Performance evaluation method and system for differential pressure plugging material for leakage control

Abstract

The invention provides a performance evaluation method and system for a differential pressure plugging material for leakage control, and belongs to the field of petroleum engineering plugging materials.The method comprises the steps that the physical and chemical performance of the differential pressure plugging material is evaluated, particle size distribution is obtained, and density, acid solubility and dispersion stability tests are conducted; testing the mechanical performance of the differential pressure plugging material to obtain a laboratory test performance curve of stretching and friction; testing and evaluating the critical starting pressure in a laboratory; performing laboratory testing and mechanism analysis on the ultimate bearing pressure to obtain a performance evaluation result; according to the method, the evaluation results of laboratory testing, theoretical simulation and mechanism analysis of the plugging material on the performance of the plugging material are comprehensively considered, the plugging material is evaluated to have the characteristics of low-pressure activation, self-adaptive plugging and high-pressure resistance, the preparation process is simple and controllable, the method can be effectively applied to micro-leakage plugging of petroleum and natural gas downhole pipe columns, and the application prospect is wide. And a reliable technical scheme is provided for shaft integrity repair.

Description

Technical Field

[0001] This invention belongs to the field of oilfield engineering plugging materials, and particularly relates to a performance evaluation method and system for differential pressure plugging materials used for leak control. Background Technology

[0002] In the oil extraction field, differential pressure sealing materials are a core technical means to solve micro-leakage in wellbore tubing, and their performance directly determines the sealing success rate and wellbore operational safety. Existing performance evaluation methods and systems for these materials have significant shortcomings and are insufficient to meet engineering requirements.

[0003] The physicochemical performance evaluation is not comprehensive: it often uses a single test of particle size distribution or fluid density, ignoring the compatibility of the acid solubility of the plugging material with the high mineralization and corrosion environment downhole, the correlation between dispersion stability and downhole delivery efficiency, resulting in laboratory data that cannot reflect the actual dispersion and retention effect of the material downhole.

[0004] Mechanical performance testing is disconnected from mechanism: Only single parameters such as tensile strength or friction coefficient are tested, and no correlation model is established between tensile properties (such as Young's modulus) and the creep capacity of the sealing material, or between friction properties (such as inter-unit friction coefficient) and the stability of the sealing layer. Therefore, it is impossible to predict the effectiveness of the sealing mechanism through mechanical performance data.

[0005] The critical start-up pressure test conditions are limited: the critical start-up pressure difference is mostly tested under a fixed flow rate, without simulating downhole multi-flow-rate conditions, and there is a lack of pressure loss model fitting and theoretical value verification, resulting in insufficient data reliability.

[0006] The evaluation of ultimate bearing pressure lacks mechanistic support: the ultimate bearing pressure value is obtained only through experimental measurement, without combining the "creep-displacement" mechanism of the sealing material to analyze the essential reasons for the difference in bearing pressure (such as the contribution of the friction coefficient to the ultimate bearing pressure), which makes it difficult to guide the optimization of material formulation.

[0007] In summary, existing evaluation methods cannot fully and accurately reflect the actual performance of differential pressure plugging materials. There is an urgent need to build a complete evaluation system that adapts to downhole operating conditions and relates to plugging mechanisms in order to solve the current technical bottlenecks. Summary of the Invention

[0008] To address the aforementioned shortcomings in the prior art, this invention provides a performance evaluation method and system for differential pressure sealing materials used in leakage control, which solves the problem that existing performance evaluation methods for differential pressure sealing materials cannot comprehensively and accurately reflect the actual performance of the materials.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On the one hand, a method for evaluating the performance of differential pressure sealing materials for leakage control is provided, comprising the following steps: S1. Conduct joint testing on the sealing material to obtain the particle size distribution, and obtain the physicochemical performance evaluation results through density, acid solubility and dispersion stability tests, and obtain the simulation scenario; S2. Based on the simulation scenario, the sealing material is made into a rubber sample for tensile and friction tests. The stress-strain curve and friction force-displacement curve are plotted, and the Young's modulus, sealing material stress, fracture stress, static friction coefficient and dynamic friction coefficient are calculated. S3. Based on the simulation scenario, a critical pressure testing device is constructed. The critical starting pressure difference is obtained through multi-condition testing, and a mathematical model of critical starting pressure is constructed. Combined with Young's modulus and leak point size, the critical starting pressure is calculated. S4. Based on the simulation scenario, the total friction force is calculated using the stress, static friction coefficient, and dynamic friction coefficient of the sealing material. Combined with the fracture stress, the ultimate bearing pressure is obtained. Based on the critical starting pressure and the ultimate bearing pressure, the performance of the sealing material is evaluated, and the performance evaluation results of the sealing material are obtained.

[0010] The beneficial effects of this invention are as follows: This invention evaluates the performance of differential pressure sealing materials by employing physicochemical performance evaluation, mechanical performance evaluation, critical start-up pressure, and ultimate bearing pressure. It relies only on conventional laboratory equipment, without the need for specially customized devices, significantly reducing equipment investment costs. Moreover, the testing steps are clear and reproducible. At the same time, it establishes a quantitative and graded evaluation system. Through quantifiable indicators such as "the deviation range between theoretical and measured values" and "curve fitting goodness," it can quickly determine whether the material performance meets the standards without the need for complex data analysis, significantly lowering the evaluation threshold. This enables a comprehensive evaluation of the performance of differential pressure sealing materials and accurately reflects the actual performance of differential pressure sealing materials.

[0011] Further, S1 includes the following steps: S101. Based on the preset particle size, the sealing material is tested in combination using a laser particle size analyzer and an optical microscope to obtain the particle size distribution. S102. Using a pre-set density bottle, measure the density of the sealing material and the density of the fluid. S103. Dry and weigh the sealing material, then immerse the dried and weighed sealing material in hydrochloric acid of a preset mass concentration, weigh the sealing material after immersion for a preset time, and calculate the degree of acid solubility. S104. The sealing material is placed into a graduated cylinder containing a pre-prepared guar gum-based liquid. The time for the sealing material with the largest particle size to settle completely is recorded. The settling time of the sealing material with the largest particle size without guar gum-based liquid is compared with that of the sealing material. Based on the density difference between the sealing material and the fluid, the dispersion stability is obtained. S105. Combining the particle size distribution of the sealing material, the density of the sealing material with the density of the fluid, the degree of acid solubility, and the dispersion stability, the physicochemical performance evaluation results are obtained. S106. Based on the physicochemical performance evaluation results, select an experimental scenario that matches the field application scenario for simulation and obtain the simulation scenario.

[0012] The beneficial effects of the above-mentioned further solutions are as follows: By improving the particle size testing range and supplementing acid solubility and dispersion stability tests, the present invention can comprehensively reflect the corrosion resistance of the plugging material in the downhole acidic and highly mineralized environment and its dispersibility during long-distance transportation, ensuring that the laboratory test data is highly compatible with the field application scenario and avoiding the risk of plugging failure due to incomplete performance evaluation.

[0013] Furthermore, S2 includes the following steps: S201. Based on the simulation scenario, the sealing material is poured into a dumbbell-shaped mold and dried to produce a dumbbell-shaped rubber sample; S202. Using a pre-set testing instrument, the rubber sample is stretched at a pre-set rate, and the stress-strain curve is recorded. S203. Based on the linear elastic segment of the stress-strain curve, the Young's modulus is calculated using the Young's modulus calculation formula. S204. Pour the sealing material into a square mold and dry it to make a square rubber sample; S205. Using a pre-set testing instrument, record the friction force and displacement between the square rubber sample and stainless steel, and between the square rubber sample and the square rubber sample, to obtain the friction force-displacement curve. S206. Based on the friction force-displacement curve, the static friction coefficient and dynamic friction coefficient are calculated.

