Deep heat storage enhanced heat removal method and system

Abstract

The invention provides a deep heat storage enhanced heat removal method and system, and relates to the technical field of deep heat storage development and utilization. A plurality of blast fracturing cracks are formed in the heat exchange section of the geothermal well through the blast fracturing technology; a heat removal structure is arranged, and heat is removed from the geothermal well through the heat removal structure; the problems that in the prior art, a conventional underground fracturing mode is adopted to increase the heat exchange area of a geothermal well in deep heat storage, the fracture shape is controlled by ground stress, fracturing cost is high, construction is complex, action time is short, and a stratum is prone to being damaged are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep thermal reservoir development and utilization, and more specifically, relates to a deep thermal reservoir enhanced heat extraction method and system. Background Art

[0002] In the field of deep thermal reservoir development and utilization, heat exchangers are commonly used to extract heat in geothermal wells by heat conduction. Since the contact area between conventional geothermal wells and deep thermal reservoirs is small, the heat source around the geothermal wells cannot be replenished in time when extracting heat, causing the temperature around the geothermal wells to drop rapidly, affecting the heat extraction effect of the heat exchangers.

[0003] At present, downhole fracturing is often used to increase the heat exchange area of ​​geothermal wells in deep heat reservoirs and improve the heat recovery rate of deep heat reservoirs. The shape of the cracks produced by conventional fracturing technology is controlled by ground stress, the fracturing cost is high, the construction is complex, the action time is short, and it is very easy to damage the formation. It is impossible to achieve low-cost and high-efficiency heat extraction. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for enhancing heat extraction from deep heat storage in order to address the deficiencies in the prior art, thereby solving the problems in the prior art of increasing the heat exchange area of ​​geothermal wells in deep heat storage by conventional downhole fracturing, the shape of the cracks being controlled by ground stress, the high cost of fracturing, the complex construction, the short action time, and the easy damage to the formation.

[0005] In order to achieve the above object, the present invention provides a deep heat storage enhanced heat extraction method, comprising:

[0006] Setting up geothermal wells;

[0007] Using explosive fracturing technology to form multiple explosive fracturing cracks in the heat exchange section of the geothermal well;

[0008] A heat extraction structure is provided, and heat is extracted from the geothermal well through the heat extraction structure.

[0009] Optionally, the geothermal is configured as a U-shaped well, so that the geothermal well comprises an injection section, the heat exchange section and a production section connected in sequence;

[0010] The heat exchange section is arranged in the heat reservoir, and the lower ends of the injection section and the production section are respectively connected to the two ends of the heat exchange section, and the upper ends of the injection section and the production section pass through the overlying stratum and extend to the ground.

[0011] Optionally, the heat extraction structure is provided including: providing injection equipment, ground storage equipment, heat extraction and utilization facilities, ground heat storage equipment and extraction equipment on the ground, and sequentially connecting the injection equipment, the ground storage equipment, the heat extraction and utilization facilities, the ground heat storage equipment and the extraction equipment through ground pipelines;

[0012] The injection equipment and the production equipment are connected to the upper ends of the injection section and the production section respectively.

[0013] Optionally, it further comprises: setting cementing casings on the outer sides of the injection section and the production section respectively;

[0014] Covering the inner wall of the extraction section with a first insulation layer;

[0015] The outer wall of the ground pipeline is covered with a second thermal insulation layer.

[0016] Optionally, extracting heat from the geothermal well through a heat extraction structure includes:

[0017] Injecting the heat exchange medium in the ground storage device into the geothermal well using the injection device;

[0018] The heat exchange medium exchanges heat with the heat reservoir in the geothermal well through a plurality of the explosive fracturing cracks;

[0019] The heat exchange medium is produced to the ground through a production well;

[0020] The heat exchange medium is transported in sequence to the ground heat storage device, the heat utilization facility and the ground storage device through the ground pipeline.

