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Title: Physico-chemical mechanisms of fault sealing : an experimental study
Author: Kay, Michael Andrew
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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This thesis presents the background, methodology, and results of an experimental study of the roles of stress, fault zone micro-structure, and environmental conditions on fault sealing. Synthetic fault gouges were tested in a suite of controlled experiments designed to elucidate the effects of a range of physical, structural, and chemical parameters on gouge reactivity. The experiments began with a series of ‘batch’ tests, designed to calibrate the purely chemical reactions. These were followed by a series of hydrostatic and non-hydrostatic pressure tests, designed to investigate the effect of burial depth and tectonic stress (confining pressure and deviatoric stress). The latter suites of experiments were conducted using a new experimental rig, designed and built specifically for this study. Each experiment used either a controlled size fraction, or a bulk mixture of particle sizes produced by crushing a rock sample to form a synthetic gouge. Highly reactive ultra-fine particles were removed to allow more accurate measurement of gouge surface area and hence reaction rates. Dissolution and precipitation rates were determined for each experiment by analysing dissolved silica concentrations of the pore fluids, using High Performance Liquid Chromatography, and applying them to a kinetic model. The non-hydrostatic tests also employed new apparatus that allowed the simultaneous measurement of fault-normal permeability and compaction throughout each experiment. The observed reaction rates have a strong dependence on temperature, particle size distribution, and pressure, in decreasing order of influence. This is consistent with field observations from a range of hydrocarbon reservoir rocks around the world. Theoretically, the finer particles would be expected to have higher specific surface energies and greater total reactive surface areas, and hence faster reaction rates. This has been confirmed by the results.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available