Hard-top horizontal well porous fracturing pressure-flow intelligent regulation and control experiment system and method

Abstract

The invention relates to the technical field of coal mining, and provides a hard-top horizontal well porous fracturing pressure-flow intelligent regulation and control experiment system and method.The experiment system comprises a transparent sample, a crustal stress true three-dimensional loading servo control system, a hydraulic servo pump pressure system and a hydraulic fracture information visualization monitoring system; a simulation shaft is arranged on one side of the transparent sample from the end face to the inside, a plurality of perforation holes which are intersected and communicated with the simulation shaft are preset in the transparent sample at intervals, and one end, close to the simulation shaft, in each perforation hole is connected with a pressure and flow dynamic distribution regulation and control system; the pressure and flow dynamic distribution regulation and control system is used for collecting pressure and flow information of the perforation and adjusting the pressure and flow of the perforation according to a pressure and flow dynamic distribution control mechanism. According to the scheme, the real situation of horizontal well multi-perforation fracturing can be simulated, a scientific basis is provided for coal mining, and uniform expansion of multiple cracks is achieved through real-time dynamic distribution of multi-perforation pressure and flow.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, and in particular to a hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system and method. Background Art

[0002] During coal mining, the control of the overlying hard roof directly affects the safe production of the mine. The hard roof has high strength, large breaking step, wide impact range, and complex mechanical behavior, which is a major problem in coal mine roof control. Especially after coal seam mining gradually enters deep, due to the typical "three highs" occurrence environment of deep rock mass, the mechanical behavior of rock strata breaking in a large spatial range of the overlying rock is extremely complex, engineering disasters occur frequently, and it is difficult to predict and effectively control, so higher requirements are put forward for the control of the thick and hard roof.

[0003] The transformation of overburden structure in deep coal mines is a key technical approach to disaster prevention and control. Among them, hydraulic fracturing technology does not require blasting operations, which can reduce costs and improve construction efficiency. It is an effective means to achieve the transformation of thick hard roof of coal seams. The multi-cluster synchronous fracturing technology of horizontal wells can divide the hard strata with good integrity into "small blocks" to the greatest extent by performing multi-cluster perforations in the same fracturing section, and opening multiple cracks that are dense and extend along the direction of the maximum principal stress at one time, thereby reducing the strength and energy storage capacity of the rock mass and reducing the risk of disasters.

[0004] However, measured data show that 30% or more of the cracks do not reach the designed production effect. During the expansion of hydraulic fractures, the initiation, extension, turning and penetration of hydraulic fractures are affected by multiple factors such as lithology, formation conditions, ground stress level and fracturing parameters. It is generally believed that during the synchronous expansion of multiple fractures, the mutual interference between adjacent fractures causes some fractures to lose their expansion stability. Limited by the existing technical level, there is still a lack of accurate understanding of the expansion process of multiple fractures. The expansion process of multiple fractures is affected by the coupling of multiple factors such as stress shadow effect, and its expansion direction, length and other characteristics are dynamically changing. The microseismic monitoring used on site is limited by its own accuracy and it is difficult to accurately locate the fracture trajectory. Numerical research still faces challenges, especially in considering the coupling between in-situ stress and lithology to determine the complex behavior of fracture expansion. Acoustic emission monitoring in experiments can determine the location of crack events, but it is difficult to accurately reconstruct the fracture morphology from the data. Due to equipment and cost limitations, CT is difficult to capture fracture expansion in real time. The geometry of hydraulic fractures is usually obtained by splitting rocks after fracturing tests. Therefore, the lack of experimental studies on the dynamic propagation process of multiple fractures limits the understanding of their competition and mutual interference mechanisms.

[0005] Moreover, relevant studies have shown that pressure and flow parameters in multi-perforation horizontal wells are key parameters that affect the path of fracture expansion. Currently, there is a lack of research on pressure and flow changes and control methods for multi-perforation fracturing in horizontal wells, and there is a lack of correct understanding of the mechanisms that cause the synchronous expansion and interactive response of multiple fractures. It is urgent to solve the impact of multi-perforation pressure, flow changes and regulation on the expansion of multiple fractures, and then realize dynamic distribution to achieve the goal of uniform expansion of multiple fractures. Summary of the invention

[0006] In order to solve the problems existing in the background technology, the present invention proposes a hard-top horizontal well multi-perforation fracturing pressure-flow intelligent control experimental system and method, which can simulate the actual situation of multi-perforation fracturing in horizontal wells, intuitively monitor the multi-crack expansion process and mutual disturbance of the perforations inside the sample, help to understand the effect of multi-perforation pressure and flow changes on crack expansion, provide a scientific basis for coal mining, and achieve uniform expansion of multiple cracks through real-time dynamic allocation of multi-perforation pressure and flow.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following scheme: a hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system, including a transparent sample, a true three-dimensional ground stress loading servo control system, a hydraulic servo pump pressure system and a hydraulic fracture information visualization monitoring system; one side of the transparent sample is provided with a simulated wellbore from the end surface inward, and a plurality of perforations intersecting and communicating with the simulated wellbore are preset at intervals in the transparent sample, and one end of the perforation close to the simulated wellbore is connected to a pressure and flow dynamic distribution control system, and the pressure and flow dynamic distribution control system is electrically connected to the hydraulic servo pump pressure system; The pressure and flow dynamic allocation control system is used to collect the pressure and flow information of the perforation, and adjust the pressure and flow of the perforation according to the pressure and flow dynamic allocation control mechanism, wherein the pressure and flow dynamic allocation control mechanism includes: The sum of all perforation injection flows is equal to the total injection flow, which is expressed as: ; The relationship between the pressure and flow rate in each perforation is: ; Among them, Q 0 and Q i are the total injection rate and the injection rate of the i-th perforation respectively; N p is the total number of perforations; Setting resistance for the regulator; is the perforation pressure; To simulate the pressure in the wellbore; is the perforation friction coefficient; To simulate the pressure in the wellbore; The true three-dimensional loading servo control system for ground stress comprises a true triaxial pressure loading test machine, a pressure plate and a pressure loading control system. During the experiment, the transparent sample is placed in the true triaxial pressure loading test machine. The pressure plate is provided with a plurality of pressure plates, and the plurality of pressure plates act on the peripheral side end and the top end of the transparent sample respectively through the pressure loading control system. The hydraulic servo pump pressure system is used to pump a set flow rate of fracturing fluid into the transparent sample; The hydraulic fracture information visualization monitoring system is used to monitor, record and process the dynamic expansion process of the fractures, the pumping pressure information and the stress evolution process of the transparent sample surface during the fracturing process.

[0008] Preferably, the pressure loading control system includes a vertical pressure loading control system, a lateral pressure loading control system, a pressure controller and pressure control software; the pressure plates acting on the lateral ends of the transparent specimen are respectively arranged on the lateral walls of the true triaxial pressure loading testing machine, and the pressure plate acting on the top of the transparent specimen is arranged on the top wall of the true triaxial pressure loading testing machine. The pressure plate located on the top wall is connected to the vertical pressure loading control system, and the pressure plate located on the lateral wall is connected to the lateral pressure loading control system. The vertical pressure loading control system and the lateral pressure loading control system are electrically connected to the pressure control software through the pressure controller.

[0009] Preferably, the pressure and flow dynamic distribution and control system includes a pressure and flow regulator, a pressure and flow sensor and a pressure and flow control system; the pressure and flow regulator and the pressure and flow sensor are arranged in the perforation at one end close to the simulated wellbore, and the pressure and flow regulator is electrically connected to the pressure and flow control system through the pressure and flow sensor.

[0010] Preferably, the hydraulic servo pump pressure system includes a plunger pump, a plunger pump controller and a plunger pump control system. The output end of the plunger pump is connected to the simulated wellbore through a pumping pipeline, and the plunger pump is connected to the plunger pump control system through the plunger pump controller; the plunger pump control system is electrically connected to the pressure and flow control system.

[0011] Preferably, the pressing plate is a transparent plate, and a reserved hole for the measuring element is provided on the side of the pressing plate close to the transparent sample, and the measuring element is arranged in the reserved hole.

[0012] Preferably, the hydraulic fracture information visualization monitoring system includes a high-speed camera, a DIC digital image monitoring system, an acoustic emission monitoring system and a multi-information processor, wherein the high-speed camera, the DIC digital image monitoring system and the acoustic emission monitoring system are electrically connected to the multi-information processor respectively; the high-speed camera and the DIC digital image monitoring system are arranged at a preset position close to the transparent sample through a mobile device, and the high-speed camera and the DIC digital image monitoring system are used to monitor the surface crack extension and the full-field stress evolution process of the transparent sample; the acoustic emission monitoring system is electrically connected to the measuring element and is used to monitor the internal crack change process of the transparent sample during the fracturing process through the measuring element; and the multi-information processor is used to visualize the internal and surface crack information of the transparent sample for monitoring, recording, storage and analysis.

[0013] Preferably, the multiple perforation flow rate dynamic allocation control conditions are: , Among them, Q 0 and Q i are the total injection rate and the injection rate of the i-th perforation respectively; N p is the total number of perforations; is the relative flow rate into the perforation.

