Supersaturated Water Injection to Recover Volatile LNAPLs
In thi supersaturated water injection (SWI) system, pressurized water containing elevated concentrations of CO2 leaves the Gas inFusion generator and flows to an injection well point.
The injection screen is located below the residual NAPL. When the carbonated water exits the well screen the pressure drops leaving the water supersaturated with CO2. Supersaturation will not persist and immediately CO2 bubbles will begin nucleating as the supersaturated water flows radially out from the well.
The distance will be dependant on many factors including the water injection rate, the water pressure and the hydraulic conductivity of the porous medium. The newly formed CO2 bubbles will rise up though the porous medium or become trapped in pores. Some of the bubbles that continue to rise will come into contact with residual NAPL ganglia. If the NAPL is volatile, the contact between the CO2 bubble and the NAPL may result in the NAPL being volatilized and incorporated into the bubble. This bubble that now contains CO2 and volatilized NAPL will continue to rise and will reach the unsaturated zone if it does not become trapped in a pore. Once the CO2 and volatilized NAPL reach the unsaturated zone they will be drawn into an extraction well by an applied vacuum and removed from the subsurface.
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