CN110306964A - A kind of visualization of hydraulic fracturing coal seam crackle and antireflective effect evaluation method - Google Patents

A kind of visualization of hydraulic fracturing coal seam crackle and antireflective effect evaluation method Download PDF

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CN110306964A
CN110306964A CN201910590503.1A CN201910590503A CN110306964A CN 110306964 A CN110306964 A CN 110306964A CN 201910590503 A CN201910590503 A CN 201910590503A CN 110306964 A CN110306964 A CN 110306964A
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gas
coal
fracturing
visualization
cabinet
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CN110306964B (en
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张超林
王恩元
刘贞堂
赵恩来
冯小军
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China University of Mining and Technology CUMT
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China University of Mining and Technology CUMT
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    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25Methods for stimulating production
    • E21B43/26Methods for stimulating production by forming crevices or fractures
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21FSAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F7/00Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose

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  • Mining & Mineral Resources (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
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  • Environmental & Geological Engineering (AREA)
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  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

A kind of visualization of hydraulic fracturing coal seam crackle and antireflective effect evaluation method, for being detected in laboratory to coal seam hydraulic fracture.Including mash gas extraction and evaluation of Fracturing Effect on Compact Sandstone after mash gas extraction, hydraulic fracturing coal body stage, pressure break before early-stage preparations stage, crustal stress load phase, pressure break.Its step is simple, detection effect is good, reinforcing gas drainage process effectively under simulation various combination mode, Simultaneous Monitoring and coal-bed gas pressure, temperature, face crack form and mash gas extraction flow can be acquired simultaneously, provide effective means to study gas drainage efficiency and optimization extraction measure under the conditions of different enhanced gas extractions.

Description

A kind of visualization of hydraulic fracturing coal seam crackle and antireflective effect evaluation method
Technical field
The present invention relates to a kind of evaluation method, it is particularly suitable in laboratory to a kind of waterpower of coal seam hydraulic fracture detection The visualization of pressure break coal seam crackle and antireflective effect evaluation method
Background technique
China's coal-bed gas condition of storage generally have " three low one is high " (low saturation, low-permeability, low reservoir pressure, High degree of metamorphism) the characteristics of, whole nation major part mining area coal seam permeability is 10-4~10-3MD, 3~4 quantity lower than the U.S. etc. Grade, it is such under the conditions of coal bed gas extraction be global problem, at the same time, a variety of reinforcing gas drainage measures also quilt in succession It proposes and implements, such as hydraulic fracturing technology, deep hole blasting is anti-reflection technology, high-pressure abradant jet current slot is anti-reflection technology, high-voltage electricity arteries and veins Break through the anti-reflection technology of coal and gas injection displacement yield-increasing technology etc..
Hydraulic fracturing technology is by injecting high pressure water into drilling, in crustal stress and high pressure water double action fracturing coal Layer makes to form several macroscopical cracks around drilling and branch crack, macroscopical crack is extended to coal seam depth, desorbs for coal-bed gas Seepage flow provides channel, improves the extraction range of drilling.It can be seen that in hydraulic fracturing process coal seam crackle development, extension Process is to influence the key factor of fracturing effect.Therefore a kind of visualization of hydraulic fracturing coal seam crackle and antireflective effect evaluation are proposed Method, main advantage include: that (1) can simulate large scale coal seam hydraulic fracture mistake under the conditions of true triaxial mining stress field Journey is more nearly the true complex geological condition in scene;(2) overall process can be carried out to coal surface crackle in hydraulic fracturing process Real time monitoring;(3) gas drainage operation evaluation fracturing effect is carried out to coal seam based on pressure break front and back.
Summary of the invention
Shortcoming is compared in view of the above technology, provides that a kind of structure is simple, and using effect is good, can simulate difference true three Axial stress, gas pressure, coal seam temperature multi- scenarios method Coal Under and gas postponing bursting process hydraulic fracturing coal seam crackle Visualization and antireflective effect evaluation method.
