WO2020113914A1

WO2020113914A1 - Process for improving heat production capacity of geothermal well

Info

Publication number: WO2020113914A1
Application number: PCT/CN2019/088844
Authority: WO
Inventors: 田振林
Original assignee: 田振林
Priority date: 2018-12-05
Filing date: 2019-05-28
Publication date: 2020-06-11
Also published as: CN109403917A; CN109403917B

Abstract

A process for improving the heat production capacity of a geothermal well. The process improves the capacity of leading geothermal energy in the rock stratum into a geothermal well by using a heat conduction well cementing technology and an enhanced conductivity fracturing technology, and achieves highly-efficient heat taking and heat exchange utilization by using a spiral plate type condensing section gravity heat pipe heat exchanger. The specific process procedures are as follows: after completing drilling a geothermal well and casing a sleeve pipe (2), carrying out the heat conduction well cementing, that is, injecting thermal insulation cement slurry in a stratum low temperature section, and injecting heat conduction cement slurry into a stratum high temperature section to complete well cementing; after solidification of the heat insulation cement slurry and the heat conduction cement slurry of the well cementing, carrying out segmented perforation and fracturing in the sleeve pipe (2) of the stratum high temperature section, producing cracks in the high temperature rock stratum, and filling the cracks with a heat conduction material to form a heat guiding belt (7) extending from the sleeve pipe (2) to the rock stratum; and finally, mounting a condensing section of the gravity heat pipe heat exchanger (8) connected to the sleeve pipe (2) on the ground to finally form a high-yield geothermal well system in which quick heat transfer in the rock stratum and highly-efficient heat exchange in a well cylinder are achieved.

Description

Process for improving heat production capacity of geothermal well

Technical field

The invention relates to the technical field of geothermal energy development, in particular to a process for improving the heat production capacity of a geothermal well.

Background technique

There is abundant geothermal energy available for exploitation within 10km of the earth's surface. Geothermal resources are a kind of clean and renewable energy without pollution. With the gradual exhaustion of traditional energy sources such as petroleum and coal, geothermal resources will become an important part of future energy. Geothermal energy can be divided into three categories: shallow geothermal energy, hydrothermal geothermal resources, and dry hot rocks. Traditional geothermal usually refers to geothermal water, but geothermal water resources are limited and require specific conditions to form, and dry hot rocks are widely distributed. Geothermal extraction technology should only take heat, not water, and use ground heat to protect groundwater resources. The extracted ground heat can be used for heating, cooling and power generation.

At present, geothermal water is injected into one well and out of one well, that is, one injection, one injection, two injections or one injection, four injections. High-pressure water is injected into the dry and hot rock formation through the water injection well. After fully absorbing the formation heat, high-temperature water and steam are injected. Produced through production wells, after heat exchange and surface circulation device treatment, cooling water is injected into the ground again to form a circulation system to realize the development of heat of dry hot rocks. In this heat extraction method, injection wells and production wells generally require an appropriate scale of fracturing, and a certain size of fractures are produced in the formation. It is difficult to connect the fractures between the injection wells and the production wells. The fluid leakage from the injection well to the fracture system is large. Water is injected into the underground dry and hot rock mass through deep wells, penetrates into the cracks of the rock formation and absorbs geothermal energy, that is, it is difficult to form a stable underground heat exchange system in the dry and hot rock mass, and it is difficult to achieve dynamic balance between the injection volume and the recovery volume; water vapor 1. There are many components and impurities in the rocks brought out of the water flow, which cause great corrosion and blockage to the operation of the ground heat exchange system.

