Sealing device, steam injection well secondary heating system and steam injection well secondary heating process

Abstract

The invention discloses a sealing device, a steam injection well secondary heating system and a steam injection well secondary heating process, and belongs to the technical field of steam drive oil extraction. The sealing device comprises a main body, an elastic piece, a pressing and holding piece and a locking piece, the main body is provided with a first annular opening provided with the elastic piece, and one end of the pressing and holding piece seals the elastic piece in the first annular opening; the other end of the elastic piece is sealed in the interval space between the locking piece and the main body through the locking piece, and the elastic piece can laterally expand to clamp the to-be-sealed pipe fitting or restore deformation through the locking piece; the system comprises a plurality of sealing devices, an electric heating pipe, a wellhead device, a steam assembly and a pipe column assembly. The process comprises the steps of tripping the electric heating pipe and sealing simultaneously. The sealing performance of a well mouth can be improved, the good sealing effect at the steam temperature is always kept, steam cannot be leaked and sprayed out, dynamic sealing is achieved, high static sealing is kept, it is guaranteed that steam can be smoothly subjected to secondary heating at the well bottom, the comprehensive utilization rate of heat energy is also increased, and the steam drive oil extraction cost is reduced.

Description

Technical Field

[0001] This application belongs to the technical field of steam flooding oil recovery, and particularly relates to a sealing device, a steam injection well secondary heating system, and a steam injection well secondary heating process. Background Art

[0002] Steam flooding oil recovery is a thermal recovery method adopted after steam soak oil recovery in heavy oil reservoirs to further improve the recovery rate. Since steam soak oil recovery can only extract the crude oil in the oil layers near each oil well, there are still a large number of dead oil zones between the oil wells. Steam flooding oil recovery is to continuously inject high-quality steam into the oil layer from the injection well. The steam continuously heats the oil layer, thereby greatly reducing the viscosity of the formation crude oil. The steam injection system in the oilfield site has large heat losses due to factors such as boiler thermal efficiency and wellbore heat insulation, and the comprehensive utilization rate of thermal energy is less than 60%. The steam flooding injection-production limit depth is only about 1000m. For ultra-deep heavy oil reservoirs (1000 - 1700m), when implementing steam flooding and SAGD technologies, it is difficult to reach the development index requirements for the bottom hole dryness.

[0003] In the existing steam flooding oil recovery technology, the comprehensive utilization rate of thermal energy is not high, which will significantly affect the oil displacement effect. If the thermal energy utilization rate is maintained, the oil production cost will increase. To solve this problem, the Drilling and Production Research Institute of Liaohe Oilfield independently developed downhole steam secondary heating technology to achieve the purpose of increasing the downhole steam dryness. However, there are still certain difficulties in the current secondary heating technology: in the steam injection well secondary heating process, how to achieve no steam leakage and maintain a good sealing effect remains to be solved. Summary of the Invention

[0004] This application aims to at least solve the technical problem of sealing in the secondary steam heating process to a certain extent. For this purpose, this application provides a sealing device, a steam injection well secondary heating system, and a steam injection well secondary heating process, which can improve the sealing performance of the wellhead, always maintain a good sealing effect at the steam temperature during the tripping process of the coiled tubing, prevent steam from leaking and spraying out, achieve dynamic sealing, ensure that the steam can be smoothly reheated at the bottom hole, and can also maintain strong static sealing during long-term steam flooding operations to avoid steam leakage. At the same time, it improves the comprehensive utilization rate of thermal energy and reduces the steam flooding oil production cost.

[0005] In the first aspect, an embodiment of this application provides a sealing device, including:

[0006] A main body for sleeving on the pipe fitting to be sealed, and a first annular opening is provided on the inner wall of the main body in contact with the pipe fitting to be sealed;

[0007] An elastic member for sleeving on the pipe fitting to be sealed, and the elastic member is placed in the first annular opening;

[0008] A pressing member, one end of which is placed in the first annular opening to enclose the elastic member within the first annular opening, and the other end of which is exposed outside the main body. The pressing member is used to be sleeved on the pipe fitting to be sealed.

[0009] A locking member is sleeved on the main body and the pipe fitting to be sealed. There is a spaced space between the locking member and the main body. The locking member contacts the pressing member and encloses the pressing member within the spaced space. When the locking member moves relative to the main body, the locking member applies or removes a force to the pressing member, so that the elastic member expands laterally to clamp the pipe fitting to be sealed or resumes its deformation.

[0010] In an alternative embodiment, the elastic member includes a bottom pad, a sealing member, and a pressing pad. The bottom pad, the sealing member, and the pressing pad are arranged in sequence from the inner end to the opening end of the first annular opening, and the pressing pad contacts the pressing member.

[0011] In an alternative embodiment, the elastic member includes a composite of graphite and perfluoroether nanomaterials, or includes a composite of graphite, perfluoroether, and polytetrafluoroethylene nanomaterials.

[0012] In an alternative embodiment, it further includes an operating end, which is connected to the outside of the locking member. The relative movement position between the locking member and the main body can be adjusted through the operating end.

[0013] In an alternative embodiment, the locking member is provided with a detection hole, and the detection hole communicates with the spaced space.

[0014] In an alternative embodiment, it further includes a wear-resistant sleeve and a protective sleeve. A second annular opening is provided on the inner side of the locking member that contacts the pipe fitting to be sealed. The wear-resistant sleeve is sleeved in the second annular opening, and the protective sleeve encloses the wear-resistant sleeve in the second annular opening. The wear-resistant sleeve and the protective sleeve are used to be sleeved on the pipe fitting to be sealed.

[0015] In a second aspect, an embodiment of the present application provides a secondary heating system for an injection well, which includes: a plurality of the above-mentioned sealing devices, a pipe fitting to be sealed, a wellhead device, a steam assembly, and a pipe string assembly. The pipe fitting to be sealed uses an electric heating pipe. A plurality of sealing devices clamp and seal the electric heating pipe at the wellhead device. The pipe string assembly is installed below the wellhead device, and the steam assembly is connected to the pipe string assembly. The steam assembly is used to inject steam into the oil layer through the pipe string assembly.

[0016] In an alternative embodiment, the steam assembly includes a steam generating device and a steam pipeline. The steam pipeline includes an inlet pipe, an outlet pipe, and a discharge pipe. The pipe string assembly includes a sleeved heat-insulating pipe and a casing. The two ends of the inlet pipe are respectively connected to the steam generating device and the heat-insulating pipe. The outlet pipe is connected to the casing, and the discharge pipe is connected to the heat-insulating pipe. The inlet pipe is provided with an inlet valve and a steam pressure gauge. The outlet pipe is provided with an outlet valve and a casing pressure gauge. The discharge pipe is provided with a discharge valve and an oil pressure gauge.

