CN111366472B - True triaxial hydraulic fracturing physical simulation equipment and method for variable core size - Google Patents
True triaxial hydraulic fracturing physical simulation equipment and method for variable core size Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
- G01N3/12—Pressure testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/003—Generation of the force
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/006—Crack, flaws, fracture or rupture
- G01N2203/0062—Crack or flaws
- G01N2203/0064—Initiation of crack
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/006—Crack, flaws, fracture or rupture
- G01N2203/0062—Crack or flaws
- G01N2203/0066—Propagation of crack
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0256—Triaxial, i.e. the forces being applied along three normal axes of the specimen
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- G—PHYSICS
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0658—Indicating or recording means; Sensing means using acoustic or ultrasonic detectors
Abstract
The invention provides true triaxial hydraulic fracturing physical simulation equipment applied to variable core size, which comprises a hydraulic pressure stabilizing source, a true triaxial simulation test stand and a comprehensive fracturing fluid injection control device, wherein the true triaxial simulation test stand is connected with the hydraulic pressure stabilizing source to provide hydraulic pressure for a fracturing experiment, the true triaxial simulation test stand is connected with the comprehensive fracturing fluid injection control device to control the injection of fracturing fluid in the experiment process, and the true triaxial simulation test stand is respectively provided with confining pressure applying devices with layering pressure application and adjustable height in the X, Y and Z directions so as to be suitable for simulating the conditions of different stress pressure applications by tightly fitting the surfaces of acting samples. The beneficial effects of the invention are: the method can be used for developing a true triaxial hydraulic fracturing experiment aiming at the underground core subjected to field coring, and researching the fracture initiation and expansion rules of the true underground stratum.
Description
Technical Field
The invention relates to the technical field of oil and gas drilling rock physical engineering, in particular to true triaxial hydraulic fracturing physical simulation equipment and method for variable core size.
Background
In recent years, along with the continuous deepening of oil gas exploration and development, unconventional oil gas resources such as shale gas, compact oil, compact gas, coal bed gas and the like have great development potential under the existing economic and technical conditions. The hydraulic fracturing technology is one of core technologies of unconventional oil and gas resource development, is widely applied to the transformation of reservoirs, and can greatly improve the productivity of unconventional oil and gas wells.
Over the course of more than 50 years of development, hydraulic fracturing technology has made dramatic progress from theoretical research to field practice. The true triaxial hydraulic fracturing physical simulation experiment is the most intuitive method for researching hydraulic fracturing fracture initiation and fracture propagation. But the current true triaxial hydraulic fracturing device ubiquitous has a series of problems: (1) The samples of most true triaxial hydraulic fracturing devices are cubic rock samples of fixed dimensions, such as 100mm x 100mm,300mm x 300mm x 300mm,400mm x 400mm, and the like. Therefore, the conventional true triaxial hydraulic fracturing equipment cannot meet the experiment requirements for core samples with different sizes; (2) The sample used by the true triaxial apparatus is generally an artificial sample (such as cement mortar) or a natural outcrop rock sample. The two samples have many differences with underground real stratum rocks in physical properties and mechanical properties, and the obtained experimental result cannot accurately reflect the real situation; (3) The current true triaxial equipment generally does not have a horizontal stress layered loading function, so that the actual ground stress distribution condition cannot be simulated; or the designed loading parts are too many and too complex, so that the problem of mutual interference of a plurality of loading parts is caused.
Disclosure of Invention
The invention overcomes the defects in the prior art, provides the true triaxial hydraulic fracturing physical simulation equipment and method for the variable core size, and can be used for developing a true triaxial hydraulic fracturing experiment aiming at an underground core subjected to field coring and researching the fracture initiation and expansion rules of a true underground stratum.
The purpose of the invention is realized by the following technical scheme.
