An extreme limited flow fracturing single-hole gunhole dynamic abrasion experiment system and method

Abstract

This invention discloses a dynamic erosion experimental system and method for single-hole perforation in extreme flow-limited fracturing. The system includes a fracturing fluid supply unit, a transparent fluid supply unit, a valve switching unit, an experimental section, a perforation morphology monitoring unit, and a jet pressure field mapping unit. The valve switching unit controls the connection between the fracturing fluid supply unit or the transparent fluid supply unit and the experimental section. The perforation morphology monitoring unit images the perforated sample. The jet pressure field mapping unit measures the pressure distribution of the jet ejected from the perforated sample during the connection between the fracturing fluid supply unit and the experimental section. This invention solves the problem of direct observation in opaque fluids through a "scouring-imaging" method. Combining sacrificial coating technology with direct measurement of jet performance, it can accurately and synchronously quantify the erosion process and its impact on jet performance, providing comprehensive and accurate data support for fracturing technology research.

Description

Technical Field

[0001] This invention relates to the field of petroleum extraction experiments, specifically to a dynamic erosion test system and method for a single-hole blast hole in extreme flow-limited fracturing. Background Technology

[0002] In the field of horizontal well multi-stage fracturing development of tight reservoirs such as shale gas, volumetric fracturing is crucial for increasing production as the industry continues to develop. Extreme Limited Entry (XLE) fracturing technology, as a key technology for achieving volumetric fracturing, plays a vital role in promoting the uniform opening and propagation of fracture clusters, thus driving the development of tight reservoirs such as shale gas, bringing new impetus and value to the energy sector, and improving the development efficiency and economic benefits of tight reservoir resources.

[0003] In previous development processes, various methods have been employed to address the issue of uniform opening and propagation of crack clusters. One common approach is perforation, which involves creating multiple holes within a section and utilizing the throttling friction generated by these holes to attempt to achieve uniform opening and propagation of crack clusters. Additionally, some researchers have studied perforation erosion by constructing specific experimental setups, such as a circulation system including a mixing tank, pump, air compressor, and experimental casing, to simulate the erosion process and provide a reference for practical applications. Furthermore, in perforation design, emphasis is placed on the initial geometric dimensions of the perforation, using them as a core design parameter. The aim is to ensure a reasonable initial frictional pressure drop through proper design, thereby promoting uniform crack propagation.

[0004] However, existing technologies have significant drawbacks. In actual fracturing processes, when high-speed proppant-carrying fluid containing a large amount of high-hardness proppant flows through the perforation, it causes severe erosion and wear on the inner wall of the perforation, resulting in a funnel-shaped orifice with continuously expanding diameter. This leads to a dynamic decrease in perforation friction, disrupting the original flow equilibrium distribution between clusters and potentially causing some fractures to stop propagating prematurely. Furthermore, existing research and experimental simulations are simple, often using constant flow rate and proppant concentration, which differs significantly from the complex "variable flow rate, variable proppant concentration" pumping procedures in the field. Simultaneously, erosion quantification is difficult. Due to the high strength of the casing steel, it is difficult to produce significant and easily measurable wear in a short time during laboratory experiments, resulting in long experimental cycles and high costs. Moreover, most studies focus on observing changes in perforation morphology after erosion, lacking direct measurement of jet performance, thus creating a gap in the relationship between erosion research and fracturing effectiveness. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and to propose a dynamic erosion test system and method for single-hole fracturing under extreme flow restriction.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] This invention provides a dynamic erosion test system for a single borehole in extreme flow-limited fracturing, comprising a fracturing fluid supply unit, a transparent fluid supply unit, a valve switching unit, an experimental section, a borehole morphology monitoring unit, and a jet pressure field mapping unit.

[0008] The fracturing fluid supply unit is used to supply fracturing fluid containing proppant;

[0009] The transparent fluid supply unit is used to supply transparent fluid;

[0010] The valve switching unit is used to control the connection between the fracturing fluid supply unit or the transparent fluid supply unit and the experimental section;

[0011] The experimental section is provided with mounting holes, which are used to install replaceable perforated samples with a sacrificial coating containing fluorescent material on their working surfaces.

[0012] The perforation morphology monitoring unit is used to image the perforated sample during the communication between the transparent fluid supply unit and the experimental section. It includes a fluorescent excitation light source and an imaging device. The fluorescent excitation light source is used to irradiate the perforated sample to excite the fluorescent material. The imaging device is provided with an optical filter that matches the emission wavelength of the fluorescent material to capture the fluorescent image emitted by the fluorescent material.

[0013] The jet pressure field mapping unit is located downstream of the outlet of the perforated sample and is used to measure the pressure distribution of the jet ejected from the perforated sample during the connection between the fracturing fluid supply unit and the experimental section.

[0014] In some embodiments, the fracturing fluid supply unit includes a mixing tank, a stirrer, a diaphragm pump, and a first injection pipeline. The mixing tank is used to hold fracturing fluid and proppant. The stirrer is disposed inside the mixing tank. The inlet of the diaphragm pump is connected to the outlet of the mixing tank. The outlet of the diaphragm pump is connected to one end of the first injection pipeline. The other end of the first injection pipeline is connected to the first input end of the valve switching unit. The output end of the valve switching unit is connected to the experimental section. A pressure detection element and a first flow detection element are provided on the first injection pipeline.

[0015] In some embodiments, the transparent fluid supply unit includes a clean water tank, a water pump, and a second injection pipe. The inlet of the water pump is connected to the outlet of the clean water tank, the outlet of the water pump is connected to one end of the second injection pipe, and the other end of the second injection pipe is connected to the second input end of the valve switching unit.

[0016] In some embodiments, the valve switching unit includes a connecting tee, an output pipe, a first control valve, and a second control valve. The first port of the connecting tee is connected to the other end of the first injection pipe via the first control valve. The second port of the connecting tee is connected to the other end of the second injection pipe via the second control valve. The third port of the connecting tee is connected to one end of the output pipe. The other end of the output pipe is connected to the connecting test section. A second flow detection element is provided on the output pipe.

[0017] In some embodiments, the dynamic erosion test system for single-hole fracturing under extreme flow restriction further includes a recovery hood, which is disposed outside the test section and has a lower opening that communicates with the stirring tank.

[0018] An overflow port is provided on the side wall of the mixing tank, and a filter screen is provided at the opening of the overflow port. The dynamic abrasion test system for single-hole blast hole under extreme flow limiting fracturing also includes a clean water recovery mechanism. The clean water recovery mechanism includes a recovery pipe and a filter. One end of the recovery pipe is connected to the overflow port, the other end of the recovery pipe is connected to the inlet of the filter, and the outlet of the filter is connected to the clean water tank.

[0019] In some embodiments, the experimental section has an observation port located above the mounting hole, and a transparent observation window is embedded in the observation port;

[0020] The aperture morphology monitoring unit also includes a fixing frame, one end of which is fixed inside the recovery hood. The fluorescence excitation light source and the imaging device are both fixed to the fixing frame, and both the fluorescence excitation light source and the imaging device are positioned above the transparent observation window.

[0021] In some embodiments, the jet pressure field mapping unit includes a measuring plate and a moving drive assembly. The surface of the measuring plate is provided with a pressure sensor array, and the moving drive assembly is connected to the measuring plate and is used to drive the measuring plate to move to adjust its distance from the outlet of the perforated sample.

[0022] In some embodiments, clearance grooves are provided on opposite side walls of the recycling hood;

[0023] The number of the moving drive components is two. Each moving drive component includes two fixed plates, a lead screw, a nut, a connecting rod, and a stepper motor. The two fixed plates are fixed to the outer wall of the recycling hood. The two ends of the lead screw are respectively rotatably disposed on the two fixed plates. The nut is threaded onto the lead screw. One end of the connecting rod is fixed to the nut. The other end of the connecting rod passes through the clearance groove and is fixedly connected to the measuring plate. The stepper motor is connected to the lead screw and is used to drive the lead screw to rotate.

[0024] In some embodiments, the measuring plate is provided with a plurality of material passage grooves.

[0025] This invention also provides a dynamic erosion test method for a single-hole borehole in extreme flow-limited fracturing, applicable to the aforementioned dynamic erosion test system for a single-hole borehole in extreme flow-limited fracturing, and includes the following steps:

[0026] The fracturing fluid supply unit is connected to the experimental section through the valve switching unit, and the fracturing fluid containing proppant is pumped to erode the perforated sample. The pressure distribution of the jet ejected from the perforated sample is measured by the jet pressure field mapping unit.

[0027] The transparent fluid supply unit is connected to the experimental section via the valve switching unit, and transparent fluid is pumped to replace the opaque fluid in the experimental section.

[0028] When the fluid in the experimental section is transparent, the fluorescent excitation light source is activated to irradiate the perforated sample, and the imaging device is used to capture the fluorescence image of the sacrificial coating to determine its current geometry and wear amount. Multiple fluorescence images captured at different times are sequentially analyzed to obtain the evolution law of the geometry and wear amount of the sacrificial coating with erosion time. The pressure distribution data of the jet ejected from the perforated sample is correlated with the evolution data of the geometry and wear amount of the sacrificial coating with erosion time to obtain the influence of the geometry and wear amount of the sacrificial coating on the pressure distribution of the jet.

[0029] Compared with existing technologies, the beneficial effects of the dynamic erosion experimental system and method for single-hole fracturing in this invention are as follows: The fracturing fluid supply unit simulates the erosion of the perforated sample by proppant-containing fracturing fluid during actual fracturing. The valve switching unit flexibly and quickly switches to a transparent fluid supply unit, creating clear observation conditions for the borehole morphology monitoring unit to utilize fluorescence imaging technology. Simultaneously, the jet pressure field mapping unit can accurately measure the jet pressure distribution under real erosion conditions. Compared with existing technologies, this invention solves the fundamental problem of unobservable erosion in opaque fluids through its unique "scouring-imaging" method, and addresses the difficulty of erosion quantification through sacrificial coating technology. It also increases the direct characterization of jet performance, achieving accurate simulation of complex conditions, high-sensitivity quantification of the erosion process, and simultaneous characterization of jet performance evolution, providing more accurate and comprehensive data support for fracturing technology research. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a dynamic erosion test system for a single-hole fracturing borehole provided in an embodiment of the present invention;

[0031] Figure 2 yes Figure 1 A schematic diagram of the structure of the valve switching unit, experimental section, orifice morphology monitoring unit and jet pressure field mapping unit;

[0032] Figure 3 yes Figure 2 A magnified view of a portion of region A in the middle;

[0033] Figure 4 yes Figure 2 A magnified view of a portion of region B in the middle;

[0034] Figure 5 yes Figure 1 A schematic diagram of the three-dimensional structure of the measuring plate in the diagram;

[0035] Explanation of reference numerals in the attached drawings: 1. Fracturing fluid supply unit; 11. Mixing tank; 111. Overflow port; 112. Filter screen; 12. Agitator; 121. Variable frequency speed control motor; 122. Agitator blades; 13. Diaphragm pump; 14. First injection pipe; 141. Pressure detection device; 142. First flow detection device; 2. Transparent fluid supply unit; 21. Clear water tank; 22. Water pump; 23. Second injection pipe; 3. Valve switching unit; 31. Connecting tee; 32. Output pipe; 321. Second flow detection device; 33. First control valve; 34. Second control valve; 4. Experiment Section; 41. Perforated sample; 411. Sacrificial coating; 42. Transparent observation window; 5. Hole morphology monitoring unit; 51. Fluorescent excitation light source; 52. Imaging equipment; 53. Fixing frame; 54. Recovery hood; 541. Displacement groove; 542. Lower opening; 6. Jet pressure field mapping unit; 61. Measuring plate; 611. Pressure sensor array; 612. Feed trough; 62. Moving drive assembly; 621. Fixing plate; 622. Lead screw; 623. Nut; 624. Connecting rod; 625. Stepper motor; 7. Clean water recovery mechanism; 71. Recovery pipe; 72. Filter. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The described embodiments are only possible technical implementations of the present invention, but are not limited thereto. Other embodiments obtained by those skilled in the art in conjunction with the embodiments of the present invention without creative effort are also within the protection scope of the present invention.

[0037] This application mainly adopts a scheme of alternating supply and monitoring of fracturing and transparent fluid. Through sophisticated system integration and innovative workflow, it achieves the effects of accurately simulating complex working conditions, highly sensitively quantifying the erosion process, and simultaneously characterizing the evolution of jet performance. The following is a further detailed description of this application.

[0038] Please refer to Figures 1-5The dynamic erosion experimental system for a single perforated borehole in extreme flow-limited fracturing provided in this application includes a fracturing fluid supply unit 1, a transparent fluid supply unit 2, a valve switching unit 3, an experimental section 4, a borehole morphology monitoring unit 5, and a jet pressure field mapping unit 6. The fracturing fluid supply unit 1 and the transparent fluid supply unit 2 are connected to the experimental section 4 via the valve switching unit 3, allowing for the supply of different fluids to the experimental section 4 on demand and at different times. The borehole morphology monitoring unit 5 and the jet pressure field mapping unit 6 operate during their respective fluid supply stages. This configuration achieves the effect of simulating the real erosion of the perforated sample 41 during the fracturing process, while accurately measuring and analyzing the morphology and jet performance of the perforated sample 41 using the "observation window" created by fluid switching without affecting the erosion experiment. This is because the valve switching unit 3 can flexibly, quickly, and accurately control the fluid supply, enabling different functional measurement units to function at their optimal times, thereby comprehensively and synchronously acquiring multi-dimensional data throughout the entire experimental process.

[0039] For details, please refer to Figure 1 The fracturing fluid supply unit 1 includes a mixing tank 11, a stirrer 12, a diaphragm pump 13, and a first injection pipe 14. The mixing tank 11 is typically made of corrosion-resistant and wear-resistant 316L stainless steel and has a large volume, allowing for the loading of fracturing fluid and proppant as abrasive according to the required experimental proportions. The stirrer 12 generally consists of a variable frequency speed-regulating motor 121 and stirring blades 122. The variable frequency speed-regulating motor 121 is installed at the top of the mixing tank 11, and the stirring blades 122 extend into the tank. By adjusting the speed of the motor 121, the fracturing fluid and proppant in the tank can be thoroughly stirred to form a stable and uniform suspension, preventing proppant sedimentation. The inlet of the diaphragm pump 13 is connected to the bottom outlet of the mixing tank 11, and it can extract the stirred fracturing fluid containing proppant through the reciprocating motion of the diaphragm. The advantage of using a pneumatic or electric diaphragm pump is that it can smoothly deliver abrasive fluids containing solid particles and provide stable pressure. Alternative pump types include screw pumps or plunger pumps capable of precisely controlling displacement and simulating complex on-site pumping procedures. The outlet of the diaphragm pump 13 is connected to one end of the first injection pipe 14, which is typically made of high-pressure resistant, corrosion-resistant metal or high-strength composite material. Its other end is connected to the first input end of the valve switching unit 3. The first injection pipe 14 must be equipped with a pressure sensor 141 and a first flow sensor 142. The pressure sensor 141 can be a high-precision pressure sensor used to monitor the pressure of the fracturing fluid in the pipe in real time, serving as a core control parameter for the experimental conditions. The first flow sensor 142 can be an electromagnetic flowmeter used to accurately measure the instantaneous flow rate of the fracturing fluid, ensuring the repeatability of the experiment.

[0040] For details, please refer to Figure 1The transparent fluid supply unit 2 includes a clear water tank 21, a water pump 22, and a second injection pipe 23. The clear water tank 21 is typically made of transparent plexiglass or PC material for easy observation of the internal water level. It stores the transparent fluid used as a flushing medium, such as clear water or other transparent liquids. The water pump 22 is generally a high-flow-rate centrifugal pump, with its inlet connected to the outlet of the clear water tank 21. It pumps the clear water out through the high-speed rotation of the impeller. The purpose of choosing a high-flow-rate centrifugal pump is to provide sufficient fluid in a very short time to quickly replace the opaque fracturing fluid in the experimental section 4, creating clear observation conditions for subsequent morphological monitoring. Centrifugal pumps have advantages such as simple structure and large flow rate. A gear pump is an alternative, suitable for conveying high-viscosity fluids; however, a centrifugal pump is more suitable here if the clear water viscosity is low. The outlet of the water pump 22 is connected to one end of the second injection pipe 23, which can also be made of corrosion-resistant metal or plastic pipe. Its other end is connected to the second input end of the valve switching unit 3.

[0041] For details, please refer to Figures 1-2 The valve switching unit 3 includes a connecting tee 31, an output pipe 32, a first control valve 33, and a second control valve 34. The connecting tee 31 is generally made of high-pressure resistant metal. Its first port is connected to the other end of the first injection pipe 14 via the first control valve 33. The first control valve 33 can be a fast-response, well-sealed electrically controlled ball valve. The ball valve's rapid opening and closing is controlled by an electrical signal from the central control system to connect or cut off the flow of fracturing fluid. Alternative control valves include pneumatically actuated angle seat valves or electric butterfly valves. Electric butterfly valves have a relatively simple structure and low flow resistance. The second port of the connecting tee 31 is connected to the other end of the second injection pipe 23 via the second control valve 34. The second control valve 34 is similar in type to the first control valve 33; the two operate in tandem to ensure that the two flow paths never cross-connect. The third interface of the connecting tee 31 is connected to one end of the output pipe 32, which is also a corrosion-resistant pipe. Its other end is connected to the experimental section 4. The output pipe 32 is equipped with a second flow detection element 321, which can also be a flow meter, used to measure the total output flow or the flow during the transparent fluid supply stage.

[0042] For details, please refer to Figures 1-3The experimental section 4 has mounting holes for installing replaceable perforation specimens 41 with a sacrificial coating 411 containing fluorescent material on their working surfaces. The perforation specimens 41 typically simulate perforations in actual fracturing, and their material can be steel similar to that of the actual casing. The core innovation lies in the sacrificial coating 411, which has a dual function: firstly, its hardness and wear resistance are lower than steel, allowing it to be significantly worn away in a short time, thus greatly shortening the experimental cycle; secondly, the fluorescent material it contains serves as the signal source for subsequent optical non-destructive testing. The sacrificial coating 411 is made by precisely mixing a resin matrix (such as epoxy resin with good adhesion and hardness) and fluorescent ceramic microspheres as the fluorescent material, and then uniformly covering the inner wall of the perforation specimen 41 using processes such as spraying.

[0043] For details, please refer to Figures 1-3 The dynamic erosion test system for single-hole fracturing under extreme flow restriction also includes a recovery hood 54, which covers the test section 4. The recovery hood 54 has a lower opening 542, which is connected to the mixing tank 11. An overflow port 111 is provided on the side wall of the mixing tank 111, and a filter screen 112 is provided at the opening of the overflow port 111. The dynamic erosion test system for single-hole fracturing under extreme flow restriction also includes a clean water recovery mechanism 7, which includes a recovery pipe 71 and a filter 72. One end of the recovery pipe 71 is connected to the overflow port 111, and the other end of the recovery pipe 71 is connected to the inlet of the filter 72. The outlet of the filter 72 is connected to the clean water tank 21.

