CN116086974A - Simulation test method for punching fracturing multiple coal beds under true triaxial stress - Google Patents

Simulation test method for punching fracturing multiple coal beds under true triaxial stress Download PDF

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Publication number
CN116086974A
CN116086974A CN202211668264.5A CN202211668264A CN116086974A CN 116086974 A CN116086974 A CN 116086974A CN 202211668264 A CN202211668264 A CN 202211668264A CN 116086974 A CN116086974 A CN 116086974A
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punching
pressure
test piece
main body
loading
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CN202211668264.5A
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Inventor
张东明
余北辰
杜苇航
王重洋
陈宇
熊紫阳
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Chongqing University
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Chongqing University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
    • G01N3/12—Pressure testing
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/164—Injecting CO2 or carbonated water
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25—Methods for stimulating production
    • E21B43/26—Methods for stimulating production by forming crevices or fractures
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/06—Measuring temperature or pressure
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F7/00—Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/22—Fuels, explosives
    • G01N33/222—Solid fuels, e.g. coal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0019—Compressive
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/003—Generation of the force
    • G01N2203/0042—Pneumatic or hydraulic means
    • G01N2203/0048—Hydraulic means

Abstract

The invention discloses a simulation test method for punching and fracturing multiple coal beds under true triaxial stress, which comprises the following steps: step one, preparing a sample; step two, preparing a simulation system for the dynamic disaster prevention and control technology of the multi-field coupling coal rock mass; thirdly, applying true triaxial prestress; step four, punching and fracturing by liquid carbon dioxide; fifthly, recording data; the feeding displacement of the nozzle is measured by a displacement sensor, the pressure sensor displays the value of the real-time injected liquid carbon dioxide, and the electromagnetic flowmeter displays the real-time flow of the injected fluid; step six, replacing the molded coal sample; step seven, repeating the step four to the step five; step eight, other tests in the same group; and step nine, finishing test data. The multi-coal-seam punching fracturing multi-coal-seam simulation under the true triaxial stress of large size can be performed, the control precision is high, punching fracturing with different injection distances can be performed, and the simulation process is more real and reliable.

Description

Simulation test method for punching fracturing multiple coal beds under true triaxial stress
Technical Field
The invention belongs to the technical field of coal seam mining simulation tests, and particularly relates to a simulation test method for punching and fracturing multiple coal seams under true triaxial stress.
Background
The existing punching fracturing coal seam simulation test mainly has the following problems: (1) By adopting hydraulic punching and fracturing, the structure of the inlet and outlet channels of the punching liquid is complex, the control precision is not high, and punching with different injection distances can not be performed. (2) The adopted model has smaller size and certain space limitation, and can not accurately simulate the real scene of punching and fracturing multiple coal beds under the true triaxial stress.
Disclosure of Invention
The invention aims to provide the simulation test method for the punching fracturing multiple coal layers under the true triaxial stress, which can be used for carrying out the simulation of the punching fracturing multiple coal layers under the true triaxial stress with high control precision, and can be used for carrying out the punching fracturing at different injection distances, so that the simulation process is more real and reliable.
The technical scheme adopted by the invention is as follows: a simulation test method for punching and fracturing multiple coal beds under true triaxial stress comprises the following steps:
step one, preparing a sample;
crushing raw coal briquettes used in research by a jaw crusher, mixing gypsum, river sand and cement to prepare a similar material simulated rock stratum, taking crushed raw coal fines as coal beds, setting the number of the coal beds to be 3, separating the coal beds by the rock stratum, compacting each layer of coal and rock stratum one by one after pavement until the test sample is paved; placing a test piece box body on a compression molding machine, preventing lateral deformation of the test piece box body in the compression process by a box body lateral deformation limiting device, firstly placing similar materials simulating rock stratum into the bottom of the test piece box body, compressing the similar materials to a preset height by the compression molding machine, then adding prefabricated raw coal dust into the test piece box body, and carrying out layered compression, wherein the maximum compression pressure can reach 10MPa, so as to form a rectangular test sample with the length of 1000X, the width of 400X and the height of 400 mm; after the pressing is finished, the test piece box body is transferred to a transfer frame from the pressing forming machine by using a truss crane;
step two, preparing a simulation system for the dynamic disaster prevention and control technology of the multi-field coupling coal rock mass;
the multi-field coupling coal and rock mass dynamic disaster prevention and control technology simulation system comprises a main body model and a transport frame; the main body model has a true triaxial simulation experiment function and comprises a main body high-pressure cavity module and a test piece box module, wherein the test piece box module is positioned in the main body high-pressure cavity module, punching interfaces are arranged in the middle of the right sides of the test piece box module and the main body high-pressure cavity module in a penetrating manner, and a flange plate is arranged outside the punching interfaces; the X direction is provided with an independent hydraulic loading device for pressurization, and the maximum loading pressure is 5000kN; the Y, Z hydraulic loading devices are respectively provided with 4 groups of independent hydraulic loading devices for pressurization, the maximum loading pressure of a single group of hydraulic loading devices is 3000kN, each group of hydraulic loading devices can be independently controlled, loading of different acting forces in the length direction of 1000mm is realized, and the true triaxial stress state of the underground reservoir can be simulated more truly;
the test piece box is sent into a true triaxial loading system through a transfer frame, so that a stress loading cushion block of the test piece box body corresponds to a pressure head in the true triaxial loading system one by one, and a punching fracturing system is connected into a punching interface through a flange plate;
