Dual flow path rodless wellbore heat extraction anti-plugging system and method

Abstract

The present application relates to oil and gas field wellbore temperature control anti-blocking technical field, especially relates to a double-flow channel rodless wellbore heat extraction anti-blocking system and method. The upper end of the downhole coaxial heat exchange pipe column is connected with the ground integrated control system through the wellhead sealing switching assembly, and the lower end is connected with the bottom gas-liquid shunt device. The downhole coaxial heat exchange pipe column is composed of an outer heat exchange pipe and a central inner pipe. The lower part of the central inner pipe is communicated with the outer heat exchange pipe through a lower circulating overflow hole, and the upper part of the central inner pipe is communicated with the outer heat exchange pipe through an upper circulating overflow hole. The beneficial effects are that the present application realizes the gravity self-circulation heat extraction anti-blocking function of the rodless, downhole pump-free self-flowing well, electric submersible pump well, gas well and horizontal well through the downhole coaxial heat exchange pipe column and the wellhead sealing switching assembly. In addition, the forced circulation mode is realized by installing an air source heat pump and an electric auxiliary heating storage tank on the ground. The wellbore anti-blocking, pipeline heat tracing and industrial and agricultural heating and other multi-scene heating requirements are solved, and the formation residual heat multi-scene application is realized.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field wellbore temperature control and anti-clogging technology, and in particular to a dual-channel rodless wellbore heat extraction and anti-clogging system and method. Background Technology

[0002] In oil and gas well production, especially in production wells without sucker rods or downhole pumps, such as heavy oil flowing wells, light oil flowing wells, natural gas wells, and coalbed methane wells, scaling and wax deposition on the pipe walls occur due to temperature drops near the surface. This reduces the fluid flow cross-section and increases flow resistance. Furthermore, declining formation energy also reduces production. Similarly, shale oil and gas wells and ESP wells also experience scaling and wax deposition near the surface, further reducing fluid flow cross-section and increasing flow resistance, leading to decreased production. Therefore, addressing the problem of scaling and wax deposition near the surface due to temperature drops is crucial. Currently, wellbore heating and anti-clogging technology primarily uses electric heating, converting electrical energy into heat energy to directly heat the wellbore fluid. Its core function is to raise the wellbore temperature above the wax precipitation point, preventing paraffin wax precipitation or melting existing wax deposits, thereby achieving anti-clogging. Its disadvantages are: since most oil wells need to be kept powered on to continuously heat the tubing near the ground, it has high energy consumption and poses safety hazards.

[0003] Our company has applied for Chinese invention patent ZL202610746386.3, entitled "Heat Pump Circulation Viscosity Reduction Device and Usage Method Based on Central Tube Closed-Circuit Heat Exchange," which is suitable for heavy oil wells using rod-type pumps. The heat exchange tube is embedded in the inner hole of a hollow sucker rod and only supports forced liquid phase circulation mode. Due to application scenarios and structural space limitations, this solution cannot be directly applied to flowing wells, ESP wells, gas wells, and horizontal wells without sucker rods or downhole pumps, as their operating conditions and structural forms are independent of each other. Therefore, a new wellbore temperature control and anti-clogging technology suitable for rodless wells needs to be designed to meet field requirements. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned deficiencies in existing technologies by providing a dual-channel rodless wellbore heat extraction and anti-clogging system and method. This invention achieves gravity-driven self-circulation heat extraction and anti-clogging functions in flowing wells, ESP wells, gas wells, and horizontal wells without sucker rods or downhole pumps through a downhole coaxial heat exchange string and a wellhead sealing switching assembly. Furthermore, a forced circulation mode is achieved by installing an air-source heat pump and an electrically auxiliary heating tank on the surface. This invention simultaneously solves heating needs in multiple scenarios, including wellbore anti-clogging, pipeline heat tracing, and industrial and agricultural heating, enabling the multi-scenario application of formation waste heat.

[0005] The present invention discloses a dual-channel rodless wellbore heat extraction and anti-clogging system, the technical solution of which includes a surface integrated control system, a downhole coaxial heat exchange string, a wellhead sealing switching assembly, and a bottom gas-liquid separator. The upper end of the downhole coaxial heat exchange string is connected to the wellhead sealing switching assembly, which is connected to the surface integrated control system via a pipeline. The downhole coaxial heat exchange string is lowered into the well along the production pipe, and the lower end of the downhole coaxial heat exchange string is connected to the bottom gas-liquid separator. The downhole coaxial heat exchange string consists of an outer heat exchange tube and a central inner tube. The central inner tube is located inside the outer heat exchange tube, and the lower part of the central inner tube is connected to the outer heat exchange tube through a lower circulation flow hole. The upper part of the central inner tube is provided with an upper circulation flow hole, which is connected to the outer heat exchange tube. The bottom gas-liquid splitter includes an upper plug, a splitter body, and a product liquid flow hole. The upper plug is provided on the upper part of the splitter body and is connected to the bottom end of the external heat exchange tube and the central inner tube respectively. The outer wall of the splitter body is provided with multiple product liquid flow holes.

[0006] Preferably, the bottom gas-liquid splitter further includes bidirectional slips and anchoring rods. Anchoring rods are fixedly connected to the lower end of the splitter body, and one or more bidirectional slips are installed on the anchoring rods.

[0007] Preferably, heat sinks are installed on the upper part of the external heat exchange tube to improve the condensation heat dissipation effect of the near-surface part; and heat absorption fins are installed on the lower part of the external heat exchange tube to improve the evaporation heat absorption effect of the external heat exchange tube at the bottom of the well.

[0008] Preferably, an upper connecting short pipe is installed at the center of the upper plug, and multiple lower circulation flow holes are provided on the side wall of the upper connecting short pipe, and the upper end of the upper connecting short pipe is connected to the lower end of the central inner pipe.

[0009] Preferably, multiple sets of straightening components are distributed between the external heat exchange tube and the production tube, and the center of the straightening component is provided with a cavity to reduce the resistance to the produced liquid gas downhole.

