Slug Catchers in Natural Gas Production - NTNU

Karam – Slug Catchers in Natural Gas Production
the slug and film length and zone are shown in Figures 4 and 5. The film length of the slug and the
slug length for a hydrodynamic flow are represented, respectively, as follows,
( ) (9)
( )
(10)
The slug frequency denoting the rate of intermittence of the slug through the pipeline, is expressed as
(11)
with L U , the slug unit length, being the sum of the slug length L S and the film length L L .
The instantaneous inlet flow rates of both gas and liquid are important slug characterization features
and crucial for the design of the slug catchers. These rates have been calculated by using the Miyoshi
et al model (1988). The equations are as follow:
- for the liquid: (12.a)
- for the gas: (12.b)
The liquid accumulation in the slug catcher should be determined in order to define the size of the slug
catcher. According to Sarica et al. (1990), a mass balance between the inlet and outlet liquid rate of the
slug catcher can be used to calculate the accumulated liquid rate and thus the accumulated liquid
volume.
[ ] [ ] [ ]
To solve the mass balance, the different parts of the equation should be determined separately. As
expressed earlier, the liquid input mass rate can be calculated with the Miyoshi et al. (1998) model
similarly to equation (12.a). The liquid discharge mass rate represents the flow rate at the outlet of the
slug catcher which is, in turn, dependent upon the flow control valve (Marquez et al., 2009). The
liquid accumulation rate can be calculated from equation (13) with the assumption of a constant liquid
density in the slug catcher and no acceleration while slug production (Sarica et al., 1990). On the other
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