Fundamentals of S-lay and Engineering Analysis Using OFFPIPE- GEP

Fundamentals of S-lay and Engineering Analysis using OFFPIPE By JBEIL Subsea Engineers Pvt. Ltd. – Oil & Gas Trainings www.globalenergypanel.com

Contents •

INTRODUCTION ABOUT OFFSHORE PIPELINE INSTALLATION

•

OFFPIPE

•

OFFSHORE PIPELINE INSTALLATION ANALYSIS

•

CASE STUDY

INTRODUCTION ABOUT OFFSHORE PIPELINE INSTALLATION

I. INTRODUCTION

•

•

•

•

•

Steel Pipe Corrosion Coating Concrete Coating Cutback Field Joint

I. INTRODUCTION J-Lay

Reel-Lay

S-Lay

Pipeline Tow

I. INTRODUCTION OFFSHORE PIPELINE INSTALLATION Offshore pipeline installation is performed by specialized lay-vessels. There are several methods to install a pipeline, the most common methods being S-lay, J-lay and reeling.

I. INTRODUCTION

I. INTRODUCTION

I. INTRODUCTION

I. INTRODUCTION

I. INTRODUCTION

I. INTRODUCTION PIPELAY BARGE

I. INTRODUCTION TENSIONER

I. INTRODUCTION STINGER

I. INTRODUCTION S-LAY CONFIGURATION

Touch Down Point

I. INTRODUCTION

I. INTRODUCTION

I. INTRODUCTION

I. INTRODUCTION

START UP

•Dead-man Anchor •Elevated Hold Back •Bow String

I. INTRODUCTION

Dead-man Anchor Start up

I. INTRODUCTION

Elevated Hold Back Start up

I. INTRODUCTION

Bow string Start up

I. INTRODUCTION

Applicable code : DNV OS F101 ALLOWABLE STRESSES - Static

Overbend Parameter Allowable Stress

On Barge

On Stinger

Sagbend

85% SMYS

72% SMYS

72% SMYS

OFFPIPE

II. OFFPIPE OFFPIPE OFFPIPE is a finite element method based computer program. It has been developed specifically for the modeling and structural analysis of nonlinear problems encountered in the installation and operation of offshore pipelines. Analysis capabilities include: • Static and dynamic pipe laying analyses for many laybarge and stinger configurations, both conventional and J-lay. • Pipelay initiation, abandonment and recovery analyses; • Calculates static pipe stresses, span lengths and deflections for irregular seabed scenarios; • Static davit-lift analyses for conventional riser installations and subsea tie-ins

II. OFFPIPE OFFPIPE The loads that are considered in the analyses are as follows: 1. Uniformly distributed pipeline self-weight including coatings. 2. Constant barge tension. 3. External hydrostatic pressure due to water column. 4. Reaction forces from the barge rollers 5. Vertical seabed reaction

II. OFFPIPE OFFPIPE The pipeline and the barge are modeled as follows: 1. Lay barge is modeled from the center of the first station up to the last roller on the barge stern then to the last roller of the stinger. 2. Lay barge is modeled through the input of the horizontal coordinates of the barge rollers and vertical coordinates or the barge radius to form a smooth pipeline profile on the barge. 3. All roller supports are modeled in terms of simple supports that resist only the downward displacement of the pipeline or cable. The pipeline or cable is free to lift off from the support when appropriate. 4. The friction force of the barge roller is very minimal if compared to the applied tension. Thus, for the purpose of analysis, the effect of frictional resistance between rollers and pipeline has been ignored. 5. The properties of steel pipeline are assumed to be linear, therefore constant modulus of elasticity has been introduced. 6. Pipeline or cable is divided into a finite number of elements. 7. The seabed is modeled as a discrete elastic foundation.

II. OFFPIPE COORDINATES IN OFFPIPE

X coordinate is the water surface direction Y Coordinate is vertical direction Z coordinate is lateral direction of the b arge

Coordinate (0,0,0) is positioned at the stern of the barge (at seawater surface level)

II. OFFPIPE TRIM AND OFFSET Trim angle is the angle between the barge deck and seawater surface due to the barge rotation in the Z coordinate

Offset is the distance of barge movement in the X, Y, Z direction which is measured from the original position of the barge. Offset usually is used for abandon and recovery and lifting analysis.

II. OFFPIPE CREATE NEW INPUT FILE

II. OFFPIPE Input / Output / Heading Data

For pipeline installation analysis, the field “HEAD” and “PRINT” shou ld be defined.

