Reservoir properties prediction using extended elastic impedance: the case of Nianga field of West African Congo basin

Abstract

Simultaneous seismic inversion and extended elastic impedance (EEI) were applied to obtain quantitative estimates of porosity, water saturation, and shale volume over Nianga field of Congo basin, West Africa. The optimum angle at which EEI log and the target petrophysical parameter give the maximum correlation was meticulously analyzed by additionally incorporating the concept of relative rock physics. Prestack seismic data were simultaneously inverted into Vp, acoustic, and gradient impedances. The last two broadband inverted volumes were projected to Chi angles corresponding to the target petrophysical parameters, and three broadband EEI volumes were obtained. At well control points, the linear trends based on specific lithology between EEI and petrophysical parameters were then used to transform EEI volumes into quantitative porosity, water saturation, and shale volume cubes. In order to obtain the reservoir facies distribution, another concept of minimum energy angle was used to generate the background EEI cube, thereby enabling the mapping of reservoir facies. From quantitative porosity, water saturation, shale content, and background EEI cubes, favorable zones have been pinpointed which may suggest possible drilling locations for future development of the field.