Seismic inversion method for mechanical parameters of fractured-vuggy reservoir based on logging ground stress constraint

Abstract

The invention relates to the field of oil and gas field exploration and development, in particular to a fracture-cavity type reservoir mechanical parameter seismic inversion method based on logging ground stress constraint. On the basis of array acoustic logging, the current crustal stress is calculated; inverting different types of seismic attributes based on the pre-stack seismic data; by optimizing the seismic attribute and the threshold value, the geometric shape carving of the fracture-cavity body is realized; based on the fracture-cavity body seismic attribute sensitivity degree, different types of fracture-cavity body seismic recognition standards are established; establishing rock mechanical parameter assignment models of different types of fractured-vuggy bodies through rock mechanical parameter inversion cycle verification; and considering stress constraint to optimize different types of fracture-vug body rock mechanical parameter assignment models, and finally realizing fracture-vug type reservoir three-dimensional rock mechanical parameter inversion. The invention provides a fracture-vug reservoir mechanical parameter seismic inversion method based on logging ground stress constraint. The method has reference value in multiple aspects of fracture-vug reservoir geomechanical modeling, ground stress field numerical simulation, engineering dessert evaluation and the like.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas field exploration and development, and particularly to a seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints. Background Art

[0002] Rock mechanical parameters, including rock Young's modulus and Poisson's ratio, are important basic data for research such as reservoir geomechanical modeling and numerical simulation of in-situ stress fields. The traditional well-seismic combination method can be used to invert rock mechanical parameters and the distribution of horizontal maximum and minimum principal stresses. However, for fracture-vuggy reservoirs, it is difficult to accurately invert their rock mechanical parameters, resulting in a large difference between the simulated horizontal maximum and minimum principal stresses and the in-situ stress values calculated by logging, making it difficult to be applied on a large scale in geomechanical modeling analysis. The main reason is that the traditional well-seismic combination model for inverting rock mechanical parameters has a large randomness, with problems such as mechanical unreasonableness and inaccurate stress. Based on stochastic simulation, the randomness is too large, the rock mechanical parameters at the matrix change too much, it is too heterogeneous, and there is no calibration standard for the rock mechanical parameters at the fractures and vugs, and it is impossible to classify and characterize complex geological conditions. Moreover, under stochastic simulation, the constraint conditions are only affected by a single seismic attribute, but a single seismic attribute can no longer well characterize the development characteristics of fracture-vuggy bodies. Finally, the simulated current in-situ stress model does not match the in-situ stress values calculated by a single well, with a large deviation. Therefore, a scientific assignment scheme for rock mechanical parameters of fracture-vuggy reservoirs needs to be proposed, and it is directly constrained by the in-situ stress values calculated by a single well. The present invention patent adopts a reservoir geomechanical method and proposes a seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints. Summary of the Invention

[0003] The present invention aims to solve the above problems and provides a seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints, which can determine the three-dimensional distribution of rock mechanical parameters of fracture-vuggy reservoirs.

[0004] The technical solution of the present invention is as follows: A seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints, the specific steps are as follows:

[0005] The first step is to calculate the current in-situ stress magnitude based on array acoustic logging;

[0006] Using array acoustic logging data, combined with rock density, calculate the magnitudes of rock Young's modulus and Poisson's ratio; according to the magnitudes of rock Young's modulus and Poisson's ratio, use the elastic mechanics model to calculate the magnitudes of the current horizontal maximum principal stress, horizontal minimum principal stress, and vertical principal stress, and establish a single-well current in-situ stress profile;

[0007] The elastic mechanics model is as follows:

[0008] For the calculation of horizontal in-situ stress, the combined spring model theory is adopted. This theory assumes that the formation is a homogeneous and isotropic linear elastic material, and there is no dislocation between strata during the geological tectonic movement, and the stress change in the horizontal direction remains constant. Based on Hooke's law, the following calculation formula is obtained:

[0009]

[0010] In formulas (1)-(2), σ Hmax is the maximum horizontal principal stress, MPa; σ hmin is the minimum horizontal principal stress, MPa; σ v is the vertical principal stress, MPa; P p is the pore pressure, MPa; v is the Poisson's ratio, dimensionless; E is the elastic modulus, GPa; α is the Biot coefficient, dimensionless; ξ H and ξ h are the strain variables in the directions of the maximum and minimum horizontal principal stresses respectively, dimensionless;

[0011] The Biot coefficient in formulas (1)-(2) is a poroelastic constant, and the Biot coefficient is estimated using the following formula:

[0012]

[0013] In formula (3), C ma -compression rate of the skeleton; C b -compression rate of the skeleton and the pore space;

[0014] The ξ H and ξ h coefficients in formulas (1)-(2) are difficult to determine directly. The measured data of σ hmin at a specific location are determined using hydraulic fracturing construction data as the constraint and calibration basis, and ξ H and ξ h are determined indirectly; during the hydraulic fracturing process, the pump shut-in pressure is the fracture closure pressure value, which is equal to the minimum horizontal principal stress σ hmin , and the calculation formula is:

[0015] σh min = p c (4)

[0016] σ Hmax = 3σ hmin - p r - p p (5)

[0017] In formulas (4)-(5), p c is the pump shut-in pressure, MPa; p r is the fracture reopening pressure, MPa.

[0018] Step 2: Inverting different types of seismic attributes based on pre-stack seismic data;

[0019] Using pre-stack seismic data, conduct pre-stack data preprocessing, complete the interpretation of key horizons and faults, construct a rock physics template to establish the mapping relationship between elastic parameters and reservoir characteristics; obtain the P-wave velocity, S-wave velocity, and density through AVO inversion, extract anisotropic parameters through elastic impedance inversion, reconstruct a high-precision velocity field through full waveform inversion, and adopt a well-seismic combination method to invert different types of seismic attributes;

[0020] The inversion of different types of seismic attributes includes maximum likelihood attributes, ant body attributes, root mean square amplitude attributes, and porosity attributes.

[0021] Step 3: Sculpting the geometric morphology of fracture-vug bodies through well-seismic combination;

[0022] Based on the optimized seismic attributes and threshold values, grid the inverted seismic attribute model, and through threshold value screening, sculpt the fracture-vug body model of the target layer in the study area;

[0023] The threshold value mentioned refers to the seismic attribute value that can effectively identify fractures and holes in complex fracture-vug bodies;

[0024] The optimized seismic attributes and threshold values mentioned refer to using the seismic data in the study area to judge the identification effects of different seismic attributes on fractures and holes in complex fracture-vug bodies, and optimizing the seismic attributes sensitive to fracture-vug bodies; according to well logging values, preliminarily determine the interval of the inverted seismic attributes.

[0025] Step 4: Establishing seismic identification criteria for different types of fracture-vug bodies;

[0026] There are differences in the sensitivity of different types of fracture-vug bodies to seismic attributes. Based on the sensitivity of different types of fracture-vug bodies to seismic attributes, establish seismic identification criteria for different types of fracture-vug bodies;

[0027] The seismic identification criteria for different types of fracture-vug bodies mentioned are to screen out the most important parameters and their values for classifying the types of fracture-vug bodies according to the seismic attributes sensitive to different types of fracture-vug bodies.

[0028] Step 5: Establishing a rock mechanics parameter assignment model for different types of fracture-vug bodies;

[0029] Based on the seismic identification criteria for fracture-vug bodies in the study area, conduct cyclic verification of rock mechanics parameter inversion, and finally obtain a rock mechanics parameter assignment model for fracture-vug bodies that conforms to the laws of geomechanics;

[0030] The laws of geomechanics mentioned refer to the fact that the rock mechanics parameters near fracture-vug bodies will change, with the Young's modulus of the rock decreasing and the Poisson's ratio increasing.

