A fracturing seepage test core clamping device

Abstract

The utility model discloses a kind of fracturing seepage test core clamping devices, it is related to the field of in-situ leaching uranium mine, to solve the technical problem that fracturing experiment and seepage experiment need to be carried out on different devices in prior art, resulting in core is disturbed, experimental result is distorted.The device includes body, confining pressure system, upper sample pressure plug and lower sample pressure plug;Its core is in that: upper sample pressure plug center is equipped with liquid injection hole and connects simulation well shaft, for injecting liquid to core center to carry out fracturing;Sample sample outer periphery is provided with percolation layer as radial flow channel;Lower sample pressure plug is then provided with liquid outlet hole for liquid export in communication with percolation layer.The utility model is integrated design, after realizing high pressure fracturing to core in single device, without taking out core can be in situ seepage simulation test, ensure the continuity of experimental process and the stability of stress state, significantly improve the accuracy and reliability of experimental data.

Description

Technical Field

[0001] This utility model relates to the field of in-situ leaching uranium mining, and in particular to a core clamping device for fracturing and seepage testing. Background Technology

[0002] Hydraulic fracturing is a key production enhancement technology in the development of low-permeability oil and gas reservoirs or in-situ leaching uranium deposits. To accurately evaluate the fracturing effect and study the seepage characteristics of the reservoir after fracturing, it is usually necessary to conduct physical simulation experiments on core samples taken from underground in the laboratory.

[0003] However, existing laboratory equipment and methods generally suffer from a fundamental flaw: fracturing experiments and seepage experiments are conducted in isolation. Typically, researchers first install core samples in a specialized fracturing apparatus, apply confining and axial pressures simulating formation stress, and then inject fracturing fluid using a high-pressure pump to fracture the core. Afterward, the fractured core must be removed from the apparatus and installed in a separate seepage apparatus specifically designed for measuring permeability for subsequent experiments.

[0004] This "fracturing-removal-transfer-reinstallation" process has two major technical drawbacks: First, newly generated fractures are usually very fragile. During removal and transfer, the stress release and mechanical disturbance experienced by the core can easily lead to unexpected closure, displacement, or even the creation of new microfractures, thus damaging the true structure of the fractures. Second, the entire process cannot maintain the in-situ stress state of the core underground, and stress is a key factor controlling fracture aperture and conductivity. Therefore, the seepage data measured by this non-in-situ, stepwise experimental method often deviates significantly from the actual situation of the reservoir after fracturing, seriously affecting the accuracy of the evaluation of fracturing effectiveness. Current technology cannot achieve both fracturing and in-situ post-fracturing testing of the same core within a single device.

[0005] In summary, there is an urgent need in the field for an integrated experimental device that can perform seepage characteristic testing on core samples immediately after fracturing, within a single device and under conditions of maintaining in-situ stress, in order to overcome the aforementioned deficiencies of the prior art. Utility Model Content

[0006] In view of this, this application provides a core clamping device for fracturing and seepage testing. The main purpose is to solve the technical problem in the prior art where the functions of fracturing and seepage testing are separated, and the tests cannot be carried out continuously under in-situ conditions, resulting in distorted experimental results.

[0007] This invention provides a core clamping device for fracturing seepage tests, comprising: a body for accommodating a sample sleeve and a confining pressure system for applying confining pressure to the sample sleeve; the sample sleeve has a cavity for placing a columnar sample; the device further comprises an upper sample plug and a lower sample plug located at both ends of the sample sleeve; the upper sample plug has an injection hole at its center for injecting fracturing fluid, and the device further comprises a simulated wellbore, which communicates with the injection hole and extends to the center of the sample; a permeation layer serving as a radial flow channel is provided between the sample and the sample sleeve; and the lower sample plug has an outlet hole communicating with the permeation layer.

[0008] Furthermore, the core clamping device for the fracturing and seepage test also includes an axial pressure system, which is used to apply axial pressure to the sample through the upper sample plug and the lower sample plug; the upper sample plug is located at the upper end of the sample, and the lower sample plug is located at the lower end of the sample.

[0009] Furthermore, the axial compression system includes a transition ring sleeve that abuts against the upper sample plug, and a threaded cap that is threadedly connected to the body and used to push the transition ring sleeve.

[0010] Furthermore, the axial compression system also includes an axial compression push rod passing through the base of the device, the end of which abuts against the lower sample plug.

