رضا آذین

Wax deposition is a common problem in oil pipelines and production systems. Wax deposition on the pipe walls reduces the effective cross section for oil flow, leading to increased repair costs, reduction and sometimes stops in oil production rate. In this study, impact of water cut, mixing rate, chemical inhibitor, and time on wax deposition were investigated in a cold finger setup. Effect of different chemical inhibitors on wax appearance temperature (WAT) was studied using viscometry and differential scanning calorimetry techniques. Disulfide oil (DSO), toluene, ethylene vinyl acetate (EVA), acetone, chloroform, methyl de-ethanol amine, p-Xylene and their mixtures used as chemical solvent. In addition, the influence of DSO, EVA copolymer, SiO2 and clay nanoparticles on rheological properties of waxy oils are investigated. The viscoelastic modulus, viscosity, pour point, surface tension and yield stress of different waxy oil samples were measured. Results indicated that 800 ppm of DSO has a good potential for reducing WAT and wax deposition mass. In addition, by using 800 ppm DSO, surface tension of original oil was reduced from 24.6 to 23.1 N.m-1, viscosity was decreased more than 90.15%, and elastic modulus at 26°C was reduced from 15600 to 347 Pa. Also, chloroform – toluene –EVA mixture with 30, 30, and 40 wt% had the greatest performance and reduced the WAT to 16.7°C. Mixtures of toluene – EVA with acetone, p-Xylene, and DSO, followed next. Moreover, deposition decreased with increasing temperature difference between oil and pipe at constant cold surface temperature and increased upon increasing temperature difference at constant oil temperature. Wax deposition in two-phase system was lower than in single-phase system, but increased by increasing water cut. It was observed that the gel point, pour point, viscosity, gel strength, and yield stress decreased upon addition of these additives to waxy oil. It was found that rheological properties of oil samples impro