Note: Descriptions are shown in the official language in which they were submitted.
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Borehole Surveying Tool Deployment
FIELD OF THE INVENTION
(0011 This invention relates to borehole surveying operations. In
particular
the invention relates to core sampling in borehole surveying operations.
BACKGROUND ART
[0002] The following discussion of the background art is intended to
facilitate
an understanding of the present invention only. The discussion is not an
acknowledgement or admission that any of the material referred to is or was
part
of the common general knowledge as at the priority date of the application.
[0003] There is a need for core sampling in borehole surveying operations.
[0004] Core samples are obtained through core drilling operations. Core
drilling is typically conducted with a core drill comprising outer and inner
tube
assemblies. The inner tube assembly comprises a core inner tube. A cutting
head is attached to the outer tube assembly so that rotational torque applied
to
the outer tube assembly is transmitted to the cutting head. A core is
generated
during the drilling operation, with the core progressively extending along the
core
inner tube as drilling progresses. When a core sample is required, the core
within the core inner tube is fractured. The inner tube assembly and the
fractured core sample contained therein are then retrieved from within the
drill
hole, typically by way of a retrieval cable (which is commonly referred to as
a
wireline) lowered down the drill hole. Once the inner. tube assembly has been
brought to ground surface, the core sample can be removed from the core inner
tube and subjected to the necessary analysis.
[0005] The inner tube assembly further comprises a backend assembly
which includes a spearhead point releasably engagable with an overshot
attached to, the end of the wireline. With this arrangement, the inner tube
assembly can be lowered into, and retrieved from, the outer tube assembly and
the drill string to which the outer tube assembly is connected.
[0006] During a borehole drilling operation there is a need to survey the
path
of the borehole to determine if the trajectory is being maintained within
acceptable limits. Surveying a borehole is usually accomplished using a
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surveying tool which is moved along the borehole to obtain the information
required, or at least data from which the required information can be
determined.
Information in relation to the path of a borehole can typically include
inclination,
azimuth and depth.
[0007]
Surveying tools typically contain sensor devices for measuring the
direction and magnitude of the local gravitational field, the Earth's magnetic
field
and/or the rate of rotation of the Earth. These measurements correspond to the
position and orientation of the surveying tool in the borehole. The position,
inclination and/or azimuth can be calculated from these measurements.
[0008] The
sensor devices can comprise accelerometers for measuring the
direction and magnitude of the local gravitational field, magnetometers for
measuring the Earth's magnetic field and/or gyroscopes for measuring the rate
of
rotation of the Earth, from which azimuth can be calculated.
[0009]
Typically, the core drilling operation is performed at an angle to the
vertical, and it is desirable for analysis purposes to have an indication of
the
orientation of the core sample relative to the underground environment from
which it was extracted. It is therefore important that there be some means of
identifying the orientation the core sample had within the underground
environment prior to it having been brought to the surface.
[0010] Core
orientation devices are used to provide an indication of the
orientation of the core sample.
[0011] The applicant's International application PCT/AU2011/000628
discloses a down hole surveying system for directional surveying of boreholes.
The down hole surveying system is configured as a tool comprising a body which
is 'sized and shaped for movement along a borehole in down hole surveying
applications. The body accommodates sensor devices comprising a gyroscope
and an accelerometer.
[0012] Downhole
surveying operations and core retrieval are typically
conducted as separate operations. In particular, it is customary to perform a
surveying operation once the inner tube assembly has been removed from the
=
drill pipe/rod during retrieval of a core sample. This involves retrieving the
inner
tube assembly using an overshot attached to the end of the wireline, and then
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=
lowering a down hole survey instrument into the borehole to perform the
surveying operation. The surveying instrument is then raised and removed from
the borehole and the inner tube assembly returned into position for the next
core
sampling operation.
[0013]
Consequently, there is downtime for both downhole surveying
operations and core retrieval.
[0014] In would
be advantageous for there to be at least some coordination
between downhole surveying and core retrieval operations to thereby reduce
downtime while the procedures are being performed.
[0015] Also,
orientation of a bottom hole assembly and more recently core
sample has been performed by using gravity based sensors, namely -
accelerometers, in angled/inclined drill hole applications, These systems have
been able to orientate a pre-determined tool face of a bottom hole assembly
down the borehole with a survey instrument by referencing the tool face of the
bottom hole assembly to the known top dead centre position as determined by
gravity based sensors.
[0016] In
vertical drilling applications where the inclination of the bottom hole
assembly is within 5 degrees of the vertical plane it is not possible to use
gravimetric sensors as a reference to top dead centre with any acceptable
accuracy. In such
applications, magnetic based sensors such as
magnetometers can be used to reference the bottom. hole assembly tool face to
magnetic North but are subject to influence from magnetic sources such as the
formation being drilled and the bottom hole assembly itself. The use of non-
magnetic materials to manufacture the bottom hole assembly can. overcome the
magnetic influence from the bottom hole assembly but are still subject to
influence from the information and this can render such a system inaccurate.
SUMMARY OF THE INVENTION
[0017] It is an
object of the present invention to overcome, or at least
ameliorate, one or more of the deficiencies of the prior art mentioned above,
or to
provide the consumer with a useful or commercial choice.
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[0018] Other objects and advantages of the present invention will become
apparent from the following description; taken in connection with the
accompanying drawings, wherein, by way of illustration and example, a
preferred
embodiment of the present invention is disclosed.
[0019] According to a first broad aspect of the present invention there is
provided an apparatus for use in a downhole survey in conjunction with core
sampling, the apparatus comprising a body adapted to receive a clOwnhole
surveying instrument, whereby the downhole surveying instrument can be
conveyed along a borehole with the apparatus and operated in the borehole.
[0020] The downhole surveying instrument may comprise a downhole survey
tool or a component thereof.
[00211 The downhole surveying instrument may, for example, cornprise a
downhole tool comprising one or more sensor devices such as orthogonal
accelerometers, magnetometers, gyroscopes, MEMS (microelectromechanical)
gyro sensors, or any combination thereof.
[0022] A suitable downhole surveying instrument may comprise the
downhole tool as described and illustrated in International application
PCT/AU2011/000628, the contents of which are incorporated herein by way of
reference. Other appropriate downhole tools can, of course, also be used.
[0023] Where the downhole surveying instrument comprises a geo-magnetic
device, it may be necessary for the body, or at least relevant parts thereof,
to be
made of material or materials which do not interfere magnetically with the geo-
magnetic device. In particular, the body, or at least relevant parts thereof,
may
need to be made of material which is non-magnetic.
[0024] Where the downhole surveying instrument does not comprise a geo-
magnetic device, the body would not necessarily need to be made of materials
which are non-magnetic. The downhole surveying tool described and illustrated
in International application PCT/AU2011/000628 is an example of an
arrangement in which the body would not necessarily need to be made of
materials which are non-magnetic.
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[0025] The body
may incorporate a cavity for accommodating the downhole
surveying instrument.
[0026]
Preferably, the body is configured to facilitate installation of the
downhole surveying instrument in the cavity. The body may, for example, be
constructed in two or more parts, with one part being selectively separable
from
another part to provide access to the cavity.
[0027] = The body may be adapted to provide cushioning to afford some
impact protection for the surveying instrument. In particular, the body may be
configured to cushion impact forces following descent into .a borehole.
[0028] The
cushioning may be provided by a cushioning mechanism
incorporated in the body.
=
[0029] The
cushioning mechanism may comprise an elastic structure such as
a spring for absorbing a shock impact. The cushioning mechanism may further
comprise a shock absorber for damping the spring oscillations.
[0030] Magnetic
braking may be utilised to slow the apparatus as it
approaches the end of its descent into a borehole. The apparatus may for
example include at least a portion of a magnetic braking system for slowing
the
apparatus in this manner.
[0031] The
apparatus may have provision for controlled positioning thereof
within the borehole for operation of the surveying instrument. The controlled
positioning provides stable support within the borehole.
[0032]
Preferably, said provision for controlled positioning within the borehole
for operation of the surveying instrument comprises means for engaging the
surrounding portion of a drill string to provide stabilization with respect to
the drill
string.
[0033] The
engaging means may be adapted to support the apparatus within
the surrounding portion of the drill- string in a circumferentially centred
manner.
With such an arrangement, the engaging means may be configured as a
centraliser.
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[0034] The
engaging means may comprise radially disposed arms biased
outwardly to contact sides of the drill string, thus centrally positioning the
apparatus within the surrounding portion of the drill string. The arms may
each
include an outer contact portion configured for contact with the inner wall of
the
=
surrounding portion of the drill string. The outer contact portion may be of
any
appropriate form, such as a pad or a roller.
[0035] In one
arrangement, the engaging means may be configured to
engage the drill string for movement therealong as the apparatus is raised or
lowered within the borehole. With this arrangement, the engaging means may
comprise a fixed structure configured as a carriage for movement along the
internal wall of the drill string.
[0036] In
another arrangement, the engaging means may be adapted for
movement between collapsed and extended conditions, whereby in the collapsed
condition it is clear of the internal wall of the drill string for movement
therealong
and in the extended condition it is in engagement with the drill string for
controlled positioning of the apparatus within the borehole to provide stable
support for operation of the surveying instrument.
[0037]
Actuation means may be provided for actuating the engaging means.
The actuation means may be triggered by contact, or at least proximity,
between
the apparatus and another downhole member. By way of example, the actuation
of the engaging means may be triggered by contact between an inner tube
assembly and an overshot assembly.
[0038] The
actuation means may be of any appropriate form; for example, -
the actuation means may comprise a mechanical actuator or some other
arrangement such as magnetic switch, proximity detector or wireless
transmission system -
[0039] The
apparatus may also be adapted to initiate operation of the
downhole surveying instrument. By way of example, the apparatus may be
adapted to initiate operation of the downhole surveying instrument as it
approaches or completes the end of its descent into the borehole. In this
regard, =
the apparatus may comprise means such as a shock logger for measuring rapid
deceleration and transmitting a command to the downhole surveying instrument.
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[0040] The
apparatus may be of any appropriate form. The apparatus may,
for example, comprise an inner tube assembly of a core drill, an overshot
assembly, or an arrangement such as a sub or a drop tool assembly adapted for
attachment to an inner tube assembly and/or to an overshot assembly.
[0041]
According to a second broad aspect of the present invention there is
provided an inner tube assembly comprising a body having an upper portion
adapted for connection to a retrieval system and a lower portion adapted to
receive a core sample during a drilling operation, the body being adapted to
receive a downhole surveying instrument, whereby the downhole surveying
instrument can be conveyed along a borehole with the inner tube assembly and -
operated in the borehole.
[0042]
Preferably, the retrieval system comprises an overshot assembly
attached to the end of a wireline.
[0043]
Preferably, the upper portion of the body is configured for
engagement with the overshot assembly in known manner.
[0044]
Preferably, the overshot assembly incorporates means operable for
controlled positioning of the body within the borehole for operation of the
surveying instrument. The controlled positioning provides stable support
within
the borehole.
[0045] More
particularly, said, means operable for controlled positioning of
the body within the borehole comprises means for controlling positioning of
the
overshot assembly within the borehole. With this arrangement, it is the
controlled .positioning of the overshot assembly within the borehole that
effectively controls the position of the body within the borehole for
operation of
the surveying instrument by Virtue of the connection between the core tube
assembly and the overshot assembly. In other words, controlling the
positioning
of the overshot assembly within the borehole has the effect of controlling the
positioning of the core inner tube assembly, and hence the position of the
body
of the core inner tube assembly in which the downhole surveying instrument is
accommodated.
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[0046] The
means operable for controlled positioning of the body within the
borehole may comprise means for engaging the surrounding portion of a drill
string to stabilise the overshot assembly with respect to the drill string.
[0047] The
engaging means may be adapted to support the overshot
assembly within the surrounding portion of the drill string in a
circumferentially
centred manner. With such an arrangement, the engaging means may be
=
configured as a centraliser.
[0048] The
engaging means may comprise radially disposed arms biased
outwardly to contact sides of the drill string, thus centrally positioning the
overshot assembly within the surrounding portion of the drill string. The arms
may each include an outer contact portion configured for contact with the
inner
wall of the surrounding portion of the drill string. The outer contact portion
may
be of any appropriate form, such as a pad or a roller.
[0049] In
one arrangement, the engaging means may be configured to
engage the drill string for movement therealong as the overshot assembly is
raised or lowered within the borehole. With this arrangement, the engaging
= means may comprise a fixed structure configured as a carriage for
movement
= along the internal wall of the drill string.
[0050] In
another arrangement, the engaging means may be adapted for
movement between collapsed and extended conditions, whereby in the collapsed
condition it is clear of the internal wall of the drill string for movement
therealong
and in the extended condition it is in engagement with the drill string for
controlled positioning of the overshot assembly within the borehole to provide
stable support for operation of the surveying instrument.
[0051]
According to a third broad aspect of the present invention there is
provided an overshot assembly comprising a body having an upper portion
= adapted for connection to a wireline and a lower portion adapted to be
releasably
connected to an inner tube assembly, the body being adapted to receive a
downhole surveying instrument, whereby the downhole surveying instrument can
be conveyed along a borehole with. the overshot assembly and operated in the
borehole.
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[0052] The downhole surveying instrument may comprise a downhole survey
tool or a component thereof.
[0053] The downhole surveying instrument may, for example, comprise a
downhole tool comprising one or more sensor devices such as orthogonal
accelerometers, magnetometers, gyroscopes, MEMS (microelectromechanical)
gyro seniors, or any combination thereof. -
[0054] A suitable downhole surveying . instrument may comprise the
downhole tool as described and illustrated in International application
PCT/AU2011/000628, the contents of which are incorporated herein by way of
reference. Other appropriate downhole tools can, of course, also be used.
[0055] Where the downhole surveying instrument comprises a gee-magnetic
device, it may be necessary for the body, or at least relevant parts thereof,
to be
made of material or materials which do not interfere magnetically with the geo-
magnetic device. In particular, the body, or at least relevant parts thereof,
may
need to be made of material which is non-magnetic.
[0056] Where the downhole surveying instrument does not comprise a geo-
magnetic device, the body would not necessarily need to be made of materials
which are non-magnetic. The downhole surveying tool described and illustrated
in International application PCT/AU2011/000628 is an example of an
arrangement in which the body would not necessarily need to be made of
materials which are non-magnetic.
[0057] Preferably, the downhole surveying instrument is operable within
the
borehole while the overshot assembly is connected to the inner tube assembly.
[0058] Preferably, the overshot assembly further comprises means operable
for controlled positioning of the body within the borehole for operation of
the
surveying instrument.
[0059] The controlled positioning provides stable support within the
borehole.
[0060] The means operable for controlled positioning of the body within
the
borehole may comprise means for engaging the surrounding drill string to
stabilise the body.
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[0061] The
engaging means may be adapted to support the body within the
drill string in a circumferentially centred manner. With such an arrangement,
the
engaging means may be configured as a centraliser.
[0062] The
engaging means may comprise radially disposed arms biased
outwardly to contact sides of the drill string, thus centrally positioning the
body
within the drill string. The arms may each include an outer contact portion
configured for contact with the inner wall of the surrounding drill string.
The outer
contact portion may be of any appropriate form, such as a pad or a roller.
[0063] In one
arrangement, the engaging means may be configured to
engage the drill string for movement therealong as the overshot assembly is
raised or lowered within the borehole. With this arrangement, the engaging
meane may comprise a fixed structure configured as a carriage for movement
along the internal wall of the drill string.
[0064] In
another arrangement, the engaging means may be adapted for
movement between collapsed and extended conditions, whereby, in the collapsed
condition it is clear of the internal wall of the drill string for movement
therealong
and in the extended condition it is in engagement with the drill string for
controlled positioning of the body within the borehole to provide stable
support
for operation of the surveying instrument.
[0065] The body
may incorporate a cavity for accommodating the downhole
surveying instrument.
[0066]
Preferably, the body is configured to facilitate installation of the
= downhole surveying instrument in the cavity. The body may, for example,
be
constructed in two or more parts, with one part being selectively separable
from
another part to provide access to the cavity.
[0067]
Preferably, the body is adapted to provide cushioning to afford some
impact protection for the surveying instrument. In particular, the body is
preferably configured to cushion impact forces when ,moving into contact with
a
=
downhole inner tube assembly following descent on the wireline.
[0068] The
cushioning may be provided by a cushioning mechanism
incorporated in the body.
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[0069] = The cushioning mechanism may comprise an elastic structure such as
a spring for absorbing a shock impact. The cushioning mechanism may further
comprise a shock absorber for damping the spring oscillations.
[0070] The
cushioning mechanism may alternatively, or additionally,
comprise a parachute, or other controlled descent system or method.
[0071] The
cushioning mechanism may be incorporated within the body
between two parts thereof.
[0072] Magnetic
braking may be utilised to slow the overshot assembly as it
approaches the end of its descent into a borehole. The overshot assembly may
for example include at least a portion of a magnetic braking system for
slowing
the overshot assembly in this manner.
[0073]
Preferably, the lower portion of the body incorporates a latching
mechanism for releasable connection to a mating formation on the inner tube
assembly. Typically, the mating formation is configured as a spear and the
latching mechanism comprises latching dogs.
[0074] The body
may incorporate an actuator for actuating the latching
mechanism to engage/disengage the formation upon engagement between the
overshot assembly and the inner core tube.
[0075]
Preferably, the overshot assembly is provided with a means for
allowing a tool face of the downhole surveying instrument to be transferred to
an
external surface of the overshot assembly. For example, an external surface of
the body of the overshot assembly may include a tool face mark, and one of the
body and a pressure barrel of the surveying instrument may include a locating
lug which is receivable in a groove in the other of the body and the pressure
barrel of the surveying instrument so that the tool face of the instrument can
thereby be synchronised with the tool face mark on the external surface of the
body. Where the downhole surveying instrument comprises one or more
gyroscopes, the tool face of the downhole surveying instrument may comprise a
gyro tool face, and the tool face mark on the external surface of the body may
comprise a gyro tool face mark.
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[0076] The
overshot assembly may be provided with a means for allowing
the tool face to be adjustably transferred to the inner tube assembly.
[0077]
According to a fourth broad aspect of the present invention there is
provided an apparatus adapted for connection to an inner tube assembly, the
apparatus comprising a body being adapted to receive a downhole surveying
instrument, whereby the downhole surveying instrument can be conveyed along
a borehole with the inner tube assembly and operated in the borehole.
[0078] The
apparatus according to the fourth broad aspect of the present
invention may comprise a sub or a drop tool assembly attachable to the inner
tube assembly.
[0079]
According to a fifth broad aspect of the present invention there is
provided a drop tool assembly comprising a body having an upper portion
adapted to be' releasably connected to a retrieval system and a lower portion
adapted to be releasably connected to an inner tube assembly, the body being
' adapted to receive a downhole surveying instrument, whereby the
downhole
surveying instrument can be conveyed along a borehole with the drop tool
assembly and operated in the borehole.
[0080]
Preferably, the retrieval system comprises an overshot assembly
attached to the end of a wireline.
[0081]
Preferably, the upper portion of the body is configured for
engagement with the overshot assembly in known manner.
[0082]
Preferably, the drop tool assembly incorporates means operable for
controlled positioning of the body within the borehole for operation of the
sUrveying instrument. The controlled positioning provides stable support
within
the borehole.
[0083] The
means operable for controlled positioning of the body within the
borehole may comprise means for engaging the surrounding drill string to
stabilise the body.
[0084] The
engaging means may be adapted to support the body within the
drill string in a circumferentially centred manner. With such an arrangement,
the
engaging means may be configured as a centraliser.
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[0085] The
engaging means may comprise radially disposed arms biased
outwardly to contact sides of the drill string, thus centrally positioning the
body =
within the drill string. The arms may each include an outer contact portion
configured for contact with the inner wall of the surrounding drill string.
The outer
contact portion may be of any appropriate form, such as a pad or a roller.
[0086] In one
arrangement, the engaging means may be configured to
engage the drill string for movement therealong as the drop tool assembly is
raised or lowered within the borehole. With this arrangement, the engaging
means may comprise a fixed structure configured as a carriage for movement
along the internal wall of the drill string.
[0087] In
another arrangement, the engaging means may be adapted for
movement between collapsed and extended conditions, whereby in the collapsed
condition it is clear of the internal wall of the drill string for movement
therealong _
and in the extended condition it is in engagement with the drill string for
controlled positioning of the body within the borehole to provide stable
support
for operation of the surveying instrument.
[0088] The body
may incorporate a cavity for accommodating the downhole
surveying instrument.
[0089]
Preferably, the body it configured to facilitate installation of the
downhole surveying instrument in the cavity. The body may, for 'example, be
constructed in two or more parts, with one part being selectively separable
from
another part to provide access to the cavity.
[0090] Magnetic
braking may be utilised to slow the drop tool assembly as it
approaches the end of its descent into a borehole. The drop tool assembly may
for example include at least a portion of a magnetic braking system for
slowing
the drop tool assembly in this manner.
[0091]
Preferably, the body has an upper portion adapted to be releasably
connected to an overshot assembly, and .a lower portion adapted to be
releasably connected to an inner tube assembly.
[0092]
Preferably, the lower portion of the body incorporates a latching
mechanism for releasable connection to a mating formation on the inner tube
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assembly. Typically, the mating formation is configured as a spear and the
latching mechanism comprises latching dogs.
[0093] The body
may incorporate an actuator for actuating the latching
mechanism to engage the formation upon engagement between the drop tool
assembly and the inner core tube.
100941
Preferably, the upper portion of the body incorporates a mating
formation. It is preferred that the mating formation is configured as a
spearhead
point.
[0095] The
downhole surveying instrument may comprise a downhole survey
tool or a component thereof.
[0096] The
downhole surveying instrument may, for example, comprise a
downhole tool c6mprising one or more sensor devices such as orthogonal
accelerometers, magnetometers, gyroscopes, MEMS (microelectromechanical)
gyro sensors, or any combination thereof.
[0097] A
suitable downhole surveying instrument may comprise the
downhole tool as described and illustrated in International application
PCT/AU2011/000628, the contents of which, as mentioned above, are
incorporated herein by way of reference. Other appropriate downhole tools can,
=
of course, also be used.
[0098] Where
the downhole surveying instrument comprises a geo-magnetic
device, it may be necessary for the body, or at least relevant parts thereof,
to be
made of material or materials which do not interfere magnetically with the geo-
magnetic device. In particular, the body or at least relevant parts thereof,
may
need to be made of material which is non-magnetic.
[0099] Where
the downhole surveying instrument does not comprise a geo-
magnetic device, the body would not necessarily need to be made of materials
which are non-magnetic. The downhole surveying tool described and illustrated
in International application PCT/AU2011/000628 is an example of an
arrangement in which the body would not necessarily need to be made of
materials which are non-magnetic.
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[00100] The downhole surveying instrument may be operable within the
borehole either while the drop tool assembly is connected to the inner tube
assembly, or when the drop tool assembly is not connected to the inner tube
assembly.
[00101] Preferably, the drop tool assembly is provided with a means for
allowing a tool face of the downhole surveying instrument to be effectively
transferred to an external surface of the drop tool assembly. For example, an
external surface of the body of the drop tool assembly may include a tool face
mark, and one of the body and a pressure barrel of the surveying instrument
may .
include a locating lug which is receivable in a groove in the other of the
body and
the pressure barrel of the surveying instrument so that the tool face of the
instrument can thereby be synchronised with the tool face mark on the external
surface of the body. Where the downhole surveying instrument comprises one
or more gyroscopes, the tool face of the downhole surveying instrument may
comprise a gyro tool face, and the tool face mark on the external surface of
the
body may comprise a gyro tool face mark.
[00102] The drop tool assembly may be provided with a means for allowing
the tool face to be adjustably transferred to the inner tube assembly.
[00103] Preferably, the drop .tool assembly also comprises a water pressure
activation system for indicating when the drop tool assembly has landed in or
otherwise reached its final position within a borehole. It is preferred that
the
water pressure activation system is operable to activate/deactivate the
doWnhole
surveying instrument.
[00104] According to a sixth broad aspect of the present invention there is
provided a downhole assembly comprising an inner tube assembly according to
the second broad aspect of the present invention in combination with an
overshot
assembly.
[00105] Preferably, the downhole assembly further comprises a release
system for allowing the overshot assembly to= be released from the inner tube
assembly while the overshot assembly and the inner tube assembly are located
downhole.
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[00106] Preferably, the downhole assembly also comprises a synchronisation
system for allowing the overshot assembly to be connected to the inner tube
assembly so that a predetermined tool face of the overshot assembly is
synchronised to the inner tube assembly. It is preferred that the.
predetermined
tool face is a predetermined gyro tool face of the overshot assembly.
[00107] Preferably, the synchronisation system comprises a profiled portion of
the overshot assembly and a profiled portion of the inner tube assembly, the
profiled portions being configured to engage with each other such that the
overshot assembly is able to rotate relative to the inner tube assembly into a
home position under its own weight or with minimal, thrust. It is preferred
that
each profiled portion comprises a respective mule shoe.
=
[00108] Preferably, he downhole assembly further comprises a locking
system for mechanically locking the inner tube assembly to intum synchronise
to
a tool face of the overshot assembly. ' It is preferred that the locking
system
comprises a flow clutch.
1001091 Alternatively, in another arrangement, a tool face position of the
inner
tube assembly is able to be synchronised to the overshot assembly by wireless
transmission.
[00110] Preferably the overshot assembly in the combination according to the
sixth broad aspect of the present invention comprises means operable for
controlled positioning of the body within the borehole for operation of the
surveying instrument.
[00111] In this regard, the overshot assembly may incorporate any one or
more of the features described above.
[00112] According to a seventh broad aspect of the present invention there is
provided a downhole assembly comprising a drop tool assembly according to the
fifth broad aspect of the present invention in combination with at least one
of an
inner tube assembly and an overshot assembly.
[00113] Preferably, the downhole assembly comprises a release system for
allowing the drop tool assembly to be released from the inner tube assembly
while the drop tool assembly is located down hole.
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[00114] Preferably, the downhole assembly also comprises a synchronisation
system for allowing the drop tool assembly to be connected to the inner tube
assembly so that a predetermined tool face of the drop tool assembly is
synchronised to the inner tube assembly. r It is preferred that the
predetermined
tool face is a predetermined gyro tool face of the drop tool assembly.
[00115] Preferably, the synchronisation system comprises a profiled portion of
the drop tool assembly and a profiled portion of the inner tube assembly, the
profiled portions being configured to engage with each other such that the
drop
tool asembly is able to rotate relative to the inner tube assembly into a home
position under its own weight or with minimal thrust. It is preferred that
each
profiled portion comprises a respective mule shoe.
[00116] Preferably, the downhole assembly further comprises a locking
system for mechanically locking the inner tube assembly to inturn synchronise
to
a tool face of the drop tool assembly. It is preferred that the locking system
comprises a flow clutch.
[00117] Alternatively, in another arrangement, a tool face position of the
inner
tube assembly is able to be synchronised to the drop tool assembly by wireless
transmission.
[00118] According to an eighth broad aspect of the present invention there is
provided a method of conducting a borehole surveying operation using a
surveying instrument accommodated in an apparatus according to the first broad
aspect of the present invention.
[00119] According to a ninth broad aspect of the present invention there is
provided a method of conducting a borehole surveying operation using a
surveying instrument accommodated in an inner tube assembly according to the
second broad aspect of the present invention.
[00120] According to tenth broad aspect of the present invention there is
provided a method of conducting a borehole surveying operation using a
surveying instrument accommodated in an overshot assembly according to the
third broad aspect of the present invention.
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=
18
[00121] According to an eleventh broad aspect of the present invention there
is provided a method of conducting a borehole surveying operation using a
surveying instrument accommodated in an apparatus according to the fourth
broad aspect of the present invention.
=
[00122] According to a twelfth broad aspect of the present invention there is
provided a method of conducting a borehole surveying operation using a
surveying instrument accommodated in a drop tool assembly according to the
fifth broad aspect of the present invention.
[00123] According to thirteenth broad aspect of the present invention there is
provided a method of conducting a borehole surveying operation using a
surveying instrument accommodated in an inner tube assembly forming part of a
combination according to the sixth broad aspect of the present invention.
[00124] According to a fourteenth broad aspect of the present invention there
is provided a method of conducting a borehole surveying operation using a
surveying instrument accommodated in a drop tool assembly forming part of a
combination according to the seventh broad aspect of the present invention.
[00125] According to a fifteenth broad aspect of the present invention there
is
provided a method of conducting a borehole surveying operation using
apparatus incorporating an onboard downhole surveying instrument, the method
comprising lowering the apparatus down the borehole, taking a measurement
down the borehole using the onboard downhole surveying instrument, and
retrieving a core sample using the apparatus.
(00126] The method may further comprise actuating the onboard downhole
surveying instrument to take the measurement in response to the apparatus
approaching or completing the end of its descent into the borehole.
[00127] Typically, the apparatus comprises an overshot assembly.
[00128] According to sixteenth broad aspect of the present invention there is
provided a method of conducting a borehole surveying operation using an inner
tube assembly incorporating an onboard downhole surveying instrument, the
method comprising deploying the inner' tube assembly in the borehole, taking a
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19 . ,
' measurement down the borehole using the onboard downhole surveying
instrument, and retrieving the inner tube assembly containing a core sample.
[00129] Preferably, the core inner tube assembly incorporating the onboard
downhole surveying instrument is retrieved from the borehole using an overshot
assembly.
[00130]
Preferably, the method further comprises controlling the position of
the core inner tube assembly within the borehole for operation-of the
surveying
instrument.
[00131]
Preferably, the act of controlling the position of the core inner tube
assembly within the borehole for operation of the surveying instrument
comprises
controlling the positioning of the overshot assembly within the borehole.
[00132] According to a seventeenth broad aspect of the present invention
there is provided a method of conducting a borehole surveying operation using
an overshot assembly according to the third broad aspect of the present
invention.
[00133) According to an eighteenth broad aspect of the present invention
there is provided a method of conducting a borehole surveying operation using
an overshot assembly incorporating an onboard downhole surveying instrument,
the method comprising lowering the overshot assembly down the borehole, =
taking a measurement down the borehole using the onboard downhole surveying
instrument, and retrieving an inner tube assembly containing a core sample
using the overshot assembly.
[00134] According to a nineteenth broad aspect of the present invention there
is provided a method of conducting a borehole surveying operation using a drop
tool assembly incorporating an onboard downhole surveying instrument, the
method comprising lowering the drop tool assembly down the borehole using the
onboard downhole surveying instrument, and retrieving an inner tube assembly
containing a core sample using the drop tool assembly and an overshot
assembly.
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= 20
[00135] The term "measurement" as used herein is taken to include any
reading, data, signal, or other input or collection of inputs received by the
downhole surveying instrument.
BRIEF DESCRIPTION OF THE DRAWINGS
[00136] In order that the invention may be more fully understood and put into
practice, a preferred embodiment thereof will now be described with reference
to
the accompanying drawings in which:
Figure 1 is a schematic side view of an inner tube assembly;
Figure 2 is a schematic side view of an overshot assembly for use in
combination with the inner tube assembly;
Figure 3 is a fragmentary side view of the bottom end of a drill string
incorporating a drill barrel connected to a series of drill rods, with the
inner tube assembly being receivable in the drill barrel in known
manner;
Figure 4 is a schematic side view of another overshot assembly;
Figure 5 depicts an overshot assembly and an inner tube assembly of
a downhole assembly;
Figure 6 depicts a drop tool assembly and an inner tube assembly of a
downhole assembly;
Figure 7 depicts a portion of the drop tool assembly body, and a
portion of the surveying instrument pressure barrel; and
=
Figure 8 depicts a water pressure activation system of the drop tool
assembly.
DESCRIPTION OF EMBODIMENTS
[00137] In the drawings, like features have been referenced with like
reference
numbers.
[00138] The preferred embodiment shown in Figures 1 to 3 of the drawings is
directed to an inner tube assembly 10 for core retrieval in core drilling
operations
for borehole surveys. The inner tube assembly 10 is configured to accommodate
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21
an onboard downhole surveying instrument, as will be explained in more detail
later. This arrangement allows for coordination between downhole surveying
and core retrieval operations in order to reduce downtime while the procedures
are being performed,
[001391 The core drilling operation is performed with a core drill comprising
an outer tube assembly 13 in conjunction with the inner tube assembly 10. The
outer tube assembly 13 is referred to as the drilling barrel and is fitted as
a
bottom end assembly 15 to a series of drill rods or drill pipes 17 which
constitute
a drill string.
[00140] The inner tube assembly 10 comprises a body 21 having a bottom
end section 23 and a top end section 25. The bottom end section 23
incorporates a core inner tube (not shown) to progressively receive a core
sample during a core drilling operation in known manner.
[00141] The top end section 25 incorporates a backend assembly which
includes a spearhead point 27 releasably engagable with an overshot assembly
30 in known manner. With this arrangement, the inner tube assembly 10 can be
lowered into, and retrieved from, the outer tube assembly 13 and the
associated
drill string 17.
[00142] The body 21 defines an internal compartment 33 adapted to
accommodate a downhole survey instrument 35, as shown in Figure 1. In this
way, the downhole survey instrument 35 is onboard the inner tube assembly 10.
The downhole survey instrument 35 would typically comprise a downhole tool
having one or more sensor devices such as orthogonal accelerometers,
magnetometers, gyroscopes, MEMS (microelectromechanical) gyro sensors, or
any combination thereof. In this preferred embodiment, the compartment 33 is
configured to receive a downhole tool of the type described and illustrated in
international application PCT/AU2011/000628, the contents of which are
incorporated herein by way of reference.
[00143] The body 21 may incorporate means (not shown) such as an IR port
or other telemetry arrangement for communication with the downhole survey
instrument to retrieve measurements therefrom.
=
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[00144] The body 21 comprises an upper portion 41 and a lower- portion 43
adapted to be releasably connected together by a fluid-tight connection 45.
The
connection 45 may comprise a threaded connection and an associated fluid seal
arrangement. The two portions 41, 43 cooperate to define the internal
compartment 33 adapted to receive and accommodate the downhole survey
instrument 35. The two portions 41, 43 can be separated by disengaging the
connection 45 to provide access to the compartment 33 for insertion and
removal
of the downhole survey instrument 35.
[00145] The core inner tube assembly 10 can be used with a conventional
overshot. Assembly.
[00146] However, it may be advantageous to use the core inner tube
assembly 10 in conjunction with an overshot assembly which has a facility to
provide controlled positioning of the body 21 of the inner tube assembly 10
within
the borehole for operation of the onboard surveying instrument 35. The
controlled positioning is intended to provide stable support of the body 21
within
the drill string 17 in order to allow the onboard surveying instrument 35 to
take
measurements which are not affected by movement and vibration.
[00147] The overshot assembly 30 shown in Figure 2 is provided with such a
facility to provide controlled positioning of the body 21 within the borehole.
[00148] In the
arrangement illustrated in Figure 2, the overshot assembly 30
comprises a body 51 having a lower end section 53 and an upper end section
55.
[00149] The lower end section 53 of the body 51 incorporates a latching
mechanism 57 for releasable connection to the spearhead point 27 on the inner
tube assembly 10. The latching mechanism 57 may comprise latching dogs of
known kind for releasable engagement with the spearhead point 27. The body
51 may also incorporate an actuator (not shown) for actuating the latching
mechanism 57 to engage/disengage the spearhead point 27 upon engagement
between the overshot assembly 30 and the inner tube assembly 10.
[00150] The upper end section 55 of the body 51 is, configured for attachment
to a wireline cable 59 of known kind, as shown in Figure 2.
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[00151] The overshot assembly 30 further comprises means 60 operable for
the above-mentioned controlled positioning of the body 21 of the inner tube
assembly 10 within the borehole. More particularly, such means 60 is operable
for controlling positioning of the overshot assembly 30 within the borehole.
With
this arrangement, it is the controlled positioning of the overshot .assembly
30
within the borehole that effectively controls the position of the body 21 of
the
inner tube assembly 10 within the borehole by virtue of the connection between
the core tube assembly 10 and the overshot assembly 30. In other words,
controlling the positioning of the overshot assembly 30 within the borehole
has
the effect of controlling the positioning of the core tube assembly 10, and
hence
the position of the body 21 of the core tube assembly 10 in which the downhole
. surveying instrument 35 is accommodated.
[00152] The position of the overshot assembly 30 is controlled by controlling
the position of the overshot body 51 within the drill string 17. For this
purpose,
the means 60 comprises engaging means 61 provided on the overshot assembly
30 for engaging the surrounding section. of the drill string 17 to stabilise
the
overshot body 51.
[00153] The engaging means 61 is configured as a centraliser 63 which is
adapted to support the body 51 within the drill string 17 in a
circumferentially
centred manner.
[00154] The centraliser 63 comprises a series of radially disposed arms 65
adapted to extend outwardly to contact sides of the drill rods 17, thus
centrally
positioning the body 51 within the surrounding section of the drill string.
The
radially disposed arms 65 are circumferentially spaced. In this preferred
embodiment, there are four radially disposed arms although other arrangements
may be used.
[00155] The arms 65 each include an.outer contact portion 67 configured for
contact with the inner wall of the surrounding section of the drill string.
The outer
contact portion 67 may be of any appropriate form, such as a pad or a roller.
[00156] In the arrangement shown, the arms 65 are adapted for movement
between collapsed and extended conditions, whereby in the collapsed condition
each arm is clear of the internal wall for the drill rods and in the extended
=
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condition it is in engagement with the drill rods for controlled positioning
of the
body 51 within the borehole to provide stable support for operation of the
surveying instrument 35 onboard the core inner tube assembly 10.
[001571 In
operation, the core drill operates in the normal way. A core is
generated during the drilling operation, with the core progressively extending
along the core inner tube within the inner tube assembly 10 as drilling
progresses. When a core sample is required, the core within the core inner
tube
is fractured to provide the core sample. The inner tube assembly 10 and the
fractured core sample contained therein are then retrieved from within the
drill
hole using the overshot assembly 30 which is lowered down to the inner tube
assembly on the wireline cable 59. As the overshot assembly 30 contacts the
inner tube assembly 10, the latching mechanism 57 engages the spearhead
point 27 on the inner tube assembly. .
[001581 Once the overshot assembly 30 has been connected to the inner tube
assembly 10, the centraliser 63 can be actuated as desired to support the body
51 within the surrounding section of the drill string 17 in a
circumferentially
centred manner. This controlled positioning provides stable support for the
body
21 of the inner tube assembly 10 within the drill string in order to allow the
onboard surveying instrument 35 to take measurements which are not affected
-
by movement and vibration. Once the measurements are taken, the centraliser
63 can be released and the overshot assembly 30 can be raised using the
wireline cable 59 to complete the core retrieval process in the conventional
manner.
[00159] The surveying instrument 35 onboard the inner tube assembly 10 can
be interrogated as required to retrieve recorded data.
[00160] It is a particular feature of the preferred embodiment that the
surveying instrument 35 is onboard the inner tube assembly 10, thereby
allowing
surveying measurements to be taken during the core collection and retrieval
process as desired. In other words, the taking of surveying measurements can
be integrated with the core collection and retrieval process, rather than
being a
separate operation as is conventional practice. This is advantageous, as it
can
reduce the downtime during which drilling operations need to be suspended in
. order for core samples to be retrieved and surveying measurements to be
taken.
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[00161] In this preferred embodiment, the downhole instrument 35 comprising
the tool of the type described and illustrated in international application
PCT/AU2011/000628 is not affected by magnetic materials in the presence of the
environment of its use, and so the body can be constructed of any appropriate
material; that is, it is not necessary to use non-magnetic materials such as
CuBe
in the construction of the body 21 of the inner tube assembly 10.
[00162] In
other preferred embodiments with which a geomagnetic device is
used as the survey instrument, it may be necessary for the body 21, or at
least
relevant parts thereof, to be made of material or materials which do not
interfere
magnetically with the geo-magnetic device. In particular, the body, or at
least
= relevant parts thereof, may need to be to be made of material which is
non-
magnetic.
[00163] The preferred embodiment shown in Figure 4 of the drawings is
directed to an overshot assembly 100 for use in a core drilling operation in a
borehole survey.
[00164] =The core drilling operation is performed with a core drill (not
shown)
fitted as a bottom end assembly to a series of drill rods, The core drill
comprises
an inner tube assembly, which includes a core tube, for core retrieval. The
core
drill also comprises an outer tube assembly.
[00165] The inner tube assembly further comprises a backend assembly
which includes a spearhead point releasably engagable with the overshot
assembly 100. In Figure 4, the spearhead point is depicted schematically and
identified by reference numeral 101.
[00166] With this arrangement, the inner tube assembly can be lowered into,
and retrieved from, the outer tube assembly and the drill string to which the
outer
tube assembly is incorporated.
[00167] The overshot assembly 100 comprises a body 105 having a lower end
107 and an upper end 109. The body defines an internal compartment 111
adapted to accommodate a downhole survey instrument. - In this way, the
downhole survey instrument is onboard the overshot assembly 100. The
downhole survey instrument would typically comprise a downhole tool having
one or more sensor devices such as orthogonal accelerometers,
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26
magnetometers, gyroscopes, MEM5 (microelectromechanical) gyro sensors, or
any combination thereof. In this preferred embodiment, the compartment 111 is
configured to receive a downhole tool of the type described and illustrated in
international application PCT/AU2011/000628, the contents of which are
incorporated herein by way of reference.
[00168] The body 105 incorporates means 108 such as an IR port or other
telemetry method for communication with the downhole survey instrument to
retrieve measurements therefrom.
[00169] The body 105 comprises an upper portion 113 and a lower portion
115, with the two portions being interconnected by a cushioning mechanism 117
adapted to provide cushioning to afford some impact protection for the
downhole
survey instrument accommodated in the compartment 111. In particular, the
cushioning mechanism 117 is adapted to cushion impact forces when the
overshot assembly 100 descends into contact with the inner tube assembly.
[00170] In the arrangement illustrated in Figure 4, the cushioning mechanism
117 comprises an elastic structure 119 configured as a spring for absorbing a
shock impact. The cushioning mechanism 117 further comprises a shock
absorber 121 for damping the spring oscillations. The shock absorber 121 may
be of any appropriate type, such as an arrangement adapted for controlled
displacement of damping fluid (comprising, for example, air and oil) to effect
a
=
damping action.
- [00171] The compartment 111 is incorporated in the upper portion 113. The
upper portion 113 comprises two sections, being a top section 123 and a bottom
section 125 adapted to be releasably connected together by fluid-tight
, connection 127. The connection 127 may comprise a threaded connection and
an associated fluid seal arrangement. The two sections 123, 125 cooperate to
define the compartment 111 adapted to receive and accommodate the downhole
survey instrument. The two sections 123, 125 are selectively separable to
provide access to the compartment 111.
[00172] The lower end 107 of the body 105 incorporates a latching
mechanism 131 for releasable connection to the spearhead point 101 on the
inner tube assembly. In this embodiment, the latching mechanism 131 =
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comprises ; latching dogs of known kind for releasable engagement with the
spearhead point 101.
[00173] The body 105 also incorporates an actuator (not shown) for actuating
the latching mechanism 131 to engage/disengage the spearhead point 101 upon
engagement between the overshot assembly 100 and the inner tube assembly.
[00174] The upper end 109 of the body 105 is configured for attachment to a
wireline cable of known kind. In the arrangement illustrated, the upper end
109
of the body 105 incorporates an eyelet 133 to which the wireline cable can be
attached. In Figure 4, the wireline cable is depicted schematically and
identified
by reference numeral 135.
[00175] The overshot assembly 100 further comprises means 140 operable
for controlled positioning of the body 105 within the borehole for operation
of the
surveying instrument accommodated within the compartment 111. The
controlled positioning is intended to provide stable support of the body 105
within
the drill string in order to allow the onboard surveying instrument to take
measurements which are not affected by movement and vibration.
[00176] The means 140 operable for controlled positioning of the body 105
within the borehole comprise engaging means 141 for engaging the adjacent .
portion of the drill string to stabilise the body.
[00177] The engaging means 141 is configured as a centraliser 143 which is
adapted to support the body 105 within the drill pipe in a circumferentially
centred
manner.
[00178] The centraliser 143 comprises a series of radially disposed arms 145
-
adapted to extend outwardly to contact sides of the drill pipe, thus centrally
positioning the body within the drill pipe. The radially disposed arms 145 are
circumferentially spaced., In this preferred embodiment, there are four
radially
disposed arms 145, although other arrangements may be used.
[00179] The arms 145 each include an outer contact portion 147 configured
= for contact with the inner wall of the surrounding drill pipe. The outer
contact
portion 147 may be of any appropriate form, such as a pad or a roller.
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[00180] In this preferred embodiment, the arms 145 are adapted for
movement between collapsed and extended conditions, whereby in the collapsed
condition each arm is clear of the internal wall for the drill pipe and in the
extended condition it is in engagement with the drill pipe for controlled
positioning
of the body 105 within the borehole to provide stable support for operation of
the
surveying instrument.
[00181] In
operation, the core drill operates in the normal way. A core is
generated during the drilling operation, with the core progressively extending
along the core inner tube within the inner tube assembly as drilling
progresses.
When a core sample is required, the core within the core inner tube is
fractured.
The inner tube assembly and the fractured core sample contained therein are
then retrieved from within the drill hole using the overshot assembly 100
which is
lowered down to the inner tube assembly on the wireline cable 135. As the
overshot assembly 100 contacts the inner tube assembly, the latching
mechanism 131 engages the spearhead point 101 on the inner tube assembly.
The impact force generated upon the overshot assembly descending into contact
with the inner tube assembly is cushioned by the cushioning mechanism 117 as
previously explained. Once the overshot assembly 100 has been connected to
the inner tube assembly, the centraliser 143 is actuated to support the body
105
within the drill pipe in a circumferentially centred manner. This controlled
positioning effects stable support of the body 105 within the drill pipe in
order to
allow the onboard surveying instrument to take measurements which are not
affected by movement and vibration. Once the measurements are taken, the
overshot assembly 100 can be raised using the wireline cable 135 to complete
the core retrieval process in the conventional manner.
[00182] It is a
particular feature of the preferred embodiment that the
surveying instrument is onboard the overshot assembly 100, thereby allowing
surveying measurements to be taken during the core retrieval process if
desired.
In other words, the taking of surveying measurements can be integrated with
the
core retrieval process, rather than being a separate operation as is
conventional
practice. This is advantageous, as it can reduce the downtime during which
drilling operations need to be suspended in order for core samples to be
retrieved and surveying measurements to be taken.
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29 =
[00183] In this preferred embodiment, the downhole tool of the type described
and illustrated in international application PCT/AU2011/000628 is not affected
by
magnetic materials in the presence of the environment of its use and so the
body
can be constructed of any appropriate material; that is, it is not necessary
to use
non magnetic materials such as CuBe in the construction of the body 105.
[00184] In other preferred embodiments with which a geo-magnetic device is
used as the survey instrument, it may be necessary for the body, or at least
relevant parts thereof, to be made of material or materials which do not
interfere
magnetically with the geo-magnetic device. In particular, the body, or at
least
relevant parts thereof, may need to be to be made of material which is non-
magnetic.
[00185] Referring to Figure 5 there is depicted an overshot assembly 200 and
an inner tube assembly 201 of a downhole assembly 202.
[00186] The overshot assembly 200 can be used in a 'core drilling operation in
a borehole survey.
[00187] The core drilling operation is performed with a core drill (not shown)
fitted as a bottom end 'assembly to a series of drill rods or pipes called a
drill
string. The core drill comprises the inner tube assembly 201, which includes a
core tube, for core retrieval. The core drill also comprises an outer tube
assembly.
[00188] The inner tube assembly 201 further comprises a backend assembly
which includes a spearhead point 101 releasably engagable with the overshot
assembly 200.
[00189] With this arrangement, the inner tube assembly 201 can be lowered
into, and retrieved from an outer tube assembly and the drill string to which
the
outer tube assembly is incorporated.
[00190] The overshot assembly 200 comprises a body 105 having a lower end
107 and an upper end 109. The body 105 defines an internal
compartment/cavity 111 adapted to accommodate a downhole survey
instrument. In this way, the downhole survey instrument would typically
comprise a downhole tool having one or more sensor devices such as orthogonal
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accelerometers, magnetometers, gyroscopes, MEMS (microelectromechanical)
gyro sensors, or any combination thereof. In this preferred embodiment, the
compartment 111 is configured to receive a downhole tool of the type described
and illustrated in International application PCT/AU2011/000628 whose contents
have been incorporated herein by reference.
[00191] Although not depicted in the drawings, the body 105 may incorporate
means such as an infrared (IR) port or other telemetry method for
communication
with the downhole survey instrument to retrieve measurements therefrom.
[00192] The body 105 comrpises an upper portion 113 and a lower portion
115. Although not shown in the drawings, the two portions 113, 115 may be
interconnected by a cushioning mechanism adapted to provide cushioning to
' afford some impact protection for the downhole survey instrument
acoommodated in the compartment 111. In
particular, the cushioning
mechanism is adapted to cushion impact forces when the overshot assembly
200 descends into contact with the inner tube assembly 201.
[00193] The cushioning mechanism could, for example, comprise an elastic
= structure configured as a spring for absorbing a shock impact. The
cushioning
mechanism may further comprise a shock absorber for damping the spring
oscillations. The shock absorber may be of any appropriate type, such as an
arrangement adapted for controlled displacement of damping fluid (comprising,
for example, air and oil) to effect a damping action.
[00194] The. compartment 111 is incorporated in the upper portion 113. The
upper portion 113 comprises two sections, being a top section 123 and a bottom
section 125 adapted to be releasably connected together by a fluid-tight
connection 127. The connection 127 may comprise a threaded connection and
an associated fluid seal arrangement. The two sections 123, 125 cooperate to
define the compartment 111 adapted to receive and accommodate the downhole
survey instrument. The two sections 123, 125 are selectively separable to
provide access to the compartment 111.
[00195] The lower end 107 of the body 105 incorporates a latching
mechanism 131 for releasable connection to the spearhead point 101 on the
inner tube assembly 201. In this preferred embodiment, the latching mechanism
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31
131 comprises latching/lifting dogs 210 of known kind for releasable
engagement
with the spearhead point 101.
[00196] The body 105 may also incorporate an actuator (not shown) for
actuating the latching mechanism 131 to engage/disengage the spearhead point
101 upon engagement between the overshot assembly 200 and the inner tube
assembly 201.
[00197] The upper end 109 of the body 105 is configured for attachment to a
wireline cable 135 of known kind. In the arrangement illustrated, the upper
end
109 of the body 105 incorporates an eyelet 133 to which the wireline cable 135
can be attached.
[00198] The overshot assembly 200 further comprises means 140 operable
for controlled positioning of the body 105 within the borehole for operation
of the
surveying instrument accommodated within the compartment 111. The
controlled positioning is intended to provide stable support of the body 105
within
the drill string in order to allow the onboard surveying instrument to take
measurements which are not affected by movement and vibration.
[00199] The means 140 operable for controlled positioning of the body 105
within the borehole comprises engaging means 141 for engaging the adjacent
portion of the drill string to stabilise the body 105.
[00200] The engaging means 141 is configured as a centraliser 143 which is
adapted to support the body 105 within the drill pipe in a circumferentially
centred
manner.
[00201] The centraliser 143 comprises a series of radially disposed arms 145
adapted to extend outwardly to contact sides of the drill pipe, .thus
centrally
positioning the body 105 within the drill pipe. The radially disposed arms 145
are
circumferentially spaced. In this preferred embodiment, there are four
radially
disposed arms 145, although other arrangements may be used.
[00202] The arms 145 each include an outer contact portion 147 configured
for contact with the inner wall of the surrounding drill pipe. The outer
contact
portion 147 may be of any appropriate form, such as a pad or a roller.
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=
32
[002031 The arms 145 may be adapted for movement between collapsed and
extended conditions, whereby in the collapsed condition each arm 145 is clear
of
the internal wall of the drill pipe and in the extended condition it is in
engagement
with the drill pipe for controlled positioning of the body 105 within the
borehole to =
provide stable support for operation of the surveying instrument.
[00204] Magnetic braking may be utilised to slow the overshot assembly 200
as it approaches the end of its descent into a borehole. The overshot assembly
200 may for example include at least a portion of a magnetic braking system
(not
depicted) for slowing the overshot assembly 200 in this manner.
[00205] The overshot assembly 200 is provided with a means 220 for allowing
a tool face of the downhole surveying instrument to be transferred to an
external
surface of the overshot assembly 200. For example, the means 220 may include
a tool face mark 221 on an external surface of the body 105, and one of the
body
105 and a pressure barrel of the surveying instrument may include a locating
lug
(not depicted) which is receivable in a groove (not depicted) in the other of
the
body 105 and the pressure barrel of the surveying instrument when the
surveying
instrument is inserted into the compartment 111 so that the tool face of the
instrument can thereby be synchronised with the tool face mark 221 on the
external surface of the body 105. Where the downhole surveying instrument
comprises one or more gyroscopes, the tool face of the downhole surveying
instrument may comprise a gyro tool face, and the tool face mark 221 on the
external surface of the body 105 may comprise a gyro tool face mark.
[00206] The overshot assembly 200 may also be provided with a means 225
for allowing the tool face to be adjustably transferred to the inner tube
assembly
201. For example, the means 225 may comprise a shaft (not depicted) which
connects the upper portion 113 to the lower portion 115 such that the upper
and
lower portions 113, 115 are able to be rotated relative to each other.
Rotation of
the lower portion 115 relative to the upper portion 115 allows the position of
a
tool face mark 226 on the lower portion 115 to be adjusted relative to the
tool
face mark 221 and a tool face mark 227 on the inner tube assembly 201. Once
the position of the tool face mark 226 has been adjusted, two nuts 228 on the
shaft can be tightened to mechanically lock the portions 113, 115 together so
as
to prevent relative rotation between the portions 113, 115. Where the tool
face
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mark 221 on the external surface of the body 105 comprises a gyro tool face
mark, the tool face marks 226, 227 also comprise gyro tool face marks.
[00207] In the case where the surveying instrument includes one or more
gyros which provide the instrument with the ability to reference true North in
any
aspect/environment, this will provide the ability to orientate core or the
bottom
hole assembly at vertical inclinations that previously could not be done with
accelerometers or magnetic sensors. By being able to detect the Earth's true
North direction, this can be reference directly to an external mark (i.e. gyro
tool
face) on the instrument/tool to give the position of the gyro tool face in
relation to
true North.
[00208] The downhole assembly 202 further comprises a release system 230
for allowing the overshot assembly 200 to be released from the inner tube
assembly 201 while the overshot assembly 200 and the inner tube assembly 201
are located downhole. The release system 230 is operable to disengage the
dogs 210 of the latching mechanism 131 from the spearhead point 101.
[00209] Additionally, the downhole assembly 202 comprises a synchronisation
system 235 for allowing the overshot assembly 200 to be connected to the inner
tube assembly 201 so that a predetermined tool face 221 of the overshot
assembly 200 is synchronised to the inner tube assembly 201.
[00210] The synchronisation system 235 comprises a profiled portion 236 of
the lower body portion 115 of the overshot assembly 200, and a profiled
portion
237 of the inner tube assembly 201. The profiled portion 236 comprises a mule
shoe 238, and the profiled portion 237 comprises a mule shoe 239. The profiled
portions 236, 237 are configured to engage with each other such that the
overshot assembly 200 is able to rotate relative to the inner tube assembly
201
into a home position under its own weight or with only minimal thrust.
[00211] Downhole assembly 202 also comprises a locking system 245 for
mechanically locking the inner tube assembly 201 to inturn synchronise to the
tool face 221 of the overshot assembly 200. The locking system 245 may
comprise a flow clutch which is provided as part of the inner tube assembly
201
and which is able to engage and disengage the connection between two co-
linear components of a rock drilling device.
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[00212] Rather than including the mechanical locking system 245, the tool
face position of the inner tube assembly 201 may be synchronised to the
overshot assembly 200 by wireless transmission.
[00213] In operation, the core drill operates in the normal way. A core is
generated during the drilling operation, with the core progressively extending
along the core inner tube within the Inner tube assembly 201 as drilling
progresses. When a core sample is required, the core within the core inner
tube
is fractured. The inner tube assembly 201 and the fractured core sample
contained therein are then retrieved from within the drill hole using the
overshot
assembly 200 which is lowered down to the inner tube assembly 201 on the
wireline cable 135. As the overshot assembly 200 contacts the inner tube
assembly 201, the latching mechanism 131 engages the spearhead point 101 on
the inner tube assembly 201. The impact force generated upon the overshot
assembly 200 descending into contact with the inner tube assembly 201 is
cushioned by the cushioning mechanism (if present). Also, if a magnetic
braking
means is present, the speed of descent of the overshot assembly 200 is slowed
as it approaches the inner tube assembly 201. Once the overshot assembly 200
has been connected to the inner tube assembly 201, the centraliser 143 is
actuated to support the body 105 within .the drill pipe in order to allow the
onboard surveying instrument to take measurements which are not affected by
movement and vibration. Once the measurements are taken, the overshot
assembly 100 can be raised using the wireline cable 135 to complete the core
retrieval process in the conventional manner.
[00214] It is a
particular feature of the preferred embodiment depicted in
Figure 5 that the surveying instrument is onboard the overshot assembly 200,
thereby allowing surveying measurements to be taken during the core retrieval
process if desired. In other words, the taking of surveying measurements can
be
integrated with the core retrieval process, rather than being a separate
operation
as is conventional practice. This is advantageous, as it can reduce the
downtime
during 'which drilling operations need to be suspended in order for core
samples
to be retrieved and surveying measurements to be taken.
[00215] In this preferred embodiment, the downhole tool of the type described
and illustrated in International application PCT/AU2011/000628 is not affected
by
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magnetic materials in the presence of the environment of its use and so the
body
can be constructed of any appropriate material; that is, it is not necessary
to use
non-magnetic materials such as Cube in the construction of the body 105.
[00216] In other embodiments with which a geo-magnetic device is used as
the survey instrument, it may be necessary for the body 105, or at least
relevant
parts thereof, to be made of material or materials which do not interfere
magnetically with the geo-magnetic device. In particular, the body, or at
least
relevant parts thereof, may need to be made of material which is non-magnetic.
[00217] Referring to Figure 6 there is depicted a drop tool assembly 250 and
an inner tube assembly 201 of a downhole assembly 252.
[00218] The drop tool assembly 250 may be used in a core drilling operation
in a borehole survey in which case the drop tool assembly 250 may be
releasably attached to the inner tube assembly 201.
[00219] The drop tool assembly 250 comprises a body/barrel 255 having a
lower end 257 and an upper end 259. The body 255 defines an internal
compartment/cavity 261 adapted to accommodate a downhole survey
instrument. In this way, the downhole survey instrument would typically
comprise a downhole tool having one or more sensor devices such as orthogonal
accelerometers, magnetometers, gyroscopes, MEMS (microelectromechanical)
gyro sensors, or any combination thereof. In this preferred embodiment, the
compartment 261 is configured to receive a downhole tool of the type described
and illustrated in International application PCT/AU2011/000628 whose contents
have been incorporated herein by reference.
[00220] The body 255 incorporates means such as an infrared (IR) port 262 or
other telemetry method for communication with the downhole survey instrument
= to retrieve measurements therefrom.
[00221] The body 255 comprises an upper portion 263 and a lower portion
265. Although not shown in the drawings, the two portions 263, 265 may be
interconnected by a cushioning mechanism adapted to provide cushioning to
afford some impact protection for the downhole survey instrument
accommodated in the compartment 261. In
particular, the cushioning
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36
mechanism is adapted to cushion impact forces when the drop tool assembly
250 descends into contact with the inner tube assembly 201.
[00222] The cushioning mechanism could, for example, comprise an elastic
structure configured as a spring for absorbing a shock impact. The cushioning
mechanism may further comprise a shock absorber for damping the spring
oscillations. The shock absorber may be of any appropriate type, such as an
arrangement adapted for controlled displacement of damping fluid (comprising
=
for example, air and oil) to effect damping action.
[00223] The compartment 261 is incorporated in the upper portion 263. The
upper portion 263 comprises two sections, being a top section 273 and a bottom
section 275 adapted to be releasably connected together by a fluid-tight
connection 277. The connection 277 may comprise a threaded connection and
an associated fluid seal arrangement. The two sections 273, 275 are
selectively
separable to provide access to the compartment 261.
[00224] The lower end 257 of the body 255 incorporates a latching
mechanism 281 for releasable connection to the spearhead point 101 on the
inner tube assembly 201. In this preferred embodiment, the latching mechanism
281 comprises latching/lifting dogs 282 of known kind for releasable
engagement
with the spearhead point 101.
[00225] The body 255 may also incorporate an actuator (not shown) for
actuating the latching mechanism 281 to engage/disengage the spearhead point
101 upon engagement between the drop tool assembly 250 and the inner tube
assembly 201.
=
[00226] The upper end 259 of the body 255 incorporates a mating formation
283 which is configured as a spearhead point 284 which is releasably engagable
with an overshot assembly (not depicted) which may also be part of the
downhole assembly 251. The overshot assembly could be of any known type, it
could even be one of the previously described overshot assemblies.
[00227] The drop tool assembly 250 further comprises means 290 operable
for controlled positioning of the body 255 within the borehole for operaton of
the
surveying instrument accommodated within the compartment 261. The
controlled positioning is intended to provide stable support of the body 255
within
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. _
37
the drill string in order to allow the onboard surveying instrument to take
measurements which are not affected by movement and vibration.
[00228] The means 290 operable for controlled positioning of the body 255
within the borehole comprises engaging means 291 for engaging the adjacent
portion of the drill string to stabilise the body 255.
[00229] The engaging means 291 is configured as a centraliser 293 which is
adapted to support the body 255 within the drill pipe in a circumferentially
centred
manner.
[00230] The centraliser 293 comprises a series of radially disposed arms 295
adapted to extend outwardly to contact sides of the drill pipe, thus centrally
positioning the body 255 within the drill pipe. The radially disposed arms 295
are
circumferentially spaced. In this preferred embodiment, there are four
radially
disposed arms 295, although other arrangements may be used.
[00231] The arms 295 each include an outer contact portion 297 configured
for contact with the inner wall of the surrounding drill pipe. The outer
contact
portion 297 may be of any appropriate form, such as a pad or a roller.
[00232] The arms 295 may be adapted for movement between collapsed and
extended conditions, whereby in the collapsed condition each arm 295 is clear
of
the internal wall of the drill pipe and in the extended condition it is in
engagement
with the drill pipe for controlled positioning of the body 255 within the
borehole to
provide stable support for operation of the surveying instrument.
[00233] Magnetic braking may be utilised to slow the drop tool assembly 250
as it approaches the end of its descent into a borehole. The drop tool
assembly
250 May for example include at least a portion of a magnetic braking system
(not
depicted) for slowing the drop tool assembly 250 in this manner.
[00234] The drop tool assembly 250 is provided with a means 300 for allowing
a tool face of the downhole surveying instrument to be transferred to an
external
surface of the drop tool assembly 250. For example, the means 300 may include
a tool face mark 301 on an external surface of the body 255, and one of the
body
255 and a pressure barrel 802 (see Figure 7) of the surveying instrument may
include a locating lug 303 which is receivable in a groove 304 in the other of
the
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38
body 255 and the pressure barrel 302 of the surveying instrument when the
surveying instrument is inserted into the compartment 261 so that a tool face
305
of the instrument can thereby be synchronised with the tool face mark 301 on
the
external surface of the body 255. When the downhole surveying instrument
comprises one or more gyroscopes, the tool face of the down hole surveying
instrument may comprise a gyro tool face, and the tool face mark 301 on the
external surface of the body 255 may comprise a gyro tool face mark.
[00235] The drop tool assembly may also be provided with a means 315 for
allowing the tool face to be adjustably transferred to the inner tube assembly
201. For example, the means 315 may comprise a shaft (not depicted) which
connects the upper portion 263 to the lower portion 265 such that the upper
and
lower portions 263, 265 are able to be rotated relative to each other.
Rotation of
the lower portion 265 relative to the upper portion 263 allows the position of
a
tool face mark 316 on the lower portion 265 to be adjusted relative to the
tool
face mark 301 and a tool face mark 227 on the inner tube assembly 201. Once
the position of the tool face mark 316 has been adjusted, two nuts 318 on the
=
shaft can be tightened to mechanically lock the portions 263, 265 together so
as
to prevent relative rotation between the portions 263, 265. Where the tool
face
mark 301 on the external surface of the body 255 comprises a gyro tool face
mark, the tool face marks 316, 227 also comprise gyro tool face marks.
[00236] The downhole assembly 251 further comprises a release system 320
for allowing the drop tool assembly 250 to be released from the inner tube
assembly 201 while the drop tool assembly 250 and the inner tube assembly 201
are located downhole. The release system 320 is operable to disengage the
dogs 282 of the latching mechanism 281 from the spearhead point 101.
[00237] Additionally, the downhole assembly 251 comprises a synchronisation
system 325 for allowing the drop tool assembly 250 to be connected to the
inner
tube assembly 201 so that a predetermined tool face 301 of the drop tool
assembly 250 is synchronised to the inner tube assembly 201.
[00238] The synchronisation system 325 comprises a profiled portion 326 of
the lower body portion 265 of the drop tool assembly 250, and a profiled
portion
327 of the inner tube assembly 201. The profiled portion 326 comprises a mule
shoe 328, and the profiled portion 327 comprises a mule shoe 329. The profiled
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39
portions 326, 327 are configured to engage with each other such that the drop
tool assembly 250 is able to rotate relative to the inner tube assembly 201
into a
home position under its own weight or with only minimal thrust.
[00239] Downhole assembly 251 also comprises a locking system 245 for
mechanically locking the inner tube assembly 201 to inturn synchronise to the
tool face 301 of the drop tool assembly 250. The locking system 245 may
_ comprise a flow clutch which is provided as part of the inner tube
assembly 201
and which is able to engage and disengage the connection between two co-
linear components of a rock drilling device.
[00240] Rather than including the mechanical locking system 245, the tool
face position of the inner tube assembly 201 may be synchronised to the drop
tool assembly-250 by wireless transmission.
[00241] The drop tool assembly 250 also includes a water pressure activation
system 330 for indicating when the drop tool assembly 250 has landed in or
otherwise reached its final position within a borehole. The water pressure
activation system 330 is operable to activate/deactiveate the downhole
surveying
instrument. With reference to Figure 8, the water pressure activation system
330
comprises a ball 331 that will indicate a spike in fluid pressure when pumped
through a plastic tube 332 once landed. In addition, it includes a V packer
333,
=
and fluid ports 334. Similar water pressure activation systems are known in
the
art, consequently the system 330 will not be further described here.
[00242] The drop tool assembly 250 and the inner tube assembly 201 may be
picked up by an overshot assembly at the same time. There is the options of
only using the drop tool assembly 250 to take a borehole survey when such a
survey is required as it may be that a gyro survey is not required each time a
core sample is obtained. In such a situation, the drop tool assembly 250 may
not
be attached to the inner tube assembly 201.
[00243] It
should be appreciated that the scope of the invention is not limited
to the scope of the preferred embodiments described.
[00244] Further, modifications and improvements can be made without
affecting the scope of the invention.
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(002451 Throughout this specification, unless the context requires otherwise,
the word "comprise" or variations such as "comprises" or "comprising", will be
understood to imply the inclusion of a stated integer or group of integers but
not
the exclusion of any other integer or group of integers.
=
=
