CN113533104A - Method for acquiring elastic parameters before and after shale water-rock action - Google Patents

Method for acquiring elastic parameters before and after shale water-rock action Download PDF

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CN113533104A
CN113533104A CN202010305635.8A CN202010305635A CN113533104A CN 113533104 A CN113533104 A CN 113533104A CN 202010305635 A CN202010305635 A CN 202010305635A CN 113533104 A CN113533104 A CN 113533104A
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rock
rock sample
phase
indentation
soaking
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李凤霞
周彤
沈云琦
李小龙
贺甲元
潘林华
刘长印
王迪
宋丽阳
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China Petroleum and Chemical Corp
Sinopec Exploration and Production Research Institute
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China Petroleum and Chemical Corp
Sinopec Exploration and Production Research Institute
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Abstract

The invention discloses a method for acquiring elastic parameters of shale before and after water-rock action, which comprises the following steps: grinding the rock sample and analyzing the mineral content of the rock; performing electron microscope scanning on the rock sample, analyzing the distribution and content of each phase in a scanning image, and determining the microstructure volume unit of the rock sample; carrying out nano indentation test on the rock sample, establishing a load and displacement curve of each indentation point, and calculating an elastic parameter of each indentation point; carrying out fluid soaking on the ballasted rock sample, carrying out electron microscope scanning and nano indentation testing, and calculating the elastic parameter of each indentation point after soaking; identifying the phase type of each indentation point by using a Gaussian mixture model according to the elastic parameters of each indentation point before and after soaking, and calculating the elastic parameter trend of each phase type; and further obtaining the macroscopic elasticity parameters of the shale rock sample to be evaluated before and after soaking according to the rock mineral content analysis result. The invention can obtain the mechanical parameters of the shale before and after the water-rock action without the limitation of the size of the rock sample.

Description

Method for acquiring elastic parameters before and after shale water-rock action
Technical Field
The invention relates to the technical field of rock mechanics, in particular to a method for acquiring elastic parameters of shale before and after a water-rock action based on rock microscopic characteristics.
Background
The rock mechanics parameters are basic parameters of a plurality of construction operations in the drilling and developing processes, are also basic basis of well wall stability analysis, hydraulic fracturing and other drilling and completion designs and oil extraction construction operations, and are related to the correctness of construction schemes and the safety of construction. On the other hand, during the drilling and completion construction process, the underground rock inevitably generates the water-rock effect with the drilling fluid or the fracturing fluid, and the mechanical property of the rock surface is changed. The accurate acquisition of mechanical parameters before and after the rock water-rock action has important significance for guiding the design of drilling and completion and evaluating the construction effect.
The bottom hole core is a precious resource and can be obtained through drilling and coring usually, the coring operation consumes a long time, the coring rate cannot be completely controlled, and the coring operation is generally only specific reservoir well sections and cannot obtain the core of the whole well section. However, the cuttings returned from the annulus in the drilling cycle process are sufficient, and the cuttings in the whole well section can be obtained, so that if sufficient well bottom cuttings resources can be utilized, a method for obtaining rock mechanical parameters through micro-testing small-size cuttings is explored, and great significance is achieved.
The indentation test is a simple and efficient means for evaluating the mechanical property of the material, can accurately and continuously measure the load-displacement data of the pressure head, can conveniently obtain related mechanical parameters, is widely applied to the research of mechanical properties of metal, thin film coatings, composite materials, biological tissues and the like at present, and has considerable prospect when the indentation test technology is applied to the acquisition of mechanical parameters of rock materials and the evaluation of the water-rock effect.
The method comprises the following steps of: firstly, a rigid flat-bottom pressure head is used for testing the mechanical property of the rock, the diameter of the pressure head in the mode reaches 0.5-2 mm, the test size is larger, and the test is still a rock macroscopic mechanical test in essence; secondly, the water-rock effect tested by the macroscopic triaxial loading experimental device can control the water temperature, water pressure and axial pressure of the rock sample during water saturation and can control the water saturation time of the rock sample, but the method is suitable for the rock sample with higher permeability, and for mud shale with extremely low permeability, the effect of completely saturating the whole rock sample in a short time is difficult to achieve; thirdly, although some schemes can qualitatively measure the damage degree of the cement action on the rock, the concrete mechanical parameters of the rock sample before and after the water-rock action cannot be quantitatively analyzed.
At present, certain achievements have been obtained in research on methods for acquiring rock mechanical parameters before and after the action of the water and rock, but macroscopic rock mechanical tests are mostly adopted in experimental methods. Aiming at the shale developed by micro-mechanical weak surfaces such as a shale seam, the micro-mechanical weak surfaces evolve and form macro cracks due to hydration, so that a rock core is broken, and the macro-mechanical test after the water-rock action cannot be carried out. Therefore, it is still necessary to explore a small-sized rock sample, and develop research on rock mechanical parameters by using a microscopic testing means, so as to make up the difficulties that macroscopic mechanical testing samples are insufficient and experimental data are not easy to obtain, and provide data support for designing a drilling and completion scheme.
Disclosure of Invention
In order to solve the technical problem, an embodiment of the present invention provides a method for obtaining elasticity parameters before and after shale water-rock action, where the method includes: grinding a shale sample to be evaluated, and analyzing the content of rock minerals; performing electron microscope scanning on the rock sample, analyzing the distribution and content of each phase in a scanning image, and determining a volume unit representing the microstructure of the rock sample based on the distribution and content; according to the volume representative unit, carrying out nano indentation test on the rock sample, establishing a load and displacement curve of each indentation point, and calculating the elastic parameter of each indentation point based on the load and displacement curve; carrying out fluid soaking on the ballasted rock sample, sequentially carrying out electron microscope scanning and nano indentation testing on the soaked rock sample, and calculating the elastic parameter of each indentation point after soaking; respectively identifying the phase type of each indentation point by using a Gaussian mixture model according to the elastic parameters of each indentation point before and after soaking, and calculating the elastic parameter trend of each phase type before and after soaking; and obtaining the macroscopic elasticity parameters of the shale rock sample to be evaluated before and after soaking according to the elasticity parameter trend and rock mineral content analysis results.
