Note: Descriptions are shown in the official language in which they were submitted.
~ 73~
UNDERWATER C~IST~S TREE CAP AND
LOCKDOWN APPARATUS
Technical Field
The present invention relates generally to underwater well-
head caps and connectors, and more particularly to a cap for an
underwater Christmas tree for capping the Christmas tree and for
locking down the connector which secures the Christmas tree to an
underwater wellhead housing.
Back~round Art
Various connectors have been employed in the past for con-
necting an underwater Christmas tree to an underwater wellh~ad
housing. One such device includes radially slidable locking dogs
circumferentially disposed in the tubular base of the Christmas
tree for engagement with the top of the wellhead housing. The
locking dogs are radially outwardly spring biased and are a~tu-
ated by an annular sleeve disposed around the locking dogs. The
sleeve has an interior tapered surface for engaging a correla-
tively tapered exterior surface of the locking dogs such that
upward movement of the sleeve permits the dogs to move further
radially outward by spring action out of engageme~t with the
wellhead housing, and downward movement o the sleeve wedges the
dogs further radially inward into engagement with the wellhead
housing.
Such connectors were often actuated hydraulically. However,
the maintenance of hydraulic actuators over prol~nged periods o~
time was uncertain and unreliable due to adverse environmental
conditions. A premature release of the Christma~ tree would be a
severe problem. Hydraulic connectors have in some cases bee~ re-
placed by mechanical operators. Such an operator can include
operating rods connected to and extending upwardly from the
- sleeve for actuating the sleeve. Pulling upward on the rods
pulls the sleeve upward with it to release the dogs, and pushing
downward on the rods pushes the sleeve downward with it ko actu-
ate the dogs.
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~7~?~ ~
Hydraulically'actuated devices"connected to the operating
rod have generally been used for actuating the rods and, hence,
the sleeve and locking dogs. Such devices remain on the rods at
the ocean floor and are subject to the same adverse environmental
conditions, such as the corrosive actlon of:salt or other miner-
als, as the hydraulic connectors, whi~h sometimes render them
inoperable. As a result, removal o the tree from the well, e.g.
for repairs to the tree or to the well, can become difficult or
impossible without costly and sometimes dangerous repairs.
To eliminate the problems associated with use of such hydrau-
lically actuated devices, the rods have sometimes been provided
with mechanical means, such as an annular notch in the rod, to
which a tool lowered from the surface can attach for securely
gripping the rod so that it can be pulled upward by the tool to
allow the dogs to be released from engagement with the wellhead
housing. Such a tool 'also is used to push the rods downward to
connect the tree to the wellhead housing.
A problem exists with use of such mechanical means on the
rods for actuating the rods. Due to jarring from production or
other operati~ns, or to environmental conditions such as currents
or thermal cycles, there is a tendency of the rods to creep
upward, thereby loosening the connection between the Christmas
tree and the wellhead housing and possibly allowin~ premature
release of the tree from the wellhead housing. It is necessary,
therefore, to keep the rods from moving upward so that the con-
nection between the Christmas tree and the wellhead housing
remains tight. Furthermore, the connection'of the tree to the
wellhead housing is generally undertaken remote from observers ox
operators, with relatively large tolerances for the interconnect-
ing parts, and under adverse environmental conditions. As a
result, there is an uncertainty as to the exact vertical position
of the rods after connection of the tree to the wellhead housing
is complete, making the locking down of the rods more difficult.
t `~ t~
The rods must be locked down at whatever vertical position
they are in after connection of the tree to the wellhead hous-
ing has ~een completed.
Other objects and advantages of the invention will
appear from the following description.
Summary of the Invention
One aspect of the present invention provides an
apparatus for an actuator which actuates a connector for
connecting one end of a tubular member to an underwater well-
head, comprising: mechanical means for mechanically maintain-
ing the actuator in the actuated position to insure the
connection of the tubular member to the wellhead, said
mechanical means including extension means for extending into
engagement with said actuator to prevent said actuator from
moving to a nonactuated position, said extension means includ-
ing a piston slidably disposed within a cylinder and activation
means for extending said piston from said cylinder whereby
said piston engages the actuator preventing the actuator from
moving to a non-actuated position.
Another aspect of this invention provides an under-
water well apparatus for connection of flowlines to an under-
water wellhead, comprising: a tubular member adapted for
connection with the flowlines; connection means for connecting
one end of said tubular member to the wellhead; an actuator
for actuating said connection means by moving from a non-
actuated position to an actuated position; and mechanical
means for mechanically maintaining said actuator in said
actuated position to insure the connection of said tubular
member to said wellhead, said mechanical means being mounted
on the other end of said tubular member and including a
plurality of probes for engagement with said actuator.
~3-
According to another aspect of the present invention,
there is provided a cap for an underwater Christmas tree
releasably connected to an underwater wellhead housing by a
mechanical connector, such mechanical connector having an
operating rod mechanically movable between a first position
actuating the connector and a second position releasing the
connector, comprising: a body; means disposed on said body
for attaching said body to the top of such Christmas tree;
engagement means depending from said body for engaging such
rod when such rod is in such first position; and locking
means carried by said engagement means for locking said
engagement means in engaged position and preventing such rod
from moving from such first position to such second position.
