CN113551999A - Visual hydraulic fracturing experimental device and method for simulating different horizontal axial difference stress conditions - Google Patents
Visual hydraulic fracturing experimental device and method for simulating different horizontal axial difference stress conditions Download PDFInfo
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- CN113551999A CN113551999A CN202111023598.2A CN202111023598A CN113551999A CN 113551999 A CN113551999 A CN 113551999A CN 202111023598 A CN202111023598 A CN 202111023598A CN 113551999 A CN113551999 A CN 113551999A
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- 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
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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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
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
- G01N3/068—Special adaptations of indicating or recording means with optical indicating or recording means
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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
- G01N2203/0042—Pneumatic or hydraulic means
- G01N2203/0044—Pneumatic means
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- 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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- G01N2203/0048—Hydraulic means
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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
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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
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0641—Indicating or recording means; Sensing means using optical, X-ray, ultraviolet, infrared or similar detectors
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Abstract
The invention discloses a visual hydraulic fracturing experimental device and a visual hydraulic fracturing experimental method for simulating different horizontal axial differential stress conditions, wherein the device comprises a pressurizing system, a fracturing system, a gelatin sample, a confining pressure adding device, an experimental model frame and a recording system; the pressurizing system comprises an air compressor, a three-way joint, an air pressure gauge and a rubber tube; the fracturing system comprises a water injection pipe and a fracturing rod; the experimental model frame comprises a confining pressure adding device, a transparent detachable base and a high stand; the invention can realize the visualization of the whole process of hydraulic crack initiation and propagation, avoids the damage to the gelatin sample in the hydraulic fracture drilling process formed by pulling out the preset solid cylindrical plastic rod, and improves the success rate of the experiment.
Description
Technical Field
The invention relates to a visual hydraulic fracturing experimental device and method, and belongs to the technical field of hydraulic fracturing experiments in coal mines.
Background
At present, the hydraulic fracturing technology is a core technical means for realizing the idea of 'mining environment reconstruction'. The essence is that the cracks are artificially produced by injecting high-pressure liquid into the coal or rock mass. The purpose of hydraulic fracturing is divided into two categories: enhance the permeability of the rock mass and improve the caving property of the rock mass. When the hydraulic fracturing aims at improving the rock caving property, the control of the initiation and expansion tracks of the hydraulic fracture is important for the evaluation of the fracturing effect.
In the prior art, the visual hydraulic fracturing experimental device and the experimental device related to the method are difficult to simultaneously realize the direct observation that the horizontal axial difference stress is not 0 and the crack initiation and expansion of the fracture in the experimental process are directly observed. Patent publication No. CN113049394A, the name is "experimental apparatus and method of simulation colliery hard roof rock stratum hydraulic fracturing" discloses a visual experimental apparatus of simulation colliery hard roof rock stratum hydraulic fracturing, and the device adopts gelatin material and ya keli pipe of transparent material to the fracture initiation and the extension direct observation and the record of hydraulic fracturing in-process, but the device has two shortcomings: firstly, the situation that the confining pressure is the same rarely occurs in the actual mining environment, but the invention can only add the same confining pressure and cannot simulate the situation that the horizontal shaft difference stress is not 0, thereby seriously restricting the application range of the invention. Secondly, the hydraulic fracturing drill hole related in the invention patent is formed by presetting a solid cylindrical plastic rod, the plastic rod needs to be pulled out before fracturing, and then a hollow cylindrical fracturing rod with an O-shaped sealing ring at one end is inserted into the drill hole. The operation step is easy to tear the wall of the drilled hole, large-size cracks are formed, experimental failure is caused, and waste of manpower, material resources and financial resources is easily caused. Patent publication No. CN113125273A, the name of "a light, visual hydraulic fracturing test presentation device" discloses a true triaxial hydraulic fracturing test presentation device that can observe the hydraulic fracturing process in real time. In the patent of the invention, the confining pressure device is a T-shaped bolt component which is arranged at equal intervals, one end of the confining pressure device is a T-shaped handle, the other end of the confining pressure device is contacted with a test piece through a spring, a T-shaped screw rod is sequentially screwed in manually during confining pressure, the test piece is directly pressurized through the spring, the components are not influenced mutually, but the pressurizing device has two problems: firstly, the pressure applied by each bolt cannot be guaranteed to be completely equal, and the confining pressure applied by a hydraulic fracturing test in a laboratory is 1000-5000 Pa, so that the confining pressure is small, and large errors are easy to generate. And secondly, the confining pressure adding devices which are arranged at equal intervals are mutually independent and directly act on the side surface of the test block, so that the side surface of the test block cannot be uniformly pressurized.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides the visual hydraulic fracturing experimental device and method for simulating different horizontal axial difference stress conditions, so that the success rate of the experiment is improved, the simulation of different horizontal axial difference stress conditions is realized, and the simulation is closer to the actual mining environment.
