U.S. patent application number 14/366377 was filed with the patent office on 2014-11-13 for extended reach drilling.
The applicant listed for this patent is FLEXIDRILL LIMITED. Invention is credited to Mark Christopher Cunliffe, Gregory Donald West.
Application Number | 20140332278 14/366377 |
Document ID | / |
Family ID | 48668890 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140332278 |
Kind Code |
A1 |
West; Gregory Donald ; et
al. |
November 13, 2014 |
EXTENDED REACH DRILLING
Abstract
Apparatus, methods and uses that allow extended reach drilling
by virtue of the provision in the drillstring and to downhole tools
collective vibrations, not tuned specifically to a single resonant
frequency, from a hammer assembly that provides vibrations of
different frequency ranges.
Inventors: |
West; Gregory Donald;
(Timaru, NZ) ; Cunliffe; Mark Christopher;
(Timaru, NZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FLEXIDRILL LIMITED |
Auckland |
|
NZ |
|
|
Family ID: |
48668890 |
Appl. No.: |
14/366377 |
Filed: |
December 18, 2012 |
PCT Filed: |
December 18, 2012 |
PCT NO: |
PCT/NZ2012/000240 |
371 Date: |
June 18, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61594072 |
Feb 2, 2012 |
|
|
|
Current U.S.
Class: |
175/57 ; 175/293;
175/296 |
Current CPC
Class: |
E21B 1/02 20130101; E21B
7/24 20130101; E21B 28/00 20130101; E21B 6/04 20130101; E21B 10/36
20130101 |
Class at
Publication: |
175/57 ; 175/296;
175/293 |
International
Class: |
E21B 7/24 20060101
E21B007/24; E21B 10/36 20060101 E21B010/36; E21B 1/02 20060101
E21B001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2011 |
NZ |
597197 |
Claims
1. A method of extended reach drilling which comprises providing a
top hammer assembly from which a drill string is dependant, the top
hammer assembly, or the top hammer assembly and the proximate
region of the drill string, being configured by mass or cross
sectional impedances, excitation features, or the like to provide
excitations to provide multiple localised bands of frequencies that
differ from the band or bands of frequencies (beat frequency)
generated at the strike interface, the variation of frequencies
sufficient to allow extended reach drilling, and operating the top
hammer assembly during operation of the drill string in an extended
reach drilling operation, without specifically tuning the drill
string for resonance, although some optimisation responsive to
different strata might occur.
2. A method as claimed in claim 1 wherein said top hammer to be
powered by hydraulic, pneumatic, electric, mechanical or
electromagnetic means.
3. A method of extended reach drilling which comprises providing a
top hammer assembly from which a drill string is dependant, the top
hammer assembly, or the top hammer assembly and the proximate
region of the drill string, being configured by impedances,
excitation features, masses, or the like to increase the spread of
vibrational frequencies to pass into and downhole along the drill
string from those generated at the impact interface of the top
hammer assembly, the method comprising operating the top hammer
assembly during drill string dependant downhole operations at a
power, or in a finite power range, into the top hammer assembly,
without reference to drill string length for resonance
purposes.
4. A method of claims 1 to 3 wherein there are subsequent uphole
frequencies reflected from those generated at the strike or impact
interface of the top hammer assembly.
5. A method of enhancing the reach of a drill string downhole using
a top hole hammer functionality, the method comprising, without
tuning for resonance, generating a spectrum where the output energy
of the hammering impacts at least to some extent is localised to
first order of magnitude spread of frequencies, yet the
configuration uphole of the drill string supporting assembly is
such that, by impedance, excitation, mass affects, or the like, a
greater spectral spread of the vibrational energy, and of
frequencies over several orders of magnitude, passes downhole
thereby to enable the extended reach drill string operations, and
operating the drill string with such a modified spectrum of
vibrational frequencies passing into it.
6. A drilling apparatus having a top hole hammering functionality
able, to support and/or provide vibration to a drill string that
extends downhole and to allow deep reach drilling activities
characterised in that a spectrum of different orders of magnitude
of vibrational frequency are or can be passed into the drill string
without reference to its length, from an impact generated spectrum
of lesser order of magnitude of vibrational frequency spread not,
of itself, able to allow the deep reach drilling activities.
