CN113514337B - Hot dry rock rupture pressure test device and method - Google Patents
Hot dry rock rupture pressure test device and method Download PDFInfo
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- CN113514337B CN113514337B CN202010272321.2A CN202010272321A CN113514337B CN 113514337 B CN113514337 B CN 113514337B CN 202010272321 A CN202010272321 A CN 202010272321A CN 113514337 B CN113514337 B CN 113514337B
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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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- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
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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
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- 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
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Abstract
The invention provides a device and a method for testing cracking pressure of hot dry rock, wherein the device comprises: the device comprises a rock sample loading system, a pressure stabilizing medium injection system and a fracturing fluid injection system; the rock sample loading system is used for applying confining pressure to the rock sample, and the rock sample is provided with a test hole (5); the rock sample loading system is provided with an acoustic emission monitoring device for monitoring the vibration waves emitted in the fracture process; the pressure stabilizing medium injection system is communicated with the rock sample loading system and is used for injecting a pressure stabilizing medium into the test hole (5); and the fracturing fluid injection system is communicated with the rock sample loading system and is used for injecting fracturing fluid into the test hole (5). By arranging the pressure stabilizing medium injection system, the test holes are ensured not to collapse or crack in the processes of confining pressure and temperature loading and fracturing fluid thermal effect injection; and (3) before the completion of the rock sample is monitored by injecting the fracturing fluid to the initial fracture, the wall of the hole is kept complete, and the measured fracture pressure value is closer to the real value of the underground rock stratum environment.
Description
Technical Field
The invention relates to the field of mechanical tests of underground rock strata, in particular to a device and a method for testing rupture pressure of dry hot rock.
Background
The hydraulic fracturing of the hot dry rock is one of the main technical means for obtaining geothermal resources at present, high-pressure fracturing fluid is pumped into a target layer through a well hole by a ground fracturing truck group, when the bottom hole fluid pressure is greater than the rock fracture pressure, a stratum is opened to form an artificial fracture, the artificial fracture is continuously expanded and extended along with the continuous injection of the fluid, a high-conductivity and complex fracture network is formed in the hot dry rock, and a fluid flow channel is established for the heat exchange convection of a subsequent heat exchange medium between an injection well and a production well.
The high-pressure fracturing fluid injected from a wellhead at the ambient temperature has larger temperature difference with an underground target layer, when the high-pressure fracturing fluid reaches the bottom of a well and contacts with rocks, the temperature of rock on the well wall is rapidly reduced, the volume of the rocks shrinks in the cooling process, so that the mechanical parameters of the rocks such as Young modulus, tensile strength, fracture toughness and the like are reduced, and the circumferential stress of the well wall is reduced. And the internal mineral components have different thermal expansion coefficients, so that different strains and displacements are generated in the cooling process, micro cracks are formed among rock mineral particles and in the rock mineral particles, and the effective stress of rocks is reduced after high-pressure fracturing fluid enters the micro cracks, so that the rocks on the well wall are easier to break. The hydraulic fracturing of the dry hot rock stratum under the thermal effect condition can generate lower fracture pressure, and after accurate fracture pressure is obtained, a wellhead device can be optimized, a fracturing construction vehicle set can be reduced, and the construction cost is reduced.
The conventional hydraulic fracturing fracture pressure testing device does not consider the influence generated by a thermal effect, and injected liquid and rock samples are both at room temperature and have no obvious temperature difference. The influence of the drilling process on the integrity of the wall of the test hole is not fully considered and monitored in the preparation of the rock sample, the internal pressure applied in the test hole is not considered in the temperature and confining pressure loading process so as to keep the stability of the wall of the test hole, the rock sample is damaged before injection fracturing, and the fracture pressure value measured when the fracturing fluid is injected is not the pressure value corresponding to the moment from the integrity state to the fracture initiation of the real rock sample but the extension pressure value of an artificial fracture.
It can be known that the existing fracture pressure testing device lacks analysis capability under the condition of thermal effect, and the existing dry hot rock fracture pressure testing method is not reasonable. Therefore, the device and the method for testing the fracturing pressure of the hot dry rock by hydraulic fracturing of the hot dry rock can accurately obtain the fracturing parameters of the stratum, and have important practical significance.
