. Reasonable arrangement of the first joint 31 and the second joint 32, thereby completing the connection portion 30 to the plurality of bimetallic composite tubes Connection. Since the second joint 32 is entirely made of a corrosion-resistant material, the present invention can satisfy the corrosion resistance requirements while ensuring the connection performance. The manufacturing technical solution of this embodiment is as follows:

1. The inner hole size of the outer tube 20 is the same as the inner hole size of the first joint 31 and the second joint 32, and is larger than the outer diameter of the inner tube 10 by 1 mm to 4 mm;

3. The thread is processed at both ends of the outer tube 20;

4. The first joint 31 and the second joint 32 are machined with threads and threaded surface treatment;

5. The outer tube 20 and the connecting portion 30 are mechanically tightened, that is, the first joint 31 is tightened at both ends of the outer tube 20; 6. The inner tube 10 is inserted into the outer tube 20 with joints at both ends;

8. Sealing at the joints at both ends with a sealing ring, applying a hydraulic pressure to the inner tube 10, so that the outer wall of the inner tube 10 and the outer tube 20 and the inner wall of the joint are in close contact with each other, and the hydraulic pressure is according to the outer tube 20 and the inner tube 10 The outer diameter, the thickness and the strength level of the material are determined; 9. The second joint 32 and the first joint 31 are mechanically tightened. The bimetal composite pipe of the invention is generally used for underground mining of oil and gas fields, and, because of its reasonable cost, can also be used as an oil and gas pipeline for oil and gas transportation. From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: The bimetal composite pipe of the present invention includes an inner pipe and an outer pipe, the inner pipe is made of a corrosion-resistant material, and the inner pipe is located outside. The inside of the tube, the bimetal composite tube further includes a connecting portion, the connecting portion is connected to the outer tube by a thread, and the inner tube is welded to the connecting portion. The connection between the connecting part and the outer tube adopts the double metal composite pipe in the form of screw connection, which avoids the weld strength drop caused by the heterogeneous metal welding which may occur, and ensures the connection performance of the oil well pipe string; the inner pipe made of corrosion resistant material ensures The corrosive medium in the tube does not contact the outer tube, which ensures the safety of the use of the bimetal composite tube. The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

A bimetal composite pipe comprising an inner pipe (10) and an outer pipe (20), wherein the inner pipe (10) is made of a corrosion resistant material, and the inner pipe (10) is located The inside of the outer tube (20), the bimetal composite tube further includes a connecting portion (30), the connecting portion (30) is connected to the outer tube (20) by a thread, and the inner tube (10) is The connecting portion (30) is welded.

The bimetal composite pipe according to claim 1, wherein the connecting portion (30) is made of a corrosion resistant material.

The bimetal composite pipe according to claim 2, wherein the outer pipe (20) is made of carbon steel or low alloy steel.

The bimetal composite pipe according to claim 2, characterized in that the outer wall of both ends of the outer pipe (20) has a thread.

The bimetal composite pipe according to claim 4, wherein the connecting portion (30) comprises a first joint (31), and the first joint (31) is located at the outer pipe (20) At one end, the connecting portion (30) further includes a second joint (32), and the second joint (32) is located at the other end of the outer tube (20).

The bimetal composite pipe according to claim 4, wherein the connecting portion (30) comprises a first joint (31), and the first joint (31) is located at the outer pipe (20) At both ends, the connecting portion (30) further includes a second joint (32), and the second joint (32) is connected to the first joint (31) at one end of the outer tube (20) by a thread.

The bimetal composite pipe according to claim 5 or 6, wherein the first joint (31) is a tubular joint, comprising a first section having a thread on the inner wall, and the first section The second section of the first first joint (31) has a thread on the outer wall of the second section.

The bimetal composite pipe according to claim 7, characterized in that the inner diameter of the second section of the first joint (31) is equal to the inner diameter of the outer pipe (20).

9. The bimetal composite pipe according to claim 8, wherein the inner pipe (10) extends across a joint between the first joint (31) and the outer pipe (20), and Soldered on the inner wall of the first joint (31) having no threaded portion.

The bimetal composite pipe according to claim 5 or 6, wherein the second joint (32) is a tubular joint having a thread on an inner wall at both ends thereof.

The bimetal composite pipe according to claim 10, wherein the inner wall of the second joint (32) has an annular protrusion (321), and the inner diameter of the protrusion (321) is equal to The inner diameter of the outer tube (20) is located between the threads on the inner wall of the two ends of the second joint (32).

The bimetal composite pipe according to claim 11, wherein the inner pipe (10) extends across a joint between the second joint (32) and the outer pipe (20), and Soldered on the inner wall of the protrusion (321).