In-situ test experimental method and experimental device for creep deformation at periphery of shaft after blasting perforation

Abstract

The invention discloses a shaft periphery creep in-situ test experimental method and experimental device after blasting perforation, and the method specifically comprises the following steps: adopting a model body similar to a surrounding rock material, driving a perforating bullet with a strain gauge into the model body from a sieve tube in the radial direction, generating a perforation crack in the model body, and separating the strain gauge from the perforating bullet; injecting slurry with a certain pressure, and enabling the slurry to permeate into perforation cracks; the loading system is started, different stresses are applied to the model body according to experimental requirements, the strain gauge performs strain test on the interior of the model body, and data are transmitted to the control system through the transmission line. Under the condition that effective deformation of perforation cracks can be guaranteed in a stress loading experiment, creep deformation testing of a model body after blasting perforation and permeability increasing is achieved, then creep deformation parameters, especially long-term slow creep deformation changing along with time, of the periphery of a shaft after blasting perforation are obtained, and the problem that after in-situ perforation in a conventional experiment is carried out, the creep deformation of the model body is influenced is solved. And in-situ strain measurement cannot be carried out in the surrounding rock.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas development, and in particular to an in-situ testing experimental method and experimental device for creep around a wellbore after explosive perforation. Background Art

[0002] During shale gas extraction, reservoir fracturing is a common method. This involves artificially creating cracks in the formation to improve the flow environment of shale gas in the reservoir and provide efficient migration pathways. This technique can effectively increase the effective area of ​​the reservoir, improve its permeability, make underground oil more easily recoverable, and thus increase oil well production.

[0003] In the early stage of fracturing, the wellbore shale may still be stable, but as time goes by, the deformation of the shale gas wellbore will continue to extend under the action of creep, and the ground stress will gradually transfer to the wellbore casing, eventually causing the shale gas wellbore to collapse and become unstable. Therefore, before shale gas extraction, in-situ creep deformation testing experiments around the wellbore are important engineering experiments.

[0004] In-situ testing of creep deformation around wellbores can evaluate the creep properties of rock or soil surrounding the wellbore and measure its creep under long-term constant loads, providing a basis for wellbore stability analysis and maintenance design. Currently, conventional experimental systems rely primarily on strain gauges placed on the specimen surface to monitor strain, or on acoustic emission and microseismic detection of internal crack development in the specimen. These methods, respectively, are surface detection and indirect detection, but lack direct in-situ testing of the specimen interior.

[0005] The Chinese invention patent with publication number CN118442046A: A fracturing system and method for methane explosion fracturing physical model experiments, which discloses methane in-situ explosion fracturing technology and creates a three-dimensional fracture network; the Chinese invention patent with publication number CN105952422A: A perforating method and hydraulic fracturing experimental method for hydraulic fracturing experiments, the disclosed technology is to carry out targeted design and processing of perforating bullets 31 through numerical simulation and field tests, and to perform real perforation on rock samples used in hydraulic fracturing experiments, so as to smoothly carry out subsequent fracturing experiments; none of these proposes in-situ strain testing of the interior of rock samples (cement samples), especially the interior of the samples after explosion, that is, there are currently few in-situ tests on the creep deformation inside the surrounding rock after explosion, which cannot provide an effective basis for the design of wellbores. Summary of the Invention

[0006] The purpose of the present invention is to provide an experimental method for in-situ testing of creep around a wellbore after explosive perforation. While ensuring effective deformation of perforation fissures in stress loading experiments, the present invention can realize in-situ testing of creep deformation inside a model body after explosive perforation permeability enhancement, further obtain creep deformation parameters around the wellbore after explosive perforation, especially the long-term slow creep deformation that changes with time, and solve the problem that in-situ strain measurement in the surrounding rock cannot be performed after in-situ perforation in conventional experiments.

