A three-dimensional geostress prediction method based on curvature properties

Abstract

This invention provides a three-dimensional geostress prediction method based on curvature attributes, belonging to the field of petroleum seismic exploration technology. The invention includes the following steps: based on centrifugal window scanning, extracting the three-dimensional maximum positive curvature and minimum negative curvature of the formation using post-stack seismic data, and calculating the maximum and minimum horizontal strain of the formation; establishing an orthotropic anisotropic shale petrophysical model, estimating the normal compaction bulk modulus; performing elastic impedance inversion using small, medium, and large angle seismic gathers to obtain angular elastic impedance volumes; obtaining the inversion results of Young's modulus, Poisson's ratio, and bulk modulus based on the angular elastic impedance volumes; and obtaining the three-dimensional geostress prediction results. This invention does not require multi-azimuth seismic data, is simple to implement, ensures the stability of the inversion results, and provides a method for three-dimensional formation pressure prediction, making three-dimensional geostress prediction feasible and yielding more accurate results.

Description

Technical Field

[0001] This invention relates to the field of petroleum seismic exploration technology, and in particular to a three-dimensional geostress prediction method based on curvature properties. Background Technology

[0002] In-situ stress refers to the stress underground that is not affected by human activity. It is composed of overlying stress caused by gravity, tectonic stress caused by geological movements, and stress generated by other underground factors. In unconventional oil and gas exploration and development, formation fracturing is a crucial step. In-situ stress prediction can provide technical guidance for formation fracturing, determining the morphology and orientation of fractures produced by hydraulic fracturing in reservoirs. Therefore, reliable in-situ stress calculation can improve the production and recovery rate of unconventional oil and gas reservoirs.

[0003] There are many methods for measuring in-situ stress, such as hydraulic fracturing, flat jack method, and strain relief. Currently, accurate in-situ stress values ​​are mainly obtained from surface in-situ stress measurements or fracturing experiments. Although these methods yield accurate values, they are time-consuming, costly, and only provide stress values ​​at a single point on the surface, not continuous values ​​for the entire well. With technological advancements, seismic data estimation has emerged as a new method for in-situ stress prediction. This method can obtain continuous stress profiles for a specific area, calculating stress even in areas with few wells. It overcomes the limitations imposed by location constraints, providing lateral prediction of stress across the entire work area. This offers theoretical guidance for well placement and hydraulic fracturing development, featuring a wide prediction range and continuous data distribution, giving it unique advantages in in-situ stress prediction.

[0004] To obtain three-dimensional geostress prediction results, current methods typically start with constitutive relations, establishing relationships between elastic parameters, anisotropic parameters, and geostress. Then, azimuth seismic data is used to invert the elastic or anisotropic parameters, thereby predicting the three-dimensional geostress. This method requires a large amount of azimuth seismic data and does not consider the significant influence of pore pressure on geostress.

[0005] The existing main three-dimensional geostress prediction technology starts from the constitutive equation, derives the relationship between linear parameters or anisotropic parameters and geostress, and then uses front-stack seismic data to predict three-dimensional geostress. The main steps are as follows: (1) Based on the generalized Hooke's law, derive the relationship between the elastic coefficient and the horizontal maximum principal stress and the horizontal minimum principal stress. Alternatively, based on the relationship between anisotropic parameters and elastic coefficients, further derive the geostress prediction equation expressed by anisotropic parameters. (2) Use multi-azimuth seismic data to invert the anisotropic parameters or elastic coefficients required for three-dimensional geostress. (3) Use the relationship established in step (1) to invert the three-dimensional geostress.

[0006] The existing technology has the following shortcomings:

[0007] 1. Multi-directional seismic data is needed, but the process of acquiring multi-directional seismic data is complex and labor-intensive. Furthermore, the technology for inverting anisotropic parameters or elastic coefficients using pre-stack seismic data is not yet mature enough, and the stability of the inversion results cannot be guaranteed.

[0008] 2. There is a strong correlation between underground in-situ stress and formation pressure, but most current methods do not consider the influence of formation pressure on in-situ stress;

[0009] 3. Although some three-dimensional geostress prediction models consider the influence of formation pressure on geostress, they do not provide a suitable three-dimensional formation pressure prediction method. Summary of the Invention

[0010] To address the problems existing in the prior art, this invention provides a three-dimensional geostress prediction method based on curvature attributes, comprising the following steps: Based on centrifugal window scanning, extracting the three-dimensional maximum positive curvature and minimum negative curvature attributes of the strata using post-stack seismic data, and calculating the maximum and minimum horizontal strain of the strata; considering the normal compaction of the strata, establishing an orthotropic anisotropic shale petrophysical model, and estimating the normal compaction bulk modulus; performing elastic impedance inversion using small-angle, medium-angle, and large-angle seismic gathers to obtain angular elastic impedance volumes; obtaining the inversion results of Young's modulus, Poisson's ratio, and bulk modulus based on the angular elastic impedance volumes; obtaining the three-dimensional formation pressure prediction results based on the inverted bulk modulus and the normal compaction bulk modulus; and calculating the three-dimensional geostress prediction results based on the inverted Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain of the strata. This invention does not require multi-azimuth seismic data, is simple to implement, ensures the stability of the inversion results, and provides a method for three-dimensional formation pressure prediction, making three-dimensional geostress prediction feasible and more accurate.

[0011] This invention provides a three-dimensional geostress prediction method based on curvature properties, comprising the following steps:

[0012] Based on centrifugal window scanning, the three-dimensional maximum positive curvature and minimum negative curvature properties of the strata are extracted using post-stack seismic data, and the maximum and minimum horizontal strain of the strata are calculated.

[0013] Considering the normal compaction of the formation, an orthotropic anisotropic shale petrophysical model is established to estimate the normal compaction bulk modulus;

[0014] Elastic impedance inversion was performed using small-angle, medium-angle, and large-angle seismic gathers to obtain angular elastic impedance volumes. Small-angle, medium-angle, and large-angle seismic gathers were then classified based on actual seismic data.

[0015] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus are obtained from the inversion of the angular elastic impedance body.

[0016] Based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained;

[0017] Based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated.

[0018] Preferably, the three-dimensional maximum positive curvature and minimum negative curvature attributes of the strata are extracted using post-stack seismic data, and the maximum horizontal strain ε of the strata is calculated using the following formula. y and minimum strain ε x :

[0019] ε x =-zK x

[0020] ε y =-zK y

[0021] in,

[0022] z is the time thickness of the stratum;

[0023] K x and K y These are the minimum negative curvature and the maximum positive curvature, respectively.

[0024] Preferably, considering the normal compaction of the formation, the process of establishing an orthotropic anisotropic shale petrophysical model includes the following steps:

[0025] Mix clay and kerogen to form clay blocks;

[0026] Multiple different polarization angles θ and azimuth angles The stacking of clay blocks simulates the stratification of shale;

[0027] Minerals were added to the clay blocks that simulated layered shale, along with normal compaction pores and cracks;

[0028] Add fluid to the dry rock skeleton.

[0029] Preferably, clay and kerogen are mixed using any one of the following models: anisotropic self-compatible approximation model, Kuster-Toksoz model, or anisotropic equivalent differential medium model, to form clay blocks.

[0030] Preferably, an anisotropic self-compatible approximation model is used to mix clay and kerogen to form clay blocks, specifically obtained through the following formula:

[0031]

[0032] in,

[0033] SCA stands for anisotropic self-compatible approximation model;

[0034] The matrix representing the elastic stiffness of the clay block;

[0035] n represents the nth component;

[0036] It is the elastic stiffness matrix of the nth component. For example, when n=1, it represents the elastic stiffness matrix of clay, and when n=2, it represents the elastic stiffness matrix of kerogen.

[0037] v n It is the percentage of the nth component by volume in the clay block;

[0038] As a tensor, it describes the effect of the inclusion clay and kerogen shapes on the equivalent medium;

[0039] N is the total number of components in the clay block; in this case, N = 2.

[0040] It is an identity matrix.

[0041] Preferably, multiple different polarization angles θ and azimuth angles are used. The superposition of clay blocks simulates the stratification of shale, specifically including:

[0042] Calculate the elastic stiffness matrix for each clay block;

[0043] The elastic stiffness matrix of different clay blocks was obtained;

[0044] The elastic stiffness matrix of layered clay is obtained.

[0045] Preferably, the Bond transformation is used to calculate the elastic stiffness matrix of each clay block to obtain the elastic stiffness matrix of different clay blocks.

[0046] The elastic stiffness matrix of each clay block is:

[0047]

[0048]

[0049] in,

[0050] θ is the polarization angle of the clay block;

[0051] The azimuth angle of the clay block;

[0052] M θ This is the coordinate transformation matrix for the polarization angle of the clay block;

[0053] This is the coordinate transformation matrix for the azimuth angle of the clay block;

[0054] The elastic stiffness matrix of different clay blocks is as follows:

[0055]

[0056] The polarization angle is θ and the azimuth angle is The elastic stiffness matrix of the clay blocks, with different clay blocks having different polarization angles and azimuth angles.

[0057] Preferably, the elastic stiffness matrix of different clay blocks is used. Substituting into Backus's average theory, we obtain the elastic stiffness matrix C of layered clay. Ba .

[0058] Preferably, minerals are added to the clay-mass-simulated layered shale, and normal compaction pores and cracks are added, specifically including:

[0059] The mineral mixture and its modulus were obtained.

[0060] Mineral mixtures and pores are added to layered clay to form a rock matrix;

[0061] Cracks are incorporated into the rock matrix to form a dry rock skeleton;

[0062] Fluid is added to the dry rock skeleton to form saturated rock under normal compaction conditions.

[0063] Preferably, the modulus of the mineral mixture is obtained by averaging the main mineral components of shale using the Hashin-Shtrikman-Hill average with the following formula. The main mineral components of shale include quartz, calcite, dolomite, and pyrite.

[0064]

[0065] in,

[0066] M HS+ and M HS- These are the upper and lower limits of the modulus of the mineral mixture, respectively.

[0067] M HSH It represents the modulus of the mineral mixture.

[0068] Preferably, the Voigt-Reuss-Hill average is used to average the main mineral components of the shale to obtain the modulus of the mineral mixture. The main mineral components of the shale include quartz, calcite, dolomite and pyrite.

[0069] Preferably, an anisotropic equivalent differential medium model is used to add mineral mixtures and pores into layered clay to form a rock matrix, and the elastic stiffness matrix of the rock matrix is ​​calculated.

[0070] Preferably, the mineral mixture and pores are added to the layered clay using an anisotropic self-compatible approximation model to form a rock matrix, and the elastic stiffness matrix of the rock matrix is ​​calculated.

[0071] Preferably, the Hudson model is used to incorporate cracks into the rock matrix to form a dry rock skeleton, and the elastic stiffness matrix of the dry rock skeleton is calculated.

[0072] Preferably, the Eshelby-Cheng model is used to incorporate cracks into the rock matrix to form a dry rock skeleton, and the elastic stiffness matrix of the dry rock skeleton is calculated.

[0073] Preferably, the anisotropic Gassmann equation is used to add fluid into the dry rock skeleton, and the elastic stiffness matrix of the saturated rock is calculated.

[0074] Preferably, the estimated normal compaction bulk modulus is as follows:

[0075]

[0076] in,

[0077] K n It is the normal compaction bulk modulus;

[0078] c 12 and c 44 These are the elastic stiffness matrices of saturated rock. The elements in the first row and second column and the fourth row and fourth column.

[0079] Preferably, the angular elastic impedance volume is obtained by using post-stack sparse pulse inversion technology, taking small-angle, medium-angle, and large-angle seismic gathers as input, specifically including:

[0080] The elastic impedance equations for Young's modulus and Poisson's ratio are obtained from the YPD equation as follows;

[0081]

[0082] in,

[0083] EI is the elastic resistance;

[0084] t is time;

[0085] θ1, θ2, and θ3 represent small, medium, and large angles, respectively.

[0086] a, b, and c are all constants;

[0087] E is Young's modulus;

[0088] E0 is the average value of Young's modulus;

[0089] ν is Poisson's ratio, and ν0 is the average value of Poisson's ratio;

[0090] ρ is density, and ρ0 is the average density.

[0091] The elastic impedance equation for the bulk modulus is derived from the Archi-Richard equation as follows:

[0092]

[0093] in,

[0094] k, l, and m are all constants;

[0095] K is the bulk modulus;

[0096] K0 is the average value of the bulk modulus;

[0097] μ is the shear modulus;

[0098] μ0 is the average value of Poisson's ratio.

[0099] Preferably, the inversion results of Young's modulus, Poisson's ratio, and bulk modulus obtained from the inversion of the angular elastic impedance body are as follows:

[0100] Substituting the inverted small-angle, medium-angle, and large-angle elastic impedance bodies into the elastic impedance equations of Young's modulus and Poisson's ratio, we obtain the inversion results of Young's modulus and Poisson's ratio.

