Fluid-Fluid Invasion Patterns and their Relevance for Geological CO2 Storage
Research output: Research › Doctoral Thesis
Two-phase flow in porous media controls many natural and industrial processes like geologic CO2 sequestration, enhanced oil recovery, water infiltration in soil, and methane venting from organic-rich sediments. When injecting a less dense fluid to displace another one within a porous domain, inertia-dominated flow gives way to fast-flow induced viscous fingering, unstable displacement and heterogeneity controlled fingering, and finally gravity- and capillary dominated flow in the periphery of the well-bore. Depending on the wetting state of the system, the hydrodynamic instabilities that ensue may change their morphology. Yet, capturing these phenomena remains a highly challenging task. In this thesis, I first study experimentally how wettability affects fluid-fluid displacement patterns in rigid granular media within the capillary and viscous fingering regime. The experiments consist of saturating a thin bed of glass beads with a viscous fluid, injecting a less viscous fluid, and analysing the invasion morphology. There are two control parameters: the injection rate of the less viscous fluid and the contact angle, which is controlled by modifying the surface chemistry of the beads. When the contact angle is small (θ <5○, drainage), the well- known transition from capillary fingering to viscous fingering is recovered as the injection rate increases. When the injection rate is fixed, we show that the invasion pattern becomes more stable as the contact angle increases (i.e., as the system transitions from drainage to imbibition), both in the capillary-fingering and viscous-fingering regimes. The results demonstrate that wettability significantly impacts multiphase flow in porous media, having a major impact on better understand enhanced oil recovery as well as geological CO2 sequestration. Injecting an immiscible, less dense, inviscid fluid into a denser, more viscous one, the interplay between gravity and capillarity dominates at low flow velocities (quasi static system). Here, I develop an experimental Hele-Shaw cell type set-up to examine gravity driven flow patterns within a layered, porous medium. That framework allows to investigate the relevant flow mechanisms at a meter-scale. Since one would expect a constant shock front type displacement, I show that the buoyant non-wetting invading phase develops a dendritic, complex evolving migration pattern over time. This is due to the non-percolating conditions. Results show that the gravity-driven flow is dominated by the intermittent episodic rise of individual non-wetting fluid patches, which are characterized by a wide distribution of cluster sizes.
|State||Published - 2014|