Study On Carbon Dioxide Dispersion In Miscible Flooding

As an important technology in enhanced oil recovery,carbon dioxide miscible flooding has been used in many oil fields,and has achieved good effects.In order to make carbon dioxide injection better and determine proper flooding parameters,mastering the law of carbon dioxide dispersion is very important.As the theoretical system of carbon dioxide dispersion is imperfect,this paper develops a relatively perfect theoretical system.It will produce great significance for a better understanding of carbon dioxide dispersion and operations of carbon dioxide injection.In terms of carbon dioxide dispersion in one dimensional unidirectional and radial miscible flooding,this paper develops different carbon dioxide convection-dispersion models which consider no adsorption,langmuir equilibrium adsorption and rate-controlled adsorption.So as to solve the mathematical model,Barakat-Clark forward difference and backward difference are used to obtain numerical model.By solving the numerical model,carbon dioxide concentration distribution is obtaind.Then the factors that influence carbon dioxide concentration distribution are studied.Results show that in one-dimensional miscible flooding,carbon dioxide concentration profile exhibits"S"shape at different locations.In radial miscible flooding,the closer away from the entrance section,the smaller will flow area be,the flow rate and carbon dioxide dispersion coefficient will become larger,so carbon dioxide concentration distribution curve will be more sharpened.In finite formation,the larger the dispersion parameter,the sooner when carbon dioxide breaks through will be,and concentration distribution of carbon dioxide in the formation will be more uniform.When considering equilibrium adsorption,the time when carbon dioxide breaks through will be delayed.When adsorption parameter a<b,CO₂concentration curve will be sharpened after CO₂ breaks through;when a>b,CO₂ concentration curve will be loosed after CO₂ breaks through.As porosity becomes smaller and injection pressure becomes larger,the time when carbon dioxide breaks through will become advanced,and concentration distribution of carbon dioxide in the formation will be more uniform.When considering rate controlled adsorption in one-dimensional radial miscible flooding,as dispersion parameter,flow rate and kinetic rate group become larger,adsorptive capacity becomes weaker,the time when carbon dioxide breaks through will become advanced,and concentration distribution of carbon dioxide in the formation will be more uniform.