At present, the use of mid-deep geothermal rock must carry out drilling, casing, and cementing. Cementing refers to the construction operation of injecting cement into the annular space between the wellbore and the casing. Because the thermal conductivity of rock is only 1.6-3.6W/(m·K), the thermal conductivity is low, and after the cement slurry is injected outside the casing to fix it, the thermal conductivity of the cement slurry is only 0.19W/(m·K)-0.65W /(m·K), which is equivalent to forming a thermal insulation layer between the casing and the rock. The thermal resistance is very large. The heat of the high-temperature rock layer away from the geothermal well is difficult to be introduced into the well. The water entering the well is heated by the high-temperature rock layer After passing through the low-temperature section of the formation, heat exchange causes heat loss, and the temperature decreases. The heat of the high-temperature rock mass in the high-temperature section of the formation is difficult to conduct to the vicinity of the wellbore. The single-well heat production is very low, resulting in low heat production and poor benefits of the current geothermal well. . In addition, the existing geothermal wells and rocks have poor heat transfer capacity, and multiple interconnected geothermal wells need to be excavated to improve the heat transfer effect, which will not only increase the engineering volume, but also change the structure of the underground rock layer and increase the risk of ground subsidence . In geothermal wells, the temperature range of the high temperature and low temperature sections of the formation is defined according to the temperature required for surface utilization. The geothermal well section above the temperature required for surface utilization is the high temperature section, and the geothermal well section below the temperature required for surface utilization is the low temperature section. .

Summary of the invention

The present invention aims to solve the defects of the prior art, and provides a process for making a geothermal well good in heat conduction, large in heat exchange and high in heat production.

The technical solution of the present invention is as follows:

The process of improving the heat production capacity of geothermal wells is to improve the ability of geothermal energy in the rock formation to be introduced into geothermal wells through heat conduction cementing technology and enhanced conductivity fracturing technology, and then complete efficient heat exchange through spiral plate condensation section gravity heat pipe heat exchanger The new geothermal well technology is used; the specific technological process is as follows: after drilling and casing of the geothermal well, heat conduction cementing is performed, that is, thermal insulation cement slurry is injected in the low temperature section of the formation, and thermal cement slurry is injected in the high temperature section of the formation to complete the cementing After the heat-insulating cement slurry and the heat-conducting cement slurry of the cementing well are solidified, perforation and fracturing are carried out in the casing in the high temperature section of the formation to generate cracks in the high-temperature rock formation, and the cracks are filled with thermally conductive material to form the secondary casing It extends to the conduction zone of the rock layer; finally, the condensation section of the gravity heat pipe heat exchanger connected to the casing is installed on the ground. The casing meets the quality requirements of the shell of the gravity heat pipe. The cooling liquid of the condensation section is organic Rankine cycle (ORC) The circulating water of working fluid or domestic heating will eventually form a high-yield geothermal well system with rapid heat transfer in the rock formation and efficient heat exchange in the wellbore.

The process of the thermal conductivity cementing technology is as follows:

After drilling reaches the designed depth, the casing is run into the wellbore, the casing meets the quality requirements of the gravity heat pipe shell, and a floating hoop is installed at the bottom of the casing as the location of the ancient well cement slurry. The outer diameter of the casing is smaller than the wellbore;

Cementing: first inject heat-insulating cement slurry into the casing, and then inject heat-conducting cement slurry into the casing. The injected heat-insulating cement slurry and heat-conductive cement slurry enter the annular space between the casing and the wellbore through the floating hoop, from the bottom of the wellbore Fill up, after the injection amount of heat-insulating cement slurry and heat-conducting cement slurry reaches the designed amount, put the rubber plug into the casing, and seal the rubber plug to the floating hoop, so that the first injected heat-insulating cement slurry is in the annular space of the low temperature section of the formation It is fixed to form a heat-insulating cement ring, and the heat-conducting cement slurry injected later is fixed in the annular space of the high-temperature section of the formation to form a heat-conducting cement ring to complete the heat conduction cementing.

The technology of the enhanced conductivity fracturing technology is as follows:

(1) Perforation: After the thermal conductivity cementing process is completed and the thermally insulated cement slurry and the thermally conductive cement slurry are solidified, segmental perforation is carried out from the casing at different heights in the high-temperature section of the formation, and the through-holes penetrated through the casing, Thermally conductive cement ring and high temperature formation;

(2) Fracturing: After perforating, water is used as the fracturing fluid to use hydraulic fracturing system to pass through the hole to fracture the rock layer. After the rock layer is cracked, the fracturing system is used to inject the medium and high pressure into the fracture. The filling fluid of the thermally conductive filler extends the crack forward and is filled with the thermally conductive filler until the crack extends to a preset length;

(3) Pressure keeping: After the fracturing, the geothermal well is kept under pressure and slowly depressurized. The water in the filling fluid flows back into the casing, and the thermally conductive filler settles in the crack and closes the crack to form a heat conduction zone. Plug the short pipe into the hole to block the hole in the wall of the pipe during perforating fracturing. The pipe expansion should be able to withstand the pressure in the casing to avoid the pressure release of the casing wall and complete the fracturing. Craftsmanship.

The condensing section of the gravity heat pipe heat exchanger is connected with the bushing, the condensing section includes a shell and a spiral plate, the spiral plate is installed in the shell, and the vertical spiral plate is installed in the shell of the condensing section as a gravity heat pipe replacement The tube side of the heat exchanger, the casing and the shell connected to it are used as the shell of the gravity heat pipe heat exchanger, the casing corresponds to the heat conduction cement ring section is the evaporation section of the gravity heat pipe heat exchanger, the casing corresponds to the insulation cement ring The section is the adiabatic section of the gravity heat pipe heat exchanger; the inner part of the spiral plate is hollow, and a center of the spiral plate is provided with an outlet pipe along the axis direction, and the upper end of the outlet pipe penetrates the top end of the shell and outward Extending, the water outlet pipe communicates with the central end of the spiral plate, the peripheral end of the spiral board is provided with a lateral water inlet pipe, one end of the water inlet pipe communicates with the peripheral end of the spiral plate, and the other end of the water inlet pipe It extends through the side wall of the casing and extends outwards; a communication pipe is also provided on the side wall of the casing.

The thermal insulation cement slurry in the cementing technology process is configured by mixing ordinary cement and water, the thermally conductive cement slurry is configured by mixing ordinary cement, thermally conductive filler and water, and the weight of the ordinary cement and thermally conductive filler in the thermally conductive cement slurry The ratio is 100: (5-100), where the fineness of the thermally conductive filler is 0.04 mm-0.5 mm.

The casing running into the wellbore in the cementing technology process is coated with an insulation coating on the outer wall of the casing corresponding to the low temperature section of the formation; the outer wall of the shell of the condensation section of the gravity heat pipe heat exchanger is coated with an insulation coating , The outer wall of the outlet pipe is coated with an insulating coating.

The filling liquid in the fracturing-enhancing fracturing technology is a mixed liquid of water and thermally conductive filler, and the weight ratio of water and thermally conductive filler is 100: (5-60), in which the thermally conductive filler is powder or the particle size is 0.15-0.45 mm, 0.45-0.90mm or 0.85-1.20mm granular.

The thermally conductive fillers in the cementing process technology or enhanced conductivity fracturing technology can all include graphene, high thermal conductivity carbon powder, silver, copper, gold, aluminum, sodium, molybdenum, tungsten, zinc, nickel, iron, and oxide. One or more components of aluminum, magnesium oxide, zinc oxide, aluminum nitride, boron nitride, and silicon carbide.

The diameter of the shell of the condensation section of the gravity heat pipe heat exchanger is larger than the diameter of the sleeve, and the connection between the lower end of the shell and the sleeve is tapered.

