MEG Regenerator / Reclaimer Design

1. MEG Regenerator / Reclaimer Design T.M. Latta, WorleyParsonsCanada M.E. Seiersten, Institute for Energy Technology – IFE S.A. Bufton, INTECSEA, WorleyParsons Group Offshore Technology Conference, Houston │ 6-9 May 2013

2. Objectives • Identify the Key Groups that contribute to a successful design of a Monoethylene Glycol (MEG) regenerator and reclaimer • Provide an overview of what they contribute • Emphasize the need to interface early during the project

3. Outline • Key Groups Involved in MEG Design • Factors Affecting Lean/Rich MEG Chemistry • Flow Assurance • Testing/Simulation • MEG Regenerator/Reclaimer Design • Conclusions • Questions

4. Key Groups Communication between all groups is critical!

5. Key Groups • Important to coordinate “ALL” groups “EARLY” in the Concept Phase to permit MEG regenerator/reclaimer design considerations to be addressed • Starting MEG regenerator/reclaimer design “AFTER” the Concept Phase is a major reason for poor unit design • MEG regenerators and reclaimers are not “Off-the-Shelf” design packages they need to be tailored to the unique aspects of the Lean/Rich MEG circuit chemistry

6. MEG Chemistry Factors Non-condensable vapors Seal Gas (N2) MEG Regenerator Overhead Condenser Vacuum Compressor Condenser Produced Water MEG Regenerator Non-condensable vapors • Lean MEG Circuit Rich MEG from MEG Regenerator Feed Filter MEG Reclaimer Overhead Condenser Product Lean MEG to Subsea Choke Salt Free Lean MEG Salty Lean MEG MEG Reclaimer Used to make salt brine Salt Handling System MEG Reclaimer by-pass Product Lean MEG Injection Pumps Salt Cake or Salt Brine Product Lean MEG Storage

7. Gas MEG Chemistry Factors Feed Gas Separator Inlet Gas Heater SUBSEA CHOKE Inlet Separator Gas • Rich MEG Circuit Inlet Liquid Filter Inlet Liquid Heater Stabilizer Feed Separator Hydrocarbon Liquids Well Head Gas Product Lean MEG from Injection Pumps Rich MEG Storage Rich MEG Flash Drum Separator MEG Regenerator MEG Regenerator Feed Filter

8. MEG Chemistry Factors • Formation water flow and composition • Acid gas partial pressure (pH) • Total water flow and Hydrate inhibition program(s) selected • Corrosion program(s) selected • Other chemicals added to the system

9. Flow Assurance • Purpose of flow assurance group (relative to MEG design) is to: • Develop hydrate inhibition program • Provide data input for corrosion study work • Provide data input for precipitation study work • What is Flow Assurance? • Ensuring “flows” go from Point A to Point B successfully • Designing and operating the system to manage challenges to the flow

10. Flow Assurance • Flows (relative to MEG design) that concern the flow assurance group • Lean MEG flow from discharge of Lean MEG injection pump to wellhead • Rich MEG flow from wellhead to inlet separator/slug catcher • Flows (relative to MEG design) that concern the hydrocarbons process group • Rich MEG flow from inlet separator/slug catcher to MEG regenerator • Lean MEG from MEG regenerator to Lean MEG injection pump

11. Flow Assurance • Major process data inputs from flow assurance that impact on Lean/Rich MEG chemistry are: • Condensed water flow • Formation water flow and composition • Acid gas partial pressures (pH) • Lean and Rich MEG flows/compositions • Any other injected chemicals • All the above data varies over the life of the facility and a profile over time needs to be developed

12. Flow Assurance • Optimization of Lean and Rich MEG flows/compositions: • Work towards optimizing the “Total” facility based on hydrate prevention and MEG system design • Important that flow assurance and hydrocarbons process groups interact • Need to discuss advantages and disadvantages of different Lean and Rich MEG target concentrations • Hydrate program will then define the design cases to be used for the MEG regenerator and reclaimer

13. Flow Assurance • Development of the corrosion control program is critical and typically involves corrosion experts from the Customer side working in conjunction with: • Flow Assurance • Testing/Simulation Facilities • Assistance and data input from flow assurance is key to defining the corrosion study design cases

14. Flow Assurance • Critical data from flow assurance for a corrosion study would be: • Acid gas partial pressure (pH) • Pipeline temperature • Formation water flow and composition including organic acid content • Condensed water flow

15. Testing/Simulation • Purpose of testing/simulation facility is to: • Provide input into the development of design cases for corrosion and precipitation studies • Perform testing/simulation work using the design cases to develop: • Corrosion control program(s) • Precipitation analysis in Lean and Rich MEG circuits • All the above data varies over the life of the facility and a profile over defined time periods needs to be developed • Impacts on Lean/Rich MEG chemistry are identified and dealt with in the design

16. Testing/Simulation • Corrosion control and precipitation analysis impact on decisions made by flow assurance and hydrocarbons process groups • Important to have Testing/Simulation Facility involvement early in the project and included in discussions with other key groups

