Note: Descriptions are shown in the official language in which they were submitted.
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A DOVVNHOLE ASSEMBLY WITH SPRING ISOLATION FILTER
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates generally to an apparatus and method
for
drilling boreholes, and particularly to a downhole assembly and method for
generating
rotating magnetic fields or sensing magnetic fields (or other such parameters)
used for
guiding directional drilling of a borehole.
2. Technical Background
[0002] In underground drilling operations such as oil and gas drilling
operations, it
is often desirable to precisely control the drilling path of a new borehole
relative to a
known location (which may be disposed within the pathway of an existing
borehole).
To do that, operators may precisely monitor the location of the drill bit
forming the new
borehole relative to the existing borehole. For example, when a group of wells
are
drilled from an offshore platform, it is often necessary to drill new wells
spaced three
meters or less from existing wells for 300 meters or more during the initial
depth
interval. Subsequently, the wells may be directionally deviated and drilled to
targets
which may be two kilometers or more away in lateral directions. In another
example
application, this procedure may be useful when twin horizontal wells are
drilled for the
steam-assisted gravity drainage (SAGD) of heavy oils. In this example, it may
be
necessary to drill one well directly above the other while maintaining a five
meter ( 2
meter) spacing over 500 meters of horizontal extension at depths of 500 or
more
meters. Moreover, the present invention may be employed in various types of
underground drilling operations such as geothermal drilling, mining, hammer
drilling
and/or other such drilling operations; and the present invention should not be
deemed to
be limited to the aforementioned examples.
[0003] The monitoring system used to control the drilling operations can
include a
magnetic field sensor that is disposed in the existing borehole and a magnetic
source
that is disposed in the new borehole. Specifically, the magnetic source
assembly may
be disposed in a drill string proximate the drill bit/tool. The magnetic
source generates
rotating magnetic fields. The sensor apparatus typically includes a
magnetometer
assembly that is configured to measure the magnetic field radiating from the
magnetic
source assembly. The sensor apparatus precisely calculates the location of the
source
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from the field measurements. In this way, the drilling of the new borehole may
be
precisely controlled to achieve a desired separation between the existing
borehole and
the new borehole.
[0004] One issue that may be associated with a magnetic source assembly
or a
sensor assembly relates to their sensitivity to stress waves. Briefly stated,
the drilling
process may generate stress waves and vibrational forces which propagate along
the
drill string to the magnetic source or sensor assembly. The stress waves may
cause the
magnetic source assembly or the sensor assembly to fail.
[0005] Another issue relates to the thermal energy generated from various
sources.
Those skilled in the drilling/mining arts will appreciate that a drill bit may
become
relatively hot during mining and drilling operations. Magnetic materials may
lose their
magnetic remanence if temperatures exceed the temperature rating of the
magnetic
material.
[0006] Another issue relates to rotationally registering the magnetic
source
assembly or the sensor assembly to the drill bit. Rotational registration
allows the
monitoring system to determine the orientation of the drill bit, as well the
location of
the drill bit, to more effectively control the drilling process.
SUMMARY OF THE INVENTION
[0007] The present invention substantially addresses the needs described
above by
providing an apparatus and method configured to substantially isolate a
downhole
assembly from the stress waves experienced during drilling operations. The
present
invention includes cooling means that direct thermal energy away from the
apparatus.
The present invention is also configured to rotationally register a downhole
assembly to
a drill bit to thus provide drill bit orientation data during the drilling
control operation.
[0008] One aspect of the present invention is directed to an apparatus
for use on a
structural member having a longitudinal axis, the structural member being
configured
to propagate stress wave energy in an operational state. The stress wave
energy is
characterized by an operational frequency spectrum. The apparatus comprises a
housing assembly including a first end, a second end, and at least one
protective
enclosure configured to accommodate at least one device. The housing assembly
is
configured to be rotationally registered to the structural member when coupled
to the
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structural member. The housing assembly is characterized by a predetermined
housing
mass. A spring arrangement is coupled between the structural member and the
first end
and/or coupled between the structural member and the second end in the
operational
state. The spring arrangement is characterized by a predetermined force-
displacement
relationship. The housing assembly and the spring arrangement form an
isolation filter
characterized by a predetermined spectral transfer function, the predetermined
spectral
transfer function being a function of the predetermined housing mass and the
predetermined force-displacement relationship. The predetermined spectral
transfer
function includes a passband having frequencies that are substantially outside
the
operational frequency spectrum wherein the stress wave energy is substantially
attenuated in the operational state so that the housing member is
substantially isolated
from the stress wave energy.
[0009] In one embodiment, the spring arrangement includes at least one
first spring
element coupled between the first end and the structural member in the
operational
state, and wherein the spring arrangement includes at least one second spring
element
coupled between the second end and the structural member in the operational
state.
[0010] In one version of the embodiment, the housing assembly is
substantially
cylindrical, and wherein the at least one first spring element and the at
least one second
spring element have an outer diameter substantially equal to an outer diameter
of the
housing assembly.
[0011] In one version of the embodiment, the at least one first spring
element
includes a plurality of first spring elements coupled in parallel between the
first end and
the structural member in the operational state, and the at least one second
spring
element includes a plurality of second spring elements coupled in parallel
between the
second end and the structural member in the operational state.
[0012] In one version of the embodiment, the plurality of first spring
elements
includes four spring elements or the plurality of second spring elements
includes four
spring elements.
[0013] In another embodiment, the spring arrangement includes at least
one
compression spring, the at least one compression spring being configured to
oppose
compression along the longitudinal axis.
[0014] In another embodiment, the at least one device includes at least
one sensor
device or at least one magnetic source element.
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[0015] In one version of the embodiment, the at least one sensor device
includes at
least one accelerometer, at least one magnetometer, a gyro sensor, at least
one
environmental sensor, a piezoelectric transducer, or a battery device.
[0016] In one version of the embodiment, the at least one protective
enclosure
includes at least one set of pockets orientated in a plane perpendicular to
the
longitudinal axis, and wherein each pocket of the at least one set of pockets
is
configured to accommodate a magnetic source element.
[0017] In another embodiment, the isolation filter is a low pass filter
and the
passband includes frequencies substantially between 0 Hz and a natural
resonant
frequency, and wherein the isolation filter includes a stopband having
frequencies
substantially greater than the natural resonant frequency, and wherein the
stress wave
energy includes frequencies within the stopband so that the stress wave energy
is
substantially attenuated in the operational state in accordance with a 1/f2
roll-off
attenuation factor, wherein f is a frequency within the operational frequency
spectrum,
and wherein the attenuation factor increases as the frequency f increases.
[0018] In another embodiment, the housing assembly is substantially
cylindrical
having an inner diameter and an outer diameter respectively defining an
interior
housing surface and an exterior housing surface; and wherein the housing
assembly
includes a first housing portion coupled to a second housing portion, each of
the first
housing portion and the second housing portion having a substantially
semicircular
cross-section so that the housing assembly has a substantially circular cross-
section
when the first housing portion is coupled to the second housing portion; and
wherein a
key channel arrangement is formed in the interior housing surface where the
first
housing portion coupled to the second housing portion, the key channel
arrangement
being configured to mate with a portion of the structural member to effect
rotational
registration.
[0019] In one version of the embodiment, the at least one protective
enclosure
includes a plurality of pockets formed in the interior housing surface or the
exterior
housing surface, each pocket of the plurality of pockets being configured to
accommodate a magnetic source device; or wherein the at least one protective
enclosure is formed in the exterior housing surface and configured to
accommodate a
sensor assembly.
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[0020] In one version of the embodiment, the magnetic source device is
selected
from a group of magnetic source devices including a permanent magnet and an
electromagnet.
[0021] In one version of the embodiment, a protective cover is disposed
over the
housing assembly in the operational state, the protective cover substantially
configured
to conform to the exterior housing surface.
[0022] In one version of the embodiment, the protective cover is disposed
over the
spring arrangement in the operational state.
[0023] In another embodiment, the predetermined force-displacement
relationship
includes a constant spring rate or a variable spring rate.
[0024] Another aspect of the present invention is directed to an assembly
comprising a structural member having a longitudinal axis, the structural
member being
configured to propagate stress wave energy in an operational state, the stress
wave
energy being characterized by an operational frequency spectrum. An apparatus
is
coupled and rotationally registered to the structural member, the apparatus
comprises a
housing assembly including a first end, a second end, and at least one
protective
enclosure configured to accommodate at least one device, the housing assembly
being
characterized by a predetermined housing mass. A spring arrangement is coupled
between the structural member and the first end and/or coupled between the
structural
member and the second end, the spring arrangement being characterized by a
predetermined force-displacement relationship. The housing assembly and the
spring
arrangement form an isolation filter characterized by a predetermined spectral
transfer
function, the predetermined spectral transfer function being a function of the
predetermined housing mass and the predetermined force-displacement
relationship.
The predetermined spectral transfer function includes a passband having
frequencies
that are substantially outside the operational frequency spectrum wherein the
stress
wave energy is substantially attenuated in the operational state so that the
housing
member is substantially isolated from the stress wave energy.
[0025] In an embodiment, the spring arrangement includes at least one
first spring
element coupled between the first end and the structural member, and at least
one
second spring element coupled between the second end and the structural
member.
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[0026] In one version of the embodiment, the at least one first spring
element and
the at least one second spring element have an outer diameter substantially
equal to an
outer diameter of the housing assembly.
[0027] In one version of the embodiment, the at least one first spring
element
includes a plurality of first spring elements coupled in parallel between the
first end and
the structural member, and wherein the at least one second spring element
includes a
plurality of second spring elements coupled in parallel between the second end
and the
structural member.
[0028] In one version of the embodiment, the plurality of first spring
elements
includes four spring elements and/or wherein the plurality of second spring
elements
includes four spring elements.
[0029] In one version of the embodiment, the structural member is a drill
rod or a
drill rod attachment including a central fluid channel configured to conduct a
pressurized fluid along the longitudinal axis in the operational state, the
structural
member including a plurality of fluid openings in a region where the
structural member
is coupled to the housing assembly, the pressurized fluid including a gas or a
liquid.
[0030] In another embodiment, the structural member includes a carrying
region, a
first shoulder member being disposed at a first end portion of the carrying
region and a
second shoulder member being disposed at a second end portion of the carrying
region,
wherein the housing assembly is coupled to the carrying region between the
first
shoulder member and the second shoulder member, and wherein the spring
arrangement includes at least one first spring element coupled between the
first end and
the first shoulder member, and at least one second spring element coupled
between the
second end and the second shoulder member.
[0031] In one version of the embodiment, the structural member further
comprises
a box portion disposed at a first end of the structural member, a pin portion
disposed at
a second end of the structural member, and a carrying region being disposed
between
the box portion and the pin portion, the box portion being configured to
accommodate a
drive element of a drill string and the pin portion being configured to
accommodate a
tool bit or a drill bit.
[0032] In another embodiment, the spring arrangement includes at least
one first
spring element and at least one second spring element, and wherein the
structural
member further comprises a first collar member and a second collar member, and
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wherein the at least one first spring element is coupled between the first end
and the
first collar member, and wherein the at least one second spring element is
coupled
between the second collar member and the second end.
[0033] In one version of the embodiment, the first collar member includes
a first
registration feature configured to rotationally register the at least one
first spring
element to an orientation feature on the structural member, and/or wherein the
second
collar member includes a second registration feature configured to
rotationally register
the at least one second spring element to an orientation feature on the
structural
member.
[0034] In another embodiment, the at least one device includes at least
one sensor
device or at least one magnetic source element.
[0035] In one version of the embodiment, the at least one sensor device
includes at
least one accelerometer, at least one magnetometer module, a gyro sensor, at
least one
environmental sensor, a piezoelectric transducer, or a battery device.
[0036] In one version of the embodiment, the at least one protective
enclosure
includes at least one set of pockets orientated in a plane perpendicular to
the
longitudinal axis, and wherein each pocket of the at least one set of pockets
is
configured to accommodate a magnetic source element.
[0037] In another embodiment, the isolation filter is a low pass filter
and the
passband includes frequencies substantially between 0 Hz and a natural
resonant
frequency, and wherein the isolation filter includes a stopband having
frequencies
substantially greater than the natural resonant frequency, wherein the stress
wave
energy includes frequencies within the stopband so that the stress wave energy
is
substantially attenuated in the operational state in accordance with a 1/f2
roll-off
attenuation factor, wherein f is a frequency within the operational frequency
spectrum
and wherein the attenuation factor increases as the frequency f increases.
[0038] In another embodiment, the predetermined force-displacement
relationship
includes a constant spring rate or a variable spring rate.
[0039] Another aspect of the present invention is directed to a method
comprising:
providing a structural member having a longitudinal axis, the structural
member being
configured to propagate stress wave energy in an operational state, the stress
wave
energy being characterized by an operational frequency spectrum; providing a
housing
assembly including a first end, a second end, and at least one protective
enclosure
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configured to accommodate at least one device, the housing assembly being
characterized by a predetermined housing mass; providing a spring arrangement,
the
spring arrangement being characterized by a predetermined force-displacement
relationship, the housing assembly and the spring arrangement forming an
isolation
filter characterized by a predetermined spectral transfer function, the
predetermined
spectral transfer function being a function of the predetermined housing mass
and the
predetermined force-displacement relationship, the predetermined spectral
transfer
function including a passband having frequencies that are substantially
outside the
operational frequency spectrum; coupling the housing assembly to the
structural
member such that the housing assembly is rotationally registered to the
structural
member; coupling the spring arrangement between the structural member and the
first
end and/or between the structural member and the second end; and entering an
operational state wherein stress wave energy propagates along the structural
member,
the stress wave energy being substantially attenuated by the isolation filter
so that the
housing member is substantially isolated from the stress wave energy.
[0040] In another embodiment, the isolation filter is a low pass filter
and the
passband includes frequencies substantially between 0 Hz and a natural
resonant
frequency, and wherein the isolation filter includes a stopband having
frequencies
substantially greater than the natural resonant frequency, wherein the stress
wave
energy includes frequencies within the stopband so that the stress wave energy
is
substantially attenuated in the operational state in accordance with a 1/f2
roll-off
attenuation factor, wherein f is a frequency within the operational frequency
spectrum
and wherein the attenuation factor increases as the frequency f increases.
[0041] Additional features and advantages of the invention will be set
forth in the
detailed description which follows, and in part will be readily apparent to
those skilled
in the art from that description or recognized by practicing the invention as
described
herein, including the detailed description which follows, the claims, as well
as the
appended drawings.
[0042] It is to be understood that both the foregoing general description
and the
following detailed description are merely exemplary of the invention, and are
intended
to provide an overview or framework for understanding the nature and character
of the
invention as it is claimed. It should be appreciated that all combinations of
the
foregoing concepts and additional concepts discussed in greater detail below
(provided
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such concepts are not mutually inconsistent) are contemplated as being part of
the
inventive subject matter disclosed herein. In particular, all combinations of
claimed
subject matter appearing at the end of this disclosure are contemplated as
being part of
the inventive subject matter disclosed herein. It should also be appreciated
that
terminology explicitly employed herein that also may appear in any disclosure
incorporated by reference should be accorded a meaning most consistent with
the
particular concepts disclosed herein.
[0043] The accompanying drawings are included to provide a further
understanding
of the invention, and are incorporated in and constitute a part of this
specification. The
drawings illustrate various embodiments of the invention and together with the
description serve to explain the principles and operation of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] In the drawings, like reference characters generally refer to the
same parts
throughout the different views. Also, the drawings are not necessarily to
scale,
emphasis instead generally being placed upon illustrating the principles of
the
invention.
[0045] Figure 1 is a cross-sectional view of a pair of horizontal, spaced
wells in
accordance with one application of the present invention;
[0046] Figure 2 is a cross-sectional view of a pair of horizontal, spaced
boreholes in
accordance with another application of the present invention;
[0047] Figure 3 is a diagrammatic depiction of a downhole assembly in
accordance
with an embodiment of the present invention;
[0048] Figure 4 is a detail view of a carriage apparatus of the downhole
assembly
depicted in Figure 3;
[0049] Figure 5 is a diagrammatic depiction of a drill rod structure of
the downhole
apparatus depicted in Figure 3 with the carriage apparatus removed;
[0050] Figure 6 is a detail view of carrying portion of the drill rod
depicted in
Figure 5;
[0051] Figure 7 is an isometric view of the carriage apparatus (with
cover) depicted
at Figure 3;
[0052] Figure 8 is an isometric view of a carriage housing portion of the
carriage
apparatus depicted at Figure 7;
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[0053] Figure 9 is an isometric view of a carriage housing in accordance
with an
alternate embodiment;
[0054] Figure 10 is a detail view of a portion of the carriage housing
depicted at
Figure 9;
[0055] Figures 11A ¨ 11C are cross-sectional views of the carriage
housing
depicted at Figure 9;
[0056] Figure 12 is a diagrammatic depiction of stress wave propagation
in a top-
hammer rock drilling operation;
[0057] Figures 13 A-B are charts showing an idealized stress wave surface
velocity
and surface acceleration resulting from the hammer blow depicted at Figure 12;
[0058] Figure 13 C-D are charts showing the idealized stress wave surface
velocity
and surface acceleration depicted at Figure 12 with reflections;
[0059] Figure 13 E-F are charts showing the stress wave surface velocity
and
surface acceleration signals depicted at Figures 13 C-D for multiple (e.g.,
ten) top
hammer blows;
[0060] Figure 14 is a diagrammatic depiction of a spring mass isolation
filter in
accordance with the present invention;
[0061] Figure 15A is a chart showing an FFT of the surface accelerations
depicted
in Figure 13F;
[0062] Figure 15B is a chart showing a transfer function for the spring
mass
isolation filter depicted at Figure 14 and implemented by the carriage
apparatus
depicted throughout;
[0063] Figure 15C is a chart showing the output of the spring mass
isolation filter
when subject to the excitations shown at Fig. 15A;
[0064] Figure 16 is a diagrammatic depiction of a downhole assembly in
accordance with an alternate embodiment of the present invention;
[0065] Figure 17 diagrammatic depiction of a downhole assembly in
accordance
with another alternate embodiment of the present invention;
[0066] Figures 18A ¨ 18D are detail views of a clamp keying arrangement
employed at Figs. 16-17;
[0067] Figure 19 is a detail view of the carriage apparatus employing the
clamping
arrangement depicted at Fig. 18D;
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[0068] Figure 20 is a cross-sectional view of the carriage apparatus
employing the
clamping arrangement depicted at Fig. 18D;
[0069] Figure 21 is a diagrammatic depiction of a downhole assembly in
accordance with yet another alternate embodiment of the present invention;
[0070] Figure 22 is a detail view of a carriage apparatus of the downhole
assembly
depicted in Figure 21;
[0071] Figure 23 is a detail view of a portion of the carriage apparatus
depicted in
Figure 21;
[0072] Figure 24 is a detail view of a carriage cover in accordance with
another
alternate embodiment of the present invention;
[0073] Figure 25 is a cross-sectional view of the carriage apparatus
depicted in
Figure 24;
[0074] Figure 26 is a detail view of a portion of the carriage apparatus
in
accordance with yet another alternate embodiment of the present invention;
[0075] Figure 27 is a diagrammatic depiction of a downhole assembly in
accordance with yet another alternate embodiment of the present invention;
[0076] Figure 28 is a detail view of a carriage apparatus of the downhole
assembly
depicted in Figure 27;
[0077] Figure 29 is a diagrammatic depiction of the sensor assembly
depicted at
Figures 27 - 28;
[0078] Figure 30 is a diagrammatic depiction of a downhole assembly in
accordance with yet another alternate embodiment of the present invention;
[0079] Figure 31 is a diagrammatic depiction of the downhole assembly
shown in
Figure 30 with a protective cover;
[0080] Figure 32 is an isometric view of a downhole assembly in
accordance with
yet another alternate embodiment of the present invention;
[0081] Figure 33 is an isometric view of the drill rod structure depicted
in Figure 32
with the carriage apparatus removed;
[0082] Figure 34 is a cross-sectional view of the carriage housing
depicted in
Figure 32;
[0083] Figure 35 is a detail view of a collar assembly depicted at Figure
32;
[0084] Figure 36 is a detail view of a collar assembly depicted at Figure
32 in
accordance with an alternate embodiment of the present invention; and
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[0085] Figures 37 and 38 are detail views of the spring elements depicted
at Figure
32.
DETAILED DESCRIPTION
[0086] Reference will now be made in detail to the present embodiments of
the
invention, examples of which are illustrated in the accompanying drawings.
Wherever
possible, the same reference numbers will be used throughout the drawings to
refer to
the same or like parts. An exemplary embodiment of the downhole assembly of
the
present invention is shown in Figure 1, and is designated generally throughout
by
reference numeral 10.
[0087] As depicted in Figure 1, a cross-sectional view of a measurement
system
1000 featuring a magnetic source apparatus 10 and a magnetic field measurement
sensor 50 is disclosed. The measurement system 100 is shown in the context of
a pair
of horizontal, spaced wells in accordance with an application of the present
invention.
This view illustrates a method and apparatus for guiding the directional
drilling of a
second borehole 3 relative to a first (previously drilled) borehole 5 such
that the new
borehole 3 is separated from the existing borehole 5 by a predetermined
distance along
their respective paths. The new borehole 3 contains a drill string 4 that
carries or
includes the downhole apparatus 10 equipped with the spring mass isolation
filter. The
drill assembly includes a drill bit 8 which is driven by suitable motors in a
conventional
manner, to rotate about a longitudinal axis of rotation and/or to reciprocate
(axially
hammer) along the longitudinal axis. The drill bit 8 may be steerable to
control the
drilling direction in response to control signals provided by a control
station 2 located
at the surface 1 (of the Earth). The magnetic source apparatus 10 includes a
plurality of
magnet elements 100 that generate an elliptically polarized rotating magnetic
field 300
that is centered at the magnetic source apparatus 10 in the new borehole 3.
The
magnetic source apparatus 10 includes a magnetic field source 100, which may
be
implemented using a permanent bar magnet 100 that is typically mounted in a
non-
magnetic portion of the assembly (not shown in this view) located at the
distal end of
the drill string behind the rotating drill bit 8. (The term "non-magnetic"
material refers
to a material that has a magnetic permeability that is comparable to air or a
vacuum).
The magnets 100 have north-south axes that are perpendicular to the
longitudinal axis 7
of the drill bit 8. Because assembly 100 rotates (and/or reciprocates) about
the
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longitudinal axis 7 with the drill bit 8, the elliptically polarized magnetic
field 300 is an
alternating magnetic field at observation point 52 (which is radially spaced
from the
magnets 100).
[0088] The existing borehole 5 is illustrative of a horizontal well of
the type which
may be used for steam assisted gravity drainage of heavy oil (SADG). Of
course, the
present invention may be employed in any type of drilling application (and/or
in any
orientation) such as oil and gas drilling operations, geothermal, hammer
drilling, top-
hammer drilling, mining and/or other such drilling operations. In the example
depicted
in Figure 1, the drill bit 8 is controlled so that the borehole 3 is drilled
directly above
borehole 5 and is spaced above it by a predetermined, substantially constant
distance.
Control of the drill bit 8 is carried out in response to measurements made in
the target
borehole 5 by a magnetic field sensor 50. The measuring tool 50 is lowered
into the
borehole 5 through a casing by means of a suitable wireline 9, with the
location, or
depth, of the measuring tool being controlled from the earth's surface in
conventional
manner from an equipment truck 200. In one embodiment, the spring mass
isolation
filter of the present invention is embodied within the magnetic field sensor
50.
[0089] Again, the magnetic field sensor 50 is located at an observation
point 52 and
may incorporate a plurality of fluxgate magnetometers having their axes of
maximum
sensitivity intersecting each other at one or more observation points and
substantially at
right angles to each other. In one embodiment, the sensor may include two
magnetometers; in another embodiment, there may be three magnetometers. If a
gradient measurement is required, there may be six magnetometers in the sensor
50.
The magnetometers measure the amplitude and the phase of two perpendicular
components of the magnetic field 300. The measuring tool 50 may also include
additional sensors such as earth's field sensors, inclinometers, and/or a
gyroscope
(depending on the application).
[0090] As embodied herein and depicted in Figure 2, a cross-sectional
view of a
pair of horizontal, spaced boreholes in accordance with another application of
the
present invention is disclosed. In this example application, an underground
rock
drilling assembly 1000 employs a movable carrier 2 having one or more booms 2-
3 connected to the carrier 2. A drilling unit 2-4 may be disposed at the
distal end of the
boom 2-3. The drilling unit 2-4 may comprise a feed beam 2-5 and a rock
drilling
machine 2-6 which drives the drill rod 4 and hence drill bit 8 into a rock
wall 1. In this
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application the drilling assembly is used to form a series of boreholes in the
rock face,
wherein each borehole is formed such that it follows a predetermined path in
three-
dimensional space within the rock wall/structure 1.
[0091] Like the application depicted at Figure 1, the measurement system
1000
features a magnetic source apparatus 10 (that includes the spring mass
isolation filter)
and a magnetic field measurement sensor 50. (Again, in some applications the
sensor
50 may include the spring mass isolation filter). In the application depicted
at Figure 2,
however, a cross-sectional view of a pair of horizontal, spaced boreholes is
shown.
Like the previous application shown at Figure 1, this view illustrates a
method and
apparatus for guiding the directional drilling of a second borehole 3 relative
to a first
(previously drilled) borehole 5 such that the new borehole 3 is separated from
the
existing borehole 5 by a predetermined distance along their respective paths.
The new
borehole 3 contains a carriage assembly having a magnetic source apparatus 10.
As
before, the magnetic field sensor 50 is located at an observation point 52 and
may
incorporate a plurality of ffircgate magnetometers (e.g., up to three) having
their axes of
maximum sensitivity intersecting each other at the observation point and
substantially
at right angles to each other. (In another embodiment there can be multiple
sets of
magnetometers (of up to three per set)). The magnetometers measure the
amplitude
and the phase of two or more perpendicular components of the magnetic field
300. The
measuring tool 50 may also include additional sensors such as earth's field
sensors,
gravity sensors, inclinometers, and/or a gyroscope depending on the
application.
[0092] As embodied herein and depicted in Figure 3, a diagrammatic
depiction of a
magnetic source downhole assembly 10 in accordance with an embodiment of the
present invention is disclosed. The downhole assembly 10 includes a carriage
apparatus
20 coupled to a structural member 4. In one embodiment, the structural member
can be
a drill rod 4, which is typically employed in the example applications
depicted at
Figures 1 and 2. However, the present invention should not be deemed to be
limited to
the example applications depicted at Figures 1 and 2.
[0093] One skilled in the art will appreciate that the present invention
may be
employed in other applications and thus, the drill rod 4 may be implemented
using any
structural member suitable for the application at hand. One such alternate
application
includes performing a borehole surveying operation. In another alternate
application,
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the carriage apparatus 20 includes a sensor assembly 16 for use in a
previously drilled
borehole, in an extant pipeline, in a borehole survey or any other suitable
application.
[0094] The drill rod 4 (or structural member) may include shoulder
members (4-2,
4-4) that are used to accommodate the carriage apparatus 20 therebetween. The
drill
rod 4 may include a box portion 4-6 (i.e., a female thread) at one end
thereof, and a pin
portion 4-1 (i.e., a male thread) at second, opposite end thereof The pin
portion 4-1
may also include a drill bit shoulder 4-10 which abuts the drill bit 8 when
the drill bit 8
is screwed onto the pin portion 4-1. The box portion 4-6 may be configured to
accommodate a drive member associated with the drilling assembly 1000 (figs. 1
and
2). The pin portion 4-1 may be configured to accommodate other tools suitable
for a
given application as well as a drill bit 8.
[0095] The carriage apparatus 20 is shown to include a protective cover
member
30. The cover member 30 is employed to protect a downhole carriage housing 12
disposed under the cover member 30, between the shoulders 4-2 and 4-4. The
cover 30
may be fastened to the housing 12 using any suitable fastener elements or
techniques
(e.g., screws, rivets, press fit, etc.).
[0096] The carriage apparatus also includes a plurality of spring
elements 14 that
are coupled between the carriage apparatus 20 and the shoulders (4-2, 4-4). As
described below, the spring elements 14 and the mass of the carriage apparatus
20 form
an isolation filter that is characterized by a low pass frequency transfer
function (Fig.
15B) that is substantially below an operational frequency spectrum (See, e.g.,
Fig.
15A).
[0097] Specifically, the low pass frequency transfer function is a
function of a
predetermined mass of the carriage apparatus and the total effective spring
rate (force-
displacement relationship) of springs 14. Specifically, each spring 14 may
have a
spring rate equal to k, where k is some numerical value. Also, the spring may
have a
variable rate. The springs 14 at each end of the carriage apparatus 20 can be
implemented as four springs 14 disposed in a parallel spring arrangement with
a
composite spring rate being substantially equal to 4k. Since there are four
springs at
each end, the total spring rate would be about 8k. The spring rate is selected
based on
the carriage apparatus mass to obtain a desired low pass frequency transfer
function
(see Fig. 15B) relative to the operational frequency spectrum (Fig. 15A).
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[0098] The operational frequency spectrum can refer to the frequency
content of
surface accelerations propagating along the drill rod as a result of a given
drilling or
mining operation. (The surface accelerations are derived from the stress wave
energy
produced by drilling/hammering). Because the frequency content of the surface
accelerations mostly includes frequencies greater than the low pass frequency
(spectral)
transfer function, the stress wave energy is attenuated and substantially
prevented from
disturbing the carriage apparatus 20. Those skilled in the art will appreciate
that the
resonant frequency is selected so that it is well below the operational
frequency
spectrum (Fig. 15A). While there may be some small amount of energy at or near
the
resonant frequency, it is not enough to induce a carriage failure mode.
[0099] As embodied herein and depicted in Figure 4, a detail view of a
carriage
apparatus 20 depicted in Figure 3 is disclosed. In this view, the cover member
30 is
removed from the carriage apparatus 20 to show the downhole housing 12. The
downhole housing 12 includes a first housing portion 12-1 and a second housing
portion 12-2. During assembly, the first housing portion 12-1 is coupled to
the second
housing portion 12-2 with the drill rod 4 therebetween so that the downhole
housing 12
is spatially registered to the drill bit 8. The gap between each edge of the
carriage
housing 12 and its respective drill rod shoulder (4-2, 4-4) is a function of
the spring
constant and carriage assembly weight, so that under typical conditions the
carriage
apparatus 20 will not contact the shoulders. If the conditions are such that
carriage
assembly 20 does make contact with a shoulder (4-2, 4-4), each spring 14 is
configured
to fully retract into its respective spring pocket 12-8 (Fig. 8) without fully
compressing.
[00100] In the magnetic source embodiment, each housing portion (12-1, 12-2)
includes a plurality of magnetic field source elements (e.g., permanent
magnets,
electromagnets) 100 disposed within respective pockets 12-3. The permanent
magnets
100 are configured to generate magnetic field 300 (as shown at Figures 1 and
2).
[00101] As noted above, the downhole housing 12 may also be configured to
accommodate a sensor assembly 16 (Figs. 27-29) wherein the housing portions
(12-1,
12-2) may include compartments configured to accommodate various sensor
components such as inclinometers (tilt sensors), magnetometers, environmental
sensors
(pressure, temperature, radiation, etc.), gravity sensors (accelerometers),
rotation
sensors (gyroscope), a power supply and/or battery, a receiver, transmitter, a
processor/controller, memory, etc., depending on the application.
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[00102] As embodied herein and depicted in Figure 5, a diagrammatic depiction
of a
drill rod structure 4 shown in Figure 3 is disclosed. (Here, the carriage
apparatus 20 is
removed for clarity of illustration). The drill rod 4 includes a source/sensor
carrying
region 4-9 disposed between the shoulder members (4-2, 4-4). (Depending on the
housing embodiment, region 4-9 either carries the magnetic source housing or
the
sensor housing). As before, the drill rod 4 may include a box portion 4-6 at
one end
thereof, and a pin portion 4-1 at second, opposite end thereof Fluid channels
4-3 and
key members 4-8 are disposed within the payload carrying region 4-9 between
the
shoulder members (4-2, 4-4). The remaining features of the drill rod were
previously
described above.
[00103] Referring to Figure 6, a detail view of carrying portion 4-9 of the
drill rod
depicted in Figure 5 is shown. In this embodiment, the carrying region 4-9
includes
four fluid channels 4-3 and two key members 4-8 disposed in a central region
of the
carrying region 4-9. Specifically, a set of two fluid channels 4-3 alternates
with a key
member 4-8 at 90 increments around the circumference of the central area of
the
carrying region 4-9. Thus, a set of two fluid channels 4-3 are disposed 180
away from
the second set of fluid channels 4-3, and one key member 4-8 is disposed 180
away
from the second key member 4-8.
[00104] Those skilled in the art will appreciate that the size and number of
the fluid
channels 4-3 may vary depending on the application. For example, the number
and size
of the fluid channels 4-3 may be a function of the type of fluid traversing
the channels
(e.g., air, water, etc.) as well as the application for which the assembly is
being used.
Those skilled in the art will appreciate that the number of fluid channels 4-3
may vary
depending on the thermal energy characteristics of the operating environment.
In
relatively warmer environments, the drill rod 4 will include additional fluid
channels 4-
3 to better direct the thermal energy away from the carriage 20. In relatively
cooler
environments, the drill rod 4 may include fewer fluid channels 4-3 (or none at
all if
cooling is not an issue in the application). The number of fluid channels 4-3
shown in
Figure 6 is merely a representative example.
[00105] The number of key members 4-8 may vary depending on the application
for
which the assembly is being used. Accordingly, more or less channels 4-3
and/or key
members 4-8 may be employed depending on the embodiment and/or application.
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[00106] The existence of fluid channels 4-3 presupposes the existence of a
central
fluid-flow channel (not shown) that extends through the entire length of the
drill rod 4
and is centered about the longitudinal axis 7 (see, e.g., Fig. 1). In one
embodiment, the
diameter of the central fluid-flow channel may be about 0.870 inches. The
outer
diameter of the source/sensor carrying region 4-9 may be about 2.470 inches.
(The fluid
transmitted through via 4-12 may be air or some other suitable fluid).
[00107] In one embodiment, the drill rod 4 is formed by a machining a steel
alloy
billet (e.g., using a CNC milling machine) to produce an integrally formed
drill rod. In
another alternate embodiment, the shoulder members (4-2, 4-4) and/or the key
members 4-8 may be formed on a steel alloy rod using a sputter-welding
process,
wherein layers of steel material are deposited and built-up along the
circumference of
the rod at appropriate locations. The built-up portions are then machined
(using, e.g., a
lathe) to form the shoulder portions (4-2, 4-4) and the key members 4-8. The
box
portion 4-6 and the pin portion 4-1 may be welded to their respective ends of
the drill
rod 4 by way of a friction-welding process. In the various alternate
embodiments, those
of ordinary skill in the art will appreciate that the shoulders (4-2, 4-4),
key members 4-
8, pin 4-1, box 4-6, and other such features may be formed and/or machined
using any
suitable fabrication method(s).
[00108] In one embodiment of the present invention, the drill rod may be
formed
using a chrome-molybdenum AISI Alloy 4140 steel bar (which has, e.g., a
tensile
strength of about 95,000 psi, and an elastic modulus within a range of about
27,557 ¨
30,458 ksi). Thus, chrome-molybdenum AISI Alloy 4140 steel bars may be
employed
in each of the fabrication and machining embodiments described above.
[00109] As embodied herein and depicted in Figure 7, an isometric view of the
carriage apparatus 20 depicted at Figure 3 is disclosed. In this view, the non-
magnetic
cover 30 is disposed over the carriage housing 12. Each set of four spring
elements 14
extend from their respective ends of the carriage housing 12. The non-magnetic
cover
30 may be formed using any suitable non-magnetic material including stainless
steel,
titanium, BeCu, aluminum, etc. In one embodiment, the cover 30 may be formed
using
an austenitic nickel-chromium alloy material such as the Inconel alloys
manufactured
by Special Metals Corporation. The austenitic nickel-chromium alloys are
oxidation-
corrosion-resistant materials well suited for service in extreme environments
subjected
to pressure and heat.
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[00110] Each spring 14 may be formed using any suitable material, but in one
embodiment, the springs 14 are formed from a chrome-silicon steel material. In
one
embodiment, the spring conforms to a spring pocket 12-8 diameter of about 3/8"
and
has an interior diameter of about 3/16". The spring rate may be about 10.5
N/mm. In
one embodiment, the springs 14 may be manufactured by McMaster-Carr and be
implemented by the McMaster-Carr Blue Chrome-Silicon Steel Die Spring PN
9573K11.
[00111] Referring to Figure 8, an isometric view of the carriage housing 12
depicted
at Figure 7 is disclosed. The carriage housing 12 includes a first housing
portion 12-1
connected to a second housing portion 12-2. As noted previously, the exterior
surface
of each housing portion includes a plurality of pockets 12-3, each pocket 12-3
being
configured to accommodate a permanent magnet 100 (not shown).
[00112] A key channel 12-6 is formed in an interior portion of the housing 12
at the
connection interface 12-4. Each key channel 12-6 is configured to accommodate
one of
the key members 4-8 therein. When the key members 4-8 are disposed within
their
respective key channels 12-6, the carriage housing 12 is rotationally
registered to a
predetermined portion of the drill bit 8, and is substantially prevented from
rotating
about the central longitudinal axis 7 of the drill string (see, e.g., Fig. 1).
[00113] Four spring pockets 12-8 are formed in each end of the carriage
housing 12,
with two spring pockets 12-8 being formed at one end of each housing portion
(12-1,
12-2). The depth of each spring pocket can be a function of the spring
composition
such that a pocket depth can allow a spring 14 to fully retract within the
pocket 12-8
without the spring becoming fully compressed into a solid cylinder.
[00114] Referring to Figure 9, an isometric view of a carriage housing 12 in
accordance with an alternate embodiment is disclosed. Descriptions of the
magnet
pockets 12-3, spring pockets 12-8 and the key channel 12-6 are omitted for
brevity's
sake since these elements were described above. In this embodiment, the
housing
portions (12-1, 12-2) include additional features such as mating pins 12-100,
mating
holes 12-10, and rivet holes 12-12. Moreover, the section B-B, section A-A and
section
C-C are shown at Figures 11A, 11B and 11C, respectively, and described below.
[00115] In this embodiment, the mating holes 12-10 are configured to
accommodate
mating pins 12-100 that are used to couple the first housing 12-1 to the
second housing
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12-2. The rivet holes 12-12 are configured to accommodate rivets which are
used to
secure the housing cover 30 to the carriage housing 12.
[00116] Referring to Figure 10, a detail view of a portion 12-2 of the
carriage
housing 12 depicted at Figure 9 is disclosed. (This drawing figure is equally
applicable
to housing portion 12-1, except that portion 12-1 would be a mirror image of
housing
portion 12-2 such that each side of the housing 12 would include a set of
mating pins
12-100). This view clearly shows that the key channel 12-6 is created by
forming a
notched region 12-60 along the edges of the housing portions (12-1, 12-2).
[00117] Referring to Figures 11A ¨ 11C, cross-sectional views of the carriage
housing depicted at Figure 9 are disclosed. Figure 11A is a cross-sectional
view
corresponding to section B-B of Figure 9. Here, the rivet holes 12-12 have an
hour-
glass shape so that the wider portions of the rivet hole 12-12 can accommodate
the
thicker head portions of a rivet, and wherein the relatively narrow portions
of the rivet
hole 12-12 are configured to accommodate the relatively narrow body portion of
a
rivet. This view also provides a sectional view of key channel 12-6 formed at
opposite
edges of housing 12. Figure 11B is a cross-sectional view corresponding to
section A-
A of Figure 9. In this view, the mating holes 12-10 configured to accommodate
mating
pins 12-100 are shown. Figure 11C is a cross-sectional view corresponding to
section
C-C of Figure 9. In this view, the section includes three magnet pockets 12-3
per
housing portion (12-1 or 12-2) for a total of six magnet pockets per section.
In
reference to Figure 9, therefore, the carriage housing 12 includes five magnet
sections
for a total of about thirty magnet pockets.
[00118] In one embodiment, the carriage housing 12 may be formed from a
cylindrical or tube-shaped material (hereinafter "stock material") that is
divided into
two halves to form the first housing portion 12-1 and the second housing
portion 12-2.
(There is no significance placed on the terms first housing or second housing
other than
the fact that the housing 12 includes two housing portions (12-1, 12-2)). In
one
embodiment, the stock material may be comprised of a Teflon PTFE resin
material that
substantially complies with UL 94V0 and ASTM D1710 standards. In other
embodiments, the tube material may be comprised of any suitable material; for
example, the material may be an acetal homopolymer (Polyoxymethylene POM)
material sometimes known as Delrin. In another example, the material may be a
Polyether ether ketone (PEEK) material, which is a colorless, organic,
thermoplastic
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polymer. In yet another embodiment, the material may be bronze or a bronze
alloy
material, titanium, stainless steel, or any suitable non-magnetic material.
Those skilled
in the art will appreciate that the materials of the tube used to form the
magnetic source
housing 12 may vary in accordance with the application since the environment
(vibrations, shock, temperature, etc.) may also differ from application to
application.
[00119] In one embodiment, the stock material may have an outer diameter (OD)
of
about 4 inches, an inner diameter (ID) of about two inches, and a wall
thickness of
about one inch. Those of ordinary skill in the art will appreciate that the
dimensions of
the stock material used to form the downhole housing 12 may vary in accordance
with
the embodiment and/or application.
[00120] Before the stock material is separated into two parts (i.e., to
form the first
housing portion 12-1 and the second housing portion 12-2), the stock material
may be
machined to include the various features depicted herein. For example, the
stock
material may be machined to include the mating pins 12-100, mating holes 12-
10, rivet
holes 12-12, magnetic source pockets 12-3, and the sensor assembly pockets 12-
27 (See
Figure 27). The rivet holes 12-12 may also be configured to accommodate any
suitable
fastener element (e.g., a pop-rivet, etc.) for connecting the first housing
portion 12-1 to
the second housing portion 12-2 during assembly. Alternatively, some or all of
the
features may be machined after the stock material is separated into two parts.
[00121] Each magnetic source pocket 12-3 is configured to accommodate a
magnetic
source element 100 and an epoxy (or other) potting material. The potting
material is
employed to hold the magnetic element 100 in place within its respective
pocket 12-3.
[00122] The magnetic sources 100 employed in the invention may vary in
accordance with the application since the environment (vibrations, shock,
temperature,
etc.) or desired operating parameters may also change in accordance with the
application. Some non-limiting examples of operating parameters may be
remanence,
coercivity, Curie temperature, etc. Accordingly, the magnetic source elements
100 may
be implemented using neodymium rare earth magnets, samarium cobalt magnets or
any
suitable magnetic source elements depending on the application. In another
embodiment, the magnetic source elements may be implemented by electromagnetic
source elements. In this embodiment, a wireline may be fed to carriage
apparatus 20
via the central fluid channel of the drill rod. The wireline would provide
electrical
power from an uphole location to the carriage 20. In another embodiment, one
of more
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piezoelectric transducers would be included in the carriage housing 12 and be
configured to convert the mechanical energy (Wh) generated by the drilling
operations
into electrical energy. The electrical energy would be stored in a battery
which would,
in turn, provide power to the electromagnets. In another embodiment, a battery
without
piezoelectric transducers can be employed.
[00123] As described herein, the key channel 12-6 may be configured as a
rectangularly-shaped channel that is machined (or otherwise formed) to
accommodate
the key element 4-8 formed in the carrying region 4-9 of the drill rod 4.
(Note that key
channel 12-6, the key element 4-8 and source-carrying region 4-9 may be
machined to
conform to any suitable geometry and is thus not limited to a rectangular
shape). In
any event, the key channel 12-6 conforms to the key element 4-8 of the drill
rod such
that the downhole housing 12 is in a fixed spatial relationship and registered
to the drill
rod 4 in at least two-dimensions. On the other hand, the reader should note
that the
downhole housing 12 is configured to slide along the source-carrying region 4-
9
between the two shoulders (4-2, 4-4) in a substantially frictionless manner
under certain
circumstances. A person skilled in the art will appreciate that the term
substantially
frictionless is predicated on the coefficient of friction of the interior
surface of the
housing 12, the coefficient of friction of the carrying region 4-8 of drill
rod 4 and the
operational characteristics of the isolation filter. In addition, the
interface between the
interior surface of the housing 12 and the surface of the carrying region 4-8
may be
packed with grease or some other lubricant material.
[00124] As embodied herein and depicted in Figure 12, a diagrammatic depiction
of
stress wave propagation in a top-hammer rock drilling application is
disclosed. Here,
the stress waves are modeled as a sequence of square or rectangular waves for
ease of
illustration. In diagram 1200, a top hammer rock drill is shown to include a
hammer/piston 2-6 that is used to impact the drill rod 4. (See, e.g., Fig. 2).
The
hammer 2-6 may be implemented using any suitable hammer type, e.g., such as a
pneumatic hammer (which uses compressed air) or a hydraulic hammer (which uses
pressurized hydraulic fluid). (The drill rod 4 is a depicted in this view as
an elongated
cylinder; in practice, however, the drill rod 4 may be of the type depicted at
Figs. 5 and
6).
[00125] During operations, examples of which are shown at Figs. 1 and 2, the
drilling motor 2-4 may simultaneously provide a reciprocating motion and a
rotational
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motion to drive the drill rod 4. The reciprocating motion provides the
hammering
action to the drill rod 4 while the rotational force slowly rotates the drill
rod 4 and drill
bit 8 in a drilling motion. As the borehole length increases, additional drill
rods can be
added to the drill string by screwing a new drill rod onto the drill string
that extends
into the borehole. The kinetic energy of the hammering action is transmitted
by the
drill rod 4 to the drill bit 8 to fragment the rock 1 during the drilling
action.
Accordingly, any sensor instrument package 16 or magnetic source package 100
attached to a down-hole drill rod 4 must be able to with-stand intense
stresses and
strains.
[00126] In this case, the isolation filter of the present invention is
configured to
substantially isolate the housing 12 from the stress, energy and power flow
associated
with the drilling. To be clear, the spring elements 14 do not function as a
damping
mechanism, but rather as a low pass filter, since the frequency spectrum of
the surface
accelerations characterizing the hammering/drilling operations are greater
than the low
pass frequency response spectrum of the isolation filter, and thus, the stress
waves are
substantially attenuated and substantially prevented from disturbing the
carriage
apparatus 20. (The surface accelerations are derived from the stress wave
energy
produced by drilling/hammering).
[00127] In step 1201, the hammer 2-6 is shown prior to impact and is shown to
have
a length "Lp" (also referred to herein as "L"). In step 1202, the hammer 2-6
moves
toward the drill rod 4 with a velocity v and strikes the drill rod 4. In step
1203, a
compressive stress wave Cy is generated in the hammer 2-6 and a compressive
stress
wave C is also generated in the drill rod 4. These stress waves are depicted
in the
diagram as an increased diameter in each element. The maximum induced
compressive
stress (G) is substantially equal to:
[00128] 6 = vE/2c (1)
Where, v is the hammer velocity, E is Young's (elastic) modulus of the
material
(hammer and drill rod), and c is the speed of sound in the hammer/rod. This
assumes
that the diameter and material of the hammer 2-6 and the drill rod 4 are the
same.
[00129] In step 1204, the stress wave Cy reaches the upper end of the hammer 2-
6
and is reflected; and the compressive stress wave C continues to propagate
down the
length of the drill rod 4. In step 1205, the reflected wave Cy propagates down
the
hammer 2-6 and is transmitted into the drill rod 4 such that the stress waves
C and Cy
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are combined. In step 1206, the combined stress wave C exits the hammer 2-6;
and in
response to being elastically compressed by the stress waves, a portion of the
drill rod 4
has been displaced. Assuming a square wave shape, the elastic compression (A)
is
substantially equal to:
A = vL/c (2)
In a typical top hammer application, 1.10 may be about 1.2 mm given a velocity
(v) of
10m/s and a hammer length (L) of about 0.6m.
[00130] In step 1207, the stress wave has a length 2L and propagates along the
drill
rod 4 at the speed of sound c, which is substantially equal to
c = Ai(E p) (3),
wherein p is the density of the drill rod material. The stress wave propagates
the initial
mechanical energy Wh to the drill bit 8, where
Wh = 1/2mv2 (4),
wherein m is the mass of the hammer 2-6. Of course, only a fraction of the
mechanical
energy Wh is applied to fragment the rock 1 (See, e.g., Fig. 2). Another
portion or
fraction of the mechanical energy is reflected back up the rod 4.
[00131] Referring to Figures 13A-B, charts showing another idealized stress
wave
surface velocity and surface acceleration resulting from the hammer blow
stress wave
depicted at Figure 12 are disclosed. In this analysis, the stress wave is
modeled as a
sinusoidal wave. Briefly stated, the stress wave surface velocity curve 1300
can be
modeled as a sine wave or a cosine wave over an interval from 0 ¨ it radians
(0 ¨
180 ). Those skilled in the art will appreciate that the form of the stress
wave 1300
depends on the rock drill, drilling parameters, the number of drill rods 4 in
a given drill
string, the type of rock being drilled, the hardness and the integrity of the
rock material,
and etc. Nonetheless, the stress wave surface velocity 1300 may be reasonably
modeled as a sinusoid (over a 0 ¨ it radian interval) to ascertain the energy
and forces
being brought to bear on the downhole housing 12 described above. The surface
acceleration 1302 is, of course, the derivative of the stress wave surface
velocity 1300.
[00132] Referring to Figure 13C-D, charts showing the idealized stress wave
and
acceleration with reflections are shown. In other words, Figure 13C shows the
stress
wave surface velocity 1300 (at Fig. 13A) along with the stress wave
reflections that
develop over time. See Fig. 12 and the related text above. Similarly, Figure
13D
shows the surface acceleration signal 1302 (Fig. 13B) along with the reflected
surface
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accelerations that develop over time (see Figure 12 and the related text).
Specifically,
Figure 13C shows that after a millisecond or so, the reflection waves 1304
begin to
propagate along the drill rod. Figure 13D shows the resultant surface
acceleration
based on the stress wave surface velocity shown at Figure 13C.
[00133] Referring to Figure 13E-F, charts showing the stress wave surface
velocity
and acceleration signals for multiple (e.g., ten) top hammer blows are
disclosed. In
these drawings the stress wave surface velocity signals 1302 and 1304 shown at
Fig.
13C are compressed as the time scale is changed from milliseconds to seconds.
Specifically, the stress wave surface velocity signals (1300 and 1304) shown
at Fig. C
are shown in a compressed form as signal 1308. The stress wave surface
velocity
signal 1308 is repeated for each hammer blow. Figure 13E, therefore, shows ten
stress
wave surface velocity signals 1308 propagating down the drill rod, one for
each of the
ten hammer blows. The surface acceleration signals (1302 and 1306) shown at
Figure
13D are likewise shown at Fig. 113F in compressed form as signal 1310. There
are
therefore ten surface acceleration bursts 1310, one for each hammer blow.
[00134] Briefly stated, therefore, the mathematical model makes the following
assumptions: first, it assumes that the stress wave is sinusoidal; and second,
it assumes
that the geometry and material of the hammer 2-6 and drill rod 4 are
substantially the
same so that they both have the same acoustic impedance. The model is based on
the
stress wave formulation steps shown at Figures 12, except that a sinusoidal
approximation is employed. The stress wave modeled by equation (5) is at some
drill
rod element a distance "x" from the top of the rod 4 at time "t." In step
1207, e.g., the
velocity ("du/dt") of a point on the drill rod can be represented by:
du/dt = -(v/2) sin[(n/2L)(x - c t)], for -2L <x - ct < 0 (5)
The velocity du/dt is based on u(x,t), which is a tiny displacement of an
element on the
drill rod from its equilibrium location x at time t. The factor "(x - ct)"
indicates that
u(x, t) describes a displacement propagating along the longitudinal axis "x"
of the drill
rod 4 toward the drill bit 8. While the shape of a wave pulse may assume any
form, x
and t must always appear in the combination with each other to satisfy the
governing
wave equation (i.e., the argument must include either (x - ct) or (x + ct). If
the
argument is (x + ct), the stress wave displacement is propagating along the
longitudinal
axis "x" of the drill rod 4 toward the hammer 2-6 and away from the drill bit
8.
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[00135] Again, while equation (5) models the stress wave as a sinusoidal wave,
those skilled in the art will appreciate that the wave could be modeled as a
trapezoidal
wave, a square wave or as a rectangular pulse. (Those skilled in the art will
appreciate
that mathematical models are only approximations of real world mechanical
phenomena). The factor 2L in equation (5) indicates that the wave has a length
2L,
which corresponds to twice the hammer's length, as shown at Figure 12.
[00136] Referring to Figure 14, a diagrammatic depiction of a mechanical
isolation
filter system 1400 in accordance with the present invention is disclosed.
Briefly stated,
the stress waves formed by the axial shocks and vibration may be substantially
reduced
by the isolation filter 1400. Before describing the filter 1400, and its
features and
benefits, it may be useful to highlight the differences between the mechanical
isolation
filter system 1400 of the present invention and a damping spring mechanism.
[00137] The mechanical isolation filter system 1400 is configured as a low
pass axial
shock and vibration filter and not as a damping mechanism. Specifically, note
that a
damping mechanism typically uses significant dissipative forces (frictional or
fluid
forces) to dampen vibrational motions; however, these dissipative frictional
forces
generate thermal energy. In contrast, the mechanical isolation filter system
1400 of the
present invention substantially isolates the sensor 16 or the magnetic sources
100 from
potentially damaging shock and vibrations (axial or otherwise) while
substantially
obviating any frictional forces. Stated differently, because of the filtering
operation,
the carriage 20 will exhibit very little oscillation, if any. As a result, the
amount of
thermal energy (heat) generated by the spring-mass filter 1400 is relatively
small when
compared to a frictional damping device.
[00138] In the various drilling applications contemplated by the present
invention,
such as a reciprocating drilling action (e.g., hammer-drilling), the
excitation frequencies
propagating along the longitudinal axis 7 of the drill rod 4 are on the order
of
approximately 100Hz and above (see Fig. 15A). The low pass isolation filter
1300 of
the present invention is configured to substantially filter out excitations
(shock and
vibration) to frequencies well below 50 Hz.
[00139] As shown in Figure 14, therefore, the mechanical isolation filter
system
1400 is comprised of the carriage apparatus 20 and the spring system 14
disposed
between the carriage apparatus 20 and the drill rod shoulders (4-2, 4-4). The
carriage
20 is modeled as a mass m that is connected between a pair of springs 14 (one
spring at
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each end), which have a spring constant "k." The springs 14 are further
connected to
the drill rod at their respective ends via the shoulders 14. As highlighted by
Figures 12
and 13A-13F, and the associated text, the stress waves generated by a
reciprocating
drilling operation (such as hammer drilling) are primarily directed along its
longitudinal
axis 7. The natural frequency of vibration of the mass and spring system (at
Fig. 14
and Figs. 30-38) is [1/(27r)]*[sqrt (2k/m)1, wherein k is the spring constant
of one
spring. Since there is one spring 14 at each end of the carriage housing 12
(and two (2)
total springs), the term "2k" is used in the natural frequency equation. (If
only one
spring 14 is employed, the natural frequency is [1/(2n)]*[sqrt (k/m)]).
[00140] Note that in the embodiments depicted Figs. 3 ¨ 11C and 16-28, there
are a
set of four (4) springs at each end (and eight (8) total), and thus the
natural frequency of
vibration of the mass and spring system is [1/(2n)]*[sqrt (8k/m)1. In these
embodiments, the spring rate k for one spring is approximately 10.5 N/mm.
After
converting the spring rate k from mm to meters, the spring rate becomes 10,500
N/m.
Accordingly, with the two sets of four springs 14 (one set at each end)
disposed in
parallel, the two sets of springs 14 would have a combined spring rate of
about 84,000
N/m. With a carriage housing 12 having a mass of about 3kg, the natural or
fundamental frequency would be f= [1/(2n)] * [sqrt (84,000/3)1 which equals
about 26
Hz.
[00141] In another example embodiment, the carriage apparatus 20 may be
coupled
between the shoulders (4-2, 4-4) by a set of two springs at each end, i.e.,
four springs
total. In this case the two sets of springs 14 would have a rate of about
42,000 N/m;
and with a carriage mass of 3 kg, the natural frequency would be about 18.8
Hz. In all
of these embodiments, a variable rate spring may be employed.
[00142] Accordingly, one skilled in the art will appreciate that the design
may be
adapted to various environmental scenarios. That is, the stress wave
parameters may
vary depending on the type of drilling/mining application, and thus, the
carriage mass,
spring rate and/or total number of springs may be selected in accordance with
a given
application. Any excitations along the longitudinal axis that are greater than
1.5 times
the natural (fundamental) frequency will be substantially attenuated (i.e.,
filtered out)
by the low pass filter 1400. The spring rate k used in the above calculations
is a
constant value; however, the present invention contemplates that the spring
rate may be
non-constant (i.e., non-linear). Thus, the present invention contemplates that
the spring
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rate may be construed to refer to or encompass any predetermined force-
displacement
relationship.
[00143] In reference to Figures 15A ¨ 15C, the plots shown in these charts
recapitulate the teachings articulated herein, e.g., at Figures 12-14 and the
associated
text. For example, Figure 15A shows a fast Fourier transform (FFT) of the
surface
accelerations depicted at Figure 13F. In Fig. 15A, most of the frequency
content of the
surface accelerations is between 100 Hz (102) and 100 KHz (105) or less. The
peak
acceleration is about 250g at about 3,500 Hz. (Note that since lg is
approximately
equal to 10 m/s2, 250g is approximately equal to about 2500 m/s2).
[00144] Figure 15B is a chart showing transfer functions (1502, 1503) for the
spring
mass isolation filter 1400 of Figure 14 (and implemented by spring 14 and mass
(carriage apparatus 20) system depicted at Figures 3-11 and 17-38. The
transfer
function curve 1502 represents the first filter example wherein the isolation
filter has
two sets of four springs 14 (one at each end) that are disposed in parallel.
In this case,
the system example is characterized by a natural frequency of about 26 Hz.
Note that
the 26 Hz natural frequency is the location of the peak frequency of curve
1502, and
represents the resonant frequency of the isolation filter 1400. Frequencies
below the
natural frequency represent the filter passband wherein the attenuation factor
is equal to
one. Frequencies greater than the 26 Hz natural frequency are attenuated with
the
curve falling off at an attenuation rate of 1/f2.
[00145] The transfer function curve 1503 represents the second filter example
wherein the isolation filter has two sets of two springs 14 (one at each end)
that are
disposed in parallel. In this case, the system example is characterized by a
natural
frequency of about 18.8 Hz. Thus, the adaptability of isolation filter 1400 to
different
drilling/mining environments should be readily apparent to the reader. As
noted herein,
the isolation filter uses very little damping to avoid generating thermal
energy. Briefly
stated, 2% of critical damping is assumed in the calculations. This damping
amount
represents small spring losses, minimal friction between the drill rod and the
carriage
assembly, etc. Also, those skilled in the art will appreciate that this
minimal amount of
damping is included in the transfer functions of Fig. 15B so that the motion
at
resonance remains finite. (If no damping is assumed in the calculations, then
the peak
attenuation multiple (at Fig. 15B) will go to infinity at resonance).
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[00146] Figure 15C is a chart showing the output of the spring mass isolation
filter
when subject to the excitations shown at Figure 15A. This chart is directed
toward the
first example wherein the filter has a 26 Hz resonant frequency. The peak
filtered
acceleration of the filter 1400 is about 5 m/s2 (i.e., about 0.5g) at
approximately 30 Hz.
Comparing the surface accelerations of Fig. 15A to the filter output chart of
Fig. 15C,
the surface acceleration curve 1500 has a peak acceleration of 250g (i.e.,
2,500 m/s2)
whereas the peak filter output is again, only about 5 m/s2. As the frequencies
of the
surface accelerations increase, the surface accelerations of the carriage
apparatus 20
decrease until they approach 0 m/s2 at about 3,000 Hz. Essentially, in stark
contrast to a
damping system, the carriage 20 becomes stationary as the vibrational
frequencies
increase.
[00147] Thus, the isolation filter implemented by the carriage apparatus 20 is
characterized by a low pass frequency transfer function 1502 (1503) that
includes pass
band frequencies that are substantially below the operational frequency
spectrum
(1500) wherein stress waves propagating along the drill rod 4 from a
predetermined
drilling operation are substantially attenuated and substantially prevented
from
disturbing the carriage apparatus 20.
[00148] As embodied herein and depicted at Figure 16, a diagrammatic depiction
of
a downhole assembly 10 in accordance with an alternate embodiment of the
present
invention is disclosed. Here, the carriage apparatus 20 is substantially
identical to those
described above, and hence, any further description is redundant and omitted
for
brevity's sake.
[00149] On the other hand, in this embodiment the drill rod 4 is modified so
that the
shoulders (4-2, 4-4) are replaced by clamped collar devices (18-1, 18-2).
Here, collar
18-1 is shown as having a smaller diameter than collar 18-2; however, the
collar
diameter size may be relatively unimportant in this case since the collars 18
can be
attached to drill rod 4 after the carriage apparatus 20 is coupled to the
drill rod 4. The
collars (18-1, 18-2) are two-piece devices that include matching tap holes 18-
3 that are
configured to accommodate a screw or other such fastener used to tighten the
collar
pieces around the drill rod 4.
[00150] In reference to Figure 17, a diagrammatic depiction of a downhole
assembly
in accordance with another alternate embodiment of the present invention is
disclosed.
Again, the carriage apparatus 20 is substantially identical to those described
above, and
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hence, any further description is redundant and omitted for brevity's sake.
This
embodiment features a hybrid drill rod 4 that is a cross between the drill rod
depicted at
Figs. 3-6 and the drill rod shown at Fig. 16. That is, the drill rod features
a shoulder 4-
4 (like Figs. 3-6) along with a collar device 18 (like Fig. 16). In other
words, the
shoulder 4-2 (Figs. 3-6) is replaced by a collar 18. Thus, the carriage
apparatus 20 or
cover 30 may be inserted over the drill pin 4-1 and moved down the drill rod 4
until the
springs 14 are coupled between the carriage 20 and the shoulder 4-4. Then, the
collar
18 is attached to secure the other set of springs 14 between the carriage 20
and the
collar 18.
[00151] Those skilled in the art will appreciate that the collar 18 may be
implemented as a two-piece shaft collar with a 60nam bore, 88mm OD, and 19rnm
width. The collar may be manufactured from 1215 lead free steel having a black
oxide
finish that increases holding power and resists corrosion. In one embodiment,
the
collar 18 may be implemented by an MSP-60-F collar arrangement manufactured by
the Ruland Manufacturing Company.
[00152] In reference to Figures 18A ¨ 18D, detail views of a clamp keying
arrangement employed at Figs. 16-17 are disclosed. In Figs. 18A-18C, a shallow
groove 4-18 may be machined or otherwise formed in the drill rod 4 to
accommodate
the collar therein. In Figs. 18B and 18C, a stop portion 4-19 is included to
substantially
prevent the collar from slipping or rotating about the drill rod 4.
[00153] Figure 18D shows a collar 18 that is disposed in situ within a groove
4-18.
The collar 18 includes a proud surface 18-4 that has a larger diameter than
the recessed
portion 18-3 adjacent thereto. The recessed portion 18-3 may be employed to
accommodate an extended-length protective cover 30.
[00154] Note that each drawing (Figs. 18A-D) shows a sectional view of the
drill rod
such that the central fluid channel 4-12 is shown. (This channel may be used
to direct a
pressurized fluid from an uphole region (e.g., control station 2 at Fig. 1) to
the drill bit
8. The fluid may be air pressurized at 150 PSI).
[00155] Referring to Figure 19, a detail view of the carriage apparatus
employing the
clamping arrangement depicted at Fig. 18D is disclosed. In this view, the
protective
cover 30 fits within the recessed portion 18-3 of the collar 18. At the same
time, the
cover 30 is substantially flush with the proud surface 18-4 of collar 18.
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[00156] Figure 20 is a cross-sectional view of the carriage apparatus 20 shown
at
Figures 18D and 19. That is, the carriage apparatus 20 is coupled to a drill
rod 4 that
employs the clamping arrangement 18 depicted at Fig. 18D. Again, the
protective
cover 30 is disposed within the recessed portion 18-3 of the collar 18 such
that it
extends over the springs 14 and the housing 12. The cover 30 is substantially
flush with
the proud surface 18-4.
[00157] As embodied herein and depicted in Figure 21, a diagrammatic depiction
of
a downhole assembly in accordance with another alternate embodiment of the
present
invention is disclosed. In this embodiment, the drill rod 4 is substantially
the same as
the one shown at Figs. 5-6. Moreover, the carriage apparatus 20 is
substantially
identical to those described in previous embodiments. Accordingly, only the
new
elements of the carriage 20 are described for the sake of brevity. Here, a
bumper
arrangement 20 is provided at each end of the carriage housing 20. The bumper
arrangement 20 includes two semi-circular pads (20-1, 20-2) that are applied
to each
end of the housing portions (12-1, 12-2).
[00158] Turning to Figures 22-23, detail views of a carriage apparatus 20 of
the
downhole assembly depicted in Figure 21 is disclosed. These views show the
bumper
arrangement 20 with greater clarity. The semi-circular pads (20-1, 20-2) take
the form
of a gasket that includes four holes 20-3. The holes 20-3 accommodate the
springs 14.
The gasket pads 20-1, 20-2 may be formed using any suitable material
configured to
protect the carriage housing 12 from a hard impact from the drill rod
shoulders (4-2, 4-
4); the materials may include rubber, polymer, composite materials, a
relatively soft
metal, etc.
[00159] As embodied herein and depicted in Figure 24, a detail view of a
carriage
cover 30 in accordance with another alternate embodiment of the present
invention is
disclosed. In this embodiment the cover 30 has one end with a relatively large
diameter
opening (as in previous embodiments) and an opposing end with a relatively
small
diameter opening. This allows the protective cover 30 to slide over the drill
rod pin 4-1
and be held in place by the drill bit 8 (not shown) when it is screwed onto
the pin 4-1.
[00160] Figure 25 is a cross-sectional view of a carriage apparatus 20
depicted in
Figure 24. Note that the cover end (left side of Fig. 25) abutting shoulder 4-
2 has a
larger diameter 30D1; and the cover end that abuts shoulder 4-10 has a smaller
diameter 30D2. Thus, the larger diameter opening is large enough to slide over
the
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shoulders (4-4, 4-10) and the carriage 20 until an end cap portion 30-1 abuts
the
shoulder 4-10. Once the drill bit 8 is threaded onto the pin 4-1, the end cap
30-1 is
firmly caught between the shoulder 4-10 and the drill bit 8 to secure the
cover to the
apparatus 10.
[00161] As embodied herein and depicted in Figure 26, a detail view of a
portion 12-
1 of the carriage apparatus in accordance with yet another alternate
embodiment of the
present invention is disclosed. Most of the housing portion 12-1 is
substantially
identical to embodiments described above, and hence, a description of
previously
described elements is omitted for brevity's sake. In this view, a series of
spring holes
12-15 are formed in the surface of the key channel 12-6. Each hole 12-15 is
configured
to accommodate a spring 15; thus, upon the assembly of housing 12, the springs
15
extend into holes 12-15 formed in each housing portion 12-1, 12-2. The springs
15 and
the carriage mass m form another filter that is configured to filter any
torqueing forces
that may be applied to the housing 12 during a rotational drilling process (in
a manner
similar to the spring isolation filter 1400 described above). In one
embodiment, the
springs 15 are manufactured using chrome-silicon steel, have a 1 inch long
free length,
and have a spring rate of 0.6 N/mm. The holes 12-15 may have a 0.2" diameter.
In one
embodiment, the springs 15 may be manufactured by McMaster-Carr and be
implemented by the McMaster-Carr Blue Chrome-Silicon Steel Die Spring PN
9657K49.
[00162] As embodied herein and depicted in Figure 27, a diagrammatic depiction
of
a downhole assembly in accordance with yet another alternate embodiment of the
present invention is disclosed. In this view, the carriage housing 12 is
configured to
accommodate a sensor assembly 16 instead of a magnetic source assembly. Here,
the
sensor carriage 20 is shown with the protective cover 30 removed. The housing
portion
12-1 is shown with a protective enclosure 12-16 formed therein. The enclosure
12-16
is configured to accommodate the sensor circuit assembly 16 and some potting
material. The potting material is employed to hold the circuit elements in
place within
the protective enclosure 12-16. The drill rod 4 and spring 14 arrangement is
substantially identical to previous embodiments described above, and thus any
description of previously described elements is omitted for brevity's sake.
[00163] Figure 28 is a detail view of a carriage apparatus 20 depicted in
Figure 27.
In this view, the protective cover 30 is shown with a cutaway view that
reveals the
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housing 12 underneath. As before, the sensor circuit 16 is disposed within the
protective enclosure 12-16 and the cover 30 serves to protect the circuitry
16.
[00164] Referring to Figure 29, a diagrammatic depiction of the sensor
assembly
depicted at Figure 27 is disclosed. The sensor assembly 16 includes various
components disposed, e.g., on a printed circuit board (PCB) and coupled
together by a
bus system 16-1. The bus system 16-1 is coupled to a microprocessor 16-2 and
computer readable memory 16-3. The sensor assembly 16 may also include an
accelerometer module 16-4, a magnetometer module 16-5, an inclinometer 16-6, a
gyro
rate sensor 16-7, as well as an environmental module 16-11.
[00165] As those skilled in the art will appreciate, the accelerometer module
16-4
may be configured to measure the Earth's gravity vector and provide the
gravity vector
components gx, gy, gz of the Earth's gravity vector g. The gyroscope 16-7 is
used for
measuring the device's orientation and/or angular velocity. The gyro 16-7 may
be
configured as a rate gyroscope which is configured to produce an output
voltage
proportional to a rate of rotation. The magnetometer module 16-5 may include a
plurality of flu,xgate magnetometers having their axes of maximum sensitivity
intersecting each other at one or more observation points and substantially at
right
angles to each other. (As before, the magnetometer module 16-5 may have a
magnetometer sensor having up to three magnetometers; and, the magnetometer
module 16-5 may have multiple magnetometer sensors). Magnetometers measure the
amplitude and the phase of two perpendicular components of the magnetic field
300.
The inclinometer may be employed to measure the angles of slope/tilt of
carriage 20
with respect to the gravity vector. The environmental sensor module 16-11 may
be
configured to measure one or more of temperature, pressure, radiation, etc.
[00166] The microprocessor 16-2 may be configured to use the sensor
inputs to
determine the spatial relationships between the borehole axis 7, borehole
inclination,
roll angle, borehole azimuth, the Earth's rotation vector, and other such
spatial
relationships.
[00167] The sensor assembly 16 also includes a piezoelectric transducer 16-
8 that is
configured to convert the mechanical energy (Wh) generated by the drilling
operations
into electrical energy. (An expression for the mechanical energy is provided
herein).
As those skilled in the relevant arts would appreciate, the piezoelectric
effect converts
mechanical strain into electric current or voltage. The electrical current is
provided to
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an electrical storage device 16-9 which includes a battery for storing the
harvested
energy. In an alternate embodiment, electrical power may be provided to the
carriage
20 (and sensor assembly 16) by way of wireline.
[00168] Finally, the sensor assembly 16 may include a transmitter device 16-10
and
a receiver 16-12. The transmitter 16-10 and receiver may be configured as a
wireless
or as a wireline transceiver configured to communicate with an uphole
telemetry
system (not shown in this view). In one embodiment, the uphole telemetry
system is
configured to manipulate all of the sensor data provided by the sensor
assembly 16
(disposed down-hole). This information, or some of the information, may be
transmitted to a driller controller (FIGs. 1 - 2) so that an appropriate
course correction
can be made (if necessary). In another embodiment, data transfer may be
effected when
the device 10 is retrieved from the downhole environment.
[00169] The microprocessor 16-2 may be configured to bi-directionally
communicate with the various components coupled to the bus 16-2. In this
embodiment, the microprocessor 16-2 may include on-board analog-to-digital
conversion (ADC) channels that accommodate the analog output signals of the
accelerometers (16-4 ¨ 16-6). The analog voltage output signal of the gyro
sensor 16-
7 may also be converted into digital signals.
[00170] The sizing and selection of the microprocessor 16-2 is considered to
be
within the skill of one of ordinary skill in the art with the following
proviso: obviously,
if the functionality of the up-hole control system is incorporated into the
down-hole
system, the computational burden of the resultant processor will necessarily
be greater.
In any event, in accordance with the embodiment of FIG. 5C, the microprocessor
16-2
may be implemented using any suitable processing device depending on
processing
speed, cost, and durability considerations. In one embodiment, therefore,
processor 16-
2 may be implemented using a 16 bit, a 32-bit, a 64 bit, or any suitable
microcontroller
coupled to any suitable computer readable media 16-3. As noted above, the
microcontroller may be more or less powerful depending on cost/processing
speed
considerations.
[00171] The term "computer-readable medium" as used herein refers to any
medium
that participates in providing data and/or instructions to the processor 16-2
for
execution. Such a medium may take many forms, including but not limited to
RAM,
PROM, EPROM, EEPROM, FLASH-EPROM or any suitable memory device, either
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disposed on-board the processor 16-2 or provided separately. In one
embodiment, the
processor 16-2 may include 256 KB of flash memory and 32 KB of SRAM.
[00172] As embodied herein and depicted in Figure 30, a diagrammatic depiction
of
a downhole assembly 10 in accordance with yet another alternate embodiment of
the
present invention is disclosed. In this view, the housing 12 is configured to
provide a
protective housing for the magnetic source elements 100. As described below,
the
magnetic source elements may be disposed within the housing 12 via the
interior of the
housing so that they are protected from the ambient environment. The magnetic
source
housing 12 is coupled to a first spring member 14-1 at a first end thereof,
and is
coupled to a second spring member 14-2 at a second end portion of the housing
12. In
this embodiment, the spring members (14-1, 14-2) may be formed by machining
metallic cylinders to form a spring structure.
[00173] The spring member 14-1 is coupled to the collar member 16-1 at a first
end
portion of the magnetic source apparatus 20; the collar members (16-1, 16-2)
function
as attachment points for the apparatus 20. Stated differently, the collar
member 16-1 is
fixedly attached to a portion of the drill string 4 proximate to the drill bit
8 (not shown
in this view). Similarly, the spring member 14-2 is coupled to a second collar
member
16-2 at a second end portion of the magnetic source apparatus 10 distal from
the drill
bit 8. The second collar member 16-2 is fixedly attached to an up-hole portion
of the
drill string 4.
[00174] As described below, the carriage apparatus 20 is configured such that
the
magnet elements 100 are rotationally registered to a registration portion of
the drill bit 8
such that measurements of the magnetic field by the sensor apparatus 50 will
include
knowledge of the drill bit (tool face) 8 orientation. This allows the
measurement system
1000 (Fig. 1) to instantaneously control the drilling direction via control
station 2.
Having said that, note that only the collar portions (16-1, 16-2) are coupled
to the drill
string 4. The carriage housing 12 and the spring members (14-1, 14-2) are
spatially
separated from a drill rod portion 4-1 and thus configured to float or glide
over the drill
rod portion 4-1 as the drill string 4 rotates (during the drilling process).
In one
embodiment, the drill rod 4-1 is not deemed to be a component part of
apparatus 10,
i.e., the apparatus 10 may be coupled to any similar structure. In another
embodiment,
the apparatus may include a drill rod 4-1 manufactured and machined especially
for
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apparatus 10; and in this case, the drill rod 4-1 would be a component part of
the
apparatus 10.
[00175] In reference to Figure 31, a diagrammatic depiction of a magnetic
source
apparatus 10" shown in Figure 30 is disclosed. In this embodiment, a
protective sleeve
1300 may be disposed over the entire assembly 10". The protective sleeve may
be
formed from any suitable material such as BeCu, stainless steel, plastic, etc.
[00176] As embodied herein and depicted in Figure 32, a diagrammatic depiction
of
a downhole apparatus 10" in accordance with another embodiment of the present
invention is disclosed. The number of components in assembly 10 is identical
to the
assembly depicted in Figure 30; however, some of the individual members may be
implemented differently. For example, in this embodiment, the spring members
(14-1,
14-2) may be implemented using a wire spring structure. Both implementations
may
have similar performance characteristics). As before, the spring members (14-
1, 14-2)
are configured to register the housing 12 so that the magnetic source elements
100 are
rotationally registered with the drill bit 8 and/or an orientation feature on
the drill bit 8.
Moreover, the collar portions (16-1, 16-2) are configured to be rotationally
registered
with the spring members (14-1, 14-2). Detail views of the collar assemblies
(16-1, 16-
2) are described below in conjunction with Figures 35 and 36.
[00177] Figure 33 is a diagrammatic depiction of the drill rod structure 4
depicted in
Figure 32 with the carriage apparatus removed. In one embodiment, the assembly
10
may include a specially fabricated drill rod that provides rotational
registration features
configured to register the source housing 12, the spring elements (14-1, 14-2)
with the
drill bit 8. Specifically, the drill bit 8 may include a drill bit
registration feature 8-1 that
is configured to be aligned with a registration mark 4-4 formed on drill rod 4-
1. At the
same time, the drill rod 4-1 also includes key indents 4-2 at each end thereof
The key
indents 4-2 are configured to accommodate a key ring portion of the collars
(16-1, 16-
2) to thus rotationally register the collars to the rod 4-1. Moreover, the
indent gap 4-20
is configured to accommodate an end portion of the wire spring (14-1, 14-2) to
rotationally register the springs (14-1, 14-2) to the drill rod 4-1. Finally,
a plurality of
cooling holes 4-3 are formed in the drill rod 4-1. The cooling holes 4-3 are
in
communication with the central fluid channel 4-10 of the drill rod 4-1. The
central
fluid channel 4-10 extends the length of the drill string 4 and allows a
cooling fluid
(such as air) to be directed from the source 200 (Figs. 1, 2) to the drill bit
8.
36
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[00178] The housing 12 is assembled such that each magnetic source 100 is
positioned over a corresponding cooling hole 4-3. Thus, the cooling holes 4-3
may be
used to rotationally register the magnetic source housing 12 to the drill rod
4-1, and
hence to the drill bit registration feature 8-1 formed on the drill bit 8. At
this point, a
few words concerning the meaning of the term "rotational registration" may be
in
order. If the drill bit registration feature 8-1 is designated as, for
example, 00, every
other feature on the drill rod will have a predetermined angular position 0
relative to
feature 8-1 when the assembly 10 is properly configured. The drill bit
orientation
feature 8-1 may be an asymmetrical feature or drill orientation that allows
the drilling
control system 2 to perform directional drilling (i.e., precisely control the
direction of
the borehole as it is being drilled). The orientation is known and programmed
in
software. The magnetic field orientation relative to the magnet source
elements 100 is
also known and programmed in software. By determining the magnetic field
orientation via the sensor assembly (Figs 1 and 2), the drill bit orientation
may also be
determined.
[00179] As before, the springs 14-1 and 14-2, along with the mass of the
carriage are
configured to form a low pass isolation filter in accordance with the
principles outlined
above. See Figs. 12 ¨ 15C and the associated text.
[00180] In reference to Figure 34, a cross-sectional view of the magnetic
source
housing 12 depicted in Figures 30 and 32 is disclosed. In this view, the
housing
portions 12-1 and 12-2 are shown as being disposed around the drill rod 4 such
that the
magnetic sources 100 are aligned with the cooling holes 4-3. In one
application, the
cooling air is directed down the pipe 4-10 at about 150 PSI. Accordingly, the
cooling
air is directed into the cooling holes 4-3 and into the gap 124 that is formed
between the
inner surface of the housing 12 and the outer surface of the drill rod 14-1.
As a result,
the cooling air is employed to direct thermal energy away from the magnets 100
and
thus lower the ambient temperature of the magnetic source elements 100.
[00181] In reference to Figure 35, a detail view of a collar assembly 16-1
depicted in
Figure 32 is disclosed. (Note that the retention collar 16-2 disposed on the
other end of
drill rod 4-1 (see Figs. 30 and 32) is of like or similar construction). The
retention
collar 16-1 may include a first collar portion 16-10 coupled to a second
collar portion
16-12 (disposed behind drill rod 4-1 and thus not shown in this view). The
first and
second collars (16-10, 16-12) may be coupled together using any suitable means
such
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as a weld 16-11 or other suitable fastener means. A first retention key 16-14
is
disposed within a key indent 4-2 (see Fig. 33) and a retention feature formed
within the
interior surface of the first collar portion 16-10, to thus rotationally
register the collar
16-1 to the drill rod 4-1. (The second collar 16-12, disposed behind the drill
rod 4-1 in
this view, also accommodates a second retention key 16-16 disposed within its
respective key indent 4-2). Note that a spring registration portion 14-10 is
disposed
within the indent gap 4-20 to rotationally register the spring 14-1 with the
drill rod 4-1.
(In reference to Fig. 37, the spring registration portion 14-10 is not
depicted for clarity
of illustration, but may be employed in that embodiment).
[00182] In reference to Figure 36, a detail view of a collar assembly 16-1
depicted in
Figure 32 in accordance with an alternate embodiment of the present invention
is
disclosed. In this alternate embodiment, the retention collar 16-1 includes a
first collar
portion 16-10 that includes a ramped sleeve 16-11 that slides over the drill
rod 4-1. A
second collar portion 16-12 slides over the ramped portion 16-11 and is
tightened by
fasteners 16-20 to exert pressure on the sleeve 16-11. The ramped sleeve 16-11
features a relatively small angle cp between the ramp and the interior surface
of the
collar portion 16-10. The angle cp may be of any suitable amount; for example,
in one
embodiment the angle cp is between 10 ¨ 2 .
[00183] In another embodiment, the attachment collars (16-1, 16-2) may also be
implemented as an end portion of the spring members (14-1, 14-2). In this
embodiment, the end-collar portion of the spring includes a registration mark
or indicia
that are aligned to a registration mark/indicia formed on the drill rod. Upon
alignment,
the end-collar may be welded to the drill rod 4-1.
[00184] In yet another embodiment of the invention, the attachment collars (16-
1,
16-2) may be integrally formed with the drill rod 4-1 itself In this
embodiment, each
attachment collar includes a spring member interface that accommodates the
spring
registration portion 14-10 to rotationally register the spring 14-1 with the
drill rod 4-1.
[00185] As embodied herein and depicted in Figures 37 and 38, detail views of
the
spring elements depicted in Figure 32 are disclosed. In Figure 37, the spring
element
14-1 is shown as being disposed over the drill rod 4-1. In this embodiment the
free
length F/L may be about 4 inches. In Figure 38, the outside diameter (ID) is
about 2.87
inches in order to accommodate the outside diameter of the drill rod 4-1. The
wire
diameter in this embodiment may be about 0.2 inches. In this embodiment, the
spring
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members 14-1, 14-2 are configured as compression springs and are implemented
as
open-coil helical springs wound or constructed to oppose compression along the
longitudinal axis 7 (see, e.g., Figs. 1, 2). (As noted previously, while the
spring
registration portion 14-10 (shown at Figure 35 and described above) is not
depicted in
Figure 37 for clarity of illustration, the springs (14-1, 14-2) may include
the registration
feature 14-10 or other such features such as 14-10 to thus provide rotational
registration).
[00186] While several inventive embodiments have been described and
illustrated
herein, those of ordinary skill in the art will readily envision a variety of
other means
and/or structures for performing the function and/or obtaining the results
and/or one or
more of the advantages described herein, and each of such variations and/or
modifications is deemed to be within the scope of the inventive embodiments
described
herein. More generally, those skilled in the art will readily appreciate that
all
parameters, dimensions, materials, and configurations described herein are
meant to be
exemplary and that the actual parameters, dimensions, materials, and/or
configurations
will depend upon the specific application or applications for which the
inventive
teachings is/are used. Those skilled in the art will recognize, or be able to
ascertain
using no more than routine experimentation, many equivalents to the specific
inventive
embodiments described herein. It is, therefore, to be understood that the
foregoing
embodiments are presented by way of example only and that, within the scope of
the
appended claims and equivalents thereto; inventive embodiments may be
practiced
otherwise than as specifically described and claimed.
[00187] All
references, including publications, patent applications, and patents, cited
herein are hereby incorporated by reference to the same extent as if each
reference were
individually and specifically indicated to be incorporated by reference and
were set
forth in its entirety herein.
[00188] All definitions, as defined and used herein, should be understood to
control
over dictionary definitions, definitions in documents incorporated by
reference, and/or
ordinary meanings of the defined terms.
[00189] The use of the terms "a" and "an" and "the" and similar referents in
the
context of describing the invention (especially in the context of the
following claims)
are to be construed to cover both the singular and the plural, unless
otherwise indicated
herein or clearly contradicted by context. The terms "comprising," "having,"
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"including," and "containing" are to be construed as open-ended terms (i.e.,
meaning
"including, but not limited to,") unless otherwise noted. The term "connected"
is to be
construed as partly or wholly contained within, attached to, or joined
together, even if
there is something intervening.
[00190] As used herein in the specification and in the claims, the phrase "at
least
one," in reference to a list of one or more elements, should be understood to
mean at
least one element selected from any one or more of the elements in the list of
elements,
but not necessarily including at least one of each and every element
specifically listed
within the list of elements and not excluding any combinations of elements in
the list of
elements. This definition also allows that elements may optionally be present
other
than the elements specifically identified within the list of elements to which
the phrase
"at least one" refers, whether related or unrelated to those elements
specifically
identified. Thus, as a non-limiting example, "at least one of A and B" (or,
equivalently,
"at least one of A or B," or, equivalently "at least one of A and/or B") can
refer, in one
embodiment, to at least one, optionally including more than one, A, with no B
present
(and optionally including elements other than B); in another embodiment, to at
least
one, optionally including more than one, B, with no A present (and optionally
including
elements other than A); in yet another embodiment, to at least one, optionally
including
more than one, A, and at least one, optionally including more than one, B (and
optionally including other elements); etc.
[00191] It should also be understood that, unless clearly indicated to the
contrary, in
any methods claimed herein that include more than one step or act, the order
of the
steps or acts of the method is not necessarily limited to the order in which
the steps or
acts of the method are recited.
[00192] Approximating language, as used herein throughout the specification
and
claims, may be applied to modify any quantitative representation that could
permissibly
vary without resulting in a change in the basic function to which it is
related.
Accordingly, a value modified by a term or terms, such as "about" and
"substantially",
are not to be limited to the precise value specified. In at least some
instances, the
approximating language may correspond to the precision of an instrument for
measuring the value. Here and throughout the specification and claims, range
limitations may be combined and/or interchanged; such ranges are identified
and
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include all the sub-ramies contained therein unless context or language
indicates
otherwise.
[00193] The recitation of ranges of values herein are merely intended to serve
as a
shorthand method of referring individually to each separate value falling
within the
range, unless otherwise indicated herein, and each separate value is
incorporated into
the specification as if it were individually recited herein.
[00194] All methods described herein can be performed in any suitable order
unless
otherwise indicated herein or otherwise clearly contradicted by context. The
use of any
and all examples, or exemplary language (e.g., "such as") provided herein, is
intended
merely to better illuminate embodiments of the invention and does not impose a
limitation on the scope of the invention unless otherwise claimed.
[00195] No language in the specification should be construed as indicating any
non-
claimed element as essential to the practice of the invention.
[00196] In the claims, as well as in the specification above, all
transitional phrases
such as "comprising," "including," "carrying," "having," "containing,"
"involving,"
"holding," "composed of," and the like are to be understood to be open-ended,
i.e., to
mean including but not limited to. Only the transitional phrases "consisting
of' and
"consisting essentially of' shall be closed or semi-closed transitional
phrases,
respectively, as set forth in the United States Patent Office Manual of Patent
Examining
Procedures, Section 2111.03.
[00197] It will be apparent to those skilled in the art that various
modifications and
variations can be made to the present invention without departing from the
spirit and
scope of the invention. There is no intention to limit the invention to the
specific form
or forms disclosed, but on the contrary, the intention is to cover all
modifications,
alternative constructions, and equivalents falling within the spirit and scope
of the
invention, as defined in the appended claims. Thus, it is intended that the
present
invention cover the modifications and variations of this invention provided
they come
within the scope of the appended claims and their equivalents.
41
