Slug Catchers in Natural Gas Production - NTNU

Karam – Slug Catchers in Natural Gas Production
ABSTRACT
Operations in deep, far and remote areas as well as cold environments have raised the problem of slug
formation. Irregular sea floor is the main concern and major reason behind the formation of these slugs. Their
presence in the pipelines has raised the flow assurance concerns. Several methods are used to inhibit such
occurrences as the use of MEG besides the erection of slug catchers at the receiving terminals. The design of
the latter challenges engineers due to the difficulty of predicting accurately slug length and volumes.
The project will focus on the design of slug catchers and then on four different field cases lying in the
Norwegian Continental Shelf. The analysis of a set of articles and theses made it possible to gather the needed
information. HYSYS was one tool in hand to calculate the gas, liquid and condensate fractions in the models.
Input data to the model were either assumed, found from previous literature work or calculated from several
correlations.
The project deliberates about two major parts. The first focuses on multiphase flow problems and slug
formation along with the different types of slug catchers available. As for the second part, the methods behind
the design of a slug catcher are brought into light. A HYSYS simulation was associated with the model to
verify the percentage of the different phases and check whether the size of the slug catcher is suitable.
As a result, the design of a slug catcher was dependent upon three major parameters. These are the length and
the inclination of the fingers of the multi-pipe catcher, the diameter of the pipeline heading to the inlet of the
slug catcher and the liquid accumulation volumes expected to be formed in the pipelines. The analysis showed
that the multi-pipe type is the mostly used especially for large slug volumes.
Regarding the simulations, HYSYS is not an accurate tool for multiphase flow analysis and estimation of
phase volumes due to the limitations of the program and the simplifications assumed. The MEG quantity
injected was smaller than what is actually used in the fields. Likewise, the volume or size of the slug catchers
should be smaller than their current size; this discrepancy is due to the larger amount of slug expected to be
formed and to the simplifications attributed to the model.
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