ES021682 000 RT 5500 0001 B (Flowline Mechanical Design)

Project No UnitDocumen

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CodeSerial No Rev. Page

ES021682 000 RT 5500 0001 B 1/87

LAKACH FEED SUBSEA DEVELOPMENT

COMESA - PEMEX EXPLORACION Y PRODUCCION

FLOWLINE MECHANICAL DESIGN

Information contained in this document is the work product of Technip USA, Inc. and embodies confidential and proprietary information of Technip USA, Inc. and/or its client. Use of this information is restricted in accordance with conditions specified by the contract between Technip USA, Inc. and its client. Technip USA, Inc. disclaims any and all liabilities for any changes or modifications to this document which are made by any person other than Technip USA, Inc.

Pages modified under this revision: All changes highlighted in yellow.

B 14-OCT-11 ISSUED FOR CLIENT APPROVAL M. ZHOU J. GONZALEZ D. LAMACCHIA

A 30-SEP-11 ISSUED FOR REVIEW AND COMMENTS M. ZHOU J. GONZALEZ D. LAMACCHIA

REV. DATE STATUSWRITTEN BY(name & sign)

CHECKED BY(name & sign)

APPROVED BY(name & sign)

CLIENT APPROVAL(name & sign)

DOCUMENT REVISIONS

Confidential C2: Do not disclose without authorization Copyright © 2010 Technip USA, Inc. All rights reserved. Technip USA, Inc. TBPE Firm Reg. No. F-3030


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COMESA – PEMEX EXPLORACION Y PRODUCCION


TABLE OF CONTENTS

1.0 INTRODUCTION..................................................................................................................4

2.0 SUMMARY...........................................................................................................................5

3.0 CONCLUSIONS...................................................................................................................8

4.0 RECOMMENDATIONS........................................................................................................8

5.0 DESIGN DATA.....................................................................................................................9

5.1 Flowline Route and Water Depths............................................95.2 Fluid Composition and Properties.............................................95.3 Design Data..........................................................................105.4 Pipe Mechanical Data............................................................115.5 Design Factors......................................................................13

6.0 DESIGN ASSUMPTIONS...................................................................................................14

7.0 METHODOLOGY...............................................................................................................14

7.1 Pressure Containment...........................................................147.2 Collapse and Buckling Propagation.........................................167.3 Local Buckling.......................................................................17

8.0 RESULTS...........................................................................................................................20

8.1 Wall Thicknesses Results.......................................................208.2 Local Buckling Check Results.................................................238.3 Hydrostatic Mill Test Check....................................................25

9.0 REFERENCES...................................................................................................................27

10.0 APPENDICES.....................................................................................................................28

Confidential C2: Do not disclose without authorization.Copyright © 2010 Technip USA, Inc. All rights reserved. Technip USA, Inc. TBPE Firm Reg. No. F-3030


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LIST OF FIGURES

Figure 1-1 Lakach Subsea Field Layout Schematic......................................................................4Figure 2-1 Pipeline Wall Thickness Summary – Lakach Field Only..............................................5Figure 2-2 Pipeline Wall Thickness Summary – Lakach Filed with Piklis Impact..........................6Figure 5-1 Lakach Bathymetry Profiles..........................................................................................9Figure 8-1 Mechanical Design Chart Results – Lakach Field Only.............................................22Figure 8-2 Mechanical Design Chart Results – Lakach Field with Piklis Impact.........................23

LIST OF TABLES

Table 2-1 Wall Thickness Requirement for Mill Test According API 1111....................................7Table 2-1 Wall Thickness Calculation Summary...........................................................................7Table 5-1 Fluid Composition........................................................................................................10Table 5-2 Flowline Design Data...................................................................................................11Table 5-3 Pipe Data.....................................................................................................................11Table 5-4 Pipeline Grade X65 Steel Properties....................................................................12Table 5-5 Coating Material Properties.........................................................................................12Table 5-6 Dimensional Tolerances..............................................................................................12Table 5-7 Design Factors according to DNV OS-F101................................................................13Table 8-1 Lakach Gas Flowline Wall Thickness Results.............................................................21Table 8-2 Maximum Loads for Local Buckling Check (Load Controlled Condition)....................24Table 8-3 Maximum Strains for Local Buckling Check (Displacement Controlled Condition).....25Table 8-4 Minimum Required Wall Thickness for Mill Test..........................................................26

