Shale oil reservoir oil saturation calculation method and related equipment
By combining continuous logging and nuclear magnetic resonance logging technologies, a calculation model for oil saturation suitable for shale oil reservoirs was established, which solved the calculation error problem caused by clay content and achieved higher accuracy reservoir evaluation.
Patent Information
- Application Number
- CN202411034062.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-30
- Publication Date
- 2026-01-30
Smart Images
Figure CN121432575A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of oil and gas exploration technology, specifically a method for calculating the oil saturation of shale oil reservoirs and related equipment. Background Technology
[0002] Oil saturation is a crucial parameter in shale oil reservoir evaluation and a key indicator in shale oil reservoir reserve calculation. However, the complex lithology, high heterogeneity, high clay content, and complex oil-water occurrence states of shale oil reservoirs limit the accurate evaluation of oil saturation, resulting in calculations that fail to meet current national reserve standards and posing significant challenges to shale oil reservoir exploration and development. Therefore, accurate calculation of shale oil saturation is fundamental for reserve calculation, sweet spot evaluation, and production capacity assessment. Currently, methods for calculating shale oil reservoir oil saturation are mainly based on pure sandstone conductivity models, incorporating the influence of clay content into the Archie method, and have developed many classic saturation models. Major international oil companies have employed different water saturation equations in shale oil and gas well logging evaluation, including Weatherford's Waxman-Smits equation and Schlumberger's Simandoux equation. Boyce and Carr (2009) evaluated the water saturation of the Marcellus Shale using the Simandoux model. Glorisso and Rattia (2012) recommended using the Simandoux model. Akbar and Musu (2017) also applied the Simandoux model to the Baong Shale in the North Sumatra Basin. Qing (2012) suggested using the shale-corrected normalized Wax-Simits formula to calculate water saturation, considering the high clay content in the shale. Wu et al. (2013) used a full shale model, considering shale content and porosity, to calculate the saturation of the Dongyuemiao Formation shale reservoir.
[0003] The above methods mainly consider the overall or microscopic influence of clay content on shale resistivity, and the calculated results generally differ from the actual saturation of shale oil reservoirs. Summary of the Invention
[0004] The purpose of this invention is to provide a method and related equipment for calculating the oil saturation of shale oil reservoirs, which solves the problem that the calculation results generally differ from the actual saturation of shale oil reservoirs when considering the overall or microscopic influence of clay content on the resistivity of shale.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] A method for calculating the oil saturation of shale oil reservoirs, comprising:
[0007] Obtain continuous logging density curves and neutron curves;
[0008] Calculation of clay content based on continuous logging density curves and neutron curves;
[0009] Determine the lateral relaxation start time for different porosities in nuclear magnetic resonance logging;
[0010] Establish the Simondu and Archie models for nuclear magnetic resonance logging, and obtain water saturation models under different reservoir oil and water occurrence states based on the Simondu and Archie models;
[0011] The reservoir oil and water occurrence state is detected, and different water saturation models are selected according to the reservoir oil and water occurrence state. The water saturation is obtained according to the clay content and the lateral relaxation start time.
[0012] Calculate oil saturation based on water saturation.
[0013] Preferably, the step of calculating the clay content based on continuous logging density curves and neutron curves specifically includes:
[0014]
[0015] V sh The mud content, φ Nsh The neutron porosity of mudstone, φ Dsh Mudstone density and porosity, φ D To calculate porosity for density, φ N Calculate porosity for neutrons.
[0016] Preferably, the steps for determining the lateral relaxation start time for different porosities using nuclear magnetic resonance logging are as follows:
[0017] In designing a mercury intrusion porosimetry capillary pressure analysis experiment, pores with a diameter greater than 50 nm are defined as macropores, and those less than 50 nm are defined as micropores.
[0018] Based on the capillary pressure curve analysis report of mercury intrusion porosimetry, the porosity corresponding to a pore diameter of 50 nm is calculated using the following formula:
[0019] por=S hg ×phit×0.01
[0020] Where por is the porosity corresponding to 50 nm, and S hg φt represents the mercury saturation level corresponding to 50 nm, and phit represents the total porosity measured experimentally.