Preferably, in the step of obtaining the macroscopic elasticity parameter of the shale rock sample to be evaluated before and after soaking according to the elasticity parameter trend and from the rock mineral content analysis result, the method comprises the following steps: calculating the volume modulus and the shear modulus of each phase type according to the elastic parameter trend of each phase type before and after soaking and the Poisson ratio of each phase type before and after soaking; and based on the rock mineral content analysis result, according to the volume modulus and the shear modulus of each phase category before and after soaking, performing cross-scale upgrading on the elastic parameters of the microscopic phases by using a multi-scale theoretical homogenization method to obtain the volume modulus, the shear modulus, the elastic modulus and the Poisson ratio of the shale rock sample to be evaluated before and after soaking.
Preferably, the step of identifying the phase type of each indentation point by using a gaussian mixture model according to the elastic parameter of each indentation point before and after soaking and calculating the elastic parameter trend of each phase type before and after soaking comprises: dividing each phase in the shale sample to be evaluated into three types, and converting the Gaussian mixture model into a form containing a single-phase Gaussian function corresponding to each phase type, a weight coefficient of the physical mechanical property, a mean parameter of the physical mechanical property and variance parameter information, wherein the phase types comprise clay minerals, carbonate rock mineral combinations and quartz mineral combinations; and respectively obtaining trend quantities comprehensively representing the elastic parameter change conditions of all the indentation points belonging to the corresponding phase types according to the elastic parameters of each indentation point before and after soaking by using the rewritten Gaussian mixture model.
Preferably, the rewritten mixture gaussian model is represented by the following expression:
Figure BDA0002455700060000031
wherein M represents the total number of phase classes, M is 3, M represents the number of each phase class, αmWeight coefficient representing each phase class, fmProbability density distribution function, x, representing each phase classnThe elastic parameter of each indentation point is shown, n is the serial number of each indentation point, and f (x)n) Representing probability of nanoindentation test rock sampleDensity distribution function, mum、σmRespectively representing the mean and variance of the gaussian distribution for each item class.
Preferably, when performing the nanoindentation test, the nanoindentation test includes: determining indentation parameters of a current test, wherein the indentation parameters include: the ballast dot matrix comprises indentation dot matrix distribution, indentation depth and indentation dot spacing, wherein the number of rows and columns of the ballast dot matrix is 15, the range of the indentation depth is 400 nm-500 nm, and the indentation dot spacing is 20 mu m; and selecting an operation area to be ballasted on the rock sample to be tested according to the volume representative unit, and carrying out nano indentation test on the operation area.
Preferably, in the step of performing electron microscope scanning on the rock sample, analyzing the distribution and content of each phase in the scanned image, and determining the volume unit representing the microstructure of the rock sample based on the distribution and content, the method comprises the following steps: scanning the rock sample by SEM-BSE (scanning Electron microscope) scanning equipment to obtain a scanning image representing the structural morphology of the shale rock sample to be evaluated; performing energy spectrum EDS analysis on the scanned image to obtain the distribution and content of each phase in the rock sample; sequentially intercepting the gradually increased square areas from the center of the scanned image according to a preset step length, determining the content of each phase corresponding to each square area, and further establishing a relation curve for the area of each square area and the content of each phase; and determining the square area with the stable content of each phase as the volume representative unit.
Preferably, the ground material of the rock sample is subjected to rock mineral composition and content analysis testing using an X-ray diffractometer.
Preferably, in the step of grinding the shale rock sample to be evaluated, the method comprises the following steps: grinding a first part of the shale rock sample to be evaluated into powder, so that the particle size of the powder is smaller than or equal to a preset powder particle size threshold value; and preparing the rock sample powder into a whole rock slice, a natural slice, an ethylene glycol saturated slice and a heating slice to obtain an object for analyzing the mineral content of the rock.
Preferably, the method further comprises: preparing a rock sample for electron microscope scanning and nano indentation testing, wherein the rock sample except the first part of the rock sample in the shale rock sample to be evaluated is wrapped by epoxy resin, the sample is an addition type sheet cylindrical sample after being solidified, and the size of the sample is 25mm in diameter and 5mm in thickness; and grinding and polishing the sample to expose one end face of the sample, sealing the rest face by the epoxy resin, enabling the upper surface and the lower surface of the sample to be parallel, enabling the roughness of the upper surface and the roughness of the lower surface to be lower than a preset roughness threshold value, and enabling the preset roughness threshold value to be 130 nm.
Preferably, the method further comprises: and comparing and analyzing the scanned images of the rock sample before and after soaking and the elastic parameter trend of each phase category to obtain an analysis result of the influence degree of each microscopic phase in the shale rock sample to be evaluated on the deterioration of the elastic mechanical parameters under the influence of the water-rock action.
Compared with the prior art, one or more embodiments in the above scheme can have the following advantages or beneficial effects:
the invention provides a method for acquiring elastic parameters of shale before and after a water-rock action. The method comprises the steps of analyzing the content of shale minerals to obtain the content of each mineral component; performing electron microscope scanning and energy spectrum analysis on the rock sample, identifying the structure and the mineral type of the rock sample, and determining the area of a representative unit area; wrapping, grinding and polishing the rock sample by using epoxy resin, carrying out dot matrix nano indentation test on the rock sample before and after the water rock action, and calculating the elastic modulus of each indentation point position according to a loaded and unloaded load-displacement curve; analyzing the indentation data by using a Gaussian mixture model to obtain the elastic modulus corresponding to rock clay minerals, carbonate rock minerals and quartz minerals; and finally, determining the macroscopic elasticity parameters of the rock sample before and after the water-rock action by using a multi-scale theoretical homogenization method. In addition, the invention can also combine the electron microscope scanning images of the rock sample before and after the water-rock action and the change of the mechanical parameters of clay minerals to obtain the analysis result of the influence degree of the shale water-rock action on the mechanical parameters. Therefore, the mechanical parameters of the rock sample before and after the rock-water-rock action can be obtained without being limited by the size of the rock sample, and further, the mechanical characteristic parameters of the rock sample before and after the rock-water-rock action of the stratum at the whole well section can be obtained by fully utilizing rock debris rock discharged from the bottom of the well, compared with the mechanical parameters obtained by the conventional triaxial mechanical experiment which are not affected by the defects of cracks and the like, the defects that the standard shale sample is not easy to saturate and experimental data is scattered are avoided, and the method has the characteristics of being more economical and more effective.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic step diagram of a method for obtaining elasticity parameters before and after shale water-rock action according to an embodiment of the present application.
