An apparatus and method for plugging abandoned wells via tubing

Abstract

This invention relates to an apparatus and method for plugging abandoned wells via tubing. The apparatus includes tubing, a technical casing, and a melting tool. The technical casing is vertically fixedly installed in the abandoned well. The tubing is vertically fixedly installed inside the technical casing, with its upper end extending vertically upwards to the outside of the upper end of the technical casing. The melting tool can be lowered through the tubing into the technical casing or open hole. After being lowered into the technical casing, the melting tool releases several metal balls and heats and melts the metal balls into liquid metal. The liquid metal cools and gradually solidifies to form a metal plug that plugs the technical casing. The advantages of this invention are its reasonable design, enabling the plugging of abandoned wells without removing the tubing, and its simple operation method. Simultaneously, it can form a dense metal plug, resulting in low cost, good gas tightness, and excellent plugging effect.

Description

Technical Field

[0001] This invention relates to the field of oil well completion technology, specifically to a device and method for sealing abandoned wells through the tubing. Background Technology

[0002] In the later stages of oil and gas resource extraction, downhole oil and gas resources are nearing depletion, necessitating well plugging to completely isolate the bottomhole oil and gas resources—a process known as well plugging abandoned wells. The plugging of abandoned oil and gas wells requires consideration of the following requirements: 1) The resulting plugging layer must provide a permanent gas seal to prevent formation oil and gas from entering the surface; 2) The resulting plugging layer must be corrosion-resistant to prevent corrosion and sealing failure in the downhole environment; 3) The resulting plugging layer must withstand a certain pressure.

[0003] In conventional abandoned well plugging, since there are oil production devices on the surface, the surface oil production equipment must first be dismantled, including the Christmas tree, tubing, and other equipment. Then, cement injection equipment is used to inject a certain amount of cement into the surface casing. After the cement has completely hardened, the abandoned well is plugged.

[0004] In the conventional well plugging process described above, cement is typically used. Cement is a brittle material, and during plugging, changes in ground stress can easily cause brittle fracture of the cement, creating pathways for oil and gas leaks.

[0005] Meanwhile, when using cement materials for sealing, the surface oil production equipment needs to be completely removed and the oil pipe at the bottom of the well needs to be completely taken out before the cement is injected. This process is relatively complicated and the preliminary preparation work is relatively long.

[0006] Furthermore, when using cement to plug abandoned wells, the time required for the cement material to fully solidify from initial injection is relatively long. During the cement solidification process, the solidification effect cannot be controlled. Therefore, the sealing effect of the resulting plug cannot be artificially intervened after the cement is injected.

[0007] When using cement to seal abandoned wells, the cement material itself is not a completely dense material, and the resulting seal may contain defects such as pores, which may affect its airtightness.

[0008] Based on the above analysis, when using cement to seal abandoned wells, due to the characteristics of cement itself and the limitations of the construction method, the sealing may fail after a period of use. That is, the oil and gas at the bottom of the well will flow to the surface through the leakage channel blocked by the cement, thus creating a safety hazard.

[0009] Leaks in offshore oil and gas wells can cause serious environmental and safety problems. Since surface facilities have already been removed, the cost of resealing abandoned wells is extremely high.

[0010] In onshore oil and gas wells, when the cement seal in an abandoned well fails, it needs to be drilled out. This requires drilling operations to completely remove the seal, followed by the injection of cement to re-seal the well. The high cost of drilling operations makes the re-sealing of abandoned wells expensive.

[0011] Based on the above considerations, for the sealing of abandoned wells, a construction scheme and sealing materials that are low in operating costs, simple to construct, have a high airtightness, are stable and reliable, and are corrosion resistant are needed.

[0012] Based on the above ideas and considering the difficulties in plugging abandoned wells, a method for plugging abandoned wells downhole via tubing is proposed. This method involves lowering the downhole plugging tool into the location to be plugged using tubing. A small metal ball is released to the plugging location and then melted using downhole heating. After the metal solidifies, a metal plugging layer is formed, completing the metal plugging of the abandoned well. This method features simple construction, good gas sealing effect, and permanent sealing. Summary of the Invention

[0013] This invention provides an apparatus and method for sealing abandoned wells through tubing, aiming to solve the problems in the prior art.