[0010] Preferably, the wellhead sealing switching assembly includes a switching assembly body, a central flow channel connector, an annular flow channel connector, a switching assembly base, a switching sliding sleeve, and a sliding sleeve mounting cavity. The inner cavity of the switching assembly body is provided with a sliding sleeve mounting cavity, the bottom of the switching assembly body is provided with a switching assembly base, the lower side wall of the switching assembly body is provided with an annular flow channel connector, and the upper side wall is provided with a central flow channel connector. The inner flow channel of the central flow channel connector communicates with the sliding sleeve mounting cavity. The lower end of the sliding sleeve mounting cavity is movably connected to the upper end of the central inner tube. The switching sliding sleeve is installed in the sliding sleeve mounting cavity and can move up and down.

[0011] Preferably, the outer diameter of the switching sleeve is smaller than the inner diameter of the central inner tube, and the upper end of the switching sleeve is provided with an annular limiting boss, the outer diameter of which is smaller than the inner diameter of the sleeve mounting cavity; when the switching sleeve moves upward to the sleeve mounting cavity, it closes the channel between the central flow channel connector and the sleeve mounting cavity; when the switching sleeve moves downward to the central inner tube, it closes the upper circulation flow hole at the top of the central inner tube.

[0012] Preferably, the outer end of the aforementioned central flow channel connector is connected to the return end of the ground integrated control system via a pipeline, a vacuum detector, and a central flow channel controllable shut-off valve assembly, and the outer end of the annular flow channel connector is connected to the supply end of the ground integrated control system via a pipeline and an annular pipe controllable shut-off valve assembly.

[0013] Preferably, the above-mentioned ground integrated control system includes a heat exchange medium storage tank, a filter purifier, a circulating pump group, an air source heat pump, an electric auxiliary heating storage tank, and a multi-scenario heating transmission pipeline. The inlet end of the heat exchange medium storage tank is connected to the central flow channel connector through a pipeline, and the outlet end of the heat exchange medium storage tank is connected to the air source heat pump through a pipeline, a filter purifier, and a circulating pump group. The outlet end of the air source heat pump is connected to the inlet of the electric auxiliary heating storage tank. One outlet of the electric auxiliary heating storage tank is connected to a ring pipeline controllable shut-off valve group through a pipeline and a control valve, and the other outlet is connected to the multi-scenario heating transmission pipeline for external heating transmission.

