Downhole electric heating steam generator and downhole electric heating steam generation system

Abstract

The present invention relates to the field of oil and gas field exploitation, and provides a downhole electric heating steam generator and a downhole electric heating steam generation system. The downhole electric heating steam generator comprises: a downhole steam generation mechanism. The downhole steam generation mechanism comprises: an outer protective tube and a plurality of heating tubes, wherein the heating tubes are arranged in the outer protective tube, and a first cavity is formed between the inner wall of the outer protective tube and the outer walls of the plurality of heating tubes. Each heating tube comprises a heating body, and the heating body comprises: a wire section and a heating section which are integrally formed. The downhole electric heating steam generation system comprises: the downhole electric heating steam generator, a power regulation device, a parameter acquisition device, a water and electricity sealing device, a water purification device, and a high-pressure load-bearing sealing wellhead. The present invention obtains steam downhole, thereby solving the problem of heat loss caused by surface steam transportation, and ensuring the dryness of the steam. The present invention obtains steam by means of an electric heating body, thereby solving the technical problem of large carbon dioxide emissions caused by steam generation of coal-fired boilers.

Description

Downhole electric heating steam generator and steam generation system

[0001] Cross-reference of related applications

[0002] This application claims the benefit of Chinese Patent Application No. 202411952111.2, filed on December 27, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of oil and gas field development technology, specifically to a downhole electric heating steam generator and a downhole electric heating steam generation system. Background Technology

[0004] Currently, heavy oil thermal recovery in oilfields mainly employs three methods: steam injection, steam drive, and steam-assisted gravity drainage. The steam in all methods originates from gas-fired boilers at surface steam stations. Water is heated into steam by the gas-fired boilers, which is then transported to each injection wellhead via surface steam pipelines. From there, the steam is transported to the target formation downhole through the tubing within each injection well. The high-temperature steam is used to reduce the viscosity of the crude oil for heavy oil extraction or displacement. However, the generation of steam by gas-fired boilers and the delivery of steam to the wells via surface steam pipelines present the following problems: First, there is significant heat loss along the pipeline, with a comprehensive heat energy utilization rate of only 60%–70%. Second, effective development of medium-deep blocks is difficult, with a dryness loss of 5%–15% along the surface injection pipeline and 20%–30% in the wellbore. Furthermore, the large injection-production pressure difference at conventional injection rates hinders the formation and expansion of the steam cavity, easily causing steam channeling between injection and production wells. Therefore, during development, the injection rate should be reduced as much as possible to minimize the injection-production pressure difference, but this also results in low bottomhole steam dryness. Taking all the above factors into account, the bottom steam dryness 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 combustion, affecting the global environment. Summary of the Invention

[0005] To address one of the aforementioned technical deficiencies, this invention provides a downhole electrically heated steam generator and a downhole electrically heated steam generation system. The downhole electrically heated steam generator uses a heating pipe installed downhole. This heating pipe receives electrical energy from a surface power source to generate heat, which in turn heats the water filling the outside of the heating pipe, thereby producing steam. On one hand, this invention generates steam downhole, solving the problem of heat loss caused by steam transported from the surface, and ensuring the dryness of the steam. On the other hand, this invention generates steam through electric heating, solving the technical problem of large amounts of carbon dioxide produced by coal-fired boilers, oil-fired boilers, and gas-fired boilers. This invention can produce steam with good quality parameters, ensuring the efficiency of heavy oil extraction without harming the environment.

[0006] The 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 pipe and a plurality of heating pipes, the plurality of heating pipes being disposed inside the outer protective pipe, a first cavity being formed between the inner wall of the outer protective pipe and the outer wall of the plurality of heating pipes, the first cavity being filled with water;

[0007] The heating element includes a heating element, which includes an integrally formed wire segment and a heating segment. 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.

[0008] The upper end of the conductor segment is connected to the power supply above the well to receive electrical energy from the power supply, and the lower end of the conductor segment is connected to the upper end of the heating section to transmit electrical energy from the power supply to the heating section.

[0009] The heating section generates heat under the action of electrical energy from the power supply, heating the water in the area corresponding to the heating section in the first cavity into steam.

[0010] In this embodiment of the invention, the heating tube further includes a thermally conductive protection tube, and the heating element is located inside the thermally conductive protection tube;

[0011] The first cavity is formed between the inner wall of the outer protective tube and the outer wall of the heat-conducting protective tube of each heating tube.

[0012] In this embodiment of the invention, the heating tube further includes an insulating filling medium, which includes a first insulating material and a second insulating material;

[0013] The first insulating material is filled between the outer wall of the conductor segment and the inner wall of the heat-conducting protection tube;

[0014] The second insulating material is filled between the outer wall of the heating section and the inner wall of the thermally conductive protective tube. This serves for insulation and heat conduction, while also ensuring that the high-temperature transmission wire and the high-temperature resistance wire do not come into contact with the outside environment.

[0015] In this embodiment of the invention, the heating element is a resistance wire.

[0016] In this embodiment of the invention, the downhole steam generating mechanism further includes: a high-temperature connector;

[0017] The high-temperature connector is located inside the outer protective tube and at the bottom of the heating tube;

[0018] The high-temperature connector is used to connect the lower ends of the heating sections of multiple heating elements into one unit.

[0019] In this embodiment of the invention, the inner wall of the outer protective tube is provided with a swirling groove, and the swirling groove is spirally arranged around the inner wall of the outer protective tube;

[0020] The upper end of the swirling groove is flush with the upper end of the heating section, and the lower end of the swirling groove is flush with the bottom of the heating section.

[0021] The swirling groove is used to accelerate water supply. The injected water is injected in a rotating manner along the spiral channel of the swirling groove, which improves the liquid disturbance performance while fully exchanging heat with the outer wall of the three heating tubes.

[0022] In this embodiment of the invention, the downhole steam generating mechanism further includes: a flow control device, which is disposed in the first cavity, and the bottom of the flow control device is flush with the bottom of the guide wire section;

[0023] The flow control device is used to unidirectionally guide water in the first cavity from the direction of the conductor segment to the direction of the heating segment.

[0024] In this embodiment of the invention, the downhole electric heating steam generator further includes: a ground connection device, the ground connection device including: multiple power supply cables, one power supply cable corresponding to one heating element, and each power supply cable being integrally formed with the corresponding heating element;

[0025] The first end of the power supply cable is connected to the power supply on the well, and the second end of the power supply cable is connected to the upper end of the conductor segment of the heating element.

[0026] In this embodiment of the invention, the ground connection device further includes a cable protection pipe, which is integrally formed with the outer protective pipe.

[0027] A second aspect of the present invention provides a downhole electric heating steam generation system, the system comprising the downhole electric heating steam generator as described above.

[0028] In this embodiment of the invention, the downhole electric heating steam generation system further includes: a power adjustment device, which is installed on the ground and has a power supply. The power adjustment 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.

[0029] In this embodiment of the invention, the downhole electric heating steam generation system further includes: a parameter acquisition device;

[0030] The parameter acquisition device is located inside the first cavity and is used to acquire parameter information of the steam generated by the downhole electric heating steam generator.

[0031] In this embodiment of the invention, the power adjustment device is connected to the parameter acquisition device and is used to receive steam parameter information collected by the parameter acquisition device, and control the power supply to adjust the output electrical energy parameters according to the steam parameter information.

[0032] In this embodiment of the invention, the parameter acquisition device includes: a signal transmission unit and a parameter acquisition unit;

[0033] The signal transmission unit is located 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;

[0034] The parameter acquisition unit is installed 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 electric heating steam generator.

[0035] The signal transmission unit is used to transmit the steam parameter information collected by the parameter acquisition unit to the ground.

[0036] In this embodiment of the invention, the parameter acquisition unit includes: a pressure sensor and a temperature sensor;

[0037] The pressure sensor is used to collect the pressure value of the steam generated by the downhole electrically heated steam generator.

[0038] The temperature sensor is used to collect the temperature value of the steam generated by the downhole electric heating steam generator.

[0039] In this embodiment of the invention, the parameter acquisition device further includes a sealing tube, which is used to wrap the signal transmission unit.

[0040] In this embodiment of the invention, the downhole electric heating steam generation system further includes: a water-electric sealing device, which 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 mutually isolated.

[0041] The first water injection channel is used to inject water into the first cavity of the downhole electrically heated steam generator;

[0042] The first cable channel is used to accommodate the plurality of power supply cables so that the plurality of power supply cables can be connected to the heating element.