The invention is realized by the following technical scheme: a visual hydraulic fracturing experimental device for simulating different horizontal axial difference stress conditions comprises a pressurizing system, a fracturing system, a gelatin sample, a confining pressure adding device, an experimental model frame and a recording system;
the pressurizing system comprises an air compressor, a three-way joint, an air pressure gauge and a rubber tube; the fracturing system comprises a water injection pipe and a fracturing rod;
the experimental model frame comprises a confining pressure adding device, a transparent detachable base and a high stand;
the confining pressure device is a cubic frame formed by enclosing and fixedly connecting four prismatic table components for applying pressure to one side of the gelatin sample, the main body of any prismatic table component is a transparent regular quadrangular table which is hollow, the transparent regular quadrangular table is not provided with an upper bottom surface, an extended cylindrical interface is arranged at the centroid of the lower bottom surface of the transparent regular quadrangular table, the transparent regular quadrangular table comprises a pair of straight side surfaces with an included angle of 90 degrees with the lower bottom surface, the transparent regular quadrangular table also comprises a pair of inclined side surfaces with an included angle of 45 degrees with the lower bottom surface, and the upper plane of the transparent regular quadrangular table is covered with a transparent heat shrinkable film through strong glue to form a sealed pressure application surface; the confining pressure adding device and the transparent detachable base form an experiment container for placing the gelatin sample, the experiment container is placed on the high foot stand, and the gelatin sample is placed in the confining pressure adding device;
the four pressurizing systems are respectively arranged on four sides of the confining pressure adding device, the air compressors of the pressurizing systems are respectively connected with the cylindrical interfaces through the rubber pipes, and the barometers are respectively connected with the rubber pipes through the three-way joints and used for monitoring the confining pressure value applied to the gelatin samples by the air compressors;
the recording system comprises three camera recording instruments which are respectively arranged right in front of the experimental model frame, on the right side of the experimental model frame and at the bottom of the experimental model frame;
the fracturing system comprises a laboratory precision injection pump for providing hydraulic pressure for fracturing the gelatin sample, the laboratory precision injection pump comprises a plunger type fracturing fluid container, one end of a water injection pipe is connected with the water outlet end of the plunger type fracturing fluid container, the other end of the water injection pipe is connected with the fracturing rod, the interior of the fracturing rod is hollow, one end, placed in the gelatin sample, of the fracturing rod is a closed end, two long and narrow openings are symmetrically distributed near the closed end of the fracturing rod, the long and narrow openings are sealed by adhesive tapes, two groups of O-shaped sealing rings are embedded in two sides of each long and narrow opening, and when the sample is prepared, the fracturing rod is preset in the gelatin sample to simulate hydraulic fracturing drilling; the position of the fracturing rod extending out of the gelatin sample is fixed through the adjustable angle component, and the fracturing rod further comprises an L-shaped grooving tool capable of penetrating into the fracturing rod.
Further, transparent detachable base and transparent regular quadrangular frustum pyramid adopt the ya keli material.
Further, the transparent heat shrinkable film is a PVC heat shrinkable film.
Furthermore, the L-shaped grooving tool consists of a thin rod and an isosceles triangle blade, and one end of the thin rod is welded and fixed with the middle point of the bottom edge of the isosceles triangle blade.
