Method and device for in-situ determination of quartz oxygen isotope in shale

Abstract

The invention provides a method and a device for in-situ determination of quartz oxygen isotope in shale, and relates to the technical field of geological prospecting, the method comprises the following steps: crushing or cutting a shale core sample to obtain a core square block, embedding the core square block into a metal target, and pre-treating to obtain a shale sample; scanning and photographing the surface of the shale sample according to a preset mode, splicing a reflected light panoramic image, judging quartz attribute characteristics and cause types of a test target through observation, and delineating the position of the test target; positioning the position of a test target according to the morphology characteristics of the test target and different surrounding reference objects in combination with the reflected light panoramic image, and performing in-situ oxygen isotope test on the test target by using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope test data; and checking each in-situ oxygen isotope measuring point pit position of the shale sample, performing quality control on in-situ oxygen isotope test data according to a checking result, and determining an in-situ oxygen isotope measuring result.

Description

Technical Field

[0001] The present invention relates to the field of geological exploration technology, and in particular to a method and device for in-situ determination of quartz oxygen isotopes in shale. Background Art

[0002] This section is intended to provide a background or context for embodiments of the present invention. No description herein is admitted to be prior art by virtue of its inclusion in this section.

[0003] Shale oil and gas, as an important unconventional oil and gas resource, is gradually increasing its share in global oil and gas production and reshaping the international energy landscape. Organic-rich shales are complex systems composed of inorganic minerals, solid organic matter, and organic-inorganic fluids. Quartz, one of the most important inorganic minerals in shale, is present at high concentrations and has a significant impact on shale reservoir properties (such as porosity) and rock mechanical properties (such as brittleness), thus affecting the storage and hydraulic fracturing of shale oil and gas. Quartz minerals in shales primarily include terrigenous detrital quartz from extra-basin sources and authigenic quartz from intra-basin sources. The distribution of large amounts of authigenic quartz, in particular, has a significant impact on the development and maintenance of pores in shale reservoirs. Therefore, understanding the formation and evolution history of authigenic quartz is crucial for a deeper understanding of shale reservoir porosity evolution. The oxygen isotope composition of quartz minerals in sedimentary rocks is widely used to study the source of diagenetic fluids, diagenetic temperature recovery, and paleoclimate reconstruction, thereby providing an important basis for a deeper understanding of the oxygen cycle in the interaction of multiple layers of the Earth's surface.

[0004] At present, the methods for in situ oxygen isotope determination in quartz minerals in sedimentary rocks are mainly divided into three categories: the first category is to take samples from rock thin sections or block slices by the micro-drilling method, and then release oxygen by the traditional fluorination method, and measure the oxygen isotope ratio by gas chromatography-isotope mass spectrometry (GC-IRMS). The second category is laser fluorination, which is to locally heat quartz particles by high-energy laser and introduce fluorinating agents at the same time to release oxygen in micro areas, and combine with GC-IRMS to measure the oxygen isotope ratio. The third category is secondary ion mass spectrometry (SIMS), which is to use high-energy ions to bombard the sample surface and sputter out secondary ions (such as 16 O - and 18 O - ) and directly measure isotope ratios using mass spectrometry. However, these methods are often used in carbonate, siliceous, and sandstone systems, but have not yet been adopted in shale systems. The main reason is that the quartz particles in shale reservoirs are too small (usually less than 10 μm), while the spatial resolution of current in situ analytical methods (including SIMS) is usually greater than 10 μm, making it impossible to accurately determine the oxygen isotope composition of quartz minerals in shale reservoirs, limiting the study of the evolutionary history of siliceous rocks.

[0005] In summary, there is an urgent need for a technical solution that can overcome the above-mentioned defects and effectively analyze and accurately measure the oxygen isotopes of quartz minerals in shale systems. Summary of the Invention

[0006] To address the challenges of existing technologies, this paper proposes a method and apparatus for in-situ determination of quartz oxygen isotopes in shale. Combining a series of petrological observation methods with nanoSIMS in-situ oxygen isotope analysis, this method can accurately determine the oxygen isotopes of different types of micron-sized quartz particles within the same shale sample, achieving high spatial resolution and precision.

[0007] In a first aspect of an embodiment of the present invention, a method for in-situ determination of quartz oxygen isotopes in shale is proposed, comprising:

[0008] Crushing or cutting a shale core sample to obtain a core block, embedding the core block in a metal target, and pre-processing to obtain a shale sample;

[0009] Scan and photograph the surface of the shale sample in a preset manner, stitch together a panoramic image of reflected light, determine the quartz property characteristics and genetic type of the test target through observation, and circle the location of the test target;

[0010] In combination with the reflected light panoramic image, the position of the test target is located according to the morphological characteristics of the test target and different surrounding reference objects, and an in-situ oxygen isotope test is performed on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope test data;

[0011] Each in-situ oxygen isotope measurement point of the shale sample is inspected, and the in-situ oxygen isotope test data is quality controlled according to the inspection results to determine the in-situ oxygen isotope measurement results.

[0012] In a second aspect of an embodiment of the present invention, a device for in-situ determination of quartz oxygen isotopes in shale is provided, comprising:

[0013] A sample preparation module is used to crush or cut the collected shale core samples to obtain core cubes, bury the core cubes in metal targets, and obtain shale samples after pretreatment;

[0014] A target positioning module is used to scan and photograph the surface of the shale sample in a preset manner, stitch together a panoramic image of reflected light, determine the quartz property characteristics and genetic type of the test target through observation, and locate the test target;

[0015] a target testing module, configured to locate the position of the test target based on the morphological features of the test target and surrounding reference objects in combination with the reflected light panoramic image, and to perform in-situ oxygen isotope testing on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope testing data;

[0016] The quality control module is used to inspect each in-situ oxygen isotope measurement point of the shale sample, perform quality control on the in-situ oxygen isotope test data according to the inspection results, and determine the in-situ oxygen isotope measurement results.

[0017] The method and device for in-situ determination of quartz oxygen isotopes in shale proposed by the present invention are as follows: a core sample of shale is crushed or cut to obtain a core block, the core block is buried in a metal target, and a shale sample is obtained through pretreatment; the surface of the shale sample is scanned and photographed in a preset manner, a reflected light panoramic image is spliced, the quartz property characteristics and genesis type of the test target are judged by observation, and the position of the test target is circled; the position of the test target is located based on the morphological characteristics of the test target and different surrounding reference objects in combination with the reflected light panoramic image, and an in-situ oxygen isotope test is performed on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope test data; each in-situ oxygen isotope measurement point of the shale sample is inspected, the in-situ oxygen isotope test data is quality controlled according to the inspection results, and the in-situ oxygen isotope determination result is determined. Through the rational arrangement and coordination of sample processing, the overall plan has achieved the rapid and accurate positioning of different types of quartz grains in shale reservoirs and in situ oxygen isotope determination to the greatest extent possible, and achieved the in situ combination of qualitative description and quantitative characterization of different types of quartz minerals, providing strong technical support for the detailed characterization of the siliceous diagenetic evolution history of shale reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 1 is a flow chart of a method for in-situ determination of quartz oxygen isotopes in shale according to an embodiment of the present invention.

[0020] Figure 2 1 is a schematic diagram of a sample preparation process according to an embodiment of the present invention.

[0021] Figure 3 FIG. 4 is a flowchart of target positioning according to an embodiment of the present invention.

[0022] Figure 4 FIG. 4 is a flowchart of a target test according to an embodiment of the present invention.

[0023] Figure 5 4 is a flow chart of quality control according to an embodiment of the present invention.

[0024] Figure 6 The figure is a schematic structural diagram of the placement of a metal target and a sample during the sample preparation process of a specific embodiment of the present invention.

[0025] Figure 7 It is a schematic diagram of zigzag scanning and photographing according to a specific embodiment of the present invention.

[0026] Figure 8 This is a schematic diagram of a typical reference object in the quartz mineral positioning process according to a specific embodiment of the present invention.

[0027] Figure 9 The figures are images of three different types of sample trays used for nanoSIMS in-situ oxygen isotope analysis according to a specific embodiment of the present invention.

[0028] Figure 10 Schematic diagram of an SEM image of a measurement point after nanoSIMS laser ablation and in-situ oxygen isotope test data in a specific embodiment of the present invention.

[0029] Figure 11 FIG. 1 is a schematic diagram of an apparatus structure for in-situ determination of quartz oxygen isotopes in shale according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided solely to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the scope of the present invention in any way. Rather, these embodiments are provided to make this disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0031] Those skilled in the art will appreciate that the embodiments of the present invention may be implemented as a system, apparatus, device, method, or computer program product. Therefore, the present disclosure may be implemented in the following forms: entirely in hardware, entirely in software (including firmware, resident software, microcode, etc.), or in a combination of hardware and software.

[0032] According to an embodiment of the present invention, a method and apparatus for in-situ determination of quartz oxygen isotopes in shale are proposed, which relates to the field of geological exploration technology. In combination with the complex and fine-grained mineral composition characteristics of shale reservoirs, the present invention designs a processing flow based on a nano-ion probe (NanoSIMS) for in-situ determination of quartz oxygen isotopes in shale, thereby achieving accurate determination of oxygen isotopes of quartz particles in fine-grained sedimentary rocks at the micron scale. The present invention was applied to shale gas reservoir samples in a certain basin and successfully revealed the in-situ oxygen isotope composition of different types of quartz particles in shale, providing a new scientific basis for understanding the siliceous diagenetic evolution history and pore evolution in shale gas reservoirs.

[0033] The principles and spirit of the present invention are explained in detail below with reference to several representative embodiments of the present invention.

[0034] Figure 1 FIG. 1 is a flow chart of a method for in-situ determination of quartz oxygen isotopes in shale according to an embodiment of the present invention. Figure 1 As shown, the method includes:

[0035] S101, crushing or cutting a shale core sample to obtain a core block, embedding the core block in a metal target, and pre-processing to obtain a shale sample;

[0036] S102, scanning and photographing the surface of the shale sample according to a preset method, stitching a reflected light panoramic image, determining the quartz property characteristics and genetic type of the test target through observation, and locating the location of the test target;

[0037] S103, combining the reflected light panoramic image with the test target and locating the test target according to the morphological characteristics of the test target and different surrounding reference objects, and performing in-situ oxygen isotope testing on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope testing data;

[0038] S104, inspecting each in-situ oxygen isotope measurement point of the shale sample, performing quality control on the in-situ oxygen isotope test data according to the inspection results, and determining the in-situ oxygen isotope measurement results.

[0039] The method for in situ determination of quartz oxygen isotopes in shale proposed in the present invention realizes the rapid and accurate positioning of different types of quartz grains in shale reservoirs and in situ oxygen isotope determination to the greatest extent possible through the reasonable arrangement and coordination of sample processing, and achieves the in situ combination of qualitative description and quantitative characterization of different types of quartz minerals, providing strong technical support for the detailed characterization of the siliceous diagenetic evolution history of shale reservoirs.

