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Title: Reservoir condition pore scale imaging of multiphase flow using X-ray microtomography
Author: Andrew, Matthew
ISNI:       0000 0004 5349 5801
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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This thesis presents the first method for the imaging of multiple fluid phases at conditions representative of subsurface flow by the use of X-ray micro-CT, focussing on four principal applications: (1) Capillary Trapping; (2) Ganglion Snap-off and remobilization; (3) Contact angle measurement; and (4) Dynamic phenomena associated with CO2 drainage. Firstly the pore-scale arrangement of CO2 after drainage and imbibition was imaged in three carbonates and two sandstones. In each sample substantial amounts of CO2 were trapped, showing that residual trapping can be used to locally immobilise CO2. The size distributions of larger residual ganglia obey power law distributions with exponents broadly consistent with percolation theory, over two orders of magnitude. To examine snap-off in more detail residual CO2 was imaged at high resolution in a single carbonate. The capillary pressures of residual ganglia were found to be inversely proportional to the radius of the largest restriction surrounding each ganglion. The remobilization of residual ganglia was assessed using a reformulation of both the capillary and Bond numbers, finding the majority of ganglia in this system were remobilized at reformulated capillary numbers of around 1. Thirdly this thesis presents the first method for the measurement of in-situ contact angle at realistic conditions by the use of micro-CT, applied to a single carbonate sample at 50oC and 10 MPa. Contact angles ranging from 35o to 55o were observed, indicating that the CO2-brine-carbonate system is weakly water-wet. Finally, we use fast synchrotron-based X-ray micro-CT to examine drainage into a brine saturated carbonate. The equilibrium capillary pressure change associated with drainage events is not sufficient to explain the accompanying snap-off, showing that dynamic forces can have a persistent impact on the pattern and sequence of the drainage process.
Supervisor: Bijeljic, Branko; Blunt, Martin Sponsor: Imperial College London
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral