Underground electric heating steam generator and steam generation system

Abstract

The invention provides an underground electric heating steam generator and a steam generation system, and belongs to the field of oil and gas field exploitation. The underground electric heating steam generator comprises an underground steam generating mechanism, the underground steam generating mechanism comprises an outer protective pipe and a plurality of heating pipes, the heating pipes are arranged in the outer protective pipe, and a first cavity is formed between the inner wall of the outer protective pipe and the outer walls of the heating pipes; the heating pipe comprises a heating body, and the heating body comprises a wire section and a heating section which are integrally formed; the underground electric heating steam generating system comprises an underground electric heating steam generator, a power adjusting device, a parameter collecting device, a hydroelectric sealing device, a water purifying device and a high-pressure bearing sealing wellhead. Steam is obtained underground, the problem of heat loss caused by ground steam conveying is solved, and the dryness of the steam is guaranteed; steam is obtained by electrically heating the heating body, and the technical problem that a large amount of carbon dioxide is generated due to the fact that a coal-fired boiler obtains steam is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field exploitation, and in particular to a downhole electric heating steam generator and a downhole electric heating steam generating system. Background Art

[0002] Currently, thermal recovery of heavy oil in oilfields primarily involves steam stimulation, steam flooding, and steam-assisted gravity drainage (SAGD). Steam is generated from gas-fired boilers at surface steam stations. Water is heated in gas-fired boilers to steam, which is then transported via surface steam pipelines to the injection wellheads. From there, it is delivered downhole through tubing in each injection well to the target formation, where the high-temperature steam reduces crude oil viscosity for heavy oil recovery or displacement. However, steam generation from gas-fired boilers and delivery of steam downhole via surface steam pipelines present several challenges. First, heat losses along the way are significant, resulting in a comprehensive thermal energy utilization rate of 60% to 70%. Second, effective development of medium- and deep-layer formations is difficult, with surface steam injection pipelines experiencing a 5% to 15% loss in steam quality and a 20% to 30% loss in wellbore quality. Furthermore, at conventional steam injection rates, the pressure differential between injection and production is large, hindering the formation and expansion of steam cavities and potentially causing steam cross-flow between injection and production wells. Therefore, steam injection rates should be minimized to minimize the pressure differential, but this also results in low bottomhole steam quality. Taking all the above factors into consideration, the steam dryness at the bottom of the well often cannot reach 50%, making it difficult to achieve efficient utilization of deep heavy oil; thirdly, the steam injection boilers used for heavy oil extraction mainly use natural gas and coal as fuel, which will produce a large amount of carbon dioxide during the combustion process, affecting the global environment. Summary of the Invention

[0003] To address one of the above-mentioned technical deficiencies, the present invention provides a downhole electrically heated steam generator and a downhole electrically heated steam generation system. The downhole electrically heated steam generator comprises a heating tube disposed downhole. The heating tube generates heat by receiving electrical energy from a surface power supply, which in turn heats water filled outside the heating tube to produce steam. On the one hand, the present invention generates steam downhole, thereby resolving the problem of heat loss caused by steam transport from the surface and ensuring the dryness of the steam. On the other hand, the present invention generates steam through electrical heating, resolving the technical problem of coal-fired boilers generating large amounts of carbon dioxide when generating steam. The present invention can produce steam with good quality parameters, ensuring the efficiency of heavy oil extraction without harming the environment.

[0004] A first aspect of the present invention provides a downhole electric heating steam generator, comprising: a downhole steam generating mechanism, the downhole steam generating mechanism comprising: an outer protective tube and a plurality of heating tubes, the plurality of heating tubes being disposed within the outer protective tube, a first cavity being formed between an inner wall of the outer protective tube and outer walls of the plurality of heating tubes, the first cavity being filled with water; The heating tube includes a heating element, and the heating element includes: an integrally formed wire segment and a heating segment, wherein the wire segment is located at the upper end of the heating element, and the heating segment is located at the lower end of the heating element; The upper end of the wire segment is connected to the power supply on the well for receiving the power from the power supply, and the lower end of the wire segment is connected to the upper end of the heating segment for transmitting the power from the power supply to the heating segment; The heating section generates heat under the action of the electric energy of the power supply, and heats the water in the area of ​​the first cavity corresponding to the heating section into steam.

[0005] In an embodiment of the present invention, the heating tube further comprises: a heat conductive protection tube, wherein the heating element is located inside the heat conductive protection tube; The first cavity is formed between the inner wall of the outer protective tube and the outer wall of the heat conductive protective tube of each heating tube.

[0006] In an embodiment of the present invention, the heating tube further comprises an insulating filling medium, and the insulating filling medium comprises: a first insulating material and a second insulating material; The first insulating material is filled between the outer wall of the wire segment and the inner wall of the thermal protection tube; The second insulating material is filled between the outer wall of the heating section and the inner wall of the thermal protection tube to provide insulation and heat conduction, while also ensuring that the high-temperature transmission wire and the high-temperature resistance wire are not in contact with the outside world.

[0007] In an embodiment of the present invention, the heating section in the heating element is a resistance wire.