[0014] Furthermore, the formula for calculating Young's modulus is as follows: ; in, Indicates Young's modulus. Indicates load, This indicates the cross-sectional area of ​​the rubber sample. This indicates the tensile strength of the rubber sample. Indicates the initial length of the rubber sample. Indicates strain, This indicates the fracture stress.

[0015] The beneficial effects of the above-mentioned further solutions are as follows: By establishing the correlation between tensile properties (Young's modulus, toughness), frictional properties (friction coefficient between elements and between elements and the wall) and the plugging mechanism, this invention can clarify the influence of material mechanical parameters on the creep capacity of plugging materials and the dynamic renewal capacity of the plugging layer, providing direct data support for material formulation optimization and helping to develop materials that are more suitable for downhole plugging needs.

[0016] Furthermore, step S3 includes the following steps: S3 includes the following steps: S301. Based on the simulation scenario, a leak point simulation component is constructed by using a preset cylindrical hole leak seam, and a critical pressure testing device including a leak point simulation component, a core holder, a flow pump and an analytical balance is constructed by filling the core holder cavity with sealing material. S302. Set the displacement flow gradient, conduct multi-condition tests using a critical pressure testing device, use a horizontal flow pump to drive the water displacement to move the sealing material towards the leak, connect the analytical balance to the outlet end, and obtain the critical start-up pressure difference by recording the minimum pressure when the outflow is zero under different flow rates. S303. Based on the fact that the fluid before sealing is incompressible and the fluid after sealing is compressible, the Reynolds number is calculated to verify that the flow in the leak point channel is laminar, and the model assumptions are obtained. S304. Based on the critical starting pressure difference, establish the flow rate formula for incompressible flow; S305, and set a three-stage pressure loss including pipeline basic pressure loss, additional pressure loss and fluid compressibility pressure loss; S306. Based on the model assumptions, the flow rate formula for incompressible flow, and the three-stage pressure loss, a mathematical model of critical start-up pressure is constructed, and the critical start-up pressure is calculated by combining Young's modulus and the leak point size.

[0017] Furthermore, step S305 includes the following steps: S3051. Based on the pipeline's own resistance, the pipeline's foundation pressure loss is obtained by measurement without the participation of sealing materials. S3052. Use sealing materials to partially seal the leak points to form micro gaps, and use the Hagen-Poiseuille formula to simplify it to obtain the additional pressure loss; S3053. Completely seal the leak point, utilize the fluid compression to drive the pressure rise, obtain the fluid compression pressure loss, and obtain the three-stage pressure loss according to the pipeline basic pressure loss, additional pressure loss and fluid compression pressure loss stages.

[0018] Furthermore, the expression for the critical start-up pressure is as follows: ; in, Indicates the critical starting pressure. This represents the correction factor for the leak size. Indicates Young's modulus; The expressions for the additional pressure loss and fluid compressibility pressure loss are as follows: ; ; ; in, Indicates additional pressure loss. Represents a simplified constant. This represents the flow rate of an incompressible stream. This indicates the actual length of the remaining leak. Indicates the diameter of the remaining leak point. Indicates the viscosity of the liquid. Indicates fluid compression pressure loss. Indicates displacement time. Indicates the compressibility coefficient of water. This indicates the initial volume of liquid in the tube.

[0019] The beneficial effects of the above-mentioned further solutions are as follows: This invention optimizes multi-flow velocity simulation conditions for critical start-up pressure and verifies the data through three-stage pressure loss, accurately reflecting the process of critical start-up pressure and improving measurement accuracy.

[0020] Furthermore, step S4 includes the following steps: S401. Based on the simulation scenario, by injecting the sealing material into the preset simulation device, and pushing the push rod at a preset rate, pressure is applied to the sealing material. In response to the failure of the sealing layer, the maximum pressure is recorded. S402. Set the sealing material and the wall of the leak point as isotropic materials. Based on the fact that when the sealing material is under force balance, the hydrostatic thrust of the liquid is less than or equal to the static friction between the sealing material and the wall or the sealing material, the pressure assumption is obtained. S403. Based on the balance between the hydrostatic thrust and the total static friction of the sealing material, the thrust of the hydrostatic pressure on the sealing material is calculated according to the hydrostatic pressure and the exposed area of ​​the sealing material in water. S404. The total friction force is calculated by calculating the static friction force between the sealing materials and the static friction force between the sealing materials and the wall surface. S405. By utilizing the total frictional force and combining it with the relationship between Young's modulus, the stress of the sealing material, and the fracture stress, the ultimate bearing pressure is obtained. S406. Based on the critical starting pressure and ultimate bearing pressure, the performance of the sealing material is evaluated to obtain the performance evaluation results of the sealing material.

[0021] Furthermore, the expression for the ultimate bearing pressure is as follows: ; in, Indicates the maximum pressure that can be withstood. This represents the total frictional force of any sealing material. This indicates the area of ​​the sealing material exposed in the water. This represents the static friction coefficient between the sealing materials. This represents the static friction coefficient between the sealing material and the wall surface. Indicates the strain of the sealing material. This indicates the actual contact area between sealing materials. This indicates the actual contact area between the sealing material and the wall surface. Indicates the sealing material under strain The stress under the condition.

[0022] The beneficial effects of the above-mentioned further solutions are as follows: This invention improves the mechanical parameter correlation calculation model for ultimate bearing pressure and, combined with critical starting pressure, enhances the reliability and universality of test data, accurately predicts the sealing triggering conditions and pressure bearing capacity of materials under different downhole flow velocities and leak sizes, provides scientific support for material selection in high-pressure conditions such as ultra-deep wells, and significantly improves the conversion efficiency and sealing success rate of differential pressure sealing materials from laboratory research and development to field application.

[0023] On the other hand, a performance evaluation system for differential pressure plugging materials used in leakage control is provided, including: The physicochemical performance evaluation module is used to conduct joint tests on the sealing materials, evaluate the particle size distribution, density, acid solubility and dispersion stability of the sealing materials, obtain the physicochemical performance evaluation results, and obtain the simulation scenario; The mechanical performance evaluation module, based on a simulation scenario, is used to test and evaluate the tensile and frictional properties of the sealing material, plot the stress-strain curve and frictional displacement curve, and calculate the Young's modulus, sealing material stress, fracture stress, static friction coefficient, and dynamic friction coefficient. The critical start-up pressure evaluation module, based on a simulation scenario, is used to construct a critical pressure testing device. It obtains the critical start-up pressure difference through multi-condition testing, constructs a mathematical model of critical start-up pressure, and calculates the critical start-up pressure by combining Young's modulus and leak point size. The ultimate pressure assessment module, based on a simulation scenario, calculates the total friction force using the stress, static friction coefficient, and dynamic friction coefficient of the sealing material. Combined with the fracture stress, it obtains the ultimate pressure. Based on the critical starting pressure and the ultimate pressure, it evaluates the performance of the sealing material and obtains the performance evaluation results.

[0024] The beneficial effects of the above-mentioned further solutions are as follows: By setting up a physicochemical performance evaluation module, a mechanical performance evaluation module, a critical starting pressure evaluation module, and an ultimate bearing pressure evaluation module, this invention covers the full-dimensional testing and mechanism analysis of the physicochemical properties, mechanical properties, critical starting pressure, and ultimate bearing pressure of the sealing material. The preparation process is simple and controllable, and it can be effectively applied to the micro-leakage sealing of oil and gas well downhole tubing, providing a reliable technical solution for wellbore integrity repair. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method of the present invention.