[0101] Substituting the small-angle, medium-angle, and large-angle elastic impedance bodies obtained from the inversion into the elastic impedance equation for the bulk modulus, we obtain the bulk modulus.

[0102] Preferably, the three-dimensional formation pressure prediction results are obtained based on the inverted bulk modulus and the normal compaction bulk modulus, specifically as follows:

[0103] Substituting the inverted bulk modulus and the normal compaction bulk modulus into the following formula, we obtain the three-dimensional formation pressure prediction results:

[0104]

[0105] in,

[0106] P p Formation pressure;

[0107] P o This refers to the pressure of the overlying strata.

[0108] P n It is the hydrostatic pressure;

[0109] K is the measured bulk modulus;

[0110] c is a constant.

[0111] Preferably, the Eaton method is used to obtain the three-dimensional formation pressure prediction results based on the inverted bulk modulus and the normal compaction bulk modulus.

[0112] Preferably, the Bower method is used to obtain the three-dimensional formation pressure prediction results based on the inverted bulk modulus and the normal compaction bulk modulus.

[0113] Preferably, the predicted results of three-dimensional geostress are calculated based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, specifically as follows:

[0114] Substituting the inversion results of Young's modulus and Poisson's ratio, along with the bulk modulus and the predicted three-dimensional formation pressure, into the following spring model formula, we obtain the predicted three-dimensional geostress:

[0115]

[0116]

[0117] in,

[0118] σ H It is the maximum horizontal principal stress;

[0119] σ h It is the minimum horizontal principal stress;

[0120] α is the Boit coefficient;

[0121] ε y It is the maximum horizontal strain of the strata;

[0122] ε x It is the minimum horizontal strain of the formation.

[0123] Preferably, the predicted results of three-dimensional geostress are calculated using a uniaxial strain model based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain of the formation, and minimum horizontal strain of the formation obtained by inversion.

[0124] Preferably, based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated using the Huang model.

[0125] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0126] (1) This invention only requires small-angle, medium-angle, and large-angle seismic gathers, without the need for multi-directional seismic data, making it simple to implement;

[0127] (2) The curvature attribute in this invention is extracted from post-stack seismic data and the stress-sensitive parameters Young's modulus and Poisson's ratio are inverted. The inversion technology of stress-sensitive parameters Young's modulus and Poisson's ratio is mature, which ensures the stability of the inversion results.

[0128] (3) The three-dimensional formation pressure prediction method based on the rock physics model of this invention takes into account the influence of formation pressure and gives a prediction model of three-dimensional formation pressure. Finally, the spring model is used to predict stable and accurate three-dimensional geostress, ensuring the accuracy of the results. Attached Figure Description

[0129] Figure 1 A flowchart of a three-dimensional geostress prediction method based on curvature properties according to an embodiment of the present invention;

[0130] Figure 2 A flowchart of a three-dimensional geostress prediction method based on curvature attributes according to another embodiment of the present invention;

[0131] Figure 3 (a) and (b) are the maximum and minimum horizontal strains of a certain stratum calculated according to an embodiment of the present invention, respectively.

[0132] Figure 4 This is a schematic diagram comparing the normal compaction bulk modulus with the measured bulk modulus obtained in one embodiment of the present invention;

[0133] Figure 5 This is a schematic diagram of a well-connected profile of a three-dimensional formation pressure prediction result obtained according to an embodiment of the present invention;

[0134] Figure 6 This is a schematic diagram of the maximum horizontal principal stress prediction result obtained from a three-dimensional geostress well-connected profile according to an embodiment of the present invention;

[0135] Figure 7 This is a schematic diagram of the minimum horizontal principal stress prediction result of a three-dimensional geostress well profile obtained according to an embodiment of the present invention;

[0136] Figure 8This is a schematic diagram comparing the maximum horizontal principal stress in the wellbore with the maximum horizontal geostress above the well, obtained from a three-dimensional geostress prediction result according to an embodiment of the present invention.

[0137] Figure 9 This is a schematic diagram comparing the minimum horizontal principal stress in the wellbore and the minimum horizontal geostress above the well, obtained from a three-dimensional geostress prediction result according to an embodiment of the present invention. Detailed Implementation

[0138] The following is in conjunction with the appendix Figure 1-9 The specific embodiments of the present invention will be described in detail below.

[0139] This invention provides a three-dimensional geostress prediction method based on curvature properties, comprising the following steps:

[0140] Based on centrifugal window scanning, the three-dimensional maximum positive curvature and minimum negative curvature properties of the strata are extracted using post-stack seismic data, and the maximum and minimum horizontal strain of the strata are calculated.

[0141] Considering the normal compaction of the formation, an orthotropic anisotropic shale petrophysical model is established to estimate the normal compaction bulk modulus;

[0142] Elastic impedance inversion was performed using small-angle, medium-angle, and large-angle seismic gathers to obtain angular elastic impedance volumes. Small-angle, medium-angle, and large-angle seismic gathers were then classified based on actual seismic data.

[0143] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus are obtained from the inversion of the angular elastic impedance body.

[0144] Based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained;

[0145] Based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated.

[0146] According to a specific embodiment of the present invention, the three-dimensional maximum positive curvature and minimum negative curvature attributes of the strata are extracted using post-stack seismic data, and the maximum horizontal strain ε of the strata is calculated using the following formula. y and minimum strain ε x :

[0147] ε x =-zK x

[0148] ε y =-zK y

[0149] in,

[0150] z is the time thickness of the stratum;

[0151] K x and K y These are the minimum negative curvature and the maximum positive curvature, respectively.

[0152] According to a specific embodiment of the present invention, considering the normal compaction of the formation, the process of establishing an orthotropic anisotropic shale petrophysical model includes the following steps:

[0153] Mix clay and kerogen to form clay blocks;

[0154] Multiple different polarization angles θ and azimuth angles The stacking of clay blocks simulates the stratification of shale;

[0155] Minerals were added to the clay blocks that simulated layered shale, along with normal compaction pores and cracks;

[0156] Add fluid to the dry rock skeleton.

[0157] According to a specific embodiment of the present invention, clay and kerogen are mixed using any one of the following models: anisotropic self-compatible approximation model, Kuster-Toksoz model, and anisotropic equivalent differential medium model, to form a clay block.

[0158] According to a specific embodiment of the present invention, clay and kerogen are mixed using an anisotropic self-compatible approximation model to form clay blocks, specifically obtained by the following formula:

[0159]

[0160] in,

[0161] SCA stands for anisotropic self-compatible approximation model;

[0162] The matrix representing the elastic stiffness of the clay block;

[0163] n represents the nth component;

[0164] It is the elastic stiffness matrix of the nth component. For example, when n=1, it represents the elastic stiffness matrix of clay, and when n=2, it represents the elastic stiffness matrix of kerogen.

