A method for evaluating the effect of drilling plugging on a simulated wellbore-formation group system fracture

Abstract

The application discloses a kind of simulation wellbore-ground formation group system fracture drilling plugging effect evaluation method, comprising: one, preparation plugging slurry;Two, to the wellbore group system fracture simulation device wellbore continuous pumping plugging slurry, after in place, again intermittent squeeze injection;Three, when the plugging slurry of any lateral visible simulation fracture entrance at the lower end of wellbore no longer flows in, at this time, the lateral visible simulation fracture is regarded as door, record door time and plugging slurry door risk is evaluated;When bridge appears in lateral visible simulation fracture, it is regarded as plugging slurry bridge success, record bridge area appearance time, bridge area duration, bridge area area ratio and the area ratio of fracture flat in lateral visible simulation fracture, and according to the data recorded, the plugging efficiency, plugging strength and plugging efficiency of plugging slurry are evaluated.The application considers wellbore squeeze door risk, group system fracture overall plugging effect and the influence of pumping mode on drilling plugging effect, can obtain more accurate evaluation result.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid loss control technology, specifically to a method for evaluating the effectiveness of drilling plugging in simulating wellbore-formation fractures. Background Technology

[0002] Mine leakage plugging is a complex process in which plugging slurry flows from the wellbore into the fractures. Due to the high degree of fracturing in fractured formations, the leakage-causing fractures connected to the wellbore usually exist in a series. However, existing methods for evaluating the effectiveness of drilling leakage plugging mainly use hydraulic or pneumatic pressurization to seal single fractures, with pressure bearing capacity and leakage rate as the main evaluation indicators. These methods neglect the impact of sealing the fracture inlet on the plugging effect and cannot simulate the variable discharge / pump pressure mode in the mine, resulting in insufficient bias in the evaluation of the plugging effect and consequently, low evaluation accuracy.

[0003] In addition, the following related technologies have been proposed in the existing technology for evaluating the effectiveness of leak sealing:

[0004] For example, patent document CN113640473A discloses an experimental device and method for testing the plugging capacity of drilling and fracturing. It includes an injection system, a simulation system, a temperature control system, a leakage system, a metering system, and a data acquisition system. It can collect parameters such as pressure, temperature, and flow rate in real time and process the data. This technology can test parameters such as pressure, temperature, and flow rate, integrating multiple high-temperature and high-pressure testing functions. It can conduct various performance evaluation experiments of temporary plugging agents under high-temperature and high-pressure dynamic conditions, and can also select experimental modules according to the characteristics of downhole leakage formations. However, this technology is still a conventional plugging capacity testing device; all experimental modules are fixed-width or aperture modules, and it cannot simulate the dynamic changes of real fractures.

[0005] For example, patent document CN114198084A discloses a simulation and evaluation device and method for plugging leaks in fractured formations. It sets up two visualization windows in the crack plugging area to more realistically simulate actual plugging construction conditions and can quantitatively evaluate the degree of mixing between the plugging material and formation fluids, as well as the retention performance of the plugging material in the leak layer. However, this technology cannot simulate high-temperature and high-pressure formation environments, nor can it conduct normal closure pressure and reverse pressure tests; furthermore, it cannot control crack width changes. Therefore, it is clear that it cannot provide accurate and reliable evaluation.

[0006] For example, patent document CN217055137U discloses a consolidation and plugging simulation evaluation device. This device can simulate consolidation and plugging construction under temperature, pressure, and fluid action, and evaluate the retention performance of the plugging slurry. However, the leakage layer simulation chamber of this device is a fixed module, without a crack width or pore size control system. It cannot achieve self-adjustment of crack or pore size width, nor can it conduct closed normal bearing pressure tests.

[0007] In summary, existing methods for evaluating the effectiveness of well plugging have the following shortcomings:

[0008] 1. Existing indoor leak prevention and plugging effect evaluation devices usually use constant pressure or constant flow to pump plugging slurry, which cannot simulate the real-time variable discharge squeezing process in the mine.

[0009] 2. Existing leak prevention and plugging effect evaluation devices usually connect the vessel body directly to the fracture module, ignoring the fact that the actual connection between the fracture and the wellbore is a narrow, converging orifice, resulting in significant differences in evaluation effects.

[0010] 3. Existing technologies using a single crack module cannot simulate the working conditions where cracks exist in a systemic form, resulting in low accuracy of evaluation results.

