CN103940962B - Underground coal mine waterfrac treatment experiments experiment room simulation system and method - Google Patents

Abstract

The invention discloses a kind of underground coal mine waterfrac treatment experiments experiment room simulation system and method, its system comprises electronic universal tester, waterfrac treatment condition simulation device, gas pressure systems, confined pressure hydraulic system, waterfrac treatment system and computing machine, waterfrac treatment condition simulation device helps simulation mechanism and lane to help surrounding environment simulation mechanism to form by lane, side simulation mechanism in lane comprises baffle plate, air permeable plate, coal petrography sample and top cutting ferrule pipe, side surrounding environment simulation mechanism in lane comprises base, cylinder barrel, cover, push-down head, first concave surface pressure head, first convex surface pressure head and piston, its method comprises step: one, assembling coal mine downhole hydraulic fracturing experiments laboratory analog system, two, coal supply rock sample loads axial compression, three, coal supply rock sample loads confined pressure, and four, coal supply rock sample loads gaseous tension, five, the coal petrography sample place of exposing in the cutting ferrule pipe of top carries out hydraulic fracturing experiments.The present invention can according to different mine shaft geology situation, and real simulation downhole hydraulic pressure break condition is stable and reliable for performance.

Description

Simulation system and method for hydraulic fracturing experiment laboratory in coal mine

technical field

The invention belongs to the technical field of underground hydraulic fracturing in coal mines, and in particular relates to a simulation system and method for an experimental laboratory of hydraulic fracturing in underground coal mines.

Background technique

In order to study the changes in the pressure and content of gas extraction after hydraulic fracturing of underground coal and rock mass, scholars at home and abroad have done a lot of on-site research. Uphole hydraulic fracturing increases permeability; the other is downhole hydraulic fracturing to increase gas recovery rate. Due to the limitations of the site, existing machinery, downhole gas environment and many experimental instruments entering the well, the on-site research has not been able to fully study the various factors that affect the hydraulic fracturing effect, so the laboratory simulates the hydraulic fracturing experiment. got developed. However, at present, most of the hydraulic fracturing experiments in the laboratory are simulated studies on the hydraulic fracturing enhancement of drilling along the axial pressure direction, and many valuable conclusions and laws have been obtained. , the research on the simulation system and method of the downhole hydraulic fracturing experiment laboratory drilling along the side of the road is relatively simple and less. Nowadays, downhole hydraulic fracturing has become an important means to improve the gas recovery rate. Research on axial pressure, confining pressure, gas pressure, drilling azimuth, drilling inclination, drill bit diameter, drilling length, whether to clean the drilling, hydraulic pressure, etc. Downhole hydraulic fracturing factors such as fracturing pressure and hydraulic fracturing time play an important role in improving the gas recovery rate.

Contents of the invention

The technical problem to be solved by the present invention is to provide a coal mine underground hydraulic fracturing experimental laboratory simulation system with simple structure, convenient implementation, simple operation, stable and reliable performance, and strong practicability in view of the above-mentioned deficiencies in the prior art.

In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a simulation system for a coal mine hydraulic fracturing experiment laboratory, which is characterized in that it includes an electronic universal testing machine, a hydraulic fracturing condition simulation device, a gas pressure system, a confining pressure A hydraulic system, a hydraulic fracturing system and a computer, the hydraulic fracturing condition simulation device is centrally placed on the base of the electronic universal testing machine, and the electronic universal testing machine is connected to the computer;

The hydraulic fracturing condition simulation device is composed of a roadside simulation mechanism and a roadside surrounding environment simulation mechanism. The outer wall of the tube is provided with a scale, and the baffle, the air-permeable plate, the coal rock sample and the top tube are wound and fixed as a whole by electrical tape, and the middle part of the baffle is provided with a first air inlet channel, The middle part of the air-permeable plate is provided with a second air-intake channel connected with the first air-intake channel, and the air-permeable plate is located around the second air-intake channel to be provided with radial ventilation holes; the surrounding environment simulation mechanism of the sidewalk includes The base, the cylinder fixedly connected to the top of the base, and the cylinder cover fixedly connected to the top of the cylinder, the side wall of the middle part of the cylinder is provided with an insertion hole for the side wall of the side wall for the side wall of the side wall to be inserted into, and the middle part of the top of the base A groove is arranged at the position, and a lower indenter is placed in the groove, and an upper semi-concave indenter, an upper semi-convex indenter and a piston are sequentially arranged directly above the lower indenter from bottom to top, and the piston Go out upwards to the outside of the cylinder cover, and the middle position of the cylinder cover is provided with a through hole for the piston to pass through. The upper end surface of the piston is located directly below the indenter of the electronic universal testing machine. The insertion hole of the roadside simulation mechanism is inserted into the cylinder, and the coal rock sample is aligned between the upper end surface of the lower indenter and the lower end surface of the upper semi-concave indenter, and the top ferrule is snapped and connected to the roadside The simulation mechanism is inserted into the hole; the base is provided with a third air inlet passage and a gas inlet connected with the third air inlet passage, and the lower pressure head is provided with a fourth air inlet passage connected with the third air inlet passage. The fourth air intake channel communicates with the first air intake channel through the first gas transmission pipeline; the base is provided with a confining pressure liquid inflow channel that communicates with the inner space of the cylinder, and the side of the base A confining pressure fluid inlet connected to the inflow channel of the confining pressure fluid is provided on the upper part, and an exhaust port is provided on the side of the cylinder, and an exhaust port plug is connected to the exhaust port;

The gas pressure system includes a compressed gas tank, the gas outlet of the compressed gas tank is connected to the gas inlet through a second gas transmission pipeline, and a pressure relief valve and a pressure gauge are arranged on the second gas transmission pipeline;

