A method for calculating the water saturation of rocks

Abstract

The present invention belongs to the technical field of rock physical property testing, and discloses a method for calculating the water saturation of rocks, which includes: obtaining a plug sample and a powder sample; measuring the rock frame modulus of the powder sample, drying the plug sample, performing water inlet treatment until it is water-saturated, and recording its density, Young's modulus and Poisson's ratio under different water-containing states; calculating the longitudinal and transverse wave velocities of the plug sample under different water-containing states accordingly, and further obtaining the longitudinal wave velocity of the pore fluid. At the same time, combining the rock frame modulus data, calculating the bulk modulus of the pore fluid of the plug sample; calculating the pore fluid saturation data of the sample under different water-containing states according to the longitudinal wave velocity and bulk modulus data of the pore fluid. The technical solution of the present invention has strong operability, accurate calculation of water saturation, low cost, and can more conveniently provide reliable water saturation information of water-rich rock masses for the prevention and control evaluation of coal mine water disasters.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock physical property testing, and particularly relates to a method for calculating the water saturation of rocks. Background Technique

[0002] Coal resources are one of the important energy resources in China. During the coal mining process, water disasters often occur, seriously affecting the safe production of mines and the development and utilization of resources. The quality of coal mine water disaster prevention technology is directly related to the production economic benefits of mines and the lives and safety of employees. The prediction of the water body distribution, material source, sand body thickness, and physical properties (porosity, water saturation) of water-rich sandstones in the coal mine roof is crucial for coal mine water disaster prevention. When exploring and developing coal, it is necessary to accurately evaluate the distribution characteristics and physical properties of water-rich sand layers in the roof. The physical property parameters of water-rich sand bodies, porosity and saturation, are important parameters in water-rich evaluation. Their accuracy directly affects the correct evaluation of the water volume in roof sandstones and is also the most difficult parameter to calculate and measure in the prediction of water-rich sandstones.

[0003] The most commonly used methods for estimating water saturation are the resistivity method and the acoustic velocity method. The resistivity method for calculating water saturation generally calculates water saturation based on models such as Archie's formula, dual-water model, and Indonesian formula. When using the resistivity method to calculate water saturation, more parameters are required, and the calculation formula is relatively cumbersome. For estimating saturation by acoustic velocity, most are based on the equivalent medium theory. Taking the Wyllie time-average equation and Wood equation as examples, when using acoustic velocity to estimate saturation, it is a difficult point to determine the density of pore fluid in the unsaturated state. At present, there are also methods using nuclear magnetic resonance-density testing methods to simulate and test the water saturation under in-situ conditions, but the cost of this nuclear magnetic resonance instrument is expensive. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for calculating the water saturation of rocks to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above purpose, the present invention provides a method for calculating the water saturation of rocks, including:

[0006] Obtain core samples, where the core samples include plug samples and powder samples;

[0007] Determine the mineral component of the powder sample to obtain rock skeleton modulus data;

[0008] Dry the plug sample, and perform water inlet treatment on the dried plug sample until the plug sample reaches the water saturation state. During the water inlet treatment of the plug sample, record the sample density, Young's modulus, and Poisson's ratio of the plug sample in different water content states;

[0009] Calculate the longitudinal and transverse wave velocities of the plunger sample under different water saturation states based on the sample density, Young's modulus, and Poisson's ratio of the plunger sample under different water saturation states;

[0010] Calculate the longitudinal wave velocity of the pore fluid of the plunger sample based on the longitudinal and transverse wave velocities of the plunger sample under different water saturation states; Calculate the bulk modulus data of the pore fluid of the plunger sample based on the Young's modulus, Poisson's ratio of the plunger sample under different water saturation states, and the rock frame modulus data;

[0011] Calculate the pore fluid saturation data of the sample under different water saturation states according to the longitudinal wave velocity of the pore fluid and the bulk modulus data of the pore fluid.

[0012] Optionally, the determination of the mineral composition of the powder sample specifically includes:

[0013] Determine the mineral composition in the powder sample by X-ray diffraction method to obtain mineral composition data, and calculate the rock frame modulus data based on the mineral composition data in combination with the VRH model.

[0014] Optionally, the specific calculation formula for the rock frame modulus data is:

[0015]

[0016] In the formula, K0 is the rock frame modulus, n is the number of minerals in the mineral composition of the powder sample determined by X-ray diffraction method, f i is the volume fraction of the i-th mineral, given by the determination of the powder sample by X-ray diffraction method, M i is the modulus of the i-th mineral.

