Marine sediments retrieved with pressure coring systems such as those used by the Integrated Ocean Drilling Program maintain samples at in situ hydrostatic pressure throughout recovery. Such pressure cores are particularly important for the study of gas hydrate-bearing sediments, which must be maintained within the gas hydrate stability field during shipboard core characterization. Until now, there has been no device capable of directly measuring a suite of physical properties on sediments contained in pressure cores without first depressurizing them. This study describes the design, construction, and deployment of the Instrumented Pressure Testing Chamber (IPTC), which was first used to measure the physical properties of pressure cores recovered ∼1530 m below the sea surface during 2005 drilling in the Gulf of Mexico. The IPTC permits drilling through the plastic liner while the core is under pressure and the sequential measurement of P- and S-wave velocities, undrained strength, and electrical conductivity. Preliminary results indicate that the seismic velocities measured on a pressure core with the IPTC are more representative of in situ seismic velocities at comparable depths than are velocities measured on conventional cores from these same depths. The flexibility of the IPTC design allows future modifications to account for restoration of effective, not just hydrostatic, stress; the addition of new types of measurements; sampling of pore fluids and sediments under pressure; and use of the device as a laboratory reactor for gas hydrates studies.
Bibliographical noteFunding Information:
We thank the crew of the MSV Uncle John for their work to obtain the cores, P. Schultheiss and J. Roberts of Geotek, Ltd. for use of the transfer and storage vessels and manipulators, and L. Stern for comments that improved the manuscript. This research was primarily supported by a contract to C.R. and J.C.S. from the Joint Industry Project for Methane Hydrate, administered by ChevronTexaco with funding from award DE-FC26-01NT41330 from DOE's National Energy Technology Laboratory. J.C.S. thanks the Goizueta Foundation at Georgia Tech for providing support for some aspects of this work. The research was completed while C.R. was on assignment at and wholly supported by the National Science Foundation (NSF). All findings are those of the authors and do not reflect the views of the DOE or NSF.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology