Note: Descriptions are shown in the official language in which they were submitted.
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DOWNHOLE VIBRATION APPARATUS AND METHOD
Statement of Related Applications
[0001] This application depends from and claims the benefit of U.S.
Provisional Patent
Application No. 61/155,601 filed on February 26, 2009.
Field of the Invention
[0002] This application relates to the drilling of an earthen bore, cementing
of a casing in
an earthen bore, improving drill bit service life and improving bonding
between a cement
liner installed around a casing in an earthen bore.
BACKGROUND
[0003] It is conventional practice to couple a drill bit to a tubular, for
example, a drill
string, and to rotate the drill bit against an end of an earthen bore to
extend the bore into
the earth's crust. A drill string may comprise slick (i.e., constant diameter)
drill collars or
enlarged (relative to the mid-section of the joints) drill collars. In casing
while drilling
applications, the drill bit is coupled to a casing. Drill cuttings are removed
from the bore
by circulating drilling fluid through a fluid passage in the drill string
(which, in drilling
applications, may be a drill string or a casing) to the drill bit, and back to
the surface
through an annulus between the drill stringand the earthen bore. As the drill
bit
penetrates the earth's crust, the drill string advances through the bore at a
rate of
penetration of the drill bit. In conventional drilling operations, the drill
string may rotate
along with the drill bit. In some drilling operations, such as casing while
drilling, the
drill bit may rotate independently of the drill string using a bottom hole
assembly (BHA)
that includes a mud motor powered by pressurized drilling fluid to rotate the
drill bit.
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The weight or load imparted to the drill bit by the drill string is a factor
that determines
the rate of penetration.
[0004] In drilling operations, it is advantageous to stabilize the rate of
advance of the
drill string through the borehole to prevent unwanted spikes in the load
imparted to the
drill bit. Intermittent or sporadic advances of the drill string within the
bore may cause
drill bit damage due to excessive loading. This problem may be greater in
bores having a
highly deviated section due to substantially greater frictional resistance
between the bore
and the drill string. In highly deviated sections of a bore, the weight of the
drill string
(and contents) bear on the floor, or downwardly disposed side, of the bore to
cause
substantially greater frictional resistance to advance of the drill string
through the bore.
The result may be intermittent and erratic advances of the drill string and
related peak
loads imparted to the drill bit.
[0005] An attempt to stabilize the rate of advance of a drill string through a
bore having
a highly deviated section uses an oscillating valve disposed within a BHA
coupled to the
drill string. Pressurized drilling fluid may be pumped through the fluid
passage in the
drill string to drive the oscillating valve to vibrate the BHA and reduce
frictional
resistance to advance of the drill string through the bore.
[0006] An oscillating valve powered by pressurized drilling fluid may consume
a
substantial portion of the mechanical energy provided to the BHA, leaving less
mechanical energy to drive the mud motor and/or to circulate and remove drill
cuttings.
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[0007] After an earthen bore is drilled to a targeted depth, it is
conventional practice to
cement a casing in the bore to prevent collapse and stabilize the bore. A
float device,
such as a float shoe or a float collar, may be coupled to the casing, and the
casing may be
run into the bore and positioned within a targeted interval. The casing may
also be
radially positioned (or "centered") within the bore using casing centralizers,
such as bow
spring centralizers, coupled at intervals along the casing to provide an
annulus between
the casing and the bore. Cement slurry is pumped through the casing with
cementing
plugs to facilitate displacement of the slurry through the float device and
into the annulus.
The cement slurry solidifies to provide a protective cement liner around the
casing.
Alternately, an inner cementing string may be run through the casing and stung
into a
mandrel, for example, a mandrel in a float device, and cement slurry may be
delivered
through the inner cementing string and the float device to the annulus.
[0008] The quality of the cement liner may be improved by conditioning the
cement
slurry within the annulus while and/or or after the cement slurry is displaced
into the
annulus. The cement slurry may be conditioned by agitation to induce turbulent
fluid
flow, disrupt fluid channeling and promote bonding of the cement liner to the
bore.
[0009] Reciprocation and/or rotation of the casing using the drilling rig are
conventional
methods of agitating a cement slurry. In substantially vertical bores, where
casing hangs
primarily in tension, casing is more easily reciprocated and/or rotated within
the bore. In
bores having highly deviated sections, reciprocating or rotating the casing
may be
difficult because the weight of the casing (and contents) bears heavily on the
floor, or
downwardly disposed side, of the bore. As a result, casing rotation and/or
reciprocation
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within a highly deviated section of a bore causes unwanted wear and stress on
the casing,
on the casing centralizers and on rig equipment used to move the casing within
the bore.
