Wellhead equipment

There are disclosed several embodiments of wellhead equipment wherein a seal assembly is installed within a frusto-conically shaped space between the bore of a first wellhead member and a conically shaped surface about a second wellhead member to close same. In one embodiment, the first member is a casing hanger landed within the bore of a subsea casing head, the second member is a tubing hanger within the head, and the seal assembly closes off a space between the bore of the casing hanger and the outer surface of the tubing hanger. In another embodiment, the first member is a surface casing head, the second member is a tubing hanger landed within the bore of the head, and the seal assembly closes off a space between the bore and hanger. In a further embodiment, the first member is a Christmas tree adapter of a surface wellhead landed on a casing head, the second member is a tubing hanger landed in the bore of the head and having an upper extension within a counterbore of the adapter, and the seal assembhly closes off a space between the counterbore of extension.

This invention relates generally to wellhead equipment or other apparatus 
wherein an annular space between a first member having a bore therethrough 
and a second member having an outer surface disposable concentrically 
within the bore is adapted to be closed by a seal assembly which forms a 
metal-to-metal seal with the bore and outer surface. More particularly, it 
relates to improvements in wellhead equipment or other apparatus of this 
type wherein, as shown in U.S. Pat. No. 4,757,860, assigned to the 
assignee of the present application, the outer surface of the second 
member is conically shaped to form a frusto-conically shaped space between 
it and the bore of the first member, and the seal assembly comprises a 
metal body having a relatively thin inner wall which is slidable over the 
outer surface to cause it to flex outwardly and thus force the outer ends 
of upwardly and outwardly and downwardly and outwardly extending legs 
about the the outer side of the wall into tight engagement with the bore. 
In one of its novel aspects, this invention relates to such equipment in 
which the first member is a casing hanger landable within the bore of a 
housing or head of a subsea wellhead and the second member is a tubing 
hanger landable within the housing bore above the casing hanger for 
suspending a tubing string within the casing string suspended from the 
casing hanger. 
In the particular embodiment of the aforementioned U.S. patent, the first 
member is a subsea casing head or housing connected to an outermost casing 
of a subsea well, and having a seat about its bore, and the second member 
is a casing hanger having a shoulder thereabout and adapted t be lowered 
into the bore on a running tool for landing on the seat so as to suspend a 
casing string connected to the hanger body within the outermost casing. 
The casing hanger body has flow passages through it to permit cement 
returns to be circulated upwardly through the annulus between the casings, 
and the seal assembly is also carried by the running tool for lowering 
with the casing hanger, and then, upon landing of the hanger, downward 
movement into the frusto-conical space between an outer surface of the 
hanger and the bore of the head so as to close the space and thus the flow 
passages. 
As disclosed in the aforementioned patent, the seal assembly also includes 
one or more seal rings or packing of elastomeric material which surround 
the inner wall of the metal body and are so arranged with respect to the 
legs about its outer side as to be expanded into tight sealing engagement 
with the bore of the second member as the legs are forced outwardly 
against the well bore. Equipment including a seal assembly of this 
construction is an improvement over prior apparatus of this general type 
in several respects, for reasons fully discussed in such patent. 
There are other types of subsea wellhead equipment wherein there is similar 
need for a seal assembly of this type. Thus, for example, it may be 
necessary to close flowways through a tubing hanger adapted to suspend a 
tubing string within an inner casing string suspended from a casing hanger 
landed within a subsea casing head. However, in this and other types of 
wellhead equipment, as well as other apparatus of this type, it may not be 
possible to lower the seal assembly into the annular space to be closed by 
means of a remotely actuated running tool, as in the case of the equipment 
of U.S. Pat. No. 4,757,860. Thus, the tubing hanger above the space 
between it and the bore of the casing hanger fits closely within the bore 
of the head, such that the tubing hanger may be locked down with the head 
by suitable locking parts on the hanger engagable with the head. However, 
to close off an annular space between the tubing hanger and bore of the 
head would expose the seal assembly which closes the annular space between 
the casing hanger and head to pressure within the annulus between the 
casing and tubing strings Thus, it may be preferred, if not necessary, to 
close off an annular space between the bore of the casing hanger and the 
outer surface of the tubing hanger, and thus close flowways through the 
tubing hanger through which cement returns in the casing/tubing annulus 
are circulated. 
