Based in Soyo, in the Zaire Province, Angola, Angola LNG is one of the largest ever single investments in the Angolan oil and gas industry. An extensive pipeline network of over 500km delivers gas from offshore oil fields to the processing and liquefaction plant at Soyo. The Angola LNG plant is a single train facility with production capacity of 5.2 million tonnes of LNG per year, plus natural gas, propane, butane and condensate.

This landmark project for Angola is unique in global LNG projects as the plant will initially be supplied with associated gas produced during oil field operations. This means the project will contribute significantly to the elimination of gas flaring in the country, allowing for the development of offshore oil reserves in an environmentally sustainable way.

The project

The Royal HaskoningDHV Protected Storage Engineering team provided geotechnical design and structural engineering (both tender design and detailed engineering) for four concrete tanks. The team also provided site supervision during the execution of soil investigations and excavation works up to foundation level as well as during construction of the tanks.

The geotechnical design had special considerations as two of the structures were situated on reclaimed land (a former riverbed), while the other two tanks were on soft soils.

The four structures were built between 2009 and 2010 for the subcontractor of the tank Toko Kanetsu KK, Japan, under contractor Bechtel, USA, for client Angola LNG, for a total construction cost of $200.000.000.

The structures were built for the storage of:

  • LNG (2 tanks, 159.000m³)
  • LPG Propane (88.000m³)
  • LPG Butane (59.000m³)
  • Condensate (108.000m³, a liquid by-product in the oil/gas industry)

The design included complex 3D finite element calculations taking into account crack formation and temperature loading. Analysed load cases included:

  • Earthquake
  • Liquid spill (leakage of the steel inner tank resulting in liquid pressure plus temperature loading)
  • Seismic loads
  • Impact loads
  • Blast loads
  • Fire loads on the roof