The West African Gas Pipeline (WAGP) Offshore Pipeline Intelligent Pigging Project
By: Afolabi Oladimeji Ogunmefun (DM Asset Integrity. WAPCo)
Summary
The West African Gas Pipeline (WAGP) network
consists of both onshore and offshore segments. The
Offshore segment is a 20” x 569km pipeline with 3
laterals of 8”x20km, 10”x 17km and 18”x14 km,
transporting natural gas from east, Itoki, Nigeria and
the west, Western Region of Ghana. In the east, the
WAGP system at Itoki Custody Transfer in Ogun State
Nigeria links into the existing Escravos-Lagos pipeline
at the Nigeria Gas Company’s Itoki Natural Gas Export
Terminal in Ogun State, Nigeria. The pipeline proceeds
to a compressor station near Badagry, Lagos State.
From there it stretches offshore to Takoradi, in Ghana,
with gas delivery laterals from the main line extending
to Cotonou (Benin), Lomé (Togo) and Tema (Ghana).
The construction of the pipeline began in 2006 and it
was commissioned in 2008. The West African Gas
Pipeline Company Limited (WAPCo) owns and
operates the pipeline.
Regulatory authorities and the company’s internal
pipeline integrity management system require periodic
cleaning of the offshore pipeline and an assessment of
its integrity. The most recent of these mandatory
activities was planned and executed early 2020.The
intelligent pigging of the offshore segment was carried
out in 36 days, from January 22, 2020 to February 25,
2020. Five (5) pig runs were done, 8004 litres of liquid,
and 5kg of debris during the pig retrieval were
evacuated. The exercise was adjudged successful,
with no stalled pigs, no failed run and pipeline safely
returned to operation.
The 2020 Inline Inspection (ILI) project:
A project of this nature for a pipeline that runs across
four countries involves complex and high level
stakeholder’s management. The significance of this
project cannot be over emphasized as the WAGP
supports energy security in three West African
countries, Ghana, Togo and Benin.
In addressing the risks and the management of the
identified stakeholders for this project, we considered
the following:

Gas supply and availability,

Gas offtake,

Contracting

Securing inspection window

Pig launch & Pig retrieval

Effluent management
I.
Gas Supply and availability
Gas availability and supply into and through WAGP is
critical to the four WAGP States as this supports their
energy security. Hence, it is important to maintain the
required volume and pressure during the inspection
and not jeopardise energy security of the nations
involved.
II.
Gas offtake
The challenge of the inspection with respect to the gas
offtake is based on reverse flow from the western
corridor, balancing the power grid of Ghana and
avoiding gas interruption at Tema, Ghana, Benin and
Togo. WAPCo’ s Takoradi Regulating and Metering
Station in Ghana which is the receipt site for the pig
must be ready to take gas when gas flow to Tema is
suspended for the pigging exercise.
III.
Contracting
The contracting has to do with, securing the intelligent
pig tool and ensuring all the required resources are
available for the proposed window, including issues
relating to flight for the IP, and the project team taking
into account weather challenges during the proposed
window. (NB. Flights could not land in Nigeria a week
after the IP came). Outside the aforementioned, we
had extensive and detailed legal review of all contracts
basically due to differences in midstream and upstream
operations and inter-country regulations.
IV.
Securing Inspection window
Consideration was given to priorities across the
operating countries, Hence, engagement of
nation’s representatives and other stakeholders.

Offtake nations need to prepare for alternative
source of fuel.

Alignment with producers and shippers to align
shutdown or critical maintenance activities to
avoid disruption.
The above necessitated the need for identification of
the various stakeholders and robust stakeholder
mapping for effective engagement and management
(see the table below)
WAGP 20" OFFSHORE PIPELINE PIGGING PROJECT
STAKEHOLDER MAPPING
KEEP THEM SATISFIED 3
MANAGE CLOSELY 4
Share intermittent report
Consult, Collaborate and engage
• Gas off-taker TOGO
• PRODUCERS/SHAREHOLDER
• Gas off-taker BENIN
• REGULATORS
• KEY OFFTAKERS
•
TRANSPORTERS & SHIPPERS
• CONTRACTORS
MONITOR
1
KEEP THEM INFORMED 2
Engagement with generic
Information on progress and
communication
changes(PROJECT ALLIES)
• COMMUNITY
• Ghana Ministry of Energy &
• CUSTOMS SERVICE
Environmental Protection Agency(EPA)
• FIRE SERVICE
• West Africa Rescue Association (WARA)
Risk
The complexity of this type of project warrants detailed
project risk assessment. In view of this, a lessons
learned work shop was held to learn from experiences
of one of WAPCo’s shareholders with similar project
(32” x 258km subsea Gas pipeline). Based on this and
the project risk assessment the following risks were
identified, considered and adequately planned for:

Stuck Pig;
o Robust procedure developed to
deal with stuck pig
o Subsea sub-contractor was put on
alert
o IP tool designed with mechanical
drive and special cups with high
mechanical properties
o Flow simulation and modelling in
conjunction with the inline inspection
contractor.
The West African Gas Pipeline (WAGP) Offshore Pipeline Intelligent Pigging Project
By: Afolabi Oladimeji Ogunmefun (DM Asset Integrity. WAPCo)
o




Progressive pigging methodology
was adopted
Low gas flow upstream the compressor
station due to low pressure
o High level stakeholders engagement
o Weekly meeting with producers and
shippers to ensure gas availability
Off taker at receipt site is not available to
offtake gas due to plant shut down
o High level stakeholders engagement
o Weekly meeting with producers and
shippers
Compressor is not available
o Redundancy plan in place
o
Critical spares and OEM support
available on standby
Effluent management facilities not adequate
o Engagement
of
experienced
contractor
o Effluent simulation with two models
o Emergency response plan in place

Fire Service on standby

Medical evacuation

Two 33,000litres evacuation
tank on standby
Project execution








Project management team set up 6 months
before the exercise.
Completed pre mobilization and equipment
inspection
3
weeks
before
project
commencement
Developed communication protocol to
manage simultaneous operations
Developed pigging checklist and Project
Execution Plan (PEP)
Weekly project team meeting 6 months before
the project, updating the pigging checklist
Weekly meeting with gas producers
Daily project meeting ( twice daily AM & PM)
The following pigs were ran
o Foam pig travelled for 5days
o Cup pig travelled for 5days
o Bi di Pig with Pipeline Data logger
(PDL) travelled 5 days
o Bi di with gauge plate travelled 5 days
o MFL AXT Combo travelled for 6 days.
Intelligent Pig tool
Challenges during execution
Effluent Management:
Given the length of the offshore pipeline (569km)
354miles) and recent liquid in flow at our Tema R & M
station, there was a high probability of liquid slug during
this exercise. Outside this, the instantaneous liquidflow rate and "energy" surge ahead of the pig was likely
to exceed the process design capacity at Takoradi
Regulating & Metering station (receipt site). Hence, the
need for slug" catching systems to handle the
intermittent liquid slugs generated by the pigging
activities as pigging effluent management system.
Based on the liquid inflow into Tema over a period and
onshore pipeline pigging effluent recovered during
2014 and 2019 intelligent pigging of 30” x 56Km
onshore pipeline, a model was developed to estimate
the volume of liquid expected during the WAGP 20” x
569km offshore pipeline pigging to be 8000litres of
liquid. This model was chosen because the liquid drop
out simulation based on the gas analysis in WAGP
pipeline did not show any sign of liquid in the line.
A multinational process company was awarded the
project, and series of design reviews, risk assessment
and pre start-up safety review ensued to ensure that
the project would be done safely without incident. The
calculated flow required to drive the IP was 70mmscfd
at 60barg. However, the system could not deliver the
70mmscfd due to restriction and piping set up.
Management of Change (MOC) was raised to increase
the pressure to 80 barg. to allow for more volume to the
off-taker. Outside the above, benzene, toluene,
ethylbenzene and xylene (BTEX), and naturally
occurring radioactive material (NORM) sampling were
conducted and communication protocol established for
simultaneous flow operation via pressure management
between a major natural gas transporter and WAPCo
Finally, given that the first four pigs (foam pig, cup pig,
brush pig and plain bidi with gauge plate) came
undamaged without any liquid and less than 5kg of
debris across 569km, a conscious decision was made
to demobilise the effluent management equipment for
the following reasons.

Intelligent pig must travel with a speed of 1.6m/s
to 1.8m/s for data quality purpose; to achieve
this, the off taker must offtake 70mmscfd. Hence
effluent management piping restriction must be
removed to achieve this.

Given that 4 pigs had been removed without
liquid, liquid was not being expected during the
Intelligent Pig (IP) run.
However, the IP run shut the Takoradi R & M station
down due to high liquid inflow into the station and we
had to improvise via valve operations and liquid
evacuation to bring the IP into the station. 8004 litres
of liquid was finally evacuated
The West African Gas Pipeline (WAGP) Offshore Pipeline Intelligent Pigging Project
By: Afolabi Oladimeji Ogunmefun (DM Asset Integrity. WAPCo)
Foam Pig at Takoradi RMS
MFL Tool at Takoradi RMS
Key issues
The following are the key issues of the project
 Non-inclusion of XYZ mapping in the
intelligent tool
 Frequent black powder into Tema station
after the inspection.
 1.5% free water detected in effluent
analysis
Result
 The project was completed ahead of
schedule
 The inspection was declared successful per
Pipeline Operators Forum 2016 (POF)
standards
 Data quality
o The collected data is overall within
the contractual agreed limits.
o The MFL-A system check shows a
primary data (sensor) loss of 0.95
%.
o The XT system check shows no
data (sensor) loss.
 Important anomalies
o No anomalies have been reported
which meet the rules as described in
POF 2016, ‘list of important
anomalies.
Benefits
The intelligent pigging exercise and it’s
execution is in total compliance with some key
tenents of WAPCo’ s Operations Excellence
Management System (OEMS) which include but
not limited to the following:
 Always operate within design and
environmental limits
 Always operate in a safe and controlled
condition
 Always maintain integrity of dedicated
system
 Always comply with all applicable rules
and regulation.
The benefit of this exercise cannot be over
emphasized. Beyond meeting regulatory
requirements and public safety, this exercise
has improved customers’ confidence in WAPCo
as a business entity. Also the exercise has given
WAPCo the required information about her
asset, and WAPCo can now strategically make
some decisions to align her actions toward
achieving her objective as a world class
organization.
Pig type
Foam pig
Cup pig
Bi Di Pig
Gauge pig
MFL
Combo
Solid
waste
3.5
o.5
0.2
Liquid
waste
8004
Remarks
Excellent
Excellent
Excellent
Excellent
Very good
Profile pig gauge plate at receive
site Takoradi