[0026] Figure 2 This is a system architecture diagram in this embodiment.

[0027] Figure 3 These are optical microscope images of the first and second part of the sample in this embodiment.

[0028] Figure 4 The images show the particle size distributions of the first and second samples obtained using a laser particle size analyzer in this embodiment.

[0029] Figure 5 This is a tensile test diagram of the rubber sample in this embodiment.

[0030] Figure 6 This is a friction test diagram of the rubber sample in this embodiment.

[0031] Figure 7 This is a schematic diagram of the critical start-up pressure measuring device in this embodiment.

[0032] Figure 8 This is a diagram showing the critical pressure test results of the first and second part of the sample in this embodiment.

[0033] Figure 9 This is a mathematical fitting diagram of the critical pressures of the first and second part of the sample in this embodiment.

[0034] Figure 10 This is a schematic diagram of the ultimate bearing pressure testing device in this embodiment.

[0035] Figure 11 This diagram shows the ultimate pressure test results for the first and second parts of the sample in this embodiment. Detailed Implementation

[0036] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0037] Before describing this embodiment, the following terms will be explained: Hagen-Poiseuille equation: Hagen-Poiseuille formula; slope: gradient.

[0038] Example 1 like Figure 1 As shown, this invention provides a performance evaluation method for differential pressure sealing materials used in leakage control, the implementation of which is as follows: S1. Conduct joint testing on the sealing material to obtain the particle size distribution, and obtain physicochemical performance evaluation results through density, acid solubility, and dispersion stability tests, and obtain simulation scenarios. The specific steps are as follows: S101. Based on the preset particle size, the sealing material is tested in combination using a laser particle size analyzer and an optical microscope to obtain the particle size distribution. S102. Using a pre-set density bottle, measure the density of the sealing material and the density of the fluid. S103. Dry and weigh the sealing material, then immerse the dried and weighed sealing material in hydrochloric acid of a preset mass concentration, weigh the sealing material after immersion for a preset time, and calculate the degree of acid solubility. S104. The sealing material is placed into a graduated cylinder containing a pre-prepared guar gum-based liquid. The time for the sealing material with the largest particle size to settle completely is recorded. The settling time of the sealing material with the largest particle size without guar gum-based liquid is compared with that of the sealing material. Based on the density difference between the sealing material and the fluid, the dispersion stability is obtained. S105. Combining the particle size distribution of the sealing material, the density of the sealing material with the density of the fluid, the degree of acid solubility, and the dispersion stability, the physicochemical performance evaluation results are obtained. S106. Based on the physicochemical performance evaluation results, select an experimental scenario that matches the field application scenario for simulation and obtain the simulation scenario.

[0039] In this embodiment, the plugging material is the material in the plugging agent that plays a decisive role in plugging, and it is usually solid; the plugging agent specifically refers to the entire liquid system, including the carrier liquid and the plugging material. To evaluate the physicochemical properties of the sealing materials, we need to obtain simulation scenarios that are highly compatible with laboratory test data and field application scenarios, so as to avoid the risk of sealing failure due to incomplete performance evaluation. Specifically, this involves particle size distribution testing, density testing, acid solubility testing, and dispersion stability testing. Particle size distribution testing: A combined laser particle size analyzer and optical microscope method was used, with the laser particle size analyzer determining the preset particle size. Particle size of sealing material within range, observed by optical microscope The above large-size sealing materials were used to record the particle size distribution range and evaluate the adaptability of multi-scale sealing materials to different leak points. Density test: The density of the sealing material and the fluid were measured using the 50mL density bottle method with a preset density bottle. The dispersion stability was evaluated by the density difference between the sealing material and the fluid. Acid solubility test: The dried and weighed plugging material is immersed in hydrochloric acid with a preset mass concentration of 20% for a preset time of 72 hours. After immersion, it is taken out, dried, and weighed again. The degree of acid solubility is calculated to evaluate the corrosion resistance of the material in the downhole acidic environment. Dispersion stability test: Use tweezers to pick up the plugging material and put it into a 50mL graduated cylinder with a preset content of 0.3% guar gum base liquid. Record the time for the largest particle size plugging material to settle completely. Compare the settling time with that without guar gum base liquid to quantify the effect of thickener on improving dispersion stability and ensure that the material does not stratify and settle during long-distance downhole transportation. The physicochemical performance evaluation results were obtained by combining the particle size distribution of the plugging material, the density of the plugging material and the fluid density, the degree of acid solubility, and the dispersion stability. Based on the physicochemical performance evaluation results, experimental scenarios adapted to the field application scenarios were selected for simulation, and simulation scenarios that highly matched the laboratory test data with the field application scenarios were set up.

[0040] S2. Based on the simulation scenario, the sealing material is made into rubber samples for tensile and friction tests. The stress-strain curve and friction force-displacement curve are plotted, and the Young's modulus, sealing material stress, fracture stress, static friction coefficient, and dynamic friction coefficient are calculated. The specific steps are as follows: S201. Based on the simulation scenario, the sealing material is poured into a dumbbell-shaped mold and dried to produce a dumbbell-shaped rubber sample; S202. Using a pre-set testing instrument, the rubber sample is stretched at a pre-set rate, and the stress-strain curve is recorded. S203. Based on the linear elastic segment of the stress-strain curve, the Young's modulus is calculated using the Young's modulus calculation formula.

[0041] In this embodiment, based on a simulation scenario, the mechanical property parameters of the sealing material are obtained through tensile and friction tests, and laboratory test performance curves are generated to reveal the supporting role of mechanical properties in the sealing mechanism. Specifically: Tensile property test: Pour the sealing material into a dumbbell-shaped mold. The dried rubber samples were prepared into dumbbell shapes and tested using a pre-set testing instrument (Shimadzu AG-50KNXPLUS electronic universal testing instrument) at a pre-set rate. Perform a stretching operation, record the stress-strain curve, and perform linear fitting. The linear elastic segment of the stress-strain curve, i.e., the strain... Using the Young's modulus calculation formula, the Young's modulus is calculated, and the expression is as follows: ; in, Indicates Young's modulus. Indicates load, This indicates the cross-sectional area of ​​the rubber sample. This indicates the tensile strength of the rubber sample. Indicates the initial length of the rubber sample. Indicates strain, Represent the fracture stress; and calculate the fracture stress and fracture strain. The toughness expression is calculated as follows: ; The creep capacity and elastic recovery of the sealing material were evaluated, and it was found that the lower the Young's modulus, the easier the sealing material is to undergo flexible creep and adapt to the morphology of the leak point; the higher the toughness, the stronger the sealing material's resistance to extrusion.

[0042] S204. Pour the sealing material into a square mold and dry it to make a square rubber sample; S205. Using a pre-set testing instrument, record the friction force and displacement between the square rubber sample and stainless steel, and between the square rubber sample and the square rubber sample, to obtain the friction force-displacement curve. S206. Based on the friction force-displacement curve, the static friction coefficient and dynamic friction coefficient are calculated.

[0043] In this embodiment, friction performance testing is performed, and preparation is carried out. and A square rubber sample, specifically a square sheet, was used to test the friction force-displacement curves of the wall friction between the sample and stainless steel, and the inter-unit friction between the samples, using a pre-set testing instrument (electronic universal material testing instrument). The static friction coefficient and dynamic friction coefficient were calculated, and the expressions are shown below: , ; in, Indicates the static friction coefficient. Represents static friction. This represents the normal force applied by the slider. This represents the coefficient of kinetic friction. Represents kinetic friction; The influence of friction coefficient on the stability of the sealing layer was analyzed, and it was found that when the friction coefficient between units is less than that with the wall, the sealing material is more easily replaced by stress-driven replacement, thus improving the density of the sealing layer.

