An anticorrosion oil casing coupling

Abstract

The utility model belongs to the technical field of oil casing coupling, specifically discloses an anticorrosive oil casing coupling which comprises a coupling main body made of super martensitic stainless steel, the inner wall of which is provided with trapezoidal internal threads, a first metal main sealing surface and a sealing groove, the end, the inner wall and the threaded part are provided with a HVOF tungsten carbide coating, and the inner proximal end is provided with a zinc-based or aluminum-based sacrificial anode ring; the two ends of the coupling main body are connected through connecting pieces to connecting sleeves provided with trapezoidal external threads, a second metal main sealing surface and a sealing convex ring. During operation, the double-metal sealing structure blocks the invasion of corrosive medium, the coating insulates the medium and resists erosion, and the sacrificial anode ring prevents the local corrosion of the body after the coating is damaged through cathodic protection. The coupling is protected by "sealing, coating and cathodic protection" in cooperation, is suitable for harsh oil and gas well environments containing CO2 and the like, has strong corrosion resistance and abrasion resistance, is reliable in sealing, has controllable cost, can significantly prolong the service life and reduce the replacement risk of mining equipment.

Description

Technical Field

[0001] This utility model relates to the field of oil casing coupling technology, specifically to an anti-corrosion oil casing coupling. Background Technology

[0002] Casing couplings are key components in the petroleum industry used to connect threaded casing. They are defined as cylindrical tubular fittings that connect externally threaded casing. This component ensures the continuity of the downhole casing through threaded connection and plays a crucial role in reinforcing the wellbore and sealing the oil and gas reservoir within the oil well structure. Its service life directly affects the overall lifespan of the oil well.

[0003] To improve corrosion resistance, some existing oil casing couplings typically have a Teflon corrosion-resistant coating on their inner wall, such as the Chinese utility model patent with announcement number CN222558480U, which discloses a corrosion-resistant oil casing coupling.

[0004] However, in actual use, it has been found that the above-mentioned oil casing coupling only uses a corrosion-resistant coating to achieve the anti-corrosion effect, which is poor. In addition, the coupling uses external threads, which are exposed. If a collision occurs during transportation, handling or going down into the well, the precision threads are easily damaged, leading to connection failure. Utility Model Content

[0005] The purpose of this utility model is to provide a corrosion-resistant oil casing coupling, which solves the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a corrosion-resistant oil casing coupling, comprising a coupling body; the inner wall of the coupling body is machined with a trapezoidal internal thread, a first metal main sealing surface, and a sealing groove, the first metal main sealing surface being located in the middle of the coupling body, the sealing groove being located at the end of the coupling body, the trapezoidal internal thread being located between the first metal main sealing surface and the sealing groove, the end and inner wall of the coupling body, as well as the trapezoidal internal thread on the inner wall, are all provided with a corrosion-resistant coating, and a sacrificial anode ring is provided inside the coupling body near the end, the corrosion-resistant coating and the sacrificial anode ring improving the corrosion resistance effect.

[0007] In a preferred embodiment of this invention, both ends of the coupling body are provided with connecting parts, and connecting sleeves are fixed on the connecting parts. The outer wall of the connecting sleeve is machined with a trapezoidal external thread that mates with the trapezoidal internal thread. The end of the connecting sleeve is machined with a second metal main sealing surface that mates with the first metal main sealing surface. A sealing convex ring that mates with the sealing groove is machined between the connecting sleeve and the connecting parts. The asymmetrical trapezoidal thread design with a negative angle load tooth side and a positive angle guide tooth side reduces the risk of thread slippage. Stress distribution is more uniform under pressure. The mating of the first and second metal main sealing surfaces, and the mating of the sealing groove and the sealing convex ring, improve the sealing effect. The connecting parts at both ends of the coupling body are the drill pipe and the oil casing, respectively.

[0008] In a preferred embodiment of this invention, the first and second main metal sealing surfaces are radially interference-fitted, with the sealing convex ring fitted within the sealing groove. The radially interference-fitted metal sealing surfaces of the first and second main metal sealing surfaces, with their two ultra-precision machined conical metal surfaces, generate extremely high contact stress, forming the first airtight and liquid-tight barrier. The contact surface between the sealing convex ring and the sealing groove also forms an auxiliary metal seal.

[0009] As a preferred embodiment of this invention, the coupling body is made of a high-performance corrosion-resistant alloy, specifically super martensitic stainless steel. 13Cr / 15Cr super martensitic stainless steel offers excellent resistance to uniform corrosion and pitting corrosion in CO2-rich environments, while being less expensive than higher-grade nickel-based alloys.