[0014] The anti-clogging method of the dual-channel rodless wellbore heat extraction anti-clogging system mentioned in this invention includes the following process: S1. The downhole coaxial heat exchange tube string is lowered into the well along the production pipe. The lower part of the central inner tube is connected to the outer heat exchange tube through the lower circulation flow hole, and the upper part of the central inner tube is connected to the outer heat exchange tube through the upper circulation flow hole. The upper end of the downhole coaxial heat exchange tube string is then connected to the wellhead sealing switching assembly through a large four-way connector and a small four-way connector. The top end of the outer heat exchange tube is fixed by the base of the switching assembly, and the top end of the central inner tube is connected to the lower part of the sliding sleeve mounting cavity. The outer side of the wellhead sealing switching assembly is connected to the surface integrated control system through pipelines and a shut-off valve group. The inlet end of the heat exchange medium storage tank of the surface integrated control system is connected to the central flow channel connector through pipelines. The outlet end of the heat exchange medium storage tank is connected to the air source heat pump through pipelines, a filter purifier, and a circulation pump group. The outlet end of the air source heat pump is connected to the inlet of the electric auxiliary heating storage tank. One outlet of the electric auxiliary heating storage tank is connected to the wellhead sealing switching assembly through pipelines and a control valve, and the other outlet is connected to a multi-scenario heating transmission pipeline for heating use in various scenarios. S2, Gravity Self-Circulation Mode: In the absence of electricity or deep well conditions, the controllable shut-off valve group of the annular pipeline and the controllable shut-off valve group of the central flow channel are closed, and the sliding sleeve is switched to be located in the sliding sleeve installation cavity, so that the upper circulation flow hole is exposed to connect the central inner pipe and the outer heat exchange pipe. When the liquid heat exchange medium flows downward along the annular flow channel of the central inner pipe and the outer heat exchange pipe, the formation temperature increases as it goes down. The liquid heat exchange medium continuously absorbs heat, and its temperature continues to rise until the heat exchange medium is vaporized. Then, it enters the central flow channel of the central inner pipe through the lower circulation flow hole and moves upward. The closer it gets to the ground, the lower the temperature becomes. The gaseous heat exchange medium gradually condenses and releases heat and turns into liquid, thereby continuously heating the liquid in the production pipe near the ground and avoiding the blockage caused by wax condensation of the produced fluid in the oil well. As the heat exchange medium reaches the upper circulation flow hole at the top of the central inner pipe, it recirculates into the annular flow channel of the central inner pipe and the outer heat exchange pipe to continue circulating, realizing gravity self-circulation operation. S3, Heat pump heating forced circulation mode: In shallow well conditions, since the depth is insufficient to provide enough heat to achieve gravity self-circulation, the controllable shut-off valve group of the annular pipeline and the controllable shut-off valve group of the central flow channel need to be opened. The heat exchange medium heated by the air source heat pump enters the annular flow channel of the central inner pipe and the outer heat exchange pipe through the circulation pump group, pipeline and the controllable shut-off valve group of the annular pipeline and flows downward, continuously heating the liquid in the production pipe near the ground and preventing the blockage caused by wax condensation of the produced fluid in the oil well. As the formation temperature increases with depth, the heat exchange medium begins to absorb heat and its temperature continues to rise. Then, it enters the central flow channel of the central inner pipe through the lower circulation flow hole and moves upward. The temperature decreases as it gets closer to the ground, and the heat exchange medium gradually releases heat, thereby reheating the liquid in the production pipe near the ground and preventing wax condensation of the produced fluid in the oil well. Then, the heat exchange medium is sent to the heat exchange medium storage tank through the sliding sleeve installation cavity and the central flow channel joint through the pipeline and the controllable shut-off valve group of the central flow channel, and is recirculated and heated by the air source heat pump to achieve the heating of the heat exchange medium. S4. Under extremely cold conditions or when there is a demand for external heating: The air source heat pump and the electric heater in the electric auxiliary heating tank are turned on in sequence to supplement the heat exchange medium in the circulation, so as to achieve forced circulation heating. In addition, the excess heat is used for heating in various scenarios through multi-scenario heating pipelines, so as to realize the reuse of the waste heat resources of the formation.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: I. This invention achieves gravity self-circulation heat extraction and anti-clogging functions in flowing wells, ESP wells, gas wells, and horizontal wells without sucker rods or downhole pumps through a downhole coaxial heat exchange tubing string and wellhead sealing switching assembly. During gravity self-circulation, the liquid heat exchange medium flows downward along the annular flow channel, continuously absorbing heat and increasing its temperature until it is vaporized. It then enters the central flow channel in the central inner tube through the lower circulation flow hole and moves upward. The gaseous heat exchange medium gradually condenses and releases heat, converting back to liquid, thereby continuously heating the liquid in the production pipe near the surface and preventing blockage caused by wax condensation of the produced fluid. Then, the heat exchange medium recirculates back into the annular flow channel, realizing the gravity self-circulation process. II. This invention achieves a forced circulation mode by installing an air-source heat pump and an electrically assisted heating storage tank on the ground. The heat exchange medium heated by the air-source heat pump enters the annular flow channel and flows downward, continuously heating the liquid in the production pipe near the ground and preventing blockage caused by wax condensation of the produced fluid from the oil well. As the formation temperature increases further down, the heat exchange medium begins to absorb heat, and its temperature is continuously replenished and increased. It then enters the central flow channel in the central inner pipe through the lower circulation flow hole and moves upward. The heat exchange medium gradually releases heat, thereby reheating the liquid in the production pipe near the ground and preventing wax condensation of the produced fluid from the oil well. Then, the heat exchange medium is sent to the heat exchange medium storage tank and is heated by the air-source heat pump again, realizing the cyclic heating of the air-source heat pump. In extremely cold conditions or when there is an external heating demand, electric heating is added, solving the heating needs of multiple scenarios such as wellbore anti-blockage, pipeline heat tracing, and industrial and agricultural heating, and realizing the multi-scenario application of formation waste heat. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the first embodiment of the present invention; Figure 2 This is a cross-sectional schematic diagram of the downhole production pipe and the downhole coaxial heat exchange tube string of the present invention; Figure 3 This is a longitudinal cross-sectional structural diagram of the wellhead sealing switching assembly of the present invention; Figure 4 This is a schematic diagram of the cross-section of the bottom gas-liquid separator; Figure 5 yes Figure 4 A schematic diagram of the structure along direction A; Figure 6 This is a schematic diagram of the ground-based integrated control system; Figure 7 This is a schematic diagram of the overall structure of the second embodiment of the present invention; Figure 8 This is a schematic diagram of the structure of the present invention in gravity self-circulation mode; Figure 9 yes Figure 4A schematic diagram of the wellhead seal switching assembly status; Figure 10 yes Figure 4 A schematic diagram of the bottom gas-liquid separator in the middle; Figure 11 This is a schematic diagram of the structure of the present invention in the forced circulation mode of heat pump heating; Figure 12 yes Figure 7 A schematic diagram of the wellhead seal switching assembly status; Figure 13 This is a schematic diagram illustrating the application of the present invention in heating systems across multiple scenarios; In the diagram: 1. Downhole coaxial heat exchange tubing string; 2. Wellhead seal switching assembly; 3. Surface integrated control system; 4. Production pipe; 5. External heat exchange pipe; 6. Central inner pipe; 7. Annular flow channel; 8. Central flow channel; 9. Bottom gas-liquid separator; 10. Centralizing component; 11. Shut-off valve assembly; 12. Vacuum detector; 13. Large four-way valve; 14. Small four-way valve; 15. Tubing head. 2.1 Switching assembly main body, 2.2 Central flow channel connector, 2.3 Annular flow channel connector, 2.4 Switching assembly base, 2.5 Switching sliding sleeve, 2.6 Sliding sleeve mounting cavity, 3.1 Heat exchange medium storage tank, 3.2 Filter purifier, 3.3 Circulating pump group, 3.4 Air source heat pump, 3.5 Electric auxiliary heating storage tank, 3.6 Control cabinet, 3.7 Multi-scenario heating external transmission pipeline, 5.1 Upper heat sink, 5.2 Lower heat absorber, 6.1 Upper circulation flow hole, 9.1 Upper plug, 9.2 Diverter body, 9.3 Produced liquid flow hole, 9.4 Bidirectional slip, 9.5 Anchoring base rod, 9.6 Upper connecting short pipe, 9.7 Lower circulation flow hole, 11.1 Annular pipeline controllable shut-off valve group, 11.2 Central flow channel controllable shut-off valve group. Detailed Implementation

[0017] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0018] Example 1, referring to Figures 1-6The present invention discloses a dual-channel rodless wellbore heat extraction and anti-clogging system, comprising a surface integrated control system 3, and further comprising a downhole coaxial heat exchange string 1, a wellhead sealing switching assembly 2, and a bottom gas-liquid separator 9. The upper end of the downhole coaxial heat exchange string 1 is connected to the wellhead sealing switching assembly 2, and the wellhead sealing switching assembly 2 is connected to the surface integrated control system 3 via a pipeline. The downhole coaxial heat exchange string 1 is lowered into the well along the production pipe 4, and the lower end of the downhole coaxial heat exchange string 1 is connected to the bottom gas-liquid separator 9. The downhole coaxial heat exchange string 1 is composed of an outer heat exchange tube 5 and a central inner tube 6. The central inner tube 6 is located in the inner cavity of the outer heat exchange tube 5, and the lower part of the central inner tube 6 is connected to the outer heat exchange tube 5 through a lower circulation flow hole 9.7. The upper part of the central inner tube 6 is provided with an upper circulation flow hole 6.1, which is connected to the outer heat exchange tube 5. The bottom gas-liquid separator 9 includes an upper plug 9.1, a separator body 9.2, and a produced fluid flow hole 9.3. The upper plug 9.1 is provided on the upper part of the separator body 9.2, and is connected to the bottom end of the external heat exchange tube 5 and the central inner tube 6 respectively through the upper plug 9.1. The outer wall of the separator body 9.2 is provided with multiple produced fluid flow holes 9.3. When used in heavy oil flowing wells or light oil flowing wells, the formation produced fluid is sprayed upward along the produced fluid flow holes 9.3. When used in natural gas wells or coalbed methane wells, the formation produced gas is sprayed upward along the produced fluid flow holes 9.3.

[0019] Reference Figures 4-5 The bottom gas-liquid splitter 9 mentioned in this invention also includes bidirectional slips 9.4 and anchoring base rods 9.5. Anchoring base rods 9.5 are fixedly connected to the lower end of the splitter body 9.2, and one or more sets of bidirectional slips 9.4 are installed on the anchoring base rods 9.5.

[0020] The upper plug 9.1 is equipped with an upper connecting short pipe 9.6 at its center. Multiple lower circulation flow holes 9.7 are provided on the side wall of the upper connecting short pipe 9.6, and the upper end of the upper connecting short pipe 9.6 is connected to the lower end of the central inner pipe 6.

[0021] Reference Figure 2 The present invention mentions that multiple sets of straightening components 10 are distributed between the external heat exchange tube 5 and the production tube 4, and the center of the straightening component 10 is provided with a cavity to reduce the resistance to the produced liquid gas downhole.

[0022] Reference Figure 3The wellhead sealing switching assembly 2 mentioned in this invention includes a switching assembly body 2.1, a central flow channel connector 2.2, an annular flow channel connector 2.3, a switching assembly base 2.4, a switching sliding sleeve 2.5, and a sliding sleeve mounting cavity 2.6. The inner cavity of the switching assembly body 2.1 is provided with a sliding sleeve mounting cavity 2.6, and the bottom of the switching assembly body 2.1 is provided with a switching assembly base 2.4. The lower side wall of the switching assembly body 2.1 is provided with an annular flow channel connector 2.3, and the upper side wall is provided with a central flow channel connector 2.2. The inner flow channel of the central flow channel connector 2.2 is connected to the sliding sleeve mounting cavity 2.6. The lower end of the sliding sleeve mounting cavity 2.6 is movably connected to the upper end of the central inner tube 6. The switching sliding sleeve 2.5 is installed in the sliding sleeve mounting cavity 2.6 and can move up and down.

[0023] Wherein, the outer diameter of the aforementioned switching sleeve 2.5 is smaller than the inner diameter of the central inner tube 6, and the upper end of the switching sleeve 2.5 is provided with an annular limiting boss, the outer diameter of which is smaller than the inner diameter of the sleeve mounting cavity 2.6; when the switching sleeve 2.5 moves upward to the sleeve mounting cavity 2.6, it closes the channel between the central flow channel connector 2.2 and the sleeve mounting cavity 2.6; when the switching sleeve 2.5 moves downward to the central inner tube 6, it closes the upper circulation flow hole 6.1 at the upper part of the central inner tube 6.

[0024] In addition, the outer end of the aforementioned central flow channel connector 2.2 is connected to the return end of the ground integrated control system 3 via pipeline, vacuum detector 12 and central flow channel controllable shut-off valve group 11.2, and the outer end of the annular flow channel connector 2.3 is connected to the supply end of the ground integrated control system 3 via pipeline and annular pipe controllable shut-off valve group 11.1.

[0025] Reference Figure 6 The ground integrated control system 3 mentioned in this invention includes a heat exchange medium storage tank 3.1, a filter purifier 3.2, a circulating pump group 3.3, an air source heat pump 3.4, an electric auxiliary heating storage tank 3.5, a control cabinet 3.6, and a multi-scenario heating external transmission pipeline 3.7. The liquid inlet of the heat exchange medium storage tank 3.1 is connected to the central flow channel connector 2.2 via a pipeline. The liquid outlet of the heat exchange medium storage tank 3.1 is connected to the air source heat pump 3.4 via a pipeline, the filter purifier 3.2, and the circulating pump group 3.3. The outlet of the air source heat pump 3.4 is connected to the inlet of the electric auxiliary heating storage tank 3.5. One outlet of the electric auxiliary heating storage tank 3.5 is connected to the ring pipeline controllable shut-off valve group 11.1 via a pipeline and a control valve, and the other outlet is connected to the multi-scenario heating external transmission pipeline 3.7 for external heating. The control cabinet 3.6 is existing technology known to those skilled in the art and is located on one side of the electric auxiliary heating storage tank 3.5.

[0026] The anti-clogging method of the dual-channel rodless wellbore heat extraction anti-clogging system mentioned in this invention includes the following process: S1. The downhole coaxial heat exchange string 1 is lowered into the well along the production pipe 4. The lower part of the inner central tube 6 is connected to the outer heat exchange pipe 5 through the lower circulation flow hole 9.7, and the upper part of the inner central tube 6 is connected to the outer heat exchange pipe 5 through the upper circulation flow hole 6.1. The upper end of the downhole coaxial heat exchange string 1 is then connected to the wellhead sealing switching assembly 2 through a large four-way connector 13 and a small four-way connector 14. The large four-way connector 13 has an oil pipe head 15 inside for fixing the production pipe 4. The top end of the outer heat exchange pipe 5 is fixed by the switching assembly base 2.4, and the top end of the inner central tube 6 is connected to the lower part of the sliding sleeve mounting cavity 2.6. The wellhead sealing switching assembly 2 is connected to the outer... The side is connected to the ground integrated control system 3 via pipelines and shut-off valve group 11. The inlet end of the heat exchange medium storage tank 3.1 of the ground integrated control system 3 is connected to the central flow channel connector 2.2 via pipelines. The outlet end of the heat exchange medium storage tank 3.1 is connected to the air source heat pump 3.4 via pipelines, filter purifier 3.2 and circulation pump group 3.3. The outlet end of the air source heat pump 3.4 is connected to the inlet of the electric auxiliary heating storage tank 3.5. One outlet of the electric auxiliary heating storage tank 3.5 is connected to the wellhead sealing switching assembly 2 via pipelines and control valves, and the other outlet is connected to the multi-scenario heating external transmission pipeline 3.7 for heating use in various scenarios. S2, Gravity Self-Circulation Mode: In the absence of electricity or deep well conditions, close the controllable shut-off valve group 11.1 of the annular pipeline and the controllable shut-off valve group 11.2 of the central flow channel, switch the sliding sleeve 2.5 to be located in the sliding sleeve mounting cavity 2.6, so that the upper circulation flow hole 6.1 is exposed to connect the central inner tube 6 and the outer heat exchange tube 5; when the liquid heat exchange medium flows downward along the annular flow channel 7 of the central inner tube 6 and the outer heat exchange tube 5, the formation temperature increases as it goes down, the liquid heat exchange medium continuously absorbs heat, and the temperature continuously rises until the heat exchange medium is vaporized, and then... The heat exchange medium enters the central flow channel 8 of the central inner tube 6 through the lower circulation flow hole 9.7 and moves upward. The closer it gets to the ground, the lower the temperature becomes. The gaseous heat exchange medium gradually condenses and releases heat and turns into a liquid, thereby continuously heating the liquid in the production pipe 4 near the ground and preventing blockage caused by wax condensation of the oil well produced fluid. As the heat exchange medium reaches the upper circulation flow hole 6.1 at the top of the central inner tube 6, it is recirculated into the annular flow channel 7 of the central inner tube 6 and the outer heat exchange tube 5 to continue circulating, realizing gravity self-circulation. This mode is suitable for poleless production wellbores in remote Gobi deserts and other arid regions without power grid coverage or resident maintenance personnel. It covers various types of crude oil flowing wells, light oil wells, natural gas wells, coalbed methane wells, and shale gas wells. It is also applicable to deep wellbore conditions. It should be noted that the deeper the wellbore, the higher the ground temperature, thus meeting the heat extraction and anti-clogging requirements of the near-surface portion of the wellbore. This mode achieves zero-power operation and effectively suppresses wax deposition and clogging problems in the wellbore. The wellbore flow resistance remains stable over a long period, avoiding formation defects caused by blockages, significantly extending the wellbore's maintenance-free cycle, and eliminating the need for additional chemicals and operating costs.

[0027] S3, Heat pump heating forced circulation mode: In shallow well conditions, because the depth is insufficient to provide enough heat to achieve gravity self-circulation, the controllable shut-off valve group 11.1 of the annular pipeline and the controllable shut-off valve group 11.2 of the central flow channel need to be opened. The heat exchange medium heated by the air source heat pump 3.4 flows downward through the circulating pump group 3.3, pipeline, and the controllable shut-off valve group 11.1 of the annular pipeline into the annular flow channel 7 of the central inner pipe 6 and the outer heat exchange pipe 5, continuously heating the liquid in the production pipe 4 near the surface and preventing blockage caused by wax condensation of the produced fluid. As the depth increases, the formation temperature rises, and the heat exchange medium... The heat exchange medium begins to absorb heat, and its temperature continuously rises. Then, it enters the central flow channel 8 inside the central inner tube 6 through the lower circulation flow hole 9.7 and moves upward. The closer it gets to the ground, the lower the temperature becomes. The heat exchange medium gradually releases heat, thereby reheating the liquid in the production pipe 4 near the ground to prevent the produced fluid from waxing and condensing. Then, the heat exchange medium is sent outward through the sliding sleeve installation cavity 2.6 and the central flow channel joint 2.2 through the pipeline and the central flow channel controllable shut-off valve group 11.2 to the heat exchange medium storage tank 3.1, where it is recirculated and heated by the air source heat pump 3.4 to achieve the heating of the heat exchange medium. This mode is suitable for conventional oil and gas production blocks with power supply, where the wellbore uses electric submersible pumps, screw pumps, or self-flowing methods for lifting, without a sucker rod structure. Common problems include wellbore wax buildup, heavy oil adhesion to the walls, and significant temperature drops along the wellbore. Traditional hot washing and dilution processes require frequent shutdowns, impacting production efficiency. This mode utilizes an air-source heat pump 3.4 for heating, actively regulating wellbore temperature, effectively inhibiting paraffin precipitation, reducing heavy oil viscosity, significantly reducing downtime, and improving production efficiency. The flow rate is infinitely adjustable, adaptable to various wellbores with different production volumes and media properties, offering strong versatility.

[0028] S4. Under extremely cold conditions or when there is a demand for external heating: The air source heat pump 3.4 and the electric heater in the electric auxiliary heating tank 3.5 are turned on in sequence to supplement the heat exchange medium in the circulation, so as to achieve forced circulation heating. In addition, the excess heat is used for heating in various scenarios through the multi-scenario heating transmission pipeline 3.7, so as to realize the reuse of the waste heat resources of the formation.

[0029] This model is suitable for oil and gas production wells in extremely cold northern regions, where the wellbore and long-distance pipelines from the wellhead to the joint station are prone to freezing and blockage in winter. At the same time, there is a stable demand for heating in the well site, field barracks, and supporting agricultural facilities, which realizes the resource-added utilization of the formation waste heat, replaces the traditional coal-fired and pure electric heating methods, and significantly reduces the overall operating cost.

[0030] Example 2, refer to Figure 1The present invention discloses a dual-channel rodless wellbore heat extraction and anti-clogging system, comprising a surface integrated control system 3, and further comprising a downhole coaxial heat exchange string 1, a wellhead sealing switching assembly 2, and a bottom gas-liquid separator 9. The upper end of the downhole coaxial heat exchange string 1 is connected to the wellhead sealing switching assembly 2, and the wellhead sealing switching assembly 2 is connected to the surface integrated control system 3 via a pipeline. The downhole coaxial heat exchange string 1 is lowered into the well along the production pipe 4, and the lower end of the downhole coaxial heat exchange string 1 is connected to the bottom gas-liquid separator 9. The downhole coaxial heat exchange string 1 is composed of an outer heat exchange tube 5 and a central inner tube 6. The central inner tube 6 is located in the inner cavity of the outer heat exchange tube 5, and the lower part of the central inner tube 6 is connected to the outer heat exchange tube 5 through a lower circulation flow hole 9.7. The upper part of the central inner tube 6 is provided with an upper circulation flow hole 6.1, which is connected to the outer heat exchange tube 5. The bottom gas-liquid separator 9 includes an upper plug 9.1, a separator body 9.2, and a produced fluid flow hole 9.3. The upper plug 9.1 is provided on the upper part of the separator body 9.2, and is connected to the bottom end of the external heat exchange tube 5 and the central inner tube 6 respectively through the upper plug 9.1. The outer wall of the separator body 9.2 is provided with multiple produced fluid flow holes 9.3, which are used for the produced fluid or produced gas in the well to pass through the flow holes 9.3.

[0031] The difference from Example 1 is: Reference Figures 7-12 The external heat exchange tube 5 of the present invention has heat dissipation fins 5.1 installed on the upper part to improve the condensation heat dissipation effect of the near-surface part; and heat absorption fins 5.2 installed on the lower part of the external heat exchange tube 5 to improve the evaporation heat absorption effect of the external heat exchange tube 5 at the bottom of the well, making full use of the heat of the formation, improving the heat exchange efficiency, and saving energy and reducing consumption.

