A method for calculating the degree of improvement of signal-to-noise ratio of single-shot data by geophone combination

Abstract

The application belongs to the field of oil and gas geophysical exploration, and discloses a kind of geophone combination to improve the calculation method of signal-to-noise ratio degree of single shot data, and the signal-to-noise ratio of geophone combination is improved multiple times compared with geophone single point G , the surface wave suppression amplitude value of geophone combination b 1, the refraction wave suppression amplitude value b 2, the reciprocal of the signal-to-noise ratio of geophone combination suppression random interference wave b 3, the amplitude ratio of surface wave and refraction wave k , the surface wave suppression coefficient, refraction wave suppression coefficient and random interference wave suppression coefficient of geophone combination are obtained, and finally the formula of the signal-to-noise ratio improvement multiple of geophone combination compared with geophone single point is obtained.The application is suitable for calculating the degree of signal-to-noise ratio of single shot data improved by geophone combination, the calculation result is clear, the reliability is strong, the calculation method is fast, and the quantitative basis can be provided for the selection of geophone combination number and group distance in seismic acquisition engineering technical design.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of oil and gas geophysical exploration, and particularly relates to a method for calculating the degree of improvement of signal-to-noise ratio of single-shot data by geophone combination. BACKGROUND

[0002] In the low signal-to-noise ratio area with developed noise, geophone combination receiving is one of the effective means to suppress interference and improve the signal-to-noise ratio of single-shot data. The geophone combination can suppress both regular interference waves and random interference waves. Among them, the regular interference waves (such as surface waves and refracted waves) are mainly suppressed by the directivity effect of the combination, and the random interference waves are suppressed by the statistical effect of the combination. Although the current research has given the calculation method of the response curve of different geophone combinations for regular interference waves and the theoretical calculation method of different geophone combinations for suppressing random interference waves to improve the signal-to-noise ratio, the calculation methods are only for a single interference wave, such as only for surface waves, only for refracted waves or only for random interference waves. There is no calculation method for comprehensively considering several interference waves together, and the degree of improvement of the overall signal-to-noise ratio of the received single shot cannot be reflected.

[0003] For example, the current geophone combination parameter calculation method based on wave equation forward modeling considers the signal-to-noise ratio of different geophone combination parameters when considering the underground scattering noise, but lacks consideration of factors such as surface waves, refracted waves and random interference generated by the near-surface. The main interference waves suppressed by geophone combination receiving include surface waves, refracted waves and random interference, and the wave equation forward modeling cannot completely simulate the actual situation of field interference. Therefore, it is of great significance to study a method for providing basis for geophone combination parameter design. SUMMARY

[0004] The purpose of the present application is to provide a method for calculating the degree of improvement of signal-to-noise ratio of single-shot data by geophone combination, which obtains the surface wave suppression coefficient, the refracted wave suppression coefficient and the random interference wave suppression coefficient of the geophone combination, and finally obtains the formula of the signal-to-noise ratio improvement multiple of the geophone combination compared with the single geophone, thereby providing a quantitative basis for the selection of the number of geophone combinations and the distance within the combination.

[0005] In order to achieve the above purpose, the technical solution adopted by the present application is as follows:

[0006] A method for calculating the degree of improvement of signal-to-noise ratio of single-shot data by geophone combination, comprising the following steps:

[0007] The ratio of the effective wave time window energy value and the interference wave time window energy value of the single geophone is obtained, the signal-to-noise ratio of the geophone combination and the single geophone is obtained, and the signal-to-noise ratio improvement multiple G of the geophone combination compared with the single geophone is calculated.

[0008] As a second limitation, the specific process of step S2 is:

[0009] S21, according to the detector single point test single shot, read the apparent velocity of the surface wave, the video rate and the apparent velocity of the refracted wave, the video rate, calculate the apparent wavelength of the surface wave, the apparent wavelength of the refracted wave;

[0010] S22, according to the detector combination parameter, get regular interference wave suppression curve;

[0011] S23, the apparent wavelength of the surface wave, the apparent wavelength of the refracted wave, is substituted into the regular interference wave suppression curve, the surface wave suppression amplitude value b1 of the detector combination, the refracted wave suppression amplitude value b2 is calculated.

[0012] As the third kind of limit, the detector combination parameter includes the number of detector combination, the group distance of detector combination.

[0013] As the fourth kind of limit, in step S3, the calculation formula of the inverse number b3 of the signal-to-noise ratio of the detector combination suppression random interference wave is:

[0014]

[0015] Wherein, alpha is the statistical effect of the detector combination on the suppression of random interference wave;

[0016]

[0017]

[0018] Wherein, m is the number of detector combination, beta is the statistical effect coefficient of the detector combination on the suppression of random interference wave, l is the order number of a detector in the detector combination, Δx is the group distance of the detector combination, R(lΔx) is the random interference wave correlation function value of the distance lΔx, R(0) is the autocorrelation function value of the random interference wave profile.

