Method for constructing artificial reservoir by acid solution dissolution in carbonate reservoir

Abstract

The application discloses a method for constructing an artificial reservoir by acid solution dissolution in a carbonate rock reservoir, and comprises the following steps: finding out the spatial range and top and bottom plate conditions of the carbonate rock reservoir through a drilling coring technology, and obtaining the lithological properties of the reservoir to evaluate the connectivity, stability and controllability of the dissolution; performing drilling, casing and cementing operations on the carbonate rock reservoir which passes the detection, and injecting a prepared acid solution system into the reservoir, realizing directional dissolution through the chemical reaction between the acid solution and the carbonate rock, controlling the shape and capacity of the main cavity of the reservoir, and forming a self-sealing layer in the far-well zone; detecting the reservoir through a water injection or gas pressure test, and supplementally injecting the acid solution or grouting to strengthen the sealing according to the detection result, so that the effective volume and long-term sealing property of the reservoir are ensured; and through the arrangement of various sensors in the process of constructing and operating the reservoir, real-time monitoring of the operation parameters of the reservoir is realized, and the safety and controllability of the reservoir are further improved.

Description

Technical Field

[0001] This invention belongs to the field of underground reservoir construction technology, and specifically relates to a method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs. Background Technology

[0002] With my country's energy structure transformation and its continued high dependence on foreign energy, the construction of safe, low-cost, and large-capacity underground storage facilities has become a key infrastructure for ensuring strategic oil and gas reserves, new energy storage (compressed air storage, hydrogen storage), and the large-scale development of geothermal energy storage. Traditional underground storage construction mainly relies on conventional technologies such as salt cavern cavitation, artificial cavern construction in dense rock masses, or the conversion of abandoned mines. However, the construction height of salt cavern storage facilities is limited by the distribution range of thick salt rock geological conditions, resulting in extremely limited spatial layout and difficulty in covering a wide area. Furthermore, the water-soluble cavity construction process involves complex dissolution reactions and long-term water erosion, leading to lengthy construction cycles, high resource consumption, and high economic costs, making it unsuitable for rapidly changing energy storage demands. The construction of dense rock mass storage facilities requires highly disruptive methods such as blasting or high-pressure hydraulic fracturing. These methods face challenges such as complex construction environments and significant operational risks. More importantly, it is difficult to precisely control the geometry and internal structure of the storage facility, resulting in unpredictable storage capacity and insufficient stability, severely restricting the safety and efficiency of subsequent storage operations. Although abandoned mines have a certain spatial foundation, the rock structure has been damaged and fissures have developed due to long-term mining activities, resulting in a significant decrease in their inherent sealing performance. Under the action of storage media, they are prone to leakage or structural instability, and cannot meet the strict requirements of modern energy storage for long-term sealing and structural integrity.

[0003] Carbonate rocks, a widely distributed geological resource in my country, possess natural advantages such as suitable burial depth and excellent rock strength, theoretically providing an ideal platform for the construction of underground reservoirs. However, in current technological practices, the application of carbonate rock reservoirs is mainly focused on production enhancement measures during oil and gas extraction, and their potential in constructing multifunctional integrated artificial reservoirs has not been fully explored.

[0004] Therefore, how to provide a method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs, through the dissolution reaction of acid with the mineral components in carbonate rocks to achieve directional acid dissolution and form a reservoir structure of "large internal cavity + outer sealing layer", is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a method for constructing artificial reservoirs in carbonate rock reservoirs by acid dissolution. This method utilizes acid to dissolve the mineral components in the carbonate rock reservoir, achieving directional cavity creation and self-sealing. Furthermore, it offers low construction costs, multiple uses, and applicability to various storage scenarios.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for constructing an artificial reservoir by acid dissolution in a carbonate rock reservoir. The method includes the following steps: determining the spatial extent and top and bottom conditions of the target carbonate rock reservoir using core drilling technology; testing the burial depth, porosity, permeability, rock mass strength, and acid dissolution characteristics of the target carbonate rock reservoir to evaluate its connectivity, stability, and controllable dissolution; performing drilling, casing, and cementing operations at the target carbonate rock reservoir, and deploying temperature sensors, pressure sensors, and flow sensors along the wellbore; and constructing an acid preparation tank and injection / production pump station on the surface. The production pump station is connected to the acid preparation tank. The acid system in the preparation tank is directionally injected into the carbonate reservoir through the production pump station to form the main cavity of the reservoir in the near-wellbore zone and a self-sealing layer in the far-wellbore zone. The effective volume and sealing performance of the reservoir are tested through water injection or gas pressure tests. If the effective volume or sealing performance is unqualified, additional acid system is injected or grouting is used to strengthen the seal. Storage medium is injected into the qualified reservoir, and the injection pressure of the storage medium does not exceed the formation pressure. After the storage medium injection is completed, the reservoir is sealed, and the operating parameters inside the reservoir are continuously monitored to ensure long-term safe operation of the reservoir.

[0007] In the first aspect, the target carbonate reservoir has a burial depth of 800-3500m, a formation pressure ≥8MPa, a formation temperature of 60-250℃, and no large fault zones or fracture zones.

[0008] In the first aspect, the target carbonate reservoir is limestone or dolomite with a porosity ≥5%.

[0009] In the first aspect, the casing is made of acid-resistant, high-strength, and fatigue-resistant alloy material, and cementing operations are performed using acid-resistant, high-sealing cement slurry.

[0010] In the first aspect, the acid system includes the addition of a corrosion inhibitor to hydrochloric acid, organic acid, terrine acid, or slow-reacting acid.

[0011] In the first aspect, the permeability of the self-sealing layer of the storage tank is ≤0.001 times the permeability of the main cavity of the storage tank.

[0012] In the first aspect, during the injection of the acid system, the shape, capacity, and sealing line position of the main cavity of the reservoir are controlled by adjusting the acid concentration, injection rate, and injection volume.

[0013] In the first aspect, the storage medium is crude oil, natural gas, compressed air, hydrogen, or geothermal working fluid.

[0014] In the first aspect, the operating parameters within the storage facility include storage pressure, temperature, permeability, or changes in the level of the sealing fluid.

[0015] In the first aspect, when the fluctuation of the sealing fluid level exceeds the set threshold, a leakage alarm is triggered, and operation is stopped in time to check the cause and carry out maintenance.

[0016] Beneficial effects: This invention provides a method for constructing an artificial reservoir in a carbonate rock reservoir using acid dissolution. First, core drilling is used to determine the spatial extent and top and bottom conditions of the target carbonate rock reservoir to obtain macroscopic geological information. Next, the depth, porosity, permeability, rock mass strength, and acid dissolution characteristics of the target carbonate rock reservoir are tested to evaluate its connectivity, stability, and controllability of dissolution, thus obtaining the reservoir's microscopic and engineering characteristics. Based on this, drilling, casing, and cementing operations are performed at the target carbonate rock reservoir, and temperature, pressure, and flow sensors are deployed along the wellbore to initially construct the reservoir. Simultaneously, an acid preparation tank and an injection-production pump station are constructed on the surface, with the injection-production pump station connected to the acid preparation tank. The acid preparation tank stores or mixes the acid, and the injection-production pump station facilitates its transport. Thus, the acid system in the acid preparation tank is directionally injected into the carbonate rock reservoir through the injection-production pump station. The system reacts with carbonate rocks, forming a large dissolution space in the near-wellbore zone, i.e., the main cavity of the reservoir. In the far-wellbore zone, due to the decrease in acid concentration or the deposition of reaction products, a region with low permeability is formed, i.e., the reservoir's self-sealing layer. The effective volume and sealing performance of the reservoir are tested through water injection tests or gas pressure tests. When the effective volume or sealing performance is unqualified, additional acid system is injected or grouting is performed to strengthen the seal, thereby blocking potential leakage channels and enhancing the reservoir's sealing performance. Subsequently, storage medium is injected into the qualified reservoir, ensuring that the injection pressure of the storage medium is always lower than the formation pressure to avoid damaging the reservoir structure and improve the stability of the reservoir structure. Finally, after the storage medium injection is completed, the reservoir is sealed, and the internal operating data of the reservoir is continuously acquired in real time through temperature sensors, in-hole sensors, and flow sensors in the wellbore. This data signal can be transmitted to the surface control center for real-time analysis and anomaly warning.

