阅读说明：本技术 一种弯折型地热井 (Bending geothermal well ) 是由 陈�峰 刘洪涛 于 2020-05-14 设计创作，主要内容包括：本发明提供了一种弯折型地热井,该弯折型地热井包括：竖直井段和弯折井段；其中,弯折井段设置在竖直井段下方且至少部分位于采热目标岩层内,竖直井段和弯折井段呈夹角设置且相连通以形成地热井本体；地热井本体内沿其内壁设有固井套管,固井套管沿地热井本体的长度方向延伸；固井套管内沿其长度方向设有取热管,并且,取热管与固井套管的内壁之间间隔设置。本发明通过与竖直井段呈夹角设置的弯折井段,增大了单位高度内地热井本体与四周岩层的接触面积,以增大采热目标岩层处取热面积,增大换热介质与四周岩层的换热面积,提升了单位投资的取热量,从而解决了取热量和投资之间的矛盾。(The invention provides a bending geothermal well, comprising: a vertical well section and a bent well section; the vertical well section and the bent well section are arranged at an included angle and communicated with each other to form a geothermal well body; a well cementation sleeve is arranged in the geothermal well body along the inner wall of the geothermal well body and extends along the length direction of the geothermal well body; the cementing casing is internally provided with a heat extraction pipe along the length direction, and the heat extraction pipe and the inner wall of the cementing casing are arranged at intervals. According to the invention, the contact area between the geothermal well body and the surrounding rock stratum in unit height is increased through the bent well section which forms an included angle with the vertical well section, so that the heat extraction area at the heat extraction target rock stratum is increased, the heat exchange area between the heat exchange medium and the surrounding rock stratum is increased, the heat extraction amount of unit investment is improved, and the contradiction between the heat extraction amount and the investment is solved.)

1. A bent geothermal well, comprising: a vertical well section (11) and a bent well section (12); wherein the content of the first and second substances,

the bent well section (12) is arranged below the vertical well section (11) and at least partially positioned in a heat production target rock stratum, and the vertical well section (11) and the bent well section (12) are arranged in an included angle and communicated to form a geothermal well body (1);

a well cementation casing (2) is arranged in the geothermal well body (1) along the inner wall of the geothermal well body, and the well cementation casing (2) extends along the length direction of the geothermal well body (1);

the heat extraction pipe (3) is arranged in the well cementation casing pipe (2) along the length direction of the well cementation casing pipe, the heat extraction pipe (3) and the inner wall of the well cementation casing pipe (2) are arranged at intervals, so that an annular channel (4) is formed between the heat extraction pipe (3) and the well cementation casing pipe (2), a heat exchange medium flows in the annular channel (4) and exchanges heat with rock strata around the geothermal well body (1), and flows into the heat extraction pipe (3) from the inlet end of the heat extraction pipe (3), so that the heat extraction pipe (3) is extracted to the ground to supply heat.

2. The bent-type geothermal well according to claim 1,

the heat extraction pipe (3) is divided into a plurality of sections along the length direction of the well cementation casing pipe (2), and comprises: the heat exchange tube comprises a heat insulation tube (31) used for slowing down heat exchange of an internal heat exchange medium and an external heat exchange medium and a heat exchange tube (32) used for promoting the heat exchange of the internal heat exchange medium and the external heat exchange medium, wherein the heat exchange tube (32) is arranged below the heat insulation tube (31) and communicated with the heat insulation tube (31).

3. The bent-type geothermal well according to claim 2,

the heat exchange tube (32) is provided with a heat exchange strengthening piece for strengthening the heat exchange between the inner heat exchange medium and the outer heat exchange medium of the heat exchange tube (32).

4. The bent-type geothermal well according to claim 3,

the reinforced heat exchange pieces are helical fins or plate fins, or the reinforced heat exchange pieces are embossing or groove structures arranged on the tube wall of the heat exchange tube (32).

5. The bent-type geothermal well according to claim 2,

the distance between the tail end of the heat-insulating pipe (31) and the isothermal layer is within a second preset range; and at the isothermal layer, the temperature of the heat exchange medium inside and outside the heat taking pipe (3) is the same.

6. A bent-type geothermal well according to any one of claims 1 to 5,

well cementation sleeve pipe (2) are followed the length direction of geothermal well body (1) is divided into a plurality of sections, include: a hold-warm section (21) to slow heat transfer between the heat transfer medium and the formation, a heat transfer section (22) to facilitate heat transfer between the heat transfer medium and the formation;

the heat exchange section (22) is arranged below the heat preservation section and communicated with the heat preservation section (21).

7. The bent-type geothermal well according to claim 6,

the distance between the tail end of the heat preservation section (21) and the isothermal stratum is within a first preset range, and the temperature of the isothermal stratum (A-A) is equal to that of the heat exchange medium at the inlet of the annular channel (4).

8. The bent-type geothermal well according to claim 6,

and a reinforced heat exchange piece is arranged on the heat exchange section (22) and used for reinforcing heat exchange between a heat exchange medium at the heat exchange section (22) and rock strata around the heat exchange section (22).

9. A bent-type geothermal well according to any one of claims 1 to 5,

the tail end of the well cementation sleeve (2) is a closed end, so that the interior of the well cementation sleeve (2) is isolated from the wall of the geothermal well body (1).

10. A bent-type geothermal well according to any one of claims 1 to 5, wherein the vertical well section (11) and the bent well section (12) are in communication with each other via a deviated well section.

Technical Field

The invention relates to the technical field of new energy and energy conservation and environmental protection, in particular to a bent geothermal well.

Background

China is wide in region and spans a plurality of climatic zones. In the rapid development of economic society, as people pursue good life more and more, heat supply becomes an important energy utilization direction. The heating mode is mainly divided into centralized heating and distributed heating. The centralized heat supply generally refers to a method for performing centralized heat supply on a larger area by adopting a thermal power plant, the main adopted primary energy is coal, but with the increasing shortage of the environment protection situation in China, the mode of adopting a coal-fired boiler of the thermal power plant for heating can discharge a large amount of flue gas, pollute the environment and protect and bear the pressure. The other common mode is distributed heat supply, currently, under the unified command of 'changing coal into gas and changing coal into electricity' in China, the heat sources of distributed heat supply commonly adopted in many cities generally comprise a gas boiler, a gas wall-mounted boiler and an electric air source heat pump, but the technologies have many problems in the operation process. The first problem is that the operation cost is high, and the heating operation cost after coal modification is increased from one square meter to twenty-more to more than thirty to sixty-more. Taking a gas wall-mounted boiler as an example, the general operation cost is more than 40-50 yuan. The heating cost of the gas boiler for central heating is over thirty yuan. Therefore, in this practical situation, the use of geothermal energy as a primary heat source for heating is an environmentally friendly and relatively low-cost technique.

