U.S. patent application number 09/078071 was filed with the patent office on 2001-08-09 for guide device.
Invention is credited to STEWART, KENNETH R., VAN-DRENTHAM SUSMAN, HECTOR F. A..
Application Number | 20010011591 09/078071 |
Document ID | / |
Family ID | 26313654 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010011591 |
Kind Code |
A1 |
VAN-DRENTHAM SUSMAN, HECTOR F. A. ;
et al. |
August 9, 2001 |
GUIDE DEVICE
Abstract
The present invention provides an active downhole cutting tool
guide device 14 for use in a hole 17 with sides between which a
hole-cutting tool 15 mounted on a drill string and provided with
said device may be disposed. The guide device 14 comprises at least
one elongate longitudinally extending hole-side engagement member
20 mounted on a body 19 disposable, in use of the device, in-line
with the drill string, so as to be movable relative to said body 19
between a retracted position and a radially outwardly displaced
position for hole-side engagement. Each engagement member 20 has
pressurised-fluid operable actuator means 24 formed and arranged
for driving said hole-side engagement member 20 between its
retracted and hole-aide engagement positions. The guide device 14
includes preasurised fluid supply means 28,18 formmed and arranged
for controlling the supply of pressurised fluid to the actuator
means 28,18 for operation thereof. In use of the guide device 14
the hole-cutting tool 15 may be directed relative to the central
longitudinal axis of the hole 17 in which the tool 15 is
disposed.
Inventors: |
VAN-DRENTHAM SUSMAN, HECTOR F.
A.; (ABERDEEN, GB) ; STEWART, KENNETH R.;
(ABERDEEN, GB) |
Correspondence
Address: |
JOHN R. CASPERSON
P.O. BOX 2174
FRIENDSWOOD
TX
77549
|
Family ID: |
26313654 |
Appl. No.: |
09/078071 |
Filed: |
May 13, 1998 |
Current U.S.
Class: |
166/298 ;
166/212; 166/241.1; 175/61; 175/73 |
Current CPC
Class: |
E21B 37/02 20130101;
E21B 7/062 20130101; E21B 17/1014 20130101; E21B 7/068 20130101;
E21B 29/06 20130101 |
Class at
Publication: |
166/298 ;
166/241.1; 166/212; 175/61; 175/73 |
International
Class: |
E21B 029/06; E21B
007/04; E21B 017/10 |
Claims
What is claimed is:
1. An active downhole cutting tool guide device for use in a hole
with sides between which a hole-cutting tool mounted on a drill
string and provided with said device may be disposed, said device
comprising at least one elongate longitudinally extending hole-side
engagement member mounted on a body, which body is disposable, in
use of the device, in-line with the drill string, so as to be
movable relative to said body between a retracted position and a
generally radially outwardly displaced position for hole-side
engagement, each said at least one engagement member having
presourised-fluid operable actuator means formed and arranged for
driving said hole-side engagement metber between said retracted and
hole-side engagement positioned said device including pressurised
fluid supply means formed and arranged for controlling the supply
of pressurized fluid, in use of the device, to said actuator means
for operation thereof, whereby in use of the device a said
hole-cutting tool may be directed relative to the central
longitudinal axis of the hole in which said tool is disposed.
2. The guide device of claim 1 wherein each said engagement member
is captively secured to said body by at least one connector.
3. The guide device of claim 2 wherein said at least one connector
is fixedly secured to said body and is formed and arranged so as to
allow sliding movement of the engagement body relative to said at
least one connector.
4. The guide device of claim 1 wherein the actuator means comprises
piston means mounted in cylinder means provided in said body, said
piston means having a proximal end in communication with said
pressurised fluid supply means, and a distal end mounted in a
respective said engagement member.
5. The guide device of claim 4 wherein said piston means distal end
and said connector means are formed and arranged so as to guide
movement of said engagement member between its retracted and
outwardly displaced positions.
6. The guide device of claim 1 wherein are provided at least three
angularly distributed engagement members.
7. The guide device of claim 6 wherein are provided at least 4
equiangularly spaced apart engagement rmembers.
