CN114646535A - Liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and experiment method - Google Patents
Liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and experiment method Download PDFInfo
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Abstract
The invention belongs to the technical field of liquid nitrogen ultralow temperature phase change fracturing, and particularly relates to a liquid nitrogen ultralow temperature and phase change fracturing effect similar simulation experiment device and an experiment method, wherein the liquid nitrogen ultralow temperature and phase change fracturing effect similar simulation experiment device comprises a two-dimensional similar simulation experiment table, a liquid nitrogen supply system, a similar material mixing system, a stress monitoring system, a microseismic monitoring system, a drilling imaging system and an XTDIC monitoring system; the beneficial effects are that: the liquid nitrogen ultralow temperature and phase change fracturing effect similar simulation experiment device and the experiment method provided by the invention simulate the permeability increase of liquid nitrogen in the coal seam by utilizing physical similar simulation, observe the liquid nitrogen ultralow temperature and phase change fracturing effect and the displacement and deformation of the overlying rock stratum, monitor the stress change condition by the pressure sensor, and observe the fracture development and evolution rule by presetting a drill hole.
Description
Technical Field
The invention belongs to the technical field of liquid nitrogen ultralow temperature phase change fracturing, and particularly relates to a liquid nitrogen ultralow temperature and phase change fracturing effect similar simulation experiment device and an experiment method.
Background
Firstly, China has abundant coal resources, and the production and consumption quantity of coal also accounts for the front of all countries in the world. Coal is used as the basic energy of China, and the primary energy consumption of coal accounts for 56.8% in 2020. The coal bed gas content and the mining depth are closely related, and the coal bed gas content and the emission quantity are gradually increased along with the rapid increase of the mining depth. According to statistics, nearly half of the existing national key coal mines are high gas mines or gas outburst mines, and with the continuous improvement of mining level, the gas accidents of the coal mines are continuously caused by the increase of the development of burial towards deep areas. Secondly, coal is a natural geologic body and has a defect structure of microcracks, pores, low strength and the like. According to statistics, the high gas coal mine in China accounts for more than 37% of the mines in China, wherein 95% of the mined coal seam belongs to the low permeability coal seam, so how to improve the permeability of the low permeability coal seam is that the gas extraction in China is performedAnd one of the keys of gas disaster prevention and control, the micro-crack expansion and new crack initiation of the coal body can directly influence the permeability of the coal. In addition, the liquid nitrogen has no pollution to the environment, is easy to prepare and low in cost, has extremely low temperature (-196 ℃), and can weaken freezing damage of the coal body, expand primary microcracks and generate new fissures after the coal body is injected with the low-temperature liquid nitrogen to form a freeze-thaw dehiscence zone. In the limited space of the coal bed, the volume of the gasified liquid nitrogen rapidly expands to generate huge expansive force to crack the coal bed, and the temperature is 1m at 21 DEG C3The gasification volume of the liquid nitrogen expands about 696 times to form a gasification high-pressure cracking zone, and the high-pressure nitrogen can drive and replace coal seam gas in a partial pressure mode to promote gas desorption and seepage, particularly liquid nitrogen circulating freeze thawing and repeated freeze thawing cracking of the coal seam, so that the effect of improving the permeability of the coal seam is more remarkable, and meanwhile, the liquid nitrogen volatilizes and needs to absorb heat to cool the coal seam to a certain extent. Then, the gas is a main factor causing coal mine gas accidents and is also a strong greenhouse gas, and the damage to the ozone layer and the generated greenhouse effect of the gas respectively reach CO 27 times and 21 times. Compared with disasters, the gas is clean energy which can be utilized in coal seams, has wide development prospect, and the amount of shallow gas resources is about 36.8 trillion m when the burial depth of China is 2000m3And the mining value is obvious. Therefore, the coal and gas resources are safely and efficiently co-mined, gas disasters can be effectively prevented and controlled, air pollution is reduced, the gas is utilized as clean energy, and the purposes of mine safety production, environmental protection, new energy supply and the like can be achieved.
With the development of scientific technology, in order to solve the problem of insufficient technology in the prior coal seam permeability increase, coal seam gas is efficiently pre-pumped and utilized, gas accidents are prevented, the problem of environmental pollution is reduced, economic benefits are maximized, and the anhydrous fracturing technology using ultralow-temperature fluid such as liquid nitrogen as fracturing fluid is gradually paid attention. The Chinese invention patent CN201810527377.0 discloses an experimental device for monitoring the effect of a liquid nitrogen fracturing coal sample in real time; the Chinese invention patent CN202110344249.4 discloses an experimental device for testing the space-time evolution and mechanical parameters of liquid nitrogen immersed coal sample cracks; chinese invention patent CN202022500372.4 discloses an experimental device for observing thermal properties and structural damage of liquid nitrogen injected coal. At present, researches such as liquid nitrogen freeze thawing and liquid nitrogen injection are mostly carried out on occurrence coal samples through laboratory experiments, and certain effective basis and theoretical support can be provided for field application of liquid nitrogen to coal seam permeability-increasing gas drainage. However, most laboratory experiments can only observe the surface cracks, internal pores and mechanical properties of the coal sample before and after freezing and thawing of liquid nitrogen and injection of liquid nitrogen, and monitor the coal deformation and damage characteristics in the whole process of freezing and thawing of liquid nitrogen to a certain extent. At present, the equipment for the liquid nitrogen ultralow temperature and phase change fracturing coal bed is less in related equipment of similar simulation experiments on the effect of the liquid nitrogen ultralow temperature and phase change fracturing coal bed and the influence on the overburden stratum.
Aiming at the technical requirements, a simulation experiment device and an experiment method for similar effects of liquid nitrogen ultralow temperature and phase change cracking are needed to be provided.
Disclosure of Invention
The invention aims to provide a liquid nitrogen ultralow temperature and phase change fracturing effect similar simulation experiment device and an experiment method aiming at the problems in the background technology, so as to perfect the similar simulation of the liquid nitrogen ultralow temperature and phase change fracturing coal bed effect and the influence on an overlying strata.
