Shale fault slippage mechanical property testing device and testing method

Abstract

The invention relates to the technical field of geotechnical engineering, and provides a shale fault slippage mechanical property test device and a test method, the test device comprises: a confining pressure loading module for applying confining pressure to a rock core sample; the axial pressure loading module is used for applying axial pressure to the rock core sample; the water injection circulating module is communicated with a water injection hole in the rock core sample so as to apply water injection pressure to the rock core sample; the monitoring module is provided with an axial sensor, a radial sensor and an ultrasonic probe, the axial sensor is arranged between the two ends of the rock core sample in the axis direction of the rock core sample, the radial sensor is connected to the peripheral face of the rock core sample in a sleeving mode, and the ultrasonic probe is arranged on the periphery of the fault surface of the rock core sample. According to the shale fault slippage mechanical property test device and the test method, activation of shale fault slippage and an influence mechanism of the shale fault slippage on rock mechanical properties can be obtained, and a theoretical basis is provided for construction of oil production engineering.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering, and in particular to a shale fault slip mechanical property test device and a test method. Background Art

[0002] Most oil and gas resources are stored in shale and are not easy to exploit. Therefore, the exploitation of shale gas and shale oil is a top priority in the oil and gas energy industry. Shale has a complex composition and most of it contains faults and fracture zones, so its mechanical properties are variable, which greatly increases the difficulty of oil production. Therefore, it is necessary to study the influence of faults and fracture zones on the shear mechanical properties of shale to provide a theoretical basis for the construction of oil production projects. In oil wells, casing is a steel pipe used to protect the outer layer of the pumping pipe. The outermost layer of the entire pumping system is in direct contact with oil or formations. During the production process of the oil field, when the load on the casing caused by factors such as engineering, geology, and production dynamic changes exceeds the bearing capacity of the casing, the casing will be damaged, that is, the casing is damaged. The layer and depth of casing damage are different, among which fault slip is one of the main causes of casing damage. Stress and formation pressure differences are the static and dynamic causes of plane slip, respectively. Under the influence of the fault dip, the horizontal component of gravity and the formation pore pressure difference on both sides of the fault will produce local stress concentration, causing local slip along the fault plane between the upper and lower plates of the fault. In order to clarify the activation of shale fault slip and its influence on the mechanical properties of rock, it is necessary to design a device and method for measuring the mechanical properties of shale fault slip. Summary of the invention

[0003] The purpose of the present invention is to provide a shale fault slip mechanical properties test device and test method, to obtain the activation of shale fault slip and its influence mechanism on rock mechanical properties, and to provide a theoretical basis for the construction of oil production projects.

[0004] The above technical objectives of the present invention are mainly achieved through the following technical solutions:

[0005] In one aspect, the present invention provides a shale fault sliding mechanical property test device, which comprises:

[0006] A confining pressure loading module for applying confining pressure to the core sample;

[0007] An axial pressure loading module for applying axial pressure to the core sample;

[0008] A water injection circulation module is connected to the water injection hole on the core sample to apply water injection pressure to the core sample to simulate fracturing construction conditions;

[0009] The monitoring module comprises an axial sensor, a radial sensor and an ultrasonic probe. The axial sensor is arranged between the two ends of the core sample along the axial direction of the core sample and is used to measure the axial pressure and axial deformation of the core sample. The radial sensor is sleeved on the outer peripheral surface of the core sample and is used to measure the radial deformation of the core sample. The ultrasonic probe is arranged on the periphery of the fault plane of the core sample and is used to measure the wave velocity of the ultrasonic wave generated by the fault plane during the test.

[0010] The shale fault slip mechanical property test device described in the present invention performs a triaxial compression test on a core sample containing a fault surface under reservoir conditions, and uses a radial sensor, an axial sensor and an ultrasonic probe to obtain the fault slip characteristics and activation conditions of the core sample under different fracturing construction conditions. The device is small and light, easy to operate, and can improve experimental efficiency.

[0011] The shale fault slip mechanical property test device described in the present invention provides conditions such as water injection, confining pressure and axial pressure to simulate the actual underground situation, so that the core sample containing the fault surface can simulate the underground fault to the greatest extent, and subsequently the stress condition on the core surface can be analyzed by observing the failure morphology of the core sample after the test and processing the experimental data, and the failure mechanism of the core can be subsequently explained.

