TERRA NOVA, JEANNE
D'ARC BASIN, CANADA
The Terra
Nova field, located 350km ESE of St John's Newfoundland and 35km
SE of Hibernia, was discovered in 1984 by Petro-Canada. Field
reserves have been estimated at 406 million barrels (Mbbl).
ENVIRONMENT
Water depths
are shallow - between 90m and 100m. The mean annual wind speed
is 35kmph, with the strongest recorded wind speed being 145kmph
and the largest recorded wave height being 25m.
The area is
characterised by the seasonal presence of floating sea ice, ranging
in thickness from 0.5m to 1.5m, produced by the freezing of the
ocean's surface layer and icebergs.
RESERVOIR
Terra Nova
is subdivided into three major structural blocks: the Graben,
the East Flank and the Far East. The field is estimated to contain
over one billion barrels of oil in place, of which about 400Mbbl
of oil are recoverable. (The Far East block, which is not yet
drilled, is expected to add at least 100Mbbl of reserves to the
300Mbbl that have already been estimated within the Graben and
East Flank). The estimated peak production rate is 125,000b/d
from the Graben and East Flank portions alone. A total of 32 wells
are planned for the Graben and East Flank blocks, including 20
production wells, ten water-injection wells and two gas injection
wells. For the Far East, a total of 12 wells are planned, including
six production wells and six injection wells. Field life is expected
to be 18 years.
DEVELOPMENT
Petro-Canada
selected the Grand Banks Alliance (SBR Offshore, Doris Conpro,
PCL Industrial Constructors, Coflexip Stena, Halliburton Canada
and FMC Canada) to carry out engineering, procurement, construction,
installation, commissioning and possibly pre-development drilling
activities up to the production of first oil. The project partners
and Grand Banks Alliance consequently established a single alliance:
the Terra Nova Alliance, with each company participating on a
risk-and-reward basis.
PRODUCTION
The subsea
layout will consist of a production well feeding into a template,
which, in turn, will be connected by flexible flowlines to a riser-base
manifold (RBM). In order to protect the subsea wells from iceberg
scour, they will be set in glory holes - large holes drilled in
the seabed in which equipment can be installed.
Flexible risers
will connect the RBM to an FPSO. The vessel will have a length
of 280m and a width of 45m. The combination of low air and water
temperatures with wind and wave action, makes superstructure icing
a consideration during the winter months. This means that an allowance
of several hundred tonnes of superstructure ice accumulation must
be factored into weight and stability calculations. There must
also be procedures for monitoring and mechanisms for controlling
ice build-up on the structure and substructures of the offshore
facilities.
Low water
temperatures require that fluids such as hydraulic control fluids
be heated or treated to lower their freezing point. Similarly,
low temperatures combined with the waxy nature of the crudes require
that the flowlines and riser are insulated to reduce wax deposition.
The FPSO is designed to operate in moderate sea ice, up to a limit
of five-tenths coverage and to disconnect, as required, to avoid
heavy pack ice and potential collisions with icebergs.
The 9000t
topsides facilities will be installed approximately 4.5m above
the main deck. They will contain the necessary equipment to produce
150,000b/d oil, and inject 250,000bbl of seawater/day and 125
MMcf/d of gas. The FPSO hull will have an integrated storage capacity
of 900,000bbl.
EXPORT
The export
system will be a tandem offloading system for the transfer of
crude oil from the storage tanks of the FPSO to ice-strengthened
shuttle tankers, ranging in weight from 80,000t to 120,000t. The
offloading system will be designed for connection to tankers in
5m significant-wave-height conditions.
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The Terra Nova field layout schematic. |
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