7. A top hammer apparatus for usage in extended reach drilling
operations characterised in that an impact produced range of
vibrations in the range of from 0 to 100 Hz not sufficiently of an
energy to allow extended reach drilling operations is modified by
passive configurational features of the assembly to allow and/or
produce bands of vibrations in each of the ranges 0 to 100 Hz, 100
Hz to 1000 Hz and 1000 Hz to 10000 Hz.
8. Apparatus of claim 7 wherein the i length of the stress waves
are very short. for example the wave length=the speed of sound in
steel (5,000 metres per second) divided by the frequency, so the
wave length at 10,000 Hz=0.5 Meters, at 1,000 Hz=5 meters, at 100
Hz=50 Meters
9. Apparatus including a drill string and drill string dependent
tool where there is provision from within and/or without the drill
string to generate for and/or to the drill string, for and/or to
the tool, or both, a frequency or a range of frequencies to provide
multiple vibration(s).
10. Apparatus as claimed in any of claims 5 to 8 wherein said
apparatus includes a top hammer that is configured with impedances,
excitation features, masses or the like to provide said
frequencies.
11. Apparatus of claim 9 wherein the range or frequency can be
defined as going from a first to a Nth range.
12. The use of a first frequency or frequency range and at least a
second frequency or second frequency range in a drill string having
a drill bit.
13. The use of claim 12 wherein any number (N) of frequencies or
frequency ranges are used.
14. The use of claim 12 or 13 wherein some or several frequencies
are non-incident.
15. An oscillating (vibrational) apparatus that outputs at least
two vibrational frequencies and/or frequency ranges with first
frequency or frequencies in the kilohertz range e.g. (>1000 Hz)
and the second frequency or frequencies in the tens hertz range
e.g. (<100 Hz) for drilling through sub terrain.
16. Apparatus of claim 15 wherein frequencies within the following
ranges 0-100 Hz, 100-1000 Hz, 1000-10,000 Hz, etc are generated by
both incident frequencies of a strike and nonincident and/or
impeded frequencies resulting from the strike.
17. A multi-oscillating (vibrational) apparatus capable of being
tailored to drill through sub terrain reliant on specified or
discrete frequency or frequency ranges for specific purposes in the
drilling function.
18. An impact/vibrational assembly capable of impacting a drill bit
on a bore face, the assembly comprising or including a drill
string, a drill bit, and a drill head, that is capable of attaching
to the drill string, wherein each of the drill string, drill bit
and drill head each have a mass, or masses, that can be excited to
vibrate at functional frequencies.
19. An assembly of claim 18 wherein the drill head provides with a
striking directly some functional frequencies and said masses
responsive to the striking provides other functional frequencies to
which at least one of the drill string and drill bit responds with
an excitation.
Description
[0001] The present invention relates to extended reach
drilling.
[0002] The invention more particularly, but not solely, relates to
methods of extended reach drilling, with a drilling apparatus able
to effect extended reach drilling and operation of a downhole drill
string in extended reach drilling with the generation and transfer
of enabling or synergistic spread of vibration. Methods of
enhancing the reach of a drill string and downhole tooling using a
top hammer, the method comprising, without specifically tuning for
resonance, generating a spectrum where the output energy of the
hammering impacts at least to some extent is localised to first
order of magnitude spread of frequencies, yet the configuration
uphole of the drill string supporting assembly (the impacting or
vibrational device) is such that, by impedance, excitation, mass
affects, or the like, a greater spectral spread of the vibrational
energy, and of frequencies over several orders of magnitude, passes
downhole and/or in combination with some subsequent frequencies
being reflected back uphole thereby to enable the extended reach
drill string operations, and operating the drill string with such a
modified spectrum of vibrational frequencies passing into it.
[0003] Top hammer drilling has been used for many years within the
mining industry to rapidly advance drill bits into ground
formations.
[0004] These top hammers have traditionally been energised by
either pneumatic or hydraulic power. Such hammers are designed to
generate large impact shock waves with minimal mechanical impedance
between the impacting piston and the drive shaft (the connection
between the piston and the drill rods) via drill rods to a drill
bit and providing large amplitude of movement, giving very rapid
penetration through relatively short distances, as has been the
requirement for blast holes--typically up to 30 meters.