the punching fracturing system comprises a punching feeding system, a punching execution system and a punching liquid supply and discharge system; the punching feed system comprises a hydraulic servo control system and a hydraulic cylinder; the punching execution system comprises a central pipe column, an outer pipe column and a nozzle, wherein the central pipe column is fixedly arranged in the outer pipe column and is coaxially arranged, the left end of the central pipe column is positioned outside the outer pipe column and extends into a punching interface through a flange plate, the nozzle is fixedly arranged at the left end of the central pipe column, and a punching liquid receiving pipe is also arranged on the flange plate in a penetrating manner; the punching liquid supply and discharge system comprises a carbon dioxide gas source, a pressure reducing valve, a first pressure gauge, an electromagnetic flowmeter, a first stop valve, a one-way valve and a pressure sensor which are sequentially connected through pipelines, wherein a high-pressure pump, an energy accumulator, a second pressure gauge and a second stop valve are sequentially connected in series and then connected to the pipeline between the one-way valve and the pressure sensor, and the pipeline behind the pressure sensor is transversely connected into a central tubular column; the punching liquid is connected into an interlayer between the central pipe column and the outer pipe column, a pipeline which is connected out transversely is arranged on the outer pipe column, and a bag filter is arranged on the pipeline; the hydraulic servo control system controls the center pipe column, the outer pipe column and the nozzle to move left and right together through the hydraulic cylinder, so that the spraying distance of the nozzle is adjusted, and the feeding displacement of the nozzle is measured by the displacement sensor;
thirdly, applying true triaxial prestress;
according to the ground stress of the stratum, a true triaxial loading system is utilized to apply the ground stress to the simulated stratum, in the process of loading the stress, a pressure head is firstly moved to enable the pressure head to be in contact with a loading cushion block, and a certain prestress is applied to achieve sigma x ＝σ y ＝σ z Then loading Z, Y, X stress in three directions one by one in a step-type mode to reach a preset ground stress value;
step four, punching and fracturing by liquid carbon dioxide;
the liquid carbon dioxide can enter the hollow part of the central pipe column from the pipeline and flow towards the nozzle along the central channel, fluid forms jet flow through the nozzle and can rush out of the channel in the coal seam, the punching liquid carries scraps to be discharged through the channel between the central pipe column and the outer pipe column, and after the nozzle is fed to a given stroke, the displacement sensor automatically controls the hydraulic servo control system to stop pushing, so that the punching effect is achieved; the test selects the jet liquid carbon dioxide punching speed to be 50mm/min,75mm/min and 100mm/min;
fifthly, recording data;
the feeding displacement of the nozzle is measured by a displacement sensor, the pressure sensor displays the value of the real-time injected liquid carbon dioxide, and the electromagnetic flowmeter displays the real-time flow of the injected fluid;
step six, replacing the molded coal sample;
repeating the second step to the third step, and then independently increasing the force applied by the upper pressure head to a new preset value;
step seven, repeating the step four to the step five;
step eight, other tests in the same group; changing the molded coal sample, changing the caliber and the spraying distance of the nozzle, or changing the liquid CO injection 2 Repeating the first to seventh steps under the conditions of speed and true triaxial stress;
and step nine, finishing test data.
As the optimization of the scheme, the shell of the main body high-pressure cavity module adopts a high-pressure sealing pressure bin structure of an outer circle and an inner circle, wherein the outer circle is surrounded by a circular ring, a left circular end cover and a right circular end cover, the front cushion block, the rear cushion block, the upper cushion block and the lower cushion block are respectively arranged on the front, the rear and the upper and the lower of the inner wall of the circular ring, the front cushion block, the rear cushion block, the upper cushion block and the lower cushion block are surrounded into a rectangular cavity for a test piece box to be placed, an axial hydraulic cylinder is arranged on the left circular end cover in a penetrating way, a punching interface is arranged in the middle part of the right circular end cover in a penetrating way, wire harness pipeline leading-out holes are respectively arranged on the left circular end cover and the right circular end cover in a penetrating way, a row of lifters are arranged on the top of the lower cushion block at intervals left and right, and the lifters can protrude out of the lower cushion block and also sink into the lower cushion block;
the test piece box is a rectangular test piece accommodating cavity formed by encircling a left side plate, a bottom plate, a top plate, a right side plate, a front side plate and a rear side plate through combining bolts, the rectangular test piece accommodating cavity is collinear with the axial lead of a high-pressure sealing pressure bin, a left pressure plate is arranged on the left side of the rectangular test piece accommodating cavity, a plurality of upper pressure plates are sequentially arranged on the top left and right sides of the rectangular test piece accommodating cavity, a plurality of front pressure plates are sequentially arranged on the front left and right sides of the rectangular test piece accommodating cavity, the axial hydraulic cylinder can penetrate through the left side plate and is connected with the left pressure plate, each upper pressure plate is connected with the top hydraulic cylinder through an upper cushion block penetrating through the upper pressure plate arranged on the top plate, each front pressure plate is connected with the lateral hydraulic cylinder through a side cushion block penetrating through the front side plate, a plurality of heating pipes and temperature control probes are arranged on the upper pressure plate, the front pressure plate, the bottom plate and the rear side plate, a plurality of ultrasonic probes are arranged on the upper openings of the upper pressure plate, the front pressure plate, the left pressure plate, the bottom plate and the right side plate, a row of rollers are arranged at intervals on the bottom of the test piece box, and when the test piece box is pushed into a main high-pressure cavity module, and the lifter is supported below the rollers;
the anti-channeling board is arranged right above the bottom plate and corresponds to the upper pressing plate one by one, a central air inlet hole and a plurality of annular grooves surrounding the central air inlet hole are formed in the anti-channeling board, all the annular grooves are communicated with the central air inlet hole through connecting grooves which are distributed in a divergent mode, an air inlet pipe transversely penetrates through the side wall of the test piece box to be connected to the bottom of the central air inlet hole, a water permeable partition plate is arranged above the anti-channeling board, filter plates are arranged at the left end and the right end of the test piece, and sealing gaskets are arranged on the upper end, the lower end, the front end and the rear end of the test piece.
