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Photo by: Roy Kaltschmidt
Seiji Nakagawa analyzes a core sample in the Rock Dynamics and Imaging Laboratory at Berkeley Lab Earth Sciences Division
ESD’s Rock Dynamics and Imaging Laboratory has capabilities to make measurements on rock, fractured rock, and soil samples over a wide range of temperature and pressure conditions needed to understand mechanical and hydrologic processes. Many studies can also be performed with concurrent X-ray computed tomography (CT) imaging, allowing not only a means of process visualization, but also another means of quantification of processes.
In these laboratories, we study processes that occur under conditions applicable to geothermal systems, carbon dioxide sequestration reservoirs, conventional oil and gas reservoirs, caprocks, unconventional oil and gas systems such as coalbed methane, gas hydrate-bearing systems, and tight hydrocarbons (shales and tight sandstones).
We use many tools in making our measurements. Hydrologic measurements are typically made applying flow of various fluids of interest through a rock core under specified chemical, saturation, pressure, and temperature conditions and measuring the resulting pressures, temperatures, and saturations. Large-capacity high-pressure syringe pumps are used to control the flow, and the needed pressure, differential pressure, and temperature sensors are appropriately distributed both outside and inside the system. Often, CT can be used to observe the spatial and temporal saturation distributions. A variety of geophysical measurements can be made as well, both independently of the hydrologic and CT measurements, or simultaneously. We can measure the effects of changing fluid saturation and saturation distribution, as well as changing rock structure using seismic compressional (P) and shear (S) wave transmission velocities at frequencies ranging from hundreds of Hz to MHz, and are developing techniques to make measurements at lower frequencies more akin to those typically used in the field. In addition to seismic wave speeds, our high-pressure low-frequency Split Hopkinson Resonant Bar Apparatus allows us to examine wave attenuation. This technique provides additional insights on fluid distribution within a sample. We can also measure electrical resistivity of samples undergoing a variety of processes to gain insight to fluid distribution and permeability.