U.S. patent application number 17/690450 was filed with the patent office on 2022-09-15 for resonance-enabled drills, resonance gauges, and related methods.
This patent application is currently assigned to Sonic Drilling Institute, LLC. The applicant listed for this patent is Sonic Drilling Institut, LLC. Invention is credited to Martin Pierre Valdo Hammann, Peter Andrew Lucon.
Application Number | 20220290500 17/690450 |
Document ID | / |
Family ID | 1000006240479 |
Filed Date | 2022-09-15 |
United States Patent
Application |
20220290500 |
Kind Code |
A1 |
Lucon; Peter Andrew ; et
al. |
September 15, 2022 |
Resonance-Enabled Drills, Resonance Gauges, and Related Methods
Abstract
Provided herein is a resonance-enabled drill, comprising a
housing; one or more force generators chosen from one or more voice
coil actuators, one or more eccentrics driven by one or more
electric motors, or combinations thereof; one or more sonic heads
coupled to the one or more force generators; a plurality of springs
coupling the housing to the one or more sonic heads; and a drill
rod disposed on its proximal end to the one or more sonic heads.
Also provided is a gauge for a sonic drill configured to display
information to an operator, for example indicating to the operator
when the drill is on or near resonance. Further provided are
methods for selecting a resonance frequency in a sonic drill.
Inventors: |
Lucon; Peter Andrew; (Butte,
MT) ; Hammann; Martin Pierre Valdo; (Rixheim,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sonic Drilling Institut, LLC |
Butte |
MT |
US |
|
|
Assignee: |
Sonic Drilling Institute,
LLC
Butte
MT
|
Family ID: |
1000006240479 |
Appl. No.: |
17/690450 |
Filed: |
March 9, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
63159435 |
Mar 10, 2021 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02D 7/18 20130101; E21B
3/02 20130101; E21B 7/24 20130101 |
International
Class: |
E21B 7/24 20060101
E21B007/24; E21B 3/02 20060101 E21B003/02 |
Claims
1. A resonance-enabled drill, comprising: a housing; one or more
force generators chosen from one or more voice coil actuators, or
one or more eccentrics driven by one or more electric motors; one
or more sonic heads coupled to the one or more force generators; a
plurality of springs coupling the housing to the one or more sonic
heads; and a drill rod disposed on its proximal end to the one or
more sonic heads.
2. The drill of claim 1, further comprising a bit disposed on the
distal end of the drill rod.
3. The drill of claim 1, wherein the one or more voice coil
actuators comprise a coil assembly rigidly disposed on the housing
or on a reflection mass and a magnet assembly disposed on the one
or more sonic heads.
4. The drill of claim 3, wherein the coil assembly of each of the
one or more voice coil actuators has little to no motion compared
to the one or more sonic heads.
5. The drill of claim 1, wherein each eccentric is driven by one
electric motor.
6. The drill of claim 5, wherein the one or more force generators
comprises two paired sets of eccentrics configured to exert no
vertical force, using a 180.degree. phase angle between the two
paired sets of eccentrics.
7. The drill of claim 6, wherein the one or more force generators
comprises two paired sets of eccentrics configured to exert full
vertical force, using a 0.degree. phase angle between the two
paired sets of eccentrics.
8. The drill of claim 1, further comprising a seal disposed between
the housing and the drill rod.
9. The drill of claim 1, further comprising a spring-damper
disposed between the drill rod and the bit.
10. The drill of claim 9, wherein the spring-damper cushions impact
of the drill bit by widening and lowering impulse magnitude,
whereby transfer of primary resonant energy to unwanted resonant
modes is lowered, and the drill bit is kept in motion and not fused
with a workpiece.
11. The drill of claim 1, further comprising an energy transfer rod
and flange adaptor disposed between the one or more sonic heads and
the drill rod.
12. The drill of claim 1, further comprising between the one or
more sonic heads a rotor disposed on the drill rod, and a stator
and stator housing disposed on the housing.
13. The drill of claim 1, wherein the kinetic energy stored in the
drill by the one or more sonic heads is directly offset by
potential energy stored within the plurality springs.
14. The drill of claim 1, further comprising a reflection mass
coupled to the one or more sonic heads through a second plurality
of springs and configured to offset the kinetic energy stored in
the drill.
15. The drill of claim 1, wherein the housing comprises a plurality
of plates and a plurality of standoffs.
16. The drill of claim 1, having a resonance frequency, and, when
the drill is on resonance, an input force is in phase with the
resultant oscillation velocity of the one or more sonic heads.
17. A gauge for a sonic drill configured to display information to
an operator when the drill is on or near resonance, wherein the
information comprises one or more parameters chosen from an
amplitude of the drill bit, a resonant frequency of the drill, a
stress state, power components of the drill, and safe operating
frequencies.
18-24. (canceled)
25. A method for selecting a resonance frequency in a sonic drill
comprising a force generator, one or more sonic heads, and a gauge,
the method comprising: measuring phase between the force generator
and the one or more sonic heads in the sonic drill; and displaying
resonance on the gauge to indicate the resonance frequency of the
drill based on the phase.
26. (canceled)
27. (canceled)
28. The method of claim 25, when the sonic drill comprises a bit,
the method further comprises maximizing the ratio between bit
motion and motion of the one or more sonic heads.
29. The method of claim 25, further comprising, when the sonic
drill comprises a bit and penetration of the bit is slowed or
ceased, reducing the weight on the bit to adjust the resonance
frequency of the drill to continue drilling.
30-36. (canceled)
Description
RELATED METHODS
[0001] This application claims the benefit of priority of U.S.
Provisional Patent Application Ser. No. 63/159,435 filed Mar. 10,
2021, the disclosure of which is incorporated by reference in its
entirety for all purposes.
[0002] The present disclosure generally relates to machines that
use resonance to transfer energy from the machine to a drill bit or
bottom hole assembly to penetrate the earth, concrete, or any
material to drill a hole or take a sample.
[0003] Generally, sonic drills have used counterrotating eccentrics
mechanically timed to generate vertical forces while canceling the
horizontal forces. The eccentrics are typically driven directly
from an internal combustion engine or by an internal combustion
engine driving hydraulics, which have response times longer than
the penetration systems response time constant. A throttle controls
these systems by engine speed or a valve or driven pump speed.
[0004] Hydraulic controls have a slow response time, making the
drill hard to control by hand. As the frequency increases and the
drill approaches resonance, the system requires less input power,
which causes the eccentrics rotation speed to increase. As a
result, the system is pulled into the resonant condition. The
operator nor the hydraulic system can respond fast enough to avoid
speeding up into the resonant peak and remaining on the resonant
peak.
[0005] What is needed is a resonance-enabled drill with quick
response times and finer control so that the drill can stay at the
recommended resonance frequency or desired operating condition
SUMMARY
[0006] The present disclosure provides a resonance-enabled drill,
comprising a housing; one or more force generators chosen from one
or more voice coil actuators, one or more eccentrics driven by one
or more electric motors, or combinations thereof; one or more sonic
heads coupled to the one or more force generators; a plurality of
springs coupling the housing to the one or more sonic heads; and a
drill rod disposed on its proximal end to the one or more sonic
heads.
[0007] In certain embodiments, the drill further comprises a bit
disposed on the distal end of the drill rod.
[0008] In certain embodiments, the one or more voice coil actuators
comprise a coil assembly rigidly disposed on the housing or on a
reflection mass, and a magnet assembly disposed on the one or more
sonic heads. In certain embodiments, the coil assembly of each of
the one or more voice coil actuators has little to no motion
compared to the one or more sonic heads.
[0009] In certain embodiments, each eccentric is driven by one
electric motor. In certain embodiments, the one or more force
generators comprise two paired sets of eccentrics configured to
exert no vertical force, using a 180.degree. phase angle between
the two paired sets of eccentrics. In certain embodiments, the one
or more force generators comprise two paired sets of eccentrics
configured to exert full vertical force, using a 0.degree. phase
angle between the two paired sets of eccentrics.
[0010] In certain embodiments, the drill further comprises a seal
disposed between the housing and the drill rod.
[0011] In certain embodiments, the drill further comprises a
spring-damper disposed between the drill rod and the bit. In
certain embodiments, the spring-damper cushions impact of the drill
bit by widening and lowering the impulse magnitude, whereby
transfer of primary resonant energy to unwanted resonant modes is
lowered, and the drill bit is kept in motion and not fused with a
workpiece.
[0012] In certain embodiments, the drill further comprises an
energy transfer rod and flange adaptor disposed between the one or
more sonic heads and the drill rod.
[0013] In certain embodiments, the drill further comprises a rotor,
stator, and stator housing disposed between the one or more sonic
heads and the drill rod. The rotor is disposed on the drill string
and the stator and stator housing each disposed on the housing,
thus allowing the sonic drill rod to rotate. In certain
embodiments, this configuration induces torsional resonances when
the input force is oscillated on the rotary motor. In these
embodiments, between the one or more sonic heads and the adapter,
when present, a rotor provide rotation torques onto the pipe. A
decoupler/stator can also be between the rotation of the pipe and
the one or more sonic heads, which are stationary. In one
configuration, the rotor, stator, and stator housing are tied
together so that the drill rod does not rotate but can oscillate
from the input torque at the rotor.
[0014] In certain embodiments, the kinetic energy stored in the
drill by the one or more sonic heads is directly offset by
potential energy stored within the plurality springs. In certain
embodiments, the drill further comprises a reflection mass coupled
to the one or more sonic heads through a second plurality of
springs and configured to offset the kinetic energy stored in the
drill.
[0015] In certain embodiments, the housing comprises a plurality of
plates and a plurality of standoffs. In certain embodiments, during
operation, the drill has a resonance frequency and, when on
resonance, an alternating input force is in phase with the
oscillation velocity of the one or more sonic heads. In certain
embodiments, the oscillating input force is provided from the
spinning eccentrics or voice coil force. In these embodiments, the
force is not constant but rather oscillates (or alternates) up and
down.
[0016] The present disclosure also provides a gauge for a sonic
drill configured to display information to an operator when the
drill is on or near resonance. The sonic drill may be any
resonance-enabled drill disclosed herein. In certain embodiments,
the information comprises one or more parameters chosen from an
amplitude of the drill bit, a resonant frequency of the drill, a
stress state, power components of the drill, and safe operating
frequencies.
[0017] In certain embodiments, the gauge indicates one or more
positions chosen from bit decoupling, a lower recommended range, a
recommended operating condition, a high recommend range, and
fusion. In certain embodiments, the power components of the drill
comprise useful power, power delivered at the bit, power absorbed
along the drill string's length, energy stored in the drill, and
wasted power.
[0018] In certain embodiments, the gauge is further configured to
display to the operator where mechanical resonance is located
compared to operating conditions of the drill.
[0019] In certain embodiments, the gauge is further configured to
show the ratio of bit motion to motion of the one or more sonic
heads.
[0020] In certain embodiments, when penetration of the drill slows
or ceases, the gauge is configured to display potential problems
with options to remedy the lower-than-desired penetration rate.
[0021] Any resonance-enabled drill disclosed herein may comprise
any gauge disclosed herein.
[0022] The present disclosure further provides a method for
selecting a resonance frequency in a sonic drill comprising a force
generator, one or more sonic heads, and a gauge. The phase is
measured between a force generator and one or more sonic heads in
the sonic drill. A resonance frequency is selected based on the
phase displayed on a gauge to indicate the relative position of the
phase for resonance of the sonic drill. In certain embodiments,
phase between the force generator and the one or more sonic heads
in the sonic drill is measured and resonance on the gauge is
displayed to indicates where the resonance frequency is relative to
the current operating frequency of the drill based on the phase
measurement.
[0023] In certain embodiments, when the sonic drill comprises a
bit, the method further comprises maximizing the ratio between the
bit motion and the motion of the one or more sonic heads. In
certain embodiments, when the sonic drill comprises a bit and
penetration of the bit is slowed or ceased, the method further
comprises reducing the weight on the bit to adjust the resonance
frequency of the drill to continue drilling.
[0024] In certain embodiments, the method further comprises
estimating the stress state of the drill. In certain embodiments,
the sonic drill selects the resonance frequency when an operating
condition changes. In certain embodiments, the operating condition
is chosen from pipe length, the ratio between the drill bit motion
and the motion of the one or more sonic heads, weight on the bit,
or the workpiece.
[0025] In certain embodiments, weight applied to the bit is greater
when drilling a workpiece with a lower soil stiffness than when
drilling a workpiece with a greater soil stiffness. In certain
embodiments, critical weight on the bit is pushed up to allow
motion at the drill bit to perform drilling. In certain
embodiments, as soil stiffness increases, less weight on bit is
required for fusing. In certain embodiments, weight on the bit is
inversely proportional to soil stiffness.
[0026] In certain embodiments, the weight applied to the bit is
great enough to provide fusing with the soil. The bit boundary
condition changes from free to fused with the soil. The soil
stiffness and viscous damping are now a part of the sonic drill
system. The drill system turns into a sensor to measure the soil
stiffness and viscous damping at the drill bit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The disclosure will be readily understood by the following
detailed description in conjunction with the accompanying drawings,
wherein like reference numerals designate like structural elements.
The drawings provide exemplary embodiments or aspects of the
disclosure and do not limit the disclosure's scope.
[0028] FIG. 1 shows a resonance-enabled drill comprising a voice
coil and a sonic head.
[0029] FIG. 2 shows a top perspective cross-section of a voice coil
in a resonance-enabled drill.
[0030] FIG. 3 shows a side plan view cross-section of the
resonance-enabled drill of FIG. 2.
[0031] FIG. 4 shows a side plan view of the resonance-enabled drill
of FIG. 2.
[0032] FIG. 5 shows a top plan view of the resonance-enabled drill
of FIG. 2.
[0033] FIG. 6 shows a resonance-enabled drill with two voice coil
actuators coupled on the same side of a sonic head.
[0034] FIG. 7 shows a resonance-enabled corer with a core barrel
assembly to take soil samples.
