The Shell UK operated Brent field is situated in UK Block 211/29, approximately 185 km northeast of Lerwick. The Brent field had been developed using four interlinked platforms, namely Brent A, Brent B, Brent C and Brent D platforms, with oil exported to Sullom Voe and gas exported to St Fergus. As part of ongoing cessation of Brent field production programme, Shell UK, since 2011, had commenced Brent Bypass project to remove the gas pipeline connection to Brent A and Brent B platforms whilst securing third party access to Far Northern Liquids and Associated Gas System (FLAGS) export gas pipeline. In order to execute the large scope efficiently and minimise the disruption to the northern gas export system, Brent Bypass project execution has been divided into Phase 1 and Phase 2.
Brent Bypass Phase 1 project was completed in late 2017, in which the scope consists of the reconfiguration of the Northern Leg Gas Pipeline and the Western Leg Gas Pipeline effectively by-passing the Brent Alpha platform and diverting the feeds from third parties tieback (e.g. Magnus, Thistle, Murchison, Statfjord, Cormorant Alpha, etc.) directly to the FLAGS export gas pipeline via a pre-installed tee on the Gjoa PLEM.
This paper presents the technical and non-technical challenges of Brent Bypass phase 1 project and how they were overcome. The challenges include (1) use of high criticality isolation tools to allow safe pipeline re-configuration due to lack of adequate system isolation infrastructure; (2) reinstating old infrastructure to allow pigging of pipeline; (3) working on large bore and multi-bore pipelines in a congested area; (4) re- connecting pipeline without using flanges or welding; (5) demonstrating long term suitability of existing pipelines, i.e. life-extension; (6) managing multiple stakeholders (operators and regulators) and (7) minimising impact to gas supplies during offshore operations.