Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
20033A8
1 BACKGROUND OF THE INVENTION
3 1. Field of the Invention:
This invention relates in general to tools for
6 running and retrieving casing hangers in subsea wells,
7 and in particular to a tool that utilizes pressure
8 intensification through differential area pistons to
9 set and retrieve the packoff for a casing hanger.
11 2. Description of the Prior Art:
12
13 The subsea well of the type concerned herein will
14 have a wellhead supported on the subsea floor. One or
more strings of casing will be lowered into the
16 wellhead from the surface, each supported on a casing
17 hanger. The casing hanger i8 a tubular member that is
18 secured to the threaded upper end of the string of
19 casing. The casing hanger lands on a landing shoulder
in the wellhead, or on a previously installed casing
21 hanger having larger diameter casing. Cement is pumped
22 down the string of casing to flow back up the annulus
23 around the string of casing. After the cement hardens,
24 a packoff is positioned between the wellhead bore and
an upper portion of the casing hanger. This seals the
26 casing hanger annulus.
27
28 One type of packoff proposed utilizes a metal seal
~9 so as to avoid deterioration with time that may occur
with elastomeric seals. Metal seals require a much
31 higher force to set than elastomeric seals. Prior art
32 running tools have employed various means to apply the
33 downward force needed to set the packoff. Some prior
- 20033~8
1 art tools use rotation of the drill string to apply
2 setting torque. It is difficult to achieve sufficient
3 torque to generate the necessary forces for a metal
4 packoff, because the running tool may be located more
than a thousand fee~ below the water surface in deep
6 water.
8 Other running tools and techniques shown in the
g patented art apply pressure to the annulus surrounding
the drill string on which the running tool is
11 suspended. The amount of annulus pressure is limited,
12 however, to the pressure rating of the riser through
13 which the drill string extends, which is normally not
14 enough to set a metal packoff.
16 Higher pressures can be achieved by pumping
17 through the drill string. However, this requires a
18 running tool with some type of ports that are opened
19 and closed from the surface. This is necessary because
cement must first be pumped down the drill string. The
21 ports may be opened and closed by dropping a ball or
22 dart. This requires a considerable amount of time,
23 however, for the ball to reach the seat. Rig time is
24 quite expensive. Another method employs raising and
lowering the drill pipe and rotating in various manners
26 to engage and disengage J-slots to open and close
27 ports. This has a disadvantage of the pins for the J-
28 slots wearing and not engaging properly.
29
Also, occasionally, a packoff may need to be
31 retrieved to the surface. A floating vessel located at
32 the surface will connect to the wellhead by means of a
33 riser. A retrieving tool is lowered on a drill string.
2~03348
1 The retrieving tool has a means for securing to the
2 packoff. Then the drill string is pulled upward to
3 release the packoff.
While this is satisfactory for elastomeric seal
6 packoffs, it is more difficult to achieve with a metal
7 packoff. Elastomeric packoffs are set at much lower
8 forces than metal packoffs. It may be difficult to
9 achieve sufficient pulling force with the drill string
to pull a metal packoff loose.
- 2003348
1 SUMMARY pF THE INVENTION
3 In this invention, the drill string axial movement
4 is used to set and retrieve the packoff. In one
embodiment, the weight of the drill string is used. In
6 another embodiment, the drill string is pulled upward.
7 The drill string weight, itself, does not have
8 sufficient force to set the packoff. The force due to
g the drill string weight is intensified by using
differential pistons. The running tool has a mandrel
11 that is connected to the drill string. The mandrel has
12 a mandrel piston that moves with the mandrel. The
13 mandrel carries a body that engages the casing hanger.
14 The body has a setting sleeve piston that has a much
larger pressure area than the mandrel piston. Sealed
16 hydraulic passages connect the chamber of the mandrel
17 piston with the chamber of the setting sleeve piston.
18
19 When setting the packoff, as the drill string is
lowered relative to the body, the mandrel piston will
21 apply hydraulic pressure to the liquid contained in the
22 passages. This pressure acts on the setting sleeve
23 piston, which in turn applies a downward force on the
24 setting sleeve. The downward force of the setting
sleeve will be much higher than the direct force from
26 the weight of the drill string because of the
27 intensification due to the differential area pistons.
28
29 Preferably the body has two parts, an upper body
and a lower body. The upper body is carried in an
31 upper position while r~ln~nq the casing hanger and
32 while cementing. Then, the mandrel and the upper body
33 are lowered relative to the lower body to position the
2003348
1 packoff.assembly in the annular space ~e~ween the
2 casing hanger and wellhead. Then, the mandrel is
3 lowered relative to both the upper body and lower body
4 to apply hydraulic pressure to the setting sleeve
piston.
7 In another embodiment, the drill pipe and mandrel
8 are pulled upward to move the sleeve downward to set
9 the packoff. In still another embodiment, the tool is
used to retrieve the packoff.
Z0033~8
1 BRIEF DESCRIPTION OF THE DRAWINGS
3 Figures la and lb are quarter sectional views of
4 a running tool constructed in accordance with this
invention, and shown in the running in and cementing
6 position.
8 Figures 2a and 2b are quarter sectional views of
9 the running tool of Figure 1, showing the packoff being
moved into position for setting after the casing hanger
11 has been cemented.
12
13 Figures 3a and 3b are quarter sectional views of
14 the running tool of Figure 1, showing the packoff when
fully set, with the mandrel in the lowermost position.
16
17 Figures 4a and 4b are quarter sectional views of
18 the running tool of Figure 1, showing the mandrel moved
19 back to an upper position relative to the upper body to
release the running tool from the casing hanger.
21
22 Figures 5a and 5b are quarter sectional views of
23 the running tool of Figure 1, showing the running tool
24 released from the casing hanger after the packoff has
been set.
26
27 Figure 6 is a partial vertical sectional view of a
28 first alternate embodiment of a running tool
29 constructed in accordance with this invention and shown
in the running in position.
31
- 2~0334~3
1Figure 7 is a partial vertical sectional view of
2 the running tool of Figure 6, and shown in a position
3 of lowering the upper body relative to the lower body.
Figure 8 is a partial vertical sectional view of
6 the running tool of Figure 6, and shown in a retrieving
7 position.
g Figure 9 is a partial vertical sectional view of a
portion of the running tool of Figure 6, in the
11 position shown in Figure 8.