[0007] To achieve the above purpose, an in-situ test device for creep around a wellbore after explosive perforation is provided, which specifically includes the following steps:

[0008] S1: Use a model body with a material similar to the surrounding rock, drill a hole through the middle of the model body, and then insert the screen into the hole;

[0009] S2, the perforating bullet with the strain gauge is radially injected into the model body from the screen tube. Under the impact of the perforating bullet explosion, perforation cracks are generated inside the model body;

[0010] The strain gauge is separated from the perforating charge, and the transmission line connected to the tail end of the strain gauge is connected to the control system outside the model body;

[0011] S3, close the screen tube and reserve an exhaust hole, inject slurry with a certain pressure, and allow the slurry to penetrate into the perforation cracks. After the slurry solidifies, remove the slurry in the screen tube;

[0012] The loading system is started and different stresses are applied to the model body according to the experimental requirements. The strain gauge performs strain testing on the inside of the model body and transmits the data to the control system through the transmission line.

[0013] In some examples of the present invention, in step S2, the plate where the strain gauge is located is connected to the perforating bullet via a colloid;

[0014] When the perforating bullet carries the strain gauge into the model body, a solvent that dissolves the colloid is injected into the perforating crack to separate the strain gauge from the perforating bullet.

[0015] In some examples of the present invention, in step S2, the plate where the strain gauge is located is connected to the perforating charge via an electromagnet;

[0016] When the perforating bullet carries the strain gauge into the model body, the control system controls the electromagnet to lose power so that the plate and the perforating bullet are separated.

[0017] In some examples of the present invention, in step S1, a fitting equation is established between the time when the perforating charge is shot into the model body and the radial distance from the perforating charge to the borehole;

[0018] In step S2, a time value is set in the control system according to the fitting equation. When the time value is reached, the control system controls the electromagnet to separate the plate from the perforating charge, completing the prediction of the fixed strain gauge position.

[0019] In some examples of the present invention, in step S1, a plurality of model bodies of the same size and material are prepared, and a drill hole of the same position and size is set on each model body, and a corresponding screen tube is inserted;

[0020] In the same environment, multiple perforating bullets are fired into different model bodies, and the time t1…t2 from the launch of multiple perforating bullets to the inside of the model body is recorded. n , and the radial distance d1…d between the perforating bullet and the borehole n , take the average value of the time and the average value of the radial distance to establish the fitting equation.

[0021] In some examples of the present invention, in step S3, the slurry is a low-strength foam cement slurry, and the compressive strength of the foam cement slurry after solidification is one-third of the strength of the model body.

[0022] The present invention also aims to provide an in-situ test experimental device for creep around a wellbore after explosive perforation. By injecting perforating bullets into a model body, perforation cracks are generated in the model body, which can simulate the explosive permeability enhancement effect during actual shale mining. The strain gauge enters the model body along with the perforating bullets, and the loading system acts on the model body to realize the measurement of the creep deformation inside the model body after explosive permeability enhancement.

[0023] An experimental device matching an in-situ test method for creep around a wellbore after explosive perforation, comprising:

[0024] A model body, the peripheral device is provided with a loading system for applying different stresses thereon;

[0025] sieve tubes, located inside the model body;

[0026] Perforating components, including perforating bullets and strain gauges;

[0027] The perforating charge is fired from the screen tube into the model body, the strain gauge is fixed on the plate and the plate is connected to the perforating charge;

[0028] The transmission line of the strain gauge is led out to the outside and connected to the control system.

[0029] In some examples of the present invention, the plate is connected to the perforating charge via a colloid, and a conductor following the transmission line is provided on the plate;

[0030] The wire is provided with a guide port near the board;

[0031] The solvent used to dissolve the colloid enters from the wire and is discharged from the guide port.

[0032] In some examples of the present invention, the sticker is attached to the perforating charge by an electromagnet;

[0033] The control system includes a time sensing component;

[0034] The time sensing component senses a period of time after the perforating bullet is fired. After receiving the time signal, the control system controls the electromagnet to separate the plate from the perforating bullet.

