U.S. patent application number 09/783084 was filed with the patent office on 2001-10-04 for hydraulic drilling rig.
Invention is credited to Byrt, Harry F., Desai, Vinod, McConnell, Dave.
Application Number | 20010025727 09/783084 |
Document ID | / |
Family ID | 22475286 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010025727 |
Kind Code |
A1 |
Byrt, Harry F. ; et
al. |
October 4, 2001 |
Hydraulic drilling rig
Abstract
A multi-purpose drilling rig has a movable pipe support cradle
which moves horizontally to transfer drill pipe from a storage area
to the well being drilled, and vice versa. The cradle travels along
a roof platform supported by load-bearing hydraulic lifting rams.
Raising or lowering the lifting rams raises or lowers the roof
platform, along with the drill pipe suspended from the cradle.
Structural towers stabilize the lifting rams against buckling and
lateral loads. Supplementary lifting capacity is provided
cradle-mounted roof rams having pistons which may extend downward
from the cradle, with the drill pipe suspended from a yoke
interconnecting the roof ram pistons. For offshore drilling, a
control system senses fluctuations in rig elevation due to wave
action, and automatically adjusts extends or retracts the rams as
required to maintain constant load on the drill bit. Also disclosed
is a method of drilling which utilizes vertical and lateral
movement of the cradle and top drive.
Inventors: |
Byrt, Harry F.; (Edmonton,
CA) ; McConnell, Dave; (Leduc, CA) ; Desai,
Vinod; (Houston, TX) |
Correspondence
Address: |
EDWARD YOO C/O BENNETT JONES
1000 ATCO CENTRE
10035 - 105 STREET
EDMONTON, ALBERTA
AB
T5J3T2
CA
|
Family ID: |
22475286 |
Appl. No.: |
09/783084 |
Filed: |
February 15, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09783084 |
Feb 15, 2001 |
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PCT/CA99/00771 |
Aug 20, 1999 |
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PCT/CA99/00771 |
Aug 20, 1999 |
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09136977 |
Aug 20, 1998 |
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6068066 |
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Current U.S.
Class: |
175/7 ; 175/52;
175/85 |
Current CPC
Class: |
E21B 19/09 20130101;
E21B 15/02 20130101; E21B 19/143 20130101 |
Class at
Publication: |
175/7 ; 175/52;
175/85 |
International
Class: |
E21B 007/128 |
Claims
The Embodiments of the invention in which an exclusive property or
privilege is claimed are as follows:
1. A drilling or service rig comprising: (a) a rig substructure
comprising a drill floor having a drill opening; (b) at least three
structural towers fixedly mounted to the rig substructure and
projecting vertically above the drill floor, said towers being in
spaced relationship to each other and encircling the drill opening;
(c) a plurality of hydraulically-actuated, telescoping lifting rams
corresponding in number to the number of towers, said lifting rams
being fixedly mounted at their lower ends to the rig substructure
and projecting vertically above the drill floor, and each lifting
ram being in proximal association with one of the towers; (d)
lateral support means associated with the towers for providing
lateral support to the lifting rams throughout their range of
telescoping operation; (e) hydraulic power means for actuating the
lifting rams such that the lifting rams may operate substantially
in unison; (f) a roof platform affixed to and supported by the
upper ends of the lifting rams, said roof platform comprising a
substantially horizontal cradle track; (g) a cradle having means
for engaging the cradle track such that the cradle may be mounted
to and moved along the cradle track; (h) cradle actuation means
mounted to the roof platform, for moving the cradle along the
cradle track; and (i) a drilling hook associated with the cradle,
for vertically supporting a drill string plus accessory components
and pipe-handling tools or service equipment.
2. The drilling rig of claim 1 wherein the cradle further comprises
heave compensation means, for regulating the vertical position of a
drill string in response to fluctuations in the elevation of the
drilling rig.
3. The drilling rig of claim 2 wherein the heave compensation means
comprises: (a) a hydraulically-actuated, telescoping roof ram
having a barrel and a piston, said roof ram being mounted to the
cradle such that the piston of the roof ram may telescope
vertically downward; (b) a yoke rigidly connected to the lower end
of the roof ram piston; and (c) hydraulic power means for actuating
the roof ram; wherein the drilling hook is associated with said
yoke.
4. The drilling rig of claim 3 wherein: (a) the number of roof rams
corresponds with the number of lifting rams; (b) each roof ram is
hydraulically connected to one of the lifting rams; (c) the
hydraulic power means comprises a plurality of hydraulic
sub-systems corresponding in number to the number of lifting rains;
and (d) each hydraulic sub-system is adapted to actuate one of the
lifting rams and its associated roof ram.
5. The drilling rig of claim 3 wherein the drill floor is adapted
to accommodate a rotary table for purposes of rotating a drill
string in association with a kelly.
6. The drilling rig of claim 3 wherein the drilling hook is adapted
to accommodate a rotary top drive for purposes of rotating a drill
string.
7. The drilling rig of claim 6 further comprising a torsion frame
rigidly affixed to and projecting downward from the cradle, said
torsion frame having a vertically-oriented torque track, and
wherein the yoke further comprises a yoke brace engaging the torque
track so as to permit vertical travel of the yoke along the torque
track.
8. The drilling rig of claim 7 wherein the torque track is adapted
for engagement by a rotary top drive so as to permit vertical
travel of the rotary top drive along the torque track.
9. The drilling rig of claim 1, further comprising control means
for actuating the hydraulic power means so as to maintain a desired
downward force on a drill bit during drilling of a well.
10. The drilling rig of claim 9 wherein the control means includes
a load cell which senses the downward force on the drill bit, and
which communicates with pressure regulation means which in turn
communicates with the hydraulic power means, for adjusting
hydraulic pressures in response to variations in said downward
force.
11. The drilling rig of claim 1 further comprising structural
cross-bracing between the towers.
12. The drilling rig of claim 1 wherein: (a) each tower comprises a
stationary section rigidly affixed to the rig substructure, plus a
telescoping section which movably engages the stationary section,
such that the telescoping section may extend above the stationary
section while cooperating with the stationary section throughout
its range of extension so as to provide structural resistance to
lateral forces acting on the tower; (b) the lifting ram associated
with each tower is positioned inside the structure of the tower;
and (c) the upper end of each telescoping section is connected to
the upper end of its corresponding lifting ram, so as to travel
concurrently therewith.
13. The drilling rig of claim 12 wherein the telescoping section is
longer than the stationary section and may extend below the
drilling floor into the rig substructure when lowered inside the
stationary section.
14. The drilling rig of claim 1 wherein each lifting ram comprises
a hydraulic cylinder having a lower portion and an upper portion, a
lower piston which may telescope downward from the lower portion of
the cylinder and an upper piston which may telescope upward from
the upper portion.
15. The drilling rig of claim 14 wherein each lifting ram is
double-acting.
16. The drilling rig of claim 4 wherein each hydraulic subsystem
comprises at least one reversible hydraulic pump.
17. A method of adding sections of drill pipe to a drill string
during well drilling operations, said method comprising the steps
of: (a) providing a drill rig comprising a drill floor with a drill
opening, a drill pipe storage area associated with the drill rig,
and a rotary top drive movable vertically by at least three
hydraulic lifting rams and horizontally along a cradle
track-mounted to a roof platform mounted to the hydraulic lifting
rams; (b) supporting a drill string positioned in the drill
opening, and disconnecting the top drive from the drill string; (c)
raising the top drive clear of the drill string; (d) moving the top
drive laterally from a position over the drill opening to a
position over the drill pipe storage area; (e) lowering the top
drive and connecting the top drive to a drill pipe section from the
drill pipe storage area; (f) raising the top drive such that the
bottom of the drill pipe section is higher than the top of the
drill string; (g) moving the top drive laterally to a position over
the drill string; (h) connecting the drill pipe section to the top
of the drill string; and (i) recommencing drilling operations.