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- Brief Descri~tion~of the Drawings
For a further understanding of the nature and objects o~ the
present invention, reference should be had to the following
detailed description, taken in conjunction with the accompanying
drawings, in which like parts are given like reference numerals
and wherein: -
~
Eigure 1 is a~ elevation, partially schematic, illus-
trating underwater wellh~ad apparatus including a Christmas
tree, with the tree cap of the present invention being
lowered by its running tool into place on top of the Christ-
mas tree;
Figure 2A is a view, partially in section and partially
in elevation, o~ the wye spool portion of the Christmas tree
of Figure 1 and the interface frame and canisters attached
thereto in which are housed the tops of the rods which
operate the mechanical connector at the tree base;
Figure 2B is a view, partially in section and partially
in elevation, of the mechanical connector and associated
operating rods which connects the Christmas tree at its base
to the ~nderwater wellhead housing;
: Figure 3 is a view, partially in section and partially
in elevation and with some parts broken away, of the tree
: cap of the present invention prior to its installation on
top of the Christmas tree;
Figure 4 is a transverse sectional view of one of the
locking probes of the txee cap of the present invention,
taken along section lines 4-4 of Figure 3;
Figure 5 is a longitudinal sectional view of one of the
locking probes of the tree cap o the present invention
disposed in a canister along with one of the mechanical
connector operating rods prior to actuation of the piston of
the lockin~ probe, the section of the locking probe being
taken along lines 5-5 of Figure 4;
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~7~
Figure 5A is a longitudinàl sectional view similar to
Figure 5 illustrating the piston of the locking probe of the
tree cap of the present invention abutting the top of the
mechanical connector operating rod after actuation of the
piston;
Figure 6 is a view, partially in longitudinal section
and partially in elevation, of one of the locking probes of
the tree cap of the present invention disposed in a canister
along with one of the mechanical connector operating rods
prior to actuation of the piston of the locking probe, with
a section of the locking probe being taken along lines 6-6
of Figure 4 to show one of the dog segments carried by the
piston; and,
Figure 6A is a view, partially in longi~udinal section
and partially in elevation, similar to Eigure 6 illustrating
the position of the piston and dog segments after actuation -
of the piston.
Description of the Preferred Embodiment
Referring initially to Figure 1, there is s~own generally a~
l apparatus comprising~a portion of an underwater wellhead which
is typically disposed at or near the bottom of a body of water
for use in production of oil and gas from benea~h such body o~
water. Underwater wellhead apparatus 1 includes an outer, large
diameter tubular wellhead housing 3 within which are disposed
. ~
inner, progressively smaller diameter tubular wellhead housings
such as those shown at 5, 7. The inside diameter of the outer
housing 3 may be 30 inches, for example, an~ the inside diameters
of the inner housings 5, 7 may be, for example, 20 inches and
13-5/8 inches, respectively. Production casing and other tubing
strings may extend from or through these wellhead housings into
the floor of the body of water and down into the well bore to the
zones from which the oil and gas are produced.
-5-
Wellhead housing 5 is provided with a ribbed portion 9 on
its outer surface near its upper end, includi~g annular no-lead
(i.e., substantially zero pitch) ribs 10 and grooves 12 there-
between, adapted for mating interconnection with other wellhead
e~uipment carrying corresponding interfitting grooves and ribs.
Ribs 10 are substantially of the same outside diameter as the
portions of wellhead housing 5 adjacent to the ribbed portion 9.
Wellhead housing 7 is similarly provided with a ribbed portion
(not shown) on its outer surface near its upper end.
Underwater wellhead apparatus 1 also includes a Christmas
tree, indicated generally at 11, which is attached at its base t~
the top of wellhead housing 7 by a mechanical connector, indi-
cated generally at 13. Mechanical connector 13 and its operating
rods are shown in greater detail in Figures 2A and 2B. The upper
portion o Christmas tree 11 includes a wye spool 15 havin~ a
vertical bore in communication with the well bore for providing
access-to the well from the surface, for example, for installing
and retrieving wireline tools, and a side bore disposed at an
angle to and in communication with the vertical bore to which
tubular flow~loops 17 are connected and through which flows the
oil and/or gas produced from the well. Flow loops 17 may be
connected through various flow control devices and systems, not
shown, such as choke nipples, to flowline hub 19. Oil and~or gas
produced from the underwater well is carried through ~he flow
loops 17 to flowline hub 19, from which it can be transported
immediately to the surace of the body of water or to some other
location or gathering or storage with oil and/or gas from other
wells, for eventual transportation to the surface.
The outside surface of the upper portion of wye spool 15 is
provided with a plurality of annular ribs 21 and grooves 23
therebetween, comprising substantially no-lead threads adapted
for mating interconnection with interfitting grooves and ribs
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~.~'7;~ 4~
disposed on the tree cap of the present invention, indicated
generally at 25.
T-ee cap 25 of the present invention is shown in Figure 1
being lowered into place on the top of Christmas tree 11, carried
by its running tool 27 attached to drill pipe 29. Tree cap
running tool 27 includes guide sleeves 31 attached to a guide
~rame 28 having upper and lower struts 33, 35, respectively.
Guide lines 37 run through guide sleeves 31, are attached to
guide posts 39 at the wellhead and extend to the platform or
vessel at the surface of the body of water to provide guidance
for the transporation of tools and eguipment back and forth
between such surface and the wellhead. Tree cap running tool 27
also includes a landing sleeve 41 which telescopically receives a
landing post 43 connected to tree 11 when running tool 27 lands
at the wellhead in order to aid in proper alignment of tree cap
25 with respect to tree 11 during installation o~ the cap on top
of the tree.
The Christmas tree 11 shown in Figure 1 is of a type used
with an underwater manifold center. Several wells are typically
located around the manifold center. The wells are drilled into
the floor of the body o water through the manifold center, and
the Christmas trees are set in place on the wells around it. The
Christmas trees are all connected into the manifold center. A
manifold tree as is shown in Figure 1 will typically have a wye
spool, e.g., as shown at 15, as its top member. ~ satellite
tree, i.e., one that sits off by itself on the floor o~ the body
of water, will typically have additional valves on top of the wye
spool, with a member known as a mandrel as its top mem~er. It
should be un~erstood, however, that use of the tree cap of the
present invention is not limited to manifold trees; the tree cap
of the present invention can be used with any type of tree having
a top member, be it a wye spool, mandrel or some other member, to
which the tree cap can attach.
.
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3~
: Referring now to Eigure 2B, there are shown the mechanical
connector 13 and rods 45 which operate the mechanical connector,
The mechanical connector 13 connects Christmas tree 11 to the top
of wellhead housing 7. The base 47 of Christmas tree 11 includes
an upper cylindrical member 49 having an upper portion 51 and a
lower portion 52 with portion 52 having an outside diameter
greater than portion 51. Between upper portion 51 and lower
~ortion 52, there is an annular flange 53 forming shoulder 55.
Lower portion 52 has a cen~ral bore 57 in communication and
coaxial with an upper reduced diame~er bore in upper portion Sl.
Base 47 of Christmas tree 11 also includes.a lower member 59
having an upper cylindrical portion 58, a frustoconical portion
63 below upper portion 58, intermediate and lower portions 65, 67
below frustoconical portion 63, and a frustoconical portion 71
below portion 67. An annular shoulder 69 is formed between
portions 65, 67, and ~n annular shoulder 73 is formed between.
portions 67, 71. Upper portion 58, frustoconical portion 63,
intermediate and lower portions 65, 67, and frustoconical portion
71 have a common central bore 75 therethrough, which is coaxial
with ~ore 57~of upper:member 49. Frustoconical portion 71 in-
cludes a conical shoulder 77 at its lower end extending to the
bottom of base 47.
Base 47 of Christmas tree 11 also includes a set o~ circum-
ferentially disposed dog segments 79 housed in a recess between
upper and lower members 49, 59. Dog segments 79 have annular
ribs 81 and grooves 83 therebetween on their inner faces for
mating interconnection with interfitting ribs and grooves on the
outside surface of wellhead housing 7. Dog segments 79 each have
a pair of transverse blind passages 84 on each side in communica-
tion with and coaxially aligned with corresponding blind passages
.on the adjacent dog segments, and in which are disposed a pair of
coil springs 85 maintained in compression. Springs 85 exert a
force normal to the adjacent surfaces of the dog segments, which
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'2 ~''`J ~
lie in radial planes, and tend to force the dog segments radially
outward. The outer surface 87 of the dog segments 79 is frusto-
conical in configuration, tapering outwardly from the top o the
dog segments downward.
Mechanical connector 13 includes a cylindrical body 89 with
an annular, outwardly extending flange 91 at its upper end. The
upper outside surface of flange 91 is beveled, at 93.
Cylindrical body 89 has a lower central bore 45 extending
from the lower end 97 of body 89 to bore 99. Bore 99 extends
from bore 95 to bore 101. Bores 99 and 101 form annular shoulder
105. Bore 101 is of larger diameter than the outside diameter of
upper portion 51 of member 49 of tree base 47. The outside
diameter of flange 53 is substantially the same as the diameter
of bore 99 to provide a mating fit. The distance between annular
shoulder 105 and the lower end 97 of body 89 is substantially the
same as the distance between annular shoulders 55, 69 of tree
base 47. Annular shoulder 105 of mechanical connector body 89
rests on shoulder 55 of tree base 47, and end 97 of body 89 rests
on annular shoulder 69 o tree base 47. Body 89 of mechanical
connector 13 is secured to tree base 47 by bolts 107 which extend
through cylindrical portion 67 of tree base 47 and are threaded
into body 89 of mechanical connector 13.
At each of three equally circumferentially spaced apart
locations around the interior surface of bore 9S of body 89,
there is a longitudinal, semicircular-shaped groove or channel
109 extending the length of bore 95. At each of such three
locations, holes 111 extend from the top of body 89 into channels
109. Holes 111 receive the lower portions 115 of operating rods
45 for insertion into channels 109. A seal plate 117 is mounted
on top of flange 91 around each of the three mechanical connector
operating rods 45, by bolts 119. A seal ring 121 is mounted
within an annular groove around the inner face of seal plate 117
for sealingly engaging the operating rods 45 to prevent corrosive
sea water or other f' ids from entering channels 109 and bore 95.