[0008] In an embodiment of the present invention, the downhole steam generating mechanism further comprises: a high-temperature connector; The high-temperature connector is arranged inside the outer protective tube, and the high-temperature connector is located at the bottom of the heating tube; The high-temperature connector is used to connect the lower ends of the heating sections of multiple heating elements into one.

[0009] In an embodiment of the present invention, the inner wall of the outer protective tube is provided with a swirl groove, and the swirl groove is spirally arranged on the inner wall of the outer protective tube; The upper end of the swirl groove is flush with the upper end of the heating section, and the lower end of the swirl groove is flush with the bottom of the heating section.

[0010] The swirl groove is used to speed up the water supply. The injected water is injected in a rotating form along the spiral channel of the swirl groove, thereby improving the liquid disturbance performance while fully exchanging heat with the outer walls of the three heating tubes.

[0011] In an embodiment of the present invention, the downhole steam generating mechanism further comprises: a flow control device, the flow control device being disposed in the first cavity, the bottom of the flow control device being flush with the bottom of the conductor segment; The flow control device is used to unidirectionally conduct water in the first cavity from the direction of the wire segment to the direction of the heating segment.

[0012] In an embodiment of the present invention, the downhole electric heating steam generator further comprises: a surface connection device, the surface connection device comprising: a plurality of power supply cables, one power supply cable corresponding to one heating element, each power supply cable being integrally formed with the corresponding heating element; The first end of the power supply cable is connected to the power supply source above the well, and the second end of the power supply cable is connected to the upper end of the wire segment of the heating element.

[0013] In an embodiment of the present invention, the ground connection device further includes: a cable protection tube, and the cable protection tube is integrally formed with the outer protective tube.

[0014] A second aspect of the present invention provides a downhole electrically heated steam generating system, the system comprising the downhole electrically heated steam generator as described above.

[0015] In an embodiment of the present invention, the downhole electric heating steam generation system also includes: a power regulation device, which is arranged on the ground, and a power supply is provided in the power regulation device. The power regulation device is connected to the upper end of the conductor segment of the downhole electric heating steam generator, and is used to provide electrical energy to the conductor segment.

[0016] In an embodiment of the present invention, the downhole electric heating steam generation system further comprises: a parameter acquisition device; The parameter acquisition device is arranged in the first cavity and is used to acquire parameter information of the steam generated by the downhole electric heating steam generator.

[0017] In an embodiment of the present invention, the power regulating device is connected to the parameter collecting device, and is used to receive steam parameter information collected from the parameter collecting device, and control the power supply to adjust the output power parameters according to the steam parameter information.

[0018] In an embodiment of the present invention, the parameter acquisition device includes: a signal transmission unit and a parameter acquisition unit; The signal transmission unit is arranged in the first cavity of the downhole electric heating steam generator, and the lower end of the signal transmission unit passes through the bottom of the heating pipe; The parameter acquisition unit is installed at the lower end of the signal transmission unit and is used to acquire parameter information of the steam generated by the downhole electric heating steam generator; The signal transmission unit is used to transmit the steam parameter information collected by the parameter collection unit to the ground.

[0019] In an embodiment of the present invention, the parameter acquisition unit includes: a pressure sensor and a temperature sensor; The pressure sensor is used to collect the pressure value of the steam generated by the downhole electric heating steam generator; The temperature sensor is used to collect the temperature value of the steam generated by the downhole electric heating steam generator.

[0020] In an embodiment of the present invention, the parameter acquisition device further includes: a sealing tube, wherein the sealing tube is used to wrap the signal transmission unit.

[0021] In an embodiment of the present invention, the downhole electric heating steam generation system further comprises: a water-electric sealing device, the water-electric sealing device comprising: a first water injection channel and a plurality of first cable channels, the first water injection channel and the plurality of first cable channels being isolated from each other; The first water injection channel is used to inject water into the first cavity of the downhole electric heating steam generator; The first cable channel is used to accommodate the multiple power supply cables so as to connect the multiple power supply cables to the heating element.

[0022] In an embodiment of the present invention, the downhole electric heating steam generation system further comprises: a water purification device, the output end of the water purification device being connected to the input end of the first water injection channel of the hydroelectric sealing device via a water pipeline; The water purification device is used to pre-purify the water entering the first cavity. It is used for filtering, deoxygenating, and reverse osmosis of the injected water, removing soluble magnesium and calcium salts from the water, fully reducing the water hardness, and preventing scaling and corrosion on the outer wall of the protective tube inside the underground electric steam generator, ensuring the long-term and efficient operation of the three heating tubes and extending their service life.

[0023] In an embodiment of the present invention, the downhole electric heating steam generation system further comprises: a high-pressure bearing sealed wellhead, the upper end of the high-pressure bearing sealed wellhead being connected to the lower end of the hydroelectric sealing device; The high-pressure bearing sealed wellhead includes: a second water injection channel and a plurality of second cable channels; The second water injection channel is in communication with the first water injection channel, and the plurality of second cable channels are in communication with the plurality of first cable channels respectively.

