Slug Catchers in Natural Gas Production - NTNU

Karam – Slug Catchers in Natural Gas Production
10- Repeating the volume calculations after finalization of all dimensions
4.2 Close-up on the formulas behind the design
Slug flow behavior must be determined first in order to be able to design and size a slug catcher
whether it is a normal slug flow or induced by pigging. A number of calculations and a set of
equations should be available and used. The slug length, slug holdup, slug velocity and translational
velocity should all be determined according to Sarica et al. (1990). The slug velocity can be defined as
the velocity of the mixture in steady state flow whereas the translational velocity, , is determined by
the equation below:
(1)
where is the velocity of the mixture, is the drift velocity and c is a constant. The drift velocity,
which is the velocity of one phase relative to a surface moving at the mixture velocity, is expressed
- for normal slug flow in vertical pipes, as:
√
(2.a)
- for normal slug flow in horizontal pipes, as:
√
(2.b)
- for normal slug flow in inclined pipes based on the Bendiksen correlation (1984), as:
(2.c)
- for pigging, as:
The constant c depends on the flow type thus if the flow is laminar, c=2. If the flow is turbulent, then
c=1.2. Otherwise, the Taitel correlation (2000) is used; it is represented as follows,
(2.d)
( ) ( )
(3)
Page 12 of 56