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Investigations of NMR T1 relaxation mechanisms in oil- and water-wet sand packs

University of British Columbia

The proton NMR relaxation parameter T, is affected by both relaxation in the bulk pore fluid and relaxation associated with the surface of the pore space. An understanding of the relative importance of these two relaxation mechanisms is a critical part of interpreting the NMR response of fluid saturated porous rocks. The first part of the thesis was an experimental study of the relaxation of protons in a sand pack filled with pyrite. Both oil- and water-wet sand packs exhibited a decrease in relaxation times of the pore fluid as the amount of pyrite in the sand was increased. I believe that the oxidation product of pyrite, Fe³⁺, is the critical component in governing the relaxation mechanism in these sand packs. The Fe³⁺ is going into solution and filling the pore fluid, decreasing the bulk solution relaxation time of the pore fluid. The Fe³⁺ is also believed to be adsorbing to the oil-water and water-sand interfaces, enhancing the surface-induced relaxation mechanisms in the oil- and water-wet sand packs. The second part of the thesis concentrated on understanding relaxation mechanisms in oil- and water-wet sand packs with pore fluids of differing pH and salinity. Changes in salinity of the pore fluid proved to have no effect on either the bulk solution or surface-induced relaxation mechanisms. Low pH pore fluid in the oil- and water-wet sands appears to bring paramagnetic species from the oil-water and water-sand interfaces into solution, decreasing bulk solution relaxation times of the pore fluids. The magnitude of the surface-induced relaxation mechanisms, quantified by determining the surface relaxivity, also increases in strength with the decrease in pore fluid pH.

Thesis/Dissertation

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2009-04-27

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http://hdl.handle.net/2429/7618

Oceanography

University of British Columbia

UBCV

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