The geothermal energy can be divided into three types of shallow geothermal energy, middle-deep geothermal energy and deep geothermal energy.

The U-shaped buried pipe ground source heat pump which is widely applied at present and has mature technology belongs to shallow geothermal energy application, the depth is generally 100-300 m deep, and the water outlet temperature is generally below 10 ℃. The depth of the geothermal energy in the middle and deep layers is generally 500-4000 m, the ground temperature is generally within 100 ℃, the temperature of the outlet water is generally 15-60 ℃, the geothermal energy is used as an energy source for building heating, the efficiency can be improved by combining a heat pump for utilization, the geothermal energy can also be directly used for heating, and the operation cost is lower. A dry hot rock power generation technology belongs to deep geothermal energy application, the depth is generally more than 5000m, and the water outlet temperature is more than 100 ℃. Is obviously limited by geological conditions.

The utilization mode of the geothermal energy in the middle and deep layers generally has two modes, one mode is a vertical single well, and the other mode is a U-shaped double well. The vertical single well is a vertical single well heat collector for geothermal heat in a middle-deep layer, generally adopts a sleeve pipe form, has smaller investment compared with a double-well mode, is convenient to construct, has good heat insulation and low heat collection quantity, generally has the heat supply capacity of 10000 plus one square meter and 15000 square meter on average, and has the initial investment of more than 180 yuan per square meter on average. The U-shaped twin-well adopts the mode of twin-well intercommunication to adopt heat, and the heat extraction is big, and average single-well heat supply can reach more than 20000 square meters, but this kind of mode investment is great, and general investment is nearly twice as that of single-well.

Disclosure of Invention

In view of the above, the invention provides a bending geothermal well, and aims to solve the problem that in the existing geothermal heat extraction, the heat extraction amount of a vertical single well is low, and the investment cost of a U-shaped double well is high, so that the contradiction exists between the heat extraction amount and the investment.

The invention provides a bending geothermal well, which comprises: a vertical well section and a bent well section; the bent well section is arranged below the vertical well section and at least partially positioned in a heat production target rock stratum, and the vertical well section and the bent well section are arranged at an included angle and are communicated to form a geothermal well body; a well cementation sleeve is arranged in the geothermal well body along the inner wall of the geothermal well body, and the well cementation sleeve extends along the length direction of the geothermal well body; the heat extraction pipe is arranged in the well cementation casing along the length direction of the well cementation casing, the heat extraction pipe and the inner wall of the well cementation casing are arranged at intervals, so that an annular channel is formed between the heat extraction pipe and the well cementation casing, a heat exchange medium flows in the annular channel and exchanges heat with rock strata around the geothermal well body, and flows into the heat extraction pipe from the inlet end of the heat extraction pipe so as to be pumped to the ground along the heat extraction pipe for heating.

Further, above-mentioned bending type geothermal well, get the heat pipe and divide into a plurality of sections along the length direction of well cementation sleeve pipe, include: the heat exchange tube is arranged below the heat preservation tube and communicated with the heat preservation tube.

Further, in the bent geothermal well, the heat exchange tube is provided with a heat exchange strengthening piece for strengthening heat exchange between the heat exchange medium inside and outside the heat exchange tube.

Further, in the above bending geothermal well, the reinforced heat exchange member is a helical fin or a plate fin, or the reinforced heat exchange member is an embossed or grooved structure arranged on the tube wall of the heat exchange tube.

Further, in the bending geothermal well, the distance between the tail end of the heat preservation pipe and the isothermal layer is within a second preset range; and at the isothermal layer, the temperatures of the heat exchange media inside and outside the heat taking pipe are the same.

Further, above-mentioned type geothermal well of buckling, the well cementation sleeve pipe is divided into a plurality of sections along the length direction of geothermal well, includes: the heat preservation section is used for slowing down heat exchange between the heat exchange medium and the stratum, and the heat exchange section is used for promoting heat exchange between the heat exchange medium and the stratum; the heat exchange section is arranged below the heat preservation section and communicated with the heat preservation section.

Further, in the bent geothermal well, the distance between the tail end of the heat preservation section and the isothermal formation is within a first preset range, and the formation temperature of the isothermal formation is equal to the temperature of the heat exchange medium at the inlet of the annular channel.

Further, in the bent geothermal well, the heat exchange section is provided with a reinforced heat exchange piece for reinforcing heat exchange between the heat exchange medium at the heat exchange section and rock strata around the heat exchange section.

Further, in the above bending geothermal well, the end of the cementing casing is a closed end, so that the interior of the cementing casing is isolated from the wall of the geothermal well body.

Further, in the bending geothermal well, the vertical well section is communicated with the bending well section through the inclined well section.

According to the bent geothermal well provided by the invention, the contact area between the geothermal well body in unit height and the surrounding rock stratum is increased through the bent well section arranged at an included angle with the vertical well section, so that the heat taking area at the heat-taking target rock stratum is increased, the heat exchange area between a heat exchange medium and the surrounding rock stratum is increased, and further the heat taking amount is increased at a certain cost, namely the heat taking amount of unit investment is increased, so that the defect that the investment needs to be increased when the heat taking amount is increased in the prior art is overcome, and the contradiction between the heat taking amount and the investment is solved.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 is a schematic structural view of a geothermal well structure according to a first embodiment of the invention;

FIG. 2 is a schematic structural view of a geothermal well structure according to a second embodiment of the invention;

FIG. 3 is a schematic structural view of a geothermal well structure according to a third embodiment of the invention;

FIG. 4 is a schematic structural view of a geothermal well structure according to a fourth embodiment of the invention;