[0035] Compared with the existing technology, the in-situ test experimental method and experimental device of creep around the wellbore after explosive perforation first shoots a perforating bullet into the model body, causing perforation cracks in the model body. This process can simulate the explosive permeability enhancement effect in actual shale mining. Then, the strain gauge enters the model body along with the perforating bullet, and the perforation cracks are sealed by slurry. The loading system acts on the model body, which can ensure that the perforation cracks are effectively deformed. In situ testing of creep deformation inside the model body after explosive perforation is achieved, and further creep deformation parameters around the wellbore after explosive perforation are obtained, especially the long-term slow creep deformation that changes with time. This solves the problem that in-situ strain measurement in the surrounding rock cannot be achieved after conventional in-situ perforation. Based on the above method, three-dimensional strain data at different directions and different depths from the hole wall inside the model body can be obtained through multiple perforating bullets, thereby providing direct data support for characterizing the three-dimensional creep characteristics of the model body, avoiding the inability to directly test the interior of the sample using conventional indirect acoustic and electrical methods and surface strain monitoring.

[0036] Under the same environment, a fitting equation is established between the time when the perforating charge enters the model body and the radial distance from the perforating charge to the borehole. According to the fitting equation, a time value is set in the control system. When the time value is reached, the control system controls the electromagnet to separate the plate from the perforating charge, thereby completing the strain test of the strain gauge at different positions in the model body. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a front view of the perforating bullet of the present invention being shot into the model body;

[0038] Figure 2 This is a front view of the strain gauge connected to the perforating bullet through the plate in the present invention;

[0039] Figure 3 It is a front view between the conductor and the transmission line in the present invention;

[0040] In the figure: 10, model body;

[0041] 20. Screen tube;

[0042] 30. Perforating component, 31. Perforating bullet, 32. Plate, 33. Strain gauge, 34. Wire assembly, 341. Wire, 342. Transmission line, 343. Guide port. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the technical solution of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of specific embodiments of the present invention. The same figure marks in the drawings represent the same parts. It should be noted that the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by persons of ordinary skill in the field to which the invention belongs. The words "first", "second" and similar terms used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "a" or "an" do not necessarily indicate a quantity limitation. Words such as "include" or "comprising" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0045] like Figure 1 、 Figure 2 As shown in the figure, this is an in-situ test device for creep around the wellbore after explosive perforation, including:

[0046] The model body 10 is externally provided with a loading system for applying different stresses thereon;

[0047] The screen tube 20 is located inside the model body 10;

[0048] The perforating component 30 includes a perforating charge 31 and a strain gauge 33;

[0049] The perforating charge 31 is fired from the screen tube 20 into the model body 10 , and the strain gauge 33 is fixed on the plate 32 , and the plate 32 is connected to the perforating charge 31 ;

[0050] The transmission line 342 of the strain gauge 33 is led out to the outside and connected to the control system;

[0051] When the perforating bullet 31 is fired into the model body 10 , the plate 32 can be separated from the perforating bullet 31 ;

[0052] Specifically, the model body 10 is made of the same material as the surrounding rock and has a square structure. The loading system is a triaxial loading test system, which is a physical property testing instrument widely used in the fields of mechanics and materials science. It can be a plurality of hydraulic cylinders for axial and circumferential pressure on the outside of the model body 10, and different stresses can be adjusted according to experimental requirements. This is an existing structure and will not be further elaborated.

[0053] In the shale gas extraction process, the perforating bullet 31 is a pyrotechnic product used to penetrate the casing and the formation during the perforating process. It can be fired by a perforator, that is, the perforating bullet 31 is installed on the perforator, and the detonating cord is led out and ignited. The perforating bullet 31 exerts a pulse load on the coal seam and the surrounding rock by jet fracturing the borehole wall, and at the same time penetrates the coal and rock mass around the borehole to form multiple radial hole cracks, which can communicate with the natural cracks in the coal seam and the surrounding rock, effectively improving the permeability of the coal and rock formation around the borehole. Since perforating experiments are difficult to conduct in shale wellbores, similar experiments are used to determine the stress changes of the coal seam before and after high-energy gas fracturing, and to examine the development of internal cracks and internal strain in the experiment. The perforating bullet 31 in this in-situ test experimental device can be improved on the actual product to meet the requirements of use in the test experiment. The strain gauge 33 is an element composed of a sensitive grid and the like for measuring strain, that is, measuring the strain around the wellbore after the explosive perforation permeability enhancement.

[0054] The control system may include processing components, analysis components, and control components, which are a general term for the peripheral components of the in-situ test experimental device. The data transmission line 342 of the strain gauge 33 is led out to the outside and connected to the control system. As explained, in order to prevent the transmission line 342 from affecting the perforating charge 31 after firing, the transmission line 342 may be wound on a rotating drum.

[0055] This in-situ test device for creep around the wellbore after explosive perforation first shoots a perforating bullet 31 into a model body 10, causing perforation cracks in the model body 10. This process can simulate the explosive permeability enhancement effect during actual shale mining. The strain gauge 33 enters the model body 10 along with the perforating bullet 31, and the loading system acts on the model body 10 to measure the creep deformation inside the model body 10 after explosive permeability enhancement.

[0056] like Figure 2 、 Figure 3 As shown, in some examples of the present invention, the plate 32 is connected to the perforating bullet 31 through a colloid, and a wire 341 following the transmission line 342 is provided on the plate 32;

[0057] The wire 341 is provided with a guide opening 343 near the mounting plate 32;

[0058] The solvent used to dissolve the colloid enters from the guide wire 341 and is discharged from the guide port 343;

[0059] Specifically, the plate 32 can be bonded to the perforating bullet 31 by epoxy resin colloid or other high-strength colloid. When the solvent contacts the colloid, the plate 32 and the perforating bullet 31 are separated.

[0060] A plate 32 is provided between the strain gauge 33 and the perforating charge 31 to prevent the strain gauge 33 from being damaged during the injection of the perforating charge 31. In particular, the strain gauge 33 is connected to the transmission line 342. That is, in this example, the wire 341 is connected to the plate 32 and plays a major role in bearing the force. When the perforating charge 31 is injected into the model body 10, the wire 341 will drive the transmission line 342 to be pulled.

[0061] The conductor 341 can be arranged side by side with the transmission line 342 to form a conductor assembly 34. In this case, the solvent used to dissolve the colloid is directly input from the conductor 341 and discharged from the guide port 343 close to the plate 32; or the conductor 341 is a hollow hose structure with a transmission line 342 inside. In this case, an annular channel is provided between the conductor 341 and the transmission line 342. The solvent used to dissolve the colloid is directly input from the annular channel and discharged from the guide port 343 close to the plate 32.

[0062] In some examples of the present invention, the sticking plate 32 is attached to the perforating bullet 31 by electromagnet adsorption;

[0063] The control system includes a time sensing component;

[0064] The time sensing element senses a period of time after the perforating bullet 31 is fired. After receiving the time signal, the control system controls the electromagnet to separate the sticking plate 32 from the perforating bullet 31.

[0065] Specifically, the electromagnet's wire 341 may be led out along with the transmission line 342;

[0066] The time sensing element starts timing with the firing of the perforating charge 31 as the initial time. When a certain time is reached, the control system receives the time signal and controls the electromagnet to lose power and separate from the perforating charge 31.

[0067] The present invention relates to an in-situ test device and method for creep around a wellbore after explosive perforation, which specifically comprises the following steps:

[0068] S1, using a model body 10 with a material similar to that of the surrounding rock, drilling a hole through the middle of the model body 10, and then inserting a screen tube 20 into the hole;

[0069] S2, placing a perforator in the screen tube 20 and radially driving a perforating charge 31 into the model body 10. The perforating charge 31 carries the strain gauge 33 into the model body 10. Under the impact of the explosion of the perforating charge 31, perforation cracks are generated in the model body 10.

[0070] The strain gauge 33 is separated from the perforating charge 31, and the transmission line 342 connected to the tail end of the strain gauge 33 is connected to the control system outside the model body 10;

[0071] S3, close the screen tube 20 and reserve an exhaust hole, inject low-strength foam cement slurry at a certain pressure, and allow the slurry to penetrate into the perforation cracks. After the slurry solidifies, remove the foam cement slurry in the screen tube 20;

[0072] The loading system is started, and different stresses are applied to the model body 10 according to the experimental requirements. The strain gauge 33 performs strain testing on the interior of the model body 10 and transmits the data to the control system via the transmission line 342;

