Effect Of Surfactant On Imbibition And Oil Displacement Efficiency In Low Permeability Fractured Reservoir

Low permeability reservoir is an important successor in China's crude oil production.However,it is easy to water breakthrough because of the fractures and difficult to establish effective displacement because of the low matrix,which leads to a large number of remaining oil in the matrix.Therefore,we take the Eastern GGY oil field as an example in this paper.The characteristics of reservoir are analyzed in fractured low permeability reservoir.On the basis,the dual percolation model of fracture displacement and matrix imbibition is verified through the fracture core water drive experiment and starting pressure test.Further,it is concluded that the effect of interfacial tension is more important than that of wettability reversal and emulsification on the imbibition by different surfactants imbibition experiments.The influence of reservoir characteristics on imbibition is studied.The effects of permeability,reservoir quality index,reservoir wettability and fracture state were revealed on the spontaneous imbibition of surfactant.On the basis of static imbibition experiment,the optimal displacement velocity is determined by the experiment of the effect of water flooding velocity.The optimal displacement velocity is determined: the optimal displacement velocity of formation water is about 0.02ml/min and the optimal displacement rate of surfactant is about 0.01ml/min.Furthermore,the influence law of matrix permeability and crack opening on dynamic imbibition of surfactant was revealed under the the optimal displacement velocity(0.02ml/min).Finally,the mechanism of microscopic displacement of imbibition was analyzed by means of NMR and established the surfactant diffusion oil displacement model to explaine the action mechanism of surfactant in the proess of imbibition.