Circa 2016, there were 86 producing structures in deepwater, seven idle structures, and
five auxiliary structures.
Producing, idle and auxiliary classification
are not a BOEM-assigned attribute but are
inferred from publicly available structure features and operator identification. Functionality
is not publicly reported and structures that
are classified as auxiliary are inferred. No
attempt is made to identify structures that
are no longer useful.
The first fixed platforms were installed in the
GoM in 1947, and by 1978 the first installations
in water depth greater than 400 ft occurred at
Bourbon in MC 311 in 428 ft water depth and
Cognac in MC 194 in 1,023 ft water depth.
Almost all of the deepwater fixed platforms
were installed to drill and complete wells from
platform rigs with full oil and gas processing capacity, and typically contain a dozen or
more dr y tree wells. Later, fixed platforms also
served as host for subsea (wet) wells and as
If subsea well production is processed at
the facility, the structure will host umbilical
and electrohydraulic control systems, storage
tanks, and related equipment. Deepwater fixed
platforms can readily accommodate subsea
tiebacks because of their structural stability
Many well-known fields are produced from
fixed platforms and several are named, including: Cerveza (year of installation, 1981),
Ligera (1982), Tequila (1984), Snapper (1985),
Boxer (1988), Bullwinkle (1988), Marquette
(1989), Tick (1991), Amberjack (1991), Alabaster (1991), Corral (1992), Pimento (1993),
Lobster (1994), Pompano (1994), Phar Lap
Shallo (1995), Spectacular Bid (1995), En-
chilada (1997), Spirit (1998), Salsa (1998),
Virgo (1999), Cyrus (2002), Tarantula (2004),
In 2015, Walter Oil and Gas installed the lat-
est fixed platform in 1,186 ft at the Coelacanth
field in EW 834.
There are only three compliant towers (C T)
in the GoM, and as their name suggests, the
structures are compliant in the sense that they
do not attempt to resist all environmental lat-
eral forces through their piling alone. Instead
the structures are designed to permit limited
movement with the waves.
CTs require less steel (strength) in con-
struction than fixed platforms and their foun-
dation bases do not expand with increasing
water depth. C Ts have a constant cross section
throughout the water column much like radio
transmission towers on land.
Lena is a guyed tower fixed with guy wires
to the seabed while Baldpate utilizes axial
tubes (articulated tower) as flex elements
and Petronius utilizes flex legs.
Lena was installed in 1983 and is near the
end of its 35-year life, generating about $18
million in 2016.
Baldpate and Petronius are of more recent
vintage being installed in 1998 and 2000 and
are still prolific producers, generating $153
and $188 million, respectively, in 2016.
Deepwater floating facilities come in a vari-
ety of types and configurations that reflect the
multiple tradeoffs in cost and risk involved in
development strategies and the preferences
of their owners.
Deepwater development is of a completely
different character than in shallow water. Reser voirs may be in unproduced geology in new
or existing basins/plays, deeper reservoirs are
characterized by higher pressure/temperature,
or challenging reservoir-fluid properties and
impurities. The complex and risky nature of the
development can be driven by location (e.g.,
seabed terrain), water depth, remoteness from
existing infrastructure, and extreme environ-
mental conditions. Frequently, combinations of
these factors are represented in a single project,
contributing to high project complexity, high
cost, and long periods between investment
sanction and first production.
Surface piercing articulating risers (spars)
and tension leg platforms (TLPs) are the most
common type, followed by semis. Only two
Wet well solutions have remote subsea
wellheads which are connected to the vessel
by steel or flexible catenary riser systems,
and in some recent cases (e.g., Olympus,
Perdido) the wellhead/tree may be positioned
directly below the structure to reduce topsides
weight – these are referred to as direct vertical access wells. Dry trees reside above the
waterline and are connected to the wellbore
with a top-tensioned riser.
Wet tree systems include all variations of
units, including floating production, storage,
and offloading vessel (FPSO), semisubmersible (semi), spars and TLPs. Dry tree solutions
are limited to spars and TLPs.
Within each floater class, configurations
have evolved into subclasses and occasionally new hybrid classes. For example, spars
come in three varieties – classic spar, truss
spar, and cell spar, and a smaller version of
the TLP is referred to as a mini TLP (MTLP)
and classified by design as SeaStar MTLP
and Moses MTLP. A larger, extended TLP
(ETLP) is under construction at Chevron’s
Big Foot field. •
Floaters in the Gulf of Mexico circa 2016. (Source: BOEM 2017)
GoM Floaters circa 2016