Performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells

Abstract

This invention discloses a performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells, belonging to the technical field of performance testing methods. This invention solves the problem that indoor testing methods cannot accurately test the pressure-bearing performance of flexible knots. First, corresponding indoor testing parameters are determined. Then, a performance testing device is set up based on these parameters. The device includes a chamber for simulating the working environment of the flexible knot. The chamber has a simulated perforation hole and an initial velocity providing mechanism for the flexible knot. During simulation, the chamber is pressurized. Under the action of hydraulic pressure and the cooperation of the initial velocity providing mechanism, the flexible knot is compressed and moves towards the simulated perforation hole to simulate the process of the flexible knot entering the perforation. The chamber is then continuously pressurized until a set positive pressure value is reached. This method can effectively test the performance of the flexible knot.

Description

Technical Field

[0001] This invention belongs to the technical field of performance testing methods, specifically relating to a performance testing method for unconventional oil and gas horizontal well segmented flexible knots. Background Technology

[0002] With rapid societal development and continuous global energy consumption, unconventional oil and gas resources are being gradually developed and utilized. Currently, proven unconventional oil and gas resources are abundant, mainly consisting of tight shale gas, shale oil, and coalbed methane. However, unconventional oil and gas resources face development challenges such as low permeability or even ultra-low permeability. How to improve the recovery rate and reserve utilization rate of low-permeability oil and gas reservoirs has gradually become an urgent problem to be solved in the domestic and international oil and gas development field.

[0003] Currently, the pumped soluble bridge plug cluster perforation combined with staged fracturing technology is widely used for fracturing stimulation. Under normal circumstances, this technology is safe, fast, has short well dwell time, and is not limited by the number of fracturing stages. However, with the development of unconventional oil and gas resources, conventional bridge plug staged fracturing is increasingly affected by well conditions. Tool string anomalies and casing deformation directly impact construction progress. According to domestic construction statistics this year, construction delays due to on-site shutdowns account for nearly 30%, and in some areas, the cost of downtime due to handling anomalies even exceeds the cost of the materials used in the well. To address this issue and improve formation fracturing uniformity and efficiency, a rope knot replacement technology has been introduced. According to existing technology, rope knots offer good perforation performance and flexible sealing. However, this flexible nature of the rope knot makes it impossible for ordinary indoor testing devices to directly and effectively test its pressure-bearing performance and effective pressure-bearing time. This is one of the direct reasons why this technology cannot be widely adopted at present. Common testing methods for detecting relevant product performance include:

[0004] ① On-site construction well testing

[0005] Using the product directly on-site and inferring its performance by observing changes in wellhead equipment pressure is not intuitive. Furthermore, many factors at the wellhead influence fracturing operations, making it impossible to directly reflect product performance. This method also disrupts the normal on-site construction schedule, significantly increasing construction costs.

[0006] ② On-site pump truck test

[0007] Testing was conducted using on-site fracturing trucks, with high displacement and high pressure used to test product performance. However, this method can only be used for short-term testing, and only if the product size is sufficient can a high throttling pressure differential be formed even if the seal is not tight, which cannot reflect the actual performance of the product.

[0008] ③ Pumping simulation test

[0009] The high displacement characteristic of low-pressure pumps is used to test product performance. This method can only simulate the pumping performance of the product's entry hole, and cannot effectively test the product's effective duration, temperature resistance, etc., which are the core performance characteristics of the knot product itself.

[0010] Based on this, in order to standardize the performance testing and indoor testing methods of the new process, given the current situation where existing methods cannot achieve truly effective results, and in order to establish industry standards for the future promotion of the process, it is necessary to develop new indoor performance testing methods. Summary of the Invention

[0011] To address the problem that existing indoor testing methods cannot accurately test the pressure-bearing performance of flexible knots, this invention provides a performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells.

[0012] The technical solution adopted in this invention is as follows:

[0013] A performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells includes the following steps:

[0014] Includes the following steps:

[0015] Step A: Determine the corresponding indoor test parameters based on the target area or the corresponding field perforation string parameters;

[0016] Step B: Set up the performance testing device according to the indoor test parameters determined in Step A. The performance testing device includes a chamber for simulating the working environment of the flexible knot, and the chamber is provided with holes simulating perforations and an initial velocity providing mechanism for providing initial velocity to the flexible knot.

[0017] Step C: Pressurize the chamber of the simulated flexible knot working environment; under the action of hydraulic pressure and the cooperation of the initial velocity providing mechanism, the flexible knot is compressed and, guided by the tail fins at both ends and the flow of liquid, moves towards the hole of the simulated perforation until the flexible knot enters the hole, so as to simulate the process of the flexible knot entering the perforation.

[0018] Step D: After the flexible knot enters the hole, the chamber of the simulated flexible knot working environment continues to be pressurized until the set positive bearing pressure value is reached;

[0019] Step F: After reaching the set positive pressure value, stop pressurizing and continuously monitor the pressure change of the chamber in the simulated flexible knot working environment to simulate the effective pressure bearing time of the flexible knot under downhole environmental conditions.

[0020] Preferably, the performance testing device includes an experimental sleeve with an outer shell inside. A first sealed cavity is formed inside the outer shell, and an internal pressure supply mechanism is connected to the first sealed cavity. A second sealed cavity is formed between the outer shell and the experimental sleeve. Liquid and pressure detection mechanisms are provided in both the first and second sealed cavities. An opening for simulating a perforation is provided on the side wall of the outer shell. A shear pin seat and a placement platform for placing a flexible knot are respectively provided on both sides of the opening in the first sealed cavity. An impact seat is slidably mounted on the shear pin seat. A limiting block that cooperates with the impact seat is also provided in the first sealed cavity. A shear pin is installed in the area between the impact seat and the limiting block on the shear pin seat. The distance from the placement platform to the opening matches the distance from the impact seat to the limiting block.

[0021] After adopting this technical solution, the hydraulic pressure exerts a force on the impact seat and the flexible knot to move towards the limiting block, compressing the shear pin until it is sheared. After shearing, the flexible knot on the seat is accelerated and released under the action of the hydraulic pressure in the first sealing chamber. Due to the restriction of the limiting block, the impact seat stops moving after reaching the designed position, thus restricting the movement of the flexible knot by the impact seat. At this time, the flexible knot is exactly aligned with the hole that needs to be sealed. Guided by the traction of the tail fins at both ends and the flow direction of the liquid in the experimental device, the flexible knot moves towards the opening on the outer shell wall and... Under the action of kinetic energy, the flexible knot is fully compressed. The flexible knot itself causes mutual contact and compression between the ropes, making the contact stress greater than the required sealing pressure value, thus completely sealing the hole. The knot itself also reaches a pressure-bearing state. Then, the first sealing cavity is continuously pressurized (since the hole sealing process is very short, it is expected to be completed within 1 second, so continuous pressurization of the first sealing cavity is sufficient) until the required positive pressure value is reached. The pressure value change in the first sealing cavity is continuously monitored to simulate the effective pressure-bearing time of the flexible knot under downhole environmental conditions.

[0022] Preferably, the second sealing cavity is connected to an external pressure supply mechanism, and step CD further includes pressurizing the second sealing cavity through the external pressure supply mechanism.

[0023] With this technical solution, internal and external pressures can be applied simultaneously during simulation testing according to experimental requirements, which can test the reverse pressure resistance of the knot.

[0024] Preferably, both ends of the outer shell are provided with openings, and an inner connector is detachably connected to one end of the opening. The limiting block is detachably connected to the other end of the outer shell. The limiting block is fixedly connected to the shear pin seat. The shear pin seat is provided with a shear pin mounting groove for installing shear pins. The internal pressure supply mechanism includes an internal pressure pipeline provided on the inner connector and an internal pressure supply port communicating with the internal pressure pipeline.

