CN109630087B - Pressurized liquid nitrogen leaching coal body fracturing anti-reflection device and anti-reflection experimental method - Google Patents
Pressurized liquid nitrogen leaching coal body fracturing anti-reflection device and anti-reflection experimental method Download PDFInfo
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- CN109630087B CN109630087B CN201910036857.1A CN201910036857A CN109630087B CN 109630087 B CN109630087 B CN 109630087B CN 201910036857 A CN201910036857 A CN 201910036857A CN 109630087 B CN109630087 B CN 109630087B
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 223
- 239000007788 liquid Substances 0.000 title claims abstract description 138
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 107
- 239000003245 coal Substances 0.000 title claims abstract description 100
- 238000002474 experimental method Methods 0.000 title claims abstract description 38
- 238000002386 leaching Methods 0.000 title claims abstract description 22
- 239000007789 gas Substances 0.000 claims abstract description 89
- 238000004321 preservation Methods 0.000 claims abstract description 37
- 238000002955 isolation Methods 0.000 claims abstract description 29
- 239000002184 metal Substances 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 7
- 238000001179 sorption measurement Methods 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims description 12
- 238000011161 development Methods 0.000 claims description 10
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 9
- 238000007789 sealing Methods 0.000 claims description 7
- 239000012780 transparent material Substances 0.000 claims description 7
- 238000001514 detection method Methods 0.000 claims description 3
- 238000012423 maintenance Methods 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 230000002349 favourable effect Effects 0.000 abstract description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 8
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical group 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012806 monitoring device Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B43/28—Dissolving minerals other than hydrocarbons, e.g. by an alkaline or acid leaching agent
- E21B43/283—Dissolving minerals other than hydrocarbons, e.g. by an alkaline or acid leaching agent in association with a fracturing process
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
- Y02P90/70—Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells
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Abstract
The invention discloses a pressurizable liquid nitrogen leaching gas-containing coal body fracturing and anti-reflection device, which comprises a heat preservation cylinder, wherein an inner cylinder is downwards connected to the center of the top wall of the heat preservation cylinder, and a gap is formed between the bottom end of the inner cylinder and the bottom wall of the heat preservation cylinder; the middle part of the inner cylinder is horizontally provided with a pressure-resistant metal net sheet, and the pressure-resistant metal net sheet divides the inner cylinder into a coal cavity and a liquid inlet cavity from top to bottom; an isolation valve is arranged in the middle of the inner cylinder and is used for separating the inner cylinder, and a valve rod of the isolation valve extends out of the heat preservation cylinder along the horizontal direction; the top wall of the heat-insulating cylinder at the top end of the inner cylinder is in threaded connection with an inner cylinder cover, and a threaded shaft body is arranged on the inner cylinder cover; the invention also discloses an anti-reflection experiment method, which can be used for carrying out liquid nitrogen leaching coal body experiments under different gas adsorption pressure conditions of the coal body, can better control the specific size of the liquid nitrogen leaching coal body, is suitable for carrying out the anti-reflection experiment on the coal body repeatedly under different experiment conditions, is favorable for obtaining an optimal anti-reflection scheme, and provides technical support for exploitation and utilization of coal bed gas.
Description
Technical Field
The invention relates to the field of coalbed methane exploitation, in particular to a liquid nitrogen fracturing permeability-increasing technology.
Background
The coalbed methane is hydrocarbon gas which is mainly composed of methane and is adsorbed on the surface of coal matrix particles, partially dissociated in coal pores or dissolved in coalbed water, is associated mineral resources of coal, belongs to unconventional natural gas, and is a clean and high-quality energy and chemical raw material which is internationally grown in the last two decades. The permeability of the coal bed is low, the extraction efficiency is seriously affected, the problems of low flowback rate, short fracturing cracks, environmental pollution and the like exist in hydraulic fracturing at present, the novel fracturing technology is key for improving the fracturing effect of the coal bed, and the low-temperature fluid is utilized to fracture the coal reservoir, so that the hydraulic fracturing method has the advantages of energy increasing, emission assisting, small damage to the coal bed and the like; the liquid nitrogen leaching coal body crack development experiment is carried out under the preset temperature condition and the pressure of a coal reservoir, but the prior art lacks a liquid nitrogen fracturing related device for experiment, the existing equipment can not realize the liquid nitrogen leaching anti-reflection experiment of the gas-containing coal, can not realize the liquid nitrogen anti-reflection experiment under the fixed or loading condition, and can not study the influence of the liquid nitrogen leaching coal sample size under the certain pressure on the coal sample crack development condition.
