An optimized method for processing shale XRD data

Abstract

The invention discloses an optimization method for processing shale XRD data. With the assistance of SEM observation and energy spectrum analysis, the target minerals and secondary minerals in the shale sample are directly and qualitatively identified; the shale sample is crushed, and the shale powder sample is tested to obtain the XRD spectrum of the shale sample; the diffraction peak in the XRD spectrum is selected according to the peak intensity, and the mineral corresponding to the selected diffraction peak is used as the target mineral for indirect identification; the characteristic peak spectrum is qualitatively analyzed: the search mineral is obtained by searching the characteristic peak spectrum, and the search mineral and the mineral with a good XRD spectrum fitting degree of the indirectly identified target mineral are matched, and a target mineral card is generated; the target mineral card is generated into a cif format file; the secondary search mineral obtained by the XRD spectrum is compared with the target mineral directly and qualitatively identified, and the cif format file of the missing mineral is imported; the invention solves the problem of inaccurate search due to the complex shale mineral components and the wide variety of minerals.

Description

Technical Field

[0001] The present invention relates to the technical field of shale processing, and in particular to an optimization method for processing shale XRD data. Background Art

[0002] Shale has very complex mineral composition characteristics. X-ray diffraction (XRD) is an important method for qualitatively or quantitatively evaluating the whole-rock mineral composition of shale. Therefore, the accurate interpretation of XRD data is particularly important. The interpretation of XRD data mainly includes qualitative identification and quantitative analysis of physical phases, among which the qualitative identification method can directly affect the accuracy of subsequent quantitative analysis.

[0003] At present, there are three main methods for qualitative identification of phases: (1) direct spectrum comparison method, which directly compares the measured sample with the spectrum of the known phase; (2) data comparison method, which compares the measured data (2θ, d, I / I1) with the standard diffraction data of known minerals; (3) electronic computer retrieval, by establishing a database of standard phase diffraction data (PDF cards), the measured data of the sample is input into the computer, and the corresponding processing software is used for retrieval.

[0004] Currently, electronic computer retrieval is usually used to analyze the physical phase, focusing on the accuracy and simplicity of the analysis process, and there is corresponding software support. At present, the more commonly used XRD data processing software includes Jade, HighScore Plus, etc. These software can improve the accuracy of qualitative identification by narrowing the search range. However, the shale mineral composition is complex, the mineral types are many, and the peak positions of the diffraction peaks are complex, resulting in low retrieval accuracy; many minerals have very low content, low diffraction peak intensity, and the signal is easily covered. It is difficult for traditional methods to effectively retrieve minerals with such peak intensity. Summary of the invention

[0005] The purpose of the present invention is to provide an optimization method for processing shale XRD data to solve the technical problems in the prior art that the shale mineral composition is complex, the mineral types are many, and the peak positions of the diffraction peaks are complex, resulting in low retrieval accuracy; many mineral contents are very low, the diffraction peak intensity is low, and the signal is easily covered, and traditional methods are difficult to effectively retrieve minerals with such peak intensity.

[0006] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] An optimization method for processing shale XRD data, characterized in that it comprises the following steps:

[0008] Qualitative identification of minerals: With the assistance of SEM observation and energy spectrum analysis, the target minerals and minor minerals in shale samples can be directly and qualitatively identified based on their relative content;

[0009] Obtaining XRD spectrum: crushing the shale sample, and testing the shale powder sample using a X-ray diffractometer to obtain the XRD spectrum of the shale sample;

[0010] Screening characteristic peak spectra: Select the diffraction peaks in the XRD spectrum according to the peak intensity, and use the minerals corresponding to the selected diffraction peaks as the target minerals for indirect identification;

[0011] Qualitative analysis of characteristic peak spectra: Qualitative analysis of characteristic peak spectra: The search minerals are obtained by searching the characteristic peak spectra, and the XRD spectra of the search minerals and the indirectly identified target minerals with good fitting degree and containing structural information are matched, and the target mineral cards are generated;

[0012] Generate cif format file: Generate cif format file from target mineral card, and each target mineral card has an identity code;

[0013] Supplement target minerals: perform computer search on the XRD spectrum, compare the secondary search minerals with the target minerals directly identified by qualitative identification, and import the cif format file of the missing minerals into the computer.

[0014] As a preferred solution of the present invention, with the assistance of SEM observation and energy spectrum analysis, a plurality of main minerals and secondary minerals are firstly qualitatively identified, and then the target minerals are screened out from the main minerals.