It is further preferred that only one of the axial hydraulic cylinders has a maximum loading pressure of 5000kN; four groups of top hydraulic cylinders and lateral hydraulic cylinders are respectively arranged, each group of hydraulic cylinders is provided with two parallel hydraulic loading systems for pressurizing, one of the hydraulic cylinders is a static load loading system, the other hydraulic cylinder is a dynamic load loading system, the maximum loading pressure of a single group of hydraulic loading devices is 3000kN, each group of hydraulic loading systems is used for independently controlling one pressing plate and is arranged on the corresponding pressing plate in a left-right centering mode, and the axial hydraulic cylinders, the top hydraulic cylinders and the lateral hydraulic cylinders can all carry out dynamic and static load loading.
It is further preferred that the annular grooves are rectangular or circular and are equally spaced apart.
Still preferably, the device further comprises a main body frame for supporting the main body model, the main body frame is of a rectangular frame structure, the left end and the right end of the main body model extend out of the main body frame, a transfer sliding rail is arranged on the right side of the main body frame, the transfer sliding rail extends to the position right below the main body high-pressure cavity module, and the width of the transfer sliding rail is smaller than the inner hollow width of the main body frame; a test piece box lifting and conveying frame and a right round end cover conveying frame are slidably mounted on the transfer slide rail, and the test piece box lifting and conveying frame can perform lifting movement and is used for supporting the test piece box; the right round end cover transfer frame top is the arc and is used for holding up right round end cover, and test piece case lift transfer frame just in time enables in the test piece case horizontal push body high pressure chamber module after rising, and the top is less than the bottom of body high pressure chamber module behind the test piece case lift transfer frame decline to the below of slide-in body high pressure chamber module for right round end cover transfer frame can slide left to the installation of settlement position right round end cover.
It is further preferred that each lifter adopts a double supporting structure which is arranged at intervals and symmetrically, each lifter adopts independent hydraulic drive, and all lifters synchronously lift.
The invention has the beneficial effects that: the multi-coal-seam punching fracturing multi-coal-seam simulation under the true triaxial stress with large size can be performed, the control precision is high, the punching fracturing with different injection distances can be performed, and the simulation process is more real and reliable; and the carbon dioxide gas source is combined to serve as punching liquid for supplying, and the punching liquid pipeline is simple in structure, safe and reliable.
Drawings
FIG. 1 is a schematic diagram of the steps of the present invention.
Fig. 2 is a system composition diagram of the present invention.
Fig. 3 is a schematic diagram of a main body model of a simulation system of a multi-field coupling coal-rock mass dynamic disaster prevention and control technology.
Fig. 4 is an interior left view of fig. 3.
Fig. 5 is a schematic structural view of the specimen box.
Fig. 6 is an interior left view of fig. 5.
Fig. 7 is a simplified view of the arrangement of a heating tube, a temperature control probe, and an ultrasonic probe.
FIG. 8 is a simplified illustration of an anti-channeling plate.
Fig. 9 is a state before the specimen box is loaded into the main body high-pressure chamber module.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
as shown in FIG. 1, a simulation test method for punching and fracturing multiple coal beds under true triaxial stress is needed by using a system diagram shown in FIG. 2, and comprises the following steps:
step one, preparing a sample.
Crushing raw coal briquettes used in research by a jaw crusher, and mixing gypsum, river sand and cement to prepare the simulated rock stratum of similar materials.
Setting the crushed raw coal fines as coal beds, setting the number of the coal beds to be 3, separating the coal beds by rock strata, compacting each coal bed one by one after the pavement of each coal bed is completed, and finishing the pavement of the sample.
The test piece box body is arranged on the compression molding machine, and lateral deformation of the test piece box body in the compression process is prevented by the box body lateral deformation limiting device.
Firstly, placing similar materials of a simulated rock stratum into the bottom of a test piece box body, pressing the similar materials to a preset height by using a press forming machine, then adding prefabricated raw coal powder into the test piece box body, and performing layered pressing, wherein the maximum pressing pressure can reach 10MPa, so as to form a rectangular test piece with the length of 1000X the width of 400X the height of 400 mm; and after the pressing is finished, transferring the test piece box body to a transfer frame from the pressing forming machine by using the truss crane.
