U.S. patent number RE29,564 [Application Number 05/609,367] was granted by the patent office on 1978-03-07 for hydraulic motion compensating apparatus.
This patent grant is currently assigned to Vetco Offshore Industries, Inc.. Invention is credited to Edward Larralde, Glen Robinson.
United States Patent |
RE29,564 |
Larralde , et al. |
March 7, 1978 |
Hydraulic motion compensating apparatus
Abstract
A compensating apparatus is suspended from a divided crown block
mounted on a derrick of a floating drilling barge, the compensating
apparatus including a single cylinder extending vertically between
and carrying divided travelling block sheaves on opposite sides
thereof, with drawwork lines passing over the divided crown block
sheaves and divided travelling block sheaves, and with the upper
portion of the cylinder extending between such lines and adapted to
move upwardly between the crown block sheaves without interference.
A piston structure, forming part of the compensating apparatus, is
slidable in the cylinder, being connected to a hook, or the like,
from which a running string, such as a drilling string, is
suspended extends into an underlying well bore, liquid under
pressure in the cylinder acting on the piston structure to support
part or all of the weight of the running string. The piston
structure and cylinder can be locked together mechanically when in
a fully contracted condition to render the compensating apparatus
ineffective.
Inventors: |
Larralde; Edward (Santa
Barbara, CA), Robinson; Glen (Oak View, CA) |
Assignee: |
Vetco Offshore Industries, Inc.
(Ventura, CA)
|
Family
ID: |
26957139 |
Appl.
No.: |
05/609,367 |
Filed: |
September 2, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
274880 |
Jul 25, 1972 |
03841607 |
Oct 15, 1974 |
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Current U.S.
Class: |
254/392; 175/5;
188/67; 254/277; 254/399; 254/900; 92/26 |
Current CPC
Class: |
E21B
19/09 (20130101) |
Current International
Class: |
E21B
19/00 (20060101); E21B 19/09 (20060101); B66D
001/48 () |
Field of
Search: |
;254/172,173,189,139
;175/5 ;187/26,17 ;166/.5 ;188/67 ;92/24,26,108,109,110 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Saifer; Robert W.
Assistant Examiner: Rowland; James L.
Claims
We claim:
1. An apparatus for maintaining a predetermined stress in a running
string disposed in a well bore and which is supported by a rig,
including a derrick and a suspension mechanism supported from the
upper portion of the derrick: comprising a travelling block
structure adapted to form part of the suspension mechanism; a hook
structure adapted to support the running string therebelow; a
motion compensating apparatus disposed between and connected to
said block structure and hook structure; said motion compensating
apparatus comprising cylinder means coaxial of said hook structure;
piston means slidable in said cylinder means and connected to said
hook structure; said travelling block structure being split and
fixedly mounted to said cylinder means on opposite sides of said
cylinder means substantially below the upper end of said cylinder
means and with said cylinder means disposed between said split
block structure; and means for maintaining a fluid medium under
pressure in said cylinder means for exerting an upward force on
said piston means as said piston means and cylinder means move
longitudinally relative to one another in both longitudinal
directions.
2. An apparatus as defined in claim 1; said block structure
comprising one or more sheaves rotatably mounted on said cylinder
means at one side thereof and one or more sheaves rotatably mounted
on said cylinder means at the opposite side thereof.
3. An apparatus as defined in claim 1; said block structure
comprising one or more sheaves rotatably mounted on said cylinder
means at one side thereof and one or more sheaves rotatably mounted
on said cylinder means at the opposite side thereof; said cylinder
means projecting upwardly beyond said sheaves.
4. An apparatus as defined in claim 1; and means for releasably
locking said piston means and cylinder means to each other when
said piston means is substantially fully telescoped within said
cylinder means to prevent relative longitudinal movement between
said piston means and cylinder means.
5. An apparatus as defined in claim 1; collet means for releasably
locking said piston means and cylinder means to each other when
said piston means is substantially fully telescoped within said
cylinder means to prevent relative longitudinal movement between
said piston means and cylinder means; and means movable
longitudinally along one of said cylinder means and piston means
for selectively shifting said collet means to locking or unlocking
position.
6. An apparatus as defined in claim 1; collet means for releasably
locking said piston means and cylinder means to each other when
said piston means is substantially fully telescoped within said
cylinder means to prevent relative longitudinal movement between
said piston means and cylinder means; and hydraulically operable
means movable longitudinally along said cylinder means for
selectively shifting said collet means to locking or unlocking
position.
