Study On Spontaneous Imbibition Of Fracturing Fluids In Enhancing Oil Recovery

With the decreasing of conventional hydrocarbon resources,it increases to exploit unconventional oil and gas reservoirs worldwide.The development technology still need to be further studied now.How to develop unconventional oil and gas reservoirs with an efficiently way becomes a technical challenge.Spontaneous imbibition is an important mechanism to development of low-permeability reservoirs.Use of surfactant can improve oil recovery.This paper researched the ability of different kinds of surfactants as additives of fracturing fluids preflush in changing wettability and decreasing interfacial tension,in addition,spontaneous imbibition experiments in cores also be studied.Results show that anionic surfactants has better performance than other kinds of surfactants.Contact angle is the determining factor,imbibition happens only when the contact angle is less than 70°.Interfacial tension has a great impact on imbibition velocity.Optimal value range is around 10^-1mN?m^-1.There is not needed for ultra low interfacial tention in this case.Study on the factors influencing spontaneous imbibition shows that effect of surfactants on oil-wet cores are better than the water-wet.Permeability effect is not monotonic,26mD has the best imbibition recovery.High temperature increases the molecule movement,thermodynamic diffusion coefficient of oil also increases,so it improves the imbibition recovery.Low salinity helps to improve the recovery in our system studied.