Gas saturation and tuning effect investigations in high seismic amplitude anomalies: a case study of the “Taadoy” field in Nigeria

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Abstract

The assumption that the presence of high seismic amplitude anomalies is mainly due to gas saturation has significantly contributed to drilling failure in “Taadoy” Field. To mitigate failure due to seismic amplitude anomalies, it is imperative to analyse the possible presence of tuning effect in high seismic amplitude anomaly in this field. Seismic to Well tie was used to identify reservoir “Res 500”. Presence of hydrocarbon anomaly was determined using seismic amplitudes cross-plot and attribute analyses. Rock Physics Template (RPT) helped to substantiate the presence of gas in the thin sand and acoustic impedance inversion revealed minimal impedance contrast between encasing shale and “Res. 500”. Wedge model revealed that reservoir “Res. 500” is 10 m thick while the RPT analysis estimated gas saturation of 25%. This implies that the high seismic amplitude anomaly is due to both gas presence and thickness of the reservoir. Amplitudes Variation with Angles (AVA) response indicated high seismic amplitudes at the top and base of the reservoir. The presence of gas causes high seismic amplitude and gradient trends especially at far angles but with minimal effect with increased gas volume. Superposition of seismic amplitudes due to both gas presence and tuning effect produced the high seismic anomaly observed in Res. 500 reservoir.

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NRIAG Journal of Astronomy and Geophysics
Volume 14, Issue 1
December 2025
Pages 1-22

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