Estimation of Petrophysical Parameters Using 3-D Seismic Data from a Field in Niger Delta, Nigeria

Estimation of petrophysical parameters have been carried out using seismic data in an Onshore Niger Delta field to assess the reservoir characteristics of the field. A pre stack seismic volume and a suite of well logs from two wells were used in the analysis. The petrophysical parameters evaluated include acoustic impedance, porosity, water saturation, hydrocarbon saturation, permeability, volume of shale, Poisson ratio and Vp/Vs ratio. An interval with low gamma ray, low volume of shale, high resistivity, low water saturation and low acoustic impedance was identified and mapped as a potential hydrocarbon reservoir with a thickness of 70ft. The extracted wavelet from the seismic data showed a zero phase, which implies that energy is concentrated at the peak. The well to seismic correlation result yielded a maximum zero lag coefficient and a high correlation coefficient of 0.815 which gives confidence that the results of this work are reliable. Seismic inversion was then performed with the seismic and log data as input using an initial model and the inversion volume showed a low acoustic impedance which confirms that the delineated interval is a hydrocarbon saturated sand. The results obtained also revealed that the reservoir sand has low volume of shale (13.88%), high porosity (31%), high permeability (67.5mD), low Vp/Vs ratio (1.35) and low Poisson ratio (0.19) which are characteristics of a typical hydrocarbon reservoir with high prospectivity and production potential. The analysis also revealed that water saturation is low in the reservoir with an average value of 0.1 and hydrocarbon saturation is high with an average value of 0.9. This results in general suggest that the reservoir sand of the study field contains probable accumulations of hydrocarbon with a significant economic value.