2. Subsea Architecture
For every new subsea development the subsea architecture (or subsea
layout) for the field has to be defined :
– Subsea wells position and possible grouping (drilling centres)
– Subsea manifolds position
– Flowlines routing
– Allocation of wells to flowlines
The definition of the subsea layout for a large size development is usually an
iterative activity involving reservoir, drilling, subsea facilities and production
operations engineers.
The issues to consider :
– Effective reservoir drainage
– Drilling trajectories feasibility and drilling costs
– Simplification of subsea facilities and CAPEX containment
– Operability during production phase
3. SUBSEA STRUCTURES
They include:
– anchors for floating platforms
– foundations for equipment installed on the seafloor
– Drilling templates
– Protection structures (wells, manifolds, …)
– structures supporting flexibles and umbilicals (arches)
The design of these structures takes into account:
– Seabed characteristics
– Hydrostatic pressure at the seafloor (up to 250 ‐ 300 bars)
– ROV accessibility and visibility for operations and
inspection
4. Deepwater Foundations
Deep water soils are in general under‐ consolidated and have
accordingly a low bearing capacity
3 types of foundations are used :
– « superficial » foundations based on mud mats
– foundations using piles installed by suction
– foundations based on piles driven deep into the soil
(underwater hammer technology limited by the water depth )
Foundation type selected based on :
• Soil mechanical characteristics
• Weight and type of loads to be supported
5. Superficial foundations
• Realized with « mud mats » in steel which dimensions depend
on the bearing capacity of the soil
• They can partially be buried
• They are used often for gravity bases
• Not recommended with horizontal loads
6. SUCTION PILES
• Allow the anchoring of the structures in
the upper layers of low consolidated
soils (5 to 25m ) which often the case in
deep offshore
• Anchoring is obtained through
penetration in the soils of « bells » in
• which a depression is created by
pumping the water trapped.
• The “bells” are circular or rectangular
and are equipped with valves
• The pumping unit is installed on a ROV connected to the suction pile.
• Combination of several “bells” on the same structure allows a very
accurate leveling
• This type of foundation can be used for gravity bases
• They resist both the vertical and horizontal loads
• Deadweights are added in case of vertical tensions.
7. SUBSEA PRODUCTION EQUIPMENT
• SPS (Subsea Production Systems)
1. Wellheads
2. Manifolds
3. Integrated wellheads and manifolds modules
4. Oil/gas/water or liquids/gas separation modules
5. Multiphase metering modules
6. Monophasic or multiphasic booster pump modules
7. Gas compressors
8. Pigging modules
9. Umbilicals
10. Flowlines and Export Pipelines
11. Risers
12. Spoolpieces
13. Mooring lines
8. SUBSEA PRODUCTION WELLS
• Modular design
• Installed by drilling
rigs
• Weight of items
limited to about 35
tones
• For most cases, direct
fixation on top of the
casings
9. Production Wells: Functions
1. During operation, safely isolate the reservoir from the subsea,
Valves are fail close.
2. Control the integrity of the annulus
3. Allow safe well maintenance (coiled tubing, heavy work‐over… ),
4. Allow safe and environmental friendly intervention on the tree
(ROV valves manoeuvring, SCM Subsea Control Module removal,
FCM Flow Control Module removal…),
5. Connection Tubing (down hole) to production system (jumper).
Isolate well from production system
6. Control well (valves, choke) production. Operation and Safety,
7. Designed to reduce the thermal losses while flowing and during
shut down
11. WELL GROUPING
Manifold
• Provides the « node » between the individual pipes coming
from the wells and the flowline to the host platform
Template
• Structure designed to closely and accurately position a
group of wells
Jumpers
• Connects Well Head (Xtree) to manifold (Prod) or flow line
(injection). Designed to keep fluid warm in case of Shut
Down. Flow all the fluid required to operate the well
(hydraulic, service, chemicals lines, electric cables).
• Jumper is a multibore line
13. MANIFOLDS
• A manifold receive production of several wells. It
permits the routing of Production wells to selected
flowlines. Manifold reduces the thermal losses
while flowing and during shut-down.
• Manifold is fitted with methanol, (against hydrates)
and Chemical injection points to protect the
production line.
• Pressure & Temperature sensors on each line to
control production and the cool down during shut
down, warming during start.
• ROV operation in case of remote operating failure.
15. Connection systems
• Purpose : to allow subsea remote connection of :
– Production, injection flowlines
– Chemical injection lines
– Control system hydraulic/electric functions
• between :
– Flowlines and SPS
– Umbilicals and SPS
– SPS components
• Different types of connectors :
– Monobore or multibore
– Vertical or horizontal
– Collet or clamp type
Connections are made remotely using subsea ROT’s (Remote
Operated Tools)