,
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The lower portion 115 of rod 45-has a threaded bottom end
123 for threadedly engaging an annular sleeve 125 mounted in ~ore
95. Sleeve 125 has three radially outwardly extendin~, semicir-
cular-shaped projections 127 at the circumferential positions
corresponding to longitudinal channels 109. The outer surface of
sleeve 125 b~tween projections 127 is of generally circular
cylindrical configuration. Sieeve 125 has a frustoconical inner
surface 129 correlatively shaped, i.e. having the same taper, to
.hat of frustoconical sur~ace 87 o~ dog segments 79. Surface 129
tapers outwardly from the top of sleeve 125 downward. Inner
surface 129 of sleeve 125 bears upon and is slidably mova~le
across surface 87 of dog segments 79. When rods 45 are m~ved
upward, sleeve 125 attached thereto also moves upward in bore 95,
projections 127 being disposed in channels 109, such that the
larger inner diameter portions of surface 129 bear upon the d~
segments 79, thereby allowing the springs 85 disposed be~wee~
each pair of dog segments to force the dog segments further
radially outward. When rods 45 are moved downward, sleeve 125
also moves downward within bore 95 and wedges the dog sesments
further radially inward, the smaller inner diameter portions o~
sur ace 129 being made to bear upon the dog segments. T~us, by
moving rods 45 up or down, sleeve 125 connected to the ~ods also
moves up or down, respectively, along with the rods, thereby
actuating the dog segments 79 and allowing do~ segments 79 to
move radially outward by spring action or forcing the dog seg-
ments to move radially inward, respectively.
Referring to Figure 2A, an interface frame indicated gener-
ally at 131 is shown disposed on wye spool 15 of Christmas tree
11. Interface frame 131 includes a ~lange plate 135 of ~enerally
triangular configuration with a central opening therein for
receiving the body of wye spool 15 Flange plate 135 is rigidly
attached to wye spool 15, as by welding. Elange plate 135 has
three holes 137 therethrough, one hole at each of its corners, in
-10-- .
~ ~'73~Z
each of which is disposed the top of a hollow cylindrical cani-
ster 133. Canisters i33 are attached to flange plate 135 at
holes 137, as by welding. Canisters 133 each hav~ a lower cylin-
drical bore 139 extending along a large portion of their length,
above which bore 139 is cylindrical counterbore 143 which creates
a frustoconical shoulder 145 therebetween. At the upper end of
counterbore 143 of each of canisters 133 there is a frustoconical
shoulder 147. An annular end plate 149 is disposed in a groove
151 around the lower inner periphery of each of canisters 133 and
is attached to the canisters, as by welding. End plate 149 has a
central opening 153 therethrough. A downwardly extending collar
155 is attached to the lower surface of each of the end plates
149. Collars 155 each have a bore 157 therethrough which bore is
coaxial with and smaller than the opening 153 in end plate l~9.
The upper end 159 of rod 45 extends through bore 1~7 and
opening 153 and is di~posed within bore 139 of canisters 133.
Near the top end 161 of rod 45 there is a circumferentially
extending annular notch or groove 163 in the rod.
A generally rectangular plate 165 is attached to one of the
canisters 133 by bolts 169 through a flange 167 at one end of
plate 165. The other end of plate 165 is attached, as ~y bolts
through a flange at the other end of the plate, to landing post
43 (Figure 1).
Canisters 133 house the tops of the rods 45, and act as
guides to keep the rods vertically aligned; that is, canisters
133 prevent the rods 45 from bending or from becoming vertically
misaligned, as such bending or misali~nment would render engage-
ment for attachment or removal of tree ll to or from wellhead
housing 7 very difficult, if not impossible, from a remote loca-
tion.
When it is desired to attach Christmas tree 11 t~ wellhead
housing 7, the tree is affixed to a tree running tool (not shown)
and lowered to the wellhead from the surface of the water or
~ .~, '73~:2
other location. In running position, the rods 45 are held in
their uppermost position such that sleeve 125 will allow do~
segments 79 to spread radially outward by spring action a suffi-
cient distance to allow them to clear the ribs on top of the
wellhead housing when the tree is lowered onto the wellhead
housing, the top of the wellhead-housing being then telescopic-
ally received within the bores 75, 57 of the tree base 47. When
the tree 11 is seated on top of the wellhead housing 7, the ribs
and grooves 81, ~3 of dog segments 79 are disposed opposite
interfitting grooves and ribs on the outer surface of the well-
head housing 7. The tree running tool then actuates the rods 45
by pushing them downward, typically by hydraulic power, thereby
pushing sleeve 125 down over dog segments 79 and forcing them
radially inward such that the ribs 81 on the dog segme~ts 79 mate
with the grooves on the upper end of the wellhead hous~g 7, and
the ribs on the wellhead housing mate with the grooves on the dog
segments. The tree running tool may then be removed to the
surface of the water or elsewhere away from the tree, leaving the
tree connected to the wellhead housing.
SinCe under normal circumstances the above tree connection
operation is undertaken remote from observers or operators, and
because of the large tolerances involved and the adver~e environ-
mental conditions such as corrosive action under which ~he opera-
tion occurs, there is an uncertainty as to the exact vertical
position of the upper terminal ends 161 of rods 45 after they are
pushed down and connection of the tree ll to the wellhead housing
7 has been accomplished. The rods all may be at one unknown
vertical position, or they may each be at a different ~ertical
position due to skewing of sleeve 125. For example, upper end
161 of rod 45 could be at the vertical position 162 sh~wn in
phantom outline in Figure 2A, or at the position s~own in ele-
vation or anywhere in between. Furthermore, there is a tendency
of sleeve 125 to become loose due to jarring from production or
.