[0035] FIG. 8 shows a resonance-enabled corer with a core barrel
assembly and two sonic heads.
[0036] FIG. 9 shows a resonance-enabled corer with a core barrel
assembly to take soil samples with a configuration to cancel forces
to the housing with opposing voice coils to cancel resultant forces
to the housing.
[0037] FIG. 10 shows the percent force with phasing two eccentric
pairs from in-phase (0.degree.) to out of phase (180.degree.).
[0038] FIG. 11 shows the phasor vector relation of the resultant
force generated between two sinusoidal forcing functions from one
force phased relative to the other.
[0039] FIG. 12 shows a meter that displays the current state of the
drill compared to the closest system resonance.
[0040] FIG. 13 shows the mode shape of (C) the displacement, (D)
acceleration, and (E) stress of the drill system for (A) different
lengths and (B) input frequencies. This example displays a single
frequency and system length configuration, but the system's length
and frequency may be adjusted.
[0041] FIG. 14 shows the (B) displacement and (C) acceleration
amplitudes of the head and bit versus the input frequency. The
plots may be swept through various lengths of pipe (A).
[0042] FIG. 15 shows a table of the resonant frequencies (in Hertz)
of the penetration system relative to the number of added sections
of drill pipe.
[0043] FIG. 16 shows (B) the plot of input power, useful power,
wasted power, and power is delivered to the bit over the operating
frequencies of the penetration system. (A) The length of pipes can
also be selected. (C) Acceleration of the head and bit is also
plotted on the lower axis and Input Power vs. Input Frequency.
[0044] FIG. 17 shows a plot indicating where resonance is located,
stable operating conditions, and unstable operation conditions for
a hydraulically driven eccentric penetration system.
[0045] FIG. 18 shows the safe operating frequencies in white, where
the operations conditions are shaded where the system stress state
is too great, and failures will likely occur.
[0046] FIG. 19 shows an eccentric-driven sonic drill, where the
eccentrics are counterrotating and timed together.
[0047] FIG. 20 shows a dual electric motor drive for a dual
eccentric sonic drill. Each motor drives a single spinning
eccentric.
[0048] FIG. 21 shows four electric motor drives for a four
eccentric sonic drill organized as two paired sets of
eccentrics.
[0049] FIG. 22 shows the potential energy and kinetic energy
changes of a resonant system of FIG. 21 as a function of time.
[0050] FIG. 23 shows the energy when the resonant system of FIG. 21
operates at a frequency below mechanical resonance.
[0051] FIG. 24 shows a single electric motor drive for a dual
eccentric sonic drill, where the eccentrics are mechanically timed
to each other. A rotor and stator drive the rotational or torsional
vibration of the pipe, allowing the pile to not rotate but to
oscillate instead.
[0052] FIG. 25 shows (B) a plot of displacement amplitude and (C)
acceleration of the head and bit versus frequency. (A) The length
of pipes can also be selected.
[0053] FIG. 26 shows a meter that displays the current state of the
drill bit compared to decoupled and fusion.
[0054] FIG. 27 shows a resonance-enabled machine configured as a
drill with a voice coil-driven system at the sonic head.
[0055] FIG. 28 displays a critical weight on bit gauge.
[0056] FIG. 29 displays that when the sonic drill was operated at
nominally constant frequency of 120 Hz between 245 seconds and 250
seconds, the weight on bit affected the system performance.
[0057] FIG. 30 shows that a higher penetration rate was observed
when the weight on bit was below the critical weight on bit.
[0058] FIG. 31 shows the tangents of the penetrations rates from
FIG. 30.
[0059] FIG. 32 displays the relative push-and-pull forces from the
hydraulic cylinder of the sonic drill that lift and push down the
sonic drill.
[0060] FIG. 33 shows the resonance meter gauge readings during
testing with a GeoProbe 8150 LS using 40 ft of 4'' drill pipe and a
coring bit.
[0061] FIG. 34 is a schematic showing the top and bottom boundary
conditions operating on the drill string of a drill rig with a
sonic driver.
[0062] FIG. 35 shows the phase between input force and the measured
head acceleration of a sonic drill as a function of frequency. The
phases at 104.5 Hz are marked for (A) no coupling at the bit, (B)
full coupling with sand, (C) full coupling with stiff clay, and (D)
full coupling with granite.
[0063] Table 1 lists reference numerals used throughout the figures
and this disclosure.
TABLE-US-00001 TABLE 1 Reference numerals 100 drill 105 energy
absorbed within the system 115 peak-to-peak energy absorbed within
the system amplitude 150 corer 200 sonic heads 205 kinetic energy
210 first sonic head 215 motion of first sonic head 220 second
sonic head 225 motion of second sonic head 230 (internal force)
reflection mass 300 housing 310 first housing plate 312 housing
ledge 320 second housing plate 330 housing shell 350 standoff 351
fastener 400 springs 405 potential energy 410 housing-to-first
sonic head spring 420 housing-to-second sonic head spring 430
first-to-second sonic head spring 440 housing-to-reflection mass
springs 500 voice coil actuator 510 first coil assembly 515 first
magnet assembly 520 second coil assembly 525 second magnet assembly
530 first eccentric 540 second eccentric 530, 540 first plurality
of eccentrics 550 third eccentric 560 fourth eccentric 550, 560
second plurality of eccentrics 600 pile/drill rod/drill string 610
seal 620 spring-damper 630 bit 640 energy transfer rod 650 flange
adaptor 660 core barrel 670 corer bit 680 stator 683 stator housing
685 rotor 700 the workpiece (concrete, strata, etc.) 800 motors 810
first motor 815 first coupling 820 second motor 825 second coupling
830 third motor 835 third coupling 710 core 840 fourth motor 845
fourth coupling k.sub.1 first spring constant k.sub.2 second spring
constant k.sub.3 third spring constant k.sub.x reflection mass
spring constant
DETAILED DESCRIPTION
Resonance-Enabled Drill
[0064] A "resonance-enabled drill" is a type of resonance-enabled
machine, such as a sonic drill or sonic penetration device, within
this disclosure. Generally, within this disclosure, "drill," "sonic
drill," and "resonance-enabled drill" are used interchangeably. In
certain embodiments, the drill is configured to function as a corer
and can also be referred to as a "resonance-enabled corer."
[0065] Resonance is defined as when an oscillation system over a
single oscillation cycle the stored energy of the drill matches the
kinetic energy stored in the drill and that results in the force
being in phase with the resultant velocity. By the definition of
resonance, a person of skill in the art would readily understand
how the drill operates. For example, when the system is on
resonance, an alternating input force is in phase with the system
oscillation velocity of the one or more sonic heads.
[0066] To slow a hydraulically driven eccentric system, finer
controls may be used for the flow driving the eccentrics. In
certain embodiments, an energy-absorbing device, such as a brake or
generator, may limit the speed. The system can reduce the input
power to keep the input frequency below resonance. Disclosed herein
is another method wherein an electric motor drives the
counterrotating eccentrics. In certain embodiments, the motor is
closed-loop controlled to control the speed. In certain
embodiments, a motor brakes the system's speed so that the
eccentrics can spin at any desired rate.
