Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR CONTROLLING A DRILLING SYSTEM FOR
DRILLING A BOREHOLE IN AN EARTH FORMATION
BACKGROUND OF THE INVENTION
[0001] This disclosure relates in general to a method and a system for
controlling a
drilling system for drilling a borehole in an earth formation. More
specifically, but
not by way of limitation, in one embodiment of the present invention a system
and
method is provided for controlling interactions between the drilling system
for drilling
the borehole and an inner surface of the borehole being drilled by the
drilling system
to provide for steering the drilling system to directionally drill a borehole
through the
earth formation. In certain aspects of the present invention, the drilling
system may be
controlled to provide that the borehole reaches a target objective.
[0002] In another embodiment of the present invention, data regarding the
functioning of the drilling system as it drills the borehole may be sensed and
interactions between the drilling system for drilling the borehole and the
inner surface
of the borehole may be controlled in response to the sensed data to provide
for
controlling operation of the drilling system. In certain aspects, interactions
between
the drilling system and the inner surface may be controlled to provide for
controlling
the interaction of the drill bit with the earth formation.
[0003] In many industries, it is often desirable to directionally drill a
borehole
through an earth formation or core a hole in sub-surface formations in order
that the
borehole and/or coring may circumvent and/or pass through deposits and/or
reservoirs
in the formation to reach a predefined objective in the formation and/or the
like.
When drilling or coring holes in sub-surface formations, it is sometimes
desirable to
be able to vary and control the direction of drilling, for example to direct
the borehole
towards a desired target, or control the direction horizontally within an area
containing hydrocarbons once the target has been reached. It may also be
desirable to
correct for deviations from the desired direction when drilling a straight
hole, or to
control the direction of the hole to avoid obstacles.
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[0004] In the hydrocarbon industry for example, a borehole may be drilled so
as to
intercept a particular subterranean-formation at a particular location. In
some drilling
processes, to drill the desired borehole, a drilling trajectory through the
earth
formation may be pre-planned and the drilling system may be controlled to
conform
to the trajectory. In other processes, or in combination with the previous
process, an
objective for the borehole may be determined and the progress of the borehole
being
drilled in the earth formation may be monitored during the drilling process
and steps
may be taken to ensure the borehole attains the target objective. Furthermore,
operation of the drill system may be controlled to provide for economic
drilling,
which may comprise drilling so as to bore through the earth formation as
quickly as
possible, drilling so as to reduce bit wear, drilling so as to achieve optimal
drilling
through the earth formation and optimal bit wear and/or the like.
[0005] One aspect of drilling is called "directional drilling." Directional
drilling is
the intentional deviation of the borehole/wellbore from the path it would
naturally
take. In other words, directional drilling is the steering of the drill string
so that it
travels in a desired direction.
[0006] Directional drilling is advantageous in offshore drilling because it
enables
many wells to be drilled from a single platform. Directional drilling also
enables
horizontal drilling through a reservoir. Horizontal drilling enables a longer
length of
the wellbore to traverse the reservoir, which increases the production rate
from the
well.
[0007] A directional drilling system may also be used in vertical drilling
operation
as well. Often the drill bit will veer off of a planned drilling trajectory
because of the
unpredictable nature of the formations being penetrated or the varying forces
that the
drill bit experiences. When such a deviation occurs, a directional drilling
system may
be used to put the drill bit back on course.
[0008] The monitoring process for directional drilling of the borehole may
include
determining the location of the drill bit in the earth formation, determining
an
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orientation of the drill bit in the earth formation, determining a weight-on-
bit of the
drilling system, determining a speed of drilling through the earth formation,
determining properties of the earth formation being drilled, determining
properties of
a subterranean formation surrounding the drill bit, looking forward to
ascertain
properties of formations ahead of the drill bit, seismic analysis of the earth
formation,
determining properties of reservoirs etc. proximal to the drill bit, measuring
pressure,
temperature and/or the like in the borehole and/or surrounding the borehole
and/or the
like. In any process for directional drilling of a borehole, whether following
a pre-
planned trajectory, monitoring the drilling process and/or the drilling
conditions
and/or the like, it is necessary to be able to steer the drilling system.
[0009] Forces which act on the drill bit during a drilling operation include
gravity,
torque developed by the bit, the end load applied to the bit, and the bending
moment
from the drill assembly. These forces together with the type of strata being
drilled and
the inclination of the strata to the bore hole may create a complex
interactive system
of forces during the drilling process.
[0010] The drilling system may comprise a "rotary drilling" system in which a
downhole assembly, including a drill bit, is connected to a drill-string that
may be
driven/rotated from the drilling platform. In a rotary drilling system
directional
drilling of the borehole may be provided by varying factors such as weight-on-
bit, the
2 0 rotation speed, etc.
100111 With regards to rotary drilling, known methods of directional drilling
include the use of a rotary steerable system ("RSS"). In an RSS, the drill
string is
rotated from the surface, and downhole devices cause the drill bit to drill in
the
desired direction. Rotating the drill string greatly reduces the occurrences
of the drill
string getting hung up or stuck during drilling.
100121 Rotary steerable drilling systems for drilling deviated boreholes into
the
earth may be generally classified as either "point-the-bit" systems or "push-
the-bit"
systems. In the point-the-bit system, the axis of rotation of the drill bit is
deviated
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from the local axis of the bottomhole assembly ("BHA") in the general
direction of
the new hole. The hole is propagated in accordance with the customary three-
point
geometry defined by upper and lower stabilizer touch points and the drill bit.
The
angle of deviation of the drill bit axis coupled with a finite distance
between the drill
bit and lower stabilizer results in the non-collinear condition required for a
curve to be
generated. There are many ways in which this may be achieved including a fixed
bend at a point in the bottomhole assembly close to the lower stabilizer or a
flexure of
the drill bit drive shaft distributed between the upper and lower stabilizer.
[0013) Pointing the bit may comprise using a downholc motor to rotate the
drill bit,
the motor and drill bit being mounted upon a drill string that includes an
angled bend.
In such a system, the drill bit may be coupled to the motor by a hinge-type or
tilted
mechanism/joint, a bent sub or the like, wherein the drill bit may be inclined
relative
to the motor. When variation of the direction of drilling is required, the
rotation of
the drill-string may be stopped and the bit may be positioned in the borehole,
using
the downhole motor, in the required direction and rotation of the drill bit
may start the
drilling in the desired direction. In such an arrangement, the direction of
drilling is
dependent upon the angular position of the drill string.
[0014) In its idealized form, in a pointing the bit system, the drill bit is
not required
to cut sideways because the bit axis is continually rotated in the direction
of the
curved hole. Examples of point-the-bit type rotary steerable systems, and how
they
operate are described in U.S. Patent Application Publication Nos.
2002/0011359;
2001/0052428 and U.S. Patent Nos. 6,394,193; 6,364,034; 6,244,361; 6,158,529;
6,092,610; and 5,113,953.
[00151 Push the bit systems and methods make use of application of force
against
the borehole wall to bend the drill-string and/or force the drill bit to drill
in a preferred
direction. In a push-the-bit rotary steerable system, the requisite non-
collinear
condition is achieved by causing a mechanism to apply a force or create
displacement
in a direction that is preferentially orientated with respect to the direction
of hole
propagation. There are many ways in which this may be achieved, including non-
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rotating (with respect to the hole), displacement based approaches and
eccentric
actuators that apply force to the drill bit in the desired steering direction.
Again,
steering is achieved by creating non co-linearity between the drill bit and at
least two
other touch points. In its idealized form the drill bit is required to cut
side ways in
order to generate a curved hole. Examples of push-the-bit type rotary
steerable
systems, and how they operate are described in U.S. Patent Nos. 5,265,682;
5,553,678; 5,803,185; 6,089,332; 5,695,015; 5,685,379; 5,706,905; 5,553,679;
5,673,763; 5,520,255; 5,603,385; 5,582,259; 5,778,992; 5,971,085.
10, [0016] Known forms of RSS are provided with a "counter rotating" mechanism
which rotates in the opposite direction of the drill string rotation.
Typically, the
counter rotation occurs at the same speed as the drill string rotation so that
the counter
rotating section maintains the same angular position relative to the inside of
the
borehole. Because the counter rotating section does not rotate with respect to
the
borehole, it is often called "geostationary" by those skilled in the art. In
this
disclosure, no distinction is made between the terms "counter rotating" and
"geo-
stationary."
[0017] A push-the-bit system typically uses either an internal or an external
counter-rotation stabilizer. The counter-rotation stabilizer remains at a
fixed angle (or
geo-stationary) with respect to the borehole wall. When the borehole is to be
deviated, an actuator presses a pad against the borehole wall in the opposite
direction
from the desired deviation. The result is that the drill bit is pushed in the
desired
direction.
[0018] The force generated by the actuators/pads is balanced by the force to
bend
the bottomhole assembly, and the force is reacted through the actuators/pads
on the
opposite side of the bottomhole assembly and the reaction force acts on the
cutters of
the drill bit, thus steering the hole. In some situations, the force from the
pads/actuators may be large enough to erode the formation where the system is
applied.
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[0019] For example, the Schlumberger Powerdrive system uses three pads
arranged
around a section of the bottomhole assembly to be synchronously deployed from
the
bottomhole assembly to push the bit in a direction and steer the borehole
being
drilled. In the system, the pads are mounted close, in a range of 1 ¨4 ft
behind the bit
and are powered/actuated by a stream of mud taken from the circulation fluid.
In
other systems, the weight-on-bit provided by the drilling system or a wedge or
the like
may be used to orient the drilling system in the borehole.
[0020] While system and methods for applying a force against the borehole wall
and using reaction forces to push the drill bit in a certain direction or
displacement of
the bit to drill in a desired direction may be used with drilling systems
including a
rotary drilling system, the systems and methods may have disadvantages. For
example such systems and methods may require application of large forces on
the
borehole wall to bend the drill-string and/or orient the drill bit in the
borehole; such
forces may be of the order of 5 kN or more, that may require large/complicated
downhole motors or the like to be generated. Additionally, many systems and
methods may use repeatedly thrusting of pads/actuator outwards into the
borehole
wall as the bottomhole assembly rotates to generate the reaction forces to
push the
drill bit, which may require complex/expensive/high maintenance synchronizing
systems, complex control systems and/or the like.
SUMMARY OF THE INVENTION
[0021] This disclosure relates in general to a method and system for
controlling a
drilling system configured for drilling or coring a borehole through a
subterranean
formation. More specifically, but not by way of limitation, embodiments of the
present invention provide for using drilling noise, i.e. the unsteady motion
of the
drilling system in the borehole during the drilling process and interactions
between
the drilling system and an inner surface of the borehole resulting from the
unsteady
motion of the drilling system to control the drilling system and/or the
drilling process.
[0022] As such, embodiments of the present invention provide for controlling
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repeated interactions between the drilling system and the inner surface of the
borehole
during the drilling process and using the control of the repeated interactions
between
the drilling system and the inner surface to control operation/functioning of
the
drilling system. In some embodiments, the repeated interactions between one or
more
sections of the drilling system and the inner surface of the borehole may be
controlled
to provide for steering the drilling system to directionally drill the
borehole. In other
embodiments, the repeated interactions between one or more sections of the
drilling
system and the inner surface of the borehole may be controlled to provide for
controlling operation of the drilling system, such as controlling operation of
the drill
bit during the drilling process.
[0023] As such, in one embodiment of the present invention, a method for
steering
a drilling system configured for drilling a borehole in an earth formation is
provided,
the method comprising:
controlling dynamic interactions between a section of the drilling
system and an inner surface of said borehole; and
using the controlled dynamic interactions between the section of the
drilling system and the inner surface of said borehole to control the drilling
system.
