Sandstone geothermal well heat extraction without water extraction high-efficiency utilization system and construction method thereof

Abstract

The present application belongs to the technical field of geothermal utilization, and discloses a sandstone heat storage geothermal well heat extraction without water extraction high-efficiency utilization system and a construction method of the system. The main technical features are as follows: the system comprises a geothermal well, a water outlet pipe, a heat exchanger and a water return pipe, a desander and a circulating pump are arranged on the water outlet pipe, a first water stop plate is arranged on the water outlet pipe below each non-bottom heat storage aquifer, and a second water stop plate is arranged on the water outlet pipe at an upper position of the middle part of the bottom heat storage aquifer. During the descending process of the recharge water, part of the recharge water flows into the corresponding heat storage aquifer when passing through each non-bottom heat storage aquifer, and the other part of the recharge water flows downward along the gap between the elastic plate and the inner wall of the well pipe. The water with a higher temperature in the bottom heat storage aquifer is supplemented into the well pipe under the pressure of the bottom heat storage aquifer. The geothermal water extracted from the whole water outlet pipe has a higher temperature and a higher heat efficiency, and the underground water is not polluted.

Description

Technical Field

[0001] This invention belongs to the field of geothermal utilization technology, and in particular relates to a high-efficiency utilization system for geothermal wells in sandstone thermal reservoirs that extracts heat without extracting water, and a method for constructing such a system. Background Technology

[0002] Geothermal energy, as a green and novel resource, boasts abundant reserves and is clean and efficient, making it a globally recognized clean energy source with significant application value. my country's geothermal resources account for approximately one-sixth of the global total. Among these, the medium-deep geothermal energy resources are equivalent to 853 billion tons of standard coal annually. In one heating season, if 10 million square meters of buildings were heated using this technology, it could replace 163,000 tons of standard coal, reducing carbon dioxide emissions by 430,000 tons and sulfur dioxide emissions by 1,360 tons. The economic benefits of clean geothermal resource development are also promising. Preliminary estimates indicate that the geothermal industry will drive direct investment of 400 billion yuan, provide nearly 800,000 jobs, and drive total investment across the entire geothermal industry chain to exceed 1 trillion yuan. By 2035, this is projected to cumulatively drive total investment across the entire geothermal industry chain to reach 5 trillion yuan.

[0003] Most of my country's medium-deep geothermal resources are located in sandstone reservoirs. The Neogene sandstone reservoirs are relatively shallow and are the main strata for geothermal development and utilization. The earliest geothermal utilization involved directly pumping up geothermal water to utilize its thermal energy. This method has the following drawbacks: First, as the intensity of mining increases year by year, the reservoir pressure also shows a downward trend, and some wells have even experienced pumping out of the reservoir and difficulties in water extraction. Second, because the underground hot water contains minerals such as sulfur, iron, and chlorine, and has a high degree of mineralization, the extensive use of geothermal resources and direct discharge not only wastes resources but also seriously pollutes the ecological environment.

[0004] To avoid environmental pollution and waste of geothermal water, current sandstone geothermal well systems extract heat but do not extract water. This involves first extracting the geothermal water for heat exchange, and then reinjecting the water after heat release. Existing sandstone geothermal well systems include a geothermal well, an outlet pipe, a heat exchanger, and a return pipe. A desander and a circulation pump are installed on the outlet pipe. The geothermal well includes a well casing, a bottom aquifer, and multiple non-bottom aquifers located above the bottom aquifer. The lower end of the outlet pipe is located below the bottom aquifer. Multiple outlet holes are provided on the well casing corresponding to the bottom and non-bottom aquifers. Due to its structure, this system has the following drawbacks: First, the reinjected water primarily moves downwards along the inner wall of the well casing and is then extracted again through the outlet pipe for heat exchange. Water from the aquifers outside the well casing can hardly enter the casing; the reinjected water can only flow downwards during its journey. Firstly, the hot water absorbs heat through the well pipe wall, but the heat absorption is minimal, resulting in a low temperature of the hot water extracted from the outlet pipe. Secondly, as the reinjection water moves downwards, it flows directly downwards in one direction due to the influence of water temperature and impact location. The water that was originally in contact with the well pipe wall is difficult to mix with the reinjection water, further reducing the temperature of the water in the outlet pipe. Thirdly, the lower end of the return pipe is located at the wellhead. Since the temperature of the formation increases with the depth of the formation, the temperature of the formation is lower than the temperature of the reinjection water within a certain distance from the wellhead, especially in winter when the surface temperature is much lower than the temperature of the reinjection water. As the reinjection water flows downwards, it dissipates heat to the outside through the well pipe wall, lowering its temperature and consequently reducing the temperature in the outlet pipe. Summary of the Invention

[0005] The first technical problem this invention aims to solve is to provide a highly efficient system for utilizing sandstone geothermal wells without extracting water, where the water temperature in the outlet pipe is close to the temperature of the aquifer from which the water is extracted, thereby improving thermal efficiency and avoiding pollution of the geothermal water in the formation.