[0044] S3. Based on the simulation scenario, a critical pressure testing device is constructed. The critical starting pressure difference is obtained through multi-condition testing, and a mathematical model of the critical starting pressure is constructed. Combining Young's modulus and leak point size, the critical starting pressure is calculated. The specific steps are as follows: S301. Based on the simulation scenario, a leak point simulation component is constructed by using a preset cylindrical hole leak seam, and a critical pressure testing device including a leak point simulation component, a core holder, a flow pump and an analytical balance is constructed by filling the core holder cavity with sealing material. S302. Set the displacement flow gradient, conduct multi-condition tests using a critical pressure testing device, use a horizontal flow pump to drive the water displacement to move the sealing material towards the leak, connect the analytical balance to the outlet end, and obtain the critical start-up pressure difference by recording the minimum pressure when the outflow is zero under different flow rates. S303. Based on the fact that the fluid before sealing is incompressible and the fluid after sealing is compressible, the Reynolds number is calculated to verify that the flow in the leak point channel is laminar, and the model assumptions are obtained. S304. Based on the critical starting pressure difference, establish the flow rate formula for incompressible flow.

[0045] In this embodiment, a critical pressure testing device is constructed based on a simulation scenario, including a horizontal flow pump, a pressure monitoring component, a leak point simulation component, and a water output monitoring component. Specifically, the leak simulation component uses For the leak in the cylindrical hole, the cavity of the core holder is filled with sealing material. The water output monitoring component uses an analytical balance, and the outlet end is connected to the analytical balance to record the water output. The advection pump drives the water to move the sealing material towards the leak. The pressure sensor monitors the displacement pressure in real time. And set the displacement flow gradient The critical start-up pressure difference was obtained by using a critical pressure testing device to conduct multi-condition tests and recording the minimum pressure when the outflow was zero under different flow rates. To establish a mathematical model for the critical start-up pressure, key model assumptions are made: the fluid before sealing is incompressible, and the fluid after sealing, i.e., when the leak is completely blocked, is compressible. The Reynolds number is then calculated. The flow within the leak channel was verified to be laminar; and the Hagen-Poiseuille equation was used to describe the additional pressure loss during partial plugging, while neglecting complex flow field disturbances. A correlation between flow rate and critical pressure is established. Based on the critical start-up pressure difference, the critical flow rate measured in the laboratory is converted into the critical pressure of the leak point in the field, and the flow rate formula based on incompressible flow is derived, as shown below: ; in, This represents the flow rate of an incompressible stream. This represents the flow coefficient, which is 0.62 for a thin-walled circular orifice. Indicates the leak area. Indicates the leakage pressure difference. This indicates the fluid density.

[0046] S305, and set a three-stage pressure loss including pipeline foundation pressure loss, additional pressure loss, and fluid compressibility pressure loss. The specific steps are as follows: S3051. Based on the pipeline's own resistance, the pipeline's foundation pressure loss is obtained by measurement without the participation of sealing materials. S3052. Use sealing materials to partially seal the leak points to form micro gaps, and use the Hagen-Poiseuille formula to simplify it to obtain the additional pressure loss; S3053. Completely seal the leak point, utilize the fluid compression to drive the pressure rise, obtain the fluid compression pressure loss, and obtain the three-stage pressure loss according to the pipeline base pressure loss, additional pressure loss and fluid compression pressure loss stages. S306. Based on the model assumptions, the flow rate formula for incompressible flow, and the three-stage pressure loss, a mathematical model of critical start-up pressure is constructed, and the critical start-up pressure is calculated by combining Young's modulus and the leak point size.

[0047] In this embodiment, a three-stage pressure loss is constructed, specifically including: Phase 1, Pipeline Foundation Pressure Loss: Considering only the pipeline's own resistance, without any sealing unit involved in plugging, the pipeline foundation pressure loss... The results were determined experimentally, without relying on formula calculations, and were used solely as a pressure benchmark for subsequent stages. Phase Two, Additional Pressure Loss: The sealing unit partially plugs the leak, creating micro-gaps, resulting in additional pressure loss. Specifically, this refers to the additional pressure loss caused by the reduction in the actual outlet size due to the sealing device, which is simplified from the Hagen-Poiseuille equation, based on... The initial expression for the additional pressure loss is obtained as follows: ; in, This indicates the total pressure loss in the pipeline. This indicates the pressure loss of the pipeline foundation, specifically the loss caused by water flowing through the pipeline. This indicates the actual length of the remaining leak. Indicates the diameter of the remaining leak point. Indicates fluid viscosity; make The simplified expression for the additional pressure loss is as follows: ; in, Represents a simplified constant; Phase 3, Fluid Compression Pressure Loss: After completely sealing the leak, the pressure rise is dominated by fluid compression, resulting in the fluid compression pressure loss, expressed as follows: ; in, This represents the pressure loss due to fluid compression, specifically the pressure required to compress water within a sealed pipe. Indicates displacement time. The compressibility coefficient of water is represented by the coefficient of water in water. Compression coefficient at time , This indicates the initial volume of liquid in the tube; Data validity was verified based on a critical start-up pressure model. According to model assumptions (incompressible flow and laminar flow state before sealing), different displacement flow rates were tested. Fitting the pressure-time curve under the condition of complete closure, the goodness of fit of the three stages is determined. Furthermore, if the deviation between the theoretical critical pressure calculated using the flow-critical pressure correlation formula and the measured value is ≤10%, then the critical initiation pressure data is considered reliable and can accurately reflect the sealing triggering characteristics of the material under complex working conditions. Combined with the sealing mechanism analysis, if the critical initiation pressure curve clearly presents three stages: "pipeline base pressure loss - additional pressure loss - fluid compressibility pressure loss," and the additional pressure loss in stage two is related to the remaining leak point size parameters (…), then… or The linear positive correlation indicates that the sealing material can gradually establish a sealing barrier through creep filling and micro-gap sealing, and the mechanism is well adapted; if the curve shows a pressure tortuous upward feature, it indicates that the material has the ability of "stress-driven replacement", and the density of the sealing layer can be improved through dynamic replacement of the sealing material. Based on the mechanical nature of creep filling leak points in sealing materials, and combined with experimental data fitting, it was confirmed that Young's modulus is positively correlated with critical pressure. Combining Young's modulus and leak point size, a correlation model was established between critical starting pressure, Young's modulus, and leak point size, as shown in the following expression: ; in, Indicates the critical starting pressure. Indicates the leakage point size correction factor; The critical starting pressure was calculated. .

[0048] S4. Based on the simulation scenario, the total friction force is calculated using the stress, static friction coefficient, and dynamic friction coefficient of the sealing material. Combined with the fracture stress, the ultimate bearing pressure is obtained. Based on the critical starting pressure and the ultimate bearing pressure, the performance of the sealing material is evaluated, yielding the performance evaluation results. The specific steps are as follows: S401. Based on the simulation scenario, by injecting the sealing material into the preset simulation device, and pushing the push rod at a preset rate, pressure is applied to the sealing material. In response to the failure of the sealing layer, the maximum pressure is recorded. S402. Set the sealing material and the wall of the leak point as isotropic materials. Based on the fact that when the sealing material is under force balance, the hydrostatic thrust of the liquid is less than or equal to the static friction between the sealing material and the wall or the sealing material, the pressure assumption is obtained. S403. Based on the balance between the hydrostatic thrust and the total static friction of the sealing material, the thrust of the hydrostatic pressure on the sealing material is calculated according to the hydrostatic pressure and the exposed area of ​​the sealing material in water. S404. The total friction force is calculated by calculating the static friction force between the sealing materials and the static friction force between the sealing materials and the wall surface. S405. By utilizing the total frictional force and combining it with the relationship between Young's modulus, the stress of the sealing material, and the fracture stress, the ultimate bearing pressure is obtained. S406. Based on the critical starting pressure and ultimate bearing pressure, the performance of the sealing material is evaluated to obtain the performance evaluation results of the sealing material.

[0049] In this embodiment, based on a simulation scenario, a hydraulic servo system with a maximum pressure of 500 MPa is used to inject sealing material into a preset syringe-type simulation device at a preset rate. Push the push rod to apply pressure to the sealing material and record the maximum pressure when the sealing layer fails; To establish a mathematical model of the ultimate pressure resistance, the following assumptions are made: the sealing unit and the wall surface of the leak point are made of isotropic materials; when the sealing unit is in force equilibrium, the thrust exerted by the hydrostatic pressure of the liquid is... Static friction between the sealing unit and the wall surface or itself; cross-linked materials under compressive strain Within the range, it conforms to Hooke's law. For non-crosslinked materials, the ultimate stress is used for calculation, and the stress change after exceeding the ultimate strain is ignored. The essence of ultimate pressure bearing is the balance between the hydrostatic thrust of the liquid and the total static friction of the sealing unit, that is: ,in, This represents the thrust exerted by the hydrostatic pressure on the sealing material. This represents the total static friction force that the sealing material resists from being pushed out. The thrust of hydrostatic pressure on the sealing material, i.e., the force exerted by hydrostatic pressure on the exposed area of ​​the sealing unit, is expressed as: ,in, Indicates the hydrostatic pressure of the liquid. This indicates the area of ​​the sealing material exposed in the water; The total friction force is calculated by calculating the static friction force between the sealing units and the static friction force between the sealing units and the wall surface. The total friction force is the sum of the static friction forces between the sealing units and between the sealing units and the wall surface, as shown in the following expression: ; in, This represents the static friction force of any sealing material. This represents the static friction coefficient between the sealing materials. This represents the normal force exerted by the sealing material on the contact surface of the sealing material. This represents the static friction coefficient between the sealing material and the wall surface. This represents the normal force exerted by the sealing material on the wall surface of the sealing material. This represents the Young's modulus of the sealing material. Indicates the strain of the sealing material. This indicates the actual contact area between sealing materials. This indicates the actual contact area between the sealing material and the wall surface; By integrating the formula for total friction force with the relationship between Young's modulus, the stress of the sealing material, and the fracture stress (Young's modulus calculation formula), the formula for calculating the ultimate bearing pressure is obtained as follows: ; in, Indicates the maximum pressure that can be withstood. This represents the total frictional force of any sealing material. Indicates the sealing material under strain The stress below; The validity of the data was verified based on the mathematical model of ultimate bearing pressure, according to the model assumptions (the sealing unit and the wall of the leak point are isotropic materials, and the hydrostatic thrust of the liquid is in equilibrium). Total static friction), for different leak point sizes ( , Cylindrical holes and , Compare the measured ultimate bearing capacity under the narrow slit with the theoretical calculated value. If the error is within a reasonable range (e.g., ...), the actual value is determined by the theoretical calculation. If the measured value deviates from the theoretical calculation value by no more than 30% for a cylindrical hole leak, then the ultimate pressure bearing capacity data is considered reliable and can truly reflect the stable pressure bearing capacity after the material is sealed. Combining mechanical property data and analyzing the ultimate pressure bearing capacity formula, if the material has a high Young's modulus and reasonable friction coefficients between units and between units and the wall (the friction coefficient between units is less than the friction coefficient with the wall), the ultimate pressure bearing capacity is significantly improved, indicating that Young's modulus and friction jointly support the high-pressure sealing requirements. Combining the sealing mechanism analysis of the ultimate pressure bearing capacity curve characteristics, if the curve rises smoothly to the peak and then becomes unstable, it indicates that the sealing material effectively fills the leak point in a single creep form, forming a dense sealing layer structure. If the curve shows a tortuous rise, it indicates that the sealing material is dynamically updated through "stress-driven replacement," continuously improving the strength of the sealing layer. Based on the critical initiation pressure and ultimate withstand pressure, the performance of the sealing material was evaluated. The results showed that both the critical initiation pressure and the ultimate withstand pressure indicated good mechanism compatibility. Multi-velocity simulation was optimized for the critical initiation pressure, and the data was verified using a pressure loss model. For the ultimate withstand pressure, a mechanical parameter correlation calculation model was established, which improves the reliability and universality of the test data. This allows for accurate prediction of the sealing triggering conditions and pressure-bearing capacity of the material under different downhole flow velocities and leak sizes, providing scientific support for material selection in high-pressure conditions such as ultra-deep wells. This significantly improves the conversion efficiency and sealing success rate of differential pressure sealing materials from laboratory research and development to field application, achieving a highly efficient performance evaluation.

[0050] Example 2 like Figure 2 As shown, this embodiment provides a performance evaluation system for differential pressure plugging materials used in leakage control, including: The physicochemical performance evaluation module is used to evaluate the particle size distribution, density, acid solubility, and dispersion stability of the sealing material. It is used to conduct joint tests on the sealing material, evaluate its particle size distribution, density, acid solubility, and dispersion stability, obtain physicochemical performance evaluation results, and acquire simulation scenarios. The mechanical performance evaluation module is used to test and evaluate the tensile and frictional properties of sealing materials. Based on the simulation scenario, it is used to test and evaluate the tensile and frictional properties of sealing materials, plot stress-strain curves and frictional force-displacement curves, and calculate Young's modulus, sealing material stress, fracture stress, static friction coefficient and dynamic friction coefficient. The critical start-up pressure evaluation module is used to test and evaluate the critical start-up pressure of sealing materials under different operating conditions. Based on simulation scenarios, it is used to build a critical pressure testing device, obtain the critical start-up pressure difference through multi-condition testing, and build a critical start-up pressure mathematical model. Combined with Young's modulus and leak point size, the critical start-up pressure is calculated. The ultimate pressure resistance evaluation module is used to test and evaluate the ultimate pressure resistance of sealing materials at different leak points. Based on a simulation scenario, it calculates the total friction force using the stress, static friction coefficient, and dynamic friction coefficient of the sealing material, and combines this with the fracture stress to obtain the ultimate pressure resistance. Based on the critical starting pressure and the ultimate pressure resistance, the performance of the sealing material is evaluated, and the performance evaluation results of the sealing material are obtained.

[0051] Example 3 In this embodiment, a specific implementation performance evaluation is carried out by setting up a first part of the sample and a second part of the sample. Part 1 Sample: 40 parts of carboxylated nitrile butadiene latex and 80 parts of deionized water were mixed evenly to prepare a latex diluent; Lower control of stirrer speed Four parts of 20% magnesium chloride activator were added dropwise to a flask, along with one part of defoamer. Stirring was stopped for 20 minutes to obtain an emulsion with micron- to millimeter-sized particles. Stirring was then resumed, and 20 parts of 20% OP-10 and 140 parts of 0.3% guar gum solution were added. Stirring for 15 minutes yielded a common differential pressure activated plugging agent. A schematic diagram of the product under an optical microscope is shown below. Figure 3 As shown in (a), (b), and (c) in the figure.

