Sea area natural gas hydrate reservoir fracturing performance evaluation method and device, electronic equipment and storage medium

Abstract

The invention discloses a sea area natural gas hydrate reservoir fracturing performance evaluation method and device, electronic equipment and a storage medium. The method comprises the following steps: selecting evaluation indexes influencing the hydrate reservoir fracturing effect, and carrying out index hierarchy division on the evaluation indexes; respectively adopting an analytic hierarchy process and an entropy weight method to determine a weight corresponding to each evaluation index, carrying out comprehensive weighting, and determining a target weight of each evaluation index; and according to the target weight of each evaluation index, constructing a fracturing index of the hydrate reservoir, and performing fracturing evaluation on the hydrate reservoir by adopting the fracturing index. By adopting the technical scheme of the embodiment of the invention, the influence of geological factors and engineering factors on the fracturing effect of the hydrate reservoir is comprehensively considered, the fracturing performance evaluation accuracy is improved, and the fracturing performance evaluation of the hydrate reservoir is more comprehensive.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas hydrate reservoir hydraulic fracturing stimulation, and particularly relates to a method and device for evaluating the fracturability of a marine natural gas hydrate reservoir, an electronic device and a storage medium. BACKGROUND

[0002] Natural gas hydrate (hereinafter referred to as hydrate) has the characteristics of large resource quantity, high energy density and clean combustion, and is considered to be an ideal alternative energy source in the 21st century. More than 90% of hydrates are stored in shallow seabed unconsolidated sediments, among which, the resource quantity of argillaceous hydrates is the most abundant, accounting for more than 90%, but the saturation and permeability of such hydrates are relatively lower, and the exploitation is more difficult. At present, the gas production of global marine hydrate test production is continuously improved, but due to the poor permeability of the reservoir, the single well production is low, and it still does not reach the threshold requirement of commercial production gas production, and effective reservoir stimulation is needed to greatly improve the hydrate gas production. Hydraulic fracturing is a key core technology for the successful development of low permeability gas reservoirs such as shale gas, and hydraulic fracturing is expected to be used for hydrate reservoir stimulation.

[0003] Fracturability evaluation is a necessary link before the implementation of hydraulic fracturing stimulation, which is used to evaluate whether the reservoir can be effectively fractured to realize stimulation. The existing fracturability evaluation method is mainly aimed at the reservoir characteristics of different types of oil and gas reservoirs such as shale, tight sandstone, sandstone, shale oil, etc., selects the geological factors affecting the fracturing effect such as rock brittleness, fracture toughness, natural weak plane (fracture development, etc.), stress environment, diagenesis and barrier shielding effect as evaluation indexes, takes the formation brittleness as the core index, determines the weight of each evaluation index by the analytic hierarchy process method, and establishes a fracturability evaluation model. The diagenetic formation can be fractured to form a hydraulic fracture, which is defaulted, and the fracturability evaluation focuses on the difficulty of forming a complex fracture network. Therefore, the existing fracturability evaluation still mainly focuses on the properties of the formation itself, and the main difference between various fracturability evaluation methods is the selection of evaluation indexes or different calculation methods of the same evaluation index. The hydrate reservoir is an unconsolidated formation, which is essentially different from the conventional diagenetic reservoir, and the existing fracturability evaluation method is not applicable.

[0004] Therefore, how to evaluate the fracturability of the marine natural gas hydrate reservoir is a problem to be solved in the field. SUMMARY

[0005] The present application provides a method and device for evaluating the fracturability of a marine natural gas hydrate reservoir, an electronic device and a storage medium, to solve the problem that the existing hydrate fracturability evaluation method cannot be applied to the fracturability evaluation of the marine natural gas hydrate reservoir.

[0006] According to an aspect of the present application, a method for evaluating the fracturability of a marine gas hydrate reservoir is provided, the method comprising:

[0007] An evaluation index affecting the fracturing effect of the hydrate reservoir is selected, and the evaluation index is divided into index levels;

[0008] Analytic hierarchy process and entropy weight method are used to determine the weight of each evaluation index and to comprehensively assign the weight, so as to determine the target weight of each evaluation index;

[0009] A hydrate reservoir fracturability index is constructed according to the target weight of each evaluation index, and the hydrate reservoir fracturability is evaluated by using the hydrate reservoir fracturability index.

[0010] According to another aspect of the present application, a device for evaluating the fracturability of a marine gas hydrate reservoir is provided, the device comprising:

[0011] An evaluation index level division module is configured to select an evaluation index affecting the fracturing effect of the hydrate reservoir, and to divide the evaluation index into index levels;

[0012] A comprehensive weight assignment module is configured to use analytic hierarchy process and entropy weight method to determine the weight of each evaluation index and to comprehensively assign the weight, so as to determine the target weight of each evaluation index;

[0013] A fracturability evaluation module is configured to construct a hydrate reservoir fracturability index according to the target weight of each evaluation index, and to evaluate the hydrate reservoir fracturability by using the hydrate reservoir fracturability index.

[0014] According to another aspect of the present application, an electronic device is provided, the electronic device comprising:

[0015] At least one processor; and

[0016] A memory connected in communication with the at least one processor; wherein,

[0017] The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor to enable the at least one processor to execute the method for evaluating the fracturability of a marine gas hydrate reservoir according to any one of the embodiments of the present application.

