Shale oil saturation calculation method, equipment, medium and program product

Abstract

The invention discloses a shale oil saturation calculation method and device, a medium and a program product, and relates to the field of petroleum and natural gas exploration, and the method comprises the steps: obtaining geological parameters of a shale oil layer to be logged; inputting the geological parameters into a pre-constructed water saturation calculation model, and outputting the water saturation of the shale oil layer; the construction process of the water saturation calculation model comprises the following steps: establishing a Simmen equation between the clay resistivity and the clay mass fraction, and a Simmen equation between the stratum resistivity and the sandstone resistivity; establishing Archie equations of the sandstone resistivity, the water saturation, the formation water resistivity and the effective porosity, and constructing a water saturation calculation model for calculating the water saturation in combination with the Simmen equation and the Archie equation; and calculating the oil saturation of the shale oil layer according to the water saturation. The method solves the problem that the calculation precision of the oil saturation of shale oil is reduced due to the fact that the logging interpretation method does not consider the influence of the conductivity of clay on the formation resistivity.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas exploration, and more specifically, to a method, device, medium and program product for calculating shale oil saturation. Background Art

[0002] At present, there are mainly two methods for logging the oil saturation of shale oil: experimental testing and logging interpretation. The experimental determination method is mainly based on downhole core samples, and common ones include nuclear magnetic resonance method and rock pyrolysis method. Nuclear magnetic resonance (NMR) distinguishes oil and water signals through the T2 relaxation spectrum, and combines light hydrocarbon suppression technology to measure the original oil saturation. The advantage is that it can provide pore-scale oil-water distribution information, but it is limited by samples and has high testing costs.

[0003] For the logging interpretation method, the currently widely used method is to establish the relationship between resistivity and oil saturation using Archie's formula, and an interpretation model needs to be established in combination with rock electrical experiment parameters. However, due to the high clay content and complex pore structure of shale, the applicability of the interpretation model is poor. At present, the logging interpretation method does not consider the influence of the conductivity of clay on the formation resistivity, which makes it impossible for the logging interpretation method to accurately describe the relationship between resistivity and water saturation in muddy formations, resulting in a decrease in the calculation accuracy of shale oil saturation. Summary of the Invention

[0004] The purpose of the present invention is to provide a method, device, medium and program product for calculating shale oil saturation. The present invention solves the problem that the logging interpretation method does not consider the influence of the conductivity of clay on the formation resistivity, which makes it impossible for the logging interpretation method to accurately describe the relationship between resistivity and water saturation in muddy formations, resulting in a decrease in the calculation accuracy of shale oil saturation.

[0005] The above technical purpose of the present invention is achieved through the following technical solutions:

[0006] In the first aspect of the present invention, a method for calculating shale oil saturation is provided. The method includes:

[0007] Obtain the geological parameters of the shale oil layer of the well to be measured;

[0008] Input the geological parameters into a pre-constructed water saturation calculation model to output the water saturation of the shale oil layer. The construction process of the water saturation calculation model is as follows: establish the Simandoux equation between clay resistivity, clay mass fraction, formation resistivity and sandstone resistivity; establish Archie's equation between sandstone resistivity, water saturation, formation water resistivity and effective porosity, and combine the Simandoux equation and Archie's equation to construct a water saturation calculation model for calculating water saturation;

[0009] Calculate the oil saturation of the shale oil layer based on the water saturation.

[0010] In one implementation, the geological parameters include shale content mass fraction, effective porosity, shale oil formation water resistivity, shale oil formation resistivity, and clay resistivity.

[0011] In one implementation, the clay mass fraction is calculated based on the shale content mass fraction and the mass fraction of fine sand powder.

[0012] In one implementation, the expression for calculating the clay mass fraction is:

[0013] V sh = V cl + aV fss + b, where V cl is the clay mass fraction, V sh is the shale content mass fraction, a is the formation factor, and b is a constant.

[0014] In one implementation, the expression of the Simandoux equation is:

[0015] where R cl is the clay resistivity, V cl is the clay mass fraction, R t is the formation resistivity, and R sd is the sandstone resistivity.

[0016] In one implementation, the expression of the Archie equation is:

[0017] where is the effective porosity, R w is the formation water resistivity, R sd is the sandstone resistivity, a is the formation factor, and S w is the water saturation.

[0018] In one implementation, the expression of the water saturation calculation model is:

[0019] where R cl is the clay resistivity, V cl is the clay mass fraction, R t is the formation resistivity, R w is the shale oil formation water resistivity, is the effective porosity, S w is the water saturation, a is the normalized weight of the contribution of fine siltstone to the shale content mass fraction, n represents the saturation exponent, and m represents the cementation exponent.

[0020] In a second aspect of the present invention, an electronic device is provided, including a memory and a processor;

[0021] A memory for storing a computer program, the computer program including program instructions;

[0022] A processor for executing the program instructions to cause the electronic device to execute the steps of a method for calculating shale oil saturation provided in the first aspect of the present invention.

[0023] In a third aspect of the present invention, there is provided a computer program product including program instructions, which when run on an electronic device, causes the electronic device to execute the steps of a method for calculating shale oil saturation provided in the first aspect of the present invention.

[0024] In a fourth aspect of the present invention, there is provided a computer-readable storage medium, the computer-readable storage medium including a computer program, which when executed by one or more processors, implements a method for calculating shale oil saturation provided in the first aspect of the present invention.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention can accurately calculate the oil saturation of shale oil reservoirs. The present invention takes into account the influence of clay minerals and is applicable to shale reservoirs rich in clay. By well logging curves and core analysis, each geological parameter in the calculation model can be determined, thereby improving the accuracy of the oil saturation calculated by the calculation model. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0028] Figure 1 is a schematic flow chart of a method for calculating shale oil saturation provided by an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of a shale oil parallel model provided by an embodiment of the present invention;

[0030] Figure 3 is a comparison chart of the calculation results of the calculation method provided by the present invention and the prior art provided by an embodiment of the present invention;

[0031] Figure 4 is a comparison chart of the oil saturation of two calculation methods provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0033] It should be noted that the term "including" or "may include" that can be used in various embodiments of the present application indicates the presence of the claimed functions, operations, or elements, and does not limit the addition of one or more functions, operations, or elements. In addition, as used in various embodiments of the present application, the terms "including", "having", and their cognates are only intended to represent specific features, numbers, steps, operations, elements, components, or combinations of the foregoing items, and should not be construed as precluding the existence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing items.

[0034] It should be understood that terms such as "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0035] First, the calculation process of the water saturation of shale oil in the current logging interpretation method is introduced as follows:

[0036] 1. Calculate the shale content: In the formula: Vsh is the shale content of the formation; GCUR is the Hilchie index, a constant used in calculating the shale content (3.7 for Tertiary formations and 2 for older formations); Ish is the relative value of the natural gamma of the target layer, also known as the shale content index, dimensionless; GR, GRmax, and GRmin are the natural gamma value, natural gamma maximum value, and natural gamma minimum value of the target layer.

[0037] 2. Relationship between the resistivity of the rock and the shale mass fraction: In the formula: Rt is the formation resistivity, Ω·m; Vsh is the shale mass fraction, 0 - 1; Rs is the resistivity of the oil and gas-bearing clay and fine siltstone part, Ω·m; Rsd is the resistivity of the pure sandstone part, Ω·m.

[0038] For the pure sandstone part, its porosity:

[0039] According to Archie's formula: In the formula: S w is the water saturation, 0 - 1; φe is the effective porosity, ranging from 0 to 1; φ sd is the porosity of the clean sandstone part; Rw is the resistivity of formation water.

[0040] 3. Calculate the resistivity of formation water: The Arps formula is an empirical formula commonly used to calculate the resistivity of formation water: where: Rw is the resistivity of formation water (Ω·m); C is the salinity of formation water (ppm or mg / L); T is the formation temperature (°C).