[0012] The shale fault slip mechanical property test device of the present invention can test the mechanical properties of the core sample with a fault surface. According to the various data monitored by the monitoring module during the axial loading process, not only can the stress-strain curve of the core sample be obtained, the fault slip time point can be judged by observing the curve change, but also the elastic modulus, Poisson's ratio and other parameters can be obtained. It is also possible to combine the multi-party monitoring data with the morphology of the core sample after destruction for unified analysis, accurately obtain the time and characteristics of the core fault slip and crack damage, and then provide a theoretical basis for the construction of oil production engineering.

[0013] In a preferred embodiment of the present invention, during the test, the wave velocity of the ultrasonic wave measured by the ultrasonic probe includes the longitudinal wave velocity and the shear wave velocity.

[0014] In this embodiment, by monitoring the longitudinal wave velocity and the transverse wave velocity during the axial loading process, the dynamic elastic modulus and the dynamic Poisson's ratio of the core sample can be obtained in combination with the stress-strain data of the core sample, providing reference data for the mechanical characteristics of the core sample.

[0015] In a preferred embodiment of the present invention, the confining pressure loading module comprises:

[0016] A confining pressure cylinder, in which a confining pressure loading cavity for placing the core sample is formed;

[0017] The oil filling pipeline is connected to the confining pressure loading chamber and is used for supplying oil into the confining pressure loading chamber to form confining pressure.

[0018] In this embodiment, the confining pressure is applied to the core sample by supplying liquid and pressurizing in a closed chamber. Not only is the structure simple, but the confining pressure formed around the core sample is relatively uniform, thereby ensuring the stability of the core sample.

[0019] In a preferred embodiment of the present invention, one end of the oil injection pipeline is connected to an oil injection pump, and a pressure gauge and a switch valve are provided on the oil injection pipeline.

[0020] In this embodiment, the oil injection pump is used to supply oil to the confining pressure loading chamber, the pressure gauge is used to observe the pressure of the oil in the confining pressure loading chamber, and the switch valve can control the opening and closing of the oil injection pipeline.

[0021] In a preferred embodiment of the present invention, the axial pressure loading module comprises:

[0022] An upper piston is arranged on the top wall of the confining pressure cylinder;

[0023] A lower piston is arranged on the bottom wall of the confining pressure cylinder, and the lower piston is opposite to the upper piston in vertical direction;

[0024] A lower pressure head is placed on the upper piston, and the core sample is placed above the lower pressure head;

[0025] An upper pressure head is placed above the core sample;

[0026] The extension of the upper piston and / or the lower piston can drive the upper piston and the lower piston to abut against the upper pressure head and the lower pressure head respectively, and drive the upper pressure head and the lower pressure head to approach each other to form axial pressure.

[0027] In this embodiment, an upper pressure head and a lower pressure head are provided as intermediate force transmission components. The upper pressure head and the lower pressure head can be adaptively designed according to the shape of the core sample, thereby facilitating the installation of the core sample. Different types of upper pressure heads and lower pressure heads can also be replaced according to the needs of different core samples.

[0028] In a preferred embodiment of the present invention, the axial sensor is connected between the upper pressure head and the lower pressure head.

[0029] In this embodiment, the upper pressure head and the lower pressure head are respectively connected to the upper and lower ends of the core sample. Since the upper and lower pressure heads are fixed-shape parts and the core sample undergoes slip deformation during the test, the test result is more accurate when the axial sensor is connected to the upper and lower pressure heads compared to connecting the axial sensor between the upper and lower ends of the core sample.

[0030] In a preferred embodiment of the present invention, a heat shrink tube is provided around the outer periphery of the core sample, and the upper and lower ends of the heat shrink tube are respectively sealed and connected to the upper pressure head and the lower pressure head.

[0031] In this embodiment, the heat shrink tube can play a sealing effect. After being fully heated, the heat shrink tube will completely adhere to the outer wall of the core sample, thereby isolating the core sample from the oil in the confining pressure loading chamber to prevent the oil from entering the core sample.

[0032] In a preferred embodiment of the present invention, the ultrasonic probe and the radial sensor are both arranged on the outer circumference of the heat shrink tube.

[0033] In a preferred embodiment of the present invention, pipeline channels are provided on the upper piston, the lower piston, the upper pressure head and the lower pressure head, and the water circulation pipeline in the water injection circulation module is passed through the pipeline channels.

[0034] In this embodiment, the water circulation pipeline is directly connected to the core sample through the pipeline channels on the piston and the pressure head, avoiding contact between the water circulation pipeline and the high-pressure oil in the confining pressure loading chamber, thereby ensuring that the water injection circulation process can proceed smoothly, while also avoiding the risk of mixing of oil and water.

