This paper describes a vapour phase method for cleaning and decontamination of a slug catcher in a gas processing plant. Corrosion and heavy metal losses required the slug catchers to be replaced. Safe decommissioning demanded the elimination of H2S, LEL and pyrophoric iron. Compromised integrity made traditional cleaning methods like circulation or pressure jetting unfeasible. The proposed method significantly reduced decontamination times and the associated effluent.

The vapour phase method using degassing chemicals entrained in steam lowered H2S and LEL levels to substantially zero and also neutralized the pyrophoric material. The entire cleaning process was conducted with a temporary H2S scrubber due to unavailability of the process flare. This method did not require the system to be liquid filled or subject to high jetting pressure, making it possible to limit the treatment pressure to below 2 barg, thus minimizing the stress on the structural integrity of the slug catcher. In addition, the slug catcher weak zones were fortified externally in preparation for decontamination.

This technique of using steam as a medium to distribute and apply the degassing chemicals throughout the slug catcher has proven to overcome the limitations of conventional cleaning methods. It further provided a viable solution to reducing the time and resources required to achieve substantially zero H2S, LEL and pyrophoric content by half.

With traditional cleaning methods, the effluent generated would be substantial, necessitating additional logistical support for transporting the waste from the offshore location. Decontamination in a steam saturated vapour phase reduced the amount of effluent generated significantly, to only one third in comparison. This resulted in a solution that was more economical and environmentally friendly. Effective decontamination eliminated the risk associated with the presence of hydrogen sulfide (H2S) gas and pyrophoric materials, ensuring the slug catcher was decommissioned safely and successfully.

For heavily compromised systems and for locations with water supply, waste management or schedule constraints, the vapour phase decontamination process has distinct advantages over conventional methods.

The resultant savings in time and resources makes this an attractive option for mainstream oil and gas processing facilities as well.

Keywords:
corrosion management, mineral, h2s management, oilfield chemistry, geologist, production chemistry, catcher, operation, deposit, fouling
Subjects:
Production Chemistry, Metallurgy and Biology, Processing Systems and Design, Pipelines, Flowlines and Risers, Pipeline transient behavior, Corrosion inhibition and management (including H2S and CO2)
Copyright 2023, Society of Petroleum Engineers DOI 10.2118/213530-MS
You can access this article if you purchase or spend a download.