Effect of bio-based flow improver on the microscopic and low-temperature flow properties of waxy crude oil

Wax formation creates flow assurance problems in the production and transportation of waxy crude oil. Flow improvers are added to waxy crude in order to reduce handling cost. Bio-based flow improvers derived from cheap renewable resources are attractive as cost-effective, eco-friendly alternatives to the conventional additives. Natural cashew nut shell liquid extracted from waste biomass (Anacardium occidentale shells) was derivatized and applied as flow improver for waxy crude oil. Effect of the additive on wax formation in crude oil was studied by cross-polarized microscopy, while the change in oil flow properties was evaluated using a rotational coaxial cylinder viscometer. Micrographs of the waxy crude were processed and analyzed with image J software. The microscopic properties of the wax crystals were characterized using Feret diameter, crystal area, aspect ratio, circularity, solidity and boundary fractal dimension. The pour point of doped crude oil was depressed by − 18 °C and the wax area fraction reduced by 40% due to wax inhibitive effect of the additive. The presence of the additive resulted in evolution of smaller, rounder and more regular wax crystals with smoother and more even surfaces indicated by reduction in the Feret diameter, aspect ratio and boundary fractal dimension of wax crystals in doped oil, and an increase in crystal circularity and solidity. The shear stress and viscosity of doped oil were reduced by 86.8% and 85.0%, respectively. The flow improvement effect of the CNSL derivative is linked to its effect on morphology and microstructure of wax crystals in the crude oil.