[0041] 4. It is also considered that the shale part has a certain property of storing oil and gas, and it is approximately considered that the water saturation in the effective porosity of this part of fine lithology is equal to the water saturation in the porosity of pure rock, and the saturation exponent n = 1. Therefore, we have: In the formula: Rsh is the resistivity of completely water-bearing shale, Ω·m.

[0042] By combining equations (5) and (7), the calculation method of water saturation can be obtained:

[0043] Based on the above calculation process, it can be seen that the logging interpretation method provided by the prior art does not consider the influence of the conductivity of clay on the formation resistivity, which makes the logging interpretation method unable to accurately describe the relationship between resistivity and water saturation in shale formations, resulting in a decrease in the calculation accuracy of oil saturation in shale oil.

[0044] Therefore, in a method for calculating oil saturation in shale provided in this embodiment, the influence of clay minerals is considered, which is applicable to shale reservoirs rich in clay. Through logging curves and core analysis, each geological parameter in the calculation model can be determined, thereby improving the accuracy of the oil saturation calculated by the calculation model.

[0045] Please refer to Figure 1 , Figure 1 , which is a schematic flow chart of a method for calculating oil saturation in shale provided by an embodiment of the present invention. As Figure 1 shown, the method includes:

[0046] S101. Obtain the geological parameters of the shale oil layer of the well to be measured.

[0047] In this embodiment, the geological parameters can be obtained through the logging curves and core analysis of the well to be measured, which are conventional technical means in the technical field and will not be elaborated in detail in this embodiment. For example, the formation resistivity (R t ): It represents the resistivity of formation rocks and is a parameter directly measured by logging curves, reflecting the conductivity of fluids in the formation.

[0048] The clay volume fraction (V cl):It represents the volume fraction of clay minerals in the formation, obtained through core analysis or logging interpretation, and reflects the influence of clay minerals on the formation resistivity.

[0049] Resistivity of clay (R cl ):It represents the resistivity of clay minerals, usually determined through experiments, and reflects the conductivity of clay minerals.

[0050] Water saturation (S w ):It represents the proportion of the volume of water in the formation to the pore volume and is a key parameter for calculating oil saturation.

[0051] Porosity (φ): It represents the proportion of the volume of pores in the formation to the total volume, obtained through logging curves or core analysis, and reflects the reservoir capacity of the formation.

[0052] Cementation exponent (m): It represents the degree of cementation between rock particles, usually determined through experiments, and reflects the structural characteristics of the rock.

[0053] Formation factor (a): It represents the relationship between the conductivity of fluids in the formation and the rock structure, usually determined through experiments.

[0054] Resistivity of formation water (R w ):It represents the resistivity of water in the formation, usually determined through experiments, and reflects the conductivity of formation water.

[0055] Saturation exponent (n): It represents the relationship between water saturation and resistivity, usually determined through experiments, and reflects the distribution characteristics of fluids in the formation.

[0056] Secondly, the geological parameters obtained in this embodiment include shale volume fraction, effective porosity, resistivity of shale oil formation water, resistivity of shale oil formation, and resistivity of clay.

[0057] Since the particle sizes of fine silt and clay are different, it is considered here that the shale content obtained from logging interpretation is the weighted sum of the volumes of clay and fine silt in the formation. Therefore, the weighted calculation formula for the shale content of the rock is V sh =V cl +aV fss +b, where V cl is the clay mass fraction, V sh is the shale mass fraction, a is the formation factor, and b is a constant. Based on this weighted calculation formula, the clay content fraction can be calculated, or it can also be called the clay volume fraction. It should be understood that a is the normalized weight of the contribution of fine silt to the shale mass fraction; b is a constant, that is, the contribution of other particle size components in the rock to the logging response value of the shale mass fraction.

