Plane Versus Elastic Wave AVO Anisotropic Synthetic Modeling in Derby Field, Southeastern Niger Delta

Abstract

AVO based Zoeppritz’s plane wave and elastic spherical wave anisotropic synthetic modelling have been investigated in Derby field, Southeastern Niger delta. The objective of the study is to investigate the influence of anisotropy on plane and elastic wave AVO synthetics modeling over shale-gas sand horizons in the field. Well log data was check shot corrected and correlated with pre-stack data and a zero phase wavelet was extracted after well conditioning and petro physical analysis. Elastic and plane wave algorithms were then used to generate offset-dependent anisotropic synthetic seismograms respectively, using p-wave sonic, s-wave and density logs and Thompsen’s epsilon (ε) and delta (σ) anisotropic logs for a transversely isotropic media. Results revealed that seismic anisotropy for AVO based analysis is better modelled with elastic rather than the conventional Zoeppritz’s plane wave model and their approximations for transversely isotropic media at larger offsets. This is attributed to the breakdown of the Zoeppritz’s plane wave model and their linearized approximations at large offsets or near the critical critical angle. Using elastic synthetic model for anisotropic AVO analysis will not only ensure that the reservoir will be adequately imaged, but misinterpretation of data and misplacement of the well will be circumvented.