Method for high-fidelity simulation of seismic reflection wave response suitable for deep saline aquifers

Abstract

The application discloses a kind of suitable for deep brackish aquifer seismic reflection wave response high fidelity simulation calculation method, the method includes S10: according to brackish aquifer development characteristics, establish brackish aquifer pore fluid rock physics model, calculate the viscosity, density, longitudinal wave velocity and bulk modulus of brackish aquifer pore fluid;S20: according to brackish aquifer development characteristics, establish brackish aquifer multi-scale rock physics model, obtain brackish aquifer equivalent stiffness matrix;S30: establish geology-seismic forward modeling;S40: utilize propagation matrix method to calculate brackish aquifer reflection and transmission coefficient matrix;S50: calculate brackish aquifer reflection wave seismic response.The application combines seismic rock physics modeling and seismic forward simulation technology, considers the viscoelasticity characteristics and thickness of brackish aquifer, is more in line with actual geological conditions, low in cost, high in accuracy, can quickly and accurately calculate deep brackish aquifer seismic reflection wave response, provides theoretical support for the evaluation and optimization of carbon storage space.

Description

Technical Field

[0001] This invention relates to the field of earthquake rock physics research technology, and specifically discloses a high-fidelity simulation calculation method for earthquake reflection wave response applicable to deep saline water layers. Background Technology

[0002] Deep saline aquifers are considered important reservoir targets for carbon dioxide geological sequestration due to their widespread distribution, sealing, and stability. With the improvement and development of geological seismic seismic storage technologies, forward modeling of seismic reflection response of saline aquifers has become a research hotspot in the field of seismic petrology as a key means to reveal the quantitative relationship between reservoir parameters and seismic response.

[0003] Deep saline aquifers, as "unusable" deep saline sandstone layers, are typically characterized by deep burial, strong heterogeneity, and well-developed pores and fractures, making them typical anisotropic viscoelastic media. The unique fluid properties of saline water cause the rock physical response and seismic wave propagation behavior of saline aquifers to differ significantly from traditional reservoirs. Existing forward modeling studies of saline aquifer reflections often neglect the influence of fluid properties such as saline water salinity and viscosity on the reflection response, making it difficult to obtain accurate reflection responses. Furthermore, conventional methods for calculating reflection responses often calculate the reflection coefficient of a single reflecting interface, neglecting reservoir thickness, viscoelastic properties, and multi-layer wavefield interference, thus failing to meet the requirements for high-fidelity modeling of saline aquifer reflection responses.

[0004] The Baztle-Wang formula provides a reliable means for calculating the properties of rock pore fluids. By considering formation temperature, formation pressure, and fluid salinity, it can accurately characterize the physical properties of pore fluids in saline reservoirs. The Chapman model simultaneously considers the influence of fractures and pore fluids of different scales on the viscoelastic properties of rocks, revealing the dispersion and attenuation characteristics of viscoelastic media, and providing theoretical support for analyzing the rock physical response of saline reservoirs. The propagation matrix method is a commonly used forward modeling method for seismic waves. While ensuring computational stability, it can accurately handle the reflection and transmission of P-waves and S-waves, interlayer interference, and thin-layer thickness tuning effects in multi-layered anisotropic viscoelastic media, and is suitable for simulating the seismic response of deep saline reservoirs.

[0005] In summary, there is an urgent need to propose a high-fidelity simulation calculation method for seismic reflection wave response that comprehensively considers the pore fluid properties, viscoelastic characteristics, and thickness of the saline aquifer, so as to provide theoretical support for the evaluation and optimization of carbon reservoir space in the saline aquifer. Summary of the Invention

[0006] To address the aforementioned problems with existing technologies, this invention proposes a high-fidelity simulation calculation method for seismic reflection wave response in deep saline water layers. This method, based on the occurrence characteristics of deep saline water layers, utilizes the Batzle-Wang formula to calculate the physical properties of pore fluids in the saline water layer, and combines the Chapman model and the propagation matrix method to perform high-fidelity simulation calculation of the seismic reflection wave response of the saline water layer.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] A high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline aquifers includes the following steps:

[0009] S10: Based on the development characteristics of the saline aquifer, establish a rock physics model of the pore fluid in the saline aquifer and calculate the viscosity, density, longitudinal wave velocity and bulk modulus of the pore fluid in the saline aquifer.

[0010] S20: Based on the development characteristics of the saline aquifer, a multi-scale rock physics model of the saline aquifer is established to obtain the equivalent stiffness matrix of the saline aquifer.