[0010] What is needed is a method to stabilize the advance of a tubular, such
as a drill
string, through an earthen bore to prevent excessive drill bit loading. What
is needed is a
method to condition a cement slurry displaced into an annulus between a
tubular, such as
a casing, and a bore. What is needed is a method to condition an annular flow
or volume
of cement slurry around a casing without imparting unwanted stress and wear on
the
casing, casing centralizers and rig equipment.
SUMMARY AND STATEMENT OF THE INVENTION
[0011] A first aspect of the invention is a method of stabilizing drill bit
loading to
extend the usable life of a drill bit comprising the steps of coupling a drill
bit to a drill
string (which may be a casing used in a casing while drilling application),
coupling a
vibration generator to the drill string, coupling a power source, such as a
battery, to the
vibration generator, running the drill string into a bore to engage the drill
bit with an end
of the bore, rotating the drill bit to extend the bore, and activating the
vibration generator
to vibrate a portion of the drill string within a highly deviated section of
the bore to
reduce frictional resistance to advance of the drill string and thereby
stabilize drill bit
loading.
[0012] A second aspect of the invention is a method of reducing frictional
resistance to
advance of a tubular through a highly deviated section of a drilled earthen
bore
comprising the steps of coupling a vibration generator to the tubular, e.g., a
casing,
coupling a power source, such as a battery, to the vibration generator,
running the tubular
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into a bore, and activating the vibration generator to vibrate a portion of
the tubular
within a highly deviated section of the bore to reduce frictional resistance
to advance of
the casing and thereby stabilize advance of the casing through the bore
towards the
targeted interval.
[0013] A third aspect of the invention is a method of conditioning a cement
slurry to
promote improved bonding between a cement liner and a bore comprises the steps
of
coupling a float device (such as a float shoe or a float collar) to a casing,
coupling a
vibration generator to the casing, coupling a power source (such as a battery)
to the
vibration generator, running the casing into a bore, displacing a volume of
cement slurry
through the casing and the float device and into an annulus between the casing
and the
bore, and activating the vibration generator to vibrate a portion of the
casing to condition
a portion of the volume of cement slurry adjacent the vibration generator.
[0014] In a fourth, fifth and sixth aspects of the invention, the vibration
generator used in
the first, second and third aspects described above may be activatable using a
pressure
sensor disposed in communication with the power source to detect an activating
condition. For example, a pressure sensor may be disposed to detect the
pressure in a
fluid passage in the drill string, the casing, in a sub or in the float
device. The pressure
sensor may be coupled to a microprocessor programmed to monitor readings of
the
pressure sensor and to recognize an activating condition or sequence. For
example, but
not in the way of limitation, the pressure sensor may detect a first
predetermined pressure
threshold, followed by a pressure trough lasting for a predetermined interval
of time,
followed by a second predetermined pressure threshold, altogether comprising a
sequence
of events recognizable by the microprocessor. In response, the microprocessor
may close
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an electrical circuit to provide current from the a power source to a motor to
activate the
vibration generator. A subsequent predetermined event or sequence may be used
to
deactivate the vibration generator.
[0015] In a seventh aspect of the invention, a method of conditioning a cement
slurry
may comprise coupling the vibration generator to a float device, such as a
float shoe or
float collar. Another embodiment of the method of conditioning a cement slurry
may
comprise coupling the vibration generator to one or more drillable components,
such as a
float device, so that the vibration generator and the float device may be
drilled or
destroyed to provide an unrestricted passage through the casing to facilitate
further
extension of the bore after the cementing step.
[0016] In an eighth aspect of the invention, an apparatus that may be used to
implement a
method described above comprises a mass rotatably coupled within a frame and
having a
mass center, a motor coupled to the mass, and a power source coupled to the
motor to
provide energy for spinning the mass on an axis offset from the mass center to
produce
reactive vibrations in the frame. The frame may then be coupled to a drill
string (as in
the first aspect), a casing (as in the second aspect) being used for drilling,
or a casing (as
in the third aspect) being cemented within a targeted interval of a bore, run
into the bore,
and the apparatus may then be activated, for example, using the method
described in the
fourth, fifth and sixth aspects, to impart vibrations to the frame to
stabilize the advance of
a tubular (as in the first and second aspects) and/or condition a cement
slurry (as in the
third aspect).
