Method for evaluating fracturing property of shale reservoir and related device

Abstract

The invention discloses a method and related device for evaluating the fracturing property of a shale reservoir, and the method comprises the steps: determining the contents of different types of minerals in the shale reservoir, obtaining the proportion of brittle minerals, and predicting the brittleness index of the shale according to an empirical formula and the proportion of the brittle minerals; calculating the cementation degree of the reservoir through natural potential logging data and natural gamma logging data or indoor rock electricity experiment data; determining a fracture toughness value of the block rock sample according to a Brazilian splitting experiment; and according to the normalized shale brittleness index, the cementing degree of the reservoir and the fracture toughness value, evaluating the fracturing property of the shale reservoir. According to the method, multiple factors such as the content and the type of minerals in the shale reservoir, the cementing degree of the reservoir and the fracture toughness of rock are comprehensively considered, so that the fracturing property of the shale reservoir is evaluated more comprehensively.

Description

Technical Field

[0001] The invention belongs to the field of hydraulic fracturing of oil and gas reservoirs, and in particular relates to a method for evaluating the fracturing property of shale reservoirs and related devices. Background Art

[0002] Shale reservoirs generally have extremely low porosity and permeability. It is difficult to efficiently develop shale resources by relying on the natural porosity and pressure of the formation. In most cases, shale reservoirs need to be transformed. Therefore, accurately identifying the fracturing sweet spots of shale reservoirs and effectively evaluating the brittleness of shale reservoirs have become the key to efficiently developing shale reservoirs, thereby achieving higher economic benefits in the future.

[0003] In the existing technology, indoor core testing can usually only evaluate specific blocks and well sections. The specific parameters are affected by the core quality, and it is impossible to achieve brittleness evaluation of the entire well section and the entire area. The brittleness evaluation method using the mineral component content method only considers the factors of mineral components, and does not consider the effects of cementation and diagenesis on rock strength, resulting in low accuracy of brittleness evaluation, weak reference, and also unable to achieve brittleness evaluation and optimization of the entire well section. In the study of brittle minerals, only the content of different minerals is simply considered, and the different degrees of influence of different minerals on brittleness are not considered, resulting in poor accuracy of brittleness evaluation results. Summary of the invention

[0004] The object of the present invention is to provide a method for evaluating the fracturing property of a shale reservoir and a related device to solve the above-mentioned problem.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A method for evaluating the fracturing properties of a shale reservoir, comprising: Determine the content of different types of minerals in the shale reservoir, obtain the proportion of brittle minerals, and predict the shale brittleness index based on the empirical formula and the proportion of brittle minerals; Calculate the cementation degree of the reservoir through natural potential logging data, natural gamma logging data or indoor rock electrical experimental data; The fracture toughness values ​​of the block rock samples were determined based on the Brazilian splitting test; The fracturing ability of shale reservoirs is evaluated based on the normalized shale brittleness index, the degree of cementation of the reservoir and the fracture toughness value.

[0006] Furthermore, the content of different types of minerals in the shale reservoir is determined to obtain the proportion of brittle minerals, including: The content of different types of minerals in shale reservoirs is determined based on X-ray diffraction experiments or X-ray diffraction logging.

[0007] Furthermore, based on the empirical formula and the proportion of brittle minerals, the shale brittleness index is predicted, including: The brittleness index MIB is calculated based on the empirical formula, the content of mineral components and the relative brittleness coefficient of each component; (1) Where: v 石英 —Quartz mineral content in shale, %; v 方解石 — Calcite mineral content in shale, %; v 白云石 —Dolomite mineral content in shale, %; v 黄铁矿 —Pyrite mineral content in shale, %; v 粘土 —Clay mineral content in shale, %.

[0008] Furthermore, the degree of cementation of the reservoir is calculated through natural potential logging data and natural gamma logging data or indoor rock electrical experimental data, including: (2) (3) (4) (5) Where: SP MAX is the maximum value of natural potential logging, SP MIN is the minimum value of natural potential logging, SP is the natural potential logging value, SP1 is the normalized natural potential logging value; GR MAX is the maximum value of natural gamma logging, GR MIN is the minimum value of natural gamma logging, GR is the natural gamma logging value, GR1 is the normalized natural gamma logging value; C1 is the diagenetic coefficient value, C MAX is the maximum value of the diagenetic coefficient, C MIN is the minimum value of the diagenetic coefficient, and C is the normalized diagenetic coefficient value.

