Effect of Hydrodynamic Parameters on the Wax Mass Density: Scale Up From Laboratory Flow Loop to Crude Production Pipelines

Abstract

The oil and gas production pipelines typically operate at high Reynolds number and low wall shear stress conditions. However, the current wax deposition prediction models were developed based on the laboratory flow loop experimental data obtained at high shear stress and low Reynolds number. It is required to have reliable experimental data, which closely resembles the field conditions to validate the existing models or fine tune the effect of scale up parameters with available laboratory data. Hydrodynamic parameters such as Reynolds number and shear stress would incorporate the effects of diameter, flow rate and viscosity collectively, thus enabling a comprehensive approach for modeling the phenomenon. However, it is necessary to understand the individual effects of Reynolds number and shear stress as they are coupled. In the present study, the effect of the hydrodynamic parameters is decoupled with specially designed flow loop experiments. The deposit thickness and wax content were measured, and the wax mass density (wax mass deposited per unit area) was calculated. Since the area of deposition is changing, the main variable analyzed in this study is the deposited wax mass density instead of the deposit thickness and wax content. From the results, it has been observed that the Reynolds number has a more dominant effect on the deposited wax mass density compared to shear stress. This behavior is observed for in house synthesized model oil and different crude oils at various experimental conditions. The results obtained in this study enhance our understanding on the deposition behavior at various hydrodynamic conditions and aids in scale up from the laboratory to field conditions. Moreover, in order to develop more accurate wax prediction models for operations particularly for waxy crude oil production lines, it is necessary to tune right scale up parameters for field applications.