FPSO Anna Nery (Marlim 2)

Project Description:

The project is for the Engineering, Procurement, and Construction of a seawater treatment system provided in two integrated process modules to deliver 38,154 m³/day (240,000 BPD) of low sulphate water for Enhanced Oil Recovery waterflood injection on the Anna Nery FPSO that’s part of the Marlim Cluster Revitalisation project for the Campos Basin, offshore Brazil.

Project Scope:

The project scope, integrated over two process modules, consists of Feed Water Booster Pumps, Electrochlorinator, Self Cleaning Coarse Strainers, Multi-Media Fine Filters, Guard Cartridge Filters, High Pressure Feed Pumps, Sulphate Removal Membrane Trains, Membrane Clean - In - Place package, Two Stage Vacuum Deaerator, Chemical Dosing Sets, Water Injection Booster Pumps, Recycle Plate and Frame Coolers, Water Injection Pumps, Plant Control System, Piping, Valves and Instrumentation.

Process Description:

Seawater is pumped using the Seawater Lift Pumps and directed to the seawater treatment system.  The raw seawater is chlorinated via the electrochlorination package and introduced into the seawater lift pump suction lines.  Sodium hypochlorite is used to limit the potential of biological activity in the downstream processes. . As the Coarse strainers are located at approximately 20m elevation the inlet seawater booster pumps are provided to boost the pressure to the coarse, media and cartridge filters.

Automatic backwashable seawater coarse strainers remove larger particulate matter from the feed stream to the SRU plant. The filtered seawater from seawater coarse strainers is used as source water for the water injection system.

The feed stream is directed to MMF pre-treatment. The system treats the SRP feed water to further remove the particles down to the level required for SRU membrane treatment. The filtrate quality is typically expected to have an SDI < 5.

Cartridge filters are installed downstream of the MMF units to prevent potential carry over of media and particulate matter from the media filters to the SRU trains. The filters will be horizontal vessels.

The filtrate water quality will ensure the SDI level as recommended by SRU membrane manufacturer is met. However with the significantly better filtrate quality of the UF membranes the requirement for downstream cleaning of the SR membranes is reduced.

The filtered seawater is routed to the suction of the Sulphate Removal Unit Feed Pumps to boost the conditioned water to the required feed pressure for the membranes.  The SR Feed Pumps operate in parallel. Antiscalant is dosed into the common suction piping of the Sulphate Removal Feed Pumps, decreasing the scaling tendency by limiting the formation of sparingly soluble salts in the membrane system. A non-oxidizing proprietary biocide for treating the SR90 membranes is also periodically batch dosed into the common suction piping of the Sulphate Removal Feed Pumps.  Finally, SBS is also dosed into the common suction piping of the Sulphate Removal Feed Pumps to remove the residual chlorine present in the seawater to prevent irreparable damage to the SR90 membranes.

The seawater flows to parallel operated Sulphate Removal Units.  The membrane trains are configured so that they maintain the maximum capacity even if one of the trains is offline for CIP.

The feed pressure to each SRU is controlled based on the permeate flow set point. The SRU produces 75% of the feed flow as low sulphate permeate Seawater.  The low sulphate SW from each SRU is merged and then directed to the deaerator. The remaining 25% of the feed flow ends up as high sulphate content reject seawater and is directed overboard.

The SRU treated seawater then enters the Vacuum Deaerator to remove dissolved oxygen from the water. Oxygen scavenger is dosed to the sump of the deaerator to chemically reduce the remaining oxygen further to the required levels.

Deaerated, low sulphate injection water from the deaerator is routed to water injection booster pumps. These pumps are provided to boost the feed pressure to the downstream systems and the water injection pumps to deliver the required water injection pressure at the package boundary. Another stream is provided to individually feed each Water Injection Pump with produced water to achieve total injection capacity. Each of the Water Injection pumps will be fed either from the Produced Water stream or the treated Seawater stream. Separate headers are provided for high pressure seawater and high pressure produced water streams to be able to inject either produced water, seawater or a blend into each WI risers (by others).  The minimum flow line of each water injection pump is recirculated back in the pump suction side via a recycle cooler to control injection water temperature during system turndown.

There is a membrane cleaning in Place (CIP) system for the SR trains. The CIP Tank capacity is designed for the 1st stage of SR membranes or 1 train of UF membranes wash. CIP Pumps and cartridge filter are designed for cleaning of 1st stage of 1 SRP train (maximum capacity). One CIP Heater is provided for each CIP tank and is sized to heat up the cleaning solution volume within 2 hours.