[0031] Step 6: Optimization of the rock mechanics parameter assignment model for different types of fracture-vug bodies based on logging-induced in-situ stress constraints;

[0032] Through continuous simulation tests and iterations, combined with the current in-situ stress magnitude of the target interval of a single well, the assignment scheme is corrected and the assignment schemes for different types of fracture-vug bodies are optimized;

[0033] The cyclic verification of the rock mechanics parameter inversion mentioned above refers to screening out seismic attributes that affect the recognition strength of different types of fracture-vug bodies through continuous simulation tests, adjusting the calculation function in combination with the current in-situ stress magnitude of the target interval of a single well, optimizing the assignment schemes for different types of fracture-vug bodies respectively, and finally obtaining the model calculation formula applicable to the target formation in the study area.

[0034] Step 7: Three-dimensional rock mechanics parameter inversion of fracture-vug reservoirs;

[0035] Based on the rock mechanics parameter assignment model for complex fracture-vug bodies, establish the Young's modulus and Poisson's ratio models of the target formation in the study area, and reveal the three-dimensional distribution of rock mechanics parameters of fracture-vug reservoirs.

[0036] The beneficial effects of the present invention are as follows: calculating the current in-situ stress magnitude based on array acoustic logging data; inversing different types of seismic attributes through the well-seismic combination method; realizing the carving of the geometric shape of fracture-vug bodies by well-seismic combination through the optimization of seismic attributes and threshold values; establishing seismic identification criteria for different types of fracture-vug bodies based on the sensitivity of seismic attributes of fracture-vug bodies; establishing a rock mechanics parameter assignment model for different types of fracture-vug bodies through the cyclic verification of rock mechanics parameter inversion; realizing the optimization of the rock mechanics parameter assignment model for different types of fracture-vug bodies considering stress constraints in combination with the current in-situ stress magnitude of the target interval of a single well, and finally realizing the three-dimensional rock mechanics parameter inversion of fracture-vug reservoirs. The present invention patent proposes a seismic inversion method for the mechanical parameters of fracture-vug reservoirs based on logging-induced in-situ stress constraints, which has reference value for multiple aspects such as geological mechanics modeling of fracture-vug reservoirs, numerical simulation of in-situ stress fields, and evaluation of "engineering sweet spots". Description of the Drawings

[0037] Figure 1 It is a flow chart of the seismic inversion method for the mechanical parameters of fracture-vug reservoirs based on logging-induced in-situ stress constraints.

[0038] Figure 2 It is a histogram of comprehensive interpretation of in-situ stress of a single well.

[0039] Figure 3 It is the inverted seismic attributes: (A) maximum likelihood attribute; (B) porosity attribute.

[0040] Figure 4 It is the fine carving and geological geometric modeling of three-dimensional fracture-vug bodies in the study area.

[0041] Figure 5 It is a seismic identification standard and type division map for different types of fracture-vug bodies in the study area.

[0042] Figure 6 It is a cyclic verification process map for the inversion of rock mechanical parameters.

[0043] Figure 7 It is a comparison map before and after the optimization of rock mechanical parameters.

[0044] Figure 8 It is a rock mechanical parameter model for the study area: (A) Young's modulus model; (B) Poisson's ratio model. Specific implementation manners

[0045] The following combines the accompanying drawings to illustrate the specific implementation manners of the present invention:

[0046] Taking the carbonate reservoir in Fuman Oilfield in the Tarim Basin in western China as an example, the specific implementation process of the present invention is described. The main body of Fuman Oilfield is located in the A'man transition zone of the northern depression. The Manshen block is located on the slope of the Tabei Uplift in the Tarim Basin. After multiple tectonic movements, the current overall structure is gentle, showing a slope inclined to the southwest. The study area has undergone the transformation of multiple tectonic activities and is superimposed with multiple stages and types of karstification, developing a typical carbonate fracture-vug type oil and gas reservoir controlled by strike-slip faults. It is the main area for increasing oil reserves and production in the current Tarim Oilfield. The randomness of the conventional well-seismic combined inversion rock mechanical parameter model is large, and there are problems such as unreasonable mechanics and inaccurate stress, especially with large deviations near the fracture-vug bodies, making it difficult to be applied on a large scale in the geomechanical modeling of fracture-vug reservoirs. Therefore, a scientific rock mechanical parameter assignment scheme needs to be proposed to support research such as geomechanical modeling of ultra-deep fracture-vug reservoirs and numerical simulation of in-situ stress fields.

[0047] The first step: Calculate the current in-situ stress magnitude based on array acoustic logging;

[0048] Using the array acoustic logging data and combining with rock density, calculate the magnitudes of rock Young's modulus and Poisson's ratio; According to the magnitudes of rock Young's modulus and Poisson's ratio, use the elastic mechanics model to calculate the magnitudes of the current maximum horizontal principal stress, minimum horizontal principal stress, and vertical principal stress, and establish a single-well current in-situ stress profile ( Figure 2 ).

[0049] The second step: Invert different types of seismic attributes based on pre-stack seismic data;

[0050] Using prestack seismic data, conduct prestack data preprocessing, complete the interpretation of key horizons and faults, construct a rock physics template to establish the mapping relationship between elastic parameters and reservoir characteristics; obtain P-wave velocity, S-wave velocity and density through AVO inversion, extract anisotropic parameters by elastic impedance inversion, and reconstruct a high-precision velocity field by full waveform inversion. Adopt the well-seismic combination method to invert different types of seismic attributes( Figure 3 ).

[0051] Step 3: Sculpt the geometric shape of fracture-vug bodies by combining well and seismic data;

[0052] On the basis of optimizing seismic attributes and threshold values, grid the inverted seismic attribute model, and screen through the threshold values to sculpt the fracture-vug body model of the target layer in the study area( Figure 4 ); the threshold value refers to the seismic attribute value that can effectively identify fractures and holes in complex fracture-vug bodies; the optimized seismic attributes and threshold values refer to using the seismic data in the study area to judge the identification effects of different seismic attributes on fractures and holes in complex fracture-vug bodies, and optimizing the seismic attributes sensitive to fracture-vug bodies; according to the logging values, preliminarily determine the interval of the inverted seismic attributes.

[0053] Step 4: Establish seismic identification criteria for different types of fracture-vug bodies;

[0054] There are differences in the sensitivity of different types of fracture-vug bodies to seismic attributes. Based on the sensitivity of different types of fracture-vug bodies to seismic attributes, establish seismic identification criteria for different types of fracture-vug bodies( Figure 5 ); the seismic identification criteria for different types of fracture-vug bodies are to screen out the most important parameters and their values for classifying the types of fracture-vug bodies according to the seismic attributes sensitive to different types of fracture-vug bodies.

[0055] Step 5: Establish a rock mechanics parameter assignment model for different types of fracture-vug bodies;

[0056] Based on the seismic identification criteria for fracture-vug bodies in the study area, conduct cyclic verification of rock mechanics parameter inversion, and finally obtain a rock mechanics parameter assignment model for fracture-vug bodies that conforms to the geological mechanics law( Figure 6 ); the geological mechanics law means that the rock mechanics parameters near the fracture-vug bodies will change, the Young's modulus of the rock decreases, and the Poisson's ratio increases.