[0021] The present invention also provides a deep heat storage enhanced heat extraction system, based on the above-mentioned deep heat storage enhanced heat extraction method, characterized in that it includes:

[0022] A geothermal well, wherein a heat exchange section of the geothermal well is formed with a plurality of explosive fracturing cracks;

[0023] The heat extraction structure is connected to the geothermal well and is used to extract heat from the geothermal well.

[0024] Optionally, the geothermal is a U-shaped well, which includes an injection section, a heat exchange section and a production section connected in sequence; the heat exchange section is arranged in a heat reservoir, the lower ends of the injection section and the production section are respectively connected to the two ends of the heat exchange section, and the upper ends of the injection section and the production section pass through the overlying strata and extend to the ground.

[0025] Optionally, the heat extraction structure comprises: a ground pipeline, an injection device, a ground storage device, a heat extraction and utilization facility, a ground heat storage device and an extraction device arranged on the ground, wherein the injection device, the ground storage device, the heat extraction and utilization facility, the ground heat storage device and the extraction device are sequentially connected via a ground pipeline;

[0026] The injection equipment and the production equipment are connected to the upper ends of the injection section and the production section respectively.

[0027] Optionally, cementing casings are respectively provided on the outsides of the injection section and the production section; the inner wall of the production section is covered with a first insulation layer; and the outer wall of the ground pipeline is covered with a second insulation layer.

[0028] Optionally, through the connection of the ground pipeline, the U-shaped well, the injection equipment, the ground storage equipment, the heat utilization facility, the ground heat storage equipment and the production equipment form a U-shaped well closed heat extraction structure.

[0029] The present invention provides a deep heat storage enhanced heat extraction method and system, which has the beneficial effect that: the deep heat storage enhanced heat extraction method uses the explosive fracturing technology to form a plurality of explosive fracturing cracks in the heat exchange section of the geothermal well. The explosive fracturing technology relies on the high energy and high pressure generated by the rapid explosion of high-energy propellants in the wellbore of the geothermal well, which can not only easily break through the high fracture pressure of the reservoir, but also form a plurality of randomly oriented explosive fracturing cracks, thereby increasing the probability of connecting the natural fracture system. It can well solve the shortcomings of the prior art based on the application of conventional fracturing technology in the heat extraction system, and achieve the effects of engineering controllability, protection of the formation, cost reduction, and improvement of deep heat storage production capacity.

[0030] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0032] Figure 1 A flow chart of a deep thermal storage enhanced heat extraction method according to an embodiment of the present invention is shown.

[0033] Figure 2 A schematic diagram of a deep heat storage enhanced heat extraction system according to an embodiment of the present invention is shown.

[0034] Description of reference numerals:

[0035] 1. Explosive fracturing cracks; 2. Injection section; 3. Heat exchange section; 4. Production section; 5. Injection equipment; 6. Ground storage equipment; 7. Heat utilization facilities; 8. Ground heat storage equipment; 9. Production equipment; 10. Ground pipelines; 11. Heat exchange medium; 12. Cementing casing; 13. First insulation layer; 14. Second insulation layer; 15. Overlying strata; 16. Heat reservoir. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0037] like Figure 1 As shown, the present invention provides a deep heat storage enhanced heat extraction method, comprising:

[0038] Setting up geothermal wells;

[0039] A plurality of explosion fracturing cracks 1 are formed in a heat exchange section 3 of a geothermal well by using an explosion fracturing technology;

[0040] A heat extraction structure is provided, and heat is extracted from the geothermal well through the heat extraction structure.

