48'' Pipeline Shore Approach Reportpdf PDF
48'' Pipeline Shore Approach Reportpdf PDF
48'' Pipeline Shore Approach Reportpdf PDF
CONSTRUCTION - 48 BONNYPIPELINE
By
TUNDE ALABI
AYOOLA OLATUNJI
Offshore development of oil and gas fields often involve laying of pipelines from offshore to the
shore to transport produced hydrocarbon for processing or sales. The transition region between
offshore and the shore also referred to as shore approach is usually prone to waves, currents and
winds and has its peculiarities regarding topography, soil properties and metocean condition. The
shore approach often poses some challenges to pipeline construction and requires a special
construction process.
This paper discusses the methods of pipeline shore approach construction and factors to consider
in selecting the method to apply. It focuses more on the pulling method and gives typical
calculations of pulling forces, pull force profile and equipment selection.
A 48 pipeline shore approach constructed with the pulling method at Bonny, West Africa is
used as a case study. The challenges encountered during construction, mitigating measures taken
and lessons learnt are shared.
Acknowledgement:
We wish to acknowledge the Shell Petroleum Development Company, Nigeria for the
permission given to use the data and information obtained on the Bonny Terminal Integrated
Project in this presentation/paper.
ii
Contents:
Section 1: Introduction 1
1.1 Background 1
1.2 Objective and Scope 1
Section 2: 48 Bonny Pipeline Shore Approach Construction 2
2.1 Introduction 2
2.2 Shore approach 48 Bonny Pipeline 3
2.3 Pipeline Shore Approach Construction Methods 3
2.4 Selection of Pipeline Route and Shore Approach Construction Method 7
2.5 Codes and Standards 8
2.6 Pull Force 9
2.7 Calculation of Buoyancy Aid to Reduce the Pulling Force 10
2.8 Hydrodynamic Forces on the Pulled Pipeline 10
2.9 Winch Capacity Calculations 11
2.10 Pull Force Profile 11
2.11 Check on Tensile Strength of Pipeline 12
Section 3: Construction 12
3.1 Construction Activities 12
3.2 Managed Risks 14
3.3 Actual Pull Force Profile 14
Section 4: Post Construction Analysis 15
4.1 Pull Force Profiles Analysis 15
4.2 Execution Challenges 16
4.3 Lessons Learnt 16
Chapter 5: Conclusion 16
References 17
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Section 1: Introduction
1.1 Background
Offshore oil and gas field development often requires transporting produced hydrocarbon in
pipelines from subsea systems or offshore facilities through the shore approach to the shore. This
includes laying a continuous pipeline from offshore to onshore. Figure 1.1 depicts a pipeline layout
showing landfall /shore approach. Pipeline shore approach construction may also apply to disposal
pipelines taking treated produced water out into the Offshore Disposal Zone to meet statutory
requirements.
The pipeline shore approach construction method is totally different from the offshore and onshore
construction methods and has its peculiar challenges arising from the environment.
At the shore approach region, metocean, nature of soil and topography play a significant role in the
selection of a construction method.
The paperr shows the calculationss for the pulll force requuired for layying the pippeline acrosss shore
approach zone
z and thee pull force profile
p and how
h it is useed to determ
mine the capaacity of the ppulling
equipmentt to be emplo
oyed. A postt constructio
on analysis iss carried outt comparing the calculatted and
actual pulll force profiles for the 48
4 pipelinee, and the chhallenges and lessons learnt on the pproject
are shared.
Section 2: 48 Bonny
y Pipeline Shore Appro
oach Projectt
2.1 Introd
duction:
The 48 x 39.5km Bo ne is an oil export pipelline that oriiginates from
onny pipelin m Bonny Teerminal
and termin
nates 32km offshore
o at the
t Single Point
P Moorinng / Pipelinee End Maniffold (SPM/P
PLEM).
The pipeline was consstructed in 2007 by Hyu
undai Heavy Industries ((HHI) and iss operated byy Shell
Petroleum Developmeent Company
y (SPDC), Nigeria.
N Figuure 2.1 show
ws the map off West Africca with
an insert of
o Bonny area, Gulf of Guinea
G he 48 pipelline.
and th
Figurre 2.1: Map of West Afrrica with an iinsert of Bonnny area [2] [3]
Environm
mental Data for Bonny [4]
[
Wiind speed: 35
5.6m/s
Seaa temp: 28 Deg.