[0014] The experimental method for intelligent control of pressure and flow rate of multi-hole fracturing in hard-top horizontal wells includes the following steps: Step 1, making a transparent sample that meets mechanical parameter requirements and has a multi-perforated horizontal well; Step 2, install the entire experimental system; Step 3, implement the experiment: first, enable the hydraulic fracture information visualization monitoring system, and input the corresponding specimen number and time information on the multi-information processor; then start the pressure and flow dynamic distribution control system, and at the same time fill the configured fracturing fluid into the plunger pump of the hydraulic servo pump pressure system, and start the hydraulic servo pump pressure system and pump the fracturing fluid into the transparent sample at a set flow rate; after the hydraulic fracturing experiment starts, when the plunger pump control system observes that the pump pressure-time curve decreases instantly and stabilizes near a certain pressure value, the hydraulic fracturing physical simulation experiment ends, wherein the dynamic control method of the pressure and flow dynamic distribution control system is: at time t, the pressure in perforation a reaches the sample cracking condition, at which time the pressure and flow of perforation a are P(a) and Q(a), respectively, and the pressure and flow of perforation b are P(a) and Q(b), and P(a)<P(b)、Q(a)> Q(b), at this time, the pressure and flow regulator feeds back the pressure and flow information to the pressure and flow control system through the pressure and flow sensor, and the pressure and flow regulator adjusts Additional resistance to flow into the crack at the moment , so that P(a)+ =P(b), the flow rate pumped into each fracture is the same; Step 4: After the experiment is over, dismantle the entire experimental system in sequence; Step 5, process and analyze experimental data: after the experiment, observe the morphology and trend of hydraulic fractures on the surface of the transparent sample and use a camera to photograph and record the transparent sample; cut and observe the transparent sample and use a camera to photograph and record the cut transparent sample; use the pump pressure-time curve to analyze the morphology of hydraulic fractures, capture the complete process of multi-perforation fracture expansion with a high-speed camera, and obtain stress information during the rupture of the transparent sample based on DIC digital image monitoring technology; scan and reconstruct the fracture morphology inside the transparent sample based on CT scanning technology, and compare and analyze the internal fracture information obtained by the acoustic emission monitoring system; summarize and analyze the pressure flow distribution control mechanism under the action of different fracturing parameter combinations.

[0015] Preferably, the method for making the transparent sample is: at least four perforation prefabricated pipes are arranged at intervals on the simulated wellbore prefabricated pipe, the simulated wellbore prefabricated pipe is arranged in a mold, the mold is filled with a sample material selected according to the mechanical characteristics of the simulated rock formation and cured for 24 days.

[0016] Preferably, the method for installing the entire experimental system is as follows: placing the transparent sample in a true three-dimensional pressure loading test machine, and placing pressure plates with reserved holes on the left and right opposite sides, the front and rear opposite sides, and the upper side of the transparent sample, respectively; placing measuring elements in the reserved holes of the pressure plates and connecting them to the acoustic emission monitoring system; using a pumping pipeline to connect the simulated wellbore in the transparent sample with a hydraulic servo pumping system and a pressure and flow dynamic distribution control system; moving a high-speed camera and a DIC digital image monitoring system to a position where the surface of the complete transparent sample can be clearly captured and connected to a multi-information processor; using a true three-dimensional loading servo control system for ground stress to apply pressure to the axial and lateral directions of the transparent sample according to the stress scheme; After the experiment, the method of dismantling the entire experimental system in sequence is as follows: shut down the hydraulic fracture information visualization monitoring system, the hydraulic servo pumping system, and the pressure and flow dynamic distribution and control system, and disconnect the fracturing fluid pumping pipeline from the hydraulic servo pumping system and the pressure and flow dynamic distribution and control system; shut down the ground stress true three-dimensional loading servo control system and stop simulating the ground stress loading; remove the pressure plate, and then remove the measuring element in the reserved hole of the pressure plate; remove the transparent sample; clean the pressure plate, the true triaxial pressure loading test machine and related lines, and then carry out maintenance.

[0017] The beneficial effects of the present invention are as follows: First, based on the technology of multi-perforation hydraulic fracturing in horizontal wells, the present scheme can reveal the law of synchronous expansion of cracks in multiple perforations in a sample and their interaction mechanism under true three-dimensional conditions. This not only overcomes the limitations of traditional single-well fracturing and multi-vertical hole fracturing tests, but also provides a more realistic and intuitive means of monitoring the crack expansion process, providing a scientific basis for coal mining.

[0018] Moreover, by adopting the pressure and flow dynamic distribution and control system, it is not only possible to accurately monitor the changes in pressure and flow entering each perforation, but also to more accurately understand the impact of pressure and flow changes on crack expansion under multi-perforation conditions. Moreover, according to the pressure and flow dynamic distribution control mechanism, the pressure and flow of each perforation can be adjusted in real time to ensure that multiple cracks are evenly distributed during the expansion process. This helps to improve the connectivity of the fracture network, promote the effective exploitation of coal resources, and reduce unnecessary energy consumption.

[0019] In addition, multiple technologies are integrated to achieve visual monitoring: combining acoustic emission positioning, high-speed cameras, DIC digital imaging technology and transparent similar materials, it is possible to achieve visual monitoring of the real-time dynamic expansion process of multiple cracks inside the rock and the full-field stress disturbance characteristics, providing a powerful tool for in-depth research on the crack expansion mechanism and helping to discover new scientific laws.

[0020] In conclusion, this scheme can carry out experimental research on different rock types and geological conditions under the influence of multiple factors, which not only helps to propose a theory to optimize the multi-cluster synchronous crack propagation mechanism, but also provides important technical support for practical engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the experimental system in the embodiment of the present invention; Figure 2 This is a schematic diagram of the transparent sample structure in an embodiment of the present invention; Figure 3 This is a schematic diagram of the transparent sample workflow structure in an embodiment of the present invention; Figure 4 It is a schematic diagram of the structure of the pressure and flow dynamic distribution control system in an embodiment of the present invention; Figure 5 It is a schematic diagram of the control workflow of the pressure and flow dynamic allocation control system in an embodiment of the present invention; Figure 6 It is a schematic diagram of simulation results before dynamic adjustment of synchronous fracturing pressure and flow rate in an embodiment of the present invention; Figure 7 It is a schematic diagram of simulation results after dynamic adjustment of synchronous fracturing pressure and flow rate in an embodiment of the present invention.

[0022] Numbers in the figure: 1. Simulated wellbore; 2. Perforation; 3. Pressure and flow regulator; 4. Pressure and flow sensor; 5. Transparent sample; 6. Pressure plate; 7. Acoustic emission monitoring system; 8. High-speed camera; 9. DIC digital image monitoring system; 10. Multi-information processor; 11. True triaxial pressure loading test machine; 12. Vertical pressure loading control system; 13. Pressure controller; 14. Pressure control software; 15. Lateral pressure loading control system; 16. Piston pump; 17. Piston pump controller; 18. Piston pump control system; 19. Pressure and flow control system. DETAILED DESCRIPTION

[0023] In order to make the present invention clearer and more understandable, the present invention is described in detail as a preferred embodiment in combination with the accompanying drawings and embodiments. It should be understood that the given embodiment is only one implementation method and does not represent all embodiments.

[0024] Embodiment 1 Combination Figure 1-Figure 7 The present embodiment provides a hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system, comprising a transparent sample 5, a true three-dimensional ground stress loading servo control system, a hydraulic servo pump pressure system and a hydraulic fracture information visualization monitoring system; a simulated wellbore 1 is provided on one side of the transparent sample 5 from the end surface inward, and a plurality of perforations 2 intersecting and communicating with the simulated wellbore 1 are preset at intervals in the transparent sample 5, and a pressure and flow dynamic distribution control system is connected to one end of the perforation 2 close to the simulated wellbore 1, and the pressure and flow dynamic distribution control system is electrically connected to the hydraulic servo pump pressure system; The pressure and flow dynamic distribution control system is used to collect the pressure and flow information of the perforation 2, and adjust the pressure and flow of the perforation 2 according to the pressure and flow dynamic distribution control mechanism, wherein the pressure and flow dynamic distribution control mechanism includes: The sum of all perforation 2 injection rates is equal to the total injection rate, which is expressed as: ; Since the pressure in the simulated wellbore is almost the same, the relationship between the pressure and flow rate at the fracture entrance is: ; Due to reservoir heterogeneity and different fracture expansion stages, the pressure p required for each fracture to continue to expand is i The pressure in the perforation 2 is different, which leads to uneven distribution, which is not conducive to the balanced expansion of the crack. Therefore, the key point of controlling flow distribution is to balance the expansion resistance difference by adjusting the resistance of the perforation 2. After setting the dynamic regulator, the relationship between the pressure and flow in each perforation 2 is: , The dynamic distribution control conditions of the multiple perforations 2 are: , The above formula shows the dynamic regulation of the dominant fractures. During the synchronous fracturing process of multiple perforations 2, the pressure and flow information are dynamically fed back to the high-precision pressure and flow sensor 4 in real time. If the pressure in perforation a reaches the sample cracking condition at time t, the pressure and flow of perforation a are P(a) and Q(a) respectively, and the pressure and flow of perforation b are P(a) and Q(b), and P(a)<P(b)、Q(a)> Q(b), at this time, the pressure and flow regulator 3 feeds back the pressure and flow information to the pressure and flow control system 19 through the pressure and flow sensor 4, and the pressure and flow regulator 3 adjusts Additional resistance to flow into the crack at the moment , so that P(a)+ =P(b), the flow rate pumped into each crack is the same, and the pressure and flow information continues to be dynamically fed back to the pressure and flow sensor 4. The pressure and flow sensor 4 also feeds back the pressure and flow information to the pressure and flow control system 19. After analysis, the pressure and flow control system 19 transmits a control signal to the pressure and flow regulator 3. The pressure and flow regulator 3 adjusts the fluid pressure and flow to achieve dynamic distribution of pressure and flow so that the cracks can expand evenly.

