Application of Synthesized Oleic Acid-Maleic Anhydride-Aniline Copolymer as a Pour-Point Depressant for Flow Assurance in Indian Waxy Crude Oil: A Comparative Study with Commercial Pour-Point Depressants

Summary Waxy crude oil contains a significant amount of paraffinic hydrocarbons, which can crystallize during transit when the temperature drops below the wax appearance temperature (WAT). This can cause increased viscosity, flow restriction, pipeline obstruction, and financial losses. By altering wax crystallization, pour-point depressants (PPDs) and wax inhibitors are frequently used to lessen these difficulties. However, many traditional PPDs have poor biodegradability and could be hazardous to the environment. This research work is concerned with the preparation of a biodegradable PPD made from oleic acid-maleic anhydride-aniline (OMA) and its application to improve the flow properties of Indian waxy crude oil at low temperatures. The performance of OMA was evaluated against that of a commercial ethylene-vinyl acetate (EVA)-based PPD (PPD-A). OMA was synthesized via free-radical polymerization and analyzed using advanced permeation chromatography (APC), thermogravimetric analysis (TGA), dynamic light scattering (DLS), X-ray diffraction (XRD), carbon/hydrogen/nitrogen/sulfur (CHNS) elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and 1H nuclear magnetic resonance (1H NMR). Wax crystal formation behavior and wax morphology were studied by differential scanning calorimetry (DSC) and cross-polarized microscopy. At 650 ppm, OMA and the commercial EVA caused a 9°C drop in the pour point of crude oil. OMA showed a 71% reduction in wax deposition, which was higher than that for commercial PPD (64.16%) at this concentration. OMA also had an excellent influence on the rheology of the crude oil, making flow restart easier and with lower energy consumption. Observations under microscopy revealed that OMA could break larger wax crystal clusters and form smaller ones. Therefore, OMA can be considered a better wax deposition inhibitor and flow enhancer than the commercial EVA. Consequently, OMA can be viewed as a prospective PPD for waxy crude-oil flow improvement.