Characterization method for quantitatively distinguishing clay minerals with different cause sources in continental facies shale

Abstract

The invention discloses a characterization method for quantitatively distinguishing clay minerals with different cause sources in continental facies shale, and relates to the technical field of characterization of reservoir minerals in the field of unconventional oil and gas resource exploration. Comprising the following steps: S1, data acquisition; s2, a type division step; s3, a data analysis step; s4, a difference source judgment and quantitative judgment step; and S5, an inversion step. The characterization method for quantitatively distinguishing the clay minerals with different cause sources, provided by the invention, provides a theoretical basis and a scientific basis for evaluating the brittleness of continental facies shale, and has important guiding significance for breaking through the bottleneck of a continental facies shale oil fracturing theory and extracting and improving efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir mineral characterization in the field of unconventional oil and gas resource exploration, and in particular to a characterization method for quantitatively distinguishing clay minerals of different genetic origins in continental shale. Background Art

[0002] Shale oil is mostly developed in continental sedimentary environments and is an important resource for achieving large-scale growth in oil and gas reserves and production. Continental shales have distinct reservoir properties, oil content, fluidity and compressibility. There is no precedent for large-scale commercial development in the world, and the mature geological theories and engineering technologies of marine shales are difficult to directly apply.

[0003] In terms of compressibility, brittleness is the key to achieving high production of shale through fracturing. After fracturing, high-brittle rock formations are prone to form complex network fractures, which can connect reservoirs over a large area and thus increase production; while low-brittle rock formations can only form simple double-wing fractures. North American exploration practices also show that shale oil zones that achieve commercial production after fracturing are all highly brittle, and the clay mineral content is generally less than 30%. It can be seen that clay minerals are closely related to the brittleness of shale, which in turn affects the production capacity of shale after fracturing. However, the clay mineral content of my country's continental shales is generally higher than the risk value of shale fracturing in North America. Whether brittleness can allow shale to achieve high production after fracturing remains to be explored.

[0004] Clay mineral types, associated minerals and secondary pores have an important influence on shale brittleness, and these factors are the result of diagenetic transformation of original clay minerals in a certain sedimentary environment. However, at present, the control mechanism of sedimentary conditions and diagenetic factors on the development and evolution of clay minerals has not been clarified, and there is a lack of key geological basis for evaluating the brittleness of continental shales. At the same time, clay minerals have different sources (sedimentary and diagenetic), but the different sources of clay minerals have not been determined, and there is a lack of key geological premises for exploring the causal relationship between the development and evolution of clay minerals and sedimentary conditions and diagenetic factors.

[0005] It can be seen that quantitatively distinguishing clay minerals of different genetic origins is crucial for evaluating the brittleness of clay-rich continental shales.

[0006] Therefore, it is an urgent problem for technicians in this field to propose a characterization method for quantitatively distinguishing clay minerals of different genetic origins in continental shales to solve the difficulties existing in the existing technology. Summary of the invention

[0007] In view of this, the present invention provides a characterization method for quantitatively distinguishing clay minerals with different genetic origins in continental shales, and provides a theoretical basis and scientific basis for the brittleness evaluation of continental shales, which has important guiding significance for breaking through the theoretical bottleneck of continental shale oil fracturing and increasing production efficiency.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A characterization method for quantitatively distinguishing clay minerals of different genetic origins in continental shale comprises the following steps:

[0010] S1. Data acquisition step: Obtain clay mineral data through whole-rock XRD and clay XRD analysis, including: total clay mineral content, clay mineral type and clay mineral ratio;

[0011] S2. Type classification step: Based on the clay mineral data obtained in S1, typical clay mineral combination types are classified according to the transformation stage signs of the appearance or disappearance of each type of clay mineral in the vertical direction;

[0012] S3, data analysis step: based on the typical clay mineral assemblage type data obtained in S2, the relevant structures of different types of typical clay mineral assemblages are qualitatively and quantitatively processed to obtain the micro-region characteristics of the typical clay mineral assemblage type;

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

[0014] S5. Inversion steps: Based on the material balance principle in the process of clay mineral transformation, the proportion of each type of sedimentary and diagenetic types in the typical clay mineral combination is quantitatively inverted, and verified by SEM-EDS crystal type identification and surface statistics.

[0015] In the above method, optionally, the specific contents in S1 include:

[0016] According to the differences in regional sedimentary facies and temperature and pressure fields, different well locations in the center and edge of the deep depression were selected for sampling, and the total content, type and proportion of clay minerals in the samples were obtained by whole-rock X-ray diffraction and clay XRD.