18. A drilling or service rig comprising: (a) a rig substructure
comprising a drill floor having a central drill opening and a pipe
storage area comprising a fingerboard for storing lengths of pipe;
(b) at least three structural towers fixedly mounted to the rig
substructure and projecting vertically above the drill floor, said
towers being in spaced relationship to each other and encircling
the drill opening; (c) a plurality of hydraulically-actuated,
telescoping lifting rams corresponding in number to the number of
towers, said lifting rams being fixedly mounted at their lower ends
to the rig substructure and projecting vertically above the drill
floor, and each lifting ram being in proximal association with one
of the towers; (d) lateral supports associated with the towers for
providing lateral support to the lifting rams throughout their
range of telescoping operation; (e) hydraulic power means for
actuating the lifting rams such that the lifting rams may operate
substantially in unison; (f) a roof platform affixed to and
supported by the upper ends of the lifting rams; (g) a drilling
hook suspended from the roof platform, for vertically supporting a
drill string plus accessory components and pipe-handling tools or
service equipment; (h) a crane, slidably mounted to the rig below
the roof platform for moving lengths of pipe laterally within the
Texas deck and centrally towards the axis of the drill opening; (i)
a pipe trough disposed substantially beneath the drill floor and
moveable between a vertical position and an inclined position
wherein the pipe trough may receive a vertical length of pipe and
incline such that a top end of the pipe is inclined towards the
drill opening axis while the bottom end is inclined away from the
drill opening axis; and (j) a lateral ram for inclining the pipe
trough.
19. The drilling rig of claim 18 wherein the roof platform further
comprises heave compensation means, for regulating the vertical
position of a drill string in response to fluctuations in the
elevation of the drilling rig.
20. The drilling rig of claim 19 wherein the heave compensation
means comprises: (a) a hydraulically-actuated, telescoping roof ram
having a barrel and a piston, said roof ram being mounted to the
roof platform such that the piston of the roof ram may telescope
vertically downward; (b) a yoke rigidly connected to the lower end
of the roof ram piston; and (c) hydraulic power means for actuating
the roof ram; wherein the drilling hook is associated with said
yoke.
21. The drilling rig of claim 20 wherein the drill floor is adapted
to accommodate a rotary table for purposes of rotating a drill
string in association with a kelly.
22. The drilling rig of claim 20 wherein the drilling hook is
adapted to accommodate a rotary top drive for purposes of rotating
a drill string.
23. The drilling rig of claim 22 further comprising a torsion frame
rigidly affixed to and projecting downward from the roof platform,
said torsion frame having a vertically-oriented torque track, and
wherein the yoke further comprises a yoke brace engaging the torque
track so as to permit vertical travel of the yoke along the torque
track.
24. The drilling rig of claim 23 wherein the torque track is
adapted for engagement by a rotary top drive so as to permit
vertical travel of the rotary top drive along the torque track.
25. The drilling rig of claim 18, further comprising control means
for actuating the hydraulic power means so as to maintain a desired
downward force on a drill bit during drilling of a well.
26. The drilling rig of claim 25 wherein the control means includes
a load cell which senses the downward force on the drill bit, and
which communicates with pressure regulation means which in turn
communicates with the hydraulic power means, for adjusting
hydraulic pressures in response to variations in said downward
force.
27. The drilling rig of claim 18 further comprising structural
cross-bracing between the towers.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to drilling rigs, and in
particular to rigs for drilling gas and oil wells, and rigs for
servicing of existing wells. Even more particularly, the present
invention relates to heavy-duty rigs for deep-water offshore
drilling from drill ships or ocean-going drilling platforms.
BACKGROUND OF THE INVENTION
[0002] Drilling an oil or gas well involves two main operations:
drilling and tripping. To commence the drilling procedure, a drill
string terminating with a drill bit is positioned within a drilling
rig and rotated such that the drill bit bores into the ground or
into the seabed, in the case of offshore drilling, until it reaches
a predetermined depth or penetrates a petroleum-bearing geological
formation. The components of the drill string such as drill collars
and drill pipe are threaded for interconnection. Depending on what
type of drive system is being used, the uppermost length of drill
pipe in the drill string is connected either to a kelly or to a top
drive, both of which are further described hereinafter. As the
drill bit advances and the top of the drill string approaches the
working platform or drill floor of the drilling rig, additional
lengths of drill pipe must be added to the drill string in order to
advance the well further into the ground. This is accomplished by
temporarily supporting the top of the drill string near the drill
floor level (using devices called "slips"), disconnecting the kelly
(or the top drive, as the case may be) from the top of the drill
string, and then lifting a new section of drill pipe into position
using the rig's elevating system and screwing it into the top of
the drill string. The kelly (or the top drive) is then reconnected
to the drill string, and drilling operations resume until it is
again necessary to add drill pipe.
[0003] Perhaps the most common and well-known drive means for
rotating a drill string is the rotary table, which is a rotating
mechanism positioned on the drill floor, and which entails the use
of a kelly, referred to previously. The kelly is essentially a
heavy, four-sided or six-sided pipe, usually about 42 feet long or
57 feet long for offshore rigs. The rotary table has rotating
bushings shaped to accommodate the kelly, plus roller bearings
which allow the kelly to slide vertically through the bushings even
as the rotary table is rotating. The kelly is suspended from the
rig's main hoist, in conjunction with various accessories required
for drilling operations such as swivel and pipe elevators. With the
kelly connected to the top of the drill string, the hoist lowers
the drill string until the lower end of the kelly is positioned
within the bushings of the rotary table. The rotary table is then
activated, rotating both the kelly and the drill string connected
to it, thereby turning the drill bit at the bottom of the drill
string and advancing the well to a greater depth. The process of
turning the drill bit to advance the hole is referred to as "making
hole".
[0004] An increasingly common alternative to the rotary table is
the top drive unit, which applies rotational drive at the top of
the drill string, rather than at the drill floor as in the case of
the rotary table. Top drive units are typically driven by either
hydraulic or electric power. A significant advantage of the top
drive is that a kelly is not required; instead, the drill string is
connected directly to the top drive, as previously described. The
top drive is supported by the rig's main hoist, and moves downward
along with the drill string as drilling progresses. A rig using a
top drive must provide some means for resisting or absorbing the
torque generated by the top drive as it rotates the drill string,
so that the top drive will be laterally and rotationally stable at
all stages of drilling. This is typically accomplished by having
the top drive travel along vertical guide rails built into the rig
superstructure.
[0005] Tripping is a necessary but unproductive part of the overall
drilling operation, and involves two basic procedures. The first
procedure is extracting drill pipe from the well (referred to in
the industry as "pulling out of hole" mode, or "POH"), and the
second is replacing drill pipe in the well ("running in hole" mode,
or "RIH"). Tripping may be necessary for several reasons, such as
for replacement of worn drill bits, for recovery of damaged drill
string components, or for installation of well casing.
[0006] In POH mode, the kelly (if there is one) is removed
temporarily, the drill string is connected to the pipe elevators,
and the drill string is then pulled partially out of the hole as
far as the hoisting mechanism and geometry of the drilling rig will
permit. The drill string is then supported by the slips so that the
section or sections of the drill pipe exposed above the drill floor
may be disconnected or "broken out" and moved away from the well.
