Lamination fracture two-stage classification shale reservoir evaluation method

Abstract

The invention relates to the technical field of shale oil exploration and development, in particular to a lamellar fracture secondary classification shale reservoir evaluation method. The method comprises the following steps: determining a target research area, respectively identifying brittle minerals and clay minerals of a shale sample in the research area, calibrating a shale deposition scale and a shale diagenesis scale, dividing lamellar fractures in the research area into deposition lamellar fractures and diagenesis lamellar fractures according to the shale deposition scale and the shale diagenesis scale, the method comprises the following steps: combining a sedimentary lamella fracture with a plurality of diagenetic lamella fractures to construct a lamella body, firstly calculating the lamella body thickness, the lamella body spacing, the lamella body penetration ratio and the lamella body curvature, then calculating an imbibition capability index, a seepage capability index and a development capability index, and finally evaluating the lamella development degree of the shale reservoir according to three obtained evaluation indexes. According to the method provided by the invention, the two-level division of the lamellitic seam level is realized, the lamellitic body is also constructed, and clear guidance can be provided for shale oil exploration and development.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil exploration and development, and in particular to a shale reservoir evaluation method for secondary classification of lamellae and fractures. Background Art

[0002] The porosity and permeability of the mud-grade matrix in shale reservoirs are very low, but the lamellae between the layered matrix not only provide a large amount of storage space for the enrichment of crude oil, but also provide seepage channels for the migration of internal fluids in shale storage.

[0003] There are literature reports on the relevant technical methods of shale lamination. He Wenyuan et al., "Main Controlling Factors and Classification Evaluation of Gulong Shale Oil Enrichment in Songliao Basin", established the classification and evaluation standards of Gulong shale oil enrichment layer by taking lamination density as the reservoir capacity evaluation parameter and combining other parameters. The lamination density is divided into three levels, namely <500, 500-1000, and ≥1000; Zheng Jiandong, "Seven Property Parameters of Gulong Shale Oil Reservoir and Logging Evaluation Method of Enrichment Layer in Songliao Basin", pointed out that the lamination density of Qingyi Member can reach up to 3000 / m, and the pore types are diverse, mainly lamination fractures and clay mineral pores, most of which are nano-scale pore throats, and the lamination fracture width is 0.79-30.44μm, good connectivity; Shao Hongmei et al., "Diagenesis of Gulong Shale in Songliao Basin - Porosity Evolution", pointed out that the clay minerals rich in Gulong Shale are mainly illite, illite-montmorillonite mixed layer, chlorite, and a small amount of kaolinite and chlorite-montmorillonite mixed layer. In the process of clay transformation, intercrystalline pores and lamellae fractures are formed to improve reservoir properties; Zhang Anda et al., "Reservoir Space Type and Oil Occurrence State of Gulong Shale in Songliao Basin", pointed out that for shales with relatively developed lamellae and lamellae fractures, crude oil is scattered in the matrix pores, and the phenomenon of crude oil enrichment along lamellae and lamellae fractures can also be seen. Since the light components of crude oil have better fluidity, the lamellae fractures are mainly composed of light components of crude oil; Zhao Haibo et al.'s "Cross-band Rock Physical Measurement of Gulong Shale in Songliao Basin" confirmed that lamellae are one of the important influencing factors of the strong anisotropy of Gulong Shale, and pointed out that this research conclusion is of great significance in the prediction of lamellae in Gulong Shale. In areas where the clay mineral content does not change much, the anisotropy parameters can be used to directly reflect the density of lamellae development. Wang Fenglan et al.'s "Reservoir Characteristics and Classification Evaluation of Gulong Shale Oil in Songliao Basin" pointed out that the lamellae in Gulong Shale are extremely developed. From the core description, the lamellae density is 500-3000 / m, and the Q1-Q3 sublayer has the largest lamellae density, reaching 1500-3000 / m. The densely developed lamellae fractures have improved the oil reservoir to a certain extent. The results of the study on microstructure characteristics and main controlling factors of continental shale oil based on digital core technology - taking the first member of the Qingshankou Formation in the Cretaceous System in the Songliao Basin as an example show that bedding fractures with an opening greater than 10 μm are the main seepage channels, which have a certain directional connectivity along the sedimentary bedding direction and together with the adjacent mudstone constitute an important layer for the development of shale oil in the first member of the Qingshankou Formation. Bedding fractures can not only contribute to the main reservoir space, but also bedding fractures with larger openings are also important seepage channels in the first member of the Qingshankou Formation. Feng Zihui's "Organic matter composition and organic pore formation evolution of the Gulong shale in the Songliao Basin" points out that the hydrocarbon conversion rate of the layered algae in the Gulong shale is high, which is perfect. After the full hydrocarbon generation, the area shrinkage rate reaches more than 85%, and a large number of nano-scale, slender strip-shaped cracks distributed along the layers are formed in the shale. The crack width is 18-289nm, and the median is 54nm. The occurrence is clay interlayer pores or intercrystalline pores, and the genesis is organic pores. The higher the abundance and maturity of organic matter, the more developed the pores and cracks. This kind of slender strip-shaped pores distributed along the layers are an important component of the pores of Gulong shale, and are also an important factor in the development of lamination cracks in Gulong shale. The porosity and permeability of the mud-grade matrix in the shale reservoir are very low, but the lamination cracks between the layered matrix not only provide a large amount of storage space for the enrichment of crude oil, but also provide seepage channels for the migration of internal fluids stored in shale. .

