Identifying gas bearing sand using simultaneous pre-stack seismic inversion method: case study of the Simian field, Offshore Nile Delta, Egypt

Abstract The West Delta Deep Marine concession offshore Egypt’s Simian field was exposed to simultaneous pre-stack inversion to test its quantitative interpretation potential. In heterogeneous submarine channel reservoirs, characterising reservoir lithology and fluid distribution and isolating gas sand, brine sand, and background shale are the key Simian field challenges. Due to poor water sand mapping, numerous Simian field wells had surprising early water production rates. Therefore, this study may investigate if pre-stack seismic data and sophisticated inversion techniques can precisely pinpoint Simian field lithology, facies changes, and fluid distribution. Concurrent pre-stack inversion estimates rock parameters, including acoustic or P-wave impedance (Zp), shear impedance or S-wave impedance (Zs), and density (ρ), which are strongly related to lithology. Before the inversion procedure, two wells were analysed in a rock physics investigation, and three angle gathers (0–15°, 15–30°, and 30–45°) were pre-stacked inverted for Zp, Zs, P-wave velocity (Vp), S-wave velocity (Vs), Vp/Vs ratio, and ρ. Lambda-Mu-Rho (LMR) analysis involves obtaining Lamé parameters by inverting Zp and Zs simultaneously, resulting in Lamda-Rho (Incompressibility) (λρ) and Mu-Rho (Rigidity) (µρ) volumes. The training process involved pre-stack inversion analysis employing angle stack seismic data and well log data, cross-validation, and Vp, Vs, and Vp/Vs volumes. Vp/Vs and Zp volumes predicted Sw values that matched well gas-water contact. The study used a test well (Simian-Di) and validated the result at a blind well location (Simian-Dj) to evaluate a pre-stack inversion approach. It found accurate predictions, suggesting better output and economic efficiency.