Post on 11-Mar-2018
Specification for Pipeline Design Premise
Specification for Pipeline Design Premise 2 of 32
CONTENTS
1.0 INTRODUCTION ................................................................................................................................................................ 3
2.0 SCOPE OF DOCUMENT.................................................................................................................................................... 4
3.0 DESIGN DATA..................................................................................................................................................................... 8
1.0 PIPE MATERIAL DATA .................................................................................................................................................... 9
4.0 ENVIRONMENTAL DATA.............................................................................................................................................. 18
5.0 PIPELINE DESIGN CRITERIA ...................................................................................................................................... 27
6.0 TIE-IN DESIGN CONSIDERATIONS ............................................................................................................................ 29
7.0 SUBSEA STRUCTURES ................................................................................................................................................... 30
8.0 GEOTECHNICAL DATA AND SEABED CONDITIONS............................................................................................ 32
9.0 REFERENCES.................................................................................................................................................................... 32
Specification for Pipeline Design Premise 3 of 32
1.0 INTRODUCTION 1.1 General
The field development will consist of two
SPAR’s in the deep‐water field location,
one for each field with a Shallow Water
Facility Platform (SWF) located on the
Continental Shelf. The water depth at the
SPAR locations is approximately 3500 feet
and for the SWF approximately 350 feet.
The export pipeline system is zoned into
deep and shallow water sections. The
basis of design for the required facilities
are as follows:
Boomvang
• Gas Export Riser ‐ 18" SCR with PLEM
containing a swivel, a Riser to PLEM
flange connection, a check valve and
tie‐in spool connector
• Oil Export Riser ‐ 16" SCR with PLEM
containing a swivel, a Riser to PLEM
flange connection, a check valve and
tie‐in spool connector
• Gas Export 18" Tie‐in Spool with
Diverless Connectors for PLEM to
Export Line Tie‐in SLED
• Oil Export 16" Tie‐in Spool with
Diverless Connectors for PLEM to
Export Line Tie‐in SLED
Nansen
• Gas Export Riser ‐ 14" SCR with PLEM
containing a swivel, a Riser to PLEM
flange connection, a check valve and
tie‐in spool connector
• Oil Export Riser ‐ 12" SCR with PLEM
containing, a swivel, a Riser to PLEM
flange connection, a check valve and
tie‐in spool connector
• Gas Export 14" Tie‐in Spool with
Diverless Connectors for SCR PLEM
and 14" infield pipeline PLEM
• Oil Export 12" Tie‐in Spool with
Diverless Connectors for SCR PLEM
and 12" infield pipeline PLEM
Nansen In‐Field Pipelines
• Infield 14" Gas Pipeline PLEM
containing a swivel, a pipeline to PLEM
flange connection, a check valve and a
spool connector.
• Infield 12" Oil Pipeline PLEM
containing a swivel, a pipeline to PLEM
flange connection, a check valve and a
spool connector.
• 14" x 0.866" WT Nansen to Boomvang
infield Gas Pipeline 14 miles in length
• 12" x 0.562" WT Nansen to Boomvang
infield Oil Pipeline 14 miles in length
• 14" to 18" Inline Tie‐in SLED
containing a 14" swivel, a pipeline to
SLED flange connection, a piggable Y
(14" to 18"), a Boomvang 18" spool
connector, a 18" pipeline connection
flange, and a 18" pipeline swivel.
• 12" to 16" Inline Tie‐in SLED
containing a 12" swivel, a pipeline to
SLED flange connection, a piggable Y
(12" to 16"), a Boomvang 16" spool
connector, a 16" pipeline connection
flange, and a 16" pipeline swivel.
Nansen ‐ Exxon Diana Pipeline Crossing
• 14" Gas line Crossing of two Exxon
Diana pipelines
• 12" Oil line crossing of two Exxon
Diana pipelines
Specification for Pipeline Design Premise 4 of 32
Deep Water Export Pipelines,
Boomvang/Nansen to SWF
• 18" x 1.0" WT Gas Export Pipeline
from the in‐line SLED at Boomvang to
the SWF a distance of approximately
40 miles, terminating with a flange in a
water depth of no less than ???
• 16" x 0.812" WT Oil Export Pipeline
from the in‐line SLED at Boomvang to
the SWF a distance of approximately
40 miles, terminating with a flange in a
water depth of no less than ???
• Export Pipeline Crossings ‐ to be
determined
Deep Water Export Pipelines Tie‐in to
SWF
• 18" x 1.0" WT Gas Export Pipeline
flanged tie‐in spool from the pipeline
to the SWF
• 16" x 0.812" WT Gas Export Pipeline
flanged tie‐in spool from the pipeline
to the SWF
Shallow Water Gas Export Pipeline SWF
to ????