[0011] Furthermore, the confining pressure system includes a rubber sleeve disposed within the body, and a confining pressure cavity for injecting pressurized fluid is formed between the rubber sleeve and the inner wall of the body.

[0012] Furthermore, the confining pressure system also includes an upper pressure ring and a lower pressure ring that are threaded to the top and bottom of the body respectively, and the upper pressure ring and the lower pressure ring are used to seal both ends of the rubber sleeve.

[0013] Furthermore, the upper circumferential surface of the lower sample plug is provided with a plurality of radial holes, which are connected to the permeation layer; the liquid outlet is a central vertical hole, and the central vertical hole is connected to the plurality of radial holes.

[0014] Furthermore, at least one sealing gasket is provided between the upper sample plug and the sample, and between the lower sample plug and the sample, to prevent fluid from flowing across the end face.

[0015] Furthermore, the sample sleeve comprises, from the inside out, the sample, the permeation layer, and the sample tube; The permeation layer is a flexible material layer with a porous or slit structure.

[0016] Furthermore, the base is composed of a base plate and a support. The base plate has a central hole through which the axial pressure push rod passes, and a sealing ring for sealing is provided on the wall of the central hole.

[0017] Beneficial effects: Compared with existing technologies, this device integrates high-pressure fracturing and seepage simulation functions into a single unit through its integrated structural design. Researchers can apply and maintain the confining pressure and axial pressure of the simulated formation, perform fracturing first, and then switch directly to the seepage experiment without removing the core sample. This ensures the continuity of the experimental process, avoids disturbances to the stress state and fracture structure caused by sample transfer, and enables the acquisition of experimental data that more closely resembles real formation conditions.

[0018] On the other hand, the device disclosed in this application achieves high-pressure fracturing by center-point injection through a "simulated wellbore"; through a "filtration layer" surrounding the core and a specially designed "lower sample plug", a clear radial seepage and outlet channel is constructed. This design in this application simulates the physical process of fracturing fluid entering the formation from the wellbore, opening the fracture, and the subsequent formation fluid flowing radially into the wellbore along the fracture.

[0019] Meanwhile, by simplifying the experimental procedure and reducing the significant time required for disassembling and installing equipment in traditional methods, experimental efficiency is significantly improved. Furthermore, by avoiding human interference with the samples, the repeatability of the experiment and the reliability of the data are also greatly enhanced.

[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0021] The accompanying drawings, as part of this utility model, are used to provide a further understanding of the present utility model. The illustrative embodiments and descriptions of the present utility model are used to explain the present utility model, but do not constitute an undue limitation of the present utility model. Obviously, the drawings described below are merely some embodiments; those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0022] In the attached diagram: Figure 1 This diagram illustrates the structure of a core clamping device for fracturing and seepage testing provided in an embodiment of the present invention. Figure 2 This diagram shows another angle of the core clamping device for fracturing and seepage testing provided in an embodiment of the present invention.

[0023] Icon labels: 1-Body, 2-Rubber sleeve, 3-Upper pressure ring, 4-Transition ring sleeve, 5-Threaded pressure cap, 6-Upper sample plug, 7-Lower sample plug, 8-Lower pressure ring, 9-Base plate, 10-Bracket, 11-Axial pressure push rod, 12-Axial pressure injection port, 13-Containing pressure injection port, 14-Outlet hole, 15-Injection hole, 16-Sample rubber sleeve, 17-Filtration layer, 18-Sealing gasket, 19-Sealing ring, 20-Containing pressure cavity, 21-Sample sleeve, 22-Simulated wellbore, 23-Axial pressure cavity, 24-Sample sample.

[0024] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the present invention in any way, but rather to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate this utility model, but are not intended to limit the scope of this utility model.

[0026] In the description of this utility model, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0027] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0028] Example like Figure 1-2 As shown, this utility model provides a core clamping device for fracturing and seepage testing. The device mainly consists of four parts: a base, a confining pressure system, an axial pressure system, and a sample system.

[0029] In one feasible embodiment, the base portion includes a base plate 9 and a support 10. The base plate 9 is a hollow disc used to support the main structure of the device. Specifically, the base plate 9 has a central hole through which the axial pressure push rod 11 passes, and a sealing ring 19 for sealing is provided on the wall of the central hole. The base plate 9 is fixed to the support 10 by bolts to ensure the stability of the entire device.