[0052] In this embodiment, the second sample consists of 40 parts of carboxylated nitrile latex and 80 parts of deionized water, which are stirred evenly to form a latex diluent; The stirring speed was controlled at 300 r / min. One part defoamer, four parts metal oxide, one part anti-scorching agent, one part accelerator, and five parts self-healing agent were added. The mixture was stirred for 20 min. Four parts of 20% magnesium chloride activator were then added dropwise to the flask. Stirring was stopped for 20 min to obtain an emulsion with micron to millimeter-sized particles. Stirring was then restarted, and 20 parts of 20% OP-10 and 140 parts of 0.3% guar gum solution were added to prepare a metal oxide ion-crosslinked, high-pressure resistant, activated sealing agent. A schematic diagram of the product under an optical microscope is shown below. Figure 3 As shown in (d), (e), and (f).

[0053] In this embodiment, particle size distribution testing was performed. A first portion of the sample and a second portion of the sample were taken, subjected to fluid sonication for 30 minutes, and then measured using a laser particle size analyzer (DLS). Particle size of the sealing material within the range, observed using a Leica DM2700P optical microscope. The above large-size sealing materials yield the following results: Figure 4 The experimental results shown indicate that the particle size distribution of the first part of the sample covers... (including) , , Micron-level peaks and (millimeter-level unit), adapter Leakage points; second part of the sample particle size distribution coverage (including) , , , Micron-level peaks and (millimeter-level unit), adapter Leakage point. Fluid density and sealing material density were determined using a 50 mL density bottle. Acid hydrolysis solubility was determined using hydrochloric acid. The solid sealing material of the sealing agent was dried and weighed, then soaked in 20% hydrochloric acid for 72 h. Finally, the sealing material was washed with deionized water, dried, and weighed. The dispersion stability test only tested the loading and unloading performance of millimeter-sized sealing materials, because the dispersion performance of the micron-sized latex sealing materials in the second part of the sample far exceeded that of the millimeter-sized latex sealing materials. After ultrasonic dispersion, the materials were added to a 50 mL graduated cylinder, and the sealing materials at the highest point were allowed to settle completely and the time was recorded. The physicochemical properties tested are shown in Table 1. Table 1 is the evaluation table of the fluid physicochemical properties of the first and second part of the sample.

[0054] Table 1

[0055] In this embodiment, tensile property testing is performed. The carboxylated butadiene nitrile latex (containing additives, but without MgCl2 activator) used to prepare the sealing agent in the first and second part of the sample is poured into a dumbbell-shaped mold and dried. The tensile properties of the rubber sheet were tested using an electronic universal testing instrument (Shimadzu AG-50KNXPLUS); the tensile curves of the first part of the specimens were divided into three stages as follows: Figure 5 And perform linear fitting, the corresponding curve is in Figure 5 The curve fitting formula, marked with a dashed line, is shown below: ; in, This represents the stress fitting formula for the first part of the specimen. Indicates stress, Indicates strain; strain For linear elastic segments, The first part represents the yield zone. As strain increases, the stress rate slows down, and the molecular chains inside the material begin to slip, resulting in plastic deformation. Above 0.70 is the plastic plateau zone, where strain continues to increase, molecular chain slippage intensifies, and the material can no longer withstand higher stresses. The calculation results are shown in Table 2, which is the mechanical property measurement table for the first and second part of the samples. The first part of the samples, under tension, yielded a Young's modulus of 0.789 MPa, a fracture stress of 0.393 MPa, a fracture strain of 2.009 kJ / m³, and a toughness of 705.82 kJ / m³. The goodness of fit of the stress-strain curve is [not specified]. From the curve characteristics, the first part of the sample has no strengthening section and low stress value in the plastic plateau section, indicating that its molecular chains are only connected by physical entanglement and have no ionic cross-linking network support. During the stretching process, the molecular chains are easy to untangle and it is difficult to form a highly oriented structure, resulting in weak tensile failure resistance, limited creep and extrusion resistance. It can only support the initial creep sealing requirements of the sealing material under low pressure conditions and cannot resist extrusion deformation under high pressure conditions. like Figure 5 As shown, the tensile curves of the second part of the specimens are divided into four stages, and linear fitting is performed simultaneously. The corresponding curves are in... Figure 5 The curve is marked with a dashed line, and the fitting formula for the curve is shown below: ; in, The stress fitting formula for the second part of the specimen; strain For linear elastic segments, This is a transition section. The range is the yield zone, and the range above 3.35 is the strengthening zone, with a fracture strain of [missing value]. 4.48, fracture stress The stress was 1.836 MPa. The calculation results are shown in Table 2. The second part of the specimens under tensile stress had a Young's modulus of 1.502 MPa, a fracture stress of 1.836 MPa, a fracture strain of 4.483 kJ / m³, and a toughness of 4877.17 kJ / m³. The stress-strain curve fit was good. It exhibits excellent creep and extrusion resistance. The steep increase in the slope of the fourth stage of the curve indicates that the molecular chains of the second part of the sample are highly oriented and have strong resistance to tensile failure, which can support the "creep-extrusion resistance" requirements of the sealing material.

[0056] Table 2

[0057] In this embodiment, friction performance testing is performed: the above-mentioned latex is used to prepare... and A square sheet-shaped sample was tested using an electronic universal testing instrument to measure its coefficient of friction with stainless steel and itself. The results are as follows: Figure 6 As shown, through the formula , ; in, Indicates the static friction coefficient. Represents static friction. This represents the normal force applied by the slider, which is 1.96 N in this case. This represents the coefficient of kinetic friction. The dynamic friction force is represented by Table 3, which shows the friction coefficients of the first and second part of the samples. The friction coefficient between the units of the first sample (1.3265) is greater than that with the wall (1.1122). This characteristic is different from the friction characteristics required by the "stress-driven replacement" mechanism. The higher friction coefficient between units makes it difficult for the units to slip relative to each other after the sealing material forms a preliminary seal at the leak point. It is impossible to update the sealing layer through the dynamic replacement process of "old units being squeezed out and new units filling in immediately". Moreover, the friction coefficient between the unit and the wall of the leak point is relatively low. The sealing material is prone to overall displacement along the wall and is difficult to adhere stably to the surface of the leak. This frictional characteristic makes the sealing layer prone to cracking due to local stress concentration after its formation. It cannot improve the density through unit replacement and can only achieve temporary sealing by physical stacking of the initial units. It is suitable for micro-leakage scenarios with low pressure and low flow rate, but it is difficult to meet the long-term stability requirements of the sealing layer under high pressure conditions. The friction coefficient between units of the second part of the sample (0.5000) is less than the friction coefficient with the wall (0.8469), which meets the requirements of the "stress-driven replacement" mechanism for frictional characteristics and can promote the replacement of sealing materials to improve the density of the sealing layer.

