MIDDLE EAST
km ( 56 mi). Both felds came onstream in
2003 at around 700 MMcf./d. Twin 20-in.
main export pipelines commence at a water
depth of 415 m ( 1,361 ft) and extend for 30
km ( 18. 6 mi) to the PLEM at a depth of 95 m
(311 ft), where 24-in. and 36-in. export lines
transports production to the shore terminal.
A 4-in. pipeline conveys MEG from shore to
the felds for hydrate inhibition via direct injection at the trees.
The Simian/Sienna (Phase II) and Sapphire (Phase III) feld developments were
the frst expansions to provide gas to a new
onshore LNG plant, with six wells at Simian, two at Sienna, and eight at Sapphire.
Flows from these felds come together at
the PLEM where the gas is commingled
into the export pipelines to shore. The Simian wells are capable of a maximum throughput of 150 MMcf/d. All the subsea wells, in
water depths beyond 1,000 m ( 3,281 ft), are
controlled from shore through an electro-hydraulic multiplexed system, with controls,
hydraulic power, and methanol injection
equipment mounted on a controls platform
in shallower water close to the PLEM.
Phase IV involved a seven-well and two-
manifold expansion centered on the Scarab/
Saffron production hub. This was followed
by an investment in booster compression
(Phase V) and the Phase VI Sequoia reser-
voir development, which comprised three
wells on Sequoia North in the western fank
of the Sapphire area and three more on the
Sequoia South area, routed to the existing
subsea Rosetta infrastructure and control
room facilities.
Further pipeline capacity and main compression were added under Phase VII, at
which point the continued development of
WDDM required new wells to access additional reserves. Phase VIII was split into
two phases, the frst adding fve wells and
two manifolds to the Sapphire feld and four
wells and a single manifold to the Scarab/
Saffron area. The second part added another well to the Scarab area, connected to the
previously installed M6 manifold, and fve
wells and a manifold within the Simian area,
linking three wells to the M2 manifold, with
the remaining two wells “daisy chained” and
connected to the remaining slot on the M1
manifold. The W37 well had an initial wellhead pressure that exceeded the rating of
the Simian area pipeline and therefore was
equipped with a high integrity pressure protection system (HIPPS).
Control systems evolution
While the overall system design has gen-
erally used proven technology, there were
challenges associated with the continued
development of the systems and the re-
quired instrumentation associated. These
included the need to avoid hydrates, control
of chemical injection, gas rate measure-
ment, and sand detection. Initially the feld
was conceived as a three-phase develop-
ment, with each phase being an eight-well,
two-manifold confguration with a four-well,
one-manifold expansion capacity. However,
the pressure to maintain production levels
to support Egypt’s national grid and the ad-
jacent LNG plant has driven the expansion
well beyond the initial fgures.
One critical consideration for the expansion was the need to supply a suffcient operating margin for the power supplies. The
system initially was designed for a defned
expansion. When those limits were exceeded, work was required with control system
vendors to defne operating scenarios and
levels of instrumentation to obtain the desired feld information.
The subsea control system for phases
I-III of the WDDM development had to address various technical challenges, including long-distance step‐outs, a chemical injection delivery network, gas and condensate
monitoring, sand detection, and interfaces
to multiple control system vendors. For
Phase I Aker Solutions (formerly Kvaerner)
supplied the subsea controls. The step out
is nominally 90 km ( 56 mi) direct to shore,
with communication through the vendor’s
proprietary protocol on a copper-based
cable network. To improve the communications, signal level repeater modules were
installed at the subsea distribution assembly
(SDA), 82 km ( 51 mi) from shore.
GE Oil & Gas (then ABB Vetco Gray)
supplied the Phase II and III subsea control
system for a network of 16 wells and four
manifolds, with the farthest well nominally
124 km ( 77 mi) from shore. Although a copper cable-based system may have been feasible, the lack of proven installations subsea
and the need to increase local manufacturing content determined the addition of a
dedicated, unmanned, controls platform 60
km ( 37 mi) from shore. This also increased
the complexity, particularly with respect to
a shore-platform link to handle all platform
communication requirements, in addition to
the subsea system. To maximize use of the
platform, the design was formulated not just
for phases II and III, but also to support later
developments, including the Saurus reservoir.
The Phase IV expansion (seven wells and
two manifolds), centered on additions to
the Scarab/Saffron production hub and exceeded the initial design capacity of a four-well and one-manifold expansion. Moreover
the requirement to acquire greater data and
to control MEG injection necessitated the
addition of wet gas fowmeters (WGFMs)
and operator-adjusted glycol control units
(GCUs), previously ROV-adjusted. A review
of the original analysis confrmed that with
the existing dual power supplies, the system
remained functional. However, should the
system be required to operate on a single
power line, studies suggested it would not
function because the power needed would
exceed the power available. At the same
The Phase II Simian M1 manifold during load-out from the Swan-Hunter yard in Wallsend, northeast
England, for installation offshore in December 2004.
