Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to well head shut-off devices which
can be employed for forming a seal in the annular space between a
cylindrical housing forming part of the well head structure and a
polished rod or other cylindrical shaft, passing through said
housing. More especially, the invention relates to devices for use
in the high pressure and high temperature steaming of relatively
intractable underground deposits of heavy hydrocarbons in order to
render the hydrocarbons liquid to allow recovery. Such steaming is
usually conducted using a well having a string of production tubing
extending downwardly into the earth co-axially centrally of an
outer tubular casing which thus defines an annulus around the pro-
duction tubing. High pressure steam is injected down the annulus
and liquid heavy hydrocarbon is produced up the production tubing.
With this operation there is risk of rupture of stuffing boxes or
other equipment connected to the production tubing during steam in-
jection or subsequently. Such rupture can result in escape of high
temperature and high pressure steam, hot liquid hydrocarbon, and
other liquids or gases such as liquid hydrocarbons, water and well
gases. Escape of hot fluids represents at least an economic loss
of the heat energy employed in the steam generation. Escapes of
other liquids or gases may be undesirable environmentally. For
example, some escaping gases may contain ~2S or other toxic gases.
Further, in some cases, the escape oE steam, gas or liquid, if
allowed to proceed unchecked, can lead to damage to well head gear,
possible injury to personnel, and blow out of the well, resulting
in upward ejection of the production tubing string and wrecking of
the well.
There have been various proposals for vapor shut-off devices for
packing off a zone of the well head equipment upwardly from the
upper end of the production tubing string, in order to interrupt
escape of steam or other high temperature vapor, but these have not
been as effective or as readily operable as desirable.
The present invention provides a well head vapor shut-off device,
comprising:
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3~
(a) a housing adapted to be connected to the upper end of
production tubing and having a vertical bore therethrough, a flow
conduit communicating with the interior of the bore for collection
of liquid flowing into the bore from the production tubing, and a
shoulder extending laterally inwardly of the bore at upper and
lower portions thereof;
(b) a pack~off member disposed in the bore and comprising a heat
resistant resiliently deformable annular sealing element of which
the middle opening extends vertically of the bore and is adapted to
receive a cylindrical shaft therethrough, and the periphery
conforms to the interior of the bore, a rigid face plate on the
upper and lower sides of the sealing element, and a rigid expansion
member tapering from adjacent one of said face plates vertically
toward the interior of the sealing element and being received in a
corresponding cavity therein;
(c) an operator member slidable vertically relative to said
pack-off member and face plates and having upper and lower
abutments facing toward the face plates on the upper and lower
sides of the sealing element, respectively; and
(d) means for reciprocating said operator member between an upper
position engaging the upper face plate on the upper shoulder and
compressing the sealing element between the upper face plate and
the lower face plate retained on the lower abutment, and a lower
position engaging the lower face plate on the lower shoulder and
compressing the sealing element between the lower face plate and
the upper face plate retained on the upper abutment, whereby in
each of said positions the sealing element is compressed vertically
and the expansion member is driven vertically inwardly relative to
said cavity, thereby expanding the sealing element laterally to
form a seal between the bore and the cylindrical shaft when
inserted therein.
In one advantageous application of the present device, the upper
end of the housing includes a gland or stuffing box forming a seal
with a polished rod passing through the middle opening of the
~%2~ 32
sealing element of the pack-off member. Often, in steam injection
operations, a sucker rod string is employed which passes downwardly
through the production tubing and is connected to a down hole pump
for pumping hydrocarbon up the produc-tion tubing and out of the
flow conduit. The sucker rod string is connected to a polished rod
passing through a stuffing box connected to the production tubing.
However, the stuffing box has to be formed with relatively soft
sealing material in order to avoid excessive frictional losses and
wear of the polished rod over pumping periods which may continue
for several months. The stuffing box sealing materials are
therefore vulnerable to damage by exposure to the high temperature
vapors and hydrocarbon products and are therefore prone to failur
leading to vapor escape therethrough. One advantage of the present
arrangement, especially when, as is usual, the shut-off device is
manually operated, is that regardless of the direction in which the
operator member is reciprocated, packing-off and sealing can be
achieved, since a seal will be achieved at either of the above-
mentioned upper and lower positions. This is advantageous since,
frequently, steam escapes are observed by, and need to be dealt
with by, well attendants who are not always completely familiar
with the all the various modes of operation of different varieties
of well head equipment. Thus valuable time can be saved in
shutting off an escape of steam from the stuffing box.
The arrangement of the invention has the further advantage that the
pack-off member carries with it its own built-in tapering expansion
member which moves upwardly and downwardly with the sealing
element, so that the pack-off member does not rely for sealing pur-
poses on alignment with a tapering internal surface of the bore.
Such tapering internal surfaces would render the construction of
the device considerably more complex where, as in the present de-
vice, seals are formed alternatively at upper and lower positions.
In a further advantageous application, the flow conduit connects
with a part of the bore intermediate the upper and lower portions
housing the said shoulders, so that in the lower pack-off position
a seal is formed preventing flow from the production tubing to the
flow conduit. With this arrangement, in the upper pack-off
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32
position a seal can he formed preventing steam escape from a gland,
if a polished rod is employed, and, in the lower pack-off position,
the flow conduit is shut off, preventing steam or other vapor
escape or liquid escape in the event of rupture of the lines
connected to flow conduit or failure of the valves or other
equipment associated with the production flow lines.
An example of a preferred form of device in accordance with the
invention will now be described, by way of example only, with
reference to the accompanying drawings, in which:
Figure 1 shows, partially schematically and partially in section,
well head equipment including a vapor shut off device in accordance
with the invention;
Figure 2 shows a vertical section, partly in side elevation,
through the device, and wherein the internal reciprocating operator
member and pack-off member are not shown for greater clarity of
illustration;
Figure 3 is a fragmentary perspective view of the operator member
and pack-off member of the device;
Figure 4 shows the device in section packed off at an upper
position;
Figure 5 shows the device packed off at a lower position; and
Figure 6 is a fragmentary perspective view of the rigid expander
element of the pack-off member of Figure 3.
Figure 1 shows a typical well head configuration, showing a tubular
outer casing 11, the upper end of which is connected to an inwardly
downwardly tapering cylindrical bowl 12, having a circular upper
flange 13. On the flange 13 and secured by bolts 14 is an adapter
or hanger flange 16. The mating surfaces of flanges 16 and 13
provide cooperating annular channels trapping a steel ring gasket
17. The central opening 18 of flange 16 has a threaded downwardly
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flaring lower portion. Into this is threaded the upper end of a
string of production tubing 19. The tubing 19 is thereby held
hanging or suspended down the well from the flange 16. A vapor
shut-off device 21 in accordance with the invention is connected on
the flange 16. As seen in more detail in Figure 2, this comprises
a tubular housing comprising upper and lower tubular members 22 and
23, with cooperating flanges 24 and 26 trapping a steel ring gasket
27 and secured together by threaded studs 28 and nuts 28a.
Likewise, the lower end of lower member 23 has an annular flange 29
formed with a sealing ring channel 31 and through-holes 32 for
sealing attachment of the device to the flange 16 using studs and
nuts 33, seen in Figure 1, going into blind holes in the flange 16.
The lower member 23 defines within it a bore 34 coaxial with and of
approximately the same diameter as the opening 18 in the hanger
flange 16. The member 23 is in the form of a tee having a flow
conduit 36 formed by a branch conduit communicating with the bore
34. Desirably, the lower member 23 and conduit 36 are formed as a
unitary body, e.g. as a one-piece casting.
As seen in Figure 1, connected to the upper end of device 21 is a
stuffing box or gland 37, through which passes a polished rod 38.