Be applied to true triaxial hydraulic fracturing physical simulation equipment that is used for variable rock core size, including hydraulic pressure steady voltage source, true triaxial analogue test frame and fracturing fluid integrated injection controlling means, true triaxial analogue test frame with hydraulic pressure steady voltage source is connected and is provided hydraulic pressure for the fracturing experiment, true triaxial analogue test frame with fracturing fluid integrated injection controlling means is connected, and the injection of control experiment in-process fracturing fluid, its characterized in that: the true triaxial simulation experiment frame is provided with a confining pressure applying device with layered pressure application and adjustable height in the X direction, the Y direction and the Z direction respectively so as to be suitable for simulating the condition of different stress pressure application on the surface of a tightly-attached action sample.
Further, confining pressure is applyed the device and is included layering pressure plate, pressure plate connecting block, hydraulic jack, liftable spiral support and spiral support sleeve, there is the sample laminating in one side of layering pressure plate, the opposite side of layering pressure plate with the pressure plate connecting block is connected, hydraulic jack does the pressure plate connecting block with layering pressure plate provides pressure, liftable spiral support's lower part is equipped with the spiral support sleeve, the spiral support sleeve passes through slide slidable and sets up on the true triaxial simulation test frame.
Further, the layered pressure plate is composed of an arrangement of metal plates of different materials and equal thickness.
Furthermore, the material of each metal plate can be any combination of two of cast iron, carbon steel, cast steel and aluminum.
Furthermore, an acoustic emission probe is arranged on the layering pressure plate and is attached to the surface of the sample.
Further, an electric heating rod is arranged on the layered pressure plate to heat the sample.
Furthermore, the comprehensive injection control device for the fracturing fluid comprises a fracturing fluid tank, a sand-carrying fluid tank and a backflow fluid tank, wherein the fracturing fluid tank, the sand-carrying fluid tank and the backflow fluid tank are respectively connected with a fluid injection pipeline through valves, and a fluid injection hole of the fluid injection pipeline is connected with a shaft in a sample.
Furthermore, the frame of true triaxial simulation test frame includes from last roof-rack, grudging post, platform and the support that connects gradually extremely down, and sets up the roof-rack the grudging post with seal box between the platform, inject silicone oil in the seal box.
Further, the liquid pressure in the seal box is the same as the applied pore pressure of the sample, and the fluid injected into the sample is prevented from leaking out due to the pressure difference.
A method for simulating a hydraulic fracture physical simulation experiment using the hydraulic fracture physical simulation experiment apparatus of claim 1, comprising the steps of:
the method comprises the following steps: placing a sample on a true triaxial test stand, adjusting the vertical position of a confining pressure applying device relative to the sample through a liftable spiral support, adjusting the horizontal position of the confining pressure applying device relative to the sample through a sliding spiral support sleeve, enabling a pressure plate to be attached to the side face of the sample, and enabling an acoustic emission probe to be in contact with the surface of the sample;
step two: injecting silicone oil into the sealing box to fill the sealing box with the silicone oil;
step three: opening a hydraulic pressure stabilizing source, respectively setting the confining pressure in the X direction, the Y direction and the Z direction according to an experimental scheme, and placing the sample for 15 minutes after the three-dimensional confining pressure reaches a specified value so that the interior of the sample reaches a stress balance state;
step six: opening the fracturing fluid comprehensive injection control device, injecting the sample, starting the fracturing process, wherein the process is as follows:
the method comprises the following steps that firstly, the fracturing fluid is injected into a control device in a comprehensive mode, and the fracturing fluid is pumped into a sample to enable the sample to generate cracks;
secondly, injecting sand-carrying fluid of the mixed sand into the fracturing fluid comprehensive injection control device;
opening a valve to enable the fluid in the sample to enter a backflow liquid tank under the action of negative pressure, and simulating a backflow condition;
step seven: and the comprehensive injection control device of the fracturing fluid closes the hydraulic pressure stabilizing source to unload the three-way confining pressure to zero, and then the sample is taken out.
The invention has the beneficial effects that:
the size of the layered pressure plate of the true triaxial apparatus is adjustable, so that the true triaxial experiment apparatus can perform experiments on samples with different sizes, and particularly can realize the experiment of cores with the diameter of 100mm to 200mm underground.
