Wetting heterogeneities in porous media

Insights from experiments of the displacement of immiscible fluids

by Julie Lynette Murison
Doctoral thesis
Date of Examination:2014-01-23
Date of issue:2014-04-28
Advisor:Dr. Matthias Schroeter
Referee:Prof. Dr. Götz Eckold
Referee:Prof. Dr. Stephan Herminghaus
Referee:Dr. Jean-Christophe Baret
Referee:Prof. Dr. Martin Sauter
Referee:Prof. Dr. Philipp Vana
Referee:Prof. Dr. Michael Buback
Persistent Address: http://dx.doi.org/10.53846/goediss-4456

 

 

Files in this item

Name:thesis.pdf
Size:74.2Mb
Format:PDF

The following license files are associated with this item:

Abstract

English

Multiphase flow in porous media is an important process for many technical and environmental applications such as fuel cells, oil recovery, CO2 storage among others. Understanding the rules that govern these flows is essential for planning of CO2 storage sites, chemical or nuclear waste sites, predicting the viability of new oil reservoirs and preventing contamination of ground water aquifers. Natural porous samples, i.e rocks and soils, have highly heterogeneous pore space, both in geometry and wettability. This complicates experiments on such samples as there is no simple method of characterisation. While it is long known that the wettability of the substrate strongly influences the immiscible flow properties this effect, and in particular the effect of heterogeneous wettability, is poorly characterised. In this work the first experimental investigation of the domain size of wetting heterogeneities in bead packs is presented, and the effect of these domains on immiscible fluid displacement is discussed. This was accomplished by creating bead packs which had the same overall surface coverages of oil and water wet regions, but differed in the spatial extensions of these domains. The immiscible flow of water and oil through these samples was characterised by measuring the capillary pressure saturation curve for each type of sample. It was determined that the capillary hysteresis varied monotonically with the spatial extension of the wetting heterogeneities. To relate this measurement to the flow behaviour the invading liquid fronts were then imaged using X-ray microtomography. The front shapes were found to depend on the wetting domain sizes of the samples, with globally smooth fronts obtained for samples with small wetting heterogeneities. Both of these observations can be related to the dissipation of energy of the flow through the medium and it is found that the size of the wetting heterogeneity can control the flow properties. The lengths scales of the heterogeneities discussed here range from sub-pore to many pores, and in this range are found to be important. However, this is not necessarily true for very small heterogeneities. Towards this goal proof of concept experiments describing how to prepare surfaces with microscopic wetting heterogeneities using polymer brushes are discussed. Polymer brush modified surfaces were also tested as a surface exhibiting stimuli-sensitive wettability.
Keywords: Porous media; mixed wettability; x-ray microtomography; capillary pressure saturation curves; two phase flow
 
Statistik