Browsing by Subject "Surface active solvent"

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Application of different types of solvents for heavy oil recovery : experimental study on dimethyl ether, organic alkalis, and surface active solvents
(2020-09-10) Baek, Kwang Hoon; Okuno, Ryosuke, 1974-; Huh, Chun; DiCarlo, David; Mohanty, Kishore K; Azom, Prince N
Various challenges in heavy oil recovery come from the low mobility of reservoir oil. For example, the heavy-oil displacement by water results in a large mobility ratio and therefore, inefficient volumetric sweep. Polymer flooding is the traditional method to improve the frontal stability of the oil displacement, but the polymer mobility is often optimized to be greater than the oil mobility because increasing the polymer viscosity adversely affects the oil production rate. The low mobility of reservoir oil also results in a large amount of steam required in steam-assisted gravity drainage (SAGD), one of the commercially successful methods of bitumen recovery. This research investigated the application of unconventional solvents for heavy oil recovery, such as dimethyl ether (DME), organic alkalis, and surface active solvents (SAS), as a potential additive to the injection fluid. These solvents are not conventionally used for enhanced oil recovery (EOR). The first part of the dissertation presents potential methods of improving the efficiency of SAGD by using water-soluble solvents. Phase-behavior data were obtained for mixtures of bitumen and water-soluble solvents. Experimental results indicated that use of organic alkalis at low concentrations (e.g., 0.5 wt% pyrrolidine) in low-salinity brine can yield efficient emulsification of bitumen in water. The affinity of the organic alkali for asphaltic bitumen was important for oil-in-water emulsification at a wide range of temperatures. The second part of the dissertation presents a potential method of improving polymer flooding by SAS that reduces the interfacial tension (IFT) between the oleic and aqueous phases. Results showed that the IFT reduction by three orders of magnitude (i.e., 15.8 to 0.025 dynes/cm) gave a reduced residual oil saturation and a delayed polymer breakthrough in polymer flooding experiments with no preceding water flood. When the straight polymer flooding resulted in an oil recovery factor of 47% at 1.0 pore-volume injected (PVI), the SAS-improved polymer flooding increased it to 63% with a SAS slug of 0.1 wt% for 0.5 PVI or 0.5 wt% for 0.1 PVI
Effects of surfactant partition coefficient and interfacial tension on the oil displacement in low-tension polymer flooding
(2021-08-12) Liu, Mingyan (M.S. in engineering); Okuno, Ryosuke, 1974-
Complex surfactant formulations have been applied to generate an ultra-low interfacial tension (IFT) (e.g., 10⁻³ mN/m) between the displacing water phase and the displaced oil phase in chemical enhanced oil recovery (CEOR), where the residual oil after waterflooding can be largely recovered as an oil bank. This thesis is concerned with a simpler, lower-cost CEOR, in which a sole additive of surface active solvent (SAS) makes low-tension displacement fronts in polymer flooding (e.g., 10⁻² mN/m) without involving ultra-low IFT microemulsion phase behavior. The main objective of this research is to technically verify such low-tension polymer (LTP) flooding for a secondary-mode oil displacement through a sandpack of 9.5 Darcy. Previous research found that 2-ethylhexanol-7PO-15EO (2-EH-7PO-15EO, or “7-15”) as SAS was able to reduce the IFT between polymer solution and reservoir oil from 15.8 mN/m to 0.025 mN/m. In this research, the effect of SAS partition coefficient on LTP flooding was studied as an additional factor for SAS optimization. In particular, the comparison between two SAS species, 2-EH-4PO-15EO (4-15) and 2-EH-7PO-25EO (7-25), was important, because they had similar IFT values, but markedly different partition coefficients. The IFT was 0.18 mN/m with 4-15 and 0.20 mN/m with 7-25; and the partition coefficients were 1.61 with 4-15 and 0.68 with 7-25 at the experimental temperature, 61°C. These two SAS species were compared in secondary-mode LTP flooding with a slug of 0.5 wt% SAS for 0.5 pore-volumes injected (PVI). The oil recovery factor at 1.0 PVI was 65% with 4-15 and 67% with 7-25. At 5.0 PVI, it was 74% with 4-15 and 84% with 7-25. Although these two SAS species gave similar IFT values, their oil-displacement efficiencies were quite different because 7-25 propagated more efficiently in the sandpack with the smaller partition coefficient. The smaller partition coefficient helped the SAS flow more efficiently in the aqueous phase with less retention in the remaining oil. Optimization of SAS likely requires taking a balance between lowering the partition coefficient and lowering the IFT. The SAS recovery at the effluent was 61% for the 4-15 SAS and 78% for the 7-25 SAS. The propagation of the 4-15 SAS was retarded approximately by 1.0 PVI in comparison to that of the 7-25 SAS. The adsorption of the 4-15 and 7-25 SAS was 0.019 mg/g sandpack and 0.020 mg/g sandpack, respectively. With a similar IFT reduction, the SAS with a smaller partition coefficient (i.e., 7-25) resulted in less retention, less retardation, and more oil production for a given amount of injection.