Fundamental Changes in In Situ Air Sparging How Patterns

Abstract

Two types of gas‐phase flow patterns have been discussed and observed in the in situ air sparging (ISAS) literature: bubble flow and air channels. A critical factor affecting the flow pattern at a given location is the grain size of the porous medium. Visualization experiments reported in the literature indicate that a change in the flow pattern occurs around 1 to 2 mm grain diameters, with air channels occurring below the transition size and bubbles above. Analysis of capillary and buoyancy forces suggests that for a given gas‐liquid‐solid system, there is a critical size that dictates the dominant force, and the dominant force will in turn dictate the flow pattern. The dominant forces, and consequently the two‐phase flow patterns, were characterized using a Bond number modified with the porous media aspect ratio (pore throat to pore body ratio). Laboratory experiments were conducted to observe flow patterns as a function of porous media size and air flow rate. The experimental results and the modified Bond number analysis support the relationship of flow patterns to grain size reported in the literature.

Flow and fracture in water-saturated, unconstrained granular beds

“…A thorough description of two-phase flow patterns (gas-liquid) when injecting gas in a rigid, saturated porous medium has been provided in the literature (see for example [48], [21] and references within). These patterns-air bubbles, percolation networks or air channels-mainly depend on the grain size, and prediction attempts have been made by the in-situ air sparging (ISAS) community.…”

“…Few experiments have previously reported the dynamics of gas rising in an unconstrained, saturated porous medium, although the different patterns for rigid porous media have been thoroughly discussed in the in-situ air sparging (ISAS) literature [48]. In sand-sized porous media, Ji et al [46] reported experimentally that gas formed channels rather than discrete bubbles or percolation (dendritic) networks.…”

Effects of air injection on flow through porous media: Observations and analyses of laboratory‐scale processes

“…40, W09203, doi:10.1029/2003WR002960, 2004 aerobic biodegradation [e.g., Reddy and Adams, 2001;Brooks et al, 1999;Ahlfeld et al, 1994;Ji et al, 1993;Marley et al, 1992;Bruell et al, 1997].…”

Leakage and Sepage of CO2 from Geologic Carbon SequestrationSites: CO2 Migration into Surface Water

“…The Bond number can be used to classify whether gas flow in saturated porous media will occur by bubble or by channel flow (Brooks et al, 1999). Bubble flow occurs when buoyancy forces dominate and gravity drives gas bubbles upward without large capillarity effects.…”

“…Capillarity will therefore be the important force in medium and fine-grained porous media. A modified Bond number can be defined to include pore body and pore throat length scales to account for the fact that buoyancy is more important in pore bodies, while capillarity is more important in pore throats (Brooks et al, 1999).…”