Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Downhole Core Orientation Tool
Field of the Invention
The present invention relates to a downhole tool and more
particularly to a downhole core orientation tool for
providing an indication of the orientation of a ground
core sample cut by a core drill.
Background of the Invention
Core sampling is used to enable geological surveying of
the ground for various purposes including exploration,
mine development and civil construction. Analysis of the
material within the core sample provides information of
the composition of the ground. Visual inspection of the
core also enables a geologist to map ore veins and
boundaries between different types of minerals. However
to do so it is necessary to precisely know the orientation
of the core relative to the ground from which it was cut.
The present inventor has developed core orientation
devices and systems which enable a geologist to precisely
determine the orientation of a core relative to the ground
sample. Such devices are disclosed in International
publication No. WO 03/038232 and International Publication
No. WO 05/078232. The orientation devices in the
aforementioned documents comprise in broad terms, a face
orientator and a bottom orientator. The face orientator
enables rotational matching of the core sample to the
orientation device. The bottom orientator provides an
indication of the lowest position in the hole from which
the core is cut. With this information a geologist is
able to rotate the core once extracted from the ground to
a position commensurate with its position prior to being
cut.
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The present invention has been developed as an enhancement
of the aforementioned devices.
It is to be understood that, if any prior art publication
is referred to herein, such reference does not constitute
an admission that the publication forms a part of the
common general knowledge in the art, in Australia or any
other country.
In the claims of this application and in the description
of the invention, except where the context requires
otherwise due to express language or necessary
implication, the words "comprise" or variations such as
"comprises" or "comprising" are used in an inclusive
sense, i.e. to specify the presence of the stated features
but not to preclude the presence or addition of further
features in various embodiments of the invention.
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Summary of the Invention
According to one aspect of the present invention there is
provided a core orientation tool for a core drill having a
core bit at a downhole end and a retrievable core tube for
receiving a core cut by said drill, said orientation tool
comprising:
a stopping system comprising a tubular stop body and a
ring extending about an outer circumferential surface of
said stop body, said ring having an expanded state where
said ring stops said stop body from passing through said
core tube and a relaxed state where said stop body can
pass through said core tube;
a trigger body extending from a downhole end of said stop
body and slidable relative to said stop body, said trigger
body extending beyond said core bit prior to commencement
of drilling; and,
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a bottom orientator providing an indication of the
location of a bottom of said core, said bottom orientator
provided with one or more orientation balls, each
orientation ball having a first state where said
orientation ball is free to move and a second state where
said orientation ball is held in position;
said bottom orientation and stopping system operatively
associated with said trigger body whereby when said
trigger body is moved from a first position to a second
position by lowering of said drill so that said
orientation tool contacts a face of said core to be cut,
the state of said orientation balls is changed from said
first state to said second state and the state of said
ring is changed from said expanded state to said relaxed
state so that as a core is cut by said drill, said core
pushes said orientation tool in an uphole direction
through said core tube.
Preferably said core orientation tool further comprises a
face orientator coupled to said trigger body, said face
orientator initially disposed forward of said trigger body
when said trigger body is in said first position, to
provide, by contact with said face, an indication of the
rotational position of the core relative to the tool.
Preferably said stop system further comprises:
a seat supported on said stop body and on which said stop
ring is seated when in said expanded state and, a
mechanism which holds said stop ring on said seat prior to
said trigger body reaching said second position, and
allows said stop ring to separate from said seat and
change to said relaxed state when said trigger body
reaches said second position.
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Preferably said mechanism comprises:
one or more stop balls retained in said stop body, and an
outer circumferential surface of said trigger body against
which each stop ball bears; said outer circumferential
surface of said trigger body having a first length of
constant outer diameter and a circumferential groove of
reduced outer diameter, wherein each stop ball bears
against said first length prior to said trigger body
reaching said second position, whereby each stop ball
extends radially of said trigger body preventing said stop
ring from separating from said seat, and after the trigger
body reaches said second position, each stop ball retracts
radially inward into said groove allowing said stop ring
to separate from said seat and change from said expanded
state to said relaxed state.
Preferably said mechanism further comprises a stop locking
sleeve disposed about said stop body, said stop locking
sleeve held against said stop ring and said seat by each
stop ball thereby holding said stop ring in said expanded
state prior to said trigger body reaching said second
position, and wherein after said trigger body reaches said
second position each stop ball retracts into said groove
and said stop locking sleeve slides away from said ring
and said seat over each of said stop balls allowing said
core tube to push said ring off said seat and said stop
locking sleeve over each of said stop balls, locking said
trigger body to said stop body.
Preferably said core orientation tool further comprises: a
shaft retained in said trigger body, and coupled at one
end to said face orientator; a trigger spring acting
between said shaft and said trigger body to bias said
shaft in an uphole direction relative to said trigger
body; and, one or more trigger balls locking said trigger
body to said shaft when said trigger body is in said first
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position for an initial distance of travel of said trigger
body relative to said stop body until said trigger body
reaches an intermediate position, at which said trigger
balls release said shaft from said trigger body allowing
said spring to advance said shaft in said uphole direction
relative to said trigger body, thereby retracting said
face orientator into said trigger body so that said
trigger body can contact said face of said core.
Preferably said trigger balls relock said shaft to said
trigger body when said trigger body reaches said second
position.
Preferably said bottom orientator comprises a ball race
for each of said orientation balls, each race comprising a
pair of opposing surfaces mounted on said shaft and
between which a respective orientation ball resides, said
opposing surfaces moveable relative to each other along
said shaft between a free position where said orientation
ball is in first state and a clamped position where said
orientation ball is in said second state, said shaft
acting to move said opposing surfaces to said clamped
position after said trigger body reaches said second
position.
According to another aspect of the invention there is
provided a downhole tool comprising:
a stopping system comprising a tubular stop body and a
ring extending about the stop body, the ring moveable
between an expanded position where the ring has a first
outer diameter and a relaxed position where the ring has a
second outer diameter less than the first outer diameter;
a trigger body extending from a downhole end of the stop
body and slidably retained in the stop body, the trigger
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body having a first length of a first outer diameter and a
groove of a reduced outer diameter; and,
one or more stop devices retained by the stop body and
disposed about the trigger body, each stop device
extending through the stop body to stop the ring from
moving from the expanded position to the relaxed position
when the one or more stop devices are in radial alignment
with the first length of the trigger body, and wherein the
one or more stop devices retract inwardly when in radial
alignment with the groove to allow the ring to move to the
relaxed position.
Optionally the downhole tool comprises a seat supported on
the stop body and on which the stop body is seated when in
the expanded state.
Optionally the downhole tool further comprises a stop
locking sleeve disposed about the stop body, the stop
locking sleeve held against the seat by the one or more
stop devices when the one or more stop devices are in
radial alignment with the first length of the tubular body
thereby holding the ring in the expanded position; the one
or more stop devices being free to retract from the stop
locking sleeve when in radial alignment with the groove
whereby the stop locking sleeve can slide away from the
stop body to allow the ring to move off the stop body and
into the relaxed position.
Optionally each of the one or more stop devices comprises
a ball.
Optionally the downhole tool further comprises a bottom
orientator providing an indication the location of a
vertically lowest point in a vertical plane intersecting
the downhole tool, the bottom orientator provided with one
or more orientation balls, each orientation ball having a
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first state where the orientation ball is free to move and
a second state where the orientation ball is held in
position.
Optionally the downhole tool further comprises a face
orientator coupled to the trigger body, the face
orientator initially disposed forward of the trigger body,
the face orientator providing, by contact with a toe of
the hole in which the downhole tool is placed, an
indication of the rotational position of the toe of the
hole relative to the downhole tool.
Optionally the downhole tool further comprises a shaft
retained in the trigger body;
a trigger spring acting between the shaft and the trigger
body to bias the shaft in an uphole direction relative to
the trigger body; and,
one or more trigger balls locking the trigger body to the
shaft in a first relative juxtaposition when the trigger
body is in a first position for an initial distance of
travel of the trigger body relative to the stop body until
the trigger body reaches an intermediate position, at
which the trigger balls release the shaft from the trigger
body allowing the trigger spring to advance the shaft in
the uphole direction relative to the trigger body.
In one embodiment the shaft comprises first and second
axially spaced recesses, the first recess being disposed
nearer an uphole end of the tool and the one or more
trigger balls are retained in the trigger body, the one or
more trigger balls partially sealed in the first recess
when the trigger body is in the first position, partially
sealed in the second recess when the trigger body is in a
second position and between the first and second recesses
when the trigger body is in the intermediate position.
