U-shaped geothermal well heating outcrop rock sample simulation experiment device and experiment method thereof

Abstract

The invention relates to a U-shaped geothermal well heating outcrop rock sample simulation experiment device and an experiment method thereof.The device comprises an outcrop rock sample heating system which comprises a plurality of outcrop rock sample models, the multiple outcrop rock sample models are combined and spliced in a U shape, water pipes are arranged in the multiple outcrop rock sample models in a penetrating mode, and each outcrop rock sample model is coated with a heating structure; the fluid circulating system comprises an outer circulating pipe, and a water pump is arranged on the outer circulating pipe; the cooling system comprises a cooling machine arranged on the outer circulating pipe, the temperature measuring system comprises a plurality of temperature measuring instruments and temperature sensing wire connectors, each temperature measuring instrument is electrically connected with each temperature sensing wire connector, and each temperature measuring instrument is used for measuring the inlet and outlet fluid temperature of the water pipe and the internal temperature of the outcrop rock sample model. The real stratum heat transfer working condition is simulated through the outcrop rock sample model, the research on the heat exchange efficiency of the U-shaped well and the stratum temperature change at the horizontal section is realized, and an experimental basis is provided for field application and optimization of the length of the horizontal section.

Description

Technical Field

[0001] The invention relates to the technical field of geothermal resource utilization, and in particular to a U-shaped geothermal well heating outcrop rock sample simulation experimental device and an experimental method thereof. Background Art

[0002] At present, the heat transfer capacity of U-shaped wells is mainly studied through numerical simulation to obtain basic laws. However, due to the relatively one-sided acquisition of basic parameters and the influence of regularity, the obtained laws have certain deviations. At the same time, since the control of experimental parameters in the conventional physical simulation test process in this aspect is difficult to be consistent with the actual formation, the experiment cannot study the influence of rock thermal conductivity on heat transfer efficiency. At the same time, the influence of cold accumulation effect on heat transfer will also be impossible to study. The above shortcomings make the experimental results have certain deviations from reality.

[0003] There are many factors that affect the heat transfer efficiency of the U-shaped well, such as fluid type, flow rate, horizontal section length, horizontal section depth, formation thermal conductivity, etc. The influence of these engineering geological parameters on the heat transfer efficiency of the U-shaped well is intuitive. In addition, the cold accumulation phenomenon is also a factor that affects the application of the U-shaped well. Cold accumulation means that during the heat exchange process of the U-shaped well, the low-temperature liquid absorbs heat from the formation, causing the formation temperature around the pipeline to drop to a lower level than the formation far away from the pipeline. This will greatly reduce the heat transfer efficiency of the U-shaped well. While reducing the efficiency, the range of cold accumulation will expand, thereby further reducing the heat transfer efficiency. Therefore, the more obvious the cold accumulation effect of the material, the lower the heat transfer efficiency of the U-shaped well. Therefore, it is necessary to determine the applicable conditions of the U-shaped well through a physical simulation experiment of U-shaped well heat exchange.

[0004] Therefore, the inventor, relying on many years of experience and practice in related industries, proposes a U-shaped geothermal well heating outcrop rock sample simulation experimental device and an experimental method thereof to overcome the defects of the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a U-shaped geothermal well heating outcrop rock sample simulation experimental device and an experimental method thereof, which simulates the actual formation heat transfer conditions through the outcrop rock sample model, realizes the research on the heat exchange efficiency of the U-shaped well and the formation temperature change in the horizontal section, and provides an experimental basis for field application and optimization of the horizontal section length.

