Preparation And Performance Evaluation Of PH Responsive High Temperature Pickering Emulsion Viscosity Reducer For Heavy Oil

With the depletion of conventional oil reserves,the exploitation of some heavy oil and super heavy oil reservoirs which are difficult to develop and utilize has been put on the agenda,especially in China.Emulsification viscosity reduction method is one of the most effective methods for heavy oil recovery at present.The key to enhance heavy oil recovery is to select emulsification viscosity reducer with excellent performance.In the process of heavy oil thermal recovery,due to the high steam temperature,the injected emulsified viscosity reducer not only needs to have good high temperature tolerance to ensure that it will not decompose due to high temperature in the injection process,but also needs to have the ability to maintain good surface activity under high temperature conditions.Pickering emulsion has been widely used in petroleum field abroad,but the research and related articles on Pickering emulsion are relatively few in China.Pickering emulsion stabilized by some solid particles can form a good o/W system,which can greatly reduce the friction between oil droplets and achieve good viscosity reduction effect.A part of the emulsion formed by the particles with their own responsiveness and certain responsiveness after grafting modification can be recycled and demulsified under certain response conditions,which is convenient for subsequent oil recovery,which brings convenient conditions for heavy oil recovery and gathering.The stable emulsion has simple particle structure,stable chemical bond and high temperature resistance.Compared with the traditional viscosity reducer,particle viscosity reducer has the advantages of better temperature resistance,environmental protection and recycling.Aiming at the high temperature and other environmental factors in the process of heavy oil thermal recovery,two new emulsion viscosity reducers Pickering emulsion viscosity reducers with chitosan and modified SiO₂ as stable particles were developed.In this paper,the SiO2-B particles from natural chitosan particles and modified SiO₂ were prepared by Pickering emulsion with crude oil and water.After a series of experiments and characterization,it was found that the two kinds of particles had strong temperature resistance.The Pickering emulsion had good stability while also had pH responsiveness.The most important point is that the viscosity reduction effect is remarkable.The final parameters of the two emulsifiers are 0.1%concentration and 1:1 oil-water ratio.Under these conditions,the viscosity reduction rate of crude oil can reach more than 99%.In order to reduce the viscosity of heavy oil without too high temperature,considering the economic problem,the chitosan emulsion viscosity reduction system can be selected.If the temperature resistance of the reagent is above 250℃in the viscosity reduction process,SiO₂-B emulsion viscosity reduction system is selected because it has better temperature resistance than chitosan emulsion viscosity reduction system.The maximum temperature resistance of chitosan emulsification system is at 200℃and 250℃.The emulsification system begins to fail around 250℃and almost has no viscosity reducing effect.SiO₂-B emulsion viscosity reducing system has higher activity before 300℃,and has better temperature resistance than chitosan emulsion viscosity reducing system.