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Optionally the bottom orientator is operatively associated
with the trigger body whereby when the trigger body slides
inwardly of the stop body from the first position to the
intermediate position, the state of the orientation balls
is changed from the first state to the second state.
Optionally the face orientator is coupled at a downhole
end of the shaft, the face orientator being retracted into
the trigger body when the trigger balls are in the
intermediate position.
In one embodiment the bottom orientator comprises a ball
race for each orientation ball, each race comprising a
pair of opposing surfaces mounted on the shaft and between
which a respective orientation ball resides, the opposing
surfaces moveable relative to each other along the shaft
between a free position where each orientation ball is in
the first state and a clamped position where each
orientation ball is in the second state, the shaft acting
to move the opposing surfaces to the clamped position
after the trigger body has reached a second position.
Optionally the downhole tool further comprises a race
spring disposed about the shaft between a shoulder on the
shaft and the ball races, the shoulder contacting the race
spring when the shaft is in the second position, the race
spring biasing the opposing surfaces of the ball springs
to the clamped position.
Brief Description of the Drawings
An embodiment of the present invention will now be
described by way of example only with reference to the
accompanying drawings in which:
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Figure 1 is a section view of an embodiment of the tool in
a first stage of operation;
Figure 2 is a section view of the tool in a second stage
of operation;
Figure 3 is a section view of the tool in a third stage of
operation;
Figure 4 is a partial cut-away view of the tool in the
first stage of operation.
Detailed Description of Preferred Embodiment
Figure 1 illustrates an embodiment of a downhole tool and
more particularly a core orientation tool 10 for a core
drill (not shown) having a core bit of conventional
construction at a downhole end and a retrievable core tube
for receiving a core cut by the drill. Typically the core
tube includes an internal core lifter case which is used
to grip the core after drilling has ceased to allow the
application of a tensile force by lifting of the drill
thereby breaking the core from the ground from which it is
cut.
The orientation tool 10 comprises a stopping system 12, a
trigger body 14 and a bottom orientator 16. The stopping
system 12 comprises a tubular stop body 18 and a ring 20
extending about an outer circumferential surface of the
stop body 18. The ring 20 has an expanded state (shown in
Figures 1 and 2) where the ring 20 prevents or otherwise
stops the tool 10 from passing through the core tube of
the drill in which the tool 10 is loaded, and a relaxed
state, shown in Figure 3, where the stop body 12 and
indeed the tool 10 can pass through the core tube. That
is, when the ring 20 is in the expanded state shown in
Figure 1, the outer diameter of the ring 20 is greater
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than the inner diameter of the core tube (incorporating a
core lifter case)thereby preventing the tool 10 from being
pushed upwardly in the uphole direction. Whereas, when
the ring 20 is in the relaxed state shown in Figure 3, it
has a reduced outer diameter enabling the ring 20 and the
associated stop body 18 and tool 10 to pass through the
core tube.
The trigger body 14 extends from a downhole end 22 of the
stop body 18 and is slidable relative to the stop body 18.
The trigger body 14 also extends beyond the core bit of
the core drill prior to the commencement of drilling. The
bottom orientator 16 provides an indication of the
location of the bottom of the core cut by the drill. The
"bottom of the core" is in reality an axial line
corresponding with the lowest point along the length of
the hole from which the core is cut. The bottom
orientator 16 is provided with one or more (in this case
three)orientation balls 24. Each orientation ball 24 has
a free state (shown in Figure 1) where it is able to
freely roll within a corresponding race 26 under the
influence of gravity, and a second state (shown in Figure
3) where each ball is held or fixed in position. The
bottom orientator 16 and the stopping system 12 are
operatively associated with the trigger body 14 so that
when the trigger body 14 is moved from a first position
(shown in Figure 1) to a second position (shown in Figure
3) by lowering of the drill in which the tool 10 is
loaded, so that the tool 10 contacts the face of the core
to be cut, the state of the orientation balls 24 is
changed from the first state to the second state, and the
state of the ring 20 is changed from the expanded state to
the relaxed state. Thus, by simply lowering the drill so
that the tool 10 contacts the face of the core to be cut,
the motion of the trigger body 14 places the orientation
balls in the second state thereby providing an indication
of the lowest axial line in the hole from which the core
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is to be cut, and changes the state of the ring 20 to the
relaxed state shown in Figure 3 so that upon cutting of
the core, the advancing core can push the entire tool 10
in an uphole direction through the core tube.
In order to match the position of the lowest line in the
hole from which the core is cut, indicated by the position
of the clamped orientation balls 24, it is necessary to
rotationally align the tool 10 with the core which has
been cut. This is achieved by use of a face orientator 28
which is coupled to the trigger body 14 via a shaft 96.
The face orientator provides an indication of the
rotational position of the core relative to the tool 10 by
physical contact with the face of the core prior to the
commencement of drilling.
Looking at the components of the tool 10 in more detail,
the stop body 18 is in the form of a short tube provided
with a number of holes 30 near, but in board of its
downhole end 22, each hole 30 retaining a corresponding
stop ball 32. Typically three holes 30 and corresponding
stop balls 32 are provided in the stop body 18 at evenly
spaced locations about the circumference of the body 18.
A longitudinal slot 34 (shown in Figure 1) is also formed
in the stop body 18 in which is partially seated a lock
ball 36 (shown in Figure 4). An inner circumferential
surface of the stop body 18 has: a first portion 38 of a
first diameter, which is dimensioned to provide an annular
space 40 between portion 38 and an outer diameter of the
trigger body 14; a second portion 42 of progressively
decreasing diameter; a third portion 44 of a constant
diameter marginally less than the outer diameter of the
trigger body 14; an arcuate portion 46; and, a portion 48
again of constant outer diameter dimensioned to define
with the outer diameter of the trigger body 14 an annular
space 50. Waterways 51 are also formed in the body 18 to
allow for the passages of liquids
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The stop system 12 further comprises a seat 52 which is
held within a circumferential groove 54 formed about the
outer diameter of the body 18. The seat 52 is provided at
its uphole end with a radially extending lip 56 which
prevents the ring 20 from passing in the uphole direction
over the seat 52. A stop locking sleeve 58 is also seated
about the outer circumference of the body 18 between the
seat 52 and the downhole end 22 of the body 18. The
sleeve 58 and stop balls 32 together form a mechanism that
holds the ring 20 in the expanded state on the seat 52
prior to the trigger body 14 reaching its second position.
However, as shown in Figure 3 when the trigger body 14
reaches the second position, the sleeve 58 is able to
separate from the seat 52 allowing the ring 20 to be
pushed off the seat 52 by action of abutment with the core
tube or more particularly, a core lifter case within the
tube.
The trigger body 14 includes a tubular portion 60 which is
able to slide axially relative to the stop body 18.
Inboard of an uphole end 62 of the tubular portion 60 is a
plurality of holes 63 each of which retains a
corresponding trigger ball 64. The outer circumference of
the tubular portion 60 has a first (and major) length 66
of constant outer diameter and, on the downhole side
thereof, a circumferential groove 68 of reduced diameter.
The groove 68 leads to a head 70 on which is attached a
shroud 72.
An uphole end of the stop body 18 is coupled internally of
a main body 74 of the tool 10. The body 74 is provided
with an internal cavity 76 which houses a coil spring 78.
A guide tube 80 is also held within the main body 74 and
is provided with a flange 82 that sits on an uphole end 84
of the main body 74. The tube 82 houses a coil spring 86.
A portion 88 of the main body 74 adjacent the uphole end
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of the body 18 has an inner diameter that is greater than
the inner diameter of the portion 48 of the body 18.
Waterways 90 are cut in the main body 74 and communicate
with the waterways 51 of the stop body 18 to provide a
flow path for fluids such as water through the tool 10.
An orientation body 92 is attached to an end of the main
body 74 distant the stop body 18. The orientation body 92
houses the bottom orientator 16 which comprises three
spaced apart and axially aligned washers 94a, 94b and 94c
(hereinafter referred to in general as "washers 94"). The
washers 94 are slidably supported on the shaft 96. With
the trigger body 14 in the first position shown in Figure
1, the washers 94 are spaced apart by respective springs
98a, 98b and 98c (hereinafter referred to in general as
"springs 98") which are disposed about the shaft 96. The
ball race 26a is formed between opposing faces of washers
94a and 94b respectively; the race 26b is formed between
the opposing surfaces of washers 94b and 94c respectively;
and, the ball race 26c is formed between the opposing
surface of washer 94c and a plug member 100 which is fixed
to an uphole end of the orientation body 92 by a screw
102.