There are still other types of wellhead equipment, such as surface rather 
than subsea wellheads in which there is a need for closing off an annular 
space between the bore of a first member and an outer surface of a second 
member disposable concentrically within the bore, but wherein, as in the 
subsea wellhead above described, the members are so arranged that the seal 
assembly may not be lowered into the space, or in which the space is 
easily accessible, but in which a complex, remotely actuated running tool 
is not required to install and set the seal assembly. 
The object of this invention is to provide such wellhead equipment or other 
apparatus of this type in which the seal assembly may be installed and set 
within the space between the first and second members, such as between the 
tubing hanger and casing hanger of a subsea wellhead, in a relatively easy 
manner, and, more particularly, without the need for a remotely actuated 
running tool or other complex auxiliary equipment. 
This and other objects are accomplished, in accordance with the illustrated 
embodiments of the present invention, by apparatus of the type described 
wherein one of the members has means for causing the seal assembly body 
and second member to move in one longitudinal direction with respect to 
one another whereby the inner conical side of the inner wall of the 
annular metal body of the seal assembly slides over the conical surface of 
the second member, and thus flexes the inner wall outwardly, and wherein 
the seal assembly has means which is engagable with the second member to 
limit outward flexing of the inner wall when the outer ends of the legs 
have been forced into tight sealing engagement with the bore of the first 
member. Thus, as previously mentioned, the apparatus of this invention 
permits the installation and setting of the seal assembly in environments 
in which the seal assembly may not be moved into the space between the 
bore and outer surface, or in which a remotely actuated running tool is 
not necessary to installation of the seal assembly. 
In certain embodiments of the invention, the means for causing such 
movement comprises a shoulder on the first member at one end of the bore 
therein which is engagable with a shoulder on the seal assembly body, as 
the first member is moved in the one longitudinal direction with respect 
to the second member so as to dispose the outer surface of the second 
member concentrically within the bore of the first member. 
In one such embodiment, the shoulder on the first member extends outwardly 
from its bore toward the bore of the casing head, and the shoulder on the 
seal assembly body extends inwardly from its conical surface and opposite 
the shoulder on the first member, such that, as above noted, the seal 
assembly may not be moved into the space between the casing hanger body 
and tubing hanger body. Thus, the second member may be a tubing hanger to 
which the seal assembly is releasably connected for lowering with it, and 
the first member may be a casing hanger body landed in the bore of a 
subsea casing head in which the tubing hanger is to be landed. 
In another such embodiment, the seal assembly is carried by the second 
member, and the shoulder extends inwardly of the bore of said first member 
such that the seal assembly may not be lowered into the space. Thus, the 
bore of the first member is movable longitudinally over the seal assembly 
body. More particularly, the second member may comprise an upward 
extension of a tubing hanger, and the first member may comprise a 
Christmas tree adapter having a counterbore which is lowered over and 
sealed with respect to the upward extension. 
In still another embodiment of the invention, the second member has a first 
part on which the conical surface is formed and a second part which is 
movable longitudinally with respect to the first part, and the means for 
moving the seal assembly body comprises a shoulder on the second part 
engagable with the shoulder on the seal assembly body, as the second part 
is moved in the one longitudinal direction with respect to the first part, 
to cause the seal assembly body to slide over the conical outer surface of 
the second member. As illustrated, the first member may comprise a surface 
casing head, and the second member may comprise a tubing hanger which is 
disposable within the bore of the casing head with its outer surface 
spaced from the bore thereof. More particularly, the tubing hanger 
comprises a nut which, in the case of a surface wellhead, is easily 
accessible from the upper end of the casing head bore, thus not requiring 
a long and complex running tool manipulation. 
In the preferred embodiments of the invention, as in the case of the 
aforementioned patent, resilient seal means is disposed about the outer 
side of the inner wall of the seal assembly body above the first leg and 
below the second leg for sealably engaging the bore, and resilient means 
is also disposed about the inner side of the inner wall for sealably 
engaging the outer surface of the second member. More particularly, in the 
illustrated embodiment of the seal assembly, the second leg is above the 
first leg and the resilient seal means about the outer side of the inner 
wall comprises a seal member confined within a recess between the first 
and second legs.

