The Application Of Nanoemulsion And Microemulsion In Oil-based Mud Cleaning And The Recycling Of Nanoemulsion

Microemulsions,formed by immiscible oil,water and surfactants are transparent or translucent and have high stability.Additionally,microemulsions are thermodynamically stable systems,which can be formed spontaneous.Nanoemulsions and microemulsions are often confused in the literatures and practical applications for their similarities,such as appearance,stability,preparation methods and so on.Nanomulsions,multiphase colloidal dispersions of the oil phase(water phase)in the water phase(oil phase),are types of special emulsions with droplet size ranging from 50 to 200 nm.Since nanoemulsions are kineticly stable systems,energy input is required for nanoemulsion formation.Nanoemulsions and microemulsions have the same properties of high stability,good solubilization of water or oil and low interfacial tensions.Furthermore,specific types of nanoemulsions or microemulsions can be prepared by surfactants and oil phase of different species and content,which could be used at different conditions.Therefore,they have significant application and potential application in drilling and completion,removing oil based mud,well stimulation and many other areas.Microemulsions are widely used in enhanced oil recovery.In recent years,microemulsions and nanoemulsions were also used in displacement spacer.Initially,water was used as displacement spacer to clean the oil base mud.With the development of drilling fluid system,especially the wide use of the oil base mud,water cannot satisfy the need.We need to improve the properties of displacement spacer.Microemulsions and nanoemulsions,a series of new drilling fluid displacement spacer,have high efficiency in cleaning.In addition,they can resistance to high temperature and high salt.Therefore,Microemulsions and nanoemulsions arouse wide concern.Nanoemulsions have high stability because of small droplet size to some dregree,but nanoemulsions will became unstable when they were placed at extra high temperature or extra low temperature.The preparation of nanoemulsions cost high energy.The repreparation of unstable emulsions not only avoids the consumption of energy and materials,but also reuses rubbish and reduces its destruction to the environment.Therefore,the repreparation of unstable emulsions has practical significance.Aiming at the above backgrounds,the thesis mainly includes two aspects as following.Firstly,to chose of recipe of oil base mud displacement spacer,we chosed series of anionic surfactants and nonionic surfactants.Then,we selected anionic surfactants(AES)and nonionic surfactants(6501)as the recipe of oil base mud displacement spacer and ascertain the assessment method of cleaning oil base mud at ambiement temperature.Additionally,we focus on the research in the influence factors of cleaning efficient,such as the species and content of surfactants,salinity of the system ect.Secondly,we research the repreparation of unstable emulsions.Aiming at the preparation methods of nanoemulsions,we invent two methods(PIC method and PIT method)to reuse nanoemulsions.Additionally,we investigate the influencing factors of these two nanoemulsions repreparation methods.