CN111257129A - True triaxial hydraulic fracturing experimental device and hydraulic fracturing experimental method - Google Patents
True triaxial hydraulic fracturing experimental device and hydraulic fracturing experimental method Download PDFInfo
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- 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
- G01N3/18—Performing tests at high or low temperatures
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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
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
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- G01N2203/0066—Propagation of crack
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- G01N2203/0058—Kind of property studied
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- G01N2203/02—Details not specific for a particular testing method
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- G01N2203/0228—Low temperature; Cooling means
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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
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Abstract
The invention discloses a true triaxial hydraulic fracturing experimental device and a hydraulic fracturing experimental method, wherein the experimental device comprises: the fracturing chamber A is used for placing a hydraulic fracturing test piece E; the true triaxial loading device B is used for independently applying triaxial stress to the hydraulic fracturing test piece E; the fracturing pump injection device C is used for pressurizing and filling fracturing fluid into the hydraulic fracturing test piece E; and the cooling and freezing device E is used for freezing the fracturing fluid and enlarging a fracture of hydraulic fracturing. The hydraulic fracturing test method comprises the following steps: 1. conventional hydraulic fracturing; 2. cooling and freezing the fracturing fluid; 3. removing liquid nitrogen and heating the hydraulic fracturing test piece; 4. and performing secondary fracturing on the hydraulic fracturing test piece. The invention has the technical effects that: the invention adds the freezing and cooling device to freeze the fracturing fluid in the hydraulic fracturing test piece, thereby increasing the fracture width of the hydraulic fracturing test piece, optimizing the hydraulic fracturing effect and providing a reliable experimental means for evaluating the volume quantification effect of the hydraulic fracturing fracture.
Description
Technical Field
The invention belongs to the technical field of hydraulic fracturing, and particularly relates to a true triaxial hydraulic fracturing experimental device and a hydraulic fracturing experimental method.
Technical Field
Laboratory experiments are one of the most basic methods of scientific research. Hydraulic fracturing technology is an effective method for improving permeability of low permeability reservoirs. The current true triaxial hydraulic fracturing experimental device comprises a fracturing chamber, a true triaxial loading device and a fracturing pump injection device; a hydraulic fracturing test piece is placed in the fracturing chamber, the true triaxial loading device independently applies three-dimensional positive pressure to the hydraulic fracturing test piece to simulate the real stress state borne by the test piece, and the fracturing pump injection device pressurizes and fills fracturing fluid into the hydraulic fracturing test piece, so that the hydraulic fracturing test piece generates a breathable crack.
The fracturing experimental device has the following defects: the fracturing fluid can rapidly crack and expand in one direction in a test piece under the action of high pressure until the test piece is damaged, the hydraulic fracturing crack generated in the test piece is single in expansion form and small in crack width, the hydraulic fracturing crack is easy to close in a triaxial stress state after fracturing is completed, subsequent fracturing effect evaluation research is influenced, for example, the crack volume of the hydraulic fracturing test piece is measured, and the existing equipment is difficult to detect extremely fine cracks.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a true triaxial hydraulic fracturing experimental device which can increase the complexity and width of a fracture and overcome the difficulty of fracture closure after fracturing is finished. The invention also provides a hydraulic fracturing test method using the true triaxial hydraulic fracturing test device.
The conception of the invention is as follows: the method comprises the steps of performing conventional hydraulic fracturing on a coal rock body, injecting liquid nitrogen into a pressing plate around a hydraulic fracturing test piece to cool the hydraulic fracturing test piece, cooling and freezing fracturing liquid in the hydraulic fracturing test piece, increasing the crack of the hydraulic fracturing test piece by using the working principle that the freezing volume of the fracturing liquid is increased, enhancing the hydraulic fracturing effect, and enabling the increased crack not to be closed any more.