The beneficial effects of the present invention are:

1. The geothermal well of the present invention uses a thermally conductive cement slurry for cementing in the high temperature section of the formation, and a heat conduction belt with high thermal conductivity is provided in the high temperature section of the formation, so that the heat in the rock layer away from the wellbore is rapidly and continuously Introduce the casing for heat exchange, generate enough heat for the liquid in the casing to generate vaporization, and greatly accelerate the heating efficiency of the liquid in the casing; because the ordinary cement slurry is used for cementing in the low temperature section of the formation, it is equivalent to the casing and the formation. A heat insulation layer is formed between them, and a heat insulation coating is applied to the casing corresponding to the low temperature section of the formation, thereby effectively avoiding the heat loss of the vaporized rising steam, so that the heat source of the formation can maximize the output, rising steam The maximum exchange of heat with the cold water in the spiral plate on the ground improves the efficiency of the use of geothermal heat and greatly increases the heat production of the geothermal well.

2. The invention realizes a closed cycle in a single well, and only a dry hot rock well can be constructed to extract the heat energy in the high-temperature rock layer, which has the characteristics of only taking heat and not taking water, and the utilization process does not affect the groundwater level and groundwater environment, and can effectively protect Geothermal resources to eliminate the adverse effects of groundwater level decline and ground subsidence; the circulating water used in the casing of the wellbore is in a closed state and does not have direct contact with the formation, effectively avoiding problems such as corrosion and blockage during the operation of the surface heat exchange system, which can enable the equipment The problems of surface corrosion and deposition of impurities are minimized.

3. The invention can realize the extraction of geothermal energy by constructing only one dry-heat rock well, which reduces the water requirement and saves the drilling cost compared with multi-well heat extraction, and the system is simple in operation and highly controllable.

4. The present invention can separately drill wells to form a geothermal production system, and can also use the present invention to realize the co-production of geothermal and oil and gas in oil or natural gas exploitation. The heat extraction in the oil production well can keep the oil pipes in the oil well at high temperature to prevent the rise of oil in the pipes. Clogging caused by waxing and scaling caused by lower temperature.

BRIEF DESCRIPTION

1 is a schematic diagram of the structure of the geothermal well and heat exchanger of the present invention;

Figure 2 is a top sectional view of the heat exchanger of the present invention;

The serial numbers and corresponding structural names in the figure are as follows:

1-wellbore, 2-casing, 3-floating hoop, 4-conducting cement ring, 5-insulating cement ring, 6-through hole, 7-conducting heat belt, 8-heat exchanger, 9-housing, 10- Spiral plate, 11-outlet pipe, 12-inlet pipe, 13-connecting pipe, 14-connecting part.

detailed description

The present invention will be further described below with reference to the drawings.

Example 1

The process of improving the heat production capacity of geothermal wells is to improve the ability of geothermal energy in the rock formation to be introduced into geothermal wells through heat conduction cementing technology and enhanced conductivity fracturing technology, and then complete efficient heat exchange through spiral plate condensation section gravity heat pipe heat exchanger A new geothermal well process; the specific process flow is as follows: after drilling and casing of the geothermal well, thermally conductive cementing is performed, that is, thermal insulation cement slurry is injected in the low temperature section of the formation, and thermal cement slurry is injected in the high temperature section of the formation to complete the cementing After the heat-insulating cement slurry and the heat-conducting cement slurry of the cementing well are solidified, perforation and fracturing are carried out in the casing in the high temperature section of the formation to generate cracks in the high-temperature rock formation, and the cracks are filled with thermally conductive material to form the secondary casing It extends to the conduction zone of the rock layer; finally, the condensation section of the gravity heat pipe heat exchanger connected to the casing is installed on the ground, and finally a high-productivity geothermal well system with rapid heat transfer of the rock layer and efficient heat exchange of the wellbore is formed.

The process of the thermal conductivity cementing technology is as follows:

(1) After the drilling reaches the designed depth, the casing 2 is run into the wellbore 1, and a floating hoop 3 is installed at the bottom of the casing 2, the outer diameter of the casing is smaller than the wellbore;

(2) Cementing: first inject heat-insulating cement slurry into casing 2, and then inject heat-conducting cement slurry into casing 2, the injected heat-insulating cement slurry and heat-conductive cement slurry enter casing 2 and wellbore through floating hoop 3 The annular space between the two is filled upwards from the bottom of the wellbore. After the amount of heat-insulating cement slurry and heat-conducting slurry reaches the designed amount, the rubber plug is placed in the casing, and the rubber plug is sealed to the floating hoop 3, so that the first insulation is injected. The cement slurry is fixed in the annular space of the low temperature section of the formation to form a heat-insulating cement ring 5, and the injected thermally conductive cement slurry is fixed in the annular space of the high temperature section of the formation to form the thermally conductive cement ring 4 to complete the thermal conductivity cementing.

(1) Perforation: After the thermal conductivity cementing process is completed and the thermally insulated cement slurry and the thermally conductive cement slurry are solidified, segmental perforation is carried out from the casing 2 at different heights in the high temperature section of the formation, and the through hole 6 is penetrated Casing 2, thermally conductive cement ring 4 and high temperature formation;

(2) Fracturing: After perforating, water is used as the fracturing fluid to perform hydraulic fracturing to the 6 through holes using a fracturing system to fracture the rock layer. After the rock layer is fractured, the fracturing system is used to inject the medium and high pressure fracture zone Filling fluid with thermally conductive filler to extend the crack forward and fill it with thermally conductive filler until the crack extends to a preset length; fracturing adopts flow-limiting fracturing technology or hydraulic sandblasting fracturing technology;

(3) Pressure holding: After the fracturing, the geothermal well is kept under pressure and slowly depressurized. The water in the filling fluid flows back into the casing 2. The thermally conductive filler settles and stays in the crack and closes the crack, forming the thermal conductivity 7. The injection through hole 6 is run down to block the short pipe, and the hole in the wall of the pipe during the fracturing is blocked by the pipe expansion method. The pipe expansion should be able to withstand the pressure in the casing to avoid the pressure release of the casing 2 pipe wall. Completion of fracturing enhanced conductivity process.

The condensing section of the gravity heat pipe heat exchanger is connected to the casing 2 in a joint, the condensing section includes a shell 9 and a spiral plate 10, the spiral plate 10 is installed in the shell 9, and the condensing section is installed in the shell 9 vertically The straight spiral plate 10 is used as the tube side of the gravity heat pipe heat exchanger, the casing 2 and the shell 9 connected with it are used as the shell of the gravity heat pipe heat exchanger, and the pipe section of the casing 2 corresponding to the thermally conductive cement ring 4 is a gravity heat pipe The evaporation section of the heat exchanger 8 and the section of the casing 2 corresponding to the heat-insulating cement ring 5 are the insulation sections of the gravity heat pipe heat exchanger; the interior of the spiral plate 10 is hollow, and the central position of the spiral plate 10 is along its axis A water outlet pipe 11 is provided in the direction. The upper end of the water outlet pipe 11 penetrates the top of the housing 9 and extends outward. The water outlet pipe 11 communicates with the central end of the spiral plate 10. The peripheral end of the spiral plate 10 is provided with a A horizontal water inlet pipe 12, one end of the water inlet pipe 12 communicates with the peripheral end of the spiral plate, the other end of the water inlet pipe 12 penetrates the side wall of the housing 9 and extends outward; a side wall of the housing 9 is further provided with a通管13。 Communication tube 13. The height of the spiral plate 10 gradually increases from the periphery to the center.

A vacuum pump is connected to the outside of the communication tube 13 to evacuate the interior of the gravity heat pipe heat exchanger. After vacuuming, the liquid working medium is added to the interior of the gravity heat pipe heat exchanger through the communication pipe 13, and then the communication The tube is sealed. The liquid working fluid will absorb the heat from the geothermal layer in the evaporation section, and then the liquid working fluid will heat up and vaporize and rise along the casing 2. When the vaporized working fluid rises to the condensation section above the ground, it will interact with the The cold water performs heat exchange work. After heat exchange, the vaporous working fluid will become liquid. Under the action of gravity, it will return to the evaporation section and be heated again to evaporate. In this way, the water in the spiral plate 10 becomes heat after heat absorption and temperature rise Water will finally come out of the water outlet pipe 11 under the action of an external water pump. The cooling liquid in the condensing section is organic Rankine cycle (ORC) working fluid or circulating water for domestic heating.

