Microbial carbonate rock pore identification method and system

Abstract

The invention discloses a microbial carbonate rock pore identification method and system, and the method comprises the steps: carrying out the image analysis of a casting body slice, and constructing a biological carbonate rock structure corresponding to the casting body slice; the plunger sample is subjected to nuclear magnetic resonance analysis, a nuclear magnetic resonance curve is obtained, and the rock structure morphological characteristics comprise pore type characteristics; determining a corresponding relation between the nuclear magnetic resonance curve and the pore type according to a predetermined corresponding relation between the curve type of the nuclear magnetic resonance curve and the pore type; drawing a microbial carbonate rock pore identification chart based on the corresponding relation between the nuclear magnetic resonance curve and the pore type; and identifying the pores of the microbial carbonate rocks by utilizing the pore identification plate of the microbial carbonate rocks. According to the method, the key technical problem of accurately identifying pores with different sizes and different types in the microbial carbonate rock by utilizing geophysical signals is solved, and powerful technical support is provided for solving the problems of pore identification and quantitative characterization of the microbial carbonate rock.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial carbonate rock analysis, and in particular to a microbial carbonate rock pore identification method and system. Background Art

[0002] Compared with other types of carbonate rocks, the pore system of microbial carbonate rocks is extremely special. Microbial carbonate rocks have a variety of pore types, including microbial-related pores (microbial framework pores, mold pores), intercrystalline pores, and secondary dissolution pores. In addition, the morphology and size of different types of pores are often quite different, including micro-nanoscale intercrystalline pores and larger-scale dissolution pores. The pore morphology is also different from that of non-microbial carbonate rocks, including various forms such as strips, foams, tubulars, and irregular shapes. The characteristics of multiple types, multiple scales, and multiple forms determine that the identification of the pore system of microbial carbonate rocks has certain technical barriers.

[0003] Microbial carbonate pores have their own unique development mechanism. For example, organic acids and methane microbial metabolites can inhibit the formation and cementation of pores to a certain extent, thus facilitating the preservation of pores. Microorganisms promote the precipitation and dolomitization of carbonate minerals through organic metabolism and inorganic mineralization. This process usually occurs in the surface-near surface environment, which can quickly transform the early stage into carbonate rocks with high compaction resistance and chemical stability, so that the connectivity and permeability of pores can be maintained during diagenesis and later transformation. The type, sorting, scale and size of microbial rock fabric affect the abundance and connectivity of pores. The pores in layered stromatolites are simple and have better connectivity. Differences in the size and sorting of clot structures cause large differences in the physical properties of clotted carbonate rocks. Microbial carbonate rocks have a specific microbial framework, which provides a material basis for the formation of early primary pores. Therefore, the formation of microbial carbonate reservoir space is mainly affected by microbial metabolic activities, microbial rock fabric, sedimentary environment and various diagenesis. The coupling of multiple geological factors brings certain difficulties to the evaluation of microbial carbonate pore systems and the restoration of pore differential evolution processes.

[0004] At present, nuclear magnetic resonance technology (NMR) has been widely used in the characterization of carbonate reservoirs, and has many advantages: ① It has a high resolution and can identify multi-scale pores from micro-nano to centimeter level, and can accurately reflect the structure and organization of the reservoir, including pore size and connectivity. ② Rapid non-destructive testing, testing under saturated water conditions, minimal damage to the sample. ③ Quantitative analysis, accurately evaluate the physical parameters of the reservoir, such as T2 curve porosity, permeability, etc.

[0005] However, it should be noted that as a three-dimensional geophysical signal, the experimental results of nuclear magnetic resonance often differ greatly from their actual geological information, especially for microbial carbonate rocks with complex pore systems, where the test errors are more obvious. In existing technical methods, there are significant differences between the two-dimensional graphical characterization results and the geophysical three-dimensional pore structure, and a close correlation has not yet been established between the observation results of mineralogy and geophysical testing results. How to use geophysical signals to accurately identify pores of different scales and types in microbial carbonate rocks is a technical problem that needs to be solved urgently in the process of reservoir characterization. Summary of the invention

[0006] The embodiments of the present invention provide a method and system for identifying pores in microbial carbonate rocks to solve the above-mentioned technical problems in the prior art.

[0007] In order to have a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended to be a general review, nor is it intended to identify key / important components or to delineate the scope of protection of these embodiments. Its only purpose is to present some concepts in a simple form as a preface to the detailed description that follows.

[0008] According to a first aspect of an embodiment of the present invention, a method for identifying pores in microbial carbonate rocks is provided.

[0009] In one embodiment, the microbial carbonate pore identification method comprises:

[0010] Obtaining a microbial carbonate rock sample, and preparing a plurality of plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample;

[0011] Performing image analysis on the casting thin section to construct a biocarbonate rock fabric corresponding to the casting thin section; and performing nuclear magnetic resonance analysis on the plunger sample to obtain a nuclear magnetic resonance curve, wherein the rock fabric morphological characteristics include pore type characteristics;

[0012] According to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, the correspondence between the nuclear magnetic resonance curve and the pore type is determined; and based on the correspondence between the nuclear magnetic resonance curve and the pore type, a microbial carbonate pore identification chart is drawn;

[0013] The microbial carbonate pore identification plate is used to identify the microbial carbonate pores.

