Slug design method for improving dilution resistance of profile control and plugging agent in cracks

Abstract

The invention provides a slug design method for improving the dilution resistance of a plugging agent in a crack, and belongs to the field of oilfield chemistry in a tertiary oil recovery technology. A slug design method for improving the anti-dilution capacity of a plugging agent in a crack mainly tests the anti-dilution capacity of the plugging agent in the crack in different slug combinations by regulating and controlling the viscosity of a front slug, the viscosity of the plugging agent and the viscosity of a rear slug, so that the optimal slug combination design is optimized. Experimental results show that the viscosity relation among the front slug, the profile control agent and the rear slug meets the following conditions: the viscosity of the front slug is gt; the viscosity of the plugging agent is gt; and when the viscosity of a rear slug is set, the anti-dilution capability of the profile control agent in a crack is optimal. The invention relates to a slug design method for improving the anti-dilution capacity of a profile control agent in a crack, mainly aims to optimally select the optimal combination of the front slug viscosity, the profile control agent viscosity and the rear slug viscosity and improve the anti-dilution capacity of the profile control agent in the crack, and has important guiding significance for the design of a fractured reservoir on-site profile control process.

Description

Technical Field

[0001] The invention belongs to the field of oilfield chemistry in tertiary oil recovery technology, and specifically relates to a slug design method for improving the anti-dilution ability of a plugging agent in a fracture. Background Art

[0002] Fractured tight oil reservoirs are an important research area for increasing oil reserves and production in the 21st century. They are widely distributed in major oil and gas fields or major basins across the country and occupy an important position in my country's oil industry. However, due to the low permeability of the reservoir matrix and the presence of fractures, the injected water flows rapidly along the large fractures during water injection development, resulting in ineffective water injection, which ultimately leads to low crude oil utilization in this type of oil reservoir, and the recovery rate is generally less than 10%. The development effect is not ideal and the economic benefits are poor. It is urgent to further increase the crude oil recovery rate by plugging water.

[0003] In the profile control of fractured tight oil reservoirs, according to the formation characteristics: low matrix reservoir permeability, large displacement pressure gradient, and low formation fracture pressure, the requirements for the process in profile control are: small segment plugging and deep plugging. Therefore, an important property that the plugging agent needs to have is anti-dilution ability. Therefore, it is urgent to invent a segment plug design method that improves the anti-dilution ability of the plugging agent in the fracture to provide guidance for the design of the on-site profile control process. Summary of the invention

[0004] The present invention mainly overcomes the shortcomings of the prior art, and the purpose of the present invention is to provide a segment plug design method for improving the anti-dilution ability of the plugging agent in the fracture. The present invention uses a visual flat plate model, and by adjusting the viscosity of the front protection segment plug, the viscosity of the plugging agent, and the viscosity of the rear protection segment plug injected into the visual flat plate model, the anti-dilution ability of the plugging agent in the fracture under different segment plug combinations is tested, and finally a segment plug design method for improving the anti-dilution ability of the plugging agent in the fracture is obtained, and the best segment plug combination is selected.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A slug design method for improving the anti-dilution capability of a plugging agent in a crack, the method comprising the following steps:

[0007] S1: Dye the clean water blue, the plugging agent black, and the protection plug red. Then use the BROOKFIELD viscometer to test the viscosity of the front protection plug, plugging agent, and rear protection plug at room temperature (25°C) and record them; then use the multifunctional core displacement device ( Figure 2) Add 1000ml of blue water to No. 1, add 1000ml of black plugging agent to the multifunctional core displacement device No. 2, add 1000ml of red pre-protection segment plug solution to the multifunctional core displacement device No. 3 (after injecting the pre-protection segment plug solution, clean the multifunctional core displacement device No. 3 and add the post-protection segment plug solution), and connect the experimental device at the same time.

[0008] S2: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0009] S3: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, and then inject 0.3 PV of plugging agent (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0010] S4: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 55.36 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0011] S5: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 106.5 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0012] S6: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, and then inject 0.3 PV of plugging agent (viscosity 106.5 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0013] S7: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 To visualize the structure diagram of the flat plate model;

[0015] Figure 2 This is the flow chart of the anti-dilution plate experiment;

[0016] Figure 3 It is a plane diagram of the plugging agent injection process when the viscosity of the front slug, the plugging agent and the post slug are all 83.12 mPa·s;

[0017] Figure 4 It is a plane diagram of the plugging agent injection process when the viscosity of the front slug and the viscosity of the rear slug are both 83.12 mPa·s and the viscosity of the plugging agent is 55.36 mPa·s;

