Method for identifying hydrothermal cause calcite in shale

Abstract

The invention relates to a method for identifying hydrothermal calcite in shale. The method comprises the following steps: preparing sample slices from calcite samples at the same layer and in different occurrence states; carrying out cathodoluminescence observation on the sample slice to obtain a cathodoluminescence picture; determining rare earth element data of each sample slice by utilizing an element geochemical analysis method; determining a forming mode of a sample slice according to the cathode luminescence photograph and the rare earth element data; wherein the formation mode comprises a later diagenesis mode and a hydrothermal deposition calcite mode.

Description

Technical Field

[0001] The present invention relates to the field of petroleum exploration technology, and in particular to a method for identifying hydrothermal calcite in shale. Background Art

[0002] At present, domestic and foreign scholars have always paid attention to hydrothermal fluids at the forefront of geological research, especially in saline lake basins. Many scholars believe that the participation of hydrothermal fluids is part of the reason for the increase in salinity in saline lake basins; at the same time, the intrusion of hydrothermal fluids will also bring a lot of nutrients, forming a microenvironment for the development of special biological communities; on the other hand, many scholars also believe that hydrothermal fluids bring thermal energy, which can cause buried source rocks to be thermally catalytic and generate hydrocarbons at an early stage. In general, hydrothermal deposition events have brought many directions and ideas to geological research. However, in the research process, how to determine the sedimentary characteristics and lithofacies types formed by hydrothermal deposition is the basis for many studies. Many scholars believe that calcite veins in shale are related to hydrothermal deposition, but many people still believe that it is related to the diagenesis process, and many studies have shown that this type of calcite vein can record the diagenetic fluid composition, temperature and pressure conditions, diagenetic fluid environment, fluid source and other information during its formation. Therefore, it is necessary to provide a method that can identify the two types of calcite veins, so it is extremely important to establish means and methods for identifying hydrothermal calcite. Summary of the invention

[0003] In view of the above problems, the present invention provides a method for identifying hydrothermal calcite in shale, based on which a petrological and geochemical characteristic map of hydrothermal calcite can be established, which is conducive to the accurate study of the effects of hydrothermal activity on sedimentary facies and the material composition of the facies.

[0004] In the first aspect, the present application provides a method for identifying hydrothermal calcite in shale, the method comprising: making sample slices from calcite samples of the same stratum and different occurrences; performing cathode luminescence observation on the sample slices to obtain cathode luminescence photographs; determining rare earth element data of each sample slice using elemental geochemical analysis; determining a formation mode of the sample slice based on the cathode luminescence photographs and the rare earth element data; wherein the formation mode includes: a late diagenetic mode and a hydrothermal deposition calcite mode.

[0005] Compared with the related art, the present application provides a method and device for identifying hydrothermal calcite in shale, the method comprising: preparing sample slices from calcite samples of the same layer and different occurrences; observing the sample slices by cathode luminescence to obtain cathode luminescence photos; determining the rare earth element data of each sample slice by elemental geochemical analysis; determining the formation mode of the sample slice according to the cathode luminescence photos and the rare earth element data; wherein the formation mode includes: late diagenesis mode and hydrothermal deposition calcite mode. The present application provides a method for comprehensively identifying the formation mode of hydrothermal calcite based on petrology and isotope geochemistry methods, which can more accurately select samples to study the influence of hydrothermal activity on the type and origin of organic matter in source rocks.

[0006] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0008] Figure 1 A flow chart of a method for identifying hydrothermal calcite in shale according to an embodiment of the present application;

[0009] Figure 2 Schematic diagram of cores, thin sections and cathodoluminescence characteristics of calcite of different occurrences in the Lucaogou Formation of the Jimusar Sag and the Shahejie Formation of the Jiyang Depression in saline lake basins in some exemplary embodiments;

[0010] Figure 3 Schematic diagram of the standardized distribution pattern of rare earth elements in calcite and surrounding rock chondrites of different occurrences in the Lucaogou Formation in the Jimsar Sag and the Shahejie Formation in the Jiyang Depression in some exemplary embodiments. DETAILED DESCRIPTION

[0011] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0012] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme defined by the claims. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.

