A pressure-dividing ultra-high temperature and ultra-high pressure core holder based on wedge seal

Abstract

A pressure-dividing ultra-high temperature and ultra-high pressure core clamp based on a wedge seal, the main components of which are a cylindrical barrel, a core sleeve, a fixer, an integrated fixer, a fastener, a pressure relief valve, etc. The barrel contains the core sleeve for holding the core, and on the left side of the core sleeve are the fixer, fastener, and end cap, respectively, and on the right end is the integrated fixer. There are pipelines at both ends of the barrel for applying axial pressure to the core and for adding confining pressure to the annular space between the fastener and the fixer. There is also a confining pressure filling pipeline for the annular space between the barrel and the core sleeve on the left end, and a hole on the upper part for pressurizing the annular space between the fasteners. There are four pressure relief valves on the barrel. The key pressure-dividing and pressure-bearing components are sealed with wedge-shaped sealing rings, and the remaining parts are sealed with O-rings to achieve the best sealing effect. The present invention is applicable to ultra-high temperature and ultra-high pressure experimental conditions. The step-by-step pressure division can reduce the pressure difference borne by the rubber ring, allowing it to withstand higher pressures, is not easily damaged, and has a simple structure, making it easy to install and disassemble.

Description

Technical Field

[0001] The invention discloses a wedge-shaped seal-based pressure-dividing ultra-high temperature and ultra-high pressure core holder suitable for indoor high-pressure core experiments. Background Art

[0002] When conducting core displacement experiments or measuring core seepage characteristics in the laboratory, a core clamp is required to protect and seal the core. Failure of the core seal may cause the experiment to fail. Currently, there are three main core sealing methods at home and abroad: mechanical seals, pneumatic seals, and hydraulic seals. Mechanical seals rely on mechanical means to compress the various components, such as using threaded fastening, but this method is only suitable for experiments with low precision requirements; pneumatic seals use air, nitrogen, etc. as sealing media to compress the sealing sleeve, but the various sealing components are prone to uneven force, causing the sealing sleeve to fail; hydraulic seals use liquid as the sealing medium, and pressurize the liquid to compress the sealing sleeve to ensure sealing.

[0003] As development progresses, exploration and development of areas with abnormally high temperatures and pressures are needed. Conventional core holders, due to their structure, material, and sealing sleeves, can experience rubber sleeve damage and seal failure during simulated high-pressure formation experiments, making them incapable of core analysis and displacement experiments under high pressure. Currently available core holders suitable for high pressure, such as patent CN103940720 A, lack sealing rings in their oil inlet lines. Confining pressure is sealed solely by the sealing rings being squeezed, which can easily damage them under excessive pressure. The components bear the entire confining pressure, without step-by-step pressure distribution. The sealing rings are O-rings, which provide poor sealing performance under high pressure. Patent CN 212031248 U improves sealing performance by combining an O-ring with a bushing structure. Patent CN205139137U uses tapered threads, which offer better sealing than conventional threads and, combined with O-ring sealing, facilitate disassembly. However, under high temperatures and pressures, the O-rings can lose their elasticity, causing permanent deformation, or be squeezed into the sealing gap, causing distortion and damage. Therefore, a wedge-shaped seal-based partial pressure ultra-high temperature and ultra-high pressure core holder suitable for high pressure is proposed by using an embedded wedge-shaped seal sleeve. Summary of the Invention

[0004] To address the issues of gas and hydraulic seals losing their elasticity and permanently deforming under high pressure, or being squeezed into the sealing gap and causing distortion and damage, a pressure-dividing ultra-high temperature and ultra-high pressure core holder based on a wedge seal has been designed. The specific technical solution is as follows:

[0005] A pressure-dividing ultra-high temperature and ultra-high pressure core holder based on wedge seal is mainly composed of a barrel, an end cover, an integrated holder, a holder, a fastener, a core sleeve, a pressure relief valve, etc. The core is installed in the core sleeve and placed in a cylindrical barrel. The experimental fluid directly pressurizes the core through the axial pressure filling pipeline. First, fluid is injected into Space 3 of the fastener through the hole in the barrel to increase pressure. When the pressure exceeds the threshold of the pressure relief valve, the fluid (air and pressurized liquid) in Space 3 flows through the pressure relief valve into Space 2 between the fastener and the holder. At this point, the pressurization rate is slowed down, and pressure is simultaneously increased in Space 2 through pipeline 10, so that the pressure in Space 2 exceeds that in Space 3. Similarly, when the pressure in Space 2 exceeds that in annular Space 1 between the barrel and the core sleeve, the pressure is released into Annular Space 1 through the pressure relief valve. The pressurization method for the integrated holder is the same as above, with Space 2 pressurized through pipeline 11. In addition, pressure is simultaneously increased on both sides to ensure that the pressure on both sides of the core is consistent. At this point, the pressure inside the clamp gradually decreases from the inside to the outside. The pressure differential experienced by the sealing ring is reduced by the step-by-step pressurization method and the multiple annular spaces. For example, if the sealing ring can withstand a pressure differential of 70 MPa, and the pressure in Space 3 is 70 MPa, the pressure in Annular Space 1 can be increased to 200 MPa. The sealing ring will not be damaged due to excessive pressure difference. At the same time, this step-by-step pressure increase method can also keep the pressure in a relatively stable state.

[0006] The retainer uses a threaded design for initial fastening, and a wedge-shaped sealing ring enhances the seal. This ring has a trapezoidal cross-section but curved edges. The sealing mechanism of this seal is completely different from that of a typical contact seal. During assembly, a typical contact seal requires a certain amount of pre-compression to create a preload on the sealing surface. A seal is established when the unit pressure per unit area exceeds the liquid pressure. Furthermore, as the liquid pressure increases, the ring is squeezed, further increasing the pressure on the sealing surface, maintaining a reliable seal. This type of seal must be installed in a groove; otherwise, it will not function properly. Compared to a typical seal, the squeeze and groove provide a better seal. Therefore, the retainer has a corresponding wedge-shaped groove for the ring, which ensures a good seal. The ring is made of polytetrafluoroethylene, which is heat-resistant and insoluble in almost all solvents. A pressure relief valve is connected to the retainer, allowing the pressure in chamber three to be released into chamber two through a channel in the retainer.

[0007] The fastener consists of two parts. The right half relies on a sealing ring to ensure a tight seal. It can be rotated or moved up and down to adjust the pipeline position and facilitate pressurization. A semicircular protrusion on the right side squeezes the holder to prevent movement. The left half has four rubber sealing rings to ensure a tight seal. The protrusion on the left end facilitates pipeline installation. The entire core holder is then secured by threads on the end cap. Pipelines pass between the holder and fastener, as well as through the integrated holder, to apply pressure to the core and to the three surrounding spaces. Two rubber sealing rings on the fastener and the pipes in the holder separate the different annular spaces to prevent confining pressure. Even if the core is not properly positioned or the pipeline is damaged, the sealing rings prevent fluid from entering the other spaces.

[0008] The pressure relief valve is mainly composed of a spring, a needle plug, a rubber ring, etc. The channel inside the pressure relief valve is connected to the spring cavity to maintain consistent pressure. There is a wedge-shaped sealing ring on the needle plug. When the spring is extended and retracted, even if the sealing in the middle part is poor, the edge part can be guaranteed to be leak-proof. Under normal circumstances, the spring is in a pressure-free state and the needle plug remains exposed. During installation, the needle plug is tightened by threads. A wedge-shaped sealing rubber ring is installed on the needle plug. The compression spring causes the needle plug to retract into the valve body, and then it is installed into the cylindrical groove. Due to the elastic force, the needle plug will automatically pop out to block the channel. When the pipeline pressure is greater than the pressure in the pressure relief valve, the spring is compressed, the needle plug enters the valve body, and the fluid in the pipeline enters the pressure relief valve to relieve pressure. When the pressure drops to the same level at both ends, the elastic force of the spring pushes the needle plug out and reseals the pipeline.

[0009] Compared with the existing core holder, the present invention has the following advantages:

[0010] (1) Core displacement experiments or core analysis can be carried out under high pressure, as close to the formation conditions as possible, to obtain relatively real core data; (2) A special wedge-shaped sealing ring is installed in the sealing groove, and the confining pressure will squeeze the sealing ring into the groove to ensure its good sealing performance under high pressure or ultra-high pressure; (3) The pressure relief valve can release pressure inward when the external pressure is too high, keeping the pressure difference from being too large, and gradually increasing the pressure to ensure that the sealing sleeve is well sealed and not damaged; (4) The structure is simple, the pressure relief is convenient, and it is easy to install and disassemble. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the structural diagram of the core holder;

[0012] Figure 2 This is the structure diagram of the pressure relief valve;

[0013] Figure 3 This is a structural diagram of the integrated retainer;

[0014] Figure 4 Figure 1 is a structural diagram of the fastener;

[0015] Figure 5 This is a structural diagram of the fixator.