[0032] The anti-clogging method of the dual-channel rodless wellbore heat extraction anti-clogging system mentioned in this invention includes the following process: S1. The downhole coaxial heat exchanger string 1 is lowered into the well along the production pipe 4. The lower part of the inner central tube 6 is connected to the outer heat exchanger tube 5 through the lower circulation flow hole 9.7, and the upper part of the inner central tube 6 is connected to the outer heat exchanger tube 5 through the upper circulation flow hole 6.1. A heat sink 5.1 is installed on the upper part of the outer heat exchanger tube 5 to improve the condensation heat dissipation effect near the surface. A lower heat absorber 5.2 is installed on the lower part of the outer heat exchanger tube 5 to improve the evaporation heat absorption effect of the outer heat exchanger tube 5 at the bottom of the well. The upper end of the downhole coaxial heat exchanger string 1 is then connected to the wellhead sealing switching assembly 2 through the large four-way connector 13 and the small four-way connector 14. The top end of the outer heat exchanger tube 5 is fixed by the switching assembly base 2.4, and the top end of the inner central tube 6 is connected to... At the lower part of the sliding sleeve installation cavity 2.6, the outside of the wellhead sealing switching assembly 2 is connected to the ground integrated control system 3 through pipelines and shut-off valve group 11. The inlet end of the heat exchange medium storage tank 3.1 of the ground integrated control system 3 is connected to the central flow channel joint 2.2 through pipelines. The outlet end of the heat exchange medium storage tank 3.1 is connected to the air source heat pump 3.4 through pipelines, filter purifier 3.2 and circulation pump group 3.3. The outlet end of the air source heat pump 3.4 is connected to the inlet of the electric auxiliary heating storage tank 3.5. One outlet of the electric auxiliary heating storage tank 3.5 is connected to the wellhead sealing switching assembly 2 through pipelines and control valves, and the other outlet is connected to the multi-scenario heating external transmission pipeline 3.7 for heating use in various scenarios. S2, Gravity Self-Circulation Mode: In the absence of electricity or deep well conditions, close the annular pipe controllable shut-off valve group 11.1 and the central flow channel controllable shut-off valve group 11.2, switch the sliding sleeve 2.5 to be located in the sliding sleeve mounting cavity 2.6, so that the upper circulation flow hole 6.1 is exposed, connecting the central inner tube 6 and the outer heat exchange tube 5; when the liquid heat exchange medium flows downward along the annular flow channel 7 of the central inner tube 6 and the outer heat exchange tube 5, the formation temperature increases as it goes down, the liquid heat exchange medium continuously absorbs heat, and the temperature continuously rises until the heat exchange medium is vaporized. Because the lower heat absorption plate 5.2 is installed at the lower part of the outer heat exchange tube 5, the evaporation heat absorption effect of the outer heat exchange tube 5 at the bottom of the well is improved. Then, After passing through the lower circulation flow hole 9.7, the heat exchange medium enters the central flow channel 8 inside the central inner tube 6 and moves upward. The closer it gets to the ground, the lower the temperature becomes. The gaseous heat exchange medium gradually condenses and releases heat, turning into a liquid state, thereby continuously heating the liquid in the production pipe 4 near the ground. Since the upper heat sink 5.1 is installed on the upper part of the outer heat exchange pipe 5, the condensation and heat dissipation effect of the near-ground part is improved, avoiding the blockage caused by wax condensation of the oil well produced fluid. As the heat exchange medium reaches the upper circulation flow hole 6.1 at the top of the central inner tube 6, it recirculates into the annular flow channel 7 of the central inner tube 6 and the outer heat exchange pipe 5 to continue circulating, realizing gravity self-circulation operation. This mode is suitable for poleless production wellbores in remote Gobi deserts and other arid regions without power grid coverage or resident maintenance personnel. It covers various types of crude oil flowing wells, light oil wells, natural gas wells, coalbed methane wells, and shale gas wells. It is also applicable to deep wellbore conditions. It should be noted that the deeper the wellbore, the higher the ground temperature, thus meeting the heat extraction and anti-clogging requirements of the near-surface portion of the wellbore. This mode achieves zero-power operation and effectively suppresses wax deposition and clogging problems in the wellbore. The wellbore flow resistance remains stable over a long period, avoiding formation defects caused by blockages, significantly extending the wellbore's maintenance-free cycle, and eliminating the need for additional chemicals and operating costs.

[0033] S3, Heat pump heating forced circulation mode: In shallow well conditions, because the depth is insufficient to provide enough heat to achieve gravity self-circulation, the controllable shut-off valve group 11.1 of the annular pipe and the controllable shut-off valve group 11.2 of the central flow channel need to be opened. The heat exchange medium heated by the air source heat pump 3.4 flows downward through the circulating pump group 3.3, pipeline, and the controllable shut-off valve group 11.1 of the annular pipe into the annular flow channel 7 of the central inner pipe 6 and the outer heat exchange pipe 5, continuously heating the liquid in the production pipe 4 near the ground, preventing blockage caused by wax condensation of the produced fluid. The upper heat sink 5.1 installed on the upper part of the outer heat exchange pipe 5 improves the heat dissipation effect near the ground. As the depth increases, the formation temperature rises, and the heat exchange medium... The medium begins to absorb heat, and its temperature continuously rises. Due to the installation of lower heat-absorbing plates 5.2 at the bottom of the external heat exchange tube 5, the heat absorption effect of the external heat exchange tube 5 at the bottom of the well is improved. Then, it enters the central flow channel 8 in the central inner tube 6 through the lower circulation flow hole 9.7 and moves upward. The closer it gets to the ground, the lower the temperature becomes. The heat exchange medium gradually releases heat, thereby reheating the liquid in the production pipe 4 near the ground to prevent the produced fluid from waxing and condensing. Then, the heat exchange medium is sent outward through the sliding sleeve installation cavity 2.6 and the central flow channel joint 2.2 through the pipeline and the central flow channel controllable shut-off valve group 11.2 to the heat exchange medium storage tank 3.1, and is recirculated and heated by the air source heat pump 3.4 to achieve the heating of the heat exchange medium. This mode is suitable for conventional oil and gas production blocks with power supply, where the wellbore uses electric submersible pumps, screw pumps, or self-flowing methods for lifting, without a sucker rod structure. Common problems include wellbore wax buildup, heavy oil adhesion to the walls, and significant temperature drops along the wellbore. Traditional hot washing and dilution processes require frequent shutdowns, impacting production efficiency. This mode utilizes an air-source heat pump 3.4 for heating, actively regulating wellbore temperature, effectively inhibiting paraffin precipitation, reducing heavy oil viscosity, significantly reducing downtime, and improving production efficiency. The flow rate is infinitely adjustable, adaptable to various wellbores with different production volumes and media properties, offering strong versatility.

