Seismic interpretation using seismic trace frequency attribute properties - a preliminary study

Time-frequency analysis (T-F) of the seismic reflection character of thin formations (Widess, 1973; Mahradi, 1983; Yang, 1988; Yin et al., 2003) is increasingly being applied to high-resolution seismic processing and interpretation, especially for sequence interpretation of complex continental facies. This includes identification and partitioning of multi-level sequences, micro-facies characterization of sedimentary layers and the cycle structure of thin sand-shale interbeds, and thickness prediction of thin reservoirs (Li, 1987; Jin, 1988; Mushen et al., 2000; Ling Yun, 2004), etc. Using different mathematical transforms e.g., Fourier transform, wavelet transform, Wigner-Vill transform, Gabor transform, etc, (Cohen, 1989; Williams et al., 1989; Boashash, 1991; Bahorich, 2002), the time-frequency analysis allows us to decompose and to depict in detail the local spectra of the input signals, so as to get an overall knowledge of their micro-structures by the relatively high resolution in the frequency domain. This paper uses the Fourier and inverse Fourier transform (full frequency band, local frequency decomposition, and superposition) to conduct the time-frequency analysis (Mushen, 1992; Du, 1998; Wang, 2000), using a bi-octave triangular broad-band recursive (exponential increase) filtering (Fig. 1) to bring out the tuning effects of thin bed thickness and lithology (Widess, 1973; Mushen, 1992; Du, 1998; Wang, 2000). The main characteristic of the filtering is that it can highlight the dominant frequencies of different frequency bands without missing out gradual changes of the frequency attributes (Fig. 2). In the study of the frequency characteristics of the seismic data from a 3D survey, using the filtering available in our time-frequency analysis software package, we find that there is a clear relationship between the multi-level ramifying structure of the frequency-time plot and the strata attributes and sedimentary cycles. This idea makes it feasible to study the sequence stratigraphy and reservoir directly from the frequency attribute of the seismic data, and also offers a new analysis alternative for highprecision geological interpretation of seismic data.