[0013] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0014] The embodiment of the present invention provides a method for identifying hydrothermal calcite in shale, such as Figure 1 As shown, the method includes steps S100-S130:

[0015] S100: Sample thin sections are made from calcite samples of the same layer and different occurrences;

[0016] S110: Observe the cathode luminescence of the sample slice to obtain a cathode luminescence photograph;

[0017] S120: Determine the rare earth element data of each sample slice using element geochemical analysis method;

[0018] S130: Determine a formation mode of the sample slice according to the cathode luminescence photograph and the rare earth element data; wherein the formation mode includes: a late diagenetic mode and a hydrothermal deposition calcite mode.

[0019] In this embodiment, the calcite samples of different occurrences include interlayer calcite samples and bedding calcite samples; specifically, calcite samples of the same layer with similar burial depth and different occurrences are prepared along the direction perpendicular to the bedding plane.

[0020] In an exemplary embodiment, the sample slices include: calcite vein sample slices and calcite surrounding rock sample slices.

[0021] In an exemplary embodiment, the cathode luminescence is a luminescence phenomenon produced on the surface of a mineral under the bombardment of an electron beam. The cathode luminescence should be performed on a rock slice under vacuum conditions. Therefore, the thickness of the sample slice is 0.04 mm and does not include a cover glass. The rock slice should be glued to the slide with non-luminescent glue to avoid interference caused by the fluorescence of the base glue during fluorescence observation. In this embodiment, the cathode luminescence uses a cathode luminometer.

[0022] In an exemplary embodiment, the method of determining the rare earth element data of each sample slice by elemental geochemical analysis includes:

[0023] In-situ micro-area trace element analysis is performed on different sample slices to determine the rare earth element data of each sample slice.

[0024] The rare earth elements include: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu elements, among which La, Ce, Pr, Nd, Sm and Eu are light rare earth elements (LREE), and Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu are heavy rare earth elements (HREE).

[0025] In an exemplary embodiment, after determining the rare earth element data of each sample slice using elemental geochemical analysis, the method further includes:

[0026] Step 1. Perform chondrite standardization on the rare earth element data to obtain standardized rare earth element data;

[0027] Step 2. Use the standardized rare earth element data to establish a rare earth element distribution characteristic curve. The standardized distribution curve of rare earth element chondrites refers to a line graph with the horizontal axis being the element name and the vertical axis being the standardized element concentration.

[0028] In an exemplary embodiment, cathodoluminescence (CL) is the visible light emitted when electrons bombard the surface of a mineral in a vacuum. 2+ and Mg 2+There is a certain connection between certain cations and the activation and quenching of cathode luminescence. Manganese is the most studied luminescence activator, and iron is the most common quencher. The ratio of these two cations controls the luminescence intensity of calcite. Since the calcite is developed in mudstone, which is a deep-water deposit, far from the shore, and has a low Fe ion concentration, the Mn / Fe ratio of the calcite formed in the later stage of diagenesis is high, so the luminescence intensity is large. The Fe concentration brought by hydrothermal activity is high, and it has not been transported and oxidized over long distances, so the Mn / Fe ratio of calcite in the sedimentary period is low, and the luminescence intensity is weak.

[0029] Therefore, the formation mode of the sample slice can be determined based on the cathode luminescence photograph, which can be specifically:

[0030] If the cathode luminescence color is orange-red, it is determined that the sample thin section is a late diagenetic model; if the cathode luminescence photo is dark red, it is determined that the sample thin section is a hydrothermal deposition calcite model.

[0031] In an exemplary embodiment, on the one hand, the concentration of rare earth elements, the minerals formed by hydrothermal deposition in the calcite veins are not diluted by deposition compared with the surrounding rocks, so their rare earth element concentration is high. On the other hand, rare earth elements are very stable elements, and their distribution pattern can reflect the source of the sediments. The in-situ main and trace elements of the calcite parts and surrounding rock parts of different bedding structures are measured, and the distribution pattern of rare earth elements after calcite chondrite standardization will be very different from the distribution pattern of surrounding rock samples. In addition, there will be certain differences in the distribution pattern of rare earth elements after chondrite standardization of calcite veins formed by diagenetic fluids and hydrothermal fluids. The rare earth elements of diagenetic fluids come from the surrounding rocks and are subjected to differentiation, which will be more enriched in light rare earth elements, while the rare earth elements in the calcite veins formed by hydrothermal fluids come from the deep crust and will be more enriched in heavy rare earth elements. Based on the above petrology and inorganic geochemistry, the core and lithofacies characteristics of hydrothermal activities in the study area can be identified.

