Organic Alkali as a Steam Additive for Improved SAGD: Experimental Study of Emulsion Phase Behavior and Viscosity

摘要

Water is the most dominant component in steam-based oil recovery methods, such as steam-assisted gravity drainage (SAGD). The central question that motivated this research is whether in-situ bitumen transport in SAGD can be substantially enhanced by generating oil-in-water (o/w) emulsion, in which the water- continuous phase acts as an effective bitumen carrier. As part of the initial stage of the research project, the main objective of this paper is to present the ability of organic alkali to form oil-in-water (o/w) emulsions that are substantially less viscous than the original bitumen. Experimental studies were conducted for emulsion phase behavior and viscosity for mixtures of Athabasca bitumen, organic alkali, and NaCl brine. Experimental variables included brine salinity, alkali concentration, water-to-oil (WOR) ratio, temperature, and sample-aging time. The phase behavior study indicated that conditions conducive to o/w emulsions are low alkali concentrations at salinities below 1,000 ppm. At a WOR of 7:3, a single phase of o/w emulsion was observed for 0.5, 1.0, 2.0 and 5.0 wt% alkali with no NaCl, and 0.5 wt% alkali at a salinity of 1,000 ppm at 373 K. At lower temperatures, 323 K and 298 K, flocculation of emulsions in these samples resulted in separation between the bitumen-rich and water-rich o/w emulsions. However, essentially all bitumen content was measured from the bitumen-rich o/w emulsion. The oil contents in these emulsions were more than 70 vol. % at 298 K and 57 vol.% at 323 K. Viscosities of these o/w emulsions ranged between 85 cp and 115 cp at 1.0 s~(-1), and between 31 cp and 34 cp at 10.0 s~(-1) at 323 K. At 298 K, they ranged between 105 cp and 250 cp at 1.0 s~(-1) and between 48 cp and 74 cp at 10.0 s~(-1). Results in this research show that, in comparison with the original bitumen, bitumen-rich o/w emulsions were 3 to 4 orders of magnitude less viscous at 298 K, and 2 orders of magnitude less viscous at 323 K.