Designed, installed and maintained by Fugro GEOS, the monitoring system is a critical element, providing real-time information to help minimise flow assurance problems in pipelines which link the two Pearl offshore platforms with the onshore plant. Using acoustic telemetry, data are sent from the seabed to the platforms and the system interfaces in real-time with the platform’s control system. When the seabed water temperature reaches a specified level, an alarm is triggered so that action can be taken to manage and maintain the flow of gas through the pipelines.
The Pearl GTL Project involves the export of natural gas under pressure from the unmanned platforms over a distance of around 60 kilometres. The compressed gas flows via pipelines, located at a depth of approximately 30 metres, to the giant onshore plant in Ras Laffan Industrial City, the largest energy project in Qatar. When the seabed water temperature falls, hydrate crystals can form in the pipeline and these could restrict the flow of gas and may seriously damage the pipelines. Injecting the flowlines with kinetic hydrate inhibitors avoids the formation of hydrates and minimises the risk of pipeline blockages.
“Monitoring the seabed water temperature has contributed to maintaining a steady flow of feed gas from the offshore platforms to the onshore facility,” said Anthony Gaffney, Director of Fugro GEOS’ Offshore Systems Division. “The ability to accurately measure the water temperature along the export pipelines and identify when kinetic hydrate inhibitors are needed eliminates the need to purchase, transport, store, pump and then remove the inhibitors and this translates into cost savings.
“Because our monitoring system does not require divers for deployment or recovery, it is readily retrofitted and recovered so intervention costs are minimised and safety is enhanced. Also, as the system uses acoustic telemetry, there is no requirement for subsea cables which may suffer damage and which would be costly to replace over the lifetime of the project.”
Under the maintenance contract Fugro GEOS provides the services of an experienced metocean engineer as well as critical upgrades to Fugro GEOS’ Weather Monitor software. Local 24-hour support in Qatar is provided by associate company Petrotec’s trained service engineers.