8. The guide device of claim 1 wherein said pressurised fluid
supply means comprises a chamber formed and arranged for fluid
passage connection, in use of the guide device, to a drilling fluid
exhaust passage at a said cutting tool.
9. The guide device of claim 1 wherein is provided a plurality of
said engagement members and wherein said preasurised fluid supply
means for each said engagement member comprises a respective
chamber formed and arranged for fluid passage connection, in use of
the guide device, via fluid passage means provided with selectively
operable control valve means, to, alternately, high and low fluid
pressure fluid passage means.
10. The guide device of claim 9 wherein is provided a Measurement
and Control While Drilling Device including said control
valves.
11. A milling apparatus suitable for use in milling a window in a
well casing and comprising a rotary milling bit, motor means for
driving the milling bit, and a guide according to claim 1 for
positioning the milling bit in contact with a selected portion of
the casing to be milled out.
12. A method of milling a window in a selected portion of a hole
casing comprising the steps of: providing a milling apparatus
according to claim 11; placing the milling apparatus within the
casing; operating the actuator means of the cutting tool guide
device so as to position the milling bit in contact with the
selected portion; and driving the milling bit so as to form a
window in the casing.
13. A stabilised hole reboring apparatus suitable for use in
reboring an asymmetrically obstructed hole, which apparatus
comprises a rotary drilling bit, motor means for driving the
drilling bit, and a guide device according to claim 1 having at
least two substantially symmetrically driven engagement members for
stabilising the drilling bit against lateral deviation in use of
the apparatus as it cuts through an obstruction.
14. A method of reboring an asymetrically obstructed hole
comprising the steps of: providing a stabilised hole reboring
apparatus according to claim 13; placing the stabilized hole
reboring apparatus inside the asymmetrically obstructed hole;
operating the actuator means of the cutting tool guide device so as
to forcibly engage the hole sides above an obstruction thereby
stabilizing the drilling bit against lateral deviation; and driving
the stabilised drilling bit so as to cut through the
obstruction.
15. A directional drilling apparatus suitable for use in
directional drilling, which apparatus comprises a rotary drilling
bit, motor means for driving the drilling bit, and a guide device
according to claim 1 having at least three angularly distributed
independently driven engagement members operable for directing the
drilling bit away from an existing drilling axis.
16. A method of directional drilling comprising the steps of:
providing a directional drilling apparatus according to claim 15;
placing the directional drilling apparatus inside a hole;
independently operating the actuator means of the respective
engagement members of the cutting tool guide device so as to
forcibly engage the hole sides so as to direct the drilling bit in
a desired direction; and driving the directed drilling bit so as to
bore a hole along a desired path.
Description
[0001] The present invention relates to an active downhole cutting
tool guide device for use in a hole with sides between which a
hole-cutting tool provided with said device may be disposed.
[0002] There is a need for guiding of downhole cutting tools for
various purposes including inter alia lateral hole cutting,
directional drilling, as well as to atabilise an existing cutting
tool advance direction against unwanted deviation therefrom.
Exisling solutions to such problems are generally cumbersome to use
and/or unsuitable for use wits coiled tubing.
[0003] There is a need for cutting windows in oil/gas well casings
used to line the sides of well holes. Well casing is however
normally very tough, thick walled steel pipe which is placed inside
a borehole of a well as a lining to secure the borehole and prevent
the walls thereof from collapsing. Casing--sometimes referred to as
casing tubing--may be seamless, spiral welded or seam welded and
may, for example, be fabricated from various API grades of steel
such as H40, J55, N80 or P110. sizes typically vary from around 4
inches (101.6 mm) OD to 30 inches (762 mm) OD, while weights
typically range from around 11 lb/ft to 200 lb/ft (16.4 kg/m to 298
kg/m approximately) depending on diameter, thickness and grade. It
has also been known to employ glass fibre reinforced plastic
casing.
[0004] It is known that the cutting of windows in oil well casing,
as required for side tracking, is a complicated process, normally
requiring the use of a large number of tools not directly related
to the cutting of the window itself, such as whipstocks, packers
etc. The normal procedure is the setting of cement plug on top of a
packer above which a so-called "whipstock" is placed. The whipstock
basically consists of a hard metal wedge which guides a window
milling drill bit gradually into the casing thus cutting a slot in
the casing. As the elope of the whipstock in of a low value the
pinching action on the drill bit is very severe therefore requiring
extremely high torque and yet a low rate of progress is achieved
due to the high friction losses of the drill bit against the
whipstockc which have to be subtracted from the total energy
available for the cutting of the window. Furthermore once the
window has been cut the whipstock and packer require to be
retrieved which is often a difficult and tedious process. To date
the duration of an average window milling job is three to four days
and often much longer.
[0005] There is also a need for stabilising drilling tools used to
clear well holes which have become obstructed to a greater or
lesser degree aa a result of deposits on the sides thereof, and/or
as a result of deformation of a well hole casing as a result of
movement of the surrounding strata. Conventional near bit
stabilisers are essentially passive devices, typically comprising a
heavy duty ring with four angularly distributed wings which more or
1els closely approach the hole sides thereby limiting the amount of
deviation of the cutting tool possible. with such stabilisers
though the resistance to deviation remains substantially constant
throughout use of the device i.e. during travel of the cutting tool
along clear sections of the hole when ease of travel is desired and
stabilisation is not required, as well as during cutting through
obstructions, so that in practice the degree of stabilization
available when it in required is substantially insufficient for
proper stabilisation.
[0006] There is a further need for improved and less cumbersome
methods of steering drilling tools for the purposes of directional
drilling. Conventional directional drilling is typically effected
by means of the use of so-called bent subs as illustrated
schematically in FIG. 1. The drilling apparatus I shown has an
indexer 2 for angular orientation of the drill bit 3 and drive
system 4 therefor. In more detail the drive system comprises motor
5, typically a moineau motot, a bent sub 7, and a bearing pack 8
which is connected to the drill bit 3. For straight ahead drilling
the whole drill string comprising jointed tubing 9 from which the
drilling apparatus 1 is supported is rotated at around 30 rpm so
that the bent sub 7 rotates and the drill bit 3 orbits around the
drill string axis while the motor 5 rotates at around 700 rpm to
drive the drill bit 3 so that the drill bit 3 in effect followe a
helical path. When it is desired to kick-off or change direction
from the existing drill string axis, the rotation of the drill
string ii stopped in an arbitrary position and the indexer 2
operated to orientate the bent sub in the desired angular
direction, The motor 5 then drives the drill bit 3 while the drill
string and bent sub 7 remain stationary, so that the drill bit 3
drills off at an angle determined by the bent sub 7. Once the
reuired new drilling direction has been established, then the slow
rotation of the whole drill string is resumed to provide straight
ahead drilling in the new direction. Thus it may be seen that not
only is the construction of the apparatus required for directional
drilling relatively complex and cumbersome, but operation thereof
is also awkward and inflexible.
[0007] It is an object of the present invention to obviate or
mitigate at least some of the aforementioned problems and
disadvantages in the prior art.
[0008] It is a further object of the present invention to provide a
cutting tool guide device which may be used with coiled tubing with
its inherently shorter positioning and retrieval times against the
use of jointed oil field tubing.
[0009] It is another object of the invention to provide a cutting
tool guide device suitable for down-hole use in a hole with sides
between which a hole-cutting tool provided with said device may be
disposed, whereby in use of the device at least one of the angle,
the orientation and the lateral offset of a hole-cutting tool
relative to the longitudinal axis of the hole in which said tool is
disposed, may be controlled.
[0010] The present invention provides in one aspect an active
downhole cutting tool guide device for use in a hole with sides
between which a hole-cutting tool mounted on a drill string and
provided with said device may be disposed, said device comprising
at least one elongate longitudinally extending hole-side engagement
member mounted on a body disposable, in use of the device, in-line
with the drill string, so as to be movable relative to said body
between a retracted position and a radially outwardly displaced
position for hole-side engagement, each said at least one
engagement member having pressurised-fluid operable actuator means
formed and arranged for driving said hole-side engagement member
between said retracted and hole-side engagement positions: said
device including preesurised fluid supply means formed and arranged
for controlling the supply of pressurised fluid, in use of the
device, to said actuator means for operation thereof, whereby in
use of the device a said hole-cutting tool may be directed relative
to the central longitudinal axis of the hole in which said tool is
disposed.
[0011] In use of the guide device of the invention, operation of
the actuator means forces one (or more) said engagement member(s)
into engagement with the hole-side, Where a resulting differential
force is exerted at different sides of the hole, the drill string
will tend to be diseplaced away from the central longitudinal axis
of the hole so that the cutting tool can be driven laterally
through the hole side and/or its forward cutting direction steered
away at an angle from the previous forward cutting direction. Where
an equal force is exerted by each of the engagement members (where
two or more symmetrically angularly distributed ones are provided)
on the hole sides around the drill string, then the drill string is
positively directed so that the existing forward cutting direction
of the cutting tool is stabilized.
[0012] Thus by means of the present invention guiding of cutting
tools in a variety of downhole situations may be achieved in a
particularly economic and effective manner.
[0013] In one form of the invention there may be used a single
engagement mermber. In this case displacement of the engagement
member into engagement with the hole sidewall to one side of the
drill string will force the cutting tool against the hole sidewall
to the other side of the drill string. This is useful in cutting
windows in well casings by driving the cutting tool, conveniently a
milling tool, laterally through the casing to cut a window
therethrough. The window may then be elongated longitudinally of
the well by driving the drill string forwards. In this type of
arrangement, the angular directioning or orientation of the cutting
tool (around the well) may be conveniently effected by means of a
so-called indexing means (which is a well known remotely operable
device used to set the angular orientation of a tool on drill
string) to control the angular orientation of the guide device and
hence of the engagement member around the well prior to operation
of the actuator means so that the cutting tool is forced against
the well casing at a desired side of the well.
[0014] In another form of the invention at least two angularly
distributed, e.g. two diametrically opposed, engagement members
mray be used so that when their actuator means are operated
simultaneously, the existing drill string direction is stabilised
against devlation, for example by asymmetrical obstruction to the
cutting tool. This is particularly useful when re-boring holes
which have become obstructed to a greater or lesser degree e.g. by
the formation of deposits therein, or by deformation of the casing
which could have arisen, for example, as a result of shifts in the
surrounding strata. Where it is merely desired to provide
stabilisation of an existing drill string direction, then control
of the angular orientation of the guide device with its engagement
members will not normally be required. Nevertheless it desired the
guide device could be used in conjunction with an indexing
device.
[0015] In yet anotter form of the invention, three or more,
conveniently four, angularly distributed engagement members are
provided in the guide device of the invention. In this case by
using a pressurised fluid supply means formed and arranged for
controlling the supply of pressurised fluid to the actuator means
of the respective engagement members so that these are selectively
operable, it is possible to use the guide device itself to control
directioning of the drill string and hence of the cutting tool, not
only simply away from the existing direction of the drill string,
but also away in a particular angular orientation around the drill
string, thereby avoiding the need for a separate indexing
means.
[0016] Conveniently in this case the preaeurised fluid supply means
includes valve means formed and arranged for controlling the
relative supply of pressurised fluid to the various actuator means,
said valve means having telemetric control signal receiving means
formed and arranged for receiving valve control signals from a
remote location, and valve actuation means coupled to said
receiving means and formed and arranged for operation of said
valves means in response to said valve control signals. A further
advantage of the invention is that by using variable opening valve
and pressure control and/or more or less rapid toggling of the
valves, the present invention allows the possibility of effectively
adjusting the angle of kick off and rate of deviation from the
drill string axis and an existing drilling line which is not
possible with conventional apparatus in which the bent sub has a
fixed predetermined offset angle which provides only a fixed rate
of deviation (angle for given forward movement).
[0017] Various forms of preweurised fluid supply means may be used
in accordance with the present invention depending inter alia on
the requirements of the particular guide device application. As
described above, for directional drilling the pressurised fluid
supply means comprises separate chambers for each actuator means
for each hole side engagement member, which chambers are connected
to the high and low pressure sides of the downhole motor and drill
string via control valves. This type of arrangement could also, in
principle, be used for other applications. More conveniently though
somewhat simpler arrangements may be used where selective control
of individual engagement members is not required as, for example,
in stabilisers and in single engagement membez applications such as
window milling apparatus. In such cases the pressurised fluid
supply means may simply comprise a connection to the upstream side
of restricted outlet drilling fluid exhaust passages at the cutting
tool bit. When fluid is flowing through these under normal cutting
tool operating conditions a substantial back pressure is built up
behind the outlets so that the actuator means is subjected to a
substantial pressure which drives the engagement member(e) to its
(their) outwardly displaced position for hole aide engagement. When
such flow is substantially reduced or stopped, the back pressure is
reduced so that the actuator means is subjected to a much lower
pressure, which will reduce the outward displacement force on the
engagement member(s) and allow the engagement member(s) to return
to its (their) retracted position.
[0018] In the case of an application such as window milling, the
cutting tool apparatus is passed down a well hole in a
substantially stationary form. Once the milling tool is in position
the drive motor is brought up to speed and substantial fluid flow
through the exhaust passages established creating a back pressure
therein, the actuator means operates to deploy the engagement
member. When the motor is stopped and/or flow reduced, the pressure
available to the actuator means falls and the engagement member
allowed to retract, thereby permitting repositioning or withdrawal
of the milling tool from the well hole.
[0019] In the case of an application such as a stabiliser, a motor
driving the cutting tool will normally be run more or less
continuously so that some back pressure is always available in the
exhaust passages. By locating the exhaust passage outlets in
cutting faces of the cutting tool so that these outlets are
occluded to a greater or lesner extent when the cutting tool is in
engagement with material to be cut, it will be appreciated that the
back pressure is significantly increased during cutting so that the
actuator means then operate to drive the engagement mem er into
hole side engagement thereby automatically providing stabilisation
of the drilling line just when it is needed. In such cases it will
be appreciated that the pressurized fluid supply means and/or
actuator means and/or any engagement member return means, typically
a return spring, will be formed and arranged so that the engagement
members are retained in a substantially retracted position at fluid
supply pressures corresponding to free or no-load running of the
cutting tool drive motor, and are only displaced outwardly at
higher fluid supply pressures corresponding to cutting by the
cutting tool.
[0020] According to another aspect of the present invention there
is provided a milling apparatus suitable for use in milling a
window in a well casing and comprising a rotary milling bite motor
means for driving the milling bit, and a guide device of the
invention for positioning the milling bit in contact with a
selected portion of the caving to be milled out.
[0021] According to yet another aspect of the present invention,
there is provided a method of milling a window in a selected
portion of a hole casing comprising the steps of:
[0022] providing a milling apparatus of the invention;
[0023] placing the milling apparatus within the casing;
[0024] operating the actuator means of the cutting tool guide
device so as to position the milling bit in contact with the
selected portion; and
[0025] driving the milling bit so as to form a window in the
casing.
[0026] Various kinds of pressurised fluid supply means may be used
in accordance with the present invention. In general the device of
the invention makes use of a drilling fluid flow passed down the
drill string for one reason or another, typically drilling fluid
exhausted from a positive displacement motor used to drive the hole
cutting tool. Alternatively a separate by-pass fluid flow passage
running in parallel with the fluid flow through the motor could be
provided for supplying the guide device. The guide device of the
present invention may be used with various kinds of down-hole
motors but is generally used with a positive displacement motor.
Although the guide device could in principle be used with a
conventional Moineau motor, it is most preferably used with a
rolling vane motor of the kind described in U.S. Pat. No.
5,518,379. (It should be noted here that the latter kind of motor
may be used in various different kinds of form including those
wherein the motor fluid flow passes radially outwards through the
rotor and stator as specifically described in said patent, or
radially inwards through the stator and then the rotor.) With this
kind of motor a separate by-pass passage could be provided down the
central longitudinal axis of the motor through the rotor though it
in generally more convenient to use the motor without such an
additional passage and simply use the fluid exhausted from the
motor.