[0043] In this embodiment of the invention, the downhole electric heating steam generation system further includes: a water purification device, the output end of which is connected to the input end of the first water injection channel of the water-electric sealing device via a water supply pipeline;

[0044] The water purification device is used to pre-purify the water entering the first cavity. It is used for filtration, deoxygenation, and reverse osmosis of the injected water, removing soluble magnesium and calcium salts, significantly reducing water hardness, preventing scaling and corrosion on the outer wall of the protective pipe inside the underground electric heating steam generator, ensuring long-term efficient operation of the three heating pipes, and extending their service life.

[0045] In this embodiment of the invention, the downhole electric heating steam generation system further includes: a high-pressure bearing sealed wellhead, the upper end of which is connected to the lower end of the hydroelectric sealing device;

[0046] The high-pressure bearing sealed wellhead includes: a second water injection channel and multiple second cable channels;

[0047] The second water injection channel is connected to the first water injection channel, and the multiple second cable channels are respectively connected to the multiple first cable channels.

[0048] In this embodiment of the invention, a second cavity is provided between the outer protective pipe and the downhole casing;

[0049] The high-pressure bearing sealed wellhead also includes a nitrogen injection channel, the output end of which is connected to the second cavity and used to inject nitrogen into the second cavity.

[0050] Nitrogen, as an inert gas, has good stability, is safe to use, and provides insulation, effectively preventing high-temperature and high-pressure steam from rising from the bottom of the well.

[0051] The downhole electrically heated steam generator uses heating pipes installed downhole. These pipes receive electrical energy from a power source above ground to generate heat, which in turn heats the water filling the outside of the heating pipes, thus producing steam. On one hand, this invention generates steam downhole, solving the problem of heat loss caused by surface steam transportation and ensuring the dryness of the steam. On the other hand, by generating steam through electric heating, this invention solves the technical problem of large amounts of carbon dioxide generated by coal-fired, oil-fired, and gas-fired boilers. This invention can produce steam with good quality parameters, ensuring the efficiency of heavy oil extraction without harming the environment.

[0052] Other features and advantages of the technical solution of the present invention will be described in detail in the following detailed embodiments section. Attached Figure Description

[0053] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0054] Figure 1 is a schematic diagram of the downhole electrically heated steam generation system provided in an embodiment of the present invention;

[0055] Figure 2 is a schematic diagram of the downhole steam generator provided in an embodiment of the present invention;

[0056] Figure 3 is a cross-sectional view of the heating section of the downhole steam generator provided in an embodiment of the present invention;

[0057] Figure 4 is a cross-sectional view of the steam outlet of the downhole steam generator provided in an embodiment of the present invention.

[0058] Explanation of reference numerals in the attached drawings: 1-Downhole steam generator, 11-Outer casing, 111-Swirl groove, 12-Heating pipe, 121-Heating element, 1211-Conducting wire segment, 1212-Heating section, 122-Heat-conducting protection pipe, 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-Surface connection device, 4-Water and electricity sealing device, 5-Water purification device, 6-High-pressure bearing sealing wellhead, 61-Nitrogen injection channel, 7-Power adjustment device, 8-Second cavity, 9-Injected oil layer. Detailed Implementation

[0059] To make the technical solutions and advantages of the embodiments of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0060] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0061] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0062] In this invention, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0063] In the process of realizing this invention, the inventors discovered that the current methods for heavy oil thermal recovery in oilfields mainly include steam injection, steam drive, and steam-assisted gravity drainage. The steam in all these methods originates from gas-fired boilers at surface steam stations. Water is heated into steam by the gas-fired boilers, which is then transported to each injection wellhead via surface steam pipelines. From there, the steam is transported to the target formation downhole through the tubing within each injection well. The high-temperature steam is used to reduce the viscosity of the crude oil for heavy oil extraction or displacement. However, the generation of steam by gas-fired boilers and the delivery of steam to the wells via surface steam pipelines present the following problems: First, there is significant heat loss along the pipeline, with a comprehensive heat energy utilization rate of only 60%–70%. Second, effective development of medium-deep blocks is difficult, with a dryness loss of 5%–15% along the surface injection pipeline and 20%–30% in the wellbore. Furthermore, the large injection-production pressure difference at conventional injection rates hinders the formation and expansion of the steam cavity, easily causing steam channeling between injection and production wells. Therefore, during development, the injection rate should be reduced as much as possible to decrease the injection-production pressure difference, but this also results in low steam dryness at the bottom of the well. Taking all the above factors into account, the bottom steam dryness 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 combustion, affecting the global environment.

[0064] To address the aforementioned problems, this invention provides a downhole electrically heated steam generator, comprising: a downhole steam generating mechanism, the downhole steam generating mechanism including: an outer protective pipe and multiple heating pipes, the heating pipes being disposed inside the outer protective pipe, a first cavity being formed between the inner wall of the outer protective pipe and the outer wall of each heating pipe, the first cavity being filled with water; each heating pipe including a heating element, the heating element including: an integrally formed conductor segment and a heating section, the conductor segment being located at the upper end of the heating element, the heating section being located at the lower end of the heating element; the upper end of the conductor segment being connected to a power supply above the well for receiving electrical energy from the power supply, the lower end of the conductor segment being connected to the upper end of the heating section for transmitting electrical energy from the power supply to the heating section; the heating section generating heat under the action of the electrical energy from the power supply, heating the water in the area corresponding to the heating section in the first cavity into steam. The downhole electrically heated steam generator uses heating pipes installed downhole. These pipes receive electrical energy from a power source above ground to generate heat, which in turn heats the water filling the outside of the heating pipes, thus producing steam. On one hand, this invention generates steam downhole, solving the problem of heat loss caused by surface steam transportation and ensuring the dryness of the steam. On the other hand, by generating steam through electric heating, this invention solves the technical problem of large amounts of carbon dioxide generated by coal-fired, oil-fired, and gas-fired boilers. This invention can produce steam with good quality parameters, ensuring the efficiency of heavy oil extraction without harming the environment.

[0065] Figure 1 is a schematic diagram of the structure of the downhole electric heating steam generation system provided in an embodiment of the present invention. As shown in Figure 1, the downhole electric heating steam generation system provided in this embodiment includes: a downhole electric heating steam generator, a water-electric sealing device 4, a water purification device 5, and a parameter acquisition device 2. The downhole electric heating steam generator includes: a downhole steam generating mechanism 1 and a surface connection device 3. The downhole electric heating steam generation system includes a downhole device and multiple surface devices. The downhole device is the downhole steam generating mechanism 1, and the surface devices include: a surface connection device 3, a water-electric sealing device 4, a water purification device 5, and a high-pressure bearing sealed wellhead 6.

[0066] Specifically, the structure of the downhole electrically heated steam generator is as follows:

[0067] Figure 2 is a structural schematic diagram of the downhole steam generating mechanism provided in an embodiment of the present invention. Figure 3 is a cross-sectional view of the heating section of the downhole steam generating mechanism provided in an embodiment of the present invention. Figure 4 is a cross-sectional view of the steam outlet of the downhole steam generating mechanism provided in an embodiment of the present invention. As shown in Figures 2-4, in this embodiment, the downhole steam generating mechanism 1 includes: an outer protective pipe 11 and a plurality of heating pipes 12. The heating pipes 12 are disposed inside the outer protective pipe 11. A first cavity 13 is formed between the inner wall of the outer protective pipe 11 and the outer wall of the plurality of heating pipes 12. The first cavity 13 is filled with water.

[0068] Furthermore, the heating pipe 12 is equipped with a heating element 121, which includes an integrally formed conductor segment 1211 and a heating segment 1212. The conductor segment 1211 is located at the upper end of the heating element 121, and the heating segment 1212 is located at the lower end of the heating element 121. The upper end of the conductor segment 1211 is connected to the power supply on the well surface to receive electrical energy from the power supply, and the lower end of the conductor segment 1211 is connected to the upper end of the heating segment 1212 to transmit electrical energy from the power supply to the heating segment 1212. The heating segment 1212 heats up under the action of the electrical energy from the power supply, heating the water in the area corresponding to the heating segment 1212 in the first cavity 13 into dry steam required for reservoir development. The dry steam is ejected from the steam outlet 16 of the downhole steam generator 1 to the injected oil layer 9 (i.e., the target oil production layer). Specifically, the heating segment 1212 heats up to heat the water in the annulus region corresponding to it in the first cavity 13. In this embodiment, the conductor segment 1211 and the heating segment 1212 are connected by a connector and welded smooth, making the conductor segment 1211 and the heating segment 1212 integrally formed. The heating element 121 provided by the present invention does not require the connection of the conductive part and the resistive heating part through a detachable downhole plug-in technology using cables or other connectors, ensuring the safety and reliability of the downhole electric heating steam generator and solving the problem in the prior art where the heating segment and the conductor segment 1211 are connected by threads, which cannot guarantee a long service life. Moreover, the integrally formed conductor segment 1211 and 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 of the thermal protection tube 122 in 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 high-temperature conductor heat downhole to improve the overall energy utilization rate. The water begins to vaporize in the middle of the heating segment, generating saturated wet steam that meets the dryness index at the steam outlet 16.