Disclosure of Invention
The invention aims to provide a device and a method for testing the fracturing pressure of hot dry rock, which aim to solve the problem that a rock sample is cracked in advance in a hydraulic fracturing pressure test of hot dry rock in the prior art, so that the fracturing parameters of a stratum can be accurately obtained.
In order to achieve the above object, the present invention provides a hot dry rock burst pressure test device, comprising: the device comprises a rock sample loading system, a pressure stabilizing medium injection system and a fracturing fluid injection system;
the rock sample loading system is used for applying confining pressure to a rock sample and heating the rock sample, and the rock sample is provided with a test hole; the rock sample loading system is provided with an acoustic emission monitoring device for monitoring the vibration waves emitted in the rock sample breaking process;
the pressure stabilizing medium injection system is communicated with the test hole and is used for injecting a pressure stabilizing medium into the test hole;
and the fracturing fluid injection system is communicated with the test hole and is used for injecting fracturing fluid into the test hole.
Optionally, the pressure stabilizing medium injection system comprises an air pressure control device and a pressure pump which are electrically connected, and the air pressure control device can control the pressure pump to start and deliver pressure; the pressure pump is communicated with a medium pipeline leading to the testing hole, and a control valve used for controlling the opening and closing of the medium pipeline is arranged on the medium pipeline.
Optionally, the pressure-stabilizing medium injection system further comprises a pressure-stabilizing medium tank, which is communicated with the medium pipeline and is used for receiving the pressure-stabilizing medium flowing back from the test hole.
Optionally, the rock sample loading system is further provided with a temperature monitoring device for monitoring the temperature in the test hole, and a temperature sensor of the temperature monitoring device is arranged in the test hole.
Optionally, the rock sample loading system comprises a sample loading device and a hydraulic servo control system, the sample loading device is used for applying confining pressure to the rock sample and heating the rock sample, the sample loading device is connected with the hydraulic servo control system through a hydraulic pipeline, and a control valve, a pressure gauge and an emptying valve are arranged on the hydraulic pipeline.
Optionally, the fracturing fluid injection system comprises a temperature control fluid tank and a hydraulic control system which are communicated, the hydraulic control system is connected with a conveying pipeline, the conveying pipeline leads to the inside of the test hole, a fluid flow control valve is arranged on the conveying pipeline, and the temperature control fluid tank is provided with a thermometer.
The invention also provides a test method for testing the hydraulic fracturing fracture pressure of the hot dry rock, which comprises the following steps:
s1, placing the rock sample in a rock sample loading system, and arranging an acoustic emission monitoring device for monitoring mechanical parameters of the rock sample;
s2, controlling the rock sample loading system to heat and apply confining pressure to the rock sample, simultaneously, conveying a pressure stabilizing medium into the test hole by a pressure stabilizing medium injection system, and recording mechanical parameters detected by the acoustic emission monitoring device in the process;
S3, when the rock sample reaches a preset temperature and a preset pressure, keeping the temperature and pressure state, simultaneously stopping conveying a pressure stabilizing medium into the test hole, and recording the corresponding mechanical parameters of the process;
s4, opening a fracturing fluid injection system, conveying fracturing fluid into the test hole, outputting a pressure stabilizing medium in the test hole along with the injection of the fracturing fluid, and recording mechanical parameters corresponding to the process;
and S5, closing the fracturing fluid injection system after the fracturing fluid reaches the preset injection amount, and recording the mechanical parameters corresponding to the process.
Optionally, the rock sample is prepared by the following method:
collecting hot dry rock meeting the test requirements, and cutting according to a preset shape and size;
processing a test hole on the cut dry hot rock to form a preselected rock sample;
and detecting the fracture condition of the preselected rock sample, and reserving the rock sample meeting the requirements.
Optionally, the method of machining a test hole in the cut hot dry rock comprises: drilling a test hole with a preset size in the geometric center of the surface of the hot dry rock, controlling the drilling speed and the drilling pressure in the drilling process, and reducing the temperature of the drill hole in real time by adopting cooling liquid so that the temperature of the liquid flowing out of the test hole is not more than 40 ℃.
Optionally, in S2, controlling the temperature rising speed of the rock sample loading system for continuously heating the rock sample within 1 ℃/min;
after S3, S4 is performed after keeping the temperature and pressure states stable for a preset time.