[0014] In one embodiment, preparing a plurality of plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample comprises:

[0015] According to predetermined specifications, plug samples are cut from the microbial carbonate rock sample, and a rock slice of predetermined thickness is cut at one end of each plug sample as a casting slice corresponding to the plug sample.

[0016] In one embodiment, performing image analysis on the casting thin section and constructing a biocarbonate rock fabric corresponding to the casting thin section comprises:

[0017] Scanning the casting thin slice to obtain a casting thin slice image;

[0018] According to the different rock fabric morphological characteristics in the microbial carbonate rock, the cast thin section image is analyzed to construct the rock fabric of the biocarbonate rock corresponding to the cast thin section;

[0019] The rock fabric morphological characteristics include rock matrix type characteristics, pore type characteristics, fracture type characteristics and cementation stage type characteristics.

[0020] In one embodiment, according to different rock fabric morphological characteristics in microbial carbonate rocks, the casting thin section image is analyzed, and the construction of the biocarbonate rock fabric corresponding to the casting thin section includes:

[0021] According to the different rock fabric morphological characteristics in microbial carbonate rocks, the casting thin section image layer was selected using Adobe Photoshop software, and the histogram pixels were viewed based on the selected layer to obtain the image pixels corresponding to the rock fabric morphological characteristics;

[0022] Based on the obtained image pixels of the rock fabric morphological features, the PSQ content of the corresponding rock fabric morphological features is calculated; and based on the calculated corresponding PSQ content, the microbial carbonate rock fabric corresponding to each casting thin section is drawn;

[0023] The microbial carbonate rock fabric is used to represent the PSQ content ratio of each rock fabric morphological feature in each casting thin section.

[0024] In one embodiment, the PSQ content is calculated as follows:

[0025] PSQ content = single rock fabric morphological characteristic pixels / total pixels*100%.

[0026] In one embodiment, the microbial carbonate pore identification method further includes:

[0027] Before determining the correspondence between the nuclear magnetic resonance curve and the pore type according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, all the obtained nuclear magnetic resonance curves are grouped, and the nuclear magnetic resonance curve with the highest frequency in each group is used as the standard nuclear magnetic resonance curve; and according to the grouping of the nuclear magnetic resonance curves, the microbial carbonate rock structures are correspondingly grouped, and the pore type with the highest frequency in each microbial carbonate rock structure is used as the standard pore type.

[0028] In one embodiment, according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, determining the correspondence between the nuclear magnetic resonance curve and the pore type includes:

[0029] According to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, the standard pore type corresponding to each standard nuclear magnetic resonance curve is determined, and the correspondence between the standard nuclear magnetic resonance curve and the standard pore type is obtained.

[0030] In one embodiment, the correspondence between the curve type of the nuclear magnetic resonance curve and the pore type includes:

[0031] When the NMR curve is a multi-peak-high amplitude T2 curve, the pore types corresponding to the NMR curve include: a combined pore type of mold pores and grid pores, and a combined pore type of dissolution pores and intercrystalline pores;

[0032] When the NMR curve is a double-peak T2 curve, the pore types corresponding to the NMR curve include: a combined pore type of intercrystalline pores and dissolution pores;

[0033] When the nuclear magnetic resonance curve is a single-peak T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: a combined pore type of intercrystalline pores, framework pores, and mold pores;

[0034] When the nuclear magnetic resonance curve is a multi-peak-low-amplitude T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: dolomite pore type.

[0035] In one embodiment, drawing a microbial carbonate pore identification chart based on the correspondence between the nuclear magnetic resonance curve and the pore type includes:

[0036] All microbial carbonate rock samples are divided into several groups. In each group of microbial carbonate rock samples, a standard nuclear magnetic resonance curve of each microbial carbonate rock sample is selected and represented by different colors or styles;

[0037] The standard pore types of the microbial carbonate rock fabric of each microbial carbonate rock sample are listed and compared with the standard nuclear magnetic resonance curve.

[0038] According to a second aspect of an embodiment of the present invention, a microbial carbonate pore identification system is provided.

[0039] In one embodiment, the microbial carbonate pore identification system comprises:

[0040] A sample preparation unit, used for obtaining a microbial carbonate rock sample, and preparing a plurality of plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample;

[0041] A sample analysis unit is used to perform image analysis on the casting thin section to construct a biocarbonate rock fabric corresponding to the casting thin section; and perform nuclear magnetic resonance analysis on the plunger sample to obtain a nuclear magnetic resonance curve, wherein the rock fabric morphological characteristics include pore type characteristics;

[0042] A chart drawing unit is used to determine the correspondence between the nuclear magnetic resonance curve and the pore type according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type; and to draw a microbial carbonate pore identification chart based on the correspondence between the nuclear magnetic resonance curve and the pore type;

[0043] The pore identification unit is used to identify the pores of the microbial carbonate rock using the microbial carbonate rock pore identification plate.