[0069] Furthermore, this invention directly heats the water injected from the surface at the bottom of the well into wet saturated steam with the required dryness, which can significantly improve the dryness of downhole steam. This improves the overall thermal energy utilization rate of the steam injection system in reservoir development and effectively solves the development challenges of medium-deep steam drive technology and steam-assisted gravity drainage technology.

[0070] In this embodiment, the heating tube 12 further includes a thermally conductive protective tube 122, with the heating element 121 located inside the thermally conductive protective tube 122; 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 form the first cavity 13. The heating section 1212 of the heating element 121 transmits heat through a 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 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.

[0071] In this embodiment, the heating tube 12 further includes an insulating filling medium, which includes a first insulating material 123 and a second insulating material 124. The first insulating material 123 is filled between the outer wall of the conductor segment 1211 and the inner wall of the heat-conducting protection tube 122; the second insulating material 124 is filled between the outer wall of the heating segment 1212 and the inner wall of the heat-conducting protection tube 122. In this embodiment, the first insulating material 123 and the second insulating material 124 are mineral insulating materials, which can ensure both insulation and heat conduction, thereby ensuring that the conductor segment 1211 and the heating segment 1212 do not come into contact with the outside world.

[0072] In this embodiment, the heating section 1212 is a resistance wire.

[0073] In this embodiment, the bottom of the downhole steam generator 1 is further provided with a high-temperature connector 14; the high-temperature connector 14 is located inside the outer protective pipe 11 and at the bottom of the heating pipe 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 unit. 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 multiple heating elements 121 generate stable and uniform heat.

[0074] Through the heating element 121 provided in this embodiment, the downhole electrically heated steam generator provided by the present invention achieves the purpose of extreme cooling and heat dissipation. Specifically, the outer wall surface of the heat-conducting 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 for well completion. The water can not only fully contact the outer wall surface of the three heating tubes 12 protective tubes to achieve the best heat exchange effect, but also fully cool the conductor section 1211 in the middle and upper part, carrying the heat from the high-temperature conductor downhole 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.

[0075] In this embodiment, the inner wall of the outer protective tube 11 is provided with a swirling groove 111, which is spirally arranged around the inner wall of the outer protective tube 11.

[0076] Furthermore, the upper end of the swirling groove 111 is flush with the upper end of the heating section 1212, and the lower end of the swirling groove 111 is flush with the bottom of the heating section 1212. The positions of the swirling groove 111 correspond to those of the heating section 1212. In this embodiment, the injected water is injected into the first cavity 13 in a rotating manner along the swirling groove 111, which can improve the liquid agitation performance while ensuring heat exchange between the injected water and the outer wall surfaces of the multiple heat-conducting protection tubes 122. The swirling groove 111 is used to accelerate water supply. The injected water is injected in a rotating manner along the spiral channel of the swirling groove 111, which improves the liquid agitation performance while fully exchanging heat with the outer wall surfaces of the heat-conducting protection tubes 122 corresponding to the heating sections 1212 of the three heating tubes 12.

[0077] In this embodiment, the heating tube 12 further includes a flow control device 15, which is disposed within the first cavity 13, with its bottom flush with the bottom of the conductor segment 1211. The flow control device 15 is used to unidirectionally guide water within the first cavity 113 from the direction of the conductor segment 1211 to the direction of the heating segment 1212. The flow control device 15 is used to unidirectionally guide water within the first cavity 13, and the guiding direction of the flow control device 15 is from the direction of the conductor segment 1211 to the direction of the heating segment 1212.

[0078] Specifically, the flow control device 15 is a one-way valve. The flow control device 15 can ensure the flow rate of water in the first cavity 13 from the direction of the conductor section 1211 to the direction of the heating section 1212, thereby enabling the heating section 1212 to generate continuous and stable steam. Moreover, the bottom of the flow control device 15 is flush with the bottom of the conductor section 1211, which can prevent the steam generated in the first cavity 13 corresponding to the heating section 1212 from moving into the first cavity 13 corresponding to the conductor section 1211 under the condition of a sudden pressure increase, thereby damaging the downhole steam generating mechanism 1.