[0021] The porosity corresponding to 50nm is used to determine the large and small porosity in nuclear magnetic resonance (NMR) logging. The specific steps are as follows: First, calculate the free fluid porosity using different NMR transverse relaxation times. Then, calculate the absolute error between the porosity and the porosity corresponding to 50nm, determine the transverse relaxation time Tc1 at which the minimum absolute error is obtained, and obtain the NMR T2 cutoff values for large and small porosity. The calculation formulas for large and small porosity are as follows:
[0022]
[0023] Where, φ l For macropore porosity, φ s S is the porosity of the small pore, S(T2) is the spectral area of T2, and T2 is the relaxation time; T c 1 represents the T2 cutoff value for large and small porosity.
[0024] Preferably, the Siemens model is:
[0025]
[0026] Among them, R t R is the deep resistivity logging value. sh The resistivity value of pure mudstone, S w R represents the water saturation value. sd This represents the resistivity value of the rock skeleton.
[0027] Preferably, pores with a diameter greater than 50 nm are defined as macropores, and those less than 50 nm are defined as micropores. The reservoir oil-water occurrence states include the presence of two-phase fluid in micropores, the presence of two-phase fluid in macropores, and the presence of two-phase fluid in both macropores and micropores.
[0028] The water saturation model for the presence of two-phase fluid in the small hole is as follows:
[0029]
[0030] Among them, R t Rw is the deep resistivity logging value, V is the formation water resistivity, and V is the deep resistivity logging value. sh For mud content, S w R represents the water saturation value. sh Here, n is the resistivity value of pure mudstone, m is the saturation index, and φ is the cementation index. s For small pore porosity, φ l denoted as macropore porosity, and 'a' as lithology coefficient.
[0031] Preferably, the water saturation model for macroporous systems with two-phase fluid is as follows:
[0032]
[0033] Preferably, the water saturation model when both large and small pores contain two-phase fluids is as follows:
[0034]
[0035] A system for calculating the oil saturation of shale oil reservoirs, comprising:
[0036] Acquisition module: Acquires continuous logging density curves and neutron curves.
[0037] The clay content calculation module is used to calculate clay content based on continuous logging density curves and neutron curves.
[0038] Relaxation start time calculation module: used to determine the lateral relaxation start time for different porosities in nuclear magnetic resonance logging;
[0039] Water saturation model acquisition module: used to establish the Simondu and Archie models for nuclear magnetic resonance logging, and to obtain water saturation models under different reservoir oil and water occurrence states based on the Simondu and Archie models;
[0040] Water saturation acquisition module: used to detect the oil and water occurrence state of the reservoir, select different water saturation models according to the oil and water occurrence state of the reservoir, and obtain water saturation based on the clay content and the lateral relaxation start time;
[0041] Oil saturation acquisition module: used to calculate oil saturation based on water saturation.
[0042] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of a method for calculating the oil saturation of a shale oil reservoir.
[0043] A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of a method for calculating the oil saturation of shale oil reservoirs. Compared with existing technologies, this invention has the following advantages: This invention provides a method for calculating the oil saturation of shale oil reservoirs. Compared with traditional oil saturation models, it fully considers the characteristics of high clay content and complex oil-water occurrence states in shale reservoirs. It can select different conductivity models according to different oil-water occurrence states of shale oil reservoirs to establish a suitable oil saturation calculation model. The calculation has a small absolute error and conforms to reserve calculation standards. This method is a key technology in reserve calculation, geological sweet spot evaluation, and production capacity evaluation processes, improving the current industry accuracy of shale oil reservoir oil saturation calculation and playing an irreplaceable role in shale oil reserve discovery and efficient development. Attached Figure Description
[0044] Figure 1This is a flowchart of a method for calculating the oil saturation of shale reservoirs according to the present invention;
[0045] Figure 2 This is a flowchart illustrating a method for calculating the oil saturation of shale reservoirs according to an embodiment of the present invention.
[0046] Figure 3 This is a scatter plot showing the average absolute error of porosity calculated at various NMR starting times for a 50 nm diameter porosity in the mercury intrusion porosimetry experiment of this invention.
