Integrating Thomsen’s Anisotropy with Seismic-Derived Anisotropy Eta and Rock Physics Model for Reservoir Quality Assessment (Case Study: Sadewa Field, Kutai Basin, East Kalimantan)

This study investigates the relationship between seismic anisotropy parameters (ε, δ, γ) and reservoir quality characteristics within interbedded sandstone-shale formations of the Sadewa Field, Kutai Basin, East Kalimantan. Utilising integrated rock core data and well log measurements from wells DSA-4 and DSA-5ST1, anisotropy parameters were derived from ultrasonic velocity measurements and correlated with petrographic, porosity, and permeability analyses. Two distinct rock types, Rock Type A (RT-A) and Rock Type B (RT-B), were identified based on anisotropy trends and reservoir quality indicators such as clay content, quartz percentage, grain size, and porosity. RT-A samples exhibited significantly higher anisotropy values and reservoir quality, attributed primarily to the presence of hydrocarbon-bearing interlayers confirmed by petrographic observations. Critical porosity and flow zone indicator analyses further supported the classification and quality differentiation of the rock types. The study demonstrates that anisotropy parameters, combined with Gamma Ray log data, providing robust diagnostic tools for discriminating lithological variations and assessing reservoir heterogeneity in complex sedimentary environments.