Research paperData report: Hybrid Pressure Coring System tool review and summary of recovery result from gas-hydrate related coring in the Nankai Project

•The hybrid pressure coring system had a 63% success rate in recovering cores.•The cores holed pressure, close to in situ hydrostatic pressures.•Analysis of pressure and temperature histories for the cores.•The Cores were analyzed at in situ hydrostatic pressure.

In the exploration phase for development of methane hydrate as an energy resource, pressure coring that maintains the in-situ hydrostatic pressure is a critically important technical issue. Such pressure core-sampling tools have been used since the 1990's; however, during core analyses, the samples were typically exposed to atmospheric conditions. The Pressure Core Analysis and Transfer System (PCATS) of Geotek, Ltd. was developed to enable pressure core samples to be analyzed at the in situ hydrostatic pressure at which they were recovered. Subsequently, a new pressure core-sampling tool, the Hybrid Pressure Coring System (Hybrid PCS), was developed in which an autoclave section connects to PCATS without releasing the in situ hydrostatic pressure. In 2012, JOGMEC successfully conducted a pressure-coring operation in the Nankai Trough offshore Japan. The basic design and features of the Hybrid PCS are described here, along with pressure-coring operations, the workflow for core analysis shipboard, pressure core sample recovery results, and technical issues. Representative examples are presented for pressure-temperature relations in the autoclave core-sampling tool during core analysis.