A SHOWCASE OF INNOVATION
Pioneering technologies have distinguished Moho
Nord from the outset. It is the first Total deepwater
project to combine two floating units—an Floating
Production Unit (FPU) and a Tension Leg Platform
(TLP)—with two separate drilling strategies and
production systems. This hybrid model is the key
to developing several reservoirs in two distinct
The light oil from the Albian carbonate reservoir
is extracted by the TLP. This is a highly innovative
technological concept using surface wellheads,
deployed for the first time by Total in Africa.
The riser skidding system likewise is an important
innovation, allowing the drilling riser to move easily
among the 27 slots and reducing the time lost
between wells. The Miocene oil is extracted using a
standard subsea loop measuring 2 by 13 kilometers
and tied directly to the FPU Likouf.
All production is gathered—via a system of risers
from the Miocene reservoir and by transfer lines
from the TLP—to the FPU Likouf. There, it is
processed before export, by pipeline, to the onshore
Djéno terminal, 75 kilometers away. The FPU Likouf
is the largest deepwater floating production unit
in the Congo, capable of processing as much as
100,000 barrels of oil per day from both reservoirs.
The decision to use a TLP—Total’s first in West
Africa—was based on geology: The carbonate
reservoirs feature very low matrix permeability, as
well as oil that is subject to asphaltene precipitation.
This requires regular well intervention to promote
productivity, such as injecting solvents to counter
naphthenate buildup. For various technical and
economic reasons, subsea development is not an
option, due to the frequency of these interventions.
Wash tanks. Total stands on the cutting edge of
deep-offshore development and draws on extensive
expertise in designing floating units, whether
Floating Production, Storage & Offloading units
(FPSOs) or Floating Production Units (FPUs).
Since installing its first FPSO off the coast of
Angola, Total has continued to improve the design
of these floating systems. One recent development
has made it possible to treat and remove water
from the oil, in the hull, by using huge wash tanks.
Carrying out this last stage of treatment in the hull
rather than on deck has important advantages, such
as limiting topsides weight while saving precious
space to optimize layout. The Moho Nord FPU
is the first floating deep-offshore unit to use this
innovation off the Congolese coast.
Hybrid loop. The Moho 1 Bis Alpha Beta loop
embodies a new Total concept in the design of
subsea operations. In contrast to a conventional
production loop, which connects two production
lines to create two lines along which the oil can
flow, the hybrid loop ties in a single production line
and a service line filled with dead oil. In the event
of extended downtime, this dead oil is injected into
the production line to prevent hydrate buildup. In
addition, the replacement of an insulated flow line
with a service line that does not need insulation
produces significant cost savings.