Helwan
Mediterranean Sea
Saffron Scarab Serpent
Sapphire Simian/Sienna
Rosetta
LNG plant
Alexandria Idku
Port Said
SuezCairo
MIDDLE EAST
Subsea power, control advances
extend West Delta Deep Marine network
Project moves from shore into deeper waters
David Smith
INTECSEA In 1999 INTECSEA (then INTEC) be- gan a front-end engineering and design (FEED) study for the West Delta Deep Marine (WDDM) concession offshore Egypt in the Mediterranean Sea. The
development was operated by the Burullus
Gas Co., a joint venture among BG, state-owned EGPC, and Edison Gas, with the latter since replaced by Petronas Carigali.
This was the frst deepwater development
offshore Egypt, and there was little associated infrastructure to draw on at the time.
The project was also pioneering as one of
the longest tiebacks to shore at 90 km ( 56
mi), taking in the Scarab/Saffron felds via
eight subsea wells and two manifolds.
INTECSEA has continued to work with
Burullus on subsequent phases of the de-
velopment, which has been expanded far-
ther from shore at 105 km ( 65 mi), and in
deeper water to 1,024 m ( 3,359 ft). Various
services have been introduced, such as sub-
sea electrical power, to allow expansion be-
yond the originally planned capacity of three
hubs, each with a maximum of 12 wells, and
three manifolds, to currently more than 50
wells and 12 manifolds. Further expansion
is planned, including the current Phase IXa,
adding potentially another 20 wells with as-
sociated manifolds.
Hydrates control
Produced gas from the WDDM felds is
sweet but the pressures and temperatures
are such that there is a continual risk of
hydrates from the produced water. Continu-
ous MEG injection, complete with corrosion
inhibitor, is necessary and it is achieved
through dedicated fow lines from the termi-
nal to each feld center. In addition, metha-
nol injection is required at start‐up and
shutdown. Depending on the development
phase, chemical injection facilities are either
located onshore or on a dedicated controls
platform 62 km ( 38. 5 mi) from shore.
The Sapphire feld also produces a signifcant amount of condensate that must be
extracted prior to the gas entering Egypt’s
National Transmission System (NTS) or the
adjacent LNG plant.
The subsea pipelines are made of carbon
steel with diameters ranging from 10-in.
for well fowlines to 20-in. and 26-in. for infeld pipelines. A pipeline end termination
(PLET) is integrated to each fowline end,
and includes a Cameron Vertical Connection
(CVC) interface. There is provision for the
fowline to slide longitudinally on the PLET
foundation to allow temperature expansion
and to avoid locked‐in forces that could result in fowline buckling. The infeld fowlines eventually terminate at the pipeline
end manifold (PLEM), where the pipeline
diameters increase to 24-in. and 36-in. to
provide the required export capacity to the
onshore plant.
Subsea equipment includes horizontal
trees, manifolds, and a remote pipeline connection system. Subsea christmas trees are
the horizontal type with the fowloop connector hub mounted directly on the tree
body. Remotely installed tie‐in jumper spools
connect the trees to the manifolds which,
like the christmas trees, are designed to suit
the CVC system.
Fishing activity may occur in water depths
down to roughly 200 m (656 ft), so the larger pipelines are designed for fshing gear
pullover loads while the 4‐in. lines and umbilicals are trenched up to this water depth.
Subsea structures in the shallower waters
are designed to be overtrawlable, while in
deeper waters the structures are upright.
From Phase IX the requirement to protect
the subsea equipment from damage has increased to 400 m ( 1,312 ft) water depth.
Development history
Under Phase 1, the Scarab/Saffron felds
were the frst to be developed via a total of
eight wells connected to two production
manifolds and controlled directly from the
shore terminal at a distance of around 90
WDDM concession location.
(All images/photos
courtesy INTECSEA)
