A sample selection method for fluid inclusion microthermometry

Abstract

The embodiment of the application provides a sample selection method for fluid inclusion micro-thermodynamic test. The method comprises the following steps: scanning a fluid inclusion slice to obtain a scanning image; placing the fluid inclusion slice under an optical microscope, observing and determining the fluid inclusions to be tested and their positions in the fluid inclusion slice through the optical microscope according to a research target; marking image positions corresponding to the positions of the fluid inclusions to be tested on the scanning image; determining final target fluid inclusions for the fluid inclusion micro-thermodynamic test according to comprehensive sample selection criteria based on all the fluid inclusions to be tested found; placing the fluid inclusion slice under the optical microscope again, determining the positions of the final target fluid inclusions in the fluid inclusion slice based on the image positions marked on the scanning image, and circumscribing the positions corresponding to the final target fluid inclusions on the fluid inclusion slice.

Description

Technical Field

[0001] This application relates to the field of fluid inclusion selection technology, specifically to a sample selection method for microthermodynamic testing of fluid inclusions. Background Technology

[0002] With the increasing demands of the petroleum industry for higher levels of oil and gas exploration, research on the detailed definition of hydrocarbon accumulation processes has become increasingly in-depth in recent years. The classification of hydrocarbon charging and accumulation phases, as well as the evolution of reservoir temperature, pressure conditions, and related fluid properties during these phases, are important aspects of quantitative research on hydrocarbon accumulation processes. Fluid inclusions, as micron-sized paleofluids sealed within minerals, serve as direct geological samples for studying these accumulation processes. Microscopic thermodynamic parameters (homogenization temperature, freezing point temperature) are crucial foundational data for fluid inclusions, effectively reconstructing the temperature and pressure conditions during accumulation and thus providing important auxiliary geological information for classifying hydrocarbon charging and accumulation phases based on the petrographic characteristics of fluid inclusions. Obtaining these microscopic thermodynamic parameters requires first conducting detailed microfacies observations of fluid inclusion thin sections using an optical microscope, followed by selecting suitable fluid inclusion samples for microscopic thermodynamic testing—this step is critical.

[0003] However, in related technologies, the sampling process for fluid inclusions typically involves directly marking the location of a potential fluid inclusion on the surface of a thin film using a pencil or marker after observation. This approach has significant drawbacks, specifically as follows:

[0004] If a fluid inclusion section contains numerous potential fluid inclusions to be tested, the locations of these inclusions are often marked on the section surface with pencils or markers to pinpoint their positions. However, since the area of ​​the pencil tip is much larger than that of the mineral grains, the pencil marks will cover the surface of the mineral grains, thus contaminating the surface and further affecting the petrographic observation of the fluid inclusions. This is especially true when the area covered by the marks happens to contain potential fluid inclusions to be tested, and the typicality of the fluid inclusions to be tested in that area is significantly better than that in the previous area, which will result in a significant loss of sample for the study. In addition, if too many circles are drawn on the surface of the fluid inclusion section to pinpoint the location of potential fluid inclusions, it will not only contaminate the fluid inclusion section, but also make it difficult to separate different areas with a blade when preparing small mineral sections for microscopic thermodynamic testing. This may increase the probability of irregular fragmentation of the mineral section, thus damaging the fluid inclusion sample to be tested. Summary of the Invention

[0005] This application provides a sample selection method for microthermodynamic testing of fluid inclusions, which solves the problem in related technologies that contaminate fluid inclusion slices and, during the subsequent preparation of small mineral slices of fluid inclusions for microthermodynamic testing, some areas may be very close together, making it difficult to cut and separate different areas with a blade, which may increase the probability of irregular breakage of the mineral slices and thus damage the fluid inclusion sample to be tested.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] This application provides a sample selection method for microthermodynamic testing of fluid inclusions, the method comprising:

[0008] The fluid inclusion thin section was scanned to obtain the scanned image;

[0009] The fluid inclusion sheet is placed under an optical microscope, and the fluid inclusion to be tested and its location in the fluid inclusion sheet are observed and determined through the optical microscope according to the research objective.

[0010] Mark the image position corresponding to the position of the fluid inclusion to be tested on the scanned image;

[0011] Based on all the fluid inclusions to be tested discovered, the final target fluid inclusions for the microthermodynamic testing of fluid inclusions were determined according to a comprehensive sampling criterion.

[0012] The fluid inclusion sheet is placed under the optical microscope again, and the position of the final target fluid inclusion in the fluid inclusion sheet is determined based on the image position marked on the scan image. The position corresponding to the final target fluid inclusion is then delineated on the fluid inclusion sheet.

[0013] Optionally, the fluid inclusion sheet is placed under the optical microscope, and the test fluid inclusion and its location within the fluid inclusion sheet are observed and determined using the optical microscope according to the research objective, including:

[0014] The magnification of the optical microscope is set to the first magnification. Based on the research objective, the fluid inclusions to be tested and their locations are observed and determined by the optical microscope at the first magnification. The host minerals that capture the fluid inclusions to be tested and the spatial occurrence characteristics of the fluid inclusions to be tested as a combination of fluid inclusions at the micrometer scale are also determined.

