Summary
Paraffin deposition was found in the RedHawk #2 subsea flowline and was
successfully removed using a xylene slug swept by produced gas from the well.
Testing indicated that the problem resulted from the interaction between glycol
and produced condensate. Overtreatment with glycol and low produced water
volumes contributed to the precipitation of paraffin and eventual plugging of
the flowline.
The objective of this procedure was to clear the restriction by pumping a
slug of xylene into the flowline and producing the well to carry the solids to
surface. Glycol can react negatively with the condensate in some dry gas wells,
resulting in paraffin precipitation. When there is sufficient water present to
mix with the glycol the problem does not occur; however, a lack of water causes
the glycol to react with the condensate and form paraffin. Clearing the
restriction would eliminate a pressure drop in the flowline, thus allowing the
well to produce at optimal rate and prolonging the well’s life. All work was
performed from the host spar facility using temporary separation equipment and
platform methanol pumps.
The RedHawk flowline restriction was successfully removed using two 25-bbl
xylene slugs which were swept from the flowline with produced gas from the
well. With the restriction removed, 982 psi of frictional loss was regained and
the well was returned to optimal production. The deposition appears to be
reoccurring, although at a much slower rate than before. However, any further
reduction in glycol usage would not guarantee effective hydrate inhibition.
Changing hydrate inhibitors is impractical because of platform equipment, and
annual cleanouts are a more cost effective option.
It is quickly becoming critical to develop means of cleaning single flowline
systems with highly efficient and low-cost methods. By understanding new
problems that arise and putting new solutions into practice, operators can
extend the life of some wells and avoid significant downtime and workover
costs.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
30 January 2008
- Meeting paper published:
5 May 2008
- Revised manuscript received:
8 October 2008
- Manuscript approved:
10 October 2008
- Published online:
5 March 2009
- Version of record:
5 March 2009
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