[0047] Figure 4 This is a diagram illustrating the calculation effect of oil saturation using similar technologies of this invention.
[0048] Figure 5 This is a block diagram of a shale reservoir oil saturation calculation system according to the present invention. Detailed Implementation
[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0050] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0051] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0052] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0053] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.
[0054] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.
[0055] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.
[0056] like Figure 1 As shown, this invention provides a method for calculating the oil saturation of shale oil reservoirs, including:
[0057] S101 acquires continuous logging density and neutron curves.
[0058] S102 calculates clay content based on continuous logging density curves and neutron curves;
[0059] S103 determines the nuclear magnetic resonance logging and calculates the lateral relaxation start time for different porosities;
[0060] S104 establishes the Simondu and Archie models for nuclear magnetic resonance logging, and obtains water saturation models under different reservoir oil and water occurrence states based on the Simondu and Archie models.
[0061] S105 detects the oil and water occurrence state of the reservoir, selects different water saturation models according to the oil and water occurrence state of the reservoir, and obtains the water saturation based on the clay content and the lateral relaxation start time.
[0062] S106 calculates the oil saturation based on the water saturation.
[0063] The detailed steps are as follows:
[0064] The clay content is calculated based on continuous logging density curves and neutron curves, using the following specific formula:
[0065]
[0066] Where, φ D Porosity is calculated based on density, where DEN is the logging density value, and ρma ρ is the skeleton density. f For fluid density, φ N Porosity is calculated using neutrons, CNL is the logging neutron value, and H... ma The hydrogen nucleus is the framework nucleus, V sh The mud content, φ Nsh The neutron porosity of mudstone, φ Dsh Mudstone density and porosity.
[0067] The calculation time for lateral relaxation of large and small porosity was determined by analyzing the capillary pressure curve of mercury intrusion porosimetry.
[0068] First, an experimental design for capillary pressure analysis using mercury intrusion porosimetry was conducted. In terms of microscopic pore size, macropores are generally defined as pores with a diameter greater than 50 nm, while those smaller than 50 nm are considered micropores. Second, based on the mercury intrusion porosimetry capillary pressure curve analysis report, the porosity corresponding to a pore diameter of 50 nm was determined using the following formula:
[0069] por=S hg ×phit×0.01 (4)
[0070] Where por represents the porosity at 50 nm, % and S hg The mercury saturation level corresponding to 50 nm is %, and phit is the experimentally measured total porosity, %.
[0071] To determine the porosity corresponding to 50nm using nuclear magnetic resonance (NMR) logging, the specific steps are as follows: First, calculate the free fluid porosity using different NMR transverse relaxation times. Then, calculate the absolute error between the porosity and the porosity corresponding to 50nm. Determine the transverse relaxation time Tc1 at which the minimum absolute error is achieved. This yields the NMR T2 cutoff values for both large and small porosity. The formulas for calculating large and small porosity are as follows:
[0072]
[0073] Where, φ l For macropore porosity, φ s S is the porosity of the small pore, S(T2) is the spectral area of T2, T2 is the relaxation time, ms; T c 1 represents the T2 cutoff value for large and small porosity, in milliseconds.
[0074] A conductivity model for a dual-porosity medium based on clay-added conductivity correction is established. First, a parallel conductivity model of pores and clay is obtained according to the Siemens model. Equations 6 and 7 are combined to obtain Equation 8.
[0075]
[0076]
[0077] Among them, R t Rsh is the resistivity value from deep resistivity logging, in ohms·m. Rsh is the resistivity value of pure mudstone, in ohms·m. w R represents the water saturation value. sd denoted as the resistivity value of the rock skeleton, in ohm·m.
[0078] Secondly, in the conductive part of the porous medium, based on Archie's formulas 9 and 10, a conductive model of a dual-porosity medium is established, and its formula is as follows:
[0079]
[0080] Where a is the lithology coefficient, b is the coefficient, m is the cementation index, and n is the saturation index. R0 is the rock resistivity at 100% saturated formation water, in ohms·m. w ρ represents the resistivity of formation water, in ohm·m.