The confining pressure hydraulic system includes a confining pressure fluid tank and a confining pressure fluid inflow pipe connected to the confining pressure fluid tank at one end, the other end of the confining pressure fluid inflow pipe is connected to the confining pressure fluid inlet, and the confining pressure fluid inflow pipe A hydraulic pump and a one-way valve are connected to it, and a section of the confining pressure fluid inflow pipe between the hydraulic pump and the one-way valve is connected to a confining pressure fluid overflow pipe, and the confining pressure fluid overflow pipe is connected to a confining pressure hydraulic pressure Force gauge and confining pressure fluid overflow valve, a section of confining pressure fluid inflow pipe between the one-way valve and confining pressure fluid inlet is connected with confining pressure fluid return pipe, and confining pressure fluid return pipe is connected with confining pressure fluid return valve;

The hydraulic fracturing system includes a water tank, and the water tank is connected with a steel pipe inserted into a drill hole on the coal rock sample through a water delivery pipeline when the hydraulic fracturing experiment is performed on the coal rock sample, and a water pump is arranged on the water delivery pipeline , water valve and water pressure gauge.

The above-mentioned underground hydraulic fracturing experimental laboratory simulation system in coal mine is characterized in that: between the base and the lower pressure head, between the base and the cylinder, between the cylinder and the cylinder cover, between the upper half concave pressure head and the upper half Sealing rings are arranged between the convex pressure heads, between the top tube and the cylinder, and between the cylinder cover and the piston.

The above-mentioned underground hydraulic fracturing experimental laboratory simulation system for coal mines is characterized in that: the cylinder is fixedly connected to the top of the base by first bolts, and the cylinder cover is fixedly connected to the top of the cylinder by second bolts.

The above-mentioned underground hydraulic fracturing experimental laboratory simulation system for coal mines is characterized in that: the shape of the outer contour of the cylinder, the shape of the outer contour of the lower pressure head, the shape of the outer contour of the coal rock sample, and the shape of the outer contour of the top tube and the shape of the outer contour of the lower part of the upper half concave indenter are cuboid, the length of the coal rock sample is equal to the length of the lower indenter and the length of the lower part of the upper half concave indenter, and the width of the coal rock sample is the same as that of the lower indenter. The width of the head, the width of the outer contour of the top tube and the width of the lower part of the upper semi-concave indenter are equal, and the height of the coal rock sample is equal to the height of the outer profile of the top tube.

The above-mentioned underground hydraulic fracturing experimental laboratory simulation system in coal mine is characterized in that: one end of the first gas transmission pipeline is connected to the first air intake channel through a first quick joint, and the first gas transmission pipeline The other end is connected to the fourth air intake passage through the second quick connector.

The present invention also provides a simulation method for underground coal mine hydraulic fracturing experiment laboratory with simple method steps and convenient implementation, which can truly simulate the stress of the underground coal rock mass in the coal mine and the gas content and pressure in the coal mine underground coal rock body. , characterized in that the method comprises the following steps:

Step 1. Assemble the simulation system of the underground hydraulic fracturing experiment laboratory of the coal mine. The specific process is as follows:

Step 101: Winding and fixing the butted baffle plate, ventilation plate, coal rock sample and jacking tube into a whole by electrical tape, and combining them into a roadside simulation mechanism;

Step 102, place the lower pressure head in the groove, connect the fourth air intake channel with the third air intake channel, and connect one end of the first gas transmission pipeline to the fourth air intake channel;

Step 103, fixing the cylinder to the top of the base;

Step 104. Insert the end of the roadside simulation mechanism with the baffle plate into the insertion hole of the roadside simulation mechanism, and observe the scale set on the outer wall of the top tube so that the coal sample is aligned on the lower pressure head on the upper end face;

Step 105, connecting the other end of the first gas delivery pipeline to the first air intake channel;

Step 106, aligning and placing the upper semi-concave indenter on the upper end surface of the coal rock sample, and placing the upper semi-convex indenter on top of the upper semi-concave indenter;

Step 107, passing the piston through the through hole provided in the middle of the cylinder cover, and fixing the cylinder cover on the top of the cylinder, while ensuring that the center of the piston is aligned with the center of the upper semi-convex indenter;

Step 108, connecting the second gas delivery pipeline to the gas inlet;

Step 109, connecting the confining pressure fluid inflow pipe to the confining pressure fluid inlet;

Step 1010, connect the electronic universal testing machine to the computer, place the hydraulic fracturing condition simulation device assembled in steps 101 to 107 on the base of the electronic universal testing machine, and make the upper end of the piston be located on the electronic universal testing machine. Just below the indenter of the universal testing machine;

Step 2. Load axial pressure on the coal rock sample: On the computer, open the pre-installed electronic universal testing machine software, operate the electronic universal testing machine software to start the electronic universal testing machine, and set the pressure head of the electronic universal testing machine to press down The speed parameter and pressure parameter of the piston, the indenter of the electronic universal testing machine presses down the piston according to the set speed parameter until the pressure parameter displayed in the electronic universal testing machine software reaches the set pressure parameter;

Step 3, load the confining pressure on the coal rock sample: remove the vent plug connected to the vent, open the vent, open the liquid inlet switch of the confining pressure fluid overflow valve, open the confining pressure hydraulic system, and The confining pressure fluid in the pressure fluid tank is pressurized by the second hydraulic pump and flows into the cylinder through the confining pressure fluid inflow pipe and the confining pressure fluid inlet. When the confining pressure fluid flows out of the exhaust port, connect the exhaust port plug to the On the exhaust port, close the exhaust port;

Step 4. Load gas pressure on the coal rock sample: open the switch of the pressure reducing valve, open the gas pressure system, the gas in the compressed gas tank is decompressed by the pressure reducing valve and then enters the first gas through the second gas transmission pipeline and the gas inlet. into the first air intake channel and the second air intake channel, and into the ventilation hole;

Step 5. Carry out a hydraulic fracturing experiment at the coal rock sample exposed in the top tube. The specific process is as follows:

Step 501, use an electric drill with a drill bit diameter of d to drill a drill hole with an azimuth angle of α, an inclination angle of β, and a length of L on the coal rock sample exposed in the top tube;

Step 502, inserting a steel pipe into the borehole;

Step 503, seal the drilled hole with a sealing material, the length of the sealed hole is n; wherein, n<L;

Step 504, connecting the water pipeline to the steel pipe;

Step 505, open the water valve, start the hydraulic fracturing system, the water in the water tank is pressurized by the water pump, enters the steel pipe through the water delivery pipeline, and hits the coal rock sample, and performs hydraulic fracturing on the coal rock sample. Cracks filled with water formed in the rock sample;

Step 506, after the fracturing time period t, close the water valve, close the hydraulic fracturing system, disconnect the water delivery pipeline connected to the steel pipe, and gradually flow out the water in the crack;

Step 507, after the water in the crack is exhausted, measure the gas pressure P at the exposed port of the steel pipe with a gas pressure measuring instrument, and measure the gas concentration φ at the exposed port of the steel pipe with a gas concentration measuring instrument;

Step 508, record the pressure parameters of the pressure head of the electronic universal testing machine set in the step 2, record the confining pressure in the step 3 displayed on the confining pressure hydraulic pressure gauge, and record the step 4 displayed on the air pressure gauge In the gas pressure, record the diameter d of the drill bit in the step 501 and the azimuth angle of the borehole as α, the inclination angle as β and the length L, record the hydraulic fracturing pressure in the step 505 displayed on the water pressure gauge, record the described The fracturing time period t in step 506, and record the gas pressure P and gas concentration φ measured in step 507.

The above-mentioned method is characterized in that before the step 502, the borehole is cleaned with a borehole cleaning solution.

The above-mentioned method is characterized in that: in the step 102, before placing the lower pressure head in the groove, first put a sealing ring in the groove; in the step 103, the cylinder barrel is fixedly connected to the base Before the top, put the sealing ring on the top of the base; in the step 104, before inserting the end of the gangway simulation mechanism with the baffle plate into the insertion hole of the gangway simulation mechanism, the Insert the sealing ring into the hole; before placing the upper semi-convex pressure head on the top of the upper semi-concave pressure head in the step 106, put the sealing ring in the upper semi-concave pressure head; in the step 107 Before the piston is passed through the through hole arranged at the middle position of the cylinder cover, a sealing ring is first placed in the through hole arranged at the middle position of the cylinder cover; in the step 107, the cylinder cover is fixedly connected to the cylinder top Before, put the seal on the top of the cylinder.

The above-mentioned method is characterized in that: in the step 103, the cylinder is fixedly connected to the top of the base using the second bolt; in the step 107, the cylinder cover is fixedly connected to the top of the cylinder by using the third bolt.

The above-mentioned method is characterized in that: the speed parameter of the pressure head of the electronic universal testing machine set in the step 2 is 0.4mm/min～0.6mm/min, and the electronic universal testing machine set in the step 2 The pressure parameter of the pressure head of the testing machine to press down the piston is 3MPa～5MPa.

Compared with the prior art, the present invention has the following advantages:

1. The simulation system of the underground hydraulic fracturing experiment laboratory of the coal mine of the present invention has a simple structure, is convenient to realize, and is easy to use and operate.

2. The simulation method of the underground hydraulic fracturing experiment laboratory of the coal mine has simple steps and is convenient to implement.

3. The present invention can realize the adjustment of the axial pressure and the confining pressure, and can truly simulate the in-situ stress of the coal and rock mass in the coal mine according to the in-situ stress of the coal and rock mass in different mines.

4. The present invention can realize the adjustment of the gas pressure, and can truly simulate the gas content and pressure in the underground coal rock body of the coal mine according to the gas reserves and pressures of different mines.

5. The present invention can measure the gas permeability enhancement of raw coal (that is, the rock sample directly taken from the mine) after underground hydraulic fracturing.

6. The present invention can provide engineering technicians with research data for engineering technicians to study axial pressure (that is, the pressure parameter of the pressing head of the electronic universal testing machine to press down the piston), confining pressure, gas pressure, diameter d of the drill bit, borehole The azimuth angle α of the borehole, the inclination angle β of the borehole, the length L of the borehole, the hydraulic fracturing pressure and the fracturing time period t affect the gas pressure P and gas concentration φ flowing out of the coal rock sample after hydraulic fracturing, and then get A method to increase the outflow gas concentration φ, and ultimately increase the gas recovery rate.

7. The present invention has low implementation cost, stable and reliable performance, strong practicability, and is convenient for popularization and use.

In summary, the present invention is easy to implement, can truly simulate the conditions of underground hydraulic fracturing according to different mine geological conditions, and can measure the influence and law of parameters such as axial pressure, confining pressure, and gas pressure on the anti-permeability effect of underground hydraulic fracturing , stable and reliable performance, helpful to improve the gas extraction rate, easy to popularize and use.

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Fig. 2 is a schematic structural diagram of a hydraulic fracturing condition simulating device of the present invention.

Explanation of reference signs:

1—baffle plate; 2—permeable plate; 3—coal rock sample;

4—top tube; 5—first air intake channel; 6—second air intake channel;

7—air vent; 8—base; 9—cylinder;

10—canister cover; 11—lower pressure head; 12—upper semi-convex pressure head;

13—piston; 14—the third intake channel; 15—gas inlet;

16—the fourth air intake channel; 17—the first gas transmission pipeline;

18—confining pressure fluid inflow channel; 19—confining pressure fluid inlet; 20—exhaust port;

21—exhaust port plug; 22—compressed gas tank; 23—second gas transmission pipeline;

24—pressure reducing valve; 25—barometer; 26—confining pressure liquid tank;

27—confining pressure fluid inflow pipe; 28—hydraulic pump; 29—confining pressure fluid overflow pipe;

30—confining pressure fluid pressure gauge; 31—confining pressure fluid overflow valve; 32—confining pressure fluid return pipe;

33—confining pressure fluid return valve; 34—water tank; 35—water pipeline;

36—water pump; 37—water valve; 38—water pressure gauge;

39—upper half concave indenter; 40—electronic universal testing machine;

41—hydraulic fracturing condition simulation device; 42—computer;

43—one-way valve; 44—sealing ring; 45—the first bolt;

46—the second bolt; 47—the steel pipe.

detailed description

As shown in Fig. 1 and Fig. 2, the underground hydraulic fracturing experimental laboratory simulation system of coal mine of the present invention comprises electronic universal testing machine 40, hydraulic fracturing condition simulation device 41, gas pressure system, confining pressure hydraulic system, hydraulic fracturing System and computer 42, the hydraulic fracturing condition simulation device 41 is centrally placed on the base of the electronic universal testing machine 40, and the electronic universal testing machine 40 is connected with the computer 42;

The hydraulic fracturing condition simulation device 41 is composed of a roadside simulation mechanism and a roadside surrounding environment simulation mechanism, and the roadside simulation mechanism includes a baffle plate 1, a gas permeable plate 2, a coal rock sample 3 and a jacking sleeve that are connected in sequence 4. The outer wall of the top ferrule 4 is provided with a scale, the baffle plate 1, the air-permeable plate 2, the coal rock sample 3 and the top ferrule 4 are wound and fixed as a whole by electrical tape, and the baffle plate 1 The middle part is provided with a first air intake channel 5, and the middle part of the air-permeable plate 2 is provided with a second air-intake channel 6 communicating with the first air-intake channel 5, and the air-permeable plate 2 is located around the second air intake channel 6 Radial air vents 7 are provided; the surrounding environment simulation mechanism of the roadside includes a base 8, a cylinder 9 fixedly connected to the top of the base 8 and a cylinder cover 10 fixedly connected to the top of the cylinder 9, and the middle part of the cylinder 9 The side wall is provided with an insertion hole for the side wall simulation mechanism to be inserted into. The middle position of the top of the base 8 is provided with a groove, and a lower pressing head 11 is placed in the groove, and the lower pressing head 11 The upper semi-concave indenter 39, the upper semi-convex indenter 12 and the piston 13 are arranged in sequence from bottom to top, the piston 13 penetrates upwards to the outside of the cylinder cover 10, and the middle position of the cylinder cover 10 is provided with A through hole for the piston 13 to pass through, the upper end surface of the piston 13 is located directly below the indenter of the electronic universal testing machine 40, and the gangway simulation mechanism is inserted into the cylinder barrel 9 from the gangway simulation mechanism insertion hole, And the coal rock sample 3 is aligned between the upper end surface of the lower indenter 11 and the lower end surface of the upper semi-concave indenter 39, and the top ferrule 4 is engaged and connected in the insertion hole of the roadside simulation mechanism; the base 8 is provided with a third intake passage 14 and a gas inlet 15 communicating with the third intake passage 14, and the lower head 11 is provided with a fourth intake passage 16 communicating with the third intake passage 14 , the fourth air intake channel 16 communicates with the first air intake channel 5 through the first gas transmission pipeline 17; the base 8 is provided with a confining pressure fluid inflow channel 18 communicating with the inner space of the cylinder 9, The side of the base 8 is provided with a confining pressure fluid inlet 19 communicating with the confining pressure fluid inflow channel 18, and the side of the cylinder 9 is provided with an exhaust port 20, and the exhaust port 20 is connected with an exhaust port plug twenty one;

The gas pressure system includes a compressed gas tank 22, the gas outlet of the compressed gas tank 22 is connected to the gas inlet 15 through a second gas transmission pipeline 23, and a pressure reducing valve 24 is arranged on the second gas transmission pipeline 23 and barometer 25;

The confining pressure hydraulic system includes a confining pressure fluid tank 26 and a confining pressure fluid inflow pipe 27 connected to the confining pressure fluid tank 26 at one end, the other end of the confining pressure fluid inflow pipe 27 is connected to the confining pressure fluid inlet 19, the A hydraulic pump 28 and a one-way valve 43 are connected to the confining pressure fluid inflow pipe 27, and a confining pressure fluid overflow pipe 29 is connected to a section of confining pressure fluid inflow pipe 27 between the hydraulic pump 28 and the one-way valve 43. A confining pressure fluid pressure gauge 30 and a confining pressure fluid overflow valve 31 are connected to the confining pressure fluid overflow pipe 29, and a confining pressure fluid inflow pipe 27 between the one-way valve 43 and the confining pressure fluid inlet 19 is connected to a confining pressure fluid overflow pipe 29. A pressure fluid return pipe 32, the confining pressure fluid return pipe 32 is connected with a confining pressure fluid return valve 33;

The hydraulic fracturing system includes a water tank 34, and the water tank 34 is connected with a steel pipe 47 inserted into a drill hole on the coal rock sample 3 when the hydraulic fracturing experiment is performed on the coal rock sample 3 through a water delivery pipeline 35. The water delivery pipeline 35 is provided with a water pump 36 , a water valve 37 and a water pressure gauge 38 .

As shown in Figure 2, in this embodiment, between the base 8 and the lower pressure head 11, between the base 8 and the cylinder 9, between the cylinder 9 and the cylinder cover 10, between the upper semi-concave pressure head 39 and the upper Sealing rings 44 are provided between the semi-convex pressure heads 12 , between the top ferrule 4 and the cylinder 9 , and between the cylinder cover 10 and the piston 13 . The cylinder 9 is fixedly connected to the top of the base 8 by first bolts 45 , and the cylinder cover 10 is fixedly connected to the top of the cylinder 9 by second bolts 46 .

