Research On Properties And Rheology Of CO₂ Flooding Produced Liquids

In order to investigate the properties of carbon dioxide flooding produced fluid,a self-developed high-pressure CO2-crude mixing container was used to mix up CO2 and three different kind of crude oil respectively under reservoir condition.After treated by CO2,the properties and rheology of the crude oil and its W/O emulsion is studied by gas chromatograph,DSC,rheological measurement,microscopic observation and other instruments.A brief summery about the impact of CO2 on waxy crude oil was given.The chemical composition changed by evolved gas can inhibit the wax dissolution and increase the wax appearance temperature of waxy crude oil.The size of wax crystals becomes smaller and disperser after treated by CO2,which gives rise to the enhancement of the gel structure and the depravation of the low-temperature flowing property.And the light component content in the crude oil is higher,the qualitative change of the system in all aspects is more unconspicuous.With the increase of the pressure of CO2 during mixing process,the gel structure of the waxy crude oil is gradual increasing,and the low-temperature flowing property is worse.With Caoqiao heavy oil as the object of experiment.the experimental result shows that the change of chemical composition can improve the polarity of Caoqiao heavy oil.The size of asphaltene aggregate and the solvation layer of asphaltene micelle become larger after treated by CO2,leading to the depravation of the flowing property.It is disadvantage to improve the stability and conductivity of asphaltene&n-heptane system.Results of the experiments for the water-in-oil emulsions prepared with waxy crude oil treated by CO2 under different pressure show that the stability of the water-in-waxy crude oil emulsions prepared by the crude oil which is treated by CO2 is strengthened.And the rheology of the waxy crude oil treated by CO2 which is under different pressure and its emulsions changes in similar laws but the rheological variation extent of the emulsions is reducing with the increasing pressure of CO2 during processing.