[0016] In the figure: 1. End cap; 2. Cylinder; 3. Integrated holder; 4. Fastener; 5. Holder; 6. Core sleeve; 7. Core; 8. Annular space 1 pressurized pipeline; 9. Axial pressure injection pipeline; 10. Space 2 pressurized pipeline; 11. Integrated fastener for space 2 pressurized pipeline; 12. Space 3 pressurized hole; 13. Wedge seal ring 1; 14. Pressure relief valve; 15. Pressure relief valve connecting channel; 16. Annular space 1; 17. Space 2; 18. Space 3; 19. Needle plug; 20. Wedge seal ring 2; 21. Spring; 22. Connecting pipe DETAILED DESCRIPTION

[0017] The present invention is further described below with reference to the accompanying drawings to facilitate understanding by those skilled in the art. However, it should be understood that the present invention is not limited to the specific embodiments described herein. Those skilled in the art will appreciate that any modifications within the spirit and scope of the present invention as defined and specified in the appended claims are fully protected.

[0018] A pressure-dividing ultrahigh temperature and ultrahigh pressure core holder based on wedge seal, as shown in the attached Figure 1, mainly composed of a cylinder, an end cover, an integrated fixture, a fixture, a fastener, a core sleeve, a pressure relief valve, etc. The core (7) is installed in the core sleeve (6) and placed in a cylindrical cylinder (2). The experimental fluid directly pressurizes the core through the axial pressure filling pipeline (9). During the pressurization process, first, the fluid is injected into the space three (18) between the fastener (4) through the space three pressure hole (12) on the cylinder to pressurize the space. When the pressure is greater than the threshold of the pressure relief valve (14), the fluid in the space three enters the space two (17) between the fastener (4) and the fixture (5) through the pressure relief valve. At this time, the pressurization speed is slowed down, and the space two is pressurized through the space two pressure pipeline (10) at the same time, so that the pressure of space two is greater than the pressure of space three; similarly, the pressure of space two is greater than When the pressure of the annular space 1 (16) between the barrel (2) and the core sleeve (6) is reduced, the pressure is released into the annular space 1 through the pressure relief valve, and the annular space 1 is pressurized through the annular space 1 pressure pipeline (8). The pressurization method of the integrated fixture (3) is consistent with the above, and the space 2 is pressurized through the integrated fixture space 2 pressure pipeline (11). In addition, the pressure on both sides starts to be increased at the same time to ensure that the pressure on both sides of the core is consistent. At this time, the pressure in the clamp gradually decreases from the inside to the outside. The pressure relief valve prevents the pressure difference of each annular space from being too large, and the sealing ring will not be easily damaged. This step-by-step pressure increase method can also keep the pressure in a relatively stable state. In addition, the step-by-step pressurization method from outside to inside can also allow air to be discharged directly from the annular space through the pipeline (10). During the pressure relief process, the surrounding pressure and the internal pressure are simultaneously relieved through the pipelines: the annular space first pressurization pipeline (8), the axial pressure filling pipeline (9), the space second pressurization pipeline (10), the integrated fixer space second pressurization pipeline (11) and the space third pressurization hole (12).

[0019] Attachment Figure 2 The middle part is a pressure relief valve, which is mainly composed of a spring, a needle plug, a rubber ring, etc. The channel (22) in the pressure relief valve is connected to the spring cavity to maintain consistent pressure. There is a wedge-shaped sealing ring (20) on the needle plug. When the spring is extended and retracted, even if the middle part is not sealed well, the edge part can be guaranteed to be leak-proof. Under normal circumstances, the spring is in a pressure-free state and the needle plug (19) remains exposed. During installation, the needle plug is tightened by threads. A wedge-shaped sealing rubber ring is installed on the needle plug. The compression spring causes the needle plug to retract into the valve body and then install it into the cylindrical groove. Due to the elastic force, the needle plug will automatically pop out to block the channel; when the pipeline pressure is greater than the pressure in the pressure relief valve, the spring is compressed, the needle plug enters the valve body, and the fluid in the pipeline enters the pressure relief valve to release pressure. When the pressure drops to the point where the pressure at both ends is equal, the elastic force of the spring pushes the needle plug out to reseal the pipeline.