[0018] Figure 5 It is a plane diagram of the plugging agent injection process when the viscosity of the front protection segment plug is 83.12 mPa·s, and the viscosity of the rear protection segment plug and the plugging agent are both 55.36 mPa·s;

[0019] Figure 6 It is a plane diagram of the plugging agent injection process when the viscosity of the front protection segment plug and the rear protection segment plug are both 83.12 mPa·s and the viscosity of the plugging agent is 106.5 mPa·s;

[0020] Figure 7 It is a plane diagram of the plugging agent injection process when the viscosity of the front protection segment plug is 83.12 mPa·s, and the viscosity of the plugging agent and the rear protection segment plug are both 106.5 mPa·s;

[0021] Figure 8 This is a plan view of the plugging agent injection process when the viscosity of the front protection segment plug is 83.12 mPa·s, the viscosity of the plugging agent is 83.12 mPa·s, and the viscosity of the rear protection segment plug is 106.5 mPa·s. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Example:

[0024] A slug design method for improving the anti-dilution capability of a plugging agent in a crack, the method comprising the following steps:

[0025] S1: Dye the clean water blue, the plugging agent black, and the protection plug red. Then use the BROOKFIELD viscometer to test the viscosity of the front protection plug, plugging agent, and rear protection plug at room temperature (25°C) and record them; then use the multifunctional core displacement device ( Figure 2 ) Add 1000ml of blue water to No. 1, add 1000ml of black plugging agent to the multifunctional core displacement device No. 2, add 1000ml of red pre-protection segment plug solution to the multifunctional core displacement device No. 3 (after injecting the pre-protection segment plug solution, clean the multifunctional core displacement device No. 3 and add the post-protection segment plug solution), and connect the experimental device at the same time.

[0026] S2: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0027] S3: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, and then inject 0.3 PV of plugging agent (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0028] S4: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 55.36 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0029] S5: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 106.5 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0030] S6: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, and then inject 0.3 PV of plugging agent (viscosity 106.5 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0031] S7: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

[0032] Embodiment 1:

[0033] This embodiment is an experimental test of a plug design method for improving the anti-dilution ability of the plugging agent in the crack. The method is to control the injection volume of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model to 0.3PV, and the injection speed of the front protection plug, the plugging agent and the rear protection plug to 8ml / min. By adjusting the viscosity of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model, the influence of different plug combinations on the anti-dilution ability of the plugging agent is observed, and the strength of the anti-dilution ability of the plugging agent is judged. The measurement method is performed according to S1 and S2, where the viscosity of the front protection plug, the plugging agent and the rear protection plug are all 83.12mPa·s.

[0034] From the plane diagram of the visualized flat plate model during the injection of the plugging agent ( Figure 3 ) It can be seen that during the entire injection process of the front protection segment plug, the plugging agent and the rear protection segment plug, after the front protection segment plug is injected, during the entire injection process of the plugging agent, the plugging agent cannot be pushed forward smoothly in the visualized flat plate model, and a part of the plugging agent is diluted during the advancement process; after the plugging agent is injected, during the entire injection process of the rear protection segment plug, the rear protection segment plug cannot completely push the plugging agent to move forward smoothly, and a part of the plugging agent is diluted during the advancement process, and its anti-dilution ability is poor.

[0035] Embodiment 2:

[0036] This embodiment is an experimental test of a plug design method for improving the anti-dilution ability of the plugging agent in the fracture. The method is to control the injection volume of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model to 0.3PV, and the injection speed of the front protection plug, the plugging agent and the rear protection plug to 8ml / min. By adjusting the viscosity of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model, the influence of different plug combinations on the anti-dilution ability of the plugging agent is observed, and the strength of the anti-dilution ability of the plugging agent is judged. The measurement method is performed according to S1 and S3, where the viscosity of the front protection plug and the rear protection plug is 83.12mPa·s, and the viscosity of the plugging agent is 55.36mPa·s.

[0037] From the plane diagram of the visualized flat plate model during the injection of the plugging agent ( Figure 4 ) It can be seen that during the entire injection process of the front protection segment plug, the plugging agent and the rear protection segment plug, after the front protection segment plug is injected, during the entire injection process of the plugging agent, the plugging agent directly breaks through the front protection segment plug and cannot be pushed forward smoothly in the visualized flat plate model. During the advancement process, part of the plugging agent is diluted; after the plugging agent is injected, during the entire injection process of the rear protection segment plug, the rear protection segment plug cannot completely push the plugging agent to move forward smoothly. During the advancement process, part of the plugging agent is diluted, and its anti-dilution ability is poor.