[0004] The existing technical methods have achieved the detection of lamellae developed in shale core samples by means of naked eye observation, polarizing microscope, scanning electron microscope, field emission electron microscope, etc., and the measurement of lamellae density, and established a reservoir classification standard with lamellae density as a reservoir capacity evaluation parameter. However, the existing research results have a weak theoretical basis and poor guidance, and mainly have the following two deficiencies: First, the classification of lamellae is not detailed enough. The lamellae developed in shale reservoirs have different scale levels, morphological characteristics, and genetic types. When describing shale lamellae, the existing technology does not divide the lamellae more finely, but only summarizes them as one type, resulting in many fine fractures. First, the information of the sections is missing, which cannot provide strong support for subsequent research and exploration, development and production; second, there is no established method for describing lamellae fractures. When describing lamellae fractures, the existing technical means only use lamellae density, that is, the number of lamellae fractures developed per meter vertically, as a single parameter to describe them, which cannot reflect other characteristics of lamellae fractures; in addition, the geological meaning corresponding to the density of lamellae fractures and the degree of their influence on shale reservoirs are unclear, and it is impossible to provide targeted guidance for development and production. Due to the strong heterogeneity of shale reservoirs, the development characteristics of lamellae fractures change very rapidly both vertically and horizontally, which will directly affect the evaluation of geological sweet spots in the exploration process and the capacity conversion capacity in the development process. Therefore, in view of the above shortcomings, a shale reservoir evaluation method with secondary classification of lamellae fractures is proposed. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The present invention provides a shale reservoir evaluation method with secondary classification of lamellae and fractures, so as to overcome the problem in the prior art that, in the process of shale reservoir evaluation, due to the lack of lamellae fracture classification standards and overall description methods, it is difficult to characterize the differences in lamellae fracture development characteristics in different areas of the reservoir, resulting in the inability to accurately identify favorable areas of shale reservoirs and guide development and production.

[0007] (II) Technical solution

[0008] In order to solve the above problems, the present invention provides a shale reservoir evaluation method for secondary classification of lamellae and fractures, comprising:

[0009] Step S1: determine the target study area, identify the brittle minerals and clay minerals of the shale samples in the study area, and calibrate the shale sedimentary scale and shale diagenetic scale of the two types of mineral particles;

[0010] Step S2: according to the shale sedimentary scale and the shale diagenetic scale calibrated in step S1, the lamellae in the target study area are divided into sedimentary lamellae and diagenetic lamellae;

[0011] Step S3: Combining the sedimentary lamellae fracture of step S2 with a plurality of diagenetic lamellae fractures to construct a lamellae body;

[0012] Step S4: according to the lamellae constructed in step S3, respectively calculating the lamellae thickness, lamellae spacing, lamellae penetration ratio and lamellae curvature;

[0013] Step S5: Based on the four lamina-related parameters determined in step S4, the imbibition capacity index, the seepage capacity index and the development capacity index are calculated again, and the lamina development degree of the shale reservoir is evaluated based on the three evaluation indices obtained.

[0014] Preferably, in step S1, the brittle mineral includes one or more of quartz, feldspar or calcite; the clay mineral includes one or more of chlorite, kaolinite, illite or montmorillonite.

[0015] Preferably, in step S4, the thickness of the lamellae body is twice the continuous distance of the diagenetic lamellae fractures, and the lamellae body spacing is the vertical distance between two adjacent sedimentary lamellae fractures.