To realize the above-mentioned technical purpose, hydraulic fracturing coal seam crackle of the invention visualization and antireflective effect evaluation method, It include: extraction watt after mash gas extraction, hydraulic fracturing coal body stage, pressure break before early-stage preparations stage, crustal stress load phase, pressure break This and evaluation of Fracturing Effect on Compact Sandstone;The specific steps are that:
1a) the coal cinder sampling projecting coal bed from coal mine region to be measured carries out field research, is taken using the coal cinder of collection in worksite Sample measures projecting coal bed relevant parameter, determines the test parameters such as crustal stress in testing program, rate of water injection, pressure break position;
The coal cinder sampling of acquisition 1b) is sieved into using broken sieve the coal grain of 0-1mm partial size, system is added water and stirred into coal grain It is spare at 6% moisture content coal sample;
6% moisture content coal sample 1c) is packed into visualization cabinet, the visualization bottom of box is equipped with spongy multi-function metal Plate, multi-function metal plate are equipped with inflating port, visualize on the left side wall of top of the box and visualization cabinet and on front side wall Equipped with multiple transparent loading plates, visualizing the transparent loading plate of top of the box there are six serial number is respectively X1-X6, visualizes cabinet There are six transparent loading plates on front side wall, and serial number is respectively Y1-Y6, and the transparent loading plate visualized on the left side wall of cabinet is Z1, each transparent loading plate are equipped with load piston, and load piston passes through box body wall connection pressurization oil cylinder;Visualize box back surface There are multiple sensor mounting hole equipped with homogenizing step, has been simutaneously arranged row's multifunctional hole-drilling, wherein multifunctional hole-drilling tail portion exists It visualizes cabinet and is equipped with external connector, gasket, multi-functional drill are equipped between external connector and the box body wall for visualizing cabinet Hole includes sealing section, fracturing section, multifunctional hole-drilling overall length 0.5m, sealing of hole segment length 0.15m, pressure break segment length 0.35m, fracturing section tube wall Air hole is distributed in circumferential and radial direction, and serial number A1-A6 is arranged to multifunctional hole-drilling, utilizes visualization in visualization cabinet 6% moisture content coal sample of the sensor mounting hole that cabinet back opens up into visualization cabinet is embedded to baroceptor respectively, most It is released after so that 6% moisture content coal sample is formed 1h under the conditions of 20MPa using load piston driving transparent loading plate afterwards all transparent Pressurization of the load plate to coal sample;
1c) cover board for visualizing cabinet and box sealing are fastened using sealing ring and screw, by high pressure gas cylinder, vacuum Pump, flow meter I are linked in sequence, and the output end of flow meter I is connected by pipeline with the inflating port of multi-function metal plate, visual Change setting jointing in the multifunctional hole-drilling of the serial number A6 at cabinet rear portion to be connected with flow meter II, visualizes cabinet rear portion Serial number A3 multifunctional hole-drilling in setting jointing be connected with the air inlet of flowmeter III, the gas outlet of flowmeter III Pipeline is connected with fracturing pump, the sealing effect of detection visualization cabinet and tracheae piping connection;
High-speed camera 1d) is installed on the outside of visualization cabinet, to monitor the visualization intracorporal variation of case;
Triaxial stress load operation 2a) is carried out to the intracorporal coal sample of visualization case, wherein coal sample top in visualization cabinet 6 pressing plate stress intensities of serial number X1-X6 be 6MPa, 6 pressing plate stress intensities of front side serial number Y1-Y6 are 8MPa;1 pressing plate stress intensity of left side serial number Z1 is 10MPa;
2b) starting vacuum pump carries out vacuum pumping to coal sample, closes vacuum until coal body air pressure inside is less than 100Pa Pump, used time about 12h;
It 2c) opens high pressure gas cylinder coal sample is carried out to fill gas operation, four stages that were divided into guarantee the air pressure of coal sample adsorption equilibrium For 1.0MPa, the first stage inflates 12h, the blowing pressure to 0.3MPa, is then shut off gas cylinder, stablizes 6h;Second stage inflation 12h, the blowing pressure to 0.6MPa are then shut off gas cylinder, stablize 6h;Phase III inflates 12h, the blowing pressure to 0.9MPa, so After close gas cylinder, stablize 6h;Fourth stage is inflated 6h, inflation and is stablized to 1.0MPa, and gas cylinder is then shut off, and the used time is total about 60h is filled with gas amount by flow meter I record in gas replenishment process;
3a) according to gas drainage process before testing program development hydraulic fracturing, A6 drilling is opened, mash gas extraction is started, and Gas drainage amount is recorded by flow meter II;
3b) extraction terminates extraction afterwards for 24 hours, unloads stress, empties gas;
4a) repeat step 2a-2c;
4b) control fracturing pump is filled the water in coal sample in visualization cabinet by the multifunctional hole-drilling of serial number A3 to setting, Rate of water injection is 10mL/s;
4c) change of the coal sample in fracturing pump the injecting process is observed by the way that the high-speed camera of visualization case-side is arranged in Change, when observing that coal petrography surface generates crack, closes fracturing pump and stop water filling;
4d) terminate above-mentioned pressure break, closing high-speed video camera unloads stress;
5a) carry out hydraulic fracturing after gas extraction process according to testing program, the multifunctional hole-drilling for opening serial number A6 is taken out Mash gas, and gas drainage amount is recorded by flow meter II;
5b) extraction terminates extraction afterwards for 24 hours, unloads stress, empties gas;
5c) change hydraulic fracturing bore position, rate of water injection condition, repeat step 1c-2c, 4a-5b, carries out other conditions Lower hydraulic fracturing and pressure break after gas extraction test.
6a) the coal body photo shot according to high-speed camera analyzes under different condition coal body surface during hydraulic fracturing The growth of crackle, propagation law, and sketch processing, analysis fracturing borehole position, water filling are carried out using the final form of PS fracture The difference fracturing parameter such as rate and fracturing crack quantity, area, the relationship between initial cracking pressure;
6b) calculating separately gas drainage rate before pressure break according to gas charge and extraction amount includes that gas drainage amount is accounted for and is filled with Amount ratio, different fracturing parameters: including fracturing borehole position, rate of water injection pressure break after gas extraction rate;And analyze fracturing crack Relationship between quantity, area, initial cracking pressure and gas drainage rate;
6c) it is based on pressure break front and back gas drainage rate size quantitative assessment hydraulic fracturing effect of increasing production, and Optimum Hydraulic pressure break Parameter.
The utility model has the advantages that
Fluid fracturing coal under the conditions of different true triaxial stress, gas pressure, coal seam temperature multi- scenarios method can be simulated indoors Reinforcing gas drainage process under layer, fluid displacement gas, gas drainage process and its various combination mode, while prison can be synchronized Coal-bed gas pressure, temperature, face crack form and mash gas extraction flow are surveyed and acquire, to study different enhanced gas extraction conditions Lower gas drainage efficiency and optimization extraction measure provide effective means.
Detailed description of the invention:
Fig. 1 is the transparent cabinet structure that hydraulic fracturing coal seam of the present invention crackle visualizes and antireflective effect evaluation method uses Schematic diagram.
Fig. 2 is that the transparent cabinet that hydraulic fracturing coal seam of the present invention crackle visualizes and antireflective effect evaluation method uses is overlooked Figure.
Fig. 3 is the transparent cabinet backsight that hydraulic fracturing coal seam of the present invention crackle visualizes and antireflective effect evaluation method uses Figure.
Fig. 4 is the loading system structure that hydraulic fracturing coal seam of the present invention crackle visualizes and antireflective effect evaluation method uses Schematic diagram.
Fig. 5 (a) is baroceptor scheme of installation of the invention.
Fig. 5 (b) is temperature sensor scheme of installation of the invention.
Fig. 5 (c) is multifunctional hole-drilling structural schematic diagram of the invention.
Fig. 6 is the camera position signal that hydraulic fracturing coal seam of the present invention crackle visualizes and antireflective effect evaluation method uses Figure.
Fig. 7 is the hydraulic fracturing combination that hydraulic fracturing coal seam of the present invention crackle visualizes and antireflective effect evaluation method uses Schematic diagram.
In figure: 1- visualization cabinet, 2- box cover, 3- cabinet cavity, 4- sealing ring, 5- sealing bolt, 6- are multi-functional Metal plate, 7- hot water radiation wire, 8- inflating port, 9- connection jaws, 10- sensor mounting hole, 11- multifunctional hole-drilling mounting hole, 12- are saturating Bright load plate, 13- load piston, 14- high-speed camera, 15- gasket a, 16- baroceptor, 17-PU pneumatic joint, 18- PU pipe, 19- gasket b, 20- data line, 21- crossover sub, 22- temperature sensor, 23- strain gauge, 24- is external to be connect Head, 25- multifunctional hole-drilling, 26- fracturing section, 27- sealing section, 28- small ventilating holes, 29- high pressure gas cylinder, 30- vacuum pump, 31- stream Meter I, 32- flow meter II, 33- flowmeter III, 34- fracturing pump.