[0030] In one feasible implementation, the confining pressure system is used to simulate the lateral compressive stress of the formation on the core sample. In this embodiment, the confining pressure system is used to apply confining pressure to the sample sleeve 21, which consists of a hollow cylindrical body 1, a flexible rubber sleeve 2 placed inside the body 1, and an upper pressure ring 3 and a lower pressure ring 8 for sealing and fixing. The rubber sleeve 2 is made of rubber and its two ends protrude outward. During installation, the rubber sleeve 2 is tightly fitted to the inner wall of the body 1, and an annular sealed cavity, i.e., the confining pressure cavity 20, is formed between the outer wall of the rubber sleeve 2 and the inner wall of the body 1. A confining pressure injection port 13 is provided on the side wall of the body 1. Hydraulic oil is injected into the confining pressure cavity 20 through the injection port and pressurized, and the pressure is then evenly applied to the sample system inside through the flexible rubber sleeve 2. The upper pressure ring 3 and the lower pressure ring 8 are respectively threadedly fixed to the upper and lower ends of the body 1, and are used to press the protruding end of the rubber sleeve 2 to ensure the sealing of the confining cavity 20. The upper pressure ring 3 and the lower pressure ring 8 are used to seal both ends of the rubber sleeve 2.

[0031] In one feasible implementation, the sample system is the core of the device, used to contain the core and achieve fracturing and seepage functions. Located inside the confining pressure system, the system consists of a sample sleeve 21, a simulated wellbore 22, and two sealing gaskets 18. The sample sleeve 21 has a cavity for placing a columnar sample 24. Specifically, from the inside out, the sample sleeve 21 comprises the sample 24, a permeation layer 17, and a sample sleeve 16. The sample 24 is a columnar core retrieved from the field, with a pre-drilled center hole simulating a wellbore. The permeation layer 17, a flexible material with a porous or fractured structure, wraps around the sample 24 and provides a uniform collection and flow path for the fluid radially seeping from the core fractures during the seepage experiment after fracturing. The outermost sample sleeve 16 encloses and constrains the entire sample, preventing it from breaking during the experiment. The simulated wellbore 22 is a thin round tube whose lower end is inserted into the central hole of the sample 24 to simulate the real injection wellbore.

[0032] In one feasible implementation, the axial compression system is used to simulate the vertical compressive stress of the formation on the core, and it is distributed on the upper and lower sides of the sample system. The system mainly includes an upper sample plug 6, a lower sample plug 7, a threaded cap 5, a transition ring 4, and an axial compression push rod 11. The upper sample plug 6 and the lower sample plug 7 are two cylindrical pressure heads that directly contact the upper and lower ends of the sample system. To prevent fluid from flowing across the upper and lower end faces of the sample 24, sealing gaskets 18 are placed between the upper sample plug 6 and the lower sample plug 7 and the sample 24, respectively.

[0033] In this embodiment, the upper sample plug 6 has a vertical injection hole 15 at its center, the upper end of which can be connected to an external high-pressure fracturing pipeline, and the lower end of which is sealed to the upper end of the simulated wellbore 22. The transition ring 4 is positioned above the upper sample plug 6. The threaded cap 5 is an annular cap with threads on its outer wall, which engages with the internal threads of the upper pressure ring 3. By rotating the threaded cap 5, the transition ring 4 and the upper sample plug 6 can be pushed downwards, thereby applying and adjusting axial pressure to the sample 24.

[0034] In one feasible embodiment, the structure of the lower sample plug 7 is another key aspect of the invention. The upper surface (the side in contact with the sample) of the lower sample plug 7 has multiple radially spaced holes evenly distributed circumferentially. These holes communicate with the permeate layer 17 surrounding the core. Simultaneously, these radial holes converge to a vertical outlet hole 14 at the center of the lower sample plug 7. This design allows the liquid collected from the permeate layer 17 to first enter the radial holes during the seepage experiment, and then be discharged through the central outlet hole 14 for measurement. The axial pressure push rod 11 abuts against the lower part of the lower sample plug 7, passes through the central hole of the base plate 9 in the device base, and its lower end can be subjected to upward axial pressure via an external hydraulic device (as shown in the axial pressure injection port 12 and axial pressure chamber 23).

[0035] In one feasible implementation, the workflow of this device is as follows: Sample loading and pressurization: The prepared sample sleeve 21 is placed into the rubber sleeve 2, and the lower sample pressure plug 7, the upper sample pressure plug 6, the transition ring sleeve 4, and the threaded pressure cap 5 are installed in sequence. Through the confining pressure injection port 13 and the axial pressure system, a preset confining pressure and axial pressure are applied to the sample 24 to simulate its original stress state underground.