7. An apparatus as defined in claim 1; said cylinder means
comprising an outer member and an inner member therewithin and
secured to said outer member, said inner and outer members being
laterally spaced from each other to provide an annular space
therebetween in which said piston means is movable; said piston
means comprising a piston in said annular space slidably sealing
against the inner wall of said outer member and the outer wall of
said inner member; said piston means further comprising a piston
rod secured to said piston and laterally spaced from said inner
wall of said outer member and in slidable sealed relation to said
outer and inner members; and means for directing said fluid medium
under pressure into the space between said piston rod and inner
wall of said outer member for action upon said piston; said piston
rod being laterally spaced from said inner member to provide a
second annular space therebetween; and means for directing said
fluid medium under pressure into said second annular space for
action upon said piston.
8. An apparatus as defined in claim 1; said cylinder means
comprising an outer member and an inner member therewithin and
secured to said outer member, said inner and outer members being
laterally spaced from each other to provide an annular space
therebetween in which said piston means is movable; said piston
means comprising a piston in said annular space slidably sealing
against the inner wall of said outer member and the outer wall of
said inner member; said piston means further comprising a piston
rod secured to said piston and laterally spaced from said inner
wall of said outer member and in slidable sealed relation to said
outer and inner members; and means for directing said fluid medium
under pressure into the space between said piston rod and inner
wall of said outer member for action upon said piston; and means
for releasably locking said piston rod and outer member to each
other when said piston and piston rod are substantially fully
telescoped within said cylinder means to prevent relative
longitudinal movement between said piston means and cylinder
means.
9. An apparatus as defined in claim 1; said cylinder means
comprising an outer member and an inner member therewithin and
secured to said outer member, said inner and outer members being
laterally spaced from each other to provide an annular space
therebetween in which said piston means is movable; said piston
means comprising a piston in said annular space slidably sealing
against the inner wall of said outer member and the outer wall of
said inner member; said piston means further comprising a piston
rod secured to said piston and laterally spaced from said inner
wall of said outer member and in slidable sealed relation to said
outer and inner members; and means for directing said fluid medium
under pressure into the space between said piston rod and inner
wall of said outer member for action upon said piston; collet means
for releasably locking said piston rod and outer member to each
other when said piston means is substantially fully telescoped
within said cylinder means to prevent relative longitudinal
movement between said piston means and cylinder means; and means
movable longitudinally along said outer member for selectively
shifting said collet means to locking or unlocking position.
10. An apparatus for maintaining a predetermined stress in a
running string disposed in a well bore and which is supported by a
rig, including a derrick: comprising a suspension mechanism
including a split crown block structure adapted to be supported
from the upper portion of the derrick; a travelling block structure
below said crown block structure and suspended therefrom by lines
passing around both structures; a hook structure adapted to support
the running string therebelow; a motion compensating apparatus
disposed between and connected to said travelling block structure
and hook structure; said motion compensating apparatus comprising
cylinder means coaxial of said hook structure; piston means
slidable in said cylinder means and connected to said hook
structure; said travelling block structure being split and fixedly
mounted to said cylinder means on opposite sides of said cylinder
means substantially below the upper end of said cylinder means and
with said cylinder means disposed between said split block
structure; and means for maintaining a fluid medium under pressure
in said cylinder means for exerting an upward force on said piston
means as said piston means and cylinder means move longitudinally
relative to one another in both longitudinal directions.
11. An apparatus as defined in claim 10, said crown block structure
comprising sets of sheaves laterally spaced from each other; said
travelling block structure comprising one or more sheaves rotatably
mounted on said cylinder means at one side thereof and one or more
sheaves rotatably mounted on said cylinder means at the opposite
side thereof.
12. An apparatus as defined in claim 10; said crown block structure
comprising sets of sheaves laterally spaced from each other; said
travelling block structure comprising one or more sheaves rotatably
mounted on said cylinder means at one side thereof and one or more
sheaves rotatably mounted on said cylinder means at the opposite
side thereof; said cylinder means projecting upwardly beyond, said
travelling block sheaves and adapted to extend between said sets of
sheaves of said crown block structure.
13. An apparatus as defined in claim 10; said cylinder means
comprising an outer member and an inner member therewithin and
secured to said outer member, said inner and outer members being
laterally spaced from each other to provide an annular space
therebetween in which said piston means is movable; said piston
means comprising a piston in said annular space slidably sealing
against the inner wall of said outer member and the outer wall of
said inner member; said piston means further comprising a piston
rod secured to said piston and laterally spaced from said inner
wall of said outer member and in slidable sealing relation to said
outer and inner members; and means for directing said fluid medium
under pressure into the space between said piston rod and inner
wall of said outer member for action upon said piston.
