Deepwater Workshop

Subsea Tie-back

PETRONAS-PETRAD

Presented by:

M Amirushah B Zakaria Project Engineer | PI | PRD | PMU

Deepwater Pipeline Design

Rigid & Flexible

Objective

Deepwater Pipeline Design Considerations

Project Execution Considerations

Conclusion

PRESENTATION OUTLINE

To give an overview and comparison between

deepwater rigid and flexible pipeline with regard to

design challenges and project execution aspect

OBJECTIVE

Main challenges for pipeline development in deepwater :

• Material selection

• Thermal insulation

• Free span

• Installation

• Repair

Flexi

ble Rigid

Gumusut - Kakap Development Project

Kikeh Development Project

DEEPWATER PIPELINE DESIGN CONSIDERATIONS

Description Rigid Flexible (unbonded)

Material A homogenous steel pipe –

carbon steel, CRA, clad etc

Consists of plastic and steel layers

which are hold by end fitting

Wall Thickness / x

Weight in Air / Water / x

Collapse Resistant / x

Minimum Bending Radius x /

Properties Comparison

Material Selection

Flexible Flowline – Courtesy of Technip Carbon steel pipe End Fitting

Legend:

/ - advantage

X - disadvantage

Description Rigid Flexible

Passive insulation Wet coated - PU, PP foam or

glass reinforced plastic, PiP

Plastic sheathes – additional foam

insulation layer can be added

Active insulation

Hot water circulation and

electrical heated PiP

Additional active heating can be added

For both, combination of insulation coating and pipeline burial can be more cost effective than the thick

insulation coating

Thermal Insulation

Courtesy of Technip

Syntactic PU Pipe-in-Pipe Flexible flowline

Description Rigid Flexible

Free Span Rectification / /

If the as laid free span length exceeds the maximum allowable free span length and confirmed with as

laid span analysis, the free span should be corrected using one of the mitigation methods:

- alteration of seabed

- mid-span supports such as mechanical legs or sand-cement bags / mattresses

Free Span

Several factors influenced the variation from the anticipated span length:

- Spanning predictions not calibrated with the actual field conditions

- Increase in laying tension to protect buckling probably increased the span length

- Accuracy of pipelaying in the pipeline corridor

Pipeline traverse on seabed

Installation

Rigid Flexible

J / S lay DP vessel

Reel lay

Reel lay

Deepwater Pipelay Vessel

Seabed

Installation Configuration

S lay Reel lay J lay

- The installable water depth by the installation vessel varies with pipe size and

weight. It can go to maximum water depth for small pipe sizes

Installation

TDP

Welding

station 1

NDT

station

Welding

station 4

Welding

station 3

Welding

station 2

Repair

station Tensioner 1 Tensioner 2 Tensioner 3

Surface

cleaning HSS

station

HDPUF

station

Station 1- 4) Welding

(GMAW using Serimax

dual torch machine)

Station 5) NDT API 1104 3 x 80 mT Tensioner Station 6) Repair (SMAW/GSFCAW)

Station 8) HSS coating

Station 7) Surface cleaning

Station 9) HDPUF injection Stinger

S lay

Installation

Installation

J lay

Workstation

Erector

J tower

Reel Drive System Vertical Lay System

Reel lay

Midline Connection

Installation

Description Rigid Flexible

Diverless Pipeline Repair

System (DPRS)

/ x

- Availability of DPRS would minimize the downtime due to pipeline damage

Repair

Pipeline damage possibly can happen due to:

- Local defect – weld defect, pin hole, internal corrosion

- Nature - landslide / seismic event, hurricane

- Anchor drag

- Installation

- Material fatigue

Permanent Repair Clamp

Vertical DPRS

Legend:

/ - advantage

X - disadvantage

Cost Comparison

Item Rigid Flexible

*Procurement Cost (USD/m) 750 – 850 2500 - 6000

**Installation vessel charter

rate (USD’000/day) - With high tension lay system (for

laying and recovering)

600 - 750

(S / J lay vessel)

~500

(Reel lay vessel)

Other materials More subsea

structure and

connection e.g.

PLET, jumper

Less subsea structure

and subsea connection

Note: *Estimated based on12” ID pipeline (with 1” GSPU insulation for rigid pipe)

**For high tension lay system, ~400t tensioner

PROJECT EXECUTION CONSIDERATIONS

Schedule Comparison

Item Rigid Flexible

Average Pipelay

Rate

*42 – 104 m/hr

(J / S lay)

**200 – 500 m/hr

Pipeline Storage

capacity

~ 4000t (min) Multiple reels Pipe length varies based on pipe size,

carousel capacity & deck size

Other activities Installation of subsea

structure, cleaning,

gauging etc

Less activities

Note: *Depends on pipe size and wall thickness

**Pipe alignment - midline connection can take hours

Understanding of the ways to manage challenges in deepwater pipeline

development will ensure safe design, safe operation and give benefit to

the overall project capital and expenditure.

CONCLUSION

THANK YOU