12
13 Figures lOa and lOb are quarter sectional views
14 of a second alternate embodiment of a running tool
constructed in accordance with this invention, and
16 shown in the running in and cementing position.
17
18 Figures lla and llb are quarter sectional views of
19 the running tool of Figures lOa and lOb, showing the
packoff being moved into position for setting after the
21 casing hanger has been cemented.
22
23 Figures 12a and 12b are quarter sectional views of
24 the running tool of Figures lOa and lOb, showing the
packoff when fully set, with the mandrel moved back to
26 an upper position.
27
28 Figures 13a and 13b are quarter sectional views of
29 the running tool of Figures lOa and lOb, showing the
running tool released from the casing hanger.
31
32
33 Figure 14 is a quarter cross-sectional view of a
34 fourth embodiment illustrating a tool constructed in
- 200;~348
1 accordance with this invention, used for retrieving a
2 packoff and shown with the mandrel in a lower
3 position.
Figure 15 is a quarter cross-sectional view of the
6 tool of Figure 14, and showing the mandrel lifted into
7 an upper position for retrieving the packoff.
2003348
1 DESCRIPTION OF THE PREFERRED EMBODIMENT
2 Referring to Figures la and lb, and more
3 particularly to Figure lb, wellhead 11 is a tubular
4 member extending upward from the subsea floor. An
internal landing shoulder 13 is located in the bore 14
6 of the wellhead 11. T~n~i ng shoulder 13 is frusto-
7 conical. A set of wickers 15 is located a short
8 distance above the landing shoulder 13. Wickers 15 are
g small, parallel, circumferential grooves.
11 A casing hanger 17 lands on the landing shoulder
12 13. Casing hanger 17 is a tubular member that is
13 secured to the upper end of a string of casing (not
14 shown). An annular clearance 19 exists between an
upper portion of the casing hanger 17 and the bore 14
16 of the wellhead 11. A set of wickers 21 is formed on
17 the casing hanger 17. Wickers 21 are of the same
18 configuration, but extend upward farther and do not
19 extend as far down as the wellhead wickers 15. Two
large circumferential grooves 23 are located on the
21 inner diameter of the upper portion of the casing
22 hanger 17.
23
24 Casing hanger 17 is lowered into place and set by
a running tool 25. R~nn~ng tool 25 includes a mandrel
26 27 that has an upper end cont~n~ng threads 26 (Fig.
27 3a) for connection to the lower end of the string of
28 drill pipe (not shown). The drill pipe will be lowered
29 through a riser (not shown) that extends from a
floating vessel down to the wellhead 11. A collar 29
31 is secured to the lower end of the mandrel 27. Collar
32 29 has exterior threads 3la, 3lb. The threads 3lb are
33 of larger diameter than the threads 3la. The threads
20033~8
1 31a, 31b are adapted to screw into mating threads
2 formed in a lower body 33.
4 An engaging element, preferably a split ring 35,
is carried by the lower body 33. The ring 35 will
6 extend from the exterior of the lower body 33. The
7 ring 35 has a pair of annular bands separated by a
8 groove on the outer side. The bands are adapted to
g mate with the grooves 23 in the casing hanger 17 to
secure the lower body 33 to the casing hanger 17. Ring
11 35 will move between an extended position shown in
12 Figure lb to a retracted position shown in Figure 5b.
13 ~
14 A plurality of linking pins 37 extend through the
lower body 33 radially inward from the ring 35. The
16 linking pins 37 are moved inward and outward by a cam
17 39, which is a solid ring. Cam 39 is carried inside a
18 cavity 40 in the lower body 33. Cam 39 has a pair of
19 lobes 41a, 4lb, which are annular bands separated by a
central recess 43. The cam 39 will move axially
21 relative to the lower body 33.
22
23 Figure lb shows the cam 39 in an upper position
24 with the lower lobe 41b pressing the linking pins 37
and the ring 35 outward. Figure 2b shows the cam 39 in
26 a lower position, with the upper lobe 41a pressing the
27 linking pins 37 and the ring 35 outward. Figure 5b
28 shows the cam 39 in an intermediate position, with the
29 recess 43 engaging the linking pins 37, which allows
the ring 35 to retract. The cam 39, linking pins 37
31 and ring 35 serve a~ connection means for releasably
32 connecting the rllnning tool 25 to the casing hanger 17.
33
2003348
1 The cam 39 is moved downward by retention means
2 comprising a split ring 45 secured in a recess 47 in
3 the mandrel 27. Split ring 45 bears against the upper
4 end of the cam 39 to cause the cam 39 to move downward
with the mandrel 27. The flexibility of the split ring
6 45 allows it to retract into the recess 47 and slide
7 past the cam 39 when the cam is located in the lower
8 position bearing against the bottom of the cavity 40.
g In Figure 2b, the split ring 45 is located a
considerable distance below the cam 39.
11
12 The cam 39 moves back to the intermediate position
13 by means of the collar 29, as shown in Figure lb. The
14 collar 29 has an upper edge that engages the lower end
of the cam 39. When the collar 29 is fully screwed
16 into the lower body 33, the upper end of the collar
17 supports the cam 39 in the upper position. In the
18 position of Figure 5b, the threads 31a and 31b have
19 contacted the mating threads in the lower body 33, but
have not yet been screwed into place. In this
21 position, the upper end of the collar 29 ~upports the
22 cam 39 in the intermediate position.
23
24 The lower body 33 is preferably constructed in two
parts, the upper portion 49 being secured by threads to
26 the lower portion. Ring 35 locates in an annular space
27 between the lower body 33 and its upper portion 49.
28 The upper portion 49 of the lower body 33 extends
29 upward concentric with the mandrel 27. Inner and outer
seals 51, 53 are located on the inner and outer
31 diameters of this lower body upper portion 49.
32
2~033~8
1 Referring to Figure la, the running tool 25 has an
2 upper body 55. Upper body 55 has an upper position
3 relative to the lower body 33 that is shown in Figures
4 la and lb and also in Figures 5a and 5b. In the other
figures, the upper body 55 is located in a lower
6 position relative to a lower body 33. The upper body
7 55 is maintained in the upper position during running
8 in and cementing by a locking element comprising a
9 split ring 57 which is shown in Figure lb.
