Three factors influenced the final development decisions, Bliek says. The first consideration was the need to minimise service interruptions from the existing platform.
“Second, (Malampaya) sits in 45 metres of water on calcareous soils, so it is very difficult to use a piled foundation. It requires some other type of foundation. And third, it’s a very remote site,” with little upstream infrastructure or lifting capacity in the region, he explains. “So we didn’t want to do any kind of extra lifts, added hook-up and commissioning, things like that.
“We selected a concept that is self-installable, that is constructed as a whole, that could be moved next to the existing platform with minimal disruption of production, and installed quickly without lifts.”
Unlike the concrete gravity based platform, the DCP’s 7750-tonne substructure rests on steel footings. The 3300-tonne topsides include two 100% compressors from Siemens driven by Rolls-Royce RB211 turbines, air cooler modules, a utility module, equipment room, pipe rack and a deck crane. The new platform is linked by 43-metre bridge, also designed by Arup, to the original Malampaya platform.
Calcareous sands were not the region’s only challenge, says Martyn Turner, Shell’s design team lead for the depletion compression project.
“I think it’s worth remembering that, as you come further north in the Philippine Islands, you’re in a seismic region and also in a typhoon region. So one of our challenges was designing for both.”
To mitigate risk, the DCP had to be designed with an air gap of 23 metres, which meant installation options were limited, he says.
“That was one of the challenges around the installation. The lift barge capability in the region is not geared up for lifts that high. So that was another reason for the selection of a self-installing platform.”