[0025] With this technical solution, the limiting block and the shear pin holder can be removed from the outer shell together, which facilitates the installation of shear pins. Multiple outer shells with different opening sizes can also be set. Then, the limiting block, the shear pin holder and the inner connector can be installed on the required outer shell, which saves experimental costs.

[0026] Preferably, the experimental sleeve has an opening on one side, and an upper connector is detachably connected to the opening. One end of the inner connector passes through the upper connector, and the inner connector is sealed to the upper connector.

[0027] With this technical solution, the outer shell can be easily inserted through the opening of the experimental sleeve, and a sealed chamber can be formed inside the experimental sleeve through the upper connector.

[0028] Preferably, a lower connector is fixedly installed inside the experimental sleeve, and one end of the outer shell with a limit block is detachably connected to the lower connector.

[0029] After adopting this technical solution, the outer shell is fixed by the lower connector.

[0030] Preferably, the experimental sleeve is also provided with a heating mechanism and a temperature detection mechanism, and step CD further includes temperature control of the performance testing device through the heating mechanism and the temperature detection mechanism.

[0031] By adopting this technical solution, the device can be heated by a heating mechanism, which can provide a continuous and stable test temperature for the experimental device and simulate the actual well conditions inside the wellbore.

[0032] Preferably, step A includes determining the opening size and the shearing pin with a corresponding shear value; wherein the opening size is equal to the test hole size; and selecting a shearing pin with a corresponding shear value according to the size of the flexible knot, wherein the flexible knot includes a main body and tail wings on both sides. When the main body size of the flexible knot is 15-20mm, a shearing pin with a shear value of 0.4-0.6t is selected; when the flexible knot size is 20-25mm, a shearing pin with a shear value of 0.5-0.7t is selected; when the flexible knot size is 25-30mm, a shearing pin with a shear value of 0.7-1t is selected; and when the flexible knot size is 30-35mm, a shearing pin with a shear value of 0.9-1.2t is selected.

[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0034] 1. The hydraulic pressure exerts a force on the impact seat and the flexible knot to move towards the limiting block, compressing the shear pin until it is sheared. After shearing, the flexible knot on the seat is accelerated and released under the hydraulic pressure of the first sealing chamber. Due to the limitation of the limiting block, the impact seat stops moving after reaching the designed position, thus restricting the movement of the flexible knot. At this point, the flexible knot is directly opposite the hole to be sealed. Guided by the traction of the tail fins at both ends and the flow of liquid within the experimental device, the flexible knot moves towards the opening on the outer wall, and its own kinetic energy... Under the action of the pressure, the flexible knot is fully compressed. The flexible knot itself causes mutual contact and compression between the ropes, making the contact stress greater than the required sealing pressure value, thus completely sealing the hole. The knot itself also reaches a pressure-bearing state. Then, the first sealing cavity is continuously pressurized (since the hole sealing process is very short, it is expected to be completed within 1 second, so continuous pressurization of the first sealing cavity is sufficient) until the required positive pressure value is reached. The pressure value change in the first sealing cavity is continuously monitored to simulate the effective pressure-bearing time of the flexible knot under downhole environmental conditions.

[0035] 2. The limiting block and the shear pin holder can be removed from the outer shell together, which facilitates the installation of shear pins. Multiple outer shells with different opening sizes can be set. Then, the limiting block, the shear pin holder and the inner connector can be installed on the required outer shell, which saves experimental costs.

[0036] 3. Heating the device through a heating mechanism can provide a continuous and stable test temperature for the experimental device, simulating the actual well conditions inside the wellbore.

[0037] 4. During simulation testing, internal and external pressures can be applied simultaneously according to experimental requirements to test the reverse pressure resistance of the knot. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of the present invention in its initial state;

[0039] Figure 2 A schematic diagram of the present invention with the flexible rope knot inserted into the hole;

[0040] Figure 3 The diagram shows the positive compressive strength of the knot at 78℃.

[0041] Figure 4 The diagram shows the positive compressive strength of the knot at 60-65℃.

[0042] Figure 5 The positive compressive strength of the knot under 180℃ temperature conditions;

[0043] Figure 6 This refers to the reverse compressive strength of the knot under normal temperature conditions.