[0165] v n It is the percentage of the nth component by volume in the clay block;

[0166] As a tensor, it describes the effect of the inclusion clay and kerogen shapes on the equivalent medium;

[0167] N is the total number of components in the clay block; in this case, N = 2.

[0168] It is an identity matrix.

[0169] According to a specific embodiment of the present invention, multiple different polarization angles θ and azimuth angles are used. The superposition of clay blocks simulates the stratification of shale, specifically including:

[0170] Calculate the elastic stiffness matrix for each clay block;

[0171] The elastic stiffness matrix of different clay blocks was obtained;

[0172] The elastic stiffness matrix of layered clay is obtained.

[0173] According to a specific embodiment of the present invention, the elastic stiffness matrix of each clay block is calculated by Bond transformation to obtain the elastic stiffness matrix of different clay blocks.

[0174] The elastic stiffness matrix of each clay block is:

[0175]

[0176]

[0177] in,

[0178] θ is the polarization angle of the clay block;

[0179] The azimuth angle of the clay block;

[0180] M θ This is the coordinate transformation matrix for the polarization angle of the clay block;

[0181] M φ This is the coordinate transformation matrix for the azimuth angle of the clay block;

[0182] The elastic stiffness matrix of different clay blocks is as follows:

[0183]

[0184] The polarization angle is θ and the azimuth angle is The elastic stiffness matrix of the clay blocks, with different clay blocks having different polarization angles and azimuth angles.

[0185] According to a specific embodiment of the present invention, the elastic stiffness matrix of different clay blocks is... Substituting into Backus's average theory, we obtain the elastic stiffness matrix C of layered clay. Ba .

[0186] According to a specific embodiment of the present invention, minerals are added to a clay block-simulated layered shale, and normal compaction pores and cracks are added, specifically including:

[0187] The mineral mixture and its modulus were obtained.

[0188] Mineral mixtures and pores are added to layered clay to form a rock matrix;

[0189] Cracks are incorporated into the rock matrix to form a dry rock skeleton;

[0190] Fluid is added to the dry rock skeleton to form saturated rock under normal compaction conditions.

[0191] According to a specific embodiment of the present invention, the modulus of the mineral mixture is obtained by averaging the main mineral components of shale using the Hashin-Shtrikman-Hill average with the following formula. The main mineral components of the shale include quartz, calcite, dolomite, and pyrite.

[0192]

[0193] in,

[0194] M HS+ and M HS- These are the upper and lower limits of the modulus of the mineral mixture, respectively.

[0195] M HSH It represents the modulus of the mineral mixture.

[0196] According to a specific embodiment of the present invention, the main mineral components of shale are averaged using the Voigt-Reuss-Hill average to obtain the modulus of the mineral mixture. The main mineral components of the shale include quartz, calcite, dolomite and pyrite.

[0197] According to a specific embodiment of the present invention, a mineral mixture and pores are added to layered clay using an anisotropic equivalent differential medium model to form a rock matrix, and the elastic stiffness matrix of the rock matrix is ​​calculated.

[0198] According to a specific embodiment of the present invention, an anisotropic self-compatible approximation model is used to add mineral mixtures and pores into layered clay to form a rock matrix, and the elastic stiffness matrix of the rock matrix is ​​calculated.

[0199] According to a specific embodiment of the present invention, the Hudson model is used to incorporate cracks into the rock matrix to form a dry rock skeleton, and the elastic stiffness matrix of the dry rock skeleton is calculated.

[0200] According to a specific embodiment of the present invention, the Eshelby-Cheng model is used to incorporate cracks into the rock matrix to form a dry rock skeleton, and the elastic stiffness matrix of the dry rock skeleton is calculated.

[0201] According to a specific embodiment of the present invention, fluid is added to a dry rock skeleton using the anisotropic Gassmann equation, and the elastic stiffness matrix of the saturated rock is calculated.

[0202] According to a specific embodiment of the present invention, the estimated normal compaction bulk modulus is specifically shown in the following formula:

[0203]

[0204] in,

[0205] K n It is the normal compaction bulk modulus;

[0206] c 12 and c 44 These are the elastic stiffness matrices of saturated rock. The elements in the first row and second column and the fourth row and fourth column.

[0207] According to a specific embodiment of the present invention, post-stack sparse pulse inversion technology is used to invert angular elastic impedance volumes by taking small-angle, medium-angle, and large-angle seismic gathers as inputs, specifically including:

[0208] The elastic impedance equations for Young's modulus and Poisson's ratio are obtained from the YPD equation as follows;

[0209]

[0210] in,

[0211] EI is the elastic resistance;

[0212] t is time;

[0213] θ1, θ2, and θ3 represent small, medium, and large angles, respectively.

[0214] a, b, and c are all constants;

[0215] E is Young's modulus;

[0216] E0 is the average value of Young's modulus;

[0217] ν is Poisson's ratio, and ν0 is the average value of Poisson's ratio;

[0218] ρ is density, and ρ0 is the average density.

[0219] The elastic impedance equation for the bulk modulus is derived from the Archi-Richard equation as follows:

[0220]

[0221] in,

[0222] k, l, and m are all constants;

[0223] K is the bulk modulus;

[0224] K0 is the average value of the bulk modulus;

[0225] μ is the shear modulus;

[0226] μ0 is the average value of Poisson's ratio.

[0227] According to a specific embodiment of the present invention, the inversion results of Young's modulus, Poisson's ratio, and bulk modulus obtained from the inversion of the angular elastic impedance body are as follows:

[0228] Substituting the inverted small-angle, medium-angle, and large-angle elastic impedance bodies into the elastic impedance equations of Young's modulus and Poisson's ratio, we obtain the inversion results of Young's modulus and Poisson's ratio.

[0229] Substituting the small-angle, medium-angle, and large-angle elastic impedance bodies obtained from the inversion into the elastic impedance equation for the bulk modulus, we obtain the bulk modulus.

[0230] According to a specific embodiment of the present invention, a three-dimensional formation pressure prediction result is obtained based on the inverted bulk modulus and the normal compaction bulk modulus, specifically as follows:

[0231] Substituting the inverted bulk modulus and the normal compaction bulk modulus into the following formula, we obtain the three-dimensional formation pressure prediction results:

[0232]

[0233] in,

[0234] P p Formation pressure;

[0235] P o This refers to the pressure of the overlying strata.

[0236] P n It is the hydrostatic pressure;

[0237] K is the measured bulk modulus;

[0238] c is a constant.