The box 37 provides, in normal service, a gas-tight seal around the
rod 38, so that gas can not escape from the upper end of the device
21, while permitting the rod 38 to be reciprocated relative to the
device 21. The stuffing box may be of a conventional form well
known to those skilled in the art and is threaded into a tapering
recess 39 formed in an upper surface of a cylindrical drive member
41 which is connected to the upper end of the member 22. As will
be readily appreciated by those skilled in the art, the stuffing
box comprises a sealing member disposed in tight sealing contact
around the polished rod. This sealing member is of a relatively
soft material so that the rod 38 can be reciprocated for prolonged
periods without excessive wear of the rod or of the sealing member
occurring. Typically, the upper end of the rod 38 is connected to
a cross member 42 suspended from cables 43 connected to a prime
mover, e.g. through a walking beam. The lower end of the rod 38
has connected to it a sucker rocl string which hangs down the well
and is connected at its lower end to a down hole pump for pumping
fluid up the tubing 19.
Shown somewhat schematically in Figure 1 are piping arrangements
for supplying steam to and for recovering flowable product from the
well. The piping comprises a pipe 44 connected to flow conduit 36,
usually by welding, and through a two-position steam on-off valve
46 to a tee 47. One arm of the tee 47 connects to a choke 48 for
regulating flow of liquid heavy hydrocarbon therethrough. The
choke is connected to a four way connector 49, another connection
of which is connected to a pipe 51 through which steam may be
supplied and through which liquid heavy hydrocarbon may be with-
drawn. Another arm of the connector 49 connects through a two-
position on-off valve 52 to the tee 47. A fourth connection of the
connector 49 is through a pipe 53 and a two-position steam on-off
valve 54 to a side conduit 56 communicating with the interior of
the bowl 12 for~ing the head of the well casing 11.
Before describing further the structure and function of the device
21, it is in order to describe a typical sequence of operations
employed in the steam injection of and hydrocarbon recovery from
the well as empioyed, Eor example, in hydrocarbon production from
heavy hydrocarbon formations such as tar sands. Normally, a cycle
of operations is employed. A first stage of the cycle may
typically consist of trickle steaming for about 24 hours wherein
valves 46 and 52 are open, valve 54 is closed and choke 48 is
closed and steam at, e.g., approximately 450F is injected through
pipe 44 and down the production tubing 19, at a relatively low flow
rate. One purpose of this is to soften and loosen any deposits of
cooled and hardened heavy hydrocarbon that may be adhering to the
inside of tne production tubing 19, so that any such deposits are
not likely to plug or block the production tubing during the
subsequent flow-back and pumping stages. Secondly, the trickle
steaming gradually heats up and expands the production tubing so as
to reduce or avoid the abrupt application to it oE mechanical
forces or shock as a result of sudden differential expansion
between the tubing 19 and casing 11O After the trickle steaming,
the valves 46 and 52 are closed and valve 54 is opened and steam
~2ZI1~1~32
injection is co~menced by introducing high temperature high
pressure steam at high flow rates through pipes 51 and 53, to the
side conduit 56 and hence down the annulus between the casing 11
and the tubing l9. The annulus is of a relatively large cross-
section and thus steam can be passed down it at high flow rates.
The high temperature steaming, e.g. at temperatures of about 650F,
may be continued for a prolonged period, e.g. for about 20 days.
The function of this steaming is to penetrate the underground
formations and to raise the temperature of the underground
deposits, thus bringing them to a temperature at which their
hydrocarbon content is rendered sufficiently liquid to flow up the
production tubing. After steam injection, the valve 54 will
typically be c]osed and the well is closed off and allowed to soak
for a prolonged period, e.g. about one month. The purpose of this
is to allow time for penetration of the formations to the greatest
extent, and it is found that the utilisation of a soaking period in
many cases increases the efficiency of the hydrocarbon production.
After the soaking period, the valve 46 and the choke 48 are opened,
and the hot liquid hydrocarbon is allowed to flow up the production
tubing 19 under the pressure built up in the underground formation
during the steam injection period. The flow rate o~ the produced
hydrocarbon through the conduit 36 and pipe 44 is limited and
controlled by the setting of the choke 48, and the produced liquid
is recovered along the pipe 51. Typically, the period of flow-back
will continue for from several days to about 1 month.
Once flow-back of liquid has ceased due to depletion of the under-
ground pressure, pumping is commenced. The prime mover is operated
to reciprocate the polished rod 38 through the stuffing box 37 and
hence reciprocate the sucker rod string connected to the polished
rod and actuate the down hole pump, so that liquid hydrocarbon in
the formation is pumped up the tubing 19 and recovered through the
conduit 36, and pipes 44 and 51 as before. Typically, pumping will
continue for several months, e.g. 3 to 4 months, until the liquid
hydrocarbon is exhausted or its production rate drops to a point
where continued production is no longer practicable. The cycle is
then recommenced starting, for example, with trickle steaming.
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In the case in which the well is provided with a polished rod and
stuffing box, exposure of the material of the sealing member of the
stuffing box to high temperature steam, hot vapours and hot liquid
hydrocarbon tends to promote relatively rapid wear and
deterioration of the seal so that there is risk of loss of the seal
around the polished rod, leading to risk of loss of steam or the
like, and possible blow out in the event that the underground
formation is highly pressurized, whether as a result of the steam
injection or through other causes. In many cases, the pipes con-
nected to the flow conduit 36 are vulnerable to damage as a resultof their extending in relatively exposed positions above ground
adjacent the well head, so that they are prone to breakage or
perforation. Further, during steam injection down the annulus,
considerable pressure builds up in the production tubing 19, in the
flow conduit 36 and in the pipes connected thereto. There is risk
that small leakages in any of the control valves, e.g. the valve
46, connected thereto, can result in an escape of high temperature
high pressure steam. At high temperatures, pressures, and flow
rates, steam has the ability to cut through metal, so that small
escapes of steam can escalate into destruction or "wash-out" of the
valve, leading to major losses. The liquid hydrocarbon often con-
tains abrasive mineral particles, especially in the case of steam
injection of tar sands, and therefore any minute perforations in
the pipes or valves connected to the flow conduit 36 are prone to
be reamed out by abrasive action of the hot liquid particulate mix-
ture escaping therethrough, thus aggravating any leakage problem.
The device, as shown in the accompanying drawings, provides means
for rapidly packing-off the interior of the housing in the event of
a failure of the stuffing box during pumping or at any other time,
for packing-off the space above the flow conduit 36 during tric~le
steam injection down the production tubing or during flow back, and
the space below the flow conduit 36 during steam injection down the
annulus or in the event of loss of sealing of the pipes or valves
connected to the flow conduit 36 at any time.
As seen in Figures 3, 4 and 5, the vapour shut-off device includes
a pack-off member which is disposed in the bore 34 and comprises a
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heat-resistant resiliently deformable sealing element 57 of annular
cross-section. The element 57 has a middle opening 58 of circular
cross-section through which the cylindrical polished rod 38 is
received. The cylindrical periphery 59 of the element 57 conforms
to the cylindrical interior of the bore 3A. Normally, there is a
small clearance between the periphery 59 of the element 57 and the
interior of the bore 34, and between the opening 58 and the
exterior of the shaft 38, so that the shaft 38 and element 57 may
be reciprocated relative to one another, and so that the element 57
may be reciprocated within the bore 34.
A rigid, e.g. steel, annular upper face plate 61 is disposed on the
upper side of the element 57. A generally annular rigid lower face
plate 62 shown in more detail in Figure 6 is disposed on the lower
side of the element 57. As seen in Figure 6, the plate 62 com-
prises a generally annular portion 63. Integral with this and
depending downwardly therefrom is a cylindrical portion 64, and on
the upper side is -formed integrally therewith a rigid expansion
collar 66, which tapers upwardly from the upper surface of the
plate 63. As seen in Figllre 6, the collar 66 is generally annular,
so that it can expand the sealing element 57 approximately uniform-
ly around its entire circumference. In the preferred form, as
shown, the collar 66 is formed by intersecting surfaces 67 and 68,
each of which is a frustum of a cone, the cones being equi-angular,
and one being inverted with respect to the other, and each being
coaxial with the sealing element 57.
As seen in Figures 3, 4 and 5, the tapering expansion member 66 is
received in a corresponding tapering annular recess in the lower
side of the expansion element 57.
Desirably, the interior diameter of the upper tubular member 22 is
slightly less than the diameter of the bore 34 of the lower member
23, and, as seen in Figure 2, the member 22 is formed adjacent its
lower end with a series, for example three inwardly projecting
splines or castellations 69 which are regularly spaced around the
interior of the bore 34. ~he lower edges of the castellations 69
and of the upper member 22 thus provide a shoulder 71 extending
0~32
laterally inwardly of the bore 34 at a relatively upper portion
thereof.
Adjacen-t its lower end~ the lower tubular member 23 is formed with
a constricted portion 72, thus likewise forming on its upper edge a
shoulder 73 extending laterally inwardly of the bore 34 adjacent a
relatively lower portion thereof.
The sealing element 57 together with the upper and lower plates 61
and 62 are supported so as to be reciprocable between the upper and
lower shoulders 71 and 73. For this purpose, the sealing element
57, and face plates 61 and 62 are penetrated by a series of verti-
cally extending bores, throuyh which are passed a corresponding
number of bars, for example in the form of bolts 74. The upper
ends of these bolts 74 are threaded into corresponding threaded
recesses in the lower surface of a hollow cylindrical stem 760 In
the preferred form, there are six of these bolts 74 arranged at
uniform spacings around the annulus of the sealing element 57. As
best seen in Figure 6, the cylindrical bores 77 through the lower
plate member 62 pass vertically through the circle which is the
apex of intersection between the conical surfaces 67 and 68 of the
expansion member 66. The bores through the element 57 and the
upper and lower face plates 61 and 62 are slightly oversized in
comparison to the diameter of the bolts 74, so that there is some
freedom of sliding movement between the element 57 and the plates
61 and 62 on the one hand and the bolts 74 on the other.
The bolts 74 have enlarged heads 74a which retain the assembly of
the lower face plate 62, the element 57 and the upper plate 61
normally in tight contact with a lower annular face 78 of the
cylindrical stem 76, without, however, the sealing element 57 being
under compression such as to significantly deform it from its
as-manufactured cylindrical condition.
The assembly of the bolts 74 together with the cylindrical stem 76
form an operator member which is slidable vertically relative to
the assembly of the sealing element 57 and face plates 61 and 62,
which together form a pack-off member.
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The drive member 41 cooperates with the operator members 74 and 76
to reciprocate the operator member vertically within the bore, and
for this purpose the drive member 41 is supported so as to be
rotatable relative to the upper tubular member 22 and is threadedly
connected to the cylindrical stem 76. As best seen in Figure 2,
the member 41 is formed with an annular step 79 which engages a
similarly-formed inner step on the inner surface of a generally
cylindrical outer race member 81. The member 81 has a pair of
opposing laterally extending bores 82 through it, through which
pass a pair of elongated rod-like handles 83 each having a threaded
extension 84 on its inner end which engages in a threaded blind
bore in the the drive member 41, thus locking the member 41 to the
race member 81.
Secured on the outer side of the upper end of the upper tubular
member 22 is a cylindrical inner race member 86. The upper portion
of the inner side of the member 86 is threaded on a corresponding
threaded formation on the outer side of the upper end of the
tubular member 22. The member 86 is further located by being
formed with an internal annular lower step 87, seating on a
corresponding step on the outer side of member 22, and by a set
screw 88 passing through a threaded bore in the member 86 into a
hole in the member 22.
Upper and lower cooperating endless ball grooves are formed in the
inner surface of the outer race member 81 and in the outer surface
of the inner race member 86, and in these endless grooves, balls 89
are disposed, having been introduced through ports (not shown)
extending from the outer side of the race member to the grooves,
which ports are subse~uently closed with plugs (not shown) threaded
therein~ The surfaces of the race members 81 and 86 may be
hardened, e.g. by carburizing or the like, so as to provide wear-
resistant surfaces permitting free rotation with reduced wear
between the inner and outer race members 81 and 86. As will be
appreciated, the balls 89 also provide a thrust resistant bearing
whereby any axial or vertical thrust forces applied to the drive
member 41 are transmitted through the race members 81 and 86 and
balls 89 to the upper tubular member 22.
Z~3~
The drive member 41 has a downward cylindrical extension 91 formed
with an upper portion 92 of enlarged diameter, which in the
assembled condition shown in Figure 2 is disposed within a
relatively constricted upper portion 93 of the tubular member 22.
Upper and lower square section grooves are formed in the inner
surface of the constricted portion 93 and disposed in each of these
grooves is a resilient high temperature-resistant elastomeric
0-ring 94 which forms a liquid and gas-tight seal between the
portions 92 and 93. A resilient metal split ring 96 is snapped
into the upper side of each of the square section grooves and each
ring 96 is expanded resiliently by the enlarged diameter portion 92
and is therefore tightly engaged around the portion 92. The rings
96 serve to reduce the tendency for the material of the 0-rings to
be extruded upwardly, resulting in failure of the seal.
The lower portion of the extension 91 is formed with a screw thread
97 of diameter such that, when the device is being assembled, they
can be passed freely through the opening defined by the portion
93. As best seen in Figure 3, the inner side of the hollow cylin-
drical stem 76 is formed with a mating screw thread 98. Desirably,
the threads 97 and 98 are Acme screw threads. The outer side of
the stem 76 is formed with longitudinally extending square section
grooves 99 corresponding in spacing and position to the castel-
lations 69 on the lower portion of the inner side of the tubular
member 22 and dimensioned so that there is clearance between the
castellations 69 and grooves 99 sufficient to permit free vertical
sliding of the stem 76 relative to the member 22, so that the
castellations serve as splines cooperating with the grooves 99 and
preventing rotation of the stem 76 relative to the member 220
In assembling the device 21, the hollow stem 76 having the face
plates 61 and 62, element 57 and bolts 74 secured thereto, is
introduced in to the lower end of the tubular member 22 before the
latter is bolted to the upper flange 26 of the lower member 23.
The thread 97 is engaged with the internal thread 98 in the stem 76
and rotated, so that a few turns of the threads are interengaged.
Subsequently, the lower member 23 is bolted on, as seen, for
example in Figures 4 and 5.
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~L22~3;2
In use, the resilient element 57, together with the upper and lower
face plates 61 and 62 can be reciprocated between upper and lower
positions shown in Figures 4 an 5, respectively, by rotating the
drive member 41 by grasping the handles 83 and pulling on one
handle while simultaneously pushing on the other in order to twist
the drive member 41 about its vertical axis. The rotation of the
threads 97 on the lower extension 91 of the drive member 41 is
effective to drive the hollow stem 76 vertically up or down since
the stem 76 is retained against rotation by the splines or castel-
lations 69 engaging in the grooves 99 in the outer side of thestem. Desirably the threads 97 and 98 are lefthanded threads so
that rotation of the drive member clockwise tends to drive the
sealing element 57 downwards to the position shown ln Figure 5,
while counter-clockwise rotation drives the element 57 upwards to
the position shown in Figure 4. The reciprocal movement of the
stem 76 together with the sealing element 57, etc., relative to the
threaded extension 91 is limited in the upper position, as shown in
Figure 4, by engagement of the upper face plate 61 against the
upper shoulders 71 and in the lower position as shown in Figure 5
by engagement of the lower face plate 62 against the lower shoulder
73, i.e. the grooves 99 run out through the upper face of the stem
and do not limit downward movement of the stem 76, and the upper
face plate 61 engages the upper shoulders 71 before the threaded
extension 91 reaches the end of the thread 98 in the bore in the
hollow stem 76 and before the upper end of the stem 76 engages on
the upper portion 92 of the extension 91 or on the constricted
upper portion of the member 22.
In the upper position as shown in Figure 4, when counter-clockwise
torque is applied to the handles 83 by hand pressure, the bolts 74,
their heads 74a and the lower face plate 62 engaged thereby, are
urged upwardly relative to the upper face plate 61 engaged on the
shoulder 71 so that the resilient element 57 is compressively
deformed longitudinally and tends to expand laterally. The plate
61 is thereby displaced slightly downwardly away from its normal
position abutting the lower side of the stem 76. Simultaneously,
the tapering expansion collar 66 reacts with the side walls of the
cavity within which it is received in the element 57 so as to tend
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~L2Z~3;~
to deform the adjacent portions of the element 57 outwardly toward
the inner side of the bore 34 and inwardly toward the outer surface
of the rod 38, thus forming a tightly-compressed pack-off in which
the resilient materia] of the element 57 is tightly engaged with
the bore 34 and with the rod 38. Similarly, in the lower position
shown in Figure 5, clockwise torque applied by hand pressure on the
handles 83 results in the lower face of the stem 76 urging the
upper plate 61 and the sealing element 57 downwardly relative to
the lower plate 62 and the expander member 66, which are retained
by the shoulder 73, and the plate 62 being displaced upwardly rela-
tive to its normal position in abutment with the upper side of the
bolt heads 78, so that a pack-off between the bore 34 and the rod
38 is achieved at this position. Although in each of these pack-
off positions the resilient reaction of the element 57 exerts a
torque on the stem 76 tending to loosen or release the pack-off,
the mechanical advantage of the threaded connection between the
stem 76 and the extension 91, the friction between the interengaged
screw threads, and the inertia of the drive member 41 and handles
83 prevent loosening rotation of the extension 91.
In the preferred mode of use of the device, in the pumping stage of
the cycle of operations described above the sealing element 57 is
positioned adjacent but not at the upper pack-off position as shown
in Figure 4 i.e. it is a few turns of the drive member 41 away from
the upper pack-off position. In the event of failure of the seal
of the stuffing box 37 during the pumping operation and of escape
of vapor or liquid under pressure through the stuffing box, a
pack-off preventing further escape can be quickly achieved by
turning the handles 83 counter-clockwise to raise the element 57 to
the upper pack-off position. Importantly, regardless of the sense
in which the handles 83 are turned, a pack-off will be achieved in
one of the two possible positions, namely upper and lower. In the
event of an escape of vapor or liquid through breakage or failure
of piping or of a valve connected to the flow conduit 36 during
pumping, an operator inadvertently turning the handles 83 counter-
clockwise will quickly reach the stop position of the upper pack-
off position and will then quickly perceive that the handles need
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to be turned in the opposite direction to achieve a pack-off in the
lower position, thus closing off flow to the flow conduit 36.
During trickle steaming and during flow back up the production
tubing 19, the device may be operated to maintain a pack-off in the
upper position of Figure 4, in order to limit exposure of the rela-
tively less durable seal member of the stuffing box 37 to steam and
other hot vapors, and to hot and usually abrasive produced liquid
hydrocarbons.
During steam injection down the annulus and during soaking of the
well, the device can be employed to maintain a pack-off in the
lower position, as shown in Figure 5, preventing exposure of the
stuffing box seal to hot or abrasive fluids and serving to prevent
escapes of gas or liquid in the event o:E accidental damage,
breakage or the like suffered by piping or valves connected to the
flow conduit 36.
In the preferred form, the lower cylindrical portion 64 of the
lower face plate 62, as seen in Figure 6, has a circumEerential
groove 101 and tapers downwardly below the groove 101 to permit a
split spring ring 102 to be snapped into the groove, as seen in
Figures 4 and 5. The ring 102 interferes with the heads of the
bolts 74 if these become loosened from their normal position tight-
ly threaded into the base of the stem 76 as a result of vibration,
and serve to stop the bolts 74, if loosened, from dropping down the
tubing 19. The spacing between the ring 102 and the heads 78 of
the bolts 74 in the normal or uncompressed condition of the sealing
element 57 is sufficient to avoid the bolt heads 78 engaging the
ring 102 when the latter is displaced upwardly in the lower pack-
off position shown in Figure 5.
Preferably, one of the face plates 61 and 62 is formed with a
recess, such as the frusto conical recess 103 tapering away from
the inner side of the face pla-te circumadjacent each point where a
bolt 74 passes through the plate 61, and the sealing member 57 is
formed with a corresponding generally frusto-conical lip 57a, so
that when the element 57 is compressed vertically between the
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plates 61 and 62 in a pack-off position, the reaction between the
tapering recess 103 and the lip 57a converges the material of the
lip 57a into tight compression around the bolt 74, so that a tight
seal is formed between the element 57 and the bolts 74, closing the
bores 57b through which the bolts 74 pass. Such tapering recesses
may be formed in the inner sides of either or both of the face
plates 61 and 62, adjacent the sealing element 57, and the portions
of the element 57 adjacent thereto provided with corresponding lip
formations, but, for convenience of machining, are formed in the
upper plate 61.