[0044] In one embodiment, when the sample preparation unit prepares a plurality of plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample, the plunger samples are cut from the microbial carbonate rock sample according to predetermined specifications, and a rock thin section of predetermined thickness is cut at one end of each plunger sample as a casting thin section corresponding to the plunger sample.

[0045] In one embodiment, when the sample analysis unit performs image analysis on the casting thin section and constructs the biocarbonate rock fabric corresponding to the casting thin section, the casting thin section is scanned to obtain a casting thin section image; according to different rock fabric morphological characteristics in microbial carbonate rock, the casting thin section image is analyzed to construct the biocarbonate rock fabric corresponding to the casting thin section; wherein the rock fabric morphological characteristics include rock matrix type characteristics, pore type characteristics, fracture type characteristics and cementation period type characteristics.

[0046] In one embodiment, when analyzing the casting thin section image according to different rock fabric morphological characteristics in microbial carbonate rocks and constructing the biological carbonate rock fabric corresponding to the casting thin section, Adobe Photoshop software is used to select a layer of the casting thin section image according to the different rock fabric morphological characteristics in microbial carbonate rocks, and a histogram pixel view is performed based on the selected layer to obtain image pixels corresponding to the rock fabric morphological characteristics; based on the obtained image pixels of the rock fabric morphological characteristics, the PSQ content of the corresponding rock fabric morphological characteristics is calculated; and based on the calculated corresponding PSQ content, the microbial carbonate rock fabric corresponding to each casting thin section is drawn;

[0047] The microbial carbonate rock fabric is used to represent the PSQ content ratio of each rock fabric morphological feature in each casting thin section.

[0048] In one embodiment, the PSQ content is calculated as follows:

[0049] PSQ content = single rock fabric morphological characteristic pixels / total pixels*100%.

[0050] In one embodiment, the sample analysis unit is also used to group all the obtained nuclear magnetic resonance curves before determining the correspondence between the nuclear magnetic resonance curve and the pore type according to a predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, and use the nuclear magnetic resonance curve with the highest frequency in each group as the standard nuclear magnetic resonance curve; and according to the grouping of the nuclear magnetic resonance curves, the microbial carbonate rock structures are correspondingly grouped, and the pore type with the highest frequency in each microbial carbonate rock structure is used as the standard pore type.

[0051] In one embodiment, when the plate drawing unit determines the correspondence between the nuclear magnetic resonance curve and the pore type according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, it determines the standard pore type corresponding to each standard nuclear magnetic resonance curve according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, and obtains the correspondence between the standard nuclear magnetic resonance curve and the standard pore type.

[0052] In one embodiment, the correspondence between the curve type of the nuclear magnetic resonance curve and the pore type includes:

[0053] When the NMR curve is a multi-peak-high amplitude T2 curve, the pore types corresponding to the NMR curve include: a combined pore type of mold pores and grid pores, and a combined pore type of dissolution pores and intercrystalline pores;

[0054] When the NMR curve is a double-peak T2 curve, the pore types corresponding to the NMR curve include: a combined pore type of intercrystalline pores and dissolution pores;

[0055] When the nuclear magnetic resonance curve is a single-peak T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: a combined pore type of intercrystalline pores, framework pores, and mold pores;

[0056] When the nuclear magnetic resonance curve is a multi-peak-low-amplitude T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: dolomite pore type.

[0057] In one embodiment, when the plate drawing unit draws the microbial carbonate pore identification plate based on the correspondence between the nuclear magnetic resonance curve and the pore type, all microbial carbonate samples are divided into several groups. In each group of microbial carbonate samples, the standard nuclear magnetic resonance curve of each microbial carbonate sample is selected and represented by different colors or styles; the standard pore types of the microbial carbonate rock structure of each microbial carbonate sample are listed and displayed in comparison with the standard nuclear magnetic resonance curve.

[0058] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0059] The present invention not only improves the accuracy of identification by quantifying petrological observation results, but also makes the description of the microbial carbonate rock pore system more refined and comprehensive. Compared with the traditional qualitative description, this quantitative method can more objectively and accurately reflect the pore characteristics of rocks, thereby improving the efficiency and quality of pore type identification. In addition, based on the quantitative statistics of multi-type rock structures (matrix, pores, cracks, cements) of microbial carbonate rocks and the integrated analysis of nuclear magnetic resonance curves, the statistical analysis method is applied to organically combine the two, and the microbial carbonate rock pore identification plate is finally established, thereby solving the key technical problem of accurately identifying pores of different scales and different types in microbial carbonate rocks using geophysical signals, and providing strong technical support for solving the problem of microbial carbonate rock pore identification and quantitative characterization.