Disclosure of Invention
The invention aims to provide a pressurizable liquid nitrogen leaching coal body fracturing and permeability increasing device, which can conveniently control liquid nitrogen liquid level, carry out low-temperature crack development experiments on coal samples, and facilitate repeated experiments after liquid level parameters and pressure parameters are changed.
In order to achieve the aim, the pressurizable liquid nitrogen leaching gas-containing coal body fracturing permeability-increasing device comprises a hollow cylindrical heat preservation cylinder, wherein the heat preservation cylinder is vertically arranged, both ends of the axial direction of the heat preservation cylinder are sealed, the center of the top wall of the heat preservation cylinder is downwards connected with a hollow cylindrical inner cylinder, and a gap is reserved between the bottom end of the inner cylinder and the bottom wall of the heat preservation cylinder; the middle part of the inner cylinder is horizontally provided with a pressure-resistant metal net sheet, and the metal net sheet divides the inner cylinder into a coal cavity and a liquid inlet cavity;
an isolation valve is arranged in the middle of the inner cylinder, the isolation valve is positioned below the pressure-resistant metal mesh and adjacent to the pressure-resistant metal mesh, the isolation valve is used for separating the inner cylinder, a valve rod of the isolation valve extends out of the heat-preserving cylinder along the horizontal direction, and the valve rod is in sealing fit with the side wall of the heat-preserving cylinder; the diameter of the meshes of the pressure-resistant metal mesh is 3 mm-7 mm;
the top wall of the heat-insulating cylinder at the top end of the inner cylinder is in threaded connection with an inner cylinder cover, a threaded shaft body (which is used for increasing the axial pressure of the coal body and is applied to the coal body through rotating and rotating) is arranged on the inner cylinder cover, a pressure sensor is arranged at the lower end of the threaded shaft body, and a impurity-removing air hole is also formed in the inner cylinder cover; a liquid nitrogen cavity is formed between the inner cylinder and the side wall of the heat preservation cylinder, and a first valve for introducing liquid nitrogen is arranged on the top wall of the heat preservation cylinder at the top end of the liquid nitrogen cavity.
The heat preservation cylinder and the inner cylinder are both made of transparent materials, the outer surface of the side wall of the inner cylinder is connected with a scale three-dimensional plate made of transparent materials, horizontal scale lines are uniformly arranged at intervals from top to bottom on the scale three-dimensional plate, 1 millimeter is arranged between two adjacent horizontal scale lines from top to bottom, the 0 scale line is positioned at the metal mesh, and Arabic numerals which are used for indicating the height of liquid nitrogen and are used for indicating the height of liquid nitrogen are carved at the tail ends of the scale lines from the 0 scale line to the top by 1 centimeter; the lower end of the threaded shaft body for increasing the axial pressure of the coal body is provided with a pressure sensor; air holes are formed in two sides of the top of the liquid inlet cavity of the inner cylinder (the convenience of discharging gas in the liquid nitrogen cavity after liquid nitrogen is added is guaranteed).
The invention also discloses an anti-reflection experiment method by using the experimental pressurizable liquid nitrogen leaching gas-containing coal sample fracturing anti-reflection device, which comprises the following steps:
the first step is the detection of tightness;
the second step is to add the coal;
the third step is to remove impurity gas;
the fourth step is gas adsorption;
the fifth step is to add liquid nitrogen;
the sixth step is that the coal body is pressurized axially;
seventh, carrying out a crack development experiment of the coal body under a preset gas pressure condition and a liquid nitrogen liquid level condition, and carrying out an experiment record;
the second to seventh steps are one experimental cycle; the experimental plan comprises N groups of preset liquid nitrogen liquid level height values and coal pressure values, wherein N is a natural number greater than or equal to 1;
and repeating the second to sixth steps by adopting a group of preset liquid nitrogen liquid level height values and gas pressure values in each experiment cycle until all experiment cycles corresponding to N groups of preset liquid nitrogen liquid level height values and coal pressure values in an experiment plan are completed.