The elevators then reengage the top of the drill string so that
more of the drill string may be pulled out of the hole. This
process is repeated until the desired portion of the drill string
has been extracted. The procedure for RIH mode is essentially the
reverse of that for POH mode.
[0007] It is well known to use cable-and-winch mechanisms for
hoisting and lowering the drill string and casing string during the
drilling of gas and oil wells. In such mechanisms, a heavy
wire-rope cable (or "drilling line") runs upward from a winch (or
"drawworks") mounted at the drill floor, then is threaded through
the sheaves of a "crown block" mounted high in the derrick or mast
of the rig, and then down through the sheaves of a "travelling
block", which moves vertically with the load being hoisted. The
entire weight of the drill string, which can be several hundred
tons, is transferred via the travelling block, drilling line, and
crown block to the rig's derrick, which accordingly must be
designed and built to withstand such loads.
[0008] A significant disadvantage of cable-and-winch rigs is that
the drilling line will deteriorate eventually, entailing complete
removal and replacement. This may have to be done several times
during the drilling of a single deep well. Drilling line cable,
being commonly as large as two inches in diameter, is expensive,
and it is not unusual for a rig to require a drilling line as up to
1,500 feet long. Replacement of the drilling line due to wear
accordingly entails a large direct expense. As well, the
inspection, servicing, and replacement of drilling line typically
results in a considerable loss of drilling time, and a
corresponding increase in the overall cost of the drilling
operation.
[0009] In hydraulic drilling rigs, hydraulic cylinders are used in
various configurations to provide the required hoisting capability.
Some hydraulic rigs also use cables and sheaves but have no winch;
others eliminate the need for cables and sheaves altogether. A
significant advantage of the latter arrangement is that vertical
hoisting forces are not transferred to the mast, but rather are
carried directly by the hydraulic cylinders. The mast therefore may
be designed primarily for wind loads and other lateral stability
forces only, and can be made much lighter and thus more economical
than it might otherwise have been.
[0010] Whatever type of rig is being used, drilling operations
require a convenient storage area for drill pipe that will be
either added to or removed from the drill string during drilling or
tripping. On many rigs, drill pipe is stored vertically, resting on
the drill floor and held at the top in a rack known as a
"fingerboard." This system requires a "derrickman" working on a
"monkey board" high up in the rig, to manipulate the top of the
drill pipe as it is moved in and out of the fingerboard. Other rigs
use a "pipe tub", which is a sloping rack typically located
adjacent to and extending below the drill floor. Drill ships and
ocean-going drilling platforms often provide for vertical or
near-vertical storage of drill pipe in a "Texas deck" located under
the drill floor, with access being provided through a large opening
in the drill floor.
[0011] When sections of drill pipe are being added during drilling,
or in RIH mode during tripping, the pipe must be transported into
position from the pipe storage area. The opposite applies in POH
mode during tripping, when pipe removed from the drill string must
be transported away from the well and then to the Texas deck. With
most if not all known drilling rigs, these pipe-handling operations
cannot be conveniently performed using the rig's main hoist,
because the main hoist typically is centered over the well hole,
and cannot be moved laterally. The pipe has to be moved laterally
using either manual effort or auxiliary machinery.
[0012] Some rigs employ an auxiliary hoist to handle drill pipe.
U.S. Pat. Re. 29,541, reissued to Russell on Feb. 21, 1978,
discloses a drilling rig having a hydraulically-actuated primary
hoist, plus an auxiliary hoist for pipe-handling purposes in
conjunction with a fingerboard. U.S. Pat. No. 4,629,014, issued to
Swisher et al. on Dec. 16, 1986, and U.S. Pat. No. 4,830,336,
issued to Herabakka on May 16, 1989, provide further examples of
rigs which use an auxiliary hoist in conjunction with a
fingerboard. Numerous other auxiliary pipe-handling and racking
systems are known in the art. These systems, however, like the
Russell, Swisher, and Herabakka rigs, have a significant drawback
in that they require each length of pipe to be handled twice and
connected to two different hoisting mechanisms during both drilling
and tripping operations. Such double handling makes drilling
operations more time-consuming and expensive.
[0013] It can readily be seen that the efficiency and economy of a
well-drilling operation will increase as the amount of time and
effort required for handling drill pipe is decreased. For this
reason, it is desirable to maximize the length of drill pipe that a
drilling rig can handle at one time during tripping or when adding
pipe during drilling. Drill pipe is typically manufactured in
31-foot-long "joints." Many smaller drilling rigs are capable of
handling only a single joint at a time. However, many known rigs
are able to handle "stands" made up of two joints ("doubles," in
industry parlance) or three joints ("triples"), and such rigs can
provide significant operational cost savings over rigs that can
handle only singles.
[0014] These rigs still have significant disadvantages, however. To
accommodate doubles and triples, they must have taller masts. For
instance, if the rig is to handle triples which are 93 feet long,
the hoist must be able to rise 100 feet or more above the drill
floor. The mast has to be even higher than that, particularly for a
drawworks-type rig, in order to accommodate hoist machinery such as
the crown block. Because of its increased height, the mast will
obviously be heavier and therefore more expensive than a shorter
mast, even though the maximum hoisting loads which the mast must be
designed for might be the same in either case. A taller mast's
weight and cost will be even further increased by the need to
design it for increased wind loads resulting from the mast's larger
lateral profile.
[0015] Tall, heavy rigs have particular drawbacks when used on
ocean-going drill platforms or drill ships. Each floating platform
or drill ship has its own particular total weight limit, made up of
dead weight plus usable load capacity. Every extra pound of rig
weight adds to the dead weight and reduces the usable load capacity
correspondingly. Extra dead weight not only increases fuel costs
for transportation, but also increases expenses for supply ships,
which must make more frequent visits because the platform or drill
ship has less available load capacity for storage of supplies.
Moreover, ocean-going rigs generally need to be even taller than
comparable land-based rigs, because they must be able to
accommodate or compensate for vertical heave of up to 15 feet or
more, in order to keep the drill bit working at the bottom of the
hole under an essentially constant vertical load when the platform
or drill ship moves up or down due to wave action.
[0016] Another problem with tall rigs in an offshore drilling
context is that the center of gravity of the rig, as well as that
of the entire drilling platform or drill ship, generally rises
higher above the water line as the mast becomes taller. This is
especially true for rigs which have heavy hoisting equipment
mounted high in the mast. When seas are calm, a high center of
gravity will not have a major practical effect on rig operations.
In stormy conditions with high seas, however, drilling and tripping
operations can become impractical or unsafe or both because of the
risk of listing or even overturning. This risk increases as the
rig's center of gravity rises, so a tall rig generally will have to
be shut down to wait out bad weather sooner than a shorter rig
would have to be shut down in the same weather.
[0017] Downtime due to weather conditions, known as "waiting on
weather" time (or "WOW" time) in offshore drilling parlance, is
extremely expensive. Experience in North Sea drilling operations
has been that WOW time averages as much as 10% of total rig
deployment time. Because the total expense of operating an offshore
rig is commonly in the range of $150,000 or more per day, it is
readily apparent that the pipe-handling economies made possible by
offshore rigs with tall masts can be offset significantly by a
corresponding risk of increased WOW time.
[0018] For all the reasons outlined above there is a need in the
well-drilling industry for a drilling rig:
[0019] (a) which is capable of handling up to triple stands of
drill pipe during both drilling and tripping operations;
[0020] (b) which can transport drill pipe to and from a pipe
storage area using the rig's primary hoist, so as to eliminate or
minimize the need for hoisting or otherwise manipulating drill pipe
using auxiliary equipment or manual labour;
[0021] (c) which does not require drill line, sheaves, or
drawworks;
[0022] (d) which does not transfer vertical hoisting loads to the
rig superstructure;
[0023] (e) which provides integral means for heave compensation, so
as to be usable for offshore drilling operations;
[0024] (f) which may be conveniently and selectively reconfigured
so as to adjust the elevation of the rig's center of gravity,
thereby enhancing the rig's stability when being used in offshore
drilling operations; and
[0025] (g) which is significantly lighter in weight than known rigs
capable of operating with triple stands of drill pipe.
SUMMARY OF THE INVENTION
[0026] In general terms, the invention is a drilling rig in which
an upper platform, or roof platform, carries a track-mounted cradle
adapted to support a drill string and associated components and
drilling equipment. The roof platform may be lifted above a drill
floor by hydraulically actuated lifting rams, and the cradle may be
moved horizontally to facilitate the handling of drill pipe during
drilling and tripping operations. Structural towers provide
resistance to lateral loads, while vertical loads from the weight
of the drill string are carried by the lifting rams.
[0027] The invention also comprises a service rig having all of the
same structural elements of the drilling rig described above.
Service rigs typically are used to install and/or pull out tubing
from a well bore. The nature of that use typically does not require
as large a scale of construction as a drilling rig. Therefore,
service rigs may be constructed on a less robust scale.
[0028] Therefore, in one aspect of the invention, the drilling or
service rig comprises:
[0029] (a) a rig substructure comprising a drill floor having a
drill opening;
[0030] (b) at least three structural towers fixedly mounted to the
rig substructure and projecting vertically above the drill floor,
said towers being in spaced relationship to each other and
encircling the drill opening;
[0031] (c) a plurality of hydraulically-actuated, telescoping
lifting rams corresponding in number to the number of towers, said
lifting rams being fixedly mounted at their lower ends to the rig
substructure and projecting vertically above the drill floor, and
each lifting ram being in proximal association with one of the
towers;
[0032] (d) lateral support means associated with the towers for
providing lateral support to the lifting rams throughout their
range of telescoping operation;
[0033] (e) hydraulic power means for actuating the lifting rams
such that the lifting rams may operate substantially in unison;
[0034] (f) a roof platform affixed to and supported by the upper
ends of the lifting rams, said roof platform comprising a
substantially horizontal cradle track;
[0035] (g) a cradle having means for engaging the cradle track such
that the cradle may be mounted to and moved along the cradle
track;
[0036] (h) cradle actuation means mounted to the roof platform, for
moving the cradle along the cradle track; and
[0037] (i) a drilling hook associated with the cradle, for
vertically supporting a drill string plus accessory components and
pipe-handling tools or service equipment.
[0038] In another aspect of the invention, the invention comprises
a drilling or service rig comprising:
[0039] (a) a rig substructure comprising a drill floor having a
central drill opening and a pipe storage area comprising a
fingerboard for storing lengths of pipe;
[0040] (b) at least three structural towers fixedly mounted to the
rig substructure and projecting vertically above the drill floor,
said towers being in spaced relationship to each other and
encircling the drill opening;
[0041] (c) a plurality of hydraulically-actuated, telescoping
lifting rams corresponding in number to the number of towers, said
lifting rams being fixedly mounted at their lower ends to the rig
substructure and projecting vertically above the drill floor, and
each lifting ram being in proximal association with one of the
towers;
[0042] (d) lateral supports associated with the towers for
providing lateral support to the lifting rams throughout their
range of telescoping operation;
[0043] (e) hydraulic power means for actuating the lifting rams
such that the lifting rams may operate substantially in unison;
[0044] (f) a roof platform affixed to and supported by the upper
ends of the lifting rams;
[0045] (g) a drilling hook suspended from the roof platform, for
vertically supporting a drill string plus accessory components and
pipe-handling tools or service equipment;
[0046] (h) a crane associated with the towers for moving lengths of
pipe laterally within the Texas deck and centrally towards the axis
of the drill opening;
[0047] (i) a pipe trough moveable between a vertical position and
an inclined position wherein the pipe trough may receive a vertical
length of pipe and incline such that a top end of the pipe is
inclined towards the drill opening axis while the bottom end is
inclined away from the drill opening axis; and
[0048] (j) a lateral ram for inclining the pipe trough.
[0049] This second aspect of the invention differs from the first
in that it does not include the cradle which moves laterally along
the roof platform. Pipe handling is accomplished with the overhead
crane and the pipe trough and its associated elements.
[0050] In preferred embodiments of either aspect of the invention,
the invention is a drilling rig and incorporates heave compensation
means, primarily intended for applications of the invention for
offshore drilling from floating platforms or drill ships, to keep
the drill bit boring into subsurface formations under a desired
constant vertical load notwithstanding any vertical heave of the
floating platform or drill ship due to wave action. This is
accomplished in the preferred embodiment by operation of the
lifting rams in co-operation with hydraulically actuated roof rams
mounted vertically to the cradle such that the pistons of the roof
rams telescope downward below the cradle. The lower ends of the
roof ram pistons are interconnected by a yoke to ensure that these
pistons move together at all times. Heave compensation may also be
accomplished, however, using the lifting rams alone, without the
need for roof rams.
[0051] In the preferred embodiment, the drill string is suspended
from the yoke, with the effect that extension or retraction of the
roof ram pistons will lower or raise the drill string. A load cell
associated with the yoke senses fluctuations in the load acting
downward on the drill string, and communicates nearly
instantaneously with the invention's hydraulic system to call for
corresponding adjustments in hydraulic pressure and hydraulic oil
flow being delivered to the lifting rams and roof rams, such that
the lifting ram pistons and roof ram pistons will be retracted or
extended as appropriate to maintain a desired vertical load on the
drill bit.
[0052] In the preferred embodiment of the invention, there is the
same number of roof rams as lifting rams, and each roof ram is
paired with a corresponding lifting ram, with both rams in each
such pair of rams being operated from a common hydraulic
sub-system. In other words, the preferred embodiment will have
multiple hydraulic sub-systems corresponding in number to the
number of lifting ram/roof ram pairings. Each hydraulic sub-system
is configured such that when it is not pressurized, the lifting
rams will be fully retracted and the roof rams will be fully
extended. As the hydraulic sub-systems are pressurized, the roof
rams will retract before the lifting rams begin to extend.
Conversely, when the system has been fully pressurized and the yoke
is at its highest possible elevation, the lifting rams will be
fully extended with the roof rams fully retracted, and as hydraulic
pressure in the system is reduced the lifting rams will retract
fully before the roof rams begin to extend.
[0053] In one embodiment, the drilling rig of the present invention
is adapted for use with a rotary table mounted in the drill floor
to rotate the drill string during drilling operations in
conjunction with a kelly. In the preferred embodiment, however, the
invention is adapted for use with a rotary top drive suspended from
the yoke, thus making a rotary table and kelly unnecessary.
[0054] In the preferred embodiment of the invention, a torsion
frame with a vertical torque track is suspended from the cradle, to
stabilize both the yoke and the rotary top drive, and in particular
to provide structural resistance to torque generated by the rotary
top drive. Both the yoke and the rotary top drive engage the torque
track so as to travel vertically along the torque track as the roof
rams are extended or retracted, with the engagement of the rotary
top drive to the torque track being such that torque may be
transferred from the rotary top drive through the torsion frame to
the cradle, which in turn transfers the torque through the roof
platform to the towers.
