American Oil and Gas Reporter - June 2016 - 86

SpecialReport: Offshore Technology
FIGURE 3
Lucius Field Layout and Subsea Architecture

three groups of mooring lines, while four
groups of mooring lines associated with
a semisubmersible would have been difficult to implement, given geotechnical
challenges identified on site. The project
also had to consider how to locate the facility to avoid landing umbilicals and
steel catenary risers (SCRs) in less desirable areas with slopes and unstable surfaces.
A wet-tree truss spar ultimately was
chosen as the development concept. This
option yielded the best project economic
metrics, considering full life-cycle economics. In general, Anadarko tended toward known technology, and proven
methods and suppliers/fabricators with a
history of delivering successfully for the
company, not only for the hull and mooring, but also for other aspects of the facility.
Anadarko previously had utilized truss
spar technology on its deepwater Boomvang, Nansen, Gunnison and Constitution
fields. Although Lucius would be larger
than any of its previous spar facilities, the
experience on those projects gave the company confidence in designing, fabricating,
and installing the hull and mooring facilities within the budget and schedule,
which was accomplished.
Largest Possible Combination
Because of the remoteness of the location, and the exploration and discovery activity around Lucius, Anadarko elected the
largest possible hull/topsides combination
that could reasonably be built, given fab86 THE AMERICAN OIL & GAS REPORTER

rication yard and installation vessel capabilities. The May 2011 production test of
the discovery well reinforced the direction
the development team had pursued initially. The facilities development team had begun engineering on the largest eight-section hull the spar supplier could fabricate
in half sections in its "high hall."
Meanwhile, the topsides engineering
team was developing topsides that could
not only support maximum production
from four initial, 8.0-inch diameter SCRs
for Lucius, but also accommodate a waterflood at an appropriate point in the future. The hull team worked cooperatively with the subsea engineering team to develop the concepts for pull tubes to support risers for future tiebacks. The topsides
manifold and allocation metering also were
set up for future tiebacks.
When ExxonMobil approached the
Lucius partnership to inquire about adding
risers and facilities to accommodate 300
MMcf/d of production from the Hadrian
South gas/condensate development, the integrated team began incorporating facilities for Hadrian South in Lucius' engineering work. By mid-2011, Lucius reservoir
and facility engineering (including the
Hadrian South tiebacks) had advanced
enough to justify purchasing long-lead
equipment and steel to begin fabricating
the hull.
Simultaneously, the oil and gas exportline option evaluation had been done to select providers based on primary commercial terms. Detailed terms and conditions
were negotiated while orders for the line

pipe were made, along with advancing negotiations with installation companies. Additional development drilling commenced
at Lucius in late 2012, and all six initial
production wells were completed by the
end of 2014.
Hadrian South is a reasonably straightforward gas/condensate development that
utilizes methanol injection at the wellhead
as the primary means of flow assurance.
The subsea system consists of looped flowlines to enable pigging. The loop is completed with a spool on the manifold. The
system is designed so that each of the two
wells can be routed up individual, nominal 10-inch carbon steel flowlines connected to risers on the Lucius spar. The system includes a four-well manifold so additional wells can be added easily.
The subsea trees allow for rates up to
200 MMcf/d a well. The Aker Solutions'
tree control systems are hydroelectric
multiplexed. The single umbilical for
Hadrian South delivers chemicals,
methanol, low-dosage hydrate inhibitors,
controls, hydraulics and communications
to the well sites. All subsea equipment was
installed safely and successfully by ExxonMobil in the latter half of 2014.
Contracting Philosophy
Most major contracts were signed either at project sanctioning or soon thereafter for the hull and mooring fabrication,
topsides fabrication, topsides installation, flowline fabrication and installation, and subsea installation. The Hadrian South topsides design was completed
in mid-2012, and all equipment was ordered at that time.
The key contracting entities from prior Anadarko spar projects were invited to
submit proposals for the Lucius facility. A
design basis was generated to identify
known differences between the last spar
development, Constitution and Lucius.
Multiple entities bid on the topsides fabrication. Heerema Marine Contractors
estimated the cost of installing the facilities as well as the flowlines/risers, and
Technip Offshore estimated hull/moorings
fabrication and delivery costs.
Since prior spar projects had been bid
competitively, the team had sufficient
data to benchmark the competitiveness of
the proposal for the hull/mooring and installation contracts, thereby satisfying internal accounting requirements. Contracts
for subsea equipment and installation, topsides equipment, etc., were tendered competitively.

American Oil and Gas Reporter - June 2016

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