By changing the material of which the pressure plate is made, the layered pressurization of horizontal stresses can be conveniently realized. The equipment can realize a small-sized hydraulic fracturing experiment of the underground real core, and the pressed rock sample can meet the size requirement of most CT equipment; therefore, the fracture initiation and expansion properties of the actual reservoir rock are researched on the premise of not damaging the rock sample.
Drawings
FIG. 1 is a schematic view of the structure of the present invention;
FIG. 2 is a schematic structural diagram of a true triaxial simulation test stand;
FIG. 3 is a schematic structural diagram of a sample confining pressure applying device for installing an acoustic emission device;
FIG. 4-1 is a front view of a layered pressure plate;
FIG. 4-2 is a side view of a layered pressure plate;
4-3 are top views of layered pressure plates;
FIG. 5 is a schematic diagram of a sample placement configuration;
in the figure:
1. a top frame; 2. an upper cover plate; 3. erecting a frame; 4. a platform; 5. a support; 6. an O-shaped sealing ring; 7. liquid injection cover plate;
8. a sample; 9. an oil jack; 10. a pressure plate connecting block; 11. a layered pressure plate; 12. a lifting spiral support; 13. A helical support sleeve; 15. a wellbore; 16. a liquid injection line; 17. a hydraulic jack priming line; 18. a rubber pad; 19. A true triaxial simulation test stand; 20. a hydraulic pressure stabilizing source; 21. a fracturing fluid comprehensive injection control device;
22. an acoustic emission probe fixing plate; 23; a liquid injection inlet end pressure gauge; 24. and a pressure electronic recorder;
26. a fracturing fluid tank; 27. a sand carrying liquid tank; 28. a back drainage liquid tank; 29. a pressure gauge; 30. a sealing box;
31-1, 31-2, 31-3, 31-4, 31-5 and a valve; 32. a latex film; 33. heat shrink tubing;
34. an acoustic emission probe fixing hole; 35. an upper pressure plate; 36. a lower pressure plate; 37. a medium pressure plate;
38. a cylindrical bore.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples.
As shown in fig. 1 and 2, the true triaxial hydraulic fracturing physical simulation equipment for variable core size mainly comprises a hydraulic pressure stabilizing source 20, a true triaxial simulation test stand 19 and a fracturing fluid comprehensive injection control device 21, wherein the true triaxial simulation test stand 19 is connected with the hydraulic pressure stabilizing source 20, the true triaxial simulation test stand 19 is connected with the fracturing fluid comprehensive injection control device 21, and the injection process of the fracturing fluid in the experiment process is controlled.
The hydraulic pressure stabilizing source 20 is provided with a pressure gauge 29 for displaying a pressure value, which is expressed as a pressure value of oil pressure in the oil jack 9, so that the confining pressure value of the three-way stress can be reflected. And the confining pressure can be accurately loaded through computer servo control.
The fracturing fluid comprehensive injection control device 21 is provided with a liquid injection inlet end pressure gauge 23 and a pressure electronic recorder 24, and can record and display the change of the pressure of the liquid injection end along with the time in real time. The fracture curve obtained by the pressure electronic recorder 24 can be used for judging the fracture initiation and extension process of the fracture in the fracturing process.
