Note: Descriptions are shown in the official language in which they were submitted.
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"PUSH / PULL SYSTEM AND SUPPORT STRUCTURE FOR
SNUBBING UNIT OR THE LIKE ON A RIG FLOOR"
FIELD OF THE INVENTION
The invention relates to rigs above a wellhead, such as snubbing units
and push / pull units, for manipulating tubing in and out of a well.
BACKGROUND OF THE INVENTION
It is well known to attach a variety of rigs such as hydraulically
operated rigs above a wellhead. For example, snubbing units are known in the
oil
and gas industry for facilitating access to a well which is under pressure
including,
for example, well operations such as well completions. A snubbing unit
includes
structure and equipment above a wellhead for manipulating tubular components
such as pipe, tubing, and bottom hole assemblies (BHA) in and out of a well
while
controlling the well under pressure.
Generally, a snubbing unit employs stationary (lower) and traveling
(upper) slip assemblies, opposingly oriented, to releasably and controllably
shift
tubular components into and out of the well through a wellhead despite the
possibility of either heavy tubular loads, which urge the tubular components
to fall
into the well, or the pressure-generated forces on the tubular components,
which
urge the tubular components out of the well. The snubbing unit is installed
above
an existing wellhead seal, such as that created by a blow-out preventer (BOP),
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incorporates its own seals to seal the tubular components as they are
introduced or
removed from the wellhead, such as through the use of a stripping head.
Most conventional snubbing units fall into either rig-assisted or self-
contained units. Rig-assisted snubbing units are typically snubbing units that
are
pivotally mounted to a truck and require assistance by an onsite service rig
so as to
winch them upright, pivoting from the truck, to a snubbing position over the
wellhead. Self-contained units are typically transported to site on a truck
and lifted
into position, over the wellhead, by a separate crane unit. During operations,
self-
contained snubbing units do not require the assistance from an on-site rig.
When snubbing in low-pressure well environments, such as wells with
surface pressures under 12,000 kPa, a compact, rig-assisted snubbing unit is
often
the ideal choice. A compact snubbing unit can be easily transported to the
well site,
such as in a 1 ton pickup truck, and is practical and cost effective for
single wells
and underbalanced drilling. Additionally, a compact snubbing unit reduces or
eliminates viewing obstructions often experienced by service rig operators
when
utilizing traditional (larger) sized snubbing units. One example of a compact
snubbing unit is the one marketed under the trade-mark MINI BRUTUS by Team
Snubbing Services Inc. of Rocky Mountain House, Alberta, Canada.
Despite the many advantages of a compact snubbing unit, the set-up
of such a unit still requires the snubbing unit to be installed above an
existing
wellhead seal and to incorporates its own seals to seal the tubular components
as
they are introduced or removed from the wellhead. Typically a compact snubbing
unit, such as the MINI BRUTUST", is installed above a blow-out preventer (BOP)
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and incorporates an RS-100 stripping head as its seal to seal the tubular
components.
Push / pull systems or push / pull units are also known in the art and
are used to manipulate tubular components in and out of a well. Push / pull
units
provide alternatives to, and/or improvements over, conventional snubbing
systems.
Such push / pull systems are generally mounted at the rig floor (e.g. on the
rotary
table) and, therefore, allow live well operations to be conducted at the rig
floor
rather than in the greatly elevated work baskets as is generally the case with
conventional snubbing units. One example of a push / pull system is that
manufactured by Tesco Corporation of Calgary, Alberta, Canada. However, the
prior art push / pull systems manufactured by Tesco Corporation is cumbersome,
large and heavy, does not have the compactness that has become associated with
compact snubbing units such as the MINI BRUTUSTm and cannot be used to
retrofit
such compact snubbing units and/or convert such units into a push / pull
system.
Applicant's prior-filed applications (U.S. serial no.s 61/148,922 and
12/464,034) and issued Canadian patent no. 2,652,068, address many of these
above-noted disadvantages, and as more clearly illustrated in Figures 1 ¨ 18
and
the following background description thereof.
