CN201794583U - Well completion evaluation experiment device for coal bed methane cave - Google Patents
Well completion evaluation experiment device for coal bed methane cave Download PDFInfo
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- CN201794583U CN201794583U CN2010205077312U CN201020507731U CN201794583U CN 201794583 U CN201794583 U CN 201794583U CN 2010205077312 U CN2010205077312 U CN 2010205077312U CN 201020507731 U CN201020507731 U CN 201020507731U CN 201794583 U CN201794583 U CN 201794583U
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Abstract
The utility model discloses a well completion evaluation experiment device for a coal bed methane cave. The device comprises a square coal rock model arranged in a framework, the bottom surface of the coal rock model is provided with an upwards extended simulation shaft, the top surface of the coal rock model is provided with a plurality of downwards extended pressure testing holes, the outer side of the coal rock model is provided with a sealed rubber sleeve, pressing plates are fixedly arranged on the outer side of the rubber sleeve and six lateral surfaces of the corresponding coal rock model, through holes are formed on the upper and lower pressing plates and the rubber sleeve corresponding to the simulation shaft and the pressure testing holes, and a pressure testing pipe with a pressure sensor is arranged in each pressure testing hole; three servo pressurization oil cylinders are arranged in three directions of the space of the outer side of the coal rock model; and a communicating device is hermetically arranged on the lower pressing plate and conducted with the simulation shaft, the upper part of the communicating device is provided with an air inlet pipe, a water inlet pipe and a pressure testing pipe with a pressure sensor, the lower part of the communicating device is provided with an electric ball valve, the lower end of the electric ball valve is connected with a pressure release pipe, and the bottom of the pressure release pipe is correspondingly provided with a coal dust collecting trough.
Description
Technical Field
The utility model relates to a well completion simulation experiment system especially relates to a coal bed gas cave well completion evaluation experimental apparatus.
Background
In 1986, Meridian oil company began to use open hole cave completion technology in san Hui's basin of America to collapse a target coal bed to enlarge a borehole to form a cave, the coal bed gas yield of a coal bed gas well after cave completion is 3-20 times that of hydraulic fracturing after perforation completion, the cost is lower than that of large-scale hydraulic fracturing, and more than 4000 coal bed gas wells in the san Hui's basin have been obtained so far, wherein 1/3 is used for cave completion, and the cumulative gas yield of cave completion accounts for 76% of the gas yield of the whole basin.
Compared with the coal bed gas cave well completion in the United states, due to the reasons of equipment and cognition, the coal bed gas cave well completion in China does not really realize bottom hole pressure excitation or stress fluctuation inside a coal bed, microcracks at the far end of a cave are not influenced by the action of periodical tensile and shearing force at all, and therefore the final effect is not ideal. Therefore, deep research needs to be carried out on the aspects of coal bed methane cave well completion yield increasing mechanism, cave making technology and the like so as to form the coal bed methane cave well completion theory and technology with independent intellectual property rights in China.
A coal bed gas well on-site cave completion method is a coal bed gas well dynamic injection/discharge cave making process, air or a mixture of air and water is injected into a shaft of a coal bed gas well within 1-6 hours at a discharge capacity of 43.5-56.6 cubic meters per minute to enable the pressure of a well mouth to reach 10Mpa, then a ground hydraulic valve is suddenly opened to quickly unload the pressure inside the shaft, a coal bed on the wall surface of the shaft is stimulated to collapse to enlarge the shaft, the processes of injecting pressure and discharging pressure relief are repeated until a stable cave is generated in the shaft, the exposed area of the coal bed is enlarged after the successful completion, the flow conductivity of a stratum is increased, tensile cracks and induced shear cracks are generated in the processes of injecting and suppressing high-pressure fluid, the shaft and a reservoir which is not damaged can be effectively communicated, self-supporting cracks in multiple directions are generated, and the cracks which are not communicated in the reservoir before are penetrated, thereby greatly improving the permeability of the reservoir around the well hole and achieving the purpose of increasing the yield.
However, because the cost and investment for carrying out the coal bed methane cave well completion field test are huge, the time consumption is long, the risk cost is high, the capability of rapid, multiple and multi-stratum experiments is not provided, the measurement and the acquisition of related experiment data are very difficult, and even if the cave well completion is successful, the yield increasing mechanism is difficult to explain and analyze, so that the research on the yield increasing mechanism and the process flow of the coal bed methane cave well completion in China is very few.
