Modelling and mapping hydrocarbon saturated sand reservoir using Poisson’s impedance (PI) inversion: a case study of Bonna field, Niger Delta swamp depobelt, Nigeria

摘要

3D seismic volume and two well logs data labelled Bonna-6 and Bonna-8 were employed in the inversion process. The data set was simultaneously inverted to produce?P- and?S-impedances, density,?VP????VS, and PI seismic attributes. An average “c” term value of 1.37 was obtained from the inverse of the slope of the crossplot of?P-impedance versus?S-impedance for Bonna-6 and Bonna-8 wells. This value was employed in the inversion process to generate the PI attribute, which aided in reducing the non-uniqueness inherent in discriminating the probable reservoir sands. Five seismic attributes slices were generated to ascertain the superiority of each attribute in delineating the probable reservoir sand. These attributes were: density,?S-impedance,?P-impedance,?VP??VS?ratio and PI. These attributes reveal low value of density (1.96???2.14?g/cc),?P-impedance (1.8?×?104???2.1?×?104) ft/s*g/cc,?S-impedance (9.2?×?103???1.1?×?104) ft/s*g/cc,?VP???VS?(1.65???1.72) and PI (4.9?×?103???5.1?×?104) ft/s*g/cc around the area inferred to be hydrocarbon saturated reservoir. Although the attributes considered reveals the same zone suspected to be probable hydrocarbon zone, PI gives a better discrimination when compared to other attributes. A distinctive spread and demarcation of the delineated hydrocarbon sand are observed in the PI attribute slice.