[0018] According to another aspect of the present application, a computer readable storage medium is provided, the computer readable storage medium stores computer instructions for enabling a processor to implement the method for evaluating the fracturability of a marine gas hydrate reservoir according to any one of the embodiments of the present application.

[0019] According to another aspect of the present application, there is provided a computer program product comprising a computer program which, when executed by a processor, implements a method for evaluating the fracturability of a marine gas hydrate reservoir as described in any embodiment of the present application.

[0020] The technical solution of the embodiment of the present application selects evaluation indexes affecting the fracturing effect of the hydrate reservoir, and divides the evaluation indexes into index levels; the analytic hierarchy process and the entropy weight method are respectively used to determine the weight corresponding to each evaluation index and to comprehensively assign the weight, to determine the target weight of each evaluation index; a hydrate reservoir fracturability index is constructed according to the target weight of each evaluation index, and the hydrate reservoir fracturability is evaluated by using the hydrate reservoir fracturability index. The technical solution of the embodiment of the present application solves the problem that the existing hydrate fracturability evaluation method only focuses on the properties of the formation itself and does not comprehensively consider various fracturing influencing factors for evaluating the fracturability of the marine gas hydrate reservoir; by comprehensively considering the influence of geological factors and engineering factors on the fracturing effect of the hydrate reservoir, the accuracy of the fracturability evaluation is improved, and the fracturability evaluation of the hydrate reservoir is more comprehensive.

[0021] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0023] Figure 1 is a flowchart of a marine gas hydrate reservoir fracturability evaluation method according to the first embodiment of the present application;

[0024] Figure 2 is a fracturability evaluation index system schematic diagram according to the first embodiment of the present application;

[0025] Figure 3 is a flowchart of a marine gas hydrate reservoir fracturability evaluation method according to the second embodiment of the present application;

[0026] Figure 4 is a flowchart of a fracturability evaluation method according to the second embodiment of the present application;

[0027] Figure 5It is a fracturing evaluation result schematic diagram provided according to the second embodiment of the present application;

[0028] Figure 6 It is a sample fracturing result schematic diagram of a physical model experiment provided according to the second embodiment of the present application;

[0029] Figure 7 It is a structure schematic diagram of a marine gas hydrate reservoir fracturing evaluation device provided according to the third embodiment of the present application;

[0030] Figure 8 It is a structure schematic diagram of an electronic device provided according to the fourth embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by the person of ordinary skill in the art without creative labor should belong to the scope of protection of the present application.

[0032] In the technical solutions of the present application, the acquisition, storage, use and processing of data all conform to the relevant provisions of laws and regulations. It should be noted that the terms "first", "second", "target", "original" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include", "equal" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0033] Embodiment one

[0034] Figure 1A flowchart of a method for evaluating the fracturability of a marine gas hydrate reservoir is provided for the first embodiment of the present application. The first embodiment can be applied to the case where the weights of each evaluation index are determined based on the analytic hierarchy process and the entropy weight method, and the weights are comprehensively assigned to construct a hydrate reservoir fracturability index, and the fracturability of the marine gas hydrate reservoir is evaluated using the fracturability index. The method can be executed by a marine gas hydrate reservoir fracturability evaluation device, which can be realized in the form of hardware and / or software and can be configured in any electronic device with network communication function. As shown in Figure 1 the method comprises:

[0035] S110, selecting evaluation indexes that affect the fracturing effect of the hydrate reservoir, and performing index level division on the evaluation indexes.

[0036] The selection of the fracturability evaluation indexes has an important influence on the accuracy of the evaluation method. There are many factors affecting the fracturability of the hydrate reservoir. When selecting the evaluation indexes, the pertinence, systematicness, relative independence and operability should be considered. The selected indexes should fully consider the unique characteristics of the hydrate reservoir, can systematically and comprehensively reflect the fracturability of the reservoir, but avoid being complicated and less overlapping, and are easy to obtain in engineering application. The hydrate reservoir in the embodiment of the present application has the characteristics of unconsolidation and strong plasticity. Based on the understanding of the research on hydrate sample mechanics and hydraulic fracturing, the evaluation indexes for evaluating the fracturability of the hydrate reservoir are determined to include geological factors and engineering factors. Therefore, the evaluation indexes include geological factor evaluation indexes and engineering factor evaluation indexes.

[0037] Referring to Figure 2 The evaluation indexes are divided into index levels, and the evaluation indexes are divided into first-level evaluation indexes and second-level evaluation indexes. The main factors affecting the fracturing effect of the hydrate reservoir are divided into two categories: geological factors and engineering factors. Therefore, the geological factor evaluation indexes and the engineering factor evaluation indexes are used as the first-level evaluation indexes for fracturability evaluation. The hydrate saturation, the secant modulus, the secant Poisson's ratio, the clay mineral content, the stress distribution and the permeability evaluation indexes included in the geological factor evaluation indexes, and the fracturing fluid displacement and the fracturing fluid viscosity evaluation indexes included in the engineering factor evaluation indexes are used as the second-level evaluation indexes.

