Multiline riser support and connection system and method for subsea wells

A support and connecting system for a multiline riser which joins a floating platform to a subsea well is shown including a support housing which mounts upon the floating platform for disconnectably mounting a termination housing to which a plurality of lines are connected. The termination housing is also connected to the platform by a cable tensioning system which adjusts the tension within its connecting cables. A termination head fits within the termination housing and connects, through a termination riser adapter, to the uppermost riser of a riser run that communicates between the platform and the subsea well. The arrangement permits the riser run to engage the floating platform during assembly and recovery of the risers. In the event of a storm or other need for emergency disconnection, the riser run may be withdrawn from the termination housing and hung off or recoved without disconnecting the lines. During production operations, the riser run floats free of the platform connected thereto solely by the multilines and tensioning system. During drilling operations, a telescoping joint connects the termination housing to the support housing.

BACKGROUND OF THE INVENTION 
The present invention relates to a subsea well installation and, more 
particularly, to a multiline riser support and connection system which 
operates in engagement with or detachment from a floating platform. 
Conventionally, in subsea well drilling and production operations, a 
floating platform or vessel on the surface of the sea is connected to a 
subsea well head by a riser run. The riser run may be either a drilling or 
production run and is comprised of a plurality of riser sections assembled 
by supporting the uppermost portion of a riser section and subsequently 
adding riser sections and lowering the assembled riser sections until the 
desired overall length is reached. 
In such operations, a spider may be used which is disposed above a rotary 
table mounted on the vessel. The spider is opened to encircle the riser 
thus permitting it to be lowered through the spider. The spider is then 
closed to support the riser section upon the table by means of a flange on 
the uppermost end of each riser section. Each new riser section is added 
to the uppermost section of the spider supported riser run by means of a 
derrick, or the like, mounted on the vessel which lifts a new riser 
section over the assembled riser run and lowers it upon the top of the 
riser run where the flange of the newly positioned riser is bolted or 
otherwise secured to the flange of the uppermost portion of the assembled 
riser. The weight of the riser run is then lifted by the derrick, the 
spider is opened, and the assembled risers or lowered into the sea to 
repeat the operation. 
During such operations, it is desirable to maintain a constant load on the 
riser run regardless of the motion of the vessel or platform. An example 
of a hydraulically operated gimbal system which supports the table that, 
in turn, supports the run is shown in U.S. Pat. No. 3,984,900, issued Oct. 
12, 1976. 
As each riser section is lowered into the sea, its weight is supported to a 
substantial extent by gas entrapped between the outer surface of the 
cylindrical wall which forms the inner tube of the riser and the inner 
surface of a cylindrical shell which forms the outer cover of the riser. 
This entrapped gas contributes to the buoyancy of the riser as described 
in greater detail in U.S. Pat. No. 3,858,401, issued Jan. 7, 1975. The 
inner tube formed by the cylindrical wall may be used for a clearance 
passageway for drilling tools attached to an operating string when the 
riser run is used for drilling operations or as a passageway through which 
the production of the well is brought to the surface during the production 
operation. 
Once the riser run has been landed on the well head and connection is made 
with the well head connector, as shown in U.S. Pat. No. 4,109,712, issued 
Aug. 29, 1978, the vertical motion of the floating platform or vessel must 
be absorbed to prevent the riser run from crushing under its own weight. 
An example of a telescoping joint used on buoyant riser sections to absorb 
the motion of a vessel is shown in U.S. Pat. No. 3,952,526, issued Apr. 
27, 1976. 
The telescoping joint which compensates for the vertical movement of the 
floating platform may be located at either the lower end of the riser 
string adjacent the well head or the upper end of the riser string 
adjacent the platform. When the telescoping joint is located at the upper 
end of the riser run adjacent the vessel, the run is dynamically hung from 
cables attached from the lower surface of the platform or vessel to a 
point below the telescoping joint. Winches are provided on the cables to 
retain a constant tension and prevent the riser run from buckling under 
its own weight. An example of such a tensioning system is shown in U.S. 
Pat. No. 3,791,442, issued Feb. 12, 1974. 
