Dissolved Organic Matter in Steam Assisted Gravity Drainage Boiler Blow-Down Water

Abstract

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.

Treatment of anin situoil sands produced water by polymeric membranes

“…Increasing hydrophobicity generally leads to more susceptibility to fouling due to the hydrophobic interactions between the membrane surface and the hydrophobic materials [38]. In this study, the organic matter present in the WLS inlet feedwater has been reported to be mainly hydrophobic acids (humic type) [4]. Since all of the membranes tested were hydrophilic (based on the contact angle values in Table 1), it was expected that the membrane surfaces would become hydrophobic after fouling.…”

“…), all indicative of the presence of naphthenic acids as the main DOM group in SAGD-produced water. However, Guha Thakurta et al [4] found that the DOM found in SAGD-produced waters are significantly different from OSPW DOM, and more like humic acids than naphthenic acids. It must be noted that every DOM molecule has a specific charge and molecular conformation which controls the rate of fouling and subsequently the performance of the membrane process [25].…”

“…(2015) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] www.deswater.com doi: 10.1080/19443994.2015.1069216 pumped to the surface where the bitumen and water are separated and the water is treated for reuse as boiler feedwater (BFW).…”

“…The high levels of DOM and TDS in the OTSG feedwater can cause numerous operational problems like fouling of pipelines and equipment, and clogging of injection wells [2][3][4]. To reduce the injection water volume, evaporators are sometimes used as a downstream BBD recovery process.…”

“…Evaporators have also been used to directly desalinate produced water to make high-quality BFW, but energy use is high. High boiler feedwater TDS and DOM results in higher blowdown volumes and necessitates recycling more low quality BBD water back to the process [4]. The chemical intensive WLS-IX scheme also suffers from high operating cost, large foot print, and excessive recycles.…”