The specific operation of the first step is as follows: closing an air hole for removing impurity gas, connecting the first valve with an air pipe of an external high-pressure nitrogen gas cylinder, and connecting the air pipe of the external high-pressure nitrogen gas cylinder with the external high-pressure nitrogen gas cylinder; the first valve and the isolation valve are opened, nitrogen is injected into the coal cavity through the high-pressure nitrogen cylinder and the first valve, and the nitrogen enters the liquid inlet cavity through a gap between the bottom end of the inner cylinder and the bottom wall of the heat preservation cylinder; when the pressure gauge shows that the pressure in the coal cavity and the liquid inlet cavity reaches a preset value, the first valve is closed; if the pressure reduction value is less than or equal to 0.01MPa after the pressure is maintained for 12 hours, continuing to carry out the second step; if the pressure reduction value is greater than 0.01MPa after the pressure is maintained for 12 hours, the first step is carried out again after the sealing maintenance of the pressurizable liquid nitrogen semi-leaching fracturing anti-reflection device is needed;
the specific operation of the second step is as follows: and opening the inner cylinder cover, putting the coal body into a coal cavity, and then connecting the impurity-removing gas hole with an external vacuum pump.
The specific operation of the third step is as follows: closing the isolation valve, and pumping the impurity gas in the coal cavity through a vacuum pump connected with the impurity gas removal hole until the vacuum gauge 14 is seen to display that the vacuum degree in the coal cavity is kept stable within three minutes;
the specific operation of the fourth step is as follows: the impurity-removing gas hole is connected with a gas pipe of an external high-pressure gas cylinder, the gas pipe of the external high-pressure gas cylinder is connected with a pressure sensor, the pressure sensor is connected with a pressure reducing valve through the gas pipe, the pressure reducing valve is connected with the high-pressure gas cylinder through the gas pipe, the first valve and the isolation valve are closed, the high-pressure gas cylinder is opened, gas is injected into a gas cavity through the control pressure reducing valve, the gas pressure in the gas cavity is controlled through a voltage sensor of the gas cavity, so that the gas is better adsorbed by the gas cavity, and when the values of the pressure sensors connected with the high-pressure gas cylinder are equal, the gas is adsorbed by the gas cavity.
The fifth step comprises the following specific operations: opening a first valve and an isolation valve, connecting the first valve with an external liquid nitrogen pipeline, connecting the external liquid nitrogen pipeline with an external liquid nitrogen source, adding liquid nitrogen into a liquid nitrogen cavity through the liquid nitrogen pipeline and the first valve, enabling the liquid nitrogen to enter the inner cylinder from bottom to top through a gap between the inner cylinder and the bottom wall of the heat preservation cylinder, and enabling the liquid nitrogen to enter a coal sample cavity after passing through a liquid inlet cavity and meshes of a pressure-resistant metal mesh;
a worker observes liquid nitrogen in the coal cavity through the transparent heat-preserving cylinder and the inner cylinder, and obtains the accurate liquid level of the liquid nitrogen according to the scales and the numbers on the scale plate; when the liquid level of the liquid nitrogen is about to reach the preset height of the experiment, closing an isolation valve (the isolation valve has a certain volume), and stopping the second step;
the sixth step comprises the following specific operations: the screw shaft body on the inner cylinder cover is rotated to apply axial pressure to the coal body in the inner cylinder, and the pressure sensor connected with the screw shaft body is used for controlling the preset value of the pressure applied by the coal body.
The invention has the following advantages:
the invention can not only study the low-temperature crack development under the condition of liquid nitrogen leaching of coal bodies, but also study the low-temperature crack development under the condition of liquid nitrogen leaching of gas-containing coal bodies, and study the coal body crack development under the condition of liquid nitrogen leaching of gas-containing coal bodies and axial pressure.
The invention has simple structure and convenient use, and is convenient for experimenters to intuitively observe and control the liquid level height of liquid nitrogen and the pressure value of gas.
The heat preservation cylinder, the inner cylinder and the scale three-dimensional plate are all made of transparent materials, so that the visibility of the liquid nitrogen liquid level monitoring device is ensured, and experimenters can intuitively and accurately observe the liquid nitrogen liquid level. The gas pressure can be effectively controlled by observing the pressure sensor.
The anti-reflection experiment method can very conveniently control the experiment pressure and the liquid level height of liquid nitrogen, is convenient for providing different experiment pressure conditions and different liquid level height conditions of liquid nitrogen, and provides a foundation for low-temperature crack development experiments (anti-reflection experiments).
The anti-reflection experiment method is simple and convenient in steps and reasonable in arrangement, and if the gas is adsorbed and balanced, the pressure values of the two pressure sensors of the device are observed in the fourth step.
In a word, the invention can better control the pressure of gas and liquid nitrogen and control the specific size of the liquid nitrogen infiltrated coal body, is suitable for repeatedly carrying out anti-reflection experiments on the coal body under different experimental conditions, is favorable for obtaining an optimal anti-reflection scheme, and provides technical support for exploitation and utilization of coal bed gas.
Drawings
Fig. 1 is a schematic structural view of the present invention.
Detailed Description
As shown in figure 1, the experimental pressurizable liquid nitrogen leaching gas-containing coal body fracturing and permeability-increasing device comprises a hollow cylindrical heat preservation cylinder 1, wherein the heat preservation cylinder 1 is vertically arranged, both axial ends of the heat preservation cylinder 1 are closed, the center of the top wall of the heat preservation cylinder 1 is downwards connected with a hollow cylindrical inner cylinder 2, and a gap is reserved between the bottom end of the inner cylinder 2 and the bottom wall of the heat preservation cylinder 1; the middle part of the inner cylinder 2 is horizontally provided with a pressure-resistant metal net sheet 3, and the pressure-resistant metal net sheet 3 divides the inner cylinder 2 into a coal cavity 4 and a liquid inlet cavity 5;
an isolation valve 6 is arranged in the middle of the inner cylinder 2, the isolation valve 6 is positioned below the pressure-resistant metal mesh 3 and adjacent to the pressure-resistant metal mesh 3, the isolation valve 6 is used for separating the inner cylinder 2, a valve rod of the isolation valve extends out of the heat-preserving cylinder 1 along the horizontal direction, and the valve rod is in sealing fit with the side wall of the heat-preserving cylinder 1; the diameter of the meshes of the pressure-resistant metal mesh 3 is 3 mm-7 mm;
the top wall of the heat preservation cylinder 1 at the top end of the inner cylinder 2 is in threaded connection with an inner cylinder cover 7, a threaded shaft body 8 for applying axial pressure to a coal sample is arranged on the inner cylinder cover 7, a pressure sensor 13 is arranged at the bottom end of the threaded shaft body 8, a impurity removal air hole 16, a vacuum gauge 14 and a vacuum pump 15 are connected with a coal sample cavity; a liquid nitrogen cavity 9 is formed between the inner cylinder 2 and the side wall of the heat preservation cylinder 1, and a first valve 10 for introducing liquid nitrogen is arranged on the top wall of the heat preservation cylinder 1 at the top end of the liquid nitrogen cavity 9.
The heat preservation cylinder 1 and the inner cylinder 2 are both made of transparent materials (such as low temperature resistant glass or plastic), the outer surface of the side wall of the inner cylinder 2 is connected with a scale three-dimensional plate (which is connected with the inner wall of the heat preservation cylinder in a sealing way) 11 made of transparent materials, horizontal scale lines 12 are uniformly arranged at intervals up and down on the scale three- dimensional plate 11, 1 millimeter is arranged between two adjacent horizontal scale lines 12 up and down, 0 scale line is positioned at the pressure-resistant metal net sheet 3, and Arabic numerals which are used for indicating the height of liquid nitrogen and are arranged at the tail end of the horizontal scale lines 12 in a certain centimeter from the 0 scale line up to the 1 centimeter; the side wall of the coal cavity 4 is provided with a pressure sensor 17. FIG. 1 is a schematic diagram, the number of scale marks in the diagram does not represent the actual number, and according to the experiment requirement, the experimental pressurizable liquid nitrogen semi-leaching fracturing anti-reflection device can be manufactured into different size models, and the number of the scale marks is correspondingly increased or decreased.