The invention provides an experimental device for evaluating the cave well completion of coal bed methane aiming at the defects of the prior art, so that the cave well completion process is effectively simulated, and the yield increasing mechanism of the cave well completion is obtained.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a coal bed gas cave well completion evaluation experimental apparatus for simulate cave well completion process, thereby reach the yield increasing mechanism of cave well completion.
The utility model aims at realizing the above, the coal bed gas cave well completion evaluation experimental device is composed of a square coal rock model and a clamping system thereof, a three-axis servo loading system, a gas-liquid pressurization injection system, a collection metering system and a monitoring processing system; the square coal rock model and the clamping system thereof are arranged in a frame, the square coal rock model and the clamping system thereof comprise a square coal rock model, the bottom surface of the coal rock model is provided with an upward extending simulation shaft, the top surface of the coal rock model is provided with a plurality of downward extending pressure measuring holes, the outer side of the coal rock model is provided with a sealing rubber sleeve, pressing plates are fixedly arranged on the outer side of the rubber sleeve and on six sides corresponding to the coal rock model, through holes are respectively arranged at the positions on the upper and lower pressing plates and the rubber sleeve corresponding to the simulation shaft and the pressure measuring holes, and pressure measuring tubes with pressure sensors are arranged in the pressure measuring holes; the three-axis servo loading system comprises three servo pressurizing oil cylinders which are arranged in three spatial directions outside the coal rock model and apply pressure to the coal rock model; the gas-liquid pressurization injection system comprises a communicating vessel which is hermetically arranged on the lower side pressure plate and communicated with the simulation shaft, the upper part of the communicating vessel is provided with an air inlet pipe, an water inlet pipe and a pressure measuring pipe with a pressure sensor, the lower part of the communicating vessel is provided with an electric ball valve, the lower end of the electric ball valve is connected with a pressure relief pipe, and the bottom end of the pressure relief pipe is correspondingly provided with a coal powder collecting water tank.
In a preferred embodiment of the present invention, the top surface of the coal rock model is provided with four pressure measuring holes.
In a preferred embodiment of the present invention, a servo valve is installed in the inlet direction of each pressurizing cylinder for precisely controlling the opening and closing of the valve and the oil feeding amount.
In a preferred embodiment of the present invention, each servo pressurizing cylinder is provided with a force sensor and a displacement sensor, and each servo pressurizing cylinder is connected with an all-digital controller for controlling the operation thereof.
In a preferred embodiment of the present invention, the air inlet pipe is connected to a first hydraulic and pneumatic pressurizing cylinder through a first passage, the air inlet pipe is connected to a second hydraulic and pneumatic pressurizing cylinder through a second passage, the two pressurizing cylinders are driven by a servo motor, the first hydraulic and pneumatic pressurizing cylinder is communicated with the air cylinder and the liquid storage tank through a first selection switch, and the second hydraulic and pneumatic pressurizing cylinder is communicated with the air cylinder and the liquid storage tank through a second selection switch; the first channel is provided with a first one-way valve for conducting the air inlet pipe in one way, and the second channel is provided with a second one-way valve for conducting the water inlet pipe in one way.
In a preferred embodiment of the present invention, the cube coal-rock model is cut from raw coal; the size of the cube coal rock model is 300mm multiplied by 300 mm; the diameter of the simulated shaft is 30mm, and the depth is 200 mm; the diameter of each pressure measuring hole is 6mm, and the drilling depth is 160 mm.
The utility model discloses an in a preferred embodiment, the central point that simulation pit shaft is located coal petrography model bottom surface puts and upwards extends the setting perpendicularly, each pressure cell should set up around the simulation pit shaft.
In a preferred embodiment of the present invention, the pressure relief pipe has a diameter of 30mm, 25mm, 20mm, 15mm, 10mm or 5 mm.
The utility model discloses a coalbed methane cave well completion evaluation experimental apparatus, can be under indoor experiment simulation stratum pressure the formation process of cave in the bold coal petrography, thereby know the mechanism of cave well completion, through the measurement of the pore pressure of different positions departments around the cave, the analysis cave forms before, the hole pressure response of surrounding coal petrography after the cave formation in-process and the cave formation, know the development and the disturbance of crack around the coal petrography among the cave well completion process, through the survey of coal petrography permeability around the cave after the cave experiment, the analysis cave well completion is to the improvement effect of coal petrography permeability, thereby can compare more comprehensive evaluation cave well completion output increase possible reason, provide new path for on-the-spot cave well completion process design. The utility model discloses a coal bed gas cave well completion evaluation experimental apparatus has low cost, low risk, different reservoir environment of simulation, reusability, both can analyze the yield increase mechanism of cave well completion, can provide the guidance for coal bed gas cave well completion on-the-spot process design again.
Drawings
The drawings are only intended to illustrate and explain the present invention and do not limit the scope of the invention. Wherein,
FIG. 1: do the utility model discloses coal bed gas cave well completion evaluation experimental apparatus's schematic structure.
FIG. 2: is a schematic sectional view of a-a in fig. 1.
FIG. 3: is a schematic sectional view of b-b in FIG. 1.
FIG. 4: do the utility model discloses well square coal petrography model and clamping system's schematic structure diagram.
FIG. 5: do the utility model discloses well gas-liquid pressurization injection system and collect measurement system's structural schematic.
FIG. 6A: does the structure schematic diagram of the middle rubber sleeve of the utility model.
FIG. 6B: is a schematic diagram of a square structure cut from the bottom surface of the rubber sleeve in fig. 6A.
FIG. 7: do the utility model discloses the structure schematic diagram that well linker and clamp plate are connected.
Detailed Description
In order to clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in fig. 1-7, the utility model provides an experimental apparatus 100 for evaluating coal bed methane cave well completion, said experimental apparatus 100 for evaluating consists of a square coal rock model and its clamping system 1, a three-axis servo loading system 2, a gas-liquid pressurized injection system 3, a collection metering system 4 and a monitoring processing system 5; the square coal rock model and the clamping system 1 thereof are arranged in a frame 6, the square coal rock model and the clamping system 1 thereof comprise a square coal rock model 11, the bottom surface of the coal rock model 11 is provided with an upward extending simulation shaft 111, the top surface of the coal rock model 11 is provided with a plurality of downward extending pressure measuring holes 112, the outer side of the coal rock model 11 is provided with a sealing rubber sleeve 12, pressing plates 13 are fixedly arranged at the outer side of the rubber sleeve 12 and on six side surfaces corresponding to the coal rock model 11, through holes are respectively arranged at the positions, corresponding to the simulation shaft 111 and the pressure measuring holes 112, of the upper pressing plate 13, the lower pressing plate 13 and the rubber sleeve 12, and pressure measuring tubes 51 with pressure sensors are arranged in each pressure measuring hole 112; as shown in fig. 1, 2 and 3, the triaxial servo loading system 2 includes three servo pressurizing cylinders 21, 22 and 23, which are disposed in three directions in a space outside the coal rock model 11 and apply pressure to the coal rock model 11; the gas-liquid pressurized injection system 3 comprises a communicating vessel 31 which is hermetically arranged on a through hole of the lower side pressure plate 13 and is communicated with the simulated shaft 111, as shown in fig. 7, an air inlet pipe 311, an water inlet pipe 312 and a pressure measuring pipe 52 with a pressure sensor are arranged at the upper part of the communicating vessel 31, an electric ball valve 41 is arranged at the lower part of the communicating vessel 31, a pressure relief pipe 42 is connected to the lower end of the electric ball valve 41, and a coal dust collecting water tank 43 is correspondingly arranged at the bottom end of the pressure relief pipe 42.
The utility model discloses a coalbed methane cave well completion evaluation experimental apparatus, can be under indoor experiment simulation stratum pressure the formation process of cave in the bold coal petrography, thereby know the mechanism of cave well completion, through the measurement of the pore pressure of different positions departments around the cave, the analysis cave forms before, the cave forms in-process and the cave forms the pressure response of surrounding coal petrography after, know the development and the disturbance of crack around the coal petrography among the cave well completion process, through the survey of the permeability of coal petrography around the cave after the cave experiment, the analysis cave well completion is to the improvement effect of coal petrography permeability, thereby can compare more comprehensive evaluation cave well completion output increase possible reason, provide new path for on-the-spot cave well completion process design.
In the present embodiment, the cubic coal-rock model 11 is formed by cutting raw coal; the size of the cube coal rock model 11 is 300mm multiplied by 300 mm; the diameter of the simulated shaft 111 is 30mm, and the depth is 200 mm; the diameter of each pressure measuring hole 112 is 6mm, and the drilling depth is 160 mm. The simulated shaft 111 is located at the center of the bottom surface of the coal rock model 11 and extends vertically upward, and the pressure taps 112 are correspondingly arranged around the simulated shaft 111 (as shown in fig. 2).
