Metal sealing structure and method for coiled tubing

Abstract

The invention relates to a metal sealing structure and method for a continuous oil pipe. The metal sealing structure for the continuous oil pipe comprises a connecting piece and an oil pipe. The connecting piece is jointed with the oil pipe; the connecting piece is fixedly connected with the oil pipe through a locking structure; and the connecting piece is hermetically connected with the oil pipe through a metal sealing layer. According to the metal sealing structure of the continuous oil pipe, the connecting piece and the oil pipe are in sealed connection through the metal sealing layer so that the metal sealing structure can be suitable for high-temperature, high-pressure and corrosive oil and gas well environments, the sealing performance and durability of the oil pipe connecting structure can be greatly improved, and the problem that the reliability is reduced after a traditional sealing ring serves for a long time is solved.

Description

Technical Field

[0001] This application relates to a metal sealing structure and method for coiled tubing, applicable to the technical field of coiled tubing sealing connections. Background Technology

[0002] Existing coiled tubing typically uses sealing rings or welding for sealing connections. Sealing rings are prone to aging and deformation under long-term high temperatures, high pressures, and corrosive media containing substances such as carbon dioxide and chloride ions, leading to seal failure. While welding can achieve reliable connections and seals, it is limited by construction conditions and safety regulations, resulting in low efficiency, high risk, and difficulty in meeting the demands of rapid operations.

[0003] On the other hand, since coiled tubing typically operates at depths of several thousand meters underground, the strength of its sealing connections must be extremely reliable; otherwise, any breakage or leakage would lead to irreparable losses. Therefore, the pressure-bearing capacity of the sealing connection structure needs to be calculated scientifically and rationally to ensure that it meets pressure requirements while maximizing sealing efficiency and minimizing costs. Summary of the Invention

[0004] The purpose of this application is to design a metal sealing structure and method for coiled tubing, aiming to solve the problem of decreased reliability of sealing rings after long-term service in existing coiled tubing metal sealing structures. Simultaneously, this application also proposes an empirical formula for calculating the pressure-bearing capacity of the sealing connection structure to guide the parameter design of the connection structure and prevent cracking or leakage in the sealing connection structure.

[0005] This application relates to a metal sealing structure for a continuous tubing, the metal sealing structure of which includes a connector and a tubing; the connector is joined to the tubing; the connector and the tubing are fixedly connected by a locking structure; the connector and the tubing are also sealed together by a metal sealing layer, the metal sealing layer being formed by heating a metal filler into a liquid state and flowing to the space between the connector and the tubing, where it cools and solidifies, thus forming a fixed seal between the connector and the tubing.

[0006] In some embodiments, the connector is provided with a packing groove and a first sealing groove in the circumferential direction; the packing groove is provided with metal packing; the metal packing fills the first sealing groove after being heated to form a metal sealing layer.

[0007] In some embodiments, the metal filler is a lead-bismuth alloy, a bismuth-based alloy, a tin-based alloy, or a gallium-based alloy.

[0008] In some embodiments, the metal filler contains at least one metallic material, such as antimony or copper.

[0009] In some implementations, the connectors and oil pipes are made of steel.

[0010] In some embodiments, the connector is further provided with a second sealing groove in the circumferential direction; a first sealing groove is disposed between the second sealing groove and the packing groove; a sealing ring is provided in the second sealing groove; the sealing ring is clamped between the connector and the oil pipe.

[0011] In some embodiments, the connector is an oil pipe fitting; the locking structure is a recess or groove, and the mating surfaces between the oil pipe fitting and the oil pipe are pressed together by the recess or groove to fix the connector to the oil pipe.

[0012] In some embodiments, the connector is a slip joint, and the locking structure is a slip structure; the rivet joint and the oil pipe are pressed together by the slip structure to fix the connector to the oil pipe.

[0013] In some embodiments, the slip structure is a clamping flap; the slip joint has a connecting section and a rotating sleeve, and multiple clamping flaps are disposed in the connecting section; the rotating sleeve is threadedly connected to the connecting section, and the clamping flaps are clamped to the oil pipe by rotation.

[0014] In some embodiments, the connector is a rivet joint, and the locking structure is a riveting structure; the rivet joint and the oil pipe are pressed together by the riveting structure to fix the connector to the oil pipe.

[0015] In some embodiments, the cross-sections of the packing groove and the first sealing groove are trapezoidal or triangular, respectively.

[0016] This application also provides a method for sealing a continuous tubing connection, used for sealing a connection between a tubing and a connector; the connector is provided with a packing groove and a first sealing groove in its circumferential direction; the sealing connection method includes the following steps:

[0017] S1: Metal filler is pre-filled into the filling tank;

[0018] S2: Connect the connector to the oil pipe and fix the connector to the oil pipe;

[0019] S3: The metal packing is heated; after the metal packing melts, it flows along the gap between the joint surface of the connector and the oil pipe to the first sealing groove, thereby forming a metal sealing layer; the metal sealing layer seals the space between the connector and the oil pipe.

[0020] S4: Allow to cool naturally to room temperature to complete the sealing connection between the oil pipe and the connector.

[0021] In some embodiments, the metal filler is a lead-bismuth alloy; the connectors and oil pipes are made of steel.

[0022] In some implementations, in step S2: the connector and the oil pipe are fixed by crimping with a recess or groove.

[0023] In some implementations, in step S2: the connector and the oil pipe are fixed together by a riveting structure.

[0024] In some implementations, in step S2: the connector is fixed to the oil pipe by a slip structure.

[0025] In some embodiments, step S1 further includes: providing a sealing ring in the circumferential direction of the connector, and such that a first sealing groove is disposed between the sealing ring and the packing groove; the sealing ring is clamped between the connector and the oil pipe to block the molten metal between the joint surfaces of the connector and the oil pipe.

[0026] The pressure-bearing capacity of the sealed connection satisfies the following empirical formula:

[0027]

[0028] Where P is the critical pressure, and the unit is MPa; d is the yield strength of the material, in MPa; d is the equivalent diameter of the annular cross-section of the metal sealing layer, in mm; D is the equivalent diameter of the packing groove in the circumferential direction, in mm.

[0029] The metal sealing structure and method for coiled tubing proposed in this application have the following technical advantages:

[0030] (1) The solution proposed in this application can overcome the problem of reliability decline of traditional sealing materials after long-term service by forming a metal sealing layer between the connector and the oil pipe.

[0031] (2) The proposed solution in this application forms a metal sealing layer by heating between the connector and the oil pipe, thereby achieving a sealed connection between the connector and the oil pipe. The connection method is simple and reliable.

[0032] (3) The proposed solution, by selecting lead-bismuth alloy, bismuth-based alloy, tin-based alloy, or gallium-based alloy as filler, can achieve heating liquefaction and flow sealing; simultaneously, it expands in volume during solidification to achieve complete sealing; and it has corrosion resistance, resistance to CO2, and Cl... - Its advantages in corrosion resistance make it particularly suitable for oil and gas field environments;

[0033] (4) This application proposes an empirical formula for calculating the pressure-bearing capacity of a sealed connection structure to guide the parameter design of the connection structure. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the recessed joint of this application.

[0035] Figure 2 This is a schematic diagram of the sealing state of the recessed joint in this application.

[0036] Figure 3 This is a schematic diagram of the connection between the recessed connector and the oil pipe in this application.

[0037] Figure 4 This is a partial cross-sectional view of the connection between the recessed joint and the oil pipe in this application.

[0038] Figure 5 This is a partial cross-sectional view of the grooved joint and the oil pipe connection of this application.

[0039] Figure 6 This is a schematic diagram of the grooved connector of this application.

[0040] Figure 7 This is a schematic diagram of the sealing state of the grooved joint in this application.

[0041] Figure 8 This is an exploded view of the slip connector of this application.

[0042] Figure 9 This is a partial schematic diagram of the slip connector of this application.

[0043] Figure 10 This is a schematic diagram of the connection between the slip connector and the oil pipe in this application.

[0044] Figure 11 This is a partial cross-sectional view of the connection between the slip joint and the oil pipe in this application.

[0045] Figure 12 This is a partial sectional view of the slip sleeve of this application.

[0046] Figure 13 This is a partial sectional view of the slip connector of this application.

[0047] Figure 14 This is a schematic diagram of the connection between the rivet joint and the oil pipe in this application.

[0048] Figure 15 This is a schematic diagram of the oil pipe structure in this application.

[0049] Figure 16 This is a partial sectional view of the connection between the rivet joint and the oil pipe in this application.

[0050] Figure 17 This is a schematic diagram of an embodiment of the joint sealing section of this application.

[0051] Figure 18 This is an equivalent direct schematic diagram of the joint sealing section of this application.

[0052] Figure 19 This is a schematic diagram of Embodiment 2 of the joint sealing section of this application.

[0053] Figure 20 This is a schematic diagram of the sealing state of the joint and oil pipe in this application.

[0054] Figure 21 This is a schematic diagram of the sealing state of the joint and oil pipe in this application.

[0055] Figure 22 This is a test curve diagram of the pressure test of the metal sealing layer of this application with an equivalent diameter of 8mm.

[0056] Figure 23 This is a test curve diagram of the pressure test of the metal sealing layer of this application with an equivalent diameter of 10mm.

[0057] In the diagram: 1. Recessed joint; 11. Recess; 12. Packing groove; 13. First sealing groove; 14. Second sealing groove; 15. Groove; 2. Oil pipe; 21. Positioning hole; 3. Groove joint; 4. Metal sealing layer; 5. Sealing ring; 6. Slip joint; 61. Connecting section; 62. Slip sleeve; 63. Clamping flap; 64. Thread; 7. Rivet joint; 71. Rivet hole; 8. Rivet; 9. Metal packing; 10. Connecting piece; 20. Locking structure. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be arbitrarily combined with each other.

[0059] like Figure 20-21 As shown, this application proposes a metal sealing structure for coiled tubing, which can be used for, for example, sealing connections between coiled tubing. The metal sealing structure for coiled tubing includes a connector 10 and tubing 2. The connector 10 and tubing 2 are joined together to achieve a connection. Specifically, the connector 10 and tubing 2 are fixedly connected by a locking structure 20 to achieve a fixed assembly of the connector 10 and tubing 2, providing positioning for further sealing connections. The connector 10 and tubing 2 are also sealed together by a metal sealing layer 4. This metal sealing layer 4 is formed by heating a metal filler 9 into a liquid state, flowing to the space between the connector 10 and tubing 2, and then cooling and solidifying. This creates a fixed seal between the connector 10 and tubing 2, improving the sealing strength between them. The metal sealing structure for coiled tubing proposed in this application, with the connector and tubing sealed by a metal sealing layer, is suitable for high-temperature, high-pressure, and corrosive oil and gas well environments. It can significantly improve the sealing performance and durability of the tubing connection structure, solving the problem of decreased reliability of traditional sealing rings after long-term service. The connector 10 proposed in this application can be various adapters, specifically a recessed connector 1, a grooved connector 3, a slip connector 6, or a rivet connector 7, or an oil pipe 2.

[0060] like Figure 20-21 As shown, in some embodiments, a packing groove 12 and a first sealing groove 13 may be provided circumferentially on the connector 10. The volume of the packing groove 12 is larger than that of the first sealing groove 13, so that the metal packing 9 in the packing groove 12, after being heated and flowing, can completely fill the first sealing groove 13 and the gap between the first sealing groove 13 and the oil pipe 2, forming an overall seal. Specifically, during the connection process between the connector 10 and the oil pipe 2, the metal packing 9 is first provided in the packing groove 12. The metal packing 9 can be powder, granules, or a strip structure. Specifically, by heating the metal packing 9, the metal packing 9 liquefies and flows from the gap between the connector 10 and the oil pipe 2 to the first sealing groove 13, and fills the first sealing groove 13 and the gap between the first sealing groove 13 and the oil pipe 2 to form a tight metal sealing layer 4. The melting point of the metal packing 9 is lower than that of the connector 10 and the oil pipe 2.

[0061] Preferably, the metal filler 9 can be a lead-bismuth alloy, a bismuth-based alloy, a tin-based alloy, or a gallium-based alloy. These metals have the advantages of low melting point, volume expansion upon solidification, strong pre-deformation ability, and corrosion resistance, and can resist CO2 and Cl. - Corrosion resistant, suitable for oil and gas field environments; specific parameters can be found in the table below:

[0062]

[0063] The four types of metal fillers 9 mentioned above can undergo slight plastic deformation during the cooling process, enhancing the sealing stress. Specifically, taking lead-bismuth alloy as an example, its melting point ranges from 300±50℃, and its volume expansion rate during solidification is ≥5%, which can effectively compensate for the sealing gap. Furthermore, the material undergoes slight plastic deformation during cooling, enhancing the sealing stress. The materials for the connector 10 and the oil pipe 2 are steel, with a melting point between 1300℃ and 1540℃. Metal heating can be achieved using electromagnetic heating, i.e., induction heating is performed on the filler groove 12 on the outer surface of the connector 10 using an electromagnetic heating device until the metal filler 9 in the filler groove 12 reaches its melting point and liquefies. Further, at least one metal material, such as antimony or copper, can be added to the metal filler 9 to improve corrosion resistance.

[0064] Specifically, calculating the pressure-bearing capacity of the metal sealing layer formed after the alloy phase change filling of the packing groove is crucial for the metal sealing structure of the coiled tubing in this application. Because this sealing connection structure is located downhole, a failure to bear pressure leading to leakage or breakage will render the entire tubing unusable, causing significant construction difficulties. Therefore, accurately calculating the pressure-bearing capacity of the metal sealing layer is essential for the successful application of this application. To this end, this application proposes an empirical formula for calculating the pressure-bearing capacity of the metal sealing layer formed after the low-temperature alloy phase change filling of the packing groove, and determining whether it meets the requirements, as follows:

[0065]

[0066] Where P is the critical pressure, in MPa, which indicates that under this pressure, the annular cross section may begin to yield over a large area, leading to permanent deformation and sealing failure. d is the yield strength of the material, in MPa; d is the equivalent diameter of the annular cross-section of the metal sealing layer, in mm; D is the equivalent diameter of the packing groove, in mm, referring to the circumferential equivalent diameter of the formed metal sealing layer.

[0067] like Figure 17 and 18 As shown, let the upper base of the trapezoidal packing trough 12 be a, the lower base be b, and the height be h. Then the cross-sectional area S1 of the trapezoid is = According to the principle of area equivalence, this trapezoidal cross-section can be equivalent to a circular cross-section with diameter d, and its area S2 = The following equation exists:

[0068] S1=S2, that is = d= .

[0069] The equivalent diameter D of the stuffing groove can be obtained by adding the obtained d value to the diameter of the solid part.

[0070] In some embodiments, the yield strength of the bismuth-based alloy Bi58Sn42In10 is calculated. ≈200MPa, assuming the tubing diameter is 38mm, the equivalent diameter of the annular cross-section of the formed metal sealing layer is d=10mm, and the equivalent circumferential diameter of the formed metal sealing layer is D=38mm; the critical pressure P is calculated to be approximately 2*200*(10 / 38) / (1-(10 / 38))=142MPa. The critical pressure P is calculated according to the above formula when the equivalent diameter of the annular packing groove cross-section of the metal sealing layer is 8, 6, 4, and 2mm respectively. The calculation results are shown in Table 2 below.

[0071] Table 2

[0072]

[0073] The results above show that the pressure-bearing capacity of the metal sealing layer formed by the low-temperature alloy phase transformation meets the requirements of oil and gas operating conditions, and different specifications of packing grooves can be selected according to different pressure conditions. The equivalent diameter d of the annular cross-section of the metal sealing layer is preferably between 2 mm and 10 mm.

[0074] In some embodiments, the outer diameter of the oil pipe was selected as 38 mm, and pressure tests were conducted with the equivalent diameter of the low-temperature alloy metal (bismuth-based alloy Bi58Sn42In10) seal selected as 8 mm and 10 mm, respectively. The test results are as follows: Figure 22 and 23 As shown, the sealing capability of its metal sealing layer meets the requirements of the petroleum industry's pressure stabilization standards.

