Note: Descriptions are shown in the official language in which they were submitted.
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PULSED ELECTRIC ROCK DRILLING, FRACTURING,
AND CRUSHING METHODS AND APPARATUS
BACKGROUND OF THE INVENTION
Technical Field:
The present invention relates to pulse powered drilling apparatuses and
methods.
The present invention also relates to insulating fluids of high relative
permittivity (dielectric
constant).
Background Art:
Processes using pulsed power technology are known in the art for breaking
mineral lumps. Fig. 1 shows a process by which a conduction path or streamer
is created
inside rock to break it. An electrical potential is impressed across the
electrodes which
contact the rock from the high voltage electrode 100 to the ground electrode
102. At
sufficiently high electric field, an
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arc 104 or plasma is formed inside the rock 106 from the high voltage
electrode to the low voltage
or ground electrode. The expansion of the hot gases created by the arc
fractures the rock. When
this streamer connects one electrode to the next, the current flows through
the conduction path, or
arc, inside the rock. The high temperature of the arc vaporizes the rock and
any water or other
fluids that might be touching, or are near, the arc. This vaporization process
creates high-
pressure gas in the arc zone, which expands. This expansion pressure fails the
rock in tension,
thus creating rock fragments.
The process of passing such a current through minerals is disclosed in U.S.
Patent No.
4,540,127 which describes a process for placing a lump of ore between
electrodes to break it into
monomineral grains. As noted in the '127 patent, it is advantageous in such
processes to use an
insulating liquid that has a high relative permittivity (dielectric constant)
to shift the electric fields
away from the liquid and into the rock in the region of the electrodes.
The '127 patent discusses using water as the fluid for the mineral
disintegration process.
However, insulating drilling fluid must provide high dielectric strength to
provide high electric fields
at the electrodes, low conductivity to provide low leakage current during the
delay time from
application of the voltage until the arc ignites in the rock, and high
relative permittivity to shift a
higher proportion of the electric field into the rock near the electrodes.
Water provides high
relative permittivity, but has high conductivity, creating high electric
charge losses. Therefore,
water has excellent energy storage properties, but requires extensive
deionization to make it
sufficiently resistive so that it does not discharge the high voltage
components by current leakage
through the liquid. In the deionized condition, water is very corrosive and
will dissolve many
materials, including metals. As a result, water must be continually
conditioned to maintain the
high resistivity required for high voltage applications. Even when deionized,
water still has such
sufficient conductivity that it is not suitable for long-duration, pulsed
power applications.
Petroleum oil, on the other hand, provides high dielectric strength and low
conductivity, but
does not provide high relative permittivity. Neither water nor petroleum oil,
therefore, provide all
the features necessary for effective drilling.
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Propylene carbonate is another example of such insulating materials in that it
has a high
dielectric constant and moderate dielectric strength, but also has high
conductivity (about twice
that of deionized water) making it unsuitable for pulsed power applications.
In addition to the high voltage, mineral breaking applications discussed
above, Insulating
fluids are used for many electrical applications such as, for example, to
insulate electrical power
transformers.
There is a need for an insulating fluid having a high dielectric constant, low
conductivity,
high dielectric strength, and a long life under industrial or military
application environments.
Other techniques are known for fracturing rock. Systems known in the art as
"boulder
breakers" rely upon a capacitor bank connected by a cable to an electrode or
transducer that is
inserted into a rock hole. Such systems are described by Hamelin, M. and
Kitzinger, F., Hard
Rock Fragmentation with Pulsed Power, presented at the 1993 Pulsed Power
Conference, and
Res, J. and Chattapadhyay, A, "Disintegration of Hard Rocks by the
Electrohydrodynamic Method"
Mining Engineering, January 1987. These systems are for fracturing boulders
resulting from the
mining process or for construction without having to use explosives.
Explosives create hazards
for both equipment and personnel because of fly rock and over pressure on the
equipment,
especially in underground mining. Because the energy storage in these systems
are located
remotely from the boulder, efficiency is compromised. Therefore, there is a
need for improving
efficiency in the boulder breaking and drilling processes.
Another technique for fracturing rock is the plasma-hydraulic (PH), or
electrohydraulic (EH)
techniques using pulsed power technology to create underwater plasma, which
creates intense
shock waves in water to crush rock and provide a drilling action. In practice,
an electrical plasma
is created in water by passing a pulse of electricity at high peak power
through the water. The
rapidly expanding plasma in the water creates a shock wave sufficiently
powerful to crush the
rock. In such a process, rock is fractured by repetitive application of the
shock wave.
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DISCLOSURE OF INVENTION
According to one aspect of the invention, there is provided a pulsed power
drilling
apparatus for passing a pulsed electrical current through a substrate, the
apparatus
comprising: a drill bit; at least one set of at least two electrodes disposed
on said drill bit
defining therebetween at least one electrode gap, said electrodes of each said
set
oriented substantially along a face of said drill bit to pass current through
the substrate;
a high-voltage pulsed power generator linked to said drill bit, delivering a
pulsed current
between said electrodes and through the substrate; an electrical power source
powering
said pulsed power generator; an electrical conduction conduit sending high-
voltage pulses
from said high-voltage pulse generator to said drill bit; and an insulating
drilling fluid
having a dielectric strength of at least 300 kV/cm (1 psec).
At least one of the electrodes is optionally compressible toward the drill
bit. The
apparatus optionally comprises a plurality of mechanical teeth disposed on the
bit. The
apparatus optionally comprises an insulating drilling fluid having an
electrical conductivity
less than approximately 10-5 mho/cm and a dielectric constant greater than
approximately
6. The insulating drilling fluid optionally comprises treated water having a
conductivity less
than approximately 10-4 mho/cm and a dielectric constant greater than
approximately 6.
The insulating fluid optionally comprises at least one oil. The insulating
fluid optionally
comprises a dielectric strength of at least approximately 300 kV/cm (1 psec),
a dielectric
constant of at least approximately 15, and a conductivity of less than
approximately 10-5
mho/cm.
At least one of the electrode sets is optionally arranged on the bit in a
configuration
that is asymmetric relative to the axis of rotational symmetry of the bit,
optionally arranged
on the bit in a configuration that is symmetric relative to the axis of
rotational symmetry of
the bit, and optionally arranged on the bit in a configuration that is
asymmetric relative to
the axis of rotational symmetry of the bit and wherein at least another one of
the electrode
sets is arranged on the bit in a configuration that is symmetric relative to
the axis of
rotational symmetry of the bit.
The electrodes are optionally radiused on a side where the electrodes contact
the
substrate. The bit is optionally substantially conical in shape. The conical
bit optionally
comprises conical sides comprising two angles. The bit optionally comprises a
geometric
shape selected from the group consisting of a substantially conical shape, a
substantially
conical and truncated
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shape, a substantially cylindrical shape, a substantially elliptical
paraboloid, and a combination
thereof. The bit optionally comprises a plurality of geometric shapes
including, but not limited to, a
substantially conical shape, a substantially conical and truncated shape, a
substantially cylindrical
shape, a substantially elliptical paraboloid, a substantially planar shape, or
a combination thereof.
The apparatus further optionally comprises a rotary drill reamer disposed on a
drill string
on which the drill bit is disposed so that the rotary drill reamer and the
drill bit operate in
conjunction on same drill string. The reamer optionally comprises a reamer
such as, but not
limited to, a drag bit, a tapered drag bit, a rotary bit, or a combination
thereof.
In the apparatus, at least one set of electrodes is optionally disposed at a
longitudinal
center of the bit and the same, or another set, optionally disposed off-center
of rotation of the bit.
The apparatus further optionally comprises an electrical conduction conduit to
send high
voltage pulses to the drill bit from the high voltage pulse generator. The
conduit optionally
comprises a cable.
In the apparatus, a high voltage pulse generator is optionally disposed on the
surface of
the ground and further comprising an electrical conduction conduit linking the
generator and the
drill bit to send high voltage pulses from the generator to the drill bit.
The apparatus further optionally comprises a pulsed power system disposed on
or near
the drill bit for conditioning electrical current received by the drill bit.
The pulse power generator optionally comprises a capacitor bank comprising a
switch
such as, but not limited to, a spark gap, a thyratron, a vacuum gap, a pseudo-
spark switch, a
mechanical switch, solid state switch, or a combination thereof.
The pulse power source optionally comprises a source such as, but not limited
to, a
rotating electromagnetic power generator located on the surface of the ground,
a rotating
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electromagnetic power generator located downhole, a utility power grid located
on the
surface, a piezoelectric power generator located downhole, a fuel cell
electric power
generator located at the surface of the ground, or a fuel cell electric power
generator
located downhole.
The apparatus further optionally comprises a cable or electrical conduction
means
to send electrical power from a power source to the high voltage pulse
generator.
Optionally, the high voltage pulse generator delivers high voltage pulses of
at least
approximately 100 kV.
The apparatus further optionally comprises passages disposed in the bit in
which a
flow of fluid is disposed for flushing debris.
According to a further aspect of the invention, there is provided a pulsed
power
drilling apparatus for passing a pulsed electrical current through a
substrate, the
apparatus comprising: a drill bit; at least one set of at least two electrodes
disposed on
said drill bit defining therebetween at least one electrode gap, said
electrodes of each
said set oriented substantially along a face of said drill bit to pass current
through the
substrate; a high-voltage pulsed power generator linked to said drill bit,
delivering a
pulsed current between said electrodes and through the substrate; an
electrical power
source powering said pulsed power generator; and an electrical conduction
conduit
sending high-voltage pulses from said high-voltage pulse generator to said
drill bit,
wherein at least one of a first of said electrode sets is arranged on said bit
in a
configuration that is asymmetric relative to an axis of rotational symmetry of
said bit and
at least one of a second of said electrode sets is arranged on said bit in a
configuration
that is symmetric relative to an axis of rotational symmetry of said bit.
The insulating fluid optionally has a conductivity of less than approximately
i0
mho/cm, optionally comprises treated water having a conductivity less than
approximately
10-4 mho/cm, and optionally comprises at least one oil. 34. The insulating
fluid optionally
comprises a dielectric strength of at least approximately 300 kV/cm (1 psec),
a dielectric
constant of at least approximately 6, and a conductivity of less than
approximately 10-5
mho/cm.
The apparatus optionally comprises a plurality of mechanical teeth disposed on
the
bit.
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The apparatus optionally comprises at least one of the electrodes that are
depressible or
compressible toward the drill bit. The electrode sets are optionally arranged
on the bit in a
configuration that is asymmetric relative to the axis of rotational symmetry
of the bit, optionally
arranged on the bit in a configuration that is symmetric relative to the axis
of rotational symmetry
of the bit, and optionally arranged on the bit in a configuration that is
asymmetric relative to the
axis of rotational symmetry of the bit and wherein at least one other of the
electrode sets is
arranged on the bit in a configuration that is symmetric relative to the axis
of rotational symmetry
of the bit. The electrodes are optionally radiused on a side where the
electrodes contact the
substrate.
The bit optionally comprises a geometric shape such as, but not limited to, a
substantially
conical shape, a substantially conical and truncated shape, a substantially
cylindrical shape, a
substantially elliptical paraboloid, or a combination thereof. The bit
optionally comprises a plurality
of geometric shapes such as, but not limited to a substantially conical shape,
a substantially
conical and truncated shape, a substantially cylindrical shape, a
substantially elliptical paraboloid,
a substantially planar shape, or a combination thereof.
The apparatus optionally comprises a rotary drill reamer disposed on a drill
string on which
the drill bit is disposed so that the rotary drill reamer and the drill bit
operate in conjunction on
same drill string, and the reamer optionally comprises a reamer such as, but
not limited to, a drag
bit, a tapered drag bit, a rotary bit, or a combination thereof.
At least one set of electrodes is optionally disposed at a longitudinal center
of the bit, and
optionally disposed off-center of rotation of the bit, or if more than one
set, in disposed in a
combination of the center of off-center.
The apparatus optionally comprises an electrical conduction conduit to send
high voltage
pulses to the drill bit from the high voltage pulse generator, and the conduit
optionally comprises a
cable.
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The high voltage pulse generator is optionally disposed on the surface of the
ground
and further comprising an electrical conduction conduit linking the generator
and the drill
bit to send high voltage pulses from the generator to the drill bit. The
apparatus further
optionally comprises a pulsed power system disposed on or near the drill bit
for
conditioning electrical current received by the drill bit.
The pulse power generator optionally comprises a capacitor bank comprising at
least one switch such as, but not limited to, a spark gap, a thyratron, a
vacuum gap, a
pseudo-spark switch, a mechanical switch, solid state switch, or a combination
thereof.
The pulse power source optionally comprises a rotating electromagnetic power
generator located on the surface of the ground, a rotating electromagnetic
power
generator located downhole, a utility power grid located on the surface, a
piezoelectric
power generator located downhole, a fuel cell electric power generator located
at the
surface of the ground, or a fuel cell electric power generator located
downhole.
The apparatus optionally comprises a cable or electrical conduction means to
send
electrical power from a power source to the high voltage pulse generator.
Optionally, the
high voltage pulse generator delivers high voltage pulses of at least
approximately 100
kV.
The apparatus optionally further comprises passages disposed in the bit and in
which a flow of fluid is disposed for flushing debris.
According to a further aspect of the invention, there is provided a pulsed
power
drilling apparatus for passing a pulsed electrical current through a
substrate, the
apparatus comprising: a drill bit; at least one set of at least two electrodes
disposed on
said drill bit defining therebetween at least one electrode gap, said
electrodes of each
said set oriented substantially along a face of said drill bit to pass current
through the
substrate; a high-voltage pulsed power generator linked to said drill bit,
delivering a
pulsed current between said electrodes and through the substrate; an
electrical power
source powering said pulsed power generator; an electrical conduction conduit
sending
high-voltage pulses from said high-voltage pulse generator to said drill bit;
and a control
system that varies or changes either or both a pulse repetition rate and a
pulse energy on
at least one asymmetric electrode as a function of azimuthal angle as it
rotates to change
a direction of drilling.
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According to yet a further aspect of the invention, there is provided a pulsed
power
drilling apparatus for passing a pulsed electrical current through a
substrate, the
apparatus comprising: a drill bit; at least one set of at least two electrodes
disposed on
said drill bit defining therebetween at least one electrode gap, said
electrodes of each
said set oriented substantially along a face of said drill bit to pass current
through the
substrate; a high-voltage pulsed power generator linked to said drill bit,
delivering a
pulsed current between said electrodes and through the substrate; an
electrical power
source powering said pulsed power generator; an electrical conduction conduit
sending
high-voltage pulses from said high-voltage pulse generator to said drill bit;
and a control
system that varies or changes either or both a pulse repetition rate and a
pulse energy
among separate sets of electrodes to change a direction of drilling.
According to still yet a further aspect of the invention, there is provided a
pulsed
power drilling apparatus for passing a pulsed electrical current through a
substrate, the
apparatus comprising: a drill bit; at least one set of at least two electrodes
disposed on
said drill bit defining therebetween at least one electrode gap, said
electrodes of each
said set oriented substantially along a face of said drill bit to pass current
through the
substrate; a high-voltage pulsed power generator linked to said drill bit,
delivering a
pulsed current between said electrodes and through the substrate; an
electrical power
source powering said pulsed power generator; an electrical conduction conduit
sending
high-voltage pulses from said high-voltage pulse generator to said drill bit;
and a plurality
of electrode sets arranged in an array.
According to still yet a further aspect of the invention, there is provided a
method for
pulsed power drilling and passing a pulsed electrical current through a
substrate, the
method comprising: drilling with a drill bit; disposing at least one set of at
least two
electrodes on the drill bit, defining therebetween at least one electrode gap,
orienting
electrodes of each set substantially along a face of the drill bit, and
passing current
through the substrate; generating a high-voltage pulse by linking a power
generator to the
drill bit, and delivering a pulsed current between the electrodes and through
the substrate;
powering the pulsed power generator with an electrical power source; sending
high-
voltage pulses from the high-voltage pulse generator to the drill bit via an
electrical
conduction conduit; and insulating with an insulating drilling fluid having a
dielectric
strength of at least approximately 300 kV/cm (1 psec).
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Another embodiment of the present invention provides a method for breaking and
drilling a mineral substrate comprising providing a drill bit, disposing at
least one set of
electrodes on the drill bit, rotating the drill bit, and delivering a pulsed
power current
between the electrodes and through the substrate to break the substrate, at
least one set
of at least two electrodes disposed on the drill bit defining there between at
least one
electrode gap, orienting the electrodes of each the set substantially along a
face of the
drill bit, disposing at least one of the electrodes so that it touches the
substrate and
another of the electrodes is disposed so that it functions in close proximity
to the substrate
for current to pass through the substrate.
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The method optionally further comprises disposing a drilling fluid about the
substrate to be
drilled. The method optionally further comprises depressing at least one of
the electrodes into the
drill bit during operation. The method optionally further comprises disposing
a plurality of
mechanical teeth on the bit.
The insulating drilling fluid optionally has an electrical conductivity less
than approximately
le mho/cm and a dielectric constant greater than approximately 6, optionally
comprises treated
water having a conductivity less than approximately le mho/cm and a dielectric
constant greater
than approximately 6, and optionally comprises at least one oil. The
insulating fluid optionally
comprises a dielectric strength of at least approximately 300 kV/cm (lpsec), a
dielectric constant
of at least approximately 15, and a conductivity of less than approximately 1e
mho/cm.
The method of further optionally comprises arranging at least one of the
electrode sets on
the bit in a configuration that is asymmetric relative to the axis of
rotational symmetry of the bit.
The method optionally comprises arranging at least one of the electrode sets
on the bit in a
configuration that is symmetric relative to the axis of rotational symmetry of
the bit. The method
optionally further comprises arranging at least one of the electrode sets on
the bit in a
configuration that is asymmetric relative to the axis of rotational symmetry
of the bit and further
arranging at least one of the electrode sets on the bit in a configuration
that is symmetric relative
to the axis of rotational symmetry of the bit.
In the method, the electrodes are optionally radiused on a side where the
electrodes
contact the substrate. The bit optionally is substantially conical in shape.
The conical bit
optionally comprises conical sides comprising two angles. The bit optionally
comprises a
geometric shape such as, but not limited to, a substantially conical shape, a
substantially conical
and truncated shape, a substantially cylindrical shape, or a substantially
elliptical paraboloid, or a
combination thereof, and optionally comprises a plurality of geometric shapes
such as, but not
limited to, a substantially conical shape, a substantially conical and
truncated shape, a
substantially cylindrical shape, a substantially elliptical paraboloid, a
substantially planar shape, or
a combination thereof.
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The method further optionally comprises disposing a rotary drill reamer and
the drill bit on
a common drill string and operating the rotary drill reamer and the drill bit
in conjunction, and the
reamer optionally comprises, but is not limited to, a drag bit, a tapered drag
bit, a rotary bit, or a
combination thereof.
The method optionally comprises disposing at least one of the set of
electrodes at a
longitudinal center of the bit or optionally off-center of rotation of the
bit, or in a combination
thereof.
The method further comprising providing an electrical conduction conduit and
sending high
voltage pulses from the high voltage pulse generator to the drill bit, and the
conduit optionally
comprises a cable.
The method optionally comprises disposing the high voltage pulse generator on
the
surface of the ground and further comprising providing an electrical
conduction conduit to link the
generator and the drill bit and sending high voltage pulses from the generator
to the drill bit. The
method optionally further comprises disposing a pulsed power system on or near
the drill bit for
conditioning electrical current received by the drill bit. In the method, the
pulse power generator
optionally comprises a capacitor bank comprising at least one switch such as,
but not limited to, a
spark gap, a thyratron, a vacuum gap, a pseudo-spark switch, a mechanical
switch, solid state
switch, or a combination thereof. The pulse power source optionally comprises
a rotating
electromagnetic power generator located on the surface of the ground, a
rotating electromagnetic
power generator located downhole, a utility power grid located on the surface,
a piezoelectric
power generator located downhole, a fuel cell electric power generator located
at the surface of
the ground, or a fuel cell electric power generator located downhole.
The method optionally comprises providing a cable or electrical conduction
means and
sending electrical power from a power source to the high voltage pulse
generator via the cable or
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electrical conduction means. The method optionally comprises delivering high
voltage
pulses of at least approximately 100 kV from the high voltage pulse generator.
The method optionally comprises disposing passages in the bit and sending a
flow
of fluid through the passages for flushing debris.
According to a further aspect of the invention, there is provided a method for
pulsed
power drilling and passing a pulsed electrical current through a substrate,
the method
comprising: drilling with a drill bit; disposing at least one set of at least
two electrodes on
the drill bit, defining therebetween at least one electrode gap, orienting
electrodes of each
set substantially along a face of the drill bit, and passing current through
the substrate;
generating a high-voltage pulse by linking a power generator to the drill bit,
and delivering
a pulsed current between the electrodes and through the substrate;
powering the pulsed power generator with an electrical power source; sending
high-
voltage pulses from the high-voltage pulse generator to the drill bit via an
electrical
conduction conduit; and arranging at least one of a first of the electrode
sets is arranged
on the bit in a configuration that is asymmetric relative to an axis of
rotational symmetry of
the bit and at least one of a second of the electrode sets on the bit in a
configuration that
is symmetric relative to an axis of rotational symmetry of the bit.
The method further optionally comprises depressing or compressing at least one
of
the electrodes into the drill bit during drilling. The method optionally
comprises arranging
at least one of the electrode sets on the bit in a configuration that is
asymmetric relative to
the axis of rotational symmetry of the bit, optionally comprises arranging at
least one of
the electrode sets on the bit in a configuration that is symmetric relative to
the axis of
rotational symmetry of the bit, and optionally comprises arranging at least
one of the
electrode sets on the bit in a configuration that
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is asymmetric relative to the axis of rotational symmetry of the bit and
arranging at least one of the
other electrode sets on the bit in a configuration that is symmetric relative
to the axis of rotational
symmetry of the bit, or in a combination thereof.
The method optionally comprises providing electrodes that are radiused on a
side where
the electrodes contact the substrate.
In the method, the bit optionally comprises a geometric shape such as, but not
limited to, a
substantially conical shape, a substantially conical and truncated shape, a
substantially cylindrical
shape, a substantially elliptical paraboloid, or a combination thereof. The
bit optionally comprises
a plurality of geometric shapes such as, but not limited to, a substantially
conical shape, a
substantially conical and truncated shape, a substantially cylindrical shape,
a substantially elliptical
paraboloid, a substantially planar shape, or a combination thereof.
The method optionally comprises disposing a rotary drill reamer and the drill
bit on a
common drill string and operating the rotary drill reamer and the drill bit in
conjunction, and the
reamer optionally comprises, but is not limited to, a drag bit, a tapered drag
bit, a rotary bit, or a
combination thereof.
The method optionally comprises disposing at least one set of electrodes at a
longitudinal
center of the bit, and optionally comprises disposing at least one set of
electrodes off-center of
rotation of the bit, and optionally comprises disposing the electrodes in a
combination of the
orientations.
