Evaluating Advances in Integrated Geophysical and Geological Methods for Unconventional Reservoir Characterization in the United States: A Narrative Review

Unconventional oil and gas reservoirs have revolutionized U.S. energy, but their complex geology and low permeability demand new characterization approaches. This narrative review critically examines recent advances in integrating geological and geophysical methods for unconventional reservoir evaluation. We synthesize how multidisciplinary approaches, ranging from pore-scale imaging to seismic and electromagnetic surveys, augmented by machine learning, reveal reservoir heterogeneity and sweet spots. Key trends include high-resolution petrophysical analyses (nuclear magnetic resonance (NMR, core imaging), geophysical innovations, and data-driven inversion and modeling frameworks. The major knowledge gaps identified in this review include linking nanoscale properties to field-scale flow, robustly quantifying induced seismic risks, and integrating the full petroleum system (source, rock, fracture networks) into models. It is concluded that continued integration of diverse data (seismic, well logs, core, and micro seismic) through advanced rock-physics and AI-driven workflows promises deeper insight into U.S. unconventional reservoirs. These trends have broad implications for exploration, production optimization, and low-carbon initiatives in unconventional plays.