New design of a floating storage and production unit

Where a pipeline cannot be employed for technical or economic reasons, the existence of facilities for temporary storage is a prerequisite for the exploitation of an oil well. The choice of an offshore storage system, of which a number of types exist, is largely governed by environmental factors at the field. The advantages and disadvantages of existing storage systems are reviewed and the design of a new "spar" type storage unit discussed. This unit is mobile, yet is well suited to use in adverse weather conditions. In addition to its role as a storage tank and a single point mooring buoy, the unit also serves for production. The design criteria, the oil system and the single point mooring section are dealt with, and also aspects of the fabrication of the unit and the methods employed to position and recover it. Introduction It is envisaged that energy requirements in the next few decades will be met from undersea sources and that the exploitation of oil wells will increasingly involve operations in deeper water and at greater distances from coasts. Although not new, the storage of oil at sea is a new aspect of offshore technology and one which is in the course of development. Various storage facilities have been developed in recent years, each with its specific advantages and shortcomings. In most cases, such facilities are designed for a particular location and are more or less rigidly attached to the seabed, or resemble a ship's hull and are anchored by means of a number of chains or are moored to a single point mooring system. Where large-volume storage units are involved, surface vessels can be used for the purpose only if the environmental factors at the location are such that no violent motions occur which impose heavy stresses on the anchorage system.