A pressure pulse downhole phase change heat generator and its working method

Abstract

The present invention relates to the field of geothermal phase change exploitation in deep wells and ultra-deep wells such as geology and petroleum, and is specifically a pressure pulse downhole phase change heat exchanger and its working method, the heat exchanger includes an upper hemispherical shell, a cylindrical shell and a lower hemispherical shell arranged in sequence from top to bottom, and is provided with three-layer casing, a counterweight, an inverted T-type piston, a pressure pulse flow limiter, a double-layer spiral baffle, and a flow direction converter; the three-layer casing is vertically penetrated at the axis of the upper hemispherical shell, the outer layer of the three-layer casing is an annular layer for injecting phase change medium, the middle layer is filled with insulation material, and the inner layer is a hollow flow channel for expansion and transportation of the phase change medium after phase change. This heat exchanger has no other energy-consuming components, and uses the pulse pressure of the phase change medium as the main driving force of the heat-carrying phase change medium after completing the heat exchange, and provides power through the process of phase change free expansion of the phase change medium absorbing heat in the heat exchanger, while realizing the return of the heat-carrying phase change medium to the ground, pumping low-temperature geothermal water to achieve efficient exploitation.

Description

Technical Field

[0001] The present invention relates to the field of geothermal phase change exploitation in deep wells and ultra-deep wells such as geology and petroleum, and in particular to a pressure pulse downhole phase change heat generator and a working method thereof. Background Art

[0002] With the development of exploration and development technology, the exploitation depth of oil and gas wells has been continuously deepened. At the end of crude oil production, the water content of oil and gas fields is relatively high. The use of abandoned deep and ultra-deep wells to carry out deep geothermal resource exploitation and the oil-heat co-production technology of deep and ultra-deep wells have also attracted more and more attention from the industry. There are many technical difficulties in the exploitation of geothermal resources in oil layers of deep and ultra-deep wells, including the problem of effective reinjection under high temperature and high pressure conditions, the problem of heat carrier fluid dissipation along the way, and the effective water lifting method at absolute depth.

[0003] In response to the problem of geothermal resource exploitation in deep and ultra-deep wells, researchers from industry enterprises and scientific research institutes have come up with a variety of solutions, such as the method of co-extracting geothermal energy and oil and gas in oil or natural gas exploitation (CN109931036A), in which casing is lowered into the well after the production well is completed, and the rock formation is perforated and fractured in the well section with higher temperature in the oil and gas layer, and heat conductive fillers are filled into the cracks to form a conductive belt, and the heat is collected through the conveying pipe in the casing and the gravity heat pipe heat exchanger to realize the convective heat transfer process; such as a high-efficiency extraction method for deep geothermal exploitation wells The mining equipment (CN114876414A) reduces heat loss by setting the extraction tube as a double-layer vacuum tube, and extracts the water with higher temperature at the bottom of the well to the wellhead, achieving the purpose of lowering the temperature below 10°C; such as a method for segmented isolation and layered mining of deep fractured geothermal energy (CN114922594A), which sets multiple underground aquifers as target layers. When one of them is selected as the mining layer, the other mining layers are closed, solving the problem of difficult mining of geothermal energy in the process of geothermal development by group pumping / reinjection of multiple layers deep apart.

[0004] The process of geothermal extraction in deep and ultra-deep wells is complex. The current geothermal extraction process in deep and ultra-deep wells is studied through methods such as fracturing, extraction and stratified extraction. However, the fracture network orientation, fracture network gap and expansion distance formed by hydraulic fracturing will vary, resulting in the accumulation of fillers in some fractures with large drop heights or even blocking the fracture network. The depth of deep and ultra-deep wells is large, and the method of lifting water to extract geothermal heat will cause large heat dissipation of geothermal water along the upstream process, and the temperature will drop significantly when it is extracted to the ground, resulting in energy waste. This is the main factor leading to the low actual extraction efficiency and high extraction cost of geothermal resources. Summary of the invention

[0005] In order to solve the problems of large heat loss and low efficiency in geothermal exploitation in deep wells and ultra-deep wells, the present invention provides a pressure pulse underground phase change heat exchanger and its working method, which has no other energy-consuming components and uses the pulse pressure of the phase change medium as the main driving force for the heat-carrying phase change medium after the heat exchange is completed. The phase change medium absorbs heat in the heat exchanger and undergoes phase change and free expansion to provide power. While the heat-carrying phase change medium returns to the ground, low-temperature geothermal water is pumped out to achieve efficient exploitation. The technical solutions adopted by the present invention are as follows:

[0006] A pressure pulse downhole phase change heat exchanger comprises an upper hemispherical shell, a cylindrical shell and a lower hemispherical shell which are arranged in sequence from top to bottom, and is provided with a three-layer casing, a counterweight, an inverted T-shaped piston, a pressure pulse flow limiter, a double-layer spiral baffle and a flow direction converter;

[0007] The three-layer casing is vertically arranged at the axis of the upper hemispherical shell, the outer layer of the three-layer casing is an annular layer for injecting phase change medium, the middle layer is filled with insulation material, and the inner layer is a hollow flow channel for expansion and transportation of the phase change medium after phase change;

[0008] The counterweight is located at the upper part of the cylindrical shell, and a phase-change medium bypass flow channel for the phase-change medium to flow downward is provided on the left side of the counterweight, a central cavity is provided in the middle, and a low-temperature geothermal water outlet is provided on the right side. The phase-change medium bypass flow channel is connected to the outer layer of the three-layer casing as an annular layer, and the central cavity is connected to the hollow flow channel of the three-layer casing. The T-shaped piston is arranged in the central cavity so as to be movable up and down, and the pressure pulse limiter is installed in the phase-change medium bypass flow channel to control its on and off; a phase-change medium upward channel is also provided in the counterweight, and the phase-change medium upward channel is used to connect the central cavity and the hollow flow channel of the three-layer casing;

[0009] The upper end of the double-layer spiral baffle is equipped with an upper cover plate and the lower end is equipped with a lower cover plate. The upper cover plate is provided with a reversing flow channel. A plurality of geothermal water annular flow channel layers and phase change medium annular flow channel layers are provided in the double-layer spiral baffle. The centralmost phase change medium annular flow channel layer is the central flow channel. Each layer of geothermal water annular flow channel layer is connected in sequence through the corresponding reversing flow channel. Each layer of phase change medium annular flow channel layer is connected in sequence through the corresponding reversing flow channel. The outermost layer of the phase change medium annular flow channel layer is connected to the phase change medium bypass flow channel. The central flow channel is used to transport the phase change medium after phase change and is connected to the middle cavity. An annular piston is provided in the innermost layer of the geothermal water annular flow channel layer. The annular piston is connected to the T-type piston to move up and down.

[0010] A geothermal water inlet is provided at the lower end of the lower hemispherical shell, and the flow direction converter is installed in the lower hemispherical shell. The flow direction converter includes a lower inlet, an upper overflow outlet, a lower overflow inlet and an upper outlet. The lower inlet is connected to the geothermal water inlet, and the upper overflow outlet and the lower overflow inlet are both connected to the shell cavity of the lower hemispherical shell. The position of the upper overflow outlet is higher than that of the lower overflow inlet, and the upper outlet is connected to the innermost geothermal water annular flow channel layer through the lower cover plate.

[0011] The pressure pulse downhole phase change heat exchanger, wherein the pressure pulse flow restrictor separates the phase change medium bypass flow channel into an upper phase change medium bypass flow channel and a lower phase change medium bypass flow channel, wherein the front end of the upper phase change medium bypass flow channel is connected to the annular layer of the three-layer casing, and the rear end of the lower phase change medium bypass flow channel is connected to the outermost phase change medium annular flow channel layer;

[0012] The pressure pulse limiter includes a conical plug, a spring II, a base and a side wall. The top of the plug is an inverted conical cavity, which is connected to the rear end of the upper phase change medium bypass flow channel. The spring II is installed on the base, and the top of the spring II is connected to the plug to drive it to move up and down. The outside of the plug and the outside of the side wall are provided with flow channels for connecting the upper phase change medium bypass flow channel and the lower phase change medium bypass flow channel.

[0013] In the above-mentioned pressure pulse downhole phase change heat exchanger, a limit sleeve and a reducing piston are provided at the lower end of the three-layer casing. The outer diameter of the limit sleeve matches the counterweight, and the inner diameter matches the reducing piston for sliding. A spring I is provided on the outer edge of the reducing piston, and the upper end of the spring I contacts the lower end of the limit sleeve. The hollow flow channel of the three-layer casing extends through the center of the limit sleeve and the center of the reducing piston to connect to the middle cavity.

[0014] The above-mentioned pressure pulse downhole phase change heat generator has an upper intersection channel provided in the upper cover plate so that the phase change medium and geothermal water can be reversed at the upper end of the double-layer spiral baffle respectively; and a lower intersection channel is provided in the lower cover plate so that the phase change medium and geothermal water can be reversed at the lower end of the double-layer spiral baffle respectively.

[0015] The above-mentioned pressure pulse downhole phase change heat exchanger, the upper intersection channel includes a phase change medium flow channel, a phase change medium reversing flow channel, a geothermal water reversing flow channel and a low-temperature geothermal water flow channel, wherein the phase change medium flow channel is connected to the middle cavity where the T-type piston is located to allow the phase change medium that has undergone phase change to circulate, the phase change medium reversing flow channel is used for the reversing circulation of the phase change medium that has not undergone phase change in the phase change medium annular flow channel layer, and the geothermal water reversing flow channel is used for the reversing circulation of geothermal water in the geothermal water annular flow channel layer. The low-temperature geothermal water flow channel is connected to the geothermal water reversing flow channel, and the low-temperature geothermal water flow channel is connected to the low-temperature geothermal water outlet upward.

[0016] In the above-mentioned pressure pulse downhole phase change heat exchanger, the boiling point of the phase change medium is lower than the geothermal layer extraction temperature, and the material of the phase change medium can be any one or more of R141b (dichloromonofluoroethane), R142b (monochlorodifluoroethane), R134a (tetrafluoroethane) or R600a (isobutane).

[0017] The present invention also relates to a working method of a pressure pulse downhole phase change heat exchanger, comprising the following steps:

[0018] S1) The phase change medium is injected into the annular layer of the three-layer casing, and the phase change medium enters the outermost phase change medium annular flow channel layer of the double-layer spiral baffle through the phase change medium bypass flow channel and circulates in the phase change medium annular flow channel layer from the outside to the inside. In this process, the pressure pulse limiter reciprocates according to the injection pressure of the phase change medium to realize the pulsed opening and closing of the phase change medium bypass flow channel; with the injection of the phase change medium, the air in the double-layer spiral baffle is compressed and the pressure increases, the central flow channel is connected with the middle cavity, and the high-pressure air pushes the T-type piston upward, and the annular piston also moves upward, so that the air in the lower hemispherical shell is sucked, and the hot water in the well enters the flow converter through the geothermal water inlet, and flows into the lower hemispherical shell cavity at the overflow outlet at the upper end of the flow converter and is enriched there; when the phase change medium is continuously injected, the pressure pulse limiter reciprocates, and the annular piston also reciprocates up and down to realize the suction of geothermal water;

[0019] S2) When the height of the geothermal water in the shell cavity of the lower hemispherical shell is greater than the height of the lower overflow inlet flowing to the converter, the geothermal water flows from the lower overflow inlet through the flow channel in the lower cover plate into the geothermal water annular flow channel layer of the outermost layer of the double-layer spiral baffle plate;

[0020] S3) Then the geothermal water flows through the geothermal water annular flow channel layer from outside to inside layer by layer. During this period, each layer of geothermal water exchanges heat with the phase change medium in the phase change medium annular flow channel layer, and the temperature of the geothermal water decreases. At the same time, the temperature of the phase change medium increases and becomes gas phase and is enriched above the double-layer spiral baffle. It enters the middle cavity through the innermost layer of the phase change medium annular flow channel layer and gathers. The continuous accumulation and increase in pressure of the gas phase change medium can also push the T-type piston upward. When the T-type piston ascends to the phase change medium upward channel, the gas phase change medium flows through the phase change medium upward channel to the hollow flow channel of the three-layer casing. Then the pressure of the gas phase change medium decreases, and the T-type piston descends to close the connection with the upward channel. Then the gas phase change medium gathers in the central cavity again to make the T-type piston ascend again, and the cycle continues.

[0021] The beneficial effects of the present invention are as follows: based on the principle that the phase change of the phase change medium and the convective heat transfer of the geothermal fluid induce the phase change of the medium to provide power, the exploitation of deep well and ultra-deep well geothermal resources is assisted, and the phase change medium and the geothermal water are subjected to convective heat exchange in the double-layer spiral baffle, and the gas phase pressure generated by the phase change expansion of the phase change medium after the heat exchange is used as the driving force, and the gas phase pressure can also be used for the pressure pulse limiter to determine whether the threshold pressure of the phase change medium needs to be continued. During the operation of the heat exchanger, the power required is only the pressure to make the phase change medium flow in, and there is no need to provide additional driving force for the reflux of the phase change medium and the driving force for the inflow and outflow of geothermal water. The energy consumption is small and no complex energy conversion is required. The three-layer casing has a heat preservation function, and can also reduce the heat loss of the phase change medium in the upward process after the phase change. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the overall structure of an embodiment of the present invention (black arrows represent phase change media, white arrows represent geothermal water);

[0023] Figure 2 This is a schematic diagram of the installation of a T-type piston according to an embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the structure of a pressure pulse current limiter according to an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of a flow channel of an upper cover plate according to an embodiment of the present invention;

[0026] Figure 5 It is a schematic diagram of the principle of the geothermal water reversing flow channel according to an embodiment of the present invention;

[0027] Figure 6 It is a schematic diagram of the principle of the phase change medium reversing flow channel and the phase change medium flow guide channel according to an embodiment of the present invention;

[0028] Figure 7 This is a schematic diagram of the principle of the lower cover plate and the flow direction converter according to an embodiment of the present invention;

[0029] Figure 8 It is a schematic cross-sectional view of a double-layer spiral baffle according to an embodiment of the present invention.

