Abstract
Most carbonate formations offer challenges for comprehensive characterization and, therefore, optimized exploration and recovery of hydrocarbon resources and for the sequestration of greenhouse gases (GHGs) to meet sustainable climate goals. The Bassein Formation in India's Western Offshore has been a prolific oil and gas producer for the last three decades. However, due to the lack of understanding about the distribution of heterogeneous facies, the recovery of hydrocarbon often proves discouraging. An insight into the patterns of seismic rock properties of such heterogenous reservoirs has promise not only for the recovery of the resources but also for the use of the formations for geological sequestration of GHG. This study investigates laboratory-measured ultrasonic velocity and attenuation behaviors in these formations and identifies a pattern between estimated elastic properties to linked facie heterogeneity and associated saturation. The interplay between rock composition, pore structure, and fluid saturation provides crucial insights for the optimized recovery of hydrocarbon from this formation. Dry ultrasonic measurements established the baseline velocity data for the samples grouped under homogeneous, intermediate, and heterogeneous categories. Upon brine saturation, while the homogeneous samples show a modest increase in velocity, the intermediate and the heterogeneous samples exhibit more pronounced velocity alterations. Also, the compressive (Vp) to shear (Vs) velocity ratio registers notable changes post-saturation, particularly in intermediate and heterogeneous samples. Amplitude attenuation analysis highlights intensified post-saturation attenuation in heterogeneous samples, with marginal changes in homogeneous samples. Additionally, this study introduces a novel approach by integrating amplitude attenuation analysis alongside velocity measurements, providing a comprehensive understanding of the seismic rock properties in carbonate formations. These findings are instrumental in quickly detecting heterogeneity and helped develop input parameters for the rock physics models to forecast elastic properties and fluid behavior in complex formations such as carbonates. This enhanced understanding of seismic rock property behavior (attenuation) will contribute to optimizing reservoir property prediction for time-lapse scenarios and identify favorable zones for hydrocarbon recovery and storage of GHGs and hydrogen in the Bassein formation.