[0011] S30: Establish a geological-seismic forward model;

[0012] S40: Calculate the reflection and transmission coefficient matrices of the saline aquifer using the propagation matrix method;

[0013] S50: Calculate the response of the reflected wave from the saline water layer.

[0014] Furthermore, the calculation of the viscosity, density, longitudinal wave velocity, and bulk modulus of the pore fluid in the saline aquifer during step S10 includes the following steps:

[0015] S101: Calculate the geothermal temperature and formation pressure at the saline aquifer based on the depth of the saline aquifer and the regional geothermal gradient and regional formation pressure gradient.

[0016] S102: Calculate the viscosity of the pore fluid based on the saline aquifer temperature and the saline aquifer pore fluid salinity;

[0017] S103: Calculate the density, P-wave velocity, and bulk modulus of the pore fluid based on the geothermal temperature, formation pressure, and salinity of the pore fluid in the saline aquifer.

[0018] Furthermore, in step S101, the formulas for calculating the ground temperature and formation pressure at the saline aquifer are as follows:

[0019] (1)

[0020] (2)

[0021] in, D The depth of the saline aquifer is measured in km.T Ground temperature, °C; T 0 represents the Earth's surface temperature, in °C. G T The geothermal gradient is expressed in °C / km. P Formation pressure, MPa; P 0 represents the surface pressure, in MPa; G P The pressure gradient is MPa / km.

[0022] Furthermore, in step S102, the viscosity of the pore fluid in the saline aquifer is calculated using the Batzle-Wang fluid model, and the calculation formula is as follows:

[0023] (3)

[0024] in, η The viscosity of the pore fluid is given in Pa·s. S This represents the mineralization degree of the pore fluid.

[0025] Furthermore, in step S103, the Batzle-Wang fluid model is used to calculate the density, longitudinal wave velocity, and bulk modulus;

[0026] The formula for calculating the density of pore fluid in a saline aquifer is as follows:

[0027] (4)

[0028] in, ρ represents the density of the pore fluid, in g / cc; The density of pure water is expressed in g / cc.

[0029] The density of pure water varies under different temperatures and pressures:

[0030] (5)

[0031] The longitudinal wave velocity of the pore fluid in the saline aquifer is calculated by the following formula:

[0032] (6)

[0033] in, ρ represents the longitudinal wave velocity of the pore fluid, in g / cc; The longitudinal wave velocity of pure water is given in m / s.

[0034] The formula for calculating the velocity of sound waves in pure water is:

[0035] (7)

[0036] in, These are the weighting coefficients;

[0037] Bulk modulus of pore fluids in saline aquifers K f The calculation formula is:

[0038] (8).

[0039] Furthermore, in step S20, assuming the saline aquifer is a viscoelastic medium that can be represented by the Chapman model, the establishment of the multi-scale rock physics model of the saline aquifer and the calculation of the equivalent stiffness matrix include the following steps:

[0040] S201: Determination of mineral composition of saline aquifer using X-ray diffraction (XRD);

[0041] S202: Calculate the bulk modulus of the saline aquifer matrix based on the measured mineral composition. K shear modulus M and Lamé constant λ and μ ;

[0042] S203: Establish a multi-scale rock physics model of the saline aquifer and calculate the stiffness matrix of fluid-saturated rocks in the saline aquifer. .

[0043] Furthermore, in step S202, the bulk modulus is calculated using the Voigt-Reuss-Hill (VRH) model. K and shear modulus M The formula is as follows:

[0044] (9)

[0045] in, and For the first i The bulk modulus and shear modulus of each component, For the first i The volume fraction of each component;

[0046] bulk modulus K and shear modulus M Convertible to Lamé constant λ and μ As shown in the following formula:

[0047] (10).

[0048] Furthermore, in step S203, it is assumed that the rock matrix of the saline aquifer sandstone contains pores, mesoscale fractures, and microscale microfractures, and is a typical HTI medium. According to the Chapman model, the stiffness matrix of the fluid-saturated rock in the saline aquifer is... It can be calculated using the following formula:

[0049]

[0050] In the formula, The elastic correction caused by microcracks, in GPa; The elastic correction caused by porosity, in GPa; The elastic correction amount caused by mesoscale cracks, in GPa; The density of microcracks; Porosity; The density of cracks at the mesoscale; Angular frequency, rad / s;

[0051] For HTI media, the expressions for each elastic tensor are further given, as shown in equations (12)-(16):

[0052]

[0053]

[0054]

[0055]

[0056] in,

[0057] (17)