[0044] In this embodiment, during the fracturing fluid supply stage, the fracturing fluid supply unit 1 is activated, and the agitator 12 mixes the fracturing fluid and proppant evenly in the mixing tank 11 to form a suspension. The diaphragm pump 13 draws the mixed fracturing fluid from the bottom of the mixing tank 11, passes through the first injection pipe 14 and the valve switching unit 3 (at this time, the first control valve 33 is open and the second control valve 34 is closed), and pumps it into the test section 4 to erode the perforated sample 41. The proppant-carrying fluid ejected from the perforated sample 41 is collected by the recovery hood 54 outside the test section and flows directly back into the mixing tank 11 through its lower opening 542, thus forming a closed circulation system that ensures the continuous supply and reuse of fracturing fluid.

[0045] During the morphology monitoring phase, valve switching unit 3 switches, and transparent fluid supply unit 2 starts. Water pump 22 pumps clean water from clean water tank 21 into experimental section 4 via second injection pipe 23 and valve switching unit 3 (at this time, second control valve 34 is open, and first control valve 33 is closed) to flush and replace residual fracturing fluid. The flushed clean water, along with a small amount of displaced fracturing fluid, enters recovery hood 54 and flows back to mixing tank 11. Due to the continuous injection of clean water, the liquid level in mixing tank 11 rises. When the liquid level reaches overflow port 111, the upper layer of clean water (located at the top due to its lower density) passes through filter screen 112 covering overflow port 111 and enters clean water recovery mechanism 7. Filter screen 112 intercepts most of any proppant particles that may overflow. The clean water then enters filter 72 through recovery pipe 71 for fine filtration, removing even finer impurities, and finally flows back to clean water tank 21, achieving the recycling of clean water and effective separation from the fracturing fluid system.

[0046] The design of this circulation system offers significant advantages. The closed-loop design of the fracturing fluid enables the reuse of the proppant-carrying fluid, saving experimental costs and simulating long-term continuous pumping conditions in the field. The clean water recovery circulation system is even more sophisticated, effectively recovering and purifying the cleaning medium through overflow and filtration mechanisms. This ensures a clear observation window while avoiding water waste and protecting equipment such as the clean water pump from damage by abrasive particles. The coordinated operation of the two circulation systems is the core of the dynamic experimental method that enables alternating "erosion-imaging," ensuring the continuity, economy, and reliability of the experimental process.

[0047] For details, please refer to Figures 1-3The perforation morphology monitoring unit 5 is used to image the perforated sample 41 during the connection between the transparent fluid supply unit 2 and the experimental section 4. It includes a fluorescence excitation source 51 and an imaging device 52. The fluorescence excitation source 51 can be a specific wavelength LED (such as a high-power ultraviolet or blue LED array) customized for the excitation wavelength of the fluorescent microspheres in the coating. The emitted light can efficiently excite the fluorescent material in the sacrificial coating 411. The imaging device 52 is equipped with an optical filter that matches the emission wavelength of the fluorescent material. This filter is crucial for achieving clear imaging; it must be a narrow-bandpass filter that allows only specific wavelengths of fluorescence to pass through while completely filtering out strong reflected light from the fluorescence excitation source 51 and all other ambient stray light. The imaging device 52 can be a high-resolution, high-frame-rate industrial HD camera. Through this filter, it can clearly capture ultra-high contrast fluorescent images with a pure black background and only the remaining coating outline emitting light. The fluorescence excitation light source 51 and the imaging device 52 are both fixed to a mounting bracket 53. One end of the mounting bracket 53 is fixed inside the recovery cover 54, which ensures the stability and repeatability of the monitoring unit position. The experimental section 4 has an observation port above the mounting hole, and a transparent observation window 42 is embedded in the observation port. The fluorescence excitation light source 51 and the imaging device 52 are both located above the transparent observation window 42.

[0048] For details, please refer to Figures 1-5The jet pressure field mapping unit 6 is located downstream of the outlet of the perforated sample 41. It measures the pressure distribution of the jet ejected from the perforated sample 41 during the connection between the fracturing fluid supply unit 1 and the experimental section 4, thereby assessing its energy and focusing ability. The jet pressure field mapping unit 6 includes a measuring plate 61 and a moving drive assembly 62. The surface of the measuring plate 61 is densely arrayed with pressure sensor arrays 611. These pressure sensors can be fast-responding, small-sized strain gauge or piezoelectric pressure sensors, capable of converting the instantaneous impact pressure signal of the jet into an acquireable electrical signal. The moving drive assembly 62 is connected to the measuring plate 61 and drives the measuring plate 61 to move along the jet axial direction to adjust its distance from the outlet of the perforated sample 41. The moving drive assembly 62 includes two fixed plates 621, a lead screw 622, a nut 623, a connecting rod 624, and a stepper motor 625. Both fixed plates 621 are fixed to the outer wall of the recovery cover 54. The two ends of the lead screw 622 are rotatably mounted on the two fixed plates 621 respectively. The nut 623 is threaded onto the lead screw 622. One end of the connecting rod 624 is fixed to the nut 623, and the other end passes through a specially made clearance groove 541 on the side wall of the recovery cover 54 and is fixedly connected to the measuring plate 61. The lead screw 622 can be driven to rotate precisely by the stepper motor 625, thereby driving the nut 623 to move along the axial direction of the lead screw 622, thereby realizing the precise adjustment of the position of the measuring plate 61. Thus, the pressure distribution at different positions can be measured through the measuring plate 61. To ensure that the sensor measures the direct impact pressure of the jet rather than the static pressure caused by fluid accumulation, the measuring plate 61 is provided with several material passages 612. These passages allow most of the jet fluid and proppant to pass through smoothly, avoiding the formation of a "water cushion" effect on the plate surface or the accumulation of particles that could damage the sensor.

[0049] The implementation principle of this embodiment is as follows: The system in this embodiment simulates the erosion of the perforated sample 41 by proppant-containing fracturing fluid on the actual fracturing process through the fracturing fluid supply unit 1. The valve switching unit 3 flexibly and quickly switches to the transparent fluid supply unit 2, creating clear observation conditions for the perforation morphology monitoring unit 5 to utilize fluorescence imaging technology. Simultaneously, the jet pressure field mapping unit 6 can accurately measure the jet pressure distribution under real erosion conditions. Compared with existing technologies, this invention solves the fundamental problem of the inability to observe in opaque fluids through the unique "erosion-imaging" method, and solves the problem of difficult erosion quantification through sacrificial coating technology. It also increases the direct characterization of jet performance, achieving accurate simulation of complex working conditions, high-sensitivity quantification of the erosion process, and simultaneous characterization of jet performance evolution, providing more accurate and comprehensive data support for fracturing technology research.

[0050] An embodiment of this application also provides a dynamic erosion test method for a single-hole borehole in extreme flow-limited fracturing, comprising the following steps:

[0051] S0, Experimental preparation and initial calibration

[0052] Before the experiment begins, the perforated sample 41 coated with sacrificial coating 411 is first installed in the experimental section 4. Fracturing fluid is prepared in the mixing tank 11 according to a predetermined sand ratio, and the agitator 12 is turned on. Then, the transparent fluid supply unit 2 is connected to the experimental section 4 via the valve switching unit 3. At t=0, a fluorescence image is taken of the un-eroded sample to obtain its initial geometry. Subsequently, the fracturing fluid supply unit 1 is switched to, and during the very short initial erosion phase (or with a sand-free base fluid), the measuring plate 61 is moved to different positions to measure the pressure field distribution of the initial jet. These data will serve as the baseline for all subsequent measurements.

[0053] S1, Simultaneous measurement of erosion and jet pressure

[0054] The fracturing fluid supply unit 1 is connected to the experimental section 4 via the valve switching unit 3. At this time, the first control valve 33 is opened and the second control valve 34 is closed, allowing the proppant-containing fracturing fluid, stirred in the mixing tank 11, to enter the experimental section 4 via the diaphragm pump 13 and the first injection pipe 14, eroding the perforated sample 41. The erosion process typically consists of two physical stages: first, the shoulder erosion stage, where the sharp edge of the shoulder is worn down, becoming smooth, and the depth direction of the perforation is worn down, resulting in a funnel shape; then, the diameter expansion erosion stage begins, where the outer diameter of the perforation begins to increase. The control system records the pressure and flow rate on the first injection pipe 14 in real time to ensure the stability of the erosion conditions. Simultaneously, the jet pressure field mapping unit 6 begins operation, with its pressure sensor array 611 on the measuring plate 61 measuring the pressure distribution of the jet ejected from the perforated sample 41 in real time, converting the pressure signal into an electrical signal through the data acquisition system and recording it. This step continues for a preset time (e.g., 60 seconds). The tools used here are mainly the various components of the experimental system mentioned earlier. The equipment requires power to operate and must ensure that the stirrer 12 can stir normally and the diaphragm pump 13 can deliver fracturing fluid stably.

[0055] S2, Rapid Scrubbing and Morphology Monitoring

[0056] Once the preset erosion time is reached, the control system immediately commands the valve switching unit 3 to connect the transparent fluid supply unit 2 to the experimental section 4. Specifically, the first control valve 33 is closed, and the second control valve 34 is opened. The water pump 22 then pumps clean water from the clean water tank 21 into the experimental section 4 at high speed through the second injection pipe 23, completely replacing the opaque fluid within the experimental section 4 in a very short time (typically less than 2 seconds). This process ensures that the water pump 22 operates normally and that the clean water sufficiently displaces the opaque fracturing fluid, filling the experimental section 4 with transparent fluid, thus creating conditions for subsequent morphology monitoring.

