Challenges in Deepwater Subsea Installation Operations

Daniel Karunakaran, Subsea7

Who we are?A company dedicated to pure play SURF (Subsea, Umbilical,

Risers and Flow lines) engineering and construction in the global oil and gas sector.

Established in 2002 from the merger of Halliburton Subsea and DSND.

Listed on the Oslo Stock Exchange since August 2005.

Earned revenues of $2.19 billion in 2007.

Employ in excess of 5,000 people globally.

Backlog at 31 December 2007 $4.2 billion

Blind Faith

Engineering, procurement, fabrication, transportation & installation.

2 x Rigid flow lines (7km)

2 x Steel Catenary Risers

Seven Oceans’ first pipe lay job.

First deepwater Steel Catenary Riser for Subsea 7

Assets: Leith Spool base, Scotland

Water Depth:2200 m

Offshore Duration: Oct 2007

Saxi Batuque, AngolaEngineering design, procurement,

fabrication and installation

16 Flow lines (50km)

32 FLETs

14 heavy suction piles

Luanda Spool base

Challenging pipe and weld design

Assets: Luanda Spool base, Skandi Navica

Water Depth: 650-810m

Offshore Duration: Sept 2007 – Jan 2008

Ormen Lange Umbilical Installation

CHALLENGESEnvironmental

• Strong current• Uneven seabed

Umbilical Properties• Low submerged weight to diameter

ratio• Low bending stiffness

Operational limitations• Maximum ROV reach 250m for

touchdown monitoring

INSTALLATION CRITERIA

2.4m Design Hs 2.5m Design Hs1.5m Design Hs

High curvature

THE DEPRESSORMain Purpose is to stabilize the catenary

• Control the touchdown point

MAIN FUNCTIONS

• Weight down the umbilical• Reduce the layback for ROV monitoring• Reduce peak tension at touchdown• Straighten the curvature at touchdown• Fulfill tight lay tolerances

DESIGN CONCEPT

• Weight element with bellmouth in both ends

• Symmetric around CoG• Lifting points• Hang-off wire and umbilical common

over boarding point• Hinged door

Lifting point Centre of gravity

DESIGN PRINCIPLE

1. Acceptable umbilical curvature through depressor

2. Support various catenary configurations

3. Easy subsea removal4. Simple and non-sophisticated

PROJECT SPECIFIC DESIGN PRINCIPLE

1. Bellmouth radius2. Inner diameter3. Required length4. Weight and operational height

above seabed

INSTALLATION CRITERIA

1.5m Design Hs

With Depressor

3.4m Design Hs

OPERATING THE DEPRESSOR

Blind Faith Deepwater SCR Installation

Pipe lay Vessel – Seven Oceans

• Built – 2007• Length – 157 m• 400Te crane capacity• 3500Te Reel• 400Te tensioner capacity• Up to 16” diameter pipes

Blind Faith Development

• Operator: Chevron• Location: Mississippi Canyon - Block 696 and Block 650• Ultra-Deepwater – 2118 m• Steel Catenary Riser (SCR)• High specification welds• 40 Te PLET• Titanium Taper Stress Joints

Challenges

• Ultra deepwater – Top tension

• PLET Handling and initiation - 40 Te PLET

Challenges

• Attachment of strakes• Entire length of SCR• 5 m / min maximum

speed

Challenges

• Welding of Titanium taper stress joint• Fatigue is critical• Very limited time to

have high quality weld• Weld performed with no

cut-outs

Blind Faith Installation

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