IPLOCA Excellence in Project Execution Award€¦ · IPLOCA Excellence in Project Execution Award...

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Date

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18-05-2016

EFU

ITO / KFM

Van Oord Offshore bv submission

IPLOCA Excellence in Project Execution Award

Tetney sealine replacement project

Van Oord Offshore bv

Project: Van Oord Offshore bv Submission IPLOCA Excellence in Project Execution Award

Client: International Pipe Line & Offshore Contractors Association


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Contents

Contents ........................................................................................................................................... 2

1. Business Profile ................................................................................................................. 3

2. Project description .......................................................................................................... 3

2.1 Project introduction ......................................................................................................... 3

2.2 Project constraints (findings) .......................................................................................... 5

3. Project execution method (solutions) .................................................................. 6

4. Project achievements ..................................................................................................... 8




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1. Business Profile

For the last decades, Van Oord Offshore has delivered on numerous worldwide projects of-

fering a variety of highly specialised offshore installation and construction projects. We have

developed and expanded our capabilities in the offshore market, evolving into a world-

renowned engineering, procurement and construction (EPC) contractor. Our fully integrated

EPC services encompass detailed design and verification, procurement of materials and as-

sociated services, and of course installation and commissioning services; all delivered in one

complete package.

The extensive range of offshore services we offer includes:

- Subsea Rock Installation

- Pipeline shore approaches

- Shallow water pipeline installation

- Offshore dredging, trenching and backfilling

- SPM (Single Point Mooring) installation

- GBS (Gravity Based Structure) installation

2. Project description

2.1 Project introduction

The Humber Refinery is owned by Phillips 66 Ltd and is located in South Killingholme, North

Lincolnshire, England. The refinery receives crude supply through a single 36 inch NB pipe-

line that runs from a Catenary Anchor Leg Mooring (CALM) buoy, located in the Humber es-

tuary, to a crude oil transfer terminal at Tetney, Lincolnshire, England. The 36inch NB crude

oil import pipeline, commissioned in 1971, has an approximate total length of 8.4km and

runs from Tetney Oil Terminal under flat agricultural land, over one river, under environ-

mentally sensitive salt marshes and sands and then beneath the seabed to a pipeline end

manifold (PLEM) located on the seabed.




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The PLEM is positioned approximately 4km from the shoreline and is connected to the tank-

er off-loading CALM buoy by a single string of 20inch NB sub-sea hoses. The buoy provides

an offloading point for tankers carrying crude oil for the Company’s Humber Refinery and

Tetney provides an intermediate store for the crude until it is pumped to the Refinery for

processing.

The monobuoy is anchored in a water depth of approximately 16 metres below chart datum.

The Humber estuary is tidal and currents can reach nearly 3.6 knots. Visibility underwater is

poor due to the amount of naturally occurring silt suspension in the water.

Inspection results gathered over a period of approximately twelve years have identified that

localised wall loss due to corrosion will result in maintenance work being necessary at four

points by 2015. In view of the age of the line and the fact that there are already four clamps

installed on the subsea section, Company has hired Van Oord Offshore to replace the sub-

sea pipeline end manifold (PLEM) and part of the transfer line.

The Tie in between the existing pipeline and the new pipeline will be at the beach around

Mean High Water at Kp 0.

The Humber Refinery is owned by Phillips 66 Ltd and is located in South Killingholme, North

Lincolnshire, England.




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2.2 Project constraints (findings)

In order to execute this project Van Oord Offshore had to overcome the following main chal-

lenging project constraints:

Environmental

The access to the working area was

restricted to offshore. All equipment

and personal had to be mobilised over

water.

During water levels higher than mean

high water the complete beach was

submerged,

7m tidal difference and high currents

Preparation and execution

Short preperation time

Beach only accesible after 1st

of march

2015

Existing pipe should be fully operational until 8th

of may 2015

New pipe should be fully operational from 12th

of july 2015

Only 65 days for the pipe to be out of operation, which coinsides with the major

maintenance shut down window of the refinery

Delay of first oil was very costly for the client therefore the project execution method

shoud be risk “free”

Scope of work Van Oord

• Removal and reconnection of the single point mooring (SPM) and subsea hoses.

• Excavation and backfilling of the trench for the new pipeline.

• Fabrication, installation and piling of a new PLEM.

• Pipe fabrication, welding and NDT.

• Field joints, in- and external corrosion coatings and concrete weight coating.

• Installation and pre-commissioning of the replacement pipeline.

• Removal of a section of the existing pipeline between kp 0 and kp 0.38.

• Removal of the existing PLEM, PLEM frame and pipeline S-bend.

• Capping the open ends of the existing pipeline.

Restricted area at Tetney beach




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3. Project execution method (solutions)

In order to overcome the project constraints Van Oord Offshore had to come with an innova-

tive project execution method as conventional execution methods were not suitable or too

risky;

A string yard on land in combination with an offshore pull was not possible due to

the land access constraint

A float and sink method would have been possible, but was considered to be too

risky due to the high currents perpendicular to the pipe trajectory

A pipe lay barge solution would have been possible but due to the shallow area this

would have involved large quantities to be dredged (not favourable for

environmental and morphological reasons)

Execution method

43 pipe strings with a length of 100m (8 pipe joints) were fabricated in a yard in

Amsterdam and loaded on the

specially designed String

Barge

The specially designed string barge and a specially designed accomodation barge

(120p) were beached and ballasted during spring tide at the beach near Tetney, for a

duration of approximatly 1.5 month.

Loading String Barge

Accommodation barge and String barge

at the beach




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The stringbarge with a dimension of 120m x 36m consisted out of the following

main items:

o 4 specially designed and build gantry cranes to move the pipestrings into

the firing line

o A pipe string stack, consisting of 43 pipe strings of 100m long stacked 4

high

o A firing line

consisting out of

adjustable rollers

to allign the strings

o Two welding and

coating locations

to connect the

strings to

eachother

Two adjustable

launchways (one to

onshore and one to

offshore) were built at the

beach to guide the pipe

from the barge to the

beach.

Thirtyeight 100m pipestrings and the PLEM were pulled offshore through a pre

dredged trench (with a curve with a radius of 10000m) to the final position using

a 600mTon winch installed

on a pull barge. After each

pull of 100m the next

section of 100m was

welded to the allready

pulled pipe.

String barge

Launchway

Pull barge




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Five 100m pipestrings were pulled over rollers towards the shore using terrestrial

equipment.

After the final pull and removal of the stringbarge the onshore section and

offshore section were connected at the beach. After the connection the section at

the beach was post

trenched.

After post trenching the new pipe was connected to the existing pipe using a

spool piece.

4. Project achievements

The innovative project execution method proofed to be a great success. The project was de-

livered in time and within budget.

The method was a robust solution in order to mitigate the project constraints. The biggest

project constraint that the working area was fully submerged during high water was used as

an advantage: during high water spring the barges with the pipe were beached, during low

water dry equipment was used to install the launch ways and to post lower the pipe at the

beach.

Using barges and not a large temporary man-made island at the beach, reduced the morpho-

logical and environmental impact at the beach significantly.

Post trenching

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