[0017] This invention achieves directional dissolution through the chemical reaction of acid with carbonate rocks, which can control the shape and volume of the reservoir's main cavity and form a self-sealing structure in the far-well zone. Simultaneously, the reservoir is tested through water injection or gas pressure tests, and supplementary acid injection or grouting is performed based on the test results to strengthen the seal, ensuring the effective volume and long-term sealing of the reservoir. Furthermore, by deploying multiple sensors during the construction and operation of the reservoir, real-time monitoring of operating parameters is achieved, further enhancing the safety and controllability of the reservoir.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a method for constructing an artificial reservoir by acid dissolution in a carbonate rock reservoir according to the present invention. Detailed Implementation

[0021] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0022] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or by existing methods.

[0024] The overall inventive concept of this invention is as follows: In the construction of traditional carbonate reservoirs, the lack of a directional control mechanism for acid dissolution reactions hinders the precise construction of the reservoir structure. Specifically, the dissolution reaction between carbonate minerals and acid is affected by the heterogeneity of the rock mass, resulting in a random diffusion pattern of dissolution paths. This leads to biased reservoir connectivity assessments, insufficient structural stability, and uncontrollable dissolution processes. Furthermore, irregular cavities easily form near the wellbore, while continuous sealing layers are difficult to generate further away. This reduces the effective volume utilization rate of the reservoir, and the sealing reliability fails to meet the safety requirements for long-term storage of the medium.

[0025] Based on this, the present invention controls the degree of reaction between acid and carbonate rock, enabling the acid to directionally dissolve and expand pores and form stable cavities in the near-well section, and achieve self-sealing through mineral precipitation in the far-well section, thereby completing the construction of a reservoir structure of "large internal cavity + external self-sealing", and improving the comprehensive utilization efficiency of carbonate rock reservoirs.

[0026] Please see Figure 1 This invention provides a method for constructing an artificial reservoir by acid dissolution in a carbonate rock reservoir. The method includes the following steps: determining the spatial extent and top and bottom conditions of the target carbonate rock reservoir using core drilling technology; testing the burial depth, porosity, permeability, rock mass strength, and acid dissolution characteristics of the target carbonate rock reservoir to evaluate its connectivity, stability, and controllable dissolution; performing drilling, casing, and cementing operations at the target carbonate rock reservoir, and deploying temperature, pressure, and flow sensors along the wellbore; and constructing an acid preparation tank and an injection-production pumping station on the surface, wherein the injection-production pumping station is connected to the... The acid preparation tank is connected; the acid system in the acid preparation tank is directionally injected into the carbonate reservoir through the injection-production pump station to form the main cavity of the reservoir in the near-wellbore zone and the self-sealing layer of the reservoir in the far-wellbore zone; the effective volume and sealing performance of the reservoir are tested through water injection tests or gas pressure tests. If the effective volume or sealing performance is unqualified, additional acid system is injected or grouting is performed to strengthen the seal; the storage medium is injected into the qualified reservoir, and the injection pressure of the storage medium does not exceed the formation pressure; after the storage medium is injected, the reservoir is sealed, and the operating parameters inside the reservoir are continuously monitored to ensure the long-term safe operation of the reservoir.