[0024] In certain aspects, the step of controlling dynamic interactions
between a
section of the drilling system and an inner surface of said borehole comprises
providing that the dynamic interactions between the section of the drilling
system and
the inner wall are non-uniform. Moreover, the step of controlling dynamic
interactions between a section of the drilling system and an inner surface of
said
borehole may comprise providing that the interactions between the section of
the
drilling system and the inner surface vary circumferentially around the
section of the
drilling system.
[0025] In rotary drilling systems, the section of the drilling system
providing for the
control of the dynamic interactions may be maintained geostationary in the
borehole
during operation of the drilling system. In certain embodiments, the dynamic
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interactions may be controlled so as to provide for steering the drilling
system. In
other embodiments, the dynamic interactions may be controlled so as to provide
for
controlling the drill bit.
[0026] In some embodiments of the present invention, controlling dynamic
interaction between at least a section of the drilling system and the inner
surface of
said borehole may comprise coupling a contact element with the drilling system
and
using the contact element to control the dynamic interaction. In a rotary
drilling
system the contact element may be held geostationary in the borehole during
operation of the drilling system.
[0027] In certain aspects of the present invention, the contact element is
configured
to produce a non-uniform dynamic interaction with the inner surface. In such
aspects,
the contact element may be asymmetrically shaped, may be configured to have a
non-
uniform compliance, may comprise a cylinder that is eccentrically coupled with
the
bottomhole assembly, may comprise an element with a non-uniform weight
distribution and/or the like.
[0028] In some embodiments, the contact element may comprise an extendable
member that may be extended outwards from the drilling system towards and/or
into
contact with the inner surface. The extendable element may be used to apply a
force
to the inner surface to control the dynamic interactions. The force applied to
the inner
surface may be less than 1 IN.
[0029] In certain aspects, the contact element may be coupled with the
drilling
system so as to provide that the contact element is disposed within a cutting
silhouette
of the drill bit. In other aspects, the contact element may be coupled with
the drilling
system so as to provide that at least a portion of the contact element is
disposed
outside the cutting silhouette of the drill bit.
[0030] In some embodiments of the present invention, a driver may be used to
alter/control the dynamic motion of the drilling system during a drilling
procedure. In
some embodiments of the present invention, a processor may be used to manage
the
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system for controlling the dynamic interactions between the drilling system
and the
inner surface. Managing the system for controlling the dynamic interactions
between
the drilling system and the inner surface may comprise positioning the system
on the
drilling system and/or moving the system on the drilling system. In certain
aspects
the managing processor may receive data from sensors regarding the drilling
process,
operation of the drilling system and/or components of the drilling system,
positions of
the drilling system and/or components of the drilling system, location of an
objective
for the borehole in the earth formation, conditions in the borehole,
properties of the
earth formation and/or parts of the earth formation in the process of being
drilled,
properties of the dynamic motion of the drilling system and/or different
sections of
the drilling system and/or the like.
[0031] In some embodiments of the present invention, control of the dynamic
interactions between the drilling system and the inner surface of the borehole
being
drilled may be provided by altering a profile of the inner-wall of the
borehole being
drilled. In certain aspects, a device such as an asymmetric drilling bit, a
secondary
drilling bit, an extendable element that extends from the drilling system to
the inner-
wall, an electro-pulse drill bit, a jetting device and/or the like may be
controlled to
provide that the inner-wall has a non-uniform profile so as to provide for
controlling
the dynamic interactions between the drilling system and the inner-wall.
[0032] In embodiments of the present invention, the system or method for
controlling the dynamic interactions between the drilling system and the inner
surface
of the borehole being drilled may be controlled in real-time to provide for
real-time
control of the drilling system. The configurations of the dynamic interaction
controller may be determined theoretically, experimentally, by modelling of
the
dynamic interactions, from experience with previous drilling processes and/or
the
like. In certain aspects, the dynamic interaction controller may comprise a
contact
element positioned less than 10 feet from the drill bit, may comprise a
contact element
disposed with an outer-surface less than millimetres inside the drilling
silhouette of
the drill bit, may comprise a contact element disposed with an outer-surface
that
9
=
81696607
extends, at least in part, of the order of millimetres outside the drilling
silhouette of the drill
bit.
[0032a] In some embodiments, there is provided a method for using dynamic
motion of a
drilling system in a borehole being drilled or cored in an earth formation by
the drilling system,
the drilling system comprising a drill bit and a drill-string, to control the
drilling system,
comprising: providing a section of the drilling system to control dynamic
interactions between
the drilling system and an inner surface of said borehole, wherein: the
section of the drilling
system is configured to provide that interactions between the section of the
drilling system and
the inner surface resulting from dynamic motion of the drilling system in the
borehole during
the drilling process vary circumferentially around the section of the drilling
system; and the
section of the drilling system is configured to provide that the interactions
between the section
of the drilling system and the inner surface are generated by dynamic motion
of the drilling
system in the borehole; maintaining the section of the drilling system
geostationary in the
borehole during the drilling process; and using the controlled dynamic
interactions between the
section of the drilling system and the inner surface of said borehole to steer
the drilling system.
[0032b] In some embodiments, there is provided a system for controlling a
drilling system for
drilling or coring a borehole in an earth formation, comprising: the drilling
system, wherein the
drilling system comprises a drill string, a bottomhole assembly and a drill
bit, and wherein the
borehole drilled by the drilling system is defined by an inner surface
comprising an inner-wall
of the borehole and a bottom of the borehole; and an interaction element
coupled around the
drilling system and configured to control dynamic interactions between the
drilling system and
the inner surface, wherein: the interaction element is configured to remain
geostationary on the
drilling system during the drilling process and is configured to provide that
interactions between
the interaction element and the inner surface resulting from dynamic motion of
the drilling
system in the borehole during the drilling process vary circumferentially
around the interaction
element; the interaction element is configured to provide that the
interactions between the
interaction element and the inner surface are generated by dynamic motion of
the drilling
system in the borehole; and the interaction element is configured to control
the dynamic
interactions between the drilling system and the inner surface to steer the
drilling system in a
direction.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0033] In the figures, similar components and/or features may have the same
reference label.
Further, various components of the same type may be distinguished by following
the
reference label by a dash and a second label that distinguishes among the
similar components.
If only the first reference label is used in the specification, the
description is applicable to any
one of the similar components having the same first reference label
irrespective of the second
reference label.
[0034] The invention will be better understood in the light of the following
description of
non-limiting and illustrative embodiments, given with reference to the
accompanying
drawings, in which:
[0035] Fig. 1 is a schematic-type illustration of a system for drilling a
borehole;
[0036] Fig. 2A is a schematic-type illustration of a system for steering a
drilling system for
drilling a borehole, in accordance with an embodiment of the present
invention;
[0037] Fig. 2B is a cross-sectional view through a compliant system for use in
the system for
steering the drilling system for drilling the borehole of Fig. 2A, in
accordance with an
embodiment of the present invention;
[0038] Figs. 3A-C are schematic-type illustrations of a cam control system for
steering a
drilling system, in accordance with an embodiment of the present invention;
[0039] Figs. 4A-C are schematic-type illustration of active gauge pad systems
for steering a
drilling system configured for drilling a borehole, in accordance with an
embodiment of the
present invention;
[0040] Fig. 5 provides a schematic-type illustration of a vibration
application
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system for steering a drilling system to directionally drill a borehole, in
accordance
with an embodiment of the present invention;
[0041] Figs. 6A and 6B illustrate systems for selectively characterizing an
inner
surface of a borehole for steering a drilling assembly to directionally drill
the
borehole, in accordance with an embodiment of the present invention;
[0042] Fig. 7A is a flow-type schematic of a method for steering a drilling
system
to directionally drill a borehole, in accordance with an embodiment of the
present
invention; and
[0043] Fig. 7B is a flow-type schematic of a method for controlling a drilling
system for drilling a borehole in an earth formation, in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0044] The ensuing description provides exemplary embodiments only, and is not
intended to limit the scope, applicability or configuration of the disclosure.
Rather,
the ensuing description of the exemplary embodiments will provide those
skilled in
the art with an enabling description for implementing one or more exemplary
embodiments. Various changes may be made in the function and arrangement of
elements of the specification without departing from the spirit and scope of
the
invention as set forth in the appended claims.
[0045] Specific details are given in the following description to provide a
thorough
understanding of the embodiments. However, it will be understood by one of
ordinary skill in the art that the embodiments may be practiced without these
specific
details. For example, systems, structures, and other components may be shown
as
components in block diagram form in order not to obscure the embodiments in
unnecessary detail. In other instances, well-known processes, techniques, and
other
methods may be shown without unnecessary detail in order to avoid obscuring
the
embodiments.
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[0046] Also, it is noted that individual embodiments may be described as a
process
which is depicted as a flowchart, a flow diagram, a structure diagram, or a
block
diagram. Although a flowchart may describe the operations as a sequential
process,
many of the operations can be performed in parallel or concurrently. In
addition, the
order of the operations may be re-arranged. Furthermore, any one or more
operations
may not occur in some embodiments. A process is terminated when its operations
are
completed, but could have additional steps not included in a figure. A process
may
correspond to a method, a procedure, etc.
[0047] This disclosure relates in general to a method and a system for
controlling a
drilling system for drilling a borehole in an earth formation. More
specifically, but
not by way of limitation, embodiments of the present invention provide for
using the
heretofore unappreciated and uninvestigated noise of the drilling process ¨
the
unsteady/transient motion of the drilling system in the borehole during the
drilling
process and the interactions between the drilling system and the borehole
resulting
from the unsteady/transient motion of the drilling system ¨ to control the
drilling
system and/or the drilling process.
[0048] In one embodiment of the present invention a system and method is
provided for controlling interactions between the drilling system for drilling
the
borehole and an inner surface of the borehole being drilled, as a result of
unsteady/transient motion of the drilling system during the drilling process,
to provide
for steering the drilling system to directionally drill a borehole through the
earth
formation. In certain aspects of the present invention, the drilling system
may be
controlled to provide that the borehole reaches a target objective or drills
through a
target objective. In another embodiment of the present invention, data
regarding the
functioning of the drilling system may be sensed and interactions between the
drilling
system for drilling the borehole and an inner surface of the borehole may be
controlled in response to the sensed data to control the drilling system, i.e.
the
interaction between the drill bit and the earth formation etc., as the
borehole is being
drilled.
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[0049] Fig. 1 is a schematic-type illustration of a system for drilling a
borehole. As
depicted, a drill-string 10 may comprise a connector system 12 and a
bottomhole
assembly 17 and may be disposed in a borehole 27. The bottomhole assembly 17
may comprise a drill bit 20 along with various other components (not shown),
such as
a bit sub, a mud motor, stabilizers, drill collars, heavy-weight drillpipe,
jarring
devices ("jars"), crossovers for various thread forms and/or the like. The
bottomhole
assembly 17 may provide force for the drill bit 20 to break the rock ¨ which
force
may be provided by weight-on-bit or the like ¨ and the bottomhole assembly 17
may
be configured to survive a hostile mechanical environment of high
temperatures, high
pressures and/or corrosive chemicals. The bottomhole assembly 17 may include a
mud motor, directional drilling and measuring equipment, measurements-while-
drilling tools, logging-while-drilling tools and/or other specialized devices.
[0050] The drill collar may comprise component of a drill-string that may be
used
to provide weight-on-bit for drilling. As such, the drill collars may comprise
a thick-
walled heavy tubular component that may have a hollowed out center to provide
for
the passage of drilling fluids through the collar. The outside diameter of the
collar
may rounded to pass through the borehole 27 being drilled, and in some cases
may be
machined with helical grooves ("spiral collars"). The drill collar may
comprise
threaded connections, male on one end and female on the other, so that
multiple
collars may be screwed together along with other downhole tools to make the
bottomhole assembly 17.