A PRIOR ART compact snubbing or push/pull unit 12 (or most of the
components thereof) is supported on a PRIOR ART load bearing apparatus or
support structure 20 having a central passage 20c of sufficient diameter to
allow
passage of tubular components T therethrough, preferably having at least one
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tensile member mount 21 to facilitate the connection of one or more tensile
members 40 between the support structure 20 and a mounting point on a rig or
rig
floor RE and having a support member or support plate 22. The support plate 22
is
adapted to be secured to, or within, the compact snubbing unit 12. The compact
snubbing unit 12 comprises stationary (lower) and traveling (upper) slip
assemblies
14s, 14t, traveling plate 15t (to support the travelling slip assembly 14t and
having a
central passage 15tc of sufficient diameter to allow passage of tubular
components
T therethrough), bottom or stationary plate 15s (to facilitate mounting of the
compact snubbing unit 12 to the support structure 20 and having a central
passage
15sc of sufficient diameter to allow passage of tubular components T
therethrough)
and a pair of jacking rams 16a, 16b securely mounted to the stationary plate
15s
and actuatable in a conventional manner to releasably and controllably shift
tubular
= components T into and out of the well through a wellhead. Preferably,
jacking rams
16a, 16b are hydraulic rams.
Jacking rams 16a, 16b are securely mounted to the compact snubbing
unit 12 in the conventional manner. The stationary plate 15s comprises paired
ram
cut-outs or recesses 15a, 15b, said ram recesses 15a, 15b being substantially
positioned at 180 across from each other around central passage 15sc and at
the
periphery of the stationary plate 15s (see FIG. 12). Further, the jacking rams
16a,
16b each comprise an annular groove 16ag, 16bg of such diameter and dimensions
to allow secure placement of the jacking rams 16a, 16b within the ram recesses
15a, 15b (see FIG. 7) and the compact snubbing unit 12 further comprises ram
keepers or ram retainers 17a, 17b. As such, jacking rams 16a, 16b are securely
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mounted to the compact snubbing unit 12 in the conventional manner, i.e. by
placing the annular grooves 16ag, 16bg of jacking rams 16a, 16b within the
respective ram recesses 15a, 15b and then bolting or otherwise fasten the ram
retainers 17a, 17b so as to maintain secure placement of the jacking rams 16a,
16b
on the stationary plate 15s (see FIGS 6-8, 10 and 11).
The support structure 20 further comprises ram openings or ram
passages 22a, 22b, in the support plate 22, each ram passage 22a, 22b being
coaxially aligned with ram recesses 15a, 15b of the stationary plate 15s and
each
ram passage 22a, 22b being of sufficient diameter to allow passage of the
jacking
rams 16a, 16b therethrough (see FIGS. 1, 5-6, 9 and 10). Preferably, ram
passages 22a, 22b, while allowing of passage of the jacking rams 16a, 16b
therethrough, are positioned and are of such dimensions so as to have the
support
structure 20 still provide some contact surface area SA or support for the ram
retainers 17a, 17b and are not so large so as to also allow passage of said
ram
retainers 17a, 17b therethrough when the compact snubbing unit 12 is mounted
to
the support structure 20 and is subject to pushing or pulling forces from the
tubular
components T. As more clearly shown in FIGS. 1-6, the support structure 20
comprises plurality of rig engaging members or legs 24 distributed around and
connected to the support plate 22.
The support plate 22 is secured to the compact snubbing unit 12 by
bolting or fastening to the stationary plate 15s in a conventional manner. The
stationary slip assembly 14s is unfastened from the stationary plate 15s,
stationary
plate 15s and ram retainers 17a, 17b are fastened directly underneath the
support
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plate 22 and stationary slip assembly 14s is placed and fastened directly
above the
support plate 22 thereby sandwiching the support plate 22 between the
stationary
slip assembly 14 and the stationary plate 15s (see FIGS. 6 and 10). As such,
support structure 20 is mounted within the compact snubbing unit 12. In
another
variation of this PRIOR ART support structure (not shown), the stationary
plate 15s
is fastened directly on top of and against the top surface of the support
plate 22 and
then the support structure 20 can more easily accommodate significant downward
forces, such as those which might be created when heavy tubular loads urge the
tubular components T to fall into the well.
During operations, the support structure 20 is positioned on a rig floor
RF above a wellhead (not shown) extending from the ground and including
standard
wellhead components and wellhead seals. Loads and downward forces from the
compact snubbing unit 12 and/or tubular components T are generally distributed
into the rig floor RF through the support structure 20 and legs 24. Where
upward
forces (e.g. where the well pressure-generated forces on the tubular
components T
urge the tubular components T out of the well) are expected to be incurred,
one or
more tensile members 40 can be utilized to further secure the support
structure 20
to the rig or rig floor RF via the tensile member mounts 21. Typically,
tensile
members 40 are chains and fasten the support structure 20 to the rig floor RF
in a
conventional manner.
FIG. 13 illustrates an alternate PRIOR ART variation of a support unit
20, which is similar to that of FIGS. 1-12, but wherein the compact snubbing
unit 12
does not comprise a stationary plate, wherein the ram passages 22a, 22b are
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adapted to act as, and have similar dimension to, the ram recesses 15a, 15b of
the
embodiment in FIGS. 1-12, and wherein the jacking rams 16a, 16b are securably
mounted directly to the support plate 22 of the support structure 20 (in a
similar or
identical manner as they are mounted to the stationary plate 15s of the
embodiment
of FIGS. 1-12) through use of ram retainers 17a, 17b.
FIGS. 14-18 illustrate the configuration of another PRIOR ART
variation of a support unit 20 which is similar to that of FIGS. 1-12, but
which further
comprising a worker platform 50 to support a worker W. The worker platform 50
places a worker W in a safe and efficient position to conduct well operations
and to
handle the tubular components T.
However, prior to installing a compact snubbing unit or push/pull unit
and/or in combination with a support structure 20, tubular components may
already
be positioned fully through a rig floor, or extend up from the wellhead
partway up
through the rig floor. For example, when tubular components are stuck in a
wellbore, then a snubbing or push/pull unit 12 may be helpful to provide
additional
force to move and loosen such stuck tubular components T. In such a case, the
tubular components T may need to be disconnected and removed; and/or the
compact snubbing unit or the push / pull unit 12 may have to be lifted into
position,
over top of such tubular component T, by a separate crane unit or the like.
This
complicates installation of the compact snubbing or push / pull unit 12, may
require
cranes or the like and adds to the installation time and cost of the compact
snubbing
or push / pull unit 12 onto the rig floor. What is needed is a compact
snubbing or
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push / pull unit and/or support structure 20 that does not suffer from the
above-
noted disadvantages and which can be easily installed onto a rig floor RF when
tubular components T are already present and extend up through the rig floor
RF.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described, by way of
example only, with reference to the accompanying drawings, wherein:
Figures 1-18 are various views of PRIOR ART support structures
supporting PRIOR ART snubbing and/or push/pull units;
Figures 19-28 are various perspective views of a first embodiment of
the invention;
Figures 29-40 are various perspective views of a second embodiment
of the invention; and
Figures 41-43 are various perspective views of a third embodiment of
the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description is of preferred embodiments by way of
example only and without limitation to the combination of features necessary
for
carrying the invention into effect. Reference is to be had to the Figures in
which
identical reference numbers identify similar components. The drawing figures
are
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not necessarily to scale and certain features are shown in schematic form in
the
interest of clarity and conciseness.
FIGS. 19-43 illustrate the configuration of three embodiments of the
present invention 10 which are somewhat similar to the PRIOR ART apparatus and
devices of FIGS. 1-18, but wherein the invention 10 is now in two parts to
facilitate
easy placement of the invention 10 around any tubular components T which may
already be positioned fully through a rig floor RF, or which extend up from
the
wellhead partway up through the rig floor RF (e.g. see Fig. 30). In these
three
embodiments, the compact snubbing or push/pull unit 12 (or most of the
components thereof) now comprise a first section 112a and a second section
112b
which, when assembled or placed together, provide the functionality of a
complete
compact snubbing unit 12. Likewise, the support structure 20 comprises a first
section 120a and a second section 120b (with the support plate 22 also being
divided into a first support plate section 122a and a second support plate
section
122b) which, when assembled or placed together, provide the functionality of a
complete support structure 20.