[0015] The observation magnification of the optical microscope is set to a second magnification. The petrographic features of a single fluid inclusion in the host mineral are determined by the optical microscope at the second magnification, and the coordinates of the fluid inclusion on the stage of the optical microscope are determined. The second magnification is greater than the first magnification.

[0016] The coordinates of the fluid inclusion to be tested on the stage of the optical microscope are used as the position of the fluid inclusion to be tested.

[0017] Optionally, before setting the magnification of the optical microscope from the first magnification to the second magnification, the method further includes:

[0018] The first micrograph is obtained by taking a microscopic photograph of the fluid inclusion to be tested at the first magnification using the optical microscope.

[0019] Before using the coordinates of the fluid inclusion to be tested on the stage of the optical microscope as the position of the fluid inclusion to be tested, the method further includes:

[0020] The fluid inclusions to be tested are photographed using the optical microscope at the second magnification to obtain a second micrograph.

[0021] Optionally, based on all the discovered fluid inclusions to be tested, and according to a comprehensive sampling criterion, the final target fluid inclusions for microthermodynamic testing of the fluid inclusions are determined, including:

[0022] Based on all the fluid inclusions to be tested discovered, and according to comprehensive sampling criteria, the first micrograph, the second micrograph, and the image position on the scanned image, the final target fluid inclusions for microthermodynamic testing of fluid inclusions are determined.

[0023] Optionally, observing and determining the location of the fluid inclusion to be tested in the fluid inclusion sheet using the optical microscope includes:

[0024] The location of the fluid inclusions to be tested and the target area where the fluid inclusions to be tested are located are observed and determined using the optical microscope.

[0025] Optionally, the target region includes multiple fluid inclusions to be tested;

[0026] The step of observing and determining the location of the fluid inclusions to be tested in the fluid inclusion sheet using the optical microscope includes:

[0027] The location of any one of the fluid inclusions to be tested in the target area is observed and determined using the optical microscope, and the determined location is used as the location of other fluid inclusions to be tested in the target area.

[0028] Optionally, the optical microscope has a mechanical stage for fixing the fluid inclusion sheet on its stage. The mechanical stage has a first coordinate axis and a second coordinate axis, the first coordinate axis is perpendicular to the second coordinate axis, and the stage can rotate 360° horizontally.

[0029] Determining the coordinates of the fluid inclusion to be tested on the stage of the optical microscope includes:

[0030] Determine the readings of the fluid inclusion body under test on the first coordinate axis and the second coordinate axis of the mechanical stage, and determine the rotation angle of the stage;

[0031] The readings on the first coordinate axis, the readings on the second coordinate axis, and the rotation angle of the stage are used as the coordinates of the fluid inclusion to be tested on the stage of the optical microscope.

[0032] Optionally, the comprehensive sampling criteria include petrographic features and the number of fluid inclusions to be tested in different target areas, as well as the distance between different target areas.

[0033] In this embodiment, a fluid inclusion sheet is scanned to obtain a scanned image, wherein fluid inclusions are developed within the fluid inclusion sheet. The fluid inclusion sheet is placed under an optical microscope, and the fluid inclusions to be tested and their positions within the fluid inclusion sheet are observed and determined according to the research objective. The image positions corresponding to the positions of the fluid inclusions to be tested are marked on the scanned image. Based on all the fluid inclusions to be tested discovered, the final target fluid inclusions for microthermodynamic testing of fluid inclusions are selected according to comprehensive sampling criteria. The position of the final target fluid inclusion on the fluid inclusion sheet is determined based on the image positions of the fluid inclusions to be tested. The position of the final target fluid inclusion is marked on the fluid inclusion sheet. In other words, in this embodiment, a scanned image of a fluid inclusion slice is obtained by scanning the fluid inclusion slice. Then, based on the research objective, the fluid inclusions to be tested and their positions within the fluid inclusion slice are observed and determined using an optical microscope. The image positions of the fluid inclusions to be tested are then marked on the scanned image. Next, based on comprehensive sampling criteria, the final target fluid inclusion for microscopic thermodynamic testing is selected from all fluid inclusions found in the entire fluid inclusion slice. Then, based on the image positions of the fluid inclusions to be tested, the position of the final target fluid inclusion on the fluid inclusion slice is determined. Finally, the position of the final target fluid inclusion is marked on the fluid inclusion slice. This method effectively avoids the problem of interference caused by directly marking too many positions on the fluid inclusion slice when observing the fluid inclusion slice under an optical microscope, thus ensuring efficient observation of the fluid inclusion slice. Meanwhile, this method can make the annotations on the fluid inclusion thin slices more representative, that is, only the final target fluid inclusions to be tested are annotated, so that only the most typical target fluid inclusions are subjected to subsequent microscopic thermodynamic testing and analysis, thereby saving experimental testing time and financial costs and greatly improving research efficiency. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating a sample selection method for microthermodynamic testing of fluid inclusions provided in an embodiment of this application;

[0035] Figure 2 This illustration shows a schematic diagram of marking the target area where all the fluid inclusions to be tested are found on a fluid inclusion sheet scan image provided by this application embodiment;

[0036] Figure 3 This is a schematic diagram showing the target region of the final test fluid inclusion determined based on comprehensive sampling criteria, as marked on a thin-film scan image of the fluid inclusion, according to an embodiment of this application. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0039] Reference Figure 1 The diagram illustrates a flowchart of a sample selection method for microthermodynamic testing of fluid inclusions, provided in an embodiment of this application. Figure 1 As shown, the sample selection method for microthermodynamic testing of fluid inclusions includes:

[0040] Step 101: Scan the fluid inclusion thin film to obtain a scanned image.

