A device and method for testing the plugging effect of a plugging agent

Abstract

The present application relates to a device and a method for testing the plugging effect of a plugging agent, the device comprising a feeding assembly for providing the plugging agent with a predetermined grading level, a testing assembly in communication with the feeding assembly, and a water tank in communication with the feeding assembly and the testing assembly, the testing assembly comprising an injection cylinder, a capillary tube in communication with the injection cylinder and used for containing the plugging agent, and a pressure tube in communication with the injection cylinder through the capillary tube, the injection cylinder and the pressure tube being respectively provided with a first pressure sensor and a second pressure sensor, the first pressure sensor and the second pressure sensor being configured to be able to detect the pressure values in the injection cylinder and the pressure tube respectively. When the plugging agent fills the capillary tube, the values of the first pressure sensor and the second pressure sensor are monitored, and the values of the first pressure sensor and the second pressure sensor after stabilization are compared, so as to evaluate the plugging effect of the plugging agent with the predetermined grading level.

Description

Technical Field

[0001] This invention relates to the field of sealing agent testing technology, and specifically to an apparatus and method for testing the sealing effect of sealing agents. Background Technology

[0002] Loss in wells is one of the most common downhole problems during drilling. Losses in fractured formations not only cause significant losses to drilling operations but also pose considerable challenges to oil and gas exploration and development. Positive leakage plugging technology can effectively solve this problem and is crucial for ensuring downhole safety, increasing drilling speed, and saving drilling costs.

[0003] Currently, bridging and plugging technology is the primary method for addressing lost circulation (WS) problems in fractured formations. This technology involves adding granular, flake-like, or fibrous plugging materials of a certain strength and size to the drilling fluid at a specific formula and appropriate concentration, and then pumping it downhole to the lost circulation site. Under the influence of pressure differential, as the drilling fluid leaks out, the bridging material acts as a bridge, fill, embed, and expand within the lost circulation channels, thereby eliminating the lost circulation and resuming drilling.

[0004] The gradation of the sealing material is crucial to the success of the sealing process. Currently, various experimental devices are available to test sealing materials. However, these devices only consider factors such as crack opening and number to assess the sealing effect, without considering the impact of the material's gradation on its sealing performance. Summary of the Invention

[0005] In view of the above-mentioned problems existing in the prior art, the present invention provides an apparatus and method for testing the sealing effect of a plugging agent, which can take into account the influence of the gradation of the plugging material on its sealing effect.

[0006] To address its technical problem, this invention provides an apparatus for testing the sealing effect of a leak-stopping agent. The apparatus includes a feeding component for providing a leak-stopping agent with a predetermined gradation, a testing component connected to the feeding component, and a water tank connected to both the feeding component and the testing component. The testing component includes an injection cylinder, a capillary tube connected to the injection cylinder and used to contain the leak-stopping agent, and a pressure pipe connected to the injection cylinder through the capillary tube.

[0007] The injection cylinder and the pressure tube are respectively equipped with a first pressure sensor and a second pressure sensor, which are configured to detect the pressure values ​​in the injection cylinder and the pressure tube, respectively.

[0008] Furthermore, the feeding assembly includes several storage bins for holding plugging materials of different particle sizes, and the outlet and inlet ends of the several storage bins are respectively connected to the mixing tank and the water tank.

[0009] Furthermore, a first pump body is provided between the storage tank and the water tank. The first pump body is configured to pump water from the water tank into the storage tank. The storage tank is provided with a pusher plate for pushing the sealing material into the mixing cylinder.

[0010] Furthermore, the inlet ends of the plurality of storage tanks are respectively provided with a plurality of first valves, which are configured to be in different open states, so that plugging materials of different particle sizes enter the mixing tank in a predetermined proportion.

[0011] Furthermore, the mixing cylinder and the injection cylinder are connected, and a second pump body is provided between the mixing cylinder and the water tank. The second pump body is configured to pump water from the water tank into the mixing cylinder, so that the pressure in the injection cylinder reaches a predetermined value.

[0012] Furthermore, the mixing tank is equipped with a motor-driven stirring element, which is configured to mix sealing materials of different particle sizes evenly in water.

