Lateral Rock Property Prediction by Post Stack Acoustic Impedance Inversion: A Case Study from Offshore Niger Delta

A post stack acoustic impedance seismic inversion study was carried out by integrating well logs and 3D seismic data obtained in a Niger Delta offshore field.  The aim was to delineate lateral variations in subsurface rock properties especially lithology and density, which could aid in petrophysical and facies modeling to constrain the extent of hydrocarbon zones in the development of the field. Log data comprising GR, density and compressional sonic logs from one well, and a 5 – 18 degree angle stack of approximately 43.05 sq.km 3D PTSM dataset were used for the study. A deterministic model-driven inversion workflow that includes forward modeling of reflection coefficients from a low frequency impedance model derived from the well logs and convolution of the reflection coefficients with a source wavelet derived from the seismic and well log data was adopted for the study. Density and acoustic impedance volumes obtained from the inversion reveal the reservoir top at the well location, and show lateral variations in these properties away from well control. The results obtained are important for accurate structural and stratigrahic interpretation to reduce the risk of exploratory and development well locations in the field.