Furthermore, the adjustable angle subassembly includes that iron stand platform and adjustable angle plastics press from both sides, and the iron stand platform is "L" shape rack that comprises crossbeam and montant, adjustable angle plastics press from both sides install on the iron stand platform with the fracturing pole links to each other.
A visual hydraulic fracturing experiment method for simulating different horizontal axial differential stress conditions by using the visual hydraulic fracturing experiment device comprises the following steps:
step one, preparing a gelatin sample: putting gelatin powder into hot water according to a certain proportion, stirring until the gelatin powder is fully melted, pouring a gelatin solution into an experimental container consisting of a confining pressure device and a transparent detachable base, wherein the liquid level is equal to the top of the experimental container;
step two, prefabricating a hydraulic fracturing drill hole: fixing a fracturing rod on an adjustable angle component, rotating the adjustable angle component to enable the fracturing rod to reach an inclination angle expected by an experiment, putting the fracturing rod into a gelatin solution, and finally putting an experiment container containing the gelatin solution, the fracturing rod and the adjustable angle component into a refrigerator for refrigeration;
step three, prefabricating a radial cutting groove: taking out a solidified gelatin sample, an experimental container consisting of a confining pressure device and a transparent detachable base, the fracturing rod and the adjustable angle assembly from a refrigerator, and cutting a radial cutting groove at the long and narrow opening position of the fracturing rod by using an L-shaped cutting groove tool to serve as an artificial weak surface for hydraulic fracture initiation;
step four, connecting a pressurizing system to apply confining pressure to the gelatin sample: the method comprises the steps of respectively connecting 4 air compressors with cylindrical interfaces through rubber pipes, respectively connecting 4 barometers with the rubber pipes through tee joints, starting the air compressors to respectively apply confining pressure on gelatin samples, observing the displayed numerical values of the barometers, adjusting valves of the air compressors to enable the applied confining pressure to respectively reach experimental expected numerical values, wherein the applied pressure on opposite surfaces of the gelatin samples is the same, and the applied pressure on adjacent surfaces of the gelatin samples is different.
And step five, performing a hydraulic fracturing experiment and recording related data: the water outlet end of a plunger type fracturing fluid container is connected with the fracturing rod through the water injection pipe, a recording system is three camera recorders which are respectively placed right in front of, on the right side of and at the bottom of the experimental model frame, the laboratory precision injection pump is started to perform hydraulic fracturing on the gelatin sample, during the hydraulic fracturing, the three camera recorders perform video recording on the whole process of the initiation and the expansion of the hydraulic fracture, and after the fracturing is completed, the transparent detachable base is opened to take out the gelatin sample.
Further, in the second step, the inclination angle of the fracturing rod is 30-90 degrees.
Further, in the third step, the gelatin solution is placed in a refrigerator to be refrigerated at the temperature of 0-3 ℃ for about 24 hours.
Further, in the fourth step, the confining pressure applied by the air compressor is 0-5000 Pa.
The invention has the beneficial effects that: the invention uses transparent gelatin experimental material, the gelatin material has similar elasticity, brittleness and other mechanical properties with the rock, the material is transparent, and the visualization of the whole process of hydraulic fracture cracking and expansion can be realized by combining a transparent confining pressure adding device. In addition, the pressurizing system applies uniform pressure to the sides of the sample by using 4 air compressors, which is the basis for achieving a horizontal differential axial stress different from 0.
Compared with the prior art, the method has the advantages that,
1. the invention uses transparent gelatin experimental material and transparent confining pressure adding device, can directly observe and record the whole process of hydraulic fracture cracking and expansion under the laboratory environment, directly forms hydraulic fracturing drill holes through the preset fracturing rods which are hollow inside, closed at one end and symmetrically distributed with two long and narrow openings sealed by adhesive tapes near the closed end, avoids the damage to gelatin samples in the hydraulic fracturing drill hole forming process by pulling out the preset solid cylindrical plastic rod, and improves the success rate of experiments.
2. The invention uses four sets of pressurizing systems to apply the same confining pressure to the opposite surfaces of the gelatin sample respectively, and applies different confining pressures to the adjacent surfaces of the gelatin sample, thereby realizing the simulation of different horizontal axial difference stress conditions and being closer to the actual mining environment.