• 18" concrete weight coated Gas
Export Pipeline from the SWF to the
??? Platform distance of
approximately ?? Miles, commencing
and terminating with a flange for
spool piece tie‐ins.
• Pipeline Crossings ‐ to be determined
Shallow Water Oil Export Pipeline from
25 feet Water Depth near shore ??? to
SWF
• 16" concrete weight coated Oil Export
Pipeline to the SWF from a near shore
tie‐in location in 25 feet water depth a
distance of approximately ?? Miles,
terminating with a flange at the SWF
platform
• Pipeline Crossings ‐ to be determined
Pipeline Trenching
• Trenching of the shallow water
pipelines in water depths of less than
200 feet.
• Trench depth – 3 feet of cover from
top of pipe.
2.0 Scope of Document
This design premise describes the design criteria and data that will be used for the detailed design of the pipelines, structures and associated piping and equipment that will be used for the Export pipeline system.
2.1 Design Codes, Standards and Regulations
2.1.1 Regulations
The following legislation and acts
relating to offshore exploration
and production in the:
Oil Transmissions Pipelines: US D.O.T.
Regulations 49 CFR Part 195; Minimum
Federal Safety Standards for Liquid
Pipelines
Gas Transmission Pipelines: US
D.O.T. Regulations 49 CFR Part 192;
Minimum Federal Safety Standards
for Gas Lines.
2.1.2 Codes and Standards
Codes for design and fabrication of
Specification for Pipeline Design Premise 5 of 32
systems and equipment shall be in
accordance with latest adopted
Codes and Standards set forth
below:
American Petroleum Institute
API RP 2A Recommended
Practice for Planning
Designing and
Constructing Fixed
Offshore Platforms
API 5L Specification for Line
Pipe
API 6A Specification for
Wellhead Equipment
API 6D Specification for
Pipeline Valves
API RP 14E Design and
Installation of
Offshore Production
Piping Systems
API 17D Specification for
Subsea Wellhead and
Christmas Tree
Equipment
API 1104 Welding of Pipelines
and Related Facilities
API 1111 Design, Construction,
Operation and
Maintenance of
Offshore Hydrocarbon
Pipelines (Limit State
Design)
American National Standards Institute (ANSI)
ANSI B 16.5 Specification for Steel
Pipe Flanges and Flanged Fittings
ANSI B 16.9 Steel Butt Weld Fittings
ANSI B16.11 Forged Fittings, Socket, Welding and Threaded
ANSI B16.20 Ring‐Joint Gasket and Grooves for Steel Pipe Flanges
ANSI B31.4 Liquid Petroleum Transportation Piping System
ANSI B 31.8 Gas Transmission and Distribution Piping Systems
American Society for Testing
Materials (ASTM) ASTM A 105 Carbon Steel Forgings
for Piping Components
ASTM A 182 Stainless Steel Fittings F 316L ASTM A 193 Alloy Steel and
Stainless Steel Bolting Materials for High Temperature Service
ASTM A 194 Carbon and Alloy Steel
Nuts and Bolts for High Pressure Temperature Service
American Society of Mechanical
Engineering (ASME)
ASME VIII Boiler and Pressure
Code ‐ Pressure Vessel ASME IX Welding Code ASME V Non‐destructive
Testing
Specification for Pipeline Design Premise 6 of 32
American Welding Society (AWS) AWS D1.1 Structural Welding
Code American Institute of Steel
Construction (AISC)
Specification for the Design,
Fabrication and Erection of Structural Steel for Buildings
National Association of Corrosion
Engineers (NACE)
MR‐01111 Sulphide Stress
Cracking Resistant
metallic Material for
Oil Field Equipment
RP‐01 Control of Internal
Corrosion in Steel
Pipeline and Piping
System
RP‐03 Metallurgical and
Inspection
Requirement for Cost
Sacrificial Anodes for
Offshore Application
RP‐06 Recommended
Practice for Control of
Corrosion on Onshore
Pipelines
National Aerospace Standards
Institute (NAS)
NAS 1638 Cleanliness
requirements of parts
used in hydraulic
systems
International Standard
ISO‐WD‐13628‐8 Design and
Operation of ROV
Interfaces with Subsea
Pt 8 Production Systems
(draft)
Det Norske Veritas
DnV Classification Notes
No. 30.4; Foundations
DnV Rules for Planning and
Execution of Marine
Operations, 1996
1.1.1 2.1.3 System of Units
American Standard Units.
Specification for Pipeline Design Premise 7 of 32
2.2 Abbreviations
API American Petroleum Institute
ASME American Society of Mechanical Engineers
CSOI Coflexip Stena Offshore Inc.
DnV Det Norske Veritas
FBE Fusion Bonded Epoxy
HDPE High Density Polyethylene Coating
MP Mile Post
LAT Lowest Astronomical Tide
RJBD R J Brown Deepwater, Inc.
