A deep carbonate geothermal reservoir exploitation system

Abstract

The present invention provides a deep carbonate geothermal reservoir exploitation system, which relates to the technical field of geothermal energy exploitation. By analyzing the physical and mechanical properties of rocks, the present invention utilizes heat flow injection to induce a thermal expansion effect to generate fractures; uses hydrochloric acid-citric acid solution to dissolve and increase the fracture width and surface area, and optimizes the solution concentration and injection rate; collects reservoir thermal conductivity and temperature data, and adjusts the injection-production well spacing and flow rate in real time to achieve thermal-fluid dynamic balance; installs thermal insulation layer materials on the inner wall of the wellbore, optimizes the thermal conductivity and thickness of the thermal insulation layer by monitoring the wellbore heat loss data, and finally generates a heat loss control rate to evaluate the thermal insulation performance, so as to achieve the efficient and sustainable exploitation of deep carbonate geothermal resources.

Description

Technical Field

[0001] The present invention relates to the technical field of geothermal energy extraction, and specifically to a deep carbonate rock geothermal reservoir extraction system. Background Art

[0002] As a clean and sustainable renewable energy source, geothermal energy has broad prospects for development and utilization. However, there are certain technical problems in the extraction of deep carbonate rock geothermal reservoirs, including complex physical and mechanical properties of reservoir rocks, difficulty in the formation and expansion of fracture channels, low thermal efficiency of the injection-production system, and serious heat loss in the wellbore. Traditional geothermal reservoir extraction technologies usually cannot fully consider the thermal expansion characteristics and rock dissolution characteristics of the reservoir, resulting in low efficiency of fracture generation and expansion. At the same time, due to the large heat loss in the wellbore during the deep well geothermal extraction process, the thermal energy utilization rate in the transmission link decreases, affecting the overall extraction efficiency. Under high temperature and high in-situ stress, it is difficult to effectively induce the formation of complex fracture networks, resulting in low reservoir stimulation efficiency. Moreover, existing geothermal extraction methods focus on heat extraction efficiency and neglect the control of wellbore heat loss, resulting in serious heat loss during long-term operation. During long-term injection-production processes, it is difficult to control the dynamic evolution laws of multiple fields of heat, fluid, solid, and chemistry, resulting in low resource utilization efficiency. Therefore, how to effectively improve reservoir fracture development, enhance the thermal-fluid dynamic balance of the injection-production system, and reduce wellbore heat loss has become a key technical problem in the development of deep carbonate rock geothermal resources.

[0003] In the prior art, the publication number CN118228926A discloses a high-efficiency intelligent extraction and reinjection system for medium-deep geothermal wells. By real-time monitoring data, the geothermal water production capacity evaluation index, geothermal water extraction effect evaluation index, and geothermal water exchange and utilization efficiency index are calculated. Based on the comprehensive management coefficient of geothermal water, the extraction and reinjection warning coefficient of the geothermal well is analyzed and compared with the preset value to comprehensively evaluate the extraction and reinjection effects of geothermal water from multiple dimensions, so as to more accurately reflect the actual situation of geothermal well extraction and reinjection.

[0004] The main problems existing in the above solution are as follows: The high-efficiency intelligent extraction and reinjection system for medium-deep geothermal wells focuses more on macroscopic real-time monitoring and data analysis, mainly used for evaluating the extraction and reinjection effects of geothermal water, and is applicable to the overall management of medium-deep geothermal wells. However, it lacks in-depth analysis and optimization means for the characteristics of the reservoir itself, especially the physical and mechanical properties of rocks, fracture generation and expansion and other microscopic processes; the formation of the fracture network is the key to affecting the thermal energy extraction efficiency, and the above solution does not involve specific optimization methods for fracture generation and expansion; it mainly focuses on evaluating and managing the extraction efficiency, but does not clearly propose specific measures to solve the problem of wellbore heat loss; the regulation means based on real-time data are relatively macroscopic, lacking the refined control ability of injection-production flow rate and dynamic pressure drop from the perspective of injection-production balance.

