Surfactant Screening For Surfactant-ploymer Flooding System And Action Mechanism Of Surfactant

In this paper several dozen kinds of surfactants were screened for the polymer/surfactant (PS) system. The non-ionic surfactant SNS-1 and modified plant carbonxylate SNHD are chosen and researched in detail. The effects of surfactant concentration, polymer concentration,salinity,temperature on interfacial tension were studied. Adsorption of surfactants on the Daqing oil sand and oil displacement efficiency of two PS systems are also studied.The results show : (1)The surfactant SNHD has a very good interfacial activity. The interfacial tension could be reduced to ultra-low (10-3 mN/m) when the concentrations are varied from 0.05% to 0.3%.The surfactant has good salt tolerance. The polymer has no effect on it. (2)The interface tension of SNS-1 system can reach 10~2mN/m. The concentration of polymer influences the time to reach the balance value. But the effect is not obvious when the concentration of polymer is smaller than 1000 mg/L. When the temperature is varied from 45@ to 50@, the interfacial tension reduces with the increasing of temperature. (3)The adsorption of carboxylate on oil sand increases to maximum and then decreases with the increasing of surfactant concentration.(4)The adsorption value of SNS-1 is 1.0 mg/g oil sand. (5)After PS flooding the rock water wettability is strengthen. The degree of wettability increases with the increasing of polymer or surfactant concentration.(6)The recovery of SNS-1 system is near to ASP system when the cost of chemistry is equal. When the concentration of polymer is 1500 mg/L, the recovery of PS flooding is higher than ASP flooding. (7)The recovery is nearly the same when the PS and ASP systems have the same cost of chemistry (8)The mechanism of PS flooding is summarized out. Besides reducing interfacial tension to increase the displacemnt efficiency and polymer increase the sweep efficiency coefficient, the elasticity of polymer also can increase the displacement efficiency.Furthermore, the influence factors of dynamic interface tension are discussed. They are salinity, surfactant concentration, aqueous viscosity and so one. The polymer is the main factor among them. Dynamic interfacial tension is controlled by surfactant diffusion before reaching minimum interface tension.