Magnetic Resonance Imaging of Hydrate Phase Transitions in Sediments

• Main Author: Veland, Veronica Flæsland
• Format: Master Thesis
• Language: English
• Published: The University of Bergen 2017
• Subjects: Magnetic Resonance Imaging; T2 Distribution Mapping; RARE; MRI; Core Analysis; CPMG; Gas hydrate; MSME; T2; 752223; Bergen; Ice; permafrost
• Online Access: https://hdl.handle.net/1956/17241

Natural gas hydrates, simplified described as gas compressed in ice, are a substance existing in large quantities around the world. Their existence requires elevated pressures and low temperature. They are therefore found in the subsurface in and below permafrost and in oceanic environments below a water column of 400-500 meters. The significant amount of gas stored in natural gas hydrates constitutes a potential as a significant contributor in ensuring future energy sustainability. However, extended research on fundamentals and characteristics of hydrates in nature, as well as production schemes, are required to be able to efficient and safely exploit this energy resource. Core-scale experiments give fast and valuable information, which is essential before larger field tests can be planned. This thesis is part of a research collaboration between Statoil and the University of Bergen in the application of magnetic resonance imaging (MRI) in laboratory petro-physics and core analysis. The new experimental design in this work includes the high field strength magnet of the 4.7 Tesla Biospec MR-scanner, by contrast to the domination of low field strengths in this kind of research. The main objective of this thesis is to show that the high field strength MRI can be applied to visualize gas hydrate phase transitions in a porous media of a sandstone core, before more advanced studies can take place. First, basic introductory experiments were conducted to illustrate the correlation of water saturation of a core and the signal intensity of the MRI measurement. Two Bentheim sandstones were measured, one with increasing water saturation for each measurement, and the other with decreasing water saturation for each measurement. Two types of MR measurements were conducted on the cores at each water saturation stage: (1) RARE, used to image and for further pixel analysis, (2) MSME, to investigate T2 relaxation. Results from the introductory experiments illustrated the strong relationship between MR signal intensity and water ...