As shown in Figure 2, in this embodiment, the shape of the outer contour of the cylinder 9, the shape of the outer contour of the lower pressure head 11, the shape of the outer contour of the coal rock sample 3, the shape of the outer contour of the top tube 4 and the shape of the upper The shape of the outer contour of the lower part of the semi-concave indenter 39 is cuboid, and the length of the coal rock sample 3 is equal to the length of the lower indenter 11 and the length of the lower part of the upper semi-concave indenter 39, and the width of the coal rock sample 3 The width of the lower pressure head 11, the width of the outer contour of the top ferrule 4 and the width of the lower part of the upper semi-concave indenter 39 are equal, and the height of the coal rock sample 3 is equal to the height of the outer contour of the top ferrule 4.

As shown in Figure 2, in this embodiment, one end of the first gas transmission pipeline 17 is connected to the first air inlet passage 5 through a first quick joint, and the other end of the first gas transmission pipeline 17 is connected to The second quick connector is connected to the fourth air intake channel 16 .

Underground coal mine hydraulic fracturing experimental laboratory simulation method of the present invention comprises the following steps:

Step 1. Assemble the simulation system of the underground hydraulic fracturing experiment laboratory of the coal mine. The specific process is as follows:

Step 101, the baffle 1, vent plate 2, coal rock sample 3 and top ferrule 4 that are butted in sequence are fixed as a whole by electrical tape, and combined into a roadside simulation mechanism;

Step 102, placing the lower pressure head 11 in the groove, and connecting the fourth intake passage 16 with the third intake passage 14, and connecting one end of the first gas delivery pipeline 17 to the fourth intake passage. On the air channel 16;

Step 103, fixing the cylinder 9 on the top of the base 8;

Step 104. Insert the end of the roadside simulation mechanism with the baffle plate 1 into the insertion hole of the roadside simulation mechanism, and by observing the scale set on the outer wall of the top ferrule 4, align the coal rock sample 3 at the The upper end surface of the lower pressure head 11; in practice, the distance from the center of the base 8 to the side of the side of the cylinder 9 with the insertion hole of the sidewalk simulation mechanism is known to be l ₁ , and the length of the coal rock sample 3 is known. Half is l ₂ , and the distance l from the side of the top ferrule 4 extending into the cylinder 9 to the side of the cylinder 9 with the insertion hole of the roadside simulation mechanism can be calculated by the formula l=l ₁ -l ₂ , and the distance l can be obtained by observing the scale arranged on the outer wall of the top tube 4;

Step 105, connecting the other end of the first gas delivery pipeline 17 to the first air intake channel 5;

Step 106, aligning and placing the upper semi-concave indenter 39 on the upper end surface of the coal rock sample 3, and placing the upper semi-convex indenter 12 on top of the upper semi-concave indenter 39;

Step 107, pass the piston 13 through the through hole provided in the middle of the cylinder cover 10, and fix the cylinder cover 10 on the top of the cylinder 9, while ensuring that the center of the piston 13 is aligned with the center of the upper semi-convex pressure head 12 just;

Step 108, connecting the second gas delivery pipeline 23 to the gas inlet 15;

Step 109, connecting the confining pressure fluid inflow pipe 27 to the confining pressure fluid inlet 19;

Step 1010, connect the electronic universal testing machine 40 with the computer 42, place the hydraulic fracturing condition simulation device 41 assembled in steps 101 to 107 on the base of the electronic universal testing machine 40, and make the upper part of the piston 13 The end face is located directly below the indenter of the electronic universal testing machine 40;

Step 2, load the axial pressure on the coal rock sample 3: on the computer 42, open the pre-installed electronic universal testing machine software, operate the electronic universal testing machine software to start the electronic universal testing machine 40, and set the electronic universal testing machine 40 The speed parameter and the pressure parameter of the pressure head pressing down the piston 13, the pressure head of the electronic universal testing machine 40 presses down the piston 13 according to the set speed parameter, until the pressure parameter displayed in the electronic universal testing machine software reaches the set pressure parameter ;

Step 3, load the confining pressure on the coal rock sample 3: remove the vent plug 21 connected to the vent 20, open the vent 20, open the inlet switch of the confining pressure liquid overflow valve 31, and open the In the confining pressure hydraulic system, the confining pressure fluid in the confining pressure fluid tank 26 is pressurized by the second hydraulic pump 37 and flows into the cylinder 9 through the confining pressure fluid inflow pipe 27 and the confining pressure fluid inlet 19. When the hydraulic fluid flows out, connect the exhaust port plug 21 to the exhaust port 20, and close the exhaust port 20;

By setting different pressure parameters of the pressure head of the electronic universal testing machine 40 to press down the piston 13 in step 2, the adjustment of the axial pressure can be realized; by operating the confining pressure fluid overflow valve 31 in step 3, the confining pressure can be adjusted The adjustment of the pressure; and then according to the in-situ stress of the coal and rock mass in different mines, it can truly simulate the in-situ stress of the coal and rock mass in the coal mine.

Step 4: Apply gas pressure to the coal rock sample 3: open the switch of the pressure reducing valve 24, open the gas pressure system, the gas in the compressed gas tank 22 is decompressed by the pressure reducing valve 24 and then passes through the second gas transmission pipeline 23 And the gas inlet 15 enters the first air intake channel 5 and the second air intake channel 6, and enters the vent hole 7;

By operating the pressure reducing valve 24 in step 4, the adjustment of the gas pressure can be realized, and the gas content and pressure in the underground coal rock body of the coal mine can be truly simulated according to the gas reserves and pressures of different mines.

