|dc.description.abstract||The offshore industry is facing many challenges when it comes to maintaining operational
efficiency. One of the biggest problems is related to flow assurance problems.
To avoid such issues, different chemicals are transported through individual lines in an
umbilical from topside into a x-mass tree or a manifold. Total has for some years worked
on a new concept where they want to replace the traditional umbilical with big tanks that
are stored on the seabed, which are refilled every sixth month. However, if it is possible to
simplify this, then the capital cost would be reduced even more.
The aim of this thesis was to look at the operational strategy, meaning how we can
transport these chemicals from one place top-side to a place subsea. Furthermore, find a
solution for the design of the system, both regarding chemicals being into separate tanks, and
tanks that contain a mixture of two or more of the chemicals, making a so-called chemicals
The approach used to answer the objectives of this thesis involves collecting relevant
scientific reports and theory by search in scientific databases as well as books and other
relevant sources online. Furthermore, calculations with focus on flow behaviour have been
conducted. Illustrations have been used to a large extent to illustrate flow behaviours in
pipelines of different diameters, and when the liquid spacer are of different length. In addition flow diagrams have been sketched to illustrate the transportation and the distribution
of the chemicals.
Due to the uncertainties on how the chemical will behave when they are sent through
the same line, they will be separated by a liquid spacer. Uzu et al. (2000) say that the
liquid spacer can vary from 100 meters to 500 meters depending on the size of the pipeline
and the length it is going to travel. However, since there is little specific knowledge on
how long it should be between different chemicals, the liquid spacer has been seen as a
Based on the injection rates provided by Total for one field case, it was founded that
biocide was injected at a much higher rate than the other production chemicals. It was,
therefore, suggested that biocide should be injected every other time.
By sending the chemicals as combinations rather as individuals a tank module based
on the chemicals being sent through a 0,5 pipeline was reduced from 16 tanks down to