Device and method for evaluating elastic modulus of laminated rock based on true triaxial scratch

Abstract

The present invention discloses a device and method for evaluating the elastic modulus of laminar rock based on true triaxial scratching, which belongs to the technical field of shale mining, and includes a liquid supply module; a true triaxial clamping module; a probe assembly, which is arranged on the true triaxial clamping module, and the inner side of the true triaxial clamping module is provided with guide rails, which are cross-distributed horizontally and vertically, and a first support is provided on the guide rail for adsorption and rotation, and a probe body is provided at the head end of the first support, and a first telescopic rod is provided between the first support and the probe body; a scratch assembly, which is arranged on a top surface rotating fixed structure, and a second support is adsorbed on the guide rail in the top surface rotating fixed structure, and a scratch cutter head is provided at the head end of the second support, and a second telescopic rod is provided between the second support and the scratch cutter head. The present invention can realize scratch experiments on laminar shale samples of any shape under true triaxial conditions, and calculate the size and distribution characteristics of the elastic modulus of the laminar shale surface by combining finite element simulation and inversion.

Description

Technical Field

[0001] The invention relates to the technical field of shale mining, and in particular to a device and a method for evaluating the elastic modulus of laminar rocks based on true triaxial scratching. Background Art

[0002] Shale oil and gas is a clean and unconventional energy resource with huge reserves, and is also one of my country's strategic energy sources. At present, most of my country's continental shale oil is laminar shale reservoirs. Due to the control of laminae on fracture penetration, the formation of artificial fracture networks by volume fracturing is greatly limited. Clarifying the rock mechanical properties of laminar shale is of great significance for the evaluation of the compressibility sweet spot of shale oil, the expansion law of fracturing fractures, and efficient development.

[0003] The thickness of the laminar shale is at the millimeter scale, showing the appearance of a "thousand-layer pancake" core. In addition, the laminar composition is diverse, showing the rhythmic characteristics of alternating felsic laminae, clay laminae, ostracod laminae and mixed laminae. The size of the traditional rock mechanics experimental sample is a columnar sample with a diameter of 2.5cm / 5cm and a length of 5cm / 10cm. The calculated mechanical parameters are overall average parameters, which are difficult to truly reflect the mechanical properties of millimeter-scale laminae. Although micro-nano indentation can obtain the mechanical properties of laminar shale, since the indentation test results are distributed as discrete points, the mechanical properties are greatly affected by the heterogeneous distribution of the laminae, and it is difficult to form a regular understanding. The scratching technology can obtain the continuous change of the mechanical properties of laminar shale, which greatly supplements the deficiencies of traditional rock mechanics testing, but there is still a lack of research in this area. The existing laminar shale scratching can only obtain hardness, fracture toughness and friction coefficient, and a unified and complete elastic modulus calculation method has not yet been established. At the same time, laminated shale is easy to break and difficult to process into standard samples. The lack of a clamp suitable for samples of arbitrary shapes is also an important factor limiting the promotion and application of scratch technology.

[0004] Therefore, how to propose a device and method that can be applicable to samples of any shape and can uniformly calculate the elastic modulus in laminated shales is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the invention

[0005] To this end, the present invention provides a device and method for evaluating the elastic modulus of laminated rock based on true triaxial scratching, so as to solve the problem of difficulty in clamping the device due to the different shapes of laminated shale in the prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] According to a first aspect of the present invention, there is provided a device for evaluating the elastic modulus of laminar rock based on true triaxial scratching, comprising:

[0008] The fluid supply module is used to inject and drain fluid into the laminar shale to simulate the chemical environment of the formation;

[0009] A true three-axis clamping module, comprising a bottom fixing plate, a side telescopic fixing structure and a top rotating fixing structure, wherein the side telescopic fixing structures are arranged on the four vertical directions of the bottom fixing plate, and a top rotating fixing structure is arranged above the bottom fixing plate;

[0010] A probe assembly is arranged on the true three-axis clamping module, comprising a first support, a first telescopic rod and a probe body, guide rails are distributed on the inner side surfaces of the bottom fixed plate, the side telescopic fixed structure and the top rotation fixed structure, the guide rails are cross-distributed horizontally and vertically, the first support is adsorbed and rotatably arranged on the guide rails, the probe body is arranged at the head end of the first support, and a first telescopic rod is arranged between the first support and the probe body;

[0011] The scratching assembly is arranged on the top surface rotating and fixing structure, and includes a second support, a second telescopic rod and a scratching cutter head. The second support is adsorbed on the guide rail in the top surface rotating and fixing structure, the head end of the second support is provided with a scratching cutter head, and a second telescopic rod is provided between the second support and the scratching cutter head.