[0016] Preferably, in step S4, the calculation formula of the page body penetration ratio is:

[0017] G=(L 1 / L)×100%(1)

[0018] Where: L——viewing length, mm; L 1 ——The length of the lamina measured within the field of view, mm; G——The penetration ratio of the lamina, %.

[0019] Preferably, in step S4, the calculation formula of the curvature of the sheet body is:

[0020] W=(L 2 / L 1 )×100%(2)

[0021] Where: L 1 ——The length of the leaf body measured in the field of view, mm; L 2 ——Total length of sedimentary lamellae in the lamellae, mm; W——Curvature of the lamellae, %.

[0022] Preferably, in step S5, the calculation formula of the imbibition capacity index is:

[0023] SX=ln100(H / D)=ln100(2d / D)(3)

[0024] Where: H is the thickness of the lamellae, mm; D is the distance between lamellae, mm; d is the average continuous distance of diagenetic lamellae, mm; SX is the imbibition capacity index, % / mm.

[0025] Preferably, in step S5, the calculation formula of the seepage capacity index is:

[0026] SL = (G / D) × 100% = ((L 1 / L)×100%)×100% / D(4)

[0027] Where: L——viewing length, mm; L 1 ——Layer length measured within the field of view, mm; G——Layer penetration ratio, %, D——Layer spacing, mm; SL——Seepage capacity index, % / mm.

[0028] Preferably, in step S5, the calculation formula of the development capability index is:

[0029] KF=ln(HWG / D)=ln(20000 0 / 000 ·d(L 2 / L) / D)(5)

[0030] Where: d is the average continuous distance of diagenetic lamellae fractures, mm; L is the length of the visual field, mm; L 2 ——Total length of sedimentary lamellae in the lamellae, mm; H——lamellae thickness, mm; W——lamellae curvature, %, G——lamellae penetration ratio, %, D——lamellae spacing, mm; KF——Development capability index, 0 / 000 / mm.

[0031] (III) Beneficial effects

[0032] The shale reservoir evaluation method with secondary classification of lamellae and fractures provided by the present invention not only realizes the secondary division of lamellae and fracture levels, but also constructs lamellae bodies, and establishes an evaluation method based on the lamellae bodies that can characterize the oil and gas storage capacity, development and utilization capacity, and fluid seepage capacity of shale reservoirs, which provides theoretical and technical support for the evaluation of favorable areas of shale oil reservoirs and can provide clear guidance for shale oil exploration and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of a shale reservoir evaluation method for secondary classification of shales and fractures according to an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of a page structure according to an embodiment of the present invention;

[0035] Figure 3 A is a millimeter-level field of view photo of a sample in an embodiment of the present invention;

[0036] Figure 3 B is a schematic diagram of shale sedimentary scale identification of a sample in an embodiment of the present invention;

[0037] Figure 3 C is a schematic diagram of identification of shale sedimentary lamellae in a sample according to an embodiment of the present invention;

[0038] Figure 4 A is a micron-scale field of view photograph of a sample in an embodiment of the present invention;

[0039] Figure 4 B is a schematic diagram of diagenetic sedimentary scale identification of a sample in an embodiment of the present invention;

[0040] Figure 4 C is a schematic diagram of identifying diagenetic sedimentary lamellae of a sample in an embodiment of the present invention;

[0041] Figure 5 This is a regional plane distribution diagram of the thickness H of the lamellae according to an embodiment of the present invention;

[0042] Figure 6 It is a regional plane distribution diagram of the page body penetration ratio G in an embodiment of the present invention;

[0043] Figure 7 This is a regional plane distribution diagram of the inter-body spacing D of an embodiment of the present invention;

[0044] Figure 8 It is a regional plane distribution diagram of the curvature W of the lamellae according to an embodiment of the present invention;

[0045] Fig. 9 It is a regional plane distribution diagram of the absorption capacity index SX of an embodiment of the present invention;

[0046] Fig.10 It is a regional plane distribution diagram of the seepage capacity index SL of an embodiment of the present invention;

[0047] Fig.11 A regional plane distribution diagram of the capability index KF is developed for an embodiment of the present invention. DETAILED DESCRIPTION

[0048] 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.

[0049] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present invention, and the drawings are not actually drawn to scale.

[0050] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, the meaning is "including but not limited to".

[0051] Figure 1 Flow chart of the shale reservoir evaluation method for two-level classification of shales and fractures according to an embodiment of the present invention. Figure 1 As shown, the present invention provides a shale reservoir evaluation method for secondary classification of lamellae and fractures, which specifically includes:

[0052] Step S1: Determine the target study area, identify the brittle minerals and clay minerals of the shale samples in the study area, and calibrate the shale sedimentary scale and shale diagenetic scale of the two types of mineral particles.

[0053] In the present evaluation method, in step S1, the brittle minerals include one or more of quartz, feldspar or calcite; and the clay minerals include one or more of chlorite, kaolinite, illite or montmorillonite.

[0054] In practical applications, in step S1, the method for calibrating the shale sedimentary scale of the sample is to perform data analysis on the diameters of all brittle mineral particles, process the data in a normal distribution manner, select the peak value, and obtain the scale of the most widely developed brittle mineral particles. The scale magnitude of the peak value is the shale sedimentary scale of the sample.

[0055] At the same time, the method for calibrating the sample shale sedimentary scale is to conduct data statistics on the diameters of clay minerals and cementing mineral particles and calculate the average diameter. The scale of this value is the shale diagenetic scale of the sample.

[0056] Step S2: According to the shale sedimentary scale and the shale diagenetic scale calibrated in step S1, the lamellae fractures in the study area are divided into sedimentary lamellae fractures and diagenetic lamellae fractures.

[0057] In this evaluation method, in step S2, the lamellae fractures in the study area need to be divided into sedimentary lamellae fractures and diagenetic lamellae fractures in the order of size first and then shape. It should be noted that the method of dividing the lamellae fracture levels by size is to classify the lamellae fractures whose straight line lengths from the beginning to the end of the lamellae fractures in the field of view are greater than or equal to the shale depositional scale as sedimentary lamellae fracture levels, and to classify the lamellae fractures whose straight line lengths from the beginning to the end of the lamellae fractures in the field of view are less than or equal to the shale diagenetic scale as diagenetic lamellae fracture levels.

[0058] In addition, in practical applications, the straight-line lengths of the beginning and end of the lamina fractures between the shale depositional scale and the shale diagenetic scale need to be divided by morphology. The method of dividing the lamina fracture levels by morphology is to classify the lamina fractures with smaller curvature and overall straight shape in the field of view as sedimentary lamina fracture levels, and classify the lamina fractures with larger curvature and overall arc shape as diagenetic lamina fracture levels.

[0059] In addition, for those foliation fractures that still cannot be classified, the ones parallel to the stratigraphic direction are classified as sedimentary foliation fracture levels, and the ones oblique to the stratigraphic direction are classified as diagenetic foliation fracture levels.

[0060] Step S3: Combining a sedimentary lamellae fracture of step S2 with a plurality of diagenetic lamellae fractures to construct a lamellae body.

[0061] In this evaluation method, in step S3, Figure 2 FIG. 1 is a schematic diagram of a page structure according to an embodiment of the present invention. Figure 2 As shown, according to the spatial coordination relationship between sedimentary foliation fractures and diagenetic foliation fractures, sedimentary foliation fractures and the diagenetic foliation fractures that directly intersect with them are combined in the field of view, and gradually expanded outward until there are no more connectable diagenetic foliation fractures, thus constructing the final foliation body.

[0062] Step S4: According to the lamellae constructed in step S3, the lamellae thickness, lamellae spacing, lamellae penetration ratio and lamellae curvature are calculated respectively.

[0063] In this evaluation method, in step S4, the thickness of the laminated body is twice the continuous distance of the diagenetic laminated fractures. In practical applications, the average continuous distance d of the diagenetic laminated fractures in the field of view is measured. Since the sedimentary laminated fractures are connected to the diagenetic laminated fractures in both the upper and lower directions, the thickness H of the laminated body is twice the continuous distance of the diagenetic laminated fractures, that is, H = 2d; further, in the field of view, the laminated body can be abstracted as a rectangular block with the sedimentary laminated fracture as the length and the diagenetic laminated fracture as the width.

[0064] In practical applications, the interlaminar spacing is the vertical distance between two adjacent sedimentary laminar fractures. The vertical distance between the unique sedimentary laminar fractures of two adjacent laminar bodies, that is, the vertical distance between two adjacent sedimentary laminar fractures, is measured to obtain the interlaminar spacing D.

[0065] At the same time, the calculation formula of the page body penetration ratio is:

[0066] G=(L 1 / L)×100%(1)

[0067] Where: L——viewing length, mm; L 1 ——The length of the lamina measured within the field of view, mm; G——The penetration ratio of the lamina, %.