[0013] Furthermore, the capillary is a tapered tube, wherein the inner diameter of the first end of the capillary connected to the injection cylinder is larger than the inner diameter of the second end of the capillary connected to the pressure tube.

[0014] Furthermore, a fourth valve is provided at the second end of the capillary tube, and the fourth valve is in the open state after the sealing agent fills the capillary tube.

[0015] Furthermore, a third pump body is provided between the pressure pipe and the water tank. The third pump body is configured to pump water from the water tank into the pressure pipe, so that the pressure inside the pressure pipe reaches a set value.

[0016] Another aspect of the present invention provides a method for testing different gradations of sealant using the apparatus according to any one of the preceding claims, comprising the following steps:

[0017] Step S1: Add sealing materials of different particle sizes to water in a predetermined ratio and mix evenly to prepare a sealing agent with a predetermined gradation grade.

[0018] Step S2: The sealing agent is filled into the capillary tube through the injection cylinder, and then the pressure in the injection cylinder is made to reach a predetermined value, and the pressure in the pressure tube is made to reach a set value, wherein the predetermined value is greater than the set value;

[0019] Step S3: After a period of time, compare the pressure changes in the injection cylinder and the pressure tube, and monitor the water flow in the capillary tube during this period;

[0020] Step S4: Based on the comparison and monitoring results in the previous steps, determine the sealing effect of the pre-graded plugging agent.

[0021] The beneficial effects of this invention are as follows: This invention provides an apparatus for testing the sealing effect of a plugging agent, comprising a feeding component for providing a plugging agent with a predetermined gradation, a testing component connected to the feeding component, and a water tank connected to both the feeding component and the testing component. The testing component includes an injection cylinder, a capillary tube connected to the injection cylinder and used to contain the plugging agent, and a pressure tube connected to the injection cylinder via the capillary tube. A first pressure sensor and a second pressure sensor are respectively installed in the injection cylinder and the pressure tube. The first and second pressure sensors are configured to detect the pressure values ​​in the injection cylinder and the pressure tube, respectively. After the plugging agent fills the capillary tube, the changes in the values ​​of the first and second pressure sensors are monitored, and the stable values ​​of the first and second pressure sensors are compared to evaluate the sealing effect of the plugging agent with the predetermined gradation. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 The diagram shows a structural schematic of a device for testing the sealing effect of a plugging agent.

[0024] Figure 2 The diagram shown is a schematic of the capillary structure.

[0025] In the figure, the following reference numerals are used: 10, feeding assembly; 11, storage bin; 111, push plate; 112, first pump body; 113, first valve; 12, mixing cylinder; 121, second pump body; 122, mixing component; 123, motor;

[0026] 20. Test assembly; 21. Injection cylinder; 211. Second valve; 212. Third valve; 22. Capillary tube; 221. Fourth valve; 23. Pressure tube; 231. Third pump body; 24. First pressure sensor; 25. Second pressure sensor;

[0027] 30. Water tank; 40. Computer. Detailed Implementation

[0028] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will now be described in detail with reference to the accompanying drawings. This drawing is a simplified schematic diagram, illustrating only the basic structure of the invention, and therefore only shows the components relevant to the invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] refer to Figure 1 As shown, the present invention provides an apparatus for testing the sealing effect of a plugging agent, comprising a feeding assembly 10, a testing assembly 20 fluidly connected to the feeding assembly 10 via a pipeline, and a water tank 30 fluidly connected to both the feeding assembly 10 and the testing assembly 20 via a pipeline. The feeding assembly 10 is used to mix stored plugging materials of different particle sizes in water at a predetermined ratio to form a plugging agent with a predetermined gradation. The mixed plugging agent is delivered to the testing assembly 20 via water in the water tank 30. The plugging effect of the plugging agent with the predetermined gradation in the testing assembly 20 is evaluated by the values ​​detected by sensors arranged in the testing assembly 20.