[0025] Among them, Q 0 and Q i are the total injection rate and the injection rate of the i-th perforation respectively; is the relative flow rate into the perforation; N p is the total number of perforations; Setting resistance for the regulator; is the perforation pressure; To simulate the pressure in the wellbore; is the perforation friction coefficient; To simulate the pressure inside the wellbore.

[0026] The true three-dimensional loading servo control system of ground stress includes a true triaxial pressure loading test machine 11, a pressure plate 6 and a pressure loading control system. During the experiment, the transparent sample 5 is placed in the true triaxial pressure loading test machine 11. The pressure plate 6 is provided with multiple, and the multiple pressure plates 6 act on the circumferential side ends and the top end of the transparent sample 5 respectively through the pressure loading control system; the hydraulic servo pumping system is used to pump a set flow rate of fracturing fluid into the transparent sample 5; the hydraulic fracture information visualization monitoring system is used to monitor, record and process the dynamic expansion process of the fractures, the pumping pressure information and the surface stress evolution process of the transparent sample 5 during the fracturing process.

[0027] The experimental system of this embodiment mainly includes a transparent sample 5, a true three-dimensional loading servo control system for ground stress, a hydraulic servo pumping system, a hydraulic fracture information visualization monitoring system, and a pressure and flow dynamic distribution control system. The visualization experiment of multi-perforation 2 synchronous fracturing based on high-speed camera and transparent materials and other related technologies can solve the problem of uneven expansion of multiple fractures in the multi-perforation 2 synchronous fracturing process of horizontal wells overlying hard roof on coal seams, which helps to reveal the dynamic expansion competition mechanism of multiple fractures and realize the effective control of the synchronous expansion path of multi-perforation 2 fractures.

[0028] Specifically, the pressure loading control system includes a vertical pressure loading control system 12, a lateral pressure loading control system 15, a pressure controller 13 and a pressure control software 14; the pressure plates 6 acting on the lateral ends of the transparent sample 5 are respectively arranged on the lateral walls of the true triaxial pressure loading test machine 11, and the pressure plates 6 acting on the top of the transparent sample 5 are arranged on the top wall of the true triaxial pressure loading test machine 11. The pressure plates 6 on the top wall are connected to the vertical pressure loading control system 12, and the pressure plates 6 on the lateral walls are connected to the lateral pressure loading control system 15. The vertical pressure loading control system 12 and the lateral pressure loading control system 15 are electrically connected to the pressure control software 14 through the pressure controller 13. During the experiment, the vertical pressure loading control system 12 and the lateral pressure loading control system 15 are used to realize the servo loading of the vertical and horizontal stresses of the transparent sample 5.

[0029] Specifically, the pressure and flow dynamic distribution and control system includes a pressure and flow regulator 3, a pressure and flow sensor 4 and a pressure and flow control system 19; the pressure and flow regulator 3 and the pressure and flow sensor 4 are arranged in the perforation 2 at one end close to the simulated wellbore 1, and the pressure and flow regulator 3 is electrically connected to the pressure and flow control system 19 through the pressure and flow sensor 4. The pressure and flow regulator 3 is used to dynamically collect the pressure and flow information entering each perforation 2 in real time and adjust the pressure and flow; the pressure and flow sensor 4 is used to collect the pressure and flow information of each perforation 2 in real time and transmit the information to the pressure and flow control system 19.

[0030] Specifically, the hydraulic servo pump pressure system includes a plunger pump 16, a plunger pump controller 17 and a plunger pump control system 18. One end of the plunger pump 16 is connected to the simulated wellbore 1 through a pumping pipeline, and the other end of the plunger pump 16 is connected to the plunger pump control system 18 through the plunger pump controller 17; the plunger pump control system 18 is electrically connected to the pressure and flow control system 19 to achieve multi-perforation 2 controllable intelligent pumping of the fracturing sample. The plunger pump control system 18 is used to record information such as pump pressure-time curve in real time.

[0031] Specifically, the pressing plate 6 is a transparent plate, specifically an acrylic transparent plate, which is convenient for observing the changes of the simulated wellbore 1 during the experiment. A measuring element reserved hole is opened on the side of the pressing plate 6 close to the transparent sample 5, and a measuring element is arranged in the reserved hole. The measuring element in this embodiment is an acoustic emission sensor. The hydraulic fracture information visualization monitoring system includes a high-speed camera 8, a DIC digital image monitoring system 9, an acoustic emission monitoring system 7 and a multi-information processor 10, and the high-speed camera 8, the DIC digital image monitoring system 9 and the acoustic emission monitoring system 7 are respectively electrically connected to the multi-information processor 10; the high-speed camera 8 and the DIC digital image monitoring system 9 are arranged at a preset position close to the transparent sample 5 through a mobile device, and the high-speed camera 8 and the DIC digital image monitoring system 9 are used to monitor the surface crack extension and the full-field stress evolution process of the transparent sample 5, and the acoustic emission monitoring system 7 is electrically connected to the measuring element, and is used to monitor the internal crack change process of the transparent sample 5 during the fracturing process through the measuring element, and the multi-information processor 10 is used to visualize the internal and surface crack information of the transparent sample 5 for monitoring, recording, storage and analysis.

