SARB - Artificial Islands

 

Challenge

The Emirate of Abu Dhabi is developing the Satah-al-Razboot (SARB) Offshore Oilfield which will add 100,000 extra barrels of crude oil a day.

Drilling works for the extraction of crude oil from 86 oil wells at the Satah-al-Razboot (SARB) Offshore Oilfield will be executed on two artificial islands (SARB-1 and SARB-2), located at a distance of 120 km from the UAE-capital Abu Dhabi. The distance between these two islands is approximately 7 km.

Oil from the wells will be transferred from the SARB artificial islands through several subsea pipelines to processing-, storage-, and export facilities to be built on the nearby island of Zirku.

Only by its location in open sea and the distance of more than 250 km to the onshore base in the Emirate of Ras-al-Khaimah (RAK), this complex and multidisciplinary project is a gigantic logistical challenge. In addition, very high standards of execution and extremely strict tolerances were imposed.

The dredging, reclamation, compaction, shore protection and harbour construction works for the construction of these offshore artificial islands were awarded under a single package to the joint venture of Middle East Dredging Company (Medco) and Dredging International. The contract was awarded under ‘Design and Build’ terms.

Our solution

The ‘Design and Build’-contract for the two artificial islands in the Satah-al-Razboot (SARB) offshore oilfield included dredging and reclamation of the island platform; construction of the perimeter shore protection by rock armour and prefabricated Accropode II® concrete blocks; construction of a mini harbour and 1,000 m of concrete block quay walls and protective breakwater; compaction and soil improvement of the reclaimed platform. The lion’s share was marine engineering construction – dredging actually represented just 18 percent of the contract.

The islands of 450 x 550 m were reclaimed at a level of plus 6.5 m, at locations where depth of the sea bottom varied between minus 13 to minus 15 m. Total dredging volume was 9.6 million m³ by trailing suction hopper dredgers (TSHD) and 2.5 million m³ by cutter suction dredgers (CSD). This eventually created a net surface above water of 230,000 m² per island. Since the reclaimed land has to be able to withstand pressures from the very heavy drilling installations and since the client imposed very stringent liquefaction criteria in case of earthquakes, important compaction works on both islands were needed, including among others by vibrations. As such, a density on the working area and on the slopes of 90 percent ‘maximum dry density’ (MDD) was achieved.

Each island comprises an operations port, with a 450-m quay wall and 400 m long breakwaters of 400 m. Quay walls were constructed by means of 2,342 prefabricated concrete blocks per island, weighing each between 50 and 70 tonnes. The bank edge protection, circumfering 1,500 m per island, was made of 38,486 Accropodes II® blocks and no less than 4.5 million tonnes of rock materials of various sizes (quarry run, underlayer and armour rock up  to 8 tonnes).

For precasting, temporary storing, and transportation of quay wall construction blocks, Accropodes, and stones and rock from the Stevin Rock quarries, an onshore base was built in Ras-al-Khaimah where at the peak of activities no less than 350 workers were employed. A fully independent 4 ha base camp was installed on Zirku island, for accomodation, site offices and supplies of basic necessities. At peak moments, up to 1,200 personnel from 32 nationalities were employed at the construction sites, in the onshore base workshops, and in the Zirku ‘village'.

The project was executed in compliance with the highest standards of quality and offshore safety.  The team achieved a remarkable safety performance of more than 11 million man hours with only 5 minor LTI's.

 

 

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