LAUSR

To further develop an understanding of the wax deposition mechanism needed to model its occurrence in subsea oil pipelines, deposition experiments using a pure n-alkane and a binary n-alkane mixture were performed in a cold finger apparatus modified to allow for reliable and accurate visualization of the wax deposit thickness as a function of time. The deposit thickness is found to grow initially but to shrink at long times as the deposit composition enriches in the wax content and the wax concentration in the surrounding oil decreases. This non-monotonic time evolution of the deposit thickness and increase in wax composition are explained and modeled using transient heat and mass transfer kinetics. The ultimate shrinkage of the deposit thickness is traced to depletion of soluble wax in the bulk oil because soluble wax continuously diffuses from the bulk oil into the deposit and precipitates there by fast precipitation kinetics.