[0036] During the fracturing stage: fracturing fluid is injected under high pressure into the simulated wellbore 22 through the injection hole 15 of the upper sample plug 6. When the pressure exceeds the rock fracturing pressure, radial cracks will be generated in the sample 24 from the central hole.

[0037] During the seepage stage: The fracturing pump is stopped, and the injection port 15 is switched to a constant pressure or constant speed injection pump connected to the seepage experiment, while maintaining the confining pressure and axial pressure constant. The injected seepage fluid (such as water or oil) enters the newly generated fracture and seeps radially outward along the fracture. The seeping fluid passes through the permeate layer 17, is collected in the radial holes of the lower sample plug 7, and finally flows out through the central outlet port 14. The flow rate and pressure are monitored by external equipment.

[0038] Through the above integrated design, this utility model successfully overcomes the functional barriers of the prior art and provides a powerful experimental tool for accurately evaluating the effect of reservoir fracturing stimulation.

[0039] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to preferred embodiments, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present utility model. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A core clamping device for fracturing and seepage testing, characterized in that, include: The body (1) for accommodating the sample sleeve (21) and the confining pressure system for applying confining pressure to the sample sleeve (21); the sample sleeve (21) is provided with a cavity for placing the sample (24). The device also includes an upper sample plug (6) and a lower sample plug (7) located at both ends of the sample sleeve (21). The upper sample plug (6) has an injection hole (15) for injecting fracturing fluid at its center, and the device also includes a simulated wellbore (22), which is connected to the injection hole (15) and extends to the center of the sample (24). A permeation layer (17) serving as a radial flow channel is provided between the sample (24) and the sample sleeve (21). The lower sample plug (7) is provided with an outlet hole (14) that communicates with the permeate layer (17).

2. The core clamping device for fracturing and seepage testing according to claim 1, characterized in that, It also includes an axial pressure system for applying axial pressure to the sample (24) through the upper sample plug (6) and the lower sample plug (7); The upper sample plug (6) is located at the upper end of the sample (24), and the lower sample plug (7) is located at the lower end of the sample (24).

3. The core clamping device for fracturing and seepage testing according to claim 2, characterized in that, The axial compression system includes a transition ring (4) that abuts against the upper sample plug (6), and a threaded cap (5) that is threadedly connected to the body (1) and used to push the transition ring (4).

4. The core clamping device for fracturing and seepage testing according to claim 3, characterized in that, The axial pressure system also includes an axial pressure push rod (11) that passes through the base of the device, and the end of the axial pressure push rod (11) abuts against the lower sample plug (7).

5. The core clamping device for fracturing and seepage testing according to claim 1, characterized in that, The confining pressure system includes a rubber sleeve (2) disposed within the body (1), and a confining pressure cavity (20) for injecting pressurized fluid is formed between the rubber sleeve (2) and the inner wall of the body (1).

6. The core clamping device for fracturing and seepage testing according to claim 5, characterized in that, The confining pressure system also includes an upper pressure ring (3) and a lower pressure ring (8) that are connected to the top and bottom of the body (1) respectively by threads. The upper pressure ring (3) and the lower pressure ring (8) are used to seal both ends of the rubber sleeve (2).

7. The core clamping device for fracturing and seepage testing according to claim 4, characterized in that, The upper circumferential surface of the lower sample plug (7) is provided with a plurality of radial holes, which are connected to the permeate layer (17); The liquid outlet (14) is a central vertical hole, and the central vertical hole is connected to the plurality of radial holes.

8. The core clamping device for fracturing and seepage testing according to claim 1, characterized in that, At least one sealing gasket (18) is provided between the upper sample plug (6) and the sample (24), and between the lower sample plug (7) and the sample (24) to prevent fluid from flowing along the end face.

9. The core clamping device for fracturing and seepage testing according to claim 1, characterized in that, The sample sleeve (21) includes, from the inside out, the sample sample (24), the permeation layer (17), and the sample tube (16). The permeation layer (17) is a flexible material layer with a porous or slit structure.

10. The core clamping device for fracturing and seepage testing according to claim 4, characterized in that, The base is composed of a base plate (9) and a bracket (10). The base plate (9) has a central hole through which the axial pressure push rod (11) passes. A sealing ring (19) for sealing is provided on the wall of the central hole.

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