FIG. 5 is a schematic structural view of a geothermal well structure according to a fifth embodiment of the invention;

FIG. 6 is a schematic structural view of a geothermal well structure according to a sixth embodiment of the invention;

fig. 7 is a schematic structural diagram of a geothermal well structure according to a seventh embodiment of the invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

Referring to fig. 1 to 7, there are shown preferred structures of the bending type geothermal well provided by the embodiment of the present invention. As shown in the drawings, the bending type geothermal well includes: a vertical well section 11 and a bent well section 12; wherein the content of the first and second substances,

vertical well section 11 extends the setting downwards from the earth's surface, and bending well section 12 sets up in vertical well section 11 below and at least part is located the heating target stratum of formation, and vertical well section 11 and bending well section 12 are the contained angle setting and are linked together in order to form geothermal well body 1. Specifically, the geothermal well body 1 is communicated with the earth surface and an underground heat reservoir so as to heat the underground heat reservoir. The vertical well section 11 extends vertically downwards from the earth surface, the top end of the bent well section 12 is communicated with the bottom end of the vertical well section 11, the top end of the bent well section and the bottom end of the vertical well section form an included angle, and at least part of the bent well section 12 is located in a heat production target rock stratum and used for heating the geothermal heat of the heat production target rock stratum to realize heating. The included angle between the vertical well section 11 and the bent well section 12 can be determined according to actual conditions, and is not limited in this embodiment. Preferably, the included angle between the vertical well section 11 and the bent well section 12 is less than or equal to 90 °, that is, the included angle between the vertical well section 11 and the bent well section 12 is an acute angle or a right angle, so as to reduce the height of the bent well section 12 extending to the underground and ensure heat extraction, that is, further improve the heat extraction amount of unit investment. Preferably, the vertical well section 11 and the bent well section 12 can communicate with each other through the slant well section 13, so as to avoid stress concentration at the connecting position of the vertical well section 11 and the bent well section 12. The heat recovery target rock stratum can be determined according to actual conditions, and is not limited in the embodiment; the geothermal well body 1 can be various drilled wells with the aperture of 80-400 mm.

A well cementation casing 2 is arranged in the geothermal well body 1 along the inner wall of the geothermal well body 1 and extends along the length direction of the geothermal well body 1. Specifically, the well cementation sleeve 2 is arranged in a geothermal well body 1 drilled downwards on the ground through a drilling machine, the well cementation sleeve 2 is sleeved inside the geothermal well body 1 along the inner wall of the geothermal well body 1 and used for isolating rock strata inside the well cementation sleeve 2 and around the geothermal well body 1, namely, the inner wall of the geothermal well body 1 is completely covered by the well cementation sleeve 2, so that a shaft of the geothermal well body 1 is sealed, water in a layer inevitably flows into the well cementation sleeve 2, and the collapse of the shaft can be prevented. Preferably, the end of the cementing casing 2 (the bottom end as shown in fig. 4) is closed to prevent formation water from entering the interior of the cementing casing 2.

The heat extraction pipe 3 is arranged in the well cementation casing 2 along the length direction of the well cementation casing, the heat extraction pipe 3 and the inner wall of the well cementation casing 2 are arranged at intervals, so that an annular channel 4 is formed between the heat extraction pipe 3 and the well cementation casing 2, a heat exchange medium flows in the annular channel 4 and exchanges heat with rock strata around the geothermal well body 1, and flows into the heat extraction pipe 3 at the inlet end (the right lower end shown in figure 4) of the heat extraction pipe 3 so as to be pumped to the ground along the heat extraction pipe 3 for heating. Specifically, an annular structure with a hollow interior is formed between the heat extraction pipe 3 and the well cementation casing 2 to serve as an annular channel 4, that is, an inlet and a downward channel of a heat exchange medium are formed, that is, the top end of the annular channel 4 serves as an inlet of the heat exchange medium, and the heat exchange medium flows along the annular channel 4 to the inlet end of the heat extraction pipe 3 to flow along the heat extraction pipe 3 and be pumped to the ground for heating. Wherein, the inlet end of the tail end of the heat taking pipe 3 is an opening end, so that the heat exchange medium flows into the heat taking pipe 3 after heat exchange; the annular channel 4 is a cold water inlet channel; wherein, the heat extraction pipe 3 can be a conventional plastic pipe or a steel wire hose, which is beneficial to lowering.

The temperature gradient due to the usual geothermal heat is 3 deg.c/100 meter deep. Generally, as the depth of a well is deeper and deeper, the temperature of the well is higher and higher, the cost of drilling the well per unit length is higher and higher, and after a certain depth, the cost per meter of the well is exponentially increased. In the embodiment, the contact area between the geothermal well body 1 in unit height and surrounding rock strata is increased by the bent well section 12 which forms an included angle with the vertical well section 11, so that the heat extraction area at the position of a heat extraction target rock stratum is increased, the heat exchange area between a heat exchange medium and the surrounding rock strata is increased, and the heat extraction amount is increased at a certain cost, namely, the heat extraction amount of unit investment is increased, so that the defect that the investment needs to be increased when the heat extraction amount is increased in the prior art is overcome, and the contradiction between the heat extraction amount and the investment is solved.

With continued reference to fig. 4-5, the cementing casing 2 is divided into several sections along the length direction of the geothermal well body 1 (vertical direction as shown in fig. 1), including: a heat preservation section 21 for slowing down the heat exchange between the heat exchange medium and the stratum and a heat exchange section 22 for promoting the heat exchange between the heat exchange medium and the stratum. The heat exchange section 22 is arranged below the heat preservation section 21 and communicated with the heat preservation section 21, and the tail end of the heat exchange section 22 is a closed end, so that the interior of the well cementation casing 2 is isolated from the well wall of the geothermal well body 1.