[0017] In an alternative embodiment, the electric heating pipe has a heating section, which is arranged at the bottom end of the electric heating pipe. The heating section is used to heat the steam at the bottom of the well.

[0018] In an alternative embodiment, the electric heating tube further includes a protective tube section connected to the bottom end of the electric heating tube along the extending direction of the electric heating tube. The protective tube section is provided with alarm holes for emitting a sound under the action of the airflow that communicates air and the tube string assembly.

[0019] In a third aspect, an embodiment of the present application provides a secondary heating process for a steam injection well, which includes the following steps:

[0020] Start the wellhead device, and lower the electric heating tube into the well through the tube string assembly under the guidance of the protective tube;

[0021] Adjust the position of the locking member relative to the main body so that at least one elastic member clamps the electric heating tube to form a dynamic seal;

[0022] After the electric heating tube reaches the oil layer, adjust the position of the locking member relative to the main body so that at least one elastic member clamps the electric heating tube to form a static seal;

[0023] Start the steam production equipment to perform primary heating to generate steam, and inject the steam into the well through the tube string assembly;

[0024] Connect the electric heating tube to power, and perform secondary heating on the steam in the well through the heating section.

[0025] In an alternative embodiment, the following steps are further included:

[0026] Close the steam production equipment, and adjust the pressure in the tube string assembly to below 5 Mpa through the gas discharge valve;

[0027] Adjust the position of the locking member relative to the main body so that at least one elastic member clamps the electric heating tube to form a dynamic seal, and at the same time open the static seal;

[0028] Lift the electric heating tube until a sound is generated when the protective tube is lifted out of the wellhead device, then release the remaining pressure through the gas discharge valve, completely lift out the electric heating tube, and close the tube string assembly.

[0029] As can be seen from the above technical solutions, the beneficial effects of the present application are:

[0030] 1. The sealing device of the present application encloses the elastic member in the first annular opening of the main body through the pressing member. In this way, while the main body clamps and seals the pipe fitting to be sealed, the elastic member can play a sealing role. The pressing member can be fixed in the spaced space between the locking member and the main body by connecting the locking member to the main body. By changing the relative position relationship between the locking member and the main body, the size of the spaced space can be changed. In this way, the locking member can apply a force or remove a force on the pressing member, thereby changing the deformation of the elastic member. When the elastic member expands laterally, it can clamp the pipe fitting to be sealed tightly, so that the sealing device has a strong sealing effect. At this time, it is suitable for static sealing under long-term construction. When the elastic member restores its deformation, it can also apply a certain clamping pressure to the pipe fitting to be sealed, maintaining the seal between the elastic member and the pipe fitting to be sealed, and realizing dynamic sealing during the process of lifting and lowering the pipe fitting to be sealed. In this way, the present application can improve the sealing performance of the wellhead, maintain a good sealing effect at the steam temperature during the process of lifting and lowering the coiled tubing, prevent steam from leaking and spraying out, realize dynamic sealing, ensure that the steam can be smoothly reheated at the bottom of the well, and can also maintain a strong static seal during long-term steam flooding operations, avoid steam leakage, improve the comprehensive utilization rate of thermal energy at the same time, and reduce the cost of steam flooding oil production.

[0031] 2. The secondary heating system for steam injection wells of the present application injects steam into the pipe string assembly through the steam assembly, and reheats the steam underground through the electric heating pipe. The electric heating pipe needs to be lowered into the pipe string assembly through the wellhead device, and a seal is formed between the wellhead device and the electric heating pipe through the sealing device. Since the sealing device can adjust the clamping effect of the elastic member on the electric heating pipe, it can clamp tightly to achieve a strong static seal, and can also just clamp to achieve dynamic seal. In this way, in the steam flooding process, a good sealing effect can be maintained, providing conditions for the steam secondary heating process, and thus being able to better solve the problems of steam dryness and steam thermal energy utilization rate.

[0032] 3. In the steam flooding heating process of the present application, the electric heating pipe is lowered into the well through the wellhead device. At the same time, through the guidance of the protection pipe, it can be safely lowered into the well in alignment with the wellhead during the lowering process. Through the adjustment of the locking member, a good sealing effect can be maintained between the elastic member and the electric heating pipe, realizing dynamic seal. In this way, a good seal is maintained during the lowering process of the electric heating pipe, and the wellhead steam will not leak. After the electric heating pipe reaches the underground position, the locking member adjusts the force of the elastic member on the electric heating pipe, thereby maintaining the seal of the entire secondary heating process of the steam injection well, meeting the sealing requirements of high temperature and high pressure, being able to complete the secondary heating of the steam at the bottom of the well, and realizing the safe and risk-free lifting and lowering of the electric heater, avoiding safety accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other embodiments and drawings can also be obtained based on these drawings.

[0034] Figure 1 The schematic diagram of the embodiment of the sealing device of the present invention is shown;

[0035] Figure 2 The schematic diagram of the steps of the embodiment of the secondary heating system of the steam injection well of the present invention is shown;

[0036] Figure 3 The schematic diagram of the steps of the partial embodiment of the secondary heating system of the steam injection well of the present invention is shown;

[0037] Reference numerals: 100, secondary heating system of steam injection well; 110, sealing device; 111, main body; 111a, first annular opening; 112, elastic member; 112a, bottom pad; 112b, sealing member; 112c, pressing pad; 113, pressing member; 114, locking member; 114a, detection hole; 114b, second annular opening; 115, operating end; 116, wear-resistant sleeve; 117, sheath; 120, coiled tubing electric heater; 121, heating section; 122, protective pipe section; 122a, alarm hole; 130, wellhead device; 131, hoisting equipment; 132, injector head; 132a, chain clamping device; 132b, adjusting member; 133, guy wire; 134, leg; 135, base; 136, wellhead pipe fitting; 137, seal; 140, pipe gripper; 150, steam assembly; 151, steam generating equipment; 152, steam pipeline; 152a, inlet pipe; 152b, inlet valve; 152c, outlet pipe; 152d, outlet valve; 152e, discharge pipe; 152f, discharge valve; 153, pressure gauge; 153a, steam pressure gauge; 153b, casing pressure gauge; 153c, oil pressure gauge; 160, pipe string assembly; 161, heat-insulating pipe; 162, casing; 163, pipe string gate; 163a, main gate; 163b, auxiliary gate; 164, packer; 200, oil reservoir. Detailed implementation manners

