In 2023, an oil and gas operator in the East China Sea needed to upgrade its 28 inch gas export pipeline (GEP), including modifications to the pig launcher and associated pipework on one offshore production platform. The 345-kilometer GEP transports natural gas from the offshore platforms to the onshore processing terminal and is one of the operator’s most critical assets. The operator considered either fully depressurizing the GEP or creating a local temporary pressure isolation at the platform.

They selected an in-line double block and monitor (DBM) isolation using the T.D. Williamson (TDW) SmartPlug® high-pressure isolation tool (HPIT). A unique aspect of the project was the ability to continue gas production through a temporary bypass pipeline while the modification work proceeded, minimizing downtime. This required two isolations performed with the same HPIT in a single launch and retrieval.

This paper outlines execution steps — from site visit and engineering through successful completion.