[0005] While this is an effective energy delivery mechanism, it
does not excite other non-impact frequencies that give rise to
other functions that aid in extended reach drilling, such as
fluidisation of the formation. In addition, these types of hammers
require the use of coarse "rope" type threads on the drill rods,
which in use, see a significant energy loss across the thread of
approximately 6% per drill thread, limiting the practical distance
that these types of drills can operate at to approximately <50
meters.
[0006] "Sonic" drill rigs, (which aim to "tune" the vibration input
to a specific resonant mode, and generally achieve the resonance by
rotating eccentric masses), are also depth limited (owing to the
substantial horsepower requirements and the practicalities of
mechanical devices operating at extremely high revolutions per
minute (RPM's) which are required with these devices when trying to
drill at second, third, or fourth resonant modes) to generally
around 100 meters.
[0007] Such difficulties can be avoided by the approach we propose
be used. Another advantage as well will be the very modest input
power requirements.
[0008] Either of the aforementioned is an, or another, object of
the invention.
[0009] The spread of vibrational frequencies proposed with the
present invention, has proven able to drill all formations, even
when large diameter drill bits/reamers (for example up to 250 mm in
diameter) are used. Moreover such--multiple mode resonant and/or
non resonant) drilling can achieve a distance of potentially
hundreds of meters, albeit at a slower rate and without excessively
large impact force, or large axial displacement in the drill string
or at the drill bit.
[0010] The present invention envisages using impact pulses and wide
spread bands of vibrations to advantage when drilling. The
invention also relates to the use downhole of a first frequency, or
a first frequency range (e.g. able to break rock with or without
resonance) and a distinct second frequency, or second frequency
range (e.g. to avoid formational grab on the drill string), to
excite, for different functionalities, the drill string and/or the
tool or bit.
[0011] Any number (N) of frequencies or frequency ranges can also
be used to advantage.
[0012] Whilst the advantages of choosing a resonant mode has been
recognised as advantageous when drilling with sinusoidal excitation
devices (rapidly rotating eccentric drives commonly used in so
called Sonic drill rigs) in underground formations, many drilling
applications occurs without reliance on solely exciting a single
resonance of the drill string.
[0013] We believe there is a considerable benefit to be derived in
including, by any suitable means, and most preferably passive
features or configurational features of a top hammer assembly,
means whereby vibrations of different frequency ranges can provide
a synergistic outcome where the resulting collective vibrations are
not tuned specifically to a single resonant frequency.
[0014] It is another object of the present invention, to derive for
the drill string and its tool or bit deliberate performance
enhancing mixed frequencies from a top hammer functionality.
[0015] In an aspect the invention is a method of extended reach
drilling which comprises
[0016] providing a top hammer assembly from which a drill string is
dependant, being configured by mass or cross section impedances
that create excitations to provide multiple localised bands of
frequencies that differ from and are not harmonics of the band or
bands of frequencies to be generated at the strike interface,
variation of frequencies sufficient to allow extended reach
drilling, and
[0017] operating the top hammer assembly during operation of the
drill string in an extended reach drilling operation, without
tuning the drillstring for resonance.
[0018] In an aspect the invention is a method of extended reach
drilling which comprises
[0019] providing a top hammer assembly from which a drill string is
dependant, the top hammer assembly, being configured by impedances
or masses to increase the spread of non-harmonic vibrational
frequencies to pass into and downhole along the drill string from
those generated at the impact interface of the top hammer
assembly,
[0020] the method comprising operating the top hammer assembly
during drill string dependant downhole operations at an input
power, without reference to drill string length for resonance
purposes.
[0021] In another aspect the invention is a method of enhancing the
reach of a drill string downhole using a top hole hammer
functionality, the method comprising, without tuning for
resonance,
[0022] generating a spectrum where the output energy of the
hammering impacts at least to some extent is localised to first
order of magnitude spread of frequencies, yet the configuration
uphole of the drill string supporting assembly is such that, by
impedance or mass effects, a greater spectral spread of the
vibrational energy, and of frequencies over several orders of
magnitude that are not harmonics of the first order of magnitude
spread of frequencies, passes downhole thereby to enable the
extended reach drill string operations, and
[0023] operating the drill string with such a modified spectrum of
vibrational frequencies passing into it.