Step two, preparing a simulation system for the dynamic disaster prevention and control technology of the multi-field coupling coal rock mass.
The multi-field coupling coal and rock mass dynamic disaster prevention and control technology simulation system is used for punching fracturing tests and comprises a main body model and a transport frame. The main body model has a true triaxial simulation experiment function and comprises a main body high-pressure cavity module and a test piece box module. The test piece box module is located in the main body high-pressure cavity module, a punching interface is arranged in the middle of the right sides of the test piece box module and the main body high-pressure cavity module in a penetrating mode, and a flange plate is arranged outside the punching interface.
The X direction of the main body model is provided with an independent hydraulic loading device for pressurization, and the maximum loading pressure is 5000kN; y, Z are provided with 4 groups of independent hydraulic loading devices for pressurization, the maximum loading pressure of a single group of hydraulic loading devices is 3000kN, each group of hydraulic loading devices can be controlled independently, loading of different acting forces in the length direction of 1000mm is realized, and the true triaxial stress state of the underground reservoir can be simulated more truly.
And (3) conveying the test piece box into a true triaxial loading system through a transfer frame, enabling a stress loading cushion block of the test piece box body to correspond to a pressure head in the true triaxial loading system one by one, and enabling the punching fracturing system to be connected into a punching interface through a flange plate.
As shown in FIG. 2, the main body model A comprises a main body high-pressure cavity module A-1 and a test piece box module A-2, wherein the test piece box module A-2 is positioned in the main body high-pressure cavity module A-1. And punching interfaces a are arranged in the middle of the right sides of the test piece box module A-2 and the main body high-pressure cavity module A-1 in a penetrating manner, and a flange plate b is arranged outside the punching interfaces.
In addition, the device also comprises four parts of a punching feeding system, a punching execution system and a punching liquid supply and discharge system.
The punching feed system mainly comprises a hydraulic servo control system and a hydraulic cylinder c, wherein the hydraulic servo control system is used for controlling the hydraulic cylinder c.
The punching execution system mainly comprises a central pipe column d, an outer pipe column e and a nozzle (not shown in the figure), wherein the central pipe column d is fixedly arranged in the outer pipe column e and coaxially arranged. The left end of the center pipe column d is positioned outside the outer pipe column e and extends into the punching interface a through the flange plate, the nozzle is fixedly arranged at the left end of the center pipe column d, and a punching liquid outlet pipe (not shown in the figure) is also arranged on the flange plate b in a penetrating manner.
The punching liquid supply and discharge system comprises a carbon dioxide gas source f, a pressure reducing valve g, a first pressure gauge h, an electromagnetic flowmeter i, a first stop valve j, a one-way valve k and a pressure sensor m which are sequentially connected through pipelines, wherein a high-pressure pump n, an energy accumulator p, a second pressure gauge q and a second stop valve r are sequentially connected in series and then connected to the pipeline between the one-way valve k and the pressure sensor m. The pipeline behind the pressure sensor m is transversely connected into the central pipe column d; in the interlayer between the punching liquid outlet pipe access center pipe column d and the outer pipe column e, a pipeline which is transversely connected out is arranged on the outer pipe column e, and a bag filter r is arranged on the pipeline. The punching liquid is sent to a nozzle through a central pipe column to punch holes; because the pressure is maintained in the nozzle, the punched liquid after punching is carried with scraps and flows out through the interlayer among the punching liquid connecting pipe, the central pipe column and the outer pipe column.
The hydraulic servo control system controls the center column d, the outer column e, and the nozzles to move left and right together through the hydraulic cylinder c, thereby adjusting the spray distance of the nozzles, and the nozzle feed displacement is measured by a displacement sensor (not shown).
And thirdly, applying true triaxial prestress.
According to the ground stress of the stratum, a true triaxial loading system is utilized to apply the ground stress to the simulated stratum, in the process of loading the stress, a pressure head is firstly moved to enable the pressure head to be in contact with a loading cushion block, and a certain prestress is applied to achieve sigma x ＝σ y ＝σ z And then loads Z, Y, X three-direction stresses one by one in a stepwise manner to reach a predetermined ground stress value.
And fourthly, punching and fracturing by liquid carbon dioxide.
The liquid carbon dioxide can enter the hollow part of the central pipe column from the pipeline and flow towards the nozzle along the central channel, fluid forms jet flow through the nozzle and can rush out of the channel in the coal seam, the punching liquid carries scraps to be discharged through the channel between the central pipe column and the outer pipe column, and after the nozzle is fed to a given stroke, the displacement sensor automatically controls the hydraulic servo control system to stop pushing, so that the punching effect is achieved; the test selects the jet liquid carbon dioxide punching speed to be 50mm/min,75mm/min and 100mm/min.
And fifthly, recording data.
The feeding displacement of the nozzle is measured by a displacement sensor, the pressure sensor displays the value of the real-time injected liquid carbon dioxide, and the electromagnetic flowmeter displays the real-time flow of the injected fluid.
And step six, replacing the molded coal sample.
Repeating the second step to the third step, and then independently increasing the force applied by the upper pressing head to a new preset value.
And step seven, repeating the step four to the step five.
Step eight, other tests in the same group; changing the molded coal sample, changing the caliber and the spraying distance of the nozzle, or changing the liquid CO injection 2 And (3) repeating the first step to the seventh step under the conditions of speed and true triaxial stress.
