Water injection facilities are now used more frequently on offshore platforms to maintain reservoir pressure and hence maintain the oil production capacity and increase oil recovery. The injection of large amounts of treated seawater at high pressure into the reservoir traditionally requires considerable equipment space and power. The system operating weight will also be high.
The development of new fields at increasing water depths has encouraged the use of new technology. The development of topside systems with high efficiency and light weight is thus a challenge for platform designers and equipment suppliers. The water injection system for the Snorre TLP represents a significant advance in the system design, resulting in considerable space savings and a weight saving of about 560 tonnes.
The Snorre Water Injection Facility is the first of a new generation of systems. Cartridge filters which are cleaned by means of sulphuric acid are used for fine filtration of the seawater. The deoxygenation of the seawater is carried out in a two stage nitrogen stripping unit, reducing the oxygen content to below 10 ppb without chemical additives. Vertical injection pumps were also selected eliminating the traditional booster pumps and lube oil system. A full scale test of this unique system was carried out in the summer 1990. Test results showed that all parts of the system were operating satisfactorily and within the design specification.