CN105716953B - Circulation variable pressure, which forces, splits simulation laboratory test method - Google Patents
Circulation variable pressure, which forces, splits simulation laboratory test method Download PDFInfo
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- CN105716953B CN105716953B CN201510069197.9A CN201510069197A CN105716953B CN 105716953 B CN105716953 B CN 105716953B CN 201510069197 A CN201510069197 A CN 201510069197A CN 105716953 B CN105716953 B CN 105716953B
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Abstract
The simulation laboratory test method split being forced for circulation variable pressure the invention discloses a kind of, study of rocks recycles failure mechanism and failure condition in pressure process.In the present invention, two groups of foil gauges are embedded in advance when pouring artificial specimen, it is every group three, mutually orthogonal two-by-two.The preset wedge shape cavity between two groups of foil gauges simultaneously, manufacture of intraocular crack inside it after artificial specimen molding, while foil gauge is sticked around man-made fracture, and position the extension in crack in artificial specimen surface gridding line.Flexible water bladder is placed in wedge shape cavity, is close to the wall surface of wedge shape cavity.Then three axis confining pressures are applied to artificial specimen, circulation variable pressure power load is carried out to artificial specimen by flexible water bladder.The present invention applies artificial specimen by flexible water bladder the circulating pressure load of different peak values, study the inherent mechanism that artificial specimen ruptures under alternating load, it determines that the initial cracking pressure when practice pressure break mode is constructed reduces amplitude, finally obtains the optimum combination of the pressure peak and load cycle number of fracture initiation.
Description
Technical field
It is forced the present invention be directed to circulation variable pressure and splits proposed simulation laboratory test method, which passes through transformation
The condition of the rock failure mechanism of rock and the mechanism of action are simulated and are studied when the mode of power CYCLIC LOADING is to pressure break.
Background technology
Hydraulic fracturing is to exploit the effective measures of low permeability oil and gas field.But for unconventional compact reservoir, in pressure break
Initial cracking pressure in the process is often very high, fails so as to cause pressure break.Therefore it needs that certain measure is taken to rise to reduce stratum
Split pressure makes stratum have more compressibility.The common means for reducing initial cracking pressure in oil field operation scene mainly have at present：
1. the mode of composite gun perforation：The high energy gas that the gunpowder of tripping in drastically expands to formation is lighted in perforating process,
High-voltage pulse is formed, further pressure break forms many cracks and then reduces initial cracking pressure inside preforation tunnel.
2. the mode of oriented perforation：In biggest principal stress direction perforation, crack crack initiation since biggest principal stress direction.
3. changing conventional perforation parameter：Increase Kong Mi, aperture, adjustment azimuth and increases gunpowder dosage.
But when by improving technique of the traditional perforation means of perforating modes and parameter to reduce stratum initial cracking pressure, perforation
The compaction of bullet causes the pollution in nearly pit shaft area, and especially to unconventional low permeability formation, this phenomenon becomes apparent.This
A kind of circulation variable pressure of disclosure of the invention, which forces, splits simulation laboratory test method, by the way of low pump pressure reverse cyclic loadings promotes rock
Fatigue rupture is generated, to reduce the initial cracking pressure in hydraulic fracturing process.However circulation variable pressure forces cracking method and also locates at present
It is not deep enough to its mechanism understanding in the state of exploration, also lack corresponding simulation laboratory test method.To solve the above problems,
The present invention, which proposes circulation variable pressure and forces, splits simulation laboratory test method, can determine that the pressure break mode to crack initiation pressure by this method
Power reduces amplitude, finds the optimum combination for making pressure peak and load cycle number, and then to the destruction machine of rock cycle pressurization
Reason and failure condition is further is furtherd investigate.
Invention content
The simulation laboratory test method split being forced for circulation variable pressure the purpose of the present invention is to provide a kind of, this method can
To simulate different pressure changeable load modes；More simple effective method is operated another object of the present invention is to provide a kind of,
The failure mechanism of rock in pressure changeable fracturing process is explored and divided by strain variation rule and fracture extension situation
Analysis determines which reduces amplitude to initial cracking pressure, and finds the pressure peak for making fracture initiation and load cycle number most
Excellent combination.
