Deepwater risers design

1. GENERAL OVERVIEW OF
DEEPWATER RISER DESIGN
Presented by
Dhanjee kumar (18NA10009)
Bhardwaj Yella (18NA30006)

3. Overview
● Introductionon
● Riser Types
● Main Selection Factors
● Design Procedure
● Dynamic Example of Riser Modeling Summary
● Summary

4. Introduction
A riser is a pipe that connects a surface
facility to a subsea system.
Offshore riser systems are conduits (or collection of
conduits) used for the safe transportation of material
(primarily fluids and gases) between the seafloor and
the host platform. These fluids may travel from the
seabed to the platform or from the platform to the
seabed.

5. Riser Types
• Based on Material Type: Steel, Flexible, Titanium and
Composite
• Based on BOP (X-‐Tree) Location: Subsea and Surface
(Dry and Wet)
• Based on Configuration Type: SCR, SLWR, Hybrid Riser, TTR
• Based on Functional Type: Drilling, Production,
Injection, Export, Completion/Workover

6. Material Type: Steel Pipe
Failure types very well known, proven technology, more suppliers

7. Material Type: Unbonded Flexible
Pipe
The main advantage of using
flexible pipes is their ability to
work under extreme dynamic
condition compared with rigid
carbon steel pipes
Only 3 suppliers: GE Oil & Gas, NOV, and Technip
Complex mechanism of failures
Heavier & expensive than steel

8. Hydroelasticity & Flexible Pipes
● Hydroelasticity of flexible pipes is an important topic in the design and operation
of offshore oil and gas production systems.
● These pipes are subjected to various hydrodynamic loads, such as internal
pressure,external waves, currents, and seabed interactions.
● The hydroelastic response of the pipes can affect their fatigue life, dynamic
behavior, andoverall reliability.
● The hydroelastic response of flexible pipes can be affected by various design
factors, suchas the pipe diameter, wall thickness, material properties, length,
curvature, and buoyancy.

9. Material Type: Titanium
Titanium alloys have a unique
combination of properties, such
as high strength, low elastic
modulus and density, which make
them attractive for use in offshore
riser systems.

10. Material Type: Composite Material
Carbon Fiber

11. Factors Affecting Hydroelastic
Behaviour of Composite materials
● Fibre orientation
● Layup sequence
● Material properties
● Loading conditions
● Environmental conditions
● Manufaturing Processes

12. Material Type: Composite Material
Advantage
● Weight
● Strength
● Corrosion
● Fatigue
● Less expensive to build
complex component
● Thermal properties
Disadvantage
▪ Orthotropic material
▪ More brittle
▪ More expensive than
steel
▪ Complex repair procedure

13. Surface x Subsea BOP
The comparison of a conventional
subsea BOP drilling system and a
surface BOP drilling system clearly
shows the reduction in size,
weight, loads, and physical deck
area required to drill a well using
surface BOP.

14. Surface x Subsea BOP
Dry x Wet Tree

15. Functional Riser Types
• Drilling
• Production
• Injection
• Export
• Completion
• Workover

16. Riser Configuration Type: SCR
● SCR is a free hanging riser with no intermediate buoys or floating
devices.
● Steel catenary risers (SCR) are an attractive technology for
deepwater field developments. SCRs are simple in design with
few complicated components.
● They require high fatigue performance, especially at the top
end and at sag bend.

17. Advantage / Disadvantage of SCR
• Simple in design with few complicated component
• Economically attractive in terms of both installation
and construction
Disadvantages:
• High top tension
• Low fatigue performance at riser top and TDZ

18. Riser Configuration Type: Lazy
Wave
● A lazy-S configuration requires a mid-water arch, tether, and
tether base, while a steep-S requires a buoy and subsea
bend stiffener

19. Advantage / Disadvantage of
Lazy wave Risers
• Reduce Top Tension
• Decouples (partially) floater and TDP
Disadvantages :
• Increase design complexity
• Increase hardware and installation cost

20. Riser Configuration Type: Top
Tension Riser
● Top tension risers (TTR) commonly referred to as “risers”
connect a subsea well to the floating vessel.
● As part of the drilling vessel's closed-loop circulating systems,
the drilling riser provides the pathway of circulating fluid from
the vessel to the wellbore and from the wellbore back to the
surface.

