Low Cost Field Development Options - 2H Offshore · Low Cost Field Development Options 18 th...

Low Cost Field Development Options

18th October 2016

Marcelo Lopes

Learn more at www.2hoffshore.com

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Agenda

Introduction

Riser Concept Feasibility Study

Basis of Design

SLWR Configuration

Extreme Storm Analysis

First Order (Wave) Fatigue Analysis

Riser Pre-lay Assessment

SLWR and Flexibles Riser Costing Comparison


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Introduction

Steel Catenary Risers often favoured for deepwater due to simplicity, versatility, reliability and cost

In deepwater Norwegian and UK North Seas, flexibles are more common due to harsh environment

In comparison, flexible risers can be limited by cost, pressure rating and integrity issues

Steel Lazy Wave Risers (SLWR) may be an alternative to flexibles but cost and technical performance needs evaluating


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Design Basis

Water Depth

The water depth at the proposed FPSO location is approximately 850m (2789ft)

Riser Pipe Specification

Flex Joint

A typical linear rotational stiffness is assumed for the Flex Joint

Parameter Value

Outer Diameter, mm (inch) 609.6 (24) Wall Thickness, mm (inch) 31.75 (1.25)

Corrosion Allowance, mm (inch) 3.0 (0.12) Material Grade API 5L X65

SMYS, MPa (ksi) 448 (65) SMUTS, MPa (ksi) 535 (77.6)


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Design Basis

Internal Fluid Densities and Pressure

Vortex Induced Vibration (VIV) Suppression

The analysis considers the top 250m of the riser to be covered with VIV suppression strakes

Vessel: Sevan Circular FPSO

Internal Fluid Internal Fluid

Density kg/m3 (ppg)

Pressure Bar (PSI)

Gas 140 (1.17) 135 (1,958) Seawater 1025 (8.55) 162 (2,350)

Production 150 (1.25) 200 (2,900) Slug 576 (4.81) 200 (2,900)


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Waves and Current Data Extreme Wave Data

Long Term Wave Data

Return Period (years) 1 10 100

Hs (m) 11.6 13.9 16.2 Tz (central) (s) 10.7 11.8 12.7 Tp (central) (s) 15.0 16.5 17.8

Hmax (3-hr) (m) 21.5 25.8 29.8 Tass (central) (s) 13.7 15.1 16.2

SWELL

Hs (m) 0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 19-20 20-21 21-22

0-1 0.05 1.33 6.67 8.67 8.00 6.47 4.40 2.93 1.67 0.93 0.45 0.21 0.09 0.04 0.02 0.01 0.00 0.00 - - - -

1-2 - - 0.13 2.07 4.27 5.67 5.47 4.80 3.47 2.33 1.40 0.80 0.44 0.23 0.11 0.05 0.03 0.01 0.01 0.00 0.00 -

2-3 - - - 0.08 0.62 1.53 2.07 2.27 2.07 1.60 1.13 0.73 0.45 0.25 0.13 0.07 0.03 0.02 0.01 0.00 0.00 0.00

3-4 - - - 0.00 0.05 0.30 0.66 0.93 1.00 0.93 0.73 0.51 0.33 0.19 0.11 0.06 0.03 0.01 0.01 0.00 0.00 -

4-5 - - - - 0.00 0.05 0.17 0.35 0.45 0.48 0.42 0.32 0.21 0.13 0.07 0.04 0.02 0.01 0.01 0.00 0.00 -

5-6 - - - - - 0.01 0.04 0.11 0.19 0.24 0.23 0.19 0.13 0.08 0.05 0.03 0.01 0.01 0.00 0.00 0.00 -

6-7 - - - - - 0.00 0.01 0.04 0.08 0.11 0.12 0.11 0.08 0.05 0.03 0.02 0.01 0.00 0.00 0.00 - -

7-8 - - - - - - 0.00 0.01 0.03 0.05 0.06 0.06 0.05 0.03 0.02 0.01 0.01 0.00 0.00 - - -

8-9 - - - - - - - 0.00 0.01 0.02 0.03 0.03 0.03 0.02 0.01 0.01 0.00 0.00 0.00 - - -

9-10 - - - - - - - 0.00 0.00 0.01 0.02 0.02 0.02 0.01 0.01 0.00 0.00 0.00 - - - -

10-11 - - - - - - - - 0.00 0.00 0.01 0.01 0.01 0.01 0.00 0.00 0.00 0.00 - - - -

11-12 - - - - - - - - - 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 - - - - -

