Offshore gas pipeline between Indonesia and Singapore completed in 2003

In July 2003, the construction of a 26 km long submarine gas pipeline between South Sumatra (Indonesia) and Singapore was completed by a joint venture of Boskalis Offshore and Jan de Nul.
The construction of this pipeline was part of a major project to transport natural gas from gas fields in South Sumatra to Singapore in order to meet with its future energy demand.


      Beach pull at Pulau Pemping

The route of the pipeline consists of two sections divided over two contracts with different clients:
-a section of 9 on behalf of PowerGas (Singapore)
-a section of 17 km on behalf of the Indonesian gas company Perusahaan Gas Negara (PGN)

The scope of the project included extensive route preparations, route survey, dredging, and elimination of unacceptable free spans and rock protection of the 28 inch pipeline.

The route of the 26 km pipeline runs from the small Indonesian island Pulau Pemping to the PowerGas receiving station on Singapore’s island Pulau Sakra.
The pipeline crosses the two busy shipping channels in the Singapore Straits, the Main Strait (westbound vessel traffic) and the Phillip Channel (eastbound), as well as the Sinki Fairway in the Port of Singapore.

The 9 km PowerGas contract was the first to be signed in 2001 and consisted of four elements:
-a 150 m onshore connection to the Pulau Sakra receiving station
-the dredging of the pipe trench
-pipe lay
-pipeline protection with rock

To dredge the pipe trench of this section, the following dredging equipment was deployed:
-the large cutter suction dredger 'Marco Polo' with a total installed power of 16,200 kW (Jan de Nul) in combination with the 1,500 m³ split hopper barges ‘Avon’, ‘WD Test’ and ‘WD Itchen’ (Boskalis)
-the 3,400 m³ split hopper dredger 'Pinta' (Jan de Nul)
-the 23,400 m³ jumbo trailing suction hopper dredger 'Queen of The Netherlands' (Boskalis)


The tshd 'Queen of the Netherlands'

In total an amount 700,000 m³ of material was dredged under difficult conditions, with plenty of steep rocky outcrops, including sharp peaks, overlain with residual soils and layers of softer marine clay.
Maintenance dredging of the trench was executed by the ‘WD Fairway’ (Boskalis) and the ‘Barent Zanen’ (Boskalis).
When dredging for the depth requirement was completed, the remaining unacceptable free spans were eliminated by means of pre-laid rock supports by Side Stone Dumping Vessel ‘Cetus’ (Boskalis).
This phase of work was completed in December 2002.

The preparatory work for the second contract (for PGN) began in July 2002 and dredging commenced in October 2002.
Seabed work along the 17 km 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. Pre-lay supports were installed to eliminate remaining unacceptable free spans.
This was an important phase of the work, where the optimum solutions for pipe laying within the agreed corridor had to be found.


      The stone-dumping vessel 'Cetus'

The equipment used on this section included Jan de Nul’s backhoe dredger ‘Jerommeke’ and Boskalis’ grab dredger ‘WH Goomai’, equipped with an 11 m³ grab and operating in water depths of up to 50 m.
The ‘Zinkoon V’ (Boskalis) equipped with a hydraulic excavator, was deployed to dredge the shore approach through the shallow reef flats at Pulau Pemping

All dredging and route preparation was completed in November 2002.
The next phase, the placing of the pre-laid supports with the side stone-dumping vessel ‘Cetus’, was completed in December 2002.

In February 2003 the subcontractor Global Industries started the pipe lay from Pulau Sakra.
The main pipe lay (24 km), with tie-in to the remaining 2 km section landing at Pulau Pemping, was completed early March 2003.


The fall pipe barge 'Zinkoon 6'

In order to protect the pipeline from anchors of the largest crude carriers, more than two million tons of rock has been dumped along the pipeline in Singapore and Indonesia by the fall pipe barges ‘Zinkoon 6’ (Boskalis) and ‘Zeepaard’ (Boskalis) as well as the side stone-dumping vessels ‘Cetus’ (Boskalis) and Pompei (Jan De Nul).

The protective rock layer is capable of withstanding the impact load of a 22-ton anchor.
Most of the rock came from Karimun, an Indonesian island some 40 km west of the pipeline route.
The rock dumping was carried out between March and July 2003.