[0009] Furthermore, the fracture toughness values ​​of the block rock samples were determined based on the Brazilian splitting test, including: (6) (7) Where: β = a / R; a is the length of the experimental notch; B is the core thickness; R is the core radius; s is the distance between the two supporting cylindrical rollers; P is the monotonically increasing compressive load applied to the central load roller of the three-point bending load; is the fracture toughness of mode I; P max is the peak load.

[0010] Furthermore, the fracturing ability of shale reservoirs is evaluated based on the normalized shale brittleness index, the cementation degree and the fracture toughness value of the reservoir, including: Establishing a shale reservoir fracturing evaluation model: (8) Where: Frac is the reservoir fracturability, MPa -3 . m -0.5 ; MIB is the reservoir brittleness index, dimensionless; K n is the rock fracture toughness index, dimensionless; C is the diagenetic coefficient, dimensionless.

[0011] Furthermore, the fracturing ability of the reservoir is calculated based on the density, sonic wave and other logging data or the experimental data such as the indoor rock triaxial compression, combined with the relevant empirical formulas.

[0012] A system for evaluating the fracturability of a shale reservoir, comprising: The shale brittleness index prediction module is used to determine the content of different types of minerals in the shale reservoir, obtain the proportion of brittle minerals, and predict the shale brittleness index based on the empirical formula and the proportion of brittle minerals; A cementation degree acquisition module is used to calculate the cementation degree of the reservoir through natural potential logging data and natural gamma logging data or indoor rock electrical experiment data; The fracture toughness value acquisition module is used to determine the fracture toughness value of the block rock sample according to the Brazilian splitting experiment; The evaluation module is used to evaluate the fracturability of shale reservoirs based on the normalized shale brittleness index, the cementation degree of the reservoir and the fracture toughness value.

[0013] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of a method for evaluating the fracturability of a shale reservoir are implemented.

[0014] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for evaluating the fracturability of a shale reservoir.

[0015] Compared with the prior art, the present invention has the following technical effects: The present invention comprehensively considers multiple factors such as the content and type of minerals in the shale reservoir, the cementation degree of the reservoir, and the fracture toughness of the rock, so as to make the evaluation of the fracturing property of the shale reservoir more comprehensive.

[0016] The content of different types of minerals is determined through X-ray diffraction experiments or X-ray diffraction logging, and the proportion and brittleness index of brittle minerals are calculated, which improves the accuracy of the evaluation.

[0017] The evaluation process is further refined by combining natural potential logging data, natural gamma logging data or indoor rock electrical experimental data to calculate the cementation degree of the reservoir.

[0018] The Brazilian splitting test is used to determine the fracture toughness value of the block rock samples. This is a scientific and commonly used rock mechanics experimental method that can accurately reflect the fracture characteristics of rocks.

[0019] A shale reservoir fracturing evaluation model was established, and the fracturing ability of shale reservoirs was comprehensively evaluated by normalizing the shale brittleness index, reservoir cementation degree and fracture toughness value, making the evaluation results more scientific and practical.

[0020] The prediction parameters required by this method can all be obtained through logging data, without the need for a large amount of field exploration and experiments, thus reducing evaluation costs and improving evaluation efficiency.

[0021] By constructing the brittleness prediction profile of the entire well section, the sweet spots of fracturing engineering can be easily screened, providing strong support for subsequent oil and gas development.

[0022] Using adjacent well data to construct a three-dimensional fracturability profile of the study area will help to comprehensively grasp and plan the fracturability of regional shale reservoirs.

[0023] In summary, this technical solution has demonstrated remarkable technical effects in terms of comprehensiveness and accuracy, scientificity and practicality, economy and efficiency, and innovation, providing strong technical support for fracturing evaluation and oil and gas development in shale reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the present invention.

[0025] Figure 2 This is a cross-sectional diagram of the reservoir brittleness and fracturability of the well in Example 1 of the present invention.

[0026] Figure 3 This is a cross-sectional diagram of the reservoir brittleness and fracturability of Well 2 of Example 2 of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings: Example 1, please refer to Figure 1 The present invention provides a method for evaluating the fracturing property of a shale reservoir, comprising: Determine the content of different types of minerals in the shale reservoir, obtain the proportion of brittle minerals, and predict the shale brittleness index based on the empirical formula and the proportion of brittle minerals; Calculate the cementation degree of the reservoir through natural potential logging data, natural gamma logging data or indoor rock electrical experimental data; The fracture toughness values ​​of the block rock samples were determined based on the Brazilian splitting test; The fracturing ability of shale reservoirs is evaluated based on the normalized shale brittleness index, the degree of cementation of the reservoir and the fracture toughness value.

[0028] By determining the content of different types of minerals in shale reservoirs, especially the proportion of brittle minerals, basic data is provided for the subsequent prediction of shale brittleness index. This step ensures the accuracy of the evaluation, because the type and content of minerals directly affect the mechanical properties of the reservoir and the fracturing effect.

[0029] The shale brittleness index is predicted by empirical formula and the proportion of brittle minerals, making the evaluation more targeted. The brittleness index is an important indicator for evaluating the fracturing ability of shale reservoirs, which reflects the difficulty of forming cracks in the reservoir during the fracturing process.

[0030] The method combines natural potential logging data, natural gamma logging data or indoor rock electrical experimental data to calculate the cementation degree of the reservoir. The cementation degree is an important factor affecting the strength of reservoir rock and the effect of fracturing. The addition of this step makes the evaluation more comprehensive.

[0031] The fracture toughness value of the block rock samples was determined through the Brazilian splitting experiment, which further enriched the evaluation content. Fracture toughness is the ability of rock to resist crack propagation, which is of great significance for predicting the expansion of cracks and the volume of reservoir transformation during fracturing.

[0032] The fracturability of shale reservoirs is comprehensively evaluated based on the normalized shale brittleness index, the cementation degree of the reservoir and the fracture toughness value. This step reflects the scientific nature of the evaluation because it comprehensively considers multiple factors that affect the fracturability of the reservoir.

[0033] In summary, this method for evaluating the fracturing ability of shale reservoirs has significant technical effects such as accuracy and pertinence, comprehensiveness and comprehensiveness, scientificity and practicality, operability and repeatability. It provides strong technical support and decision-making basis for fracturing evaluation and oil and gas development of shale reservoirs.

[0034] Example 2, the present invention provides a method for evaluating the fracturing properties of a shale reservoir, specifically comprising: Determine the content of different types of minerals in shale reservoirs based on X-ray diffraction experiments and X-ray diffraction logging, and analyze the proportion of brittle minerals such as quartz feldspar. Predict shale brittleness based on prediction formulas and brittle mineral content. Predict the degree of cementation of the reservoir based on natural potential logging and natural gamma logging data or indoor rock electrical experimental data, and conduct a comprehensive analysis of rock brittleness by combining the brittleness prediction results and cementation prediction results. Predict the tensile strength of the reservoir based on parameters such as density logging, and calculate the logging value of the reservoir fracture toughness.

[0035] The fracture toughness of rock samples in the predicted area is determined based on the Brazilian splitting experiment.

[0036] The fracturing ability of shale oil reservoirs is evaluated based on the normalized brittleness index, the degree of brittle mineral bonding and fracture toughness.

[0037] Based on the evaluation results, a new method for predicting the fracturing properties of shale oil reservoirs using parameters such as mineral composition logging, natural potential logging and natural gamma logging was established; Furthermore, the brittleness index is calculated by an empirical formula taking into account the mineral component content and the relative brittleness coefficient of each component. The greater the relative content of the brittle component, the stronger the brittleness. This brittleness index evaluation method is called the mineral component content and brittleness coefficient index method MIB.

[0038] (1) Where: v 石英 —Quartz mineral content in shale, %; v 方解石 — Calcite mineral content in shale, %; v 白云石 —Dolomite mineral content in shale, %; v 黄铁矿 —Pyrite mineral content in shale, %; v 粘土 —Clay mineral content in shale, %.

[0039] Furthermore, the degree of cementation of shale oil reservoirs can be predicted based on the natural potential logging curve and natural gamma logging curve or indoor rock electrical data.

[0040] Furthermore, the degree of cementation of shale oil reservoir is calculated: (2) (3) (4) Where: SP is the natural potential logging value, GR is the natural gamma logging value, and C is the diagenetic coefficient.

[0041] Diagenetic coefficient evaluation results

[0042] According to the above results, it can be seen that the larger the diagenetic coefficient, the smaller the fracturing ability, so the diagenetic coefficient is normalized by formula (4-8).

[0043] (5) The fracture toughness index of shale oil reservoirs was further calculated through the Brazilian splitting experiment: (6) (7) Where: β = a / R; a is the length of the experimental notch; B is the core thickness; R is the core radius; s is the distance between the two supporting cylindrical rollers; P is the monotonically increasing compressive load applied to the central load roller of the three-point bending load; is the fracture toughness of mode I; P max is the peak load.

[0044] Furthermore, considering the fracture toughness value of the reservoir, combined with the influence of the brittleness index and cementation degree, a new shale reservoir fracturing evaluation model was established: (8) Where: Frac is the reservoir fracturability, MPa-3.m-0.5; MIB is the reservoir brittleness index, dimensionless; KC is the rock fracture toughness index, dimensionless; C is the diagenetic coefficient, dimensionless.

[0045] Furthermore, the shale oil reservoir brittleness index prediction module is used to determine the content of different types of minerals in the shale reservoir based on X-ray diffraction experiments and X-ray diffraction logging, analyze the proportion of brittle minerals such as quartz feldspar, and consider the different influence coefficients of different minerals on brittleness. The shale brittleness is predicted based on empirical formulas and the content of brittle minerals.

[0046] The shale oil reservoir cementation prediction module is used to predict the cementation degree of the reservoir based on natural potential logging and natural gamma logging data or indoor experiments, and to conduct a comprehensive analysis of rock brittleness by combining the brittleness prediction results and the cementation degree prediction results.

[0047] The shale oil reservoir fracture toughness prediction module is used to calculate the logging value of the reservoir's fracture toughness based on density, acoustic wave and other logging data combined with relevant empirical formulas.

[0048] The shale oil reservoir fracture toughness experimental analysis module is used to determine the fracture toughness experimental values ​​of rock samples in the predicted area based on the Brazilian splitting experiment.

[0049] The shale oil reservoir brittleness evaluation module is used to evaluate the fracturability of shale oil reservoirs based on the normalized brittleness index, brittle mineral bonding degree and fracture toughness value experiments. Based on the evaluation results, the mineral component logging, natural potential and natural gamma logging are used to predict the fracturability of shale oil reservoirs.

[0050] Example 3 The present invention provides a method for evaluating the fracturing property of a shale reservoir, comprising the following steps: Step 1: Based on the L287 well of the Chang 7 shale oil reservoir in the Ordos Basin, the mineral components obtained by X-ray diffraction experiments were evaluated in combination with the formula. The MIB brittleness index was calculated by formula (1) for the selected cores numbered 1 and 2, and the MIB of core 1 was 0.981 and that of core 2 was 0.987.

[0051] Step 2: The cementation index of the corresponding core position is obtained through the natural potential and natural gamma logging curves to evaluate the cementation of the core. Through the analysis and calculation of the logging data, the cementation index of core No. 1 is 0.617, and the cementation index of core No. 2 is 0.26. It can be seen that the degree of cementation of core No. 1 is significantly higher than that of core No. 2.

[0052] Step 3: According to the degree of cementation obtained in step 2, combined with the mineral component brittleness index obtained in step 1, the compressibility of the core is analyzed. Since the difference between the two cores in the MIB brittleness analysis is small, and considering that this calculation method only considers the influence of brittle minerals, it is more affected by cementation, and combined with the degree of cementation, it is predicted that the compressibility of core No. 2 is stronger.

[0053] Step 4: Perform triaxial compression test and Brazilian splitting test on the cores, test the experimental data of the cores, obtain the experimental value of fracture toughness, and further verify the accuracy of the method. The fracture toughness is calculated by formula (6)-(7), and the fracture toughness of core No. 1 is 0.81, and the fracture toughness of core No. 2 is 0.76. The fracability model Frac is constructed to calculate the fracability of core No. 1 to be 0.728, which is significantly lower than 0.835 of core No. 2.

[0054] Step 5: Calculate the fracturability of the reservoir at the selected depth through logging data. The fracturability of core 1 is 0.669, which is lower than 0.673 of core 2. Combined with the correlation distribution between fracturability and actual production data, the accuracy and feasibility of the prediction method are further proved.

[0055] Example 4 A method for quantitatively evaluating the fracturability of shale oil reservoirs by integrating rock mechanical properties and geostress fields of the present invention comprises the following steps: Step 1: Based on the mineral components obtained from the X-ray diffraction experiment of the M138 well in the Ordos Basin, the evaluation was carried out in combination with the formula. The MIB brittleness index was calculated by formula (1) for the selected cores numbered 1 and 2, and the MIB of core 1 was 0.985 and that of core 2 was 0.949.

[0056] Step 2: The cementation index of the corresponding core position is obtained through the natural potential and natural gamma logging curves to evaluate the cementation of the core. Through the analysis and calculation of the logging data, the cementation index of core No. 1 is 0.292, and the cementation index of core No. 2 is 0.246. It can be seen that the cementation degree of core No. 1 is higher than that of core No. 2.

[0057] Step 3: According to the degree of cementation obtained in step 2, combined with the brittleness index of the mineral components obtained in step 1, the compressibility of the core is analyzed. Since the MIB brittleness analysis of core No. 1 is slightly higher than that of core No. 2, and considering that this calculation method only considers the influence of brittle minerals, it is more affected by cementation, and combined with the degree of cementation, it is predicted that the brittleness of core No. 2 may be relatively strong.

[0058] Step 4: Perform triaxial compression test and Brazilian splitting test on the cores, test the experimental data of the cores, obtain the experimental value of fracture toughness, and further verify the accuracy of the method. The fracture toughness is calculated by formula (6)-(7), and the fracture toughness of core No. 1 is 0.73, and the fracture toughness of core No. 2 is 0.76. The fracability formula constructed by the construction shows that the fracability of core No. 1 is 0.814, which is lower than 0.822 of core No. 2.

[0059] Step 5: Calculate the fracturability of the reservoir at the selected depth through logging data. The fracturability of core 1 is 0.599, which is lower than 0.606 of core 2. Combined with the correlation distribution between fracturability and actual production data, the accuracy and feasibility of the prediction method are further proved.

[0060] Principles of the evaluation method Shale oil reservoir fracturing can only achieve higher economic benefits if a complex and large-scale complex fracture network is obtained. Brittleness refers to the physical property of whether shale is easy to form a complex and large fracture network, which has nothing to do with physical properties such as porosity, permeability, and oil saturation. Reservoir properties such as porosity, permeability, and oil saturation belong to the category of fracturing geological sweet spots and have nothing to do with reservoir brittleness. However, some patents include the above properties in fracturing, confusing the basic concepts.

[0061] The fracturing ability of shale oil reservoirs should be considered from two aspects: obtaining a complex fracture network and obtaining a large stimulation volume. The probability of obtaining a complex fracture network mainly depends on the brittleness of the reservoir.

[0062] This evaluation method effectively predicts the brittleness of shale reservoirs as a criterion for judging the complexity of fractures, and no patent has been considered in this regard; The brittleness of shale reservoirs mainly depends on the content of brittle minerals in the reservoirs. In addition, the degree of rock cementation will also affect the strength of the reservoir to a certain extent, thereby affecting the fracturing effect of the reservoir. However, no patent has yet considered this aspect.

[0063] In another embodiment of the present invention, a system for evaluating the fracturability of a shale reservoir is provided, which can be used to implement the above-mentioned method for evaluating the fracturability of a shale reservoir. Specifically, the system includes: The shale brittleness index prediction module is used to determine the content of different types of minerals in the shale reservoir, obtain the proportion of brittle minerals, and predict the shale brittleness index based on the empirical formula and the proportion of brittle minerals; A cementation degree acquisition module is used to calculate the cementation degree of the reservoir through natural potential logging data and natural gamma logging data or indoor rock electrical experiment data; The fracture toughness value acquisition module is used to determine the fracture toughness value of the block rock sample according to the Brazilian splitting experiment; The evaluation module is used to evaluate the fracturability of shale reservoirs based on the normalized shale brittleness index, the cementation degree of the reservoir and the fracture toughness value.

[0064] The division of modules in the embodiments of the present invention is schematic and is only a logical function division. There may be other division methods in actual implementation. In addition, each functional module in each embodiment of the present invention may be integrated into one processor, or may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated modules may be implemented in the form of hardware or in the form of software functional modules.

[0065] In another embodiment of the present invention, a computer device is provided, the computer device comprising a processor and a memory, the memory is used to store a computer program, the computer program comprises program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, which are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of a method for evaluating the fracturability of shale reservoirs.

[0066] In another embodiment of the present invention, the present invention further provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the method for evaluating the fracturability of a shale reservoir in the above embodiment.