Specifically, because the temperature near the ground surface is low, the heat exchange section 22 is disposed below the heat preservation section 21, the heat exchange section 22 is communicated with the heat preservation section 21, and a head end (as shown in fig. 4) of the heat exchange section 22 is detachably connected with a tail end (as shown in fig. 4) of the heat preservation end 11, or may be a fixed connection manner, which is not limited in this embodiment; the ends of the heat exchange section 22 may be plugged with cementing cement. Preferably, the head end (top end as shown in fig. 4) of the heat-retaining section 21 may be located at the surface, the distance between the tail end of the heat-retaining section 21 and the isothermal formation a-a may be within a first preset range, the formation temperature of the isothermal formation a-a is equal to the temperature of the heat exchange medium at the inlet of the annular channel 4, that is, at the inlet of the annular channel 22 located at the surface, and the first preset range may be determined according to actual conditions, for example, may be within five meters above and below the isothermal formation a-a, or may be other ranges, which is not limited in this embodiment; further preferably, the terminal end of the hold-warm section 11 may be located at the isothermal formation a-a; in this embodiment, the heat exchange medium is taken as water for illustration, the temperature of the water introduced into the heat exchanger 2 is 45 ℃, that is, the temperature of the heat exchange medium at the inlet of the annular channel 4 is 45 ℃, and the isothermal formation a-a is the location of the formation temperature of 45 ℃, of course, the isothermal formation a-a, that is, the end location of the heat preservation section 21, may be determined according to actual conditions, and is not limited in this embodiment. In order to improve the heat exchange effect of the heat exchange medium at the heat exchange section 22, preferably, a heat exchange enhancement member (not shown in the figure) is disposed on the heat exchange section 22 for transferring heat to the heat exchange section 22, so as to enhance the heat exchange between the heat exchange medium at the heat exchange section 22 and the rock strata around the heat exchange section 22, and further improve the heat exchange efficiency, so as to fully utilize the geothermal energy of the rock strata. Preferably, the pipe wall thickness of heat preservation section 21 is 1.5~3 times of heat transfer section 22, and thicker heat preservation section 21 not only can strengthen the heat preservation effect, can strengthen its mechanical strength moreover, can bear great dead weight and pulling force, and correspondingly, thin heat transfer section 22 dead weight is light, and heat transfer effect is good. Wherein, the thermal insulation section 21 may be a PVC (Polyvinyl chloride) pipe, a PPR (polypropylene random copolymer) pipe, a glass fiber reinforced plastic pipe, a carbon steel pipe wrapped with a thermal insulation material, or a cast iron pipe with a thermal insulation coating, and in order to ensure the thermal insulation effect of the thermal insulation section 21, preferably, the thermal conductivity coefficient of the thermal insulation section 21 is less than or equal to 0.25W/(mK); that is, the heat preservation section 21 is partially or completely subjected to heat preservation treatment, for example, the casing of the section is wrapped with a heat preservation material, or coated with a heat preservation coating, or a double-layer casing is adopted to block the heat of the reinjection water from dissipating to the stratum. The heat exchange section 22 can be a temperature-resistant pipeline with good heat conductivity, such as a PPR pipe, a PVC pipe, a carbon steel pipe, a cast iron pipe or a stainless steel pipe, and the like, and the heat conductivity coefficient is greater than or equal to 20W/(mK); the heat-exchange reinforcing members may be various fins, or may be an embossed structure or a grooved structure on the tube wall of the heat-exchange section 22; that is, part or all of the heat exchange section 22 is subjected to special treatment, which may be, but not limited to, adding fins, grooving, embossing, reducing the thickness of the tube wall, selecting a material with good heat conductivity, etc.; the heat exchange between the recharge water and the outer stratum or the hot rock layer of the geothermal well casing can be accelerated by increasing the heat exchange area or reducing heat conduction barrier and the like.

In order to improve the stability of the well cementation casing 2, preferably, the head end of the heat exchange section 22 is located at a position where the formation temperature is greater than a threshold value, and a fixed section is arranged and connected between the heat exchange section 22 and the heat preservation section 21; the threshold value is greater than the temperature of the heat exchange medium at the inlet of the annular channel 4. Specifically, the head end of the heat preservation section 21 can be located at the ground surface, and the distance between the tail end of the heat preservation section 21 and the head end of the fixing section and the isothermal stratum A-A is within a first preset range; the head end of the fixed section is connected with the tail end of the heat preservation section 21, and the fixed section and the heat preservation section can be connected through a flange; the end of the fixed section and the head of the heat exchange section 22 are both located at a position where the formation temperature is greater than the threshold value and are connected, for example, the two may be connected by a screw thread or other connection methods, which is not limited in this embodiment. The threshold may be 60 ℃, or may be another value determined according to actual conditions, such as 45 ℃, which is not limited in this embodiment. The fixed section can be conventional well cementation sleeve pipe such as steel pipe, can satisfy requirements such as resistance to compression, anticorrosive, resistant/heat preservation on the one hand, on the other hand, compares in the PVC pipeline, and conventional well cementation sleeve pipe's cost is lower, has realized the economic design.

Of course, the cementing casing 2 may also be four or more sections, which is not limited in this embodiment.

In the embodiment, as the temperature of the stratum is continuously increased along with the increase of the depth from the ground surface to the underground, the temperature of the reinjection water injected from a geothermal wellhead is higher than that of the shallow stratum at the initial stage, the reinjection water can radiate the shallow stratum through the sleeve in the process of injecting the reinjection water into the annular space between the geothermal well sleeve and the heat extraction pipe from the wellhead and flowing downwards, so as to avoid excessive heat loss of the reinjection water in the injection process, the heat exchange between the heat exchange medium and the stratum is slowed down through the heat preservation section 21 arranged at the upper part, under the protection of the heat preservation section 21, the heat exchange medium can flow to the deep stratum without losing a large amount of heat energy to the stratum through the pipe wall of the heat preservation section 21, and further, the heat loss of the heat exchange medium at the region close to the ground surface is avoided; through setting up heat transfer section 22 in geothermal well lower part, because heat transfer medium gets into behind heat transfer section 22, heat transfer medium's temperature is less than the stratum temperature, heat in the stratum will be through the pipe wall of heat transfer section 22 to heat transfer medium conduction, heat transfer section 22 has good heat conductivity, can promote the formation heat to the heat transfer medium transmission, accelerate heat transfer rate, heat transfer medium to obtain more heat energy flows back to the earth's surface through getting heat pipe 3, improve the temperature of getting heat pipe 3 export heat transfer medium promptly, heat transfer medium output is the user heat supply, both accomplished only to the heat of target underground heat reservoir, do not get water, heat exchange efficiency has been improved simultaneously, heat transfer effect has been improved, and then the heat supply of geothermal well and the utilization ratio of geothermal energy have been improved.