APPENDICES

Appendix 1: Wall Thickness Calculation – Without Piklis Impact................................................28Appendix 2: Wall Thickness Calculation – With Piklis Impact.....................................................40Appendix 3: LCC Local Buckling Check for Installation Condition (Without Piklis Impact)..........52Appendix 4: LCC Local Buckling Check for Hydrotest Condition (Without Piklis Impact)...........55Appendix 5: LCC Local Buckling Check for Operation Condition (Without Piklis Impact)...........58Appendix 6: DCC Local Buckling Check for Installation Condition (Without Piklis Impact).........61Appendix 7: DCC Local Buckling Check for Hydrotest Condition (Without Piklis Impact)...........64Appendix 8: DCC Local Buckling Check for Operation Condition (Without Piklis Impact)..........67Appendix 9: LCC Local Buckling Check for Installation Condition (With Piklis Impact)...............70Appendix 10: LCC Local Buckling Check for Hydrotest Condition (With Piklis Impact)..............73Appendix 11: LCC Local Buckling Check for Operation Condition (With Piklis Impact)..............76Appendix 12: DCC Local Buckling Check for Installation Condition (With Piklis Impact)............79Appendix 13: DCC Local Buckling Check for Hydrotest Condition (With Piklis Impact)..............82Appendix 14: DCC Local Buckling Check for Operation Condition (With Piklis Impact).............85



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1.0 INTRODUCTION

The Lakach gas field is located in the Gulf of Mexico (GOM), 98 km SE of the City of

Veracruz (Veracruz) and 131 km NE from Coatzacoalcos (Veracruz), in water depths

ranging from 750 meters to 1250 meters.

PEMEX’s objective is to develop the Lakach field reserves of up to 1.3 tcf of gas to a

maximum production of 400 MMscfd, targeting first gas the last trimester of 2014. Lakach

will be developed using a direct subsea tie-back to a new onshore gas plant near Lerdo

de Tejada (Veracruz). From this location, gas will be put into the SNG Mexican gas

transportation system (National Gas Pipeline Network).

The Lakach field development will have a subsea manifold cluster configuration with

seven (7) subsea wells and 65 km of dual 457 mm (18-inch) OD flowlines to an onshore

gas plant as shown on Figure 1-1. The main components of the system are as follows:

Pipelines to transport the gas to shore

Subsea horizontal trees, manifolds and jumpers, PLETs, ILSs and ILTs

Umbilicals

Onshore gas receiving plant

Figure 1-1 Lakach Subsea Field Layout Schematic



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Piklis field has been recently discovered by PEMEX. It is located at about 25 km to the NE

of Lakach, at a maximum water depth of 1930 meters. PEMEX expects that the lakach

pipelines will be able to handle a commingled Lakach/Piklis production not to exceed 400

MMSCFD.

The objective of this document is to present calculations, methodology and results of the

mechanical design of the 457 mm (18 inch) OD gas flowlines described above, in

accordance with DNV OS-F101 2010 [1].

2.0 SUMMARY

The mechanical design of the gas flowlines was based on the DNV OS-F101 2010 [1]. Detailed results are presented in section 6.0. All calculation spreadsheets are also enclosed in APPENDICES of this document.

Figure 2-1 presents a wall thicknesses chart summary for all cases analyzed, without considering Piklis impact.

Figure 2-2 Pipeline Wall Thickness Summary – Lakach Field Only



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With Piklis impact considered, the wall thicknesses chart summary for all cases analyzed is shown in Figure 2-2.

Figure 2-3 Pipeline Wall Thickness Summary – Lakach Filed with Piklis Impact

The pipeline wall thicknesses, in Figure 2-1 and Figure 2-2 above, represent the final design solution for the gas flowlines. It can be seen that the internal burst pressure governs the design.

Buckle arrestors are required to cover buckle propagation pressure. Buckle arrestors will be installed in water depths greater than 500 meters (KP > 45+900) for Lakach field only and 600 meters (KP > 47+400) for Lakach filed with Piklis impact, respectively.

The flowline wall thickness calculation MathCAD spreadsheets are presented in Appendices 1 and 2 of this document.

Note that the wall thickness design results shown in the above Figure 2-1 and Figure 2-2 did not include the mill test check. If the mill test will be performed, the hoop stress should be limited to the minimum of 96% SMYS and 84% SMTS, per DNV OS-F101 [1]



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Section 7 E102. Table 2-1 below summarizes the minimum required wall thicknesses for mill test per API 1111 [4] criteria.

Table 2-1 Wall Thickness Requirement for Mill Test According API 1111

CaseDesign

Pressure(kgf/cm2)

Mill Test Pressure [1]

(kgf/cm2)

Minimum Required Wall

Thickness,mm (inch)

Lakach Field Only 330 412.5 21.95 (0.864)

With Piklis Impact 400 500.0 26.06 (1.026)

Note: [1] per API 1111 [4], with pressure ratio Ph/Pd = 1.25.

The selected wall thicknesses for the gas flowlines are shown in Table 2-1. It can be seen that the mill test requirement did not affect the wall thickness selected for the Lakach field without Piklis impact. However, with Piklis impact considered, the wall thickness selected for flowline Section 2 should be increased from 25.40 mm (1.000 inch) to 28.58 mm (1.125 inch) which is the same as the wall thickness for Section 1.

Table 2-2 Wall Thickness Calculation Summary

Section KP Range

Water Depth Range, meter

Calculated Wall Thickness, mm (inch)

Selected WT, mm (inch)

Minimum WT for Internal

Pressure

Minimum WT for System

Test

Minimum WT for

Collapse

MinimumWT for Buckle

Propagation

Without Mill Test

With Mill Test

Lakach Field Only

10 –

45+9000 - 500

23.50(0.925)

21.21(0.835)

15.19(0.598)

23.67(0.932)

23.83(0.938)

23.83(0.938)

245+900

– 63+000

500 - 1200

21.59(0.846)

21.21(0.835)

20.24(0.797)

32.92(1.296)

22.23(0.875)

22.23(0.875)

With Piklis Impact

10 –

47+4000 - 600

27.58(1.086)

25.17(0.991)

16.03(0.631)

25.35(0.998)

28.58(1.125)

28.58(1.125)

247+400

– 63+000

600 - 1200

25.22(0.993)

25.17(0.991)

20.24(0.797)

32.92(1.296)

25.40(1.000)

28.58(1.125)

A preliminary local buckling check has been performed according to DNV OS F-101 Section 6 D600 [1] in order to estimate the maximum combined loads and strains which



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can occur in the flowline for each selected wall thickness without considering mill test. All spreadsheets for these checks are presented in Appendices 3 to 14.

Specific local buckling check of the selected wall thicknesses will be performed as the flowline design progresses. Design verification of wall thickness according to local buckling criteria will be performed in the corresponding reports as listed below:

Flowline Bottom Roughness Analysis Report (ES021682-000-RT-5500-0003)

Flowline Lateral Buckling Analysis Report (ES021682-000-RT-5500-0002)

3.0 CONCLUSIONS

Based on the design results, the following conclusions can be drawn:

The wall thickness design was governed by the internal burst pressure.

Buckle arrestors are required in water depths greater than 500 meters (KP > 45+900) for Lakach field only and 600 meters (KP> 47+400) for Lakach field with Piklis impact.

If the mill test for the UOE pipe can be waived per client agreement according DNV OS-F101 [1] Section 7 E107, two different wall thicknesses would be selected for the Lakach gas flowline according to the water depth range, as shown in Table 2-1. Larger pipe wall thicknesses are required with Piklis impact considered.

If a mill test will be performed with test pressure limited to 1.25 times of design pressure (per API 1111), the wall thicknesses selected for the flowline Section 2 (KP 47+400 – 63+000) will be increased from 25.4 mm (1.000 inch) to 28.58 mm (1.125 inch) with Piklis impact considered.

4.0 RECOMMENDATIONS

The recommendations are summarized as follows.

Perform mill test with test pressure limited to 1.25 times of design pressure. Buck arrestor design should be performed as the flowline design progresses. Further verification of wall thickness against local buckling criteria should be

performed with flowline bottom roughness analysis and flowline lateral buckling analysis.



