Geothermal well heat exchange structure

Abstract

The utility model discloses a geothermal well heat exchange structure which comprises a geothermal well upper stratum and a geothermal well lower heat storage stratum, a cement paste filling body is filled in the geothermal well, the cement paste filling body is downwards provided with a cavity, and a water stop plug is arranged between the geothermal well upper stratum and the geothermal well lower heat storage stratum. One end of the water inlet heat preservation pipe is located outside the geothermal well, and the other end of the water inlet heat preservation pipe is located at the bottom end of the cavity; the other end of the water return heat preservation pipe is located at the top end of the cavity. On one hand, the problems that part of geothermal wells are poor in water quality, high in mineralization degree and difficult to use are solved, on the other hand, the heat exchange efficiency of'heat taking without water taking 'of a single well of the geothermal well is improved, the use value of the geothermal well is excavated to the maximum extent, and the geothermal well has great significance on the premise that a low-carbon environment-friendly life style is advocated nowadays.

Description

Technical Field

[0001] The utility model relates to the technical field of geothermal wells, in particular to a heat exchange structure of a geothermal well. Background Art

[0002] Under the premise of advocating a low-carbon and environment-friendly lifestyle nowadays, clean heat can be obtained by using medium-deep geothermal wells. At present, it is usually necessary to drill a geothermal well with a depth of 1000 - 4000m, and pump deep geothermal water to the ground for heating, bathing, planting, aquaculture, etc. However, in some areas of our country, due to the large salinity and poor water quality of deep geothermal water, the development and utilization method of pumping geothermal water to the ground will cause problems such as pipeline scaling and environmental pollution. For example, the salinity of geothermal water in some geothermal wells in Xining City and Dalian City is greater than 10000mg / L. Considering the problems of pipeline scaling and water treatment cost, the geothermal water in this case basically does not have the value of exploitation, so the deep geothermal resources cannot be obtained by pumping water.

[0003] In recent years, the technology of "extracting heat without extracting water" for single geothermal wells has been developed in our country. A coaxial casing heat exchanger can be installed in the geothermal well. Water circulates in a closed loop inside the heat exchanger without contacting the formation, and the deep heat is extracted through the heat exchange between the outer wall of the casing and the formation, realizing disturbance-free heat exchange underground; however, the heat obtained by this technology is limited compared with the way of pumping heat, resulting in a longer investment payback period for the project. Content of the Utility Model

[0004] In view of the deficiencies in the above problems, the utility model provides a heat exchange structure of a geothermal well.

[0005] To achieve the above object, the utility model provides a heat exchange structure of a geothermal well, including an upper formation of the geothermal well and a lower heat storage formation of the geothermal well. The geothermal well is filled with a cement slurry filling body, and a cavity is opened downward in the cement slurry filling body. A water stop plug is arranged between the upper formation of the geothermal well and the lower heat storage formation of the geothermal well. An inlet heat preservation pipe and a return water heat preservation pipe are arranged on the water stop plug. One end of the inlet heat preservation pipe is located outside the geothermal well, and the other end is located at the bottom end of the cavity; one end of the return water heat preservation pipe is located outside the geothermal well, and the other end is located at the top end of the cavity.

[0006] Preferably, a sealing cement layer is arranged above the water stop plug.

[0007] Preferably, an inlet casing is arranged on the side wall of the upper formation of the geothermal well, and a bonding cement layer is arranged between the outer wall of the inlet casing and the side wall of the upper formation of the geothermal well.

[0008] Preferably, the inlet casing is a steel inlet casing.

[0009] Preferably, the water stop plug is made of a circular sealing material.

[0010] Preferably, the inlet water heat preservation pipe is a PVC pipe, a PP pipe or a steel pipe, with an outer diameter of 20-100 mm and a heat insulation layer provided on the outer wall.

[0011] Preferably, the return water heat preservation pipe is a PVC pipe, a PP pipe or a steel pipe, with an outer diameter of 20-100 mm and a heat insulation layer provided on the outer wall.

[0012] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0013] On the one hand, the present utility model solves the problem that the water quality of some geothermal wells is poor and the salinity is high and difficult to utilize. On the other hand, it improves the heat exchange efficiency of "extracting heat without taking water" of a single geothermal well, maximizes the use value of the geothermal well, and has great significance under the premise of advocating a low-carbon and environmentally friendly lifestyle today. Description of the Drawings

[0014] Figure 1 is a schematic diagram of the heat exchange structure of the geothermal well of the present utility model;

[0015] Figure 2 is a schematic diagram of the completion of the geothermal well of the present utility model;

[0016] Figure 3 is a schematic diagram of the heat storage transformation of the geothermal well of the present utility model;

[0017] Figure 4 is a schematic diagram after the heat storage transformation of the geothermal well of the present utility model. Detailed Embodiments

[0018] To make the objectives, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0019] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present utility model. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0020] In the description of the present utility model, it should also be noted that, unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0021] The following further describes the present utility model in detail with reference to the Figures 1-4 accompanying drawings:

[0022] Referring to Figure 1 , the present utility model provides a geothermal well heat exchange structure, including a geothermal well, which includes an upper formation 1.1 of the geothermal well and a lower heat reservoir formation 1.2 of the geothermal well. The geothermal well is filled with a cement slurry filling body 3.4, and a cavity 2.3 is formed downward in the cement slurry filling body 3.4. A water stop plug 5.1 is provided between the upper formation 1.1 of the geothermal well and the lower heat reservoir formation 1.2 of the geothermal well. An inlet heat preservation pipe 6.1 and a return water heat preservation pipe 6.3 are provided on the water stop plug 5.1. One end of the inlet heat preservation pipe 6.1 is located outside the geothermal well, and the other end is located at the bottom end of the cavity 2.3; one end of the return water heat preservation pipe 6.3 is located outside the geothermal well, and the other end is located at the top end of the cavity 2.3. The area below the water stop plug 5.1 forms a geothermal well heat exchange section 6.2.

[0023] In this embodiment, a sealed cement layer is provided above the water stop plug 2.3.

[0024] Furthermore, an inlet casing 2.1.1 is provided on the side wall of the upper formation 1.1 of the geothermal well. A bonding cement layer is provided between the outer wall of the inlet casing 2.1.1 and the side wall of the upper formation 1.1 of the geothermal well, and this bonding cement layer uses well cement 2.1.2.

[0025] In this embodiment, the inlet casing 2.1.1 is a steel inlet casing. The water stop plug 5.1 is made of a circular sealing material. The inlet heat preservation pipe 6.1 is a PVC pipe, a PP pipe, or a steel pipe, with an outer diameter of 20 - 100 mm and a heat insulation layer provided on its outer wall. The return water heat preservation pipe 6.3 is a PVC pipe, a PP pipe, or a steel pipe, with an outer diameter of 20 - 100 mm and a heat insulation layer provided on its outer wall.

[0026] Referring to Figure 2, the geothermal well includes the upper formation 1.1 of the geothermal well and the lower heat reservoir formation 1.2 of the geothermal well; the geothermal conditions of the upper formation 1.1 of the geothermal well are poor, and the geothermal conditions of the lower heat reservoir formation 1.2 of the geothermal well are good. The formation contains geothermal water, but the water quality is poor and the salinity is high, and it does not have the value of being directly pumped out for development and utilization. In order to fix the upper formation of the geothermal well, after this section is drilled by the drill rig, a casing 2.1.1 needs to be lowered, and the cement slurry for well cementing 2.1.2 is filled between the outer wall of the casing and the borehole wall to consolidate the casing, so as to continue drilling the lower heat reservoir section formation. The cement slurry for well cementing 2.1.2 used in this section is ordinary cement, and the upper formation of the geothermal well forms the upper well-cemented section 2.1 of the geothermal well. The casing 2.1.1 is a casing, generally made of steel, and its function is to prevent the upper borehole from collapsing and ensure the normal drilling of the lower borehole section. The lower heat reservoir formation 1.2 of the geothermal well is the lower heat reservoir section 2.2 of the geothermal well, with an open hole, generally with a hole diameter greater than 152 mm. The geothermal water stored in the heat reservoir formation 1.2 flows out and fills this well section, and due to the water pressure, the water level surface 2.2.1 of the geothermal water will rise to the position of the upper well-cemented section 2.1 of the geothermal well.

[0027] Refer to Figure 3 , the grouting system 3.1 is used to inject cement slurry with high thermal conductivity into the geothermal well. The grouting needs to be injected under pressure to ensure that the cement slurry can spread into the formation of the heat reservoir section in the lower part of the geothermal well, forming a water-blocking curtain 3 that blocks the geothermal water in the heat reservoir formation, but has the property of high thermal conductivity and can conduct the heat of the heat reservoir formation to the lower section of the geothermal well. The cement slurry filling body 3.4 injected into the geothermal well by the grouting system 3.1 through the grouting pipe 3.3 is the filling body 3.5 after the cement slurry injected into the geothermal well solidifies. A valve 3.2 is provided on the grouting pipe 3.3, and the function of the valve 3.2 is to control the volume and pressure of the cement slurry in the grouting pipe 3.3. In order to spread the cement slurry filling body entering the heat reservoir section, a water-blocking curtain that blocks the geothermal water in the heat reservoir formation is formed, but it has the property of high thermal conductivity and can conduct the heat of the heat reservoir formation to the lower section of the geothermal well.