Preferably, first section 120a of the support structure 20 supports the
first section 112a of the compact snubbing unit 12, along with a portion of
the
second section 112b. More preferably, second section 120b of the support
structure 20 supports the remaining portion of the second section 112b of the
compact snubbing unit 12; e.g. see Fig. 19. In the three embodiments of FIGS
19-
42, the first section 120a of the support unit 120a also comprises the ram
passages
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22a, 22b, which allow passage of the jacking rams 16a, 16b therethrough.
However, in other embodiments (not shown), ram passages may be on the second
section or one ram passage may be on each section. Additionally, in these
three
embodiments, first section 120a and second section 120b of the support
structure
20 preferably further comprise central passage recesses 20ca, 20cb which: (i)
each
have an opening or entry RO of sufficient dimension to allow a tubular
component T
to, at least, be partially placed into the recess and (ii) when the first and
second
sections 120a, 120b of the support unit 20 are placed together or adjacent to
each
other, create the central passage 20c of sufficient diameter to allow passage
of
tubular components T therethrough; see FIGS. 30 and 36.
Preferably, in the three embodiments of FIGS. 19-43, the first section
112a of the compact snubbing unit 12 comprises a first section of the
travelling plate
115ta, a first section of the stationary plate 115sa, a first portion 114sa of
the
stationary (lower) slip assembly 14s which is associated with the first
section of the
stationary plate 115sa, and a first portion 114ta of the traveling (upper)
slip
assembly 14t which is associated with the first section of the traveling plate
115ta.
Preferably, both the jacking rams 16a, 16b are operably associated with the
first
section 112a of the snubbing unit 12. However, in other embodiments (not
shown)
the jacking rams 16a, 16b may be associated with the section 112b of the
compact
snubbing unit 12; or one jacking ram is associated with each of the first and
second
sections 112a, 112b. More preferably, the first and second sections 114sa,
114sb
of the stationary slip assembly 14s are each, respectively, mounted to the
first and
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second sections 120a, 120b of the support structure 20; preferably on the
first and
second sections 122a, 122b of the support plate 22, respectively.
Further, in the three embodiments of FIGS. 19-43, the second section
112b of the compact snubbing unit 12 comprises a second section of the
travelling
plate 115tb, a second section of the stationary plate 115sb, a second portion
114sb
of the stationary (lower) slip assembly 14s which is associated with the
second
section of the stationary plate 115sb, and a second portion 114tb of the
traveling
(upper) slip assembly 14t which is associated with the second section of the
traveling plate 115tb. Preferably, the first and second sections 114ta, 114tb
of the
traveling slip assembly 14t are pivotally connected, such as at a pivot point
15p via
a hinge 15h (see FIGS. 21 and 43).
Preferably, a guard plate 70 having a first section 170a and a second
section 170b is provided, with first section 170a thereof mounted to the top
of the
first section of the traveling slip 114ta and with the second section 170b
thereof
positionable over the top of the second section of the traveling slip 114tb;
preferably
via support members 72. Guard plate 70 further comprises a central passage 70c
of sufficient diameter to allow passage of tubular components T therethrough.
First
and second sections 170a, 170b of the guard plate 70 are preferably hinged via
hinge 70h at pivot point 70p. Advantageously, hinged guard plate 70 and
support
members 72 provides additional support (and hinging functionality) for the
first and
second sections 114ta, 114tb of the traveling slip assembly 14t which are
pivotally
connected, at a pivot point 15p (see FIG. 21).
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Preferably, although not necessary, first and second sections 120a,
120b of the support structure 20 are connected together via a hinge 60 at
pivot point
P, to allow the first and second sections 120a, 120b to pivot with respect to
each
other around a substantially vertical pivot axis. Advantageously, hinge 60
allows
each of first and second sections 120a, 120b to still substantially support
each other
(and, hence, the entire support structure 20) in an upright manner on the rig
floor
RF with only two legs 24 on each of said second sections 120a, 120b. In
embodiments of the support structure 20 wherein first and second sections
120a,
120b are provided without a hinge (not shown), additional legs 24 may be
provide
on each section 120a, 120b (to stabilize each section), or additional
operators may
need to be provided to maintain separated sections 120a, 120b upright until
they
are fastened securely together around a tubular component T.
More advantageously, the support structure 20 (and any snubbing unit
or push/pull unit thereon) can be moved or shuffled along the rig floor RF
and, if any
tubular components T are positioned through a rig floor or partially extend up
from
the wellhead through the rig floor, the first and second sections 120a, 120b
can be
pivoted to open up the central passage 20c sufficiently to allow the support
structure
to move and fit around such tubular components T (e.g. move in direction M as
shown in FIG. 30). Then, once the support structure 20 is sufficiently placed
around
20 the tubular components T, first and second sections 120a, 120b are
pivoted to fully
close around said tubular components T, and thereby also providing full
functionality
of the support unit and/or compact snubbing or push/pull unit (e.g. see FIG.
36). In
another embodiment (not shown), first and second sections 120a, 120b of the
12
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support structure 20 are not pivotally connected and can simply be maneuvered
independently to be placed around tubular components T as desired. Even more
advantageously, by pivoting (instead of simply have two separate first and
second
sections 120a, 120b of the support structure 20 and associated sections of
snubbing unit), a single operator can usually manipulate the support structure
20
(and snubbing unit) on his own between an open (e.g. FIG. 30) and a closed
(e.g.
FIG. 36) configuration; e.g. such as by shuffling the hinged device along the
rig floor
RF and around the tubular components T.
Preferably, and as illustrated in the embodiment of FIGS. 29-40, a
hydraulic ram-based actuator 80 is provided to pivot first and second sections
120a,
120b, so as to actuate the support unit 20 between the open (e.g. FIG. 30) and
the
closed (e.g. FIG. 36) configuration. Actuator 80 preferably comprises
hydraulic ram
82, a first linkage member 84 to operably connect actuator 80 to the first
section
120a and a second linkage member 86 to operably connect the actuator 80 to the
second section 120b (e.g., see FIG. 30). As ram 82 is actuated between a
retracted
and an extended position (see FIGS. 30 and 36, respectively), the first and
second
section 120a, 120b are moved about hinge 60 (at pivot point P) so as to move
the
support unit 20 between the open (FIG. 30) and a closed (FIG. 36)
configurations.
Preferably, and as illustrated in the embodiment of FIGS. 41-43, one
or more bolt-down connector plates 90 are provided to enable an operator to
securely fasten first and second sections 120a, 120b together, when the
support
unit 20 is in a closed configuration. More preferably, connector plates 90
comprise
a plurality of bolt holes which can align with corresponding bolt holes (not
show) in
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the relevant section of the support plate 22, thereby allowing bolts to be
placed
therethrough (i.e. through both the connector 90 and the relevant sections 22,
122a,
122b of support plate). Even more preferably, similar connector plates (not
shown)
are provided to securely fasten various components of the first and second
sections
112a, 112b of the snubbing unit or push/pull unit 12 together (such as on
relevant
sections of traveling plate 14t, 114ta, 114tb or stationary plate 15s, 115sa,
115sb).
Advantageously, such connector plates 90 for the support unit 20 and/or for
the
snubbing or push/pull unit 12, along with hinge 60, provide structural support
to
these embodiments of the support structure 20 and thereby provide an
additional
safety factor during operation (i.e. to securely keep the respective first and
second
sections together). More advantageously, connector plates 90 and appropriately
aligned bolt holes and bolts thereth rough could also act as a hinge 60 if so
desired.
Unless otherwise specified, it is preferred that the components of the
invention be made of steel or other suitable high-strength materials capable
of
taking stresses and strains during its intended use during well operations.
Those of ordinary skill in the art will appreciate that various
modifications to the invention as described herein will be possible without
falling
outside the scope of the invention.
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