[0006] The object of the present invention is achieved by providing a U-shaped geothermal well heating outcrop rock sample simulation experimental device, comprising:

[0007] An outcrop rock sample heating system comprises a plurality of outcrop rock sample models, wherein the plurality of outcrop rock sample models are assembled along a U-shaped combination, and the outcrop rock sample models are used to simulate real strata, and the number of outcrop rock sample models in a horizontal section is adjusted to simulate different horizontal section lengths; water pipes are inserted into the plurality of outcrop rock sample models, and the water pipes are used to simulate casings; a heating structure is coated on each of the outcrop rock sample models, and the heating structure is used to heat each of the outcrop rock sample models with adjustable temperature to simulate the characteristics of strata depth changing with temperature;

[0008] A fluid circulation system, comprising an external circulation pipe whose two ends are respectively connected to the two ends of the water pipe, and a water pump is arranged on the external circulation pipe, and the water pump is used to control the circulation of the fluid;

[0009] A cooling system, comprising a cooling machine arranged on the external circulation pipe, wherein the inlet of the cooling machine is communicated with the outlet of the water pipe, the outlet of the cooling machine is communicated with the inlet of the water pump, and the outlet of the water pump is communicated with the inlet of the water pipe;

[0010] The temperature measurement system includes multiple temperature measuring instruments and temperature sensing wire joints. Each of the temperature sensing wire joints is buried in each of the outcrop rock sample models. Each of the temperature measuring instruments is electrically connected to each of the temperature sensing wire joints. Each of the temperature measuring instruments is used to measure the inlet and outlet fluid temperatures of the water pipe and the internal temperature of the outcrop rock sample model.

[0011] In a preferred embodiment of the present invention, a first one-way valve and a second one-way valve are arranged on the external circulation pipe between the water pump and the inlet of the water pipe, the first one-way valve and the second one-way valve allow fluid to flow from the water pump to the water pipe, and a flow meter and a pressure gauge are arranged between the first one-way valve and the second one-way valve.

[0012] In a preferred embodiment of the present invention, a filter is arranged on the external circulation pipe between the outlet of the water pipe and the cooling machine, and a third one-way valve is arranged between the outlet of the water pipe and the filter, and the third one-way valve allows the fluid to flow from the water pipe to the cooling machine.

[0013] In a preferred embodiment of the present invention, a U-shaped water pipe groove is arranged along the inner edge of the outcrop rock sample model, the water pipe is arranged in the water pipe groove, and bentonite is filled between the outer wall of the water pipe and the upper inner wall of the water pipe groove.

[0014] In a preferred embodiment of the present invention, the outcrop rock sample model includes an upper rock sample and a lower rock sample that are buckled together, a lower water trough is arranged on the lower rock sample, and an upper water trough is arranged on the upper rock sample, and the lower water trough and the upper water trough are buckled together to form the water pipe trough.

[0015] In a preferred embodiment of the present invention, a plurality of cable grooves are arranged in the outcrop rock sample model, a temperature sensing wire is passed through each of the cable grooves, a first end of each of the cable grooves passes through the water pipe groove, each of the temperature sensing wire joints is located at the first end of each of the cable grooves, and a second end of each of the cable grooves extends to the outer surface of the outcrop rock sample model.

[0016] In a preferred embodiment of the present invention, the cross-sections of the water pipe trough and the wire trough are rectangular.

[0017] In a preferred embodiment of the present invention, the heating structure is a heating felt, and temperature regulators are arranged at intervals on the heating felt.

[0018] In a preferred embodiment of the present invention, the heating structure includes a constant temperature heating plate, and the constant temperature heating plate is connected to a temperature control box.

[0019] In a preferred embodiment of the present invention, the measuring temperature range of the thermometer is -50 to 250°C.

[0020] The object of the present invention can also be achieved by providing a U-shaped geothermal well heating outcrop rock sample simulation experimental method, comprising the following steps:

[0021] Step S1: assembling the aforementioned U-shaped geothermal well heating outcrop rock sample simulation experimental device;

[0022] Step S2: setting the temperature of the heating structure, continuously heating the outcrop rock sample model for a set time, and the rock is completely heated;

[0023] Step S3: start fluid circulation;

[0024] Step S4: After the cycle is stable, read the data of each temperature measuring instrument;

[0025] Step S5: The experiment ends and the data is processed.

