Brittleness evaluation method and apparatus for unconventional oil and gas reservoir, and device, medium and product

Abstract

Provided are a brittleness evaluation method and apparatus for an unconventional oil and gas reservoir, and a device, a medium and a product. In the brittleness evaluation method for an unconventional oil and gas reservoir, on the basis of a fundamental principle that, under uniaxial / triaxial compression conditions, rocks with higher brittleness consume less energy during failure and undergo smaller deformation, two parameters, i.e., uniaxial / triaxial compressive failure energy of the rocks and the deformation of the rocks during failure, are combined. The compressive failure energy parameter and deformation parameter of the rocks are obtained by using a stress-strain curve of the rocks, and the brittleness of reservoir rocks is evaluated according to the magnitude of deformation per unit energy during a rock failure, thereby realizing the rapid and accurate evaluation of the brittleness of the reservoir rocks, and thus providing theoretical guidance for the selection of a target reservoir to be fractured and the design of a fracturing scheme.

Description

Methods, apparatus, equipment, media and products for evaluating the brittleness of unconventional oil and gas reservoirs

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 2025100631859, filed on January 15, 2025, entitled “Method, Apparatus, Equipment, Medium and Product for Evaluating the Brittleness of Unconventional Oil and Gas Reservoirs”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of unconventional oil and gas reservoir exploration and development technology, and in particular to a method, apparatus, equipment, medium and product for evaluating the brittleness of unconventional oil and gas reservoirs. Background Technology

[0004] Unconventional oil and gas reservoirs possess complex geological characteristics, making it difficult to accurately predict geological and engineering sweet spots. When fracturing unconventional oil and gas reservoirs, assessing the brittleness of the reservoir rock is crucial for selecting appropriate fracturing sections, designing fracturing operations, determining the volume of fracture network stimulation, and evaluating oil and gas production. Currently, the oil and gas development field primarily evaluates reservoir rock brittleness through well logging, seismic inversion, and laboratory rock mechanics experiments. However, most brittleness index assessment methods do not accurately match the results of reservoir rock brittleness assessments with the fracturing effects of unconventional reservoirs, resulting in low accuracy in field applications.

[0005] Therefore, there is an urgent need to establish a rock brittleness calculation method that can accurately evaluate reservoir rock brittleness and match the volume of reservoir fracturing stimulation. Summary of the Invention

[0006] This application provides a method, apparatus, equipment, medium, and product for evaluating the brittleness of unconventional oil and gas reservoirs, in order to at least partially solve the above-mentioned problems.

[0007] The first aspect of this application provides a method for evaluating the brittleness of unconventional oil and gas reservoirs, the method comprising:

[0008] Obtain stress-strain data from core samples of the target unconventional oil and gas reservoir in uniaxial or triaxial compression tests;

[0009] Determine the peak strain of the target unconventional oil and gas reservoir core sample under uniaxial or triaxial compression based on the stress-strain data.

[0010] The total energy before the peak of the core sample from the target unconventional oil and gas reservoir is determined based on the peak strain.

[0011] The rock brittleness value of the target unconventional oil and gas reservoir is determined based on the peak strain and the total energy before the peak. Optionally, stress-strain data of the core sample from the target unconventional oil and gas reservoir obtained from uniaxial compression or triaxial compression tests are acquired, including:

[0012] Obtain stress-strain data from core samples of multiple fracturing sections of the target unconventional oil and gas reservoir in uniaxial or triaxial compression tests;

[0013] Based on the stress-strain data, the rock brittleness value of the target unconventional oil and gas reservoir is determined, including:

[0014] Based on the stress-strain data of core samples from multiple fracturing sections, the rock brittleness values ​​of each fracturing section were obtained.

[0015] The method further includes:

[0016] The rock brittleness values ​​of multiple fracturing sections are compared, and the fracturing section with the highest rock brittleness value is determined as the target fracturing section.

[0017] Based on the target fracturing section, an engineering sweet spot selection recommendation for the target unconventional oil and gas reservoir is output.

[0018] Optionally, stress-strain data are obtained from core samples of the target unconventional oil and gas reservoir during uniaxial or triaxial compression tests, including:

[0019] The stress-strain data of core samples from unconventional oil and gas reservoirs are obtained from uniaxial or triaxial compression tests under different environmental conditions, including confining pressure, temperature and / or fluid conditions.

