DEEPWATER CASE STUDIES
Stones nearing first
production in the
Gulf of Mexico
Shell’s project features many industry firsts
Royal Dutch Shell plc expects first production this year from the Stones project in the ultra-deepwater Gulf of Mexico. Dis- covered in 2005, Stones is located in the Walker Ridge area bout 200 mi (322 km) offshore Louisiana in about 9,500 ft ( 2,896 m) of water. Sanctioned in May 2013, Stones consists
of an FPSO connected to subsea infrastructure located in the Lower
The development will start with two subsea production wells tied
back to the FPSO with six more production wells to be added later
on. The reservoir depth is around 26,500 ft ( 8,077 m) below sea
level and 17,000 ft ( 5,181 m) below the mudline. First phase production is expected to reach 50,000 boe/d with recoverable reserves
of 250 MMboe out of 2 Bboe of oil in place. Multi-phase pumping
is planned for a later phase. Shell is 100% owner and operator of the
In July 2013, Shell commissioned SBM Offshore to supply and
lease an FPSO. The initial contract is for 10 years with options to extend to 20 total years. The total asset value of the FPSO is estimated
at $1 billion.
The converted Suezmax FPSO features a turret with a disconnectable buoy (buoyant turret mooring) that allows it to weather-vane in normal conditions and disconnect from the FPSO upon the
approach of a hurricane. According to SBM Offshore, not only is
this the world’s largest disconnectable buoy, but also it is the first
with steel lazy wave risers – steel pipe with in-line buoyancy that absorbs the vessel’s motion and boosts riser performance at extreme
The mooring system also incorporates the ability to adjust line
tension during operations by use of an in-line mooring connector.
In November 2015, construction of the FPSO Turritella was com-
pleted and the vessel set sail from the Keppel Shipyard in Singa-
pore. The vessel is a typical Generation 2 design with a processing
capacity of up to 60,000 b/d of oil and 15 MMcf/d of gas treatment
and export. No water injection facilities are specified, and the Suez-
max hull is able to store 800,000 bbl of crude oil with total topsides
weight reaching 7,000 tons.
The FPSO Turritella is owned and operated by a joint venture
owned by affiliated companies of SBM Offshore (55%), Mitsubishi
Corp. (30%), and Nippon Yusen Kabushiki Kaisha (15%).
While the Turritella is not Shell’s first FPSO in the world, it is the
operator’s first FPSO in the Gulf of Mexico.
In January 2016, the vessel arrived in the Gulf. In June, InterMoor
completed the final tensioning and chain cutting operations on the
FPSO. On July 29, the United States Coast Guard’s Certificate of
Compliance was issued. Ready for start-up is the next necessary
step in supporting well operations, according to SBM Offshore, before commercial production and first oil. At first production the
Turritella will be the world’s deepest floating production unit at 9,500 ft.
As for Stones’ subsea infrastructure, in May 2013, the operator
ordered eight subsea trees, a subsea manifold, topsides and subsea
controls, and associated equipment from FMC Technologies.
In August 2013, Technip secured an engineering, procurement,
and installation contract. The company installed the subsea production system which consists of dual 8-in. insulated flowlines associated with pipeline end terminations (PLET), and dual 8-in. steel lazy
wave risers. It also installed the Stones lateral gas pipeline which
consists of a single 8-in. gas pipeline associated with PLET, in-line
sled, and a single 8-in. steel lazy wave riser. Two years later, Technip
was contracted for engineering of the required second PLETs; fabrication of the PLETs and piles; installation of the subsea production
system; and inclusive of associated project management, engineering, and stalk fabrication.
In August 2015, Shell commissioned OneSubsea to supply subsea
processing systems. Following a technology qualification program,
the company will deliver the industry’s first 15,000-psi subsea pump
system, which will be tied back to the FPSO Turritella. The subsea
processing systems scope includes a dual pump station with two
3-MW single-phase pumps and two subsea control modules, a topsides power and control module, a barrier-fluid hydraulic power unit
with associated spares, as well as installation and maintenance tools.
Manufacturing and testing will take place at OneSubsea’s facility in
Horsøy, Norway, for delivery in early 2018. •
The Turritella is Shell’s first
FPSO in the Gulf of Mexico.
(Photo courtesy InterMoor)