MTL Mean Tide Level
MSL Maximum Still Water Level
NB Nominal Bore
OD Outside Diameter
PP Polypropylene
SBPD Standard Barrel per Day
SCE Safety Critical Element
SMCFD Standard Million Cubic Feet per Day
SMYS Specified Minimum Yield Stress
UTM Universal Transverse Mercator
WPP Wellhead Protector Platform
WT Wall Thickness
ANSI
Specification for Pipeline Design Premise 8 of 32
3.0 Design Data
3.1 Pipeline Sizes
The pipelines shall be designed in accordance with the regulation and design codes set forth in
Section 1.3. The Deep‐Water pipeline sizes are shown in Table 3.1. The diameters will be
confirmed during the flow assurance design checks.
Nominal OD/Service No. Actual Nominal Grade
OD WT
18" Gas Export 1 18” 1.0 API 5L X60
16" Oil Export 1 16” 0.812 API 5L X60
14" Gas in‐field 1 14” 0.866 API 5L X60
12" Oil in‐field 1 12.75” 0.562 API 5L X60
18" SCR Gas Export 1 18” 1.0 API 5L X60
16" SCR Oil Export 1 16” 0.812 API 5L X60
14" SCR Gas in‐field 1 14” 0.866 API 5L X60
12" SCR Oil in‐field 1 12.75” 0.562 API 5L X60
Table 3.1
Deep Water Pipeline Sizes
Note 1: Wall thickness for rigid tie‐in spools – to be determined
Note 2: Pipe Grade to be checked during design
The Shallow Water pipeline sizes are shown in Table 3.2. These sizes are to be confirmed during
the flow assurance design checks.
NOMINAL OD/SERVICE NO. ACTUAL NOMINAL GRADE
OD WT
18" Gas Export 1 18” TBD API 5L TBD
16" Oil Export 1 16” TBD API 5L TBD
Table 3.2
Shallow Water Pipeline Sizes
Note 1: Wall thickness for rigid tie‐in spools – to be determined
Specification for Pipeline Design Premise 9 of 32
3.2 Pipe Material Data
Deep Water Pipeline Material data is summarized in Table 3.3.
Parameter Units 18”
Gas Export
6"
Oil Export
14" Infield Gas
12" Infield Oil
Negative Manufacturing Tolerance (1)
%
+/‐10
+/‐10
+/‐10
+12.5/ ‐10
Poissons Ratio
‐ 0.3 0.3 0.3 0.3
Material ‐ Carbon Steel
Carbon Steel Carbon Steel
Carbon
Steel
Material Grade
‐ API 5L X60
API 5L X60 API 5L X60
API 5L X60
SMYS KSI 60 60 60 60 Youngs Modulus
KSI 29 x 103 29 x 103 29 x 103 29 x 103
Density 1bf/ft3
490 490 490 7850
Linear Thermal Expansion Coefficient
1/°F
6.5 x 10‐
6
6.5 x 10‐6
6.5 x 10‐
6
6.5 x 10‐6
Thermal Conductivity
BTU/ hr
ft/ºF
26 26 26 26
Corrosion Allowance
inch TBA TBA TBA TBA
Table 3.3
Deep Water Pipeline Material Data
Specification for Pipeline Design Premise 10 of 32
Shallow Water Pipeline Material data is summarized in Table 3.4
Parameter
Units 18”
Gas Export
16"
Oil Export
14" Infield Gas
12" InfieldOil
Negative Manufacturing Tolerance (1) %
Poissons Ratio ‐ 0.3 0.3 0.3 0.3 Material ‐ Carbon
Steel Carbon Steel Carbon
Steel Carbon
Steel Material Grade ‐ SMYS KSI Youngs Modulus KsI 29 x 103 29 x 103 29 x 103 29 x
103 Density 1bf/ft3 490 490 490 490 Linear Thermal Expansion Coefficient
1/ºF
6.5 x 10‐6
6.5 x 10‐6
6.5 x 10‐
6
6.5 x 10‐6
Thermal Conductivity BTU/ hr ft/ºF
26 26 26 26
Corrosion Allowance ‐ inch TBA TBA TBA TBA
Table 3.4
Shallow Water Pipeline Material Data
3.3 Pipeline Coatings
Deep Water Pipeline Coating properties are given in Table 3.5.
Layer Thickness
(mils)
Density
(1lb/ft3)
Thermal
Conductivity
(BTU/hr ft/ºF)
FBE 6 90 0.173
Cohesive 6 56 0.13
Solid Polypropylene 87 56 0.13
Table 3.5
Deepwater Pipeline Coating System
Field Joint Coatings are: Pipeline – To be advised
Spoolpiece – To be advised
Specification for Pipeline Design Premise 11 of 32
Shallow Water Pipeline Coating properties are given in Table 3.6.
Layer Thickness
(mils)
Density
(1bf/ft3)
Thermal
Conductivity
(BTU/hr ft/ºF)
FBE 14 90 0.173
Slip Coat 4 90 0.173
Concrete Weight Coating TBD TBD TBD
Table 3.6
Corrosion Protection Coating and weight coating
Field Joint Coatings are: Pipeline – To be advised
Spoolpiece – To be advised
3.4 Other Densities
Density of Seawater = 64 lb/ft3
Density of Oil = TBD lb/ft3
Density of Weight Coating = 165 or 190 lb/ft3
Density of Gas = TBD lb/ft3
3.5 Design Pressures and Temperatures
Design pressure and temperature for the flowlines and risers are given in Table 3.7.
PIPELINES DESIGN PRESSURE
(PSIG)
MAXIMUM DESIGN
TEMPERATURE
(°F)
MINIMUM DESIGN
TEMPERATURE
(°F)
18" Gas Export
16" Oil Export
14" Gas in‐field
12" Oil in‐field
18" SCR Gas Export
16" SCR Oil Export
14" SCR Gas in‐field
12" SCR Oil in‐field
Table 3.7
Specification for Pipeline Design Premise 12 of 32
Design Pressure and Temperature
3.6 Operating Conditions
3.5.1 Production Conditions
Maximum Normal Flowing Pressure Oil Export
Maximum Shut in Pressure Oil Export
Maximum Normal Flowing Pressure Gas Export
Maximum Shut in Pressure Gas Export
Table 3.8
Wellhead Pressures for HSP‐Lifted Production Wells
FLOWING TEMPERATURE XX% OIL (START OF
LIFE)
xx% water (end of life)
Maximum Oil Flowing Temperature
Minimum Allowable oil flowing temperature
Maximum Gas Flowing Temperature
Minimum Allowable Gas flowing temperature
Table 3.9
Production temperature Limits
3.5.2 Design Production Rates – Boomvang
Design Production Rate
Peak Oil Case Transition Case Peak Water Case
Oil (sbpd) Reservoir Water (sbpd) Gas (mmscfd)
Table 3.10
Boomvang Design Production Rates
Specification for Pipeline Design Premise 13 of 32
3.5.3 Design Production Rates – Nansen
Design Production Rate
Peak Oil Case Transition Case Peak Water Case
Oil (sbpd) Reservoir Water (sbpd) Gas (mmscfd)
Table 3.11
Nansen Design Production Rates
3.5.4 Operating Conditions – Gas Export Line
The 18‐inch gas export pipeline is designed for a maximum flowrate of TBD mmscfd, at a normal operating pressure of TBD psig.
3.5.5 Gas Fluid Characteristics
Table 3.12 presents the export gas composition.
Component BOOMVANG MOL%
NANSEN MOL %
CO2 N2 C1 C2 C3 IC4 NC4 IC5 NC5 NC6 NC7 TOTAL 100%
Table 3.12
Export Gas Composition
Specification for Pipeline Design Premise 14 of 32
3.5.6 Oil Fluid Characteristics Table 3.13 presents the export oil composition..
Component Boomvang % Nansen % TOTAL 100% 100%
Table 3.13
Export Oil Composition
Table 3.14 presents expected Gas flowrates for each year.
Boomvang Nansen
Year mmscfd mmscfd
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
Table 3.14
Gas Export Flowrates
Specification for Pipeline Design Premise 15 of 32
3.7 Design Life
The design life of all pipelines, risers, J‐
tubes and subsea facilities is 20 years.
3.8 Corrosion Protection
An external anti‐corrosion coating and
sacrificial anodes in accordance with
RP‐06 will prevent the external
corrosion of the pipelines and subsea
facilities.
The following design data will be used in the design of anodes:
Design Data Units Buried Value Unburied
Value
Mean Bare Steel Current Density (1) mA/ft2
Final Bare Steel Current Density (1) mA/ft2
Electrolyte Resistivity ohm ft
Anode Potential mV
Protective Potential mV
Current Capacity Ah/1b
Utilisation Factor ‐
Anode Density 1b/ft3
Table 3.15 External Corrosion Design Data
The coating breakdown factors (for all pipelines) are given in Table 3.16.
Initial Mean Final Reference
Concrete Coated/FBE
3‐Layer PP 1.5% 3% 4.8% Norsok
Table 3.16 Coating Breakdown Factors
Compatibility with the SPAR Corrosion Protection Systems shall be ensured.
Specification for Pipeline Design Premise 16 of 32
3.9 Tie‐in Flanges
Shallow Water Pipeline tie‐ins will be via flanges, including swivel ring flanges
where appropriate. Tie‐in Flanges will be in accordance with ASME B16.5. The following ratings will be used for the pipeline flanges.
Line Size 18" Gas Export 16" Oil Export
Type ANSI ANSI
Flange Rating
Flange
Material
ASTM
ASTM
Gasket
Gasket
Material
Bolts
Nuts (1)
Table 3.17 Flanges Rating
Note (1): All nuts and studs to suit hydraulic tensioning equipment.
Line Size 18" Gas
Export
16" Oil Export 14" Gas Export
Pipeline
12" Oil
Export
Pipeline
Type
Flange Rating
Flange Material
Gasket
Gasket Material
Bolts
Nuts (1)
Table 3.18 Deep Water Flanges Rating
Note (1): All nuts and studs to suit hydraulic tensioning equipment.
Specification for Pipeline Design Premise 17 of 32
3.10 Pigging Philosophy
All pipelines shall be designed to enable effective testing and pre‐commissioning.
During operation ‐ TO BE PROVIDED BY CLIENT
3.11 Trenching
The shallow water pipelines will be trenched from 200 feet water depth.
Pipeline Minimum Trench Depth
to Top of Pipe
18" Gas Export 3 foot
16" Oil Export 3 foot
Table 3.19
Minimum Trench Depths
3.12 Mechanical Protection
3.13 SPAR J‐Tube Data
The J‐Tube shall be designed by others to accommodate and to allow installation of the 18”,
16”,14” and 12.75” SCR’s
J‐Tube Ref. Description OD (inch)
WT (inch) 3.13.1.1 Mate
rial
Hang‐Off Flange
Table 3.20 J‐Tube Details
Specification for Pipeline Design Premise 18 of 32
4.0 ENVIRONMENTAL DATA
4.1 Water Depth
The water depth at LAT across the Development Area varies as detailed in Table 4.1.
Location Water Depth (LAT) (feet)
Boomvang Spar Location 3450
Nansen Spar Location 3680
SWF Location ~350
Gas Export Tie‐in Platform Location ~200
Table 4.1 Water Depth Variation
The minimum and maximum water depths along the pipelines at LAT are summarized in Table 4.2.
Pipeline Maximum Water Depth (feet)
Minimum Water Depth (feet)
18" Gas Export to SWF 3450 ~350
16" Oil Export to SWF 3450 ~350
18" Gas Export to SWF to
BA538
~350 ~200
16" Oil Export to SWF to
shore
~350 25
14" Gas in‐field 3680 3450
12" Oil in‐field 3680 3450
18" SCR Gas Export 3450 ‐
16" SCR Oil Export 3450 ‐
14" SCR Gas in‐field 3680 ‐
12" SCR Oil in‐field 3680 ‐
Table 4.2 Maximum and Minimum Water Depths along the Pipelines
Specification for Pipeline Design Premise 19 of 32
4.2 Water Levels
4.2.1 Boomvang and Nansen SPAR Location
4.1.1.1 Design Water Levels
Condition 4.1.1.2 (feet)
100 Year Maximum
50 Year Maximum
10 Year Maximum
1 Year Maximum
HAT
MHWS
MHWN
MTL
MLWN
MLWS
LAT
50 Year Minimum
100 Year Minimum
Table 4.3 Design Water Levels
4.2.2 Shallow Water Facilities
Data Value (ft)
Highest Extreme Still Water Level – 100 Year Return Period
Highest Extreme Still Water Level – 1 Year Return Period
Highest Astronomical Tide (HAT)
Mean Tidal Level (MTL)
Lowest Astronomical Tide (LAT)
Lowest Extreme Still Water Level – 100 Year Return Period
Table 4.4
Specification for Pipeline Design Premise 20 of 32
4.2.3 Gas Export Tie‐in Structure at BA 538
Data Value (ft)
Highest Extreme Still Water Level – 100 Year Return Period
Highest Extreme Still Water Level – 1 Year Return Period
Highest Astronomical Tide (HAT)
Mean Tidal Level (MTL)
Lowest Astronomical Tide (LAT)
Lowest Extreme Still Water Level – 100 Year Return Period
Table 4.5 Gas Export Tie‐in Structure Water Levels
4.3 Seawater Properties
Seawater Kinematic Viscosity at 4°C = 1.57 x 10‐6 m2/sec Thermal conductivity of seawater = 0.5936 w/m°C Specific heat capacity of seawater = 3900 J/kg°K
4.4 Waves
4.4.1 SPAR Location Boomvang and Nansen
The tables 4.6 4.7 4.8 and 4.9 contain data that shall be used in the design of all pipelines in the
Boomvang and Nansen Field Locations.
Direction Hs Tz
Hmax (3 hr) Tmax Range Tmax
(from) (ft) (sec) (ft) (sec) (sec)
North
North‐East
East
South‐East
South
South‐West
West
North‐West Table 4.6
Extreme Maximum and Significant Wave Heights and Associated Periods by Direction
Return Period 1 Year
Specification for Pipeline Design Premise 21 of 32
Direction Hs Tz
Hmax (3 hr) Tmax Range Tmax
(from) (ft) (sec) (ft) (sec) (sec)
North
North‐East
East
South‐East
South
South‐West
West
North‐West
Table 4.7
Extreme Maximum and Significant Wave Heights and Associated Periods by Direction
Return Period 10 Years
Direction Hs Tz
Hmax (3 hr) Tmax Range Tmax
(from) (ft) (sec) (ft) (sec) (sec)
North
North‐East
East
South‐East
South
South‐West
West
North‐West
Table 4.8
Extreme Maximum and Significant Wave Heights and Associated Periods by Direction
Return Period 50 Years
Specification for Pipeline Design Premise 22 of 32
Direction Hs Tz
Hmax (3 hr) Tmax Range Tmax
(from) (ft) (sec) (ft) (sec) (sec)
North
North‐East
East
South‐East
South
South‐West
West
North‐West Table 4.9
Extreme Maximum and Significant Wave Heights and Associated Periods by Direction Return Period 100 Years
NOTE SIMILAR INFORMATION WILL BE REQUIRED FOR THE ROUTE LENGTH TO SWF PLATFORM,
THE ROUTE FROM SWF TO SHORE, THE ROUTE SWF TO BA538
Table 4.10 contains wave data for the SWF location.
1 Year Return Period Data 100 Year Return Period Data
Wave
Direction Hs Tz
Hmax Tmax Hs Tz
Hmax Tmax
(from) (ft) (s) (ft) (s) (ft) (s) (ft) (s)
North
North‐East
East
South‐East
South
South‐
West
West
North‐
West
Omni‐
Directiona
l
Table 4.10
SWF Tie‐in Structure Design Wave Data
Specification for Pipeline Design Premise 23 of 32
4.4.3 Gas Export Tie‐in Structure
Table 4.11 contains wave data for the BA538 location.
.
1 Year Return Period Data 100 Year Return Period Data
Wave
Direction Hs Tz
Hmax Tmax Hs Tz
Hmax Tmax
(from) (ft) (s) (ft) (s) (ft) (s) (ft) (s)
North
North‐East
East
South‐East
South
South‐
West
West
North‐
West
Omni‐
Directiona
l
Table 4.11
Gas Export Tie‐in Structure Design Wave Data
Specification for Pipeline Design Premise 24 of 32
4.5 Steady Current
4.5.1 Boomvang and Nansen SPAR Locations
Tables 4.12 and 4.13 contain current velocity data for the Boomvang and Nansen locations. This
data shall be adopted in the design of all Boomvang and Nansen pipelines in the field block
locations.
The current profile including loop currents with water depth for 1 year and 50 year are given
below.
Height Direction (towards)
N NE E SE S SW
W NW
(ft)
15.0
6
3
1
0.0
Table 4.12
Return Period 1 Year ‐ Near Bed Current Profiles
Height Direction (towards)
N NE E SE S SW W NW
(m)
15
6
13
1
0.0
Table 4.13
Return Period 50 Year ‐ Near Bed Current Profiles
Specification for Pipeline Design Premise 25 of 32
4.5.2 Boovang and Nansen SCR’s
Table 4.14 contains current for the water column at the Boomvang and nansen Platform Locations.
This data will be used in the design the SCR.
Current Direction
(from)
1 Year Return
Period
10 Year Return
Period
100 Year Return
Period
North
Depth
North‐East
East
South‐East
South
South‐West
West
North‐West
Omni‐Directional
Table 4.14
SCR Current data
Specification for Pipeline Design Premise 26 of 32
4.6 Temperatures
Depth Mean Sea Temperature Profiles
Summer Winter
(m) (°F) (°F)
Surface
Seabed
Table 4.15
Mean Sea Temperature Profiles
Depth Extreme Minimum Extreme Maximum
(feet) (°F) (°F)
0
Seabed
Table 4.16
50 Year Maximum and Minimum Sea Temperature Profiles
4.7 Marine Growth
Marine growth is considered negligible in the pipeline design.
Marine growth of 1 inch is applied to all structural members for post installation load conditions.
The submerged density of the marine growth shall be taken as 375 kg/m3.
Specification for Pipeline Design Premise 27 of 32
5.0 PIPELINE DESIGN CRITERIA
5.1 Pipeline Stability
The following design conditions for stability shall be considered for pipelines and umbilicals. Each shall have a minimum stability safety factor of 1.1.
