A method and system for testing the performance of a lost circulation material for drilling fluids

Abstract

The application relates to the technical field of drilling fluid plugging, in particular to a performance testing method and system for a plugging agent for drilling fluid, which comprises the following steps: determining the real-time equivalent hydraulic width of a simulated fracture according to an import pressure, an export pressure and an injection flow rate; adjusting an upper limit of an injection speed and a stepped pressure boosting step length, and performing stepped pressure boosting injection until a preset injection stage end condition is met; obtaining plugging performance data in the stepped pressure boosting injection process, and obtaining filtration loss data of a waiting-on-cement stage after the waiting-on-cement stage ends, and obtaining scouring data of a scouring stage after the scouring stage ends; and determining a comprehensive performance evaluation index of the plugging agent according to the plugging performance data, the filtration loss data and the scouring data. The method can improve the reliability of the evaluation result, and make the evaluation result comprehensively and truly reflect the comprehensive plugging capacity of the plugging agent under actual working conditions.

Description

Technical Field

[0001] This application relates to the field of drilling fluid plugging technology, specifically to a method and system for testing the performance of plugging agents for drilling fluids. Background Technology

[0002] In oil and gas well drilling operations, well leakage caused by formation fractures is a common and complex downhole situation. Adding a plugging agent to the drilling fluid to seal the fractures in the leakage formation is the main method for dealing with well leakage. Before being used in the field, the plugging agent needs to be tested and evaluated in the laboratory to provide a basis for the selection and formulation optimization of the plugging agent.

[0003] Currently, the performance testing of plugging agents for drilling fluids is usually carried out by gradually increasing the pressure according to a preset step pressure increment until the sealing layer is breached or the preset upper limit of injection volume is reached. Finally, the sealing effect of the plugging agent is evaluated based on the breach pressure or the cumulative injection volume.

[0004] However, the process of bridging and filling cracks with sealing materials is dynamic and the effective flow state of cracks changes continuously with the sealing process. Gradually increasing the pressure according to the preset step-by-step pressure increase is difficult to adapt to the real-time changes in the crack state, and the performance dimensions that can be evaluated are relatively singular. As a result, the test results cannot fully and truly reflect the comprehensive sealing ability of the sealing agent under actual working conditions, and have low guidance value for field operations. Summary of the Invention

[0005] To address the technical problems of how gradually increasing pressure according to preset step increments is difficult to adapt to real-time changes in fracture conditions, and how the performance dimensions that can be evaluated are relatively limited, resulting in test results that cannot comprehensively and accurately reflect the overall sealing capability of the plugging agent under actual working conditions, this application aims to provide a method and system for testing the performance of drilling fluid plugging agents. The specific technical solution adopted is as follows:

[0006] This application provides a method for testing the performance of a plugging agent for drilling fluids, comprising: real-time acquisition of the inlet pressure, outlet pressure, and injection flow rate of the simulated fracture during the injection of the plugging agent into a simulated fracture; determining the real-time equivalent hydraulic width of the simulated fracture based on the pressure difference between the inlet pressure and the outlet pressure and the injection flow rate; adjusting the upper limit of the injection rate and the step-by-step pressure increase step size based on the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width, and performing step-by-step pressure-boosting injection according to the adjusted final upper limit of the injection rate and the final step-by-step pressure increase step size until the preset injection stage end condition is met; acquiring plugging performance data during the step-by-step pressure-boosting injection process, acquiring filtration loss data during the waiting-to-set-out stage after the settling stage, and acquiring scouring data during the scouring stage after the scouring stage; and determining a comprehensive performance evaluation index of the plugging agent based on the plugging performance data, the filtration loss data, and the scouring data.

[0007] Optionally, determining the real-time equivalent hydraulic width of the simulated fracture based on the pressure difference between the inlet pressure and the outlet pressure and the injection flow rate includes: acquiring the geometrical parameters of the simulated fracture and the dynamic viscosity of the test fluid; determining the difference between the inlet pressure and the outlet pressure as the pressure difference between the inlet pressure and the outlet pressure; and determining the real-time equivalent hydraulic width based on the pressure difference, the injection flow rate, the geometrical parameters of the simulated fracture, and the dynamic viscosity of the test fluid.

[0008] Optionally, the above-mentioned adjustment of the upper limit of injection velocity and the step size of step pressurization based on the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width, and the execution of step pressurization injection according to the adjusted final upper limit of injection velocity and the final step size of step pressurization, until the preset injection stage end condition is met, includes: for each pressurization injection, determining the parameter convergence factor of this pressurization injection based on the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width; determining the final step size of step pressurization and the final upper limit of injection velocity based on the parameter convergence factor of this pressurization injection and the number of steps of this pressurization injection; under the constraint of satisfying the final upper limit of injection velocity for each pressurization injection, performing pressurization injection according to the final step size of step pressurization for each pressurization injection; and entering the next stage of pressurization when the pressure difference after each pressurization injection meets the stability judgment condition, until the preset injection stage end condition is met.

[0009] Optionally, determining the final step size and final injection speed limit of the current pressurization injection based on the parameter convergence factor and the number of steps in the current pressurization injection includes: determining the final injection speed limit as the product of the preset benchmark injection speed limit and the parameter convergence factor; determining the final step size as the product of the preset benchmark pressurization step size and the parameter convergence factor when the number of steps in the current pressurization injection is the first time; and obtaining the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment, and determining the final step size as the product of the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment and the preset benchmark pressurization step size and the parameter convergence factor when the number of steps in the current pressurization injection is not the first time.

[0010] Optionally, determining the final step size for this pressurization injection based on the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment, and the product of the preset benchmark pressurization step size and the parameter convergence factor, includes: determining the product of the preset benchmark pressurization step size and the parameter convergence factor as the initial step size for this pressurization injection; determining the width change corresponding to each adjustment based on the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment; determining the step size adjustment coefficient for this pressurization injection based on the width change corresponding to each adjustment; and correcting the initial step size for this pressurization injection based on the step size adjustment coefficient to obtain the final step size for this pressurization injection.

[0011] Optionally, determining the step size adjustment coefficient for this pressurization injection based on the width change corresponding to each adjustment includes: extracting the maximum width change from the width change of the most recent first preset number of times and the most recent width change corresponding to the most recent adjustment from the width change corresponding to each adjustment; determining the step size adjustment coefficient based on the first ratio between the most recent width change and the maximum width change, and the second ratio between the real-time equivalent hydraulic width before this pressurization injection and the equivalent hydraulic reference width.

[0012] Optionally, the method further includes: if the pressure difference after any stage of pressurization injection decreases more than a preset threshold within a preset monitoring period, lowering the final injection rate limit of the any stage of pressurization injection to a preset protection value, pausing the adjustment of the injection rate limit, and restoring the final step-by-step pressurization step size of the any stage of pressurization injection to a preset reference pressurization step size; continuously monitoring the pressure difference, and if the pressure difference meets the stability judgment condition, updating the equivalent hydraulic reference width to the real-time equivalent hydraulic width at the current moment, restoring the adjustment of the injection rate limit and the step-by-step pressurization step size, and continuing to execute the step-by-step pressurization injection.

[0013] Optionally, the above-mentioned preset injection stage termination conditions include any one of the following: the injection pressure reaches the preset pressure upper limit, the real-time equivalent hydraulic width reaches the preset width lower limit threshold, or the cumulative injection volume reaches the preset cumulative volume upper limit.

[0014] Optionally, the filtration loss data includes the cumulative filtration loss and the condensation duration, and the flushing data includes the flushing failure flow rate. The determination of the comprehensive performance evaluation index based on the plugging performance data, the filtration loss data, and the flushing data includes: obtaining the cumulative injection volume during the injection phase, the final equivalent hydraulic width at the end of the injection phase, and the breakthrough event information; determining the filtration loss rate based on the cumulative filtration loss and the condensation duration; determining the step size evolution stability value based on the step size adjustment coefficient corresponding to the second preset number of pressurized injections in the last injection phase; and determining the comprehensive performance evaluation index based on the cumulative injection volume, the final equivalent hydraulic width at the end of the injection phase, the breakthrough event information, the filtration loss rate, the flushing failure flow rate, and the step size evolution stability value.

[0015] This application also provides a performance testing system for drilling fluid plugging agents, used to implement any of the above-mentioned optional drilling fluid plugging agent performance testing methods, including a data acquisition module, a width analysis module, a pressurized injection module, and a performance evaluation module: the data acquisition module is used to acquire the inlet pressure, outlet pressure, and injection flow rate of the simulated fracture in real time during the injection of plugging agent into the simulated fracture; the width analysis module is used to determine the real-time equivalent hydraulic width of the simulated fracture based on the pressure difference between the inlet pressure and the outlet pressure and the injection flow rate; the pressurized injection module is used to determine the real-time equivalent hydraulic width based on the real-time equivalent hydraulic width. The relative relationship between the injection speed and the equivalent hydraulic reference width is used to adjust the upper limit of the injection speed and the step size of the step pressurization. The step pressurization injection is then performed according to the adjusted final upper limit of the injection speed and the final step size of the step pressurization until the preset injection stage end condition is met. The data acquisition module is also used to acquire the sealing performance data during the step pressurization injection process, and to acquire the filtration loss data during the condensation stage after the condensation stage ends, and the scouring data during the scouring stage after the scouring stage ends. The performance evaluation module is used to determine the comprehensive performance evaluation index of the plugging agent based on the sealing performance data, the filtration loss data and the scouring data.

[0016] This application has the following beneficial effects:

[0017] This application collects inlet pressure, outlet pressure, and injection flow rate in real time throughout the entire process of injecting the plugging agent, and determines the real-time equivalent hydraulic width of the simulated crack accordingly, enabling continuous monitoring of the sealing progress of the simulated crack during the test. Simultaneously, using the equivalent hydraulic reference width as a benchmark, the upper limit of the injection rate and the step-by-step pressurization increment are adjusted based on the relative relationship between the real-time equivalent hydraulic width and this benchmark. Step-by-step pressurization injection is then performed according to the adjusted parameters, ensuring that the parameters of the pressurized injection always match the current sealing state of the simulated crack. This guarantees that the test can gradually and accurately approach the true pressure-bearing limit of the sealing layer, improving the accuracy of the evaluation results. Furthermore, based on this, a comprehensive performance evaluation index is determined by integrating the sealing performance data from the injection stage, the filtration loss data from the condensation stage, and the scouring data from the scouring stage, improving the reliability of the evaluation results. This allows the evaluation results to comprehensively and accurately reflect the comprehensive sealing capability of the plugging agent under actual working conditions, thereby guiding on-site operations. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for testing the performance of a plugging agent for drilling fluid, provided in one embodiment of this application.

[0019] Figure 2 This is a structural diagram of a drilling fluid plugging agent performance testing system provided in one embodiment of this application. Detailed Implementation

[0020] The following description, in conjunction with the accompanying drawings, details the specific scheme of a drilling fluid plugging agent performance testing method and system provided in this application.

[0021] Please see Figure 1 The diagram illustrates a method flowchart for testing the performance of a plugging agent for drilling fluid according to an embodiment of this application.

[0022] like Figure 1 As shown, the performance testing methods for the drilling fluid plugging agent include S101-S105.

[0023] S101. During the process of injecting plugging agent into the simulated crack, the inlet pressure, outlet pressure, and injection flow rate of the simulated crack are collected in real time.

[0024] It should be understood that the process of injecting the plugging agent into the simulated crack is an injection stage for testing the performance of the plugging agent through the simulated crack. This injection stage is used to evaluate the bridging and sealing capacity and pressure limit of the plugging agent.

[0025] In one alternative implementation, before injecting the sealing agent into the simulated crack, the sealing slurry can be prepared according to the product standard requirements of the sealing agent. A template suitable for the type of leak layer to be simulated can be selected and placed into the test cup to form a test assembly. The sealing slurry is injected into the test container and an initial pressure is applied. The stirring device is turned on, and the stirring rate is set to the minimum rate that prevents the bridging sealing material from sinking to the bottom of the tank. The sealing slurry is heated to the test temperature, and then the sealing agent is injected into the simulated crack.

[0026] It should be understood that the simulated crack is formed by a template inserted into the test cup and adapted to the type of leak to be simulated. The template specifications determine the geometric parameters of the simulated crack. The test container is a pressure vessel containing the plugging slurry. The stirring device is used to maintain the suspension of the bridging material in the plugging slurry during the test to prevent it from settling and causing the concentration of the injected slurry to deviate from the prepared concentration.

[0027] Optionally, pressure sensors can be installed at the inlet and outlet ends of the simulated crack, a flow meter can be installed in the inlet pipeline, a filtrate collector and a flow meter can be installed at the outlet end, and a flow meter can be installed in the flushing pipeline. Data can be continuously collected at a preset sampling frequency after the test begins.

[0028] Optionally, the preset sampling frequency should be no less than 10Hz to ensure that transient changes in pressure and flow during the crack sealing process (especially the sudden drop in differential pressure when the sealing layer is breached) can be fully captured.

[0029] It should be understood that the inlet pressure is the pressure of the plugging grout at the inlet end of the simulated crack, the outlet pressure is the pressure of the plugging grout at the outlet end of the simulated crack, and the injection flow rate is the volume of plugging grout injected into the simulated crack per unit time, which is measured by the flow meter of the inlet end pipeline.

[0030] S102. Determine the real-time equivalent hydraulic width of the simulated fracture based on the pressure difference between the inlet and outlet pressures and the injection flow rate.

[0031] Among them, the pressure difference is the difference between the inlet pressure and the outlet pressure, which reflects the flow resistance when the plugging slurry flows through the simulated crack. The real-time equivalent hydraulic width is the channel width corresponding to the current flow resistance after the simulated crack is equivalent to a regular flow channel. It is used to characterize the effective flow width that the simulated crack currently allows fluid to pass through. The larger the real-time equivalent hydraulic width, the more unobstructed the crack and the lower the degree of blockage.

[0032] Understandably, the geometric width of a simulated fracture cannot be directly measured, but there is a definite hydrodynamic relationship between flow resistance and channel width—at the same flow rate, the narrower the channel, the greater the pressure differential required to maintain flow. Therefore, the current effective flow width of the simulated fracture can be calculated backwards based on the pressure differential and the injection flow rate.

[0033] In one alternative implementation, the geometric parameters of the simulated fracture and the dynamic viscosity of the test fluid can be obtained; the difference between the inlet pressure and the outlet pressure can be determined as the pressure differential between the inlet pressure and the outlet pressure; and the real-time equivalent hydraulic width can be determined based on the pressure differential, the injection flow rate, the geometric parameters of the simulated fracture, and the dynamic viscosity of the test fluid.

[0034] Among them, the geometric parameters of the simulated crack include crack length and crack height, which are known geometric parameters of the simulated crack; dynamic viscosity is the viscosity parameter of the test fluid (i.e., plugging grout), which can be pre-determined by a viscometer at the test temperature before the test.

[0035] Optionally, the real-time equivalent hydraulic width can be determined based on a parallel plate crack flow model. The parallel plate crack flow model simplifies a natural or artificial crack into a gap between two smooth, parallel, infinitely large plates. According to the cubic law of viscous fluid flow between parallel plates (i.e., the flow rate through the gap between the parallel plates is proportional to the cube of the gap opening (i.e., the distance between the two plates), the fluid is simulated to flow laminarly in the simulated crack. Based on this cubic law, the real-time equivalent hydraulic width can be determined.

[0036] Optionally, the real-time equivalent hydraulic width satisfies the following formula:

[0037]

[0038] in, It represents the real-time equivalent hydraulic width, with the dimension of length (e.g., mm). This indicates the dynamic viscosity of the test fluid, expressed in Pascal-seconds (MPa·s). Indicates the crack length, with the dimension of length (e.g., mm). This indicates the injection flow rate, in mm³ / s. The pressure difference is expressed in MPa. Indicates the height of the crack, with the dimension of length (e.g., mm). It is a very small positive number, used to prevent the denominator from being 0, and its dimensions are the same as... Consistent, the example value is 10 −6 .

[0039] The formula is obtained by inversely solving the cube law. When the injection flow rate is constant, the larger the pressure difference, the narrower the channel. Therefore, the real-time equivalent hydraulic width is inversely related to the pressure difference and is cubically related. When the pressure difference is constant, the larger the injection flow rate, the wider the channel. Therefore, the real-time equivalent hydraulic width is positively related to the injection flow rate.

[0040] S103. Based on the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width, adjust the upper limit of the injection speed and the step size of the step pressurization, and perform step pressurization injection according to the adjusted final upper limit of the injection speed and the final step size of the step pressurization until the preset injection stage end condition is met.

[0041] The equivalent hydraulic reference width serves as a reference benchmark for the sealing process. During the injection of plugging agent into the simulated fracture, it can be initially set as the real-time equivalent hydraulic width of the simulated fracture in its initial state before the plugging agent is injected, and can be updated subsequently based on the pressure difference.

[0042] The injection speed limit refers to the maximum flow rate that the injection pump is allowed to perform injection per unit time. The injection speed used by the injection pump during actual injection should not exceed this injection speed limit. The step-up pressure increment is the pressure increment of each step-up pressure injection process.

[0043] It should be understood that step-by-step pressurization injection refers to an injection method in which the injection pressure is increased step by step according to the step size, and the pressure is maintained and monitored after each pressurization.

[0044] Understandably, as the sealing material gradually bridges and fills the crack, the effective flow width of the crack continuously decreases. If injection is consistently performed at the initially preset upper limit of injection speed and stepped pressure increase step, pressure overshoot will occur when the crack has already narrowed significantly, damaging the formed sealing layer and making the test unable to reflect the true pressure-bearing limit of the sealing layer. Therefore, the embodiments of this application use the equivalent hydraulic reference width as a benchmark, and adjust the upper limit of injection speed and stepped pressure increase step according to the relative relationship between the real-time equivalent hydraulic width and the benchmark, to approach the sealing limit in a gentler and more precise manner, thereby improving the accuracy of pressure-bearing limit determination.

[0045] Optionally, the preset injection stage termination condition may include any one of the following: the injection pressure reaches the preset pressure upper limit, the real-time equivalent hydraulic width reaches the preset width lower limit threshold, or the cumulative injection volume reaches the preset cumulative volume upper limit.

[0046] The preset pressure limit is the highest injection pressure allowed during the injection phase, representing the safety boundary of the equipment. When the injection pressure reaches the preset pressure limit, it indicates that the sealing layer strength of the plugging agent is no less than the pressure resistance level corresponding to the preset pressure limit. Continuing to increase the pressure exceeds the safety limit of the equipment, and it is impossible to further explore its pressure resistance limit under higher pressure. At this time, the step-by-step pressure injection can be stopped, that is, the injection phase ends.

[0047] Optionally, the preset pressure limit can be set to the maximum test pressure specified in the test standard or the expected pressure requirement of the target leak layer.

[0048] The preset lower limit threshold is the width boundary for determining when a crack is close to complete sealing, representing the physical limit of sealing. When the real-time equivalent hydraulic width reaches the preset lower limit threshold, it indicates that the sealing material has fully bridged, filled, and compacted in the crack, and has reached the standard of complete sealing. If the pressure is increased or the sealing agent is injected, there is no significant room for the real-time equivalent hydraulic width to decrease. At this point, the step-by-step pressurization injection can be stopped, that is, the injection stage ends.

[0049] Optionally, the preset lower limit threshold can be taken as 1% to 5% of the equivalent hydraulic reference width.

[0050] The preset cumulative upper limit is the maximum volume of the grout allowed to be injected into the simulated crack, representing the material consumption boundary. When the cumulative injection volume reaches the preset cumulative upper limit, it indicates that the sealing ability of the grout has reached a stable state under this cumulative injection volume, and continuing injection will not substantially change the sealing effect. At this time, the step-by-step pressurization injection can be stopped, that is, the injection stage ends.

[0051] Optionally, the preset cumulative limit can be set to the capacity of the test container.

[0052] It should be understood that the cumulative injection volume is the total volume of plugging slurry that enters the simulated crack during the entire injection phase, which can be read from the plugging slurry flow meter installed between the injection pump and the simulated crack inlet.

[0053] S104. Obtain the plugging performance data during the step-by-step pressurization injection process, and obtain the filtration loss data during the waiting-to-condense stage after the condensation stage ends, and obtain the flushing data during the flushing stage after the flushing stage ends.