And step nine, finishing test data.
In order to meet different experimental requirements, 5 nozzles with different calibers are designed to be replaceable, and the calibers of the nozzles are respectively 2, 4, 6, 8 and 10 mm.
Specific test scheme:
Figure BDA0004015367770000101
as shown in fig. 3-4, the main body model of the simulation system for the dynamic disaster prevention and control technology of the multi-field coupling coal rock mass mainly comprises a main body high-pressure cavity module and a test piece box.
The shell 1 of the main body high-pressure cavity module is of a high-pressure closed pressure bin structure which is formed by combining an outer circle and an inner circle surrounded by bolts through a circular ring 3, a left circular end cover 4 and a right circular end cover 5. A front cushion block 2, a rear cushion block 9, an upper cushion block 10 and a lower cushion block 11 are respectively arranged on the front, the rear, the upper and the lower of the inner wall of the circular ring 3. The front cushion block 2, the rear cushion block 9, the upper cushion block 10 and the lower cushion block 11 enclose a rectangular cavity for the test piece box to be placed.
An axial hydraulic cylinder 6 is arranged on the left round end cover 4 in a penetrating manner, and a punching interface is arranged in the middle of the right round end cover 5 in a penetrating manner.
The left round end cover 4 and the right round end cover 5 are respectively penetrated with a wire harness pipeline leading-out hole 7, a row of lifters 8 are arranged at the top of the lower cushion block 11 at left and right intervals, and the lifters 8 can protrude out of the lower cushion block 11 and also can sink into the lower cushion block 11. Each lifter 8 adopts a double-wheel structure which is arranged at intervals front and back and symmetrically, realizes front and back double support, and has balanced and stable stress. Each lifter 8 is driven by a separate hydraulic pressure, and all lifters 8 are controlled to synchronously lift and lower through a control system.
Referring to fig. 3-6, the test piece box is a rectangular test piece accommodating cavity surrounded by the left side plate 12, the bottom plate 13, the top plate 14, the right side plate 15, the front side plate 23 and the rear side plate 24 and combined with bolts, and the rectangular test piece accommodating cavity is collinear with the axial lead of the high-pressure closed pressure bin, so that the rectangular test piece is centered in the main body model. A left pressing plate 16 is arranged on the left side in the rectangular test piece accommodating cavity, a plurality of upper pressing plates 17 are arranged on the top left and right in sequence, and a plurality of front pressing plates 18 are arranged on the front left and right in sequence. The axial hydraulic cylinders 6 can penetrate through the left side plate 12 and are connected with the left pressing plate 16, each upper pressing plate 17 is connected with a top hydraulic cylinder 20 through an upper cushion block 19 penetrating through the top plate 14, the top hydraulic cylinder 20 is provided with a hydraulic piston 20a, the upper cushion block 19 is acted on through the hydraulic piston 20a, and then the upper pressing plate 17 applies load to the rectangular test piece. Each front platen 18 is connected to a lateral hydraulic cylinder 22 by a side block 21 mounted through a front side plate 23, the lateral hydraulic cylinder 22 also having a hydraulic piston, through which the side block 21 is acted upon by the hydraulic piston, and the rectangular test piece is loaded by the front platen 18.
Referring to fig. 3 to 7, a plurality of heating pipes 27 and temperature control probes 28 are installed in the openings of the upper platen 17, the front platen 18, the bottom plate 13, and the rear plate 24, and a plurality of ultrasonic probes 29 are installed in the openings of the upper platen 17, the front platen 18, the left platen 16, the bottom plate 13, the rear plate 24, and the right plate 15. A row of rollers 26 are mounted at left and right intervals on the bottom of the test piece box through a lining plate 25, and when the test piece box is pushed into the main body high-pressure cavity module, the lifter 8 is supported below the rollers 26.
Preferably, a high-frequency vibrator is arranged on the cavity of the axial hydraulic cylinder 6, high-speed vibration is generated under the action of a high-pressure air source, and high-frequency vibration force can be transmitted to the test piece right through the corresponding hydraulic cavity, the hydraulic piston and the left pressing plate 16.
The anti-channeling plates 30 corresponding to the upper pressing plates 17 one by one are arranged right above the bottom plate 13, a central air inlet hole 30a and a plurality of annular grooves 30b surrounding the central air inlet hole 30a are formed in the anti-channeling plates 30, and all the annular grooves 30b are communicated with the central air inlet hole 30a through communication grooves 30c which are distributed in a divergent mode, and an air inlet pipe transversely penetrates through the rear side wall of the test piece box and is connected to the bottom of the central air inlet hole 30 a. The annular grooves 30b are rectangular or circular and are equally spaced apart.
The air inlet pipe transversely passes through the rear side wall of the test piece box and is connected to the bottom of the central air inlet hole 30a, and a water permeable partition plate 31 is arranged above the anti-channeling plate 30. The design of internal anti-channeling is combined with the water permeable partition plate for use, so that the punching experiment can be completed better due to the good sealing performance.
The filter plates 32 are installed at the left and right ends of the test piece, and the sealing gaskets 33 are installed at the front and rear sides of the test piece.
The inner cavity of the test piece box can be provided with a rectangular test piece with the length of 1000 times the width of 400 times the height of 400mm, and the internal pressure resistance of the main body high-pressure cavity module is 10MPa.