In order to achieve the purpose, the invention adopts the technical scheme that:
liquid nitrogen ultralow temperature and phase change fracturing effect similar simulation experiment device and experiment method are characterized in that: the device comprises a two-dimensional analog simulation experiment table, a liquid nitrogen supply system, a similar material mixing system, a stress monitoring system, a microseismic monitoring system, a borehole imaging system and an XTDIC monitoring system.
Preferably, the two-dimensional simulation experiment table comprises an experiment table base 42, the experiment table base 42 is in an i shape, two similar experiment table supports 41 are welded on the experiment table base 42, the two similar experiment table supports 41 are respectively positioned at two ends of the experiment table base 42, the two similar experiment table supports 41 have a certain width, the lower ends of the two similar experiment table supports 41 are welded with the bottom cross beam 36, the upper ends of the two similar experiment table supports 41 are detachably connected with two baffles 8, the two baffles 8 are respectively and symmetrically arranged at the front side and the rear side of the similar experiment table supports 41, so that two of said similar bench supports 41, bottom cross-member 36 and two baffles 8 form an uncapped cubic space, pouring a coal seam 27 into the bottom of the cubic space, and pouring mixed overburden similar material 10 into the top of the coal seam 27; a plurality of support columns 35 are fixedly connected between the experiment table base 42 and the bottom cross beam 36.
Preferably, the two similar experiment table supports 41 are made of channel steel, the two similar experiment table supports 41 are provided with a plurality of support bolt holes 7, two ends of the two baffles 8 are respectively provided with baffle bolt holes 801, and the two baffles 8 are mounted between the two similar experiment table supports 41 through bolts and nuts 9.
Installing two baffle plates 8 between two similar experiment table supports 41, wherein the two baffle plates 8 are symmetrical front and back, the similar experiment table supports 41 have width, the two baffle plates 8, the similar experiment table supports 41 which are symmetrical left and right and the bottom cross beam 36 form an uncapped cubic space, overburden similar materials 10 are mixed and poured into the upper part of a coal seam 27, bolts penetrate through support bolt holes 7 of the similar experiment table supports 41 and baffle plate bolt holes 801 of the baffle plates 8, then nuts 9 are screwed, and the left similar experiment table supports 41 and the right similar experiment table supports 41 are simultaneously carried out; two baffles 8 are installed sequentially upward according to the thickness and final height of similar material 10 in the overburden during each compaction.
Preferably, the liquid nitrogen supply system comprises a self-pressurization liquid nitrogen tank 2, universal wheels 1 are installed at the bottom of the self-pressurization liquid nitrogen tank 2, an ultralow temperature heat-preservation pipe 6 is connected to the top of the self-pressurization liquid nitrogen tank 2, the other end of the ultralow temperature heat-preservation pipe 6 is connected with a coal seam pre-buried liquid nitrogen pipeline 39 through an ultralow temperature resistant butt joint valve 46, the middle of the coal seam pre-buried liquid nitrogen pipeline 39 is pre-buried in a coal seam 27, the tail end of the coal seam exposed by the coal seam pre-buried liquid nitrogen pipeline 39 is placed in a liquid nitrogen collection tank 25, a plurality of liquid nitrogen outflow ports 3901 are arranged on the coal seam pre-buried liquid nitrogen pipeline 39, a tank body valve 3 and a pressure gauge 4 are installed at the top of the self-pressurization liquid nitrogen tank 2, a liquid outlet valve 5 is installed on the ultralow temperature heat-preservation pipe 6, the liquid outlet valve 5 is close to the self-pressurization liquid nitrogen tank 2, and a liquid nitrogen stop valve 26 is installed on the coal seam pre-buried liquid nitrogen pipeline 39, the liquid nitrogen stop valve 26 is close to the liquid nitrogen collection tank 25.
Preferably, an ultralow temperature-resistant sealing ring is arranged at the joint of the ultralow temperature heat preservation pipe 6 and the ultralow temperature-resistant butt joint valve 46.
Opening a switch of a universal wheel 1 to push a self-pressurization liquid nitrogen tank 2 to a proper position, butting an ultra-low temperature heat preservation pipe 6 with an ultra-low temperature resistant butt joint valve 46, opening the ultra-low temperature resistant butt joint valve 46 to enable liquid nitrogen to pass through, opening a liquid nitrogen collecting tank 25 to put the end of a coal seam pre-buried liquid nitrogen pipeline 39 exposed out of the coal seam into the tank, opening a liquid nitrogen stop valve 26, then opening a tank body valve 3, then opening a liquid outlet valve 5, enabling the liquid nitrogen to flow into the liquid nitrogen collecting tank 25 from the self-pressurization liquid nitrogen tank 2 through a pressure gauge 4, through the liquid outlet valve 5, through the ultra-low temperature resistant heat preservation pipe 6, through the ultra-low temperature resistant butt joint valve 46 to reach the coal seam pre-buried liquid nitrogen pipeline 39, through the liquid nitrogen stop valve 26, closing the liquid nitrogen stop valve 26 at the moment, enabling the liquid nitrogen to flow into the coal seam from a liquid nitrogen outflow port 3901, and closing the ultra-low temperature resistant butt joint valve 46, the tank body valve 3 and the liquid outlet valve 5 when the reading number of the pressure gauge 4 is continuously and greatly increased, and moving the liquid nitrogen collection tank 25 to the ultralow temperature resisting butt joint valve 46, and detaching the ultralow temperature heat preservation pipe 6 to enable liquid nitrogen in the pipeline to flow into the liquid nitrogen collection tank 25.
The liquid nitrogen has extremely low temperature, firstly absorbs the heat of the coal bed to generate temperature stress so as to lead the coal bed to generate cracks, and the liquid nitrogen obtains the heat and changes the heat from a liquid state to a gas state to generate huge expansive force to further crack the coal bed.
