A quantitative characterization method for differentiating clay minerals of different origins in continental shale.

Abstract

This invention discloses a quantitative characterization method for differentiating clay minerals of different origins in continental shale, relating to the field of reservoir mineral characterization technology in unconventional oil and gas resource exploration. It includes: S1, data acquisition step; S2, type classification step; S3, data analysis step; S4, difference source determination and quantitative determination step; S5, inversion step. The quantitative characterization method for differentiating clay minerals of different origins provided by this invention offers a theoretical basis and scientific evidence for the brittleness evaluation of continental shale, and has significant guiding significance for breaking through the theoretical bottleneck of continental shale oil fracturing and improving production efficiency.

Description

Technical Field

[0001] This invention relates to the field of reservoir mineral characterization technology in the exploration of unconventional oil and gas resources, and particularly to a quantitative characterization method for differentiating clay minerals of different origins in continental shale. Background Technology

[0002] Shale oil is mostly developed in terrestrial sedimentary environments and is an important resource for achieving large-scale growth in oil and gas reserves and production. Terrestrial shale has distinct characteristics of reservoir, oil-bearing, fluidity and compressibility. There is no precedent for large-scale commercial development worldwide. Mature geological theories and engineering technologies for marine shale are difficult to apply directly.

[0003] In terms of compressibility, brittleness is key to achieving high production in shale through fracturing. Highly brittle rock formations are prone to forming complex network fractures after fracturing, which can connect reservoirs over a large area, thereby increasing production; while low-brittle rock formations can only form simple biplane fractures. North American exploration practices also show that shale oil zones achieving commercial production after fracturing generally have high brittleness, and clay mineral content is generally below 30%. It is evident that clay minerals are closely related to shale brittleness, thus affecting the production capacity after shale fracturing. However, the clay mineral content of continental shale in my country is generally higher than the fracturing risk value for shale in North America, and whether brittleness can allow for high production after shale fracturing remains to be explored.

[0004] Clay mineral types, associated minerals, and secondary porosity significantly influence shale brittleness, and these factors are the result of diagenetic alteration of original clay minerals within a specific sedimentary environment. However, the control mechanisms of sedimentary conditions and diagenetic factors on clay mineral development and evolution are currently unclear, lacking a crucial geological basis for evaluating the brittleness of continental shale. Furthermore, while clay minerals have diverse origins (sedimentary and diagenetic), the sources of these differences have not been determined, and the key geological prerequisites for exploring the genetic relationship between clay mineral development and evolution and sedimentary conditions and diagenetic factors are lacking.

[0005] It is evident that quantitatively distinguishing clay minerals from different origins is crucial for evaluating the brittleness of clay-rich continental shale.

[0006] Therefore, proposing a quantitative characterization method to differentiate clay minerals of different origins in terrestrial shale to overcome the difficulties of existing technologies is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides a quantitative characterization method for distinguishing clay minerals of different origins in continental shale. This method provides a theoretical basis and scientific evidence for evaluating the brittleness of continental shale, and has important guiding significance for breaking through the theoretical bottleneck of fracturing in continental shale oil and improving production efficiency.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A quantitative characterization method for differentiating clay minerals of different origins in continental shale includes the following steps:

[0010] S1. Data acquisition steps: Clay mineral data are obtained through whole-rock XRD and clay XRD analysis, including: total clay mineral content, type of clay mineral, and proportion of clay mineral;

[0011] S2. Type Classification Steps: Based on the clay mineral data obtained in S1, and according to the transformation stage markers of the appearance or disappearance of each type of clay mineral in the vertical direction, typical clay mineral assemblage types are classified.

[0012] S3. Data Analysis Steps: Based on the typical clay mineral assemblage data obtained in S2, qualitative and quantitative processing is performed on the relevant structures of different types of typical clay mineral assemblages to obtain the micro-area characteristics of typical clay mineral assemblage types.

[0013] S4. Steps for determining and quantifying the source of difference: Based on the illite polymorph theory, the XRD polymorph peak spectrum of clay is fitted to the typical clay mineral assemblage type to determine and quantify the source of difference, illite.

[0014] S5. Inversion Steps: Based on the principle of material balance in the transformation process of clay minerals, the proportions of various sedimentary and diagenetic types in typical clay mineral assemblages are quantitatively inverted and verified by SEM-EDS crystal form identification and area statistics.

[0015] The above method, optionally, includes the following specific content in S1:

[0016] Based on the regional sedimentary facies zones and temperature and pressure field differences, samples were taken from different well locations in the center and edge of the deep depression. Whole-rock X-ray diffraction and clay XRD were used to obtain the total content, type and proportion of clay minerals in the samples.

[0017] The clay mineral types include: kaolinite, montmorillonite, illite, chlorite, and mixed-layer clay.

[0018] The above method, optionally, includes the following specific content in S2:

[0019] Typical clay mineral assemblages are classified based on the appearance of mixed layers of montmorillonite, the disappearance of montmorillonite, and the rapid decrease of kaolinite.

[0020] Using clay mineral assemblages as research units, we conducted vertical and horizontal cross-analysis of single wells to clarify the differences in the genesis and proportions of various types of clay minerals in different clay mineral assemblages.

[0021] The above method, optionally, includes the following specific content in S3:

[0022] S301 Qualitative characterization: The occurrence of typical clay mineral microregions was observed using a combined scanning electron microscope-catholuminescence-energy dispersive spectroscopy method, including: occurrence, crystal form, grain size and distribution differences;

[0023] S302 Statistical Quantification: SEM-EDS synchronous field-of-view imaging stitching technology and electron microscopy imaging stitching technology are applied, and the surface energy spectrum of the micro-area is simultaneously combined.

[0024] By progressively magnifying the grid viewpoint through image processing statistics, the representational surface area of ​​the sample is obtained, thus meeting the statistical quantification requirements.

[0025] S303 Micro-region Feature Extraction: Within the characterization area, the content of different types of clay minerals in the area is statistically analyzed; based on differences in color, grayscale, and occurrence, image processing software is used to distinguish the types of clay minerals in the micro-region, and the micro-region content information of each type of clay mineral is obtained.

[0026] The above method can optionally characterize the surface region: smaller than this field of view, the matrix distribution is unstable; larger than this field of view, the matrix distribution remains stable and unchanged.

[0027] As can be seen from the above technical solution, compared with the prior art, the characterization method of the present invention for quantitatively distinguishing clay minerals of different origins in terrestrial shale has the following beneficial effects:

[0028] Based on the illite polymorphism theory and the material balance theory, a comprehensive method combining XRD diffraction, SEM / TEM, and radioisotope dating is used to characterize the proportion of sedimentary and diagenetic clay minerals of the same type. The quantitative characterization method for distinguishing clay minerals from different origins provides a theoretical basis and scientific evidence for the evaluation of the brittleness of continental shale, and has important guiding significance for breaking through the theoretical bottleneck of fracturing in continental shale oil and improving production efficiency. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 A flowchart of a characterization method for quantitatively distinguishing clay minerals of different genetic origins in terrestrial shale, provided by the present invention;

[0031] Figure 2 The flowchart for determining and quantifying the sources of clay mineral differences provided by this invention;

[0032] Figure 3 The present invention provides mineral transformation markers and assemblage types for the Qingshankou Formation shale clay.

[0033] Figure 4 A schematic diagram of the method for obtaining the representational region provided by the present invention;

[0034] Figure 5 A flowchart for classifying and quantifying matrix porosity within a characterization region provided by this invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0037] This invention can be used in a wide variety of general-purpose or special-purpose computing device environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor devices, distributed computing environments including any of the above devices, etc.

[0038] Reference Figure 1 and Figure 2 As shown, this invention discloses a quantitative characterization method for differentiating clay minerals of different origins in continental shale, comprising the following steps:

[0039] S1. Data acquisition steps: Clay mineral data are obtained through whole-rock XRD and clay XRD analysis, including: total clay mineral content, type of major clay minerals and proportion of major clay minerals;

[0040] S2. Type Classification Steps: Based on the clay mineral data obtained in S1, and according to the transformation stage markers of the appearance or disappearance of each type of clay mineral in the vertical direction, typical clay mineral assemblage types are classified.

[0041] S3. Data Analysis Steps: Based on the typical clay mineral assemblage data obtained in S2, qualitative and quantitative processing is performed on the relevant structures of different types of typical clay mineral assemblages to obtain the micro-area characteristics of typical clay mineral assemblage types.

[0042] S4. Steps for determining and quantifying the source of difference: Based on the illite polymorph theory, the XRD polymorph peak spectrum of clay is fitted to the typical clay mineral assemblage type to determine and quantify the source of difference, illite.

[0043] S5. Inversion Steps: Based on the principle of material balance in the transformation process of clay minerals, the proportions of various sedimentary and diagenetic types in typical clay mineral assemblages are quantitatively inverted and verified by SEM-EDS crystal form identification and area statistics.

[0044] Furthermore, the specific content of S1 includes:

[0045] Based on the regional sedimentary facies zones and temperature and pressure field differences, samples were taken from different well locations in the center and edge of the deep depression. Whole-rock X-ray diffraction and clay XRD were used to obtain the total content, type and proportion of clay minerals in the samples.

[0046] The clay mineral types include: kaolinite, montmorillonite, illite, chlorite, and mixed-layer clay.

[0047] Furthermore, the specific content of S2 includes:

[0048] Based on the transformation markers such as the appearance of mixed layers of montmorillonite, the disappearance of montmorillonite, and the rapid decrease of kaolinite, typical clay mineral assemblages are classified.

[0049] Using clay mineral assemblages as research units, we conducted vertical and horizontal cross-analysis of single wells to clarify the differences in the genesis and proportions of various types of clay minerals in different clay mineral assemblages.

[0050] Specifically, ① based on the regional sedimentary facies zones and temperature and pressure field differences, samples were taken from different well locations in the center and edge of the deep depression, and whole-rock X-ray diffraction (XRD) and clay XRD were used to obtain the total content, type and proportion of clay minerals in the samples.

[0051] ② The main clay mineral types include: kaolinite (K), montmorillonite (S), illite (I), chlorite (C) and mixed-layer (I / S); chlorite content in continental shale is low and is not considered as a major type.

[0052] ③ The clay mineral evolution sequence shows the characteristics of montmorillonite and kaolinite successively decreasing and disappearing, while illite increases and gradually becomes dominant; based on the transformation markers such as the appearance of illite-montmorillonite mixed layers, the disappearance of montmorillonite and the rapid decrease of kaolinite, typical clay mineral assemblages can be roughly divided.

[0053] For example: montmorillonite + kaolinite + illite, montmorillonite + kaolinite + illite + illite-montmorillonite mixed layer, kaolinite + illite + illite-montmorillonite mixed layer (such as...) Figure 3 ).

[0054] ⑤ Using clay mineral assemblages as research units, conduct vertical cross-analysis of single wells and horizontal cross-analysis between wells to clarify the differences in the origin and proportion of various types of clay minerals in different clay mineral assemblages.

[0055] Furthermore, the specific content of S3 includes:

[0056] S301 Qualitative characterization: The occurrence of typical clay mineral microregions was observed using a combined scanning electron microscope-catholuminescence-energy dispersive spectroscopy method, including: occurrence, crystal form, grain size and distribution differences;

[0057] S302 Statistical Quantification: SEM-EDS synchronous field-of-view imaging stitching technology and electron microscopy imaging stitching technology are applied, and the surface energy spectrum of the micro-area is simultaneously combined.

[0058] By progressively magnifying the grid viewpoint through image processing statistics, the representational surface area of ​​the sample is obtained, thus meeting the statistical quantification requirements.

[0059] S303 Micro-region Feature Extraction: Within the characterization area, the content of different types of clay minerals in the area is statistically analyzed; based on differences in color, grayscale, and occurrence, image processing software is used to distinguish the types of clay minerals in the micro-region, and the micro-region content information of each type of clay mineral is obtained.

[0060] Furthermore, the characterization of the surface area is as follows: the matrix distribution is unstable when the field of view is smaller than this, and the matrix distribution remains stable when the field of view is larger than this.

[0061] Specifically, ① the combined method of scanning electron microscopy-catholuminescence-energy dispersive spectroscopy (SEM-CL-EDS) was used to observe the occurrence of typical clay mineral microregions, including: occurrence, crystal form, grain size and distribution differences (qualitative characterization).

[0062] ② The application of SEM-EDS simultaneous field-of-view imaging and stitching technology, utilizing electron microscopy imaging and stitching techniques, achieves compatibility between a large field of view and high resolution, and simultaneously combines in-situ surface area energy dispersive spectroscopy (EDS) of micro-regions. Through image processing and statistical analysis of progressively magnified grid fields, the characterization surface area of ​​the sample is obtained. Figure 4 This achieves the requirement of statistical quantification (with representativeness). (Representational domain: matrix distribution is unstable below this field of view, and stable and unchanged above this field of view).

