Note: Descriptions are shown in the official language in which they were submitted.
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WEIGHT COMPENSATION DEVICE
This invention relates to an apparatus and a method
for facilitating connection or disconnection of a tubular
to or from a string of tubulars, and is particularly, but
not exclusively for facilitating the connection or
disconnection of casing to or from a string of casing
using a top drive or a travelling block of a derrick of
an oil or gas well.
During the drilling of oil and gas wells it is
necessary to connect and disconnect tubulars for use
therein. Recently, there has been the need to use casing
of a very large diameter for lining the well. In
particular, modern casing may be forty-eight inches in
diameter.
The weight of a single joint of-,modern casing causes
many problems. In particular, casing is usually threaded.
When a joint of casing is connected and disconnected from
the string of casing, there is a high probability that
the threads will become damaged by collisions
therebetween.
It has been proposed to use a device called a
"single joint compensating elevator" as disclosed in EP-
A-0 171 144. The device enables the weight of a single
joint to be compensated for, such that when the joint is
lowered or raised to or from a string, the effective
weight of the joint is zero. A pneumatic bellows or the
like allows small adjustments to be made to allow the
joint of casing to be made up to the string of casing.
The device also allows over compensation to be made, such
that upon disconnection of a joint from the string of
casing, the joint springs from the string of casing. The
device depends from the primary elevator of the rig, with
a single joint elevator depending therefrom.
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The above described_arrangement requires the device
to be attached to the elevator prior to each connection
or disconnection and removed therefrom prior to lowering
or raising the string, which is carried out by the
primary elevator. This procedure wastes valuable rig
time.
The present invention provides an apparatus for
facilitating the connection or disconnection of a tubular
to or from a string of tubulars, which apparatus
comprises a weight compensating device which can be
suspended from a travelling block or a top drive or a
swivel, characterised in that said apparatus further
comprises a member which can support a primary elevator
and which can, in use, be raised and lowered by said
weight compensating device to enable a tubular to be
raised and lowered with respect to a string of tubulars
and which can move to a load bearing position in which it
can raise and lower said string of tubulars.
Preferably, said member comprises a stem arranged
substantially in parallel with said weight compensating
device.
Advantageously, said stem is rigid.
Preferably, said stem comprises an end stop which
rests on the top of said apparatus when said member is in
its load bearing position.
Advantageously, said stem comprises a yoke for
attachment of the primary elevator.
Preferably, said weight compensating device
comprises at least one piston and cylinder.
Advantageously, said at least one piston and
cylinder is pneumatically operated.
Preferably, said primary elevator is rotatable with
respect to said weight compensating device.
Advantageously, said apparatus further comprises a
motor for rotating said primary elevator.
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Preferably, said apparatus further comprises a brake
for inhibiting rotation of said primary elevator.
Advantageously, said weight compensating device is
shear pinned to said primary elevator.
Preferably, said apparatus is provided with said
primary elevator.
The preseat invention also provides .a method for
facilitating the connection of a tubular to a string of
tubulars using an apparatus in accordance with the
present invention, said method comprising the steps of
positioning a tubular in the primary elevator of said
apparatus, lowering said primary elevator to bring said
tubular into contact with a string of-.tubulars held in a
spider therebelow, and connecting said tubular to said
string of tubulars, and lowering said string of tubulars
on said primary elevator.
The present invention further provides a method for
facilitating the disconnection of a tubular from a string
of tubulars using an apparatus in accordance with the
.present invention, said method comprising the steps of
positioning the primary elevator on a string of tubulars,
lifting said string of tubulars from a well bore,
securing said string of tubulars in a spider,
disconnecting a tubular, the weight compensating device
of said apparatus compensating or overcompensating for
the weight of said tubular, and raising the tubular clear
of said string of tubulars
There is also provided an elevator provided with a
bearing to facilitate rotation between said elevator and
an item held in said elevator.
In another aspect, the invention provides an
apparatus for facilitating the connection or
disconnection of a tubular to or from a string of
tubulars, the apparatus- comprising a weight
compensating device which can be suspended from a
travelling block or a top drive or a swivel, a
central support member for supporting a primary
elevator and extending through a hole in a support
assembly such that the central support member can be
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raised and lowered by the weight compensating device
to enable a tubular attached to the primary elevator
to be raised and lowered with respect to a string of
tubulars, and a stop on the central support member
for engaging a top surface of the support assembly in
a load bearing position in which it can raise and
lower the string of tubulars.