[0060] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0062] Figure 1 is a schematic flow chart of a method for identifying pores in microbial carbonate rocks according to an exemplary embodiment;

[0063] Figure 2 is a structural block diagram of a microbial carbonate pore identification system according to an exemplary embodiment;

[0064] Figure 3 is a schematic diagram of a microbial dolomite rock fabric discrimination chart according to an exemplary embodiment;

[0065] Figure 4 is a schematic diagram showing the decomposition characteristics of various structures of microbial carbonate rock and the PSQ content according to an exemplary embodiment;

[0066] Figure 5 is a schematic diagram showing the statistical content of each structure of microbial carbonate rock according to an exemplary embodiment;

[0067] Figure 6 is a schematic diagram of rock structures of different types of microbial carbonate rocks according to an exemplary embodiment;

[0068] Figure 7 is a schematic diagram of a microbial carbonate pore type identification chart based on NMR T2 curve and rock fabric quantitative statistics according to an exemplary embodiment;

[0069] Figure 8 is a schematic diagram of a scanning image of a microbial carbonate rock full-view casting thin section according to an exemplary embodiment;

[0070] Fig. 9 are core and thin-section photographs of two types of microbial carbonate rocks according to an exemplary embodiment;

[0071] Fig.10 It is a statistical representation of the content of each fabric of the microbial carbonate rock of the Qigebulak Formation according to an exemplary embodiment;

[0072] Fig.11 It is a schematic diagram of NMR T2 curve of microbial carbonate rock of Qigebulak Formation according to an exemplary embodiment. DETAILED DESCRIPTION

[0073] The following description and accompanying drawings fully illustrate the specific embodiments of this article so that those skilled in the art can practice them. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. The scope of the embodiments of this article includes the entire scope of the claims, as well as all available equivalents of the claims. Herein, the terms "first", "second", etc. are only used to distinguish one element from another, without requiring or implying any actual relationship or order between these elements. In fact, the first element can also be called the second element, and vice versa. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the structure, device or equipment including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such structure, device or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the structure, device or equipment including the elements. Each embodiment is described in a progressive manner herein, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0074] The terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. in this document indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this document and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of this document, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, it can also be the internal communication of two elements, it can be a direct connection, or it can be an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0075] As used herein, the term "plurality" means two or more than two, unless otherwise specified.

[0076] In this document, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B.

[0077] In this article, the term "and / or" is a description of the association relationship between objects, indicating that three relationships may exist. For example, A and / or B means: A or B, or, A and B.

[0078] It should be understood that, although the various steps in the flow chart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the figure may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0079] Each module in the device or system of the present application can be implemented in whole or in part by software, hardware, or a combination thereof. The above modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to the above modules.

[0080] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0081] Figure 1 An embodiment of a microbial carbonate pore identification method of the present invention is shown.

[0082] In this optional embodiment, the microbial carbonate pore identification method includes:

[0083] Step S101, obtaining a microbial carbonate rock sample, and preparing a plurality of plunger samples and corresponding casting thin slices based on the microbial carbonate rock sample;

[0084] Step S103, performing image analysis on the casting thin section to construct a biocarbonate rock fabric corresponding to the casting thin section; and performing nuclear magnetic resonance analysis on the plunger sample to obtain a nuclear magnetic resonance curve, wherein the rock fabric morphological characteristics include pore type characteristics;

[0085] Step S105, determining the correspondence between the nuclear magnetic resonance curve and the pore type according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type; and drawing a microbial carbonate pore identification chart based on the correspondence between the nuclear magnetic resonance curve and the pore type;

[0086] Step S107, using the microbial carbonate pore identification plate to identify the microbial carbonate pores.

[0087] Figure 2 An embodiment of a microbial carbonate pore identification system of the present invention is shown.

[0088] In this optional embodiment, the microbial carbonate pore identification system includes:

[0089] The sample preparation unit 201 is used to obtain a microbial carbonate rock sample and prepare a plurality of plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample;

[0090] The sample analysis unit 203 is used to perform image analysis on the casting thin section to construct a biocarbonate rock fabric corresponding to the casting thin section; and perform nuclear magnetic resonance analysis on the plunger sample to obtain a nuclear magnetic resonance curve, wherein the rock fabric morphological characteristics include pore type characteristics;

[0091] A plate drawing unit 205 is used to determine the correspondence between the nuclear magnetic resonance curve and the pore type according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type; and draw a microbial carbonate pore identification plate based on the correspondence between the nuclear magnetic resonance curve and the pore type;

[0092] The pore identification unit 207 is used to identify the pores of the microbial carbonate rock using the microbial carbonate rock pore identification plate.

[0093] In the above optional embodiment, when preparing a plurality of plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample, the plunger samples can be cut from the microbial carbonate rock sample according to predetermined specifications, and a rock thin section of predetermined thickness can be cut at one end of each plunger sample as the casting thin section corresponding to the plunger sample.