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5.0 DESIGN DATA

The data used for the Lakach gas flowline mechanical design are referenced in Subsea Basis of Design [3], unless noted otherwise.

5.1 Flowline Route and Water Depths

In Lakach field development, two 457 mm (18 inch) OD gas flowlines will transport the gas to the shore. Simplified bathymetry profiles are shown in Figure 5-1. The center line of the flowline route will follow Route 2 (pink line in the figure). The water depths along the flowline route range from zero (shore) to 1200 meters.

Perfil Batimétrico

-1200

-1000

-800

-600

-400

-200

0

200

0 4000 8000 12000 16000 20000 24000 28000 32000 36000 40000 44000 48000 52000 56000 60000

Distancia (m)

Ele

vac

ión

(m

)

Ruta 1 Ruta 2 Ruta 3 Ruta original

Figure 5-4 Lakach Bathymetry Profiles

5.2 Fluid Composition and Properties

Fluid composition for the Lakach field is given in Table 5-1.



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Table 5-3 Fluid Composition

Component %Mol Component %Mol

Nitrogen 1.03 C9 0.039

Carbon Dioxide 0.026 C10 0.04

Hydrogen Sulfide 0 C11 0.034

Methane 95.069 C12 0.028

Ethane 1.968 C13 0.025

Propane 0.719 C14 0.018

i-Butane 0.169 C15 0.018

n-Butane 0.207 C16 0.012

i-Pentane 0.085 C17 0.011

n-Pentane 0.079 C18 0.008

n-Hexane 0.101 C19 0.006

M-C-Pentane 0.03 C20 0.005

Benzene 0.022 C21 0.004

Cyclo-hexane 0.013 C22 0.004

n-Heptanes 0.087 C23 0.003

M-C-Hexane 0.04 C24 0.003

Toluene 0.011 C25 0.002

N-Octanes 0.063 C26 0.002

E-Benzene 0.004 C27 0.002

M/P-Xylene 0.006 C28 0.001

O-Xylene 0.004 C29 0.001

C30+ 0.004

Molecular weight 17.663

Molar Mass C30+ 750

5.3 Design Data

The flowline design data including pressure, temperature and corrosion allowance are

listed in the Table 5-2.



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Table 5-4 Flowline Design Data

Note: [1] provided by preliminary flow assurance analysis [2] Lakach well shut-in pressure from preliminary flow assurance

analysis and per agreement with the client.

5.4 Pipe Mechanical Data

Subsea production flowlines will be made of carbon steel line pipe. Internal coating is not

considered. The flowlines will have 3 mm of three layer polypropylene (3LPP) external

corrosion coating.

Table 5-3 summarizes the preliminary line sizes, grade, and material coatings for the gas

flowlines.

Table 5-5 Pipe Data

Description Parameter Value / Type

Pipe

Length 65 km each

OD 457 mm (18 inch)

API Grade API 5L X65 (SMAW)

Corrosion Coating

Material 3LPP

Thickness 3 mm (minimum)

The properties of X65 line pipe are specified in Table 5-4. The coating material properties

are presented in Table 5-5.


Parameter Value

Design Pressure [2]

330 kgf/cm2 - without Piklis Impact

400 kgf/cm2 - with Piklis ImpactDesign Temperature

50 oC

Fluid Content Desity

30.4 – 285.1 kg/m3

(1.9 – 17.8 lb/ft3) [1]

Corrosion Allowance

1.58 mm (1/16 inch) [1]


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Table 5-6 Pipeline Grade X65 Steel Properties

Parameter Value

Steel Density 7850 kg/m3

Young’s Modulus of Elasticity 207 x 109 N/m2

Poisson’s Ratio 0.3

Coefficient of Linear Expansion 11.7 x 10-6 °C

Thermal Conductivity 45 W/mK

Specified Minimum Yield Strength

450 MPa

Specified Minimum Tensile Strength

535 MPa

Table 5-7 Coating Material Properties

MaterialDensity(kg/m3)

Thickness (mm)

3LPP

FBE 1440

3.0PE Adhesive 900

Solid UV PP 900

The dimension tolerances are listed in Table 5-6. DNV tolerances are applied unless

noted otherwise. The line pipe should be manufactured in accordance with the relevant

specifications (such as API 5L [2]) where the tighter tolerance may apply.