[0024] In another aspect the invention is a drilling apparatus
having a top hammer functionality able to provide vibration to a
drill string that extends downhole and to allow deep reach drilling
activities characterised in that a spectrum of different orders of
magnitude of vibrational frequency is passed into the drill string
without reference to its length, from an impact generated spectrum
of lesser order of magnitude of vibrational frequency spread, the
impact generated spectrum not, of itself, able to allow the deep
reach drilling activities.
[0025] In another aspect the invention is a top hammer assembly
usage in extended reach drilling operations characterised in that
an impact produced range of vibrations in the range of from 0 to
100 Hz not sufficiently of an energy to allow extended reach
drilling operations is modified by mass or impedances of the
assembly to allow and/or produce bands of non-harmonic vibrations
(with respect to the impact vibrations) in each of the ranges 0 to
100 Hz, 100 Hz to 1000 Hz and 1000 Hz to 10000 Hz. It is this
frequency rich vibrational content that cause the down hole tools
(drill rods, drill bits, reamers etc) to become excited and vibrate
at multiple frequencies--but with (compared to conventional top
hammers) small displacement amplitudes that minimise frictional
damping in the drill string and therefore allows for efficient
energy transfer to the drill bit which collectively and
synergistically allow extended reach drilling operations.
[0026] Preferably the wavelength of the vibrations are very short
for example the wave length=the speed of sound in steel (5,000
metres per second) divided by the frequency, so the wave length at
10,000 Hz=0.5 Meters, at 1,000 Hz=5 meters, at 100 Hz=50 metres
[0027] Preferably the impulse length of the stress waves are very
short and synergistically allow extended reach drilling
operations.
[0028] Also describe is apparatus including a drill string and
drill string dependent tool where there is provision from within
and/or without the drill string to generate for and/or to the drill
string, for and/or to the tool, or both, a frequency or a range of
frequencies to provide multiple vibration(s).
[0029] The range or frequency could be defined as going from a
first to a Nth range.
[0030] Also described is the use of a first frequency or frequency
range and at least a second frequency or second frequency range in
a drill string having a drill bit.
[0031] Optionally any number (N) of frequencies or frequency ranges
can be used.
[0032] Whilst all frequencies can be generated (e.g. by an
oscillator) to be incident downhole some or several frequencies can
be non-incident (e.g. reflected).
[0033] And such reflected and/or incident frequencies may be caused
to vary by the nature of the overall apparatus.
[0034] Also described is an oscillating (vibrational)apparatus that
outputs at least two vibrational frequencies and/or frequency
ranges with first frequency or frequencies in the kilohertz range
e.g. (>1000 Hz) and the second frequency or frequencies in the
tens hertz range e.g. (<100 Hz) for drilling through sub
terrain.
[0035] Envisaged are frequencies within the following ranges 0-100
Hz, 100-1000 Hz, 1000-10,000 Hz, etc.
[0036] Also described is a multi-oscillating (vibrational)
apparatus capable of being tailored to drill through sub terrain
reliant on specified or discrete frequency or frequency ranges for
specific purposes in the drilling function.
[0037] Also described is an impact/vibrational assembly capable of
impacting a drill bit on a bore face, the assembly comprising or
including
[0038] a drill string,
[0039] a drill bit, and
[0040] a drill head, that is capable of attaching to the drill
string,
[0041] wherein each of the drill string, drill bit and drill head
each have a mass, or masses, that can be excited to vibrate at
functional frequencies.
[0042] Preferably the drill head provides with a striking directly
some functional frequencies and said masses responsive to the
striking provides other functional frequencies to which at least
one of the drill string and drill bit responds with an
excitation.
[0043] Optionally the excitation is by means of one or more
oscillator(s) whether in the drill string, in the drill head, in
the drill bit, or some hybrid of those choices.
[0044] The device may optionally or preferably have dampers that
negate non useful frequencies.
[0045] Preferably the primary vibrational frequencies are totally
or in part generated by, hydraulic, pneumatic, eccentric drive,
electromagnetic, electric, or mechanical top hammer
functionality.