[0035] In a preferred embodiment of the present invention, a water filter gasket is provided between the upper pressure head, the lower pressure head and the core sample, and the water in the water circulation pipeline can enter the water injection hole through the water filter gasket and / or the water in the water injection hole can flow back into the water circulation pipeline through the water filter gasket.

[0036] In this embodiment, the water filter gasket can filter the water flowing in the water circulation pipeline to prevent impurities generated in the core sample from entering the water circulation pipeline.

[0037] In a preferred embodiment of the present invention, the water injection circulation module comprises:

[0038] A water injection pipeline is connected to an upper water injection hole opened on the core sample and connected to the fault surface;

[0039] The water outlet pipeline is connected with the lower water injection hole opened on the core sample and connected with the fault surface.

[0040] In this embodiment, the cooperation of the water injection pipeline and the water outlet pipeline can simulate underground fracturing construction conditions, and the water injection rate is controlled by adjusting the water injection pipeline, thereby simulating different fracturing construction conditions.

[0041] In a preferred embodiment of the present invention, one end of the water injection pipeline and one end of the water outlet pipeline are both connected to a borehole pressure pump, the water injection pipeline and the water outlet pipeline are both provided with an oil-water isolator and a switch valve, and the water injection pipeline is also provided with a pressure gauge.

[0042] In this embodiment, the pore pressure pump is used to maintain the water pressure in the pipeline, the oil-water isolator is used to separate the oil mixed in the water, the switch valve is used to control the opening and closing of the corresponding pipeline, and the pressure gauge is used to monitor the water pressure in the pipeline.

[0043] On the other hand, the present invention also provides a method for testing the mechanical properties of shale fault sliding, the testing method is implemented using the shale fault sliding mechanical properties testing device as described above, and the testing method comprises:

[0044] Prepare and install a fixed core sample, and set an axial sensor, a radial sensor and an ultrasonic probe on the core sample;

[0045] Start the confining pressure loading module to load the core sample with confining pressure, so that it reaches a predetermined confining pressure and remains constant;

[0046] Start the water injection circulation module to achieve a predetermined water injection rate and keep it constant;

[0047] The axial pressure loading module is started to load axial pressure on the core sample, and the axial sensor, radial sensor and ultrasonic probe are turned on at the same time to monitor the changes of the core sample and the fault surface.

[0048] The shale fault slip mechanical property testing method of the present invention can test the mechanical properties of the core sample with a fault plane. According to the various data monitored by the monitoring module during the axial loading process, not only can the stress-strain curve of the core sample be obtained, the fault slip time point can be judged by observing the curve change, but also the elastic modulus, Poisson's ratio and other parameters can be obtained. It is also possible to combine the multi-party monitoring data with the morphology of the core sample after destruction for unified analysis, accurately obtain the time and characteristics of the core fault slip and crack damage, and conduct a subsequent explanation of the core damage mechanism, thereby providing a theoretical basis for the construction of oil production engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0050] The accompanying drawings described herein are only for explanation purposes and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the figures are only schematic, used to help understand the present invention, and are not specifically limited to the shapes and proportional dimensions of the various components of the present invention. Those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to the teachings of the present invention.

[0051] Figure 1 It is a structural schematic diagram of the shale fault sliding mechanical property test device of the present invention;

[0052] Figure 2 It is a schematic structural diagram of the core sample and the upper and lower pressure heads of the present invention.

[0053] Description of reference numerals:

[0054] 10. Core sample; 11. Fault plane; 12. Upper water injection hole; 13. Lower water injection hole; 14. Heat shrink tube;

[0055] 20. Confining pressure cylinder; 21. Oil injection pipeline; 22. Oil injection pump; 23. First pressure gauge; 24. First switch valve;

[0056] 30. Upper piston; 31. Lower piston; 32. Upper pressure head; 33. Lower pressure head; 34. Water filter gasket;

[0057] 40. Water injection pipeline; 41. Water outlet pipeline; 42. Borehole pressure pump; 43. Second pressure gauge; 44. Oil-water separator; 45. Switch valve;

[0058] 50. Axial sensor; 51. Radial sensor; 52. Ultrasonic probe. DETAILED DESCRIPTION

[0059] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0060] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only embodiment.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0062] Implementation method 1:

[0063] The present invention provides a shale fault sliding mechanical properties test device, such as Figure 1 and Figure 2 As shown, it includes a confining pressure loading module, an axial pressure loading module, a water injection circulation module and a monitoring module. Among them, the confining pressure loading module is used to apply confining pressure to the core sample 10; the axial pressure loading module is used to apply axial pressure to the core sample 10; the water injection circulation module is connected to the water injection hole on the core sample 10 to apply water injection pressure to the core sample 10 to simulate the fracturing construction conditions; the monitoring module has an axial sensor 50, a radial sensor 51 and an ultrasonic probe 52, the axial sensor 50 is arranged between the two ends of the core sample 10 along the axial direction of the core sample 10, and is used to measure the axial pressure and axial deformation of the core sample 10, the radial sensor 51 is sleeved on the outer peripheral surface of the core sample 10, and is used to measure the radial deformation of the core sample 10, and the ultrasonic probe 52 is arranged on the periphery of the fault plane 11 of the core sample 10, and is used to measure the wave velocity of the ultrasonic wave generated by the fault plane 11 during the test.

[0064] The shale fault slip mechanical properties test device described in the present invention performs a triaxial compression test on a core sample 10 containing a fault surface 11 under reservoir conditions, and uses a radial sensor 51, an axial sensor 50 and an ultrasonic probe 52 to obtain the fault slip characteristics and activation conditions of the core sample 10 under different fracturing construction conditions. The device is small and light, easy to operate, and has high experimental efficiency.

[0065] The shale fault slip mechanical properties test device described in the present invention provides water injection, confining pressure and axial pressure conditions to simulate the actual underground situation, so that the core sample 10 containing the fault surface 11 can simulate the underground fault to the greatest extent, and subsequently the stress condition on the core surface can be analyzed by observing the failure morphology of the core sample 10 after the test and processing the experimental data, and the failure mechanism of the core can be subsequently explained.

[0066] The shale fault slip mechanical property test device of the present invention can test the mechanical properties of the core sample 10 provided with the fault surface 11. According to the various data monitored by the monitoring module during the axial loading process, not only the stress-strain curve of the core sample 10 can be obtained, the fault slip time point can be judged by observing the curve change, but also the elastic modulus, Poisson's ratio and other parameters can be obtained. It is also possible to combine the multi-party monitoring data with the morphology of the core sample 10 after destruction for unified analysis, accurately obtain the time and characteristics of the core fault slip and crack damage, and then provide a theoretical basis for the construction of oil production engineering.

[0067] The specific structure of each part of the shale fault slip mechanical properties test device of the present invention, as well as the position and connecting pipelines between the parts will be described in detail below.

[0068] First, the structure of the core sample 10 of the present invention is described. Figure 2 As shown, the core sample 10 is cylindrical as a whole, and a fault plane 11 is obliquely opened in the middle of the cylinder. The core sample 10 is divided into an upper and lower part by the fault plane 11, and the fault plane 11 is used to simulate underground cracks. Furthermore, a water injection hole is opened on the core sample 10, and the water injection hole is connected to the fault plane 11, and water is injected into the water injection hole to simulate the underground fracturing operation environment; specifically, an upper water injection hole 12 is opened in the upper half of the core sample 10, and a lower water injection hole 13 is opened in the lower half of the core sample 10. The upper water injection hole 12 and the lower water injection hole 13 both extend along the axial direction of the core sample 10 and extend to the fault plane 11. The upper and lower end surfaces of the core sample 10 need to be smoothed to prevent the core sample 10 from being crushed during the experiment.

[0069] The shale fault slip mechanical property test device of the present invention has a confining pressure loading module, which is used to apply pressure to the circumferential outer side of the core sample 10, thereby simulating the circumferential high pressure environment underground.

[0070] In this embodiment, if Figure 1 As shown, the confining pressure loading module includes a confining pressure cylinder 20 and an oil injection pipeline 21. Among them, a confining pressure loading cavity for placing the core sample 10 is formed in the confining pressure cylinder 20; the oil injection pipeline 21 is connected to the confining pressure loading cavity, and is used to supply oil to the confining pressure loading cavity to form confining pressure. The confining pressure loading cavity is relatively closed, with thick walls and a large bottom, which can withstand a large pressure and can be used to simulate the high-pressure environment of deeper formations. The confining pressure cylinder 20 has an openable and closable cylinder cover and an oil unloading hole (not shown in the figure), which facilitates the installation of various components in the confining pressure cylinder 20 and the discharge of oil.

[0071] The confining pressure is applied to the core sample 10 by supplying liquid to the closed chamber for pressurization. This not only has a simple structure, but also forms a more uniform confining pressure around the core sample 10 , thereby ensuring the stability of the core sample 10 .

