A method and device for measuring water saturation of core

Abstract

The present invention belongs to the technical field of reservoir rock physical property testing, and discloses a method and device for measuring the water saturation of a core, including establishing an equivalent circuit model based on a capillary pore unit; calculating the circuit parameters of the equivalent circuit model under different water saturations; reading the characteristic value on the image by drawing the curve of the imaginary part and the real part of the electric spectrum impedance of the rock sample under different water saturations; and determining the water saturation of the core by drawing the intersection diagram of the imaginary part characteristic value of the impedance, the real part characteristic value of the impedance and the water saturation. The method solves the problem that the current traditional core water parameter testing method requires a large amount of laboratory testing and data processing, which consumes time and energy. The method is simple to operate, does not require tedious calculation and fitting processes, and has wide applicability.

Description

Technical Field

[0001] The invention relates to the technical field of reservoir rock physical property testing, and in particular to a method and a device for measuring core water saturation. Background Art

[0002] Before the development of oil and gas fields, it is crucial to determine the reserves of oil and gas reservoirs. Rock water saturation is one of the important parameters of rock physical properties and is also the core parameter for determining the effective reserves of oil and gas reservoirs. On the other hand, the water saturation test of reservoir sampling cores is an important means to study rock wettability and determine rock porosity and permeability. At present, the core water saturation test method is mainly an indoor experimental test method, mainly including weight method, specific gravity method, infrared method, nuclear magnetic resonance method, and electrical spectrum impedance method.

[0003] Among them, the principles of the weight method and specific gravity method are relatively simple and intuitive, but they often require cutting rock samples to destroy the surface of the rock. The test accuracy is highly sensitive to the shape of the rock itself and the repetitive process. In addition, the repeated measurement time and cost are relatively high and are not suitable for low-permeability and dense rock samples. The infrared method needs to process complex spectral signals, and the nuclear magnetic resonance itself requires very expensive equipment and professional test analysts. The testing and operation of both methods and the professionalism of the testers are very challenging. Compared with the weight method and specific gravity method, the electric spectrum impedance method has the advantages of non-invasiveness, high sensitivity, rapidity, and repeatability. Compared with the infrared method and the nuclear magnetic resonance method, the electric spectrum impedance method has the characteristics of simple equipment, low cost, and low test and analysis threshold. Therefore, the electric spectrum impedance method is currently the most widely used method for testing the water content of samples, especially in the coal industry. In terms of the test interpretation principle, the electric spectrum impedance method relies on the equivalent circuit model of the rock sample established by it. The basic principles and ideas of the existing many electrical spectrum impedance curves for interpreting test parameters are as follows: first, a physical model is established based on the pore connectivity structure of the (coal) rock sample, and then a corresponding equivalent circuit model is established to generate an electrical spectrum impedance curve chart of the equivalent circuit. Next, the electrical spectrum impedance curve obtained through the test is fitted with the theoretical curve of the equivalent circuit model, and finally, the physical properties of the rock sample are inverted based on the fitting accuracy.

[0004] The pore connectivity model currently used by commonly used rock samples (coal samples) is mainly based on the classic Cole-Cole model (proposed by Cole and Cole in 1941, assuming that the pore units in the rock are in a series-parallel relationship of resistance and capacitance, which is essentially a model of parallel cylindrical channels). Although there have been many improvements subsequently, they are also mainly focused on improving the cylindrical tube model of connected channels, which is mainly reflected in the improvement from equal-diameter cylindrical channels to non-equal-radius combined cylindrical channels. These improvements are actually still a parallel connectivity model, which does not consider the vertical connectivity of the rock sample pores. Therefore, this invention proposes a new electrical spectrum impedance curve chart for determining the water saturation of the core, while considering the horizontal and vertical pore connectivity inside the core, solving the problem of not considering vertical connectivity in the current core test model. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above existing problems, the present invention is proposed.