[0073] Specifically, after the perforating bullet 31 is shot into the model body 10, perforation cracks are generated in the model body 10, and then low-strength foam cement slurry is injected into the perforation cracks;

[0074] Low-strength foamed cement can collapse and deform. Without affecting the perforation cracks, the low-strength foamed cement can solidify and bond the strain gauge 33 to the surrounding similar materials (model body 10). This can ensure the effective deformation of the perforation cracks during the stress loading experiment, so that the strain gauge 33 can be used to test the strain well, and further obtain the creep deformation parameters around the wellbore after explosive perforation, especially the long-term slow creep deformation that changes with time. This solves the problem of being unable to measure strain in situ in the surrounding rock after in-situ perforation in conventional experiments.

[0075] In addition, in step S2, multiple perforating charges 31 can be driven into the model body 10 from the screen tube 20 at different forces. That is, the multiple perforating charges 31 can obtain three-dimensional strain data at different positions and depths from the hole wall of the model body 10, thereby providing direct data support for characterizing the three-dimensional creep characteristics of the model body, avoiding the inability to directly test the interior of the sample using conventional indirect acoustic and electrical methods and surface strain monitoring.

[0076] In some examples of the present invention, in step S2, the plate 32 where the strain gauge 33 is located is connected to the perforating bullet 31 via colloid;

[0077] When the perforating bullet 31 carries the strain gauge 33 into the model body 10, the solvent enters the plate 32 from the wire 341 to dissolve the colloid, and the strain gauge 33 is separated from the perforating bullet 31.

[0078] In some examples of the present invention, in step S1, a fitting equation is established between the time when the perforating charge 31 is shot into the model body 10 and the radial distance from the perforating charge 31 to the borehole;

[0079] In step S2, a time value is set in the control system according to the fitting equation. When the time value is reached, the control system controls the electromagnet to separate the plate 32 from the perforating charge 31, completing the prediction of the position of the fixed strain gauge 33.

[0080] Furthermore, in step S1, a plurality of model bodies 10 of the same size and material are prepared, and a drill hole of the same position and size is set on each model body 10, and a corresponding screen tube 20 is inserted;

[0081] In the same environment, multiple perforating bullets 31 are fired into different model bodies 10, and the time t1...t2 from the firing of the multiple perforating bullets 31 to the interior of the model body 10 is recorded. n , and the radial distance d1...d between the perforating bullet 31 and the borehole n , take the average value of the time and the average value of the radial distance, and establish a fitting equation for time and distance;

[0082] Specifically, in step S2, a time value is set in the control system. Specifically, the time value is within a range from zero to an average value. Starting from the time value when the perforating charge 31 is fired, the control system controls the electromagnet to separate the plate 32 from the perforating charge 31. At this time, the position of the strain gauge 33 is predicted and determined based on the linear fitting equation.

[0083] Before the experiment begins, a fitting equation for the launch time and distance of the perforating charge 31 is established under the same environment. This fitting equation can be a linear fitting equation. During the experiment, that is, in step S2, the linear fitting equation can be used to set time as a variable to predict the position where the strain gauge 33 separates from the perforating charge 31, thereby completing the strain test of the strain gauge 33 at different positions in the model body 10.

[0084] In some examples of the present invention, the compressive strength of the foamed cement slurry after solidification is one third of the strength of the model body 10 .

[0085] The above describes in detail an exemplary implementation of an experimental device for in-situ testing creep around a wellbore after explosive perforation proposed in the present invention with reference to a preferred embodiment. However, it will be understood by those skilled in the art that, without departing from the concept of the present invention, various modifications and variations can be made to the above-mentioned specific embodiments, and various technical features and structures proposed in the present invention can be combined in various ways without exceeding the scope of protection of the present invention, which is determined by the appended claims.

Claims

1. An in-situ test method for creep around the wellbore after explosive perforation, characterized in that: The specific steps include: S1, using a model body (10) with a material similar to that of the surrounding rock, drilling a through hole in the middle of the model body (10), and then inserting a screen tube (20) into the drill hole; S2, the perforating bullet (31) carrying the strain gauge (33) is radially driven into the model body (10) from the screen tube (20), and under the impact of the explosion of the perforating bullet (31), perforating cracks are generated in the model body (10); The strain gauge (33) is separated from the perforating bullet (31), and the transmission line (342) connected to the tail end of the strain gauge (33) is connected to the control system outside the model body (10); S3, closing the screen tube (20) and leaving an exhaust hole, injecting slurry at a certain pressure, allowing the slurry to penetrate into the perforation cracks, and after the slurry solidifies, clearing the slurry in the screen tube (20); The loading system is started, and different stresses are applied to the model body (10) according to the experimental requirements. The strain gauge (33) performs strain testing on the inside of the model body (10), and transmits the data to the control system through the transmission line (342).

2. The in-situ test method for creep around the wellbore after explosive perforation according to claim 1 is characterized in that: In step S2, the plate (32) where the strain gauge (33) is located is connected to the perforating bullet (31) through colloid; After the perforating bullet (31) carries the strain gauge (33) into the model body (10), a solvent for dissolving the colloid is injected into the perforating cracks to separate the strain gauge (33) from the perforating bullet (31).

3. The in-situ test method for creep around the wellbore after explosive perforation according to claim 1 is characterized in that: In step S2, the plate (32) where the strain gauge (33) is located is connected to the perforating bullet (31) via an electromagnet; When the perforating bullet (31) carrying the strain gauge (33) enters the interior of the model body (10), the control system controls the electromagnet to lose power so that the sticking plate (32) is separated from the perforating bullet (31).

4. The in-situ test method for creep around the wellbore after explosive perforation according to claim 3 is characterized in that: In step S1, a fitting equation is established between the time when the perforating bullet (31) is shot into the model body (10) and the radial distance from the perforating bullet (31) to the borehole; In step S2, a time value is set in the control system according to the fitting equation. When the time value is reached, the control system controls the electromagnet to separate the sticking plate (32) from the perforating bullet (31), thereby completing the prediction of the position of the fixed strain gauge (33).

5. The in-situ test method for creep around the wellbore after explosive perforation according to claim 4 is characterized in that: In step S1, a plurality of model bodies (10) of the same size and material are prepared, and a drill hole of the same position and size is set on each model body (10), and a corresponding screen tube (20) is inserted; In the same environment, multiple perforating bullets (31) are fired into different model bodies (10), and the time t1...t2 from the firing of the multiple perforating bullets (31) to the inside of the model body (10) is recorded. n , and the radial distance d1...d between the perforating bullet (31) and the borehole n , take the average value of the time and the average value of the radial distance to establish the fitting equation.

6. The in-situ test method for creep around the wellbore after explosive perforation according to any one of claims 1 to 5, characterized in that: In step S3, the slurry is a low-strength foam cement slurry, and the compressive strength of the foam cement slurry after solidification is one third of the strength of the model body (10).

7. An experimental device matching the in-situ test method for creep around the wellbore after explosive perforation as claimed in claim 1, characterized in that: include: A model body (10) is provided with a loading system for applying different stresses thereon; A screen tube (20) is located inside the model body (10); A perforating component (30) having a perforating bullet (31) and a strain gauge (33); A perforating bullet (31) is fired from a screen tube (20) into the interior of a model body (10), a strain gauge (33) is fixed on a plate (32), and the plate (32) is connected to the perforating bullet (31); The transmission line (342) of the strain gauge (33) is led out to the outside and connected to the control system.

8. The in-situ test device for creep around the wellbore after explosive perforation according to claim 7 is characterized in that: The plate (32) is connected to the perforating bullet (31) via a colloid, and a conductor (341) following the transmission line (342) is provided on the plate (32); The wire (341) is provided with a guide opening (343) near the pasting plate (32); The solvent used to dissolve the colloid enters from the guide wire (341) and is discharged from the guide port (343).

9. The in-situ test device for creep around the wellbore after explosive perforation according to claim 7 is characterized in that: The sticking plate (32) is adsorbed and connected to the perforating bullet (31) by an electromagnet; The control system includes a time sensing component; The time sensing component senses a period of time after the perforating bullet (31) is fired, and after receiving the time signal, the control system controls the electromagnet to separate the sticking plate (32) from the perforating bullet (31).

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