Welding to tie-in the 32-in. gas export pipeline at Total E&P's Bongkot field and at Unocal's Erawan field in the Gulf of Thailand was accomplished by Clough Stena (Asia) joint Venture, Perth, in water 60-80 m deep.
The job employed hyperbaric welding in a sealed and de-watered steel chamber fitted around each tie-in location.
DOG LEG
The Bongkot tie-in involved installation of a dogleg approximately 65 m long and weighing 50 metric tons. The segment was required to absorb thermal expansion of the pipeline.
The spoolpiece was prefabricated ashore by Clough Stena, transported to the site, and deployed from the Essar Stena 1. Two welds were completed from inside the habitat, one between the riser and the spool and the second between the spool and the pipeline.
RISER WELDING
The Erawan tie-in. involved the pipeline end being welded directly to the riser. Clough Stena says that to provide access for welding, it was necessary to lift the riser in its clamps on the jacket and lower the completed pipeline/riser after tie in.
The pipeline was sidewalked to obtain correct alignment and only one tie-in weld was required, according to Clough Stena.
Copyright 1993 Oil & Gas Journal. All Rights Reserved.
