Removal of oil from produced waters

Oil production generates a significant amount of water byproduct known as produced water. Following primary gravity separation, produced water is normally disposed of by injection into the formation from which it came. However, high amounts of suspended solids or oil in the produced water may cause significant problems if the injection formation becomes clogged. This study evaluated the effectiveness of coalescence/filtration and dissolved air flotation in treating two produced water samples obtained from Saskatchewan heavy oil production sites. In the coalescence/filtration experiments, percentage removals of oil and suspended solids were observed as high as 97 and 91 percent, respectively. In the dissolved air flotation experiments, maximum oil and suspended solids removals were 77 and 59 percent, respectively.;In the dissolved air flotation experiments, recycle pressure and recycle ratio were evaluated for statistical significance. Additionally, suitable ranges were identified for two process design variables, air to solids ratio and surface loading rate. A preliminary investigation into the use of polymers with dissolved air flotation was conducted, with maximum oil and suspended solids removals of 94 percent and 66 percent, respectively.;Mechanisms of filtration and coalescence were identified and observed through experimental data and mathematical models. The maximum coalescence efficiency observed was 3 percent at the lowest flow rate. Coalescence efficiencies decreased with increasing flow rate. Experimental data for single and two-phase flow were shown to fit the Carmen-Kozeny filtration equation. Coalescence/filtration was described as a first order rate equation using the Crickmore model.