The invention provides a true triaxial hydraulic fracturing experimental device, which comprises a fracturing chamber, a fracturing chamber and a hydraulic fracturing test piece, wherein the fracturing chamber is used for placing a hydraulic fracturing test piece; the true triaxial stress loading device is used for independently applying three-dimensional positive pressure to the hydraulic fracturing test piece so as to simulate the true stress state of the hydraulic fracturing test piece; the fracturing pump injection device is used for pressurizing and filling fracturing fluid into the hydraulic fracturing test piece, and the hydraulic fracturing test piece is subjected to swelling fracture to generate a gas permeable fracture; the cooling and freezing device is used for freezing fracturing fluid in the fracture, so that the volume of the fracturing fluid is increased, and the volume of the hydraulic fracturing fracture is increased.
The invention provides a hydraulic fracturing test method using the true triaxial hydraulic fracturing test device, which comprises the following steps:
step 1, performing conventional hydraulic fracturing on a hydraulic fracturing test piece;
step 3, injecting distilled water to remove liquid nitrogen, and heating the hydraulic fracturing test piece;
and 4, performing secondary fracturing on the hydraulic fracturing test piece.
Compared with the prior art, the invention has the technical effects that:
according to the true triaxial hydraulic fracturing experimental device, the freezing and cooling device is additionally arranged, the fracturing fluid in the hydraulic fracturing test piece is frozen, the volume of the fracturing fluid is increased, and the fracture width of the hydraulic fracturing test piece is increased. The cost is lower, the operability is stronger, the true triaxial hydraulic fracturing experimental device of the invention has two parts: one part is the current true triaxial hydraulic fracturing experimental apparatus, and the other part is a cooling and freezing device. Through the combination of the two, the invention can effectively increase the complexity of the fracture and the width of the fracture, and overcomes the problem that the fracture is easy to close after fracturing is completed. A reliable experimental means is provided for improving the hydraulic fracturing effect of a laboratory, quantifying the size of a hydraulic fracturing fracture and evaluating the hydraulic fracturing effect.
According to the hydraulic fracturing test method, as the fracturing fluid in the hydraulic fracturing test piece is frozen in the step 2, the freezing volume of the fracturing fluid is increased, and the fracture of the hydraulic fracturing test piece is increased; and (4) performing secondary fracturing on the hydraulic fracturing test piece, increasing the width of the fracture of the hydraulic fracturing test piece, enhancing the hydraulic fracturing effect, and enabling the fracture after repeated hydraulic fracturing to be not closed any more.
Drawings
The drawings of the invention are illustrated as follows:
FIG. 1 is a schematic structural diagram of a true triaxial hydraulic fracturing experimental apparatus of the present invention;
FIG. 2 is a left side view of the fracturing chamber of FIG. 1;
fig. 3 is a diagram of the arrangement of the fracturing cavity in fig. 1.
In the figure, A, a fracturing chamber; B. a true triaxial loading device; C. a fracturing pump injection device; D. a cooling and freezing device; E. hydraulic fracturing test pieces; 1. a Z-axis pipeline; 2. A Y-axis pipeline; 3. an X-axis pipeline; 4. a left press plate; 5. a right pressure plate; 6. an upper pressure plate; 7. a lower pressing plate; 8. a front platen; 9. a rear pressing plate; 10. a left platen liquid nitrogen storage line; 11. a right platen liquid nitrogen storage line; 12. an upper platen liquid nitrogen storage pipeline; 13. a lower platen liquid nitrogen storage line; 14. a servo pump station; 15. a liquid nitrogen storage tank; 16. a liquid injection pump; 17. a left oil cylinder; 18. feeding an oil cylinder; 19. a fracturing cavity; 20. a pressure acquisition instrument; 21. a fracturing pump; 22. a liquid nitrogen recovery valve; 23. a liquid nitrogen recovery container; 24. a front platen liquid nitrogen storage pipeline; 25. a rear platen liquid nitrogen storage pipeline; 26. a temperature sensor; 27. a box body; 28. fracturing the pipeline; 29. a hole sealing section; 30. a temperature sensor wire; 31. a temperature sensor acquisition instrument; 32. fracturing the pipe; 34. a first four-way valve; 35. a distilled water tank; 36. a distilled water line valve; 37. a liquid nitrogen line valve; 38. a front oil cylinder; 39. a second four-way valve.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
in this patent application, for the purpose of clearly describing each component and the positional relationship, the terms of orientation such as "upper", "lower", "left", "right", "front" and "rear" are used, and these terms of orientation are referred to the arrangement position of the above drawings, and the terms of orientation are changed when the actual use position is changed, and thus, the scope of protection of the patent is not limited.