Drawings
The invention is further illustrated below with reference to the figures and examples.
FIG. 1 is a schematic top view of the present invention in hydraulic fracturing;
FIG. 2 is a schematic sectional view taken along line A-A of FIG. 1;
FIG. 3 is a schematic view of a prismoid member of the present invention;
FIG. 4 is a perspective view of a confining pressure applying device according to the present invention;
FIG. 5 is a schematic view of an experimental model stand according to the present invention;
FIG. 6 is a schematic view of an L-shaped grooving tool of the present invention;
FIG. 7 is a schematic view of a fracturing stem of the present invention;
FIG. 8 is a schematic diagram of a hydraulic fracturing borehole prepared by the experimental apparatus of the present invention;
FIG. 9 is a schematic view of the experimental apparatus for preparing radial slots according to the present invention.
In the figure: 1. an air compressor; 2. a three-way joint; 3. a barometer; 4. a hose; 5. a cylindrical interface; 6. a transparent removable base; 7. a high foot rest; 8. a transparent regular quadrangular frustum pyramid; 81. a straight side surface; 82. a beveled side; 9. gelatin samples; 10. a transparent heat shrinkable film; 11. an adhesive tape; 12. a fracturing stem; 13. an adjustable angle assembly; 131. an iron stand; 132. an angle-adjustable plastic clip; 14. a water injection pipe; 15. a laboratory precision syringe pump; 16. a ram fracturing fluid container; 17. a camera recorder; 18. an O-shaped sealing ring; 19. radially grooving; 20. a prismatic table member; 21. a confining pressure adding device; 22. an "L" shaped grooving tool; 221. a thin rod; 222. an isosceles triangular blade; 23. an elongated opening; 24. and (5) an experimental model frame.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the specification, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any inventive step, are within the scope of the present invention.
Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail but are intended to be part of the specification as appropriate.
The visual hydraulic fracturing experimental device for simulating different horizontal axial differential stress conditions, which is shown in fig. 1-9, comprises a pressurizing system, a fracturing system, a gelatin sample 9, a confining pressure adding device 21, an experimental model frame 24 and a recording system;
the pressurizing system comprises an air compressor 1, a three-way joint 2, a barometer 3 and a rubber tube 4; the fracturing system includes a water injection pipe 14 and a fracturing stem 12;
the experimental model frame 24 comprises a confining pressure adding device 21, a transparent detachable base 6 and a high stand 7;
the confining pressure device 21 is a cubic frame formed by enclosing and fixedly connecting four frustum pyramid components 20 for applying pressure to one side of the gelatin sample 9, the main body of any frustum pyramid component 20 is a transparent regular frustum pyramid 8, the transparent regular frustum pyramid 8 is hollow, the transparent regular frustum pyramid 8 does not have an upper bottom surface, an outward-extending cylindrical interface 5 is arranged at the centroid of the lower bottom surface of the transparent regular frustum pyramid 8, the transparent regular frustum pyramid 8 comprises a pair of straight side surfaces 81 with an included angle of 90 degrees with the lower bottom surface, the transparent regular frustum pyramid 8 further comprises a pair of inclined side surfaces 82 with an included angle of 45 degrees with the lower bottom surface, and the upper plane of the transparent regular frustum pyramid 8 is covered with a transparent heat-shrinkable film 10 through strong glue to form a sealing pressure-applying surface; the confining pressure device 21 and the transparent detachable base 6 form an experiment container for placing the gelatin sample 9, the experiment container is placed on the high foot stand 7, and the gelatin sample 9 is placed in the confining pressure device 21;
the four pressurizing systems are respectively arranged on four sides of the confining pressure adding device 21, the air compressor 1 of the pressurizing system is respectively connected with the cylindrical interface 5 through the rubber tube 4, and the barometer 3 is respectively connected with the rubber tube 4 through the three-way joint 2 and is used for monitoring the confining pressure value of the air compressor 1 on the gelatin sample 9;
the recording system comprises three camera recording instruments 17, and the three camera recording instruments 17 are respectively arranged in the front, right side and bottom of the experiment model frame 24;
the fracturing system comprises a laboratory precision injection pump 15 for providing hydraulic pressure for fracturing the gelatin sample 9, wherein the laboratory precision injection pump 15 comprises a plunger type fracturing fluid container 16, one end of a water injection pipe 14 is connected with the water outlet end of the plunger type fracturing fluid container 16, the other end of the water injection pipe 14 is connected with a fracturing rod 12, the interior of the fracturing rod 12 is hollow, one end, placed in the gelatin sample 9, of the fracturing rod 12 is a closed end, two long and narrow openings 23 are symmetrically distributed near the closed end of the fracturing rod 12, the long and narrow openings 23 are sealed by adhesive tapes 11, two groups of O-shaped sealing rings 18 are embedded in two sides of each long and narrow opening 23, and when the sample is prepared, the fracturing rod 12 is preset in the gelatin sample 9 to simulate hydraulic fracturing drilling; the position of the fracturing rod 12 extending out of the gelatin sample 9 is fixed by the angle adjusting component 13, and the L-shaped grooving tool 22 capable of penetrating into the interior of the fracturing rod 12 is further included.
