Frequency dependent seismic reflection analysis: a path to new direct hydrocarbon indicators for deep water reservoirs
Yoo, Seung Chul
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To better study frequency related e?ects such as attenuation and tuning, we developed a frequency dependent seismic re?ection analysis. Comprehensive tests on full waveform synthetics and observations from the Teal South ocean bottom seismic (OBS) data set con?rmed that normal moveout (NMO) stretch could distort both frequency and amplitude information severely in shallow events and far o?set traces. In synthetic tests, our algorithm recovered amplitude and frequency information ac-curately. This simple but robust target oriented NMO stretch correction scheme can be used on top of an existing seismic processing ?ow for further analyses. By combining the NMO stretch correction, spectral decomposition, and crossplots of am-plitude versus o?set (AVO) attributes, we tested the frequency dependent work?ow over Teal south and Ursa ?eld data sets for improved reservoir characterization. As expected from NMO stretch characteristics, low frequencies have been less a?ected while mid and high frequency ranges were a?ected considerably. In seismic attribute analysis, the AVO crossplots from spectrally decomposed prestack data con?rmed the improved accuracy and e?ectiveness of our work?ow in mid and high frequency regions. To overcome poor spectral decomposition results due to low signal to noise ratio (S/N) in the Teal South application, we also implemented a substack scheme that stacks adjacent traces to increase S/N ratio while reducing the amount of data to process and increasing the accuracy of the spectral decomposition step. Synthetic tests veri?ed the e?ectiveness of this additional step. An application to the Ursa, Gulf of Mexico, deep water data set showed signi?cant improvement in high frequency data while correcting biased low frequency information.