Effect of ammonium based ionic liquids on the rheological behavior of the heavy crude oil for high pressure and high temperature conditions

Abstract

Heavy crude oil (HCO) production, processing, and transportation forms several practical challenges to the oil and gas industry, due to its higher viscosity. Understanding the shear rheology of this HCO is highly important to tackle production and flow assurance. The environmental and economic viability of the conventional methods (thermal or dilution with organic solvents), force the industry to find an alternative. The present study was constructed to investigate the effect of eco-friendly ionic liquids (ILs) on the HCO's rheology, at high temperature and high pressure. Eight different alkyl ammonium ILs were screened for HCO's shear rheology at the temperatures of 25–100 °C and for pressures 0.1–10 MPa. The addition of ILs reduced the HCO's viscosity substantially from 25 to 33% from their original HCO viscosity. Also, it aids to reduce the yield stress to about 15–20% at all the studied experimental conditions. Furthermore, the viscoelastic property of the HCO was studied for both strain-sweep and frequency-sweep and noticed the ILs helps to increase HCO's loss modulus (G″) by reducing storage modulus (G′), it leads to the reduction of the crossover point around 25–32% than the standard HCO. Mean the ILs addition with HCO converts its solid-like nature into liquid-like material. Besides, the effect ILs chain length was also studied and found the ILs which has lengthier chain length shows better efficiency on the flow-ability. Finally, the microscopic investigation of the HCO sample was analyzed with and without ILs and witnessed that these ILs help to fragment the flocculated HCO into smaller fractions. These findings indicate that the ILs could be considered as the better alternative for efficient oil production, processing, and transportation. • Aliphatic ionic liquids reduce the viscosity of heavy oil significantly. • Ionic liquid with [HSO 4 ] - or [H 2 PO 4 ] - anion shows better efficiency. • Ionic liquids addition with heavy oil converts its solid-like nature into liquid-like material. • Ionic liquids helps fragment the flocculated heavy oil into a smaller fraction. • Greater the chain length of ionic liquid, higher is the tendency on improving flow-ability.