[0041] A scanner can be used to scan fluid inclusion sheets to obtain scanned images. The scanner can produce two-dimensional images, thus allowing for the generation of two-dimensional scanned images of fluid inclusion sheets. Furthermore, high-resolution scanners are preferred.

[0042] It should be noted that when the scanner can perform high-resolution scanning imaging of fluid inclusion thin sections in both single-polarized light and cross-polarized light optical modes, it is only necessary to select the single-polarized light mode to obtain a high-resolution scan image and save the original electronic image.

[0043] Step 102: Place the fluid inclusion slice under an optical microscope and, based on the research objective, observe and determine the fluid inclusions to be tested and their locations within the fluid inclusion slice using an optical microscope.

[0044] Since the fluid inclusions in fluid inclusion slices are typically on the micrometer scale, they are difficult for operators to observe directly with the naked eye. Therefore, it is necessary to place the fluid inclusion slices under an optical microscope to observe the fluid inclusions within the slices, and then, based on the research objectives, determine the fluid inclusions to be tested and their locations within the fluid inclusion slices.

[0045] It should be noted that the optical microscopes used must be polarizing microscopes and fluorescence microscopes. The selected fluorescence microscope must be configured with ultraviolet fluorescence mode. In this mode, microscopic fluorescence observation of fluid inclusion thin sections is performed to distinguish between brine inclusions and hydrocarbon inclusions containing liquid unsaturated hydrocarbons, and to identify the fluorescence color of liquid unsaturated hydrocarbons under fluorescence excitation. When the optical microscope is a polarizing microscope, microscopic petrographic features of all types of fluid inclusions in the fluid inclusion thin sections are observed under single polarized light. Specific aspects of microscopic petrographic feature observation of fluid inclusion thin sections using polarizing and fluorescence microscopes include: the type, size, shape, color, phase, gas-liquid ratio, bubble agitation rate, fluorescence, phase number, and distribution and occurrence of the fluid inclusions.

[0046] In some implementations, step 102 can be implemented as follows: The magnification of the optical microscope is set to a first magnification. Based on the research objective, the fluid inclusions to be tested and their locations are observed and determined using the optical microscope at the first magnification. The host minerals that capture the fluid inclusions to be tested and the spatial occurrence characteristics of the fluid inclusion assemblages containing the fluid inclusions to be tested at the micrometer scale are also determined. The magnification of the optical microscope is set to a second magnification. The petrographic characteristics of individual fluid inclusions to be tested within the host minerals are determined using the optical microscope at the second magnification. The coordinates of the fluid inclusions to be tested on the stage of the optical microscope are also determined. The second magnification is greater than the first magnification. The coordinates of the fluid inclusions on the stage of the optical microscope are used as the location of the fluid inclusions to be tested.

[0047] Because fluid inclusions are trapped within host minerals, when observing the fluid inclusions under an optical microscope, it is necessary to first locate the host mineral that has trapped them. Since the host mineral is relatively large compared to the fluid inclusions, a lower magnification of the optical microscope can be used. The host mineral is located first in the fluid inclusion section, and then the individual fluid inclusion to be tested is located within the host mineral. Specifically, the optical microscope is set to its first magnification, and the spatial occurrence characteristics of the host mineral trapping the fluid inclusion and the fluid inclusion assemblages containing it at the micrometer scale are determined using this first magnification. Then, the optical microscope is set to its second magnification, and the petrographic characteristics of the individual fluid inclusion to be tested within the host mineral are determined using this second magnification.

[0048] Fluid inclusion assemblages refer to a group of fluid inclusions that formed approximately at the same time and are genetically related in petrography. The possible spatial distribution of fluid inclusion assemblages includes: distribution along the growth lattice of mineral crystals, along microscopic healed fractures, and along grain deformation boundaries. Furthermore, the petrographic characteristics of fluid inclusions include: size, shape, color, phase, gas-liquid ratio, and fluorescence.

[0049] It should be noted that setting the observation magnification of an optical microscope to the first magnification is achieved by switching between different magnification objectives. Similarly, setting the observation magnification to the second magnification is also achieved by switching between different magnification objectives. Both the first and second magnifications can be set according to actual needs, as long as the first magnification is less than the second magnification. For example, a 10x or 20x objective lens can be used for the first magnification observation, while a 50x, 63x, or 100x objective lens can be used for the second magnification observation.