11 When the upper body 55 is in the upper position,
12 split ring 57 locates in a recess 59 formed on the
13 outer diameter of the mandrel 27. In both the upper
14 and lower positions of the upper body 55, split ring 57
remains located in a cavity 61 contained in the lower
16 portion of the upper body 55. Cavity 61 has a radial
17 width that is at least as wide as the radial thickness
18 of the split ring 57 so as to allow the split ring 57
19 to expand outward into the cavity 61. This allows the
split ring 57 to move out of the mandrel recess 59 as
21 shown in Figure 2b, to enable the mandrel 27 to be
22 lowered relative to the upper body 55.
23
24 A plurality of pins 63 extend radially outward
from split ring 57. Pins 63 engage a latch ring 65
26 that is also split. Latch ring 65 has outer threads 67
27 and inner grooves 69. The inner grooves 69 engage
28 mating grooves in the upper body 55 to retain the latch
29 ring 65 with the upper body 55. The latch ring threads
67 are configured to ratchet past and engage mating
31 threads 71 formed in the upper portion of the c~sing
32 hanger cavity 40. The threads 67, 71, are of a saw-
33 tooth configuration.
2003348
2In Figure lb, the latch ring 65 is positioned
3above the casing hanger threads 71. In Figures 2b and
43b, the latch ring 65 is engaging the threads 71. When
5engaging the threads 71, the latch ring 65 expands
6outward. The pins 63 move outward, allowing the split
7ring 57 to move outward. This withdraws the split ring
857 from the recess 59. While engaging the threads 71,
gthe grooves 69 move outward to some extent from the
10mating grooves in the upper body 55, but still remain
11in engagement. The latch ring 65 and associated
12elements serve as means for latching the upper body 55
13to the lower body 33 when the upper-body 55 is in the
14lower position, to prevent any axial movement of the
15upper body 55 relative to the lower body 33.
16
17Referring to Figure la, the upper body has an
18outer portion 73 that is substantially the diameter of
19the wellhead bore 14. The outer portion 73 depends
20from the upper body 55. A setting sleeve 75 is carried
21on the upper body outer portion 73. Setting sleeve 75
22is secured by a ring 76 that is fixed to the outer
23portion 73 80 that the sleeve 75 can move axially a
24limited extent relative to the upper body 55. A key
25(not shown) causes the setting sleeve 75 to rotate in
26unison with the upper body 55.
27
28Referring to Figure lb, the setting sleeve 75 i8 a
29tubular member that extends downward from the upper
30body 55. A threaded ring 77 is located on the lower
31end of the setting ~leeve 75. Threaded ring 77 is a
328pl it, ratchet type ring that engages threads in a
33wedge ring 79. The wedge ring 79 is secured to a metal
Z003348
1 seal packoff 81 by means of a collar 82. The packoff
2 81 has a central annular cavity 83 that receives the
3 wedge ring 79.
The setting sleeve 75 will move the packoff 81
6 from an upper position shown in Figure lb to a lower
7 position shown in the other figures. In the lower
8 position, the packoff 81 is located in the annular
g clearance 19 between the casing hanger 17 and the
lo wellhead 11. Furthermore, the setting sleeve 75 will
11 move the wedge ring 79 downward from the upper position
12 shown in Figure lb to a setting position shown in
13 Figure 3b. In that position, the wedge ring 79 expands
14 portions of the packoff 81 on both sides of the cavity
83 to form a metal seal.
16
17 While running the casing hanger 17 in and while
18 cementing, fluid in the riser and wellhead bore 14 is
19 free to flow up through a return flow passage 85 in the
setting sleeve 79 and a return flow passage 86 in the
21 upper body 55 (Fig. la). There are also return flow
22 passages through the casing hanger 17, but these are
23 not shown in the drawings.
24
The lower body upper portion 49 sealingly locates
26 between the upper body 55 and the setting sleeve 75.
27 This is not a closed chamber, however, as fluid is free
28 to flow out through the passage 87 shown in Figure la.
29
After the upper body 55 has been moved to its
31 lower position shown in Figure 2b, the setting sleeve
32 75 is then moved downward relative to the upper body 55
33 to set the packoff 81. This is handled by a setting
2003;~48
1 sleeve piston 89 shown in Figure la. The setting
2 sleeve piston 89 is carried in a chamber 90 located
3 between the upper body inner portion 91 and upper body
4 outer portion 73. The setting sleeve piston 89 has
seals 92 that will sealingly slide within chamber 90.
6 The chamber 90 of the setting sleeve piston 89 is
7 supplied with a substantially incompressible liquid,
8 such as hydraulic fluid, through hydraulic passages 93.
g The hydraulic passages 93 communicate with a chamber 95
formed between the bore of the upper body 55 and the
11 exterior of the mandrel 27, as shown in Figure lb.
12
13 A mandrel piston 97 is sealingly carried in the
14 chamber 95. The mandrel piston 97 is integrally formed
on the mandrel 27 and protrudes outward. Chamber 95
16 is sealed by seals 98 on the mandrel piston 97. The
17 hydraulic passage 93 communicates the chamber 95 of the
18 mandrel piston 97 with the chamber 90 of the setting
19 sleeve piston 89. The hydraulic fluid contAine~ in the
chambers 90, 95 and passage 93 is sealed from any
21 exterior fluids in the riser (not shown), wellhead bore
22 14 or within the drill pipe (not shown). Downward
23 movement of the mandrel piston 97 increases the
24 pressure of the hydraulic fluid in the passage 93 to
move the setting sleeve piston 89 downward.
26
27 The transverse cross-sectional area of the mandrel
28 piston 97, or pressure area, is much less than the
29 cross-sectional area or pressure area of the setting
sleeve piston 89. Consequently, the downward force on
31 the mandrel 27 due to the drill string weight is
32 greatly intensified. That is, the downward force
33 exerted by the piston 89 on the setting sleeve 75 will
- 20~3348
1be much higher than the downward force on the mandrel
227, which is limited to the weight of the drill string.
3Preferably, a sufficient difference exists between
4the pressure areas to increase a drill string weight on
5mandrel piston 97 of 20,000 pounds to provide a setting
6force on the setting sleeve piston 89 of about 500,000
7pounds.
9 Referring to Figure 2a, a series of teeth or
castellations 99 are formed on the upper side of the
11 mandrel piston 97. The castellations 99 have slots
12 (not shown) between them that are adapted to engage a
13 pin 101. Pin 101 is located at the upper end of the
14 upper body 55. Pin 101 is secured in threads in the
upper body 55. A collar 103 is located on the upper
16 end of the upper body 55. A wiper seal 105 is
17 positioned between the collar 103 and the outer
18 diameter of the mandrel 27.
19
In operation, the casing (not shown) will be
21 lowered into the well. The upper end of the casing
22 will be secured to the lower end of the casing hanger
23 17. As shown in Figure lb, the running tool 25 will be
24 connected to the casing hanger 17 through the ring 35.
The upper end of the mandrel 27 of the running tool 25
26 is connected to the lower end of a string of drill pipe
27 (not shown). The entire assembly is then lowered into
28 the well until the casing hanger 17 lands on the
29 landing shoulder 13 in the wellhead 11, as shown in
Figure lb.
31
32 Then, cement is pumped down the drill pipe. The
33 cement will flow through the bore of the mandrel 27 to
17
2003348
1 the bottom of the casing string, then back up the
2 annulus surrounding the casing string. The returns
3 from the cement will flow through the passages (not
4 shown) in the casing hanger 17, and up through the
passages 85 (Fig. lb) and passages 86 (Fig. la) to the
6 surface through the riser (not shown).
8 After the cement has set sufficiently, the drill
g string is rotated to the right. This disengages the
threads 31a, 31b from the lower body 33, as can be seen
11 by comparing Figure lb with Figure 2b. Once unscrewed,
12 the drill string is lowered, allowing the mandrel 27 to
13 move downward.
14
As mandrel 27 moves downward, the lower body 33
16 will remain stationary because it is seated in the
17 casing hanger 17. The upper body 55 will move downward
18 with the mandrel 27. This occur~ because the split
19 ring 57 (Fig. lb) retains the upper body 55 with the
mandrel 27 for a certain distance. The cam 39 will
21 also move downward with the mandrel 27 for a short
22 distance until it reaches the bottom of cavity 40. The
23 split ring 45 will bear against the top of the cam 39,
24 causing this downward movement. When the cam 39 is in
the lower position shown in Figure 2b, the ring 35 will
26 be maintained in the engaged position by means of the
27 upper lobe 4la. Once the cam 39 reaches the lower
28 position, the split ring 45 will contract into the
29 recess 47 and slide on past the cam 39.
31 The downward movement of the mandrel 27 con~inues
32 until the latch ring 65 (Fig. lb) engages the threads
33 71 in the lower body 33. When this occurs, the latch
18
Z003348
1 ring 65 snaps outward. This allows the split ring 57
2 to expand outward from the recess 59 in the mandrel 27.
3 The mandrel 27 is then free to move further downward
4 relative to the upper body 55, as illustrated in Figure
2b.
7 When the upper body 55 is in the lower position,
8 the packoff 81 will be properly positioned in the
9 annular clearance 19 between the casing hanger 17 and
the wellhead 11. The upper body 55 will be latched to
11 the lower body 33 so that it can not move upward
12 because of the latch ring 65. This is the position
13 shown in Figure 2b.
14
Continued downward movement of the mandrel 27
16 relative to the upper body 55 and lower body 33 causes
17 a pressure increase in the chambers 90, 95 and
18 hydraulic passage 93. The pressure increase acts on
19 the setting sleeve piston 89. The setting sleeve
piston 89 acts on the setting sleeve 75. The setting
21 sleeve 75 applies downward force to the wedge ring 79.
22 The wedge ring 79 moves downward into the cavity 83,
23 which sets the packoff 81. The inner portion of the
24 packoff 81 embeds into the casing hanger wickers 21.
The outer portion of the packoff 81 embeds into the
26 wellhead bore wickers 15. The setting position is
27 illustrated in Figure 3b. When fully set, the upper
28 end of the setting sleeve 75 will be substantially
29 flush with the upper end of the lower body upper
portion 49.
31
32 After testing, the running tool 25 may be
33 retrieved from the casing hanger 17. First, the drill
19
- 2003348
1 string is picked up to pull the mandrel 27 upward. At
2 a certain distance, the castellations 99 (Fig. 2a) will
3 engage the pin 101 as shown in Figure 4a. Then, the
4 drill string i8 rotated to the right again. The
mandrel 27 will rotate. The castellations 99 and pin
6 101 will cause the upper body 55 to rotate with the
7 mandrel 27. This will cause the threaded ring 77 to
8 unscrew from the wedge ring 79. This rotation will
9 also cause the latch ring 65 to unscrew from thethreads 71. The mandrel 27 may then be picked up.
11 This is the position shown in Figures 5a and 5b.
12
13 As the mandrel 27 is picked up, the recess 59 will
14 move up and engage the split ring 57. This will cause
the upper body 55 to begin moving upward with the
16 mandrel 27. The collar 29 will contact the lower side
17 of the cam 39 and move it up to intermediate position
18 shown in Figure 5b. The threads 31a and 31b will
19 contact the mating threads in the lower body 33 to
limit the upward movement of the collar 29 to the
21 position shown in Figure 5b. The intermediate position
22 of the cam 39 allows the ring 35 to retract. The
23 entire running tool 25 may then be pulled to the
24 surface.
26 In the embodiments of Figures 6-9, the elements
27 which are similar to the first embodiment are either
28 not discussed, or when discussed, are indicated with a
29 prime symbol. The principal difference is in the
manner of releasing the lower body 33' from the casing
31 hanger 17'. The mandrel 27' is secured by threads to
32 an annular insert 107, which may be considered a part
33 of the lower body 33'. The insert 107 has left-hand
2003348
1 threads 108 which secure the insert 107 to the lower
2 body 33'. While downhole, the insert 107 does not
3 unscrew from the lower body 33', rather it is removed
4 and installed only during disassembly and assembly at
the surface.
7 An annular stop 109 is formed on the upper end of
8 the insert 107, extending into the cavity 40' of the
g lower body 33'. The stop 109 serves as stop means for
preventing a cam 111 from moving downward from its
11 lower position shown in Figures 6, 7. Cam 111 is
12 axially movable from the lower position shown in
13 Figures 6, 7 to the upper position shown in Figure 8.
14 Cam 111 has a central lobe 113 that pushes outward on
link pins 37' and split ring 35' when cam 111 is in the
16 lower position. The lobe 113 maintains the split ring
17 35' in an engaged position with the casing hanger 17'.
18 When in the upper position of Figure 8, the lobe 113
19 passes above the link pins 37', allowing the split ring
35' to retract.
21
22 Cam 111 has an inner diameter that slidingly
23 receives the mandrel 27'. An annular slot 115, shown
24 more clearly in Figure 9, is located in the inner
diameter of cam 111. Slot 115 inclines downward and
26 outward relative to the axis of mandrel 27'.
27
28 A spring element such as a split ring 117 locates
29 in the slot 115. Split ring 117 has a circular
transverse cross-section and is considerably smaller in
31 cross-sectional diameter than the height of the slot
32 115. Split ring 117 is biased inward into engagement
33 with the mandrel 27'.
2003348
2 A recess 119 is formed on the exterior of the
3 mandrel 27', at a point so that it is initially above
4 the cam 111. As shown in Figure 9, the upper edge ll9a
and the lower edge ll9b of the recess are bevelled.
6 The upper edge ll9a faces downward and outward, and the
7 lower edge ll9b faces downward and inward.
g In operation of the second embodiment, after the
cement has set, the drill string and mandrel 27' are
11 rotated to the right to unscrew the mandrel 27' from
12 the lower body 33'. The insert 107 will not unscrew
13 because of the left-hand threads. As the mandrel moves
14 downward, the cam 111 remains stationary. The recess
119 will slide past the split ring 117, as indicated in
16 Figure 7. The upper edge ll9a pushes the split ring
17 117 outward into the slot 115 as it moves past.
18
19 The packoff 81' is set in the same manner as
described in the first embodiment. To release the
21 running tool 25', the drill string and the mandrel 27'
22 are picked up. The recess 119 will move up and engage
23 the ring 117. The lower edge ll9b will push the ring
24 117 against the inclined upper edge of slot 115. The
inclination of the lower edge ll9b and the upper edge
26 of slot 115 are substantially the same. This traps the
27 ring 117 between the lower edge ll9b and the upper
28 edge of slot 115. This locks the cam 111 to the
29 mandrel 27 for upward movement.
31 As the cam 111 moves upward, the lobe 113 passes
32 above the link pin 37'. This allows the ring 35' to
33 retract, releasing the lower body 33' from the casing
22
2003348
1 hanger ~7'. The setting sleeve 75' releases from the
2 packoff wedge ring 79' by a straight upward pull. The
3 grooves or threads on the ring 77' are configured to
4 allow releasing with a moderate upward pull. No
rotation is necessary.
7 The upper body 55' will remain in the lower
8 position relative to lower body 33' as the running tool
9 25' is retrieved to the surface. The latch ring 65' is
not unscrewed from the threads 71' until the running
11 tool 25' is at the surface. Consequently, there will
12 be no structure such as the castellations 99 or pin 101
13 (Fig 2a) for locking the mandrel 27'-to the upper body
14 55' for rotation.
16
17 A third embodiment is shown in Figures lOa through
18 13b. Referring to Figures lOa and lOb, and more
19 particularly to Figure lOb, wellhead 211 is a tubular
member extending upward from the subsea floor. An
21 internal l~n~ng shoulder 213 is located in the bore
22 214 of the wellhead 211. T~n~ing shoulder 213 is
23 frusto-conical. A set of wickers 215 is located a
24 short distance above the landing shoulder 213. Wickers
215 are small, parallel, circumferential grooves.
26
27 A casing hanger 217 lands on the landing shoulder
28 213. Casing hanger 217 is a tubular member that is
29 secured to the upper end of a string of casing (not
shown). An annular clearance 219 exists between an
31 upper portion of the casing hanger 217 and the bore 214
32 of the wellhead 211. Return flow passages 218 extend
33 through the casing hanger 217 to return fluid from the
34 annulus surrounding the casing with the annular
2~03348
1 clearanc,e 219 during cementing before the casing hanger
2 is fully set.
4 A set of wickers 221 is formed on the casing
hanger 217. Wickers 221 are of the same configuration,
6 but extend upward farther and do not extend as far down
7 as the wellhead wickers 215. Two large circumferential
8 grooves 223 are located on the inner diameter of the
9 upper portion of the casing hanger 217.
11 Casing hanger 217 is lowered into place and set by
12 a running tool 225. Running tool 225 includes a
13 mandrel 227 that has an upper end containing threads
14 226 (Fig. 12a) for connection to the lower end of the
string of drill pipe (not shown). The drill pipe will
16 be lowered through a riser (not shown) that extends
17 from a floating vessel down to the wellhead 211. A
18 shoulder 229 is secured to the lower end of the mandrel
19 227. Mandrel 227 has exterior threads 231a, 231b. The
threads 23lb are of larger diameter than the threads
21 23la. The threads 23la, 23lb are adapted to screw into
22 mating threads formed in a lower body 233.
23
24 An engaging element, preferably a split ring 235,
is carried by the lower body 233. The ring 235 will
26 extend from the exterior of the lower body 233. The
27 ring 235 has a pair of annular bands separated by a
28 groove on the outer side. The bands are adapted to
29 mate with the grooves 223 in the casing hanger 217 to
secure the lower body 233 to the casing hanger 217.
31 Ring 235 will move between an extended position shown
32 in Figure lOb to a retracted position shown in Figure
33 14b.
24
20()3348
2 A plurality of linking pins 237 extend through the
3 lower body 233 radially inward from the ring 235. The
4 linking pins 237 are moved inward and outward by a cam
239, which is a solid ring. Cam 239 is carried inside
6 a cavity 240 in the lower body 233. Cam 239 has a pair
7 of lobes 24la, 24lb, which are annular bands separated
8 by a central recess 243. The cam 239 will move axially
9 relative to the lower body 233.
11 Figure lOb shows the cam 239 in an upper position
12 with the lower lobe 241b pressing the linking pins 237
13 and the ring 235 outward. Figure llb shows the cam 239
14 in a lower position, with the upper lobe 241a pressing
the linking pins 237 and the ring 235 outward. Figure
16 13b shows the cam 239 in an intermediate position, with
17 the recess 243 engaging the linking pins 237, which
18 allows the ring 235 to retract. The cam 239, linking
19 pins 23~ and ring 235 serve as connection means for
releasably connecting the running tool 225 to the
21 casing hanger 217.
22
23 The cam 239 i5 held in the upper and the
24 intermediate positions by means of a shoulder 229 which
engages the lower end of the cam 239. When the mandrel
26 227 is fully screwed into the lower body 233, the upper
27 end of the shoulder 229 supports the cam 239 in the
28 upper position. Pins 245 are secured to the cam 239
29 and extend through holes in the bottom of cavity 240.