[0239] According to a specific embodiment of the present invention, the Eaton method is used to obtain the three-dimensional formation pressure prediction results based on the inverted bulk modulus and the normal compaction bulk modulus.

[0240] According to a specific embodiment of the present invention, based on the inverted bulk modulus and the normal compaction bulk modulus, the Bower method is used to obtain the three-dimensional formation pressure prediction results;

[0241] According to a specific embodiment of the present invention, the predicted result of three-dimensional geostress is calculated based on the inverted Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain of the formation, and minimum horizontal strain of the formation, as follows:

[0242] Substituting the inversion results of Young's modulus and Poisson's ratio, along with the bulk modulus and the predicted three-dimensional formation pressure, into the following spring model formula, we obtain the predicted three-dimensional geostress:

[0243]

[0244]

[0245] in,

[0246] σ H It is the maximum horizontal principal stress;

[0247] σ h It is the minimum horizontal principal stress;

[0248] α is the Boit coefficient;

[0249] ε y It is the maximum horizontal strain of the strata;

[0250] ε x It is the minimum horizontal strain of the formation.

[0251] According to a specific embodiment of the present invention, based on the inverted Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain of the formation, and minimum horizontal strain of the formation, the predicted results of three-dimensional geostress are calculated using a uniaxial strain model.

[0252] According to a specific embodiment of the present invention, based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain and minimum horizontal strain of the formation obtained by inversion, the predicted results of three-dimensional geostress are calculated using the Huang model.

[0253] Example 1

[0254] According to a specific embodiment of the present invention, the three-dimensional geostress prediction method based on curvature properties of the present invention will be described in detail below.

[0255] This invention provides a three-dimensional geostress prediction method based on curvature properties, comprising the following steps:

[0256] Based on centrifugal window scanning, the three-dimensional maximum positive curvature and minimum negative curvature properties of the strata are extracted using post-stack seismic data, and the maximum and minimum horizontal strain of the strata are calculated.

[0257] Considering the normal compaction of the formation, an orthotropic anisotropic shale petrophysical model is established to estimate the normal compaction bulk modulus;

[0258] Elastic impedance inversion was performed using small-angle, medium-angle, and large-angle seismic gathers to obtain angular elastic impedance volumes. Small-angle, medium-angle, and large-angle seismic gathers were then classified based on actual seismic data.

[0259] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus are obtained from the inversion of the angular elastic impedance body.

[0260] Based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained;

[0261] Based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated.

[0262] Example 2

[0263] According to a specific embodiment of the present invention, the three-dimensional geostress prediction method based on curvature properties of the present invention will be described in detail below.

[0264] This invention provides a three-dimensional geostress prediction method based on curvature properties, comprising the following steps:

[0265] Based on centrifugal window scanning, the three-dimensional maximum positive curvature and minimum negative curvature properties of the strata are extracted using post-stack seismic data, and the maximum and minimum horizontal strain of the strata are calculated.

[0266] Considering the normal compaction of the formation, an orthotropic anisotropic shale petrophysical model is established to estimate the normal compaction bulk modulus;

[0267] Elastic impedance inversion was performed using small-angle, medium-angle, and large-angle seismic gathers to obtain angular elastic impedance volumes. Small-angle, medium-angle, and large-angle seismic gathers were then classified based on actual seismic data.

[0268] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus are obtained from the inversion of the angular elastic impedance body.

[0269] Based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained;

[0270] Based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated.

[0271] Considering normal formation compaction, the process of establishing an orthotropic anisotropic shale petrophysical model includes the following steps:

[0272] An anisotropic self-compatible approximation model was used to mix clay and kerogen to form clay blocks;

[0273] Multiple different polarization angles θ and azimuth angles The stacking of clay blocks simulates the stratification of shale;

[0274] Minerals were added to the clay blocks that simulated layered shale, along with normal compaction pores and cracks;

[0275] Add fluid to the dry rock skeleton;

[0276] Using post-stack sparse pulse inversion technology, small-angle, medium-angle, and large-angle seismic gathers are used as input to invert angular elastic impedance volumes, specifically including:

[0277] The elastic impedance equations for Young's modulus and Poisson's ratio are obtained from the YPD equation as follows;

[0278]

[0279] in,

[0280] EI is the elastic resistance;

[0281] t is time;

[0282] θ1, θ2, and θ3 represent small, medium, and large angles, respectively.

[0283] a, b, and c are all constants;

[0284] E is Young's modulus;

[0285] E0 is the average value of Young's modulus;

[0286] ν is Poisson's ratio;

[0287] ν0 is the average value of Poisson's ratio;

[0288] ρ is density, and ρ0 is the average density.

[0289] The elastic impedance equation for the bulk modulus is derived from the Archi-Richard equation as follows:

[0290]

[0291] in,

[0292] k, l, and m are all constants;

[0293] K is the bulk modulus;

[0294] K0 is the average value of the bulk modulus;

[0295] μ is the shear modulus;

[0296] μ0 is the average value of Poisson's ratio.

[0297] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus obtained from the angular elastic impedance volume inversion are as follows:

[0298] Substituting the inverted small-angle, medium-angle, and large-angle elastic impedance bodies into the elastic impedance equations of Young's modulus and Poisson's ratio, we obtain the inversion results of Young's modulus and Poisson's ratio.

[0299] Substituting the small-angle, medium-angle, and large-angle elastic impedance bodies obtained from the inversion into the elastic impedance equation for the bulk modulus, we obtain the bulk modulus.

[0300] Example 3

[0301] According to a specific embodiment of the present invention, the three-dimensional geostress prediction method based on curvature properties of the present invention will be described in detail below.

[0302] This invention provides a three-dimensional geostress prediction method based on curvature properties, comprising the following steps:

[0303] Based on centrifugal window scanning, the three-dimensional maximum positive curvature and minimum negative curvature properties of the strata are extracted using post-stack seismic data, and the maximum and minimum horizontal strain of the strata are calculated.

[0304] Considering the normal compaction of the formation, an orthotropic anisotropic shale petrophysical model is established to estimate the normal compaction bulk modulus;

[0305] Elastic impedance inversion was performed using small-angle, medium-angle, and large-angle seismic gathers to obtain angular elastic impedance volumes. Small-angle, medium-angle, and large-angle seismic gathers were then classified based on actual seismic data.

[0306] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus are obtained from the inversion of the angular elastic impedance body.

[0307] Based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained;

[0308] Based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated.

[0309] Considering normal formation compaction, the process of establishing an orthotropic anisotropic shale petrophysical model includes the following steps:

[0310] Mix clay and kerogen to form clay blocks;

[0311] Multiple different polarization angles θ and azimuth angles The stacking of clay blocks simulates the stratification of shale;

[0312] Minerals were added to the clay blocks that simulated layered shale, along with normal compaction pores and cracks;

[0313] Add fluid to the dry rock skeleton;

[0314] Using post-stack sparse pulse inversion technology, small-angle, medium-angle, and large-angle seismic gathers are used as input to invert angular elastic impedance volumes, specifically including:

[0315] The elastic impedance equations for Young's modulus and Poisson's ratio are obtained from the YPD equation as follows;

[0316]

[0317] in,

[0318] EI is the elastic resistance;

[0319] t is time;

[0320] θ1, θ2, and θ3 represent small, medium, and large angles, respectively.

[0321] a, b, and c are all constants;

[0322] E is Young's modulus;

[0323] E0 is the average value of Young's modulus;

[0324] ν is Poisson's ratio;

[0325] ν0 is the average value of Poisson's ratio;

[0326] ρ is density, and ρ0 is the average density.

[0327] The elastic impedance equation for the bulk modulus is derived from the Archi-Richard equation as follows:

[0328]

[0329] in,

[0330] k, l, and m are all constants;

[0331] K is the bulk modulus;

[0332] K0 is the average value of the bulk modulus;

[0333] μ is the shear modulus;

[0334] μ0 is the average value of Poisson's ratio.

[0335] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus obtained from the angular elastic impedance volume inversion are as follows:

[0336] Substituting the inverted small-angle, medium-angle, and large-angle elastic impedance bodies into the elastic impedance equations of Young's modulus and Poisson's ratio, we obtain the inversion results of Young's modulus and Poisson's ratio.

[0337] Substituting the small-angle, medium-angle, and large-angle elastic impedance bodies obtained from the inversion into the elastic impedance equation for the bulk modulus, we obtain the bulk modulus.

[0338] Multiple different polarization angles θ and azimuth angles The superposition of clay blocks simulates the stratification of shale, specifically including:

[0339] Calculate the elastic stiffness matrix for each clay block;

[0340] The elastic stiffness matrix of different clay blocks was obtained;

[0341] The elastic stiffness matrix of layered clay is obtained.

[0342] The elastic stiffness matrix of each clay block was calculated using the Bond transformation to obtain the elastic stiffness matrix of different clay blocks.

[0343] The elastic stiffness matrix of each clay block is:

[0344]

[0345]

[0346] in,

[0347] θ is the polarization angle of the clay block;

[0348] The azimuth angle of the clay block;

[0349] M θ This is the coordinate transformation matrix for the polarization angle of the clay block;

[0350] This is the coordinate transformation matrix for the azimuth angle of the clay block;

[0351] The elastic stiffness matrix of different clay blocks is as follows:

[0352]

[0353] The polarization angle is θ and the azimuth angle is The elastic stiffness matrix of the clay blocks, with different clay blocks having different polarization angles and azimuth angles.

[0354] The elastic stiffness matrix of different clay blocks Substituting into Backus's average theory, we obtain the elastic stiffness matrix C of layered clay. Ba .

[0355] Minerals were added to the clay blocks simulating layered shale, along with normal compaction porosity and fractures, specifically including:

[0356] The mineral mixture and its modulus were obtained.

[0357] Mineral mixtures and pores are added to layered clay to form a rock matrix;

[0358] Cracks are incorporated into the rock matrix to form a dry rock skeleton;

[0359] Fluid is added to the dry rock skeleton to form saturated rock under normal compaction conditions.

[0360] The modulus of the mineral mixture was obtained by averaging the major mineral components of shale using the Hashin-Shtrikman-Hill average with the following formula. The major mineral components of shale include quartz, calcite, dolomite, and pyrite.

[0361]

[0362] in,

[0363] M HS+ and M HS- These are the upper and lower limits of the modulus of the mineral mixture, respectively.

[0364] M HSH It represents the modulus of the mineral mixture.

[0365] Using an anisotropic equivalent differential medium model, mineral mixtures and pores were added to layered clay to form a rock matrix, and the elastic stiffness matrix of the rock matrix was calculated.

[0366] The Hudson model was used to incorporate cracks into the rock matrix, forming a dried rock skeleton, and the elastic stiffness matrix of the dried rock skeleton was calculated.

[0367] By introducing fluid into a dry rock skeleton using the anisotropic Gassmann equation, the elastic stiffness matrix of the saturated rock was calculated.

[0368] The estimated bulk modulus of normal compaction is given by the following formula:

[0369]

[0370] in,

[0371] K n It is the normal compaction bulk modulus;

[0372] c 12 and c 44 These are the elastic stiffness matrices of saturated rock. The elements in the first row and second column and the fourth row and fourth column.

[0373] Example 4

[0374] According to a specific embodiment of the present invention, the three-dimensional geostress prediction method based on curvature properties of the present invention will be described in detail below.

[0375] This invention provides a three-dimensional geostress prediction method based on curvature properties, comprising the following steps:

[0376] Based on centrifugal window scanning, the three-dimensional maximum positive curvature and minimum negative curvature properties of the strata are extracted using post-stack seismic data, and the maximum and minimum horizontal strain of the strata are calculated.

[0377] Considering the normal compaction of the formation, an orthotropic anisotropic shale petrophysical model is established to estimate the normal compaction bulk modulus;

[0378] Elastic impedance inversion was performed using small-angle, medium-angle, and large-angle seismic gathers to obtain angular elastic impedance volumes. Small-angle, medium-angle, and large-angle seismic gathers were then classified based on actual seismic data.

[0379] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus are obtained from the inversion of the angular elastic impedance body.

[0380] Based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained;

[0381] Based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated.

[0382] Considering normal formation compaction, the process of establishing an orthotropic anisotropic shale petrophysical model includes the following steps:

[0383] Mix clay and kerogen to form clay blocks;

[0384] Multiple different polarization angles θ and azimuth angles The stacking of clay blocks simulates the stratification of shale;

[0385] Minerals were added to the clay blocks that simulated layered shale, along with normal compaction pores and cracks;

[0386] Add fluid to the dry rock skeleton;

[0387] Using post-stack sparse pulse inversion technology, small-angle, medium-angle, and large-angle seismic gathers are used as input to invert angular elastic impedance volumes, specifically including:

[0388] The elastic impedance equations for Young's modulus and Poisson's ratio are obtained from the YPD equation as follows;

[0389]

[0390] in,

[0391] EI is the elastic resistance;

[0392] t is time;

[0393] θ1, θ2, and θ3 represent small, medium, and large angles, respectively.

