April 2010 Vol. 237 No. 4

Projects

Subsea 7 Completes Diverless Pipeline Repair Off Angola

Subsea 7 Inc. repaired the Girassol Pipeline in the Girassol field, 210 km northwest of Luanda, Angola for Total E&P Angola last year. The project was a diverless operation in 1,350 meters of water. A design competition by Total resulted in Subsea 7 being awarded a contract for the design, manufacture, testing and operation of a deepwater pipeline repair system (PRS). The system was used to repair a 12-inch water-injection pipeline in the Girassol field.

The PRS comprises a permanent equipment set made up of a spool deployment frame, rigid spool piece, end connection skids and two mechanical pipeline connectors together with a suite of ROV-deployed or operated tools for preparing and aligning the pipeline prior to the connector installation. The PRS is the latest addition to Subsea 7’s pipeline repair capabilities which include grouted and hyperbaric welded solutions.

The project management and engineering was performed at Subsea 7’s office in Aberdeen, Scotland and supported by Subsea 7’s facilities in Luanda. The offshore phase involved two separate phases. In the first phase, the permanent works equipment was installed on the seabed at the damage location. In the second phase, the ends of the damaged pipeline were lifted, prepared and aligned before the mechanical connectors were installed, set and tested with annulus tests onto the previously installed spool piece. Final confirmation of the repair was achieved by a pipeline leak test from the Girassol FPSO which was completed in December.
Graham Sharland, Subsea 7’s COO – Africa Region, said it was essential to repair this damage which could have resulted in lower performance in drainage of the reservoir. He added, “The project success reveals not only the technological advances implemented in the oil business but also the massive involvement of Angola and its staff in conducting research and development of high level studies required in this area.”