Molecular Simulation Studies Of The Mechanism During Flue Gas Displacement Of Reservoir Oil

In order to satisfy the needs of the speeding up economic development and petroleum resources,seek a kind of mining effect,the economic benefits of high oil recovery technology is imminent.Flue gas injection oil production can reduce greenhouse gas emission,increase oil recovery and it is a win-win economic and environmental engineering.However,the study of the flue gas flooding oil,there is still less.Furthermore,the microscopic mechanism of flue gas flooding is not clear,greatly limits the application of flue gas enhanced oil recovery.The micro-mechanism studying of flue gas flooding by molecular simulation method,can make up for the lack of oil and gas flooding mechanism theory research and provide theoretical guidance for flue gas flooding.The micro-process of oil volume expansion showed that dodecane molecules chain extension which in the interface between oil and gas would provide more space for gas diffusion,so more nitrogen and carbon dioxide went into the oil phase.Through the calculation of between different molecular interactions in nitrogen-dodecane system and carbon dioxide-dodecane system,it could be seen that the interaction between gas and dodecane energy was one of the main reasons for the volume expansion and dispersion forces in the non-bonded interaction energies accounted for dominance.Based on the results of crude nitrogen and carbon dioxide swelling,we found that swelling of crude oil was better in carbon dioxide than that in nitrogen and carbon dioxide solubility in oil was higher.Research on the process of flue gas displacing oil,it could be found that the whole oil displacement process could be divided into several stages.The first was that carbon dioxide adsorbed onto the rock surface and nitrogen diffused into the oil phase after gas went into nano-pore.After that,the carbon dioxide molecules of oil stripped the oil molecules adsorbed on the wall surface,and then gas diffused into the oil phase.This leaded to the volume expansion of oil,the mobility of oil drop increasing,which was beneficial to the displacement of crude oil.The number of the oil molecules adsorbed on the pore wall gradually decreased.The part of oil molecules dissolved into the flue gas,and the other part was displaced to the right side of nano-channel.Through the analysis of the density distribution and the radial distribution function of oil molecules,the microscopic mechanism of flue gas flooding was studied from the perspective of quantity.Finally through the radial distribution found along the channel radius of nitrogen and carbon dioxide molecules,it can be found that carbon dioxide in flue gas stripped oil on the wall surface and swelled crude oil and nitrogen provided driving energy during oil displacement.Oil displacement process about different proportion of flue gas were also studied in this chapter,the study found that mixed with the ratio of 1:2 of nitrogen and carbon dioxide has the best oil displacement effect.In addition,this chapter also analyzed the influence of temperature and pressure on flue gas flooding,it was found that increasing the pressure and temperature are favorable for oil displacement.