[0030] In the figure: 1 is a three-layer casing, 2 is an upper hemispherical shell, 5 is a spring I, 6 is a limit sleeve, 7 is a counterweight, 8 is a different-diameter piston, 9 is a T-type piston, 10 is a pressure pulse limiter, 11 is an upper intersection channel, 12 is a lower intersection channel, 13 is a lower hemispherical shell, 14 is a geothermal water inlet, 15 is a low-temperature geothermal water outlet, 16 is an upper cover plate, 17 is a cylindrical shell, 18 is a double-layer spiral baffle, 19 is a flow direction converter, 20 is a lower cover plate,

[0031] 41 is an upper phase change medium side flow channel, 42 is a lower phase change medium side flow channel, 43 is a phase change medium upflow channel,

[0032] 91 is an annular piston, 92 is a central cavity, 93 is an interface, 94 is a spring II,

[0033] 101 is an inverted cone cavity, 102 is a plug, 103 is a spring II, 104 is a base, 105 is a cylinder wall,

[0034] 111 is a phase change medium flow channel, 112 is a geothermal water reversing flow channel, 113 is a phase change medium reversing flow channel, 114 is a low-temperature geothermal water flow channel,

[0035] 181 is the outermost geothermal water annular flow channel, 182 is the outermost phase change medium annular flow channel, 183 is the innermost geothermal water annular flow channel, 184 is the innermost phase change medium annular flow channel, 185 is the central flow channel,

[0036] 191 is the end inlet, 192 is the upper overflow outlet, 193 is the lower overflow inlet, 194 is the upper outlet,

[0037] 201 is the first boss, 202 is the second boss, and 203 is the third boss. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is explained in detail below in conjunction with the accompanying drawings. The following embodiments are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical terms used have the same meanings as those commonly understood by those skilled in the art to which the present application belongs. It should be noted that the terms used are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application.

[0039] This embodiment is a pressure pulse downhole phase change heat exchanger. Figure 1 As shown, the upper hemispherical shell 2, cylindrical shell 17 and lower hemispherical shell 13 are arranged in sequence from top to bottom to form a container shell of the phase change heat exchanger. A vertical three-layer sleeve 1, a counterweight 7, an inverted T-shaped piston 9, a pressure pulse limiter 10, a double-layer spiral baffle 18, and a flow direction converter 19 are arranged in the container shell.

[0040] The axis of the upper hemispherical shell 2 is provided with a through hole to install a three-layer casing 1. The outer layer of the three-layer casing 1 is an annular structure for injecting phase change medium, the middle layer is filled with insulation material, and the center layer is a hollow flow channel for expansion and transportation of the phase change medium after phase change.

[0041] The counterweight 7 is arranged on the upper part of the cylindrical shell 17, and can be connected to the upper hemispherical shell 2 by flange or thread. The counterweight 7 is provided with multiple cavities or flow channels, such as the middle cavity for the upward flow of the phase change medium and the installation of the T-type piston 9, the left side is provided with a bypass channel and the pressure pulse current limiter 10 is installed, and the right side is provided with a geothermal water discharge channel, etc. The counterweight 7 can be set as an integral structure through turning, milling and drilling, and can also be set as a split structure for the convenience of later maintenance, connected by threads.

[0042] A limiting sleeve 6 and a reducing piston 8 are arranged in sequence below the three-layer sleeve 1. The outer diameter of the limiting sleeve 6 matches the counterweight 7, and the inner diameter matches the reducing piston 8. A spring Ⅰ5 is sleeved on the outer edge of the reducing piston 8. The upper end of the spring Ⅰ5 contacts the lower end of the limiting sleeve 6. Specifically, a spring seat can be arranged at the upper end of the T-type piston 9 to support the reducing piston 8 and the spring Ⅰ5. When the T-type piston 9 moves up and down, the spring Ⅰ5 simultaneously causes the reducing piston 8 to slide in the limiting sleeve 6. The hollow flow channel of the three-layer sleeve 1 is connected to the center of the limiting sleeve 6 and the center of the reducing piston 8 and extends to the T-type piston 9. The spring Ⅰ5, the T-type piston 9, and the reducing piston 8 are all made of materials that are resistant to high temperature, pressure, and corrosion.

