Salt crystallization inhibition system for gas injection and brine discharge tubular column of salt cavern gas storage

Abstract

The invention relates to a salt-cavern gas storage gas injection brine discharge pipe column salt crystallization inhibition system, and relates to the technical field of oil and gas exploitation, the salt-cavern gas storage gas injection brine discharge pipe column salt crystallization inhibition system comprises a pipe column system, a temperature sensor module and a heating device, the pipe column system comprises a brine discharge inner pipe, and the bottom of the brine discharge inner pipe extends to a brine layer at the bottom of a salt cavern cavity to form a brine discharge channel; the heating device is installed on the outer side of the brine discharging inner pipe and used for heating brine in the brine discharging inner pipe, and the temperature sensor module is embedded into the inner wall of the brine discharging inner pipe and used for monitoring temperature data of the brine in the brine discharging inner pipe in real time. According to the scheme, the heating device is matched with the brine discharging inner pipe, and the system can directly and continuously provide heat for brine in the brine discharging inner pipe, so that the temperature of the brine is increased, the solubility of salt is remarkably improved, and salt precipitation caused by temperature reduction in the brine rising process is fundamentally inhibited.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, and in particular to a salt crystallization inhibition system for a salt cavern gas storage injection and brine discharge pipeline. Background Technology

[0002] Salt cavern gas storage facilities have become core facilities for strategic natural gas reserves due to their excellent sealing and safety stability. A key process in their construction is "gas injection and brine drainage," which involves injecting high-pressure natural gas or other gases (hydrogen) to replace the saturated brine in the salt cavern with brine through drainage pipes to the ground, thereby creating a pure gas storage space.

[0003] However, during the brine drainage process in deep salt cavern gas storage facilities (often buried at depths greater than 2000 meters), "crystallization blockage" has become a prominent problem restricting construction efficiency and safety. These salt caverns are characterized by high bottom-hole temperatures (>80℃), high brine concentrations (>300g / L), and complex compositions. As saturated brine rises along the tubing string, its temperature rapidly drops from the high bottom-hole temperature to ambient surface temperature (a temperature difference of over 30℃) due to the formation temperature gradient, causing the brine to enter a supersaturated state and resulting in the precipitation of large amounts of salt crystals. These crystals continuously adhere to the tubing wall, growing rapidly, especially in low-flow-rate sections and rough areas of the tubing wall, ultimately reducing the flow area of ​​the tubing string or even causing complete blockage. This forces operational interruptions, requiring costly unblocking operations and severely delaying the construction schedule.

[0004] Currently, the industry lacks effective technologies and dedicated tubing systems that fundamentally address this problem at its mechanistic level. Conventional chemical scale inhibitors have limited effectiveness in high-temperature and high-salt environments and present cost and environmental issues; mechanical scraping and other unblocking methods are passive remedies and cannot achieve continuous operation. Therefore, there is an urgent need for an innovative tubing system that can proactively intervene at the structural design level to inhibit crystal precipitation and adhesion. Summary of the Invention

[0005] The purpose of this invention is to provide a salt crystallization inhibition system for the brine injection and discharge tubing of a salt cavern gas storage facility, which can prevent crystals from forming during the brine discharge process and thus blocking the flow of the tubing.

[0006] To achieve the above objectives, this application provides a salt crystallization inhibition system for a salt cavern gas injection and brine removal tubing string, used for gas injection and brine removal operations in a bottom-hole salt cavern cavity, comprising:

[0007] The tubular system includes a brine discharge inner tube, the bottom of which extends to the brine layer at the bottom of the salt cavern cavity, forming a brine discharge channel.

[0008] A heating device is installed on the outside of the brine draining inner tube to heat the brine inside the draining inner tube;

[0009] A temperature sensor module is embedded in the inner wall of the brine draining tube to monitor the brine temperature data in the brine draining tube in real time.

[0010] The heating device is electrically connected to the temperature sensor module to control the heating operation of the heating device based on the brine temperature data, so as to inhibit salt crystallization and blockage.

[0011] Preferably, the tubular system further includes:

[0012] The outer tube and the brine discharge inner tube are located inside the outer tube and are used to introduce displacement gas into the salt cavern cavity;

[0013] The production casing has its lower end connected to the salt cavern cavity, and both the outer tube and the brine discharge inner tube are located inside the production casing.

[0014] Preferably, it also includes a packer, which is disposed on the tubing system to stabilize the pressure of the tubing system.

