Shale oil reservoir brittleness evaluation method and equipment based on mineral dispersibility and storage medium

Abstract

The invention discloses a shale oil reservoir brittleness evaluation method and equipment based on mineral dispersibility and a storage medium, and the method comprises the steps: coring an evaluation reservoir section of a target well, and obtaining the percentage content of core minerals and rock mechanical parameters; calculating the hidden modulus of brittle minerals by using a coring test result, calculating the mass of rock core brittle minerals and clay mineral isolate, and calculating the distribution complexity of the rock sample by combining the mass of each mineral isolate; unseparated substances of the rock core are explained as the mass of main substances, and the surface brittleness index is calculated according to the mass of each mineral main substance of the rock core; and through the distribution complexity and the surface brittleness index, a rock comprehensive brittleness factor is obtained, and reservoir brittleness quantitative evaluation is carried out. According to the method, the influence degree of the main body minerals and the dispersed minerals influencing the rock brittleness on the brittleness is quantitatively represented for the first time, and the shale oil reservoir brittleness of any block can be quantitatively evaluated only by acquiring underground actual rock core basic data.

Description

Technical Field

[0001] This invention relates to the field of oil and gas engineering, and in particular to a method, equipment and storage medium for evaluating the brittleness of shale oil reservoirs based on mineral dispersion during the exploration and development process. Background Technology

[0002] Rock brittleness is a key rock mechanics parameter for evaluating reservoir compressibility and whether volumetric fracturing can form complex fracture networks. It plays a crucial role in the study of tight reservoir geological characteristics, fracture propagation patterns, and optimization of reservoir stimulation perforation schemes. Currently, various oilfields are conducting extensive downhole coring to study reservoir characteristics and geomechanical features, providing a basis for optimizing volumetric fracturing technology.

[0003] Through research, the following methods are mainly used to evaluate the brittleness and compressibility of unconventional tight reservoir rocks: (1) Zhou Lihong (Evaluation and application of factors affecting the compressibility of continental shale oil rocks - taking Kong 2 section of Cangdong Depression as an example [J]. China Petroleum Exploration, 2019, 24(5):670-678) By comprehensively considering the three factors of rock brittleness, natural fractures and geostress, a fracture network index model was established to conduct qualitative analysis and quantitative characterization of the compressibility of typical continental shale oil rocks developed in Kong 2 section of Cangdong Depression in Dagang exploration area, and further optimize the perforation parameters of horizontal wells and the fracturing construction parameters. (2) Zhao Zhihong (Patent No.: CN201910757761.4) proposed a shale brittleness evaluation method based on mechanical heterogeneity. This method determines the mineral component deviation coefficient according to the mineral composition of shale; determines the dynamic Young's modulus and dynamic Poisson's ratio of various minerals; and determines the estimated Young's modulus and estimated Poisson's ratio of the reservoir using the component model based on the dynamic Young's modulus and dynamic Poisson's ratio of various minerals. Through linear fitting, the corresponding fitted Young's modulus and fitted Poisson's ratio are obtained, and the brittleness coefficient is calculated. (3) Yi Qinfan (Patent No.: CN202210135674.7) proposed a continental shale oil reservoir brittleness evaluation method. This method mainly involves collecting rock samples from the target layer, conducting core mineral composition and composition tests and mineral crystal morphology analysis, and further defining a brittleness index to quantitatively evaluate the brittleness of shale oil reservoirs by comprehensively considering factors such as mineral content, crystal form and occurrence.

[0004] The above survey shows that current research methods focus on evaluating rock brittleness based on single factors such as rock mechanical parameters or mineral composition. However, the brittleness of shale oil reservoirs is determined by both rock mechanical parameters and mineral composition, particularly the degree of dispersion among different minerals. Therefore, this invention patent proposes a novel approach to quantitatively evaluate rock brittleness from the perspective of considering mineral dispersion, thereby providing a basis for shale oil reservoir characteristic research and reservoir stimulation optimization. Summary of the Invention

[0005] To address the shortcomings of current technologies, this invention proposes a method for evaluating the brittleness of shale oil reservoirs based on mineral dispersion. This method overcomes the deficiencies of existing technologies and achieves quantitative evaluation of rock brittleness from a novel perspective that considers the degree of mineral dispersion.