[0050] It should also be noted that the research objectives for fluid inclusion studies in hydrocarbon-bearing sedimentary basins mainly include three aspects: the first objective is to reconstruct the evolution of temperature and pressure conditions during reservoir diagenesis; the second objective is to classify hydrocarbon charging and accumulation phases and determine the charging and accumulation time; and the third objective is to reconstruct the evolution of reservoir temperature and pressure conditions during key hydrocarbon accumulation phases. Specifically, the first objective focuses on fluid inclusions captured in diagenetic minerals from different phases. Since hydrocarbon charging and accumulation is part of the diagenetic event, the first objective also focuses on fluid inclusions captured in relevant diagenetic minerals during the hydrocarbon charging and accumulation stage. The second and third objectives focus only on fluid inclusions captured during the hydrocarbon charging and accumulation stage, namely hydrocarbon inclusions from different phases and their associated contemporaneous brine inclusions.

[0051] In the embodiments of this application, the relevant diagenetic minerals in the oil and gas sedimentary basins mainly include: authigenic quartz, various types of carbonate minerals (calcite, dolomite, ferrocalcite, ferrodolithite, siderite), zeolite minerals (turbidite, analcime, zeolite), anhydrite, fluorite, etc.

[0052] In addition, in some implementations, before setting the magnification of the optical microscope to the second magnification, the method may further include: taking a microscopic photograph of the fluid inclusion to be tested at the first magnification using the optical microscope to obtain a first microscopic photograph; before using the coordinates of the fluid inclusion to be tested on the stage of the optical microscope as the position of the fluid inclusion to be tested, the method may further include: taking a microscopic photograph of the fluid inclusion to be tested at the second magnification using the optical microscope to obtain a second microscopic photograph.

[0053] The optical microscope has a photographic function. Before setting the magnification to the second magnification, a first micrograph is taken at the first magnification of the fluid inclusion to be tested. This is equivalent to taking a micrograph of the host mineral that captures the fluid inclusion within a thin section of the fluid inclusion, thus obtaining a micrograph of the host mineral. Before using the coordinates of the fluid inclusion on the stage of the optical microscope as the position of the fluid inclusion to be tested, a second micrograph is taken at the second magnification of the optical microscope, thus obtaining a micrograph of a single fluid inclusion within a thin section of the fluid inclusion. The micrograph of the host mineral records the petrographic characteristics of the host mineral and the fluid inclusion assemblages containing the fluid inclusion to be tested. The micrograph of the fluid inclusion to be tested records the petrographic characteristics of the individual fluid inclusion, facilitating subsequent comparisons or operations based on the petrographic characteristics of the fluid inclusions.

[0054] In addition, in some implementations, the location of the fluid inclusion to be tested in the fluid inclusion sheet can be determined by observing and determining the location of the fluid inclusion to be tested and the target area where the fluid inclusion to be tested is located in the fluid inclusion sheet by observing and determining the location of the fluid inclusion to be tested in the fluid inclusion sheet and the target area where the fluid inclusion to be tested is located by observing and determining the location of the fluid inclusion to be tested in the fluid inclusion sheet by using an optical microscope.

[0055] In the process of observing and determining the location of the fluid inclusions to be tested and the target region of the fluid inclusions in a fluid inclusion thin film using an optical microscope, as many potential fluid inclusions to be tested and their target regions as possible can be selected for microscopic thermodynamic testing. Specifically, under an optical microscope, after observing the entire fluid inclusion thin film, all potential fluid inclusions to be tested and their target regions should be searched for. Figure 2 As shown, in Figure 2 In the diagram, circles represent the target area containing the fluid inclusion to be tested; numbers represent the identification number of the target area. The entire fluid inclusion sheet refers to the entire area of ​​the mineral slide bonded to the surface of the glass slide with adhesive.

[0056] It should be noted that the potential fluid inclusions to be tested are: when the first research objective is achieved, specifically gas-liquid two-phase brine inclusions captured in relevant diagenetic minerals of each stage; when the second and third research objectives are achieved, specifically gas-liquid two-phase brine inclusions associated with hydrocarbon inclusions of different stages captured during the hydrocarbon charging and accumulation stage. These gas-liquid two-phase brine inclusions can be captured in the crystals of relevant diagenetic minerals or in the micro-healed fractures of grains in the diagenetic stage.

[0057] Furthermore, when observing the entire range of fluid inclusion sections using an optical microscope, each potential fluid inclusion to be tested needs to be moved to the center of the crosshairs of the eyepiece by adjusting the mechanical stage on the optical microscope stage. Simultaneously, photomicrographs need to be taken at the first magnification of the optical microscope and at the second magnification.

[0058] In addition, in this embodiment, potential fluid inclusions to be tested and their corresponding target regions need to be numbered according to the order of discovery. Specifically, potential fluid inclusions to be tested and their corresponding target regions need to be numbered according to the order of discovery. This numbering allows for quick determination of the number of fluid inclusions to be tested and the corresponding number of target regions within the fluid inclusion slice, facilitating a rapid understanding of the distribution information of the fluid inclusion samples within the fluid inclusion slice. In this embodiment, the target region is the host mineral.

[0059] The numbering rules can be as follows: the numbering pattern of potential fluid inclusions to be tested is set as "potential fluid inclusion to be tested + serial number", for example: potential fluid inclusion to be tested 1, potential fluid inclusion to be tested 2, potential fluid inclusion to be tested 3, and so on; the numbering pattern of the target area where the potential fluid inclusion to be tested is located is set as "target area + serial number", for example: target area 1, target area 2, target area 3, and so on.

