A method for determining the core of an ancient buried hill based on the fluctuation of rock mechanical structure

Abstract

The present invention relates to the field of oil and gas field exploration and development, and in particular, to a method for determining the core of an ancient buried hill based on the volatility of rock mechanical structure. The method comprises: (1) high-precision geological geometric modeling; (2) pre-stack data-driven inversion initial model; (3) inversion of the three-dimensional distribution data volume of current dynamic rock mechanical parameters; (4) conversion of the three-dimensional distribution data volume of current static rock mechanical parameters; (5) calculation of the spatial volatility of rock mechanical structure; (6) determination of the scale of structural fracture development; and (7) determination of the core of an ancient buried hill. The present invention proposes a method for determining the core of an ancient buried hill based on the volatility of rock mechanical structure. The determination result has certain reference significance for multiple aspects such as the inversion of ancient and modern rock mechanical parameters, the prediction of structural fracture distribution, and the evaluation of "geological sweet spots".

Description

Technical Field

[0001] The present invention relates to the field of oil and gas field exploration and development, and in particular to a method for judging the core of an ancient buried hill based on the volatility of rock mechanics structure. Background Art

[0002] The formation of geological "sweet spots" in oil and gas reservoirs must meet certain structural conditions. Paleomorphology has a significant control effect on the distribution of high-quality reservoirs and the sedimentary system of oil and gas basins. High-quality reservoirs are usually developed in the core of ancient buried hills. Current research mostly relies on the residual thickness method and backstripping method. The recovery results are basically the paleogeomorphological characteristics of a specific stratum or a specific period. Moreover, the results are difficult to quantitatively study the paleogeomorphological characteristics, and the steps are cumbersome and have great inaccuracy. Therefore, how to quickly and accurately determine the core of the ancient buried hill is a practical problem faced in oil and gas geology. The patent of this invention proposes a method for determining the core of the ancient buried hill based on the volatility of rock mechanical structure. The identification results are accurate and can effectively guide the evaluation of the geological "sweet spots" of buried hill reservoirs. Summary of the Invention

[0003] The present invention aims to solve the above problems and provides a method for determining the core of an ancient buried hill based on the volatility of rock mechanical structure. The method can quickly and accurately determine the core of an ancient buried hill.

[0004] The technical solution of the present invention is: a method for determining the core of an ancient buried hill based on the volatility of rock mechanical structure, the specific steps are as follows:

[0005] S1 high-precision geological geometry modeling determines the current structural morphology based on well logging data, mud logging data, pre-stack seismic data and geological data. After multiple modifications and adjustments, a high-precision geological geometry model is established. The high-precision geological geometry model is a model constructed based on the fault model and the top and internal interface models of the work area. The fault model is established based on the fault plane obtained by seismic data interpretation, and the top and internal interfaces are fitted based on the top and internal interfaces of the work area obtained by structural interpretation. The grid unit size of the high-precision geological model is 1-8 meters.

[0006] The S2 pre-stack data drives the inversion initial model. Based on the pre-stack seismic data and geological stratification data, the initial model is established. The P-wave and S-wave reflectivity terms and density reflectivity terms corresponding to the initial model are obtained according to the Aki-Richards approximate equation. The obtained reflectivity terms are convolved with the wavelets extracted from the work area to obtain a synthetic artificial data set. The residual is obtained by comparing it with the actual data set, and the initial model is modified according to the residual multiple times to finally obtain the initial model. The initial model includes a P-wave velocity model, a S-wave velocity model, and a density model. The Aki-Richards approximate equation is:

[0007]

[0008] In formula (1), R PPθ is the reflection coefficient of the synthetic seismic record, dimensionless; θ is the incident angle, °; R P is the longitudinal wave velocity reflectivity term, dimensionless; R S is the shear wave velocity reflectivity term, dimensionless; R D is the density reflectivity term, dimensionless; V P is the longitudinal wave velocity, m / μs; V S is the shear wave velocity, m / μs.