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0039] It should be noted that all the directional indications in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0040] In the present invention, unless otherwise clearly defined and limited, the terms "connection", "fixation", etc. shall be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0041] In addition, in the present invention, descriptions such as "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0042] The following describes the present application with reference to the accompanying drawings and specific embodiments:

[0043] Please refer to Figure 1, in the embodiment of the first aspect of the present application, a sealing device 100 is provided, which includes a main body 111, an elastic member 112, a pressing member 113 and a locking member 114. The main body 111 adopts an annular structure and is used to be sleeved on the pipe fitting to be sealed. The main body 111 contacts the pipe fitting to be sealed and seals the gap therebetween. The inner wall of the main body 111 in contact with the pipe fitting to be sealed is provided with a first annular opening 111a. As shown in the figure, the first annular opening 111a is recessed from the top end inside the main body 111. The pipe fitting to be sealed is a tubular structure, such as a pipe string, a logging tool, an electric heating pipe 120, etc. In the present application, the electric heating pipe 120 is taken as an example for illustration; the elastic member 112 is made of a soft material. For example, the material of the elastic member 112 is rubber, and the elastic member 112 is also an annular structure. The elastic member 112 is used to be sleeved on the pipe fitting to be sealed. The elastic member 112 is placed in the first annular opening 111a. In this way, the elastic member 112 seals the pipe fitting to be sealed in the inner direction of the main body 111 in the first annular opening 111a. The height of the elastic member 112 is less than the depth of the first annular opening 111a; the pressing member 113 is an annular structure and is generally in a T shape. The bottom end of the pressing member 113 is placed in the first annular opening 111a and closes the elastic member 112 in the first annular opening 111a. This end fills the unfilled position in the upper part of the first annular opening 111a. The top end of the pressing member 113 is exposed outside the main body 111. The size of the top end of the pressing member 113 is larger than that of the bottom end. The pressing member 113 is used to be sleeved on the pipe fitting to be sealed. In this way, on the outer side of the pipe fitting to be sealed, an acting force can be applied to the elastic member 112 by acting on the pressing member 113.

[0044] The above-mentioned locking member 114 has an annular structure, similar to the function of a nut. The difference is that the locking member 114 is sleeved on the main body 111 and the pipe fitting to be sealed. The upper part of the locking member 114 contacts and clamps the pipe fitting to be sealed. The lower part of the locking member 114 is recessed with a threaded groove from the bottom end. The outer periphery of the main body 111 is provided with threads. In this way, the locking member 114 is threadedly connected to the main body 111. There is a spaced space between the locking member 114 and the main body 111. The locking member 114 contacts the pressing member 113 and encloses the pressing member 113 in the spaced space. As shown in the figure, the inner wall of the locking member 114 abuts against the top of the pressing member 113. For convenient positioning, a clamping groove can be provided to fix the pressing member 113. When the locking member 114 moves relative to the main body 111, the locking member 114 applies or removes a force to the pressing member 113, that is, the locking member 114 can be tightened or loosened on the main body 111 by rotation. In this way, the size of the spaced space can be changed. The locking member 114 can interact with the pressing member 113, and the pressing member 113 acts on the elastic member 112 to cause the elastic member 112 to expand laterally to clamp the pipe fitting to be sealed or restore its deformation. In an alternative embodiment, the locking member 114 is provided with a detection hole 114a, and the detection hole 114a communicates with the spaced space. The detection hole 114a is a circular small hole, and a sealing material, such as rubber, is embedded therein. When steam leaks, the detection hole 114a can be opened under a relatively small pressure, which is convenient for detecting whether there is a leak and providing a monitoring basis on site. When a leak is found, the sealing can be strengthened in time.

[0045] In the existing steam flooding for oil recovery, the comprehensive utilization rate of thermal energy is not high, which will significantly affect the oil displacement effect. In order to improve the utilization rate of thermal energy, the existing technology adopts the downhole steam secondary heating technology to improve the dryness of downhole steam. However, at present, steam leakage is likely to occur during secondary heating. This is because steam injection requires a certain pressure to maintain a steam environment with a certain pressure, and the sealing requirements are relatively high. Especially when lifting out of the wellhead, it is required that the sealing device 110 can withstand a temperature of 330 °C and a pressure of 20 Mpa, and the temperature-resistant time for steam huff and puff wells is not less than 20 days, and the steam flooding wellhead is not less than one year. This poses relatively high requirements on the sealing device 110. Once steam leakage occurs, safety accidents are likely to occur, and it is easy to cause injury by high temperature and high pressure. The existing sealing device 110 cannot meet the requirements and cannot achieve the sealing effect under long-term construction.

[0046] In this application, the elastic member 112 is enclosed within the first annular opening 111a of the main body 111 by the pressing member 113. In this way, while the main body 111 clamps and seals the pipe fitting to be sealed, the elastic member 112 can play a sealing role. The pressing member 113 can be fixed in the spaced space between the locking member 114 and the main body 111 by connecting the locking member 114 to the main body 111. By changing the relative positional relationship between the locking member 114 and the main body 111, the size of the spaced space can be changed. In this way, the locking member 114 can apply a force or remove a force on the pressing member 113, thereby changing the deformation of the elastic member 112. When the elastic member 112 expands laterally, it can clamp the pipe fitting to be sealed tightly, so that the sealing device 110 has a strong sealing effect. At this time, it is suitable for static sealing under long-term construction. When the elastic member 112 resumes its deformation, it can also apply a certain clamping pressure to the pipe fitting to be sealed, maintaining the seal between the elastic member 112 and the pipe fitting to be sealed. During the process of lifting and lowering the pipe fitting to be sealed, dynamic sealing can be achieved. In this way, this application can improve the sealing performance of the wellhead, and maintain a good sealing effect at the steam temperature during the process of lifting and lowering the coiled tubing. Steam will not leak out, realizing dynamic sealing, ensuring that steam can be smoothly reheated at the bottom of the well, and can also maintain a strong static seal during long-term steam flooding operations, avoiding steam leakage. At the same time, it improves the comprehensive utilization rate of thermal energy and reduces the cost of steam flooding oil production.