14. An apparatus as defined in claim 10; said cylinder means
comprising an outer member and an inner member therewithin and
secured to said outer member, said inner and outer members being
laterally spaced from each other to provide an annular space
therebetween in which said piston means is movable; said piston
means comprising a piston in said annular space slidably sealing
against the inner wall of said outer member and the outer wall of
said inner member; said piston means further comprising a piston
rod secured to said piston and laterally spaced from said inner
wall of said outer member and in slidable sealing relation to said
outer and inner members; and means for directing said fluid medium
under pressure into the space between said piston rod and inner
wall of said outer member for action upon said piston; and means
for releasably locking said piston rod and outer member to each
other when said piston means is substantially fully telescoped
within said cylinder means to prevent relative longitudinal
movement between said piston means and cylinder means.
15. An apparatus as defined in claim 10, said cylinder means
comprising an outer member and an inner member therewithin and
secured to said outer member, said inner and outer members being
laterally spaced from each other to provide an annular space
therebetween in which said piston means is movable; said piston
means comprising a piston in said annular space slidably sealing
against the inner wall of said outer member and the outer wall of
said inner member; said piston means further comprising a piston
rod secured to said piston and laterally spaced from said inner
wall of said outer member and in slidable sealing relation to said
outer and inner members; and means for directing said fluid medium
under pressure into the space between said piston rod and inner
wall of said outer member for action upon said piston; collet means
for releasably locking said piston rod and outer member to each
other when said piston means is substantially fully telescoped
within said cylinder means to prevent relative longitudinal
movement between said piston means and cylinder means; and means
movable longitudinally along said outer member for selectively
shifting said collet means to locking or unlocking position. .Iadd.
16. An apparatus useful for maintaining a predetermined stress in a
running string positioned in well bore and supported by a rig
including suspension mechanism for which the running string is
suspended, said apparatus including a travelling block structure
adapted to form part of the suspension mechanism, a support
structure adapted to support the running string therebelow, a
motion compensating apparatus disposed between and connected to
said travelling block structure and support structure, said motion
compensating apparatus comprising cylinder means coaxial of said
support structure, piston means slidable in said cylinder means and
connected to said support structure, said travelling block
structure being split and fixedly mounted to said cylinder means on
opposite sides of said cylinder means substantially below the upper
end of said cylinder means and with said cylinder means disposed
between said split travelling block structure, and means on said
cylinder means for connection to a source of fluid pressure for
maintaining a fluid medium under pressure in said cylinder means
for exerting an upward force on said piston means as said piston
means and cylinder means move longitudinally relative to one
another in both longitudinal directions. .Iaddend..Iadd. 17. An
apparatus as defined in claim 16; said travelling block structure
comprising one or more sheaves rotatably mounted on said cylinder
means at one side thereof and one or more sheaves rotatably mounted
on said cylinder means at the opposite side thereof. .Iaddend.
.Iadd. 18. An apparatus as defined in claim 16; said travelling
block structure comprising one or more sheaves rotatably mounted on
said cylinder means at one side thereof and one or more sheaves
rotatably mounted on said cylinder means at the opposite side
thereof, said cylinder means projecting upwardly beyond said
sheaves..Iaddend. .Iadd. 19. An apparatus as defined in claim 16;
and means for releasably locking said piston means and cylinder
means to each other when said piston means is substantially fully
telescoped within said cylinder means to prevent relative
longitudinal movement between said piston means and cylinder
means..Iaddend. .Iadd. 20. An apparatus as defined in claim 16;
said cylinder means comprising an outer member and an inner member
therewithin and secured to said outer member, said inner and outer
members being laterally spaced from each other to provide an
annular space therebetween in which said piston means is movable,
said piston means comprising a piston in said annular space
slidably sealing against the inner wall of said outer member and
the outer wall of said inner member, said piston means further
comprising a piston rod secured to said piston and laterally spaced
from said inner wall of said outer member and in slidable sealed
relation to said outer and inner members, means for directing a
fluid medium under pressure into the space between said piston rod
and inner wall of said outer member for acting upon said piston,
said piston rod being laterally spaced from said inner member to
provide a second annular space therebetween, and means for
directing said fluid medium under pressure into said second annular
space for action upon said piston. .Iaddend. .Iadd. 21. An
apparatus useful for maintaining a predetermined stress in a
running string disposed in a well bore and which is supported by a
