Packed-bed microreactors for understanding of the dissolution kinetics and mechanisms of asphaltenes in xylenes

Comparative Static and Dynamic Analyses of Solvents for Removal of Asphaltene and Wax Deposits above- and below-Surface at an Iranian Carbonate Oil Field

During production from oil wells, the deposition of asphaltene and wax at surface facilities and porous media is one of the major operational challenges. The crude oil production rate is significantly reduced due to asphaltene deposition inside the reservoir. In addition, the deposition of these solids inside the surface facilities is costly to oil companies. In this study, the efficiency of different solvents in dissolving asphaltene and wax was investigated through static and dynamic tests. The analysis of solid deposits from the surface choke of one of the Iranian carbonate oil fields showed that they consisted of 41.3 wt % asphaltene, and the balance was predominantly wax. In addition, the asphaltenes obtained from the surface choke solid deposits had a more complex structure than that of asphaltenes extracted from the crude oil itself. The static tests showed that xylene, toluene, gasoline, kerosene, and gas condensate had the highest efficiencies in dissolving solid deposits; conversely, diesel had a negative impact on dissolving solid deposits. Static tests on pure asphaltene showed that, among the tested solvents, gas condensate and diesel had a negative effect on the solubility of asphaltene. The dynamic core flooding results showed that asphaltene deposition inside the cores reduced the permeability by 79-91%. Among the tested solvents, xylene, gasoline, and kerosene resulted in the highest efficacy in restoring the damaged permeability, and higher efficiency was obtained with an equivalent solvent injection rate of 1 bbl/min versus 3 bbl/min.

An automated microfluidic system for the investigation of asphaltene deposition and dissolution in porous media

Asphaltenes, among the most complex components of crude oil, vary in their molecular structure, composition, and self-assembly in porous media. This complexity makes them challenging in laboratory characterization methods. In the present work, a novel microfluidic device was designed to access in situ transient, high-fidelity information on asphaltene deposition and dissolution within porous media. The automated microfluidic device features three independent 4.5 μL packed-bed microreactors on the same chip. The deposition of asphaltenes was investigated at five different temperatures (ranging from 25-65 °C) in addition to dissociation with xylenes. Our findings demonstrate a decrease in the dispersity of asphaltene nanoaggregates in the porous media when the deposition temperature is increased. Furthermore, the direct quantification of the dissociation solvent was made possible by in situ Raman spectroscopy. The average occupancy of xylenes and xylene-free porous media (or unrecognized sites) was estimated to be 0.41 and 0.66, respectively. It was observed that asphaltenes deposited at higher deposition temperatures are more difficult to dissociate by xylenes than those deposited at lower temperatures. In order to develop efficient remediation treatments in energy production operations, the convoluted behaviours of asphaltenes in porous media must be understood on a molecular level. Automated microfluidic systems have the potential to streamline treatment designs, improve their efficiency, and enable the design of green chemistry in conventional energy production operations.