[0007] Therefore, the technical problem solved by the present invention is that the existing core water saturation measurement model cannot take vertical connectivity into consideration and requires a large amount of laboratory testing and data processing, which is time-consuming and labor-intensive.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] In a first aspect, an embodiment of the present invention provides a method for measuring water saturation of a core, comprising:

[0010] Establish an equivalent circuit model based on capillary pore units;

[0011] Calculate the circuit parameters of the equivalent circuit model at different water saturations;

[0012] By plotting the curves of the imaginary and real parts of the electric spectrum impedance of the rock sample at different water saturations, the characteristic values ​​on the image are read;

[0013] The water saturation of the core is determined by drawing the cross-plot of the imaginary eigenvalue of impedance, the real eigenvalue of impedance and water saturation.

[0014] As a preferred solution of the method for measuring the water saturation of the core of the present invention, the capillary pore unit includes horizontal pore units in the same direction as the direction of the external electric field E and vertical pore units perpendicular to the direction of the external electric field E;

[0015] An equivalent circuit model is constructed by equating the horizontal pore unit to a circuit unit in which a resistor Rw is connected in parallel with a capacitor Ce, and the vertical pore unit to a capacitor Cw connected in series with the capacitor Ce.

[0016] The horizontal pore unit is a pore-throat structure, and the pore and throat diameters are d p and d t , the pore length in each horizontal pore unit is l p , the throat length is l t , the length of the horizontal pore unit is l e = l p +l t , the length of the vertical pore unit is d s .

[0017] As a preferred solution of the method for measuring the water saturation of the core according to the present invention, based on the geometric structure of the horizontal pore unit in the pore capillary model, the equivalent resistance of the fluid in the pore space connected to the pore unit of the oil-bearing rock is obtained as follows:

[0018]

[0019] Among them, S w is the water saturation of the pore unit, A e is the cross-sectional area of ​​the pore throat, ρ w is the pore fluid resistivity;

[0020] When the pores contain oil and water two-phase fluids, without considering the polarization of polar molecules, the resistivity of the pore fluid is expressed as

[0021]

[0022] Among them, C NaCl is the mineralization of NaCl solution in the pore fluid, and T is the temperature of the pore fluid.

[0023] As a preferred solution of the method for measuring the water saturation of the core according to the present invention, in the horizontal pore unit, the pore surface perpendicular to the direction of the external electric field is regarded as a parallel plate capacitor, and the capacitance of the two-phase fluid in the horizontal pore unit is expressed as:

[0024]

[0025] Among them, ε wateris the dielectric constant of the salt solution in the pores, ε oil is the dielectric constant of the oil in the pores;

[0026] In the vertical pore unit, the pore surface perpendicular to the external electric field direction is also regarded as a parallel plate capacitor. The two-phase fluid capacitance of the vertical pore unit is expressed as:

[0027]

[0028] Where k is the electrostatic constant.

[0029] As a preferred solution of the method for measuring the water saturation of the core according to the present invention, the capacitance value of Ce and Cw in series is C, which is expressed as:

[0030]

[0031] The unit impedance of the equivalent circuit is expressed as:

[0032]

[0033] Among them, ω=2πf is the angular frequency, f is the frequency, and i is the imaginary unit.

[0034] The total electrical impedance is expressed as:

[0035]

[0036] Where a is the number of pore units in each capillary, and b is the number of horizontal capillaries per unit cross-sectional area;

[0037] make The real part is expressed as:

[0038]

[0039] The imaginary part is expressed as:

[0040]

[0041] As a preferred solution of the method for measuring the water saturation of the core of the present invention, wherein: with the frequency as the abscissa value, the imaginary part and the real part of the impedance as the ordinate value, respectively draw the curves of the imaginary part and the real part of the impedance changing with the frequency at different water saturations;

[0042] From the impedance imaginary part image, read the minimum modulus value corresponding to the water saturation, which is defined as the characteristic value H;

[0043] On the real part of the impedance graph, read the stable value of the corresponding water saturation at low frequency, which is defined as the characteristic value L.

