Analysis of Viscous Mechanism of Heavy Oil Based on Density Functional Theory (DFT)

Abstract

Density functional theory (DFT) in quantum mechanics is widely used in the calculation of interaction energy between molecules due to its high accuracy and relatively small amount of calculation, and plays an important role in catalysis, metal coordination, supramolecular arrangement and stacking and other fields. The viscosity and flow characteristics of heavy oil are closely related to its internal composition and structure. However, the composition of heavy oil is very complex. This article focuses on the analysis of the main components and structure of heavy oil, and further studies the viscosity inducing and viscosity reducing mechanisms of heavy oil. Using the B3LYP scheme of density functional theory algorithm in quantum chemistry ab initio Gaussian-03 program ω 97 basis groups were fully optimized for the above model compounds and hydrogen bonding interaction models. Structural optimization of resin and asphaltene molecules was carried out using B3LYP/6.31G (d. p), with a minimum frequency of positive values and no imaginary frequencies, indicating that the optimized structure is stable. Through analysis, the polar group of resin and asphaltene in heavy oil is the main structure factor of viscous oil. The intermolecular van der Waals forces, π−π forces between aromatic layers, and hydrogen bonding are the main forces between heavy oil molecules. The main factors causing viscosity in heavy oil are the strong interaction force between large molecules and aggregated supermolecules, and the difficulty in thermal movement; The stacking, entanglement, interpenetration, and curling of macromolecular chains and circular molecules further increase the flow resistance, which is also an important factor in increasing the viscosity of heavy oil. Clarifying the viscous mechanism of heavy oil can lead to targeted molecular design of heavy oil viscosity reducing agents, significantly improving the viscosity reduction rate of heavy oil.

Copyright 2023, IFEDC Organizing Committee.

This paper was prepared for presentation at the 2023 International Field Exploration and Development Conference in Wuhan, China, 20–22 September 2023.

This paper was selected for presentation by the IFEDC Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the IFEDC Technical Team and are subject to correction by the author(s). The material does not necessarily reflect any position of the IFEDC Technical Committee its members. Papers presented at the Conference are subject to publication review by Professional Team of IFEDC Technical Committee. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of IFEDC Organizing Committee is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of IFEDC. Contact email: paper@ifedc.org.