In all of the systems described above, the multilines or hoses connected 
between the floating platform or vessel and the riser run which are 
ultimately connected to the well head must pass from the vessel to the 
uppermost riser and connect thereto by threaded connectors or other 
suitable means. These lines include flow lines, injection lines, and sales 
lines when the drill rig is being operated in the production phase. In the 
drilling operation, the lines include supply and return lines for a 
hydraulic drilling fluid, commonly called mud, and choke and kill lines 
for blowout protection. An example of a blowout-preventer used in an upper 
most riser of a drilling riser run is shown in the U.S. Pat. No. 3,791,442 
patent. 
While a floating platform generally operates in quiescent seas, clearly the 
platform or vessel will be subjected to storms during some of its drilling 
or production operation. At this time, the operation is terminated and the 
riser run is withdrawn from the well head. The run is then attached to the 
floating platform or vessel and allowed to extend vertically into the sea 
or "hung off" until the storm has passed. During a conventional emergency 
disconnect, the system described above requires men to disconect the 
multilines or hoses from the riser run while hung off in a bosun's chair 
in a dangerous area called the "moonpool" area. The moonpool is the well 
exposed to the sea which surrounds the riser run and extends through the 
hull of the ship. 
BRIEF DESCRIPTION OF THE INVENTION 
Therefore, it is the primary object of the present invention to provide a 
riser support and connection system and method which eliminates the need 
to disconnect or connect multiple lines or hoses to and from a drilling or 
production riser run while the run is being assembled, used, hung off or 
retrieved. 
Another object of the present invention is to provide a support and 
connection system which eliminates a mechanical coupling between the riser 
run and the platform or vessel during production operation but for the 
connection of hoses and cables for reducing the power required to operate 
the system. 
Other objects of the present invention are to provide a support and 
connection system which is safer to operate, requires less time to 
operate, eliminates the need for a telescoping joint during production 
operation, and exposes an operator to less danger by eliminating the 
requirement for the operator to work in a dangerous area. 
In accomplishing these and other objects, there is provided a subsea well 
apparatus having a riser run connected to a floating platform or vessel 
through a support and connection system that comprises a support housing 
permanently attached to the rotary table support beams which attach 
directly to the frame of the floating platform or vessel. Detachably 
connected to the support housing is a termination housing to which are 
connected all hoses or flow lines and tensioning cables. Mounted within 
the termination housing is a termination head having passageways which 
communicate with ports located within the termination housing that, in 
turn, communicate with the hoses and flow lines connected to the housing. 
The termination head is connected to a termination riser adapter joint 
which provides the mechanical connection to the uppermost riser and also 
provides passage for the multiple flow lines between the termination head 
to the uppermost riser and down to the well head. 
The system thus described permits the hoses including flow lines, injection 
lines, sales lines, and supply and return lines to be connected to the 
termination housing, through the termination heads (which functions as a 
manifold) and then through the riser adapter to the uppermost buoyant 
production riser. The termination housing which mounts the termination 
head is sized with an opening sufficiently large enough to permit the 
passage of all risers and other equipment normally lowered through the 
vessel or floating platform to the well head at the bottom of the sea 
during either drilling or production operations. The hoses are permanently 
connected to the termination housing which receives the termination head. 
The termination housing connects to the support housing during assembly 
and retrieval and is disconnected therefrom during The drilling and 
production operations. Thus, it is no longer necessary to disconnect hoses 
for the various lines whiel assembling or retrieving the riser run. 
Further, should an emergency disconnect be required due to a rising storm, 
the support and connection system may be raised into a connected 
engagement with the support housing and the riser run lifted from the 
termination housing by removing the termination head and raising it, the 
adapter joint and riser run to a level where a spider may be inserted for 
permanently mounting the riser run upon a gimbaled platform. Throughout 
this operation, not a single hose need be disconnected thus speeding up 
the shutdown process and eliminating hazardous duty for the operators. 
After a storm has subsided, the riser run may be lowered quickly into its 
operating position by placing the termination head into the termination 
housing and then disconnecting the termination housing from the support 
housing and lowering the riser run by tensioning means to a desired 
floating position. In the lowered position during a production operation, 
there is no mechanical connection between the riser run and the floating 
platform other than the hoses and cables which apply a constant tension to 
the production riser run. If the riser run is being used in a drilling 
operation, a telescoping joint is connected to the termination housing 
which, in turn, connects the riser run to the support housing. 