By arranging the pressure stabilizing medium injection system, the test holes are ensured not to collapse or crack in the processes of confining pressure and temperature loading and fracturing fluid thermal effect injection; and (3) before the completion of the rock sample is monitored by injecting the fracturing fluid to the initial fracture, the wall of the hole is kept complete, and the measured fracture pressure value is closer to the real value of the underground rock stratum environment.
Drawings
FIG. 1 is a schematic diagram of a hot dry rock burst pressure test rig in accordance with an embodiment of the present invention;
FIG. 2 is a top view of a rock sample after being clamped by a load plate in accordance with one embodiment of the present invention;
fig. 3 is a schematic flow chart of a test method for testing hydraulic fracture pressure of hot dry rock according to an embodiment of the present invention.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, the present invention will be further described in detail with reference to the accompanying drawings and examples. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.
Referring to fig. 1, the present embodiment provides a hot dry rock burst pressure test device, including: the device comprises a rock sample loading system, a pressure stabilizing medium injection system and a fracturing fluid injection system; the rock sample loading system is used for applying confining pressure to and heating a rock sample 30, and the rock sample 30 is provided with a test hole 5; the rock sample loading system is provided with an acoustic emission monitoring device for monitoring vibration waves (micro acoustic phenomenon) emitted in the process of breaking the rock sample 30; the voltage stabilizing medium injection system is communicated with the test hole and is used for injecting a voltage stabilizing medium into the test hole 5; and the fracturing fluid injection system is communicated with the test hole and used for injecting fracturing fluid into the test hole 5. The pressure stabilizing medium adopted by the pressure stabilizing medium injection system can be air, inert gas and the like, and plays a role in the test of balancing the external confining pressure and the pressure in the test hole 5, so that the test hole 5 is prevented from generating cracks in advance. In the embodiment, the pressure stabilizing medium injection system and the fracturing fluid injection system are provided with independent power sources respectively for providing corresponding medium conveying power. By arranging the pressure stabilizing medium injection system, the test hole 5 is ensured not to collapse or crack in the processes of confining pressure and temperature loading and fracturing fluid thermal effect injection; before the rock sample 30 is detected to be complete to initial fracture by injecting the fracturing fluid, the wall of the hole is kept complete, and the detected fracture pressure value is closer to the real value of the underground rock stratum environment.
For a rock sample loading system, the existing loading equipment can be adopted, and the requirements such as uniform pressure application, controllable temperature rise and the like can be met. In the embodiment, the rock sample loading system comprises a sample loading device and a hydraulic servo control system 9, wherein the sample loading device is used for applying confining pressure and heating to a rock sample 30, and comprises a loading plate 1, a test box heating layer 2, a test box insulating layer 3 and a loading cylinder 4; the loading mode of the rock sample 30 adopts a gantry type reaction mechanism, and three-way confining pressure is applied to the rock sample 30 through the loading cylinder 4 in the vertical direction and two orthogonal horizontal directions. The rock sample 30 is clamped by the loading plate 1, the loading plate 1 is mainly used for clamping the rock sample 30 and controlling loading precision, loading cylinder acting holes are formed in 6 surfaces of the test box (comprising the test box heating layer 2 and the test box heat insulation layer 3), and the loading cylinders 4 linearly extend and shorten in the axial direction through the loading cylinder acting holes under the hydraulic action. And the rock sample 30 is insulated between the loading plate 1 and the test box heating layer 2 by filling cellucotton, so that the internal temperature can reach the real temperature of the underground rock stratum. The loading cylinder 4 of the sample loading device is connected with the hydraulic servo control system 9 through a hydraulic pipeline, and a control valve 6, a pressure gauge 7 and an emptying valve 8 are arranged on the hydraulic pipeline. Specifically, the three loading cylinders 4 are respectively connected with a hydraulic servo control system 9 through hydraulic pipelines, a control valve 6 controls the loading speed of the three-way stress, a pressure gauge 7 displays the pressure of the hydraulic pipelines, and an emptying valve 8 realizes unloading of the three-way stress.
Referring to fig. 2, in this embodiment, the acoustic emission monitoring device includes an acoustic emission probe 22 and an acoustic emission monitoring system 10, four loading plates 1 around the rock sample 30 are provided with acoustic emission monitoring holes 21, the acoustic emission probe 22 is installed inside the loading plates, and the acoustic emission probe 22 is connected to the acoustic emission monitoring system 10 to transmit the detected mechanical parameters to the acoustic emission monitoring system 10.