[0014] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0015] An apparatus for sealing abandoned wells via tubing includes tubing, a technical casing, and a melting tool. The technical casing is vertically fixedly installed in the abandoned well. The tubing is vertically fixedly installed inside the technical casing, with its upper end extending vertically upwards to the outside of the upper end of the technical casing. The melting tool can be lowered through the tubing into the technical casing or into the open hole. After being lowered into the technical casing, the melting tool can release several metal balls and heat and melt the metal balls into liquid metal. The liquid metal cools and gradually solidifies to form a metal plug to seal the technical casing.

[0016] The beneficial effects of this invention are as follows: During the operation, firstly, the melting tool is lowered into the casing or open hole to be plugged using a method conceivable to those skilled in the art; then, the melting tool releases a metal ball, and the metal ball is heated and melted to form a metal sealing plug. The metal sealing plug is used to plug the casing, thereby achieving the plugging of abandoned wells, with a better plugging effect.

[0017] This invention is reasonably designed and can seal abandoned wells without removing the tubing. The operation method is simple. At the same time, it can form a dense metal seal, which is low in cost, has good gas tightness, and has a good sealing effect.

[0018] Based on the above technical solution, the present invention can be further improved as follows.

[0019] Furthermore, the melting tool includes a storage chamber, an elastic ring, and a heater. The lower end of the storage chamber is open and equipped with a window switch valve. Several metal balls are placed inside the storage chamber. The heater is installed at the lower end of the storage chamber. The elastic ring includes an elastic umbrella frame and an elastic sleeve. The umbrella frame is fitted over the heater, and the sleeve is fixedly fitted over the lower part of the umbrella frame.

[0020] The beneficial effect of adopting the above-mentioned further solution is that during the operation, when the storage chamber is lowered into the tubing, the entire elastic ring is in a contracted state; when the storage chamber is lowered into the technical casing, the elastic ring is not constrained by the tubing and bounces radially, and adheres to the inner wall of the technical casing, so as to better contact the subsequently released metal ball.

[0021] Furthermore, the upper end of the umbrella frame is fixedly connected to the heater, and its lower end is slidably connected to the heater; the lower end of the heater is coaxially fitted with a spring and a retaining ring, the retaining ring is fixedly connected to the upper end of the spring, and under the elastic force of the spring, it abuts against the lower end of the elastic ring, and the elastic ring can fit against the inner wall of the technical sleeve under the compression of the retaining ring and the spring.

[0022] The advantages of adopting the above-mentioned further solution are that the structure is simple and the design is reasonable. By using springs and retaining rings, the elastic ring can always be in contact with the inner wall of the oil pipe or the inner wall of the technical casing, so as to achieve stable lowering.

[0023] Furthermore, the upper end of the heater is connected to the lower end of the storage compartment by a pin. When the pulling force it receives exceeds its maximum shear force, the pin will break, causing the storage compartment to separate from the heater.

[0024] The advantages of adopting the above-mentioned further solution are that the structure is simple and the design is reasonable. After the metal seal is formed, the storage chamber can be pulled upward. When the pulling force is greater than the maximum shear force of the pin, the pin breaks and the storage chamber separates from the heater. The storage chamber can be reused by the abandoned well at the lifting point.

[0025] Furthermore, it also includes a coiled tubing system located on the formation at the wellhead of the abandoned well, which is connected to the melting tool via coiled tubing.

[0026] The beneficial effect of adopting the above-mentioned further scheme is that, during the operation, firstly, the melting tool is lowered into the technical casing to be plugged through the tubing via the coiled tubing lowering system; then, the melting tool releases a metal ball, and the metal ball is heated and melted to form a metal sealing plug. The technical casing is then plugged using the metal sealing plug, thereby achieving the plugging of the abandoned well, with a better plugging effect.

[0027] Furthermore, a tree is fixedly installed at the wellhead of the abandoned well, and the upper end of the tubing is fixedly connected to and communicates with the lower end of the tree.

[0028] The advantages of adopting the above-mentioned further scheme are that it has a simple structure and reasonable design, and the melting tool can be lowered without removing the wellhead.

[0029] Furthermore, an annular packer is fixedly installed between the technical casing and the oil pipe.

[0030] The advantages of adopting the above-mentioned further scheme are that it has a simple structure, reasonable design, and the use of packers can further increase the sealing effect of abandoned wells.

[0031] Furthermore, an intermediate sleeve is also fixedly fitted outside the technical sleeve.

[0032] The advantages of adopting the above-mentioned further scheme are that it has a simple structure, reasonable design, and can protect the technical casing and tubing by using an intermediate casing.

