Knarr / Rosebank FPSO Seawater Treatment
A redeployed FPSO seawater treatment system upgraded with additional ultrafiltration capacity, a zero-liquid-discharge biocide solution, and process improvements based on seven years of operating experience.
From Knarr to Rosebank, Treatment That Travels
The seawater treatment system installed on the FPSO had already accumulated seven years of operational experience before the vessel was prepared for redeployment to the Rosebank field. For the new operating requirements, Vulkan applied this experience to expand and improve the existing treatment system rather than approaching the project as an entirely new installation. The scope included additional ultrafiltration capacity, a zero-liquid-discharge solution for biocide treatment, and improvements to the process and control systems. Commissioning and startup are planned for 2026.
The Challenge
Redeploying an existing FPSO to a new field creates a different engineering challenge from designing a new treatment plant. The existing seawater treatment system needed to be adapted to increased treatment requirements while making effective use of the equipment and operating knowledge already available. The objective was to increase capability while maintaining a reliable and integrated seawater treatment process. The project required:
- Increased seawater treatment capacity
- Improved environmental handling of biocide streams
- Integration with existing sulphate removal and deaeration systems
- Process and control-system modifications
- Application of operational lessons accumulated over several years
The Vulkan Solution
Vulkan's scope focused on expanding and improving the existing seawater treatment system. Ultrafiltration provides an important barrier ahead of the downstream membrane systems by removing suspended solids and other contaminants from the incoming seawater. The solution improves the management of biocide-containing process streams and supports tighter environmental performance without compromising the requirements of the seawater treatment process. Together with ultrafiltration and chemical treatment, these systems prepare seawater for injection by controlling particles, sulphate concentration, dissolved oxygen, and other parameters that can affect reservoir and equipment performance. These improvements were based on lessons learned from several years of operating the treatment technology and were incorporated to improve system operation, monitoring, and maintainability. One of the key advantages of the project was the availability of extensive operating experience from the existing seawater treatment system. Seven years of operational history provided practical knowledge of membrane behaviour, system interactions, maintenance requirements, chemical treatment, and control philosophy. Vulkan used this experience to support the engineering of the upgraded system and reduce the need to relearn known operational behaviour after redeployment.
- Ultrafiltration (UF) expansion — two added trains
- Zero-liquid-discharge (ZLD) biocide solution
- Sulphate removal & deaeration carried over
- Process & control-system improvements
- Experience transfer from 7 years of Knarr operation
- Commissioning & startup (2026)
The Result
The upgraded Rosebank seawater treatment system combines proven equipment with increased capacity and targeted process improvements. The result is an integrated seawater treatment system prepared for its next operating phase. The project demonstrates how operating experience from an existing installation can be transferred directly into a redevelopment project through: Application of long-term operational experience Commissioning and startup support
- Additional ultrafiltration capacity
- Improved biocide management
- Continued sulphate removal and deaeration
- Process and control-system optimization
- Application of long-term operational experience
- Commissioning and startup support