Only one axial hydraulic cylinder 6 has a maximum loading pressure of 5000kN; four groups of top hydraulic cylinders 20 and side hydraulic cylinders 22 are respectively arranged, each group of hydraulic cylinders is provided with two parallel hydraulic loading systems for pressurizing, one of the hydraulic cylinders is a static load loading system, the other hydraulic loading system is a dynamic load loading system, the maximum loading pressure of a single group of hydraulic loading devices is 3000kN, each group of hydraulic loading systems is used for independently controlling one pressing plate and is arranged on the corresponding pressing plate in a left-right centering mode, and the axial hydraulic cylinders 6, the top hydraulic cylinders 20 and the side hydraulic cylinders 22 can be used for loading dynamic and static loads.
As shown in fig. 9, the multi-field coupling coal-rock mass dynamic disaster prevention and control technology simulation system comprises a main body model, a main body frame 37 for supporting the main body model, a transfer sliding rail 36, a test piece box lifting and conveying frame 34 and a right round end cover conveying frame 35. The specimen box lifting and lowering transfer frame 34 and the right round end cap transfer frame 35 are collectively referred to as a transfer frame.
The main body frame 37 is used for supporting a main body model, the main body frame 37 is of a rectangular frame structure, and the left end and the right end of the main body model extend out of the main body frame 37. The right side of main part frame 37 is provided with and transports slide rail 36, and transport slide rail 36 extends to the main part high pressure chamber module under, and transport slide rail 36's width is less than the interior empty width of main part frame 37. The transfer slide rail 36 is slidably provided with a specimen box lifting and transferring frame 34 and a right round end cover transferring frame 35, and the specimen box lifting and transferring frame 34 can perform lifting and transferring movements and is used for supporting the specimen box. The top of the right round end cover transferring frame 35 is arc-shaped and is used for supporting the right round end cover 5, the test piece box lifting transferring frame 34 just enables the test piece box to be horizontally pushed into the main body high-pressure cavity module after being lifted, and the top of the test piece box lifting transferring frame 34 is lower than the bottom of the main body high-pressure cavity module after being lowered, so that the test piece box lifting transferring frame slides into the lower part of the main body high-pressure cavity module, and the right round end cover transferring frame 35 can slide leftwards to a set position to install the right round end cover 5.
The main characteristics of the main body model are as follows:
(1) The shell of the main body high-pressure cavity module adopts a high-pressure sealing pressure bin with an outer circle and an inner circle, wherein the outer circle and the inner circle are surrounded by a circular ring, a left circular end cover and a right circular end cover which are combined with bolts, and the structure of the high-pressure sealing pressure bin is quite different from that of the traditional pressure bin with an outer square and an inner square which are surrounded by six plates; meanwhile, the test piece box is rectangular, so that the mounting of the test piece box is met, the front, rear, upper and lower cushion blocks with special shapes are creatively arranged on the front, rear, upper and lower sides of the inner wall of the high-pressure sealing pressure bin respectively, and a rectangular cavity for the test piece box to be placed is formed by the front, rear, upper and lower cushion blocks, so that an outer round and inner square test piece box mounting environment is formed, the internal pressure resistance is stronger, the sealing capability is better, the internal pressure resistance can be up to 10MPa, and a better test environment is provided for a punching fracturing multi-coal-bed simulation test under true triaxial stress;
(2) The lifter is supported below the rollers, so that the test piece box can be pushed in and pulled out more easily and laborsaving, the automation degree of installation is improved, and the large-scale simulation test operation is easier and laborsaving;
(3) The upper pressing plate, the front pressing plate, the bottom plate and the rear side plate are provided with a plurality of heating pipes and temperature control probes, and the upper pressing plate, the front pressing plate, the left pressing plate, the bottom plate, the rear side plate and the right side plate are provided with a plurality of ultrasonic probes, so that a fractured rock mass seepage test under the three-dimensional stress-seepage-temperature multi-field coupling condition can be developed; and combine the anti-channeling board that sets up directly over the bottom plate, the baffle that permeates water is installed to the top of anti-channeling board, installs the filter in the left and right sides both ends of test piece, installs sealed pad around about the test piece, can prevent the channeling, can guarantee again that the gas permeability is good to possess and filter and seal multiple effect.