With continued reference to fig. 4-5, the heat extraction pipe 3 is divided into several sections along the length direction of the cementing casing 2 (vertical direction as shown in fig. 4), including: a heat preservation pipe 31 for slowing down the heat exchange of the internal and external heat exchange media and a heat exchange pipe 32 for promoting the heat exchange of the internal and external heat exchange media. The heat exchange pipe 32 is arranged below the heat preservation pipe 31 and communicated with the heat preservation pipe 31.

Specifically, the heat extraction pipe 3 is divided into several sections along the length direction of the cementing casing 2, i.e., along the length direction of the heat extraction pipe 3. Because the temperature near the earth surface is lower, the heat exchange tube 32 is arranged below the heat preservation tube 31, and the heat exchange tube 32 is communicated with the heat preservation tube 31, so that the heat exchange between the heat exchange medium in the heat preservation tube 31 and the heat exchange medium with lower temperature outside the heat preservation tube 31 when the heat exchange medium flows upwards from the heat taking tube 3 after heat exchange in the annular channel 4 is slowed down, further the heat loss in the flowing process of the heat exchange medium is avoided, and the heat supply capacity of the geothermal well is improved. At the heat exchange tube 32, the temperature of the heat exchange medium inside and outside the heat exchange tube 32 is lower than that of the well cementation sleeve 2, so that in order to fully utilize geothermal energy, the heat exchange tube 32 promotes the heat exchange medium inside and outside the heat exchange tube 32 to exchange heat with the rock stratum around the well cementation sleeve 2, so as to ensure the full absorption and utilization of the geothermal energy, improve the utilization rate of the geothermal energy and improve the heat supply capacity of the geothermal well. Preferably, the head end (top end as shown in fig. 4) of the heat preservation pipe 31 can be arranged above the ground surface to be connected with a heating device, so that the heat exchange medium pumped out from the heat taking pipe 3 can be guided into the heating device for heating; the distance between the end B-B (the bottom end as shown in fig. 4) of the heat-insulating pipe 31 and the isothermal layer is within a second preset range, the temperature of the heat exchange medium inside and outside the pipe wall of the heat-taking pipe 3 at the isothermal layer is the same, and the second preset range can be determined according to actual conditions, for example, the second preset range may be within five meters above and below the isothermal layer, or may be within other ranges, which is not limited in this embodiment. To further improve the heat exchange effect of the heat exchange medium at the heat exchange tube 32, preferably, a heat exchange enhancement member (not shown in the figure) is disposed on the heat exchange tube 32 for transferring heat to the heat exchange tube 32, so as to enhance the heat exchange between the heat exchange medium inside and outside the heat exchange tube 32, and further improve the heat exchange efficiency, so as to fully utilize the geothermal energy of the rock stratum.

The heat insulation pipe 31 may be a sleeve with good heat insulation performance, or a double-layer sleeve filled with heat insulation material or vacuum, or a thickened pipe, or a heat insulation coating added on the inner and outer walls of the pipeline to improve the heat insulation performance, so as to prevent a large amount of heat energy from being dissipated outwards when heated hot water flows through the section, that is, the heat insulation pipe 31 may be a steel pipe, a glass fiber reinforced plastic pipe, or a plastic pipe with heat insulation, such as a PE (polyethylene) pipe, a PVC pipe, or a PPR pipe; the heat preservation pipe 31 can also be a double-layer sleeve pipe, and a heat insulation layer or a vacuum layer is filled between the double-layer pipes; the heat preservation pipe 31 can also be a thickened pipe, namely, the wall thickness is increased, so that the heat preservation effect is enhanced, the mechanical strength is enhanced, and the heavy dead weight and the tensile force can be borne; the heat preservation pipe 31 can also be provided with a heat preservation layer on the inner wall and/or the outer wall of the pipe wall so as to improve the heat insulation performance and avoid the heated hot water from dissipating a large amount of heat energy outwards when flowing through the section; wherein, the heat-insulating layer can be a heat-insulating coating (such as a nano ceramic coating and a silicon-aluminum fiber coating), composite heat-insulating cotton (rock wool, polyurethane foaming heat-insulating material and the like); the wall thickness of the section can be simply thickened to increase the heat insulation performance, and the heat conductivity coefficient is not higher than 0.2W/mK; the heat-insulating anticorrosive heat-insulating coating can be formed by coating a coating formed by doping one or more of hollow glass beads, expanded pearl powder, silica aerogel and the like into a coating system.

The heat exchange pipe 32 can be a PPR pipe, a carbon steel pipe or a cast iron pipe with good heat conductivity, and the heat conductivity coefficient is greater than or equal to 20W/(mK); the heat-transfer enhancement member can be various fins such as helical fins, rolled fins, sleeved fin tubes, plate fin fins, or can be an embossing structure or a grooving structure on the tube wall of the heat exchange tube 32 to locally thin the tube wall or integrally thin the tube wall, so as to shorten the heat transfer path and further improve the heat exchange effect of the internal and external media of the heat exchange tube 32.

In order to improve the stability of the heat extraction pipe 3, a fixed pipe is preferably arranged and connected between the heat exchange pipe 32 and the heat preservation pipe 31. Specifically, the head end of the heat preservation pipe 31 can be located above the ground surface, the distance between the tail end of the heat preservation pipe 31 and the head end of the fixed pipe and the isothermal layer is within a second preset range, the head end of the fixed pipe is connected to the tail end of the heat preservation pipe 31, and the head end of the fixed pipe and the isothermal layer can be connected through hot melting; the end of the fixed tube and the head end of the heat exchange tube 32 are located at positions and connected, for example, the two can be connected by a flange, or other connection methods, which is not limited in this embodiment. The threshold may be 60 ℃, or may be another value determined according to actual conditions, such as 45 ℃, which is not limited in this embodiment. The fixed pipe can be a glass steel pipe, and the surface of the fixed pipe is also coated with a heat insulation nano ceramic coating so as to slow down the heat exchange of the internal heat exchange medium and the external heat exchange medium.