[0058] S102. Input the geological parameters into a pre-constructed water saturation calculation model to output the water saturation of the shale oil layer. The construction process of the water saturation calculation model is as follows: establish the Simandoux equation between clay resistivity, clay mass fraction, formation resistivity, and sandstone resistivity; establish the Archie equation between sandstone resistivity, water saturation, formation water resistivity, and effective porosity, and combine the Simandoux equation and the Archie equation to construct a water saturation calculation model for calculating water saturation.

[0059] In this embodiment, from the mechanism of cation exchange, it can be known that the additional conductivity of shale is mainly caused by the cation exchange of clay, while the cation exchange ability of fine silt is limited. Therefore, for shale with different silt indices, there are significant differences in additional conductivity. By optimizing the parallel conductivity model of "pure rock" and "shale" into a parallel model of "pore fluid free ions" and "clay cation exchange", as Figure 2 shown. That is, shale is incorporated into the rock skeleton, and it is considered that the calculated S w is the total water saturation in the pores of the rock skeleton composed of sand grains of different sizes within the detection range of the logging instrument, and it is considered that the micropores with almost no contribution to the effective pore volume between extremely fine clay particles do not have the ability to store and permeate oil and gas, that is, S w = 1. Therefore, the Simandoux equation is: where, R cl is the clay resistivity, V cl is the clay mass fraction, R t is the formation resistivity, R sd is the sandstone resistivity.

[0060] Shale (including fine silt) has various distribution forms (laminated, dispersed, structural shale). Different clay minerals basically exist in a dispersed form in the pore walls (chlorite, illite) and pore spaces (illite, kaolinite) in the reservoir. Therefore, consider using the dispersed shale sandstone model to improve the Simandoux formula, and consider that shale sandstone is composed of "dispersed clay" and "sandstone skeleton and formation water containing free ions in the skeleton" in parallel conductivity. For the part of free ion conductivity in the pore fluid, its Archie equation is: where, is the effective porosity, R w is the formation water resistivity, R sd is the sandstone resistivity, a is the formation factor, S w is the water saturation.

[0061] Combining the Simandoux equation and the Archie equation provided in this embodiment, an optimized water saturation calculation model for calculating water saturation can be obtained, that is: where, R cl is the clay resistivity, Vcl is the clay mass fraction, R t is the formation resistivity, R w is the resistivity of shale oil formation water, is the effective porosity, S w is the water saturation, a is the normalized weight of the contribution of siltstone to the shale mass fraction, n represents the saturation exponent, and m represents the cementation exponent.

[0062] As Figure 3 shown, it is the difference in the calculation results between the improved Simandoux formula and the conventional Simandoux formula in terms of water saturation.

[0063] It should be understood that R cl readings should be taken at the stable pure shale with the highest possible natural gamma value in the entire well section, or obtained through clay mineral analysis data.

[0064] S103, the oil saturation of the shale oil formation is calculated based on the water saturation. It should be noted that the oil saturation calculated in the present invention can be applied to the prediction of the oil saturation of continental shale oil. Secondly, it also has certain reference significance for the prediction of the oil saturation of shale oil in areas with complex tectonic evolution.

[0065] In this embodiment, since the water saturation has been calculated, the calculation method of the oil saturation is as follows:

[0066] S o = 1 - S w ; where S o is the oil saturation of the shale oil. As Figure 4 shown, using the formula S o = 1 - S w to calculate the oil saturation of the shale oil reservoir and compare the results of the two methods, it can be seen that the oil saturation obtained by the calculation method provided in this embodiment is closer to the measured value.

[0067] This application embodiment also provides an electronic device. Among them, the electronic device includes a processor, a memory, a communication interface, and at least one communication bus for connecting the processor, the memory, and the communication interface. The memory includes but is not limited to a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (PROM), or a portable read-only memory (CD-ROM), and this memory is used for relevant instructions and data.