Step 5. Carry out a hydraulic fracturing experiment at the coal rock sample 3 exposed in the top ferrule 4, and the specific process is as follows:

Step 501, use an electric drill with a drill bit diameter of d to drill a drill hole with an azimuth angle of α, an inclination angle of β, and a length of L on the coal rock sample 3 exposed in the top tube 4;

Step 502, inserting a steel pipe 47 into the borehole; in practice, the length of the steel pipe 47 is slightly less than the length L of the borehole, and the diameter of the steel pipe 47 is slightly less than the diameter of the borehole, that is, the diameter d of the drill bit;

Step 503, seal the drilled hole with a sealing material, the length of which is n; wherein, n<L; in specific implementation, the sealing material is epoxy resin glue;

Step 504, connecting the water pipeline 35 to the steel pipe 47;

Step 505, open the water valve 37, start the hydraulic fracturing system, the water in the water tank 34 is pressurized by the water pump 36, enters the steel pipe 47 through the water delivery pipeline 35, and hits the coal rock sample 3, and the coal rock sample 3. Hydraulic fracturing was carried out, and cracks filled with water were formed on the coal rock sample 3;

Step 506: After the fracturing time period t, close the water valve 37, close the hydraulic fracturing system, disconnect the water delivery pipeline 35 connected to the steel pipe 47, and gradually flow out the water in the crack;

Step 507, after the water in the crack is exhausted, measure the gas pressure P at the exposed port of the steel pipe 47 with a gas pressure measuring instrument, and measure the gas concentration φ at the exposed port of the steel pipe 47 with a gas concentration measuring instrument;

Step 508, record the pressure parameters of the pressure head of the electronic universal testing machine 40 set in the step 2 to press down on the piston 13, record the confining pressure in the step 3 shown on the confining pressure gauge 30, and record the pressure on the air pressure gauge 25 Show the gas pressure in step 4, record the diameter d of the drill bit in the step 501 and the azimuth angle of the borehole as α, the inclination angle as β and the length L, record the hydraulic fracturing in the step 505 displayed on the water pressure gauge 38 pressure, record the fracturing time period t in step 506, and record the gas pressure P and gas concentration φ measured in step 507. The data that above record obtains is provided to engineering technical personnel, and engineering technical personnel can research axial pressure (being the pressure parameter that the pressure head of electronic universal testing machine 40 depresses piston 13), confining pressure, gas pressure, the diameter d of drill bit, drill bit. The azimuth angle α of the hole, the inclination angle β of the borehole, the length L of the borehole, the hydraulic fracturing pressure and the fracturing time period t have an effect on the gas pressure P and gas concentration φ flowing out of the hydraulic fracturing of the coal rock sample 3, and then improved The method of the outflow gas concentration φ, and finally improve the gas recovery rate.

In this embodiment, before the step 502, the borehole cleaning fluid is used to clean the borehole. During specific implementation, the drilling cleaning fluid is acetone or alcohol. By cleaning the boreholes, it is also possible for engineering and technical personnel to study the influence of whether the boreholes are cleaned on the gas pressure P and gas concentration φ flowing out of the coal rock sample 3 after hydraulic fracturing.

In this embodiment, before placing the lower pressure head 11 in the groove in the step 102, put the sealing ring 44 in the groove; in the step 103, the cylinder 9 is fixedly connected to the base 8 top, first put the sealing ring 44 on the top of the base 8; in the step 104, before inserting the end of the gangway simulation mechanism with the baffle plate 1 into the insertion hole of the gangway simulation mechanism, first place the Put the sealing ring 44 into the hole of the lane side simulation mechanism; in the step 106, before placing the upper semi-convex indenter 12 on the top of the upper semi-concave indenter 39, put the sealing ring 44 in the upper semi-concave indenter 39. Ring 44; in the step 107, before the piston 13 is passed through the through hole arranged at the middle position of the cartridge cover 10, the sealing ring 44 is first placed in the through hole arranged at the middle position of the cartridge cover 10; In step 107 , before the cylinder cover 10 is fixedly connected to the top of the cylinder 9 , a sealing ring 44 is placed on the top of the cylinder 9 . In the step 103, the cylinder 9 is fixedly connected to the top of the base 8 by using the second bolt 45; in the step 107, the cylinder cover 10 is fixedly connected to the top of the cylinder 9 by using the third bolt 46.

In this embodiment, the speed parameter of the pressure head of the electronic universal testing machine 40 set in the step 2 to press down the piston 13 is 0.4mm/min～0.6mm/min, and the electronic universal testing machine set in the step 2 The pressure parameter of the pressure head of the machine 40 to press down the piston 13 is 3MPa～5MPa.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still belong to the technical aspects of the present invention. within the scope of protection of the scheme.

Claims (10)

