Study On Effect Of Surfactants And Ferric Salts On Viscosity And Colloid Stability Of Crude Oils

The objective of this study was aim to viscosity reduction and transport capacity increase in the pipeline for the HJ, DH and RD crude oils. First, several surfactants and a self-made Schiff base were used to study the effect on viscosity of three crude oils. For HJ crude oil, all the selected surfactants caused viscosity increase except Cetyltrimethyl Ammonium Bromide (CTAB). For DH crude oil, Cetylpyridinium Chloride had the most significant effect on the viscosity reduction. The Schiff base could obviously reduce the viscosity of RD crude oil.Secondly, three ferric salts including Fe(NO₃)₃, FeCl₂ and FeCl₃ were selected. The effect of ferric salts on the viscosity change, mass fraction normalized conductivity, composition and molecular weight of SARA fractions in HJ and RD crude oil was studied in accordance with the type, concentration of ferric salts and solvents. It was showed that the ferric salts could increase the viscosity of HJ or RD crude oil more or less. The increase in viscosity was more significant when ferric salts was dissolved in methanol than in DMF, and the effect of Fe(NO₃)₃ and FeCl₂ on the viscosity increase was more obvious than that of FeCl₃. As the concentration of ferric salt increased, the colloid stability parameters (CSP) of the residue decreased. This proved that the addition of ferric salt accelerated the asphaltene coagulation in the oil. It was speculated that aggregation caused resin turn to asphaltene as the content of asphaltene of the residue system increased after the addition of ferric salt. And as the molecular weight of asphaltene increased, it was proved that ferric salt accelerated the aggregation of asphaltene.In addition, the conductivity of asphaltene dissolved in toluene increased. That's because the polarity and conductance of asphaltene increased as the ferric salts. In a word, the invasion of ferric salts into the crude oil or residue would accelerate the aggregation and coagulation of asphaltene and ultimately caused the system viscosity to increase and colloid stability to decrease.