Rock sample loading system still is provided with and is used for monitoring the temperature monitoring devices 14 of test hole 5 internal temperature, temperature monitoring devices 14's temperature sensor 13 set up in test hole 5 to obtain the temperature parameter that temperature sensor 13 detected, under test box heating layer 2 and test box heat preservation 3 parcels, rock sample 30 is heated and is kept at target temperature.
In a specific embodiment, the pressure stabilizing medium injection system comprises an air pressure control device 15 and a pressure pump 12 which are electrically connected, wherein the air pressure control device 15 can control the starting and the conveying pressure of the pressure pump 12; the pressure pump 12 is communicated with a medium pipeline leading to the testing hole 5, and a control valve 16 for controlling the opening and closing of the medium pipeline is arranged on the medium pipeline.
In order to facilitate the reverse backflow of the pressure stabilizing medium during the test, in this embodiment, the pressure stabilizing medium injection system further includes a pressure stabilizing medium tank 11, and the pressure stabilizing medium tank 11 is communicated with the medium pipeline and is used for receiving the pressure stabilizing medium flowing back from the test hole 5. The reverse reflux of the pressure stabilizing medium begins to occur when the fracturing fluid injection system injects the fracturing fluid into the test hole 5, and along with the continuous injection of the fracturing fluid, the original pressure stabilizing medium in the test hole 5 flows into the pressure stabilizing medium tank 11 through the medium pipeline. The flow direction of the pressure-stabilizing medium can be achieved by providing a plurality of control valves 16, in particular by providing a control valve 16 in each of the branch medium lines leading to the pressure pump 12 and the pressure-stabilizing medium tank 11, and then by providing a control valve 16 in the main medium line. The control of the medium flow direction can be achieved by adjusting the open and closed states of the respective valves 16.
In this embodiment, the fracturing fluid injection system comprises a temperature control liquid tank 17 and a hydraulic control system 19 which are communicated, the hydraulic control system 19 is connected with a conveying pipeline, the conveying pipeline leads to the inside of the test hole 5, a fluid flow control valve 20 is arranged on the conveying pipeline, and the temperature control liquid tank 17 is provided with a thermometer 18. A pressure gauge can be arranged on the conveying pipeline so as to detect the conveying pressure of the pipeline. Wherein, the fracturing fluid can adopt water.
The embodiment also provides a method for testing the hydraulic fracturing fracture pressure of the hot dry rock, and the device for testing the hydraulic fracturing fracture pressure of the hot dry rock is adopted for testing, and referring to fig. 3, the method comprises the following steps:
s1, placing the rock sample in a rock sample loading system, and arranging an acoustic emission monitoring device for monitoring mechanical parameters of the rock sample; the mechanical parameters comprise detectable signals such as vibration waves (micro-acoustic phenomenon) and the like emitted in the rock sample fracture process, and the acoustic emission monitoring device can be selected from the acoustic emission monitoring devices in the hot dry rock fracture pressure test device provided by the embodiment;
s2, controlling the rock sample loading system to heat and apply confining pressure to the rock sample, simultaneously conveying a pressure stabilizing medium into a test hole of the rock sample, and recording mechanical parameters detected by the acoustic emission monitoring device in the process; the purpose of conveying the pressure stabilizing medium is to ensure the stability of the rock sample and avoid the premature cracking of a test hole, wherein the speed of heating and applying confining pressure is in direct proportion to the quantity of the pressure stabilizing medium introduced into the test hole, namely the higher the pressurizing speed is, the larger the conveying quantity of the pressure stabilizing medium is, thereby ensuring that the rock sample does not crack in advance;
S3, when the rock sample reaches a preset temperature and a preset pressure, keeping the temperature and pressure state, simultaneously stopping conveying a pressure stabilizing medium into the test hole, and recording the corresponding mechanical parameters of the process; the preset temperature and the preset pressure are the temperature and the pressure of the real underground rock stratum, and the specific values are determined according to the test requirements;
s4, opening a fracturing fluid injection system, conveying fracturing fluid into the test hole, outputting a pressure stabilizing medium in the test hole along with the injection of the fracturing fluid, and recording mechanical parameters corresponding to the process;
and S5, closing the fracturing fluid injection system after the fracturing fluid reaches the preset injection amount, and recording the mechanical parameters corresponding to the process.