With reference now to the details of the above described drawings, the 
subsea wellhead of FIGS. 1 to 4 is shown to comprise a casing head or 
housing 20 having a bore 21 therethrough and adapted to be installed at 
the subsea floor with its lower end connected to an outermost casing (not 
shown) which extends downwardly from the casing head into the wellbore. 
The upper end of the casing head (also not shown) is adapted for 
connection to a blowout preventer stack which is in turn connected to a 
riser pipe which extends upwardly to the water surface. 
A casing hanger 22 is shown lowered into and landed within the bore of the 
casing head for suspending a casing string connected thereto within an 
outer casing suspended from another casing hanger on which the casing 
hanger 22 has been landed. The casing hanger 22 comprises a body 23 having 
passages 24 therethrough which connect the annular space between the inner 
and outer casings within an annular space 25 between the bore of the 
casing head and an outer surface 26 of the casing hanger body 23. As 
described in the aforementioned prior U.S. Pat. No. 4,757,860, this 
annular space is adapted to be closed, following landing of the hanger, 
and circulation of cement upwardly through the flow passages, by means of 
a seal assembly 27. 
Thus, as also described in such patent, the outer surface 26 of the hanger 
is conically shaped and converges upwardly and inwardly so as to form an 
upwardly opening frusto-conical space into which the seal assembly 27 has 
been lowered. More particularly, and again as described in the 
aforementioned patent, both the casing hanger and the seal assembly are 
lowered on a running tool (not shown) which, upon landing of the casing 
hanger, is remotely actuated to lower the seal assembly with respect to 
the casing hanger body and thus cause it to slide downwardly along the 
surface 26 and thus be flexed outwardly into sealing engagement with the 
bore of the casing head. When the seal assembly has been so lowered and 
installed, both the seal assembly and casing hanger are locked down within 
the tubing head in any suitable manner as by means described in the 
aforementioned patent. 
In accordance with one novel aspect of the present invention, a tubing 
hanger 28 comprising a body 29 and a seal assembly 30 carried thereby are 
lowered by a running tool (not shown) into the bore of the casing head so 
as to land the tubing hanger in the head above the casing hanger 22 and 
install and set the seal assembly 30 within an annular space between an 
outer surface 31 of the tubing hanger and a bore 32 through the casing 
hanger body. Thus, the seal assembly closes the annular space between the 
tubing and casing hangers, and thereby prevents well fluid from passing 
upwardly through the space and flowways in the hanger and into the annular 
space between the casing hanger 22 and bore of the casing head. As shown, 
the tubing hanger has an outwardly enlarged portion which carries locking 
means for locking engagement with the bore of the head in order to hold it 
down within the bore of the casing head when fully landed therein. 
The outer surface 31 of the tubing hanger is conically shaped and converges 
downwardly so as to form a downwardly opening frusto-conical space between 
it and the bore 32 of the casing hanger body. Thus, as will be described 
to follow, upon landing of the seal assembly on the casing hanger, and 
subsequent lowering of the tubing hanger body with respect to the seal 
assembly, surface 31 is caused to slide downwardly over the inner side of 
the seal assembly to cause it to flex outwardly into sealing engagement 
between the surface 31 and the bore 32 of the casing hanger. 
As best shown in FIG. 2 to 4, the seal assembly 30 includes an annular 
metal body 33 having an upper end received about and connected by one or 
more shear pins 34 to a reduced diameter portion 35 of the body of the 
tubing hanger beneath its upper enlarged end. The body of the seal 
assembly further includes a relatively thin inner wall 36 at its lower end 
having a conically shaped inner side 37 for disposal opposite the 
conically shaped outer surface 31 of the tubing hanger body when the seal 
assembly is landed. 
As shown, and as will be described in more detail to follow, the lower end 
of the seal assembly body also includes upper and lower legs 38 and 39 
which extend respectively outwardly and downwardly and outwardly and 
upwardly from the outer side of the inner wall 36, and a packing 40 of 
resilient material confined between the legs and the outer side of the 
inner wall 36. The outer ends of the legs and the outer surface of the 
packing are spaced from the bore 32 of the casing hanger body, as the 
lower end of the seal assembly is lowered into the bore, as shown in FIG. 