[0058] (18)

[0059] (19)

[0060] (20)

[0061] (twenty one)

[0062] (twenty two)

[0063] (twenty three)

[0064] (twenty four)

[0065] (25)

[0066] (26)

[0067]

[0068] In the formula, λ and μ is the Lamé constant of the rock matrix obtained in step S202, in GPa; K is the bulk modulus of the rock mechanism; Poisson's ratio of the rock matrix; V s denoted as the transverse wave velocity of the rock matrix, in m / s; The density and longitudinal wave velocity of the pore fluid obtained in step S103 are given in g / cc. The longitudinal wave velocity of the pore fluid obtained in step S103 is denoted as m / s. is the bulk modulus of the pore fluid obtained in step S103, in GPa; r The aspect ratio of the crack; Let be the relaxation time at the microscale, in seconds; Let be the relaxation time at the mesoscale, in seconds;

[0069] and It is positively correlated with the viscosity of the pore fluid and can be calculated by the following formula:

[0070] (28)

[0071] In the formula, Let be the radius of the mesoscale crack, in meters. Rock grain size, in meters; For the volume of a single microcrack, m 3 ; Viscosity of the pore fluid calculated for step S102, Pa·s; The critical stress is given in Pa. c 1 represents the number of interconnected pores and cracks; k For penetration rate, md.

[0072] Furthermore, in step S30, when establishing the geological-seismic model, the actual geological conditions of carbon dioxide sequestration in the saline aquifer need to be considered. A three-layer geological-seismic model is set up, with the upper and lower layers being mudstone as the caprock and shielding layer, and the middle layer being the carbon reservoir in the saline aquifer. The upper and lower layers are set as isotropic media, and the middle layer is set as an anisotropic viscoelastic media.

[0073] Furthermore, in step S40, the P-wave incident reflection and transmission coefficient matrix r is calculated using the propagation matrix method, as shown in the following equation:

[0074] (29)

[0075] In the formula Reflectance coefficient Rpp for The first element is A1, which is the propagation matrix of the upper medium; A2, which is the propagation matrix of the lower medium; and B, which is the propagation matrix of the intermediate layer. P-wave incident vector ,

[0076] Where A1 is:

[0077] (30)

[0078] A2 is:

[0079] (31)

[0080] B is the thickness of the intermediate layer. h The relevant matrix is ​​represented as follows:

[0081] (32)

[0082] T( z )for:

[0083] (33)

[0084] In the formula, i The imaginary unit is the variable. , , W, Z The subscripts P and S correspond to the qP wave and qS wave, respectively, and 1 and 2 represent the upper and lower media, respectively. The abbreviation is omitted as follows:

[0085] (34)

[0086] (35)

[0087] (36)

[0088] (37)

[0089] In the formula, p.v. Indicates the principal value that takes a complex value, for γ The symbol "+" represents a qP wave, and the symbol "" represents a qP wave. "Represents the qS wave, c 11 、 c 13 、c 33 、c 55 The elastic constant of the medium is expressed in GPa. ρ Density of the medium, g / cc;

[0090] s The slowness of a horizontal wave is expressed as:

[0091] (38)

[0092] For isotropic media v p For anisotropic media, this is a constant value. v p It can be expressed by the following formula:

[0093] (39)

[0094] (40)

[0095] s z The vertical wave slowness is expressed as:

[0096] (41)

[0097] In the formula, K 1. K 2 and K 3 are respectively:

[0098] (42)

[0099] In equation (41), (+, ) represents a downward-propagating qP wave, i.e. (+,+) represents a downward-propagating qS wave, i.e. ;( , ) represents an upward-propagating qP wave; ,+) represents an upward-propagating qS wave.

[0100] Furthermore, in step S50, the method for calculating the reflected wave response includes the following steps:

[0101] S501: Select a seismic wavelet and calculate its spectrum; use Fourier transform to calculate the spectrum of the seismic wavelet. W(f) The formula is as follows:

[0102] (43)

[0103] In the formula, W(t) For time-domain seismic wavelets;

[0104] S502: Multiply the frequency domain reflection coefficient by the frequency domain seismic wavelet to calculate the reflected wave amplitude spectrum; reflected wave amplitude spectrum U(f)The calculation formula is as follows:

[0105] (44)

[0106] In the formula, W(f) For frequency domain seismic wavelets, R(f) The frequency domain reflection coefficient;

[0107] S503: Perform an inverse Fourier transform on the amplitude spectrum of the reflected wave to obtain the reflected wave seismic record. u(t) The formula is as follows:

[0108] (45)

[0109] Compared with the prior art, the present invention has the following beneficial effects:

[0110] 1. This invention combines rock physics modeling and seismic forward modeling methods. By introducing the Batzle-Wang formula, it accurately calculates the physical parameters of saline water and combines the Chapman model to characterize the fluid-rock coupling effect. The Chapman model simultaneously considers the influence of fractures and pore fluids of different scales on the viscoelastic properties of rocks, revealing the dispersion and attenuation characteristics of viscoelastic media, and providing a reliable theoretical analysis method for the identification and optimization of carbon reservoir space in saline water layers.