Claims (6)

1. A simulation test method for punching and fracturing multiple coal beds under true triaxial stress is characterized by comprising the following steps of: the method comprises the following steps:
step one, preparing a sample;
crushing raw coal briquettes used in research by a jaw crusher, mixing gypsum, river sand and cement to prepare a similar material simulated rock stratum, taking crushed raw coal fines as coal beds, setting the number of the coal beds to be 3, separating the coal beds by the rock stratum, compacting each layer of coal and rock stratum one by one after pavement until the test sample is paved; placing a test piece box body on a compression molding machine, preventing lateral deformation of the test piece box body in the compression process by a box body lateral deformation limiting device, firstly placing similar materials simulating rock stratum into the bottom of the test piece box body, compressing the similar materials to a preset height by the compression molding machine, then adding prefabricated raw coal dust into the test piece box body, and carrying out layered compression, wherein the maximum compression pressure can reach 10MPa, so as to form a rectangular test sample with the length of 1000X, the width of 400X and the height of 400 mm; after the pressing is finished, the test piece box body is transferred to a transfer frame from the pressing forming machine by using a truss crane;
step two, preparing a simulation system for the dynamic disaster prevention and control technology of the multi-field coupling coal rock mass;
the multi-field coupling coal and rock mass dynamic disaster prevention and control technology simulation system comprises a main body model and a transport frame; the main body model has a true triaxial simulation experiment function and comprises a main body high-pressure cavity module and a test piece box module, wherein the test piece box module is positioned in the main body high-pressure cavity module, punching interfaces are arranged in the middle of the right sides of the test piece box module and the main body high-pressure cavity module in a penetrating manner, and a flange plate is arranged outside the punching interfaces; the X direction is provided with an independent hydraulic loading device for pressurization, and the maximum loading pressure is 5000kN; the Y, Z hydraulic loading devices are respectively provided with 4 groups of independent hydraulic loading devices for pressurization, the maximum loading pressure of a single group of hydraulic loading devices is 3000kN, each group of hydraulic loading devices can be independently controlled, loading of different acting forces in the length direction of 1000mm is realized, and the true triaxial stress state of the underground reservoir can be simulated more truly;
the test piece box is sent into a true triaxial loading system through a transfer frame, so that a stress loading cushion block of the test piece box body corresponds to a pressure head in the true triaxial loading system one by one, and a punching fracturing system is connected into a punching interface through a flange plate;
the punching fracturing system comprises a punching feeding system, a punching execution system and a punching liquid supply and discharge system; the punching feed system comprises a hydraulic servo control system and a hydraulic cylinder; the punching execution system comprises a central pipe column, an outer pipe column and a nozzle, wherein the central pipe column is fixedly arranged in the outer pipe column and is coaxially arranged, the left end of the central pipe column is positioned outside the outer pipe column and extends into a punching interface through a flange plate, the nozzle is fixedly arranged at the left end of the central pipe column, and a punching liquid receiving pipe is also arranged on the flange plate in a penetrating manner; the punching liquid supply and discharge system comprises a carbon dioxide gas source, a pressure reducing valve, a first pressure gauge, an electromagnetic flowmeter, a first stop valve, a one-way valve and a pressure sensor which are sequentially connected through pipelines, wherein a high-pressure pump, an energy accumulator, a second pressure gauge and a second stop valve are sequentially connected in series and then connected to the pipeline between the one-way valve and the pressure sensor, and the pipeline behind the pressure sensor is transversely connected into a central tubular column; the punching liquid is connected into an interlayer between the central pipe column and the outer pipe column, a pipeline which is connected out transversely is arranged on the outer pipe column, and a bag filter is arranged on the pipeline; the hydraulic servo control system controls the center pipe column, the outer pipe column and the nozzle to move left and right together through the hydraulic cylinder, so that the spraying distance of the nozzle is adjusted, and the feeding displacement of the nozzle is measured by the displacement sensor;
thirdly, applying true triaxial prestress;
according to the ground stress of the stratum, a true triaxial loading system is utilized to apply the ground stress to the simulated stratum, in the process of loading the stress, a pressure head is firstly moved to enable the pressure head to be in contact with a loading cushion block, and a certain prestress is applied to achieve sigma x ＝σ y ＝σ z Then loading Z, Y, X stress in three directions one by one in a step-type mode to reach a preset ground stress value;
step four, punching and fracturing by liquid carbon dioxide;
the liquid carbon dioxide can enter the hollow part of the central pipe column from the pipeline and flow towards the nozzle along the central channel, fluid forms jet flow through the nozzle and can rush out of the channel in the coal seam, the punching liquid carries scraps to be discharged through the channel between the central pipe column and the outer pipe column, and after the nozzle is fed to a given stroke, the displacement sensor automatically controls the hydraulic servo control system to stop pushing, so that the punching effect is achieved; the test selects the jet liquid carbon dioxide punching speed to be 50mm/min,75mm/min and 100mm/min;
fifthly, recording data;
the feeding displacement of the nozzle is measured by a displacement sensor, the pressure sensor displays the value of the real-time injected liquid carbon dioxide, and the electromagnetic flowmeter displays the real-time flow of the injected fluid;
step six, replacing the molded coal sample;
repeating the second step to the third step, and then independently increasing the force applied by the upper pressure head to a new preset value;
step seven, repeating the step four to the step five;
step eight, other tests in the same group; changing the molded coal sample, changing the caliber and the spraying distance of the nozzle, or changing the liquid CO injection 2 Repeating the first to seventh steps under the conditions of speed and true triaxial stress;
and step nine, finishing test data.
