Issue 18, 2022

A micro-scale rheometer to study foam texture and flow resistance in planar fractures

Abstract

We designed and fabricated a new microfluidic device to better enable study of foam microstructure and rheology in planar fractures. The design phase included stress–strain finite element analysis to enhance the pressure tolerance of the device. The optimized design is a 2 cm wide by 7.75 cm long rough fracture that includes 25 posts to anchor the glass cover plate. The posts simulate asperities and provide structural support during bonding of a glass cover plate to the device. Importantly, the new design illustrates improved ability to sustain large differential pressure compared to previous designs in the literature. The rheometer permits study of the relationship among foam bubble morphology, pressure drop, and flow rates. Our findings validated the previous, sparse microvisual studies mentioned in the literature and confirmed that small quality foam, ranging from 20 to 50% gas by volume, contains dispersed bubbles separated by liquid lenses. In this range, the distribution of bubble sizes was roughly 80–90% small uniform bubbles and only 10–20% of larger and more elongated bubbles. Additionally, our studies reveal that foam apparent viscosity is a strong function of foam quality, velocity, and texture (i.e., bubble size). Apparent viscosity of foam ranged from 100 to 600 cP for the conditions studied. High quality foams in fractures are independent of gas flow rates but very sensitive to liquid flow rates. On the other hand, low quality foams are sensitive to gas flow rates but independent of liquid flow rates.

Graphical abstract: A micro-scale rheometer to study foam texture and flow resistance in planar fractures

Article information

Article type
Paper
Submitted
01 Jul 2022
Accepted
29 Jul 2022
First published
01 Aug 2022

Lab Chip, 2022,22, 3489-3498

Author version available

A micro-scale rheometer to study foam texture and flow resistance in planar fractures

N. Nazari and A. R. Kovscek, Lab Chip, 2022, 22, 3489 DOI: 10.1039/D2LC00595F

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