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

[0018] In the above method, optionally, the specific contents of S2 include:

[0019] The typical clay mineral assemblage is divided by the appearance of illite-montmorillonite mixed layers, the disappearance of montmorillonite and the rapid decrease of kaolinite as transformation marks;

[0020] Taking clay mineral assemblages as the research unit, vertical cross-comparison analysis of single wells and horizontal cross-comparison analysis between wells were carried out to clarify the differences in the origins and proportions of various types of clay minerals in different clay mineral assemblages.

[0021] In the above method, optionally, the specific contents in S3 include:

[0022] S301 Qualitative characterization: Use the combined method of scanning electron microscopy, cathodoluminescence and energy spectrum to observe the occurrence of typical clay minerals in micro-areas, including: occurrence, crystal form, particle size and distribution differences;

[0023] S302 Statistical quantification: Apply SEM-EDS synchronous field imaging stitching technology and electron microscope imaging stitching technology, and simultaneously combine the in-situ surface energy spectrum of the micro-area;

[0024] Through the image processing statistics of the grid field of view that is gradually enlarged, the representative surface area of ​​the sample is obtained to obtain the statistical quantification requirements;

[0025] S303 Micro-area feature extraction: within the characterization area, count the surface contents of different types of clay minerals; based on the differences in color, grayscale, and occurrence, use image processing software to distinguish the types of clay minerals in the microscopic area and obtain the micro-area surface content information of each type of clay mineral.

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

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

[0028] Based on the illite polymorphic theory and material balance theory, the comprehensive method of XRD diffraction, SEM / TEM and radioactive isotope dating is used to characterize the proportion of sedimentary and diagenetic types of clay minerals of the same type. The characterization method of quantitatively distinguishing clay minerals of different genetic origins provides a theoretical basis and scientific basis for the evaluation of the brittleness of continental shale, and has important guiding significance for breaking through the theoretical bottleneck of continental shale oil fracturing and increasing production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 A flow chart of a characterization method for quantitatively distinguishing clay minerals of different genetic origins in continental shales provided by the present invention;

[0031] Figure 2 A flow chart for determining and quantifying the sources of clay mineral differences provided by the present invention;

[0032] Figure 3 The Qingshankou Formation shale clay mineral transformation markers and combination types provided by the present invention;

[0033] Figure 4 A schematic diagram of the method for obtaining a characterization area provided by the present invention;

[0034] Figure 5 A flow chart for classifying and quantifying matrix pores within a characterization surface provided by the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. 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 process, method, article or device including the elements.

[0037] The present invention can be used in many general or special computing device environments or configurations, such as personal computers, server computers, handheld or portable devices, tablet devices, multi-processor devices, distributed computing environments including any of the above devices or devices, etc.

[0038] Reference Figure 1 and Figure 2 As shown, the present invention discloses a method for quantitatively distinguishing clay minerals of different genetic origins in continental shale, comprising the following steps:

[0039] S1. Data acquisition step: Obtain clay mineral data through whole rock XRD and clay XRD analysis, including: total clay mineral content, types of major clay minerals and proportions of major clay minerals;

[0040] S2. Type classification step: Based on the clay mineral data obtained in S1, typical clay mineral combination types are classified according to the transformation stage signs of the appearance or disappearance of each type of clay mineral in the vertical direction;

[0041] S3, data analysis step: based on the typical clay mineral assemblage type data obtained in S2, the relevant structures of different types of typical clay mineral assemblages are qualitatively and quantitatively processed to obtain the micro-region characteristics of the typical clay mineral assemblage type;

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

[0043] S5. Inversion steps: Based on the material balance principle in the process of clay mineral transformation, the proportion of each type of sedimentary and diagenetic types in the typical clay mineral combination is quantitatively inverted, and verified by SEM-EDS crystal type identification and surface statistics.

[0044] Furthermore, the specific contents of S1 include:

[0045] According to the differences in regional sedimentary facies and temperature and pressure fields, different well locations in the center and edge of the deep depression were selected for sampling, and the total content, type and proportion of clay minerals in the samples were obtained by whole-rock X-ray diffraction and clay XRD.

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

[0047] Furthermore, the specific contents of S2 include:

[0048] The typical clay mineral assemblage is divided according to transformation signs such as the appearance of illite-montmorillonite mixed layers, the disappearance of montmorillonite and the rapid decrease of kaolinite.

[0049] Taking clay mineral assemblages as the research unit, vertical cross-comparison analysis of single wells and horizontal cross-comparison analysis between wells were carried out to clarify the differences in the origins and proportions of various types of clay minerals in different clay mineral assemblages.

