Flow Visualization and 3D Measurements of Nano-Particle Transport in Rock-Based 2.5D Ceramic Micro-Models

Most flow visualizations and flow measurements to understand particle mobility in porous media are typically performed in transparent microfluidic devices (micro-models) with 2D pore-throat networks. Nano-particle mobility studies to date have been limited to micro-models made of transparent thermoplastic or silicone-based materials. In an effort to fabricate materials close to reservoir rock, ceramic micro-model has been designed and micro fabricated by our group to study nano-particle transport in rock-based ceramic micro-model. A Confocal Micro-Particle Image Velocimetry (C-μPIV) technique augmented with associated post processing algorithms [1] is used in obtaining 3D distributions of nano-particle velocity and concentration at selected locations of the ceramic micro-model. Furthermore, a novel in-situ, nondestructive method of measuring 3D geometry of non-transparent ceramic micro-model is described and validated. The particle experiment uses 860 nm fluorescence labeled polystyrene neutrally buoyant, and electrically neutral nano-particles. The data was acquired using confocal laser-scanning microscope to quantify 3D particle transport at selected observation locations. In addition, fluorescence microscope was used to measure in-situ geometry of porous media. Results of detailed 3D measurements of nano-particle velocity and particle concentration from experiment conducted at a constant flow rate of 30 nL/min in the rock-based micro-model are presented and discussed. Particle velocities range from 0 to 20.93 μm/sec in magnitude, and average concentration range from 6.02 × 10³ to 6.79 × 10³ particles at inlet channel while velocities range from 0 to 73.63 μm/sec and concentration range from 4.9 × 10¹ to 1.45 × 10³ particles at selected observation locations of the ceramic micro-model. 3D velocity fields at selected locations also indicate that mean velocity closer to the top wall is comparatively higher than bottom wall, because of higher planar porosity and smooth pathway for the nano-particles closer to the top wall. The three dimensional micro-model geometry reconstructed from the fluorescence data can be used to conduct numerical simulations of the flow in the as-tested micro-model for future comparisons to experimental results after incorporating particle transport and particle-wall interaction models.