[0043] Specifically, a bypass channel is opened on the left side of the counterweight 7 and a pressure pulse limiter 10 is provided. Figure 2 As shown, the bypass channel is divided into an upper phase change medium bypass channel 41 and a lower phase change medium bypass channel 42 by the pressure pulse restrictor 10, and the lower phase change medium bypass channel 42 is connected to the outermost phase change medium annular channel 182. Figure 3 As shown, the pressure pulse flow limiter 10 mainly includes a conical plug 102, a spring II 103, a base 104 and a side wall 105. The upper part of the plug 102 is an inverted cone cavity 101, which is connected to the upper phase change medium bypass flow channel 41. The spring II 103 is installed on the base 104, and the top of the spring II 103 is connected to the plug 102 to make it move up and down. The outer side of the plug 102 and the outer side of the side wall 105 are provided with a flow channel for connecting the upper phase change medium bypass flow channel 41 and the lower phase change medium bypass flow channel 42. When there is more liquid in the inverted cone cavity 101, the plug 102 is under pressure greater than the supporting force of the spring II 103, and moves downward to enlarge its flow channel. On the contrary, the plug 102 moves upward to reduce the flow channel. In this way, the plug 102 reciprocates and cooperates with the T-type piston 9 to realize the function of pressure pulse.

[0044] like Figure 2 and Figure 4As shown, the T-type piston 9 is installed in the middle cavity below the counterweight 7, and an annular piston 91 is installed below the T-type piston 9. The annular piston 91 matches the innermost geothermal water annular flow channel 183, and can be driven by the T-type piston 9 to move up and down to suck the geothermal water. The annular piston 91 can be made of high temperature resistant rubber material. The middle cavity is connected to the phase change medium uplink channel 43 of the phase change medium through the interface 93.

[0045] An upper cover plate 16 is screwed to the bottom of the cavity, which is used to cooperate with the double-layer spiral baffle plate 18. An upper intersection channel 11 is provided in the upper cover plate 16 to achieve the switching of the phase change medium and the geothermal water at the upper end of the double-layer spiral baffle plate 18. Similarly, a lower cover plate 20 is screwed to the bottom of the double-layer spiral baffle plate 18, and a lower intersection channel 12 is provided in the lower cover plate 20 to achieve the switching of the phase change medium and the geothermal water at the lower end of the double-layer spiral baffle plate 18. Figure 4 and Figure 8 The central flow channel 185 of the double-layer spiral baffle 18 is connected to the middle cavity below the counterweight 7 for the circulation of phase change medium. The adjacent outer layer of the central flow channel 185 is the innermost geothermal water annular flow channel 183, and then outward is the innermost phase change medium annular flow channel 184. After that, the geothermal water annular flow channel 183 and the phase change medium annular flow channel 184 are spaced apart, so that heat exchange between the phase change medium and the geothermal water can be realized. The outermost layer of the double-layer spiral baffle 18 is the outermost phase change medium annular flow channel 182, which is used for the inflow of phase change medium.

[0046] Upper cover plate 16 structure Figures 4 to 6 As shown, the upper intersection channel 11 of the upper cover plate 16 includes a phase change medium flow channel 111, a phase change medium reversing flow channel 113, a geothermal water reversing flow channel 112 and a low-temperature geothermal water flow channel 114, wherein the phase change medium flow channel 111 is connected to the middle cavity where the T-type piston 9 is located to allow the phase change medium that has undergone phase change to circulate, the phase change medium reversing flow channel 113 is used for the reversing circulation of the phase change medium that has not undergone phase change in each layer, and the geothermal water reversing flow channel 112 is used for the reversing circulation of geothermal water in each layer. The low-temperature geothermal water flow channel 114 is connected to the geothermal water reversing flow channel 112, the upper port of the innermost geothermal water annular flow channel 183 is connected to the low-temperature geothermal water flow channel 114, and the low-temperature geothermal water flow channel 114 is connected to the low-temperature geothermal water outlet 15 upward.

[0047] like Figure 7As shown, the lower cover plate 20 is a three-layer boss structure as a whole, with a lower intersection channel 12 arranged below, the first boss 201 connected to the outermost side of the double-layer spiral baffle 18, the third boss 203 connected to the central flow channel 185, the innermost geothermal water annular flow channel 183 and the innermost phase change medium annular flow channel 184, and the second boss 202 connected to other annular flow channels of the double-layer spiral baffle 18. Geothermal water reversing flow channels and phase change medium reversing flow channels are arranged on the first boss 201 and the second boss 202, respectively, and the lower intersection channel 12 is connected to the outermost geothermal water annular flow channel 181.