[0032] In an exemplary embodiment, determining the formation mode of the sample slice according to the cathode luminescence photograph and the rare earth element data includes:

[0033] If the rare earth element distribution characteristic curve of the thin section of the calcite vein sample is different from the rare earth element distribution characteristic curve of the thin section of the calcite surrounding rock sample, and the rare earth element concentration of the thin section of the calcite vein sample is greater than the rare earth element concentration of the thin section of the calcite surrounding rock sample, then the calcite vein sample thin section is determined to be a hydrothermal deposition model;

[0034] If the rare earth element distribution characteristic curve of the calcite vein sample thin section is the same as the rare earth element distribution characteristic curve of the calcite surrounding rock sample thin section, and the rare earth element concentration of the calcite vein sample thin section is less than the rare earth element concentration of the calcite surrounding rock sample thin section, then the calcite vein sample thin section is determined to be a late diagenetic depositional model.

[0035] In an exemplary embodiment, the formation mode of the sample flake is determined by combining the cathode luminescence photograph and the rare earth element data, including:

[0036] If the luminescence characteristic of the calcite vein sample thin section is dark red, and the rare earth element concentration of the calcite vein sample thin section is greater than the rare earth element concentration of the calcite surrounding rock sample thin section, it is determined that the calcite vein sample thin section is a hydrothermal deposition model;

[0037] If the luminescence characteristic of the calcite vein sample thin section is orange-red, and the rare earth element concentration of the calcite vein sample thin section is less than the rare earth element concentration of the calcite surrounding rock sample thin section, it is determined that the calcite vein sample thin section is formed by late diagenesis.

[0038] The embodiments of the present application have the following technical effects:

[0039] The present invention provides for the first time a method for identifying differences in hydrothermal calcite formation patterns, which has the following advantages:

[0040] 1. The present invention fully considers the insufficiency of relying solely on petrology to identify the origin of hydrothermal fluids. Cathodoluminescence combined with in-situ inorganic geochemical data can lay a reliable geological foundation for hydrothermal fluid identification.

[0041] 2. The methods and means used in the present invention are relatively simple, have strong timeliness, and supplementary experiments are also very simple.

[0042] Example 1

[0043] This example implements a method for identifying hydrothermal calcite in shale. The specific process is as follows:

[0044] The first step is to prepare samples of calcite samples with similar burial depths and different occurrences in the same layer along the direction perpendicular to the bedding plane;

[0045] The second step is to observe the cathode luminescence of the sample slice and obtain a cathode luminescence photograph;

[0046] The third step is to determine the rare earth element data of each sample slice using elemental geochemical analysis;

[0047] Step 4: Establish the rare earth element distribution characteristic curve.

[0048] In this step, the specific establishment process includes:

[0049] 1. Perform chondrite standardization on the rare earth element data to obtain standardized rare earth element data;

[0050] 2. Use the standardized rare earth element data to establish the rare earth element distribution characteristic curve.

[0051] Step 5: Determine the formation mode of the sample slice based on the cathode luminescence photograph, which specifically includes:

[0052] If the cathode luminescence photograph has a high luminescence intensity, it is determined that the sample thin section is in a late diagenetic mode;

[0053] If the cathode luminescence photograph has a low luminescence intensity, it is determined that the sample slice is in the hydrothermal deposition calcite mode.

[0054] Step 6: Determine the formation mode of the sample slice based on the rare earth element data, including:

[0055] If the rare earth element concentration of the thin section of the calcite vein sample is greater than that of the calcite surrounding rock sample; in addition, the distribution pattern of heavy rare earth elements (HREE) and light rare earth elements (LREE) in the surrounding rock is different from that of the calcite vein, that is, the concentration of heavy rare earth elements in the surrounding rock is much smaller than that of light rare earth elements, while the concentration of heavy rare earth elements in the calcite vein is similar to that of light rare earth elements, then the thin section of the calcite vein sample is determined to be a hydrothermal deposition model;

[0056] If the rare earth element concentration in the thin section of the calcite vein sample is lower than that in the thin section of the calcite surrounding rock sample; the distribution pattern of heavy rare earth elements (HREE) and light rare earth elements (LREE) in the surrounding rock is no different from that in the calcite vein, that is, the concentration of heavy rare earth elements is much lower than that of light rare earth elements, then the thin section of the calcite vein sample is determined to be a late diagenetic depositional model.

