Note: Descriptions are shown in the official language in which they were submitted.
123~2816
OFFSHORE STRUCTURE INCORPORATION
A CONDUCTOR DEFLECTI~G SYSTEM
tD#77,437-F~
BACKGROUND OF THE INVENTION
.
Platforms and structures which are used for
offshore work in varying depths of water find utility for a
number of purposes. Often such platforms are utilized to
support equipment and like material for drilling offshore
wells to produce gas and/or crude oil.
Because the platforms are so expensive,
particularly for use in deep water, they are often used as
gathering centers for a plurality of remote or dispersed
wells in addition to on-platform wells. Thus, while a
particular offshore reservoir might embody any number of
producing wells, the production flow from the remote wells
can be carried through subsea pipelines to a single desired
gathering point.
Platforms or s~ructures of the type presently
contemplated are utili~ed to gather the crude product,
whether it be gas or oil, into a central treating area.
From there it can be transshipped by way of vessels or other
means, or merely pumped to a central station onshore for
further processing.
Since the product carrying pipelines are disposed
at the ocean floor, it is necessary that they be led from
the remote well head to the foot of the offshore structure.
From there the pipeline is connected to a suitable extension
of the pipeline or riser so that the product can be either
pumped or forced by its own preScure upwardly through the
riser to the deck of the platform.
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Platforms of this type are normally provided with
a working deck which is supported above the water's surface
by at least one, and preferably by a number of heavy support
legs. The latter serve not only to position the platform
firmly at the offshore site but also provide support and
protection to the plurality of on-platform well conductors
and the risers which normally extend from one or more
pipelines up to the deck.
During the fabricating step of an offshore
platform, normally the required complement of well conductor
guides and risers are preplaced within the structure so that
they are an integral part thereof when the platform is
installed at the offshore site. However, often the number
of risers which are initially built into the structure is
insufficient to accommodate the number of remote or
dispersed wells that have later been discovered and found to
be productive. It therefore may become necessary at a
future date to install additional risers for pipelines to be
gathered into the foot of the structure.
When adding risers not previously planned for, it
is necessary to safeguard them against damage which might be
- caused by water forces or floating objects such as debris,
ice and the like. It is also necessary to minimize the
weight and size of the added risers and their attachments
and supports.
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In such an instance, the riser can be made as a
heavy walled self-protective member. However, this would not
minimize weight and size. It is considered more practical to
pass one or more risers directly through an existing or added
ver-tical protective member. In platforms with on-platform
wells, guides are preinstalled in the structure during fabrica-
tion to protect and stabilize the on-platform well conductors.
Usually, extra conductor slots are provided beyond the minimum
required.
In platforms where an extra conductor slot or slots
are available and additional pipeline risers are required, the
addition of the protective vertical member into the existing
unused conductor slot and guides will be most practical. If
no conductor slots remain unused, the addition of the protective
vertical member with necessary supports may be accomplished in
a manner somewhat similar to the on-platform well conductors.
SUMM~RY OF THE INVENTION
The present invention provides in an offshore struc-
ture for operating from an embedded position in a body of water
to treat hydrocarbon fluids which are received from underwater
pipelines, which structure includes; a deck holding hydrocarbon
treating equipment, and at least one leg which extends between
the floor of said body of water to the deck whereby to elevate
the latter beyond the water's surface, the improvement therein
of; a multi-segment riser conductor means depending from said
structure embedded in the said floor, and including a plurality
of riser guides enclosed therein and vertically arranged to
slidably register a downwardly moving riser, in a substantially
vertical disposition, and a riser deflector forming an integral
part of said riser conductor means and defining a plurality of
multi-directional lateral openings for diverting risers out-
wardly from within the riser conductor means, and being spaced
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288-2744
beneath said plurality of riser guides and above said floor,
whereby to engage the lower end of a downwardly moving riser
and to thereby urge the said lower end away from said vertical
disposition, through a wall of said riser conductor and onto
the said floor as the riser is progressively lowered. If placed
in an existing well conductor slot, no modifications to the
platform structure are required and no increase in original
design loadings or weight added to the deck is created.
The upright member is thus provided with upper and
lower spaced apart segments which are connected by an inter-
mediate connecting element disposed therebetween. Said upright
member extends to and into the ocean floor. It is, most essen-
tially, capable of permitting a number of risers to be lowered
therethrough and which are deflected outwardly in a desired
direction or directions. Further, it protects the risers and
supports the riser weight.
DESCRIPTION OF THE DRAWINGS
Figure 1 is an elevation view of an offshore struc-
ture of the type contemplated. Figure 2 is a cross-sectional
view taken along line 2-2 of Figure 1. Figure 3 is a
segmentary view on an enlarged scale of a part of the vertical
member or riser conductor shown in Figure 1. Figure 4 is a
cross-sectional view of a portion of the riser conductor shown
in Figure 3. Figure 5 is a segmentary view of a section of the
vertical member shown in Figure 3.
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In achieving the above noted objectives, there is
disclosed an offshore platform 10 as shown in'Figure 1,
which is positioned in a body of water. The platform is
comprised primarily of deck 11 which lS maintained above the
water's surface, and which holds equipment normally utilized
in drilling for offshore wells and for receiving flows of
produced fluids. While not presently shown, deck ll would
normally hold`a number of storage tanks and similar
equipment capable of processing hydrocarbon fluids such as
gas and crude oil which are piped from remote wells.
Deck 11 is supported in its elevated position
above the water by at least one, and preferably by a
plurality of elongated legs 12 and 13. The latter are
normally construc~ed of relatively heavy walled steel, and
in sufficient numbers to safely support the deck.
