A physics-driven workflow for gas-sand identification in Pliocene turbidites using pre-stack inversion and seismic attributes, offshore Egypt

Abstract

This study presents a physics-driven workflow that integrates pre-stack simultaneous inversion of P-impedance, S-impedance, and density with multi-attribute analysis and geo-body extraction to resolve thin, isolated gas-sand channels in the compartmentalized Pliocene turbidite system of the Sapphire Field, offshore Nile Delta, Egypt. Unlike conventional post-stack inversion or AI-based bright-spot detection, our approach leverages rock-physics-guided cross-plotting (Vp/Vs vs. P-impedance), validated by blind-well testing, to achieve robust lithology–fluid discrimination under sparse well control. Gas-sand facies are reliably identified by low P-impedance (< 18 (m/s)·(g/cm3)) and Vp/Vs ratios (< 1.65), while gradient magnitude and variance attributes delineate channel edges and fault-related compartmentalization with high fidelity. Critically, the workflow overcomes thin-bed resolution limitations through elastic trend analysis rather than absolute layer thickness, offering a transferable methodology for similar clastic deepwater plays worldwide. However, uncertainties persist in ultra-thin beds (< 9 m) due to seismic bandwidth constraints (~ 10–60 Hz), and inversion reliability depends on accurate low-frequency modeling and angle-stack quality. By bridging first-principles rock physics with high-resolution seismic attributes, this study advances quantitative interpretation and delivers actionable insights for exploration risk reduction and optimal well placement