[0005] The above information disclosed in the background art section is only used to enhance the understanding of the background of the present disclosure, and thus it may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0006] The object of the present invention is to provide a deep carbonate geothermal reservoir exploitation system to solve the problems raised in the above background art.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A deep carbonate geothermal reservoir exploitation system, the specific steps include:

[0009] A rock analysis module, used to obtain deep carbonate reservoir rocks before exploitation and analyze the physical and mechanical properties of the reservoir rocks, where the physical and mechanical properties include the elastic modulus, Poisson's ratio and coefficient of thermal expansion of the rocks;

[0010] A fracture generation module, used to first inject high-temperature heat flow into the reservoir to cause a thermal expansion effect, generate thermal stress to form initial fractures in the reservoir, and then calculate the injection intensity of the high-temperature heat flow;

[0011] A fracture propagation module, used to inject a hydrochloric acid-citric acid composite solution into the initial fractures to dissolve the carbonate fracture walls, increase the fracture width and surface area, and obtain the fracture propagation volume and fracture propagation radius in real time, and adjust the solution concentration and solution injection rate according to the change of the fracture propagation volume;

[0012] An injection-production balance module, used to measure the initial temperature of the reservoir and the outlet temperature of the production well, generate the optimal spacing of the injection and production wells, determine the location of the injection well, and calculate the injection-production pressure drop, inject cold water into the deep carbonate geothermal reservoir through the injection well, and adjust the injection flow rate in real time to make the injection-production pressure drop within the standard pressure drop range;

[0013] A heat loss calculation module, used to install a multi-layer composite thermal insulation material on the inner wall of the production wellbore to form a heat insulation layer, obtain the thermal conductivity of the thermal insulation material, measure the length of the production wellbore and the temperature difference between the fluid temperature in the production wellbore and the surrounding formation rocks during exploitation, generate the theoretical wellbore heat loss, and collect the outlet fluid temperature and inlet fluid temperature of the production wellbore to generate the actual heat loss;

[0014] A heat loss optimization module, used to generate a heat loss control rate based on the theoretical wellbore heat loss and the actual heat loss, and judge whether it is necessary to optimize the thermal conductivity and thickness of the thermal insulation material according to the size of the heat loss control rate. Further, the magnitude of the thermal stress that forms the initial fractures in the reservoir is:

[0015]

[0016] Wherein, σre denotes the thermal stress, α denotes the coefficient of thermal expansion of the reservoir rock, E denotes the elastic modulus of the reservoir rock, and T inj denotes the injection temperature of the high-temperature heat flow, and T rock denotes the temperature of the reservoir rock, and ε denotes the Poisson's ratio of the reservoir rock;

[0017] The high-temperature heat flow is water vapor with a temperature higher than the temperature of the reservoir rock;

[0018] The formula for calculating the injection intensity of the high-temperature heat flow is:

[0019]

[0020] where e denotes the injection intensity of the high-temperature heat flow, k1 denotes the thermal conductivity of the reservoir rock, and △r denotes the penetration radius of the high-temperature heat flow, that is, the farthest distance that the injected heat flow can affect in the reservoir.

[0021] Furthermore, the principle for adjusting the solution concentration and the solution injection rate is:

[0022] Through microseismic monitoring technology, the change curve of the fracture volume and the fracture propagation radius R frac (t) at each moment are obtained in real time to generate the fracture volume V frac (t) at each moment. The fracture propagation radius R frac (t) at each moment and the target fracture propagation radius R tar (t) at each moment are compared, and the fracture propagation volume V frac (t) at each moment and the target fracture propagation volume V tar (t) at each moment are compared to adjust the injection parameters of the solution. The principle is:

[0023] When V frac (t) > V tar (t), the fracture propagation volume increases too fast, so the solution concentration is reduced and the solution injection rate is decreased;

[0024] When V frac (t) < V tar (t), the fracture propagation volume increases too slowly, so the solution concentration is increased and the solution injection rate is increased;

[0025] When R frac (t) < R tar (t), the fracture propagation range is insufficient and the solution coverage range is insufficient, so the solution injection rate is increased.

[0026] Furthermore, the formula for generating the spacing between injection and production wells is:

[0027]

[0028] Among them, L well represents the optimal spacing of injection-production wells, k1 represents the thermal conductivity of reservoir rocks, △T represents the difference between the initial temperature of the reservoir and the outlet temperature of the production well, and Q0 represents the reference injection flow rate.