[0054] It should be understood that the complete testing process for plugging agents includes the injection phase, the settling phase, and the flushing phase. The injection phase is used to evaluate the plugging agent's bridging and sealing capabilities and pressure resistance under dynamic injection conditions; the settling phase is used to evaluate the tightness and filtration characteristics of the plugging layer under static conditions; and the flushing phase is used to evaluate the plugging layer's resistance to damage under drilling fluid circulation flushing conditions.

[0055] The plugging performance data during the step-increase injection process are data recorded during the injection phase that reflect the bridging and plugging capabilities of the plugging agent.

[0056] Optionally, the plugging performance data includes the cumulative injection volume, the final equivalent hydraulic width (i.e., the real-time equivalent hydraulic width of the simulated fracture at the end of the injection stage), breakthrough event information (i.e., whether the plugging layer has broken through, the number of breakthroughs, and the pressure of each breakthrough, which can be recorded each time the plugging layer breaks through during the injection stage), and the step size adjustment coefficient corresponding to each pressurized injection (which can be obtained during the pressurized injection process).

[0057] It should be understood that once the preset injection phase end conditions are met, the injection phase ends and the setting phase begins. At this time, the injection pump and inlet valve can be closed to stop the injection of the plugging slurry, allowing the sealing layer to stand under static conditions for a period of time (the standing time is the preset setting time, determined according to the plugging agent product standard or experimental design, usually 30 minutes). During the standing period, the plugging material in the sealing layer continues to hydrate, expand, and compact, while the fluid in the fracture slowly passes through the sealing layer under the action of pressure difference. During this process, filtration data is collected. After the preset setting time is reached, the setting phase ends and the flushing phase begins. At this time, the circulation pump and flushing valve are turned on, allowing simulated drilling fluid to pass through the surface of the sealing layer or fracture channels, simulating the circulating flushing effect of drilling fluid on the sealing layer during actual drilling. During this process, flushing data is collected.

[0058] Optionally, the filtration loss data includes cumulative filtration loss and condensation duration. Cumulative filtration loss is the total amount of fluid lost through the sealing layer during the condensation period, which can be read from a filtration loss flow meter installed after the simulated crack outlet and connected to the filtrate collector; condensation duration is the settling time from when the injection pump is turned off to when the circulation pump is turned on.

[0059] Optionally, the flushing data includes flushing flow rate, flushing failure flow rate, and flushing cumulative time. The flushing flow rate is the simulated drilling fluid flow rate output by the circulating pump, which can be collected in real time by a flow meter on the flushing pipeline. The flushing failure flow rate refers to the flushing flow rate corresponding to the destruction of the sealing layer under the action of circulating flushing. If the sealing layer is not destroyed during the flushing stage, the maximum flushing flow rate at the end of the flushing stage is taken as the flushing failure flow rate. The flushing cumulative time is the total duration from the start to the end of flushing.

[0060] S105. Based on the sealing performance data, filtration loss data, and flushing data, determine the comprehensive performance evaluation index of the plugging agent.

[0061] Among them, the comprehensive performance evaluation index is used to evaluate the overall sealing performance of the plugging agent.

[0062] It is understandable that if a plugging agent has high pressure resistance during the injection stage but suffers from severe filtration loss during the solidification stage, or fails rapidly during the scouring stage, it will not be able to meet the plugging requirements in actual drilling. Therefore, the data from the three stages are integrated into a comprehensive performance evaluation index, so that only plugging agents that perform in a balanced manner in the three dimensions of bridging, static filtration loss, and scouring resistance can obtain a high comprehensive plugging performance evaluation, so that the evaluation results can be aligned with the needs of actual downhole working conditions.

[0063] The methods provided in S101-S105 above collect inlet pressure, outlet pressure, and injection flow rate in real time throughout the entire process of injecting the plugging agent, and determine the real-time equivalent hydraulic width of the simulated crack accordingly. This allows for continuous monitoring of the sealing process of the simulated crack during the test. Simultaneously, using the equivalent hydraulic reference width as a benchmark, the upper limit of the injection speed and the step-by-step pressurization increment are adjusted based on the relative relationship between the real-time equivalent hydraulic width and this benchmark. Step-by-step pressurization injection is then performed according to the adjusted parameters, ensuring that the parameters of the pressurized injection always match the current sealing state of the simulated crack. This guarantees that the test can gradually and accurately approach the true pressure-bearing limit of the sealing layer, improving the accuracy of the evaluation results. Furthermore, a comprehensive performance evaluation index is determined by integrating the sealing performance data from the injection stage, the filtration loss data from the condensation stage, and the scouring data from the scouring stage. This improves the reliability of the evaluation results, enabling them to comprehensively and accurately reflect the comprehensive sealing capability of the plugging agent under actual working conditions, thereby guiding on-site operations.

[0064] In one implementation of this application embodiment, the above-mentioned S103 can be specifically implemented by S201-S204.

[0065] S201. For each pressurization injection, the parameter convergence factor of this pressurization injection is determined based on the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width.

[0066] It should be understood that the parameter convergence factor is used to characterize the current remaining flow capacity of the simulated crack. The larger the parameter convergence factor, the stronger the current remaining flow capacity of the simulated crack and the lower the degree of blockage.

[0067] Optionally, the ratio between the real-time equivalent hydraulic width and the equivalent hydraulic reference width can be determined as the parameter convergence factor.

[0068] It is understandable that when the simulated crack has not been effectively sealed, the closer the real-time equivalent hydraulic width is to the equivalent hydraulic reference width, the closer the parameter convergence factor is to 1. As the sealing progresses, the real-time equivalent hydraulic width decreases, and the parameter convergence factor decreases accordingly.

[0069] It should be understood that the convergence factor of the parameters used in each pressurization injection is calculated based on the real-time equivalent hydraulic width at the latest moment before this pressurization injection.

[0070] S202. Based on the convergence factor of the parameters for this boost injection and the number of steps for this boost injection, determine the final step size of the boost injection and the upper limit of the final injection speed.

[0071] The step number is the sequence number of the current boost injection in the entire step boost injection process, used to distinguish whether this boost is the first boost.

[0072] Optionally, the product of a preset baseline injection speed limit and a parameter convergence factor can be used to determine the final injection speed limit for this pressurized injection.

[0073] It should be understood that the preset baseline injection speed limit refers to the maximum injection flow rate that the injection pump is allowed to reach in the initial state. This value can be set in advance by the experimenter based on the geometric parameters of the simulated crack device, the rheological properties of the test fluid, and the experimental design requirements before the test begins.

[0074] For example, the preset baseline injection rate can be set to an empirical value of 100 mL / min.

[0075] Understandably, when the residual flow capacity of the simulated crack is strong, the final upper limit of the injection rate should be close to the preset benchmark injection rate upper limit, that is, allow the plugging agent to be delivered into the simulated crack at a higher speed as soon as possible; as the sealing process of the simulated crack progresses, the upper limit of the injection rate should be reduced accordingly to prevent high-speed injection from damaging the sealing layer.