[0051] Gravity acts on the large mass of the drill collar(s) to provide a
large
downward force that may be needed by the drill bit 20 to efficiently break
rock and
drill through the earth formation. To accurately control the amount of force
applied to
the drill bit 20, a driller may carefully monitors the surface weight measured
while the
drill bit 20 is just off a bottom surface 41 of the borehole 27. Next, the
drill-string
(and the drill bit), may be slowly and carefully lowered until it touches the
bottom
surface 41. After that point, as the driller continues to lower the top of the
drill-string,
more and more weight is applied to the drill bit 20, and correspondingly less
weight is
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measured as hanging at the surface. If the surface measurement shows 20,000
pounds
[9080 kg] less weight than with the drill bit 20 off the bottom surface 41,
then there
should be 20,000 pounds force on the drill bit 20(in a vertical hole).
Downhole
sensors may be used to measure weight-on-bit more accurately and transmit the
data
to the surface.
[0052] The drill bit 20 may comprise one or more cutters 23. In operation, the
drill
bit 20 may be used to crush and/or cut rock at the bottom surface 41 so as to
drill the
borehole 27 through an earth formation 30. The drill bit 20 may be disposed on
the
bottom of the connector system 12 and the drill bit 20 may be changed when the
drill
bit 20 becomes dull or becomes incapable of making progress through the earth
formation 30. The drill bit 20 and the cutters 23 may be configured in
different
patterns to provide for different interactions with the earth formation and
generation
of different cutting patterns.
[0053] A conventional drill bit 20 operates by boring a hole slightly larger
than the
maximum outside diameter of the drill bit 20, the diameter/gauge of the
borehole 27
resulting from the reach of the cutters of the drill bit 20 and the
interaction of the
cutters with the rock being drilled. This drilling of the borehole 27 by the
drill bit 20
is achieved through a combination of the cutting action of the rotating drill
bit 20 and
the weight on the bit created as a result of the mass of the drill-string.
Generally, the
drilling system may include a gauge pad(s) which may extend outward to the
gauge of
the borehole 27. The gauge pads may comprise pads disposed on the bottomhole
assembly 17 or pads on the ends of some of the cutters of the drill bit 20
and/or the
like. The gauge pads may be used to stabilize the drill bit 20 in the borehole
27.
[0054] The connector system 12 may comprise pipe(s) ¨ such as drillpipe,
casing or
the like ¨ coiled tubing and/or the like. The pipe, coiled tubing or the like
of the
connector system 12 may be used to connect surface equipment 33 with the
bottomhole assembly 17 and the drill bit 20. The pipe, coiled tubing or the
like may
serve to pump drilling fluid to the drill bit 20 and to raise, lower and/or
rotate the
bottomhole assembly 17 and/or the drill bit 20.
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[0055] In some systems, the surface equipment 33 may comprise a topdrive,
rotary
table or the like (not shown) that may transfer rotational motion via the
pipe, coiled
tubing or the like to the drill bit 20. In some systems, the topdrive may
consist of one
or more motors ¨ electric, hydraulic and/or the like ¨ that may be connected
by
appropriate gearing to a short section of pipe called a quill. The quill may
in turn be
screwed into a saver sub or the drill-string itself. The topdrive may be
suspended
from a hook so that it is free to travel up and down a derrick. Pipe, coiled
tubing or
the like may be attached to the topdrive, rotary table or the like to transfer
rotary
motion down the borehole 27 to the drill bit 20.
[0056] In some drilling systems, drilling motors (not shown) may be disposed
down
the borehole 27. The drilling motors may comprise electric motors hydraulic-
type
motors and/or the like. The hydraulic-type motors may be driven by drilling
fluids or
other fluids pumped into the borehole 27 and/or circulated down the drill-
string. The
drilling motors may be used to power/rotate the drill bit 20 on the bottom
surface 41.
Use of drilling motors may provide for drilling the borehole 27 by rotating
the drill bit
without rotating the connector system 12, which may be held stationary during
the
drilling process.
[0057] The rotary motion of the drill bit 20 in the borehole 27, whether
produced by
a rotating drill pipe or a drilling motor, may provide for the crushing and/or
scraping
20 of rock at the bottom surface 41 to drill a new section of the borehole
27 in the earth
formation 30. Drilling fluids may be pumped down the borehole 27, through the
connector system 12 or the like, to provide energy to the drill bit 20 to
rotate the drill
bit 20 or the like to provide for drilling the borehole 27, for removing
cuttings from
the bottom surface 41 and/or the like.
[0058] In some drilling systems, hammer bits may be used pound the rock
vertically
in much the same fashion as a construction site air hammer. In other drilling
systems,
downhole motors may be used to operate the drill bit 20 or an associated drill
bit or to
provide energy to the drill bit 20 in addition to the energy provided by the
topdrive,
rotating table, drilling fluid and/or the like. Further, fluid jets,
electrical pulses and/or
CA 02694858 2010-01-27
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the like may also be used for drilling the borehole 27 or in combination with
the drill
bit 17 to drill the borehole 27.
[0059] In certain drilling processes, a bent pipe (not shown), known as a bent
sub,
or an inclination/hinge type mechanism may be disposed between the drill bit
20 and
the drilling motor. The bent sub or the like may be positioned in the borehole
to
provide that the drill bit 20 meets the face of the bottom surface 41 in such
a manner
as to provide for drilling of the borehole 27 in a particular direction,
angle, trajectory
and/or the like. The position of the bent sub may be adjusted in the borehole
without
a need to remove the connector system 12 and/or the bottomhole assembly 17
from
the borehole 27. However, directional drilling with a bent sub or the like may
be
complex because of forces in the borehole during the drilling process may make
the
bent sub difficult to manoeuvre and/or to effectively use to steer the
drilling system.
[0060] During a drilling operation, forces which may act on the drill bit 20
may
include gravity, torque developed by the drill bit 20, the end load applied to
the drill
bit 20, the bending moment from the drilling system including the connector
system
12 and/or the like. These forces together with the type of formation being
drilled and
the inclination of the drill bit 20 to the face of the bottom surface 41 of
the borehole
27 may create a complex interactive system of applied and reactionary forces.
Various systems have sought to provide for directional drilling by
controlling/applying these large forces to bend/shape/direct/push the drilling
system
and/or using these large forces and/or generating reaction forces from pushing
outward into the earth formation 30 to orient the drilling system in the
borehole
and/or relative to the bottom of the borehole 27 and/or to push the drill bit
20 so as to
steer the drilling system to directionally drill the borehole 27.
2 5 [0061] However, systems that use forces of the drilling process, for
example, the
end load, to steer the drilling system may be complicated and may not provide
for
accurate steering of the drilling system. Moreover, systems that steer the
drilling
system by moving/orienting the drilling system in the borehole and/or pushing
the
drill bit 20 may require generation dow-nhole of large forces of over 1 IN
and/or
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extension of elements from the drilling string a considerable distance beyond
the
cutting range of the drill bit ¨ i.e. far beyond the silhouette of the drill
bit, where the
silhouette may be defied by the outer cutting edge of the drill bit 20 ¨ in
order to
generate the reaction forces used to move/orient the drilling system and/or to
push the
drill bit 20. To push or move the drilling system in the borehole when the
drilling
system is rotating may also require synchronization of application of thrusts
by
actuators against the wall of the borehole 27. Such power generation, large
extension
beyond the cutting silhouette of the drill bit 20 and/or thrust
synchronization may
require large and/or expensive motors and/or operation and control of complex
synchronization systems and may complicate and/or increase the cost of the
drilling
machinery and the drilling process.
[0062] When drilling straight with a conventional drilling system, without
application of lateral forces or the like, Applicants have determined that the
drill bit
may, essentially, "vibrate" in the borehole 27, with the vibrations comprising
15 repeated movement of the drill bit 20 in directions other than a
drilling direction. The
terms vibration/oscillation are used herein to describe repeated movements of
the
drilling system during the drilling process that may be in a direction in the
borehole
other than the drilling direction and may be random in nature.
[0063] These vibrations/oscillations of the drilling system may be limited by
the
20 effects of the cutters impacting and extending the surface of the hole
and by the gauge
pads or the like hitting the wall of the borehole 27. In tests, it was found
that drilling
systems comprising drill bits without gauge pads produce a borehole with a
diameter
that was significantly larger than equivalent drilling systems comprising
drill bits and
gauge pads. Analyzing results from these tests, it was determined that during
operation of the drilling system, the bottomhole assembly 17 repeatedly
undergoes a
motion that involves movements away from a central axis of the bottomhole
assembly
17 and/or the drill bit 20, i.e. in a radial direction towards an inner-wall
40 of the
borehole 27, during the drilling process. Analysis of various drilling
operations found
that the gauge pads confine this radial motion of the bottomhole assembly 17
and/or
17
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the drill bit 20 so as to produce a borehole with a smaller bore. The gauge
pads of
conventional drilling systems being deployed to minimize/eliminate the
vibrational
motion of the drilling system to provide a smaller/regular bore.
[0064] From experimentation and analysis of drilling systems, Applicants found
that when the drill bit 20 drills into the earth formation 30 the cutters 23
may not
uniformly interact with the earth formation, for example chips may be
generated from
the earth formation 30, and, as a results, an unsteady motion, being a motion
in a
direction other then a longitudinal/forward motion of the bottomhole assembly
17
and/or the drill bit 20, may be generated in the bottomhole assembly 17 and/or
the
drill bit 20. Furthermore, Applicants have analyzed the operation of the
drilling
system and found that in addition to the unsteady/transient motion during
operation of
the drilling system, the application of force through the connector system 12
and the
drill bit 20 on to the earth formation 30 at the bottom of the borehole 27,
the
operation/rotation of the drill bit 20, the interaction of the drill bit 20
with the earth
formation 30 at the bottom of the borehole 27 (wherein the drill bit 20 may
slip, stall,
be knocked off of a drilling axis and/or the like), the rotational motion of
the
connector system 12, the operation of the topdrive, the operation of the
rotational
table, the operation of downhole motors, the operation of drilling aids such
as fluid
jets or electro-pulse systems, the bore of the borehole 20 ¨ which may be
irregular ¨
and and/or the like may generate motion in the bottomhole assembly 17 and/or
the
drill bit 20, and this motion may be a repeated, random, transient motion,
wherein at
least a component of the motion is not directed along an axis of the
bottomhole
assembly 17 and/or the drill bit 20 and is instead directed radially outward
from a
longitudinal-type axis at a center of the bottomhole assembly 17 and/or the
drill bit
20. As such, during a drilling operation, the kinetics of the bottomhole
assembly 17
may comprise both a longitudinal motion 37 in the drilling direction as well
as
transient radial motions 36A and 36 B, wherein the transient radial motions
36A and
36 B may comprise any motion of the bottomhole assembly 17 directed away from
a
central axis 39 of the borehole 27 being drilled and/or a central axis of the
bottomhole
assembly 17 and/or the drill bit 20.
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[0065] In general, it has been determined that the radial motion of the
bottomhole
assembly 17 during the drilling process may be random, transient in nature. As
such,
the bottomhole assembly 17 may undergo repeated random radial/unsteady motion
throughout the drilling process. For purposes of this specification, the
repeated
radial/unsteady motion of the bottomhole assembly 17 in the borehole 27 during
the
drilling process may be referred to as a dynamic motion, a radial motion, an
unsteady
motion, a radial-dynamic motion, a radial-unsteady motion, a dynamic or
unsteady
motion of the bottomhole assembly 17 and/or the drill-string, a repeated
radial
motion, a repeated dynamic motion, a repeated unsteady motion, a vibration, a
vibrational-type motion and/or the like.