[0040] In order to explain the above-mentioned method of in-situ determination of quartz oxygen isotopes in shale more clearly, each step is described in detail below.

[0041] In one embodiment, S101, a shale core sample is crushed or cut to obtain a core block, and the core block is embedded in a metal target, and a shale sample is obtained through pretreatment.

[0042] The specific process of the pretreatment is: grinding and polishing the core block, performing argon ion polishing and coating treatment on the polished surface of the shale, and obtaining a shale sample.

[0043] The dimensions of the core block are 5 mm in length, 5 mm in width, and 2 to 3 mm in thickness;

[0044] The metal target is made of tin (Sn) or indium (In), with tin being the more affordable metal. The metal target diameter is 25mm, 12.5mm, or 10mm, with 25mm typically used to allow multiple samples to be placed simultaneously within a single target. The target can hold 2-8 samples of the core cube, typically 4 or 6.

[0045] The argon ion polishing time is 1 to 4 hours;

[0046] The coating treatment adopts carbon plating, gold plating or platinum plating, usually platinum plating, and the coating thickness is 5-30nm, usually 10nm.

[0047] Sample preparation is the basis for subsequent analysis and determination. Figure 2 The specific process is:

[0048] S101-1, crushing or cutting the collected shale core sample into cubes;

[0049] S101-2, embedding multiple core blocks in a metal target and mechanically polishing the exposed surface of the shale to obtain a smooth shale surface;

[0050] S101-3, using an argon ion polisher to polish the polished surface of the shale again to obtain a highly smooth shale surface;

[0051] S101-4, performing coating treatment on the polished surface of the metal target sample to obtain a shale sample.

[0052] The prepared shale samples can lay the foundation for subsequent scanning electron microscopy (SEM) and nanoscale secondary ion probe mass spectrometry (nonoSIMS) analysis.

[0053] In one embodiment, S102, the surface of the shale sample is scanned and photographed according to a preset method, and a reflected light panoramic image is spliced ​​to determine the quartz property characteristics and genesis type of the test target through observation, and the location of the test target is circled.

[0054] refer to Figure 3 The specific process is:

[0055] S102-1, using an optical microscope, observe the surface of the shale sample under reflected light conditions, and take photos in a zigzag scanning pattern. Use image processing software to stitch the scanned reflected light photos together to obtain a stitched reflected light image of the shale sample, and preliminarily delineate the test target area based on the mineral morphological characteristics;

[0056] S102-2, placing the metal target sample in the sample chamber of the scanning electron microscope, observing the circled test target area in the secondary electron mode, analyzing the mineral properties of the test target using the energy dispersive X-ray spectroscopy configured by the scanning electron microscope, and screening out different types of quartz minerals based on the morphological characteristics of the target minerals;

[0057] S102-3, using a scanning electron microscope coupled with a cathodoluminescence instrument, taking cathodoluminescence photos of the screened quartz mineral particles, and determining the origin of the quartz based on the cathodoluminescence response;

[0058] S102-4, circle all test target positions on the reflected light stitching image, and mark the quartz property characteristics and genesis types of the test targets.

[0059] In this embodiment, an optical microscope is used to observe the surface of the shale sample to be tested under reflected light conditions, and the sample is scanned and photographed in a zigzag pattern. The scanned reflected light photographs are then spliced ​​using image processing software to obtain a panoramic image of the sample, and the potential test target area is preliminarily delineated based on the morphological characteristics of the minerals. The metal target sample is placed in the SEM sample chamber, and in the secondary electron mode, the circled potential test target area is observed in focus. The mineral properties of the potential test target are analyzed using the energy dispersive X-ray spectroscopy (EDS) configured by the SEM, and different types of quartz minerals are preliminarily screened out based on the morphological characteristics of the target minerals. A scanning electron microscope-cathodoluminescence (SEM-CL) combination is used to take CL photographs of the screened quartz mineral particles, and the CL response is used to determine the genesis of the quartz (i.e., terrigenous detrital quartz or authigenic quartz). On the reflected light spliced ​​image, all potential test target locations are circled, and the genesis type of the test target is indicated.

[0060] The reflected light condition is single polarization reflected light, and the objective lens magnification is 2 times (2X), 5 times (5X) or 10 times (10X), and the 5X mode is usually used.

[0061] When analyzing the mineral properties of the test target using energy dispersive X-ray spectroscopy (EDS) configured with a scanning electron microscope, point analysis, line analysis, or surface analysis is used, with point analysis being generally preferred for higher efficiency. When the (EDS) elemental composition shows a double peak characteristic of Si and O, it is determined to be quartz mineral.

[0062] When judging the origin of quartz by cathodoluminescence (CL) response, terrigenous detrital quartz shows strong CL response (bright cathodoluminescence characteristics), while authigenic quartz shows weak CL response (dim or no cathodoluminescence characteristics).

[0063] In one embodiment, S103, in combination with the reflected light panoramic image, the position of the test target is located according to the morphological characteristics of the test target and different surrounding reference objects, and an in-situ oxygen isotope test is performed on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope test data.

[0064] refer to Figure 4 The specific process includes:

[0065] S103-1, placing the metal target sample and the standard sample target sample in a sample tray, placing the sample tray into a sample chamber of a nanoscale secondary ion probe mass spectrometer, and performing vacuum treatment to reach an ultra-high vacuum level;

[0066] S103-2: Using an optical microscope configured with a nanoscale secondary ion probe mass spectrometer, combined with a spliced ​​image of reflected light from the shale sample, the test target is located based on the morphological characteristics of the test target and surrounding reference objects, and the position information of each test target is saved one by one;

[0067] S103-3, based on the saved position information of each test target, use the nanoscale secondary ion probe mass spectrometer to perform in-situ oxygen isotope testing on the test target, and record the in-situ oxygen isotope test data of all test targets.

