Effect of Additives on Asphaltene Precipitation

Oil components are complex mixtures of different hydrocarbons. Deposition of heavy complex organic components of crude oil may cause several problems in production, transportation and treatment processes of crude oil. Asphaltene precipitation is a kind of these deposits. Asphaltenes are complex organic mixtures with relative polarity. Asphaltenes in crude oil are as colloidal particles which are stabilized by oil resins. Any change in thermodynamic conditions like pressure, temperature and composition may cause colloidal destabilization of oil and results in formation of asphaltene precipitation which may cause several problems such as: Reduction of permeability and oil production, canalization of oil flow and increasing pressure drop, velocity reduction and blocking well bores, increasing oil viscosity in low temperatures and disability in pumping through pipelines. These problems require huge amount of costs to be solved. So, finding appropriate solutions such as increasing chemical inhibitors to prevent or reduce amount of deposition is well recognized around the world. In this work, effect of different concentrations of seven additives on formation of asphaltene precipitation in existing crude oils (Bangestan, Cheshmeh Khosh and Asmari crude oils) has been examined. Experiments have been based on ASTM-D3279-97 standard method. The used additives are n-Heptane, n-Hexane, Toluene, O-Xylene, P-Xylene, Naphthalene and 8-Hydroxyquinoline. Based on the experimental results, adding n-heptane and n-hexane to crude oils will result in formation of asphaltene precipitation and by incrementing these n-Akanes’ concentrations, percent of precipitation will be increased until a constant amount is reached. Toluene, O-Xylene and P-Xylene are industrial solvents which were used in the experiments. The amount of asphaltene precipitation will be decreased by adding these solvents to existing oils. Also, Naphthalene and 8-Hydroxyquinoline decreased asphaltene precipitation in range of conducted experiments due to their aromaticity.