U.S. patent application number 10/090373 was filed with the patent office on 2002-10-10 for guide apparatus.
Invention is credited to Harris, Gary Lawrence, Stewart, Kenneth Roderick, Van Drentham-Susman, Hector F.A..
Application Number | 20020144815 10/090373 |
Document ID | / |
Family ID | 9910404 |
Filed Date | 2002-10-10 |
United States Patent
Application |
20020144815 |
Kind Code |
A1 |
Van Drentham-Susman, Hector F.A. ;
et al. |
October 10, 2002 |
Guide apparatus
Abstract
The present invention provides a down-hole tool guide apparatus
6 suitable for use in controlling movement of a down-hole apparatus
1 provided with a pressurised working fluid supply in a borehole P.
The apparatus comprises: a body 7 having a chamber 13 in which is
slidably mounted a piston 14. A high pressure end 13a of the
chamber 13 is connected 36 to the pressurised working fluid supply
10 for supplying pressurised working fluid to a high pressure side
32 of said piston 14. A low pressure end 13b of the chamber 13 is
connected with the outside of the guide apparatus 6 and is provided
with a spring 16 for applying a biasing force to the low pressure
side 17 of the piston 14 corresponding to a predetermined threshold
pressure of the pressurised fluid supply at the high pressure side
of the piston 14. The body 7 mounts at least one shoe 25 having an
engagement face 26. The piston 14 is operatively coupled to a shoe
displacement mechanism 18, 19, 28, 29 so that the shoe 25 is held
in a stowed position when the piston 14 is urged towards the high
pressure end 13a of the chamber 13 by the spring 16, and is
displaced outwardly so that the engagement face 26 projects
outwardly of the body 7 when the piston 14 is displaced towards the
low pressure end 13b of the chamber by supply of pressurised
working fluid at a pressure higher than said threshold
pressure.
Inventors: |
Van Drentham-Susman, Hector
F.A.; (Inverurie, GB) ; Harris, Gary Lawrence;
(Humble, TX) ; Stewart, Kenneth Roderick; (Blairs,
GB) |
Correspondence
Address: |
John R. Casperson
PO Box 2174
Friendswood
TX
77549
US
|
Family ID: |
9910404 |
Appl. No.: |
10/090373 |
Filed: |
March 4, 2002 |
Current U.S.
Class: |
166/241.1 ;
166/212; 166/243 |
Current CPC
Class: |
E21B 23/04 20130101;
E21B 17/1021 20130101 |
Class at
Publication: |
166/241.1 ;
166/212; 166/243 |
International
Class: |
E21B 023/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 2001 |
GB |
0105946.8 |
Claims
What is claimed is:
1. A down-hole tool guide apparatus suitable for use in controlling
movement of a down-hole apparatus provided with a pressurised
working fluid supply in a borehole, said apparatus comprising: a
body having a chamber in which is slidably mounted a piston, said
body being formed and arranged for connection of a high pressure
end of said chamber to the pressurized working fluid supply in use
of the apparatus for supplying pressurized working fluid to a high
pressure side of said piston, said body being further formed and
arranged for connecting a low pressure end of said chamber with the
outside of said guide apparatus, said body being provided with a
resilient biasing device formed and arranged for applying a biasing
force to said piston corresponding to a predetermined threshold
pressure of the pressurised fluid supply at the high pressure side
of said piston, so as to urge said piston towards the high pressure
end of the chamber, said body mounting at least one shoe, each said
shoe having a radially outwardly facing longitudinally extending
engagement face, said piston being operatively coupled to a shoe
displacement mechanism formed and arranged so that said shoe is
held in a stowed position when said piston is urged towards the
high pressure end of said chamber by the resilient biasing means,
and said shoe is displaced outwardly so that said engagement face
projects outwardly of the body when said piston is displaced
towards the low pressure end of the chamber by supply of
pressurised working fluid at a pressure higher than said threshold
pressure.
2. An apparatus as claimed in claim 1 wherein is provided a single
said shoe, whereby said apparatus may be used as a kick-off
tool.
3. An apparatus as claimed in claim 1 wherein is provided a
plurality of angularly distributed said shoes, whereby said
apparatus may be used as a centralising or anchoring tool.
4. An apparatus as claimed in claim 3 wherein said shoe engagement
faces are provided with longitudinally extending ridges, whereby
said apparatus may be used as a centralising tool.
5. An apparatus as claimed in claim 3 wherein said shoe engagement
faces are provided with part annularly extending ridges, whereby
said apparatus may be used as an anchoring tool.
6. An apparatus as claimed in claim 3 wherein is provided a single
said piston and chamber operatively coupled to a shoe displacement
mechanism for each of said shoes.
7. An apparatus as claimed in claim 1 wherein said shoe
displacement mechanism comprises a camming device formed and
arranged for acting between the piston and shoe(s) so as to provide
a progressive radially outward displacement of said shoe(s) in
response to an axial displacement of the piston.
8. An apparatus as claimed in claim 1 wherein said shoe
displacement mechanism comprises a linkage having spaced apart
portions pivotally connected to respective ones of the shoe(s) and
the piston, said shoe(s) being captively mounted to said body so
that a progressive radially outward displacement of said shoe(s) is
provided in response to an axial displacement of the piston.
9. An apparatus as claimed in claim 1 wherein said chamber and
piston are annular.
10. An apparatus as claimed in claim 9 wherein a conduit for said
pressurised working fluid supply extends through said chamber along
a central longitudinal axis thereof.
11. An apparatus as claimed in claim 1 wherein said resilient
biasing device comprises a helical spring.
12. An apparatus as claimed in claim 1 wherein said resilient
biasing device has a predetermined preloaded so as to require a
pressurised fluid threshold pressure for initiating piston
displacement, in the range from 5 to 20 bar.
13. An apparatus as claimed in claim 1 wherein said resilient
biasing device has a variable spring rate.
14. An apparatus as claimed in claim 1, wherein said chamber is
connected to the interior of a pressurised fluid supply conduit,
via at least one perforation in said conduit.
15. An apparatus as claimed in claim 1 wherein the pressurised
fluid supply is provided, downstream of its connection to the high
pressure end of said chamber, with a flow restrictive nozzle in
order to increase the backpressure thereat and the pressure
differential obtained for a given pressurised fluid flow rate.
16. A pressurised fluid operated downhole cutting tool apparatus
having a pressurised fluid--operated motor drivingly connected to a
cutting tool and a pressurised fluid supply, wherein is provided a
guide apparatus according to claim 2.
17. An apparatus as claimed in claim 16 wherein said guide
apparatus is mounted between the motor and the cutting tool.
18. An apparatus as claimed in claim 16 wherein said motor is
selected from a positive displacement motor and a turbine.
19. A pressurised fluid operated downhole apparatus provided with
an anchoring tool comprising a guide apparatus according to claim
3.
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 apparatus may be disposed.
[0002] There is a need for guiding of downhole cutting tools for
various purposes including inter alia lateral or kick-off hole
cutting, directional drilling, as well as to stabilise an existing
cutting tool advance direction against unwanted deviation
therefrom. Existing solutions to such problems are generally
cumbersome to use and/or unsuitable for use with 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 slope of the whipstock is 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
whipstock 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 as 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
less 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 is required is substantially insufficient for
proper stabilisation.
[0006] 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.
[0007] It is a further object of the present invention to provide a
cutting tool guide apparatus which may be used with coiled tubing
with its inherently shorter positioning and retrieval times against
the use of jointed oil field tubing.
[0008] It is another object of the invention to provide a cutting
tool guide apparatus 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.
[0009] The present invention provides a down-hole tool guide
apparatus suitable for use in controlling the path of the cutting
tool of a down-hole cutting apparatus provided with a pressurised
working fluid supply in a borehole, said apparatus comprising: a
body having a chamber in which is slidably mounted a piston, said
body being formed and arranged for connection of a high pressure
end of said chamber to the pressurized working fluid supply in use
of the apparatus for supplying pressurized working fluid to a high
pressure side of said piston, said body being further formed and
arranged for connecting a low pressure end of said chamber with the
outside of said guide apparatus, said low pressure end of said
chamber being provided with a resilient biasing device formed and
arranged for applying a biasing force to said piston corresponding
to a predetermined threshold pressure of the pressurised fluid
supply at the high pressure side of said piston, so as to urge said
piston towards the high pressure end of the chamber, said body
mounting at least one shoe, each said shoe having a radially
outwardly facing longitudinally extending engagement face, said
piston being operatively coupled to a shoe displacement mechanism
formed and arranged so that said shoe is held in a stowed position
when said piston is urged towards the high pressure end of said
chamber by the resilient biasing means, and said shoe is displaced
outwardly so that said engagement face projects outwardly of the
body when said piston is displaced towards the low pressure end of
the chamber by supply of pressurised working fluid at a pressure
higher than said threshold pressure.
[0010] Thus with an apparatus of the present invention, it is
possible to apply a guiding force to a down-hole cutting tool as
and when required, simply by increasing the flow of working fluid.
In general the guide apparatus of the present invention is intended
for use with a pressurised fluid operated cutting tool apparatus
wherein is employed a fluid operated motor such as a turbine or
positive displacement motor and pressurised fluid is also supplied
to the cutting tool for lubrication thereof, carrying away cuttings
etc. Typically the guide apparatus would be mounted between the
motor and the cutting tool, the latter normally being supported on
a thrust bearing unit. With such a cutting tool apparatus the
pressurised fluid pressure applied to the high pressure side of the
cylinder(s) can be simply increased by increasing the flow rate of
the pressurised fluid supply delivered down the drill string. The
pressurised fluid supply is generally provided, downstream of the
cylinder , with a flow restrictive nozzle in order to increase the
backpressure thereat and the pressure differential obtained for a
given pressurized fluid flow rate. By suitable choice of the
diameter of the flow restriction nozzle, it is possible to adjust
the pressure differential obtained for a given flow rate. This has
the advantage of simultaneously increasing the motor torque and/or
speed and the fluid supply to the cutting tool which is exactly
what is required when kicking-off or cutting through an asymmetric
hole obstruction. Conversely when kicking-off or cutting through an
obstruction, the guiding apparatus is automatically brought into
operation by the working fluid pressure increase which occurs with
such operations.
[0011] In one form of the invention there may be used a single
shoe. In this case displacement of the shoe 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 shoe
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.
[0012] In another form of the invention at least two angularly
distributed, e.g. two diametrically opposed, or three, four or
more, symmetrically distributed, shoes may be used. These may be
displaced together by a single piston common thereto, or
alternatively there may be used two or more separate pistons for
the various shoes. In this case when the cylinder(s) is (are)
displaced, the existing drill string direction is stabilised
against deviation, 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 apparatus with its shoes
will not normally be required. Nevertheless if desired the guide
apparatus could be used in conjunction with an indexing device.
[0013] It will be appreciated that by varying the preloading of the
resilient biasing means it is possible to adjust the fluid pressure
threshold required to activate the guide device by displacement of
the piston. Typically there could be used a threshold pressure in
the region of from 5 to 20 Bar, for example, about 10 Bar, when a
positive displacement motor is used. Furthermore by choice of a
suitable spring rate, which may moreover be linear or non-linear,
it is possible to modify the rate of extension of the shoe(s) with
increasing fluid pressure, for example, in order to control the
force applied to the cutting tool.
[0014] Any convenient kind of shoe displacement mechanism may be
used in accordance with the present invention. Thus, for example,
there could be used a cam mechanism, in which a cam is rotated to
deploy the shoe(s).
[0015] Conveniently there is used a linkage mechanism captively
secured to the piston and comprising a plurality of pivotally
connected links. If used as a stabilizer form of guide apparatus of
the invention, the shoes will be maintained parallel to the drill
string. With the kick-off tool form of guide apparatus the shoe may
lie at a slight angle to the drill string as the tool is pushed
over to one side of the tube and the tool bends.
[0016] The tool guide apparatus may be connected to the pressurised
working fluid supply in any suitable manner. In general the tool
guide apparatus will have a working fluid conduit extending axially
through its centre which can be coupled to the working fluid
conduit(s) exiting the motor stage and running through the thrust
bearing assembly to the cutting tool. In such cases there is
conveniently employed a perforated connector for coupling the
working fluid conduit extending through the guide apparatus to that
of the thrust bearing, for tapping off working fluid pressure
directly or indirectly into the high pressure end of the guide
apparatus chamber. By varying the cross sectional area of the
perforation(s), the amount of pressure drawn off in this way can be
suitably adjusted.
[0017] 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:
[0018] FIGS. 1 and 2 are general side elevations of a bottom hole
assembly with a kick-off tool of the invention in its retracted and
deployed conditions;
[0019] FIGS. 3 and 4 are detailed sectional elevations of the
kick-off tool;
[0020] FIG. 5 is a detail front elevation of the kick-off tool in
its retracted condition;
[0021] FIG. 6 is a transverse section of the kick-off tool in the
plane VI-VI in FIG.4;
[0022] FIG. 7 is a sectional elevation of a centralizing tool of
the invention;
[0023] FIGS. 8 and 9 are schematic transverse sections through the
centralizing tool of FIG. 7 in its deployed and retracted
condition; and
[0024] FIG. 10 is a longitudinal section of a cutting tool suitable
for use with a kick-off tool according to FIGS. 3 to 6 for window
milling.
[0025] FIGS. 1 and 2 show (schematically) a bottom hole assembly 1
suspended from a coiled tubing drill string 2 and comprising a
downhole motor 3 and drill bit 4 supported on a thrust bearing unit
5 with a kick-off tool 6 of the invention mounted between the
thrust bearing 5 and the motor 3. In FIG. 1 the kick-off tool 6 is
in its inactive or stowed condition, whilst in FIG. 2 the kick-off
tool is shown fully extended.
[0026] As shown in FIGS. 3 and 4 the kick-off tool 6 comprises a
generally tubular body 7 having a reduced internal diameter upper
portion 8 and a larger internal diameter lower portion 9. A fluid
supply tube 10 extends along the central longitudinal axis X-X of
the body 7 closely fitting the interior 11 of the upper body
portion 8 and spaced from the interior 12 of the lower body portion
9 so as to define an annular chamber 13 therebetween. An annular
piston 14 is slidably mounted between the fluid supply tube 10 and
the interior 12 of the lower body portion 9. A central intermediate
diameter body portion 15 houses a helical spring 16 which engages
the upper end 17 of the piston 14 for resiliently biasing the
piston 14 downwardly.
[0027] The upper end 17 of the piston 14 has secured thereto a
connector 18 which is pivotally connected 19 to the lower end 20 of
a shoe assembly 21, the upper end 22 of which is pivotally
connected 23 to part 24 of the upper body portion 8. In more detail
the shoe assembly 21 comprises an elongate shoe member 25 having an
outer engagement surface 26 with closely spaced longitudinally
extending ridges 27 for positive engagement in use of the tool with
the side of a hole or pipe and stabilizing the tool against angular
displacement whilst permitting longitudinal displacement--for
example, for window milling (longitudinal hole elongation). The
ends 25a,25b of the shoe member 25 are connected by respective link
members 28, 29 to the piston 14 and upper body portion 8, so that
the shoe assembly 21 is movable between a stowed radially retracted
configuration as shown in FIG. 3 with the shoe member 25 and link
members 28, 29 fully extended longitudinally, and a deployed
radially extended configuration as shown in FIG. 4 with the shoe
member 25 and link members 28, 29 partially collapsed together
longitudinally.
[0028] The working end portion 30 of the piston 14 has a reduced
diameter and is slidably received within a sleeve 31 mounted within
the annular chamber 13 in order to reduce the surface area of the
working end face 32 of the piston 14 thereby to reduce the force
exerted on the shoe assembly 21 for a given differential fluid
pressure exerted thereon.
[0029] The lower end 33 of the fluid supply tube 10 is connected
via a tubular coupling 34 (see FIG. 4) to a further fluid supply
tube section 35 extending through a thrust bearing unit 5. The
tubular coupling 34 has a number of apertures 36 which connect the
interior 37 of the fluid supply tube 10 to the high pressure end
13a of the annular chamber 13 below the piston working end face 32
for supplying fluid pressure thereto. Inside the coupling 34 is
provided a flow restriction nozzle 38 for increasing the fluid
pressure diverted to the chamber 13. The back-pressure generated
and the pressure differential obtained for a given flow rate can be
adjusted by selecting a suitable flow restriction nozzle diameter.
The low pressure end 13b of the annular chamber 13 above the piston
14 is open to the outside of the guide apparatus 6 around the shoe
member 25 (see FIGS. 3 to 6).
[0030] In use of the kick-off tool of FIGS. 3 to 6, under normal
operating conditions, the shoe member 25 is held in its retracted
position by the spring 16. When the differential fluid supply
pressure exerted on the working end face 32 is increased by
increasing the flow rate of the pressurized fluid, then the piston
14 is forced upwardly thereby partly collapsing the shoe assembly
21 and forcing out the shoe member 25 into a radially outwardly
deployed position in engagement with one side 40 of the hole or
pipe 41 inside which the bottom hole assembly 1 is disposed and
forcing the latter towards the other side 42 of the hole or pipe 41
in order to, for example, bring a window cutting tool (not shown)
into engagement therewith, deviate the drilling direction etc.
[0031] FIGS. 7 to 9 show a centralizing tool 43 of the invention
for use in centralizing a bottom hole assembly 1 and stabilizing it
against unwanted deviations e.g. due to asymmetric obstructions in
the hole or pipe 41 or other asymmetric resistance to the advance
of the bottom hole assembly 1. The centralizing tool 43 is of
essentially similar construction to the kick-off tool 6 of FIGS. 1
to 6 but with three symmetrically angularly distributed shoe
assemblies 21A, 21B, 21C instead of the one shoe assembly 21 of the
kick-off tool 6, and similar components corresponding generally to
those of the latter are indicated by like reference numbers. In
this case when the differential fluid supply pressure applied to
the piston working end face 32 is increased the shoe members 25 are
brought into engagement with the sides 45 of the hole or pipe 41
around the tool 43 so that the bottom hole assembly 1 is held
firmly in the centre of the hole or pipe 41 against unwanted
deviations therefrom.
[0032] As may be seen in Fig.6, the side 46 of the kick-off tool 6
has a substantially larger radius of curvature (comparable to that
of the tool with the shoe assembly 21 in its deployed, radially
extended position) than that of the tool 6 in its radially
retracted condition. By this means the surface area of the tool
side 46 which is forced into engagement with the pipe side 42 in
which, for example, a hole is to be cut, is maximized thereby
spreading the load thereon, whilst at the same time maximizing ease
of movement of the tool 6 along the pipe 41 when the shoe assembly
21 is in its radially retracted condition.
[0033] FIG. 10 is a longitudinal section of a cutting tool suitable
for use with a kick-off tool according to FIGS. 3 to 6 for window
milling. In more detail the cutting tool 47 has an outer generally
cylindrical cutting surface 48 which may have carbide inserts or
crushed carbide particles or similar cutting materials brazed or
attached on to it. This cylindrical cutting surface 48 will cut
during the initial perforating operation as the kick-off tool 6 is
actuated and pushes laterally the milling tool 47 into the wall of
the tubing P (see FIGS. 1-2). The front end face 49 of the tool has
a central recess 50 made of a generally conical form. This end face
49 will also be coated with an abrasive cutting coating e.g.
crushed carbide. Once the perforation has been made and the BHA
starts to advance down the well to elongate axially the perforation
to form a window in the tubing P, the end face 49 will be the
cutting face. The conical recess 50 of the end face 49 is designed
to stabilise the BHA so that it does not drift back into the centre
of the tube P, by tending to centralise the cutting 47 in the wall
of the tubing P. (If a flat face or an external conical face is
used, the tool tends to push back in towards the centre of the
tubing).
[0034] It will be appreciated that various modifications may be
made to the above described embodiment without departing from the
scope of the present invention. Thus, for example, although in
FIGS. 3, 4 and 7, the piston-cylinder device 14, 13 is shown
connected to the lower end of the shoe assembly, the
piston-cylinder device could also be connected to the upper end
thereof. It is believed that in use a piston located connected at
the lower end could be advantageous as if the tool becomes
difficult to operate, e.g. because of contaminants in the
pressurized fluid causing a blockage, then in the process of
withdrawing the tool from the hole the piston is pushed back by the
force of the springs and the lever action of the shoe without
having to overcome the effect of the blockage or debris above the
piston. To encourage the shoe to retract on pull out of the hole,
the angle of the links 28 and 29 at full extension should be less
than 90.degree. from centreline of the body and preferably in the
range from 30 to 60.degree..
[0035] Also, if it is desired to provide axial stabilization
against longitudinal displacement of the tool--for example in use
as a perforating tool, where a hole is to be made in the wall of
the casing/tubing but a window is not required, or in use as an
anchor, then, instead of longitudinally extending grooves and
ridges 27, there could be used part-annular grooves and ridges. In
use as an anchor the guide apparatus would be positioned between
the downhole motor 3 and the coiled tubing/drill string 2. As a
stabiliser the guide apparatus may be positioned between the
downhole motor 3 and the coiled tubing/drill string 2 or between
the downhole motor 3 and the bearing section 5.
[0036] To reduce the possible bending of the bottom hole assembly 1
between the drill bit 4 and the guide apparatus 6 it may be
advantageous to integrate the bearing section 5 and the guide
apparatus 6 into a single unit.
* * * * *