[0024] In an embodiment of the present invention, a second cavity is provided between the outer protective tube and the downhole casing; The high-pressure bearing sealed wellhead further comprises: a nitrogen injection channel, the output end of which is in communication with the second cavity and is used for injecting nitrogen into the second cavity.

[0025] As an inert gas, nitrogen has good stability, is safe to use, and has a heat-insulating effect, effectively preventing high-temperature and high-pressure steam from rising from the bottom of the well.

[0026] The downhole electric steam generator utilizes a heating tube installed underground. The heating tube receives electricity from an aboveground power source to generate heat, which in turn heats water contained within the heating tube, thereby generating steam. This method generates steam underground, eliminating the heat loss associated with surface steam transportation and ensuring steam dryness. Furthermore, the method utilizes electric heating to generate steam, eliminating the technical issue of coal-fired boilers generating large amounts of carbon dioxide. This method produces steam with excellent quality parameters, ensuring efficient heavy oil extraction without compromising the environment.

[0027] Other features and advantages of the technical solution of the present invention will be described in detail in the specific implementation section below. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 Schematic diagram of the structure of a downhole electric heating steam generation system provided by an embodiment of the present invention; Figure 2 1 is a schematic structural diagram of a downhole steam generating mechanism provided by an embodiment of the present invention; Figure 3 is a cross-sectional view of a heating section of a downhole steam generating mechanism provided by an embodiment of the present invention; Figure 4 It is a cross-sectional view of the steam outlet of the downhole steam generating mechanism provided in an embodiment of the present invention.

[0029] Description of Reference Numerals 1-downhole steam generating mechanism, 11-outer protective pipe, 111-swirl groove, 12-heating tube, 121-heating element, 1211-wire segment, 1212-heating segment, 122-thermal protection tube, 123-first insulating material, 124-second insulating material, 13-first cavity, 14-high-temperature connector, 15-flow control device, 16-steam outlet, 2-parameter acquisition device, 3-ground connection device, 4-hydroelectric sealing device, 5-water purification device, 6-high-pressure bearing sealed wellhead, 61-nitrogen injection channel, 7-power regulation device, 8-second cavity, 9-injected oil layer. DETAILED DESCRIPTION

[0030] To make the technical solutions and advantages of the embodiments of the present invention more clearly understood, exemplary embodiments of the present invention are further described in detail below with reference to the accompanying drawings. It should be noted that the embodiments described are only a portion of the embodiments of the present invention, and are not an exhaustive list of all embodiments. It should be noted that the embodiments of the present invention and the features thereof may be combined with each other unless they conflict.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0033] In the present invention, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood broadly. For example, they may refer to fixed or detachable connections, or integration; mechanical or electrical connections, or communication; direct or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0034] During the development of this invention, the inventors discovered that currently, heavy oil thermal recovery in oilfields primarily involves steam stimulation, steam flooding, and steam-assisted gravity drainage. Steam is generated from gas-fired boilers at surface steam stations. Water is heated in gas-fired boilers to steam, which is then transported to the injection wellheads via surface steam pipelines. From there, it is delivered to the target formation downhole via tubing within each injection well. High-temperature steam is used to reduce crude oil viscosity for heavy oil recovery or displacement. However, steam generation from gas-fired boilers and delivery of steam downhole via surface steam pipelines present the following challenges: First, significant heat losses along the way, resulting in a comprehensive thermal energy utilization rate of 60% to 70%. Second, effective development of medium- and deep-layer formations is difficult, with surface steam injection pipelines experiencing a 5% to 15% loss in steam quality and a 20% to 30% loss in wellbore quality. Furthermore, at conventional steam injection rates, the pressure differential between injection and production is significant, hindering the formation and expansion of steam cavities and potentially causing steam cross-talk between injection and production wells. Therefore, during development, the steam injection rate should be minimized to reduce the pressure differential, but this also results in low steam quality downhole. Taking all the above factors into consideration, the steam dryness at the bottom of the well often cannot reach 50%, making it difficult to achieve efficient utilization of deep heavy oil; thirdly, the steam injection boilers used for heavy oil extraction mainly use natural gas and coal as fuel, which will produce a large amount of carbon dioxide during the combustion process, affecting the global environment.

[0035] In response to the above problems, an embodiment of the present invention provides a downhole electric heating steam generator, comprising: a downhole steam generating mechanism, the downhole steam generating mechanism comprising: an outer protective tube and a plurality of heating tubes, the heating tubes being arranged inside the outer protective tube, a first cavity being formed between the inner wall of the outer protective tube and the outer wall of each heating tube, the first cavity being filled with water; the heating tubes comprising a heating element, the heating element comprising: an integrally formed wire segment and a heating segment, the wire segment being located at the upper end of the heating element, and the heating segment being located at the lower end of the heating element; the upper end of the wire segment being connected to an uphole power supply for receiving electric energy from the power supply, the lower end of the wire segment being connected to an upper end of the heating segment for transmitting electric energy from the power supply to the heating segment; the heating segment being heated under the action of the electric energy from the power supply, heating the water in the area corresponding to the heating segment in the first cavity into steam. The downhole electric steam generator utilizes a heating tube installed underground. The heating tube receives electricity from an aboveground power source to generate heat, which in turn heats water contained within the heating tube, thereby generating steam. This method generates steam underground, eliminating the heat loss associated with surface steam transportation and ensuring steam dryness. Furthermore, the method utilizes electric heating to generate steam, eliminating the technical issue of coal-fired boilers generating large amounts of carbon dioxide. This method produces steam with excellent quality parameters, ensuring efficient heavy oil extraction without compromising the environment.