Other objects and advantages of the supporting and connection system of the 
present invention will become apparent to those skilled in the art after 
consideration of the following specification and appended drawings 
wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, a subsea well assembly 10 is shown in FIG. 1 
including a platform or vessel 12 floating upon the sea 14 over a subsea 
well head 16 located on the sea bottom 18. The connection between the 
vessel 12 and well head 16 is achieved by a plurality of buoyant riser 20 
joined end-to-end and lowered into the sea from the vessel 12 by a derrick 
22 mounted thereon over an opening 23, through the vessel hull, known as a 
moonpool. 
At the base of the derrick 22 is a stationary platform 24 supported upon 
I-beams 26 mounted directly to the vessel's superstructure. The stationary 
platform 24 is provided with a large opening 27 therein for receiving and 
mounting a rotating table, not shown. The rotating table has a square 
aperture therein for driving oil well tools. Sections of the rotating 
table may be removed to provide access to the area below the table 24 or 
allow large oil well tools to be lowered by the derrick 22 therethrough 
into the moonpool 23 and down to the well head. 
When assembling a production riser run, for example, a lower production 
riser termination 28, FIG. 2, is first placed upon the platform 24 by 
inserting a handling tool 30 into the uppermost portion of the production 
riser termination 28 and lifting. The riser termination 28 is connected to 
cables 32 and then lowered below the platform 24 where it may be 
restrained from further lowering by a spider 34 shown in FIG. 7. The riser 
handling tool 30 is next used to raise a buoyant riser 20 into position 
over the riser termination 28. After the lower portion of riser 20 is 
bolted to the upper portion of riser termination 28, the spider 34 is 
removed and the two assembled risers lowered until the top of the riser 20 
is aligned with platform 24 at which time the spider 34 is replaced to 
retain the assembled risers in the desired position. 
This procedure is repeated again and again until the desired length of 
riser run has been established. It is not uncommon for such a riser to 
extend some 6,000 feet from the vessel 12 to the sea bottom 18. A similar 
technique is used when assembling a drilling riser run. 
As best seen in FIG. 3, the stationary platform 24 incudes a support 
housing 36 mounted to the lower surfaces of the I-beams 26 which, in turn, 
mount to the super structure of the vessel 12. Disconnectably mounted to 
the support housing 36 is a termination housing 38 having radially 
extending ears 40 to which are attached cable termination clamps 42 by 
pins 44. The cable clamps 42 clamp the lower end of a tension cable 42 
which is wrapped around a winch pulley 48 connected to suitably driven 
winches, not shown. During the assembly of the production riser run, for 
example, the support housing 36 and termination housing 38 are locked in 
the position shown in FIG. 3 by a plurality of locking cylinders 50 which 
may be hydraulically operated to force locking pawls 52 into an annular 
groove 54, FIGS. 5 and 6. 
Prior to lowering the first or lowermost production riser termination 28 
through the opening 27 in platform 24, a split bore protection tool 56, as 
best seen in FIG. 4, is lowered into the connected assembly comprising the 
support housing 36 and termination housing 38. The split bore protector 56 
is generally tubular in shape and is comprised of two semicircular halves 
having one end thereof joined by a hinge, not shown. The bore protector 56 
is retained by a plurality of locking cylinders 58 mounted in housing 36 
whose pawls 60 engages an annular groove 62 in the upper, outer surface of 
the split bore protector 56, FIG. 6. 
The function of the protector 56 is to shield the longitudinal bore 64 of 
support housing 36 and the longitudinal bore 66 of termination housing 38 
while the various risers 20 are inserted through the longitudinal bores of 
each housing. It will be noted that the longitudinal bore 64 within 
support housing 36 is cylindrical and generally parallel with the outer 
surface of that housing. However, the longitudinal bore 66 within housing 
68 is generally tapered with its smaller diameter located at the lower end 
of the housing. This tapered surface 66 further supports the split bore 
protector 56. 