In another aspect, the invention provides a
compensator system for compensating for a weight of at
least one joint, the at least one joint comprising a
wellbore tubular member, the compensating system for
use below a wellbore apparatus, the wellbore apparatus
for supporting the at least one joint, the
compensation system comprising a joint compensator
suspended below the wellbore apparatus and connected
thereto for selectively compensating for the weight of
the at least one joint, a lower elevator suspended
below and interconnected with the joint compensator
for releasably holding the at least one joint, a
wellbore elevator connected to the wellbore apparatus
for selectively supporting the joint compensator and
the at least one joint, and a connection sub having a
top connected to and below the joint compensator, a
mid portion extending through the wellbore elevator,
and a bottom portion, the lower elevator being
suspended below.and connected to the bottom portion of
the connection sub.
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For a better understanding of the invention,
reference will now be made, by way of example, to the
accompanying drawings, in which:
Figure 1 is a typical prior art arrangement for
facilitating the connection of a tubular to a string of
tubulars, the arrangement incorporating a single joint
compensating elevator;
Figure 2A is a front view of an apparatus in
accordance with the invention, in use;
Figure 2B is an enlarged side view of part of the
apparatus of Figure 2A;
Figure 3 is a cross sectional view of the apparatus
of Figure 2A;
Figure 4A is a schematic representation of a
compensating device, in use;
Figure 4B is an enlarged schematic representation of
part of the apparatus of Figure 4A;
Figures 4C-F are schematic representations of
alternative compensating devices which may be used in the
apparatus of Figure 2A;
Figures 5A-C are schematic representations of a
control unit incorporating the control panel of Figure
4A;
Figures 6A-G are schematic representations of
various stages involved in a method according to the
present invention using the apparatus as shown in Figure
2A;
Figure 7A is a front view of a primary elevator;
Figure 7B is a top plan view of the primary elevator
of Figure 7A; and
Figure 7C is a cross-section of the elevator of
Figure 7A.
Referring to Figure 1 there is shown a prior art
arrangement for facilitating the connection of a tubular
to a string of tubulars, the arrangement including a
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single joint compensator J.
The single joint compensator J depends from a
primary elevator (not shown) which is attached by bails
(not shown) to a top drive (not shown) or a travelling
block (not shown) of a derrick (not shown).
A single joint elevator E depends from the single
joint compensator J via a swivel T and cables C. The
single joint elevator E is shown supporting a joint of
casing P that is to be connected the top of a string of
casing N held in the slips (not shown) in the floor of
the rig.
A tong 0 is located below the single joint elevator
E and is positioned about the joint of casing P. The tong
O is used to rotate the joint of casing to facilitate
connection with the string of casing N.
The single joint compensator J is controlled from a
control console S which receives compressed air from a
rig air supply A. The control console S is located on the
floor of the rig nearby. An air hose H extends from the
control console S to the single joint compensator J.
Referring now to Figures 2A, 2B and Figure 3, there
is shown an apparatus in accordance with the invention
generally identified by reference numeral 1 retaining a
joint of casing JC.
The apparatus 1 comprises a supporting bracket 2
having two lifting lugs 3 fixed thereto for attachment to
bails (not shown) of a top drive or travelling block. The
supporting bracket 2 is provided with a plate 4 which is
attached thereto by bolts 5 with a spacer 6 arranged
therebetween. A central hole 7 runs through the plate 4,
the spacer 6 and the supporting bracket 2. A lower plate
8 is welded to the bottom of the supporting bracket 2.
Bushings 9 and 10 are provided in the supporting bracket
2 to facilitate rotation of a stem 11 provided in the
central hole 7.
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Four piston and cylinders 12, 13, 12' and 13', are
spaced about the plate 4 and attached thereto by lugs 14
and 15 via pins 16 and 17. The lower ends of the piston
and cylinders 12, 13, 12' and 13' are attached to a lower
support 18 via lugs 19, 20, 19' and 20' and shear pins
21, 22, 21' and 22' . The shear pins 21, 22, 21' and 22'
are provided such that in the event of overloading the
piston and cylinders 12, 13, 12' and 13', the shear pins
21, 22, 21' and 22' will shear releasing the piston and
cylinders 12, 13, 12' and 13' from connection between the
supporting bracket 2 and the lower support 18.
The lower support 18 comprises a plate 23 which is
provided with a central hole 24 therethrough for stem 11
to pass through. A rotatable plate 25 is fast with the
stem 11 and is seated on bearings 26. The bearings 26 are
supported by the lower support 18.
The stem 11 is provided with an upper stop 27. Upon
full extension of said piston and cylinders 12, 13, 12'
and 13', the upper stop 27 engages the plate 4 and
transfers any weight from the piston and cylinder 8 and 9
thereto. The weight held by the stem 11 is transferred
through the plate 4, the spacer 6 to the supporting
bracket 2 and to the bails (not shown).
The lower end of the stem 11 extends below the lower
support 18 and is provided with a yoke 28 for retaining
the arms 29 and 30 of a primary elevator 31.
A motor 32 is mounted to the underside of plate 18
to rotate the stem 11. A shield 33 protects the motor 32.