[0020] Based on the stress-strain data, the rock brittleness value of the target unconventional oil and gas reservoir is determined, including:

[0021] Based on the stress-strain data obtained under various environmental conditions, the rock brittleness value of the target unconventional oil and gas reservoir under various environmental conditions is determined.

[0022] The method further includes:

[0023] Based on the rock brittleness values ​​of the target unconventional oil and gas reservoir under various environmental conditions, the brittleness evolution law of the target unconventional oil and gas reservoir as environmental conditions change is obtained.

[0024] Based on the aforementioned brittleness evolution law, recommendations for selecting engineering sweet spots for the target unconventional oil and gas reservoir are provided.

[0025] Optionally, determining the total pre-peak energy of the core sample from the target unconventional oil and gas reservoir based on the peak strain includes:

[0026] From initial strain 0 to peak strain ε p Integrating the stress-strain curves within the range yields the total peak energy U of the rock sample. p :

[0027] Optionally, determining the rock brittleness value based on the peak strain and the pre-peak total energy includes: determining the rock brittleness value based on the following formula:

[0028] Wherein, BI represents the rock brittleness value.

[0029] Optionally, the stress-strain data is determined using the following steps:

[0030] Drill and core samples are taken from the target unconventional oil and gas reservoir, and the core samples are processed into cylindrical test samples.

[0031] Uniaxial or triaxial compression tests were conducted on the cylindrical test sample to obtain stress-strain data of the target unconventional oil and gas reservoir core sample in the uniaxial or triaxial compression test.

[0032] During the uniaxial or triaxial compression test, the stress loading rate is less than 0.05 mm / min.

[0033] A second aspect of this application provides an unconventional oil and gas reservoir brittleness evaluation device, the unconventional oil and gas reservoir brittleness evaluation device comprising:

[0034] The acquisition module is used to acquire stress-strain data of core samples from unconventional oil and gas reservoirs obtained in uniaxial or triaxial compression tests.

[0035] The first determining module is used to determine the peak strain of the target unconventional oil and gas reservoir core sample under uniaxial compression or triaxial compression based on the stress-strain data.

[0036] The second determining module is used to determine the total pre-peak energy of the core sample of the target unconventional oil and gas reservoir based on the peak strain.

[0037] The third determining module is used to determine the rock brittleness value of the target unconventional oil and gas reservoir based on the peak strain and the total energy before the peak.

[0038] A third aspect of this application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executed, implements the unconventional oil and gas reservoir brittleness evaluation method as described in the first aspect of this application.

[0039] The fourth aspect of this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the unconventional oil and gas reservoir brittleness evaluation method as described in the first aspect of this application.

[0040] The fifth aspect of this application provides a computer program product, including a computer program / instructions, which are implemented by a processor as the steps in the unconventional oil and gas reservoir brittleness evaluation method described in the first aspect of this application.

[0041] In this application, addressing the mismatch between current assessments of unconventional oil and gas reservoir brittleness and reservoir stimulation effects, a method for evaluating the brittleness of unconventional oil and gas reservoirs is proposed. This method evaluates the brittleness of unconventional oil and gas reservoirs based on the relationship between the failure energy and deformation behavior of the rock, enabling rapid and accurate assessment of reservoir rock brittleness and providing theoretical guidance for target reservoir selection and fracturing scheme design. The energy and deformation required for rock failure are direct manifestations of rock brittleness. The proposed method for calculating the brittleness index of unconventional oil and gas reservoir rocks utilizes the fundamental principle that the greater the rock brittleness, the less energy is consumed and the smaller the rock deformation under uniaxial / triaxial compression conditions. It combines the uniaxial / triaxial compressive failure energy and the deformation at failure, using the stress-strain curve to obtain the compressive failure energy and deformation parameters. The brittleness of the reservoir rock is evaluated by the deformation per unit energy at failure. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 is a flowchart of the steps of the unconventional oil and gas reservoir brittleness evaluation method provided in the embodiments of this application;

[0044] Figure 2 shows the configuration of rock mechanics test specimens in the unconventional oil and gas reservoir brittleness evaluation method provided in the embodiments of this application.

[0045] Figure 3 shows the stress-strain curves of uniaxial or triaxial compression and the total energy before the peak (U) in the unconventional oil and gas reservoir brittleness evaluation method provided in the embodiments of this application. p Peak strain at failure (ε) p ) Schematic diagram;

[0046] Figure 4 is a graph of the brittleness index of unconventional reservoir rocks calculated in the unconventional oil and gas reservoir brittleness evaluation method provided in the embodiments of this application;

[0047] Figure 5 is a stress-strain curve of shale core under different confining pressures in the unconventional oil and gas reservoir brittleness evaluation method provided in the embodiments of this application.

[0048] Figure 6 is a graph showing the evaluation results of the brittleness of shale under different confining pressures in the unconventional oil and gas reservoir brittleness evaluation method provided in the embodiments of this application.

[0049] Figure 7 is a graph showing the effect of rock brittleness evaluation on different unconventional oil and gas reservoirs in the project using the unconventional oil and gas reservoir brittleness evaluation method provided in the embodiments of this application.

[0050] Figure 8 shows a typical hydraulic fracturing curve in Case 2 provided in the embodiments of this application, which illustrates the real-time data of injection pressure and discharge rate during the fracturing process.

[0051] Figure 9 is the pressure-power curve in Example 2 provided in the embodiments of this application, where the fracturing power is determined by the injection pressure and the displacement.

[0052] Figure 10 is a schematic diagram showing the relationship between reservoir rock brittleness and fracturing energy per unit reservoir stimulation volume in different well sections of unconventional oil and gas in different regions in engineering, obtained from the unconventional oil and gas reservoir brittleness evaluation method provided in the embodiments of this application.

[0053] Figure 11 schematically shows a block diagram of a computing processing apparatus for performing the method according to this application; and

[0054] Figure 12 schematically illustrates a storage unit for holding or carrying program code that implements the method according to this application. Specific Implementation

[0055] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] First, the technical terms involved in the embodiments of this application will be explained:

[0057] Geological sweet spots: In oil and gas exploration and development, geological sweet spots refer to areas or strata rich in oil and gas that can be effectively developed under current economic and technological conditions. Specifically, geological sweet spots include the following aspects: Physical property sweet spots: These refer to areas or strata in tight oil reservoirs that have relatively high porosity and permeability relative to the overall tight background. Reservoir sweet spots: These refer to areas or strata in low-abundance oil-bearing backgrounds that have relatively high oil saturation, and the petroleum is light (relatively low density and viscosity), has relatively high pressure states (pressure coefficient greater than 1), and relatively high reserve abundance. Physical property sweet spots and reservoir sweet spots are collectively referred to as geological sweet spots, which, from a geological perspective, indicate areas or strata where tight oil is relatively concentrated and enriched. Geological sweet spots determine the resource potential of tight oil, while engineering sweet spots determine the development effectiveness of tight oil. The identification and evaluation of geological sweet spots are of significant guiding importance for oil and gas exploration and development, helping to determine the areas most likely to yield high production, thereby optimizing exploration and development strategies.

[0058] Engineering sweet spots, particularly in oil and gas geology, refer to areas of oil and gas reservoirs that are also easily fractured for development, building upon the geological sweet spots. In oil and gas exploration and development, "engineering sweet spots" and "geological sweet spots" together constitute the so-called "double sweet spots." Geological sweet spots refer to areas rich in oil and gas reservoirs, while engineering sweet spots are areas where these reservoirs are easily fractured for development. In practical applications, the prediction of engineering sweet spots typically relies on well logging and seismic exploration. These techniques allow for detailed evaluation of the geological parameters of well sites and the assessment of the distribution of core parameters (e.g., porosity, permeability, and brittleness).

[0059] Unconventional oil and gas reservoirs: Unconventional oil and gas refers to oil and gas resources that cannot be produced at natural industrial levels using traditional technologies. New technologies are needed to improve reservoir permeability or fluid viscosity for economical extraction; these are continuous or quasi-continuous accumulations. A reservoir is a rock formation capable of storing and permeating fluids. Therefore, unconventional oil and gas reservoirs refer to rock formations capable of storing and permeating unconventional oil and gas resources.

[0060] This application provides a flowchart of a method for evaluating the brittleness of unconventional oil and gas reservoirs, as shown in Figure 1. Specifically, the method for evaluating the brittleness of unconventional oil and gas reservoirs includes the following steps:

[0061] S101, Obtain stress-strain data from core samples of the target unconventional oil and gas reservoir in uniaxial or triaxial compression tests;

[0062] S102, Determine the peak strain of the target unconventional oil and gas reservoir core sample under uniaxial compression or triaxial compression based on the stress-strain data;

[0063] S103, Determine the total pre-peak energy of the core sample of the target unconventional oil and gas reservoir based on the peak strain;

[0064] S104, Determine the rock brittleness value of the target unconventional oil and gas reservoir based on the peak strain and the total energy before the peak.