[0068] The sample trays include at least: a 50.8 mm diameter sample tray (2 inches in this embodiment, equivalent to 50.8 mm), which can hold one 25.4 mm diameter target, two 12.7 mm diameter targets, and two 10 mm diameter targets; a 25.4 mm diameter sample tray, which can hold four 10 mm diameter targets; and a 50.8 mm diameter sample tray, which can hold eight 10 mm diameter targets.

[0069] The ultra-high vacuum level is a pressure less than 10 -9 mbar;

[0070] When locating the test target position based on the morphological characteristics of the test target and different surrounding reference objects, the reference objects for reference include at least: the morphological characteristics of the edge position of the shale sample, the distribution of bioclastics, the distribution of microscopic components (for example, graptolite epidermis), the distribution of metallic minerals (for example, pyrite), the distribution of vein bodies, and the distribution of microcracks.

[0071] In this embodiment, a metal target sample and a standard sample target sample are placed in a sample tray at the same time, and the sample tray is sent to a nanoscale secondary ion probe mass spectrometer (nanoSIMS) sample chamber for vacuum treatment to reach an ultra-high vacuum level. Using an optical microscope configured with nanoSIMS, combined with a spliced ​​image of reflected light from the test sample, the test target position identified above is accurately located based on the morphological characteristics of the test target and its surrounding minerals, and the position information of each test target is saved one by one. In situ oxygen isotope testing is performed on the above-mentioned saved test targets using nanoSIMS, and the oxygen isotope test data of all test targets are saved.

[0072] In one embodiment, S104 , each in-situ oxygen isotope measurement point of the shale sample is inspected, and quality control is performed on the in-situ oxygen isotope test data according to the inspection results to determine the in-situ oxygen isotope measurement results.

[0073] refer to Figure 5 The specific process includes:

[0074] S104-1, placing the metal target sample after the in-situ oxygen isotope test into the sample chamber of the scanning electron microscope, and inspecting the measurement point position and measurement point area corresponding to each test target in the secondary electron mode;

[0075] The inspection methods include one or more of the following:

[0076] Check whether there are laser ablation pits in the measuring point area. If there are no laser ablation pits in the measuring point area, the test data of the measuring point is determined to be invalid and the test data is discarded;

[0077] Check whether the measuring point is offset from the predetermined measuring point. If so, further check whether the measuring point is located at a quartz mineral. If not, remove the test data of the measuring point.

[0078] Check whether the measuring point area is a smooth surface and whether there are micro-cracks on the surface. If it is not a smooth surface or there are micro-cracks, remove the test data of the measuring point;

[0079] Check whether the measuring point area contains organic matter. If so, remove the test data of the measuring point;

[0080] S104-2, retain or eliminate the test data based on the inspection results, perform quality control on the test data, and determine the in situ oxygen isotope determination results.

[0081] In this embodiment, the metal target sample after nanoSIMS in situ oxygen isotope testing is observed again by SEM to check the exact position and accuracy of each measurement point, thereby deciding whether to retain or eliminate each test data, thereby achieving quality control of the in situ oxygen isotope data and ultimately determining the in situ oxygen isotope measurement results.

[0082] It should be noted that although the operations of the method of the present invention are described in a specific order in the above embodiments and drawings, this does not require or imply that these operations must be performed in this specific order, or that all illustrated operations must be performed to achieve the desired results. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0083] The method for in-situ determination of quartz oxygen isotopes in shale of the present invention is described below with reference to a specific embodiment.

[0084] refer to Figure 5 As shown, the method of the present invention for in-situ determination of quartz oxygen isotopes in shale includes four main steps: sample preparation, target positioning, target testing, and quality control. It is applied to shale in a certain basin. The specific processing flow is as follows:

[0085] S501, sample preparation; sample cutting, metal target preparation, argon ion polishing, coating treatment.

[0086] The collected shale core samples were cut into core blocks with a length × width × height = 5 mm × 5 mm × 3 mm;

[0087] Stick the double-sided tape on the circle with a diameter of 25mm on the glass plate, stick the 6 shale core blocks on the glass plate in order, and record the relative positions. After the sample is placed, stick the PVC casting mold with an inner diameter of 25mm to the center of the glass plate, overlapping with the above-mentioned circle, and gently press it to make a seamless connection between the mold and the double-sided tape. Cut about 30g of metal tin, put it in a heating cup, and pour the molten metal tin into the mold with a depth of 5mm. After cooling to room temperature, take out the glass plate, remove the mold from the glass plate, and take out the cast metal target sample. Figure 6 The figure shows a schematic diagram of the metal target and sample placement during the sample preparation process according to a specific embodiment of the present invention. In the figure, D = diameter; L = length; W = width; H = height. The exposed side of the shale core block in the metal target is mechanically polished to obtain a smooth shale sample surface.

[0088] The polished surface of the shale sample was polished with argon ions using a Hitachi ion milling device (model IM4000) for 3 hours to obtain a highly smooth shale sample surface.