[0067] The resonance-enabled drills disclosed herein comprise a
force generator, such as one or more voice coil actuators or one or
more pairs of eccentrics.
[0068] Voice Coil Actuators
[0069] A voice coil actuator commonly drives mechanical systems
with linear motion. The coil assembly is disposed on the sonic head
because it is lighter than the magnet assembly and losses from the
inertia of the oscillating mass prevent the heavier mass from being
the sonic head. Examples include loudspeakers to generate
sound/music. Care has been taken to reduce the coil assembly's
weight mounted to the speaker to provide the best performance with
the highest efficiency.
[0070] With the coil moving, power wires delivering current to the
coil are always being fatigued, limiting the life for the voice
coil and the power wires delivering current to the coil. As
disclosed herein, the voice coil is mounted to housing to mitigate
fatigue and increase reliability. Still, up to now, this
configuration caused reduced performance and lower efficiency. By
configuring the voice coil assembly in a resonance-enabled drill,
the kinetic energy stored in the drill by the voice coil
assemblies' moving masses is directly offset by potential energy
stored within the drill's springs. Therefore, heavier voice coil
assemblies can be mounted on a sonic head of the resonance-enabled
drill without losing performance or efficiency.
[0071] The one or more sonic heads are configured to operate on a
resonant mode shape. The one or more sonic heads are out of phase
of one another. Each of the one or more sonic heads is coupled to
the housing through a plurality of springs. When more than one
sonic head is present, the sonic heads are also coupled with each
other through a second plurality of springs. The drill is
configured so that the forces transferred to the housing through
the coupling springs between the one or more sonic heads and the
housing are at or near zero over the drill's operating range around
its resonant frequency.
[0072] In resonance-enabled drills driven by a voice coil, the
range of frequencies can and will vary. A person of skill in the
art understands to select a frequency range suitable for operating
the resonance-enabled drill under the conditions needed for the
selected workpiece. For example, the voice coil may operate between
60 Hz and 2,000 Hz (2 kHz), such as between 60 Hz and 100 Hz,
between 100 Hz and 200 Hz, between 200 Hz and 300 Hz, between 300
Hz and 400 Hz, between 400 Hz and 500 Hz, between 500 Hz and 600
Hz, between 600 Hz and 700 Hz, between 700 Hz and 800 Hz, between
800 Hz and 900 Hz, between 100 Hz and 1 kHz, between 1 kHz and 1.1
kHz, between 1.1 kHz and 1.2 kHz, between 1.2 kHz and 1.3 kHz,
between 1.3 kHz and 1.4 kHz, between 1.4 kHz and 1.5 kHz, between
1.58 kHz and 1.6 kHz, between 1.6 kHz and 1.7 kHz, between 1.7 kHz
and 1.8 kHz, between 1.8 kHz and 1.9 kHz, or between 1.9 kHz and 2
kHz. In certain embodiments, the frequency is greater than 60 Hz.
In certain embodiments, the frequency is less than 2 kHz. In
certain embodiments, the frequency is between 60 Hz and 250 Hz,
such as between 60 Hz and 150 Hz.
[0073] FIG. 1 shows a resonance-enabled drill 100, comprising a
housing 300, a sonic head 210 coupled to the housing 300 by a first
plurality of springs 410, a coil assembly 510 disposed on the
housing 300, a voice coil magnet assembly 515 coupled to the sonic
head 210, a drill rod 600 disposed on the proximal end to the sonic
head 210 and on the distal end to a bit 630. A seal 610 is disposed
between the drill rod 600 and the housing 300. The voice coil
actuator 500 comprises a coil assembly 510 and a magnet assembly
515. In this embodiment of the single sonic head resonance-enabled
drill 100, the voice coil magnet assembly 515 is disposed beneath
and coupled to the sonic head 210. During operation, the bit 630
contacts the workpiece 700, which can be soil, strata, rock
formation, concrete, or other natural or manmade feature, to form a
borehole.
[0074] Optionally, the resonance-enabled drill 100 further
comprised a spring-damper 620 disposed between the drill rod 600
and the bit 630. The spring-damper 620 widens or flattens the
impulse load from the drill bit 630. For example, if a
resonance-enabled drill 100 made of only steel impacts a rock
formation 700, the formation has infinite impedance and reflects
the impact fully onto the drill rod 600. The impact creates an
impulse load and excites all resonant frequencies of the resonant
system. With repeated blows, the energy quickly transitions from
the primary resonant mode to a broadband of resonant frequencies,
fusing the drill bit 630 with the formation 700.
[0075] By disposing a spring-damper 620 (with or without internal
damping) between the drill bit 630 and the drill rod 600, the bit
630 can move with the end of the drill rod 600 during normal
operation. When a hard substrate is encountered and impulse loads
are generated, the spring-damper 620 cushions the impact by
widening and lowering the impulse magnitude. This lowers the
transfer of the primary resonant energy to unwanted resonant modes,
keeping the drill bit 630 in motion and not fused with the strata
700. The bit's 630 susceptibility to fusing is lessened, the useful
range of weight on bit 630 is widened, and the acceleration force
and energy onto the bit 630 are lessened during drilling, causing
less wear and extending the service life.
[0076] In certain embodiments, the spring-damper 620 comprises a
resilient member, such as a spring or a viscoelastic medium. The
damping within the spring-damper 620 is rate-dependent. When
present, the spring gives. The load through the transient impact
transfers by the damping or viscous part of the viscoelastic
medium.
[0077] Referring to FIGS. 2-5, the housing 300 comprises a first
housing plate 310 and a second housing plate 320. The sonic head
210 is coupled to the first housing plate 310 by a plurality of
housing-to-sonic head springs 410. The sonic head 210 is coupled to
the second housing plate 320 by a second plurality of
housing-to-sonic head springs 410.
[0078] In certain embodiments, the resonance-enabled drill further
comprises an energy transfer rod 640 and flange adaptor 650
disposed between the sonic head 210 and the drill rod 600. In this
configuration, the seal 610 is disposed between the energy transfer
rod 640 and the housing 300.
[0079] Standoffs provide strength and rigidity to the machine.
Separate resonant modes do not occur within the machine's
structure. For instance, each sonic head 200 is assumed to be a
rigid body, and the standoffs 350 ensure that each mass acts as a
rigid body during machine operation. The number of standoffs in the
plurality can be selected to accommodate the size of the machine,
such as between 1 and, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
15, 20, 25, 30, 35, 40, 45, 50, 75, or 100. A large machine
typically contains more standoffs than a smaller machine for
strength and rigidity. Each standoff 350 is matched with springs
410 and fasteners 351, so as the number of standoffs 350 increases,
so do the number of springs 410 and fasteners 351.
[0080] FIG. 6 shows a resonance-enabled drill 100 with two voice
coil actuators 500 coupled on the same side of a sonic head 210.
Each voice coil comprises a coil assembly and a magnet assembly. A
first coil assembly 510 and second coil assembly 520 are disposed
on the housing 300. A first magnet assembly 515 and second magnet
assembly 525 are coupled to the sonic head 210.
[0081] FIG. 7 shows a resonance-enabled drill 150 with a core
barrel 660 and a corer bit 670 to take soil samples. The core
barrel 660 is disposed on the proximal end to the sonic head 210.
The corer bit 670 is disposed on the distal end of the core barrel
660.
[0082] FIG. 8 shows a resonance-enabled corer 150 with a core
barrel 660, a corer bit 670, and two sonic heads 210,220. The first
sonic head 210 is rigidly coupled to a first magnet assembly 515, a
plurality of housing-to-first moving mass springs 410, a plurality
of housing to second moving mass springs 420, and a plurality of
first moving mass to second moving mass springs 430. The first
sonic head 210 is further coupled to a housing ledge 312 by a
plurality of housing-to-first sonic head springs 410 and to a
second sonic head 220 by a plurality of first-to-second sonic head
springs 430. The second sonic head 220 is coupled to the housing
300 via a plurality of housing-to-second sonic head springs 420 and
the first sonic head 210 by a plurality of first-to-second sonic
head springs 430. In certain embodiments, the first coil assembly
510 is rigidly coupled to the housing 300 and has little to no
motion compared to the sonic heads 210,220.
[0083] FIG. 9 shows a resonance-enabled corer 150 with a core
barrel 660 and corer bit 670 with a configuration to cancel forces
to the housing 300 with opposing voice coils 500 to cancel
resultant forces to the housing 300. In this embodiment, the first
sonic head 210 is rigidly coupled to a first magnet assembly 515, a
plurality of housing-to-first moving mass springs 410, a plurality
of housing to second moving mass springs 420, a plurality of first
moving mass to second moving mass springs 430. The first sonic head
210 is further coupled to a housing ledge 312 by a plurality of
housing-to-first sonic head springs 410 and to a second sonic head
220 by a plurality of first-to-second sonic head springs 430. A
first voice coil assembly 510 is disposed the top surface of the
housing 300 inside the drill 150. The first voice coil assembly 510
is coupled to the first magnetic assembly 515.
[0084] The second sonic head 220 is coupled to the housing 300 via
a plurality of housing-to-second sonic head springs 420 and the
first sonic head 210 by a plurality of first-to-second sonic head
springs 430. The second voice coil assembly 520 is disposed on the
bottom surface of the housing 300 inside the drill 150, pointing in
the opposite direction of the first voice coil 510. The second
voice coil assembly 520 is coupled to the second magnetic assembly
525. If the housing springs 410,420 are not completely offset, they
can be adjusted to cancel the resultant forces to the housing
300.
[0085] FIG. 10 shows the percent force with phasing two eccentric
pairs from in-phase (0.degree.) to out of phase (180.degree.). The
vector math for the resultant force of the pair of eccentrics is
provided. The vector math represents the image in FIG. 11, which
shows the phasor vector relation of the resultant force generated
between two sinusoidal forcing functions from one force phased
relative to the other. FIG. 12 shows a meter that displays the
current state of the drill compared to the closest system
resonance.
[0086] FIG. 13 shows the mode shape of (C) the displacement, (D)
acceleration, and (E) stress of the drill system for (A) different
lengths and (B) input frequencies. This example displays a single
frequency and system length configuration, but its length and
frequency may be adjusted. In certain embodiments, these plots
represent angular displacement, angular acceleration, and angular
stress for a corer rod undergoing torsional forces from the one or
more sonic heads.
[0087] FIG. 14 shows the (B) displacement and (C) acceleration
amplitudes of the head and bit versus the input frequency. The
plots (A) may be swept through various lengths of pipe.
[0088] FIG. 15 shows a table of the undamped resonant frequencies
of the penetration system relative to the number of added sections
of drill pipe.
[0089] FIG. 16 shows (B) the plot of input power, useful power,
wasted power, and power is delivered to the bit over the operating
frequencies of the penetration system. (A) The length of pipes can
also be selected. (C) Acceleration of the head and bit is also
plotted on the lower axis and Input Power vs. Input Frequency.
[0090] FIG. 17 shows a plot indicating where resonance is located,
stable operating conditions, and unstable operation conditions.
With a hydraulic system driving spinning eccentrics, an unstable
condition is encountered below resonance.
[0091] FIG. 18 shows the safe operating frequencies in white, where
the operations conditions are shaded where the system stress state
is too great, and failures will likely occur. The failures are
caused by overstressing the system at various locations, which may
cause instant failure, or the system may be fatigued
prematurely.
[0092] Eccentrics
[0093] In certain embodiments, the force generator comprises one or
more eccentrics. In certain embodiments, a motor drives each
eccentric. In such embodiments, the motors are electrically
synchronized. When a primary signal is generated, both motors are
controlled by the primary signal. These motors counterrotate in
relation to each other. Electric motors have not been used
previously because the control system for electrically controlling
motors to sync to one another has just recently been achieved. The
industry has not understood that the current operating conditions
are not recommended and could be improved using electric motors.
One favorable operating condition is identified. It is often found
below resonance, where the ratio of drill head motion amplitude
over drill bit motion amplitude is minimal.
[0094] The drill bit generally moves more than the sonic head,
permitting a higher transfer of power to the drill bit to drill.
The drill may be unstable at this location and need less energy
than at lower frequencies. The drill eccentrics rotational speed
may increase, and the system is pulled through the favorable
operating point. Therefore, with current technology, sonic drills
may not be able to operate in such conditions.
[0095] In certain embodiments, the resonance-enabled drill
comprises double eccentrics, such as four in total, with phase
control. FIG. 36 shows an eccentric-driven sonic drill 100, where
the eccentrics 530,540 are counterrotating and timed together. The
resonance-enabled drill 100 comprised a housing 300, a sonic head
210 disposed within the housing 300, a plurality of eccentrics
530,540 disposed within the sonic head 210 and coupled to a motor
810 through a coupling 815, a drill rod 600 is coupled to the sonic
head 210 at the proximal end. A drill bit 630 is coupled to the
distal end of the drill rod 600. This drill 100 can be configured
as a corer 150 for a single rod length for sampling.
[0096] FIG. 37 shows a dual electric motor drive 810,820 for a dual
eccentric sonic drill 100. Each motor drives a single spinning
eccentric. That is, motor 810 drives eccentric 530 through coupling
815, and motor 820 drives eccentric 540 through coupling 825. The
eccentrics 530,540 in this embodiment are counterrotating and
electrically synchronized.
[0097] FIG. 38 shows four electric motors 810,820,830,840 driving
four eccentrics 530,540,550,560 in a sonic drill 100. The
eccentrics 530,540,550,560 are organized into two paired sets of
eccentrics, 530,540 and 550,560. Each motor drives a single
spinning eccentric. That is, motor 810 drives eccentric 530 through
coupling 815, motor 820 drives eccentric 540 through coupling 825,
motor 830 drives eccentric 550 through coupling 835, and motor 840
drives eccentric 560 through coupling 845.
[0098] FIG. 39 shows the potential energy and kinetic energy
changes of a resonant system of FIG. 21 as a function of time. The
total amount of energy in the system is constant and no energy is
absorbed within the system. FIG. 40 shows the energy when the
resonant system of FIG. 21 operates at a frequency below mechanical
resonance. At this state, the potential energy amplitude is greater
than the kinetic energy amplitude and the system uses additional
energy to balance the system. This additional energy is absorbed
within the system during operation.
[0099] FIG. 41 shows a cross section view of a single electric
motor 810 drive for a dual eccentric 530,540 sonic drill 100,
comprising a rotor 685 between the sonic head 210 and the drill rod
600 and surrounded by a stator 680 and a stator housing 683. The
eccentrics 530,540 are mechanically timed to each other. The rotor
685 and stator 680 drive the rotation of the drill rod 600. The
rotor 685 and stator 680 can also be configured to drive torsional
vibration of the pipe, allowing the pile 600 to not rotate but
oscillate instead. The drill bit 630 oscillates rotationally. The
torsional modes operate at different frequencies than the vertical
oscillations, allowing the bit 630 to impact at different locations
for each vertical oscillation.
[0100] FIG. 42 shows (B) a plot of displacement amplitude and (C)
acceleration of the head and bit versus frequency. (A) The length
of pipes can also be selected. The resonance conditions are
displayed with a dashed line, and a potential operating point is
defined as a long dash. The operating point has a recommended
bit-to-head amplitude ratio, allowing energy to be delivered at the
bit while minimizing the acceleration impact at the sonic head.
Because this condition can be in the unstable operating range,
standard hydraulically driven rigs cannot operate under this
condition.
[0101] In certain embodiments, the resonance-enabled drill
comprises two sets of counterrotating eccentrics. Each set spins at
the same frequency, with one set, phased differently from the other
set. In certain embodiments, at startup, the eccentrics are driven
at 180.degree. out of phase from one another, which cancels all
vertical forces. The vertical force amplitude is adjusted by
changing the phase between the two sets of eccentrics. As the
eccentric's phase approaches 0.degree., the force approaches 100%
force, which is the total force of the four eccentrics
(m*r*.omega..sup.2), where `m` is the mass of the eccentric, `r` is
the distance from the center of rotation to the center of mass of
the eccentric, and `.omega.` is the angular speed of the eccentric
rotation.
[0102] Commercially-available eccentric-driven drills use one set
of eccentrics and operate at full force. In certain embodiments,
the drill comprises a knob which an operator can use while drilling
to adjust the input force amplitude to the drill. The operator can
operate on or near resonance and then adjust the input force
amplitude until the desired operating conditions are met. The
adjustment of the input force amplitude changes the phase between
the two pairs of eccentrics. The desired operating conditions
include, but are not limited to, head acceleration, bit
acceleration, input power, stress state within the system,
penetration rate, energy transferred into and stored in various
sub-systems, etc. The acceleration is related to the displacement,
velocity, and jerk through the frequency of oscillation, and any of
these can also be used. The stress state in the system can be
maximum, mean, amplitude, etc.
[0103] In certain embodiments, torsional modes for the drill string
use a rotary motor as the torsional driver. The torsional resonant
modes are similar to the axial resonant modes. During operation,
the torsional motor drives the oscillations at different
frequencies, permitting the bit to impact at different rotational
locations with each blow. The buttons on the bit hit virgin
material and did not impact the same location. Also, the rotation
oscillation acts as a paddle to loosen materials, such as clays,
and move the loosened materials during drilling.
[0104] In certain embodiments, the drill comprises two classes of
force generators, wherein the one or more voice coil actuators are
tuned to a first frequency range and the one or more eccentrics are
tuned to a second frequency range.
Drill Bit Plug
[0105] When drilling in soil, such as non-cemented clay, sand, and
the like, the most common configuration for geotechnical drilling,
the drill bit is selected accordingly. In these embodiments, the
drill bit comprises tungsten carbide, steel with tungsten carbide
inclusions or pellets, or the like. In certain embodiments, the
drill bit is configured with an aggressive geometry to tear off and
remove soil.
[0106] When encountering a boulder or hard layer, the conventional
drill bit will be unable to progress and wear off rapidly. The
sonic bit plug is a downhole wireline tool that latches into the
bottom hole assembly (BHA) and expands underneath the conventional
drill bit to the full string diameter or slightly more. Sonic
motion is activated, and the pushdown force is applied to the drill
string. The borehole can be progressed over a short penetration
without rotation or circulation.
[0107] The sonic generator can be powered with air or fluid
pressure or electric power.
[0108] In certain embodiments, rotation may remove the cuttings
underneath the bit. The whole string can be gently rotated with a
wireline bit-plug inside. Alternatively, the sonic bit plug could
include a rotation capability, such as powered by electricity or
air.
[0109] In certain embodiments, circulation cools the drill bit and
evacuates the cuttings from the borehole. When present, circulation
may be achieved through reverse circulation by injecting air at the
bottom but inside the drill string at the top of the sonic bit
plug. Reversed circulation is effective but may generate static
pressure in the borehole slightly lower than the ambient
hydrostatic, destabilizing the borehole. Reversed circulation
cannot be applied to some types of soils, such as sand or highly
fragmented rock. In certain embodiments, the sonic bit plug is
pulled out of the borehole, and the borehole is cleaned up by
gentle rotation with low Weight on Bit (WoB). In this instance,
conventional fluid circulation and reaming may also be
performed.
Interface
[0110] Commercially available drills have digital displays or
analog displays that give the drilling operator the drill frequency
and head acceleration but cannot be configured to display the
resonance state. In certain embodiments, the resonance-enabled
drill comprises a gauge configured to display information to the
operator when the drill is on or near resonance. To be clear, the
gauge continuously displays information, not just when the drill is
on or near resonance. The gauge can indicate to the operator when
the drill is operating on or near resonance. For example, the gauge
displays to an operator where mechanical resonance is located
compared to operating conditions of the drill. In certain
embodiments, the drill is no longer at resonance and the gauges
displays information on the stress state and safe operating
conditions of the drill. In certain embodiments, the display
comprises a list or visual cues of the current system setup's
resonant frequencies. In certain embodiments, the display is
digital, analog, or a combination thereof.
[0111] Commercially available drills do not indicate what the bit
is doing. In certain embodiments, the resonance-enabled drill
comprises a gauge configured to display the amplitude of the drill
bit to the operator. The higher the drill bit motion, the better
penetration. In these embodiments, the drill shows the bit
amplitude to the operator. In certain embodiments, the
resonance-enabled drill further comprises a secondary gauge
configured to show the ratio of bit motion to the sonic head
motion. In many situations, the operator is recommended to maximize
this ratio. Commercially available drills only present the
penetration rate and sound to the operator to describe the drill's
vibratory state. These indicators are misleading because the sound
is only generated by motion at the sonic head and is not a good
indicator of bit motion.
[0112] Based on system parameters and the operating conditions,
stress states are also estimated and configured to display on a
gauge for the operator in certain embodiments. Failures are common
because the readout to the operator is only at the sonic head.
Still, with various drilling conditions, bit and bottom hole
assembly configurations, and lengths and geometry of pipes, the
stress states change. Therefore, the same amplitude of motion at
the sonic head can generate drastically different stress conditions
below ground.
[0113] The displays in commercially available drills show the total
power delivered to the sonic head for performing work. The total
power is broken into real and reactive power. The real power is
what the system uses to do work, such as drilling. The reactive
power drives the drill bit may be unused and reflected onto the
driver, causing high power input. In certain embodiments, the
resonance-enabled drill is configured to display the power
components of the drill to the operator. These components include,
but are not limited to, useful power, power delivered at the bit,
power absorbed along the drill string's length, energy stored in
the drill, and wasted power (reactive power).
[0114] During penetration, the drill bit may become a node, coupled
with and fused to the workpiece. As the resonant condition changes,
the resonance-enabled drill has a fixed node at the bottom of the
string. When this occurs, the drill bit motion goes to zero or near
zero, and penetration stops. When the penetration slows or ceases,
the resonance-enabled drill is configured to display potential
problems with options to remedy the lower-than-desired penetration
rate. For example, when penetration is slowed or ceased, the
resonance-enabled drill is configured to indicate to the operator
that the weight on the bit should be reduced. In other saturations,
the resonance-enabled drill may indicate when the weight on the bit
is too great, causing potential fusing of the bit or damage to the
workpiece if a sample is being taken. This indication may include a
shift in the resonant frequency or be calculated from the drill's
measurements. A list of resonant frequencies with the bit fused to
the bottom also helps the operator because those are the resonant
frequencies to operate on if the operator does not know what they
are.
[0115] Based on the drilling configuration and system, the
resonance-enabled drill is also configured to display safe
operating frequencies for the operator in certain embodiments. If
the operator tries to operate outside the safe operating ranges,
then the resonance-enabled drill indicated such to the
operator.
[0116] FIG. 26 shows a meter that displays the current state of the
drill bit compared to decoupled and fusion. A recommended operating
condition exists between the bit decoupled state (where the drill
bit is not engaged with the workpiece) and fusion (where the drill
bit acts as a node or fused to the workpiece). The indicator
displays the system operator where the system is operating compared
to the recommended conditions and if it is approaching bit
decoupling or fusion. The displayed information is referred to as
the critical weight on bit.
[0117] FIG. 27 shows a resonance-enabled machine configured as a
drill with a voice coil-driven system at the sonic head. An
internal force reflection mass 230 reacts to the opposing forces
from the voice coil independent of the ground. The system uses the
inertia of the reflection mass to react to the force imparted on
the sonic head without transmitting the force to the housing.
Sensor
[0118] The sonic drill is a resonant system. When the system is
operated on mechanical resonance, the system has a low impedance,
which means it has a high resultant output compared to the input.
The low impedance, allows the system to become a sensor and the
system can be monitored through measurements than can be used to
calculate changes in the boundary conditions, energy absorption,
and damage to the system. An example, is when a force is applied at
the sonic head that applies a very large weight on bit. The very
large weight on bit is enough to fuse the bit with the soil. The
boundary condition changes based on the new boundary condition at
the bit. There will be a new resonant frequency based on the soil
stiffness at the drill bit. The systems new measured phase between
the input force amplitude and the resultant head acceleration
oscillation can be used to calculate the soil stiffness at the
drill bit.
[0119] The preceding description is given for clearness of
understanding only. No unnecessary limitations should be
understood, as modifications within the disclosure's scope may be
apparent to those having ordinary skill in the art. Throughout the
specification, where compositions are described as including
components or materials, it is contemplated that the compositions
can also consist essentially of, or consist of, any combination of
the recited components or materials, unless described otherwise.
Likewise, where methods are described as including steps, it is
contemplated that the methods can also consist essentially of, or
consist of, any combination of the recited steps, unless described
otherwise. The disclosure illustratively disclosed herein suitably
may be practiced in the absence of any element or step which is not
specifically disclosed herein.
EXAMPLES
Example 1
[0120] Referring to FIG. 8, the resonance-enabled corer operated at
zero or near-zero alternating force transmitted to frame during
operation. When operating the device of FIG. 8 with a measured
.+-.60 g (.+-.588 m/s.sup.2) of oscillation acceleration at the
second sonic head and drawing an average of 120 W, the system cored
a 1'' diameter (2.54 cm) hole with a 0.5 core in a 3'' thick (7.62
cm) piece of sandstone in under 3 minutes.
Example 2
[0121] Testing was performed on a GeoProbe.TM. 8150 LS using 40 ft
of 4'' drill pipe and a coring bit. The coring was performed in a
riverbed with various sizes of gravel, boulders, and sand. If too
much weight was added to the bit by drill pipe, head weight, or
push down force fusion was initiated at the bit.
[0122] FIG. 29 displays that when the sonic drill was operated at a
nominally constant frequency of 120 Hz between 245 seconds and 250
seconds, the weight on the bit affected the system performance.
Counterintuitively, less weight on a bit increased the penetration
rate.
[0123] In FIGS. 30 and 31, the contrasting solid arrows XYX and
dashed arrows XYZ show a higher penetration rate XYX was observed
when the weight on bit was below the critical weight on bit.
Conversely, when the weight on bit exceeded the critical weight on
bit, the system's penetration rate decreased along with the
subsequent acceleration. See FIG. 29.
[0124] FIG. 32 displays the relative push-and-pull forces from the
hydraulic cylinder of the sonic drill that lift and push down the
sonic drill. The observed critical weight on the bit line was
displayed. Here, by reducing the weight on the bit, the resultant
system acceleration increased, resulting in higher energy transfer
to the bit for higher penetration rates.
[0125] FIG. 33 shows the resonance meter gauge readings during
testing with a GeoProbe.TM. 8150 LS using 40 ft of 4'' drill pipe
and a coring bit. As the frequency was increased from 60 Hz to
operation at 120 Hz, the gauge went through resonance the drill was
operated above resonance.
[0126] A gauge displays the difference between phase estimate from
the model for the no coupling at the bit and the actual
measurement. As the phase deviates, the gauge moves based on the
coupling caused by the weight on the bit. The gauge has a cutoff
between 5 and 45 degrees for the critical weight on bit. The gauge
has a green zone between 0 and 45 degrees and, on some
applications, a yellow zone between a value between 0 and 45
degrees and 45 degrees. After 45 degrees or the determined cutoff
for the critical weight on the bit, the gauge will be red,
indicating that the controller has exceeded the critical weight on
the bit.
Example 3
[0127] Referring to FIG. 34, the sonic drill system was continuous
with boundary conditions on each end. The boundary condition at the
top of the drill string comprised the sonic driver internal force,
sonic head mass, input force, damping force, and the air spring or
isolator force. The top boundary condition can be expressed as
Equation 1:
E d .times. s .times. A d .times. s .times. .differential. u
.function. ( 0 , t ) .differential. x = m s .times. h .times.
.differential. 2 u .function. ( 0 , t ) .differential. t 2 + c d
.times. s .times. .differential. u .function. ( 0 , t )
.differential. t + k a .times. s .times. u .function. ( 0 , t ) - F
o .times. sin .function. ( .omega. f .times. t ) Equation .times. 1
##EQU00001##
where m.sub.sh is the mass of the sonic head, c.sub.ds is the
damping at the sonic head, k.sub.as is the spring rate at the sonic
head, F.sub.o is the input force amplitude, .omega..sub.f is the
input angular frequency of the input force, t is the time, u is the
motion at any point along the x-axis, E.sub.ds is the elastic
modulus of the drill string, and A.sub.ds is the cross-sectional
area of the drill string.
[0128] The boundary condition at the bit end of the drill string
comprised the bit mass and strata coupling internal force, strata
damping force, and strata restoring force. The bottom boundary
condition can be expressed as Equation 2:
E d .times. s .times. A d .times. s .times. .differential. u
.function. ( L ds , t ) .differential. x = - m d .times. b .times.
.differential. 2 u .function. ( L ds , t ) .differential. t 2 - c d
.times. b .times. .differential. u .function. ( L ds , t )
.differential. t - k d .times. b .times. u .function. ( L d .times.
s , t ) Equation .times. 2 ##EQU00002##
where m.sub.db is the mass of the drill bit, c.sub.db is the
damping at the drill bit, k.sub.db is the stiffness at the drill
bit, and L.sub.ds is the length of the drill system.
[0129] The spring rate at the drill bit was minimal when the bit
was free. The resonant frequency was lowest compared to when the
bit interacted with the soil. Assuming different soil types of
dense sand (1250 lbf*in.sup.-3 (3.38.times.10.sup.8 N*m.sup.-3)),
extremely stiff clay (4680 lbf*in.sup.-3 (1.27.times.10.sup.9
N*m.sup.-3)), and granite (rock, 1.58.times.10.sup.6 lbf*in.sup.-3
(4.28.times.10.sup.11N*m.sup.-3)). The equivalent spring rate onto
the bit was the values above multiplied by the bit frontal
area.
[0130] The phase between the input force at the sonic head and the
resultant acceleration of the sonic head was measured. The critical
weight on the bit was defined when the weight onto the bit during
oscillation coupled with the soil/strata being drilled and the
boundary condition at the bit changed because the soil stiffness
acted onto the bit. If the bit were suspended, the bit impacted the
soil/strata and did not couple but instead received quick transient
impulses from the short contact with the strata each cycle. If the
sonic drill were operating under the critical weight on the bit,
the drill had equivalent phase readouts as the model without spring
coupling at the bit for the drill during drilling operations. As
the bit started to interact enough with the soil, where the soil
stiffness acted as a boundary condition onto the sonic drill system
at the drill bit, the resultant phase started to shift.
[0131] A commercial sonic drill has been modeled with 40 feet of
drill pipe, a 2-foot stub, and a drill bit on the end. The sonic
drill modeled with a minimal spring rate on the drill bit provided
a measured phase reading similar to FIG. 34. At -90.degree. of
phase difference between the input force and the resultant
acceleration at the sonic head, the system is on mechanical
resonance (Point A on FIG. 34). The input force and velocity are in
phase with one another. For this example, the system operated at
.about.104.5 Hz. If the system is held operating at .about.104.5 Hz
and additional downforce is applied, which applied more weight on
the bit, the downforce may change if the soil stiffness coupling is
enough.
[0132] When the weight on the bit was too great, the bit coupled
with the soil or strata. The soil stiffness influenced the bit. If
the weight on the bit was very great, the bit fully coupled to the
soil or strata, and the soil stiffness acted as a spring on the
bit. Here, the bit fused onto the soil and became a node. This
transition took the bit from a freer boundary condition to a fixed
boundary condition. If the soil or strata is rock, the soil
stiffness is so great that it allows no motion at the bit.
[0133] If the soil is dense sand and enough weight on bit is
applied that the drill bit is fused with the soil so that all the
soil stiffness is pushing on the drill bit, then the boundary of
the system changes and the measured phase changes based on the soil
stiffness. At the point of fusing with dense sand, the measured
phase reads -46.degree., shifted from Point A to Point B in FIG.
34, while the system is still operating at the same frequency. The
system's resonant frequency has shifted up to 106.5 Hz by changing
the boundary condition. With the bit fused, the system has lost the
ability to dissipate energy by drilling through the strata.
Instead, the system has to dissipate the energy within the system.
In many cases, the system cannot dissipate energy, and the
oscillations grow until failure occurs. If the soil stiffness is
greater than dense sand, as with stiff clay, the same conditions
will occur, but the phase shift is greater than that of dense
sand.
[0134] With stiff clay, the resonant frequency can shift from 104.5
Hz to 112 Hz, and the phase measured at 104.5 Hz now drops to
-10.degree., a shift from Point A to Point C in FIG. 34. Hard rock
is an extreme case. If drilling through granite, the phase will
shift above the 150 Hz operating range of the drill, and the phase
will be within 10.degree. of -180.degree. out of phase, which is
the case when the system is very far from mechanical resonance,
shift from A to D in FIG. 35.
[0135] From these plots, with soils with lower soil stiffness,
sands, and low stiffness clays, the weight applied to the bit can
be greater than the systems with large soil stiffness, high
stiffness clays, and rock. Because the system behaves similarly
with the low weight on the bit with the low stiffness clays and
sands, whereas pushing up to the critical weight on bit allows
motion at the drill bit to perform drilling, and the system
performs as intended with a free boundary condition at the drill
bit. However, with stiff clays, the weight on the bit needs to be
more closely monitored. After all, it can become fused, and then
the drill will be in a refusal state where the bit cannot move
because it has fused to the boundary condition. The resonant
condition has shifted, but the resonant condition is the new
boundary condition where the bit is fused with the strata, making
it impossible to uncouple the drill bit from the strata once fusing
has. As the soil stiffness increases, less weight on bit is
required for fusing. Therefore, less weight on bit should be used
when drilling through stiff clays than sands and even less weight
when drilling through rock than clays.
[0136] If the weight on bit is intentionally applied large enough
to provide fusing of the drill bit to the soil, then the drill
system may be used as a sensor to detect the change in system
response of phase difference between the input force and the
resultant acceleration at the sonic head to determine the soil
stiffness. In FIG. 34, the system responses change because of the
soil type and this method was described above to determine the
critical weigh on bit, but the measured phase can be used to
calculate the soil stiffness. One such method is to create a curve
of the change is drill phase performance vs. the soil stiffness and
this can be used to determine the type of soil at the drill
bit.
[0137] The practice of a method disclosed herein, and individual
steps thereof, can be performed manually and/or with the aid of or
automation provided by electronic equipment. Although processes
have been described concerning embodiments, a person of ordinary
skill in the art will readily appreciate that other ways of
performing the methods' acts may be used. For example, the order of
various of the steps may be changed without departing from the
method's scope or spirit unless described otherwise. Some of the
individual steps can also be combined, omitted, or further
subdivided into additional steps.
[0138] It is appreciated that certain features of the invention,
which are, for clarity, described in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Various features of the invention, which are, for
brevity, described in the context of a single embodiment, may also
be provided separately or in any suitable subcombination. All
patents, publications, and references cited herein are fully
incorporated by reference. In case of conflict between the present
disclosure and incorporated patents, publications, and references,
the present disclosure should control.
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