[0057] For example:

[0058] Figure 3 In Figures b and d of the results, the rare earth element concentration of the thin section of the calcite vein sample is greater than that of the calcite surrounding rock sample; in addition, the distribution characteristics of heavy rare earth elements (HREE) and light rare earth elements (LREE) in the thin section of the calcite surrounding rock sample are different from those of the calcite vein, that is, the concentration of heavy rare earth elements in the surrounding rock is much smaller than that of light rare earth elements, while the concentration of heavy rare earth elements in the calcite vein is similar to that of light rare earth elements, which confirms that the thin section of the calcite vein sample is a hydrothermal deposition model;

[0059] Figure 3In Figure f, the rare earth element concentration of the calcite vein sample thin section is lower than that of the calcite host rock sample thin section; the distribution characteristics of heavy rare earth elements (HREE) and light rare earth elements (LREE) in the calcite host rock sample thin section are no different from those of the calcite vein, that is, the concentration of heavy rare earth elements is much lower than that of light rare earth elements, which determines that the calcite vein sample thin section is a late diagenetic deposition model.

[0060] Step 7: Comprehensively determine the formation mode of the sample slice based on the cathode luminescence photograph and the rare earth element data, as follows:

[0061] If the luminescence characteristic of the calcite vein sample thin section is dark red, and the rare earth element concentration of the calcite vein sample thin section is greater than the rare earth element concentration of the calcite surrounding rock sample thin section, it is determined that the calcite vein sample thin section is a hydrothermal deposition model;

[0062] If the luminescence characteristic of the calcite vein sample thin section is orange-red, and the rare earth element concentration of the calcite vein sample thin section is less than the rare earth element concentration of the calcite surrounding rock sample thin section, it is determined that the calcite vein sample thin section was formed by late diagenesis.

[0063] Example 2

[0064] Take the Permian Lucaogou Formation in Jimusar Depression and the Shahejie Formation in Jiyang Depression as examples.

[0065] The Lucaogou Formation in the Jimsar Sag and the Shahejie Formation in the Jiyang Depression are both saline lake deposits. From the core and thin section observations, both strata contain a large amount of carbonate minerals, and calcite veins are well developed in both strata, and both are developed in high-abundance shales. It can be seen that the formation of calcite veins is related to the enrichment of organic matter. Therefore, clearly identifying the genesis of calcite veins is of great significance to the enrichment mechanism of organic matter in shale.

[0066] The present invention takes the cathode luminescence and in-situ micro-area major and trace element analysis methods of calcite vein samples from the Lucaogou Formation in the Jimusar Depression and the Shahejie Formation in the Jiyang Depression as examples to illustrate the analysis method of the present invention.

[0067] Step 1. Collect core samples rich in calcite veins from the Lucaogou Formation in the Jimusar Sag and the Shahejie Formation in the Jiyang Depression, such as Figure 2 Figure a in the middle shows a 3702.67 m bedding vein calcite core sample from Well X1 in Jimusar Sag. Figure 2 Figure d in the middle shows the 3711.73 m cross-layer vein calcite core sample from Well X1 in Jimusar Sag. Figure 2 Figure g in the middle shows a 3642.13 m bedding vein calcite core sample from Well X2 in the Jiyang Depression.

[0068] Step 2. Cathodoluminescence analysis

[0069] 1) The collected core samples were pre-treated by oil washing, glue curing, grinding and two-side polishing, and cut into 5*4*1.5cm rock blocks along the vertical layer, and the rock blocks were made into 0.04mm cathode luminescent slices.

[0070] 2) Use a cathode luminescence instrument to observe the sample. First, place the sample into the sample chamber, make sure the sample chamber is sealed, open the vacuum valve, and evacuate the chamber. When the vacuum degree of the sample chamber reaches the measurement range, observe with a low-power objective lens, and adjust the beam spot size, current, and voltage of the electron beam according to the luminescence intensity of the sample to be measured. The cathode luminescence instrument of the calcite mineral emits orange-red-yellow-orange-red light or dark color. Take photos of the luminescence display of different calcite-containing samples under the microscope and keep them.