As shown in fig. 1, 2 and 3, the true triaxial hydraulic fracturing experimental apparatus of the present invention includes:
the fracturing chamber A is used for placing a hydraulic fracturing test piece E; the true triaxial loading device B is used for independently applying triaxial stress to the hydraulic fracturing test piece E so as to simulate the true stress state of the hydraulic fracturing test piece; the fracturing pump injection device C is used for pressurizing and filling fracturing fluid into the hydraulic fracturing test piece E, and the hydraulic fracturing test piece is subjected to swelling fracture to generate a gas permeable fracture; and the cooling and freezing device D is used for freezing the fracturing fluid, so that the volume of the fracturing fluid is increased, and the fracture of hydraulic fracturing is enlarged.
The fracturing chamber A comprises a box body 27, a front oil cylinder 38, an upper oil cylinder 18 and a left oil cylinder 17 are respectively fixed on the front side, the upper side and the left side of the outer part of the box body 27, plungers of the three oil cylinders extend into the box body, and the strokes of the oil cylinders meet the triaxial stress loading requirement of a hydraulic fracturing test piece; the inner wall of the box body is provided with a rear pressing plate 9, a right pressing plate 5, a lower pressing plate 7, a front pressing plate 8, an upper pressing plate 6 and a left pressing plate 4; plungers of the front oil cylinder 38, the upper oil cylinder 18 and the left oil cylinder 17 are directly contacted with the front pressing plate 8, the upper pressing plate 6 and the left pressing plate 4 to carry out triaxial stress pressurization on the test piece; liquid nitrogen storage pipelines are correspondingly arranged on the inner wall surfaces of the six pressing plates.
The true triaxial loading device B is characterized in that a servo pump station 14 injects hydraulic oil through a Z-axis pipeline 1, an X-axis pipeline 2 and a Y-axis pipeline 3 respectively to independently load triaxial stress on a hydraulic fracturing test piece E through an upper oil cylinder 18, a left oil cylinder 17 and a front oil cylinder 38. The true triaxial hydraulic fracturing device independently controls triaxial stress loading, and the maximum pressure is 70 MPa.
The fracturing pump injection device C comprises a fracturing pump 21, a fracturing pipe 32 and a pressure acquisition instrument 20, wherein the fracturing pump 21 is communicated with the pre-buried fracturing pipe 32 of the hydraulic fracturing test piece through a fracturing pipeline 28, and the pressure acquisition instrument 20 is arranged on the fracturing pipeline 32.
The cooling and freezing device D comprises an injection power system, a liquid nitrogen storage pipeline and a liquid nitrogen recovery device; the injection power system comprises a liquid injection pump 6, wherein a liquid inlet of the liquid injection pump 6 is connected with a distilled water tank 35 through a pipeline provided with a distilled water pipeline valve 36, the other pipeline provided with a liquid nitrogen pipeline valve 37 is connected with a liquid nitrogen storage tank 15, and a liquid outlet of the liquid injection pump 6 is connected with a liquid nitrogen storage pipeline through a pipeline. The liquid injection pump 16 can inject distilled water or liquid nitrogen into the liquid nitrogen storage pipeline through a distilled water pipeline valve 36 or a liquid nitrogen pipeline valve 37.
The liquid nitrogen storage pipeline comprises a left pressing plate liquid nitrogen storage pipeline 10, a right pressing plate liquid nitrogen storage pipeline 11, an upper pressing plate liquid nitrogen storage pipeline 12, a lower pressing plate liquid nitrogen storage pipeline 13, a front pressing plate liquid nitrogen storage pipeline 24 and a rear pressing plate liquid nitrogen storage pipeline 25; a liquid outlet of the liquid injection pump 6 is connected with a front port of a first four-way valve 34, and three rear ports of the first four-way valve 34 are respectively connected with a left pressing plate liquid nitrogen storage pipeline 10, an upper pressing plate liquid nitrogen storage pipeline 12 and a rear pressing plate liquid nitrogen storage pipeline 25; pipeline 24 is stored with left clamp plate liquid nitrogen to preceding clamp plate liquid nitrogen storage pipeline 10 intercommunication, and pipeline 11 is stored with top board liquid nitrogen storage pipeline 12 intercommunication is stored to right clamp plate liquid nitrogen, and pipeline 25 intercommunication is stored with back clamp plate liquid nitrogen to the clamp plate liquid nitrogen storage pipeline 13 of holding down, guarantees that a liquid nitrogen pipeline can store the pipeline to six liquid nitrogen and pour into liquid nitrogen or distilled water into simultaneously.
The liquid nitrogen recovery device comprises a liquid nitrogen recovery container 23, and liquid outlets of a front pressing plate liquid nitrogen storage pipeline 24, a right pressing plate liquid nitrogen storage pipeline 11 and a lower pressing plate liquid nitrogen storage pipeline 13 are respectively communicated with three front ports of a second four-way valve 39; a liquid nitrogen recovery valve 22 is arranged on the pipeline of the rear end port of the second four-way valve 39 and then is connected with a liquid nitrogen recovery container 23.
As shown in fig. 3, a temperature sensor 26 is disposed on the inner wall of the fracturing cavity 19, and the temperature sensor 26 is connected to a temperature sensor collector 31 outside the fracturing chamber a through a sealing section 29 of the fracturing cavity 19 by a temperature sensor line 30.
The invention provides a hydraulic fracturing test method using the true triaxial hydraulic fracturing test device, which comprises the following steps:
step 1, performing conventional hydraulic fracturing on a hydraulic fracturing test piece, and specifically comprising the following steps:
step 11), cutting a raw coal sample which is retrieved on site and is large enough to prepare a standard hydraulic fracturing test piece with the size of 100 mm multiplied by 100 mm, and drilling a hole with the size of 55 mm by using a core drill rod with the diameter of 25 mm to form a fracturing cavity; placing the pre-processed fracturing pipe into a fracturing cavity and sealing holes by using epoxy resin AB glue; while burying the fracturing pipe, putting a temperature sensor in the fracturing cavity of the test piece;
step 12), placing the hydraulic fracturing test piece in a fracturing chamber, and starting a servo pump station to respectively inject hydraulic oil to a Z-axis pipeline, an X-axis pipeline and a Y-axis pipeline to load triaxial pressure on the hydraulic fracturing test piece to a rated value; the true triaxial hydraulic fracturing experimental device independently controls triaxial stress loading, and the maximum pressure is 70 MPa;
and step 13), starting a fracturing pump to perform conventional hydraulic fracturing on the hydraulic fracturing test piece E, and closing the fracturing pump when the pressure of the hydraulic fracturing acquisition instrument suddenly drops by more than 30%.
opening a liquid nitrogen pipeline valve 37, closing a distilled water pipeline valve 36, and starting a liquid nitrogen injection pump 16 to respectively inject liquid nitrogen into a left pressing plate liquid nitrogen storage pipeline 10, a right pressing plate liquid nitrogen storage pipeline 11, an upper pressing plate liquid nitrogen storage pipeline 12, a lower pressing plate liquid nitrogen storage pipeline 13, a front pressing plate liquid nitrogen storage pipeline 24 and a rear pressing plate liquid nitrogen storage pipeline 25 of the true triaxial hydraulic fracturing experimental device; the temperature sensor collector 31 monitors the temperature in the inner wall of the fracturing cavity 19 in real time, and the temperature of the temperature sensor collector is lower than minus 5 ℃ and is kept for at least 10 min.