[0047] In an alternative embodiment, the elastic member 112 includes a bottom pad 112a, a sealing member 112b, and a pressing pad 112c. The bottom pad 112a, the sealing member 112b, and the pressing pad 112c are arranged in sequence from the inner end to the open end of the first annular opening 111a, and the pressing pad 112c contacts the pressing member 113. The main body 111 adopts a stainless steel chromium plating process, with the sealing member 112b embedded. The sealing member 112b is a circular ring member, and 8 - 10 circular ring members are stacked and pressed tightly by the copper bottom pad 112a and the copper pressing pad 112c. At the same time, the electric heating pipe 120 is sealed to prevent the steam at the lower end from leaking. In an alternative embodiment, the locking member 114 adopts a hammering cap nut and is threadedly connected to the main body 111. The sealing device 110 further includes an operating end 115, which is connected to the outer side of the locking member 114. The relative moving position between the locking member 114 and the main body 111 can be adjusted through the operating end 115. The operating end 115 is rod-shaped. One end of the operating end 115 is welded to the outer side wall of the locking member 114, or an insertion structure is adopted. Rotating the operating end 115 clockwise can cause the hammering cap nut to rotate downward and compress the pressing member 113, and then compress the pressing pad 112c to press the sealing member 112b tightly, achieving tight sealing. The tightness of the hammering cap nut seal can be adjusted according to the downhole steam pressure. The hammering cap nut can be struck and locked with a sledgehammer to increase the sealing strength.

[0048] In an alternative embodiment, the elastic member 112 includes a nanomaterial composite of graphite and perfluoroether, or a nanomaterial composite of graphite, perfluoroether, and polytetrafluoroethylene. Under high temperature and high pressure, strict requirements are imposed on the sealing material, and the existing sealing device 110 cannot achieve dynamic and static sealing well. Among them, for the dynamic sealing elastic member 112, a nanomaterial composite of graphite and perfluoroether is used. At high temperature, the elastic member 112 can become soft to achieve soft sealing, with a pressure resistance of 5 MPa and a temperature resistance of 330 °C. During the lowering process of the coiled tubing electrothermal tube 120, soft-sealing dynamic sealing is achieved, with wear resistance and tight sealing, ensuring the safe lowering and retrieval of the coiled tubing electrothermal tube 120 and preventing steam leakage. For the static sealing elastic member 112, a nanomaterial composite of graphite, perfluoroether, and polytetrafluoroethylene is used. It also has a certain hardness after high temperature and does not become soft, enabling hard sealing, with a pressure resistance of 25 MPa and a temperature resistance of 330 °C for long-term sealing without deformation, preventing heat from being transferred to the upper-level dynamic sealing device 110 and achieving long-term reliable sealing.

[0049] In an alternative embodiment, a wear-resistant sleeve 116 and a sheath 117 are further included. A second annular opening 114b is provided inside the locking member 114 in contact with the pipe fitting to be sealed. The wear-resistant sleeve 116 is disposed in the second annular opening 114b, and the sheath 117 encloses the wear-resistant sleeve 116 in the second annular opening 114b. The wear-resistant sleeve 116 and the sheath 117 are used to be sleeved on the pipe fitting to be sealed. Specifically, both the wear-resistant sleeve 116 and the sheath 117 are provided as annular joints. The wear-resistant sleeve 116 has a centering function. When the electrothermal tube 120 is lowered into the well, a wear-resistant material layer is coated on the inner annular wall of the wear-resistant sleeve 116. Using existing wear-resistant materials, it can play a role in centering when the electrothermal tube 120 is eccentrically worn. The sheath 117 protects the lowering channel of the coiled tubing electrothermal tube 120, with a diameter slightly larger than that of the electrothermal tube 120. Made of copper, it has a guiding and centering function, guiding the protective tube at the bottom end of the electrothermal tube 120 into the sealing device 110.

[0050] Please refer to Figure 2, in the embodiments of the second aspect of the present application, a secondary heating system 100 for steam injection wells is provided, which includes: a plurality of the above-mentioned sealing devices 110, pipe fittings to be sealed, a wellhead device 130, a steam assembly 150, and a pipe string assembly 160. The pipe fittings to be sealed use an electric heating pipe 120, which is a coiled tubing and can be continuously lowered or lifted into the well through the wellhead device 130. The wellhead device 130 uses existing wellhead equipment, including devices with various functions such as running and pulling, blowout prevention, etc., which are commonly used equipment on site. A plurality of sealing devices 110 clamp and seal the electric heating pipe 120 at the wellhead device 130. The pipe string assembly 160 is installed below the wellhead device 130. The pipe string assembly 160 is the pipe string installed in the well on site. The steam assembly 150 is connected to the pipe string assembly 160. The steam assembly 150 is used to inject steam into the oil layer 200 through the pipe string assembly 160. The steam assembly 150 is equipment and pipe fittings for generating steam and injecting steam into the pipe string. For example, a steam generator is connected to the tubing and casing 162 through a pipeline. Due to the use of a plurality of sealing devices 110, the sealing device 110 includes a main body 111, an elastic member 112, a pressing member 113, and a locking member 114. Then there are a plurality of locking members 114 and corresponding elastic members 112. By adjusting the locking member 114, the clamping force of the elastic member 112 on the electric heating pipe 120 can be realized, so as to adjust the sealing effect of the elastic member 112 on the outer circumference of the electric heating pipe 120. When dynamic sealing is required, a smaller clamping force can be adjusted so that the elastic member 112 and the electric heating pipe 120 can just be sealed, and it does not affect the lifting and lowering of the electric heating pipe 120. When static sealing is required, a larger clamping force can be adjusted so that the elastic member 112 tightly clamps the electric heating pipe 120 and fixes it relatively, preventing high-temperature and high-pressure steam from leaking at the sealing device 110.

[0051] In the existing steam flooding oil production system, the driving is carried out by injecting steam from the wellhead into the well. The steam heating system is mainly steam heating equipment on the ground. After generating steam, it is connected to the pipe string through a pipeline and the steam is directly injected into the well. However, in this steam heating method, the comprehensive utilization rate of thermal energy does not exceed 60%. The reason is that during the process of steam from the wellhead to the well bottom, heat will be dissipated to the surrounding of the wellbore in a long path. In this way, a large amount of heat is lost for the steam reaching the bottom of the well, and the steam dryness increases, which will significantly affect the oil displacement effect. If the steam temperature is directly increased on the ground, the construction cost will be significantly increased, and the problem of steam dryness cannot be well solved.

