Poly(ethylene-co-vinyl acetate)(EVA) as wax inhibitor of a Brazilian crude oil: oil viscosity , pour point and phase behavior of organic solutions

摘要

Several techniques have been used to minimize the problems caused by the wax deposition , and the continuous addition of polymeric inhibitors is considered an attractive technologycal alternative. The addition of copolymers like polyacrylates, polymethacrylates or poly(ethylene-co-vinyl acetate)(ENA) permit to inhibit th deposition phenomenon; no9nehteles , this effect is specific, i.e.similar copolymers present different performace depending on their physical-chemical properties in solution. In this work , the influence of the EVA vinyl acetate content on the viscosity and the pour point of a Brazilian crude oil were ealuated . A correlation between both results was also obtained. The phase behavior and the solubility parameter of EVA copolymers, with different vinyl acetate contents, were investigated in various solvents together with an evaluation of the eficiency of these copolymers as pour point depressants for two different samples of crude oil. EVA copolymers containing 20, 30,40 and 80 wt.% of vinyl acetate were used and tests with the crude oil were carried out using 50, 500, 1000 and 5000 ppm of EVA as additive. The results obtained from viscosit influence in the reduction of oil viscosit, at an optimm concentration. The pour pont results revealed EVA 30 to be the most efficient. The results obtained from both experiments showed that the viscosity and the pour point behaviors do not show good correlation . Not only the solubility parameter and the vinyl acetate content, but also the molecular weight and polydispersty have an important influence on both phase behavior and pour point depression. Furthermore, it was confirmed that the additive must present a reduced solubilit at a temperature close to the crude oil cloud point. This however, is not the only factor that determines the eficiency of the addivtive as paraffin/was deposition inibitor