[0033] Furthermore, a surface sleeve is also fixedly fitted outside the intermediate sleeve.

[0034] The advantages of adopting the above-mentioned further scheme are that it has a simple structure, reasonable design, and can protect the intermediate casing, technical casing and tubing by using the surface casing.

[0035] This invention provides a method for sealing abandoned wells using a tubing, which is implemented using the apparatus described above, and includes the following specific steps:

[0036] S1: The melting tool is lowered into the technical casing through the tubing at the location to be sealed;

[0037] S2: The melting tool releases the metal ball and heats and melts the metal ball to form a metal seal.

[0038] The beneficial effect of adopting the above-mentioned further solutions is that the present invention provides a method for sealing abandoned wells through tubing. The method is reasonably designed and can complete the sealing of abandoned wells without removing the tubing. The operation method is simple. At the same time, it can form a dense metal seal, which is low in cost, has good gas tightness, and has a good sealing effect. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the ground coiled tubing lowering system in this invention when a molten tool is lowered through a coiled tubing.

[0040] Figure 2 This is a diagram showing the state of the melting tool as it is lowered to the designated position in this invention.

[0041] Figure 3 This is a schematic diagram of the structure when the metal ball in the storage chamber of the melting tool in this invention is released into the elastic ring;

[0042] Figure 4 This is a schematic diagram of the structure when the metal ball is melted into a liquid state after the heater is activated in this invention;

[0043] Figure 5 This is a schematic diagram of the structure when the storage compartment is removed after being separated from the heater in this invention;

[0044] Figure 6 This is a schematic diagram of the sealing plug structure formed after the bottom of the well is sealed in this invention;

[0045] Figure 7 This is a schematic diagram of the structure of the elastic ring of the melting tool in this invention when it is open;

[0046] Figure 8 This is a schematic diagram of the structure of the elastic ring of the melting tool in this invention when it retracts.

[0047] The attached diagram lists the components represented by each number as follows:

[0048] 1. Coiled tubing system; 2. Christmas tree; 3. Formation; 4. Packer; 5. Surface casing; 6. Coiled tubing; 7. Melting tool; 71. Heating controller; 72. Window valve; 73. Heater; 74. Retaining ring; 75. Elastic ring; 76. Storage compartment; 78. Spring; 79. Pin; 8. Tubing; 9. Metal ball; 10. Metal plug; 11. Technical casing; 12. Intermediate casing. Detailed Implementation

[0049] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0050] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0051] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0052] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0053] Example 1

[0054] like Figures 1 to 8 As shown, this embodiment provides a device for sealing abandoned wells via tubing, including tubing 8, a technical casing 11, and a melting tool 7. The technical casing 11 is vertically fixedly installed in the abandoned well. The tubing 8 is vertically fixedly installed inside the technical casing 11, with its upper end extending vertically upward to the outside of the upper end of the technical casing 11. The melting tool 7 can be lowered into the technical casing 11 or into the open hole via the tubing 8. After the melting tool 7 is lowered into the technical casing 11, it can release several metal balls 9 and heat and melt the metal balls 9 to make them melt into liquid metal. After the liquid metal cools and gradually solidifies, it forms a metal sealing plug 10 to seal the technical casing 11.

[0055] During the operation, firstly, the melting tool 7 is lowered into the technical casing 11 to be plugged through the tubing in a manner that can be conceived by those skilled in the art; then, the melting tool releases the metal ball 9, and the metal ball 9 is heated and melted to form a metal sealing plug 10. The metal sealing plug 10 is used to plug the technical casing 11, thereby achieving the plugging of the abandoned well, with a good plugging effect.

[0056] This embodiment is reasonably designed and can complete the sealing of abandoned wells without removing the tubing. The operation method is simple. At the same time, it can form a dense metal seal, which is low in cost, has good gas tightness, and has a good sealing effect.

[0057] Example 2

[0058] Based on Embodiment 1, in this embodiment, the melting tool 7 includes a storage chamber 76, an elastic ring 75, and a heater 73. The lower end of the storage chamber 76 is open and equipped with a window switch valve 72. A plurality of metal balls 9 are placed inside the storage chamber 76. The heater 73 is installed at the lower end of the storage chamber 76. The elastic ring 75 includes an elastic umbrella frame and an elastic sleeve. The umbrella frame is fitted over the heater 73, and the sleeve is fixedly fitted over the lower part of the umbrella frame.