3, but are adapted to be flexed outwardly into sealing engagement with the 
bore 32 upon lowering of the tubing hanger body with respect to the seal 
assembly, following landing of the seal assembly, as will be described in 
connection with FIG. 4. 
The seal assembly body also includes an intermediate wall 41 which is 
tapered downwardly and inwardly from the upper end of the seal assembly 
body to an upper extension 42 of the inner wall 36. As shown, a conically 
shaped seat 43 on the upper side of the wall 41 is spaced beneath a 
conically shoulder 44 between the reduced diameter portion 35 and a 
further reduced diameter portion 46 of the tubing hanger body above the 
outer surface 31 thereof. The outer side of the wall 42 and the inner side 
of the outer portion 46 of the tubing hanger body are cylindrical and 
permit free vertical movement of the tubing hanger body with respect to 
the seal assembly from the position of FIG. 3 to the position of FIG. 4. 
As the tubing hanger and seal assembly are lowered onto the casing hanger, 
the lower side 47 of the wall 43 of the seal assembly body is adapted to 
land upon a seat or shoulder 48 on the upper end of the tubing hanger 
body, both surfaces being downwardly and inwardly conically shaped. This 
then will locate the legs 38 and 39 and packing 40 on the inner wall 36 of 
the lower end of the seal assembly opposite the cylindrical bore 32 in the 
tubing hanger body, as shown in FIG. 3. At this time, downward force may 
be applied to the tubing hanger body, through the running tool, so as to 
shear pins 34 and thus lower shoulder 44 onto seat 43 to land the tubing 
hanging body on the seal assembly, and thus land the tubing hanger as well 
as the seal assembly within the bore of the casing head. 
As previously mentioned, this downward movement of the tubing hanger body 
will cause its outer conical surface 31 to slide downwardly over the inner 
side 37 of the inner wall of the seal assembly body and thus flex it 
outwardly to cause the outer ends of the legs 38 and 39 and the outer 
diameter of the packing 40 to sealably engage the bore 32. A seal ring 49 
is carried within a groove about the inner side of the inner wall 
generally intermediate the legs 38 and 39, a tight seating engagement of 
the surface 31 with the inner side of the inner wall of the seal assembly. 
As described in connection with the aforementioned U.S. Pat. No. 4,757,860, 
the forcing of the outer ends of the legs 38 and 39 against the bore of 
the casing hanger will cause the upper leg to be flexed downwardly and 
inwardly and the lower leg to be flexed upwardly and inwardly thus 
compressing the packing 40 to cause its outer diameter to be forced 
outwardly into tight sealing engagement with the bore 32. 
The upper end of the seal assembly body also has a lost motion connection 
with the tubing hanger body which permits the tubing hanger body to move 
downwardly with respect to the seal assembly, in order to set the seal 
assembly, but then move upwardly with respect thereto and lift the seal 
assembly with it in order to retrieve the seal assembly with the tubing 
hanger, it desired. For this purpose, a screw 50 threaded into the reduced 
diameter portion 20 of the upper end of the tubing hanger just below the 
shear pin 34 is received within a slot 51 formed in the upper end of the 
tubing hanger body and of a length to permit the above described relative 
movement between the tubing hanger and seal assembly. 
As also shown in the drawings, the casing hanger has a groove 53 formed 
thereabout above the bore 32 which may be useful, for example, in landing 
one or more tools within the casing hanger during completion of the well. 
Although the upper end of this groove may have a diameter substantially 
smaller than the bore 32, the shear pin 34 holds the inner wall at the 
lower and of the seal assembly body in a raised position, prior to being 
flexed inwardly, in which it is retracted beneath the outer surface of the 
tubing hanger to permit the legs 38 and 39 and packing 40 to be moved 
freely against the upper end of the groove and into a position opposite 
the bore 32. 
The surface wellhead shown in FIGS. 5 to 9 comprises a casing head or 
housing 60 having a bore 61 therethrough and connected at its lower end to 
an outermost casing string (not shown) extending into the well bore. As in 
the case of the subsea wellhead of FIGS. 1 to 4, the surface wellhead also 
includes one or more casing hangers 62 lowered into and landed within the 
bore of the casing head for suspending casing strings therefrom, and an 
annular space between an outer surface of each of the casing hangers and 
the bore of the casing head may be closed off following the circulation of 
cement therethrough during the completion of the well. 