[0006] To solve the above problems, the technical solution adopted by the sandstone geothermal well heat extraction without water extraction high-efficiency utilization system of the present invention is as follows:

[0007] A high-efficiency geothermal well system for heat extraction without water extraction in sandstone geothermal reservoirs includes a geothermal well, an outlet pipe, a heat exchanger, and a return pipe. A desander and a circulation pump are installed on the outlet pipe, and a circulation pump is installed on the return pipe. The geothermal well includes a well casing, a bottom aquifer, and multiple non-bottom aquifers located above the bottom aquifer. The lower end of the outlet pipe is located below the bottom aquifer. Multiple outlet holes are provided on the well casing corresponding to the bottom and non-bottom aquifers. A first water-stop plate is installed on the outlet pipe located near the middle of the clay layer below each non-bottom aquifer. A second water-stop plate is installed on the outlet pipe located slightly above the middle of the bottom aquifer. The first and second water-stop plates include a fixed plate and an elastic plate fixed to the outlet pipe. The radially outer side of the elastic plate contacts the inner wall of the well casing. The outer diameter of the fixed plate is smaller than the inner diameter of the well casing.

[0008] Its additional technical features are:

[0009] A baffle is installed on the outlet pipe below the return water pipe;

[0010] The spoiler is spindle-shaped with symmetrical upper and lower parts;

[0011] The spacing between adjacent spoilers is 20-30 meters;

[0012] The temperature of the stratum corresponding to the lower end of the return water pipe is greater than or equal to the temperature of the reinjection water.

[0013] The second technical problem to be solved by the present invention is to provide a construction method for the above-mentioned efficient utilization system of geothermal wells for heat extraction without water extraction in sandstone thermal reservoirs.

[0014] To solve the above problems, the technical solution adopted in the construction method of the sandstone geothermal well heat extraction without water extraction high-efficiency utilization system of the present invention is as follows:

[0015] The method includes the following steps:

[0016] The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers; if it is an existing geothermal well, it is to directly measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers.

[0017] The second step is to set a second water stop plate at a height h1 from the lowest point of the outlet pipe, based on the measured depth and thickness of each thermal aquifer. The thickness of the bottom thermal aquifer is 1 / 2 × h1 ≤ 1 × thickness of the bottom thermal aquifer.

[0018] The third step is to install the lowest first waterstop plate on the outlet pipe at the middle position of the clay layer above the bottom thermal aquifer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers.

[0019] The fourth step is to install the corresponding first waterstop plate on the outlet pipe at the middle position of the clay layer below the non-bottom thermal aquifer near the uppermost thermal aquifer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers.

[0020] Fifth, repeat step four until the first waterstop is installed on all the outlet pipes in the clay layer below all non-bottom thermal aquifers.

[0021] Step 6: Install a circulation pump and a sand remover at the corresponding location on the outlet pipe;

[0022] Step 7: Connect the upper end of the outlet pipe to the heat source inlet pipe of the heat exchanger.

[0023] Step 8: Install a circulation pump on the return water pipe, connect the upper end of the return water pipe to the heat source outlet pipe of the heat exchanger, and insert the lower end of the return water pipe into the well pipe.

[0024] Step 9: Seal the wellhead plate.

[0025] As a further improvement to this method, the method includes the following steps:

[0026] The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers; if it is an existing geothermal well, it is to directly measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers.

[0027] The second step is (i) to set a second water stop plate at a height h1 from the lowest point of the outlet pipe based on the measured depth and thickness of each thermal aquifer. The thickness of the bottom thermal aquifer is 1 / 2 × the thickness of the bottom thermal aquifer ≦ h1 ≦ 1 × the thickness of the bottom thermal aquifer.

[0028] (ii) Install a baffle plate above the second waterstop plate;

[0029] The third step, (i) is to install the lowest first waterstop plate on the outlet pipe at the middle position of the clay layer above the bottom thermal aquifer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers.