The element 57 is preferably a heat-resistant elastomer having
sufficient resilience that, on release of the pressure to which the
element is subjected during pack-off, it retracts laterally so tnat
adequate clearance is restored between it, the rod 38 and the inner
surfaces of the bore 34 to permit reciprocation of the rod 38 and
travel of the sealing element between its upper and lower pack~off
positions. Suitable heat resistant elastomers are known to those
skilled in the art, and are employed in known blow-out preventer
devices intended for high temperature service.
~arious modifications may be made to the device. For example, the
lower side of the upper plate 61 may be formed with a downwardly
tapering expander element similar to the expander element 65,
received in a corresponding tapering recess in the upper side of
the element 57, and the upper side of the lower plate 62 may be
planar.
Instead of using a screw thread and spline arrangement for recipro-
cating the pack-off member constituted by the element 57 and plates
61 and 62 between its upper and lower positions, other arrangements
may of course be employed. For example, one or more hydraulic
cylinders can be provided within the upper tubular member 22, with
pistons connecting downwardly to the bolts 74, and operable by
fluid pressure leads passing through the side wall of the member
22. Such arrangements, however, greatly increase the complexity
and cost of the device and thereEore a hand-operable screw thread
is preferred.
~ 16 -
In other advantageous forms, the element 57 together with the
plates 61 and 62 may be supported to reciprocate between upper and
lower shoulders both of which are disposed above the flow conduit
36, and are spaced apart so that the assembly of the element 57 and
plates 61 and 62 has only a small degree of freedom of vertical
travel, so that regardless of the sense in which the handles 83 are
rotated, the assembly is rapidly brought .into engagement with one
or the other o:E the two shoulders and a pack-off achieved with
great rapidity.
In other forms, instead of a reciprocatiny polished rod 38, a shaft
which is normally vertically stationary is passed through the drive
member 41 and assembly of plates 61 and 62 and the sealing element
57. Such shaft may be secured to the upper end of the drive member
in sealing fashion without requiring a stuffing box or other recip-
rocation-permitting sealing arrangement, and may for example be a
hollow shaft through which thermocouples or the like may be passed
in order to monitor the well temperatures at various levels.
The preferred form of the present device as shown in the
accompanying drawings has numerous advantages.
Since the means for reciprocating the operator member, namely the
drive member and the extension 97 thereof, form a seal with the
tubular housing 22 at the O-rings 94, the thrust exerted by
pressurized fluid within the bore 34 is transmitted to the thrust-
resistant bearing between the housing 22 and the drive member 41,
and the pressure within the bore 34 acts equally on the upper and
on the lower sides of the assembly of the operator member (stem 76
and bolts 74) and the pack-off member (the element 57 and the
plates 61 and 62). This assembly of the operator member and pack-
off member is therefore free-floating within the bore 34. This,
therefore, greatly facilitates moving the pack-off member in the
presence of fluid under pressure in the bore 34 and is not driven.
vertically in one direction or the other into tight binding engage-
ment with the screw threads 97 oE the extension 91 of the drive
member 41 and permits the production tubing 19 to be packed-off or,
~IL2~ 3~
if desired, to be opened, under pressure, by rotation of the drive
member 41.
As noted above, the screw-threaded drive for the pack-off member
provides a mechanical advantage, thus allowing a tight pack-off of
the production tubing by application of hand pressure only. A
further advantage of the arrangement shown, wherein the diameter of
the threads on the extension of the drive member 41 and on the stem
76 are less than the diameter of the bore 34, is that in the event
of solidified hydrocarbon or other solids caking on the threads, it
is relatively easy to overcome any tendency of the threads toward
sticking by applying hand pressure to the handles 83. For example,
the handles 83 may each be about 12 inches long, and merely by way
of example, it may be mentioned that the diameter of the screw
threads on the stem 76 and drive member 41 may each be about 2 1/2
inches so that a considerable turning moment can be applied to the
threads in order to free the movement of the drive member 41
relative to the stem 76.
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