-12-
~ ~'73~7~Z
other operations or from the adverse environmental ronditions,
e.g. currents, in which the tree operates. The tree cap of the
present invention overcomes these problems by providing a posi-
tive lockdown for the operating rods at whateve-r vertical posi-
tion they occupy after connection of the tree 11 to the wellhead
housing 7 is complete, thereby preventing the sleeve from being
shaXen loose to weaken the connection of the tree to the wellhead
housing.
When it is desired to remove the Christmas tree from the
wellhead, e.g., for repairs or if the well is to be shut down,
the tree cap of the present invention iæ removed from the top of
the tree and the tree running tool is lowered to the tree.
Grasping probes of the tree running tool are inserted in~o the
tops of the canis~ters 133 and feel for and ~rip or attach them-
selves to the rods 45 at the notches 163. The rods are then
pulled up by the tree-running tool, typically hydraulically,
~which pulls up the sleeve 125 and releases the dog segments from
mating interconnection with the wellhead housing and thereby
releases the Christmas tree. The tree may then be remo~ed from
the wellhead.
Referring now to F~gure 3, the tree cap 25 of the present
invention includes a cam ring 201, a body 203, a base plate 205
~and locking probes 207. Cam ring 201 has a lower internal frus-
toconical bore 209 and an upper cylindrical counterbore 215
creating shoulder 213 An 0-ring type seal 233 is disposed in an
inner annular groove 235 in bore 209 of cam ring 201. The out-
side surface o~ cam ring 201 is generally cylindrical having an
annular flange 221 around its mid-portion. Below flange 221 of
cam ring 201, there is a reduced diameter cylindrical portion 227
ha~ing a shallow annular channel 223 creating annular shoulder
225 and annular shoulder 229. Cam ring 201 has a lower frusto-
conical outer surface 231 extending ~rom the bottom o~ cylindri-
cal portion 227 to lower end 211 of cam ring 201.
~' .
-13-
737~
Body 203 of tree cap 25 comprises a generally hollow ma-
chined forging ha~ing a cylindrical 1ange plate 237 at its top
with a chamfered upper annular corner 241. Flange plate 237 has
a bore 243 to receive a plate 245 secured to body 203 by bolts
247. The plate 245 has a central opening therethrough to receive
a non-return valve 249. Body 203 includes a cylindrical neck 251
below flange plate 237, neck 251 having a central bore 252 there-
through in communication with the opening in plate 245 and through
which non-return valve 249 extends. Below neck 251, b~dy 203 has
a frustoconical portion 253 with a central bore 2~4 in its upper
portion coaxial with the bore 252 in neck 251 and through which
non-return valve 249 also extends. The lower portion of frus-
toconical portion 253 has an internal blind bore 255 creating
cavity 256. Below frustoconical portion 253 of body 203, body
203 has a second frustoconical portion 257 having less of a taper
than frustoconical portion 253. Erustoconical portion 257 has an
internal bore 259 creating a cavity 261 therewi~hin. Body 203 o~
tree cap 25 includes a hollow cylindrical portion 263 below
frustoconical portion 257, with an outwardly extendin~ annular
flange 265 being disposed around the lower end of cylindrical
portion 263. Cylindrical portion 263 of body 203 has an internal
bore 267 continuous with bore 259 of frustoconical p~rtion ~57.
A shoulder 269 extends from the lower end of bor~ 267 to the
bottom end 271 OI body 203. The bottom end 271 of body 203 is
disposed on the upper surface of base plate 205. Body 203 is
secured to base plate 205, as by welding.
A stainless steel AX-type ring gasket 273, which may be, for
example, eleven inches in diameter, is held in place with the
side of its upper lip against the sides of bore 255 by a set of
four retaining bolts 275. Bolts 275 are threadedly disposed in
- passages extending throu~h the wall of body 203, and engage the
upper lip of gasket 273 such that a small degree of free movement
of the gasket 273 is allowed.
~.
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73~
Six dog sesments 277 of generally rectangular shape are
equally circumferentially spaced apart and disposed in correla~
tively shaped openings in the wall of frustoconical portion 257
of body 203. Dog segments 277 have ribs 279 and grooves 2el
therebetween on their inner faces which are adapted to mate with
interfitting grooves 23 and ribs 21 on the top of wye spool 15.
Springs 283 disposed in blind channels in the sides of dog seg-
ments 277 exert a force normal to the adjacent radial-plane
surface of the body 203 and tend to force dog segments 277 radi-
ally outward. The outside surface 285 of dog segments 277 is
tapered correlatively to internal bore 209 of cam ring 201.
The internally tapered surface 209 of cam rin~ 201 bears
upon the outside surfaces 285 of dog segments 277. When cam ring
201 is moved downward over the body 203, the dog sesments 277 are
wedged further radially inward due to the direction of taper of
surface 209. When cam ring 201 is moved upward, the dog segments
277 are allowed to move further radially outward by spring action.
Thus, operation of dog segments 277 with respect to mov~ment of
cam ring 201 up or down over them i5 like the operation o~ dog
segments 79. of mechanical connector 13 with respect to movement
of sleeve 125 up or down over them.
An O-ring type seal 287 is disposed in an annular groo~e
around the outside surface of frustoconical portion 257 of body
203, below dog segments 277. O-ring seal 287 is like O-ring seal
233.
Base plate 205 of tree cap 25 is generally triangular in
configuration with a central opening therein in communication
with and coaxial with cavity 261 of body 203. At each of the
three corners of base plate 205, there is a hole through the
plate below which and coaxial with which are attached three
locking probes 207. Locking probes 207 are each secured to the
base plate 205 by six bolts 289. On one side of base plate 205,
a vertically extending locating pin 291 is mounted on pin base
Z93, which is secured to the plate 205 by bolts 295.
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~ ~ 73 ~ 2
A plurality of U-pipe assemblies 297 are disposed o~ base
plate 205 around the base of flange 265 of body 203. U-~ipe
assemblies 297 are disposed in openings through the base plate
205 and are secured to the base plate 205 by a retainer plate 299
bolted to the underside of base plate 205. -Each end o each
U-pipe is provided with the female half of a self-sealing Aero-
~uip type coupling therewithin. Typically, fifteen U-pipe assem-
blies 297 are provided for tree cap 25. When the tree cap 25 is
installed on top of tree ll, the female halves of the Aeroquip
couplings mate with male halves of Aeroquip couplings disposed in
pipes located on the tree 11 to form sealed connections for
tubing leading to well control apparatus, such as valve actua-
tors, used in controlling production from the well. As the
Aeroquip couplings on the U-pipes contact their corresponding
male halves on the tree, check valves within the couplings are
automatically unseated and Conoseal-type metal gaskets are aner-
glzed-to seal against leakage to the environment. If a blanking
rather than a coupling function is required at any o~ the loca-
tions of U-pipe assemblies 297, the pipes of such assemblies are
provided wit~ blanks rather than Aeroquip couplings.
When it is desired to attach tree cap 25 to the Christmas
tree 11, cap 25 is secured to its running tool 27 and lowered to
the tree on drill pipe 29. Locating pin 291 is telescopically
received in a s~eeve on the running tool 27 to assure that the
cap 25 is not attached to its running tool in an incorrect posi-
tion. When the cap 25 is being lowered to the tree, ~am ring 201
is held in a raised or running position by three shear pins 301
inserted through transverse passages in frustoconical surface 231
of cam ring 201 and into blind passages 303 in the upper exterior
surface 2~5 of three of the dog segments 277, e.~., a shear pin
is disposed in every other one of the six dog segments.
When the tree cap is landed on top of the tree, the locking
probes 207 are telescopically received in canisters 133, shown in
16-
3~
Figure 5A, attached to wye spool 15, and the upper end of wye
spool 15 is telescopical~y received in the cavity 261 of body 203
of cap 25. The U-pipe assemb~ies with their female halves o~ the
Aeroquip couplings mate with the male halves of such couplings on
the tree. Ribs 279 of dog segments 277 are disposed generally
opposite grooves 23 on wye spool 15, and ribs 21 of wye spool 15
are disposed'generally opposite grooves 281 of dog segments 277.
Cam ring 201 is forced down by the tree cap running t301, typi-
cally by hydraulic power, shearing pins 301 and sliding the
'internally tapered surface 209 of the cam ring 201 downward over
dog segments 277. The ribs ~79 and grooves 281 of dog segments
277 are wedged radially inward into locking interconnection with
the wye spool's grooves 23 and ribs 21. When cam ring 201
reaches the bottom of its travel, seal 233 of cam ring 201 seal-
ingly engages the outer surface of portion 257 of body 203, and
seal 287 of body 203-sealingly engages the inner surface of bore
209 of cam ring 201. Thus, dog segments 277 are seali~gly pro-
tected from adverse environmental conditions, such as the corro-
.
sive action of sea water. When cam ring 201 is forced down overdog segments 277 to lock them to the wye spool, AX-type gasket
seal 273 is made up simultaneously by a camming action associated
with the locking process into metal-to-metal sealin~ engagement
wiih the top of wye spool 15. The camming action results from
the fact that the ribs 279 and grooves 281 of dog segments 277
are in slight vertical misalignment with the grooves 23 and ribs
21 of wye spool 15 prior to actuation of dog segments 277, where-
upon when dog segments 277 are pressed inward into locking ron-
nection with wye spool 15, tree cap 25 is simultaneously forced
downward, providing the force necessary to make up AX-type gasket
seal 273. The cap seals 233, 2R7 are tested by applying ~luid of
5,000 p.s.i. pressure to the cap cavity through non-return valve
24g in the top of body 203, from a surface control panel via the
cap running tool 27. The cap cavity is also monitored through
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~ 7~3~ ~
valve 249 for well fluids leaking past crown plugs, not shown, o
tree 11. Control line seals such as the Conoseal gaskets in the
U-pipe couplings are tested to fluid pressures of 3,000 p.s.i.
from the surface through an electro-hydraulic control module.
Referring to Figure 5, there~is shown one of the locking
probes 207 of tree cap 25 telescopically disposed in one of the
canisters 133 attached to wye spool 15. Figure 5 illustrates the
positions of probe 207, rod 45 and canister 133, after the tree
cap has been landed on top of the tree and the cam ring has been
actuated by the tree cap running tool, locking the cap to the
tree, but prior to removal of the tree cap running tool 27 to the
surface. Locking probe 207 has a generally hollow cylindricaL
body or housing 351 having an upper portion 353 and a lower
reduced diameter portion 355 forming annular shoulder 357.
Housing 351 has a central bore 359 extending the leng~h thereof.
A nose cone 365 o~ generally frustoconical shapç is mounted to
the bottom 363 of housing 351 by bolts 367 threaded into housing
351. Nose cone 365 has an internal bore 375 coaxial with a~d
smaller in diameter than bore 359 of housing 351. At the lower
end 377 o~_nose cone 365 there is a frustoconical shoulder 379.
An annular flange 373 projecting upwardly from cone 365 is slid-
ingly raceived within central bore 359.
The upper counterbore 143 and bore 139 of canister 133 are
dimensioned so as to receive and slidingly engage portions 353,
355 of housing 351 of probe 207. Shoulder 357 of housing 351
rests upon shoulder 145 of canister 133, shoulders 357, 145
providing a limit to downward travel of locking probe 207 within
canister 133.
At the upper end of housing 351, an annular collar 387 is
disposed within bore 359 and is retained therein by sc~ews 389
threadedly disposed in transverse passages 391 through housing
351 and extending into transverse recesses 393 in the peripheral
surface of collar 387. Collar 387 has a central aperture 395
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i3 ~}~
tnerein and upper and lower frustoconic21 shoulders 397, 399,
~,~
respect~vely, which are in communication with and coaxial to hole
431 in base plate 205.
A cylindrical piston 403 is telescopically disposed within
central bore 359 of housing 351. Piston 403 has a lower reduced
diameter portion ~07 forming annular shoulder 409, portion 407
being slidingly received by bore 375 of nose cone 365. The outer
periphery of shoulder 409 is beveled, at 411.
Piston ao3 has an internal central bore 413 and a closure
cap 16 at its bottom forming an inwardly tapering conical sur
ace gl5. Closure cap 416 includes a bleed passage gl7 from the
bottom o~ surface 415 to the lower end 419 of piston 4~3. An
~ular ~lange 421, haviny an internal diameter smaller ~han bore
413, extends inwardly from the upper end of piston 403~
A coil spring 429 is disposed in compression between the
bottom face 431 of collar 387 and the top end 427 of piston 403.
Referring also to Figure 4, transverse passage 433 exte~d~
~ through the upper portion of piston 403. A recess 435 is formed
: in the inside surface of upper portion 353 of housing 3~1. ~
; double-head~d trigger 437 is slideably disposed in passage 433.
: T, isger 437 includes a shaft 439 with blunt head 441 attached to
its inside end and frustoconical head 443 attached to its ou~side
: end. The outer end of head 443 is disposed in recess 435 in the
wall of housing 351.
A cylindrical actuating pin 445 mounted on tree c~p runnin~
tool 27 extends through hole 401 in plate 205, through the cen-
tral aperture 395 in collar 387, through coil spring 429, and is
slidingly rec~i~ed in the aperture in annular flange ~21 of
piston 4~3 for insertion into ~ore 413. Pin 45 has a ~rusto-
conical bottom 446. Upon the insertion of pin 445 into the
aperture in flange 421, the inside end of head 441 of trigger 437
a~uts ~he frustoconical surface 446 of the pi~ 445 camming trig-
ger 437 ou~waxdly into recess 435. With the e~d of head 443 of
, . -19-
trigger 437 disposed in recess 435 in the wall of housing 351 and
the end of head 441 of trigger 437 abutting pin 445, piston 403
is restrained from being forced downward by spring 429.
When pin 445 is withdrawn from the-inside of locking probe
207, i.e., when tree cap running tool~ 27 is removed to the sur~
face, trigger 437 is free to move radially inward. The downward
force exerted on the top of piston 403 by spring 429 is transmit-
ted through the piston body to the frustoconical head 443 of
~rigger 437 and the walls of recess 435. The radial component of
this force causes trigger 437 to slide radially inward in passage
g33, such that head 443 of trigger 437 is cammed out of and
removed from recess 435. ~emoval of head 443 of trigger 437 from
recess 435 eliminates the restraint on downward movement ofi
piston 403, and piston 403 is pushed downward by spring 429 until
the bottom end 419 of piston ~03 abuts the top end 161 of operat-
ing rod 45.
Figure 5A illustrates the positions of piston 403, spring
4~9 and trigger 437 after actuation of piston 403. The bottom
end 419 of piston 403 abuts the top end 161 of rod 45. Spring
429 has been-longitudi~ally extended a distance such that it
maintains its downward force against the top of piston 403.
Spring 429 does not, however, push down on the top of piston ~03
with sufficient force to push rod 45 down any farther than it was
prior to actuation of piston 403. Trigger 437 is prevented from
being completely expelled radially into the bore of piston 403 by
a retaining screw 447 which is threadedly disposed in a longitu-
dinal passage exten ing from the top end of piston 403 to trans-
verse passage 433. Retaining screw 447 extends into passage 433
and between heads 441, 443 of trigger 437 a sufficient distance
to prevent head a43 from passing radially inward beyond retaining
screw 447.
Referring to Figure 6, there is sho~n another view of one of
the locking probes 207 disposed in canister 133 prior to actua-
..
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~ 737~2
tion of the piston 403. Each piston 403 ~arries a set of four
equally circumferentially spaced apart do~ segments 449 disposed
in recesses 451 in the walls of piston 403. Dog segments 449
have outwardly, upwardly facing teeth 453 on their outside faces
which bear upon the inside surface of the walls of housing 351 of
locking probe 207. The inside faces 450 of dog segments 449 abut
the back walls 452 of recesses 451. The inside faces 450 of dog
segments 449 are tapered inward from the bottoms of the dog
segments upward, and the back walls ~52 of recesses 451 are
correlatively tapered. A coil spring 455 in compression extends
from the top of each do~ segment 449 through a longitudinal
passage 457 in piston 403 to a cap screw 459. Cap screws 459 are
threadedly disposed in longitudinal passages extending from the
top end of piston 403 to passages 457. Springs 4~5 exert a force
upon dog segments 449, tending to push them downward~
After actuation of the piston 403 by removing pin 45 from
within the loc~ing probe 207, dog segments 449 are forced down~
ward by springs 455 as piston 403 is forced downward into abut-
ment with rod 45 by spring 429. As shown in Figure 6A, after
actuation of piston 403, dog segments 449 are disposed near the
: bottom end 363 of housing 351 but remain entirely within housing
351. If an upward force is exerted upon the bottom end 419 o~
piston 403, teeth 453 of dog segments a49 will bite int~ the
internal surface of the wall~ of housing 351 due to the shape of
the teeth and the wedging action of tapered walls 452 of recesses
451 attempting to slide upward with respect to the c~rrelatively
tapered faces 450 of dog segments 449. When teeth 453 of dog
segments 449 bite into the walls of housing 351, upw~rd travel of
piston 403 is prevented. Thus, rods 45 cannot move upward once
piston 403 is actuated, since the top of each rod abuts the
bottom end of a piston which itself cannot be forced upw,ard due
: : to the gripping and wedging action of dog segments 449. Pistons
403 when actuated thereby provide a positive lockdo~n for rods
.
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737~
45, preventing their upward movement and consequent loosening ~f
the connection between Christmas tree 11 and wellhead housing 7.
In assembling the locXing probes 207 with their spring
loaded pistons 403, nose cones 365 are first attached to the
bottoms of housings 351. Trigger 437 and retaining screw 447 are
mounted on the piston 403, and locking dogs 4 9 are set in place
in their recesses 451. Piston 403 is then inserted into housing
351 such that a transverse passage 501 (Figures 4 and 53 through
the wall of housing 351 aLigns coaxially with a corresponding
transverse passage 503 in the wall of piston 403. When passages
501, 503 are so coaxially aligned, passage 433 in pisto~ 403 is
coaxially aligned with recess 435 in housing 351. A slave screw
505, shown in phantom outline in Figures 4 and 5, is then in-
serted into passages 501~ 503 such that it extends into passaga
S03 while remaining partially in passage 501, thereby preventing
vertical movement of piston 403 in housing 351. Springs 455 are
then inserted into their passages and cap screws ~59 are in-
stalled, compressing springs 455. Spring 429 is then placed atop
piston 403 and compressed with the aid o~ a compression tool, not
shown, and c~llar 387 with retaining screws 389 is installed atop
compressed spring 429. When tree cap 25 is installed on running
tool 27 for lowering to the wellhead, triggers 437 are cammed ~y
pins 445 of tool 27 radially outward into recesses 435 in hous-
ings 351 of locking probes 207. With triggers 437 restrained in
recesses 435 and channels 433 by pins 445, slave screws 505 are
removed and piston 403 is then in a cocked or loaded state, ready
to spring downward when pins 445 are withdrawn.
When it is desired to remove Christmas tree 11 from the
wellhead, e.g., for repairs to the tree or the well, tree cap
running tool 27 is lowered to tree 11, cam ring 201 is lifted by
running tool 27, typically hydraulically, thereby releasing dog
segments 277 from wye spool 15. Cap 25 is then removed by lift-
ing it vertically, the locking probes 207 being removed from
..
: .' ' ' .
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'737~
canisters 133 and exposing the tops of rods 45 to access by a
tree running tool, not shown. The tree running tool is then
lowered to tree 11 and rods 45 are grasped and pulled upward by
the tool, typically by hydraulic power, thereby releasing dog
segments 79 from wellhead housing 7, as described previously.
All major metal components of tree cap 25, e.g., cam
ring 201, body 203, base plate 205 and locking probe housing 351
and piston 403, may be constructed of an alloy steel such as AISI
4130 steel. The parts of tree cap 25 exposed to sea water may be
coated with a protective finish such as epoxy paint. Moving
parts, such as dog segments 277, 79 should be lubricated with a
durable lubricant such as, for example, Shell salt-resistant
chassis grease.
Because many varying and different embodiments may be
made within the scope of the inventive concept herein taught, and
because many modifications may be made in the embodiment herein
detailed, it should be understood that the details described
herein are to be interpreted as illustrative and not in a limit-
ing sense.
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. .,