[0036] Figure 1 Schematic diagram of the structure of the underground electric heating steam generation system provided by the embodiment of the present invention. Figure 1As shown, this embodiment provides an underground electric heating steam generating system, comprising: an underground electric heating steam generator, a hydroelectric sealing device 4, a water purification device 5 and a parameter acquisition device 2, wherein the underground electric heating steam generator comprises: an underground steam generating mechanism 1 and a ground connection device 3; the underground electric heating steam generating system comprises an underground device and multiple ground devices, wherein the underground device is a underground steam generating mechanism 1, and the ground device comprises: a ground connection device 3, a hydroelectric sealing device 4, a water purification device 5 and a high-pressure load-bearing sealed wellhead 6.

[0037] Specifically, the specific structure of the underground electric heating steam generator is as follows: Figure 2 is a structural diagram of a downhole steam generating mechanism provided by an embodiment of the present invention, Figure 3 is a cross-sectional view of a heating section of a downhole steam generating mechanism provided by an embodiment of the present invention, Figure 4 : is a cross-sectional view of the steam outlet of the downhole steam generating mechanism provided by an embodiment of the present invention, as shown in FIG. Figure 2-4 As shown, in this embodiment, the downhole steam generating mechanism 1 includes: an outer protective tube 11 and a plurality of heating tubes 12, wherein the heating tubes 12 are arranged inside the outer protective tube 11, and a first cavity 13 is formed between the inner wall of the outer protective tube 11 and the outer walls of the plurality of heating tubes 12, and the first cavity 13 is filled with water; Furthermore, the heating tube 12 is provided with a heating element 121. This element 121 comprises an integrally formed conductor segment 1211 and a heating segment 1212. Conductor segment 1211 is located at the upper end of the heating element 121, while heating segment 1212 is located at the lower end. The upper end of conductor segment 1211 is connected to a power source above the wellbore to receive power from the power source, while the lower end of conductor segment 1211 is connected to the upper end of heating segment 1212 to transmit power from the power source to heating segment 1212. The heating segment 1212 generates heat from the power source, heating the water in the area of ​​the first cavity 13 corresponding to the heating segment 1212 to produce the high-quality steam required for reservoir development. The high-quality steam is ejected from the steam outlet 16 of the downhole steam generating mechanism 1 into the oil layer 9 (i.e., the target layer for oil production). Specifically, the heat generated by the heating segment 1212 is used to heat the water in the corresponding annular area of ​​the first cavity 13. In this embodiment, the wire segment 1211 and the heating segment 1212 are connected by a connector and welded and smoothed, so that the wire segment 1211 and the heating segment 1212 are integrally formed. The heating element 121 provided by the present invention does not need to be connected by a cable or other connector through a detachable downhole plug-in technology to connect the conductive part to the resistive heating part, thereby ensuring the safety and reliability of the downhole electric heating steam generator, and solving the problem in the prior art that the heating segment and the wire segment 1211 are connected by threads and cannot guarantee a long service life. In addition, the integrally formed wire segment 1211 and the heating segment 1212 can ensure the pressure resistance of the heating element 121. The water in the first cavity 13 can not only fully contact the outer wall surface of the thermal protection tube 122 in the three heating tubes 12 to achieve the best heat exchange effect, but also fully cool the wire segment 1211 in the middle and upper part, carry the heat generated by the high-temperature wire to the downhole, and improve the overall energy utilization rate. Water begins to vaporize in the middle of the heating section, and generates saturated wet steam that meets the dryness index at the steam outlet 16.

[0038] Furthermore, the present invention heats the water injected from the surface directly at the bottom of the well into wet saturated steam of the required dryness, significantly increasing the dryness of the downhole steam. This improves the overall thermal energy utilization of the steam injection system for reservoir development, effectively resolving the development challenges of mid- to deep-layer steam flooding and steam-assisted gravity drainage technologies.

[0039] In this embodiment, the heating tube 12 further includes: a thermally conductive protective tube 122, the heating element 121 is located inside the thermally conductive protective tube 122; the first cavity 13 is formed between the inner wall of the outer protective tube 11 and the outer wall of the thermally conductive protective tube 122 of each heating tube 12. The heating section 1212 of the heating element 121 transmits the wire to the outer thermally conductive protective tube 122, and the thermally conductive protective tube 122 heats the water in the first cavity 13 according to the heat transmitted by the heating section 1212, heating it into dry steam required for oil reservoir development. In this embodiment, on the one hand, the thermally conductive protective tube 122 has the function of conducting heat and dissipating heat into the water in the first cavity 13; on the other hand, the thermally conductive protective tube 122 is used to protect the heating element 121 placed inside.