[0044] Figure 7 Diagram of the external structure of the outer shell after the flexible knot is inserted into the opening;

[0045] Among them, 1-internal pressure supply mechanism, 2-external pressure supply mechanism, 3-inner connector, 4-upper connector, 5-experimental sleeve, 6-outer shell, 7-flexible knot, 8-impact seat, 9-shear nail seat, 10-shear nail, 11-limiting block, 12-lower connector, 13-heating mechanism, 14-opening. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, 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. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0047] In the description of the embodiments of this application, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing this application 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 application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] like Figure 1-2As shown, a performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells is described. In this embodiment, the performance testing device includes an experimental casing 5, an outer shell 6 inside the experimental casing 5, a first sealed cavity formed inside the outer shell 6, an internal pressure supply mechanism 1 connected to the first sealed cavity, and a second sealed cavity formed between the outer shell 6 and the experimental casing 5. Liquid and pressure detection mechanisms are provided in both the first and second sealed cavities. An opening 14 for simulating perforation is provided on the side wall of the outer shell 6. A shear pin seat 9 and a placement platform for placing flexible knots 7 are respectively provided on both sides of the opening 14 in the first sealed cavity. An impact seat 8 is slidably provided on the shear pin seat 9. A limiting block 11 that cooperates with the impact seat is also provided in the first sealed cavity. A shear pin 10 is installed on the shear pin seat 9 in the area between the impact seat 8 and the limiting block 11. The distance from the placement platform to the opening 14 matches the distance from the impact seat 8 to the limiting block 11.

[0049] In this embodiment, the second sealing cavity is connected to an external pressure supply mechanism 2, and the external pressure pipeline of the external pressure supply mechanism 2 is connected to the second sealing cavity.

[0050] In this embodiment, a controller and a display screen are also included. The external pressure supply mechanism 2, the internal pressure detection mechanism, the internal pressure supply mechanism 1, the heating mechanism 13, and the temperature detection mechanism are all electrically connected to the controller and the display screen.

[0051] In this embodiment, both ends of the outer shell 6 are provided with openings, and an inner connector 3 is connected to one end of the opening through a threaded seal (with a sealing gasket). The limiting block 11 is connected to the other end of the outer shell 6 through a threaded seal (with a sealing gasket). The limiting block 11 is fixedly connected to the shear pin seat 9. The shear pin seat 9 is provided with a shear pin mounting groove for installing shear pins 10. The shear pins 10 are installed in the shear pin mounting groove by bolts. The internal pressure supply mechanism 1 includes an internal pressure pipeline provided on the inner connector 3 and an internal pressure supply port communicating with the internal pressure pipeline.

[0052] In this embodiment, the experimental sleeve 5 has an opening on one side, a sealing gasket at the opening, and an upper connector 4 is threadedly connected thereto. The inner connector 3 passes through the upper connector 4 and is threadedly and sealed to the upper connector 4.

[0053] In this embodiment, a lower connector 12 is fixedly installed inside the experimental sleeve 5, and one end of the outer shell 6 is provided with a limit block 11 and is threadedly connected to the lower connector 12.

[0054] In this embodiment, the experimental sleeve 5 is also provided with a heating mechanism 13 and a temperature detection mechanism. The heating mechanism 13 consists of several resistance wires disposed on the outer wall of the experimental sleeve 5, and the temperature detection mechanism is a temperature sensor.

[0055] The method of using this invention is as follows: including the following steps:

[0056] Step A: Based on the target area or the corresponding field perforation string parameters, determine the corresponding indoor test parameters. The indoor test parameters include determining the size of the opening 14 and the shear pin 10 with the corresponding shear value. The size of the opening 14 is equal to the size of the test hole. Select a shear pin with the corresponding shear value according to the size of the flexible knot 7. When the size of the flexible knot 7 is 15-20mm, select a shear pin 10 with a shear value of 0.4-0.6t; when the size of the flexible knot 7 is 20-25mm, select a shear pin 10 with a shear value of 0.5-0.7t; when the size of the flexible knot 7 is 25-30mm, select a shear pin 10 with a shear value of 0.7-1t; and when the size of the flexible knot 7 is 30-35mm, select a shear pin 10 with a shear value of 0.9-1.2t.