12-13 - - - - - - - - - 0.00 0.00 0.00 0.00 0.00 0.00 0.00 - - - - - -

13-14 - - - - - - - - - - 0.00 0.00 0.00 0.00 0.00 - - - - - - -

14-15 - - - - - - - - - - - 0.00 0.00 0.00 - - - - - - - -

Tp (s)


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Hang-off Configuration

FPSO

MWL

15.70m Draft

29m

Flexible joint hang-off angle of 18deg relative to

FPSO vertical axis

Flexible joint hang-off location at base bottom edge of the main hull of

the FPSO


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Configuration


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Design Codes and Standards

Design Stage Codes & Standards Check

Pipe and Material Selection

API Spec 5L Material selection

Wall Thickness Sizing API-RP-2RD Burst, collapse, buckle propagation, load capacity, and reelability (strain)

Strength API-RP-2RD Serviceability, ultimate, and accidental

limit states

Fatigue DNV-GL-RP-0005

{DNV-GL-RP-C203} API-RP-2RD

Fatigue limit state, 1/Σ(damage)>design life


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Analysis Load Case Matrix

Riser Application

Riser OD (in)

Load Case Internal

Fluid Pressure

(bar)

Internal Fluid Density (kg/m3)

Mooring Line

Offset Environmental

Loading

API Allowable vM/Yield

Export 24

Operating Gas 135 140 Intact 6% 1 Year 0.67 Extreme Gas 135 140 Intact 10% 100 Year 0.8 Survival Gas 135 140 Failed 12% 100 Year 1

Installation Empty 0 0 Intact No Offset 1 Year 0.8 Hydrotest Sea Water 162 1025 Intact 3% 1 Year 0.9

Wave Fatigue

Gas 135 140 Intact No offset Long Term Wave

Loading n/a

Production 24

Operating Production

Fluid 200 150 Intact 6% 1 Year 0.67

Extreme Production

Fluid 200 150 Intact 10% 100 Year 0.8

Survival Production

Fluid 200 150 Failed 12% 100 Year 1

Installation Empty 0 0 Intact No Offset 1 Year 0.8 Temporary Slug 200 576 Intact 6% 1 Year 0.8 Hydrotest Sea Water 240 1025 Intact 3% 1 Year 0.9

Wave Fatigue

Production Fluid

200 150 Intact No offset Long Term

Wave Loading n/a


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Effective Tension

Compression of up to 53Te is found in the

sag bend region for gas export riser. Learn more at www.2hoffshore.com

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Extreme – Far Offset

Production riser overstressed by up to 4% at buoyant section.


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First Order Fatigue

Minimum fatigue life below the target life of

200 years in both the TDZ and hang-off region. Learn more at www.2hoffshore.com

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Hang-off Sensitivity Assessment

FPSO

MWL

15.70m Draft

2m

Flexible joint hang-off angle of 18deg relative to

FPSO vertical axis

Flexible joint hang-off location at base bottom edge of the main hull of

the FPSO

Hang-off location moved towards the centre of the hull

Worst load cases from the strength analysis assessed for the new hang-off location

Wave fatigue analysis is repeated


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Production Fluid - Extreme – Far Offset

Acceptable response for all the

dynamic analysis and riser configurations. Learn more at www.2hoffshore.com

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First Order Fatigue - Results

Fatigue life at the hang-off >200 years target

with a DNV C1 Class weld for the top 250m of the riser. Learn more at www.2hoffshore.com

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Riser Pre-lay Assessment

Stress response of the risers if pre-laid

on the seabed is within design limits. Learn more at www.2hoffshore.com

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Capex costs for flexible risers are expected to be similar to SLWR’s costs

Material Cost for Flexible > SLWR due to its complexity

Installation cost for SLWR > Flexible as a result of the offshore welding requirement

Engineering costs for SLWR > Flexibles mainly due to qualifications requirement

SLWR and Flexibles CAPEX Costing Comparison

Item % of the Total Cost

SLWR Flexible

Material cost per riser 18.8% 66.4%

Installation and transportation

43.9% 17.9%

Engineering, commissioning

37.4% 15.7%


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Conclusion

SLWR option is potentially feasible, however some issues such as hang-off fatigue, hydrotest and internal fluid variation need to be addressed

Compression at the sag bend region is expected, it should be confirmed that compression is acceptable

Low fatigue life in the hang-off region is expected;

Better weld quality (DNV C1 Class) in the first 250m of the riser from the hang-off can also be specified to improve fatigue performance

Cost for flexible are expected to be similar to the SLWR - Number of flexibles is result of limiting inner diameter


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Acknowledgements

2H Offshore

Gilles Gardner

Phil Ward

Rohit Shankaran

Norske Shell

Ali Anaturk


Questions?


http://www.2hoffshore.com/

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