[0079] In this embodiment, the downhole electrically heated steam generator further includes a surface connection device 3, which comprises multiple power supply cables, each power supply cable corresponding to a heating element 121, and each power supply cable being integrally formed with its corresponding heating element 121; each power supply cable is integrally formed with each heating element 121; the first end of each power supply cable is connected to the power supply above ground, and the second end of each power supply cable is connected to the upper end of the conductor segment 1211 of the heating element 121. The surface connection device 3 further includes a cable protection pipe, which is integrally formed with the outer protective pipe 11.

[0080] In this embodiment, the downhole electric heating steam generator further includes a power adjustment device 7, the power supply is located in the power adjustment device 7, the power adjustment device 7 is installed above the well, and the power adjustment device 7 is connected to the upper end of the conductor segment 1211 to provide electrical energy to the conductor segment 1211.

[0081] In this embodiment, the downhole electric heating 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 electric heating 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 its lower end passes through the bottom of the heating pipe 12. The parameter acquisition unit is installed 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 electric heating steam generator. The signal transmission unit is used to transmit the steam parameter information acquired by the parameter acquisition unit to the surface.

[0082] In this embodiment, the parameter acquisition device 2 is a pressure and temperature sensing testing device. The pressure and temperature sensing testing device extends through a signal transmission unit to the bottom of the integrated heating tube, reaching the steam generation point at the bottom of the downhole electric heating steam generator, for real-time measurement of the temperature and pressure values ​​of the steam generated by the downhole electric heating steam generator. Specifically, the parameter acquisition unit includes a pressure sensor and a temperature sensor.

[0083] 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.

[0084] 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 and seal the signal transmission unit.

[0085] In this embodiment, the power adjustment device 7 is connected to the parameter acquisition device 2 and is used to receive steam parameter information collected by the parameter acquisition device 2, and control the power supply to adjust the output electrical energy parameters according to the steam parameter information. Specifically, the power adjustment device 7 is also connected to the signal transmission unit of the parameter acquisition device 2, and receives steam parameter signals collected by the parameter acquisition unit through the signal transmission unit. The power adjustment device 7 adjusts the electrical energy parameters of the power supply cable to the ground connection device 3 according to the steam parameter signals collected by the parameter acquisition unit, so as to adjust the heat generation of the downhole heating element 121. Further, the adjustment of the electrical energy parameters of the power supply cable includes: adjusting the electric heating power, electric heating method, and electric heating time of the power supply.

[0086] In this embodiment, the materials of each component of the downhole electrically heated steam generator have temperature and pressure resistance characteristics. Specifically, the material of the conductor section 1211 is copper wire core, and the tube wall, sealing head, connector and sealing strip of the heat-conducting protection tube 122 are made of high-temperature resistant alloy steel; the resistance wire of the heating section 1212 is made of high-temperature resistant nickel-chromium alloy.

[0087] In this embodiment, the outer protective tube 11 and the cable protection tube are made of flexible material.

[0088] The water and electricity sealing device 4 described in this embodiment 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;

[0089] The first water injection channel is used to inject water into the first cavity 13 of the downhole steam generator 1;

[0090] 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 121.

[0091] 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 water-electric 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 reverse osmosis the injected water to remove soluble magnesium and calcium salts, effectively reduce water hardness, prevent scaling and corrosion on the outer wall of the heat-conducting protection tube 122 of each heating tube 12, ensure long-term efficient operation of the heating tube 12, and extend its service life.

[0092] 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;

[0093] The high-pressure bearing sealed wellhead 6 includes: a second water injection channel and multiple second cable channels;

[0094] The second water injection channel is connected to the first water injection channel, and the multiple second cable channels are respectively connected to the multiple first cable channels.

[0095] In this embodiment, the high-pressure bearing sealing wellhead 6 enables the suspension of the integrated downhole electric heating steam generator, and the water-electric sealing device 4 enables the insulation and sealing of the electricity and water of the integrated downhole electric heating steam generator, ensuring the stability and safety of the water and electricity transmission at the wellhead during the long-term operation of the integrated downhole electric heating steam generator.