[0030] (ii) Install a baffle plate above the first waterstop plate;

[0031] Step 4, (a) Based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers, install the corresponding first waterstop plate on the outlet pipe at the middle position of the clay layer below the non-bottom thermal aquifer near the upper layer.

[0032] (ii) Install a baffle plate above the first waterstop plate;

[0033] Fifth, repeat step four until the first waterstop is installed on the outlet pipes of all non-bottom thermal aquifers below the clay layer and the baffle is installed above the first waterstop.

[0034] Step 6: Install a circulation pump and a sand remover at the corresponding location on the outlet pipe;

[0035] Step 7: Connect the upper end of the outlet pipe to the heat source inlet pipe of the heat exchanger.

[0036] Step 8: Install a circulation pump on the return water pipe, connect the upper end of the return water pipe to the heat source outlet pipe of the heat exchanger, and insert the lower end of the return water pipe into the well pipe.

[0037] Step 9: Seal the wellhead plate.

[0038] As a further improvement to this method, the method includes the following steps:

[0039] The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each aquifer from the wellhead, the thickness of each aquifer, and the thickness of the clay layer between adjacent aquifers. Based on the reinjection geothermal water temperature, the formation with the same temperature as the reinjection geothermal water is measured and designated as the reinjection outlet formation. If it is an existing geothermal well, the depth of each aquifer from the wellhead, the thickness of each aquifer, and the thickness of the clay layer between adjacent aquifers are measured directly. Based on the reinjection geothermal water temperature, the formation with the same temperature as the reinjection geothermal water is measured and designated as the reinjection outlet formation.

[0040] The second step is (i) to set a second water stop plate at a height h1 from the lowest point of the outlet pipe based on the measured depth and thickness of each thermal aquifer. The thickness of the bottom thermal aquifer is 1 / 2 × the thickness of the bottom thermal aquifer ≦ h1 ≦ 1 × the thickness of the bottom thermal aquifer.

[0041] (ii) Install a baffle plate above the second waterstop plate;

[0042] The third step, (i) is to install the lowest first waterstop plate on the outlet pipe at the middle position of the clay layer above the bottom thermal aquifer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers.

[0043] (ii) Install a baffle plate above the first waterstop plate;

[0044] Step 4, (a) Based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers, install the corresponding first waterstop plate on the outlet pipe at the middle position of the clay layer below the non-bottom thermal aquifer near the upper layer.

[0045] (ii) Install a baffle plate above the first waterstop plate;

[0046] Fifth, repeat step four until the first waterstop is installed on the outlet pipes of all non-bottom thermal aquifers below the clay layer and the baffle is installed above the first waterstop.

[0047] Step 6: Install a circulation pump and a sand remover at the corresponding location on the outlet pipe;

[0048] Step 7: Connect the upper end of the outlet pipe to the heat source inlet pipe of the heat exchanger.

[0049] Step 8: Install a circulation pump on the return water pipe, connect the upper end of the return water pipe to the heat source outlet pipe of the heat exchanger, insert the lower end of the return water pipe into the well pipe, and position the lower end of the return water pipe below the formation of the set reinjection outlet.

[0050] Step 9: Seal the wellhead plate.

[0051] The efficient utilization system for sandstone geothermal wells that extracts heat without extracting water, provided by this invention, has the following advantages compared with existing technologies:

[0052] Firstly, the system includes a geothermal well, an outlet pipe, a heat exchanger, and a return pipe. A desander and a circulation pump are installed on the outlet pipe, and a circulation pump is installed on the return pipe. The geothermal well includes a well casing, a bottom aquifer, and multiple non-bottom aquifers located above the bottom aquifer. The lower end of the outlet pipe is located below the bottom aquifer. Multiple outlet holes are provided on the well casing corresponding to the bottom and non-bottom aquifers. A first water-stop plate is installed on the outlet pipe near the middle of the clay layer below each non-bottom aquifer, and a second water-stop plate is installed on the outlet pipe slightly above the middle of the bottom aquifer. The first and second water-stop plates... The second waterstop includes a fixed plate and an elastic plate fixed to the outlet pipe. The radially outer side of the elastic plate contacts the inner wall of the well pipe. The outer diameter of the fixed plate is smaller than the inner diameter of the well pipe. During the recharge water descent, the first waterstop located below the non-bottom thermal aquifer generates a certain resistance to the downward flowing water, increasing the water pressure above the first waterstop. The recharge water flows into the thermal aquifer through the outlet holes in the well pipe wall, allowing some of the recharge water to enter the thermal aquifer. Under pressure, the periphery of the elastic plate of the first waterstop bends downward, creating a gap between the elastic plate and the inner wall of the well pipe. The recharge water flows downward along the gap between the elastic plate and the inner wall of the well pipe. Thus, after passing through each... When a non-bottom-level thermal aquifer is encountered, some reinjection water flows into the corresponding thermal aquifer, while the rest flows downwards along the gap between the elastic plate and the inner wall of the well pipe. When the reinjection water reaches above the second waterstop, under pressure, some flows into the upper part of the bottom thermal aquifer, while the rest flows downwards along the gap between the elastic plate of the second waterstop and the inner wall of the well pipe. At this point, because some reinjection water enters the non-bottom-level thermal aquifer during downward flow, the pressure in the lower end of the well pipe decreases. The higher-temperature water in the bottom thermal aquifer, under its pressure, replenishes the well pipe, increasing the overall water output from the well pipe. Geothermal water has a high temperature and high thermal efficiency, and it will not pollute groundwater. The first and second water-stop plates include a fixed plate and an elastic plate fixed to the outlet pipe. Under pressure, the elastic plate deforms to form a water channel between the elastic plate and the inner wall of the well pipe. It also prevents blockage caused by foreign objects on the inner wall of the well pipe when installing the outlet pipe and pulling it upward. The second water-stop plate is installed at a position of 1 / 2 × bottom thermal aquifer thickness ≤ h1 ≤ 1 × bottom thermal aquifer thickness. Even if the upper aquifer is blocked and cannot be reinjected, the reinjection water will enter the aquifer above the lowest aquifer and flow into the well from the aquifer below the water-stop plate, forming a small formation circulation in the aquifer for sufficient heat exchange.

[0053] Secondly, since a baffle is installed on the outlet pipe below the return water pipe, after the recharge water flows out of the return water pipe and passes through the top baffle, it impacts the baffle above the baffle, and the water flow changes from vertical to horizontal or diagonally downward, so that the recharge water in the well pipe can fully exchange heat with the well pipe wall, and the temperature further increases during the downward flow of the recharge water.

[0054] Thirdly, since the baffle is symmetrically shaped like a spindle, it not only facilitates the agitation of the reinjection water in the well pipe, but also allows the reinjection water in the well pipe to fully exchange heat with the well pipe wall, so that when installing the water outlet pipe and pulling the water outlet pipe upward, it will not be blocked by foreign objects on the inner wall of the well pipe.

[0055] Fourth, since the spacing between adjacent spoilers is 20-30 meters, the turbulence effect is better;

[0056] Fifth, because the formation temperature corresponding to the lower end of the return water pipe is greater than or equal to the temperature of the reinjection water, and because the return water pipe is insulated, the reinjection water flows directly downwards from the area where the formation temperature is higher than the temperature of the reinjection water. This creates a closed water column above the lower end outlet of the return water pipe up to the wellhead plate, almost preventing mixing with the reinjection water at the lower end of the return water pipe. This avoids heat loss from the reinjection water. The reinjection water flowing downwards from the lower end outlet of the return water pipe continues to flow with increasing formation depth. During this flow, the reinjection water remains in a heat-absorbing state, preventing heat loss. Attached Figure Description

[0057] Figure 1 Schematic diagram of the installation of the waterstop plate in a high-efficiency utilization system for geothermal wells in sandstone thermal reservoirs that extracts heat without extracting water.

[0058] Figure 2 Schematic diagram of waterstop plate;

[0059] Figure 3 Schematic diagram of a high-efficiency utilization system for geothermal wells in sandstone thermal reservoirs that extracts heat without extracting water;

[0060] Figure 4 Schematic diagram of water flow in a high-efficiency system for geothermal wells in sandstone thermal reservoirs that extracts heat without extracting water.

[0061] Figure 5 Schematic diagram of spoiler. Detailed Implementation

[0062] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a more detailed explanation of the efficient utilization system for geothermal wells in sandstone geothermal reservoirs that extracts heat without extracting water, and the construction method of the system.