[0089] Finally, the polished surface of the metal target sample was coated with platinum using a Hitachi ion sputtering instrument (model E-1045). The coating material was 10 nm thick. It is particularly important to note that if the coating is too thick (such as 30 nm), the morphological characteristics of the minerals on the shale sample surface will be difficult to distinguish through an optical microscope. If the coating is too thin (such as 5 nm), the conductivity will be too poor during the nanoSIMS analysis, resulting in poor test results.

[0090] S502, target positioning; panoramic image scanning, SEM-EDS-CL observation and testing, target attribute recognition.

[0091] Using a Leica 4500P polarizing microscope, under single polarized reflected light conditions, the surface of the shale sample to be tested was observed through a 5X objective lens and a 5X eyepiece, and the surface of the shale sample was scanned in a "zigzag" pattern (from left to right, from top to bottom), and the image was photographed and saved. Figure 7 The figure shows a schematic diagram of a zigzag scanning and photographing process according to a specific embodiment of the present invention. Subsequently, the scanned reflected light photographs were reconstructed and spliced ​​in a zigzag order using the image processing software Photoshop, with duplicate areas removed to create a panoramic image of the surface of the sample to be tested. Potential test target areas were initially identified based on the reflected light morphological characteristics of the quartz mineral and its associated minerals, with particular attention paid to the following:

[0092] 1. Since the edges of shale samples are easiest to track, prioritize finding suitable targets at the sample edges. Furthermore, because quartz minerals are rigid particles, even after argon ion polishing, they still exhibit high protrusions and a relatively smooth surface. Therefore, some quartz aggregates form quartz aggregates or silt layers, which can be easily identified under reflected light conditions.

[0093] 2. Siliceous radiolarians have very typical biological structural characteristics. They are usually round, with nano-scale quartz particles in the middle and chalcedony on the outer layer. Under the condition of transmitted positive polarized light, they show radial and wavy extinction characteristics. They are a very pure type of authigenic quartz. In some cases, siliceous radiolarians can also be composed entirely of chalcedony.

[0094] 3. In the shale of this area, a large amount of graptolite organic matter is developed, which has unique morphological characteristics (such as long strips, less pore development, and aggregated distribution). Therefore, using larger graptolite organic matter as a reference, suitable targets to be tested can be found around the graptolite organic matter.

[0095] 4. Since pyrite has very strong reflective characteristics, it can be used as a landmark mineral, especially the combination pattern formed by multiple pyrite particles, which is often unique. Marking quartz particles near this pyrite combination pattern can easily be tracked again.

[0096] 5. Based on the distribution and morphological characteristics of veins (such as calcite veins and dolomite veins) or microcracks (which may be formed during the sample preparation process) in the shale sample, search for quartz particles near these veins or microcracks as potential targets to be tested. Figure 8 FIG. 1 is a schematic diagram of a typical reference object in the quartz mineral positioning process according to a specific embodiment of the present invention.

[0097] The metal target sample was placed in the sample chamber of a high-resolution cold-field environmental scanning electron microscope (Hitachi S-8000). In secondary electron mode, the potential test target area identified above was observed. The properties of the target mineral were analyzed using energy-dispersive X-ray spectroscopy (EDS) configured in the SEM. The EDS data showed double peaks of Si and O, indicating quartz mineral. Combined with the morphological characteristics of the quartz mineral, the potential genesis of the quartz mineral was preliminarily determined, mainly including the following situations:

[0098] 1. Some isolated quartz minerals with angular edges may be terrigenous detrital quartz.

[0099] 2. Some amorphous quartz minerals with rounded edges often gather together to form irregular agglomerates, and the intercrystalline pores are filled with pyroasphalt. This type of quartz mineral may be authigenic quartz.

[0100] 3. The nano-quartz grains on the edge and inside of chalcedony in siliceous radiolarians are all authigenic quartz.

[0101] 4. The quartz minerals filling the vein body are usually authigenic quartz.

[0102] The metal target sample was placed in the sample chamber of the SEM-CL instrument. The SEM model was Zeiss Supra55Sapphire, equipped with a high-resolution imaging and spectral analysis cathodoluminescence imaging system (model: Gatan Mono CL4). In the secondary electron mode, the quartz grains circled above were observed and photographed, and in the CL mode, CL photography was performed on the same area. If the CL image showed bright luminescence features, it indicated that the observed quartz grains were terrigenous detrital quartz. If the CL image showed dim or no luminescence features, it indicated that the observed quartz grains were authigenic quartz.

[0103] In the reflected light mosaic image, the positions and properties of all potential test targets circled were checked, and the genesis type (i.e., terrigenous detrital quartz or authigenic quartz) of the target to be tested was noted one by one based on the EDS data and CL luminescence characteristics.

[0104] S503, target testing; nanoSIMS in situ oxygen isotope determination.

[0105] Place the metal target sample (25.4 mm in diameter) and the standard sample target sample (12.7 mm in diameter) in the No. 1 sample pan among the three sample pans. Figure 9 As shown, there are images of three different types of sample trays for nanoSIMS in-situ oxygen isotope analysis according to a specific embodiment of the present invention. In the figure, 1 inch corresponds to 25.4 mm. Sample tray No. 1 is a sample tray with a diameter of 50.8 mm (2 inches in this embodiment, converted to 50.8 mm), which is used to place one target sample with a diameter of 25.4 mm (1 inch), two target samples with a diameter of 12.7 mm (1 / 2 inch) and two target samples with a diameter of 10 mm; sample tray No. 2 is a sample tray with a diameter of 25.4 mm (1 inch), which is used to place four target samples with a diameter of 10 mm; sample tray No. 3 is a sample tray with a diameter of 50.8 mm (2 inches), which is used to place eight target samples with a diameter of 10 mm. The sample tray is placed in the sample chamber of a nanoscale secondary ion probe mass spectrometer (model: Cameca NanoSIMS 50L) and vacuumed to reach an ultra-high vacuum level of less than 10 -9 mbar;

[0106] The nanoSIMS was used to analyze the microstructure of the samples using an optical microscope (magnification of 400X and field size of 1000 × 1000 μm). 2 ), combined with the reflected light from the test sample, the full-viewing-area image is stitched together. The approximate location of the target mineral is used to preliminarily locate the target mineral. Based on the morphological characteristics of the target mineral (e.g., quartz, radiolarian chalcedony), its surrounding minerals (e.g., pyrite), microcracks, and veins, the target is accurately located. The target's location information is then saved in the system. Subsequently, the above steps are repeated to save the location information of each target.

[0107] NanoSIMS was used to perform in-situ oxygen isotope testing on the above-mentioned preserved target. The test spot was 5 μm. Before the oxygen isotope testing on the target and after all the targets were tested, a standard sample (UWQ-1 quartz standard was used as the standard sample; δ 18O=12.33±0.07‰V-SMOW) is tested. During the test of the target, the standard sample needs to be tested 4 to 6 times every 30 to 40 measuring points to obtain the instrument mass fractionation (IMF) that occurs during the oxygen isotope ratio test, and it is used to correct the oxygen isotope value of the test target.

[0108] S504, quality control; scanning electron microscope measurement point inspection, data retention and deletion.

[0109] After the nanoSIMS in-situ oxygen isotope test, the metal target sample was placed back into the sample chamber of the Hitachi S-8000 SEM and the exact position of each test target was checked in the secondary electron mode. Figure 10 The figure shows a schematic diagram of the SEM image of the measurement point after nanoSIMS laser ablation and the in-situ oxygen isotope test data of a specific embodiment of the present invention. Part A is the SEM image, and Part B is a schematic diagram of the in-situ oxygen isotope test data. The lower left corner of the figure is the parameter record of the scanning electron microscope imaging, which is used to illustrate information such as the image acquisition equipment, conditions, mode and scale. SU8000 represents the scanning electron microscope model used, which is a high-resolution cold field emission scanning electron microscope suitable for observing the microscopic morphology of samples. 10.0kV means that the acceleration voltage is 10 kilovolts, which means that the electron beam emitted by the electron gun is accelerated to an energy of 10kV, which is used to excite the sample to generate secondary electron signals. 11.8mm means that the working distance is 11.8 millimeters, that is, the distance from the sample surface to the objective lens, which affects the depth of field and resolution of the image. ×350 means that the magnification of the image is 350 times, that is, the object in the image is magnified 350 times compared to the actual object. SE(L): SE stands for Secondary Electron Imaging mode, and L indicates low vacuum mode or a specific detector configuration, which is used to highlight surface topographic details. 100μm indicates a scale of 100 microns, meaning that 1 unit length in the image corresponds to 100 microns in the actual sample. This is used to measure the actual size of the measured pits.

[0110] In this regard, we focus on checking the following situations:

[0111] 1. If there is no laser ablation pit in the nanoSIMS measurement point area, the data of the measurement point is invalid and should be eliminated.

[0112] 2. Whether the nanoSIMS measurement point is offset from the predetermined measurement point. If so, whether the measurement point position is quartz mineral. If not, the measurement point should be eliminated.

[0113] 3. Check whether the nanoSIMS measurement point area is a smooth surface or whether there are microcracks on the surface. If it is not a smooth surface or there are microcracks, the measurement point should be eliminated.

[0114] 4. Whether the nanoSIMS measurement point area contains other impurities (such as organic matter). If other impurities exist, the measurement point should be eliminated.

[0115] By checking the data of each measuring point, it is decided whether to retain or eliminate the data, thereby achieving quality control of the in situ oxygen isotope data.

[0116] After introducing the method of the exemplary embodiment of the present invention, next, reference is made to Figure 11 An apparatus for in-situ determination of quartz oxygen isotopes in shale according to an exemplary embodiment of the present invention is introduced.

[0117] The implementation of the apparatus for in-situ determination of quartz oxygen isotopes in shale can be referenced to the implementation of the aforementioned method, and any repetitions will not be repeated. The terms "module" or "unit" used below may refer to a combination of software and / or hardware that implements a predetermined function. Although the apparatus described in the following embodiments is preferably implemented using software, implementation using hardware, or a combination of software and hardware, is also possible and contemplated.

[0118] Based on the same inventive concept, the present invention also proposes a device for in-situ determination of quartz oxygen isotopes in shale, such as Figure 11 As shown, the device includes:

[0119] The sample preparation module 110 is used to crush or cut the collected shale core sample to obtain a core block, bury the core block in a metal target, and obtain a shale sample after pretreatment;

[0120] The target positioning module 120 is used to scan and photograph the surface of the shale sample in a preset manner, stitch together a panoramic image of reflected light, determine the quartz property characteristics and genetic type of the test target through observation, and locate the test target;

[0121] The target testing module 130 is configured to locate the position of the test target based on the morphological characteristics of the test target and surrounding reference objects in combination with the reflected light panoramic image, and perform in-situ oxygen isotope testing on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope testing data;

[0122] The quality control module 140 is used to inspect each in-situ oxygen isotope measurement point of the shale sample, perform quality control on the in-situ oxygen isotope test data according to the inspection results, and determine the in-situ oxygen isotope measurement results.