[0048] The main body inside the lower hemispherical shell 13 is a hollow structure, and a flow converter 19 is provided at its axial position to prevent frequent high-pressure impact of geothermal water from damaging the double-layer spiral baffle 18 and the lower intersection channel 12. The flow converter 19 includes a lower inlet 191, an upper overflow outlet 192, a lower overflow inlet 193 and an upper outlet 194. The lower inlet 191 is connected to the geothermal water inlet 14, and the upper overflow outlet 192 and the lower overflow inlet 193 are both connected to the shell cavity of the lower hemispherical shell 13. The upper overflow outlet 192 is located higher than the lower overflow inlet 193, and the upper outlet 192 is connected to the outermost geothermal water annular flow channel layer 181 through the lower cover plate 20. Figure 7 As shown, the geothermal water enters from the lower inlet 191 of the flow converter 19 and flows upward, and flows into the lower hemispherical shell 13 at the upper overflow outlet 192 of the flow converter 19. When the height of the geothermal water in the lower hemispherical shell 13 reaches the lower overflow inlet 193, it flows upward through the upper outlet 194 to the lower intersection channel 12, and then enters the outermost geothermal water annular flow channel 181.

[0049] The temperature of the phase change medium is selected according to the depth of the deep well and the ultra-deep well and the water temperature of the geothermal layer. The boiling point of the phase change medium should be lower than the mining temperature of the geothermal layer. The material of the phase change medium can be R141b dichloromonofluoroethane, R142b monochlorodifluoroethane, R134a tetrafluoroethane, R600a isobutane, etc. When in use, the phase change medium is slowly injected along the outer tube of the three-layer casing 1, and the phase change medium flows into the inverted cone cavity 101 through the upper phase change medium bypass flow channel 41 and is enriched there. When the injection pressure of the phase change medium is greater than the supporting force of the spring II 103, the spring II 103 is compressed, the plug 102 moves downward, and the inverted cone cavity 101 is connected with the lower phase change medium bypass flow channel 42. As the pressure on the plug 102 decreases, the spring II 103 returns to its original length, and the plug 102 blocks the inverted cone cavity 101 and the lower phase change medium bypass flow channel 42, and the pulse effect is achieved in this cycle. The phase change medium flows into the lower phase change medium bypass flow channel 42 , passes through the upper cover plate 16 and flows into the outermost phase change medium annular flow channel 182 .

[0050] While the plug 102 is moving downward, the air in the double-layer spiral baffle 18 pushes the T-type piston 9 upward, and the T-type piston 9 drives the annular piston 91 upward, thereby producing a suction effect on the air in the lower hemispherical shell 13. The hot water in the well enters the flow converter 19 through the geothermal water inlet 14, flows into the lower hemispherical shell 13 at the outlets on both sides of the flow converter 19 and is enriched there. When the phase change medium is continuously injected and the plug 102 reciprocates multiple times, the suction process of the geothermal water is realized. When the height of the geothermal water is greater than the water inlet height of the flow converter 19, the geothermal water enters the innermost geothermal water annular flow channel 183 through the lower intersection channel 12.

[0051] In the double-layer spiral baffle 18, the phase change medium annular flow channel layer and the geothermal water annular flow channel layer are arranged at intervals, and a heat exchange process between the phase change medium and the geothermal water occurs in each layer of the flow channel. Since the boiling point of the phase change medium is lower than the temperature of the geothermal water, the phase change medium changes into a gas phase with a smaller density after heating, and will quickly enrich in the upper space of the flow channel. In order to avoid the occurrence of "gas plugs" blocking the flow channel, a linear phase change medium guide channel 111 is opened at the top of the flow channel of each layer of the phase change medium, which is directly connected to the central cavity at the T-type piston 9, so that the gas phase change medium gathers in the central cavity. When the gas phase phase change medium pressure is greater than When the gravity of the T-type piston 9 and the pressure of the spring Ⅰ5 are greater than the pressure of the gas-phase phase change medium, the T-type piston 9 moves downward to close the interface 93, and then the gas-phase phase change medium gathers in the central cavity again, causing the T-type piston 9 to move upward again, and the cycle continues.

[0052] In this embodiment, in order to ensure that the phase change medium and the geothermal water have sufficient opportunities for convective heat exchange, the double-layer spiral baffle 18 is set to 10 layers in total, including five layers of phase change medium flow channel layers and five layers of geothermal water flow channel layers. Each layer of phase change medium flow channel layer can have convective heat exchange with the geothermal water layers on both sides thereof, ensuring that the phase change medium is already in the gas phase before flowing into the innermost layer of phase change medium annular flow channel 184. During the up and down suction process of the T-type piston 9, the geothermal water flows from the outermost geothermal water annular flow channel 181 through the guide channel of the upper and lower cover plates to the innermost geothermal water annular flow channel 183, and finally flows out through the low-temperature geothermal water guide channel 114 and the low-temperature geothermal water outlet 15, thus realizing the entire underground phase change medium phase change heat exchange, free expansion, reciprocating motion and geothermal water extraction process.