Specific embodiment
Embodiments herein is described further below according to attached drawing:
Of the invention is a kind of using the hydraulic fracturing coal seam crackle visualization of above-mentioned apparatus and antireflective effect evaluation method, preceding Mash gas extraction and pressure after mash gas extraction, hydraulic fracturing coal body stage, pressure break before preparation stage phase, crustal stress load phase, pressure break Split effect assessment;
As shown in Figure 1, Figure 2 and Figure 3, using the visualization cabinet 1 of rectangular parallelepiped structure, visualizing cabinet 1 includes cabinet chamber Body 3 and the box cover 2 that top is arranged in are equipped with sealing ring 4 and utilize sealing bolt 5 between cabinet cavity 3 and box cover 2 Fixed, 3 rear wall of cabinet cavity is uniformly provided with multiple for installing multiple types sensor mounting hole 10 and multifunctional hole-drilling peace Hole 11 is filled, the sensor of installation includes baroceptor 16, temperature sensor 22, strain gauge 23, multifunctional hole-drilling installation Multifunctional hole-drilling 25 is equipped in hole 11, the bottom in cabinet cavity 3 is equipped with and the big multi-function metals such as visualization 1 bottom of cabinet Plate 6,6 material of multi-function metal plate are that the preferable foam metal of gas permeability is constituted, and 6 bottom of multi-function metal plate is equipped with and cabinet chamber The inflating port 8 of external side connection, inflating port 8 are connected by pipeline with air supply system;
The loading system includes being arranged in the top canister cover board of visualization cabinet 1, in the left side wall of cabinet cavity 3 With in front side wall be equipped with multiple transparent loading plates 12, each transparent loading plate 12 be equipped with load piston 13, load piston 13 wear Cross box body wall connection pressurization oil cylinder;
The air supply system includes high pressure gas gas cylinder, and gas pressure is not less than 6MPa, and high pressure gas cylinder passes through vacuum pump benefit It is connect with tracheae pipeline with the inflating port 8 on the multi-function metal plate 3 in visualization cabinet 1, tracheae pipeline is equipped with flowmeter;
The temperature control system includes the hot water radiation wire 7 that 6 surface of multi-function metal plate is arranged in, and hot water radiation wire 7 passes through more function The connection jaws 9 and temperature-adjusting device connection being arranged on energy metal plate 6, for the coal being arranged in visualization cabinet 1 Sample is heated;
The baroceptor 16 is inserted into from the sensor mounting hole 10 in 1 outside of visualization cabinet using gasket a15, 16 tail end of baroceptor is connected by data line 20 with acquisition and control system, and one is equipped on the inside of sensor mounting hole 10 Root is extended on the PU pipe 18 inside coal sample, by adjusting the position of 18 open end of PU pipe to test different location gas pressure Power is wherein equipped with PU pneumatic joint 17 between PU pipe 18 and visualization 1 box body wall of cabinet.
As Fig. 5 (a) and Fig. 5 (b) temperature sensor 22 with 23 mounting structure of strain gauge identical, temperature sensor 22 data lines 20 connected with 23 tail portion of strain gauge are fixed on visualization cabinet 1 by crossover sub 21 and gasket a15 Sensor mounting hole 10 in, the data line 20 on 23 head of temperature sensor 22 and strain gauge is embedded in coal sample and is needed Detect the position of temperature or stress.
As shown in Fig. 5 (c), multifunctional hole-drilling 25, the multifunctional hole-drilling 25 are set in multifunctional hole-drilling mounting hole 11 Tail portion is equipped with external connector 24 on visualization cabinet 1, and sealing is equipped between external connector 24 and the box body wall for visualizing cabinet 1 A15 is padded, visualizes and is equipped with gasket b19 on the inside of the box body wall of cabinet 1 between multifunctional hole-drilling 25, multifunctional hole-drilling 25 protrudes into Part in coal sample includes sealing section 27 and fracturing section 26,25 overall length 0.5m of multifunctional hole-drilling, 0.15m long, the pressure break of sealing section 27 26 long 0.35m of section, fracturing section 26 tube wall is circumferential and radial direction is distributed with multiple small ventilating holes 28,28 aperture 2mm of small ventilating holes, Spacing 5mm arrangement, has the function of pressure break, displacement, extraction.
