Using Petro-physical Parameters and Rock Attributes Derived from 4-D

A 4-D seismic data comprising of two 3-D seismic volumes acquired at different vintages were successfully applied to identify the presence of by-passed oil opportunities in the water-driven reservoirs in an offshore area of bonny island in south-south part of Nigeria. Cross-plots of rock attributes from well data were carried out to validate their sensitivity to reservoir fluids and lithology and to constrain the interpretation of the time lapse inversion results. 4-D inversion of the base and monitor seismic volumes were performed to directly generate acoustic impedance volumes, from which other rock attributes and petro-physical parameters were extracted. From the analysis, production induced effects due to fluid and pressure changes were mapped and sections of potentially undrained hydrocarbons detected. From the analysis of results, by-passed hydrocarbon prospects were suspected to be at the north (HC_1), northwest (HC_2 and HC_4) and the southwest (HC_3) of the present producing well locations in the field. These are due to the low acoustic impedance, lambda, and Poisson impedance rock attribute values, low water saturation, and relatively high pressure regimes.