[0068] In addition, the calculation formula of the lamella curvature is:

[0069] W=(L 2 / L 1 )×100%(2)

[0070] Where: L 1 ——The length of the leaf body measured in the field of view, mm; L 2 ——Total length of sedimentary lamellae in the lamellae, mm; W——Curvature of the lamellae, %.

[0071] Furthermore, within a field of view, the average values ​​of three parameters, namely, interlaminar spacing D, interlaminar penetration ratio G, and interlaminar curvature W, are calculated by weighted averaging.

[0072] Step S5: Based on the four lamina-related parameters determined in step S4, the imbibition capacity index, the seepage capacity index and the development capacity index are calculated again, and the lamina development degree of the shale reservoir is evaluated based on the three evaluation indices obtained.

[0073] In this evaluation method, in step S5, the calculation formula of the imbibition capacity index is:

[0074] SX=ln100(H / D)=ln100(2d / D)(3)

[0075] Where: H is the thickness of the lamellae, mm; D is the distance between lamellae, mm; d is the average continuous distance of diagenetic lamellae, mm; SX is the imbibition capacity index, % / mm.

[0076] At the same time, the calculation formula of the seepage capacity index is:

[0077] SL = (G / D) × 100% = ((L 1 / L)×100%)×100% / D(4)

[0078] Where: L——viewing length, mm; L 1 ——Layer length measured within the field of view, mm; G——Layer penetration ratio, %, D——Layer spacing, mm; SL——Seepage capacity index, % / mm.

[0079] In addition, the calculation formula of the development capability index is:

[0080] KF=ln(HWG / D)=ln(20000 0 / 000 ·d(L 2 / L) / D)(5)

[0081] Where: d is the average continuous distance of diagenetic lamellae fractures, mm; L is the length of the visual field, mm; L 2 ——Total length of sedimentary lamellae in the lamellae, mm; H——lamellae thickness, mm; W——lamellae curvature, %, G——lamellae penetration ratio, %, D——lamellae spacing, mm; KF——Development capability index, 0 / 000 / mm.

[0082] It should be noted that the larger the SX, the stronger the sweep capacity and the greater the degree of reservoir development and utilization; the larger the SL, the stronger the permeability of the shale reservoir; the larger the KF, the larger the corresponding single well EUR and the stronger the ability of capacity conversion.

[0083] In practical applications, sampling is carried out in different areas and locations of the target study area, and the three parameters SX, SL and KF are finally obtained through observation, measurement and calculation, and relatively high-value points are selected as advantageous areas for exploration and development.

[0084] The shale reservoir evaluation method for secondary classification of lamellae provided by the present invention is based on the identification of brittle minerals, clay minerals and lamellae in shale samples, and by introducing the definition of shale sedimentary scale and shale diagenetic scale that characterize the scale level, the lamellae are divided into two types: sedimentary lamellae and diagenetic lamellae, and the two types of lamellae are further coordinated and combined to construct lamellae bodies. In other words, the lamellae body is both a combined unit composed of two-level lamellae and a basic unit used to describe the lamellae in the method of the present invention; further, the parameters such as the thickness of the lamellae, the spacing between the lamellae, the penetration ratio of the lamellae and the curvature of the lamellae are obtained by measuring the shale samples, and the evaluation indexes such as the imbibition capacity index, the seepage capacity index and the development capacity index are calculated.

[0085] In practical applications, this evaluation method not only realizes the secondary division of lamina fracture levels, but also combines two different levels of lamina fractures to create a lamina body geological model. Moreover, based on the lamina body, an evaluation method is established that can characterize the oil and gas storage capacity, development and utilization capacity, and fluid seepage capacity of shale reservoirs. The evaluation of favorable areas of shale oil reservoirs provided by the present invention provides theoretical and technical support, and can provide clear guidance for shale oil exploration and development.

[0086] At present, because lamellae fractures differ in scale, morphology and even genesis, it is necessary to establish a standard for classifying lamellae fractures, establish lamellae bodies according to the development characteristics and coordination combination relationships of fractures of different levels, and describe shale lamellae fractures.

[0087] In order to realize the level classification of lamellae fractures, it is necessary to introduce two parameters: shale deposition scale and shale diagenetic scale. For this purpose, this evaluation method publicly gives the definitions of shale deposition scale and shale diagenetic scale. Specifically, the definition of shale deposition scale is: the spatial scale corresponding to the rock characteristics formed by sedimentation in shale samples is mainly controlled by the size of brittle mineral particles. The order of magnitude of the average diameter of brittle minerals is the shale deposition scale of the sample.

[0088] In addition, the definition of shale diagenetic scale is: the spatial scale corresponding to the rock characteristics formed by diagenesis in shale samples is mainly controlled by the size of authigenic mineral particles. The order of magnitude of the average diameter of clay minerals and cementing minerals is the shale diagenetic scale of the sample.

[0089] In practical applications, sedimentary scale and diagenetic scale are used to measure and calibrate the size of lamellae, and then determine the level of lamellae.

[0090] In addition, a laminated body is a collection of laminated fractures of different levels, which can be described from multiple angles such as length, thickness, and spacing. The definition of a laminated body is: a laminated body is a fracture network complex composed of sedimentary laminated fractures and directly or indirectly connected diagenetic laminated fractures. Its outer contour is long and can be evaluated by parameters such as thickness, spacing, penetration ratio, and curvature.

[0091] In this evaluation method, the thickness (H), spacing (D), length (L, L 1 , L 2 ) and other data to obtain parameters such as lamina penetration ratio (G) and lamina tortuosity (W), and then calculate the imbibition capacity index SX, seepage capacity index SL and development capacity index KF, ​​and compare and evaluate the development and utilization capacity, fluid seepage capacity and production capacity conversion capacity of shale oil reservoirs.

[0092] The following is a detailed description of the specific implementation process of this shale reservoir evaluation method for two-level classification of lamellae and fractures:

[0093] Step 1: Determine the target study area, identify the brittle minerals and clay minerals of the shale samples in the study area, and calibrate the shale sedimentary scale and shale diagenetic scale of the two types of mineral particles.

[0094] In this example, the JHG block of the Daqing Oilfield shale oilfield was taken as the research object to carry out the evaluation of shale reservoirs with secondary classification of lamellae and fractures. Figure 3 A is a millimeter-level field of view photo of a sample in an embodiment of the present invention, Figure 4 A is a micron-scale field photograph of a sample in an embodiment of the present invention. Figure 3 A and Figure 4As shown in A, existing technologies are used to carry out mineral identification work in shale samples in the study area, and brittle minerals such as quartz, feldspar, calcite, and clay minerals such as chlorite, kaolinite, illite, and montmorillonite in the samples are identified, and the size of mineral particles is measured and counted.

[0095] In practical applications, existing technologies are used to identify fractures and pores in shale samples in the study area, and fractures and pores are calibrated in different magnification fields from small to large. Furthermore, the morphological characteristics and scale levels of fractures and pores are described and measured, and the spatial position relationship between fractures and mineral particles is clarified.

[0096] In this example, the shale sedimentation scale is controlled by sedimentation and its characteristics are closely related to the size of brittle mineral particles. Figure 3 B is a schematic diagram of shale sedimentary scale identification of a sample in an embodiment of the present invention. Figure 3 As shown in B, the scale of this peak is the shale sedimentary scale of the sample; the shale diagenetic scale is controlled by burial diagenesis, and its performance characteristics are closely related to the particle size of clay minerals and cementing minerals. Figure 4 B is a schematic diagram of the identification of the diagenetic sedimentary scale of a sample in an embodiment of the present invention. Figure 4 As shown in B, the scale of this value is the shale diagenetic scale of the sample.

[0097] Step 2: According to the calibrated shale depositional scale and shale diagenetic scale, the lamellae fractures in the study area are divided into sedimentary lamellae fractures and diagenetic lamellae fractures.

[0098] In this embodiment, the shales are first divided according to their scale. The shales are divided into sedimentary shales and diagenetic shales from large to small, corresponding to the shales' scale. Figure 3 C is a schematic diagram of identifying shale sedimentary fractures in a sample of an embodiment of the present invention. Figure 3 As shown in C, the lamellae fractures in the field of view whose straight line length from the beginning to the end is greater than or equal to the shale deposition scale are classified as sedimentary lamellae fractures; Figure 4 C is a schematic diagram of identifying diagenetic sedimentary lamellae fractures in a sample according to an embodiment of the present invention. Figure 4 As shown in C, the lamellae fractures in the field of view whose straight line length from beginning to end is less than or equal to the shale diagenetic scale are divided into diagenetic lamellae fracture grades.

[0099] In practical applications, it is also divided according to the form, such as Figure 3 C and Figure 4 As shown in C, the lamellae with smaller curvature and overall straight shape in the field of view are classified as sedimentary lamellae fractures; the lamellae with larger curvature and overall arc shape are classified as diagenetic lamellae fractures. In addition, for those lamellae fractures that still cannot be classified, those parallel to the stratigraphic direction are classified as sedimentary lamellae fractures, and those oblique to the stratigraphic direction are classified as diagenetic lamellae fractures.

[0100] Step 3: Combine a sedimentary foliation fracture with multiple diagenetic foliation fractures to construct a foliation body.

[0101] In this embodiment, according to the spatial coordination relationship between the two levels of lamination fractures, multiple diagenetic lamination fractures and one sedimentary lamination fracture are combined to construct a lamination body. In practical applications, sedimentary lamination fractures and diagenetic lamination fractures directly intersecting with them are first combined in the field of view to construct the original lamination body; then, the diagenetic lamination fractures connected to the diagenetic lamination fractures in the original lamination body are incorporated into the lamination body in the field of view, and gradually expanded outward until there are no more diagenetic lamination fractures that can be connected, so as to construct the final lamination body.

[0102] Step 4: Based on the constructed lamellae, calculate the lamellae thickness, lamellae spacing, lamellae penetration ratio and lamellae curvature respectively.

[0103] In this embodiment, Figure 5 FIG. 1 is a regional plane distribution diagram of the thickness H of the sheet body according to an embodiment of the present invention. Figure 5 As shown in the figure, the H values ​​of all sample points in the JHG block are obtained to clarify the planar distribution characteristics of the parameter H. In practical applications, the length L of the entire field of view is measured, and further, the length L of the foliation body is measured in the field of view. 1 Furthermore, through formula (1), the page body penetration ratio G is obtained: Figure 6 FIG. 1 is a regional plane distribution diagram of the body penetration ratio G of an embodiment of the present invention, as shown in FIG. Figure 6 As shown, the G values ​​of all sample points in the JHG block are obtained to clarify the plane distribution characteristics of the parameter G; in this embodiment, Figure 7 FIG. 1 is a regional plane distribution diagram of the inter-body spacing D of an embodiment of the present invention, such as Figure 7 As shown in the figure, the D values ​​of all sample points in the JHG block are obtained, and the planar distribution characteristics of the parameter D are clarified; in practical applications, the curvature W of the foliation body mainly reflects the curvature of the only sedimentary foliation fracture inside the foliation body, and the total length L of the sedimentary foliation fracture in the foliation body is measured. 2 , by using formula (2), the curvature W of the lamellae is calculated. Figure 8 FIG. 1 is a regional plane distribution diagram of the curvature W of the lamellae according to an embodiment of the present invention, as shown in FIG. Figure 8 As shown, the W values ​​of all sample points in the JHG block are obtained, and the planar distribution characteristics of the parameter W are clarified.

[0104] Step 5: Based on the determined four lamella-related parameters, the imbibition capacity index, seepage capacity index and development capacity index are calculated again, and the lamella development degree of the shale reservoir is evaluated based on the three evaluation indices obtained.

[0105] In this embodiment, based on the lamellar body parameters obtained in step 4, evaluation indexes are established from three aspects, namely, imbibition capacity, flow capacity, and storage capacity, to evaluate the degree of lamina development in the shale reservoir.

[0106] In practical applications, within a field of view, the average values ​​of various parameters of the description volume are calculated by weighted average method, and the imbibition capacity index SX is calculated by formula (3). The larger the imbibition capacity index, the stronger the sweep capacity and the greater the reservoir development degree; the seepage capacity index SL is calculated by formula (4). The larger the seepage capacity index, the stronger the permeability; the development capacity index KF is calculated by formula (5). The larger the development capacity index, the larger the corresponding single well EUR and the stronger the capacity conversion ability.

[0107] In this embodiment, sampling is performed at different locations and depths in the target study area, and observation, measurement, and calculation are finally performed to obtain the high-value points, and the high-value points are selected as the advantageous areas. Fig. 9 This is a regional plane distribution diagram of the absorption capacity index SX of an embodiment of the present invention, Fig.10 This is a regional plane distribution diagram of the seepage capacity index SL according to an embodiment of the present invention. Fig.11 The regional plane distribution diagram of the capability index KF developed for the embodiment of the present invention is as follows: Figures 9 to 11 As shown, the values ​​of the three parameters SX, SL, and KF of all sample points in the JHG block are obtained, and the planar distribution characteristics of the three parameters are clarified.