The true triaxial simulation test stand 19 includes: the device comprises a top frame 1, an upper cover plate 2, a vertical frame 3, a platform 4, a support 5, an O-shaped sealing ring 6, a liquid injection cover plate 7, a rubber pad 8 with a hole in the middle, an oil jack 9, a pressure plate connecting block 10, a layered pressure plate 11, a liftable spiral support 12, a spiral support sleeve 13, a slide way 14, a shaft 15, a liquid injection pipeline 16, an oil jack liquid injection pipeline 17 and a sample 18;
the whole frame of the true triaxial simulation test frame 19 consists of a top frame 1, a vertical frame 3, a platform 4 and a support 5, other devices and parts are all arranged on the frame, a sealing box 30 is arranged on the frame, silicone oil is injected into the sealing box 30, the liquid pressure in the sealing box 30 is the same as the applied pore pressure of the sample 8, and the fluid injected into the sample 8 is prevented from leaking out due to the action of pressure difference; wherein, the layered pressure plate 11 and the pressure plate connecting block 10 are connected by hexagon socket head cap screws, and together form a confining pressure applying device. Wherein the pressure plate connecting block 10 is arranged on the liftable spiral support 12, and the liftable spiral support 12 is arranged on the pressure plate connecting block; the screw support sleeve 13 is arranged below the sample holder, and the height of the pressure plate connecting block 10 is adjusted by rotating the liftable screw support 12, so that the height of the upper surface of the pressure plate 10 is adjusted to be consistent with that of the upper surface of the sample 18. In addition, the spiral support sleeve 13 can slide on the slide way 14, and the adaptability to samples with different sizes is realized by adjusting the front-back distance between the pressure plate and the samples. The applying mode of confining pressure provides pressure through the oil jack 9, and the oil jack 9 is connected with the hydraulic pressure stabilizing source 21 through the oil jack liquid injection pipeline 17. The hydraulic pressure is provided by a hydraulic pressure stabilizing source 20 to drive the oil jack 9 to move, so that a confining pressure applying device consisting of a layered pressure plate 11 and a pressure plate connecting block 10 is pushed to provide confining pressure for the sample. The upper part of the sample 18 is provided with a rubber pad 9 with a hole in the middle, so as to ensure the sealing property of the injected liquid. The upper part of the middle perforated rubber pad 9 is provided with an injection cover plate 7, the middle of the cover plate is provided with a protruding injection hole, the injection hole is connected with a shaft 15 in a sample and is connected with an external injection pipeline 16, and an O-shaped sealing ring is arranged around the injection hole to ensure the sealing performance in the injection process. The upper cover plate 2 is arranged above the liquid injection cover plate 7 and is connected with the top frame 1 through screws.
In order to carry out true triaxial experiments on underground rock core samples with different sizes, the invention provides a confining pressure applying device which mainly comprises a pressure plate connecting block and a pressure plate, wherein the samples with different sizes are subjected to true triaxial fracturing experiments by changing the size of the pressure plate, the pressure plate connecting block is connected with the pressure plate through an inner hexagonal screw, and the experiments on the rock cores with the diameters from 100mm to 200mm under the well can be realized;
the invention also provides a sample confining pressure applying device which can be used for installing an acoustic emission device, and the sample confining pressure applying device comprises: the acoustic emission probe comprises a pressure plate connecting block 10, a pressure plate for mounting an acoustic emission probe, an acoustic emission probe fixing plate 22 and an acoustic emission probe fixing hole 34. The pressure plate connecting block 10 is connected with a pressure plate for mounting an acoustic emission probe through an inner hexagonal screw, the acoustic emission probe fixing plate 22 is connected with the pressure plate for mounting the acoustic emission probe through an inner hexagonal screw, and the acoustic emission probe penetrates through the pressure plate through an acoustic emission probe fixing hole 34 and is attached to the surface of a sample; the pressure plate is made of metal plates with different materials and equal thicknesses, the pressure plate and the pressure plate connecting block 10 are fixedly connected through hexagon socket head cap screws, two cylindrical through holes are formed in the pressure plate, and electric heating rods are placed in the through holes; the pressure plates referred to above may be either layered pressure plates 11 or non-layered pressure plates;
the principle that the layered pressure plate 11 can realize layered pressing as shown in fig. 4-1, 4-2 and 4-3 is as follows: the pressure plate only deforms elastically during the pressure application process, and when the right end of the combined layered pressure plate 11 applies the same acting force through the pressure plate connecting block 10, the Young modulus and the Poisson ratio of different materials are different, so that the acting force of the contact end surfaces of the different materials and the sample is different, namely the stress is different in magnitude. Therefore, by adjusting the material composition of the combined layered pressure plate 11, calculation and application of different stresses in the horizontal direction can be realized; two cylindrical perforations 38 are made in the laminating pressure plate 11 and an electrical heating rod is placed to heat the sample 8 as the laminating pressure plate 11 is in direct contact with the sample 8.