In accordance with another novel aspect of the present invention, the 
surface wellhead also includes a tubing hanger whose body 64 is lowered 
into the bore of the casing head and landed on the casing hanger 62, as 
shown in FIG. 5, and a seal assembly 63 for closing the space between an 
outer surface 66 about the body of the tubing hanger and the bore 61 
through the casing head. More particularly, and as will be described more 
fully hereinafter, the surface 66 is conically shaped to form an upwardly 
opening frusto-conical space, and the seal assembly is of a shape and 
construction for flexing outwardly into sealing engagement between the 
tubing hanger surface and bore so as to close the space. As shown, the 
tubing hanger carries locking elements 67 which are adapted to be moved 
into the groove 68 formed in the bore of the casing head so as to hold 
down the tubing hanger down in the head when landed therein. 
The surface wellhead also includes a Christmas tree adapter 68 adapted to 
be landed on the upper end of the casing head and connected thereto by a 
connector 69 having locking elements 69A adapted to be cammed into locking 
engagement with the adapter and head by means of bolts 69B. As shown, the 
adapter 68 has a bore 70 therethrough including a counterbore 71 at its 
lower end, and the body of the tubing hanger has an upward tubular 
extension 72 which is adapted to be received in the counterbore as the 
Christmas tree adapter is landed on and connected to the casing head. More 
particularly, the upper extension 72 of the tubing hanger has an outer 
conical surface 73 which is spaced from the counterbore 31 to form an 
upwardly facing frusto-conically shaped space between them and a seal 
assembly 74 is wedged into the space so as to seal with respect both the 
counterbore 71 and the outer surface 72 of the tubular extension and the 
us close the space upon landing and connection of the adapter. Thus, like 
the seal assembly of the subsea wellhead, seal assembly 74 may not be 
lowered into the space to close it. 
Seal assembly 63 is quite similar to the seal assembly of the subsea 
wellhead previously described, in that it includes a metal body having a 
relatively thin inner wall 75, and legs 77 and 78 which extend downwardly 
and outwardly and upwardly and inwardly, respectively, from the outer side 
of the inner wall, so as to contain a packing 79 of resilient material 
therebetween. In this case, however, there are two sets of such legs and 
packings spaced one above the other, thus providing redundant seals. 
As in the case of the seal assembly 30, the inner side of the wall 75 is 
conically tapered downwardly and outwardly for sliding along the outer 
surface 66 of the tubing hanger body so as to cause the inner wall to be 
flexed outwardly and thereby cause the outer ends of the legs and the 
packings to be tightly engaged with the bore of the casing head. As in the 
case of the seal assembly 63, a seal ring 81 is disposed within a groove 
about the inner side of the inner wall 75 generally vertically 
intermediate each upper and lower set of legs to form a resilient as well 
as a metal-to-metal seal between the seal assembly and the tubing hanger. 
In addition to providing redundant seals, the two sets of upper and lower 
legs define a space 80 between the lower leg of the upper leg of the lower 
set into which fluid may be injected through a ball check valve 82 in a 
fitting 83 mounted in the casing head. This may be useful in injecting 
packing or the like into the space, or in injecting test fluid into the 
space for testing either or both of the upper and fluid fluid to the 
packing. 
Except for size, the sealing assembly 74 is substantially identical to 
sealing assembly 65 in that it comprises a metal body having a relatively 
thin, inner wall 85 having an inner side which is conically shaped 
downwardly and outwardly to conform generally with the conical shape of 
the outer surface 73 of the tubular extension 72 for sliding downwardly 
therealong in order to flex the inner wall outwardly. Seal assembly 74 
also includes two vertically spaced apart sets of upper and lower the legs 
86 and 87 which extend respectively downwardly and outwardly and upwardly 
and outwardly from the outer side of the inner wall 85, as well as packing 
88 of resilient material confined between each set of upper and lower 
legs. Thus, upon outward flexing of the inner wall 85, the outer end of 
the legs and packings are flexed into tight sealing engagement with the 
counterbore 71, so as to close the annular space between the extension and 
the counterbore. 