[0060] It should be noted that the number of potential fluid inclusions to be tested in each target region can be one or more. When recording the observation results, it is necessary to record them accurately. For example, target region 1 includes 5 potential fluid inclusions to be tested (1-5), and target region 2 includes 3 potential fluid inclusions to be tested (6-8).

[0061] In addition, in some implementations, the target region includes multiple fluid inclusions to be tested; the implementation method of observing and determining the position of the fluid inclusions to be tested in the fluid inclusion sheet by optical microscopy can be: observing and determining the position of any one fluid inclusion to be tested in the target region by optical microscopy, and using the determined position as the position of other fluid inclusions to be tested in the target region.

[0062] If multiple fluid inclusions to be tested exist in the same target area, i.e., in the same host mineral, since these fluid inclusions to be tested are in the same target area, i.e., they are located in the same host mineral and are close to each other, it is sufficient to select any one of the fluid inclusions to be tested to obtain its location information. The location of any one fluid inclusion to be tested can be used as the location of other fluid inclusions to be tested in the target area.

[0063] It should be noted that the location of any fluid inclusion to be tested serves as the basis for subsequent relocation of the host mineral, as well as for locating other fluid inclusions to be tested in this target area.

[0064] In some implementations, the stage of the optical microscope is equipped with a mechanical stage for fixing the fluid inclusion sheet. The mechanical stage has a first coordinate axis and a second coordinate axis, the first coordinate axis is perpendicular to the second coordinate axis, and the stage can rotate horizontally by 360°. The method for determining the coordinates of the fluid inclusion to be tested on the stage of the optical microscope can be as follows: determine the readings of the fluid inclusion to be tested on the first coordinate axis and the second coordinate axis of the mechanical stage, and determine the rotation angle of the stage; use the readings on the first coordinate axis, the readings on the second coordinate axis of the mechanical stage, and the rotation angle of the stage as the coordinates of the fluid inclusion to be tested on the stage of the optical microscope.

[0065] Because the mechanical stage on the optical microscope stage has a first coordinate axis and a second coordinate axis, with the first coordinate axis perpendicular to the second, determining the coordinates of the fluid inclusion to be tested involves determining the readings of the fluid inclusion on the first and second coordinate axes, as well as the rotation angle of the stage—that is, determining two readings and one rotation angle. After determining the readings on the first and second coordinate axes, and the rotation angle of the stage, these two readings and the rotation angle can be used as the coordinates of the fluid inclusion on the optical microscope stage, thus determining its coordinates. Furthermore, after determining the coordinates of the fluid inclusion on the optical microscope stage, it is possible to quickly and effectively reposition and locate the potential fluid inclusion using the optical microscope, and also to quickly and effectively relocate the target area where the fluid inclusion is located.

[0066] It should be noted that when determining the readings of the fluid inclusions under test on the first coordinate axis, the readings on the second coordinate axis, and the rotation angle of the stage, the fluid inclusions under test need to be kept at the center of the crosshairs of the eyepiece of the optical microscope to ensure the accuracy of the coordinates of the fluid inclusions under test on the stage of the optical microscope.

[0067] Furthermore, in this embodiment, when observing fluid inclusion sections using an optical microscope, the rotation angle of the stage can be set to 90°. This facilitates both the observation of microscopic petrographic features of the fluid inclusion sections and the recording of the location information of potential fluid inclusions to be tested. In this state, the long side of the fluid inclusion section held on the mechanical stage of the stage is perpendicular to the observer's line of sight, and the short side of the fluid inclusion section is parallel to the observer's line of sight. Of course, the rotation angle of the stage can also be other values, for example, a rotation angle of 60°, or even 45°. This embodiment does not limit the specific values ​​in this regard.

[0068] In addition, in this embodiment of the application, when recording the position of a potential fluid inclusion to be tested, the orientation information of the fluid inclusion sheet placed on the mechanical stage of the stage can also be recorded, that is, the left and right order of the fluid inclusion sheet, so as to avoid the positioning failure caused by the 180° orientation reversal when repositioning the potential fluid inclusion to be tested due to the left and right order of the fluid inclusion sheet being reversed.

[0069] Step 103: Mark the image position corresponding to the position of the fluid inclusion to be tested on the scanned image.

[0070] In this process, after the scanner scans the fluid inclusion sheet, a scanned image is obtained. The scanned image then corresponds to the fluid inclusion sheet. Once the location of the fluid inclusion to be tested in the fluid inclusion sheet is determined, the corresponding image location can be found on the scanned image.

[0071] Specifically, once each potential fluid inclusion to be tested is detected under an optical microscope, its location is marked on the scanned image. This can be achieved by opening the scanned image of the fluid inclusion section using image processing software. After locating the host mineral that captured the potential fluid inclusion, the markings can be made on the scanned image, such as... Figure 2 As shown. When annotating a scanned image, circles or other shapes can be drawn for annotation, such as triangles. The specific shape used for annotation is not limited in this embodiment. The color of the annotated shape should be bright for easy identification.