[0040] In this embodiment, the heating tube 12 further includes an insulating filling medium, comprising a first insulating material 123 and a second insulating material 124. The first insulating material 123 is filled between the outer wall of the wire segment 1211 and the inner wall of the thermally conductive protective tube 122; the second insulating material 124 is filled between the outer wall of the heating segment 1212 and the inner wall of the thermally conductive protective tube 122. In this embodiment, the first insulating material 123 and the second insulating material 124 are mineral insulating materials, which provide both insulation and thermal conductivity, thereby protecting the wire segment 1211 and the heating segment 1212 from external contact.

[0041] In this embodiment, the heating section 1212 is a resistance wire.

[0042] In this embodiment, a high-temperature connector 14 is further provided at the bottom of the downhole steam generating mechanism 1; the high-temperature connector 14 is provided inside the outer protective tube 11 and at the bottom of the heating tube 12; the high-temperature connector 14 is used to connect the lower ends of the heating sections 1212 of multiple heating elements 121 into one. Specifically, the high-temperature connector 14 is used to connect the lower ends of the heating sections 1212 of each heating element 121 in a star shape. The high-temperature connector 14 is used to ensure that the heating sections 1212 of the multiple heating elements 121 generate heat stably and evenly.

[0043] Through the heating element 121 provided in this embodiment, the downhole electric heating steam generator provided by the present invention achieves the purpose of extreme cooling and heat dissipation. Specifically, the outer wall surface of the thermally conductive protective tube 122 of the multiple heating tubes 12 and the inner wall surface of the outer protective tube 11 form a first cavity 13. The first cavity 13 is a water injection channel, which is lowered into the casing to complete the well. The water can not only fully contact the outer wall surface of the protective tube of the three heating tubes 12 to achieve the best heat exchange effect, but also fully cool the conductor segment 1211 in the middle and upper part, carrying the heat generated by the high-temperature conductor to the underground to improve the overall energy utilization rate. The water begins to vaporize in the middle of the heating section, generating saturated wet steam that meets the dryness index at the outlet.

[0044] In this embodiment, a swirl groove 111 is provided on the inner wall of the outer protective tube 11 . The swirl groove 111 is spirally arranged on the inner wall of the outer protective tube 11 .

[0045] Furthermore, the upper end of the swirl groove 111 is flush with the upper end of the heating section 1212, and the lower end of the swirl groove 111 is flush with the bottom of the heating section 1212. The position of the swirl groove 111 corresponds to the heating section 1212. In this embodiment, the injected water is injected into the first cavity 13 along the swirl groove 111 in a rotating form, which can improve the liquid disturbance performance while ensuring that the injected water exchanges heat with the outer wall surfaces of the multiple thermal protection tubes 122. The swirl groove 111 is used to speed up the water supply, and the injected water is injected in a rotating form along the spiral channel of the swirl groove 111, which improves the liquid disturbance performance while fully exchanging heat with the outer wall surfaces of the thermal protection tubes 122 corresponding to the heating sections 1212 of the three heating tubes 12.

[0046] In this embodiment, the heating tube 12 further includes a flow control device 15 disposed within the first cavity 13. The bottom of the flow control device 15 is flush with the bottom of the wire segment 1211. The flow control device 15 is configured to unidirectionally conduct water within the first cavity 113 from the direction of the wire segment 1211 to the heating segment 1212. The flow control device 15 is configured to unidirectionally conduct water within the first cavity 13, and the conduction direction of the flow control device 15 is from the direction of the wire segment 1211 to the heating segment 1212.

[0047] Specifically, the flow control device 15 is a one-way conduction valve, which can ensure that the water in the first cavity 13 flows from the direction of the wire segment 1211 to the direction of the heating segment 1212, so that the heating segment 1212 generates continuous and stable steam, and the bottom of the flow control device 15 is flush with the bottom of the wire segment 1211, which can prevent the steam generated in the first cavity 13 corresponding to the heating segment 1212 from moving into the first cavity 13 corresponding to the wire segment 1211 when the pressure suddenly increases, thereby damaging the downhole steam generating mechanism 1.

[0048] In this embodiment, the downhole electric steam generator further includes a surface connection device 3, which includes a plurality of power supply cables, one power supply cable corresponding to each heating element 121, each power supply cable being integrally formed with the corresponding heating element 121; each power supply cable being integrally formed with each heating element 121; a first end of each power supply cable being connected to an uphole power supply, and a second end of each power supply cable being connected to the upper end of a wire segment 1211 of the heating element 121. The surface connection device 3 further includes a cable protection tube, which is integrally formed with the outer protective tube 11.

[0049] In this embodiment, the downhole electric heating steam generator also includes: a power regulating device 7, the power supply is located in the power regulating device 7, the power regulating device 7 is arranged above the well, and the power regulating device 7 is connected to the upper end of the conductor segment 1211, for providing electrical energy to the conductor segment 1211.

