The Study Of Selective Behavior Of ScCO₂ Flooding In Oil Recovery By Molecular Dynamics Simulations

Supercritical Carbon Dioxide?scCO₂?flooding is a new technology widely used in petrochemical field.ScCO₂ has potential advantages which is attracting the extensive attention from experts and researchers worldwide.The application of CO₂ bring a glimmer of hope for environmental pollution and crisis of petroleum resource.However,the interaction between CO₂ and oil reservoirs during the process of CO₂-enhancing oil recovery?CO₂-EOR?is complex,and this confusion limits the deepening of theories and application.This thesis adopted molecular dynamics simulations to study the dissolving and detachment mechanism with CO₂/oil/silica surface models.In this work,we examined the high selectivity of CO₂toward the apolar components of crude oil for the well understanding of mechanism.In this work,the mechanism of oil detachment by CO₂ at different temperatures?303 K,323 K,343 K,363 K and 383 K?was investigated.The results showed that there existed an optimum range of temperature for CO₂ to detach the oil film from the silica surface and improve oil mobility.Mobility of oil molecules could be improved effectively by CO₂molecules when the temperature was around 343 K.High selectivity toward the apolar components is one of main features of CO₂.We gave insights into the mechanisms of CO₂ selective extraction inducing the wettability alteration of an oil reservoir.The results indicate that CO₂ could disrupt the structure of crude oil.As a result,the polar components of crude oil remained on the oil reservoir rock surface.Next,the wettability of the rock surface was further investigated,and the results indicate that the wettability of the rock surface altered from hydrophobic to hydrophilic after CO₂ flooding.We carried out MD investigations on the selective behavior of CO₂ for the multicomponent which contained asphaltene,resin and alkane.We obtained series of oil adsorbed structures that is expected to facilitate the preparation of interaction with CO₂flooding.Furthermore,the asphaltene precipitation process and mechanism in CO₂ flooding were studied from the micro-perspective.The research could provide clues for further studies on the application of CO₂ flooding.