rig which includes a derrick; said apparatus including a suspension
mechanism including a split crown block structure adapted to be
supported from the upper portion of the derrick, a travelling block
structure below said crown block structure and suspended therefrom
by lines passing around both structures, a support structure
adapted to support the running string therebelow, a motion
compensating apparatus disposed between and connected to said
travelling block structure and support structure, said motion
compensating apparatus comprising cylinder means coaxial of said
support structure, piston means slidable in said cylinder means and
connected to said support structure, said travelling block
structure being split and fixedly mounted to said cylinder means on
opposite sides of said cylinder means substantially below the upper
end of said cylinder means and with said cylinder means disposed
between said split block structure, and means for directing a fluid
medium under pressure into said cylinder means for exerting an
upward force on said piston means as said piston means and cylinder
means move longitudinally relative to one another in both
longitudinal directions..Iaddend. .Iadd. 22. An apparatus as
defined in claim 21; said crown block structure comprising sets of
sheaves laterally spaced from each other, said travelling block
structure comprising one or moe sheaves rotatably mounted on said
cylinder means at one side thereof and one or more sheaves
rotatably mounted on said cylinder means at the opposite side
thereof..Iaddend. .Iadd. 23. An apparatus as defined in claim 21;
said crown block structure comprising sets of sheaves laterally
spaced from each other, said travelling block structure comprising
one or more sheaves rotatably mounted on said cylinder means at one
side thereof and one or more sheaves rotatably mounted on said
cylinder means at the opposite side thereof, said cylinder means
projecting upwardly beyond said travelling block sheaves and
adapted to extend between said sets of sheaves of said crown block
structure..Iaddend. .Iadd. 24. An apparatus as defined in claim 21;
said cylinder means comprising an outer member and an inner member
therewithin and secured to said outer member, said inner and outer
members being laterally spaced from each other to provide an
annular space therebetween in which said piston means is movable,
said piston means comprising a piston in said annular space
slidably sealing against the inner wall of said outer member and
the outer wall of said inner member, said piston means further
comprising a piston rod secured to said piston and laterally spaced
from said inner wall of said outer member and in slidable sealing
relation to said outer and inner members, means for directing said
fluid medium under pressure into the annular space between said
piston rod and inner wall of said outer member for action upon said
piston, said piston rod being laterally spaced from said inner
member to provide a second annular space therebetween, and means
for directing said fluid medium under pressure into said second
annular space for action upon said piston. .Iaddend. .Iadd. 25. On
a floating drilling platform of the type having a derrick, an upper
crown block assembly having a plurality of sheaves mounted on the
derrick, a lower travelling block assembly having a plurality of
sheaves, powered cable means interconnecting the travelling block
assembly and the crown block assembly, a rotary carrier for
supporting the drill string below the travelling block, and a
hydraulic heave compensator between the travelling block assembly
and the rotary carrier; said crown block being formed with a
vertical opening passing between said sheaves and said heave
compensator comprising a central cylinder mounted on the travelling
block assembly and arranged to pass through said vertical opening
while the travelling block is selectively raised by the cable
means, a piston in said cylinder having a rod projecting downwardly
to said carrier, and coupling means for selectively coupling said
carrier to the travelling block assembly when the piston is raised
in the cylinder. .Iaddend.
Description
The present invention relates to apparatus for controlling the
stress in a running string, and more particularly to apparatus used
on or in connection with a floating vessel or barge for maintaining
the strain in a running string, such as a pipe string,
substantially constant while being used in the performance of
diverse functions in a subaqueous well bore, such as drilling and
completion operations therein, despite vertical movement of the
vessel while such operations are being performed.
It has been proposed to provide a compensating apparatus between
the travelling block and hook of a well bore ring mounted on a
vessel floating in a body of water and used in drilling a
subaqueous well bore, or performing other operations therein, to
maintain the stress in a running string, such as a string of drill
pipe, used in drilling the well bore underlying the body of water,
at a substantially constant value. Such compensating apparatus
includes a cylinder supported from the travelling block and a
piston slidable therein connected to the hook, a desired liquid
pressure being maintained in the cylinder for exerting an upward
supporting force on the piston, which supporting force remains
substantially constant despite relative telescopic movement between
the cylinder and piston portions of the compensating apparatus,
resulting from heaving of the drilling vessel under tide, wind and
wave conditions.
In the application of James W. E. Hanes and Edward Larralde, Ser.
No. 69,759, filed Sept. 4, 1970, for "Motion Compensating
Apparatus," now Pat. No. 3,714,995 it has been proposed to avoid
reduction in the extent of vertical movement available in a derrick
mounted on the floating vessel, as a result of interposing a
compensating apparatus between the travelling block and hook. The
length added between the travelling block and hook materially
lessens the available maximum travel of the drawbacks or hoisting
apparatus, requiring the raising and lowering of shorter stands of
drill pipe in the well bore, which thereby increases the time
required in making a round trip of the pipe in the well bore. In
U.S. Pat. No. 3,714,995, significant height saving advantages have
been realized when used with standard crown blocks from which the
travelling block is suspended by the drawworks lines. Such height
advantages result from employing a pair of cylinders and pistons
which straddle or overlap the travelling block, such pair of
cylinders and pistons of necessity being eccentric with respect to
the center line or axis of the travelling block and hook suspended
therebelow, which introduces a bending or binding tendency in the
compensating apparatus.
By virtue of the present invention, a compensating apparatus is
provided which is so related to the travelling block and hook as to
provide for an increase in the maximum stroke of the compensating
apparatus without adversely affecting the required height of the
derrick.
A further objective of the present invention is to provide a
divided crown block, with a single compensating cylinder and
associated piston suspended therefrom which will be concentrically
disposed with respect to the hook therebelow, in order that the
mass of the apparatus and the forces acting thereon are applied in
a concentric manner, thereby eliminating any tendency for bending,
binding or seizing to occur in parts of the apparatus, and also
minimizing wear of the seals and bearings embodied in the
apparatus.
Yet a further object of the invention is to employ the cylinder of
the compensating apparatus as a portion of the travelling block
itself, as by mounting the sheaves of the travelling block on
opposite sides of the cylinder, this arrangement being employed in
connection with a divided crown block, the divided or split crown
block having a gap therebetween into which the cylinder can move,
thereby resulting in increase in the stroke or travel of the
apparatus.
A further object of the invention is to provide a lock device
between the cylinder and piston portions of the compensating
apparatus which is concentrically disposed with respect to the
cylinder and piston portions of the apparatus, enabling the
compensating apparatus to be rendered inoperative during "round
tripping" of the drill pipe, or the like, suspended from the
apparatus, the lock being operative upon full telescopic or
contracted movement of the piston structure within the cylinder.
The locking together of the travelling block and hook, and their
release from one another, can be effected from a remote point under
the control of the operator.
This invention possesses many other advantages, and has other
objects which may be made more clearly apparent from a
consideration of a form in which it may be embodied. This form is
shown in the drawings accompanying and forming part of the present
specification. It will now be described in detail, for the purpose
of illustrating the general principles of the invention; but it is
to be understood that such detailed description is not to be taken
in a limiting sense.
REFERRING TO THE DRAWINGS
FIG. 1 is a diagrammatic view of an apparatus embodying the
invention, illustrated in connection with a rig mounted on a
floating vessel for drilling a well bore underlying a body of
water;
FIG. 2 is a diagrammatic, enlarged view, parts being shown in
section, of the compensating apparatus illustrated in FIG. 1;
FIGS. 3a, 3b and 3c together constitute an enlarged quarter
sectional view, parts being shown in elevation, of the apparatus
disclosed in FIG. 2, FIGS. 3b and 3c being lower continuations of
FIGS. 3a and 3b, respectively; and
FIGS. 4a and 4b together constitute an enlarged longitudinal
section of the apparatus disclosed in FIGS. 3a, 3b and 3c, parts
being illustrated in elevation, disclosing the compensating
apparatus fully contracted and locked in an inoperative position,
FIG. 4b, being a lower continuation of FIG. 4a.
An apparatus is illustrated in the drawings in connection with the
drilling of a vertical well bore W from a subaqueous floor F above
which a drilling barge B, or other floating vessel, is located, the
barge being suitably anchored against lateral displacement for the
purpose of holding a drilling string S in centered relation with
respect to the well bore. A drill bit A is secured to the lower end
of the drill string, such as a string of drill pipe .Iadd.or drill
.Iaddend.casing, the upper or kelly portion K of the drill string
passing through the usual rotary table T rotated by a suitable
drive mechanism (not shown). The upper end of the kelly is secured
to a swivel C, which is, in turn, suspended from a hook H connected
to the lower portion of a motion compensating apparatus D
operatively connected to a travelling block structure E suspended
from a crown block structure M, mounted on the upper portion of the
derrick N, through the use of the usual lines L connected to a
drawworks P mounted on the drilling barge, the drawworks permitting
the drill string S to lower as the well bore W is cut by the bit
A.
A mudline R is connected to the swivel C for the purpose of pumping
drilling mud, or the like, down the drill string S for discharge
from the bit A, for the purpose of removing the cuttings produced
by the latter. While the drill bit A is rotated by the drill string
S, appropriate drilling weight is imposed thereon. Usually, the
drilling weight is provided by a suitable length of drill collars
disposed in the lower portion of the drill string immediately above
the drill bit, the drill string above the drill collars being
maintained in tension by the drawworks P, lines L and compensating
apparatus D.
The compensating apparatus D permits the floating vessel B and the
mechanism carried thereby to shift vertically relative to the well
bore W, without appreciably modifying the stress in the drill
string S, and, therefore, the drilling weight imposed on the drill
bit A. Through maintenance of liquid pressure in the compensating
apparatus, the tension or strain in the drill string S is
maintained substantially constant at a selected value, despite the
heaving of the floating vessel in the body of water. A system for
maintaining pressure of the liquid in the cylinder 10 of the
compensating apparatus at a selected constant value includes an
accumulator arrangement 11, disclosed diagrammatically in FIG. 1,
in which the pressure of a gas 12 in the accumulator is transferred
through a piston 13 to a liquid medium 14 in the accumulator, and
through the lines 15, 15a to the cylinder of the compensating
apparatus. One such system is illustrated in the application of
Edward Larralde, Ser. No. 222,919, filed Feb. 2, 1972, for
"Variable Rate Hydraulic-Pneumatic Weight Control and Compensating
Apparatus."
As specifically shown, the compensating apparatus includes the
cylinder structure 10, embodying an elongate outer cylinder sleeve
16 threadedly connected at its upper end to an upper cylinder head
17, and at its lower end to a lower cylinder head 18. Disposed
within the outer cylinder sleeve 16 is a coaxial inner cylinder
sleeve 19 threadedly secured to the upper head 17 and terminating
in a lower head 20. A piston structure 21 is shiftable
longitudinally along both inner and outer cylinder sleeves 19, 16,
the structure including an upper annular piston 22 slidably sealing
against the inner wall 23 of the outer sleeve 16 and the outer wall
24 of the inner sleeve, leakage between the piston and sleeves
being prevented by suitable inner and outer seal rings 25, 26
mounted on the piston and sealingly engaged with the outer and
inner walls 24, 23. This piston is threadedly or otherwise suitably
secured to a tubular piston rod 27, the outer periphery 28 of which
is spaced laterally from the inner cylinder wall 23, to define an
annular cylinder space 29 therebetween, the piston rod also being
spaced laterally from the inner sleeve 19 to provide an annular
space 30 therebetween. The inner head 20 is in slidable relation to
the inner wall 31 of the tubular piston rod, leakage of fluid
therebetween being prevented by suitable seal rings 32 on the inner
head slidably and sealingly engaging against the inner wall of the
tubular piston rod. The lower cylinder head 18 carries a suitable
rod seal 33 sealingly engaging against the periphery 28 of the
piston rod 27.
The piston rod 27 extends through the lower cylinder head 18 and
has its lower portion threadedly secured to a lower lock member 35
suitably secured, as by means of a plurality of screws 36, to an
adapter 37 having an upper inner flange 37a resting upon an outer
flange 35a of the lock member 35 and forming part of a gimbal 38
secured to the lower hook H, which depends therefrom and which is
coaxially arranged with respect to the cylinder sleeves 16, 19 and
the piston structure 21. The gimbal includes trunnions 39 extending
from opposite sides of a cross-head 40, and which are pivotally
mounted in the adapter 37, the cross-head having a transverse pin
41 connected to the upper portion 42 of the hook and lying in the
same plane as the trunnions 39, being disposed 90 degrees with
respect thereto. It is apparent that the hook H can pivot about the
axis of the transverse pin 41 and also about the axis of the
trunnions 39, which provides for a universal movement of the hook
with respect to the piston rod 27.
The travelling block structure E is actually integrated into the
cylinder 10. Thus, the cylinder sleeve 16 has trunnions or bearing
supports 42 suitably secured, as by use of welding material 43, on
opposite sides of the cylinder substantially below the upper
cylinder head 17, there being a plurality of sheaves 44 rotatably
mounted on each of said trunnions through suitable intervening
roller or other bearings (not shown), the bearings and a housing 45
enclosing the lower portion of the sheaves being retained on the
trunnions 42 by a suitable nut 46 threaded on the outer portion of
each trunnion.
