In response to an urgent request from BP Norway, Fugro Seacore successfully completed a unique and challenging anchor pile remediation drilling works for a new four-legged water injection jacket, standing in 76m of water in the Valhall Field, part of the Norwegian Sector of the North Sea.
Fugro Seacore mobilised the Teredo 10/40 reverse ciculation drill onto the Rowan Gorilla 7 jack-up platform. Initially core samples were taken inside the pile prior to drilling and cleaning out the material which was inside the pile, down to what was found to be the deformed pile toes. This then enabled the field owner and BP operator to evaluate how to rectify the problems they had been encountering before Fugro Seacore were contracted.
Following vigorious audits and inspections, BP Norway awarded the approx £1m pile remediation contract to Seacore, one of Europe's largest specialist marine offshore construction and exploration drilling contractors. Within just two weeks of receiving the initial enquiry from BP, Fugro Seacore had mobilised all its equipment and drilling crew prior to commencing the intense and challenging 30-day project.
Working from the Rowan Gorilla 7's rotary drilling table, Fugro Seacore initially used its own crawler-based Comacchio automated drill rig for coring activities. ASD riser casing was drilled into the material inside the pile, prior to using a Geobor S coring string to take samples within the SHD riser down to the pile's deformed toe. Material inside the piles consisted of very dense sand and extremely stiff clay with strength ranging between 450-600Kpa. Fugro Seacore also cored through a steel section of the deformed pile toe and recovered the sample to surface for analysis.
Cores were assessed prior to Fugro Seacore replacing the Comacchio with its own hydraulically operated Teredo 10/40 reverse circulation drill rig, complete with riser pipe and bottom hole assemply with 2.2m diameter bit. The drill bit was lowered through the splash zone and through the water column for guidance by a ROV into the top of the upstanding tubular steel pile. Using reverse ciculation and side discharge to exhaust drill cuttings from the riser above sea level, the crew cleared the inside of the pile down to the heavily deformed toe.
BP Norway's crew followed on, running a TV camera and logging sonar down each pile to check diameters to evaluate pile deformation. The data obtained from Fugro Seacore's successful remediation contract will be used by BP Norway to rectify the problem of the upstanding jacket anchor piles.
"Fugro Seacore responded very rapidly to our request and we were extremely pleased at the speed and success of this unique and very challenging pile remediation contract," commented Richard Harland, BP's Project Superintendent.