A method and device for determining shale soft porosity using gas logging as a constraint

Abstract

The present invention discloses a method and device for determining the soft porosity of shale using gas logging as a constraint. The method includes obtaining a first curve of the total porosity variation over time obtained by a porosity gas logging experiment of a rock sample, and a second curve of the pressure variation over time, determining the position on the second curve where the slope begins to be less than a set slope threshold, and using the corresponding total porosity as the hard porosity; determining multiple pressures between the pressure at the position and the minimum pressure; for each pressure, obtaining a first soft porosity from the total porosity, and determining a second soft porosity at the pressure based on the correspondence between the fracture density and the test pressure and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed; correcting the current correspondence until the determined second soft porosity meets the error requirement, thereby obtaining an optimized correspondence. This method can determine the soft porosity at any pressure using the Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil and gas exploration and development, and in particular to a method and device for determining shale soft porosity using a gas logging method as a constraint. Background Art

[0002] Calculating shale porosity is a key technology for shale oil resource evaluation. Shale pores are composed of hard pores (inorganic pores in the rock skeleton) and soft pores (organic pores in the kerogen). Soft pores are generally defined as pores or fractures with an aspect ratio less than 0.01.

[0003] Hard pores basically do not change under the action of pressure, so an increase in overburden pressure will not lead to a decrease in hard porosity, while soft porosity will decrease due to the closure of soft pores. During the thermal evolution of shale, as the temperature rises, organic matter continues to decompose, and the fluid type gradually changes from oil to gas, causing the soft porosity to increase with increasing temperature. During this process, the hard porosity does not change much.

[0004] Existing shale porosity research techniques cannot dynamically determine the soft porosity of shale under varying pressures. However, studying the seismic wave dispersion effect of shale reservoirs requires studying soft porosity, and research into the mining potential of shale reservoirs also requires determining both total porosity and soft porosity. Summary of the Invention

[0005] To enrich process routes and increase options, an embodiment of the present invention provides a method and apparatus for determining shale soft porosity using gas logging as a constraint. This method and apparatus can determine the soft porosity at any pressure by optimizing the correspondence between fracture density and test pressure, utilizing the Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed.

[0006] In a first aspect, an embodiment of the present invention provides a method for determining shale soft porosity using a gas logging method as a constraint, comprising:

[0007] Based on the experimental data of fracture density and test pressure of multiple shale samples in the shale reservoir, the corresponding relationship between fracture density and test pressure is established;

[0008] Obtaining a first curve of total porosity versus test time and a second curve of pressure versus test time obtained through a porosity gas testing experiment for a target rock sample in the reservoir, determining a position on the second curve where the slope begins to be less than a set slope threshold, and using the total porosity corresponding to the position as hard porosity;

[0009] determining a plurality of test pressures between the pressure at the location and the minimum pressure;

[0010] For each test pressure, the difference between the total porosity and the hard porosity corresponding to the first curve is used as the first soft porosity at that pressure. The second soft porosity at that pressure is determined based on the current corresponding relationship and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed.

[0011] The current correspondence is corrected until the error between the second soft porosity determined according to the current correspondence and the first soft porosity meets the set error requirement, and an optimized correspondence is obtained, which is used to determine the soft porosity under the set pressure based on the Poisson's ratio and Young's modulus of the rock sample to be tested when the soft pores are completely closed.

[0012] In a second aspect, an embodiment of the present invention provides a device for determining shale soft porosity using a gas logging method as a constraint, comprising:

[0013] A corresponding relationship establishment module is used to establish a corresponding relationship between fracture density and test pressure based on experimental data pairs of fracture density and test pressure of multiple shale samples in the shale reservoir;

[0014] a gas logging hard porosity determination module, configured to obtain a first curve showing the variation of total porosity versus test time, obtained through a porosity gas logging experiment, and a second curve showing the variation of pressure versus test time, for a target rock sample in the reservoir, determine a position on the second curve where the slope begins to fall below a set slope threshold, and use the total porosity corresponding to the position as the hard porosity;

[0015] a plurality of test pressure determination modules for determining a plurality of test pressures between the pressure at the location and a minimum pressure;

[0016] a soft porosity determination module configured to, for each test pressure, use the difference between the total porosity corresponding to the first curve and the hard porosity as the first soft porosity at the pressure, and determine the second soft porosity at the pressure based on the current correspondence and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed;

[0017] The corresponding relationship optimization module is used to correct the current corresponding relationship until the error between the second soft porosity determined according to the current corresponding relationship and the first soft porosity meets the set error requirement, thereby obtaining an optimized corresponding relationship, which is used to determine the soft porosity under a set pressure based on the Poisson's ratio and Young's modulus of the rock sample to be tested when the soft pores are completely closed.

[0018] In a third aspect, an embodiment of the present invention provides a computer storage medium storing computer executable instructions. When the computer executable instructions are executed by a processor, the method for determining shale soft porosity using gas logging as a constraint is implemented.

[0019] In a fourth aspect, an embodiment of the present disclosure provides a server comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for determining the soft porosity of shale using the gas logging method as a constraint is implemented.

[0020] The beneficial effects of the above technical solutions provided by the embodiments of the present invention include at least:

[0021] (1) The method for determining the soft porosity of shale using the gas logging method as a constraint provided by the embodiment of the present invention uses the soft porosity determined using the gas logging experimental data of the rock sample porosity as a constraint condition, and corrects the correspondence between the fracture density and the test pressure until the soft porosity determined using the corrected correspondence condition is close to the constraint condition, thereby obtaining an optimized correspondence between the fracture density and the test pressure. On this basis, it is possible to determine the soft porosity at any pressure using the Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed.

[0022] (2) The method for determining the soft porosity of shale using the gas measurement method as a constraint provided in the embodiment of the present invention is based on the optimization of the corresponding relationship between the fracture density and the test pressure. It only requires the Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed to determine the soft porosity under any pressure. The Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed can be calculated through the measurement results of the longitudinal and transverse wave velocities under high pressure conditions. The measurement of the longitudinal and transverse wave velocities under high pressure conditions is easy to implement and is non-destructive to the rock sample.

[0023] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0026] Figure 1 This is a flow chart of a method for determining shale soft porosity using gas logging as a constraint in an embodiment of the present invention;

[0027] Figure 2 This is an example diagram of the fitting results of the corresponding relationship between crack density and test pressure in an embodiment of the present invention;

[0028] Figure 31. The graphs of total porosity versus test time and pressure versus test time in accordance with an embodiment of the present invention are exemplary graphs;

[0029] Figure 4 Schematic diagram of the structure of an apparatus for determining the soft porosity of shale using the gas logging method as a constraint in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0031] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0032] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention belongs. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

[0033] The pore structure of rocks can generally be idealized as consisting of intergranular pores between mineral particles and microcracks connecting these pores. Therefore, the pore structure of rocks can be characterized as a composition of hard and soft pores of varying pore shapes. The pore shape is typically represented by the pore aspect ratio α. In real rocks, soft pores have a wide variety of distribution shapes and cannot be represented by a single pore aspect ratio; instead, a continuous pore aspect ratio distribution should be used. The method of David and Zimmerman (2012) can be used to invert the continuous pore structure of reservoir rocks using dry data from ultrasonic measurements.

[0034] (1) α is defined as the pore aspect ratio, which is used to characterize the shape of the pore.

[0035] (2) Calculate K by measuring the ultrasonic longitudinal and shear wave velocities at high pressurestiff and μ stiff .

[0036] K stiff and μ stiff The bulk modulus and shear modulus are when the soft pores in the rock are completely closed. Both belong to the elastic modulus of the rock. The bulk modulus and shear modulus can be calculated by the longitudinal and shear wave velocities using existing public methods.

[0037] (3) Define φ s Hard porosity.

[0038] (4) K0 and μ0 are the bulk modulus and shear modulus of the rock particle matrix, respectively, which are obtained through rock mechanics experimental measurements.

[0039] (5) The above variables satisfy the Mori-Tanaka formula (1973) under two assumptions: first, the rock contains only hard pores, and second, the hard pores in the rock have only a single pore aspect ratio.

[0040]

[0041]

[0042] Formula (1) and (2) K stiff and μ stiff are the bulk modulus and shear modulus when the soft pores are completely closed, φ s is the hard porosity, K0 and μ0 are the bulk modulus and shear modulus of the rock particle matrix, respectively, P s and Q s The aspect ratio α s is the pore shape expression of the function and is only used as an intermediate parameter in the derivation of the formula.