The invention also discloses an anti-reflection experiment method by using the experimental pressurizable liquid nitrogen leaching preset gas-containing coal body fracturing anti-reflection device, which is characterized by comprising the following steps of:
the first step is the detection of tightness;
the second step is to add the coal sample;
the third step is to remove impurity gas, namely vacuumize the cavity of the coal.
The fourth step is gas adsorption;
the fifth step is to add liquid nitrogen;
the sixth step is to pressurize the coal;
seventh, carrying out a crack development experiment of the coal sample under a preset pressure condition and a liquid nitrogen liquid level condition, and carrying out an experiment record;
the second to seventh steps are one experimental cycle; the experimental plan comprises N groups of preset liquid nitrogen liquid level height values and coal sample cavity 4 pressure values, wherein N is a natural number which is more than or equal to 1;
and (3) repeating the second to sixth steps by adopting a group of preset liquid nitrogen liquid level height values and coal pressure values in each experimental cycle until all experimental cycles corresponding to N groups of preset liquid nitrogen liquid level height values and coal pressure values in the experimental plan are completed.
The specific operation of the first step is as follows: the first valve 10 is connected with an air pipe of an external high-pressure nitrogen gas cylinder, and the air pipe of the external high-pressure nitrogen gas cylinder is connected with the external high-pressure nitrogen gas cylinder; the first valve 10 and the isolation valve 6 are opened, nitrogen is injected into the coal cavity 4 through the high-pressure nitrogen pipe and the first valve 10, and the nitrogen enters the liquid inlet cavity 5 through a gap between the bottom end of the inner cylinder 2 and the bottom wall of the heat preservation cylinder 1; when the pressure sensor 17 displays that the pressure in the coal cavity 4 and the liquid inlet cavity 5 reaches a preset value, the first valve 10 is closed; if the pressure reduction value is less than or equal to 0.01MPa after the pressure is maintained for 12 hours, continuing to carry out the second step; if the pressure reduction value is greater than 0.01MPa after the pressure is maintained for 12 hours, the first step is carried out again after the sealing maintenance of the pressurizable liquid nitrogen semi-leaching fracturing anti-reflection device is needed;
the specific operation of the second step is as follows: the inner cylinder cover 7 is opened, the coal body is put into the coal body cavity 4, and then the impurity removing air hole 16 is connected with an external vacuum pump.
The specific operation of the third step is as follows: closing the first valve 10 and the isolation valve 6, and pumping the impurity gas in the coal cavity through a vacuum pump 15 connected with an impurity gas removal hole 16 until the vacuum gauge 14 is seen to show that the vacuum degree in the coal cavity is stable within three minutes;
the specific operation of the fourth step is as follows: the impurity-removing gas hole 16 is connected with a gas pipe of an external high-pressure gas cylinder, the gas pipe of the external high-pressure gas cylinder is connected with a pressure sensor, the pressure sensor is connected with a pressure reducing valve through the gas pipe, the pressure reducing valve is connected with the high-pressure gas cylinder through the gas pipe, the isolation valve 6 is closed, the high-pressure gas cylinder is opened, gas is injected into the coal sample cavity 4 through the control pressure reducing valve, the pressure of the gas is controlled through the pressure sensor 17 of the coal cavity, so that the coal body can absorb the gas better, and when the pressure sensor 17 in the coal cavity is equal to the pressure sensor connected with the high-pressure gas cylinder in value, the gas absorption of the coal body is balanced.
The fifth step comprises the following specific operations: opening a first valve 10 and an isolation valve 6, connecting the first valve 10 with an external liquid nitrogen pipeline, connecting the external liquid nitrogen pipeline with an external liquid nitrogen source (such as a liquid nitrogen tank), adding liquid nitrogen into a liquid nitrogen cavity 9 through the liquid nitrogen pipeline and the first valve 10, enabling the liquid nitrogen to enter the inner cylinder 2 from bottom to top through a gap between the inner cylinder 2 and the bottom wall of the heat preservation cylinder 1, and enabling the liquid nitrogen to enter a coal cavity 4 after passing through meshes of a liquid inlet cavity 5 and a pressure-resistant metal mesh 3;
the staff observes the liquid nitrogen in the coal cavity 4 through the transparent heat-preserving cylinder 1 and the inner cylinder 2, and obtains the accurate liquid level of the liquid nitrogen according to the scales and the numbers on the scale three-dimensional plate 11; when the liquid level of the liquid nitrogen is about to reach the preset experimental height, the first valve 10 and the isolation valve 6 are closed, and the fifth step is stopped;
the sixth step comprises the following specific operations: the screw shaft body 8 on the inner cylinder cover 7 is rotated to apply axial pressure to the coal body in the inner cylinder, and the pressure sensor 13 connected with the screw shaft body 8 is used for controlling the preset value of the pressure applied by the coal body.
The above embodiments are only for illustrating the technical solution of the present invention, and it should be understood by those skilled in the art that although the present invention has been described in detail with reference to the above embodiments: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention, which is intended to be encompassed by the claims.
Claims (1)
1. The anti-reflection experimental method by using the pressurizable liquid nitrogen leaching coal body fracturing anti-reflection device is characterized by comprising the following steps of:
the pressurizable liquid nitrogen leaching coal body fracturing permeability-increasing device comprises a hollow cylindrical heat preservation cylinder, wherein the heat preservation cylinder is vertically arranged, both axial ends of the heat preservation cylinder are closed, the center of the top wall of the heat preservation cylinder is downwards connected with a hollow cylindrical inner cylinder, and a gap is reserved between the bottom end of the inner cylinder and the bottom wall of the heat preservation cylinder; the middle part of the inner cylinder is horizontally provided with a pressure-resistant metal net sheet, and the metal net sheet divides the inner cylinder into a coal cavity and a liquid inlet cavity;
an isolation valve is arranged in the middle of the inner cylinder, the isolation valve is positioned below the pressure-resistant metal mesh and adjacent to the pressure-resistant metal mesh, the isolation valve is used for separating the inner cylinder, a valve rod of the isolation valve extends out of the heat-preserving cylinder along the horizontal direction, and the valve rod is in sealing fit with the side wall of the heat-preserving cylinder; the diameter of the meshes of the pressure-resistant metal mesh is 3 mm-7 mm;
the top wall of the heat-insulating cylinder at the top end of the inner cylinder is in threaded connection with an inner cylinder cover, a threaded shaft body for increasing the axial pressure of the coal body is arranged on the inner cylinder cover, a pressure sensor is arranged at the lower end of the threaded shaft body, and a impurity-removing air hole is also formed in the inner cylinder cover; a liquid nitrogen cavity is formed between the inner cylinder and the side wall of the heat preservation cylinder, and a first valve for introducing liquid nitrogen is arranged on the top wall of the heat preservation cylinder at the top end of the liquid nitrogen cavity;
the heat preservation cylinder and the inner cylinder are both made of transparent materials, the outer surface of the side wall of the inner cylinder is connected with a scale three-dimensional plate made of transparent materials, horizontal scale lines are uniformly arranged at intervals from top to bottom on the scale three-dimensional plate, 1 millimeter is arranged between two adjacent horizontal scale lines from top to bottom, the 0 scale line is positioned at the metal mesh, and Arabic numerals which are used for indicating the height of liquid nitrogen and are used for indicating the height of liquid nitrogen are carved at the tail ends of the scale lines from the 0 scale line to the top by 1 centimeter; the lower end of the threaded shaft body for increasing the axial pressure of the coal body is provided with a pressure sensor; air holes are formed in two sides of the top of the liquid inlet cavity of the inner cylinder;
the anti-reflection experiment method comprises the following steps:
the first step is the detection of tightness;
the second step is to add the coal;
