Efficient acquisition method of quasi-VSP data based on acoustic velocity logging

Abstract

The present invention provides a method for obtaining pseudo-VSP data by using sonic logging velocity data. The method matches the sonic logging velocity data with the VSP data, and uses the high-frequency and low-frequency components of the layered system to obtain the pseudo-VSP velocity of the sonic logging velocity data. The sonic logging velocity data can be used to calculate geophysical parameters such as Q value and Tar value related to underground formations that can only be obtained from VSP data. The utilization efficiency and application field of the sonic logging velocity data are expanded, and an important basis can be provided for processing such as seismic velocity modeling and imaging, amplitude correction and absorption attenuation compensation.

Description

Technical Field

[0001] The present invention relates to the field of data processing and information extraction in oil and gas seismic exploration, and specifically to a method for obtaining pseudo-VSP data using acoustic velocity logging data. By processing the acoustic velocity logging data, geophysical parameters that could originally only be obtained with VSP data can be obtained, thereby expanding the application field of the acoustic velocity logging data and providing an important basis for seismic velocity modeling and imaging, amplitude correction, absorption attenuation compensation and other processing. Background Art

[0002] Acoustic wave velocity logging is the most commonly used logging method. It is used to calculate and determine the porosity, lithology and pore fluid properties of the formation by measuring the time difference △t (the inverse of the formation longitudinal wave velocity) of the formation sliding wave based on the propagation speed of sound waves in the formation.

[0003] Vertical seismic profiling (VSP) technology achieves underground exploration through ground excitation and in-well reception. Since VSP technology has more direct reservoir description (absorption attenuation, velocity, anisotropy, etc.) capabilities, better time-depth calibration capabilities, and higher resolution than ground seismic, it is widely used in fine characterization of complex structures around wells, reservoirs, and fluid spatial distribution, etc. It is an indispensable bridge between ground seismic, well logging, and geological information. The underground geophysical parameters obtained from VSP data have high vertical resolution, and can obtain true and reliable Tar values, Q values, velocity, and anisotropy parameters, which can be used to constrain ground seismic data processing and imaging, and improve the accuracy of reservoir target imaging.

[0004] However, in actual production, compared with conventional acoustic velocity logging, VSP data acquisition has a long construction time and high cost, and the quantity and density of VSP data are less than conventional acoustic velocity logging. Therefore, the availability of VSP data and the measurement range of various geophysical parameters are limited. Therefore, the spatial acquisition density advantage of conventional acoustic velocity logging and the detection advantage of VSP data are fully combined to realize the mapping of acoustic velocity logging data to pseudo-VSP data, which can improve the utilization efficiency of acoustic velocity logging data, open up the well data data foundation of well control constraint surface seismic processing, and provide a richer and more effective data benchmark for amplitude compensation, Q compensation, velocity modeling and anisotropy processing. Summary of the invention

[0005] The purpose of the present invention is to provide a method for efficiently acquiring pseudo-VSP data based on acoustic velocity logging. The advantage of the present invention is that the acoustic velocity logging data can be used to obtain various geophysical parameters such as underground Tar value, Q value, velocity, etc. that can only be obtained from VSP data, and the application of acoustic velocity logging data in seismic data processing and imaging can be realized. The method includes the following main steps:

[0006] (1) Input the acoustic logging velocity data and VSP velocity data of the well, and match the effective data range of the acoustic logging velocity and VSP velocity according to the following formula:

[0007]

[0008] Among them, i is the depth sampling number, ∩ represents the matching processing operator, V a is the acoustic logging velocity, V vsp is the VSP speed, V aa and V vspa They represent the sonic logging velocity and VSP velocity after matching processing within the data range, respectively;

[0009] (2) The sampling rate of the acoustic logging velocity and the sampling rate of the VSP velocity data are matched, as shown in the following formula:

[0010]

[0011] Among them, V ar and V vspr They represent the acoustic logging velocity and VSP velocity after data sampling rate matching, IN(V vspa ) is the depth sampling interval of the VSP velocity after matching processing, RS(·) represents the resampling processing of the data;

[0012] (3) Using the logging layer data, the acoustic logging velocity and VSP velocity are processed for layered system velocity matching. The layered system matching is performed according to the following formula to obtain the low-frequency approximate component and high-frequency detail component of the acoustic logging velocity and VSP velocity in each layer:

[0013]

[0014] Among them, L and H are the low-frequency and high-frequency decomposition filters established respectively, * represents the convolution operation, and D a is the low-frequency approximation coefficient of the acoustic logging velocity, G a is the high-frequency detail coefficient of acoustic logging velocity, D vsp is the low-frequency approximation coefficient of the VSP velocity, G vsp is the high frequency detail coefficient of VSP velocity;

[0015] (4) When both acoustic logging velocity and VSP velocity data are available for N wells in the study area, the average value of the low-frequency approximate component difference between the acoustic logging velocity and the VSP velocity of each layer in all wells is calculated:

[0016]

[0017] D a,n and Dvsp,n are the low-frequency approximation coefficients of the acoustic logging velocity and the VSP velocity of the nth well, respectively;

[0018] (5) Select the wells in the study area that only have acoustic logging velocity, and calculate the low-frequency approximate component and high-frequency detail component of the acoustic logging velocity in each layer:

[0019] SWT(V a )=[D a (i) = L*V a (i),G a (i) = H * V a (i)]

[0020] Using the result of step (4), calculate the low-frequency approximate component of the pseudo-VSP velocity in each layer based on the acoustic logging velocity:

[0021] D vspf (i) = D a (i)+Dif(i)

[0022] By inverse transforming ISWT(·), the pseudo-VSP velocity based on the acoustic logging velocity is obtained:

[0023] V vspf (i) = ISWT[D vspf (i),G a (i)]

[0024] (6) Using the empirical relationship between velocity and Q value, the pseudo-VSP-Q value based on acoustic logging velocity is obtained:

[0025] Q vspf (i) = a·[V vspf (i)] b +c

[0026] Where a, b, and c are the empirical coefficients of the relationship between speed and Q value in different regions;

[0027] (7) k is fitted from the pseudo-VSP velocity based on the sonic logging velocity using a linear equation of the following form:

[0028]

[0029] The pseudo-VSP-Tar value based on acoustic velocity logging is:

[0030] Tar vspf =-k. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1It is the sonic logging velocity and VSP velocity data of a well in the work area. The ordinate is depth, unit is m, and the abscissa is velocity, unit is m / s. The valid data range of sonic logging velocity is 1636.75-7532.625m, the sampling rate is 0.125m, and the valid data range of VSP velocity is 30-7960m, the sampling rate is 20m.

[0032] Figure 2 It is the sonic logging velocity and VSP velocity after the effective data range and data sampling rate are matched. The effective data range of the sonic logging velocity and VSP velocity is 1640-7520m, and the sampling rate is 20m.

[0033] Figure 3 This is the result of velocity matching processing of the acoustic logging velocity layering system using the method of the present invention, and the acoustic logging velocity and the VSP velocity are well matched.

[0034] Figure 4 This is the result of using the method of the present invention to correct the original sonic logging velocity, and the sonic logging velocity and the VSP velocity are well matched. DETAILED DESCRIPTION

[0035] (1) Acoustic logging velocity V of a well in the collection area a With VSP speed V vsp ,like Figure 1 As shown in FIG. 1 , the effective data range and data sampling rate of the acoustic logging velocity and the VSP velocity are matched to achieve the matching and unification of the acoustic logging velocity and the VSP velocity in data, as shown in FIG. Figure 2 As shown;

[0036] (2) Perform layered velocity matching on the acoustic logging velocity and the VSP velocity, respectively. Figure 3 , obtain the low-frequency approximate component D of the acoustic logging velocity in each layer a and high frequency detail component G a ; Obtain the low-frequency approximate component D of the VSP velocity in each layer vsp and high frequency detail component G vsp

[0037] (3) Calculate the low-frequency approximate coefficient D of the acoustic logging velocity in each layer a Low frequency approximation coefficient D of VSP velocity vsp If there are multiple wells in the study area with both acoustic logging velocity and VSP velocity data, calculate the low-frequency approximate coefficient D of the acoustic logging velocity of each layer in the multiple wells in the study area. a,n Low frequency approximation coefficient D of VSP velocity vsp,n The average of the differences;