[0038] Embodiment 3:

[0039] This embodiment is an experimental test of a plug design method for improving the anti-dilution ability of the plugging agent in the fracture. The method is to control the injection volume of the front protection plug, the plugging agent and the rear plug injected into the visual flat plate model to 0.3PV, and the injection speed of the front protection plug, the plugging agent and the rear protection plug to 8ml / min. By adjusting the viscosity of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model, the effect of different plug combinations on the anti-dilution ability of the plugging agent is observed, and the strength of the anti-dilution ability of the plugging agent is judged. The measurement method is performed according to S1 and S4, where the viscosity of the front protection plug is 83.12mPa·s, and the viscosity of the rear protection plug and the plugging agent is 55.36mPa·s.

[0040] From the plane diagram of the visualized flat plate model during the injection of the plugging agent ( Figure 5) It can be seen that during the entire injection process of the front protection segment plug, the plugging agent and the rear protection segment plug, after the front protection segment plug is injected, during the entire injection process of the plugging agent, the plugging agent directly breaks through the front protection segment plug and cannot be pushed forward smoothly in the visualized flat plate model. During the advancement process, part of the plugging agent is diluted; after the plugging agent is injected, during the entire injection process of the rear protection segment plug, the rear protection segment plug cannot completely push the plugging agent to move forward smoothly. During the advancement process, part of the plugging agent is diluted, and its anti-dilution ability is poor.

[0041] Embodiment 4:

[0042] This embodiment is an experimental test of a plug design method for improving the anti-dilution ability of the plugging agent in the crack. The method is to control the injection volume of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model to 0.3PV, and the injection speed of the front protection plug, the plugging agent and the rear protection plug to 8ml / min. By adjusting the viscosity of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model, the influence of different plug combinations on the anti-dilution ability of the plugging agent is observed, and the strength of the anti-dilution ability of the plugging agent is judged. The measurement method is performed according to S1 and S5, where the viscosity of the front protection plug and the rear protection plug is 83.12mPa·s, and the viscosity of the plugging agent is 106.5mPa·s.

[0043] From the plane diagram of the visualized flat plate model during the injection of the plugging agent ( Figure 6 ) It can be seen that during the entire injection process of the front protection segment plug, the plugging agent and the rear protection segment plug, after the front protection segment plug is injected, during the entire injection process of the plugging agent, the plugging agent cannot be pushed forward smoothly in the visualized flat plate model, and a part of the plugging agent is diluted during the advancement process; after the plugging agent is injected, during the entire injection process of the rear protection segment plug, the rear protection segment plug cannot completely push the plugging agent to move forward smoothly, and a part of the plugging agent is diluted during the advancement process, and its anti-dilution ability is poor.

[0044] Embodiment 5:

[0045] This embodiment is an experimental test of a plug design method for improving the anti-dilution ability of the plugging agent in the crack. The method is to control the injection volume of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model to 0.3PV, and the injection speed of the front protection plug, the plugging agent and the rear protection plug to 8ml / min. By adjusting the viscosity of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model, the influence of different plug combinations on the anti-dilution ability of the plugging agent is observed, and the strength of the anti-dilution ability of the plugging agent is judged. The measurement method is performed according to S1 and S6, where the viscosity of the front protection plug is 83.12mPa·s, and the viscosity of the plugging agent and the rear protection plug are both 106.5mPa·s.

[0046] From the plane diagram of the visualized flat plate model during the injection of the plugging agent ( Figure 7 ) It can be seen that during the entire injection process of the front protection segment plug, the plugging agent and the rear protection segment plug, after the front protection segment plug is injected, during the entire injection process of the plugging agent, the plugging agent is basically pushed forward smoothly in the visualized flat plate model, and a small part of the plugging agent is diluted during the advancement process; after the plugging agent is injected, during the entire injection process of the rear protection segment plug, the rear protection segment plug cannot completely push the plugging agent to move forward smoothly, and a part of the plugging agent is diluted during the advancement process, and its anti-dilution ability is poor.

[0047] Embodiment 6:

[0048] This embodiment is an experimental test of a plug design method for improving the anti-dilution ability of the plugging agent in the fracture. The method is to control the injection volume of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model to 0.3PV, and the injection speed of the front protection plug, the plugging agent and the rear protection plug to 8ml / min. By adjusting the viscosity of the front protection plug, the plugging agent and the rear protection plug injected into the visual flat plate model, the influence of different plug combinations on the anti-dilution ability of the plugging agent is observed, and the strength of the anti-dilution ability of the plugging agent is judged. The measurement method is performed according to S1 and S7, where the viscosity of the front protection plug is 55.36mPa·s, the viscosity of the plugging agent is 83.12mPa·s, and the viscosity of the rear protection plug is 106.5mPa·s.