The casing 2 running into the wellbore 1 in the cementing technology process is coated with an insulating coating on the outer wall of the casing corresponding to the low temperature section of the formation to avoid heat exchange between the rising steam and the low temperature section of the formation, resulting in heat loss; The outer wall of the shell 9 of the condensing section of the gravity heat pipe heat exchanger is coated with an insulating coating, and the outer wall of the outlet pipe 11 is coated with an insulating coating to reduce heat loss during heat exchange and enable normal temperature water energy in the spiral plate 10 Maximum absorption of heat from high-temperature formations.

The diameter of the shell 9 of the condensing section of the gravity heat pipe heat exchanger is larger than the diameter of the sleeve 2. The lower end of the shell 9 and the connection part of the sleeve 2 have a large and small taper in the way 14 to facilitate the condensing of the rising steam and reflux Into the casing 2 of the geothermal well.

The working principle of the geothermal well according to the present invention is as follows: As shown in Fig. 1-2, the casing 2 and the casing 9 which are inserted into the wellbore 1 are connected to a shell as a gravity heat pipe heat exchanger, and then a spiral is installed above the top of the wellbore In the plate-type condensing section, during production, an external vacuum device is connected to the communication pipe 13 to evacuate the casing 2 and the condensing section casing to form a negative pressure, and then add normal temperature water to the casing 2 through the communication pipe 2 , Water enters the inside of the wellbore, because the cementing material of the high temperature section of the formation is a thermally conductive cement ring 4, and the heat conduction zone 7 filled with high thermal conductivity material in the high temperature section of the formation can quickly and continuously enter the heat in the rock layer away from the wellbore The casing 2 exchanges heat, and the normal temperature water that enters the bottom of the wellbore is rapidly heated in the high temperature section of the formation. After heating and vaporization, the steam rises to the condensation section of the gravity heat pipe heat exchanger under the pressure difference, and the spiral plate 10 in the condensation section passes through The water pipe 12 is filled with normal temperature water, and the water in the spiral plate 10 exchanges heat with the rising steam. The hot water after heat exchange and heating is output from the water outlet pipe 11 for heating the ground. The steam after the heat exchange condenses into water droplets and acts under gravity It flows back into the casing 2 through the conical connection, and heats and vaporizes again in the high temperature section of the formation in the casing 2, completing a cycle process, so that the cycle is repeated, and the geothermal source is continuously output to use.

In the geothermal well of the present invention, a thermally conductive cement slurry is used for cementing in the high temperature section of the formation, and a heat conduction belt with high thermal conductivity is provided in the high temperature section of the formation, so that the heat in the rock layer away from the wellbore is quickly and continuously introduced into the sleeve The heat exchange of the pipe generates enough heat for the liquid in the casing 2 to generate vaporization, which greatly speeds up the heating efficiency of the liquid in the casing 2; because the ordinary cement slurry is used for cementing in the low temperature section of the formation, it is equivalent to A heat insulation layer is formed between the formations, and a heat insulation coating is applied on the outer casing of the corresponding low temperature section, thereby effectively avoiding the heat loss caused by the vaporization of the rising steam, so that the heat source of the formation can maximize the output, The rising steam exchanges heat with the cold water in the spiral plate 10 on the ground to the utmost extent, improves the use efficiency of the geothermal heat, and greatly improves the heat production of the geothermal well.

