Adaptability Evaluation Of Surfactant Flooding In Low(Extra-low) Permeability Reservoir

Low(extra-low)permeability reservoir usually has problems of high injecting pressure,low oil recovery and easily water channeling.This paper studied the adaptability of surfactant flooding and profile control in low(extra-low)permeability reservoir with experiments as main method.First,three types of surfactants are selected to evaluate the influence of emulsifying effect on flooding control,interface tension,emulsifying capacity and viscosity of surfactants are measured.Results show that,BS has ultra-low interface tension and weak emulsifying capacity,AES has relatively high interface tension and strong emulsifying capacity,BA has ultra-low interface tension and strong emulsifying capacity.Surfactant flooding simulation experiments are performed to evaluate the influence of surfactant with different properties on displacement efficiency in low(extra-low)permeability reservoir,using synthetic homogeneous short cores and long cores.Results show that,displacement efficiency of BS with ultra-low interface tension and weak emulsifying capacity is much lower than that of AES with relatively high interface tension(10-1mN/m)and strong emulsifying capacity.This means that emulsifying capacity is more important than ultra-low interface tension for increasing displacement efficiency.Surfactant flooding simulation experiments are performed to evaluate the adaptability of surfactant with different properties to increase sweep efficiency in low(extra-low)permeability reservoir,using synthetic heterogeneous cores.Results show that,in low(extra-low)permeability reservoir,AES with relatively high interface tension and strong emulsifying capacity can enhance oil recovery much more than BS with ultra-low interface tension and weak emulsifying capacity.This means that deep profile control effect caused by the emulsification between surfactant and oil counts more than ultra-low interface tension.BA with ultra-low interface tension and strong emulsifying capacity can increase recovery much more than AES and BS.Combining experiment results with consideration of cost,this paper suggests that properties of surfactant that is adaptable for flooding and profile control in low(extra-low)permeability reservoir are strong emulsifying capacity and moderate low interface tension.