Note: Descriptions are shown in the official language in which they were submitted.
CA 02289301 1999-11-10
CASING HAMMER ASSEMBLY FOR CABLE TOOL DRILLING APPARATUS
Background of the Inventiion
This invention relates to well drilling equipment, and in particular to cable
tool drilling
apparatus. The invention involves a casing hammer assembly for a cable tool
drilling apparatus,
as well as related equipment: and the cable tool drilling apparatus itself.
Cable tool drilling apparatus is well known. Typical cable tool drilling
involves utilization
of an impact drilling string extending through a length of casing pipe. After
the impact operations
have proceeded for a while, the drilling string is withdrawn from the casing
pipe and a heavy
annular hammer is clamped to the drill stem. The drill stem is then returned
to the casing pipe,
and the impact operation resumes with the annular hammer then being repeatedly
raised and
released as in the drilling phase to drive the casing pipe farther into the
ground. Once the casing
pipe has been driven to a desired further depth, the drilling string is again
raised, the annular
hammer is removed, and the: impact drilling operation resumes. This process is
then repeated
many dozens of times in order to sink a well of a desired depth.
As can be appreciated'. from the: nature of this kind of an operation, the
impact drilling must
be interrupted many times in order to drive the casing further into the
ground. In fact, most of
the time spent "drilling" is actually spent running the drilling apparatus
into and out of the bore
hole, not in the actual drilling process itself.
A further disadvantage of impact drilling is the fact that the drill bit is
often well down the
bore hole from the end of the casing pipe. The drilling operation then often
causes excessive
amounts of loose materials to cave into the bore hole, thereby requiring
additional time and effort
to remove the excessive amount of material that accumulates. Also, water is a
necessary lubricant
CA 02289301 1999-11-10
used in the drilling process, and often it is necessary for an operator to
climb up the drilling mast
in order to access the top of the casing pipe in order to inject water,
therefore also consuming
additional time as well as wear and itear on the operator.
In order to eliminate the constant shifting between impact drilling and
sinking ofthe casing
pipe, other apparatus has lbeen developed to make the drilling process a more
continuous
operation. For example, U.S. Patent No. 5,310,014 discloses a cable tool
drilling apparatus which
includes a separate driving ram which allows the drilling string to be passed
through the ram and
permits the ram to be utilized at the same time that the impact drilling
process proceeds. While
a significant improvement over the prior intermittent drilling operation, the
apparatus of this
patent has its own disadvantages. First, the ram is relatively long and must
fit over the casing
pipe. Thus, a different size of ram must be employed for every different
diameter of casing pipe.
Also, because of the relativelly long length of the ram, the final casing pipe
cannot be driven close
the ground and must be cut at an acceptable height above the ground. In
addition, because the
ram is constantly driven up and down axially in relation to the casing pipe,
there is the potential
for damage of the pipe during the hanimering operation, unless the ram is held
fairly precisely in
relation to the casing pipe. Also, in order to move the ram out of alignment
with the casing pipe,
it must be lifted to a significant height, and then shifted in some manner,
such as by swinging the
entire derrick assembly to one side or the other, a time consuming process.
Summary of the Invention
The invention relates to an iniproved casing hammer assembly for a cable tool
drilling
apparatus, and the resulting cable tool drilling apparatus. The casing hammer
assembly includes
an upstanding hammer housing with means for mounting the hammer housing on a
casing pipe.
A central aperture is provided through the hammer housing with the aperture
being formed to
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permit drilling apparatus to pass freely through the hammer housing into and
out of the casing
pipe upon which the hammer housirig is mounted. A guide is provided proximate
and at least
partially surrounding the cer.itral aperture, and an impact anvil is provided,
surrounding the guide
and secured to the hammer housing. A reciprocal hammer is mounted on the guide
in the housing
and is positioned to strike the impact anvil. Means is provided for actuating
the hammer, this
means comprising an eccentric which is connected for periodically raising and
releasing the
hammer, and a motor for driving the eccentric.