[0012] Furthermore, the side telescopic fixing structure includes a side base, a coarse adjustment telescopic rod and a vertical pressure plate. The side base and the vertical pressure plate are vertically arranged around the bottom fixed plate. A coarse adjustment telescopic rod is provided between the side base and the vertical pressure plate, and a liquid injection and discharge port is provided on the vertical pressure plate.

[0013] Furthermore, the top surface rotating and fixing structure includes a vertical support rod, a horizontal support rod, a first rotating shaft, a second rotating shaft and a top surface pressure plate, the vertical support rod is vertically arranged on one side of the bottom surface fixing plate, the horizontal support rod is transversely arranged on the vertical support rod, a first rotating shaft is arranged between the vertical support rod and the horizontal support rod, the top surface pressure plate is arranged on the horizontal support rod, and a second rotating shaft is arranged between the top surface pressure plate and the horizontal support rod.

[0014] Furthermore, the scratching assembly also includes a horizontal diverter, the second telescopic rod is provided with a horizontal diverter, the scratching cutter head is connected to the second telescopic rod through the horizontal diverter, and a displacement sensor, an infrared limiter and a pressure sensor are also provided between the horizontal diverter and the scratching cutter head.

[0015] Furthermore, an infrared scanning module and a heating module are also provided on the inner side surfaces of the bottom fixed plate, the side telescopic fixed structure and the top rotation fixed structure.

[0016] According to a second aspect of the present invention, a method for evaluating the elastic modulus of laminar rock based on true triaxial scratching is provided, comprising:

[0017] Step S1: placing a laminar shale sample on a bottom fixed plate, moving a side telescopic fixed structure and a top rotating fixed structure toward the laminar shale sample, and scanning a projection area of ​​the laminar shale sample;

[0018] Step S2: driving the probe assembly within the projection area to move and apply a load, so that the laminar shale sample is sealed and fixed in the true triaxial clamping module;

[0019] Step S3: supplying liquid to and heating the laminar shale sample in the true triaxial clamping module through the liquid supply module to simulate the chemical environment of the formation;

[0020] Step S4: driving the scratching assembly on the top surface rotation fixed structure to scratch the scratch surface in the laminar shale sample with a constant force or a constant displacement, and the probe assembly on the guide rail at the scratching position moves relatively statically with the scratching assembly, recording the scratching data of the laminar shale sample, and obtaining the elastic modulus of the laminar shale sample;

[0021] Step S5: Based on the scratch direction of the laminar shale sample, draw the distribution curve of the elastic modulus along the scratch direction, cut the elastic modulus distribution area equally, calculate the average value and variance of the elastic modulus in different distribution areas, and select the distribution area with high average value and low variance as the engineering sweet spot.

[0022] Furthermore, in step S4, the scratching data of the laminar shale sample is recorded to obtain the elastic modulus of the laminar shale sample, specifically:

[0023] Step S401: Select the tangential stress of the scratch , Normal stress and scratch width As a variable, with the normal displacement , elastic modulus , yield stress , Poisson's ratio , Sliding friction coefficient and the probe deflection angle β, a dimensionless relationship is established;

[0024] Step S402: Based on the dimensionless relationship above, obtain the Y / E and The first dimensionless equation and Y / E and The second dimensionless equation of

[0025] Step S403: Based on the fitting of the first dimensionless equation and the second dimensionless equation, establish the elastic modulus E and and The third dimensionless equation of ;

[0026] Step S404: Obtaining tangential stress during the scratching process , Normal stress and normal displacement , the elastic modulus is calculated according to the third dimensionless equation .

[0027] Furthermore, the Y / E and The first dimensionless equation of is:

[0028] ;

[0029] in, is the normal stress, is the yield stress, is the elastic modulus, is the normal displacement, β is the probe deflection angle, , and is the dimensionless parameter of the first dimensionless equation.

[0030] Furthermore, the Y / E and The second dimensionless equation is:

[0031] ;

[0032] in, is the tangential stress, is the yield stress, is the elastic modulus, is the normal displacement, β is the probe deflection angle, , and is the dimensionless parameter of the second dimensionless equation.

[0033] Furthermore, the elastic modulus E is and The third dimensionless equation is:

[0034] ;

[0035] in, is the normal stress, is the tangential stress, is the yield stress, is the elastic modulus, is the normal displacement, and is the fitting parameter.

