Study On The Mobility Control Effect Of Polymer/Surfactant Flooding On EOR

Reservior physical property of West 3 Area in Dagang oilfield is of high permeability and high porosity,with a strong heterogeneity on the whole.After years of water flooding,it is presently in the period of high water cut and it is more difficult to“stabilize oil and control water",carrying out EOR techniques in a large extent is extremely urgent.Polymer/Surfactant(S/P)system can effectively reduce interfacial tension,improve mobility ratio and change rock wettability,which not only amplifies swept volume but improves displacement efficiency.In order to improve the technical economy effect of S/P flooding,on the basis of reservior geology property,development situation and existing problems in Dagang oilfield,experimental study on the relationship between mobility ratio of binary combination and its viscosity,interfacial tension,polymer molecular thread size,resistance factor and residual resistance factor is carried out through the technical means of instrumental testing,chemical analysis and physical simulationthe thesis,which is theoretically directed by physical chemistry,high polymer chemistry,reservior engineering.Results show that with the increase of surfactant concentration,there is a slight decrease in viscosity of S/P system and a decreasing tendency of interfacial tension with oil,finally ultra interfacial tension(with magnitude 10-3mN/m)is realized.Polymer relative molecular thread size Dh is directively proportional to polymer relative molecule mass,and is inversely proportional to polymer concentration and solvent water salinity.Surfactant causes polymer molecular thread size Dh to increase,resulting in narrowing of light intensity distribution.According to geology and fluid properties in target oilfield,polymer relative molecule mass that fits S/P flooding is 2500×104 by referrence to experimental results of compatibility between oil displacement agent and rock pore size.With the increase of viscosity ratio of polymer to oil(μp/μo),S/P flooding "Output/Input" has a tendency of first increase and then decrease.Rational range of viscosity ratio is 0.81-0.94.With the increase of oil viscosity,mean permeability of rock and permeability variation coefficient,mobility control contribution of S/P flooding to recovery increases,however,that to oil displacement efficiency decreases.Mobility control contribution of S/P flooding is greater than 60 percent,which is the principal contradiction that restricts economic effect of S/P flooding and is also research direction of developing efficient oil displacement agent in low cost.