A leaching experiment was conducted at 4 °C to simulate the transport of phenoland chloride from a quiescent, viscous Cold Lake W/O emulsion into flowingfresh water. Test results indicated that phenol and chloride were transferredthrough different mechanisms. The rate-determining step for phenol transportwas the slow molecular diffusion of phenol in emulsion. This was successfullymodelled by a de-coupled second order diffusion equation from which thediffusion coefficient of phenol in emulsion was determined to be 2.2×10−8 cm2/s. Chloride was transported through directcontact of the emulsified water droplets with the leaching water in an 82 µmthick coalescence layer. The transport was essentially complete in less thantwo days and no further leaching was observed for the rest of the experiment.The bulk emulsified water was stable with no coalescing or segregation withtime. The phenol/ chloride transport model can be readily scaled to predict themass transfer of these two chemicals from a contaminated zone into a flowingaquifer as shown in a subsequent paper. No appreciable air oxidation norbiological degradation of phenol was detected during the experimental timeframe (61 days).
Similar to coal gasification, the Cold Lake steam stimulation process alsogenerates highly toxic by-products downhole In the formation. Theseby-products. Including various types of Phenols, carboxylic acids and otherhigh molecular weight acidic compounds generically classified as humicacids1, are weak acids. Being soluble both in bitumen andespecially In the igh pH stearn condensate these compounds are brought to thesurface by the produced water and bitumen. Cold Lake bitumen tends to form astable highly viscous water-in oil-emulsion with the produced water underminimal stress. The water content In the emulsion can be as high as 40%. Afterseparation, part of the produced water is softened and re-cycled for steamgeneration and the excess produced water, together with other harmful wastestreams are Injected through a disposal well Into an Isolated zone to avoidaquifer contamination.
In 1988, a leaky seal in the abandoned well C713 at Cold Lake caused anaccidental spill of bitumen (in the form of a water-In-oil emulsion) andproduced water into a near-surface aquifer zone where the bitumen and theproduced water were in a danger of being contacted by the flowingaqulfer2. Although the W/O emulsion was practically immobile at theformation temperature of 4 °C due to its high viscosity, the toxic phenoliccompounds could still be expected to leach slowly into the flowing stream.posing a threat of potential groundwater contamination. To assess theenvironmental impact of phenol contamination on groundwater water was producedfrom a newly drilled well and continuously monitored for chloride and phenollevels. In the meantime, experiments were designed and conducted in the lab tostudy the rate nd mechanism of the release of phenol into fresh water.Experiments were also carried out to quantify the extent of natural degradationof phenol via air oxidation and biological pathways.