Of course, the heat removal pipe 3 may also have four or more sections, which is not limited in this embodiment. In specific implementation, the sections of the heat-taking pipe 3 may be connected by hot melting, screwing, welding, or other connection methods, which is not limited in this embodiment.

In this embodiment, the heat-collecting pipe 3 may be a combination of one or more than two different pipes, for example, a combination of a steel pipe, a glass fiber reinforced plastic pipe, a polyethylene plastic pipe, and a cast iron pipe, and the joints between the pipes are in a screw thread manner or a fusion connection manner, so that the heat-insulating pipe 31 and the heat-exchanging pipe 32 may also be a combination of various pipes.

In this embodiment, one or more of the bent geothermal wells may form a group, and multiple groups of the bent geothermal wells may jointly supply heat to the outside, or a single group of the bent geothermal wells may jointly supply heat to the outside.

The direction of the arrows in fig. 1 to 7 indicates the flow direction of the heat exchange medium.

The utility model provides a geothermal well gets hot structure, including five kinds of embodiments, the concrete description is as follows:

referring to fig. 1, fig. 1 is a schematic structural diagram of a geothermal well structure according to a first embodiment of the present invention. As shown in the figure, the bending geothermal well comprises a vertical well section 11, an inclined well section 13 and a geothermal well body 1 formed by the horizontally arranged bending well section 12, the lower end of the vertical well section 11 is close to a heat extraction target dry-hot rock stratum, and the part of the inclined well section 13 and the bending well section 12 are positioned in the heat extraction target dry-hot rock stratum.

A well cementation sleeve 2 is arranged in the whole geothermal well body 1, the lower port of the well cementation sleeve 2 is sealed by well cementation cement, underground water in a stratum through which the geothermal well body 1 penetrates is prevented from seeping into the well cementation sleeve 2 and mixing with reinjection water injected from the ground, in addition, the well cementation sleeve 1 which is put in can support an exposed well wall, and collapse of a well shaft is avoided. The cementing casing 2 is a carbon steel pipe with good heat conductivity, the outer wall of the cementing casing close to the ground surface is wrapped with heat insulation materials (such as rock wool) to form a heat insulation section 21, the tail end of the heat insulation section 21 is positioned in an isothermal stratum A-A, the temperature of the isothermal stratum, namely the stratum at the position, is equal to the temperature of the recharge water injected from the water inlet of the geothermal well, the part of the cementing casing below the heat insulation section 21 is a heat exchange section 22, and the inner wall of the heat exchange section 22 is provided with a groove for increasing the heat exchange between the recharge water and the wall of the cementing casing and the stratum outside the casing.

And (2) descending the heat extraction pipe 3 into the well cementation sleeve 2 so as to form an annular channel 4 between the heat extraction pipe 3 and the well cementation sleeve 2, injecting back irrigation water with a certain temperature into the dry hot rock stratum through a water inlet, wherein the water inlet is communicated with the annular channel 4, the back irrigation water can slowly radiate heat to the stratum through the heat preservation section 21 in the process of flowing downwards along the annular channel 4, and can absorb heat transferred from the wall of the heat extraction pipe, along with the increase of the depth, the back irrigation water starts to exchange heat from the stratum after flowing through the tail end of the heat preservation section 21, namely the isothermal stratum A-A, enters a heat extraction target stratum, fully exchanges heat with the target stratum, then enters the heat extraction pipe 2 and flows back to the ground to finish underground heat extraction.

Referring to fig. 2, fig. 2 is a schematic structural diagram of a geothermal well structure according to a second embodiment of the present invention. As shown in the figure, the bending geothermal well comprises a geothermal well body 1 formed by a vertical well section 11 and a bending well section 12, and an included angle between the bending well section 12 and the horizontal direction can be 80 °. The lower end of the vertical well section 11 is close to the hot dry rock formation of the heat production target, and most of the bent well section 12 is positioned in the hot dry rock formation.

A well cementation sleeve 2 is arranged in the whole geothermal well body 1, and a lower port of the well cementation sleeve 2 is plugged by well cementation cement, so that underground water in a stratum penetrated by the geothermal well body 1 is prevented from seeping into the well cementation sleeve 2, and a shaft is prevented from collapsing.

And a heat extraction pipe 3 is downwards arranged from the inside of the well cementation sleeve 2 to the heat extraction target dry-hot rock stratum, so that an annular channel 4 is formed between the heat extraction pipe 3 and the well cementation sleeve 2, irrigation water at a certain temperature is injected into the dry-hot rock stratum through a water inlet, the water inlet is communicated with the annular channel 4, the irrigation water enters the heat extraction pipe from the tail end of the heat extraction pipe 3 after exchanging heat with the high-temperature dry-hot rock stratum through the well cementation sleeve 2, flows back to the ground and is extracted from the outlet end of the heat extraction pipe 3, and heat extraction on the underground dry-hot rock stratum is completed.

In order to enable the recharge water to have a long enough heat exchange path, the tail end of the heat taking pipe 3 is close to the lower end of the well cementation casing pipe 2, the distance between the heat taking pipe and the heat taking pipe is 5-10 meters, the recharge water enters the heat taking pipe 3 from the tail end of the heat taking pipe 3 to flow back, in order to obtain more heat, the heat taking pipe 3 is composed of a heat insulation pipe 31 and a heat exchange pipe 32, the joint of the two sections is located at the position with the minimum temperature difference between the inside and the outside of the heat taking pipe 3, namely the position B-B, the heat insulation pipe 31 is located at one end, close to the ground. The outer wall of the heat exchange tube 32 is provided with a helical fin to enhance the heat exchange capability of the section of the heat extraction tube. The wall of the heat preservation pipe 31 is coated with the nano ceramic coating, so that the heat conductivity of the heat preservation section of the heat taking pipe is reduced, and the reflux water extracted from the water outlet end of the heat taking pipe is ensured to have higher temperature.

Referring to fig. 3, fig. 3 is a schematic structural diagram of a geothermal well structure according to a third embodiment of the present invention. As shown in the figure, the bending geothermal well comprises a vertical well section 11, an inclined well section 13 and a geothermal well body 1 formed by the horizontally arranged bending well section 12, the lower end of the vertical well section 11 is close to a heat extraction target dry-hot rock stratum, and the part of the inclined well section 13 and the bending well section 12 are positioned in the heat extraction target dry-hot rock stratum.