Preferably, the similar material mixing system comprises a chassis 18, a chassis wheel 17 is mounted at the bottom of the chassis 18, a movable handrail 11 is connected to one side of the chassis 18 through a bearing, a rotating shaft 19 is connected to the top of the chassis 18 through a bearing, a similar material mixing chamber 13 is fixedly connected to the top of the rotating shaft 19, a stirrer 12 is mounted in the similar material mixing chamber 13, a motor 14 is mounted at the top of the chassis 18, the motor 14 is used for driving the rotating shaft 19, and the motor 14 is electrically connected with a controller 16 through a control wire 15.
Preferably, the stirrer 12 comprises a top plate 1203, a stirring head 1202 is fixedly connected to the middle of the lower end face of the top plate 1203, and a scraping sheet 1201 is fixedly connected to the edge of the lower end face of the top plate 1203.
Firstly, lifting up the stirrer 12 with the scraping sheet 1201 and the stirring head 1202, pouring similar materials mixed according to a certain proportion into the similar material mixing cavity 13, putting down the stirrer 12, the scraping sheet 1201 and the stirring head 1202, operating the controller 16 to enable the motor 14 to work through the control line 15, driving the rotating shaft 19 with the similar material mixing cavity 13 to also start rotating through the motor 14, stirring the similar materials through the stirring head 1202, adding a proper amount of water after uniformly stirring, continuously stirring through the stirring head 1202 while scraping the materials attached to the inner wall of the similar material mixing cavity 13 through the scraping sheet 1201 along with the rotation of the rotating shaft 19 and the similar material mixing cavity 13, controlling the motor 14 to stop working through the controller 16 after proper stirring so as to stop stirring, then lifting up the stirrer 12, the scraping sheet 1201 and the stirring head 1202, putting down the similar material mixing cavity 13 through the movable handrail 11, after the material is poured out, the movable handrail 11 is lifted and the similar material mixing chamber 13 is returned to its original position.
Preferably, the stress monitoring system comprises a bottom wireless pressure sensor 40 installed between the coal seam 27 and the bottom cross beam 36 and a plurality of wired pressure sensors C buried in the overburden similar material 10, the bottom wireless pressure sensor 40 and the wired pressure sensors C are connected with a pressure signal receiving processor 44 through a pressure signal transmission line 45, and the pressure signal receiving processor 44 is electrically connected with a pressure data display 43.
The pressure acquisition is divided into two modules, wherein one module is that the bottom wireless pressure sensor 40 at the bottom of the coal seam 27 receives and transmits pressure changes at various places caused by liquid nitrogen ultralow temperature and phase change induced cracking of the coal seam to the pressure signal receiving processor 44 for preprocessing, and reads the pressure changes on the pressure data display 43; when the overburden rock layer is constructed, the wired pressure sensor C is embedded into the overburden rock layer simulated by similar materials, the change of force in the overburden rock layer caused by liquid nitrogen ultralow temperature and phase change fracturing of the coal layer is received by the wired pressure sensor C, the change is transmitted to the pressure signal receiving processor 44 through the pressure signal transmission line 45 to be preprocessed, and the preprocessing is displayed on the pressure data display 43, so that the pressure change and redistribution rule in the whole coal layer and the overburden rock layer in the liquid nitrogen ultralow temperature and phase change process can be obtained.
Preferably, the microseismic monitoring system comprises a microseismic sensor A embedded in overburden similar material 10, the microseismic sensor A is electrically connected with a microseismic signal processor 28, and the microseismic signal processor 28 is connected with a display screen 30 through a first signal transmission line 29.
The microseismic sensor A receives signals generated by cracking of the coal bed and the overlying rock layer due to ultralow temperature of liquid nitrogen and phase change and transmits the signals to the microseismic signal processor 28 for processing, and a processing result is displayed on the display screen 30 through the first signal transmission line 29; the method comprises the steps of capturing a vibration signal generated by micro-fracture of a rock stratum caused by a pressure change process through a micro-seismic sensor A embedded in the overlying rock stratum, analyzing and processing the vibration signal, obtaining time, space and strength information such as time, position, magnitude of vibration, energy and the like of the rock stratum during fracture, and evaluating the stability of the overlying coal seam fractured by liquid nitrogen according to fusion and clustering of a large amount of micro-seismic event information.
Preferably, the borehole imaging system comprises a plurality of prefabricated boreholes B arranged in the overburden similar material 10, the prefabricated boreholes B are internally provided with borehole peepers 20, the borehole peepers 20 are connected with distance receptors 22 through second signal transmission lines 21, and the distance receptors 22 are connected with borehole imaging controllers 24 through distance measurement signal lines 23.
Preferably, the distance receptor 22 is connected with the distance measuring signal line 23 in a sliding manner, the distance measuring signal line 23 passes through the distance receptor 22, and fixed pulleys are arranged at the left lower part, the right lower part and the upper part of the distance receptor 22.
Set up through drilling imaging controller 24, drilling peep at appearance 20 and connect foremost and prefabricated drilling B top parallel and level, select to begin to gather on drilling imaging controller 24, peep at the drilling appearance 20 and slowly stretch into prefabricated drilling B at the uniform velocity, the picture and the video of surveying transmit to drilling imaging controller 24 through second signal transmission line 21 and range finding signal line 23, distance receptor 22 judges through the length of pulley perception range finding signal line 23 that drilling peeps at appearance 20 and stretches into the distance, drilling imaging controller 24 peeps at the picture of appearance 20 transmission and the distance of distance receptor 22 feedback through the drilling and generates continuous picture.
Preferably, the XTDIC system comprises an XTDIC observation body 37 and a compensation light source 34, a high-definition camera 38 is mounted on the top of the XTDIC observation body 37, the high-definition camera 38 is electrically connected with an XTDIC system controller 33, the XTDIC system controller 33 is connected with an XTDIC system analysis processor 31 through a connection line 32, and the XTDIC system analysis processor 31 is electrically connected with a display screen 30.