[0015] As a preferred solution of the present invention, the XRD spectrum of the shale sample is imported into the HighScore Plus software, and the obvious characteristic peaks in the XRD spectrum, that is, the diffraction peaks with high peak intensity, are selected, and the mineral is used as the target mineral for indirect identification.

[0016] As a preferred embodiment of the present invention, there is a cross-set between the indirectly identified target minerals and the directly qualitatively identified target minerals, and the cross-set is the publicly identified target minerals.

[0017] As a preferred embodiment of the present invention, the specific implementation steps of qualitative analysis of characteristic peak spectra are:

[0018] Setting peak search conditions for characteristic peaks, so as to obtain corresponding search minerals from a database of standard phase diffraction data using the search conditions, and capturing a peak spectrum screenshot corresponding to the search mineral from the characteristic peak spectrum;

[0019] Compare the search mineral with the target mineral directly identified by qualitative analysis, determine the remaining minerals in the target mineral except the search mineral, reset the peak search conditions of the remaining minerals, and obtain the peak spectrum screenshot corresponding to the remaining minerals from the database of the standard phase diffraction data;

[0020] Screenshots of the peak spectra of the searched mineral and the remaining minerals are taken, and compared with the XRD spectra of the indirectly identified target minerals respectively;

[0021] Select minerals with strong peaks that have good fitting and structural information, and generate target mineral cards.

[0022] As a preferred solution of the present invention, the steps of comparing the peak spectrum screenshots of the search mineral and the remaining minerals with the XRD spectrum of the indirectly identified target mineral are as follows:

[0023] Taking the peak intensity of the diffraction peak in the peak spectrum screenshot as the first comparison condition, determining the peak intensity of the diffraction peak according to the X-axis direction of the peak spectrum screenshot, and selecting a waveform with the same peak intensity from the XRD spectrum of the indirectly identified target mineral;

[0024] Taking the diffraction peak trough intensity in the peak spectrum screenshot as the second comparison condition, the trough intensity of the diffraction peak is determined according to the X-axis direction of the peak spectrum screenshot, and the waveform with the same trough intensity is selected from the XRD spectrum of the indirectly identified target mineral

[0025] Taking the diffraction peak width in the peak spectrum screenshot as the third comparison condition, determining the peak width corresponding to the rising starting point and the falling end point of the diffraction peak according to the X-axis direction of the peak spectrum screenshot, and selecting a waveform with the same peak width span from the XRD spectrum of the indirectly identified target mineral;

[0026] Select the minerals with the same number of waveforms with the same peak intensity distribution and the same waveform width span in the XRD spectrum and a good waveform fitting degree, and prepare the target mineral card according to the mineral name defined in the XRD spectrum.

[0027] As a preferred solution of the present invention, the search conditions for peak finding include: peak width, trough width and peak base width.

[0028] As a preferred solution of the present invention, the specific implementation steps of generating a cif format file are: input the PDF number or ICSD number of the target mineral card into the FindIt software, retrieve and export the cif format file of the target mineral, wherein the PDF number or ICSD number exists as an identity code in the target mineral card information.

[0029] As a preferred embodiment of the present invention, the steps for supplementing the target mineral are as follows:

[0030] The XRD spectrum of the shale sample is imported into HighScore Plus software, and the qualitative minerals are identified by setting peak search conditions. The qualitative minerals are compared with the target minerals directly identified by qualitative identification. If there are no remaining minerals, quantitative analysis is directly performed;

[0031] If there are remaining minerals, the cif format file corresponding to the remaining minerals is imported into the HighScore Plus software.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention uses the target minerals identified by SEM observation and energy spectrum analysis to supplement the cif format file of the missing minerals, so that the shale qualitative analysis can find low-content minerals and all kinds of minerals, solve the problem of difficult retrieval due to low content of minerals, avoid missed selection of minerals, greatly optimize the processing of shale XRD data, and use SEM observation and energy spectrum analysis to qualitatively identify the target minerals, reduce the possibility of wrong selection of minerals, solve the problem of inaccurate retrieval due to complex shale mineral components and a wide variety of minerals, and greatly improve the accuracy of shale XRD qualitative analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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.

[0035] Figure 1 The present invention is a flowchart of a method for optimizing shale XRD data processing according to an embodiment of the present invention.

[0036] Figure 2 This is the characteristic peak X-ray diffraction pattern of a typical shale sample according to an embodiment of the present invention.