[0032] Example 2 This embodiment provides an experimental method for intelligent control of multi-hole fracturing pressure and flow rate in a hard-top horizontal well, comprising the following steps: Step 1, making a transparent sample 5 that meets the mechanical parameter requirements and has a multi-perforation 2 horizontal well. First, obtain the physical and mechanical parameters of the hard roof rock, carry out the ratio of rock-like materials to obtain the material ratio consistent with the physical and mechanical parameters of the hard roof rock, and use chemical materials such as polymethyl methacrylate to synthesize transparent materials with consistent mechanical parameters as mold filling materials. The specific method is: at least four perforation 2 prefabricated pipes are arranged at intervals on the simulated wellbore 1 prefabricated pipe, the simulated wellbore 1 prefabricated pipe is arranged in the mold, the mold is filled with mold filling materials and cured for 24 days to form a 200mm×200mm×200mm cubic rock-like material model body, i.e., a transparent sample 5, wherein the configured simulated wellbore 1 has a length of 150mm and a diameter of 12mm, and the perforation 2 is 6mm. Considering the interference of pressure and flow distribution between the multi-perforations 2, four to six perforations 2 are set, and dynamic intelligent adjustment is performed to reflect the control effect of multi-perforation 2 fracturing in the horizontal well of the real formation.

[0033] Step 2, installing the entire experimental system, specifically: placing the transparent sample 5 in a true three-dimensional pressure loading test machine, and placing pressure plates 6 with reserved holes on the left and right opposite sides, front and back opposite sides and the upper side of the transparent sample 5, respectively, placing acoustic emission sensors in the reserved holes of the pressure plate 6 and connecting them to the acoustic emission monitoring system 7; using a pumping pipeline to connect the simulated wellbore 1 in the transparent sample 5 to the hydraulic servo pumping system and the pressure and flow dynamic distribution and control system; moving the high-speed camera 8 and the DIC digital image monitoring system 9 to clearly capture the surface of the complete transparent sample 5 and connecting them to the multi-information processor 10; using the ground stress true three-dimensional loading servo control system to apply 8MPa, 3MPa and 5MPa pressures to the axial and lateral directions of the transparent sample 5 according to the stress scheme.

[0034] Step 3, implement the experiment: first, enable the hydraulic fracture information visualization monitoring system, and input the corresponding specimen number, time and other information on the multi-information processor 10; then start the pressure and flow dynamic distribution and control system, and at the same time fill the configured fracturing fluid into the plunger pump 16 of the hydraulic servo pump pressure system, and start the hydraulic servo pump pressure system and pump the fracturing fluid into the transparent sample 5 at a flow rate of 100 ml / min; after the hydraulic fracturing experiment starts, when the plunger pump control system 18 observes that the pump pressure-time curve decreases instantly and stabilizes near a certain pressure value, the hydraulic fracturing physical simulation experiment ends.

[0035] Step 4: After the experiment is over, dismantle the entire experimental system in sequence. Turn off the hydraulic fracture information visualization monitoring system, hydraulic servo pumping system, and pressure and flow dynamic distribution control system, disconnect the fracturing fluid pumping pipeline from the hydraulic servo pumping system and the pressure and flow dynamic distribution control system; turn off the ground stress true three-dimensional loading servo control system and stop simulating ground stress loading; remove the pressure plate 6, and then remove the measuring element in the reserved hole of the pressure plate 6; remove the transparent sample 5; clean the pressure plate 6, the true triaxial pressure loading test machine 11 and related lines and perform maintenance.

[0036] Step 5, processing and analyzing experimental data: after the experiment, observe the morphology and trend of hydraulic fractures on the surface of transparent sample 5 and use a camera to photograph and record the transparent sample 5; cut and observe the transparent sample 5 and use a camera to photograph and record the cut transparent sample 5; use the pump pressure-time curve to analyze the morphology of hydraulic fractures, and the high-speed camera 8 captures the complete process of crack expansion of multiple perforations 2, and obtains the stress information of the transparent sample 5 during the rupture process based on the DIC digital image monitoring technology; scan and reconstruct the crack morphology inside the transparent sample 5 based on the CT scanning technology, and compare and analyze the internal crack information obtained by the acoustic emission monitoring system 7; summarize and analyze the crack expansion evolution law, geometric morphology and induced stress evolution law caused by the pressure flow changes of different perforations 2 under the dynamic distribution of pressure flow, and propose a pressure flow distribution control mechanism under the action of different fracturing parameter combinations.