[0027] Specifically, this invention provides a method for constructing an artificial reservoir in a carbonate rock reservoir using acid dissolution. First, core drilling is used to determine the spatial extent and top and bottom conditions of the target carbonate rock reservoir to obtain macroscopic geological information. Next, the depth, porosity, permeability, rock mass strength, and acid dissolution characteristics of the target carbonate rock reservoir are tested to evaluate its connectivity, stability, and controllability of dissolution, thus obtaining the reservoir's microscopic and engineering characteristics. Based on this, drilling, casing, and cementing operations are performed at the target carbonate rock reservoir, and temperature, pressure, and flow sensors are deployed along the wellbore to initially construct the reservoir. Simultaneously, an acid preparation tank and an injection-production pump station are constructed on the surface, with the injection-production pump station connected to the acid preparation tank. The acid preparation tank stores or mixes the acid, and the injection-production pump station facilitates its transport. Thus, the acid system in the acid preparation tank is directionally injected into the carbonate rock reservoir through the injection-production pump station. The acid system reacts with carbonate rocks, forming a large dissolution space in the near-wellbore zone, i.e., the main cavity of the reservoir. In the far-wellbore zone, due to the decrease in acid concentration or the deposition of reaction products, a region with low permeability is formed, i.e., the reservoir's self-sealing layer. The effective volume and sealing performance of the reservoir are tested through water injection tests or gas pressure tests. When the effective volume or sealing performance is unqualified, additional acid system is injected or grouting is performed to strengthen the seal, blocking potential leakage channels and enhancing the reservoir's sealing performance. Subsequently, storage medium is injected into the qualified reservoir, ensuring that the injection pressure of the storage medium is always lower than the formation pressure to avoid damaging the reservoir structure and improve the stability of the reservoir structure. Finally, after the storage medium injection is completed, the reservoir is sealed, and the internal operating data of the reservoir is continuously acquired in real time through temperature sensors, in-hole sensors, and flow sensors in the wellbore. This data signal can be transmitted to the surface control center for real-time analysis and anomaly early warning. This invention achieves directional dissolution through the chemical reaction of acid with carbonate rocks, which can control the shape and volume of the reservoir's main cavity and form a self-sealing structure in the far-well zone. Simultaneously, the reservoir is tested through water injection or gas pressure tests, and supplementary acid injection or grouting is performed based on the test results to strengthen the seal, ensuring the effective volume and long-term sealing of the reservoir. Furthermore, by deploying multiple sensors during the construction and operation of the reservoir, real-time monitoring of operating parameters is achieved, further enhancing the safety and controllability of the reservoir.

[0028] In some possible embodiments, the target carbonate reservoir is buried at a depth of 800-3500m, with a formation pressure ≥8MPa, a formation temperature of 60-250℃, and no large fault zones or fracture zones.

[0029] In this application, by selecting carbonate reservoirs that meet specific geological conditions, the effectiveness and controllability of the acid dissolution process, as well as the long-term stability and sealing of the reservoir, are ensured. Specifically, a burial depth between 800-3500m ensures sufficient overlying strata pressure, providing a stable confining pressure environment for the formation of the reservoir's main cavity, preventing the collapse of the reservoir's roof or sidewalls during dissolution or later storage medium injection. Simultaneously, this burial depth range is typically accompanied by higher ground temperature and pressure, which is conducive to the acid reaction. Formation pressure ≥8MPa helps maintain the structural integrity of the reservoir, especially during acid and storage medium injection, effectively resisting external stress and reducing the risk of reservoir deformation or rupture. Formation temperature between 60-250℃ significantly increases the chemical reaction rate between the acid and carbonate rocks, allowing the acid to dissolve the rock more efficiently and thoroughly, thereby forming the desired reservoir cavity of the required shape and capacity within a reasonable timeframe. Simultaneously, the high temperature also facilitates the diffusion and penetration of the acid system, promoting the formation of a self-sealing layer. Furthermore, selecting an area free from large fault zones or fracture zones is crucial to ensuring the sealing and stability of the storage facility. Large fault zones or fracture zones are potential channels for fluid leakage. If the storage facility is located in such areas, acid may spread uncontrollably along these channels, leading to uncontrolled corrosion, failure to form an effective storage cavity and self-sealing layer, and even leakage of the stored medium. Therefore, selecting an area free from such defects ensures the directionality and controllability of acid corrosion, guaranteeing the integrity and long-term sealing performance of the storage facility. These geological conditions collectively provide a solid geological foundation for the successful construction and safe operation of artificial storage facilities, avoiding engineering failures or safety hazards caused by unsuitable geological conditions.

[0030] In some possible embodiments, the target carbonate reservoir is limestone or dolomite with a porosity ≥5%.