[0050] In this embodiment, the downhole electrically heated steam generation system further includes: a parameter acquisition device 2; the parameter acquisition device 2 is disposed within the first cavity 13 and is used to acquire parameter information of the steam generated by the downhole electrically heated steam generator. The parameter acquisition device 2 includes: a signal transmission unit and a parameter acquisition unit; the signal transmission unit is disposed within the first cavity 13, and the lower end of the signal transmission unit passes through the bottom of the heating tube 12; the parameter acquisition unit is mounted at the lower end of the signal transmission unit; the parameter acquisition unit is used to acquire parameter information of the steam generated by the downhole electrically heated steam generator; the signal transmission unit is used to transmit the steam parameter information acquired by the parameter acquisition unit to the surface.

[0051] In this embodiment, the parameter acquisition device 2 is a pressure and temperature sensor test device. The pressure and temperature sensor test device extends through a signal transmission unit into the bottom of the integrated heating tube to the steam generating area at the bottom of the downhole electric steam generator, and is used to measure the temperature and pressure of the steam generated by the downhole electric steam generator in real time. Specifically, the parameter acquisition unit includes: a pressure sensor and a temperature sensor; The pressure sensor is used to collect the pressure value of the steam generated by the downhole electric heating steam generator; the temperature sensor is used to collect the temperature value of the steam generated by the downhole electric heating steam generator.

[0052] In this embodiment, the parameter acquisition device 2 further includes a sealing tube, which is used to wrap the signal transmission unit. Furthermore, the sealing tube is used to protect the signal transmission unit and seal the signal transmission unit.

[0053] In this embodiment, the power regulating device 7 is connected to the parameter acquisition device 2, and is used to receive the parameter information of the steam collected from the parameter acquisition device 2, and control the power supply to adjust the parameters of the output electric energy according to the parameter information of the steam. Specifically, the power regulating device 7 is also connected to the signal transmission unit of the parameter acquisition device 2, and receives the parameter signal of the steam collected from the parameter acquisition unit through the signal transmission unit. The power regulating device 7 adjusts the electric energy parameters of the power supply cable supplied to the ground connection device 3 according to the parameter signal of the steam collected by the parameter acquisition unit, so as to adjust the heating value of the downhole heating element 121. Furthermore, the adjustment of the electric energy parameters of the power supply cable includes: adjusting the electric heating power, electric heating method and electric heating time of the power supply.

[0054] In this embodiment, the materials used for various components of the downhole electric steam generator are heat-resistant and pressure-resistant. Specifically, the conductor segment 1211 is made of a copper core, the wall of the thermal protection tube 122, its sealing head, connector, and sealing strip are made of high-temperature-resistant alloy steel, and the resistance wire of the heating segment 1212 is made of a nickel-chromium alloy, a high-temperature-resistant resistor material.

[0055] In this embodiment, the outer protective tube 11 and the cable protection tube are made of flexible materials.

[0056] In this embodiment, the water and electricity sealing device 4 includes: a first water injection channel and a plurality of first cable channels, wherein the first water injection channel and the plurality of first cable channels are isolated from each other; The first water injection channel is used to inject water into the first cavity 13 of the downhole steam generating mechanism 1; The multiple first cable channels are used to accommodate multiple power supply cables of the downhole electric heating steam generator, so that the multiple power supply cables are connected to the heating body 121.

[0057] In this embodiment, the output end of the water purification device 5 is connected to the input end of the first water injection channel of the hydroelectric sealing device 4 via a water supply pipe. The water purification device 5 is used to pre-purify the water entering the first cavity 13. The water purification device 5 is used to filter, deoxygenate, and perform reverse osmosis operations on the injected water to remove soluble magnesium and calcium salts from the water, fully reducing the water hardness and preventing scaling and corrosion on the outer wall of the thermal protection tube 122 of each heating tube 12, thereby ensuring the long-term and efficient operation of the heating tube 12 and extending its service life.

[0058] In this embodiment, the upper end of the high-pressure bearing sealing wellhead 6 is connected to the lower end of the hydroelectric sealing device 4; The high-pressure bearing sealed wellhead 6 includes: a second water injection channel and a plurality of second cable channels; The second water injection channel is in communication with the first water injection channel, and the plurality of second cable channels are in communication with the plurality of first cable channels respectively.

[0059] In this embodiment, the high-pressure load-bearing sealed wellhead 6 realizes the suspension of the integrated downhole electric heating steam generator, and the water-electric sealing device 4 realizes the insulation and sealing of electricity and water of the integrated downhole electric heating steam generator, ensuring the stability and safety of the transmission of water and electricity at the wellhead during the long-term operation of the integrated downhole electric heating steam generator.

[0060] In this embodiment, a second cavity 8 is defined between the outer protective tube 11 and the downhole casing. The high-pressure bearing sealed wellhead 6 further includes a nitrogen injection channel 61. The output end of the nitrogen injection channel 61 communicates with the second cavity 8 for injecting nitrogen into the second cavity 8. In this embodiment, nitrogen is injected into the second cavity 8 through the nitrogen injection channel 61. Nitrogen is an inert gas with good stability and safety, and it is more effective in preventing the upward migration of high-temperature and high-pressure steam from the bottom of the well.

