Unlocking Deepwater Tiebacks with Subsea Desulphatation Technology

Abstract SPRINGS® (Subsea PRocessing and INjection Gear for Seawater) is a technology for subsea water treatment and injection. The technology aims to unlock new tiebacks in deep water that previously would be unviable due to congested topside and/or long step-out. The subsea station can be connected to the topside with only a power and control cable, thanks to the following features: The control system does not require control fluid since all subsea valves are actuated electrically.The large subsea pumps do not require any barrier fluidRegular membrane disinfection is performed by a chemical, which can be stored directly subsea The scope of this paper is to describe the technology and illustrate the steps of the significant collaborative work performed by the technology partners to achieve the completion of the process qualification and industrialization. The qualification roadmap, which has been recently completed, not only progressively derisked the technology, but also offered design and operational insights to improve and optimize the original concept, conceived in 2009 specifically to address deepwater tiebacks applications. The process was fully qualified both with laboratory hyperbaric tests on membranes, conducted in 2010 and with an offshore deepwater campaign in 2014. Further process optimizations and improvements have been obtained in the subsequent years thanks to an onshore pilot, using raw water from a nearby basin, run in parallel with the industrialization of the subsea system components. The industrialization, started in 2016, has been successfully completed in 2024 with the qualification to API 17Q TRL 4 or greater of all the building blocks necessary to operate the system in an all-electric mode. The typical application scenarios for subsea water desulphatation are both greenfields (long, deep tiebacks to new/existing Topside), satellites and brownfields (debottlenecking of the existing facilities). The paper presents the results of the technical-economical evaluations conducted considering the deployment of the subsea seawater treatment and the related benefits and challenges. The outcomes of the qualification activities, including tests of equipment, and optimization of design and process parameters, show that the challenges posed by the subsea environment have been tackled and lessons learned are available for a project deployment. The paper presents the updated evaluations for the technology application, the latest outcomes of the industrialization program and the process optimization results from the onshore pilot that has been running over the last 5 years.