| Abstract |
This study conducts an in-depth rock physics analysis of the Bakken and Three Forks formations within the Williston Basin, emphasizing the role of fluid types, saturation levels, pore structure, and frequency on defining rock properties. The objective is to enhance seismic interpretation and reservoir characterization by developing rock physics templates (RPTs) for these specific formations. We explore how pore structure heterogeneity influences velocity sensitivity over a broad frequency range and varied fluid types. By integrating both Gassmann and Biot theories for fluid substitution and considering frequency-dependent velocity via Geertsma-Smit approximation, the study models fluid properties, and their interaction with the rock matrix, supported by case studies from the Bakken formation. Findings from this study reveal that gas-water systems are more frequency-dependent compared to oil-water systems. Moreover, the frequency-dependent velocity modeling revealed that combining pore structure with varying porosity and permeability levels can significantly influence the velocity-frequency relationship. The research further delineates the complex interplay between the Vp/Vs ratio and acoustic impedance, pore morphology, and fluid saturation. Notably, crack-like pores are linked with larger Vp/Vs ratios, while interparticle and vuggy pores show a more homogeneous stiffness distribution. The proposal of geology-dependent RPTs emphasize the need to consider lithological and diagenetic variations for accurate seismic interpretations. |
, Lotfi Allam 
