(179z) Asphaltene Adsorption at the Oil–Rock Interface in Sandstone Reservoirs

Asphaltenes are polar, surface-active components of heavy oil that strongly interact with rock surfaces. Their deposition at the oil–rock interface disrupts fluid flow and alters rock wettability, reducing the efficiency of enhanced oil recovery (EOR) operations. Additionally, asphaltene adsorption can lead to downstream challenges such as catalyst poisoning, pipeline blockages, and equipment failure. A molecular-level understanding of asphaltene adsorption is therefore essential to develop effective mitigation strategies and design better solvents. In this study, we probed the structural and energetic behavior of model asphaltenes in the oil phase (dodecane) near the silica surface representative of sandstone reservoirs using molecular dynamics simulations. We employed umbrella sampling to calculate the potential of mean force (PMF) profiles and corresponding adsorption/desorption energy barriers for five model asphaltenes (asphaltene-phenol (APH), asphaltene-pyrrole (APY), asphaltene-thiophene (ATH), quinolinohopane (QHP), and thio-isorenieratane (TIR)) as well as dodecane (DOD). We found that the arrangement of oil-phase molecules near the surface affects the adsorption of asphaltene molecules, leading to competition in which the molecule exhibiting stronger interaction than the oil phase preferentially adsorbs. We observed that APH, QHP, and ATH preferentially adsorb near the surface, TIR remains in the oil phase, and APY shows equal preference between the surface and oil phase. The adsorption strength of asphaltenes is largely influenced by heteroatom–surface interactions. Asphaltenes containing polar heteroatoms (APH, QHP, and APY) form more hydrogen bonds with the surface, resulting in higher desorption energy barriers than non-polar counterparts (ATH and TIR). Our results also revealed that the desorption energy barrier of asphaltenes correlates positively with the number of hydrogen bonds formed with the surface. We observed that the anchoring mechanism of the asphaltenes significantly affects their orientation near the surface. Asphaltene with aliphatic chain anchoring (APY, TIR) lie flat along the surface, while those with heteroatom anchoring (APH) adopt a near-perpendicular orientation.

These insights contribute to understanding interfacial behaviour and can support the development of novel solvents for more efficient EOR and refining processes.

References:

• Shubham Chobe, Prashil Badwaik, Ateeque Malani. Probing the energy landscapes and adsorption behavior of asphaltene molecules near the silica surface: Insights from molecular simulations. Fluid Phase Equilibria 2025, 591,114295. https://doi.org/10.1016/j.fluid.2024.114295
• Prashil Badwaik, Shubham Chobe, Ateeque Malani. Computational Study of Asphaltene Adsorption on Carbonate Surface: Role of Molecular Structure and Oil Phase. Energy & Fuels 2024, 38 (18) , 17355-17369. https://doi.org/10.1021/acs.energyfuels.4c01744
• Shubham Chobe, Prashil Badwaik, Ateeque Malani. Adsorption of Light Oil on Rock Surfaces: A Molecular Dynamics Study. 2024, 515-523. https://doi.org/10.1007/978-981-97-5419-9_44