Transparent removable base 6 and transparent positive quadrangular frustum pyramid 8 adopt ya keli material.
The transparent heat shrinkable film 10 is a PVC heat shrinkable film.
The L-shaped grooving tool 22 comprises a thin rod 221 and an isosceles triangle blade 222, wherein one end of the thin rod 221 is fixedly welded with the middle point of the bottom edge of the isosceles triangle blade 222.
The adjustable angle component 13 comprises an iron stand 131 and an adjustable angle plastic clamp 132, the iron stand 131 is an L-shaped stand formed by a cross beam and a vertical rod, and the adjustable angle plastic clamp 132 is installed on the iron stand 131 and connected with the fracturing rod 12.
A visual hydraulic fracturing experiment method for simulating different horizontal axial difference stress conditions comprises the following steps:
step one, preparing a gelatin sample: putting gelatin powder into hot water according to a certain proportion, wherein the weight ratio of the gelatin powder to the gelatin solution is 4-20%, stirring until the gelatin powder is fully melted, pouring the gelatin solution into an experimental container consisting of a confining pressure device 21 and a transparent detachable base 6, and keeping the liquid level equal to the top of the experimental container;
step two, prefabricating a hydraulic fracturing drill hole: fixing a fracturing rod 12 on an adjustable angle component 13, rotating the adjustable angle component 13 to enable the fracturing rod 12 to reach an inclination angle expected by an experiment, putting the fracturing rod 12 into a gelatin solution, and finally putting an experiment container containing the gelatin solution, the fracturing rod 12 and the adjustable angle component 13 into a refrigerator for refrigeration;
step three, prefabricating a radial cutting groove: taking out the solidified gelatin sample 9, the experimental container consisting of the confining pressure device 21 and the transparent detachable base 6, the fracturing rod 12 and the adjustable angle assembly 13 from the refrigerator, and cutting a radial cutting groove 19 at the position of a long and narrow opening 23 of the fracturing rod 12 by using an L-shaped cutting groove tool 22 to serve as an artificial weak surface for hydraulic fracture initiation;
step four, connecting a pressurizing system to apply confining pressure to the gelatin sample: 4 air compressors 1 are respectively connected with the cylindrical interface 5 through rubber pipes 4, 4 barometers 3 are respectively connected with the rubber pipes 4 through tee joints 2, the air compressors 1 are started to respectively apply confining pressure on the gelatin samples 9, the numerical values displayed by the barometers 3 are observed, the valves of the air compressors 1 are adjusted to enable the applied confining pressure to respectively reach the expected experimental numerical values, the pressures applied to the opposite surfaces of the gelatin samples 9 are the same, and the pressures applied to the adjacent surfaces of the gelatin samples 9 are different.
