A Novel Hydroxylpropyl Sulfobetaine Surfactant for High Temperature and High Salinity Reservoirs

Abstract

Abstract Reservoirs with high temperature and high salinity are widely distributed in various countries, which contribute an important percentage of oil output in the world. Pilot tests show that chemical flooding technique is one of effective EOR (Enhanced Oil Recovery) ways to improve the oil recovery for mature oilfields. The key technology of chemical flooding is to develop high efficiency surfactants with low cost. In this paper, the betaine surfactant has been synthesized with cheap raw material of fatty acid, and its functional group of hydroxylpropyl sulfo hydrophilic group can improve the heat resistant and salt tolerant abilities of the surfactant. The surfactant was characterized by Infrared Spectra, Raman Spectra and Element Analyzer. The analytical data show that the surfactant is consistent with the designed molecular structure, hydroxylpropyl sulfobetaine. The interfacial tension between the sulfobetaine solution and crude oils achieve ultra-low values (less than 1.0×10-2 mN/m) with temperature range from 30 °C to 90 °C, or salinity range from 20000 mg/L to 120000 mg/L, when the surfactant concentrations are from 0.05 wt% to 0.3 wt%. The parameters of hydroxypropyl sulfobetaine show that it is a suitable candidate for the oil-displacing agent due to its good long-term stability (within 180 days), low critical micelle concentration (4.74×10-5 mol/L), low dynamic adsorptions (0.44–0.72 mg/g), good injectivity and mobility. Oil recoveries increased 20 % - 24 % (OOIP, Original Oil In Place) after water flooding, with both weak alkali ASP and alkali-free SP formulations combined the sulfobetaine. And the oil displacement efficiencies of weak alkali ASP or alkali-free SP flooding have reached to 73 % - 76 %. Excellent properties of the hydroxypropyl sulfobetaine indicate that it is a promising surfactant, which can be applied in reservoirs with high temperature and high salinity.