U.S. patent number 3,877,520 [Application Number 05/389,248] was granted by the patent office on 1975-04-15 for subsea completion and rework system for deep water oil wells.
Invention is credited to Paul S. Putnam.
United States Patent |
3,877,520 |
Putnam |
April 15, 1975 |
SUBSEA COMPLETION AND REWORK SYSTEM FOR DEEP WATER OIL WELLS
Abstract
A subsea completion system for a plurality of wells drilled from
a single template, the template being divided into a plurality of
wellhead sections and a plurality of equipment sections. Each
wellhead section of the template has a concentric stab ring around
the wellhead with the production and service tubing extending from
the stab rings of the respective wellhead sections to similar stab
rings in the equipment sections of the template. Well completion
modules, header modules, separator modules, and power equipment
modules are individually connected by means of a mating stab ring
at the bottom of the modules to the respective stab rings in the
template sections after the template is placed on the sea floor and
the wells are drilled. Each well completion module includes the
production tree, tubing, hydraulic controls, and equipment
necessary to operate the well, the tubing and hydraulic lines
terminating in the bottom stab ring for connection to the template.
An upper stab ring is provided at the top of each module with
tubing extending directly to the tubing connections in the lower
stab ring through diverters. A multiposition diverter unit is
attachable from the surface to the upper stab ring and can be
operated to connect a riser to any one of the tubing connections in
the stab ring, providing a direct tubing path between the riser and
any one of the tubing connections in the corresponding section of
the template. The direct tubing connection provides access for the
setting or removal of plugs in the tubing in each template section
from the surface through the associated module. This permits the
tubing in the template to be shut off, permitting removal of any of
the modules from the surface.
Inventors: |
Putnam; Paul S. (Whittier,
CA) |
Family
ID: |
23537459 |
Appl.
No.: |
05/389,248 |
Filed: |
August 17, 1973 |
Current U.S.
Class: |
166/366 |
Current CPC
Class: |
E21B
33/038 (20130101); E21B 41/08 (20130101); E21B
33/076 (20130101); E21B 23/12 (20200501); E21B
43/017 (20130101) |
Current International
Class: |
E21B
23/12 (20060101); E21B 43/00 (20060101); E21B
33/03 (20060101); E21B 23/00 (20060101); E21B
33/038 (20060101); E21B 43/017 (20060101); E21B
33/076 (20060101); E21b 033/035 () |
Field of
Search: |
;166/.5,.6,75 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Attorney, Agent or Firm: Christie, Parker & Hale
Claims
What is claimed is:
1. A subsea well completion apparatus comprising: a template frame
positioned on the sea floor, the template frame having a plurality
of sections, each section including a plurality of stab connectors,
flow tubing mounted in the template frame for inter-connecting the
stab connectors of different sections, a plug-seating nipple in
each flow line below each flow line stab connector for receiving
and seating a removable line plug, a plurality of wellhead
completion modules, each module having a top and a bottom, the
bottom including a plurality of stab connectors adapted to engage
the stab connectors of one of said template frame sections to
complete flow line connections between the module and the template
frame, the top including a plurality of stab connectors, flow lines
in the module extending between stab connectors in the bottom and
top of the module, a well completion valve tree in each completion
module, the tree including casing connector means in the bottom for
connecting the tree to the wellhead casing, and means including
tool diverters connecting the flow lines in the module to the valve
tree for providing a path for pump-down tools through the flow
lines in the template into the well through the tree while
providing a line tool path into the flow line in the template
through said flow lines extending between the top and bottom stab
connectors of the module.
2. Apparatus of claim 1 further including a nipple in each flow
line adjacent the stab connectors in the top of each completion
module for receiving and seating a removable line plug.
3. Apparatus of claim 1 wherein the centers of the flow line stab
connectors in the top are equally spaced around a common
circle.
4. Apparatus of claim 2 further including a multi-position diverter
for selectively connecting each of the flow line stab connectors in
the top of a module to a single riser, and means for removably
securing the diverter to the top of the module.
5. Apparatus as defined in claim 1 wherein each completion module
includes a housing, the stab connectors opening through the top and
bottom walls of the housing, and means for sensing the level of oil
accumulated and trapped within the housing.
6. Apparatus of claim 1 wherein the mating stab connectors in each
section of the template frame and the bottom of the associated
module are positioned in a ring extending around the associated
wellhead.