[0076] In one optional implementation, when the number of steps for this boost injection is the first, the product of the preset baseline boost step size and the parameter convergence factor is determined as the final step size for this boost injection.

[0077] It should be understood that the preset benchmark pressure increase step size refers to the basic magnitude of the pressure increase at each stage during the step-by-step pressure injection process, with the unit being MPa. Its value can be preset by the experimenter according to the test accuracy requirements before the test begins.

[0078] For example, for conventional sealant performance testing, the preset benchmark pressure step can be set to 0.5 MPa, while for sealant performance testing with higher accuracy requirements, the preset benchmark pressure step can be set to 0.2 MPa.

[0079] It should be understood that the product of the preset benchmark pressure increment and the parameter convergence factor is equivalent to proportionally converting the pressure increment designed for the initial wide channel to the current remaining flow capacity of the simulated crack: when the simulated crack is still wide, this product is close to the preset benchmark pressure increment, and the disturbance of each pressure increment matches the channel's capacity; when the simulated crack narrows, this product decreases synchronously, and the disturbance of each pressure increment converges to the level that the current channel can withstand.

[0080] It is understandable that since this is the first time that the pressure injection has been performed, it means that there are currently no historical adjustment records available for trend analysis. The product has fully reflected the only available crack state information. Therefore, the product can be directly determined as the final step size for this pressure injection.

[0081] In another optional implementation, if the number of steps for this pressurization injection is not the first time, the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment can be obtained, and the final step size of this pressurization injection can be determined based on the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment and the product of the preset benchmark pressurization step size and the parameter convergence factor.

[0082] It is understandable that if this pressurization injection step is not the first one, it means that at least one complete adjustment and pressurization process has been carried out. At this time, we can further analyze the actual effect before and after each adjustment, so that the final step pressurization step not only reflects the current degree of crack sealing, but also reflects the evolution trend of the effect of each adjustment, so that the step length adjustment becomes more and more accurate as the sealing process progresses.

[0083] In one optional implementation, the product of a preset baseline pressurization step size and a parameter convergence factor can be used to determine the initial stepped pressurization step size for this pressurization injection; the width change corresponding to each adjustment can be determined based on the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment; the step size adjustment coefficient for this pressurization injection can be determined based on the width change corresponding to each adjustment; and the initial stepped pressurization step size for this pressurization injection can be corrected based on the step size adjustment coefficient to obtain the final stepped pressurization step size for this pressurization injection.

[0084] Understandably, when the number of steps in this pressurization injection is not the first time, the product of the preset benchmark pressurization step size and the parameter convergence factor only reflects the static plugging state of the simulated crack at the current moment and does not incorporate the evolution trend of the plugging process. Therefore, this product can be used as the initial step size of this pressurization injection. On this basis, the step size adjustment coefficient is superimposed with the trend correction to obtain the final step size of this pressurization injection.

[0085] Optionally, the difference between the real-time equivalent hydraulic width before each adjustment and the real-time equivalent hydraulic width after the adjustment can be determined as the width change for each adjustment. The width change corresponding to each adjustment is used to characterize the promoting effect of each adjustment on the sealing process. When the width change is greater than 0, it indicates that the crack width has decreased and the sealing degree has increased after the adjustment, and the adjustment is effective; when the width change is less than or equal to 0, it indicates that the adjustment is ineffective or has a poor effect.

[0086] In one optional implementation, the maximum width change among the width changes of the most recent first preset number of times and the most recent width change corresponding to the most recent adjustment are extracted from the width change corresponding to each adjustment; the step size adjustment coefficient is determined based on the first ratio between the most recent width change and the maximum width change, and the second ratio between the real-time equivalent hydraulic width before the current pressurization injection and the equivalent hydraulic reference width.

[0087] It should be understood that the maximum width change among the width changes in the most recent first preset number of times can represent the best effect actually achieved by the adjustment strategy in the test phase similar to the current time. Using this maximum width change as a benchmark for measuring the most recent width change can ensure that the benchmark is in a similar blocking process to the current simulated crack state, thus guaranteeing the synchronicity and comparability of the benchmark.

[0088] It should be noted that when the maximum width change is less than or equal to zero, it means that in the most recent first preset number of adjustments, none of the adjustments have resulted in a positive reduction in the width of the simulated crack. In other words, there is no effective adjustment level to refer to in the most recent stage. The reason for this may be that the simulated crack is close to being completely sealed and there is no room for further width reduction, or it may be that the sealing process has stalled and the adjustment has failed to promote sealing. In this case, the first ratio can be directly assigned to a preset non-negative lower limit value, such as 0.05, so that the current pressurized injection can be carried out in small steps for fine exploration until the preset injection stage end condition is met.

[0089] In addition, when the first ratio is negative, in order to avoid the physically meaningless situation that the final step boost step size is negative due to the negative step size adjustment coefficient, the first ratio can also be assigned the above-mentioned preset non-negative lower limit value.

[0090] For example, the first preset number of times can be the most recent 3 to 5 times.

[0091] Understandably, the closer the first ratio is to 1, the closer the current adjustment efficiency is to the optimal level of the most recent stage, and the adjustment range can be maintained, so the step size adjustment coefficient should be larger; the closer the first ratio is to 0, the more the actual effect of the most recent adjustment has obviously diminished, and the promotion effect of the adjustment strategy on the blocking process has weakened, so the adjustment range should be reduced accordingly, and the step size adjustment coefficient should be smaller.

[0092] It should be understood that the second ratio is used to characterize the remaining sealing space of the simulated crack. The closer the second ratio is to 1, the closer the real-time equivalent hydraulic width before this pressurization injection is to the equivalent hydraulic reference width. At this time, the crack has not been effectively sealed, and the adjustment intensity should be maintained to accelerate the sealing. The step size adjustment coefficient should be larger. The closer the second ratio is to 0, the closer the simulated crack is to complete sealing. At this time, the adjustment amplitude should be automatically reduced to finely explore the sealing limit. The step size adjustment coefficient should be smaller.

[0093] It should be noted that neither the real-time equivalent hydraulic width nor the equivalent hydraulic reference width before this pressurization injection were zero or negative.

[0094] Optionally, the product of the first ratio and the second ratio can be determined as the step size adjustment coefficient.

[0095] Optionally, the product of the step size adjustment factor and the initial step size of the current pressurization injection can be determined as the final step size of the current pressurization injection.

[0096] S203. Under the constraint of satisfying the upper limit of the final injection speed for each boost injection, boost injection is performed according to the final step size of the boost injection.

[0097] Specifically, the actual injection rate of each boosted injection should be less than or equal to the upper limit of the final injection rate of that boosted injection, and the injection pressure used for each boosted injection should be the injection pressure used in the previous boosted injection plus the final step size of the boosted injection, and this injection pressure should be maintained.

[0098] S204. If the pressure difference after each pressurization injection meets the stability judgment condition, proceed to the next pressurization stage until the preset injection stage end condition is met.

[0099] It should be understood that the stability criteria are used to determine whether the plugging layer has reached a stable state under the current pressure level.

[0100] Optionally, the stability determination condition can be: the pressure difference fluctuation after each pressurization injection within a preset stabilization time is less than the stability criterion threshold.

[0101] It should be understood that the pressure difference after each pressurization injection is the pressure difference between the inlet pressure and the outlet pressure monitored in real time within a preset stabilization period after each pressurization injection, and the pressure difference fluctuation is the absolute value of the difference between the maximum and minimum pressure difference within the preset stabilization period.

[0102] For example, the preset stabilization time can be an empirical value of 30s to 120s, and the stabilization criterion threshold can be 1% to 5% of the average value of the pressure difference monitored within the preset stabilization time.

[0103] Optionally, if the pressure difference after each pressurization injection does not meet the stability criteria, it indicates that the sealing layer is not yet stable. In this case, the pressure difference should be monitored and the pressurization injection should be maintained.

[0104] In one optional implementation, during the pressurization injection process, if the pressure difference after any stage of pressurization injection decreases more than a preset threshold within a preset monitoring period, the upper limit of the final injection rate of that stage of pressurization injection can be lowered to a preset protection value, the adjustment of the upper limit of the injection rate can be paused, and the final step-by-step pressurization step size of that stage of pressurization injection can be restored to a preset reference pressurization step size. The pressure difference is continuously monitored, and if the pressure difference meets the stability judgment condition, the equivalent hydraulic reference width is updated to the real-time equivalent hydraulic width at the current moment, the adjustment of the upper limit of the injection rate and the step-by-step pressurization step size can be restored, and the step-by-step pressurization injection can continue.

[0105] The preset breakthrough threshold is used to determine whether the blocking layer has been breached.

[0106] It is understandable that when the sealing layer is crushed, the flow resistance of the simulated crack drops sharply, and the pressure difference will drop significantly in a short period of time. Therefore, if the pressure difference after any level of pressurization injection decreases more than the preset breakthrough threshold within the preset monitoring time, it can be determined that the sealing layer has been breached.

[0107] For example, the preset monitoring duration can be an empirical value of 1 to 5 seconds, and the preset breakthrough threshold should be higher than the above-mentioned stability criterion threshold, for example, 10% to 30% of the current pressure difference.

[0108] Optionally, when it is determined that the sealing layer has been breached, the breach pressure of this breach can also be recorded.

[0109] Understandably, at the moment the sealing layer is breached, the flow regime within the simulated fracture changes drastically, and the pressure differential and flow rate are in a non-steady state. The calculated real-time equivalent hydraulic width at this point is a distorted, spiked value. If the injection velocity upper limit is adjusted based on this distorted real-time equivalent hydraulic width, an incorrect and excessively large injection velocity upper limit will be obtained, causing secondary impact on the remaining sealing layer. Therefore, after a breach is determined, the currently used final injection velocity upper limit should be immediately lowered to the preset protection value, and adjustments to the injection velocity upper limit should be suspended. The currently used final step pressure increase step size should be restored to the preset baseline pressure increase step size, allowing the simulated fracture to pass through the non-steady-state period under low-disturbance conditions.

[0110] It should be understood that the preset protection value is the upper limit of the low injection speed allowed after the limit is exceeded. For example, it can be 10% to 30% of the preset baseline injection speed upper limit.

[0111] Optionally, the injection pressure used in the last boost injection can be updated to the injection pressure under the current stable state.

[0112] Understandably, after a breach occurs, the fracture forms a new flow structure containing a residual sealing layer, and its width reference is no longer the same as the initial state before the breach. Once the pressure difference meets the stability criteria again and the flow enters a stable period, the equivalent hydraulic reference width can be updated to the real-time equivalent hydraulic width at the current moment. That is, the actual state of the new structure after the breach is used as the new adjustment reference. At the same time, the pressure anchor point is synchronously reset to the actual injection pressure under the current stable state. The restored step pressurization starts again from the true low-pressure state, and then the step pressurization injection continues, so that the parameter adjustment after the breach is still based on the true and stable width reference, and the residual sealing capacity of the sealing layer after the breach is evaluated.

[0113] The methods provided in S201-S204 above obtain the parameter convergence factor through the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width. This ensures that the final step size of each pressurization and the upper limit of the final injection rate are based on the latest crack sealing state at that time. During the first pressurization, the product of the preset benchmark pressurization step size and the parameter convergence factor is directly used. During subsequent pressurizations, a step size adjustment coefficient is further introduced, making the step size adjustment increasingly precise as the sealing process evolves. This avoids over-rushing damage caused by coarse step sizes in the later stages of sealing, and also avoids unnecessary excessive refinement and prolonged testing. At the same time, after each pressurization stage, the stability of the sealing layer is confirmed through stability judgment conditions before proceeding to the next stage, ensuring that each pressure load acts on a stable sealing structure. Thus, by determining the parameter convergence factor, determining the upper limit of the injection rate and the final step size of the pressurization, pressurization under constraints, and stability judgment, the complete control loop allows the test to approach the pressure limit with a level of precision matching the actual sealing capacity of the material, improving the objectivity and repeatability of the test results.

[0114] In one implementation of this application embodiment, the above-mentioned S105 can be specifically implemented by S301-S304.

[0115] S301. Obtain the cumulative injection volume during the injection phase, the final equivalent hydraulic width at the end of the injection phase, and the breakthrough event information.

[0116] The breakthrough event information includes whether a breakthrough occurred during the injection phase, the breakthrough pressure for each breakthrough, and the total number of breakthroughs.

[0117] S302. Determine the filtration rate based on the cumulative filtration loss and the duration of condensation.

[0118] Alternatively, the cumulative filtration loss can be divided by the condensation duration to obtain the filtration rate.

[0119] The filtration rate is used to characterize the filtration control capability of the plugging layer under static conditions. The smaller the filtration rate, the denser the plugging layer is under static conditions and the stronger its filtration control capability.

[0120] S303. Determine the stable value of the step size evolution based on the step size adjustment coefficient corresponding to the second preset number of pressurized injections in the last injection stage.

[0121] It should be understood that the step size evolution stability value is used to characterize the stable state of the step size adjustment amplitude in the later stage of the injection phase.

[0122] Optionally, the average value of the step size adjustment coefficient corresponding to the second preset number of boost injections in the last injection phase can be used as the step size evolution stability value.

[0123] For example, the second preset number of times can be taken as an empirical value of 3 times.

[0124] Optionally, if the preset injection phase termination condition is met only when the first pressurization injection occurs during the injection phase, and there is no step size adjustment coefficient, then the step size evolution stability value can be assigned to 1, representing a neutral state in which no trend correction is applied during the injection phase.

[0125] S304. Determine the comprehensive performance evaluation index based on the cumulative injection volume, the final equivalent hydraulic width at the end of the injection phase, the breakthrough event information, the filtration rate, the scouring failure flow rate, and the step size evolution stability value.

[0126] In this embodiment of the application, it can be determined whether a breakthrough has occurred during the injection stage based on the breakthrough event information, and then different methods are adopted to determine the comprehensive performance evaluation index according to whether a breakthrough has occurred.

[0127] Optionally, when determining the comprehensive performance evaluation index, an equivalent hydraulic width qualification threshold can be set according to the sealing qualification standard corresponding to the target leakage layer type, and the sealing density can be measured by the equivalent hydraulic width qualification threshold and the final equivalent hydraulic width at the end of the injection stage.

[0128] Alternatively, if a breakthrough occurs during the injection phase, the overall performance evaluation index can be determined using the following formula:

[0129]

[0130] in, This represents the comprehensive performance evaluation index. It represents the average breakthrough pressure, with the dimension of pressure (such as MPa). It can be obtained by averaging all breakthrough pressures in the breakthrough event information. This indicates the cumulative injection volume, measured in volume (e.g., mL). This indicates that the total number of attempts has been exceeded. This represents the equivalent hydraulic width qualification threshold, with the dimension being length (e.g., mm). It represents the final equivalent hydraulic width at the end of the injection phase, with the dimension of length (e.g., mm). This indicates the flow rate at which the scouring fails, and the dimension is volumetric flow rate (e.g., mL / min). This represents the stable value of the step size evolution, and is a dimensionless parameter. This indicates the filtration rate, with the dimension being volumetric flow rate (e.g., mL / min). and To prevent zero protection items, An example value is 10. -6 Dimensions and Consistent, An example value is 10. -6 Dimensions and Consistent.

[0131] In this formula, To improve blocking efficiency and overcome stability factors. This value represents the average pressure bearing capacity of the sealing layer during multiple breakthroughs; a higher value indicates that the sealing layer can withstand pressure loads. This indicates the amount of material consumed; the less material consumed to achieve the same pressure level, the higher the sealing efficiency. The frequency of breakthroughs indicates that the sealing layer has repeatedly failed and is less stable, thus penalizing frequent breakthroughs. The final sealing density factor, For fixed qualification standards, The value represents the final density of the sealing layer after repeated pressure repair; the smaller the value, the more tightly the simulated crack is sealed. As a robust factor across all stages, The larger the value, the stronger the resistance to erosion. This characterizes the stable state of the step size adjustment amplitude in the later stage of injection, reflecting the smoothness of the test process during the injection phase. The static compactness of the plugging layer during the condensation stage is characterized; the smaller the filtration rate, the denser the plugging layer.

[0132] In the above formula, The dimensions are pressure / volume (e.g., MPa / mL). The ratio of lengths is dimensionless. Since it is a dimensionless ratio of volumetric flow rate, the dimension of the comprehensive performance evaluation index is pressure / volume (e.g., MPa / mL).

[0133] By multiplying these three factors, any factor approaching zero will cause the overall performance evaluation index to approach zero. This ensures that only sealants that demonstrate balanced performance across dimensions such as pressure resistance, material usage, density, impact resistance, and low filtration loss can achieve a high overall performance evaluation index.

[0134] Alternatively, if no breakthrough occurs during the injection phase, the overall performance evaluation index can be determined using the following formula:

[0135]

[0136] In this formula, To prevent zero protection, its dimensions are the same as... Consistent, the example value is 10 −6 , Used to comprehensively evaluate the sealing density and material utilization rate during the injection stage, that is, the smaller the final equivalent hydraulic width and the smaller the cumulative injection volume, the more compact the sealing is achieved with less material; The meaning is the same as the breakthrough situation.

[0137] It should be noted that in this formula, Its dimension is the reciprocal of (length × volume) (e.g., 1 / (mm·mL)), and it is related to the breakthrough condition. The dimensions (pressure / volume, such as MPa / mL) are different; the comprehensive performance evaluation index under the two working conditions is used as a relative evaluation index within its respective working condition, and no numerical comparison is made across working conditions. Therefore, the difference in dimensions does not affect the reliability of the evaluation results.

[0138] The methods provided in S301-S304 above integrate the cumulative injection volume, final equivalent hydraulic width, and breakthrough event information during the injection phase; the filtration rate determined by the cumulative filtration loss and the duration of the waiting period during the solidification phase; the scouring failure flow rate during the scouring phase; and the stable value of the step size evolution reflecting the stable state of the step size adjustment in the later stage of injection, into a comprehensive performance evaluation index. Different integration structures are adopted according to whether a breakthrough occurs: under breakthrough conditions, the average breakthrough pressure and the number of breakthroughs reflect the sealing efficiency and stability during repeated pressure processes; under non-breakthrough conditions, the final equivalent hydraulic width and the cumulative injection volume reflect the sealing density and material utilization rate. This ensures that the evaluation conclusions have both a comparable historical benchmark and are aligned with the actual downhole plugging requirements, achieving an accurate, comprehensive, and reproducible quantitative evaluation of the comprehensive plugging performance of the plugging agent.

[0139] This application also provides a drilling fluid plugging agent performance testing system for implementing any of the above-mentioned optional drilling fluid plugging agent performance testing methods.

[0140] like Figure 2 As shown, the drilling fluid plugging agent performance testing system 40 includes a data acquisition module 401, a width analysis module 402, a pressurization injection module 403, and a performance evaluation module 404.

[0141] The data acquisition module 401 is used to collect the inlet pressure, outlet pressure and injection flow rate of the simulated crack in real time during the injection of plugging agent into the simulated crack.

[0142] The width analysis module 402 is used to determine the real-time equivalent hydraulic width of the simulated fracture based on the pressure difference between the inlet and outlet pressures and the injection flow rate.

[0143] The pressurized injection module 403 is used to adjust the upper limit of injection speed and the step-by-step pressurization step size according to the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width, and to perform step-by-step pressurized injection according to the adjusted final upper limit of injection speed and the final step-by-step pressurization step size until the preset injection stage end condition is met.

[0144] The data acquisition module 401 is also used to acquire the plugging performance data during the step-by-step pressurization injection process, and to acquire the filtration loss data of the waiting-to-condense stage after the condensation stage ends, and to acquire the flushing data of the flushing stage after the flushing stage ends.

[0145] The performance evaluation module 404 is used to determine the comprehensive performance evaluation index of the plugging agent based on the sealing performance data, filtration loss data, and flushing data.

[0146] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0147] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for testing the performance of a plugging agent for drilling fluids, characterized in that, include: The inlet pressure, outlet pressure, and injection flow rate of the simulated fracture were collected in real time during the injection of plugging agent into the simulated fracture. The real-time equivalent hydraulic width of the simulated fracture is determined based on the pressure difference between the inlet and outlet pressures and the injection flow rate. Based on the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width, the upper limit of the injection speed and the step size of the step pressurization are adjusted, and step pressurization injection is performed according to the adjusted final upper limit of the injection speed and the final step size of the step pressurization until the preset injection stage end condition is met. Acquire the plugging performance data during the step-by-step pressurization injection process, and acquire the filtration loss data during the waiting-to-condense stage after the condensation stage ends, and acquire the flushing data during the flushing stage after the flushing stage ends. Based on the sealing performance data, the filtration loss data, and the flushing data, a comprehensive performance evaluation index for the plugging agent is determined.