Table 5-8 Dimensional Tolerances

Dimension Seam Welded Linepipe

WT negative tolerance-1mm per DNV OS-F101 or

-1.5mm per API 5L [1] (for WT>20mm)

Out of roundness (OOR)

1.5%

Note: [1] API tolerance of -1.5 mm was used for conservative design of the welded pipe.



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5.5 Design Factors

The design factors considered for the Lakach gas flowline mechanical design, according

to DNV OS-F101 [1], are indicated in Table 5-7.

Table 5-9 Design Factors according to DNV OS-F101

Factor SymbolCollapse & Buckling

Internal Pressure

Safety Class - Low Medium

Material Resistance Factor m 1.15 1.15

Material Strength Factor u 0.96 0.96

Fabrication Factor for UOE pipe fab 0.85 0.85

Safety Class Resistance Factor sc 1.040 1.138

Load Effect Factor for Functional Load (Static) f 1.20 1.20

Environmental Load e 0.70 0.70

Condition Load Effect Factor c 1.07 1.07

Resistance Strain Factor ε 2.0 2.5

Minimum Strain Hardening h 0.92 0.92

Girth Weld Factor gw 0.95-1.00 0.95-1.00



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6.0 DESIGN ASSUMPTIONS

The wall thickness design methodology per DNV-OS F101 2010 [1] limit state criteria, as

described in the following Section 7.0 does not include the mill test check. This implies the

assumption that the mill test for the UOE pipe is omitted according DNV OS-F101 [1]

Section 7 E107.

If the mill test will be performed for the UOE pipe, the wall thickness selected should also

satisfy the criteria in DNV OS-F101 [1] Section E100 or API RP 1111 [4].

7.0 METHODOLOGY

The wall thickness of the Lakach gas flowline was determined according to the

DNV OS-F101 2010 [1] limit state criteria, taking into account pressure

containment and collapse. Buckle propagation was also calculated in the DNV

code [1].

Local buckling was also checked for the selected wall thickness in order to

estimate maximum bending moments or strains according DNV OS-F101 [1]

criteria.

7.1 Pressure Containment

According to DNV OS-F101 Section 5 D200 [1], the pressure containment (bursting) has

been checked against the following criteria:

pli−pe≤pb ( t1 )γ sc γm

The wall thickness for pressure containment has been calculated for the yielding limit

state and bursting limit state according to the formulations below, contained in Section 5

D203 [1]:

For yielding limit state:

pb ( t1 )=2t1

D−t1f y2√3



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For bursting limit state:

pb ( t1 )=2t1

D−t1

f u

1 .152√3

The maximum resultant thickness has been adopted.

In addition, the system test pressure has been checked according to DNV OS-F101

Section 5 B203 [1].

The local test pressure shall meet the following requirement:

for Medium and High safety class during normal operation,

plt≥1 .05 pli

and for Low safety class during normal operation,

plt≥1 .03 pli

For pressure containment safety class, Medium is considered for the Lakach gas flowline.

The local incidental pressure (pli) has been calculated according to the following equation:

pli=γ inc pd+gh ρcont Section 4 B202 [1]

Where:

inc = safety factor assumed equal to 1.10;pd = design pressure;g = gravitational acceleration;h = vertical distance from reference point to sea surface;cont = density of contents.



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Finally, the commercial wall thickness is defined adding the corrosion allowance and percentage of fabrication tolerance to the nominal wall thickness. Thus, the final wall thickness is given by:

t final=t1+t corr

(1−%t fab) Section 13 E300 [1]

7.2 Collapse and Buckling Propagation

Wall thicknesses defined for the pressure containment has been checked with respect to collapse provided in DNV OS-F101 [1] Section 5 D400 and buckling propagation verifications in DNV OS-F101 [1] Section 5 D500.

For collapse check, the external pressure (Pe) at any point along the pipeline shall meet the following criterion:

Pe − Pmin≤pc

γm γ sc Section 5 D402 [1]

Where:

Pmin = minimum internal pressure (“zero” for as-laid pipeline)m = material resistance factor;sc = safety factor class resistance factor.