The method optionally comprises providing an electrical conduction conduit and
sending
high voltage pulses from the high voltage pulse generator to the drill bit via
the conduit, and the
conduit optionally comprises a cable.
The method optionally comprises disposing the high voltage pulse generator on
the
surface of the ground and further comprising providing an electrical
conduction conduit, linking
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the generator and the drill bit via the conduit, and sending high voltage
pulses from the
generator to the drill bit via the conduit. The method optionally comprises
disposing a
pulsed power system on or near the drill bit for conditioning electrical
current received by
the drill bit. The pulse power generator optionally comprises a capacitor bank
comprising
at least one switch such as, but not limited to, a spark gap, a thyratron, a
vacuum gap, a
pseudo-spark switch, a mechanical switch, solid state switch, or a combination
thereof.
The pulse power source comprises a source such as, but not limited to, a
rotating
electromagnetic power generator located on the surface of the ground, a
rotating
electromagnetic power generator located downhole, a utility power grid located
on the
surface, a piezoelectric power generator located downhole, a fuel cell
electric power
generator located at the surface of the ground, or a fuel cell electric power
generator
located downhole.
The method optionally comprises providing a cable or electrical conduction
means
and sending electrical power from a power source to the high voltage pulse
generator via
the cable or electrical conduction means. The method optionally comprises
delivering high
voltage pulses of at least approximately 100 kV from the high voltage pulse
generator.
The method optionally comprises disposing passages in the bit and providing a
flow
of fluid in the passages for flushing debris.
According to still yet a further aspect of the invention, there is provided a
method for
pulsed power drilling and passing a pulsed electrical current through a
substrate, the
method comprising: drilling with a drill bit; disposing at least one set of at
least two
electrodes on the drill bit, defining therebetween at least one electrode gap,
orienting
electrodes of each set substantially along a face of the drill bit, and
passing current
through the substrate; generating a high-voltage pulse by linking a power
generator to the
drill bit, and delivering a pulsed current between the electrodes and through
the substrate;
powering the pulsed power generator with an electrical power source; sending
high-
voltage pulses from the high-voltage pulse generator to the drill bit via an
electrical
conduction conduit; and varying or changing both a pulse repetition rate and a
pulse
energy on at least one asymmetric electrode as a function of azimuthal angle
as it rotates
to change a direction of drilling.
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According to a further aspect of the invention there is provided a method for
pulsed
power drilling and passing a pulsed electrical current through a substrate,
the method
comprising: drilling with a drill bit; disposing at least one set of at least
two electrodes on
the drill bit, defining therebetween at least one electrode gap, orienting
electrodes of each
set substantially along a face of the drill bit, and passing current through
the substrate;
generating a high-voltage pulse by linking a power generator to the drill bit,
and delivering
a pulsed current between the electrodes and through the substrate; powering
the pulsed
power generator with an electrical power source; sending high-voltage pulses
from the
high-voltage pulse generator to the drill bit via an electrical conduction
conduit; and
varying or changing both a pulse repetition rate and a pulse energy among
separate sets
of electrodes to change a direction of drilling.
According to a further aspect of the invention there is provided a method for
pulsed
power drilling and passing a pulsed electrical current through a substrate,
the method
comprising: drilling with a drill bit; disposing at least one set of at least
two electrodes on
the drill bit, defining therebetween at least one electrode gap, orienting
electrodes of each
set substantially along a face of the drill bit, and passing current through
the substrate;
generating a high-voltage pulse by linking a power generator to the drill bit,
and delivering
a pulsed current between the electrodes and through the substrate; powering
the pulsed
power generator with an electrical power source; sending high-voltage pulses
from the
high-voltage pulse generator to the drill bit via an electrical conduction
conduit; and
arranging a plurality of drill bits in an array.
Another embodiment of the present invention provides an electrical insulating
formulation comprising a first, carbon-based material having a dielectric
constant greater
than approximately 2.6, second, carbon-based material, different from the
first material,
having a dielectric constant greater than approximately 10.0, the first
material at least
partially miscible with the second material and the insulating formulation
having low
electrical conductivity.
The first material and the second material are preferably substantially non-
aqueous.
The first material optionally comprises one or more oils, optionally comprises
one or
more natural or synthetic oils, optionally comprises castor oil, optionally
comprises jojoba
oil, and optionally comprises mineral oil
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The second material optionally comprises one or more solvents, optionally
comprises one
or more carbonates, optionally comprises one or more alkylene carbonates, and
optionally
comprises butylene carbonate.
In the formulation, the first material optionally comprises a solution
comprising one or more
oils and the first material is in a concentration of from between
approximately 1.0 and 99.0
percent by volume and wherein the second material comprises a solution
comprising one or more
alkylene carbonates and the second material is in a concentration of from
between approximately
1.0 and 99.0 percent by volume.
In the formulation, the first material optionally comprises a solution
comprising one or more
oils and the first material is in a concentration of from between
approximately 40.0 and 95.0
percent by volume and wherein the second material comprises a solution
comprising one or more
alkylene carbonates and the second material is in a concentration of from
between approximately
5.0 and 60.0 percent by volume.
In the formulation, the first material optionally comprises a solution
comprising one or more
oils and the first material is in a concentration of from between
approximately 65.0 and 90.0
percent by volume and wherein the second material comprises a solution
comprising one or more
alkylene carbonates and the second material is in a concentration of from
between approximately
10.0 and 35.0 percent by volume.
In the formulation, the first material optionally comprises a solution
comprising one or more
oils and the first material is in a concentration of from between
approximately 75.0 and 85.0
percent by volume and wherein the second material comprises a solution
comprising one or more
alkylene carbonates and the second material is in a concentration of from
between approximately
15.0 and 25.0 percent by volume.
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The first material and the second material are preferably biodegradable,
preferably, non-
toxic and preferably not hazardous to the environment.
Another embodiment of the present invention provides a method for drilling in
hard
materials comprising providing a first material having a dielectric constant
of greater than
approximately 2.6, mixing the first material with a second material having a
dielectric constant
greater than approximately 10.0 to provide an insulating formulation
comprising a low electrical
conductivity, and disposing the formulation about a drilling environment to
provide electrical
insulation for a drilling process. The first material and the second material
are preferably
substantially non-aqueous.
The first material optionally comprises one or more oils, optionally comprises
one or more
natural or synthetic oils, optionally comprises castor oil, optionally
comprises jojoba oil, and
optionally comprises mineral oil. The second material optionally comprises one
or more solvents,
optionally comprises one or more carbonates, optionally comprises one or more
alkylene
carbonates, and optionally comprises butylene carbonate.
The first material optionally comprises a solution comprising one or more oils
and the first
material is in a concentration of from between approximately 1.0 and 99.0
percent by volume and
wherein the second material comprises a solution comprising one or more
alkylene carbonates
and the second material is in a concentration of from between approximately
1.0 and 99.0 percent
by volume.
The first material optionally comprises a solution comprising one or more oils
and the first
material is in a concentration of from between approximately 40.0 and 95.0
percent by volume
and wherein the second material comprises a solution comprising one or more
alkylene
carbonates and the second material is in a concentration of from between
approximately 5.0 and
60.0 percent by volume.
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The formulation, the first material optionally comprises a solution comprising
one or more
oils and the first material is in a concentration of from between
approximately 65.0 and 90.0
percent by volume and wherein the second material comprises a solution
comprising one or more
alkylene carbonates and the second material is in a concentration of from
between approximately
10.0 and 35.0 percent by volume.
The formulation, the first material optionally comprises a solution comprising
one or more
oils and the first material is in a concentration of from between
approximately 75.0 and 85.0
percent by volume and wherein the second material comprises a solution
comprising one or more
alkylene carbonates and the second material is in a concentration of from
between approximately
15.0 and 25.0 percent by volume.
The first material and the second material are preferably biodegradable,
preferably, non-
toxic and preferably not hazardous to the environment.
Another embodiment of the present invention provides an electrical insulating
formulation
comprising, castor oil, butylene carbonate. a dielectric strength of at least
approximately 300
kV/cm (lpsec), a dielectric constant of at least approximately 6, and a
conductivity of less than
approximately le mho/cm. The formulation optionally comprises a conductivity
of less than
approximately 10-6 mho/cm.
Another embodiment of the present invention provides an assembly for creating
a
pressure pulse in a liquid-filled cavity within a fracturable material, the
assembly comprising, a
transducer, an integral energy storage component disposed in the transducer, a
cable connected
to the transducer storage component for delivery of electric current, and a
plurality of electrodes in
the transducer for converting the electrical current into a plasma pressure
source.
The assembly optionally further comprising a switch disposed in the transducer
to connect
the energy storage component to the electrodes. The assembly optionally
further comprises a
high voltage capacitor bank to provide a high voltage pulse to the transducer
via the cable. The
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capacitor bank optionally comprises a switch such as, but not limited to, a
spark gap, a thyratron,
a vacuum gap, a pseudo-spark switch, a mechanical switch, a solid state
switch, or a combination
thereof. The assembly optionally further comprises an inductive storage
component to provide a
high voltage pulse to the transducer via the cable.
The energy storage component optionally comprises a capacitor bank, and
optionally
comprises an inductive energy storage unit.
Another embodiment of the present invention provides an assembly for creating
pressure
waves in a liquid to fracture material, the assembly comprising a transducer,
and one or more
pairs of electrodes disposed on the transducer, the electrodes defining a gap
therebetween
through which an electrical current passes to create pressure through
expansion of liquid as it
undergoes a phase change to gas or plasma.
More than one set of electrodes is optionally arranged in parallel, and
optionally arranged
in a line or series of straight lines. The electrode sets are optionally
arranged in a geometric
configuration, and the configuration may comprise a configuration such as, but
not limited to, a
straight line, a curve, a circle, a spiral, or a combination thereof.
The electrode sets are optionally disposed in the transducer so that the
electrodes provide
capacitance between each intermediate electrode and the ground structure of
the transducer.
The capacitance is optionally formed via a liquid disposed between the
intermediate electrode and
the ground structure. The capacitance is optionally formed via a capacitor
disposed between the
intermediate electrode and the ground structure.
The capacitor optionally comprises a solid or liquid dielectric material. The
assembly
optionally comprises a liquid or capacitor between the electrodes to form the
capacitance. The
assembly optionally comprises an integral energy storage module to supply
electrical energy to a
multi-gap transducer. The assembly optionally further comprises an energy
storage device
located away from the fracturable material and area wherein the fracturable
material is disposed,
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and a cable to connect the integral energy storage module to the energy
storage device.
Another embodiment of the present invention comprises a method for breaking
mineral
particles comprising suspending the particles in a liquid disposed in a
container, the liquid
comprising a dielectric constant higher than the particles, disposing a
plurality of electrodes in the
liquid, sending an electric voltage pulse to the electrodes wherein the pulse
is tuned to electrical
characteristics of the container and liquid to provide a rise of voltage
sufficient to allocate an
electric field in the mineral particles with sufficient stress to fracture the
mineral particles, and
passing sufficient current through the mineral particles to fracture the
mineral particles.
The liquid optionally flows slowly upward in a column so that small, fractured
particles are
carried upward by the upwardly flowing liquid while larger, heavier,
unfractured particles sink past
the electrodes. The gaps between the electrodes optionally are larger than the
size of the
mineral particles. The liquid flows optionally flows slowly upward in a column
so that small,
fractured particles are carried upward by the upwardly flowing liquid while
larger, heavier,
unfractured particles sink past the electrodes, and wherein gaps between the
electrodes are
larger than the size of the mineral particles.