[0031] In this application, by specifying the target carbonate reservoir as limestone or dolomite and requiring a porosity of not less than 5%, the selected reservoir is ensured to have good chemical reactivity with acid and sufficient initial storage space. Limestone and dolomite, as the main carbonate rock types, have mineral components (calcium carbonate or calcium-magnesium carbonate) that can react with acid to form pores and fractures, thus efficiently expanding the reservoir's main cavity. Simultaneously, a porosity of not less than 5% ensures a well-developed pore network within the reservoir, allowing the injected acid system to penetrate more uniformly and deeply into the rock matrix, preventing premature depletion of the acid near the wellbore or the formation of irregular dissolution channels.

[0032] In some possible embodiments, the casing is made of acid-resistant, high-strength, fatigue-resistant alloy material, and cementing operations are performed using acid-resistant, high-sealing cement slurry.

[0033] In this application, by employing casing made of acid-resistant, high-strength, and fatigue-resistant alloy materials during drilling, casing installation, and cementing operations at the target carbonate reservoir, the casing effectively resists the chemical corrosion of acidic systems, preventing degradation or perforation of the casing material in acidic environments. The use of acid-resistant, high-sealing cement slurry for cementing operations ensures that the cement sheath not only firmly fixes the casing in the wellbore, forming a stable support structure, but also resists the erosion of the cement stone by the acidic system, preventing cement sheath deterioration and failure. This application, through the combined application of casing and cement slurry, constructs a wellbore system with excellent stability and sealing performance under acidic, high-pressure, and fatigue stress environments, providing a solid guarantee for subsequent acid injection, reservoir formation, and the long-term safe operation of the stored medium.

[0034] In some possible embodiments, the acid system includes the addition of a corrosion inhibitor to hydrochloric acid, organic acid, terrine acid, or slow-reacting acid.

[0035] Specifically, this application adds a corrosion inhibitor to the acid system, enabling the acid to effectively dissolve carbonate rocks during injection, forming the main cavity of the reservoir and a self-sealing layer. The corrosion inhibitor reduces the corrosion rate of the acid on downhole equipment. By adding a corrosion inhibitor to the acid system, not only can the dissolution effect of the acid on carbonate rocks be guaranteed, but the integrity of downhole equipment and wellbore can also be protected, ensuring the safety and controllability of the acid injection process.

[0036] In some possible embodiments, the permeability of the self-sealing layer of the storage tank is ≤0.001 times the permeability of the main cavity of the storage tank.

[0037] In this application, by directionally injecting an acid system into a carbonate reservoir, the acid concentration is high and the acidity is strong near the injection well. This rapidly dissolves minerals in the carbonate rock, such as calcite (CaCO3), dolomite (CaMg(CO3)2), small amounts of clay minerals, and siliceous minerals, releasing Ca2+ after dissolution. 2+ Mg 2+ CO3 2- Si 4+Plasma dissolves the rock skeleton, expanding pores and cavities, increasing permeability, and forming the main cavity of the reservoir. Acid diffuses further, its concentration decreasing and pH increasing until the solution reaches supersaturation, leading to mineral precipitation. The main precipitated minerals include calcite (CaCO3), dolomite (CaMg(CO3)2), kaolinite, illite, and other clay minerals, along with small amounts of quartz and silicate gel. These precipitated minerals fill the pores and fractures far from the well, significantly reducing permeability and forming a dense self-sealing layer, ultimately constituting a stable structure of "near-well large cavity reservoir + surrounding dense sealing layer." In a specific embodiment, the permeability of the reservoir's self-sealing layer is ≤0.001 times the permeability of the main reservoir cavity, enabling it to form an extremely dense barrier. When the storage medium is injected into the main reservoir cavity, the extremely low permeability of the self-sealing layer greatly restricts the leakage path, effectively preventing the loss of the storage medium.

[0038] In some possible embodiments, during the acid system injection process, the shape, capacity, and sealing line position of the reservoir body cavity are controlled by adjusting the acid concentration, injection rate, and injection volume.

