Capabilities
In recent years, researchers have also upgraded the geotechnical capabilities of the Gas Hydrates Physical Properties Laboratory. Geotechnical measurements provide critical information about the strength, behavior, and hydraulic properties of sediments, results important for gas hydrate reservoir and geohazard studies.
Major equipment includes two load frames and cells for consolidation and triaxial testing, a standalone conventional oedometer for one-dimensional consolidation, and fall‐cone penetrometer. Whenever possible, data acquisition and control of the geotechnical devices have been automated.
Research conducted by the USGS Gas Hydrates Project sometimes requires the synthesis of gas hydrate as a pure phase or within sediments. The group works closely with the USGS Earthquake Program in Menlo Park, California, where the ice method for synthesizing pure-phase gas hydrate was pioneered. The Physical Properties Laboratory built upon that pure-phase work and began synthesizing gas hydrate from aqueous phase (dissolved) methane, a mechanism that is likely widespread in natural systems.
In some experiments, the Gas Hydrates Physical Properties Laboratory uses benchtop transparent micromodels (microfluidic pore models). Micromodels are etched from non-reactive materials (e.g., glass) to have specific two- or three-dimensional morphologies that mimic sediment pores and throats. USGS Gas Hydrates Project researchers have particularly focused on how fine-grained sediments (“fines”) migrating with fluids could clog porous media. These studies have particular significance for analyzing the migration of gas and fluids to a wellbore during production testing of gas hydrate reservoirs. The group works closely with the USGS Earthquake Program in Menlo Park, California, where expertise in scanning Electron Microscopy (SEM) allows visualization of even the fine-grained sediment particles in support of how we interpret other measurement results, such as from consolidation or flow-clogging tests.
To support research on methane bubbles emitted from the seafloor as gas migrates through sediments or as gas hydrate degrades, the Physical Properties Laboratory also manages a counterflow device capable of isolating and holding stationary a single gas bubble or a gas bubble coated in hydrate. For the hydrate former, the instrument uses the noble gas xenon, which forms hydrate at close to ambient pressures and temperatures. The counterflow device is used to estimate the rates of formation and dissolution of hydrate shells around gas bubbles and to measure the rise velocity and acoustic properties of hydrate-coated gas bubbles.
