WATERtech 2012 Banff, AB Dissolved Organic Matter Characterization of SAGD Produced Water Effects on Produced Water Treatment Subhayan Guha Thakurta, Abhijit Maiti, and Subir Bhattacharjee Department of Mechanical Engineering University of Alberta, Edmonton, Canada. April 11-13, 2012
Outline Overview of SAGD produced water (PW) treatment Water chemistry management challenges: Reduce blowdown water disposal Reduce make up water Improve reliability of treatment processes Knowledge of water chemistry Snapshot of the chemistry of blow-down water Dissolved organic matter (DOM) Concluding remarks 2
Typical SAGD Surface Treatment Basis: SOR= 3.0 100 bbl bitumen 3
Schematic of Surface Treatment 4
Characteristics of Different Oil Field Produced Water and SAGD Blow-Down Characteristics Oil Field Produced Water 1 Oil Sands Produced Water 2 SAGD BBD (Our Study) ph 7.4-8.5 7.11 11.2-10.3 Conductivity 1400-5000 1540 10000-18000 (µs/cm) TSS (mg/l) 97-25-65 TDS (mg/l) 700-2000 - 12000-17000 TOC (mg/l) 68-140 232 500-2500 Silica (mg/l as Si) 7-14 - 94-256 1 Mondal, S., Wickramashingh, S. (2008) J. Membr. Sci. 322, 162-170 2 Petersen, M.A., Grade, H. (2011) Ind. Eng. Chem. Res. 50, 12217-12224 5
UNDERSTANDING THE CHEMISTRY OF SAGD PW Chemistry of the Blow Down Water 6
Evaporation SAGD Blowdown Water Evaporation End of the pipe water represents cumulative effect of all chemistries. Analysis as potential BFW 67% condensate 100 ml BBD Detailed analysis of chemistry 7 33% concentrate
Evaporation of Produced Water ph Characterization Methods Inorganic and physical properties Condensate 67 % Concentrate 33 % Characterization Acidification Boiler feed quality water Finger print of dissolved organics (a) Removal of DOM and silica (ph range: 2-11). (b) Fouling effects on membranes (ph: 8-10.5). Fluorescence Excitation- Emission Matrices TSS 8
Potentiometric Titration of BBD Acid-titration of BBD water performed to different end-points using a potentiometric true equilibrium auto-titrator (QC- Titrate) 9
Acidification of Blow-Down ph 10
% Removal Silica and DOM Removal on Acidification 100 90 80 70 60 50 40 30 20 10 0 0 % Removal of DOM % Removal of Silica 0 35.7 % 69 % 40.1 % 91 % 93 % 44.1 % 3 45.3 % SUVA value 77 % 46.8 % 10.5 6.1 5.5 4.1 3.5 2 4.5 1.5 0.5 ph of Solution 4 3.5 2.5 2 1 0 4.21 3.87 SUVA Value 3.67 84 % 2.57 2.51 10.5 6.1 5.5 4.1 3.5 2 ph of Solution 2.21 11
Methanol Extracted Organics (MEO) Acidification of BBD to ph ~2 Separation and drying precipitates at 70 0 C Extraction of Methanol Extractable Organics (MEO) Evaporation of methanol and preparation of aqueous solution of MEO Dissolution of organics from precipitate in methanol ph adjusted to ~2, precipitation of MEO ph adjusted to ~10.5 complete dissolution of MEO 12
Effects of ph on Aqueous Methanol Extracted Organics The MEO fraction of DOM precipitates independently with acidification CHNS analysis of acid precipitated organics C (Wt %) H (Wt %) N (Wt %) S (Wt %) This behavior can be attributed to the protonation of organic acid salts to a free acid form, which become insoluble in aqueous media and precipitate at low ph 18.08 2.23 0.25 0.29 13
Ion-Exchange Fractionation Soxhlet Extraction (HPoN) HPiB HPiA BBD Non - ionic HCl Elution HPoB ph Adjustment & Recycle Cationic Anionic HPiN HPoA HPo free BBD HPiB free BBD Hydrophobic fractions Hydrophilic fractions 14
DOM Fractions in BBD 39 % 3 % 13 % 6 % 10 % 29 % Hydrophobic acid and hydrophilic neutral are the major fractions Hydrophobic neutral is the next major fraction 7
Analytical Techniques Excitation-emission matrix (Fluorescence spectroscopy) Ex/Em ranges: 200 to 500 nm Step sizes: 10 nm for excitation 5 nm for emission Other analytical techniques used are TOC analysis, SUVA 254, ATR-FTIR spectroscopy 16
Excitation Excitation EEMs of BBD- Organics and Naphthenic Acids 500 500 450 Raw BBD 450 Naphthenic Acids 400 83 400 350 161 336 350 17 300 250 436 336 200 200 250 300 350 400 450 500 Emission 300 250 230 200 204 139 200 250 300 350 400 450 500 Emission Signature of commercial Naphthenic acid (NA) not observed in BBD Ex/Em 230/350
Excitation Excitation BBD v/s OSPW 500 500 450 Raw BBD 450 OSPW 400 83 400 350 300 250 436 161 336 336 200 200 250 300 350 400 450 500 Emission 350 300 250 516 153 285 200 200 250 300 350 400 450 500 Emission The BBD does not contain NA signatures NA is a principal DOM component in OSPW 18
FLUORESCENCE SIGNATURES OF DOM FRACTIONS OBTAINED FROM ION-EXCHANGE FRACTIONATION 11
Typical NOM EEMs Fluorophore type Excitation-emission wavelength (nm) fluorescence peaks Humic like 300-370/400-500 Tryptophan Tyrosine 225-237/340-381 and 275/340 225-237/309-321 and 275/310 Hudson, N.; Baker, A.; Reynolds, D. Fluorescence analysis of dissolved organic matter in natural, waste and polluted waters-a review. River Research and Applications 2007, 23, 631 649. 14
Structures of Humic Acid Model Structure: Aiken GR, McKnight D,Weshaw RL, MacCarthy P. 1985. An introduction to humic substances in soil, sediment and water. Humic Substances in Soil, Sediment and Water, John Wiley & Sons: New York; 203. 12
Structures of Tryptophan and Tyrosine Tryptophan Tyrosine Hudson, N.; Baker, A.; Reynolds, D. Fluorescence analysis of dissolved organic matter in natural, waste and polluted waters-a review. River Research and Applications 2007, 23, 631 649. 22
Excitation Excitation EEMs Contour of Acidic DOMs 500 500 450 400 HPoA 116 450 400 HPiA Tryptophan like 350 308 350 146 300 228 300 97 57 250 250 200 200 250 300 350 400 450 500 Emission Humic like Ex/Em: 325/420 200 200 250 300 350 400 450 500 Emission Ex/Em: 340/425 23
Excitation Excitation 500 EEMs Contour of Basic DOMs 500 450 HPoB Tyrosine like 450 HPiB 400 400 350 350 54 300 250 184 67 127 300 250 126 102 54 200 200 250 300 350 400 450 500 Emission Ex/Em:260-290/280-320 200 200 250 300 350 400 450 500 Emission Ex/Em:210-225/310,350 24
Excitation Excitation EEMs Contour of Neutral DOMs 500 500 450 400 HPoN Tyrosine like 450 400 HPiN Tryptophan like 350 350 300 250 228 174 200 200 250 300 350 400 450 500 Emission 93 300 83 250 125 223 83 200 125 200 250 300 350 400 450 500 Emission Ex/Em: 240/350 Ex/Em: 220/300 25
SUVA 254 SUVA 254 value of DOM fractions: Fraction s HPoB 0.61 SUVA 254 HPoA 3.62 HPoN 3.95 HPiB 1.11 HPiA 2.03 SUVA 254 = (UV Abs 254 / TOC) *100 Presence of aromatic content in the HPoA and HPoN Lower aromatic content in the other fractions HPiN 0.18 26
Excitation Membrane Fractionation BBD Permeate Permeate YM10 Cutoff: 10 kda YM3 Cutoff: 3 kda YC05 Cutoff: 500 Da 500 500 500 450 Permeate of 10 kda 450 Permeate of 3kDa 450 Permeate of 0.5 kda 400 350 170 400 350 179 400 350 280 300 250 410 290 300 413 296 300 532 784 532 250 413 250 Wide 560molecular weight distribution 647 in individual 200 200 250 300 350 400 450 500 Emission organic fractions 200 200 250 300 350 400 450 500 Emission 406 200 200 250 300 350 400 450 500 Emission 27
Molecular Weight Distribution Molecular weight range Percentage DOM in permeate > 10 kda 8 % > 3 kda 10 kda > 0.5 kda 3 kda 19 % 33 % < 0.5 kda 40 % Nanofiltration (500 Da) retains 60% of DOM; a significant fraction is too small for NF removal 40% of organic matter in BBD is of molecular weight less than 500 Da 28
Intensity FTIR Results 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0-0.2 1024 1270 1032 1188 1761 Permeate of 10 kda Permeate of 3 kda Permeate of 0.5 kda 1000 1500 2000 2500 3000 Wavenumber (cm -1 ) 2870 10 kda: Silica peaks at 1032 cm -1 3 kda: Very weak peaks obtained at 1024 and 1188 cm -1 0.5 kda: Peaks At 2870 cm -1 C-H stretching At 1761 cm -1 for C=O At 1270 cm -1 for C-O 29
Concluding remarks DOM in SAGD blow-down water consists of low molecular weight compounds Hydrophobic acids and hydrophilic neutrals are the major fractions in the SAGD blow-down water Membrane filtration is unable to separate the DOM fractions based on size exclusion Knowledge of physico-chemical characteristics of SAGD fluids is the first step toward building a program for treatment 30
NSERC Industrial Research Chair in Water Quality Management for Oil Sands Extraction Contributors: Sunalini Sinha, Summer Intern, UofA Dr. David Pernitsky, Suncor Energy Dr. Amir Mahmoudkhani, Kemira Dr. Jonathan Martin, UofA Ni Yang, UofA Email: Subir.B@ualberta.ca 31