[0123] This study uses a nano-ion probe (nanoSIMS) with a test spot size of just 5μm, far exceeding the precision of traditional SIMS (spatial resolution >10μm) and laser fluorination methods. This method enables in situ oxygen isotope determination of micron-sized quartz particles (typically <10μm) in shale. This method can accurately analyze the isotopic signatures of authigenic quartz in shale reservoirs (e.g., nanoquartz within siliceous radiolarians and amorphous authigenic quartz aggregates), filling a gap in the study of siliceous diagenesis and evolution in the shale field.

[0124] In the sample preparation process, this application has also made optimization and improvement. A metal tin target (1 inch diameter) can be used to embed 4-6 5mm×5mm×2-3mm sample blocks, taking into account both sample capacity and operating costs. Argon ion polishing is performed for 1-4 hours (preferably 3 hours) to eliminate mechanical polishing scratches. A 10nm platinum coating is applied to balance conductivity and morphological resolution. During the test, UWQ-1 quartz standard samples are inserted before and after the test and every 30-40 measurement points to calibrate the instrument mass fractionation (IMF) to ensure δ 18 The accuracy reaches ±0.07‰; after the test, the measuring points are checked through SEM secondary electron images to confirm the existence of laser ablation pits, position offset, surface smoothness, and whether there are impurities (such as organic matter). Invalid data is eliminated to establish a closed-loop quality control system of sample preparation-testing-calibration.

[0125] In the overall processing flow, the process of optical microscope reflected light panoramic scanning, SEM-EDS mineral property analysis, and SEM-CL cathodoluminescence identification of origin is used to complete morphological feature delineation, mineral qualitative analysis, and isotope quantitative testing. Zigzag scanning is used to stitch panoramic images, and quartz grains are quickly located in combination with reference objects such as sample edges, bioclasts (such as graptolites), and pyrite. Quartz is identified based on the Si / O double peak characteristics displayed by EDS elemental composition, and CL luminescence intensity is used to distinguish between terrigenous detrital quartz (strong luminescence) and authigenic quartz (weak to no luminescence), enabling in situ determination of genetic type. Based on nanoSIMS combined with positioning information, targeted testing is carried out on quartz of different genesis, establishing an integrated process from qualitative description to quantitative characterization. This avoids the disconnect between isotope data and mineral origin caused by blind sampling in traditional methods, providing strong technical support for quartz isotope analysis in shale reservoirs.

[0126] The method and device for in-situ determination of quartz oxygen isotopes in shale proposed by the present invention are as follows: a core sample of shale is crushed or cut to obtain a core block, the core block is buried in a metal target, and a shale sample is obtained through pretreatment; the surface of the shale sample is scanned and photographed in a preset manner, a reflected light panoramic image is spliced, the quartz property characteristics and genesis type of the test target are judged by observation, and the position of the test target is circled; the position of the test target is located based on the morphological characteristics of the test target and different surrounding reference objects in combination with the reflected light panoramic image, and an in-situ oxygen isotope test is performed on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope test data; each in-situ oxygen isotope measurement point of the shale sample is inspected, the in-situ oxygen isotope test data is quality controlled according to the inspection results, and the in-situ oxygen isotope determination result is determined. Through the rational arrangement and coordination of sample processing, the overall plan has achieved the rapid and accurate positioning of different types of quartz grains in shale reservoirs and in situ oxygen isotope determination to the greatest extent possible, and achieved the in situ combination of qualitative description and quantitative characterization of different types of quartz minerals, providing strong technical support for the detailed characterization of the siliceous diagenetic evolution history of shale reservoirs.

[0127] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, apparatus, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0128] The present invention is described with reference to flowcharts and / or block diagrams of methods and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0129] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0130] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0131] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for in-situ determination of quartz oxygen isotopes in shale, characterized in that: include: Crushing or cutting a shale core sample to obtain a core block, embedding the core block in a metal target, and pre-processing to obtain a shale sample; Scan and photograph the surface of the shale sample in a preset manner, stitch together a panoramic image of reflected light, determine the quartz property characteristics and genetic type of the test target through observation, and circle the location of the test target; In combination with the reflected light panoramic image, the position of the test target is located according to the morphological characteristics of the test target and different surrounding reference objects, and an in-situ oxygen isotope test is performed on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope test data; Each in-situ oxygen isotope measurement point of the shale sample is inspected, and the in-situ oxygen isotope test data is quality controlled according to the inspection results to determine the in-situ oxygen isotope measurement results.

2. The method for in-situ determination of quartz oxygen isotopes in shale according to claim 1, characterized in that: The shale core sample is crushed or cut to obtain a core block, the core block is embedded in a metal target, and a shale sample is obtained through pretreatment, including: The core block is ground and polished, and the polished surface of the shale is subjected to argon ion polishing and coating treatment to obtain a shale sample.

3. The method for in-situ determination of quartz oxygen isotopes in shale according to claim 1, characterized in that: Scan and photograph the surface of the shale sample in a preset manner, stitch together a panoramic image of reflected light, determine the quartz property characteristics and genetic type of the test target through observation, and locate the location of the test target, including: Using an optical microscope, the surface of the shale sample was observed under reflected light conditions, and photographed in a zigzag pattern. The scanned reflected light photographs were stitched together using image processing software to obtain a reflected light stitching image of the shale sample. The test target area was preliminarily delineated based on the mineral morphology. The metal target sample is placed in the sample chamber of the scanning electron microscope. The circled test target area is observed in the secondary electron mode. The mineral properties of the test target are analyzed using the energy dispersive X-ray spectroscopy configured by the scanning electron microscope. Different types of quartz minerals are screened out based on the morphological characteristics of the target minerals. Using a scanning electron microscope coupled with a cathodoluminescence instrument, the selected quartz mineral particles were photographed by cathodoluminescence, and the origin type of the quartz was determined by the cathodoluminescence response. On the reflected light stitching image, all test target positions are circled, and the quartz property characteristics and genesis types of the test targets are marked.

