Integration of triaxial testing and pore-scale visualization of methane hydrate bearing sediments

• Published in: Review of Scientific Instruments
• Main Authors: Seol, Yongkoo, Lei, Liang, Choi, Jeong-Hoon, Jarvis, Karl, Hill, Daniel
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Institute of Physics 2019
• Subjects: Methane hydrate
• Online Access: https://oceanrep.geomar.de/id/eprint/48985/; https://oceanrep.geomar.de/id/eprint/48985/1/Seol.pdf; https://doi.org/10.1063/1.5125445

Understanding mechanical interactions between hydrate and hosting sediments is critical for evaluating formation stability and associated environmental impacts of hydrate-bearing sediments during gas production. While core-scale studies of hydrate-bearing sediments are readily available and some explanations of observed results rely on pore-scale behavior of hydrate, actual pore-scale observations supporting the larger-scale phenomena are rarely available for hydrate-bearing sediments, especially with methane as guest molecules. The primary reasons for the scarcity include the challenge of developing tools for small-scale testing apparatus and pore-scale visualization capability. We present a testing assembly that combines pore-scale visualization and triaxial test capability of methane hydrate-bearing sediments. This testing assembly allows temperature regulation and independent control of four pressures: influent and effluent pore pressure, confining pressure, and axial pressure. Axial and lateral effective stresses can be applied independently to a 9.5 mm diameter and 19 mm long specimen while the pore pressure and temperature are controlled to maintain the stability of methane hydrate. The testing assembly also includes an X-ray transparent beryllium core holder so that 3D computed tomography scanning can be conducted during the triaxial loading. This testing assembly permits pore-scale exploration of hydrate-sediment interaction in addition to the traditional stress-strain relationship. Exemplary outcomes are presented to demonstrate applications of the testing assembly on geomechanical property estimations of methane-hydrate bearing sediments.