[0094] Specifically, the core samples and field hand specimens were described macroscopically, the sampling information was recorded in detail, the microbial carbonate rock type was preliminarily determined, and representative samples were selected for casting thin sections and plunger sample preparation; plunger samples with a diameter of 2.5 cm and a length of 3 to 8 cm were prepared for nuclear magnetic resonance (NMR) testing. At one end of each plunger sample, a rock thin section with a thickness of 3 to 5 mm was cut for the preparation of casting thin sections, thereby achieving a strict correspondence between rock fabric statistics and NMR test samples.

[0095] In the above optional embodiment, when performing image analysis on the casting thin section and constructing the biocarbonate rock fabric corresponding to the casting thin section, the casting thin section is image scanned to obtain a casting thin section image; according to the different rock fabric morphological characteristics in microbial carbonate rocks, the casting thin section image is analyzed to construct the biocarbonate rock fabric corresponding to the casting thin section; wherein the rock fabric morphological characteristics include rock matrix type characteristics, pore type characteristics, fracture type characteristics and cementation period type characteristics.

[0096] When analyzing the cast thin section image according to the different rock fabric morphological characteristics in the microbial carbonate rock and constructing the biological carbonate rock fabric corresponding to the cast thin section, the cast thin section image is layer selected using Adobe Photoshop software according to the different rock fabric morphological characteristics in the microbial carbonate rock, and the histogram pixel is viewed based on the selected layer to obtain the image pixels of the corresponding rock fabric morphological characteristics; based on the obtained image pixels of the rock fabric morphological characteristics, the PSQ content (PSQ porosity) of the corresponding rock fabric morphological characteristics is calculated; and based on the calculated corresponding PSQ content, the microbial carbonate rock fabric corresponding to each cast thin section is drawn; wherein the microbial carbonate rock fabric is used to represent the PSQ content proportion of each rock fabric morphological characteristic in each cast thin section. The calculation formula of the PSQ content is: PSQ content = single rock fabric morphological characteristic pixel / total pixels*100%.

[0097] Specifically, a full-view scanning image of the casting thin section is obtained using a fully automatic scanning polarizing microscope for subsequent rock fabric statistics; the image format is jpg, tiff, bmp, etc. Figure 3 The plate shown in the figure preliminarily identifies the morphological characteristics of each rock fabric in the microbial carbonate rock casting image, including the matrix (mudstone matrix, microbial framework), various pores (framework pores, mold pores, intercrystalline pores, intergranular pores, and dissolution pores), cracks, and multi-stage cements. This facilitates quantitative statistics in subsequent steps. Import the full scan image of the casting thin section into Adobe Photoshop software, click "All" in the "Select" menu, call out "Histogram" in the "Window" menu, and record the total pixels of the entire image in real time. Click "Color Range" in the "Select" menu, then click the "Color Area" representing the pores, and click "OK" to complete the selection of all pores in the field of view. Extract the selected pores to different layers; view the pixels representing the pores in the histogram and record them in real time. Note: In this step, the pores are accurately selected by selecting the size of the "Tolerance" in the "Color Range". Use the manual selection tool in Adobe Photoshop to select different rock fabrics in the microbial carbonate rock in turn, record the pixels of each fabric in real time, and extract the image of each fabric to different layers (such as Figure 4 Repeat the above steps until the statistics of all samples are completed and the “microbial carbonate rock fabric statistics table” is compiled as shown in the figure. Figure 5 As shown in the figure, the proportions of different types of matrix, different types of pores and different stages of cement were calculated to obtain the PSQ content based on the Adobe Photoshop Quantification (PSQ) method. Based on the statistical results, the “rock fabrics of different types of microbial carbonate rocks” (such as Figure 6 shown).

[0098] In the above optional embodiment, when performing nuclear magnetic resonance analysis on the plunger sample to obtain a nuclear magnetic resonance curve, the experimental instrument can be a Newmai MicroMR23-060H-1 medium-sized low-field nuclear magnetic resonance analyzer, and the experimental method can be based on the petroleum and natural gas industry standard "SY / T6490-2007 Laboratory Measurement Specifications for Nuclear Magnetic Resonance Parameters of Rock Samples".

[0099] Before determining the correspondence between the nuclear magnetic resonance curve and the pore type based on the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, all the obtained nuclear magnetic resonance curves are grouped, and the nuclear magnetic resonance curve with the highest frequency in each group is used as the standard nuclear magnetic resonance curve; and based on the grouping of the nuclear magnetic resonance curves, the microbial carbonate rock fabrics are correspondingly grouped, and the pore type with the highest frequency in each microbial carbonate rock fabric is used as the standard pore type.

[0100] In addition, when determining the correspondence between the nuclear magnetic resonance curve and the pore type based on the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, the standard pore type corresponding to each standard nuclear magnetic resonance curve is determined based on the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, and the correspondence between the standard nuclear magnetic resonance curve and the standard pore type is obtained.

[0101] Among them, the correspondence between the curve type of the nuclear magnetic resonance curve and the pore type includes: when the nuclear magnetic resonance curve is a multi-peak-high amplitude T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: a combined pore type of mold pores and framework pores, and a combined pore type of dissolution pores and intercrystalline pores; when the nuclear magnetic resonance curve is a double-peak T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: a combined pore type of intercrystalline pores and dissolution pores; when the nuclear magnetic resonance curve is a single-peak T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: a combined pore type of intercrystalline pores, framework pores and mold pores; when the nuclear magnetic resonance curve is a multi-peak-low amplitude T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: dolomite pore type.

[0102] Specifically, the multi-peak and high T2 curves (MHT) have multiple characteristic peaks, and at least two characteristic peaks have pore signals >100n / a, and the characteristic peak T2 is between 100ms and 10000ms. The PSQ statistical results of samples with this kind of nuclear magnetic characteristics show that there are at least two or more pore types, among which the frequency of microbial mold pores and microbial framework pores appearing at the same time is the highest, and the frequency of dissolution pores and intercrystalline pores appearing at the same time is second. Therefore, the MHT curve indicates two types of pore combinations, one is the pore combination of microbial mold pores + microbial framework pores, and the other is the pore combination of dissolution pores + intercrystalline pores.

[0103] Double-peak T2 curves (DPT) have two similar characteristic peaks. The pore signals of the two characteristic peaks are >100n / a, and the characteristic peaks T2 are between 10ms~100ms and 100ms~10000ms respectively. For samples with this kind of NMR characteristics, the PSQ statistical results of most of these samples are mainly intercrystalline pores and dissolution pores. Therefore, the DPT curve represents the pore combination of intercrystalline pores + dissolution pores.

[0104] Single-peak T2 curves (SPT) have one characteristic peak, the pore signal of the characteristic peak is >100n / a, and the characteristic peak T2 ranges from 10ms to 10000ms. This type of sample is mainly characterized by a single pore type, mainly intercrystalline pores, followed by a small amount of microbial mold pores and microbial framework pores, and basically no dissolution pores. Therefore, the SPT curve represents the pore combination characteristics of a single intercrystalline pore + a small amount of microbial framework pores and mold pores.

[0105] Multi-peak and Low T2 curves (MLT) have unclear characteristic peaks or multiple characteristic peaks, and the pore signals of the characteristic peaks are all lower than 100n / a. PSQ statistics show a low pore content, and the PSQ content of most samples is less than 3%. Therefore, the MLT type indicates a dense microbial dolomite pore structure.

[0106] In the above optional embodiment, if Figure 7As shown, when drawing the microbial carbonate rock pore identification chart based on the correspondence between the nuclear magnetic resonance curve and the pore type, all microbial carbonate rock samples are divided into several groups. In each group of microbial carbonate rock samples, the standard nuclear magnetic resonance curve of each microbial carbonate rock sample is selected and represented by different colors or styles; the standard pore types of the microbial carbonate rock rock structure of each microbial carbonate rock sample are listed and displayed in comparison with the standard nuclear magnetic resonance curve.

[0107] The following explanation is given for the judgment chart:

[0108] a. The MHT-type T2 spectrum indicates a multi-type and multi-scale microbial carbonate pore system; the interior of the sample is mainly composed of microbial framework pores, microbial mold pores, dissolution pores and cracks; the MHT-type microbial carbonate with residual structure is mainly composed of intercrystalline pores and dissolution pores; the PSQ content is about 5% to 25%.

[0109] b. DPT-type microbial carbonate rocks show obvious diagenetic alteration phenomena, and the original morphology of microbial-related pores has been transformed; only a small number of microbial framework pores and microbial mold pores are preserved; the pore types are mainly intercrystalline pores and dissolution pores; the PSQ content is about 10%.

[0110] c. The primary pore types of SPT-type microbial carbonate rocks are relatively single, with only 1 to 2 types of pores in most of the tested samples; SPT-type residual structure microbial carbonate rocks are mainly intercrystalline pores with uniform pore sizes, with fewer dissolution pores; the PSQ content is about 5%.

[0111] d. No obvious primary microbial-related pores were found in the MLT-type microbial carbonate samples under the cast thin section, and there were few dissolution pores. The primary fabrics such as microbial laminae and mud crystal matrix were well preserved. The MLT-type T2 curve usually has no obvious characteristic peak or the characteristic peak pore signal is low, and the PSQ content is about 3% or even lower. Therefore, the MLT type usually indicates a pore system in which both primary microbial-related pores and secondary dissolution pores are not developed.

[0112] In order to facilitate the understanding of the above technical scheme of the present invention, the above technical scheme of the present invention is further detailed and described below through specific implementation cases. In this specific implementation case, the analysis and testing methods involved, unless otherwise specified, refer to conventional methods commonly used in the industry. At the same time, professional terms such as "microbial framework holes" and "microbial mold holes" that appear in the case are all recognized terms in the field and will not be repeated here. The sample in this embodiment is the microbial carbonate rock of the Qigebulak Formation of the Sinian System in the Keping area of ​​the Tarim Basin, with a geological age of about 580Ma to 560Ma.

[0113] Step S1, preferably a typical microbial carbonate rock sample is used to prepare a casting thin section and a plunger sample, the casting thin section sampling position is one end of the plunger sample, the sample number is strictly marked, and the plunger sample number corresponds to the casting thin section number one by one.

[0114] Step S2, using a fully automatic scanning microscope to obtain a full-view scanning image of the sample (such as Figure 8 The pore types such as microbial mold pores, microbial framework pores, intercrystalline pores and dissolution pores in microbial carbonate rocks were preliminarily identified (as shown in Figure 2). Fig. 9 The full scan image of the casting thin section was imported into Adobe Photoshop software, and the percentage of each structure in the full scan image of the casting thin section was quantitatively counted to compile a "microbial carbonate rock structure statistics table" as shown in the figure below. Fig.10 shown.

[0115] exist Fig. 9 In the figure, a) microbial framework pores, present in stromatolite carbonate rocks, cast thin section, single polarized light; (b) microbial framework pores and microbial mold pores, present in foamy spongestone carbonate rocks, cast thin section, single polarized light; (c) microbial framework pores and microbial mold pores, a partial enlargement of (b), cast thin section, single polarized light; (d) microbial mold pores, present in foamy spongestone carbonate rocks, cast thin section; (e) microbial framework pores and dissolution pores, present in residual structure carbonate rocks, cast thin section, single polarized light; (f) intercrystalline pores and dissolution pores, present in residual structure carbonate rocks, cast thin section, single polarized light.

[0116] Step S3, low-field nuclear magnetic resonance analysis is performed on the above plunger samples. Compile the nuclear magnetic resonance (NMR) T2 curves of different microbial carbonate plunger samples (such as Fig.11 As shown in the figure, the T2 curves are integrated and classified. Based on the characteristics of the NMR T2 curves, the pore development of the samples is preliminarily judged, and the matching relationship between the NMR T2 curves and the rock fabric is preliminarily determined. According to the actual situation of the samples, there are four types of NMR T2 curves, namely, Multi-peak and High T2 curves (MHT), Double-peak T2 curves (DPT), Single-peak T2 curves (SPT) and Multi-peak and Low T2 curves (MLT), which represent different pore structure types respectively.

[0117] Step S4, using different types of microbial carbonate pore system identification plates to identify the pore types of microbial carbonate rocks. MHT's foam spongestone carbonate rocks and stromatolite carbonate rocks are often dominated by microbial-related pores, such as microbial mold pores and microbial framework pores. In addition, there are a small number of dissolution pores; MHT's residual structural microbial rocks have more intercrystalline pores and dissolution pores. The MHT-type T2 spectra of the three different lithology samples all have peaks of pore signals within different relaxation time ranges, indicating that there are multi-scale pores such as micropores, mesopores, and macropores in the samples. It is worth noting that the quantitative statistical results under the microscope also match this. Almost all MHT-type samples have rich pore types and high PSQ content (5% to 25%). The bimodal (DPT) microbial carbonate rocks show obvious diagenetic alteration. The original morphology of microbial-related pores has been modified. The microbial grid pores and microbial mold pores in the foamed sponge carbonate rocks have been subjected to different degrees of dissolution and cementation, and only a small amount of primary pores are preserved. The pore types of residual structure microbial carbonate rocks are mainly intercrystalline pores and dissolution pores. The corresponding quantitative statistics of pores show that the total PSQ content of DPT samples is about 10%, of which the PSQ content of intercrystalline pores and dissolution pores is about 5%, while the PSQ content of microbial-related pores and cracks is about 1-2%. The primary pore types of SPT microbial carbonate rocks are relatively single, and there are only 1-2 types of pores in most of the tested samples. For example, there are only a small number of microbial grid pores and microbial mold pores in sample P1-278, and the pore size is uniform, mainly intercrystalline pores, and only a small number of microbial mold pores exist. Most MLT-type microbial carbonate rock samples have no obvious primary microbial-related pores even under cast thin sections, and there are few dissolution pores. MLT-type T2 curves usually have no obvious characteristic peaks or the characteristic peak pore signals are low, and the porosity is usually less than 2%.

[0118] The results show that the above method has good practicability for identifying pore types of ancient microbial carbonate rocks.

[0119] The present invention is not limited to the structures which have been described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for identifying pores in microbial carbonate rocks, characterized in that: include: Obtaining a microbial carbonate rock sample, and preparing a plurality of plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample; Performing image analysis on the casting thin section to construct a biocarbonate rock fabric corresponding to the casting thin section; and performing nuclear magnetic resonance analysis on the plunger sample to obtain a nuclear magnetic resonance curve, wherein the rock fabric morphological characteristics include pore type characteristics; According to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, the correspondence between the nuclear magnetic resonance curve and the pore type is determined; and based on the correspondence between the nuclear magnetic resonance curve and the pore type, a microbial carbonate pore identification chart is drawn; The microbial carbonate pore identification plate is used to identify the microbial carbonate pores.