[0030] Combination Figure 1 As shown, in some embodiments, the feeding assembly 10 includes a plurality of storage tanks 11 for holding different particle sizes of sealing materials, a mixing cylinder 12 communicating with the plurality of storage tanks 11, and a mixing element 122 disposed within the mixing cylinder 12. Each of the plurality of storage tanks 11 is provided with a pusher plate 111 for pushing the sealing material into the mixing cylinder 12. The outlet and inlet ends of the plurality of storage tanks 11, parallel to the pusher plate 111, are respectively connected to the mixing cylinder 12 and the water tank 30. A first pump body 112 and a plurality of first valves 113 are sequentially arranged along the pipeline between the storage tanks 11 and the water tank 30 in the direction from the water tank 30 to the storage tanks 11. The plurality of first valves 113 are respectively disposed at the inlet ends of the plurality of storage tanks 11.

[0031] The first pump body 112, driven by an external power source, pumps water from the water tank 30 to several storage tanks 11. The water pressure then drives the pusher plate 111, which pushes plugging materials of different particle sizes into the mixing tank 12. By adjusting the opening positions of several first valves 113, the movement distance of the pusher plate 111 in each storage tank 11 can be controlled, thereby controlling the amount of plugging material of each particle size entering the mixing tank 12. This allows the plugging materials of various particle sizes to be mixed to form a plugging agent of a predetermined gradation.

[0032] In some embodiments, the mixing tank 12 is connected to the water tank 30 via a pipe, and a second pump body 121 is provided on the pipe between the mixing tank 12 and the water tank 30. The second pump body 121 can pump water from the water tank 30 to the mixing tank 12, thereby increasing the flowability of the sealing agent entering the mixing tank 12.

[0033] In some embodiments, the input end of the agitator 122 is connected to the output end of the motor 123. Under the electrical drive of an external power source, the motor 123 can drive the agitator 122 to rotate within the mixing tank 12. Under the stirring action of the agitator 122, the plugging materials of different particle sizes entering the mixing tank 12 are mixed evenly to form a plugging material. In some embodiments, the agitator 122 can be a stirring paddle or a stirring rod.

[0034] Recombined Figure 1 As shown, in some embodiments, the test assembly 20 includes an injection cylinder 21 connected to the stirring cylinder 12 via a pipe, a plurality of capillary tubes 22 in fluid communication with the injection cylinder 21, and a pressure pipe 23 disposed at the end of the capillary tubes 22 away from the injection cylinder 21. A second valve 211 is provided on the pipe between the injection cylinder 21 and the stirring cylinder 12. After the second valve 211 is opened, the sealing agent in the stirring cylinder 12 can enter the injection cylinder 21. The injection cylinder 21 is also connected to a water tank 30 via a pipe, and a third valve 212 is provided on the pipe between the injection cylinder 21 and the water tank 30. After the third valve 212 is opened, the water in the injection cylinder 21 can be filtered and returned to the water tank 30 for use in the next experiment.

[0035] refer to Figure 2 As shown, in some embodiments, the capillary 22 is generally a tapered tube, with one end of the capillary 22 connected to the injection cylinder 21 as the first end and the other end connected to the pressure tube 23 as the second end. The inner diameter of the first end is larger than the inner diameter of the second end. Therefore, the sealing agent in the injection cylinder 21 can easily enter the interior of the capillary 22, thereby filling the capillary 22. In some embodiments, the inner diameter of the capillary is in the range of 0.5 mm to 2.0 mm.

[0036] A fourth valve 221 is also provided at the second end of the capillary tube 22. When the sealing agent in the injection cylinder 21 is filled into the capillary tube 22, the fourth valve 221 is in the closed state. After the sealing agent is completely filled, the fourth valve 221 is opened. By measuring the pressure in the injection cylinder 21 and the pressure pipe 23, it is determined whether the water in the injection cylinder 21 has passed through the capillary tube 22 into the pressure pipe 23 to balance the pressure in the injection cylinder 21 and the pressure pipe 23, thereby evaluating the sealing effect of the sealing agent of the predetermined grade.

[0037] Combination Figure 1As shown, in some embodiments, at least three capillary tubes 22 are connected in parallel to form a test group to simulate the branching of a fracture in an actual formation. In this embodiment, three test groups are connected in parallel between the injection cylinder 21 and the pressure pipe 23. These three test groups can simulate multiple fractures in the underground rock formation and also increase the number of connecting channels between the injection cylinder 21 and the pressure pipe 23, avoiding the influence of accidental factors on the experiment.