[0081] Based on the characteristics of the oil-water occurrence state in the reservoir, a corresponding conductivity model is established. When two-phase fluid exists in the pore, the formula is as follows:
[0082]
[0083] When a two-phase fluid exists in a macropore, the formula is as follows:
[0084]
[0085] When two-phase fluids exist in both large and small pores, the formula is as follows:
[0086]
[0087] Step 4: Select different saturation models based on the reservoir's oil-water occurrence state. When two-phase fluids exist in the pores, combining equations 8 and 11, we obtain the following formula:
[0088]
[0089] When a two-phase fluid exists in a macropore, combining equations 8 and 12, we obtain the following equation:
[0090]
[0091] When two-phase fluids exist in both the large and small orifices, combining equations 8 and 13, we obtain the following equation:
[0092]
[0093] Step 5: Calculate the reservoir oil saturation, which is given by the following formula:
[0094] S O=1-S W (17)
[0095] Among them, S o Oil saturation, %.
[0096] Example:
[0097] Taking experimental and logging data from a certain well as an example, the technical solution of the present invention is illustrated below. A brief flowchart of the embodiment is as follows: Figure 2 The specific steps are as follows:
[0098] (1) Obtain conventional logging data, and use the neutron curve and density curve in conventional logging to determine the clay content according to Formula 1, Formula 2 and Formula 3.
[0099] (2) Obtain the capillary pressure curve experimental data of mercury intrusion method, extract the mercury saturation corresponding to a diameter of 50 nm, and calculate the corresponding porosity using formula 4.
[0100] (3) Obtain nuclear magnetic resonance (NMR) logging data, and calculate the free fluid porosity using different NMR lateral relaxation start times (e.g., 6ms, 8ms, 10ms, 12ms, 14ms). Then, calculate the absolute error of the porosity corresponding to a 50nm diameter. Determine the lateral relaxation start time used for the porosity corresponding to the minimum error, and use it as the lateral relaxation cutoff value for large and small pores. Figure 3 The scatter plot of the average absolute error of porosity calculated for a 50 nm diameter porosity in mercury intrusion porosimetry experiments with respect to various NMR start times shows that the error is minimized when Tc1 = 10 ms. Therefore, Tc1 is determined to be 10 ms.
[0101] (4) Using nuclear magnetic resonance T2 spectrum, calculate macropore porosity and micropore porosity according to formulas 5 and 6 respectively.
[0102] (5) Based on formulas 8, 11, 12 and 13, establish three conductivity models for different oil-water occurrence states, namely formulas 14, 15 and 16.
[0103] (6) The oil and water occurrence state of the reservoir is determined by using the self-wetting and two-dimensional nuclear magnetic resonance experiments. For example, in this embodiment, the oil and water content in both large and small pores is determined by the self-wetting and two-dimensional nuclear magnetic resonance experiments. Water is mainly found in the small pores, and there are two-phase fluids in the small pores. The water saturation is calculated using formula 14.
[0104] (7) Calculate the oil saturation using Formula 17. Figure 4The diagram shows the effect of calculating oil saturation by the present invention and similar technologies. It can be seen that the oil saturation calculated by the present invention is more consistent with the analyzed oil saturation. Through error analysis (as shown in Table 1 below), it can be seen that the average absolute error of the oil saturation calculated by the present invention is 3.9%.
[0105] Table 1 Error Analysis Table
[0106]
[0107] like Figure 5 As shown, the present invention also provides a system for calculating the oil saturation of shale oil reservoirs, comprising:
[0108] Acquisition module: Acquires continuous logging density curves and neutron curves.
[0109] The clay content calculation module is used to calculate clay content based on continuous logging density curves and neutron curves.
[0110] Relaxation start time calculation module: used to determine the lateral relaxation start time for different porosities in nuclear magnetic resonance logging;
[0111] Water saturation model acquisition module: used to establish the Simondu and Archie models for nuclear magnetic resonance logging, and to obtain water saturation models under different reservoir oil and water occurrence states based on the Simondu and Archie models;
[0112] Water saturation acquisition module: used to detect the oil and water occurrence state of the reservoir, select different water saturation models according to the oil and water occurrence state of the reservoir, and obtain water saturation based on the clay content and the lateral relaxation start time;
[0113] Oil saturation acquisition module: used to calculate oil saturation based on water saturation.