[0015] Preferably, the heating device includes:

[0016] An annular magnetohydrodynamic cavity is fixed to the outer wall of the brine discharge inner tube;

[0017] The magnetic fluid heating medium, filled inside the annular magnetic fluid cavity, can generate heat under the action of an alternating magnetic field;

[0018] An excitation coil, wound around the outer wall of a toroidal magnetohydrodynamic cavity, is used to generate an alternating magnetic field when energized.

[0019] Preferably, annular heat-conducting fins are provided between the magnetic fluid cavity and the outer wall of the brine discharge inner pipe to enhance the efficiency of heat transfer from the magnetic fluid cavity to the brine in the brine discharge inner pipe.

[0020] Preferably, the magnetic fluid heating medium is a mixed suspension of iron oxide nanoparticles and high flash point heat transfer oil.

[0021] Preferably, the excitation coil includes an inner copper wire and an outer sheath made of polyimide material.

[0022] Preferably, the anti-crystallization temperature threshold set by the temperature sensor module is not lower than 90% of the initial stable temperature at the bottom of the well.

[0023] Preferably, it also includes a downhole circuit, in which the temperature sensor module and the excitation coil are connected to form a closed-loop control system.

[0024] Preferably, the production casing is cemented with cementing cement to isolate fluids from different formations.

[0025] Compared to the aforementioned background technologies, this solution, by adapting the heating device to the brine discharge inner pipe, allows the system to directly and continuously provide heat to the brine within the pipe, thereby increasing the brine temperature and significantly improving salt solubility. This fundamentally suppresses salt precipitation caused by temperature drops during brine ascent. Simultaneously, a temperature sensor module is cleverly positioned on the outer wall of the discharge inner pipe, enabling real-time and accurate monitoring of the tubing temperature. This provides crucial data for the intelligent control of the heating device, ensuring heating precision and efficiency. Compared to existing wellhead heating and mechanical descaling solutions, this invention integrates the heating function within the tubing system, achieving close-range, active temperature control of the salt crystallization area. This not only effectively avoids the risk of blockage in the discharge inner pipe but also reduces maintenance costs and safety hazards caused by crystallization blockage, significantly improving the overall operational efficiency and reliability of the salt cavern gas storage facility. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a steam injection brine column for preventing crystallization blockage in an embodiment of this application;

[0028] Figure 2 This is a schematic diagram of the heating device for a steam injection and brine discharge column to prevent crystallization blockage in an embodiment of this application;

[0029] Figure 3 The graph shows the relationship between the solubility of sodium chloride and temperature at different temperatures.

[0030] Figure 4 This is a graph showing the relationship between the amount and depth of sodium chloride precipitation with and without a heating device.

[0031] The components are: 1. Brine drain inner pipe; 2. Outer pipe; 3. Production sleeve; 4. Salt cavern cavity; 5. Heating device; 6. Packer; 7. Heating device cavity; 8. Temperature sensor module; 9. Magnetic fluid heating medium; 10. Excitation coil; 11. Annular heat-conducting fins. Detailed Implementation

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] It should be noted that the directional terms such as "upper end," "lower end," "left side," and "right side" mentioned below are defined based on the accompanying drawings in the instruction manual.

[0035] Please see Figures 1 to 3 A salt crystallization suppression system for a salt cavern gas storage injection and brine discharge tubing string is disclosed. This system is used for injection and brine discharge operations within a bottom salt cavern cavity 4. The system includes a tubing string system, a heating device 5, and a temperature sensor module 8. The tubing string system includes a brine discharge inner tube 1, the bottom of which extends to the brine layer at the bottom of the salt cavern cavity 4, forming a brine discharge channel. The heating device 5 is installed on the outside of the brine discharge inner tube 1 to heat the brine inside. The temperature sensor module 8 is embedded in the inner wall of the brine discharge inner tube 1 to monitor the brine temperature data in real time. The heating device 5 is electrically connected to the temperature sensor module 8, and the module controls the heating operation of the heating device 5 based on the brine temperature data to suppress salt crystallization blockage.

[0036] This solution effectively suppresses salt crystallization by actively controlling the temperature inside the brine discharge tubing. The system includes a tubing system, a heating device 5, and a temperature sensor module 8. The tubing system comprises an inner brine discharge pipe 1, which serves as the brine discharge channel and extends directly to the brine layer in the bottom salt cavern 4, ensuring smooth brine discharge. To fundamentally address the salt crystallization problem, the heating device 5 is installed on the outside of the inner brine discharge pipe 1, continuously and effectively heating the brine flowing inside. Furthermore, the temperature sensor module 8 is precisely embedded in the inner wall of the inner brine discharge pipe 1, enabling real-time and direct monitoring of the actual temperature data of the brine inside the pipe.