the third step is to remove impurity gas;
the fourth step is gas adsorption;
the fifth step is to add liquid nitrogen;
the sixth step is that the coal body is pressurized axially;
seventh, carrying out a crack development experiment of the coal body under a preset gas pressure condition and a liquid nitrogen liquid level condition, and carrying out an experiment record;
the second to seventh steps are one experimental cycle; the experimental plan comprises N groups of preset liquid nitrogen liquid level height values and coal pressure values, wherein N is a natural number greater than or equal to 1;
repeating the second to sixth steps by adopting a group of preset liquid nitrogen liquid level height values and gas pressure values in each experiment cycle until all experiment cycles corresponding to N groups of preset liquid nitrogen liquid level height values and coal pressure values in an experiment plan are completed;
the specific operation of the first step is as follows: closing the impurity-removing air hole, connecting the first valve with an air pipe of an external high-pressure nitrogen gas cylinder, and connecting the air pipe of the external high-pressure nitrogen gas cylinder with the external high-pressure nitrogen gas cylinder; the first valve and the isolation valve are opened, nitrogen is injected into the coal cavity through the high-pressure nitrogen cylinder and the first valve, and the nitrogen enters the liquid inlet cavity through a gap between the bottom end of the inner cylinder and the bottom wall of the heat preservation cylinder; when the pressure gauge shows that the pressure in the coal cavity and the liquid inlet cavity reaches a preset value, the first valve is closed; if the pressure reduction value is less than or equal to 0.01MPa after the pressure is maintained for 12 hours, continuing to carry out the second step; if the pressure reduction value is greater than 0.01MPa after the pressure is maintained for 12 hours, the sealing maintenance is required to be carried out on the pressurizable liquid nitrogen leaching coal body fracturing and anti-reflection device, and then the first step is carried out again;
the specific operation of the second step is as follows: opening the inner cylinder cover, putting the coal body into the coal body cavity, and then connecting the impurity-removing gas hole with an external vacuum pump;
the specific operation of the third step is as follows: closing the isolation valve, and pumping the impurity gas in the coal cavity through a vacuum pump connected with the impurity gas removal hole until the vacuum gauge (14) is seen to display that the vacuum degree in the coal cavity is kept stable within three minutes;
the specific operation of the fourth step is as follows: connecting the impurity-removing gas hole with a gas pipe of an external high-pressure gas cylinder, connecting the gas pipe of the external high-pressure gas cylinder with a pressure sensor, connecting the pressure sensor with a pressure reducing valve through the gas pipe, connecting the pressure reducing valve with the high-pressure gas cylinder through the gas pipe, closing a first valve and an isolating valve, opening the high-pressure gas cylinder, injecting gas into a gas cavity through a control pressure reducing valve, controlling the gas pressure in the gas cavity through a voltage sensor of the gas cavity, so that the gas is better adsorbed by the gas cavity, and balancing the gas adsorption by the gas when the values of the pressure sensor in the gas cavity and the pressure sensor connected with the high-pressure gas cylinder are equal;
the fifth step comprises the following specific operations: opening a first valve and an isolation valve, connecting the first valve with an external liquid nitrogen pipeline, connecting the external liquid nitrogen pipeline with an external liquid nitrogen source, adding liquid nitrogen into a liquid nitrogen cavity through the liquid nitrogen pipeline and the first valve, enabling the liquid nitrogen to enter the inner cylinder from bottom to top through a gap between the inner cylinder and the bottom wall of the heat preservation cylinder, and enabling the liquid nitrogen to enter a coal sample cavity after passing through a liquid inlet cavity and meshes of a pressure-resistant metal mesh;
a worker observes liquid nitrogen in the coal cavity through the transparent heat-preserving cylinder and the inner cylinder, and obtains the accurate liquid level of the liquid nitrogen according to the scales and the numbers on the scale three-dimensional plate; when the liquid level of the liquid nitrogen is about to reach the preset height of the experiment, closing the isolation valve, and stopping the second step;
the sixth step comprises the following specific operations: the screw shaft body on the inner cylinder cover is rotated to apply axial pressure to the coal body in the inner cylinder, and the pressure sensor connected with the screw shaft body is used for controlling the preset value of the pressure applied by the coal body.
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