Abstract

Distinguishing lithology from pore-fill remains a persistent challenge, even when employing Elastic Inversion techniques especially for silty sand reservoirs. In Cambay Basin, India, thin clastic reservoirs of silty shaly nature with low permeability are developed within Cambay shale. In study area, Walod field, these silty thin reservoirs produce hydrocarbon. However, petrophysical evaluation and identification through elastic inversion are difficult. Challenges of identifying and evaluating these heterogeneous reservoirs are addressed in present study. The primary difficulty lies in the complex interplay between lithological variations and fluid responses, compounded by the ambiguity introduced by the well-known “equivalence” problem. This paper proposes a novel transformation methodology aimed at resolving this ambiguity. By leveraging outputs from elastic inversion, a relationship between Vp/Vs and new attenuationrelated attributes—SQp and SQs are derived through the lens of rock physics. These attributes serve as effective proxies: SQp correlates strongly with gamma-ray logs, while SQs aligns with resistivity data. Together, they enable clear identification of hydrocarbon-bearing zones. Furthermore, the study demonstrate that these derived attributes can be applied to predict petrophysical properties with high accuracy, offering significant potential for enhanced subsurface characterization