PRESSURE CORING IN MARINE SEDIMENTS: INSIGHTS INTO GAS HYDRATE SYSTEMS AND FUTURE DIRECTIONS

Pressure core barrels were developed to accurately characterize gas hydrate concentration and composition in marine sediments, and were first deployed successfully on Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) expeditions. Gas hydrates are ice-like solids that consist of a gas guest molecule (most commonly methane) within a cage of water molecules, and can can occur in high concentration in continental margin and permafrost sediments. Hydrates represent a large potential energy source, are a potential target for CO₂ sequestration, and are a major pool in the global carbon cycle. Collection of samples with intact hydrate and maintaining in situ properties is a key challenge in investigating gas hydrates.

A recent focus on deepwater, coarse-grained, high-concentration hydrate reservoirs as a potential energy resource has motivated hydrate drilling and pressure coring expeditions in Japan, India, China, and the U.S., as well as the capability to perform a variety of analyses under pressure and transfer pressurized cores to shore-based laboratories. Pressurized cores can now be analyzed with X-ray imaging, and for physical properties, geomechanical properties, permeability, and microbial activity while maintaining the of samples pressure and temperature within the hydrate stability field. These pressure coring efforts have resulted in an improved understanding of hydrate formation processes, reservoir conditions, and the fundamental properties of hydrate-bearing sediments.

Beyond characterization of hydrate systems, preservation of in situ properties and gas content/composition of sediments by pressure coring has the potential to illuminate deep microbial processes, the geomechanical conditions that can influence submarine slope failures, and the properties of hydrocarbon-bearing mudrocks.