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The relationships between geophysical attributes (such as seismic velocities and attenuation, electrical conductivity, and dielectric constant) and rock properties (such as porosity, permeability, and fluid saturation) are provided by rock-physics measurements and/or theoretical understanding. These relationships can be complex because of coupling between different environmental parameters, including stress, pore pressure, and temperature. Also, geochemical and biological processes can alter rock pore structure and grain contacts over time, resulting in changes in geophysical signatures. The primary objective of this research is to improve our understanding of rock physics through laboratory experiments and theoretical and numerical model development.
The focus of our laboratory efforts is towards increasing our experimental knowledge base for geophysical properties of rocks and sediments that are either not well described by conventional rock physics models (e.g., poorly consolidated sands and clays, gas hydrates, fractured rock) or have yet to be fully exploited (e.g., seismic attenuation, seismo-electric response).
Rock-property measurements are carried out primarily at the Rock and Soil Physics Lab. This facility has electronics instrumentation and mechanical equipment needed to perform a variety of geophysical measurements, including seismic, electrical, electromagnetic, and fluid flow, under low to moderate confining pressures. Experiments requiring detailed information about the porous microstructure and fluid saturations at the pore level are carried out using our x-ray computed tomography (CT) scanner in the Rock Imaging Lab, or using the focused ion beam (FIB) located at Berkeley Lab’s National Center for Electron Microscopy. Other facilities at the Berkeley Lab Advanced Light Source (ALS) are also used for microtomography of geologic materials, including fluid-infiltrated porous media. Complementary theoretical and numerical modeling efforts are also conducted to explore the dynamics of poroelastic and seismoelectric responses in rock that contains one or multiple fluid phases. The models are developed based upon laboratory and field observations, and validated by laboratory and field data.