Wax Deposition in Stratified Oil/Water Flow
2012
Hoffmann, Rainer | Amundsen, Lene | Huang, Zhenyu | Zheng, Sheng | Fogler, H Scott
While diffusion as the major mechanism for wax deposition has been investigated in past decades, wax gelation has mostly been studied in quiescent conditions and is considered to be less significant than diffusion in flow conditions. In this study, gelation has been observed as a major mechanism for the formation of wax deposits in oil/water stratified flow. The experiments are carried out in a state-of-the-art flow loop using a North Sea gas condensate and formation water. The flow map study using reflex camera and X-ray tomography reveals that most of the completely stratified flows occur at low total flow rates of oil and water, which correspond to low shear stresses at the wall. It was found that the carbon number distributions of the wax deposits formed in this region have very low fractions of heavy components and are very close to the distribution of the deposit that is only formed by gelation. It was further revealed that the deposit thickness increases with increasing degree of gelation, which corresponds to decreasing shear stress of the fluids at the wall. This finding is consistent with previous studies from single-phase experiments where lower oil velocities are found to result in much higher deposit thicknesses and low wax fractions in the deposits.
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