Casino pipeline: novel pipeline integrity inspection

The Casino offshore pipeline required inspection to demonstrate the integrity of the pipeline and allow the operating life of the pipeline to be extended. There were numerous challenges in performing a conventional internal pipeline inspection which would have required diver operations to install and operate subsea pig launchers. Two alternative inspection methods were used to inspect the high priority sections of the pipeline, at the pipeline tees and in the horizontal directionally drilled (HDD) section of pipeline at the coastline crossing.The pipeline tees and well flowlines were inspected using an external magnetic flux inspection tool deployed by remotely operated vehicle (ROV), to test for top-of-line corrosion. Bi-directional pigging from the onshore valve station, offshore for 30 km using gas from the host gas plant and then return to the shore using gas from the offshore wells allowed for inspection of the HDD pipeline with a total of 10 bi-direction pig runs completed. The pig position was accurately predicted by monitoring the operating conditions of the pipeline and confirmed by displacement past the subsea well closest to shore (Casino 5). The novel pigging methods brought significant benefits for cost, schedule and reduced EHS exposure by avoiding diver operations. The cost of the overall inspection program was less than 25% of the conventional inspection methods and was achieved a year earlier than if a dive support vessel (DSV) had been mobilised. The bi-directional pigging campaign proved to be highly successful.