Enhancing the properties of heavy crude oil in the Maysan field using low molecular weight solvents in a high-speed extraction unit equipped with top baffles

Abstract

Heavy crude oils present major challenges in transportation and front-end processing due to their extremely high viscosity and low API gravity. This work introduces an integrated experimental–statistical–mechanistic framework to evaluate the effect of four low–molecular-weight solvents-toluene, xylene, light naphtha, and n-hexane-on the rheology and density of Missan heavy crude oil using a high-speed baffled extraction unit designed to ensure uniform mixing. Bench-scale experiments were performed at solvent loadings of 4–12 wt% and temperatures of 15–45℃, with viscosity and API gravity measured before and after dilution. Aromatic solvents (toluene) demonstrated superior upgrading performance, achieving viscosity reductions of 63.2% at 25 ℃ and 63.4% at 35 ℃, and API increasing of 5.3°API at 12 wt% loading and all operating temperatures. One-way ANOVA confirmed that solvent type had a highly significant influence on both viscosity and API gravity across all temperatures (p < 0.0001). Predictive viscosity–temperature correlations of Arrhenius type (μ =Ae^−BT,R² > 0.996) and linear dose–response models (VR =a +bC) captured the observed rheological behavior with high fidelity. Mechanistic analysis attributes the superior efficacy of aromatic solvents to strong π–π interactions enabling asphaltene peptization, while aliphatic solvents act primarily through dilution. The results define solvent-selection and dosage windows relevant to pipeline hydraulics and field operations, and demonstrate that optimized aromatic–aliphatic co-blends provide a tunable, low-complexity strategy for improving the flow ability of Iraqi heavy crude oils.

Keywords

Heavy crude oil / Missan field / Solvents / Viscosity reduction / API gravity / Asphaltenes

CRediT authorship contribution statement

Luay Ahmed Khamees: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology. Jasim I. Humadi: Methodology, Funding acquisition, Formal analysis, Data curation, Conceptualization. Farah Nabeel Abdulrazzaq: Resources, Methodology, Investigation.

Data and code availability

Not Applicable.

Ethical approval

Not Applicable.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This research is supported by the Department of Petroleum and Gas Refining Engineering, College of Petroleum Process Engineering, University of Tikrit, Iraq.

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