The Study of Flow Characteristic in the Riser Pipe from the Subsea Wellhead to Kikeh FPSO

The study focuses on the flow characteristic within the riser pipe in the deepwater
environment. Deepwater environment presents significant flow assurance difficulties
such as solid formation like hydrate formation that could blocks the fluid delivery to
the riser top due to high pressure and low temperature at the sea bed. Furthermore,
severe slugging could causes large pressure fluctuation at the riser base and riser top
which reduces the production rate and damages the topsides equipments. Hence, extra
expenditure needed to be spent to overcome these flow assurance problems. Kikeh
Field is the country's first deepwater development in offshore with 1300m of water
depth which is operated by Murphy Sabah Oil Co. Ltd and PETRONAS Carigali
Sdn. Bhd. One of the wells of Kikeh field, Kikeh-1 well that has 205.5 'F ~f reservoir
temperature and 4595 psig of reservoir pressure above the bubble point is adopted to
be the case study. The objective of this study is to study the flow characteristic of the
oil in horizontal and vertical flow affected by various gas flow rates, oil flow rates
and the internal pipeline diameters for Kikeh-1 well. The tendency of hydrate
formation and severe slugging formation were also included in the study. PIPESIM
software was used to simulate the tendency of hydrate formation based on the Kikeh-
1 well's compositional components, whilst the flow patterns are identified by using
Aziz and Mandhane correlations. Different flow patterns and the conditions where
hydrate would form contribute a significant reference to deepwater riser and flowline
design. The study concluded that at production rate or 13,000 bpd, the superficial gas
velocity has to be at below 3 ft/s for horizontal flow and below 0.1 ft/s of modified
superficial gas velocity for vertical flow in order to avoid slug flow. Besides, the
pipeline should be able to withstand 5,000 psia and operates at least about 750 'F.
Such conditions would prevent the hydrate formation to occur in the pipeline. Hence,
by understanding the tendency of hydrate formation and the conditions of slug flow
to occur which might causes severe slugging, a reliable pipeline could be designed
with optimum specifications in order to prevent flow assurance problems.