[0037] The specific embodiments of the present invention are described in detail above with reference to the drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. Hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system, characterized by: It comprises a transparent specimen (5), a true three-dimensional ground stress loading servo control system, a hydraulic servo pump pressure system and a hydraulic fracture information visualization monitoring system; a simulated wellbore (1) is provided on one side of the transparent specimen (5) from the end surface inward, a plurality of perforations (2) intersecting and communicating with the simulated wellbore (1) are preset at intervals in the transparent specimen (5), one end of the perforations (2) close to the simulated wellbore (1) is connected to a pressure and flow dynamic distribution control system, and the pressure and flow dynamic distribution control system is electrically connected to the hydraulic servo pump pressure system; The pressure and flow rate dynamic distribution control system is used to collect the pressure and flow rate information of the perforation (2), and adjust the pressure and flow rate of the perforation (2) according to the pressure and flow rate dynamic distribution control mechanism, wherein the pressure and flow rate dynamic distribution control mechanism includes: The sum of the injection rates of all perforations (2) is equal to the total injection rate, which is expressed as: ； The relationship between the pressure and flow rate in each perforation (2) is: ； Among them, Q0 and Q i are the total injection rate and the injection rate of the ith perforation respectively; N p is the total number of perforations; Setting resistance for the regulator; is the perforation pressure; To simulate the pressure in the wellbore; is the perforation friction coefficient; To simulate the pressure in the wellbore; The true three-dimensional loading servo control system for ground stress comprises a true triaxial pressure loading test machine (11), a pressure plate (6) and a pressure loading control system. During the experiment, the transparent sample (5) is placed in the true triaxial pressure loading test machine (11). The pressure plate (6) is provided with a plurality of pressure plates, and the plurality of pressure plates (6) respectively act on the peripheral side ends and the top end of the transparent sample (5) through the pressure loading control system. The hydraulic servo pumping system is used to pump a set flow rate of fracturing fluid into the transparent sample (5); The hydraulic fracture information visualization monitoring system is used to monitor, record and process the dynamic expansion process of the fractures, the pumping pressure information and the surface stress evolution process of the transparent sample (5) during the fracturing process.

2. The hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system according to claim 1 is characterized by: The pressure loading control system comprises a vertical pressure loading control system (12), a lateral pressure loading control system (15), a pressure controller (13) and pressure control software (14); the pressure plates (6) acting on the lateral ends of the transparent specimen (5) are respectively arranged on the lateral walls of the true triaxial pressure loading test machine (11), the pressure plates (6) acting on the top of the transparent specimen (5) are arranged on the top wall of the true triaxial pressure loading test machine (11), the pressure plates (6) located on the top wall are connected to the vertical pressure loading control system (12), the pressure plates (6) located on the lateral walls are connected to the lateral pressure loading control system (15), and the vertical pressure loading control system (12) and the lateral pressure loading control system (15) are electrically connected to the pressure control software (14) via the pressure controller (13).

3. The hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system according to claim 1 is characterized by: The pressure and flow dynamic distribution and control system comprises a pressure and flow regulator (3), a pressure and flow sensor (4) and a pressure and flow control system (19); the pressure and flow regulator (3) and the pressure and flow sensor (4) are arranged in the perforation (2) at one end close to the simulated wellbore (1), and the pressure and flow regulator (3) is electrically connected to the pressure and flow control system (19) via the pressure and flow sensor (4).

4. The hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system according to claim 3 is characterized by: The hydraulic servo pump pressure system comprises a plunger pump (16), a plunger pump controller (17) and a plunger pump control system (18); the output end of the plunger pump (16) is connected to the simulated wellbore (1) via a pumping pipeline; the plunger pump (16) is connected to the plunger pump control system (18) via the plunger pump controller (17); and the plunger pump control system (18) is electrically connected to the pressure and flow control system (19).

5. The hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system according to claim 1 is characterized by: The pressing plate (6) is a transparent plate, and a reserved hole is provided on the side of the pressing plate (6) close to the transparent sample (5), and a measuring element is provided in the reserved hole.

6. The hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system according to claim 5 is characterized by: The hydraulic fracture information visualization monitoring system comprises a high-speed camera (8), a DIC digital image monitoring system (9), an acoustic emission monitoring system (7) and a multi-information processor (10). The high-speed camera (8), the DIC digital image monitoring system (9) and the acoustic emission monitoring system (7) are electrically connected to the multi-information processor (10) respectively. The high-speed camera (8) and the DIC digital image monitoring system (9) are arranged at a preset position close to the transparent sample (5) through a mobile device. The high-speed camera (8) and the DIC digital image monitoring system (9) are used to monitor the surface crack extension and full-field stress evolution process of the transparent sample (5). The acoustic emission monitoring system (7) is electrically connected to the measuring element and is used to monitor the internal crack change process of the transparent sample (5) during the fracturing process through the measuring element. The multi-information processor (10) is used to visualize, monitor, record, store and analyze the internal and surface crack information of the transparent sample (5).

7. The hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental system according to claim 1 is characterized by: The control conditions for the dynamic distribution of the flow rates of the plurality of perforations (2) are: ， Among them, Q0 and Q i are the total injection rate and the injection rate of the i-th perforation (2), respectively; N p is the total number of perforations (2); is the relative flow rate into the perforation (2).

8. An experimental method using the hard-top horizontal well multi-porous fracturing pressure-flow intelligent control experimental system according to any one of claims 1 to 7, characterized in that: The steps include: Step 1, making a transparent sample (5) that meets mechanical parameter requirements and has a horizontal well with multiple perforations (2); Step 2, install the entire experimental system; Step 3, implement the experiment: first, activate the hydraulic fracture information visualization monitoring system, and input the corresponding specimen number and time information on the multi-information processor (10); then start the pressure and flow dynamic distribution control system, and at the same time fill the configured fracturing fluid into the plunger pump (16) of the hydraulic servo pump pressure system, and start the hydraulic servo pump pressure system and pump the fracturing fluid into the transparent sample (5) at a set flow rate; after the hydraulic fracturing experiment begins, when the plunger pump control system (18) observes that the pump pressure-time curve decreases instantly and stabilizes near a certain pressure value, the hydraulic fracturing physical simulation experiment ends, wherein the dynamic control method of the pressure and flow dynamic distribution control system is: at time t, the pressure in perforation a reaches the sample cracking condition, at which time the pressure and flow of perforation a are P(a) and Q(a), respectively, and the pressure and flow of perforation b are P(a) and Q(b), and P(a)<P(b)、Q(a)> Q(b), at this time, the pressure and flow regulator (3) feeds back the pressure and flow information to the pressure and flow control system (19) through the pressure and flow sensor (4), and the pressure and flow regulator (3) adjusts Additional resistance to flow into the crack at the moment , so that P(a)+ =P(b), the flow rate pumped into each fracture is the same; Step 4: After the experiment is over, dismantle the entire experimental system in sequence; Step 5, processing and analyzing experimental data: after the experiment, observe the morphology and trend of the hydraulic fractures on the surface of the transparent sample (5) and use a camera to record the transparent sample (5); cut and observe the transparent sample (5) and use a camera to record the cut transparent sample (5); use a pump pressure-time curve to analyze the morphology of the hydraulic fractures, use a high-speed camera (8) to capture the complete process of the multi-perforation (2) crack expansion, and obtain the stress information of the transparent sample (5) during the rupture process based on the DIC digital image monitoring technology; scan and reconstruct the internal fracture morphology of the transparent sample (5) based on the CT scanning technology, and compare and analyze the internal fracture information obtained by the acoustic emission monitoring system (7); summarize and analyze the pressure flow distribution control mechanism under the action of different fracturing parameter combinations.

9. The hard-top horizontal well multi-hole fracturing pressure-flow intelligent control experimental method according to claim 8, characterized in that: The transparent sample (5) is prepared by arranging at least four perforated (2) prefabricated pipes at intervals on a simulated wellbore (1) prefabricated pipe, placing the simulated wellbore (1) prefabricated pipe in a mold, filling the mold with a sample material selected according to the mechanical characteristics of the simulated rock formation, and curing the mold for 24 days.

10. The hard-top horizontal well multi-pore fracturing pressure-flow intelligent control experimental method according to claim 8, characterized in that: The method for installing the entire experimental system is as follows: placing the transparent sample (5) in a true three-dimensional pressure loading test machine, and placing pressure plates (6) with reserved holes on the left and right opposite sides, the front and rear opposite sides, and the upper side of the transparent sample (5), respectively; placing measuring elements in the reserved holes of the pressure plate (6) and connecting them to the acoustic emission monitoring system (7); connecting the simulated wellbore (1) in the transparent sample (5) with the hydraulic servo pumping system and the pressure and flow dynamic distribution control system by using a pumping pipeline; moving a high-speed camera (8) and a DIC digital image monitoring system (9) to a position where the surface of the complete transparent sample (5) is clearly captured and connected to a multi-information processor (10); using a true three-dimensional ground stress loading servo control system to apply pressure to the transparent sample (5) in the axial and lateral directions according to the stress scheme; After the experiment is over, the method of dismantling the entire experimental system in sequence is as follows: shut down the hydraulic fracture information visualization monitoring system, the hydraulic servo pumping system, and the pressure and flow dynamic distribution control system, disconnect the fracturing fluid pumping pipeline from the hydraulic servo pumping system and the pressure and flow dynamic distribution control system; shut down the ground stress true three-dimensional loading servo control system and stop simulating ground stress loading; remove the pressure plate (6), and then remove the measuring element in the reserved hole of the pressure plate (6); remove the transparent sample (5); clean the pressure plate (6), the true triaxial pressure loading test machine (11) and related lines, and then perform maintenance.

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