The pins 245 provide an upper limit for the movement of
31 the cam 239.
32
- 2003348
1In the position of Figure 13b, the threads 23la
2and 23lb have contacted the mating threads in the lower
3body 233, but have not yet been screwed into place. In
4this position, the shoulder 229 supports the cam 239 in
5the intermediate position.
7 The lower body 233 is preferably constructed in
8 two parts, the upper portion 249 being secured by
g threads to the lower portion. Ring 235 locates in an
annular space between the lower body 233 and its upper
11 portion 249. The upper portion 249 of the lower body
12 extends upward concentric with the mandrel 227. Inner
13 and outer seals 251, 253 are located on the inner and
14 outer diameters of this lower body upper portion 249.
16 Referring to Figure lOa, the running tool 225 has
17 an upper body 255. Upper body 255 has an upper
18 position relative to the lower body 233 that is shown
19 in Figures lOa and lOb and also in Figures 13a and 13b.
In the other figures, the upper body 255 is located in
21 a lower position relative to a lower body 233. The
22 upper body 255 moves to the lower position by its own
23 weight and by the contact of a downward facing shoulder
24 257 on the exterior of mandrel 227, which is shown in
Figure lla.
26
27 A split latch ring 265 is carried on the exterior
28 of the lower end of the upper body 255. Latch ring 265
29 has outer threads 267. The latch ring threads 267 are
configured to ratchet past and engage mating threads
31 271 formed in the upper portion of the casing hanger
32 cavity 240. The threads 267, 271 are of a saw-tooth
33 configuration.
2(~03348
2 In Figures lOa and lOb, the latch ring 265 is
3 positioned above the casing hanger threads 271. In
4 Figures llb and 12b, the latch ring 265 is engaging the
threads 271. The latch ring 265 and threads 271 serve
6 as means for latching the upper body 255 to the lower
7 body 233 when the upper body 255 is in the lower
8 position, to prevent any axial movement of the upper
g body 255 relative to the lower body 233.
11 Referring to Figure lOa, the upper body 255 has an
12 outer portion 273 that is substantially the diameter of
13 the wellhead bore 214. The outer portion 273 depends
14 from the upper body 255. A setting sleeve 275 is
carried on the upper body outer portion 273. Setting
16 sleeve 275 is secured by a ring 276 that is fixed to
17 the outer portion 273 so that the sleeve 275 can move
18 axially a limited extent relative to the upper body
19 255. A key (not shown) causes the setting sleeve 275
to rotate in unison with the upper body 255.
21
22 Referring to Figure lOb, the setting sleeve 275 is
23 a tubular member that extends downward from the upper
24 body 255. A threaded ring 277 is located on the lower
end of the setting sleeve 275. Threaded ring 277 is a
26 split, ratchet type ring that engages threads in a
27 wedge ring 279. The wedge ring 279 i8 secured to a
28 metal seal packoff 281 by means of a collar 282. The
29 packoff 281 has a central annular cavity 283 that
receives the wedge ring 279.
31
32 The setting sleeve 275 will move the packoff 281
33 from an upper position shown in Figure lOb to a lower
27
2003348
1 position shown in the other figures. In the lower
2 position, the packoff 281 is located in the annular
3 clearance 219 between the casing hanger 217 and the
4 wellhead 211. Furthermore, the setting sleeve 275 will
move the wedge ring 279 downward from the upper
6 position shown in Figure lOb to a setting position
7 shown in Figure 12b. In that position, the wedge ring
8 279 expands portions of the packoff 281 on both sides
9 of the cavity 283 to form a metal seal.
11 While running the casing hanger 217 in and while
12 cementing, fluid in the riser and wellhead bore 214 is
13 free to flow up through a return flow passage 285 in
14 the setting sleeve 279 and a return flow passage 286 in
the upper body 255 (Fig. lOa).
16
17 The lower body upper portion 249 sealingly locates
18 between the upper body 255 and the setting sleeve 275.
19 This is not a closed chamber, however, as fluid is free
to flow out through the passages (not shown) in the
21 setting sleeve 275.
22
23 After the upper body 255 has been moved to its
24 lower position shown in Figure llb, the setting sleeve
275 is then moved downward relative to the upper body
26 255 to set the packoff 281. This is handled by a
27 setting sleeve piston 289 shown in Figure lOa. The
28 setting sleeve piston 289 is carried in a chamber 290
29 located between the upper body inner portion 291 and
upper body outer portion 273. The setting sleeve
31 piston 289 has seals 292 that will sealingly slide
32 within chamber 290. During the setting process, the
33 chamber 290 of the setting sleeve piston 289 will
2003348
1 receive a substantially incompressible liquid, such as
2 hydraullc fluid, through hydraulic passages 293. The
3 hydraulic passages 293 communicate with a chamber 295
4 formed between the bore of the upper body 255 and the
exterior of the mandrel 227, as shown in Figure lla.
7 A mandrel piston 297 is sealingly carried in the
8 chamber 295. The mandrel piston 297 is secured to the
9 mandrel 227 for movement therewith and protrudes
outward. The chamber 295 extends upward from the
11 mandrel piston 297 when the mandrel piston 297 is in
12 the lower position shown in Figure llb. Chamber 295 is
13 sealed by seals 298 on the mandrel piston 297. The
14 hydraulic passage 293 communicates the chamber 295 of
the mandrel piston 297 with the chamber 290 of the
16 setting sleeve piston 289. The hydraulic fluid
17 contained in the chambers 290, 295 and passage 293 is
18 sealed from any exterior fluids in the riser (not
19 shown), wellhead bore 214 or within the drill pipe (not
shown). Upward movement of the mandrel piston 297
21 increases the pressure of the hydraulic fluid in the
22 passage 293 to move the setting sleeve piston 289
23 downward.
24
The transverse cross-sectional area or pressure
26 area of the mandrel piston 297 is much less than the
27 cross-sectional area or pressure area of the setting
28 sleeve piston 289. Consequently, the upward force on
29 the mandrel 227 due to the drill string tension is
greatly intensified. That is, the downward force
31 exerted by the setting sleeve piston 289 on the setting
32 sleeve 275 will be much higher than the upward force on
33 the mandrel 227. Preferably, the pressure area of the
29
20033A8
1 mandrel piston 297 is about one-tenth that of the
2 pressure area of the setting sleeve piston 289, so that
3 60,000 pounds pull on the drill string will provide a
4 setting force of 600,000 pounds.