[0072] In addition, in this embodiment of the application, detailed coordinate information of the host mineral on the stage can also be recorded on the scanned image of the fluid inclusion sheet. The coordinate information refers to the position information of any potential fluid inclusion to be tested within the host mineral to determine the coordinate information of the host mineral. The coordinate information includes the readings of the first coordinate axis, the readings of the second coordinate axis, and the rotation angle of the stage read from the mechanical stage.

[0073] In addition, in this embodiment of the application, if the potential fluid inclusions to be tested and their target areas are numbered according to the order of discovery, the number of the target area where the fluid inclusion to be tested is located and the numbering information of all the fluid inclusions to be tested in the target area can also be recorded on the scanned image of the fluid inclusion sheet.

[0074] In addition, the target area is the host mineral where the fluid inclusions to be tested are located. Once the location of the corresponding host mineral is determined, all fluid inclusions to be tested within that host mineral can be efficiently located and searched in the subsequent process.

[0075] Step 104: Based on all the fluid inclusions to be tested discovered, and according to the comprehensive sampling criteria, determine the final target fluid inclusions for the microthermodynamic testing of fluid inclusions.

[0076] The comprehensive sampling criteria include petrographic characteristics, the number of fluid inclusions to be tested in different target areas, and the distance between different target areas. Petrographic characteristics refer to the size, shape, gas-liquid ratio, bubble agitation rate, etc., of individual potential fluid inclusions to be tested.

[0077] In some implementations, step 104 can be implemented as follows: based on all the fluid inclusions to be tested found, and according to the comprehensive sampling criteria, the first micrograph, the second micrograph, and the image position on the scanned image, the final target fluid inclusion for the microthermodynamic testing of the fluid inclusions is determined.

[0078] The first micrograph is a micrograph of the host mineral that captures the fluid inclusions to be tested, the second micrograph is a micrograph of a single fluid inclusion to be tested, and the image position on the scanned image is the position of the fluid inclusion to be tested on the scanned image of the fluid inclusion slice.

[0079] In addition, based on comprehensive sampling criteria, the first and second micrographs, the image positions on the scanned images, and other information recorded on the scanned images, the final target fluid inclusions for microthermodynamic testing of fluid inclusions can be determined. Other information includes, but is not limited to, the identification number of the fluid inclusion to be tested, the orientation of the fluid inclusion slice on the mechanical stage, the location of the target region where the fluid inclusion to be tested is located, and the number of potential fluid inclusions to be tested in each target region.

[0080] In addition, when determining the final target fluid inclusion for microthermodynamic testing of fluid inclusions based on comprehensive sampling criteria, the first micrograph, the second micrograph, the image position on the scanned images, and other information recorded on the scanned images, the following six principles must be met simultaneously. The six principles are as follows:

[0081] The first principle is that the size (major axis) of a single potential fluid inclusion to be tested should not be less than 2 μm. This fluid inclusion size is the minimum size requirement that will allow for successful subsequent micro-thermodynamic testing of fluid inclusions. In sedimentary rocks, the optimal size for a single potential fluid inclusion to be tested is 5-10 μm.

[0082] The second principle is that the shape of a single potential fluid inclusion to be tested should preferably be regular. Regular shapes can be: circular, near-circular, elliptical, elongated, triangular, rectangular, and square, etc.; while irregularly shaped potential fluid inclusions to be tested are not preferred because such fluid inclusions may have undergone later modification and rebalancing or rupture and leakage of fluid.

[0083] The third principle is that the selected single potential fluid inclusion to be tested should be a gas-liquid two-phase brine inclusion. The volume of the air bubbles in the gas-liquid two-phase brine inclusion should not be too large, and the gas-liquid ratio should be between 5% and 20% for optimal results.

[0084] The fourth principle is that the preferred gas-liquid two-phase brine inclusions should be fluid inclusions in which the bubbles are visibly jumping due to Brownian motion. Gas-liquid two-phase brine inclusions in which the bubbles do not jump are not preferred.

[0085] The fifth principle is to compare the number of fluid inclusions developed in different target regions and select the target region with the relatively larger number as the preferred region.

[0086] The sixth principle is to take into account the distance between different target areas. In order to facilitate the subsequent preparation of small fluid inclusion mineral pieces for microthermodynamic testing of fluid inclusions by cutting with a blade, the distance between different target areas should not be too close. If different target areas are too close to each other, it is necessary to combine the first, second, third, fourth and fifth principles mentioned above to select and determine the optimal target area.

[0087] Based on the above six sampling principles, the final target fluid inclusion sample and its target region for microthermodynamic testing of fluid inclusions were determined, such as... Figure 3 As shown, in Figure 3 In the diagram, circles represent the target regions where the fluid inclusions to be tested are located; numbers represent the number of the target regions where the fluid inclusions to be tested are located; all selected final target fluid inclusion samples are the most typical and most suitable samples for performing microthermodynamic tests on each fluid inclusion thin section.

[0088] Step 105: Place the fluid inclusion slice under the optical microscope again, determine the position of the final target fluid inclusion in the fluid inclusion slice based on the image position on the scan image, and delineate the position corresponding to the final target fluid inclusion on the fluid inclusion slice.

