Subsea Water Treatment Pilot Testing at the Ekofisk Field in the North Sea

Abstract

A new subsea water treatment system for injection water has been developed and has undergone several phases of testing. A full-scale water treatment module has been built and is currently being tested at the Ekofisk field offshore Norway to determine its viability under North Sea field conditions. A hybrid configuration approach is used, as the test is based on utilizing existing infrastructure to minimize project cost. The subsea water treatment system was therefore installed next to a fixed platform and connected to topsides through a flexible hose for water supply and an umbilical for power and communication of the subsea water treatment module. The disinfected water is lifted to the platform deck through a retrieveable lift pump, and the treated water is then analyzed before injection into the reservoir through a high-pressure pump and converted production well. The primary objective with the test is to replicate the results from a similar full-scale version that was tested in sheltered environments in a fjord on the Norwegian west coast, which would verify the water treatment module's performance and reliability through seasonal variations and thereby demonstrate its ability to deliver injection water of a quality in real offshore conditions. The secondary objective is related to Ekofisk requirements and reservoir related impacts of injecting water treated by this new submerged water treatment technology. The results from this test will not become available until second half of 2019. The commissioning phase has been completed, and the results achieved so far are within expectations, with high disinfection capabilities and equipment regularity. The particle content in the water was generally higher than previous inshore testing, which was not a surprise due to the harsh environment and relatively shallow water (∼70m) in the Ekofisk Area. The project has recently moved into the longterm testing phase. The results from this phase will become available second half of 2019.