[0041] Specifically, in order to solve the problems in the prior art of using conventional downhole fracturing methods, such as liquid injection high-pressure fracturing technology, to increase the heat exchange area of ​​geothermal wells in deep heat storage, the existing crack shape is controlled by ground stress, the fracturing cost is high, the construction is complicated, the action time is short, and it is very easy to damage the formation; the deep heat storage enhanced heat extraction method provided by the present invention uses explosive fracturing technology to form a plurality of explosive fracturing cracks 1 in the heat exchange section 3 of the geothermal well. The explosive fracturing technology relies on the high energy and high pressure generated by the rapid explosion of high-energy propellants in the wellbore of the geothermal well, which can easily break through the high fracture pressure of the reservoir and form a plurality of randomly oriented explosive fracturing cracks 1, thereby increasing the probability of connecting the natural fracture system. It can well solve the shortcomings of the prior art based on the application of conventional fracturing technology in the heat extraction system, and achieve the effects of engineering controllability, formation protection, cost reduction, and improvement of deep heat storage capacity.

[0042] Optionally, the geothermal is set as a U-shaped well, so that the geothermal well includes an injection section 2, a heat exchange section 3 and a production section 4 connected in sequence;

[0043] The heat exchange section 3 is arranged in the heat reservoir 16, and the lower ends of the injection section 2 and the production section 4 are respectively connected to the two ends of the heat exchange section 3, and the upper ends of the injection section 2 and the production section 4 pass through the overlying stratum 15 and extend to the ground.

[0044] Specifically, the injection section 2 and the production section 4 are both vertical wells, and the heat exchange section 3 is a horizontal well arranged in the heat reservoir 16. In this embodiment, the heat reservoir 16 is a deep heat reservoir and a heat source. The overlying stratum 15 ensures that the heat of the deep heat reservoir will not be lost to the atmosphere through the stratum.

[0045] In this embodiment, explosive fracturing is used to form explosive fracturing cracks 1, which increases the heat exchange area between the deep heat reservoir and the U-shaped well, thereby enhancing the heat extraction efficiency of the heat exchange medium 11 in the U-shaped well; the cracks produced by explosive fracturing are not controlled by ground stress, and multiple randomly oriented cracks can be formed in the deep heat reservoir, increasing the probability of connecting the natural fracture system and enhancing the heat exchange efficiency.

[0046] Optionally, the explosive fracturing technology includes gunpowder loading and detonation, and the gunpowder loading and detonation mainly include the following steps:

[0047] 1. Select appropriate perforating bullets according to actual fracturing requirements;

[0048] 2. Load the perforating bullet into the explosive fracturing gun and install it in the working pipe string;

[0049] 3. Run the operating pipe string into the heat exchange section of the geothermal well and perform perforation according to the design requirements;

[0050] 4. Connect the detonation monitoring equipment;

[0051] 5. It can be made to explode by pressurizing the pipe or controlling it with cables;

[0052] 6. After fracturing is completed, observe the oil pressure and casing pressure. If there is no abnormality, remove the operating pipe string.

[0053] Specifically, the steps of gunpowder loading and detonation in the explosive fracturing technology include selecting appropriate perforating bullets, loading the perforating bullets into the explosive fracturing gun and fixing them in the working pipe string, cleaning and inspecting the working pipe string and perforating casing, inserting the working pipe string into the heat exchange section in the geothermal well according to the design requirements and accurately positioning the position and angle of the perforating gun, connecting the detonation monitoring equipment and selecting appropriate detonators and cables, performing the explosive operation and monitoring the explosive effect through in-pipe pressurization or cable control, evaluating the fracturing effect and proposing a plan for inspecting and maintaining the wellbore before the working pipe string. The above steps need to be carried out strictly in accordance with the operating procedures and operating processes to ensure the safety and reliability of the explosive fracturing operation.

[0054] Optionally, setting up the heat extraction structure includes: setting up an injection device 5, a ground storage device 6, a heat extraction and utilization facility 7, a ground heat storage device 8 and an extraction device 9 on the ground, and connecting the injection device 5, the ground storage device 6, the heat extraction and utilization facility 7, the ground heat storage device 8 and the extraction device 9 in sequence through a ground pipeline;

[0055] The injection device 5 and the production device 9 are connected to the upper ends of the injection section 2 and the production section 4 respectively.