And step five, performing a hydraulic fracturing experiment and recording related data: the water outlet end of a plunger type fracturing fluid container 16 is connected with the fracturing rod 12 through the water injection pipe 14, a recording system comprises three camera recorders 17 which are respectively arranged right in front of, on the right side of and at the bottom of the experimental model frame, the laboratory precision injection pump 15 is started to carry out hydraulic fracturing on the gelatin sample 9, video recording is carried out on the whole process of the initiation and expansion of a hydraulic fracture through the three camera recorders 17 during the hydraulic fracturing, and the transparent detachable base 6 is opened to take out the gelatin sample 9 after the fracturing is completed.
In the second step, the inclination angle of the fracturing rod 12 is 30-90 degrees.
In the third step, the gelatin solution is placed in a refrigerator to be refrigerated at the temperature of 0-3 ℃ for about 24 hours.
In the fourth step, the confining pressure applied by the air compressor 1 is 0-5000 Pa.
One embodiment is:
referring to fig. 1 to 9, the experimental model frame 24 is composed of a transparent acrylic square frustum 8, a transparent heat-shrinkable film 10, a transparent detachable base 6 and a high stand 7, the acrylic square frustum 8 is hollow, the size of the bottom surface of the square frustum 8 is 500 mm × 500 mm, 4 side surfaces are isosceles trapezoids with a base × height =500 mm × 20 mm, the inner diameter of the cylindrical interface 5 is 8 mm, the transparent heat-shrinkable film 10 is made of PVC heat-shrinkable film, the PVC heat-shrinkable film is tightly bonded to the side surfaces of the acrylic square frustum 8 by strong glue to form a square confining device 21 for applying pressure to one side of the gelatin sample 9, the number of the square frustum members 20 is four, and the oblique side surfaces 82 of the glue forming an angle of 45 degrees with the bottom surface are fixedly connected by strong confining to form a square confining device 21, the confining pressure adding device 21 and the transparent detachable base 6 form an experiment container for placing the gelatin sample 9, and the inner space of the experiment container is 460 mm multiplied by 460 mm. The device comprises an air compressor 1, a three-way joint 2, a barometer 3 and a rubber tube 4, wherein the air compressor 1 is a small air compressor which is respectively connected with a cylindrical interface 5 through the rubber tube 4, the barometer 3 is a high-precision barometer which is respectively connected with the rubber tube 4 through the three-way joint 2 and used for monitoring the value of confining pressure exerted on a gelatin sample 9 by the air compressor 1, during an experiment, the pressures exerted on opposite surfaces of the gelatin sample 9 are the same, and the pressures exerted on adjacent surfaces of the gelatin sample 9 are different, so that different horizontal axial difference stress applying conditions are achieved; the recording system is three camera recording instruments 17 which are respectively arranged right in front of the experimental model frame, on the right side of the experimental model frame and at the bottom of the experimental model frame and used for recording crack initiation and expansion of cracks in the experimental process.
The fracturing system is characterized in that hydraulic pressure is provided by a laboratory precision injection pump 15 to fracture the gelatin sample 9, the laboratory precision injection pump 15 further comprises a plunger type fracturing fluid container 16, and the water outlet end of the plunger type fracturing fluid container 16 is connected with the fracturing rod 12 through the water injection pipe 14. The fracturing rod 12 is hollow inside, the size is 500 mm, the inner diameter is 10 mm, the fracturing rod 12 is placed at one end of the gelatin sample 9 and is closed, two long and narrow openings 23 are symmetrically distributed near the closed end of the fracturing rod 12, the long and narrow openings 23 are sealed by using an adhesive tape 11, two groups of O-shaped sealing rings 18 are embedded in two sides of each long and narrow opening 23, when a sample is prepared, the fracturing rod 12 is preset in the gelatin sample 9, a hydraulic fracturing drill hole is simulated, the position of the fracturing rod 12 extending out of the gelatin sample 9 is fixed on an iron stand 131 through an adjustable angle plastic clamp 132 in an adjustable angle component 13, the inclination angle of the fracturing rod 12 is adjusted by using the adjustable angle component 13, before fracturing, an L-shaped grooving tool 22 is used for entering the fracturing rod 12, a radial grooving 19 is cut in the gelatin sample 9 through the long and narrow openings 23 to be used as an artificial weak surface for hydraulic fracture initiation, during fracturing, the laboratory precision injection pump 15 is adjusted to reach the required fracturing flow velocity and flow for fracturing, and after fracturing is completed, the transparent detachable base 6 is opened to take out the gelatin sample 9.