5.1.1 Temporary Stability
The pipelines lying on the seabed, empty, shall be shown to be stable laterally and vertically for a one year return period significant wave with associated current conditions. Spoolpieces shall be shown to be vertically stable for a one year return period maximum wave and associated current conditions. However, shorter return periods may be used for checking stability for installation loadcases.
5.1.2 Permanent Stability
All the lines shall be shown to be both laterally and vertically stable under 100 year return period significant wave with associated current conditions on bottom and under 10 year return period significant wave with associated current conditions in the trenched condition. Spoolpieces shall be shown to be vertically stable, under 100 year return period maximum wave with associated current conditions.
5.2 Concrete Mattress Stability
Concrete mattress stability shall be checked for the 100 year return period maximum wave with associated current.
5.3 Pipeline Routing
The pipeline routing shall be selected in consideration of the following:‐
• Optimizing the line length • Obstructions e.g. wrecks, rock
outcrops, subsea wellheads • Routing of other pipeline and cable
in the area • Long term pipeline stability • Avoidance of shallow banks • Avoidance of excessive spans • Restrictions of SPAR mooring lines • Environmental restricted areas • Ordinance disposal locations
5.4 Mechanical Design
The pipelines shall be designed to provide mechanical integrity to avoid failures due to:
• Instability during the installation
and operation • Excessive yielding • Buckling • Fatigue • Brittle fracture • Corrosion, Internal and External • Vortex shedding induced vibrations • External impacts
5.5 Fluid Velocity Amplification
In the case of liquid pipelines the amplification effect shall be considered, where the flow velocity shall be modified by the following equations:
Specification for Pipeline Design Premise 28 of 32
V = V (1+RZ
)i u
2
2
Where
Vi is the increased velocity in metres per second
Vu is the uniform flow velocity in metres per second
R is the radius of obstruction in metres
z is the distance between the centre line of the obstruction to the centre of the member in metres.
5.6 Pipeline Expansion
The pipeline expansion due to temperature and pressure will be calculated taking account of frictional forces between the pipelines and the seabed inclusive of any backfill. Expansion spoolpieces shall be provided to achieve acceptable loads on the risers. The expansion analysis will include the hydrotest loadcase to carry out on equivalent stress check at this condition.
5.7 Hydraulic Analysis
The hydraulic analysis will include a
thermal assessment of the pipeline
performed to confirm:
• Design maximum temperature
profiles for mechanical design.
• Design minimum/maximum
contents densities.
Modelling of the process conditions
will include throughput, contents
properties, pipeline properties
(including coatings) and backfill
insulation properties.
The analysis will assume both
maximum design and maximum
operating conditions. The results of
the thermal assessment determined
during the hydraulic analysis will
generally be used for mechanical
design. In specific instances e.g.
upheaval buckling assessment
consideration may be given to the use
of alternative maximum operating
conditions provided full justification is
supplied.
5.8 Span Analysis
The allowable length for the free
spanning of the pipelines shall be
determined in accordance with API RP
1111, for the cases listed below with
consideration to the trenched,
untrenched and mattress covered
conditions.
• Installation – empty and flooded
subject to either a 3 month or a 1‐
year return period wave and
associated current loading
• Hydrotest – flooded with hydrotest
internal pressure subject to a 1‐
year return period wave and
associated current loading
• Operation – with product subject
to 100‐year return period wave
and associated current
Limiting lengths for pipeline allowable
spans shall be calculated for the
following design criteria:
Specification for Pipeline Design Premise 29 of 32
• Static stress for the maximum
design wave.
• No crossflow vortex induced
vibrations for the maximum design
wave plus associated current.
• No In‐line vortex induced
vibrations for the significant wave
plus associated current.
5.9 Allowable Stresses
The pipelines shall be designed to
satisfy the requirements of Section 3.1,
in respect to allowable stresses.
5.10 Upheaval Buckling Analysis
The propensity for upheaval buckling
shall be determined considering an
idealised sinusoidal shaped pipeline
over imperfection heights of 0.1m to
0.5m in increments of 0.1m. Pipelines
shall be considered water filled for
determination of the pipeline
wavelength at the imperfection.
The pipeline profile shall match the
insitu seabed profile. The backfill cover
shall be considered to have a constant
height above the pipeline.
5.11 Construction/Installation Loads
CSOI have direct responsibility for all
installation engineering required to lay
the pipelines on‐bottom, trench,
backfill (as required) and tie‐in.
Installation engineering shall be in
general compliance with the
regulations and codes as set forth in
Section 1.3.
6.0 TIE‐IN DESIGN CONSIDERATIONS This section describes the various design considerations and methods of analysis which will be utilised in the detailed design of tie‐in spools. Loadcases and allowable stresses are given in Section 5.