[0072] Further, such as Figure 1 As shown, one end of the oil injection pipeline 21 is connected to an oil injection pump 22, and a first pressure gauge 23 and a first switch valve 24 are provided on the oil injection pipeline 21. The oil injection pump 22 is used to supply oil to the confining pressure loading chamber, the first pressure gauge 23 is used to observe the pressure of the oil in the confining pressure loading chamber, and the first switch valve 24 can control the opening and closing of the oil injection pipeline 21.

[0073] The shale fault slip mechanical property test device of the present invention also has an axial pressure loading module for applying pressure to the upper and lower ends of the core sample 10 to simulate the axial high pressure environment underground.

[0074] In this embodiment, if Figure 1 and Figure 2 As shown, the axial pressure loading module includes an upper piston 30, a lower piston 31, an upper pressure head 32 and a lower pressure head 33. The upper piston 30 is arranged on the top wall of the confining pressure cylinder 20; the lower piston 31 is arranged on the bottom wall of the confining pressure cylinder 20, the lower piston 31 is opposite to the upper piston 30 up and down and can be telescopically moved; the lower pressure head 33 is placed on the upper piston 30, and the core sample 10 is placed above the lower pressure head 33; the upper pressure head 32 is placed above the core sample 10; wherein, the extension of the upper piston 30 and / or the lower piston 31 can drive the upper piston 30 and the lower piston 31 to abut against the upper pressure head 32 and the lower pressure head 33 respectively, and drive the upper pressure head 32 and the lower pressure head 33 to approach each other to form axial pressure.

[0075] The upper pressure head 32 and the lower pressure head 33 are arranged between the piston and the core sample 10 as intermediate force transmission components. The upper pressure head 32 and the lower pressure head 33 can be adaptively designed according to the shape of the core sample 10, thereby facilitating the installation of the core sample 10. Different types of upper pressure heads 32 and lower pressure heads 33 can also be replaced according to the needs of different core samples 10.

[0076] The shale fault slip mechanical property test device of the present invention also has a water injection circulation module for injecting water into the fault surface 11 of the core sample 10, thereby simulating the underground fracturing construction environment.

[0077] In this embodiment, if Figure 1 and Figure 2 As shown, the water injection circulation module includes a water injection pipeline 40 and a water outlet pipeline 41. The water injection pipeline 40 is connected to the upper water injection hole 12 opened on the core sample 10 and connected to the fault surface 11; the water outlet pipeline 41 is connected to the lower water injection hole 13 opened on the core sample 10 and connected to the fault surface 11.

[0078] The cooperation of the water injection pipeline 40 and the water outlet pipeline 41 can simulate underground fracturing construction conditions. At the same time, the water injection rate can be controlled by adjusting the water injection pipeline 40 to simulate different fracturing construction conditions.

[0079] Further, such as Figure 1 As shown, one end of the water injection pipeline 40 and one end of the water outlet pipeline 41 are connected to a bore pressure pump 42 , and both the water injection pipeline 40 and the water outlet pipeline 41 are provided with an oil-water separator 44 and a second switch valve 45 , and the water injection pipeline 40 is also provided with a second pressure gauge 43 .

[0080] The pore pressure pump 42 is used to maintain the water pressure in the pipeline and control the water flow rate in the pipeline. The oil-water separator 44 is used to separate the oil mixed in the water. The second switch valve 45 is used to control the opening and closing of the corresponding pipeline. The second pressure gauge 43 is used to monitor the water pressure in the pipeline.

[0081] The shale fault slip mechanical property test device of the present invention also has a monitoring module for monitoring parameters such as force magnitude and deformation amount of the core sample 10 during axial pressurization, so as to provide data support for subsequent characteristic analysis of fault slip and crack damage.

[0082] In this embodiment, if Figure 1 and Figure 2 As shown, the monitoring module includes an axial sensor 50 , a radial sensor 51 and an ultrasonic probe 52 .

[0083] The axial sensor 50 is connected between the upper pressure head 32 and the lower pressure head 33, and is used to measure the axial pressure and axial deformation of the core sample 10. The upper pressure head 32 and the lower pressure head 33 are respectively connected to the upper and lower ends of the core sample 10. Since the upper pressure head 32 and the lower pressure head 33 are fixed shape parts, and the core sample 10 undergoes slip deformation during the test, the axial sensor 50 is connected to the upper pressure head 32 and the lower pressure head 33, and the test result is more accurate. Preferably, multiple axial sensors 50 are arranged at intervals along the circumferential direction of the core sample 10 to improve the accuracy of the measurement data.

