Visbreaking of Heavy Oil in a Mixed Solvent of Subcritical Water and Light Aromatics

Abstract

To achieve high-efficiency viscosity reduction in a mild hydrothermal environment, the visbreaking of heavy oil in a mixed solvent of subcritical water (sub-CW) and light aromatics was investigated. By solubilizing sub-CW in heavy oil, the dealkylation involved in visbreaking follows not only a free radical mechanism but also an ionic mechanism. The further introduction of light cycle oil rich in light aromatics but containing olefin groups has a complicated influence on visbreaking. Because of the presence of olefin groups, the viscosity reduction efficiency is initially reduced. In addition, the condensation to asphaltenes is promoted in the late visbreaking stage. However, these adverse effects are offset by the promotion of the solubilization of sub-CW in heavy oil by light aromatics. With enhanced dealkylation in both free radical and ionic mechanisms, a viscosity reduction rate of over 90% and reduced asphaltene formation can be obtained in the middle stage of visbreaking.

A Review of High‐Temperature Foam for Improving Steam Flooding Effect: Mechanism and Application of Foam

“…Moreover, the addition of surfactant has great potential to reduce the interfacial tension (IFT) between oil and water, thereby reducing the surface free energy between oil and water, emulsifying heavy oil into water, and promoting the fluidity of heavy oil emulsification, thus producing more oil. [21][22][23] However, surfactants will interact with components heavy oil and rock surface. Molecular dynamics (MD) can be used to understand the interaction between different distillate/heavy oil/asphalts and surfactants and is widely used to reveal the wettability changes of reservoir rocks at molecular scale.…”

“…The population balance model was designed to only correct k rg or μ g in porous media. These two parameters are always interrelated in Darcy's law, such as in Equation (23). This equation can be considered effective in the liquid phase, but it is problematic in the gas phase because it is discontinuous.…”

Continuous Visbreaking of Heavy Oil in the Presence of Hot Compressed Water

“…Visbreaking involves many types of free radical reactions, which can be roughly divided into opposite processes of dealkylation and condensation . Dealkylation consists of a series of elementary reactions, such as the homolytic C–C cleavage of alkyl substituents of aromatics to form primary alkyl C radicals, the H-abstraction of primary alkyl C radicals from another heavy oil molecule to form secondary alkyl C radicals, and the β-scission of the formed secondary alkyl C radicals. ,, As dealkylation occurs, the alkyl substituents connecting the aromatic segments of the heavy oil molecule are broken or shortened. Consequently, the viscosity of the heavy oil is reduced, while the yield of light components is increased.…”