An engineering bionic experiment system and method for evaluating the effect of borehole self-adaptive plugging based on NMR

Abstract

The present application relates to the field of gas extraction drilling plugging, in particular to a drilling adaptive plugging effect evaluation engineering bionics experiment system and method based on NMR; the system comprises drilling equipment, high-field nuclear magnetic resonance equipment, ultrasonic tomography equipment, plugging equipment, confining pressure heating and cooling circulation equipment; the method is: preparing coal samples and building simulation field, drilling construction process hole crack real-time dynamic imaging, first plugging and plugging section hole crack dynamic imaging and plugging effect evaluation, changing simulation field parameters to form first plugging failure, secondary plugging and plugging effect evaluation, repeating the above steps, realizing the adaptive plugging process and effect evaluation of "plugging-plugging failure-plugging again"; realizing the real-time dynamic evolution visualization process of hole crack in the drilling construction process, realizing the visualization research of the flow of plugging material in the crack in the multiple hole sealing process, realizing the research of the interaction mechanism between the plugging material and the coal body under the action of multiple field coupling.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas extraction drilling hole plugging, in particular to a drilling adaptive plugging effect evaluation engineering bionic experiment system and method based on NMR. BACKGROUND

[0002] Coalbed methane, as a domestic unconventional natural gas resource with abundant reserves, has a huge reserve of 3.68 trillion cubic meters, but its development and utilization amount has not reached 1% of the proven amount. Methane, as the main component of coalbed methane, has a greenhouse effect 20 times that of CO2 and a 7 times greater damage to the ozone layer than CO2. Its reasonable exploitation and utilization will have important significance for the protection of the ecological environment.

[0003] However, stress concentration occurs during roadway construction and extraction drilling construction, causing damage to the coal body around the drilling hole, resulting in different shapes of cracks around the roadway and drilling hole, and the gas in the coal seam migrates in these cracks. Macroscopic and microscopic cracks constitute a crack network. With the destruction of mining stress and the continuous gas extraction, the crack network continuously evolves, the number of cracks increases, the opening changes, and the gas pressure around the drilling hole changes. These cracks provide a seepage channel for air in the coal roadway to enter the extraction drilling hole, thereby causing a sharp decline in gas extraction concentration.

[0004] With the demand for sealing of micro cracks around the hole, more and more researches on dynamic sealing materials such as gel materials, polymer materials and new non-solid materials are being conducted. The evaluation of the sealing effect of these materials on the cracks around the hole mainly relies on gas concentration monitoring, pressure difference and performance testing of sealing materials.

[0005] However, there are still the following problems: first, the evaluation dimension is single and the sealing process cannot be realized in real time visualization: these methods can only reflect the sealing effect through indirect parameters (such as concentration, pressure, water retention, etc.), and cannot directly and real-time observe the diffusion path of the sealing material in the cracks around the hole and the sealing density; second, the existing experimental device cannot accurately simulate the dynamic imaging of the whole process of crack evolution around the hole during in-situ drilling construction; third, the bionic adaptability of the existing experimental device to the real sealing process is insufficient: drilling hole sealing is faced with the multi-field coupling of factors such as ground stress, ground heat and gas pressure, and the existing experimental device is difficult to simulate and reveal the interaction mechanism of sealing materials and coal body under the complex action of multi-field coupling.

[0006] Therefore, it is urgent to develop an experimental system integrating multi-field coupling, engineering bionic design and high-precision dynamic monitoring technology to study the real-time evolution of the surrounding fissures during the drilling process, the flow law and visualization of the sealing material in the fissures during the first sealing process, and the visualization of the dynamic evolution process of the multiple sealing fissures under the action of multi-field coupling, so as to provide reference data for determining the length of the sealing section of the drilling, expose the possible defects of the sealing material in the real environment in advance, shorten the verification period from the laboratory to the field, provide high-resolution dynamic data of the fissure network for supporting the digital twin technology of drilling sealing, and realize intelligent sealing of the drilling. SUMMARY

[0007] The present application overcomes the shortcomings of the prior art and aims to provide an engineering bionic experimental system for evaluating the adaptive sealing effect of drilling based on NMR, so as to realize the visualization process of the real-time dynamic evolution of the surrounding fissures during the drilling process, realize the flow and filling process of the sealing material in the fissures around the drilling during the multiple sealing process of the drilling, and realize the research on the interaction mechanism between the sealing material and the coal body under the action of multi-field coupling.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is as follows: an engineering bionic experimental system for evaluating the adaptive sealing effect of drilling based on NMR, comprising drilling equipment, high-field nuclear magnetic resonance equipment, ultrasonic tomography equipment, sealing equipment, and confining pressure heating and cooling circulation equipment.

[0009] The drilling equipment comprises a drill rod, and a drill bit is arranged at one end of the drill rod.

[0010] The high-field nuclear magnetic resonance device comprises a cylindrical shell composed of two nested inner and outer glass fiber epoxy tubes, the inner glass fiber epoxy tube is externally bonded with a radio frequency coil to form a radio frequency magnetic field, the outer glass fiber epoxy tube is externally mounted with a gradient coil to form a static magnetic field, a loadable sample holder is mounted in the inner cavity of the inner glass fiber epoxy tube, the body of the loadable sample holder is a hollow non-magnetic open-ended holder, a plurality of telescopic sample supports are arranged at the lower middle part of the inner side of the holder, a confining pressure fluid inlet is arranged at the lower left end of the holder, and a confining pressure fluid outlet is arranged at the upper right end of the holder; an axial loading device for loading coal bodies is further mounted on the inner side of the holder; the axial loading device comprises a circular ring-shaped pressing plate and a hole-containing circular pressing plate arranged at the two ends of the holder respectively, a closed cover is arranged in the hollow part of the circular ring-shaped pressing plate, the center of the closed cover is provided with a seepage hole, sample fixers I and II at the same horizontal height are respectively mounted on the inner sides of the circular ring-shaped pressing plate and the hole-containing circular pressing plate, and a plurality of axial loading rods are respectively mounted on the outer sides of the circular ring-shaped pressing plate and the hole-containing circular pressing plate; a T-shaped tee is further threadedly connected to the center hole of the hole-containing circular pressing plate, and an electric throttling valve is arranged on the T-shaped tee.

[0011] The ultrasonic tomography device comprises a plurality of transmitting transducers, a plurality of transmitting amplifiers and a plurality of receiving transducers; the plurality of transmitting amplifiers are uniformly arranged and installed on the outer side of the circular ring-shaped pressing plate in a circumferential arrangement, the transmitting transducers are overlapped and installed on the transmitting amplifiers, and the receiving transducers are installed on the outer side of the hole-containing circular pressing plate and arranged in position corresponding to the transmitting amplifiers.

[0012] The plugging device comprises two plugging bags, a plugging section is formed between the two plugging bags, a feeding pipe is in common communication with the two plugging bags, the feeding pipe arranged in the plugging bag is provided with a flow injection hole, and a blasting valve is arranged on the surface of each plugging bag; the feeding end of the feeding pipe is sequentially connected with a pressure maintaining valve I, a constant pressure intelligent grouting pump and a plugging material storage tank from near to far.

[0013] The confining pressure heating and cooling circulation device comprises a pressure maintaining valve II, a confining pressure fluid heating instrument, a confining pressure fluid injection pump, a confining pressure fluid storage tank, a confining pressure fluid cooling instrument, an accumulator and a pressure maintaining valve III which are sequentially connected together through heat preservation heat pipes; the pressure maintaining valve II is connected with the confining pressure fluid inlet through a heat preservation heat pipe, and the pressure maintaining valve III is connected with the confining pressure fluid outlet through a heat preservation heat pipe; the confining pressure fluid storage tank, the confining pressure fluid injection pump and the confining pressure fluid heating instrument are commonly connected with a data acquisition device through control lines; the data acquisition device is electrically connected with a control system; the data acquisition device acquires real-time data of the residual amount of fluid in the confining pressure fluid storage tank, the flow and pressure of the confining pressure fluid injection pump and the temperature of the confining pressure fluid heating instrument, and then transmits the data to the control system.

[0014] As a further limitation of the technical scheme of the application, the drill rod is provided with a central hole along the central axis in the axial direction, and the outer surface of the drill rod is provided with a wide-toothed groove thread which is recessed in the drill rod body, and the drill bit comprises four inclined column type cutters which are symmetrically arranged on the end surface of the drill rod, and each of the four inclined column type cutters is correspondingly provided with a claw type atomizing nozzle, one end of the claw type atomizing nozzle is communicated with the central hole of the drill rod, and the other end faces the inclined column type cutter.

[0015] As a further limitation of the technical scheme of the application, the radio frequency coils are uniformly adhered to the outside of the inner glass fiber epoxy resin pipe, capacitors are welded between adjacent coils to store energy and change the frequency of the coils, and then an inductance plate, a circuit distributor and a cable are installed; the outer glass fiber epoxy resin pipe is engraved with an annular groove, the gradient coils are uniformly attached and glued in the annular groove of the outer glass fiber epoxy resin pipe, and then a cooling pipe is wound on the gradient coils to absorb the heat generated by the coils; the inner glass fiber epoxy resin pipe containing the radio frequency coils is inserted into the outer glass fiber epoxy resin pipe containing the gradient coils, liquid nitrogen is filled between the two and sealed.

[0016] As a further limitation of the technical scheme of the application, the outer side of the circular ring-shaped pressing plate is welded with axial loading rods I, II, III and IV which are parallel to the central axis of the clamping cylinder, and the outer side of the hole-containing circular pressing plate is welded with axial loading rods V, VI, VII and VIII which are parallel to the central axis of the clamping cylinder.

[0017] As a further limitation of the technical scheme of the application, the inner side of the sample fixator I is provided with a circular ring-shaped rubber gasket; and the inner side of the sample fixator II is provided with a hole-containing rubber gasket.

[0018] As a further limitation of the technical scheme of the application, the number of the transmitting transducers, the transmitting amplifiers and the receiving transducers is eight, and the eight transmitting amplifiers are arranged in a circle and installed on the outer side of the circular ring-shaped pressing plate at 30°, 60°, 120°, 150°, 210°, 240°, 300° and 330°, and the eight receiving transducers are installed on the outer side of the hole-containing circular pressing plate and correspondingly arranged with the transmitting amplifiers.

[0019] As a further limitation of the technical scheme of the application, the confining pressure fluid injection pump has an adjustment range of 0-60 MPa and an adjustment accuracy of 0.10 MPa, the confining pressure fluid heating instrument has a temperature control range of 0-70℃, a temperature rising rate of ≥10℃ / min and an accuracy of 0.01℃, the confining pressure fluid cooling instrument is provided with a temperature measuring device inside to measure the temperature of the input fluid, and the confining pressure fluid cooling instrument is also provided with a condenser and a condensing agent inside, the condensing agent is carbon dioxide (R744), the temperature control range is 0-40℃, and the temperature falling rate is ≥10℃ / min.

[0020] The application also provides a NMR-based self-adaptive evaluation method for plugging effect of a borehole, which is implemented by using the above-mentioned engineering bionic experimental system and includes the following steps.

[0021] S1, preparing a sample: obtaining a complete coal sample from a coal mine, grinding the sample to meet the size of a holder, sleeving a thermoplastic sleeve on the coal sample, the length of the thermoplastic sleeve being greater than the length of the coal sample, placing the coal sample wrapped by the thermoplastic sleeve into a clamping cylinder, and placing the clamping cylinder on an extendable sample support, adjusting the height of the extendable sample support to make the two ends of the coal sample match with sample fixers I and II respectively, and adjusting an axial loading device to gradually clamp the coal sample;

[0022] S2, forming an underground simulation field: determining the axial loading stress, the magnitude of confining pressure, the amount of gas injection, and the temperature of confining fluid according to the determined in-situ stress parameters, gas content and pressure parameters, and temperature of the coal mine, starting the axial loading device, adjusting the loading speed to 0.1 mm / min, slowly loading to the pre-stress, stopping loading, opening the confining fluid injection pump to set the initial confining pressure and inject confining fluid, opening the confining fluid heating instrument and recording the initial temperature t1, setting the initial pre-heating temperature t2, opening the confining fluid cooling instrument and recording the temperature curve of the outflowing confining fluid changing with time, taking the stable value t3 after the curve is stable, calculating the heat loss according to the temperature difference Δt=t3-t2, re-adjusting the heating temperature t4 of the confining fluid heating instrument to make the internal temperature of the coal body reach the preset temperature t0, and gradually increasing the axial pressure and confining pressure to reach the actual pressure of the coal mine, gradually injecting gas into the coal body from the T-shaped three-way pipe, and letting the gas flow out from the seepage hole of the closure cap, and performing subsequent experiments after 48 hours of gas injection;

[0023] S3, real-time evolution dynamic imaging of fractures around a borehole in a drilling process: removing the closure cap, starting the nuclear magnetic resonance device, determining the resonance frequency, spectral width, sampling point number, accumulation number, relaxation delay, and pulse sequence after the field strength is stable and the magnetic field uniformity is corrected, starting the drilling device to form a borehole at the axial center of the coal sample after the device normally operates for a period of time, continuously and uninterruptedly collecting the T2 transverse relaxation time weighted signals of the fracture water in the coal body around the borehole by the nuclear magnetic system with the drilling of the drill bit 1-2, and observing the dynamic evolution process of the fracture network around the borehole, recording the data set Q1 according to the nuclear magnetic resonance data collected after the drilling is completed, reconstructing the three-dimensional structure D1 of the fractures through image processing and three-dimensional reconstruction, determining the maximum axial length L0 of the fracture network, and thus determining the length L of the plugging section. 1 H, and thus observing the dynamic evolution process of the fracture network around the borehole, recording the data set Q1 according to the nuclear magnetic resonance data collected after the drilling is completed, reconstructing the three-dimensional structure D1 of the fractures through image processing and three-dimensional reconstruction, determining the maximum axial length L0 of the fracture network, and thus determining the length L of the plugging section.