6 Referring to Figure llb, a lug 299 is formed on
7 the upper side of the mandrel piston 297. The lug 299
8 is adapted to engage a slot 301 (Fig. lOa). Slot 301
9 is located at the upper interior of the upper body 255.
When engaged, as shown in Figures lOa and 13a, the
11 upper body 255 will rotate with the mandrel 227.
12
13 In operation, the casing (not shown) will be
14 lowered into the well. The upper end of the casing
will be secured to the lower end of the casing hanger
16 217. As shown in Figure lOb, the running tool 225 will
17 be connected to the casing hanger 217 through the ring
18 235. The upper end of the mandrel 227 of the running
19 tool 225 i8 connected to the lower end of a string of
drill pipe (not shown). Hydraulic fluid will be
21 located in the passages 93. The entire assembly is
22 then lowered into the well until the casing hanger 217
23 lands on the landing shoulder 213 in the wellhead 211,
24 as shown in Figure lOb.
26 Then, cement is pumped down the drill pipe. The
27 cement will flow through the bore of the mandrel 227 to
28 the bottom of the casing string, then back up the
29 annulus surrounding the casing string. The returns
from the cement will flow through the passages 218 in
31 the casing hanger 217, and up through the passages 285
32 (Fig. lOb) and passages 286 (Fig. lOa) to the surface
33 through the riser (not shown).
2003348
2 After the cement has set sufficiently, the drill
3 string is rotated to the right. This disengages the
4 threads 231a, 231b from the lower body 233, as can be
seen by comparing Figure 10b with Figure llb. Once
6 unscrewed, the drill string is lowered, allowing the
7 mandrel 227 to move downward.
9 As mandrel 227 moves downward, the lower body 233
will remain stationary because it is seated in the
11 casing hanger 217. The mandrel piston 297 moves
12 downward in mandrel chamber 295, drawing hydraulic
13 fluid from the setting sleeve chamber 290 and passages
14 293 into the mandrel chamber 295. The upper body 255
under its own weight is free to move downward with the
16 mandrel 227. The cam 239 is also free to move
17 downward under its own weight as shoulder 229 moves
18 down. When cam 239 is at the bottom of cavity 240,
19 mandrel piston 297 will bear against the top of cam
239, stopping further downward movement of mandrel 227.
21 When the cam 239 is in the lower position shown in
22 Figure llb, the ring 235 will be maintained in the
23 engaged position by means of the upper lobe 241a.
24
When mandrel 227 is in its lower position shown
26 in Figures lla, llb, the latch ring 265 (Fig. lb) will
27 be aligned with the threads 271 in the lower body 233.
28 When this occurs, the latch ring 265 snaps outward into
29 engagement with the threads 271. The mandrel shoulder
257 will assure that the upper body 255 reaches the
31 lower position shown in Figures lla, llb.
32
2003348
1 When the upper body 255 is in the lower position,
2 the packoff 281 will be properly positioned in the
3 annular clearance 219 between the casing hanger 217 and
4 the wellhead 211. The upper body 255 will be latched
to the lower body 233 so that it can not move upward
6 because of the latch ring 265. The mandrel piston 297
7 will be located in a lower position at the bottom of
8 the chamber 295.
The drill string is then lifted upward. The
11 upward movement of the mandrel 227 relative to the
12 upper body 255 and lower body 233 causes the mandrel
13 piston 297 to push hydraulic fluid through passage 293
14 into the setting sleeve chamber 290. Continued upward
movement of the mandrel piston 297 causes a pressure
16 increase in the chambers 290, 295 and hydraulic passage
17 293. The pressure increase acts on the setting sleeve
18 piston 289.
19
The setting sleeve piston 289 acts on the setting
21 sleeve 275. The setting sleeve 275 applies downward
22 force to the wedge ring 279. The wedge ring 279 moves
23 downward into the cavity 283, which sets the packoff
24 281. The inner portion of the packoff 281 embeds into
the casing hanger wickers 221. The outer portion of
26 the packoff 281 embeds into the wellhead bore wickers
27 215. The setting position is illustrated in Figures
28 12a, 12b. When fully set, the upper end of the setting
29 sleeve 275 will be substantially flush with the upper
end of the lower body upper portion 249.
31
32 After testing, the running tool 225 may be
33 retrieved from the casing hanger 217. First, the drill
2003348
1 string is picked up to pull the mandrel 227 upward. At
2 a certain distance, the lug 299 (Fig. lla) will engage
3 the slot 301 as shown in Figure 13a. Then, the drill
4 string is rotated to the right again. The mandrel 227
will rotate. The lug 299 and slot 301 will cause the
6 upper body 255 to rotate with the mandrel 227. This
7 will cause the threaded ring 277 to unscrew from the
8 wedge ring 279. This rotation will also cause the
9 latch ring 265 to unscrew from the threads 271. The
mandrel 227 may then be picked up.
11
12 As the mandrel 227 is picked up, the shoulder 229
13 will contact the lower side of the cam 239 and move it
14 up to the intermediate position shown in Figure 13b.
The threads 231a and 231b will contact the mating
16 threads in the lower body 233 to limit the upward
17 movement of the shoulder 229 to the position shown in
18 Figure 13b. The intermediate position of the cam 239
19 allows the ring 235 to retract. The entire running
tool 225 may then be pulled to the surface as shown in
21 Figures 13a, 13b.
22
23 Referring to Figure 14, wellhead 411 will be
24 located on the subsea floor. A riser (not shown) will
extend from a floating vessel down to the wellhead. A
26 casing hanger 413 is landed in the wellhead 411.
27 Casing hanger 413 will be connected to a string of
28 casing (not shown) ext~n~ing into the well. A packoff
29 415 locates in an annular space between the casing
hanger 413 and the bore of the wellhead 411 to seal the
31 annulus surrounding the casing.
32
33
2003348
1 In the embodiment shown, packoff 415 has a metal
2 seal 417. A wedge ring 419 locates within an annular
3 central cavity in the seal 417. A running tool (not
4 shown) moves the wedge ring 419 downward to set the
packoff 415, forcing the inner and outer walls of seal
6 417 farther apart to form a metal seal. The wedge ring
7 419 remains with the packoff 415 after the packoff 415
8 is set. It has threads or grooves 421 on its upper end
9 on the inner wall to be used in retrieving the packoff
415 at a later date.