Preferably, the compensation light source 34 comprises a tripod 3401, a light source is mounted on the top of the tripod 3401, the front end of the light source is a light source searchlighting end 3404, the rear end of the light source is a light source control end 3403, the light source control end 3403 is connected with a high-definition camera 38 through a power transmission line 3402, and an angle adjusting knob 3405, a height adjusting knob 3406 and a top fixing knob 3407 are arranged on the tripod 3401; the height of the tripod 3401 is adjusted by the height adjusting knob 3406, the light source parts such as the light source control end 3403, the light source searchlighting end 3404, the angle adjusting knob 3405 and the like are fixed on the tripod 3401 by the top end fixing knob 3407, and the irradiation angle of the light source at the light source searchlighting end 3404 is adjusted by the angle adjusting knob 3405.
Before observation, speckle threshold processing is carried out on the surfaces of the coal seam 27 and the overburden similar material 10, all the parts are connected, the display screen 30, the XTDIC system analysis processor 31 and the XTDIC system controller 33 are started, software on the display screen 30 controls the XTDIC system analysis processor 31, then the high-definition camera 38 is started through the XTDIC system controller 33, the compensation light source 34 is started, the light intensity of the light source irradiating end 3404 on the coal seam 27 and the overburden similar material 10 is adjusted at the light source control end 3403, after the intensity of an observation picture on the display screen 30 is proper, the light source is stopped to be adjusted, and the original position calibration is carried out before the phase change fracturing of the coal seam is not started; the high definition camera 38 observes the signal and transmits it to the XTDIC system controller 33, then to the XTDIC system analysis processor 31 through the connection line 32, and finally to the display 30 on the XTDIC software.
Compared with the defects and shortcomings of the prior art, the invention has the following beneficial effects:
(1) the liquid nitrogen ultralow temperature and the phase change fracturing coal bed are not applied on site, and the liquid nitrogen provides effective basis and theory for the coal bed permeability-increasing gas extraction field application, and still aims to be further researched. Meanwhile, the technical means of observing structural damage changes before and after the liquid nitrogen acts on the coal body and in the acting process in the laboratory is gradually improved, and the device provided by the invention improves the technology and method for effectively monitoring the liquid nitrogen ultralow temperature and phase change induced cracking coal bed effect in the laboratory.
(2) Due to the complex occurrence condition of the coal bed, the natural coal bed contains water and has different temperatures due to reasons such as buried depth, surrounding rock permeability and the like, and the liquid nitrogen freezes and melts the coal body under the condition, so that the cracking and permeability increasing and gas displacement effects are more obvious, and the high-efficiency gas extraction is more facilitated. The method simulates the occurrence condition of the coal bed in a laboratory, performs liquid nitrogen permeability increase on the coal bed, observes the effect of the liquid nitrogen ultralow temperature and phase change fracturing coal bed and the influence on the overburden stratum, and provides effective basis and theory for field application of permeability increase gas drainage of the liquid nitrogen ultralow temperature and phase change fracturing coal bed.
(3) The device provided by the invention simulates the permeability increase of the liquid nitrogen of the coal bed, observes the ultralow temperature and phase change cracking effect of the liquid nitrogen and the displacement and deformation of the overburden rock by utilizing physical simulation, monitors the stress change condition by a pressure sensor, and observes the crack development and evolution rule by presetting a drill hole.
Drawings
For a more clear understanding of the present invention, the present disclosure is further described by reference to the drawings and illustrative embodiments, which are provided for illustration and are not to be construed as limiting the disclosure.
FIG. 1 is a system diagram of a liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment of the present invention;
FIG. 2 is a schematic view of the structure of the stirrer according to the present invention;
FIG. 3 is a schematic structural view of a wired pressure sensor pre-buried in an overburden according to the present invention;
FIG. 4 is a schematic view of the structure of the baffle plate of the present invention;
FIG. 5 is a schematic view of the structure of a microseismic sensor of the present invention;
FIG. 6 is a schematic diagram of the XTDIC observation system of the present invention;
fig. 7 is a partially enlarged view of a coal seam embedded liquid nitrogen pipeline in the invention.
Shown in the figure: the device comprises universal wheels 1, a self-pressurization liquid nitrogen tank 2, a tank body valve 3, a pressure gauge 4, a liquid outlet valve 5, an ultralow-temperature heat preservation pipe 6, support bolt holes 7, a baffle plate 8, baffle plate bolt holes 801, nuts 9, overburden similar materials 10, a movable handrail 11, a stirrer 12, a scraping sheet 1201, a stirring head 1202, a top plate 1203, a similar material mixing cavity 13, a motor 14, a control line 15, a controller 16, a chassis wheel 17, a chassis 18, a rotating shaft 19, a borehole peeping instrument 20, a transmission line 21, a distance receptor 22, a distance measuring signal line 23, a borehole imaging controller 24, a liquid nitrogen collection tank 25, a liquid nitrogen stop valve 26, a coal seam 27, a microseismic signal processor 28, a signal transmission line 29, a display screen 30, an XTDIC system analysis processor 31, a connecting line 32, an XTDIC system controller 33, a compensation light source 34, a tripod 3401, a power transmission line 3402, a light source control end 3403, a light source searchlighting end 3404, a light source, The device comprises an angle adjusting knob 3405, a height adjusting knob 3406, a top end fixing knob 3407, a support column 35, a bottom cross beam 36, an XTDIC observation main body 37, a high-definition camera 38, a coal seam pre-buried liquid nitrogen pipeline 39, a liquid nitrogen outflow port 3901, a bottom wireless pressure sensor 40, a similar experiment table support 41, an experiment table base 42, a pressure data display 43, a pressure signal receiving processor 44, a pressure signal transmission line 45 and an ultralow temperature resistant butt joint valve 46.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
Liquid nitrogen ultralow temperature and phase change fracturing effect similar simulation experiment device and experiment method are characterized in that: the two-dimensional simulation experiment table comprises a liquid nitrogen supply system, a similar material mixing system, a stress monitoring system, a microseismic monitoring system, a borehole imaging system and an XTDIC monitoring system.
