mostafa dehghanizadeh

One of the most important issues in EOR is asphaltene deposition. Asphaltene is partly dissolved in oil, partly in steric-colloidal form and partly in micellar form depending on the composition of crude oil. Adding dispersing agents to oil, which are functionally similar to natural resin, prevents the aggregation of asphaltenes in crude oil. Inhibition strength is a capability of the inhibitor to delay formation of asphaltene flocculates, which depends on the interaction between the inhibitor and asphaltene particles. In this study, the onset of asphaltene precipitation was evaluated using a viscometric method in the presence of three types of inhibitors. In order to determine stabilization (dispersion) strength, the context of “effective adsorption point” of inhibitor is introduced by the use of the shear effects of asphaltene aggregates. The results showed that the inhibitor was adsorbed on asphaltene micelles and the stabilization strength increased with increasing inhibitor concentration. The comparison between colloidal instability index (CII) and the stabilization strength of the inhibitor indicated that the inhibition and stabilization strengths of the studied inhibitors were much higher than the natural resins.

The organic deposition particularly asphaltenes has many detrimental effects on the oil industries, such as plugging in pipelines, wellbore and facilities and subsequently, considerable reduction in well productivity.Asphaltenes are the most polar fractions, which they have been dispersed as colloidal clusters in crude oil. The accumulation of these clusters lead to the flocculation of colloids, and accordingly, formation of precipitation. Adding inhibitor is one of the ways to prevent clustering of asphaltene precipitation in crude oil. In this study, the effect of inhibitors to prevent asphaltene precipitation was investigated by viscometric method. At first, the different concentrations (1000 ppm, 2000 ppm, 10000 ppm and 20000 ppm) of some aromatic, anionic and nonionic inhibitors were prepared in a dead crude oil sample, and then the inhibition strength of samples was measured. The results showed that inhibition strength of inhibitors in low to moderate (1000 ppm – 10000 ppm) concentrations has a regular pattern, and it is associated with functional groups in chemical structure of inhibitors.