II. OFFPIPE Input / Output / Heading Data HEAD Screen

Problem input/output units : “1” : English unit “2” : SI unit

II. OFFPIPE Input / Output / Heading Data PRIN Screen

II. OFFPIPE Input / Output / Heading Data PRIN Screen

“1” means that the parameter shall be calculated and displayed in the OFFPIPE output, “0” means that the parameter shall not be calculated and displayed in the OFFPIPE output (will be the same if the field is left blank)

II. OFFPIPE Pipe and A&R Cable Data

“PIPE” and “COAT” field should be defined. “CABL” is defined for the pipelay initiation and abandon and recovery analysis.

II. OFFPIPE Pipe and A&R Cable Data PIPE – Pipe Properties

Pipeline length is defined for pipeline initiation on ly. Pipeline length indicates the pipeline length on the barge which is measured from the first support position.

II. OFFPIPE Pipe and A&R Cable Data COAT – Coating Properties

II. OFFPIPE Pipe and A&R Cable Data COAT – Coating Properties

II. OFFPIPE Pipelay Vessel Data

“TENS” and “BARG” field should be defined for pipelay, abandon and recovery analysis. For Davit lifting analysis, “DAVI’ should be defined, and the “TENS” is not defined.

II. OFFPIPE Pipelay Vessel Data BARG – Barge Data and Geometry

Number of station is used to specify the number of the pipe nodes on the barge (include rollers and tensioner). For davit lifting analysis, number of station is used to specify the number of davit lift. The laybarge trim angle is the angle between the deck and the water surface.

II. OFFPIPE Pipelay Vessel Data BARG – Barge Data and Geometry “More -> Support Data” (Pipe Support Data and Geometry) Horizontal distance of the support (X), measured from the stern of the barge. The X = 0 is selected at the stern of the barge. Vertical distance or height of support on barge (Y), measured from the deck of the barge. Support type: “1” : Simple pipe support “2” : Pipe tensioner/winch Note: * Davit Spacing is defined for davit lifting analysis only.

II. OFFPIPE Pipelay Vessel Data TENS – Tension

II. OFFPIPE Pipelay Vessel Data TENS – Tension

II. OFFPIPE Stinger Data

II. OFFPIPE Stinger Data STIN – Stinger Data and Geometry

II. OFFPIPE Stinger Data STIN – STIN – Stinger Data and Geometry “More -> Support Data (Support configuration on Stinger)” Horizontal distance of the support on stinger (X), measured from stern stern of the barge. Since the stinger position is behind the stern, the negative value shall be applied in this distance. Vertical distance distance or height h eight of support on stinger (Y), measured from surface water elevation. Negative value indicates the support position is under the surface water elevation.

II. OFFPIPE Sagbend and Seabed Data

“GEOM”, “SOIL”, and “CURR” should be defined for pipeline installation analysis.

II. OFFPIPE Sagbend and Seabed Data GEOM – GEOM – Sagbend Pipe Geometry Data

Sagbend element length is defined to determined the distance between nodes at the sa gbend region. The selected water depth is the maximum water depth, considering wave, tidal, and storm surge condition. “X Coord. Of Free Free End” field is only defined for davit lifting analysis

II. OFFPIPE Sagbend and Seabed Data SOIL – Seabed Soil Properties

II. OFFPIPE Sagbend and Seabed Data SOIL – Seabed Soil Properties

This field is used to define the lateral friction of the soil.

II. OFFPIPE RUN / END / Misc. Data

II. OFFPIPE RUN / END / Misc. Data

II. OFFPIPE OFFPIPE RUN AND RESULT Run the File

II. OFFPIPE OFFPIPE RUN AND RESULT Offpipe Result






II. OFFPIPE – Dynamic Analysis

Modes of Motion Linear

Oscillatory

• Heave

• Heave

• Surge

• Pitch

• Sway

• Roll

Rotational

Non-oscillatory

• Pitch

• Surge

• Roll

• Sway

• Yaw

• Yaw

II. OFFPIPE

•

Wind Loads

•

Current Loads

•

Wave Loads

Wind Loading Wind is treated as a Time-Invariant Environment Force, f 



1 

2

2

 C D AU w

Density of Air

A = Structure Projected Area normal to the wind flow U = mean wind velocity, generally taken at an elevation of 10 m from the water surface w

CD is the Wind Drag Coefficient

Wind Loading Wind is treated as a Time-Invariant Environment Force, f 



1 

2

2

 C D AU w

Density of Air

A = Structure Projected Area normal to the wind flow U = mean wind velocity, generally taken at an elevation of 10 m from the water surface w

CD is the Wind Drag Coefficient

Current Loading

Force

f

1 

2

 C D AU

2

 fluid density A = structure projected area normal to the flow U = uniform flow velocity CD is the Drag Coefficient. 