[0044] As a preferred embodiment of the method for calculating the water saturation of the core according to the present invention, the water saturation S w is the horizontal axis value, the imaginary impedance eigenvalue H and the real impedance eigenvalue L are the vertical axis values, and the cross-plots of water saturation and eigenvalues ​​are drawn respectively;

[0045] The core water saturation is directly determined by the cross-plot.

[0046] In a second aspect, an embodiment of the present invention provides a device for measuring water saturation of a core, characterized in that it includes:

[0047] Equivalent module, to establish an equivalent circuit model based on capillary pore units;

[0048] A calculation module calculates the circuit parameters of the equivalent circuit model under different water saturations;

[0049] The reading module reads the characteristic values ​​on the image by drawing the curves of the imaginary and real parts of the rock sample electrical spectrum impedance at different water saturations;

[0050] The determination module determines the water saturation of the core by drawing the intersection diagram of the imaginary eigenvalue of impedance, the real eigenvalue of impedance and water saturation.

[0051] In a third aspect, an embodiment of the present invention provides a computing device, including:

[0052] Memory and processor;

[0053] The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the one or more programs are executed by the one or more processors, the one or more processors implement the method for measuring core water saturation as described in any embodiment of the present invention.

[0054] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the method for calculating the water saturation of a core.

[0055] Beneficial effects of the present invention: A method for measuring the water saturation of a core provided by the present invention proposes an electrical spectrum impedance curve plate method for quickly determining the water parameters of the core. By establishing an equivalent circuit model of a core containing horizontal pores and vertical pores, the curve shape and characteristics of the imaginary and real parts of impedance changing with frequency under different water saturations are read, and the relationship between the minimum modulus value of the imaginary part of impedance, the maximum modulus value of the real part and the water saturation is determined on the curve. The water saturation of the core is quickly determined directly on the intersection diagram of the modulus value and the water saturation. The operation is simple and the mine applicability is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0057] Figure 1 This is an overall flow chart of a method for measuring water saturation of a core according to an embodiment of the present invention;

[0058] Figure 2 A schematic diagram of a device for calculating core water saturation according to an embodiment of the present invention;

[0059] Figure 3 A schematic diagram of a rock sample pore measuring cylinder network for a method for measuring water saturation of a rock core according to an embodiment of the present invention;

[0060] Figure 4 A schematic diagram of a basic pore unit of a method for measuring water saturation of a core according to an embodiment of the present invention;

[0061] Figure 5 An equivalent circuit model of a pore unit in a method for calculating core water saturation according to an embodiment of the present invention;

[0062] Figure 6 A schematic diagram of an equivalent circuit model of the entire capillary pore network of the method for measuring core water saturation according to an embodiment of the present invention;

[0063] Figure 7 The imaginary part curves of the electrical spectrum impedance of rock samples with different water saturations Sw according to the method for measuring the water saturation of a core according to an embodiment of the present invention;

[0064] Figure 8 The real part curve of the electrical spectrum impedance of rock samples with different water saturations Sw according to the method for measuring the water saturation of the core according to one embodiment of the present invention;

[0065] Fig. 9 A cross-plot of the impedance imaginary part eigenvalue H and the water saturation Sw of the method for measuring the water saturation of a core according to an embodiment of the present invention;

[0066] Fig.10 This is a cross-plot of the real part characteristic value L of impedance and the water saturation Sw of the method for calculating the water saturation of the core described in one embodiment of the present invention. DETAILED DESCRIPTION

[0067] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0068] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0069] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0070] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0071] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0072] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0073] Example 1

[0074] Reference Figure 1—8 is an embodiment of the present invention, which provides a method for measuring water saturation of a core, characterized in that it includes:

[0075] S100: Establish an equivalent circuit model based on capillary pore units;