[0057] Step B: Set up the performance testing device according to the indoor test parameters determined in Step A, including assembling the device, placing the flexible knot 7 on the placement seat, and installing the shear nail 10 onto the shear nail seat 9, etc.

[0058] Step C: Pressurize the first sealing cavity with the internal pressure supply mechanism 1, and heat the entire device with the heating mechanism 13 to simulate the real environment; under the action of hydraulic pressure, the impact seat 8 and the flexible knot 7 move to the side closer to the limiting block 11, so that the impact seat 8 squeezes the shear nail 10, and the flexible knot 7 is compressed under the combined action of the blocking force of the impact seat 8 on the flexible knot 7 and the hydraulic force.

[0059] Step D: As Figure 1-2 As shown, after the shear pin 10 cuts, the flexible knot 7 on the placement platform is accelerated and released under the action of hydraulic pressure. When the impact seat 8 contacts the limiting block 11, the flexible knot 7 is exactly above the opening 14. Under the traction of the tail wings at both ends and the guidance of the flow of liquid in the first sealing cavity, the flexible knot 7 moves towards the opening 14. Due to the full compression of the flexible knot 7, the mutual contact and compression between the ropes caused by the flexibility of the flexible knot 7 itself makes the contact stress greater than the pressure value required for sealing, thereby completely sealing the opening 14 (e.g., Figure 7 As shown), the flexible knot 7 itself has reached a pressure-bearing state. When the flexible knot 7 enters the opening 14, it continues to pressurize the first sealing cavity. Since the process of sealing the hole is very short, it is expected to be completed within 1 second. Therefore, it is sufficient to continuously pressurize the first sealing cavity until the required positive pressure value is reached. If necessary, the external pressure supply mechanism 2 can be used to adjust the pressure of the second sealing cavity to test the reverse pressure bearing capacity of the knot.

[0060] Step F: After reaching the set positive pressure value, stop pressurizing and continuously monitor the pressure value change in the first sealing cavity to simulate the effective pressure bearing time of the flexible knot 7 under downhole environmental conditions.

[0061] like Figure 3 As shown: The test content is the positive pressure bearing capacity of the knot at 78℃; the curve in the pressure curve graph is the pressure curve, and the pressure value is the pressure value of the first sealing chamber, indicating that the highest positive pressure bearing capacity of the knot in this test is 70MPa;

[0062] like Figure 4 As shown: The test content is the positive pressure bearing capacity of the knot at 60-65℃; the curve in the pressure curve graph is the pressure curve, and the pressure value is the pressure value of the first sealing cavity, indicating that the highest positive pressure bearing capacity of the knot in this test is 50MPa.

[0063] like Figure 5 As shown: The test content is the positive pressure bearing capacity of the knot under the condition of 180℃; the upper curve in the pressure curve is the temperature curve at 180℃, and the lower curve in the pressure curve is the pressure value of the first sealing cavity, indicating that the highest positive pressure bearing capacity of the knot in this test is 70MPa.

[0064] like Figure 6 As shown; the test content is the reverse pressure bearing capacity of the knot under normal temperature conditions; the pressure curve is a temperature curve and a pressure curve. The pressure value is the pressure value of the second sealing cavity, indicating that the highest reverse pressure bearing capacity of the knot in this test is 7.2 MPa.