[0066] The dynamic and/or unsteady motion of the bottomhole assembly 17 during
the drilling of the borehole 27 may cause/result in the bottomhole assembly 17
repeatedly coming into contact with and/or impacting an inner surface of the
borehole
27 throughout the drilling process. The inner surface of the borehole 27
comprising
the inner-wall 40 and the bottom surface 41 of the borehole 27, i.e. the
entire surface
of the earth formation 30 that defines the borehole 27. As discussed
previously, the
dynamic and/or unsteady motion of the bottomhole assembly 17 may be random in
nature and, as such, may cause/result in random intermittent/repeat contact
and/or
impact between the bottomhole assembly 17 and the inner surface during the
drilling
process.
[0067] The intermittent/repeated contact and/or impact between the drill-
string 10
and the inner surface during the drilling process resulting from dynamic
and/or
unsteady motion of the bottomhole assembly 17 may occur between one or more
sections/components of the drill-string 10 and the inner surface. For example,
the
sections/components may be a section of the drill-string 10 proximal to the
drill bit
20, the bottomhole assembly 17, a component of the bottomhole assemble 17,
such as
for example a drill collar, gauge pads, stabilizers, a motor housing, a
section of the
connector system 12 and/or the like. For purposes of this specification, the
interactions between the drill-string 10 and the inner surface caused
by/resulting from
19
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the dynamic and/or unsteady of the bottomhole assembly 17 may be referred to
as
dynamic interactions, unsteady interactions, radial motion interactions,
vibrational
interactions and/or the like.
[0068] Fig. 2A is a schematic-type illustration of a system for steering a
drilling
system for drilling a borehole, in accordance with an embodiment of the
present
invention. In Fig. 2A, the drilling system for drilling the borehole may
comprise the
bottomhole assembly 17, which may in-turn comprise the drill bit 20. The
drilling
system may provide for drilling a borehole 50 having an inner-wall 53 and a
drilling-
face 54.
[0069] During the drilling process, the drill bit 20 may contact the drilling-
face 54
and crush/displace rock at the drilling-face 54. In an embodiment of the
present
invention, a collar assembly 55 may be coupled with the bottomhole assembly 17
by a
compliant element 57. The collar assembly 55 may be a tube, cylinder,
framework or
the like. The collar assembly 55 may have an outer-surface 55A.
[0070] In certain aspects where the collar assembly 55 comprises a tube,
cylinder
and/or the like the outer-surface 55A may comprise the outer-surface of the
tube/cylinder and/or any pads, projections and/or the like coupled with the
outer
surface of the tube/cylinder. The collar assembly 55 may have roughened
sections,
coatings, projections on its outer surface to provide for increased frictional
contact
between an outer-surface of the collar assembly 55 and the inner-wall 53. The
collar
assembly 55 may comprise pads configured for contacting the inner-wall 53.
[0071] In certain aspects, the collar assembly 55 may comprise a gauge pad
system.
In aspects where the collar assembly 55 may comprise a series of elements,
such as
pads or the like, the outer-surface 55A may be defined by the outer-surfaces
of each
of the elements (pads) of the collar assembly 55. In an embodiment of the
invention,
the collar assembly 55 may be configured with the bottomhole assembly 17 to
provide
that the outer-surface 55A engages, contacts, interacts and/or the like with
the inner-
wall 53 and/or the drilling-face 54 during the drilling process as a result of
the
CA 02694858 2010-01-27
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dynamic motion of the bottomhole assembly 17. The design/profile/compliance of
the outer-surface 55A and/or the disposition of the outer-surface 55A relative
to a
cutting silhouette of the drill bit 20 may provide for controlling the dynamic
interaction between the outer-surface 55A and the inner-wall 53 and/or the
drilling-
face 54.
[0072] The compliant element 57 may comprise a structure that provides a
lateral
movement of the collar assembly 55 relative to the drill bit 20, where the
lateral
movement is a movement that is, at least in part directed, towards a center
axis 61 of
the bottomhole assembly 17. In certain aspects, the collar assembly 55 may
itself be
configured to be laterally compliant and may be coupled to the bottomhole
assembly
17 and/or may be a section of the bottomhole assembly 17, without the use of
the
compliant element 57.
[0073] In one embodiment of the present invention, the compliant element 57
may
not be uniformly-circumferentially compliant. In such an embodiment, one or
more
sections of the compliant element 57 disposed around the circumference of the
compliant element 57 may be more laterally compliant than other sections of
the
compliant element 57.
[0074] As observed previously, during the drilling process the bottomhole
assembly
17 or one or more sections of the bottomhole assembly 17 may undergo dynamic
interactions with the inner-wall 53 and/or the drilling-face 54. In an
embodiment of
the present invention, the collar assembly 55 may be configured to provide
that
dynamic motion of the bottomhole assembly 17 produces dynamic interactions
between the collar assembly 55 and the inner-wall 53 and/or the drilling-face
54
during the drilling process. In different aspects of the present invention,
different
relative outer-circumferences as between the collar assembly 55 and the
bottomhole
assembly 17 and/or the drill bit 20 may provide for different dynamic
interactions
between the collar assembly 55 and the inner-wall 53 and/or the drilling-face
54.
Modeling, theoretical analysis, experimentation and/or the like may be used to
select
differences in the relative outer-circumference between the collar assembly 55
and the
21
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bottomhole assembly 17 and/or the drill bit 20 for a particular drilling
process to
produce the wanted/desired dynamic interaction.
[0075] In an embodiment of the present invention in which the lateral
compliance
varies circumferentially around the compliant element 57, the dynamic
interaction
between the collar assembly 55 and the inner-wall 53 and/or the drilling-face
54 may
not be uniform circumferentially around the collar assembly 55. Merely by way
of
example, the compliant element 57 may comprise an area of decreased compliance
59B and an area of increased compliance 59A. In certain aspects, dynamic
interactions between the collar assembly 55 and the inner-wall 53 and/or the
drilling-
face 54 above a section of the compliant element 57 having increased lateral
compliance, i.e., the area of increased compliance 59A, may be damped in
comparison with dynamic interactions between the collar assembly 55 and the
inner-
wall 53 and/or the drilling-face 54 above a section of the compliant element
57 having
decreased lateral compliance, i.e., the area of decreased compliance 59B.
[0076] In some embodiments of the present invention, the collar assembly 55
may
be configured to provide that the collar assembly 55 is coupled with the
bottomhole to
provide that collar assembly 55 is disposed entirely within a cutting
silhouette 21 of
the drill bit 20, the cutting silhouette 21 comprising the edge-to-edge
cutting profile of
the drill bit 20. In other embodiments of the present invention, the collar
assembly
55, a section of the collar assembly 55, the outer-surface 55A and/or a
section of the
outer-surface 55A may extend beyond the cutting silhouette 21. Merely by way
of
example, the collar assembly 55 may be coupled with the bottomhole assembly 17
to
provide that the outer outer-surface 55A is of the order of 1-10s of
millimeters inside
the cutting silhouette 21. In other aspects, and again merely by way of
example, the
collar assembly 55 may be coupled with the bottomhole assembly 17 to provide
that
at least a portion of the outer-surface 55A extends in the range up to 10s of
or more
millimeters beyond the cutting silhouette 21.
[0077] Fig. 2B is a cross-sectional view through a compliant system for use in
the
system for steering the drilling system for drilling the borehole of Fig. 2A,
in
22
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accordance with an embodiment of the present invention. The compliant element
57
viewed in cross-section in Fig. 2B comprises the area of increased compliance
59A
and the area of decreased compliance 59B. In certain aspects, there may only
be a
single area in the compliant element 57 that has an increased or a decreased
compliance relative to the rest of and/or the other areas of the compliant
element 57.
In other aspects, the compliant element 57 may comprise any configuration of
compliance that produces non-uniform compliance around the compliant element
57
[0078] In Fig. 2B, the compliant element 57 is depicted as a solid cylindrical
structure, however, in different aspects of the present invention, the
compliant
element 57 may comprise other kinds of structures, such as a plurality of
compliant
elements arranged around the bottomhole assembly 17 and configured to couple
the
collar assembly 55 to the bottomhole assembly 17, an assembly of support
elements
capable of coupling the collar assembly 55 to the bottomhole assembly 17 and
providing lateral movement of the collar assembly 55 and/or the like. In other
aspects
of the present invention, the collar assembly 55 may itself be a structure
with integral
compliance, wherein the integral compliance may be selected to be non-uniform
around the collar assembly 55 and the collar assembly 55 may be coupled with
the
bottomhole assembly 17 or maybe a section of the bottomhole assembly 17
without
the compliant element 57. In still further aspects, the collar assembly 55 may
comprise a plurality of compliant elements, such as pads or the like, the
plurality of
compliant elements being coupled with the bottomhole assembly 17 and at least
one
of the compliant elements having a compliance that is different from the other
compliant elements.
[0079] In an embodiment of the present invention, the area of increased
compliance
59A may be disposed on the compliant element 57 so as to be diametrically
opposite
the area of decreased compliance 59B. In such an embodiment, the compliant
element 57 may prevent the collar assembly 55 from moving inwards at the
location
of the area of decreased compliance 59B (upwards as depicted in Fig. 2A), but
may
allow the collar assembly 55 to move inwards at the area of increased
compliance
23
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WO 2009/022115 PCT/GB2008/002706
59A (downward as depicted in Fig. 2A). As a result, the drill bit 20, as it
undergoes
dynamic motion during the drilling process, may interact with the inner-wall
53
and/or the drilling-face 54 and may tend to move, be oriented or
preferentially
crush/remove rock in the direction of and/or towards the area of increased
compliance
59A (upward as depicted in Fig. 2A). In such an embodiment, as a result of the
compliant element 57 having a selected non-uniform compliance, during the
drilling
process, as a result of the dynamic motion of the bottomhole assembly 17 and
the drill
bit 20, the compliant element 57 may provide for the drilling system to be
steered and
may provide for directional drilling of the borehole 50. The non-uniform
interaction
of the drilling system and the inner surface of the borehole 27 may also be
used to
control the interactions of, and as a result the functioning of, the drill bit
20 with the
earth formation, during the drilling process.
[0080] In embodiments of the present invention, any non-uniform
circumferential
compliance of the collar assembly 55 or the compliant element 57 may provide
for
steering/controlling the drilling system. The amount of differential
compliance in the
collar assembly 55 and/or the compliant element 57 and/or the profile of the
non-
uniform compliance of the collar assembly 55 and/or the compliant element 57
may
be selected to provide the desired steering response and/or control of the
drill bit 20.
Steering response and/or drill bit response of a drilling system for a
compliance
differential and/or a circumferential compliance profile may be determined
theoretically, modeled, deduced from experimentation, analyzed from previous
drilling processes and/or the like.
[0081] In embodiments of the present invention configured for use with a
drilling
system that does not involve the use of a rotating drill bit or where a
housing of the
drilling system, e.g., a housing of the bottomhole assembly is non-rotational,
the
collar assembly 55 and/or the compliant element 57 may be coupled with the
drilling
system or the housing. In such an embodiment, the drilling system may be
disposed
in the borehole with the area of increased compliance 59A disposed at a
specific
orientation to the drill bit 20 to provide for drilling of the borehole 50 in
the direction
24
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of the area of increased compliance 59A. To change the direction of drilling
by the
drilling system, the position of the area of increased compliance 59A may be
changed.
[0082] In some embodiments, a positioning device 65 ¨ which may comprise a
motor, a hydraulic actuator and/or the like ¨ may be used to rotate/align the
collar
assembly 55 and/or the compliant element 57 to provide for drilling of the
borehole
50 by the drilling system in a desired direction. The positioning device 65
may be in
communication with a processor 70. The processor 70 may control the
positioning
device 65 to provide for desired directional drilling. The processor 70 may
determine
a position of the collar assembly 55 and/or the compliant element 57 in the
borehole
50 from manual intervention, an end point objective for the borehole, a
desired
drilling trajectory, a desired drill bit response, a desired drill bit
interaction with the
earth formation, seismic data, input from sensors (not shown) ¨ which may
provide
data regarding the earth formation, conditions in the borehole 50, drilling
data (such
as weight on bit, drilling speed and/or the like) vibrational data of the
drilling system,
dynamic interaction data and/or the like ¨ data regarding the
location/orientation of
the drill bit in the earth formation, data regarding the trajectory/direction
of the
borehole and/or the like.
[0083] The processor 70 may be coupled with a display (not shown) to display
the
orientation/direction/location of the borehole 50, the drilling system, the
drill bit 20,
the collar assembly 55, the compliant element 57, the drilling speed, the
drilling
trajectory and/or the like. The display may be remote from the drilling
location and
supplied with data via a connection such as an Internet connection, web
connection,
telecommunication connection and/or the like, and may provide for remote
operation
of the drilling process. Data from the processor 70 may be stored in a memory
and/or
communicated to other processors and/or systems associated with the drilling
process.
[0084] In another embodiment of the present invention, the steering/drill bit
functionality control system may be configured for use with a rotary-type
drilling
system in which the drill bit 20 may be rotated during the drilling process
and, as
such, the drill bit 20 and/or the bottomhole assembly 17 may rotate in the
borehole 50.
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In such an embodiment, the collar assembly 55 and/or the compliant element 57
may
be configured so that motion of the collar assembly 55 and/or the compliant
element
57 is independent or at least partially independent of the rotational motion
of the drill
bit 20 and/or the bottomhole assembly 17. As such, the collar assembly 55 may
be
held geostationary in the borehole 50 during the drilling process.
[0085] In certain aspects, the collar assembly 55 and/or the compliant element
57
may be a passive system comprising one or more cylinders disposed around the
drilling system. The one or more cylinders may in some instances be disposed
around
the bottomhole assembly 17 of the drilling system. The one or more cylinders
may be
configured to rotate independently of the drilling system. In such aspects,
the one or
more cylinders may be configured to provide that friction between the one or
more
cylinders and the formation may fix, prevent rotational motion of, the one or
more
cylinders relative to the rotating drilling system. In certain aspects of the
present
invention, the one or more cylinders may be locked to the bottomhole assembly
when
there is no weight-on-bit, and hence no drilling of the borehole, and then
oriented and
unlocked from the bottomhole assembly when weight-on-bit is applied and
drilling
commences; the friction between the one or more cylinders and the inner
surface
maintaining the orientation of the one or more cylinders. In some aspects of
the
present invention, the one or more cylinders may be coupled with the
bottomhole
assembly 17 by a bearing or the like.
[0086] In some embodiments of the present invention, the positioning of the
one or
more cylinders may be provided, as in a non-rotational drilling system, by the
positioning device 65, which may rotate the one or more cylinders to change
the
location of an active area of the cylinder in the borehole 50 to change the
drilling
direction and/or the functioning of the drill bit 20. For example, the
compliant
element 57 may comprise a cylinder and maybe rotated around the bottomhole
assembly 17 to change a location of the area of increased compliance 59A
and/or the
area of decreased compliance 59B to change the drilling direction of the
drilling
system resulting from the dynamic interaction between the collar assembly 55
and the
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inner-wall 53. Alternatively, an active control may be used to maintain a
desired
orientation/position of the collar assembly 55 and/or the compliant element 57
with
respect to the bottomhole assembly 17 during the drilling process. In addition
this
type of device could be used in a motor assembly to replace the bent sub. This
could
bring benefits in terms of tripping the assembly into the hole through tubing
and
completion restrictions and when drilling straight in rotary mode.
[0087] Figs. 3A-C are schematic-type illustrations of a cam control system for
steering a drilling system, in accordance with an embodiment of the present
invention.
Fig. 3A illustrates the directional drilling system with the cam control
system, in
accordance with an embodiment of the present invention. In Fig 3A, a drilling
system
is drilling the borehole 50 through an earth formation. The drilling system
comprises
the bottomhole assembly 17 disposed at an end of the borehole 50 to be/being
drilled.
The bottomhole assembly 17 comprises the drill bit 20 that contacts the earth
formation and drills the borehole 50.
[0088] In an embodiment of the present invention, a gauge pad assembly 73 may
be
coupled with the bottomhole assembly 17 by a compliant coupler 76. The gauge
pad
assembly 73 may comprise a drill collar, a cylinder, non-cutting ends of one
or more
cutters of the drill but 20 and/or the like. Fig. 3B illustrates the gauge pad
assembly
73 in accordance with one aspect of the present invention. As depicted, the
gauge pad
assembly 73 comprises a cylinder 74A with a plurality of pads 74B disposed on
the
surface of the cylinder 74A. In some aspects, the plurality of pads 74B may
have
compliant properties while in other aspects the plurality of pads 74B may be
non-
compliant and may comprise a metal. In some embodiments of the present
invention,
the gauge pad assembly 73 may itself be compliant and the compliant gauge pad
assembly may be coupled with/ an element of the bottomhole assembly 17 without
the
compliant coupler 76.
[0089] In one embodiment of the present invention, a cam 79 may be coupled
with
the bottomhole assembly 17. The cam 79 may be moveable on the bottomhole
assembly 17. In an embodiment of the present invention, the cam 79 may
comprise
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an eccentric/non/symmetrical cylinder. The cam 79 may be moveable so as to
contact
the gauge pad assembly 73. The gauge pad assembly 73 may be configured to
contact
the inner-wall 53 and/or the drilling-face 54 during the process of drilling
the
borehole 50. The gauge pad assembly 73 may be directly coupled with the
-- bottomhole assembly 17, coupled to the bottomhole assembly 17 by a coupler
76 or
the like. The coupler 76 may comprise a compliant/elastic type of material
that may
allow for movement of the gauge pad assembly 73 relative to the bottomhole
assembly 17.
[0090] The cam 79 may be actuated by a controller 80. The controller 80 may
-- comprise a motor, hydraulic system and/or the like and may provide for
moving the
cam 79 and/or maintaining the cam 79 to be geostationary in the borehole 50
during
the drilling process. In some aspects, the cam 79 may comprise a cylinder with
an
outer surface 81 and an indent 82 in the outer surface 81. In such aspects,
during the
drilling process, the controller 80 may provide for moving the cam 79 to an
active
-- position wherein the outer surface 81 may be proximal to or in contact with
the gauge
pad assembly 73. In some embodiments of the present invention, there may not
be a
controller 80 and the cam 79 may, for example, be set to the active position
prior to
locating the bottomhole assembly 17 in the borehole 50.
[0091] In one embodiment of the present invention, the cam 79 may be used to
-- control the dynamic interactions between the gauge pad assembly 73 and the
inner-
wall 53 and/or the drilling-face 54 by providing that the properties of the
gauge pad
assembly 73 are non-uniform around the gauge pad assembly 73. In further
embodiments of the present invention, instead of using the cam 79 to change
the
properties, positioning and/or the like of the gauge pad assembly 73,
piezoelectric,
-- hydraulic and/or other mechanical actuators may be used to provide that the
gauge
pad assembly 73 has non-uniform properties that may and the non-uniform
properties
may be used to control the dynamic interactions between the gauge pad assembly
73
and the inner-wall 53 and/or the drilling-face 54.
[0092] In the active position, i.e., where the cam 79 is engaged with the
gauge pad
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assembly 73, movement of the gauge pad assembly 73 in a lateral direction,
i.e.
towards a central axis of the bottotnhole assembly 17 and/or the borehole 50
may be
resisted by the cam 79. In the active position, the indent 82 may be separated
from
the gauge pad assembly 73 by a spacing 83, where the spacing 83 is greater
than the
spacing between the gauge pad assembly 73 and the outer surface 81 at the
other
positions around the system. As such, a part of the gauge pad assembly 73
above the
indent 82 may have more freedom/ability to move laterally in comparison to the
other
sections of the gauge pad assembly 73 disposed above the outer surface 81.
Consequently, interactions between the gauge pad assembly 73 and the inner-
wall 53
and/or the drilling-face 54 during the drilling process will not be uniform
around the
gauge pad assembly 73.
100931 In certain aspects of the present invention, the cam 79 may be used to
control an offset of the gauge pad assembly 73, either to produce the offset
of the
gauge pad assembly 73 to steer the drilling system or to mitigate the offset
in the
gauge pad assembly 73 to provide for straight drilling. In embodiment for
controlling
operation of the drill bit 20 the cam 79 may be used to control an offset of
the gauge
pad assembly 73, either to produce the offset of the gauge pad assembly 73 to
produce
a certain behaviour of the drill bit 20 or to mitigate the offset in the gauge
pad
assembly 73 to different behaviour of the drill bit 20.
[0094] The cam 79 may comprise an eccentric cylinder. In operation, the cam 79
may be engaged with the gauge pad assembly 73 and may provide that at least a
section of the gauge pad assembly 73 may be over gauge with respect to the
drill bit
20. As a result, the gauge pad assembly 73 being over-gauged may interact with
the
inner-surface of the borehole 50 in a non-uniform manner. The cam 79 may have
a
section with a steadily varying outer-diameter to provide for steadily varying
the
gauge/diameter of at least a section of the gauge pad assembly 73 during a
drilling
process.
[0095] During the drilling process, the bottomhole assembly 17 may undergo
dynamic motion in the borehole 50 resulting in dynamic interactions between
the
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bottomhole assembly 17 and the inner-surface of the borehole 50. In an
embodiment
of the present invention, because of the greater compliance of the gauge pad
assembly
73 above the indent 82 compared to the compliance of the gauge pad assembly 73
at a
position on the opposite side of the gauge pad assembly 73 relative to the
indent,
repeated dynamic interactions between the gauge pad assembly 73 and the inner-
wall
53 and/or the drilling-face 54 will cause the drilling system to drill in a
drilling
direction 85, where the drilling direction 85 is directed in the direction of
the of the
indent 82. When engaged, the cam 79 may prevent the gauge pad assembly 73
moving inwards (upwards as drawn), but may allow the gauge pad assembly 73 to
move in opposite direction (downwards as drawn). As a result, the drill bit 20
will
move, vibrate, upward relative to the gauge pad assembly 73 and hence provide
for
drilling by the drilling system in an upward direction, towards the indent 82,
to
produce an upward directed section of the borehole 50.
[0096] In an embodiment of the present invention, the cam 79 may provide for
offsetting the axis of the gauge pad assembly 73 from the axis of the drill
bit 20 in a
geostationary plane. In certain aspects, the offsetting of the gauge pad
assembly 73
by the cam 79 may be provided while the gauge pad assembly 73 is rotating with
the
drill bit 20 and/or the bottomhole assembly 17.
[0097] When using a drilling system to drill a curved section of a borehole,
for
example a curved section with a 10 degree /100 ft deflection, the actual side
tracking
of the borehole may be small; for example, in such a curved section, for a
forward
drilling of the borehole of 150 mm (6 in) the side tracking of the borehole is
0.07 mm.