[0039] In this application, by coordinating the acid concentration, injection rate, and injection volume during the acid injection process, precise control over the morphology, capacity, and sealing line position of the reservoir's main cavity is achieved. Specifically, the acid concentration determines the acid's activity and dissolving power. High-concentration acid rapidly dissolves and forms cavities in the near-wellbore zone, while low-concentration acid is gradually depleted in the far-wellbore zone, which is beneficial for forming a self-sealing layer. The injection rate affects the acid's range of action and reaction time in the reservoir. By adjusting the injection rate, the propagation speed of the acid towards the far-wellbore zone can be controlled, thereby affecting the expansion boundary of the reservoir's main cavity and the formation area of ​​the self-sealing layer. The injection volume directly determines the total amount of carbonate rock dissolved, thus precisely controlling the final capacity of the reservoir's main cavity. In a specific embodiment, a higher concentration and injection rate of acid can be used initially to quickly form the framework of the reservoir's main cavity; subsequently, the acid concentration and injection rate can be reduced to allow the acid to fully react in the far-wellbore zone, forming a dense self-sealing layer and precisely defining the position of the sealing line. Meanwhile, by combining real-time monitoring data from temperature, pressure, and flow sensors, these parameters can be adjusted in a feedback manner to address the impact of formation heterogeneity.

[0040] In some possible embodiments, the storage medium is crude oil, natural gas, compressed air, hydrogen, or geothermal working fluid.

[0041] Specifically, this application combines the constructed artificial reservoir with a specific storage medium, thereby diversifying the reservoir's functions and expanding its application scenarios. In carbonate rock reservoirs, an artificial reservoir with a main cavity and a self-sealing layer is formed through acid dissolution technology. Its structural characteristics and sealing performance have been rigorously tested and can meet the storage requirements of different media.

[0042] In some possible embodiments, the operating parameters within the reservoir include reservoir pressure, temperature, permeability, or changes in the level of the sealing fluid.

[0043] To ensure the long-term stability and safety of storage facilities, continuous monitoring of their operation is essential. This application establishes baseline data on the storage facility's operational status by monitoring key parameters such as pressure, temperature, permeability, and sealant level changes in real time or periodically. Any abnormal fluctuations in parameters—for example, a sustained drop in storage pressure may indicate a leak, an abnormal rise in temperature may foreshadow a chemical reaction, an increase in permeability may indicate self-sealing failure, or a drop in sealant level may reflect leakage—can be detected promptly. This specific parameter monitoring mechanism transforms abstract "operating parameters" into quantifiable indicators, enabling operators to accurately grasp the storage facility's operational status. This allows for early warning and intervention of potential risks, effectively preventing storage facility failures or safety accidents due to inadequate monitoring and significantly improving the operational reliability of the storage facility.

[0044] In some possible embodiments, when the fluctuation of the sealing fluid level exceeds a set threshold, a leakage alarm is triggered, and operation is stopped in time to check the cause and perform maintenance.

[0045] In this application, water, brine, or a specific sealing liquid can be used to seal the storage tank. The operation of the storage tank can be judged by the change in its liquid level. Specifically, a liquid level sensor or pressure sensor can be installed inside the storage tank to obtain the liquid level height. The normal operation of the storage tank can be judged based on the change in the liquid level height. When the change in liquid level height exceeds the set threshold, a leakage alarm is triggered, prompting the construction personnel to immediately stop operation, check the cause of the abnormal liquid level, take corresponding remedial maintenance measures, and then check whether the sealing performance of the storage tank meets the usage requirements.