[0017] Optionally, the drying treatment of the plunger sample specifically includes:

[0018] Conduct a drying treatment on the plunger sample, record the sample weight after completing the current drying treatment round, repeat the drying treatment process until the difference in the corresponding sample weights in adjacent drying treatment rounds is less than a preset threshold, then stop the drying treatment and record the weight of the plunger sample.

[0019] Optionally, the water injection treatment of the dried plunger sample until the plunger sample reaches the water saturation state specifically includes:

[0020] Put the dried plunger sample into the sample tank cavity, and conduct multiple water injection treatments on the plunger sample based on the preset confining pressure data and the preset single water injection volume until the plunger sample reaches the water saturation state and stop the water injection treatment.

[0021] Optionally, the specific calculation formula for the bulk modulus data of the pore fluid is:

[0022] Calculate the bulk modulus K of the plunger sample under different water content states based on the Young's modulus and Poisson's ratio of the plunger sample under different water content states:

[0023]

[0024] In the formula, E f is the Young's modulus, and v f is the Poisson's ratio;

[0025] Establish a relationship between the bulk modulus and the bulk modulus of the pore fluid according to the Gassmann equation:

[0026]

[0027] In the formula, K sf , K sg , K sw are the bulk moduli of the rock under different water injection times, the gas-saturated rock, and the water-saturated rock, respectively; K g , K w are the bulk moduli of the gas and the water, respectively; K0 is the rock frame modulus, and K f is the bulk modulus of the pore fluid to be determined.

[0028] Optionally, the specific calculation formula for the longitudinal wave velocity of the pore fluid is:

[0029] Calculate the shear modulus μ of the plunger sample under different water content states:

[0030]

[0031] In the formula, E f is the Young's modulus, and v f is the Poisson's ratio;

[0032] Establish the relationship between the longitudinal wave velocity V p of the rock under different water content states and the longitudinal wave velocity V f of the pore fluid based on the Wyllie time equation:

[0033]

[0034] In the formula, V fp , V gp , V wp represent the rock velocities under different water injection times, the gas-saturated rock velocity, and the water-saturated rock velocity, respectively; V w , V g are the longitudinal wave velocities of the seismic wave in water and gas, respectively.

[0035] Optionally, the specific calculation formula for the pore fluid saturation data is as follows:

[0036]

[0037] In the formula, K f , V f are the bulk modulus and velocity of the pore fluid under different water injection times respectively; ρ g , ρ w are the gas density and water density respectively, and S w is the pore fluid saturation data.

[0038] The technical effects of the present invention are as follows:

[0039] The method for calculating the water saturation of rocks based on a low-frequency velocity testing instrument provided by the present invention is applicable to the testing of the water saturation of rocks. It includes core collection and sample preparation, determination of mineral components; low-frequency velocity testing under different water-containing states; a calculation module for the bulk modulus of the pore fluid in the unsaturated state; a calculation module for the velocity of the pore fluid in the unsaturated state; and a calculation module for the water saturation of rocks. Based on the low-frequency velocity testing, the present invention combines rock physics experiments and the equivalent medium theory, and proposes a method and system for calculating the water saturation of rocks. This method has low cost, strong operability, and accurate calculation of water saturation, and can more conveniently provide reliable water saturation information of water-rich rock masses for the evaluation of coal mine water disaster prevention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0041] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0042] Figure 1 is a schematic flow chart of a method and system for calculating the water saturation of rocks in an embodiment of the present invention;

[0043] Figure 2 is a schematic diagram of a low-frequency velocity testing system under different water-containing states in an embodiment of the present invention.

[0044] Description of reference numerals: 1. Pressure pump; 2. Pressure valve 1; 3. Fluid container; 4. Pressure valve 2; 5. Intake gas cylinder; 6. Pressure valve 3; 7. Outlet gas cylinder; 8. Pressure valve 4; 9. Fluid container; 10. Pressure valve 4; 11. Pressure valve 5; 12. Rubber tube; 13. Strain gauge 1; 14. Strain gauge 2; 15. Strain gauge 3; 16. Rubber tube; 17. Cavity of sample tank; 18. Pulse exciter; 19. Metal shell of sample tank; 20. Wheatstone bridge; 21. Pressure valve 6; 22. Test system; 23. Standard metal block; 24. Sample to be measured; 25. Standard metal block. Detailed implementation manners

[0045] The various exemplary implementation manners of the present invention will now be described in detail. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0046] It should be understood that the terms used in the present invention are only for describing particular implementation manners and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods, any method similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0048] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of this application are merely exemplary.