[0063] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5The diagram shows a structural schematic of a high-efficiency utilization system for sandstone geothermal wells that extracts heat without extracting water. This system includes a geothermal well 1, an outlet pipe 2, a heat exchanger 3, and a return pipe 4. A desander 5 and a circulation pump 6 are installed on the outlet pipe 2, and a circulation pump 6 is installed on the return pipe 4. The geothermal well 1 includes a well pipe 7, a bottom aquifer 8, and multiple non-bottom aquifers 9 located above the bottom aquifer 8. The lower end of the outlet pipe 2 is located below the bottom aquifer 9. Multiple outlet holes 10 are provided on the well pipe 7 corresponding to the bottom aquifer 9 and the non-bottom aquifer 8. A first water-stop plate 11 is installed on the outlet pipe 2 near the middle of the clay layer 18 below each non-bottom aquifer 8, and a second water-stop plate 12 is installed on the outlet pipe 2 located slightly above the middle of the bottom aquifer 9. Figure 2 As shown, the first water-stop plate 11 and the second water-stop plate 12 include a fixed plate 13 and an elastic plate 14 fixed to the water outlet pipe 2. The radial outer side of the elastic plate 14 contacts the inner wall surface of the well pipe 7, and the outer diameter of the fixed plate 13 is smaller than the inner diameter of the well pipe 7.

[0064] During the descent of the reinjection water, the first waterstop 11 located below the non-bottom thermal aquifer 8 creates resistance to the downward flow of the reinjection water, increasing the water pressure above the first waterstop 11. The reinjection water flows into the thermal aquifer through the outlet 10 of the well pipe 7, causing some of the reinjection water to enter the thermal aquifer 8. Under pressure, the periphery of the elastic plate 14 of the first waterstop 11 bends downward, creating a gap between the elastic plate 14 and the inner wall of the well pipe 7. The reinjection water flows downward along the gap between the elastic plate 14 and the inner wall of the well pipe 7. Thus, when passing through each non-bottom thermal aquifer 8, some reinjection water flows into the corresponding thermal aquifer, while the other part flows downward along the gap between the elastic plate and the inner wall of the well pipe. When the reinjection water flows above the second waterstop 9, under pressure, part of the reinjection water flows into the upper part of the bottom thermal aquifer 9, while the other part flows downward along the gap between the elastic plate 14 of the second waterstop 12 and the inner wall of the well pipe 7. At this time, because some of the reinjection water enters the non-bottom thermal aquifer 8 during the downward flow, the pressure in the well pipe at the lower end of the outlet pipe decreases. The water with a higher temperature in the bottom thermal aquifer 9 is replenished into the well pipe 7 under the pressure of the bottom thermal aquifer 9, so that the geothermal water extracted from the outlet pipe 2 has a higher temperature and higher thermal efficiency, and will not cause pollution to the groundwater. The first waterstop 11 and the second waterstop 12 include a fixed plate 13 and an elastic plate 14 fixed to the outlet pipe 2. Not only does the elastic plate deform under pressure to form a drainage channel between the elastic plate 14 and the inner wall of the well pipe 7, but it also prevents blockage caused by foreign objects on the inner wall of the well pipe when installing the outlet pipe 2 and pulling the outlet pipe 2 upward. The second waterstop plate 12 is installed at a position of 1 / 2 × bottom thermal aquifer thickness ≦h1 ≦1 × bottom thermal aquifer thickness. Even if the upper aquifer is blocked and cannot be reinjected, the reinjection water will enter the aquifer above the lowest aquifer and flow into the well from the aquifer below the waterstop plate, forming a small formation circulation in the aquifer for sufficient heat exchange.

[0065] like Figure 3 , Figure 4 and Figure 5 As shown, a baffle plate 15 is installed on the outlet pipe 2 below the return water pipe 4. After the recharge water flows out of the return water pipe 4 and passes through the top baffle plate 15, it impacts the baffle plate 15. The water flow changes from vertical to horizontal or diagonally downward, so that the recharge water in the well pipe can fully exchange heat with the high temperature well pipe wall. During the downward flow of the recharge water, the temperature further increases.

[0066] The baffle 15 is a symmetrical spindle shape, which not only facilitates the agitation of the reinjection water in the well pipe, but also allows the reinjection water in the well pipe to fully exchange heat with the well pipe wall, so that when installing the water outlet pipe and pulling the water outlet pipe upward, it will not be blocked by foreign objects on the inner wall of the well pipe.

[0067] The spacing between adjacent spoilers 15 is 20-30 meters, which improves the airflow effect.

[0068] The lower end of the return water pipe 4 corresponds to a formation temperature greater than or equal to that of the reinjection water. Because the return water pipe is insulated, the reinjection water flows directly downwards from a location where the formation temperature is higher than the reinjection water temperature. This creates a closed water column 17 above the outlet of the lower end of the return water pipe 4 up to the wellhead plate 16, preventing almost any mixing with the reinjection water at the lower end of the pipe and thus avoiding heat loss. The reinjection water flowing from the outlet of the lower end of the return water pipe 4 flows downwards, increasing in depth as it flows into the formation. Throughout this flow, the reinjection water remains in a heat-absorbing state, preventing heat loss.