[0028] Refer to Figure 4, the drill pipe 4.1 is driven by a drill rig at the upper part and connected to the drill bit 4.2 at the lower part; the drill bit 4.2 is used to drill the solidified cement slurry filling body in the geothermal well to re - form the geothermal well cavity 2.3; the geothermal well cavity 2.3 is an open - hole, with the periphery being the cement slurry filling body and containing no water; the water - stop plug 5.1 is located at the top surface of the lower heat storage section 2.2 of the geothermal well, made of rubber or other sealable materials, circular, used to seal off the lower heat storage section 2.2 and the upper cementing section 2.1 of the geothermal well, and the water inlet heat - insulating pipe 6.1 and the return water heat - insulating pipe 6.3 pass through it. Between the upper part of the water - stop plug 5.1 and the ground is the upper - section cement slurry body 5.2 of the geothermal well, which is filled and sealed by cement grouting and is airtight and waterproof. The water inlet heat - insulating pipe 6.1 is made of materials such as PVC, PP, steel, etc., with an outer diameter of 20 - 100 mm and an external heat - insulating layer, passing through the upper - section cement slurry body 5.2 and the water - stop plug 5.1 of the geothermal well and entering the bottom of the geothermal well. The return water heat - insulating pipe 6.3 is made of materials such as PVC, PP, steel, etc., with an outer diameter of 20 - 100 mm and an external heat - insulating layer, passing through the upper - section cement slurry body 5.2 and the water - stop plug 5.1 of the geothermal well and entering the upper part of the lower heat storage section 2.2 of the geothermal well.

[0029] The usage method of this geothermal well heat - exchange structure includes:

[0030] After the geothermal well is completed, through the grouting system 3.1 on the ground, a cement slurry with high thermal conductivity is injected into the well under high pressure, so that the cement slurry can diffuse into the formation 1.2 of the heat storage section 2.2 at the lower part of the geothermal well to form a water - proof curtain 3.5 that blocks the geothermal water in the heat storage formation, but has the property of high thermal conductivity and can conduct the heat of the heat storage formation to the lower section of the geothermal well.

[0031] Then use the drill rig to drill open the cement slurry filling body 3.4 formed in the geothermal well to re - form the geothermal well cavity 2.3. At this time, the periphery of the lower cavity of the geothermal well is the cement slurry filling body and contains no water.

[0032] Then place the water - stop plug 5.1 equipped with the water inlet heat - insulating pipe 6.1 and the return water heat - insulating pipe 6.3 at the top surface of the lower heat storage section 2.2 of the geothermal well. The water inlet heat - insulating pipe 6.1 enters the bottom of the geothermal well, and the return water heat - insulating pipe 6.3 enters the upper part of the lower heat storage section 2.2 of the geothermal well.

[0033] Then, in the upper cementing section 2.1 of the geothermal well between the upper part of the water - stop plug 5.1 and the ground, inject cement to make it airtight and waterproof.

[0034] Finally, inject water or a fluid with high thermal conductivity from the water inlet heat - insulating pipe 6.1 to fill the heat - exchange section 6.2 of the geothermal well. The water or the fluid with high thermal conductivity in the heat - exchange section 6.2 of the geothermal well is heated by the heat storage formation 1.2 and then flows out to the ground through the return water heat - insulating pipe 6.3, realizing the extraction of underground heat.

[0035] The geothermal water flowing back to the ground can be used for heating ground buildings, greenhouse planting, aquaculture and other purposes. It is clean and environmentally friendly. After the heat of the geothermal water is reduced, it can be circulated back to the heat exchange section 6.2 of the geothermal well through the inlet heat preservation pipe 6.1 to achieve uninterrupted heat exchange.

[0036] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A geothermal well heat exchange structure, the geothermal well comprising an upper formation of the geothermal well and a lower heat reservoir formation of the geothermal well, characterized in that, It includes that a cement slurry filling body is filled in the geothermal well, a cavity is opened downward in the cement slurry filling body, a water stop plug is arranged between the upper formation of the geothermal well and the lower heat storage formation of the geothermal well, an inlet heat preservation pipe and a return water heat preservation pipe are arranged on the water stop plug, one end of the inlet heat preservation pipe is located outside the geothermal well, and the other end is located at the bottom end of the cavity; one end of the return water heat preservation pipe is located outside the geothermal well, and the other end is located at the top end of the cavity.

2. The geothermal well heat exchange structure according to claim 1, wherein, A sealing cement layer is arranged above the water stop plug.

3. The geothermal well heat exchange structure according to claim 1, wherein, An inlet casing is arranged on the side wall of the upper formation of the geothermal well, and a bonding cement layer is arranged between the outer wall of the inlet casing and the side wall of the upper formation of the geothermal well.

4. The geothermal well heat exchange structure according to claim 3, characterized in that, The inlet casing is a steel inlet casing.

5. The geothermal well heat exchange structure according to claim 1, wherein, The water stop plug is made of a circular sealing material.

6. The geothermal well heat exchange structure according to claim 1, wherein The inlet heat preservation pipe is a PVC pipe, a PP pipe or a steel pipe, its outer diameter is 20-100 mm and a heat insulation layer is arranged on the outer wall.

7. The geothermal well heat exchange structure according to claim 1, characterized in that, The return water heat preservation pipe is a PVC pipe, a PP pipe or a steel pipe, its outer diameter is 20-100 mm and a heat insulation layer is arranged on the outer wall.

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