[0057] S3, Fluorescence Imaging and Data Correlation Analysis

[0058] When the fluid in experimental section 4 is transparent, the fluorescence excitation source 51 of the perforation morphology monitoring unit 5 is immediately activated to irradiate the perforation sample 41. The fluorescence excitation source 51 emits light of a specific wavelength, exciting the fluorescent material in the sacrificial coating 411 on the working surface of the perforation sample 41. An optical filter on the imaging device 52, matching the emission wavelength of the fluorescent material, filters out other interfering light. The imaging device 52 captures the fluorescence image emitted by the fluorescent material, forming a high-contrast contour map. By processing this fluorescence image using professional image analysis software (e.g., edge detection, pixel calibration), the geometric morphology and wear amount of the sacrificial coating 411 at the current moment (e.g., throat diameter, inlet chamfer radius, etc.) can be accurately calculated. By performing sequential analysis of multiple fluorescence images captured at different times, the evolution law of the geometric morphology and wear amount of the sacrificial coating 411 with erosion time can be obtained.

[0059] For example, in a displacement of 0.56m 3 / min, sand concentration 150kg / m 3 Under typical operating conditions, the internal diameter of the orifice is expected to expand rapidly within 0-600 seconds, while around 1500 seconds, the burr-shaped opening formed by erosion will penetrate the casing wall thickness, causing a significant change in the external diameter of the orifice. The data collected by this experimental system can generate a quantitative relationship graph between the orifice deformation growth and the erosion time.

[0060] Finally, the jet pressure distribution data collected in S1 is correlated with the data on the evolution of the geometry and wear of the sacrificial coating 411 over erosion time obtained in this step. For example, a relationship curve between "peak pressure at the jet center vs. orifice diameter" can be plotted, or a corresponding mathematical model can be established to quantitatively determine the specific influence of the geometry and wear of the sacrificial coating 411 on the jet pressure distribution. This process requires specialized image analysis and data analysis software to process the data, and it is essential to ensure the image quality of the imaging device 52 and the measurement accuracy of the pressure sensor.

[0061] Furthermore, the data obtained from this experimental system can be used to verify and develop theoretical models for predicting pit erosion. For example, the widely used erosion rate (∈ m The prediction model is The model indicates that the pore erosion rate increases with pore flow velocity according to a power law, while it follows a linear function with increasing sand content. Where C... W V represents the sand content of the sand-carrying liquid. pHere, K represents the particle velocity, and K is a model coefficient. This experiment can provide high-precision abrasion rate data under different flow velocities and sand contents, which can be used to calibrate coefficients in the model (such as the K value, with a reference value of 2.745 × 10⁻¹²), or to propose a modified model more suitable for complex working conditions.

[0062] Meanwhile, the experimental data is also crucial for validating the numerical simulations. The calculation steps for erosion deformation typically include: 1. Establishing a stable flow field based on CFD; 2. Exporting the flow field data format; 3. Setting particle injection conditions; 4. Performing transient calculations of erosion deformation. The high-resolution images of the porosity evolution process obtained in this experiment provide the most direct and reliable validation benchmark for these numerical simulations.

[0063] The implementation principle of this embodiment is as follows: Based on the aforementioned experimental system, the method utilizes the system's functional modules to perform experimental operations according to a specific sequence of steps. By measuring jet performance during the erosion stage and geometric morphology during the scouring stage, and by conducting periodic intermittent cycles, the influence of morphological changes caused by erosion on jet performance can be directly and quantitatively revealed. This overcomes the shortcomings of existing technologies, such as the lack of direct measurement of jet performance and the inability to observe the erosion process in real time, providing strong experimental evidence and theoretical support for the optimization of ultimate flow-limited fracturing technology.

[0064] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A dynamic erosion experiment system of an extreme limited flow fracturing single-hole perforation, characterized in that, It includes a fracturing fluid supply unit, a transparent fluid supply unit, a valve switching unit, an experimental section, a borehole morphology monitoring unit, and a jet pressure field mapping unit; The fracturing fluid supply unit is used to supply fracturing fluid containing proppant; The transparent fluid supply unit is used to supply transparent fluid; The valve switching unit is used to control the connection between the fracturing fluid supply unit or the transparent fluid supply unit and the experimental section; The experimental section is provided with mounting holes, which are used to install replaceable perforated samples with a sacrificial coating containing fluorescent material on their working surfaces. The perforation morphology monitoring unit is used to image the perforated sample during the communication between the transparent fluid supply unit and the experimental section. It includes a fluorescent excitation light source and an imaging device. The fluorescent excitation light source is used to irradiate the perforated sample to excite the fluorescent material. The imaging device is provided with an optical filter that matches the emission wavelength of the fluorescent material to capture the fluorescent image emitted by the fluorescent material. The jet pressure field mapping unit is located downstream of the outlet of the perforated sample and is used to measure the pressure distribution of the jet ejected from the perforated sample during the communication between the fracturing fluid supply unit and the experimental section. The jet pressure field mapping unit includes a measuring plate and a moving drive assembly. The surface of the measuring plate is provided with an array of pressure sensors. The moving drive assembly is connected to the measuring plate and is used to drive the measuring plate to move to adjust its distance from the outlet of the perforated sample.