[0059] During the operation, when the storage chamber 76 is lowered into the oil pipe 8, the elastic ring 75 is in a contracted state; when the storage chamber 76 is lowered into the technical sleeve 11, the entire elastic ring 75 is no longer constrained by the oil pipe 8 and bounces radially open, and sticks to the inner wall of the technical sleeve 11, so as to better contact the metal ball 9 released later.

[0060] When the storage chamber 76 is lowered into the oil pipe 8, both the umbrella frame and the pouch are in a retracted state; when the storage chamber 76 is lowered into the technical sleeve 11, both the umbrella frame and the pouch are in an extended state, and the upper edge of the pouch is just in contact with the inner wall of the technical sleeve 11, ensuring that the metal ball 9 can be completely contained by the pouch, and the liquid metal formed after the metal ball 9 melts is completely inside and above the pouch.

[0061] Preferably, in this embodiment, the heater 73 employs a chemical combustion method, igniting the chemical propellant inside the heater 73. The ignited propellant rapidly releases heat, melting the metal balls 9 piled outside the melting tool 7. After the internal heater 73 stops releasing heat, as the temperature decreases, the liquid metal gradually solidifies to form a metal sealing plug 10.

[0062] It should be noted that the aforementioned chemical combustion agents are generally oxygen-free aluminothermic agents formed by aluminum with iron oxide, copper oxide, etc.

[0063] Example 3

[0064] Based on Embodiment 2, in this embodiment, the upper end of the umbrella frame is fixedly connected to the heater 73, and its lower end is slidably connected to the heater 73; the lower end of the heater 73 is coaxially sleeved with a spring 78 and a retaining ring 74, the retaining ring 74 is fixedly connected to the upper end of the spring 78, and under the elastic force of the spring 78, it abuts against the lower end of the elastic ring 75, and the elastic ring 75 can fit against the inner wall of the technical sleeve 11 under the compression of the retaining ring 74 and the spring 78.

[0065] The scheme has a simple structure and reasonable design. By using spring 78 and retaining ring 74, the elastic ring 75 can always be in contact with the inner wall of oil pipe 8 or the inner wall of technical sleeve 11, so as to achieve stable lowering.

[0066] Preferably, in this embodiment, the storage compartment 76 has a cylindrical structure, which is reasonably designed and better matches the oil pipe 8 and the technical casing 11.

[0067] In addition, a heating controller 71 is fixedly installed on the top of the storage compartment 76, and the heating controller 71 is connected to the heater 73 via a line.

[0068] It should be noted that the friction between the elastic ring 75 and the inner wall of the oil pipe 8 or the technical casing 11 is less than the weight of the entire melting tool 7. Therefore, the fit between the elastic ring 75 and the oil pipe 8 or the technical casing 11 does not affect the lowering of the entire melting tool 7.

[0069] Example 4

[0070] Based on any one of Embodiments 2 to 3, in this embodiment, the upper end of the heater 73 is connected to the lower end of the storage compartment 76 by a pin 79. When the pulling force on the pin 79 is greater than its maximum shear force, the pin 79 will break, causing the storage compartment 76 to separate from the heater 73.

[0071] The scheme has a simple structure and reasonable design. After the metal sealing plug 10 is formed, the storage chamber 76 can be pulled upward. When the pulling force is greater than the maximum shear force of the pin 79, the pin breaks and the storage chamber 76 is separated from the heater 73. The storage chamber 76 can be reused by the abandoned well at the lifting point.

[0072] After all the liquid metal has completely solidified, the through-pipe melting tool 7 is pulled up through the coiled tubing 6. When the downward pulling force is greater than the maximum shear force of the pin 79 located in the middle of the through-pipe melting tool 7, the pin 79 will be sheared, causing the heater 73 and the storage chamber 76 to separate. The coiled tubing 6 will then pull the storage chamber 76 to the ground.

[0073] After the formed metal sealant 10 has cured, the sealing effect of the metal sealant 10 is tested according to the standards for sealing abandoned wells, and the sealing effect is evaluated based on the experimental results. Once the formed metal sealant 10 fully meets the requirements for sealing abandoned wells, the ground installation is removed, completing the metal sealing operation for the abandoned well.

[0074] Example 5

[0075] Based on the above embodiments, this embodiment also includes a coiled tubing system 1, which is located on the formation 3 at the wellhead of the abandoned well and is connected to the melting tool 7 via a coiled tubing 6.

[0076] During the operation, firstly, the melting tool 7 is lowered into the technical casing 11 through the tubing 8 via the coiled tubing lowering system 1 to the position to be plugged; then, the melting tool 7 releases a metal ball, and the metal ball 9 is heated and melted to form a metal sealing plug 10. The metal sealing plug 10 is used to plug the technical casing 11, thereby achieving the plugging of the abandoned well, with a good plugging effect.

[0077] Preferably, in this embodiment, one end of the continuous tubing 6 is fixedly connected to the upper end of the storage chamber 76, and the other end is wound around the continuous tubing lowering system 1, which can release or retract the continuous tubing 6.

[0078] It should be noted that the above-mentioned continuous tube inlet system 1 adopts existing technology, and its specific structure and principle will not be described in detail here.

[0079] Example 6

[0080] Based on the above embodiments, in this embodiment, a tree 2 is fixedly installed at the wellhead of the abandoned well, and the upper end of the tubing 8 is fixedly connected to and communicates with the lower end of the tree 2.

[0081] The scheme has a simple structure and reasonable design, and can achieve the lowering of the melting tool 7 without removing the oil well tree 2.

[0082] Based on the above scheme, a pipeline is fixedly installed on the wellhead 2, the upper end of the oil pipe 8 is connected to the lower end of the pipeline, and the continuous oil pipe 6 passes through the pipeline, that is, the melting tool 7 is directly lowered through the pipeline.

[0083] In addition, pulleys are rotatably installed on the top of the production tree 2 and at the wellhead of the abandoned well, and the coiled tubing 6 rotates and fits against the upper side of the two pulleys, which is a reasonable design.

[0084] Example 7

[0085] Based on the above embodiments, in this embodiment, an annular packer 4 is fixedly installed between the technical casing 11 and the oil pipe 8.

[0086] The scheme has a simple structure and reasonable design. The use of packer 4 can further increase the sealing effect of abandoned wells.

[0087] The packer 4 is tightly attached to the inner wall of the technical sleeve 11 to achieve a seal.

[0088] Example 8

[0089] Based on the above embodiments, in this embodiment, an intermediate sleeve 12 is also fixedly sleeved outside the technical sleeve 11.

[0090] The scheme has a simple structure and reasonable design. The intermediate casing 12 can protect the technical casing 11 and the oil pipe 8.

[0091] Based on the above scheme, the lower end of the above-mentioned technical sleeve 11 extends to the lower end of the intermediate sleeve 12.

[0092] Example 9

[0093] Based on the above embodiments, in this embodiment, a surface sleeve 5 is also fixedly sleeved outside the intermediate sleeve 12.

[0094] The scheme has a simple structure and reasonable design. The surface casing 5 can protect the intermediate casing 12, the technical casing 11 and the oil pipe 8.

[0095] Based on the above scheme, the lower end of the intermediate sleeve 12 extends to the lower end of the surface sleeve 5.

[0096] Example 10

[0097] Based on the above embodiments, this embodiment also relates to a method for sealing abandoned wells through tubing, which is implemented using the device for sealing abandoned wells through tubing as described above, and includes the following specific steps:

[0098] S1: The melting tool 7 is lowered into the sealing position inside the technical casing 11 via the oil pipe 8;

[0099] S2: The melting tool 7 releases the metal ball 9 and heats and melts the metal ball 9 to form a metal sealing plug 10.

[0100] This embodiment provides a method for sealing abandoned wells through tubing. The method is reasonably designed and can complete the sealing of abandoned wells without removing the tubing. The operation is simple. At the same time, it can form a dense metal seal, which is low in cost, has good gas tightness, and has a good sealing effect.

[0101] The working principle of this invention is as follows:

[0102] 1) The tubing melting tool 7 is lowered into the plugging position via the surface 3, the production tree 2, and the coiled tubing lowering system 1; 2) The window switch valve 72 of the tubing melting tool 7 is opened via cable to release the metal balls 9 stored inside and allow them to flow into the plugging position; 3) The downhole heater 73 is turned on via the surface control to heat the metal balls 9. After all the metal balls melt, a dense metal plug 10 is formed; 4) An evaluation experiment on the plugging of abandoned wells is conducted to complete the metal plugging of abandoned wells.

[0103] The evaluation test for the sealing of abandoned wells mentioned above is the wellhead pressure test, which involves injecting a certain amount of water into the wellhead according to the downhole pressure and pressurizing it to make the pressure-bearing capacity of the sealing layer meet the requirements. For details, please refer to the relevant drilling and completion wellhead pressure test standards.