[0057] Step 6: Optimize the rock mechanics parameter assignment model for different types of fracture-vug bodies based on logging-induced in-situ stress constraints;

[0058] Through continuous simulation tests and iterations, combined with the current in-situ stress magnitude of the target interval of a single well, correct the assignment scheme and optimize the assignment schemes for different types of fracture-vug bodies( Figure 7); The cyclic verification of the inversion of rock mechanical parameters refers to continuously simulating and testing, screening out seismic attributes that affect the recognition strength of different types of fracture-vug bodies, combining the current in-situ stress magnitude of the target interval of a single well, adjusting the calculation function, optimizing the assignment schemes for different types of fracture-vug bodies respectively, and finally obtaining a model calculation formula applicable to the target layer of the study area.

[0059] Step 7: Inversion of three-dimensional rock mechanical parameters of fracture-vug reservoirs;

[0060] Based on the rock mechanical parameter assignment model for complex fracture-vug bodies, establish the Young's modulus and Poisson's ratio models of the rock for the target layer of the study area ( Figure 8 ), and reveal the distribution of three-dimensional rock mechanical parameters of fracture-vug reservoirs.

[0061] In an exemplary embodiment, it includes a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, it implements the steps in the above-mentioned reservoir geomechanics experiment method under the action of multi-stage tectonic stress.

[0062] The present invention has been described by way of example above, but the present invention is not limited to the above specific embodiments. Any modification or variation based on the present invention falls within the scope of protection required by the present invention.

Claims

1. The seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging geostress constraints is implemented as follows: The first step: Calculate the current geostress magnitude based on array acoustic logging; Using array acoustic logging data and combining with rock density, calculate the Young's modulus and Poisson's ratio of the rock; According to the magnitudes of the Young's modulus and Poisson's ratio of the rock, use the elastic mechanics model to calculate the magnitudes of the current maximum horizontal principal stress, minimum horizontal principal stress, and vertical principal stress, and establish a single-well current geostress profile; The second step: Invert different types of seismic attributes based on pre-stack seismic data; Using pre-stack seismic data, conduct pre-stack data preprocessing, complete the interpretation of key horizons and faults, construct a rock physics template to establish the mapping relationship between elastic parameters and reservoir characteristics; Obtain the P-wave velocity, S-wave velocity, and density through AVO inversion, extract anisotropic parameters through elastic impedance inversion, reconstruct a high-precision velocity field through full waveform inversion, and use the well-seismic combination method to invert different types of seismic attributes; The third step: Sculpt the geometric shape of fracture-vug bodies by combining well and seismic data; Based on the optimized seismic attributes and threshold values, grid the inverted seismic attribute model, and screen through the threshold values to sculpt the fracture-vug body model of the target layer in the study area; The fourth step: Establish seismic identification criteria for different types of fracture-vug bodies; There are differences in the sensitivity of different types of fracture-vug bodies to seismic attributes. Based on the sensitivity of different types of fracture-vug bodies to seismic attributes, establish seismic identification criteria for different types of fracture-vug bodies; The fifth step: Establish a mechanical parameter assignment model for different types of fracture-vug bodies; According to the seismic identification criteria for fracture-vug bodies in the study area, conduct cyclic verification of rock mechanical parameter inversion, and finally obtain a mechanical parameter assignment model for fracture-vug bodies that conforms to the laws of geomechanics; The sixth step: Optimize the mechanical parameter assignment model for different types of fracture-vug bodies based on logging geostress constraints; Through continuous simulation tests and iterations, combined with the current geostress magnitude of the single-well target interval, correct the assignment scheme and optimize the assignment schemes for different types of fracture-vug bodies; The seventh step: Invert the three-dimensional rock mechanical parameters of fracture-vuggy reservoirs.