[0009] S3 Inversion of the current dynamic rock mechanics parameter three-dimensional distribution data body, substitute the P-wave velocity model, S-wave velocity model, and density model into the rock mechanics parameter calculation formula, calculate the dynamic rock mechanics parameters, and invert the current dynamic rock mechanics parameter three-dimensional distribution data body; the rock mechanics parameter calculation formula is:

[0010]

[0011] In formulas (2)-(3), E d is the dynamic Young's modulus of rock, GPa; μ d is the dynamic Poisson's ratio of rock, dimensionless; ρ b is the density model, g / cm 3 ;Δt p is the longitudinal wave velocity model, μs / m; Δt s is the shear wave velocity model, μs / m.

[0012] S4 converts the current static rock mechanics parameter three-dimensional distribution data body, conducts rock triaxial mechanics experiments under the in-situ stress environment of underground rocks, tests the corresponding static rock mechanics parameters, determines the rock mechanics parameter static-dynamic conversion model, substitutes the determined rock mechanics parameter static-dynamic conversion model into the current dynamic rock mechanics parameter three-dimensional distribution data body, and establishes the current static rock mechanics parameter three-dimensional distribution data body; the rock mechanics parameter dynamic-static conversion model is: conduct intersection analysis on the dynamic rock mechanics parameters and the static rock mechanics parameters, and establish a numerical relationship between the two.

[0013] S5 calculates the spatial fluctuation of rock mechanical structure, reading the average value of rock mechanical parameters in each longitudinal grid unit and calculating the spatial fluctuation of rock mechanical structure of the longitudinal grid unit; the calculation of the spatial fluctuation of rock mechanical structure of the longitudinal grid unit is:

[0014]

[0015] In formulas (4)-(5), is the average value of rock mechanics parameters, N iis the rock mechanical parameter within each grid unit, m is the number of grid units in the vertical direction, dimensionless; σ is the spatial volatility of the rock mechanical structure of the vertical grid unit.

[0016] S6 Determination of the scale of development of structural fractures: Determine the scale of development of structural fractures at different structural positions on the plane based on the spatial volatility of the rock mechanical structure of the longitudinal grid unit; the scale of development of structural fractures is: divided into microscale, small scale, medium scale and large scale structural fractures according to the difference in rock mechanical structure volatility. When the rock mechanical volatility is between 0 and 300, it is the area of ​​development of microscale structural fractures; when the rock mechanical volatility is between 300 and 500, it is the area of ​​development of small scale structural fractures; when the rock mechanical volatility is between 500 and 800, it is the area of ​​development of medium scale structural fractures; when the rock mechanical volatility is between 800 and 1000, it is the area of ​​development of large scale structural fractures.

[0017] The core of the S7 buried hill was determined based on the scale of structural fracture development at different structural positions on the plane. The area with large structural fracture scale and low density was the core of the buried hill, while the area with small structural fracture scale and high density was the low area of ​​the ancient structure.

[0018] The beneficial effects of the present invention are: through high-precision geological geometric modeling, combined with pre-stack data and in-situ rock mechanics experiments to obtain the three-dimensional distribution data body of current static rock mechanics parameters, the rock mechanics structure fluctuations in different structural parts are calculated, the volatility of the rock mechanics structure is clarified, and the development scales of structural fractures in different structural parts are identified. Through the development scales of structural fractures in different structural parts, the core of the ancient buried hill can be judged.

[0019] The present invention proposes a method for determining the core of an ancient buried hill based on the volatility of rock mechanical structure. The method has high practical value, low judgment cost, strong operability, and can greatly reduce manpower and financial expenditures. The judgment results have certain reference significance for many aspects, such as the inversion of ancient and modern rock mechanical parameters, the prediction of structural fracture distribution, and the evaluation of "geological sweet spots". BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of a method for determining the core of a buried hill based on the spatial fluctuation of rock mechanical structure.

[0021] Figure 2 It is a high-precision geological model of the Bozhong X well area.

[0022] Figure 3 The P-wave, S-wave, and density models for the Bozhong X well area: (a) P-wave; (b) S-wave; (c) density.

[0023] Figure 4 The distribution of three-dimensional dynamic rock mechanical parameters inverted in the Bozhong X well area: (a) Young's modulus of rock; (b) Poisson's ratio of rock.

[0024] Figure 5 Dynamic-static conversion model of rock mechanical parameters: (a) dynamic-static conversion model of rock Young's modulus; (b) dynamic-static conversion model of rock Poisson's ratio.

[0025] Figure 6 The three-dimensional static rock mechanical parameter distribution of the Bozhong X well area: (a) Young's modulus of rock; (b) Poisson's ratio of rock.

[0026] Figure 7 This is the spatial fluctuation of rock mechanical structure in the study area of ​​Bozhong x well area.

[0027] Figure 8 It is the core location of the ancient buried hill in the study area of ​​Bozhong X well area. DETAILED DESCRIPTION

[0028] The following describes specific embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, this embodiment provides a method for determining the core of an ancient buried hill based on the volatility of rock mechanical structure, including the following steps:

[0030] S1 high-precision geological geometry modeling, based on well logging data, mud logging data, pre-stack seismic data and geological data to determine the current structural morphology, after multiple modifications and adjustments to establish a high-precision geological geometry model. The specific process is: based on the fault model of Bozhong X well area and the top and internal interface model of Bozhong X well area, the model is constructed. The fault model is established based on the fault plane obtained by interpreting the seismic data of Bozhong X well area. The top and internal interfaces are fitted based on the top and internal interfaces of Bozhong X well area obtained by structural interpretation. Figure 2 Meter-level high-precision geological geometry model of the Bozhong X well area.

[0031] S2 pre-stack data drives the inversion initial model. Based on pre-stack seismic data and geological layering data, an initial model is established. The P-wave and S-wave reflectivity terms and density reflectivity terms corresponding to the initial model are obtained according to the Aki-Richards approximate equation. The obtained reflectivity terms are convolved with the wavelets extracted from the work area to obtain a synthetic artificial gather. By obtaining the residuals from the actual gather data, the initial model is modified based on the residuals after repeated iterations. Finally, the initial model is obtained. The specific process is as follows: Based on the pre-stack seismic data and geological layering data of the Bozhong x well area, an initial model is established. The P-wave and S-wave reflectivity terms and density reflectivity terms corresponding to the initial model are obtained according to the Aki-Richards approximate equation:

[0032]

[0033] In formula (1), R PPθ is the reflection coefficient of the synthetic seismic record, dimensionless; θ is the incident angle, °; R P is the longitudinal wave velocity reflectivity term, dimensionless; R S is the shear wave velocity reflectivity term, dimensionless; R D is the density reflectivity term, dimensionless; V P is the longitudinal wave velocity, m / μs; V S is the shear wave velocity, m / μs.

[0034] The obtained reflectivity term is convolved with the wavelet extracted from the Bozhong x well area to obtain a synthetic artificial gather. The residual is obtained by comparing it with the actual gather data, repeating the iteration several times and correcting the initial model according to the residual, and finally obtaining Figure 3 P-wave velocity model, S-wave velocity model, and density model of Bozhong X well area.

[0035] S3 Inversion of the current dynamic rock mechanical parameter three-dimensional distribution data volume, substitute the P-wave velocity model, S-wave velocity model, and density model into the rock mechanical parameter calculation formula, calculate the dynamic rock mechanical parameters, and invert the current dynamic rock mechanical parameter three-dimensional distribution data volume. The specific process is: substitute the P-wave velocity and S-wave velocity and density of the Bozhong x well area into the rock mechanical parameter calculation formula:

[0036]

[0037] In formulas (2)-(3), E d is the dynamic Young's modulus of rock, GPa; μ d is the dynamic Poisson's ratio of rock, dimensionless; ρ b is the density model, g / cm 3 ;Δt p is the longitudinal wave velocity model, μs / m; Δt s is the shear wave velocity model, μs / m. Calculate the dynamic rock mechanics parameters and get Figure 4 The three-dimensional distribution data of current dynamic rock mechanical parameters in the Bozhong x well area.

[0038] S4 converts the current static rock mechanics parameter three-dimensional distribution data volume, conducts rock triaxial mechanics experiments under in-situ stress environment of underground rocks, tests the corresponding static rock mechanics parameters, determines the rock mechanics parameter dynamic-static conversion model, substitutes the determined rock mechanics parameter dynamic-static conversion model into the current dynamic rock mechanics parameter three-dimensional distribution data volume, and establishes the current static rock mechanics parameter three-dimensional distribution data volume. The specific process is: conduct rock triaxial mechanics experiments under in-situ stress environment of underground rocks in Bozhong x well area, test the corresponding static rock mechanics parameters, conduct intersection analysis on dynamic rock mechanics parameters and static rock mechanics parameters, establish the numerical relationship between the two, and obtain Figure 5 The rock mechanics parameter dynamic-static conversion model is substituted into the three-dimensional distribution data of the current dynamic rock mechanics parameters in the Bozhong x well area to establish Figure 6 The three-dimensional distribution data of current static rock mechanical parameters in the Bozhong x well area.

[0039] S5 calculates the spatial fluctuation of rock mechanical structure, reads the average value of rock mechanical parameters in each longitudinal grid unit, and calculates the spatial fluctuation of rock mechanical structure of longitudinal grid unit. The specific process is: read the average value of rock mechanical parameters in each longitudinal grid unit of Bozhong x well area, and calculate the spatial fluctuation of rock mechanical structure of longitudinal grid unit of Bozhong x well area:

[0040]

[0041] In formulas (4)-(5), is the average value of rock mechanics parameters, N i is the average value of the rock mechanical parameters in each grid unit, m is the number of grid units in the vertical direction, dimensionless; σ is the spatial volatility of the rock mechanical structure. Figure 7 Spatial fluctuation of rock mechanical structure in Bozhong X well area.

[0042] S6 Determination of the scale of structural fracture development: Determine the scale of structural fracture development at different structural locations on the plane based on the spatial volatility of the rock mechanical structure of the longitudinal grid unit. The specific process is as follows: Determine the scale of structural fracture development at different structural locations on the plane based on the spatial volatility of the rock mechanical structure of the Bozhong X well area. When the rock mechanical volatility is between 0 and 300, it indicates the development of micro-scale structural fractures in the Bozhong X well area; when the rock mechanical volatility is between 300 and 500, it indicates the development of small-scale structural fractures in the Bozhong X well area; when the rock mechanical volatility is between 500 and 800, it indicates the development of medium-scale structural fractures in the Bozhong X well area; and when the rock mechanical volatility is between 800 and 1000, it indicates the development of large-scale structural fractures in the Bozhong X well area.

[0043] S7 Ancient buried hill core is determined based on the scale of structural fracture development at different structural positions on the plane. The position with large structural fracture scale and small density is the ancient buried hill core, and the position with small structural fracture scale and large density is the ancient structural low position. The specific process is as follows: Based on the scale of structural fracture development at different structural positions on the plane of Bozhong x well area, the ancient buried hill core is determined. The position with large structural fracture scale and small density is the ancient buried hill core, and the position with small structural fracture scale and large density is the ancient structural low position. Figure 8 The location of the core of the ancient buried hill in the Bozhong X well area.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining the core of an ancient buried hill based on the volatility of rock mechanical structure, characterized in that: The method specifically comprises the following steps: S1 high-precision geological geometry modeling: Based on well logging data, mud logging data, pre-stack seismic data and geological data, the current structural morphology is determined and a high-precision geological geometry model is established; S2 pre-stack data-driven inversion initial model: Based on pre-stack seismic data and geological layering data, an initial model is established. The P-wave and S-wave reflectivity terms and density reflectivity terms corresponding to the initial model are obtained according to the Aki-Richards approximate equation. The obtained reflectivity terms are convolved with wavelets extracted from the work area to obtain synthetic artificial gathers. The residuals are obtained by comparing the synthetic artificial gathers with the actual gather data. The initial model is modified based on the residuals after repeated iterations. S3 Inversion of the three-dimensional distribution data of current dynamic rock mechanical parameters: Substitute the P-wave velocity model, S-wave velocity model, and density model into the rock mechanical parameter calculation formula to calculate the dynamic rock mechanical parameters and invert the three-dimensional distribution data of current dynamic rock mechanical parameters; S4: Convert the current static rock mechanics parameter three-dimensional distribution data volume, conduct triaxial rock mechanics experiments under in-situ stress environment of underground rocks, test the corresponding static rock mechanics parameters, determine the dynamic-static conversion model of rock mechanics parameters, substitute the determined dynamic-static conversion model of rock mechanics parameters into the current dynamic rock mechanics parameter three-dimensional distribution data volume, and establish the current static rock mechanics parameter three-dimensional distribution data volume; S5 rock mechanics structure spatial fluctuation calculation, read the average value of rock mechanics parameters in each longitudinal grid unit, and calculate the rock mechanics structure spatial fluctuation of the longitudinal grid unit; S6 structural fracture development scale determination, based on the spatial fluctuation of the rock mechanical structure of the vertical grid unit, determines the structural fracture development scale at different structural positions on the plane; The core of the S7 buried hill was determined based on the scale of structural fracture development at different structural positions on the plane. The area with large structural fracture scale and low density was the core of the buried hill, while the area with small structural fracture scale and high density was the low area of ​​the ancient structure.

2. The method for determining the core of an ancient buried hill based on rock mechanical structure fluctuation according to claim 1, characterized in that: The high-precision geological geometric model in step S1 is a model constructed based on a fault model and a top and internal interface model of the work area. The fault model is established based on the fault plane obtained by interpreting seismic data, and the top and internal interfaces are fitted based on the top and internal interfaces of the work area obtained by tectonic interpretation. The grid unit size of the high-precision geological model is 1-8 meters.

3. The method for determining the core of an ancient buried hill based on rock mechanical structure fluctuation according to claim 1, characterized in that: The initial models in step S2 are: longitudinal wave velocity model, shear wave velocity model, and density model.

4. The method for determining the core of an ancient buried hill based on rock mechanical structure fluctuation according to claim 1, characterized in that: The Aki-Richards approximation equation in step S2 is: In formula (1), R PPθ is the reflection coefficient of the synthetic seismic record, dimensionless; θ is the incident angle, °; R P is the longitudinal wave velocity reflectivity term, dimensionless; R S is the shear wave velocity reflectivity term, dimensionless; R D is the density reflectivity term, dimensionless; V P is the longitudinal wave velocity, m / μs; V S is the shear wave velocity, m / μs.

5. The method for determining the core of an ancient buried hill based on rock mechanical structure fluctuation according to claim 1, characterized in that: The rock mechanics parameter calculation formula in step S3 is: In formulas (2)-(3), E d is the dynamic Young's modulus of rock, GPa; μ d is the dynamic Poisson's ratio of rock, dimensionless; ρ b is the density model, g / cm 3 ;Δt p is the longitudinal wave velocity model, μs / m; Δt s is the shear wave velocity model, μs / m.

6. The method for determining the core of an ancient buried hill based on rock mechanical structure fluctuation according to claim 1, characterized in that: The rock mechanics parameter dynamic-static conversion model in step S4 is: performing intersection analysis on the dynamic rock mechanics parameters and the static rock mechanics parameters to establish a numerical relationship between the two.

7. The method for determining the core of an ancient buried hill based on rock mechanical structure fluctuation according to claim 1, characterized in that: The spatial fluctuation of the rock mechanical structure of the longitudinal grid unit calculated in step S5 is: In formulas (4)-(5), is the average value of rock mechanics parameters, N i is the rock mechanical parameter within each grid unit, m is the number of grid units in the vertical direction, dimensionless; σ is the spatial volatility of the rock mechanical structure of the vertical grid unit.

8. The method for determining the core of an ancient buried hill based on rock mechanical structure fluctuation according to claim 1, characterized in that: The scale of structural fracture development in step S6 is: divided into microscale, small scale, medium scale and large scale structural fractures according to the difference in rock mechanical structural volatility. When the rock mechanical volatility is between 0 and 300, it is the microscale structural fracture development area; when the rock mechanical volatility is between 300 and 500, it is the small scale structural fracture development area; when the rock mechanical volatility is between 500 and 800, it is the medium scale structural fracture development area; when the rock mechanical volatility is between 800 and 1000, it is the large scale structural fracture development area.

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