[0036] The present invention has the following advantages:

[0037] The device provided by the present invention comprises a liquid supply module, which is used for injecting and discharging liquid into laminar shale to simulate the chemical environment of the formation; a true three-axis clamping module, which comprises a bottom fixed plate, a side telescopic fixed structure and a top rotating fixed structure, wherein the side telescopic fixed structures are arranged in the vertical directions of the four sides of the bottom fixed plate, and the top rotating fixed structure is arranged above the bottom fixed plate; a probe assembly, which is arranged on the true three-axis clamping module, comprises a first support, a first telescopic rod and a probe body, guide rails are distributed on the inner side surfaces of the bottom fixed plate, the side telescopic fixed structure and the top rotating fixed structure, and the guide rails are cross-distributed in the horizontal and vertical directions, a first support is adsorbed and rotated on the guide rail, a probe body is arranged at the head end of the first support, and a first telescopic rod is arranged between the first support and the probe body; a scratching assembly, which is arranged on the top rotating fixed structure, comprises a second support, a second telescopic rod and a scratching cutter head, a second support is adsorbed on the guide rail in the top rotating fixed structure, a scratching cutter head is arranged at the head end of the second support, and a second telescopic rod is arranged between the second support and the scratching cutter head.

[0038] The true triaxial clamping module and probe assembly provided by the present invention can fix laminated shale samples of any shape therein, so as to simulate the chemical environment of the stratum for the laminated shale samples conveniently. The shale samples are scratched by the scratching assembly, and the tangential stress, normal stress and normal displacement during the scratching process are measured. The elastic modulus is calculated according to the third dimensionless equation, and the distribution curve of the elastic modulus along the scratching direction is obtained. This provides a new experimental system and testing technology for the evaluation of the compressibility sweet spot and the expansion capacity of the fracturing crack of unconventional energy shale oil, and also has potential application value in engineering and technical fields such as deep soft rock tunnel support, slope stability control, and mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0040] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0041] Figure 1 A schematic diagram of the structure of the device provided in Example 1 of the present invention;

[0042] Figure 2 A schematic diagram of the structure of a probe assembly provided in Example 1 of the present invention;

[0043] Figure 3 A schematic diagram of the structure of a scratching assembly provided in Example 1 of the present invention;

[0044] Figure 4 A schematic diagram of the scribing process of the device provided in Example 1 of the present invention;

[0045] Figure 5 Y / E- at different probe deflection angles β provided in Example 2 of the present invention The change curve diagram of

[0046] Figure 6 Y / E- at different pressure head deflection angles β provided in Example 2 of the present invention The change curve diagram of

[0047] Figure 7 A planar distribution diagram of the elastic modulus provided in Example 2 of the present invention;

[0048] In the figure:

[0049] 1 Liquid supply module; 2 True three-axis clamping module; 201 Bottom fixed plate; 202 Side telescopic fixed structure; 2021 Side base; 2022 Coarse adjustment telescopic rod; 2023 Vertical pressure plate; 203 Top rotation fixed structure; 2031 Vertical support rod; 2032 Horizontal support rod; 2033 First rotation axis; 2034 Second rotation axis; 2035 Top pressure plate; 3 Probe assembly; 301 First support; 302 First telescopic rod; 303 Probe body; 4 Scratch assembly; 401 Second support; 402 Second telescopic rod; 403 Scratch cutter head; 5 Liquid injection port; 6 Horizontal diverter. DETAILED DESCRIPTION

[0050] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are 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 are within the scope of protection of the present invention.

[0051] Example 1

[0052] According to a first aspect of the present invention, Figure 1-Figure 3 As shown, a device for evaluating the elastic modulus of laminar rock based on true triaxial scratching is provided, comprising:

[0053] The liquid supply module 1 is composed of a controllable temperature and pressure reactor and a metering pump. The body of the controllable temperature and pressure reactor is provided with a heating tube, which can heat the liquid in the reactor. There is a piston inside the reactor, and the upper part of the piston is simulated formation water. The metering pump is connected to the injection / discharge port at the bottom of the controllable temperature and pressure reactor through a stainless steel pressure-resistant pipeline. Liquid is injected into the bottom of the piston through the metering pump, thereby pushing the piston to move upward, and the simulated formation water of the required temperature is injected into the true triaxial scratch equipment at a constant pressure to simulate the formation chemical environment of the sample.

