A method, apparatus, and computer equipment for quantitatively evaluating the compressive strength of laminated continental shale.

Abstract

This invention discloses a method, apparatus, and computer equipment for quantitatively evaluating the compressive strength of lamellar continental shale, belonging to the fields of petroleum geology and reservoir geomechanics. The method includes: S1, selecting lamellar continental shale samples from core wells in a specific region; S2, determining the mineral types and contents of pure mudstone and pure sandstone; S3, processing the shale samples into plunger samples to obtain sandy lamellar parameters; S4, determining the uniaxial compressive strength of the plunger samples; S5, fitting the relationship between sandy lamellar parameters and uniaxial compressive strength; and S6, preparing artificial samples with preset lamellar shale samples and fitting the relationship between sandy lamellar parameters and uniaxial compressive strength of adjacent areas of the artificial samples. This invention can accurately obtain the compressive strength of shale formations, addressing the complex lamellar parameters in actual continental shale formations. This provides better guidance for fracturing design in shale oil reservoirs, facilitates economical and effective screening of fracturing "sweet spots," and reduces exploration and development risks and costs.

Description

Technical Field

[0001] This invention relates to the fields of oil and gas geology and reservoir geomechanics, and in particular to a method, apparatus and computer equipment for quantitatively evaluating the compressive strength of lamellar continental shale, thereby guiding shale fracturing and stimulation techniques. Background Technology

[0002] With the continuous advancement of conventional oil and gas resource exploration and development, shale oil has gradually become a hotspot in global oil and gas exploration in recent years. Continental shale, characterized by high-quality source rocks, diverse reservoir spaces, widespread oil content, and good mobility, represents the main direction for future shale oil exploration and development. Laminated structures are widely developed in shale formations; laminated continental shale, consisting of organic-rich mudstone interbedded with thin layers of fine siltstone, is an important replacement resource and a primary target for increasing reserves and production in the near term. Shale oil reservoirs are characterized by low porosity and low permeability, necessitating large-scale hydraulic fracturing for commercial development. Hydraulic fracturing, as a core technology in shale oil development, can create a fracture network in shale reservoirs, significantly increasing permeability, allowing shale oil to enter the wellbore more efficiently from matrix pores.

[0003] The mechanical properties of shale play a crucial role in the initiation, propagation, and extension of artificial fractures during hydraulic fracturing, influencing fracturing efficiency and shale oil production. Compressive strength, as an important mechanical parameter, plays a vital role in evaluating reservoir fracturability. Understanding the compressive strength of lamellar continental shale allows for better planning and optimization of hydraulic fracturing designs, thereby reducing construction costs. Therefore, as a key target for future exploration and development, quantitatively evaluating the compressive strength of lamellar continental shale is of great significance for selecting favorable fracturing zones. However, current research on the compressive strength of lamellar continental shale is limited. Therefore, considering the limited number of core wells and the complex lamellar parameters in actual formations, it is necessary to explore a simple and accurate quantitative evaluation method for obtaining the compressive strength of lamellar continental shale. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method, apparatus, and computer equipment for quantitatively evaluating the compressive strength of lamellar continental shale. The aim is to provide a method, apparatus, and computer equipment capable of accurately obtaining the compressive strength of lamellar shale formations, given the complex lamellar parameters in actual continental shale formations. This will better guide the fracturing design of shale oil reservoirs, facilitate the economical and effective screening of fracturing "sweet spots," reduce exploration and development risks and costs, and provide guidance for promoting wellbore stability, hydraulic fracturing technology, and fracturing stimulation design in shale oil extraction.

[0005] To achieve the above objectives, the present invention provides a method for quantitatively evaluating the compressive strength of laminated continental shale, comprising the following steps:

[0006] S1. Select lamellar continental shale samples from core wells in a certain area, including pure mudstone, single sandy lamellar, multiple sandy lamellar, and pure sandstone;

[0007] S2. Determine the types and contents of minerals contained in pure mudstone and pure sandstone;

[0008] S3. All shale samples were processed into plunger samples to obtain sandy laminar parameters for single and multiple sandy laminar layers.

[0009] S4. Measure the uniaxial compressive strength of the plunger sample;

[0010] S5. Fitting the relationship between sand texture parameters and uniaxial compressive strength;

[0011] S6. Based on the mineral composition of pure mudstone and pure sandstone in the actual geological samples of the adjacent area, prepare artificial samples of layered shale with preset sandy layering parameters, and fit the relationship between the sandy layering parameters of the artificial samples and the uniaxial compressive strength.

[0012] Furthermore, the sand texture parameters include the sand texture thickness and the number of sand texture lines.

[0013] Furthermore, in step S2, the types and contents of minerals contained in pure mudstone and pure sandstone are determined by X-ray diffraction experiments; in step S6, the mineral composition of pure mudstone and pure sandstone in actual geological samples from the adjacent area is determined by X-ray diffraction experiments.

[0014] Furthermore, in step S3, the shale sample is processed into a plunger sample by waterless wire cutting.

[0015] Furthermore, in step S3, the shale sample can be processed into a plunger sample by liquid nitrogen cryo-cutting.

[0016] Furthermore, in step S4, the uniaxial compressive strength of the plunger sample is determined by a uniaxial compression test.

[0017] Furthermore, in step S3, the standard size of the plunger sample is 25 mm * 50 mm.

[0018] Furthermore, in step S3, the unevenness error of the two end faces of the plunger sample is less than 0.05 mm, the error along the height diameter of the plunger sample is less than 0.3 mm, and the maximum deviation of the end face perpendicular to the axis of the plunger sample is less than 0.25°.

[0019] Furthermore, in step S5, the relationship between the sand texture parameters and the uniaxial compressive strength is fitted, and the quadratic function relationship between the uniaxial compressive strength of the plunger sample and the total thickness of the sandpaper texture is obtained as follows:

[0020] σ=68.48443+1.88724·H-0.00938·H 2

[0021] Where H is the total thickness of the laminations, H = n·h, n is the number of laminations, h is the thickness of a single lamination, and σ is the uniaxial compressive strength;

[0022] Furthermore, in step S6, after preparing the artificial sample of the layered shale sample, the artificial sample is processed into a plunger sample to obtain the sandy layer parameters of a single sandy layer and multiple sandy layers. Then, steps S4 and S5 are repeated to fit the relationship between the sandy layer parameters and the uniaxial compressive strength.

[0023] The present invention also provides a device for quantitatively evaluating the compressive strength of laminated continental shale, comprising a data acquisition module, a first measurement module, a processing module, a second measurement module, and a fitting module;

[0024] The acquisition module is used to select laminated continental shale samples from core wells in a certain area, including pure mudstone, single sandy lamellar, multiple sandy lamellar, and pure sandstone.

[0025] The first measuring module is used to determine the types and contents of minerals contained in pure mudstone and pure sandstone;

[0026] The processing module is used to process shale samples into plunger samples to obtain sandy layer parameters of single sandy layers and multiple sandy layers.

[0027] The second measuring module is used to measure the uniaxial compressive strength of the plunger sample;

[0028] The fitting module is used to fit the relationship between the sand texture parameters and the uniaxial compressive strength.

[0029] The present invention also provides a computer device comprising one or more processors and one or more memories, wherein the one or more memories store at least one instruction, the at least one instruction being loaded and executed by the one or more processors to perform operations as described above in the method for quantitatively evaluating the compressive strength of layered continental shale.

[0030] The present invention provides a method, apparatus, and computer equipment for quantitatively evaluating the compressive strength of laminated continental shale, which has at least the following beneficial effects:

[0031] By first obtaining the sandy laminar parameters of laminar continental shale samples, and then fitting the relationship between the sandy laminar parameters and uniaxial compressive strength, and then preparing artificial samples of laminar shale based on sandy laminar parameters from other locations, the relationship between laminar parameters from other locations and uniaxial compressive strength is finally obtained. This invention can accurately obtain the compressive strength of laminar continental shale formations, taking into account the complex laminar parameters in actual continental shale formations. It establishes a method for quantitatively evaluating the influence of laminar continental shale on compressive strength, which can better guide the fracturing construction design of shale oil reservoirs, facilitate the economical and effective screening of fracturing "sweet spots," and reduce exploration and development risks and costs. This invention has certain guiding significance for promoting wellbore stability, hydraulic fracturing technology, and fracturing stimulation design in shale oil extraction. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating a method for quantitatively evaluating the compressive strength of laminated continental shale according to an embodiment of the present invention.

[0033] Figure 2 In the figures (a) to (d), the samples are pure mudstone, mudstone with a single sandpaper texture, mudstone with multiple sandpaper textures, and pure sandstone, respectively, representing an embodiment of the present invention.

[0034] Figure 3 This is a uniaxial compressive stress-strain curve of sandy layered shale with different thicknesses, according to an embodiment of the present invention.

[0035] Figure 4 This is a graph showing the fitting relationship between uniaxial compressive strength and sandy texture thickness according to an embodiment of the present invention.

[0036] Figure 5 (a) to (f) are schematic diagrams of artificial samples of pure mudstone, 1-striped layer, 3-striped layer, 5-striped layer, 8-striped layer and pure sandstone, respectively, according to an embodiment of the present invention.

[0037] Figure 6 This is a functional module block diagram of the device for quantitatively evaluating the compressive strength of layered continental shale according to the present invention;

[0038] Figure 7 This is a schematic structural block diagram of a computer device according to the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0040] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0041] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0042] To better understand the purpose, structure, and function of this invention, the following detailed description, in conjunction with the accompanying drawings, describes a method, apparatus, and computer device for quantitatively evaluating the compressive strength of layered continental shale.

[0043] Example 1

[0044] like Figure 1 As shown, a method for quantitatively evaluating the compressive strength of laminated continental shale includes the following steps:

[0045] S1. Select lamellar continental shale samples from core wells in a certain area, including pure mudstone, single sandy lamellar, multiple sandy lamellar, and pure sandstone, etc.

[0046] S2. Referring to the X-ray diffraction analysis method for clay minerals and common non-clay minerals in sedimentary rocks SY / T 5163-2018, the mineral types and contents contained in pure mudstone and pure sandstone were determined by X-ray diffraction experiments.

[0047] S3. All shale samples were processed into plunger samples to obtain sandy laminar parameters for single and multiple sandy laminar layers.

[0048] S4. Determine the uniaxial compressive strength of the plunger sample;

[0049] S5. Fitting the relationship between sand texture parameters and uniaxial compressive strength;

[0050] S6. Based on the mineral composition of pure mudstone and pure sandstone in the actual geological samples of the adjacent area, prepare artificial samples of layered shale with specific layering parameters, and fit the relationship between the sandy layering parameters of the artificial samples and the uniaxial compressive strength.

[0051] The parameters of the sand texture include the thickness of the sand texture and the number of sand textures. The number of sand textures can be read directly by the naked eye, and the thickness of the sand texture can be measured by a ruler.

[0052] In step S6, after preparing the artificial sample of the layered shale sample, the artificial sample is processed into a plunger sample to obtain the sandy layer parameters of a single sandy layer and multiple sandy layers. Then, steps S4 and S5 are repeated to fit the relationship between the sandy layer parameters and the uniaxial compressive strength.

[0053] Example 2

[0054] In this embodiment, a typical core sample from a shale oil well in Block A is selected as an example:

[0055] Firstly, typical core samples from shale oil wells in Block A of China were selected. X-ray diffraction experiments were used to determine the mineral types and contents of pure mudstone and pure sandstone. Then, the shale samples were processed into plunger samples using waterless linear cutting or liquid nitrogen cryogenic cutting methods to obtain sandy laminar parameters, such as... Figure 2 As shown, the samples are pure mudstone, mudstone with a single sandy layer (2 mm thick), mudstone with multiple sandy layers (2 mm thick * 8 layers), and pure sandstone, respectively. The standard size of the plunger sample is 25 mm * 50 mm. The unevenness error of the two end faces of the plunger sample is less than 0.05 mm, the error along the diameter of the plunger sample is less than 0.3 mm, and the maximum deviation of the end face perpendicular to the plunger sample axis is less than 0.25°. The uniaxial compressive strength of the four samples was then determined by uniaxial compression test (e.g., ...). Figure 3 As shown in Table 1, the results indicate that pure mudstone has the lowest uniaxial compressive strength at 64.63 MPa, while pure sandstone has the highest at 139.48 MPa. The uniaxial compressive strengths of mudstone with a single sandy layer and mudstone with multiple sandy layers are in the middle range, at 76.81 MPa and 95.47 MPa, respectively.

[0056] Table 1. Laminar parameters and uniaxial compressive strength of actual geological samples

[0057]

[0058] Then, as Figure 4 As shown in Table 2, the relationship between the sandy texture parameters and the uniaxial compressive strength was fitted, and the uniaxial compressive strength (σ) of the sample and the total thickness of the sandy texture showed a good quadratic function relationship as follows:

[0059] σ=68.48443+1.88724·H-0.00938·H 2 The correlation coefficient reached 0.96602. The closer the correlation coefficient is to 1, the better the fit. The thickness of the striation H is equal to the number of striations n and the thickness of a single striation h. In this example, h = 2 mm.

[0060] Table 2. Functional relationship between uniaxial compressive strength and total thickness of sandy texture layer

[0061]

[0062] When implementing large-scale and widespread applications in the future, the mineral composition and distribution pattern of the laminae should be considered based on the actual geological conditions (e.g., Figure 5 Artificial samples were fabricated using the method shown in Table 3, and the relevant data on the lamellar parameters and uniaxial compressive strength of the artificial samples were obtained.

[0063] Table 3. Laminar flow parameters and uniaxial compressive strength of artificial samples

[0064]

[0065] The laminar parameters and uniaxial compressive strength of artificial samples are then fitted to obtain a more accurate compressive strength of laminar shale oil reservoirs.

[0066] The preparation of artificial samples of lamellar shale is a relatively mature technology, and will not be elaborated upon here. The preparation of artificial samples includes the following steps: Step 1: Obtain a downhole core; Step 2: Scan and measure the lamellar development characteristics in the core to obtain the lamellar ratio, single-layer thickness, density, and occurrence characteristics; Step 3: Analyze the mineral content of the rock matrix and lamellars; Step 4: Measure the mineral density of the rock matrix and lamellars using the Leigh bottle method; Step 5: Prepare core raw materials according to the mineral composition, density, and lamellar development characteristics of the rock; Step 6: Press the sample in a device according to the different lamellar angles required for the research. Detailed steps can be found in the Chinese invention patent "A Method for Preparing Artificial Cores of Lamellar Shale".

[0067] Example 3

[0068] The present invention also provides a device 400 for quantitatively evaluating the compressive strength of laminated continental shale, comprising a data acquisition module 401, a first measurement module 402, a processing module 403, a second measurement module 404, and a fitting module 405;

[0069] The sampling module 401 is used to select laminated continental shale samples from core wells in a certain region, including pure mudstone, single sandy lamellar, multiple sandy lamellar, and pure sandstone.

[0070] The first measuring module 402 is used to determine the types and contents of minerals contained in pure mudstone and pure sandstone;

[0071] The processing module 403 is used to process shale samples into plunger samples to obtain sandy layer parameters of single sandy layers and multiple sandy layers.

[0072] The second measuring module 404 is used to measure the uniaxial compressive strength of the plunger sample;

[0073] The fitting module 405 is used to fit the relationship between the sand texture parameters and the uniaxial compressive strength.

[0074] The present invention also provides a computer device 100, the computer device including one or more processors 200 and one or more memories 300, the one or more memories 300 storing at least one instruction, the at least one instruction being loaded and executed by the one or more processors 200 to perform the operations performed by the above-described method for quantitatively evaluating the compressive strength of layered continental shale.