2. The simulation test method for punching fracturing multiple coal beds under true triaxial stress according to claim 1, wherein: the shell (1) of the main body high-pressure cavity module adopts a high-pressure sealing pressure bin structure of an outer circle and an inner circle, wherein the outer circle is surrounded by a circular ring (3), a left circular end cover (4) and a right circular end cover (5) through bolts, a front cushion block (2), a rear cushion block (9), an upper cushion block (10) and a lower cushion block (11) are respectively arranged on the front, the rear, the upper cushion block (9), the upper cushion block (10) and the lower cushion block (11) on the inner wall of the circular ring (3), a rectangular cavity is surrounded by the front cushion block (2), the rear cushion block (9), the upper cushion block (10) and the lower cushion block (11) and is just used for placing a test piece box, an axial hydraulic cylinder (6) is arranged on the left circular end cover (4) in a penetrating way, a punching interface is arranged on the middle part of the right circular end cover (5), wire harness pipeline leading-out holes (7) are respectively arranged on the left circular end cover (4) and the right circular end cover (5) in a penetrating way, a row of lifters (8) are arranged on the top left and right at intervals, and a row of lifters (8) can protrude out from the lower cushion block (11) and also sink into the lower cushion block (11);
the test piece box is a rectangular test piece accommodating cavity which is surrounded by a left side plate (12), a bottom plate (13), a top plate (14), a right side plate (15), a front side plate (23) and a rear side plate (24) through combining bolts, the axis of the rectangular test piece accommodating cavity and a high-pressure sealing pressure bin are collinear, a left pressure plate (16) is arranged on the left side in the rectangular test piece accommodating cavity, a plurality of upper pressure plates (17) and a plurality of front pressure plates (28) are arranged on the left side, the top of the rectangular test piece accommodating cavity in turn, a plurality of front pressure plates (6) are arranged on the left side and the right side, the axial hydraulic cylinders (6) can penetrate through the left side plate (12) and the left pressure plate (16), each upper pressure plate (17) is connected with the top hydraulic cylinder (20) through an upper cushion block (19) penetrating through the top plate (14), each front pressure plate (18) is connected with a lateral hydraulic cylinder (22) through a side cushion block (21) penetrating the front side plate (23), a plurality of heating pipes (27) and temperature control probes (28) are arranged on the left side and right side of the top pressure plate (18), the front pressure plate (13), the rear side plate (24) and the left side plate (16) are provided with a plurality of ultrasonic probes (29), a row of rollers (26) are arranged at left and right intervals at the bottom of the test piece box through a lining plate (25), and when the test piece box is pushed into the main body high-pressure cavity module, the lifter (8) is supported below the rollers (26);
just above bottom plate (13) be provided with upper pressure plate (17) one-to-one prevent channeling board (30), central inlet port (30 a) and a plurality of ring channel (30 b) around central inlet port (30 a) have been seted up on prevent channeling board (30), and all ring channel (30 b) and central inlet port (30 a) are through being the tie groove (30 c) intercommunication that divergently distributes, intake pipe lateral wall access of passing test piece case the bottom of central inlet port (30 a), water permeable baffle (31) are installed to the top of prevent channeling board (30), filter (32) are installed at the left and right sides of test piece, install sealing pad (33) around about the test piece.
3. The simulation test method for punching fracturing multiple coal beds under true triaxial stress according to claim 2, wherein: only one axial hydraulic cylinder (6) has a maximum loading pressure of 5000kN; four groups of top hydraulic cylinders (20) and lateral hydraulic cylinders (22) are respectively arranged, each group of hydraulic cylinders is provided with two parallel hydraulic loading systems for pressurizing, one hydraulic loading system is a static load loading system, the other hydraulic loading system is a dynamic load loading system, the maximum loading pressure of a single group of hydraulic loading devices is 3000kN, each group of hydraulic loading systems is used for independently controlling one pressing plate and is arranged on the corresponding pressing plate in a left-right centering mode, and the axial hydraulic cylinders (6), the top hydraulic cylinders (20) and the lateral hydraulic cylinders (22) can all carry out dynamic and static load loading.
4. The simulation test method for punching fracturing multiple coal beds under true triaxial stress according to claim 2, wherein: the annular grooves (30 b) are rectangular or circular and are distributed at equal intervals.
5. The simulation test method for punching fracturing multiple coal beds under true triaxial stress according to claim 2, wherein: the main body frame (37) is used for supporting the main body model, the main body frame (37) is of a rectangular frame structure, the left end and the right end of the main body model extend out of the main body frame (37), a transfer sliding rail (36) is arranged on the right side of the main body frame (37), the transfer sliding rail (36) extends to the position right below the main body high-pressure cavity module, and the width of the transfer sliding rail (36) is smaller than the inner space width of the main body frame (37); a test piece box lifting and transporting frame (34) and a right round end cover transporting frame (35) are slidably arranged on the transporting slide rail (36), and the test piece box lifting and transporting frame (34) can perform lifting movement and is used for supporting the test piece box; the top of the right round end cover transferring frame (35) is arc-shaped and is used for supporting the right round end cover (5), the test piece box lifting transferring frame (34) can be just in time pushed into the main body high-pressure cavity module after being lifted, the top of the test piece box lifting transferring frame (34) is lower than the bottom of the main body high-pressure cavity module after being lowered, so that the test piece box lifting transferring frame can slide into the lower side of the main body high-pressure cavity module, and the right round end cover transferring frame (35) can slide leftwards to a set position to install the right round end cover (5).
6. The method for simulating the multi-coal seam by punching and fracturing under the true triaxial stress according to claim 2,
the method is characterized in that: each lifter (8) adopts a double supporting structure which is arranged at intervals and symmetrically,
each lifter (8) is driven by independent hydraulic pressure, and all lifters (8) synchronously lift.
CN202211668264.5A 2022-12-23 2022-12-23 Simulation test method for punching fracturing multiple coal beds under true triaxial stress Pending CN116086974A (en)

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