[0038] S120, respectively using the analytic hierarchy process and the entropy weight method to determine the weights of each evaluation index and comprehensively assigning the weights to determine the target weights of each evaluation index.

[0039] The analytic hierarchy process can be a decision-making method that decomposes a complex decision-making problem into target, criterion, scheme and other levels, and calculates the weight and sorts through the combination of qualitative and quantitative. The entropy weight method can be a method for objectively determining the index weight in a multi-index evaluation system through data distribution characteristics. The core is to measure the amount of information of an index by using information entropy, and the smaller the entropy value, the higher the weight.

[0040] In the embodiment of the application, the analytic hierarchy process and the entropy weight method are used to determine the weight corresponding to each evaluation index, respectively, and the analytic hierarchy process weight and the entropy weight corresponding to each evaluation index are fused to comprehensively assign the weight to each evaluation index. For example, the analytic hierarchy process is used to determine that the weight of evaluation index A is B, the entropy weight method is used to determine that the weight of evaluation index A is C, and the weight B and the weight C are fused to obtain the target weight of evaluation index A.

[0041] In the embodiment of the application, the analytic hierarchy process and the entropy weight method are used to determine the weight corresponding to each evaluation index, respectively, and the analytic hierarchy process weight and the entropy weight corresponding to each evaluation index are fused to comprehensively assign the weight to each evaluation index. For example, the analytic hierarchy process is used to determine that the weight of evaluation index A is B, the entropy weight method is used to determine that the weight of evaluation index A is C, and the weight B and the weight C are fused to obtain the target weight of evaluation index A.

[0042] The fracturing index is used to evaluate whether the natural gas hydrate reservoir can be fractured to form a hydraulic fracture and the effect of forming the hydraulic fracture, which can help to identify an optimal fracturing horizon, optimize a fracturing design strategy and improve the efficiency of reservoir reconstruction and yield increase.

[0043] In the embodiment of the application, the fracturing index of the hydrate reservoir is constructed according to the target weight of each evaluation index, and the fracturing index is used to evaluate the fracturing property of the hydrate reservoir. The greater the fracturing index, the better the fracturing property of the hydrate reservoir.

[0044] The embodiment of the application provides a method for evaluating the fracturing property of a natural gas hydrate reservoir in a sea area. The evaluation index affecting the fracturing effect of the hydrate reservoir is selected, the evaluation index is divided into index levels according to a standard, the analytic hierarchy process and the entropy weight method are used to determine the weight corresponding to each evaluation index and comprehensively assign the weight, the target weight of each evaluation index is determined, the fracturing index of the hydrate reservoir is constructed according to the target weight of each evaluation index, and the fracturing index is used to evaluate the fracturing property of the hydrate reservoir. The technical scheme of the embodiment of the application comprehensively considers the influence of geological factors and engineering factors on the fracturing effect of the hydrate reservoir, improves the accuracy of the fracturing property evaluation, and makes the evaluation of the fracturing property of the hydrate reservoir more comprehensive.

[0045] Embodiment two

[0046] Figure 3A flow chart of a method for evaluating the fracturing property of a marine natural gas hydrate reservoir is provided in Embodiment Two of the present application. Embodiment Two of the present application is further optimized on the basis of the above-mentioned embodiments, and can be combined with each optional scheme in one or more of the above-mentioned embodiments. As shown in FIG. 10, the method comprises the following steps. Figure 3

[0047] In S310, an evaluation index affecting the fracturing effect of the hydrate reservoir is selected, and the evaluation index is divided into index levels.

[0048] After the evaluation index affecting the fracturing effect of the hydrate reservoir is obtained, actual data of the evaluation index is obtained, and the actual data of the evaluation index is processed to serve as basic data for calculating the weight by the entropy weight method.

[0049] In view of the characteristics of the hydrate reservoir that is not diagenetic and strong plastic, evaluation index data affecting the fracturing effect of the hydrate reservoir is obtained, and the evaluation index data is standardized. The evaluation index data is actual data of the evaluation index, and serves as basic data for calculating the weight by the entropy weight method. The standardization can be a preprocessing technique for converting to dimensionless pure values, and the core purpose is to eliminate dimensional differences. In the present embodiment, the evaluation index is standardized to convert to dimensionless pure values, so as to subsequently calculate the corresponding weight of the evaluation index by the entropy weight method.

[0050] As an optional but non-limiting implementation manner, the evaluation index data affecting the fracturing effect of the hydrate reservoir is obtained, and the evaluation index data is standardized, including but not limited to steps A1-A2.

[0051] In S A1, the evaluation index data affecting the fracturing effect of the hydrate reservoir is obtained according to logging data, experimental test data or engineering operation data.

[0052] In S A2, the evaluation index data is standardized.

[0053] The evaluation index data is obtained by logging data, experimental test data or engineering operation data, and serves as basic data for calculating the weight by the entropy weight method. Since the dimensions of the evaluation indexes can be different, the original evaluation index data needs to be standardized.

