Rules of Gum and Asphaltene Precipitation in CO2 Miscible Flooding: A Case Study of Donghe 6 Reservoir

A set of high temperature and high pressure miscible and precipitation experimental device was designed, and a new judgment method of miscible flooding was proposed. By establishing a discrimination diagram of formation type changing with the proportion of injected CO2, it qualitatively judged whether the injected gas and stratum fluid were miscible, and characterized the change law of gum and asphaltene through the method of relative precipitation amount. The experiment shown that the mechanism of CO2 flooding in Donghe 6 reservoir was primary contact miscible; The relative precipitation of asphaltene increased rapidly and then decreased slowly with the increase of injection proportion, while the relative precipitation of gum decreased first and then increased with the increase of injection proportion; After gas injection, the reservoir was exploited by depletion. With the pressure decreasing, saturated hydrocarbons were preferentially recovered, and the asphaltene content of formation crude oil increased rapidly.