It is apparent that the travelling block E is split or divided,
being arranged on opposite sides of the cylinder 10, which permits
the drawworks lines L to pass successfully over such sheaves 44 and
corresponding sheaves 50 forming a part of the crown block M, the
crown block being split or divided and providing a gap 51 between
its two portions. It is apparent that the crown block is suitably
supported on the upper end of the derrick N.
The travelling block E and the compensator apparatus D secured
thereto can be elevated by the drawworks P to a maximum position in
which the split travelling block sheaves 44 are disposed closely
adjacent to the crown block sheaves 50, the cylinder 10 entering
the gap or space 51 between the crown block sheaves. Accordingly, a
maximum range of travel is achievable, offsetting the length added
to the apparatus by the compensator portion D of the apparatus
disposed below the sheaves 44 and intervening between the sheaves
44 and the hook H.
The liquid under pressure from the accumulator 11 can pass into and
out of the annular cylinder space 29 through an inlet and outlet
port 60 in the lower cylinder head to which one of the liquid lines
15 is suitably connected. The liquid under pressure in such annular
cylinder space acts in an upward direction over the annular piston
22 across the annular area of the cylinder space 29 to exert an
upward force on the piston, the tubular piston rod 27 and the hook
H and other apparatus suspended therefrom. Similarly, the liquid
under pressure can pass through the line 15a connected to an inlet
and outlet port 61 in the upper cylinder head 17, and through a
central passage 62 in the inner cylinder sleeve 19 which
communicates through a lower port 63, immediately above the inner
head 20, with the annular space 30 between the outer wall 24 of the
inner cylinder sleeve and the tubular piston rod 27, this liquid
under pressure also acting in an upward direction over the inner
portion of the annular piston 22 and assisting in the supporting of
the piston rod 27 and the mechanism suspended therefrom.
As the drilling barge or vessel heaves in the water, the liquid
under pressure will pass into and out of the annular cylinder
spaces 29, 30, permitting longitudinal travel of the outer and
inner cylinders 16, 19 along the piston rod 27 without
substantially affecting the pressure of the liquid in the cylinder
spaces 29, 30, which continues to exert a substantially constant
upward force on the piston 22 and the piston rod depending
therefrom, the liquid passing into and from the accumulator 11,
with the pressure of the gas 12 maintaining the substantially
constant unit pressure in the liquid 14. Thus, a constant stress or
tension is maintained on the drilling string S, without varying its
relative position within the well bore W as the drilling barge B
and cylinder 10 move vertically under the action of wind, wave and
tide.
At times, it is desirable for the motion compensator apparatus D to
be rendered inoperative, as, for example, during withdrawal of the
drill pipe S, or its relowering from the drilling barge into the
well bore. With the apparatus illustrated, the cylinder 10 and
piston structure 21 are mechanically locked together when the
piston 22 occupies its uppermost position within the cylinder 10;
in effect, securing the hook H in a predetermined position with
respect to the travelling block E so that they operate as a unit
during the raising and lowering of the travelling block. As
disclosed, the lower lock member 35 secured to the piston rod 27
has an external lock flange 70 thereon provided with a downwardly
facing lock surface 71. The lower cylinder head 18 has an upper
lock member 72 threadedly secured thereto and depending therefrom,
and through which the piston rod 27 is slidable, which also has an
upper external lock flange 73 thereon provided with an upwardly
tapering lock surface 74, which are oppositely disposed with
respect to the lower lock flange 70 and its lock surface 71. A
collet type of lock device 75 is carried by the upper lock member
72, this lock device including an upper head 76 suitably secured to
the upper lock member 72 by means of a plurality of screws 77a.
Integral with and depending from the head 76 are a plurality of
circumferentially arranged spring-like arms 77 terminating in lock
dogs 78, each dog having an inner recess 79 in which the upper and
lower lock flanges 73, 70 can be received when they are disposed
adjacent to one another. The dogs 78 have upper lock surfaces 80
and lower lock surfaces 81 spaced from one another and defining the
upper and lower ends of the recesses 79, and which conform to the
upper and lower lock surfaces 74, 71 on the flanges 73, 70.