Fig. 2 is a specific flowchart of a method for obtaining elasticity parameters before and after shale water-rock interaction according to an embodiment of the present application.
Fig. 3 is a schematic diagram illustrating a process of selecting a representative volume unit in the method for obtaining the elasticity parameters of the shale before and after the shale water-rock action according to the embodiment of the present application.
Fig. 4 is a schematic diagram of the effect of preparing a rock sample for electron microscope scanning and nanoindentation testing in the method for obtaining elastic parameters of shale before and after the shale water rock action according to the embodiment of the present application.
Fig. 5 is a schematic working diagram of a fluid soaking process in the method for obtaining the elasticity parameters of the shale before and after the shale water-rock action according to the embodiment of the application.
Fig. 6 is a schematic view of a load and displacement curve corresponding to a certain indentation point in the method for obtaining elastic parameters of shale before and after a shale water-rock action according to the embodiment of the present application.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
The rock mechanics parameters are basic parameters of a plurality of construction operations in the drilling and developing processes, are also basic basis of well wall stability analysis, hydraulic fracturing and other drilling and completion designs and oil extraction construction operations, and are related to the correctness of construction schemes and the safety of construction. On the other hand, during the drilling and completion construction process, the underground rock inevitably generates the water-rock effect with the drilling fluid or the fracturing fluid, and the mechanical property of the rock surface is changed. The accurate acquisition of mechanical parameters before and after the rock water-rock action has important significance for guiding the design of drilling and completion and evaluating the construction effect.
The bottom hole core is a precious resource and can be obtained through drilling and coring usually, the coring operation consumes a long time, the coring rate cannot be completely controlled, and the coring operation is generally only specific reservoir well sections and cannot obtain the core of the whole well section. However, the cuttings returned from the annulus in the drilling cycle process are sufficient, and the cuttings in the whole well section can be obtained, so that if sufficient well bottom cuttings resources can be utilized, a method for obtaining rock mechanical parameters through micro-testing small-size cuttings is explored, and great significance is achieved.
The indentation test is a simple and efficient means for evaluating the mechanical property of the material, can accurately and continuously measure the load-displacement data of the pressure head, can conveniently obtain related mechanical parameters, is widely applied to the research of mechanical properties of metal, thin film coatings, composite materials, biological tissues and the like at present, and has considerable prospect when the indentation test technology is applied to the acquisition of mechanical parameters of rock materials and the evaluation of the water-rock effect.
The method comprises the following steps of: firstly, a rigid flat-bottom pressure head is used for testing the mechanical property of the rock, the diameter of the pressure head in the mode reaches 0.5-2 mm, the test size is larger, and the test is still a rock macroscopic mechanical test in essence; secondly, the water-rock effect tested by the macroscopic triaxial loading experimental device can control the water temperature, water pressure and axial pressure of the rock sample during water saturation and can control the water saturation time of the rock sample, but the method is suitable for the rock sample with higher permeability, and for mud shale with extremely low permeability, the effect of completely saturating the whole rock sample in a short time is difficult to achieve; thirdly, although some schemes can qualitatively measure the damage degree of the cement action on the rock, the concrete mechanical parameters of the rock sample before and after the water-rock action cannot be quantitatively analyzed.
At present, certain achievements have been obtained in research on methods for acquiring rock mechanical parameters before and after the action of the water and rock, but macroscopic rock mechanical tests are mostly adopted in experimental methods. Aiming at the shale developed by micro-mechanical weak surfaces such as a shale seam, the micro-mechanical weak surfaces evolve and form macro cracks due to hydration, so that a rock core is broken, and the macro-mechanical test after the water-rock action cannot be carried out. Therefore, it is still necessary to explore a small-sized rock sample, and develop research on rock mechanical parameters by using a microscopic testing means, so as to make up the difficulties that macroscopic mechanical testing samples are insufficient and experimental data are not easy to obtain, and provide data support for designing a drilling and completion scheme.
Therefore, in order to solve the technical problem, the invention provides a method for acquiring elastic parameters before and after shale water-rock action. Firstly, grinding a small-size rock debris rock sample to prepare a glass slide and carrying out accurate rock mineral content analysis on the glass slide; cutting, grinding and polishing a rock sample from the same small-size rock debris, scanning the rock sample by SEM-BSE (scanning Electron microscope) equipment, quantitatively analyzing the mineral composition of a scanning surface, and selecting a rock sample microstructure volume representative unit (REV) based on the mineral composition; then designing the water-rock action time of the rock sample, and carrying out fluid soaking on the rock sample; and then, carrying out nano indentation test on the rock sample before and after soaking, analyzing data point data corresponding to the load-displacement curve of each indentation point to obtain micro-physical mechanics parameters (physical mechanics parameters of each indentation point), identifying mechanical parameters of clay minerals, carbonate rock minerals and quartz minerals in the shale by using a Gaussian mixture model based on the micro-physical mechanics parameters, and carrying out cross-scale upgrading on the micro-physical mechanics parameters by combining a multi-scale theoretical homogenization method to obtain mechanical parameters of the rock before and after the water-rock action under the macro scale. Therefore, the process of obtaining the mechanical parameters (particularly the elastic parameters) before and after the rock water-rock action is not limited by the size of the rock sample, the rock debris generated by the bottom of the well can be fully utilized to obtain the mechanical parameters before and after the rock water-rock action of the stratum rock sample in the whole well section, and the method has the characteristics of high economy and high efficiency.
In addition, the method can also analyze the mechanical parameter degradation influence caused by the shale water-rock action by comparing the scanning electron microscope pictures of the rock debris rock sample before and after the water-rock action and the mechanical parameter difference of the clay mineral, the carbonate rock mineral and the quartz mineral, so as to obtain the hydration expansion of the clay mineral and the degradation result of the mechanical parameter caused by the shale water-rock action. Thereby providing data support for formation analysis and well completion project design.