[0043] (6) Measure K d and μ d , are the effective bulk modulus and equivalent shear modulus of the rock sample containing porosity, respectively.

[0044] (7) The Mori-Tanaka formula (1973) is modified again. In this case, the matrix modulus of the rock skeleton is the combination of the bulk modulus and the shear modulus (K stiff and μ stiff )replace.

[0045]

[0046]

[0047] In formulas (3) and (4), φ c is the soft porosity; Pc and Q c The aspect ratio α c is the soft pore shape expression of the function, which is only used as an intermediate parameter in the derivation of the formula.

[0048] (8) Define ε as the crack density and ν as the crack density. stiff is the Poisson's ratio of the rock when the soft pores are completely closed.

[0049] (9)Use Formula (5) is further derived and transformed from Formula (3) and Formula (4):

[0050]

[0051]

[0052] (10) Establish the relationship between crack density and pressure:

[0053]

[0054] In formula (8), ε is the crack density, ε0 ​​is the initial crack density of the rock sample under zero pressure conditions, p is the test pressure, is the pressure value determined by fitting.

[0055] (11) Calculate the minimum initial aspect ratio α using the following formula i :

[0056]

[0057] In formula (9), ε p is the crack density of the rock sample with specific soft pores under the effective pressure P, and ε0 is the initial crack density of the rock sample under zero pressure.

[0058] (12) Substituting formula (8) into formula (9), further transformation yields:

[0059]

[0060] E stiff is the Young's modulus of the rock when the soft pores are completely closed. The pressure test is divided into n equal intervals of △p. Here, it is similar to the concept of integration. The larger n is, the smaller dp is. The calculated α i The smaller the change, the higher the accuracy of the aspect ratio. This formula can calculate the minimum initial aspect ratio α at each pressure point i , further integration and accumulation can be used to calculate the crack aspect ratio at each pressure point.

[0061] (13) The soft porosity can be calculated by substituting the crack aspect ratio α calculated by equation (10) and the crack density ε calculated by equation (8) into equation (5).

[0062] The embodiments of the present invention provide a method and apparatus for determining the soft porosity of shale using gas logging as a constraint, which can determine the soft porosity at any pressure by using the Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed.

[0063] Example

[0064] The embodiment of the present invention provides a method for determining the soft porosity of shale using gas logging as a constraint. Figure 1 As shown, the following steps are included:

[0065] Step S11: establishing a corresponding relationship between fracture density and test pressure based on experimental data pairs of fracture density and test pressure of multiple shale samples in the shale reservoir.

[0066] According to the experimental data of fracture density and test pressure of multiple shale samples in the shale reservoir, the above formula (8) is determined by data fitting. ε0 can be determined by experiment or by fitting deduction, thus obtaining the corresponding relationship between crack density and test pressure. The fitting results of the corresponding relationship between crack density and test pressure can be found in Figure 2 As shown, the experimental measurement curve is the curve obtained by directly connecting the experimental data two by two.

[0067] Step S12: Obtain a first curve showing the change in total porosity versus test time, and a second curve showing the change in pressure versus test time, obtained through a porosity gas testing experiment for a target rock sample in the reservoir. Determine the position on the second curve where the slope begins to be less than a set slope threshold, and use the total porosity corresponding to the position as the hard porosity.

[0068] See also Figure 3 As shown, there are example graphs of the first curve (curves 2 and 4) of total porosity changing with test time and the second curve (curves 1 and 3) of pressure changing with test time obtained through porosity gas testing experiments, where curves 1 and 2 are measurement results parallel to the shale bedding direction, and curves 3 and 4 are measurement results perpendicular to the shale bedding direction.

[0069] Step S13: Determine a plurality of test pressures between the pressure at the position and the minimum pressure.

[0070] Multiple test pressures between the pressure at the specified location and the minimum pressure are determined based on the set pressure interval. The smaller the set pressure interval, the higher the calculation accuracy, but also the greater the computational effort. Therefore, the pressure interval can be determined based on a combination of the required accuracy and the computational effort.

[0071] Step S14: For each test pressure, the difference between the total porosity and the hard porosity corresponding to the first curve is used as the first soft porosity under the pressure. The second soft porosity under the pressure is determined based on the current corresponding relationship and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed.

