Drag Reduction of Emulsified Acid System: Leveraging Carbon Nano Dots (CNDs) as Drag-Reducing Agents (DRAs) for Improved Pipeline Performance

Carbon nanodots (CNDs) are promising materials that are gaining widespread use in various applications within the petroleum industry, including enhanced oil recovery, nanofluid applications, corrosion inhibition, lubrication, and environmental remediation. This study proposes an innovative approach to reducing the viscosity and drag of EAS in pipes by incorporating CNDs into the EAS. The results are very promising in terms of reducing the viscosity and drag reduction of EAS, which leads to improved flow efficiency, saves energy, delivers acid deeper into the formation, improves the wormholes, and reduces the operational cost. The objective of this study is to utilize carbon nanodots (CNDs)as drag-reducing agents (DRAs) for the emulsified acid system (EAS) in pipes. CNDs are environmentally friendly and widely available, easy-to-synthesize nanomaterials that possess unique properties and are utilized in various applications across different industries. CNDs are characterized by their biocompatibility and chemical stability, and the CNDs’ sizes are usually less than 10 nanometers. Several experiments have been conducted to investigate the utilization of CNDs as DRAs for the EAS. Firstly, EAS was prepared based on a commercial formulation. Then, the developed EAS was initially tested for conductivity and drop-test to ensure that the continuous phase of the emulsion (outer phase) is diesel. After that, the thermal stability for the range of temperatures and the rheological properties of the EAS were evaluated to meet the criteria of field operation. Then, flow experiments of EASs were conducted before and after adding the DRAs (CNDs) to investigate the effect of CNDs on reducing the drag of EASs. The results show that CNDs can work as viscosity reducers as well as DRA for the EAS. Adding the CNDs to the EAS reduces the viscosity at two different HCl concentrations (15 and 20%). CNDs reduce the EAS viscosity in the presence of corrosion inhibitors as well as other additives such as iron controls, showing their compatibility with field formulation. The drag reduction was achieved in the range of temperatures investigated in this study. The conductivity, drop-test, stability, and rheology experiments were conducted again for the sample taken from the flow loop after the flow experiment, and the results were consistent, ensuring CNDs work as DRA. The developed EAS with CNDs was robust in terms of field mixing procedures and thermally stable. The CNDs can be used as DRA for the EAS, which will reduce the drag in pipes, increase pumping rates, and save energy.