[0065] In this embodiment of the application, in step S102, the stress-strain curve of the rock sample can be analyzed to obtain the peak strain (ε) under uniaxial / triaxial compression. p Specifically, the point with the largest strain in the stress-strain curve can be taken as the peak strain.

[0066] In this embodiment, the area under the compressive stress-strain curve represents the work done by the external force on the rock, and also represents the energy required throughout the entire process from loading until the rock fails. Therefore, the total energy before the peak can be determined based on the area under the stress-strain curve and the peak strain.

[0067] The energy required for rock failure and the deformation behavior are direct manifestations of rock brittleness. This application proposes a method for calculating the brittleness index of unconventional oil and gas reservoir rocks, utilizing the fundamental principle that the greater the rock brittleness, the less energy is consumed and the smaller the rock deformation under uniaxial / triaxial compression conditions. By combining the uniaxial / triaxial compressive failure energy and the rock deformation at failure, the compressive failure energy and deformation parameters are obtained using the rock's stress-strain curve. The brittleness of the reservoir rock is evaluated by the magnitude of deformation per unit energy at failure.

[0068] In this embodiment of the application, the stress-strain data can be determined using the following steps:

[0069] S100 involves drilling and coring the target unconventional oil and gas reservoir, and processing the core samples into cylindrical test samples.

[0070] S200, a uniaxial or triaxial compression test is carried out on the cylindrical test sample to obtain stress-strain data of the target unconventional oil and gas reservoir core sample in the uniaxial or triaxial compression test.

[0071] In this embodiment of the application, the preparation process of the test sample includes: drilling and coring the target unconventional oil and gas reservoir, and processing the core samples into cylindrical test samples.

[0072] In this embodiment of the application, the in-situ stress characteristics (e.g., confining pressure) and in-situ environmental parameters such as temperature and fluid in the reservoir environment can also be obtained.

[0073] In this embodiment of the application, the reservoir rock compression failure test process includes: taking the test sample from the above steps to carry out a uniaxial compression test or a triaxial compression test. If conditions permit, a triaxial compression test under in-situ reservoir environmental conditions can also be carried out to obtain stress-strain data of the reservoir core under uniaxial compression or triaxial compression conditions, and to plot the stress-strain curve.

[0074] In this embodiment of the application, during practical application, core samples can be obtained from unconventional oil and gas reservoirs through drilling. The obtained core samples are processed into cylinders with a diameter of 50 mm and a height of 100 mm, or a diameter of 25 mm and a height of 50 mm. This allows for the acquisition of in-situ stress characteristics and temperature parameters within the reservoir environment.

[0075] Specifically, in the embodiments of this application, the specimen configuration of the prepared rock mechanics test (uniaxial compression test or triaxial compression test) is shown in Figure 2.

[0076] In this embodiment of the application, in practical application, uniaxial or triaxial compression tests can be carried out on the core sample. When conditions permit, triaxial compression tests under reservoir temperature and pressure conditions can be carried out. The loading rate must meet the requirements of quasi-static loading of rock. It is recommended that the loading rate be less than 0.05 mm / min. The compression stress-strain curve of the reservoir core under uniaxial / triaxial conditions can be obtained.

[0077] In an optional implementation, step S103 includes: adjusting the initial strain 0 to the peak strain ε. p Integrating the stress-strain curves within the range yields the total peak energy U of the rock sample. p :

[0078] In this embodiment, load and rock sample deformation data are obtained from uniaxial or triaxial compression tests, and then the stress (σ) and strain (ε) of the rock are calculated. Further analysis of the stress-strain curve of the rock sample yields the peak strain (ε) under uniaxial or triaxial compression. p ).

[0079] This application's embodiments determine the pre-peak total energy based on the area of ​​the stress-strain curve at the peak strain. Specifically, the pre-peak total energy (Ufront) of the rock sample is obtained by integrating the stress-strain curve from the initial strain 0 to the peak strain range. p ).