[0024] S4, first plugging, dynamic imaging of filling of borehole plugging section hole fissure and plugging effect evaluation: after the drilling is completed, the drilling hole is closed with a closure cap, then the confining fluid heating instrument is heated to a certain temperature, the confining fluid is heated for a period of time, the water in the coal body is dried through heat conduction of the confining fluid, and the water in the coal body cannot be imaged in the nuclear magnetic resonance equipment; according to the length L of the hole sealing section determined in S3, the plugging bag and the feeding pipe are connected according to the length, after the connection is completed, the closure cap is opened, the plugging bag and the feeding pipe are put into the drilling hole, the constant pressure intelligent grouting pump is opened, the initial grouting pressure is set, the plugging material is injected into the plugging bag and the drilling hole, the nuclear magnetic imaging system is observed, after two bright color ellipsoidal balls are formed, the grouting pressure is increased, the burst valve is broken through, the plugging material flows into the plugging section, the grouting pressure is kept constant, the plugging material is continuously injected until the entire drilling hole is filled, the migration of the plugging material in the drilling hole is observed through the nuclear magnetic real-time imaging, and the water content of the plugging material in the drilling hole is calculated according to the T2 transverse relaxation time data of the nuclear magnetic resonance 1 H, and the data set Q2 is recorded, the fissure visualization three-dimensional structure D2 is obtained through image processing and three-dimensional reconstruction, the coincidence degree of the data sets Q1 and Q2 is combined and compared, and whether D1 / D2 is in the fault tolerance interval is calculated;

[0025] S5, once plugging failure, change simulation field parameters, new fissure appears around the plugged drilling hole or original fissure develops: the ultrasonic tomography equipment is opened, the transducer array is connected to the data acquisition module of the ultrasonic tomography system, the transmission parameters are set, including the center frequency of the transducer, the transmission voltage, the pulse bandwidth or waveform, the imaging speed, the receiving parameters are set, including the sampling rate, the gain, the data saving format, the channel is set to bidirectional transmission, the confining pressure, the axial pressure and the gas pressure are changed to make the new fissure or the original fissure around the drilling hole expand and develop, the transducer is started in the set order to perform tomographic scanning and data acquisition, the propagation time and the amplitude are extracted, the sound velocity distribution map is reconstructed, and the sound velocity abnormal area is marked, that is, when the sound velocity decreases by 5% or more and 3 frames appear continuously, the new fissure can be determined, all two-dimensional images of the layers are stacked into three-dimensional voxel images, and then the fissure structure is rendered and analyzed to obtain three-dimensional images and the data set W1, and the data observed by the ultrasonic tomography is fed back to the computer;

[0026] S6, secondary plugging: the computer compares the nuclear magnetic resonance real-time data with the new fissure ultrasonic tomography data transmitted in step S5, the number, opening and void volume of the new fissures are determined by comparing the data of Q2 and W1, so that the amount of plugging material to be injected is determined to avoid excessive grouting pressure and cause coal fracturing, further, the computer controls the plugging equipment to supplement the plugging material into the drilling hole, at this time, the nuclear magnetic resonance real-time imaging observes that the new fissure or fissure network is filled with the plugging material, the new imaging data is compared with the ultrasonic tomography data in S5, the compaction degree of the plugging is calculated to determine whether the plugging effect is good or bad;

[0027] S7, the steps of S5, S6 are repeated, that is, the self-adaptive sealing process and effect evaluation of sealing-sealing failure-resealing of the borehole under different ground stress, geothermal environment and gas pressure can be realized.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) Full-process dynamic monitoring, for the first time, NMR in-situ characterization in the life cycle of the borehole "construction process borehole crack dynamic evolution imaging-dynamic sealing of borehole cracks after hole forming-sealing failure under multi-field coupling-resealing" is realized, and the process and sealing effect evaluation of borehole adaptive sealing are realized. (2) Multi-source signal joint evaluation of sealing effect: for single and indirect traditional evaluation method, the present application shows the flow state of sealing material in the borehole in real time, seals the imaging of the borehole crack, accurately and directly characterizes the filling process and the compactness of the filled borehole crack, and avoids the reasons such as possible gas concentration reduction and pressure reduction. (3) Enhance the bionic adaptability of experiment and field: through the simulation of the interaction of sealing material under the coupling of factors such as ground stress, gas pressure and geothermal, the possible defects of sealing material in the real environment are exposed in advance, the test cycle of sealing material improvement is shortened, and the field cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the drilling equipment of the present application.

[0031] Figure 2 It is a side view of the drill bit.

[0032] Figure 3 It is a schematic diagram of the structure of the high-field nuclear magnetic resonance equipment of the present application.

[0033] Figure 4 It is a schematic diagram of the structure of the ultrasonic imaging equipment of the present application.

[0034] Figure 5 It is a schematic diagram of the structure of the sealing equipment of the present application.

[0035] Figure 6 It is a schematic diagram of the structure of the confining pressure heating and cooling cycle equipment of the present application.

[0036] Figure 7 It is the development process of the coal body crack in the drilling process of the present application.

[0037] Figure 8 It is a schematic diagram of the present application for sealing the borehole crack of coal body.

[0038] Figure 9 It is a schematic diagram of the installation of the axial loading device and the ultrasonic tomography imaging equipment.

[0039] The markings in the image are as follows:

[0040] 1-1. Drill rod; 1-2. Drill bit; 1-3. Claw-type atomizing nozzle; 1-4. Wide-toothed thread; 1-5. Inclined column cutter; 1-6. Drill hole; 2-1. Clamping sleeve; 2-2. Telescopic sample support frame; 2-3. Confining pressure fluid inlet; 2-4. Confining pressure fluid outlet; 2-5. Thermoplastic sleeve; 2-6. Circular pressure plate; 2-7. Sealing cap; 2-8. Seepage hole; 2-9. Axial loading rod I; 2-10. Axial loading rod II; 2-11. Axial loading rod III; 2-12. Axial loading rod IV; 2-13. Sample holder I; 2-14. Circular rubber gasket; 2-15. Circular pressure plate with hole; 2-16. Axial loading rod V; 2-17. Axial loading rod VI; 2-18. Axial loading rod VII; 2-19. Axial... Loading rod VIII, 2-20, Sample holder II, 2-21, Perforated rubber gasket, 2-22, T-shaped tee, 2-23, Radio frequency coil, 2-24, Gradient coil, 3-1 Transmitting transducer, 3-2, Transmitting amplifier, 3-3, Receiving transducer, 4-1, Sealing material storage tank, 4-2, Constant pressure intelligent grouting pump, 4-3, Pressure holding valve I, 4-4, Feeding pipe, 4-5, Sealing bag, 4-6, Injection hole, 4-7, Bursting valve, 4-8, Sealing section; 5-1, Confining pressure fluid storage tank, 5-2, Confining pressure fluid injection pump, 5-3, Confining pressure fluid heater, 5-4, Pressure holding valve II, 5-5, Pressure holding valve III, 5-6, Accumulator, 5-7, Confining pressure fluid cooler, 5-8, Insulated heating pipe, 6, Coal sample, 7, Filling crack. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments.

[0042] Example 1

[0043] like Figure 7 As shown, an engineering biomimetic experimental system for evaluating the adaptive hole plugging effect based on NMR includes drilling equipment, high-field nuclear magnetic resonance equipment, ultrasonic tomography equipment, plugging equipment, and confining pressure heating and cooling circulation equipment.

[0044] like Figure 1 As shown, the drilling equipment includes a drill rod 1-1, with a drill bit 1-2 at one end. The drill rod 1-1 has a hollow structure inside its center along its axial direction (i.e., a central hole is formed along the central axis). The outer surface of the drill rod 1-1 has a wide-toothed thread 1-4 recessed into its body. During drilling, small, broken coal pieces are screwed out of the borehole through the wide-toothed thread 1-4. Figure 2As shown, the drill bit 1-2 includes four inclined column type cutters 1-5 arranged symmetrically on the end face of the drill rod 1-1, and the inside of each of the four inclined column type cutters 1-5 is correspondingly provided with a claw type atomizing nozzle 1-3; one end of the claw type atomizing nozzle 1-3 is communicated with the central hole of the drill rod 1-1, and the other end is directed to the inclined column type cutter 1-5; the inclined column type cutter 1-5 is made of polycrystalline diamond compact, and the designed inclined direction is consistent with the drilling direction; the claw type atomizing nozzle 1-3 is fixed on the end of the drill bit by screwing, and the designed size is smaller than the diameter of the drill rod;

[0045] As shown in the figure, Figure 3 As shown, the high-field nuclear magnetic resonance device includes a cylindrical shell composed of two nested inner and outer glass fiber epoxy resin tubes, the inner glass fiber epoxy resin tube is bonded with a radio frequency coil 2-23 on the outside to form a radio frequency magnetic field, and the outer glass fiber epoxy resin tube is provided with a gradient coil 2-24 to form a static magnetic field, the radio frequency coil 2-23 is uniformly bonded on the outside of the inner glass fiber epoxy resin tube, capacitors are welded between adjacent coils to store energy and change the frequency of the coils, and then an inductance plate, a circuit distributor and a cable are installed; the outer glass fiber epoxy resin tube is engraved with an annular groove, the gradient coil 2-24 is uniformly pasted and glued in the annular groove of the outer glass fiber epoxy resin tube, and then a cooling pipe is wound on the gradient coil 2-24 to absorb the heat generated by the coil; the inner glass fiber epoxy resin tube containing the radio frequency coil 2-23 is inserted into the outer glass fiber epoxy resin tube containing the gradient coil 2-24, liquid nitrogen is filled between the two and sealed, so that it is in an ultra-low temperature environment of 4K, the gradient coil 2-24 is energized to form a superconducting magnet, and after the device is started and the frequency is adjusted, a static magnetic field is formed inside the chamber; a loading sample holder is installed in the inner cavity of the inner glass fiber epoxy resin tube, and the loading sample holder is sent into the magnetic field and suspended through a guide rail; the loading sample holder body is a hollow non-magnetic and high-mechanical-strength open-ended clamping cylinder 2-1, the cylinder wall can withstand a maximum confining pressure of 120MPa, the inside of the clamping cylinder is designed to be smooth, a plurality of telescopic sample supports 2-2 are arranged at the lower middle part of the inside of the clamping cylinder 2-1, the telescopic sample supports 2-2 are made of carbon fiber and have a load capacity of ≥10kN, a confining pressure fluid inlet 2-3 is arranged at the lower left end of the clamping cylinder 2-1, and a confining pressure fluid outlet 2-4 is arranged at the upper right end of the clamping cylinder 2-1 (the confining pressure fluid inlet and outlet are connected to the confining pressure heating and cooling equipment through a sealing ring gasket, a nut and a confining pressure heating and cooling equipment); an axial loading device for loading coal bodies is also installed in the clamping cylinder 2-1, the loading force is 0-500kN, and the loading speed is controlled to be 0.0-50mm / min;

[0046] The axial loading device comprises a circular ring-shaped pressing plate 2-6 and a hole-containing circular pressing plate 2-15 arranged at two ends of the clamping cylinder 2-1 respectively, the hollow part of the circular ring-shaped pressing plate 2-6 is provided with a closing cover 2-7, the center of the closing cover 2-7 is provided with a seepage hole 2-8, the inner side surfaces (the adjacent surfaces of the circular ring-shaped pressing plate 2-6 and the hole-containing circular pressing plate 2-15) of the circular ring-shaped pressing plate 2-6 and the hole-containing circular pressing plate 2-15 are respectively provided with a sample fixer I 2-13 and a sample fixer II 2-20 at the same horizontal level, the outer side of the circular ring-shaped pressing plate 2-6 is welded with an axial loading rod I 2-9, an axial loading rod II 2-10, an axial loading rod III 2-11 and an axial loading rod IV 2-12 which are parallel to the central axis of the clamping cylinder 2-1, and the outer side of the hole-containing circular pressing plate 2-15 is welded with an axial loading rod V 2-16, an axial loading rod VI 2-17, an axial loading rod VII 2-18 and an axial loading rod VIII 2-19 which are parallel to the central axis of the clamping cylinder 2-1 (as shown in Figure 9 The center hole of the hole-containing circular pressing plate 2-15 is also threadedly connected with a T-shaped three-way pipe 2-22, and the T-shaped three-way pipe 2-22 is provided with an electric throttle valve.

[0047] As shown in Figure 4 The ultrasonic tomography equipment comprises eight transmitting transducers 3-1, eight transmitting amplifiers 3-2 and eight receiving transducers 3-3; the eight transmitting amplifiers 3-2 are arranged in a circle and are evenly installed at the outer side of the circular ring-shaped pressing plate 2-6 at 30°, 60°, 120°, 150°, 210°, 240°, 300° and 330°, the transmitting transducers 3-1 are overlapped and installed on the transmitting amplifiers 3-2, and the eight receiving transducers 3-3 are installed at the outer side of the hole-containing circular pressing plate 2-15 and are correspondingly arranged with the transmitting amplifiers 3-2.

[0048] As shown in Figure 5 The plugging device comprises two plugging bags 4-5, a plugging section 4-8 is formed between the two plugging bags 4-5, and the two plugging bags 4-5 are commonly connected with a feeding pipe 4-4 which is connected in a penetrating mode between the plugging bags and the feeding pipe 4-4, the feeding pipe 4-4 in the plugging bag 4-5 is provided with an injection hole 4-6, the surfaces of the two plugging bags 4-5 are oppositely provided with burst valves 4-7 which are located at the inner side of the plugging section 4-8, the feeding end of the feeding pipe 4-4 is sequentially connected with a pressure maintaining valve I 4-3, a constant pressure intelligent grouting pump 4-2 and a plugging material storage tank 4-1 from near to far, the slurry is firstly filled into the plugging bag 4-5 and then filled into the hole plugging section 4-8 through the burst valve.

[0049] As shown in Figure 6As shown, the confining pressure heating and cooling cycle device comprises a pressure maintaining valve II 5-4, a confining pressure fluid heating instrument 5-3, a confining pressure fluid injection pump 5-2, a confining pressure fluid storage tank 5-1, a confining pressure fluid cooling instrument 5-7, an accumulator 5-6 and a pressure maintaining valve III 5-5 connected in sequence through heat preservation heat pipes 5-8, the pressure maintaining valve II 5-4 is connected with the confining pressure fluid inlet 2-3 through the heat preservation heat pipe 5-8, and the pressure maintaining valve III 5-5 is connected with the confining pressure fluid outlet 2-4 through the heat preservation heat pipe 5-8; the confining pressure fluid storage tank 5-1, the confining pressure fluid injection pump 5-2 and the confining pressure fluid heating instrument 5-3 are connected with a data collector through control lines respectively, the data collector is electrically connected with a control system, the data collector collects the residual amount of fluid in the confining pressure fluid storage tank 5-1, the flow and pressure of the confining pressure fluid injection pump 5-2 and the temperature data of the confining pressure fluid heating instrument 5-3 in real time, and then transmits them to the control system, the control system dynamically adjusts the working parameters by analyzing these data, so as to accurately control the flow rate, pressure and temperature of the confining pressure fluid.

[0050] Further, the inner side (i.e. the side in contact with the coal sample 6) of the sample holder I 2-13 is provided with a circular ring rubber gasket 2-14; the inner side (i.e. the side in contact with the coal sample 6) of the sample holder II 2-20 is also provided with a rubber gasket 2-21 containing holes.

[0051] Further, the confining pressure fluid injection pump 5-2 has an adjustment range of 0-60 MPa and an adjustment accuracy of 0.10 MPa, the confining pressure fluid injection pump 5-2 is connected with the confining pressure fluid heating instrument 5-3, the temperature control range is 0-70℃, the temperature rising rate is ≥10℃ / min, the accuracy is 0.01℃, the confining pressure fluid heating instrument 5-3 is connected with the pressure maintaining valve II 5-4, and the accuracy is 0.01 MPa.

[0052] In particular, the fluid heating instrument 5-3 is provided with a temperature measuring device inside, which can measure the temperature of the input fluid and then heat it through the built-in serpentine electric heating ring tube; the pressure maintaining valve II 5-4 and the confining pressure fluid heating instrument 5-3 are connected through the heat preservation heat pipe 5-8, the output end is connected with the confining pressure fluid inlet 2-3 of the sample holder through the heat preservation heat pipe 5-8, and the interface is connected through the self-tightening flange.

[0053] The input end of the pressure maintaining valve III 5-5 and the confining pressure fluid outlet 2-4 of the sample holder are connected through the self-tightening flange, and the pressure maintaining range of the pressure maintaining valve III 5-5 is 0-80 MPa; in particular, the accumulator 5-6 and the pressure maintaining valve III 5-5 are connected through the high-pressure pipeline, the accumulator 5-6 is provided with a flexible diaphragm bag filled with gas inside, the relative pressure drop is 10%-30%, the accumulator 5-6 is connected with the multi-stage pressure reducing valve through the high-pressure pipeline, and the pressure drop range of the multi-stage pressure reducing valve is 0-40 MPa.

[0054] The temperature measuring device is arranged in the confining pressure fluid cooling instrument 5-7, the input fluid can be measured, the condenser pipe and the condensing agent are arranged in the confining pressure fluid cooling instrument 5-7, the condensing agent is carbon dioxide (R744), the temperature control range is 0-40 DEG C, the cooling rate is >= 10 DEG C / min, the output end of the confining pressure fluid cooling instrument is connected with the confining pressure fluid storage tank, and circulation is formed.

[0055] Example 2

[0056] A kind of NMR-based drilling adaptive plugging effect evaluation method, using the engineering bionics experimental system of above-mentioned example 1, as shown in Figure 7 And 8 As shown, comprising the following steps:

[0057] S1, preparing sample: from the complete coal sample is prepared from the mine, the sample is polished to meet the size of the holder, the thermoplastic sleeve 2-5 is sleeved on the coal sample 6, the length of the thermoplastic sleeve 2-5 is greater than the length of the coal sample 6, the coal sample 6 wrapped by the thermoplastic sleeve 2-5 is placed in the clamping cylinder 2-1 and placed on the telescopic sample support 2-2, the height of the telescopic sample support 2-2 is adjusted to make the coal sample 6 two ends respectively consistent with the sample fixator I 2-13 and the sample fixator II 2-20, the axial loading device is adjusted, and the coal sample 6 is gradually clamped; the thermoplastic sleeve 2-5 arranged on the surface of the coal sample 6 has a temperature resistance of 0 DEG C to 100 DEG C and a tensile strength of >= 50 MPa.

