Unravelling an anomalous seismic response using seismic modelling: a case study from Cauvery Basin, offshore East Coast India

摘要

Seismic data interpretation and seismic attribute analysis are two fundamental processes in geological model building and reservoir characterization. Detailed analysis of amplitude, phase and frequency plays a vital role in the de-risking of a prospect in terms of reservoir presence and its quality. Here, the significance of forward modelling is illustrated in unravelling an anomalous seismic response in a complex geological set-up through detailed investigation of a prospect in the Cauvery Basin, offshore East Coast of India. The bright anomalous amplitudes of the identified prospect have been modelled using sand and shale properties from offset wells drilled in the basin. A possibility of constructive interference of individual waveforms from various interfaces has been proposed to explain the anomalous amplitudes. The prospect was subsequently drilled and the post-drill results have confirmed the proposed hypothesis. Synthetic modelling using in-situ and edited logs exemplify the concept of interference and its effect on composite amplitudes resulting from summation of individual waveforms. Additionally, post drill analysis of the prospect along with the forward modelling supports the hypothesis of interference.