--> Identification of Hydrocarbon Reservoirs from Seismic Gathers AVO Analysis in the Offshore Niger Delta, by A. Adekanle; #90037 (2005)
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Identification of Hydrocarbon Reservoirs from Seismic Gathers Previous HitAVONext Hit Analysis in the Offshore Niger Delta

A. Adekanle
Federal University of Technology, Akure, Nigeria

Amplitude Variation with Offset (Previous HitAVONext Hit) analysis was carried out in an offshore Niger Delta field. The study consisted of forward modeling from rock parameters measured from well logs and Previous HitAVONext Hit analysis of events on pre-stack time migrated seismic gathers. Forward modeling predicted specific Previous HitAVONext Hit behaviour of hydrocarbon bearing reservoir sands in the field. Density, compressional and shear wave Previous HitvelocityNext Hit logs, combined with a wavelet extracted from recorded seismic gathers were used to generate synthetic seismic gathers and Gassmann fluid substitution models. These synthetics supported key observations made of the Previous HitAVONext Hit response in the field data. Previous HitAVONext Hit attributes (intercept and Previous HitgradientNext Hit) were derived from analysis of Common Depth Point (CDP) gathers obtained from a 3D Ocean Bottom Cable (OBC) seismic survey. The attributes were cross-plotted to establish trends against which anomalous amplitude behaviour were identified. Reflections related to shales and brine sands exhibit a relatively small range of orientations creating a dominant "background trend" against which anomalous events related to hydrocarbon-saturated reservoirs show clear deviations. On the basis cross-plot analysis (reflectivity Previous HitversusNext Hit offset / angle and and intercept Previous HitversusNext Hit Previous HitgradientNext Hit), Class 3 type Previous HitAVOTop anomalies are shown to be associated with hydrocarbons in the field. This anomalous amplitude behaviour allows identification of hydrocarbon reservoirs in this area of the Niger Delta.