[0029] Furthermore, the calculation formula for the injection-production pressure drop is:

[0030]

[0031] Among them, △P represents the injection-production pressure drop, Q inj represents the real-time injection flow rate, that is, the volume of cold water injected into the deep carbonate geothermal reservoir through the injection well per unit time, μ represents the fluid viscosity of cold water, h represents the height of reservoir fractures, and w represents the width of reservoir fractures.

[0032] Furthermore, the formula based on which the theoretical wellbore heat loss is generated is:

[0033]

[0034] Among them, E loss represents the theoretical wellbore heat loss, x represents the thermal conductivity of the insulation layer, H represents the length of the production wellbore, T fluid represents the fluid temperature in the production wellbore, T wall represents the rock temperature of the production wellbore wall, r out represents the outer radius of the insulation layer, r in represents the inner radius of the insulation layer;

[0035] The formula based on which the actual heat loss is generated is:

[0036]

[0037] Among them, E act represents the actual heat loss, represents the fluid mass flow rate of cold water, c represents the specific heat capacity of the fluid, T in represents the fluid temperature at the inlet of the production wellbore, T out represents the fluid temperature at the outlet of the production wellbore.

[0038] Furthermore, the principle based on which the heat loss control rate is generated is:

[0039]

[0040] Among them, X represents the heat loss control rate;

[0041] When X < 0, select a material with a higher thermal conductivity as the insulation layer, and reduce the outer radius of the insulation layer or increase the inner radius of the insulation layer.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] By injecting high-temperature heat flow, the present invention triggers the thermal expansion effect of the rocks in the deep carbonate geothermal reservoir, generates thermal stress to form initial fractures, avoids the strong disturbance of the formation by high-pressure mechanical equipment, reduces the operation difficulty and equipment cost, and at the same time reduces the destructive impact on the reservoir. By adjusting the injection heat flow intensity, the formation position and scale of the fractures can be accurately controlled, the directional controllability of the fracture network in the reservoir can be improved, and the reservoir development efficiency can be enhanced; the generation and subsequent expansion steps of the initial fractures directly determine the permeability and heat storage capacity of the reservoir, and an efficient fracture network is constructed, providing a good flow channel for the subsequent injection-production balance of geothermal fluid.

[0044] The present invention also collects the thermal conductivity and temperature data of the reservoir, and combines with the real-time monitoring of the injection and production flow rates to dynamically adjust the pressure of the injection pump, realizing the thermal-fluid dynamic balance of the injection and production wells, effectively avoiding the problems of excessive reservoir cooling or excessive pressure loss; in the existing geothermal exploitation technologies, the injection-production flow rates and pressures are usually fixed values, and it is difficult to adjust them in real time according to the dynamic changes of the reservoir conditions. The patent solution calculates the injection-production parameters through the dynamic balance formula and flexibly adjusts the pressure of the injection pump by combining the real-time monitoring data, making the injection-production process more adaptable and precise; by measuring multiple parameters of the wellbore and realizing dynamic optimization, the heat loss can be more accurately controlled, and the heat loss control rate is generated to judge whether it is necessary to adjust the type and thickness of the thermal insulation material, which can adapt to the changes of different geological conditions and wellbore depths, ensuring the efficient operation of the deep carbonate geothermal exploitation system in different environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the system module of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0047] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "comprising" or "including" mean that the elements or objects appearing before this term cover the elements or objects listed after this term and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left" and "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0048] Embodiment:

[0049] Please refer to Figure 1 , the present invention provides a technical solution:

[0050] A deep carbonate geothermal storage and exploitation system, the specific steps include:

[0051] A rock analysis module, configured to obtain deep carbonate reservoir rocks before exploitation and analyze the physical and mechanical properties of the reservoir rocks, where the physical and mechanical properties include the elastic modulus, Poisson's ratio and coefficient of thermal expansion of the rocks;

[0052] In this embodiment, the principle of obtaining deep carbonate reservoir rocks is:

[0053] Drill through a core bit to obtain a complete reservoir rock sample from the geothermal reservoir, measure the compressive strength and elastic modulus of the reservoir rock sample through a uniaxial compression test; simulate the in-situ stress conditions in the deep reservoir through a triaxial compression test to measure the Poisson's ratio of the reservoir rock sample; determine the coefficient of thermal expansion of the reservoir rock sample through a dilatometer;

[0054] The elastic modulus and Poisson's ratio of the rock determine the degree of deformation of the rock under stress, and are used to predict the scale and shape of fractures in the reservoir under external stimulation; the main mechanism of heat flow-induced fractures is the thermal expansion effect, and the coefficient of thermal expansion of the reservoir rock determines the influence of temperature change on the stress distribution of the rock, thereby affecting the fracture generation efficiency.

