| Summary: | Natural gas hydrates exist in large quantities around the world, located in the subsurface of permafrost and oceanic environments. Future energy harvest from production of methane gas encapsulated in natural gas hydrates can be made viable through extended research on fundamental characteristics of hydrates and proposed production schemes. Experimental studies of hydrates on core-scale give fast and valuable input to aid in planning of field tests, and the controlled environment in which laboratory tests are conducted enables the possibility to look at individual parameters. In this thesis methane gas hydrates have been formed in sandstone cores with high intrinsic permeability. The initial brine salinity has been kept at 3.50 wt% sodium chloride and initial water saturation has ranged between 0.57-0.70 [fraction of pore volume]. Three cores were subsequently injected with a mixture of 60% N2 + 40% CO2 [mole percent] and pure nitrogen to induce recovery of methane gas, and the potential of fluid flow through the cores were especially examined. A stepwise pressure reduction scheme was performed on cores containing both pure methane hydrates and mixed CH4 + CO2 hydrates. The pressure depletions were conducted from one end of the cores, and differential pressures were monitored along with recognitions of dissociation pressures. One MRI (magnetic resonance imaging) experiment was performed using cyclopentane hydrates at atmospheric pressure for initial testing of a new MRI instrument. The formation of hydrates was conducted with temperatures varying between 0-4 °C, and the final hydrate saturation seemed to increase when formation temperatures were less than approximately 1 °C. Salinities and initial water saturations were kept fairly constant, but the results have been implemented with earlier research conducted by the hydrate research group at the Department of Physics and Technology. The observed trends related to hydrate growth can be summarized as followed: increased hydrate saturation for intermediate initial ...
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