[0080] In this embodiment, the mechanical data (stress-strain data) obtained from mechanical tests (uniaxial compression or triaxial compression tests) can be analyzed to obtain the peak strain (ε) at rock sample failure. p ) and pre-peak total energy (U pFor example, stress-strain curves of rocks under uniaxial or triaxial loading versus pre-peak total energy (U). p Peak strain at failure (ε) p The schematic diagram is shown in Figure 3.

[0081] In an optional implementation, step S104:

[0082] The brittleness value of rock is determined based on the following formula:

[0083] Wherein, BI represents the rock brittleness value.

[0084] In this embodiment of the application, a brittleness index is established based on the energy and strain characteristics of rock brittle failure to obtain a rock brittleness value. Based on this rock brittleness value, the brittleness differences of unconventional reservoir rocks can be compared.

[0085] In this embodiment of the application, the brittleness index diagram of unconventional reservoir rocks calculated based on stress-strain data obtained during the compression loading process is shown in Figure 4. During the compression loading process, the peak strain (ε) at failure of the reservoir rock ranges from 0 to 0.05, and the pre-peak compressive strain energy does not exceed 5 MJ / m³. The brittleness index diagram of the reservoir rock was plotted based on the peak strain and compressive strain energy. It can be intuitively observed from Figure 4 that the smaller the peak strain and the smaller the pre-peak compressive strain energy, the larger the brittleness index of the rock.

[0086] In one optional implementation, the unconventional oil and gas reservoir brittleness evaluation method includes the following steps:

[0087] S201, obtain stress-strain data from core samples of multiple fracturing sections of the target unconventional oil and gas reservoir in uniaxial or triaxial compression tests;

[0088] S202, based on the stress-strain data of the core samples from multiple fracturing sections, the rock brittleness values ​​of each fracturing section are obtained;

[0089] S203, compare the rock brittleness values ​​of multiple fracturing sections and determine the fracturing section with the largest rock brittleness value as the target fracturing section;

[0090] S204, Based on the target fracturing section, output engineering sweet spot selection suggestions for the target unconventional oil and gas reservoir.

[0091] Based on the method provided in the embodiments of this application, in practical applications, the differences in reservoir rock brittleness in different regions / fractured wells / fractured sections can be determined by comparing the brittleness values ​​corresponding to different regions, different fractured sections, or different fractured well cores. This can guide engineering embodiments to select the target fractured section based on the brittleness of different rocks, and further guide the selection of the sweet spot in engineering.

[0092] In one optional implementation, the unconventional oil and gas reservoir brittleness evaluation method includes the following steps:

[0093] S301, Obtain stress-strain data from uniaxial or triaxial compression tests of core samples from the target unconventional oil and gas reservoir under different environmental conditions, wherein the environmental conditions include: confining pressure conditions, temperature conditions and / or fluid conditions.

[0094] S302, Based on the stress-strain data obtained under various environmental conditions, determine the rock brittleness value of the target unconventional oil and gas reservoir under various environmental conditions;

[0095] S303, Based on the rock brittleness values ​​of the target unconventional oil and gas reservoir under various environmental conditions, the brittleness evolution law of the target unconventional oil and gas reservoir as environmental conditions change is obtained.

[0096] S304, Based on the aforementioned brittleness evolution law, output engineering sweet spot selection suggestions for the target unconventional oil and gas reservoir.

[0097] In this embodiment of the application, the triaxial compression mechanics test can apply environmental variables such as temperature, pressure, and fluid in the in-situ environment of the reservoir to evaluate the brittleness of the reservoir rock under in-situ environmental conditions. In this embodiment of the application, the confining pressure, temperature, and fluid conditions can also be changed during the mechanical test to predict the brittleness evolution law of the reservoir rock as environmental variables change.

[0098] Furthermore, based on this brittleness evolution law and actual engineering needs, recommendations for selecting engineering sweet spots can be generated. Specifically, after evaluating the brittleness of rocks at different reservoir locations using the brittleness evaluation method provided in the embodiments of this application, the more brittle the reservoir rocks, the more favorable the candidate for engineering sweet spots.

[0099] To demonstrate the effectiveness of the methods provided in the embodiments of this application, the following specific implementation examples are provided to verify the methods provided in the embodiments of this application.

[0100] Case 1: Evaluation of the brittleness of reservoir rocks under different reservoir confining pressures.