[0076] Furthermore, the capillary pore units include horizontal pore units in the same direction as the direction of the external electric field E and vertical pore units perpendicular to the direction of the external electric field E;

[0077] like Figure 5 As shown, the equivalent circuit model is constructed by equivalently treating the horizontal pore unit to a circuit unit in which a resistor Rw is connected in parallel with a capacitor Ce, and the vertical pore unit to a capacitor Cw connected in series with the capacitor Ce;

[0078] The horizontal pore unit is a pore-throat structure, and the pore and throat diameters are d p and d t , the pore length in each horizontal pore unit is l p , the throat length is l t , the length of the horizontal pore unit is l e = l p +l t , the length of the vertical pore unit is d s .

[0079] It should be noted that if Figure 3 The figure shows a new type of pore capillary model, in which gray represents rock, white represents pore channels, and dashed lines represent repeating units. The model is composed of multiple horizontal capillary bundles and vertical capillary bundles. After the new capillary model is evenly divided in the vertical and horizontal directions, the entire model consists of Figure 4 The pores shown are composed of multiple identical pore units.

[0080] Since the direction of ion accumulation in the horizontal pores is consistent with that in the vertical pores, the equivalent capacitance Ce of the vertical pores is considered to be connected in series with the equivalent capacitance Cw of the horizontal pores, and the equivalent circuit of the entire rock can be considered to be composed of multiple such units connected in series and in parallel, such as Figure 6 shown.

[0081] S200: Calculate the circuit parameters of the equivalent circuit model under different water saturations;

[0082] Furthermore, based on the geometric structure of the horizontal pore unit in the pore capillary model, the equivalent resistance of the fluid in the pore space connected by the pore unit of the oil-bearing rock is obtained as:

[0083]

[0084] Among them, Sw is the water saturation of the pore unit, A e is the cross-sectional area of ​​the pore throat, ρ w is the pore fluid resistivity;

[0085] When the pores contain oil and water two-phase fluids, without considering the polarization of polar molecules, the resistivity of the pore fluid is expressed as

[0086]

[0087] Among them, C NaCl is the mineralization of NaCl solution in the pore fluid, and T is the temperature of the pore fluid.

[0088] Furthermore, in the horizontal pore unit, the pore surface perpendicular to the external electric field is regarded as a parallel plate capacitor, and the capacitance of the two-phase fluid in the horizontal pore unit is expressed as:

[0089]

[0090] Among them, ε water is the dielectric constant of the salt solution in the pores, ε oil is the dielectric constant of the oil in the pores;

[0091] In the vertical pore unit, the pore surface perpendicular to the external electric field direction is also regarded as a parallel plate capacitor. The two-phase fluid capacitance of the vertical pore unit is expressed as:

[0092]

[0093] Where k is the electrostatic constant.

[0094] Furthermore, the capacitance value of Ce and Cw in series is C, which is expressed as:

[0095]

[0096] The unit impedance of the equivalent circuit is expressed as:

[0097]

[0098] Among them, π=2πf is the angular frequency, f is the frequency, and i is the imaginary unit.

[0099] The total electrical impedance is expressed as:

[0100]

[0101] Where a is the number of pore units in each capillary, and b is the number of horizontal capillaries per unit cross-sectional area;

[0102] make The real part is expressed as:

[0103]

[0104] The imaginary part is expressed as:

[0105]

[0106] S300: By drawing the curves of the imaginary and real parts of the rock sample electrical spectrum impedance at different water saturations, the characteristic values ​​on the image are read;

[0107] Furthermore, with the frequency as the abscissa value and the imaginary and real parts of the impedance as the ordinate values, the curves of the imaginary and real parts of the impedance changing with the frequency at different water saturations are plotted respectively;

[0108] like Figure 7 As shown, from the impedance imaginary part image, the minimum modulus value corresponding to the water saturation is read and defined as the characteristic value H;

[0109] like Figure 8 As shown, on the real part of the impedance graph, the stable value of the corresponding water saturation at low frequency is read and defined as the characteristic value L.