[0072] The process of determining the second soft porosity for each test pressure condition may include:

[0073] (1) Determine the crack density at this pressure using the current correspondence.

[0074] According to the specific data of the test pressure, the crack density under the pressure is determined by formula (8).

[0075] (2) According to the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed, the fracture aspect ratio under the pressure is determined.

[0076] The Poisson's ratio and Young's modulus when the soft pores are completely closed can be determined based on the longitudinal and shear wave velocity measurement results when the test pressure is higher than the set pressure, that is, determined by the high-pressure longitudinal and shear wave velocity measurement results.

[0077] According to the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed, the minimum initial aspect ratio corresponding to the pressure interval is determined by formula (10); based on the minimum initial aspect ratio corresponding to the pressure interval, the fracture aspect ratio under this pressure is determined by the integral accumulation method.

[0078] (3) Determine the soft porosity at this pressure based on the crack density and crack aspect ratio.

[0079] According to the crack density and crack aspect ratio, the soft porosity under this pressure is determined using formula (5):

[0080] Step S15: Correct the current corresponding relationship until the error between the second soft porosity determined according to the current corresponding relationship and the first soft porosity meets the set error requirement, thereby obtaining an optimized corresponding relationship.

[0081] The correspondence between the optimized fracture density and the test pressure is used to determine the soft porosity at a set pressure based on the Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed.

[0082] The method for determining the soft porosity of shale using gas logging as a constraint provided by an embodiment of the present invention uses the soft porosity determined using data obtained from a gas logging experiment on a rock sample porosity as a constraint condition, and corrects the correspondence between the fracture density and the test pressure until the soft porosity determined using the corrected correspondence condition is close to the constraint condition, thereby obtaining an optimized correspondence between the fracture density and the test pressure. On this basis, it is possible to determine the soft porosity at any pressure using the Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed.

[0083] The method for determining the soft porosity of shale using the gas measurement method as a constraint provided in an embodiment of the present invention, based on the optimization of the correspondence between fracture density and test pressure, only requires the Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed to determine the soft porosity under any pressure. The Poisson's ratio and Young's modulus of the rock sample when the soft pores are completely closed can be calculated through the measurement results of the longitudinal and transverse wave velocities under high-pressure conditions. The measurement of the longitudinal and transverse wave velocities under high-pressure conditions is easy to implement and is non-destructive to the rock sample.

[0084] Based on the inventive concept of the present invention, an embodiment of the present invention further provides a device for determining the soft porosity of shale using the gas logging method as a constraint. The structure of the device is as follows: Figure 4 Shown, including:

[0085] A corresponding relationship establishing module 41 is used to establish a corresponding relationship between fracture density and test pressure based on experimental data pairs of fracture density and test pressure of multiple shale samples in the shale reservoir;

[0086] The gas logging hard porosity determination module 42 is configured to obtain a first curve showing the total porosity of the target rock sample in the reservoir changing with test time, and a second curve showing the pressure changing with test time, obtained through a porosity gas logging experiment, determine a position on the second curve where the slope begins to fall below a set slope threshold, and use the total porosity corresponding to the position as the hard porosity;

[0087] a plurality of test pressure determination modules 43 for determining a plurality of test pressures between the pressure at the location and the minimum pressure;

[0088] a soft porosity determination module 44 configured to, for each test pressure, use the difference between the total porosity and the hard porosity corresponding to the first curve as the first soft porosity at the pressure, and determine the second soft porosity at the pressure based on the current correspondence and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed;

[0089] The correspondence optimization module 45 is used to correct the current correspondence until the error between the second soft porosity determined according to the current correspondence and the first soft porosity meets the set error requirement, thereby obtaining an optimized correspondence, which is used to determine the soft porosity under a set pressure based on the Poisson's ratio and Young's modulus of the rock sample to be tested when the soft pores are completely closed.

[0090] In some embodiments, the corresponding relationship establishing module 41 establishes the corresponding relationship between the crack density and the test pressure, for:

[0091] The corresponding relationship between crack density and test pressure is established as:

[0092]

[0093] Where ε is the crack density, ε0 ​​is the initial crack density of the rock sample under zero pressure conditions, p is the test pressure, is the pressure value determined by fitting.

[0094] In some embodiments, the soft porosity determination module 44 determines the second soft porosity under the pressure based on the current corresponding relationship and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed, for:

[0095] The fracture density under the pressure is determined using the current corresponding relationship; the fracture aspect ratio under the pressure is determined based on the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed; and the soft porosity under the pressure is determined based on the fracture density and the fracture aspect ratio.

[0096] In some embodiments, the multiple test pressure determination module 43 determines multiple test pressures between the pressure at the location and the minimum pressure, for:

[0097] At set pressure intervals, multiple test pressures between the pressure at the position and the minimum pressure are determined.

[0098] In some embodiments, the soft porosity determination module 44 determines the fracture aspect ratio at the pressure according to the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed, for:

[0099] According to the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed, the minimum initial aspect ratio corresponding to the pressure interval is determined by the following formula:

[0100]

[0101] Among them, α i is the minimum initial aspect ratio, v stiff and E stiffare the Poisson's ratio and Young's modulus when the soft pores are completely closed, respectively, and Δp is the pressure interval;

[0102] Based on the minimum initial aspect ratio corresponding to the pressure interval, the fracture aspect ratio under the pressure is determined by integration and accumulation.

[0103] In some embodiments, the soft porosity determination module 44 determines the soft porosity under the pressure according to the fracture density and the fracture aspect ratio, and is configured to:

[0104] Based on the fracture density and fracture aspect ratio, the soft porosity at this pressure is determined using the following formula:

[0105]

[0106] Where ε is the crack density, α is the crack aspect ratio, and φ c Soft porosity.

[0107] Regarding the apparatus in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0108] Based on the inventive concept of the present invention, an embodiment of the present invention further provides a computer storage medium, wherein the computer storage medium stores computer executable instructions, and when the computer executable instructions are executed by a processor, the method for determining shale soft porosity using gas logging as a constraint is implemented.

[0109] Based on the inventive concept of the present invention, an embodiment of the present invention further provides a server, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the method for determining the soft porosity of shale using the gas logging method as a constraint is implemented.

[0110] Unless otherwise specifically stated, terms such as process, calculate, compute, determine, display, and the like may refer to the actions and / or processes of one or more processing or computing systems, or similar devices, that manipulate and convert data represented as physical (e.g., electronic) quantities within registers or memories of a processing system into other data similarly represented as physical quantities within the memories, registers, or other such information storage, transmission, or display devices of the processing system. Information and signals may be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0111] It should be understood that the specific order or hierarchy of steps in the disclosed processes is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of the present disclosure. The accompanying method claims present elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0112] In the foregoing detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that embodiments of the claimed subject matter require more features than are recited in each claim. On the contrary, as reflected in the appended claims, the invention comprises less than all the features of any individual disclosed embodiment. The appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0113] Those skilled in the art will also appreciate that the various illustrative logic blocks, modules, circuits, and algorithmic steps described in conjunction with the embodiments herein may be implemented as electronic hardware, computer software, or a combination thereof. In order to clearly illustrate the interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps described above are generally described around their functions. Whether such functions are implemented as hardware or software depends on the specific application and the design constraints imposed on the entire system. A skilled person may implement the described functions in an adaptable manner for each specific application, but such implementation decisions should not be interpreted as departing from the scope of protection of this disclosure.

[0114] The steps of the methods or algorithms described in conjunction with the embodiments herein may be directly embodied as hardware, software modules executed by a processor, or a combination thereof. The software module may be located in a RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, register, hard disk, removable disk, CD-ROM, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium may also be an integral part of the processor. The processor and storage medium may be located in an ASIC. The ASIC may be located in a user terminal. Of course, the processor and storage medium may also be present in a user terminal as discrete components.

[0115] For software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described in this application. These software codes can be stored in a memory unit and executed by a processor. The memory unit can be implemented within the processor or external to the processor. In the latter case, it is communicatively coupled to the processor via various means, which are well known in the art.