[0075] like Figure 17-21 As shown, in some embodiments, in order to form a metal sealing layer 4 between the connector 10 and the oil pipe 2, a second sealing groove 14 is further provided in the circumferential direction of the connector 10, and a first sealing groove 13 is disposed between the second sealing groove 14 and the packing groove 12. Specifically, a sealing ring 5 may be provided in the second sealing groove 14, which may be an O-ring silicone ring or a rubber ring. The sealing ring 5 is clamped between the connector 10 and the oil pipe 2, which can seal the connector 10 and the oil pipe 2. More importantly, it can block the liquefied flowing metal liquid, so that the liquefied flowing metal liquid can fully penetrate into the first sealing groove 13 and the gap between the connector 10 and the oil pipe 2, forming a complete metal sealing layer 4 and improving the sealing effect.

[0076] like Figure 17-19 As shown, in some embodiments, the packing groove 12, the first sealing groove 13, and the second sealing groove 14 are all annular grooves. The cross-sections of the packing groove 12 and the first sealing groove 13 can be designed as trapezoidal or triangular, that is, the sides of the packing groove 12 and the first sealing groove 13 are inclined surfaces. Designing the cross-section of the packing groove 12 as trapezoidal or triangular allows the metal packing 9, after being heated into a liquid state, to flow rapidly along its inclined surface to the gap between the connector 10 and the oil pipe 2 under the action of gravity, thus achieving a seal. Designing the cross-section of the first sealing groove 13 as trapezoidal or triangular allows the metal sealing layer 4 solidified in the first sealing groove 13 to be squeezed out of the groove by the force of the inclined surface, making the metal sealing layer 4 between the connector 10 and the oil pipe 2 stronger and more stable.

[0077] like Figure 1-4As shown in Figures 20-21, in some embodiments, the connector 10 is an oil pipe joint, which can be a recessed connector 1. The locking structure 20 can be designed as a recess 11, that is, multiple recesses 11 can be provided along the circumference of the outer surface of the recessed connector 1; the mating surfaces between the recessed connector 1 and the oil pipe 2 are pressed together by the recesses 11 to fix the connector 10 to the oil pipe 2. Specifically, a crimping tool can be used to crimp the outer surface of the oil pipe 2 along the position of the recesses 11 of the recessed connector 1, so that the outer surface of the oil pipe 2 forms a recess that engages with the recesses 11 of the recessed connector 1, thereby achieving fixation.

[0078] like Figure 5-7 As shown in Figures 20-21, in some embodiments, the connector 10 is an oil pipe joint, which can be a grooved connector 3. The locking structure 20 can be designed as a groove 15, that is, at least one groove 15 can be provided around the outer surface of the grooved connector 3. The mating surfaces between the oil pipe joint and the oil pipe 2 are pressed together by the groove 15 to fix the grooved connector 3 to the oil pipe 2. Specifically, a crimping tool can be used to crimp the outer surface of the oil pipe 2 along the groove 15 of the grooved connector 3, so that the outer surface of the oil pipe 2 is engaged with the groove 15 of the grooved connector 3 to achieve fixation.

[0079] like Figure 8-13 As shown in Figures 20-21, in some embodiments, the connector 10 is a slip joint 6, and the locking structure 20 is a slip structure. Specifically, the end of the oil pipe 2 is inserted into the rivet joint 7, and the rivet joint 7 and the oil pipe 2 are pressed together by the slip structure to fix the connector 10 to the oil pipe 2. Figure 8-13 As shown, the slip structure consists of clamping flaps 63. The slip connector 6 has a connecting section 61 and a rotating sleeve 62. The rotating sleeve 62 is fitted onto the connecting section 61 and connected to the connecting section 61 via threads 64. Multiple clamping flaps 63 are disposed on the connecting section 61 and can be deformed by the compression of the rotating sleeve 62 to clamp the oil pipe 2. During use, the oil pipe 2 is inserted into the connecting section 61, and the clamping flaps 63 are gradually compressed and deformed by rotating the rotating sleeve 62, thereby clamping the oil pipe 2.

[0080] like Figure 14-16 As shown in Figures 20-21, in some embodiments, the connecting member 10 is a rivet joint 7, and the locking structure 20 is a riveting structure. The rivet joint 7 and the oil pipe 2 are pressed together by the riveting structure to fix the connecting member 10 to the oil pipe 2. Specifically, the riveting structure includes rivet holes 71, positioning holes 21, and rivets 8. Multiple rivet holes 71 are respectively provided in the circumferential direction of the rivet joint 7, and multiple positioning holes 21 are respectively provided on the outer wall surface of the oil pipe 2. The rivets 8 are passed through the rivet holes 71 and pressed into the positioning holes 21 by the riveting fixture to fix the connecting member 10 to the oil pipe 2.

[0081] like Figure 20-21 As shown, this application also proposes a method for sealing a continuous tubing connection, used for sealing the connection between the tubing 2 and the connector 10. Specifically, the sealing connection method includes the following steps:

[0082] S1: Pre-treatment, a filling groove 12 and a first sealing groove 13 are reserved in the circumferential direction of the connector 10, the sealing surface is cleaned, and metal filler 9 is pre-filled in the filling groove 12; the metal filler 9 can be powder or granules, or it can be an arc-shaped strip structure.

[0083] S2: Connect and fix the connector 10 to the oil pipe 2 to form a preset sealing space between the connector 10 and the oil pipe 2;

[0084] S3: Place the joined connector 10 and oil pipe 2 vertically, and then heat the metal filler 9 to form a liquid metal. Under the action of gravity, the liquid metal can flow along the gap between the joint surfaces of the connector 10 and the oil pipe 2 to the first sealing groove 13, and solidify after cooling to form a metal sealing layer 4. The metal sealing layer 4 seals the space between the connector 10 and the oil pipe 2, specifically including the gap between the connector 10 and the oil pipe 2 and inside the first sealing groove 13.

[0085] S4: Allow to cool naturally to room temperature to complete the sealed connection between oil pipe 2 and connector 10.

[0086] In this application, the connector 10 is first fixedly joined to the oil pipe 2, and then heated to form a metal sealing layer 4 for sealing. After the sealing connection between the oil pipe 2 and the connector 10 is completed, a pressure test can be performed on the sealing connection structure to verify the integrity of the seal.

[0087] like Figure 20-21 As shown, in some embodiments, the metal filler 9 can be a lead-bismuth alloy, a bismuth-based alloy, a tin-based alloy, or a gallium-based alloy; the material of the connector 10 is steel. Taking the lead-bismuth alloy as an example, its melting point ranges from 300±50℃, while the melting point of steel is between 1300℃ and 1540℃. Thus, the lead-bismuth alloy in the filler groove 12 can be heated by electromagnetic heating on the connector 10. When heated to 300±50℃, it is maintained for 8 to 12 minutes until the liquid lead-bismuth alloy completely penetrates the first sealing groove 13 and the gap between the connector 10 and the oil pipe 2. Then, it is cooled to allow the liquid lead-bismuth alloy to solidify and form a lead-bismuth alloy sealing layer.

[0088] like Figure 20-21As shown, in some embodiments, step S1 further includes: providing a sealing ring 5 in the circumferential direction of the connector 10, and placing a first sealing groove 13 between the sealing ring 5 and the packing groove 12; the sealing ring 5 is clamped between the connector 10 and the oil pipe 2 to seal the molten metal between the joint surfaces of the connector 10 and the oil pipe 2. Specifically, a second sealing groove 14 is also reserved in the circumferential direction of the connector 10, and the first sealing groove 13 is placed between the second sealing groove 14 and the packing groove 12. A sealing ring can be provided in the second sealing groove 14, and the sealing ring is clamped between the connector 10 and the oil pipe 2 to seal the molten metal, preventing the molten metal from seeping into the gap below the second sealing groove 14, so that the liquefied molten metal can fully fill the first sealing groove 13 and the gap between the connector 10 and the oil pipe 2, forming a complete metal sealing layer 4.

[0089] like Figure 1-7 As shown, in some embodiments, in step S2: the connector 10 and the oil pipe 2 can be fixedly connected by a crimping recess 11 or a groove 15. For example... Figure 14-16 As shown, the connector 10 and the oil pipe 2 can also be fixedly connected by a riveting structure. Figure 8-13 As shown, the connector 10 and the oil pipe 2 can also be fixedly connected by a slip structure.

[0090] This application also proposes a continuous tubing sealing connection method that utilizes the melting point difference between the metal packing and the metal connector for external heating, causing the metal packing to form a metal sealing layer and sealing it between the connector and the tubing. The method of this application is simple and convenient to operate, and the resulting sealing structure has better reliability.

[0091] Although the embodiments disclosed in this application are as described above, the content is merely for the purpose of facilitating understanding of this application and is not intended to limit this application. Any person skilled in the art to which this application pertains may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this application; however, the scope of patent protection of this application shall still be determined by the scope defined in the appended claims.

Claims

1. A metal sealing structure for a continuous tubing, characterized in that, The metal sealing structure of the continuous tubing includes a connector and a tubing, wherein the connector is joined to the tubing; the connector and the tubing are fixedly connected by a locking structure, and the connector and the tubing are also sealed by a metal sealing layer, which is formed by heating metal filler into a liquid state and flowing to the space between the connector and the tubing to cool and solidify, thereby forming a fixed seal between the connector and the tubing.

2. The metal sealing structure of the coiled tubing according to claim 1, characterized in that, The connector is provided with a filling groove and a first sealing groove in the circumferential direction. The filling groove is provided with metal filler. When the metal filler is heated, it fills the first sealing groove to form the metal sealing layer.

3. The metal sealing structure of the coiled tubing according to claim 2, characterized in that, The metal filler is a lead-bismuth alloy, a bismuth-based alloy, a tin-based alloy, or a gallium-based alloy, and the metal filler contains at least one of antimony or copper. The connector and the oil pipe are made of steel.

4. The metal sealing structure of the coiled tubing according to claim 2, characterized in that, The connector is further provided with a second sealing groove in the circumferential direction. The first sealing groove is disposed between the second sealing groove and the packing groove. A sealing ring is provided in the second sealing groove, and the sealing ring is clamped between the connector and the oil pipe.

5. The metal sealing structure for coiled tubing according to any one of claims 1 to 4, characterized in that, The connector is an oil pipe joint, and the locking structure is a recess or groove; the mating surfaces of the oil pipe joint and the oil pipe are pressed together by the recess or groove to fix the connector to the oil pipe.

6. The metal sealing structure for coiled tubing according to any one of claims 1 to 4, characterized in that, The connector is a slip joint, and the locking structure is a slip structure; the rivet joint and the oil pipe are pressed together by the slip structure to fix the connector to the oil pipe.

7. The metal sealing structure for coiled tubing according to any one of claims 1 to 4, characterized in that, The connector is a rivet joint, and the locking structure is a riveting structure; the rivet joint and the oil pipe are pressed together by the riveting structure to fix the connector to the oil pipe.

8. A method for sealing and connecting continuous tubing, used for sealing the connection between tubing and connectors; characterized in that, The connector is provided with a filling groove and a first sealing groove in its circumferential direction; the sealing connection method includes the following steps: S1: Metal filler is pre-filled into the filler groove; S2: Connect the connector to the oil pipe and fix the connector to the oil pipe; S3: The metal filler is heated; after the metal filler melts, it flows along the gap between the connector and the oil pipe joint surface to the first sealing groove, thereby forming a metal sealing layer; the metal sealing layer seals the space between the connector and the oil pipe. S4: Allow the oil pipe to cool naturally to room temperature to complete the sealed connection between the oil pipe and the connector.

9. The method for sealing and connecting continuous tubing according to claim 8, characterized in that, The metal filler is a lead-bismuth alloy, a bismuth-based alloy, a tin-based alloy, or a gallium-based alloy; The metal filler contains at least one of antimony or copper; The connecting component and the oil pipe are made of steel; Step S1 also includes: A sealing ring is provided in the circumferential direction of the connector, and the first sealing groove is disposed between the sealing ring and the packing groove; the sealing ring is clamped between the connector and the oil pipe to block the molten metal between the joint surfaces of the connector and the oil pipe.

10. The method for sealing and connecting continuous tubing according to claim 8 or 9, characterized in that, The pressure-bearing capacity of the sealed connection satisfies the following empirical formula: Where P is the critical pressure, and the unit is MPa; d is the yield strength of the material, in MPa; d is the equivalent diameter of the annular cross-section of the metal sealing layer, in mm; D is the equivalent diameter of the packing groove in the circumferential direction, in mm.

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