[0054] The true three-axis clamping module 2 includes a bottom fixing plate 201, a side telescopic fixing structure 202 and a top rotating fixing structure 203. The side telescopic fixing structures 202 are arranged on the four vertical sides of the bottom fixing plate 201, and a top rotating fixing structure 203 is arranged above the bottom fixing plate 201.

[0055] The probe assembly 3 is arranged on the true three-axis clamping module 2, and includes a first support 301, a first telescopic rod 302 and a probe body 303. Metal guide rails with an interval of 10 mm are distributed on the inner side of the bottom fixed plate 201, the side telescopic fixed structure 202 and the top rotating fixed structure 203, and the guide rails are cross-distributed in the horizontal and vertical directions. The first support 301 is arranged on the guide rail for adsorption and rotation. The first support 301 is a spherical support, and the spherical support can make the probe body 303 rotate within a certain range. The probe body 303 is arranged at the head end of the first support 301, and the probe body 303 is wrapped with a rubber sleeve for protecting the probe body 303. A first telescopic rod 302 is arranged between the first support 301 and the probe body 303. The first telescopic rod 302 is a hydraulic telescopic rod, and the height of the probe body 303 is adjusted by the first telescopic rod 302.

[0056] The scratching assembly 4 is arranged on the top surface rotating fixed structure 203, and includes a second support 401, a second telescopic rod 402 and a scratching cutter head 403. The second support 401 is adsorbed on the guide rail inside the top surface rotating fixed structure 203, the scratching cutter head 403 is provided at the head end of the second support 401, and a second telescopic rod 402 is provided between the second support 401 and the scratching cutter head 403.

[0057] The side telescopic fixed structure 202 includes a side base 2021, a coarse adjustment telescopic rod 2022 and a vertical pressing plate 2023. The side base 2021 and the vertical pressing plate 2023 are vertically arranged around the bottom fixed plate 201. A coarse adjustment telescopic rod 2022 is arranged between the side base 2021 and the vertical pressing plate 2023. A liquid injection and drainage port 5 is arranged on the vertical pressing plate 2023, and liquid is injected and discharged into the laminar shale sample through the liquid injection and drainage port 5. The coarse adjustment telescopic rod 2022 is driven by a motor to make the vertical sample plate against the laminar shale sample, and the vertical pressing plate 2023 is used to apply x-axis and y-axis pressure to the laminar shale sample.

[0058] The top surface rotating fixed structure 203 includes a vertical support rod 2031, a horizontal support rod 2032, a first rotating shaft 2033, a second rotating shaft 2034 and a top surface pressure plate 2035. The vertical support rod 2031 is vertically arranged on one side of the bottom surface fixed plate 201, the horizontal support rod 2032 is transversely arranged on the vertical support rod 2031, the first rotating shaft 2033 is arranged between the vertical support rod 2031 and the horizontal support rod 2032, the top surface pressure plate 2035 is arranged on the horizontal support rod 2032, and the second rotating shaft 2034 is arranged between the top surface pressure plate 2035 and the horizontal support rod 2032. The first rotating shaft 2033 and the second rotating shaft 2034 are driven by a motor. The first rotating shaft 2033 can make the horizontal support rod 2032 rotate vertically, and the second rotating shaft 2034 can make the top pressure plate 2035 rotate horizontally, so that the top pressure plate 2035 can move and flip to the top of the shale sample to apply z-axis pressure to the laminated shale sample.

[0059] The scratching assembly 4 also includes a horizontal deflector 6, which is provided on the second telescopic rod 402. The scratching cutter head 403 is connected to the second telescopic rod 402 through the horizontal deflector 6. A displacement sensor, an infrared stopper and a pressure sensor are also provided between the horizontal deflector 6 and the scratching cutter head 403. The horizontal deflector 6 is used to control the rotation and locking of the scratching cutter head 403. The pressure sensor can monitor the applied pressure in real time. There are four infrared stoppers on the pressure sensor. When the scratch is carried out in a certain direction, two infrared stoppers in parallel directions are activated to monitor whether the scratch direction is offset. The experimenter can control the coarse adjustment of the displacement of the true three-axis clamping module 2 and the fine adjustment of the displacement of the probe assembly 3 through the touch display screen, can control the system temperature and pressure, can control the movement and scratching of the scratching cutter head 403, and display it on the touch display screen after being processed by the smart chip.

[0060] An infrared scanning module and a heating module are also provided on the inner side surfaces of the bottom fixed plate 201, the side telescopic fixed structure 202 and the top rotating fixed structure 203. The infrared scanning module is used to scan the laminated shale samples on the bottom fixed plate 201, and the heating module is used to heat the laminated shale samples to simulate the formation temperature.