The invention realizes a closed cycle in a single well, and the construction of a dry hot rock well can realize the extraction of heat energy in a high-temperature rock layer. It has the characteristics of only taking heat and not taking water. The utilization process does not affect the groundwater level and groundwater environment, and can effectively protect geothermal resources. , To eliminate the adverse effects of groundwater level decline and ground subsidence; the circulating water used in the casing of the wellbore is in a closed state, not in direct contact with the stratum, effectively avoiding the problems of corrosion and blockage during the operation of the ground heat exchange system, which can make the equipment surface corrode And the problem of depositing impurities is minimized.

The invention can realize the extraction of geothermal energy by constructing only one dry hot rock well, which reduces the water requirement and saves drilling cost compared with multi-well heat extraction, and the system has simple operation and high controllability.

The invention can separately drill a well to form a geothermal production system, and can also use the invention to realize the co-extraction of geothermal and oil and gas in oil or natural gas exploitation. The heat extraction in the oil production well can keep the oil pipe in the oil well high to prevent the temperature in the pipe from rising because of the temperature drop Causes waxing, scaling and clogging.

In the present invention, the installation form of the geothermal well is a vertical well. In addition to the forms listed in the present invention, any other forms of geothermal wells, such as U-shaped butt wells and L-shaped wells, etc., using the form of the present invention are within the protection scope of the present invention within.

Claims

The process of improving the heat production capacity of geothermal wells is characterized by improving the ability of geothermal energy in the rock formation to be introduced into geothermal wells through heat conduction cementing technology and enhanced conductivity fracturing technology, and then through the spiral plate condensing section gravity heat pipe heat exchanger to complete the efficient A new geothermal well process for heat extraction and heat exchange; the specific technological process is as follows: after drilling and casing of the geothermal well, conducting heat conduction cementing, that is, injecting thermal insulation cement slurry in the low temperature section of the formation and thermal cement in the high temperature section of the formation The slurry is cemented; after the heat-insulating cement slurry and the heat-conducting cement slurry of the cementing cement are solidified, perforation and fracturing are carried out in the casing in the high temperature section of the formation to generate cracks in the high temperature rock layer and fill the cracks with thermally conductive material Form a heat conduction zone extending from the casing to the rock formation; finally install the condensation section of the gravity heat pipe heat exchanger connected to the casing on the ground, and finally form a high-yield geothermal well system with rapid rock layer heat transfer and efficient wellbore heat transfer.
The process for improving the heat production capacity of a geothermal well according to claim 1, wherein the process of the thermal conductivity cementing technology is as follows:

(1) After the drilling reaches the designed depth, the casing (2) is run into the wellbore (1), and a floating hoop (3) is installed at the bottom of the casing (2), the outer diameter of the casing is smaller than the wellbore;

(2) Cementing: first inject heat-insulating cement slurry into the casing (2), then inject heat-conducting cement slurry into the casing (2), the injected heat-insulating cement slurry and heat-conductive cement slurry enter through the floating hoop (3) The annular space between the casing (2) and the wellbore is filled upwards from the bottom of the wellbore. After the injection amount of the heat-insulating cement paste and the heat-conducting cement paste reaches the designed amount, the rubber plug is placed in the casing and the rubber plug seals the floating hoop (3), so that the first injected heat-insulating cement slurry is fixed in the annular space of the low-temperature section of the formation to form the heat-insulating cement ring (5), and the later-injected heat-conducting cement slurry is fixed in the annular space of the high-temperature section of the formation to form the heat-conductive cement Ring (4) to complete heat conduction cementing.
The process for improving the heat production capacity of a geothermal well according to claim 2, wherein the process of the enhanced conductivity fracturing technology is as follows:

(1) Perforation: After the thermal conductivity cementing process is completed and the thermal insulation cement paste and the thermal conductivity cement paste are solidified, segmental perforation is carried out from the casing (2) at different heights in the high temperature section of the formation 6) Shoot through casing (2), thermally conductive cement ring (4) and high temperature formation;

(2) Fracturing: After perforating, water is used as the fracturing fluid to use the fracturing system to conduct hydraulic fracturing to the through hole (6), which causes the rock layer to rupture and produce cracks. Inject filling fluid with thermally conductive filler to extend the crack forward and fill it with thermally conductive filler until the crack extends to a preset length;