[0052] In this application, steam is injected into the tubing string assembly 160 through the steam assembly 150, and the steam in the wellbore is reheated by the electric heating pipe 120. The electric heating pipe 120 needs to be lowered into the tubing string assembly 160 through the wellhead device 130, and a seal is formed between the wellhead device 130 and the electric heating pipe 120 through the sealing device 110. Since the sealing device 110 can adjust through the elastic member 112, the clamping effect of the elastic member 112 on the electric heating pipe 120 can be adjusted, that is, it can be clamped tightly to achieve a strong static seal, or it can just be clamped to achieve a dynamic seal. In this way, a good sealing effect can be maintained in the steam flooding process, providing conditions for the steam reheating process, and thus the problems of steam dryness and steam thermal energy utilization rate can be better solved.

[0053] In an alternative embodiment, the electric heating pipe 120 has a heating section 121. The heating section 121 can adopt a resistor or other electronic devices that can be energized for heating. The heating section 121 is connected to the energizing device on the ground, such as a power source, through the internal wiring of the electric heating pipe 120. The heating section 121 is arranged at the bottom end of the electric heating pipe 120. Through the heating section 121, the steam can be reheated at the bottom of the well, so as to increase the temperature of the steam. After the heating section 121 of the electric heating pipe 120 is energized, the temperature can rise to 450 °C, and the steam is heated at the position of the oil layer 200, which is beneficial to the oil layer 200 being heated to reduce viscosity. For steam soak wells, it can increase the dryness and promote oil production. For steam flooding wells, it can increase the dryness, increase the dryness of the surrounding connected wells, reduce the viscosity, and improve the production capacity. In an alternative embodiment, the electric heating pipe 120 further includes a protection pipe section 122. The protection pipe section 122 is connected to the bottom end of the electric heating pipe 120 along the extension direction of the electric heating pipe 120. The protection pipe section 122 and the heating section 121 are fixed by welding, and a precision welding method can be used to form a weld. The protection pipe section 122 is provided with an alarm hole 122a that penetrates inside and outside. The alarm hole 122a is used to emit a sound under the action of the airflow connecting the air and the inside of the tubing string assembly 160. Specifically, a 2-mm round hole is drilled at a distance of one meter from the weld on the protection pipe as the alarm hole 122a. In this way, the electric heating pipe 120 can be detected and prompted when it exits the wellhead through the alarm hole 122a.

[0054] Please refer to Figure 3, in an alternative embodiment, the steam assembly 150 includes a steam generating device 151 and a steam pipeline 152. The steam pipeline 152 includes an intake pipe 152a, an outlet pipe 152c, and a relief pipe 152e. The tubing string assembly 160 includes a nested heat-insulating pipe 161 and a casing 162. The heat-insulating pipe 161 is a pipe fitting with a vacuum interlayer in the middle. For example, the heat-insulating pipe is designed as a double layer with a vacuum between the two layers to facilitate heat insulation. Alternatively, the heat-insulating pipe 161 is an oil pipe coated with a heat-insulating material layer, and the heat-insulating material is an existing conventional material. The casing 162 is also an existing conventional pipe fitting. In this embodiment, a flared mouth is connected to or provided at the bottom end of the heat-insulating pipe 161. The flared mouth structure is an existing conventional tool, and the edge of the lowermost heat-insulating pipe 161 expands outward to facilitate steam flow. The steam assembly 150 further includes a pressure gauge 153, which includes a steam pressure gauge 153a, an annulus pressure gauge 153b, and an oil pressure gauge 153c. Both ends of the intake pipe 152a are respectively connected to the steam generating device 151 and the heat-insulating pipe 161. The outlet pipe 152c is connected to the casing 162, and the relief pipe 152e is connected to the heat-insulating pipe 161. The above connections are all arranged in the connection manner of existing conventional pipelines. The intake pipe 152a is provided with an intake valve 152b and a steam pressure gauge 153a. The steam entering the heat-insulating pipe 161 is controlled through the intake valve 152b. The outlet pipe 152c is provided with an outlet valve 152d and an annulus pressure gauge 153b. If the annulus pressure is too high, the fluid can be discharged through the outlet valve 152d. The relief pipe 152e is provided with a relief valve 152f and an oil pressure gauge 153c. When it is necessary to relieve the pressure in the heat-insulating pipe 161, the pressure is relieved through the relief valve 152f. The above pressure gauges 153 respectively detect the pressure on the corresponding pipe fittings. In an alternative embodiment, the tubing string assembly 160 further includes a tubing string gate 163 and a packer 164. The tubing string gate 163 includes a main gate 163a and a sub-gate 163b. Both the main gate 163a and the sub-gate 163b are provided on the wellhead pipe fitting 136. In this way, the passage in the heat-insulating pipe 161 can be closed through the main gate 163a and the sub-gate 163b to prevent the internal fluid from leaking. The packer 164 is a device used in conventional oilfields and is provided between the casing 162 and the heat-insulating pipe 161 at the bottom of the well. In this way, the annulus can be sealed to facilitate steam flooding. Sometimes the sealing is not very tight. By opening the outlet valve 152d on the left side of the casing 162 and observing the annulus pressure gauge 153b, the steam pressure in the annular space between the heat-insulating pipe 161 and the casing 162 can be determined.

[0055] In an alternative embodiment, the wellhead device 130 includes a pipe handling device 131, an injector head 132, guy wires 133, legs 134, a base 135, wellhead pipe fittings 136, and a seal 137. The pipe handling device 131 uses existing equipment for pipe handling operations, which is a conventional device at the oilfield site and is used for the lifting and lowering of pipe strings. The injector head 132 is a commonly used injector head installation device at the oilfield site and is used to control the alignment of the pipe string when being lifted and lowered into the wellhead pipe fittings 136. The guy wires 133 are ropes pulled around the injector head 132. The legs 134 are rods supporting at the four bottom corners of the injector head 132. The base 135 is a plate fixed to the ground for installing the injector head 132. The wellhead pipe fittings 136 are related devices located at the wellhead on-site, including hangers, slips, etc., and also belong to the conventional wellhead device 130. The seal 137 uses a commonly used blowout preventer in the oilfield for sealing through the blowout preventer. In an alternative embodiment, the system further includes a pipe gripper 140. The pipe gripper 140 is a slip structure that clamps on the outer wall of the electric heating pipe 120 and is fixed in the wellhead pipe fittings 136, and also belongs to existing conventional parts to prevent the electric heating pipe 120 from falling.

