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Natural Gas
Cawthorne Channel Associated Gas-gathering Project, Nigeria –
Elimination of Gas Flaring
a report by
Bob Rust, Colin Gamblin and Charles Ellinas
Oil, Gas and Petrochemicals, Mott MacDonald Ltd
Eliminating gas flaring (see Figure 1) is a vital step forwards, both A Unique Project
ecologically and economically, worldwide but especially for Nigeria. In this project, engineering ingenuity, environmental and fiscal benefits,
With reports estimating that flaring represents an annual economic improving the living conditions of the local population, boosting the
loss to the country of about US$2.5 billion, coupled with the air economy of Nigeria and delivering a massive environmental benefit
pollution, contribution to global warming and rainforest damage combine to create a unique venture with a variety of benefits.
caused by the flares, it is clear that it this a problem that needed
tackling. Such was the goal of Daewoo (Daewoo Engineering and The project represents one of the biggest implementations of concepts
Construction Company Limited) and Mott MacDonald’s work on the developed by Mott MacDonald for Shell for the elimination of flaring.
Shell Petroleum Development Company’s (SPDC) Cawthorne Nonetheless, the project had its challenges, both on the engineering
Channel associated gas-gathering project in Nigeria. The project is side and within the communities, with the needs of the local people
crucial to the country’s goal of eliminating flaring. The importance, being taken on board. Building gas plants in the middle of mangrove
uniqueness and success of this project was recognised at the British swamps is understandably a challenge in itself, and it was down to the
Expertise awards in November 2007, where Mott MacDonald was resourcefulness of the team to come up with solutions that enabled the
named Large Consultancy Firm of the Year in the ‘Tangible Visible project to succeed.
Project’ category for its work on the Cawthorne Channel associated
gas-gathering project. Challenges Met with Ingenuity
Faced with having to build three gas plants in such challenging
The Task environments, the team deployed a variety of approaches to
Mott MacDonald’s task involved making the initial concept workable facilitate the construction of these structures. The gas plant at
and completing the front-end design. This was followed by detailed Awoba was constructed on concrete barges. Plant modules were
engineering design, including preparing specifications and assembled in the US on these barges, which were then transported
requisitions for all materials to be purchased by the engineering,
procurement, construction and commissioning (EPCC) contractor
Daewoo for all facilities and pipelines, as well as providing all
specialist technical support as required by Daewoo during
Eliminating gas flaring is a
construction and commissioning. The project included construction
of three gas plants, one booster compressor station and
vital step forwards, both
approximately 71km of gas-gathering and export pipelines. The
ecologically and economically,
development also included the installation of turbine and gas-
for Nigeria.
engine-driven compression trains, gas dehydration and power
generation facilities and associated utilities (see Figure 2).
The Results
The project is recovering some 200 million standard cubic feet per day to Nigeria and slotted into place, instead of spending two years
(mmscfd) of associated gas from the Cawthorne Channel, Awoba and working on-site in the swamp. In this way the surrounding mangrove
Krakama oilfields located in the eastern swamp area of the Niger delta. area was spared a great deal of disruption and potential
SPDC gathers, compresses and conditions the gas from five existing environmental damage (see Figure 3). At Cawthorne, the plant was
flowstations and distributes dry high-pressure gas to various consumers, built on a sand pad; three years before the project started, Shell
including the Nigerian Liquefied Natural Gas Company (NLNG). dredged sand into the swamp and built a pad for the plant (see
Figure 4). The design of the plant at Krakama took a different
Without this project, gas flaring from this region of the Niger delta approach again, being built on a steel platform.
would continue, polluting the atmosphere with carbon dioxide,
nitrous oxide and sulphur dioxide, released when the 200mmscfd of The project involved taking mostly standard designs and putting
gas is burned off. Not only does gas flaring cause environmental them together in unique ways in order to solve the engineering
problems, it is also a complete waste for the economy of Nigeria. challenges that arose throughout the project. These designs had
Now, however, the gas is being treated and transported to a plant for previously been developed by Mott MacDonald for SPDC for the
liquefaction and export, generating income for Nigeria. Thus, instead Odidi associated gas-gathering project. This pioneered the gas-
of contributing to global warming and the greenhouse effect, this gathering and treatment concepts in the mid-1990s, when the gas
gas will be burned cleanly and transformed into heat and electricity. flaring elimination programme was initiated by SPDC.
© TOUCH BRIEFINGS 2009
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