[0019] The present application adopts the above technical scheme, compared with the prior art, the technical progress obtained is:

[0020] (1) the calculation result of the present application is clear, the reliability is strong, the calculation method is fast, and the quantitative basis can be provided for the selection of the number of detector combination and the group distance in the seismic acquisition engineering technical design;

[0021] (2) the present application is based on the test single shot data of the actual detector single point, comprehensively considers the influence of the surface wave, the refracted wave and the random interference wave on the single shot data, proposes a calculation method of combining the surface wave, the refracted wave and the random interference wave together when the detector combination, and reflects the signal-to-noise ratio improvement degree of the detector combination compared with the detector single point;

[0022] (3) The application can quantitatively calculate different signal-to-noise ratio improvement degrees corresponding to different detector combination parameters, such as the number of combinations and the distance within the group, so as to provide a basis for the determination of the detector combination.

[0023] The application belongs to the field of oil and gas geophysical exploration and is suitable for calculating the degree of signal-to-noise ratio improvement of detector combination for single-shot data. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The test single shot of the detector combination and the test single shot of the detector single point are used for the implementation of the application.

[0025] Figure 2 The regular interference suppression curve of the detector combination of the embodiment of the application is used for the implementation of the embodiment of the application.

[0026] Figure 3 The random interference wave correlation function value curve of the embodiment of the application is used for the implementation of the embodiment of the application. DETAILED DESCRIPTION

[0027] The application will be further described below in combination with the embodiments, but those skilled in the art should understand that the application is not limited to the following embodiments, and any improvement and change made on the basis of the specific embodiments of the application is within the protection scope of the claims of the application.

[0028] The application is a method for calculating the degree of signal-to-noise ratio improvement of detector combination for single-shot data.

[0029] This embodiment takes a certain 3D seismic acquisition project in the southwestern Tarim Basin as an example for illustration, wherein the number of detector combinations in the region is 40, the distance within the detector combination group is 3.5 m, the specific surface wave suppression coefficient, the refraction wave suppression coefficient and the random interference wave suppression coefficient of the southwestern Tarim Basin are obtained under the detector combination parameters, and finally the formula of the signal-to-noise ratio improvement multiple of the detector combination compared with the detector single point is obtained, thereby providing a quantitative basis for the selection of the detector combination parameters in the southwestern Tarim Basin.

[0030] This embodiment specifically includes the following steps:

[0031] S1, the signal-to-noise ratios of the detector combination and the detector single point are respectively calculated through the test single shot of the detector combination and the test single shot of the detector single point, and the signal-to-noise ratio improvement multiple G of the detector combination compared with the detector single point is calculated.

[0032] The specific process of this step is as follows:

[0033] S11, obtain the effective wave time window and the interference wave time window when the geophone combination, calculate the energy value of the effective wave time window and the energy value of the interference wave time window; and obtain the effective wave time window and the interference wave time window when the geophone single point, calculate the energy value of the effective wave time window and the energy value of the interference wave time window, as shown in the figure Figure 1 , which is the interference wave time window and the effective wave time window obtained from the test single shot of the geophone combination and the test single shot of the geophone single point, wherein the black box is the interference wave time window and the gray box is the effective wave time window;

[0034] , wherein the energy value of the effective wave time window obtained when the geophone combination is 0.068mv, and the energy value of the interference wave time window is 0.021mv; the energy value of the effective wave time window obtained when the geophone single point is 0.069mv, and the energy value of the interference wave time window is 0.059mv;

[0035] S12, calculate the ratio of the energy value of the effective wave time window and the energy value of the interference wave time window when the geophone combination, and the ratio of the energy value of the effective wave time window and the energy value of the interference wave time window when the geophone single point, obtain the signal-to-noise ratio of the geophone combination and the geophone single point, and calculate the signal-to-noise ratio of the geophone combination in the Tarim Basin Tarim southwest area when the number of geophone combinations is 40 and the group distance of the geophone combination is 3.5m, the signal-to-noise ratio of the geophone combination is improved by G=2.80 times compared with the geophone single point;

[0036] S2, according to the test single shot of the geophone single point, calculate the apparent wavelength of the surface wave and the apparent wavelength of the refracted wave, and then calculate the surface wave suppression amplitude value b1 and the refracted wave suppression amplitude value b2 of the geophone combination according to the regular interference wave suppression curve obtained from the geophone combination parameters;

[0037] , the specific process of this step is:

[0038] S21, according to the test single shot of the geophone single point, read the apparent velocity and video rate of the surface wave and the apparent velocity and video rate of the refracted wave, and calculate the apparent wavelength of the surface wave and the apparent wavelength of the refracted wave;

[0039] , wherein the apparent velocity of the surface wave is 320m / s, and the video rate is 4-9Hz; the apparent velocity of the refracted wave is 3162m / s, and the video rate is 12-27Hz; through calculation, the apparent wavelength of the surface wave is 35-80m, and the apparent wavelength of the refracted wave is 117-263m;

[0040] S22, according to the geophone combination parameters, obtain the regular interference wave suppression curve through the klang software, as shown in the figure Figure 2 ;

[0041] , wherein the geophone combination parameters include the number of geophone combinations and the group distance of the geophone combination;

[0042] S23, the apparent wavelength of the surface wave, the apparent wavelength of the refracted wave are substituted into the regular interference wave suppression curve, and the surface wave suppression amplitude value b1 and the refracted wave suppression amplitude value b2 of the geophone combination are calculated;

[0043] The apparent wavelength of the surface wave and the apparent wavelength of the refracted wave can be obtained from the regular interference wave suppression curve of Figure 2 The response value corresponding to the surface wave is 0.49 on average, and the response value corresponding to the refracted wave is 0.06 on average. Through calculation, the surface wave suppression amplitude value b1 is 0.51, and the refracted wave suppression amplitude value b2 is 0.94;

[0044] S3, carry out random interference wave characteristic investigation, obtain the random interference correlation function value curve of the region, and calculate the inverse of the signal-to-noise ratio of the geophone combination suppressing random interference wave b3;

[0045] In this step, the calculation formula of the inverse of the signal-to-noise ratio of the geophone combination suppressing random interference wave b3 is:

[0046]

[0047] Wherein, α is the statistical effect of the geophone combination on the suppression of random interference wave;

[0048]

[0049]

[0050] Wherein, m is the number of geophone combinations, β is the statistical effect coefficient of the geophone combination on the suppression of random interference wave, l is the order number of a geophone in the geophone combination, Δx is the group distance of the geophone combination, and R(lΔx) is the random interference wave correlation function value at a distance lΔx, as shown in Figure 3 The random interference wave correlation function value corresponding to each lΔx can be determined by Figure 3

[0051] When the number of geophone combinations is 40 and the group distance of the geophone combination is 3.5m, the statistical effect coefficient β of the geophone combination on the suppression of random interference wave is 0.28, the statistical effect α of the geophone combination on the suppression of random interference wave is 5.59, and the inverse of the signal-to-noise ratio of the combination suppressing random interference b3 is 0.18;

[0052] ​S4. From the test single shot at the detector point, obtain the surface wave amplitude of 0.028μV and the refracted wave amplitude of 0.025μV, and obtain the surface wave to refracted wave amplitude ratio k = 1.12. Substitute the detector combination's signal-to-noise ratio improvement factor G = 2.80 compared to the detector single point obtained in step S1, the detector combination's surface wave suppression amplitude value b1 = 0.51 and refracted wave suppression amplitude value b2 = 0.94 obtained in step S2, and the reciprocal of the detector combination's signal-to-noise ratio improvement factor b3 = 0.18 obtained in step S3 into the following formula to calculate the detector combination's surface wave suppression coefficient a1, refracted wave suppression coefficient a2, and random interference wave suppression coefficient a3. Finally, obtain the formula G for the detector combination's signal-to-noise ratio improvement factor compared to the detector single point.

[0053]

[0054] a1 + a2 + a3 = 1;

[0055]

[0056] Where c is a factor, with a value range of 1 to 1.15, and in this embodiment, c = 1 is taken; the surface wave suppression coefficients a1 = 0.17, a2 = 0.15, and a3 = 0.68 are calculated;

[0057] The final formula for the improvement in signal-to-noise ratio of the detector combination compared to a single detector is as follows:

[0058]

[0059] By obtaining the specific surface wave suppression coefficient, refracted wave suppression coefficient, and random interference wave suppression coefficient for the southwestern region of the Tarim Basin under the given detector combination parameters, a formula for the signal-to-noise ratio improvement factor of the detector combination compared to the single-point detector can be obtained, providing a quantitative basis for the selection of detector combination parameters in the southwestern region of the Tarim Basin.