In embodiments of the present invention, because the side tracking to produce
curved
sections with deflections of the order of 10 degree per 100 feet is small, the
system for
producing controlled, non-uniform dynamic interactions with the inner surface
of the
borehole during the drilling process may only need to generate a small
deflection of
the borehole. In experiments with embodiments of the present invention,
control of
the dynamic interactions using collar/gauge-pad assemblies with an eccentric
circumferential profile relative to a center axis of the bottomhole assembly
and/or the
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drill bit, including eccentric profiles that were over-gauge and/or under-
gauge relative
to the drill bit, produced steering of curved sections of the borehole with
such desired
curvatures.
[0098] In certain aspects of the present invention, to minimize power
requirements,
the gauge pad assembly 73 may be mounted on the compliant coupler 76 with the
axis
of the gauge pad assembly 73 coinciding with the axis of the drill bit 20
and/or the
cutting system that may comprise the drill bit 20. In an embodiment of the
present
invention, steering of the drilling system may be achieved by using the cam 79
to
constrain the direction of the compliance of the compliant coupler 76 so the
gauge
pad assembly 73 may move in one direction, but is very stiff (there is a
resistance to
radial movement) in the opposite direction. In certain aspects, to steer the
drilling
system to drill straight, that cam 79 may be engaged so as to make the
movement of
the gauge pad assembly 73 system stiff (resistant to radial motion) in all
directions.
[0099] In an embodiment of the present invention, the gauge pad assembly 73
may
comprise a single ring assembly carrying the gauge pads in gauge with the
drill bit 20.
In certain aspects, a small over or under gauge may be tolerable. In
alternative
embodiments, the pads on the gauge pad assembly 73 may be mounted on the ring
assembly independently and/or may be independently controlled. The gauge pad
assembly 73 may be mounted on a stiff compliant structure and may move
radially
relative to the drill bit 20. The cam 79 may be eccentric and may be
configured to be
geostationary when steering the drilling system and drawn in, removed and/or
the like
when the drill-string is being tripped or steering is not desired. By
maintaining the
cam 79 in a geostationary position, the active part of the cam 79, such as the
indent 83
or the like, may be maintained in a geostationary position relative to the
borehole 50
to provide for drilling of the borehole 50 in a desired direction, for example
in the
direction of the geostationary indent 83. In certain aspects, the cam 79 may
be
geostationary and the gauge pads or the like may be free to rotate during the
drilling
process.
[0100] As provided previously, various methods may be used to couple the gauge
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pad assembly 73 with the drill bit 20 and/or the bottomhole assembly 17. In
certain
aspects, the mounting may be radially compliant, but may also be capable of
transmitting torque and axial weight to the bottomhole assembly 17. In one
embodiment of the present invention, the compliant coupler 76, which may be a
mounting or the like, may comprise a thin walled cylinder with slots cut in
the
cylinder so as to allow radial flexibility but maintain tangential and axial
stiffness.
Other embodiments may include bearing surfaces to transmit the weight and/or
pins
and/or pivoting arms which may be used to transmit the torque.
101011 Using a configuration of the gauge pad assembly 73 and/or the compliant
coupling 76 that may keep the indent 82 (or an over-gauge, under-gauge section
of the
cam 79 or a combination of the cam 79 and the gauge pad assembly 73 or a
radially
stiff or radially compliant section of the gauge pad assembly 73)
geostationary in the
borehole 50, the drilling system may be controlled to directionally drill the
borehole
50. In some embodiments of the present invention, the processor 75 may be used
to
manage the controller 80 to provide for rotation of the cam 79 during or
between
drilling operations to continuously control the direction of the drilling
process. In
some embodiments, the indent 82 may have a graded profile 82A to provide for a
varying depth of the indent 82. In such embodiments, the relative compliance
of the
gauge pad assembly 73 between a section of the gauge pad assembly 73 above the
indent 82 relative to a section of the gauge pad assembly 73 not above the
indent 82
may be varied. In this way, in certain embodiments of the present invention an
acuteness (0) 86 of the drilling direction 85 may be variably controlled.
[0102] In some aspects of the present invention, a plurality of indents may be
provided in the cam 79 to provide for control of the interactions between the
gauge
pad assembly 73 and the inner-wall 53. The plurality of indents may be
disposed at
different positions around the circumference of the cam 79 to provide the
desired
steering effect. Furthermore, a plurality of cams may be used in conjunction
with one
or more gauge pad assemblies on the bottomhole assembly 17 to provide
different
steering effects during the drilling process.
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[0103] Figs. 4A-C are schematic-type illustration of active gauge pad systems
for
controlling a drilling system configured for drilling a borehole, in
accordance with an
embodiment of the present invention. In an embodiment of the present
invention, an
active gauge pad 100 may be used to control a drilling system for drilling a
borehole
that may comprise a drill pipe 90 coupled with a bottomhole assembly 95. The
bottomhole assembly 95 may comprise a drill bit 97 for drilling the borehole.
The
active gauge pad 100 may comprise a drill collar, a gauge pad, a section of
the
bottomhole assembly, a tubular assembly, a section of the drill bit and/or the
like that
may interact with the inner surface of the borehole being drilled in a non-
uniform
manner.
[0104] The active gauge pad 100 may comprise a disc, a cylinder, a plurality
of
individual elements ¨ for example a series of pads disposed around the
circumference
of the bottomhole assembly 95 or the drill pipe 90 ¨ that may be coupled with
the
drilling system and may interact with the inner surface of the borehole being
drilled
during the drilling process. In certain aspects, to provide for repeated
interaction
between the active gauge pad 100 or the like and the inner surface of the
borehole, the
active gauge pad 100 may be coupled with the drilling system so as to be less
than 20
feet from the drill bit 97. In other aspects, the active gauge pad 100 may be
coupled
with the drilling system so as to be less than 10 feet from the drill bit 97.
[0105] In embodiments of the present invention, the active gauge pad 100 may
be
moveable in the borehole. As such, the active gauge pad 100 may be aligned in
the
borehole using an actuator or the like to an orientation in the borehole to
produce the
desired control of the drilling system as a result of the non-uniform
interactions of the
active gauge pad 100, as oriented in the borehole, with the inner surface of
the
borehole. Using a processor or the like to control positioning of the active
gauge pad
100 in the borehole, the operation and/or steering of the drilling system may
be
controlled/managed, and this control/management may, in some aspects, occur in
real-time.
[0106] In Fig. 4A the active gauge pad 100 is coupled with the bottomhole
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assembly 95 to provide for interaction with the inner surface of the borehole
being
drilled at a location proximal to the drill bit 97. In a drilling system in
which the drill
pipe 90, the bottom hole assembly 95 and/or the like are rotated during
drilling
operations the active gauge pad 100 may be configured to be held geostationary
during drilling operations. An actuator, frictional forces and/or the like may
be used
to hold the active gauge pad 100 geostationary. Merely by way of example, in
one
embodiment of the present invention, the active gauge pad may be coupled with
the
bottomhole assembly 95 at a distance of less than 10-20 feet behind the drill
bit 97.
[0107] Fig. 4B illustrates one embodiment of the active gauge pad of the
system
depicted in Fig. 4A. In Fig. 4B, in accordance with an embodiment of the
present
invention, an active gauge pad 100A may comprise an element that is
asymmetric.
By coupling the asymmetric active gauge pad with the drill-string so that an
outer-
surface of the gauge pad 100A extends beyond an outer-surface of the drill
string, the
outer surface of the asymmetric active gauge pad may interact with the inner
surface
of the borehole being drilled. Since the active gauge pad 100A has a non-
symmetrical
outer surface, the active gauge pad 100A may interact with the inner surface
of the
borehole as a result of dynamic motion of the drill-string during the drilling
process in
a non-uniform way that will depend upon the non-symmetrical configuration of
the
active drill pad 100A.
[0108] Merely by way of example, the active gauge pad 100A may be asymmetric
in design and may be configured to be coupled with the bottomhole assembly as
provided in Fig. 4A at a distance in a range of several inches to 10-20 feet
behind the
drill bit. In some embodiments, the active gauge pad 100A may comprise a
uniform
cylinder and may be arranged eccentrically on the bottomhole assembly to
provide for
a non-uniform interaction with the inner surface as a result of the dynamic
motion of
the drill string.
[0109] In certain embodiments, the active gauge pad 100A may comprise a
geostationary tube and may be slightly under gauge on one side. In other
embodiments, the active gauge pad 100A may be under gauge on one side and over
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gauge on the opposite side. In some aspects, the active gauge pad 100A may
comprise a plurality of geostationary tubes that are under/over gauged
circumferentially and that may be coupled around the circumference of the
drill pipe
90 ancUor the bottomhole assembly 95. In some embodiments of the present
invention, the active gauge pad 100A may be configured to provide that the
active
gauge pad 100A is coupled with the drill string so that the active gauge pad
100A is
disposed entirely with a cutting silhouette of the drill bit; the cutting
silhouette
comprising the edge-to-edge cutting profile of the drill bit. In other
embodiments of
the present invention, a section or all-of-the active gauge pad 100A may
extend
beyond the cutting silhouette of the drill bit.
[0110] Merely by way of example, the active gauge 100A may be coupled with the
drill-string to provide that the outer surface of the active gauge 100A is of
the order of
1-10s of millimeters inside the cutting silhouette. In other aspects, and
again merely
by way of example, the active gauge 100A may be coupled with the drill-string
to
provide that at least a portion of the outer surface of the active gauge pad
100A
extends in the range of tenths to lOs of more millimeters beyond the cutting
silhouettes.
[0111] In an embodiment of the present invention, the active gauge pad 100A ¨
because the active gauge pad 100A is non-concentric with the bottomhole
assembly,
asymmetric and/or the like ¨ may interact with the inner surface of the
borehole being
drilled as a result of radial motion of the drilling system in the borehole
during the
drilling process in a non-uniform manner. Repeated dynamic interactions
between
the active gauge pad 100A, as depicted in Fig. 4B, and the inner surface of
the
borehole during a drilling process may result in the drilling system tending
to drill in a
downward direction 103, as provided in the figure. By maintaining the active
gauge
pad 100A geostationary during the drilling process, the active gauge pad 100A
may
be used to steer the drilling system.
[0112] In an embodiment of the present invention, by making the active gauge
pad
100A under-gauged at least one circumferential location around the
circumference of
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the active gauge pad 100A, a small gap between the active gauge pad 100A and
the
inner surface may be created that may be used to steer the drill bit 97. As
such, in
some embodiments of the present invention, the drilling system may be steered
by use
of contact surfaces on the bottomhole assembly. 95 that may be within the
profile cut
by the cutters and/or without pushing the contact surfaces out beyond the cut
profile.
[0113] Fig. 4C illustrates a further embodiment of the active gauge pad of the
system depicted in Fig. 4A. In Fig. 4C an active gauge pad 100B may comprise a
collar 105 coupled with an extendable element 107. The collar 105 may comprise
a
cylinder, disc, drill collar, gauge pad, a section of the bottomhole assembly
95, a
section of the drill-string, a section of the drill pipe and or the like.
[0114] In an embodiment of the present invention, the extendable element 107
may
be an element that may be controlled to change the circumferential profile of
the
collar 105. The extendable element 107 may be controlled/actuated by a
controller
110. The controller 110 may comprise a motor, a hydraulic system and/or the
like.
In an embodiment of the present invention, the controller 110 may actuate the
extendable element 107 to extend outward from the bottomhole assembly 95 so as
to
change dynamic interactions between the active gauge pad 100B and the inner
surface
of the borehole being drilled, resulting from radial/dynamic motion of the
drilling
system in the borehole during the drilling process.