[0071] 3) In the cathodoluminescence microscopic observation, the calcite veins appear dark red, indicating that the calcite is rich in Fe during its formation process. It should not be formed by diagenesis, but may be formed by other fluid sources - such as hydrothermal fluids during the sedimentary period. Because the surrounding rocks are all shales, formed in deep water environments, with low Fe / Mn ratios, the calcite veins appear orange-red and other bright colors. Figure 2 The cathode luminescence of the calcite veins in the source rocks of the Lucaogou Formation in Figures c and f in the middle shows dark red, which may be formed by exogenous fluid-hydrothermal fluid. There are some orange-red luminescence features around the calcite veins, which should be formed by later diagenetic metasomatism. Figure 2 The cathode luminescence characteristics of the calcite veins in the Shahejie Formation in the middle i picture are mainly orange-red, indicating that the source of the fluid material forming the calcite may be the surrounding rock and it was formed by late diagenesis.

[0072] Step 3. In situ micro-area major and trace element analysis

[0073] 1) Experimental instruments and conditions

[0074] The instrument for in-situ micro-area major and trace elements is an inductively coupled plasma mass spectrometer equipped with a coherent 193nm excimer laser ablation system. During the laser ablation process, helium is used as the carrier gas and argon is used as the compensation gas to adjust the sensitivity. The two are mixed through a T-type connector before entering the ICP. The laser energy is 80mJ, the frequency is 5Hz, and the laser beam spot diameter is 80μm.

[0075] 2) Micro-area analysis object

[0076] Combined with cathode luminescence photographs, in-situ major and trace element analysis was performed on the calcite veins and adjacent surrounding rocks of different samples;

[0077] 3) Data processing and comparison of rare earth element distribution characteristics

[0078] The rare earth elements in the calcite veins and surrounding rocks of different samples were standardized by chondrites, and the horizontal axis was plotted for the element category and the vertical axis was the logarithmic coordinate of the standardized concentration for different samples. The experimental results are as follows: Figure 3 Figure b in the middle is a schematic diagram of the chondrite standardization of the 3702.67m bedding vein calcite sample from Well X1 in Jimusar Sag. Figure 3 Figure d in the middle is a schematic diagram of the standardized chondrite of the 3711.73 m interlayer vein calcite sample from Well X1 in Jimusar Sag. Figure 3 Figure f in the middle is a schematic diagram of the chondrite standardization of the 3642.13 m bedding-parallel vein calcite sample from Well X2 in the Jiyang Depression.

[0079] contrast Figure 3 Middle B picture and Figure 3 As shown in Figure d, the distribution characteristics of rare earth elements in calcite veins and surrounding rocks in the samples of the Lucaogou Formation in Jimusar Sag. The rare earth element concentration of calcite veins is significantly higher than that of surrounding rocks, indicating that the source of the fluid that formed calcite was not sedimentary water, but should be from hydrothermal fluids, because the calcite formed by hydrothermal fluids has not experienced dilution during transportation and sedimentation, and the concentration is relatively high. On the other hand, the rare earth element distribution pattern of calcite veins is significantly different from that of surrounding rocks. The concentration of heavy rare earth elements (HREE) in calcite veins is similar to that of light rare earth elements (LREE), and the concentration of heavy rare earth elements in surrounding rocks is significantly lower than that of light rare earth elements (LREE), indicating that the source of the material forming the calcite veins is inconsistent with the material transported by terrigenous sources, further indicating that the formation of the calcite veins in the Lucaogou Formation is related to hydrothermal fluids.

[0080] contrast Figure 3 Figure f in the middle shows the rare earth element concentration and distribution pattern of the calcite veins and surrounding rocks of the Shahejie Formation in the Jiyang Depression. The rare earth element concentration of the calcite veins of the Shahejie Formation is much lower than that of the surrounding rocks. In addition, the distribution pattern of heavy rare earth elements and light rare earth elements in the calcite veins is consistent with that of the surrounding rocks, that is, the concentration of heavy rare earth elements is significantly lower than that of light rare earth elements, indicating that the fluid source of the calcite veins of the Shahejie Formation is consistent with that of the surrounding rocks. The overall low concentration is mainly due to the fact that the materials that form the calcite veins come from the surrounding rocks. Affected by the fractionation effect, the concentration of rare earth elements dissolved from the surrounding rocks will become lower, which ultimately leads to a low element concentration in the veins.