[0049] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0050] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will describe this application in detail with reference to the drawings and in combination with the embodiments.

[0051] Example 1

[0052] As Figure 1 - Figure 2 shown, in this embodiment, a method for calculating the water saturation of rock is provided, including: obtaining a core sample, where the core sample includes a plug sample and a powder sample; performing mineral component determination on the powder sample to obtain rock skeleton modulus data; drying the plug sample, performing water injection treatment on the dried plug sample until the plug sample reaches the water saturation state, and recording the sample density, Young's modulus, and Poisson's ratio of the plug sample in different water content states during the water injection treatment of the plug sample; calculating the longitudinal and transverse wave velocities of the plug sample in different water content states based on the sample density, Young's modulus, and Poisson's ratio of the plug sample in different water content states; calculating the longitudinal wave velocity of the pore fluid of the plug sample based on the longitudinal and transverse wave velocities of the plug sample in different water content states; calculating the bulk modulus data of the pore fluid of the plug sample based on the Young's modulus and Poisson's ratio of the plug sample in different water content states and the rock skeleton modulus data; calculating the pore fluid saturation data of the sample in different water content states according to the longitudinal wave velocity of the pore fluid and the bulk modulus data of the pore fluid.

[0053] Based on low-frequency velocity testing, this embodiment combines rock physics experiments and the equivalent medium theory to propose a method and system for calculating the water saturation of rock. This method has low cost, strong operability, and accurate calculation of water saturation, and can relatively conveniently provide reliable water saturation information of water-rich rock masses for the prevention and control evaluation of coal mine water hazards.

[0054] The following further describes the specific embodiments of this embodiment with reference to the accompanying drawings. As Figure 1 shown, this embodiment includes the following specific steps:

[0055] S10: Core collection, sample preparation, and mineral component determination. Determine the sampling position h i , sample length, and sample number of the samples obtained from the drilling according to the "Core Analysis Method" (GB / T 29172-2012), and seal and store the samples. Since coal samples are brittle and soft, the samples are processed into plug-shaped samples with a diameter of 25 mm and a length of 50 mm by wire cutting. The coal samples are processed into coal powder samples with a particle size less than 200 mesh according to the "Preparation Method of Coal Samples" (GB / T 474-2008). According to the standards of the "Determination Method of Minerals in Coal" (GB / T 7560-2001) and the "X-ray Diffractometer" (JB / T 11144-2011), the mineral components in the samples are determined by X-ray diffraction to obtain the mineral components of the samples.

[0056] Feasible, S10 specifically includes: obtaining 1-core samples through drilling and sampling, and using RTK to locate the position of the drilling point. Record the sampling position of the samples obtained from the drilling as h = 400 m, the sample length as 40 cm, and the sample number as Z-15-1, and seal and store the samples. Since the coal samples are brittle and soft, the samples are processed into plunger-shaped samples with a diameter of 25 mm and a length of 50 mm by wire cutting. The remaining samples after the cylindrical column samples are intercepted from the core are crushed into 3-coal powder samples with a particle size less than 200 mesh. According to the standards of "Methods for Determination of Minerals in Coal" (GB / T 7560-2001) and "X-ray Diffractometer" (JB / T 11144-2011), the mineral components in the samples are determined by X-ray diffraction method to obtain the mineral components of the samples.

[0057] S20: Low-frequency velocity test under different water content states. Dry the samples, weigh them every 8 hours of drying until the difference in weight between the two consecutive weighings is less than 0.001 g, and record the mass m of the dry samples g , and use the stress-strain method to test the Young's modulus E of the dry plunger samples g , and the Poisson's ratio is v g . Place the dry plunger samples into the sample tank cavity, open the water inlet valve, rotate the water inlet valve, close the water inlet valve every 1 scale of water inlet, open the air inlet valve, and adjust the confining pressure of the sample tank cavity to Sv = ρgh. Record the weight of the sample tank and the samples as m i , and i is the number of water inlets. After each water inlet, the sample mass is m i - m0, where m0 is the weight of the sample tank and the water delivery pipeline when containing water. And test the Young's modulus E of the samples after each water inlet f , and the Poisson's ratio is v f . After multiple water inlets, when the change in the sample mass before and after does not exceed 0.001 g, it is considered that the sample is water-saturated, record the sample mass as m w , and test the Young's modulus E of the water-saturated samples w , and the Poisson's ratio is v w .