[0110] S400: Determine the core water saturation by drawing a cross plot of the imaginary eigenvalue of impedance, the real eigenvalue of impedance and water saturation.

[0111] Furthermore, the water saturation S w is the horizontal axis value, the imaginary impedance eigenvalue H and the real impedance eigenvalue L are the vertical axis values, and the cross-plots of water saturation and eigenvalues ​​are drawn respectively;

[0112] The core water saturation is directly determined by the cross-plot.

[0113] It should be noted that in the double logarithmic coordinates, H and L vary with water saturation S. w The impedance of the rock sample is measured by an impedance analyzer, and the water saturation is directly determined from the characteristic plate without the need for complex fitting and inversion.

[0114] The above is a schematic scheme of a method for measuring core water saturation in this embodiment. It should be noted that the technical scheme of the device for measuring core water saturation and the technical scheme of the method for measuring core water saturation are of the same concept, and the details of the technical scheme of the device for measuring core water saturation in this embodiment that are not described in detail can all be referred to the description of the technical scheme of the method for measuring core water saturation.

[0115] Figure 2It is a structural schematic diagram of a device for measuring water saturation of a core provided by the present invention. This embodiment can be applied to the method for measuring water saturation of a core.

[0116] See also Figure 2 In this embodiment, the device for measuring the water saturation of the core includes:

[0117] An equivalent module 101 is used to establish an equivalent circuit model based on a capillary pore unit;

[0118] A calculation module 201 calculates circuit parameters of an equivalent circuit model under different water saturations;

[0119] The reading module 301 reads the characteristic value on the image by drawing the curves of the imaginary part and the real part of the electric spectrum impedance of the rock sample at different water saturations;

[0120] The determination module 401 determines the water saturation of the core by drawing a cross-plot of the imaginary part eigenvalue of the impedance, the real part eigenvalue of the impedance and the water saturation.

[0121] This embodiment also provides a computing device, which is applicable to the method for measuring the water saturation of a core, and includes:

[0122] Memory and processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the method for measuring core water saturation as proposed in the above embodiment.

[0123] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0124] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for calculating the water saturation of the core as proposed in the above embodiment is implemented.

[0125] The storage medium proposed in this embodiment and the data storage method proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be found in the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0126] Example 2

[0127] Reference Fig. 9 , 10 , is an embodiment of the present invention, which provides a method for measuring the water saturation of the core. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through comparative experiments.

[0128] The specific details of this embodiment are as follows:

[0129] Under laboratory conditions, a core with a known water saturation of 85% (calculated by nuclear magnetic resonance) was tested, and the frequency of the impedance analyzer used was 1 to 1000 Hz. Since the impedance real part cross-plot is measured under low frequency conditions of 1 to 10 Hz, and the impedance imaginary part cross-plot is measured under high frequency conditions of 100 to 200 Hz, the two test results in Table 1 were used for analysis. The real part characteristic value L = 4.85×105Ω was measured at low frequency (2 Hz). According to Fig.10 The water saturation is 86.6%; the real characteristic value H = 2.46 × 105Ω is measured by high frequency (150Hz). Fig. 9 The water saturation is 84.7%. In comparison, the present invention has a smaller error than the weighing method (4.71% relative error) and the Cole-Cole model method (23.5% relative error), with an average relative error of 0.7647%.

[0130] Table 1 Comparison of test results of examples

[0131]

[0132] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for measuring core water saturation, characterized in that: include: Establish an equivalent circuit model based on capillary pore units; Calculate the circuit parameters of the equivalent circuit model at different water saturations; By plotting the curves of the imaginary and real parts of the electric spectrum impedance of the rock sample at different water saturations, the characteristic values ​​on the image are read; The water saturation of the core is determined by drawing the cross-plot of the imaginary eigenvalue of impedance, the real eigenvalue of impedance and water saturation; Wherein, the capillary pore units include horizontal pore units in the same direction as the direction of the external electric field E and vertical pore units perpendicular to the direction of the external electric field E; An equivalent circuit model is constructed by equating the horizontal pore unit to a circuit unit in which a resistor Rw is connected in parallel with a capacitor Ce, and the vertical pore unit to a capacitor Cw connected in series with the capacitor Ce. The horizontal pore unit is a pore-throat structure, and the pore and throat diameters are d p and d t , the pore length in each horizontal pore unit is l p , the throat length is l t , the length of the horizontal pore unit is l e = l p +l t , the length of the vertical pore unit is d s ; In the vertical pore unit, the pore surface perpendicular to the external electric field direction is also regarded as a parallel plate capacitor. The two-phase fluid capacitance of the vertical pore unit is expressed as: Where k is the electrostatic constant; With frequency as the horizontal axis value and the imaginary and real parts of impedance as the vertical axis values, the curves of the imaginary and real parts of impedance changing with frequency at different water saturations are drawn respectively; From the impedance imaginary part image, read the minimum modulus value corresponding to the water saturation, which is defined as the characteristic value H; On the real part of the impedance graph, read the stable value of the corresponding water saturation at low frequency, which is defined as the characteristic value L.

2. The method for calculating core water saturation according to claim 1, characterized in that: Based on the geometric structure of the horizontal pore unit in the pore capillary model, the equivalent resistance of the fluid in the pore space connected by the pore unit of the oil-bearing rock is obtained as: Among them, S w is the water saturation of the pore unit, A e is the cross-sectional area of ​​the pore throat, ρ w is the pore fluid resistivity; When the pores contain oil and water two-phase fluids, without considering the polarization of polar molecules, the resistivity of the pore fluid is expressed as Among them, C NaCl is the mineralization of NaCl solution in the pore fluid, and T is the temperature of the pore fluid.

3. The method for calculating core water saturation according to claim 2, characterized in that: In the horizontal pore unit, the pore surface perpendicular to the external electric field is regarded as a parallel plate capacitor, and the capacitance of the two-phase fluid in the horizontal pore unit is expressed as: Among them, ε water is the dielectric constant of the salt solution in the pores, ε oil is the dielectric constant of the oil in the pores.

4. The method for calculating core water saturation according to claim 3, characterized in that: The capacitance value of Ce and Cw in series is C, which is expressed as: The unit impedance of the equivalent circuit is expressed as: Among them, ω = 2πf is the angular frequency, f is the frequency, and i is the imaginary unit; The total electrical impedance is expressed as: Where a is the number of pore units in each capillary, and b is the number of horizontal capillaries per unit cross-sectional area; make The real part is expressed as: The imaginary part is expressed as:

5. The method for calculating core water saturation according to claim 4, characterized in that: Water saturation S w is the horizontal axis value, the imaginary impedance eigenvalue H and the real impedance eigenvalue L are the vertical axis values, and the cross-plots of water saturation and eigenvalues ​​are drawn respectively; The core water saturation is directly determined by the cross-plot.

6. A device for measuring the water saturation of a core, using the method for measuring the water saturation of a core as claimed in any one of claims 1 to 5, characterized in that: include: An equivalent module (101) is used to establish an equivalent circuit model based on a capillary pore unit; A calculation module (201) calculates circuit parameters of an equivalent circuit model at different water saturations; A reading module (301) reads characteristic values ​​on the image by drawing curves of the imaginary and real parts of the electrical spectrum impedance of the rock sample at different water saturations; The determination module (401) determines the water saturation of the core by drawing a cross-plot of the imaginary part eigenvalue of the impedance, the real part eigenvalue of the impedance and the water saturation.

7. A computing device comprising: Memory and processor; The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the method for measuring core water saturation according to any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for measuring core water saturation as described in any one of claims 1 to 5.

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