[0081] Therefore, the above-mentioned petrological and micro-area element geochemical characteristics can be combined to accurately analyze the origin of calcite veins and identify calcite in the hydrothermal deposition mode.

[0082] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A method for identifying hydrothermal calcite in shale, characterized in that: The method comprises: Sample thin sections were made from calcite samples of the same layer and different occurrences; Conduct cathode luminescence observation on the sample slice to obtain a cathode luminescence photograph; Elemental geochemical analysis was used to determine the rare earth element data of each sample thin section; The formation mode of the sample slice is determined according to the cathode luminescence photograph and the rare earth element data; wherein the formation mode includes: a late diagenetic mode and a hydrothermal deposition calcite mode.

2. The method for identifying hydrothermal calcite in shale according to claim 1, characterized in that: The calcite samples of different occurrences include interlayer calcite samples and bedding-parallel calcite samples.

3. The method for identifying hydrothermal calcite in shale according to claim 1, characterized in that: The sample slices include: calcite vein sample slices and calcite surrounding rock sample slices.

4. The method for identifying calcite deposition patterns according to claim 1, characterized in that: The thickness of the sample slice was 0.04 mm, excluding the cover glass.

5. The method for identifying calcite deposition patterns according to claim 1, characterized in that: The method of determining the rare earth element data of each sample slice by elemental geochemical analysis includes: In-situ micro-area trace element analysis is performed on different sample slices to determine the rare earth element data of each sample slice.

6. The method for identifying calcite deposition patterns according to claim 5, characterized in that: The rare earth elements include: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu elements, among which La, Ce, Pr, Nd, Sm and Eu are light rare earth elements, and Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu are heavy rare earth elements.

7. The method for identifying calcite deposition patterns according to claim 5, characterized in that: After determining the rare earth element data of each sample thin section using elemental geochemical analysis, the method further comprises: Performing chondrite standardization on the rare earth element data to obtain standardized rare earth element data; The rare earth element distribution characteristic curve is established using the standardized rare earth element data.

8. The method for identifying calcite deposition patterns according to claim 1, characterized in that: The process of determining the formation mode of the sample slice according to the cathode luminescence photograph is as follows: If the cathode luminescence is orange-red, it is determined that the sample thin section is a late diagenetic model; If the cathode luminescence is dark red, it is determined that the sample thin section is a hydrothermal deposition calcite model.

9. The method for identifying the calcite formation mode according to claim 7, characterized in that: The process of determining the sample flake formation mode based on the rare earth element data is as follows: If the rare earth element distribution characteristic curve of the thin section of the calcite vein sample is different from the rare earth element distribution characteristic curve of the thin section of the calcite surrounding rock sample, and the rare earth element concentration of the thin section of the calcite vein sample is greater than the rare earth element concentration of the thin section of the calcite surrounding rock sample, then the calcite vein sample thin section is determined to be a hydrothermal deposition model; If the rare earth element distribution characteristic curve of the calcite vein sample thin section is the same as the rare earth element distribution characteristic curve of the calcite surrounding rock sample thin section, and the rare earth element concentration of the calcite vein sample thin section is less than the rare earth element concentration of the calcite surrounding rock sample thin section, then the calcite vein sample thin section is determined to be a late diagenetic depositional model.

10. The method for identifying the calcite formation mode according to claim 9, characterized in that: Determining the formation mode of the sample slice according to the cathode luminescence photograph and the rare earth element data includes: If the luminescence characteristic of the calcite vein sample thin section is dark red, and the rare earth element concentration of the calcite vein sample thin section is greater than the rare earth element concentration of the calcite surrounding rock sample thin section, it is determined that the calcite vein sample thin section is a hydrothermal deposition model; If the luminescence characteristic of the calcite vein sample thin section is orange-red, and the rare earth element concentration of the calcite vein sample thin section is less than the rare earth element concentration of the calcite surrounding rock sample thin section, it is determined that the calcite vein sample thin section was formed by late diagenesis.

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