Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02462183 2004-03-29
TITLE OF THE INVENTION
Pump Rod Clamp And Blowout Preventer
FIELD OF THE INVENTION
This invention relates generally to a pump rod clamp and blowout preventer as
may be
used on oil, gas water wells, and in particular a new and improved pump rod
clamp and
blowout preventer having an enhanced polished rod clamping or gripping
capability.
CA 02462183 2004-03-29
BACKGROUND OF THE INVENTION
The use of pump rod clamps and blowout preventers on oil, gas and water wells
is a
common occurrence. Pump rod clamps are used generally to hold the pump or
polished
rod and may take any one of a wide variety of forms ranging from a pair of
rams that are
driven radially inward in order to contact the pump rod and hold it in place,
to wedges
that may be inserted around the rod, to a pair of clamping members that may be
bolted
around the exterior surface of the rod and hung from a mandrel or other
support
member. Regardless of the particular structure of the clamp, its primary
purpose is to
either suspend the rod within the well, and/or to prevent rotational movement
of the
pump rod.
Blowout preventers (or BOP's as they are typically called) are critical pieces
of
equipment that are used to seal off the well and contain its contents under a
variety of
different situations. For example, during the servicing of a wellhead one or
more
blowout preventers are often used to seal against the pump or polished rod to
contain the
contents of the well when downstream equipment is removed or disassembled for
servicing. In other instances blowout preventers may be used to seal off a
well where
the pump rod is removed, or in the event of a failure of the pump rod.
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Blowout preventers that are used in producing oil and gas wells are most
commonly
comprised of a pair of rams that are received within cylinders or bores
extending
through a BOP housing and situated generally perpendicular to the longitudinal
axis of
the well casing. Typically the end of each ram has a semi-circular channel on
its face
to allow it to seal against the exterior surface of the polished rod when
driven inwardly.
The faces of the rams may include an elastomer or other sealing mechanism to
ensure
that a fluid tight seal is created when the rams fully engage the polished
rod. Examples
of such prior existing blowout preventers are described in United States
patents
4,860,826, 5,746,249, and 5,875,841.
While currently available blowout preventers are generally effective in
sealing around
a polished rod and preventing the contents of a well from escaping, they
nevertheless
suffer from a number of inherent limitations. In order to ensure a tight seal
between the
rams and the polished rod, particularly where the well is a high pressure well
or contains
natural gas or hydrogen sulfide, operators have developed a tendency to drive
the rams
inwardly against the polished rod using a considerable amount of force. While
doing so
has the effect of compressing the elastomer against the rod and helping to
ensure a good
seal, in many cases the metal faces of the rams are also driven into contact
with the
exterior surface of the rod. In some cases rig hands intentionally drive the
faces of the
rams into the polished rod as a means to not only seal off the well, but to
also effectively
act as a rod clamp to hold the polished rod in place. Where the pump in
question is a
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reciprocating pump, the rams may be used to maintain or hold the weight of the
rod
while work is performed upon components downstream of the BOP. Where the pump
is a rotary style pump, the rams may be used to both hold the weight of the
polished rod
and to prevent rotation caused through backspin forces applied to the rotor of
the pump
by the head of fluid in the well. In either case, use of the BOP rams to not
only seal the
well but to grasp or clamp the rod can have the effect of marking or scoring
the exterior
surface of the rod and/or the face of the ram, neither of which is desirable.
Further, when
the metallic faces of the rams contact the exterior of the polished rod an
electrical
connection will be formed therebetween, which in some circumstances may also
be
undesirable.
Currently available polished rod clamps are also not without their
limitations. Where
the well is equipped with a separate polished rod clamp the overall height of
the
wellhead will be increased by the height of the clamp. Use of a dedicated rod
clamp
also results in an increase in equipment cost and represents a further
mechanical
component that may malfunction or fail. In addition, the use of a separate
polished rod
clamp does not prevent an operator from over tightening the BOP rams and
causing their
metal faces to score or damage the surface of the polished rod.
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SUMMARY OF THE INVENTION
The invention therefore provides a pump rod clamp and blowout preventer that
is in the
form of a single component capable of both sealingly engaging a polished rod
to prevent
the escape of fluid from a well, while at the same time providing an enhanced
ability to
clamp or grip the rod and to prevent or retard axial andlor rotational
movement. In one
embodiment the invention further provides a mechanism by which the polished
rod may
be clamped and securely held without scoring or damaging the exterior surface
of the
rod, and without the formation of an electrical bonding between the invention
and the
pump rod.
Accordingly, in one of its aspects the invention provides a pump rod clamp for
gripping
a pump rod in an oil, gas or water well, the pump rod clamp comprising a
central
housing having a longitudinal bore for receiving a pump rod; a plurality of
clamping
members receivable within said central housing; and, one or more actuators to
cause
said clamping members to be moved between an activated position where they
grippingly engage the exterior surface of the pump rod and a deactivated
position where
they are released from contact with the exterior surface of the pump rod, each
of said
clamping members having a leading face that includes one or more gripping
inserts
releasably secured thereto, said gripping inserts having outer faces generally
aligned
with the exterior surface of the pump rod and fox grippingly engaging the pump
rod
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when said clamping members are in said activated position such that force
exerted by
each individual clamping member against the pump rod is concentrated and
distributed
over said outer faces of said one or more gripping inserts of said individual
clamping
member.
In a further aspect the invention provides a pump rod clamp for gripping a
pump rod in
an oil, gas or water well, the pump rod clamp comprising a central housing
having a
longitudinal bore for receiving a pump rod, said central housing including at
least one
pair of opposed radial bores generally perpendicular to said longitudinal bore
and having
interior ends terminating at said longitudinal bore; a ram received within
each of said
opposed radial bores, each of said rams having a leading face generally
directed toward
the exterior surface of the pump rod; and, one or more actuators to cause said
rams to
be moved within said opposed radial bores between an activated position where
said
rams grippingly engage the pump rod to limit rotational and axial movement
thereof,
and a deactivated position where said rams are disengaged from the pump rod,
each of
said rams including one or more gripping inserts releasably securable to their
leading
faces such that when said rams are in said activated position said gripping
inserts contact
the exterior surface of the pump rod, said gripping inserts having outer faces
with an
arcuate shape generally corresponding to the curvature of the exterior of the
pump rod
and coated with a ceramic material, said ceramic material enhancing the
ability of said
gripping inserts to grippingly engage the pump rod and providing an
electrically
6
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CA 02462183 2004-03-29
insulative barrier between said pump rod clamp and the pump rod when said
clamping
members are in said activated position.
The invention also concerns a clamping blowout preventer for gripping a pump
rod in
an oil, gas or water well, the clamping blowout preventer comprising a central
housing
having a longitudinally oriented bore for receiving a pump rod, said central
housing
including at least two radially opposed bores generally perpendicular to said
longitudinal
bore and having interior ends terminating at said longitudinal bore; a ram
received
within each of said radially opposed bores, each of said rams having a leading
face
generally directed toward the exterior surface of the pump rod, said leading
faces of said
rams including one or more gripping inserts releasably secured thereto; at
least one
actuator to cause said rams to be moved between an activated and deactivated
position,
when in said activated position said rams driven inwardly toward the pump rod
causing
said gripping inserts to grippingly engage the exterior surface of the pump
rod and to
limit axial and rotational movement thereof, when in said deactivated position
said rams
retracted from the pump rod permitting said gripping inserts to be released
from
engagement with the pump rod; and, a seal secured to each of said rams such
that the
seals on opposed rams engage both the exterior surface of the pump rod and one
another
when said rams are in said activated position, to limit well fluids from
escaping from the
well.
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CA 02462183 2004-03-29
In yet a further aspect the invention provides a pump rod clamp for gripping a
pump rod
in a oil, gas or water well, the pump rod clamp comprising central housing
having a
longitudinal bore for receiving a pump rod; a plurality of clamping members
received
within said central housing; and, one or more actuators to cause said clamping
members
to be moved between an activated position where they grippingly engage the
exterior
surface of the pump rod and a deactivated position where they are released
from contact
with the exterior surface of the pump rod, each of said clamping members
comprising
a ram received within a radial bore extending through said central housing
generally
perpendicular to said longitudinal bore and having an interior end terminating
at said
longitudinal bore, each of said rams having a leading face with an arcuate
channel
thereon for grippingly engaging the pump rod when said rams are in said
activated
position, said arcuate channel coated with a ceramic material to enhance the
ability of
said arcuate channel to grippingly engage the pump rod and to provide an
electrically
insulative barrier between said pump rod clamp and the pump rod when said rams
are
in said activated position.
Further aspects and advantages of the invention will become apparent from the
following description taken together with the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, and to show more clearly
how it may
be carried into effect, reference will now be made, by way of example, to the
accompanying drawings which show the preferred embodiments of the present
invention
in which:
Figure 1 is a side view of a typical oil or gas well having an embodiment of a
pump rod
clamp and blowout preventer in accordance with one embodiment of the present
invention mounted thereon;
Figure 2 is a side sectional view of a preferred embodiment of the pump rod
clamp and
blowout preventer of Figure 1 shown in an open configuration;
Figure 3 is a sectional view taken along the line 3-3 of Figure 2;
Figure 4 is a side sectional view of the pump rod clamp and blowout preventer
of Figure
2 shown in a closed configuration;
Figure 5 is a sectional view taken along the line 5-5 of Figure 4;
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CA 02462183 2004-03-29
Figure 6 is a side perspective view of a ram of a pump rod clamp and blowout
preventer
according to a preferred embodiment of the invention;
Figure 7 is a front or end view of the face of the ram of Figure 6; and,
Figure 8 is a sectional view taken along the line 8-8 of Figure 7;
Figure 9 is a side sectional view of an alternate embodiment of the pump rod
clamp and
blowout preventer of the present invention;
Figure 10 is a side elevational view of a gripping insert in accordance with
one
embodiment of the invention;
Figure 11 is a sectional view along the line 11-11 of Figure 10;
Figure 12 is a front view of the gripping insert of Figure 10;
Figure 13 is an upper side perspective view of the gripping insert of Figure
10; and,
Figure 14 is an upper side perspective view of the pump rod clamp and blowout
preventer.
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CA 02462183 2004-03-29
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention may be embodied in a number of different forms. However,
the
specification and drawings that follow describe and disclose only some of the
specific
fortes of the invention and are not intended to limit the scope of the
invention as defined
in the claims that follow herein.
Figure I is a cross sectional view of a relatively standard oil well. It will
be appreciated
that depending upon the particular well in question, the set up of the well
and the type
of equipment used could vary substantially. Figure 1 depicts but one example
of a
producing well. In Figure 1 the well is comprised generally of a casing 1 that
extends
from the surface of the earth down into an the oil bearing strata. Situated
within the
casing is a tubing string 2. Within the tubing string there is located a
polished rod 3 for
driving a downhole pump 4. In the embodiment shown, the pump is a rotary pump
with
polished rod 3 connected to a rotary drive head 5. Where casing 1 exits the
earth there
is provided a casing bowl 6 to which is mounted a flow tee 7. Immediately
above flow
tee 7 is a pump rod clamp and blowout preventer 8 constructed in accordance
with one
of the preferred embodiments of the present invention. The exterior structure
of the
pump rod clamp and blowout preventer is shown in Figure 14.
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Details of the internal structure of pump rod clamp and blowout preventer 8
are shown
in Figure 2. The embodiment of the pump rod and blowout preventer shown in
Figure
2 comprises, in general, a central housing 9 having a longitudinal bore 10
extending
therethrough and for receiving a pump rod 3. Central housing 9 may contain
upper and
lower flanges or threaded connections, 1 l and 12 respectively, for mounting
the housing
to wellhead equipment. As is common with most blowout preventers, central
housing
9 further includes a pair of opposed radial bores 13 and 14 that are generally
perpendicular to, and that terminate at, longitudinal bore 10. A pair of
clamping
members 15 and 16, which in the embodiment shown in the attached drawings are
in the
general form of a pair of rams, are slidably received within bores 13 and 14.
One or
more actuators 17 are used to cause clamping members 15 and 16 to be moved
between
an activated position where they extend into longitudinal bore 10 to a point
where they
may grippingly engage the exterior surface of the pump rod, to a deactivated
position
where there are released from contact with the exterior surface of the pump
rod and
retracted outwardly through bores 13 and 14. A variety of different actuators
may be
utilized in order to move the clamping members or rams between their activated
and
deactivated positions. Such mechanisms include manual, hydraulic, pneumatic,
or
electric means. In the embodiment shown, actuators 17 are comprised of a pair
of sterns
18, that are each threadably received within a bore 19 situated within blowout
preventer
plugs 20 received within radial bores 13 and 14. The inner most ends 21 of the
stems
are attached to the clamping members or rams, but are free to rotate relative
thereto.
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CA 02462183 2004-03-29
The outer most ends of the stems extend beyond central housing 9 such that
they may
be rotated manually, electrically, pneumatically or hydraulically, in order to
drive the
clamping members or rams either inwardly or outwardly relative to longitudinal
bore 10.
A stem lock 31, at the outermost end of each plug 20, may be used to permit
the stems
to be locked in place in order to prevent unintentional or accidental rotation
and
movement of the clamping members.
In a preferred embodiment of the invention, rams 15 and 16 have a leading face
22 that
is directed generally toward longitudinal bore 10 (and hence the exterior
surface of a
pump rod received within the longitudinal bore). Leading faces 22 include an
arcuate
channel 23 positioned thereon and in general alignment with longitudinal bore
10 and
a pump rod received therein. Arcuate channels 23 are positioned in such a
manner that,
when the rams are moved inwardly to their activated position, leading faces 22
encompass the pump rod, and depending upon the particular embodiment of the
invention in concern, grippingly engage the exterior surface of the rod.
As shown in Figures 2 through 8, each of clamping members or rams 15 and 16 in
one
embodiment include one or more gripping inserts 24 releasably secured to their
leading
faces 22 within arcuate channel 23. Gripping inserts 24 have outer faces 25
that are
generally aligned with the exterior surface of the pump rod and that
grippingly engage
the rod when the rams are in their activated position. In this manner the
loading or force
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CA 02462183 2004-03-29
applied to the rams by actuators 17 will be concentrated and distributed over
the outer
faces 25 of gripping inserts 24. Where the total combined surface area of the
outer faces
of the gripping inserts on each individual ram is less than the surface area
of arcuate
channel 23 there will be a concentrated load applied to the exterior surface
of the pump
rod through the gripping inserts. This concentration of load assists in
gripping the
polished or pump rod to securely hold it in place when the rams have been
moved to
their activated position by means of actuator 17.
To enhance their ability to transmit concentrated loads from the rams to the
pump rod,
gripping inserts 24 are preferably formed from a hardened metal or steel
Further, outer
faces 25 of gripping inserts 24 are preferably arcuate in shape, generally
corresponding
to the curvature of the exterior surface of the pump rod. Outer faces 25 may
also include
horizontal, vertical or horizontally inclined ridges or teeth to enhance
gripping of the
pump rod and limit or prevent rotational and/or longitudinal movement.
To increase the ability of device 8 to grippingly engage the exterior surface
of a pump
rod, in a preferred embodiment of the invention outer faces 25 of gripping
inserts 24 are
coated with a ceramic material 32 (see Figures 10 through 13). The ceramic
coating
upon the gripping inserts serve to present a hard, non-metallic surface for
engaging the
exterior of the pump rod without scoring or galling the rod. Traditional rod
clamps that
permit metal-to-metal contact often gall the surface of the rod and create
burs, ridges,
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CA 02462183 2004-03-29
and other marks which can have the effect of ripping or tearing packing
material when
the rod is pulled from the well. In contrast, gripping inserts 24, having a
ceramic coated
outer face, reduce the likelihood of damage to the exterior of the rod. The
concentrated
loading applied through the gripping inserts has a tendency to create small
indentations
within the rod's exterior surface, as opposed to scratches, galling, scoring,
or other
forms of damage. Any small indentations formed on the surface of the rod will
have no
detrimental effect upon packing material and/or seals when the rod is removed
from the
well. To further enhance the ability of gripping inserts 24 to securely hold
the pump rod
the ceramic coating applied to their outer faces may have a slightly roughened
texture.
The ceramic coating upon gripping inserts 24 also serves to present an
electrically
insulative barrier between the pump rod and the rod clamp when the rams are in
their
activated position. The electrically insulated barrier between the rod and the
grippers
helps to ensure that no static sparks are created between the rod and the
grippers, and
insulates the entirety of the pump rod clamp and blowout preventer from the
rod to
prevent electrical arcing should there be an electrical short in electrical
equipment
connected to the wellhead.
In a preferred embodiment of the invention each ram contains a pair of
gripping inserts
24 that are generally in vertical alignment. The individual gripping inserts
may be
releasably secured to the ram in a variety of ways. For example, in the
attached drawings
CA 02462183 2004-03-29
the inserts are received within bores 26 within the leading face of each ram.
Bores 26
and gripping inserts 24 may be threaded to allow the inserts to be screwed
into the bores.
Alternatively, and as shown in Figures 6 and 8, the gripping inserts may be
pressed into
the bores and held in place by means of pins or alien screws 27. In either
instance, it
will be appreciated that the gripping inserts may be easily and quickly
replaced in the
field should it become necessary. In a further embodiment of the invention,
the gripping
inserts 24 may include a longitudinal bore 30 extending therethrough (see
Figures 7, 8,
11 and 13) to permit a pin or bolt to be screwed into the inserts so they may
be "jacked"
out of the face of the ram for replacement.
From a thorough understanding of the invention, those skilled in the art will
appreciate
that the described device may operate as a pump rod clamp to gripping secure
or hold
a pump rod in an oil, gas or water well. The device may also operate as a pump
rod
clamp and blowout preventer for both holding the pump rod and to seal the well
to
prevent or limit the escape of fluids therefrom. Where the device is
constructed in such
a fashion, clamping members 15 and 16 will sealingly engage against both the
pump rod
and one another to seal off the well. In this embodiment of the invention, the
clamping
members include an elastomeric seal 28 upon their leading faces. With the
clamping
members in their activated position, the seals on each ram will engage the
exterior of the
pump rod, and will engage each other within the annulus surrounding the pump
rod, to
maintain well control in a manner similar to the operation of currently
available BOP's.
16
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Additional seals 29 are positioned between the exterior surface of the rams
and the
interior surface of opposed radial bores 13 and 14 to prevent the escape of
fluid
therebetween. As in the case of conventional blowout preventers, seals 28 and
29 may
be either separate sealing elements or may be of unitary construction.
Figure 9 shows an alternate embodiment of the invention wherein the arcuate
channels
23 on the clamping members or rams are themselves coated with a ceramic
material and
contact the exterior surface of the pump rod directly when the rams are moved
to their
activated position. As in the case of the embodiment described above, coating
the
contact portions of the rams with ceramic material enhances the ability of the
rams to
engage the pump rod and to prevent or limit rotational and axial movement of
the rod
without scoring or galling the rod's outer surface. The lack of metal-to-metal
contact
between the rams and the rod once again presents an electrically insulative
baxrier
between the pump rod and the rams, minimizing the risk of sparks, static
shocks or
arcing in the event of a short in electrical components attached to the
wellhead. With
the clamping members in their activated position such that arcuate channels 23
grippingly engage the pump rod, the rams will also tend to seal the well to
help prevent
or limit the escape of fluids. In gas wells, high pressure wells, where
hydrogen sulfide
is present, or any other situation where an enhanced degree of well control is
desired or
necessary, the rams may include seals 28 and 29 that function essentially in
the same
manner as in the embodiments described above.
17
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CA 02462183 2004-03-29
The pump rod clamp and blowout preventer described herein provides a mechanism
by
which a pump rod may be securely held within a well to prevent or limit
rotational
and/or axial movement of the rod while at the same time preventing or
substantially
limiting scoring and galling of the rod's surface. Minimizing or limiting
scoring or
galling of the rod reduces the likelihood of damage being caused to packing or
sealing
elements when the rod is removed from the well. The inclusion of a ceramic
coating
upon either gripping inserts (in one embodiment), or the face of the rams (in
an alternate
embodiment), enhances the ability of the device to firmly grasp the rod
without causing
damage to its outer surface, while presenting an electrically insulative
barrier between
the rod and the wellhead equipment. In the embodiment of the invention that
includes
removable gripping inserts positioned on the face of the rams, there exists
the added
advantage of concentrating the load applied by the rams to the rod upon the
smaller
surface area of the inserts. Should it become necessary to change a gripping
insert on
account of damage, ar to accommodate a different sized rod, doing so can be
accomplished quickly and easily in the field by merely removing the existing
inserts and
replacing them without the need to replace or machine the entire ram.
It is to be understood that what has been described are the preferred
embodiments of the
invention and that it may be possible to make variations to these embodiments
while
staying within the broad scope of the invention. Some of these variations have
been
discussed while others will be readily apparent to those skilled in the art.
18
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