[0101] In this case, shale cores from a shale gas reservoir in Sichuan were processed into cylinders with a diameter of 25 mm and a height of 50 mm. Uniaxial compression tests were conducted on the cores under no confining pressure, and triaxial compression tests were conducted under 20 MPa, 40 MPa, and 70 MPa conditions. The compressive stress-strain curves of the reservoir rock under different confining pressures were obtained, as shown in Figure 5.

[0102] The physical and mechanical parameters of shale under different confining pressures were calculated based on the stress-strain curves. The brittleness index of shale under different confining pressures was calculated using the brittleness index calculation formula of this application, as detailed in Table 1 below. The relationship between the brittleness parameters of shale under different confining pressures and the change of confining pressure is shown in Figure 6. As the confining pressure increases, the brittleness of shale gradually decreases, indicating that the method provided in the embodiments of this application can accurately predict the impact of confining pressure on the brittleness of reservoir rocks.

[0103] Table 1 Elastic physical parameters and brittleness values ​​of shale under different confining pressures

[0104] Case 2: The relationship between reservoir rock brittleness assessment and fracturing energy per unit reservoir stimulation volume in fracturing well sections in different regions.

[0105] In this case, core samples from different well sections of unconventional oil and gas reservoirs (tight gas and shale gas) were collected and processed into cylinders with a diameter of 25 mm and a height of 50 mm. Triaxial compression tests were conducted on these core samples under corresponding reservoir confining conditions without confining pressure, obtaining stress-strain curves for different reservoir rocks. The brittleness index of different reservoir rocks was then calculated using the method provided in this application, as shown in Figure 7. A typical hydraulic fracturing curve is shown in Figure 8, which displays real-time data of injection pressure and displacement during fracturing, further illustrating the relationship between injection pressure and displacement over time. Multiplying the injection pressure by the displacement yields the fracturing power curve shown in Figure 9, where the fracturing power is determined by the injection pressure and displacement. The total fracturing energy of the fracturing section is obtained by numerically integrating the fracturing power curve over the entire fracturing operation time. The total fracturing energy and total stimulated volume for different well sections in this case are detailed in Table 2. Dividing the total fracturing energy by the corresponding reservoir stimulated volume (SRV) of the well section yields the fracturing energy required per SRV. Figure 10 shows the relationship between the brittleness index (BI) of reservoir rocks in different well sections and the fracturing energy required per unit SRV. Figure 10 illustrates that the higher the brittleness index, the more brittle the reservoir rock, and the more brittle the reservoir rock, the easier it is to fracturize, and the less energy is required to stimulate a unit SRV. Figure 10 also demonstrates the engineering applicability and high accuracy of the reservoir rock brittleness evaluation method provided in the embodiments of this application.

[0106] Table 2 Total fracturing energy and total stimulation volume for different fracturing well sections

[0107] Therefore, in this embodiment of the application, the engineering applicability of the brittleness evaluation method proposed in this embodiment of the application is verified based on real field construction data.

[0108] In this embodiment of the application, it is recommended to use 3 to 5 rock cores when conducting rock mechanics tests.

[0109] Furthermore, in this application, the fracturing energy required for the stimulation unit SRV can be determined based on the total pre-peak energy of the target unconventional oil and gas reservoir, the total fracturing energy of the fracturing reservoir stimulation volume of the corresponding well section of the target unconventional oil and gas reservoir can be further determined, and engineering recommendations on injection pressure and displacement can be further output.

[0110] Based on the same inventive concept, this application also provides an unconventional oil and gas reservoir brittleness evaluation device, which includes:

[0111] The acquisition module is used to acquire stress-strain data of core samples from unconventional oil and gas reservoirs obtained in uniaxial or triaxial compression tests.

[0112] The first determining module is used to determine the peak strain of the target unconventional oil and gas reservoir core sample under uniaxial compression or triaxial compression based on the stress-strain data.

[0113] The second determining module is used to determine the total pre-peak energy of the core sample of the target unconventional oil and gas reservoir based on the peak strain.

[0114] The third determining module is used to determine the rock brittleness value of the target unconventional oil and gas reservoir based on the peak strain and the total energy before the peak.

[0115] Optionally, the acquisition module is specifically used to: acquire stress-strain data of core samples from multiple fracturing sections of the target unconventional oil and gas reservoir obtained in uniaxial or triaxial compression tests;

[0116] The third determining module is specifically used to: obtain the rock brittleness value of each of the multiple fracturing sections based on the stress-strain data of the core samples of the multiple fracturing sections;

[0117] The device further includes:

[0118] The comparison module is used to compare the rock brittleness values ​​of multiple fracturing sections and determine the fracturing section with the highest rock brittleness value as the target fracturing section.

