Acoustic insights into facies-dependent pattern and characterization for aiding exploration, enhanced recovery and sequestration efforts in bassein carbonate formations, West Coast India

Most carbonate formations pose significant challenges for comprehensive characterization, which often limits optimized hydrocarbon exploration and recovery. The Bassein Formation in India’s West Coast 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 hydrocarbons often proves discouraging. This study investigates laboratory-measured ultrasonic velocity and attenuation behaviors in representative carbonate core samples to identify patterns between the estimated elastic properties, facies 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 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 rock physics models to forecast elastic properties and fluid behavior in complex formations such as carbonates. This improved understanding of seismic rock-property variations (attenuation) can significantly aid reservoir characterization, production optimization, and time-lapse monitoring in complex carbonate formations such as the Bassein.