1. A simulation system for a hydraulic fracturing experiment laboratory in a coal mine, characterized in that it includes an electronic universal testing machine (40), a hydraulic fracturing condition simulation device (41), a gas pressure system, a confining pressure hydraulic system, and a hydraulic fracturing system and computer (42), the hydraulic fracturing condition simulation device (41) is centered and placed on the base of the electronic universal testing machine (40), and the electronic universal testing machine (40) is connected with the computer (42); The hydraulic fracturing condition simulation device (41) is composed of a roadside simulation mechanism and a roadside surrounding environment simulation mechanism, and the roadway simulation mechanism includes a baffle (1), a gas-permeable plate (2), a coal sample (3) and the top tube (4), the outer wall of the top tube (4) is provided with a scale, the baffle plate (1), the vent plate (2), the coal rock sample (3) and the top The ferrule (4) is wound and fixed as a whole by electrical tape, the middle part of the baffle plate (1) is provided with a first air inlet channel (5), and the middle part of the air-permeable plate (2) is provided with a first air inlet channel (5) the second air intake channel (6) connected to each other, and the surroundings of the second air intake channel (6) on the said air permeable plate (2) are provided with radial ventilation holes (7); The environment simulation mechanism comprises a base (8), a cylinder (9) fixedly connected to the top of the base (8) and a cylinder cover (10) fixedly connected to the top of the cylinder (9), the middle side wall of the cylinder (9) There is an insertion hole for the roadside simulation mechanism to be inserted into the top, and a groove is arranged at the middle position of the top of the base (8), and a lower pressing head (11) is placed in the groove, and the lower pressure head (11) is placed in the groove. Right above the head (11) are provided with an upper semi-concave pressure head (39), an upper semi-convex pressure head (12) and a piston (13) from bottom to top, and the piston (13) passes upwards to the cylinder cover ( 10) the outside, and the middle position of the cylinder cover (10) is provided with a through hole for the piston (13) to pass through, and the upper end surface of the piston (13) is located directly below the indenter of the electronic universal testing machine (40) , the lane side simulation mechanism is inserted into the cylinder (9) from the lane side simulation mechanism insertion hole, and the coal rock sample (3) is aligned on the upper end surface of the lower pressure head (11) and the upper semi-concave pressure head ( 39) between the lower end faces, the top ferrule (4) is snapped and connected in the insertion hole of the roadside simulation mechanism; the base (8) is provided with a third air intake passage (14) and a third A gas inlet (15) connected to the air inlet passage (14), and a fourth air inlet passage (16) connected to the third air inlet passage (14) is provided on the lower pressure head (11). The four air intake channels (16) are communicated with the first air intake channel (5) through the first gas transmission pipeline (17); the base (8) is provided with a surrounding wall that communicates with the inner space of the cylinder (9). The pressure fluid inflow channel (18), the side of the base (8) is provided with a confining pressure fluid inlet (19) communicating with the confining pressure fluid inflow channel (18), and the side of the cylinder (9) is provided with an exhaust Port (20), the exhaust port (20) is connected with an exhaust port plug (21); The gas pressure system includes a compressed gas tank (22), the gas outlet of the compressed gas tank (22) is connected to the gas inlet (15) through a second gas transmission pipeline (23), and the second gas transmission pipeline (23) is provided with relief valve (24) and air pressure gauge (25); The confining pressure hydraulic system includes a confining pressure fluid tank (26) and a confining pressure fluid inflow pipe (27) connected to the confining pressure fluid tank (26) at one end, and the other end of the confining pressure fluid inflow pipe (27) is connected to the confining pressure fluid inflow pipe (27). The pressure fluid inlet (19) is connected, and the hydraulic pump (28) and the one-way valve (43) are connected on the said confining pressure fluid inflow pipe (27), and the valve between the hydraulic pump (28) and the one-way valve (43) A confining pressure fluid inflow pipe (27) is connected with a confining pressure fluid overflow pipe (29), and the confining pressure fluid overflow pipe (29) is connected with a confining pressure fluid pressure gauge (30) and a confining pressure fluid overflow pipe (29). Valve (31), a section of confining pressure fluid inflow pipe (27) between the one-way valve (43) and confining pressure fluid inlet (19) is connected with confining pressure fluid return pipe (32), and the confining pressure fluid returns The pipe (32) is connected with a confining pressure fluid return valve (33); The hydraulic fracturing system includes a water tank (34), and the water tank (34) is inserted into the coal rock sample (3) through the water delivery pipeline (35) when performing hydraulic fracturing experiments on the coal rock sample (3). The steel pipes (47) in the borehole are connected, and the water delivery pipeline (35) is provided with a water pump (36), a water valve (37) and a water pressure gauge (38). 2. The underground hydraulic fracturing experimental laboratory simulation system for coal mine according to claim 1, characterized in that: between the base (8) and the lower pressure head (11), between the base (8) and the cylinder (9) between the cylinder (9) and the cylinder cover (10), between the upper semi-concave indenter (39) and the upper semi-convex indenter (12), between the top tube (4) and the cylinder (9) A sealing ring (44) is arranged between the cylinder cover (10) and the piston (13). 3. The underground hydraulic fracturing experiment laboratory simulation system for coal mine according to claim 1, characterized in that: the cylinder barrel (9) is fixedly connected to the top of the base (8) by the first bolt (45), and the cylinder barrel (9) is fixed on the top of the base (8). The cover (10) is fixedly connected to the top of the cylinder barrel (9) by the second bolt (46). 4. according to the described simulation system of coal mine underground hydraulic fracturing experiment laboratory of claim 1, it is characterized in that: the shape of described cylinder barrel (9) outer contour, the shape of lower pressure head (11) outer contour, coal rock sample (3) The shape of the outer contour, the shape of the outer contour of the top tube (4) and the shape of the lower outer contour of the upper semi-concave indenter (39) are all cuboid, and the length of the coal rock sample (3) is the same as that of the lower The length of the indenter (11) is equal to the length of the lower part of the upper semi-concave indenter (39), and the width of the coal rock sample (3) is the same as the width of the lower indenter (11) and the outer contour of the top tube (4). The width is equal to the width of the lower part of the upper semi-concave pressure head (39), and the height of the coal rock sample (3) is equal to the height of the outer contour of the top tube (4). 5. according to the described simulation system of coal mine hydraulic fracturing experiment laboratory of claim 1, it is characterized in that: one end of the first gas transmission pipeline (17) passes through the first quick connector and the first air inlet channel (5 ) is connected, and the other end of the first gas transmission pipeline (17) is connected to the fourth air inlet passage (16) through a second quick connector. 