American Oil and Gas Reporter - June 2015 - 96

SpecialReport: Offshore & Subsea Technology

The Sevan Louisiana is drilling additional Delta House wells this
year, with Seadrill's dual-BOP West Neptune performing the frac
pack completions. Both dynamically positioned drill ships are
under three-year contracts to LLOG. Production is scheduled to
ramp up through the end of 2015 as seven wells already drilled
in the area begin producing to the FPS. At least four more LLOGoperated fields eventually could tie into the host platform.

address the problem.
As in most deepwater projects, the topsides weight budget was
a challenge already, without the additional burden of a crude stabilization unit. To address the weight issues, LLOG first decided to integrate some equipment that previously had been planned
as skid-mounted units built off site. This change increased costs,
but saved approximately 500 tons of payload by eliminating the
weight of the associated skids. While this helped the weight situation, further changes were necessary.
LLOG decided to relax some aspects of the generic FPS design basis. First, the minimum crude gravity was raised from
25 to 28 degrees, which reduced retention time and vessel size.
The crudes from Delta House wells are significantly lighter, so
relaxing the specification was not an issue for the fields (if 25degree gravity oil was delivered to the FPS, the process would
still work, but the FPS probably would not achieve its full 80,000
bb/d capacity, depending on the relative amounts of oil, gas and
water).
Second, the gas export specification was relaxed from ANSI
1,500 to ANSI 900, since the gas export destination chosen was
ANSI 900. At the Delta House final weigh in, LLOG confirmed
it had achieved its goal of 1,000 tons of spare payload.
Construction And Installation

Hull construction went well, with first steel cutting in March
2013 and hull delivery in March 2014. The biggest challenge during hull construction was managing the effects of other projects
in the same dry dock, which interfered with the footprint of the
Delta House pontoon. The hull was transported from Korea on
a heavy-lift transport vessel and arrived in Ingleside in May 2014.
Topsides construction began in December 2012. The deck was
integrated onto the hull on June 17, 2014. The biggest challenge
96 THE AMERICAN OIL & GAS REPORTER

with the topsides was the design-while-build process, which was
focused on keeping the engineering drawings ahead of construction. Floating the main deck over the truss and the integration lift
of 9,580 tons were the largest ever performed at Kiewit's yard.
The fully integrated FPS sailed from Ingleside in September 2014,
and all 12 mooring lines were fully installed and appropriately
tensioned in October.
Each anchor field is being developed with wet trees flowing
to subsea manifolds and then on to the FPS through the two infield steel catenary riser flow loops. Two of the fields use a single, four-slot manifold with looped six-inch flowlines. Marmalard
is being developed with two daisy-chained, four-slot manifolds
(allowing for up to eight wells) with looped eight-inch flowlines.
The looped lines allow flexibility to direct a given well to a
specific flowline to improve production. The looped lines also
facilitate pigging and hydrate removal, if required. Three-phase
subsea meters allocate production to individual wells, and electro-hydraulic umbilicals control the wells and convey chemicals
to each wellhead.
Delineation And Completion

LLOG drilled an additional well at Marmalard that indicated
apparent communication between the discovery well and delineation well over a distance of 3.5 miles. Some new pay zones were
found in the delineation well also. As a result of the delineation
drilling, Marmalard's expected reserve range increased significantly.
LLOG also drilled a successful discovery in the third field, and
followed that with two delineation wells. With six wells drilled,
the low, most likely and high-end reserves for the project more
than doubled, compared with distribution at project sanctioning,
when only two wells had been drilled.
The first two Delta House wells were drilled by the Ensco 8502
in 2012-13, the next two were drilled by the Noble Amos Runner in 2011-12, and the Ensco 8503 drilled the sixth well in late
2014. The dynamically positioned Sevan Louisiana drilled the seventh well earlier this year, and also is scheduled to drill the eighth
and ninth wells in 2015.
The Seadrill West Neptune dynamically positioned drill ship
was delivered to Delta House in late 2014, and has performed the
majority of the completions. With two blowout preventer stacks
onboard, one BOP could be tested and recertified while the other was in use. That saved at least 12 days in completing each well,
compared with using a single BOP stack that must be recertified
and tested after each use. Both the Sevan Louisiana and the West
Neptune are under three-year contracts with LLOG.
Each well was completed with frac packs. Reservoirs with shale
breaks between pay zones have multiple frac packs to maximize
production and utilize smart-well technology to manage zone
changes. LLOG used a single wing to ensure the frac pack would
access the formation beyond any near-wellbore damage from the

American Oil and Gas Reporter - June 2015

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