The invention discloses a kind of the simulation laboratory test method split, study of rocks cycle pressurization are forced for circulation variable pressure
Failure mechanism in the process and failure condition.It is embedded to two groups of foil gauges in advance when pouring artificial specimen, every group three, two two-phases
It is mutually orthogonal；The preset wedge shape cavity between two groups of foil gauges simultaneously, manufacture of intraocular crack inside it after artificial specimen molding, together
When stick foil gauge around man-made fracture, and position the extension in crack in artificial specimen surface gridding line；Wedge-shaped empty
Flexible water bladder is placed in chamber, is close to the wall surface of wedge shape cavity.Then three axis confining pressures are applied to artificial specimen, passes through flexible water bladder pair
Artificial specimen carries out circulation variable pressure power load.The present invention applies artificial specimen by flexible water bladder the circulating pressure of different peak values
Load studies the inherent mechanism that artificial specimen ruptures under alternating load, determines the crack initiation when practice pressure break mode is constructed
Pressure reduction amplitude finally obtains the optimum combination of the pressure peak and load cycle number of fracture initiation.
Circulation variable pressure as described above, which forces, splits laboratory test analogy method, wherein the artificial specimen generally uses
Cement and the mixing of quartz sand 1: 1 pour, and artificial specimen is cuboid, and size is 300mm × 300mm × 600mm or 300mm
×300mm×300mm。
Circulation variable pressure as described above forces splits laboratory test analogy method, wherein the artificial specimen is pouring
In the process, the position of center line in the end face of 300mm × 300mm of rectangle artificial specimen reserves wedge shaped cavity, depth
For 70-150mm, opening width 20-30mm, wedge shape cavity runs through the front/rear end of artificial specimen.
Circulation variable pressure as described above, which forces, splits laboratory test analogy method, wherein the artificial specimen was pouring
Cheng Zhong places one group of embedded strain sensor respectively up and down in front of artificial specimen inner wedge cavity, and every group comprising mutually orthogonal
3 foil gauges.
Circulation variable pressure as described above, which forces, splits laboratory test analogy method, wherein along wedge shape cavity bottom manufacturer
Work crack, man-made fracture length 2mm-5mm.
Circulation variable pressure as described above, which forces, splits laboratory test analogy method, wherein the surrounding at man-made fracture tip is used
Sand paper polishes to be formed than shallower concave surface, is foil gauge reserved space, and stick 4 foil gauges, 8 altogether.
Circulation variable pressure as described above, which forces, splits laboratory test analogy method, wherein around foil gauge and wedge shape cavity
The positioning grid lines for drawing 10mm × 10mm, the length of extension and the observation of position to facilitate crack are demarcated.
Circulation variable pressure as described above, which forces, splits laboratory test analogy method, wherein in the wedge shape cavity of artificial specimen
Flexible water bladder is placed, the wall surface of wedge shape cavity is close to, the wherein bearing capacity of pressure-bearing water pocket is not less than 15MPa.
Circulation variable pressure as described above, which forces, splits laboratory test analogy method, wherein flexible water bladder connects force (forcing) pump, setting
The peak value of cyclic loading and action time and number open force (forcing) pump, apply cyclic loading to artificial specimen.
Circulation variable pressure as described above, which forces, splits laboratory test analogy method, wherein per the certain number of CYCLIC LOADING, need by
Artificial specimen takes out the distance of observation fracture extension.Record water pocket pressure loading data simultaneously take pictures to test specimen fracture pattern.
From the above mentioned, the circulation variable pressure being directed to of the invention forces the laboratory test analogy method split, which can
It repeats to pressurize, cost is relatively low, and there is no complicated sealing problems, can intuitively observe very much the state of fracture initiation, hands over convenient for research
The inherent mechanism of the rock failure mechanism of rock under varying load determines that the pressure break mode reduces amplitude to initial cracking pressure, to realize pressure peak
The purpose of load, cycle-index and the optimum combination of action time.
Description of the drawings
The following drawings are only intended to schematically illustrate and explain the present invention, not delimit the scope of the invention.Wherein
Fig. 1 is to force to split laboratory test simulation system structure and side to artificial specimen sample progress circulation variable pressure in the present invention
The schematic diagram of method.
Fig. 2 is the loading curve of cyclic loading, wherein P0Crack when being straight line Slow loading starts the startup pressure extended
Power, α P0It is the pressure peak of repeat load.
Drawing reference numeral explanation：
1, artificial specimen 2, wedge shape cavity 3, flexible water bladder 4, man-made fracture 5, positioning grid lines 6, flush type are orthogonal
Foil gauge group 7, patch type foil gauge 8, signal transmssion line 9, force (forcing) pump 10, fluid injection pipeline
Specific implementation mode
For a clearer understanding of the technical characteristics, objects and effects of the present invention, implement below by specific
Example and the present invention is described in further detail in conjunction with attached drawing.
Fig. 1 is to force to split laboratory test simulation system structure and side to artificial specimen sample progress circulation variable pressure in the present invention
The schematic diagram of method；Fig. 2 is the loading curve of cyclic loading, wherein P0Crack when being straight line Slow loading starts the startup extended
Pressure, α P0It is the pressure peak of repeat load.
The invention discloses a kind of the simulation laboratory test method split, study of rocks cycle pressurization are forced for circulation variable pressure
Failure mechanism in the process and failure condition.In the present invention, it is embedded to two groups of foil gauges 6 when manufacturing artificial test specimen 1 in advance, every group
Three and mutually orthogonal two-by-two, the preset wedge shape cavity 2 between two groups of foil gauges, artificial specimen 1 manufacture inside it after being molded
Man-made fracture 4, while foil gauge 7 is sticked around man-made fracture 4, and draw positioning grid lines 5；It is placed in wedge shape cavity 2 soft
Property water pocket 3, is close to the wall surface of wedge shape cavity 2.Then three axis confining pressures are applied to artificial specimen 1, and is followed by the application of flexible water bladder 3
Ring pressure changeable load.The present invention applies artificial specimen by flexible water bladder 3 the circulating pressure load of different peak values, studies alternation
The inherent mechanism that artificial specimen 1 ruptures under load determines that the initial cracking pressure being used in when the practical pressure break mode is constructed reduces width
Degree, finally obtains the optimum combination of the pressure peak and load cycle number of fracture initiation.
Cuboid artificial specimen 1 is generally poured using cement and the mixing of quartz sand 1: 1, and 1 size of artificial specimen is length
Cube size is 300mm × 300mm × 600mm or 300mm × 300mm × 300mm.
During actually pouring, the position of center line in the end face of 300mm × 300mm of artificial specimen 1 opens a wedge
Shape cavity 2, depth 70-150mm, opening width 20-30mm run through front/rear end.And it is attached in test specimen inner wedge cavity 2
Two groups of foil gauges 6 are closely placed, every group of foil gauge 3 is mutually orthogonal two-by-two, pays attention to staying in signal wire joint outside artificial specimen 1.
In the bottom manufacture of intraocular crack 4 of wedge shape cavity 2,4 length of man-made fracture is 2mm-5mm, and man-made fracture 4 is run through
Front/rear end on, it is foil gauge reserved space that the surrounding at 4 tip of crack, which is polished with sand paper and to be formed than shallower concave plane, and
Stick 4 foil gauges 7, artificial specimen 8 altogether.
Straight-line groove is delineated on rock sample surface, is the arrangement reserved space of signal transmssion line 8, signal wire 8 connects number
According to all reading strains inside and outside collector acquisition test specimen；The positioning of 10mm × 10mm is drawn around foil gauge 7 and wedge shape cavity 2
Grid lines 5, to facilitate crack 4 extension length and tip location observation calibration.
Flexible water bladder 3 is placed in the wedge shape cavity 2 of artificial specimen 1, and is close to the wall surface of wedge shape cavity 2.Experiment process
In, sample is placed on true triaxial test platform, three axis confining pressures are applied to artificial specimen 1.
Flexible water bladder 3 is connected into force (forcing) pump 9, setting cycle pressure load cycle load mode, dead time and number are opened
Force (forcing) pump 9 is opened, hydraulic pressure load is applied to artificial specimen 1 by flexible water bladder 3.
Artificial specimen 1, need to be taken out the distance of observation fracture extension by the certain number of often cycle pressurization.Record flexible water bladder 3
Pressure loading data and fracture shape are taken pictures, and finding makes the optimal of the pressure peak of fracture initiation and load cycle number
Combination.Strain data is analyzed with the changing rule of load, the mechanism of fatigue rupture is further analyzed, while being compared in straight line
Under Slow loading, the magnitude of load that circulation variable pressure power is reduced is calculated.
The above is the schematical specific implementation mode of the present invention, is not limited to the scope of the present invention.It is any
Those skilled in the art, do not depart from the design of the present invention and under the premise of principle made by variation and modification on an equal basis, should all
It belongs to the scope of protection of the present invention.
Claims (7)
1. a kind of circulation variable pressure, which forces, splits simulating lab test method, which is characterized in that be embedded in advance when pouring artificial specimen
Two groups of foil gauges, it is every group three, mutually orthogonal two-by-two；Simultaneously between two groups of foil gauges prefabricated wedge shape cavity, artificial specimen at
Manufacture of intraocular crack inside it after type, while foil gauge is sticked around man-made fracture, and in the gridding of artificial specimen surface
Line positions the extension in crack；Flexible water bladder is placed in wedge shape cavity, is close to the wall surface of wedge shape cavity；Then to artificial specimen
Apply three axis confining pressures, circulation variable pressure power load is carried out to artificial specimen by flexible water bladder；By flexible water bladder to artificial specimen
Apply the circulating pressure load of different peak values, studies the inherent mechanism that artificial specimen ruptures under alternating load, determine practice
When the pressure break mode is constructed initial cracking pressure reduce amplitude, finally obtain fracture initiation pressure peak and load cycle number most
Excellent combination.