[0037] Figure 3 The figure shows the changes in mineral composition of a typical shale sample before and after XRD data optimization in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] like Figure 1 As shown, the present invention provides an optimization method for processing shale XRD data, comprising the following steps:

[0040] The first step is qualitative identification of minerals: with the assistance of SEM observation and energy spectrum analysis, the target minerals and minor minerals in the shale samples are directly and qualitatively identified based on the relative content of the minerals.

[0041] With the assistance of SEM observation and energy spectrum analysis, a variety of major and minor minerals are first qualitatively identified, and then the target minerals are screened out from the major minerals.

[0042] It should be noted that the imaging principle of SEM (electron microscope) is as follows: the electron beam generated by the electron gun is focused by the electromagnetic lens, the scanning coil controls the electron beam to scan the sample, and interacts with the sample to generate various physical signals, and the detector converts the physical signals into image information. Different morphologies of the sample show different contrasts (brightness differences between different parts of the image), so the scanning electron microscope can observe the surface morphology of the sample.

[0043] Therefore, by analyzing the surface morphology of the sample observed by SEM and comparing it with the distribution patterns of different minerals in shale (such as calcite, quartz, talc, montmorillonite, illite, dolomite, feldspar and sepiolite, etc.), the types of minerals contained in the shale sample can be obtained.

[0044] The second step is to obtain the XRD spectrum: the shale sample is crushed and the shale powder sample is tested using a X-ray diffractometer to obtain the XRD spectrum of the shale sample, such as Figure 2 shown.

[0045] The specific implementation steps are as follows: the shale sample is crushed to 200 mesh in an agate mortar, and the shale powder sample is tested using a Bruker D8Advance X-ray diffractometer. The scanning angle of the sample is 3° to 70°, and the step length is 0.04° (2θ), so as to obtain the XRD spectrum of the shale sample.

[0046] XRD includes X-ray single crystal diffraction and X-ray powder diffraction. X-ray single crystal diffraction mainly utilizes the radiation of X-rays in the crystal, collects the diffraction points and uses professional software to analyze the structure of the crystal; X-ray powder diffraction usually compares the powder diffraction spectrum with the standard spectrum to perform phase analysis. In this embodiment, X-ray powder diffraction is used to perform phase analysis on the minerals in the shale.

[0047] The third step is to screen the characteristic peak spectrum: select the diffraction peaks in the XRD spectrum according to the peak intensity, and use the minerals corresponding to the selected diffraction peaks as the target minerals for indirect identification.

[0048] The XRD spectrum of the shale sample was imported into the HighScore Plus software, and the obvious characteristic peaks in the XRD spectrum, that is, the diffraction peaks with high peak intensity, were selected, and the mineral was used as the target mineral for indirect identification.

[0049] It should be noted that the XRD spectrum has a horizontal coordinate of 2θ, so we can know the grazing angle θ (the complementary angle of the incident angle, also known as the Bragg angle). Then we can find the crystal plane-to-crystal plane spacing d corresponding to the spectrum line.

[0050] The vertical axis of the XRD spectrum is the intensity of the spectrum line; if it is a photo or photosensitive film, it is the brightness of the light spot. It mainly indicates the physical meaning of the factors affecting the diffraction intensity and their calculation methods. The intensity of the diffraction line can reflect the microscopic structure information in the crystal, so the process of diffraction intensity analysis is also the process of completing the crystal structure judgment; diffraction intensity analysis is an important part of the basic theory of diffraction analysis.

[0051] Among them, there is an intersection set between the indirectly identified target minerals and the directly qualitatively identified target minerals, and the intersection set is the publicly identified target minerals.

[0052] The fourth step is qualitative analysis of the characteristic peak spectrum: the search mineral is obtained by searching the characteristic peak spectrum, the search mineral is well fitted with the XRD spectrum of the indirectly identified target mineral and contains structural information, and the target mineral card is generated.

[0053] The operation of searching for peaks in characteristic peak spectra to obtain searched minerals is the same as the electronic computer search method for qualitative identification of physical phases in the prior art, that is, by establishing a database of standard physical phase diffraction data (PDF cards), the measured XRD spectra of shale samples are input into the computer, and the corresponding processing software, HighScore Plus software, is used for search. For shale, electronic computers are usually used to search and analyze physical phases, focusing on the accuracy and simplicity of the analysis process, and there is corresponding software support.

[0054] Among them, the specific implementation steps of the qualitative analysis of the characteristic peak spectrum are:

[0055] 1. Set the peak search conditions for the characteristic peaks, use the search conditions to obtain the corresponding search minerals from the database of standard phase diffraction data (PDF card), and capture the peak spectrum screenshot corresponding to the search mineral from the characteristic peak spectrum.