[0060] According to the above formula G, when the parameters of the detector combination, namely the number of detectors m and the intergroup spacing Δx of the detector combination, change, the surface wave suppression amplitude value b1, the refracted wave suppression amplitude value b2, and the reciprocal b3 of the detector combination's suppression of random interference waves to improve the signal-to-noise ratio can be obtained from steps S2 and S3. Substituting these values ​​into formula G, the theoretical improvement factor of the single-shot signal-to-noise ratio of different detector combination parameters (number of detectors m and intergroup spacing Δx) in the southwestern region of the Tarim Basin compared to a single detector point can be calculated. This provides a quantitative basis for the selection of detector combination parameters. As shown in Table 1, the improvement factor of the signal-to-noise ratio of the detector combination in the southwestern region of the Tarim Basin compared to a single detector point is as follows:

[0061] Table 1 SNR improvement factor of geophone combination compared with geophone single point

[0062]

[0063]

[0064] It should be noted that the above only describes the preferred embodiments of the present application and is not used to limit the present application. Although the present application is described in detail with reference to the above embodiments, those skilled in the art can modify the technical solutions described in the embodiments or equivalently replace some technical features thereof. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for calculating the degree of improvement of signal-to-noise ratio of single-shot data by geophone combination, characterized in that, The method comprises the following steps: S1, calculate the signal-to-noise ratio of the geophone combination and the geophone single point respectively through the test single shot of the geophone combination and the test single shot of the geophone single point, and calculate the signal-to-noise ratio improvement multiple of the geophone combination compared with the geophone single point G ; S2, according to the detector single point test single shot, calculate the apparent wavelength of surface wave, the apparent wavelength of refraction wave, then according to the regular interference wave suppression curve obtained by the detector combination parameter, calculate the surface wave suppression amplitude value of detector combination b 1, refraction wave suppression amplitude value b 2; S3, carry out random interference wave characteristic investigation, obtain random interference wave correlation function value curve, calculate the inverse of the signal-to-noise ratio of the geophone combination suppressing random interference wave b 3; S4, from the detector single point test shot, get the surface wave amplitude and refraction wave amplitude, get the surface wave, refraction wave amplitude ratio k , the signal-to-noise ratio of the detector combination obtained in step S1 is improved by multiple times G , the surface wave suppression amplitude value of the detector combination obtained in step S2 b 1, the refraction wave suppression amplitude value b 2, and the inverse of the signal-to-noise ratio of the detector combination obtained in step S3 to suppress random interference wave b 3 is brought into the following formula to obtain the surface wave suppression coefficient, refraction wave suppression coefficient and random interference wave suppression coefficient of the detector combination, and finally obtain the formula of the signal-to-noise ratio of the detector combination compared with the detector single point G ; ； ； ； wherein, a 1 is a surface wave suppression coefficient, a 2 is a refracted wave suppression coefficient, a 3 is a random interference wave suppression coefficient, c is a constant factor, and has a value range of 1-1.

15.

2. The method of claim 1, wherein the method further comprises: The specific process of step S1 is: S11, through the test single shot of the geophone combination and the test single shot of the geophone single point, the effective wave time window and the interference wave time window when the geophone combination is obtained, the energy value of the effective wave time window and the energy value of the interference wave time window are calculated; and the effective wave time window and the interference wave time window when the geophone single point is obtained, the energy value of the effective wave time window and the energy value of the interference wave time window are calculated; S12, the ratio of the energy value of the effective wave time window and the energy value of the interference wave time window when the detector is combined, and the ratio of the energy value of the effective wave time window and the energy value of the interference wave time window when the detector is single-point, the signal-to-noise ratio of the detector combination and the detector single-point is obtained, and the signal-to-noise ratio of the detector combination is calculated compared with the signal-to-noise ratio of the detector single-point G。 3. The method of claim 1, wherein the method further comprises: The specific process of step S2 is: S21, according to the test single shot of the geophone single point, the apparent velocity and the apparent frequency of the surface wave and the apparent velocity and the apparent frequency of the refracted wave are read, the apparent wavelength of the surface wave and the apparent wavelength of the refracted wave are calculated; S22, according to the geophone combination parameters, the regular interference wave suppression curve is obtained; S23, the apparent wavelength of the surface wave, the apparent wavelength of the refracted wave are substituted into the regular interference wave suppression curve, and the surface wave suppression amplitude value of the geophone combination is calculated b 1. the refracted wave suppression amplitude value b 2.

4. The method of claim 3, wherein the method further comprises: The geophone combination parameters include the number of the geophone combination, the group interval of the geophone combination.

5. The method of claim 1, wherein the method further comprises: In step S3, the detector combines the suppressed random interference waves to improve the inverse of the signal-to-noise ratio b The calculation formula of 3 is: ； wherein α is the statistical effect of the detector combination on random interference waves; ； wherein, m is the number of geophone combinations, β is the statistical effect coefficient of geophone combination to random interference wave suppression, l is the serial number of a geophone in the geophone combination, Δx is the group interval of geophone combination, R lΔx is the random interference wave correlation function value of distance lΔx , R is the autocorrelation function value of random interference wave profile.​

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