Summary
A novel technique has been developed for optimizing hydrate-inhibitor dose
rates by monitoring the actual hydrate safety margin. The technique is based on
measuring acoustic velocity and electrical conductivity in an aqueous sample
taken from the pipeline/separator. The developed system then determines salt
and organic inhibitor concentration (e.g., methanol, monoethylene glycol, and
kinetic hydrate inhibitors). In the case of thermodynamic inhibitors, the
information is then fed to a thermodynamic model determining the hydrate
stability zone (HSZ). Superimposing the pipeline operating conditions (e.g.,
pressure and temperature profile), the developed system can determine the
hydrate safety margin. The system can provide warning if the operating
conditions are inside the HSZ or if too much inhibitor is being injected.
The technique can be used in optimizing inhibitor-injection rates, reducing
the impact on the environment and operational costs. It can also improve
production-system reliability by constant monitoring the hydrate safety margin
and protecting the system against pump malfunction and/or changes in process
variables (e.g., water cut).
This technique has been developed through a joint-industry project, and its
performance has been intensively evaluated using synthetic samples and real
produced-water samples by the authors and the project sponsors in field trials.
The results demonstrate that this system can be used for different inhibitor
systems, including methanol (MeOH)/NaCl, monoethylene glycol (MEG)/NaCl, and
kinetic-hydrate-inhibitor/salt systems, with good accuracy.
The developed system can have a major impact on reducing the
inhibitor-injection rates and environmental impact and improving the
reliability of production systems against risks associated with hydrate
formation. The developed system can be laboratory-based, a mobile unit, or
online, with near-real-time samples taken from live pipelines/separators.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
29 June 2011
- Meeting paper published:
23 May 2011
- Revised manuscript received:
20 November 2011
- Manuscript approved:
17 January 2012
- Published online:
8 November 2012
- Version of record:
13 November 2012
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