[0058] Feasible, S20 specifically includes: drying the sample to be tested - 24, weighing it every 8 hours of drying until the difference in weight between the two consecutive weighings is less than 0.001 g, and record the mass of the dry sample to be tested - 24 as 61.07 g. Use the stress-strain method to test the Young's modulus E of the dry plunger sample to be tested - 24 g = 45 GPa, and the Poisson's ratio is v g= 0.21. Place the dry plunger sample - 24 to be measured into the sample tank cavity - 17, start the pressure pump - 1, open the water inlet valve - 4, open the pressure valve - 11, rotate the water inlet valve - 4. Every time 5 mL of water is inlet, close the water inlet valve - 10 and close the pressure valve - 21. Open the air inlet valve - 6 and adjust the confining pressure of the sample tank cavity - 17 to Sv = 2300 * 9.8 * 400 / 1000000 = 9.016 MPa. Record the overall weight m of the sample tank - 19 i is 20.06607 kg. Denote the number of water inlet times as 1, the weight of the tank body and internal components m0 = 20 kg. After the first water inlet, the sample weight is m i - m0 = 66.07 g. And test the Young's modulus E of the sample - 24 to be measured after each water inlet f = 54, and the Poisson's ratio is v f = 0.20. After multiple water inlets, when the mass change of the sample - 24 to be measured before and after is no more than 0.001 g, it is considered that the sample - 24 to be measured is water - saturated. Record the overall weight m of the sample tank - 19 i is 20.07107 kg, record the mass of the sample - 24 to be measured as m w = 71.07 g, and test the Young's modulus E of the water - saturated sample - 24 to be measured gw = 64, and the Poisson's ratio is v gs = 0.13.

[0059] In step S20, it further includes:

[0060] S201: The low - frequency velocity test method under different water - containing states is characterized in that on the basis of the original sample tank of the HK N - B type intelligent ultrasonic longitudinal and transverse wave automatic tester, a water container connection path is added. A first air valve is provided on the connection path between the sample tank and the nitrogen cylinder, a second air valve is provided on the connection path between the sample tank and the water container, a signal excitation device is provided at the lower part of the sample tank body, and a strain gauge and a strain receiving device are provided inside the sample tank body.

[0061] Implementable, in this embodiment, a water container connection path is added on the basis of the original sample tank - 19 of the HK N - B type intelligent ultrasonic longitudinal and transverse wave automatic tester. The water container connection path consists of the pressure pump - 1, the pressure valve - 2, the water container - 3, the pressure valve - 4, the pressure valve - 11, the pressure valve - 12, the pressure valve - 10, and the water container - 9. Among them, the pressure valves - 4 and - 10 are used to measure the water flow rate; the pressure valves - 11 and - 21 are used to measure the pressure. The nitrogen cylinder - 5, the pressure valve - 6, and the inner cavity of the sample tank - 17 belong to the air inlet channel, and the air pressure acts on the rubber hose sleeve - 16 to control the confining pressure S during the experiment vAfter the experiment, open the pressure valve - 8, and the gas enters the gas return cylinder - 7 through the gas return channel. A pulse exciter - 18, strain gauges - 14, 15, and 16 are provided at the lower part inside the sample cylinder. Strain gauges - 14 and 15 measure the strain of the sample, and strain gauge - 16 measures the strain of the standard aluminum sample. The strain gauges are connected to a bridge - 20, which converts the strain signal into a digital - analog signal and transmits it to the test system - 22, and through processing and calculation, the Young's modulus E and Poisson's ratio v of the sample under different water - content states are obtained.

[0062] The low - frequency velocity test method under different water - content states is characterized in that, based on the measured Young's modulus E and Poisson's ratio v calculate the bulk modulus K, shear modulus μ, longitudinal wave velocity V of the rock under different water - content states p , and transverse wave velocity V s .

[0063] Specifically: taking the dry sample to be measured - 24 as an example, the measured Young's modulus E and Poisson's ratio v are 45 GPa and 0.21 respectively. Based on calculate the bulk modulus K = 25 GPa, shear modulus μ = 18.75 GPa, longitudinal wave velocity V of the rock under different water - content states p = 4.51 km / s, and transverse wave velocity V s = 2.76 km / s.