[0067] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0068] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0069] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0070] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for evaluating the fracturing properties of a shale reservoir, characterized in that: include: Determine the content of different types of minerals in the shale reservoir, obtain the proportion of brittle minerals, and predict the shale brittleness index based on the empirical formula and the proportion of brittle minerals; Calculate the cementation degree of the reservoir through natural potential logging data, natural gamma logging data or indoor rock electrical experimental data; The fracture toughness values ​​of the block rock samples were determined based on the Brazilian splitting test; The fracturing ability of shale reservoirs is evaluated based on the normalized shale brittleness index, the degree of cementation of the reservoir and the fracture toughness value.

2. A method for evaluating the fracturing properties of a shale reservoir according to claim 1, characterized in that: Determine the content of different types of minerals in shale reservoirs and obtain the proportion of brittle minerals, including: The content of different types of minerals in shale reservoirs is determined based on X-ray diffraction experiments or X-ray diffraction logging.

3. A method for evaluating the fracturing properties of a shale reservoir according to claim 2, characterized in that: According to the empirical formula and the proportion of brittle minerals, the shale brittleness index is predicted, including: The brittleness index MIB is calculated based on the empirical formula, the content of mineral components and the relative brittleness coefficient of each component; （1） Where: v 石英 —Quartz mineral content in shale, %; v 方解石 — Calcite mineral content in shale, %; v 白云石 —Dolomite mineral content in shale, %; v 黄铁矿 —Pyrite mineral content in shale, %; v 粘土 —Clay mineral content in shale, %.

4. The method for evaluating the fracturability of a shale reservoir according to claim 1, characterized in that: The degree of reservoir cementation is calculated through natural potential logging data, natural gamma logging data or indoor rock electrical experimental data, including: （2） （3） （4） （5） Where: SP MAX is the maximum value of natural potential logging, SP MIN is the minimum value of natural potential logging, SP is the natural potential logging value, SP1 is the normalized natural potential logging value; GR MAX is the maximum value of natural gamma logging, GR MIN is the minimum value of natural gamma logging, GR is the natural gamma logging value, GR1 is the normalized natural gamma logging value; C1 is the diagenetic coefficient value, C MAX is the maximum value of the diagenetic coefficient, C MIN is the minimum value of the diagenetic coefficient, and C is the normalized diagenetic coefficient value.

5. The method for evaluating the fracturing property of a shale reservoir according to claim 1, characterized in that: The fracture toughness values ​​of the block rock samples were determined based on the Brazilian splitting test, including: (6) (7) Where: β = a / R; a is the length of the experimental notch; B is the core thickness; R is the core radius; s is the distance between the two supporting cylindrical rollers; P is the monotonically increasing compressive load applied to the central load roller of the three-point bending load; is the fracture toughness of mode I; P max is the peak load.

6. The method for evaluating the fracturability of a shale reservoir according to claim 1, characterized in that: The fracturing ability of shale reservoirs is evaluated based on the normalized shale brittleness index, the cementation degree and fracture toughness value of the reservoir, including: Establishing a shale reservoir fracturing evaluation model: (8) Where: Frac is the reservoir fracturability, MPa -3 . m -0.5 ; MIB is the reservoir brittleness index, dimensionless; K n is the rock fracture toughness index, dimensionless; C is the diagenetic coefficient, dimensionless.

7. A method for evaluating the fracturing properties of a shale reservoir according to claim 6, characterized in that: The fracturing ability of the reservoir is calculated based on the density, sonic wave and other logging data or the experimental data such as the indoor rock triaxial compression, combined with the relevant empirical formulas.

8. A system for evaluating the fracturability of a shale reservoir, characterized in that: include: The shale brittleness index prediction module is used to determine the content of different types of minerals in the shale reservoir, obtain the proportion of brittle minerals, and predict the shale brittleness index based on the empirical formula and the proportion of brittle minerals; A cementation degree acquisition module is used to calculate the cementation degree of the reservoir through natural potential logging data and natural gamma logging data or indoor rock electrical experiment data; The fracture toughness value acquisition module is used to determine the fracture toughness value of the block rock sample according to the Brazilian splitting experiment; The evaluation module is used to evaluate the fracturability of shale reservoirs based on the normalized shale brittleness index, the cementation degree of the reservoir and the fracture toughness value.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for evaluating the fracturability of a shale reservoir as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for evaluating the fracturability of a shale reservoir as claimed in any one of claims 1 to 7 are implemented.

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