[0026] In a preferred embodiment of the present invention, the assembly steps of the U-shaped geothermal well heating outcrop rock sample simulation experimental device include:

[0027] Step S11: assembling a plurality of outcrop rock sample models along a U-shape according to set specifications; placing water pipes and temperature sensing line joints inside the outcrop rock sample models, and filling with bentonite;

[0028] Step S12: Wrapping the outcrop rock sample model with a heating structure;

[0029] Step S13: Connect the fluid circulation system, the cooling system and the outcrop rock sample heating system.

[0030] In a preferred embodiment of the present invention, the number of outcrops is changed, and steps S2 to S4 are repeated to simulate the effect of different horizontal section lengths on the heat exchange efficiency.

[0031] In a preferred embodiment of the present invention, the fluid flow rate is adjusted and steps S2 to S4 are repeated to simulate the heat exchange efficiency of the U-shaped well at different flow rates.

[0032] In a preferred embodiment of the present invention, the temperature of the heating structure is adjusted, and steps S2 to S4 are repeated to simulate the heat exchange efficiency of the U-shaped well under different geothermal gradients.

[0033] As described above, the U-shaped geothermal well heating outcrop rock sample simulation experimental device and the experimental method thereof of the present invention have the following beneficial effects:

[0034] The present invention can simulate the temperature changes of the inlet, outlet and outcrop under different parameters (different rock thermal conductivity, different geothermal flow, different formation temperature, different flow velocity, different horizontal section length), and provide an experimental basis for the optimization of the horizontal section length of the U-shaped well and the determination of the cold accumulation range of the rock formation.

[0035] The present invention simulates the actual stratum heat transfer condition through the outcrop rock sample model, so that the experimental results are universal and can be directly applied in engineering practice;

[0036] The invention can measure the cold accumulation range of rock formations, and provide an experimental basis and a theoretical basis for selecting the type of formation to be drilled in a U-shaped well. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0038] in:

[0039] Figure 1 : It is a schematic diagram of the simulation experimental device for heating outcrop rock samples by a U-shaped geothermal well of the present invention.

[0040] Figure 2 : It is a schematic diagram of the outcrop rock sample heating system of the present invention.

[0041] Figure 3 : It is a schematic diagram of the lower half rock sample of the present invention.

[0042] Figure 4 : It is a flow chart of the simulation experimental method of heating outcrop rock samples by a U-shaped geothermal well of the present invention.

[0043] In the figure:

[0044] 1. Outcrop rock sample heating system;

[0045] 11. Outcrop rock sample model; 111. Upper half rock sample; 112. Lower half rock sample;

[0046] 12. Water pipes;

[0047] 13. Heating structure; 131. Heating felt; 132. Temperature regulator; 133. Constant temperature heating plate; 134. Temperature control box;

[0048] 14. Water pipe trough;

[0049] 15. Bentonite;

[0050] 16. Wire duct;

[0051] 2. Fluid circulation system;

[0052] 21. External circulation pipe; 22. Water pump; 23. First one-way valve; 24. Second one-way valve; 25. Flow meter; 26. Pressure gauge; 27. Filter; 28. Third one-way valve;

[0053] 3. Cooling system;

[0054] 31. Cooling machine;

[0055] 4. Temperature measurement system;

[0056] 41. Thermometer; 42. Temperature sensing wire connector. DETAILED DESCRIPTION

[0057] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0058] The specific embodiments of the present invention described herein are only used to explain the purpose of the present invention and cannot be understood as limiting the present invention in any way. Under the guidance of the present invention, technicians can conceive of any possible variations based on the present invention, which should be considered to belong to the scope of the present invention. It should be noted that when an element is referred to as "arranged on" another element, it can be directly on the other element or there can also be a central element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a central element at the same time. The terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, or it can be the internal communication of two elements, it can be directly connected, or it can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are only for illustrative purposes and do not represent the only implementation method.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0060] like Figures 1 to 3 As shown, the present invention provides a U-shaped geothermal well heating outcrop rock sample simulation experimental device, comprising:

[0061] The outcrop rock sample heating system 1 comprises a plurality of outcrop rock sample models 11, which are assembled along a U-shaped combination. By adjusting the number of outcrop rock sample models in the horizontal section, the influence of different horizontal section lengths on the heat exchange efficiency can be simulated, and the preferred range of the horizontal section of the U-shaped well can be studied at the same time; the outcrop rock sample model 11 is used to simulate the real formation, so that the various parameters used in the experiment are closer to the real working conditions, and the experimental results are more reliable; a water pipe 12 (iron water pipe) is inserted into the plurality of outcrop rock sample models 11, and the water pipe 12 is used to simulate the casing. The water pipe is made of the same material as the casing, which can effectively control the heat transfer coefficient and make the result more accurate; each outcrop rock sample model is coated with a heating structure 13, and the heating structure 13 is used to heat each outcrop rock sample model with adjustable temperature to simulate the characteristics of the formation depth changing with temperature; the heating structure 13 heats the outcrop rock sample model 11, so that the outcrop rock sample model reaches the real formation temperature from the outside to the inside, and its temperature can be adjusted according to the situation, and the heating temperature of each outcrop rock sample model is different;

[0062] The fluid circulation system 2 includes an outer circulation pipe 21 whose two ends are respectively connected to the two ends of the water pipe. A water pump 22 is arranged on the outer circulation pipe 21. The water pump 22 is used to control the fluid circulation. The fluid circulation system 2 can control the fluid flow rate and simulate the real working condition of the U-shaped well heat exchange fluid circulation in the experiment.

[0063] The cooling system 3 includes a cooler 31 disposed on the external circulation pipe 21, the inlet of the cooler 31 is connected to the outlet of the water pipe 12, the outlet of the cooler 31 is connected to the inlet of the water pump 22, and the outlet of the water pump 22 is connected to the inlet of the water pipe 12; the cooling system 3 is used to cool the fluid that has been heated by the outcrop rock model to room temperature for the next circulation; the water pump 22 extracts the heated fluid and sends it to the cooler 31, under the action of the cooler 31, the fluid is cooled to room temperature, and then re-injected into the water pipe 12 in the outcrop rock model to complete the circulation;

[0064] The temperature measuring system 4 includes a plurality of temperature measuring instruments 41 and a plurality of temperature sensing wire joints 42. Each temperature sensing wire joint 42 is buried in each outcrop rock sample model 11. Each temperature measuring instrument 41 is electrically connected to each temperature sensing wire joint 42. Each temperature measuring instrument 41 is used to measure the inlet and outlet fluid temperatures of the water pipe and the internal temperature of the outcrop rock sample model, and to measure the heat exchange efficiency of the U-shaped well and the cold accumulation range.

[0065] The U-shaped geothermal well heating outcrop rock sample simulation experimental device of the present invention can simulate the temperature changes of the inlet, outlet and inside of the outcrop under different parameters (different rock thermal conductivity, different geothermal flow, different formation temperature, different flow velocity, different horizontal section length), and provide an experimental basis for the optimization of the horizontal section length of the U-shaped well and the determination of the cold accumulation range of the rock formation;

[0066] The present invention simulates the actual stratum heat transfer condition through the outcrop rock sample model, so that the experimental results are universal and can be directly applied in engineering practice;

[0067] The invention can measure the cold accumulation range of rock formations, and provide an experimental basis and a theoretical basis for selecting the type of formation to be drilled in a U-shaped well.

