Viscous fingering instability in emulsions displacements
Date
2009
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Abstract
When a less viscous fluid displaces a more viscous fluid, the difference in the mobility of the two fluids leads to an interfacial instability which is commonly referred to as viscous fingering. It is encountered in a wide variety of applications that include petroleum engineering (oil drilling and recovery) , environmental engineering (soil decontamination, solute transport in aquifers) and chemical engineering (chromatography and polymer processing). Understanding and controlling this instability is crucial for the success of many industrial processes and in particular in oil recovery where in situ emulsion formation and flow occurs at some stage of the recovery process. These emulsions display interesting rheological behavior that may vary from simple Newtonian behavior to complex viscoelastic behavior depending on factors such as the intrinsic properties of the continuous and dispersed phases, volume fraction of the dispersed phase, deformable droplets or internal fluid circulation. The objective of this research work is to understand the flow dynamics of emulsions and its effects on viscous fingering instability. In order to understand the physics of these flow displacements, experiments were carried out displacing oil-in-water (0/W) emulsions by water in a rectilinear Hele-Shaw cell. In this investigation, different concentrations of emulsions and different injection rates of displacing fluids were considered and their effects on finger pattern were examined. The displacements were carried at different aging times ranging from the initial time of emulsion preparation that is referred to as fresh emulsions to more than 24 hours after preparation that is referred to as aged emulsions. The drop size analysis showed that the emulsions were stable and the average drop size did not change significantly during the aging period. The rheological measurements showed that as the aging time of emulsions increased there was a trend for viscosity increase which was sometimes accompanied by a change to non- ewtonian behaviour. Overall, lower concentration fresh emulsions showed Newtonian behavior with some discrepancy in viscosities from one sample to another and the displacement results did not show any obvious trends in the finger structures and sweep efficiency. On the other hand, aged emulsions showed non-Newtonian shear thinning behavior with more consistency in the viscosity measurements. Flow displacements of these aged emulsions revealed that the complexity of finger structures and sweep efficiency increased with an increase in the injection rate. Possible interpretations and physical explanations of the results are presented in the thesis.
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Bibliography: p. 182-196
Some pages are in colour.
Some pages are in colour.
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Citation
Enjamoori, S. (2009). Viscous fingering instability in emulsions displacements (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/3223