[0116] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it will be appreciated by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to encompass all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is encompassed in a manner similar to the term "including," as explained in terms of "including," used as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or." The terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

Claims

1. A method for determining shale soft porosity using gas logging as a constraint, characterized in that: include: Based on the experimental data of fracture density and test pressure of multiple shale samples in the shale reservoir, the corresponding relationship between fracture density and test pressure is established; Obtaining a first curve of total porosity versus test time and a second curve of pressure versus test time obtained through a porosity gas testing experiment for a target rock sample in the reservoir, determining a position on the second curve where the slope begins to be less than a set slope threshold, and using the total porosity corresponding to the position as hard porosity; determining a plurality of test pressures between the pressure at the location and the minimum pressure; For each test pressure, the difference between the total porosity and the hard porosity corresponding to the first curve is used as the first soft porosity at that pressure. The second soft porosity at that pressure is determined based on the current corresponding relationship and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed. The current correspondence is corrected until the error between the second soft porosity determined according to the current correspondence and the first soft porosity meets the set error requirement, and an optimized correspondence is obtained, which is used to determine the soft porosity under the set pressure based on the Poisson's ratio and Young's modulus of the rock sample to be tested when the soft pores are completely closed.

2. The method according to claim 1, wherein The establishing of the corresponding relationship between the crack density and the test pressure includes: The corresponding relationship between crack density and test pressure is established as: Where ε is the crack density, ε0 ​​is the initial crack density of the rock sample under zero pressure conditions, p is the test pressure, is the pressure value determined by fitting.

3. The method according to claim 1, wherein Determining the second soft porosity under the pressure based on the current corresponding relationship and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed includes: Determine the crack density at this pressure using the current correspondence; Determine the fracture aspect ratio under the pressure according to the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed; The soft porosity at this pressure is determined based on the fracture density and fracture aspect ratio.

4. The method according to claim 3, wherein Determining a plurality of test pressures between the pressure at the location and the minimum pressure comprises: At set pressure intervals, multiple test pressures between the pressure at the position and the minimum pressure are determined.

5. The method according to claim 4, wherein Determining the fracture aspect ratio under the pressure based on the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed includes: According to the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed, the minimum initial aspect ratio corresponding to the pressure interval is determined by the following formula: Among them, α i is the minimum initial aspect ratio, v stiff and E stiff are the Poisson's ratio and Young's modulus when the soft pores are completely closed, respectively, and Δp is the pressure interval; Based on the minimum initial aspect ratio corresponding to the pressure interval, the fracture aspect ratio under the pressure is determined by integration and accumulation.

6. The method according to claim 3, wherein Determining the soft porosity under the pressure according to the crack density and the crack aspect ratio includes: Based on the fracture density and fracture aspect ratio, the soft porosity at this pressure is determined using the following formula: Where ε is the crack density, α is the crack aspect ratio, and φ c Soft porosity.

7. The method according to any one of claims 1 to 6, characterized in that: The Poisson's ratio and Young's modulus when the soft pores are completely closed are determined based on the longitudinal and transverse wave velocity measurement results when the test pressure is higher than the set pressure.

8. A device for determining the soft porosity of shale using gas logging as a constraint, characterized in that: include: A corresponding relationship establishment module is used to establish a corresponding relationship between fracture density and test pressure based on experimental data pairs of fracture density and test pressure of multiple shale samples in the shale reservoir; a gas logging hard porosity determination module, configured to obtain a first curve showing the variation of total porosity versus test time, obtained through a porosity gas logging experiment, and a second curve showing the variation of pressure versus test time, for a target rock sample in the reservoir, determine a position on the second curve where the slope begins to fall below a set slope threshold, and use the total porosity corresponding to the position as the hard porosity; a plurality of test pressure determination modules for determining a plurality of test pressures between the pressure at the location and a minimum pressure; a soft porosity determination module configured to, for each test pressure, use the difference between the total porosity corresponding to the first curve and the hard porosity as the first soft porosity at the pressure, and determine the second soft porosity at the pressure based on the current correspondence and the Poisson's ratio and Young's modulus of the target rock sample when the soft pores are completely closed; The corresponding relationship optimization module is used to correct the current corresponding relationship until the error between the second soft porosity determined according to the current corresponding relationship and the first soft porosity meets the set error requirement, thereby obtaining an optimized corresponding relationship, which is used to determine the soft porosity under a set pressure based on the Poisson's ratio and Young's modulus of the rock sample to be tested when the soft pores are completely closed.

9. A computer storage medium, characterized in that The computer storage medium stores computer executable instructions, which, when executed by a processor, implement the method for determining shale soft porosity using gas logging as a constraint according to any one of claims 1 to 7.

10. A server, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for determining the soft porosity of shale using a gas logging method as a constraint as claimed in any one of claims 1 to 7 is implemented.

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