Note: Descriptions are shown in the official language in which they were submitted.
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sACKGROU n pF THH IyyENTZ~~
Field of the Inventions This invention concerns a
drilling tool for sinking swells in underground rock forma-
tions, where the direction for drilling can be selected.
l.0 State of the Art: In a known version of such a
drilling tool, a sealed hydraulic system with a hydraulic
reservoir and a hydraulic pump is accommodated in the
drilling tool to act on force-transmitting elements. The
force-transmitting elements act on control runners that are
pressed against the wall of the borehole.
SUM~3ARY OF THE INVENTION
This invention is based oz~ the problem of creating
a drilling tool of the type described above with an essen-
tially simplified hydraulic system for controlling the
force-transmitting elements.
The drilling tool according to this invention uses
the drilling mud which is already present in the borehole as
the hydraulic medium to impart the required directional
forces, so this greatly simplifies the design of the tool.
The hydraulic pressure chambers of the force-transmitting
3o elements preferably have a flow passing through them at all
times, at least apart from periodic interruptions, so the
accumulation of sediment is effectively prevented.
The force-transmitting elements can induce a
displacement of the outer casing of the drilling tool
together with the tool drive shaft, but instead of this the
tool drive shaft can also be supported so it can be shifted
radially to a limited extent in the outer casing and can be
shifted from one position in the outer casing into another
position for directional purposes by means of a number of
force transmitting elements distributed around the
periphery. Such a design shifts the movement of components
which is necessary for a change in direction into the
interior of the drilling tool, thereby simplifying the
design of the outer casing.
BRIEF I7ESGlRIP~ION DF UHF DRAWINGS
ATumerous other details and advantages are derived
from the following description and the figures which illus-
trate several practical examples of the abject of this
ZO invention in schematic detail. The figures show the
followings
FIG. 1 shows a cutaway schematic diagram of a
drilling tool according to this invention with force-
transmitting elements which act on the pressure pieces that
can be applied to the wall of the borehole (shown in a
longitudinal sectional view ;
FIG. 2 shows a diagram lice FIG. 1 of a drilling
tool with the drive shaft of the tool supported so it can
move radially to a limited extent in the outer casing and
with force-transmitting elements that act on the drive
shaft;
FIG. 3 shows a section along line III-III in FIG.
1?
FIG. 4 shows a section along line IV-IV in FIG. 2;
2S FIG. 5 shows a sectional diagram li3ce FIG. 4 to
illustrate a modified version;
FIG. 6a shows a hydraulic circuit diagram for a
drilling tool according to FIG. ? with different control
valve locations in the right and left halves;
FIG. 6b shows a modified hydraulic circuit diagram
according to FIG. 2; arad
FIGS. 7 to 9 show schematic diagrams of different
arrangements of force-transmitting elements in the drilling
tool.
,1~FSCRI~TION QF T~IE~REFERREp FNIDODIMFNT
FIG. 1 illustrates a drilling Coal for sinking
wells in underground rock formations where the drilling tool
consists of an outer casing 1 with a stabiliser 100 and a
drive shaft 3 that rotates in outer casing 1 and carries
rotary drill bit 2 on its projecting end. Outer casing 1
can be connected to a drill string 5 as indicated schemat-
ically in FIGS.. 1 and 2 by connecting means, especially an
~.A upper connecting thread ~4 as illustrated in the drilling
tool according to FIGS. 1 and 2, so that drilling mud can be
supplied to the drilling tool through the drill string. The
drive shaft 3 of the drilling tool is driven by a hydraulic
drive motor (not shown), e.g., a Moineau motor or a turbine,
Z5 accommodated in the upper area of the drilling tool in the
outer casing 1.
Outer casing 1 is provided with four hydraulically
operated force°transmitting elements 6, 7, 8, 9 distributed
around its periphery. These force-transmitting elements are
2o arranged in the same plane and form a group. Preferably
each drilling tool has several groups of force-transmitting
elements 6 to 9 arranged with some spacing between them
where preferably the force-transmitting elements that are
aligned vertically above each other and act in the same
25 direction are hydraulically controlled together for their
joint operation.
For hydraulic operation of force-transmitting
elements 6, 7, 8, 3, a control device is provided having an
electrically operated control valve for each force--
30 transmitting element or when there are several groups of
force-transmitting elements arranged above each other there
is one electrically operated control valve for each group of
similarly acting force-transmitting elements. FIG. 1 shows
only the control valves 10 and 12 far acting on force-
35 transmitting elements 6 and 8 or similarly acting force-
3
2~~~~3~°~1~>
transmitting elements. However, it is self-evident that
corresponding valves can also be provided for force-trans-
mitting elements 7 and 9. The electromagnets 14, 16 of
control valves lo, 12 are connected to a signal generator as
indicated schematically by 18 for the drilling tool accord-
ing to FIG. 2. This signal generator 18 is shown together
with another signal generator 19 that may be provided for
different control functions as illustrated schematically in
FIG. 2 and with a measured value sensox 20 for positional
.0 data on the drilling tool is also part of the control system
for the force-transmitting elements. In FIG. 2, a measured
value sensor is shown schematically at 20 and other measured
value sensors 21, 22 for positional data may also be pro-
vided, as indicated in FIG. 2. The electric power supply
can be provided by batteries 23 which can be accommodated in
an annular space 24 of outer casing 1 like the other elec-
tric and sensing parts of the control ecguipment. Instead of
a power source provided by batteries 24, power can also be
supplied with the help of an electric generator driven by a
2~ turbine. The turbine can be operated by drilling mud.
Force-transmitting elements ~, 7, 8, 9 and other
corresponding force-transmitting elements that act in the
same way and are connected in parallel all act on pressure
members 26, 27, 28, 29 which are supported in or on outer
casing 1 so they can be shifted inward and outward and can
be applied to the wall 30 of the borehole at a central angle
of 90° corresponding to the four force-transmitting elements
6, 7, 8, 9.
Fach hydraulic pressure chamber 32, 33, 34, 35 for
a force-transmitting element 6, 7, 8, 9 can be acted on
optionally with drilling mud of a high pressure or drilling
mud of a low pressure through a connecting channel 35, 37,
38, 39 and the respective control ~,ralve, such as valves 10
and 12 for connecting channels 36 and 38. For this purpose,
a feed line is provided above the group of force-
transmitting elements 6, 7, 8, 9 for each connecting channel
36, 37, 38, 39. Only feed lines 4Q, 42 for connecting
channels 36 and 38 are illustrated in FIG. 1. These feed
lines are controlled by the respective control valve (li3ce
control valves 2.0, 12) and communicate with an annular gap
43 'that is connected to drilling mud of a higher pressure by
branch line 44 leading to center bore 45 in the drive shaft
3.
Connecting channels 36, 37, 38, 39 each open into
the annular space 50 through a throttle point and thus open
into an area of drilling mud of a lower pressure as shown in
FIG. Z by 46 and 48 for the connecting channels 36, 38.
In the version according to FIG. ~., a pressure
develops in connecting channels 36, 37, 38, 39 and the
~.5 pressure chambers 32, 33, 34, 35 connected to the former
when the Control valve is open in 'the version according tn
FIG. 1 and this pressure is higher than the pressure es~tab--
lished when the control valves (such as l0 and 12) are each
closed. In the latter case, a pressure corresponding to the
pressure in the drilling mud in the annular space develops
in the connecting channels 36, 37, 38, 39 by way of their
connection to annular space 50, and this pressure is lower
than the pressure of the drilling mud in the drilling tool
1.
In the example illustrated in FIG. 1, connecting
channels 36, 37, 38, 39 are each connected between the ends
thereof to their respective pressure chamber 32, 33, 34, 35
of the force-transmitting elements 6, 7, 8, 9 by way of a
branch channel 56, 57, 58, 59, and the change in pressure in
the pressure chambers corresponds to the change in pressure
that develops on the whole in the connecting channels 36,
37, 38, 39 which receive drilling mud of a high pressure at
one end and drilling mud of a lower pressure at the other
end.
Instead of this arrangement, however, it is also
5
possible for two separate connecting channels 'to be provided
for each hydraulic pressure chamber of a force-transmitting
elements, whexe one channel is connected to drilling mud of
a higher pressure and the other channel is connected to
drilling mud of a lower pressure and a cowtrol valve is
provided for a connecting channel or channel part that is
acted on by either the high or low drilling mud pressure.
In certain cases separate control valves can also be pro-
vided in both connecting channels or channel parts. This
l0 permits a special gradation in pressure, e.g., by means of a
differential pressure, especially when the control valves
are provided with a valve body that merely reduces the cross
section of flow of the valve channel in the closed end
position but does not completely seal off the valve channel,
x5 which can be desirable in order to maintain a steady flow
through the pressure chambers and connecting channels.
Tn a modification of the communication of the
connecting channels 36, 37, 38, 39 to drilling mud of a high
pressure and drilling mud of a low pressure as provided in
20 the version according to FIGS. 1. and 2, it is also possible
to have the action of the high-pressure drilling mud derive
from a drilling mud channel like drilling mud channel ~5 in
the outer casing 1 in the direction of flow in front of a
throttle point and to have the action of low-pressure
25 drilling mud derived from the same drilling mud channel
after the throttle point.
As an alternative, the action of high-pressure
drilling mud can also be derived from the annular space 50
surrounding outer casing Z in the direction of flow in front
30 of a throttle point for the drilling mud flowing through the
annular space and the action with low-pressure drilling mud
is derived from the annular space 50 after such a throttle
point. Such a throttle point is farmed, for example, by a
stabiliser. If the force-transmitting elements are pistons
35 66, 67, 68, 69 (FIG. 3) or 266, 267, 268, 269 (FIG. 5j as iS
6
~~~~~~3
the case with the force-transmitting element 6, 7, 8, 9 and
206, 207, x08, 209 which are held in cylinder spaces in
outer casing 1, then the sealing gap between the piston and
cylinder can form the connecting channel or channel part
that communicates with the low-pressure drilling mud. In
this case but also otherwise, the surfaces facing each other
are preferably protected with a hard metal.
The control valves preferably have a design with
an unbranched valve channel that can be varied only in its
lp cross section of flow and is either released by the valve
bodies or is completely or partially closed off in the
closed position. The latter design has the advantage that
when the control valve is closed, i~t forms only a throttling
element.
The pistons 66, 67, 68, 69 provided in the version
according to FIG. 1 act on the inside of pressure members
26, 27, 28, 29 which are designed as stabilizer ribs and are
guided on guide projections 76, 77, 78, 79 of outer casing 1
where their movement is limited by stops 80.
In contrast with the version of the drilling tool
according to FIG. 1, the drive shaft 3 of the drilling tool
in the version according to FIG. 2 is supported so it has
limited radial mobility in outer casing 1 and can be shifted
from one position in outer casing 1 to another position for
directional purposes by means of four force-transmitting
elements 106, 107, 108, 109 (FIG. 4j or 206, 207, 208, 209
(FIG. 5) or a multiple thereof when there are several groups
acting in parallel. The force-transmitting elements 106,
107, 108, 109 are designed as folded bellows pistons which
each surround a pressure chamber 132, 133, 134, 1.35 that is
connected by connecting channels 136, 137, 138, 139 (FIG. 4)
to the drilling mud in the manner described above in con-
junction with the version described according to FIGS. 1 and
3. This is also true of the version according to FIG. 5
with the connecting channels 236, 237, 238, 239 illustrated
7
there and connected to pressure chambers 236, 237, 238, 239.
The arrangement in FIG. 2 of control valves 110, 112 with
their electromagnetic drives 114 and 116 also corresponds to
that according to FIG. 2.
Of the groups of force-transmitting elements
acting on the drive shaft 3 or the pressure members 26, 27,
28, 29, preferably one group of force-transmitting elements
is provided for defining a basic position for drive shaft 3
and/or pressure members 26, 27, 28, 29. This group of
force-transmitting elements 306, 308, FIGS. 1 and 6) has
stepped pistons 316, 318 that act as centering pistons and
move against a stop. In the end position next to the stop,
such pistons 316, 318 define a basic position or a centered
position for pressure members 26, 27, 28, 29. A similar
J.6 design with the drilling tool according to FIG. 2 would
impart a corresponding basic position or a centered position
to drive shaft 3.
The farce-transmitting elements 306, 308 that
define the basic position, i.e., the centered position for
drive shaft 3 and/or pressure members 26, 27, 28, 29, may be
hydraulically operated independently of the other force-
transmitting elements, either in the sense of separate,
independent control or in the sense of constant, uncon-
trolled activation. In the first case, the force-
transmitting elements that determine the centered position
can be connected totally or partially to the area of lower
pressure drilling mud, in order to minimize the resistance
thereof to desired displacement of the drive shaft 3 or
outer casing by the other groups of force-transmitting
elements. In the second case, the dominant force-
transmitting elements for the determination of the centered
position form a fail-safe device which, in the case of
failure of the control device, ensures that the drilling
operation may continue in a linear path. For normal opera-
Lion it must, however, be ensured that the force-
8
transmitting elements which determine a displacement of the
drive shaft 3 ar the force-transmitting members (26, 27, 28,
29) in outer casing 1 from their basic positions transfer
considerably larger farces out the drive shaft 3 of the
present members 26, 27, 28, 29 than the forces applied by
the force-transmitting elements determining 'the original
position. This can be accomplished through an appropriate
design of the pressure surfaces of the respective force-
transmitting elements or by providing several groups of
I,e force-transmitting elements for the changes in directions.
Such an overcoming of the force-transmitting elements deter-
mining the centered position by the force-transmitting
elements determining directional displacement can, however,
also be obtained with common activation of all fo:rce-
25 transmitting elements and common control.
Essentially, it is also possible to combine an
external control unit according to FIG. 1 and an internal
control unit according to FIG. 2 in one drilling tool, so
this permits double control of direction and directional
20 displacement.
The version according to FIG. 5 provides a com-
bined internal and external control system for a drilling
tool. Pistons 266, 267, 268, 269 border a pressure chamber
232, 233, 234, 235 at one end which also forms the pressure
25 chamber for pistons 466, 467, 468 and 469 of a force-
transmitting element 406, 407, 408, 409 that eats on pres-
sure members 426, 427, 428, 429. These pressure members
426, 427, 428 and 429 may be designed as stabilizer ribs and
may be guided along outer casing ~. as described in con-
3~ junction with the FIG. 1, Pressure chambers 232, 233, 234,
235 are respectively acted on by drilling mud from connec~t-
ing channels 236, 237, 238, 239 as described in conjunction
with FIG. 1 above.
As indicated in FIGS. 2, 4 and 5, the force-
35 transmitting elements 106, 107, 108, 109 and 206, 207, 208,
9
209 act on a bushing 81 which may have web-like flattened
areas in the areas of pressure engagement with the force-
transmitting elements. Bushing 81 borders a cylindrical
bearing shell 82 in which drive shaft 3 is mounted so it can
rotate. Bearing shell 82 may also be a corotational part of
drive shaft 3. This prevents wear and improves the load
distribution.
the right half of FIG. 6a shows a hydraulic plan
for the embodiment of FIG. 2 with a control valve 110 in the
3~ area of connecting channel 136 with a higher drilling mud
pressure and the left half of this figure shows a version
with an arrangement of a control valve 210 in the area of
connecting channel 136 where the drilling mud pressure is
lower. In both examples, throttle points 48 are provided in
Z5 the area of connecting channel 136 not provided with cowtrol
valves 110, 210 in a manner corresponding to throttle points
48 of FIG. 1.
FIG. 6b represents an activation diagram for an
example according to FIG. 2, in which the force-transmitting
20 elements 306, 308 that determine the original position of
drive shaft 3 are exposed to an independent, uncontrolled
force by a branch channel such as 136a, 138a that branches
off from a connecting channel 136, 138 above its control
valve 110. Thus, force-transmitting elements 306, 308 are
25 exposed to a constant activation pressure, which is still
effective even if the activation mechanism for the foree-
transmitting elements 106, 108 should fail, for example as a
result of a defect in the electronics of the control device.
Finally, FIGS. 7, 8 and 9 schematically illustrate
30 variations in the arrangement of the force-transmitting
elements within the drilling tool. FIG. 7 shows an arrange-
ment of force-transmitting elements 106, 108 acting on drive
shaft 3 close to the drill bit end of the drilling tool,
while FIG. 8 shows a version with force-transmitting ele-
35 menu acting on pressure members 26, 28 located close to the
end of the drilling tool opposite drill bit 2. t a 'the
version according to ~'IG< 9 shows a design with pressure
members 26, 28 acted on by force-transmitting elements, in
this case arranged close to the drilling bit end of the
drilling tool.
1 ~,