After the uppermost riser 20 has been lowered through the opening 27 and 
retained upon the stationary platform 24 by spider 34, FIG. 7, a 
termination raiser adapter joint 68 is placed upon the uppermost riser and 
bolted thereto by a plurality of bolts 70, FIG. 9. Connected to the top of 
the termination riser adapter 38 is a termination head 72 connected 
thereto by bolts 74, FIG. 9. Once the riser adapter 68 and termination 
head 72 have been bolted into place, FIG. 7, the derrick 22 raises the 
assembled production riser tool 30 and the spider 34 is removed to enable 
the adapter 68 and termination head 72 to be lowered into position, FIG. 
8. The outer tapered surface of the termination head 72 snuggly engages 
the tapered bore 66 of termination housing 38. A locking cylinder 76 is 
hydraulically actuated, for example, to urge pawls 78 into an annular 
groove 80 found within the outer surface of the termination head 72, FIG. 
9. 
With the termination head 72 locked into place in the termination housing 
38, the production tool 30 picks up the weight of the assembled production 
riser and the hydraulic locking cylinder 50 is unlocked by removing 
hydraulic fluid pressure, for example. This permits the termination 
housing 38 and termination head 72 to be freed from the support housing 36 
and lowered into the sea under the control of cables 46 and tensioning 
pulleys 48. As the cable lowers the riser assembly, the lower production 
riser 28 is placed in contact with the well head 16 and connection is made 
between the risers 20 and the well head 16 as taught in U.S. Pat. No. 
4,109,712. 
As best seen in FIG. 10, the production operation of the subsea well 
assembly 10, assumed when the riser run 20 with its termination head 72 
and termination housing 38 separates from the support housing 36, includes 
no mechanical connection to the vessel 12 but for the tensioning cables 46 
and the connections of a plurality of lines or hoses 82. These multilines 
82 include hydraulic lines which carry hydraulic fluid from the vessel 12 
to the well head 16 via the risers 20. The lines include flow lines, 
injection lines and sales lines. Each hose 82 is connected to the 
termination housing 38 by a suitable hose connector 84. Radiating from the 
tapered bore 66 of the termination housing 38 are a plurality of ports 86, 
FIG. 9, which communicate with the hydraulic hose connectors 84 which are 
mounted upon the outer surface of the housing 38 and are sealed thereto by 
suitable seals, such as O-rings 88. In the embodiment shown, only four 
hydraulic hoses 82 and connectors 84 are illustrated for simplicity. In 
the preferred embodiment, twelve or more lines or hoses may be connected 
to the termination housing 38. At least one of the multilines may be 
larger than the others to form, for example, a sales outlet line 90. The 
sales outlet line 90 also connects through a connector 84 sealed to the 
outer surface of the termination housing 38 by O-rings 88 and communicates 
to the tapered inner surface 66 via a port 92. 
Once in place, the termination head 72 acts as a manifold in that it is 
provided with a plurality of passageways 94 which are aligned with and 
communicate with the ports 86 and 92 found within the termination housing 
38. A typical passageway 94, FIG. 9, communicates with port 86 and is 
formed in a T rotated 90.degree. with the leg of the T extending 
horizontally to communicate with port 86. The top of the T of passageway 
94 is vertically aligned with one end closed by a plug 96 having a pipe 
thread for sealing the passageway 94. The other end of passageway 94 
communicates through a top flange 98 in the raiser adapter 68 with a flow 
line 100. The flow line 100 mounts between the top flange 98 and a bottom 
flange 102 and is secured within each flange by welding or a threaded 
insert. It will be understood that each passageway 94 wihtnin the 
termination head 72 communicates with a flow line 100 mounted between 
flanges 98 and 102 within adapter riser 68. 
Each passageway 94 is sealed to a flow line 100 by seals 104. These same 
seals are used to seal the lower surface of the adapter 68 against the 
upper surface of the uppermost riser 20. The center of termination head 72 
is provided with a vertical bore 106 which does not pass completely 
through the termination head 72. A horizontal bore 108 communicates with 
bore 106 to create a passageway which communicates with the sales outlet 
line 90. A pair of seals 110, such as a packer seals, surround the 
passageways 94 within the termination head 72 and also surround the bore 
108 for sealing the passageways and bore as the termination head 72 is 
mounted into the termination housing 38. Similarly, a single seal 112 
surrounds the bore 106 to seal that passageway against the upper surface 
of the adapter 68. Adapter 68 is provided with a longitudinal bore 114 
which communicates between the termination head bore 106 and a center bore 
116 within the cylindrical tube 118 which forms the center of riser 20. 