[0053] The above are only preferred implementations of the present application. It should be pointed out that for ordinary technicians in this technical field, several changes or improvements can be made without departing from the principles of the present application. These changes or improvements should also be regarded as the scope of protection of the present application.

Claims

1. A pressure pulse downhole phase change heat generator, characterized in that: It comprises an upper hemispherical shell (2), a cylindrical shell (17) and a lower hemispherical shell (13) which are arranged in sequence from top to bottom, and a three-layer casing (1), a counterweight (7), an inverted T-shaped piston (9), a pressure pulse limiter (10), a double-layer spiral baffle (18) and a flow direction converter (19) are arranged therein; The three-layer casing (1) is vertically penetrated at the axis of the upper hemispherical shell (2), the outer layer of the three-layer casing (1) is an annular layer for injecting phase change medium, the middle layer is filled with thermal insulation material, and the inner layer is a hollow flow channel for expansion and transportation of the phase change medium after phase change; The counterweight (7) is located at the upper part of the cylindrical shell (17); a phase change medium bypass flow channel for a phase change medium to flow downward is provided on the left side of the counterweight (7); a middle cavity is provided in the middle; and a low-temperature geothermal water outlet (15) is provided on the right side; the phase change medium bypass flow channel is communicated with the annulus layer of the three-layer casing (1); the middle cavity is communicated with the hollow flow channel of the three-layer casing (1); the T-shaped piston (9) is arranged in the middle cavity so as to be movable up and down; the pressure pulse current limiter (10) is installed in the phase change medium bypass flow channel to control its on and off; a phase change medium upward channel (43) is also provided in the counterweight (7); the phase change medium upward channel (43) is used to communicate with the middle cavity and the hollow flow channel of the three-layer casing (1); The double-layer spiral baffle (18) is provided with an upper cover plate (16) at the upper end and a lower cover plate (20) at the lower end. The upper cover plate (16) is provided with a reversing flow channel. A plurality of geothermal water annular flow channel layers and phase change medium annular flow channel layers are provided inside the double-layer spiral baffle (18). The centralmost phase change medium annular flow channel layer is the central flow channel (185). Each layer of geothermal water annular flow channel layers is connected in sequence via the corresponding reversing flow channel. Each layer of phase change medium annular flow channel layers is connected in sequence via the corresponding reversing flow channel. The outermost layer of the phase change medium annular flow channel layer (182) is connected to the phase change medium bypass flow channel. The central flow channel (185) is used to transport the phase change medium after phase change and is connected to the middle cavity. An annular piston (91) is provided in the innermost layer of the geothermal water annular flow channel layer (183). The annular piston (91) is connected to the T-type piston (9) to move up and down. A geothermal water inlet (14) is provided at the lower end of the lower hemispherical shell (13); the flow direction converter (19) is installed in the lower hemispherical shell (13); the flow direction converter (19) comprises a lower inlet (191), an upper overflow outlet (192), a lower overflow inlet (193) and an upper outlet (194); the lower inlet (191) is connected to the geothermal water inlet (14); the upper overflow outlet (192) and the lower overflow inlet (193) are both connected to the shell cavity of the lower hemispherical shell (13); the position of the upper overflow outlet (192) is higher than the position of the lower overflow inlet (193); and the upper outlet (194) is connected to the innermost geothermal water annular flow channel layer via a lower cover plate (20).

2. The pressure pulse downhole phase change heat generator according to claim 1, characterized in that: The pressure pulse flow restrictor (10) divides the phase change medium bypass flow channel into an upper phase change medium bypass flow channel (41) and a lower phase change medium bypass flow channel (42); the front end of the upper phase change medium bypass flow channel (41) is connected to the annular layer of the three-layer casing (1), and the rear end of the lower phase change medium bypass flow channel (42) is connected to the outermost phase change medium annular flow channel layer; The pressure pulse flow limiter (10) comprises a conical plug (102), a spring II (103), a base (104) and a side wall (105); the upper portion of the plug (102) is an inverted conical cavity (101); the inverted conical cavity (101) is connected to the rear end of an upper phase change medium bypass flow channel (41); the spring II (103) is mounted on the base (104); the top of the spring II (103) is connected to the plug (102) to drive the plug to move up and down; and flow channels are provided on the outer side of the plug (102) and the outer side of the side wall (105) for connecting the upper phase change medium bypass flow channel (41) and the lower phase change medium bypass flow channel (42).

