Drilling equipment with adaptor for steering long boreholes

Drilling equipment for steering relatively long boreholes in rock strata comprises an adaptor for installation adjacent to the drill bit, the adaptor having an inner rotary component drivably connected between the drill rod assembly and the drill bit and a relatively outer component. Releasable latch means are provided having two operational modes in the first of which the inner and outer components are fixedly engaged for rotary motion and in the second mode of which the inner component can rotate relative to the outer component. Also actuatable means are provided for controlling the operational mode of the releasable latch means.

This invention relates to drilling methods and equipment. 
In particular, although not exclusively, the present invention relates to 
drilling methods and equipment used for drilling long exploratory bore 
holes in rock strata. 
It is known for such drilling equipment to comprise a rotary drill bit 
mounted on the end of an extensible drill rod constituted by a plurality 
of connected drill rod sections which are rotated by a drilling machine 
and which are induced into the generally horizontally extending borehole 
to increase its length. It is common practice for the drill bit to have an 
overall diameter slightly greater than that of the drill rod and for 
collars or stabilizer to be fitted around the end portion of the drill rod 
adjacent to the drill bit in order to determine the cutting horizon of the 
drill bit. Depending upon whether the drill operator desires the drill bit 
to be urged to move upwardly or downwardly relative to the adjacent rock 
strata, the axial positions of these stabilizer relative to the bit must 
be varied. 
A problem with the use of such collars is that in order to reposition these 
collars it is necessary to withdraw all the strings of assembled drill 
rods. It will be appreciated that this can be a time consuming and tedious 
operation particularly when the borehole is very long and particularly 
when the original type of adaptor might have to be refitted once the 
correct or desired cutting orientation or horizon is achieved. 
An object of the present invention is to provide improved drilling 
equipment. 
According to one aspect of the present invention a method of drilling a 
borehole in rock strata comprises the steps of directing a rotary drill 
string including a drilling bit to form the borehole, and providing the 
drill string with a steering adaptor having two alternative operational 
modes, in the first mode of which a radially outer portion of the steering 
adaptor rotates with the drill string and in the second operational mode 
of which the drill string rotates independently of the radially outer 
portion, of the steering adaptor, means are provided for controlling 
sections of the operational mode of the steering adaptor. 
Preferably, the means is activated by probe means fed down the borehole. 
Alternatively, the means is activated by remote control means. 
According to a second aspect, the present invention drilling equipment 
provides steering adaptor for association with a rotary drilling bit 
mountable on a rotary drill rod string for forming a borehole, the adaptor 
comprising a relatively inner rotary component drivably connectable to the 
drill rod and to the drilling bit or drivably connectable to connector 
components enabling the rotary component to be drivably connectable to the 
drill rod and to the drilling bit, a relatively outer component arranged 
at least part way around inner rotary component, releasable latch means 
having two operational modes in the first mode of which the inner and 
outer components are fixedly engaged for rotary motion and the second mode 
of which the inner component can rotate relative to the outer component, 
and actuatable means for controlling the operational mode of the 
releasable latch means. 
Preferably, the releasable latch means comprises a pivotally mounted latch. 
Conveniently, the pivotally mounted latch is provided on the inner 
component. 
Advantageously, the pivotally mounted latch is resiliently biassed into one 
of its operational modes. 
Conveniently, the actuatable means comprises a releasing element for urging 
the pivotally mounted latch to move against its resilient bias. 
Preferably, the actuatable means comprises a pivotally mounted retaining 
latch operable to retain the releasing element in a position urging the 
pivotally mounted latch against the action of its resilient bias. 
Advantageously, the retaining latch is mounted on a bush slidably mounted 
along the inner rotary component. 
Preferably, the bush is slidable along the inner rotary component under the 
action of a resilient bias. 
Advantageously, the resilient bias comprises two springs. 
Conveniently, the two springs act on a common slide member slidable along 
the inner rotary component. 
Advantageously, the resilient bias acts on the releasing element. 
Preferably, the drilling equipment comprises probe means slidable along an 
axial passage defined by the drill rod, the probe means actuating the 
actuation means to control the releasable latch means.

The drawings relate to rotary drilling equipment for drilling long 
boreholes in rock strata, at least a portion of the borehole extending 
generally horizontally through the strata. The drilling equipment 
comprises a rotary drill rod string 1 only one small end portion of which 
is shown in the drawing constituted by a plurality of drill rod sections 
connected end to end to define an axial passageway 2 extending 
substantially the length of the borehole. In operation the passageway 
permits pressurised drilling fluid to be pumped along the borehole to a 
rotary drilling bit (not shown) mounted on the extreme end of the drilling 
rod assembly in order to wash away broken rock particles produced during 
the cutting or drilling operation. The particles return along the borehole 
in a relatively outer passageway defined between the outermost cylindrical 
surface of the drilling rod assembly and the boundary rock wall of the 
borehole. 
In operation the end of the drill rod string remote from the rotary 
drilling bit and extending from the borehole is drivably connected to the 
driven chuck of a drilling machine which as well as rotary the drill rod 
assembly urges the assembly further into the borehole. 
The drilling equipment also comprises a steering adaptor mounted between 
the end of the drill rod assembly remote from the drilling machine and the 
drill bit, the adaptor comprising a relatively inner rotary component 10 
drivably connected to connector components 11 and 12 enabling the rotary 
component to be drivably connected to the drill rod 1 and to the rotary 
drill bit (not shown). The drill bit is mounted directly on the threaded 
portion 13 of the connector component 12. 
In other embodiments the inner component is connected directly onto the 
drill rod assembly and/or onto the drill bit. 
As seen in the drawings the connecting and inner components define flow 
passages for pressurised drilling fluid fed along the passage 2 towards 
the drill bit to wash away broken rock particles produced during the 
drilling or cutting operation. Arrows y define one flow path taken by the 
pressurised fluid. The particles are washed away from the drill bit along 
a passage defined between the drill rod assembly and the boundary rock 
walls of the borehole. 
The adaptor further comprises an outer component 16 (see FIGS. 1 and 3) 
extending around the inner rotary component 10 and having rock cutting 
elements 18 arranged in three circumferentially spaced banks around the 
outer component. As seen in FIG. 3 the outer wall of the outer component 
has axially extending recesses 19 permitting the return flow of drilling 
fluid from the drill bit. Arrow z in FIG. 3 denotes the direction of 
rotation of the rotary cutter bit. The operation of the cutting elements 
18 will be explained later in the specification. 
The adaptor also comprises releasable latch means constituted by three 
pivotally mounted latches 20 (only one of which is shown in FIG. 1 and 
only a pivot support pin 21 of which is shown in FIG. 2). Each latch is 
capable of pivoting from a first operational mode in which a lip 23 on the 
latch engages in an associated recess 22 provided in the outer component 
into a second operational mode in which the lip 23 is clear or disengaged 
from the recess 22. In FIG. 1 the lip is denoted in both its alternative 
operational modes, however, the reference number 23a is used to denote the 
lip in its disengaged operational mode. 
The latch is urged to pivot into its engaged operational mode with the lip 
23 engaged in the recess 22 by a resiliently mounted plunger 25 tending to 
move under the action of a spring 26 arranged between the plunger 25 and a 
stop pin 27. Pivotal movement of the latch 20 beyond the engaged 
operational mode is prevented by a further stop pin 28 engaged by an 
abutment stop 29 provided on the latch. In FIG. 5 only the inner component 
10 and the latch support pins 21 are shown. 
The releasable latch means are urged to move from their engaged operational 
modes and against the action of the resilient biasses 25, 26, 27 by the 
action of a releasing finger element 30 slidable along an axial bore 31 
provided by the inner rotary component 10. The releasing finger element 30 
constitutes part of actuatable means for controlling operation of the 
releasable latch means. The actuatable means further comprises a pivotally 
mounted latch 34 carried by a bush 35 slidably mounted along a slideway 36 
defined by the connector component 11. Movement of the bush 35 along the 
slideway is against the action of resilient means comprising two springs 
37 and 38 arranged to abut opposite sides of a slide member 39 also 
slidable along the slideway 36. The slide members 39 constitutes the head 
portion of the releasing finger element 30 and moves with the element 30. 
The spring 38 is arranged to act between a fixed shoulder 40 provided on 
the inner rotary component 10 and the slide member 39. The spring 37 is 
arranged to act between the slide members 39 and a shoulder 41 provided on 
the bush 35. 
In use the bush 35 is urged to slide along the slideway 36 until a lip 42 
provided on latch 34 engages in an annular retaining recess 43 (as 
indicated in FIG. 2) provided in the connector component 11. With the lip 
42 of the latch 34 engaged in the retaining recess the releasing finger 
element 30 is moved along the passage 31 towards a drill bit sufficiently 
for the element 30 to contact the latch 20 which thereby is pivoted into 
its released operational mode. Movement of the bush 35 will be explained 
later in this specification. 
The drilling equipment also provides probe means comprising a probe 
activating tool 50 which is slidable along the passageway 2 defined by the 
drill rod assembly 1. The probe activating tool is slidable along the 
passageway 2 in a direction towards the drill bit under the action of 
pressure drilling fluid fed into the passageway 3. Seals 51 are provided 
on the tool 50 such that it effectively forms a piston slidable within the 
passageway 2. The probe activating tool 50 is moved along the passage 2 in 
a direction away from the drill bit by a wire (not shown) trailing behind 
the tool and secured to an eyelet 52. When it is required to remove the 
probe activating tool from the adaptor the wire is hauled back along the 
borehole either manually or by a winch. 
The probe activating tool 50 carries a removal releasing probe 60 (see FIG. 
2) engaging in an axial bore 61 provided in the front of the tool, the 
probe being retained in position by a removable cross screw 62 engaging an 
annular grove 63 formed in the probe. From FIG. 2 it will be appreciated 
that the probe 60 extends forwardly by distance sufficient to urge the 
latch 34 to pivot into a released mode in which the lip 42 is clear of or 
released from the recess 43 thereby allowing the bush 35 to move along the 
passageway 36 of the connecting component under the action of the springs 
37 and 38. Operation of the releasing probe 60 will be explained in more 
detail later in the specification. 
The probe activating tool 50 also carries a removal locking probe 65 which 
in use can be engaged in the bore 61 and retained in position by the 
removable cross screw 62 and which when mounted on the front of the 
activating tool 50 abuts the bush 35 which thereby is urged to move along 
the slideway 36 against the action of the springs 37 and 38 in order to 
enable the latch 34 to engage in the recess 43, the activating tool 50 
together with the locking probe 65 being urged along the slideway 36 by 
the action of the pressurised fluid in the passage 2 provided by the drill 
rod assembly 1. It will be appreciated that although both the probes 60 
and 65 are shown in FIG. 2 in position on the activating tool 50 in 
practise only one of the probes is fitted to the tool at any one time (as 
will be explained later in this specification), the selection of the 
particular probe is determined upon whether the drilling machine operator 
desires the drilling bit to climb in the rock strata or to drill 
downwards. 
In operation, the drilling equipment is aligned at a desired orientation to 
the rock strata and the drilling procedure started with the drill rod 
assembly fitted with the drill bit directed generally horizontally into 
the rock strata. In a typical installation the latch 20 of the releasable 
latch means is in its released mode such that the rotary component 10 
rotates freely relative to the outer component 16 which provides a 
substantially non-rotary stabilizer for the drill bit. The latch 20 is 
retained in its released mode by the finger element 30 which is retained 
in its advanced position under the action of the springs 37 and 38, the 
bush 35 initially being pushed forward into a position in which the lip 42 
of the latch 34 is engaged in the recess 43 to retain the bush 35 in its 
forward position as seen in FIG. 2. 
When the borehole has been drilled into the rock strata to an appreciable 
depth and the drill rod assembly tends to lay along the floor of the 
borehole the action of the adaptor tends to direct the drill bit such that 
the newly formed section of the borehole tends to be inclined upwardly at 
a relatively shallow angle. Upon the borehole approaching a maximum 
desired height in the rock strata the probe activating tool 50 fitted with 
the probe 60 is fed along the passage 2 under the action of the pressure 
fluid as previously mentioned. Upon the activating tool reaching the 
adaptor the probe 60 enters the axial bore 70 of the bush 35 to engage the 
inwardly protruding latch 34 which thereby is pivoted about support 67 to 
disengage the lip 42 of the latch from the recess 43. Location of the 
probe 60 in the bore 70 is aided by the tapered inlet 71. Upon the release 
of the lip 42 from the recess the bush 35 is urged to slide rearwardly 
along the slideway 36 under the actions of the springs 37 and 38. 
Simultaneously, the springs urge the head 39 of the finger element 30 to 
move rearwardly thereby withdrawing the finger element clear of the 
latches 20 which move under the action of the resilient biasses 25, 26, 27 
to engage the lips 23 in the recesses 22. Thus, the outer component 16 now 
is fixedly secured to the rotary inner component 10 for rotational 
movement. 
Once the latches 20 are engaged in the recesses 43 the activating rod is 
withdrawn from the borehole by use of the aforementioned trailing wire 
connected to the eyelet 52, the supply of pressure fluid being previously 
turned off. It will be appreciated that the use and removal of the 
activating tool 50 is a relatively rapid procedure delaying the drilling 
operation for only a relatively short period of time. 
Upon drilling being restarted the outer component now rotates with the 
drilling rod assembly and the cutting elements 18 tend to cut rock from 
around the borehole sides to increase the borehole diameter in the 
vicinity of the rotating drill bit. The adaptor which tends to lie on the 
floor of the borehole tends to follow the newly formed floor of the 
enlarged diameter borehole and thereby the rotating drill bit tends to 
follow a lower cutting horizon within the rock strata and the newly formed 
section of the borehole tends to follow a downwardly inclined direction. 
Upon the borehole approaching a maximum desired depth in the rock strata 
the probe activating tool 50 once more is fed along the passageway 2 
defined by the drill rod assembly 1, the tool being fitted with the probe 
65. The thrust exerted by the pressure fluid on the tool 50 is sufficient 
for the probe 65 to move the bush 35 along the slideway 36 against the 
action of the springs 37 and 38, the bush being moved away from the 
abutment stop 66 sufficiently for the lip 42 of the latch 34 to engage in 
the recesses 43 (as indicated in FIG. 2). Upon the lip entering the recess 
the bush 35 is locked in its foremost position and the activating tool 50 
together with the probe 65 can be removed by hauling the wire secured to 
the eyelet 52. 
As the bush 35 is moved forwardly along the slideway 36 against the action 
of the springs 37 and 38 the same springs urge the finger element 30 to 
move forwardly along the axial bore of the inner component 10. 
This forward movement of the finger element 30 causes the element to engage 
the latches 20 which thereby are pivoted about the supports 21 to release 
the lips 23 from the recesses 22, the lips moving into a released position 
as indicated at 23a in FIG. 1. The latch means is retained in the released 
operational mode by the finger element 30 which is retained in its forward 
position under the actions of the compressed springs 37 and 38. 
In the described embodiment two separate springs 37 and 38 are provided 
because it is considered that in operation the stationary (ie 
non-rotating) latch means 20, 25, 26 may resist forward movement of the 
finger element along the axial bore of the inner component. It is foreseen 
that the spring 37 will take up the full forward movement of the bush 35 
to allow the latch 34 to engage the recess 43 to retain the bush in its 
forward position. Upon the drilling operation restarting following the 
removal of the activating tool 50 it is anticipated the rotary movement of 
the inner component will free the latch means 20, 25, 26 and allow the 
finger element to move to its fully advanced position under the action of 
the springs 37 and 38, the spring 38 becoming fully compressed. 
With the latch means 20, 25, 26 in the released mode the inner component 10 
is free to rotate relative to the outer component 16 and as previously 
explained the drill bit tends to be directed along an inclined upward 
path. 
Thus, by use of the drill equipment constructed in accordance with the 
present invention it is possible to guide the borehole to within a desired 
accuracy, the adaptor being urged from one operational mode to its other 
operational mode relatively quickly and simply. 
In order that the pressurised drilling fluid can reach the drill bit during 
the drilling operation to adequately lubricate and cool the drill bit as 
well as to wash away particles of rock produced during drilling annular 
seals 80 are provided between the inner and outer components 10 and 16. 
In other embodiments of the invention remotely operated means are provided 
on the steering adaptor for moving the latch means between its two 
operational modes, the means being controlled by remote control means 
located remote from the borehole.