[0034] S4. Under extremely cold conditions or when there is a demand for external heating: The air source heat pump 3.4 and the electric heater in the electric auxiliary heating tank 3.5 are turned on in sequence to supplement the heat exchange medium in the circulation, so as to achieve forced circulation heating. In addition, the excess heat is used for heating in various scenarios through the multi-scenario heating transmission pipeline 3.7, so as to realize the reuse of the waste heat resources of the formation.

[0035] This model is applicable to oil and gas production wells in extremely cold northern regions, where the wellbore and long-distance pipelines from the wellhead to the joint station are prone to freezing and blockage in winter; refer to Figure 13 It is also suitable for long-distance pipelines, centralized heating, and supporting agricultural facilities with stable heating needs, realizing the resource-added utilization of ground waste heat, replacing traditional coal-fired and pure electric heating methods, and significantly reducing overall operating costs.

[0036] The above description is merely a partial preferred embodiment of the present invention. Any person skilled in the art can modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A dual-channel rodless wellbore heat extraction and anti-clogging system, comprising a surface integrated control system (3), characterized in that: Also includes The well is equipped with a coaxial heat exchange tube string (1), a wellhead sealing switching assembly (2), and a bottom gas-liquid separator (9). The upper end of the coaxial heat exchange tube string (1) is connected to the wellhead sealing switching assembly (2), and the wellhead sealing switching assembly (2) is connected to the surface integrated control system (3) through a pipeline. The coaxial heat exchange tube string (1) is lowered into the well along the production pipe (4), and the lower end of the coaxial heat exchange tube string (1) is connected to the bottom gas-liquid separator (9). The coaxial heat exchange tube string (1) is composed of an outer heat exchange tube (5) and a central inner tube (6). The central inner tube (6) is located in the inner cavity of the outer heat exchange tube (5), and the lower part of the central inner tube (6) is connected to the outer heat exchange tube (5) through the lower circulation flow hole (9.7). The upper part of the central inner tube (6) is provided with an upper circulation flow hole (6.1), which is connected to the outer heat exchange tube (5) through the upper circulation flow hole (6.1). The bottom gas-liquid splitter (9) includes an upper plug (9.1), a splitter body (9.2), and a product liquid flow hole (9.3). The upper plug (9.1) is provided on the upper part of the splitter body (9.2), and is connected to the bottom end of the external heat exchange tube (5) and the central inner tube (6) respectively through the upper plug (9.1). The outer wall of the splitter body (9.2) is provided with multiple product liquid flow holes (9.3). The wellhead sealing switching assembly (2) includes a switching assembly body (2.1), a central flow channel connector (2.2), an annular flow channel connector (2.3), a switching assembly base (2.4), a switching sliding sleeve (2.5), and a sliding sleeve mounting cavity (2.6). The inner cavity of the switching assembly body (2.1) is provided with a sliding sleeve mounting cavity (2.6), the bottom of the switching assembly body (2.1) is provided with a switching assembly base (2.4), the lower side wall of the switching assembly body (2.1) is provided with an annular flow channel connector (2.3), and the upper side wall is provided with a central flow channel connector (2.2). The inner flow channel of the central flow channel connector (2.2) is connected to the sliding sleeve mounting cavity (2.6). The lower end of the sliding sleeve mounting cavity (2.6) is movably connected to the upper end of the central inner tube (6). The switching sliding sleeve (2.5) is installed in the sliding sleeve mounting cavity (2.6) and can move up and down. The outer diameter of the switching sleeve (2.5) is smaller than the inner diameter of the central inner tube (6). The upper end of the switching sleeve (2.5) is provided with an annular limiting boss, the outer diameter of which is smaller than the inner diameter of the sleeve mounting cavity (2.6). When the switching sleeve (2.5) moves upward to the sleeve mounting cavity (2.6), it closes the channel between the central flow channel connector (2.2) and the sleeve mounting cavity (2.6). When the switching sleeve (2.5) moves downward to the central inner tube (6), it closes the upper circulation flow hole (6.1) at the top of the central inner tube (6).

2. The dual-channel rodless wellbore heat extraction and anti-clogging system according to claim 1, characterized in that: The bottom gas-liquid splitter (9) also includes bidirectional slips (9.4) and anchoring base rods (9.5). Anchoring base rods (9.5) are fixedly connected to the lower end of the splitter body (9.2), and one or more bidirectional slips (9.4) are installed on the anchoring base rods (9.5).

3. The dual-channel rodless wellbore heat extraction and anti-clogging system according to claim 2, characterized in that: The upper plug (9.1) is equipped with an upper connecting short pipe (9.6) at its center. Multiple lower circulation flow holes (9.7) are provided on the side wall of the upper connecting short pipe (9.6), and the upper end of the upper connecting short pipe (9.6) is connected to the lower end of the central inner pipe (6).

4. The dual-channel rodless wellbore heat extraction and anti-clogging system according to claim 3, characterized in that: Multiple sets of straightening components (10) are distributed between the external heat exchange tube (5) and the production tube (4), and the center of the straightening component (10) is provided with a cavity to reduce the resistance to the produced liquid gas downhole.

5. The dual-channel rodless wellbore heat extraction and anti-clogging system according to claim 4, characterized in that: The outer end of the central flow channel connector (2.2) is connected to the return end of the ground integrated control system (3) via a pipeline, a vacuum detector (12) and a central flow channel controllable shut-off valve group (11.2), and the outer end of the annular flow channel connector (2.3) is connected to the supply end of the ground integrated control system (3) via a pipeline and annular pipe controllable shut-off valve group (11.1).