[0114] Preferably, the step of calculating the clay content based on continuous logging density curves and neutron curves specifically includes:
[0115]
[0116] V sh The mud content, φ Nsh The neutron porosity of mudstone, φ Dsh Mudstone density and porosity, φ D To calculate porosity for density, φ N Calculate porosity for neutrons.
[0117] The specific steps for determining the lateral relaxation start time for different porosities in nuclear magnetic resonance logging are as follows:
[0118] In designing a mercury intrusion porosimetry capillary pressure analysis experiment, pores with a diameter greater than 50 nm are defined as macropores, and those less than 50 nm are defined as micropores.
[0119] Based on the capillary pressure curve analysis report of mercury intrusion porosimetry, the porosity corresponding to a pore diameter of 50 nm is calculated using the following formula:
[0120] por=S hg ×phit×0.01
[0121] Where por is the porosity corresponding to 50 nm, and S hg φt represents the mercury saturation level corresponding to 50 nm, and phit represents the total porosity measured experimentally.
[0122] The porosity corresponding to 50nm is used to determine the large and small porosity in nuclear magnetic resonance (NMR) logging. The specific steps are as follows: First, calculate the free fluid porosity using different NMR transverse relaxation times. Then, calculate the absolute error between the porosity and the porosity corresponding to 50nm, determine the transverse relaxation time Tc1 at which the minimum absolute error is obtained, and obtain the NMR T2 cutoff values for large and small porosity. The calculation formulas for large and small porosity are as follows:
[0123]
[0124] Where, φ l For macropore porosity, φ s S is the porosity of the small pore, S(T2) is the spectral area of T2, and T2 is the relaxation time; T c 1 represents the T2 cutoff value for large and small porosity.
[0125] The Simondu model is:
[0126]
[0127] Among them, R t R is the deep resistivity logging value. sh The resistivity value of pure mudstone, S w R represents the water saturation value. sd This represents the resistivity value of the rock skeleton.
[0128] Pores with a diameter greater than 50 nm are defined as macropores, and those less than 50 nm are defined as micropores. The reservoir oil-water occurrence states include the presence of two-phase fluid in micropores, the presence of two-phase fluid in macropores, and the presence of two-phase fluid in both macropores and micropores.
[0129] The water saturation model for the presence of two-phase fluid in the small hole is as follows:
[0130]
[0131] Among them, R tV is the deep resistivity logging value. sh For mud content, S w R represents the water saturation value. sh Here, n is the resistivity value of pure mudstone, m is the saturation index, and φ is the cementation index. s For small pore porosity, φ l denoted as macropore porosity, and 'a' as lithology coefficient.
[0132] The water saturation model for macroporous two-phase fluids is as follows:
[0133]
[0134] The water saturation model for two-phase fluids present in both large and small pores is as follows:
[0135]
[0136] An embodiment of the present invention provides a terminal device. This terminal device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the various method embodiments described above. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the various device embodiments described above.
[0137] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.
[0138] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.
[0139] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.
[0140] The memory can be used to store the computer program and / or module. The processor implements various functions of the terminal device by running or executing the computer program and / or module stored in the memory and calling the data stored in the memory.
[0141] If the modules / units integrated into the terminal device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.
[0142] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art, guided by the specification, can make many other modifications without departing from the scope of the claims of the present invention, and all of these modifications are within the scope of protection of the present invention.
Claims
1. A method for calculating oil saturation of a shale oil reservoir, characterized by, The method comprises the following steps: obtaining continuous logging density curve and neutron curve; calculating shale content based on the continuous logging density curve and the neutron curve; determining nuclear magnetic resonance logging, and calculating transverse relaxation initial time of different porosities; establishing a SIT model and an Archie model of the nuclear magnetic resonance logging, and obtaining a water saturation model under different oil-water occurrence states of the reservoir based on the SIT model and the Archie model; detecting the oil-water occurrence state of the reservoir, selecting different water saturation models according to the oil-water occurrence state of the reservoir, and obtaining water saturation according to the shale content and the transverse relaxation initial time; calculating oil saturation according to the water saturation.