[0069] The technical solution adopted in the construction method of the above-mentioned sandstone geothermal well heat extraction without water extraction high-efficiency utilization system is as follows:

[0070] The method includes the following steps:

[0071] The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers; if it is an existing geothermal well, it is to directly measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers.

[0072] The second step is to set a second waterstop plate 12 at a height h1 from the lowest point of the outlet pipe, based on the measured depth and thickness of each thermal aquifer. The thickness of the bottom thermal aquifer is 1 / 2 × h1 ≦ 1 × 9.

[0073] The third step is to install a first waterstop plate 11 at the bottom of the outlet pipe at the middle of the clay layer 18 above the bottom thermal aquifer 9, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer 18 between adjacent thermal aquifers.

[0074] The fourth step is to install the corresponding first waterstop plate 11 on the outlet pipe at the middle position of the clay layer 18 below the non-bottom thermal aquifer 8 near the uppermost layer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers.

[0075] Fifth step, repeat the fourth step until the first water stop plate 11 is installed on the water outlet pipe 2 at all locations of the clay layer 18 below the bottom thermal aquifer.

[0076] Step 6: Install the circulation pump 6 and the sand separator 5 at the corresponding positions on the outlet pipe 2;

[0077] Step 7: Connect the upper end of the outlet pipe 2 to the heat source inlet pipe of the heat exchanger 3.

[0078] Step 8: Install the circulation pump 6 on the return water pipe 4, connect the upper end of the return water pipe to the heat source outlet pipe of the heat exchanger, and insert the lower end of the return water pipe into the well pipe.

[0079] Step 9: Seal the wellhead plate 16.

[0080] As a further improvement to this method, the method includes the following steps:

[0081] The method includes the following steps:

[0082] The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers; if it is an existing geothermal well, it is to directly measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers.

[0083] The second step, (a) is to set a second water stop plate 12 at a height h1 from the lowest point of the outlet pipe based on the measured depth and thickness of each thermal aquifer. The thickness of the bottom thermal aquifer 9 is 1 / 2 × h1 ≦ 1 × thickness of the bottom thermal aquifer 9.

[0084] (ii) Install a baffle plate 15 above the second waterstop plate 12;

[0085] The third step, (i) is to install the lowest first waterstop plate 11 on the water outlet pipe 2 at the middle position of the clay layer 18 above the bottom thermal aquifer 9, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers.

[0086] (ii) Install a baffle plate above the first waterstop plate;

[0087] Step 4, (i) Based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers, install the corresponding first water stop plate 11 on the outlet pipe 2 located in the middle of the clay layer 18 below the non-bottom thermal aquifer 8 near the upper layer.

[0088] (ii) Install a baffle plate 15 above the first waterstop plate 11;

[0089] Fifth step, repeat the fourth step until the first water stop plate 11 is installed on the water outlet pipe 2 corresponding to the position of the clay layer 18 below all non-bottom thermal water-bearing layers 8 and the baffle plate 15 is installed above the first water stop plate 11.

[0090] Step 6: Install the circulation pump 6 and the sand separator 5 at the corresponding positions on the outlet pipe 2;

[0091] Step 7: Connect the upper end of the outlet pipe 2 to the heat source inlet pipe of the heat exchanger 3.

[0092] Step 8: Install the circulation pump 6 on the return water pipe 4, connect the upper end of the return water pipe 4 to the heat source outlet pipe of the heat exchanger 3, and insert the lower end of the return water pipe into the well pipe.

[0093] Step 9: Seal the wellhead plate 16.

[0094] As a further improvement to this method, the method includes the following steps:

[0095] The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each aquifer from the wellhead, the thickness of each aquifer, and the thickness of the clay layer between adjacent aquifers. Based on the reinjection geothermal water temperature, the formation with the same temperature as the reinjection geothermal water is measured and designated as the reinjection outlet formation. If it is an existing geothermal well, the depth of each aquifer from the wellhead, the thickness of each aquifer, and the thickness of the clay layer between adjacent aquifers are measured directly. Based on the reinjection geothermal water temperature, the formation with the same temperature as the reinjection geothermal water is measured and designated as the reinjection outlet formation.

[0096] The second step, (a) is to set a second water stop plate 12 at a height h1 from the lowest point of the outlet pipe based on the measured depth and thickness of each thermal aquifer. The thickness of the bottom thermal aquifer 9 is 1 / 2 × h1 ≦ 1 × thickness of the bottom thermal aquifer 9.

[0097] (ii) Install a baffle plate 15 above the second waterstop plate 12;

[0098] The third step, (i) is to install the lowest first waterstop plate 11 on the water outlet pipe 2 at the middle position of the clay layer 18 above the bottom thermal aquifer 9, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers.

[0099] (ii) Install a baffle plate above the first waterstop plate;

[0100] Step 4, (i) Based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers, install the corresponding first water stop plate 11 on the outlet pipe 2 located in the middle of the clay layer 18 below the non-bottom thermal aquifer 8 near the upper layer.

[0101] (ii) Install a baffle plate 15 above the first waterstop plate 11;

[0102] Fifth step, repeat the fourth step until the first water stop plate 11 is installed on the water outlet pipe 2 corresponding to the position of the clay layer 18 below all non-bottom thermal water-bearing layers 8 and the baffle plate 15 is installed above the first water stop plate 11.

[0103] Step 6: Install the circulation pump 6 and the sand separator 5 at the corresponding positions on the outlet pipe 2;

[0104] Step 7: Connect the upper end of the outlet pipe 2 to the heat source inlet pipe of the heat exchanger 3.

[0105] Step 8: Install circulation pump 6 on return water pipe 4, connect the upper end of return water pipe 2 to the heat source outlet pipe of heat exchanger 3, insert the lower end of return water pipe into well pipe, and position the lower end of return water pipe below the set reinjection outlet formation.

[0106] Step 9: Seal the wellhead plate.

[0107] The scope of protection of this invention is not limited to the above embodiments. Any system whose structure is the same as or similar to the efficient utilization system for geothermal wells in sandstone geothermal reservoirs that extracts heat without extracting water, and whose construction method is the same as or similar to that method, falls within the scope of protection of this invention.

Claims

1. A high-efficiency system for heat extraction without water extraction from a sandstone geothermal well, comprising a geothermal well, an outlet pipe, a heat exchanger, and a return pipe, wherein a desander and a circulation pump are installed on the outlet pipe, and a circulation pump is installed on the return pipe; the geothermal well includes a well casing, a bottom aquifer, and multiple non-bottom aquifers located above the bottom aquifer; the lower end of the outlet pipe is located at the lowest point of the bottom aquifer; and multiple water outlet holes are provided on the well casing corresponding to the bottom aquifer and the non-bottom aquifers, characterized in that: A first water-stop plate is installed on the outlet pipe corresponding to the middle position of the clay layer below each of the non-bottom thermal aquifers, and a second water-stop plate is installed on the outlet pipe at the upper middle position of the bottom thermal aquifer. Both the first and second water-stop plates include a fixed plate and an elastic plate fixed to the outlet pipe. The radial outer side of the elastic plate contacts the inner wall of the well pipe. The outer diameter of the fixed plate is smaller than the inner diameter of the well pipe, and the elastic plate can bend and deform downward under the pressure of the reinjection water, so that part of the reinjection water enters the corresponding thermal aquifer through the outlet hole, and the other part flows downward through the gap formed between the elastic plate and the inner wall of the well pipe. Above each of the first and second waterstop plates, a baffle plate is fixedly installed on the water outlet pipe. The baffle plate is spindle-shaped with vertical symmetry, and the distance between adjacent baffle plates is 20-30 meters. The lower end of the return water pipe is inserted into the well pipe, and the formation temperature at the lower end is greater than or equal to the temperature of the reinjection water.

2. The efficient utilization system for sandstone geothermal wells that extracts heat without extracting water, as described in claim 1, is characterized in that: The outer diameter of the widest part of the spoiler is smaller than the inner diameter of the well pipe.

3. The construction method of the sandstone geothermal well heat extraction without water extraction high-efficiency utilization system according to claim 1 or 2, characterized in that: The method includes the following steps: The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers; if it is an existing geothermal well, it is to directly measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers. The second step is to set a second water stop plate at a height h1 from the lowest point of the outlet pipe, based on the measured depth and thickness of each thermal aquifer. The thickness of the bottom thermal aquifer is 1 / 2 × h1 ≤ 1 × thickness of the bottom thermal aquifer. The third step is to install the lowest first waterstop plate on the outlet pipe at the middle position of the clay layer above the bottom thermal aquifer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers. The fourth step is to install the corresponding first waterstop plate on the outlet pipe at the middle position of the clay layer below the non-bottom thermal aquifer near the uppermost layer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers. Fifth, repeat step four until the first waterstop is installed on all the outlet pipes in the clay layer below all non-bottom thermal aquifers. Step 6: Install a circulation pump and a sand remover at the corresponding location on the outlet pipe; Step 7: Connect the upper end of the outlet pipe to the heat source inlet pipe of the heat exchanger. Step 8: Install a circulation pump on the return water pipe, connect the upper end of the return water pipe to the heat source outlet pipe of the heat exchanger, and insert the lower end of the return water pipe into the well pipe. Step 9: Seal the wellhead plate.