[0111] 2. The seismic forward modeling method proposed in this invention takes into account the viscoelastic properties and thickness of the saline layer, and uses the propagation matrix method to maintain the high-fidelity characteristics of the seismic response. It realizes the systematic simulation and analysis of the reflection wave response of deep saline layers, which is more in line with the actual geological conditions and can quickly and accurately calculate the seismic reflection wave response of deep saline layers.

[0112] 3. This method is low in cost and highly operable, and can efficiently and stably calculate the seismic response of saline aquifers, making up for the shortcomings of existing technologies in the characterization of saline aquifer reservoirs, and providing innovative technical support for the optimization of deep saline aquifers. Attached Figure Description

[0113] Figure 1 This is a flowchart of a high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers, according to the present invention.

[0114] Figure 2 This is a schematic diagram of an ideal geological-seismic forward model.

[0115] Figure 3 The graph shows the variation of the reflection coefficient with frequency and incident angle when the saline water layer is 10m thick.

[0116] Figure 4This is a spectral distribution diagram of the 50Hz Ricker wavelet, reflection coefficient, and reflected wave seismic record.

[0117] Figure 5 This is a single-channel forward modeling record of a saline aquifer with a thickness of 5m and an incident angle of 30 degrees.

[0118] Figure 6 This is a single-channel forward modeling record of a saline aquifer with a thickness of 10m and an incident angle of 30 degrees.

[0119] Figure 7 This is a single-channel forward modeling record of a saline aquifer with a thickness of 15m and an incident angle of 30 degrees.

[0120] Figure 8 This is a single-channel forward modeling record of a saline aquifer with a thickness of 20m and an incident angle of 30 degrees.

[0121] Figure 9 This is a single-channel forward modeling record of a saline aquifer with a thickness of 25m at an incident angle of 30 degrees. Detailed Implementation

[0122] To make the objectives, technical solutions, and advantages 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. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0123] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings, such as... Figure 1 As shown, it includes the following steps:

[0124] S10: Based on the development characteristics of the saline aquifer, establish a rock physics model of the pore fluid in the saline aquifer and calculate the viscosity, bulk modulus, and longitudinal wave velocity of the pore fluid in the saline aquifer.

[0125] Specifically, in step S10, the viscosity, bulk modulus, and longitudinal wave velocity of the pore fluid in the saline aquifer are calculated:

[0126] S101: Calculate the geothermal temperature and formation pressure at the saline aquifer based on the depth of the saline aquifer and the regional geothermal gradient and regional formation pressure gradient.

[0127] The formulas for calculating the ground temperature and formation pressure at the saline aquifer are as follows:

[0128] (1)

[0129] (2)

[0130] in, D The depth of the saline aquifer is measured in km. T Ground temperature, °C; T 0 represents the Earth's surface temperature, in °C. G T The geothermal gradient is expressed in °C / km. P Formation pressure, MPa; P 0 represents the surface pressure, in MPa; G P The pressure gradient is MPa / km.

[0131] S102: Calculate the viscosity of the pore fluid based on the saline aquifer temperature and the saline aquifer pore fluid salinity.

[0132] In this embodiment, the viscosity of the pore fluid in the saline aquifer is calculated using the Batzle-Wang fluid model. The calculation formula is as follows:

[0133] (3)

[0134] in, η Where is the viscosity of the pore fluid, Pa·s; S This represents the mineralization degree of the pore fluid.

[0135] S103: Calculate the density, P-wave velocity, and bulk modulus of the pore fluid based on the geothermal temperature, formation pressure, and salinity of the pore fluid in the saline aquifer.

[0136] In this embodiment, the Batzle-Wang fluid model is used to calculate the density, longitudinal wave velocity, and bulk modulus.

[0137] The formula for calculating the density of pore fluid in a saline aquifer is as follows:

[0138] (4)

[0139] in, ρ represents the density of the pore fluid, in g / cc; The density of pure water is expressed in g / cc.