[0020] When installing the core holder, first install the core sleeve, install the pressurized pipelines at both ends of the core sleeve, then install the fixture through the thread to fix the position of the core, add a confining pressure filling pipeline to the left end fixture, and add a sealing ring between the pipeline and the fixture; then install the fastener, continuously adjust the pressurized pipeline in space 2 by rotation, and finally tighten the end cover, and fix the entire device with the threads on the end cover; adjust the integrated fixture on the right to contact the core, seal the core with the sealing ring on it, and finally fix it with the end cover.

[0021] The present invention is not limited to the above-mentioned embodiments. For those skilled in the art, various modifications of the present invention are possible. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A pressure-dividing ultra-high temperature and ultra-high pressure core holder based on a wedge seal, characterized by: It mainly consists of a barrel, an end cover, an integrated fixture, a fixture, a fastener, a core sleeve, and a pressure relief valve. The core is installed in the core sleeve and placed in a cylindrical barrel. The experimental fluid directly pressurizes the core through the axial pressure filling pipeline. The integrated fixture and the fixture are both provided with corresponding wedge-shaped grooves for installing a wedge-shaped sealing ring. The pressure relief valve consists of a spring, a needle-shaped plug, and a wedge-shaped sealing ring. The needle-shaped plug is provided with a wedge-shaped sealing ring. The holder is fastened by threads and sealed by a wedge-shaped sealing ring. A pressure relief valve is provided on the holder to relieve pressure. A connecting pipe is provided on the holder to connect the space on the left side of the holder with the lower part of the pressure relief valve. The fastener consists of two parts. The right half is used for adjustment and has a wedge-shaped sealing ring for sealing. The installation position of the fastener can be adjusted by continuous rotation to ensure convenient pipeline installation. The right half protruding part is semicircular and can squeeze the fixture to ensure that the fixture does not move. The left half protruding part is convenient for pipeline installation, and the middle space is used to achieve pressure distribution. The integrated fixture has two spaces for pressure distribution. The left side of the integrated fixture directly contacts the core to prevent axial movement of the core. There are two pipes on the integrated fixture, one for axial pressure injection and the other for the pressurized pipeline in the integrated fixture space. The integrated design facilitates installation and removal. The multi-space partial pressure type pressurization is adopted. By adjusting the space between the integrated fixture, the fixture and the fastener, the pressure is gradually divided, so that the pressure difference of each space is reduced. During the pressurization process, the fluid is first injected into the space three between the fasteners through the space three pressure hole on the cylinder to pressurize. When the pressure is greater than the pressure relief valve threshold, the fluid in space three enters the space two between the fastener and the fixture through the pressure relief valve. At this time, the pressurization speed is slowed down, and the space two is pressurized through the space two pressure pipeline at the same time, so that the pressure of space two is greater than the pressure of space three. Similarly, when the pressure of space two is greater than the pressure of the annular space one between the cylinder and the core sleeve, the pressure is reduced through the pressure relief valve. When the pressure is discharged into the annular space one, the pressurization method of the integrated fixture is the same as the above. The space two is pressurized through the integrated fixture space two pressure pipeline. In addition, the pressure on both sides starts to be injected at the same time to ensure that the pressure on both sides of the core is consistent. At this time, the pressure in the clamp gradually decreases from the inside to the outside. The pressure relief valve ensures that the pressure difference in each annular space will not be too large, and the sealing ring will not be easily damaged. This step-by-step pressurization method can also keep the pressure relatively stable. During the pressure relief process, the confining pressure and internal pressure are simultaneously discharged through the annular space one pressure pipeline, the axial pressure injection pipeline, the space two pressure pipeline, the integrated fixture space two pressure pipeline and the space three pressure hole at both ends.

2. A wedge-sealed pressure-dividing ultra-high temperature and ultra-high pressure core holder according to claim 1, characterized in that: The cylinder is arranged as a terraced structure.

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