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By Gas Hydrates Project Hydrate Pressure Core Analysis Laboratory (HyPrCAL)

In addition to analyzing pressure cores, the USGS Gas Hydrates Project also contributes expertise in transport and storage of these special samples.

Using a design originated by Georgia Tech, USGS researchers have overseen the construction and certification of special storage chambers that can be used to maintain, monitor, and transport pressure core samples from the field site to specialized laboratories. 

 Junbong Jang and Stephen Phillips loading a pressure core chamber into a shipping box
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 A pressure core collected during the 2017 Gulf of Mexico gas hydrate field program (GOM2) led by the University of Texas, has been transferred into a pressure core transport chamber in Austin, Texas prior to moving the core to USGS Woods Hole for study. 
 

Understanding the properties of gas hydrate-bearing sediment and the behavior of a gas hydrate reservoir over time (geologic time, or on human scales if gas hydrates are tapped as an energy resource) requires understanding properties of the sediment itself. After measuring sediment core properties in the presence of gas hydrate, the gas hydrate is dissociated (broken down) by depressurizing the core.  The gas is collected and can be analyzed in the Gas Hydrates Project Biogeochemistry Laboratory investigate where the reservoir gas was generated and how the reservoir might have formed. 

3 separate images of sediment samples
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Once removed from the pressure core testing tool, this specimen shows that it is not a homogeneous sediment.  The mostly fine-grained sample (dark sediment in all three images) easily breaks apart at a thin layer of coarse-grained sediment (light sediment on the inner core surfaces of images (i) and (ii). The light-colored coarse-grained layer can be seen running through the dark, fine-grained, clay-rich specimen in image (iii). Images like this assist interpretations of the measured data because gas hydrates in specimens like this are generally localized in the coarse-grained sediment, not evenly distributed through all sediment types.

The sediment remaining in the depressurized core barrel is then recovered, characterized and tested in the Gas Hydrates Project Physical Properties Laboratory. The measurements conducted there inform not only how the pressure core data should be interpreted, but also how a gas hydrate production well should be constructed to endure changes in sediment properties over the well’s extended operational lifetime. 

Image shows two scientists moving a sample of the gas hydrate
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A pressure core containing hydrate-bearing sediments recovered from beneath the seafloor during the NGHP-02 drilling expedition in the Indian Ocean in 2015 is delivered by Mike Mimitz (Geotek Ltd., blue coveralls) to the Woods Hole Coastal and Marine Science Center in March 2017 after the core’s 10,000 mile sea voyage from Japan.