2. The extreme limited-entry fracturing single-hole perforation dynamic erosion experiment system according to claim 1, characterized in that, The fracturing fluid supply unit includes a mixing tank, a stirrer, a diaphragm pump, and a first injection pipeline. The mixing tank is used to hold fracturing fluid and proppant. The stirrer is located inside the mixing tank. The inlet of the diaphragm pump is connected to the outlet of the mixing tank. The outlet of the diaphragm pump is connected to one end of the first injection pipeline. The other end of the first injection pipeline is connected to the first input end of the valve switching unit. The output end of the valve switching unit is connected to the test section. The first injection pipeline is equipped with a pressure detection device and a first flow detection device.

3. The extreme limited-entry fracturing single-hole perforation dynamic erosion experiment system according to claim 2, characterized in that, The transparent fluid supply unit includes a clean water tank, a water pump, and a second injection pipe. The inlet of the water pump is connected to the outlet of the clean water tank, the outlet of the water pump is connected to one end of the second injection pipe, and the other end of the second injection pipe is connected to the second input end of the valve switching unit.

4. The extreme limited-entry fracturing single-hole perforation dynamic erosion experiment system according to claim 3, characterized in that, The valve switching unit includes a connecting tee, an output pipe, a first control valve, and a second control valve. The first port of the connecting tee is connected to the other end of the first injection pipe via the first control valve. The second port of the connecting tee is connected to the other end of the second injection pipe via the second control valve. The third port of the connecting tee is connected to one end of the output pipe. The other end of the output pipe is connected to the experimental section. A second flow detection element is provided on the output pipe.

5. The extreme limited-entry fracturing single-wellbore perforation dynamic erosion test system of claim 4, wherein, It also includes a recovery hood, which is installed outside the experimental section and has a lower opening that communicates with the mixing tank. An overflow port is provided on the side wall of the mixing tank, and a filter screen is provided at the opening of the overflow port. The dynamic abrasion test system for single-hole blast hole under extreme flow limiting fracturing also includes a clean water recovery mechanism. The clean water recovery mechanism includes a recovery pipe and a filter. One end of the recovery pipe is connected to the overflow port, the other end of the recovery pipe is connected to the inlet of the filter, and the outlet of the filter is connected to the clean water tank.

6. The extreme limited-entry fracturing single-wellbore perforation dynamic erosion test system of claim 5, wherein, The experimental section has an observation port located above the mounting hole, and a transparent observation window is embedded in the observation port; The aperture morphology monitoring unit also includes a fixing frame, one end of which is fixed inside the recovery hood. The fluorescence excitation light source and the imaging device are both fixed to the fixing frame, and both the fluorescence excitation light source and the imaging device are positioned above the transparent observation window.

7. The extreme limited-entry fracturing single-wellbore dynamic erosion experiment system according to claim 5, characterized in that, The recycling hood has clearance grooves on its opposite side walls; The number of the moving drive components is two. Each moving drive component includes two fixed plates, a lead screw, a nut, a connecting rod, and a stepper motor. The two fixed plates are fixed to the outer wall of the recycling hood. The two ends of the lead screw are respectively rotatably disposed on the two fixed plates. The nut is threaded onto the lead screw. One end of the connecting rod is fixed to the nut. The other end of the connecting rod passes through the clearance groove and is fixedly connected to the measuring plate. The stepper motor is connected to the lead screw and is used to drive the lead screw to rotate.

8. The dynamic erosion test system for single-hole fracturing according to claim 1, characterized in that, The measuring plate is provided with several material passage slots.

9. A method for dynamic erosion experiment of limit rate fracture single-hole perforation, characterized in that, The dynamic erosion test system for single-hole fracturing as described in any one of claims 1-8 is applicable and includes the following steps: The fracturing fluid supply unit is connected to the experimental section through the valve switching unit, and the fracturing fluid containing proppant is pumped to erode the perforated sample. The pressure distribution of the jet ejected from the perforated sample is measured by the jet pressure field mapping unit. The transparent fluid supply unit is connected to the experimental section via the valve switching unit, and transparent fluid is pumped to replace the opaque fluid in the experimental section. When the fluid in the experimental section is transparent, the fluorescent excitation light source is activated to irradiate the perforated sample, and the imaging device is used to capture the fluorescence image of the sacrificial coating to determine its current geometry and wear amount. Multiple fluorescence images captured at different times are sequentially analyzed to obtain the evolution law of the geometry and wear amount of the sacrificial coating with erosion time. The pressure distribution data of the jet ejected from the perforated sample is correlated with the evolution data of the geometry and wear amount of the sacrificial coating with erosion time to obtain the influence of the geometry and wear amount of the sacrificial coating on the pressure distribution of the jet.

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