[0011] 4. Existing technologies that use pressure-bearing capacity and leakage as the main indicators have biases in performance evaluation.

[0012] Therefore, there is an urgent need for a convenient, reliable, and realistic method for evaluating the effectiveness of well plugging in the formation of fractures. Summary of the Invention

[0013] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a method for evaluating the drilling plugging effect of simulating wellbore-formation fractures. This invention considers the risks of wellbore injection and sealing, the overall plugging effect of the formation fractures, and the impact of pumping methods on the drilling plugging effect. Based on indoor experiments, it can form a set of evaluation indicators that are more in line with field plugging construction, thereby obtaining more accurate evaluation results. This is of great significance for controlling drilling fluid loss during drilling of fractured oil and gas reservoirs.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] A method for evaluating the effectiveness of drilling plugging in simulating wellbore-formation fractures, characterized by the following steps:

[0016] Step 1: Prepare the sealing grout using a grout mixing system;

[0017] Step 2: Adjust the pumping system's delivery rate according to the leakage plugging construction discharge rate of the mine to be simulated, and then control the pumping system to continuously pump the leakage plugging slurry into the wellbore of the wellbore system fracture simulation device. After the leakage plugging slurry is pumped into place, intermittent injection is carried out. The wellbore system fracture simulation device includes a wellbore, and at least two transverse visible simulated fractures are connected to the lower end of the wellbore. The other end of each transverse visible simulated fracture is connected to a manifold.

[0018] Step 3: When the plugging slurry no longer flows into the inlet of any transverse visual simulated fracture at the lower end of the wellbore, the transverse visual simulated fracture is considered as a sealed-off area. The sealing time is recorded, and the sealing slurry sealing risk is evaluated based on the sealing time.

[0019] When bridging occurs within the transversely visible simulated crack, the grouting is considered to have successfully bridged the crack. The time of bridging appearance, duration of bridging, and ratio of the bridging area to the area of ​​the crack plate in the transversely visible simulated crack are recorded. Based on the recorded data, the sealing efficiency, sealing strength, and sealing effectiveness of the grout are evaluated.

[0020] In step two, the intermittent squeezing and plugging slurry is injected by starting the pump for 5 minutes and then stopping it for 5 minutes, for a total of 30 minutes. The pump discharge rate of the intermittent squeezing is adjusted according to the intermittent squeezing discharge rate of the mine to be simulated, and can be less than, equal to or higher than the conveying discharge rate.

[0021] In step three, the risk assessment of sealing off includes two indicators: sealing efficiency and sealing degree. The calculation methods are as follows:

[0022] Door sealing efficiency: β 封门 =t 封门 / t 总 , where t 封门 The time it takes for the crack entrance to seal off, s; t 总 The total experimental time is in seconds.

[0023] Door sealing level: λ 封门 =h 封门 / h f , where h 封门 The height of the sealed entrance to the crack, in cm; h f This represents the total crack height.

[0024] In step three, the calculation methods for sealing efficiency and sealing strength are as follows:

[0025] Blocking efficiency: β 封堵 =t 架桥 / t 总 , where t 架桥 The time it takes for a bridging structure to form within the crack is s; t 总 The total experimental time is in seconds.

[0026] Sealing strength: λ 封堵 =A 30s / A t , where A 30s The area of ​​the sealing zone 30 seconds after the start of bridging within the crack, expressed in cm². 2 A t The area of ​​the sealing zone within the crack at the end of the experiment, in cm². 2 .

[0027] The transverse visual simulated crack includes a frame, two crack plates and two crack width adjustment plates. The two crack width adjustment plates are sealed and fixed to the upper and lower parts of the two crack plates, respectively. The crack plates are enclosed by the crack width adjustment plates to form a crack channel. The frame is detachably clamped and fixed to both ends of the crack plates. The transverse visual simulated crack is connected to the wellbore and the manifold through the frame.

[0028] The crack plate is made of transparent PVC material, and the thickness of the crack width adjustment plate is 1-10mm.

[0029] The widths of the crack channels in each of the transversely visible simulated cracks may be the same or different.

[0030] The wellbore is provided with a viewing window and a scale parallel to the viewing window along the longitudinal direction.