[0140] The density of pure water varies under different temperatures and pressures:

[0141] (5)

[0142] The longitudinal wave velocity of the pore fluid in the saline aquifer is calculated by the following formula:

[0143] (6)

[0144] in, ρ represents the longitudinal wave velocity of the pore fluid, in g / cc; The longitudinal wave velocity of pure water is given in m / s.

[0145] The formula for calculating the velocity of sound waves in pure water is:

[0146] (7)

[0147] in, These are the weighting coefficients;

[0148] Bulk modulus of pore fluids in saline aquifers K f The calculation formula is:

[0149] (8).

[0150] S20: Based on the development characteristics of the saline aquifer, a multi-scale rock physics model of the saline aquifer is established to obtain the equivalent stiffness matrix of the saline aquifer.

[0151] Specifically, in step S20, the calculation of the equivalent stiffness matrix of the saline water layer includes the following steps:

[0152] S201: Determination of mineral composition of saline aquifer using X-ray diffraction (XRD);

[0153] In this embodiment, the mineral composition of the saline aquifer sandstone in a certain study area was determined, as shown in Table 1:

[0154] Table 1. Mineral composition of saline aquifer sandstone in a certain study area

[0155]

[0156] S202: Calculate the bulk modulus of the saline aquifer matrix based on the measured mineral composition. K shear modulus M and Lamé constant λ and μ ;

[0157] In this embodiment, the Voigt-Reuss-Hill (VRH) model is used to calculate the bulk modulus. K and shear modulus M The formula is as follows:

[0158] (9)

[0159] in, and For the first i The bulk modulus and shear modulus of each component, For the first i The volume fraction of each component.

[0160] bulk modulus K and shear modulus M Convertible to Lamé constant λ and μ As shown in the following formula:

[0161] (10)

[0162] S203: Establish a multi-scale rock physics model of the saline aquifer and calculate the stiffness matrix of fluid-saturated rocks in the saline aquifer. .

[0163] In this embodiment, it is assumed that the rock matrix of the saline aquifer contains pores, mesoscale fractures, and microscale microfractures, and is a typical HTI medium. According to the Chapman model, the stiffness matrix of the fluid-saturated rock in the saline aquifer is... It can be calculated using the following formula:

[0164]

[0165] In the formula, The elastic correction caused by microcracks, in GPa; The elastic correction caused by porosity, in GPa; The elastic correction amount caused by mesoscale cracks, in GPa; The density of microcracks; Porosity; This refers to the density of cracks at the mesoscale. ω is the angular frequency, in rad / s.

[0166] For HTI media, the expressions for each elastic tensor are further given, as shown in equations (12)-(16).

[0167]

[0168]

[0169]

[0170]

[0171] in,

[0172] (17)

[0173] (18)

[0174] (19)

[0175] (20)

[0176] (twenty one)

[0177] (twenty two)

[0178] (twenty three)

[0179] (twenty four)

[0180] (25)

[0181] (26)

[0182]

[0183] In the formula, λ and μ The Lamé constant of the rock matrix obtained in step S202 is given in GPa. Poisson's ratio of the rock matrix; V s denoted as the transverse wave velocity of the rock matrix, in m / s; The density and longitudinal wave velocity of the pore fluid obtained in step S103 are given in g / cc. The longitudinal wave velocity of the pore fluid obtained in step S103 is denoted as m / s. is the bulk modulus of the pore fluid obtained in step S103, in GPa; r The aspect ratio of the crack; Let be the relaxation time at the microscale, in seconds; Let be the relaxation time at the mesoscale, in seconds.

[0184] and It is positively correlated with the viscosity of the pore fluid and can be calculated by the following formula:

[0185] (28)

[0186] In the formula, Let be the radius of the mesoscale crack, in meters. Where is the rock grain size, in meters; For the volume of a single microcrack, m 3 ; Viscosity of the pore fluid calculated for step S102, Pa·s; The critical stress is given in Pa. c 1 represents the number of interconnected pores and cracks; k Let md be the rock permeability.

[0187] In particular, in actual implementation, the parameters of the Chapman model need to be set according to the actual geological conditions of the study area. The parameters used in this embodiment are shown in Table 2.

[0188] Table 2 Input parameters of the Chapman model

[0189]

[0190] S30: Establish a geological-seismic forward model;

[0191] In this embodiment, considering the actual geological conditions of carbon dioxide sequestration in saline aquifers, a three-layer geological-seismic model is established, such as... Figure 2 As shown, the upper and lower layers are mudstone, which serves as the caprock and shielding layer, respectively, while the middle layer is a saline-water carbon reservoir. The upper and lower layers are designed as isotropic media, and the middle layer is designed as an anisotropic viscoelastic media.