[0055] A fracture generation module, configured to first inject a high-temperature heat flow into the reservoir to cause a thermal expansion effect, generate thermal stress to form initial fractures in the reservoir, and then calculate the injection intensity of the high-temperature heat flow;

[0056] In this embodiment, the magnitude of the thermal stress for forming initial fractures in the reservoir is

[0057]

[0058] Among them, σ re represents the thermal stress, α represents the coefficient of thermal expansion of the reservoir rock, E represents the elastic modulus of the reservoir rock, and T inj represents the injection temperature of the high-temperature heat flux, and T rock represents the temperature of the reservoir rock, and ε represents the Poisson's ratio of the reservoir rock;

[0059] The formula for calculating the injection intensity of the high-temperature heat flux is as follows:

[0060]

[0061] Among them, e represents the injection intensity of the high-temperature heat flux, k1 represents the thermal conductivity of the reservoir rock, and △r represents the penetration radius of the high-temperature heat flux, that is, the farthest distance that the high-temperature heat flux can affect in the reservoir.

[0062] The high-temperature heat flux mentioned above represents water vapor with a temperature higher than that of the reservoir rock. The purpose of generating the injection intensity of the high-temperature heat flux is to precisely induce the formation and initial expansion of fractures by controlling the thermal stress. The reservoir rock has a certain tensile strength. Only when the tensile stress applied from the outside, which is the thermal stress in this solution, exceeds the tensile strength, will the rock break and form fractures. When the temperature T inj of the injected high-temperature heat flux is higher than the temperature of the reservoir rock, thermal stress is generated, and the higher T inj , the greater the thermal stress, the faster the generation rate of the initial fractures, and the larger the volume of the fractures; the penetration radius △r of the high-temperature heat flux reflects the range of the action of the thermal stress on the reservoir rock, that is, the distance range within which the high-temperature heat flux can be effectively transmitted and produce a thermal expansion effect on the rock. Based on the heat conduction theory, the formula for calculating the penetration radius of the heat flux is as follows:

[0063]

[0064] Among them, △r represents the penetration radius of the high-temperature heat flux, t represents the action time of the high-temperature heat flux, β represents the thermal diffusivity of the reservoir rock, ρ represents the density of the reservoir rock, and c p represents the specific heat capacity of the reservoir rock.

[0065] The fracture expansion module is used to inject a hydrochloric acid-citric acid composite solution into the initial fractures to dissolve the carbonate rock fracture wall, increase the fracture width and surface area, and obtain the fracture expansion volume and fracture expansion radius in real time, and adjust the solution concentration and solution injection rate according to the change of the fracture expansion volume;

[0066] In this embodiment, the crack expansion volume represents the difference between the real-time fracture volume after injecting the composite solution and the initial fracture volume of the reservoir, and the fracture expansion radius represents the difference between the real-time fracture radius after injecting the composite solution and the initial fracture radius of the reservoir; the ultimate goal is to make the actual fracture volume V frac as close as possible to the designed target fracture volume V tar ;

[0067] R dissolve represents the dissolution rate of the solution to the rock, which is mainly related to the concentration of the solution. The higher the solution concentration, the faster the dissolution rate.

[0068] The principle for adjusting the solution concentration and the solution injection rate is as follows:

[0069] Through the microseismic monitoring technology, the change curve of the fracture volume and the fracture expansion radius R frac (t) at each moment are obtained in real time, and the fracture volume V frac (t) at each moment is generated. The fracture expansion radius R frac (t) at each moment is compared with the target fracture expansion radius R tar (t) at each moment, and the fracture expansion volume V frac (t) at each moment is compared with the target fracture expansion volume V tar (t) at each moment, and the injection parameters of the solution are adjusted. The principle is as follows:

[0070] When V frac (t) > V tar (t), the fracture expansion volume increases too fast. Reduce the solution concentration and the solution injection rate;

[0071] When V frac (t) < V tar (t), the fracture expansion volume increases too slowly. Increase the solution concentration and the solution injection rate;

[0072] When R frac (t) < R tar (t), the fracture expansion range is insufficient and the solution coverage range is insufficient. Increase the solution injection rate.