A well cementation sleeve 2 is arranged in the whole geothermal well body 1, and a lower port of the well cementation sleeve 2 is plugged by well cementation cement, so that underground water in a stratum penetrated by the geothermal well body 1 is prevented from seeping into the well cementation sleeve 2, and a shaft is prevented from collapsing.

And a heat extraction pipe 3 is arranged in the well cementation sleeve 2 towards the heat extraction target dry-hot rock stratum, so that an annular channel 4 is formed between the heat extraction pipe 3 and the well cementation sleeve 2, reinjection water with a certain temperature is injected into the dry-hot rock stratum through a water inlet, the water inlet is communicated with the annular channel 4, the reinjection water enters the heat extraction pipe from the tail end of the heat extraction pipe 3 after exchanging heat with the high-temperature dry-hot rock stratum through the well cementation sleeve 2, flows back to the ground and is extracted from the outlet end of the heat extraction pipe 3, and heat extraction on the underground dry-hot rock stratum is completed.

In order to obtain more heat, the heat taking pipe 3 is composed of a heat insulation pipe 31 and a heat exchange pipe 32, the position B-B of the joint of the two sections is located 5 meters below the minimum position of the temperature difference between the inside and the outside of the heat taking pipe 3, the heat insulation pipe 31 is located at one end of the heat taking pipe 3 close to the ground surface, and the heat exchange pipe 32 is located at one end of the dry heat rock stratum. The heat exchange tube 32 is a carbon steel tube with good heat conductivity to enhance the heat exchange capability of the heat extraction tube. The heat-insulating pipe 31 is a glass fiber reinforced plastic pipe with relatively poor heat conductivity, and ensures that the return water extracted from the outlet end of the heat-extracting pipe has a relatively high temperature.

Referring to fig. 4, fig. 4 is a schematic structural diagram of a geothermal well structure according to a fourth embodiment of the invention. As shown in the figure, the bending geothermal well comprises a geothermal well body 1 formed by a vertical well section 11 and a bending well section 12, and an included angle between the bending well section 12 and the horizontal direction can be 70 °. The lower end of the vertical well section 11 is close to the hot dry rock formation of the heat production target, and most of the bent well section 12 is positioned in the hot dry rock formation.

A well cementation sleeve 2 is arranged in the whole geothermal well body 1, and a lower port of the well cementation sleeve 2 is plugged by well cementation cement, so that underground water in a stratum penetrated by the geothermal well body 1 is prevented from seeping into the well cementation sleeve 2, and a shaft is prevented from collapsing.

And a heat extraction pipe 3 is arranged in the well cementation sleeve 2 towards the heat extraction target dry-hot rock stratum, so that an annular channel 4 is formed between the heat extraction pipe 3 and the well cementation sleeve 2, reinjection water with a certain temperature is injected into the dry-hot rock stratum through a water inlet, the water inlet is communicated with the annular channel 4, the reinjection water enters the heat extraction pipe from the tail end of the heat extraction pipe 3 after exchanging heat with the high-temperature dry-hot rock stratum through the well cementation sleeve 2, flows back to the ground and is extracted from the outlet end of the heat extraction pipe 3, and heat extraction on the underground dry-hot rock stratum is completed. The well cementation casing 2 is a carbon steel pipe with good heat conduction performance, the outer wall of the well cementation casing close to the ground surface is coated with a heat preservation coating to form a heat preservation section 21, the tail end of the heat preservation section 21 is located in an isothermal stratum A-A, the temperature of the isothermal stratum, namely the stratum at the isothermal stratum, is equal to the temperature of the reinjection water injected from the water inlet of the geothermal well, the part of the well cementation casing below the heat preservation section 21 is a heat exchange section 22, and fins are arranged on the inner wall of the heat exchange section 22 and used for increasing the heat exchange between the reinjection water and the wall of the well cementation casing.

In order to obtain more heat, the heat taking pipe 3 is composed of a heat insulation pipe 31 and a heat exchange pipe 32, the B-B position of the joint of the heat taking pipe and the heat exchange pipe is located 5 meters above the minimum position of the temperature difference of the water inside and outside the heat taking pipe 3, the heat insulation pipe 31 is located at one end of the heat taking pipe 3 close to the ground surface, and the heat exchange pipe 32 is located at one end of a heat collecting target stratum. The heat exchange tube 32 is a 10mm thick corrosion-resistant cast iron or polyethylene tube, and the embossing on the tube wall makes part of the area thinner to enhance the heat exchange capability of the section of heat extraction tube. The heat preservation pipe 31 is a 10mm anticorrosive cast iron pipe or polyethylene pipe, and a heat preservation layer is additionally arranged, so that the heat conduction performance is reduced, and the reflux water extracted from the water outlet end of the heat extraction pipe is ensured to have higher temperature.

Referring to fig. 5, fig. 5 is a schematic structural diagram of a geothermal well structure according to a fifth embodiment of the present invention. As shown in the figure, the bending geothermal well comprises a geothermal well body 1 formed by a vertical well section 11 and a bending well section 12, and an included angle between the bending well section 12 and the horizontal direction can be 70 °. The lower end of the vertical well section 11 is close to the hot dry rock formation of the heat production target, and most of the bent well section 12 is positioned in the hot dry rock formation.

A well cementation sleeve 2 is arranged in the whole geothermal well body 1, and a lower port of the well cementation sleeve 2 is plugged by well cementation cement, so that underground water in a stratum penetrated by the geothermal well body 1 is prevented from seeping into the well cementation sleeve 2, and a shaft is prevented from collapsing.

And a heat extraction pipe 3 is downwards arranged from the inside of the well cementation sleeve 2 to the heat extraction target dry-hot rock stratum, so that an annular channel 4 is formed between the heat extraction pipe 3 and the well cementation sleeve 2, irrigation water at a certain temperature is injected into the dry-hot rock stratum through a water inlet, the water inlet is communicated with the annular channel 4, the irrigation water enters the heat extraction pipe from the tail end of the heat extraction pipe 3 after exchanging heat with the high-temperature dry-hot rock stratum through the well cementation sleeve 2, flows back to the ground and is extracted from the outlet end of the heat extraction pipe 3, and heat extraction on the underground dry-hot rock stratum is completed.