[0049] From the plane diagram of the visualized flat plate model during the injection of the plugging agent ( Figure 8) It can be seen that during the entire injection process of the front protection segment plug, the plugging agent and the rear protection segment plug, after the front protection segment plug is injected, during the entire injection process of the plugging agent, the plugging agent can be pushed forward smoothly in the visualized flat plate model, and the plugging agent is basically not diluted during the advancement process; after the plugging agent is injected, during the entire injection process of the rear protection segment plug, the rear protection segment plug can completely push the plugging agent to move forward smoothly, and during the advancement process, the plugging agent is almost not diluted, and its anti-dilution performance is very good.

[0050] From the above experiments, it can be seen that by adjusting the viscosity of the front protection slug, the viscosity of the plugging agent and the viscosity of the rear protection slug, and observing the dilution of the plugging agent under six different slug combinations, it is found that when the viscosity of the front protection slug is less than that of the plugging agent, and the viscosity of the plugging agent is less than that of the rear protection slug, the anti-dilution ability of the plugging agent is the best.

[0051] The above is only a specific experimental example of the present invention, and does not limit the present invention in any form. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the above-displayed technical content without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the scope of the technical solution of the present invention.

Claims

1. A slug design method for improving the anti-dilution ability of a plugging agent in a crack, characterized in that: The following steps are involved: S1: Dye the clean water blue, the plugging agent black, and the protection segment plug red. Then use the BROOKFIELD viscometer to test the viscosity of the front protection segment plug, plugging agent and rear protection segment plug at room temperature (25°C) and record them; then add 1000ml of blue-dyed water to the multifunctional core displacement device (Figure 2) No. 1, add 1000ml of black plugging agent to the multifunctional core displacement device No. 2, and add 1000ml of red front protection segment plug solution to the multifunctional core displacement device No. 3 (after injecting the front protection segment plug solution, clean the multifunctional core displacement device No. 3 and add the rear protection segment plug solution), and connect the experimental device at the same time. S2: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent. S3: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, and then inject 0.3 PV of plugging agent (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent. S4: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 55.36 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent. S5: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 106.5 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent. S6: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, and then inject 0.3 PV of plugging agent (viscosity 106.5 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent. S7: Inject 1.0 PV of blue water into the visualized flat plate model at a certain speed, then inject 0.3 PV of pre-protection segment plug solution (viscosity 55.36 mPa·s) into the visualized flat plate model at the same speed, then inject 0.3 PV of plugging agent (viscosity 83.12 mPa·s) into the visualized flat plate model at the same speed, then clean the multifunctional core displacement device No. 3, add the post-protection segment plug solution, connect the experimental device, and then inject 0.3 PV of post-protection segment plug solution (viscosity 106.5 mPa·s) into the visualized flat plate model to observe the dilution of the plugging agent.

2. A slug design method for improving the anti-dilution ability of a plugging agent in a crack, characterized in that: The distribution of underground through-type large cracks was simulated using a visualized flat plate model. The model was made of two visualized flat plates. The outer dimensions of the flat plate model were 1000×200 mm, the inner dimensions (cracks) were 940×140 mm, and the surrounding 30 mm was a sealed area. The height of the crack was 1 mm, and the total volume of the crack was 131.6 cm3 (as shown in Figure 1).

3. A method for designing a slug for improving the anti-dilution capability of a plugging agent in a fracture as claimed in claim 1, characterized in that By adjusting the viscosity of the front protection plug, the viscosity of the plugging agent, and the viscosity of the rear protection plug, the anti-dilution ability of the plugging agent in the fracture under different plug combinations was tested.

4. A method for designing a slug for improving the anti-dilution capability of a plugging agent in a fracture as claimed in claim 1, characterized in that When the viscosity relationship among the front protection segment plug, the plugging agent and the rear protection segment plug satisfies: the viscosity of the front protection segment plug > the viscosity of the plugging agent > the viscosity of the rear protection segment plug, the plugging agent has the best anti-dilution ability in the crack.

5. A method for designing a slug for improving the anti-dilution capability of a plugging agent in a fracture as claimed in claim 1, characterized in that When the viscosity of the front protection segment plug is greater than or equal to the viscosity of the plugging agent, and the viscosity of the plugging agent is greater than or equal to the viscosity of the rear protection segment plug, the plugging agent is diluted and destroyed in the cracks, and its anti-dilution ability is poor.

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