In accordance with the preferred form of the invention, also included is means
for laterally
shifting the hammer housing in relation to the casing pipe. The means for
lateral shifting
comprises a retractable arm which is fixed above the hammer housing. The
retractable arm
comprises a first stationary member and a second movable member which is
secured to the
stationary member. The movable rnember is pivotally secured at one end to the
stationary
member, and a hydraulic cylinder connected to the members is provided for
actuating the movable
member.
In the preferred form of the invention, the guide surrounding the central
aperture
preferably comprises a central tube. The tube extends from top to bottom in
the hammer housing,
and is sufficiently large to allow the drilling apparatus to pass freely
through the hammer housing.
The invention includes means biasing the hammer toward the impact anvil. In
accordance
with the preferred form of the invention, the biasing means comprises at least
one compression
spring which bears between the hammer housing and the hammer. The spring is
mounted to
accentuate the driving force of the hammer against the anvil.
In accordance with the invention, the eccentric comprises a rotatable shaft
having an offset
hammer operator at one end. A sleeve is freely mounted on the shaft for
revolving relative to the
shaft, and the shaft includes a radially protruding lug. The sleeve includes
an extension shaped
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CA 02289301 1999-11-10
to engage the lug in order to rotate the shaft in unison with the sleeve when
the extension engages
the lug. The motor is drivingly connected to the sleeve for rotating the
sleeve, preferably by an
endless chain drive.
A flexible support is provideci in the hammer housing above the anvil, with
the hammer
operator engaging the flexible support. Preferably the flexible support
comprises a chain which
is secured between the hamrner housing and the hammer, and the hammer operator
comprises a
gear wheel mounted on an arm which extends radially from one end of the
rotatable shaft. A pair
of the chains and a pair of the gear wheels, on opposite ends of the rotatable
shaft, are preferred
for proper driving of the hammer. The motor, which may be conventional, is
preferably a
hydraulic motor.
The means for mounting the hammer housing on a casing pipe preferably
comprises a
collar extending from the irripact anvil. The collar is formed so that a
single apparatus can be
utilized to drive various diar.neters of casing pipes without being changed.
Means is also provided for positioning and holding the hammer housing above
the casing
pipe. In accordance with the preferred form of the invention, the means for
positioning and
holding comprises cable pulleys mounted atop the hammer housing adjacent to
the central
aperture, with a hoist cable engaged in the pulleys. The hoist cable extends
to the derrick in a
conventional fashion.
For ease of water injection, the invention also includes a water injection
port on the
hammer housing, the port leading to the central tube.
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The apparatus according to the invention forms part of a cable tool drilling
apparatus, being suspended from a portable derrick which is used in a
generally
conventional fashion. The drilling string extends from the derrick on one
cable, and
the hammer housing is suspended from the derrick on a second cable. The
retractable
arm is suspended from the derrick above the greatest extent of vertical travel
of the
hammer housing and is positioned to engage both cables in order to shift both
the
hammer housing and the drilling string laterally in order to provide easy
access by the
operator to the casing pipe.
According to an aspect of the present invention, there is provided a casing
hammer assembly for a cable tool drilling apparatus, comprising
a. an upstanding hammer housing,
b. means for mounting said hammer housing on a casing pipe,
c. a central aperture through said hammer housing being formed to permit
drilling apparatus to pass freely through said hammer housing into and out of
the
casing pipe upon which said hammer housing is mounted,
d. a guide proximate and at least partially surrounding said central
aperture,
e. an impact anvil surrounding said guide and secured to said hammer
housing,
f. a reciprocal hammer mounted on said guide and positioned to strike
said impact anvil, and
g. means for actuating said hammer, comprising
i. an eccentric connected for periodically raising and releasing said
CA 02289301 2003-09-10
hammer, said eccentric comprising a rotatable shaft having an offset
hammer operator at one end and a sleeve freely mounted on said shaft for
revolving relative to said shaft, said shaft including a radially protruding
lug
and said sleeve including an extension shaped to engage said lug to rotate
said
shaft in unison with said sleeve when said extension engages said lug, and
ii. a motor for driving said eccentric.