[0075] Shale oil, as an important unconventional oil and gas resource, is characterized by its wide distribution and huge reserves, and is considered an important alternative to conventional energy. Shale deformation and fracturing mechanisms have a significant impact on drilling and reservoir stimulation; the fracture morphology and strength directly affect the effectiveness of fracturing. Therefore, analyzing and testing the compressive strength of shale lamellar structures in actual areas to obtain the relationship between lamellar parameters and compressive strength is of great significance for predicting fracture development and evaluating reservoir mechanics in continental shale. It can also provide a reference for reservoir fracturing stimulation and wellbore stability early warning, aiming to improve the accuracy of shale reservoir fracturing assessment, thereby optimizing perforation well locations and formations, and improving fracturing effectiveness.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for quantitatively evaluating the compressive strength of laminated continental shale, characterized in that, Includes the following steps: S1. Select lamellar continental shale samples from core wells in a certain area, including pure mudstone, single sandy lamellar, multiple sandy lamellar, and pure sandstone; S2. Determine the types and contents of minerals contained in pure mudstone and pure sandstone; S3. All shale samples are processed into plunger samples to obtain sandy laminar parameters for single and multiple sandy laminar layers; the sandy laminar parameters include sandy laminar thickness and number of sandy laminar layers; S4. Measure the uniaxial compressive strength of the plunger sample; S5. Fitting the relationship between sand texture parameters and uniaxial compressive strength; S6. Based on the mineral composition of pure mudstone and pure sandstone in the actual geological samples of the adjacent area lacking core wells, prepare artificial samples of laminated shale with preset sandy laminar parameters, and fit the relationship between the sandy laminar parameters of the artificial samples and the uniaxial compressive strength. In step S5, the relationship between the sand texture parameters and the uniaxial compressive strength is fitted, and the uniaxial compressive strength of the plunger sample and the total thickness of the sand texture have the following quadratic function relationship: σ=68.48443+1.88724·H-0.00938·H 2 Where H is the total thickness of the sandy texture, H = n·h, n is the number of sandy textures, h is the thickness of a single sandy texture, and σ is the uniaxial compressive strength; In step S6, after preparing the artificial sample of the layered shale sample, the artificial sample is processed into a plunger sample to obtain the sandy layer parameters of a single sandy layer and multiple sandy layers. Then, steps S4 and S5 are repeated to fit the relationship between the sandy layer parameters and the uniaxial compressive strength.

2. The method for quantitatively evaluating the compressive strength of laminated continental shale according to claim 1, characterized in that, In step S2, the types and contents of minerals contained in pure mudstone and pure sandstone are determined by X-ray diffraction experiments; in step S6, the mineral composition of pure mudstone and pure sandstone in actual geological samples from adjacent areas is determined by X-ray diffraction experiments.

3. The method for quantitatively evaluating the compressive strength of laminated continental shale according to claim 1, characterized in that, In step S3, the shale sample is processed into a plunger sample by waterless wire cutting or liquid nitrogen cryogenic cutting.

4. The method for quantitatively evaluating the compressive strength of lamellar continental shale according to claim 1, characterized in that, In step S4, the uniaxial compressive strength of the plunger sample is determined by a uniaxial compression test.

5. The method for quantitatively evaluating the compressive strength of laminated continental shale according to claim 1, characterized in that, In step S3, the unevenness error of the two end faces of the plunger sample is less than 0.05 mm; the diameter error along the height direction of the plunger sample is less than 0.3 mm; and the maximum deviation of the end face perpendicular to the axis of the plunger sample is less than 0.25°.

6. A computer device, characterized in that, The computer device includes one or more processors and one or more memories, wherein at least one instruction is stored in the one or more memories and is loaded and executed by the one or more processors to perform the operations performed by the method for quantitatively evaluating the compressive strength of layered continental shale as described in any one of claims 1 to 5.

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