Block constraint time-lapse seismic difference inversion method and system based on reflectivity method

Abstract

The invention discloses a block constraint time-lapse seismic difference inversion method and system based on a reflectivity method. The method comprises the steps of: obtaining a forward operator intime-lapse seismic difference inversion through adoption of the reflectivity method; utilizing logging data to forward simulate an angle gather to perform well-to-seismic calibration, performing related comparison with a well-side seismic trace, determining a time-depth conversion relationship, and picking up horizon information; performing wavelet extraction on the actual difference seismic record at different angles based on a linear convolution model; establishing a full-band interpolation result model in combination with the logging data, and obtaining a low-frequency initial model of difference inversion through smoothing processing; constructing an objective function of difference inversion based on a Bayesian inversion reasoning framework to obtain a residual error of a forward simulation record and an actual record, adding an optimized super Laplace block constraint into the Bayesian framework, and establishing a difference inversion formula; and carrying out time-lapse seismicdifference inversion, carrying out iterative calculation, and terminating iteration when the variation amplitude of the obtained calculation result is smaller than a threshold value, so as to obtaina time-lapse seismic inversion result.

Description

technical field [0001] The invention relates to the technical field of time-lapse seismic reservoir monitoring, in particular to a block-constrained time-lapse seismic difference inversion method, system, computer equipment and computer-readable storage medium based on the reflectivity method, which are used for high-resolution time-lapse seismic Accurate, high-resolution reservoir differential elastic parameter estimation. Background technique [0002] Time-lapse seismic reservoir monitoring technology has been successfully applied to monitor reservoir changes in the process of oil and gas production, so as to find dead oil areas, determine new well locations and optimize injection-production schemes, thereby improving reservoir recovery. However, the production process of oil reservoirs will be accompanied by water injection or gas injection. On the one hand, the oil saturation of the oil reservoir is changed due to the oil production and water or gas injection. On the oth...

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Problems solved by technology

[0006] 1. This method often uses the approximate formula of the Zoeppritz equation for calculation, which simplifies the solution process. However, this method is a linear approximation for small angles. Therefore, in the case of large angles (such as greater than 30°), the calculated reflection coefficient error is relatively large. Big

[0007] 2. The calculation process of this method is based on the assumption of a single interface and only calculates the reflected wave information once, ignoring the influence of transmission loss, interlayer multiple waves and interlayer converted waves, which will lead to certain errors in the final difference inversion results

[0008] 3. This method is based on the assumption of elasticity, ignoring the effects of attenuation and dispersion. The actual underground medium is not completely elastic. The attenuation effect of seismic waves will cause wavelet amplitude reduction and waveform distortion, reducing the resolution of seismic records.

[0009] 4. The differential elastic parameters obtained by inversion are often blocky. This method does not describe the blocky boundaries clearly enough, and it is difficult to obtain high-sparse differential inversion results under Gaussian and Laplace constraints.

[0010] 5. Tuning interference affects the resolution of the inversion results. Since the traditional method is derived based on the assumption of a single interface, the inversion resolution is affected by interface tuning; even if the precise Zoeppritz equation is used for calculation during the time-lapse seismic difference inversion process, Due to the loss of more multiple wave information in order to consider the transmission, the forward calculation operator in the difference inversion cannot be accurately calculated, thus affecting the result of the difference inversion

[0011] In summary, in the existing time-lapse seismic difference inversion process, due to the characteristics of the difference elastic parameters, small-angle linear approximation, incomplete waveform simulation, and ignoring the attenuation effect, the accuracy of the conventional difference inversion results is not enough , the resolution is reduced; therefore, there is an urgent need for a time-lapse seismic difference inversion method that can solve the above problems, achieve more accurate and higher-resolution inversion results, and meet the actual reservoir seismic reservoir characterization requirements

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