[0046] In another aspect the invention is A top hammer for use
with/in drilling apparatus at an input frequency in extended reach
drilling operations configured with mass or impedances that limit
resonance(s) in the drilling apparatus at the input frequency by
creating multiple localised bands of frequencies that differ from
and are not harmonics of the band or bands of frequencies (beat
frequency) generated at a strike interface of the top hammer, the
variation of frequencies sufficient to allow extended reach
drilling.
[0047] As used herein "extended reach" contemplates drilling to
greater, and indeed very much greater than, say, 50 metres.
[0048] It is envisaged that the capabilities are to allow downhole
operations (drilling, reaming, etc) that extend for deeper than the
depths of 30 metres, 50 metres and 100 metres acknowledged as depth
limits for existing techniques.
[0049] As used herein the term "(s)" following a noun means one or
both of the singular or plural forms.
[0050] As used herein the term "and/or" means "and" or "or". In
some circumstances it can mean both.
[0051] This invention may also be said broadly to consist in the
parts, elements and features referred to or indicated in the
specification of the application, individually or collectively, and
any or all combinations of any two or more of said parts, elements
or features, and where specific integers are mentioned herein which
have known equivalents in the art to which this invention relates,
such known equivalents are deemed to be incorporated herein as if
individually set forth.
[0052] A preferred form of the present invention will now be
described with reference to the accompany drawings in which
[0053] FIG. 1 shows a conventional hydraulic/pneumatic top hammer
arrangement, the impact device being on the right and involving a
hammering shuttle (commensurate to its impact face in
cross-section) responsive to input pressure(s) and exhaust
actuation (shown diagrammatically) and subject to drill string
rotation apparatus to drive a downhole drill bit or other downhole
tool, these top hammers generating significant impact force of
(relatively) long duration which provides significant force and
large amplitudes of movement of the drill bit into the
formation--but with most of the impact energy in frequencies at or
near the beat frequency (the number of hammer impacts per second)
but without generating significant additional frequency rich
vibrational content of very short duration
[0054] FIG. 2 shows a typical impact graph resulting at the
interface from the hammering effect of an arrangement as in FIG.
1,
[0055] FIG. 3 shows a sonic drill arrangement, this time reliant on
eccentrics to generate substantially sinusoidal inputs, but again
showing a drill string rotational apparatus and a downhole drill
bit,
[0056] FIG. 4 shows a typical sinusoidal output of such an
eccentric driven vibrational arrangement for sonic drilling,
[0057] FIG. 5 is the conceptual arrangement of the present
invention showing an impact device to the right acting down a drill
string to a drill bit or other downhole tool (optionally via a
spring), the impact device being hereinafter described in more
detail by reference to an example,
[0058] FIG. 6 shows an extended reach hydraulic or pneumatic top
hammer arrangement as an example in accordance with the present
invention to be the impact device at the right of, for example, the
layout as in FIG. 5 or to operate without the spring arrangement
shown,
[0059] FIG. 7 shows a still further embodiment reliant on a
hydraulic or pneumatic top hammer arrangement,
[0060] FIGS. 5, 6, & 7 showing embodiments of an extended reach
Top hammer device, whereby the various masses, dimensional changes
and stiffnesses of the assembly encourage a broad band pulse of
vibrational energy to be transmitted to the dill string when
excited by a short duration impact ( 0.0005 s) of relatively low
energy (compared with a conventional Top hammer) whereby the high
frequency vibrations are believed to reduce frictional losses in
the drill string and the drill bit (or other tools) vibrate at a
multitude of frequencies and low-mid frequency vibrations excite
drill rod vibrational modes with very small amplitude of movement
(compared to a conventional Top hammer, and
[0061] FIG. 8 shows a typical spectral plotplot
(Amplitude/Frequency) of the response downhole resulting from an
impact when using an extended top reach hammer such as shown in
FIG. 5, 6, or 7
[0062] Within the drilling and construction industries, there is an
ongoing need to drill/ream or otherwise manipulate the ground
formation at higher speeds or with greater efficiency. Various
devices such as top hammers and down the hole hammers have been
used to good effect in these challenging environments, however our
testing has shown that in addition to using an impact device with
various masses and impedences which generate frequency rich
vibrations, this when used in association with specifically
designed ground engaging tools (drill rods, reamers, compactors,
drill bits etc) which are receptive to at least one vibrational
frequency (delivered via the drill rods), can give substantial
performance improvements. This concept is the basis for this
invention. The concept of downhole excitation is not new and
several methods have been used such as;
[0063] Hammer devices--these produce impulses to the ground
engaging tool--(but the tool is not designed to become excited by
these impulses) in a random manner but the ground engaging device
(drill bit/reamer etc) is not designed to become independently
excited
[0064] Resonance devices--(such as eccentric drive "sonic" devices)
strive to resonate the entire drill string--thus causing an axial
(hammering) movement back and forth of the drill bit.
[0065] As can be seen in FIG. 1 conventional hydraulic or pneumatic
top hammers strive to have a very similar cross section between the
piston and the impact face. This is required for optimum energy
transfer and amplitude of movement from the hammer to the drill
rods and ultimately the drill bit. (impedance matching).
[0066] Shown is an impact device 1 with a reciprocatable piston,
anvil or shuttle 2 as the hammer to strike at least one impact face
3 forming part of or connecting vibrationally to the drill string
of drill rods 4 down to the downhole tool 5. A rotational drive
apparatus 6 to rotate the drill string of rods 4 is provided.
[0067] To be noted is the close cross-sectional relationship of the
member 2 to the drill string of rods.
[0068] This design results in a very clean impact wave at
(substantially) the frequency of the strike of the piston(beat
frequency) with minimal loss of energy through the system and
maximum force and displacement at the rock face. See FIG. 2.
[0069] This arrangement drills hard rock very rapidly--although the
distance (or depth) capability is typically less than 50
meters.
[0070] The eccentric vibrational apparatus 8 of FIG. 3 generates
likewise into a drill string of rods 7 to a drill bit 9, the drill
string being rotatable by a drive 10.
[0071] The sonic drill system of FIG. 3 generates a smooth
sinusoidal force wave (as in FIG. 4) from the input of the rapidly
rotating eccentric masses.
[0072] For this system to be effective the drill rods themselves
are excited to resonance--thereby giving amplitude to the drill
bit. While this system is very effective in overburden and non
cohesive ground conditions the input speed of the eccentric drives
needs to be constantly adjusted to enable the ever changing drill
string length to be kept in resonance.
[0073] Apart from drivability issues the depth to which sonic drill
rigs can operate is ultimately dictated by the speed to which the
eccentrics can be rotated. It is also important to note that there
is a one to one relationship between the input frequency and the
drill rod/bit frequency (e.g. if 100 Hz is required to maintain
resonance in the drill string--then an input frequency of 100 Hz is
required).
[0074] Our device is quite different to these systems in that what
we propose allows the drill bit to become excited and therefore
oscillate INDEPENDENTLY and at higher frequencies than the drill
string.
[0075] We are aware of a system that endeavours to achieve similar
results--this being the Wiercigroch patent # US 2010/0319994 A1.
This device is a very complex apparatus that uses piezoelectric
transducers, in conjunction with complex algorithms and computer
control, to try and resonate a drill bit at a similar frequency to
the resonant frequency of the formation being drilled.
[0076] There has also been work done by Uitto Et al--U.S. Pat. No.
4,671,366 whereby they measure the stress wave and actively modify
the spectrum of the stress wave.
[0077] Keskiniva WO 2010/037905 A1 has a feed back device for
controlling reflected stress waves.
[0078] Keskiniva U.S. Pat. No. 7,891,437B2 looks to optimise impact
force and the length of the stress wave.
[0079] Watanabe U.S. Pat. No. 6,454,021 B1 uses a magnetostrictive
material with an electrical pulse and coil to alter the pulse
characteristics of the drilling machine.
[0080] None of the above art deliberately induces multiple
frequencies (in fact quite the converse) to enhance extended reach
drilling operations.
[0081] Our device by contrast is not a feed back driven device--nor
is it like a hammer drill, rod and bit or a sonic drill rod and
bit. Rather by having an understanding of the frequency(s)
generated by either a hammering device or resonant device--testing
has shown that it is possible to design the ground engaging tool as
a separate spring/mass system that itself becomes
excited--independently of any excitation or vibration happening
within the drill string--giving impressive productivity gains. See
the discussion below about FIG. 8.
[0082] FIG. 5 shows a system with an impact device 11 such as will
be described with respect to the present invention driving directly
or indirectly down a drill string of rods 12 to a drill bit or
other downhole tool 13. A spring 14 can be provided in the drill
string.
[0083] FIG. 6 shows a preferred embodiment. An impact device 15
interacts with a drill string 16 to a drill bit 17 or other
downhole tool. The drill string 16 is one with drill rods 18 and a
drive to rotate the drill string. This drive 19 can be positioned
appropriately.
[0084] Shown as part of the impact device 15 are primary and
secondary masses 20 and 21 respectively. Masses 20 and 21 are
movable relative to the surrounding structure 22 (e.g. by moving
one or the other of the shuttling anvil or its surround, or both).
As can be seen, at least for the mass 20, there is shown a pair of
opposed impact faces A and B to act alternately and respectively
with impact faces A and B of the surround structure 22.
[0085] With the input pressure (preferably being hydraulic or
pneumatic) and exhausting being provided, appropriate reciprocating
or shuttling of a known kind can be created.
[0086] It can be seen however that, transverse to the reciprocation
axis, the cross-sectional extent of the masses 20 and 22 is quite
significantly different from that of the drill string 16 and thus
will act as impedances.
[0087] The discussion below in respect to the response/spectrum
plot of FIG. 8 is achievable with an embodiment typified by FIG.
6.
[0088] The quite different embodiment of FIG. 7 shows another
alternative way (again with input pressures and exhaust pressures)
able to cause, as a piston, the member 23, as an anvil, to move
backwards and forwards in alignment with the drill string direction
so as to impact on impact face 24 and impact face 25. In this
arrangement an isolation spring 26 can be provided and there can be
input to turn the drill bit from zone 27.
[0089] It is to be noted also that there is the option of adding an
impedance in the way of a change in cross-sectional area of the
drill string by addition of a mass 28 which acts on the member 29
connected via drill rods 30 to the drill bit 31.
[0090] A similar output to that disclosed in the spectral plot of
FIG. 8 is achievable.
[0091] With regards to the extended reach hydraulic or pneumatic
top hammer, of which FIG. 6 is an example, it is clear that the
design is significantly different from both the conventional top
hammers or sonic drive systems.
[0092] We have found by contrast to the conventional system of FIG.
1, that by designing this system with significant changes in mass
and stiffnesses we get a significant reduction of force through the
hammer--(e.g. if the input strike force is 40 ton--the resulting
force being passed from the hammer to the drill rods may be only
approx. 15 ton).
[0093] However while the peak force is diminished through this
design--the initial impact frequency is broken into multiple
frequencies of varying magnitude as the impact wave travels
longitudinally through the hammer and causes the primary and
secondary masses (there may be more than two) connected by various
stiffnesses to vibrate over a wide band of distinct frequencies.
These distinct stress wave vibrations move down the drill string to
the drill bit.
[0094] It is speculated that the larger amplitude vibrations carry
out the majority of the rock breaking--while the higher frequency
vibrations also assist in localised rock fracture--but more
importantly cause fluidization of the formation being drilled and
minimise "frictional grab" (damping)on the drill rods.
[0095] The multiple frequencies generated by this arrangement can
clearly be seen in the response spectrum plot of FIG. 8--with
distinct frequencies in the 10's of Hz--100's of Hz and 1,000 Hz.
Each of these multiple frequencies are the result of a single input
strike--in reality the impact the impact (strike) rate of this
hammer is from 50 Hz to many hundreds of Hz. These high frequency
impacts are readily achievable if the hammer is set up to impact in
both directions (on both the A-A faces and the B-B impact
faces).
[0096] In practice this arrangement has allowed us to drill in
excess of 150 meters--allowing for true extended reach top hammer
drilling operations.
[0097] In our testing we have found that an appropriately designed
reaming tool and "supplied" with an impact frequency input of 50 Hz
is capable of itself vibrating in excess of 1,000 Hz. In fact, if
the desired excitation of the ground engaging device, is 1,000 Hz,
then the input vibration (from any suitable source) can be at any
sub harmonic frequency such as 500 Hz, or 250 Hz, or 125 Hz
etc.
[0098] As example of the present invention, with reference to FIG.
6 or 7, a hammer that provides an initial impact or hitting force
of 40 tonnes will provide an output force at the drill bit of
between 12-15 tonnes. Such a hammer will be operated at 50 Hz. The
reduction in peak force, being between 25-27 tonnes, is into the
creation of the multiple frequencies as shown in the spectral plot
of FIG. 8 or some other version with multiple localised bands of
frequencies, each with its own amplitude spread.
[0099] The data (spectral plot) of FIG. 8 shows how a reamer can be
excited to over 1,000 Hz. The input frequency from the top hammer
while only generating 50 Hz resulted in dramatically faster
penetration rates owing to the response.
[0100] FIGS. 6 and 7 suggest how a hydraulic or pneumatic top
hammer can achieve outcomes wanted. The piston or hammer is
propelled into the drive shaft by (probably) hydraulic or pneumatic
energy, or mechanical energy (e.g. rotating eccentric masses). By
adding/changing the position and/or number of masses of various
stiffness's and by altering the mass/stiffness of the piston the
spectral spread varies.
[0101] Ideally the top hammer assembly usage in the extended reach
drilling operations is characterised in that an impact produced
range of vibrations in the range of from 0 to 100 Hz, not
sufficiently of an energy to allow extended reach drilling
operations, is modified, by passive configurational features of the
assembly, to allow and/or produce bands of vibrations in each of
the ranges 0 to 100 Hz, 100 Hz to 1000 Hz and 1000Hz to 10000 Hz
which collectively and synergistically allow extended reach
drilling operations.
[0102] We believe there is an advantage in generating a profile of
multiple spectrum vibrational frequencies that, when combined,
together, provide numerous advantages over conventional
technologies including the following:
[0103] Ability to drill a hole with a greater diameter than
conventional methods allow.
[0104] Allowing easy penetration through loose overburden
formations (clay, sand, gravel etc) while at the same time having
enough penetration power to drill through hard competent rock
formations.
[0105] Ability to drill and recover quality core samples through
various formations (rock/clay etc)--whereby most conventional
systems have either not enough penetrative power to drill competent
rock--or so much impact energy that the desired rock sample is
reduced to dust.
[0106] Ability to drill deeper through a minimisation of friction
on the drill string which allows for extended reach operations
(e.g. oil tube drilling, or in long horizontal sections) which
conventional mechanisms are not able to achieve.
[0107] Can be used as a double acting hammer to generate higher
impact frequencies
[0108] Not necessary to tune the oscillating force and or the drill
string to vibrate/oscillate in a single resonant mode as with
"sonic" drilling.
[0109] Preferably the apparatus is able to deliver two (or more)
identifiable frequency bands via the drill string to the formation
that is being drilled. Such frequencies can be generated by a top
hammer apparatus that is made up of different components--wherein
each component has differing masses each connected by varying
stiffness elements and varying ratio dampers that results in the
apparatus having several differing natural frequencies. Each
natural frequency can be determined by the usual formulae for such
systems with appropriate changes made to the masses and stiffness
of the material of each component to alter the natural frequencies
generated.
[0110] While this system may not be as effective in drilling rapid
small diameter holes in hard rock over short distances (as with
conventional percussive drills)--the various frequencies and
impedances mean that using more aggressive threaded drill rod
connectors that are not "rope" style is practical--these different
threads are not prone to cyclic loosening and tightening.
[0111] The present invention is to generate multi frequencies that
allows drilling in various formations to long
distances--potentially hundreds of meters.
[0112] The specific vibrations work to minimise friction on the
drill string, and are sufficient to allow competent rock formations
to be penetrated.
[0113] In practice the frequencies could provide at least one
frequency in the kilohertz range (above one thousand Hz) and
another frequency operating in the tens of Hz range (e.g. 60 Hz).
Such frequencies are dependent on the masses of each individual
part making up the drilling assembly, where each part has its own
inherent natural frequencies such that the combination of
frequencies generated can enhance, cancel out, or maintain the
multitude of frequencies generated.
* * * * *