[0061] In this embodiment, the specific installation and implementation process of the underground electric heating steam generator is as follows: The integrated surface connection device 3 and downhole steam generating mechanism 1 of the downhole electric steam generator are sequentially threaded through the hydroelectric seal 4 and the high-pressure bearing sealed wellhead 6. The system is then lowered into the casing using a coiled tubing injection device until it reaches the desired location downhole. The integrated downhole steam generating mechanism 1 is then suspended from the high-pressure bearing sealed wellhead 6, and the hydroelectric seal 4 isolates and seals the power supply cable from the waterway.

[0062] During the setting process, nitrogen is injected into the annulus between the wellhead casing and the outer wall of the outer protective tube 11 (i.e., the second cavity 8) to achieve hermetic sealing. Nitrogen, as an inert gas, has good stability and is safe to use. It can more effectively prevent the high-temperature and high-pressure steam at the bottom of the well from rising.

[0063] During the completion water injection and steam production process, water undergoes frequency conversion and high-pressure purification in the water purification unit 5 before being injected through the hydroelectric seal 4 above the wellhead. It then passes through the annulus (i.e., first cavity 13) between the outer wall of the thermally conductive protective tube 122 and the inner wall of the outer protective tube 11 and is injected downhole. Electricity then flows through the surface power regulator 7, the hydroelectric seal 4, and the high-pressure bearing sealed wellhead 6, into the conductor segment 1211 of the downhole steam generating mechanism 1. Conductor segment 1211 transmits the electrical energy to the heating segment 1212. The heat generated by the heating segment 1212 is transferred to the thermally conductive protective tube 122, where it comes into contact with the feed water. This heat is then directly heated at the bottom of the well, converting the water into the desired wet saturated steam. This steam is then ejected from the steam outlet 16 of the downhole steam generating mechanism 1 into the target oil layer 9 (i.e., the target oil layer).

[0064] During the test, the parameter acquisition device 2 is started to collect the pressure parameter data and temperature parameter data of the generated steam and transmit them to the power regulation device 7 online in real time, so as to realize the rapid response and coordinated linkage control of the input electrical parameters and water parameters.

[0065] The present invention uses downhole high-power electric heating to directly heat water underground to generate steam. Compared with the traditional boiler steam injection method, it can effectively circumvent and solve the problem of heat loss in long-distance steam transmission, realize effective heating of deep-layer heavy oil, and achieve efficient recovery of deep-layer heavy oil.

[0066] More importantly, the present invention can achieve a disruptive change in the "electricity-for-heat" approach in heavy oil thermal recovery, introduce self-consumption and comprehensive utilization of green electricity, gradually replace ground gas boilers, and significantly increase the proportion of clean energy used in heavy oil thermal recovery, thus helping the green and low-carbon transformation of heavy oil thermal recovery development.

[0067] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0068] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

[0069] The above describes in detail the optional embodiments of the present invention in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the technical concept of the embodiments of the present invention, a variety of simple variations can be made to the technical solutions of the embodiments of the present invention, and these simple variations all fall within the scope of protection of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction, and as long as the combination does not violate the concept of the embodiments of the present invention, it should also be regarded as the content disclosed in the embodiments of the present invention.

Claims

1. An underground electric heating steam generator, characterized in that: include: A downhole steam generating mechanism is disposed in a downhole casing, the downhole steam generating mechanism comprising: an outer protective tube and a plurality of heating tubes, the plurality of heating tubes being disposed inside the outer protective tube, a first cavity being formed between an inner wall of the outer protective tube and outer walls of the plurality of heating tubes, the first cavity being filled with water; The heating tube includes a heating element, and the heating element includes: an integrally formed wire segment and a heating segment, wherein the wire segment is located at the upper end of the heating element, and the heating segment is located at the lower end of the heating element; The upper end of the wire segment is connected to the power supply on the well for receiving the power from the power supply, and the lower end of the wire segment is connected to the upper end of the heating segment for transmitting the power from the power supply to the heating segment; The device generates heat under the action of the electric energy of the power supply, and heats the water in the area corresponding to the heating section in the first cavity into steam.

2. The underground electric heating steam generator according to claim 1, characterized in that: The heating tube further comprises: a heat-conducting protection tube, wherein the heating element is located inside the heat-conducting protection tube; The first cavity is formed between the inner wall of the outer protective tube and the outer wall of the heat conductive protective tube of each heating tube.

3. The underground electric heating steam generator according to claim 2, characterized in that: The heating tube further includes an insulating filling medium, wherein the insulating filling medium includes: a first insulating material and a second insulating material; The first insulating material is filled between the outer wall of the wire segment and the inner wall of the thermal protection tube; The second insulating material is filled between the outer wall of the heating section and the inner wall of the thermal protection tube.

4. The underground electric heating steam generator according to claim 1, characterized in that: The heating section is a resistance wire.