4. The method for in-situ determination of quartz oxygen isotopes in shale according to claim 1, characterized in that: In combination with the reflected light panoramic image, the position of the test target is located according to the morphological characteristics of the test target and different surrounding reference objects, and an in-situ oxygen isotope test is performed on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope test data, including: The metal target sample and the standard sample target sample are placed in a sample tray, and the sample tray is placed in a sample chamber of a nanoscale secondary ion probe mass spectrometer for vacuum treatment to reach an ultra-high vacuum level; Using an optical microscope equipped with a nanoscale secondary ion probe mass spectrometer and combining it with a spliced ​​image of reflected light from the shale sample, the test target is located based on the morphological characteristics of the test target and surrounding reference objects, and the position information of each test target is saved one by one. According to the saved position information of each test target, the nanoscale secondary ion probe mass spectrometer is used to perform in-situ oxygen isotope testing on the test target, and the in-situ oxygen isotope test data of all test targets are recorded.

5. The method for in-situ determination of quartz oxygen isotopes in shale according to claim 1, characterized in that: Inspect each in-situ oxygen isotope measurement point of the shale sample, perform quality control on the in-situ oxygen isotope test data according to the inspection results, and determine the in-situ oxygen isotope measurement results, including: The metal target sample after in-situ oxygen isotope testing is placed in the sample chamber of the scanning electron microscope. In the secondary electron mode, the measurement point position and measurement point area corresponding to each test target are inspected. The inspection method includes one or more of the following: Check whether there are laser ablation pits in the measuring point area. If there are no laser ablation pits in the measuring point area, the test data of the measuring point is determined to be invalid and the test data is discarded; Check whether the measuring point is offset from the predetermined measuring point. If so, further check whether the measuring point is located at a quartz mineral. If not, remove the test data of the measuring point. Check whether the measuring point area is a smooth surface and whether there are micro-cracks on the surface. If it is not a smooth surface or there are micro-cracks, remove the test data of the measuring point; Check whether the measuring point area contains organic matter. If so, remove the test data of the measuring point; The test data are retained or eliminated based on the inspection results, and the test data are quality controlled to determine the in situ oxygen isotope determination results.

6. The method for in-situ determination of quartz oxygen isotopes in shale according to claim 1, characterized in that: The dimensions of the core block are 5 mm in length, 5 mm in width, and 2 to 3 mm in thickness; The metal target is made of tin or indium, and has a diameter of 25 mm, 12.5 mm or 10 mm. The number of samples of the core blocks embedded in the metal target is 2-8.

7. The method for in-situ determination of quartz oxygen isotopes in shale according to claim 2, characterized in that: The argon ion polishing time is 1 to 4 hours; The coating treatment adopts carbon coating, gold coating or platinum coating, and the coating thickness is 5-30nm.

8. The method for in-situ determination of quartz oxygen isotopes in shale according to claim 3, characterized in that: The reflected light condition is single polarized reflected light, and the objective lens magnification is 2x, 5x or 10x; When analyzing the mineral properties of the test target using energy dispersive X-ray spectroscopy configured with a scanning electron microscope, point analysis, line analysis, or surface analysis is used. When the elemental composition shows a double peak characteristic of Si and O, it is determined to be quartz mineral; When judging the origin of quartz by cathodoluminescence response, terrigenous detrital quartz exhibits bright cathodoluminescence characteristics, while authigenic quartz exhibits dim or no cathodoluminescence characteristics.

9. The method for in-situ determination of quartz oxygen isotopes in shale according to claim 4, characterized in that: The sample trays shall include at least: a 50.8mm diameter sample tray, which can hold one 25.4mm diameter target sample, two 12.7mm diameter target samples, and two 10mm diameter target samples; a 25.4mm diameter sample tray, which can hold four 10mm diameter target samples; and a 50.8mm diameter sample tray, which can hold eight 10mm diameter target samples. The ultra-high vacuum level is a pressure less than 10 -9 mbar; When locating the test target position based on the morphological characteristics of the test target and different surrounding reference objects, the reference objects for reference include at least: the morphological characteristics of the edge position of the shale sample, the distribution of bioclastics, the distribution of microscopic components, the distribution of metal minerals, the distribution of veins and the distribution of microcracks.

10. A device for in-situ determination of quartz oxygen isotopes in shale, characterized in that: include: A sample preparation module is used to crush or cut the collected shale core samples to obtain core cubes, bury the core cubes in metal targets, and obtain shale samples after pretreatment; A target positioning module is used to scan and photograph the surface of the shale sample in a preset manner, stitch together a panoramic image of reflected light, determine the quartz property characteristics and genetic type of the test target through observation, and locate the test target; a target testing module, configured to locate the position of the test target based on the morphological features of the test target and surrounding reference objects in combination with the reflected light panoramic image, and to perform in-situ oxygen isotope testing on the test target using a nanoscale secondary ion probe mass spectrometer to obtain in-situ oxygen isotope testing data; The quality control module is used to inspect each in-situ oxygen isotope measurement point of the shale sample, perform quality control on the in-situ oxygen isotope test data according to the inspection results, and determine the in-situ oxygen isotope measurement results.

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