D C
Waater depth: 5-8m
Tid
de: 2.2/3.6m
m
Meean Sea Leveel (MSL): 1.43m
Waave height: 1.05/1.44m
1
Figu
ure 2.2: Bon
nny Shore Approach
A in Gulf
G of Guinnea [4]
Also, depeending on th
he nature of the beach, a cofferdam
m may be connstructed to manage efffects of
tidal moveement of watter, waves an
nd current. The
T inside oof the cofferddam is excavvated to ensuure the
pipe is su
ubmerged du
uring pullin han being drragged on soil. The trrenched section is
ng rather th
backfilled and the site is reinstated
d on complettion. Floaterrs may be atttached to redduce pull forrce.
The key equipment reequired inclu
ude: piling machine,
m dreedger, excavvator, lay baarge, pulling winch
y vessel.
and survey
to its end with the aid of a pull head and it is pulled by means of a winch installed on a barge
offshore.
2.3.3 Tunneling
Tunneling is a method whereby a tunnel or shaft is constructed from the shore below the shore
approach to come out of the seabed and the pipeline is built in the tunnel which may accommodate
a bundle of pipes to be laid. Figure 2.5 shows the sketch of the Kalsto shore approach tunnel, a
landfall pipeline crossing with the pipelines placed in 600 metres of concrete tunnel at the
Norwegian coastline with a rocky bottom and large topographical variations. [7]
2.3.4 Oth
her Pipeline Shore Apprroach Construction Meethods
Other meth
hods of pipeeline shore ap
pproach con
nstruction incclude:
A variiant of botto
om tow metthod where a welded piipe is towedd to site, aliigned at thee shore
approaach and drop
pped in a tren
nch in a conttrolled mannner.
In shore approach
hes with tidaal flats / sw
wampy terraain a trench is excavateed with a drredger/
excavaator and a baarge is used to
t weld the pipeline
p whicch is floatedd and droppeed in the trennch.
A com
mbination of pulling
p and tunneling
t orr HDD methoods may be uused.
Social / Commercial
C activities: Pipeline ro
oute or shorre approachh constructioon method having
negative im
mpact on en
nvironmentaally sensitivee areas or ddisrupting coommercial aand daily acctivities
should be avoided.
Pulling
Winch Cofferdam
Pulling
cable Pulling
Head Pipeline
Seab
Shore
SHORE Approach Friction
i. Pull force with pipe at touchdown point, Pi, (see Figure 2.8) is:
(Weight of cable section submerged) x (Friction factor) + (weight of cable section in air) x (Friction
factor) + Back tension
9
Pulling
Winch
Beach
Cable
Pulling Pi
Head
Touchdown
Point
ii. Pull force with a section of the pipe at touchdown point, Pii, (see Figure 2.9) is:
(Weight of cable section submerged)(Friction factor) + (Weight of cable section in air) x (Friction
Factor) + (Submerged weight of pull head and pipe) (Friction Factor) + Back tension
Pulling
Winch
Beach Cable
Pulling
Head Pipeli
Touchdown
Point
iii. Pull force with pull head at tie-in point, Piii, (see Figure 2.10) is:
(Weight of cable in air) (Friction factor) + (Weight of pipe section and pull head in air) (Friction
factor)+ (Submerged weight of pipe) (Friction factor) + Back tension
10
Pulling
Winch Pulling
Head Beach
Pipeline
Touchdown
Point
The total pull force is determined with pull force, Piii, above and is used for the selection of pulling
winch and confirmation of cable selection with factors of safety provided.
The pull force profile over the pull length is plotted with the calculations made above.
Calculated Pull Force was 226 MTon (2216KN)
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Trenching and cofferdam construction can be carried out to overcome or reduce the effect of the
cross flow on the pipeline being installed.