6. A method utilizing simulation system as claimed in claim 1 to carry out the simulation of the hydraulic fracturing experiment laboratory in coal mine, is characterized in that the method may further comprise the steps: Step 1. Assemble the simulation system of the underground hydraulic fracturing experiment laboratory of the coal mine. The specific process is as follows: Step 101, the baffle plate (1), air-permeable plate (2), coal rock sample (3) and jacking sleeve (4) which are butted in sequence are fixed as a whole by electrical tape, and combined into a roadway simulation mechanism; Step 102, place the lower pressure head (11) in the groove, connect the fourth air intake channel (16) with the third air intake channel (14), and connect the first gas transmission pipeline (17 ) is connected to the fourth air intake channel (16); Step 103, fixing the cylinder (9) on the top of the base (8); Step 104, insert one end of the roadside simulation mechanism with the baffle (1) into the insertion hole of the roadside simulation mechanism, and observe the scale set on the outer wall of the top tube (4) to make the coal rock sample (3) Aligning is located on the upper end surface of the lower pressure head (11); Step 105, connecting the other end of the first gas delivery pipeline (17) to the first air intake channel (5); Step 106, aligning and placing the upper semi-concave indenter (39) on the upper end surface of the coal rock sample (3), and placing the upper semi-convex indenter (12) on top of the upper semi-concave indenter (39); Step 107, pass the piston (13) through the through hole provided in the middle of the cylinder cover (10), and fix the cylinder cover (10) on the top of the cylinder (9), while ensuring the center of the piston (13) Align with the center of the upper semi-convex pressure head (12); Step 108, connecting the second gas delivery pipeline (23) to the gas inlet (15); Step 109, connecting the confining pressure fluid inflow pipe (27) to the confining pressure fluid inlet (19); Step 1010, connect the electronic universal testing machine (40) with the computer (42), and center the hydraulic fracturing condition simulation device (41) assembled in steps 101 to 107 on the base of the electronic universal testing machine (40) On, and make the upper end face of piston (13) be positioned at the indenter of described electronic universal testing machine (40) just below; Step 2, load the axial pressure on the coal rock sample (3): on the computer (42), open the pre-installed electronic universal testing machine software, operate the electronic universal testing machine software to start the electronic universal testing machine (40), and set The pressure head of the electronic universal testing machine (40) presses down the speed parameter and the pressure parameter of the piston (13), and the pressure head of the electronic universal testing machine (40) presses down the piston (13) according to the set speed parameter until it is displayed on the electronic The pressure parameter in the universal testing machine software reaches the set pressure parameter; Step 3: Apply confining pressure to the coal rock sample (3): remove the vent plug (21) connected to the vent (20), open the vent (20), and open the confining pressure fluid overflow valve ( 31) to open the confining pressure hydraulic system, the confining pressure fluid in the confining pressure fluid tank (26) is pressurized by the second hydraulic pump (37) and then flows into the pipe (27) and the confining pressure fluid through the confining pressure fluid The liquid inlet (19) flows into the cylinder (9), and when the exhaust port (20) has confining pressure liquid flowing out, connect the exhaust port plug (21) to the exhaust port (20), and close the exhaust port ( 20); Step 4, load the gas pressure on the coal rock sample (3): open the switch of the pressure reducing valve (24), open the gas pressure system, and the gas in the compressed gas tank (22) is decompressed by the pressure reducing valve (24) Enter the first air intake channel (5) and the second air intake channel (6) through the second gas transmission pipeline (23) and the gas inlet (15), and enter the air vent (7); Step 5. Carry out a hydraulic fracturing experiment at the coal rock sample (3) exposed in the top tube (4), the specific process is as follows: Step 501, use an electric drill with a drill bit diameter of d to drill a drill hole with an azimuth angle of α, an inclination angle of β, and a length of L on the coal rock sample (3) exposed in the top tube (4); Step 502, inserting a steel pipe (47) into the borehole; Step 503, seal the drilled hole with a sealing material, the length of the sealed hole is n; wherein, n<L; Step 504, connecting the water pipeline (35) to the steel pipe (47); Step 505, open the water valve (37), start the hydraulic fracturing system, the water in the water tank (34) is pressurized by the water pump (36), enters the steel pipe (47) through the water delivery pipeline (35), and hits the On the coal rock sample (3), the coal rock sample (3) is subjected to hydraulic fracturing, and a fissure filled with water is formed on the coal rock sample (3); Step 506, after the fracturing time period t, close the water valve (37), close the hydraulic fracturing system, disconnect the water delivery pipeline (35) connected to the steel pipe (47), and the water in the crack gradually outflow; Step 507, after the water in the crack is exhausted, measure the gas pressure P at the exposed port of the steel pipe (47) with a gas pressure measuring instrument, and measure the gas concentration φ at the exposed port of the steel pipe (47) with a gas concentration measuring instrument; Step 508, record the pressure parameters of the pressure head of the electronic universal testing machine (40) set in the step 2 to press down the piston (13), and record the confining pressure in the step 3 displayed on the confining pressure hydraulic pressure gauge (30) , record the gas pressure in the step 4 shown on the air pressure gauge (25), record the diameter d of the drill bit in the step 501 and the azimuth angle of the borehole as α, the inclination angle as β and length L, record the water pressure gauge (38) The hydraulic fracturing pressure in step 505 shown above, record the fracturing time period t in step 506, and record the gas pressure P and gas concentration φ measured in step 507. 7. The method according to claim 6, characterized in that: before the step 502, the borehole is cleaned with a borehole cleaning solution. 8. The method according to claim 6, characterized in that: in the step 102, before placing the lower pressing head (11) in the groove, first put a sealing ring (44) in the groove; In the step 103, before the cylinder (9) is fixedly connected to the top of the base (8), put the sealing ring (44) on the top of the base (8); Before inserting one end of the baffle plate (1) into the insertion hole of the gangway simulation mechanism, put a sealing ring (44) in the insertion hole of the gangway simulation mechanism; Before the head (12) is placed on the top of the upper half concave pressure head (39), put the sealing ring (44) in the upper half concave pressure head (39); in the step 107, the piston (13) passes through Before being arranged in the through hole at the middle position of the cylinder cover (10), put the sealing ring (44) in the through hole arranged at the middle position of the cylinder cover (10); in the step 107, put the cylinder cover ( 10) Before being fixedly connected to the top of the cylinder (9), put the sealing ring (44) on the top of the cylinder (9). 9. The method according to claim 6, characterized in that: in the step 103, the cylinder barrel (9) is fixedly connected to the top of the base (8) by using a second bolt (45); in the step 107, the barrel The cover (10) is fixedly connected to the top of the cylinder barrel (9) by adopting the third bolt (46). 10. according to the described method of claim 6, it is characterized in that: the electronic universal testing machine (40) of the electronic universal testing machine (40) set in the speed parameter of pressing down piston (13) is 0.4mm/min～0.6mm /min, the pressure parameter of the pressure head depressing the piston (13) of the electronic universal testing machine (40) set in the step 2 is 3MPa～5MPa.