Reservoir Characterisation Using Seismic Inversion Techniques for Mapping of Prospects

Abstract

Reservoir Characterization using integrated 3-D seismic and well log data of M oil field, Niger Delta, was carried out with the aim of identifying reservoir rocks from qualitative interpretation of subsurface seismic view of M oil field through rock properties and acoustic impedance inversion analyzed in some selected reservoirs from the oil field. Rock attributes such as Lame’s parameters terms (λρ and μρ), Vp/Vs, P - Impedance, S - Impedance from available petrophysical data obtained from the field were discriminated, which better describe the reservoir of interest (M - 5000). Inversion of the post-stack seismic data was also carried out to generate acoustic impedance, V_P/V_S, I_P, I_S, λρ and μρ volumes. Data slices of the inverted acoustic impedance volumes were then generated to observe the locations if along hydrocarbon charged sands, wet sands or shales channels. Three wells (M-1, M-2 and M-3) were analysed and M-5000 was identified as reservoir of interest. Inversion result in M oil field revealed that the P-wave / Gamma ray curve is bounded by the top of M-5000 on inverted volumes with the lowest values of V_P/V_S (1.9290), I_P (18176), λρ (6.7), and μρ (18.68), which indicate hydrocarbon (gas) charged sands. It means that Gas saturation is detected at the depth interval of 6449 – 6537 m (88 m thickness) M-2. Based on these observations, we conclude that seismic inversion of the post-stack seismic data can be used as good indicator of lithology and pore fluid contrasts and to predict the presence of hydrocarbon accumulation in the porous gas and oil sands to reduce drilling risk.