[0050] Specifically, ① based on the differences in regional sedimentary facies and temperature and pressure fields, different well locations in the center and edge of the deep depression were selected for sampling, 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 types of clay minerals include: kaolinite (K), montmorillonite (S), illite (I), chlorite (C) and mixed layer (I / S). The chlorite content in continental shale is low and is not considered as the main 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 signs such as the appearance of illite-montmorillonite mixed layers, the disappearance of montmorillonite and the rapid decrease of kaolinite, the typical clay mineral assemblage 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 Taking clay mineral assemblages as the research unit, conduct vertical cross-comparison analysis of single wells and horizontal cross-comparison analysis between wells to clarify the differences in the origins and proportions of various types of clay minerals in different clay mineral assemblages.

[0055] Furthermore, the specific contents of S3 include:

[0056] S301 Qualitative characterization: Use the combined method of scanning electron microscopy, cathodoluminescence and energy spectrum to observe the occurrence of typical clay minerals in micro-areas, including: occurrence, crystal form, particle size and distribution differences;

[0057] S302 Statistical quantification: Apply SEM-EDS synchronous field imaging stitching technology and electron microscope imaging stitching technology, and simultaneously combine the in-situ surface energy spectrum of the micro-area;

[0058] Through the image processing statistics of the grid field of view that is gradually enlarged, the representative surface area of ​​the sample is obtained to obtain the statistical quantification requirements;

[0059] S303 Micro-area feature extraction: within the characterization area, count the surface contents of different types of clay minerals; based on the differences in color, grayscale, and occurrence, use image processing software to distinguish the types of clay minerals in the microscopic area and obtain the micro-area surface content information of each type of clay mineral.

[0060] Furthermore, the face domain is characterized: if the field of view is smaller than this field of view, the matrix distribution is unstable; if the field of view is larger than this field of view, the matrix distribution is stable and unchanged.

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

[0062] ② Apply SEM-EDS synchronous field of view imaging stitching technology, use electron microscope imaging stitching technology to achieve the compatibility of large field of view and high resolution, and simultaneously combine the micro-area in-situ surface energy spectrum (EDS). Through the image processing statistics of the grid field of view gradually enlarged, the characterization surface of the sample is obtained ( Figure 4 ), to achieve the statistical quantification requirements (representative). (Characterization domain: the matrix distribution is unstable when the field of view is smaller than this field of view, and the matrix distribution is stable and unchanged when the field of view is larger than this field of view).

[0063] ③ In the characterization area, count the surface content of different types of clay minerals. Based on the differences in color, grayscale, and occurrence, use image processing software (such as Image J) to distinguish the various types of clay minerals in the microscopic area, identify and extract the micro-area surface content information of each type of clay mineral, and meet the needs of classification statistics ( Figure 5 );

[0064] In a specific embodiment, ① Precondition judgment: Ignore the degradation of illite to kaolinite in the regional scope. Clay mineral transformation is mainly limited to two types: illitization of montmorillonite (formation temperature <120°C, SI / SI) and illitization of kaolinite (formation temperature >120°C, KI), and the transformation temperatures of the two are roughly alternating and do not overlap ( Figure 3 Stages can be seen at a depth of 1650m). (montmorillonite: S; illite-montmorillonite mixed layer: I / S; illite: I; kaolinite: K).

[0065] Illitization of montmorillonite:

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

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

[0068] Illitization of kaolinite:

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

[0070] ③ Preliminary determination of various clay minerals based on geological analysis: montmorillonite and kaolinite decrease monotonically with burial depth and can be considered to be of sedimentary origin; the illite-montmorillonite mixed layer is calculated using the mixed layer coefficient, in which the illite is of diagenetic origin and the montmorillonite is of sedimentary origin; illite has two sources, which require further determination and quantification.

[0071] ④ Illite source determination and quantification: According to illite polymorphic 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 the diagenetic belt. Therefore, the 2M1 polymorph can be determined as sedimentary type, and the 1Md / 1M polymorph can be determined as diagenetic type. Based on this, Profex software was used to fit the XRD diffraction peak spectra of the two illite polymorphs to quantify the relative content of sedimentary and diagenetic illite.

[0072] ⑤ Inversion of relative contents of montmorillonite and kaolinite: On the basis of the determination of illite source and based on the material balance principle in the transformation process, the contents of montmorillonite and kaolinite consumed in the illite petrochemical process are inverted, and the contents of montmorillonite and kaolinite in the XRD test results are added as the total contents of original sedimentary montmorillonite and kaolinite.

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

[0074] Diagenetic events: Ignore as zero

[0075] Montmorillonite: terrigenous debris (XRD test value)

[0076] Kaolinite: terrigenous debris (XRD test value)

[0077] Illite: terrigenous debris (XRD test value)

[0078] Assemblage A / B boundary: the earliest growth age of authigenic illite, the starting point of illite-smectite mixed layer development, and the ground temperature

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

[0080] Diagenetic events: transformation of montmorillonite to mixed layers of illite and montmorillonite, and transformation of mixed layers of illite and montmorillonite to illite

[0081] First, the I / S is divided into montmorillonite and illite through the R sequence of the illite-montmorillonite mixed layer, and the kaolinite content remains unchanged.