[0073] The injection-production balance module is used to measure the initial temperature of the reservoir and the temperature at the outlet of the production well, generate the optimal spacing between the injection and production wells, determine the location of the injection well, calculate the injection-production pressure drop, inject cold water into the deep carbonate geothermal reservoir through the injection well, and adjust the injection flow rate in real time so that the injection-production pressure drop is within the standard pressure drop range;

[0074] In this embodiment, the formula for generating the spacing between the injection and production wells is as follows:

[0075]

[0076] Among them, L well represents the optimal spacing between injection and production wells, k1 represents the thermal conductivity of the reservoir rock, △T represents the difference between the initial temperature of the reservoir and the outlet temperature of the production well, and Q0 represents the reference injection flow rate.

[0077] The purpose of this embodiment is to determine the spacing between the injection well and the production well based on known parameters such as the outlet temperature of the production well, so that the injection-production well spacing can meet the stable heat exchange process of the reservoir and make full use of the reservoir heat, thereby determining the location of the injection well.

[0078] The purpose of optimizing the injection-production well spacing is to avoid premature heat breakthrough while ensuring the full utilization of geothermal resources, that is, the injected cold water directly penetrates into the production well, resulting in the ineffective extraction of geothermal energy.

[0079] The higher the thermal conductivity of the reservoir rock, the higher the heat transfer efficiency of the geothermal reservoir. When the cold water flows through the reservoir fractures, it can absorb the heat in the rock more quickly, so the distance required to reach the target temperature difference is shorter. That is, when the thermal conductivity is high, the heat propagation range is wide and the speed is fast, and a smaller injection-production well spacing is selected; when the thermal conductivity is low, the heat flow propagation range is small, and the cold water needs a longer path to absorb enough heat, and a larger injection-production well spacing is selected;

[0080] The injection-production well spacing directly affects the residence time of the cold water in the reservoir. The heat absorption of the fluid is proportional to the residence time. When a high temperature difference is required, a larger injection-production well spacing is needed to allow the cold water to absorb heat repeatedly. When a low temperature difference is required, a smaller injection-production well spacing is designed;

[0081] The greater the injection flow rate, the faster the propagation speed of the cold water in the reservoir, indicating that the cold water needs a shorter distance to reach the production well. The greater the injection flow rate, the faster the moving speed of the injected fluid, and a smaller injection-production well spacing is required to maintain a stable heat exchange process; the smaller the injection flow rate, the slower the moving speed of the injected fluid, and a larger injection-production well spacing is required to make full use of the reservoir heat.

[0082] The calculation formula for the injection-production pressure drop is:

[0083]

[0084] Among them, △P represents the injection-production pressure drop, Q inj represents the real-time injection flow rate, that is, the volume of cold water injected into the deep carbonate rock geothermal reservoir through the injection well per unit time, μ represents the fluid viscosity of the cold water, h represents the height of the reservoir fracture, and w represents the width of the reservoir fracture.

[0085] The dynamic balance formula reflects the pressure loss when the injected fluid flows in the reservoir. Excessive pressure drop may cause damage to the reservoir fractures, while too small pressure drop may lead to insufficient fluid flow and low heat transfer efficiency. According to the calculation results of the pressure drop, the injection flow rate Q of the injection-production system is dynamically adjusted inj , ensuring the balance of the pressure gradient and heat flow distribution in the reservoir, avoiding thermal breakthrough or fluid waste. When the injection-production pressure drop is too large, the injection flow rate is reduced; when the injection-production pressure drop is too small, the injection flow rate is increased.

[0086] The standard pressure drop range represents a reasonable range of the pressure difference between the injection well and the production well, taking into account both formation stability and fluid circulation efficiency. Usually, the specific value is 5 to 15 MPa.

