NAPL recovery using carbon dioxide-supersaturated water injection: Distribution of the carbon dioxide gas phase

Gas inFusion(TM) is a novel remedial technology that dissolves CO2 into water under pressure for NAPL recovery. As the supersaturated liquid flows through the porous medium gas evolution occurs in situ as the system returns to thermodynamic equilibrium. The evolution of gas bubbles leads to NAPL recovery by two mechanisms: (1) volatilization and (2) mobilization by the NAPL spreading in a film around the rising bubbles.;Based on the results of these tests, enhanced CO2 levels above the hydrostatic pressure were observed up to 5.5--7.0 m from the injection point and the gas phase up to ∼5.3 m. It was not possible to determine the impact hydraulic control had on the lateral distribution of CO2 due to problems with the experiment. The distribution of the gas phase was heterogeneous with CO2 gas pockets forming below low permeability layers, as evidenced by surface GPR, permeameter tests, and grain size analyses. These gas pockets accumulated until, sufficient pressure built up to overcome the displacement pressure of these lower permeability layers. At this point there is evidence of CO2 breakthrough in the cross-borehole GPR data and physical observations of gas bubbles at the water table. These observations are consistent with previous investigations, which indicate that although the Borden aquifer is homogeneous, distinct horizontal layering is present with sufficient variations in permeability/displacement pressure to trap and cause some lateral spreading of a gas phase. The evidence of channeling and the impact of heterogeneities on gas distribution are consistent with air sparging studies. (Abstract shortened by UMI.).