Note: Descriptions are shown in the official language in which they were submitted.
CA 02874639 2014-12-11
AXIALLY AMPLIFIED PULSING TOOL
FIELD OF THE INVENTION
This invention relates to an amplification tool and a method of drilling for
pressure pulse amplification during drilling.
BACKGROUND
Conventional vertical oil and gas wells are drilled by rotary drilling from a
surface derrick. A drill string extends from the surface derrick to a drill
bit located at
the lower end of the drill string. The drill string is typically suspended
from blocks at
the derrick or from a top drive. In conventional drilling, the drill string
itself is rotated
from the surface.
Directional drilling is used when reservoirs are laterally distanced from the
surface derrick. In directional drilling there may be a generally vertical
section
and/or an inclined section down to a depth, followed by sections which deviate
laterally from the vertical plane. The drill bit for lateral directional
drilling may be
rotated by the drill string from the surface during the generally vertical
and/or inclined
sections, and/or it may be rotated by a mud motor located above the drill bit.
In the
laterally inclined and/or horizontal stage of drilling, the drill bit is
typically rotated by a
downhole mud motor. Drilling fluid, often a drilling mud, is pumped from the
surface,
downwardly through the drill string, through the drill bit, and then upwardly
in the
annulus between the drill string and the borehole back to the surface. Drill
cuttings
and rock chips are carried from the drill bit back to the surface. The drill
string
typically includes drill pipe, sections of drill collars and drilling tools
such as reamers,
drilling jars, drilling shock tools, hammer tools, and measurement-while-
drilling
(MWD) tools.
During the lateral or horizontal phases of drilling, a portion of the drill
string is
in direct contact with the borehole, which causes significant frictional
resistance,
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particularly if and when the drill string is sliding and not rotating. If the
drill string
stops, the friction between the drill string and the borehole makes it
difficult to
advance the drill string into the borehole when drilling is restarted.
Overcoming the
friction between the borehole and the drill sting helps the driller to provide
the
optimal amount of weight on the drill bit for maximum penetration rate. If
undue
force is needed to overcome the friction, damage to the downhole drilling
equipment
can occur, and penetration rates are reduced.
Directional drilling uses a technology and devices known as measurement-
while drilling (MWD) to communicate the azimuth and inclination of the
borehole to
the surface. The MWD devices are electromechanical devices located above the
drill bit in the bottomhole assembly (BHA). The MWD device typically transmits
data
to the surface using mud-pulse telemetry. The MWD device produces pressure
pulses in the drilling fluid such that a parameter of the pulses, for example
the pulse
frequency and/or the pulse amplitude, is dependent on a measured parameter,
for
example the inclination of the borehole. The MWD devices may use positive-
pulse,
negative-pulse or continuous-wave systems. When the fluid flow through the
drill
string is restricted by operation of a valve, or poppet, a pressure pulse is
created, the
leading edge of which is a rise in pressure. This method is generally termed
positive
mud pulse telemetry. The term negative mud pulse telemetry is typically used
to
describe systems in which a valve opens a passage to the lower pressure
environment outside the drill string (i.e., the annulus between the drill
string and the
borehole), thus generating a negative pressure pulse having a falling leading
edge.
At the surface, the pressure pulses from the MWD device are analysed or
decoded
to determine a relevant measured borehole parameter. Devices to generate
pulses
for mud pulse telemetry (i.e., MWD devices) are more fully described in, for
example, US Patent Nos. 3,958,217, 4,905,778, 4,914,637 and 5,040,155.
As above, the weight on the drill bit (weight-on-bit, or WOB) is an important
factor for drilling penetration rates at the rock face. In directional
drilling, the WOB is
high in a vertical stage of the drilling, but is considerably lessened in the
laterally
inclined or horizontal stages of the drilling. Specific downhole tools exist
to increase
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the penetration rates. One class of tools uses a water hammer effect to create
pulsation of the flow of the drilling fluid through the drill bit to increase
penetration
rates. In these tools, the direction of the pulse is toward the drill bit. A
second class
of tools, known as shock tools, use a pressure pulse to deliver a force on the
drill
string to agitate or vibrate the drill string to overcome the friction between
the drill
string and the borehole in the lateral section of the drilled borehole. Some
shock
tools use a pressure pulse to act on a piston, creating a force proportional
to the
area of the piston multiplied by the amplitude of the pressure pulse. Shock
tools
may create a pulse in either direction, i.e., toward or away from the drill
bit. Shock
tools are advantageously positioned proximate the bent section of the
borehole,
where the drill string moves away from a generally vertical inclination to a
more
lateral inclination. In this position, the shock tool is used to vibrate the
drill string,
where the friction between the BHA and the borehole is the greatest. Another
type
of tool creates a hammer effect on the drill bit, with the pulses acting on an
anvil in
the direction of the drill bit. A few exemplary tools are summarized below.
US Patent 6,279,670 to Eddison et al., describes a downhole flow pulsing tool
for use with a pressure responsive device as a shock tool which expands and
retracts in response to the pressure pulses created by the tool. The tool
includes a
housing with a throughbore for drilling fluid and a valve in the bore with a
valve
member which is moveable to vary the area of a passage in the bore. A fluid
actuated positive displacement motor (mud motor) drives the valve member to
vary
the flow passage area. Expansion and retraction of the shock tool provides a
percussive effect at the drill bit.
US Patent 6,053,261 to Walter describes a tool to provide a cyclical water
hammer effect and water pulsating effect. A hollow housing defines a primary
flow
passage carrying a drilling fluid, and an elongated conduit with an upstream
and a
downstream end defining a main flow passage therethrough. The downstream end
communicates with the primary flow passage and a by-pass flow passage
extending
lengthwise of the conduit from the upstream to the downstream ends. A nozzle
located in the hollow housing adjacent to and spaced from the upstream end of
the
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conduit discharges flow from the primary passage into the main flow passage.
The
space between the nozzle and the upstream end provides communication between
the main flow passage and the by-pass flow passage. An axially movable valve
member is located in the downstream end of the conduit to co-operate with a
valve
seat downstream of the valve member to interrupt the flow through the conduit.
One
or more passages downstream of the valve seat provide communications between
the main flow passage and the by-pass passage in a region downstream of the
valve
seat. A spring urges the valve member toward an open position in the upstream
direction. The valve member is adapted to close in response to flow along the
valve
member, thus interrupting the flow through the conduit and creating a water
hammer
pulse which travels upstream through the conduit and the nozzle and also
through
the space between the nozzle and the upstream end of the conduit. The pulse
also
travels downstream along the by-pass passage and through the further passages
to
the region downstream of the valve member, to momentarily equalize water
hammer
pressures on upstream and downstream sides of the valve member. The spring
acts on the valve member under these equalized pressures such that flow in the
conduit again commences and the valve member closes again. The above recited
sequence of events is repeated to produce the cyclical water hammer and flow
pulsating effect.
Unfortunately, the amplitude (or pressure) of the pressure pulses created by
the MWD devices are typically too low to be useful in the water hammer and/or
shock tools pulsing tools. Drilling operators are reluctant to increase the
amplitude
of the MWD pulse, since this can result in undue wear on the MWD and other
downhole tools and/or interfere with the frequency or amplitude parameters of
the
MWD pulses that need to be read at the surface. US Patent 6,588,518 to Eddison
indicates that the MWD pulse may be modified to above 500 psi, although there
is
no teaching provided for such modification. Furthermore, MWD devices are
typically
operated at pressures closer to 300 psi, or lower, not the greater than 500
psi pulse
range suggested by Eddison.
The downhole mud motor, which is powered by the pressurized drilling mud
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injected into the drill string from the surface, is typically located downhole
above the
drill bit and rotates the bit to advance the borehole. The water hammer and
pulsing
shock tools create pressure pulses with one or more valves or flow throttling
devices.
These tools are more effective when they generate a larger pressure pulse. The
pressure pulses from downhole water hammer and/or pulsing shock tools are
found
to interfere with the frequency/amplitude parameters of the MWD device, making
it
more difficult for the drilling operator to analyse the MWD signals at the
surface.
SUMMARY
Broadly stated, there is provided a method of drilling a borehole which
includes:
a) generating pressure pulses in a drilling fluid in drill string;
b) allowing the pressure pulses to act on one or more axially aligned pistons
in an amplification tool connected in the drill string to produce a force to
drive a force
responsive device in the drill string; and
c) wherein each of the one or more pistons has a piston face, a first fluid
chamber on one side of the piston face, and a second fluid chamber on the
other
side of the piston face, the first fluid chamber being in fluid communication
with the
drilling fluid and the second fluid chamber being in fluid communication with
a
pressurized fluid held at a set pressure within the amplification tool;
such that the pressure pulses acting in the drilling fluid in the first fluid
chamber of the one or more pistons moves the one or more pistons with the
force
which is amplified by an amount proportional to the surface area of the piston
faces
and a multiple of the number of the one or more pistons.
Also provided is an amplification tool adapted for mounting on a drill string
containing a drilling fluid, the drill string having a drill bit, a pulse
generating device
adapted to create pressure pulses in the drilling fluid, and a force
responsive device
on the drill string adapted to impart a force on a portion of the drill
string. The
amplification tool includes a stationary, pressure-containing, tubular housing
connected in the drill string and having a throughbore to permit passage of
the
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drilling fluid therethrough such that the pressure pulses from the pulse
generating
device may travel through the throughbore of the housing to the force
responsive
device. One or more axially aligned, tubular pistons are sealed for limited
longitudinal movement within the housing. Each of the one or more pistons has
a
piston face, a piston throughbore co-extensive with the housing throughbore, a
first
fluid chamber on one side of the piston face and a second fluid chamber on the
other side of the piston face. The first fluid chamber is adapted for fluid
communication with the drilling fluid in the housing throughbore, and the
second fluid
chamber is adapted for fluid communication with a pressurized fluid held at a
set
pressure within the housing. Pressure pulses acting in the drilling fluid in
the first
fluid chamber of the one or more pistons moves the one or more pistons with an
amplified force which is proportional to the surface area of the piston faces
and a
multiple of the number of the one or more pistons, for delivery to the force
responsive device.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective view of one exemplary placement of the
axially amplified pulsing tool (AAPT) in a drill string for directional
drilling.
FIG. 2 is an enlarged view of portion A of FIG. 1, showing exemplary
components at the drill bit end of the drill string.
FIG. 3 is an enlarged view of portion B of FIG. 1, showing one embodiment of
the AAPT tool.
FIG. 4 is a cross sectional view of the AAPT tool along the longitudinal axis,
showing a gas chamber component at the drill bit-facing end of the tool, a
shock tool
component at the surface-facing end of the tool, and an amplification portion
of the
tool between these ends. This placement of the AAPT tool on the drill string
exemplifies one pulsing embodiment to reduce friction at the bent section of
the drill
string.
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FIG. 5 is a sectional view along line A-A of FIG. 4 showing the spline mandrel
details.
FIG. 6 is a perspective view of one of the pressure balanced sleeves for the
pistons of FIG. 4.
FIG. 7 is the sectional view of the tool as shown in FIG. 4, but with shading
to
show the paths of the drilling mud, pressurized fluid and pressurized gas in
the gas
chamber and amplification portion of the tool. The path of the drilling mud is
shown
with dark grey shading in the housing throughbore bore and on one side of each
piston. The path of the pressurized fluid is shown with broken lines extending
from
the gas chamber of the tool to the pressure balance sleeves and to the other
side of
each piston. The path of the pressurized gas is shown with light grey shading
in the
gas chamber. Oil in the shock tool component is shown in white (no shading).
DETAILED DESCRIPTION
Having reference to Figs. 1 - 7, one exemplary embodiment of an
amplification tool is shown generally at 10. The tool 10 is shown and
described
herein in use with an integral shock tool component 12. A shock tool is but
one
example of a force responsive device which might be used with the
amplification tool
10. However, it should be understood the amplification tool 10 may have other
applications in a drill string, and need not include the shock tool component
12 as an
integral component or at all.
In Figs. 1-3, the amplification tool 10 is shown to be positioned in the drill
string 11 adjacent (i.e., proximate to) to the a bent section 11 b of the
drill string,
where the drill string deviates from a generally vertical orientation to a
generally
laterally inclined or horizontal orientation. The amplification tool 10 in
this
embodiment includes an integral shock tool component 12 as a force responsive
device which can be used to deliver an amplified force to overcome frictional
losses
which are particularly high at the bent section llb of the drill string. The
drill bit lla
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is located at the rock face end of the drill string 11. A downhole power
section,
typically a mud motor 11c, is located above the drill bit 11a. Drilling fluid,
typically a
drilling mud, in the drill string 11 rotates the mud motor 11c to rotate the
drill bit lla
below the mud motor 11c. The mud motor 11 c is connected through an adjustable
bent housing lld and a bearing assembly lle to the drill bit 11a. Above the
mud
motor 11c is a rotor keeper sub/adapter 11f and a drill collar llg for housing
the
measurement-while-drilling (MWD) device 11h. In Figs. 1-3, the amplification
tool 10
is shown to be located in the drill string 11 above the MWD device 11h and
below
the bent section llb of the drill string, separated by additional sections of
the drill
string 11.
Other placements and applications for the amplification tool 10 are possible,
as will be evident to those skilled in the art. The tool may be integrated
with, or used
separately with, other downhole tools, for example other spring bias devices,
shock
tools, hammer devices, and water hammer devices. While the tool 10 is shown
and
described herein as being responsive to pressure pulses in the drilling fluid
from an
MWD device, it will be evident to those skilled in the art that other pulse
generating
devices, for example valves or throttling devices, might be used to generate
pressure pulses in the drilling fluid.
Turning to Fig. 4, the amplification tool 10 is shown to include a pressure-
containing housing 13 in several sections and a continuous internal
throughbore 15,
also in sections, for passage of the drilling fluid through the tool 10. Each
of the
sections of the housing 13 and the components forming the continuous
throughbore
15 are sealed together, for example with 0-ring seals 38 at threaded or other
connections, as is well known to those skilled in the art. A shock tool
component 12
is shown at a mandrel end portion 10a of the tool 10 (which is surface-facing
in Fig.
4). A pressure balance end portion 10b of the tool 10 is shown in Fig. 4 to be
drill
bit-facing. An amplification portion 10c is located between the end portions
10a and
10b. As noted above, this is only one exemplary application for the tool 10,
and it
will be evident that the tool 10 may be located differently, and may, for
example, be
flipped end for end, in other applications. The mandrel end portion 10a is
shown to
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include a box end component 10d, for threaded connection into the drill
string, while
the pressure balance end portion 10b is shown to include a pin end component
10e,
for threaded connection into the drill string, as is conventional.
The shock tool component 12 includes components commonly included in a
spring-biassed shock tool, in which springs are mounted between axially
aligned
telescoping parts (mandrel and spline) such that a force acting on a piston
connected to the mandrel separates the telescoping parts to axially extend the
telescoping parts and to impart axial movement in the drill string. As shown
in the
exemplary embodiment of Fig. 4, the shock tool component 12 is adapted to use
a
plurality of BelleviIleTM spring washers 14 to move a spring mandrel 16 within
a
spring housing 18 through a limited longitudinal distance "L", in response to
pressure
pulses moving in the drilling fluid in the internal throughbore 15 of the
tool. The
spring mandrel 16 is threaded at one end 16a to a spline mandrel 22. The
spline
mandrel 22 is housed within a mandrel housing 24 and a spline housing 26. The
spline mandrel 22 is sealed within the housings 24, 26 for movement with the
spring
mandrel 16. A plurality of spline keys 28, as better shown in the cross
sectional Fig.
5, prevent rotation of the spline mandrel 22 within the mandrel and spline
housings
24, 26. The opposite end 16b of the spring mandrel 16 is threaded to a shock
tool
piston 32, held within a shock tool piston housing 34. Each of the spline
mandrel,
spring mandrel and shock tool piston 22, 16, 32 are threadedly connected
together
and are hollow to provide the continuous throughbore 15 for a continuous fluid
passage for the drilling fluid pumped being from the surface. Each of the
mandrel
housing, spline housing, spring housing and shock tool piston housing 24, 26,
18, 34
are pressure-containing housings with seals (see piston seals 36, rod seals
37, 0-
ring seals 38 and wiper seal 40) between the housings and the mandrels/shock
piston. Guide or wear rings 42 may be included between the housings and the
mandrels/shock pistons for smooth longitudinal movement of the mandrels 22, 16
and shock piston 32 within the housings 24, 26, 18, 34.
The shock tool annular spaces 43 between the mandrels/shock piston 22, 16,
32 and the housings 24, 26, 18, 34 are oil-filled through ports 44, and closed
off with
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oribital oil plugs 45. The path of the oil-filled annular spaces 43, ports 44,
and
channels 44a communicating between the components of the shock tool 12 are
best
seen in Fig. 7, wherein the oil-filled annular spaces 43 are shown in white
(no
shading, marked 142). The spring washers 14 are spaced apart and held within
the
spring annulus 46 between the spring mandrel 16 and the spring housing 18 by a
spring sleeve 48 at one end 50, a spacer 52 at the other end 54 and a guide
washer
56 and guide ring 42 intermediate the ends 50, 54. The shock tool piston 32
includes a piston face 60. A shock tool piston chamber 62 is located on one
side of
the piston face 60 (downhole-facing in Fig. 4). The shock tool piston chamber
62 is
in fluid communication with the drilling fluid through ports 64 opening into
the
throughbore 15 of the shock tool piston 32. In this manner, the shock tool
piston 32
is able to transmit pressure pulses within the drilling fluid to the spring
mandrel 16
and thus to the spline mandrel 22 for limited longitudinal axial movement
(distance
12).
The longitudinal travel of the mandrels/spring piston "L" is set by the
spacing
of of shoulders S1, S2 formed in the inner wall of the spline housing 26, and
shoulders S3, S4 formed in the spring sleeve 48. The shoulders S1, S2
determine
the weight-on-bit (WOB) travel of the spline mandrel in the downhole direction
of
travel, while the shoulders S3, S4 determine the limited longitudinal movement
of
the amplification tool 10 in the opposite direction. This distance "L", for
example
1.125 inches, is the amount of oscillating movement that the shock tool
components
can make as the mandrels/shock tool piston 22, 16, 32 expand and retract
within the
housings 24, 26, 18, 34 to impart an axially amplified force on the drill
string 11. A
small preload on the spring washers 14 is typically set. This preload ensures
the
spring washers 14 are held tight in the spring housing 18, without rattling.
The amplification tool 10 is shown in Fig. 4 to include one or more, axially
aligned and threadedly connected pistons. In Fig. 4, three pistons 66, 68, 70
are
shown. In other embodiments, the tool may include at least one piston, for
example
two or more pistons, or for example from two to seven pistons. The number of
pistons may be varied according to the application for the tool, and the
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amount of amplification for the particular application. Since each of the
pistons may
be generally similar (except for the outermost pistons and their connections
to
components located above and below), for ease of description, like parts of
each
piston are labelled with the same reference numerals in the Figures. The
pistons
66, 68 and 70 are hollow to provide the continuous throughbore 15 for passage
of
the drilling fluid through the tool 10. The pistons 66, 68, 70 are generally
tubular
shaped with a sealing end 72, a mid-section 74 and a connecting end 76. For a
first
stage piston 66 and a second stage piston 68, the connecting ends 76 are
threaded
so that the pistons 66, 68 and 70 may be connected together for simultaneous
longitudinal movement. For third stage (last stage) piston 70, the connected
end 76
is not threaded, but is adapted for a sliding connection to components at the
pressure balance end 10b of the tool 10, as more fully described below.
The pistons 66, 68, 70 are held within a piston housing section 78, with each
piston housing section 78 being threaded together with each other, or with the
components of the housing 13 located above or below, to form the pressure-
containing housing 13 of the tool 10. The pistons 66, 68, 70 are each mounted
for
sealed movement within a pressure balance sleeve 80 for limited axial movement
through the longitudinal distance "L". The pressure balance sleeve 80 is
stationary
and is sealed within the housing section 78 (stepped shoulders 81 in the inner
bore
of the housing section 78 hold the pressure balance sleeve in place). The
pistons
66, 68, 70 include a piston face 82 (downhole-facing) at the sealing end 72 of
the
pistons. The piston face 82 is sealed within a pressure balance sleeve 80 such
that
a first fluid chamber 86 is formed on one side of the piston face 82 (i.e.,
the
downhole- or drill bit-facing side of the piston face 82 in Fig. 4) and a
second fluid
chamber 88 is formed on the other side of the piston face 82 (i.e, the mandrel-
or
surface-facing side of the piston face 82 in Fig. 4). The various seals for
the pistons
66, 68, 70, pressure balance sleeves 80 and housing sections 78 components are
shown as 0-rings 38, piston seals 36, along with guide rings 42, although
other
known seals and/or guides may be used.