In this embodiment, four pressure measuring holes 112 are formed in the top surface of the coal rock model 11, the pressure measuring pipes 51 are respectively inserted into the pressure measuring holes 112, epoxy resin glue is injected into a gap between the outer wall surface of the pressure measuring pipe 51 and the pressure measuring holes 112 for sealing, the pressure measuring pipe 51 is a stainless steel pipe with a diameter of 3mm, the pressure measuring pipe 51 penetrates out of the pressure plate 13 through a corresponding through hole with a diameter of about 10mm on the upper pressure plate 13, a pressure sensor is connected to each pressure measuring pipe 51 to form four sensor pressure measuring points A, B, C, D for collecting pressure data of each pressure measuring point, and the other end of the pressure sensor is connected to a data collecting plate on a computer.
In the present embodiment, the pressure measuring hole 112 is not located at the center of the cube coal rock model 11, and the pressure measuring tube 51 and the pressure plate 13 always have relative displacement when triaxial compressive stress is applied, so that the plurality of through holes drilled in the upper pressure plate 13 have a diameter of about 10mm, and are mainly used for connecting the pipe joint of the pressure measuring tube 51 with a pressure sensor through the outside of the pressure plate, and the pressure plate 13 does not shear the pressure measuring tube 51 when the cube coal rock model 11 is deformed (relative displacement).
Further, the servo pressurizing oil cylinders 21, 22 and 23 are used for servo loading of triaxial different pressure stresses on the cuboid coal rock model 11, the servo pressurizing oil cylinder 21 is a horizontal (X) pressurizing oil cylinder, the servo pressurizing oil cylinder 22 is a horizontal (Y) pressurizing oil cylinder, and the two pressurizing oil cylinders 21 and 22 are mainly used for servo loading of the pressure stresses in the horizontal direction; the servo pressurizing oil cylinder 23 is a vertical pressurizing oil cylinder and is mainly used for loading vertical pressure stress; three all-digital EDC220 controllers are needed for servo control of the three-direction pressurizing oil cylinders, and one servo oil source is used for supplying oil to the three-direction pressurizing oil cylinders. A servo valve is installed in the inlet direction of each pressurizing oil cylinder and used for accurately controlling the opening and closing of a valve and the oil inlet amount, a force sensor and a displacement sensor are installed on three pressurizing oil cylinders, the force sensor and the displacement sensor are further connected with a force amplifier and a displacement amplifier, the servo valve is mainly used for amplifying signals of the displacement sensor and the force sensor, the obtained force and displacement data are more accurate, the force application and stroke of the pressurizing oil cylinders are accurately controlled, and the coal rock model 11 is guaranteed not to be crushed in the servo pressurizing load process. In the present embodiment, a microcomputer is used to program all the full digital EDC220 controllers and collect data to output graphs and curves.
In this embodiment, a pressing plate 14 may be further disposed outside each pressing plate 13, and the output surface of the servo-pressing cylinder is attached to the pressing plate 14 (as shown in fig. 1, 2 and 3).
In the embodiment, the square coal rock model and the clamping system thereof are the core of the coal bed methane cave well completion evaluation experimental device, the model structure can realize the evaluation of cave well completion and the simulation test of hydraulic fracturing, and the design realizes the multifunction of the equipment; the pressure plate 13 and the rubber sleeve 12 are mainly used for ensuring the sealing performance of the model when triaxial anisotropic compressive stress is loaded. The conventional triaxial fracturing experiment generally does not relate to the sealing problem inside a sample, or the pressure leakage problem is generally not considered when the sample is pressurized inside the sample, while the coalbed methane cave well completion evaluation experiment device is mainly used for simulating the mechanism process of the cave well completion of a gas well, testing the parameters of the cave well completion and analyzing the mechanism of the cave well completion to obtain the adaptability, the matching reservoir condition and the yield increase mechanism of the cave well completion.