[0061] The specific experimental process is as follows:

[0062] Take a block of laminated shale, spray epoxy resin / curing agent with a thickness of about 1 cm on the surface to seal the laminated shale, and after the surface epoxy resin cools and solidifies, use wire cutting to process a sample surface for scratch test measurement.

[0063] The test machine is turned on, and the system self-checks. The system determines whether the probe assembly 3 is working properly. After the self-check, the coarse adjustment telescopic rod 2022 is retracted to the shortest, and the first telescopic rod 302 of the probe body 303 is extended to the longest. The laminated shale sample sprayed with epoxy resin is gently placed on the probe assembly 3 on the bottom fixing plate 201 of the sample placement, with the scratch side facing up. According to the data of the pressure sensor in the probe assembly 3, the first telescopic rod 302 of the probe body 303 with a pressure of 0 is automatically retracted to the shortest. At this time, the coarse adjustment telescopic rod 2022 on the x-axis and y-axis is controlled on the touch screen to make the vertical pressure plate 2023 and the bottom fixed plate 201 and other vertical pressure plates 2023 all sealed, so that the probe body 303 is close to the laminated shale but not touching it. The infrared scanning module scans the projection area of ​​the laminated shale sample from the plane, and the probe body 303 within the projection area is precisely loaded by the first telescopic rod 302, and the loading load is controlled to 5N. The probe body 303 outside the projection area is shortened to the shortest by the first telescopic rod 302.

[0064] Specifically, when the vertical surface of the sample is uneven, after the probe body 303 contacts the uneven surface, the first support 301 will rotate, and the contact point between the rubber sleeve and the sample surface will be flattened into a small plane, thereby applying a load.

[0065] Further, check whether the top pressure plate scratching tool head 403 is normal, and then use the touch screen to flip the top pressure plate downward. At this time, the top pressure plate 2035 will automatically move to the top of the true three-axis clamping module 2, and the infrared scanning module on it will automatically scan the area of ​​the scratch surface of the laminar shale sample. According to the maximum rectangle principle, the scratching tool head 403 is placed above the maximum rectangular projection that can be scratched, such as Figure 4 As shown in a in the figure, all the probe bodies 303 are shortened to the shortest by using the first telescopic rod 302, and then the top surface pressure plate 2035 is tightly covered to make the whole device airtight, and the first telescopic rod 302 of the probe body 303 in the projection area of ​​the laminar shale sample is extended, and the probe body 303 touches the shale scratch surface and is precisely loaded to 5N.

[0066] Connect the vacuum pump to the joint of the true triaxial clamping module 2, evacuate the sample for 1 hour, heat the simulated formation water in the reactor to the target temperature, and then use the metering pump to inject liquid into the bottom of the piston to push the piston upward. Inject the simulated formation water of the required temperature into the true triaxial scratch equipment to simulate the formation chemical environment of the sample and soak it for a period of time.

[0067] When the experiment officially begins, first set the position to be scratched or indented on the smart gimbal. The position to be scratched must be parallel to one of the rails of the probe assembly 3. Then apply temperature and confining pressure. When applying confining pressure, the z-axis direction should apply the maximum pressure of the three axes. The three axes simultaneously slowly apply loads to the target load and increase the temperature to the target temperature. After a period of stabilization, start the scratch experiment. First, determine the constant force or constant displacement loading on the smart gimbal, such as Figure 4 As shown in b and c, the scratching cutter head 403 is extended to touch the shale surface through the second telescopic rod 402, and the load is loaded to 5N. At this time, the probe group on the guide rail where the scratching position is located will move relatively still with the scratching cutter head 403.

[0068] Specifically, the probe body 303 is spherical and can work while rolling. The displacement sensor and pressure sensor connected to the scratching blade 403 will automatically record data. Figure 4 As shown in d in FIG. 1 , the probe body 303 behind the scratching blade 403 re-applies the load to the scratched surface.