[0054] ​Optionally, in the aspect of geological index parameter acquisition, hydrate reservoir sample acquisition is difficult and costly, and part of the hydrate reservoirs in the sea have logging data, and the reservoir physical property parameters in the logging section can be continuously acquired through the logging data, and the reservoir geological physical property parameters are acquired through the logging data in the embodiments of the present application. The physical property parameters acquired through the logging data and the physical property parameters measured through indoor experiments can be converted through an empirical formula. Since the weight calculated by the entropy weight method reflects the difference degree of the index values, a unified data source can be used for the same index.

[0055] If the experimental test method is needed to determine the values of each evaluation index, the following method is used for calculation:

[0056] The hydrate saturation value can be acquired through logging data interpretation or obtained through experimental testing, and the experimental testing calculation formula is:

[0057] ;

[0058] Among them, represents the hydrate saturation, and are the hydrate volume and the reservoir pore volume, respectively.

[0059] The elastic modulus can be acquired through logging data interpretation or obtained through experimental testing; when the experimental testing method is used, the secant modulus is used instead, and the calculation formula is as follows:

[0060] ;

[0061] Among them, represents the secant modulus, is the 50% strength, is the deformation amount corresponding to the 50% strength.

[0062] The Poisson's ratio can be acquired through logging data interpretation or obtained through experimental testing; when the experimental testing method is used, the secant Poisson's ratio is used instead, and the calculation formula is as follows:

[0063] ;

[0064] Among them, represents the secant Poisson's ratio, and are the lateral strain and the longitudinal strain corresponding to the 50% strength, respectively.

[0065] The clay mineral content can be acquired through logging data interpretation or obtained through experimental testing, and when the experimental testing method is used, the calculation formula is as follows,

[0066] ;

[0067] wherein, represents the clay mineral content, and respectively represent the clay mineral content and the total mineral content.

[0068] The horizontal stress difference coefficient is used to represent the stress distribution, and the calculation formula is as follows:

[0069] ;

[0070] wherein, , respectively represent the maximum and minimum horizontal principal stresses of the reservoir.

[0071] The permeability (K) is obtained by well logging data interpretation or experimental testing. When the experimental testing method is used, the standard testing method is used for testing.

[0072] When the engineering factor data is obtained, the fracturing fluid discharge (Q) and the fracturing fluid viscosity (μ) are engineering parameters that can be actively controlled in fracturing construction. The reservoir conditions and construction tools and equipment are comprehensively selected. Since there is no engineering implementation case for hydrate reservoir fracturing, the hydraulic fracturing engineering factor data is used as a reference for the characteristics of the shallow soft unconsolidated formation of the reservoir.

[0073] The standardization process includes standardization of forward index data and reverse index data. Hydrate saturation, secant modulus, stress distribution, fracturing fluid discharge, and fracturing fluid viscosity are forward index data, and permeability, clay mineral content, and secant Poisson's ratio are negative index data. The greater the forward index data or the smaller the negative index data, the better the fracturability.

[0074] wherein, the standardization of the forward index data is represented as:

[0075]

[0076] The standardization of the reverse index data is represented as:

[0077]

[0078] wherein, represents the standardized value of the jth evaluation index data of the ith sample, represents the jth evaluation index data of the ith sample, and respectively represent the maximum and minimum values of the jth evaluation index data.

[0079] ​The hydrate reservoir in the embodiment of the present application is an un-diagenetic formation, has the characteristic of significant plasticity, breaks out of the idea of conventional diagenetic formation fracturability evaluation based on rock brittleness, comprehensively considers the influence of geological factors and engineering factors on the fracturing effect of the hydrate reservoir, improves the accuracy of the fracturability evaluation, and the established fracturability evaluation method is more suitable for the hydrate reservoir.

[0080] S320, the first weight of the primary evaluation index in the hydrate reservoir fracturability is determined by using the analytic hierarchy process.

[0081] The first weight of the primary evaluation index in the hydrate reservoir fracturability is determined by using the analytic hierarchy process. The physical property condition of the hydrate reservoir itself is the basis for whether the fracturing can be implemented, the geological factors are considered to be more important than the engineering factors, a judgment matrix is established, and Table 1 is referred to.

[0082] Table 1: Judgment matrix of primary evaluation index of fracturability

[0083]

[0084] The characteristic vector of the primary evaluation index is calculated That is, the weight of the geological factor index is 0.83, and the weight of the engineering factor index is 0.17.

[0085] S330, the second weight of the secondary evaluation index in the primary evaluation index is determined by using the analytic hierarchy process.

[0086] The second weight of the secondary evaluation index in the primary evaluation index is determined by using the analytic hierarchy process, and a judgment matrix is established, which is referred to in Table 2 and Table 3.

[0087] Table 2: Weight calculation judgment matrix of secondary evaluation index of fracturability geological factors

[0088]

[0089] Table 3: Weight calculation judgment matrix of secondary evaluation index of fracturability engineering factors

[0090]

[0091] The weight calculation result of the secondary evaluation index of the geological factors is obtained by calculating Table 2, as shown in Table 4. Optionally, the secondary evaluation index of the geological factors is more, and the consistency check of the geological factor judgment matrix is required, and the consistency check has a general specification step, which is not described in detail here. The consistency check of the geological factor judgment matrix meets the consistency requirement.