[0058] S2, forming an underground simulation field: according to the determined ground stress parameters, gas content and pressure parameters, temperature and the like in the mine, the axial loading stress, the size of the confining pressure, the gas injection amount, the confining pressure fluid temperature and the like are determined, the axial loading device is first started, the loading speed is adjusted to 0.1 mm / min, the pre-stress is slowly loaded and stopped after loading, the confining pressure fluid injection pump 5-2 is opened to set the initial confining pressure and inject the confining pressure fluid, the confining pressure fluid heater 5-3 is opened and the initial temperature t1 is recorded, the initial pre-heating temperature t2 is set, the confining pressure fluid cooler 5-7 is opened and the curve of the temperature change of the outflowing confining pressure fluid with time is recorded, after the curve is stable, the stable value t3 is taken, the heat loss is calculated according to the temperature difference At = t3-t2 feedback to the computer, the heating temperature t4 of the confining pressure fluid heater 5-3 is adjusted again so that the internal temperature of the coal body reaches the preset temperature t0, the axial pressure and the confining pressure are gradually increased to the actual pressure size in the mine, the gas is gradually injected into the coal body from the T-shaped three-way pipe, the gas flows out from the seepage hole 2-8 of the closed cover 2-7, and the subsequent experiment is carried out after the gas is injected for 48 hours.

[0059] S3, real-time imaging of the evolution of the fissure around the hole during drilling: remove the closure cap 2-7, start the nuclear magnetic resonance device, after the field strength is stable and the magnetic field homogeneity is corrected, determine the resonance frequency, spectral width, sample point number, accumulation number, relaxation delay, pulse sequence, etc., wait for the device to run normally for a period of time, start the drilling device to form a drill hole at the axial center of the coal sample 6, the drill bit 1-2 drills while the claw-shaped atomizing nozzle 1-3 sprays water, as the drill bit 1-2 drills, the nuclear magnetic system continuously and uninterruptedly collects the T2 (transverse relaxation time) data of the water in the fissure network around the drill hole 1 H and real-time imaging, so as to observe the dynamic evolution process of the fissure network around the hole, after the drilling is completed, record the data set Q1 according to the nuclear magnetic resonance data, reconstruct the fissure three-dimensional structure D1 through image processing and three-dimensional reconstruction, determine the maximum axial length L0 of the fissure network, and thus determine the length L of the sealing section 4-8.

[0060] S4, first sealing, dynamic imaging of the filling of the fissure around the hole in the sealing section of the drill hole and evaluation of the sealing effect: after the drill hole is completed, the drill hole is closed using the closure cap 2-7, then the temperature of the confining fluid heating instrument 5-3 is raised, the confining fluid is heated for a period of time, the water in the coal body is dried through heat conduction of the confining fluid, until it cannot be imaged in the nuclear magnetic resonance device; according to the length L of the hole sealing section determined in S3, connect the sealing bag 4-5 and the feeding pipe 4-4 according to the length, after the connection is completed, open the closure cap 2-7, put the sealing bag 4-5 and the feeding pipe 4-4 into the drill hole, open the constant-pressure intelligent grouting pump 4-2, set the initial grouting pressure, slowly inject the sealing material into the sealing bag 4-5 and the drill hole, observe the nuclear magnetic imaging system, after two bright color ellipsoids are formed, increase the grouting pressure, break through the blasting valve 4-7, the sealing material flows into the sealing section 4-8, and the grouting pressure is kept constant, the sealing material is continuously injected until the entire drill hole is filled, the migration of the sealing material in the drill hole is observed through real-time imaging, and the T2 (transverse relaxation time) data of the water in the sealing material 1 H and record the data set Q2, process to obtain the fissure visualization three-dimensional structure D2 through image processing and three-dimensional reconstruction, combine and compare the coincidence degree of the data sets Q1 and Q2, and calculate whether D1 / D2 is in the fault tolerance interval.

[0061] S5, once the plugging failure, change the simulation field parameters, the sealed borehole hole around the new fracture or the original fracture development: open the ultrasonic tomography equipment, the transducer array access ultrasonic tomography system data acquisition module, set the transmission parameters (transducer center frequency, transmission voltage, pulse bandwidth or waveform, imaging speed, etc.) and receiving parameters (sampling rate, gain, data saving format, etc.), channel settings for bidirectional transmission, change the confining pressure, axial pressure, gas pressure so that the borehole hole around the new fracture or the original fracture expansion and development, according to the set order to start the transmitter to carry out tomographic scanning and data acquisition, propagation time and amplitude extraction, reconstruction of sound velocity distribution map, mark the sound velocity anomaly area (when the sound velocity drop ≥5% and continuous 3 frames, can be determined as new fracture), all layers of two-dimensional image stack into three-dimensional voxel image, then render and analyze the fracture structure, get three-dimensional image and data set W1, the ultrasonic tomography observation data feedback to the computer.

[0062] S6, secondary plugging: computer contrast nuclear magnetic resonance real-time data and step S5 transferred new fracture ultrasonic tomography data, by comparing Q2 and W1 data, determine the number of new cracks, opening and other void volume, so as to determine the amount of plugging material injection to avoid excessive grouting pressure and cause coal fracturing, further, the computer control plugging equipment to supplement the plugging material to the borehole, at this time, nuclear magnetic resonance real-time imaging, observation of new, developed fracture (or fracture network) is filled with plugging material, new imaging data and S5 ultrasonic tomography data comparison, calculate the density of the plugging to determine the good or bad of the plugging effect.

[0063] S7, cycle repeat S5, S6 steps, that is, the adaptive plugging process and effect evaluation of borehole plugging-plugging failure-replugging under different ground stress, geothermal environment, gas pressure.