[0084] The radial sensor 51 is sleeved on the outer circumference of the core sample 10 to measure the radial deformation of the core sample 10 ; the radial sensor 51 is arranged at a position radially opposite to the position of the fault plane 11 of the core sample 10 .

[0085] The ultrasonic probe 52 is arranged on the periphery of the fault plane 11 of the core sample 10, and is used to measure the wave velocity of the ultrasonic wave generated by the fault plane 11 during the test. Preferably, the wave velocity of the ultrasonic wave measured by the ultrasonic probe 52 includes the longitudinal wave velocity and the transverse wave velocity. By monitoring the longitudinal wave velocity and the transverse wave velocity during the axial loading process, the dynamic elastic modulus and the dynamic Poisson's ratio of the core sample 10 can be obtained in combination with the stress-strain data of the core sample 10, providing reference data for the mechanical property analysis of the core sample 10.

[0086] The shale fault sliding mechanical property test device of the present invention also has a signal acquisition and processing system and a computer, which are used to control the operation of the test device and simultaneously collect, analyze and display the data collected by each sensor.

[0087] like Figure 1 As shown, the signal acquisition and processing system is electrically connected to the axial sensor 50, the radial sensor 51 and the ultrasonic probe 52. During the experiment, the signal acquisition and processing system continuously obtains the test data of each sensor, and then pre-processes the data and sends it to the computer's graphical user interface, where it is displayed in various forms for analysis and processing by the experimenter.

[0088] The structure and technical effects of a preferred embodiment of the shale fault slip mechanical properties testing device of the present invention will be further described below.

[0089] According to one embodiment of the present invention, Figure 2 As shown, a heat shrink tube 14 is sleeved around the outer periphery of the core sample 10 , and the upper and lower ends of the heat shrink tube 14 are sealedly connected to the upper pressure head 32 and the lower pressure head 33 respectively. The ultrasonic probe 52 and the radial sensor 51 are both arranged on the outer periphery of the heat shrink tube 14 .

[0090] The heat shrink tube 14 can play a sealing role. After being fully heated, the heat shrink tube 14 will completely adhere to the outer wall of the core sample 10, thereby isolating the core sample 10 from the oil in the confining pressure loading chamber to prevent the oil from entering the core sample 10.

[0091] According to one embodiment of the present invention, Figure 1 and Figure 2 As shown, pipeline channels are provided on the upper piston 30, the lower piston 31, the upper pressure head 32 and the lower pressure head 33, and the water injection pipeline 40 and the water outlet pipeline 41 in the water injection circulation module are correspondingly arranged in the pipeline channels.

[0092] The water injection pipeline 40 and the water outlet pipeline 41 are directly connected to the core sample 10 through the pipeline channels on the piston and the pressure head, avoiding the contact between the pipeline and the high-pressure oil in the confining pressure loading chamber, thereby ensuring that the water injection cycle process can proceed smoothly, and also avoiding the risk of mixing of oil and water.

[0093] According to one embodiment of the present invention, Figure 2 As shown, a water filter gasket 34 is provided between the upper pressure head 32 and the lower pressure head 33 and the core sample 10. The water in the water injection pipeline 40 can enter the upper water injection hole 12 through the water filter gasket 34, and the water in the lower water injection hole 13 can flow back into the water outlet pipeline 41 through the water filter gasket 34.

[0094] The water filter gasket 34 can filter the water flowing in the pipeline to prevent impurities generated in the core sample 10 from entering the pipeline.

[0095] Implementation method 2:

[0096] The present invention also provides a method for testing the mechanical properties of shale fault sliding. The testing method is implemented using the shale fault sliding mechanical properties testing device as described in the first embodiment. The testing method comprises the following steps:

[0097] Step S1: preparing and installing a fixed core sample 10, and setting an axial sensor 50, a radial sensor 51 and an ultrasonic probe 52 on the core sample 10;

[0098] Step S2: starting the confining pressure loading module to load the core sample 10 with confining pressure, so that the confining pressure reaches a predetermined confining pressure and remains constant;

[0099] Step S3: Start the water injection circulation module to achieve a predetermined water injection rate and keep it constant;

[0100] Step S4: start the axial pressure loading module to load axial pressure on the core sample 10 , and simultaneously start the axial sensor 50 , the radial sensor 51 and the ultrasonic probe 52 to monitor the changes of the core sample 10 and the fault plane 11 .