[0010] As a preferred embodiment of this invention, the corrosion-resistant coating is an ultra-high-speed oxygen fuel sprayed tungsten carbide coating. Its extreme hardness (>1100 HV) provides exceptional wear and erosion resistance, protecting against the impact of formation sand particles and high-speed fluids. The coating formed by the HVOF process has extremely low porosity (<1%), effectively isolating corrosive media from contact with the base metal.

[0011] As a preferred embodiment of this invention, the sacrificial anode ring is made of a zinc-based or aluminum-based alloy. This alloy ring has a more negative electrochemical potential than the coupling substrate material, thus becoming the sacrificial anode. When the coating experiences minor damage due to extreme operating conditions, the infiltrating electrolyte preferentially corrodes the anode ring, thereby providing cathodic protection to the coupling body and greatly suppressing localized corrosion (such as pitting and crevice corrosion) of the coupling body.

[0012] Compared with the prior art, the beneficial effects of this utility model are: This utility model features a double-metal sealing structure that achieves efficient airtight and liquid-tight isolation, reducing the intrusion of corrosive media at the source. At the same time, the threaded connection is stable and adaptable to the working conditions of oil casing. The super martensitic stainless steel matrix itself is resistant to uniform CO2 corrosion and pitting corrosion. Combined with the physical isolation of the low-porosity tungsten carbide coating and the emergency cathodic protection of the sacrificial anode ring, a triple anti-corrosion barrier is formed, which can effectively resist various types of corrosion such as uniform corrosion, pitting corrosion, and crevice corrosion. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the exploded structure of this utility model; Figure 2 This is a three-dimensional structural diagram of the main body of the coupling of this utility model; Figure 3 This is a schematic diagram of the internal structure of the coupling body of this utility model; Figure 4 This is a schematic diagram of the connector structure of this utility model.

[0014] In the figure: 1. Coupling body; 101. Trapezoidal internal thread; 102. First metal main sealing surface; 103. Sealing groove; 104. Corrosion-resistant coating; 105. Sacrificial anode ring; 2. Connector; 201. Connecting sleeve; 202. Trapezoidal external thread; 203. Second metal main sealing surface; 204. Sealing convex ring. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0016] In the description of this utility model, it should be noted that the terms "vertical", "up", "down", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0017] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0018] Please see Figure 1-4 This utility model provides a technical solution: a corrosion-resistant oil casing coupling, including a coupling body 1; the inner wall of the coupling body 1 is machined with a trapezoidal internal thread 101, a first metal main sealing surface 102 and a sealing groove 103, the first metal main sealing surface 102 is located in the middle of the coupling body 1, the sealing groove 103 is located at the end of the coupling body 1, the trapezoidal internal thread 101 is located between the first metal main sealing surface 102 and the sealing groove 103, the end and inner wall of the coupling body 1 and the trapezoidal internal thread 101 on the inner wall are all provided with a corrosion-resistant coating 104, and a sacrificial anode ring 105 is provided inside the coupling body 1 near the end.

[0019] Furthermore, each end of the coupling body 1 is provided with a connector 2, which is the drill pipe and the oil casing, respectively. A connecting sleeve 201 is fixed on the connector 2. A trapezoidal external thread 202 is machined on the outer wall of the connecting sleeve 201 to mate with the trapezoidal internal thread 101. A second metal main sealing surface 203 is machined at the end of the connecting sleeve 201 to mate with the first metal main sealing surface 102. A sealing convex ring 204 is machined between the connecting sleeve 201 and the connector 2 to mate with the sealing groove 103. The asymmetrical trapezoidal thread design with a negative angle load tooth side and a positive angle guide tooth side reduces the risk of thread slippage. The stress distribution is more uniform under pressure. The mating of the first metal main sealing surface 102 and the second metal main sealing surface 203, and the mating of the sealing groove 103 and the sealing convex ring 204, improve the sealing effect.

[0020] Furthermore, the first metal main sealing surface 102 and the second metal main sealing surface 203 are radially interference-fitted, and the sealing convex ring 204 is fitted into the sealing groove 103. The radial interference fit between the first metal main sealing surface 102 and the second metal main sealing surface 203, with two ultra-precision machined conical metal surfaces, generates extremely high contact stress, forming the first airtight and liquid-tight barrier. The contact surface between the sealing convex ring 204 and the sealing groove 103 also forms an auxiliary metal seal.