[0065] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells, characterized in that: Includes the following steps: Step A: Determine the corresponding indoor test parameters based on the target area or the corresponding field perforation string parameters; Step B: Set up the performance testing device according to the indoor test parameters determined in Step A. The performance testing device includes a chamber for simulating the working environment of the flexible knot, and the chamber is provided with holes simulating perforations and an initial velocity providing mechanism for providing initial velocity to the flexible knot. Step C: Pressurize the chamber of the simulated flexible knot working environment; under the action of hydraulic pressure and the cooperation of the initial velocity providing mechanism, the flexible knot (7) is compressed and, under the traction of the tail wings at both ends and the guidance of the liquid flow, moves towards the hole of the simulated perforation until the flexible knot (7) enters the hole, so as to simulate the process of the flexible knot entering the perforation. Step D: After the flexible knot (7) enters the hole, the chamber of the simulated flexible knot working environment continues to be pressurized until the set positive bearing pressure value is reached; Step F: After reaching the set positive pressure value, stop pressurizing and continuously monitor the pressure value change of the chamber in the simulated flexible knot working environment to simulate the effective pressure bearing time of the flexible knot (7) under the downhole environment conditions. The performance testing device includes an experimental sleeve (5), an outer shell (6) is provided inside the experimental sleeve (5), a first sealed cavity is formed inside the outer shell (6), an internal pressure supply mechanism (1) is connected to the first sealed cavity, a second sealed cavity is formed between the outer shell (6) and the experimental sleeve (5), and liquid and pressure detection mechanisms are provided in both the first and second sealed cavities. An opening (14) for simulating a perforation is provided on the side wall of the outer shell (6). A shear pin seat (9) and a placement platform for placing a flexible knot (7) are respectively provided on both sides of the opening (14) in the first sealed cavity. An impact seat (8) is slidably provided on the shear pin seat (9). A limiting block (11) that cooperates with the impact seat is also provided in the first sealed cavity. A shear pin (10) is installed in the area between the impact seat (8) and the limiting block (11) on the shear pin seat (9). The distance from the placement platform to the opening (14) matches the distance from the impact seat (8) to the limiting block (11).

2. The performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells according to claim 1, characterized in that: The second sealing cavity is connected to an external pressure supply mechanism (2), and step CD further includes pressurizing the second sealing cavity through the external pressure supply mechanism (2).

3. The performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells according to claim 1, characterized in that: Both ends of the outer shell (6) are provided with openings, and an inner connector (3) is detachably connected to one end of the opening. The limiting block (11) is detachably connected to the other end of the outer shell (6). The limiting block (11) is fixedly connected to the shear pin seat (9). The shear pin seat (9) is provided with a shear pin mounting groove for installing shear pins (10). The internal pressure supply mechanism (1) includes an internal pressure pipeline provided on the inner connector (3) and an internal pressure supply port communicating with the internal pressure pipeline.

4. The performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells according to claim 3, characterized in that: The experimental sleeve (5) has an opening on one side, and an upper connector (4) is detachably connected to the opening. One end of the inner connector (3) passes through the upper connector (4), and the inner connector (3) and the upper connector (4) are sealed together.

5. The performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells according to claim 3, characterized in that: The experimental sleeve (5) is fixedly provided with a lower connector (12), and the outer shell (6) is provided with a limit block (11) at one end which is detachably connected to the lower connector (12).

6. The performance testing method for segmented flexible knots in unconventional oil and gas horizontal wells according to claim 1, characterized in that: Step CD also includes temperature control of the performance testing device through a heating mechanism (13) and a temperature detection mechanism.

7. The performance testing method for unconventional oil and gas horizontal well segmented flexible knots according to any one of claims 1-6, characterized in that: Step A includes determining the size of the opening (14) and the determination of the shear pins (10) with corresponding shear values; in The size of the opening (14) is equal to the size of the test hole; select a shear pin (10) with a corresponding shear value according to the size of the flexible knot (7). The flexible knot (7) includes a main body and tail wings on both sides. When the main body size of the flexible knot (7) is 15-20mm, select a shear pin (10) with a shear value of 0.4-0.6t. When the size of the flexible knot (7) is 20-25mm, select a shear pin (10) with a shear value of 0.5-0.7t. When the size of the flexible knot (7) is 25-30mm, select a shear pin (10) with a shear value of 0.7-1t. When the size of the flexible knot (7) is 30-35mm, select a shear pin (10) with a shear value of 0.9-1.2t.

Images