In this embodiment, the rubber sleeve 12 is a cubic silica gel case (as shown in fig. 6A and 6B), the size of which is slightly smaller than that of the cubic coal rock model 11, when the cubic coal rock model 11 is placed in the rubber sleeve 12, a block 121 with a diameter of 260mm × 260mm is cut from the bottom surface of the integral hexahedral rubber sleeve, then the cubic coal rock model 11 is placed in the rubber sleeve 12, then the cut block 121 is attached to the bottom (and then appropriately sealed), the through hole 122 with a diameter of 40mm is further opened in the middle of the block 121, and the through hole 122 is used for communicating the simulated wellbore 111 with the communicator 31. Because the size of the rubber sleeve 12 is smaller than that of the cubic coal rock model 11 (the rubber sleeve is a cubic shell with the side length of 295 mm), the rubber sleeve 12 can be tightly attached to the coal rock model 11, so that the coal rock model 11 can be completely isolated from the outside, the rubber sleeve 12 can be sealed under high pressure (more than 20 MPa) by six pressing plates 13 outside the rubber sleeve, and the rubber sleeve is compressed because the pressure is transmitted between the pressing plates 13 and the coal rock model 11 through the rubber sleeve, so that the pressure cannot flow on one surface of the coal rock model 11.
As shown in fig. 4, in the present embodiment, the two adjacent pressing plates 13 are respectively provided with the pressing plate fixing blocks 131, and when the pressing plates 13 are mounted, the adjacent pressing plate fixing blocks 131 are connected by bolts to fix the pressing plates 13 in one direction, so that the mounted pressing plates are not scattered.
In this embodiment, the communicating vessel 31 is mainly used to connect the gas inlet pipeline and the liquid inlet pipeline, discharge gas or liquid inside the simulated shaft 111, and suppress pressure and release coal dust generated during the circulation process; the pressure sensor connected to the pressure tube 52 on the communicator forms a pressure measurement point E (shown in FIG. 7) for the exit of the simulated wellbore 111.
As shown in fig. 5, the air inlet pipe 311 is connected to a first hydraulic and pneumatic cylinder 331 through a first passage 321, the air inlet pipe 312 is connected to a second hydraulic and pneumatic cylinder 332 through a second passage 322, the two cylinders 331 and 332 are driven by a servo motor 34, the first hydraulic and pneumatic cylinder 331 is communicated with the air cylinder 36 and the liquid storage tank 37 through a first selection switch 351, and the second hydraulic and pneumatic cylinder 332 is communicated with the air cylinder 36 and the liquid storage tank 37 through a second selection switch 352; the first channel 321 is provided with a first one-way valve 381 of a one-way conduction air inlet pipe, and the second channel 322 is provided with a second one-way valve 382 of a one-way conduction water inlet pipe.
In this embodiment, the gas cylinder 36 (which is a nitrogen cylinder) and the liquid storage tank 37 mainly provide a gas source and a liquid source for the pressurized injection system, and are connected to the hydraulic and pneumatic pressurizing cylinders 331 and 332, so that the hydraulic and pneumatic pressurizing cylinders compress gas or liquid for pressurization through the servo motor 34 and the ball screw 39, and the pressurized gas or liquid enters the gas inlet pipe and/or the water inlet pipe through the check valve, and is injected into the simulated wellbore 111 through the communicating device 31.
In the present embodiment, pressure relief pipes 42 with different diameters can be connected to the rear surface of the communicating vessel lower electric ball valve 41, and the pressure relief speed can be changed by changing the diameter of the pressure relief pipe 42, so that different cave-making effects and yield-increasing stimulation effects can be generated. In this embodiment, the pressure relief tube may have a diameter of 30mm, 25mm, 20mm, 15mm, 10mm or 5 mm. The coal dust and fluid collapsed during the pressure relief cycle are led out by the pressure relief pipe 42, collected by the coal dust collection water tank 43, and finally collected by the coal dust collection box (not shown). The bottom surface of the pulverized coal collecting box is a conical surface, water is stored in the middle of the pulverized coal collecting box, the larger pulverized coal collecting box is placed at the upper end of the conical surface, the lower end of the conical surface is a dust collecting box, all collected pulverized coal is placed into a drying box for drying and weighing, and accurate metering is achieved.
The following description is made of the experimental process of the present invention:
firstly, the purpose of experiment is as follows: obtaining the pressure of an initial cave generated by injecting nitrogen gas, pressurizing and decompressing the circulating coal and rock sample, namely threshold pressure through pressure testing; the process of producing stable cave and the excitation to coal and rock.
II, initial conditions of the experiment: the surface cleat direction of the installed coal rock sample is parallel to the direction of the maximum horizontal main stress (the pressurizing direction of a horizontal X pressurizing oil cylinder or the pressurizing direction of a horizontal Y pressurizing oil cylinder), the coal rock sample is marked as M1, the diameter of a pressure relief pipe on a communicating vessel is 30mm, the minimum horizontal main stress is loaded by 5MPa, the maximum horizontal main stress is loaded by 7MPa, and the vertical stress is loaded by 11 MPa; or the maximum horizontal main stress and the minimum horizontal main stress are loaded by 5MPa, and the vertical stress is loaded by 11 MPa.
