Well Based Elastic Attribute Analysis for Reservoir Characterization in Ek-field Niger Delta

Abstract

Derived elastic attributes has been used to discriminate rock and fluid properties in EK Field using well logs data. These derived rock attributes were analyzed in cross-plot space for target reservoirs. The log analysis for delineated reservoir B20 shows an average volume of shale (7.5%), total porosity (33.9%) and water saturation (29.3%). Cross-plots of elastic rock attributes (Vp/Vs, Lambda-Rho (λρ), Mu-Rho (μρ), Poisson ratio and acoustic impedance) were used as fluid and lithology indicators and in reservoir characterization. The cross plots results shows distinct separation of hydrocarbon sand, brine sand and shale. Low Poisson’s ratio (0.2-0.26), Lambda-Rho (7 GPa*g/cc -10 GPa*g/cc), Vp/Vs (1.6-1.8), low acoustic impedance and high Mu-Rho values indicate hydrocarbon sands. The intermediate values of Poisson’s ratio (0.2-0.26), Lambda-Rho (17 GPa*g/cc - 21GPa*g/cc) , Vp/Vs ratio (2.05-2.3),  relatively high acoustic impedance and Mu-rho  indicated brine sand while high Poisson’s ratio (0.35-0.41), Lambda-rho (24 GPa*g/cc -27 GPa*g/cc), Vp/Vs ratio (2.3-2.5), high acoustic impedance and low Mu-Rho indicated shale.  The cross-plot models all show similar result of hydrocarbon sand characterized by high porosity, low water saturation and volume of shale. The well based elastic attribute analyses established useful relationships between elastic derived seismic attributes and reservoir properties in delineating lithology and reservoir fluid for better understanding of reservoirs in the Niger Delta field.