[0055] In one alternative embodiment, the invention will be adapted
for use with a rotary top drive but will not have heave
compensation means. In that case, the rotary top drive may be
rigidly mounted to the cradle such that torque from the rotary top
drive will be transferred directly into the cradle without the need
for a torsion frame. This alternative embodiment may have
particular application for drilling wells on land; i.e., where
there is no requirement to compensate for heave.
[0056] In one embodiment of the invention, the towers will be
freestanding and of a fixed height generally corresponding to the
maximum height to which it is desired to be able to raise the roof
platform. Structural cross-bracing may be provided between two or
more of the towers to enhance the towers' stability and rigidity.
In embodiments featuring fixed-height towers, each lifting ram will
be located close to one of the towers, and lateral support means
associated with the towers may be deployed such that the lifting
rams are structurally stabilized by the towers throughout their
range of telescoping operation.
[0057] In the preferred embodiment of the invention, each tower has
a stationary section plus a telescoping section inside the
stationary section, with each lifting ram being positioned inside
its corresponding tower. The upper end of each telescoping section
is connected to the upper end of the corresponding lifting ram,
such that activation of the lifting rams will cause the telescoping
sections of the towers to rise out of or retract within the
stationary sections. Each telescoping section co-operates
structurally in all positions with its corresponding stationary
section such that each tower is capable of resisting lateral forces
acting thereon.
[0058] More preferably, the telescoping sections will be of such
length that they may extend below the drill floor within the rig
substructure when they are lowered. The stationary sections of the
masts may therefore be made shorter in height, for a given roof
platform travel range, than would be required if the telescoping
sections did not extend below the drill floor.
[0059] The lifting rams may comprise single-acting or double-acting
hydraulic cylinders, but the precise configuration of the lifting
rams is not critical to the concept or function of the
invention.
[0060] In yet another aspect of the invention, the invention is a
method of drilling comprising the steps of:
[0061] (a) providing a drill rig comprising a drill floor with a
drill opening, a drill pipe storage area associated with the drill
rig, and a rotary top drive movable vertically and
horizontally;
[0062] (b) supporting a drill string positioned in the drill
opening, and disconnecting the top drive from the drill string;
[0063] (c) raising the top drive clear of the drill string;
[0064] (d) moving the top drive laterally from a position over the
drill opening to a position over the drill pipe storage area;
[0065] (e) lowering the top drive and connecting the top drive to a
drill pipe section from the drill pipe storage area;
[0066] (f) raising the top drive such that the bottom of the drill
pipe section is higher than the top of the drill string;
[0067] (g) moving the top drive laterally to a position over the
drill string;
[0068] (h) connecting the drill pipe section to the top of the
drill string; and
[0069] (i) recommencing drilling operations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0070] Embodiments of the invention will now be described with
reference to the accompanying drawings, in which numerical
references denote like parts referred to herein, and in which:
[0071] FIG. 1 is an elevational view of the preferred embodiment of
one aspect of the invention, showing the top drive at its lowest
position above the drill floor and centered over the drill opening,
with the lifting rams fully retracted and the roof rams fully
extended.
[0072] FIG. 2 is an elevational view of the embodiment of FIG. 1,
showing the top drive partially elevated above the drill floor and
centered over the drill opening, with the lifting rams and the roof
rams fully retracted.
[0073] FIG. 2A is an elevational view of the top drive and torsion
frame of the embodiment of FIG. 1.
[0074] FIG. 3 is an elevational view showing the top drive at its
highest position above the drill floor and centered over the drill
opening, with the lifting rams fully extended and the roof rams
fully retracted.
[0075] FIG. 4 is an elevational view showing the top drive at its
highest position above the drill floor, but shifted horizontally
away from the centerline of the drill opening.
[0076] FIG. 5 is an elevational view showing the top drive at its
lowest position above the drill floor, but shifted horizontally
away from the centerline of the drill opening.
[0077] FIG. 6 is a plan view of the roof platform, showing the
cradle positioned such that the top drive is centered over the
drill opening.
[0078] FIG. 7 is a plan view of the upper platform, showing the
cradle positioned such that the top drive is shifted horizontally
away from the centerline of the drill opening.
[0079] FIG. 8 is a schematic diagram of one of the hydraulic
sub-systems of a preferred embodiment of the invention, for
operating the lifting rams and roof rams.
[0080] FIG. 9 is a cross-sectional view of one tower showing one
embodiment of the rollers which stabilize the telescoping
towers.
[0081] FIG. 10 is an elevational view of an alternative embodiment
of the invention showing the overhead crane and the pivoting pipe
trough.
[0082] FIG. 11 is a plan view of the drill floor of the embodiment
illustrated in FIG. 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0083] Referring to the Figures, the preferred embodiment of the
present invention is a drilling rig, generally denoted by reference
numeral (10), having a substructure (20) and a drill floor (22).
The construction of the drilling rig and its operation may be
conveniently adapted to the construction and operation of a service
rig by a person skilled in the art. It is intended that the
appended claims also encompass service rigs comprising the relevant
elements described herein.
[0084] Drill floor (22) has a drill opening (24) for passage of a
string of drilling pipe, or drill string (90), downward through the
substructure (20). Substructure (20) may be erected on land, or
alternatively may form part of a drill ship or an ocean-going
drilling platform. In the preferred embodiment, the substructure
(20) will incorporate a Texas deck (26) for storage of drill
pipe.
[0085] The drilling rig also has a number of structural towers (30)
rigidly anchored to the substructure (20), spaced apart from each
other, and projecting vertically above the drill floor (22). The
primary function of the towers (30) is to provide structural
resistance to lateral loads such as wind, and they are not required
to carry significant vertical loads other than their dead weight.
The preferred embodiment comprises four towers (30) located so as
to form the comers of a square or a rectangle when viewed in plan,
as illustrated in FIGS. 6 and 7. However, it is conceptually
possible for the invention to have as few as three and perhaps more
than four towers (30), arranged in any of a variety of
configurations.
[0086] The drilling rig also has a number of hydraulically-actuated
lifting rams (40). In the preferred embodiment, the number of
lifting rams (40) corresponds to the number of towers (30). The
lifting rams (40) are anchored to the substructure (20) at or below
the drill floor (22) such that they extend vertically above the
drill floor (22). As will be explained in greater detail
hereinafter, the lifting rams (40) provide the hoisting capacity
required to support the drill string (90) during drilling of a
well, or to pull the drill string (90) out of the well during
tripping operations. Accordingly, the lifting rams (40) require
sufficient structural capacity to carry the total weight of the
drill string (90), plus the weight of drilling accessories and
other drilling rig components referred to later herein.
[0087] Each lifting ram (40) is positioned in close proximity to a
particular one of the towers (30) so that the towers (30) may be
conveniently used to stabilize the lifting rams (40) against
lateral loads, and to brace the lifting rams (40) against lateral
buckling when carrying heavy compression loads from the weight of
the drill string (90). Accordingly, lateral support means (not
shown) will be provided to brace each lifting ram (40) back to its
corresponding tower (30) at desired positions.
[0088] In the preferred embodiment of the invention, the lateral
support means associated with each tower (30) and lifting ram (40)
combination will comprise a number of roller wheels having
horizontal rotational axes. Three or more roller wheels are
provided for each position at which bracing for the lifting ram
(40) is desired, with the positions of the roller wheels being
angularly separated around the perimeter of the lifting ram (40).
The roller wheels are mounted to the tower (30) using
scissor-action mechanisms or other suitable mechanisms which will
allow each roller wheel to be retracted to a first position
adjacent to the framework of the tower (30), and then to be
extended horizontally, and perpendicularly to the roller wheel's
rotational axis, to a second position at which the roller wheel is
in firm contact with the lifting ram (40). When all of the roller
wheels at a particular bracing point are in their second positions
in contact with the lifting ram (40), they will co-operate to brace
the lifting ram (40) and to transfer to the tower (30) any lateral
stability forces which may be action on the lifting ram (40). When
the lifting ram (40) is being actuated, the roller wheels will
rotate, while remaining in firm contact with the lifting ram (40)
even as it moves vertically relative to the roller wheels. The
roller wheels thus are able to provide continuously effective
lateral bracing to the lifting ram (40) at all times.
[0089] In the preferred embodiment, roller wheel control means (not
shown) will be provided to control the position of the roller
wheels. The roller wheel control means may comprise a system of
limit switches which will be tripped sequentially as the lifting
rams (40) are actuated, signalling each set of roller wheels to be
deployed into position in contact with its corresponding lifting
ram (40) when the lifting ram (40) is in a selected configuration.
Also in the preferred embodiment, the roller wheels of the lateral
support means will be made of a durable and resilient material,
such as a synthetic polymer, which may make resilient rolling
contact against the lifting rams (40) without damaging the surface
of the lifting rams (40).
[0090] In an alternative embodiment illustrated in FIG. 9, the
lifting ram is braced within the telescoping tower (32) by diagonal
struts (33). The telescoping tower (32) is then braced within the
stationary tower (31) by dual rollers (35) at each corner as shown
in FIG. 9.
[0091] As illustrated in FIGS. 3, 4, and 8, each lifting ram (40)
includes a main cylinder (41) which in the preferred embodiment is
formed by flanging together an upper cylinder (41 a) and a lower
cylinder (41b). Each lifting ram (40) further includes an upper
piston (42a) and a lower piston (42b) which travel inside the upper
cylinder (41 a) and the lower cylinder (41b) respectively. Each
piston (42a or 42b) is connected to a piston rod (43a or 43b), said
piston rods each having a hollow longitudinal passage (not shown)
for passage of hydraulic fluid. As illustrated in FIG. 8, each main
cylinder (41) also comprises a main chamber (44) between the upper
piston (42a) and the lower piston (42b), an upper annular chamber
(45a) between the upper piston rod (43a) and the upper cylinder
(41a), and a lower annular chamber (45b) between the lower piston
rod (43b) and the lower cylinder (41b). Both the upper piston (42a)
and the lower piston (42b) have vertical passages (not shown)
coinciding with the longitudinal passages in the piston rods (43a,
43b), such that hydraulic fluid may pass through the pistons (42a,
42b) and the piston rods into the main chamber (44). The lower end
of the lower piston rod (43b) is affixed to the substructure (20)
while the upper end of the upper piston (43a) is connected to and
supports a roof platform (50) which in turn supports a cradle (60),
as indicated in FIGS. 1 through 5.
[0092] The towers (30) may be of a fixed length generally
corresponding to the maximum extension of the lifting rams (40).
However, in the preferred embodiment illustrated in FIGS. 1 through
5, the towers (30) will be of telescoping construction and
operation, each tower (30) having a stationary section (31)
anchored to the substructure (20), plus a telescoping section (32)
which is positioned inside the stationary section (31) such that it
may be retracted within the stationary section (31) and may
telescope vertically above the stationary section (31). As shown in
FIGS. 1 through 5, such telescopic movement of the towers (30) is
provided for in the preferred embodiment by positioning the lifting
rams (40) inside their corresponding towers (30) rather than
adjacent thereto, and by connecting the upper ends of the lifting
rams (40) to the uppers ends of their corresponding telescoping
sections (32), so that extending or retracting the lifting rams
(40) will effect a corresponding extension or retraction of the
telescoping sections (32) and in turn will raise or lower the roof
platform (50).
[0093] The roof platform (50) is mounted upon the upper ends of the
lifting rams (40). In the preferred embodiment and as shown in
FIGS. 1 through 7, the roof platform (50) is illustrated as being
of trussed construction with a square or rectangular shape in plan.
However, the shape and form of construction are not critical to the
function of the roof platform (50). The roof platform (50) has a
horizontal cradle track (52) comprising two cradle track rails
(52a) which run parallel to each other as shown in FIGS. 6 and 7.
Also as shown in FIGS. 6 and 7, the roof platform (50) has a
platform opening (54) generally corresponding to the space between
the cradle track rails (52a). In the preferred embodiment of the
invention, and for purposes which will be explained hereinafter,
the roof platform (50) has an optional cantilevered section (56)
and the platform opening (54) extends into the cantilevered section
(56), all as shown in FIGS. 1 through 7.
[0094] The cradle (60) is mounted on the cradle track (52),
engaging the cradle track rails (52a) in such fashion that the
cradle (50) may be rollingly or slidingly moved along the cradle
track (52). Such movement of the cradle (60) is effected by cradle
actuation means, which in the preferred embodiment is a pair of
hydraulically-actuated cradle rams (61) mounted to the roof
platform (50) as shown in FIGS. 6 and 7.
[0095] A drilling hook (66) is provided in association with the
cradle (60), for supporting a drill string plus pipe-handling
equipment such as a swivel and pipe elevators. In one embodiment,
the invention will be adapted for use with a rotary table (not
shown) mounted in the drill floor (22), in which embodiment the
pipe-handling equipment supported by the drilling hook (66) will
include a kelly (not shown). In the preferred embodiment, however,
the invention will be adapted for use with a rotary top drive (70)
suspended from the drilling hook (66). In embodiments of the
invention which will accommodate a rotary top drive (70), the
cradle (60) also comprises a torsion frame (80), to resist the
considerable torque generated by the rotary top drive (70) as it
rotates a drill string (90), thereby preventing unwanted rotational
instability in the rotary top drive (70), and to transfer such
torque to the towers (30).
[0096] For effective drilling, the drill bit (not shown) at the
bottom of the drill string must exert a relatively constant force
on the subsurface material which the drill bit is boring into. This
is comparatively simple to accomplish when drilling on land.
However, when drilling offshore wells from a drill ship or floating
platform, wave action will cause vertical oscillation, or heave of
the drill ship or floating platform. For this reason, the preferred
embodiment of the invention will have heave compensation means,
which provide for vertical movement of the drilling rig relative to
the drill string while maintaining a constant vertical load on the
drill bit.
[0097] In the preferred embodiment of the invention, as illustrated
in FIGS. 1 through 8, the heave compensation means comprises four
hydraulic roof rams (62), each of which comprises a roof ram
cylinder (62a), a roof ram piston (62b) which may travel vertically
within the roof ram cylinder (62a), and a roof ram piston (62c). As
illustrated in FIG. 8, each roof cylinder (62a) includes a primary
chamber (63a) and an annular secondary chamber (63b). The roof rams
(62) are mounted to the cradle (60) in substantially vertical
orientation such that the roof ram pistons (62b) extend downward
below the cradle (60). A yoke (64) is provided to interconnect the
lower ends of the roof ram pistons (62b) to ensure that the roof
ram pistons (62b) will move in unison. In the preferred embodiment,
the drilling hook (66) is connected to the yoke (64) as illustrated
in FIGS. 1 and 5, and typically will be any of several types of
heavy-duty drilling hook which are readily available from drilling
equipment supply companies. The drill string (90) thus is
effectively supported by the roof rams (62), which transfer the
weight of the drill string (90) to the cradle (60).
[0098] It will be readily seen that the vertical position of the
drill string (90) relative to the drill floor (22) and rig
substructure (20) may be controlled by selectively extending or
retracting the roof ram pistons (62b) as well as by controlling the
position of the lifting rams (40). In the preferred embodiment, the
invention will comprise control means, which may be a load cell
(not shown) associated with the yoke (64), for sensing variations
in the load being exerted on the drill bit, such as will occur when
the absolute elevation of the rig substructure (20) changes due to
wave action, and for electronically adjusting the hydraulic
pressure being delivered to the lifting rams (40) and the roof rams
(62) as necessary to maintain a relatively constant load on the
drill bit.
[0099] Because of the configuration of the hydraulic power system
used in the preferred embodiment, as will be described in further
detail below, the lifting rams (40) may be used for heave
compensation in addition to the roof rams (62). The roof rams (62)
must be retracted (raised) fully before the lifting rams (40) will
extend and, conversely, the lifting rams (40) must be fully
retracted before the roof rams (62) will extend (lower). For
example, if the control mechanism calls for the hydraulic system to
lower the roof platform (50) while the roof rams (62) are fully
retracted, the lifting rams (40) will retract first, lowering the
drill string (90), and the roof rams (62) will begin to extend
(lower) only after the lifting rams (40) are fully retracted.
Conversely, if the control means calls for the drill string (90) to
be lifted when the lifting rams (40) are fully retracted (lowered)
and the roof rams (62) are extended, the roof rams (62) will
retract first, raising the drill string (90), and the lifting rams
(40) will begin to extend, raising the drill string (90) further,
only after the roof rams (62) are fully retracted. Therefore, in
the preferred embodiment, the lifting rams (40) and the roof rams
(62) co-operate to constitute the heave compensation means.
[0100] The preferred embodiment of the invention thus will have
roof rams (62) and will also be adapted for use with a rotary top
drive (70) as illustrated in FIGS. 1 through 5. Accordingly, the
torsion frame (80) of the preferred embodiment must be capable of
performing its function regardless of the vertical position of the
rotary top drive (70) as it moves with the roof rams (62). The
torsion frame (80) is therefore rigidly connected to the cradle
(60) and extends below the cradle (60) at least as far as it is
possible for the rotary top drive (70) to be lowered below the
cradle (60). The torsion frame (80) has a vertical torque track
(82), preferably comprising a pair of torque track rails (82a) as
generally illustrated in FIG. 2a. The rotary top drive (70) has a
top drive brace (72) as the torque track engagement means which may
slidingly or rollingly engage the torque track (82) such that the
rotary top drive (70) may move vertically while being guided and
rotationally restrained by the torque track rails (82a) and the
torsion frame (80).
[0101] To enhance the overall lateral and rotational stability of
the rotary top drive (70) and the roof ram pistons (62b), the yoke
(64) of the preferred embodiment will have a yoke brace (65) which
also slidingly or rollingly engages the torque track rails (82a)
such that it may move vertically while being guided and
rotationally restrained by the torsion frame (80).
[0102] Besides transferring torque to the towers (30), the yoke
brace (65) and the top drive brace (72) also ensure that the top
drive (70) and the yoke (64) remain aligned vertically with the
roof rams (62) as the roof rams (62) move up and down.
[0103] The lifting rams (40) and the roof rams (62) are actuated
hydraulically using conventional and well-known large-capacity
hydraulic pumps and hydraulic control systems. In the preferred
embodiment and as shown schematically in FIG. 8, each lifting, ram
(40) and its corresponding roof ram (62) are served by a dedicated
hydraulic sub-system (100) Therefore, in the preferred embodiment
with four lifting rams (40) and four roof rains (62), there are
four hydraulic subsystems (100), each comprising one or more
hydraulic pumps (102) and and a pressure valve (104). As
schematically depicted in FIG. 8, hydraulic fluid conduits (103)
carry hydraulic fluid between the various components of the
hydraulic sub-systems (100). The four hydraulic subsystems (100)
are co-ordinated by means of a control system (not shown) which
ensures that the four lifting rams (40) lift and retract the roof
platform (50) in unison.
[0104] The hydraulic pumps are preferably reversible pumps to speed
up retraction of the lifting rams (42) and roof rams (62) to lower
the roof platform (50).
[0105] In the preferred embodiment, the lifting rams (40) are
double-acting, which means that hydraulic fluid is supplied not
only to the main chamber (44) but also to the upper and lower
annular chambers (45a, 45b). The pistons (42a, 42b) match the
inside diameter of the cylinder (41) at 12" while the piston rods
(43a, 43b) each have a small outside diameter of 10". It will be
appreciated that the dimensions herein provided are examples only
and are not intended to be limiting of the invention. The main
chamber (44) is open to the annular chambers (45a, 45b) such that
the hydraulic pressure within them is always equal. However, the
difference in surface area between the upper side and lower side of
each piston (42a or 42b) causes the lifting, rams (40) to react to
changes in hydraulic pressure. By using double-acting lifting rams
(40), the seals (not shown) of the pistons (42a, 42b) are always
lubricated. Of course, the invention is not limited to
double-acting rams, as single-acting rams are also suitable for use
with the present invention.
[0106] Each individual lifting ram (40) is also hydraulically
connected to a particular roof ram (62), with the main chamber (44)
of each lifting ram (40) being in fluid communication with its
corresponding roof ram cylinder (62a) through the hollow upper
piston rod (43a) of the lifting ram (40). The roof rams (62) act
oppositely to the lifting rams (40) in that retraction of the roof
ram pistons (62b) into the roof ram cylinders (62a), so as to raise
the top drive (70) and drill string (90), is effected by
pressurizing the annular secondary chambers of the roof ram
cylinders (62a), as shown in FIG. 8. In contrast, and also as shown
in FIG. 8, retraction of the lifting ram pistons (42a, 42b) into
the upper cylinders (41a) and the lower cylinders (41b) of the
lifting rams (40) is effected by pressurizing the main chambers
(44) of the main cylinders (41), not the annular chambers (45a,
45b) thereof.
[0107] In the preferred embodiment, the inside diameter of the roof
ram cylinders (62a) and the roof ram piston rods (62c) have a
diameter such that the roof rams (62) will activate first when the
hydraulic system is pressurized. Only when the roof rams (62) are
fully retracted, raising the top drive (70), will the lifting rams
(40) begin to extend and further raise the top drive (70).
Conversely, when the hydraulic pumps (102) are reversed, the
lifting rams (40) will retract first, thus lowering the top drive
(70), and only after the lifting rams (40) are fully retracted will
the roof rams (62) begin to extend, further lowering the top drive
(70).
[0108] A method of use of the drilling rig according to the present
invention is illustrated in FIGS. 1 to 5, which show in sequence a
POH-mode tripping operation where a triple stand of drill pipe is
extracted, broken out and stored in the Texas deck (26). In FIG. 1,
the roof platform is lowered completely by retracting the lifting
rams (40). The top of the drill string (90) is the engaged by pipe
elevators (not shown) associated with the top drive (70). The
cradle (60) is centred on the roof platform (50) such that the yoke
(64) is centred over the drill opening (24).