Another embodiment of the present invention provides an apparatus for breaking
mineral
particles comprising a container, a liquid disposed in the container in which
the particles are
suspended, the liquid comprising a dielectric constant higher than the
particles, a plurality of
electrodes disposed in the liquid, and a pulsed power source for sending an
electric voltage pulse
to the electrodes wherein the pulse is tuned to electrical characteristics of
the container and the
liquid to provide a rise of voltage sufficient to allocate an electric field
in the mineral particles with
sufficient stress to fracture the mineral particles. The liquid optionally
flows slowly upward in a
column so that small, fractured particles are carried upward by the upwardly
flowing liquid while
larger, heavier, unfractured particles sink past the electrodes. The gaps
between the electrodes
optionally are larger than the size of the mineral particles. The liquid
optionally flows slowly
upward in a column so that small, fractured particles are carried upward by
the upwardly flowing
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liquid while larger, heavier, unfractured particles sink past the electrodes,
and wherein gaps
between the electrodes are larger than the size of the mineral particles.
Other objects, advantages and novel features, and further scope of
applicability of the
present invention will be set forth in part in the detailed description to
follow, taken in conjunction
with the accompanying drawings, and in part will become apparent to those
skilled in the art upon
examination of the following, or may be learned by practice of the invention.
The objects and
advantages of the invention may be realized and attained by means of the
instrumentalities and
combinations pointed out in the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The accompanying drawings, which are incorporated into and form a part of the
specification, illustrate one or more embodiments of the present invention
and, together with the
description, serve to explain the principles of the invention. The drawings
are only for the purpose
of illustrating one or more preferred embodiments of the invention and are not
to be construed as
limiting the invention. In the drawings:
Fig. 1 shows an electrocrushing process of the prior art;
Fig. 2 shows an end view of a coaxial electrode set for a cylindrical bit of
an embodiment
of the present invention;
Fig. 3 shows an alternate embodiment of Fig. 2;
Fig. 4 shows an alternate embodiment of a plurality of coaxial electrode sets;
Fig. 5 shows a conical bit of an embodiment of the present invention;
Fig. 6 is of a dual-electrode set bit of an embodiment of the present
invention;
Fig. 7 is of a dual-electrode conical bit with two different cone angles of an
embodiment of
the present invention;
Fig. 8 shows an embodiment of a drill bit of the present invention wherein one
ground
electrode is the tip of the bit and the other ground electrode has the
geometry of a great circle of
the cone;
Fig. 9 shows the range of bit rotation azimuthal angle of an embodiment of the
present
invention;
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Fig. 10 shows an embodiment of the drill bit of the present invention having
radiused
electrodes;
Fig. 11 shows the complete drill assembly of an embodiment of the present
invention;
Fig. 12 shows the reamer drag bit of an embodiment of the present invention;
Fig. 13 shows a solid-state switch or gas switch controlled high voltage pulse
generating
system that pulse charges the primary output capacitor of an embodiment of the
present
invention;
Fig. 14 shows an array of solid-state switch or gas switch controlled high
voltage pulse
generating circuits that are charged in parallel and discharged in series to
pulse-charge the output
capacitor of an embodiment of the present invention;
Fig. 15 shows a voltage vector inversion circuit that produces a pulse that is
a multiple of
the charge voltage of an embodiment of the present invention;
Fig. 16 shows an inductive store voltage gain system to produce the pulses
needed for the
FAST Drill of an embodiment of the present invention;
Fig. 17 shows a drill assembly powered by a fuel cell that is supplied by fuel
lines and
exhaust line from the surface inside the continuous metal mud pipe of an
embodiment of the
present invention;
Fig. 18 shows a roller-cone bit with an electrode set of an embodiment of the
present
invention;
Fig. 19 shows a small-diameter electrocrushing drill of an embodiment of the
present
invention;
Fig. 20 shows an electrocrushing vein miner of an embodiment of the present
invention;
Fig. 21 shows a water treatment unit useable in the embodiments of the present
invention;
Fig. 22 shows a high energy electrohydraulic boulder breaker system (HEEB) of
an
embodiment of the present invention;
Fig. 23 shows a transducer of the embodiment of Fig. 22;
Fig. 24 shows the details of the an energy storage module and transducer of
the
embodiment of Fig. 22;
Fig. 25 shows the details of an inductive storage embodiment of the high
energy
electrohydraulic boulder breaker energy storage module and transducer of an
embodiment of the
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present invention;
Fig. 26 shows the embodiment of the high energy electrohydraulic boulder
breaker
disposed on a tractor for use in a mining environment;
Fig. 27 shows a geometric arrangement of the embodiment of parallel electrode
gaps in a
transducer in a spiral configuration.
Fig. 28 shows details of another embodiment of an electrohydraulic boulder
breaker
system;
Fig. 29 shows an embodiment of a virtual electrode electrocrushing process;
Fig. 30 shows an embodiment of the virtual electrode electrocrushing system
comprising a
vertical flowing fluid column;
Fig. 31 shows a pulsed power drilling apparatus manufactured and tested in
accordance
with an embodiment of the present invention; and
Fig. 32 is a graph showing dielectric strength versus delay to breakdown of
the insulating
formulation of the present invention, oil, and water.
MODES(S) FOR CARRYING OUT THE INVENTION
The present invention provides for pulsed power breaking and drilling
apparatuses and
methods. As used herein, "drilling" is defined as excavating, boring into,
making a hole in, or
otherwise breaking and driving through a substrate. As used herein, "bit" and
"drill bit" are defined
as the working portion or end of a tool that performs a function such as, but
not limited to, a
cutting, drilling, boring, fracturing, or breaking action on a substrate
(e.g., rock). As used herein,
the term "pulsed power" is that which results when electrical energy is stored
(e.g., in a capacitor
or inductor) and then released into the load so that a pulse of current at
high peak power is
produced. "Electrocrushing" ("EC") is defined herein as the process of passing
a pulsed electrical
current through a mineral substrate so that the substrate is "crushed" or
"broken".
Electrocrushinq Bit
An embodiment of the present invention provides a drill bit on which is
disposed one or
more sets of electrodes. In this embodiment, the electrodes are disposed so
that a gap is formed
between them and are disposed on the drill bit so that they are oriented along
a face of the drill bit.
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In other words, the electrodes between which an electrical current passes
through a mineral
substrate (e.g., rock) are not on opposite sides of the rock. Also, in this
embodiment, it is not
necessary that all electrodes touch the mineral substrate as the current is
being applied. In
accordance with this embodiment, at least one of the electrodes extending from
the bit toward the
substrate to be fractured and may be compressible (i.e., retractable or
depressible) into the drill bit
by any means known in the art such as, for example, via a spring-loaded
mechanism.
Generally, but not necessarily, the electrodes are disposed on the bit such
that at least one
electrode contacts the mineral substrate to be fractured and another electrode
that usually
touches the mineral substrate but otherwise may be close to, but not
necessarily touching, the
mineral substrate so long as it is in sufficient proximity for current to pass
through the mineral
substrate. Typically, the electrode that need not touch the substrate is the
central, not the
surrounding, electrode.
Therefore, the electrodes are disposed on a bit and arranged such that
electrocrushing
arcs are created in the rock. High voltage pulses are applied repetitively to
the bit to create
repetitive electrocrushing excavation events. Electrocrushing drilling can be
accomplished, for
example, with a flat-end cylindrical bit with one or more electrode sets.
These electrodes can be
arranged in a coaxial configuration.
Fig. 2 shows an end view of such a coaxial electrode set configuration for a
cylindrical bit,
showing high voltage or center electrode 108, ground or surrounding electrode
110, and gap 112
for creating the arc in the rock. Variations on the coaxial configuration are
shown in Fig. 3. A
non-coaxial configuration of electrode sets arranged in bit housing 114 is
shown in Fig. 4. Figs. 3-
4 show ground electrodes that are completed circles. Other embodiments may
comprise ground
electrodes that are partial circles, partial or compete ellipses, or partial
or complete parabolas in
geometric form.
For drilling larger holes, a conical bit is preferably utilized, especially if
controlling the
direction of the hole is important. Such a bit may comprise one or more sets
of electrodes for
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creating the electrocrushing arcs and may comprise mechanical teeth to assist
the
electrocrushing process. One embodiment of the conical electrocrushing bit has
a single set of
electrodes, preferably arranged coaxially on the bit, as shown in Fig. 5. In
this embodiment,
conical bit 118 comprises a center electrode 108, the surrounding electrode
110, the bit case or
housing 114 and mechanical teeth 116 for drilling the rock. Either, or both,
electrodes may be
compressible. The surrounding electrode preferably has mechanical cutting
teeth 109
incorporated into the surface to smooth over the rough rock texture produced
by the
electrocrushing process. In this embodiment, the inner portion of the hole is
drilled by the
electrocrushing portion (i.e., electrodes 108 and 110) of the bit, and the
outer portion of the hole is
drilled by mechanical teeth 116. This results in high drilling rates, because
the mechanical teeth
have good drilling efficiency at high velocity near the perimeter of the bit,
but very low efficiency at
low velocity near the center of the bit. The geometrical arrangement of the
center electrode to the
ground ring electrode is conical with a range of cone angles from 180 degrees
(flat plane) to about
75 degrees (extended center electrode).
An alternate embodiment is to arrange a second electrode set on the conical
portion of the
bit. In such an embodiment, one set of the electrocrushing electrodes operates
on just one side
of the bit cone in an asymmetrical configuration as exemplified in Fig. 6
which shows a dual-
electrode set conical bit, each set of electrodes comprising center electrode
108, surrounding
electrode 110, bit case or housing 114, mechanical teeth 116, and drilling
fluid passage 120.
The combination of the conical surface on the bit and the asymmetry of the
electrode sets
results in the ability of the dual-electrode bit to excavate more rock on one
side of the hole than
the other and thus to change direction. For drilling a straight hole, the
repetition rate and pulse
energy of the high voltage pulses to the electrode set on the conical surface
side of the bit is
maintained constant per degree of rotation. However, when the drill is to turn
in a particular
direction, then for that sector of the circle toward which the drill is to
turn, the pulse repetition rate
(and/or pulse energy) per degree of rotation is increased over the repetition
rate for the rest of the
circle. In this fashion, more rock is removed by the conical surface electrode
set in the turning
direction and less rock is removed in the other directions (See Fig. 9,
discussed in detail below).
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Because of the conical shape of the bit, the drill tends to turn into the
section where greater
amount of rock was removed and therefore control of the direction of drilling
is achieved.
In the embodiment shown in Fig. 6, most of the drilling is accomplished by the
electrocrushing (EC) electrodes, with the mechanical teeth serving to smooth
the variation in
surface texture produced by the EC process. The mechanical teeth 116 also
serve to cut the
gauge of the hole, that is, the relatively precise, relatively smooth inside
diameter of the hole. An
alternate embodiment has the drill bit of Fig. 6 without mechanical teeth 116,
all of the drilling
being done by the electrode sets 108 and 110 with or without mechanical teeth
109 in the
surrounding electrode 110.
Alternative embodiments include variations on the configuration of the ground
ring
geometry and center-to-ground ring geometry as for the single-electrode set
bit. For example,
Fig. 7 shows such an arrangement in the form of a dual-electrode conical bit
comprising two
different cone angles with center electrodes 108, surrounding or ground
electrodes 110, and bit
case or housing 114. In the embodiment shown, the ground electrodes are tip
electrode 111 and
conical side ground electrodes 110 which surround, or partially surround, high
voltage electrodes
108 in an asymmetric configuration.