The two-dimensional analog simulation experiment table comprises an experiment table base 42, wherein the experiment table base 42 is I-shaped, the experiment table base 42 is welded with two similar experiment table supports 41, the two similar experiment table supports 41 are respectively positioned at two ends of the experiment table base 42, the two similar experiment table supports 41 have a certain width, the lower ends of the two similar experiment table supports 41 are welded with the bottom cross beam 36, the upper ends of the two similar experiment table supports 41 are detachably connected with two baffle plates 8, the two baffle plates 8 are respectively symmetrically arranged at the front side and the rear side of the similar experiment table supports 41, so that two of said similar laboratory bench supports 41, bottom cross-member 36 and two baffle-panels 8 form an uncapped cubic space, pouring a coal seam 27 into the bottom of the cubic space, and pouring mixed overburden similar material 10 into the top of the coal seam 27; a plurality of support columns 35 are fixedly connected between the experiment table base 42 and the bottom cross beam 36. The two similar experiment table supports 41 are made of channel steel, a plurality of support bolt holes 7 are formed in the two similar experiment table supports 41, baffle bolt holes 801 are formed in two ends of the two baffles 8 respectively, and the two baffles 8 are mounted between the two similar experiment table supports 41 through bolts and nuts 9.
The liquid nitrogen supply system comprises a self-pressurization liquid nitrogen tank 2, universal wheels 1 are installed at the bottom of the self-pressurization liquid nitrogen tank 2, the top of the self-pressurization liquid nitrogen tank 2 is connected with an ultra-low temperature heat preservation pipe 6, the other end of the ultra-low temperature heat preservation pipe 6 is connected with a coal seam pre-buried liquid nitrogen pipeline 39 through an ultra-low temperature resistant butt joint valve 46, the middle part of the coal seam pre-buried liquid nitrogen pipeline 39 is pre-buried in the coal seam, the tail end of the coal seam pre-buried liquid nitrogen pipeline 39 exposed out of the coal seam is placed in the liquid nitrogen collecting tank 25, a plurality of liquid nitrogen outlets 3901 are arranged on the coal seam pre-buried liquid nitrogen pipeline 39, a tank body valve 3 and a pressure gauge 4 are arranged at the top of the self-pressurization liquid nitrogen tank 2, the ultra-low temperature heat preservation pipe 6 is provided with a liquid outlet valve 5, the liquid outlet valve 5 is arranged close to the self-pressurization liquid nitrogen tank 2, and a liquid nitrogen stop valve 26 is installed on the coal seam pre-buried liquid nitrogen pipeline 39, and the liquid nitrogen stop valve 26 is close to the liquid nitrogen collecting tank 25. The junction of the ultra-low temperature insulation pipe 6 and the ultra-low temperature resistant butt joint valve 46 is provided with an ultra-low temperature resistant sealing ring.
The liquid nitrogen has extremely low temperature, firstly absorbs the heat of the coal bed to generate temperature stress so as to lead the coal bed to generate cracks, and the liquid nitrogen obtains the heat and changes the heat from a liquid state to a gas state to generate huge expansive force to further crack the coal bed.
The similar material mixing system comprises a chassis 18, a chassis wheel 17 is mounted at the bottom of the chassis 18, a movable handrail 11 is connected to one side of the chassis 18 through a bearing, a rotating shaft 19 is connected to the top of the chassis 18 through a bearing, a similar material mixing cavity 13 is fixedly connected to the top of the rotating shaft 19, a stirrer 12 is mounted in the similar material mixing cavity 13, a motor 14 is mounted at the top of the chassis 18, the motor 14 is used for driving the rotating shaft 19, and the motor 14 is electrically connected with a controller 16 through a control wire 15. The stirrer 12 comprises a top plate 1203, a stirring head 1202 is fixedly connected to the middle of the lower end face of the top plate 1203, and a scraping sheet 1201 is fixedly connected to the edge of the lower end face of the top plate 1203.
The stress monitoring system comprises a bottom wireless pressure sensor 40 installed between the coal seam 27 and the bottom cross beam 36 and a plurality of wired pressure sensors C buried in the overburden similar material 10, wherein the bottom wireless pressure sensor 40 and the wired pressure sensors C are connected with a pressure signal receiving processor 44 through a pressure signal transmission line 45, and the pressure signal receiving processor 44 is electrically connected with a pressure data display 43.
The pressure acquisition is divided into two modules, wherein one module is that the bottom wireless pressure sensor 40 at the bottom of the coal seam 27 receives and transmits pressure changes at various places caused by liquid nitrogen ultralow temperature and phase change induced cracking of the coal seam to the pressure signal receiving processor 44 for preprocessing, and reads the pressure changes on the pressure data display 43; when the overburden rock layer is constructed, the wired pressure sensor C is embedded into the overburden rock layer simulated by similar materials, the change of force in the overburden rock layer caused by liquid nitrogen ultralow temperature and phase change fracturing of the coal layer is received by the wired pressure sensor C, the change is transmitted to the pressure signal receiving processor 44 through the pressure signal transmission line 45 to be preprocessed, and the preprocessing is displayed on the pressure data display 43, so that the pressure change and redistribution rule in the whole coal layer and the overburden rock layer in the liquid nitrogen ultralow temperature and phase change process can be obtained.
The microseismic monitoring system comprises a microseismic sensor A embedded in overburden similar materials 10, the microseismic sensor A is electrically connected with a microseismic signal processor 28, and the microseismic signal processor 28 is connected with a display screen 30 through a first signal transmission line 29.