[0056] In an alternative embodiment, the injector head 132 is provided with a chain clamping device 132a and an adjuster 132b. Both the chain clamping device 132a and the adjuster 132b use devices commonly used at oilfield wellheads. For example, the chain clamping device 132a is the chain clamping device 132a of the injector head 132 (CN200920016079.1), and the adjuster 132b uses a lifting platform driven by a hydraulic cylinder to adjust the verticality of the electric heating pipe 120. The electric heating pipe 120 is lowered into the injector head 132 through the pipe handling device 131, clamped by the chain clamping device 132a, and lowered into the upper and lower static sealing devices 110, dynamic sealing devices 110, and wellhead pipe fittings 136 until it reaches the position of the downhole oil layer 200. When lowering the electric heating pipe 120, when the head of the protection pipe enters the upper dynamic sealing device 110 of the wellhead, if there is still a deviation, the hydraulic adjustment device at the injector head 132 can be continuously adjusted for fine-tuning to make the electric heating pipe 120 of the coiled tubing enter in a vertical straight line with the wellhead pipe fittings 136, ensuring no deviation and no scraping.

[0057] In the third aspect embodiment of the present application, a steam injection well secondary heating process is provided, which includes the following steps:

[0058] S1. Start the wellhead device 130, and guide the electric heating pipe 120 through the pipe column assembly 160 into the well. Specifically, align the electric heating pipe 120 with the wellhead through the tripping device 131 to ensure accurate alignment, adjust the injection head 132 to the right position, align the chain clamping device 132a with the wellhead, and initially tighten the four tension ropes 133 without strangling them. The height of the four legs 134 can be fine-tuned to make the inclination angle of the four legs 134 consistent with the wellhead. 133 uses thread tightening to achieve fine adjustment; then the injection head 132 is precisely adjusted, and the adjustment piece 132b on the injection head 132 is used to make fine adjustments forward, backward, left and right, so that the end of the electric heating tube 120 is accurately aligned with the wellhead, so that the electric heating tube 120 of the coiled tube does not scrape the wellhead when it is lowered into the wellhead. When it just enters the chain clamping device 132a, it should be operated slowly. The protective tube connected to the end of the electric heating tube 120 is welded to the bottom of the electric heating tube 120. When the head of the protective tube enters the inlet, if there is still deviation, the hydraulic adjustment device of the injection head 132 can be adjusted to make fine adjustments, so that the electric heating tube 120 and the wellhead enter in a vertical straight line to ensure that there is no deflection or scraping. After entering the wellhead, start to slowly lower it at a uniform speed, and always pay attention to the weight of the lifting and lowering equipment 131 to prevent the downhole pipe from hanging on the wall and getting stuck. The weight has an alarm value setting, and it will automatically shut down if it exceeds the set range. There are also preset lifting and lowering forces to prevent overload in lifting and lowering, so as to protect the continuous tube heater from encountering resistance and breaking.

[0059] S2. Adjust the position of the locking piece 114 relative to the main body 111 so that at least one elastic piece 112 clamps the electric heating tube 120 to form a dynamic seal. There are multiple sealing devices 110, and at least one of the sealing devices 110 is used for dynamic sealing. For example, one sealing device 110 is used as a dynamic sealing structure, while other sealing devices 110 are not used, or all sealing devices 110 are used for dynamic sealing. During dynamic sealing, it is only necessary to adjust the locking piece 114 so that the elastic piece 112 and the electric heating tube 120 can maintain sealing under 5 MPa, so as to meet the requirements of lifting the continuous tube electric heating tube 120 with dynamic pressure under 5 MPa. Generally, safe lifting and lowering operations are performed without pressure, that is, the electric heating pipe 120 is lowered before steam is injected, and when the electric heating pipe 120 is pulled out, the steam in the well is depressurized, which can be lowered to below 5MPa. The coiled tube electric heating pipe 120 is pulled out through the dynamic sealing device 110, and the steam in the well can also be depressurized to zero, and a pressure-free operation is adopted. The wellhead dynamic sealing device 110 can be omitted, and this process is safer. It is difficult to achieve zero or very small pressure in the well. The pressure of the steam-throwing well can be relatively low. The pressure of the steam-driven well is difficult to control because of the connected well or gas channeling well. Therefore, a well-killing vehicle group is required to perform water injection and pressure reduction operations when necessary.

[0060] S3. After the electric heating pipe 120 reaches the oil layer 200, by adjusting the position of the locking member 114 relative to the main body 111, at least one elastic member 112 clamps the electric heating pipe 120 to form a static seal. After the coiled tubing electric heating pipe 120 reaches the oil layer 200 section, by rotating the locking member 114, the elastic member 112 expands laterally, strengthening the seal between the elastic member 112 and the electric heating pipe 120. The static seal can be used for long-term sealing. In an alternative embodiment, two sealing devices 110 are used, divided into upper and lower levels. The upper-level sealing device 110 is used for dynamic sealing, and the lower-level sealing device 110 is used for static sealing. The lower-level static sealing device 110 can prevent the steam heat from being transferred to the upper-level dynamic sealing device 110, achieving long-term reliable sealing. If the sealing device 110 of the static seal leaks, the sealing device 110 of the upper-level dynamic seal can also achieve the function of re-sealing, realizing short-term static sealing, with a pressure resistance of 25 MPa, allowing sufficient time for operation. By venting and relieving pressure through the steam release valve 152f at the wellhead, when the pressure inside the pipe string drops below 5 MPa, the electric heating pipe 120 can be withdrawn through the dynamic seal to prevent steam leakage and prevent accidents from occurring.

[0061] S4. Start the steam generation equipment 151 to generate steam by primary heating, and inject the steam into the wellbore through the pipe string assembly 160. For steam huff and puff wells, the running and pulling equipment 131 and the injector head 132 can be left at the well site. The injector head 132 and the chain clamping device 132a no longer clamp the electric heating pipe 120 of the coiled tubing to prevent the steam from heating up the wellhead and causing the electric heating pipe 120 to break due to the lifting force at the chain clamping device 132a. At this time, after the electric heating pipe 120 reaches the position of the oil layer 200 in the wellbore, two pipe clamps 140 are installed on the seal 137 at the wellhead to clamp the electric heating pipe 120 with appropriate force to ensure that the pipe clamps 140 do not slip off and the electric heating pipe 120 does not fall off. The injector head 132 waits for the operation of withdrawing the electric heating pipe 120 and then moves away from the well site together with the running and pulling equipment 131. Given the dryness of the boiler steam, by observing the steam pressure gauge 153a, and opening the steam release valve 152f on the right side of the heat insulation pipe 161 to observe the oil pressure gauge 153c and the casing pressure gauge 153b, the situation of injecting steam into the oil layer 200 at the bottom of the well can be analyzed.