[0119] The output module is used to output engineering sweet spot selection suggestions for the target unconventional oil and gas reservoir based on the target fracturing section.

[0120] Optionally, the acquisition module is specifically used to: acquire stress-strain data obtained from uniaxial or triaxial compression tests of core samples of the target unconventional oil and gas reservoir under different environmental conditions, wherein the environmental conditions include: confining pressure conditions, temperature conditions and / or fluid conditions;

[0121] The third determining module is specifically used to: determine the rock brittleness value of the target unconventional oil and gas reservoir under various environmental conditions based on the stress-strain data obtained under various environmental conditions.

[0122] The device further includes:

[0123] The analysis module is used to obtain the brittleness evolution law of the target unconventional oil and gas reservoir as environmental conditions change, based on the rock brittleness value of the target unconventional oil and gas reservoir under various environmental conditions.

[0124] The output module is used to output engineering sweet spot selection suggestions for the target unconventional oil and gas reservoir based on the brittleness evolution law.

[0125] Optionally, the second determining module is specifically used for:

[0126] From initial strain 0 to peak strain ε p Integrating the stress-strain curves within the range yields the total peak energy U of the rock sample. p :

[0127] Optionally, the third determining module is specifically used for:

[0128] The brittleness value of rock is determined based on the following formula:

[0129] Wherein, BI represents the rock brittleness value.

[0130] Optionally, the stress-strain data is determined using the following steps:

[0131] Drill and core samples are taken from the target unconventional oil and gas reservoir, and the core samples are processed into cylindrical test samples.

[0132] Uniaxial or triaxial compression tests were conducted on the cylindrical test sample to obtain stress-strain data of the target unconventional oil and gas reservoir core sample in the uniaxial or triaxial compression test.

[0133] During the uniaxial or triaxial compression test, the stress loading rate is less than 0.05 mm / min.

[0134] Based on the same inventive concept, embodiments of this application also provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the steps in the unconventional oil and gas reservoir brittleness evaluation method as described in any of the above embodiments.

[0135] Based on the same inventive concept, embodiments of this application also provide a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps in the unconventional oil and gas reservoir brittleness evaluation method described in any of the above embodiments.

[0136] Based on the same inventive concept, this application provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps in the unconventional oil and gas reservoir brittleness evaluation method described in any of the above embodiments.

[0137] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0138] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0139] The various component embodiments of this application can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some or all of the components in the computing processing device according to the embodiments of this application. This application can also be implemented as a device or apparatus program (e.g., a computer program and computer program product) for performing part or all of the methods described herein. Such an implementation of this application can be stored on a computer-readable medium, or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0140] For example, Figure 11 illustrates a computing processing device that can implement the methods according to this application. This computing processing device conventionally includes a processor 1010 and a computer program product or computer-readable medium in the form of a memory 1020. The memory 1020 can be an electronic memory such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM. The memory 1020 has a storage space 1030 for program code 1031 for performing any of the method steps described above. For example, the storage space 1030 for the program code may include various program codes 1031 for implementing the various steps in the methods described above. These program codes can be read from or written to one or more computer program products. These computer program products include program code carriers such as hard disks, compact discs (CDs), memory cards, or floppy disks. Such computer program products are typically portable or fixed storage units as described with reference to Figure 12. This storage unit may have storage segments, storage spaces, etc., arranged similarly to the memory 1020 in the computing processing device of Figure 11. The program code may be compressed, for example, in a suitable form. Typically, the storage unit includes computer-readable code 1031', which is code that can be read by a processor such as 1010, which, when run by a computing processing device, causes the computing processing device to perform the various steps in the method described above.

[0141] The terms "an embodiment," "embodiment," or "one or more embodiments" as used herein mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of this application. Furthermore, please note that the examples of the phrase "in one embodiment" do not necessarily all refer to the same embodiment.

