Steam assisted gravity drainage (SAGD) boiler blow-down (BBD) water contains high concentrations of dissolved organic matter (DOM) and total dissolved solids (TDS). A detailed understanding of the BBD chemistry, particularly the DOM composition, is important for better management and recycle of this water. In this study, we fractionated the dissolved organic matter in the BBD using DAX-8, Dowex, and Duolite resins into hydrophobic and hydrophilic fractions of acid, base, and neutral compounds. Additionally, the DOM was fractionated on the basis of size by filtering the BBD through a series of membranes with progressively tighter molecular weight cutoffs of 10, 3, and 0.5 kDa. Fluorescence excitation−emission matrix spectroscopy (EEMs), specific UV absorbance (SUVA), and FTIR were used to characterize the water samples and the different fractions. The ion exchange fractionation revealed that the DOM contained a high percentage of hydrophobic acids (39%) and hydrophilic neutrals (28.5%). The different ion exchange fractions had distinct fluorescence excitation−emission signatures. The permeate samples from the membrane fractionation, on the other hand, did not reveal any significant difference in the fluorescence EEM spectra, indicating that the hydrophilic and hydrophobic constituents of the DOM could not be separated on the basis of pore size by these membranes. The SAGD boiler blow-down water was found to be significantly concentrated in DOM compared to oil sands mining process affected water.

In thermally enhanced oil recovery operations, particularly in steam-assisted gravity drainage (SAGD), boiler blowdown (BBD) containing high concentrations of dissolved organic matter (DOM), dissolved silica, and total dissolved solids (TDS) is generated. To develop efficient tools for managing this blowdown, a detailed understanding of its chemistry is required. In this study, BBD was evaporated to yield ∼66% condensate and ∼33% concentrate blowdown (CBD). Detailed characterization of the BBD and CBD water was conducted. The effect of acidification was also studied. The acidification coprecipitates the silica and DOM, with over 90% of the silica and over 40% of the DOM precipitating at pH 4. Ultrafiltration treatment was also examined, and a major fraction of the silica and DOM in the CBD was found to foul a 100 kDa ultrafiltration membrane in the pH range of 7.5 to 9. The analysis revealed that the dominant fouling mechanism was cake filtration, indicating the formation of a silica−DOM precipitate layer on the membrane surface. These studies can provide insight regarding management options for SAGD disposal water.

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