The above description is only exemplary of the present invention and should not be taken as limiting the invention, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. The utility model provides a visual hydraulic fracturing experimental apparatus of different horizontal axis difference stress condition of simulation which characterized in that: comprises a pressurizing system, a fracturing system, a gelatin sample (9), a confining pressure adding device (21), an experiment model frame (24) and a recording system;
the pressurization system comprises an air compressor (1), a three-way joint (2), an air pressure gauge (3) and a rubber tube (4); the fracturing system comprises a water injection pipe (14) and a fracturing stem (12);
the experimental model frame (24) comprises a confining pressure adding device (21), a transparent detachable base (6) and a high stand (7);
the confining pressure device (21) is a cubic frame formed by enclosing and fixedly connecting four prismatic table components (20) for applying pressure to one side of a gelatin sample (9), the main body of any prismatic table component (20) is a transparent regular quadrangular table (8), the transparent regular quadrangular table (8) is hollow, the transparent regular quadrangular table (8) does not have an upper bottom surface, an extended cylindrical interface (5) is arranged at the centroid of the lower bottom surface of the transparent regular quadrangular table (8), the transparent regular quadrangular table (8) comprises a pair of straight side surfaces (81) with an included angle of 90 degrees with the lower bottom surface, the transparent regular quadrangular table (8) further comprises a pair of inclined side surfaces (82) with an included angle of 45 degrees with the lower bottom surface, and the upper plane of the transparent regular quadrangular table (8) is covered with a transparent heat shrinkage film (10) through strong glue to form a sealing pressure application surface; the confining pressure adding device (21) and the transparent detachable base (6) form an experiment container for placing the gelatin sample (9), the experiment container is placed on the high foot stand (7), and the gelatin sample (9) is placed in the confining pressure adding device (21);
the four pressurizing systems are respectively arranged on four sides of the confining pressure adding device (21), the air compressor (1) of the pressurizing system is respectively connected with the cylindrical connector (5) through the rubber pipe (4), and the barometer (3) is respectively connected with the rubber pipe (4) through the three-way connector (2) and is used for monitoring the confining pressure value applied to the gelatin sample (9) by the air compressor (1);
the recording system comprises three camera recording instruments (17), and the three camera recording instruments (17) are respectively placed right in front of the experiment model frame (24), on the right side of the experiment model frame and at the bottom of the experiment model frame;
the fracturing system comprises a laboratory precision injection pump (15) for providing hydraulic pressure for fracturing the gelatin sample (9), the laboratory precision injection pump (15) comprises a plunger type fracturing fluid container (16),
one end of a water injection pipe (14) is connected with a water outlet end of the plunger type fracturing fluid container (16), the other end of the water injection pipe (14) is connected with the fracturing rod (12), the interior of the fracturing rod (12) is hollow, one end, placed into the gelatin sample (9), of the fracturing rod (12) is a closed end, two long and narrow openings (23) are symmetrically distributed near the closed end of the fracturing rod (12), the long and narrow openings (23) are sealed by adhesive tapes (11), two groups of O-shaped sealing rings (18) are embedded into two sides of each long and narrow opening (23), and when a sample is prepared, the fracturing rod (12) is preset in the gelatin sample (9) to simulate hydraulic fracturing drilling; the position of the fracturing rod (12) extending out of the gelatin sample (9) is fixed through an adjustable angle component (13), and the fracturing rod further comprises an L-shaped grooving tool (22) which can penetrate into the fracturing rod (12).
2. The visual hydraulic fracturing experimental device for simulating different horizontal axial differential stress conditions according to claim 1, wherein: the transparent detachable base (6) and the transparent regular quadrangular frustum pyramid (8) are made of acrylic materials.
3. The visual hydraulic fracturing experimental device for simulating different horizontal axial differential stress conditions according to claim 1, wherein: the transparent heat shrinkable film (10) is a PVC heat shrinkable film.
4. The visual hydraulic fracturing experimental device for simulating different horizontal axial differential stress conditions according to claim 1, wherein: the L-shaped grooving tool (22) consists of a thin rod (221) and an isosceles triangle blade (222), wherein one end of the thin rod (221) is welded and fixed with the middle point of the bottom edge of the isosceles triangle blade (222).
5. The visual hydraulic fracturing experimental device for simulating different horizontal axial differential stress conditions according to claim 1, wherein: the adjustable angle component (13) comprises an iron stand (131) and an adjustable angle plastic clamp (132), the iron stand (131) is an L-shaped stand formed by a cross beam and a vertical rod, and the adjustable angle plastic clamp (132) is installed on the iron stand (131) and connected with the fracturing rod (12).
6. A visual hydraulic fracturing experimental method for simulating different horizontal axial differential stress conditions by using the experimental device as claimed in any one of claims 1 to 5, which is characterized by comprising the following steps:
step one, preparing a gelatin sample: putting gelatin powder into hot water in proportion, stirring until the gelatin powder is fully melted, pouring the gelatin solution into an experimental container consisting of a confining pressure device (21) and a transparent detachable base (6), wherein the liquid level is equal to the top of the experimental container;
step two, prefabricating a hydraulic fracturing drill hole: fixing a fracturing rod (12) on an adjustable angle assembly (13), rotating the adjustable angle assembly (13) to enable the fracturing rod (12) to reach an inclination angle expected by an experiment, putting the fracturing rod (12) into a gelatin solution, and finally putting an experiment container containing the gelatin solution, the fracturing rod (12) and the adjustable angle assembly (13) into a refrigerator for refrigeration;
step three, prefabricating a radial cutting groove: taking out a solidified gelatin sample (9), an experimental container consisting of a confining pressure adding device (21) and a transparent detachable base (6), the fracturing rod (12) and the adjustable angle component (13) from a refrigerator, and cutting a radial cutting groove (19) at the position of a long and narrow opening (23) of the fracturing rod (12) by using an L-shaped cutting groove tool (22) to be used as an artificial weak surface for hydraulic fracture initiation;
step four, connecting a pressurizing system to apply confining pressure to the gelatin sample: respectively connecting 4 air compressors (1) with the cylindrical interface (5) through rubber pipes (4), respectively connecting 4 barometers (3) with the rubber pipes (4) through tee joints (2), starting the air compressors (1) to respectively apply confining pressure on gelatin samples (9), observing the display numerical values of the barometers (3), adjusting valves of the air compressors (1) to enable the applied confining pressure to respectively reach experimental expected numerical values, wherein the pressures applied to opposite surfaces of the gelatin samples (9) are the same, and the pressures applied to adjacent surfaces of the gelatin samples (9) are different;
and step five, performing a hydraulic fracturing experiment and recording related data: the water outlet end of a plunger type fracturing fluid container (16) is connected with the fracturing rod (12) through the water injection pipe (14), the recording system is three camera recording instruments (17) which are respectively placed right in front of, on the right side of and at the bottom of the experimental model frame, the laboratory precision injection pump (15) is started to perform hydraulic fracturing on the gelatin sample (9), video recording is performed on the whole process of initiation and expansion of the hydraulic fracture through the three camera recording instruments (17), and the transparent detachable base (6) is opened to take out the gelatin sample (9) after fracturing is completed.
7. The visual hydraulic fracturing experimental method for simulating different horizontal axial differential stress conditions according to claim 6, is characterized in that: in the second step, the inclination angle of the fracturing rod (12) is 30-90 degrees.
8. The visual hydraulic fracturing experimental method for simulating different horizontal axial differential stress conditions as claimed in claim 6, wherein in the third step, the gelatin solution is placed in a refrigerator with a refrigerating temperature of 0 ℃ to 3 ℃ and a refrigerating time of about 24 hours.
9. The visual hydraulic fracturing experimental method for simulating different horizontal axial difference stress conditions according to claim 6, wherein in the fourth step, the confining pressure applied by the air compressor (1) is 0-5000 Pa.
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Application publication date: 20211026 |