[0192] In this embodiment, the physical property parameters of the isotropic upper and lower media are set according to the actual geological conditions, as shown in Table 3.

[0193] Table 3 Physical property parameters of upper and lower layers of media

[0194]

[0195] S40: Calculate the reflection and transmission coefficient matrices of the saline aquifer using the propagation matrix method;

[0196] Specifically, in step S40, the P-wave incident reflection and transmission coefficient matrix r is calculated using the propagation matrix method, as shown in the following equation:

[0197] (29)

[0198] In the formula Reflectance coefficient R pp for The first element A1 is the propagation matrix of the upper medium, A2 is the propagation matrix of the lower medium, and B is the propagation matrix of the intermediate layer. P-wave incident vector .

[0199] Where A1 is:

[0200] (30)

[0201] A2 is:

[0202] (31)

[0203] B is the thickness of the intermediate layer. h The relevant matrix is ​​represented as follows:

[0204] (32)

[0205] T( z )for:

[0206] (33)

[0207] In the formula, i The imaginary unit is the variable. , , W, Z The subscripts P and S correspond to the qP wave and qS wave, respectively, and 1 and 2 represent the upper and lower media, respectively. The abbreviation is omitted as follows:

[0208] (34)

[0209] (35)

[0210] (36)

[0211] (37)

[0212] In the formula, p.v. Indicates the principal value that takes a complex value, for γ The symbol "+" represents a qP wave, and the symbol "" represents a qP wave. "Represents the qS wave, c 11 、 c 13 、c 33 、c 55 The elastic constant of the medium is expressed in GPa. ρ The density of the medium is expressed in g / cc.

[0213] s The slowness of a horizontal wave is expressed as:

[0214] (38)

[0215] For isotropic media v p For anisotropic media, this is a constant value. v p It can be expressed by the following formula:

[0216] (39)

[0217] (40)

[0218] s z The vertical wave slowness is expressed as:

[0219] (41)

[0220] In the formula, K 1. K 2 and K 3 are respectively:

[0221] (42)

[0222] In equation (41), (+, ) represents a downward-propagating qP wave, i.e. (+,+) represents a downward-propagating qS wave, i.e. ;( , ) represents an upward-propagating qP wave; ,+) represents an upward-propagating qS wave.

[0223] Figure 3 The figure shows the distribution of the reflection coefficient of a 10m thick saline aquifer under different incident angles and frequencies. As can be seen from the figure, the reflection coefficient changes periodically with frequency, and a similar pattern exists under different incident angles.

[0224] S50: Calculate the seismic response of the reflected waves from the saline aquifer.

[0225] Specifically, in step S50, the calculation of the seismic response of the saline water layer reflected waves includes the following steps:

[0226] S501: Select a suitable seismic wavelet and calculate its spectrum;

[0227] In this embodiment, a 50Hz Lake wavelet is selected, and the spectrum of the seismic wavelet is calculated using Fourier transform. W(f) The formula is as follows:

[0228] (43)

[0229] In the formula, W(t) It is a time-domain seismic wavelet.

[0230] S502: Multiply the frequency domain reflection coefficient by the frequency domain seismic wavelet to calculate the amplitude spectrum of the reflected wave. U(f) The calculation formula is as follows:

[0231] (44)

[0232] In the formula, W(f) For frequency domain seismic wavelets, R(f) This is the frequency domain reflection coefficient.

[0233] Figure 4 The image shows the spectrum of the Ricker wavelet, reflection coefficient, and reflected wave seismic record when the saline aquifer thickness is 10m. It can be seen that the dominant frequency of the Ricker wavelet is around 50Hz, the dominant frequency of the reflection coefficient is around 130Hz, and the dominant frequency of the reflected wave seismic record is around 55Hz.

[0234] S503: Perform an inverse Fourier transform on the amplitude spectrum of the reflected wave to obtain the time-domain reflected wave seismic record. The formula is as follows:

[0235] (45)

[0236] Figures 5-9 The image shows single-channel seismic forward modeling records at different aquifer thicknesses under a 30-degree incident angle. Figure 5 This is a single-track forward modeling record of a saline aquifer with a thickness of 5m. Figure 6 This is a single-channel forward modeling record of a saline aquifer with a thickness of 10m. Figure 7 This is a single-channel forward modeling record of a saline aquifer with a thickness of 15m. Figure 8 This is a single-channel forward modeling record of a saline aquifer with a thickness of 20m. Figure 9 This is a single-channel forward modeling record of a saline aquifer with a thickness of 25m. As can be seen from the figure, the greater the thickness of the saline aquifer, the longer the time span of the top and bottom interfaces.