Claims

1. An NMR-based engineering bionic experimental system for evaluating the self-adaptive plugging effect of a borehole, characterized in that, The drilling device, the high-field nuclear magnetic resonance device, the ultrasonic tomography device, the plugging device, and the confining pressure heating and cooling circulation device are included. The drilling device includes a drill rod (1-1), and one end of the drill rod (1-1) is provided with a drill bit (1-2). The high-field nuclear magnetic resonance device includes a cylindrical shell composed of two nested inner and outer glass fiber epoxy resin tubes, an RF coil (2-23) is adhered to the outside of the inner glass fiber epoxy resin tube to form an RF magnetic field, a gradient coil (2-24) is installed on the outer glass fiber epoxy resin tube to form a static magnetic field, a loadable sample holder is installed in the inner cavity of the inner glass fiber epoxy resin tube, the main body of the loadable sample holder is a hollow non-magnetic clamping cylinder (2-1) with open ends, a plurality of telescopic sample supports (2-2) are arranged at the lower middle part of the inner side of the clamping cylinder (2-1), a confining pressure fluid inlet (2-3) is arranged at the lower left end of the clamping cylinder (2-1), and a confining pressure fluid outlet (2-4) is arranged at the upper right end of the clamping cylinder (2-1); an axial loading device for loading coal bodies is also installed in the clamping cylinder (2-1); the axial loading device includes a circular ring-shaped pressing plate (2-6) and a hole-containing circular pressing plate (2-15) arranged at the two ends of the clamping cylinder (2-1), respectively, a closure cover (2-7) is arranged in the hollow part of the circular ring-shaped pressing plate (2-6), the center of the closure cover (2-7) has a seepage hole (2-8), the inner sides of the circular ring-shaped pressing plate (2-6) and the hole-containing circular pressing plate (2-15) are respectively provided with a sample fixator I (2-13) and a sample fixator II (2-20) at the same horizontal height, and a plurality of axial loading rods are arranged on the outer sides of the circular ring-shaped pressing plate (2-6) and the hole-containing circular pressing plate (2-15); a T-shaped tee pipe (2-22) is also threadedly connected to the center hole of the hole-containing circular pressing plate (2-15), and an electric throttle valve is arranged on the T-shaped tee pipe (2-22); The ultrasonic tomography device includes a plurality of transmitting transducers (3-1), a plurality of transmitting amplifiers (3-2), and a plurality of receiving transducers (3-3); the plurality of transmitting amplifiers (3-2) are uniformly arranged and installed on the outer side of the circular ring-shaped pressing plate (2-6) in a circular arrangement, the transmitting transducers (3-1) are overlapped and installed on the transmitting amplifiers (3-2), and the receiving transducers (3-3) are installed on the outer side of the hole-containing circular pressing plate (2-15) and correspond to the positions of the transmitting amplifiers (3-2). The plugging device comprises two plugging bags (4-5), a plugging section (4-8) is formed between the two plugging bags (4-5), and a feeding pipe (4-4) is in common communication with the two plugging bags (4-5), the feeding pipe (4-4) in the plugging bag (4-5) is provided with an injection hole (4-6), and the surfaces of the two plugging bags (4-5) are provided with blast valves (4-7) in opposite directions, respectively, the feeding end of the feeding pipe (4-4) is sequentially connected with a pressure maintaining valve I (4-3), a constant pressure intelligent grouting pump (4-2), and a plugging material storage tank (4-1) from near to far. The confining pressure heating and cooling circulation device comprises a pressure maintaining valve II (5-4), a confining pressure fluid heating instrument (5-3), a confining pressure fluid injection pump (5-2), a confining pressure fluid storage tank (5-1), a confining pressure fluid cooling instrument (5-7), an accumulator (5-6), and a pressure maintaining valve III (5-5) which are sequentially connected together through heat preservation heat pipes (5-8), the pressure maintaining valve II (5-4) is connected with the confining pressure fluid inlet (2-3) through the heat preservation heat pipe (5-8), the pressure maintaining valve III (5-5) is connected with the confining pressure fluid outlet (2-4) through the heat preservation heat pipe (5-8), the confining pressure fluid storage tank (5-1), the confining pressure fluid injection pump (5-2), and the confining pressure fluid heating instrument (5-3) are commonly connected with a data collector through control lines, respectively, the data collector is electrically connected with a control system, and the data collector collects the residual amount of fluid in the confining pressure fluid storage tank (5-1), the flow and pressure of the confining pressure fluid injection pump (5-2), and the temperature data of the confining pressure fluid heating instrument (5-3) in real time, and then transmits the data to the control system.

2. The NMR-based engineering bionic experimental system for evaluating self-adaptive plugging effect of a borehole according to claim 1, characterized in that, The drill rod (1-1) is provided with a central hole along the central axis in the axial direction, and the outer surface of the drill rod (1-1) is provided with a wide-toothed groove thread (1-4) which is recessed in the body of the drill rod (1-1), the drill bit (1-2) comprises four inclined column type cutters (1-5) which are symmetrically arranged on the end surface of the drill rod (1-1), and the inner sides of the four inclined column type cutters (1-5) are respectively provided with claw type atomizing nozzles (1-3), one end of the claw type atomizing nozzle (1-3) is communicated with the central hole of the drill rod (1-1), and the other end faces the inclined column type cutter (1-5).

3. The NMR-based engineering bionic experimental system for evaluating the self-adaptive plugging effect of a borehole according to claim 1, characterized in that, The radio frequency coils (2-23) are uniformly adhered to the outside of the inner glass fiber epoxy resin pipe, capacitors are welded between adjacent coils to store energy and change the frequency of the coils, and then an inductance plate, a circuit distributor and a cable are installed; the outer glass fiber epoxy resin pipe is engraved with an annular groove, the gradient coils (2-24) are uniformly attached and glued in the annular groove of the outer glass fiber epoxy resin pipe, and then a cooling pipe is wound on the gradient coils (2-24) to absorb the heat generated by the coils; the inner glass fiber epoxy resin pipe containing the radio frequency coils (2-23) is inserted into the outer glass fiber epoxy resin pipe containing the gradient coils (2-24), liquid nitrogen is filled between the two and sealed.

4. The NMR-based engineering bionic experimental system for evaluating self-adaptive plugging effect of a borehole according to claim 1, characterized in that, The outer side of the circular ring pressing plate (2-6) is welded with axial loading rod I (2-9), axial loading rod II (2-10), axial loading rod III (2-11) and axial loading rod IV (2-12) which are parallel to the central axis of the clamping cylinder (2-1), and the outer side of the circular pressing plate with holes (2-15) is welded with axial loading rod V (2-16), axial loading rod VI (2-17), axial loading rod VII (2-18) and axial loading rod VIII (2-19) which are parallel to the central axis of the clamping cylinder (2-1).

5. The NMR-based engineering bionic experimental system for evaluating the self-adaptive plugging effect of a borehole according to claim 1, characterized in that, The inner side of the sample holder I (2-13) is provided with a circular rubber gasket (2-14); the inner side of the sample holder II (2-20) is also provided with a rubber gasket with holes (2-21).

6. The NMR-based engineering bionic experimental system for evaluating self-adaptive plugging effect of a borehole according to claim 1, characterized in that, The number of the transmitting transducers (3-1), transmitting amplifiers (3-2) and receiving transducers (3-3) is eight, eight transmitting amplifiers (3-2) are arranged in a circle and are installed at 30°, 60°, 120°, 150°, 210°, 240°, 300° and 330° on the outer side of the circular ring pressing plate (2-6), and eight receiving transducers (3-3) are installed on the outer side of the circular pressing plate with holes (2-15) and are arranged correspondingly with the transmitting amplifiers (3-2).

7. The NMR-based engineering bionic experimental system for evaluating self-adaptive plugging effect of a borehole according to claim 1, characterized in that, The confining fluid injection pump (5-2) has an adjustment range of 0-60MPa and an adjustment accuracy of 0.10MPa, the confining fluid heating instrument (5-3) has a temperature control range of 0-70℃, a temperature rising rate of ≥10℃ / min and an accuracy of 0.01℃, the confining fluid cooling instrument (5-7) is provided with a temperature measuring device inside to measure the temperature of the input fluid, and the confining fluid cooling instrument (5-7) is provided with a condenser and a condensing agent inside, the condensing agent is carbon dioxide R744, the temperature control range is 0-40℃, and the temperature falling rate is ≥10℃ / min.

