Decentralized Subsea Water Treatment and Injection System for Unlocking FPSO Hydrocarbon Processing Capacity and Reduce Costs

Abstract

Abstract Voidage replacement is a pre-requisite to optimize production and hydrocarbon recovery in oil fields. Sometimes, deep water production systems suffer from low water injection (WI) uptime and the natural declining reservoir pressure. The congested FPSO topside makes modifications and upgrades expensive with long shutdowns. Therefore, complementing existing WI with subsea water treatment and injection may be considered attractive. Moving process subsea allows for simplifying new developments and enables long tiebacks with ‘local’ and decentralized water treatment and injection. Subsea seawater treatment for water injection has several inherent advantages compared to topside treatment. One significant aspect is the increased flexibility afforded to reservoir engineers in improving effective reservoir management by providing the opportunity to implement any desired water injection capacity, anywhere and anytime. In addition, the ability to provide ‘tailor made’ water for injection into oil reservoirs, that may be phased, is seen as a game changing opportunity for offshore oilfield production companies wishing to produce more, produce faster, and produce cheaper. The solution, qualified for water depths down to 3,000 m, enables weight reduction and simplification of the topside process equipment, with its associated maintenance requirements and HSE footprint and enables more active reservoir management. The short distance the water travels, and the unique approach to water treatment make the subsea solution attractive with reduced energy and chemical consumption. The modular approach and flexibility provide more freedom to manage the subsurface uncertainties, mitigating risks and pursuing upsides. The process advantages of the seawater treatment plant being on the seabed allows for a design that is simplified compared to a corresponding topside plant. The all-electric design also has the capabilities to be installed, moved, and reused on the seabed with minimum impact on topside infrastructure. There are several aspects of the design that reduce the HSE impact of water injection. This includes lower power consumption (reducing carbon footprint) and no (or significantly reduced) liquid chemical requirement; hence, lower handling exposure for operators, improving the operational safety.