[0058] Table 3

[0059] In this embodiment, as Figure 7 As shown, the critical pressure testing device consists of a horizontal flow pump (displacement flow rate). ), pressure sensor (accuracy ±0.1Pa), core holder (cavity volume 250 mL, built-in) (Cylindrical hole leakage), analytical balance (accuracy ±0.001g, record water output); And set the operating conditions: simulate downhole temperature The displacement medium was water; test procedure: inject 20 mL of sample fluid into the core holder, close the control valve, and set the flow rate of the advection pump from... The pressure is gradually increased, and the pressure curve and water output are recorded in real time. When the water output drops to 0 and the pressure rises at a constant rate, it is determined that the critical start-up pressure has been reached, and the corresponding flow rate is the critical flow rate. The calculated critical starting pressure values ​​for different displacement flow rates are shown in Table 4. Table 4 contains the calculated parameters, values, and measured values ​​of the critical pressure. Red = 4.5 represents the Reynolds number for different flow velocities when the diameter is 4.5. Experimental results are as follows... Figure 8 As shown, the critical initiation pressure of both plugging agents increases significantly with increasing displacement flow rate. This phenomenon stems from the fact that increased flow velocity exacerbates the scouring effect of the plugging material at the leak point, requiring a higher pressure differential to drive stable adhesion of the unit and fill the leak. Furthermore, the second sample, due to the rigid network formed by the cross-linking of nano-metal oxides, exhibits a significantly higher Young's modulus (1.502 MPa) than the first sample (0.789 MPa), making it more sensitive to flow velocity changes and resulting in a higher overall critical pressure. Both sealants can withstand a pressure of 20 MPa after sealing; A successful seal can be confirmed when the pressure rises at a constant rate and there is no liquid leakage; the first batch of samples was tested at a critical flow rate of... The first part of the sample was sealed, while the second part of the sample required... By assuming incompressible flow, the flow rate formula for incompressible flow is used. The relationship between laboratory flow rate and pressure difference at the construction site was established. The calculated critical pressures were 21.11 Pa (first part of the sample) and 337.73 Pa (second part of the sample). The theoretical values ​​were calculated, and the deviations were compared with the measured values. 8% (average deviation of 6.2% for the first batch of samples and 7.8% for the second batch of samples). Young's modulus is positively correlated with critical pressure, according to the critical starting pressure formula. The critical starting pressure was calculated; due to the increase in E, the critical starting pressure of the second part of the sample was 337.73 Pa, which was significantly higher than the critical starting pressure of 21.11 Pa of the first part of the sample.

[0060] Table 4

[0061] In this embodiment, the pressure-time curves of the first and second part of the sample are fitted according to a three-stage pressure loss model, as follows: Figure 9 As shown, Stage 1 represents the pipeline foundation pressure loss stage. The pressure of the first batch of samples remained below 0.15 MPa, while the pressure of the second batch remained below 0.2 MPa, indicating no effective sealing. Stage 2 represents the additional pressure loss stage. The pressure increase of the first batch of samples reached over 0.03 MPa / min, and the increase of the second batch exceeded 0.1 MPa / min, indicating that the sealing material gradually filled the leak, and the decrease in leak volume led to an increase in additional pressure loss. Stage 3 represents the fluid compression stage, where the pressure increased linearly, indicating complete sealing of the leak. The second batch of samples... , The pressure rises with fluctuations under high flow rate, which is a characteristic of the sealing material's dynamic renewal through "stress-driven replacement." After some units are squeezed out of the leak point, new units immediately fill the gap, continuously improving the density of the sealing layer. In contrast, the curve of the first part of the sample shows no obvious fluctuations, relying solely on the creep filling of a single unit, indicating weaker structural stability of the sealing layer. The three-stage goodness of fit was verified after complete sealing. This confirms that the critical start-up pressure model can accurately describe the pressure changes after complete closure; in stage two... and The direct proportionality between the two can explain the phenomenon that the pressure rises more rapidly in the second part of the sample due to the high filling efficiency of the multi-scale sealing unit.

[0062] In this embodiment, Next, according to Figure 10 The first and second part of the sample were injected into a syringe-type simulation device (with different slits at the bottom). , Cylindrical hole , (slit); use a hydraulic servo testing machine to push the push rod at a rate of 10 mm / min and record the maximum pressure when the sealing layer fails; Experimental results are as follows Figure 11 As shown, the formula for calculating the ultimate bearing pressure is... The calculated theoretical ultimate pressure and the comparison with the measured values ​​are shown in Table 5 below. Table 5 shows the calculated and measured values ​​of the ultimate pressure under different leakage conditions, and the errors are all within a reasonable range. The ultimate pressure that both sealing agents can withstand decreases significantly with the increase of the leak size and the increase of morphological complexity. This is because the larger the leak size, the larger the contact area that the sealing material needs to cover. Moreover, due to the large aspect ratio of the slit leak, the sealing material is prone to deformation and slippage along the gap direction, requiring more units to work together to "bridge and fill" to maintain stability. The second part of the sample has a rigid network formed by the cross-linking of nano-metal oxides, which has stronger resistance to deformation and a smaller pressure attenuation. From the curve characteristics, the curve of the first part of the sample mostly shows a "gradual rise-sudden drop", indicating that the sealing material fills the leak with a single creep. The curve of the second part of the sample often shows a tortuous rise, confirming that it strengthens the sealing layer through "stress-driven replacement". The error between the theoretical calculation value and the measured value is within 25% (the average deviation of the first part of the sample is 20.3%, and the average deviation of the second part of the sample is 12.9%), which verifies the effectiveness of the model.

[0063] Table 5

[0064] In this embodiment, based on the mechanical parameters obtained from tensile performance testing (Young's modulus of the first part of the sample is 0.789 MPa, and the coefficient of friction between units is 1.3265; Young's modulus of the second part of the sample is 1.502 MPa, and the coefficient of friction between units is 0.5000), the ultimate bearing capacity is determined by the synergistic effect of Young's modulus and the coefficient of friction. Although the coefficient of friction between units of the second part of the sample is lower than that of the first part of the sample, its Young's modulus is 1.9 times that of the first part of the sample. The cross-linked network can effectively constrain the deformation of molecular chains, making the sealing material less prone to plastic flow under high pressure. At the same time, the coefficient of friction between the unit and the wall surface of the second part of the sample (0.8469) is higher than that between units, which conforms to the "stress-driven replacement" mechanism. It can fill the micro gaps through dynamic unit renewal, further improving the compactness and bearing capacity of the sealing layer. Therefore, its ultimate bearing capacity is generally 4-8 times that of the first part of the sample.

Claims

1. A method for evaluating the performance of differential pressure sealing materials used for leakage control, characterized in that, Includes the following steps: S1. Conduct joint testing on the sealing material to obtain the particle size distribution, and obtain the physicochemical performance evaluation results through density, acid solubility and dispersion stability tests, and obtain the simulation scenario; S2. Based on the simulation scenario, the sealing material is made into a rubber sample for tensile and friction tests. The stress-strain curve and friction force-displacement curve are plotted, and the Young's modulus, sealing material stress, fracture stress, static friction coefficient and dynamic friction coefficient are calculated. S3. Based on the simulation scenario, a critical pressure testing device is constructed. The critical starting pressure difference is obtained through multi-condition testing, and a mathematical model of critical starting pressure is constructed. Combined with Young's modulus and leak point size, the critical starting pressure is calculated. S4. Based on the simulation scenario, the total friction force is calculated using the stress, static friction coefficient, and dynamic friction coefficient of the sealing material. Combined with the fracture stress, the ultimate bearing pressure is obtained. Based on the critical starting pressure and the ultimate bearing pressure, the performance of the sealing material is evaluated, and the performance evaluation results of the sealing material are obtained.

2. The performance evaluation method for differential pressure sealing materials for leakage control according to claim 1, characterized in that, S1 includes the following steps: S101. Based on the preset particle size, the sealing material is tested in combination using a laser particle size analyzer and an optical microscope to obtain the particle size distribution. S102. Using a pre-set density bottle, measure the density of the sealing material and the density of the fluid. S103. Dry and weigh the sealing material, then immerse the dried and weighed sealing material in hydrochloric acid of a preset mass concentration, weigh the sealing material after immersion for a preset time, and calculate the degree of acid solubility. S104. The sealing material is placed into a graduated cylinder containing a pre-prepared guar gum-based liquid. The time for the sealing material with the largest particle size to settle completely is recorded. The settling time of the sealing material with the largest particle size without guar gum-based liquid is compared with that of the sealing material. Based on the density difference between the sealing material and the fluid, the dispersion stability is obtained. S105. Combining the particle size distribution of the sealing material, the density of the sealing material with the density of the fluid, the degree of acid solubility, and the dispersion stability, the physicochemical performance evaluation results are obtained. S106. Based on the physicochemical performance evaluation results, select an experimental scenario that matches the field application scenario for simulation and obtain the simulation scenario.

