Comparative analysis of the effect of plant-based and petroleum-based wax inhibition additives on heavy crude oil in the Niger-Delta

Abstract

This study investigates the use of plant-based oils-soybean oil (SO), coconut oil (CO), and their biofuels, and petroleum distillates, namely automotive gas oil (AGO) and premium motor spirit (PMS) as potential wax inhibitors. At various volume concentrations (3 %, 5 %, 10 %), the impact of the additives on the pour point, rheology, and wax deposition of a heavy waxy crude oil sample from the Niger-Delta was investigated. The ASTM standard test procedures were used, using the cold finger apparatus for wax deposition test and paraffin inhibition efficiency determination. It was observed that though all the additives tested could reduce crude oil viscosity, SO and CO had the least effect compared with their biofuels and petroleum distillates (which had the greatest effect). PMS reduced the yield point (YP) significantly at all concentrations, while AGO reduced it only at a low concentration (3 %). The plant oils and biodieselts had a poor effect on YP. Again PMS had the most effect on pour point reduction, followed by AGO. SO and SO biodiesel (SOBD) showed a similar trend, raising the pour point at low concentrations, while reducing the same at higher concentrations. CO and COBD both reduced the pour point at all concentrations. The cold finger wax deposition test ultimately revealed that SO is a good wax crystal modifier. At a high concentration, its paraffin inhibition efficiency is almost comparable to that of AGO and PMS at reduced concentration. Its flow improvement property is however relatively poor, as it could not improve the YP and pour point of the crude oil significantly. In comparison with CO, however, SO shows greater potential for wax inhibition and flow improvement, while AGO and PMS show excellent results. The plant oil biodiesels (SOBD and COBD), however, showed more promise than the original plant oils (SO and CO) in flow improvement, but are less attractive in wax inhibition.