[0021] Furthermore, the coupling body 1 is made of a high-performance corrosion-resistant alloy, specifically super martensitic stainless steel. 13Cr / 15Cr super martensitic stainless steel offers excellent resistance to uniform corrosion and pitting corrosion in CO2-rich environments, at a lower cost than higher-grade nickel-based alloys.

[0022] Furthermore, the corrosion-resistant coating 104 is a tungsten carbide coating applied using ultra-high-speed oxygen fuel spraying. Its extreme hardness (>1100 HV) provides exceptional wear and erosion resistance, protecting against the impact of formation sand particles and high-speed fluids. The coating formed by the HVOF process has extremely low porosity (<1%), effectively isolating corrosive media from contact with the base metal.

[0023] Furthermore, the sacrificial anode ring 105 is made of a zinc-based or aluminum-based alloy. The electrochemical potential of this alloy ring is more negative than that of the coupling substrate material, thus becoming a sacrificial anode. When the coating suffers minor damage due to extreme operating conditions, the infiltrating electrolyte will preferentially corrode the anode ring, thereby providing cathodic protection to the coupling body and greatly suppressing localized corrosion (such as pitting and crevice corrosion) of the coupling body.

[0024] In summary, the connecting sleeve 201 is connected to the trapezoidal internal thread 101 of the coupling body 1 through the trapezoidal external thread 202. At the same time, the first metal main sealing surface 102 and the second metal main sealing surface 203 form a radial interference fit, and the sealing convex ring 204 is embedded in the sealing groove 103, forming a double metal sealing structure to achieve airtight and liquid tight barriers, preferentially blocking formation sand particles, high-speed fluids and corrosive media (such as CO2-containing fluids) from intruding into the coupling.

[0025] The high-speed oxygen fuel spraying (HVOF) tungsten carbide coating on the end, inner wall and threaded parts of the coupling body 1 isolates the corrosive medium from the base metal with low porosity (<1%), while resisting sand impact and fluid erosion with high hardness (>1100HV), reducing the risk of coating damage.

[0026] The zinc-based / aluminum-based alloy sacrificial anode ring 105 inside the coupling has an electrochemical potential lower than that of the coupling substrate (super martensitic stainless steel). When the coating is slightly damaged, the electrolyte preferentially corrodes the sacrificial anode ring 105, thus preventing pitting corrosion, crevice corrosion and other localized corrosion of the coupling body through the cathodic protection effect, forming a layered protection system of "sealing-coating-cathodic protection".

[0027] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A corrosion-resistant oil casing coupling, characterized in that: The coupling body (1) includes a trapezoidal internal thread (101), a first metal main sealing surface (102) and a sealing groove (103) processed on the inner wall of the coupling body (1). The first metal main sealing surface (102) is located in the middle of the coupling body (1), the sealing groove (103) is located at the end of the coupling body (1), the trapezoidal internal thread (101) is located between the first metal main sealing surface (102) and the sealing groove (103), and the end and inner wall of the coupling body (1) and the trapezoidal internal thread (101) on the inner wall are all provided with a corrosion-resistant coating (104). A sacrificial anode ring (105) is provided inside the coupling body (1) near the end.

2. The anti-corrosion oil casing coupling according to claim 1, characterized in that: Both ends of the coupling body (1) are provided with connectors (2), and a connecting sleeve (201) is fixed on the connector (2). A trapezoidal external thread (202) that mates with the trapezoidal internal thread (101) is machined on the outer wall of the connecting sleeve (201). A second metal main sealing surface (203) is machined at the end of the connecting sleeve (201). A sealing convex ring (204) that mates with the sealing groove (103) is machined between the connecting sleeve (201) and the connector (2).

3. The anti-corrosion oil casing coupling according to claim 1, characterized in that: The first metal main sealing surface (102) and the second metal main sealing surface (203) are radially interference-fitted, and the sealing convex ring (204) is fitted into the sealing groove (103).

4. The anti-corrosion oil casing coupling according to claim 1, characterized in that: The main body of the coupling (1) is made of a high-performance corrosion-resistant alloy, which is super martensitic stainless steel.

5. The anti-corrosion oil casing coupling according to claim 1, characterized in that: The corrosion-resistant coating (104) is a tungsten carbide coating applied by ultra-high-speed oxygen fuel spraying.

6. The anti-corrosion oil casing coupling according to claim 1, characterized in that: The sacrificial anode ring (105) is made of zinc-based or aluminum-based alloy.

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