[0096] In this embodiment, a second cavity 8 exists between the outer casing 11 and the downhole casing. The high-pressure bearing sealed wellhead 6 further includes a nitrogen injection channel 61, the output end of which is connected to the second cavity 8 for injecting nitrogen gas into the second cavity 8. In this embodiment, nitrogen gas is injected into the second cavity 8 through the nitrogen injection channel 61. Nitrogen gas is an inert gas with good stability and safe use, and it more effectively prevents high-temperature and high-pressure steam from rising from the bottom of the well.

[0097] In this embodiment, the specific installation process of the downhole electric heating steam generator is as follows:

[0098] The integrated ground connection device 3 of the downhole electric heating steam generator and the downhole steam generating mechanism 1 are sequentially passed through the water-electric sealing device 4 and the high-pressure bearing sealing wellhead 6, and lowered into the casing through the continuous pipe injection device until the required position downhole is reached. Subsequently, the integrated downhole steam generating mechanism 1 is suspended at the high-pressure bearing sealing wellhead 6, and the water-electric sealing device 4 completes the isolation and sealing of the power supply cable and water circuit.

[0099] During the setting process, nitrogen is injected into the annulus (i.e., the second cavity 8) between the wellhead casing and the outer wall of the outer casing 11 to form a gas seal. Nitrogen, as an inert gas, has good stability and is safe to use, and it is more effective in preventing high-temperature and high-pressure steam from rising from the bottom of the well.

[0100] During the well completion water injection heating and steam production process, water undergoes frequency conversion and high-pressure purification treatment by the water purification device 5, and is then injected into the well through the water-electric sealing device 4 above the wellhead. It passes through the annular space (i.e., the first cavity 13) between the outer wall of the heat-conducting protection pipe 122 and the inner wall of the outer protective pipe 11. Electricity is transmitted from the surface power regulating device 7 through the water-electric sealing device 4 and the high-pressure bearing sealed wellhead 6 to the conductor segment 1211 of the downhole steam generating mechanism 1. The conductor segment 1211 transmits electrical energy to the heating section 1212, which generates heat that is transferred to the heat-conducting protection pipe 122, contacting the feed water and directly heating the water at the bottom of the well into the required wet saturated steam. This steam is then ejected from the steam outlet 16 of the downhole steam generating mechanism 1 to the injected oil layer 9 (i.e., the target oil production layer).

[0101] During the test, the parameter acquisition device 2 is activated to collect the pressure and temperature parameters of the generated steam and transmit them to the power control device 7 in real time, so as to realize the rapid response and coordinated control of the input electrical and water parameters.

[0102] This invention uses high-power electric heating downhole to directly heat water and generate steam. Compared with traditional boiler steam injection methods, it can effectively avoid and solve the problem of heat loss during long-distance steam transmission, achieve effective heating of deep heavy oil, and enable high-efficiency extraction of deep heavy oil.

[0103] More importantly, this invention can realize a disruptive transformation of "electricity for heat" in heavy oil thermal recovery, introduce green electricity self-consumption and comprehensive utilization, gradually replace ground gas boilers, significantly increase the proportion of clean energy used in the process of heavy oil thermal recovery, and help the development of heavy oil thermal recovery to achieve a green and low-carbon transformation.

[0104] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0105] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0106] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details described above. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. As long as such combination does not violate the spirit of the embodiments of the present invention, it should also be considered as the content disclosed by the embodiments of the present invention.

Claims

1. An electrically heated downhole steam generator characterized by, include: The downhole steam generator is installed inside the downhole casing. The downhole steam generator includes an outer casing and multiple heating pipes. The multiple heating pipes are located inside the outer casing. A first cavity is formed between the inner wall of the outer casing and the outer wall of the multiple heating pipes. The first cavity is filled with water. The heating element includes a heating element, which includes an integrally formed wire segment and a heating segment. 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 conductor segment is connected to the power supply above the well to receive electrical energy from the power supply, and the lower end of the conductor segment is connected to the upper end of the heating section to transmit electrical energy from the power supply to the heating section. The heating section generates heat under the action of electrical energy from the power supply, heating the water in the area corresponding to the heating section in the first cavity into steam.

2. The downhole electrically heated steam generator of claim 1, wherein, The heating tube further includes a thermally conductive protection tube, and the heating element is located inside the thermally conductive protection tube; The first cavity is formed between the inner wall of the outer protective tube and the outer wall of the heat-conducting protective tube of each heating tube.