A brake 34 is provided for engaging the stem 11 to
inhibit rotation thereof.
The stroke length of the piston and cylinders is
preferably twice the length of the thread of the casing
being connected. About 36cm (14 inches) is appropriate
for threads of 13cm to 18cm (5 to 7 inches) in length
which allows 18cm1 (7 inches) of upward and 18cm (7
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inches) of downward movement. The stroke is commensurate
with the length of the piston which may be chosen as
desired.
Figure 2B shows a scale 35 marked on to the piston
of the piston and cylinder 13 to give an indication to
the operator of the stroke position. The scale could be
in the form of markers, indicia, numerals, or stripes. As
an alternative to physical marks, an electronic sensor or
other position indicator could be used. Another
alternative would be to measure the quantities of fluid
in the cylinder to determine stroke position.
Referring to Figures 6A to 6H, there is shown the
apparatus 1 in use. The apparatus 1 is hung from a
travelling block TB (or a top drive) by bails B. The
bails B are connected to the lugs 3 of the supporting
bracket 2.
For connection of a joint JC of casing to a string
ST of casing, the joint JC is placed in the primary
elevator 31 (Fig. 6A-B). The piston and cylinders 12, 13,
12' and 13' are now set to compensate for the weight of
the joint JC by use of a control console CC. Once set,
the same setting may be used for subsequent joints of the
same weight. The travelling block TB (or top drive) is
then lowered so that the pin on the lower end of the
joint JC enters the box of the upper end of the string ST
of casing (Fig. 6C-D). Since the weight of the joint JC
is compensated for, the threads of the pin and box are
unlikely to be damaged if they collide. A stabbing guide
may be used during this procedure to guide the pin into
the box.
A motor 32 may now be used to rotate the joint JC in
order to threadly mate the joint JC with the string ST. A
power tong 0 is then used to torque the connection up to
the required torque. Make-up can hence be conducted with
the weight of the joint J being compensated for (Fig.
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6F).
The piston and cylinders 12, 13, 12' and 13' are now
extended and the apparatus 1 raised until stop 27 of the
stem 11 abuts the plate 4 of the supporting bracket 2
(Fig 6G-H) and slightly raises the string ST. The spider
SP in the floor of the rig is then released. The entire
string ST is held by the apparatus 1. The weight of the
string ST is taken through the yoke 28, the stem 11 and
the supporting bracket 2. The string ST is then lowered
by the travelling block TB (or top drive) into the well
bore WL. The travelling block TB is lowered by operation
of a draw works DW via cable CS running over a crown
block CB located at the top of a rig RG. The spider SP is
then reapplied to the string ST. Primary elevator 31 is
then removed from the string ST. The apparatus 1 is
raised by the travelling block TB (or top drive) in
readiness for a subsequent joint.
For disconnection of a joint JC from a string ST,
the primary elevator 31 is placed around the top of the
string ST. The piston and cylinders 12, 13, 12' and 13'
are extended until the stop 27 of the stem 11 abuts the
plate 4 of the supporting bracket 2. The apparatus 1 is
now raised until the primary elevator 31 abuts the box of
the top joint JC of the string ST. The spider SP in the
floor of the rig is released. The entire weight of the
string ST is taken by the apparatus 1. The weight of the
string ST is taken through the yoke 28, the stem 11 and
the supporting bracket 2. The travelling block TB (or top
drive) is raised, lifting the string ST until a joint JC
is (or two or three joints are) above the spider SP (Fig
6G-H).
The spider SP is reapplied to the string ST. The
elevator 31 is lowered until the spider SP takes the full
weight of the string ST. The piston and cylinders 12, 13,
12' and 13' are now set to compensate for slightly
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greater than the expected weight of the joint JC, (or the
weight of two or three joints as required) . A power tong
0 is used to break the connection between the joint JC
and the string ST. The power tong 0 is then removed. The
stem 11 may now be rotated by the motor 32 until the
joint JC is free from the string ST. The piston and
cylinders 12, 13, 12' and 13' are over compensating for
the weight of the joint JC and hence the joint JC is
lifted from the string ST. Damping is provided by the
piston and cylinders 12, 13, 12' and 13' so that the
joint JC does not "bounce" back on to the top of the
string ST.
The joint JC is removed from the primary elevator 31
and placed in a rack using pipe handling equipment (not
shown). The apparatus 1 is now ready for the
disconnection of subsequent joints from the string ST.
Referring now to Figures 4A and 4B there is shown
schematically, an apparatus 100. The apparatus 100 is
attached to a top drive D by a shackle 101 and bails 102.
