Subsea Water Treatment and Injection Station

Abstract

AbstractDescriptionMany reservoirs in the UKCS are experiencing rapid pressure drop, reduced production, low recovery rates and high water cuts. More fields are also being developed as subsea fields. Moving the water treatment and injection to the seabed offers opportunity for improved recovery. Such a complete subsea water flooding system is now available as a Subsea Water Treatment and Injection Station with qualified technology for the first time, providing a change in mindset for offshore recovery by enabling treatment and injection subsea.ApplicationTreating water at depth, and injecting from the seabed, enables cost-effective developments avoiding expensive flow-lines. 4D-seismic reveals that optimal positioning of water injection wells is not always technical or economical reachable from platform. With maximum flexibility and without the traditional topside restrictions, an improved reservoir drainage strategy enables increased/enhanced recovery. The technology is therefore applicable for all offshore fields at any stage of their production life.The unique merging of proven technology into a standard template provides operators with a turn-key ready station for subsea water injection of treated water. The Subsea Water Treatment and Injection Station contains water treatment, injection pump(s), and injection trees. The station ties back to host with an umbilical, providing power and controls. Future systems may also include membrane modules.The subsea water injection and treatment concept is applicable to Subsea Production and Processing Systems. With an added separator, fields with high water cut can be processed subsea to re-inject produced water.ConclusionsThe new subsea seawater treatment system has recently completed successful 24 months of trials on the seabed with the help of two global JIP ̀s. The new water treatment system provides water superior in quality compared to that achieved by a traditional topsides water treatment plant in areas important for water injection for IOR. – I.e. a lower degree of bacterial concentration, good disinfection and solids reduction.In this paper, system capabilities and experience from testing together with membranes will be presented.