[0064] S30: Pore - fluid bulk - modulus calculation module in the unsaturated state. Using the Young's modulus E of the sample tested by the stress - strain method in S20 f , and Poisson's ratio is v s , based on calculate the bulk modulus of the water - bearing rock after different water - intake times, which can be obtained by ρ = m / V. Based on the Gassmann equation establish the relationship between the bulk modulus of the rock and the pore - fluid volume model under different fluid - saturation states. The calculation formula for the fluid bulk modulus in the rock after different water - intake times can be expressed as where K f is the fluid bulk modulus to be obtained; K sf , K sg , K sw are the bulk moduli of the rock after different water - intake times, the gas - saturated rock bulk modulus, and the water - saturated rock bulk modulus respectively; K g , K w are the gas bulk modulus and water bulk modulus respectively;

[0065] K0 is the rock - skeleton modulus, which is calculated by combining the XRD analysis results with the VRH model:

[0066]

[0067] In the formula, K0 is the rock frame modulus, n is the number of minerals in the mineral components of the powder sample by X-ray diffraction method, and f i , is the volume fraction of the i-th mineral, given by the measurement of the powder sample by X-ray diffraction method, and M i is the modulus of the i-th mineral.

[0068] It is feasible that S30 specifically includes: using the Young's modulus E of the sample tested by the stress-strain method in S20 f , the Poisson's ratio is v s , and based on calculate the bulk modulus of the water-bearing rock after different water injection times. The bulk moduli K of the dry sample, unsaturated fluid rock sample, and saturated water rock sample are: 25 GPa, 28.66 GPa, and 33.33 GPa respectively. Among them, under different water-bearing states, the rock density ρ = m / V can be calculated. The densities ρ of the sample, unsaturated fluid rock sample, and saturated water rock sample are: 2.49 g / cm 3 , 2.69 g / cm 3 , 2.89 g / cm 3 . K0 is the rock frame modulus, which can be calculated from the XRD analysis results combined with the VRH model . Among them, the mineral components of the sample are 40% quartz, 28% feldspar, 19% dolomite, 8% calcite, and 5% clay minerals. Using the VRH model to calculate K0 is 45.5 GPa. The mineral moduli can be obtained by querying the rock physics handbook, as shown in Table 1.

[0069] Table 1 Mineral bulk modulus

[0070]

[0071] Based on the Gassmann equation establish the relationship between the bulk modulus of the rock and the pore fluid volume model under different fluid saturation states.

[0072] The calculation formula for the bulk modulus of the fluid in the rock after different water injection times can be expressed as: Among them, K f is the bulk modulus of the fluid to be determined, the bulk modulus of the gas K g = 0.000142 GPa, and the bulk modulus of water K w = 2.2 GPa. Substituting the above parameters, we can get K f = 0.722 GPa.

[0073] S40: Pore fluid velocity calculation module in the unsaturated state. Based on the Wyllie time equation establish the longitudinal wave velocity V of the rock under different water injection times pThe relationship with the pore fluid velocity V f According to Calculate the pore fluid velocity V under different water injection times f , where V fp , V gp , V wp respectively represent the rock velocity, gas-saturated rock velocity, and water-saturated rock velocity under different water injection times; V w , V g are the longitudinal wave velocities of seismic waves in water and gas respectively.

[0074] It is feasible. S40 specifically includes: According to Calculate the bulk modulus of the water-bearing rock after different water injection times. The bulk moduli K of the dry sample, unsaturated fluid rock sample, and water-saturated rock sample are: 25.00 GPa, 28.66 GPa, and 33.33 GPa respectively. According to Calculate the shear modulus of the water-bearing rock after different water injection times. The shear moduli μ of the dry sample, unsaturated fluid rock sample, and water-saturated rock sample are: 18.75 GPa, 22.77 GPa, and 27.12 GPa respectively. According to The longitudinal wave velocities of the dry sample, unsaturated fluid rock sample, and water-saturated rock sample are 4.48 km / s, 4.68 km / s, and 4.90 km / s respectively. According to Calculate the pore fluid velocity V under different water injection times f , where V w = 1450 m / s, V g = 340 m / s. Substituting the above parameters, the pore fluid velocity V f = 791.7 m / s.

[0075] S50: Rock pore water saturation calculation module. According to Calculate the density of the mixed fluid. According to the mixed fluid model ρ mix = S w ρ w +(1 - S w )ρ g Establish the calculation formula for the water saturation of rock pores where K f , V f are the bulk modulus and velocity of the pore fluid under different water injection times respectively; ρ g , ρ w are the gas and water densities respectively.