21. Advantage
• Field proven
• Efficient drilling
• Fast access to wellbore
Disadvantage :
• Riser weight
• Interference problem

22. Riser Configuration Type: Hybrid
Riser
● Hybrid risers (HRs) consist of a vertical bundle of steel pipes
supported by external buoyancy.

23. Advantages:
• Pre-‐installable
• Low vessel payload
• Decoupled from vessel motion
Disadvantages:
• Increased design complexity
• High CAPEX compared to other riser types
• Interference issues

24. Key Selection Factors
• Water depth
• Environmental conditions
• Geographical location
• Reservoir pressure and temperature
• Corrosive fluids
• Number of wellheads
• Wellhead type
• Cost and schedule
• Operator

25. Water depth – SCR Application

26. Water depth – Flexible Application

27. Environmental conditions

28. Environmental conditions

29. Geographical location / Operator Preference
Geographical breakdown flexible riser pipe.

30. DESIGN PROCEDURE

31. Flow chart of a Composite Riser design

32. Overview
• Pre-‐FEED
▪ Determine technically feasible riser solutions
▪ Determine cost comparison between riser solutions
▪ Identify risks associated with riser system
▪ Concept selection

33. Overview
• FEED
▪ Further develop selected concept (or concepts) to enable
Operator to commence the Execution Phase with high
degree of confidence and low level of risk
▪ Develop documentation to enable an ITT (invitation to
tender) package to be issued to Execution Phase
contractors
• Detail Design
▪ Detailed design of the riser system to enable fabrication
and installation

34. Design Procedure: Design Basis
• Required information: Riser pipe properties,
riser system data (flex joint, bending stiffener,
buoyancy modules, etc.), wellhead data, subsea
equipment (BOP, LMRP, Lower flex joint), water
depth, environmental condition, conductor
data, soil properties, vessel data, fatigue details,
hydrodynamic properties, pressure,
temperature, etc.

35. Design Procedure: Methodology
TTR stack-‐up

36. Design Procedure: Methodology
• compliant riser profile

37. Modeling Considerations
• Built the FE global model;
• Most components can be modeled as pipe
elements with the key properties defined:
– Bending stiffness
– Axial stiffness
– Mass
– Drag diameter
– Buoyancy diameter

38. Commercial
Software
• Riser Global FEA:
• Flexcom
• Orcaflex
• DeepRiser
• Ansys
• Abaqus
• Riser VIV software
• Shear 7
• VIVA
• VIVANA

39. Riser Analysis Type
• Collapse, Burst and buckling checks
• Top tension determination
• Operability analysis
• Drift-‐off analysis
• Recoil analysis
• Hang-‐off analysis
• Riser installation analysis
• Fatigue analysis (VIV, VIM and wave fatigue)

40. Design Criteria & Standards Code
• Drilling Riser (API RP 16Q)
Envelope Parameter API RP 16Q Limit AMJIG Limit
Drilling
Mean Flex-‐Joint Angle 2 2
Maximum Flex-‐Joint Angle 4 4
von Mises/Yield Stress 0.67 0.67
Extreme, Non-‐
Drilling
Maximum Flex-‐Joint Angle 90% of Max 90% of Max
von Mises/Yield Stress 0.67 0.80
Survival, Non-‐
Drilling
Maximum Flex-‐Joint Angle 90% of Max 90% of Max
von Mises/Yield Stress 0.67 1.00

41. Design Criteria & Standards Code
• Production Riser (API RP 2RD)

42. Summary
• There are diverse riser types
• Riser design is complex task that involve
several iteration analysis, involving
inter-‐ discipline iteration;
• Some time, technical factor are overpassed
by not technical factor;

43. THANK YOU