[0115] In some embodiments of the present invention, the active gauge pad 100B
may be configured to provide that when extended the active gauge pad 100B is
disposed entirely with the cutting silhouette of the drill bit. In other
embodiments of
the present invention, a section or the entire extended/partially extended
active gauge
pad 100B may extend beyond the cutting silhouette of the drill bit. Merely by
way of
example, the active gauge 100B may be coupled with the drill-string to provide
that
the outer surface of the active gauge 100B in an extended position is of the
order of 1-
10 mm inside the cutting silhouette. In other aspects, and again merely by way
of
example, the active gauge 100B may be coupled with the drill-string to provide
that at
least a portion of the outer surface of the active gauge pad 100B when
extended or
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=
partially extended extends in the range of tenths of millimeters to 10s or
more
millimeters beyond the cutting silhouettes.
[0116] In an embodiment of the present invention, the interactions between the
active gauge pad 100B and the inner surface may be controlled by the
positioning/extension of the extendable element 107 to provide for steering of
the
drilling system and directional drilling of the borehole being drilled by the
drilling
system. In certain aspects, the processor 70 may receive data regarding a
desired
drilling direction, data regarding the drilling process, data regarding the
borehole, data
regarding conditions in the borehole, seismic data, data regarding formations
surrounding the borehole and/or the like and may operate the controller 110 to
provide the positioning/extension of the extendable element 107 to steer the
drilling
system. In an embodiment of the present invention, the extendable element 107
may
be extendable to adjust the dynamic interactions between the active gauge pad
100
and the inner surface of the borehole being drilled. This may require a simple
passive
extension of the extendable element 107 so that the active gauge pad 100 has a
non-
uniform shape around a central axis of the drilling system and/or the
borehole,
without having to apply a thrust or force on the inner surface.
[0117] In certain aspects, however, the extendable element 107 may be
positioned,
extended so as to exert a force on the inner surface. Merely by way of
example, in
certain embodiments, the extendable element 107 may exert a force of less than
1 kN
on the inner surface to provide for both exertion of a reaction force from the
inner
surface on the drilling system and control of the dynamic interactions between
the
drilling system and the inner surface. Operating the extendable element 107 to
provide for exertion of forces of less than 1 kN may be advantageous as such
forces
may not require large downhole power consumption/ power sources, may reduce
size
and complexity of the controller 110 and/or the like.
[0118] In an embodiment of the present invention, the bottomhole assembly 95,
the
drill bit 97, the active gauge pad 100 and/or the like may be configured to
have an
unevenly distributed mass. The mass of the bottomhole assembly 95, the drill
bit 97,
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the active gauge pad 100 and/or the like may vary circumferentially or the
like to
provide that the unsteady motion of the drilling system and/or the interaction
between
the drilling system and the inner surface of the borehole is not uniform. As
such, the
non-uniform weighting of the drilling system may provide for control of and/or
steering of the drilling system. Merely by way of example, the drill collar
which
provides weight-on-bit, may be cylinder with a non-uniform weight
distribution. In
certain aspects, the cylindrical drill collar may be rotated to change the
profile of the
non-uniform weight/mass distribution in relation to the wellbore to provide a
desired
control of the drilling system and/or steering of the drilling system.
[0119] In some embodiments of the present invention, instead of or in
combination
with the gauge pads, drill collar and/or the like, the drill string may be
shaped to
provide for controlling unsteady interactions with the inner surface. For
example, the
bottomhole assembly 95 may be asymmetrically shaped, have asymmetrical
compliance and/or the like. Furthermore, in accordance with some embodiments
of
the present invention the drill bit 97 may be asymmetrical, have an
asymmetrical
compliance, have non-uniform cutting properties and/or the like. Moreover, the
drilling system may be configured to enhance the unsteady motion of the
drilling
system during the drilling process. Modeling, experimentation and/or the like
may be
used to design drilling systems with enhanced unsteady motion. Positioning of
the
cutters on the drill bit 97, cutter operation parameters may be used to
provide for
enhanced unsteady motion. In some embodiments of the present invention, the
drilling system may incorporate a flexible/compliant coupling, a bent sub
and/or the
like (not shown) that may act to enhance unsteady interactions, enhance
control of the
drilling system from unsteady interactions and/or the like.
[0120] Fig. 5 provides a schematic-type illustration of a repeated radial
motion
actuator system for steering a drilling system to directionally drill a
borehole, in
accordance with an embodiment of the present invention. In an embodiment of
the
present invention, a drilling system may comprise the drill-string 140 ¨ that
may, in-
turn, comprise the bottom hole assembly 95 ¨ and the drilling system may be
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configured for drilling a borehole through an earth formation.
[0121] In certain embodiments, a radial motion generator 150 may be attached
to
the drill-string 140. The radial motion generator 150 may be configured to
generate
radial motion of the bottomhole assembly 95 in the borehole; where radial
motion
may be any motion of the bottomhole assembly 95 directed away from the central
axis of the borehole towards the inner-wall of the borehole. The radial motion
generator 150 may comprise a mechanical vibrator, acoustic vibrator and/or the
like
that may produce repeated radial motion, such as vibrations, of the bottomhole
assembly 95. The radial motion generator 150 may be tuned to the physical
characteristics of the drill-string 140 and/or the bottomhole assembly 95 to
provide
for enhancing the radial motion produced.
[0122] In an embodiment of the present invention, interactions between the
bottomhole assembly 95 and the inner surface of the borehole may be generated,
enhanced, altered and/or the like by the radial motion generator 150. The
radial
motion generator 150 may provide for steering the drill-string 140 by
creating,
applying, changing and/or the like interactions between the bottomhole
assembly and
the inner surface of the borehole. By steering the drill-string 140, the
borehole being
drilled by the drill-string 140 maybe directionally drilled. A processor 155
may be
used to control the radial motion generator 150 to generate interactions
between the
bottomhole assembly 95 and the inner surface so as to provide for steering of
the drill-
string 140 in a desired direction.
101231 In some embodiments of the present invention, the radial motion
generator
150 may be used in combination with other methods of creating non-uniform
unsteady interactions between the drilling system and the inner surface of the
borehole being drilled, such as described in this specification. In such
embodiments,
the radial motion generator 150 may provide for enhancing or dampening
unsteady
motion of the drill-string to enhance/damp the effect of the unsteady
interaction
controller and/or to control the unsteady interaction controller. In this way,
the
unsteady interaction controller may act as a controller/manager of the
unsteady
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interaction controller and may itself be controlled by a processor to provide
for
controlling/steering the drilling system and/or enhancing damping the non-
uniform
unsteady motion interactions between the unsteady interaction controller and
the inner
surface of the borehole.
[0124] Figs. 6A and 6B illustrate systems for selectively characterizing an
inner
surface of a borehole for steering a drilling assembly to directionally drill
the
borehole, in accordance with an embodiment of the present invention. In a
drilling
process, a drill-string 160 may be used to drill a borehole through an earth
formation.
The drill-string 160 may comprise a bottomhole assembly 165 and a coupler 170
that
may couple the bottomhole assembly 165 with equipment at or proximal to a
surface
location. The bottomhole assembly may comprise a drill bit 173 that may
comprise a
plurality of teeth 174 for scrapping/crushing rock in the earth formation to
create/extend the borehole being drilled.
[0125] During the drilling process, the inner surface of the borehole being
drilled
may be somewhat regular in shape and may be defined by an outer diameter of
the
drill bit 173. Generally, the inner surface is somewhat circular in shape.
Properties of
different portions of the earth formation may cause irregularities in the
shape of the
inner surface. In 6A, in accordance with an embodiment of the present
invention, a
shaping device 180 may interact with the inner surface to change/shape the
inner
surface. The shaping device 180 may comprise a fluid jet system for jetting a
fluid
onto the inner surface, a drill bit configured for laterally drilling into the
inner surface,
a scraper for scraping the inner surface and/or the like.
[0126] In an embodiment of the present invention, the shaping device 180 may
be
used to change the profile of the inner surface to provide for controlling
interactions
between the bottomhole assembly 165 and the inner surface. In certain aspects,
a
gauge pad 185 may be coupled with the bottomhole assembly 165 proximal to the
drill bit 173 and may be configured to interact with the inner surface during
drilling of
the borehole by the drilling system. Where the inner surface is relatively
uniform,
random interactions between gauge pad 185 and the inner surface resulting from
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radial motion of the bottomhole assembly 165 during the drilling process may
on
average be uniform and may not affect the direction of drilling. In an
embodiment of
the present invention, the shaping device 180 may contour/shape the inner
surface to
control the interactions between the gauge pad 185 and the inner surface. In
certain
aspects of the present invention, the bottomhole assembly 165 may not comprise
the
gauge pad 185 and the interactions may be directly between the bottomhole
assembly
165 and the inner surface.
[0127] In an embodiment of the present invention, by controlling the
interactions
between the gauge pad 185 and the inner surface the drilling system may be
steered.
In certain aspects, the shaping device 180 may be maintained geostationary
during a
steering procedure to provide for accurately selecting the region of the inner
surface
to be shaped by the shaping device 180 during the drilling process when the
drill-
string 140 and/or components of the drill-string 140 may be moving/rotating
within
the borehole.
[0128] The shaping device 180 may comprise water jets mounted between the
gauge cutters and the gauge pads of the drill bit. The water jets or the like
may be
used to undercut the earth formation in front of the gauge pad to generate a
gap
between the inner surface and the gauge pad that may provide for vibrational
steering
of the drilling system in accordance with an embodiment of the present
invention. In
other embodiments, an electro-pulse system may be mounted in front of the
gauge
pads and may be used to soften up a section of the inner surface to allow the
gauge
pad to crush the material of this section to generate the gap to provide for
vibrational
steering of the drilling system in accordance with an embodiment of the
present
invention. In other embodiments, the electro-pulse system may be used to
generate
the gap directly.
[0129] In Fig. 6B the drill bit 173 may be configured to drill a borehole with
a
selectively non-uniform inner surface. In certain aspects, a tooth 190 of the
drill bit
173 may be configured to be selectively activated to provide a contour on the
inner
surface. In other aspects, different techniques may be used to control the
drill bit 173
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to selectively shape the inner surface. By controlling the contours, shape of
the inner
surface of selectively placing grooves, indents or the like in the inner
surface the
interaction between the inner surface and the bottomhole assembly 165,
resulting
from radial motion of the bottomhole assembly 165 during drilling of the
borehole,
may be controlled and the direction of drilling may, as a result, also be
controlled. In
certain aspects, the drill bit 173 may comprise a mechanical cutter that may
be
deployed to preferentially cut one side of the inner surface.
[0130] Fig. 7A is a flow-type schematic of a method for steering a drilling
system
to directionally drill a borehole, in accordance with an embodiment of the
present
invention. In step 200, a drilling system may be used to drill a section of a
borehole
through an earth formation. The drilling system may comprise a drill-string
attached
to surface equipment or the like. The drill-string may itself comprise a
bottomhole
assembly comprising a drill bit for contacting the earth formation and
drilling the
section of the borehole through the earth formation. The bottomhole assembly
may
be linked to the surface equipment by drill pipe, casing, coiled tubing or the
like. The
drill bit may be powered by a top drive, rotating table, motor, drilling fluid
and/or the
like. During the drilling process the drill-string may undergo random motion
in the
borehole, which random motion may include radial vibrations that cause the
drill-
string to repeatedly contact an inner surface of the borehole during the
drilling
process. The interactions between the drill-string and the inner surface
resulting from
the radial vibrations may be most pronounced at the bottom of the borehole
where
interactions may occur between the bottomhole assembly and the inner surface.
[0131] In step 210, the vibrational-type interactions between the drill-string
and the
inner surface may be controlled. In certain embodiments of the present
invention, the
2 5 control of the dynamic interactions may occur at the bottom of the
borehole. In some
embodiments of the present invention, devices may be used at the bottom of the
borehole to provide that the vibrational-type interactions of the bottomhole
assembly
and the inner surface are not uniform. In such embodiment, the step of
controlling the
vibrational-type interactions between the drill-string and the inner surface
may
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comprise damping and/or enhancing at locations around the circumference of the
inner surface the vibrational-type interactions between the bottomhole
assembly and
the inner surface. The damping and/or enhancing locations around the
circumference
of the inner surface may be maintained or varied as the borehole is drilled.
In certain
aspects, a plurality of devices may be used to create a non-uniform
interaction
between the bottomhole assembly and the inner surface.
[0132] In an embodiment of the present invention, an interaction element may
be
used in step 212 to provide for controlling the dynamic interactions. The
interaction
element may be an independent element such as a drill collar, gauge pad
assembly,
cylinder or the like that may be coupled with the drill-string, and in some
aspects the
bottomhole assembly, may be a section of the drill-string, such as a section
of the
bottomhole assembly, or the like. The interaction element may be configured to
provide for uniform interaction between the interaction element and the
interior
surface of the borehole being drilled.
[0133] Generally, the borehole being drilled is a borehole in the earth
formation
with essentially a cylindrical inner surface. As such, in some aspects the
interaction
element may comprise an element with a profile that is non-uniform with
respect to a
center axis of the drill-string and/or the borehole. Merely by way of example,
the
interaction element may comprise an eccentric cylinder coupled with the
bottomhole
assembly; wherein as coupled with the bottomhole assembly a center axis of the
eccentric cylinder is not coincident with a center axis of the bottomhole
assembly. In
another example, the interaction element may comprise a series of pads
disposed
around the bottomhole assembly and configured to contact cylindrical inner
surface of
the borehole during the drilling process, wherein at least one of the pads is
configured
to extend outward from the bottomhole assembly by a lesser or greater extent
than the
other pads.
[0134] In other embodiments, the interaction element may comprise an element
with non-uniform compliance. Merely by way of example, the compliant element
may comprise an element with certain compliance and a section of the element
with
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an increased or decreased compliance relative to the certain compliance of the
rest of
the element, and be configured to provide that at least a part of the area of
increased
or decreased compliance and at least a part of the element with the certain
compliance
may each contact the cylindrical inner surface during the drilling process as
a result of
dynamic motion of the bottomhole assembly. In some embodiments of the present
invention, an actuator may be used to change the characteristics of the
interaction
element, such as to actuate the interaction element from an element that
interacts
uniformally with the inner surface of the borehole to one that interacts in a
non-
uniform manner with the inner surface.
101351 In certain embodiments of the present invention, the interaction
element,
whether being an element with a non-uniform profile, a non-uniform compliance
and/or the like, may not be configured to exert a pressure on the inner
surface or to
thrust against the inner surface, but rather may be passive in nature and
interact with
the inner surface due to dynamic motion of the drill-string during the
drilling process.
For example, the interaction element may comprise an extendible element that
is
extended outward from the drill-string. In some aspects, forces may be applied
by the
extendible element on to the inner surface, but for simplicity and economic
reasons
the forces may only be small in nature, i.e. forces less than about 1 kN.
[0136] In some embodiments of the present invention, the interaction element
may
be configured so as not to extend beyond and/or be disposed entirely within a
silhouette of the cutters of the drill bit. In other embodiments, the
interaction element
may have at least a portion that may extend beyond the silhouette of the drill
bit. In
certain aspects of the present invention, the interaction element may extend
in the
range of 1 mm to lOs of millimetres outside the silhouette of the drill bit
and/or the
cutters, with such an extension range providing for steering/controlling the
drilling
system.
[0137] In certain aspects of the present invention where the interaction
element
comprises one or more extendable elements, the one or more extendable elements
may be extended so as not to extend beyond and/or be disposed entirely within
a
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silhouette of the cutters and/or the drill bit. In other aspects, the one or
more
extendable elements may be extended to provide that at least a portion of the
one or
more extendable elements extends beyond the silhouette of the cutters and/or
the drill
bit. Steering of the drilling system may be provided in certain embodiments of
the
present invention by extending the one or more extendable elements extend in
the
range of 1-10 mm beyond the silhouette of the cutters and/or the drill bit. In
such
embodiments, unlike directional drilling systems using reaction forces, thrust
against
the borehole wall for steering, only a small amount of power and/or minimal
downhole equipment may be used/needed to actuate and/or maintain the
extendable
elements in the desired extension beyond the silhouette of the cutters and/or
the drill
bit.
[0138] In some aspects using a plurality of devices, the combination of
devices may
be configured to provide for non-uniform interactions between the drill-string
and the
inner surface circumferentially around the drill-string and, in such
configurations,
coupling of the plurality of the devices with the drill-string in a manner in
which the
effect of one device on the dynamic interactions cancels out the effect of
another of
the devices may be avoided. Devices that may be used to control the dynamic
interactions may include, among other devices: gauge pads, drill collars,
stabilizers
and/or the like that may be non-concentrically arranged on the bottomhole
assembly;
gauge pads, drill collars, stabilizers and/or the like that may be configured
to have
non-uniform circumferential compressibility; devices for changing the
profile/shape/contour of the inner surface; drill bits configured to drill a
borehole with
an irregular inner surface; and/or the like.
[0139] In step 220, the drilling system may be steered by controlling the
vibrational-type interactions between the drill-string and the inner surface
of the
borehole. In an embodiment of the present invention, the devices used to
control the
dynamic interactions between the drill-string and the inner surface of the
borehole
may be selectively positioned in the borehole to provide that the dynamic
interactions
steer the drilling system. In drilling systems in which at least a portion of
the drill-
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string rotates during the drilling process the devices may be held
geostationary in the
borehole to provide for the steering. In certain embodiments of the present
invention,
the devices used to control the dynamic interactions between the drill-string
and the
inner surface of the borehole may be selectively positioned on the drill-
string prior to
drilling a section of the borehole to provide the desired steering of the
drilling system.
In certain aspects, the devices used to control the dynamic interactions
between the
drill-string and the inner surface of the borehole may be re-positioned prior
to drilling
a further section of the borehole. In embodiments where an actuator, such as a
cam or
the like, is used to change the properties of the device used to control the
dynamic
interactions between the drill-string and the inner surface of the borehole,
the cam
rather than the device used to control the dynamic interactions may be
selectively
positioned and/or repositioned during the drilling process.
[0140] In some embodiments of the present invention, means for controlling the
position in the borehole, orientation in the borehole, location and/or
orientation on the
drill-string of the device used to control the dynamic interactions between
the drill-
string and the inner surface of the borehole and/or a device for actuating the
device
used to control the dynamic interactions between the drill-string and the
inner surface
of the borehole, such as a cam or the like, may be used to move the device
used to
control the dynamic interactions between the drill-string and the inner
surface of the
borehole during the drilling process.
[0141] In step 230, the drilling system is steered to drill the borehole in a
desired
direction. In an embodiment of the present invention, a desired direction for
the
section of the borehole to be drilled may be determined and the device used to
control
the dynamic interactions may be positioned in the borehole and/or on the drill-
string
so as to steer the drilling system to drill the section of the borehole in the
desired
direction. In certain aspects, a processor may control the position,
orientation and/or
the like of the device used to control the dynamic interactions in the
borehole and/or
on the drill-string to provide that the section of the borehole to be drilled
is drilled in
the desired direction. In certain embodiments, data from sensors disposed on
the
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drill-string, data from sensors disposed in the borehole, data from sensors
disposed in
the earth formation proximal to the borehole, seismic data and/or the like may
processed by the processor to determine a position orientation of the device
used to
control the dynamic interactions for the desired drilling direction.
[0142] Fig. 7B is a flow-type schematic of a method for controlling a drilling
system for drilling a borehole in an earth formation, in accordance with an
embodiment of the present invention. In step 240, a drilling system comprising
a
drill-string and a drill bit configured to drill a borehole in an earth
formation may be
used to drill a section of a borehole. In step 250, data regarding operation
of the drill-
string and/or the drill bit during the drilling process may be sensed. The
data may
include such things as weight-on-bit, rotation speed of the drilling system,
hook load,
torque and/or the like. Additionally, data may be gathered from the borehole,
the
surface equipment, the formation surrounding the borehole ancUor the like and
data
may be input regarding intervention/drilling processes being or about to be
implemented in the drilling process. For example, pressures and/or
temperatures in
the borehole and the formation may be determined, seismic data may be acquired
form the borehole and/or the formation, drilling fluid properties may be
identified
and/or the like.
[0143] In step 260, the sensed data regarding the drilling system and/or data
regarding the earth formation and/or conditions in the borehole being drilled
and/or
the like may be processed. The processing may be determinative/probabilistic
in
nature and may identify current and/or potential future states of the drilling
system.
For example, conditions and/or potential drilling system conditions such as
inefficient
performance of the drill bit, stalling of the drill bit and/or the like may be
identified.
[0144] In some embodiments of the present invention, a processor receiving
sensed
data may be used to manage the controlling of the unsteady-motion-interactions
between the drilling system and the inner surface of the borehole. For
example,
magnetometers, gravimeters, accelerometers, gyroscopic systems and/or the like
may
determine amplitude, frequency, velocity, acceleration and/or the like of the
drilling
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system to provide for understanding of any unsteady motion of the drilling
system.
The data from the sensors may be sent to the processor for processing and
values for
the unsteady motion of the drilling system may be displayed, used in a control
system
for controlling the unsteady interactions of the drillstring, processed with
other data
from the earth formation, wellbore and/or the like to provide for management
of the
control system for controlling the unsteady interactions of the drillstring
and/or the
like. Merely by way of example, communication of the sensed data to the
processor
may be made via a telemetry system, a fiber optic, a wired drill pipe, wired
coiled
tubing, wireless communication and/or the like.
[0145] In step 270, vibrational-type interactions between the drill-string and
an
inner surface of the borehole being drilled may be controlled. Control of the
interactions between the drill-string and an inner surface of the borehole may
be
provided by changing/manipulating/altering contact characteristics of a
section of the
bottomhole assembly, a section of the drill-string, the cutters of the drill
bit, a profile
of the inner surface of the borehole and/or the like. The contact
characteristics may
be characteristics associated with an outer-surface of the section of the
bottomhole
assembly, the section of the drill-string, the cutters of the drill bit and/or
the like that
may contact the inner surface of the borehole during the drilling process. The
contact
characteristics may comprise a profile/shape of the outer-surface (i.e. may
comprise
an eccentric shape of the outer-surface around a central axis of the drilling
system,
bottomhole assembly, drill bit and/or the like, may comprise sections of the
outer-
surface that may be over-gauge and/or under-gauge) may comprise a non-uniform
compliance around the outer-surface and/or the like.
[0146] In step 280, the controlled vibrational-type interactions between the
drill-
string and the inner surface of the borehole may be used to control the
operation/functionality of the drilling system. For example, when whirring of
the drill
bit of the drilling system may be detected or predicted, the vibrational-type
interactions between the drill-string and the inner surface of the borehole
may be
controlled to eliminate, reduce and/or prevent the whirring. In an embodiment
of the
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present invention, the functionality of the drilling system may be determined
from the
processed data and may be altered by controlling the interactions between the
drill-
string and an inner surface of the borehole. In this way, embodiments of the
present
invention may provide new systems and methods for controlling operation of a
drilling system.
[0147] The invention has now been described in detail for the purposes of
clarity
and understanding. However, it will be appreciated that certain changes and
modifications may be practiced within the scope of the appended claims.
Moreover,
in the foregoing description, for the purposes of illustration, various
methods and/or
procedures were described in a particular order. It should be appreciated that
in
alternate embodiments, the methods and/or procedures may be performed in an
order
different than that described.
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