| Wax deposition under two-phase water-in-oil and oil-in-water dispersed flow were investigated in this study. For the case of water-in-oil, the deposition test of South Pelto crude oil with water cut of 0%, 16%, and 35% were conducted in a mini-pilot scale flow loop. A pipe-in-pipe test section (ID = 1.65 cm) and a rectangular duct test section (Dhy = 2.20 cm) were used for deposition testing. The initial inner wall temperature is controlled to be about 85 -- 87°F. The test fluid temperature was set to be about 105 -- 107 °F. A high temperature gas chromatograph with flame ionization detector (HTGCFID) and a differential scanning calorimeter (DSC) were used to analyze wax deposits. The results reveal that the deposit contains only a trace amount of water (less than 2% v/v) for oil continuous phase cases. The deposit surface of the turbulent fully-developed flow region is smooth. The deposit surface for the case of laminar emulsion flow with 35% water cut has many streamwise grooves. The crossover of the thickness versus time trends for the tests conducted under different flow conditions was observed. The initial thickness growth rate increases with the flow rate. After the crossover period ends, the deposit formed under a lower flow rate condition has a higher thickness. The late time deposit thickness, wax fraction and the average carbon number of the deposit were found to be correlated with the shear stress, heat transfer, and Reynolds number. The shear effect on the deposit thickness and composition is observed. At the similar initial heat flux through the deposit, the increase in shear stress increases the deposit wax fraction, increases the deposit average carbon number, and decreases the late time deposit thickness. The effect of water on wax deposition is mainly on the deposit surface roughness, hydrodynamics, and heat transfer. A new deposition mechanistic model for two-phase oil-water flow where oil is the continuous phase was developed and validated against this study's experimental data. The fitting parameters used in the model are the deposit maximum tolerable shear stress and the initial growth rate modifier.;For the case of oil-in-water, only a preliminary investigation was conducted. It was found that water is not the medium for wax transport. Water was trapped inside the deposit at the high concentration (more than 22% w/w) of wax in oil case. The oil film formation on the aluminum surface and wax surface were observed. Based on these observations, the assumption of oil film formation on the deposit surface during oil-water wax deposition is proposed in this study. |
