Control of Asphaltene Deposition by Chemical Inhibitors in Calcite Pore: Molecular Dynamics Approach

Abstract

Asphaltene deposition is a major problem during oil production and transportation that imposes extra treatment costs and reduces oil production. Historically, various chemical inhibitors have been developed to resolve the asphaltene deposition issue. However, the inhibitors are usually effective for a specific type of crude oil and asphaltene since asphaltene's nature is different for various oil samples. To develop a proper chemical inhibitor, the interaction between the inhibitor and asphaltene needs to be explored. This work employs a molecular dynamics (MD) simulation strategy to study asphaltene deposition on a calcite surface considering chemical inhibitors. Two asphaltene structures with potential to form hydrogen bond (A2) and without potential to form hydrogen bond (A3) are considered in this study. The selected inhibitors, including noctylphenol (OP) and 1-butyl-3-methylimidazolium chloride (as an ionic liquid (IL)), can form van der Waals, Coulomb, and hydrogen bonds with asphaltene molecules. The results show that the OP reduces the asphaltene aggregation by attaching to the asphaltene through hydrogen bonds. In the presence of OP, the Lennard-Jones (LJ) and Coulomb energies between asphaltene (A2) and calcite are reduced by 400 and 1000 kJ/mol units, leading to the asphaltene deposition reduction by adsorbing on the calcite surface and providing a hindrance layer. The IL is able to cope with the quadrupole−quadrupole interaction between asphaltene polyaromatic cores and reduce the asphaltene face-to-face aggregation. However, IL cannot provide a hindrance layer near the calcite surface since it does not have a long hydrocarbon tail. Therefore, the combination of inhibitors can benefit the inhibition process as both prevention mechanisms will be active. The 3:1 OP−IL ratio shows the optimum efficiency. At this ratio, inhibitors reduce the aggregation from 20 to less than 10 and the deposition rate from 1 to 0.8 compared to the case without the inhibitors. Also, the deposited aggregates have low compaction with a spherical shape, which is easy to dislodge in a dynamic situation. This research aims to demystify the asphaltene−inhibitor behaviors during asphaltene deposition, which can be a useful practice for designing of future chemical inhibitors for flow assurance issues.

High Throughput Prescreening of Asphaltene Chemical Inhibitors Using Molecular Dynamics Approach

“…For instance, the periodic boundary conditions need to be removed using “ gmx trajconv ” and “ -pbc whole ” function, and any molecules except the target molecules subjected to aggregate or deposit, asphaltene in our case, need to be eliminated from the box. The accuracy and reliability of the scripted code were verified in our previous papers. , …”

“…The accuracy and reliability of the scripted code were verified in our previous papers. 66,82 The code considers asphaltenes to be aggregated if the closest atom of two adjacent asphaltenes is less than 0.35 nm (the value is reported in the literature). 45 From the prediction of aggregates, the code can measure the average aggregation number, aggregate size, and aggregate density.…”

Performance Investigation of Asphaltene Adsorption at a Carbonate Rock Surface: Spectroscopy Experiment and Molecular Simulation

“…Besides the experimental investigation, the theoretical calculation of molecular simulation (MS) can be utilized as an available method to allow direct observations of the interfacial phenomenon. With the rapid development of information technology, the MDS method has become a powerful tool to explore and reveal interaction mechanisms at the molecular scale in a wide range of conditions. , A series of studies have been reported on the interfacial investigation of asphaltene, including asphaltene precipitation in CO 2 flooding by Fang et al, the control of asphaltene deposition by chemical inhibitors in calcite pores by Ghamartale et al, the diffusion and distribution of asphaltene on a quartz surface by Wu et al, C5Pe adsorption configurations on silica surfaces by Ji et al, and calcite–organic molecule–water interaction mechanism by Chai et al Hence, MDS methods can serve as useful tools to provide microscopic findings to confirm the macroscopic experimental results.…”

Influence of Ionic Liquids on the Aggregation and Preaggregation Phenomena of Asphaltenes in Model Solvent Mixtures by Molecular Dynamics Simulations and Quantum Mechanical Calculations: The Effect of Cation’s Shape and Size

“…This effect is not observed for octyl phenol, whose main interaction with asphaltenes is through hydrogen bonding. This group also studied the influence of the same ionic liquid on deposition of asphaltenes over calcite pores 17 and concluded that, although the IL additive reduced the faceto-face aggregation of asphaltenes, it did not prevent deposition because it was unable to form a barrier layer near the calcite surface due to its short alkyl side chain. In both cases, the only solvent tested was n-heptane, which is a challenging test for the additive but not the solvent environment that best mimics crude oil.…”