[0394] a, b, and c are all constants;

[0395] E is Young's modulus;

[0396] E0 is the average value of Young's modulus;

[0397] ν is Poisson's ratio;

[0398] ν0 is the average value of Poisson's ratio;

[0399] ρ is density, and ρ0 is the average density.

[0400] The elastic impedance equation for the bulk modulus is derived from the Archi-Richard equation as follows:

[0401]

[0402] in,

[0403] k, l, and m are all constants;

[0404] K is the bulk modulus;

[0405] K0 is the average value of the bulk modulus;

[0406] μ is the shear modulus;

[0407] μ0 is the average value of Poisson's ratio.

[0408] The inversion results of Young's modulus, Poisson's ratio, and bulk modulus obtained from the angular elastic impedance volume inversion are as follows:

[0409] Substituting the inverted small-angle, medium-angle, and large-angle elastic impedance bodies into the elastic impedance equations of Young's modulus and Poisson's ratio, we obtain the inversion results of Young's modulus and Poisson's ratio.

[0410] Substituting the small-angle, medium-angle, and large-angle elastic impedance bodies obtained from the inversion into the elastic impedance equation for the bulk modulus, we obtain the bulk modulus.

[0411] Based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained, specifically:

[0412] Substituting the inverted bulk modulus and the normal compaction bulk modulus into the following formula, we obtain the three-dimensional formation pressure prediction results:

[0413]

[0414] in,

[0415] P p Formation pressure;

[0416] P o This refers to the pressure of the overlying strata.

[0417] P n It is the hydrostatic pressure;

[0418] K is the measured bulk modulus;

[0419] c is a constant.

[0420] Based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated as follows:

[0421] Substituting the inversion results of Young's modulus and Poisson's ratio, along with the bulk modulus and the predicted three-dimensional formation pressure, into the following spring model formula, we obtain the predicted three-dimensional geostress:

[0422]

[0423]

[0424] in,

[0425] σ H It is the maximum horizontal principal stress;

[0426] σ h It is the minimum horizontal principal stress;

[0427] α is the Boit coefficient;

[0428] ε yIt is the maximum horizontal strain of the strata;

[0429] ε x It is the minimum horizontal strain of the formation.

[0430] Multiple different polarization angles θ and azimuth angles The superposition of clay blocks simulates the stratification of shale, specifically including:

[0431] Calculate the elastic stiffness matrix for each clay block;

[0432] The elastic stiffness matrix of different clay blocks was obtained;

[0433] The elastic stiffness matrix of layered clay is obtained.

[0434] The elastic stiffness matrix of each clay block was calculated using the Bond transformation to obtain the elastic stiffness matrix of different clay blocks.

[0435] The elastic stiffness matrix of each clay block is:

[0436]

[0437]

[0438] in,

[0439] θ is the polarization angle of the clay block;

[0440] The azimuth angle of the clay block;

[0441] M θ This is the coordinate transformation matrix for the polarization angle of the clay block;

[0442] This is the coordinate transformation matrix for the azimuth angle of the clay block;

[0443] The elastic stiffness matrix of different clay blocks is as follows:

[0444]

[0445] The polarization angle is θ and the azimuth angle is The elastic stiffness matrix of the clay blocks, with different clay blocks having different polarization angles and azimuth angles.

[0446] The elastic stiffness matrix of different clay blocks Substituting into Backus's average theory, we obtain the elastic stiffness matrix C of layered clay. Ba .

[0447] Minerals were added to the clay blocks simulating layered shale, along with normal compaction porosity and fractures, specifically including:

[0448] The mineral mixture and its modulus were obtained.

[0449] Mineral mixtures and pores are added to layered clay to form a rock matrix;

[0450] Cracks are incorporated into the rock matrix to form a dry rock skeleton;

[0451] Fluid is added to the dry rock skeleton to form saturated rock under normal compaction conditions.

[0452] The modulus of the mineral mixture was obtained by averaging the major mineral components of shale using the Hashin-Shtrikman-Hill average with the following formula. The major mineral components of shale include quartz, calcite, dolomite, and pyrite.

[0453]

[0454] in,

[0455] M HS+ and M HS- These are the upper and lower limits of the modulus of the mineral mixture, respectively.

[0456] M HSH It represents the modulus of the mineral mixture.

[0457] Using an anisotropic equivalent differential medium model, mineral mixtures and pores were added to layered clay to form a rock matrix, and the elastic stiffness matrix of the rock matrix was calculated.

[0458] The Hudson model was used to incorporate cracks into the rock matrix, forming a dried rock skeleton, and the elastic stiffness matrix of the dried rock skeleton was calculated.

[0459] By introducing fluid into a dry rock skeleton using the anisotropic Gassmann equation, the elastic stiffness matrix of the saturated rock was calculated.

[0460] The estimated bulk modulus of normal compaction is given by the following formula:

[0461]

[0462] in,

[0463] K n It is the normal compaction bulk modulus;

[0464] c 12 and c 44 These are the elastic stiffness matrices of saturated rock. The elements in the first row and second column and the fourth row and fourth column.

[0465] like Figure 5 As shown, the accuracy of the three-dimensional formation pressure predicted by this invention is verified by comparing it with the formation pressure on the well surface.

[0466] like Figure 6 The three-dimensional in-situ stress prediction results of this invention are presented. To verify the accuracy of the results, the seismic prediction results of well A along the wellbore are compared with the in-situ stress above the wellbore. Figure 7 As shown, the three-dimensional geostress results predicted by the method of the present invention are verified to be reasonable and correct.

[0467] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A three-dimensional geostress prediction method based on curvature attributes, characterized in that, Includes the following steps: Based on centrifugal window scanning, the three-dimensional maximum positive curvature and minimum negative curvature properties of the strata are extracted using post-stack seismic data, and the maximum and minimum horizontal strain of the strata are calculated. Considering the normal compaction of the formation, an orthotropic anisotropic shale petrophysical model is established to estimate the normal compaction bulk modulus; Elastic impedance inversion was performed using small-angle, medium-angle, and large-angle seismic gathers to obtain angular elastic impedance volumes. Small-angle, medium-angle, and large-angle seismic gathers were then classified based on actual seismic data. The inversion results of Young's modulus, Poisson's ratio, and bulk modulus are obtained from the inversion of the angular elastic impedance body. Based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained; Based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain and minimum horizontal strain of the formation obtained by inversion, the predicted results of three-dimensional geostress are calculated. Specifically, based on the inverted bulk modulus and the normal compaction bulk modulus, the three-dimensional formation pressure prediction results are obtained as follows: Substituting the inverted bulk modulus and the normal compaction bulk modulus into the following formula, we obtain the three-dimensional formation pressure prediction results: in, Formation pressure; This refers to the pressure of the overlying strata. It is the hydrostatic pressure; This is the measured bulk modulus; c It is a constant; Specifically, based on the Young's modulus, Poisson's ratio, three-dimensional formation pressure, maximum horizontal strain, and minimum horizontal strain obtained from the inversion, the predicted results of three-dimensional geostress are calculated as follows: Substituting the inversion results of Young's modulus and Poisson's ratio, along with the bulk modulus and the predicted three-dimensional formation pressure, into the following spring model formula, we obtain the predicted three-dimensional geostress: in, It is the maximum horizontal principal stress; It is the minimum horizontal principal stress; It is the Boit coefficient; It is the maximum horizontal strain of the strata; It is the minimum horizontal strain of the formation.