[0056] Specifically, through the connection of the ground pipeline 10, the U-shaped well, the injection equipment 5, the ground storage equipment 6, the heat utilization facility 7, the ground heat storage equipment 8 and the production equipment 9 form a U-shaped well closed heat extraction structure; the heat exchange medium 11 will not directly contact the deep heat storage, reducing the problems of groundwater level drop, ground subsidence, and tail water recharge blocking the formation.

[0057] Optionally, it further includes: setting cementing casings 12 on the outsides of the injection section 2 and the production section 4 respectively;

[0058] The inner wall of the extraction section 4 is covered with a first heat insulating layer 13;

[0059] The outer wall of the ground pipeline is covered with a second insulation layer 14 .

[0060] Specifically, the inner wall of the production section 4 of the U-shaped well is covered with insulating material to prevent the heat exchange medium 11 from losing heat when passing through the overlying formation 15 during production; the outer wall of the ground pipeline is covered with insulating material to prevent the heat exchange medium 11 from losing heat during ground transportation.

[0061] Optionally, extracting heat from a geothermal well through a heat extraction structure includes:

[0062] The heat exchange medium 11 in the ground storage device 6 is injected into the geothermal well by using the injection device 5;

[0063] The heat exchange medium 11 exchanges heat with the heat reservoir 16 in the geothermal well through a plurality of explosive fracturing cracks 1;

[0064] Using a production well to produce the heat exchange medium 11 to the ground;

[0065] The heat exchange medium 11 is transported to the ground heat storage device 8, the heat utilization facility 7 and the ground storage device 6 in sequence through the ground pipeline.

[0066] Specifically, the above-mentioned heat extraction method forms a ground heat extraction cycle, and the heat exchange medium 11 can be recycled to achieve the effect of cost saving.

[0067] The present invention also provides a deep heat storage enhanced heat extraction system, based on the above-mentioned deep heat storage enhanced heat extraction method, characterized in that it includes:

[0068] A geothermal well, wherein a heat exchange section 3 of the geothermal well is formed with a plurality of explosive fracturing cracks 1;

[0069] The heat extraction structure is connected to the geothermal well and is used to extract heat from the geothermal well.

[0070] Specifically, multiple explosive fracturing cracks 1 are formed in the heat exchange section 3 of the geothermal well by the explosive fracturing technology. The explosive fracturing technology relies on the high energy and high pressure generated by the rapid explosion of high-energy propellants in the wellbore of the geothermal well. It can not only easily break through the high fracture pressure of the reservoir, but also form multiple randomly oriented explosive fracturing cracks 1, increasing the probability of connecting the natural fracture system. It can well solve the shortcomings of the existing technology based on the application of conventional fracturing technology in the heat extraction system, and achieve the effect of engineering controllability, protection of formations, cost reduction, and improvement of deep heat storage capacity.

[0071] Optionally, the geothermal is a U-shaped well, which includes an injection section 2, a heat exchange section 3 and a production section 4 connected in sequence; the heat exchange section 3 is arranged in the heat reservoir 16, the lower ends of the injection section 2 and the production section 4 are respectively connected to the two ends of the heat exchange section 3, and the upper ends of the injection section 2 and the production section 4 pass through the overlying stratum 15 and extend to the ground.

[0072] Specifically, the injection section 2 and the production section 4 are both vertical wells, and the heat exchange section 3 is a horizontal well arranged in the heat reservoir 16. In this embodiment, the heat reservoir 16 is a deep heat reservoir and a heat source. The overlying stratum 15 ensures that the heat of the deep heat reservoir will not be lost to the atmosphere through the stratum.