11
12 A retrieving tool 423 is used to retrieve the
13 packoff 415 after it has been set. Retrieving tool 423
14 has a central, axial mandrel 425. Mandrel 425 has
threads 427 on its upper end, which serve as connection
16 means for connecting the mandrel 425 to the lower end
17 of the string of conduit, such as a string of drill
18 pipe (not shown).
19
A mandrel piston 429 is integrally formed on the
21 mandrel 425. Mandrel piston 429 extends radially
22 outward from the mandrel 425 and has seals 431 on its
23 outer diameter. An exterior cylindrical wall 433 of
24 smaller diameter than mandrel piston 429 is formed on
the mandrel 425 above the mandrel piston 429.
26
27 The mandrel piston 429 slidingly and sealingly
28 engages a bore 435 of a body 437. A pressure chamber
29 439 is defined by the space between the bore 435 of
body 437 and the exterior wall 433 of mandrel 425. The
31 pressure area of mandrel piston 429 is the transverse
32 cross-sectional area of the mandrel piston 429. This
33 pressure area corresponds to the difference between the
34
2003348
1 diameter. of the bore 435 and the outer diameter of the
2 exterior wall 433.
4 Body 437 has a landing shoulder 441 on its lower
end that serves as means for landing the retrieving
6 tool 423 on the upper end of the casing hanger 413.
7 Body 437 is tubular, having an exterior wall 443 that
8 is cylindrical. Seals 445 are located on the exterior
9 wall 443.
11 A retrieving sleeve piston 447 is carried by
12 mandrel 425. The retrieving sleeve piston 447 is an
13 annular member for carrying packoff 415. Retrieving
14 sleeve piston 447 has an inner diameter containing
seals 449 which sealingly engage the exterior wall 433
16 of mandrel 425. A retrieving sleeve 451 is integrally
17 formed with and depends downward from the retrieving
18 sleeve piston 447. The retrieving sleeve 451 has an
19 inner cylindrical wall 453. The inner wall 453
sealingly and slidingly engages the exterior wall 443
21 of the body 437.
22
23 A latch means for latching into the packoff 415 is
24 carried on the outer wall of the retrieving sleeve 451.
This latch means comprises a split latch ring 455. The
26 latch ring 455 is retained on its upper end by a collar
27 457 and is located in a recess 459 on the retrieving
28 sleeve 451. The latch ring 455 has grooves on its
29 exterior adapted to latch into and engage the grooves
421 on the packoff wedge ring 419. Once engaged, the
31 retrieving sleeve 451 will be locked to the packoff
32 wedge ring 419, so that upward movement of the
2003348
1 retrieving sleeve 451 will cause upward movement of the
2 wedge ring 419.
4 The retrieving sleeve piston 447 serves as
reacting means in fluid communication with the pressure
6 chamber 439 for upward movement relative to the body
7 437 in response to a pressure increase in the pressure
8 chamber 439. The retrieving sleeve piston 447 has a
9 pressure area that is greater than the pressure area of
the mandrel piston 429. The pressure area of the
11 retrieving sleeve piston 447 is the transverse cross-
12 sectional area that is bounded on the inner side by the
13 mandrel exterior wall 433 and on the-outer side by the
14 body exterior wall 443. The chamber 439 is filled
with a substantially incompressible hydraulic fluid and
16 is sealed from the exterior of the retrieving tool 423
17 by means of the seals 431, 445, and 449.
18
19 A pair of stop rings 461 located on the mandrel
425 serve as a stop to limit downward movement of the
21 mandrel 425 relative to the retrieving sleeve piston
22 447 and body 437. The body 437 i8 retained with the
23 retrieving tool 423 by means of a downward facing
24 retention shoulder 463 formed on the exterior wall 443
of the body 437. The retention shoulder 463 is adapted
26 to engage a plurality of pins 465 (only one shown)
27 located on the lower end of the retrieving sleeve 451.
28
29 In operation, to retrieve packoff 415, the
retrieving tool 423 is lowered on a string of conduit,
31 such as drill pipe. Initially, the retrieving sleeve
32 piston 447 will be located in contact with the upper
33 side of the mandrel piston 429. The body 437 will be
36
2003348
1 located in a lower position (not shown) with the
2 retention shoulder 463 in contact with the retention
3 pins 465. The body 437 will first land on the upper
4 end of the casing hanger 413. Continued downward
movement of mandrel 425 results in the stop rings 461
6 contacting the upper end of retrieving sleeve piston
7 447. The weight of the drill string pushes down on the
8 retrieving sleeve piston 447, causing the latch ring
9 455 to ratchet into engagement with the grooves 421 of
the packoff 415.
11
12 Then, the drill string is pulled upward. The
13 mandrel piston 429 will cause a pressure increase in
14 the hydraulic fluid. The pressure of the hydraulic
fluid in the chamber 439 acts against the retrieving
16 sleeve piston 447. The piston 447 will start to move
17 upward, pulling the wedge ring 419 upward from the seal
18 417.
19
The pressure in the pressure chamber 439 i8 equal
21 to the upward force on the mandrel 425 divided by the
22 pressure area of the mandrel piston 429. The force
23 exerted on the packoff assembly 415 is equal to the
24 pressure in the pressure chamber 439 times the pressure
area of the retrieving sleeve piston 447. For example,
26 if the pressure area of the retrieving sleeve 447 is
27 ten times that of the pressure area of the mandrel
28 piston 429, then the upward force exerted by the
29 retrieving sleeve 451 will be ten times that of the
upward force pulled on the drill string. The
31 intensification of the force provides a sufficient
32 force for retrieving a metal seal packoff 415.
33
2003348
1 When in the uppermost position, the retrieving
2 tool 423 appears as shown in Figure 2. Continued
3 upward pulling will retrieve the entire packoff
4 assembly 415. A new packoff can then be lowered in
place and set using a running tool (not shown).
7 The invention has significant advantages. A high
8 force is achieved by using the differential pistons.
9 This high force enables the setting of metal packoffs.
Annulus fluid pressure is not needed. There is no need
11 for dropping balls or darts, or to shift pins in J-
12 slots in order to pump fluid down the drill pipe. The
13 running tool can be released after ~etting by pulling
14 upward and rotating in one embodiment, or by straight
upward pull in the other embodiment. In another
16 embodiment, the tool is able to retrieve a metal seal
17 packoff by intensifying the actual force pulled on the
18 drill string.
19
38