[0092] Table 4: Analytic hierarchy process result of secondary index of geological factors

[0093]

[0094] The characteristic vector of the secondary evaluation index of the engineering factor is obtained by calculating Table 3 That is, the fracturing fluid discharge index weight is 0.25, and the fracturing fluid viscosity index weight is 0.75.

[0095] S340, the third weight of the secondary evaluation index in the hydrate reservoir fracturability is determined by using the entropy weight method.

[0096] The third weight of the secondary evaluation index in the hydrate reservoir fracturability is determined by using the entropy weight method, and the data of each secondary evaluation index is shown in Table 5.

[0097] Table 5: Data of secondary evaluation index of fracturability

[0098]

[0099] The data of each secondary evaluation index is standardized, the weight of each secondary evaluation index is calculated according to the principle of entropy weight method, and the result is shown in Table 6.

[0100] Table 6: Result of secondary index weight calculated by entropy weight method

[0101]

[0102] S350, the target weight of each secondary evaluation index in the hydrate reservoir fracturability is determined by comprehensively weighting the secondary evaluation index according to the first weight, the second weight and the third weight.

[0103] The first weight, the second weight and the third weight are fused to comprehensively weight the secondary evaluation index, so as to determine the target weight of each secondary evaluation index in the hydrate reservoir fracturability.

[0104] It can be understood that the first weight is a kind of substitute, which is used to distinguish the different weights of the corresponding logic executed before and after in the embodiment, therefore, the weight appearing for the first time in this paper is called the first weight, and the other recipients appearing after the first weight are called the second weight, and the following will not be repeated.

[0105] As an optional but not limited implementation manner, the target weight of each secondary evaluation index in the hydrate reservoir fracturability is determined by comprehensively weighting the secondary evaluation index according to the first weight, the second weight and the third weight, which includes but is not limited to steps B1-B2:

[0106] Step B1: according to the first weight and the second weight, the fourth weight of the secondary evaluation index determined by using the analytic hierarchy process in the hydrate reservoir fracturability is determined;

[0107] Step B2: the fourth weight and the third weight are comprehensively weighted to determine the target weight of each secondary evaluation index in the hydrate reservoir fracturability.

[0108] Wherein, referring to Figure 4 The subjective weight calculated by the analytic hierarchy process and the objective weight calculated by the entropy weight method are combined to comprehensively weight to determine the target weight of each secondary evaluation index in the hydrate reservoir fracturability. Optionally, first, the first weight of the primary evaluation index in the hydrate reservoir fracturability and the second weight of the secondary evaluation index in the primary evaluation index determined by the analytic hierarchy process are fused to determine the fourth weight of the secondary evaluation index in the hydrate reservoir fracturability; then the fourth weight of the secondary evaluation index in the hydrate reservoir fracturability determined by the analytic hierarchy process and the third weight of the secondary evaluation index in the hydrate reservoir fracturability determined by the entropy weight method are comprehensively weighted to determine the target weight of each secondary evaluation index in the hydrate reservoir fracturability, as shown in Table 7.

[0109] Table 7 Target weight of evaluation index

[0110]

[0111] Wherein, the target weight of each secondary evaluation index in the hydrate reservoir fracturability is represented as:

[0112]

[0113] Wherein, is the target weight of the jth secondary evaluation index in the hydrate reservoir fracturability, is the fourth weight of the jth secondary evaluation index determined by the analytic hierarchy process, is the third weight of the jth secondary evaluation index determined by the entropy weight method.

[0114] The subjective weight calculated by the analytic hierarchy process and the objective weight calculated by the entropy weight method are combined to comprehensively weight in the embodiment of the present application, which reflects the subjective understanding of researchers on the hydrate reservoir fracturability and reflects the objective law, so that the hydrate reservoir fracturability evaluation method constructed in the embodiment of the present application is more reasonable.

[0115] S360, constructing a hydrate reservoir fracturability index according to the target weight of each evaluation index, and using the fracturability index to evaluate the hydrate reservoir fracturability.

[0116] Wherein, the fracturability index of the hydrate reservoir is calculated according to the standardized value and the target weight of each evaluation index, and the hydrate reservoir is evaluated based on the fracturability index. ​​

[0117] As an optional but non-limiting implementation, the target weight of each evaluation index is used to construct a hydrate reservoir fracturability index, and the hydrate reservoir is evaluated for fracturability by using the fracturability index, including but not limited to steps C1-C2:

[0118] Step C1: The normalized evaluation index is given a target weight according to the target weight of each evaluation index, and a hydrate reservoir fracturability index is constructed.

[0119] Step C2: The hydrate reservoir is evaluated for fracturability by using the fracturability index; the greater the fracturability index, the better the hydrate formation fracturability.

[0120] The hydrate reservoir fracturability index is constructed according to the normalized value and target weight of each evaluation index, and is represented as:

[0121]

[0122] The hydrate reservoir fracturability index is represented as: The jth evaluation index data after normalization.

[0123] The hydrate reservoir fracturability index is constructed according to the target weight of each evaluation index determined according to Table 7, and is represented as:

[0124]

[0125] The hydrate saturation normalized value is represented as: The normalized value of the modulus of rupture is represented as: The normalized value of the fracturing fluid viscosity is represented as: The normalized value of the modulus of rupture Poisson's ratio is represented as: The normalized value of the clay mineral content is represented as: The normalized value of the horizontal stress distribution is represented as: The normalized value of the reservoir permeability is represented as: The normalized value of the fracturing fluid displacement is represented as:

[0126] The hydrate reservoir fracturability index constructed according to the embodiments of the present application is used to evaluate the hydrate reservoir fracturability. The fracturability index is calculated by substituting each evaluation index, the greater the fracturability index, the better the hydrate reservoir fracturability, and the better the fracturing effect.

[0127] In an optional scheme of the embodiments of the present application, there are no engineering implementation examples of hydrate reservoir hydraulic fracturing in sea areas, and it is difficult to effectively monitor the fracturing effect after actual fracturing.​​​​

[0128] The application example of the application is to prepare an artificial sample close to the physical characteristics of a hydrate reservoir in a sea area, to carry out a fracturing physical simulation experiment by using a true triaxial hydraulic fracturing experimental device, and to evaluate the fracturability by a physical model experiment. The prepared sample is a cube with a size of 200mmx200mmx200mm, and the hydrate saturation is 40%. The fracturing fluid is dimethyl silicone oil, and the viscosity is adjusted to 30, 50 and 100mPa·s respectively. The experimental scheme and the fracturability index calculation results are shown in Table 8, and the fracturability index calculation results of each sample are shown in Figure 5 Sample 5 has the largest fracturability index, so the fracturability is the best, and the fracturing results are shown in Figure 6 The crack penetrates through the whole sample along the direction of the maximum principal stress, the crack deflection is less, and the crack propagation is the most sufficient. The fracturing experiment results of each sample are consistent with the theoretical results of the application example.

[0129] Table 8 Fracturability evaluation experiment scheme and fracturability index

[0130]

[0131] The application example of the application provides a fracturability evaluation method for a hydrate reservoir in a sea area. The hydrate reservoir is an unconsolidated formation, and has the characteristics of significant plasticity. The conventional fracturability evaluation method based on the brittleness of the rock is abandoned. The influence of geological factors and engineering factors on the fracturing effect of the hydrate reservoir is comprehensively considered. The established fracturability evaluation method is more suitable for the hydrate reservoir, and the accuracy of the fracturability evaluation is improved. The subjective weight calculated by the analytic hierarchy process and the objective weight calculated by the entropy weight method are combined to comprehensively assign the weight. The subjective understanding of the researchers on the fracturability of the hydrate reservoir is reflected, and the objective law is also reflected. The fracturability evaluation method is more reasonable. The established fracturability evaluation index provides a theoretical basis for the fracturing feasibility evaluation and the fracturing horizon optimization of the hydrate reservoir, and the fracturability evaluation of the hydrate reservoir is more comprehensive.

[0132] Example three

[0133] Figure 7 A structure diagram of a hydrate reservoir fracturability evaluation device provided by the application example three is shown in Figure 7 As shown in the figure, the device comprises:

[0134] The evaluation index level division module 710 is used to select the evaluation indexes that affect the fracturing effect of the hydrate reservoir, and to divide the evaluation indexes into index levels.

[0135] The comprehensive weighting module 720 is configured to determine the weight of each evaluation index by using the analytic hierarchy process and the entropy weight method respectively, and to determine the target weight of each evaluation index by comprehensive weighting.

[0136] The fracturability evaluation module 730 is configured to construct a hydrate reservoir fracturability index according to the target weight of each evaluation index, and to evaluate the fracturability of the hydrate reservoir by using the hydrate reservoir fracturability index.

[0137] Optionally, the index levels of the evaluation indexes are divided into first-level evaluation indexes and second-level evaluation indexes, the first-level evaluation indexes include geological factor evaluation indexes and engineering factor evaluation indexes, the second-level evaluation indexes include the hydrate saturation, the secant modulus, the secant Poisson's ratio, the clay mineral content, the ground stress distribution and the permeability evaluation indexes included in the geological factor evaluation indexes, and the fracturing fluid displacement and the fracturing fluid viscosity evaluation indexes included in the engineering factor evaluation indexes.

[0138] Optionally, the comprehensive weighting module is specifically configured to:

[0139] determine a first weight of the first-level evaluation indexes in the hydrate reservoir fracturability by using the analytic hierarchy process;

[0140] determine a second weight of the second-level evaluation indexes in the first-level evaluation indexes by using the analytic hierarchy process;

[0141] determine a third weight of the second-level evaluation indexes in the hydrate reservoir fracturability by using the entropy weight method;

[0142] comprehensively weight the second-level evaluation indexes according to the first weight, the second weight and the third weight, so as to determine the target weight of each second-level evaluation index in the hydrate reservoir fracturability.

[0143] Optionally, the comprehensive weighting module is further specifically configured to:

[0144] determine a fourth weight of the second-level evaluation indexes in the hydrate reservoir fracturability by using the analytic hierarchy process according to the first weight and the second weight;

[0145] comprehensively weight the fourth weight and the third weight, so as to determine the target weight of each second-level evaluation index in the hydrate reservoir fracturability.