[0073] Optionally, the heat extraction structure includes: a ground pipeline, an injection device 5, a ground storage device 6, a heat extraction and utilization facility 7, a ground heat storage device 8 and an extraction device 9 arranged on the ground, and the injection device 5, the ground storage device 6, the heat extraction and utilization facility 7, the ground heat storage device 8 and the extraction device 9 are sequentially connected through the ground pipeline;

[0074] The injection device 5 and the production device 9 are connected to the upper ends of the injection section 2 and the production section 4 respectively.

[0075] In this embodiment, explosive fracturing is used to form explosive fracturing cracks 1, which increases the heat exchange area between the deep heat reservoir and the U-shaped well, thereby enhancing the heat extraction efficiency of the heat exchange medium 11 in the U-shaped well; the cracks produced by explosive fracturing are not controlled by ground stress, and multiple randomly oriented cracks can be formed in the deep heat reservoir, increasing the probability of connecting the natural fracture system and enhancing the heat exchange efficiency.

[0076] Optionally, cementing casings 12 are respectively provided on the outside of the injection section 2 and the production section 4 ; the inner wall of the production section 4 is covered with a first insulation layer 13 ; and the outer wall of the ground pipeline is covered with a second insulation layer 14 .

[0077] Specifically, the inner wall of the production section 4 of the U-shaped well is covered with insulating material to prevent the heat exchange medium 11 from losing heat when passing through the overlying formation 15 during production; the outer wall of the ground pipeline is covered with insulating material to prevent the heat exchange medium 11 from losing heat during ground transportation.

[0078] Optionally, through the connection of the ground pipeline 10, the U-shaped well, the injection equipment 5, the ground storage equipment 6, the heat utilization facility 7, the ground heat storage equipment 8 and the production equipment 9 form a U-shaped well closed heat extraction structure.

[0079] Specifically, in the U-well closed heat extraction structure, the heat exchange medium 11 will not come into direct contact with the deep heat storage, thereby reducing problems such as groundwater level drop, ground subsidence, and tailwater recharge clogging of the formation.

[0080] In summary, in this embodiment, when the deep heat storage enhanced heat extraction system provided by the present invention is used, based on the above-mentioned deep heat storage enhanced heat extraction method, the specific steps are as follows:

[0081] The first step is to construct a U-shaped well. The injection section 2 and the production section 4 both penetrate the overlying stratum 15 of the deep heat reservoir. The heat exchange section 3 is located in the deep heat reservoir. The positions of the injection section 2 and the production section 4 of the U-shaped well can be selected according to the heat flow direction of the deep heat reservoir.

[0082] The second step is to use the explosive fracturing technology to generate a plurality of irregularly shaped explosive fracturing cracks 1 around the heat exchange section 3 located in the deep heat reservoir. The explosive fracturing cracks 1 are all located around the heat exchange section 3 to enhance the heat exchange effect between the heat exchange medium 11 in the U-shaped well and the deep heat reservoir.

[0083] Step 3: After fracturing, complete the construction of the subsequent heat extraction structure and establish a deep heat storage enhanced heat extraction system; use the injection equipment 5 to inject the heat exchange medium 11 in the ground storage equipment 6 into the U-shaped well for heat extraction; the heat exchange medium 11 is transported to the heat exchange section 3 located in the deep heat storage through the injection section 2 for heat extraction; the heat exchange medium 11 exchanges heat with the deep heat storage through the explosive fracturing crack 1 in the heat exchange section 3; the ground production equipment 9 will produce the heat exchange medium 11 after heat extraction through the production section 4 to the ground; the inner wall of the production section 4 is covered with insulation material to prevent the heat exchange medium 11 from passing through the overlying stratum 15 during production and causing heat loss; after the heat exchange medium 11 is produced from the ground, it is transported to the ground heat storage equipment 8 for centralized storage through the ground pipeline, and then transported to the heat utilization facility 7 through the ground pipeline for heat exchange utilization. After the heat is utilized, the cooled heat exchange medium 11 can be injected into the ground storage equipment 6 through the ground pipeline, and can be used for heat extraction again.

