Fluid and Lithology Discrimination for Reservoir Characterization of HAX Field, Offshore Niger Delta

Abstract

Fluid and lithology discrimination for reservoir characterization of HAX field, offshore Niger Delta was carried out in this study. Three reservoir intervals, R_4500, R_5500, and R_6500 were picked, identified, and correlated across the four wells; but only the R_5500 reservoir was analyzed. The cross-plot analysis of elastic rock properties with reservoir properties such as Vp/Vs ratio against Acoustic Impedance, Lambda-Rho against Vp/Vs, Mu-Rho against Density, and Lambda-Rho against Mu-Rho colour-coded by gamma ray, water saturation, and density respectively was carried out for fluid and lithology discrimination. The result of these elastic rock properties when colour-coded with gamma ray distinguished reservoir R_5500 into the sand zone and shale zone for the four wells, these results depict lithology discrimination as predominantly found in the Niger Delta basin. Consequently, when colour–coded by water saturation reservoir R_5500 was distinguished into three zones namely the hydrocarbon bearing zone, brine sand zone and shale zone indicative of both lithology and fluid discrimination. From these cross-plots, the clusters with the least water saturation correspond to highly charged hydrocarbon saturation sand while clusters with maximum water saturation correspond to non-hydrocarbon zone (brine sand and shale). Finally, when colour–coded by density reservoir R_5500 was distinguished into four zones namely gas sand zone and oil sand zone, brine sand zone, and shale zone indicating fluid types. The result shows relatively lower Acoustic Impedance, Vp/Vs ratio, lambda-rho, mu-rho, and density (as the colour-code) values indicating hydrocarbon bearing sand while the relatively higher Acoustic Impedance, Vp/Vs ratio, lambda-rho, mu-rho and density (as the colour-code) values are associated with non-hydrocarbon zone (shale and brine sand). This study has been able to discriminate hydrocarbon reservoirs using the cross-plots of elastic rock properties in the zone of interest and proven that the HAX field is viable in terms of hydrocarbon prospects and highly economical for production.