Fig. 1 is a schematic step diagram of a method for obtaining elasticity parameters before and after shale water-rock action according to an embodiment of the present application. Referring to fig. 1, a method for obtaining elastic parameters before and after shale water-rock action (hereinafter referred to as "shale water-rock action analysis method") according to the present invention will be described. First, step S110 grinds a shale rock sample to be evaluated, and performs accurate rock mineral content analysis. It should be noted here that the shale rock sample to be evaluated selected by the present invention is the debris that is displaced from the borehole annulus during the drilling process (drilling cycle) because such debris is comparable to conventional core coring tests (where the core size is about the same as in conventional coring tests)
Figure BDA0002455700060000071
) The required rock sample is sufficient but much smaller in size. Since the debris is irregularly shaped, the larger of these sizes can be selected, preferably the size of the debris in the embodiments of the present inventionIs greater than 10mm in length and width, respectively, and is greater than 2mm in thickness.
Step S120, performing electron microscope scanning test on the shale rock sample to be evaluated, analyzing the distribution and content of each phase in a scanned image, and then determining a volume unit representing the microstructure of the rock sample according to the analysis result of the distribution and content of each phase in the image. Then, in step S130, according to the volume representative unit, a nano indentation test is performed on the shale rock sample to be evaluated at present, a load and displacement curve of a corresponding indentation point is established, and then, a mechanical property parameter (elastic parameter) of each indentation point is calculated by using the drawn curve. Then, step S140 is to soak the ballasted rock sample with a fluid, and the soaked rock debris and rock sample is sequentially subjected to an electron microscope scanning test and a nano indentation test according to the methods described in step S120 and step S130, and the mechanical property parameter (elastic parameter) of each indentation point after soaking is calculated, so as to enter step S150. It should be noted that the fluid soaking process of step S140 is a process for simulating the water-rock interaction between the fluid such as drilling fluid or fracturing fluid and the rock debris and rock sample downhole.
Step S150 is to identify the phase type of each indentation point by using a gaussian mixture model according to the mechanical property parameters (elastic parameters) of each indentation point before and after soaking, and calculate the elastic parameter trend of each phase type before and after soaking. The rock debris rock sample contains a plurality of phases, but the elastic performance of some phase substances is similar, so the invention divides the phases in the rock debris rock sample into three phases of soft, medium and hard according to the mineral hardness type, thereby obtaining clay mineral composition (soft), carbonate rock mineral composition (medium) and quartz mineral composition (hard). In step S150, the elasticity parameter trend is the most representative elasticity parameter data based on the indentation point size class obtained from the elasticity parameters belonging to the same class of physical phases when the elasticity parameter description evaluation is performed for such physical phases. Therefore, in order to simplify the complexity of the construction process of the macroscopic model of the rock debris and rock sample and maintain the accuracy of the mechanical characteristic parameters of the final rock debris and rock sample, in step S150, the method classifies the phases of the rock debris and rock sample, and further calculates the trend quantity of the elastic parameter data with the most representative of each phase type before and after soaking for the same rock debris and rock sample, thereby laying a good foundation for the subsequent step S160.
Step S160 is to obtain the macroscopic elastic parameters of the shale rock sample to be evaluated before and after soaking according to the elastic parameter trend data of each phase category before and after soaking obtained in step S150 and the rock mineral content analysis result obtained in step S110. In this way, in step S160, according to the mineral content analysis result of the rock debris rock sample obtained in step S120 and the elastic parameter data based on the indentation point size level, which is most representative of each phase type before and after soaking, a macroscopic mechanical parameter model of the shale rock sample before and after soaking is respectively constructed, so that a macroscopic elastic parameter based on the shale rock sample size level to be evaluated before and after soaking is obtained. Therefore, the invention provides a technical scheme for obtaining the elastic parameters before and after the shale water-rock action based on the rock micro-physical mechanics characteristics, the whole process is not limited by the size of the shale rock sample to be evaluated, and is not influenced by the defect that the rock sample is damaged due to the micro-cracks in the shale under the water-rock action, and the elastic parameters before and after the shale water-rock action are conveniently and efficiently obtained.
It should be noted that the shale water-rock interaction analysis method provided by the embodiment of the present invention can obtain the elastic parameters of the mechanical property parameters before and after the shale water-rock interaction, and the technical concepts similar to the present invention are also within the protection scope of the present invention for obtaining other types of mechanical property parameters.
Fig. 2 is a specific flowchart of a method for obtaining elasticity parameters before and after shale water-rock interaction according to an embodiment of the present application. The shale water-rock action analysis method proposed by the present invention is explained in detail with reference to fig. 1 and 2. First, step S201 prepares a rock sample for analysis of rock mineral content, proceeding to step S202. In the embodiment of the invention, in order to ensure the accuracy of the subsequent rock mineral content analysis test, the electron microscope scanning test and the nano indentation test, the same shale debris rock sample to be evaluated needs to be respectively prepared into rock samples required by different tests.
In step S201, cutting the obtained shale debris rock sample to be evaluated to obtain a first part of rock sample in the current shale debris rock sample, and grinding the first part of rock sample into powder, so that the particle size of the powder is smaller than or equal to a preset powder particle size threshold (wherein the preset powder particle size threshold is preferably 15 μm); then, the rock sample powder is made into a whole rock slice, a natural slice, an ethylene glycol saturated slice and a heating slice, so that a slide object for rock mineral content analysis and test is obtained. Specifically, the rock sample for rock mineral analysis is obtained by cutting any one part of the shale chip rock sample to be evaluated at present, then grinding the part into powder, preparing the powder, screening the powder step by using sieves with different meshes, finally enabling the particle size of the powder to be less than or equal to 15 mu m, and further preparing the powder into whole rock slices, natural slices, ethylene glycol saturated slices and heating slices so as to obtain the rock mineral analysis rock sample.
Step S202 continues to prepare the rock sample for the electron microscope scanning test and the nanoindentation test. In the embodiment of the present invention, the preparation process of the rock sample required for the electron microscope scanning test is similar to the preparation process of the rock sample required for the nanoindentation test, so the present invention takes the process of preparing the rock sample required for the electron microscope scanning test as an example, and the step S202 is described. Firstly, wrapping rock samples except the first part of rock samples in the shale debris rock samples to be evaluated at present by using epoxy resin, solidifying the wrapped rock sample samples to form a flaky cylindrical sample, wherein the size of the flaky cylindrical sample is 25mm in diameter and 5mm in thickness; and then, grinding and polishing the current sheet-shaped cylindrical sample to expose one end face of the sample subjected to grinding and polishing treatment, sealing the rest face with epoxy resin, enabling the upper surface and the lower surface of the current sample to be parallel, and enabling the roughness of the upper surface and the roughness of the lower surface to be lower than a preset roughness threshold value. Wherein the preset roughness threshold is preferably 130 nm. In this way, rock samples for electron microscopy scanning tests and for nanoindentation tests were obtained.
Fig. 4 is a schematic diagram of the effect of preparing a rock sample for electron microscope scanning and nanoindentation testing in the method for obtaining elastic parameters of shale before and after the shale water rock action according to the embodiment of the present application. When preparing a rock sample for electron microscope scanning and nanoindentation testing, the rock sample except the first part of rock sample in the shale debris rock sample to be evaluated at present is required to be wrapped by epoxy resin, the added rock sample is a flaky cylindrical shape with the size of 25mm and the thickness of 5mm after the sample is solidified, then the sample in the flaky cylindrical shape is finely ground and polished, only one end face of the rock sample is exposed, the rest faces are sealed by the epoxy resin, and finally the upper surface and the lower surface of the rock sample are parallel, and the surface roughness is lower than 130nm, as shown in fig. 4.
After the preparation of all the tested rock samples is completed, the process proceeds to step S203. Step S203 is to perform rock mineral component and content analysis tests on the current rock sample grinding object by using an X-ray diffractometer for the rock sample for analyzing the rock mineral content obtained in step S201. Specifically, the rock mineral composition of the shale rock sample powder for analyzing the rock mineral content obtained in step S201 is analyzed by an X-ray diffractometer. Wherein the shale mineral components (shale internal phases) include: the mineral composition comprises quartz, potash feldspar, plagioclase feldspar, calcite, dolomite, pyrite, clay minerals and the like, wherein each mineral component has a different crystal structure, and the minerals need to be identified by an X-ray map so as to obtain content data of each mineral.
After the mineral composition and content data of the rock sample are obtained, the process proceeds to step S204. And step S204, performing electron microscope scanning test on the rock debris and rock sample for electron microscope scanning test obtained in step S202, analyzing the distribution and content of each phase in the scanning image, and determining a volume unit representing a stable rock sample microstructure in the scanning image based on the distribution and content. Specifically, in step S204, firstly (step S2041), SEM-BSE scanning is performed on the rock debris and rock sample for electron microscope scanning test obtained in step S202 by using an electron microscope scanning device, so as to obtain a scanning image for characterizing the structural morphology of the shale rock sample to be evaluated. And then (step S2042) performing energy spectrum EDS analysis on the currently obtained scanning image to obtain distribution and content information of all phases of the rock sample in the image.
Fig. 3 is a schematic diagram illustrating a process of selecting a representative volume unit in the method for obtaining the elasticity parameters of the shale before and after the shale water-rock action according to the embodiment of the present application. As shown in fig. 3, (step S2043) according to a preset square side length expansion step length, taking the center of the microscopic phase scanning image subjected to phase distribution and content analysis obtained in step S2042 as the center, sequentially intercepting the square regions gradually increasing according to the step length, and determining the distribution and content information of various rock sample phases corresponding to the image of each square region, thereby establishing a relation curve between the region area and the content of various phases, wherein the horizontal axis of the curve represents the area of the square region, and the vertical axis represents the content data of various phases (different phase data are marked with different colors). In this way, a plot is obtained representing the area of the regions of different phases as a function of the content of the corresponding phase. Finally, (step S2044) the square area where the content data of each phase tends to be stable is determined as a volume representative unit, so that the subsequent nanoindentation test will be performed according to the area of this square area.
Next, after the completion of the electron microscope scanning test of the rock sample before soaking, the process proceeds to step S205. Step S205 performs the nanoindentation test on the rock debris rock sample for the nanoindentation test (or the completion of the scanning test by the electron microscope) obtained in step S202 according to the volume representative unit, thereby establishing a load-displacement curve (of each indentation point) with respect to the current nanoindentation test result. Specifically, in step S205, first (step S2051), the indentation parameters required by the current nanoindentation test need to be determined. Wherein, the indentation parameters include but are not limited to: indentation dot matrix distribution, indentation depth, indentation point spacing and ballast area. The number of rows and columns of the ballast dot matrix is 15, the indentation depth is preferably in the range of 400nm to 500nm, and the indentation dot pitch is preferably 20 μm. Then, (step S2052) according to the volume representative unit determined in step S204, a working area to be ballasted is selected on the rock debris and rock sample for the nanoindentation test obtained in step S202, and the nanoindentation test conforming to the indentation parameter is performed on the current working area.
Fig. 6 is a schematic view of a load and displacement curve corresponding to a certain indentation point in the method for obtaining elastic parameters of shale before and after a shale water-rock action according to the embodiment of the present application. Finally, (step S2053) after completing the nanoindentation test (before soaking), a load and displacement curve (where each indentation point corresponds to one load and displacement curve) regarding loading and unloading of each indentation point corresponding to the current nanoindentation test process is drawn, as shown in fig. 6. It should be noted that, since the process of plotting the load-displacement curve is a mature technology in the prior art, it is not specifically described herein.
Furthermore, the invention adopts a dot matrix method in the nano indentation test method, a square area is randomly selected on the rock sample to be tested as the ballast area, the area of the square area is slightly larger than the volume representative unit determined in the step S204, the ballast matrix points are distributed as 15 multiplied by 15, the indentation depth is between 400nm and 500nm, so that the rigid pressure head can ballast the rock sample phase without cutting rock debris, and can press through the phase, and the ballast and displacement curve can accurately reflect the mechanical property parameters of the mineral single phase. In addition, the distance between the indentation points is about 20 μm, so that the mutual interference between two adjacent indentation points is avoided. In addition, it should be noted that the strain rate during ballasting needs to be controlled to not more than 0.05s-1To eliminate the effect of the ballast rate.
In this way, after completing the nanoindentation test on the rock sample before soaking, the process proceeds to step S206. Step S206 obtains the elastic parameters (including but not limited to elastic modulus and poisson ratio) at each indentation point in the rock sample of the rock debris before soaking by using the indentation point elastic parameter calculation formula according to the ballast and displacement curve of each indentation point obtained by the nano indentation test of the rock sample before soaking. It should be noted that, in view of the fact that the poisson ratio is less sensitive to the elastic modulus, in the embodiment of the present invention, an empirical value may be given to the poisson ratio value. Wherein, the indentation point elasticity parameter calculation formula is represented by the following expression:
Figure BDA0002455700060000111
wherein P represents the load data of the current indentation point, PmaxMost representative of the current impression pointLarge load, h represents displacement data of current indentation point, hmaxShowing the displacement corresponding to the maximum load of the current indentation point, A showing the projected area of the contact area between the indenter and the rock, S showing the slope of the initial point of the unloading curve in the load-displacement curve of the current indentation point, H showing the hardness of the rock, ErRepresenting the reduced elastic modulus, E and ν respectively representing the elastic modulus and Poisson's ratio of the rock sample at the current indentation point, Etip、νtipThe modulus of elasticity and poisson's ratio of the diamond indenter are shown, respectively.
And (5) after the elastic parameters of each indentation point in the rock sample of the rock debris before current soaking are obtained, entering step S207, and performing fluid soaking on the rock sample subjected to the nano indentation test in step S205. Fig. 5 is a schematic working diagram of a fluid soaking process in the method for obtaining the elasticity parameters of the shale before and after the shale water-rock action according to the embodiment of the application. In step S207, a fluid soaking process is used to simulate the water-rock action of the rock debris-rock sample in the downhole, the water-rock action time of the rock sample soaking process is designed, as shown in fig. 5, the ballasted rock sample is soaked in the prepared fluid (in the embodiment of the present invention, the type and content of the fluid used in the fluid soaking process are consistent with those of the fluid used in the downhole water-rock action), the soaking time is recorded, the sample is taken out after the set soaking time is reached, the fluid soaking process is completed, the soaked rock debris-rock sample is obtained, and the process then proceeds to step S208.
Step S208 is to perform an electron microscope scanning test on the soaked rock debris and rock sample obtained in step S207 again according to the electron microscope scanning test process described in step S204, and obtain a corresponding volume representative unit, so as to enter step S209. Step S209, according to the nanoindentation test process described in step S205, performs nanoindentation test after replacing the indentation area of the soaked rock debris and rock sample obtained in step S207, obtains the ballast and displacement curve of each indentation point in the soaked rock debris and rock sample, and then proceeds to step S210. It should be noted that step S208 is similar to step S204, and step S209 is similar to step S205, which are not repeated herein.
Step S210 obtains an elastic parameter (where the elastic parameter includes, but is not limited to, an elastic modulus and a poisson ratio) at each indentation point in the soaked rock debris rock sample by using the indentation point elastic parameter calculation formula according to the ballast and displacement curve of each indentation point corresponding to the currently soaked rock sample, and then the process proceeds to step S211.
The lattice ballasting of the nano indentation test cannot ensure that all indentation points are ballasted to the rock sample phase completely, and partial indentation points are ballasted to the interfaces of different phases, so that the single-phase mechanical properties of minerals cannot be accurately reflected. Therefore, in the embodiment of the invention, the mechanical parameter distribution of each mineral single phase can be considered to be subjected to Gaussian distribution, and the rock comprises multiple phases, so that the full-lattice data is subjected to mixed Gaussian distribution. Therefore, in step S211, it is necessary to count the elastic modulus data of all the indentation points and classify and identify each phase by using a gaussian mixture model. Considering that no strict limit exists among the numerical values of the mechanical parameters of each microscopic phase, the rock minerals are roughly divided into three types of combinations of soft, medium and hard, the soft mineral combination corresponds to clay minerals, the neutral mineral corresponds to carbonate rock mineral combination, and the hard mineral corresponds to quartz mineral combination, so that the mixed Gaussian distribution is decomposed into three single Gaussian distributions.
Step S211 is to divide each phase in the shale debris rock sample to be evaluated into three types according to rock hardness, based on the three types of phases, convert (rewrite) the Gaussian mixture model into a form containing a single-phase Gaussian function corresponding to each phase type, a weight coefficient of single-phase mechanical properties, a mean parameter of the single-phase mechanical properties and variance parameter information of the single-phase mechanical properties, and then enter step S212. These three phase classes are preferably: clay mineral composition corresponding to soft hardness mineral composition, carbonate rock mineral composition corresponding to neutral hardness mineral composition, and quartz mineral composition corresponding to hard hardness mineral composition. Wherein, the rewritten Gaussian mixture model is expressed by the following expression:
Figure BDA0002455700060000121
wherein M represents the total number of phase classes, M is 3, M represents the number of each phase class, αmWeight coefficient representing each phase class, fmProbability density distribution function, x, representing each phase classnThe elastic parameter of each indentation point is shown, n is the serial number of each indentation point, and f (x)n) Representing the probability density distribution function, mu, of the nanoindentation test rock samplem、σmRespectively representing the mean and variance of the gaussian distribution for each item class.
Step S212, by using the rewritten Gaussian mixture model, according to the elastic parameters of each indentation point in the rock sample of the rock debris before soaking, a trend quantity which comprehensively represents the change situation of the elastic parameters of all the indentation points belonging to the same phase type is obtained, so that the trend quantity of the elastic parameters of each phase type in the rock sample before soaking is obtained, and according to the elastic parameters of each indentation point in the rock sample of the rock debris after soaking, a trend quantity which comprehensively represents the change situation of the elastic parameters of all the indentation points belonging to the same phase type is obtained, so that the trend quantity of the elastic parameters of each phase type in the rock sample after soaking is obtained. Preferably, in the embodiment of the present invention, the elasticity parameter trend of each phase category represents an average value (μ) of the elasticity parameters of all the fracture points belonging to the current phase category, so as to use the average value as the data based on the size class of the fracture points, which is most capable of comprehensively evaluating or describing the variation trend of the elasticity parameters of the current phase category, among all the elasticity parameters belonging to the phase category. Thus, the preparation for constructing the model of the macroscopic mineralogical mechanical characteristics of the three-dimensional rock sample is completed, and the process proceeds to step S213.
Step S213, according to the elastic parameter trend of each phase category before and after soaking and the rock mineral content analysis result obtained in step S212, performing cross-scale upgrade on the elasticity parameters of the microscopic phases by using a multi-scale theoretical homogenization method to obtain macroscopic elasticity parameters based on the shale rock sample to be evaluated at the size level before and after soaking, so as to convert the elasticity parameters corresponding to the nanoscale microscopic phases into elasticity parameters corresponding to the millimeter-scale macroscopic rock sample. Specifically, first (step S2131) the volume modulus and the shear modulus corresponding to each phase category before soaking are obtained from the poisson ratio of each phase category before soaking by using the phase category volume and shear modulus calculation formula according to the elastic parameter trend of each phase category before soaking, and the volume modulus and the shear modulus of each phase category before soaking are obtained from the poisson ratio of each phase category after soaking by using the phase category volume and shear modulus calculation formula according to the elastic parameter trend of each phase category after soaking. Wherein, the calculation formula of the phase classification volume and the shear modulus is represented by the following expression:
Figure BDA0002455700060000131
wherein, KJBulk modulus, G, representing the phase classJShear modulus, E, for each phase classJShows the trend of the elastic parameter (preferably, the elastic parameter here shows the trend of the elastic modulus), v, of each phase classJShowing the trend of the elasticity parameter for each phase class (preferably, the elasticity parameter here shows the poisson ratio trend). Among them, the tendency of the poisson ratio of the clay mineral composition is preferably 0.3, the tendency of the poisson ratio of the carbonate rock mineral composition is preferably 0.2, and the tendency of the poisson ratio of the quartz mineral composition is preferably 0.15.
After the volume modulus and the shear modulus corresponding to each phase category before and after soaking are obtained, (step S2132) cross-scale upgrading is performed on the elasticity parameter of the microscopic phase by using a multi-scale theoretical homogenization method according to the volume modulus and the shear modulus of each phase category before soaking on the basis of the accurate rock mineral content analysis result obtained in step S203 to obtain the volume modulus, the shear modulus, the elasticity modulus and the poisson ratio of the shale sample to be evaluated at the size level before soaking, and cross-scale upgrading is performed on the elasticity parameter of the microscopic phase by using the multi-scale theoretical homogenization method according to the volume modulus and the shear modulus of each phase category after soaking to obtain the volume modulus, the shear modulus, the elasticity modulus and the poisson ratio of the shale sample to be evaluated at the size level after soaking. The expression of the multi-scale theoretical homogenization method is as follows:
Figure BDA0002455700060000141
wherein, KhomDenotes the macroscopic bulk modulus, G, of the shale rock sample before or after soakinghomExpressing the macroscopic shear modulus, K, of the shale rock sample before or after soaking0、G0Respectively representing the bulk modulus and shear modulus, K, of the clay-based phase mineral before and after soakingI、GIRespectively representing the corresponding bulk modulus and shear modulus of inclusion phase minerals before and after soaking, I representing the sequence numbers of other phase minerals except clay minerals in the shale debris rock sample to be evaluated, n representing the total number of other phase minerals except clay minerals in the shale debris rock sample to be evaluated, fIData representing the content of mineral inclusions in the mineral inclusion phase, Ehom、νhomRespectively representing the macroscopic elastic modulus and Poisson's ratio of the shale rock sample before soaking or after soaking.
It should be noted that the inclusion phase minerals are other phase minerals in shale rocks besides clay minerals, such as: quartz, potash feldspar, plagioclase feldspar, calcite, dolomite, pyrite, and the like. The content data of these inclusion phase minerals are obtained from the rock mineral content analysis test results of the above step S203. In addition, the bulk modulus and the shear modulus corresponding to each inclusion phase mineral are preferably the bulk modulus and the shear modulus corresponding to the carbonate rock mineral combination or the quartz mineral combination to which the current inclusion phase mineral belongs, that is, obtained from step S2131.
Thus, through the steps S201 to S213, the macroscopic elasticity parameters of the shale rock sample to be evaluated before and after soaking are obtained based on the microscopic physical and mechanical characteristic parameters of the small-size rock debris rock sample, so that the elasticity parameters of the shale rock sample before and after water-rock action are obtained.
In addition, the shale water-rock action analysis method further comprises the following steps: and comparing and analyzing the electron microscope scanning images of the shale rock sample to be evaluated before and after soaking, and comparing and analyzing the elastic parameter trend corresponding to each microscopic phase category to obtain the analysis result of the influence degree of each microscopic phase in the shale rock sample to be evaluated on the deterioration of the elastic mechanical parameters under the influence of the water-rock action. Specifically, the method can analyze that each microscopic phase category in the shale can cause hydration expansion of clay minerals under the influence of the water-rock effect, so that mechanical characteristic parameters are deteriorated.
Namely, performing comparative analysis on the electron microscope scanning images of the rock samples before and after the water-rock action to obtain the main microscopic minerals which act with the fluid in the shale and are expansive clay minerals; meanwhile, compared with the elastic parameter difference of clay minerals, carbonate rock minerals and quartz minerals before and after the water-rock action, the main mechanism of the clay shale for the elastic parameter deterioration after the water-rock action is the hydration action of the clay minerals.
The embodiment of the invention provides a method for acquiring elastic parameters before and after shale water-rock action based on rock microscopic characteristics. The method comprises the steps of analyzing the content of shale minerals to obtain the content of each mineral component; performing electron microscope scanning and energy spectrum analysis on the rock sample, identifying the structure and the mineral type of the rock sample, and determining the area of a representative unit area; wrapping, grinding and polishing the rock sample by using epoxy resin, carrying out dot matrix nano indentation test on the rock sample before and after the water rock action, and calculating the elastic modulus of each indentation point position according to a loaded and unloaded load-displacement curve; analyzing the indentation data by using a Gaussian mixture model to obtain the elastic modulus corresponding to rock clay minerals, carbonate rock minerals and quartz minerals; and finally, determining the macroscopic elasticity parameters of the rock sample before and after the water-rock action by using a multi-scale theoretical homogenization method. In addition, the invention can also combine the electron microscope scanning images of the rock sample before and after the water-rock action and the change of the mechanical parameters of clay minerals to obtain the analysis result of the influence degree of the shale water-rock action on the mechanical parameters. Therefore, the mechanical parameters of the rock sample before and after the rock-water-rock action can be obtained without being limited by the size of the rock sample, and further, the mechanical characteristic parameters of the rock sample before and after the rock-water-rock action of the stratum at the whole well section can be obtained by fully utilizing rock debris rock discharged from the bottom of the well, compared with the mechanical parameters obtained by the conventional triaxial mechanical experiment which are not affected by the defects of cracks and the like, the defects that the standard shale sample is not easy to saturate and experimental data is scattered are avoided, and the method has the characteristics of being more economical and more effective.
Although the embodiments of the present invention have been described above, the above descriptions are only for the convenience of understanding the present invention, and are not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. A method for obtaining pre-and post-shale-lithology elasticity parameters, the method comprising:
grinding a shale sample to be evaluated, and analyzing the content of rock minerals;
performing electron microscope scanning on the rock sample, analyzing the distribution and content of each phase in a scanning image, and determining a volume unit representing the microstructure of the rock sample based on the distribution and content;
according to the volume representative unit, carrying out nano indentation test on the rock sample, establishing a load and displacement curve of each indentation point, and calculating the elastic parameter of each indentation point based on the load and displacement curve;
carrying out fluid soaking on the ballasted rock sample, sequentially carrying out electron microscope scanning and nano indentation testing on the soaked rock sample, and calculating the elastic parameter of each indentation point after soaking;
respectively identifying the phase type of each indentation point by using a Gaussian mixture model according to the elastic parameters of each indentation point before and after soaking, and calculating the elastic parameter trend of each phase type before and after soaking;
and obtaining the macroscopic elasticity parameters of the shale rock sample to be evaluated before and after soaking according to the elasticity parameter trend and rock mineral content analysis results.
2. The method as claimed in claim 1, wherein the step of obtaining the macroscopic elasticity parameters of the shale rock sample to be evaluated before and after soaking from the rock mineral content analysis results according to the elasticity parameter trend comprises:
calculating the volume modulus and the shear modulus of each phase type according to the elastic parameter trend of each phase type before and after soaking and the Poisson ratio of each phase type before and after soaking;
and based on the rock mineral content analysis result, according to the volume modulus and the shear modulus of each phase category before and after soaking, performing cross-scale upgrading on the elastic parameters of the microscopic phases by using a multi-scale theoretical homogenization method to obtain the volume modulus, the shear modulus, the elastic modulus and the Poisson ratio of the shale rock sample to be evaluated before and after soaking.
3. The method according to claim 1 or 2, wherein the step of respectively identifying the phase type of each indentation point by using a Gaussian mixture model according to the elasticity parameter of each indentation point before and after soaking and calculating the elasticity parameter trend of each phase type before and after soaking comprises the following steps:
dividing each phase in the shale sample to be evaluated into three types, and converting the Gaussian mixture model into a form containing a single-phase Gaussian function corresponding to each phase type, a weight coefficient of the physical mechanical property, a mean parameter of the physical mechanical property and variance parameter information, wherein the phase types comprise clay minerals, carbonate rock mineral combinations and quartz mineral combinations;
and respectively obtaining trend quantities comprehensively representing the elastic parameter change conditions of all the indentation points belonging to the corresponding phase types according to the elastic parameters of each indentation point before and after soaking by using the rewritten Gaussian mixture model.
4. The method of claim 3, wherein the adapted Gaussian mixture model is represented by the following expression:
Figure FDA0002455700050000021
wherein M represents the total number of phase classes, M is 3, M represents the number of each phase class, αmWeight coefficient representing each phase class, fmProbability density distribution function, x, representing each phase classnThe elastic parameter of each indentation point is shown, n is the serial number of each indentation point, and f (x)n) Representing the probability density distribution function, mu, of the nanoindentation test rock samplem、σmRespectively representing the mean and variance of the gaussian distribution for each item class.
5. The method of claim 1, when performing the nanoindentation test, comprising:
determining indentation parameters of a current test, wherein the indentation parameters include: the ballast dot matrix comprises indentation dot matrix distribution, indentation depth and indentation dot spacing, wherein the number of rows and columns of the ballast dot matrix is 15, the range of the indentation depth is 400 nm-500 nm, and the indentation dot spacing is 20 mu m;
and selecting an operation area to be ballasted on the rock sample to be tested according to the volume representative unit, and carrying out nano indentation test on the operation area.
6. The method according to claim 1, wherein the step of performing electron microscope scanning on the rock sample, analyzing the distribution and content of various phases in the scanned image, and based on the analysis, determining the volume units representing the microstructure of the rock sample comprises:
scanning the rock sample by SEM-BSE (scanning Electron microscope) scanning equipment to obtain a scanning image representing the structural morphology of the shale rock sample to be evaluated;
performing energy spectrum EDS analysis on the scanned image to obtain the distribution and content of each phase in the rock sample;
sequentially intercepting the gradually increased square areas from the center of the scanned image according to a preset step length, determining the content of each phase corresponding to each square area, and further establishing a relation curve for the area of each square area and the content of each phase;
and determining the square area with the stable content of each phase as the volume representative unit.
7. The method of claim 1, wherein the mill of the rock sample is subjected to rock mineral composition and content analysis testing using an X-ray diffractometer.
8. The method according to any one of claims 1 to 7, wherein the step of grinding the shale rock sample to be evaluated comprises:
grinding a first part of the shale rock sample to be evaluated into powder, so that the particle size of the powder is smaller than or equal to a preset powder particle size threshold value;
and preparing the rock sample powder into a whole rock slice, a natural slice, an ethylene glycol saturated slice and a heating slice to obtain an object for analyzing the mineral content of the rock.
9. The method of claim 8, further comprising: preparing a rock sample for electron microscopy scanning and nanoindentation testing, wherein,
wrapping rock samples except the first part of rock samples in the shale rock samples to be evaluated by using epoxy resin, solidifying the samples, and forming a flaky cylindrical sample in an additive mode, wherein the size of the sample is 25mm in diameter and 5mm in thickness;
and grinding and polishing the sample to expose one end face of the sample, sealing the rest face by the epoxy resin, enabling the upper surface and the lower surface of the sample to be parallel, enabling the roughness of the upper surface and the roughness of the lower surface to be lower than a preset roughness threshold value, and enabling the preset roughness threshold value to be 130 nm.
10. The method according to any one of claims 1 to 9, further comprising:
and comparing and analyzing the scanned images of the rock sample before and after soaking and the elastic parameter trend of each phase category to obtain an analysis result of the influence degree of each microscopic phase in the shale rock sample to be evaluated on the deterioration of the elastic mechanical parameters under the influence of the water-rock action.
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