Figure 2.11: Typical pipeline designed to approach the shore at 90 degrees [1]
12
Wire
drum
Winch
Steelwire Pullhead
Rotating
pulleys
Static
pulley
Power
pack Pulldirection
Anchoring
13
Total
Pull
CapacityofWinch
Force
(Tonnes)
Breakout Lowwater
Friction
Highwater
Running
Friction
Laybarge
Tension Touchdown
Point
Laybarge DistancefromLaybarge(m) S
Figure 2.13: Pull force profile showing low water, high water and breakout/running friction [1]
Typical values for variants of friction factor - breakout friction factors are: Pipe on beach 1.0; Pipe
on seabed 0.9 (medium sand); Wire on beach 1.3; Wire on seabed 1.3. [1]
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Section 3: Construction
3.1 Construction activities include:
Survey
Constructing Winch Yard and Access Road
Constructing a cofferdam
Trenching
Installation of 2 winch system and hold back anchor
Barge set up and deployment of messenger rope
Running of pulling wires
Pipe string production on barge and pay out
Pulling pipeline string towards landfall
Post trenching
As-built survey
Reinstatement of Winch Yard and Beach crossing
15
Figure 3.4: Pulling of 48 Bonny Pipeline from the shore with lay barge at background [4]
Figures: 3.5, 3.6: Pull head and pipe pulled to the shore [4]
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PullForceProfile48''ShoreApproachPipeline
3,500
3,000
PullForce(KN)
2,500
2,000
1,500
1,000 Start(KN)
Finish(KN)
500 Average(KN)
0 1 2 3 4 5 6 7 8 9 10 11 12
NoofPipesPulled(x10)
PullForceProfile48''PipelineShoreApproach
3,500
3,000
2,500
PullForce(KN)
2,000
1,500
1,000 Winch(KN)
Plan(KN)
500
AvActual(KN)
0 1 2 3 4 5 6 7 8 9 10 11 12
NoofPipesPulled(x10)
Figure 3.8: Calculated and Actual Pull Force Profiles for 48 pipeline
and it was pulled against the sand mass. The maximum pull force calculated was 2216 KN against
maximum actual start pull force of 3114 KN (a difference of approximately 32%). The additional
pull force required was however taken care of by the safety factor built into the winch capacity.
Referring to figure 3.8, there is a fair correlation between the calculated and actual pull force
profiles for the 48 pipeline. Both showed the same trend of pull force increasing with pull distance
and the friction factor of 1.3, for the cable against seabed and sand appears conservative enough to
take care of breakout friction factor experienced at initial stage of pull. Also, the friction factors of
0.9 and 1.0 are adequate for the pipe and pull head against the seabed and sand respectively. Taking
an average, the pull forces were: calculated 1868KN and actual 1979KN (a difference of 6%).
The variance between the calculated and actual pull forces at the tail end of the pulling activity also
showed the effect of the shallow end where a good section of the pipeline was pulled close to the
seabed thereby increasing the pull force unlike when a good section of the pipe was submerged and
pipe buoyancy was higher. This may call for the need to vary the friction factor upward when pull
head is pulled close to the beach.
Need to define and monitor sea state limits for pipe lay down/abandonment
Continuous interface management with stakeholders.
Section 5: Conclusion
The pulling method for pipeline shore approach construction is favoured in areas with benign
metocean conditions, low social activities, gradual slope and without outcrops and rocks.
The actual pull force profile recorded during construction of pipeline shore approach for the 48
Bonny pipeline was compared with the calculated pull force profile and found to be fairly
comparable. Challenges and lessons learnt on the project were shared in this paper.
References
1. JEE Pipeline, Riser and Subsea Engineering Courses: Installation Calculation for Subsea
Pipelines; JEE Limited Kent, England, 2008.
2. Map of West Africa, Reference No. 4242, UNITED NATIONS, Depart. of Peacekeeping Ops.,
Cartographic Sect.; UNHCR website (2005).
3. Bonny Map Satellite Images of Bonny; Maplandia.com; Maplandia website (2011).
4. Bonny Terminal Integrated Project, SPDC, Nigeria, 2007.
5. Braestrup, M. W.; Andersen, Jan B.; Andersen, L. W.; Bryndum, M.S.; Christensen, C. J. and
Nielsen, Niels-J. R.; Design & Installation of Marine Pipelines; Blackwell Sc, Oxford, 2005.
6. OES, Oil and Gas Engineered Systems; Pipeline Approach HDD Photographs; OES,
Australia, 2009.
7. Berge, B.; Waagaard, K. and Harneshaug, K.; Pipeline Shore Approach Tunnel at Kalsto: The
Damage and the Repair; OTC, Houston, Texas, May, 1993.
8. Alabi, O.; Pipeline Shore Approach / Tie-in Engineering and Construction; Faculty of
Engineering, University of Aberdeen, 2012.
9. King, C.A.M.; Beaches and Coasts; St. Martin Press, New York, 1972.
10. Palmer, Andrew C. and King, Roger A.; Subsea Pipeline Engineering; PennWell Corporation,
Oklahoma, US, 2004.
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