The method can be implemented according to the hot dry rock burst pressure test device provided by the embodiment, and other devices capable of realizing the functions can be adopted according to the steps.
Recording data detected by the acoustic emission monitoring device in the above steps is a continuous process, data recording runs through the whole test process, no interruption time exists, and data recording is not interrupted along with the interruption of the steps, wherein for S1, the data detected by the acoustic emission monitoring device can be collected and recorded as required.
In step S3, "when the preset temperature and the preset pressure are reached, the temperature and pressure state are maintained" means that the confining pressure is not increased any more, and the temperature value is not increased any more, so that the loading environment (pressure and temperature) is kept stable, and the real environment of the underground rock formation is simulated more truly. In step S3, the predetermined injection amount is determined according to the size of the test hole designed to ensure that the maximum burst pressure value of the rock sample is generated before or when the predetermined injection amount is reached throughout the test. Considering that the rock sample is fractured and then generates cracks, the fracturing fluid flows into the cracks, therefore, the preset injection amount is usually larger than the volume of the test hole, for example, the preset injection amount can be designed to be 1.5-2 times of the volume of the test hole, when the preset injection amount is completely injected, the rock sample is necessarily fractured, and the maximum fracture pressure value of the rock sample is necessarily generated. The recorded data detected by the acoustic emission monitoring device in the processes of S2-S5 is a series of data, and the data amount is determined by the detection frequency and the detection time detected by the acoustic emission monitoring device.
Wherein the rock sample is prepared by the following method: collecting hot dry rock meeting the test requirements, and cutting according to a preset shape and size; processing a test hole on the cut dry hot rock to form a preselected rock sample; and detecting the fracture condition of the preselected rock sample, and reserving the preselected rock sample meeting the requirements as a rock sample for later test. The method for processing the test holes in the cut dry hot rock comprises the following steps: drilling a test hole with a preset size in the geometric center of the surface of the hot dry rock, controlling the drilling speed and the drilling pressure in the drilling process, and reducing the temperature of the drill hole in real time by adopting cooling liquid so that the temperature of the liquid flowing out of the test hole is not more than 40 ℃.
Preferably, in S2, controlling the temperature rise speed of the rock sample loading system for continuously heating the rock sample within 1 ℃/min; after S3, S4 is performed after keeping the temperature and pressure states stable for a preset time. The methods can avoid the occurrence of cracks in the rock sample before the injection of the fracturing fluid and improve the stability of the rock sample.
In order to describe the test method provided by the embodiment in more detail, the embodiment provides the following examples, which are implemented by using the hot dry rock burst pressure test device provided by the embodiment, and the specific steps are as follows:
1. the method comprises the steps of collecting hot dry rock meeting test requirements, cutting test rock which meets the loading size and is 300mm multiplied by 300mm, and enabling a rock sample to be free of obvious macroscopic natural cracks and obvious lithological changes after being cut to be visually checked for surface integrity.
2. A test hole with a diameter of 50mm and a depth of 200mm is drilled in the geometric center of the rock surface of the test rock. The drilling speed and the drilling pressure need to be controlled in the drilling process, the temperature of the drilled hole is reduced in real time by using warm water of 20 ℃ to avoid the drilled hole from being damaged, the temperature of the liquid flowing out is monitored by using an infrared temperature measuring instrument, and the temperature of the liquid is controlled not to exceed 40 ℃.
3. The superficial layer of the inner wall surface of the hole 5 is not obviously cracked and the rock debris is not fallen through visual observation and test, and then the electronic Computed Tomography (Computed Tomography) technology is adopted to ensure that the crack with the length exceeding 5mm is not generated near the hole to be tested in the preparation process of the rock sample, and specifically, the CT scanning technology is used for monitoring the micro-damage crack at the deep part of the hole (which cannot be reached by visual observation) and the inside of the rock sample (which is damaged by high temperature in the drilling process) after the hole is drilled. After the detected rock sample is ensured to be complete, the rock sample can be used for the following test.
4. And clamping the rock sample by using 6 loading plates 1, and putting the rock sample into a test platform. The media line is inserted into the test well 5. A temperature sensor 13 is also inserted into the test well 5. Connecting the hydraulic servo control system 9 with the loading cylinders 4 in three directions, applying different confining pressure conditions to the rock sample, simulating different ground stress conditions, wherein the acoustic emission probe 22 is actually on the loading plate 1, and the acoustic emission probe 22 is already in place when the rock sample is clamped by the loading plate 1. The purpose of the acoustic emission probe 22 is to detect the relevant stress parameters (acoustic emission phenomena) that are generated during the crack formation, and therefore the acoustic emission probe 22 is first acoustically fired and then pressurized.
5. The acoustic emission probe 22 is placed in the acoustic emission monitoring hole 21, and the acoustic emission probe 22 is in contact with the surface of the rock sample. The temperature of the whole rock sample is controlled by the outer part of the loading plate 1 through the test box heating layer 2 and the test box heat insulation layer 3.
6. Prior to the temperature and confining pressure loading process, the liquid flow control valve 20 is first closed and the control valve 16 is opened. And then the temperature and the confining pressure adopt a simultaneous loading mode, so that the change process of the deposition environment of the rock is represented more accurately, and finally the environment state of the actual stratum is achieved.
7. And in the confining pressure loading process, high-pressure gas is pumped into the test hole 5 at the same time, the gas pressure is monitored and controlled to be higher than the collapse pressure of the test hole 5 under the confining pressure until a confining pressure target value is reached, and the gas pressure is kept stable. The high pressure gas pressure injected by the pressure pump 12 during loading cannot exceed the burst pressure of the test well 5 at the confining pressure. The temperature of the heating layer 2 of the test box is controlled to rise to the target parameters at the speed of 1 ℃/min, so that the rapid expansion and damage of the rock sample caused by too fast temperature rise are avoided.
8. And when the temperature, the confining pressure and the equilibrium air pressure reach target values, keeping each parameter stable for 5 min.
9. Clean water is adopted as a fracturing fluid test medium, is stored in a temperature control liquid tank 17 in advance in a constant temperature mode, and is injected into a test hole 5 through a liquid flow control valve 20 by a hydraulic control system 19. The gas flow control valve 16 may be closed during injection of the low temperature fracturing fluid to effect a thermal effect. 20ml of fracturing fluid is pumped, and the injection pressure is required to be lower than the fracture pressure of the rock sample. If during injection the pressure in the test hole rises rapidly, the gas flow control valve 16 is opened to vent the previously pumped gas in the pre-set hole 5 so that the pressure in the test hole 5 is always below the burst pressure and above the collapse pressure. When the low-temperature fracturing fluid is contacted with the wall of the high-temperature rock sample hole, the mechanical strength of the rock is reduced through the thermal effect, and the generation of micro cracks is induced.
10. After 20ml of fracturing fluid is injected, the stability is carried out for 2min, and the sufficient heat exchange is realized. And further injecting 30ml of fracturing fluid, gradually opening the test hole 5, and obtaining a fracture pressure value.
11. The whole temperature and confining pressure loading process, the heat effect process and the rupture process are all used for carrying out data acquisition on each thermometer and each pressure gauge at 1s time intervals. The time interval for data acquisition by the acoustic emission device is also 1 s.
12. And closing the hydraulic servo control system 9, the air pressure control system 15 and the hydraulic control system 19, opening the emptying valve 8 and unloading the confining pressure, and finally closing the acoustic emission monitoring system 10 and the temperature monitoring device 14.
13. And taking out the rock sample after the test is finished, and photographing to record the appearance of the rock sample. Then, it was compared with the destruction phenomenon occurring inside the rock sample before and after the fracture by using the Computed Tomography (Computed Tomography), and the fracture mechanism and the fracture extension size were analyzed. And splitting the rock sample, cutting slices on the wall of the test hole and the fracture position, and observing the change of the microstructure of the rock under the influence of the thermal effect by using a scanning electron microscope.
In the above embodiments, the skilled person can adjust the relevant parameters according to the actual experimental requirements.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. The utility model provides a hot dry rock rupture pressure test device which characterized in that includes: the device comprises a rock sample loading system, a pressure stabilizing medium injection system and a fracturing fluid injection system;
the rock sample loading system is used for applying confining pressure to the rock sample and heating the rock sample, and the rock sample is provided with a test hole (5); the rock sample loading system is provided with an acoustic emission monitoring device for monitoring the vibration waves emitted in the rock sample breaking process;
the pressure stabilizing medium injection system is communicated with the test hole (5) and is used for injecting a pressure stabilizing medium into the test hole (5);
the fracturing fluid injection system is communicated with the test hole (5) and is used for injecting fracturing fluid into the test hole (5);
The pressure stabilizing medium injection system controls the rock sample loading system to heat and apply confining pressure to the rock sample, meanwhile, the pressure stabilizing medium injection system conveys pressure stabilizing medium into a test hole of the rock sample, and records mechanical parameters detected by the acoustic emission monitoring device in the process; and when the rock sample reaches the preset temperature and the preset pressure, keeping the temperature and pressure states, stopping conveying the pressure stabilizing medium into the test hole, and recording the mechanical parameters corresponding to the process.
2. The hot dry rock burst pressure test testing device as claimed in claim 1, wherein the pressure stabilizing medium injection system comprises an air pressure control device (15) and a pressure pump (12) which are electrically connected, the air pressure control device (15) can control the pressure pump (12) to start and deliver pressure; the pressure pump (12) is communicated with a medium pipeline leading to the testing hole (5), and a control valve (16) used for controlling the opening and closing of the medium pipeline is arranged on the medium pipeline.
3. The hot dry rock burst pressure test rig according to claim 2, wherein the surge medium injection system further comprises a surge medium tank (11), the surge medium tank (11) being in communication with the medium line for receiving surge medium flowing back from the test bore (5).
4. The hot dry rock burst pressure test rig according to claim 1, wherein the rock sample loading system is further provided with a temperature monitoring device (14) for monitoring the temperature within the test bore (5), the temperature sensor (13) of the temperature monitoring device (14) being disposed within the test bore (5).
5. The dry hot rock burst pressure test device as claimed in claim 1, characterized in that the rock sample loading system comprises a sample loading device and a hydraulic servo control system (9), the sample loading device is used for applying confining pressure and heating to the rock sample, the sample loading device and the hydraulic servo control system (9) are connected through a hydraulic pipeline, and a control valve (6), a pressure gauge (7) and an air release valve (8) are arranged on the hydraulic pipeline.
6. The hot dry rock burst pressure test device as claimed in claim 1, wherein the fracturing fluid injection system comprises a temperature control fluid tank (17) and a hydraulic control system (19) which are communicated, the hydraulic control system (19) is connected with a conveying pipeline, the conveying pipeline leads into the test hole (5), a fluid flow control valve (20) is arranged on the conveying pipeline, and the temperature control fluid tank (17) is provided with a thermometer (18).
7. A test method for testing hydraulic fracturing fracture pressure of hot dry rock is characterized by comprising the following steps:
s1, placing the rock sample in a rock sample loading system, and arranging an acoustic emission monitoring device for monitoring mechanical parameters of the rock sample;
s2, controlling the rock sample loading system to heat and apply confining pressure to the rock sample, simultaneously conveying a pressure stabilizing medium into a test hole of the rock sample by a pressure stabilizing medium injection system, and recording mechanical parameters detected by the acoustic emission monitoring device in the process;
s3, when the rock sample reaches a preset temperature and a preset pressure, keeping the temperature and pressure state, simultaneously stopping conveying a pressure stabilizing medium into the test hole, and recording the corresponding mechanical parameters of the process;
s4, opening a fracturing fluid injection system, conveying fracturing fluid into the test hole, outputting a pressure stabilizing medium in the test hole along with the injection of the fracturing fluid, and recording mechanical parameters corresponding to the process;
and S5, closing the fracturing fluid injection system after the fracturing fluid reaches the preset injection amount, and recording the mechanical parameters corresponding to the process.
8. The test method of claim 7, wherein the rock sample is prepared by:
Collecting hot dry rock meeting the test requirements, and cutting according to a preset shape and size;
processing a test hole on the cut dry and hot rock to form a preselected rock sample;
and detecting the fracture condition of the preselected rock sample, and reserving the rock sample meeting the requirements.
9. Test method according to claim 8, characterized in that the method of machining test holes in the cut hot dry rock comprises: drilling a test hole with a preset size in the geometric center of the surface of the hot dry rock, controlling the drilling speed and the drilling pressure in the drilling process, and reducing the temperature of the drill hole in real time by adopting cooling liquid so that the temperature of the liquid flowing out of the test hole is not more than 40 ℃.
10. The test method according to claim 7, wherein in S2, the temperature rise rate of the rock sample loading system for continuously heating the rock sample is controlled within 1 ℃/min;
after S3, S4 is performed after keeping the temperature and pressure states stable for a preset time.
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