[0062] S5. Energize the electric heating pipe 120, and use the heating section 121 to perform secondary heating on the steam in the well. For steam flooding wells, electric heating is required for a long time of 1 - 3 years. The workover rig 131 and the injector head 132 cannot be placed on the well site for a long time. At this time, after the electric heating pipe 120 is lowered to the position of the underground oil layer 200, a pipe gripper 140 is installed on the seal 137 at the wellhead to grip the electric heating pipe 120. Install two at a time with moderate force to ensure that the pipe gripper 140 does not slip off and the electric heating pipe 120 does not fall off. The pipe gripper 140 uses trapezoidal threads to frictionally tighten with the electric heating pipe 120, which does not damage the skin of the electric heating pipe 120 and can hold a weight of several tons. The two pipe grippers 140 provide double protection. The wellhead is coordinated by two cranes to detach the electric heating pipe 120 from the workover rig 131 and then separate it from the injector head 132. The electric heating pipe 120 is then connected to the power supply cabinet at the site through a high-altitude arc bracket to dock the cable and continue to supply power to the electric heating pipe 120 in the well for heating. At this time, the workover rig 131 and the injector head 132 can be removed from the well site.

[0063] In the prior art, the secondary heating process for steam injection wells is driven by injecting steam from the wellhead into the well. The steam heating system is mainly steam heating equipment on the ground. After generating steam, it is connected to the pipe string through a pipeline and the steam is directly injected into the well. For this way of injecting steam, only the equipment for producing steam needs to be connected to the pipe string to inject the steam. Although there is research on using secondary heating in the prior art, it is not easy to construct on site. In the secondary heating process, problems with sealing are likely to occur. It is required to avoid steam leakage during the process of pulling out and lowering the downhole heating equipment, and the sealing should be good when pulling out and lowering the pipe, and also good during the long-term steam flooding process. The current process does not meet the requirements.

[0064] In this application, the electric heating pipe 120 is lowered to the well through the wellhead device 130. At the same time, through the guidance of the protection pipe, it can be safely lowered to the well while aligning with the wellhead during the lowering process. Through the adjustment of the locking member 114, a good sealing effect can be maintained between the elastic member 112 and the electric heating pipe 120 to achieve dynamic sealing. In this way, good sealing is maintained during the lowering process of the electric heating pipe 120, and the wellhead steam will not leak. After the electric heating pipe 120 reaches the downhole position, the locking member 114 is used to adjust the acting force of the elastic member 112 on the electric heating pipe 120, so as to maintain the sealing of the entire secondary heating process of the steam injection well, meet the sealing requirements of high temperature and high pressure, and be able to complete the secondary heating of the steam at the bottom of the well. In this way, the electric heater can be pulled out and lowered safely without risk, avoiding safety accidents; at the same time, the temperature and pressure of the steam at the bottom of the well are increased, and the dryness is greatly improved, which is conducive to the high-temperature and high-pressure diffusion of the steam, improving the steam sweep effect and the heating efficiency of steam flooding.

[0065] In an alternative embodiment, the following steps are further included:

[0066] S6. After the secondary steam heating is completed, the steam flooding operation ends at this time. Shut down the steam generation equipment 151 to stop generating steam. Adjust the pressure in the pipe string assembly 160 to below 5 Mpa through the gas discharge valve, that is, open the gas discharge valve, and the steam is discharged through the gas discharge pipe 152e. Observe through the oil pressure gauge 153c and adjust the pressure to below the above value.

[0067] S7. Adjust the position of the locking member 114 relative to the main body 111 so that at least one elastic member 112 clamps the electric heating tube 120 to form a dynamic seal, and at the same time open the static seal. For example, by rotating the operation end 115, the spacer space is compressed, so that the locking member 114 exerts a force on the pressing member 113. The elastic member 112 is compressed in the vertical direction, and then laterally expands to exert a force for dynamic sealing on the electric heating tube 120. This force is less than the force of the static seal. Then, operate the operation end 115 of the other sealing device 110 in the reverse direction, so that the locking member 114 exits a certain distance in the loosening direction, and the elastic member 112 no longer exerts a force on the electric heating tube 120, and the static seal is opened.

[0068] S8. Lift the electric heating tube 120 until a sound is generated when the protection tube is lifted out of the wellhead device 130. Then, release the remaining pressure through the gas discharge valve, completely lift out the electric heating tube 120, and close the pipe string assembly 160. Specifically, lift the electric heating tube 120 at a relatively slow speed. When the bottom end of the electric heating tube 120 is about one meter away from the wellhead, if it is lifted out under pressure at 5 Mpa, a sound will be generated when the alarm hole 122a at the protection tube just passes the wellhead. Through the alarm hole 122a, it can be ensured that the pressure inside and outside the protection tube is the same, so that the protection tube will not be deformed or damaged under high temperature and high pressure. At this time, the weld can also be seen, indicating that it is still one meter away from getting out of the well. Then, mark the electric heating tube 120 of the coiled tubing at the position where it gets out of the well. When the electric heating tube is slowly lifted about 80 cm, close the main gate 163a to prevent steam from spraying out, and then lift out the seal 137 to complete the lifting operation.

[0069] If it is a non-pressure lifting electric heating pipe 120, open the pressure relief through the air release valve 152f until the pressure is released to zero. The static seal device 110 is in an open state, and the dynamic seal device 110 applies an appropriate force for sealing. The above-mentioned pulling-out process is the same. At the wellhead, the electric heating pipe 120 can be slowly lifted, observing the weld at a distance of one meter until there is still a distance of 1 meter. If the weld cannot be seen due to the contamination of the electric heating pipe 120 by underground oil and water, steam will not spout out after the protection pipe is pulled out because there is no pressure in the well. The main valve 163a can be quickly closed to complete the operation of pulling out the electric heating pipe 120 of the coiled tubing from the wellhead seal 137. Then, lift the electric heating pipe 120 out of the dynamic seal device 110 and close the auxiliary valve 163b to complete the pulling-out operation. The auxiliary valve 163b can also be used as a shear gate. Once the dynamic seal device 110 and the static seal device 110 fail and a serious steam leakage accident occurs at the wellhead, and the electric heater pipe is stuck at the wellhead fitting 136 and the wellhead cannot be closed, the auxiliary valve 163b, that is, the shear gate, can be closed first to cut the electric heating pipe 120 and let it fall into the bottom of the well, and then the main valve 163a is closed, and the steam will not leak. Subsequently, through operations, the electric heating pipe 120 in the well is salvaged, and finally, the electric heating pipe 120 is retrieved from the injector head 132 through the hoisting equipment 131 to complete the high-power downhole electric heating operation.