2. The three-dimensional geostress prediction method based on curvature attributes according to claim 1, characterized in that, The maximum positive curvature and minimum negative curvature properties of the strata were extracted using post-stack seismic data, and the maximum horizontal strain of the strata was calculated using the following formula. and minimum strain : in, It is the time thickness of the strata; and These are the minimum negative curvature and the maximum positive curvature, respectively.

3. The three-dimensional geostress prediction method based on curvature attributes according to claim 1, characterized in that, Considering normal formation compaction, the process of establishing an orthotropic anisotropic shale petrophysical model includes the following steps: Mix clay and kerogen to form clay blocks; Multiple different polarization angles and azimuth The stacking of clay blocks simulates the stratification of shale; Minerals were added to the clay blocks that simulated layered shale, along with normal compaction pores and cracks; Add fluid to the dry rock skeleton.

4. The three-dimensional geostress prediction method based on curvature attributes according to claim 3, characterized in that, Clay blocks were formed by mixing clay and kerogen using any one of the following models: the anisotropic self-compatible approximation model, the Kuster-Toksoz model, or the anisotropic equivalent differential medium model.

5. The three-dimensional geostress prediction method based on curvature attributes according to claim 4, characterized in that, Multiple different polarization angles and azimuth The superposition of clay blocks simulates the stratification of shale, specifically including: Calculate the elastic stiffness matrix for each clay block; The elastic stiffness matrix of different clay blocks was obtained; The elastic stiffness matrix of layered clay is obtained.

6. The three-dimensional geostress prediction method based on curvature attributes according to claim 5, characterized in that, The elastic stiffness matrix of each clay block was calculated using the Bond transformation to obtain the elastic stiffness matrix of different clay blocks. The elastic stiffness matrix of each clay block is: in, The polarization angle of the clay block; The azimuth angle of the clay block; This is the coordinate transformation matrix for the polarization angle of the clay block; This is the coordinate transformation matrix for the azimuth angle of the clay block; The elastic stiffness matrix of different clay blocks is as follows: The polarization angle is azimuth angle is The elastic stiffness matrix of the clay blocks, with different clay blocks having different polarization angles and azimuth angles.

7. The three-dimensional geostress prediction method based on curvature attributes according to claim 6, characterized in that, The elastic stiffness matrix of different clay blocks Substituting into Backus's average theory, we obtain the elastic stiffness matrix of layered clay. .

8. The three-dimensional geostress prediction method based on curvature attributes according to claim 7, characterized in that, Minerals were added to the clay blocks simulating layered shale, along with normal compaction porosity and fractures, specifically including: The mineral mixture and its modulus were obtained. Mineral mixtures and pores are added to layered clay to form a rock matrix; Cracks are incorporated into the rock matrix to form a dry rock skeleton; Fluid is added to the dry rock skeleton to form saturated rock under normal compaction conditions.

9. The three-dimensional geostress prediction method based on curvature attributes according to claim 8, characterized in that, The modulus of the mineral mixture was obtained by averaging the major mineral components of shale using the Hashin-Shtrikman-Hill average with the following formula: in, and These are the upper and lower limits of the modulus of the mineral mixture, respectively. It represents the modulus of the mineral mixture.

10. The three-dimensional geostress prediction method based on curvature attributes according to claim 9, characterized in that, Using an anisotropic equivalent differential medium model, mineral mixtures and pores were added to layered clay to form a rock matrix, and the elastic stiffness matrix of the rock matrix was calculated. .

11. The three-dimensional geostress prediction method based on curvature attributes according to claim 10, characterized in that, The Hudson model was used to incorporate cracks into the rock matrix, forming a dried rock skeleton, and the elastic stiffness matrix of the dried rock skeleton was calculated. .

12. The three-dimensional geostress prediction method based on curvature attributes according to claim 11, characterized in that, By introducing fluid into a dry rock skeleton using the anisotropic Gassmann equation, the elastic stiffness matrix of the saturated rock was calculated. .

13. The three-dimensional geostress prediction method based on curvature attributes according to claim 12, characterized in that, The estimated bulk modulus of normal compaction is given by the following formula: in, It is the normal compaction bulk modulus; and These are the elastic stiffness matrices of saturated rock. The elements in the first row and second column and the fourth row and fourth column.

14. The three-dimensional geostress prediction method based on curvature attributes according to claim 1, characterized in that, Using post-stack sparse pulse inversion technology, small-angle, medium-angle, and large-angle seismic gathers are used as input to invert angular elastic impedance volumes, specifically including: The elastic impedance equations for Young's modulus and Poisson's ratio are derived from the YPD equation as follows: in, It is elastic resistance; It is time; , and These are small angle, medium angle, and large angle, respectively. , and All are constants; It is Young's modulus; It is the average value of Young's modulus; It is Poisson's ratio; It is the average value of Poisson's ratio; It's density. It is the average density; The elastic impedance equation for the bulk modulus is derived from the Archi-Richard equation as follows: in, , and All are constants; It is the bulk modulus; It is the average value of the bulk modulus; It is the shear modulus; It is the average value of Poisson's ratio.

15. The three-dimensional geostress prediction method based on curvature attributes according to claim 14, characterized in that, The inversion results of Young's modulus, Poisson's ratio, and bulk modulus obtained from the angular elastic impedance volume inversion are as follows: Substituting the inverted small-angle, medium-angle, and large-angle elastic impedance bodies into the elastic impedance equations of Young's modulus and Poisson's ratio, we obtain the inversion results of Young's modulus and Poisson's ratio. Substituting the small-angle, medium-angle, and large-angle elastic impedance bodies obtained from the inversion into the elastic impedance equation for the bulk modulus, we obtain the bulk modulus.

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