Gas Compression Systematically Delays the Onset of Viscous Fingering

Area of Science:

• Fluid dynamics
• Multiphase flow
• Interfacial phenomena

Background:

• Viscous fingering occurs when a less viscous fluid displaces a more viscous fluid in porous media or Hele-Shaw cells.
• Fingering is classically driven by gas injection, with intensity typically governed by the capillary number (Ca) for incompressible gases.
• Existing research focuses on suppressing fingering, often under assumptions of steady flow and incompressible fluids.

Purpose of the Study:

• To investigate the impact of gas compressibility on the onset and intensity of viscous fingering in Hele-Shaw cells.
• To identify key dimensionless parameters that control gas-driven fingering when compressibility effects are significant.
• To demonstrate that gas compressibility is a critical factor in understanding and controlling fingering phenomena.

Main Methods:

• Experimental study using Hele-Shaw cells to observe gas-liquid displacement patterns.
• Systematic variation of the dimensionless compressibility number (C) and capillary number (Ca).
• Analysis of flow dynamics under unsteady injection rates induced by gas compression.

Main Results:

• Gas compression leads to unsteady injection rates, deviating from steady-state models.
• The dimensionless compressibility number (C) emerges as the primary control parameter for unsteady injection rates.
• Increasing C demonstrably delays the onset of viscous fingering, particularly at high capillary numbers (Ca).

Conclusions:

• Gas compressibility is a fundamental, yet often overlooked, factor in gas-driven viscous fingering.
• The compressibility number (C) provides a new framework for understanding and potentially suppressing fingering.
• Controlling gas compressibility offers a novel strategy for managing multiphase flow instabilities.