C3.2.1. Topside Separation_2020

1. Offshore Production Technology
Separation Systems
Marine & Offshore Technology

2. Learning Outcomes
1. Understand the process flow of the Separation Module
onboard the FPSO
2. Explain, by means of a diagram, the separation process
inside a 3-phase separator for well fluids coming
onboard the FPSO

3. 1. Understand the process flow of the
Separation Module onboard the FPSO

4. FPSO Layout
http://tiny.cc/DEOPT_FPSO

5. Typical Specification of (Dead) Crude Oil
Flow rate : 60,000 BOPD
Temperature : 50C minimum @ shuttle tanker
Pressure : 10 bara
TVP : 0.73 bara @ 38C (10.6 psia @ 100F)
RVP : 0.46 bara (6.7 psi)
BS&W : 0.5%
Salt Content : 1900 milligramme/litre (mg/l)
H2S Content : 1.0 ppm
Total sulphur : 0.3% wt
CO2 Content : 0.005 mole % (50 ppm)

6. Primary Production System

7. Oil Separation
Produced fluids flows from
• production risers
• via a turret
• manifold
to HP Separator

8. Oil Separation

9. Turret Mooring System
• Swivel arrangement
could allow to add or
change out module.

10. Formation of Slug and Slug Flow
Liquids accumulating
in Pipeline Low Spots
Types of 2-phase Flow
2-phase pipeline
liquid

11. Slug Catcher
• Such surges of gas and liquid often require the use of
Slug Catchers before the entry of the fluid into the
separators
• Slug Catcher is designed to catch slugs of production
fluid which may occur depending on the flow regime
within the subsea flowlines and risers
• On the FPSO, a cylindrical shaped slug-catcher is used
to save space

12. Slug Catcher used on Land Installations
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13. Slug Catcher – Cylindrical Form
Horizontal Slug Catcher
Vertical Slug Catcher
Pipe-fitting Slug Catcher

14. Sand Removal
Sand-Jetting
Use of Vortex Unit

15. High Pressure Separator
• Designed to handle the required amount of gross
liquids consisting of the required production rate of
crude oil and a coincident maximum produced water
flow-rate.
• The corresponding maximum associated gas flow-rate
is a function of the gas-oil ratio (GOR).
• The HP Separator will operate normally at around 11
bara.

16. Separator –
Principle of Separation into Oil, Water and Gas

17. Separator –
Principle of Separation into Oil, Water and Gas

18. Pre-Sand Removal
Inside of a Separator (water side)
Sand removal unit
Demister
(Mist extractor)

19. HP Separator

20. HP Separator
Produced Gas valves Pre-heater bf separation
Produced Gas valves Produced oil Produced water
Level gauge

21. High Pressure Separator
• Produced water from the HP
Separator flows to a produced
water treatment package
consisting of hydro-cyclones and
a degasser.
• Gas from the HP Separator is
routed to the first two stages of
the HP Compression train then
through the gas dehydration
package for final water removal
and into the final stage of HP
Compression.
Degasser mounted on
top of hydro-cyclones
Hydro-cyclone unit

22. Sand Removal
Sand removal units mounted
before HP Separator
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23. Pre-Heaters
Plate-Type Heat Exchanger Shell-and-Tube Heat Exchanger

24. Schematic Representation of 3-stage Separator
Crude oil drop-lines into storage tanks

25. Low Pressure Separator
• To achieve the specification suitable for storing dead
crude aboard the shuttle tankers, the crude oil from the
HP Separator is routed to the LP separator via a crude
oil heater.
• This raises the temperature of the crude oil to normally
around 80C.
• The hot crude oil is then flashed down to around 1.3
bara in the LP separator.

26. Low Pressure Separator

27. Low Pressure Separator
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28. Low Pressure Separator
• Produce a dead crude oil product to the correct Reid
Vapour Pressure (RVP) and True Vapour Pressure (TVP)
specification suitable for shuttle tanker export.
• Pre-heater and a crude oil heater provides the
separation system with the necessary flexibility to
handle start-up transient conditions, variations in crude
arrival temperatures and changes in the fluid
composition.

29. Electrostatic Coalescer
• An electrostatic coalescer aids
in the coalescing of water
droplets as they pass through
the electrical field produced by
the grid within the coalescer.
• This equipment may be
necessary to achieve low
BS&W (Basic Sediment &
Water) specifications of
around 0.5%.
• This vessel must always run
liquid full.

30. Electrostatic Coalescer
Operating Principle

31. Electrostatic Coalescer
• To achieve the required tanker export Base, Sediment
& Water (B&SW) specification of normally 0.5% the
crude oil is routed from the LP separator to an
electrostatic coalescer.
• Decision to install an electrostatic coalescer or not
depends on how easy the oil and water emulsion
formed as part of the production process breaks down.
• Significant cost saving in equipment cost can be
achieved if this item of equipment can be eliminated.

32. Electrostatic Coalescer
Example only – not used on FPSOs.

33. Transfer Pumps
• After the crude has passed through the electrostatic
coalescer, it is pumped by the crude oil transfer pumps
into the ship's storage tanks in the case of a FPSO or to a
Floating Storage Unit (FSU) in the case of a Floating
Production Facility (FPF).
Heating coils (steam) for maintaining
crude temperature

34. Transfer Pumps
Transfer pumps module

35. Principal Equipment
Slug-catcher 1 × 100%
Pre-heater 1 × 100%
HP Separator 1 × 100%
Crude Oil Heater 2 × 50%
LP Separator 1 × 100%
Electrostatic Coalescer 1 × 100%
Crude Oil Transfer Pumps 2 × 100%

36. Principal Equipment
Pre-heater
• This is to heat the
incoming production
fluids at start-up to
help separation within
the HP separator until
such time as the system
is up and running and
the normal operating
fluid arrival
temperature has been
established. Crude oil pre-heater

37. Separation System
HP (Primary three-phase Separator)
• Bulk of the production fluids consisting of oil, gas and
water are separated in this vessel.
• Depending on crude type this vessel may have a
residence time from 5 to 20 minutes.

38. Separation System
Oil Heater, Crude
• Primary source of heat (can be from
heating coil) to raise the crude oil
temperature to a level consistent
with producing the required RVP
and TVP specification dead crude
suitable for shuttle tanker loading.
• The combination of high crude
temperature and near atmospheric
separation pressure in the LP
separator are essential in helping to
produce a dead crude.

39. Separation System
LP Separator
• Usually, this is the final stage of three-phase separation.
• The LP separator usually operates just above
atmospheric pressure.

40. Methods of Emulsion Treatment
First step - destabilization of the emulsion by:
• Chemical Dozing (Demulsifier)
• Heating
• Thermo-chemical methods
Second step - Coalescence of droplets by:
• Coalescing plates
• Filtering
• Fibrous packing
• Heating
• Electric field (Electrostatic Dehydrator)
Third step - Gravity Separation:
• Gravity settling (inside the storage tanks)
• Centrifuging

41. Material for Use
Process Vessels Carbon steel lined vessels (lining can be epoxy or
stainless steel cladding).
Heat Exchangers Titanium Plate-type HE
Carbon Steel Shell and Tube HE
Pumps Carbon Steel

42. 2. Explain, by means of a diagram, the
separation process inside a 3-phase
separator for well fluids coming onboard the
FPSO

43. Key Diagram to draw
Separator –
Principle of Separation into Oil, Water and Gas
Baffle / Weir
Oil level
Sensor
Water level
Sensor

44. Separator –
Principle of Separation into Oil, Water and Gas
1. As the three-phase fluid enter the separator, the
momentum absorber would facilitate the liquid (oil and
water) to go down to the bottom of the tank.
2. Based on the residence time required, the oil and water
would separate based on gravity principle.
3. Once the water hit the water level sensor, the valve
would open for discharge to the next station.
4. The oil would overflow over the baffle (or weir) to the
oil compartment and when the oil hits the oil level
sensor, the valve would open for discharge to the next
station.
5. The gas would go through the mist extractor for fluids
to condense before discharge through the gas outlet.
Key Points