[0068] Further, if Figure 1 As shown, a first one-way valve 23 and a second one-way valve 24 are arranged on the outer circulation pipe 21 between the water pump 22 and the inlet of the water pipe 12. The first one-way valve 23 and the second one-way valve 24 allow the fluid to flow from the water pump to the water pipe. A flow meter 25 and a pressure gauge 26 are arranged between the first one-way valve 23 and the second one-way valve 24. The fluid circulation system can control the fluid flow rate, and in the experiment, it simulates the real working conditions of the U-shaped well heat exchange fluid circulation. The outer circulation pipe 21 can be replaced by a convenient, highly plastic and adaptable leather hose; the water pump is used to control the fluid circulation, and the flow rate can be controlled by changing the pump pressure.

[0069] Further, if Figure 1 As shown, a filter 27 is provided on the outer circulation pipe 21 between the outlet of the water pipe and the cooler, and a third one-way valve 28 is provided between the outlet of the water pipe and the filter. The third one-way valve 28 allows the fluid to flow from the water pipe to the cooler. The cooling system is used to cool the produced fluid heated by the outcrop to room temperature for the next circulation.

[0070] Further, if Figure 2 As shown, a water pipe groove 14 is set in the outcrop rock sample model 11, a water pipe 12 is set in the water pipe groove 14, and bentonite 15 is filled between the outer wall of the water pipe and the upper inner wall of the water pipe groove. The bentonite is used to fill the gap between the water pipe and the upper inner wall of the water pipe groove. Since the outcrop is hard and has no rheological properties, it cannot be processed in contact with the water pipe and the temperature sensing line during processing, so a certain amount of excess will flow out and be filled with bentonite.

[0071] Further, if Figure 2 As shown, the outcrop rock sample model 11 includes an upper rock sample 111 and a lower rock sample 112 which are buckled together. A lower water trough is arranged on the lower rock sample, and an upper water trough is arranged on the upper rock sample. The lower water trough and the upper water trough are buckled together to form a water pipe trough 14.

[0072] Further, if Figure 2 , Figure 3 As shown, a plurality of cable grooves 16 are arranged in the outcrop rock sample model 11, and a temperature sensing wire is passed through each cable groove 16. The first end of each cable groove 16 passes through the water pipe groove 14, and each temperature sensing wire joint is located at the first end of each cable groove 16. The second end of each cable groove extends to the outer surface of the outcrop rock sample model.

[0073] Furthermore, it is inconvenient to process the pipe into a circular shape according to the shape of the pipe, so the cross-sections of the water pipe groove 14 and the wire groove 16 are set to be rectangular.

[0074] Further, if Figure 2 As shown, the heating structure can be a heating felt 131, and a temperature regulator 132 is arranged at intervals on the heating felt 131. The heating felt and the temperature regulator are used to heat the outcrop rock sample model, and different outcrops are heated at different temperatures, so that the characteristics of the formation depth changing with temperature can be simulated.

[0075] Further, if Figure 1 As shown, the heating structure can also be a constant temperature heating plate 133, and the constant temperature heating plate 133 is connected to a temperature control box 134. The constant temperature heating plate 133 and the temperature control box 134 are used to heat the outcrop rock sample model, and different outcrops are heated at different temperatures, so that the characteristics of the depth of the formation changing with temperature can be simulated.

[0076] Furthermore, the thermometer 41 is a temperature sensing line type thermometer, and the measuring temperature range of the thermometer is -50 to 250° C. It meets the experimental requirements and can replace the temperature sensing line. Its function is to read the temperature in real time and record the temperature change trend.

[0077] The present invention also provides a U-shaped geothermal well heating outcrop rock sample simulation experimental method (the steps are as follows Figure 4 As shown), comprising the following steps:

[0078] Step S1: assembling the aforementioned U-shaped geothermal well heating outcrop rock sample simulation experimental device;

[0079] Specifically, the assembly steps include:

[0080] Step S11: multiple outcrop rock sample models 11 are assembled along a U-shape according to set specifications; water pipes 12 and temperature sensing line joints 42 are placed inside the multiple outcrop rock sample models 11, and bentonite 15 is filled;

[0081] Step S12: wrapping a plurality of outcrop rock sample models 11 with a heating structure 13; in a specific embodiment, a heating felt 131 is used to wrap the outcrop rock sample models 11;

[0082] Step S13: Connect the fluid circulation system, the cooling system and the outcrop rock sample heating system.

