Description

The gravity storage base comprises a circular reinforced concrete storage tank. Four ballast/deballast cells are arranged at quarter points around the storage tank, and these extend by 2.5 metres below the underside of the storage base.
The storage tank also features an integrated 12 metre diameter separation cell for the treatment of seawater ballast prior to discharge to the sea.The capacity of the storage base is dependent upon the situation with issues such as remoteness, nature of tanker operations and the ability to shut-in the field all having a bearing on the capacity chosen. A standard storage capacity of 200,000 barrels has been used in development, though this can be increased to 300,000 barrels subject to constraints imposed by buoyant uplift and cost etc.

Export

In the case of the oil production buoy a number of options are available for the export of the produced oil. These include using the hydrostatic pressure differential between the stored oil and surrounding seawater. In tests this has performed well with an average flow rate of 25,000 barrels per hour being sustained. This produces a loading time of 8 hours for a 200,000 barrel capacity storage unit which is comparable with achieved flow rates for existing offshore loading facilities. This works well in deeper water where a sufficient pressure differential exists. In shallower waters (below 100 metres) it may be necessary to use a tanker mounted booster pump.