[0031] The manifold is vertically connected to the end of the horizontally visible simulated crack. The lower and upper ends of the manifold are respectively connected to a first valve and a second valve, and the upper end of the manifold is connected to the collection tank via the second valve and a pipeline.

[0032] The pumping system includes a screw pump and a switch valve fixed at the outlet end of the screw pump.

[0033] Pressure measuring points are provided on the transverse visual simulated crack, and pressure sensors are installed in the pressure measuring points.

[0034] A first flow meter is installed between the pumping system and the wellbore, and a second flow meter is installed at the upper end of the manifold.

[0035] The advantages of using this invention are:

[0036] 1. Compared with existing drilling plugging effect evaluation methods, the present invention can simulate different numbers of fractures connected to the wellbore, and can realize the overall plugging effect evaluation of the fracture system.

[0037] 2. This invention takes into account the risk of sealing the entrance of the fracture during the process of injecting the plugging slurry from the wellbore into the fracture, which helps to further improve the accuracy of the evaluation results.

[0038] 3. This invention uses a screw pump to achieve variable displacement and pumping, which is closer to the actual leak-stopping construction conditions compared with the existing leak prevention and plugging effect evaluation device using hydraulic or pneumatic loading.

[0039] 4. This invention proposes an evaluation index that comprehensively considers sealing risk, sealing efficiency, and sealing strength, thus solving the problem of evaluation effect deviation that exists when pressure bearing capacity and leakage are the main evaluation indicators.

[0040] 5. This invention takes into account the actual working conditions of mine plugging construction and can form a set of evaluation indicators that are more in line with mine plugging construction based on indoor experiments. It has the advantages of accurate and reliable evaluation and has high practical and promotional value in the field of evaluation of oil and gas drilling fluid leakage control effect. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the front view structure of the present invention (I);

[0042] Figure 2 This is a three-dimensional structural diagram of the present invention;

[0043] Figure 3 This is a top view schematic diagram of the structure of the present invention;

[0044] Figure 4 This is a schematic diagram (II) of the main view plane structure of the present invention;

[0045] Figure 5 for Figure 4 A schematic diagram of the right-side view structure;

[0046] Figure 6 for Figure 4 Cross-sectional view at point A in the middle;

[0047] Figure 7 This is a schematic diagram of the transversely visible simulated crack structure in this invention;

[0048] Figure 8 This is a diagram showing the sealing status of grouped cracks in Example 1 after 30 minutes;

[0049] Figure 9 This is a pressure change curve of a group of cracks during the sealing process in Example 1;

[0050] Figure 10 This is a graph showing the leakage rate variation of a group of cracks during the sealing process in Example 1;

[0051] Figure 11 This is a diagram showing the sealing status of grouped cracks at 30 minutes in Example 2;

[0052] Figure 12 This is a distribution diagram of the bridging zone at the tail of a 3mm cracked flat plate in Example 2 at 30 min 20 s.

[0053] Figure 13 This is a pressure change curve of a group of cracks during the sealing process in Example 2;

[0054] Figure 14 This is a graph showing the leakage rate variation of a group of cracks during the sealing process in Example 2;

[0055] Figure 15This is a diagram showing the sealing status of grouped cracks in Example 3 after 30 minutes;

[0056] Figure 16 This is a distribution diagram of the area below the exit of the (2&3)-3mm crack plate in Example 3;

[0057] Figure 17 This is a distribution diagram of the area above the exit of the (2&3)-3mm crack plate in Example 3;

[0058] Figure 18 This is a distribution diagram of the exit of the (2&3)-2mm crack plate in Example 3;

[0059] Figure 19 This is a pressure change curve of a group of cracks during the sealing process in Example 3;

[0060] Figure 20 This is a graph showing the leakage rate change of a group of cracks during the sealing process in Example 3.

[0061] The diagram is marked as follows:

[0062] 1. Slurry mixing system; 2. Pumping system; 3. First flow meter; 4. Well shaft; 5. Lateral visual simulated fracture; 6. Manifold; 7. First valve; 8. Second valve; 9. Second flow meter; 10. Pressure sensor; 11. Collection tank; 41. Scale; 51. Fracture plate; 52. Fracture width adjustment plate; 53. Fracture channel; 54. Frame. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this application clearer, the present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of this application.

[0064] In this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0065] The terms "first" and "second," etc., used in the specification and claims of this invention are used to distinguish different objects, not to describe a specific order of objects. For example, "first target object" and "second target object," etc., are used to distinguish different target objects, not to describe a specific order of target objects.

[0066] In this invention, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0067] This invention provides a method for evaluating the effectiveness of drilling plugging in simulating wellbore-formation fractures. The method involves a slurry preparation system 1, a pumping system 2, a wellbore fracture simulation device, and a control and monitoring module, such as... Figure 1-6 As shown, the structure, position, and connection relationships of each component are as follows:

[0068] The grout preparation system 1 includes a preparation container and a stirrer located inside the preparation container, used to prepare the sealing grout. Specifically, it can prepare sealing grout of 10% WNDK-2, sealing grout of 10% LCM-2, sealing grout of 10% WNHTK-fine, etc., as needed.

[0069] Pumping system 2 includes a screw pump connected to the configuration container and a switch valve fixed at the outlet end of the screw pump for conveying the plugging slurry.

[0070] The wellbore system fracture simulation device includes a vertically arranged wellbore 4. The wellbore 4 has a viewing window and a scale 41 parallel to the viewing window along its longitudinal direction. The upper end of the wellbore 4 is connected to a screw pump in a pumping system 2, and the lower end of the wellbore 4 is connected to at least two transversely visible simulated fractures 5. The specific number of transversely visible simulated fractures 5 can be set according to actual needs. The other end of each transversely visible simulated fracture 5 is connected to a manifold 6, which is vertically connected to the end of the transversely visible simulated fracture 5. The lower and upper ends of the manifold 6 are respectively connected to a first valve 7 and a second valve 8, and the upper end of the manifold 6 is connected to a collection tank 11 via the second valve 8 and a pipeline. This invention, through the wellbore system fracture simulation device, can more realistically simulate the actual working conditions of mine plugging construction, thereby obtaining more accurate evaluation results.

[0071] It should be noted that the collection tank 11 in this invention can be set up separately, but in practical applications it can also be set up as follows: Figure 4 , 5 As shown, the configuration container is used as the collection tank 11, so there is no need to set up a separate collection tank 11. The plugging slurry after the experiment will eventually flow into the configuration container, which also helps to reduce the amount of plugging slurry used.

[0072] Furthermore, such as Figure 7As shown, the transverse visual simulated crack 5 includes a frame 54, crack plates 51, and crack width adjustment plates 52. The crack plates 51 are preferably made of transparent PVC material. The gap width between two crack plates 51 is 1–10 mm, controlled by crack width adjustment plates 52 of varying thicknesses (1–10 mm). There are two crack plates 51 and two crack width adjustment plates 52. The two crack width adjustment plates 52 are respectively sealed and fixed to the upper and lower parts of the two crack plates 51. The two crack plates 51, through the two crack width adjustment plates 52, can enclose a crack channel 53 for the sealing slurry to pass through. The frame 54 is detachably clamped and fixed to both ends of the crack plates 51. Each transverse visual simulated crack 5 is connected to the wellbore 4 and the manifold 6 through the frame 54. Furthermore, during experiments, the width of the crack channel 53 in each transverse visual simulated crack 5 can be set to be the same or different, depending on actual needs.

[0073] The control and monitoring module includes pressure sensors 10, a first flow meter 3, and a second flow meter 9. The number of pressure sensors 10 is the same as the number of transverse visual simulated cracks 5. Each transverse visual simulated crack 5 has a pressure measuring point, and each pressure sensor 10 is installed within a pressure measuring point. The first flow meter 3 is installed between the pumping system 2 and the wellbore 4. The number of second flow meters 9 is the same as the number of manifolds 6, and each second flow meter 9 is installed at the upper end of each manifold 6. This invention, through the pressure sensors 10 and flow meters, can monitor the pressure and flow rate of the plugging slurry in real time during the experiment and adjust accordingly, thereby further improving the accuracy of the evaluation results.

[0074] Based on the above, the drilling plugging effect evaluation method of the present invention includes the following steps:

[0075] Step 1: Prepare the sealing grout using grout mixing system 1.

[0076] Step 2: Adjust the pumping capacity of pumping system 2 according to the leakage plugging construction discharge rate of the simulated mine. Then, control pumping system 2 to continuously pump leakage plugging slurry into the wellbore 4 of the wellbore fracture simulation device. After the leakage plugging slurry is pumped into place, intermittent injection is performed. The intermittent injection method is to start the pump for 5 minutes and then stop the pump for 5 minutes, accumulating 30 minutes of operation. In addition, the pump discharge rate of intermittent injection is adjusted according to the intermittent injection discharge rate of the simulated mine, and can be less than, equal to, or higher than the delivery discharge rate.

[0077] Step 3: When the plugging slurry at the inlet of any transverse visual simulated fracture 5 at the lower end of the wellbore 4 no longer flows in, the transverse visual simulated fracture 5 is considered as a sealed door. The sealing time is recorded, and the risk of the plugging slurry sealing the transverse visual simulated fracture 5 is evaluated based on the sealing time.

[0078] When bridging occurs within the transversely visible simulated crack 5, the grouting is considered to have successfully bridged the crack. The time of bridging appearance, duration of bridging, and area ratio of the bridging area to the area of ​​the crack plate 51 in the transversely visible simulated crack 5 are recorded. Based on the recorded data, the sealing efficiency, sealing strength, and sealing effectiveness of the grout are evaluated.

[0079] Specifically, the risk assessment of door sealing in this step includes two indicators: door sealing efficiency and door sealing degree, and their calculation methods are as follows:

[0080] Door sealing efficiency: β 封门 =t 封门 / t 总 , where t 封门 The time it takes for the crack entrance to seal off, s; t 总 The total experimental time is in seconds.

[0081] Door sealing level: λ 封门 =h 封门 / h f , where h 封门 The height of the sealed entrance to the crack, in cm; h f This represents the total crack height.

[0082] In addition, the calculation methods for blocking efficiency and blocking strength are as follows:

[0083] Blocking efficiency: β 封堵 =t 架桥 / t 总 , where t 架桥 The time it takes for a bridging structure to form within the crack is s; t 总 The total experimental time is in seconds.

[0084] Sealing strength: λ 封堵 =A 30s / A t , where A 30s The area of ​​the sealing zone 30 seconds after the start of bridging within the crack, expressed in cm². 2 A t The area of ​​the sealing zone within the crack at the end of the experiment, in cm². 2 .

[0085] Step 4: End the experiment after evaluation.

[0086] To verify the accuracy of this invention, this invention uses... Figure 1 The invention will be further explained by referring to two horizontally visible simulated cracks 5 in the middle and left sides, in conjunction with specific embodiments.

[0087] Example 1

[0088] In this embodiment, the crack channel widths of the simulated transverse cracks on the left and right sides are 1 mm and 4 mm, respectively, and the plugging grout is 10% WNDK-2. Its evaluation test is as follows: Figures 8 to 10 As shown, 10% WNDK-2 plugging grout poses no risk of sealing the cracks within 1-4mm grouped cracks, but has no sealing capability.

[0089] Example 2

[0090] In this embodiment, the crack channel widths of the simulated transverse cracks on the left and right sides are 2mm and 3mm, respectively, and the plugging grout is 10% LCM-2. Its evaluation test is as follows: Figures 11 to 14 As shown, 10% LCM-2 forms an effective bridge within 2&3mm grouped cracks (10% LCM-2 can determine bridging in 2&3mm grouped cracks), with a bridging time of 3min20s and a bridging duration of 26min40s. It has high sealing stability, with no gate-closing phenomenon and no risk of gate-closing.

[0091] Example 3

[0092] In this embodiment, the crack channel widths of the left-side transverse visual simulated crack and the right-side transverse visual simulated crack are 2mm and 3mm, respectively. The plugging grout is 10% WNHTK-fine, and its evaluation test is as follows. Figures 15 to 20 As shown, 10% WNTHK-fine exhibited effective bridging in both 2mm and 3mm grouped cracks. The bridging time in the 2mm crack was 7 min 23 s, with a duration of 10 min 12 s, while the bridging time in the 3mm crack was 5 min 36 s, with a duration of 24 min 24 s. 10% WNHTK-fine showed 90% sealing at the entrance of the 2mm crack, indicating a high risk of sealing, while 10% sealing occurred at the entrance of the 3mm crack, indicating a lower risk of sealing.

[0093] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any changes made based on the design principles of the present invention, or any non-creative modifications made thereon, shall fall within the scope of protection of the present invention.

