Royal Dutch Shell PLC said divers closed a relief valve, stopping a small oil leak seeping from a subsea well flowline to its Gannet Alpha platform in the UK North Sea. The leak started on Aug. 10, prompting Shell to isolate and depressurize the flowline.
No oil has been released since Aug. 19, said Shell, which is continuously monitoring the site to ensure the valve closure was fully successful. A surveillance flight on Aug. 20 found no oil on the surface.
Shell and UK environmental authorities previously said they expected the oil will be naturally dispersed through wave action (OGJ Online, Aug. 15, 2011).
An estimated 1,300 bbl of oil spilled into the North Sea, Shell said earlier. Weather and waves are breaking up oil sheen on the surface that once measured 31 km by 4.3 km. The Marine Coastguard’s Aug. 20 estimate was the sheen covers 6.7 sq km.
Response plans include putting 36 concrete mats on the depressurized flowline to secure it to the seabed.