The respective legs 12 and 13 are provided with
the necessary cross bracing 14 and 16 to strengthen the
structure as a whole and to assure its integrity for
resisting the severe conditions normally experienced at an
offshore site where the unit is installed.
In the instance of a fluid gathering unit,
platform 10 is prefe,rably located at a central or gathering
point for a number of pipelines 17. The latter are brought
to the structure from remotely positioned wells. Often,
such wells are disposed at the ocean floor and flow both gas
and crude oil that is produced, through a well head, and
which flows through pipeline 17.
1 Z;~7~86
At the platform, pipeline 17 is connected to a
conductor or riser 18, which extends upwardly to deck 11 and
terminates at tanks or other processing facilities.
The normal form of conductor or riser 18, utilized
for directing fluids to deck 11, is fabricated of steel. As
shown in Figure 1, a plurality of the conductors and risers
18 are initially installed in the structure either for
carrying fluids or for directing a drill string into the
substrate. However, illustrative of the instant invention,
the elongated upright riser conductor 20 is positioned in a
manner that it can be provided with one or more subsequently
installed risers.
Referring to Figure 3, the riser conductor 20 is
comprised of an upper guide segment 21 which extends
upwardly to engage deck 11. This guide section may
optionally include a plurality of longitudinally spaced,
conical guides 22, which are fixed in a desired pattern
within guide plate 23.
A series of optional guide plates 23 are spaced
sufficiently apart within riser conductor 20 to permit a
subsequently inserted riser 19 to be lowered from deck 11,
and to be held and in substantially vertical alignment.
The lower end of the riser conductor 20 is
comprised of lower segment 24. The two segments 21 and 24
are connected and maintained in axial alignment by an
intermediate member 26.
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Referring to Figures 4 and 5, said intermediate
member 26 in one embodiment includes a plurality of
upstanding gusset plates 27, 28, 29 and 31. The latter are
joined by welding along a common edge, to define an
elongated cruciform cross-section. This drawing embodiment
illustrates an example of a four chamber cross-section.
Other multi-chamber cross-sections are also applicable to
the structure as required by the number of risers to be
inserted.
Although the particular configuration of
intermediate member 26 can be varied, it must of necessity
be structurally adequate to function as an integral part of
the riser conductor. Thus, the thickness and grade of steel
of plates 27, 28, 29 and 31 constitutes primarily a design
function.
~ s seen in Figure 4, the respective upright gusset
plates of member 26 form longitudinal, radial segments 32,
33, 34 and 36 therebetween. Preferably said segments will
divide member 26 into discrete peripheral compartments for
receiving one or more downwardly lowering risers such as 19.
Member 26 is rigidly fastened by welding, grouting
or bolting into the adjacent spaced apart end openings of
respective aligned sections 21 and 24. The degree of
overlapping of the circular segments 21 and 24 with a
cooperating portion of member 26, will be sufficient to
assure that said member 26 is capable of supporting the
subsequently inserted conduits 19.
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~ s shown in Figures 4 and 5, member 26 is provided
with means for intercepting and deflecting a downwardly
moving riser 19. Said means includes at least one, and if
need be, a plurality of deflector plates or shoes 41, 42, 43
and 44. The latter are arranged longitudinally along one or
more of the peripheral compartments in said member.
Each deflector plate or shoe combination such as
41 or 44, is disposed beneath, and in substantial alignment
with a conical guide piece 22. Thus, as riser 19 is lowered
from deck 11, it will reqister in the series of vertically
aligned conical pieces 22. The conductor will then be
guided such that further descent will cause its lower end to
eventually engage the deflector plate therebeneath.
In another embodiment, the shoe or plate, when
only one is utilized such as 42, is generally elongated and
may incorporate a gradual curvature. At its upper end~
plate 42 is disposed adjacent to gusset 28 at a point spaced
downwardly from the plate top surface. Plate 42 is further
disposed with one longitudinal edge contiguous to the edge
surface of gusset plate 29. Thus, as a lowering riser 19
engages the deflecting surface of shoe 42, the riser will be
restrained from outward movement by conical piece 22, but
will be urged outwardly as shown in Figure 3. The opposing
forces acting on the riser will deflect the lower end
thereof away from the riser conductor at a point above the
mud line adjacent to the structure 10.
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In an alternate embodiment of the rlser deflector
arrangement, a plurality of, or combination of shoes 43 and
45 are disposed within one longitudinal sector 36 of member
26 to form a trough-like path for riser 19. Thus, as the
latter is lowered past conical guide piece 22, the riser end
will engage the junction of the contiguous shoes 43 and 45
and thereby be maintained in relatively accurate alignment.
Thereafter, as it is further lowered, its end will be urged
outwardLy and terminate at a desired point to permit said
riser end to be connected to a pipeline 17.
It is appreciated that the disposition of guide
member 26, together with its various conductor deflecting
shoes, is such as to give the subsequently inserted riser 19
a desired arrangement or disposition adjacent to the mud
line. The respective shoes, such as 41, are thus
prearranged within said member 26 so that the risers, if
subsequently lowered, will assume a position compatible with
contemplated incoming pipelines 17.
By varying the angles of deflection and the
disposition of the various shoes 41, the risers 19 can be
made to deflect in predetermined directions to assure they
will leave the platform in a desired direction.
The respective shoes, such as 42 and 43, as shown
in Figure 5 can be braced against distortion by braces 46
disposed rearwardly thereof and spaced to support the
deflecting unit.
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Although modifications and variations of the
invention can be made without departing from the spiri~ and
scope thereof, only such limitations should be imposed as
are indicated in the appended claims.
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