[0037] Through the electrical connection between the heating device 5 and the temperature sensor module 8, the system can achieve intelligent closed-loop control: the brine temperature data collected in real time by the temperature sensor module 8 is transmitted to the heating device 5 as a control signal, thereby precisely adjusting the heating intensity and duration of the heating device to ensure that the brine temperature is maintained within a safe range sufficient to inhibit salt crystallization, thus effectively preventing the blockage of the brine discharge column and ensuring the continuity and efficiency of the gas injection and brine discharge operation.

[0038] The core crystallization suppression method of the brine crystallization suppression system in the brine injection and discharge pipe column of the salt cavern gas storage is to achieve real-time, precise, and dynamic temperature control of the brine in the discharge pipe 1 through magnetic fluid heating technology. Specifically, the system uses a temperature sensor module 8 embedded in the inner wall of the discharge pipe 1 to continuously monitor the brine temperature. When the monitored temperature is lower than the preset anti-crystallization temperature threshold (not lower than 90% of the initial stable temperature at the bottom of the well), the excitation coil 10 generates an alternating magnetic field after being energized. This magnetic field acts on the magnetic fluid heating medium 9 (composed of a mixture of iron oxide nanoparticles and high flash point heat transfer oil suspension) filled in the annular magnetic fluid cavity 7. The magnetic fluid medium generates heat efficiently under the action of the alternating magnetic field. This heat is rapidly and uniformly transferred to the brine in the discharge pipe 1 through efficient heat transfer structures such as the annular heat-conducting fins 11, raising its temperature. When the brine temperature reaches or exceeds the threshold, the system correspondingly reduces or stops heating. This process connects the temperature sensor module 8 to the excitation coil 10 via the downhole circuit, forming an intelligent closed-loop control system. This ensures that the brine temperature is always maintained within a safe range sufficient to suppress salt supersaturation precipitation, fundamentally eliminating the risk of salt crystallization clogging the brine discharge string from a physical perspective, and ensuring the continuity and efficiency of the gas injection and brine discharge operation.

[0039] In some embodiments, the tubing system further includes an outer tube 2 and a production sleeve 3. An inner brine discharge tube 1 is disposed inside the outer tube 2 and is used to introduce displacement gas into the brine cavity 4;

[0040] The lower end of the production casing 3 is connected to the salt cavern 4, and both the outer pipe 2 and the brine discharge inner pipe 1 are located inside the production casing 3. The production casing 3 is cemented with cementing cement to isolate fluids from different formations.

[0041] To further improve the tubing system, in addition to the core brine discharge inner tubing 1, it also includes an outer tubing 2 and a production casing 3, forming a multi-layered concentric tubing structure to optimize the integrity and functionality of downhole operations. The production casing 3, as the outermost layer, connects to the salt cavern cavity 4 at its lower end and is cemented according to industry standards using cementing cement to reliably isolate different formation fluids, thereby ensuring the structural integrity of the wellbore, preventing fluid cross-contamination, and ensuring environmental safety. Both the outer tubing 2 and the brine discharge inner tubing 1 are located inside the production casing 3, forming a nested layered layout.

[0042] Specifically, refer to the appendix Figure 1The inner drain pipe 1 is located inside the outer pipe 2. Displacement gas (e.g., natural gas) is injected into the salt cavern cavity 4 through the annulus between the outer pipe 2 and the inner drain pipe 1 or other channels to displace and drain the brine. The inner drain pipe 1 serves to drain the brine and inhibit salt crystallization. This multi-layered tubular design not only supports the complex requirements of gas injection and brine drainage operations but also provides a stable structural foundation for the integration of heating devices and sensor modules, ensuring the safe, stable, and efficient operation of the salt cavern gas storage facility.

[0043] The crystallization suppression system also includes a packer 6, which is disposed on the tubing system to stabilize the pressure in the tubing system. In some preferred embodiments, the packer 6 is further included to improve the stability and safety of the crystallization suppression system. The packer 6 is disposed on the entire tubing system and its function is to achieve effective isolation of different annulus or tubing regions.

[0044] By forming a reliable seal, packer 6 can control and stabilize the pressure environment inside the tubing system. This stable pressure not only ensures the smooth injection of displacement gas and the discharge of brine, preventing fluid backflow, tubing damage, or operational interruptions that may occur due to pressure fluctuations, but more importantly, it helps maintain the uniformity of the fluid environment monitored and controlled by heating device 5 and temperature sensor module 8, thereby ensuring the effective implementation of salt crystallization inhibition methods. In this way, packer 6 provides crucial support for the stable operation of the entire system, further improving the reliability and efficiency of gas injection and brine discharge operations.