[0063] ③ Within the characterization area, the content of different types of clay minerals in the area is statistically analyzed. Based on differences in color, grayscale, and occurrence, image processing software (such as ImageJ) is used to distinguish different types of clay minerals in the micro-region, identify and extract the content information of each type of clay mineral in the micro-region, and meet the requirements for classification statistics. Figure 5 );

[0064] In a specific embodiment, ① the premise is: the degradation of illite to kaolinite within a specific region is not considered. Clay mineral transformation is mainly limited to two types: illitization of montmorillonite (formation temperature <120℃, SI / SI) and illitization of kaolinite (formation temperature >120℃, KI), and the transformation temperatures of the two types roughly alternate and do not overlap. Figure 3 Stages are visible at a depth of 1650m. (Montmorillonite: S; I / S mixed illite-montmorillonite: I; Illite: I; Kaolinite: K).

[0065] Illite petrification of montmorillonite:

[0066] 1.57 montmorillonite + 10 H₂O + 3.93 K → 1.0 illite

[0067] +1.57Na+3.14Ca+4.28Mg+4.78Fe+24.66Si+57O+11.4OH+15.7H2O.

[0068] The illite-based petrochemical treatment of kaolinite:

[0069] 3Al2Si2O5(OH)4 (kaolinite) + 2K+ = 2KAl3Si3O 10 (OH)₂(illite) + 2H⁺ + 3H₂O

[0070] ③ Preliminary identification of various clay minerals based on geological analysis: Montmorillonite and kaolinite decrease monotonically with burial depth and can be considered as sedimentary sources; illite-montmorillonite mixed layers are calculated based on the mixing coefficient, and illite in the mixed layers is of diagenetic source and montmorillonite is of sedimentary source; illite has two sources and needs further identification and quantification.

[0071] ④ Illite Origin Determination and Quantification: According to the illite polymorph theory, the main illite polymorphs are 2M1 (formation temperature > 280℃) and 1Md / 1M (formation temperature < 200℃). Shale generally does not undergo illite recrystallization, and there is no authigenic illite with a formation temperature > 280℃ in diagenetic zones. Therefore, the 2M1 polymorph can be identified as sedimentary, while the 1Md / 1M polymorph can be identified as diagenetic. Based on this, the XRD diffraction peak spectra of the two illite polymorphs were fitted using Profex software to quantify the relative contents of sedimentary and diagenetic illite.

[0072] ⑤ Relative content inversion of montmorillonite and kaolinite: Based on the determination of illite source, and based on the principle of material balance in the transformation process, the content of montmorillonite and kaolinite consumed in the illiteification process is inverted, and the content of montmorillonite and kaolinite in the XRD test results is added to obtain the total content of original sedimentary montmorillonite and kaolinite.

[0073] Combination ①: S+K+I — Sedimentary environment

[0074] Diagenetic events: Neglected as zero

[0075] Montmorillonite: Terrigenous debris (XRD values)

[0076] Kaolinite: Terrigenous debris (XRD values)

[0077] Illite: Terrigenous Debris (XRD Values)

[0078] Boundary line between combination A and B: earliest age of authigenic illite growth, starting point of illite-smectite mixed-layer development, geothermal temperature

[0079] Combination ②: S+K+I+I / S — sedimentary environment, diagenetic environment

[0080] Diagenetic events: transformation of montmorillonite to illite-montmorillonite mixed-bed strata, and transformation of illite-montmorillonite mixed-bed strata to illite.

[0081] First, using the illite-montmorillonite mixed-layer R sequence, the I / S ratio was divided into montmorillonite and illite, while the kaolinite content remained unchanged.

[0082] Montmorillonite = XRD test value + estimated value of montmorillonite mixed layer

[0083] Illite = Terrigenous clastic material (XRD values) + Autogenic diagenesis (XRD values ​​+ Illite-Montene mixed-layer inference values)

[0084] Kaolinite content remains unchanged: Previous experimental studies have shown that 50℃ is the minimum time for montmorillonite to begin illite transformation, and 120-140℃ is the time when montmorillonite illite transformation stops, which is also the time when kaolinite illite transformation begins.