[0087] The heat loss calculation module is used to install a multi-layer composite insulation material on the inner wall of the production wellbore to form a heat insulation layer, obtain the thermal conductivity of the insulation material, measure the length of the production wellbore and the temperature difference between the fluid temperature in the production wellbore and the surrounding formation rock, generate the theoretical wellbore heat loss, and collect the fluid temperature at the outlet of the production wellbore and the fluid temperature at the inlet of the production wellbore to generate the actual heat loss;

[0088] In this embodiment, the formula for generating the theoretical wellbore heat loss is:

[0089]

[0090] Among them, E loss represents the theoretical wellbore heat loss, x represents the thermal conductivity of the heat insulation layer, H represents the length of the production wellbore, T fluid represents the fluid temperature in the production wellbore, T wall represents the rock temperature of the production wellbore wall, r out represents the outer radius of the heat insulation layer, r in represents the inner radius of the heat insulation layer;

[0091] The formula for generating the actual heat loss is:

[0092]

[0093] Among them, E act represents the actual heat loss, represents the fluid mass flow rate of cold water, c represents the specific heat capacity of the fluid, T in represents the fluid temperature at the inlet of the production wellbore, T out represents the fluid temperature at the outlet of the production wellbore.

[0094] The theoretical wellbore heat loss reflects the theoretical heat loss of the produced fluid in the insulation layer of the production wellbore under the designed insulation structure, that is, only considering the heat conduction loss in the production wellbore and ignoring the external influence. The actual heat loss represents the actual loss of temperature between the inlet and outlet of the production wellbore, that is, the heat loss of the produced fluid during the process of flowing in and out in the production wellbore.

[0095] The heat loss optimization module is used to generate a heat loss control rate based on the theoretical wellbore heat loss formula and the actual heat loss, and determine whether it is necessary to optimize the thermal conductivity coefficient and thickness of the insulation material according to the magnitude of the heat loss control rate.

[0096] In this embodiment, the principle for generating the heat loss control rate is as follows:

[0097]

[0098] Among them, X represents the heat loss control rate.

[0099] The heat loss control rate reflects the difference between the actual heat loss and the theoretical heat loss. The closer the value is to 1, the closer the insulation is to the ideal state, and the more effective the heat loss control is. If X < 0, it means that the actual heat loss is higher than the theoretical heat loss, and it is necessary to re-optimize, select a material with a higher thermal conductivity coefficient as the insulation layer, and reduce the outer radius of the insulation layer or increase the inner radius of the insulation layer.

[0100] The above formulas are all dimensionless and take their numerical values for calculation. The formula is a formula obtained by collecting a large amount of data for software simulation to get the closest to the real situation. The preset parameters in the formula are set by those skilled in the art according to the actual situation.

[0101] The above embodiments can be implemented in whole or in part by software, hardware, firmware, or any other combination. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. Those skilled in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed by hardware or software methods depends on the specific application and design constraints of the technical solution.

[0102] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units. They can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0103] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application.

Claims

1. A deep carbonate geothermal reservoir exploitation system, characterized in that, Specifically include: A rock analysis module, which is used to obtain deep carbonate reservoir rocks before mining and analyze the physical and mechanical properties of the reservoir rocks. The physical and mechanical properties include the elastic modulus, Poisson's ratio, and thermal expansion coefficient of the rocks; A fracture generation module, which is used to first inject high-temperature heat flow into the reservoir to cause a thermal expansion effect, generate thermal stress to form initial fractures in the reservoir, and then calculate the injection intensity of the high-temperature heat flow; A fracture propagation module, which is used to inject a hydrochloric acid-citric acid composite solution into the initial fractures to dissolve the carbonate fracture walls, increase the fracture width and surface area, and obtain the fracture propagation volume and fracture propagation radius in real time. Adjust the solution concentration and solution injection rate according to the change of the fracture propagation volume; An injection-production balance module, which is used to measure the initial temperature of the reservoir and the outlet temperature of the production well, generate the optimal spacing of the injection-production wells, determine the location of the injection well, and calculate the injection-production pressure drop. Inject cold water into the deep carbonate geothermal reservoir through the injection well and adjust the injection flow rate in real time to make the injection-production pressure drop within the standard pressure drop range; A heat loss calculation module, which is used to install a multi-layer composite thermal insulation material on the inner wall of the production wellbore to form a thermal insulation layer, obtain the thermal conductivity of the thermal insulation material, measure the length of the production wellbore and the temperature difference between the fluid mined in the production wellbore and the surrounding formation rocks, generate the theoretical wellbore heat loss, and collect the outlet fluid temperature and inlet fluid temperature of the production wellbore to generate the actual heat loss; A heat loss optimization module, which is used to generate a heat loss control rate based on the theoretical wellbore heat loss and the actual heat loss, and judge whether it is necessary to optimize the thermal conductivity and thickness of the thermal insulation material according to the size of the heat loss control rate.

