Molecular Dynamics Simulation Of Oil-water Interface Interaction Of Amphiphilic Molybdenum Sulfide Nanosheets

Low permeability and ultra-low permeability reservoirs are rich in oil and gas resources,but their development is difficult,exhibiting low recovery and poor efficiency for surfactant flooding.Many scholars have developed new injection nanoparticles to enhance oil recovery,but the effect is not ideal.Therefore,it is necessary to develop new injection agents to enhance oil recovery.Our laboratory synthesized amphiphilic molybdenum sulfide nanosheets,which have played a good role in wetting,amphiphilic,emulsification,and viscosity reduction.However,the microscopic properties of the molybdenum sulfide nanosheets and the microscopic interaction have not been systematically described.In order to solve this problem,molecular dynamics simulation is employed to study the properties of molybdenum sulfide nanosheets,the dispersion stability of amphiphilic molybdenum sulfide nanosheets in aqueous and the microscopic interaction mechanisms at an oil-water interface.This work provides theoretical support for the oil displacement ability of amphiphilic molybdenum sulfide nanosheets in low and ultra-low permeability reservoirs.The molecular dynamics simulation is used to optimize the optimum size of molybdenum sulfide nanosheets and to study the interaction mechanism of molybdenum sulfide nanosheets at the oil-water interface.Three size models of molybdenum sulfide nanosheets are established to study the interfacial coverage and interfacial tension of molybdenum sulfide nanosheets at the oil-water interface and optimize the size of molybdenum sulfide nanosheets.The adsorption morphology,intersection angle and stress of the optimal molybdenum sulfide nanosheet at the oil-water interface are analyzed.The stress at each point on the nanosheet affectted the intersection angle,which not only affectted the interface coverage but also had a competitive relationship,leading to the fluctuation of the tension at the oil-water interface.The optimal adsorption and covalent structures of amphiphilic molybdenum sulfide nanosheets are determined by quantum mechanics calculation and molecular dynamics simulation.The thickness and stable configuration of amphiphilic molybdenum sulfide nanosheets is determined by experimental measurement and theoretical investigation.The adsorption energy between molybdenum sulfide nanosheets and 18 carbon straight chain alkanes are calculated by quantum mechanics,and the optimal adsorption structure of amphiphilic molybdenum sulfide nanosheets is determined.The total energy of each covalent structure of amphiphilic molybdenum sulfide nanosheet is calculated by molecular dynamics simulation,and the lowest energy structure is determined to be the optimal amphiphilic molybdenum sulfide nanosheet structure.The dispersion stability of amphiphilic molybdenum sulfide nanosheets in an aqueous solution is studied by molecular dynamics simulation.The aqueous solution model of amphiphilic molybdenum sulfide nanosheets with or without surfactant is established.The stability of amphiphilic molybdenum sulfide nanosheets in surfactant solution is studied by model visualization analysis,vertical centroid distance between amphiphilic molybdenum sulfide nanosheets and comparison of energy changes of each system.The dispersion of amphiphilic molybdenum sulfide nanosheets in a surfactant aqueous is determined by studying the density distribution,absorbability and diffusion of the system.To study the compatibility of surfactants and amphiphilic molybdenum sulfide nanosheets aqueous solution,surfactant optimization is performed.The oil-water interface characteristics of surfactant on amphiphilic molybdenum sulfide nanosheets are studied by molecular dynamics simulation.The oil-water interface model and the oil-water interface model of surfactant amphiphilic molybdenum sulfide nanosheet are established.The adsorption morphology of amphiphilic molybdenum sulfide nanosheets,the included angle of oil-water interface,the interaction energy of oil and water and the change of oil-water interface tension in the two groups of models with or without surfactant will be studied to clarify the influence of surfactant on the oil-water interface characteristics of amphiphilic molybdenum sulfide nanosheets.This work will provide guidance for the interaction mechanism of amphiphilic molybdenum sulfide nanosheets at the oil-water interface,and lay a theoretical foundation for the application of amphiphilic molybdenum sulfide nanosheets in oilfield enhanced oil recovery research.