[0085] Combined B / C boundary line: montmorillonite extinction line, kaolinite decreasing trend inflection point, geothermal temperature

[0086] Combination ③: K+I+I / S — sedimentary environment, diagenetic environment

[0087] Diagenetic events: transformation of kaolinite to illite, transformation of montmorillonite to illite-montmorillonite mixed-layer formation, and transformation of illite-montmorillonite mixed-layer formation to illite.

[0088] Montmorillonite = authigenic diagenesis (estimated value of illite-montmorillonite mixed strata)

[0089] Illite = Terrigenous clastic material (XRD values) + Autogenic diagenesis (XRD values ​​+ Illite-Monganite mixed-layer inference + Kaolinite inference)

[0090] Kaolinite = XRD test value + Calculated kaolinite value

[0091] ⑥ Finally, SEM-EDS area statistics of clay minerals of the same type but different occurrences were performed to verify the results.

[0092] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0093] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A quantitative characterization method for differentiating clay minerals of different origins in continental shale, characterized in that, Includes the following steps: S1. Data acquisition steps: Obtain clay mineral data through whole-rock XRD and clay XRD analysis, including: total clay mineral content, type of clay mineral, and proportion of clay mineral; S2, Type Classification Steps: Based on the clay mineral data obtained in S1, and according to the transformation stage markers of the appearance or disappearance of each type of clay mineral in the vertical direction, typical clay mineral assemblage types are classified. S3. Data Analysis Steps: Based on the typical clay mineral assemblage data obtained in S2, qualitative and quantitative processing is performed on the relevant structures of different types of typical clay mineral assemblages to obtain the micro-area characteristics of typical clay mineral assemblage types. S4. Determination and Quantification of the Source of Difference: Based on the illite polymorph theory, the XRD polymorph peak spectra of clay are fitted to typical clay mineral assemblage types to determine and quantify the source of difference, illite. S5. Inversion Steps: Based on the principle of material balance in the transformation process of clay minerals, the proportions of various sedimentary and diagenetic types in typical clay mineral assemblages are quantitatively inverted and verified by SEM-EDS crystal form identification and area statistics.

2. The characterization method for quantitatively distinguishing clay minerals of different genetic origins in terrestrial shale according to claim 1, characterized in that, The specific content of S1 includes: Based on the regional sedimentary facies zones and temperature and pressure field differences, samples were taken from different well locations in the center and edge of the deep depression. Whole-rock X-ray diffraction and clay XRD were used to obtain the total content, type and proportion of clay minerals in the samples. The clay mineral types include: kaolinite, montmorillonite, illite, chlorite, and mixed-layer clay.

3. The characterization method for quantitatively distinguishing clay minerals of different origins in terrestrial shale according to claim 2, characterized in that, The specific content of S2 includes: Typical clay mineral assemblages are classified based on the appearance of mixed layers of montmorillonite, the disappearance of montmorillonite, and the rapid decrease of kaolinite. Using clay mineral assemblages as research units, we conducted vertical and horizontal cross-analysis of single wells to clarify the differences in the genesis and proportions of various types of clay minerals in different clay mineral assemblages.

4. The characterization method for quantitatively distinguishing clay minerals of different origins in terrestrial shale according to claim 2, characterized in that, The specific content of S3 includes: S301 Qualitative characterization: The occurrence of typical clay mineral microregions was observed using a combined scanning electron microscope-catholuminescence-energy dispersive spectroscopy method, including: occurrence, crystal form, grain size and distribution differences; S302 Statistical Quantification: SEM-EDS synchronous field-of-view imaging stitching technology and electron microscopy imaging stitching technology are applied, and the surface energy spectrum of the micro-area is simultaneously combined. By progressively magnifying the grid viewpoint through image processing statistics, the representational surface area of ​​the sample is obtained, thus meeting the statistical quantification requirements. S303 Micro-region Feature Extraction: Within the characterization area, the content of different types of clay minerals in the area is statistically analyzed; based on differences in color, grayscale, and occurrence, image processing software is used to distinguish the types of clay minerals in the micro-region, and the micro-region content information of each type of clay mineral is obtained.

5. The characterization method for quantitatively distinguishing clay minerals of different origins in terrestrial shale according to claim 4, characterized in that, Characterization region: The matrix distribution is unstable when it is smaller than this field of view, and stable and unchanged when it is larger than this field of view.

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