[0089] Specifically, step 105 can be implemented as follows;

[0090] Step (a): Place the fluid inclusion thin slices on the mechanical stage of the optical microscope stage in the correct left-right orientation, and at the same time, adjust the rotation angle of the stage to the preset angle, for example, adjust the rotation angle to 90°.

[0091] Step (b): Based on the location of the host mineral containing the final target fluid inclusion delineated in the scanned image of the fluid inclusion section and the specific coordinates of the host mineral, set the magnification of the optical microscope to the first magnification and observe to find the corresponding host mineral at the first magnification. Then, based on the occurrence characteristics shown in the microfacies photograph of the final target fluid inclusion, locate the corresponding final target fluid inclusion in the host mineral. When locating the final target fluid inclusion, the fluid inclusion section needs to be moved by adjusting the mechanical stage to move the final target fluid inclusion under the crosshairs of the eyepiece of the optical microscope. If there are multiple final target fluid inclusions in the host mineral, only one needs to be selected for location and moved under the crosshairs of the eyepiece of the optical microscope. When using the optical microscope to observe and locate the final target fluid inclusion and its host mineral, it must be done in single polarized light mode.

[0092] Step (c): Adjust the aperture size of the optical microscope so that the circular aperture area through which the single-polarized light penetrates the fluid inclusion thin slice gradually decreases until the reduced circular aperture area covers the entire host mineral; if the host mineral particles are large, the reduced circular aperture area only needs to cover all the final target fluid inclusions in the host mineral; in addition, the diameter of the reduced circular aperture is best between 3-4 mm.

[0093] Step (d): Once the circular aperture has shrunk to a suitable size, use a marker to trace the outline projected by the circular aperture onto the surface of the fluid inclusion sheet, thereby locating the final test target fluid inclusion and its target area on the fluid inclusion sheet. A 2B pencil is preferred as the marker, and the tip should be fine, not coarse.

[0094] For the fluid inclusion sheet, repeat steps (a) to (d) until all the selected final test target fluid inclusions and their target regions are delineated on the fluid inclusion sheet.

[0095] It should be noted that in step (c), the diameter of the reduced circular aperture is best between 3-4 mm for the following reasons: When preparing small fluid inclusion plates for subsequent microthermodynamic testing of fluid inclusions, it is necessary to cut out the defined target area with a blade, and the size of the cut fluid inclusion plates needs to be able to be placed in the quartz crucible of the hot and cold stage equipment for microthermodynamic testing. The inner diameter of the quartz crucible is 15 mm, and the length of each side of the prepared fluid inclusion plates should usually be controlled at around 5-7 mm. Therefore, the diameter of the reduced circular aperture is best set at 3-4 mm.

[0096] It should also be noted that in step (d), a 2B pencil is preferred for the following reason: In the subsequent preparation of small fluid inclusion slides for microthermodynamic testing, a crucial step is to immerse the entire fluid inclusion slide in acetone to dissolve the adhesive, separating the slide from the glass slide and facilitating subsequent cutting. Since the pencil lead is primarily composed of graphite, the graphite markings will not dissolve in the acetone solution, thus preserving the clear and intact location markings of the final target fluid inclusion on the surface of the slide. If an oil-based marker is used instead, the ink will be easily dissolved and destroyed by the acetone solution, leading to the disappearance of the final location markings of the target fluid inclusion on the surface of the slide. In addition, the darker color of the 2B pencil makes the final location markings of the fluid inclusions to be tested, drawn on the surface of the fluid inclusion sheet with a 2B pencil, clearer and easier to identify.

[0097] In this embodiment, a fluid inclusion sheet is scanned to obtain a scanned image; the fluid inclusion sheet is placed under an optical microscope, and the fluid inclusions to be tested and their positions in the fluid inclusion sheet are observed and determined according to the research objective; the image positions corresponding to the positions of the fluid inclusions to be tested are marked on the scanned image; based on all the fluid inclusions to be tested found, the final target fluid inclusions for microthermodynamic testing of fluid inclusions are determined according to a comprehensive sampling criterion; the fluid inclusion sheet is placed under an optical microscope again, and the position of the final target fluid inclusion in the fluid inclusion sheet is determined based on the image positions on the scanned image, and the position corresponding to the final target fluid inclusion is delineated on the fluid inclusion sheet. In other words, in this embodiment, a scanned image is obtained by scanning a fluid inclusion sheet. Then, the test fluid inclusion and its location are observed and determined using an optical microscope. The image location of the test fluid inclusion is then marked on the scanned image. The final location of the target fluid inclusion is determined, and finally, the final location of the target fluid inclusion is delineated on the fluid inclusion sheet. This effectively avoids the problem of contaminating the fluid inclusion sheet due to excessive markings, which would affect the observation of the fluid inclusion sheet under an optical microscope. This ensures efficient observation of the fluid inclusion sheet. Furthermore, the markings on the fluid inclusion sheet are more representative, as only the final target fluid inclusion is marked. This allows for subsequent microscopic thermodynamic testing and analysis only on the most typical target fluid inclusions, resulting in highly representative test data. It also avoids wasting time and money testing atypical target fluid inclusion samples and greatly improves research efficiency.