2. The deep carbonate geothermal reservoir exploitation system according to claim 1, wherein: The magnitude of the thermal stress that forms the initial fractures in the reservoir in the fracture generation module is: Among them, σ re represents the thermal stress, α represents the coefficient of thermal expansion of the reservoir rock, E represents the elastic modulus of the reservoir rock, T inj represents the injection temperature of the high-temperature heat flux, T rock represents the reservoir rock temperature, and ε represents the Poisson's ratio of the reservoir rock; The high-temperature heat flow is water vapor with a temperature higher than the temperature of the reservoir rocks; The formula based on which the injection intensity of the high-temperature heat flow is calculated is: where, e represents the injection intensity of the high-temperature heat flow, k1 represents the thermal conductivity of the reservoir rocks, and △r represents the penetration radius of the high-temperature heat flow, that is, the farthest distance that the injected heat flow can affect in the reservoir.

3. The deep carbonate geothermal reservoir exploitation system according to claim 1, wherein: The principle based on which the solution concentration and solution injection rate are adjusted is: By using microseismic monitoring technology, the change curve of the fracture volume and the fracture propagation radius R frac (t) at each moment are obtained in real time, and the fracture volume V frac (t) at each moment is generated. The fracture propagation radius R frac (t) at each moment and the target fracture propagation radius R tar (t) are compared, and the fracture propagation volume V frac (t) at each moment and the target fracture propagation volume V tar (t) are compared to adjust the injection parameters of the solution. The principle is as follows: When V frac (t) > V tar (t), the growth rate of the crack expansion volume is too fast, so reduce the solution concentration and the solution injection rate; When V frac (t) < V tar (t), the growth of the crack expansion volume is too slow. Increase the solution concentration and accelerate the solution injection rate; When R frac (t) < R tar (t), the crack propagation range is insufficient and the solution coverage range is insufficient, so the solution injection rate is increased.

4. A deep carbonate geothermal reservoir exploitation system according to claim 1, characterized in that: The formula based on which the spacing of the injection-production wells is generated in the injection-production balance module is: Among them, L well represents the optimal spacing of injection-production wells, k1 represents the thermal conductivity of reservoir rocks, △T represents the difference between the initial temperature of the reservoir and the outlet temperature of the production well, and Q0 represents the reference injection flow rate.

5. The deep carbonate geothermal reservoir exploitation system according to claim 4, characterized in that: The calculation formula for the injection-production pressure drop in the injection-production balance module is: Among them, △P represents the injection-production pressure drop, and Q inj represents the real-time injection flow rate, that is, the volume of cold water injected into the deep carbonate geothermal reservoir through the injection well per unit time. μ represents the fluid viscosity of the cold water, h represents the height of the reservoir fracture, and w represents the width of the reservoir fracture.

6. The deep carbonate geothermal reservoir exploitation system according to claim 1, wherein: The formula based on which the theoretical wellbore heat loss is generated in the heat loss calculation module is: Among them, E loss represents the theoretical wellbore heat loss, x represents the thermal conductivity of the insulation layer, H represents the length of the production wellbore, T fluid represents the fluid temperature in the production wellbore, T wall represents the rock temperature of the production wellbore wall, r out represents the outer radius of the insulation layer, r in represents the inner radius of the insulation layer; The formula based on which the actual heat loss is generated is: Among them, E act represents the actual heat loss, represents the fluid mass flow rate of the cold water, c represents the specific heat capacity of the fluid, T in represents the fluid temperature at the inlet of the production wellbore, T out represents the fluid temperature at the outlet of the production wellbore.

7. A deep carbonate geothermal reservoir exploitation system according to claim 6, characterized in that: The principle based on which the heat loss control rate is generated in the heat loss optimization module is: where, X represents the heat loss control rate; When X < 0, select a material with a higher thermal conductivity as the thermal insulation layer, and reduce the outer radius of the thermal insulation layer or increase the inner radius of the thermal insulation layer.

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