This article, written by JPT Technology Editor Judy Feder, contains highlights of paper OTC 30440, “Floating LNG 1 Relocation: Another World’s First,” by Muhammad Fakhruddin Jais, Wan Mahsuri Wan Hashim, and Ariff Azhari Ayadali, Petronas, et al., prepared for the 2020 Offshore Technology Conference Asia, originally scheduled to be held in Kuala Lumpur, Malaysia, 17–19 August. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission.
Floating liquefied natural gas (FLNG) allows LNG to be processed hundreds of kilometers away from land to unlock gas reserves in remote and stranded fields previously uneconomical to monetize. The complete paper describes the operator’s fast-tracking of a 450-km FLNG unit relocation from Sarawak to Sabah offshore Malaysia. The time from selecting the new field to unloading LNG at the new location was 13 months. The complete paper discusses pre-execution and engineering studies, relocation preparation and execution, and challenges encountered, including timeline, cost minimization, and manning.
Introduction
Since 2016, Petronas has operated its first floating LNG production, storage, and offloading facility offshore Sarawak. During the tenure of operation, cargo was delivered successfully to customers worldwide.
An opportunity to help a different gas supplier monetize another stranded field offshore Sabah, approximately 450 km away from the unit’s original location, presented itself. The new opportunity was deemed feasible for several reasons.
- The identified location is still within Malaysian waters and thus is subject to similar authority and regulations.
- Operation within the same country ensures common support from vendor and contractors to some extent.
- The two fields have similar gas profiles and water depth.
The project team determined that these factors would result in minimal modification at both FLNG and up-stream facilities to meet minimum shut-down from project sanction until first LNG cargo was produced.
Pre-Execution and Engineering Studies
To fast-track the project, an evaluation was conducted of the new feed-gas composition and modification of both up-stream and FLNG facilities. Long-lead items (LLIs) were identified, and studies were conducted to secure the items. One of the identified LLIs was the flexible pipeline from the upstream facilities to the FLNG. A flow-assurance study covered the steady-state and transient operation for the flexible line. This study confirmed the size of the pipeline and defined the functional requirement for the flexible pipeline procurement. Among the key parameters identified were the pipeline’s thermal conductivity and design pressure. During the feasibility stage, a steady-state study was conducted to determine the length of the flexible line in order to meet the landing pressure and temperature at the FLNG. Instead of requiring additional cooler, the flexible line was extended 2 km to take advantage of the Joule-Thomson cooling effect resulting from the pressure drop across the pipeline.
In addition to defining the LLI properties, the flow-assurance study also examined the transient operation for both upstream and FLNG upon the closure of the riser shutdown valve. The study assessed flow-assurance issues, such as hydrates and adequacy of the slug receiver during the transient operation, that might arise, and defined the start-up and commissioning sequence for the facilities.