Study on Modified Starch Gel Physicochemical Characteristics and Parameters Quantification

Both laboratory and oil field tests have documented that enhanced oil recovery can be obtained by performing positioning blockage technology with the lower cost and the higher strength. Modified starch gel (MSG) is the preferred gel for positioning blockage technology considering its resistance abilities on temperature, salty and shear of the graft copolymerization between starch and allyl monomer. Due to the complexity of the reaction which is fractional and its rate bases on velocity, the physicochemical characteristics of MSG are totally different from conventional gel. Based on published data, graft copolymerization reaction rate equation with velocity and concentration is established and physical process for generated copolymer adsorption is characterized, which agreed with documented experimental facts. The dynamic characteristics of injection pressure are obtained by laboratory displacement experiment, which is designed including the early water driving stage, the middle MSG driving stage and the subsequent water driving stage. The quantitative results of characteristic parameters, such as residual resistance coefficient, maximum adsorption amount and viscosity, are achieved by fitting the injection pressure curve of laboratory displacement experiment using numerical simulation technology by CMG software. The viscosity of gel is about three times higher than that of polymer. MSG system had good gelation property which is helpful to enhance the plugging ability. (paper)