[0069] Example 2

[0070] According to a second aspect of the present invention, a method for evaluating the elastic modulus of laminar rock based on true triaxial scratching is provided, comprising:

[0071] Step S1: placing a laminar shale sample on the bottom fixed plate 201, moving the side telescopic fixed structure 202 and the top rotating fixed structure 203 toward the laminar shale sample, and scanning the projection area of ​​the laminar shale sample;

[0072] Step S2: driving the probe assembly 3 within the projection area to move and apply a load, so that the laminar shale sample is sealed and fixed in the true triaxial clamping module 2;

[0073] Step S3: supplying liquid to and heating the laminar shale sample in the true triaxial clamping module 2 through the liquid supply module 1 to simulate the chemical environment of the formation;

[0074] Step S4: driving the scratching assembly 4 on the top surface rotating fixed structure 203 to scratch the scratch surface in the laminar shale sample with constant force or constant displacement, and the probe assembly 3 on the guide rail at the scratching position moves relatively statically with the scratching assembly 4, recording the scratching data of the laminar shale sample, and obtaining the elastic modulus of the laminar shale sample;

[0075] Step S5: Based on the scratch direction of the laminar shale sample, draw the distribution curve of the elastic modulus along the scratch direction, cut the elastic modulus distribution area equally, calculate the average value and variance of the elastic modulus in different distribution areas, and select the distribution area with high average value and low variance as the engineering sweet spot.

[0076] In step S4, the scratching data of the laminar shale sample is recorded to obtain the elastic modulus of the laminar shale sample, which is specifically:

[0077] Step S401: Select the tangential stress of the scratch , Normal stress and scratch width As a variable. You can use the normal displacement , elastic modulus , yield stress , Poisson's ratio , Sliding friction coefficient And the probe deflection angle β is dimensionlessly combined:

[0078] ;

[0079] Selection and As independent variables, other quantities can be expressed by these two quantities. According to the Π theorem, the following dimensionless numbers can be obtained:

[0080] ;

[0081] The effect of Poisson's ratio can be ignored, so the following relationship can be obtained:

[0082] ;

[0083] Applying the Π theorem of dimensionless analysis to make the parameters dimensionless, we can also get:

[0084] .

[0085] Step S402: Based on the dimensionless relationship above, obtain the Y / E and The first dimensionless equation and Y / E and The second dimensionless equation of

[0086] Scratch width and sliding friction coefficient For dimensionless functions During the scratch test, the normal deformation of the sample is affected by the elastic modulus, that is, the first dimensionless equation becomes:

[0087]

[0088] Right now ;

[0089] in, is the normal stress, is the yield stress, is the elastic modulus, is the normal displacement, β is the probe deflection angle, , and is the dimensionless parameter of the first dimensionless equation.

[0090] The yield strength determines the tangential failure of the sample to a large extent. In order to improve the accuracy of the fitting formula, the dimensionless function The relationship between Y / E and the deflection angle β of the pressure head is analyzed. It should be noted that this process always follows the dimensionless homogenization principle, that is, the dimensions of the horizontal and vertical coordinates are both 1, that is, the second dimensionless equation becomes:

[0091]

[0092] Right now ;

[0093] in, is the tangential stress, is the yield stress, is the elastic modulus, is the normal displacement, β is the probe deflection angle, , and is the dimensionless parameter of the second dimensionless equation.

[0094] Step S403: Based on the fitting of the first dimensionless equation and the second dimensionless equation, establish the elastic modulus E and and The third dimensionless equation of ;

[0095]

[0096] Right now ;

[0097] in, is the normal stress, is the tangential stress, is the yield stress, is the elastic modulus, is the normal displacement, and is the fitting parameter.

[0098] Step S404: Use a scratch tester to scratch the surface of the laminae sample perpendicular to the laminae direction, keep the interval > 1 cm and scratch in parallel for more than 5 times (to prevent the previous scratch from interfering with the subsequent scratch results). During the scratching process, obtain the tangential stress , Normal stress and normal displacement , the elastic modulus is calculated according to the third dimensionless equation .

[0099] Since the interval between the two scratches is more than 1 cm, the curve needs to be encrypted. The middle line between the two curves is the average value of the elastic modulus of the two curves. The scratch curve points are discretized and the plane distribution diagram of the elastic modulus is drawn. The elastic modulus distribution area is cut equally, and the regional elastic modulus data is statistically analyzed to calculate the average value and variance. The area with high average value and low variance is preferred as the engineering sweet spot.

[0100] The specific implementation is as follows:

[0101] The deflection angle of the scratching tool head is set to β = 0°, 30°, 45°, and 60°. The yield stress and elastic modulus obtained by indentation test are: Y1 = 50MPa / E1 = 3.7GPa, Y2 = 65MPa / E2 = 6.4GPa, Y3 = 78MPa / E3 = 13.3GPa, and Y4 = 93MPa / E4 = 31.7GPa. Substitute into the finite element simulation model and draw the following Figure 5 As shown, the Y / E and Graph showing the effect of different elastic moduli and indenter deflection angles on the dimensionless normal stress.

[0102] The increase in the value of Y / E causes The value of Y / E increases steadily. When Y / E is less than 0.009, the probe deflection angle β The influence of Y / E is small, while the value of When Y / E is greater than 0.012, The value shows a trend of decreasing first and then increasing with the increase of the deflection angle of the pressure head, and the dimensionless normal load reaches the maximum value when β=0°. The following first equation is fitted with the 3D-Plane function, where the unit of Young's modulus is MPa.

[0103] .

[0104] Draw as Figure 6 As shown, Y / E and , showing the relationship between different elastic moduli and probe deflection angles and dimensionless tangential stress. The increase in the value of Y / E causes The value of β drops sharply. The influence is greater. When the pressure head deflection angle is 60°, It reaches the maximum value. It is worth noting that the dimensionless tangential stress values ​​when the probe deflection angle is 0° and 45° are close. When Y / E is less than 0.008, the value of β=45° is larger; and when Y / E is greater than 0.008, the dimensionless shear stress value of β=0° is larger. The following second equation is fitted with the 3D-Plane function:

[0105] .

[0106] Scratch test is carried out on the sample surface, and the scratch direction is perpendicular to the lamination direction. Multiple scratches must be parallel to each other and the interval is more than 1 cm. According to the scratch test results, the tangential stress , Normal stress and normal displacement Parameters such as can be collected according to the mechanical parameter sensor, and the probe deflection angle β can be set in advance, so the scratch result is combined with the first equation and the second equation for the yield stress and elastic modulus The two unknowns form a set of linear equations with two variables, and the elastic modulus and yield stress of the material are calculated based on the scratch test. That is:

[0107] .

[0108] Since the interval between the two scratches is more than 1 cm, the curve needs to be encrypted. The middle line between the two curves is the average value of the elastic modulus of the two curves. And the scratch curve points are discretized, such as Figure 7 As shown, a plane distribution diagram of the elastic modulus is drawn. The elastic modulus distribution area is cut into equal parts, and statistical analysis is performed on the regional elastic modulus data to calculate the average value and variance. The area with high average value and low variance is selected as the engineering sweet spot.

[0109] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A device for evaluating the elastic modulus of laminar rock based on true triaxial scratch, characterized in that: include: A fluid supply module (1) is used to inject and drain fluid into the laminar shale to simulate the chemical environment of the formation; A true three-axis clamping module (2), comprising a bottom surface fixing plate (201), a side telescopic fixing structure (202) and a top surface rotation fixing structure (203), wherein the side telescopic fixing structures (202) are arranged on four vertical directions of the bottom surface fixing plate (201), and a top surface rotation fixing structure (203) is arranged above the bottom surface fixing plate (201); A probe assembly (3) is arranged on the true three-axis clamping module (2), comprising a first support (301), a first telescopic rod (302) and a probe body (303); guide rails are distributed on the inner side surfaces of the bottom fixed plate (201), the side telescopic fixed structure (202) and the top rotation fixed structure (203); the guide rails are cross-distributed in the horizontal and vertical directions; the first support (301) is adsorbed and rotatably arranged on the guide rails; the probe body (303) is arranged at the head end of the first support (301); and a first telescopic rod (302) is arranged between the first support (301) and the probe body (303); A scratching assembly (4) is arranged on the top surface rotating fixed structure (203), comprising a second support (401), a second telescopic rod (402) and a scratching cutter head (403); the second support (401) is adsorbed on a guide rail in the top surface rotating fixed structure (203); the scratching cutter head (403) is arranged at the head end of the second support (401); and a second telescopic rod (402) is arranged between the second support (401) and the scratching cutter head (403); The top surface rotating fixed structure (203) comprises a vertical support rod (2031), a horizontal support rod (2032), a first rotating shaft (2033), a second rotating shaft (2034) and a top surface pressing plate (2035), wherein the vertical support rod (2031) is vertically arranged on one side of the bottom surface fixing plate (201), the horizontal support rod (2032) is transversely arranged on the vertical support rod (2031), a first rotating shaft (2033) is arranged between the vertical support rod (2031) and the horizontal support rod (2032), the top surface pressing plate (2035) is arranged on the horizontal support rod (2032), and a second rotating shaft (2034) is arranged between the top surface pressing plate (2035) and the horizontal support rod (2032).