2. The method of claim 1, wherein, The step of calculating shale content based on the continuous logging density curve and the neutron curve specifically comprises the following steps: V sh φmud Nsh φmud Dsh φmud D φmud N φmud 3. The method of claim 1, wherein, The step of determining nuclear magnetic resonance logging and calculating transverse relaxation initial time of different porosities specifically comprises the following steps: designing a mercury injection capillary pressure analysis experiment, defining pores with a pore diameter greater than 50 nm as large pores and pores with a pore diameter less than 50 nm as small pores in the micro-pore size, obtaining the porosity corresponding to the pore diameter of 50 nm according to the mercury injection capillary pressure curve analysis report, and the specific formula is as follows por = S hg x phit x 0.01 wherein por is the porosity size corresponding to 50 nm, S hg is the mercury intrusion saturation size corresponding to 50 nm, and phit is the total porosity measured experimentally; determining the large and small porosities of the nuclear magnetic resonance logging by using the porosity corresponding to the pore diameter of 50 nm, and the specific steps are as follows: first, calculating the free fluid porosity by using different nuclear magnetic transverse relaxation times, then calculating the absolute error of the porosity corresponding to the pore diameter of 50 nm, determining the transverse relaxation time Tc1 when the minimum absolute error is obtained, and obtaining the nuclear magnetic T2 cutoff value of the large and small porosities, and the calculation formula of the large and small porosities is as follows: where φ l is the macroporosity, φ s is the mesoporosity, S(T2) is the T2 spectral area, T2 is the relaxation time; T c 1 is the T2 cutoff value for macroporosity and mesoporosity.
4. The method of claim 1, wherein, The SIT model is as follows: where R t is the deep resistivity log value, R sh is the pure shale resistivity value, S w is the water saturation value, R sd is the rock matrix resistivity value, and V sh is the shale content.
5. The method of claim 1, wherein, defining pores with a pore diameter greater than 50 nm as large pores and pores with a pore diameter less than 50 nm as small pores, and the oil-water occurrence state of the reservoir includes two-phase fluid in small pores, two-phase fluid in large pores, and two-phase fluid in both large and small pores; the water saturation model when two-phase fluid exists in small pores is as follows: wherein R t is the deep resistivity log value, Rw is the formation water resistivity, V sh is the shale content, S w is the water saturation value, R sh is the pure shale resistivity value, n is the saturation exponent, m is the cementation exponent, φ s is the small pore porosity, φ l is the large pore porosity, and a is the lithology coefficient.
6. The method of claim 5, wherein, the water saturation model when two-phase fluid exists in large pores is as follows:
7. The method of claim 6, wherein, the water saturation model when two-phase fluid exists in both large and small pores is as follows:
8. A shale oil reservoir oil saturation calculation system characterized by, The method comprises the following steps: an obtaining module: used for obtaining continuous logging density curve and neutron curve; a shale content calculation module: used for calculating shale content based on the continuous logging density curve and the neutron curve; a relaxation initial time calculation module: used for determining nuclear magnetic resonance logging, and calculating transverse relaxation initial time of different porosities; a water saturation model obtaining module: used for establishing a SIT model and an Archie model of the nuclear magnetic resonance logging, and obtaining a water saturation model under different oil-water occurrence states of the reservoir based on the SIT model and the Archie model; a water saturation obtaining module: used for detecting the oil-water occurrence state of the reservoir, selecting different water saturation models according to the oil-water occurrence state of the reservoir, and obtaining water saturation according to the shale content and the transverse relaxation initial time; an oil saturation obtaining module: used for calculating oil saturation according to the water saturation.
9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the steps of the shale oil reservoir oil saturation calculation method according to any one of claims 1 to 7.
10. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 9. The computer program is executed by the processor to realize the steps of the shale oil reservoir oil saturation calculation method according to any one of claims 1 to 7.