[0056] 2. Compare the search mineral with the target mineral identified by direct qualitative identification, determine the remaining minerals in the target mineral except the search mineral, reset the peak search conditions for the characteristic peaks of the remaining minerals, and obtain the peak spectrum screenshot corresponding to the remaining minerals from the database (PDF card) of the standard phase diffraction data.

[0057] 3. Take screenshots of the peak spectra of the searched mineral and the remaining minerals, and compare them with the XRD spectra of the indirectly identified target minerals.

[0058] 4. Select minerals with good strong peak fitting and structural information, and generate target mineral cards.

[0059] Among them, the search conditions for peak finding include: peak width, trough width and peak base width.

[0060] Furthermore, the peak spectrum screenshots of the search mineral and the remaining minerals are respectively compared with the XRD spectrum of the indirectly identified target mineral as follows:

[0061] (1) using the peak intensity of the diffraction peak in the peak spectrum screenshot as the first comparison condition, determining the peak intensity of the diffraction peak according to the X-axis direction of the peak spectrum screenshot, and selecting a waveform with the same peak intensity from the XRD spectrum of the indirectly identified target mineral;

[0062] (2) Taking the diffraction peak trough intensity in the peak spectrum screenshot as the second comparison condition, determining the trough intensity of the diffraction peak according to the X-axis direction of the peak spectrum screenshot, and selecting waveforms with the same trough intensity from the XRD spectrum of the target mineral indirectly identified

[0063] (3) taking the diffraction peak width in the peak spectrum screenshot as the third comparison condition, determining the peak width corresponding to the rising starting point and the falling end point of the diffraction peak according to the X-axis direction of the peak spectrum screenshot, and selecting a waveform with the same peak width span from the XRD spectrum of the indirectly identified target mineral;

[0064] (4) Select minerals with the same number of peak intensity distribution waveforms and the same peak width span in the XRD spectrum and with a good waveform fitting degree, and prepare target mineral cards according to the mineral names defined in the XRD spectrum.

[0065] Step 5, generate cif format file: generate cif format file from target mineral card, and each target mineral card has an identity code.

[0066] The specific implementation steps for generating a cif format file are: input the PDF number or ICSD number of the target mineral card into the FindIt software, retrieve and export the cif format file of the target mineral, where the PDF number or ICSD number exists as an identity code in the target mineral card information.

[0067] Step 6: Supplement the target minerals: perform computer search on the XRD spectrum, compare the secondary search minerals with the target minerals directly identified by qualitative analysis, and import the cif format file of the missing minerals into the computer.

[0068] The steps to achieve target mineral replenishment are:

[0069] The XRD spectrum of the shale sample is imported into HighScore Plus software, and the qualitative minerals are identified by setting peak search conditions. The qualitative minerals are compared with the target minerals directly identified by qualitative identification. If there are no remaining minerals, quantitative analysis is directly performed;

[0070] If there are remaining minerals, the cif format file corresponding to the remaining minerals is imported into the HighScore Plus software.

[0071] Step 7: Quantitative analysis of target minerals: Correct and quantify all target minerals in cif format files, such as Figure 3 shown.

[0072] The contents of quantitative refinement mainly include: background, unit cell parameters, atomic occupancy (occ), temperature factor (beq), etc., and correction of possible preferred orientation, etc. The indicators for judging the results of the refinement are mainly the R factor, namely Rwp (fitting value), Rexp (fitting expectation) and goodness of fit gof (Rwp / Rexp). The fitting expectation Rewp of shale samples is less than or close to 10, and the goodness of fit Gof is less than or close to 2. Within the normal range, the quantitative refinement can be completed. The specific working principle is the same as the implementation process of using HighScore Plus software for phase qualitative and quantitative analysis in the prior art, so it will not be repeated in this article.

[0073] Therefore, this embodiment uses the target minerals identified by SEM observation and energy spectrum analysis to supplement the cif format file of missing minerals, so that the qualitative analysis of shale can find low-content minerals and all kinds of minerals, solve the problem of difficult retrieval due to low content of minerals, avoid missed selection of minerals, greatly optimize the processing of shale XRD data, and use SEM observation and energy spectrum analysis to qualitatively identify target minerals, reduce the possibility of misselection of minerals, solve the problem of inaccurate retrieval due to complex shale mineral components and a wide variety of minerals, and greatly improve the accuracy of shale XRD qualitative analysis.

[0074] In summary, this implementation method combines the qualitative identification of SEM observation and energy spectrum analysis with the quantitative refinement of HighScore Plus software, which not only improves the accuracy of quantitative analysis, but also ensures the rigor of qualitative analysis, and greatly optimizes the processing of shale XRD data.

[0075] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. An optimization method for processing shale XRD data, characterized in that: The following steps are involved: Qualitative identification of minerals: With the assistance of SEM observation and energy spectrum analysis, the target minerals and minor minerals in the shale sample can be directly and qualitatively identified according to the relative content of the minerals. By analyzing the surface morphology of the sample observed by SEM and comparing it with the distribution morphology of different minerals in the shale, the types of minerals contained in the shale sample can be obtained; Obtaining XRD spectrum: crushing the shale sample, and testing the shale powder sample to obtain the XRD spectrum of the shale sample; Screening characteristic peak spectra: Select the diffraction peaks in the XRD spectrum according to the peak intensity, and use the minerals corresponding to the selected diffraction peaks as the target minerals for indirect identification. The specific screening method is: import the XRD spectrum of the shale sample into the HighScore Plus software, select the obvious characteristic peaks in the XRD spectrum, that is, the diffraction peaks with high peak intensity, and use the minerals as the target minerals for indirect identification; Qualitative analysis of characteristic peak spectra: setting peak search conditions for characteristic peaks, obtaining corresponding search minerals from the database of standard phase diffraction data using the search conditions, and capturing peak spectrum screenshots corresponding to the search minerals from the characteristic peak spectra; Compare the search mineral with the target mineral directly identified by qualitative analysis, determine the remaining minerals in the target mineral except the search mineral, reset the peak search conditions of the remaining minerals, and obtain the peak spectrum screenshot corresponding to the remaining minerals from the database of the standard phase diffraction data; Screenshots of the peak spectra of the searched mineral and the remaining minerals are taken, and compared with the XRD spectra of the indirectly identified target minerals respectively; Select minerals with strong peaks that have good fitting and structural information, and generate target mineral cards; Generate cif format file: Generate cif format file from target mineral card, and each target mineral card has an identity code; Supplement target minerals: Import the XRD spectrum of the shale sample into HighScore Plus software, identify the minerals by setting peak search conditions, compare the qualitative minerals with the target minerals directly identified by qualitative analysis, and directly perform quantitative analysis if there are no remaining minerals; If there are remaining minerals, the cif format file corresponding to the remaining minerals is imported into the HighScore Plus software.

2. The optimization method for processing shale XRD data according to claim 1, characterized in that: There is an intersection set between the indirectly identified target minerals and the directly qualitatively identified target minerals, and the intersection set is the publicly identified target minerals.

3. The optimization method for processing shale XRD data according to claim 1, characterized in that: The steps of comparing the peak spectrum screenshots of the search mineral and the remaining minerals with the XRD spectrum of the indirectly identified target mineral are as follows: Taking the peak intensity of the diffraction peak in the peak spectrum screenshot as the first comparison condition, determining the peak intensity of the diffraction peak according to the X-axis direction of the peak spectrum screenshot, and selecting a waveform with the same peak intensity from the XRD spectrum of the indirectly identified target mineral; Taking the diffraction peak trough intensity in the peak spectrum screenshot as the second comparison condition, the trough intensity of the diffraction peak is determined according to the X-axis direction of the peak spectrum screenshot, and the waveform with the same trough intensity is selected from the XRD spectrum of the indirectly identified target mineral Taking the diffraction peak width in the peak spectrum screenshot as the third comparison condition, determining the peak width corresponding to the rising starting point and the falling end point of the diffraction peak according to the X-axis direction of the peak spectrum screenshot, and selecting a waveform with the same peak width span from the XRD spectrum of the indirectly identified target mineral; Select the minerals with the same number of waveforms with the same peak intensity distribution and the same waveform width span in the XRD spectrum and a good waveform fitting degree, and prepare the target mineral card according to the mineral name defined in the XRD spectrum.

4. The optimization method for processing shale XRD data according to claim 1, characterized in that: The search conditions for peak finding include: peak width, trough width and peak base width.

5. The optimization method for processing shale XRD data according to claim 1, characterized in that: The specific implementation steps for generating a cif format file are: input the PDF number or ICSD number of the target mineral card into the FindIt software, retrieve and export the cif format file of the target mineral, wherein the PDF number or ICSD number exists as an identity code in the target mineral card information.

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