[0045] The heating device 5 includes an annular magnetic fluid cavity 7, a magnetic fluid heating medium 9, and an excitation coil 10. The annular magnetic fluid cavity 7 is fixed to the outer wall of the brine discharge inner pipe 1; the magnetic fluid heating medium 9 is filled inside the annular magnetic fluid cavity 7 and can generate heat under the action of an alternating magnetic field; the excitation coil 10 is wound around the outer wall of the annular magnetic fluid cavity 7 and is used to generate an alternating magnetic field after being energized.

[0046] In some preferred embodiments, the heating device 5 employs a magnetic fluid heating mechanism to effectively heat the brine inside the brine draining inner tube 1. This device mainly includes an annular magnetic fluid cavity 7, a magnetic fluid heating medium 9, and an excitation coil 10. The annular magnetic fluid cavity 7 is cleverly fixed to the outer wall of the brine draining inner tube 1, forming a tightly fitted heating area. The magnetic fluid heating medium 9, filled inside, generates heat under the action of an alternating magnetic field, thus directly heating the brine draining inner tube 1. The excitation coil 10, wound around the outer wall of the cavity, generates the required alternating magnetic field after being energized, driving the magnetic fluid heating medium 9 to heat up. This heat prevents crystallization of the brine inside the brine draining inner tube 1.

[0047] In some embodiments, annular heat-conducting fins 11 are provided between the magnetic fluid cavity 7 and the outer wall of the brine draining inner pipe 1 to enhance the efficiency of heat transfer from the magnetic fluid cavity to the brine in the brine draining inner pipe 1. The magnetic fluid heating medium 9 is a mixed suspension of iron oxide nanoparticles and high flash point heat-conducting oil. To optimize heat transfer efficiency and ensure that heat can be transferred rapidly and efficiently from the magnetic fluid cavity to the brine in the brine draining inner pipe 1, annular heat-conducting fins 11 are specially provided between the magnetic fluid cavity 7 and the outer wall of the brine draining inner pipe 1. These fins increase the heat transfer area and significantly enhance the efficiency of heat conduction. In specific implementations, this high-performance magnetic fluid heating medium 9 is usually formed by a mixed suspension of iron oxide nanoparticles and high flash point heat-conducting oil. The selection of iron oxide nanoparticles ensures the magnetic responsiveness of the medium, while the high flash point heat-conducting oil ensures the stability and safety of the medium under high-temperature operating conditions, further improving the reliability and performance of the entire heating system.

[0048] In some embodiments, the excitation coil 10 includes an inner copper conductor and an outer sheath of polyimide material. The excitation coil 10 takes into account both conductivity and insulation protection. Specifically, it includes an inner copper conductor and an outer sheath of polyimide material. The copper conductor, as the core component, has excellent conductivity and can efficiently carry current to generate the required alternating magnetic field. The polyimide material is a high-performance engineering plastic with excellent high-temperature resistance, corrosion resistance, high insulation strength, and mechanical strength, making it ideal for harsh downhole environments. As the outer sheath, it effectively protects the copper conductor from the effects of downhole high temperatures, high pressures, corrosive fluids, and mechanical wear, ensuring the long-term stable and reliable operation of the excitation coil.

[0049] In some embodiments, the anti-crystallization temperature threshold set by the temperature sensor module 8 is no less than 90% of the initial stable temperature at the bottom of the well. The temperature sensor module 8 plays a crucial role in the crystallization suppression strategy, and its anti-crystallization temperature threshold of no less than 90% of the initial stable temperature at the bottom of the well means that the system does not raise the temperature to an arbitrary high temperature, but rather sets a relatively conservative but effective lower limit based on the actual initial stable temperature at the bottom of the salt cavern. For example, if the initial stable temperature at the bottom of the well is 80°C, then the anti-crystallization temperature threshold is set at least at 72°C. This setting ensures that the brine temperature at the bottom of the well is always maintained within a safe range that effectively inhibits salt crystallization, while avoiding unnecessary overheating, thereby saving energy and extending equipment life.

[0050] In some embodiments, the crystallization suppression system further includes a downhole circuit, and the temperature sensor module 8 and the excitation coil 10 are connected through the downhole circuit to form a closed-loop control system.