[0038] In some embodiments, the pressure pipe 23 is connected to the water tank 30, and a third pump body 231 is also provided between the pressure pipe 23 and the water tank 30. The third pump body 231 can pump water from the water tank 30 to the pressure pipe 23 and bring the pressure in the pressure pipe 23 to a set value, thereby simulating the distal pressure of an actual formation fracture. The set value can be determined based on data from the actual production and construction process on site.

[0039] In some embodiments, the test assembly 20 further includes a first pressure sensor 24 disposed within the injection cylinder 21 and a second pressure sensor 25 disposed within the pressure pipe 23. Both the first pressure sensor 24 and the second pressure sensor 25 are electrically connected to the computer 40. The first pressure sensor 24 detects the pressure within the injection cylinder 21 and transmits the pressure value to the computer 40. The second pressure sensor 25 detects the pressure in the pressure pipe 23 and transmits the pressure value to the computer 40. In some embodiments, the first pressure sensor 24 is installed at the end of the injection cylinder 21 that communicates with the stirring tank 12, and the first pressure sensor 24 detects that the pressure at the inlet end of the injection cylinder 21 has reached a predetermined value. This predetermined value is determined based on the injection pressure at the wellhead during actual production.

[0040] In some embodiments, a flow meter (not shown) electrically connected to a computer 40 is also provided between the fourth valve 221 and the pressure pipe 23. The flow meter is able to monitor the liquid flow within the capillary 22 throughout the test.

[0041] Recombined Figure 1As shown, the operation of the device for testing the sealing effect of a plugging agent provided by the present invention is as follows: The first pump body 112, the second pump body 121, and the third pump body 231 are turned on. Under the electrical drive of an external power source, the first pump body 112, the second pump body 121, and the third pump body 231 pump water from the water tank 30 into several storage tanks 11, a mixing cylinder 12, and a pressure pipe 23, respectively. When the pressure in the pressure pipe 23 rises to the set value, the third pump body 231 stops pumping water into the pressure pipe 23 and maintains the pressure value in the pressure pipe 23 at the set value. Due to the different opening degrees of the several first valves 113, several push plates 111 push the plugging materials of various particle sizes from the several storage tanks 11 into the mixing cylinder 12 according to a predetermined ratio. Under the electrical drive of an external power source, the motor 123 drives the stirring element 122 to rotate. Under the stirring action of the stirring element 122, the plugging materials of various particle sizes are mixed evenly in the water to form a plugging agent.

[0042] With the second valve 211 opened, water continues to be pumped into the mixing tank 12 by the second pump body 121. The sealing agent in the mixing tank 12 then enters the injection tank 21 and then the capillary tube 22. At the same time, sealing materials of various particle sizes in several storage tanks 11 are still pushed into the mixing tank 12 in a predetermined ratio to maintain the concentration of sealing material in the sealing agent.

[0043] When the first pressure sensor 24 detects that the pressure value in the injection cylinder 21 has reached a predetermined value, the first pump body 112 and the second pump body 121 stop pumping. The predetermined value is greater than the set value. After 12 to 15 minutes, the sealing agent fills each capillary tube 22. The fourth valve 221 is opened, connecting the injection cylinder 21 to the pressure tube 23 through the capillary tube 22. The flow meter monitors the water flow in the capillary tube 22 in real time. After 3 to 5 minutes, once the detection values ​​of the first pressure sensor 24 and the second pressure sensor 25 have stabilized, the pressure value in the injection cylinder 21 and the pressure value in the pressure tube 23 are compared. The greater the difference between the pressure value in the injection cylinder 21 and the pressure value in the pressure tube 23, the more it indicates that the water in the injection cylinder 21 has not entered the pressure tube 23 through the capillary tube 22, which means that the gradation level of the sealing agent in this test is good. If the pressure value in injection cylinder 21 is small or even equal to the pressure value in pressure pipe 23, it indicates that the water in injection cylinder 21 enters pressure pipe 23 through capillary tube 22, which means that the gradation grade of the sealing agent in this test is not good.