[0070] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", "optional example" or "optional implementation manner" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0071] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0072] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present application. The scope of the present application is defined by the claims and their equivalents.

Claims

1. A sealing device, characterized in that, Comprising: A main body (111) for sleeving on a pipe fitting to be sealed, and a first annular opening (111a) is provided on the inner wall of the main body (111) in contact with the pipe fitting to be sealed; An elastic member (112) for sleeving on the pipe fitting to be sealed, and the elastic member (112) is placed in the first annular opening (111a); A pressing member (113), one end of which is placed in the first annular opening (111a) to enclose the elastic member (112) in the first annular opening (111a), and the other end is exposed outside the main body (111), and the pressing member (113) is for sleeving on the pipe fitting to be sealed; A locking member (114) sleeved on the main body (111) and the pipe fitting to be sealed, and there is a spaced space between the locking member (114) and the main body (111), the locking member (114) contacts the pressing member (113) and encloses the pressing member (113) in the spaced space; when the locking member (114) moves relative to the main body (111), the locking member (114) applies or removes a force to the pressing member (113) so that the elastic member (112) expands laterally to clamp the pipe fitting to be sealed or restores its deformation.

2. The sealing device according to claim 1, characterized in that The elastic member (112) includes a bottom pad (112a), a sealing member (112b) and a pressing pad (112c), and the bottom pad (112a), the sealing member (112b) and the pressing pad (112c) are arranged in sequence from the inner end to the open end of the first annular opening (111a), and the pressing pad (112c) contacts the pressing member (113).

3. The sealing device according to claim 1 or 2, characterized in that The elastic member (112) includes a nano-material composite of graphite and perfluoroether, or includes a nano-material composite of graphite, perfluoroether and polytetrafluoroethylene.

4. The sealing device according to claim 1, characterized in that, It further includes an operating end (115) connected to the outside of the locking member (114), and the relative moving position between the locking member (114) and the main body (111) can be adjusted through the operating end (115).

5. The sealing device according to claim 1, characterized in that, The locking member (114) is provided with a detection hole (114a), and the detection hole (114a) communicates with the spaced space.

6. The sealing device according to claim 1, characterized in that, It further includes a wear-resistant sleeve (116) and a sheath (117), a second annular opening (114b) is provided on the inner side of the locking member (114) in contact with the pipe fitting to be sealed, the wear-resistant sleeve (116) is arranged in the second annular opening (114b), and the sheath (117) encloses the wear-resistant sleeve (116) in the second annular opening (114b), and the wear-resistant sleeve (116) and the sheath (117) are for sleeving on the pipe fitting to be sealed.

7. Steam injection well secondary heating system, characterized in that, Comprising: A plurality of the sealing devices, the pipe fittings to be sealed, the wellhead device (130), the steam assembly (150), and the pipe string assembly (160) according to any one of claims 1-6, wherein the pipe fittings to be sealed adopt an electric heating pipe (120), and a plurality of the sealing devices clamp and seal the electric heating pipe (120) at the wellhead device (130), the pipe string assembly (160) is installed below the wellhead device (130), the steam assembly (150) is communicated with the pipe string assembly (160), and the steam assembly (150) is used to inject steam into the oil layer (200) through the pipe string assembly (160).

8. The steam injection well secondary heating system according to claim 7, characterized in that, The steam assembly (150) includes a steam generating device (151) and a steam pipeline (152), the steam pipeline (152) includes an intake pipe (152a), an outlet pipe (152c), and a discharge pipe (152e), the pipe string assembly (160) includes a sleeved heat insulation pipe (161) and a casing (162), two ends of the intake pipe (152a) are respectively communicated with the steam generating device (151) and the heat insulation pipe (161), the outlet pipe (152c) is communicated with the casing (162), the discharge pipe (152e) is communicated with the heat insulation pipe (161), the intake pipe (152a) is provided with an intake valve (152b) and a steam pressure gauge (153a), the outlet pipe (152c) is provided with an outlet valve (152d) and an annulus pressure gauge (153b), and the discharge pipe (152e) is provided with a discharge valve (152f) and an oil pressure gauge (153c).

9. The steam injection well secondary heating system according to claim 8, wherein The electric heating pipe (120) has a heating section (121), and the heating section (121) is arranged at the bottom end of the electric heating pipe (120) and is used for heating steam at the bottom of the well.

10. The steam injection well secondary heating system according to claim 8, wherein, The electric heating pipe (120) further includes a protective pipe section (122), which is connected to the bottom end of the electric heating pipe (120) along the extending direction of the electric heating pipe (120), and the protective pipe section (122) is provided with an alarm hole (122a), and the alarm hole (122a) is used for emitting a sound under the action of the airflow that connects air and the inside of the pipe string assembly (160).

11. A secondary heating process for steam injection wells, characterized in that, Including the following steps: Start the wellhead device (130), and lower the electric heating pipe (120) into the well through the pipe string assembly (160) under the guidance of the protective pipe; Adjust the position of the locking member (114) relative to the main body (111) so that at least one of the elastic members (112) clamps the electric heating pipe (120) to form a dynamic seal; After the electric heating pipe (120) reaches the oil layer (200), adjust the position of the locking member (114) relative to the main body (111) so that at least one of the elastic members (112) clamps the electric heating pipe (120) to form a static seal; Start the steam generating device (151) to generate steam by primary heating, and inject the steam into the well through the pipe string assembly (160); Electrically connect the electric heating pipe (120), and perform secondary heating on the steam in the well through the heating section (121).

12. The secondary heating process for steam injection wells according to claim 11, characterized in that, Further including the following steps: Shut down the steam generating device (151), and adjust the pressure in the pipe string assembly (160) to below 5 Mpa through the air discharge valve; Adjust the position of the locking member (114) relative to the main body (111) so that at least one of the elastic members (112) clamps the electric heating tube (120) to form a dynamic seal, and at the same time open the static seal; Lift the electric heating tube (120) until a sound is generated when the protective tube is pulled out of the wellhead device (130), then release the remaining pressure through the air discharge valve, completely pull out the electric heating tube (120), and close the pipe string assembly (160).

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