2. The method for testing the performance of a plugging agent for drilling fluid according to claim 1, characterized in that, The process of determining the real-time equivalent hydraulic width of the simulated fracture based on the pressure difference between the inlet and outlet pressures and the injection flow rate includes: Obtain the geometric parameters of the simulated crack and the dynamic viscosity of the test fluid; The difference between the inlet pressure and the outlet pressure is defined as the pressure differential between the inlet pressure and the outlet pressure. The real-time equivalent hydraulic width is determined based on the pressure difference, the injection flow rate, the geometric parameters of the simulated crack, and the dynamic viscosity of the test fluid.

3. The method for testing the performance of a plugging agent for drilling fluid according to claim 1, characterized in that, The step involves adjusting the upper limit of the injection rate and the step size of the step pressurization based on the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width, and then performing step-by-step pressurization injection according to the adjusted final upper limit of the injection rate and the final step size of the step pressurization until the preset injection stage end condition is met, including: For each pressurization injection, the parameter convergence factor for this pressurization injection is determined based on the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width. Based on the convergence factor of the parameters for this pressurization injection and the number of steps for this pressurization injection, determine the final step size of the pressurization injection and the upper limit of the final injection speed. Under the constraint of satisfying the upper limit of the final injection rate for each pressurized injection, pressurized injection is performed according to the final step size of the pressurized injection for each pressurized injection. If the pressure difference after each pressurization injection meets the stability criteria, the next pressurization stage begins, continuing until the preset injection stage termination criteria are met.

4. The method for testing the performance of a plugging agent for drilling fluid according to claim 3, characterized in that, The determination of the final step size and the upper limit of the final injection rate for this pressurization injection, based on the convergence factor of the parameters used in this pressurization injection and the number of steps in this pressurization injection, includes: The product of the preset baseline injection speed limit and the parameter convergence factor is determined as the final injection speed limit for this pressurized injection. If this is the first time that a boost injection has been performed, the product of the preset baseline boost step size and the parameter convergence factor will be determined as the final step size for this boost injection. If the number of steps in this pressurization injection is not the first time, obtain the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment, and determine the final step size of this pressurization injection based on the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment and the product of the preset benchmark pressurization step size and the parameter convergence factor.

5. The method for testing the performance of a plugging agent for drilling fluid according to claim 4, characterized in that, The final step size for this pressurization injection is determined based on the real-time equivalent hydraulic width of the simulated fracture before and after each adjustment, and the product of the preset benchmark pressurization step size and the parameter convergence factor. This includes: The product of the preset benchmark boost step size and the parameter convergence factor is determined as the initial step size for this boost injection. The width change corresponding to each adjustment is determined based on the real-time equivalent hydraulic width of the simulated crack before and after each adjustment. The step size adjustment coefficient for this pressurization injection is determined based on the corresponding width change in each adjustment. The initial step size of the boost injection is corrected according to the step size adjustment coefficient to obtain the final step size of the boost injection.

6. The method for testing the performance of a plugging agent for drilling fluid according to claim 5, characterized in that, The step size adjustment coefficient for this pressurization injection is determined based on the width change corresponding to each adjustment, including: Extract the maximum width change from the width changes of the most recent first preset number of times, and the most recent width change corresponding to the most recent adjustment from the width change corresponding to each adjustment; The step size adjustment coefficient is determined based on the first ratio between the most recent width change and the maximum width change, and the second ratio between the real-time equivalent hydraulic width before this pressurization injection and the equivalent hydraulic reference width.

7. The method for testing the performance of a plugging agent for drilling fluid according to claim 4, characterized in that, The method further includes: If the pressure difference after any stage of boost injection decreases more than a preset threshold within a preset monitoring period, the upper limit of the final injection rate of the boost injection at any stage will be lowered to a preset protection value, the adjustment of the upper limit of the injection rate will be paused, and the final step boosting step size of the boost injection at any stage will be restored to a preset reference boosting step size. The pressure difference is continuously monitored. When the pressure difference meets the stability judgment condition, the equivalent hydraulic reference width is updated to the real-time equivalent hydraulic width at the current moment, the adjustment of the upper limit of injection speed and the step pressurization step size is restored, and the step pressurization injection is continued.

8. The method for testing the performance of a plugging agent for drilling fluid according to claim 1, characterized in that, The pre-defined injection phase termination conditions include: The injection pressure reaches the preset pressure upper limit, the real-time equivalent hydraulic width reaches the preset width lower limit threshold, or the cumulative injection volume reaches the preset cumulative volume upper limit, whichever of the following conditions applies.

9. The method for testing the performance of a plugging agent for drilling fluid according to claim 6, characterized in that, The filtration loss data includes cumulative filtration loss and condensation duration; the flushing data includes flushing failure flow rate; and the determination of the comprehensive performance evaluation index of the plugging agent based on the sealing performance data, the filtration loss data, and the flushing data includes: Obtain the cumulative injection volume during the injection phase, the final equivalent hydraulic width at the end of the injection phase, and information on the breakthrough event; The filtration rate is determined based on the cumulative filtration loss and the duration of condensation. The step size evolution stability value is determined based on the step size adjustment coefficient corresponding to the second preset number of pressurized injections in the last injection phase. The comprehensive performance evaluation index is determined based on the cumulative injection volume, the final equivalent hydraulic width at the end of the injection phase, the breakthrough event information, the filtration loss rate, the scouring failure flow rate, and the step size evolution stability value.

10. A performance testing system for drilling fluid plugging agents, used to implement the performance testing method for drilling fluid plugging agents as described in any one of claims 1-9, characterized in that, It includes a data acquisition module, a width analysis module, a boost injection module, and a performance evaluation module: The data acquisition module is used to collect the inlet pressure, outlet pressure, and injection flow rate of the simulated fracture in real time during the injection of plugging agent into the simulated fracture. The width analysis module is used to determine the real-time equivalent hydraulic width of the simulated fracture based on the pressure difference between the inlet and outlet pressures and the injection flow rate. The pressurized injection module is used to adjust the upper limit of injection speed and the step pressurization step size according to the relative relationship between the real-time equivalent hydraulic width and the equivalent hydraulic reference width, and to perform step pressurized injection according to the adjusted final upper limit of injection speed and the final step pressurization step size until the preset injection stage end condition is met. The data acquisition module is also used to acquire the plugging performance data during the step-by-step pressurization injection process, and to acquire the filtration loss data during the condensation phase after the condensation phase ends, and to acquire the flushing data during the flushing phase after the flushing phase ends. The performance evaluation module is used to determine the comprehensive performance evaluation index of the plugging agent based on the sealing performance data, the filtration loss data, and the flushing data.

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