Improvement of Flow Properties of Waxy Crude Oil through Pipeline Using Biodegradable Pour-Point Depressants Synthesized from Plant-Based Fatty Acid: Modeling and Application Studies

Summary Production and transportation of waxy crude oil pose significant flow assurance problems due to wax or paraffin deposition in pipelines, especially at lower temperatures, which lead to complex rheological properties of crude oil. Pour Point Depressants (PPDs) improve crude oil flow and modify the wax crystallization process are essential processing aids in resolving these problems. In the present research, polyethylene glycol (PEG)-based fatty esters as environmentally friendly PPDs are synthesized using stearic acid [polyethylene glycol stearate (PEGS)] and lauric acid [polyethylene glycol laurate (PEGL)] to address the limitations of nonbiodegradable, toxic, and conventional PPDs. The synthesized PPDs are characterized through Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and dynamic light scattering (DLS) studies. The efficiency of PEGS and PEGL having short and long alkyl groups is evaluated by determining pour point, rheology, differential scanning calorimetry, and wax deposition studies of Indian crude oil. PEGS shows a significant drop of 15°C at a minimum dosage of 600 ppm, while PEGL produces a reduction of 12°C. Both PEGL and PEGS significantly decrease viscosity, with reductions of 57–76% at 30°C. Yield stress drops by more than 30% at 30°C after treatment by both PPDs. PEGS is more efficient than PEGL because its longer alkyl chains can more closely mimic wax particles. The Casson model, representing shear-thinning behavior, better explains the behavior after doping with PEGS and PEGL, while untreated crude oil is found to follow the Bingham plastic model. Density functional theory (DFT) simulations show that the wax crystals are more likely to interact with PEGS or PEGL than to combine with other wax molecules. Additionally, studies conducted under the OECD (Organization for Economic Cooperation and Development) standard reveal that PEGS and PEGL are biodegradable. This research work presents a promising, environment-friendly approach toward the flow assurance of waxy crude oil.