[0237] The calculation results from the examples demonstrate that the method of this invention has significant advantages in reflecting the seismic response of deep saline aquifers. Traditional seismic forward modeling methods often only consider the rock skeleton and ideal fluid characteristics, failing to fully characterize the influence of saline water on the propagation characteristics of seismic waves, resulting in large deviations between simulation results and reality. This invention accurately calculates saline water physical parameters by introducing the Batzle-Wang formula, characterizes the fluid-rock coupling effect by combining it with the Chapman model, and maintains the high-fidelity characteristics of the seismic response using the propagation matrix method, thus achieving a systematic simulation and analysis of the reflected wave response of deep saline aquifers. This invention overcomes the shortcomings of existing technologies in the characterization of saline aquifer reservoirs and provides innovative technical support for the optimal selection of deep saline aquifers.

[0238] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0239] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers, characterized in that, Including the following steps: S10: Based on the development characteristics of the saline aquifer, establish a rock physics model of the pore fluid in the saline aquifer and calculate the viscosity, density, longitudinal wave velocity and bulk modulus of the pore fluid in the saline aquifer. S20: Based on the development characteristics of the saline aquifer, a multi-scale rock physics model of the saline aquifer is established to obtain the equivalent stiffness matrix of the saline aquifer. S30: Establish a geological-seismic forward model; S40: Calculate the reflection and transmission coefficient matrices of the saline aquifer using the propagation matrix method; S50: Calculate the reflected wave response of the saline water layer; The calculation method for the response of the saline layer reflection wave includes the following steps: S501: Select the seismic wavelet and calculate the spectrum of the seismic wavelet using Fourier transform; S502: Multiply the frequency domain reflection coefficient with the frequency domain seismic wavelet to calculate the amplitude spectrum of the reflected wave; S503: Perform an inverse Fourier transform on the amplitude spectrum of the reflected wave to obtain the seismic record of the reflected wave.

2. The high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers according to claim 1, characterized in that: In step S10, calculating the viscosity, density, longitudinal wave velocity, and bulk modulus of the pore fluid in the saline aquifer includes the following steps: S101: Calculate the geothermal temperature and formation pressure at the saline aquifer based on the depth of the saline aquifer and the regional geothermal gradient and regional formation pressure gradient. S102: Calculate the viscosity of the pore fluid based on the saline aquifer temperature and the saline aquifer pore fluid salinity; S103: Calculate the density, P-wave velocity, and bulk modulus of the pore fluid based on the geothermal temperature, formation pressure, and salinity of the pore fluid in the saline aquifer.

3. The high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers according to claim 2, characterized in that: In step S101, the formulas for calculating the ground temperature and formation pressure at the saline aquifer are as follows: (1) (2) in, D The depth of the saline aquifer is measured in km. T Ground temperature, °C; T 0 represents the Earth's surface temperature, in °C. G T The geothermal gradient is expressed in °C / km. P Formation pressure, MPa; P 0 represents the surface pressure, in MPa; G P The formation pressure gradient is expressed in MPa / km.

4. The high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers according to claim 2, characterized in that: In step S102, the viscosity of the pore fluid in the saline aquifer is calculated using the Batzle-Wang fluid model. The calculation formula is as follows: (3) in, η Where is the viscosity of the pore fluid, Pa·s; S This represents the mineralization degree of the pore fluid.

5. The high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers according to claim 2, characterized in that: In step S103, the density, longitudinal wave velocity, and bulk modulus are calculated using the Batzle-Wang fluid model; The formula for calculating the density of pore fluid in a saline aquifer is as follows: (4) in, ρ represents the density of the pore fluid, in g / cc; The density of pure water is expressed in g / cc. The density of pure water varies under different temperatures and pressures: (5) The longitudinal wave velocity of the pore fluid in the saline aquifer is calculated by the following formula: (6) in, ρ represents the longitudinal wave velocity of the pore fluid, in g / cc; The longitudinal wave velocity of pure water is given in m / s. The formula for calculating the velocity of sound waves in pure water is: (7) in, These are the weighting coefficients; Bulk modulus of pore fluids in saline aquifers K f The calculation formula is: (8)。 6. The high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers according to claim 1, characterized in that: In step S20, assuming the saline aquifer is a viscoelastic medium represented by the Chapman model, the establishment of the multi-scale rock physics model of the saline aquifer and the calculation of the equivalent stiffness matrix include the following steps: S201: Determination of mineral composition of saline aquifer using X-ray diffraction; S202: Calculate the bulk modulus of the saline aquifer matrix based on the measured mineral composition. K shear modulus M and Lamé constant λ and μ ; S203: Establish a multi-scale rock physics model of the saline aquifer and calculate the stiffness matrix of fluid-saturated rocks in the saline aquifer. .