(3) Pressure keeping: After the fracturing, the geothermal well is kept under pressure and slowly depressurized. The water in the filling fluid flows back into the casing (2), and the thermally conductive filler settles in the cracks and closes the cracks, forming a thermal conductivity zone (7 ), then insert the plugging short tube at the injection through hole (6), and use the tube expansion method to block the hole in the tube wall during the perforation fracturing. The tube expansion should be able to withstand the pressure in the casing to avoid the casing (2) Relieve the pressure on the pipe wall and complete the fracturing process.
The process for improving the heat production capacity of a geothermal well according to claim 3, characterized in that the condensation section of the gravity heat pipe heat exchanger is connected to the casing (2), and the condensation section includes a shell (9) 3. Spiral plate (10), the spiral plate (10) is installed in the shell (9), and the vertical spiral plate (10) is installed in the shell (9) of the condensation section as the tube side of the gravity heat pipe heat exchanger , The casing (2) and the shell (9) connected with it are used as the shell of the gravity heat pipe heat exchanger, the casing (2) corresponds to the heat conduction cement ring (4), the section is the gravity heat pipe heat exchanger (8) In the evaporation section, the section of the casing (2) corresponding to the insulated cement ring (5) is the insulation section of the gravity heat pipe heat exchanger; the inner part of the spiral plate (10) is hollow, and the central position of the spiral plate (10) is along A water outlet pipe (11) is arranged in the axial direction, the upper end of the water outlet pipe (11) penetrates the top of the casing (9) and extends outward, and the water outlet pipe (11) and the central end of the spiral plate (10) The outer end of the spiral plate (10) is provided with a transverse water inlet pipe (12). One end of the water inlet pipe (12) communicates with the outer peripheral end of the spiral plate, and the other end of the water inlet pipe (12) penetrates The side wall of the housing (9) extends outward; a communication tube (13) is also provided on the side wall of the housing (9).
The process for improving the heat production capacity of a geothermal well according to claim 2, characterized in that the thermal insulation cement slurry in the cementing technology process is configured by mixing ordinary cement and water, and the thermally conductive cement slurry is composed of ordinary cement and thermally conductive filler Mixed with water, the weight ratio of common cement and thermally conductive filler in the thermally conductive cement slurry is 100: (5-100), and the fineness of the thermally conductive filler is 0.04mm-0.5mm.
The process for improving the heat production capacity of a geothermal well according to claim 4, characterized in that the casing (2) running into the wellbore (1) in the cementing technology process corresponds to the casing outer wall of the low temperature section of the formation A heat insulating coating is coated on the outer wall; the outer wall of the shell (9) of the condensation section of the gravity heat pipe heat exchanger is coated with an insulating coating, and the outer wall of the outlet pipe (11) is coated with an insulating coating.
The process for improving the heat production capacity of a geothermal well according to claim 3, characterized in that the filling fluid in the fracturing-enhancing fracturing technology is a mixture of water and thermally conductive filler, and the weight ratio of water and thermally conductive filler is 100: (5-60), wherein the thermally conductive filler is in the form of powder or particles with a particle size of 0.15-0.45mm, 0.45-0.90mm or 0.85-1.20mm.
The process for improving the heat production capacity of a geothermal well according to any one of claims 5 or 7, wherein the thermally conductive filler includes graphene, high thermal conductivity carbon powder, silver, copper, gold, aluminum, sodium, molybdenum, One or more components of tungsten, zinc, nickel, iron, aluminum oxide, magnesium oxide, zinc oxide, aluminum nitride, boron nitride, and silicon carbide.
The process for improving the heat production capacity of a geothermal well according to claim 4, characterized in that: the diameter of the shell (9) of the condensation section of the gravity heat pipe heat exchanger is larger than the diameter of the casing (2). The connecting portion (14) of the lower end and the sleeve (2) has a large and small taper.