Synthesis And Evaluation Of Hydrophobically Associated Cationic Starch

Starch is a kind of ideal green material due to its abundant resource,low cost and biodegradation. Most of modified starch has a wide range of application in oilfields. Besides cationic groups,a small amount of hydrophobic groups are introduced into hydrophobically associated cationic starch.Therefore,it has some unique performances on hydrophobically associating water soluble polymer.And it will have great application prospect in oil field.In this paper,hydrophobically associated cationic starch (PSADH)has been synthesized through graft polymerization of DMDAAC,HA and AM onto soluble starch by micellar polymerization technique. The effect of initiator dosage,monomers and starch ratio,surfactant concentration,cationic monomer dosage,reaction temperature,reaction time and pH value on graft copolymerization reaction have been studied,and the optimal reaction conditions were determined:content of initiator is 2.2×10-3mol/L,ratio of monomers and starch is 2.5:1,content of surfactant is 3%,content of cationic monomer is15%,pH value is 6,reaction temperature is 50℃,reaction time is 4h.In this paper,the relationships between apparent viscosity of PSADH solution and polymer concentration,salinity,temperature,shear rate and surfactant have been researched. The results showed that above the critical associated concentration,PSADH solution exhibited some good characteristics such as effective viscosity increase,tolerance to temperature,salinity and shear rate. Moreover,adequate surfactant SDS can increase the viscosity of PSADH solution.In this study,the water plugging properties of PSADH were evaluated,and its feasible application used as flocculant and viscosifier in oilfields also were discussed. Their mechanisms were analysed based on the molecular structure of PSADH.The results showed that,to be used as a water shutoff agent,PSADH exhibited good temperature and salt tolerance,flush resistance and good oil/water selectivity. Moreover,PSADH gel system also exhibited good properties for water shutoff. And PSADH also can be used as flocculant and viscosifier for drilling fluid.