According to another aspect of the invention, there is provided a cable tool
drilling apparatus, comprising
a. a portable derrick,
b. a drilling string extending from said derrick,
c. an upstanding hammer housing,
d. means extending from said derrick for mounting said hammer housing
on a casing pipe,
e. a central aperture through said hammer housing being formed to permit
said drilling string to pass freely through said hammer housing into and out
of the
casing pipe upon which said hammer housing is mounted,
f. a guide tube at least partially surrounding said central aperture,
g. an impact anvil surrounding said guide tube and secured to said
hammer housing,
h. a reciprocal hammer mounted on said guide tube and positioned to
strike said impact anvil,
i. means for actuating said hammer, comprising
i. an eccentric connected for periodically raising and releasing
said hammer, said eccentric comprising a rotatable shaft having an offset
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CA 02289301 2003-09-10
hammer operator at one end and a sleeve freely mounted on said shaft for
revolving relative to said shaft, said shaft including a radially protruding
lug
and said sleeve including an extension shaped to engage said lug to rotate
said
shaft in unison with said sleeve when said extension engages said lug,
ii. a motor for driving said eccentric, and
j. a retractable arm mounted on said derrick for laterally shifting said
hammer housing.
Brief Description of the Drawings
The invention is described in greater detail in the following description of
an
example embodying the best mode of the invention, taken in conjunction with
the
drawing figures, in which:
Figure 1 illustrates a prior art cable tool drilling apparatus prior to the
improvements of the present invention,
Figure 2 is a side elevational illustration of utilization of the invention to
sink
a casing pipe while the cable tool drilling process proceeds,
Figure 3 is a rear elevational illustration of the invention, with the hammer
housing positioned on the casing pipe,
Figure 4 is a view similar to Figure 3, but with the hammer housing and
drilling string shifted laterally by the retractable arm,
Figure 5 is an enlarged elevational view of the top of the hammer housing,
illustrating the pulley arrangement for positioning of the hammer housing,
Figure 6 is a top plan view of the apparatus illustrated in Figure 5,
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Figure 7 is a top plan view of the retractable arm according to the invention,
when
retracted and in relation to the cables for the drilling string and hammer
housing,
Figure 8 is a view similar to Figure 7, but with the retractable arm extended
to laterally
shift the cables and therefore the harnmer housing and the drilling string,
Figure 9 is a front ellevational view of the hammer housing according to the
invention,
Figure 10 is a side elevational view thereof,
Figure 11 is a view similar to Figure 9, but with the housing shield removed
to illustrate
the internal components of the hammer housing,
Figure 12 is a view similar to Figure 10 but with the housing shield again
removed,
Figures 13, 14 and 15 are views similar to Figure 12, and illustrating the
sequence of
operation of the hammer within the liammer housing,
Figure 16 is a greatly enlarged view of the portions of the apparatus utilized
in the hammer
housing to raise and release the impact hammer,
Figure 17 is a side elevational view of the apparatus illustrated in Figure
16, looking from
the right side of Figure 16, and
Figure 18 is a similar illustration, but taken looking from the left side of
Figure 16.
Description of an Example
Embodying the Best Mode of the Invention
Turning first to Figure 1, illustrated is a prior art cable tool drilling
apparatus which has
been improved by that illustrated and described in relation to Figures 2
through 18. The prior art
cable tool drilling apparatus is designated generally at 10, and includes a
truck 12 or other
appropriate vehicle having an extendible vertical derrick 14 from which a
drilling
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string 16 is suspended for in:ipact drilling purposes. The drilling string 16
includes a drill stem 18
which extends into the casing pipe 20 of a partially drilled well.