The microseismic sensor A receives signals generated by cracking of the coal bed and the overlying rock layer due to ultralow temperature of liquid nitrogen and phase change and transmits the signals to the microseismic signal processor 28 for processing, and a processing result is displayed on the display screen 30 through the first signal transmission line 29; the method comprises the steps of capturing a vibration signal generated by micro-fracture of a rock stratum caused by a pressure change process through a micro-seismic sensor A embedded in the overlying rock stratum, analyzing and processing the vibration signal, obtaining time, space and strength information such as time, position, magnitude of vibration, energy and the like of the rock stratum during fracture, and evaluating the stability of the overlying coal seam fractured by liquid nitrogen according to fusion and clustering of a large amount of micro-seismic event information.
The drilling imaging system comprises a plurality of prefabricated drill holes B arranged in the similar material 10 of the overlying strata, drilling peeping instruments 20 are installed in the prefabricated drill holes B, the drilling peeping instruments 20 are connected with distance receptors 22 through second signal transmission lines 21, and the distance receptors 22 are connected with a drilling imaging controller 24 through distance measuring signal lines 23. The distance sensor 22 is connected with the distance measuring signal line 23 in a sliding mode, the distance measuring signal line 23 penetrates through the distance sensor 22, fixed pulleys are arranged on the left lower portion and the right lower portion of the distance sensor, and fixed pulleys are arranged on the upper portion of the middle of the distance sensor.
The XTDIC system includes XTDIC observation main part 37 and compensation light source 34, high definition digtal camera 38 is installed at XTDIC observation main part 37 top, high definition digtal camera 38 electric connection has XTDIC system control ware 33, XTDIC system control ware 33 is connected with XTDIC system analysis treater 31 through connecting wire 32, XTDIC system analysis treater 31 electric connection has display screen 30. The compensation light source 34 comprises a tripod 3401, a light source is mounted at the top of the tripod 3401, the front end of the light source is a light source searchlighting end 3404, the rear end of the light source is a light source control end 3403, the light source control end 3403 is connected with a high-definition camera 38 through a power transmission line 3402, and an angle adjusting knob 3405, a height adjusting knob 3406 and a top fixing knob 3407 are arranged on the tripod 3401; the height of the tripod 3401 is adjusted by the height adjusting knob 3406, the light source parts such as the light source control end 3403, the light source searchlighting end 3404, the angle adjusting knob 3405 and the like are fixed on the tripod 3401 by the top end fixing knob 3407, and the irradiation angle of the light source at the light source searchlighting end 3404 is adjusted by the angle adjusting knob 3405.
Example 2
The working process of the invention is as follows:
firstly, two-dimensional similar simulation experiment table is assembled, bolts penetrate through support bolt holes 7 of a similar experiment table support 41 and baffle bolt holes 801 of baffles 8, nuts 9 are screwed, the left similar experiment table support 41 and the right similar experiment table support 41 are simultaneously screwed, the baffles 8 are installed on the similar experiment table support 41, the two baffles 8 are symmetrical front and back, meanwhile, the similar experiment table support 41 has a width, the two baffles 8, the similar experiment table support 41 and the bottom cross beam 36 which are symmetrical left and right, form an unsealed cubic space, the bottom wireless pressure sensors 40 are sequentially placed in series on the bottom cross beam 36 at the lowest layer, A4 paper is laid on the bottom wireless pressure sensors 40 to prevent upper layer materials from falling from gaps, coal seams 27 are laid on the bottom wireless pressure sensors, and coal seam pre-buried liquid nitrogen pipelines 39 are buried in the coal seams 27.
Secondly, preparing similar simulation materials, weighing sand, gypsum and whiting powder of each layer of the overburden according to the designed similarity ratio, lifting 1201 the stirrer 12 with the scraping sheet and 1202 stirring head as shown in figure 2, pouring the similar materials mixed according to the proportion into 1 similar material mixing cavity 3, putting down the stirrer 12, 1201 scraping sheet and 1202 stirring head, operating the controller 16 to enable the motor 14 to start working through the control line 15, driving the rotating shaft 19 with the motor 14 to start rotating with the similar material mixing cavity 13, stirring the similar materials by the stirring head 1202, adding a proper amount of water after uniform stirring, continuously stirring by the stirring head 1202, scraping the materials 1201 attached to the inner wall of the similar material mixing cavity 13 to scrape down the materials attached to the inner wall of the similar material mixing cavity 13, controlling the motor 14 to stop stirring through the controller 16 after proper stirring is achieved, lifting the stirrer 12, the scraping plate 1201 and the stirring head 1202, putting down the similar material mixing cavity 13 through the movable handrail 11, pouring the materials in the similar material mixing cavity 13 into a cubic space which is not covered by the two baffles 8 on the coal seam 27, the similar experiment table supports 41 and the bottom cross beam 36 which are bilaterally symmetrical, leveling and compacting through a tool, dividing and jointing the materials in the direction vertical to the baffles 8 after compacting to reach about the lower layer, then scattering a mica sheet and compacting, continuously paving the upper layer of materials, embedding the A, C sensor into an overlying rock stratum in the paving process according to the position shown in the figure 1, embedding the sensor C into the sensor C shown in figure 3, taking out a preset drill hole of the round pipe after the round pipe is embedded and built in advance in the building process to form the sensor B, and airing the similar rock stratum for the next experiment.
Then, observing the prefabricated drill hole B which is not affected by liquid nitrogen cracking, sequentially connecting a drilling peep device 20, a transmission line 21, a distance receptor 22, a distance measuring signal line 23 and a drilling imaging controller 24, turning on a switch of the drilling imaging controller 24 to enable a drilling imaging system to start working, enabling the foremost end of the connection of the drilling peep device 20 to be flush with the top end of the prefabricated drill hole B, selecting to start acquisition on the drilling imaging controller 24, slowly and uniformly extending the drilling peep device 20 into the prefabricated drill hole B, transmitting detected pictures and videos to the drilling imaging controller 24 through the transmission line 21 and the distance measuring signal line 23, enabling the distance receptor 22 to sense the length of the distance measuring signal line 23 through a pulley to judge the extending distance of the drilling peep device 20, enabling the drilling imaging controller 24 to generate continuous pictures through the pictures transmitted by the drilling peep device 20 and the distance fed back by the distance receptor 22, the system is temporarily shut down after acquisition is complete.
Then, setting is performed before the XTDIC system observation, speckle threshold processing is performed on the surfaces of the coal seam and the overlying rock stratum, all the parts are connected, as shown in fig. 6, the display screen 30, the XTDIC system analysis processor 31 and the XTDIC system controller 33 are started, the XTDIC system analysis processor 31 is controlled through software on the display screen 30, the high-definition camera 38 is started through the XTDIC system controller 33, the compensation light source 34 is started, the illumination intensity of the light source probing end 3404 on the similar rock stratum and the coal seam is adjusted through the light source control end 3403, after the illumination intensity of an observation picture on the display screen 30 is appropriate, the light source adjustment is stopped, the original position calibration is performed before the phase change fracturing of the coal seam is not started, and then the XTDIC monitoring system is kept stable to ensure that the position cannot move.
Further, the stress monitoring system is operated, as shown in fig. 1, by connecting the pressure signal transmission line 45 to the pressure signal receiving processor 44; the bottom wireless pressure sensor 40 transmits the signal to the pressure signal receiving processor 44 by wireless propagation; the pressure data display 43 is connected to the pressure signal receiving processor 44 and is turned on, and the data should be smooth when the fracturing is not initiated.
Finally, the microseismic monitoring system is operated, and all parts are installed and connected as shown in figure 1; as shown in fig. 5, the microseismic sensor a is connected with the microseismic signal processor 28 by a signal wire, the microseismic signal processor 28 and the display screen 30 are turned on, and the received data is null when cracking does not start.
After each observation system is started, as shown in fig. 1 and 7, a switch of a universal wheel 1 is opened to push a self-pressurization liquid nitrogen tank 2 to be at a proper position, an ultralow temperature heat-preservation pipe 6 is connected with an ultralow temperature-resistant butt joint valve 46, the ultralow temperature-resistant butt joint valve 46 is opened to enable liquid nitrogen to pass through, a liquid nitrogen collection tank 25 is opened, the tail end of a coal seam pre-buried liquid nitrogen pipeline 39 exposed out of a coal seam is placed into the tank, a liquid nitrogen stop valve 26 is opened, a tank body valve 3 is opened, a liquid outlet valve 5 is opened, liquid nitrogen passes through the ultralow temperature heat-preservation pipe 6 from the liquid outlet valve 5 through the ultralow temperature-resistant butt joint valve 46 from the self-pressurization liquid nitrogen tank 2 through a pressure gauge 4 and then reaches the coal seam pre-buried liquid nitrogen pipeline 39, the liquid nitrogen stop valve 26 flows into the liquid nitrogen collection tank 25, the liquid nitrogen stop valve 26 is closed at the moment, and the liquid nitrogen flows into the coal seam from a liquid nitrogen outflow port 3901; when the indication number of the pressure gauge 4 is continuously and greatly increased, the ultralow temperature resisting butt joint valve 46, the tank body valve 3 and the liquid outlet valve 5 are closed, the liquid nitrogen collecting tank 25 is moved to the ultralow temperature resisting butt joint valve 46, the ultralow temperature heat preservation pipe 6 is detached, and liquid nitrogen in the pipeline flows into the liquid nitrogen collecting tank 25.
Carrying out continuous observation, stopping the acquisition work of the three systems of the stress monitoring system, the microseismic monitoring system and the XTDIC monitoring system after the data of the XTDIC monitoring system and the stress monitoring system are stable, repeating the drilling imaging observation of the prefabricated drill hole B, opening a switch of a drilling imaging controller 24 to enable the drilling imaging system to start working, connecting the most front end of a drilling peep instrument 20 with the top end of the prefabricated drill hole B, selecting to start acquisition on the drilling imaging controller 24, slowly and uniformly extending the drilling peep instrument 20 into the prefabricated drill hole B, transmitting the detected pictures and videos to the drilling imaging controller 24 through a transmission line 21 and a distance measuring signal line 23, judging the extending distance of the drilling peep instrument 20 through the length of the distance measuring signal line 23 sensed by a distance sensor 22 through a pulley, generating continuous pictures through the pictures transmitted by the drilling peep instrument 20 and the distance fed back by the distance sensor 22 by the drilling imaging controller 24, and (3) comparing the drilling form before fracturing, and observing the influence effect and rule of the ultra-low temperature of the liquid nitrogen and the phase change fracturing coal bed on the internal fracture of the overburden.
The experimental device can realize two-dimensional similar simulation of the liquid nitrogen ultralow temperature and phase change fractured coal bed through the process, and can simultaneously test the temperature stress fractured coal bed generated by the liquid nitrogen ultralow temperature action and the huge expansive force fractured coal bed generated by liquid nitrogen phase change from multiple aspects of integral stress, overburden stress, surface stress and deformation, fracture times, position and energy, borehole deformation and internal fracture development.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. Liquid nitrogen ultralow temperature and phase change fracturing effect similar simulation experiment device and experiment method are characterized in that: the device comprises a two-dimensional analog simulation experiment table, a liquid nitrogen supply system, an analog material mixing system, a stress monitoring system, a microseismic monitoring system, a borehole imaging system and an XTDIC monitoring system.
2. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 1 are characterized in that: the two-dimensional similar simulation experiment table comprises an experiment table base (42), wherein the experiment table base (42) is I-shaped, two similar experiment table supports (41) are welded on the experiment table base (42), the two similar experiment table supports (41) are respectively positioned at two ends of the experiment table base (42), the two similar experiment table supports (41) have a certain width, a bottom cross beam (36) is welded at the lower end of the two similar experiment table supports (41), two baffles (8) are detachably connected at the upper end of the two similar experiment table supports (41), the two baffles (8) are respectively symmetrically arranged at the front side and the rear side of the similar experiment table supports (41), so that the two similar experiment table supports (41), the bottom cross beam (36) and the two baffles (8) form an unsealed cubic space, and a coal seam (27) is poured into the bottom of the cubic space, pouring mixed overburden-like material (10) into the top of the coal seam (27); a plurality of supporting columns (35) are fixedly connected between the experiment table base (42) and the bottom cross beam (36).
3. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 2 are characterized in that: the liquid nitrogen supply system comprises a self-pressurization liquid nitrogen tank (2), universal wheels (1) are installed at the bottom of the self-pressurization liquid nitrogen tank (2), the top of the self-pressurization liquid nitrogen tank (2) is connected with an ultra-low temperature heat preservation pipe (6), the other end of the ultra-low temperature heat preservation pipe (6) is connected with a coal seam pre-embedded liquid nitrogen pipeline (39) through an ultra-low temperature resistant butt joint valve (46), the middle part of the coal seam pre-embedded liquid nitrogen pipeline (39) is pre-embedded in a coal seam (27), the end of the coal seam pre-embedded liquid nitrogen pipeline (39) exposed out of the coal seam is placed into a liquid nitrogen collection tank (25), a plurality of liquid nitrogen outflow ports (3901) are arranged on the coal seam pre-embedded liquid nitrogen pipeline (39), a tank body valve (3) and a pressure gauge (4) are installed at the top of the self-pressurization liquid nitrogen tank (2), a liquid outlet valve (5) is installed on the ultra-low temperature heat preservation pipe (6) and is close to the self-pressurization liquid nitrogen tank (2), and a liquid nitrogen stop valve (26) is installed on the coal seam pre-buried liquid nitrogen pipeline (39), and the liquid nitrogen stop valve (26) is close to the liquid nitrogen collecting tank (25).
4. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 1 are characterized in that: the similar material mixing system comprises a chassis (18), a chassis wheel (17) is installed at the bottom of the chassis (18), a movable handrail (11) is connected to one side of the chassis (18) through a bearing, a rotating shaft (19) is connected to the top of the chassis (18) through a bearing, a similar material mixing cavity (13) is fixedly connected to the top of the rotating shaft (19), a stirrer (12) is installed in the similar material mixing cavity (13), a motor (14) is installed at the top of the chassis (18), the motor (14) is used for driving the rotating shaft (19), and the motor (14) is electrically connected with a controller (16) through a control line (15).
5. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 2 are characterized in that: the stress monitoring system comprises a bottom wireless pressure sensor (40) installed between a coal seam (27) and a bottom cross beam (36) and a plurality of wired pressure sensors (C) buried in overburden similar materials (10), wherein the bottom wireless pressure sensor (40) and the wired pressure sensors (C) are connected with a pressure signal receiving processor (44) through pressure signal transmission lines (45), and the pressure signal receiving processor (44) is electrically connected with a pressure data display (43).
6. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 2 are characterized in that: the microseismic monitoring system comprises a microseismic sensor (A) embedded in an overburden similar material (10), the microseismic sensor (A) is electrically connected with a microseismic signal processor (28), and the microseismic signal processor (28) is connected with a display screen (30) through a first signal transmission line (29).
7. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 1 are characterized in that: the drilling imaging system comprises a plurality of prefabricated drill holes (B) arranged in overburden similar materials (10), drilling peeping instruments (20) are installed in the prefabricated drill holes (B), the drilling peeping instruments (20) are connected with distance receptors (22) through second signal transmission lines (21), and the distance receptors (22) are connected with a drilling imaging controller (24) through ranging signal lines (23).
8. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 7 are characterized in that: the distance sensor (22) is connected with the distance measuring signal line (23) in a sliding mode, the distance measuring signal line (23) penetrates through the distance sensor (22), fixed pulleys are arranged on the left lower portion, the right lower portion and the middle upper portion of the distance sensor (22).
9. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 1 are characterized in that: the XTDIC system includes XTDIC observation main part (37) and compensation light source (34), high definition digtal camera (38) are installed at XTDIC observation main part (37) top, high definition digtal camera (38) electric connection has XTDIC system control ware (33), XTDIC system control ware (33) are connected with XTDIC system analysis treater (31) through connecting wire (32), XTDIC system analysis treater (31) electric connection has display screen (30).
10. The liquid nitrogen ultralow temperature and phase change cracking effect similar simulation experiment device and the experiment method according to claim 9 are characterized in that: the compensation light source (34) comprises a tripod (3401), a light source is installed at the top of the tripod (3401), the front end of the light source is a light source searchlighting end (3404), the rear end of the light source is a light source control end (3403), the light source control end (3403) is connected with a high-definition camera (38) through a power transmission line (3402), and an angle regulation knob (3405), a height adjustment knob (3406) and a top end fixing knob (3407) are arranged on the tripod (3401).
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115452596A (en) * | 2022-10-06 | 2022-12-09 | 中国矿业大学 | Liquid CO 2 Cold-leaching fracturing coal body simulation test system and method |
| CN118030005A (en) * | 2024-04-11 | 2024-05-14 | 四川泓腾能源集团有限公司 | Liquid nitrogen fracturing device and use method |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115452596A (en) * | 2022-10-06 | 2022-12-09 | 中国矿业大学 | Liquid CO 2 Cold-leaching fracturing coal body simulation test system and method |
| CN115452596B (en) * | 2022-10-06 | 2023-09-22 | 中国矿业大学 | Liquid CO 2 Cold leaching fracturing coal body simulation test system and method |
| CN118030005A (en) * | 2024-04-11 | 2024-05-14 | 四川泓腾能源集团有限公司 | Liquid nitrogen fracturing device and use method |
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