[0038] (4) Select the wells in the study area that only have acoustic velocity logging, and calculate the low-frequency approximate component D of the acoustic logging velocity in each layer. a and high frequency detail component G a ; Using the difference in the decomposition approximation coefficients between the acoustic logging velocity and the VSP velocity, the low-frequency approximate component D of the pseudo-VSP velocity in each layer based on the acoustic logging velocity is calculated. vsp ; Through inverse transformation processing, the pseudo-VSP velocity V of the acoustic logging velocity is obtained vspf ,like Figure 4 As shown;

[0039] (5) Set the empirical coefficients a, b, and c of the work area, and use the empirical formula of the relationship between velocity and Q value to obtain the pseudo-VSP-Q value Q based on acoustic velocity logging. vspf After obtaining the pseudo-VSP average velocity based on acoustic velocity logging, the pseudo-VSP-Tar value of acoustic velocity logging can also be determined by fitting the slope of the linear equation.

[0040] The advantages and novelties of the present invention are as follows: (1) for exploration areas lacking VSP data, conventional acoustic velocity logging can still be used to realize the conversion of acoustic logging velocity data into pseudo-VSP data, thereby improving the utilization efficiency of acoustic logging velocity data and saving the cost of additional VSP data acquisition; (2) the method of the present invention can fully combine the spatial acquisition density advantage of conventional acoustic velocity logging and the detection advantage of VSP data, providing a data benchmark for seismic amplitude compensation, Q compensation, velocity modeling and anisotropy processing.

[0041] The above embodiments are only used to illustrate the present invention, wherein the various implementation steps of the method can be changed, and any equivalent transformations and improvements based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for efficiently acquiring pseudo-VSP data based on acoustic velocity logging, mainly comprising the following steps: (1) Input the acoustic logging velocity data and VSP velocity data of the well, and match the effective data range of the acoustic logging velocity and VSP velocity according to the following formula: Among them, i is the depth sampling number, ∩ represents the matching processing operator, V a is the acoustic logging velocity, V vsp is the VSP speed, V aa and V vspa They represent the sonic logging velocity and VSP velocity after matching processing within the data range, respectively; (2) The sampling rate of the acoustic logging velocity and the sampling rate of the VSP data are matched, as shown in the following formula: Among them, V ar and V vspr They represent the acoustic logging velocity and VSP velocity after data sampling rate matching, IN(V vspa ) is the depth sampling interval of the VSP velocity after matching processing, RS(·) represents the resampling processing of the data; (3) Using the logging layer data, the acoustic logging velocity and VSP velocity are processed for layered system velocity matching. The layered system matching is performed according to the following formula to obtain the low-frequency approximate component and high-frequency detail component of the acoustic logging velocity and VSP velocity in each layer: Among them, L and H are the low-frequency and high-frequency decomposition filters established respectively, * represents the convolution operation, and D a is the low-frequency approximation coefficient of the acoustic logging velocity, G a is the high-frequency detail coefficient of acoustic logging velocity, D vsp is the low-frequency approximation coefficient of the VSP velocity, G vsp is the high-frequency detail coefficient of VSP velocity; (4) When both acoustic logging velocity and VSP velocity data are available for N wells in the study area, the average value of the low-frequency approximate component difference between the acoustic logging velocity and the VSP velocity of each layer in all wells is calculated: D a,n and D vsp,n are the low-frequency approximation coefficients of the acoustic logging velocity and the VSP velocity of the nth well, respectively; (5) Select the wells in the study area that only have acoustic logging velocity, and calculate the low-frequency approximate component and high-frequency detail component of the acoustic logging velocity in each layer: SWT(V a )=[D a (i)=L*V a (i),G a (i)=H*V a (i)] Using the result of step (4), calculate the low-frequency approximate component of the pseudo-VSP velocity in each layer based on the acoustic logging velocity: D vspf (i)=D a (i)+Dif(i) By inverse transforming ISWT(·), the pseudo-VSP velocity based on the acoustic logging velocity is obtained: V vspf (i)=ISWT[D vspf (i),G a (i)] (6) Using the empirical relationship between velocity and Q value, the pseudo-VSP-Q value based on acoustic logging velocity is obtained: Q vspf (i)=a·[V vspf (i)] b +c Where a, b, and c are the empirical coefficients of the relationship between speed and Q value in different regions; (7) k is fitted from the pseudo-VSP velocity based on the sonic logging velocity using a linear equation of the following form: The pseudo-VSP-Tar value based on acoustic velocity logging is: Takes vspf =-k.

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