Optimized Surfactant IFT and Polymer Viscosity for Surfactant-Polymer Flooding in Heterogeneous Formations
- Yefei Wang (China U. of Petroleum East China) | Fulin Zhao (China U. of Petroleum Beijing) | Baojun Bai (Missouri U of Science & Tech)
- Document ID
- Society of Petroleum Engineers
- SPE Improved Oil Recovery Symposium, 24-28 April, Tulsa, Oklahoma, USA
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 1.6.9 Coring, Fishing, 2.5.2 Fracturing Materials (Fluids, Proppant), 4.1.2 Separation and Treating, 5.7.2 Recovery Factors, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 4.3.4 Scale, 5.4.1 Waterflooding, 4.1.5 Processing Equipment, 2.4.3 Sand/Solids Control, 5.3.4 Reduction of Residual Oil Saturation, 5.6.5 Tracers, 4.6 Natural Gas, 5.3.2 Multiphase Flow
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Surfactant Polymer flooding (SP flooding) has drawn more attention than Alkaline Surfactant Polymer flooding (ASP flooding) in China due to the difficulty of demulsification and the scale formation problem from the alkali in ASP. Traditionally, the primary requirement for the surfactant in SP flooding is the lowest interfacial tension (IFT). However, core flooding tests performed in a series of heterogeneous models have demonstrated there exist optimized surfactant IFT and polymer viscosity for SP flooding, which can maximize the oil recovery of a heterogeneous formation. The optimized surfactant IFT has a low value but not the lowest possible value, and polymer viscosity is at an appropriately high value, but not the highest possible value. This paper summarizes and analyzes more than 40 core flooding test results and provides possible mechanisms for the results.
Polymer flooding has been widely applied to enhance oil recovery in China (Wang et al., 2009, Zhou et al., 2007). However, polymer flooding can only improve sweep efficiency with mobility control but it cannot be used to improve microscopic displacement efficiency (Zhao et al., 2001). Alkali and/or surfactant are/is added to polymer solution to form binary or tertiary combined flooding, that is, ASP flooding (Nasr-El-Din et al., 1994, Zerpaa et al., 2005, Carreroa et al., 2007) or SP flooding (Noïk et al., 1997, Langevin et al.,1997, Roshanfekr et al., 2009, Rai et al.,2009). The combined flooding processes can not only improve sweep efficiency but it can also improve displacement efficiency through increased capillary number. Combined flooding technologies have been considered to be the most potential tertiary oil recovery technologies (Wang et al., 2000, Cao et al., 2002, Li et al., 2005 Vargo et al., 1999, Kessel et al., 1989).
Alkali can react with some components of crude oil to produce surface active substances called surfactants, but it can also react with silicate minerals, aluminosilicate minerals, calcium and magnesium compounds, which will result in the formation of scales (Katsanis et al., 1983). Moreover, alkali stabilized emulsions in production fluids are too stable to be broken. The problems associated with scale formation and stabilized emulsions have made people more interested in the technology of surfactant-polymers (Fu et al., 2004, Yang et al., 2004).
Normally, the primary requirement for the surfactant in SP flooding is the lowest IFT (for example, ultralow IFT). This is because the capillary number can increase to 10-2 and the residual oil is close to zero when IFT reaches the ultra low value (Chatzis et al., 1984). However, this requirement is based on the condition of having a homogenous reservoir.
Core flooding tests have been performed on a series of heterogeneous models and the results show there exist optimized surfactant IFT and polymer viscosity for SP flooding, which can maximize the recovery of heterogeneous formation. The optimized surfactant IFT is at a low value, but not the lowest possible value, and polymer viscosity is at an appropriately high value, but not at the highest possible value.
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