The characteristic resistance for external pressure (Pc) shall be calculated as:

( pc−pel)( pc2−pp

2 )=pc pel p p f 0Dt2 Section 5 D401 [1]

Where:

pel=2 E( t 2D )

3

1−ν2 Elastic pressure

pp=2 f yα fab

t2D Plastic Pressure



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f 0=Dmax−Dmin

D Ovality

Buckle propagation has been checked according to the DNV OS-F101 [1] Section D500. The external pressure (Pe) shall meet the requirement given below.

Pe ≤¿¿

p pr ¿γm γsc

Where:

ppr=35×f y×α fab

γm×γ SC

×( t2D )2 .5

Section 5 D501 [1]

In above calculations, the wall thickness t2 has been considered (corrosion allowance has been subtracted from the nominal thickness).

Propagation buckling cannot be initiated unless local buckling has occurred. In case the external pressure exceeds the criteria given above, buckle arrestors should be installed. Buckle arrestor design will be performed in a separated document.

7.3 Local Buckling

The selected wall thickness was checked for local buckling according DNV OS-F101 [1] criteria. Both load controlled and displacement controlled conditions were checked to determine the maximum bending moments and strains.

Loads and moments which pipeline is subjected must satisfy the following condition:

for internal overpressure (Hydrostatic Test and Operation Condition)

[γ SC⋅γm⋅

|M sd|α c⋅M p

+ ( γSC⋅γm⋅Ssd

α c⋅Sp)2]2

+(α p⋅pi−pe

α c⋅pb ( t2 ))2

≤1

Section 5 D605 [1] for external overpressure (Installation Condition)

[γ SC⋅γm⋅

|M sd|α c⋅M p

+ ( γSC⋅γm⋅Ssd

α c⋅Sp)2]2

+(γ SC⋅γm⋅pe−pminpc( t2 ) )

2

≤1

Section 5 D607 [1]



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Where:

Msd = design bending moment; Ssd = design effective axial force; pi = internal pressure; pe = external pressure; pmin = minimum internal pressure (“zero” for as-laid pipeline) Mp = plastic moment resistance given by:

M p=f y⋅(D−t2)2⋅t2 Sp = characteristic plastic axial force resistance given by:

Sp=f y⋅π⋅(D−t2 )⋅t2

pb(t2) = burst pressure; pc(t2) = characteristic collapse pressure; αc = flow stress parameter accounting for strain hardening; αp = factor accounting for effect of D/t2 ratio.

t2=t for installation and hydrostatic test condition and

t2=t−tcorr for operation.

Longitudinal compressive strain (bending moment and axial forces) to which the pipeline is subjected must satisfy the following condition:

for internal overpressure

ε sd≤εc

γ E Section 5 D608 [1]

ε c=0 .78⋅( t2D−0.01)⋅(1+5.75⋅pmin−pe

pb)⋅αh

−1 .5⋅α gw

for external overpressure

( εsd

εc

γE)0.8

+pe−pmin

pc

γSC⋅γm

≤1

Section 5D508 [1]

ε c=0 .78⋅( t2D−0.01)⋅α h−1.5⋅α gw



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Where:

εsd = design compressive strain; αh = maximum allowed yield to tensile ratio; αgw = girth weld factor; E = resistance strain factor

To estimate maximum values for bending moments according local buckling check (load controlled condition), the following methodology has been considered:

For installation condition, an effective axial force of 150 kN has been assumed for each section studied and bending moment was changed until local buckling unity check becomes 1.00;

For hydrostatic test condition, an effective axial force has been calculated according to section 4 G309 of DNV OS F-101 [1], considering internal pressure test in the line for each pipeline wall thickness and bending moment was changed until local buckling unity check becomes 1.00;

For operation condition, an effective axial force has been calculated as percentage of effective axial force according to section 4 G309 of DNV OS F-101 [1], considering internal pressure and corresponding temperature variation in the line for each pipeline section. This percentage is assumed equal to 25% of effective axial force once that lateral buckling can occur and may cause a moment increment.

A similar procedure was used for displacement controlled condition local buckling check. Maximum strain values were calculated for installation, hydrostatic test and operational conditions by changing functional strain until the local buckling check reached the value of 1.00.