7. A high-fidelity calculation method for seismic reflection wave response applicable to deep saline water layers according to claim 6, characterized in that: In step S202, the bulk modulus is calculated using the Voigt-Reuss-Hill model. K and shear modulus M The formula is as follows: (9) in, and For the first i The bulk modulus and shear modulus of each component, For the first i The volume fraction of each component; bulk modulus K and shear modulus M Convert to Lamé constant λ and μ As shown in the following formula: (10)。 8. A high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers according to claim 6, characterized in that: In step S203, it is assumed that the rock matrix of the saline aquifer sandstone contains pores, mesoscale fractures, and microscale microfractures, and is a typical HTI medium. According to the Chapman model, the stiffness matrix of the fluid-saturated rock in the saline aquifer is... Calculated by the following formula: (11) In the formula, The elastic correction caused by microcracks, in GPa; The elastic correction caused by porosity, in GPa; The elastic correction amount caused by mesoscale cracks, in GPa; The density of microcracks; Porosity; This refers to the density of cracks at the mesoscale. Angular frequency, rad / s; For HTI media, the expressions for each elastic tensor are further given, as shown in equations (12)-(16). (12) (13) (14) (15) (16) in, (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27) In the formula, λ and μ The Lamé constant of the rock matrix obtained in step S202 is given in GPa. Poisson's ratio of the rock matrix; V s denoted as the transverse wave velocity of the rock matrix, in m / s; The density of the pore fluid obtained in step S103 is given in g / cc. The longitudinal wave velocity of the pore fluid obtained in step S103 is denoted as m / s. is the bulk modulus of the pore fluid obtained in step S103, in GPa; r The aspect ratio of the crack; Let be the relaxation time at the microscale, in seconds; Let be the relaxation time at the mesoscale, in seconds; i' The imaginary unit; and It is positively correlated with the viscosity of the pore fluid and can be calculated by the following formula: (28) In the formula, Let be the radius of the mesoscale crack, in meters. Rock grain size, in meters; For the volume of a single microcrack, m 3 ; Viscosity of the pore fluid calculated for step S102, Pa·s; The critical stress is given in Pa. c 1 represents the number of interconnected pores and cracks; k For penetration rate, md.

9. A high-fidelity simulation calculation method for seismic reflection wave response applicable to deep saline water layers according to claim 1, characterized in that: In step S40, the P-wave incident reflection and transmission coefficient matrix r is calculated using the propagation matrix method, as shown in the following equation: (29) In the formula Reflectance coefficient R pp for The first element is A1, which is the propagation matrix of the upper medium; A2, which is the propagation matrix of the lower medium; and B, which is the propagation matrix of the intermediate layer. P-wave incident vector ; Where A1 is: (30) A2 is: (31) B is the thickness of the intermediate layer. h The relevant matrix is ​​represented as follows: (32) T( z )for: (33) In the formula, i' The imaginary unit is the variable. , , W, Z The subscripts P and S correspond to the qP wave and qS wave, respectively, and 1 and 2 represent the upper and lower media, respectively. The abbreviation is omitted as follows: (34) (35) (36) (37) In the formula, pv Indicates the principal value that takes a complex value, for γ The symbol "+" represents a qP wave, and the symbol "" represents a qP wave. "Represents the qS wave, c 11 、c 13 、 c 33 、c 55 GPa represents the elastic constant of the medium; ρ The density of the medium is expressed in g / cc. s The slowness of a horizontal wave is expressed as: (38) For isotropic media v p For anisotropic media, this is a constant value. v p It can be expressed by the following formula: (39) (40) s z The vertical wave slowness is expressed as: (41) In the formula, K 1. K 2 and K 3 are respectively: (42) In equation (41), (+, ) represents a downward-propagating qP wave, i.e. (+,+) represents a downward-propagating qS wave, i.e. ;( , ) represents an upward-propagating qP wave; ,+) represents an upward-propagating qS wave.

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