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[0017] A power source for providing energy to a motor may, in one embodiment,
comprise a battery having a high power-density including, but not limited to,
a nickel-
cadmium battery, a nickel-metal-hydride battery or a lithium-ion battery.
While high
power-density batteries may provide for optimal performance of the vibration
generator,
a conventional lead acid battery may also be used.
[0018] A mass to be spun to produce vibrations may, in one embodiment,
comprise an
elongate member of a high density material, such as lead, or it may comprise a
substrate
to which weighted attachments are secured to provide a mass center offset from
an axis
about which the mass is spun. It will be understood that factors affecting the
frequency
and magnitude of vibrations includes the weight of the mass, the offset
between the axis
of rotation and the mass center, the angular velocity of spinning of the mass
and the
relative size of the sub, float device or other frame to which the mass is
secured.
[0019] The foregoing, as well as other, objects, features, and advantages of
the invention
will be more fully appreciated and understood by reference to the drawings,
described
below, and to the claims appended hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Fig. 1 is an illustration of a drilling rig on the earth's surface and
a drill string
extending from the rig into an earthen bore.
[0021] Fig. 1A is a section view taken at position 1A-1A along the drill
string of Fig. 1.
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[0022] Fig. 2 is a section view of one embodiment of a vibrating sub having a
vibration
generator and coupled within a drill string adjacent a drill bit.
[0023] Fig. 3 is an illustration of a drilling rig on the earth's surface and
a casing being
installed in a targeted interval in a highly deviated section of the bore.
[0024] Fig. 3A is a section view taken at position 3A-3A along the casing of
Fig. 3.
[0025] Fig. 4 is a section view of an alternate embodiment of a drill sub
having a
vibration generator.
[0026] Fig. 5 is a section view of an embodiment of a float device having a
vibration
generator.
DETAILED DESCRIPTION
[0027] Fig. 1 is an illustration of a drilling rig 1 on the earth's surface 5
and a tubular 8
extending from the rig 1 into an earthen bore 2 drilled into the earth's crust
3. A drill bit
50 and a vibration generator 10 are coupled to the tubular 8. The vibration
generator 10
is illustrated in Fig. 1 as being disposed within a highly deviated section 7
of the bore 2.
A highly deviated section 7 is a section of the bore 2 disposed at a
substantial angle from
vertical. The highly deviated section may be horizontal. The tubular 8 in Fig.
1 may
comprise a drill string or a casing, the latter being likely in casing while
drilling
applications.
[0028] Fig. 1A is a section view taken at position 1A-1A on Fig. 1. Fig. 1A
illustrates
the nature of the frictional resistance to advance of the tubular 8 and a bore
2 in a highly
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deviated section (see reference number 7 of Fig. 1A) of the bore 2. Fig. 1A
illustrates
how the weight of the tubular 8 (and contents) bears downwardly on the
supporting floor,
or downwardly disposed side, of the bore 2. The large reaction force applied
by the bore
2 to support the tubular 8 substantially increases frictional resistance to
advance of the
tubular 8 through the bore 2.
[0029] Fig. 2 is an enlarged section view of the embodiment of the vibration
generator 10
of Fig. 1 comprising a sub 12 having a first threaded connection 12A, a second
threaded
connection 12B, and a fluid passage 22 therebetween. The fluid passage 22
illustrated in
Fig. 2 deviates from an axis 88 of the tubular 8. The first threaded
connection 12A of the
sub 12 is coupled to a mating connection 8A of an adjacent tubular segment 8B
of the
tubular 8, and the second threaded connection 12B of the sub 12 is coupled to
a mating
connection 50A of the drill bit 50 (not shown in section) disposed against the
end 2A of
the bore 2. The vibration generator 10 of Fig. 2 comprises a mass 14 rotatably
coupled to
the sub 12, a motor 18 coupled to the mass 14 and a power source 20 coupled to
the
motor 18 through electrical conduit 29. Activation of the motor 18 using the
power
source 20 spins the mass 14 on an axis including the axle first portion 14A
and axle
second portion 14B, but offset from a mass center 14C.
[0030] Fig. 3 is an illustration of a drilling rig 1 on the earth's surface 5
and a casing 30
disposed in a targeted interval in a highly deviated section 7 of the bore 2.
A plurality of
centralizers 52 are received on the casing 30 at intervals along the casing 30
to provide an
annulus 28 between the casing 30 and the bore 2. A float device 60 is coupled
to the
casing 30 to facilitate displacement of cement slurry from a fluid passage
(not shown)
within the casing 30 and into the annulus 28.