[0146] Optionally, the comprehensive weighting module is further specifically configured to:

[0147] the target weight of each second-level evaluation index in the hydrate reservoir fracturability is represented as:

[0148] , ;

[0149] wherein, is a target weight of the jth secondary evaluation index in the hydrate reservoir fracturability, is a fourth weight of the jth secondary evaluation index determined by using the analytic hierarchy process, is a third weight of the jth secondary evaluation index determined by using the entropy weight method.

[0150] Optionally, the fracturability evaluation module is specifically used for:

[0151] According to the target weight of each evaluation index, the target weight is given to the evaluation index after standardization processing, and a hydrate reservoir fracturability index is constructed.

[0152] The fracturability of the hydrate reservoir is evaluated by using the fracturability index; the greater the fracturability index, the better the hydrate reservoir fracturability.

[0153] Optionally, the fracturability evaluation module is specifically used for:

[0154] The hydrate reservoir fracturability index is expressed as:

[0155] ;

[0156] wherein, represents the hydrate reservoir fracturability index, represents the jth evaluation index after standardization processing.

[0157] The sea natural gas hydrate reservoir fracturability evaluation device provided in the embodiment of the present application can execute the sea natural gas hydrate reservoir fracturability evaluation method provided in any embodiment of the present application, has the corresponding functions and beneficial effects of executing the sea natural gas hydrate reservoir fracturability evaluation method, and the detailed process is described in the foregoing embodiment of the sea natural gas hydrate reservoir fracturability evaluation method.

[0158] Embodiment four

[0159] Figure 8 A structural schematic diagram of an electronic device 10 that can be used to implement embodiments of the present application is shown. The electronic device is intended to represent various forms of digital computers, such as laptops, desktops, tablets, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The electronic device can also represent various forms of mobile devices, such as personal digital assistants, cellular telephones, smart phones, wearable devices (e.g., headsets, glasses, watches, etc.), and other similar computing devices. The components shown here, their connections and relationships, and their functions, are meant to be examples only, and are not intended to limit the implementations of the present application described and / or claimed in this document.

[0160] As shown in Figure 8 The electronic device 10 includes at least one processor 11, and a memory, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., connected to the at least one processor 11 in communication, wherein the memory stores a computer program executable by the at least one processor. The processor 11 can perform various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 12 or the computer program loaded from the storage unit 18 into the random access memory (RAM) 13. In the RAM 13, various programs and data required for the operation of the electronic device 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0161] A plurality of components in the electronic device 10 are connected to the I / O interface 15, including an input unit 16, such as a keyboard, a mouse, etc., an output unit 17, such as various types of displays, a speaker, etc., a storage unit 18, such as a magnetic disk, an optical disk, etc., and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information / data with other devices through a computer network, such as the Internet, and / or various telecommunication networks.

[0162] The processor 11 can be various general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 11 performs various methods and processes described above, such as the method for evaluating the fracturability of a marine gas hydrate reservoir.

[0163] In particular, the processes described above with reference to the flowcharts can be implemented as a computer software program according to embodiments of the present application. For example, embodiments of the present application include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for executing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network through the communication unit 19, or installed from the storage unit 18, or installed from the ROM 12. When the computer program is executed by the processor 11, the above-mentioned functions defined in the methods of the embodiments of the present application are performed.

[0164] In some embodiments, the marine gas hydrate reservoir fracturability evaluation method can be implemented as a computer program tangibly embodied in a computer readable storage medium, e.g., storage unit 18. In some embodiments, parts or all of the computer program can be loaded and / or installed onto electronic device 10 via, e.g., ROM 12 and / or communication unit 19. When the computer program is loaded onto RAM 13 and executed by processor 11, one or more steps of the above-described marine gas hydrate reservoir fracturability evaluation method can be performed. Alternatively, in other embodiments, processor 11 can be configured to perform the marine gas hydrate reservoir fracturability evaluation method by way of other any suitable means (e.g., by way of firmware).

[0165] Various implementations of the systems and techniques described above can be realized in digital electronic circuitry, integrated circuitry, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a system on a chip (SOC), a complex programmable logic device (CPLD), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and / or interpretable on a programmable system including at least one programmable processor, which can be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

[0166] Computer programs used to implement the methods of the present application can be written in any combination of one or more programming languages. These computer programs can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the computer program running on the processor implements the functions / operations specified in the flowcharts and / or the block diagrams. The computer program can be executed entirely on a machine, partially on a machine and partially on a remote machine or entirely on a remote machine or server.

[0167] In the context of the present application, a computer-readable storage medium can be a tangible medium that can contain or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. A computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium can be a machine-readable signal medium. More specific examples of a machine-readable storage medium will include one or more lines of a program of instructions in a transitory signal, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0168] To provide for interaction with a user, the systems and techniques described here can be implemented on an electronic device having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the electronic device. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0169] The systems and techniques described here can be implemented in a computing system that includes a back end component (e.g., as a server), or that includes a middleware component (e.g., an application server), or that includes a front end component (e.g., a user computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back end, middleware, or front end components. The components of the system can be interconnected by any form or medium of digital communication (e.g., a communication network). Examples of communication networks include a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0170] The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server can be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system, to solve the defects of large management difficulty and weak business scalability in traditional physical host and VPS service.

[0171] It should be understood that the various forms of flow shown above can be reordered, added to, or have steps deleted. For example, the steps described in the present application can be performed in parallel, in series, or in a different order, as long as the desired results of the technical solutions of the present application can be achieved, which are not limited herein.

[0172] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for evaluating the fracturability of a marine gas hydrate reservoir, characterized by, The method comprises: selecting evaluation indexes affecting the fracturing effect of the hydrate reservoir, and performing index level division on the evaluation indexes; respectively determining the weights of the evaluation indexes corresponding to the evaluation indexes by using an analytic hierarchy process and an entropy weight method, and performing comprehensive weighting to determine target weights of the evaluation indexes; constructing a hydrate reservoir fracturability index according to the target weights of the evaluation indexes, and performing fracturability evaluation on the hydrate reservoir by using the hydrate reservoir fracturability index.

2. The method of claim 1, wherein, The index level division of the evaluation indexes is divided into first-level evaluation indexes and second-level evaluation indexes, the first-level evaluation indexes include geological factor evaluation indexes and engineering factor evaluation indexes, the second-level evaluation indexes include the hydrate saturation, the secant modulus, the secant Poisson's ratio, the clay mineral content, the stress distribution and the permeability evaluation indexes included in the geological factor evaluation indexes, and the fracturing fluid displacement and the fracturing fluid viscosity evaluation indexes included in the engineering factor evaluation indexes.

3. The method of claim 1, wherein, The respectively determining the weights of the evaluation indexes corresponding to the evaluation indexes by using an analytic hierarchy process and an entropy weight method, and performing comprehensive weighting to determine target weights of the evaluation indexes, comprises: determining first weights of the first-level evaluation indexes in the hydrate reservoir fracturability by using an analytic hierarchy process; determining second weights of the second-level evaluation indexes in the first-level evaluation indexes by using an analytic hierarchy process; determining third weights of the second-level evaluation indexes in the hydrate reservoir fracturability by using an entropy weight method; performing comprehensive weighting on the second-level evaluation indexes according to the first weights, the second weights and the third weights to determine target weights of the second-level evaluation indexes in the hydrate reservoir fracturability.

4. The method of claim 3, wherein, The performing comprehensive weighting on the second-level evaluation indexes according to the first weights, the second weights and the third weights to determine target weights of the second-level evaluation indexes in the hydrate reservoir fracturability, comprises: determining fourth weights of the second-level evaluation indexes in the hydrate reservoir fracturability determined by using an analytic hierarchy process according to the first weights and the second weights; performing comprehensive weighting on the fourth weights and the third weights to determine the target weights of the second-level evaluation indexes in the hydrate reservoir fracturability.

5. The method of claim 4, wherein, The performing comprehensive weighting on the fourth weights and the third weights to determine the target weights of the second-level evaluation indexes in the hydrate reservoir fracturability, comprises: the target weights of the second-level evaluation indexes in the hydrate reservoir fracturability are represented as: ， ； wherein, is the target weight of the jth secondary evaluation index in the fracturability of the hydrate reservoir, is the fourth weight of the jth secondary evaluation index determined by the analytic hierarchy process, is the third weight of the jth secondary evaluation index determined by the entropy weight method.

6. The method of claim 1, wherein, The constructing a hydrate reservoir fracturability index according to the target weights of the evaluation indexes, and performing fracturability evaluation on the hydrate reservoir by using the hydrate reservoir fracturability index, comprises: assigning target weights to the evaluation indexes after standardization according to the target weights of the evaluation indexes, and constructing a hydrate reservoir fracturability index; performing fracturability evaluation on the hydrate reservoir by using the hydrate reservoir fracturability index; wherein the greater the hydrate reservoir fracturability index is, the better the hydrate reservoir fracturability is.

7. The method of claim 6, wherein, The assigning target weights to the evaluation indexes after standardization according to the target weights of the evaluation indexes, and constructing a hydrate reservoir fracturability index, comprises: the hydrate reservoir fracturability index is represented as: ； wherein, represents a hydrate reservoir fracturability index, represents the jth evaluation index after normalization processing.

8. An apparatus for evaluating the fracturability of a marine gas hydrate reservoir, the apparatus comprising: The device comprises: The evaluation index level division module is configured to select evaluation indexes that affect the fracturing effect of the hydrate reservoir and divide the evaluation indexes into different levels. The comprehensive weighting module is configured to determine the weight of each evaluation index by using the analytic hierarchy process and the entropy weight method respectively and to determine the target weight of each evaluation index by comprehensive weighting. The fracturability evaluation module is configured to construct a hydrate reservoir fracturability index according to the target weight of each evaluation index and to evaluate the fracturability of the hydrate reservoir by using the hydrate reservoir fracturability index.

9. An electronic device, comprising: The electronic device comprises: at least one processor; and a memory connected to the at least one processor in communication; wherein the memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor to enable the at least one processor to perform the hydrate reservoir fracturability evaluation method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer instructions for enabling the processor to perform the hydrate reservoir fracturability evaluation method according to any one of claims 1-7 when executed.

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