Experimental investigation of wax deposition from waxy oil mixtures

Abstract

Wax deposition is a common problem in oil pipelines and production systems. 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. Results suggested that WAT reduced with increasing inhibitor concentration, with 800?ppm being the optimum. Also, chloroform–toluene–ethylene vinyl acetate (EVA) mixture with 30, 30, and 40 wt% had the highest performance and reduced the WAT to 16.7?°C. Mixtures of toluene—EVA with acetone, p-xylene, and disulfide oil (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. EVA–toluene, 2 wt% DSO, 2 wt% acetone, and 2 wt% p-xylene mixtures reduced the deposition to 23.33, 21.71, 32.14, and 12.5%, but addition of 2 wt% of EVA–DSO–acetone mixture reduced deposition to 35.74%. At similar operating conditions, flow turbulence has greater impact on reducing wax deposition, and its effect is enhanced using a proper inhibitor.