[0104] The method provided by this invention can seal abandoned wells without removing the tubing, and the operation is simple. Simultaneously, it can form a dense metal sealing plug 10 with good gas tightness. Finally, because the properties of the metal material and the casing material are similar, the resulting metal sealing plug 10 has high bonding strength with the casing, effectively resisting creep caused by ground stress at the bottom of the well. Its construction scheme is relatively simple, and it can form a permanent, dense, stable, and reliable metal sealing plug.

[0105] In summary, the method for sealing abandoned wells through the tubing provided by this invention has the advantages of low construction cost and good sealing effect.

[0106] It should be noted that all electronic components involved in this invention adopt existing technology, and all the above-mentioned components are electrically connected to the controller, and the control circuit between the controller and each component is existing technology.

[0107] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0108] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for sealing abandoned wells through tubing, characterized in that: The system includes a tubing (8), a technical casing (11), and a melting tool (7). The technical casing (11) is vertically fixed in the abandoned well. The tubing (8) is vertically fixed inside the technical casing (11), with its upper end extending vertically upwards to the outside of the upper end of the technical casing (11). The melting tool (7) can be lowered into the technical casing (11) or the open hole via the tubing (8). After the melting tool (7) is lowered into the technical casing (11), it can release several metal balls (9) and heat and melt the metal balls (9) to make them melt into liquid metal. The liquid metal is then cooled. After solidification, a metal sealing plug (10) is formed to seal the technical sleeve (11); the melting tool (7) includes a storage chamber (76), an elastic ring (75) and a heater (73). The lower end of the storage chamber (76) is open and equipped with a window switch valve (72). Several metal balls (9) are placed inside the storage chamber (76); the heater (73) is installed at the lower end of the storage chamber (76). The elastic ring (75) includes an elastic umbrella frame and an elastic sleeve. The umbrella frame is fitted outside the heater (73), and the sleeve is fixedly fitted at the lower part of the umbrella frame.

2. The device for sealing abandoned wells via tubing according to claim 1, characterized in that: The upper end of the umbrella frame is fixedly connected to the heater (73), and its lower end is slidably connected to the heater (73); the lower end of the heater (73) is coaxially fitted with a spring (78) and a retaining ring (74), the retaining ring (74) is fixedly connected to the upper end of the spring (78), and under the elastic force of the spring (78), it abuts against the lower end of the elastic ring (75), and the elastic ring (75) can fit against the inner wall of the technical sleeve (11) under the compression of the retaining ring (74) and the spring (78).

3. The device for sealing abandoned wells through the oil pipe according to claim 1, characterized in that: The upper end of the heater (73) is connected to the lower end of the storage compartment (76) by a pin (79). When the lifting force of the pin (79) is greater than its maximum shear force, the pin (79) will break, causing the storage compartment (76) to separate from the heater (73).

4. The apparatus for sealing abandoned wells through the tubing according to any one of claims 1-3, characterized in that: It also includes a coiled tubing system (1), which is located on the formation (3) at the wellhead of the abandoned well and is connected to the melting tool (7) via a coiled tubing (6).

5. The apparatus for sealing abandoned wells through the tubing according to any one of claims 1-3, characterized in that: An oil production tree (2) is fixedly installed at the wellhead of the abandoned well, and the upper end of the oil pipe (8) is fixedly connected to and communicates with the lower end of the oil production tree (2).

6. The apparatus for sealing abandoned wells through the tubing according to any one of claims 1-3, characterized in that: An annular packer (4) is fixedly installed between the technical casing (11) and the oil pipe (8).

7. The apparatus for sealing abandoned wells through the tubing according to any one of claims 1-3, characterized in that: An intermediate sleeve (12) is also fixedly fitted outside the technical sleeve (11).

8. The device for sealing abandoned wells through the oil pipe according to claim 7, characterized in that: A surface sleeve (5) is also fixedly fitted outside the intermediate sleeve (12).

9. A method for sealing abandoned wells through tubing, characterized in that: The device for sealing abandoned wells via tubing as described in any one of claims 1-8 is used, comprising the following specific steps: S1: The melting tool (7) is lowered into the sealing position inside the technical casing (11) via the oil pipe (8); S2: The melting tool (7) releases the metal ball (9) and heats and melts the metal ball (9) to form a metal sealing plug (10).

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