DHI Analysis Using Seismic Frequency Attribute On Field-AN Niger Delta, Nigeria

Abstract

Effect of hydrocarbon gas on the seismic frequency attributes was studied and considered for applicability as Direct Hydrocarbon indicator (DHI) in the AN reservoir in the Niger Delta basin. Matching Pursuit algorithm for the spectral decomposition was adopted for frequency attributes analysis at 10Hz to 35Hz, along the interpreted reservoir top. Three frequency surface attributes were co-rendering and color blending to highlight the effect of gas in the reservoir. Gas filled sand exhibits distinctly higher frequency amplitudes at low frequency bands of 15Hz to 25Hz despite a subtle hardness of the sand relative to the overburden thick shale. High frequency amplitude expression in the low frequency (15Hz-25Hz) band observed in the gas reservoir is found to be a consistent character of overpressured gas reservoirs within the Niger Delta basin. It was concluded, therefore based on time-frequency seismic character of the gas sand, that frequency attribute can be used as a direct hydrocarbon indicator for the sandstone gas reservoir in the Niger Delta.