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

[0083] Illite = terrigenous debris (XRD test value) + diagenetic authigenic (XRD test value + illite-montmorillonite mixed layer estimated value)

[0084] The kaolinite content remains unchanged: Previous experimental studies have shown that 50°C is the minimum time for montmorillonite to begin illitization, and 120-140°C is the time when montmorillonite illitization stops, which is also the time when kaolinite illitization starts.

[0085] Combined B / C dividing line: montmorillonite extinction line, kaolinite trend reduction inflection point, ground temperature

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

[0087] Diagenetic events: transformation of kaolinite to illite, transformation of montmorillonite to mixed layers of illite and montmorillonite, transformation of mixed layers of illite and montmorillonite to illite

[0088] Montmorillonite = diagenetic authigenic (calculated value of illite-montmorillonite mixed layer)

[0089] Illite = terrigenous debris (XRD test value) + diagenetic authigenic (XRD test value + illite-montmorillonite mixed layer estimated value + kaolinite estimated value)

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

[0091] ⑥Finally, SEM-EDS surface statistics of clay minerals of the same type but different occurrences were carried out for verification.

[0092] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without creative work.

[0093] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for quantitatively distinguishing clay minerals of different genetic origins in continental shales, characterized in that: The following steps are involved: S1. Data acquisition step: Obtain clay mineral data through whole-rock XRD and clay XRD analysis, including: total clay mineral content, clay mineral type and clay mineral ratio; S2. Type classification step: Based on the clay mineral data obtained in S1, typical clay mineral combination types are classified according to the transformation stage signs of the appearance or disappearance of each type of clay mineral in the vertical direction; S3, data analysis step: based on the typical clay mineral assemblage type data obtained in S2, the relevant structures of different types of typical clay mineral assemblages are qualitatively and quantitatively processed to obtain the micro-region characteristics of the typical clay mineral assemblage type; S4. Steps for determining and quantifying the source of differences: Based on the illite polymorphic theory, the clay XRD polymorphic peak spectrum is fitted to the typical clay mineral combination type to determine and quantify the source of the differences, the illite; S5. Inversion steps: Based on the material balance principle in the process of clay mineral transformation, the proportion of each type of sedimentary and diagenetic types in the typical clay mineral combination is quantitatively inverted, and verified by SEM-EDS crystal type identification and surface statistics.

2. The method for quantitatively distinguishing clay minerals of different genetic origins in continental shale according to claim 1, characterized in that: The specific contents of S1 include: According to the differences in regional sedimentary facies and temperature and pressure fields, different well locations in the center and edge of the deep depression were selected for sampling, and the total content, type and proportion of clay minerals in the samples were obtained by whole-rock X-ray diffraction and clay XRD. Among them, clay mineral types include: kaolinite, montmorillonite, illite, chlorite and mixed layer.

3. The method for quantitatively distinguishing clay minerals of different genetic origins in continental shale according to claim 2, characterized in that: The specific contents of S2 include: The typical clay mineral assemblage is divided by the appearance of illite-montmorillonite mixed layers, the disappearance of montmorillonite and the rapid decrease of kaolinite as transformation marks; Taking clay mineral assemblages as the research unit, vertical cross-comparison analysis of single wells and horizontal cross-comparison analysis between wells were carried out to clarify the differences in the origins and proportions of various types of clay minerals in different clay mineral assemblages.

4. The method for quantitatively distinguishing clay minerals of different genetic origins in continental shale according to claim 2, characterized in that: The specific contents of S3 include: S301 Qualitative characterization: Use the combined method of scanning electron microscopy, cathodoluminescence and energy spectrum to observe the occurrence of typical clay minerals in micro-areas, including: occurrence, crystal form, particle size and distribution differences; S302 Statistical quantification: Apply SEM-EDS synchronous field imaging stitching technology and electron microscope imaging stitching technology, and simultaneously combine the in-situ surface energy spectrum of the micro-area; Through the image processing statistics of the grid field of view that is gradually enlarged, the representative surface area of ​​the sample is obtained to obtain the statistical quantification requirements; S303 Micro-area feature extraction: within the characterization area, count the surface contents of different types of clay minerals; based on the differences in color, grayscale, and occurrence, use image processing software to distinguish the types of clay minerals in the microscopic area and obtain the micro-area surface content information of each type of clay mineral.

5. The method for quantitatively distinguishing clay minerals of different genetic origins in continental shale according to claim 2, characterized in that: Characterization domain: The matrix distribution is unstable if the field of view is smaller than this field of view, and is stable if the field of view is larger than this field of view.

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