And 3, injecting distilled water to remove liquid nitrogen, and heating the hydraulic fracturing test piece, wherein the method comprises the following steps:
step 31), opening a liquid nitrogen recovery valve 22 to discharge liquid nitrogen from the left pressing plate liquid nitrogen storage pipeline 10, the right pressing plate liquid nitrogen storage pipeline 11, the upper pressing plate liquid nitrogen storage pipeline 12, the lower pressing plate liquid nitrogen storage pipeline 13, the front pressing plate liquid nitrogen storage pipeline 24 and the rear pressing plate liquid nitrogen storage pipeline 25 and recover the liquid nitrogen into a liquid nitrogen recovery container 23;
step 32), closing the liquid nitrogen pipeline valve 37, opening the distilled water pipeline valve 36, starting the liquid nitrogen injection pump 16 to inject distilled water into the distilled water tank 35, discharging liquid nitrogen which is not discharged from the left pressing plate liquid nitrogen storage pipeline 10, the right pressing plate liquid nitrogen storage pipeline 11, the upper pressing plate liquid nitrogen storage pipeline 12, the lower pressing plate liquid nitrogen storage pipeline 13, the front pressing plate liquid nitrogen storage pipeline 24 and the rear pressing plate liquid nitrogen storage pipeline 25 by the injected distilled water, and keeping the temperature of the temperature sensor acquisition instrument 31 to be higher than 10 ℃ for at least 5 min.
And 4, performing secondary fracturing on the hydraulic fracturing test piece:
and restarting the fracturing pump 21 to fracture the hydraulic fracturing test piece E for the second time. Stopping the fracturing pump 21 when the fracturing fluid leaks out of the hydraulic fracturing test piece E;
and starting the servo pump station 14 to unload the confining pressure of the hydraulic fracturing test piece E to 0 MPa, and taking out the hydraulic fracturing test piece E.
The method adds the steps of cooling, freezing the fracturing fluid in the hydraulic fracturing test piece, adding the step of secondary fracturing, increasing the fracture width of the hydraulic fracturing test piece, enhancing the hydraulic fracturing effect, and enabling the fracture after repeated hydraulic fracturing to be not closed.
Claims (10)
1. A true triaxial hydraulic fracturing experimental apparatus, comprising: the fracturing chamber is used for placing a hydraulic fracturing test piece; the true triaxial stress loading device is used for independently applying triaxial stress to the hydraulic fracturing test piece so as to simulate the true stress state of the hydraulic fracturing test piece; the fracturing pump injection device is used for pressurizing and filling fracturing fluid into the hydraulic fracturing test piece, and the hydraulic fracturing test piece is subjected to swelling fracture to generate a gas permeable fracture; it is characterized by also comprising: the cooling and freezing device is used for freezing the fracturing fluid in the fracture, so that the volume of the fracturing fluid is increased, and the volume of the hydraulic fracturing fracture is increased.
2. The true triaxial hydraulic fracturing experimental apparatus of claim 1, wherein: the fracturing chamber comprises a box body, wherein a front oil cylinder, an upper oil cylinder and a left oil cylinder are respectively fixed on the front side, the upper side and the left side of the outer part of the box body; the inner wall of the box body is provided with a rear pressing plate, a right pressing plate and a lower pressing plate, a front pressing plate, an upper pressing plate and a left pressing plate, and plungers of a front oil cylinder, an upper oil cylinder and a left oil cylinder are directly contacted with the front pressing plate, the upper pressing plate and the left pressing plate to independently apply triaxial stress to a test piece; liquid nitrogen storage pipelines are correspondingly arranged on the inner wall surfaces of the six pressing plates.
3. The true triaxial hydraulic fracturing experimental apparatus of claim 2, wherein: the true triaxial loading device comprises a servo pump station, and the servo pump station is correspondingly connected with an upper oil cylinder, a left oil cylinder and a front oil cylinder through a Z-axis pipeline, an X-axis pipeline and a Y-axis pipeline.