The specific steps are that:
It 1a) from the projecting coal bed middle sampling in coal mine region to be measured and carries out field research, utilizes the coal cinder sampling of collection in worksite Projecting coal bed relevant parameter is measured, determines the test parameters such as crustal stress in testing program, rate of water injection, pressure break position;
The coal cinder sampling of acquisition 1b) is sieved into using broken sieve the coal grain of 0-1mm partial size, system is added water and stirred into coal grain It is spare at 6% moisture content coal sample;
1c) as shown in figure 4,6% moisture content coal sample is packed into visualization cabinet 1, visualization 1 bottom of cabinet is equipped with spongy Multi-function metal plate 3, multi-function metal plate 3 are equipped with the left side of inflating port 8,1 top of visualization cabinet and visualization cabinet On wall and front side wall is equipped with multiple transparent loading plates 12, and there are six serial numbers point for the transparent loading plate 12 at 1 top of visualization cabinet Not Wei X1-X6, visualize 1 front side wall of cabinet on transparent loading plate 12 there are six serial number be respectively Y1-Y6, visualize cabinet 1 Left side wall on transparent loading plate 12 be Z1, each transparent loading plate 12 be equipped with load piston 13, load piston 13 pass through Box body wall connection pressurization oil cylinder;Visualization box back surface, which is equipped with homogenizing step, multiple sensor mounting hole 10, has been simutaneously arranged One row's multifunctional hole-drilling 25, wherein 25 tail portion of multifunctional hole-drilling is equipped with external connector 24, external connector 24 on visualization cabinet 1 It is equipped with gasket 4 between the box body wall of visualization cabinet 1, serial number A1-A6 is set to multifunctional hole-drilling, in visualization cabinet 6% moisture content coal sample of the sensor mounting hole 10 opened up using visualization 1 body back of case into visualization cabinet 1 is embedded to respectively Baroceptor 16, finally using load piston 13 drive transparent loading plate 12 make 6% moisture content coal sample under the conditions of 20MPa at Pressurization of all transparent loading plates 12 to coal sample is released after type 1h;
1c) as shown in fig. 7, being fastened the cover board for visualizing cabinet 1 and box sealing using sealing ring and screw, by high pressure Gas cylinder 29, vacuum pump 30, flow meter I 31 are linked in sequence, and the output end of flow meter I 31 passes through pipeline and multi-function metal plate 3 Inflating port 8 is connected, and jointing 24 and flow is arranged in the multifunctional hole-drilling 25 of the serial number A6 at visualization 1 rear portion of cabinet It counts II 32 to be connected, visualizes and jointing 24 and flowmeter are set in the multifunctional hole-drilling 25 of the serial number A3 at 1 rear portion of cabinet III 33 air inlet is connected, and the gas outlet pipeline of flowmeter III 33 is connected with fracturing pump 34, detection visualization cabinet 1 and gas The sealing effect of pipe piping connection;
1d) as shown in fig. 6, installing high-speed camera 14 on the outside of visualization cabinet 1, to monitor 1 in visualization cabinet Variation;
Triaxial stress load operation 2a) is carried out to the coal sample in visualization cabinet 1, wherein in visualization cabinet 1 in coal sample 6 12 stress intensities of transparent loading plate of the serial number X1-X6 in portion are 6MPa, 6 transparent loadings of front side serial number Y1-Y6 12 stress intensity of plate is 8MPa;1 12 stress intensity of transparent loading plate of left side serial number Z1 is 10MPa;
2b) starting vacuum pump 30 carries out vacuum pumping to coal sample, closes vacuum until coal body air pressure inside is less than 100Pa Pump 30, used time about 12h;
It 2c) opens high pressure gas cylinder 29 coal sample is carried out to fill gas operation, four stages that were divided into guarantee coal sample adsorption equilibrium gas Pressure is 1.0MPa, and the first stage inflates 12h, the blowing pressure to 0.3MPa, is then shut off gas cylinder 29, stablizes 6h;Second stage is filled Gas 12h, the blowing pressure to 0.6MPa are then shut off high pressure gas cylinder 29, stablize 6h;Phase III inflates 12h, the blowing pressure extremely 0.9MPa is then shut off high pressure gas cylinder 29, stablizes 6h;Fourth stage is inflated 6h, inflation and is stablized to 1.0MPa, and height is then shut off Air bottle 29, used time amount to about 60h, are recorded in gas replenishment process by flow meter I 31 and be filled with gas amount;
3a) according to gas drainage process before testing program development hydraulic fracturing, the multifunctional hole-drilling of serial number A6 is opened, is opened Beginning mash gas extraction, and gas drainage amount is recorded by flow meter II 32;
3b) extraction terminates extraction afterwards for 24 hours, unloads stress, empties gas;
4a) repeat step 2a-2c;
4b) control fracturing pump 34 by the multifunctional hole-drilling 25 of serial number A3 to setting in visualization cabinet 1 in coal sample Water filling, rate of water injection 10mL/s;
4c) coal sample is observed in 34 the injecting process of fracturing pump by the way that the high-speed camera 14 of visualization 1 side of cabinet is arranged in Variation, when observe coal petrography surface generate crack when, close fracturing pump 34 stop water filling;
4d) terminate above-mentioned pressure break, closing high-speed video camera 14 unloads stress;
5a) carry out hydraulic fracturing after gas extraction process according to testing program, opens the multifunctional hole-drilling 25 of serial number A6 Mash gas extraction, and gas drainage amount is recorded by flow meter II 32;
5b) extraction terminates extraction afterwards for 24 hours, unloads stress, empties gas;
5c) change hydraulic fracturing bore position, rate of water injection condition, repeat step 1c-2c, 4a-5b, carries out other conditions Lower hydraulic fracturing and pressure break after gas extraction test.