[0027] In general the actuator means are formed and arranged so
that when the pressure of the fluid supply is increased, the
actuators operate to drive the engagement member(s) from their
retracted position to their radially outwardly displaced position.
Advantageously the device includes resilient biasing means formed
and arranged for returning the engagement member(s) to their
retracted position when the fluid pressure is reduced again.
Conveniently the actuator means are in the form of piston means
mounted in cylinder means provided in said body of the guide device
with a proximal end face in communication with said pressurised
fluid supply and a distal end in driving abutment with a respective
engagement member.
[0028] The pressure of the fluid flow to which the actuator means
is subjected may be controlled in various ways known in the art
including, for example, suitable telemetrically controlled valve
means which may be operated so as to increase and reduce flow
resistance downstream of the actuator means and hence back pressure
whereby the fluid pressure acting on the actuator means may be
varied. Advantageously though the actuator means are in
communication with a fluid flow passage means which exhausts at the
cutting tool, especially at a cutting surface thereof. This has the
particular advantage that while the cutting tool is engaged with
material to be cut, the fluid flow passage means outlet means is
substantially occluded thereby increasing resistance to fluid flow
and thus the back pressure in said fluid flow passage means so that
the actuator means is exposed to an increased pressure, which in
turn causes the engagement member (s) to be deployed and provide
active positive directioning and guidance of the cutting tool. Once
the material has been cut through and the outlets are no longer
occluded by said material fluid flow increases and the pressure in
the fluid flow passage means falls thereby allowing the engagement
members to be retracted clear of the hole sides thereby in turn
allowing the drill string to be freely advanced or retracted. Thus
the operation of the actuator means can in such cases be
substantially self-regulating with an increased displacement force
being applied by the actuator means to the engagement member(s) as
increased resistance to cutting (from the material being cut
through) is experienced which is when the strongest guiding force
is required i.e. the engagement members require to be forced more
powerfully against the hole sides. Furthermore, should the motor
begin to stall during the course cutting, then the motor speed will
begin to fall which results in a reduced fluid flow through the
cutting tool which in turn results in a lower back pressure and
thus reduced pressure at the actuator means. this in turn reduces
the outward displacement force on the engagement member(s) so that
these retract to a greater or lesser degree thereby reducing
resistance to rotation of the drill string from friction between
the engagement member(a) and the hole sides, and thus allow the
motor speed to pick up again. Thus in this respect the guide device
of the invention provides a further degree of self-regulation and a
still further advantage over the prior art.
[0029] It will readily be appreciated that by configuring and/or
dimnensioning the preueurised fluid supply passages to the actuator
means and the actuator means themselves suitably, a required
displacement force to be applied to the engagement member(s) may be
derived from a given fluid pressure. Typically there may be used an
arrangement in which the fluid pressure at the actuator means is
150 to 200 psi (10 to 14 bar) when the cutting tool is running free
and back pressure from the fluid outlets in the cutting tool is at
a minimum, rising to 600 to 700 psi (41 to 48 bar) when the cutting
tool is fully engaged with material being cut. in the case of those
embodiments in which each engagement member is provided with a
separate respective pressurised fluid supply chamber to allow
independent control of the engagement members via a CMWD device
(e.g. for directional drilling), the chambers are alternately
connected to the high pressure and low pressure sides of the drill
motor and drill string which would typically have a pressure
differential of the order of 1200 to 1500 psi (83 to 103 bar).
[0030] According to another aspect of the present invention there
is provided a milling apparatus suitable for use in milling a
window in a well casing and comprising a rotary milling bit, motor
means for driving the milling bit, and a guide device of the
invention for positioning the milling bit in contact with a
selected portion of the casing to be nilled out.
[0031] According to yet another aspect of the present invention,
there is provided a method of milling a window in a selected
portion of a hole casing comprising the steps of:
[0032] providing a milling apparatus of the invention;
[0033] placing the milling apparatus within the casing;
[0034] operating the actuator means of the cutting tool guide
device so as to position the milling bit in contact with the
selected portion; and
[0035] driving the milling bit Bo as to form a window in the
casing.
[0036] In a further aspect the present invention provides a
stabilised hole reboring apparatus suitable for use in reboring an
asymmetrically obstructed hole, which apparatus comprises a rotary
drilling bit, motor means for driving the drilling bit, and a guide
device of the invention having at least two substantially
yummetrically driven engagement members for stabilising the
drilling bit against lateral deviation in use of the apparatus as
it cuts through an obstruction.
[0037] The present invention also provides a method of reboring an
asymmetrically obstructed hole comprising the steps of:
[0038] providing a stabilised hole reboring apparatus of the
invention;
[0039] placing the stabilised hole reboring apparatus inside the
asymmetrically obstructed hole;
[0040] operating the actuator means of the cutting tool guide
device so as to forcibly engage the hole sides above an obstruction
thereby stabilizing the drilling bit against lateral deviation;
and
[0041] driving the stabilised drilling bit so an to cut through the
obstruction.
[0042] In a still further aspect the present invention provides a
directional drilling apparatus suitable for use in directional
drilling, which apparatus comprises a rotary drilling bit, motor
means for driving the drilling bit, and a guide device of the
invention having at least three angularly distributed independently
driven engagement members operable for directing the drilling bit
away from an existing drilling axis.
[0043] The present invention also provides a method of directional
drilling compriin the steps of:
[0044] providing a directional drilling apparatus of the
invention;
[0045] placing the directional drilling apparatus inside a
hole;
[0046] independently operating the actuator means of the respective
engagement members of the cutting tool guide device so as to
forcibly engage the hole sides so as to direct the drilling bit in
a desired direction; and
[0047] driving the directed drilling bit so an to bore a hole along
a desired path.
[0048] As noted hereinbefore the actuator means for the respective
engagement members may be independently operated by means of
telemetric control. Various suitable kinds of telemetry are well
known in the art. Conveniently there may be used so-called mud
pulse telemetry in which the pressure applied to the drilling mud
flow passed down the drill string has superimposed thereon a more
or less rapidly changing pressure signal which is used to transmit
data via a suitable pulse code containing synchronisation pulses
and data bit pulses. Such telemetry means may also be used to
monitor the drilling direction during the course of drilling using
conventional MWD (measurement while drilling) techniques to
facilitate accurate control of the guide device and thereby of the
drilling direction.
[0049] A further particular advantage of the directional drilling
guide device of the present invention is that it may be used with
coiled tubing which has considerable operational advantages over
conventional jointed tubing in downhole operations.
[0050] Conveniently the actuator means are in the form of piston
means mounted in cylinder means provided in said body of the guide
device with a proximal end face in communication with said
pressurised fluid supply and a distal end in driving abutment with
a respective engagement member.
[0051] Further preferred features and advantages of the invention
will appear from the following detailed description given by way of
example of some preferred embodiments illustrated with reference to
the accompanying drawings in which:
[0052] FIG. 1 is a schematic elevation of a conventional
directional drilling apparatus;
[0053] FIG. 2 is schematic side elevation of a drilling apparatus
with a directional drilling guide device of the invention;
[0054] FIG. 3 is sectional side elevation of the guide device and
drill bit of the emnbodiment of FIG. 2;
[0055] FIGS. 4 and 5 are transverse sections of the guide device of
FIG. 3;
[0056] FIG. 6 is a sectional side elevation of the guide device and
milling bit of a milling apparatus of the invention;
[0057] FIGS. 7 and 8 are transverse sections of the guide device of
FIG. 6;
[0058] FIG. 9 is a sectional side elevation of a stabilizer guide
device and drill bit of a hole clearing apparatus of the invention;
and
[0059] FIGS. 10 and 11 are transverse sections of the guide device
of FIG. 9.
[0060] FIG. 2 shows a drilling apparatus 10 mounted at the end of a
coiled tubing 11 and comprising a MCWD (Measurement & Control
While Drilling) device 12 above a positive displacement rolling
vane motor 13 (similar to that of U.S. Pat. No. 5,518,379), below
which is mounted a guide device 14 and a drilling bit 15. The MCWD
device 12 has a set of telemetrically controlled valves 16 which
toggle connection of the high pressure and low pressure sides of
the drill motor 13 and drill string via fluid flow pipes 18 to
respective chambers of the guide device 14 as further explained
hereinbelow.
[0061] In more detail, the guide device 14 comprises a central,
generally octagonal section, body 19 having four elongate hole side
engagement members 20 captively secured thereto by bolts 21. Each
said engagement member 20 is provided with an actuator meane in the
form of a series of pistons 22 mounted in cylinder bores 23 in the
body 19 with a distal end 24 located in a blind hole 25 in the base
26 of the engagement member 20 in abutment with the engagement
member 20, and a proximal end 27 inside a pressurised fluid supply
chamber 28. Return coil spring means 29 are mounted around the
captive securing bolts 21 for biasing the engagement mtnembers 20
radially inwardly into their retracted positions.
[0062] When the chambers 23 are connected to the low pressure side
of the drill string and drill motor via the control valves 16, the
return springs tend to force the pistons 22 back into the chambers
20, draining any excess fluid therein back into the low pressure
side of the drill string. When fluid pressure is increased inside
the chambers 28 (by toggling the control valves 16 of the MCWD
device 12 to connect to the high pressure side of the drill motor
and drill string), the pistons 24 are displaced radially outwardly
against the force of the return springs 29 into engagement with the
sides of the well hole 17 as shown in the drawings. In these
drawings the engagement members 20 are all shown equally displaced
corresponding to equal opening of the control valves 16. This
arrangement provides good stabilisation against lateral deviation.
For the purposes of directional drilling, the control valves 16 are
operated unequally by means of specific telemetric control
instructions, so that at least one chamber 29 has a greater fluid
pressure and the correeponding engagement member 20 is subjected to
a greater driving force, than at least one other neig bouring
chamber 28 and engagement member 20, whereby the engagement members
20 are displaced asymmetrically around the device with the result
that the central axis of the guide device body 19 and hence of the
drill bit 15 connected thereto is offset from the central axis of
the well hole 17 above the drill bit 15 whereby the drill bit kicks
off along a new drilling line at an angle to the existing one. As
discussed hereinbefore, the guide device of the present invention
offers a high degree of control and flexibility in relation to the
kick off angle.
[0063] As may be seen from a comparison of FIGS. 1 and 2, the
apparatus required for directional drilling in accordance with the
present invention are considerably simpler in construction and ease
of operation than conventional apparatus, with the need for bent
subs, gear boxes, and extra motors being avoided. In addition, the
present invention allows conventional indexing means to be
dispensed with, although it in also possible to use a guide device
of the invention in combination with a conventional indexing means
if desired.
[0064] The guide devices of the apparatus of FIGS. 6 to 11 are
similar in a number of respects to that of FIGS. 2 to 5, and like
parts are indicated by like reference numbers. In both cases there
is no need for independent control of different engagement members
20 so that there is no requirement for independent pressurised
fluid supply chambers with associated fluid flow control, the or
each engagement member being subjected to just one fluid pressure
at any given time. Thus in the case of the stabilizer device 29
shown in FIGS. 9 to 11, the engagement members 20 are all displaced
equally and symmetrically whereby the central axis of the body 19
is stabilieed in line with central axis of the hole 17 therearound
and against lateral deviation upon the hole clearing bit 30 coming
into engagement with an asymmetrical obstruction 31 at one side of
the hole 17.
[0065] In the well casing window cutting apparatus 40 of FIGS. 6 to
8, the guide device 41 has only a single engagement member 20. When
the actuator means comprising the pistons 22 is operated to
displace the engagement member 20 radially outwardly against the
side 42 of the hole casing 43, the milling bit 44 is driven against
a portion 45 of the side 46 of the hole casing 43 in which it is
desired to form a window. The angular orientation of the engagement
mnember 20 and hence the portion of the hole casing 43 which will
be engaged by the milling bit 44, is controlled by a conventional
indexing device 2 mounted above a motor 12 (not shown in FIGS. 6 to
8). Once the milling bit 44 has cut through to the outside of the
casing 43, the apparatus may be driven down the hole progressively
to elongate the window (not shown) along the length of the casing
43.
* * * * *