Static and dynamic evaluation of a novel solution path on asphaltene deposition and drag reduction in flowlines: An experimental study

Abstract

Asphaltene, as a destructive fraction of crude oil, reduces productivity by deposition in wells, pipelines and porous media and causes additional pressure drop on the fluid flow. The AUT-Force 110 multifunctional additive has been developed for the first time by the team of researchers of this paper, which has been identified as an inhibitor, dispersant and solvent for asphaltene sediment and its effectiveness has previously been proven. In this study, first, two crude oil sample from southwestern fields of Iran were selected. The selection criteria were differences in asphaltene molecular structure. The structure and molecular geometry of asphaltene have been determined using elemental analysis, Fourier-transform infrared spectroscopy (FTIR) and Carbon-13 (C13) nuclear magnetic resonance test. Then asphaltene was coated onto metal powder surface (crude oil pipeline simulator) by means of a unique process. The steel coated with asphaltene was then washed with AUT-Force 110 to determine its effectiveness in separating the asphaltene adsorbed onto the metal surface. SEM images clearly showed that the multifunctional additive, regardless of asphaltene type, was able to change the mechanism of asphaltene adsorption at the metal surface from multilayer to single layer. In addition, Energy-dispersive X-ray spectroscopy (EDX) demonstrated that in the presence of AUT-Force 110, iron (as the main constituent of metal powder) would increase by more than 12% in acidic asphaltene and more than 4% in basic asphaltene. AUT-Force 110 can also remove acidic and basic groups of asphaltene from metal powder surface by altering the electrostatic properties of the surface. The results of the spectroscopy showed that in addition to polar compounds, the multifunctional additive also reduces the amount of aliphatic and paraffinic functional groups at the surface of metal powder. In addition to static conditions, the efficiency of AUT-Force 110 in fluid flow condition was also investigated. For this purpose, two separate laboratory setups were designed and implemented. In the first setup, the surface charge of asphaltene flocs was determined in the presence of an electric field and the results of the zeta potential measurement test were verified. Asphaltene was often observed around the positive electrode (cathode), indicating that the predominant charge of asphaltene samples is negative. However, the higher the number of nitrogenous agents in asphaltene, the lower the amount of asphaltene accumulated around the cathode. In the second setup, a pipeline with accessories was designed to investigate the performance of the AUT-Force 110 as a drag force reducer in the pipeline. The reduction of drag force by AUT-Force 110 occurs with increasing fluid flow rate in the pipe. An increase in the flow rate is equivalent to growth in fluid flow turbulence, which could ultimately provide a better environment for drag reducer to function more efficiently.