4. The true triaxial hydraulic fracturing experimental apparatus of claim 3, wherein: the fracturing pump injection device comprises a fracturing pump, a fracturing pipe and a pressure acquisition instrument, wherein the fracturing pump is communicated with the fracturing pipe pre-embedded in the hydraulic fracturing test piece through a fracturing pipeline, and the pressure acquisition instrument is arranged in the fracturing pipeline.
5. The true triaxial hydraulic fracturing experimental apparatus of any one of claims 1 to 4, wherein: the cooling and freezing device comprises an injection power device, a liquid nitrogen storage pipeline and a liquid nitrogen recovery device; the injection power device comprises a liquid injection pump, a liquid inlet of the liquid injection pump is connected with a distilled water tank through a pipeline provided with a distilled water pipeline valve, the other pipeline provided with a liquid nitrogen pipeline valve is connected with a liquid nitrogen storage tank, and a liquid outlet of the liquid injection pump is connected with a liquid nitrogen storage pipeline through a pipeline;
the liquid nitrogen storage pipeline comprises a left pressing plate liquid nitrogen storage pipeline, a right pressing plate liquid nitrogen storage pipeline, an upper pressing plate liquid nitrogen storage pipeline, a lower pressing plate liquid nitrogen storage pipeline, a front pressing plate liquid nitrogen storage pipeline and a rear pressing plate liquid nitrogen storage pipeline; a liquid outlet of the liquid injection pump is connected with a front port of the first four-way valve, and three rear ports of the first four-way valve are respectively connected with a left pressing plate liquid nitrogen storage pipeline, an upper pressing plate liquid nitrogen storage pipeline and a rear pressing plate liquid nitrogen storage pipeline; the front pressing plate liquid nitrogen storage pipeline is communicated with the left pressing plate liquid nitrogen storage pipeline, the right pressing plate liquid nitrogen storage pipeline is communicated with the upper pressing plate liquid nitrogen storage pipeline, and the lower pressing plate liquid nitrogen storage pipeline is communicated with the rear pressing plate liquid nitrogen storage pipeline;
the liquid outlets of the front pressing plate liquid nitrogen storage pipeline, the right pressing plate liquid nitrogen storage pipeline and the lower pressing plate liquid nitrogen storage pipeline are respectively communicated with three front ports of the second four-way valve; and a rear port of the second four-way valve is connected with a liquid nitrogen recovery container, and a liquid nitrogen recovery valve is arranged between the second four-way valve and the liquid nitrogen recovery container.
6. The true triaxial hydraulic fracturing experimental apparatus of claim 5, wherein: a temperature sensor is placed on the inner wall of the fracturing cavity, and the temperature sensor is connected with a temperature sensor acquisition instrument through a temperature sensor line and a hole sealing section of the fracturing cavity.
7. A hydraulic fracturing test method using the true triaxial hydraulic fracturing test apparatus of any one of claims 1 to 6, comprising the steps of:
step 1, performing conventional hydraulic fracturing on a hydraulic fracturing test piece;
step 2, injecting liquid nitrogen into a pressing plate around the hydraulic fracturing test piece, and cooling and freezing the fracturing liquid in the hydraulic fracturing test piece;
step 3, injecting distilled water to remove liquid nitrogen, and heating the hydraulic fracturing test piece;
and 4, performing secondary fracturing on the hydraulic fracturing test piece.
8. The hydraulic fracture testing method of claim 7, wherein in step 1, the conventional hydraulic fracturing comprises the steps of:
step 11), cutting a raw coal sample which is retrieved on site and is large enough to prepare a standard hydraulic fracturing test piece with the size of 100 mm multiplied by 100 mm, and drilling a hole with the size of 55 mm by using a core drill rod with the diameter of 25 mm to form a fracturing cavity; placing the pre-processed fracturing pipe into a fracturing cavity and sealing holes by using epoxy resin AB glue; while burying the fracturing pipe, putting a temperature sensor in the fracturing cavity of the test piece;
step 12), placing the hydraulic fracturing test piece in a fracturing chamber, and starting a servo pump station to respectively inject hydraulic oil to a Z-axis pipeline, an X-axis pipeline and a Y-axis pipeline to load triaxial pressure on the hydraulic fracturing test piece to a rated value;
and step 13), starting a fracturing pump to perform conventional hydraulic fracturing on the hydraulic fracturing test piece E, and closing the fracturing pump when the pressure of the hydraulic fracturing acquisition instrument suddenly drops by more than 30%.
9. The hydraulic fracturing test method of claim 8, wherein in step 2, the fracturing fluid is subjected to cooling and freezing by:
opening a liquid nitrogen pipeline valve (37), closing a distilled water pipeline valve (36), and starting a liquid nitrogen injection pump (16) to respectively inject liquid nitrogen into a left pressing plate liquid nitrogen storage pipeline (10), a right pressing plate liquid nitrogen storage pipeline (11), an upper pressing plate liquid nitrogen storage pipeline (12), a lower pressing plate liquid nitrogen storage pipeline (13), a front pressing plate liquid nitrogen storage pipeline (24) and a rear pressing plate liquid nitrogen storage pipeline (25) of the true triaxial hydraulic fracturing experimental device; the temperature sensor acquisition instrument (31) monitors the temperature in the inner wall of the fracturing cavity (19) in real time, and the temperature of the temperature sensor acquisition instrument is lower than minus 5 ℃ and is kept for at least 10 min.
10. The hydraulic fracturing test method of claim 9, wherein in step 3, removing the liquid nitrogen and raising the temperature of the hydraulic fracturing test piece comprises the steps of:
step 31), opening a liquid nitrogen recovery valve (22) to discharge liquid nitrogen of a left pressing plate liquid nitrogen storage pipeline (10), a right pressing plate liquid nitrogen storage pipeline (11), an upper pressing plate liquid nitrogen storage pipeline (12), a lower pressing plate liquid nitrogen storage pipeline (13), a front pressing plate liquid nitrogen storage pipeline (24) and a rear pressing plate liquid nitrogen storage pipeline (25) and recovering the liquid nitrogen into a liquid nitrogen recovery container (23);
step 32), closing the liquid nitrogen pipeline valve (37), opening the distilled water pipeline valve (36), starting the liquid nitrogen injection pump (16) to inject distilled water into the distilled water tank (35), discharging liquid nitrogen which is not discharged from the left pressing plate liquid nitrogen storage pipeline (10), the right pressing plate liquid nitrogen storage pipeline (11), the upper pressing plate liquid nitrogen storage pipeline (12), the lower pressing plate liquid nitrogen storage pipeline (13), the front pressing plate liquid nitrogen storage pipeline (24) and the rear pressing plate liquid nitrogen storage pipeline (25) by the injected distilled water, and keeping the temperature of the temperature sensor acquisition instrument 31 to be higher than 10 ℃ for at least 5 min.
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| CN111894550A (en) * | 2020-06-23 | 2020-11-06 | 中国矿业大学 | Simulation test system and method for fracturing of upward drilling hole low-temperature fluid |
| CN112033811A (en) * | 2020-07-24 | 2020-12-04 | 中国矿业大学 | Simulation experiment system and method for cracking of upward drilling hole low-temperature fluid |
| CN113281191A (en) * | 2021-05-25 | 2021-08-20 | 中国科学院武汉岩土力学研究所 | High-low temperature fracturing test device and test method based on same |
| CN113804718A (en) * | 2021-09-08 | 2021-12-17 | 西安科技大学 | Multi-dimensional parameter testing device and method for water ice phase change frost heaving effect |
| CN114165204A (en) * | 2021-11-12 | 2022-03-11 | 中国石油大学(华东) | Real-time visual monitoring experiment device and method for hydraulic fracture network evolution process under reservoir conditions |
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