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8.0 RESULTS

The mechanical design was carried out using in-house verified spreadsheets based on DNV OS-F101 standard [1], which are presented in Appendices of this document. The following sections present the wall thickness results summary for the Lakach gas flowline.

8.1 Wall Thicknesses Results

The calculated wall thicknesses (WT) and the selected API wall thicknesses are presented in the Table 8-1 below. Both cases were considered with and without considering Piklis impact. The calculated wall thicknesses include minimum required wall thicknesses against the criteria of operational burst pressure, system hydrostatic test, collapse and buckle propagation. Results show that different wall thicknesses were selected for two flowline sections based on the water depth (WD) range. Note that the wall thickness design per DNV limit state criteria described above did not include the hydrostatic mill test check.



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Table 8-10 Lakach Gas Flowline Wall Thickness Results

Flowline

SectionCondition

Wall Thickness, mm (inches)

Calculated WT Selected WT

Lakach Field Only

Section 1

(WD: 0 – 500 meters)

Operational Burst Pressure

23.50(0.925)

23.83(0.938)

System Test21.21

(0.835)

Collapse 15.19(0.598)

Buckle Propagation 23.67(0.932)

Section 2

(WD: 500 – 1200 meters)


21.59

(0.846)

22.23(0.875)

System Test21.21

(0.835)

Collapse 20.24(0.797)


With Piklis Impact

Section 1



27.58(1.086)

28.58

(1.125)

System Test25.17

(0.991)

Collapse 16.03(0.631)


Section 2

(WD: 600 – 1200 meters)


25.22(0.993)

25.40

(1.000)

System Test25.17

(0.991)

Collapse 20.24(0.797)


Figure 8-1 and Figure 8-2 present the wall thicknesses chart summary for Lakach field only and Lakach filed with Piklis impact, respectively. The flowline route profile is also plotted in the charts.



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Figure 8-5 Mechanical Design Chart Results – Lakach Field Only



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Figure 8-6 Mechanical Design Chart Results – Lakach Field with Piklis Impact

It can be seen in the figure above that the selected wall thicknesses cover the internal pressure and the collapse pressure but do not cover the buckle propagation pressure. This means that if there is an initial dent after the installation, the buckle formed will propagate along the pipeline. Thus, Buckle arrestors will have to be adopted in flowline section 2 (with WD > 500 meters for Lakach field only and WD > 600 meters for Lakach filed with Piklis impact).

8.2 Local Buckling Check Results

Maximum loads (bending moments and effective axial forces) and strains values for local buckling check are presented in Table 8-2 and 8-3 respectively. Values indicate limit loads to avoid local buckling in pipeline. Detailed local buckling check results for load control condition (LCC) and displacement controlled condition (DCC) are enclosed in Appendices 3 to14.



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Table 8-11 Maximum Loads for Local Buckling Check (Load Controlled Condition)

Flowline

SectionCondition

Loads

Effective

Axial Force

SF (kN)

Bend Moments

MF (kN*m)

Lakach Field Only

Section 1


Installation 150 1215

Hydrostatic Test 1820 1175

Operation 1555 1065

Section 2

(WD: 500 – 1200 meters)



Operation 345 1034

With Piklis Impact

Section 1




Operation 1822 1290

Section 2

(WD: 600 – 1200 meters)



Operation 436 1177



t TypeMaterial


ES021682 000 RT 5500 0001 B 25/87




Table 8-12 Maximum Strains for Local Buckling Check (Displacement Controlled Condition)

Flowline

Section Condition

Maximum Compressive Strain

εF

Lakach Field Only

Section 1


Installation 0.775%

Hydrostatic Test 0.782%

Operation 0.680%

Section 2

(WD: 500 – 1200 meters)

Installation 0.305%


Operation 0.200%

With Piklis Impact

Section 1


Installation 0.995%


Operation 0.910%

Section 2

(WD: 600 – 1200 meters)

Installation 0.500%


Operation 0.400%

8.3 Hydrostatic Mill Test Check

The mill test check was performed according to the criteria in DNV OS-F101 [1] Section 7 E100 and API 1111 [4]. The hoop stress limit is the minimum of 96% SMYS and 84% SMTS per DNV OS-F101 [1] Section 7 E102. Table 8-4 below summarizes the minimum required wall thicknesses for different hydrostatic mill test pressures. The detailed calculations are contained in Appendices 1 and 2. Since DNV-OS-F101 criteria only provide the upper limit of the mill test pressure, it is recommended that API 1111 criteria are used for the mill test.



t TypeMaterial


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Table 8-13 Minimum Required Wall Thickness for Mill Test

Code

Ratio of Mill Test to Design

Pressure

Mill Test Pressure(kgf/cm2)

Minimum Required Wall

Thickness,mm (inch)

Lakach Field Only

DNV-OS-F101 1.4 x1.1 = 1.54 [1] 508.2 26.44 (1.041)

API 1111 1.25 412.5 21.95 (0.864)

With Piklis Impact

DNV-OS-F101 1.4 x1.1 = 1.54 [1] 616.0 31.37 (1.235)

API 1111 1.25 500.0 26.06 (1.026)

Note: [1] The maximum ratio of mill test to incident pressure is 1.4, while the ratio of incident to design pressure is 1.1.



t TypeMaterial


ES021682 000 RT 5500 0001 B 27/87




9.0 REFERENCES

1. DNV OS-F101, Submarine Pipeline Systems, October 2010.

2. API 5L Specification for Line Pipe, 44th Edition, October 2007 (Addendum 2, April 2010).

3. Subsea Basis of Design, ES021682-000-JSD-3660-0001, Technip U.S.A.

4. API RP 1111, Design, Construction, and Maintenance of Offshore Hydrocarbon Pipelines (Limit State Design), 4th Edition, December 2009.



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10.0 APPENDICES

Appendix 1: Wall Thickness Calculation – Without Piklis Impact



t TypeMaterial


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t TypeMaterial


ES021682 000 RT 5500 0001 B 30/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 31/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 32/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 33/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 34/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 35/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 36/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 37/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 38/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 39/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 40/87




Appendix 2: Wall Thickness Calculation – With Piklis Impact



t TypeMaterial


ES021682 000 RT 5500 0001 B 41/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 42/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 43/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 44/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 45/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 46/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 47/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 48/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 49/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 50/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 51/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 52/87




Appendix 3: LCC Local Buckling Check for Installation Condition (Without Piklis Impact)



t TypeMaterial


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t TypeMaterial


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t TypeMaterial


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Appendix 4: LCC Local Buckling Check for Hydrotest Condition (Without Piklis Impact)



t TypeMaterial


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t TypeMaterial


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t TypeMaterial


ES021682 000 RT 5500 0001 B 58/87




Appendix 5: LCC Local Buckling Check for Operation Condition (Without Piklis Impact)



t TypeMaterial


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t TypeMaterial


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t TypeMaterial


ES021682 000 RT 5500 0001 B 61/87




Appendix 6: DCC Local Buckling Check for Installation Condition (Without Piklis Impact)



t TypeMaterial


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t TypeMaterial


ES021682 000 RT 5500 0001 B 63/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 64/87




Appendix 7: DCC Local Buckling Check for Hydrotest Condition (Without Piklis Impact)



t TypeMaterial


ES021682 000 RT 5500 0001 B 65/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 66/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 67/87




Appendix 8: DCC Local Buckling Check for Operation Condition (Without Piklis Impact)



t TypeMaterial


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t TypeMaterial


ES021682 000 RT 5500 0001 B 69/87






t TypeMaterial


ES021682 000 RT 5500 0001 B 70/87




Appendix 9: LCC Local Buckling Check for Installation Condition (With Piklis Impact)



t TypeMaterial


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Appendix 10: LCC Local Buckling Check for Hydrotest Condition (With Piklis Impact)



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t TypeMaterial


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Appendix 11: LCC Local Buckling Check for Operation Condition (With Piklis Impact)



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Appendix 12: DCC Local Buckling Check for Installation Condition (With Piklis Impact)



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Appendix 13: DCC Local Buckling Check for Hydrotest Condition (With Piklis Impact)



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Appendix 14: DCC Local Buckling Check for Operation Condition (With Piklis Impact)



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ES021682 000 RT 5500 0001 B (Flowline Mechanical Design)

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