6a) the coal body photo shot according to 14 machine of high-speed camera analyzes under different condition coal body table during hydraulic fracturing The growth of facial cleft line, propagation law, and sketch processing, analysis fracturing borehole position, note are carried out using the final form of PS fracture The difference fracturing parameter such as water speed rate and fracturing crack quantity, area, the relationship between initial cracking pressure;
6b) calculating separately gas drainage rate before pressure break according to gas charge and extraction amount includes that gas drainage amount is accounted for and is filled with Amount ratio, different fracturing parameters: including fracturing borehole position, rate of water injection pressure break after gas extraction rate;And analyze fracturing crack Relationship between quantity, area, initial cracking pressure and gas drainage rate;
6c) it is based on pressure break front and back gas drainage rate size quantitative assessment hydraulic fracturing effect of increasing production, and Optimum Hydraulic pressure break Parameter.
Several testing programs that the present embodiment given below is enumerated:
Drilling in upper table in pressure position is hydraulic fracturing drilling.

Claims (1)

1. a kind of visualization of hydraulic fracturing coal seam crackle and antireflective effect evaluation method, characterized by comprising: early-stage preparations rank Mash gas extraction and fracturing effect are commented after mash gas extraction, hydraulic fracturing coal body stage, pressure break before section, crustal stress load phase, pressure break Valence;The specific steps are that:
It 1a) from the projecting coal bed middle sampling in coal mine region to be measured and carries out field research, the coal cinder of collection in worksite is utilized to be measured by sampling Projecting coal bed relevant parameter determines the test parameters such as crustal stress in testing program, rate of water injection, pressure break position;
The coal cinder sampling of acquisition 1b) is sieved into using broken sieve the coal grain of 0-1mm partial size, adds water and stirs and is made into coal grain 6% moisture content coal sample is spare;
6% moisture content coal sample 1c) is packed into visualization cabinet, the visualization bottom of box is equipped with spongy multi-function metal plate, more Function metal plate is equipped with inflating port, visualizes on the left side wall of top of the box and visualization cabinet and front side wall is equipped with more A transparent loading plate, visualizing the transparent loading plate of top of the box there are six serial number is respectively X1-X6, visualizes cabinet front wall On transparent loading plate there are six serial number be respectively Y1-Y6, visualizing transparent loading plate on the left side wall of cabinet is Z1, each Transparent loading plate is equipped with load piston, and load piston passes through box body wall connection pressurization oil cylinder;Box back surface is visualized to be equipped with Even step has multiple sensor mounting hole, has been simutaneously arranged row's multifunctional hole-drilling, wherein multifunctional hole-drilling tail portion is visualizing Cabinet is equipped with external connector, and gasket is equipped between external connector and the box body wall for visualizing cabinet, and multifunctional hole-drilling includes Sealing section, fracturing section, multifunctional hole-drilling overall length 0.5m, sealing of hole segment length 0.15m, pressure break segment length 0.35m, fracturing section tube wall it is circumferential and Air hole is distributed in radial direction, and serial number A1-A6 is arranged to multifunctional hole-drilling, is carried on the back in visualization cabinet using visualization cabinet 6% moisture content coal sample of the sensor mounting hole that portion opens up into visualization cabinet is embedded to baroceptor respectively, finally uses Load piston driving transparent loading plate releases all transparent loading plates after so that 6% moisture content coal sample is formed 1h under the conditions of 20 MPa Pressurization to coal sample;