The cementing casing 2 is a carbon steel pipe with good heat conductivity, the outer wall of the cementing casing close to the ground surface is coated with a heat-insulating coating to form a heat-insulating section 21, the tail end of the heat-insulating section 21 is positioned in an isothermal stratum A-A, the temperature of the isothermal stratum, namely the stratum at the position, is equal to the temperature of the reinjection water injected from the water inlet of the geothermal well, and the cementing casing part which is connected with the tail end (the bottom end shown in figure 5) of the heat-insulating section 21 and is positioned below the isothermal stratum A-A is a heat exchange section 22 for the reinjection water to exchange heat with the wall of the cementing casing and the stratum outside.

In order to obtain more heat, the heat extraction pipe 3 consists of a heat preservation pipe 31 and a heat exchange pipe 32, the joint B-B position of the heat extraction pipe and the heat exchange pipe is located at the position with the minimum temperature difference between the inside and the outside of the heat extraction pipe 3, the part of the heat extraction pipe between the B-B position and the ground surface belongs to the heat preservation pipe 31, and the part of the heat extraction pipe from the position below the B-B position to the bottom of the geothermal well belongs to the heat exchange pipe 32. Compared with a heat exchange tube 32 which is made of a glass steel tube with the thickness of 10mm, the heat insulation tube 31 is made of a glass steel tube with the thickness of 20mm, the heat conduction performance of the heat insulation tube is reduced by increasing the thickness of the tube, the section is prevented from radiating too fast, and the backflow water extracted from the outlet end of the heat extraction tube is guaranteed to have higher temperature.

Referring to fig. 6, fig. 6 is a schematic structural view of a geothermal well structure according to a sixth embodiment of the present invention. As shown in the figure, the bending geothermal well comprises a geothermal well body 1 formed by a vertical well section 11 and a bending well section 12, and an included angle between the bending well section 12 and the horizontal direction can be 70 °. The lower end of the vertical well section 11 is close to the hot dry rock formation of the heat production target, and most of the bent well section 12 is positioned in the hot dry rock formation.

A well cementation sleeve 2 is arranged in the whole geothermal well body 1, and a lower port of the well cementation sleeve 2 is plugged by well cementation cement, so that underground water in a stratum penetrated by the geothermal well body 1 is prevented from seeping into the well cementation sleeve 2, and a shaft is prevented from collapsing.

And a heat extraction pipe 3 is downwards arranged from the inside of the well cementation sleeve 2 to the heat extraction target dry-hot rock stratum, so that an annular channel 4 is formed between the heat extraction pipe 3 and the well cementation sleeve 2, irrigation water at a certain temperature is injected into the dry-hot rock stratum through a water inlet, the water inlet is communicated with the annular channel 4, the irrigation water enters the heat extraction pipe from the tail end of the heat extraction pipe 3 after exchanging heat with the high-temperature dry-hot rock stratum through the well cementation sleeve 2, flows back to the ground and is extracted from the outlet end of the heat extraction pipe 3, and heat extraction on the underground dry-hot rock stratum is completed.

The well cementation casing 2 is a carbon steel pipe with good heat conduction performance, and fins are arranged on the inner wall of the casing below an isothermal stratum A-A (the temperature of the stratum at the isothermal stratum is equal to the temperature of the reinjection water injected from the water inlet of the geothermal well) and are used for enhancing the heat exchange effect of the reinjection water with the wall of the well cementation casing and the stratum outside the casing.

In order to obtain more heat, grooves are formed in the pipe wall of the heat taking pipe 2 below the position B-B, so that the thickness of the local pipe wall is reduced, the heat exchange effect is enhanced, and the temperature difference between the inside and the outside of the heat exchange pipe at the position B-B is the minimum.

Referring to fig. 7, fig. 7 is a schematic structural view of a geothermal well structure according to a seventh embodiment of the present invention. As shown in the figure, the bending geothermal well comprises a geothermal well body 1 formed by a vertical well section 11 and a bending well section 12, and an included angle between the bending well section 12 and the horizontal direction can be 70 °. The lower end of the vertical well section 11 is close to the hot dry rock formation of the heat production target, and most of the bent well section 12 is positioned in the hot dry rock formation.

A well cementation sleeve 2 is arranged in the whole geothermal well body 1, and a lower port of the well cementation sleeve 2 is plugged by well cementation cement, so that underground water in a stratum penetrated by the geothermal well body 1 is prevented from seeping into the well cementation sleeve 2, and a shaft is prevented from collapsing.

And a heat extraction pipe 3 is downwards arranged from the inside of the well cementation sleeve 2 to the heat extraction target dry-hot rock stratum, so that an annular channel 4 is formed between the heat extraction pipe 3 and the well cementation sleeve 2, irrigation water at a certain temperature is injected into the dry-hot rock stratum through a water inlet, the water inlet is communicated with the annular channel 4, the irrigation water enters the heat extraction pipe from the tail end of the heat extraction pipe 3 after exchanging heat with the high-temperature dry-hot rock stratum through the well cementation sleeve 2, flows back to the ground and is extracted from the outlet end of the heat extraction pipe 3, and heat extraction on the underground dry-hot rock stratum is completed.

In order to enable the return water in the heat extraction pipe 2 to still obtain the heat of the heat extraction target stratum, fins are arranged on the pipe wall of the part of the heat extraction pipe 2, which is positioned in the pipe and has the water temperature higher than the water temperature outside the pipe, so that the heat exchange capacity of the heat extraction pipe is enhanced.

In summary, the bending geothermal well provided by the embodiment has the advantages that the contact area between the geothermal well body in unit height and the surrounding rock stratum is increased through the bending well section which forms an included angle with the vertical well section, so that the heat extraction area at the position of the heat extraction target rock stratum is increased, the heat exchange area between the heat exchange medium and the surrounding rock stratum is increased, the heat extraction amount is increased at a certain cost, namely, the heat extraction amount of unit investment is increased, the defect that the investment needs to be increased when the heat extraction amount is required to be increased in the prior art is overcome, and the contradiction between the heat extraction amount and the investment is solved.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.