2. The device for evaluating elastic modulus of laminar rock based on true triaxial scratching according to claim 1, characterized in that: The side telescopic fixing structure (202) comprises a side base (2021), a coarse adjustment telescopic rod (2022) and a vertical pressing plate (2023); the side base (2021) and the vertical pressing plate (2023) are vertically arranged around the bottom fixing plate (201); a coarse adjustment telescopic rod (2022) is arranged between the side base (2021) and the vertical pressing plate (2023); and a liquid injection and discharge port (5) is provided on the vertical pressing plate (2023).

3. The device for evaluating elastic modulus of laminar rock based on true triaxial scratching according to claim 1, characterized in that: The scratching assembly (4) further comprises a horizontal deflector (6), the second telescopic rod (402) being provided with the horizontal deflector (6), the scratching cutter head (403) being connected to the second telescopic rod (402) via the horizontal deflector (6), and a displacement sensor, an infrared limit stopper and a pressure sensor being provided between the horizontal deflector (6) and the scratching cutter head (403).

4. The device for evaluating elastic modulus of laminar rock based on true triaxial scratching according to claim 1, characterized in that: An infrared scanning module and a heating module are also provided on the inner side surfaces of the bottom surface fixing plate (201), the side surface telescopic fixing structure (202) and the top surface rotation fixing structure (203).

5. A method for evaluating the elastic modulus of laminar rock based on true triaxial scratching, applied to the device for evaluating the elastic modulus of laminar rock based on true triaxial scratching as claimed in any one of claims 1 to 4, characterized in that: include: Step S1: placing a laminar shale sample on a bottom fixed plate (201), moving a side telescopic fixed structure (202) and a top rotating fixed structure (203) toward the laminar shale sample, and scanning a projection area of ​​the laminar shale sample; Step S2: driving the probe assembly (3) within the projection area to move and apply a load, so that the laminar shale sample is sealed and fixed in the true triaxial clamping module (2); Step S3: supplying liquid to and heating the laminar shale sample in the true triaxial clamping module (2) through the liquid supply module (1) to simulate the chemical environment of the formation; Step S4: driving the scratching assembly (4) on the top surface rotating fixed structure (203) to scratch the scratch surface in the laminar shale sample using a constant force or a constant displacement, and the probe assembly (3) on the guide rail at the scratching position moves relatively statically with the scratching assembly (4), recording scratching data of the laminar shale sample, and obtaining the elastic modulus of the laminar shale sample; Step S5: Based on the scratch direction of the laminar shale sample, draw the distribution curve of the elastic modulus along the scratch direction, cut the elastic modulus distribution area equally, calculate the average value and variance of the elastic modulus in different distribution areas, and select the distribution area with high average value and low variance as the engineering sweet spot.

6. The method for evaluating the elastic modulus of laminar rock based on true triaxial scratching according to claim 5, characterized in that: In step S4, the scratching data of the laminar shale sample is recorded to obtain the elastic modulus of the laminar shale sample, which is specifically: Step S401: Select the tangential stress of the scratch , Normal stress and scratch width As a variable, with the normal displacement , elastic modulus , yield stress , Poisson's ratio , Sliding friction coefficient and the probe deflection angle β, a dimensionless relationship is established; Step S402: Based on the dimensionless relationship above, obtain the Y / E and The first dimensionless equation and Y / E and The second dimensionless equation of Step S403: Based on the fitting of the first dimensionless equation and the second dimensionless equation, establish the elastic modulus E and and The third dimensionless equation of ; Step S404: Obtaining tangential stress during the scratching process , Normal stress and normal displacement , the elastic modulus is calculated according to the third dimensionless equation .

7. The method for evaluating the elastic modulus of laminar rock based on true triaxial scratching according to claim 6, characterized in that: The Y / E and The first dimensionless equation of is: ； in, is the normal stress, is the yield stress, is the elastic modulus, is the normal displacement, β is the probe deflection angle, , and is the dimensionless parameter of the first dimensionless equation.

8. The method for evaluating the elastic modulus of laminar rock based on true triaxial scratching according to claim 6, characterized in that: The Y / E and The second dimensionless equation is: ； in, is the tangential stress, is the yield stress, is the elastic modulus, is the normal displacement, β is the probe deflection angle, , and is the dimensionless parameter of the second dimensionless equation.

9. The method for evaluating elastic modulus of laminar rock based on true triaxial scratching according to claim 6, characterized in that: The elastic modulus E and and The third dimensionless equation is: ； in, is the normal stress, is the tangential stress, is the yield stress, is the elastic modulus, is the normal displacement, and is the fitting parameter.

Images