As shown in FIGS. 5 and 6, a nut 90 is threadedly connected about the upper 
end of the body of the tubing hanger for vertical movement with respect to 
it between an upper position, as shown in FIG. 6, wherein the body of the 
seal assembly 65 assumes an upper, unflexed position with respect to the 
tubing hanging body, and a lower position, as shown in FIG. 5, wherein the 
seal assembly has been forced downwardly to cause its inner wall to slide 
over the outer surface of the tubing hanger and thus be flexed outwardly 
into sealing engagement between the tubing hanger and bore of the casing 
head. As shown in FIG. 6, when in its upper unflexed position, the outer 
ends of the legs 77 and 78 and packings 79 of the seal assembly are spaced 
from the bore of the tubing hanger to permit the seal assembly to move 
freely into the bore of the casing head. 
More particularly, the seal assembly body includes a flange 92 at its upper 
end having a shoulder or seat 93 on its top side engagable by a shoulder 
94 on the lower end of the nut 90, and a shoulder 95 which projects 
inwardly for seating upon a shoulder or seat 96 about the tubing hanger 
body above the tapered outer surface thereof. As the nut 90 is turned 
downwardly to lower the seal assembly from the FIG. 5 to the FIG. 6 
position and thus flex the inner wall 75 outwardly to tightly engage the 
outer ends of the legs and the packing with the bore, the shoulder 95 
lands on seat 96 to prevent further outward flexing. A C-ring 97 is 
disposed about grooves in the outer sides of the nut and flange 92 so as 
to hold them together during assembly. 
As previously described, since the tubing hanger is installed in the upper 
end of the surface casing head, the nut 90 is accessible for manipulation, 
prior to installation of the Christmas tree adapter, without the need for 
a long, remotely operated running tool. Instead, the upper end of the nut 
may be provided with notches or the like to receive conventional tools for 
torquing it up when the seal assembly is to be set. 
In similar fashion, the seal assembly 74 includes a flange 98 at its upper 
end having a shoulder 99 at its top side adapted to be engaged by a 
downwardly facing shoulder 100 at the upper end of the counterbore 71 upon 
assembly of the seal assembly over the upper end of the extension and 
adapter 73 over the upper end of the seal assembly 74. In that position of 
the seal assembly, shoulder 101 on the lower end of the inner side of the 
flange 98 is spaced above shoulder or seat 102 on the upper end of the 
tubing hanger extension, and the outer ends of the legs 86 and 87 as well 
as the outer diameter of the packing 88 are spaced from the counter bore 
in the adapter so that the adapter will move freely over the seal 
assembly. 
As the bolts of the connector 69 are initially made up to connect the 
adapter to the casing head, shoulder 100 forces the seal assembly body 
downwardly within the space between the outer surface of the tubing hanger 
and the bore of the casing head. This causes the inner wall of the seal 
assembly to slide downwardly over the outer surface of the extension, 
thereby flexing the inner wall outwardly. Upon continued outward flexing 
of the inner wall, the outer ends of the legs 86 and 87 as well as the 
outer diameter of the packing 88 are brought into tight sealing engagement 
with the counterbore 71 and thus, together with the tight engagement of 
the inner side of the inner wall and seal rings 103 carried thereabout and 
the outer surface of the tubing hanger extension, close the space between 
the extension and adapter. At this time, shoulder 101 moves into 
engagement with shoulder 102 to limit further downward movement of the 
seal assembly. Thus, the seal assembly has been installed and set without 
a running tool or other remotely operable means, and instead merely in 
response to relative vertical movement between the tubing hanger extension 
and the tree adapter. 
From the foregoing it will be seen that this invention is one well adapted 
to attain all of the ends and objects hereinabove set forth, together with 
other advantages which are obvious and which are inherent to the 
apparatus. 
It will be understood that certain features and subcombinations are of 
utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of the 
claims. 
As many possible embodiments may be made of the invention without departing 
from the scope thereof, it is to be understood that all matter herein set 
forth or shown in the accompanying drawings is to be interpreted as 
illustrative and not in a limiting sense.