The plug member 100 is formed with an axial passage 104 in
which slides an end cap 106 screwed to an uphole end 108
of the shaft 96.
An anchor system 110 is attached to the plug member 100
and acts to anchor the tool 10 on an internal surface of
the core tube, preventing the tool 10 from falling out of
the core tube by the action of gravity.
The anchor system 110 comprises an anchor body 112 which
receives a portion of the end plug 100 and, seats about
its outer diameter an anchor sleeve 114 which is able to
move axially relative to the anchor body 112 to a position
limited in the uphole direction by a stop ring 116 seated
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in a groove 118 formed near an uphole end of the body 112.
Anchor spring 120 is seated on the outer diameter of the
anchor body 112 and resides between a shoulder 122 formed
in the anchor body and an internal seat 124 formed in the
anchor sleeve 114. The spring 120 biases the anchor
sleeve 114 in an uphole direction to abut the stop ring
116. A plurality of anchor balls 126 are retained in the
anchor sleeve 114 but have respective portions that extend
radially from the anchor sleeve 114 when the anchor sleeve
is abutted against the stop ring 116. In this position
the anchor balls 126 are in contact with a constant outer
diameter portion 128 of the anchor body 112. However
moving in a downhole direction from the constant diameter
portion 128 the anchor body 122 is formed with a further
portion 130 of progressively reducing outer diameter.
The shaft 96 extends through the trigger body 14, guide
tube 80, washers 94 and into the passage 104 of the plug
member 100. A downhole end 132 of the shaft 96 is
attached by a grub screw 134 to the face orientator 28.
In this particular embodiment, the face orientator 28 is
in the style of a VAN RUTH orientator comprising a
plurality of elongate circumferentially arranged pins 136
which are retained in, and can slide axially of, a core
block 138. The core block 138 is formed with a pair of
parallel spaced apart radial flanges 140 through which
each pin 136 extends. A plurality of rubber bands or 0-
rings (not shown) extend about the pins 136 between the
flanges 140 to act as a brake holding the pins 136 in
position in the absence of a force applied along the
length of the pins 136.
A pin 142 is held within the head 70 of the trigger body
14 and extends transversely into a longitudinal slot or
keyway 144 formed near the downhole end 132 of the shaft
96. The engagement of the pin 142 in a slot 144 prevents
relative rotational motion between the shaft 96 (and thus
the face orientator 28) and the trigger body 14. Relative
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rotational motion between the trigger body 14 and the stop
body 18 (and thus also the main body 74) is prevented by
the lock ball 36 which resides within the slot 34 formed
in the stop body 18, and a parallel underlying slot 146
formed in the tubular portion 60 of the trigger body 14.
The shaft 96 comprises to separate rods 148 and 150 which
are screw-coupled together. Trigger spring 152 is
disposed about the rod 148 inside the trigger body 14. A
downhole end of the spring 152 abuts an internal shoulder
154 formed in the tubular portion 60 adjacent the head 70.
An uphole end of the spring 152 abuts an increased
diameter portion 156 of the rod 148. The increased
diameter portion 156 is formed with a first
circumferential recess 158 at an end near the rod 150, and
a second axially spaced recess 160 formed nearer the
downhole end of the shaft 96.
A plurality of rubber 0-rings or seals 162 (see Figure 2)
are provided in the rod 150, main body 74, flange 82, plug
member 100 and end cap 106. These 0-rings or seals 162
prevent the escape of a light oil (not shown) held within
the orientation body 92 and which envelopes the
orientation balls 24.
The orientation body 92 comprises an inner clear
polycarbonate sleeve 164 which extends between the main
,
body 74 and the plug member 100; and, an overlying outer
stainless steel sleeve 166. The sleeve 166 provides
protection to the polycarbonate sleeve 164. After the
tool 10 has been used, the outer stainless steel sleeve
166 is removed so that the position of the balls 24 can be
viewed through the clear polycarbonate sleeve 164.
Neither of the sleeves 164 or 166 is designed to bear any
substantial axial load.
The operation of the tool 10 will now be described.
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The orientation tool 10 when initially inserted into a
core tube is in the configuration shown in Figure 1, with
the pins 136 of the face orientator 28 extending from a
downhole end of the shroud 72, the shaft 96 locked to the
trigger body 14 by virtue of the trigger balls 64 being
seated in the first circumferential recess 158 and bearing
against the portions 46 and 48 of the inner surface of
stop body 18, the ring 20 in the expanded state seated on
the seat 52 and held in that state by the combination of
the sleeve 58 and stop balls 32; the spring 152 in a
relatively compressed state and the springs 78, 86, 98 and
120 in a relatively expanded state. The spring 120, being
in a relatively expanded state, urges the anchor sleeve
114 against the ring 116 so that the anchor balls 126 ride
on the constant diameter portion 128 of the anchor body
112.
The tool 10 is loaded into a downhole end of the core tube
by first inserting the anchor body 112. The anchor system
110 is arranged so that when the anchor sleeve 114 abuts
against the ring 116, the balls 126 extend radially at a
distance greater than the internal diameter of the core
tube. Therefore initially the anchor sleeve 114 slides
axially away from the ring 116 so that the anchor balls
126 ride along the portion 130 having a progressively
reduced outer diameter. This causes the balls 126 to
effectively move radially inward reducing the radial
extent of the balls 126 so that they can now enter the
core tube, thereby allowing the orientation tool 10 to be
inserted into the core tube. The tool 10 is inserted into
the core tube until the ring 20 abuts a downhole end of
the core tube (and more particularly the core lifter case
within the core tube). The anchor spring 120 is
continually biasing the anchor sleeve 114 in an uphole
direction urging the balls 126 to ride up the tapered
portion 130 to a position where they bear against the
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inner diameter of the core tube. This effectively anchors
the orientation tool 10 to the core tube thus preventing
it from falling out. It should be appreciated that any
force applied to the orientation tool 10 in a downhole
direction further wedges the balls 126 against the inner
diameter of the core tube. Further, by appropriate
selection of the spring 120, the anchor system 110 also
provides a braking effect against motion of the tool in an
opposite direction. The degree of braking effect is
dependent on the spring constant of the spring 120. This
braking effect is particularly useful when the tool 10, or
another tool to which a similar braking system is applied
is used in an uphole configuration to reduce the speed of
the tool 10 or other tool when travelling back under the
influence of gravity.
The core tube is then lowered into a core drill via a
conventional wire line, with the core drill being
suspended above a toe of the hole to be drilled. With the
core tube seated within the core drill, the pins 136 of
the face orientation 128, and the shroud 72 of the trigger
body 14 extend axially beyond and through a core bit
attached to the core drill. Prior to imparting torque to
the drill, the drill is lowered onto the toe of the hole.
This results in the pins 136 contacting the toe of the
hole which will form a face of the core to be drilled.
Accordingly the pins 136 slide axially in an uphole
direction to positions which correspond with the profile
of the core face. This continues until the toe of the
hole (ie face of the core to be cut) contacts a downhole
end of the shroud 72. Now the load (ie the weight) of the
core drill is transferred onto the trigger body 14 causing
the trigger body 14 to slide axially in an uphole
direction relative to the stop body 18. Since the shaft
96 is locked to the trigger body 14 by virtue of the
trigger balls 64 sitting in the groove 158, the shaft 96
moves axially in an uphole direction in unison with the
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trigger body 14. As this occurs, the trigger balls 64
roll along the portion 48 of the internal diameter of the
stop body 18. Eventually the balls 64 roll out of the
stop body 18 and into the portion 88 of the main body 74.
The portion 88 has an increased outer diameter in
comparison with the portion 48. Thus, the balls 64 are
able to move in a radially outward direction and disengage
from the circumferential recess 158. The shaft 96 is now
released from the trigger body 14. When this occurs, the
spring 152 is able to expand thereby causing the shaft 96
to slide axially in an uphole direction relative to the
trigger body 14. This in turn acts to retract the face
orientator 28 to a position wholly within the shroud 72 as
indicated in Figure 2.
The action of the spring 152 causes the shaft 96 to slide
axially to a position where the second circumferential
recess 160 is located adjacent the trigger balls 64.
Additionally, the shaft 96, and in particular the rod 150
is positioned so that the race spring 86 now applies a
light pressure or bias to the washers 94, causing them to
concertina in the uphole direction against the bias of
springs 98. This in turn leads to a reduction in the
width of the races 26 within which the orientation balls
24 ride. However it may not be sufficient to place the
orientation balls 24 in the second state where they are
clamped from rotation within their respective races 26.
With reference to Figure 3 lowering of the core drill
forces the trigger body 14, shaft 96 and trigger balls 64
to move in an uphole direction relative to the stop body
18. As a consequence, the trigger balls 64 commence to
ride up the inner diameter of the main body 74 onto the
reduced inner diameter portion 89. This causes the
trigger balls 64 to move radially inward and seat in the
circumferential groove 160, effectively relocking the
trigger body 14 to the shaft 96. This motion further
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causes the shaft 96 to travel in an uphole direction
relative to the orientation body 92 so that the pressure
applied by the spring 86 to the washers 94 increases to
the extent that the orientation balls 24 are now
effectively clamped and placed in a second position where
they are no longer able to rotate within their respective
races 26. Shortly thereafter, the continued lowering of
the drill onto the toe of the hole causes the trigger body
14 to slide relative to the anchor body 18 to a position
where the grooves 68 underlies the stop balls 32. The
stop balls 32 are now free to move radially inward to a
position where they no longer hold the stop lock sleeve
58. As a result, the core tube, which abuts the ring 20
is now able to slide the ring 20 off the seat 52 in a
downhole direction. The ring 20, being in the form of a
snap ring relaxes or contracts about the outer diameter of
the body 18 thereby reducing its outer diameter, and the
sleeve 58 slides over the stop balls 32 as shown in Figure
3. The stop balls 32, being retained by the stop body 18
and seated in the groove 68, lock the trigger body 14 to
the stop body 18. Due to the contraction of the ring 20,
continued lowering of the core drill 20 now results in the
tool 10 being effectively pushed in an uphole direction
within the core tube.
The core drill is further lowered onto the toe of the hole
until the core bit contacts the toe of the hole. The
occurrence of this event is indicated in a conventional
manner.
Torque may now be applied to the drill causing a core to
be cut. As the core is cut it advances into the core tube
pushing the entire orientation tool 10 inwardly of the
core tube.
Once drilling has ceased, and the core has been broken by
the lifting of the core drill, the core tube with the
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orientation tool 10 and core sample is retrieved by a
conventional wire line. The orientation tool 10 together
with the core sample are removed from the core tube and
the shroud 72 detached from the head 70 of the trigger
body 14. The sleeve 166 is also removed from the
orientation body 92.
The tool 10 and the core sample are rotationally aligned
by matching the profile of the pins 136 to the face of the
core. The outer circumference of the core is now marked
with a line collinear with the position of the clamped
orientation balls 24, which can be viewed through the
transparent sleeve 164. The line marked on the outer
diameter of the core denotes the bottom of the core.
The core block 138 can be removed from the tool 10 by
unscrewing of the grub screw 134 and kept with the core
sample as a permanent record of the core orientation. To
this end, the core block 138 should also be marked with a
line in alignment with the balls 24. It is further
advantageous for the core block 138 to be made from a
relatively cheap material such as a plastics material.
Now that an embodiment of the present invention has been
described in detail it will be apparent to those skilled in
the relevant arts that numerous modifications and variations
may be made without departing from the basic inventive
concepts. Most notably, if desired, the face orientator 28
may also be provided with a marker such as a pencil for
producing a mark on the face of the core to be drilled.
This produces a degree of redundancy in the face marker 28
whereby the mark produced by the pencil together with the
profile of the pins 136 may be used to match the rotational
position of the tool 10 to the core. In the event that the
mark produced by the pencil and the profile of the pins 136
do not coincide, a geologist will be given an indication
that the orientation of the core is unreliable and therefore
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should not be used. Alternately, all of the pins 136 may
simply be replaced by a single pencil or other marker to
produce mark on the face of the core.
It is further possible to modify the face orientator 28 in a
manner similar to that described in relation to co-pending
International Publication No. WO 05/078232 so as to include
a demountable disc and face marker, such as a pencil. The
demountable disc would be seated on the shaft 132 within the
shroud 72 and marked simultaneously with the core by the
marker. The disc can subsequently be marked after retrieval
of the core with a mark in alignment with the orientation
balls 24. Thus the demountable disc will bear both a mark
in alignment with the mark produced on the core face by the
marker, and a second mark in alignment with the orientation
balls 24 providing an indication of the location of the
bottom of the core. The demountable disc may then be held
as a permanent record of the core sample.
All such modifications and variations together with others
that would be obvious to a person of ordinary skill in the
art are deemed to be within the scope of the present
invention the nature of which is to be determined from the
above description.