[0051] In some embodiments, the crystallization inhibition system further includes a downhole circuit for intelligent and automated temperature control. The temperature sensor module 8 is connected to the excitation coil 10 via the downhole circuit, forming a closed-loop control system. In this closed-loop system, the temperature sensor module 8 monitors the temperature of the brine in the brine discharge pipe 1 in real time. When the monitored temperature is lower than the set anti-crystallization temperature threshold, the temperature sensor module 8 sends a signal to the excitation coil 10 via the downhole circuit, activating or increasing the current in the excitation coil to generate a stronger alternating magnetic field, thereby activating the magnetic fluid heating medium 9 to generate heat and raise the brine temperature. Once the temperature reaches or exceeds the threshold, the system will correspondingly reduce or stop heating, achieving precise temperature regulation, thereby dynamically and effectively inhibiting salt crystallization and ensuring unobstructed flow through the brine discharge pipe.

[0052] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0053] The salt crystallization suppression system for the brine injection and discharge pipeline of the salt cavern gas storage facility provided in this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the solution and core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A salt cavern gas storage gas injection and brine displacement string salt crystallization inhibition system for use in a gas injection and brine displacement operation in a bottom hole salt cavern cavity (4), characterized by, The application relates to a pipe string system for preventing salt crystallization and plugging. The pipe string system comprises a brine discharging inner pipe (1) extending to the brine layer at the bottom of a salt cavern cavity (4) to form a brine discharging channel; a heating device (5) installed outside the brine discharging inner pipe (1) for heating the brine in the brine discharging inner pipe; and a temperature sensor module (8) embedded in the inner wall of the brine discharging inner pipe (1) for monitoring the brine temperature data in the brine discharging inner pipe (1) in real time. The heating device (5) and the temperature sensor module (8) are electrically connected, and the heating work of the heating device (5) is controlled according to the brine temperature data to inhibit salt crystallization and plugging. The pipe string system further comprises an outer pipe (2) in which the brine discharging inner pipe (1) is arranged, and a production casing (3) in which the outer pipe (2) and the brine discharging inner pipe (1) are arranged. A packer (6) is arranged on the pipe string system to stabilize the pressure of the pipe string system.

2. A salt cavern gas storage facility gas injection brine displacement string salt crystallization suppression system as defined in claim 1, wherein, The heating device (5) comprises a ring-shaped magnetic fluid cavity (7) fixed to the outer wall of the brine discharging inner pipe (1), a magnetic fluid heating medium (9) filled in the ring-shaped magnetic fluid cavity (7) and capable of generating heat under the action of an alternating magnetic field, and an excitation coil (10) wound on the outer wall of the ring-shaped magnetic fluid cavity (7) for generating an alternating magnetic field after being electrified. The magnetic fluid cavity (7) and the outer wall of the brine discharging inner pipe (1) are provided with a ring-shaped heat conduction fin (11) for enhancing the heat transfer efficiency from the magnetic fluid cavity to the brine in the brine discharging inner pipe (1). The magnetic fluid heating medium (9) is a mixed suspension of ferroferric oxide nanoparticles and high-flash-point heat-conducting oil.

3. A salt cavern gas storage facility gas injection brine displacement string salt crystallization suppression system as defined in claim 1, wherein, The excitation coil (10) comprises copper wires on the inner side and a polyimide material outer skin.

4. A salt cavern gas storage facility gas injection brine removal pipe string salt crystallization suppression system as defined in claim 1, wherein, The temperature sensor module (8) is provided with a crystallization prevention temperature threshold value of not less than 90% of the initial stable temperature at the bottom of the well. The temperature sensor module (8) and the excitation coil (10) are connected through a downhole circuit to form a closed-loop control system. The production casing (3) is cemented by well cementing to isolate the fluids of different strata. ​ 5. A salt cavern gas storage facility gas injection brine displacement string salt crystallization suppression system as defined in claim 4, wherein, ​ 6. A salt cavern gas storage facility gas injection brine displacement string salt crystallization suppression system as defined in claim 4, wherein, ​ 7. A salt cavern gas storage facility gas injection brine removal pipe string salt crystallization suppression system as defined in claim 4 wherein, ​ 8. A salt cavern gas storage facility gas injection brine removal pipe string salt crystallization suppression system as defined in claim 1 wherein, ​ 9. A salt cavern gas storage facility gas injection brine displacement string salt crystallization suppression system according to any one of claims 1 to 8, wherein, ​ 10. A salt cavern gas storage facility gas injection brine displacement string salt crystallization suppression system as defined in claim 2, wherein, ​

Images