[0101] The shale fault slip mechanical property testing method of the present invention can test the mechanical properties of the core sample 10 provided with the fault plane 11. According to the various data monitored by the monitoring module during the axial loading process, not only the stress-strain curve of the core sample 10 can be obtained, the fault slip time point can be judged by observing the curve change, but also the elastic modulus, Poisson's ratio and other parameters can be obtained. It is also possible to combine the multi-party monitoring data with the morphology of the core sample 10 after destruction for unified analysis, accurately obtain the time and characteristics of the core fault slip and crack damage, and conduct a subsequent explanation of the core damage mechanism, thereby providing a theoretical basis for the construction of oil production engineering.

[0102] The following will describe in detail the various steps of the shale fault slip mechanical properties testing method of the present invention.

[0103] In step S1, open the cover of the confining pressure cylinder 20, place the lower pressure head 33 on the lower piston 31, and then place the prepared core sample 10 on the lower pressure head 33, install a water filter gasket 34 in the middle, and put a heat shrink tube 14 on the outer sleeve of the core sample 10, and then place the water filter gasket 34 and the upper pressure head 32 on the top of the core sample 10. After fixing with self-adhesive glue, fully heat the heat shrink tube 14 to make it completely fit the core sample 10 to achieve a sealing effect. Then install the axial sensor 50, radial sensor 51 and ultrasonic probe 52 in the corresponding positions and connect them to the external signal acquisition and processing system through wires. Then close the barrel cover to make the confining pressure cylinder 20 completely sealed.

[0104] In step S2, the first switch valve 24 and the oil injection pump 22 on the oil injection line 21 are opened to inject oil into the confining pressure cylinder 20, and the first pressure gauge 23 on the oil injection line 21 is observed at the same time. When the oil pressure in the confining pressure cylinder 20 reaches a predetermined pressure, the first switch valve 24 is closed to keep the pressure in the confining pressure cylinder 20 stable.

[0105] In step S3, the pore pressure pump 42, the oil-water separator 44 and the second switch valve 45 on the water injection pipeline 40 and the water outlet pipeline 41 are turned on, and the water injection rate is controlled to a predetermined water injection rate and kept constant.

[0106] In step S4, the lower piston 31 is controlled to rise slowly, so as to drive the lower pressure head 33, the core sample 10 and the upper pressure head 32 to move upward until the upper pressure head 32 contacts the upper piston 30, and then the axial sensor 50, the radial sensor 51 and the ultrasonic probe 52 are turned on, after which the lower piston 31 continues to rise slowly to start axial loading.

[0107] In the process of applying axial pressure to the core sample 10, the axial sensor 50 obtains the axial pressure F and axial deformation H of the core sample 10, and the ultrasonic probe 52 obtains the longitudinal wave velocity V generated by the core sample 10. p and shear wave velocity Vs, and then the following test results related to the core sample 10 are obtained:

[0108] Axial stress σ:

[0109]

[0110] Axial strain ε1:

[0111]

[0112] Radial strain ε2;

[0113]

[0114] Elastic modulus E:

[0115]

[0116] Poisson's ratio μ:

[0117]

[0118] Dynamic elastic modulus E d :

[0119]

[0120] Dynamic Poisson's ratio μ d :

[0121]

[0122] Wherein, D is the diameter of the core sample 10; H is the axial displacement of the core sample 10; L is the length of the core sample 10; I is the radial displacement of the core sample 10; and ρ is the density of the core sample 10.

[0123] According to the above calculation formula, the stress-strain curve of the core sample 10 can be obtained through the corresponding program in the computer, and the time point of fault slip can be determined by observing the change of the curve. In addition, parameters such as elastic modulus and Poisson's ratio can be obtained, providing data support for the experimenters' subsequent characteristic analysis of fault slip and crack damage.

[0124] After the experiment, the axial pressure is first released, and then the confining pressure is released, the water injection is stopped, and the oil in the confining pressure tube 20 is discharged, and then the core sample 10 is taken out.

[0125] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A shale fault sliding mechanical properties test device, characterized in that: include: a confining pressure loading module for applying confining pressure to the core sample (10); an axial pressure loading module for applying axial pressure to the core sample (10); A water injection circulation module is connected to the water injection hole on the core sample (10) to apply water injection pressure to the core sample (10) to simulate fracturing construction conditions; The monitoring module comprises an axial sensor (50), a radial sensor (51) and an ultrasonic probe (52); the axial sensor (50) is arranged between the two ends of the core sample (10) along the axial direction of the core sample (10) and is used to measure the axial pressure and axial deformation of the core sample (10); the radial sensor (51) is sleeved on the outer peripheral surface of the core sample (10) and is used to measure the radial deformation of the core sample (10); the ultrasonic probe (52) is arranged on the outer periphery of the fault plane (11) of the core sample (10) and is used to measure the wave velocity of the ultrasonic wave generated by the fault plane (11) during the test.