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[0031] Fig. 3A is a section view taken at position 3A-3A along the casing of
Fig. 3 and
illustrates the stand-off between the casing 30 and the bore 2 provided by the
bow springs
52a of the centralizer 52. The resulting annulus 28 receives a cement slurry
69 therein to
form a cement liner upon curing of the cement slurry. As can be seen in Fig.
3A,
vibration of the casing 30, especially vibration having a radial displacement
as will be
generated by the apparatus illustrated in Figs. 3, 4 and 5, will condition the
cement slurry
69 within the annulus 28 and promote improved cement liner bonding to the bore
2.
[0032] Fig. 4 is a section view of an alternate embodiment of a vibration
generator 30
comprising a sub 32 having a first connection 30A with threads 31A, a second
connection
30B with threads 31B, a fluid passage 42 therebetween, and a vibration
generator 30
comprising a mass 34, a motor 38 coupled to the mass 34, and a power source 40
coupled
to the motor 38 through an electrical conduit 49. Activation of the motor 38
using the
power source 40 spins the mass 34 on an axis including axle first portion 34A
and axle
second portion 34B but offset from a mass center 34C to vibrate the sub 32 and
a tubular
(not shown in Fig. 4 -- see Fig. 3).
[0033] Fig. 5 is an enlarged section view of the float device 62 of Fig. 3.
The float
device 62 comprises a threaded connection 60A at which it may be coupled to a
casing
(see Fig. 3 - float device is illustrated in Fig. 5 decoupled from the
casing). The float
device 62 further comprises a vibration generator comprising a mass 66
rotatably coupled
to the float device 62, a motor 68 coupled to the mass 66, and a power source
64 coupled
to the motor 68. Activation of the motor 68 using the power source 64 spins
the mass 66
about an axis including axle first portion 66A and axle second portion 66B but
offset
from a mass center 66C. The float device 62 of Fig. 5 further comprises a
module 67
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comprising a pressure sensor and a microprocessor. The module 67 is in fluid
communication with a fluid passage inlet 61 within the threaded connection 60A
through
a channel 67A in the float device 62. The fluid passage inlet 61 is separated
from a fluid
passage outlet 63 by a check valve comprising a ball 57 movably captured
between a
restriction 59 and a spring 58. It will be understood that the ball 57 is
disposed by the
spring 58 against the restriction 59 to prevent flow through the restriction
59 until the
pressure in the fluid passage inlet 61 exceeds the pressure in the fluid
passage outlet 63
by a differential that is sufficient to overcome the force of the spring 58
against the ball
57, at which time fluid (not shown) will flow from the fluid passage inlet 61,
past the ball
57, through the fluid passage outlet 63 and through the exit port 74.
Operating in this
manner, the float device 62 prevents fluid within the bore 2 (see Fig. 3) from
flowing into
the fluid passage inlet 61 and entering the casing 30 (see Fig. 3).
[0034] The terms "comprising," "including," and "having," as used in the
claims and
specification herein, shall be considered as indicating an open group that may
include
other elements not specified. The terms "a," "an," and the singular forms of
words shall
be taken to include the plural form of the same words, such that the terms
mean that one
or more of something is provided. The term "one" or "single" may be used to
indicate
that one and only one of something is intended. Similarly, other specific
integer values,
such as "two," may be used when a specific number of things is intended. The
terms
"preferably," "preferred," "prefer," "optionally," "may," and similar terms
are used to
indicate that an item, condition or step being referred to is an optional (not
required)
feature of the invention.
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[0035] From the foregoing detailed description of specific embodiments of the
invention,
it should be apparent that an apparatus and a method for stabilizing the
advance of a
tubular through a bore that is novel has been disclosed, and that an apparatus
and a
method for conditioning a cement slurry in an annulus has been disclosed.
Although
specific embodiments of the apparatuses and methods are disclosed herein, this
is done
solely for the purpose of describing various features and aspects of the
invention, and is
not intended to be limiting with respect to the scope of the invention. It is
contemplated
that various substitutions, alterations, and/or modifications, including but
not limited to
those implementation variations which may have been suggested herein, may be
made to
the disclosed embodiments without departing from the spirit and scope of the
invention
as defined by the appended claims which follow.
[0036] While embodiments of the invention have been described herein, various
modifications of the apparatus and method of the invention may be made without
departing from the spirit and scope of the invention, which is more fully
defined in the
following claims.
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