[0076] It is feasible. S50 specifically includes: According to the calculation formula for the water saturation of rock pores where K f , V fare the bulk modulus and velocity of pore fluid under different water injection times; gas ρ g = 0.0012 g / cm 3 , water density ρ w = 1 g / cm 3 . Substituting the above parameters, the water saturation S w = 95.5%.

[0077] The technical solution described in this embodiment has strong operability, accurate calculation of water saturation, and low cost, and can relatively conveniently provide reliable water saturation information of water-rich rock masses for the prevention and control evaluation of coal mine water disasters.

[0078] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for calculating the water saturation of a rock, characterized in that, Including: Obtaining core samples, where the core samples include plug samples and powder samples; Performing mineral component determination on the powder samples to obtain rock frame modulus data; Performing drying treatment on the plug samples, performing water injection treatment on the dried plug samples until the plug samples reach the water saturation state, and recording the sample density, Young's modulus, and Poisson's ratio of the plug samples in different water content states during the water injection treatment process of the plug samples; Calculating the longitudinal and transverse wave velocities of the plug samples in different water content states based on the sample density, Young's modulus, and Poisson's ratio of the plug samples in different water content states; Calculating the longitudinal wave velocity of the pore fluid of the plug samples based on the longitudinal and transverse wave velocities of the plug samples in different water content states; Calculating the bulk modulus data of the pore fluid of the plug samples based on the Young's modulus and Poisson's ratio of the plug samples in different water content states and the rock frame modulus data; Calculating the pore fluid saturation data of the samples in different water content states according to the longitudinal wave velocity of the pore fluid and the bulk modulus data of the pore fluid; The specific calculation process of the bulk modulus data of the pore fluid is as follows: Calculating the bulk modulus K of the plug samples in different water content states based on the Young's modulus and Poisson's ratio of the plug samples in different water content states; where E f is the Young's modulus, and v f is the Poisson's ratio; Establishing a relationship between the bulk modulus and the bulk modulus of the pore fluid according to the Gassmann equation; Where, K sf , K sg , K sw are the bulk moduli of rock for different water injection times, gas-saturated rock, and water-saturated rock, respectively; K g , K w are the bulk moduli of gas and water, respectively; K0 is the bulk modulus of the rock skeleton, and K f is the bulk modulus of the pore fluid to be determined; The specific calculation process of the longitudinal wave velocity of the pore fluid is as follows: Based on Wyllie's time equation, establish the relationship between the longitudinal wave velocity V of rocks in different water saturation states p and the longitudinal wave velocity V f of pore fluids: Where, V fp , V gp , V wp represent the rock velocity, gas-saturated rock velocity, and water-saturated rock velocity under different water injection times, respectively; V w , V g are the longitudinal wave velocities of seismic waves in water and gas, respectively. The specific calculation formula of the pore fluid saturation data is as follows: where K f , V f are the bulk modulus and velocity of the pore fluid under different numbers of water inflows respectively; ρ g , ρ w are the gas and water densities respectively, and S w is the pore fluid saturation data.

2. The method for calculating the water saturation of a rock according to claim 1, characterized in that, The performing mineral component determination on the powder samples specifically includes: Performing mineral component determination on the powder samples according to the X-ray diffraction method to obtain mineral component data, and calculating the rock frame modulus data based on the mineral component data in combination with the VRH model.

3. A method for calculating the water saturation of a rock according to claim 2, characterized in that, The specific calculation formula of the rock frame modulus data is as follows: Where, K0 is the rock skeleton modulus, n is the number of minerals in the mineral components of the powder sample by X-ray diffraction method, f i is the volume fraction of the i-th mineral, given by the measurement of the powder sample by X-ray diffraction method, M i is the modulus of the i-th mineral.

4. A method for calculating the water saturation of a rock according to claim 1, characterized in that, The performing drying treatment on the plug samples specifically includes: Performing drying treatment on the plug samples, recording the sample weight after completing the current drying treatment round, repeating the drying treatment process until the difference in the corresponding sample weights in adjacent drying treatment rounds is less than a preset threshold, then stopping the drying treatment and recording the weight of the plug samples.

5. A method for calculating the water saturation of a rock according to claim 1, characterized in that, The performing water injection treatment on the dried plug samples until the plug samples reach the water saturation state specifically includes: Placing the dried plug samples into the sample tank cavity, and performing multiple water injection treatments on the plug samples based on preset confining pressure data and preset single water injection volume until the plug samples reach the water saturation state and stop the water injection treatment.

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