3. The performance evaluation method for differential pressure sealing materials for leakage control according to claim 1, characterized in that, S2 includes the following steps: S201. Based on the simulation scenario, the sealing material is poured into a dumbbell-shaped mold and dried to produce a dumbbell-shaped rubber sample; S202. Using a pre-set testing instrument, the rubber sample is stretched at a pre-set rate, and the stress-strain curve is recorded. S203. Based on the linear elastic segment of the stress-strain curve, the Young's modulus is calculated using the Young's modulus calculation formula. S204. Pour the sealing material into a square mold and dry it to make a square rubber sample; S205. Using a pre-set testing instrument, record the friction force and displacement between the square rubber sample and stainless steel, and between the square rubber sample and the square rubber sample, to obtain the friction force-displacement curve. S206. Based on the friction force-displacement curve, the static friction coefficient and dynamic friction coefficient are calculated.

4. The performance evaluation method for differential pressure sealing materials for leakage control according to claim 3, characterized in that, The formula for calculating Young's modulus is as follows: in, Indicates Young's modulus. Indicates load, This indicates the cross-sectional area of ​​the rubber sample. This indicates the tensile strength of the rubber sample. Indicates the initial length of the rubber sample. Indicates strain, This indicates the fracture stress.

5. The performance evaluation method for differential pressure sealing materials for leakage control according to claim 1, characterized in that, S3 includes the following steps: S301. Based on the simulation scenario, a leak point simulation component is constructed by using a preset cylindrical hole leak seam, and a critical pressure testing device including a leak point simulation component, a core holder, a flow pump and an analytical balance is constructed by filling the core holder cavity with sealing material. S302. Set the displacement flow gradient, conduct multi-condition tests using a critical pressure testing device, use a horizontal flow pump to drive the water displacement to move the sealing material towards the leak, connect the analytical balance to the outlet end, and obtain the critical start-up pressure difference by recording the minimum pressure when the outflow is zero under different flow rates. S303. Based on the fact that the fluid before sealing is incompressible and the fluid after sealing is compressible, the Reynolds number is calculated to verify that the flow in the leak point channel is laminar, and the model assumptions are obtained. S304. Based on the critical starting pressure difference, establish the flow rate formula for incompressible flow; S305, and set a three-stage pressure loss including pipeline basic pressure loss, additional pressure loss and fluid compressibility pressure loss; S306. Based on the model assumptions, the flow rate formula for incompressible flow, and the three-stage pressure loss, a mathematical model of critical start-up pressure is constructed, and the critical start-up pressure is calculated by combining Young's modulus and the leak point size.

6. The performance evaluation method for differential pressure sealing materials for leakage control according to claim 5, characterized in that, S305 includes the following steps: S3051. Based on the pipeline's own resistance, the pipeline's foundation pressure loss is obtained by measurement without the participation of sealing materials. S3052. Use sealing materials to partially seal the leak points to form micro gaps, and use the Hagen-Poiseuille formula to simplify it to obtain the additional pressure loss; S3053. Completely seal the leak point, utilize the fluid compression to drive the pressure rise, obtain the fluid compression pressure loss, and obtain the three-stage pressure loss according to the pipeline basic pressure loss, additional pressure loss and fluid compression pressure loss stages.

7. The performance evaluation method for differential pressure sealing materials for leakage control according to claim 6, characterized in that, The expression for the critical start-up pressure is as follows: in, Indicates the critical starting pressure. This represents the correction factor for the leak size. Indicates Young's modulus; The expressions for the additional pressure loss and fluid compressibility pressure loss are as follows: in, Indicates additional pressure loss. Represents a simplified constant. This represents the flow rate of an incompressible stream. This indicates the actual length of the remaining leak. Indicates the diameter of the remaining leak point. Indicates the viscosity of the liquid. Indicates fluid compression pressure loss. Indicates displacement time. Indicates the compressibility coefficient of water. This indicates the initial volume of liquid in the tube.

8. The performance evaluation method for differential pressure sealing materials for leakage control according to claim 1, characterized in that, S4 includes the following steps: S401. Based on the simulation scenario, by injecting the sealing material into the preset simulation device, and pushing the push rod at a preset rate, pressure is applied to the sealing material. In response to the failure of the sealing layer, the maximum pressure is recorded. S402. Set the sealing material and the wall of the leak point as isotropic materials. Based on the fact that when the sealing material is under force balance, the hydrostatic thrust of the liquid is less than or equal to the static friction between the sealing material and the wall or the sealing material, the pressure assumption is obtained. S403. Based on the balance between the hydrostatic thrust and the total static friction of the sealing material, the thrust of the hydrostatic pressure on the sealing material is calculated according to the hydrostatic pressure and the exposed area of ​​the sealing material in water. S404. The total friction force is calculated by calculating the static friction force between the sealing materials and the static friction force between the sealing materials and the wall surface. S405. By utilizing the total frictional force and combining it with the relationship between Young's modulus, the stress of the sealing material, and the fracture stress, the ultimate bearing pressure is obtained. S406. Based on the critical starting pressure and ultimate bearing pressure, the performance of the sealing material is evaluated to obtain the performance evaluation results of the sealing material.

9. The performance evaluation method for differential pressure sealing materials for leakage control according to claim 8, characterized in that, The expression for the ultimate bearing pressure is as follows: in, Indicates the maximum pressure that can be withstood. This represents the total frictional force of any sealing material. This indicates the area of ​​the sealing material exposed in the water. This represents the static friction coefficient between the sealing materials. This represents the static friction coefficient between the sealing material and the wall surface. Indicates the strain of the sealing material. This indicates the actual contact area between sealing materials. This indicates the actual contact area between the sealing material and the wall surface. Indicates the sealing material under strain The stress under the condition.

10. A performance evaluation system for differential pressure plugging materials for leakage control, applied to the performance evaluation method for differential pressure plugging materials for leakage control as described in any one of claims 1-9, characterized in that, include: The physicochemical performance evaluation module is used to conduct joint tests on the sealing materials, evaluate the particle size distribution, density, acid solubility and dispersion stability of the sealing materials, obtain the physicochemical performance evaluation results, and obtain the simulation scenario; The mechanical performance evaluation module, based on a simulation scenario, is used to test and evaluate the tensile and frictional properties of the sealing material, plot the stress-strain curve and frictional displacement curve, and calculate the Young's modulus, sealing material stress, fracture stress, static friction coefficient, and dynamic friction coefficient. The critical start-up pressure evaluation module, based on a simulation scenario, is used to construct a critical pressure testing device. It obtains the critical start-up pressure difference through multi-condition testing, constructs a mathematical model of critical start-up pressure, and calculates the critical start-up pressure by combining Young's modulus and leak point size. The ultimate pressure assessment module, based on a simulation scenario, calculates the total friction force using the stress, static friction coefficient, and dynamic friction coefficient of the sealing material. Combined with the fracture stress, it obtains the ultimate pressure. Based on the critical starting pressure and the ultimate pressure, it evaluates the performance of the sealing material and obtains the performance evaluation results.

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