Rock Physics of Unconventional Reservoirs, volume II

Book excerpt: Unconventional resources with commercial interest in the world mainly include heavy oils, shales, coalbed methane, and tight gas sands. The production and development of these resources has changed the global energy supply pattern. Quantitative interpretation of geophysical data in the exploration, well-logging, and engineering development of unconventional resources requires a comprehensive understanding of physical properties of rocks and their relationships. The research of rock physics provides an interdisciplinary treatment of physical properties, whether related to geological, geophysical, or geomechanical methodologies. The development of new rock physics methods is essential when integrating core, well-log, seismic data to improve the accuracy of formation evaluation and reservoir characterization. The composition, internal structure, and thermodynamic environment of reservoir rocks are complex and vary with different regions. This becomes particularly evident for unconventional reservoirs with strong macro- and micro-scopic heterogeneities. The diversity of exploration targets and complexity of reservoir characteristics pose great challenges to the applicability of existing rock physics experiments and theories. There are potential risks in directly using existing empirical relations and physical models to guide geophysical interpretation since spurious results may occur. Therefore, it is imperative to explore more applicable rock physics methods according to the petrophysical nature of actual reservoirs.