As shown in Fig. 7, the bit may comprise two or more separate cone angles to
enhance
the ability to control direction with the bit. The electrodes can be laid out
symmetrically in a sector
of the cone, as shown in Fig. 5 or in an asymmetric configuration of the
electrodes utilizing ground
electrode 111 as the center of the cone as shown in Fig. 7. Another
configuration is shown in Fig.
8A in which ground electrode 111 is at the tip of the bit and hot electrode
108 and other ground
electrode 110 are aligned in great circles of the cone. Fig. 8B shows an
alternate embodiment
wherein ground electrode 111 is the tip of the bit, other ground electrode 110
has the geometry of
a great circle of the cone, and hot electrodes 108 are disposed there between.
Also, any
combination of these configurations may be utilized.
It should be understood that the use of a bit with an asymmetric electrode
configuration
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can comprise one or more electrode sets and need not comprise mechanical
teeth. It should also
be understood that directional drilling can be performed with one or more
electrode sets.
The EC drilling process takes advantage of flaws and cracks in the rock. These
are
regions where it is easier for the electric fields to breakdown the rock. The
electrodes used in the
bit of the present invention are usually large in area in order to intercept
more flaws in the rock
and therefore improve the drilling rate, as shown in Fig. 5. This is an
important feature of the
invention because most electrodes in the prior art are small to increase the
local electric field
enhancement.
Fig. 9 shows the range of bit rotation azimuthal angle 122 where the
repetition rate or
pulse energy is increased to increase excavation on that side of the drill
bit, compared to the rest
of the bit rotation angle that has reduced pulse repetition rate or pulse
energy 124. The bit rotation
is referenced to a particular direction relative to the formation 126, often
magnetic north, to enable
the correct drill hole direction change to be made. This reference is usually
achieved by
instrumentation provided on the bit. When the pulsed power system provides a
high voltage pulse
to the electrodes on the side of the bit (See Fig. 6), an arc is struck
between one hot electrode
and one ground electrode. This arc excavates a certain amount of rock out of
the hole. By the
time the next high voltage pulse arrives at the electrodes, the bit has
rotated a certain amount,
and a new arc is struck at a new location in the rock. If the repetition rate
of the electrical pulses
is constant as a function of bit rotation azimuthal angle, the bit will drill
a straight hole. If the
repetition rate of the electrical pulses varies as a function of bit rotation
azimuthal angle, the bit will
tend to drift in the direction of the side of the bit that has the higher
repetition rate. The direction
of the drilling and the rate of deviation can be controlled by controlling the
difference in repetition
rate inside the high repetition rate zone azimuthal angle, compared to the
repetition rate outside
the zone (See Fig. 9). Also, the azimuthal angle of the high repetition rate
zone can be varied to
control the directional drilling. A variation of the invention is to control
the energy per pulse as a
function of azimuthal angle instead of, or in addition to, controlling the
repetition rate to achieve
directional drilling.
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Fast Drill System
Another embodiment of the present invention provides a drilling
system/assembly utilizing
the electrocrushing bits described herein and is designated herein as the FAST
Drill system. A
limitation in drilling rock with a drag bit is the low cutter velocity at the
center of the drill bit. This is
where the velocity of the grinding teeth of the drag bit is the lowest and
hence the mechanical
drilling efficiency is the poorest. Effective removal of rock in the center
portion of the hole is the
limiting factor for the drilling rate of the drag bit. Thus, an embodiment of
the FAST Drill system
comprises a small electrocrushing (EC) bit (alternatively referred to herein
as a FAST bit or FAST
Drill bit) disposed at the center of a drag bit to drill the rock at the
center of the hole. Thus, the EC
bit removes the rock near the center of the hole and substantially increases
the drilling rate. By
increasing the drilling rate, the net energy cost to drill a particular hole
is substantially reduced.
This is best illustrated by the bit shown in Fig. 5 (discussed above)
comprising EC process
electrodes 108 and 100 set at the center of bit 114, surrounded by mechanical
drag-bit teeth 116.
The rock at the center of the bit is removed by the EC electrode set, and the
rock near the edge of
the hole is removed by the mechanical teeth, where the tooth velocity is high
and the mechanical
efficiency is high.
As noted above, the function of the mechanical drill teeth on the bit is to
smooth off the
tops of the protrusions and recesses left by the electrocrushing or plasma-
hydraulic process.
Because the electrocrushing process utilizes an arc through the rock to crush
or fracture the rock,
the surface of the rock is rough and uneven. The mechanical drill teeth smooth
the surface of the
rock, cutting off the tops of the protrusions so that the next time the
electrocrushing electrodes
come around to remove more rock, they have a larger smoother rock surface to
contact the
electrodes.
The EC bit preferably comprises passages for the drilling fluid to flush out
the rock debris
(i.e., cuttings) (See Figs. 6). The drilling fluid flows through passages
inside the electrocrushing
bit and then out] through passages 120 in the surface of the bit near the
electrodes and near the
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drilling teeth, and then flows up the side of the drill system and the well to
bring rock cuttings to
the surface.
The EC bit may comprise an insulation section that insulates the electrodes
from the
housing, the electrodes themselves, the housing, the mechanical rock cutting
teeth that help
smooth the rock surface, and the high voltage connections that connect the
high voltage power
cable to the bit electrodes.
Fig. 10 shows an embodiment of the Fast drill high voltage electrode 108 and
ground
electrodes 110 that incorporate a radius 176 on the electrode, with electrode
radius 176 on the
rock-facing side of electrodes 110. Radius 176 is an important feature of the
present invention to
allocate the electric field into the rock. The feature is not obvious because
electrodes from prior
art were usually sharp to enhance the local electric field.
Fig. 11 shows an embodiment of the FAST Drill system comprising two or more
sectional
components, including, but not limited to: (1) at least one pulsed power FAST
drill bit 114; (2) at
least one pulsed power supply 136; (3) at least one downhole generator 138;
(4) at least one
overdrive gear to rotate the downhole generator at high speed 140; (5) at
least one downhole
generator drive mud motor 144; (6) at least one drill bit mud motor 146; (7)
at least one rotating
interface 142; (8) at least one tubing or drill pipe for the drilling fluid
147; and (9) at least one cable
148. Not all embodiments of the FAST Drill system utilize all of these
components. For example,
one embodiment utilizes continuous coiled tubing to provide drilling fluid to
the drill bit, with a cable
to bring electrical power from the surface to the pulsed power system. That
embodiment does not
require a down-hole generator, overdrive gear, or generator drive mud motor,
but does require a
downhole mud motor to rotate the bit, since the tubing does not turn. An
electrical rotating
interface is required to transmit the electrical power from the non-rotating
cable to the rotating drill
bit.
An embodiment utilizing a multi-section rigid drill pipe to rotate the bit and
conduct drilling
fluid to the bit requires a downhole generator, because a power cable cannot
be used, but does
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not need a mud motor to turn the bit, since the pipe turns the bit. Such an
embodiment does not
need a rotating interface because the system as a whole rotates at the same
rotation rate.
An embodiment utilizing a continuous coiled tubing to provide mud to the drill
bit, without a
power cable, requires a down-hole generator, overdrive gear, and a generator
drive mud motor,
and also needs a downhole motor to rotate the bit because the tubing does not
turn. An electrical
rotating interface is needed to transmit the electrical control and data
signals from the non-rotating
cable to the rotating drill bit.
An embodiment utilizing a continuous coiled tubing to provide drilling fluid
to the drill bit,
with a cable to bring high voltage electrical pulses from the surface to the
bit, through the rotating
interface, places the source of electrical power and the pulsed power system
at the surface. This
embodiment does not need a down-hole generator, overdrive gear, or generator
drive mud motor
or downhole pulsed power systems, but does need a downhole motor to rotate the
bit, since the
tubing does not turn.
Still another embodiment utilizes continuous coiled tubing to provide drilling
fluid to the drill
bit, with a fuel cell to generate electrical power located in the rotating
section of the drill string.
Power is fed across the rotating interface to the pulsed power system, where
the high voltage
pulses are created and fed to the FAST bit. Fuel for the fuel cell is fed down
tubing inside the
coiled tubing mud pipe.
An embodiment of the FAST Drill system comprises FAST bit 114, a drag bit
reamer 150
(shown in Fig. 12), and a pulsed power system housing 136 (Fig. 11).
Fig. 12 shows reamer drag bit 150 that enlarges the hole cut by the
electrocrushing FAST
bit, drag bit teeth 152, and FAST bit attachment site 154. Reamer drag bit 150
is preferably
disposed just above FAST bit 114. This is a conical pipe section, studded with
drill teeth, that is
used to enlarge the hole drilled by the EC bit (typically, for example,
approximately 7.5 inches in
diameter) to the full diameter of the well (for example, to approximately 12.0
inches in diameter).
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The conical shape of drag bit reamer 150 provides more cutting teeth for a
given diameter of hole,
thus higher drilling rates. Disposed in the center part of the reamer section
are several passages.
There is a passage for the power cable to go through to the FAST bit. The
power cable comes
from the pulsed power section located above and/or within the reamer and
connects to the FAST
drill bit below the reamer. There are also passages in the reamer that provide
oil flow down to
the FAST bit and passages that provide flushing fluid to the reamer teeth to
help cut the rock and
flush the cuttings from the reamer teeth.
Preferably, a pulse power system that powers the FAST bit is enclosed in the
housing of
the reamer drag bit and the stem above the drag bit as shown in Fig. 11. This
system takes the
electrical power supplied to the FAST Drill for the electrocrushing FAST bit
and transforms that
power into repetitive high voltage pulses, usually over 100 kV. The repetition
rate of those pulses
is controlled by the control system from the surface or in the bit housing.
The pulsed power
system itself can include, but is not limited to:
(1) a solid state switch controlled or gas-switch controlled pulse generating
system with a
pulse transformer that pulse charges the primary output capacitor (example
shown in Fig. 13);
(2) an array of solid-state switch or gas-switch controlled circuits that are
charged in
parallel and in series pulse-charge the output capacitor (example shown in
Fig. 14);
(3) a voltage vector inversion circuit that produces a pulse at about twice,
or a multiple of,
the charge voltage (example shown in Fig. 15);
(4) An inductive store system that stores current in an inductor, then
switches it to the
electrodes via an opening or transfer switch (example shown in Fig. 16); or
(5) any other pulse generation circuit that provides repetitive high voltage,
high current
pulses to the FAST Drill bit.
Fig. 13 shows a solid-state switch or gas switch controlled high voltage pulse
generating
system that pulse charges the primary output capacitor 164, showing generating
means 156 to
provide DC electrical power for the circuit, intermediate capacitor electrical
energy storage means
158, gas, solid-state, or vacuum switching means 160 to switch the stored
electrical energy into
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pulse transformer 162 voltage conversion means that charges output capacitive
storage means
164 connecting to FAST bit 114.
Fig. 14 shows an array of solid-state switch or gas switch 160 controlled high
voltage pulse
generating circuits that are charged in parallel and discharged in series
through pulse transformer
162 to pulse-charge output capacitor 164.
Fig. 15 shows a voltage vector inversion circuit that produces a pulse that is
a multiple of
the charge voltage. An alternate of the vector inversion circuit that produces
an output voltage of
about twice the input voltage is shown, showing solid-state switch or gas
switching means 160,
vector inversion inductor 166, intermediate capacitor electrical energy
storage means 158
connecting to FAST bit 114.
Fig. 16 shows an inductive store voltage gain system to produce the pulses
needed for the
FAST Drill, showing the solid-state switch or gas switching means 160,
saturable pulse
transformers 168, and intermediate capacitor electrical energy storage means
158 connecting to
the FAST bit 114.
The pulsed power system is preferably located in the rotating bit, but may be
located in the
stationary portion of the drill pipe or at the surface.
Electrical power for the pulsed power system is either generated by a
generator at the
surface, or drawn from the power grid at the surface, or generated down hole.
Surface power is
transmitted to the FAST drill bit pulsed power system either by cable inside
the drill pipe or
conduction wires in the drilling fluid pipe wall. In the preferred embodiment,
the electrical power is
generated at the surface, and transmitted downhole over a cable 148 located
inside the
continuous drill pipe 147 (shown in Fig.11).
The cable is located in non-rotating flexible mud pipe (continuous coiled
tubing). Using a
cable to transmit power to the bit from the surface has advantages in that
part of the power
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conditioning can be accomplished at the surface, but has a disadvantage in the
weight, length,
and power loss of the long cable.
At the bottom end of the mud pipe is located the mud motor which utilizes the
flow of
drilling fluid down the mud pipe to rotate the FAST Drill bit and reamer
assembly. Above the
pulsed power section, at the connection between the mud pipe and the pulsed
power housing, is
the rotating interface as shown in Fig. 11. The cable power is transmitted
across an electrical
rotating interface at the point where the mud motor turns the drag bit. This
is the point where
relative rotation between the mud pipe and the pulsed power housing is
accommodated. The
rotating electrical interface is used to transfer the electrical power from
the cable or continuous
tubing conduction wires to the pulsed power system. It also passes the
drilling fluid from the non-
rotating part to the rotating part of the drill string to flush the cuttings
from the EC electrodes and
the mechanical teeth. The pulsed power system is located inside the rigid
drill pipe between the
rotating interface and the reamer. High voltage pulses are transmitted inside
the reamer to the
FAST bit.
In the case of electrical power transmission through conduction wires in rigid
rotating pipe,
the rotating interface is not needed because the pulsed power system and the
conduction wires
are rotating at the same velocity. If a downhole gearbox is used to provide a
different rotation rate
for the pulsed power/bit section from the pipe, then a rotating interface is
needed to accommodate
the electrical power transfer.
In another embodiment, power for the FAST Drill bit is provided by a downhole
generator
that is powered by a mud motor that is powered by the flow of the drilling
fluid (mud) down the
drilling fluid, rigid, multi-section, drilling pipe (Fig. 11). That mudflow
can be converted to
rotational mechanical power by a mud motor, a mud turbine, or similar
mechanical device for
converting fluid flow to mechanical power. Bit rotation is accomplished by
rotating the rigid drill
pipe. With power generation via downhole generator, the output from the
generator can be inside
the rotating pulsed power housing so that no rotating electrical interface is
required (Fig. 11), and
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only a mechanical interface is needed. The power comes from the generator to
the pulsed power
system where it is conditioned to provide the high voltage pulses for
operation of the FAST bit.
Alternatively, the downhole generator might be of the piezoelectric type that
provides
electrical power from pulsation in the mud. Such fluid pulsation often results
from the action of a
mud motor turning the main bit.
Another embodiment for power generation is to utilize a fuel cell in the non-
rotating section
of the drill string. Fig. 17 shows an example of a FAST Drill system powered
by fuel cell 170 that
is supplied by fuel lines and exhaust line 172 from the surface inside the
continuous metal mud
pipe 147. The power from fuel cell 170 is transmitted across the rotating
interlace 142 to pulsed
power system 136, and hence to FAST bit 114. The fuel cell consumes fuel to
produce electricity.
Fuel lines are placed inside the continuous coiled tubing, which provides
drilling fluid to the drill
bit, to provide fuel to the fuel cell, and to exhaust waste gases. Power is
fed across the rotating
interface to the pulsed power system, where the high voltage pulses are
created and fed to the
FAST bit.
As noted above, there are two primary means for transmitting drilling fluid
(mud) from the
surface to the bit: continuous flexible tubing or rigid multi-section drill
pipe. The continuous
flexible mud tubing is used to transmit mud from the surface to the rotation
assembly where part
of the mud stream is utilized to spin the assembly through a mud motor, a mud
turbine, or another
rotation device. Part of the mudf low is transmitted to the FAST bits and
reamer for flushing the
cuttings up the hole. Continuous flexible mud tubing has the advantage that
power and
instrumentation cables can be installed inside the tubing with the mudflow. It
is stationary and not
used to transmit torque to the rotating bit. Rigid multi-section drilling pipe
comes in sections and
cannot be used to house continuous power cable, but can transmit torque to the
bit assembly.
With continuous flexible mud pipe, a mechanical device such as, for example, a
mud motor, or a
mud turbine, is used to convert the mud flow into mechanical rotation for
turning the rotating
assembly. The mud turbine can utilize a gearbox to reduce the revolutions per
minute. A
downhole electric motor can alternatively be used for turning the rotating
assembly. The purpose
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of the rotating power source is primarily to provide torque to turn the teeth
on the reamer and the
FAST bit for drilling. It also rotates the FAST bit to provide the directional
control in the cutting of
a hole. Another embodiment is to utilize continuous mud tubing with downhole
electric power
generation.
In one embodiment, two mud motors or mud turbines are used: one to rotate the
bits, and
one to generate electrical power.
Another embodiment of the rigid multi-section mud pipe is the use of data
transmitting
wires buried in the pipe such as, for example, the Intelipipe manufactured by
Grant Prideco. This
is a composite pipe that uses magnetic induction to transmit data across the
pipe joints, while
transmitting it along wires buried in the shank of the pipe sections.
Utilizing this pipe provides for
data transmission between the bit and the control system on the surface, but
still requires the use
of downhole power generation.
Another embodiment of the FAST Drill is shown in Fig. 18 wherein rotary or
roller-cone bit
174 is utilized, instead of a drag bit, to enlarge the hole drilled by the
FAST bit. Roller-cone bit
174 comprises electrodes 108 and 110 disposed in or near the center portion of
roller cone bit
174 to excavate that portion of the rock where the efficiency of the roller
bit is the least.
Another embodiment of the rotating interface is to use a rotating magnetic
interface to
transfer electrical power and data across the rotating interface, instead of a
slip ring rotating
interface.
In another embodiment, the mud returning from the well loaded with cuttings
flows to a
settling pond, at the surface, where the rock fragments settle out. The mud
then cleaned and
reinjected into the FAST Drill mud pipe.
Electrocrushinq Vein Miner
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Another embodiment of the present invention provides a small-diameter,
electrocrushing
drill (designated herein as "SED") that is related to the hand-held
electrohydraulic drill disclosed in
U.S. Patent No. 5,896,938 (to a primary inventor herein), incorporated herein
by reference.
However, the SED is distinguishable in that the electrodes in the SED are
spaced in such a way,
and the rate of rise of the electric field is such, that the rock breaks down
before the water breaks
down. When the drill is near rock, the electric fields break down the rock and
current passes
through the rock, thus fracturing the rock into small pieces. The
electrocrushing rock
fragmentation occurs as a result of tensile failure caused by the electrical
current passing through
the rock, as opposed to compressive failure caused by the electrohydraulic
(EH) shock or
pressure wave on the rock disclosed in U.S. Patent No. 5,896,938, although the
SED, too, can be
connected via a cable from a box as described in the '938 patent so that it
can be portable. Fig.
19 shows a SED drill bit comprising case 206, internal insulator 208, and
center electrode 210
which is preferably movable (e.g., spring-loaded) to maintain contact with the
rock while drilling.
Although case 206 and internal insulator 208 are shown as providing an
enclosure for center
electrode 210, other components capable of providing an enclosure may be
utilized to house
electrode 210 or any other electrode incorporated in the SED drill bit.
Preferably, case 206 of the
SED is the ground electrode, although a separate ground electrode may be
provided. Also, it
should be understood that more than one set of electrodes may be utilized in
the SED bit. A
pulsed power generator as described in other embodiments herein is linked to
said drill bit for
delivering high voltage pulses to the electrode. In an embodiment of the SED,
cable 207 (which
may be flexible) is provided to link a generator to the electrode(s). A
passage, for example cable
207, is preferably used to deliver water down the SED drill.
This SED embodiment is advantageous for drilling in non-porous rock. Also,
this
embodiment benefits from the use concurrent use of the high permittivity
liquid discussed herein.
Another embodiment of the present invention is to assemble several individual
SED drill
heads or electrode sets together into an array or group of drills, without the
individual drill
housings, to provide the capability to mine large areas of rock. In such an
embodiment, a vein of
ore can be mined, leaving most of the waste rock behind. Fig. 20 shows such an
embodiment of
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a mineral vein mining machine herein designated Electrocrushing Vein Miner
(EVM) 212
comprising a plurality of SED drills 214, SED case 206, SED insulator 208, and
SED center
electrode 210. This assembly can then be steered as it moves through the rock
by varying the
repetition rate of the high voltage pulses differentially among the drill
heads. For example, if the
repetition rate for the top row of drill heads is twice as high but contains
the same energy per
pulse as the repetition rate for the lower two rows of drill heads, the path
of the mining machine
will curve in the direction of the upper row of drill heads, because the rate
of rock excavation will
be higher on that side. Thus, by varying the repetition rate and/or pulse
energy of the drill heads,
the EVM can be steered dynamically as it is excavating a vein of ore. This
provides a very useful
tool for efficiently mining just the ore from a vein that has substantial
deviation in direction.
In another embodiment, a combination of electrocrushing and electrohydraulic
(EH) drill bit
heads enhances the functionality of the EVM by enabling the EVM to take
advantage of ore
structures that are layered. Where the machine is mining parallel to the
layers, as is the case in
mining most veins of ore, the shock waves from the EH drill bit heads tend to
separate the layers,
thus synergistically coupling to the excavation created by the EC electrodes.
In addition,
combining electrocrushing drill heads with plasma-hydraulic drill heads
combines the compressive
rock fracturing capability of the plasma-hydraulic drill heads with the
tensile rock failure of the EC
drill heads to more efficiently excavate rock.
With the EVM mining machine, ore can be mined directly and immediately
transported to a
mill by water transport, already crushed, so the energy cost of primary
crushing and the capital
cost of the primary crushers is saved. This method has a great advantage over
conventional
mechanical methods in that it combines several steps in ore processing, and it
greatly reduces the
amount of waste rock that must be processed. This method of this embodiment
can also be used
for tunneling.
The high voltage pulses can be generated in the housing of the EVM,
transmitted to the
EVM via cables, or both generated elsewhere and transmitted to the housing for
further
conditioning. The electrical power generation can be at the EVM via fuel cell
or generator, or
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transmitted to the EVM via power cable. Typically, water or mining fluid flows
through the structure
of the EVM to flush out rock cuttings.
If a few, preferably just three, of the EC or PH drill heads shown in Fig. 20
are placed in a
housing, the assembly can be used to drill holes, with directional control by
varying the relative
repetition rate of the pulses driving the drill heads. The drill will tend to
drift in the direction of the
drill head with the highest pulse repletion rate, highest pulse energy, or
highest average power.
This electrocrushing (or EH) drill can create very straight holes over a long
distance for improving
the efficiency of blasting in underground mining, or it can be used to place
explosive charges in
areas not accessible in a straight line.
Insulating Drilling Fluid
An embodiment of the present invention also comprises insulating drilling
fluids that may
be utilized in the drilling methods described herein. For example, for the
electrocrushing process
to be effective in rock fracturing or crushing, it is preferable that the
dielectric constant of the
insulating fluid be greater than the dielectric constant of the rock and that
the fluid have low
conductivity such as, for example, a conductivity of less than approximately 1
0-6 mho/cm and a
dielectric constant of at least approximately 6.
Therefore, one embodiment of the present invention provides for an insulating
fluid or
material formulation of high permittivity, or dielectric constant, and high
dielectric strength with low
conductivity. The insulating formulation comprises two or more materials such
that one material
provides a high dielectric strength and another provides a high dielectric
constant. The overall
dielectric constant of the insulating formulation is a function of the ratio
of the concentrations of
the at least two materials. The insulating formulation is particularly
applicable for use in pulsed
power applications.
Thus, this embodiment of the present invention provides for an electrical
insulating
formulation that comprises a mixture of two or more different materials. In
one embodiment, the
formulation comprises a mixture of two carbon-based materials. The first
material preferably
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comprises a dielectric constant of greater than approximately 2.6, and the
second material
preferably comprises a dielectric constant greater than approximately 10Ø
The materials are at
least partly miscible with one another, and the formulation preferably has low
electrical
conductivity. The term "low conductivity" or "low electrical conductivity", as
used throughout the
specification and claims means a conductivity less than that of tap water,
preferably lower than
approximately le mho/cm, more preferably lower than 10-6 mho/cm. Preferably,
the materials
are substantially non-aqueous. The materials in the insulating formulation are
preferably non-
hazardous to the environment, preferably non-toxic, and preferably
biodegradable. The
formulation exhibits a low conductivity.
In one embodiment, the first material preferably comprises one or more natural
or
synthetic oils. Preferably, the first material comprises castor oil, but may
comprise or include
other oils such as, for example, jojoba oil or mineral oil.
Castor oil (glyceryl triricinoleate), a triglyceride of fatty acids, is
obtained from the seed of
the castor plant. It is nontoxic and biodegradable. A transformer grade castor
oil (from
CasChem, Inc.) has a dielectric constant (i.e., relative permittivity) of
approximately 4.45 at a
temperature of approximately 22 C (100 Hz).
The second material comprises a solvent, preferably one or more carbonates,
and more
preferably one or more alkylene carbonates such as, but not limited to,
ethylene carbonate,
propylene carbonate, or butylene carbonate. The alkylene carbonates can be
manufactured, for
example, from the reaction of ethylene oxide, propylene oxide, or butylene
oxide or similar oxides
with carbon dioxide.
Other oils, such as vegetable oil, or other additives can be added to the
formulation to
modify the properties of the formulation. Solid additives can be added to
enhance the dielectric or
fluid properties of the formulation.
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The concentration of the first material in the insulating formulation ranges
from between
approximately 1.0 and 99.0 percent by volume, preferably from between
approximately 40.0 and
95.0 percent by volume, more preferably still from between approximately 65.0
and 90.0 percent
by volume, and most preferably from between approximately 75.0 and 85.0
percent by volume.
The concentration of the second material in the insulating formulation ranges
from
between approximately 1.0 and 99.0 percent by volume, preferably from between
approximately
5.0 and 60.0 percent by volume, more preferably still from between
approximately 10.0 and 35.0
percent by volume, and most preferably from between approximately 15.0 and
25.0 percent by
volume.
Thus, the resulting formulation comprises a dielectric constant that is a
function of the ratio
of the concentrations of the constituent materials. The preferred mixture for
the formulation of the
present invention is a combination of butylene carbonate and a high
permittivity castor oil wherein
butylene carbonate is present in a concentration of approximately 20% by
volume. This
combination provides a high relative permittivity of approximately 15 while
maintaining good
insulation characteristics. In this ratio, separation of the constituent
materials is minimized. At a
ratio of below 32%, the castor oil and butylene carbonate mix very well and
remain mixed at room
temperature. At a butylene carbonate concentration of above 32%, the fluids
separate if
undisturbed for approximately 10 hours or more at room temperature. A property
of the present
invention is its ability to absorb water without apparent effect on the
dielectric performance of the
insulating formulation.
An embodiment of the present invention comprising butylene carbonate in castor
oil
comprises a dielectric strength of at least approximately 300 kV/cm (I psec),
a dielectric constant
of approximately at least 6, a conductivity of less than approximately 105
mho/cm, and a water
absorption of up to 2,000 ppm with no apparent negative effect caused by such
absorption. More
preferably, the conductivity is less than approximately 10-6 mho/cm.
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The formulation of the present invention is applicable to a number of pulsed
power
machine technologies. For example, the formulation is useable as an insulating
and drilling fluid
for drilling holes in rock or other hard materials or for crushing such
materials as provided for
herein. The use of the formulation enables the management of the electric
fields for
electrocrushing rock. Thus, the present invention also comprises a method of
disposing the
insulating formulation about a drilling environment to provide electrical
insulation during drilling.
Other formulations may be utilized to perform the drilling operations
described herein. For
example, in another embodiment, crude oil with the correct high relative
permittivity derived as a
product stream from an oil refinery may be utilized. A component of vacuum gas
crude oil has
high molecular weight polar compounds with 0 and N functionality. Developments
in
chromatography allow such oils to be fractionated by polarity. These are
usually cracked to
produce straight hydrocarbons, but they may be extracted from the refinery
stream to provide high
permittivity oil for drilling fluid.
Another embodiment comprises using specially treated waters. Such waters
include, for
example, the Energy Systems Plus (ESP) technology of Complete Water Systems
which is used
for treating water to grow crops. In accordance with this embodiment, Fig. 21
shows water or a
water-based mixture 128 entering a water treatment unit 130 that treats the
water to significantly
reduce the conductivity of the water. The treated water 132 then is used as
the drilling fluid by the
FAST Drill system 134. The ESP process treats water to reduce the conductivity
of the water to
reduce the leakage current, while retaining the high permittivity of the
water.
High Efficiency Electrohvdraulic Boulder Breaker
Another embodiment of the present invention provides a high efficiency
electrohydraulic
boulder breaker (designated herein as "HEEB") for breaking up medium to large
boulders into
small pieces. This embodiment prevents the hazard of fly rock and damage to
surrounding
equipment. The HEEB is related to the High Efficiency Electrohydraulic
Pressure Wave Projector
disclosed in U.S. Patent No. 6,215,734 (to the principal inventor herein),
incorporated herein by
reference.
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Fig. 22 shows the HEEB system disposed on truck 181, comprising transducer
178, power
cable 180, and fluid 182 disposed in a hole. Transducer 178 breaks the boulder
and cable 180
(which may be of any desired length such as, for example, 6-15 m long)
connects transducer 178
to electric pulse generator 183 in truck 181. An embodiment of the invention
comprises first
drilling a hole into a boulder utilizing a conventional drill, filling the
hole is filled with water or a
specialized insulating fluid, and inserting HEEB transducer 178 into the hole
in the boulder. Fig.
23 shows HEEB transducer 178 disposed in boulder 186 for breaking the boulder,
cable 180, and
energy storage module 184.
Main capacitor bank 183 (shown in Fig. 22) is first charged by generator 179
(shown in
Fig. 22) disposed on truck 181. Upon command, control system 192 (shown in
Fig. 22 and
disposed, for example, in a truck) is closed connecting capacitor bank 183 to
cable 180. The
electrical pulse travels down cable 180 to energy storage module 184 where it
pulse-charges
capacitor set 158 (example shown in Fig. 24), or other energy storage devices
(example shown in
Fig. 25).
Fig. 24 shows the details of the HEEB energy storage module 184 and transducer
178,
showing capacitors 158 in module 184, and floating electrodes 188 in
transducer 178.
Fig. 25 shows the details of the inductive storage embodiment of HEEB energy
storage
module 184 and transducer 178, showing inductive storage inductors 190 in
module 184, and
showing the transducer embodiment of parallel electrode gaps 188 in transducer
178. The
transducer embodiment of parallel electrode gaps (Fig. 25) and series
electrode gaps (Fig. 24)
can reach be used alternatively with either the capacitive energy store 158 of
Fig. 24 or the
inductive energy store 190 of Fig. 25.
These capacitors/devices are connected to the probe of the transducer assembly
where
the electrodes that create the pressure wave are located. The capacitors
increase in voltage from
the charge coming through the cable from the main capacitor bank until they
reach the breakdown
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voltage of the electrodes inside the transducer assembly. When the fluid gap
at the tip of the
transducer assembly breaks down (acting like a switch), current then flows
from the energy
storage capacitors or inductive devices through the gap. Because the energy
storage capacitors
are located very close to the transducer tip, there is very little inductance
in the circuit and the
peak current through the transducers is very high. This high peak current
results in a high energy
transfer efficiency from the energy storage module capacitors to the plasma in
the fluid. The
plasma then expands, creating a pressure wave in the fluid, which fractures
the boulder.
The HEEB system may be transported and used in various environments including,
but not
limited to, being mounted on a truck as shown in Fig. 22 for transport to
various locations, used
for either underground or aboveground mining applications as shown in Fig. 26,
or used in
construction applications. Fig. 26 shows an embodiment of the HEEB system
placed on a tractor
for use in a mining environment and showing transducer 178, power cable 180,
and control panel
192.
Therefore, the HEEB does not rely on transmitting the boulder-breaking current
over a
cable to connect the remote (e.g., truck mounted) capacitor bank to an
electrode or transducer
located in the rock hole. Rather, the HEEB puts the high current energy
storage directly at the
boulder. Energy storage elements, such as capacitors, are built into the
transducer assembly.
Therefore, this embodiment of the present invention increases the peak current
through the
transducer and thus improves the efficiency of converting electrical energy to
pressure energy for
breaking the boulder. This embodiment of the present invention also
significantly reduces the
amount of current that has to be conducted through the cable thus reducing
losses, increasing
energy transfer efficiency, and increasing cable life.
An embodiment of the present invention improves the efficiency of coupling the
electrical
energy to the plasma into the water and hence to the rock by using a multi-gap
design. A
problem with the multi-gap water spark gaps has been getting all the gaps to
ignite because the
cumulative breakdown voltage of the gaps is much higher than the breakdown
voltage of a single
gap. However, if capacitance is placed from the intermediate gaps to ground
(Fig. 24), each gap
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ignites at a voltage similar to the ignition voltage of a single gap. Thus, a
large number of gaps
can be ignited at a voltage of approximately a factor of 2 greater than the
breakdown voltage for a
single gap. This improves the coupling efficiency between the pulsed power
module and the
energy deposited in the fluid by the transducer. Holes in the transducer case
are provided to let
the pressure from the multiple gaps out into the hole and into the rock to
break the rock (Fig. 24).
In another embodiment, the multi-gap transducer design can be used with a
conventional
pulsed power system, where the capacitor bank is placed at some distance from
the material to
be fractured, a cable is run to the transducer, and the transducer is placed
in the hole in the
boulder. Used with the HEEB, it provides the advantage of the much higher peak
current for a
given stored energy.
Thus, an embodiment of the present invention provides a transducer assembly
for creating
a pressure pulse in water or some other liquid in a cavity inside a boulder or
some other
fracturable material, said transducer assembly incorporating energy storage
means located
directly in the transducer assembly in close proximity to the boulder or other
fracturable material.
The transducer assembly incorporates a connection to a cable for providing
charging means for
the energy storage elements inside the transducer assembly. The transducer
assembly includes
an electrode means for converting the electrical current into a plasma
pressure source for
fracturing the boulder or other fracturable material.
Preferably, the transducer assembly has a switch located inside the transducer
assembly
for purposes of connecting the energy storage module to said electrodes.
Preferably, in the
transducer assembly, the cable is used to pulse charge the capacitors in the
transducer energy
storage module. The cable is connected to a high voltage capacitor bank or
inductive storage
means to provide the high voltage pulse.
In another embodiment, the cable is used to slowly charge the capacitors in
the transducer
energy storage module. The cable is connected to a high voltage electric power
source.
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Preferably, the switch located at the primary capacitor bank is a spark gap,
thyratron,
vacuum gap, pseudo-spark switch, mechanical switch, or some other means of
connecting a high
voltage or high current source to the cable leading to the transducer
assembly.
In another embodiment, the transducer electrical energy storage utilizes
inductive storage
elements.
Another embodiment of the present invention provides a transducer assembly for
the
purpose of creating pressure waves from the passage of electrical current
through a liquid placed
between one or more pairs of electrodes, each gap comprising two or more
electrodes between
which current passes. The current creates a phase change in the liquid, thus
creating pressure
in the liquid from the change of volume due to the phase change. The phase
change includes a
change from liquid to gas, from gas to plasma, or from liquid to plasma.
Preferably, in the transducer, more than one set of electrodes is arranged in
series such
that the electrical current flowing through one set of electrodes also flows
through the second set
of electrodes, and so on. Thus, a multiplicity of electrode sets can be
powered by the same
electrical power circuit.
In another embodiment, in the transducer, more than one set of electrodes is
arranged in
parallel such that the electrical current is divided as it flows through each
set of electrodes
(Fig. 25). Thus, a multiplicity of electrode sets can be powered by the same
electrical power
circuit.
Preferably, a plurality of electrode sets is arrayed in a line or in a series
of straight lines.
In another embodiment, the plurality of electrode sets is alternatively
arrayed to form a
geometric figure other than a straight line, including, but not limited to, a
curve, a circle (Fig. 25),
or a spiral. Fig. 27 shows a geometric arrangement of the embodiment
comprising parallel
electrode gaps 188 in the transducer 178, in a spiral configuration.
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Preferably, the electrode sets in the transducer assembly are constructed in
such a way as
to provide capacitance between each intermediate electrode and the ground
structure of the
transducer (Fig. 24).
In another embodiment, in the plurality of electrode sets, the capacitance of
the
intermediate electrodes to ground is formed by the presence of a liquid
between the intermediate
electrode and the ground structure.
In another embodiment, in the plurality of electrode sets, the capacitance is
formed by the
installation of a specific capacitor between each intermediate electrode and
the ground structure
(Fig. 24). The capacitor can use solid or liquid dielectric material.
In another embodiment, in the plurality of electrode sets, capacitance is
provided between
the electrode sets from electrode to electrode. The capacitance can be
provided either by the
presence of the fracturing liquid between the electrodes or by the
installation of a specific
capacitor from an intermediate electrode between electrodes as shown in Fig.
28. Fig. 28 shows
the details of the HEEB transducer 178 installed in hole 194 in boulder 186
for breaking the
boulder. Shown are cable 180, the floating electrodes 188 in the transducer
and liquid between
the electrodes 196 that provides capacitive coupling electrode to electrode.
Openings 198 in the
transducer which allow the pressure wave to expand into the rock hole are also
shown.
Preferably in the multi-electrode transducer, the electrical energy is
supplied to the multi-
gap transducer from an integral energy storage module.
Preferably in the multi-electrode transducer, the energy is supplied to the
transducer
assembly via a cable connected to an energy storage device located away from
the boulder or
other fracturable material.
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Virtual Electrode Electro-Crushinct Process
Another embodiment of the present invention comprises a method for crushing
rock by
passing current through the rock using electrodes that do not touch the rock.
In this method, the
rock particles are suspended in a flowing or stagnant water column, or other
liquid of relative
permittivity greater than the permittivity of the rock being fractured. Water
is preferred for
transporting the rock particles because the dielectric constant of water is
approximately 80
compared to the dielectric constant of rock which is approximately 3.5 to 12.
In the preferred embodiment, the water column moves the rock particles past a
set of
electrodes as an electrical pulse is provided to the electrodes. As the
electric field rises on the
electrodes, the difference in dielectric constant between the water and the
rock particle causes
the electric fields to be concentrated in the rock, forming a virtual
electrode with the rock. This is
illustrated in Fig. 29 showing rock particle 200 between high voltage
electrodes 202 and ground
electrode 203 in liquid 204 whose dielectric constant is significantly higher
than that of rock
particle 200.
The difference in dielectric constant concentrated the electric fields in the
rock particle.
These high electric fields cause the rock to break down and current to flow
from the electrode,
through the water, through the rock particles, through the conducting water,
and back to the
opposite electrode. In this manner, many small particles of rock can be
disintegrated by the
virtual electrode electrocrushing method without any of them physically
contacting both
electrodes. The method is also suitable for large particles of rock.
Thus, it is not required that the rocks be in contact with the physical
electrodes and so the
rocks need not be sized to match the electrode spacing in order for the
process to function. With
the virtual electrode electrocrushing method, it is not necessary for the
rocks to actually touch the
electrode, because in this method, the electric fields are concentrated in the
rock by the high
dielectric constant (relative permittivity) of the water or fluid. The
electrical pulse must be tuned to
the electrical characteristics of the column structure and liquid in order to
provide a sufficient rate
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of rise of voltage to achieve the allocation of electric field into the rock
with sufficient stress to
fracture the rock.
Another embodiment of the present invention, illustrated in Fig. 30, comprises
a reverse-
flow electro-crusher wherein electrodes 202 send an electrocrushing current to
mineral (e.g., rock)
particles 200 and wherein water or fluid 204 flows vertically upward at a rate
such that particles
200 of the size desired for the final product are swept upward, and whereas
particles that are
oversized sink downward.
As these oversized particles sink past the electrodes, a high voltage pulse is
applied to the
electrodes to fracture the particles, reducing them in size until they become
small enough to
become entrained by the water or fluid flow. This method provides a means of
transporting the
particles past the electrodes for crushing and at the same time
differentiating the particle size.
The reverse-flow crusher also provides for separating ash from coal in that it
provides for
the ash to sink to the bottom and out of the flow, while the flow provides
transport of the fine coal
particles out of the crusher to be processed for fuel.
Industrial Applicability
The invention is further illustrated by the following non-limiting example(s).
Example 1
An apparatus utilizing FAST Drill technology in accordance with the present
invention was
constructed and tested. Fig. 31 shows FAST Drill bit 114, the drill stem 216,
the hydraulic motor
218 used to turn drill stem 216 to provide power to mechanical teeth disposed
on drill bit 114, slip
ring assembly 220 used to transmit the high voltage pulses to the FAST bit 114
via a power cable
inside drill stem 216, and tank 222 used to contain the rocks being drilled. A
pulsed power
system, contained in a tank (not shown), generated the high voltage pulses
that were fed into the
slip ring assembly. Tests were performed by conducting 150 kV pulses through
drill stem 216 to
the FAST Bit 114, and a pulsed power system was used for generating the 150 kV
pulses. A
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drilling fluid circulation system was incorporated to flush out the cuttings.
The drill bit shown in
Fig. 5 was used to drill a 7 inch diameter hole approximately 12 inches deep
in rock located in a
rock tank. A fluid circulation system flushed the rock cuttings out of the
hole, cleaned the cuttings
out of the fluid, and circulated the fluid through the system.
Example II
A high permittivity fluid comprising a mixture of castor oil and approximately
20% by
volume butylene carbonate was made and tested in accordance with the present
invention as
follows.
1. Dielectric Strength Measurements.
Because this insulating formulation of the present invention is intended for
high voltage
applications, the properties of the formulation were measured in a high
voltage environment. The
dielectric strength measurements were made with a high voltage Marx bank pulse
generator, up
to 130 kV. The rise time of the Marx bank was less than 100 nsec. The
breakdown
measurements were conducted with 1-inch balls immersed in the insulating
formulation at
spacings ranging from 0.06 to 0.5 cm to enable easy calculation of the
breakdown fields. The
delay from the initiation of the pulse to breakdown was measured. Fig. 32
shows the electric field
at breakdown plotted as a function of the delay time in microseconds. Also
included are data from
the Charlie Martin models for transformer oil breakdown and for deionized
water breakdown
(Martin, T. H., A. H. Guenther, M Kristiansen "J. C. Martin on Pulsed Power"
Lernum Press,
(1996)).
The breakdown strength of the formulation is substantially higher than
transformer oil at
times greater than 10 sec. No special effort was expended to condition the
formulation. It
contained dust, dissolved water and other contaminants, whereas the Martin
model is for very well
conditioned transformer oil or water.
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2. Dielectric Constant Measurements.
The dielectric constant was measured with a ringing waveform at 20 kV. The
ringing high
voltage circuit was assembled with 8-inch diameter contoured plates immersed
in the insulating
formulation at 0.5-inch spacing. The effective area of the plates, including
fringing field effects,
was calibrated with a fluid whose dielectric constant was known (i.e.,
transformer oil). An
aluminum block was placed between the plates to short out the plates so that
the inductance of
the circuit could be measured with a known circuit capacitance. Then, the
plates were immersed
in the insulating formulation, and the plate capacitance was evaluated from
the ringing frequency,
properly accounting for the effects of the primary circuit capacitor. The
dielectric constant was
evaluated from that capacitance, utilizing the calibrated effective area of
the plate. These tests
indicated a dielectric constant of approximately 15.
3. Conductivity Measurements.
To measure the conductivity, the same 8-inch diameter plates used in the
dielectric
constant measurement were utilized to measure the leakage current. The plates
were separated
by 2-inch spacing and immersed in the insulating formulation. High voltage
pulses, ranging from
70-150kV were applied to the plates, and the leakage current flow between the
plates was
measured. The long duration current, rather than the initial current, was the
value of interest, in
order to avoid displacement current effects. The conductivity obtained was
approximately
1 micromho/cm [1X10-6 (ohm-cm)-1].
4. Water Absorption.
The insulating formulation has been tested with water content up to 2000 ppm
without any
apparent effect on the dielectric strength or dielectric constant. The water
content was measured
by Karl Fisher titration.
5. Energy Storage Comparison.
The energy storage density of the insulating formulation of the present
invention was
shown to be substantially higher than that of transformer oil, but less than
that of deionized water.
Table 1 shows the energy storage comparison of the insulating formulation, a
transformer oil, and
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water in the 1 sec and 10 sec breakdown time scales. The energy density (in
joules/cm3) was
calculated from the dielectric constant (6,60) and the breakdown electric
field (Ebd - kV/cm). The
energy storage density of the insulating formulation is approximately one-
fourth that of water at 10
microseconds. The insulating formulation did not require continuous
conditioning, as did a water
dielectric system. After about 12 months of use, the insulating formulation
remained useable
without conditioning and with no apparent degradation.
Table 1. Comparison of Energy Storage Density
Time = 1 psec Time = 10 psec
Dielectic kV/ Energy kV/c Energy
Fluid Constant cm Density m Density
Insulating 15 380 9.59E-02 325 7.01E-02
formulation
Trans. Oil 2.2 500 2.43E-02 235 5.38E-03
Water 80 600 1.27E+00 280 2.78E-01
Energy density = 1/2* 6 * 60*Ebd*Ebd j/cm3
6. Summary.
A summary of the dielectric properties of the insulating formulation of the
present invention
is shown in Table 2. Applications of the insulating formulation include high
energy density
capacitors, large-scale pulsed power machines, and compact repetitive pulsed
power machines.
Table 2. Summary of Formulation Properties
Dielectric Strength = 380 kV/cm (1 psec)
Dielectric = 15
Constant
Conductivity = 1e-6 mho/cm
Water absorption = up to 2000 ppm with no apparent ill effects
The preceding examples can be repeated with similar success by substituting
the
generically or specifically described compositions, biomaterials, devices
and/or operating
conditions of this invention for those used in the preceding examples.
=
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30
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