[0006] This invention proposes a novel method for quantitatively evaluating rock brittleness from the perspective of considering the degree of mineral dispersion. The specific steps of this method include:

[0007] Step S01: Core the target well's evaluation reservoir section to obtain the core mineral percentage and rock mechanical parameters;

[0008] Step S02: Calculate the hidden modulus of brittle minerals using the test results in step S01, calculate the mass of the brittle mineral and clay mineral separations from the core, and calculate the distribution complexity of the rock sample by combining the masses of each mineral separation.

[0009] The unseparated material in the core is interpreted as the main mass, and the surface brittleness index is calculated from the main mass of each mineral in the core.

[0010] Step S03: Obtain the comprehensive brittleness factor of the rock by using the distribution complexity and surface brittleness index, and conduct a quantitative evaluation of reservoir brittleness.

[0011] Specifically, in step S01, the percentage content of minerals in the core is obtained by X-ray diffraction.

[0012] Specifically, in step S01, the Young's modulus of the rock core is obtained through a triaxial mechanical testing system.

[0013] Specifically, the method for determining the hidden modulus of brittle minerals in step S02 is as follows:

[0014]

[0015] In the formula: E c E represents the hidden modulus of brittle minerals, in MPa; z To test Young's modulus, MPa; m n E represents the percentage content of clay minerals, %; n is the Young's modulus of clay minerals, in MPa.

[0016] Specifically, the method for calculating the mass of the brittle mineral and clay mineral separations from the core in step S02 is as follows:

[0017]

[0018] G i =m i -C i (i∈[1,n-1]) (3)

[0019]

[0020] G n =m n -C n (5)

[0021] Where: m i There are n kinds of minerals, each with a different percentage content; E mi The value represents the Young's modulus of a single mineral, in MPa; C i For the mass of each brittle mineral isolate, %; C n The mass of the clay mineral separation is expressed as %; G i For the main components of each brittle mineral, %; G n The percentage represents the bulk mass of clay minerals.

[0022] Specifically, the method for calculating the complexity of rock sample distribution in step S02 is as follows:

[0023]

[0024] In the formula: B c The complexity of rock sample distribution is dimensionless; |E mi -E c | min This corresponds to the theoretical minimum value of the formula; This corresponds to the theoretical maximum value of the formula.

[0025] Specifically, the method for calculating the surface brittleness index in step S02 is as follows:

[0026]

[0027] In the formula: B g It is the surface brittleness index, dimensionless.

[0028] Specifically, the method for calculating the comprehensive brittleness factor of rock in step S03 is as follows:

[0029] B v =B c B g (8)

[0030] In the formula: B v It is the overall brittleness factor of rocks and has no dimension.

[0031] Specifically, in step S03, when the comprehensive brittleness factor of the rock is 0... V When the overall brittleness factor is less than or equal to 0.40, it is considered a poorly brittle reservoir; when the overall brittleness factor is less than or equal to 0.40... V When the overall rock brittleness factor is less than or equal to 0.70, it is considered a moderately brittle reservoir; when the overall rock brittleness factor is 0.70... V When the value is less than or equal to 1.0, it is a highly brittle reservoir. ​​​

[0032] The present invention also provides an electronic device, including a memory, a processor, and a program stored in the memory and running on the processor, characterized in that the processor executes the program to implement the steps of the above-described method for evaluating the brittleness of shale oil reservoirs based on mineral dispersion.

[0033] The present invention also provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores instructions that, when the instructions are executed on a terminal device, cause the terminal device to perform the steps of the above-described method for evaluating the brittleness of shale oil reservoirs based on mineral dispersion.

[0034] The beneficial effects of this invention include at least the following: This invention is the first to quantitatively characterize the influence of the main minerals and dispersed minerals on rock brittleness. The degree of separation between minerals is evaluated by the complexity of the dispersed minerals, and the influence of brittle minerals on rock brittleness is evaluated by the brittleness index of the main mineral surface. Only the actual downhole core data is needed to quantitatively evaluate the brittleness of any block of shale oil reservoir. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0036] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0038] like Figure 1As shown, this invention provides a method for evaluating the brittleness of shale oil reservoirs based on mineral dispersion. First, core samples are taken from the target well's evaluation reservoir section to obtain its mineral percentages and rock mechanical parameters. Second, the hidden modulus of brittle minerals is calculated using the individual mineral mechanical parameters and their percentages, combined with the rock mechanical parameters measured from the core. This is used to calculate the mass of brittle mineral and clay mineral separations from the core. The distribution complexity of the rock sample is then calculated from the combined mass of each mineral separation, thus evaluating the degree of mineral dispersion in the reservoir. Based on this, the unseparated material from the core is interpreted as the main mass, and the surface brittleness index is calculated from the main mass of each mineral in the core, thereby evaluating the macroscopic brittleness of the reservoir. Finally, combining the distribution complexity of the core and the surface brittleness index, a new comprehensive rock brittleness factor is quantified. The higher the value, the better the rock brittleness, thus achieving the purpose of quantitative evaluation.

[0039] To achieve the above technical objectives, the present invention provides the following technical solution, which includes the following steps in sequence:

[0040] Step S01: Core the target well's evaluation reservoir section to obtain the core mineral percentage and rock mechanical parameters;

[0041] Preferably, step S01 is as follows:

[0042] (S011) Preparation of shale oil reservoir cores: Core samples were taken from the target shale oil reservoir to prepare standard rock samples with a diameter of 2.5 cm and a length of 5 cm. The standard rock samples were then dried in an oven at 100°C until constant weight.

[0043] (S012) Measurement of mineral percentage content: The percentage content of each mineral is obtained by processing the rock sample using an X-ray diffractometer;

[0044] (S013) Test rock mechanical parameters: Measure the Young's modulus of the rock core using a triaxial mechanical testing system;

[0045] Step S02: Calculate the hidden modulus of brittle minerals using the test results in step S01, calculate the mass of the brittle mineral and clay mineral separations from the core, and calculate the distribution complexity of the rock sample by combining the masses of each mineral separation.

[0046] The unseparated material in the core is interpreted as the main mass, and the surface brittleness index is calculated from the main mass of each mineral in the core.

[0047] Preferably, step S02 is as follows:

[0048] (S021) Calculate the hidden modulus of brittle minerals: After removing the influence of clay minerals, the modulus is obtained by combining the Young's modulus measured from the core and the percentage content of minerals. The calculation formula is as follows:

[0049]

[0050] In the formula: E z To test Young's modulus, MPa; m n E represents the percentage content of clay minerals, %; n E represents the Young's modulus of clay minerals, in MPa; c is the hidden modulus of brittle minerals, in MPa.

[0051] (S022) Calculate the mass of the separated brittle minerals and clay minerals: It is obtained by the numerical difference between the Young's modulus of a single mineral and the hidden modulus of a brittle mineral, and the calculation formula is as follows:

[0052]

[0053] G i =m i -C i (i∈[1,n-1]) (3)

[0054]

[0055] G n =m n -C n (5)

[0056] Where: m i There are n kinds of minerals, each with a different percentage content; E mi The value represents the Young's modulus of a single mineral, in MPa; C i For the mass of each brittle mineral isolate, %; C n The mass of the clay mineral separation is expressed as %; G i For the main components of each brittle mineral, %; G n The percentage represents the bulk mass of clay minerals.

[0057] (S023) Calculate the distribution complexity of rock samples: The main complexity in rock samples comes from the distribution state of dispersed minerals. The calculation formula is as follows:

[0058]

[0059] In the formula: B c The complexity of rock sample distribution is dimensionless; |E mi -E c | min Therefore, the theoretical minimum value of this formula is... This formula has a theoretical maximum value. The theoretical maximum value is the percentage of minerals (excluding clay minerals) whose Young's modulus differs the most from the latent modulus of brittle minerals. For example, in a rock sample, the difference between the latent modulus of quartz and the latent modulus of brittle minerals is |E mi -E cThe maximum value is 40% clay mineral content, so the theoretical maximum value is obtained when the quartz content is 60%.

[0060] (S024) Calculate the surface brittleness index: The magnitude of the surface brittleness index depends on the combination pattern between the mass of the main material. The calculation formula is as follows:

[0061]

[0062] In the formula: B g It is the surface brittleness index, dimensionless.

[0063] Step S03: Obtain the comprehensive brittleness factor of the rock by using the distribution complexity and surface brittleness index, and conduct a quantitative evaluation of reservoir brittleness.

[0064] Combining the complexity of rock sample distribution and the surface brittleness index, the comprehensive brittleness factor of the rock is calculated from the perspective of mineral separation state. The larger the value, the stronger the brittleness of the reservoir rock. The calculation method is as follows:

[0065] B v =B c B g (8)

[0066] In the formula: B v It is the overall brittleness factor of rocks and has no dimension.

[0067] Preferably, based on the summary of practical results, it can be divided into the following three levels: when the comprehensive brittleness factor of the rock is 0... V When the overall brittleness factor is less than or equal to 0.40, it is considered a poorly brittle reservoir; when the overall brittleness factor is less than or equal to 0.40... V When the overall rock brittleness factor is less than or equal to 0.70, it is considered a moderately brittle reservoir; when the overall rock brittleness factor is 0.70... V When the value is less than or equal to 1.0, it is a highly brittle reservoir.

[0068] Application Examples

[0069] This example provides a method for evaluating the brittleness of shale oil reservoirs based on mineral dispersion, as detailed below:

[0070] Step S01: Core sampling is performed on the target well's evaluation reservoir section to obtain its mineral percentage and rock mechanical parameters. Specific details are as follows:

[0071] (S011) Preparation of shale oil reservoir cores: In this embodiment, rock samples from wells HY-1, HY-4 and HY-7 in the shale oil reservoir block were selected and prepared into standard columnar cores, numbered K1, K2 and K3.

[0072] ​​​(S012) Measurement of mineral percentage: The percentage of each mineral was obtained by processing the rock sample with an X-ray diffractometer. The results are shown in Table 1.

[0073] (S013) Testing rock mechanical parameters: The Young's modulus of the rock core was measured using a triaxial mechanical testing system, and the results are shown in Table 1.

[0074] Table 1. Mineral composition and Young's modulus

[0075]

[0076] Step S02 specifically includes:

[0077] (S021) Calculate the hidden modulus of brittle minerals: The calculation is performed using formula (1), where the Young's modulus of clay minerals is 21914 MPa. The calculation results of each core are shown in Table 2.

[0078] Table 2. Hidden Modulus of Brittle Minerals

[0079]

[0080] (S022) Calculate the mass of the brittle mineral and clay mineral separation: In this example, there are mainly 5 kinds of minerals, so the value of n is 5. Among them, the Young's modulus of the single minerals is 64839 MPa for feldspar, 105309 MPa for dolomite, 95943 MPa for quartz, 78011 MPa for calcite, and 21914 MPa for clay minerals. The calculation is performed using formulas (2)-(5), and the results are shown in Table 3.

[0081] Table 3. Mass of Mineral Separates and Mass of Main Substances

[0082]

[0083] (S023) Calculate the distribution complexity of rock samples: Calculate using formula (6) constructed based on the relationship between the separated samples, where |E mi -E c | min The theoretical minimum value is 0. For core K1, |E mi -E c | max For feldspar, for core K2, |E mi -E c | max For dolomite, for core K3, |E mi -E c | max Feldspar The theoretical maximum values ​​are shown in Table 4. The rock sample distribution complexity was calculated from these values, as shown in Table 4.

[0084] Table 4. Complexity of Rock Sample Distribution

[0085]

[0086] (S024) Calculate the surface brittleness index: The index is calculated based on the mass of the main material. The result can be obtained using formula (7), as shown in Table 5.

[0087] Table 5. Surface Brittleness Index of Rock Samples

[0088] Core number Rock sample distribution complexity Surface brittleness index K1 0.49 1.24 K2 0.42 1.28 K3 0.63 1.22

[0089] Step S03: Combining the distribution complexity of the core and the surface brittleness index, calculate the comprehensive brittleness factor of the rock to achieve quantitative evaluation. The specific content is as follows:

[0090] Combining the complexity of rock sample distribution and the surface brittleness index, the comprehensive brittleness factors of rock samples K1 to K3 were calculated using formula (8) to obtain values ​​of 0.61, 0.54, and 0.77, respectively. Therefore, the brittleness strength ranking is K3 > K1 > K2. According to the grade classification results in step 3), rock samples K1 and K2 correspond to medium-brittle reservoirs, while rock sample K3 corresponds to a strongly brittle reservoir.

[0091] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for evaluating the brittleness of shale oil reservoirs based on mineral dispersion, characterized in that, Includes the following steps: step S01: Core samples are taken from the reservoir section of the target well to obtain the percentage of mineral content and rock mechanical parameters. Step S02: Calculate the hidden modulus of brittle minerals using the test results in step S01, calculate the mass of the brittle mineral and clay mineral separations from the core, and calculate the distribution complexity of the rock sample by combining the masses of each mineral separation. The unseparated material in the core is interpreted as the main mass, and the surface brittleness index is calculated from the main mass of each mineral in the core. Step S03: Obtain the comprehensive brittleness factor of the rock by using the distribution complexity and surface brittleness index, and conduct a quantitative evaluation of reservoir brittleness.

2. In the brittleness evaluation method of shale oil reservoir based on mineral dispersion according to claim 1, the percentage content of core minerals is obtained by X-ray diffraction in step S01.

3. In the brittleness evaluation method of shale oil reservoir based on mineral dispersion according to claim 1, the Young's modulus of the core is obtained by a triaxial mechanical testing system in step S01.

4. The brittleness evaluation method for shale oil reservoirs based on mineral dispersion according to claim 1, wherein the method for determining the hidden modulus of brittle minerals in step S02 is as follows: In the formula: E c E represents the hidden modulus of brittle minerals, in MPa; z To test Young's modulus, MPa; m n E represents the percentage content of clay minerals, %; n is the Young's modulus of clay minerals, in MPa.

5. The brittleness evaluation method for shale oil reservoirs based on mineral dispersion according to claim 1, wherein the method for calculating the complexity of rock sample distribution in step S02 is as follows: In the formula: B c The complexity of rock sample distribution is dimensionless; |E mi -E c | min This corresponds to the theoretical minimum value of the formula; This corresponds to the theoretical maximum value of the formula.

6. The brittleness evaluation method for shale oil reservoirs based on mineral dispersion according to claim 1, wherein the surface brittleness index calculation method in step S02 is as follows: In the formula: B g It is the surface brittleness index, dimensionless.

7. The method for evaluating the brittleness of shale oil reservoirs based on mineral dispersion according to claim 1, wherein the method for calculating the comprehensive brittleness factor of the rock in step S03 is as follows: B v =B c B g (8) In the formula: B v It is the overall brittleness factor of rocks and has no dimension.

8. The brittleness evaluation method for shale oil reservoirs based on mineral dispersion according to claim 1, wherein in step S03, when the comprehensive brittleness factor of the rock is 0... V When the overall brittleness factor is less than or equal to 0.40, it is considered a poorly brittle reservoir; when the overall brittleness factor is 0.40... V When the overall rock brittleness factor is less than or equal to 0.70, it is considered a moderately brittle reservoir; when the overall rock brittleness factor is 0.70... V When the value is less than or equal to 1.0, it is a highly brittle reservoir.​​​ 9. An electronic device comprising a memory, a processor, and a program stored in the memory and running on the processor, characterized in that, When the processor executes the program, it implements the steps of the shale oil reservoir brittleness evaluation method based on mineral dispersion as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed on a terminal device, cause the terminal device to perform the steps of the shale oil reservoir brittleness evaluation method based on mineral dispersion as described in any one of claims 1-8.

Images