Claims

1. A method for evaluating the effectiveness of drilling plugging in simulating wellbore-formation fractures, characterized in that... Includes the following steps: Step 1: Prepare the sealing grout using a grout mixing system (1); Step 2: Adjust the pumping capacity of the pumping system (2) according to the leakage discharge of the mine to be simulated, and then control the pumping system (2) to continuously pump the leakage slurry into the wellbore (4) of the wellbore system fracture simulation device. After the leakage slurry is pumped into place, intermittent injection is carried out. The wellbore system fracture simulation device includes a wellbore (4), and the lower end of the wellbore (4) is connected to at least two transverse visible simulated fractures (5). The other end of each transverse visible simulated fracture (5) is connected to a manifold (6). Step 3: When the plugging slurry no longer flows into the inlet of any transverse visible simulated crack (5) at the lower end of the wellbore (4), the transverse visible simulated crack (5) is regarded as a gate, the gate sealing time is recorded, and the gate sealing risk is evaluated based on the gate sealing efficiency and gate sealing degree. When bridging occurs within the transversely visible simulated crack (5), it is considered that the bridging grout has been successfully bridging. The time of bridging appearance, duration of bridging, area of ​​bridging and area ratio of crack plate (51) in transversely visible simulated crack (5) are recorded. The sealing efficiency, sealing strength and sealing effectiveness of the grout are evaluated based on the recorded data. In step three, the calculation methods for sealing efficiency and sealing degree are as follows: Door sealing efficiency: ,in The time, in seconds, is the time it takes for the crack entrance to seal off. The total experimental time is in seconds. Level of sealing: ,in The height of the sealed entrance to the crack, in cm; This represents the total crack height.

2. The method for evaluating the drilling plugging effect of simulated wellbore-formation fractures according to claim 1, characterized in that: In step two, the intermittent injection of plugging slurry is carried out by starting the pump for 5 minutes and then stopping it for 5 minutes, for a total of 30 minutes. The pump discharge rate of the intermittent injection is adjusted according to the intermittent injection discharge rate of the mine to be simulated.

3. The method for evaluating the drilling plugging effect of simulated wellbore-formation fractures according to claim 1 or 2, characterized in that: In step three, the calculation methods for sealing efficiency and sealing strength are as follows: Blocking efficiency: ,in The time, in seconds, for the bridging to occur within the crack; The total experimental time is in seconds. Sealing strength: ,in, The area of ​​the sealing zone 30 seconds after the start of bridging within the crack, expressed in cm². 2 ; The area of ​​the sealing zone within the crack at the end of the experiment, in cm². 2 .

4. The method for evaluating the drilling plugging effect of simulated wellbore-formation fractures according to claim 1, characterized in that: The transverse visual simulated crack (5) includes a frame (54), two crack plates (51) and two crack width adjustment plates (52). The two crack width adjustment plates (52) are respectively sealed and fixed on the upper and lower parts of the two crack plates (51). The crack plates (51) are enclosed by the crack width adjustment plates (52) to form a crack channel (53). The frame (54) is detachably clamped and fixed at both ends of the crack plates (51). The transverse visual simulated crack (5) is connected to the wellbore (4) and the manifold (6) through the frame (54).

5. The method for evaluating the drilling plugging effect of simulated wellbore-formation fractures according to claim 4, characterized in that: The crack plate (51) is made of transparent PVC material, and the crack width adjustment plate (52) has a thickness of 1~10mm.

6. The method for evaluating the drilling plugging effect of simulated wellbore-formation fractures according to claim 1, characterized in that: The widths of the crack channels (53) in each of the transverse visual simulated cracks (5) are the same or different.

7. The method for evaluating the drilling plugging effect of simulating wellbore-formation fractures according to claim 1, characterized in that: The manifold (6) is vertically connected to the end of the horizontally visible simulated crack (5). The lower end and the upper end of the manifold (6) are respectively connected to the first valve (7) and the second valve (8), and the upper end of the manifold (6) is connected to the collection tank (11) through the second valve (8) and the pipeline.

8. The method for evaluating the drilling plugging effect of simulated wellbore-formation fractures according to claim 1, characterized in that: Pressure measuring points are provided on the transverse visual simulated crack (5), and pressure sensors (10) are provided in the pressure measuring points.

9. The method for evaluating the drilling plugging effect of simulated wellbore-formation fractures according to claim 1, characterized in that: A first flow meter (3) is provided between the pumping system (2) and the wellbore (4), and a second flow meter (9) is provided at the upper end of the manifold (6).

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