[0068] The communication interface is used to receive and send data. The processor can be one or more CPUs. When the processor is a single CPU, the CPU can be a single-core CPU or a multi-core CPU. The processor in the electronic device is used to read one or more programs stored in the memory and perform the following operations: obtain the geological parameters of the shale oil layer of the well to be measured; input the geological parameters into a pre-constructed water saturation calculation model and output the water saturation of the shale oil layer; wherein, the construction process of the water saturation calculation model is: establish the Simandoux equation between the clay resistivity, clay mass fraction, formation resistivity and sandstone resistivity; establish the Archie equation between the sandstone resistivity, water saturation, formation water resistivity and effective porosity, and combine the Simandoux equation and the Archie equation to construct a water saturation calculation model for calculating the water saturation; calculate the oil saturation of the shale oil layer according to the water saturation.

[0069] It should be noted that the specific implementation of each operation can be the corresponding description of the method embodiment shown above Figure 1 The electronic device can be used to execute a shale oil saturation calculation method in the method embodiment of the present application as described above, and will not be elaborated here specifically.

[0070] The embodiment of the present application also provides a computer-readable storage medium. The computer-readable storage medium is a memory device in a computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and this storage space stores the operating system of the terminal. And, one or more instructions suitable for being loaded and executed by the processor are also stored in this storage space. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. One or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the shale oil saturation calculation method in the above embodiment. Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0071] An embodiment of the present application also provides a computer program product including program instructions. The computer program product can be software or a program product including program instructions that can run on a computing device or be stored in any available medium. When the computer program product runs on at least one electronic device, at least one electronic device is caused to execute a method for calculating shale oil saturation.

[0072] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calculating shale oil saturation, characterized in that the method Including: Obtaining geological parameters of the shale oil layer of the well to be measured; Inputting the geological parameters into a pre-constructed water saturation calculation model to output the water saturation of the shale oil layer; wherein, the construction process of the water saturation calculation model is as follows: establishing the Simandoux equation between the clay resistivity, clay mass fraction, formation resistivity and sandstone resistivity; establishing the Archie equation between the sandstone resistivity, water saturation, formation water resistivity and effective porosity, and combining the Simandoux equation and the Archie equation to construct a water saturation calculation model for calculating the water saturation; Calculating the oil saturation of the shale oil layer according to the water saturation.

2. The method according to claim 1, wherein The geological parameters include shale mass fraction, effective porosity, water resistivity of the shale oil layer, resistivity of the shale oil layer and clay resistivity.

3. The method according to claim 2, wherein The clay mass fraction is calculated according to the shale mass fraction and the mass fraction of fine sand powder.

4. The method according to claim 3, characterized in that, The expression for calculating the clay mass fraction is: V sh = V cl + aV fss + b, where V cl is the clay mass fraction, V sh is the shale mass fraction, a is the formation factor, and b is a constant.

5. The method according to claim 1, characterized in that, The expression of the Simandoux equation is: Among them, R cl is the resistivity of clay, V cl is the mass fraction of clay, R t is the formation resistivity, R sd is the resistivity of sandstone.

6. The method according to claim 5, wherein The expression of the Archie equation is: Among them, is the effective porosity, R w is the resistivity of formation water, R sd is the resistivity of sandstone, a is the formation factor, S w is the water saturation.

7. The method according to claim 6, wherein The expression of the water saturation calculation model is: Among them, R cl is the resistivity of clay, V cl is the mass fraction of clay, R t is the formation resistivity, R w is the resistivity of shale oil formation water, is the effective porosity, S w is the water saturation, a is the normalized weight of the contribution of siltstone to the shale mass fraction, n represents the saturation exponent, and m represents the cementation exponent.

8. An electronic device, characterized in that, Including a memory and a processor; The memory is used to store a computer program, and the computer program includes program instructions; The processor is used to execute the program instructions so that the electronic device executes the steps of a method for calculating shale oil saturation according to any one of claims 1 to 7.

9. A computer program product comprising program instructions, characterized in that, When the program instructions are run by the electronic device, the electronic device is caused to execute the steps of a method for calculating shale oil saturation according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a computer program, and when the computer program is executed by one or more processors, a method for calculating shale oil saturation according to any one of claims 1 to 7 is implemented.

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