7. Subsea well completion apparatus for providing completion of
wells drilled in the sea floor comprising: a frame adapted to be
positioned on the sea floor, the frame having an opening through
which a well is drilled, a plurality of flow lines mounted on and
secured to the frame, a plurality of stab connectors mounted on the
frame and positioned in proximity to said opening, the flow lines
terminating in the stab connectors, and plug-seating nipple means
for receiving a line plug positioned in each of the flow lines, an
enclosed wellhead completion module including a valve tree and flow
lines connected to the valve tree, means connecting the valve tree
to the top of the well, and a plurality of flow line stab
connectors on the end of the flow lines in the completion module
and positioned on the bottom of the module to engage the stab
connectors in the frame when the valve tree is connected to the
well.
8. Apparatus of claim 7 wherein the stab connectors extend
vertically.
9. Apparatus of claim 8 wherein the completion module further
includes a plurality of tube connectors opening at the top of the
module, and tube means including line tool diverters in the module
connecting the upper connectors to the stab connectors in the
bottom of the module.
10. Apparatus of claim 9 further including a multi-position wire
line diverter, means removably securing the multi-position diverter
to the top of the completion module, the diverter including means
engaging all of the connectors in the top of the module, a riser
connector, and rotating means selectively coupling the riser
connector to each of the connectors in the top of the module.
11. Apparatus of claim 10 wherein each module further includes tool
diverter means in the fluid flow lines between the top and bottom
of the module.
12. Apparatus of claim 10 further comprising a diverter assembly
for selectively coupling any of the fluid flow lines in a module to
a common riser extending above the module, the diverter assembly
including a plurality of stab connectors adapted to simultaneously
engage the stab connectors in the top of a module, and means for
detachably securing the diverter assembly to the top of a
module.
13. Apparatus of claim 12 wherein the diverter assembly includes
rotary positioned coupling means for selectively coupling any one
of the stab connectors to the riser.
14. Apparatus of claim 12 wherein the template frame further
includes a plurality of vertically projecting guide posts secured
to the frame around each connector element position, the diverter
assembly including guide means engaging said posts for guiding the
diverter assembly into position directly above any selected one of
the well positions.
15. Apparatus of claim 12 further comprising a plurality of
hydraulic control line connectors in the connector ring, matching
hydraulic control line stab connectors in the bottom of the module,
a plurality of hydraulic control line connectors in the top of the
module, and a plurality of matching hydraulic control line stab
connectors in the diverter assembly, and valve means in the module
actuated by the diverter assembly when connected to the top of a
module for cutting off all hydraulic control lines from the
connectors in the bottom of the module, whereby hydraulic control
of the module through the template is interrupted by connecting the
diverter assembly to the top of the module.
16. Apparatus for subsea completion and operation of oil and gas
wells comprising: a template frame adapted to be positioned on the
sea floor, the template frame including a plurality of connector
elements, each element including a plurality of stab connectors,
and fluid flow lines interconnecting the stab connectors of
different connector elements, each flow line including plug-seating
nipples for receiving a line plug, and a plurality of modules for
completing and operating wells drilled adjacent selected ones of
said connector elements, each module including means detachably
securing the module to a wellhead, a plurality of fluid line stab
connectors mounted in the bottom of the module adapted to engage
the stab connectors of the associated connector element in
fluid-tight relationship when the module is secured to the
associated wellhead, a plurality of flow line stab connectors
opening at the top of the module, and flow lines extending directly
between the stab connectors in the top to associated stab
connectors in the bottom of the module, the flow lines being
adapted to guide a wire line tool through the top of a module into
the fluid flow lines in the template frame to set or remove plugs
in said plug seating nipples below the connector elements.
17. Apparatus of claim 16 wherein each module further includes plug
seating nipples in each of said fluid flow lines extending between
the top and bottom of the module.
18. A multiline diverter assembly comprising a group of flow line
connectors arranged in a circle, a single flow line connector
positioned along the axis of rotation of said circle, a fluid flow
line section, rotating coupling means connecting one end of said
section to said single connector, power-operated connector means
positioned on the other end of said section and adapted to connect
and disconnect said section from any one of said flow line
connectors, and power-operated indexing means for rotating said
section to move the power-operated connector means into engaging
position with any one of the group of flow line connectors.
19. Apparatus of claim 18 further including control means for
successively disconnecting the power-operated connector means from
a flow line connector, rotating said flow line section to a
position opposite the next flow line connector, and reconnecting
the power-operated connector means.
20. Apparatus for subsea completion and operation of oil and gas
wells comprising: a template frame adapted to be positioned on the
sea floor, a plurality of modules adapted to be removably mounted
on top of the template frame, each module being positioned at one
of said sections, the template frame including a plurality of fluid
flow lines extending between the sections, each fluid flow line
including a vertically extending stab connector at each end, each
fluid flow line further including a plug-seating nipple for
receiving a line plug, each module including a plurality of
vertically extending stab connectors at the bottom of the module
positioned to engage the stab connectors terminating the fluid flow
lines in the associated template section, a plurality of stab
connectors opening at the top of each module, and flow lines
extending between stab connectors at the bottom of a module and
associated stab connectors at the top of a module for directing a
wire line tool through the module to the plug-seating nipples in
the associated flow lines in the template frame.
21. Apparatus of claim 20 wherein a portion of the modules includes
a wellhead valve tree for connecting to a wellhead, and a portion
of the modules includes header means for fluid connecting groups of
fluid flow lines in the module to individual flow lines in the
module.
22. Apparatus of claim 20 wherein each module further includes plug
seating nipples in each of said fluid flow lines extending between
the top and bottom of the module.
23. Apparatus of claim 20 wherein each module further includes tool
diverter means in the fluid flow lines between the top and bottom
of the module.
24. Apparatus of claim 20 further comprising a diverter assembly
for selectively coupling any of the fluid flow lines in a module to
a common riser extending above the module, the diverter assembly
including a plurality of stab connectors adapted to simultaneously
engage the stab connectors in the top of a module, and means for
detachably securing the diverter assembly to the top of a
module.
25. Apparatus of claim 24 wherein the diverter assembly includes
rotary positioned coupling means for selectively coupling any one
of the stab connectors to the riser.
26. Apparatus of claim 24 wherein the template frame further
includes a plurality of vertically projecting guide posts secured
to the frame around each connector element position, the diverter
assembly including guide means engaging said posts for guiding the
diverter assembly into position directly above any selected one of
the well positions.
Description
FIELD OF THE INVENTION
This invention relates to the operation of subsea oil and gas
wells, and more particularly, is concerned with apparatus for
completing and operating producing wells on the ocean floor
entirely from the surface without the use of divers.
BACKGROUND OF THE INVENTION
In recent years, the search for oil and gas reserves has been
concentrated more and more in off-shore fields. This in turn has
led to developments in techniques for drilling and completing wells
in deeper and deeper waters. In typical operations, single
exploratory wells may be drilled from a floating vessel. If
significant reserves are located by the exploratory well, this well
is usually plugged because the present cost of completing a single
subsea well does not justify an attempted completion. At shallower
depths, a permanent drilling platform is then erected from which
typically 18 or 20 wells can be drilled and completed. With the
drilling platform, the wellhead is at the surface with all
completion equipment being available on the platform. Thus the
operation of the well is not substantially different from the
operation of a well on land.
However, in the case of deep-water wells in 500 feet to over 1,000
feet of water depth, the building of a platform rising above the
surface of the water becomes very costly if not completely
impractical. This has given rise to a considerable effort in
designing equipment for completing the wells on the ocean floor
after they have been drilled from floating platforms. Various
proposals have been made for handling production from subsea
completed wells. Such systems usually require submerged manned
supervision for repair and maintenance of equipment. The use of
submarines, special diving bells, or other kinds of bubble-type
life support system surrounding the wellhead have all been proposed
but with obvious limitations. There have also been proposals for
single well subsea completion systems which are designed to be
installed and operated without the aid of divers or submersibles.
See for example, the article "Diverless Subsea Completion System
for Deep-Water Oil Wells" by C. B. Reeds and P. R. Seligman, Paper
No. OTC 1594, Fourth Annual Offshore Technology Conference, May,
1972. However, such known systems have not been proved effective
for a multiple well installation. Flowline connections are
complicated by the horizontal position of the connections and
remotely controlled valves are required to control fluid pressures
during the connect and disconnect operation. No environmental
control for the completion equipment is provided.
SUMMARY OF THE PRESENT INVENTION
The present invention is directed to equipment by which a multiple
well installation can be completed on the ocean floor and in which
all operation of the wells, including workover, equipment repair,
water or gas injection, and other operating requirements of the
wells during the life of the wells, can be carried out from the
surface of the water. This is accomplished by providing a permanent
base that serves as a drilling template for a plurality of wells.
All equipment for operating the wells, including production trees,
headers, separators, and power sources is arranged in modules that
are removably attached to the template by stab connectors. All flow
lines and hydraulic lines interconnecting the modules are mounted
in the template but no valves or other moving parts are located in
the template. Plugs can be set or removed from each of the flow
lines in the template where they connect into any one of the
modules. This can be done with the modules in place from the
surface by means of a multiple diverter that connects a riser
through the top of a module to any one of the flow lines in the
template, permitting a wire line to be passed from the surface
directly into any selected one of the flow lines in the template.
By setting plugs in the flow lines in the template, either by
pumping the plugs down the flow lines or using a wire line tool, a
module can be isolated from the rest of the system without the use
of valves in the template so that it can be removed to the surface
for repair or replacement.
The multiple diverter assembly can also be used to guide a module
into position, the assembly then being returned to the surface. In
this way, the different modules mounted on the template can share
common vertical guide rods. The template includes only flow lines,
hydraulic lines, and electrical cables. No active elements, such as
switches, valves, pumps, or the like, are provided in the template.
All connections to the template are made vertically so as to be
easily carried out from the surface. All active equipment is
mounted in enclosed modules that can be removed from the template
by setting plugs from the surface in any associated lines in the
template.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention,
reference should be made to the accompanying drawings, wherein:
FIG. 1 is an isometric view of a sub-sea wellhead installation
according to the present invention;
FIG. 2 is a sectional view of a wellhead completion module;
FIG. 3 is a top view of the wellhead completion module;
FIG. 4 is a top view of a stab ring assembly in the template;
FIG. 5 is an enlarged detail drawing of the area shown within the
circled line 5 of FIG. 2;
FIG. 6 is a sectional view taken on the lines 6--6 of FIG. 2;
FIG. 7 is a sectional view of a header module;
FIG. 8 is a sectional view of a portion of a multi-position
diverter;
FIGS. 9 and 10 are sectional views showing the hydraulic actuator
mechanism for the multi-position diverter of FIG. 8;
FIG. 11 is a detailed sectional view of the stab connector assembly
for the multi-position diverter;
FIG. 12 is a schematic diagram of the hydraulic control system for
the multi-position diverter; and
FIG. 13 is a detailed sectional view showing a hydraulic line stab
connector and valve.
DETAILED DESCRIPTION
Referring to FIG. 1, there is shown a multiple well installation on
the ocean floor. The numeral 10 indicates generally a template
frame which is lowered onto the ocean floor and serves as both a
template for drilling a plurality of wells and as a base for
equipment used in the completion and operation of the wells after
they are drilled. The frame 10 is of open tubular construction
consisting of two parallel grids, an upper grid indicated generally
at 12 and a lower grid indicated generally at 14, preferably welded
from sections of pipe. The two grids are supported in spaced
parallel relationship by vertical pipes 20 to form a plurality of
cubical sections. The pipes are welded or otherwise joined to form
a rigid integral structure.
In the center of each of the square openings of the upper grid 12
is mounted an annulus of flat ring 22 supported by diagonal frame
members 24 which extend outwardly to the four corners of each
section of the upper grid structure 12. Guide rods 25 project
upwardly at each of the pipe intersections of the upper grid
12.
In a typical installation, a number of cubical sections of frame 10
would be used as the template for slant drilling one well from each
section. Each well is drilled by conventional floating drilling
equipment which utilizes the guide rods 25 and ring 22 to position
the drilling equipment and locate the top of the well. As the well
is drilled, surface casing is set through the central opening of
the associated ring 22 and cemented in place, the top of the casing
projecting up into the opening in the ring 22 to form the wellhead,
as indicated at 50 in FIG. 2. Blowout preventors (not shown) are
attached to the top of the casing and the well is drilled down to
the producing formation.
After the drilling is completed, the tubing is run and hung in the
wellhead, plugs are set in the tubing string prior to removing the
blow-out preventors and drilling equipment. All of the completion
equipment, including the production tree, valving, and related
equipment needed to control flow of the well is mounted in a module
which is lowered into position and attached to the wellhead in a
manner hereinafter described. Three of these wellhead equipment
modules are shown in FIG. 1, as indicated at 26, 27, and 28.
In addition to each of the wellhead sections with their completion
equipment modules, the template frame 10, in a typical
installation, includes sections for mounting additional modules,
such as one or more header modules 29. One header module serves as
a conduit system with suitable valving for controlling the flow of
oil and/or gas under pressure from a group of wells. The header
modules 29 in turn connect into a single gathering header 30 having
a connector assembly 31 off to one side for connecting into a
terminal assembly 32 for a group of pipes going to a gathering
point (not shown). In addition, the typical installation may
include one or more power equipment modules 33 which serve as a
source of electrical and hydraulic power for operating all the
other modules. In addition, separator modules may also be
incorporated.
While the internal design and construction of the various types of
modules differs depending upon their function, the external
features are quite similar. Thus each module includes an outer
enclosure 40 having a top 42 in the form of a truncated cone which
terminates in an upper stab plate 44 at its upper end with a
central axially aligned mandrel 46. The bottom 48 of each module
enclosure 40 includes a connector stab ring 49 (see FIG. 2) which
mates with the ring 22 at a module location in the template frame.
A central hydraulically operated connector 56 in the bottom of each
module locks onto a central mandrel 54 that is fixed relative to
the template frame 10. The mandrel 54, in the case of the wellhead
section, is part of a casing head 52 attached to the top of the
well casing. The mandrel may be directly attached to the frame 10
or the ring 22 for those sections not used for drilling.
The template 10 includes production tubing which may include four
lines going to each well. Typically there is one flow line and one
service line for each well completion. The additional two lines may
be provided for dual completion or provide for water and/or gas
injection. In order to permit "pigging" tools which can be pumped
down the lines, a minimum radius of five feet is provided for all
in the tubing. The four flow lines terminate in stab connector
receptable units, indicated at 62, which are mounted in the ring
22. Immediately below each stab connector unit 62 is a nipple 64
for seating a conventional wireline-operated plug (not shown). Also
mounted in the ring 22 are a plurality of hydraulic pressure line
connectors 66. Hydraulic lines (not shown) extend from these
connectors below the ring 22 to corresponding connectors in the
ring 22 associated with the mounting of the power equipment module
33. These hydraulic lines are used to control all valving
operations within the wellhead completion module 26 from the power
equipment module 33. The hydraulic lines, apart from the
connectors, have not been shown in the drawings for the sake of
clarity. The use of hydraulic controls for valves and the like is
well known in the art.
The wellhead completion module 26, when in position, connects onto
the mandrel 54 through a connector 56 on the bottom of a production
tree 58. The stab ring 49 has flow line mandrels 68 which engage
the connectors 62 in the ring 22 to provide a fluid-tight coupling
with the flow lines into the wellhead completion module. In
addition, the stab ring 49 includes a plurality of hydraulic line
connectors (not shown) which engage the hydraulic line connectors
66 in the stab ring 22 to provide hydraulic connections into the
module 26 from the template.
The flow lines within the module 26 extend in large radius loops
into the production tree 58. The flow line and service line are
connected into the production tree through diverters 70, 72, 74,
and 76. The diverters 70 and 72 permit direct access from the top
of the module 26 into the tubing within the well bore. Thus the
diverter 70 connects to a vertical tubing section 78 which extends
into a central fitting 80 at the top of the production tree 58
which terminates in the mandrel 46 projecting above the stab plate
44. A conventional riser with a stab connector can be attached to
the mandrel 46 from the surface to permit access into the well
tubing from the surface for rework tools, or the like. The tubing
section 78 may be controlled by a hydraulically operated valve 82
and may also include a nipple for receiving a conventional plug to
back up the valve 82 and insure that no fluid under pressure can
escape from the well out through the tubing 78.
Similarly, the diverters 74 and 76 are connected by vertical tubing
sections 86 and 88 to stab connector fittings 90 and 92,
respectively, mounted in the upper stab plate 44. Again, each of
these tubes is provided with hydraulically controlled valves 94 and
96. In addition, nipples 98 and 99 are provided just below the stab
connector fittings 90 and 92 for receiving removable plugs.
Initially plugs are set in the nipples 64 at the terminus of the
flow lines within the template frame 10 before the frame is lowered
and secured in place on the ocean floor. After the well is drilled
and it is desired to mount the well completion module in place, a
multiple diverter assembly 100 is connected to the top of the
module before the module is lowered into place. The multiple
diverter assembly includes a connector stab ring 102 having stab
connector elements 101 which mate with the connectors 90, 92 and a
sealed off connector 103 that engages and locks onto the central
mandrel 46. There are also hydraulic line connectors 105 in the
stab plate 44 which engage corresponding hydraulic line connectors
107 in the stab ring 102. Hydraulic lines (not shown) extend from
the surface and are connected into the module to provide control of
the module. The hydraulic line connectors 107 when inserted in the
connectors 105 are arranged to block the control lines going to the
connectors in the base of the module so as to prevent normal
control from the power module while the multiple diverter assembly
100 is connected to the module.
As shown in detail in FIG. 13, the stab connector 105 has an
interior chamber 109 having an inlet passage 111 and an outlet
passage 112. A second inlet passage 113 receives the nipple of the
stab connector when the multiple diverter unit 100 is attached to
the module. Inside the chamber 109 is a valve plunger 115, the
upper end of which normally seats against a valve seat 117 at the
stab connector inlet 115. A spring 119 urges the valve against the
seat 117. The inlet 111, which is connected by a hydraulic line
(not shown) to a stab connector in the base of the module, is
normally fluid-coupled to the outlet 112 to provide a control of
some hydraulic device within the module through the template.
However, when the multiple diverter 100 is in position, the stab
connector entering the inlet 113 forces the plunger 115 downwardly
against the spring into position to seal off the inlet 111. Thus
hydraulic control is switched from the inlet 111 to the inlet 113.
This insures that control within the module is transferred from the
template to the surface through the multiple diverter 100 while it
is attached to the top of the module.
The upper end of the multiple diverter assembly 100 includes a
conical frame 106 and a base 104 joined by the frame 106 to a
mandrel 108 by which the assembly can be attached to a riser (not
shown). The base 104 in turn has a plurality of tube sections 110
which are coupled by the associated connectors to the tube sections
86, 88 within the wellhead completion module 26.
The multiple diverter assembly 100, described below in detail,
includes a rotary assembly including a tubing section 114 which
terminates in its upper end in a rotary coupling 116 that couples
the tubing section 114 to the mandrel 108. The lower end of the
tubing section 114 is joined to a retractable connector assembly
indicated generally at 118 mounted on a rotary plate 120. The plate
120 is rotated by a hydraulic motor 122. The multiple diverter
assembly is described in more detail below in connection with FIG.
8.
The wellhead completion module 26, with the multiple diverter
assembly 100 connected to it, is lowered from the surface by a
riser connected to the mandrel 108. The multiple diverter assembly
is provided with suitable guide means including four parallel
annular guide members 124 which are supported on the ends of
radially extending arms 126 joined at their inner ends to the
periphery of the stab ring 102. The guide members 124 engage the
vertical guide posts or rods 25 projecting upwardly at the four
corners of each section of the upper grid 12 of the template frame
10. By this arrangement, once the module 26 is guided into position
and stabbed into the connector ring 22 and placed in operative
condition, the multiple diverter assembly 100 can be detached from
the mandrel 46 and pulled to the surface. Since the module itself
does not have any guide members which engage the vertical guide
posts 25 of the frame 10, the guide posts can be shared by
adjoining sections. Thus each module does not require its own set
of guide posts in the template frame.
Once the wellhead completion module 26 is lowered into position,
the plugs in the flow lines in the template are removed. This is
accomplished by angularly positioning and engaging the rotary
assembly so as to provide a connection to each one of the tubes 110
in succession and running a wire line tool from the surface through
the riser, through the top of the module 26 and each corresponding
one of the tubes 86, 88 through the associated one of the diverters
74 and 76 to release and remove each of the plugs in the template
flow lines. Each plug is withdrawn vertically through the module 26
and the multiple diverter 100.
After the plugs are removed from each of the flow lines in this
manner, plugs may then be set in the nipples 98 and 99 adjacent the
top of the module and the multiple diverter assembly 100 can then
be detached from the top of the module 26 and the well placed in
production.
If after the well is in production, any rework is required, a
conventional riser can be attached to the mandrel 46 to permit
rework tools to be lowered through the production tree 58 into the
well. If for any reason it is necessary to replace or repair the
production tree or any of the related valves or controls within the
module 26, the multiple diverter assembly 100 can be lowered into
position and stabbed into the top of the module 26. The plugs are
then removed from the nipples 98 and 99 and plugs are set in the
nipples 64 within the template frame 10 below the connector ring
22, and the tubing within the well is plugged below the mandrel 54.
The entire module 26 can then be detached at the connectors mounted
in the rings 22 and the wellhead connector 56, and the module 26
then can be pulled to the surface.
One of the significant features of this arrangement is that the
well and all associated flow lines and service lines can be sealed
off by removable plugs and there is no reliance on
remotely-controlled valves for this purpose. No valves are required
within the template assembly which is permanently mounted on the
floor of the ocean. All valves are mounted within the removable
modules. All terminations of flow lines within the template frame
10 are accessible by wire line tools from the surface without
disconnecting or removing any of the modules. One module can be
removed from the system without affecting the rest of the system in
any way. All flow lines extending to the various wells remain under
pressure even if one or more of the modules is removed from the
system. There is no dependence on remotely controlled valves which
could be inadvertently operated, permitting any of the flow lines
to be accidentally opened to the sea with the attendant escape of
oil or gas into the environment.
Another feature of the present invention is that each module is
fully enclosed, except that sea water may be permitted to enter
from the bottom to fill the space within the module. A plurality of
vertically spaced sensors 130 are mounted in the wall of the module
enclosure for sensing the presence of saltwater within the module.
If there is any leakage of oil or gas within the module, it will
displace the saltwater at the top, forcing the level of the
saltwater downwardly. The sensing elements 130 provide a means of
remotely monitoring any leakage, permitting remedial action to be
taken whenever any leak in the system develops. The sensors may be
a pair of spaced electrical terminals which are effectively shorted
out by the saltwater which is a good conductor of electricity. When
the saltwater is displaced by oil or gas, the resistivity of the
gap increases abruptly. This change in resistivity can be sensed by
conventional resistance measuring means.
Referring to FIG. 7, there is shown a typical header module for a
group of five wells. As in the case of the wellhead completion
module, the header module includes a cylindrical outer shell 121
having a truncated conical top 123 and a flat bottom 124. A stab
ring 126 in the bottom of the module engages a mating stab ring 22
in the template frame 10. For a header servicing five wells, for
example, a total of 12 flow lines are connected to the header
module through the stab ring 127. The header is designed to provide
a pair of lines for each well, a flow line and a service line.
The sectional view of FIG. 7 shows the five flow lines from five
different wells coming into the stab ring 22, as indicated at 131,
132, 134, 136, and 138. An output flow line 140 goes to a separator
module. Each of the flow lines is provided with a nipple for
setting a plug, such as indicated at 142, positioned where the flow
line connects to the stab ring 22.
Within the header module, each of the line connections from the
stab ring 126 is connected through a valve, such as indicated at
144, into a standard diverter 146. One branch of the diverter 146
is connected by a section of tubing 148 through a plug nipple 150
to a connector element in an upper stab connector ring 152. Each of
the tubing sections 148 may include a hydraulically operated valve,
such as indicated at 154. A mandrel 156 is provided for attaching
the multiple diverter to the top of the module. However, the
mandrel, as shown, does not provide for connection to any internal
part of the header module, but may be used for this purpose.
The diverters on each of five incoming flow lines from the
respective wells are connected by tubing loops, such as indicated
at 158, to the outgoing flow line through a group of
series-connected diverters 160. These loops permit a pigging tool
to be forced through the header from the line 140 and diverted to
any one of the five wells serviced by the header. The header module
can be provided with sensors, such as indicated at 162, for sensing
the level of saltwater within the module. Both the upper and lower
stab rings provide connections for all electricl and hydraulic
lines to operate the valves and to operate the connector to release
the connection between the module and the template frame.
The power modules and separator modules are similarly arranged with
suitable stab connectors at both the bottom and the top of the
module enclosures, permitting a multiple diverter 100 to be
attached to the top of the module and permitting wire line tools to
set plugs through the module into the flow lines below the module.
The design of such hydraulic power equipment and oil, gas, and
water separators is well known and forms no part of the present
invention. Therefore detailed description of these modules is not
believed necessary to teach the invention.
All the components required to implement the invention as thus far
described are conventional components presently available on the
market, with the exception of the multiple diverter. The standard
hydraulically operated diverters, stab rings, valves, plugs, etc.,
are of conventional design.
A suitable design for a hydraulically operated multiline diverter
is shown in FIGS. 8, 9, and 10. As shown in FIG. 8, the mandrel 108
at its lower end is provided with a flange 164 which is bolted or
otherwise secured to a collar 166 at the upper end of the conical
frame 106. The mandrel 108 has a counterbore 168 which receives the
upper end of the tubing section 114, the tubing being rotatable
within the bore 168 and being provided with suitable rotary seals
to withstand full tubing pressure.
The tubing 114 is curved so that the lower end of the tubing is
offset from the central axis of rotation of the upper end of the
tubing 114. As pointed out above, the tubing 114 provides a
rotating assembly which includes a rotating plate 120 that slidably
engages the mating base plate 104. The rotating assembly includes a
frame plate 170 which is secured at its lower end to the rotary
plate 120 and which is welded or otherwise secured to the length of
tubing 114 to provide rigidity to the assembly. Rotation of the
plate 120 about the central axis of revolution moves the connector
assembly 118 through 360.degree.. The hydraulic actuator 122,
hereinafter described in detail, applies rotary motion to the plate
120 so as to position the connector 118 in alignment with any one
of a plurality of tubing sections 110 attached to the plate 104 at
angularly spaced positions.
Details of a suitable hydraulic actuator for the multiple diverter
is shown in FIGS. 9 and 10. The actuator includes a shaft 172
terminating in an upper cap 174 which may, for example, be
hexagonal in shape or have some other non-circular shape by which
it is keyed in a corresponding opening in the rotating plate 120.
The shaft 172 extends through a central opening 176 in the fixed
base 104. Journaled on the outside of the shaft 172 is a rotatable
collar 178 which extends between the bottom of the base 104 and a
retaining washer 180 secured to the lower end of the shaft 172 by a
nut 182. An overrunning clutch assembly, indicated generally at
184, concentrically positioned between the inside of the collar 178
and the shaft 172, permits torque to be transmitted in only one
direction of rotation of the collar 178 to the shaft 172. Angular
rotation is imparted to the collar 178 through a pair of downwardly
projecting pins 186 which engage a hydraulic actuator assembly,
indicated generally at 188 supported below the end of the shaft 172
from the frame base 104 by a housing 190.
The hydraulic actuator assembly 188 includes a pair of double-ended
piston assemblies 192 and 194. Each of these double-ended piston
assemblies includes a central yoke element 196 which slidably
engages one of the associated pins 186, whereby reciprocal motion
of the double-ended piston assemblies moves the pins 186 in a
direction to impart rotation to the associated collar 178. Each end
of each double-ended piston assembly terminates in a piston, as
indicated at 198 and 200, that extends into a telescoping cylinder
including a cylinder head 202 and telescoping cylinder element 204.
By this arrangement, fluid under pressure admitted to either end of
the double-ended piston moves the piston laterally and moves the
pin 186 through sufficient distance to impart a 90 degree increment
of rotation to the collar 178. As indicated by the dotted line 206,
a stop element may be provided on the inside of the cylinder head
for limiting the stroke of the double-ended piston to provide for
limited angular rotation of the collar 178. For example, angular
rotation might be limited to 45.degree. where the multiple diverter
is to be moved through eight angular diverter positions. The
overrunning clutch 184 insures that with each reciprocal stroke of
the double-ended pistons, the shaft 172 is advanced angularly in
one direction through whatever angle of rotation is provided by the
maximum length of stroke of the actuator pistons.
FIG. 11 shows the connector assembly 118 for providing a
fluid-tight connection between the rotating tubing section 114 and
any one of the plurality of tube sections 110 extending below the
base 104. The connector assembly 118 includes a housing 210 which
threadably engages a counterbore opening 212 in the moving plate
120. A nipple 214 slidably engages an internal bore 216 in the
lower end of the housing 210. The upper end of the nipple 214
slidably engages a bore 218 in a coupling member 220, the upper end
of which is joined to the tube section 114 and which is threaded
into the member 210. A piston 222 integral with the nipple 214
slides within an enlarged cylindrical portion 224 within the
coupling member 220. As shown in FIG. 11, the nipple 214, when in
its lower or extended position, has the lower end 226 seated in a
bore 227 in a connector element 228. The connector element 228 is
threadably secured to the base 104 and provides a coupling to the
tubing section 110 by means of a coupling assembly 229.
A hydraulic fitting 230 admits fluid under pressure into an annular
chamber 232 through which fluid is admitted to the region below the
piston 222 at 233. Thus fluid pressure admitted through the
coupling 230 forces the piston 222 and associated nipple 214
upwardly, withdrawing the lower end 226 from its seating position
in the connector element 228. When the nipple 214 is fully
retracted, the movable plate 120 is free to be rotated relative to
the base 104 by the hydraulic motor 122 to the next line connector
position in the base 104.
A second hydraulic fitting 234 admits fluid under pressure into an
annular chamber 236 into the region above the piston 222. Thus
fluid under pressure through the fitting 234 pushes the piston 222
and associated nipple 214 downwardly into position to engage the
connector element 228. The internal bore 227 of the connector
element 228 is tapered, as indicated at 238, as is the outer lower
surface of the nipple 214, as indicated at 240. This permits the
nipple 214 to stab into the connector element 228 even though there
is slight misalignment between the nipple 214 and the connector
element 228.
FIG. 12 shows the hydraulic arrangement for operating the multiline
diverter assembly 100. An advancing cycle is initiated by applying
fluid under pressure to a hydraulic line 242 which goes to the
fitting 230 on the connector assembly 118. This causes the nipple
214 to be retracted from the connector element 228. The line 242 is
also connected through a pressure-operated valve 244 to one side of
the double-ended pistons in the actuator assembly 188. When the
pressure in the line 242 builds up to a predetermined level, it
opens the valve 244, permitting one side of the double-ended
pistons of the actuator 188 to move in a direction to advance the
rotating plate 120 and position the connector assembly 118 opposite
the next connector position on the base 104. Hydraulic pressure is
then switched to a hydraulic line 246 connected to the hydraulic
fitting 234, admitting fluid under pressure to the back side of the
piston 222 and advancing the nipple 214 to engage the associated
connector element 228 at the new connector position. A
pressure-operated valve 248 then admits fluid under pressure from
the line 246 to the other end of the double-ended pistons of the
actuator assembly 188 to reset the actuator and complete the
indexing cycle. Thus it will be seen that each cycle causes the
nipple to be retracted, the diverter to be advanced to the next
connector position, the nipple to be set to provide a sealed
connection, and the actuator to be reset.
From the above description it will be seen that the present
invention provides an apparatus by which a group of subsea wells
can be completed and serviced entirely from the surface of the sea
by having all wellhead equipment mounted in modules which can be
positioned or replaced on the top of each wellhead using surface
equipment. One of the significant features of the invention is the
ability to enter the wellhead or the flow lines connected to the
module from the surface through the module itself without removal
of the module. This arrangement permits plugs to be set or removed
by wireline tools or by pump-down tools from the surface after the
modules are in position. The multi-position diverter which can be
secured to the top of a module by stab connections permits any one
of the flow lines to be entered by a wireline or pump-down tool
from the surface through a common riser.
* * * * *