The illustration in Figure 1 depicts the typical point in the drilling
operation where the well
has been drilled a desired distance beneath the end of the casing pipe 20,
leaving a relatively long
unprotected hole 22. As ilhjstrated, it is common that the sides of the hole
22 cave into the hole
during the drilling operatiOn, requiring a tremendous amount of additional
material to be
withdrawn during the drilling operation than would be necessary to simply
accommodate the
casing pipe 20.
As illustrated in Figure 1, in order to drive the casing pipe 20 in the prior
art apparatus,
the drilling string 20 is withdrawn from the hole 22 sufficiently to expose a
portion of the drill
stem 18. At this point, a hammer assembly 24 is clamped to the drill stem 18,
and then
reciprocating operation of the cable tool drilling apparatus impacts the
hammer assembly 24 on
the casing pipe 20, driving 1:he casing pipe 20 into the ground. Then, the
hammer assembly 24
must be removed for the drilling process to continue. This start/stop
operation is repeated dozens
of times for each length of casing pipe 20 as it is sunk into the ground,
leading to a long, involved
and arduous process to drill a well using the prior art apparatus 10.
Figure 2 is view similar to Figure 1, but illustrating utilization of the
improvements of the
present invention. Parts that remain the same as the prior art cable tool
drilling apparatus 10 of
Figure 1 bear the same reference nurnerals.
In accordance with the invention, a casing hammer assembly is provided,
including an
upstanding hammer housing 26. The hammer housing 26 includes an extending
collar 28 for
mounting the hammer housing 26 on the casing pipe 20. As best illustrated in
Figures 9 through
15, the collar 28 is shaped to accommodate varying sizes of casing pipes.
Therefore, as
illustrated, the collar 28 has a flared shape to fit within large diameter
casing pipes, and can also
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CA 02289301 1999-11-10
be formed internally (not illustrated) so that smaller casing pipe, such as
the casing pipe 20
illustrated in Figure 2, fits Nvithin the collar 20.
The hammer housing 26 employs appropriate external shields 30 through 36 to
protect
the operating elements of the casing hammer assembly of the invention. The
shields 30 through
36 are removed in Figures 11 through 15 so that the internal elements of the
hammer housing 26
are exposed.
The hammer housing 26 includes a central aperture which is surrounded by a
guide in the
form of a central tube 38 extending from top to bottom in the hammer housing
26. As illustrated,
the central tube 38, which is cylindrical, forms the central aperture and
pennits the drilling string
16 to freely pass through the hammer housing 26 into and out of the casing
pipe 20.
An impact anvi140 surrounds; the central tube 38 and is bolted to the hammer
housing 26.
The collar 28 extends from, and fon:-ns part of, the impact anvil 40.
A reciprocal hamme:r 42 is mounted on the central tube 38 and is positioned to
repeatedly
strike the impact anvi140 for sinking of a casing pipe 20 into the ground. The
reciprocal hammer
42 is normally at rest against the impact anvil 40, and is biased in that
orientation by a
compression spring 44 which bears between the hammer housing 26 and the top of
the reciprocal
hammer 42.
An eccentric is utilized in order to raise the hammer 42 and then release it
for impact
against the anvil 40 (and therefore the casing pipe 20 upon which the hammer
housing 26 is
mounted). The eccentric is composed of identical mechanisms employing a pair
of chains 46 and
48 on opposite sides of the central tube 38. Each of the chains 46 and 47 is
secured to a
respective bracket 50 and 52 mounted in the hammer housing 26. The brackets 50
and 52 can
employ appropriate cushioning to absorb impact received through the respective
chains 46 and
48 as the hammer 42 is operated. The chain 46 passes from the bracket 50 over
a first gearwheel
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or sprocket 54 and then over a second sprocket 56 and is appropriately secured
to the top of the
hammer 42. Similarly, the; chain 48 extends from the bracket 52 over a first
gearwheel or
sprocket 58 and then over a second gearwheel or sprocket 60 to a fixed
attachment atop the
hammer 42.
The sprockets 56 and 60 are appropriately secured for rotation in place to the
hammer
housing 26. The sprockets 54 and 58, however, are, as best illustrated in
Figures 16 through 18,
mounted on a respective arm 62 and 64 extending radially from opposite ends of
a rotatable shaft
66. The shaft 66 is mounted for rotation in a bracket assembly 68 secured to
the top of the
hammer housing 26. The shaft 66 also passes through a sleeve 70 which is
freely mounted on the
shaft 66 for revolving relative to the shaft. The sleeve 70 is driven, in
turn, by a chain 72 engaged
on a gearwheel 74 formed on the sleeve 70, the chain 72 being driven by a
hydraulic motor 76
which drives a sprocket 78 over which the chain 72 passes. The motor 76 is
operated
hydraulically by means of hydraulic fluid provided through hoses 80 from a
hydraulic source on
the truck 12 (the source not being shoivn in detail). The motor 76 can be
driven in a conventional
fashion, and is therefore not further described.
A lug 82 protrudes radially from the shaft 66. The lug 82 is engaged by a
small extension
84 of the sleeve 70. By "smalll", it is meant that the extension 84 extends
for only a portion of the
circumference of the sleeve 70, an appropriate amount to be sufficiently
strong, but less than 180
and preferably on the order of'about 90 or less, the reason for which will
become apparent below
when the operation of the reciprocal liammer 42 is explained.
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An annular guide 86 is mounted atop the hammer housing 26, the guide 86 being
flared
as illustrated. The guide 86 includes an outlet 88 in axially registration
with the central tube 38
and is flared in order to aid feeding of'the drill string 16 into and through
the hammer housing 26.
Three cable pulleys 90, 92 and 94 are mounted on the guide 86 as illustrated,
and a cable 96 is
threaded through the cable pulleys 90 through 94 and extends upwardly through
appropriate
pulleys on the top of the den-ick 14, one end of the cable 96 being wrapped on
a drum 98 on the
truck 12 (Figure 3), and the other end of the cable 96 being fixed to the
derrick at 100 (Figure 3).
Thus, by operation of the dn.im 98 in a conventional fashion, the hammer
housing can be raised
or lowered as desired for placement on the casing 20.
As illustrated in Figure 4, the liammer housing 26, with the drill string 16
extending there
into, can be laterally shifted away frorn the casing pipe 20 to allow access
to the casing pipe. To
this end, a retractable arm 102 is fixed to the derrick 14 above the hammer
housing 26. As best
shown in Figures 7 and 8, the retractable arm is composed of a stationary
member 104 and a
movable member 106. The niovable member 106 is pivotally secured at one end to
the stationary
member 104. A hydraulic cylinder 108 is connected between the members 104 and
106 to pivot
the movable member 106 when desired. A stop 110 is mounted on the movable
member 106 to
retain the cables 96 and the cable for the drill string 16, as will be
explained below.
For providing lubricating water down the casing 20 during the drilling
operation, a water
injection port 112 is provided at the top of the hammer housing 26. The water
injection port 112
opens into the outlet 88 of the guide 86, thereby allowing injected water to
pass through the
central tube 38 into the casing pipe 20. The water injection port 112 is
connected to an
appropriate source of water (not illustrated), and water control can be by
various means, such as
a push button control for ease of metering drilling water.
In operation, the hammer housing 26 is first located atop a casing pipe 20 by
means of
CA 02289301 1999-11-10
operation of the drum 98 and cable 96. When the hammer housing 26 is in place,
the drill string
16 is then fed through the guide 86 and through the central tube 38 into the
casing pipe 20.
Impact drilling using the drill string 16 then proceeds in a conventional
fashion.
At the same time, however, the operator can also operate the reciprocal hammer
42 within
the hammer housing 26 to assure that the bottom of the casing 20 is always
close to the bottom
of the hole 22, in close proximity to where drilling occurs, as illustrated in
Figure 2. Thus, unlike
the prior art method illustrated in Figure 1, excessive caving of the walls of
the hole 22 does not
occur and therefore excessive cuttings need not be removed during the drilling
operation.
The impact operatiori of the reciprocal hammer 42 is best illustrated in
Figures 13 through
15 in relation to the eccentric: which is best illustrated in Figures 16
through 18. As the motor 76
operates, the sleeve 70 rotates about the shaft 66 until the extension 84
engages the lug 82. That
occurs in the position illustrated in Figure 13. Then, as the sleeve 70 is
further rotated, because
the lug 82 is seated in the extension 84, the shaft 66 also begins to rotate,
rotating the arms 62
and 64 and therefore the sprockets 54 .and 56. This, in turn, begins to force
the two chains 46 and
48 outwardly (to the left as illustrated in Figures 13 through 15, thereby
raising the hammer 42
against the force of the spririg 44 until the hammer 42 is elevated to the
position illustrated in
Figure 14. At this point, the hammer 42 beings to reverse direction as the
sprockets 54 and 56
move downwardly and inwardly. Thereafter, gravity and the force of the spring
44 cause the shaft
66 to freely rotate in the counterclockwise direction in relation to Figures
13 through 15 so that
the hammer 42 is essentially free and is forced downwardly by the force of
gravity in combination
with the force of the spring 44, impacting on the anvil 40 as illustrated in
Figure 15. When impact
occurs, the sprockets 54 and 58, on their respective arms 62 and 64, are
rotated to the orientation
illustrated in Figure 15. However, the sleeve 70, which is driven by the chain
72, is approximately
180 behind the rotation of the shaft 66, and therefore "catches up" with the
extension 84 once
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CA 02289301 1999-11-10
again engaging the lug 82. This process is then repeated for so long as the
motor 76 is driven,
with the impact of the hamlrier 42 on the anvi140 driving the casing pipe 20
into the ground. This
process continues until the casing pipe 20 is driven as far as possible, and
then, in a conventional
fashion, a further length of casing pipe 20 is secured to the lower casing
pipe 20 and is driven as
the drilling operation progresses.
In order to gain access to the casing pipe 20 at any time, the drill string 18
is raised until
the drill stem 18 is within the hamme,r housing 26, protruding slightly if at
all from the collar 28.
Then, the drum 98 is operated to raise the hammer housing 26 until the collar
28 is free above the
top of the casing pipe 20. Then, referring to Figures 3, 4, 7 and 8, the
hydraulic cylinder 108 of
the retractable arm 102 is activated, capturing the cables 96 and the cable of
the drill string 16
against the stop 110 as illustrated in Figure 8, and shifting the hammer
housing 26 and the drill
string 16 laterally, as illustrated in Figure 4, so that the casing pipe 20
can easily be accessed.
The invention provides many advantages over prior art cable tool drilling.
First, the
invention allows simultaneous sinking of the casing pipe 20 as the drilling
operation continues.
Second, because the bottom of the casing pipe 20 extends close to the bottom
of the hole 22
being drilled, the amount of cuttings to be cleaned from the hole is
substantially reduced, thereby
greatly increasing the efficiency ofthe drilling operation. Third, by use
ofthe retractable arm 102,
it is easy to move the drill string 16 and the hammer housing 20 to one side
to easily gain access
to the top of the casing pipe 20. Fourth, by the orientation of the cable 96
through the cable
pulleys 90 through 94, not only is the cable 96 free of the central area
through which the drill
string passes, but also the hammer housing 26 can be well balanced for lifting
that is essentially
axial in direction. Fifth, the hammer 42, located within the hammer housing
26, strikes only on
the anvil 40 at the top of the casing pipe 20. Thus, no parts of the hammering
apparatus are
moving on the inside or outside of the casing pipe 20, eliminating the
possibility of damage or
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binding. Sixth, water injection is very simple through the injection port 112,
eliminating the need
for an operator to possibly climb 20 feet or more up the derrick 14 for water
injection. Various
other advantages will be apparent to one skilled in the art.
Various changes cari be made to the invention without departing from the
spirit thereof
or scope of the following claims.
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