[0044] Based on the above-described apparatus, the present invention also provides a method for testing the sealing effect of a plugging agent, comprising the following steps.

[0045] In step S1, sealing materials of different particle sizes are added to water in a predetermined ratio and mixed evenly to prepare a sealing agent with a predetermined gradation level.

[0046] In practice, the first pump body 112 and the second pump body 121 pump water from the water tank 30 into several storage tanks 11 and a mixing cylinder 12, respectively. Due to the varying degrees of opening of the several first valves 113, several push plates 111 push the sealing materials of different particle sizes from the storage tanks 11 into the mixing cylinder 12 according to a predetermined ratio. Under the stirring action of the agitator 122, the sealing materials of different particle sizes are mixed evenly in the water to form a sealing agent.

[0047] In step S2, the sealing agent is filled into the capillary tube 22 through the injection cylinder 21, and the pressure inside the injection cylinder 21 is brought to a predetermined value. Simultaneously, the pressure in the pressure tube 23 is brought to a set value. The predetermined value is greater than the set value.

[0048] In practice, the second valve 211 is opened, and the second pump body 121 continues to pump water into the mixing tank 12. The sealing agent in the mixing tank 12 then enters the injection tank 21 and subsequently the capillary tube 22. Simultaneously, sealing materials of various particle sizes from the storage tanks 11 are still pushed into the mixing tank 12 in a predetermined ratio to maintain the concentration of the sealing material in the sealing agent. When the first pressure sensor 24 detects that the pressure in the injection tank 21 has reached a predetermined value, the first pump body 112 and the second pump body 121 stop pumping.

[0049] In step S3, after a period of time, the pressure value in the injection cylinder 21 is compared with the pressure value in the pressure pipe 23.

[0050] In the specific implementation, after 12 to 15 minutes, the sealing agent fills each capillary tube 22. The fourth valve 221 is opened, so that the injection cylinder 21 is connected to the pressure tube 23 through the capillary tube 22. After 3 to 5 minutes, after the detection values ​​of the first pressure sensor 24 and the second pressure sensor 25 stabilize, the pressure value changes in the injection cylinder 21 and the pressure tube 23 are compared.

[0051] In step S4, based on the comparison results in step S3, the sealing effect of the predetermined grade of plugging agent is determined.

[0052] In practice, if the pressure difference between the injection cylinder 21 and the pressure in the pressure tube 23 is within the range of 5 MPa to 10 MPa, it indicates that the water in the injection cylinder 21 did not enter the pressure tube 23 through the capillary tube 22, which means that the gradation of the sealing agent in this experiment is good. If the pressure difference between the injection cylinder 21 and the pressure in the pressure tube 23 is less than 5 MPa, or even equal, it indicates that the water in the injection cylinder 21 entered the pressure tube 23 through the capillary tube 22, and it is preliminarily judged that the gradation of the sealing agent in this experiment is poor.

[0053] In practice, testers can combine the data changes from each flow meter to comprehensively judge the sealing effect of the pre-defined gradation grade of the plugging agent. If the difference between the pressure value in injection cylinder 21 and the pressure value in pressure pipe 23 is less than 5 MPa, and at least three flow meters detect water in injection cylinder 21 entering pressure pipe 23 through capillary tube 22, it indicates that the gradation grade of the plugging agent in this group of experiments is poor. If the difference between the pressure value in injection cylinder 21 and the pressure value in pressure pipe 23 is less than 5 MPa, and at most two flow meters detect water in injection cylinder 21 entering pressure pipe 23 through capillary tube 22, it can be preliminarily judged that the gradation grade of the plugging agent in this group of experiments is good. Testers can consider repeating this group of experiments to avoid the influence of accidental factors on the test results.

[0054] In the description of this invention, 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; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] It should be understood that the terms "length", "width", "up", "down", "front and back", "left and right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., 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 the present invention and simplifying the description, and are not intended to 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 the present invention.

[0056] The above description, based on the preferred embodiments of the present invention, provides guidance. Those skilled in the art can make various changes and modifications without departing from the scope of the invention. The technical scope of this invention is not limited to the contents of the specification but must be determined according to the claims.

