Research And Analysis Of The Influencement Of Carbon Dioxide Flooding On Asphaltene Precipitation

During the developing of Heavy oil reservoir, ashpaltene can easily precipitate fromcrude oil system because of the change of pressure, temperature, and oil fractions factors,causing reservoir damage and the pipeline blocked, especially in the carbon dioxide floodingwell, the injection of carbon dioxide can break up the balance of oil system and causeprecipitation of asphaltene.The physical properties of three heavy oil sample from Shengli Oilfield carbon dioxideFlooding well are obtained by measuring density, freezing point and the content of resin andasphaltene, On this basis studying the influence of alkane, fragrant, resin, asphaltene, clay onprecipitate threshold by viscosity method and conductivity method. Using carbon dioxide coreflooding simulation device, through the orthogonal experimental design, research and analysisthe influence of different permeability, temperature, displacement pressure and displacementvelocity on amount of precipitation of asphaltene in cores, then compare these factors byrange analyze. Analysis the asphaltene precipitating mechanism basis on the above problemand develop removers of asphaltene, Existing removers have several problems, such as needlarge amount, short operating cycle, high toxicity and environmental damage. Using water,organic solvents, emulsion and dispersing agents to prepare low toxicity removers ofasphaltene precipitation, developed removers for asphaltene precipitation with good stability，obvious clear performance on asphaltene precipitation by evaluating the stability of theemulsion, the speed of dissolution of the asphaltene. The results show that removersdeveloped in emulsifier content of8%, and stirring speed of800r/min will be better. Usingcore displacement apparatus to simulate the process of cleaning near wellbore asphalteneprecipitation, experiment results shows that the recovering rate of permeability of corerecovers can reach40%.