In
the oil pipeline transportation system, wax deposition will
reduce the effective circulation area, weaken the overall pipeline
transportation capacity, and even block the pipeline, which seriously
threatens the safety of the pipeline flows. In the actual production
of oil fields and the transportation of oil products, except for the
single-phase waxy crude oil, under most conditions, operations are
performed using multiphase mixed transportation, so it is necessary
to determine the wax deposition characteristics in those pipeline
systems. In this Review, three new wax deposition mechanisms proposed
in recent years and several typical experimental devices were summarized,
the wax deposition in oil–water and oil–gas flow systems
and the wax–hydrate coupling deposition in oil–gas–water
flow system flows were concluded; the mathematical models were also
categorized based on the three flow systems. Meanwhile, it highlighted
the fact that, in the two-phase flow, because of the complexity of
the flow pattern and the presence of the second interface on the wax
deposition process, independent theoretical research on the mechanism
of wax deposition is particularly necessary; based on this, a more-accurate
wax deposition prediction model can also be developed. For the coupled
deposition of wax-hydrate in the three-phase flow system, experimental
instruments such as FBRM, PVM and molecular dynamics simulations could
be used to study the distribution characteristics and interaction
rules of wax crystals and hydrate particles from a microscopic perspective.
On the other hand, the mechanism of wax crystal and hydrate coupling
deposition by additives such as antiwax agents, hydrate inhibitors,
antipolymerization agents, and pipeline transportation conditions
can be investigated experimentally to better control the deposition
process during pipeline operation and ensure the safe flow in the
transportation system.
