Abstract

Water is one of the cheapest and the most abundant injection fluid for oil extraction. Hence, as the hydrocarbon production increases, the amount of water injected escalates which brings the necessity of the proper management and treatment of produced water. The produced water quality can vary greatly depending on water injection processes employed. Thus, we aim to develop a thorough understanding of the expected quality of produced water originating from different thermal enhanced oil recovery (EOR) processes to manage oilfield waters. In this study, produced water from steam flooding (SF), steam assisted gravity drainage (SAGD), solvent-SAGD (S-SAGD), hot water injection (HWI), and in-situ combustion (ISC) processes were characterized. The anions and cations were analyzed by an ion chromatography. Total dissolved solids (TDS), conductivity, pH, total organic content, and average particle sizes of colloids were measured. The stability of colloids was determined by Zeta potential. All analyses were performed on the produced water samples collected at different three stages of the processes; at the initial, intermediate, and final stage of each process. As expected, conductivity strongly correlated with the concentration of the ions present in produced water samples. Sulfate and total organic carbon (TOC) concentrations showed a linear relation. During steam and hot water based injection processes, which were conducted with quartz and kaolinite mixtures, clay-water interaction was found significant, and this interaction increases with injected fluid temperature. Based on zeta potential measurements, the produced water from steam based EOR processes exhibited higher stability than ISC. In other words, the colloids in produced water originated from ISC was more prompt to settlement which makes produced water from ISC good candidate for chemical coagulation. The steam based processes indicated lower TDS value in produced water than ISC, however, when the produced volumes were considered, ISC had advantages due to significantly low volumes of produced waters. Our results indicate that the proper selection of the bitumen extraction method impacts the bitumen-water interaction and produced water management becomes feasible.

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