3. The electrically heated downhole steam generator of claim 2, wherein, The heating element further includes an insulating filling medium, which includes: a first insulating material and a second insulating material; The first insulating material is filled between the outer wall of the conductor segment and the inner wall of the heat-conducting protection tube; The second insulating material is filled between the outer wall of the heating section and the inner wall of the heat-conducting protection tube.

4. The downhole electrically heated steam generator of claim 1, wherein, The heating element is a resistance wire.

5. The downhole electrically heated steam generator of claim 1, wherein, The downhole steam generator also includes a high-temperature connector; The high-temperature connector is located inside the outer protective tube and 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 unit.

6. The electrically heated downhole steam generator of claim 1, wherein, The inner wall of the outer protective tube is provided with a swirling groove, which is spirally arranged around the inner wall of the outer protective tube; The upper end of the swirling groove is flush with the upper end of the heating section, and the lower end of the swirling groove is flush with the bottom of the heating section.

7. The electrically heated downhole steam generator of claim 1, wherein, The downhole steam generating mechanism further includes: a flow control device, which is disposed in the first cavity, and the bottom of the flow control device is flush with the bottom of the guide wire section; The flow control device is used to unidirectionally guide water in the first cavity from the direction of the conductor segment to the direction of the heating segment.

8. The electrically heated downhole steam generator of claim 1, wherein, The downhole electric heating steam generator also includes: a ground connection device, which includes: multiple power supply cables, one power supply cable corresponding to one heating element, and each power supply cable is integrally formed with its corresponding heating element. The first end of the power supply cable is connected to the power supply on the well, and the second end of the power supply cable is connected to the upper end of the conductor segment of the heating element.

9. The electrically heated downhole steam generator of claim 8, wherein, The ground connection device also includes a cable protection pipe, which is integrally formed with the outer protective pipe.

10. An electrically heated downhole steam generation system, characterized by The system includes the downhole electrically heated steam generator as described in any one of claims 1-9.

11. The downhole electrically heated steam generation system of claim 10, wherein, The downhole electric heating steam generation system further includes a power adjustment device, which is installed on the ground and has a power supply. The power adjustment device is connected to the upper end of the conductor segment of the downhole electric heating steam generator to provide electrical energy to the conductor segment.

12. The downhole electrically heated steam generation system of claim 11, wherein, The downhole electrically heated steam generation system also includes: a parameter acquisition device; The parameter acquisition device is located inside the first cavity and is used to acquire parameter information of the steam generated by the downhole electric heating steam generator.

13. The downhole electrically heated steam generation system of claim 12, wherein, The power adjustment device is connected to the parameter acquisition device and is used to receive steam parameter information collected by the parameter acquisition device, and control the power supply to adjust the output electrical energy parameters according to the steam parameter information.

14. The downhole electrically heated steam generation system of claim 12, wherein, The parameter acquisition device includes: a signal transmission unit and a parameter acquisition unit; The signal transmission unit is located 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 acquisition unit to the ground.

15. The downhole electrically heated steam generation system of claim 14, wherein, 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 electrically heated 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 downhole electrically heated steam generation system of claim 14, wherein, The parameter acquisition device further includes a sealing tube, which is used to wrap the signal transmission unit.

17. The downhole electrically heated steam generation system of claim 10, wherein, The downhole electric heating steam generation system further includes: a water-electric sealing device, which includes: a first water injection channel and multiple first cable channels, wherein the first water injection channel and the multiple first cable channels are mutually isolated. The first water injection channel is used to inject water into the first cavity of the downhole electrically heated 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 downhole electrically heated steam generation system of claim 17, wherein, The downhole electric heating steam generation system also includes a water purification device, the output end of which is connected to the input end of the first water injection channel of the water-electric sealing device via a water supply pipeline. The water purification device is used to pre-purify the water entering the first cavity.

19. The downhole electrically heated steam generation system of claim 18, wherein, The downhole electric heating steam generation system also includes: 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 multiple second cable channels; The second water injection channel is connected to the first water injection channel, and the multiple second cable channels are respectively connected to the multiple first cable channels.

20. The downhole electrically heated steam generation system of claim 19, wherein, There is a second cavity between the outer casing and the downhole casing. The high-pressure bearing sealed wellhead also includes a nitrogen injection channel, the output end of which is connected to the second cavity and used to inject nitrogen into the second cavity.

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