[0142] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0143] In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for evaluating the brittleness of unconventional oil and gas reservoirs, characterized in that, The method includes: Obtain stress-strain data from core samples of the target unconventional oil and gas reservoir in uniaxial or triaxial compression tests; Determine the peak strain of the target unconventional oil and gas reservoir core sample under uniaxial or triaxial compression based on the stress-strain data. The total energy before the peak of the core sample from the target unconventional oil and gas reservoir is determined based on the peak strain. The rock brittleness value of the target unconventional oil and gas reservoir is determined based on the peak strain and the total energy before the peak.

2. The method for evaluating the brittleness of unconventional oil and gas reservoirs according to claim 1, characterized in that, Obtain stress-strain data from core samples of the target unconventional oil and gas reservoir during uniaxial or triaxial compression tests, including: Obtain stress-strain data from core samples of multiple fracturing sections of the target unconventional oil and gas reservoir in uniaxial or triaxial compression tests; Based on the stress-strain data, the rock brittleness value of the target unconventional oil and gas reservoir is determined, including: Based on the stress-strain data of core samples from multiple fracturing sections, the rock brittleness values ​​of each fracturing section were obtained. The method further includes: The rock brittleness values ​​of multiple fracturing sections are compared, and the fracturing section with the highest rock brittleness value is determined as the target fracturing section. Based on the target fracturing section, an engineering sweet spot selection recommendation for the target unconventional oil and gas reservoir is output.

3. The method for evaluating the brittleness of unconventional oil and gas reservoirs according to claim 1, characterized in that, Obtain stress-strain data from core samples of the target unconventional oil and gas reservoir during uniaxial or triaxial compression tests, including: The stress-strain data of core samples from unconventional oil and gas reservoirs are obtained from uniaxial or triaxial compression tests under different environmental conditions, including confining pressure, temperature and / or fluid conditions. Based on the stress-strain data, the rock brittleness value of the target unconventional oil and gas reservoir is determined, including: Based on the stress-strain data obtained under various environmental conditions, the rock brittleness value of the target unconventional oil and gas reservoir under various environmental conditions is determined. The method further includes: Based on the rock brittleness values ​​of the target unconventional oil and gas reservoir under various environmental conditions, the brittleness evolution law of the target unconventional oil and gas reservoir as environmental conditions change is obtained. Based on the aforementioned brittleness evolution law, recommendations for selecting engineering sweet spots for the target unconventional oil and gas reservoir are provided.

4. The method for evaluating the brittleness of unconventional oil and gas reservoirs according to claim 1, characterized in that, The total pre-peak energy of the core sample from the target unconventional oil and gas reservoir is determined based on the peak strain, including: From initial strain 0 to peak strain ε p Integrating the stress-strain curves within the range yields the total peak energy U of the rock sample. p :

5. The method for evaluating the brittleness of unconventional oil and gas reservoirs according to claim 4, characterized in that, Determining the rock brittleness value based on the peak strain and the total energy before the peak includes: determining the rock brittleness value based on the following formula: Wherein, BI represents the rock brittleness value.

6. The method for evaluating the brittleness of unconventional oil and gas reservoirs according to any one of claims 1-5, characterized in that, The stress-strain data were determined using the following steps: Drill and core samples are taken from the target unconventional oil and gas reservoir, and the core samples are processed into cylindrical test samples. Uniaxial or triaxial compression tests were conducted on the cylindrical test sample to obtain stress-strain data of the target unconventional oil and gas reservoir core sample in the uniaxial or triaxial compression test. During the uniaxial or triaxial compression test, the stress loading rate is less than 0.05 mm / min.

7. A device for evaluating the brittleness of unconventional oil and gas reservoirs, characterized in that, The unconventional oil and gas reservoir brittleness evaluation device includes: The acquisition module is used to acquire stress-strain data of core samples from unconventional oil and gas reservoirs obtained in uniaxial or triaxial compression tests. The first determining module is used to determine the peak strain of the target unconventional oil and gas reservoir core sample under uniaxial compression or triaxial compression based on the stress-strain data. The second determining module is used to determine the total pre-peak energy of the core sample of the target unconventional oil and gas reservoir based on the peak strain. The third determining module is used to determine the rock brittleness value of the target unconventional oil and gas reservoir based on the peak strain and the total energy before the peak.

8. An electronic 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, it implements the unconventional oil and gas reservoir brittleness evaluation method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the method for evaluating the brittleness of unconventional oil and gas reservoirs as described in any one of claims 1 to 6.

10. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps in the unconventional oil and gas reservoir brittleness evaluation method according to any one of claims 1 to 6.

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