[0046] Example: Constructing an oil reservoir from a carbonate rock formation (1) Core samples of the target carbonate reservoir were obtained by drilling and coring technology. The spatial range, thickness and top and bottom lithology of the reservoir were determined by combining regional geological data. The connectivity and dissolution controllability of the reservoir were also determined. Then, a carbonate reservoir with a burial depth of 800m, a porosity of 8% and a formation pressure of 8.0MPa was selected as an artificial reservoir to be dissolved. (2) Drilling operations were carried out at this location, and acid-resistant alloy casing was installed, and acid-resistant cement was used for cementing operations to ensure the integrity and sealing of the wellbore; while the casing was being installed, temperature sensors, pressure sensors and flow sensors were installed along the wellbore to monitor the internal environmental parameters of the reservoir in real time. (3) An acid preparation tank is built on the ground for preparing and storing acid, which consists of 10% hydrochloric acid and corrosion inhibitor; at the same time, an injection and production pump station is also built, which is connected to the acid preparation tank through a pipeline so as to inject into the reservoir at a constant rate. (4) The prepared acid solution is injected into the carbonate reservoir through the injection and production pump station to form an effective reservoir cavity near the injection well, and a self-sealing layer is formed due to mineral precipitation far away from the injection well. (5) After continuous injection for 30 days, a sealing test is conducted on the artificial reservoir formed. A certain amount of water is injected into the reservoir, and the pressure change of the reservoir is monitored to detect the effective volume and sealing of the reservoir. If the effective volume does not reach the expected capacity or the sealing of the reservoir is insufficient, acid solution can be injected or grouting can be used to reinforce it until the requirements are met. (6) Inject oil into the qualified storage tank and control the injection pressure to 3.0 MPa. After the injection is completed, inject clean water to seal the well or storage tank. During the operation of the storage tank, continuously monitor the pressure, temperature and well flow rate in the storage tank to obtain the storage tank status in a timely manner and ensure the long-term operation of the storage tank.

[0047] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0048] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0049] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for constructing artificial reservoirs in carbonate rock reservoirs by acid dissolution, characterized in that, The method includes the following steps: The spatial extent and top and bottom conditions of the target carbonate reservoir were determined by core drilling technology. The burial depth, porosity, permeability, rock mass strength and acid solubility characteristics of the target carbonate reservoir were tested to evaluate the connectivity, stability and controllability of dissolution of the carbonate reservoir. Drilling, casing, and cementing operations were carried out at the target carbonate reservoir, and temperature, pressure, and flow sensors were installed along the wellbore. An acid preparation tank and an injection-production pumping station are constructed on the ground, with the injection-production pumping station connected to the acid preparation tank; The acid system in the acid preparation tank is injected directionally into the carbonate reservoir through the injection and production pump station to form the main cavity of the reservoir in the near-wellbore area and the self-sealing layer of the reservoir in the far-wellbore area. The effective volume and sealing performance of the storage tank are tested by water injection test or air pressure test. If the effective volume or sealing performance is not up to standard, acid system is injected or grouting is used to strengthen the sealing. Inject the storage medium into the qualified storage tank, and the injection pressure of the storage medium shall not exceed the formation pressure; After the storage medium is injected, the storage tank is sealed, and the operating parameters inside the storage tank are continuously monitored to ensure the long-term safe operation of the storage tank.

2. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 1, characterized in that, The target carbonate reservoir has a burial depth of 800-3500m, a formation pressure ≥8MPa, a formation temperature of 60-250℃, and no large fault zones or fracture zones.

3. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 1, characterized in that, The target carbonate reservoir is limestone or dolomite with a porosity ≥5%.

4. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 1, characterized in that, The casing is made of acid-resistant, high-strength, and fatigue-resistant alloy material, and cementing operations are carried out using acid-resistant, high-sealing cement slurry.

5. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 1, characterized in that, The acid system includes the addition of corrosion inhibitors to hydrochloric acid, organic acid, terrine acid, or slow-reacting acid.

6. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 1, characterized in that, The permeability of the self-sealing layer of the storage tank is ≤0.001 times the permeability of the main cavity of the storage tank.

7. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 1, characterized in that, During the acid injection process, the shape, capacity, and sealing line position of the main cavity of the storage tank are controlled by adjusting the acid concentration, injection rate, and injection volume.

8. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 1, characterized in that, The storage medium is crude oil, natural gas, compressed air, hydrogen, or geothermal working fluid.

9. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 1, characterized in that, Operating parameters within the storage facility include storage pressure, temperature, permeability, or changes in the level of the sealing fluid.

10. The method for constructing artificial reservoirs by acid dissolution in carbonate rock reservoirs according to claim 9, characterized in that, When the fluctuation of the sealing fluid level exceeds the set threshold, a leakage alarm is triggered. Operation should be stopped immediately, the cause investigated, and maintenance performed.

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