Properties Evaluation Of Surfactant With Low Interfacial Tension Used In EOR

The mature oilfields(Daqing, Shengli, Liaohe, Xinjiang, Zhongyuan)all have entered the high water-cut development period in China. How to further promote oil recovery has important meaning for oil production. Chemical flooding is a leading measure to EOR. Theory and field experiments indicate that the ultra-low interfacial tension can favor to dramatically improve oil displacement efficiency. Surfactant with ultra-low interfacial tension without alkali is the key of combined flooding.This paper selected two surfactants with low interfacial tension, and evaluated their performance according to the requirements to surfactant used oilfield. Gemini surfactant chosen in the experiment could reach ultra-low oil-water interfacial tension with crude oil coming from different oilfield, between surfactant concentration 0.05% and 0.3%. The ultra-low interfacial tension could maintain within 90 days in the reservoir condition, which meets the demand of application. Within NaCl concentration of 2400～10000mg/L, salinity has no obvious effect on interfacial tension and the surfactant suits to the oilfield injected water. The surfactant does not affect the viscosity of hydrolyzed polyacrylamide(HPAM) and could be used as surfactant/polymer flooding.The solubility of low interfacial tension surfactanst is not very well. Their could not be completely dissolved in water under normal temperature, the same as that even in reservoir temperature. The static adsorption amount of surfactants is 3.5mg/g and 5.78mg/g analyzed by Sulfur-nitrogen analytical instrument and the UV spectrophotometer, respectively, which is larger than that of alkyl benzene sulfonate sodium(less than2mg/g sand). The bigger adsorption amount may be the common characteristic of surfactant with low interfacial tension.The surfactants with Low interfacial tension has better oil-displacement capacity, which could be used for surfactant flooding and surfactant/polymer combination flooding (SP flooding). The surfactant/polymer flooding could increase the oil recovery more than 15% after water flooding for high-middle permeability core under Daqing oilfield condition. The EOR would be 12.3% for low permeability core at the same condition with above. For the high-temperature and low permeability core in the reservoir condition of Jiangsu oilfield,low interfacial tension surfactant flooding could improve the oil recovery more than 5%, and combination flooding of low interfacial tension surfactant and polymer microsphere could increase oil recovery more than 10% after water flooding .