1c) cover board for visualizing cabinet and box sealing are fastened using sealing ring and screw, by high pressure gas cylinder, vacuum pump, stream Meter I is linked in sequence, and the output end of flow meter I is connected by pipeline with the inflating port of multi-function metal plate, in visualization case Jointing is arranged in the multifunctional hole-drilling of the serial number A6 at body rear portion to be connected with flow meter II, visualizes the sequence at cabinet rear portion Number for A3 multifunctional hole-drilling in setting jointing be connected with the air inlet of flowmeter III, the gas outlet pipeline of flowmeter III It is connected with fracturing pump, the sealing effect of detection visualization cabinet and tracheae piping connection;
High-speed camera 1d) is installed on the outside of visualization cabinet, to monitor the visualization intracorporal variation of case;
Triaxial stress load operation 2a) is carried out to the intracorporal coal sample of visualization case, wherein visualizing the sequence on coal sample top in cabinet It number is 6 MPa for 6 pressing plate stress intensities of X1-X6,6 pressing plate stress intensities of front side serial number Y1-Y6 are 8 MPa;1 pressing plate stress intensity of left side serial number Z1 is 10 MPa;
2b) starting vacuum pump carries out vacuum pumping to coal sample, until coal body air pressure inside closes vacuum pump, use less than 100 Pa When about 12h;
It 2c) opens high pressure gas cylinder coal sample is carried out to fill gas operation, four stages that were divided into guarantee that the air pressure of coal sample adsorption equilibrium is 1.0MPa, first stage inflate 12h, the blowing pressure to 0.3 MPa, are then shut off gas cylinder, stablize 6h;Second stage inflation 12h, The blowing pressure is then shut off gas cylinder, stablizes 6h to 0.6 MPa;Phase III inflates 12h, the blowing pressure to 0.9 MPa, then Gas cylinder is closed, 6h is stablized;Fourth stage is inflated 6h, inflation and is stablized to 1.0 MPa, and gas cylinder is then shut off, and the used time is total about 60h is filled with gas amount by flow meter I record in gas replenishment process;
3a) according to gas drainage process before testing program development hydraulic fracturing, A6 drilling is opened, starts mash gas extraction, and pass through Flow meter II records gas drainage amount;
3b) extraction terminates extraction afterwards for 24 hours, unloads stress, empties gas;
4a) repeat step 2a-2c;
4b) control fracturing pump is filled the water in coal sample in visualization cabinet by the multifunctional hole-drilling of serial number A3 to setting, is filled the water Rate is 10mL/s;
Variation of the coal sample in fracturing pump the injecting process 4c) is observed by the way that the high-speed camera of visualization case-side is arranged in, when When observing that coal petrography surface generates crack, closes fracturing pump and stop water filling;
4d) terminate above-mentioned pressure break, closing high-speed video camera unloads stress;
5a) carry out hydraulic fracturing after gas extraction process according to testing program, opens the multifunctional hole-drilling extraction watt of serial number A6 This, and gas drainage amount is recorded by flow meter II;
5b) extraction terminates extraction afterwards for 24 hours, unloads stress, empties gas;
5c) change hydraulic fracturing bore position, rate of water injection condition, repeat step 1c-2c, 4a-5b, carries out other conditions and be lauched Force split and pressure break after gas extraction test.
6a) the coal body photo shot according to high-speed camera analyzes under different condition coal body face crack during hydraulic fracturing Growth, propagation law, and the final form of PS fracture is utilized to carry out sketch processing, analyzes fracturing borehole position, rate of water injection Etc. the relationship between different fracturing parameters and fracturing crack quantity, area, initial cracking pressure;
Gas drainage rate includes that gas drainage amount accounts for charge ratio before 6b) calculating separately pressure break according to gas charge and extraction amount Example, different fracturing parameters: including fracturing borehole position, rate of water injection pressure break after gas extraction rate;And analyze fracturing crack quantity, Relationship between area, initial cracking pressure and gas drainage rate;
6c) it is based on pressure break front and back gas drainage rate size quantitative assessment hydraulic fracturing effect of increasing production, and Optimum Hydraulic fracturing parameter.
CN201910590503.1A 2019-07-02 2019-07-02 Hydraulic fracturing coal seam crack visualization and permeability increasing effect evaluation method Active CN110306964B (en)

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