Thirdly, experimental steps:
(0) the coal rock sample is installed in the model system, and anisotropic compressive stress is loaded on the coal rock model sample for experiments through the triaxial servo loading system.
(1) The pressure sensors at the 5 pressure detection points A, B, C, D, E were checked for a pressure of 0, and after all the pressure sensors were determined to be 0, the experiment was started.
(2) Before the circulation of gas injection pressure building/pressure relief, a gas-liquid pressurized injection system is started to inject 0.3MPa of nitrogen (the pressure of a simulated shaft is 0.3MPa) in 2 seconds.
(3) When the gas injection starts, 5 pressure sensors are started simultaneously, and pressure data of each pressure detection point is recorded.
(4) And when the gas pressure in the simulated shaft reaches 0.3MPa, closing the gas-liquid pressurized injection system, observing the pressure change of the 5 pressure detection points, and checking the air tightness of the whole device. If the pressure drops to a certain value at point E (measuring the pressure in the simulated wellbore) then it will tend to stabilize, indicating that the gas tightness is normal at low pressure. After stabilizing for a period of time, opening an electric ball valve on the communicating vessel, starting pressure relief, closing the electric ball valve until the pressure data of 5 pressure sensors are all 0, and starting a gas injection pressure-building/pressure-relief circulation experiment.
(5) And starting a gas-liquid pressurized injection system, rapidly injecting nitrogen, and enabling the gas pressure in the simulated shaft to reach 4.5MPa within 20-60 seconds.
(6) When the gas injection starts, 5 pressure sensors are started simultaneously, and pressure data of each pressure detection point is recorded.
(7) And when the gas pressure in the simulated shaft reaches 4.5MPa, keeping the pressurization pressure unchanged, and observing the pressure change of the 5 pressure sensors until the pressure of the 5 pressure sensors is 4.5MPa or the pressure of the 5 pressure sensors is equal and close to 4.5 MPa.
(8) And (3) rapidly releasing the pressure by using a pressure relief pipe with the diameter of 30mm, and recording pressure change dynamic data of each pressure detection point in the pressure relief process.
(9) The coal dust sprayed in the pressure relief process is collected through the coal dust collecting box, the coal dust is stained with in the pressure relief pipeline and sprayed into the water tank, and the collected coal dust is dried and weighed. (note: the density of the coal is generally 1434Kg/m3) Thereby estimating the volume of the resulting eye. And closing the electric ball valve, reinstalling the pressure relief pipeline, and replacing the pulverized coal collection water tank with clean water of the same quantity to prepare for the next gas injection/pressure relief cycle.
(10) If the amount of the injected coal dust is very small, specifically less than 30-50 g, or the pressure is relieved, a pressure curve with a large reduction amplitude does not appear in the pressure detection point A, B, C, D, it indicates that no cavern is generated in the simulated shaft or the initial condition for generating the cavern is not reached.
(11) And (3) repeating the steps (1) to (10) for 5 times, determining that the initial condition of the cavity is unrelated to the cycle number in the pressure state, and recording the pressure change dynamic data of each pressure detection point every time.
(12) When the initial cave is not generated, the injection pressure of nitrogen is increased by 0.5MPa every time, and the steps (1) to (11) are repeated, so that experience shows that pressure relief pipes with the same diameter are quickly relieved under the same stress condition for different coal rocks, and a threshold pressure for generating the initial cave is provided.
(13) When the injection pressure reaches the threshold pressure in the experimental process, an initial cave is generated in the simulated shaft when the pressure is quickly relieved, and the judgment condition is that a large amount of coal dust is sprayed out, specifically more than 40-50 g, or a relatively obvious pressure reduction curve appears in the pressure detection point A, B, C, D.
(14) Collecting coal dust sprayed in the pressure relief process, including the coal dust adhered in the pressure relief pipeline and the coal dust sprayed into the water tank, drying and weighing the collected coal dust. And (4) reinstalling the pressure relief pipeline, replacing the pulverized coal collection water tank with quantitative clean water, and preparing for the next gas injection pressurization/pressure relief cycle.
(15) And (3) repeating the steps (1) to (10) under the condition that the highest pressure is the door pressure limiting pressure, performing another cycle of gas injection pressure building/pressure relief, quickly injecting nitrogen, setting the nitrogen injection speed to be 20-60 seconds, pressurizing to the threshold pressure, and then keeping the pressure until the pressures of the 5 pressure sensors are equal to the threshold pressure or tend to be stably close to the threshold pressure.
(16) And (3) rapidly releasing pressure by using a pressure relief pipe with the diameter of 30mm, and recording data of each pressure point in the pressure relief process and the weight of the sprayed coal dust. Cleaning the pressure relief pipeline and the coal dust collecting water tank.
(17) Keeping the conditions constant, repeating the steps (15) and (16) until the amount of the coal dust injected is very small, specifically less than 20-50g, so that a stable cave is formed, and generally circulating 5-10 times to achieve the stable cave condition.
(18) After the stable cave is formed, scanning the coal rock sample M1 with the stable cave formed by adopting an X-ray CT scanner, and observing the development direction of the cave and the development direction of the crack.
(19) And after CT scanning, cutting the coal rock sample M1, cutting the coal rock sample in a direction vertical to the horizontal direction of the simulated shaft, and observing the development direction of the cave and the specific crack in the coal rock sample.
(20) Taking a small-diameter coal core (with the diameter of 25mm) from a coal rock sample M1 with a stable cave formed, and respectively drilling along a face-to-face cutting direction and an end-to-face cutting direction, wherein the face-to-face cutting direction is adjacent to the cave part and the coal core adjacent to the wall surface of the coal sample, and the numbers are M1-FX0 and M1-FX 1; the coal cores of the hole part adjacent to the end cutting direction and the wall surface adjacent to the coal sample are numbered M1-BX0 and M1-BX 1; 0 represents a near cave and 1 represents a near wall.
(21) And performing a permeability determination experiment on the small-diameter coal core, measuring the permeability of the small-diameter coal core, and comparing the permeability determination experiment with the permeability experimental data of the coal core in the coal face cleat and end cleat directions of the raw coal without the cave experiment.
From the above, the utility model discloses application coal bed gas cave well completion evaluation experimental apparatus can carry out deep research in aspects such as coal bed gas cave well completion production increase mechanism and cave making technique to form the coal bed gas cave well completion theory and the technique of the independent intellectual property right of china, on-the-spot cave well completion technology investment is huge, and is long consuming time, and the risk cost is high, does not have fast, many times, the ability of many stratum experiments, and experimental data is very difficult to gather, and even cave well completion is successful, its production increase mechanism also is difficult to explain and analyze. And the utility model discloses coal bed gas cave well completion evaluation experimental apparatus has low cost, low risk, different reservoir environment of simulation, reusability, can be with the yield mechanism of analysis cave well completion, can provide the guidance for coal bed gas cave well completion on-the-spot process design again.
The above description is only exemplary of the present invention, and is not intended to limit the scope of the present invention. Any person skilled in the art should also realize that such equivalent changes and modifications can be made without departing from the spirit and principles of the present invention.
Claims (8)
1. The utility model provides a coal bed gas cave completion evaluation experimental apparatus which characterized in that: the evaluation experimental device consists of a square coal rock model and a clamping system thereof, a three-axis servo loading system, a gas-liquid pressurizing injection system, a collection metering system and a monitoring processing system; the square coal rock model and the clamping system thereof are arranged in a frame, the square coal rock model and the clamping system thereof comprise a square coal rock model, the bottom surface of the coal rock model is provided with an upward extending simulation shaft, the top surface of the coal rock model is provided with a plurality of downward extending pressure measuring holes, the outer side of the coal rock model is provided with a sealing rubber sleeve, pressing plates are fixedly arranged on the outer side of the rubber sleeve and on six sides corresponding to the coal rock model, through holes are respectively arranged at the positions on the upper and lower pressing plates and the rubber sleeve corresponding to the simulation shaft and the pressure measuring holes, and pressure measuring tubes with pressure sensors are arranged in the pressure measuring holes; the three-axis servo loading system comprises three servo pressurizing oil cylinders which are arranged in three spatial directions outside the coal rock model and apply pressure to the coal rock model; the gas-liquid pressurization injection system comprises a communicating vessel which is hermetically arranged on the lower side pressure plate and communicated with the simulation shaft, the upper part of the communicating vessel is provided with an air inlet pipe, an water inlet pipe and a pressure measuring pipe with a pressure sensor, the lower part of the communicating vessel is provided with an electric ball valve, the lower end of the electric ball valve is connected with a pressure relief pipe, and the bottom end of the pressure relief pipe is correspondingly provided with a coal powder collecting water tank.
2. The coalbed methane cave completion evaluation experimental device of claim 1, wherein: and four pressure measuring holes are formed in the top surface of the coal rock model.
3. The coalbed methane cave completion evaluation experimental device of claim 1, wherein: and a servo valve is respectively arranged in the inlet direction of each pressurizing oil cylinder and used for accurately controlling the opening and closing of the valve and the oil inlet amount.
4. The coalbed methane cave completion evaluation experimental device of claim 1, wherein: and each servo pressurizing oil cylinder is provided with a force sensor and a displacement sensor and is connected with a full digital controller for controlling the action of the servo pressurizing oil cylinder.
5. The coalbed methane cave completion evaluation experimental device of claim 1, wherein: the air inlet pipe is connected with a first water pressure and air pressure pressurizing cylinder through a first channel, the air inlet pipe is connected with a second water pressure and air pressure pressurizing cylinder through a second channel, the two pressurizing cylinders are driven by a servo motor, the first water pressure and air pressure pressurizing cylinder is communicated with the air storage bottle and the liquid storage tank through a first selection switch, and the second water pressure and air pressure pressurizing cylinder is communicated with the air storage bottle and the liquid storage tank through a second selection switch; the first channel is provided with a first one-way valve for conducting the air inlet pipe in one way, and the second channel is provided with a second one-way valve for conducting the water inlet pipe in one way.
6. The coalbed methane cave completion evaluation experimental device of claim 1, wherein: the cubic coal-rock model is formed by cutting raw coal; the size of the cube coal rock model is 300mm multiplied by 300 mm; the diameter of the simulated shaft is 30mm, and the depth is 200 mm; the diameter of each pressure measuring hole is 6mm, and the drilling depth is 160 mm.
7. The coalbed methane cave completion evaluation experimental device of claim 6, wherein: the simulation shaft is located at the center of the bottom surface of the coal rock model and vertically extends upwards, and the pressure measuring holes are correspondingly arranged around the simulation shaft.
8. The coalbed methane cave completion evaluation experimental device of claim 6, wherein: the diameter of the pressure relief pipe is 30mm, 25mm, 20mm, 15mm, 10mm or 5 mm.
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| CN102373919A (en) * | 2010-08-27 | 2012-03-14 | 中国石油大学(北京) | Experimental apparatus for evaluating coalbed methane cave well completion |
| CN102519768A (en) * | 2011-12-21 | 2012-06-27 | 中联煤层气有限责任公司 | Rock sample sealing structure used for three dimensional permeability determination |
| CN102680647A (en) * | 2012-04-20 | 2012-09-19 | 天地科技股份有限公司 | Coal-rock mass grouting reinforcement test bed and test method |
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| CN102680647B (en) * | 2012-04-20 | 2015-07-22 | 天地科技股份有限公司 | Coal-rock mass grouting reinforcement test bed and test method |
| CN102680647A (en) * | 2012-04-20 | 2012-09-19 | 天地科技股份有限公司 | Coal-rock mass grouting reinforcement test bed and test method |
| CN103195401A (en) * | 2013-04-01 | 2013-07-10 | 中国矿业大学 | Coal reservoir yield increasing transforming experiment device under stratum conditions |
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| CN106124380A (en) * | 2016-06-22 | 2016-11-16 | 太原理工大学 | A kind of similarity simulation experiment is measured the device and method of coal column breathability |
| CN106124380B (en) * | 2016-06-22 | 2019-01-15 | 太原理工大学 | The device and method of coal column gas permeability is measured in a kind of similarity simulation experiment |
| CN108533173A (en) * | 2018-04-18 | 2018-09-14 | 中煤科工集团西安研究院有限公司 | Gas medium power makes cave coal dust and returns row's mechanism simulation experimental provision and method |
| WO2020087861A1 (en) * | 2018-10-29 | 2020-05-07 | 中国矿业大学 | Coalbed methane horizontal well hole collapse de-stressed mining simulation test method |
| WO2020087860A1 (en) * | 2018-10-29 | 2020-05-07 | 中国矿业大学 | Coalbed methane horizontal well hole collapse pressure relief mining simulation test system |
| CN111472729A (en) * | 2020-03-27 | 2020-07-31 | 中国科学院广州能源研究所 | Natural gas hydrate cave well completion evaluation testing device and method |
| CN111472729B (en) * | 2020-03-27 | 2021-07-16 | 中国科学院广州能源研究所 | Evaluation and test method for natural gas hydrate cave well completion |
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