6.1 Expansion Spool Layout
A complete configuration of the tie‐in spools will be prepared and will take account of the following:‐ ‐ Platform riser layout ‐ Subsea pipeline route (platform
approaches) ‐ Minimum bend radius ‐ Spool pieces to be located as far as practicable clear of crane operating areas Maximum bend angle 90° Design pressure and temperature Environmental loading where applicable Mattress loading/protection The same allowable equivalent stresses are applicable as the pipeline (see Section 1.3).
6.2 Expansion Spool Design
The tie‐in spools shall be designed to account for:
‐ Yielding ‐ Fatigue ‐ Vortex shedding ‐ Corrosion ‐ Erosional effects in cross‐
sectional area around bends ‐ Stability ‐ Flange loads
Specification for Pipeline Design Premise 30 of 32
‐ Mechanical or external forces ‐ Pigging requirements
6.3 PLEM to SLED and PLEM to PLEM Spool Layouts
A configuration of the PLEM and connecting pipelines and spoolpieces will be prepared and will take account the following: ‐ PLEM and SLED orientation ‐ Subsea pipeline route ‐ SCR Loading ‐ Minimum bend radius ‐ Maximum bend angle 90° ‐ Design pressure and temperature ‐ Environmental loading where applicable ‐ Mattress loading/protection
The same allowable equivalent stresses are applicable as the pipeline (see Section 1.3)
6.4 Tie‐in Spool Design
The tie‐in spools shall be designed to account for:
- Yielding - Fatigue - Vortex Shedding - Corrosion - Erosional effects in cross
sectional area around bends - Stability - Flange loads - Mechanical or external forces - Pigging requirements
7.0 SUBSEA STRUCTURES
7.1 General
Subsea structures for Boomvang and Nansen comprise the following:
• Boomvang SCR 18” PLEM’: Pipeline end manifold is flange connected to the
SCR. PLEM contains a check valve. The SCR to
PLEM connection also requires a swivel.
• Boomvang SCR 16” PLEM’: Pipeline end manifold is flange connected to the
SCR. PLEM contains a check valve. The SCR to
PLEM connection also requires a swivel.
• Boomvang 18” Export Line SLED: Export pipeline has an inline sled to accommodate
the connection of the 14” Nansen pipeline.
Connection is made through a piggable Y. The SLED
has a diverless connector for the 18” Boomvang
spool link. The 14” line is flanged into the Y on the
installation vessel. Swivels are required on both
inline connections to the SLED
Specification for Pipeline Design Premise 31 of 32
• Boomvang 16” Export Line SLED: Export pipeline has an inline sled to accommodate
the connection of the 14” Nansen pipeline.
Connection is made through a piggable Y. The SLED
has a diverless connector for the 18” Boomvang
spool link. The 14” line is flanged into the Y on the
installation vessel. Swivels are required on both
inline connections to the SLED
• Nansen infield line 18” PLEM’: PLEM is flange connected to the infield pipeline.
PLEM contains a check valve and a diverless
connector for the spool link to the SCR PLEM. The
SCR to PLEM connection also requires a swivel.
• Nansen infield Line 16” PLEM’: PLEM is flange connected to the infield pipeline.
PLEM contains a check valve and a diverless
connector for the spool link to the SCR PLEM. The
SCR to PLEM connection also requires a swivel.
• Nansen SCR 14” PLEM’: PLEM is flange connected to the SCR. PLEM
contains a diverless connector for the spool link to
the infield line PLEM. The SCR to PLEM connection
also requires a swivel.
• Nansen SCR 12.75” PLEM’: PLEM is flange connected to the SCR. PLEM
contains a diverless connector for the spool link to
the infield line PLEM. The SCR to PLEM connection
also requires a swivel.
7.1.1 Installation
The structures shall be designed to be
installable with the pipelines from the
Coflexip Stena Deep Blue installation
vessel
7.1.2 Access
The design shall make due allowances
for ROV access for installation support,
tie‐in works, future inspections. ROV
access shall be ensured for inspection
and operation ov valves.
7.2 Associated Piping
7.4.1 General
Piping shall be designed in accordance
with the regulations set forth in Section
1.3, to be compatible with the
adjoining pipelines. Piping systems
shall be configured to provide a safe,
functional, serviceable and economic
routing.
Specification for Pipeline Design Premise 32 of 32
7.4.2 Stress Analysis
Piping will be analysed using the Triflex
proprietary software. Pipe supports
shall be located such that stresses
induced by both installation and
operating conditions do not exceed
code allowables.
Allowable stresses shall be in
accordance with the regulations set
forth in Section 1.3, as summarised in
Table 7.4.1.
The stress analysis shall take account of
pressure, temperature, buoyancy and
hydrodynamic loading (where
applicable). 8.0 GEOTECHNICAL DATA AND SEABED
CONDITIONS
TO be provided after route survey’s
9.0 REFERENCES