6. The dual-channel rodless wellbore heat extraction and anti-clogging system according to claim 5, characterized in that: The ground integrated control system (3) includes a heat exchange medium storage tank (3.1), a filter purifier (3.2), a circulation pump group (3.3), an air source heat pump (3.4), an electric auxiliary heating storage tank (3.5), and a multi-scenario heating export pipeline (3.7). The inlet end of the heat exchange medium storage tank (3.1) is connected to the central flow channel connector (2.2) through a pipeline. The outlet end of the heat exchange medium storage tank (3.1) is connected to the air source heat pump (3.4) through a pipeline, the filter purifier (3.2), and the circulation pump group (3.3). The outlet end of the air source heat pump (3.4) is connected to the inlet of the electric auxiliary heating storage tank (3.5). One outlet of the electric auxiliary heating storage tank (3.5) is connected to the ring pipeline controllable shut-off valve group (11.1) through a pipeline and a control valve, and the other outlet is connected to the multi-scenario heating export pipeline (3.7) for external heating.

7. The dual-channel rodless wellbore heat extraction and anti-clogging system according to claim 6, characterized in that: The upper part of the external heat exchange tube (5) is equipped with heat sink (5.1) to improve the condensation heat dissipation effect of the near-ground part; the lower part of the external heat exchange tube (5) is equipped with heat absorption plate (5.2) to improve the evaporation heat absorption effect of the external heat exchange tube (5) at the bottom of the well.

8. A method for preventing blockage using the dual-channel rodless wellbore heat extraction anti-blockage system as described in claim 6, characterized in that: The process includes the following: S1. The downhole coaxial heat exchange tube string (1) is lowered into the well along the production pipe (4). The lower part of the inner central tube (6) is connected to the outer heat exchange tube (5) through the lower circulation flow hole (9.7), and the upper part of the inner central tube (6) is connected to the outer heat exchange tube (5) through the upper circulation flow hole (6.1). The upper end of the downhole coaxial heat exchange tube string (1) is then connected to the wellhead sealing switching assembly (2) through the large four-way connector (13) and the small four-way connector (14). The top end of the outer heat exchange tube (5) is fixed by the switching assembly base (2.4), and the top end of the inner central tube (6) is connected to the lower part of the sliding sleeve mounting cavity (2.6). The outer side of the wellhead sealing switching assembly (2) is connected by pipelines and shut-off valves. Group (11) is connected to the ground integrated control system (3). The inlet end of the heat exchange medium storage tank (3.1) of the ground integrated control system (3) is connected to the central flow channel connector (2.2) through a pipeline. The outlet end of the heat exchange medium storage tank (3.1) is connected to the air source heat pump (3.4) through a pipeline, filter purifier (3.2) and circulation pump group (3.3). The outlet end of the air source heat pump (3.4) is connected to the inlet of the electric auxiliary heating storage tank (3.5). One outlet of the electric auxiliary heating storage tank (3.5) is connected to the wellhead sealing switching assembly (2) through a pipeline and control valve, and the other outlet is connected to the multi-scenario heating export pipeline (3.7) for heating use in multiple scenarios. S2, Gravity Self-Circulation Mode: In the absence of electricity or deep well conditions, the controllable shut-off valve group (11.1) of the annular pipeline and the controllable shut-off valve group (11.2) of the central flow channel are closed, and the switching sleeve (2.5) is located in the sleeve mounting cavity (2.6), so that the upper circulation flow hole (6.1) is exposed to connect the central inner tube (6) and the outer heat exchange tube (5); when the liquid heat exchange medium flows downward along the annular flow channel (7) of the central inner tube (6) and the outer heat exchange tube (5), the formation temperature increases as it goes down, the liquid heat exchange medium continuously absorbs heat, and the temperature continuously rises until the heat exchange medium is vaporized, and then... After passing through the lower circulation flow hole (9.7), the medium enters the central flow channel (8) of the central inner tube (6) and moves upward. The closer it gets to the ground, the lower the temperature becomes. The gaseous heat exchange medium gradually condenses and releases heat and is converted into a liquid state, thereby continuously heating the liquid in the production pipe (4) near the ground and avoiding the blockage caused by wax condensation of the oil well produced fluid. As the heat exchange medium reaches the upper circulation flow hole (6.1) at the top of the central inner tube (6), it is recirculated into the annular flow channel (7) of the central inner tube (6) and the outer heat exchange tube (5) to continue circulating, realizing gravity self-circulation operation. S3, Heat pump heating forced circulation mode: In shallow well conditions, since the depth is insufficient to provide enough heat to achieve gravity self-circulation, the controllable shut-off valve group (11.1) of the annular pipeline and the controllable shut-off valve group (11.2) of the central flow channel need to be opened. The heat exchange medium heated by the air source heat pump (3.4) enters the annular flow channel (7) of the central inner pipe (6) and the outer heat exchange pipe (5) through the circulating pump group (3.3), pipeline and the controllable shut-off valve group (11.1) and flows downwards, continuously heating the liquid in the production pipe (4) near the ground, avoiding the blockage caused by wax condensation of the oil well produced fluid; as the depth increases, the formation temperature increases, and the heat exchange medium... The heat exchange medium begins to absorb heat, and its temperature continues to rise. Then, it enters the central flow channel (8) in the central inner tube (6) through the lower circulation flow hole (9.7) and moves upward. The closer it gets to the ground, the lower the temperature becomes. The heat exchange medium gradually releases heat, thereby reheating the liquid in the production pipe (4) near the ground to prevent the produced fluid from waxing and condensing. Then, the heat exchange medium is sent to the heat exchange medium storage tank (3.1) through the pipeline and the central flow channel controllable shut-off valve group (11.2) along the sliding sleeve installation cavity (2.6) and the central flow channel joint (2.2). It is then recirculated and heated by the air source heat pump (3.4) to achieve the heating of the heat exchange medium. S4. Under extremely cold conditions or when there is a demand for external heating: The air source heat pump (3.4) and the electric heater in the electric auxiliary heating tank (3.5) are turned on in sequence to supplement the heat exchange medium in the circulation and achieve forced circulation heating. In addition, the excess heat is used for heating in various scenarios through the multi-scenario heating transmission pipeline (3.7) to realize the reuse of the waste heat resources of the stratum.

Images