2. According to the seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging geostress constraints described in claim 1, it is characterized in that: The elastic mechanics model described in the first step is as follows: For the calculation of horizontal geostress, the combined spring model theory is adopted. This theory assumes that the formation is a homogeneous and isotropic linear elastic material, and during the geological tectonic movement, there is no dislocation between strata, and the stress change in the horizontal direction remains constant; Based on Hooke's law, the following calculation formula is obtained: In Formulas (1)-(2), σ Hmax is the maximum horizontal principal stress, in MPa; σ hmin is the minimum horizontal principal stress, in MPa; σ v is the vertical principal stress, in MPa; P p is the pore pressure, in MPa; v is the Poisson's ratio, dimensionless; E is the elastic modulus, in GPa; α is the Biot coefficient, dimensionless; ξ H and ξ h are the strain amounts in the directions of the horizontal maximum and minimum principal stresses respectively, dimensionless; The Biot coefficient in formulas (1)-(2) is a poroelastic constant, and the Biot coefficient is estimated using the following formula: In formula (3), C ma - compression ratio of the b - skeleton; C - compression ratio of the skeleton and the pore space; ξ in Formulas (1)-(2) H and ξ h The coefficients are difficult to directly determine. The measured data of the actual measurement points at specific positions are used to determine σ hmin as the basis for constraint and calibration, and ξ H and ξ h are indirectly determined; during the hydraulic fracturing process, the pump shut-off pressure is the fracture closure pressure value, which is equal to the horizontal minimum principal stress σ hmin , and the calculation formula is as follows: σh min = p c (4) σ Hmax = 3σ hmin -p r -p p (5) In Formulas (4)-(5), p c is the pump shutdown pressure, in MPa; p r is the fracture reopening pressure, in MPa.

3. The seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints according to claim 1, characterized in that: The inversion of different types of seismic attributes described in the second step includes maximum likelihood attributes, ant body attributes, root mean square amplitude attributes, and porosity attributes.

4. The seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints according to claim 1, wherein: The threshold value described in the third step refers to the seismic attribute value that can effectively identify fractures and holes in complex fracture-vug bodies.

5. The seismic inversion method for mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints according to claim 1, characterized in that: The preferred seismic attributes and threshold values described in the third step refer to using the seismic data of the study area to judge the identification effects of different seismic attributes on fractures and complex fracture-vug bodies, and selecting the seismic attributes sensitive to fracture-vug bodies; and initially determining the interval of the inverted seismic attributes according to the logging values.

6. The method for seismic inversion of mechanical parameters of fractured-vuggy reservoirs based on logging-induced in-situ stress constraints according to claim 1, wherein: The seismic identification criteria for different types of fracture-vug bodies described in the fourth step are to screen out the main parameters and their values for classifying the types of fracture-vug bodies according to the seismic attributes sensitive to different types of fracture-vug bodies.

7. The method for seismic inversion of mechanical parameters of fractured-vuggy reservoirs based on logging in-situ stress constraints according to claim 1, wherein: The geological mechanics law described in the fifth step means that the rock mechanics parameters near the fracture-vug bodies will change, the Young's modulus of the rock decreases, and the Poisson's ratio increases.

8. The method for seismic inversion of mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints according to claim 1, characterized in that: The cyclic verification of the inversion of rock mechanics parameters described in the fifth and sixth steps refers to continuously simulating and testing to screen out the seismic attributes that affect the identification strength of different types of fracture-vug bodies, combining the current in-situ stress magnitude of the target interval of the single well, adjusting the calculation function, optimizing the assignment schemes for different types of fracture-vug bodies respectively, and finally obtaining the model calculation formula applicable to the target layer of the study area.

9. The method for seismic inversion of mechanical parameters of fracture-vuggy reservoirs based on logging in-situ stress constraints according to claim 1, wherein: The specific steps for the inversion of three-dimensional rock mechanics parameters of fracture-vug reservoirs in the seventh step are: based on the rock mechanics parameter assignment model of complex fracture-vug bodies, establishing the Young's modulus and Poisson's ratio models of the target layer of the study area to reveal the distribution of three-dimensional rock mechanics parameters of fracture-vug reservoirs.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by a processor, it implements the steps in the method for seismic inversion of mechanical parameters of fracture-vug reservoirs based on logging in-situ stress constraints as described in any one of claims 1-9.

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