4. The construction method of the sandstone geothermal well heat extraction without water extraction high-efficiency utilization system according to claim 1 or 2, characterized in that: The method includes the following steps: The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers; if it is an existing geothermal well, it is to directly measure the depth of each geothermal aquifer from the wellhead, the thickness of each geothermal aquifer, and the thickness of the clay layer between adjacent geothermal aquifers. The second step is (i) based on the measured depth and thickness of each thermal aquifer, a second water stop is set at a height h1 from the lowest point of the outlet pipe, 1 / 2 × bottom thermal aquifer thickness ≦ h1 ≦ 1 × bottom thermal aquifer thickness. (ii) Install a baffle plate above the second waterstop plate; The third step, (i) is to install the lowest first waterstop plate on the outlet pipe at the middle position of the clay layer above the bottom thermal aquifer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers. (ii) Install a baffle plate above the first waterstop plate; Step 4, (a) Based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers, install the corresponding first waterstop plate on the outlet pipe at the middle position of the clay layer below the non-bottom thermal aquifer near the upper layer. (ii) Install a baffle plate above the first waterstop plate; Fifth, repeat step four until the first waterstop is installed on the outlet pipes of all non-bottom thermal aquifers below the clay layer and the baffle is installed above the first waterstop. Step 6: Install a circulation pump and a sand remover at the corresponding location on the outlet pipe; Step 7: Connect the upper end of the outlet pipe to the heat source inlet pipe of the heat exchanger. Step 8: Install a circulation pump on the return water pipe, connect the upper end of the return water pipe to the heat source outlet pipe of the heat exchanger, and insert the lower end of the return water pipe into the well pipe. Step 9: Seal the wellhead plate.

5. The construction method of the sandstone geothermal well heat extraction without water extraction high-efficiency utilization system according to claim 1 or 2, characterized in that: The method includes the following steps: The first step, if it is a newly formed geothermal well, is to construct the well and measure the depth of each aquifer from the wellhead, the thickness of each aquifer, and the thickness of the clay layer between adjacent aquifers. Based on the reinjection geothermal water temperature, the formation with the same temperature as the reinjection geothermal water is measured and designated as the reinjection outlet formation. If it is an existing geothermal well, the depth of each aquifer from the wellhead, the thickness of each aquifer, and the thickness of the clay layer between adjacent aquifers are measured directly. Based on the reinjection geothermal water temperature, the formation with the same temperature as the reinjection geothermal water is measured and designated as the reinjection outlet formation. The second step is (i) based on the measured depth and thickness of each thermal aquifer, a second water stop is set at a height h1 from the lowest point of the outlet pipe, 1 / 2 × bottom thermal aquifer thickness ≦ h1 ≦ 1 × bottom thermal aquifer thickness. (ii) Install a baffle plate above the second waterstop plate; The third step, (i) is to install the lowest first waterstop plate on the outlet pipe at the middle position of the clay layer above the bottom thermal aquifer, based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers. (ii) Install a baffle plate above the first waterstop plate; Step 4, (a) Based on the measured depth of each thermal aquifer, the thickness of each thermal aquifer, and the thickness of the clay layer between adjacent thermal aquifers, install the corresponding first waterstop plate on the outlet pipe at the middle position of the clay layer below the non-bottom thermal aquifer near the upper layer. (ii) Install a baffle plate above the first waterstop plate; Fifth, repeat step four until the first waterstop is installed on the outlet pipes of all non-bottom thermal aquifers below the clay layer and the baffle is installed above the first waterstop. Step 6: Install a circulation pump and a sand remover at the corresponding location on the outlet pipe; Step 7: Connect the upper end of the outlet pipe to the heat source inlet pipe of the heat exchanger. Step 8: Install a circulation pump on the return water pipe, connect the upper end of the return water pipe to the heat source outlet pipe of the heat exchanger, insert the lower end of the return water pipe into the well pipe, and position the lower end of the return water pipe below the formation of the set reinjection outlet. Step 9: Seal the wellhead plate.

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