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8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
http://slidepdf.com/reader/full/2011-hpht-subsea-design-john-mcgrail-2h 1/23
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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HPHT – SubseaDesign Challenges
John McGrail
2H Offshore Engineering Ltd
20th January 2011
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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Overview
What is HPHT
The subsea design problem Solutions
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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Courtesy: Dave Turner BP
129 Deg C 149 Deg C 177 Deg C 260 Deg C 260 Deg C
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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Where is the HPHT?
North Sea,
Norway,
GOM Brazil (Sub Salt/Presalt)
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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Deep Water
HPHT – The Design Problem ?
Corrosiveconditions
HP>10,000psi
Internal
Shut-in
HT>121 Deg C MaxOperating Temp
P r o b l e m R
e l a t i v e M a
g n i t u d e
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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How to Design for HPHT
Bigger
Standard technology, just bigger
Stronger
Higher strength materials
More resistant
Improved corrosion resistance
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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OPT USA 2003
12-3/4 INCH OD Nominal Wall Thickness Comparison for API 1111 & 2RD Codes10,000ft Water Depth, 300kg/m3 Fluid, 135 Deg C Design Temp
X65 Grade Pipe, 3mm Corrosion Al lowance, 12 Deg Top Angle
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
5,000 10,000 15,000Design Pressue at Mudline (psi)
W a l l T h i c k n e s s
( m m )
API-1111 API 2RD
Pipe Manufacturing Limit?
Bigger - Pipe Wall Sizing
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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Bigger – The Knock-on Effects
Extreme self-weight loads compound wallthickness requirements
Results in loads at the limit of:
Installation vessels
Host production vessels
Introduces fatigue issues from fluctuatingaxial loads
Thicker walls Impact pipe weldability
Increased cycle times
Reduced fatigue performance
Reduced pipe availability
Reduced flow area
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Stronger:Increased Material Grade
Stronger materials essential to maintain line pipe size feasibilityfor standard line pipe manufacturing processes
Alternative is forged pipe – expensive and lack of availability But – weldability is a problem…….
Example HP deepwater drilling riser sizing data below:
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Stronger Flexible Pipe:Design Limits?
Flexible Pipe Present Range of Application
(Adapted from TECHNIP’s Presentation at Dry Tree & Riser Forum)
• The 7.5-inch ID flexible pipedeveloped for water injection on
Thunder Horse is a landmark as it
established important records:Design Pressure (shut-in) = 10,000psiDesign Water Depth = 6300ft (1920m) Allowable lifetime= 16.5 years (limited
by sour service)
• More recently, Telemark 4-inch IDoil production flexible pipe has been
developed for installation on:Design Pressure (shut-in) = 12,500psiDesign Water Depth = 4500ft (1372m)
Allowable lifetime= 20 years
Telemark
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More Resistance:Corrosive Conditions
HPHT = Internal corrosion problems
HPHT wells often associated with corrosive / sour conditions:
CO2
H2S
Sour service performance sensitive to: Partial pressures of H2S present, and pH of the production fluid
Stresses in the pipe
Material properties of the pipe – flaws/grain structure
Hardness of the steel
Problem for high pressure, high strength steel, high loadapplications (i.e. HPHT scenarios)
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CO2 Corrosion (Sweet Corrosion)Corrosion Rate vs Partial Pressure and Temp
Partial pressure of CO2 (MPa)
Temperature of 25°C
C
o r r o s i o n r a t e
( m m / y e a r )
Temperature (°C)
C o
r r o s i o n r a t e (
m m / y e a r )
Heavy Pitting and General Wall Loss
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H2S Fatigue Life:Reduction Factor 10-100
Source: High pressure riser designs for ultra deepwater; J. Murray et al,
In air
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1
100
0.01 0.1 1 10
H2S Partial Pressure (psi)
C a
r b o n
D i o x i d e P
a r t i a l P r e s s u r e
( p s i
Material Selection
NACE
Low alloy steels
Non
NACE
13% Cr
(410, F6NM)Super Duplex Inconel 625
Source : Oilfield Metallurgy – Lloyd-Thomas Consultancy
7 I n c r e a
s i n g C o s t
HPHT
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Clad Pipe – Inconel 625 – Metallurgical orMechanically Lined
8/13/2019 2011 - HPHT Subsea Design - John McGrail 2H
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Installation:Large Wall Thickness / Cladding
Time / Cost:
Installation is Majority of Pipeline /Riser CAPEX
12-3/4” OD x 12.7 mm wt pipe joint
45 minutes to weld, inspect and applyinsulation field joint on
12-3/4” OD x 40.0 mm wt pipe joint
100 minutes
Clad pipe a further impact
Loads:
Heavy pipe = large lay tensions
Demanding vessel specifications
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The HPHT Solutions - Materials?
Materials Technology – key requirement:
Higher strength steels
70-80ksi offshore weldable 125ksi for use with mechanical connectors
Cost effective base material cladding
Development of alternative materials: Titanium / Aluminium alloys
Composites
Image: Composites World
Image: Timet
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The HPHT Solutions - Installation?
More efficient offshore weldingprocesses
Higher speed Higher strength materials
Improved AUT and ECAcapability for thick walled / clad
pipe
Friction welding?
Electron beam welding?
Laser welding?
Image: TWI
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The HPHT Solutions?
Installation
Greater lift / lay capacity for heavier pipelines and risers
Other Equipment
HPHT qualification required for:
Flexible pipe – HT qualification program ongoing (150ºC target)
Flexible joints (HPHT containing)
Connection system & sealing technology (flanges, connectors)
Image: Oil StatesImage: SRP
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Summary
HPHT is not a linear extrapolation, ‘bigger’ wont work just on its own –Technology changes are necessary
Material and welding technology is critical to success
Alternatives to conventional welding are needed that are faster and canwork with higher strength steel
Alternative materials – lightness, strength and corrosion resistance Composites
Titanium / Aluminium
Alternatively…………Subsea HIPPS / subsea processing? Solve some ofthe problems away from long pipeline / riser sections
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Questions?
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