water injection system had two design cases Case A – Injection of 100,000 barrels of water per day (BWPD) (662 m3/hr), injection pumps operating in parallel with a discharge pressure of 3,000 psi (207 bar) Case B – 60,000/65,000 BWPD (397/431 m3/hr), pumps in series /parallel, discharge pressure is 3,000 psi (207 bar) and 30,000/35,000 BWPD (198/232 m3/hr) with a discharge pressure of 5,000 psi (345 bar) The two duty seawater lift pumps discharged water at 1,590 m3/hr and 30.5 psi (2.1 barg) to the seawater filters. These comprised six dual media (garnet and anthracite) filter beds. Normal flow was downwards. Backwash flow of water and air was upwards with flush water discharged overboard. Backwashing was initiated by a high differential pressure across a filter bed. Filtered water was routed to the top of the deaerator. This was a vertical vessel 12.6 m high and 4.0 m diameter, the internals comprise a packed bed. Air was stripped from the water by an upflow of fuel gas, gas/air was routed from the top of the vessel to the flare. Oxygen scavenger was injected into the deaerator vessel to remove any residual oxygen. Deaerated water was drawn from the base of the vessel by the deaerator pumps and was transferred to the cold water header operating at 90 psig (6.2 barg). Process and utility coolers were supplied from the cold water header, warm water from the coolers was routed to the degassing drum where any air or gas was removed. From the degassing drum water passed to the injection filters. Water was filtered in the water injection filters, one duty and one on standby/backwash. From the filters water was routed to the water injection pumps. The three water injection pumps each had a capacity of 221 m3/hr with a differential head of 2068.5 metres (209 bar). The pumps discharged to the 3,000 psi manifold and wellheads. The single water injection booster pump (221 m3/hr, 1,379 m (139 bar) differential head) took its suction from the discharge of the water injection pumps and discharged to the 5,000 psi (345 bar) manifold and wellheads. There were eight water injection wells, each well had a capacity of 15,000 BWPD (99.4 m3/hr). Buzzard An alternative configuration and technology is used on the Buzzard field in the North Sea. Seawater lift pumps deliver 4,000m3/hr at 12 barg to the seawater coarse filtration package. After filtration the water