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Title: MRI studies and modelling of two phase-liquid systems in porous media
Author: Johns, M. L.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1999
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Hydrocarbon ganglia, trapped in the pore space of a ballotini packing by capillary forces, were selectively imaged using MRI. The geometric characteristics of these ganglia were monitored as they dissolved into a surrounding mobile aqueous phase. In particular the surface area of the ganglia was quantified during the course of dissolution. This was then included into a one-dimensional advection-dispersion model of the ganglia dissolution process, which contained only one free parameter, the mass transfer coefficient. The model predicted the experimental data reasonably well, but tended to over-predict dissolution after long time periods. Heterogeneity in pore-scale flow was identified as an explanation for this. The one-dimensional model was extended to systems composed of smaller packing material where imaging of the ganglia was no longer possible. The surface area of the ganglia was quantified by monitoring the diffusion of the hydrocarbon molecules inside the ganglia using pulsed field gradient nuclear magnetic resonance. An alternative three-dimensional model of the dissolution process was developed based on the used of cellular automata. Three-dimensional velocity images of the mobile aqueous phase surrounding the dissolving ganglia were acquired using MRI, and included into this modelling approach. Ganglia formation following an imbibition process, in which water displaced the hydrocarbon from the pore space of the packing, was also investigated using MRI. the results of this experimental investigation were compared with those produced by application of an invasion percolation model to a pore network representation of the pore space. Reasonable agreement between the experimental data and this modelling approach was produced. This pore network was generated using a pore thinning algorithm which segments the pore space into individual pores. An evaluation of this algorithm using different packing structures was also performed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available