8. A method for evaluating the effect of plugging a borehole based on NMR, using the engineering bionic experimental system according to any one of claims 1-7, characterized in that, The method comprises the following steps: S1, preparing a sample: obtaining a complete coal sample from a coal mine, polishing the sample to meet the size of the holder, sleeving a thermoplastic sleeve (2-5) on the coal sample (6), the length of the thermoplastic sleeve (2-5) being greater than the length of the coal sample (6), placing the coal sample (6) wrapped by the thermoplastic sleeve (2-5) into the clamping cylinder (2-1) and on the telescopic sample support (2-2), adjusting the height of the telescopic sample support (2-2) to make the two ends of the coal sample (6) coincide with the sample holder I (2-13) and the sample holder II (2-20) respectively, and adjusting the axial loading device to gradually clamp the coal sample (6); S2, forming an underground simulation field: according to the determined underground stress parameters, gas content and pressure parameters, temperature, the axial loading stress, the size of the confining pressure, the gas injection amount and the confining pressure fluid temperature, first start the axial loading device, adjust the loading speed to 0.1mm / min, slowly load to the pre-stress and stop loading, open the confining pressure fluid injection pump (5-2) to set the initial confining pressure and inject the confining pressure fluid, open the confining pressure fluid heating instrument (5-3) and record the initial temperature t1, set the initial pre-heating temperature t2, open the confining pressure fluid cooling instrument (5-7) and record the temperature curve of the outflowing confining pressure fluid with time, after the curve is stable, take the stable value t3, according to the temperature difference Δt=t3-t2, feedback to the computer and calculate the heat loss, adjust the heating temperature t4 of the confining pressure fluid heating instrument (5-3) again so that the internal temperature of the coal body reaches the preset temperature t0, increase the axial pressure and the confining pressure to gradually reach the actual pressure size in the mine, gradually inject gas into the coal body from the T-shaped three-way pipe, the gas flows out from the seepage hole (2-8) of the closed cover (2-7), after 48 hours, subsequent experiments are carried out; S3, real-time imaging of the evolution of the fissure around the borehole during drilling: remove the closure cap (2-7), start the NMR device, after the static magnetic field reaches the stable field strength and the magnetic field uniformity correction, determine the resonance frequency, spectral width, sampling point number, accumulation number, relaxation delay and pulse sequence, after the device is running normally for a period of time, start the drilling device to form a borehole at the axial center of the coal sample (6), with the drilling of the drill bit (1-2), the NMR system continuously and uninterruptedly collects the T2 transverse relaxation time weighted signal of the water in the fissure network around the borehole 1 H, and real-time imaging, so as to observe the dynamic evolution process of the fissure network around the borehole, after the drilling is completed, according to the NMR data collected and the data set Q1 recorded, through image processing and three-dimensional reconstruction, the fissure three-dimensional structure D1 is reconstructed, the maximum axial length L0 of the fissure network is determined, and the length L of the plugging section (4-8) is determined. S4, first plugging, dynamic imaging of hole plugging section hole fissure filling and plugging effect evaluation: after drilling, the drilling hole is closed with a closure cap (2-7), then the confining fluid heating instrument (5-3) is heated to heat the confining fluid for a period of time, the water in the coal body is dried by heat conduction of the confining fluid, until it cannot be imaged in the nuclear magnetic resonance equipment; according to the length L of the hole sealing section determined in S3, the plugging bag (4-5) and the feeding pipe (4-4) are connected according to the length, after the connection is completed, the closure cap (2-7) is opened, the plugging bag and the feeding pipe (4-4) are put into the drilling hole, the constant pressure intelligent grouting pump (4-2) is opened, the initial grouting pressure is set, the plugging material is injected into the plugging bag and the drilling hole, the nuclear magnetic imaging system is observed, after two bright color ellipsoids are formed, the grouting pressure is increased, the burst valve (4-7) is broken through, the plugging material flows into the plugging section (4-8), the grouting pressure is kept constant, the plugging material is continuously injected until the entire drilling hole is filled, the migration of the plugging material in the drilling hole is observed by real-time imaging of the nuclear magnetic resonance, and the T2 transverse relaxation time data of the plugging material in the water collected by the nuclear magnetic resonance are recorded as a data set Q2, the fissure visualization three-dimensional structure D2 is obtained by image processing and three-dimensional reconstruction, the coincidence degree of the data sets Q1 and Q2 is combined and compared, and whether D1 / D2 is in the fault tolerance interval is calculated. 1 H's T2 transverse relaxation time data and record data set Q2, by image processing and three-dimensional reconstruction, process to get fissure visualization three-dimensional structure D2, combined and compared with the coincidence degree of data set Q1 and Q2, calculate whether D1 / D2 is in the fault tolerance interval; S5, once plugging failure, change the simulation field parameters, new cracks or original cracks develop around the sealed borehole: open the ultrasonic tomography imaging equipment, connect the transducer array to the data acquisition module of the ultrasonic tomography system, set the transmission parameters including the center frequency of the transducer, the transmission voltage, the pulse bandwidth or the waveform and the imaging speed, set the receiving parameters including the sampling rate, the gain and the data saving format, set the channel to bidirectional transmission, change the confining pressure, the axial pressure and the gas pressure to make the new cracks or the original cracks around the borehole expand and develop, start the transmitter according to the set order to perform tomographic scanning and data acquisition, extract the propagation time and the amplitude, reconstruct the sound velocity distribution map, mark the sound velocity abnormal area, that is, when the sound velocity decreases ≥5% and 3 frames appear continuously, it is determined that new cracks are generated, stack all two-dimensional images of the layers into three-dimensional voxel images, then render and analyze the crack structure to obtain three-dimensional images and data set W1, and feed the data observed by the ultrasonic tomography to the computer; S6, secondary plugging: the computer compares the real-time nuclear magnetic resonance data with the ultrasonic tomography data of the new cracks transmitted in step S5, determines the number of new cracks and the open gap volume by comparing the data of Q2 and W1, so as to determine the amount of plugging material to be injected to avoid excessive grouting pressure and cause coal fracturing, further, the computer controls the plugging equipment to supplement the plugging material to the borehole, at this time, the real-time nuclear magnetic resonance imaging observes that the new cracks or crack networks are filled with the plugging material, the new imaging data are compared with the ultrasonic tomography data in S5, the plugging density is calculated to judge the plugging effect; S7, repeat steps S5 and S6, that is, the adaptive plugging process and effect evaluation of plugging-plugging failure-replugging of the borehole under different ground stress, ground thermal environment and gas pressure can be realized.

Images