Equation is similar to Wind Loading

Waves  Sea

comprises a myriad of waves.  Irregular or Random wave is changing it’s form from time to time  It is a superposition of many simple, regular, harmonic wave components.

Irregular Seaway

J. Ray McDermott – Jebel Ali,

Wave Spectra 

Wave Energy ≈ Amplitude2



Intensity of the sea is characterized by it’s total Energy



Wave Energy Spectrum or Wave Spectrum shows how the total energy of sea is distributed according to the frequencies of the various wave components


Wave Spectra

Spectrum Models Pierson Moskowitz Bretschneider ISSC ITTC JONSWAP Ochi


II. OFFPIPE

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS USING OFFPIPE

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS

GENERAL FLOWCHART OF PIPELINE INSTALLATION ANALYSIS USING OFFPIPE:

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS PIPELAY INITIATION ANALYSIS • Pipeline initiation is performed at the start-up water depth. • Pipeline initiation is usually performed using DMA (Dead Man Anchored) Method. • During pipeline initiation the pullhead at the end of pipeline is connected with the cable. • During pipeline initiation activity, the pipe joint is added on the barge and welded until the pipeline profile touch the seabed. • The barge tension is maintained in order to result the acceptable stresses. Pipeline Initiation Activity is performed by considering the increasing of pipeline length due to th e pipe joint addition. The considered case for pipeline initiation a re given below. • Pullhead position after tensioner • Pullhead position near to the barge stern • Pullhead position at the stinger • Pullhead position just after the stinger • Pullhead position at the sagbend region • Pullhead position prior to rest on seabed • Pulhead position resting on the seabed

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS PIPELAY INITIATION ANALYSIS The offpipe calculation is performed for several times (depend on the number of the case), by changing the pipeline length value.

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS PIPELAY INITIATION ANALYSIS - CASES

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS PIPELAY INITIATION ANALYSIS - SUMMARY

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS NORMAL PIPELAY ANALYSIS • Normal pipelay is performed at the various water depth in order to get the applied tensions an d barge configuration during installation activity. • If any variation of wall thickness and coating parameters is applied along the p ipeline route, static installation analysis should be performed based on this wall thickness and coatings variation

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS NORMAL PIPELAY ANALYSIS – FLOWCHART

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS NORMAL PIPELAY ANALYSIS – CASE

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS NORMAL PIPELAY ANALYSIS – OFFPIPE INPUT LIST

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS NORMAL PIPELAY ANALYSIS – OFFPIPE OUTPUT LIST

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS NORMAL PIPELAY ANALYSIS – SUMMARY

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS ABANDON AND RECOVERY ANALYSIS

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS ABANDON AND RECOVERY ANALYSIS – FLOWCHART

The offpipe calculation is performed for several times (depend on the number of the case), by changing the cable length value.

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS ABANDON AND RECOVERY ANALYSIS – CASES

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS ABANDON AND RECOVERY ANALYSIS – OFFPIPE INPUT LIST

III. OFFSHORE PIPELINE INSTALLATION ANALYSIS ABANDON AND RECOVERY ANALYSIS – OFFPIPE OUTPUT LIST







III. OFFSHORE OFFSHOR E PIPELINE PIP ELINE INST IN STALLA ALLATION TION ANAL ANALYSIS YSIS ABANDON AND RECOVERY ANALYSIS – ANALYSIS – OFFPIPE OUTPUT LIST

III. OFFSHORE OFFSHOR E PIPELINE PIP ELINE INST IN STALLA ALLATION TION ANAL ANALYSIS YSIS ABANDON AND RECOVERY RECOVERY ANALYSIS ANALYSIS - SUMMARY

III. OFFSHORE OFFSHOR E PIPELINE PIP ELINE INST IN STALLA ALLATION TION ANAL ANALYSIS YSIS Other Advanced Uses of OFFPIPE

• Single Point Lift • Multi Point Davit Lift Analysis • Midline Tie-in Analysis • Riser analysis

END OF SLIDES

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Fundamentals of S-lay and Engineering Analysis Using OFFPIPE- GEP

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