Preferably, the layered pressure panel 11 is divided into three layers, wherein upper and lower layersThe two pressure plates 35, 36 are made of cast iron and have an elastic modulus of 100GPa, and the intermediate pressure plate 37 is made of steel and has an elastic modulus of 200GPa. After completion of the installation of sample 8 and the apparatus, the strain corresponding to the three pressure plates was dl/l =0.00005 assuming that a displacement of dl =0.002mm was applied with the oil jack. The stress applied to the surfaces of different materials can be calculated according to linear elasticity mechanics as follows: sigma Cast iron ＝50MPa；σ Steel =100MPa. The stress applied to the steel surface is 2 times that of the cast iron material, namely sigma is equal to the displacement Cast iron /σ Steel ＝E Cast iron /E Steel 。
Given the same displacement of 0.002mm, the stress applied to sample 8 by the layered pressure plate 11 of different materials is shown in table 1:
TABLE 1 stress applied to samples by pressure plates of different materials
In summary, the laminated pressure plate 11 is divided into three layers, wherein the upper and lower pressure plates 35, 36 are made of different materials, and the material of the pressure plate is different from that of the middle pressure plate 37;
or the upper and lower pressure plates 35, 36 are made of the same material, but different from the pressure plate 37;
the upper and lower pressure plates 35, 36 are made of any one or two of cast iron, carbon steel, cast steel and aluminum, and the middle pressure plate 37 is made of any one of cast iron, carbon steel, cast steel and aluminum.
The invention also provides a sample preparation method for the true triaxial test of the soft rock sample. Due to the high permeability of soft rock, the low strength of the sample, the transport and loading processes may cause damage to the sample. Therefore, for soft rock, a layer of impermeable membrane is added around the sample, and the impermeable membrane has certain strength and can prevent the sample from being damaged in the process of transporting and preventing the sample.
A method for simulating a hydraulic fracturing physical experiment by using true triaxial hydraulic fracturing physical simulation equipment for underground rock cores with different sizes comprises the following steps:
the method comprises the following steps: placing a sample 8 on a true triaxial test stand 19, wrapping the sample 8 with a latex film 32 and a heat shrinkable tube 33 before an experiment as shown in fig. 5, so as to ensure the sealing property of the sample 8, adjusting the vertical position of a confining pressure applying device relative to the sample 8 by a lifting spiral support 13, adjusting the horizontal position of the confining pressure applying device relative to the sample 8 by sliding a spiral support sleeve 13, so that a layered pressure plate 11 is attached to the side surface of the sample 8, and a sound emission probe is contacted with the surface of the sample 8;
step two: injecting silicone oil into the seal box 30 to fill the seal box 30 with the silicone oil;
step three: opening a hydraulic pressure stabilizing source 20, respectively setting the confining pressure in the X direction, the Y direction and the Z direction according to an experimental scheme, and placing the sample 8 for 15 minutes after the three-dimensional confining pressure reaches a specified value so as to enable the interior of the sample 8 to reach a stress balance state;
step six: open fracturing fluid and synthesize injection control device 21, annotate the liquid to sample 8, begin the fracturing process, the process is as follows:
firstly, injecting liquid by utilizing a fracturing fluid comprehensive injection control device 21, and pumping the fracturing fluid into the sample to generate cracks in the sample 8;
secondly, injecting the sand-carrying fluid mixed with the sand into a fracturing fluid comprehensive injection control device 21;
thirdly, opening a valve 31-5, closing valves 31-1, 31-2, 31-3 and 31-4 to enable fluid in the sample 8 to enter the return liquid tank 28 under the action of negative pressure, and simulating the return situation;
step seven: and (3) comprehensively injecting the fracturing fluid into the control device 21, closing the hydraulic pressure stabilizing source 20 to enable the three-way confining pressure to be unloaded to be zero, and then taking out the sample 8.
Example 1
As shown in fig. 1, the true triaxial hydraulic fracturing physical simulation experiment equipment applied to cores with different sizes in a well according to the invention performs a true triaxial hydraulic fracturing experiment on a cubic core sample 8 with the size of 100mm × 100mm × 100mm, and comprises the following steps in sequence:
the method comprises the following steps: a100 mm by 100mm pressure plate 11 is selected to mount the acoustic emission probe and an acoustic emission probe mount plate 22 is mounted on the pressure plate as shown in FIG. 3. Then connecting the pressure plate to a pressure plate connecting block (10) to obtain a confining pressure loading device for a cubic core sample experiment of 100mm multiplied by 100 mm;
step two: the sample 8 is placed on a true triaxial test stand 19, and a confining pressure loading device is placed above the liftable spiral support 12 around the sample according to the diagram. The horizontal position of the support relative to the sample is adjusted by sliding the spiral support sleeve 13, and the vertical position of the liftable spiral support 12 relative to the sample is adjusted by rotating the liftable spiral support, so that the layered pressure plate 11 is attached to the side surface of the sample 8. Then, the acoustic emission probe penetrates through an acoustic emission probe fixing hole in the pressure plate, the probe is made to contact with the surface of the sample 8, and finally the probe is fixed to complete the installation of the acoustic emission device;
step three: a100 mm multiplied by 100mm square rubber pad with a hole in the middle is placed on the upper surface of a sample, then a 100mm multiplied by 100mm square liquid injection cover plate 7 is placed above the rubber pad 18, and finally the upper cover plate 2 is fixed on the top frame 1 through screws. The installation of the true triaxial test stand 19 is completed;
step four: connecting a true triaxial test stand 19, a comprehensive fracturing fluid injection control device 21 and a hydraulic pressure stabilizing source 20 according to a mode shown in figure 1;
step five: and (3) opening the hydraulic pressure stabilizing source 20, and respectively setting the confining pressure in the X direction, the Y direction and the Z direction according to the experimental scheme. After the three-dimensional confining pressure reaches a specified value, placing the sample for 15 minutes to enable the interior of the sample to reach a stress balance state, and preparing to carry out the next experiment;
step six: open fracturing fluid and synthesize injection control device 21, annotate liquid to sample 8, annotate the liquid simultaneously, can observe notes liquid end pressure through annotating liquid entry end pressure gauge 23 and pressure electronic record appearance 24, the fracturing process as follows:
firstly, injecting liquid by utilizing a fracturing fluid comprehensive injection control device 21, and pumping the fracturing fluid into the sample to generate cracks in the sample 8;
secondly, injecting sand-carrying fluid of the mixed sand into a control device 21 by utilizing comprehensive injection of fracturing fluid;
thirdly, opening a valve 31-5, closing valves 31-1, 31-2, 31-3 and 31-4 to enable the fluid in the sample 8 to enter the backflow liquid tank 28 under the action of negative pressure, and simulating the backflow condition;
step seven: after the experiment is finished, the comprehensive fracturing fluid injection control device 21 is closed, the hydraulic pressure stabilizing source 20 is closed, the three-way confining pressure is unloaded to zero, and then the sample is taken out.
While one embodiment of the present invention has been described in detail, the present invention is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Claims (7)
1. The utility model provides a real triaxial hydraulic fracturing physical simulation equipment for variable rock core size, includes hydraulic pressure steady voltage source (20), real triaxial simulation test frame (19) and fracturing fluid comprehensive injection controlling means (21), real triaxial simulation test frame (19) with hydraulic pressure steady voltage source (20) are connected and are provided hydraulic pressure for the fracturing experiment, real triaxial simulation test frame (19) with fracturing fluid comprehensive injection controlling means (21) are connected, control the injection of fracturing fluid in the experimentation, its characterized in that: the true triaxial simulation test frame (19) is respectively provided with confining pressure applying devices which apply pressure in a layered manner and have adjustable heights in the X direction, the Y direction and the Z direction so as to be suitable for simulating the conditions of applying pressure with different stresses on the surface of a sample with close fit;
the confining pressure applying device comprises a layered pressure plate (11), a pressure plate connecting block (10), an oil jack (9), a liftable spiral support (12) and a spiral support sleeve (13), wherein a sample is attached to one side of the layered pressure plate (11), the other side of the layered pressure plate is connected with the pressure plate connecting block (10), the oil jack (9) provides pressure for the pressure plate connecting block (10) and the layered pressure plate (11), the spiral support sleeve (13) is arranged on the lower portion of the liftable spiral support (12), and the spiral support sleeve (13) is slidably arranged on the true triaxial simulation test frame (19) through a slide way;
the layered pressure plate (11) is divided into three layers and is formed by arranging equal-thickness metal plates made of different materials, and the metal plates are made of any combination of cast iron, carbon steel, cast steel and aluminum;
the core is a real underground core subjected to field coring.
2. The true triaxial hydraulic fracturing physical simulation equipment for variable core size of claim 1, wherein: and an acoustic emission probe is arranged on the layered pressure plate (11) and is attached to the surface of the sample.
3. The true triaxial hydraulic fracturing physical simulation equipment for variable core sizes according to claim 2, wherein: an electric heating rod is arranged on the layering pressure plate (11) to heat the sample (8).
4. The true triaxial hydraulic fracturing physical simulation equipment for variable core size of claim 1, wherein: the comprehensive injection control device for the fracturing fluid comprises a fracturing fluid tank (26), a sand carrying fluid tank (27) and a back-flowing fluid tank (28), wherein the fracturing fluid tank (26), the sand carrying fluid tank (27) and the back-flowing fluid tank (28) are respectively connected with a fluid injection pipeline (16) through valves, and a fluid injection hole of the fluid injection pipeline (16) is connected with a shaft (15) in a sample (8).
5. The true triaxial hydraulic fracturing physical simulation apparatus for variable core size according to any one of claims 1 to 4, wherein: the frame of true triaxial simulation test frame (19) includes from last roof-rack (1), grudging post (3), platform (4) and support (5) that connect gradually extremely down, and sets up roof-rack (1) grudging post (3) with seal box between platform (4), inject silicon oil in seal box (30).
6. The true triaxial hydraulic fracturing physical simulation equipment for variable core sizes according to claim 5, wherein: the liquid pressure in the sealed box (30) is the same as the applied pore pressure of the sample (8), and the fluid injected into the sample (8) is prevented from leaking out due to the pressure difference.
7. A method for simulating a hydraulic fracture physical experiment using the hydraulic fracture physical simulation device of claim 6, wherein: the method comprises the following steps:
the method comprises the following steps: placing a sample (8) on a true triaxial simulation test stand (19), adjusting the vertical position of a confining pressure applying device relative to the sample (8) through a liftable spiral support (12), adjusting the horizontal position of the confining pressure applying device relative to the sample (8) through a sliding spiral support sleeve (13), enabling a layering pressure plate (11) to be attached to the side surface of the sample (8), and enabling an acoustic emission probe to be in contact with the surface of the sample (8);
step two: injecting silicone oil into the sealing box (30) to fill the sealing box (30) with the silicone oil;
step three: opening a hydraulic pressure stabilizing source (20), respectively setting the confining pressure in the X direction, the Y direction and the Z direction according to an experimental scheme, and placing the sample (8) for 15 minutes after the three-direction confining pressure reaches a specified value, so that the interior of the sample (8) reaches a stress balance state;
step four: opening a fracturing fluid comprehensive injection control device (21), injecting the sample (8) and starting a fracturing process, wherein the process comprises the following steps:
the method comprises the following steps that firstly, the fracturing fluid is injected by utilizing a comprehensive injection control device (21), and the fracturing fluid is pumped into a sample (8), so that cracks are generated in the sample (8);
secondly, injecting sand-carrying fluid of the mixed sand into a control device (21) by utilizing the comprehensive injection of the fracturing fluid;
thirdly, opening a valve to enable the fluid in the sample (8) to enter a backflow liquid tank (28) under the action of negative pressure, and simulating the backflow condition;
step five: and the comprehensive injection control device (21) of the fracturing fluid closes the hydraulic pressure stabilizing source (20), so that the three-way confining pressure is unloaded to zero, and then the sample (8) is taken out.
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| CN113432975B (en) * | 2021-06-11 | 2022-09-27 | 中国石油大学(北京) | Detection device and detection system for rock sample pressurization test |
| CN114184486B (en) * | 2021-12-08 | 2023-12-12 | 西南科技大学 | Rock fracture toughness measuring device and method under high-temperature and high-pressure conditions |
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