2. The microbial carbonate pore identification method according to claim 1, characterized in that: The preparation of several plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample includes: According to predetermined specifications, plug samples are cut from the microbial carbonate rock sample, and a rock slice of predetermined thickness is cut at one end of each plug sample as a casting slice corresponding to the plug sample.

3. The microbial carbonate pore identification method according to claim 1, characterized in that: Performing image analysis on the casting thin section and constructing a biocarbonate rock fabric corresponding to the casting thin section comprises: Scanning the casting thin slice to obtain a casting thin slice image; According to the different rock fabric morphological characteristics in the microbial carbonate rock, the cast thin section image is analyzed to construct the rock fabric of the biocarbonate rock corresponding to the cast thin section; The rock fabric morphological characteristics include rock matrix type characteristics, pore type characteristics, fracture type characteristics and cementation stage type characteristics.

4. The microbial carbonate pore identification method according to claim 3, characterized in that: According to the different rock fabric morphological characteristics in the microbial carbonate rock, the casting thin section image is analyzed, and the rock fabric of the biocarbonate rock corresponding to the casting thin section is constructed, including: According to the different rock fabric morphological characteristics in microbial carbonate rocks, the casting thin section image layer was selected using Adobe Photoshop software, and the histogram pixels were viewed based on the selected layer to obtain the image pixels corresponding to the rock fabric morphological characteristics; Based on the obtained image pixels of the rock fabric morphological features, the PSQ content of the corresponding rock fabric morphological features is calculated; and based on the calculated corresponding PSQ content, the microbial carbonate rock fabric corresponding to each casting thin section is drawn; The microbial carbonate rock fabric is used to represent the PSQ content ratio of each rock fabric morphological feature in each casting thin section.

5. The microbial carbonate pore identification method according to claim 4, characterized in that: The calculation formula of the PSQ content is: PSQ content = single rock fabric morphological characteristic pixels / total pixels*100%.

6. The microbial carbonate pore identification method according to claim 5, characterized in that: Also includes: Before determining the correspondence between the nuclear magnetic resonance curve and the pore type according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, all the obtained nuclear magnetic resonance curves are grouped, and the nuclear magnetic resonance curve with the highest frequency in each group is used as the standard nuclear magnetic resonance curve; According to the grouping of nuclear magnetic resonance curves, the microbial carbonate rock fabrics are grouped accordingly, and the pore type with the highest frequency in each microbial carbonate rock fabric is taken as the standard pore type.

7. The microbial carbonate pore identification method according to claim 6, characterized in that: According to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, determining the correspondence between the nuclear magnetic resonance curve and the pore type includes: According to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type, the standard pore type corresponding to each standard nuclear magnetic resonance curve is determined, and the correspondence between the standard nuclear magnetic resonance curve and the standard pore type is obtained.

8. The microbial carbonate pore identification method according to claim 7, characterized in that: The corresponding relationship between the curve type of the NMR curve and the pore type includes: When the NMR curve is a multi-peak-high amplitude T2 curve, the pore types corresponding to the NMR curve include: a combined pore type of mold pores and grid pores, and a combined pore type of dissolution pores and intercrystalline pores; When the NMR curve is a double-peak T2 curve, the pore types corresponding to the NMR curve include: a combined pore type of intercrystalline pores and dissolution pores; When the nuclear magnetic resonance curve is a single-peak T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: a combined pore type of intercrystalline pores, framework pores, and mold pores; When the nuclear magnetic resonance curve is a multi-peak-low-amplitude T2 curve, the pore types corresponding to the nuclear magnetic resonance curve include: dolomite pore type.

9. The microbial carbonate pore identification method according to claim 8, characterized in that: The microbial carbonate pore identification chart based on the correspondence between NMR curves and pore types includes: All microbial carbonate rock samples are divided into several groups. In each group of microbial carbonate rock samples, a standard nuclear magnetic resonance curve of each microbial carbonate rock sample is selected and represented by different colors or styles; The standard pore types of the microbial carbonate rock fabric of each microbial carbonate rock sample are listed and compared with the standard nuclear magnetic resonance curve.

10. A microbial carbonate rock pore identification system, characterized in that: include: A sample preparation unit, used for obtaining a microbial carbonate rock sample, and preparing a plurality of plunger samples and corresponding casting thin sections based on the microbial carbonate rock sample; A sample analysis unit is used to perform image analysis on the casting thin section to construct a biocarbonate rock fabric corresponding to the casting thin section; and perform nuclear magnetic resonance analysis on the plunger sample to obtain a nuclear magnetic resonance curve, wherein the rock fabric morphological characteristics include pore type characteristics; A chart drawing unit is used to determine the correspondence between the nuclear magnetic resonance curve and the pore type according to the predetermined correspondence between the curve type of the nuclear magnetic resonance curve and the pore type; and to draw a microbial carbonate pore identification chart based on the correspondence between the nuclear magnetic resonance curve and the pore type; The pore identification unit is used to identify the pores of the microbial carbonate rock using the microbial carbonate rock pore identification plate.

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