DOI: https://doi.org/10.24028/gzh.0203-3100.v40i2.2018.128878

Seismic coherence in the presence of signal time-delay fluctuations

Yu. K. Tyapkin, I. V. Mendrii, O. Yu. Shchegolikhin, O. M. Tiapkina

Abstract


One of the main seismic attributes widely used to identify and study lateral changes in the geological environment, such as pinch-outs, faults, fractured zones, and buried paleochannels, is the coherence of seismic images. In the article, a new method for calculation of this popular seismic attribute is proposed. It is based on a generalized mathematical model of the seismic image. The model allows for arbitrary variations of not only signal amplitudes and noise variances, but also residual signal time delays within a space-time window that slides along the image and wherein the coherence calculation is performed. The residual time delays are fluctuations in the arrival times of the signal after subtracting the trend approximated by first- or second-order polynomials. An iterative algorithm for an optimized estimation of the parameters of the generalized mathematical model of the seismic image, which are necessary for the new method of calculating coherence, is described. The algorithm uses deterministic regularization. The proposed method is tested and compared with one of the traditional analogs on synthetic data. Moreover, the new coherence measure has been successfully used in the study of fractured zones in coal-bearing strata of the Donetsk basin and in the study of a gas field in the Dnieper-Donets depression.


Keywords


seismic coherence; generalized seismic image model; residual time delays; projection onto а convex set; fractured zone; buried paleochannel

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