3. The pressure pulse downhole phase change heat generator according to claim 1, characterized in that: A limit sleeve (6) and a different-diameter piston (8) are provided at the lower end of the three-layer sleeve (1); the outer diameter of the limit sleeve (6) matches the counterweight (7), and the inner diameter matches the different-diameter piston (8) for sliding; a spring I (5) is provided on the outer edge of the different-diameter piston (8); the upper end of the spring I (5) contacts the lower end of the limit sleeve (6); and the hollow flow channel of the three-layer sleeve (1) is connected to the center of the limit sleeve (6) and the center of the different-diameter piston (8) and extends to connect to the middle cavity.

4. The pressure pulse downhole phase change heat generator according to claim 1, characterized in that: An upper intersection channel (11) is provided in the upper cover plate (16) to allow the phase change medium and the geothermal water to be reversed at the upper end of the double-layer spiral baffle plate (18); and a lower intersection channel (12) is provided in the lower cover plate (20) to allow the phase change medium and the geothermal water to be reversed at the lower end of the double-layer spiral baffle plate (18).

5. The pressure pulse downhole phase change heat generator according to claim 4 is characterized in that: The upper intersection channel (11) comprises a phase change medium flow guide (111), a phase change medium reversing flow channel (113), a geothermal water reversing flow channel (112) and a low-temperature geothermal water flow guide (114), wherein the phase change medium flow guide (111) is connected to the middle cavity where the T-shaped piston (9) is located to allow the phase change medium that has undergone phase change to circulate, the phase change medium reversing flow channel (113) is used for the reversing flow of the phase change medium that has not undergone phase change in the phase change medium annular flow channel layer, and the geothermal water reversing flow channel (112) is used for the reversing flow of geothermal water in the geothermal water annular flow channel layers; the low-temperature geothermal water flow guide (114) is connected to the geothermal water reversing flow channel (112), and the low-temperature geothermal water flow guide (114) is connected upwardly to the low-temperature geothermal water outlet (15).

6. The pressure pulse downhole phase change heat generator according to claim 1, characterized in that: The boiling point of the phase change medium is lower than the exploitation temperature of the geothermal layer, and the material of the phase change medium is any one or more of R141b, R142b, R134a or R600a.

7. A method for operating a pressure pulse downhole phase change heat generator according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1) A phase change medium is injected into the annular layer of the three-layer casing (1), and the phase change medium enters the outermost phase change medium annular flow channel layer (182) of the double-layer spiral baffle (18) through the phase change medium bypass channel and flows through the phase change medium annular flow channel layer from the outside to the inside layer by layer. In this process, the pressure pulse limiter (10) reciprocates according to the injection pressure of the phase change medium to realize the pulsed opening and closing of the phase change medium bypass flow channel; as the phase change medium is injected, the air in the double-layer spiral baffle (18) is compressed and the pressure increases, and the central flow channel (185) When the phase change medium is connected to the middle cavity, the high-pressure air pushes the T-shaped piston (9) upward, and the annular piston (91) also moves upward, thereby producing a suction effect on the air in the lower hemispherical shell (13). The hot water in the well enters the flow converter (19) through the geothermal water inlet (14), flows into the shell cavity of the lower hemispherical shell (13) at the overflow outlet (192) at the upper end of the flow converter (19) and is enriched there. When the phase change medium is continuously injected, the pressure pulse limiter (10) reciprocates in a cycle, and the annular piston (91) also reciprocates up and down, thereby realizing the suction of the geothermal water. S2) when the height of the geothermal water in the shell cavity of the lower hemispherical shell (13) is greater than the height of the lower overflow inlet (193) of the flow direction converter (19), the geothermal water flows from the lower overflow inlet (193) through the flow channel in the lower cover plate (20) into the geothermal water annular flow channel layer (181) of the outermost layer of the double-layer spiral baffle plate (18); S3) Then the geothermal water flows through the geothermal water annular flow channel layer from the outside to the inside. During this period, each layer of geothermal water exchanges heat with the phase change medium in the phase change medium annular flow channel layer. The temperature of the geothermal water decreases. At the same time, the temperature of the phase change medium increases and turns into a gas phase, which is enriched above the double-layer spiral baffle (18). The gas phase change medium enters the middle cavity through the innermost layer of the phase change medium annular flow channel layer (184) and gathers. The continuous accumulation of the gas phase change medium increases the pressure, which can also push the T-type piston (9) upward. When the T-type piston (9) ascends to the phase change medium upward channel (43), the gas phase change medium flows through the phase change medium upward channel (43) to the hollow flow channel of the three-layer casing (1). Then, the pressure of the gas phase change medium decreases, and the T-type piston (9) descends to close the connection with the upward channel (43). Then, the gas phase change medium gathers in the central cavity again, causing the T-type piston (9) to ascend again, and the cycle continues.

Images