Normally, the spring arms 77 shift the lock dogs 78 laterally
outwardly into a position permitting upward movement of the lower
lock flange 70 through the lower ends of the lock dogs, and into a
position substantially contacting the upper lock flange 73, as
illustrated in FIG. 4b. With the lock flanges in such abutting or
adjacent position, the lock dogs 78 can be shifted inwardly to a
position in which the upper and lower lock dog surfaces 80, 81
engage the companion lock surfaces 74, 71 on the lock flanges 73,
70, thereby securing the piston 21 and cylinder 10 to one another,
preventing their relative longitudinal movement,
As specifically disclosed, the actuation of the lock device 75 may
be effected from a remote point. Thus, an annular piston 85 is
provided within a lock cylinder 86, the upper portion of which is
threadedly secured to the lower cylinder head 18, which actually
constitutes an upper head 87 of the lock cylinder. The annular
piston is disposed in the space between the upper lock member 72
and the cylinder 86, an actuator sleeve 88 integral with and
depending from this piston 85 being provided which extends
downwardly within a lower cylinder portion 89 of substantially
lesser internal diameter than the upper portion of the cylinder 86,
and in which the sleeve 88 is slidable. The spring arms 77 and lock
dogs 78 are disposed within the lower cylinder portion 89. The
lower portion of the sleeve is constituted as an internal cam 90
having its inner surface inclined in a downward and outward
direction and adapted to engage companion cam surfaces 91 on the
lock dogs, for the purpose of shifting the dogs 78 laterally
inwardly upon downward movement of the piston 85 and its sleeve 88
within the cylinder 86. Such downward movement occurs as a result
of feeding hydraulic fluid through a line 94 connected to the upper
portion of the cylinder 86 and adapted to direct liquid under
pressure into the cylinder above the piston 85, for the purpose of
forcing the piston 85 and its cam 90 downwardly when the lower lock
member 35 abuts the upper lock member 72, causing the cam to shift
the lock dogs 78 inwardly to the locking position illustrated in
FIG. 4b. The angle of taper of the cam surface 90 and the companion
surfaces 91 on the dogs is relatively small, actually constituting
a self-locking angle, such that the dogs 78 are retained in a
position locking the piston structure 21 and cylinder structure 10
against longitudinal movement with respect to each other in the
absence of fluid pressure in the cylinder 86 above the lock piston
85.
In the event the lock is to be released, liquid under pressure is
forced through a suitable line 95 communicating with the cylinder
86 below the piston when it is in its lower position, this fluid
acting in an upward direction on the piston, to elevate the piston
85 and its associated sleeve 88 within the cylinder 86 and relative
to the lock dogs 78, placing the piston and sleeve in the position
illustrated in FIG. 3b. When the cam surface 90 is out of
.[.arrangement.]. .Iadd.engagement .Iaddend.with the lock dogs 78,
the spring arms 77 will inherently expand to their outer position,
permitting the piston rod 27 to move freely within the cylinder 10.
If this were not to occur, a relative downward force exerted on the
piston rod 27, as by the weight suspended therefrom, will cause its
tapered lock surface 71 to force the lock dogs 78 to their lateral
outward or unlocked position illustrated in FIG. 3b.
By virtue of the apparatus described, a compensating apparatus has
been provided that permits a desired maximum movement of the
travelling block without requiring an undue derrick height. The
divided crown block M and the straddling relationship between the
cylinder 10 and the sheaves 44 permit the apparatus to be elevated
within the derrick to such an extent that the full required
elevation of the drilling string within the derrick can occur, in
essentially the same manner as if a compensating apparatus were not
present. The dividing of the crown block permits the cylinder 10 to
pass between its two portions without interference, enabling a
greater elevation of the travelling block to occur, as compared to
the provision of an unsplit or undivided crown block. Even in the
absence of a split crown block, the required travel of the
travelling block E can still occur without interference by the
compensator apparatus D, because of the straddled or overlapping
relation between the split travelling block and the compensator
cylinder 10. The provision of a single compensator cylinder and a
single piston operating therein, related in a concentric manner to
the apparatus suspended therefrom, results in forces being applied
to the several parts in a concentric manner, thus eliminating
bending, binding or seizing tendencies on the parts, as well as
minimizing loads on seals and bearing surfaces. The concentric
locking device enables the compensator portion of the apparatus to
be rendered inoperative, permitting joint movement of the
travelling block E and the hook H to the same extent as if the
compensating apparatus D were not present. With the apparatus in a
locked condition, there is no necessity for retaining liquid under
pressure in the cylinder 10. The concentric locking device is
simpler than the type of locking device illustrated in U.S. Pat.
No. 3,714,995, the ease of effecting locking and unlocking being
greatly increased. Such selective locking or unlocking of the
travelling block and hook can be effected from a remote point under
the control of the operator .
* * * * *