[0109] In first part of the lifting phase of operation, as shown in
FIG. 2, the roof rams are actuated to lift the top drive (70) to
the top of the torsion frame, which lifts the drill string (90) a
distance equal to the length of travel of the pistons within the
roof rams (62). Next, the lifting rams (40) are actuated to lift
the roof platform (50) which in turn lifts the drill string (90)
out of the hole, as shown in FIG. 3. Because of the dimensions of
the telescoping towers (30) and the lifting rams (40), a triple
stand of drill pipe (91) may be completely lifted out of the hole.
The triple (91) may then be broken out by conventional means while
the drill string (90) is supported by slips (not shown) or other
conventional means.
[0110] The cradle (60) is then moved laterally by the cradle rams
(61) until the triple (91) is positioned over the Texas deck (26)
as shown in FIG. 4. The lifting process is reversed to lower the
triple (91) into the Texas deck (26). The hydraulic system is first
actuated to reverse and retract the lifting rams (40) and second to
extend and lower the roof rams until the triple (91) is placed in a
storage position in the Texas deck (26), as shown in FIG. 5. The
triple (91) is then disconnected and left in storage. The cradle
(60) may then be returned, by means of the cradle rams (61), to its
centered position over the drill opening (24) so that the next
three sections of drill pipe may be engaged and pulled by repeating
the method of the present invention.
[0111] It may be readily seen that the steps outlined above may be
reversed for tripping in RIH mode, and similarly for making hole. A
triple (or perhaps some other length of drill pipe) is lifted out
of the Texas deck (26) as needed, and then moved laterally by the
cradle (60) so that the bottom of the triple (91) may be connected
to the top of the drill string (90) projecting above the drill
opening (24). Drilling may then be continued by activating the top
drive (70) so as to rotate the drill bit (not shown) into the
subsurface formation being drilled. The top drive (70) and drill
string (90) are lowered as drilling progresses, firstly by lowering
(retraction) of the lifting rams (40), and secondly by lowering
(extension) of the roof rams (62), until the drill bit has advanced
the length of a triple (91). The lowering of the lifing rams (40)
and the roof rams (62) may be controlled by the load cell and
control system described above.
[0112] In the preferred embodiment, the roof platform (50) will
have cantilevered section (56) as previously mentioned. It will be
readily seen from FIGS. 6 and 7 and from the preceding description
of the invention that the cradle (60) may be moved out to the end
of the cantilevered section (56) such that the hoisting facility
provided by the lifting rams (40) and the roof rams (62) may be
used to lift items located outboard of the towers (40) on the same
side of the rig as the cantilevered section (56). The cantilevered
section (56) may advantageously extend beyond the sides of a drill
ship or drilling platform on which the rig is mounted, such that
the rig's hoisting capacity may be used to unload equipment or
supplies from supply ships positioned adjacent to the drill ship or
drilling platform.
[0113] In an alternative embodiment illustrated in FIGS. 10 and 11,
the cradle and its associated elements are eliminated. The torsion
frame (80) is rigidly fixed to the roof platform such that the top
drive (70) is centred over the drill opening (24). In this
embodiment, the four stationary towers (31) are cross-connected at
the top of each tower by lateral trusses (135) which serve to
further stabilize the stationary towers (31).
[0114] Pipe handling is accomplished with an overhead crane (100)
which is moves laterally along the bottom of one such lateral truss
(135). The crane (100) may also move centrally, towards the central
axis of the drill opening (24). Movement of the crane is
accomplished by suspending the crane from rails or tracks (101) and
by motor or hydraulic means, which is well known in the art.
Drilling pipe (92) is stored in a Texas deck storage area (26)
below the drill floor immediately below the crane (100). The pipe
(92) is racked along fingerboards (120) and a pipe alley (122)
permits lateral movement of the pipe through the Texas deck.
[0115] A pivoting pipe trough (102) and a lateral hydraulic ram
(104) is provided as shown in FIG. 10. A telescoping pipe centering
arm (139) is also provided at the drill floor (22), over the drill
opening (24). These elements, together with the overhead crane
(100), allow pipe (92) to be transported from the Texas deck (26)
to be added to the drill string (90) when drilling and allow pipe
to be removed from the drill string (90) and replaced in the Texas
deck (26) when tripping. A rolling or sliding skate (not shown) is
provided at the bottom of the pipe alley (122) which partially
supports and stabilizes the bottom end of a length of pipe (91) as
it is moved through the pipe alley (139) by the crane (100).
[0116] The pipe trough (102) pivots along a horizontal axis (103),
below the drill floor (22) such that the top end of the pipe trough
(102) moves towards the drill opening (24) while the bottom end of
the pipe trough (102) moves along a line (124) which substantially
bisects the Texas deck (26). A guide (106) is positioned to
stabilize the pivoting movement of the pipe trough (102). The
lateral hydraulic ram (104) pivots the pipe trough (102) away from
the vertical. The pivot point (103) is approximately two-thirds up
the pipe trough (102). Therefore, when the lateral ram (104) is
deactivated, the weight of the bottom of the pipe trough (102)
returns the pipe trough (102) to its vertical position.
[0117] The Texas deck (26) will be deep enough to store tiple
stands (91) of pipe to be used in the drilling process. The Texas
deck (26) may also include an area (110) for assembling triple
stands of pipes from single lengths of pipe, as is well-known in
the art. This will be advantageous on an ocean-going vessel as
singles may be combined into triples while the vessel is travelling
to the drilling location, making productive use of that time.
[0118] In another variation embodied in this embodiment, the roof
rams (62) are hydraulically actuated from a separate hydraulic
circuit (not shown) from the main lifting rams (40) and the number
of roof rams (62) is reduced from four to two.
[0119] In POH-mode operation, the top drive (70) is lowered
completely by extending the roof rams (62) while the roof platform
(50) is lowered completely by retracting the lifting rams (40). The
top of the drill string (90) is engaged by pipe elevators (not
shown) associated with the top drive (70). The drill string (90) is
then lifted out of the hole by extending the lifting rams (40). A
triple length of pipe (91) is completely lifted out above the drill
floor (22) and broken by conventional means while the drill string
(90) is supported by slips (not shown) or other conventional
means.
[0120] Once the triple (91) is broken out and suspended above the
drill floor, the pipe centering arm (139) pushes the bottom of the
triple (91) towards the top of the pipe trough (102) while the
lateral ram (104) pivots the pipe trough by pushing the top of the
pipe trough towards the drill opening (24). Once the bottom of the
triple is in position above the pipe trough, the roof platform is
lowered until the triple (91) is contained within the pipe trough,
as is shown in FIG. 10. At this point, the top of the triple (91)
is disconnected from the top drive (70) pipe elevator and the pipe
trough is allowed to return to its vertical position (102', 91') by
retracting the lateral ram (104).
[0121] As will be appreciated, the top drive pipe elevator is then
fully lowered, in position to attach to the drill string again to
pull out another length of pipe. The triple (91) within the pipe
trough may now be moved into position within the Texas deck (26) by
the crane (100) which also has a pipe elevator (not shown) for
attaching to the top of the triple (91). Once the triple (91) is
attached to the crane (100) The steps of pulling out pipe and
moving the pipe into storage may be accomplished at the same time
by the configuration of this embodiment.
[0122] As is readily apparent, when making hole or in RIH mode, the
above steps are reversed. Again, while pipe is being run into the
hole, the next triple stand of pipe may be brought into position by
the crane and lateral ram.
[0123] The above described preferred embodiments are illustrative
of the claimed invention and are not intended to be limiting. As
will be apparent to those skilled in the art, various
modifications, adaptations and variations of the foregoing specific
disclosure can be made without departing from the scope of the
present invention.
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