2. The shale fault sliding mechanical properties testing device according to claim 1, characterized in that: The confining pressure loading module comprises: A confining pressure cylinder (20) having a confining pressure loading cavity formed therein for placing the core sample (10); An oil injection pipeline (21) is connected to the confining pressure loading chamber and is used to supply oil to the confining pressure loading chamber to form confining pressure.

3. The shale fault sliding mechanical properties testing device according to claim 2, characterized in that: One end of the oil injection pipeline (21) is connected to an oil injection pump (22), and a pressure gauge and a switch valve (45) are provided on the oil injection pipeline (21).

4. The shale fault sliding mechanical properties testing device according to claim 2, characterized in that: The axial pressure loading module comprises: An upper piston (30) is arranged on the top wall of the confining pressure cylinder (20); A lower piston (31) is arranged on the bottom wall of the confining pressure cylinder (20), and the lower piston (31) and the upper piston (30) are opposite to each other in vertical direction; A lower pressure head (33) is placed on the upper piston (30), and the core sample (10) is placed above the lower pressure head (33); An upper pressure head (32) is placed above the core sample (10); The extension of the upper piston (30) and / or the lower piston (31) can drive the upper piston (30) and the lower piston (31) to abut against the upper pressure head (32) and the lower pressure head (33) respectively, and drive the upper pressure head (32) and the lower pressure head (33) to approach each other to form axial pressure.

5. The shale fault sliding mechanical properties testing device according to claim 4, characterized in that: The axial sensor (50) is connected between the upper pressure head (32) and the lower pressure head (33).

6. The shale fault sliding mechanical property test device according to claim 4, characterized in that: The outer periphery of the core sample (10) is sheathed with a heat shrink tube (14), and the upper and lower ends of the heat shrink tube (14) are respectively sealed and connected to the upper pressure head (32) and the lower pressure head (33).

7. The shale fault sliding mechanical property test device according to claim 6, characterized in that: The ultrasonic probe (52) and the radial sensor (51) are arranged on the outer periphery of the heat shrink tube (14).

8. The shale fault sliding mechanical property test device according to claim 4, characterized in that: The upper piston (30), the lower piston (31), the upper pressure head (32) and the lower pressure head (33) are all provided with pipeline channels, and the water circulation pipeline in the water injection circulation module is passed through the pipeline channels.

9. The shale fault sliding mechanical property test device according to claim 8, characterized in that: A water filter gasket (34) is provided between the upper pressure head (32), the lower pressure head (33) and the core sample (10), and water in the water circulation pipeline can enter the water injection hole through the water filter gasket (34) and / or water in the water injection hole can flow back into the water circulation pipeline through the water filter gasket (34).

10. The shale fault sliding mechanical property test device according to claim 1, characterized in that: The water injection circulation module comprises: A water injection pipeline (40) is connected to an upper water injection hole (12) opened on the core sample (10) and connected to the fault surface (11); The water outlet pipeline (41) is connected to a lower water injection hole (13) opened on the core sample (10) and connected to the fault surface (11).

11. The shale fault sliding mechanical property test device according to claim 10, characterized in that: One end of the water injection pipeline (40) and one end of the water outlet pipeline (41) are both connected to a borehole pressure pump (42), and both the water injection pipeline (40) and the water outlet pipeline (41) are provided with an oil-water separator (44) and a switch valve (45), and the water injection pipeline (40) is also provided with a pressure gauge.

12. A method for testing the mechanical properties of shale fault sliding, characterized in that: The test method is implemented by using the shale fault sliding mechanical property test device described in any one of claims 1 to 11, and the test method comprises: A core sample (10) is prepared and installed, and an axial sensor (50), a radial sensor (51) and an ultrasonic probe (52) are arranged on the core sample (10); Starting the confining pressure loading module to load confining pressure on the core sample (10) so that the confining pressure reaches a predetermined confining pressure and remains constant; Start the water injection circulation module to achieve a predetermined water injection rate and keep it constant; The axial pressure loading module is started to load axial pressure on the core sample (10), and the axial sensor (50), the radial sensor (51) and the ultrasonic probe (52) are simultaneously turned on to monitor changes in the core sample (10) and the fault plane (11).

13. The method for testing the mechanical properties of shale fault sliding according to claim 12, characterized in that: During the test, the wave velocity of the ultrasonic wave measured by the ultrasonic probe (52) includes the longitudinal wave velocity and the transverse wave velocity.

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