Imbibition And Oil Displacement Mechanism Of Micro-nano Pores In Tight Reservoir

At present,it is more and more difficult to develop conventional reservoirs,so the tight reservoirs and other unconventional reservoirs are gradually put into development.Imbibition is one of the superior development methods of tight reservoir.It is particularly important to research the displacement mechanism and the influencing factors of imbibitions.By analyzing the properties of different surfactants,interfacial tension,wettability and other factors,the influence of crude oil startup mechanism was studied.Surfactant was used for microscopic oil displacement experiment,and the influencing factors and mechanism of microscopic imbibition oil recovery were summarized.The following work has been carried out and the following research results have been obtained:1)The interfacial tension,contact angle,adhesion work and static imbibition effect were studied and evaluated by 10 °C temperature gradient in the range of 40°C-80°C.There is a start-up temperature for crude oil start-up.With the increase of temperature,the interfacial tension,contact angle,adhesion work and so on are basically reduced,and the crude oil is easier to be produced with the increase of temperature.Surfactants can reduce the threshold of start-up temperature to achieve the purpose of enhancing oil recovery.2)Adhesion work and theoretical adhesion work decrease can be used to judge the difficulty of crude oil start-up.The penetration of surfactant and the effectiveness of start-up crude oil can be judged by penetration rate,penetration force and the actual adhesion work.The actual adhesion work difference is large,and it is easier to separate from the rock surface.High penetration force and high penetration rate can accelerate the surfactant to reach the target position and act quickly.Surfactants can improve the wettability and reduce the interfacial tension,and then reduce the adhesion work of crude oil on the rock surface,making it easier to separate from the rock surface.3)The microscopic visual model was used to conduct the imbibition oil displacement experiment.The surfactant can improve the recovery efficiency of 22.93 % under water-wet condition and 34.95 % under oil-wet condition.The main functions of imbibition agent are as follows: reducing interfacial tension to make oil easier to migrate;forming oil belt mechanism by coalescence;emulsifying and viscosity reducing to make small oil droplets easier to migrate;expanding swept volume and enhancing oil recovery.JFC-2 can synergistically improve the ability of anionic-nonionic surfactant to change wettability and reduce interfacial tension.Capillary lifting is an important parameter to verify the changing wettability of surfactant and displacement ability of crude oil.The higher the lifting crude oil is,the better the effect of surfactant is.In the boundary region of the two wettability models,there is a phenomenon similar to the single capillary lifting experiment,and there is an obvious imbibition phenomenon.Surfactants can promote crude oil discharge and increase crude oil recovery by imbibition in micropores.