The threaded end 96 of the piston housing section 78 for the third (last
stage)
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piston 70 is shown in Fig. 4 to be threaded to a pressure balance housing
section
100 of the pressure-containing housing 13, and the connected end 76 of the
third
piston 70 allows for telescoping, sliding movement within a stationary hollow
pressure balance tube 102 in a manner to provide the continuous throughbore 15
for
passage of the drilling fluid through the tool 10. The pressure balance
housing
section 100 and pressure balance tube 102 are part of a gas chamber component
104 provided at the pressure balance end 10b of the tool 10. The gas chamber
component 104 has the function of providing a pressurized fluid supply within
the
tool 10, separate from the drilling fluid. The pressurized fluid is generally
a non-
compressible fluid such as oil, which may thus be held at a set pressure
within the
housing 13 and thus within the tool 10. The gas chamber component 104 is more
fully described hereinbelow.
The first fluid chamber 86 for each piston face 82 communicates through
drilling fluid ports 105 formed in the wall of the mid-section 74 of the
pistons 66, 68,
70 through to the continuous throughbore 15 such that the first fluid chamber
86 is in
fluid communication with the drilling fluid. The second fluid chamber 88 on
the other
side of the each piston face 82 is in fluid communication with the pressurized
fluid
held at a set pressure set by the gas in the gas chamber component 104. The
set
pressure may be set at the surface by the drilling operator, before the tool
10 is run
in the drill string 11, to approximate a downhole pressure of the drilling
fluid at an
expected downhole location of the amplification tool 10, for example at the
location
as shown in Fig. 1. This set pressure is generally the pressure within the
piston
housing sections 78, and thus within the tool 10. As shown in Figs. 4 and 6,
the
pressure balance sleeves 80 include circumferentially spaced pressure balance
ports 106 and pressure balance channels 108 which allow the pressurized fluid
from
the gas chamber component 104 to travel through circumferentially spaced
piston
housing conduits 109 formed in the wall of each piston housing section 78 to
the
annular space 79 between the pressure balance sleeve 80 and the piston housing
section 78 and to fill the second fluid chamber 88 on the other side of each
piston
face 82. In this way, the pressures on either side of the piston face 82 can
be
generally balanced in a manner to allow the pistons 66, 68, 70 to amplify
pressure
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pulses in the drilling fluid, for example from the MWD device, and thus create
an
amplified force for the force responsive device (such as the shock tool
component
12). It should be understood that, the term "generally balanced", as used
herein and
in the claims to refer to the pressures on either side of the piston face 82,
does not
imply equal. Rather, a pressure difference across the piston faces will still
allow the
tool to work to generate an amplified force. For example, a pressure imbalance
of
about 500 psi may still generate an amplified force, depending on the size of
the
initial pressure pulse and the number of pistons. Thus, the term "generally
balanced" refers to a set pressure in the pressurized fluid which will
approximate the
downhole pressure of the drilling fluid at the tool location, but includes a
pressure
balance range sufficient to still generate an amplified force for the pressure
pulse
being received by the tool 10 with the number of pistons in the tool.
It will be understood that the porting, channels and conduits as described
above for the shock tool component 12 and for the amplification portion 10c of
the
tool 10, are provided and sized to reduce any dampening effect of fluid travel
within
the tool 10.
The piston face 82 of each piston 66, 68, 70 is shown in Fig. 4 to be stepped
such that the surface areas of piston face portion 82a and 82b (shown in Fig.
4 for
piston 66) are combined to form the total surface area of the piston face 82
that is
acted on by the drilling fluid, and thus the pressure pulses in the drilling
fluid.
The gas chamber component 104 of the tool 10 includes a pressure balance
housing 100 threaded at one end 110 to the housing section 78 of the third
(last
stage) piston 70 and threaded at the other end 112 to a charge sub 114. The
housing 100 and charge sub 114 form sections of the pressure-containing
housing
13 of the tool 10. The hollow pressure balance tube 102 extends through, and
seals
on, the pressure balance housing 100. The charge sub 114 is formed with a
central
bore 116 which communicates with the pressure balance tube 102, such that the
pressure balance tube 102 and the central bore 116 form the continuous
throughbore 15 for passage of the drilling fluid through the tool 10. A
pressure
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balanced annular piston 118 is sealed with piston seals 120 and guide rings 42
in
the annulus 124 formed between the pressure balance housing 100 and the
pressure balance tube 102. The pressurized fluid, such as pressurized oil, is
filled
on the side of the piston 118 facing the pistons 66, 68, 70 and a pressurized
gas
such as nitrogen is filled on the side of the piston 118 facing the charge sub
114. 0-
ring seals 38 are included between the housing section 78 for the third piston
70 and
the pressure balance housing 100 and the pressure balance tube 102, as well as
between the pressure balance housing 100 and the charge sub 114 and between
the pressure balance tube 102 and the charge sub 114.
To set the pressure within the gas chamber tool, a charging conduit 128 is
formed in the outer wall of the charge sub 114, to communicate through a high
pressure check valve 130 to the annulus 124 on the side of the piston 118
facing the
charge sub 114. The conduit 128 is sealed with an orbital plug 132. The
pressurized fluid, such as oil, is filled through level plug 134 on the piston-
facing side
of the annular piston 118, to provide pressurized fluid in the pressurized
fluid path
through to orbital plug 135. In the initial set-up, the pressure balance
piston 118 is
moved longitudinally within the annulus 124 to set the volume of the
pressurized
fluid needed to fill the path of the pressurized fluid through to the second
fluid
chamber for each piston 66, 68, 70. This volume will vary with the number of
pistons 66, 68, 70.
In Fig. 7, only the paths of the fluids/gases are marked. The path of the
drilling fluid is marked 136. The path of the pressurized fluid such as oil is
marked
138. The path of the pressurized gas is marked 140. The separate path of the
oil in
the shock tool 12 is marked 142 (no shading).
Other Exemplary Embodiments/Applications
As set out above, while the amplification tool 10 and method of drilling have
been described herein with an integral shock tool component 12 as a force
responsive device, and adapted to allow pressure pulses from an MWD device to
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CA 02874639 2014-12-11
act on the piston faces 82 of pistons 66, 68, 70, the tool 10 is not limited
to
applications with shock tools, or to using MWD pulses.
In other embodiments, the method and/or amplification tool 10 may be
modified to be used with other drilling tools, for example to provide an
amplified
force to drive a hammer or water hammer at the drill bit. In such
applications, the
tool 10 may be reversed in the direction of the piston movement to apply force
toward the drill bit. The tool 10 may be located proximate the drill bit in
such
applications.
In other embodiments, the method and/or tool 10 might be modified such that
the shock tool component or a spring bias device is provided separately from
the
tool to provide an amplified force in either direction in a drill string, for
example to
reduce frictional losses in the drill string.
In other embodiments, the method and/or tool 10 might be modified to include
a spring instead of a gas chamber to provide the set pressure on the
pressurized
fluid.
In other embodiments, the method and/or tool 10 might be modified to use
more than one amplification tool 10 in the drill string.
In still other embodiments, the method and/or tool 10 might include the
components of the pressure balance end portion 10b and the amplification
portion
10c, for producing an amplified force to a simple spring device in the drill
string for
producing amplified pressure pulses in the drilling fluid. When coupled with
an
MWD device, this embodiment of the tool 10 can produce an amplified MWD
pressure pulse in the drilling fluid for detection at the surface. It will be
appreciated
that a major advantage of the amplification tool 10 is that the amplified
pressure
pulse derived from the MWD pulse is generally of the same frequency as the MWD
pulse, so does not interfere with analysing the MWD pulse at the surface.
CA 02874639 2014-12-11
Example
It will now be apparent that the amplification tool 10 as described above
(AAPT tool) does not work using the annulus pressure from the borehole
(external
the drill string). A simple, non-limiting comparative example is provided to
highlight
the problem with using the annulus pressure and an internal tool pressure to
create
a pressure differential across piston faces, such as is shown in the prior art
devices
of US Patent 8,322,463 to Walter.
US Patent 8,322,463 - Prior Art Patent
In Walter's tool, one side of the pistons feels the internal bore pressure of
the
drilling mud (for example, 2000 psi) and the other side of the pistons feels
the
annulus borehole pressure external of the drill string, which is much lower
than the
pressure of the drilling mud (for example 1000 psi). Assuming a pulse pressure
of
300 psi is applied to a piston with a piston face area of 5.6in2, in one stage
of the
tool (i.e., one piston) the output force is (2000-1000)x5.6in2 = 5,600 lbs
(push force).
When the tool feels a pulse of 300 psi the output force is (2300-1000)x5.6in2=
7,280
lbs (push force). While there is no teaching in the patent, it is evident to
the inventor
of this application that, without a preload on the spring, some of the
available travel
in the shock tool will be used up or sacrificed in the initial push force.
Thus, for the
purposes of this comparative example calculation, the springs are assumed to
be
preloaded, for example by 5,600 lbs to isolate the pulse force and maintain
full
theoretical range of travel for the tool. With this preload, the tool
generates
7,280-5,600 = 1,680 lbs force output. Now, if a second piston is added to get
more
force, with 2 stages the output force is double, for example 11,200 and 14,560
lbs
push force. In that case, the springs would require an initial set preload of
11,200
lbs. The tool now generates 14,560-11,200 = 3,360 lbs force. With such a high
preload on the springs, this 3,360 lbs push translates into a very small
movement,
less than about 1/8". With three stages of a third piston, the preload on the
springs
is so high that the pulse force is not strong enough to move the springs, and
the tool
is not moving. Instead, the tool is dead in the borehole. This scenario
becomes
worse as the spread increases between the internal tool and annulus pressures,
16
CA 02874639 2014-12-11
which is likely to be the case.
ii) AAPT Tool Example
In contrast, the AAPT tool works using a charged gas pressure chamber at a
set pressure within the tool. One side of the piston feels the internal bore
pressure
of the drilling fluid (say 2000 psi) and the other side of the piston feels
the set charge
pressure, which is pre-set to approximate the downhole pressure of the
drilling fluid
at a downhole location of the AAPT tool, for example an estimated internal
bore
pressure might be 2000 psi. In one stage of the AAPT tool (one piston, with a
piston
surface area of 5.6in2) the output force is (2000-2000)x5.6in2= 0 lbs (at
rest, without
the pressure pulse). However, when the tool feels a pulse of about 300 psi,
for
example from the MWD device, the output force is (2300-2000)x5.6in2= 1,680
lbs.
The spring in the AAPT tool may be preloaded a little, as described above, to
hold
the spring washers tightly in the housing to avoid rattling. However, unlike
the
situation in the above-noted Walter tool, because the piston(s) of the AAPT
tool are
generally balanced with the pressurized fluid opposing the internal pressure
of the
drilling fluid, the springs of the AAPT tool do not need to be preloaded to
offset a
large pressure imbalance across the pistons. The AAPT tool generates 1,680 lbs
force minus the small spring preload. Adding subsequent stages (pistons)
multiplies
the pulse by the number of additional pistons, since the internal bore
pressure is
balanced on either side of the pistons. Thus, adding a second piston (two
stages),
produces a force of 3,360 lbs, and a third piston (three stages) produces a
force of
5,040 lbs. Setting the charge pressure for the pressurized fluid to
approximate the
actual bore pressure where the tool is located downhole provides the strongest
output force. The output force diminishes as the span increases between the
set
charge pressure and bore pressure. The AAPT tool is charged at the surface by
the
drilling operator, prior to use, with the predicted downhole pressure. The
internal
bore pressure during testing at the surface is substantially less than what
the internal
bore pressure is when the AAPT tool is downhole.
As used herein and in the claims, the word "comprising" is used in its
non-limiting sense to mean that items following the word in the sentence are
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CA 02874639 2014-12-11
included and that items not specifically mentioned are not excluded. The use
of the
indefinite article "a" in the claims before an element means that one of the
elements
is specified, but does not specifically exclude others of the elements being
present,
unless the context clearly requires that there be one and only one of the
elements.
All references mentioned in this specification are indicative of the level of
skill
in the art of this invention. All references are herein incorporated by
reference in
their entirety to the same extent as if each reference was specifically and
individually
indicated to be incorporated by reference. However, if any inconsistency
arises
between a cited reference and the present disclosure, the present disclosure
takes
precedence. Some references provided herein are incorporated by reference
herein
to provide details concerning the state of the art prior to the filing of this
application,
other references may be cited to provide additional or alternative device
elements,
additional or alternative materials, additional or alternative methods of
analysis or
application of the invention.
The terms and expressions used are, unless otherwise defined herein, used
as terms of description and not limitation. There is no intention, in using
such terms
and expressions, of excluding equivalents of the features illustrated and
described, it
being recognized that the scope of the invention is defined and limited only
by the
claims which follow. Although the description herein contains many specifics,
these
should not be construed as limiting the scope of the invention, but as merely
providing illustrations of some of the embodiments of the invention.
One of ordinary skill in the art will appreciate that elements and materials
other than those specifically exemplified can be employed in the practice of
the
invention without resort to undue experimentation. All art-known functional
equivalents, of any such elements and materials are intended to be included in
this
invention. The invention illustratively described herein suitably may be
practised in
the absence of any element or elements, limitation or limitations which is not
specifically disclosed herein.
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