The cylindrical tube 118 is surrounded by a second cylindrical wall 120 
which forms the outer portion of the buoyant riser 20 wherein the gas that 
provides the buoyancy for the riser is trapped between the outer surface 
of tube 118 and the inner surface of shell 120. The upper end of tube 118 
comprises an outwardly directed flange 122 which is concentrically aligned 
with an outwardly directed flange 124 formed on the upper end of shell 
120. A plurality of tubes 125 are mounted between flanges 122 and 124 and 
a similar set of flanges at the lowermost end of each riser 20 to 
communicate between the vessel 12 and well head 16 via flow lines 100 and 
hoses 82 and 90. A ring of bolts 126 may be used to join the tube 118 to 
shell 120. The bolted flange formed by flanges 122 and 124 is the flange 
under which the spider 34 is placed to retain the riser assembly in the 
position shown in FIG. 7. 
It will be understood that the outer diameter of flanges 122 and 124 must 
be small enough to fit through the inner diameter of the split bore 
protector 56, FIG. 4, and bores 64 and 66 of support housing 36 and 
termination housing 38, respectively. The bolts 70 which pass through the 
lower flange 102 of the adapter 68 are threadably mounted within the 
flange 122 formed on the riser 20 to connect the adapter 68 to the riser 
20. 
As seen in FIGS. 9 and 10, the upper end of the adapter head 72 is provided 
with a webbed mating portion 128 whose upper surface has been tapered at 
130. The taper 130 assists in aligning the locked assembly of the 
termination housing 38 and termination head 72 with the support housing 36 
as the termination housing and head is raised into position under the 
support housing. Once the termination housing has been raised into the 
proper position by the winching action of pulleys 48 and cable 46, the 
hydraulic locking cylinders 50 mounted on housing 38 are actuated to urge 
pawls 52 in to groove 54 in housing 36. An inner aperture 131 of the 
webbed portion 128 is provided with an inwardly directed taper 132 which 
provides an aligning seat as the production riser handling tool 30 is 
inserted into aperture 131. 
An alternate configuration to that shown in FIG. 9 may be accomplished by 
removing plugs 96 and arranging the passageways 94 with vertical access to 
the top of the termination head 72, FIG. 9. The flow lines 100 which 
extend through each riser section 20, as shown by riser flow line 125, may 
be closed at the lowermost production riser by a plug valve which is 
actuated into an open condition by tensioning a wire line. Using this 
arrangement, individual flow lines may be pressurized and tested while the 
risers 20 are being assembled. 
The riser run described until now has been described as a production riser. 
It will be understood that a drilling riser may also be used with the 
present invention. When a drilling riser is used, the riser is not 
permitted to float free of the platform. Rather, a telescoping section, 
not shown, similar to the section described in U.S. Pat. No. 3,952,526 is 
connected between the termination housing 38 and support housing 36. The 
upper most end of the telescoping section is provided with a 
blowout-preventer, such as that shown in U.S. Pat. No. 3,791,442, which 
fits into the bore 64 of support housing 36. During a drilling operation, 
the cable tension system formed by cables 46 retains the riser run in the 
vertical position desired while the telescoping section absorbs the 
vertical displacement between the platform and the well head 16 on the sea 
floor. After initial connection, the multilines connected to the 
termination housing 38 need not be disconnected therefrom during assembly, 
use or while hung off or retrieved. 
The unique method of connecting a riser run and supporting that run during 
its operation may now be described with reference to the foregoing 
drawings. It will be understood that the method described is described as 
if a production riser and production operation were involved; however, the 
method is the same for a drilling riser and drilling operation unless 
otherwise noted. 