17. Testing/Simulation • Flow assurance data input is required for a successful corrosion study to be carried out • The corrosion control program can change over the life of the facility depending on whether or not there is formation water breakthrough • Typically filming inhibitors are used when there is formation water breakthrough • Typically pH stabilizers are used when no formation water is present

18. Testing/Simulation • Film forming inhibitor: • Molecules adsorb on steel surface (typically ~100 ppm added) • Gives ~ 10-200 ppm Fe in rich MEG • pH stabilization: • Increase the HCO3-/CO32- concentration to enhance formation of protective FeCO3 on steel surface (Add a base (0.1-0.5 M) to the MEG) • Gives ~1-20 ppm Fe in rich MEG

19. Testing/Simulation • If the corrosion program is to be switched due to formation water breakthrough it is important to have a change-over strategy developed • Lean/Rich MEG chemistry is greatly affected by the type of corrosion program(s) employed • Need to determine corrosion control program(s) early on in the project • Corrosion control needs to be determined before conducting any precipitation analysis studies

20. Testing/Simulation • Identify if a precipitation study needs to be conducted to ensure there are no detrimental affects to the operation • Both flow assurance and hydrocarbons process data input are required for a successful precipitation study to be carried out • Precipitation study can only be done after corrosion control program is defined

21. Precipitation Study • Developing the cases • Reveal what ionic species may precipitate out and to what extent • Maximum MEG reclaimer percent bypass • Establish a suitable bypass for normal operation to control salt content in Lean MEG based on an appropriate safety margin • Developing Lean MEG specification • Define measures required to reduce the precipitation risk

22. Lean/Rich MEG Circuit Locations • Wellhead • Upstream of Lean MEG Injection point, Subsea Choke inlet (production gas + Lean MEG at this point), Subsea Choke outlet • Pipeline • Inlet (high temperature), coldest section at seafloor, Inlet Separator • Inlet Liquid Heater • Rich MEG Flash Drum • MEG Regenerator • Feed Filter Outlet, MEG Regenerator Bottoms • Lean MEG Bypass around MEG Reclaimer • Lean MEG Product • Storage Tank, Injection Pump, coldest section at seafloor

23. MEG System Design Objectives • Key objectives in the design: • CAPEX • OPEX • Smooth operation • Reliability • Key objectives that need to be considered for platforms: • Footprint • Weight

24. Seal Gas (N2) Vacuum Compressor MEG Regenerator/Reclaimer Design Non-Condensable Vapors Condenser Non-Condensable Vapors ~ 50 wt% MEG Overhead Condenser MEG Regenerator Overhead Condenser • MEG Regenerator & MEG Reclaimer System Overhead Receiver Chemical Injection Overhead Receiver MEG Reclaimer Salty Lean MEG Salt Free Lean MEG Hydrocarbons Rich MEG Feed Chemical Injection Produced Water Salt Handling System Heating Medium Supply Used to make salt brine MEG Reclaimer by-pass Hydrocarbons ~ 80 – 90 wt% MEG Heating Medium Return Salt Slurry Product Lean MEG to Storage Salt Cake or Salt Brine

25. Hydrocarbons Process Group • Purpose of the hydrocarbons process group is to • Develop precipitation study to optimize MEG reclaimerbypass • Develop design basis for MEG regenerator and MEG reclaimer using flow assurance process data and precipitation study data • Since conditions change over time this needs to be accounted for in the design and can greatly influence the design strategy employed • Important for hydrocarbons process group to interface at start of project with flow assurance and testing/simulation facility to ensure proper precipitation study is performed

26. Hydrocarbons Process Group • There are three possible options that can be employed for the MEG Recovery System which are: • MEG regenerator only • MEG regenerator and reclaimer combined flash and distillation vessel • MEG regenerator distillation column and separate MEG reclaimer flash drum

27. MEG Regenerator Design • Design considerations for MEG Regenerator: • Feed filtration (all sources of suspended solids) • Operating temperature and pressure • Water removal and pH • Acid gas removal (CO2 and H2S) • Hydrocarbons removal • Injected chemicals (how do they distribute) • Fouling of equipment • Sparing philosophy

28. MEG Reclaimer Design • Design considerations for MEG Reclaimer: • Establishing the design MEG reclaimer bypass • Operating temperature and pressure • Solids loading (suspended + forced precipitated) • Hydrocarbons removal • Injected chemicals (how do they distribute) • Fouling of equipment • Sparing philosophy

29. MEG System Objective • Ultimate goal is to produce a Lean MEG product which is “on-spec” which takes into consideration: • MEG wt% • Dissolved solids • Suspended solids • Oxygen concentration

30. Conclusions • The main oversight in many Monoethylene Glycol (MEG) regenerator/reclaimerprojects is not taking into consideration the above aspects early enough to positively influence the design and operability of the units • Not considering these facets in the initial design process usually results in non-optimized MEG regenerator/reclaimer units that are unreliable and difficult to operate