2. a kind of circulation variable pressure as described in claim 1, which forces, splits simulating lab test method, it is characterised in that：Artificial specimen
Using cement and quartz sand mixing pour, artificial specimen size be cuboid, size be 300mm × 300mm × 600mm or
300mm×300mm×300mm。
3. a kind of circulation variable pressure as described in claim 1, which forces, splits simulating lab test method, it is characterised in that：Actually pouring
During building, the position of center line in the end face of 300mm × 300mm of rectangle artificial specimen opens a wedge shape cavity, cavity
Wedgewise, depth 70-150mm, opening width 20-30mm run through front/rear end, are split along wedge shape cavity manufacture of intraocular
Seam, man-made fracture length 2mm-3mm.
4. a kind of circulation variable pressure as described in claim 1, which forces, splits simulating lab test method, it is characterised in that：Pouring people
During work test specimen, one group of foil gauge is placed respectively up and down in front of test specimen inner wedge cavity, every group includes pairwise orthogonal
3 foil gauges.
5. a kind of circulation variable pressure as described in claim 1, which forces, splits simulating lab test method, it is characterised in that：Use sand paper
Scrobicula face will be polished around the man-made fracture tip on test specimen front/rear end respectively, pastes 4 strains in the scrobicula face later
Piece, front/rear end paste altogether 8 foil gauges.
6. a kind of circulation variable pressure as claimed in claim 5, which forces, splits simulating lab test method, it is characterised in that：In foil gauge
And the artificial specimen surface around wedge shape cavity indicates the positioning grid lines of 10mm × 10mm.
7. a kind of circulation variable pressure as described in claim 1, which forces, splits simulating lab test method, it is characterised in that often cycle adds
Certain number is pressed, need to artificial specimen be taken out to the distance of observation fracture extension, and demarcate position.
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| CN106153463A (en) * | 2016-09-19 | 2016-11-23 | 安徽理工大学 | A kind of monitoring method of standard rock sample internal strain |
| CN107575203B (en) * | 2017-10-12 | 2019-09-24 | 中国石油大学(北京) | A kind of loose sand hydraulic fracturing simulator that can observe fracture pattern in real time |
| CN110375686B (en) * | 2019-07-09 | 2021-07-23 | 武汉理工大学 | Wireless flexible microstrip patch antenna sensor array for monitoring cracks and strain of metal structure |
| CN113668623A (en) * | 2021-08-24 | 2021-11-19 | 中国建筑第八工程局有限公司 | Mechanical property test device and method for connection node of assembled cup groove |
| CN114199686A (en) * | 2021-11-05 | 2022-03-18 | 武汉二航路桥特种工程有限责任公司 | Model test device and method for disease evolution law of tunnel lining of operation highway |
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| JP2904209B1 (en) * | 1998-02-10 | 1999-06-14 | 東海ゴム工業株式会社 | Opening / closing valve device for pressure water channel and pressure resistance testing device for hose using the same |
| CN100498273C (en) * | 2006-05-17 | 2009-06-10 | 中国葛洲坝集团股份有限公司 | Method for testing damage and load characteristics of concrete fracture test |
| CN101968348B (en) * | 2010-09-07 | 2012-05-02 | 中国石油大学(北京) | Method for visually monitoring fracture crack |
| CN102031954B (en) * | 2010-12-30 | 2013-06-12 | 河南理工大学 | Coal and rock bore hydraulic fracture experimental apparatus |
| CN102289980B (en) * | 2011-05-24 | 2013-05-15 | 中国石油大学(北京) | Method for preparing preset cracks in hydrofracture simulation specimen |
| CN102279131B (en) * | 2011-07-18 | 2013-04-24 | 中国石油大学(北京) | Simulation experiment method of coal seam hydraulic fracture |
| CN103266888A (en) * | 2013-05-21 | 2013-08-28 | 中国石油大学(华东) | System and method for visualization fracturing simulation experiment |
| CN103592186A (en) * | 2013-11-29 | 2014-02-19 | 重庆大学 | Device and experimental method for researching shale hydraulic-fracturing damage evolution under true triaxial loading condition |
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