Claims

1. An apparatus for testing the sealing effect of a plugging agent, comprising a feeding assembly (10) for providing a plugging agent having a predetermined gradation grade, a testing assembly (20) connected to the feeding assembly (10), and a water tank (30) connected to the feeding assembly (10) and the testing assembly (20), the testing assembly (20) comprising an injection cylinder (21), a capillary tube (22) connected to the injection cylinder (21) and for containing the plugging agent, and a pressure tube (23) connected to the injection cylinder (21) through the capillary tube (22). in, A first pressure sensor (24) and a second pressure sensor (25) are respectively provided in the injection cylinder (21) and the pressure tube (23). The first pressure sensor (24) and the second pressure sensor (25) are configured to detect the pressure changes in the injection cylinder (21) and the pressure tube (23), respectively.

2. The apparatus for testing the sealing effect of a plugging agent according to claim 1, characterized in that, The feeding assembly (10) includes several storage tanks (11) for holding different particle sizes of plugging materials. The outlet and inlet ends of the several storage tanks (11) are respectively connected to the mixing tank (12) and the water tank (30).

3. The apparatus for testing the sealing effect of a plugging agent according to claim 2, characterized in that, A first pump body (112) is provided between the storage tank (11) and the water tank (30). The first pump body (112) is configured to pump water from the water tank (30) into the storage tank (11). The storage tank (11) is provided with a push plate (111) for pushing the sealing material into the mixing cylinder (12).

4. The apparatus for testing the sealing effect of a plugging agent according to claim 3, characterized in that, The inlet ends of the plurality of storage tanks (11) are respectively provided with a plurality of first valves (113), which are configured to be in different open states, so that plugging materials of different particle sizes enter the mixing tank (12) in a predetermined proportion.

5. The apparatus for testing the sealing effect of a plugging agent according to claim 3, characterized in that, The mixing cylinder (12) and the injection cylinder (21) are connected. A second pump body (121) is provided between the mixing cylinder (12) and the water tank (30). The second pump body (121) is configured to pump water from the water tank (30) into the mixing cylinder (12) so that the pressure in the injection cylinder (21) reaches a predetermined value.

6. The apparatus for testing the sealing effect of a plugging agent according to claim 2, characterized in that, The mixing tank (12) is equipped with a stirring element (122) driven by a motor (123), and the stirring element (122) is configured to mix sealing materials of different particle sizes evenly in water.

7. The apparatus for testing the sealing effect of a plugging agent according to any one of claims 1 to 6, characterized in that, The capillary tube (22) is a tapered tube, wherein the inner diameter of the first end of the capillary tube (22) connected to the injection cylinder (21) is greater than the inner diameter of the second end of the capillary tube (22) connected to the pressure tube (23).

8. The apparatus for testing the sealing effect of a plugging agent according to claim 7, characterized in that, The second end of the capillary tube (22) is provided with a fourth valve (221). When the sealing agent fills the capillary tube (22), the fourth valve (221) is in the open state.

9. The apparatus for testing the sealing effect of a plugging agent according to claim 1, characterized in that, A third pump body (231) is provided between the pressure pipe (23) and the water tank (30). The third pump body (231) is configured to pump water from the water tank (30) into the pressure pipe (23) so that the pressure in the pressure pipe (23) reaches a set value.

10. A method for testing the sealing effect of a sealing agent using the apparatus according to any one of claims 1 to 9, characterized in that, Includes the following steps, Step S1: Add sealing materials of different particle sizes to water in a predetermined ratio and mix evenly to prepare a sealing agent with a predetermined gradation grade. Step S2: The sealing agent is filled into the capillary tube through the injection cylinder, and then the pressure in the injection cylinder is made to reach a predetermined value, and the pressure in the pressure tube is made to reach a set value, wherein the predetermined value is greater than the set value; Step S3: After a period of time, compare the pressure changes in the injection cylinder and the pressure tube, and monitor the water flow in the capillary tube during this period; Step S4: Based on the comparison and monitoring results in Step S3, determine the sealing effect of the pre-graded plugging agent.

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