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Article Type

Research Paper

Corresponding Author

Aysel V. Gasimzade

Abstract

High-paraffin crude oils create persistent difficulties during production, transportation, and storage. Their elevated content of paraffinic hydrocarbons makes them highly sensitive to cooling: temperature reduction initiates nucleation and crystal growth, leading to the formation of bulky wax deposits. These deposits restrict flow, block pipelines, foul equipment surfaces, increase pumping energy requirements, and significantly raise operational costs. For this reason, chemical treatment with depressant-type additives is widely applied as a practical approach for controlling wax deposition.

In this study, the performance of two individual reagents, Difron-3971 and HY-154, together with a newly developed composite formulation (DHC), was investigated using a laboratory-prepared model oil obtained by blending several high-paraffin field samples. Wax deposition and its inhibition were evaluated using the cold-finger technique under controlled temperature gradients. Rheological properties were measured with a Brookfield rotational rheometer, and the main flow parameters—yield stress (τ₀) and plastic viscosity (μₚ)—were determined according to the Bingham–Shvedov rheological model. The hydrocarbon group composition of the deposits was analyzed by gas chromatography, while wax-crystal morphology and size distribution were examined using polarized-light optical microscopy.

In the absence of additives, the model oil displayed pronounced non-Newtonian behavior during cooling. This behavior was accompanied by sharp increases in τ₀ and μₚ and by the formation of large plate-like paraffin crystals with sizes of approximately 80–100 µm. Difron-3971 provided moderate inhibition efficiency, reducing the wax-deposit mass by about 40% at 300 g/t and up to ~80% at 600 g/t. HY-154 showed a maximum inhibition efficiency of approximately 65%. The DHC composite exhibited the highest performance among the tested formulations. At a dosage of 600 g/t, the mass of wax deposits decreased by up to ~95%, the plastic viscosity approached near-Newtonian values, and the average crystal size was reduced to approximately 5–10 µm, indicating a strong synergistic interaction between the components of the composite formulation.

These results indicate that the use of single depressant additives alone does not provide sufficient control of wax crystallization in high-paraffin systems. Composite formulations that combine depressant activity with solvent-active components provide a more effective strategy for wax management, improving crude-oil flow stability, lowering energy consumption during pumping, and enhancing the reliability of pipeline transportation.

Keywords

high-paraffin model oil; deposition; rheology; composite reagents; plastic viscosity; yield stress

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