COMPLETION of a 26-km pipeline linking the Indonesian island of Pulau Pemping with Pulau Sakra (Jurong, Singapore) at the end of this year will bring gas from south Sumatra’s onshore fields to Singapore. In relation to its size, Singapore has a high density population of 4.3 million people. This factor, together with the rapid expansion of commercial energy use and lack of indigenous energy resources, places heavy demands on power supply. Furthermore, Singapore has environmental goals which place emphasis on clean fuels for power generation. For this reason, Singapore Power subsidiary PowerGas has embarked on a major project to transport natural gas from Indonesia.
Boskalis Offshore BV is responsible for the Pulau Pemping Pulau Sakra gasline construction, acting as main contractor for this major pipeline project. The project consists of contracts with two clients, with 9km undertaken in Singapore on behalf of PowerGas, and 17km in Indonesia for PGN (Perusahaan Gas Negara). Ben Mooibroek, Boskalis offshore’s regional manager for the Far East and Pacific Area, says: “This project is a significant milestone. We are confronting a challenging environment in the Singapore Straits, with difficult subsoils along the route. The scope of work includes extensive route preparations, route survey, dredging, elimination of unacceptable free-spans, and rock protection of the 28-in line.”
The 26 km pipeline crosses the two busy shipping channels in the Singapore Strait – the Main Strait (westbound vessel traffic) and the Philip Channel (eastbound). The 9-km PowerGas contract was the first to be signed in November 2001, and its completion is scheduled imminently. The scope of work consists of four elements: a 150-m onshore connection to the Pulau Sakra receiving station, the dredging / route preparation works, pipeline installation, and pipe protection. The pre-pipelay dredging under this contract allows a 25-m free water depth requirement for vessel navigation in the Singapore Port area.
In July of last year, preparatory work began for the PGN contract, and dredging commenced in October. Seabed work along the 17km stretch differed from the PowerGas section of the route, in that the main task was seabed levelling rather than dredging for depth requirements. The route, however, featured areas of hard material requiring removal, and pre-lay supports were installed to eliminate remaining unacceptable freespans.
Pipelaying from Pulau Sakra began in January. The pipe was produced by Europipe of Germany, and the pipelay is being executed by subcontractor Global Industries. The main pipelay (24km), with tie-in to the remaining 2-km section landing at Pulau Pemping, was completed in March, and a fibre-optic cable has been piggy-backed to the pipeline. Rock protection works along the stretch from Pulau Sakra and into the Strait requires around 700,000 tonnes of rock to protect the gas pipeline against damage from anchors of up to 22 tonnes. These protection works have been undertaken by the fallpipe barge Zinkoon 6 and the side-stone-dumping vessel Cetus. Rock-dumping commenced in late March, following hydrotesting, and was completed in May. The Zinkoon 6 and Cetus have now moved to the PGN stretch, where 1.3 million tonnes of rock will be dumped. The main source of the rock is at Karimun, an Indonesian island some 40km west of the pipeline route.