Application of Seismic Attributes and Acoustic Impedance Inversion to Enhance Seismic Interpretation in a Mature Niger Delta field

Abstract

Improving oil production to maximize investment is a struggle in mature fields. This task often requires performing thorough seismic interpretation using integrated approaches. This research focuses on the application of wireline log data and 3D seismic volume, using seismic attributes and acoustic impedance inversion techniques, to enhance seismic interpretation. The procedure begins with the loading of well logs, checkshot and seismic data, followed by horizon mapping and seismic attribute analysis. Well-to-seismic correlation was done to tie formation tops and seismic reflectors. Then crossplot analysis was done for feasibility studies. The final phase was seismic inversion using a model to generate acoustic impedance volumes. Results from amplitude analysis from the two horizons indicate the presence of high amplitudes as well as low amplitudes. High amplitudes are shown on the both amplitude maps in and around the southwestern portions of both reservoirs. Gamma-ray versus acoustic impedance crossplots show clusters forming into three overlapping zones inferred to probably be shale, shaly-sand and hydrocarbon saturated sands zones in both plots. The inverted acoustic impedance values on the seismic ranged from 2.01 to 2.25 × 10⁴ ft/s * g/cc, with purple and blue colors matching to shaley sands. The intermediate acoustic impedance values ranged from 1.81 to 1.96 × 10⁴ ft/s * g/cc, with red colours correlating to shaley sands. Low acoustic impedance values ranging from 1.56 to 1.60 × 10⁴ ft/s * g/cc concur with hydrocarbon saturated sands with green and yellow colors. The well A and C locations in both sands have very high acoustic impedance values, although the values towards the center of the horizons are rather low. Very low acoustic impedance values have been observed in the southwestern regions of the Sand A and B fields. Other areas of the field exhibit high acoustic impedance values, indicating shale zones. The inversion outcomes show that different types of lithology facies can potentially be distinguished in the study area. A high potential prospect was defined along the central regions of the high structure of both reservoirs Sand A and Sand B. There is a possibility of hydrocarbon-filled sandstones in the central parts of both reservoirs from the low acoustic impedance values obtained.