[0083] Step S2: setting the temperature of the heating structure 13, continuously heating the outcrop rock sample model for a set time, and the rock is completely heated;

[0084] In a specific embodiment, the outcrop rock sample model is heated continuously for one week (7 days) to ensure that the rock is completely heated;

[0085] Step S3: start fluid circulation;

[0086] Step S4: After the cycle is stable, read the data of each temperature measuring instrument;

[0087] Preferably, the number of outcrops is changed, and steps S2 to S4 are repeated to simulate the effect of different horizontal section lengths on heat exchange efficiency;

[0088] Preferably, the fluid flow rate is adjusted, and steps S2 to S4 are repeated to simulate the heat exchange efficiency of the U-shaped well at different flow rates;

[0089] Preferably, the temperature of the heating structure is adjusted, and steps S2 to S4 are repeated to simulate the heat exchange efficiency of the U-shaped well under different geothermal gradients;

[0090] Preferably, the power of the heating plate is adjusted, and steps S2 to S4 are repeated to simulate the heat exchange efficiency of the U-shaped well under different geothermal flows;

[0091] Preferably, the outcrop type is changed, and steps S2 to S4 are repeated to simulate the heat exchange efficiency of the U-shaped well under different thermal conductivities;

[0092] Step S5: The experiment ends and the data is processed.

[0093] As described above, the U-shaped geothermal well heating outcrop rock sample simulation experimental device and the experimental method thereof of the present invention have the following beneficial effects:

[0094] The present invention can simulate the temperature changes at the inlet, outlet and inside the outcrop under different parameters (different formation temperature, different flow rate, different horizontal section length), providing an experimental basis for the optimization of the horizontal section length of the U-shaped well and the determination of the cold accumulation range of the rock formation;

[0095] The present invention simulates the actual stratum heat transfer condition through the outcrop rock sample model, so that the experimental results are universal and can be directly applied in engineering practice;

[0096] The invention can measure the cold accumulation range of rock formations, and provide an experimental basis and a theoretical basis for selecting the type of formation to be drilled in a U-shaped well.

[0097] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any person skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A U-shaped geothermal well heating outcrop rock sample simulation experimental device, characterized in that: include, An outcrop rock sample heating system comprises a plurality of outcrop rock sample models, wherein the plurality of outcrop rock sample models are assembled along a U-shaped combination, and the outcrop rock sample models are used to simulate real strata, and the number of outcrop rock sample models in a horizontal section is adjusted to simulate different horizontal section lengths; water pipes are inserted into the plurality of outcrop rock sample models, and the water pipes are used to simulate casings; a heating structure is coated on each of the outcrop rock sample models, and the heating structure is used to heat each of the outcrop rock sample models with adjustable temperature to simulate the characteristics of strata depth changing with temperature; A fluid circulation system, comprising an external circulation pipe whose two ends are respectively connected to the two ends of the water pipe, and a water pump is arranged on the external circulation pipe, and the water pump is used to control the circulation of the fluid; A cooling system, comprising a cooling machine arranged on the external circulation pipe, wherein the inlet of the cooling machine is communicated with the outlet of the water pipe, the outlet of the cooling machine is communicated with the inlet of the water pump, and the outlet of the water pump is communicated with the inlet of the water pipe; The temperature measurement system includes multiple temperature measuring instruments and temperature sensing wire joints. Each of the temperature sensing wire joints is buried in each of the outcrop rock sample models. Each of the temperature measuring instruments is electrically connected to each of the temperature sensing wire joints. Each of the temperature measuring instruments is used to measure the inlet and outlet fluid temperatures of the water pipe and the internal temperature of the outcrop rock sample model.

2. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 1, characterized in that: A first one-way valve and a second one-way valve are arranged on the external circulation pipe between the water pump and the inlet of the water pipe. The first one-way valve and the second one-way valve allow fluid to flow from the water pump to the water pipe. A flow meter and a pressure gauge are arranged between the first one-way valve and the second one-way valve.

3. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 2, characterized in that: A filter is arranged on the external circulation pipe between the outlet of the water pipe and the cooling machine, and a third one-way valve is arranged between the outlet of the water pipe and the filter. The third one-way valve allows the fluid to flow from the water pipe to the cooling machine.

4. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 1, characterized in that: A U-shaped water pipe groove is arranged along the inner edge of the outcrop rock sample model, the water pipe is arranged in the water pipe groove, and bentonite is filled between the outer wall of the water pipe and the upper inner wall of the water pipe groove.

5. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 4, characterized in that: The outcrop rock sample model comprises an upper rock sample and a lower rock sample which are buckled together, a lower water trough is arranged on the lower rock sample, and an upper water trough is arranged on the upper rock sample, and the lower water trough and the upper water trough are buckled together to form the water pipe trough.

6. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 4, characterized in that: A plurality of cable grooves are arranged in the outcrop rock sample model, each of which is provided with a temperature-sensitive wire, a first end of each of the cable grooves passes through the water pipe groove, each of the temperature-sensitive wire joints is located at the first end of each of the cable grooves, and a second end of each of the cable grooves extends to the outer surface of the outcrop rock sample model.

7. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 6, characterized in that: The cross sections of the water pipe trough and the wire trough are arranged in a rectangular shape.

8. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 1, characterized in that: The heating structure is a heating felt, and temperature regulators are arranged at intervals on the heating felt.

9. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 1, characterized in that: The heating structure comprises a constant temperature heating plate, and a temperature control box is connected to the constant temperature heating plate.

10. The U-shaped geothermal well heating outcrop rock sample simulation experimental device according to claim 1, characterized in that: The measuring temperature range of the thermometer is -50 to 250°C.

11. A U-shaped geothermal well heating outcrop rock sample simulation experimental method, characterized in that: The following steps are involved: Step S1: assembling the U-shaped geothermal well heating outcrop rock sample simulation experimental device as described in any one of claims 1 to 10; Step S2: setting the temperature of the heating structure, continuously heating the outcrop rock sample model for a set time, and the rock is completely heated; Step S3: start fluid circulation; Step S4: After the cycle is stable, read the data of each temperature measuring instrument; Step S5: The experiment ends and the data is processed.

12. The U-shaped geothermal well heating outcrop rock sample simulation experimental method according to claim 11, characterized in that: The assembly steps of the U-shaped geothermal well heating outcrop rock sample simulation experimental device include: Step S11: assembling a plurality of outcrop rock sample models along a U-shape according to set specifications; placing water pipes and temperature sensing line joints inside the outcrop rock sample models, and filling with bentonite; Step S12: Wrapping the outcrop rock sample model with a heating structure; Step S13: Connect the fluid circulation system, the cooling system and the outcrop rock sample heating system.

13. The U-shaped geothermal well heating outcrop rock sample simulation experimental method according to claim 11, characterized in that: The number of outcrops was changed and steps S2 to S4 were repeated to simulate the effect of different horizontal section lengths on the heat transfer efficiency.

14. The U-shaped geothermal well heating outcrop rock sample simulation experimental method according to claim 11, characterized in that: The fluid flow rate is adjusted and steps S2 to S4 are repeated to simulate the heat exchange efficiency of the U-shaped well at different flow rates.

15. The U-shaped geothermal well heating outcrop rock sample simulation experimental method according to claim 11, characterized in that: The temperature of the heating structure is adjusted, and steps S2 to S4 are repeated to simulate the heat exchange efficiency of the U-shaped well under different geothermal gradients.

Images