A safety chain CH is provided between the shackle
101 and the apparatus 100. A shear pin 103 or other
device links the apparatus 100 to the shackle 101. In the
event that the shear pin 103 shears, the safety chain CH
will prevent the apparatus 100 from falling on to the
floor of the rig. The shear pin 103 may be designed to
shear at 2.7 tonnes (3 tons) . This arrangement protects
the apparatus 100 from being subjected to the entire
weight of the string if the piston and cylinders fail to
extend to allow transfer of weight through the stem. The
chain should be designed to fail at three times the
expected load.
A control console CC is provided for controlling the
apparatus 101. The apparatus 100 is linked to the control
console by control line H.
Figures 4C to 4F show four arrangements of piston
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and cylinders. Figure 4C shows two piston and cylinders
104 and 105 in parallel with each other. Figure 4D shows
on piston and cylinder 106. Figure 4E shows three piston
and cylinders 107, 108 and 109 in parallel with each
other. Figure 4F shows four piston and cylinders 110,
111, 112 and 113 in parallel with each other.
The piston and cylinders have a bore of 182cmz
(28.27 square inches); a rod area of 9.58cm2 (1.485
square inches) ; an effective area (bore minus rod) of
172cm2 (26.8 square inches) and is able to support about
1.1 tonnes (2500 pounds). The pressure of the pneumatic
fluid inside the cylinder is about 6.4 Bar (93.3psi). The
pressure required to support two tons is about 5.5 Bar
(80psi).
The embodiment of Fig. 4C can support 5 tons at 6.4
Bar (93.3psi) and 4 tons at 5.5 Bar (80psi).
The embodiment of Fig. 4E can support 7.5 tons at
6.4 Bar (93.3psi) and 6 tons at 5.5 Bar (80psi).
The embodiment of Fig. 4F can support 10 tons at 6.2
Bar (90psi) and 8 tons at 5.5 Bar (80psi). If a multi
piston and cylinder apparatus is used, and light tubulars
are to be handled, only one or more piston and cylinders
need be used. The other piston and cylinders can vent
through vent V.
Figure 4G shows schematically a circuit diagram of a
linked piston and cylinder arrangement generally
identified by reference numeral 200. Flow lines 201 and
202 link the two lower interiors of the cylinder 203, 204
and 205, 206 of the cylinders 110, 111, 112 and 113. A
flow line 207 links the two flow lines 201 and 202. The
flow line 207 leads to a.control console CS. Pistons 208,
209, 210 and 211 are connected to piston rods 212, 213,
214 and 215 a portion of which extends below a plate 216
on to which the cylinders are mounted. An upper plate may
be arranged on top of the cylinders for stability. A
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manifold may be used for providing each cylinder with
equal quantities of fluid for even actuation thereof.
Each cylinder may be provided with an isolation valve for
selectively venting each cylinder.
Figures 5A-5C show an embodiment of a control
console CS for use with the system of Figure 4A. The
control console SC includes a fluid hose reel 301 on a
base 302, a make-up pressure indicator 303, a break-out
pressure indicator 304, a make-up regulator pressure
control know 305, a make-up relief valve control knob
306, and a break-out regulator pressure control knob 307.
Figures 7A-7C show an elevator 400 according to the
present invention with a body 401 with parts 402 and 403
hinged together by hinge 404 for selective emplacement
around and removal from a tubular, releasable locking
apparatus 405, a bore 406 through the body, lifting ears
407 on the body, a shoulder 408 around the top of the
bore 406, and a roller bearing apparatus 409 with halves
410 and 411 on the shoulder 408 each with a plurality of
roller bearings 412. A collar or other appropriate part
of a tubular (not shown) may rest and move on the roller
bearings 412 and thus rotation of the collar (and of,
therefore, the tubular and other tubulars connected to
and beneath it) is facilitated.
The primary elevator 31 may have such roller bearing
apparatus or, alternatively, any suitable known roller
and/or bearing devices or mechanisms may be used on the
shoulder 408 or on a top portion of the elevator 400.
Such bearing and/or roller apparatus may also be provided
for multiple (dual, quad, etc.) string elevators.
In the embodiment of Figure 2A, there are four
piston and cylinders used, which may be hydraulic or
pneumatic, in this embodiment, however any number could
be used including one, two, three, four, five or six. A
bellows air spring may be used instead of the piston and
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cylinders.
If required, the motor 32 can be used to rotate the
entire string for purposes such as facilitating insertion
of tubulars into the well bore.
It should be noted that the above apparatus could be
used for connecting and disconnecting any sort of tubular
including casing, liner, thin walled pipe, drill pipe or
any tool for connection or disconnection to of from a
string of tubulars.
It is envisaged that the stem could be an enlarged
piston rod of a piston and cylinder of the weight
compensating device. An end stop may be provided on the
end of the piston rod to transfer the weight of a string
of tubulars to a support when the piston is in a fully
extended position.
It is also envisaged that the stem could be a chain.