[0098] In addition, in the embodiments of this application, the interval between the selected final target areas is moderate, which facilitates efficient subsequent cutting to prepare small mineral fragments of fluid inclusions for microthermodynamic testing of fluid inclusions, and greatly reduces the probability of irregular breakage of the mineral fragments, thereby avoiding damage to the fluid inclusion sample to be tested.

[0099] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0100] Although optional embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the optional embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0101] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used merely to distinguish one entity from another, and do not necessarily require or imply any such actual relationship or order between these entities. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or terminal device that includes that element.

[0102] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the principles and implementation methods of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A sample selection method for microthermodynamic testing of fluid inclusions, characterized in that, The method includes: The fluid inclusion thin section was scanned using a scanner to obtain the scanned image; The fluid inclusion sheet is placed under an optical microscope, and the fluid inclusion to be tested and its location in the fluid inclusion sheet are observed and determined through the optical microscope according to the research objective. Mark the image position corresponding to the position of the fluid inclusion to be tested on the scanned image; Based on all the fluid inclusions to be tested discovered, the final target fluid inclusions for microthermodynamic testing of fluid inclusions are determined according to a comprehensive selection criterion, which includes petrographic characteristics, the number of fluid inclusions to be tested in different target regions, and the distance between different target regions. The fluid inclusion sheet is placed under the optical microscope again, and the position of the final target fluid inclusion in the fluid inclusion sheet is determined based on the image position on the scanned image. The position corresponding to the final target fluid inclusion is then delineated on the fluid inclusion sheet.

2. The sample selection method for microthermodynamic testing of fluid inclusions according to claim 1, characterized in that, The fluid inclusion slice is placed under the optical microscope, and the fluid inclusions to be tested and their locations within the fluid inclusion slice are observed and determined using the optical microscope according to the research objective, including: The magnification of the optical microscope is set to the first magnification. Based on the research objective, the fluid inclusions to be tested and their locations are observed and determined by the optical microscope at the first magnification. The host minerals that capture the fluid inclusions to be tested and the spatial occurrence characteristics of the fluid inclusions to be tested as a combination of fluid inclusions at the micrometer scale are also determined. The observation magnification of the optical microscope is set to a second magnification. The petrographic features of a single fluid inclusion in the host mineral are determined by the optical microscope at the second magnification, and the coordinates of the fluid inclusion on the stage of the optical microscope are determined. The second magnification is greater than the first magnification. The coordinates of the fluid inclusion to be tested on the stage of the optical microscope are used as the position of the fluid inclusion to be tested.

3. The sample selection method for microthermodynamic testing of fluid inclusions according to claim 2, characterized in that, Before setting the magnification of the optical microscope to the second magnification, the method further includes: The first micrograph is obtained by taking a microscopic photograph of the fluid inclusion to be tested at the first magnification using the optical microscope. Before using the coordinates of the fluid inclusion to be tested on the stage of the optical microscope as the position of the fluid inclusion to be tested, the method further includes: The fluid inclusions to be tested are photographed using the optical microscope at the second magnification to obtain a second micrograph.

4. The sample selection method for microthermodynamic testing of fluid inclusions according to claim 3, characterized in that, Based on the discovery of all the fluid inclusions to be tested, and according to a comprehensive selection criterion, the final target fluid inclusions for microthermodynamic testing of the fluid inclusions are determined, including: Based on all the fluid inclusions to be tested discovered, and according to comprehensive sampling criteria, the first micrograph, the second micrograph, and the image position on the scanned image, the final target fluid inclusions for microthermodynamic testing of fluid inclusions are determined.

5. The sample selection method for microthermodynamic testing of fluid inclusions according to claim 1, characterized in that, The step of observing and determining the location of the fluid inclusions to be tested in the fluid inclusion sheet using the optical microscope includes: The location of the fluid inclusions to be tested and the target area where the fluid inclusions to be tested are located are observed and determined using the optical microscope.

6. The sample selection method for microthermodynamic testing of fluid inclusions according to claim 5, characterized in that, The target region includes multiple fluid inclusions to be tested; The step of observing and determining the location of the fluid inclusions to be tested in the fluid inclusion sheet using the optical microscope includes: The location of any one of the fluid inclusions to be tested in the target area is observed and determined using the optical microscope, and the determined location is used as the location of other fluid inclusions to be tested in the target area.

7. The sample selection method for microthermodynamic testing of fluid inclusions according to claim 2, characterized in that, The optical microscope has a mechanical stage on its stage for fixing the fluid inclusion sheet. The mechanical stage has a first coordinate axis and a second coordinate axis. The first coordinate axis is perpendicular to the second coordinate axis, and the stage can rotate 360° horizontally. Determining the coordinates of the fluid inclusion to be tested on the stage of the optical microscope includes: Determine the readings of the fluid inclusion body under test on the first coordinate axis and the second coordinate axis, and determine the rotation angle of the stage; The readings on the first coordinate axis, the readings on the second coordinate axis, and the rotation angle of the stage are used as the coordinates of the fluid inclusion to be tested on the stage of the optical microscope.

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