5. The underground electric heating steam generator according to claim 1, characterized in that: The downhole steam generating mechanism further includes a high-temperature connector; The high-temperature connector is arranged inside the outer protective tube, and the high-temperature connector is located at the bottom of the heating tube; The high-temperature connector is used to connect the lower ends of the heating sections of multiple heating elements into one.

6. The underground electric heating steam generator according to claim 1, characterized in that: The inner wall of the outer protective tube is provided with a swirl groove, and the swirl groove is spirally arranged on the inner wall of the outer protective tube; The upper end of the swirl groove is flush with the upper end of the heating section, and the lower end of the swirl groove is flush with the bottom of the heating section.

7. The underground electric heating steam generator according to claim 1, characterized in that: The downhole steam generating mechanism further includes: a flow control device, the flow control device being disposed in the first cavity, the bottom of the flow control device being flush with the bottom of the conductor segment; The flow control device is used to unidirectionally conduct water in the first cavity from the direction of the wire segment to the direction of the heating segment.

8. The underground electric heating steam generator according to claim 1, characterized in that: The underground electric heating steam generator further includes: a ground connection device, the ground connection device including: a plurality of power supply cables, one power supply cable corresponding to one heating element, and each power supply cable is integrally formed with the corresponding heating element; The first end of the power supply cable is connected to the power supply source above the well, and the second end of the power supply cable is connected to the upper end of the wire segment of the heating element.

9. The underground electric heating steam generator according to claim 8, characterized in that: The ground connection device further includes: a cable protection tube, wherein the cable protection tube is integrally formed with the outer protection tube.

10. An underground electric heating steam generation system, characterized in that: The system comprises the downhole electrically heated steam generator according to any one of claims 1-9.

11. The underground electric heating steam generation system according to claim 10, characterized in that: The downhole electric heating steam generating system also includes: a power regulating device, which is arranged on the ground and has a power supply. The power regulating device is connected to the upper end of the conductor segment of the downhole electric heating steam generator and is used to provide electrical energy to the conductor segment.

12. The underground electric heating steam generation system according to claim 11, characterized in that: The downhole electric heating steam generation system further includes: a parameter acquisition device; The parameter acquisition device is arranged in the first cavity and is used to acquire parameter information of the steam generated by the downhole electric heating steam generator.

13. The underground electric heating steam generation system according to claim 12, characterized in that: The power regulating device is connected to the parameter collecting device, and is used to receive the parameter information of the steam collected from the parameter collecting device, and control the power supply to adjust the parameters of the output electric energy according to the steam parameter information.

14. The underground electric heating steam generation system according to claim 12, characterized in that: The parameter acquisition device includes: a signal transmission unit and a parameter acquisition unit; The signal transmission unit is arranged in the first cavity of the downhole electric heating steam generator, and the lower end of the signal transmission unit passes through the bottom of the heating pipe; The parameter acquisition unit is installed at the lower end of the signal transmission unit, and the parameter acquisition unit is used to acquire parameter information of the steam generated by the downhole electric heating steam generator; The signal transmission unit is used to transmit the steam parameter information collected by the parameter collection unit to the ground.

15. The underground electric heating steam generation system according to claim 14, characterized in that: The parameter acquisition unit includes: a pressure sensor and a temperature sensor; The pressure sensor is used to collect the pressure value of the steam generated by the downhole electric heating steam generator; The temperature sensor is used to collect the temperature value of the steam generated by the downhole electric heating steam generator.

16. The underground electric heating steam generation system according to claim 14, characterized in that: The parameter acquisition device further includes a sealing tube, which is used to wrap the signal transmission unit.

17. The underground electric heating steam generation system according to claim 10, characterized in that: The downhole electric heating steam generation system further includes: a water-electric sealing device, the water-electric sealing device including: a first water injection channel and a plurality of first cable channels, the first water injection channel and the plurality of first cable channels being isolated from each other; The first water injection channel is used to inject water into the first cavity of the downhole electric heating steam generator; The plurality of first cable channels are used to accommodate a plurality of power supply cables of the downhole electric heating steam generator, so that the plurality of power supply cables are connected to the heating element.

18. The underground electric heating steam generation system according to claim 17, characterized in that: The downhole electric heating steam generation system further comprises: a water purification device, the output end of the water purification device being connected to the input end of the first water injection channel of the hydroelectric sealing device via a water pipeline; The water purification device is used to purify the water entering the first cavity in advance.

19. The underground electric heating steam generation system according to claim 18, characterized in that: The downhole electric heating steam generation system further comprises: a high-pressure bearing sealed wellhead, the upper end of which is connected to the lower end of the hydroelectric sealing device; The high-pressure bearing sealed wellhead includes: a second water injection channel and a plurality of second cable channels; The second water injection channel is in communication with the first water injection channel, and the plurality of second cable channels are in communication with the plurality of first cable channels respectively.

20. The underground electric heating steam generation system according to claim 19, characterized in that: There is a second cavity between the outer protective pipe and the downhole casing. The high-pressure bearing sealed wellhead further comprises: a nitrogen injection channel, the output end of which is in communication with the second cavity and is used for injecting nitrogen into the second cavity.

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