[0108] In practical applications, through the secondary classification of lamellae and fractures and the establishment of lamellae bodies to carry out reservoir evaluation, three advantageous imbibition areas, five advantageous seepage areas, and five advantageous development areas were identified in the JHG block, providing clear guidance for further exploration and development.

[0109] The shale reservoir evaluation method with secondary classification of lamellae and fractures provided by the present invention not only realizes the secondary division of lamellae and fracture levels, but also constructs lamellae bodies, and establishes an evaluation method based on the lamellae bodies that can characterize the oil and gas storage capacity, development and utilization capacity, and fluid seepage capacity of shale reservoirs, which provides theoretical and technical support for the evaluation of favorable areas of shale oil reservoirs and can provide clear guidance for shale oil exploration and development.

[0110] The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A shale reservoir evaluation method based on two-level classification of shales and fractures. It is characterized in that include: Step S1: determine the target study area, identify the brittle minerals and clay minerals of the shale samples in the study area, and calibrate the shale sedimentary scale and shale diagenetic scale of the two types of mineral particles; Step S2: according to the shale sedimentary scale and the shale diagenetic scale calibrated in step S1, the lamellae in the target study area are divided into sedimentary lamellae and diagenetic lamellae; Step S3: Combining the sedimentary lamellae fracture of step S2 with a plurality of diagenetic lamellae fractures to construct a lamellae body; Step S4: according to the lamellae constructed in step S3, respectively calculating the lamellae thickness, lamellae spacing, lamellae penetration ratio and lamellae curvature; Step S5: Based on the four lamina-related parameters determined in step S4, the imbibition capacity index, the seepage capacity index and the development capacity index are calculated again, and the lamina development degree of the shale reservoir is evaluated based on the three evaluation indices obtained.

2. The shale reservoir evaluation method of secondary classification of shading fractures according to claim 1, It is characterized in that In the step S1, the brittle mineral includes one or more of quartz, feldspar or calcite; the clay mineral includes one or more of chlorite, kaolinite, illite or montmorillonite.

3. The shale reservoir evaluation method of secondary classification of shading fractures according to claim 1, It is characterized in that In step S4, the thickness of the lamina body is twice the continuous distance of the diagenetic lamina fractures, and the lamina body spacing is the vertical distance between two adjacent sedimentary lamina fractures.

4. The shale reservoir evaluation method of secondary classification of shales and fractures according to claim 1, It is characterized in that In step S4, the calculation formula of the page body penetration ratio is: G=(L 1 / L)×100% (1) Where: L——viewing length, mm; L 1 ——The length of the lamina measured within the field of view, mm; G——The penetration ratio of the lamina, %.

5. The shale reservoir evaluation method of secondary classification of shading fractures according to claim 1, It is characterized in that In step S4, the calculation formula of the curvature of the sheet body is: W=(L 2 / L 1 )×100% (2) Where: L 1 ——The length of the leaf body measured in the field of view, mm; L 2 ——Total length of sedimentary lamellae in the lamellae, mm; W——Curvature of the lamellae, %.

6. The shale reservoir evaluation method of secondary classification of shading fractures according to claim 1, It is characterized in that In step S5, the calculation formula of the absorption capacity index is: SX=ln100(H / D)=ln100(2d / D) (3) Where: H is the thickness of the lamellae, mm; D is the distance between lamellae, mm; d is the average continuous distance of diagenetic lamellae, mm; SX is the imbibition capacity index, % / mm.

7. The shale reservoir evaluation method of secondary classification of shading fractures according to claim 1, It is characterized in that In step S5, the calculation formula of the seepage capacity index is: SL=(G / D)×100%=((L 1 / L)×100%)×100% / D (4) Where: L——viewing length, mm; L 1 ——Layer length measured within the field of view, mm; G——Layer penetration ratio, %, D——Layer spacing, mm; SL——Seepage capacity index, % / mm.

8. The shale reservoir evaluation method of secondary classification of shading fractures according to claim 1, It is characterized in that In step S5, the calculation formula of the development capability index is: KF=ln(HWG / D)=ln(20000 0 / 000 ·d(L 2 / L) / D) (5) Where: d is the average continuous distance of diagenetic lamellae fractures, mm; L is the length of the visual field, mm; L 2 ——Total length of sedimentary lamellae in the lamellae, mm; H——lamellae thickness, mm; W——lamellae curvature, %, G——lamellae penetration ratio, %, D——lamellae spacing, mm; KF——Development capability index, 0 / 000 / mm.

Images