[0084] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A deep heat storage enhanced heat extraction method, characterized in that: include: Setting up geothermal wells; Using explosive fracturing technology to form multiple explosive fracturing cracks in the heat exchange section of the geothermal well; A heat extraction structure is provided, and heat is extracted from the geothermal well through the heat extraction structure.

2. The deep heat storage enhanced heat extraction method according to claim 1, characterized in that: The geothermal well is set as a U-shaped well, so that the geothermal well includes an injection section, a heat exchange section and a production section connected in sequence; The heat exchange section is arranged in the heat reservoir, and the lower ends of the injection section and the production section are respectively connected to the two ends of the heat exchange section, and the upper ends of the injection section and the production section pass through the overlying stratum and extend to the ground.

3. The deep heat storage enhanced heat extraction method according to claim 2, characterized in that: The heat extraction structure is provided by: providing injection equipment, ground storage equipment, heat extraction and utilization facilities, ground heat storage equipment and extraction equipment on the ground, and connecting the injection equipment, the ground storage equipment, the heat extraction and utilization facilities, the ground heat storage equipment and the extraction equipment in sequence through ground pipelines; The injection equipment and the production equipment are connected to the upper ends of the injection section and the production section respectively.

4. The deep heat storage enhanced heat extraction method according to claim 3 is characterized in that: Also includes: Cementing casings are respectively arranged on the outer sides of the injection section and the production section; Covering the inner wall of the extraction section with a first insulation layer; The outer wall of the ground pipeline is covered with a second thermal insulation layer.

5. The deep heat storage enhanced heat extraction method according to claim 3 is characterized in that: The step of extracting heat from the geothermal well by means of a heat extraction structure comprises: Injecting the heat exchange medium in the ground storage device into the geothermal well using the injection device; The heat exchange medium exchanges heat with the heat reservoir in the geothermal well through a plurality of the explosive fracturing cracks; The heat exchange medium is produced to the ground through a production well; The heat exchange medium is transported in sequence to the ground heat storage device, the heat utilization facility and the ground storage device through the ground pipeline.

6. A deep heat storage enhanced heat extraction system, based on the deep heat storage enhanced heat extraction method according to any one of claims 1 to 5, characterized in that: include: A geothermal well, wherein a heat exchange section of the geothermal well is formed with a plurality of explosive fracturing cracks; The heat extraction structure is connected to the geothermal well and is used to extract heat from the geothermal well.

7. The deep heat storage enhanced heat extraction system according to claim 6 is characterized in that: The geothermal is a U-shaped well, which includes an injection section, a heat exchange section and a production section which are connected in sequence; the heat exchange section is arranged in a heat reservoir, the lower ends of the injection section and the production section are respectively connected to the two ends of the heat exchange section, and the upper ends of the injection section and the production section pass through the overlying stratum and extend to the ground.

8. The deep heat storage enhanced heat extraction system according to claim 7, characterized in that: The heat extraction structure comprises: a ground pipeline, an injection device, a ground storage device, a heat extraction and utilization facility, a ground heat storage device and an extraction device arranged on the ground, wherein the injection device, the ground storage device, the heat extraction and utilization facility, the ground heat storage device and the extraction device are sequentially connected via a ground pipeline; The injection equipment and the production equipment are connected to the upper ends of the injection section and the production section respectively.

9. The deep heat storage enhanced heat extraction system according to claim 8, characterized in that: The outsides of the injection section and the production section are respectively provided with cementing casings; the inner wall of the production section is covered with a first insulation layer; and the outer wall of the ground pipeline is covered with a second insulation layer.

10. The deep heat storage enhanced heat extraction system according to claim 8, characterized in that: Through the connection of the ground pipeline, the U-shaped well, the injection equipment, the ground storage equipment, the heat utilization facility, the ground heat storage equipment and the production equipment form a U-shaped well closed heat extraction structure.

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