Hard streaks, polarity, and phase in reflection seismic data: Stratton field

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Conference Proceeding

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© 2018 SEG. Seismic interpretation is often based on the analysis of amplitude anomalies, and these can depend strongly on the seismic wavelet present in the data. However, if the wavelet polarity or phase is not known or if fine-scale impedance variations are complex, a direct interpretation of the anomaly can be difficult and ambiguous. The readily available Stratton data set contains a dome-like feature that may be interpreted as exhibiting a bright-spot indicator for a gas reservoir, yet on closer examination is probably due to a hard layer with a gradational base. This feature provoked our interest in modeling domes with various wavelet phases. We generated synthetic data from 1-D and 2-D models, for different impedance profiles, thicknesses, and wavelet phases. The results demonstrate that the seismic response from a layer with impedance contrast that decreases with depth is quite different from that of a layer with constant impedance contrast when the bed thickness is greater than 1/4 of wavelength. On the other hand, a thin bed with constant impedance contrast and a 90ºwavelet may strongly resemble a thick bed with a gradational base and a 0ºwavelet (and vice-versa). We believe that the anomaly we have observed in Stratton data represents a reef-type of structure with higher impedance than surrounding beds, with that difference decreasing gradually with depth.

Publication Title

2018 SEG International Exposition and Annual Meeting, SEG 2018