During assembly, the termination housing 38 is raised by tension cables 46 
and locked by hydraulic cylinders 50 to the support housing 36. Hoses 82 
and 90 including flow lines, injection lines and sales lines are then 
connected to the housing 38. The split bore protector 56 is then installed 
within the support housing 36 and termination housing 38 and locked into 
position by hydraulic locking dogs 58. Next, the production riser 
termination 28 is lowered through the bore within the protector 56 and 
landed upon the spider 34. A production riser 20 is then attached to the 
production riser termination 28 and the two are lowered through the 
stationary table 24, support housing 36 and termination housing 38 landing 
the flanges 122 and 124 of riser 20 on the riser spider 34 positioned 
above the stationary table 24. Each additional riser 20 is attached in a 
similar manner until the desired length has been extended into the sea 
whereupon the split bore protector 56 is removed. Next, the riser adapter 
joint 68 and the termination head 72 are assembled and raised with the 
production handling tool 30 over the uppermost production riser 20 where 
the last joint is made fast by insertion of bolts 70. The assemblied riser 
run is then lowered until the termination head 72 lands in the tapered 
bore 66 of termination housing 38 and is locked in place by hydraulic 
locking dogs 76. The weight of the production riser run 20 is then lifted 
from the stationary table 24 with tool 30 prior to unlocking the support 
housing 36 by deactivating the hydraulic locking dogs 50. Lastly, the 
production riser run 20 including the disengaged termination head 72 and 
termination housing 38 is lowered until the weight is taken by tensioning 
cables 46. Thereafter, the lowering continues with the weight on the 
tension cables until the lower production riser termination 28 lands on 
and engages the well head 16. 
It will now be seen that production of the subsea well 10 may continue with 
no mechanical connection between the vessel 12 and riser run 20 but for 
the tensioning cable 46 and hoses 82 and 90. This eliminates the need for 
telescoping joints and substantially reduces the amount of energy needed 
to operate the winch pulleys 48. 
If a drilling riser is assembled, an additional step of placing a 
telescoping section atop the riser adapter joint 68 is required. When the 
termination housing 38 and termination head 72 are disengaged from the 
support housing 36 and lowered, the telescoping section is lowered with 
them until its upper section lands in the support housing 36. 
During production or drilling operations, should a storm create the 
necessity to disconnect the riser run 20 from the well head 16, the method 
of operation is as follows: first, the handling tool 30 is installed in 
the aperture 131 of the termination head 72; second, the riser is released 
from its connection at the well head 16 and the riser run 20 is pulled in 
a vertical direction with the handling tool 30 until the termination 
housing 38 engages the support housing 36; third, the hydraulic locking 
dogs 50 are actuated to lock the termination housing 38 to the support 
housing 36; fourth, the four locking dogs 76 that lock the termination 
head 72 to the termination housing 38 are released; and, finally, the 
pulling of the riser 20 continues until the uppermost riser 20 has been 
pulled so that its flange 122-124 can be landed on the spider 34 resting 
on the platform 24 which, in turn, mounts upon energy-absorbing gimbals. 
Through this arrangement, the riser run 20 may be disconnected from the 
well head 16 and placed in the hung off position without the need for 
disconnecting a single hose or exposing personnel to a dangerous work area 
in bosun's chairs over the moonpool. 
Should it be desired to recover the remaining portion of the riser run 20, 
this may be accomplished by continuing to pull the riser run until the 
uppermost riser clears the table 24 whereupon the protector 56 may be 
installed within the support housing 36. The remaining portions of the 
riser run 20 are is recovered in the conventional manner through the table 
24 utilizing the riser spider 34. 
As the riser run 20 is assembled back into its production or drilling 
configuration, it will be understood that the termination head 72 is 
lowered snuggly into the termination housing 38. In this position, the 
seals 110, which are packer type seals permanently fixed within the 
tapered surface of the termination head 72, seal the passageways between 
the hoses 82 and 90 and the riser adapter 68. Thus, it will be seen that 
the hoses 82 and 90 permanently connected to the outer surface of the 
termination housing 38 are automatically disconnected by the disconnection 
and rising of the termination head 72. Utilizing this arrangement, it is 
possible to make and break all hydraulic connections without the need for 
manually disconnecting a single connector 84. 
While the present invention has been described utilizing a separate support 
housing 36 and a separate riser adapter 68, it will be understood that the 
support housing may be built into the platform 24 as a permanent member 
thereof and need not be considered a separate piece. Similarly, the riser 
adapter may be built into the termination head and need not be a separate 
piece. Other modifications and variations of the present invention will 
become apparent to those skilled in the art after considering the 
following claims: