Note: Descriptions are shown in the official language in which they were submitted.
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FLUID OR SLURRY PULSING CASING/LINER SHOE
FIELD OF THE INVENTION
The present invention relates generally to drilling and completion of
wellbores, and to a shoe that imparts a pulsing action to fluid or slurry
being pumped
therethroug h.
BACKGROUND OF THE INVENTION
In the oil and gas production industry, welibores drilled into the earth to
access hydrocarbons from subsurface formations are typically lined with metal
tubulars lowered into the wellbore in an assembly of tubulars connected end to
end
to form a string. Such wellbore lining is generally referred to as casing, and
is
typically cemented into place once a desired depth has ben reached. Often,
after
such installation of a first casing string, the depth of the wellbore is
extended by
drilling a smaller bore through the bottom of the cemented-in casing. Further
casing
of smaller diameter than the first can then be run into the second bore
through the
first section of casing and then cemented in place in a similar process.
When running casing into a previously drilled wellbore, a casing string
may encounter obstructions preventing it from reaching the desired depth, such
as
ledges, collapsed borehole sections, or other discontinuities of the wellbore.
Accordingly, there have been publications proposing to cut or mill away
such obstructions during running of a casing string driving a rotatable casing
shoe
that is carried on the bottom end of the casing string and equipped with
cutting
edges or abrasive elements. U.S. Patent No. 7,849,927 and U.S. Patent
Application
Publication No. 2010/0032170 disclose such solutions, in which the rotatable
shoe
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and the fluid-operated drive mechanism for same are sacrificial, i.e. intended
to be
left downhole during cementing of the casing string, and are drillable,
soluble or
degradable so as not to prevent further drilling of the wellbore past the
bottom of the
cemented casing.
However, rotatable mounting of a casing shoe and a mechanism for
using energy from the pumped fluid to drive rotation of the shoe contribute to
the
complexity of such solutions, which runs counteractive to the desire to keep
sacrificial parts simplistic and cost-efficient.
Applicant therefore proposes an alternative to rotationally driven
abrading or cutting casing shoes for reaming, washing, or breaking down
wellbore
obstructions while running casing.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided an
apparatus for running a casing/liner string into a pre-drilled wellbore, the
apparatus
comprising:
a casing/liner shoe body arranged at an upper end thereof for coupling
to a bottom end of the casing/liner string in a manner fluidly coupling an
interior of
the body with an interior of the casing/liner string, the interior of the body
having a
generally cylindrical chamber formed therein and defined by a cylindrical
inner wall
and opposed generally transverse end walls and having a central longitudinal
chamber axis through said chamber;
fluid inlet passages extending through a first one of said end walls
nearest the upper end of the body and arranged so as to discharge pressure
fluid
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into said chamber in a generally spiral manner and so as to create a fluid
vortex in
said chamber when said fluid inlet passages are communicated with pressure
fluid
source through the interior of the casing/liner string;
plural fluid discharge passages disposed in an opposite second one of
said end walls and having respective fluid inlet ports in communication with
said
chamber for receiving pressure fluid flow for discharging pressure fluid from
said
body.
Preferably the fluid inlet ports of the fluid discharge passages are
positioned radially inward from the cylindrical inner wall of the chamber.
Preferably the fluid discharge passages are entirely situated radially
inward from the cylindrical inner wall of the chamber.
Preferably the fluid inlet ports of the fluid discharge passages are
located nearer the central longitudinal chamber axis than the inner
cylindrical wall
thereof.
Preferably each fluid discharge passage has a central longitudinal
discharge passage axis that is acutely angled relative to the central
longitudinal
chamber axis and each fluid inlet passage has a central longitudinal inlet
passage
axis that is acutely angled relative to the central longitudinal chamber axis,
the
central longitudinal discharge passage axes having smaller acute angles
relative to
the central longitudinal chamber axis than said central longitudinal inlet
passage
axes have relative to the central longitudinal chamber axis.
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Preferably there is provided a flow interruption member movably
disposed within the chamber to interrupt flow of pressure fluid from the inlet
passages to the discharge passages.
Preferably the flow interruption member has a diameter at least three
times that of the discharge passages.
Preferably the flow interruption member is ball-shaped.
Preferably the flow interruption member is composed of one or more
drillable materials.
Preferably the flow interruption member is wearable away by flow the
pressure fluid over time to break down into sufficiently small pieces for exit
form the
body through the discharge passages.
According to a second aspect of the invention there is provided a
method for running a casing/liner string into a pre-drilled wellbore, the
method
comprising running the casing/liner string into the wellbore with a shoe at a
bottom
end thereof and pumping fluid through the casing/liner string to the shoe,
from which
the fluid is discharged into the wellbore in a pulsating manner.
According to a third aspect of the invention there is provided a method
,
for reaming, washing or breaking down obstructions in a pre-drilled wellbore,
the
method comprising running a casing/liner string into the wellbore with a shoe
at a
bottom end of the casing/liner string and pumping fluid through the
casing/liner string
to the shoe, from which the fluid is discharged into the wellbore in a
pulsating
manner.
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The methods may comprise flowing the fluid through an internal
chamber of the shoe in which a movable flow interruption member is disposed to
alternatively allow and block flow of the fluid through each of a number of
discharge
passages exiting the internal chamber to an exterior of the shoe, thereby
discharging
5 the fluid in the pulsating manner.
The methods may comprise breaking down the flow interruption
member gradually over time by the flow of the fluid therepast, after which the
fluid is
continues to discharge in the pulsating manner as a result of configuration of
inlet
passages to the interior chamber in a manner causing a spiral action on the
fluid as
it enters the chamber to create a fluid vortex therein.
The methods may further comprise cementing the casing/liner string
and the shoe in the wellbore when the casing/liner string has reached a
desired
depth.
The methods may further comprise drilling through the cemented shoe.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate exemplary
embodiments of the present invention and are not necessarily to scale:
Figure 1 is a perspective view of a casing shoe of the present
invention, with a body thereof partially cut away for illustrative purposes.
Figure 2 is an overhead plan view of the casing shoe body of Figure 1,
as viewed from line II¨ II thereof.
Figure 3 is a cross-sectional view of the casing shoe body of Figure 1
as taken along line Ill ¨ Ill thereof.
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Figure 4 is a cross-sectional view of the casing shoe of Figure 1, as
would be viewed along line IV ¨ IV of Figure 3, with a plug thereof removed
for ease
of illustration.
DETAILED DESCRIPTION
Figure 1 shows a casing shoe apparatus for pulsatingly discharging
fluid at the bottom of a well casing string while running the same into a
previously
drilled wellbore so that the pulsing fluid action will act to break up and
obstructions
from the wellbore. The apparatus is generally designated by the numeral 20 and
includes a body having a cylindrical peripheral wall 22 that is internally
threaded, as
schematically shown at 23, at its upper end for threaded coupling to the
bottom end
of a casing string, for example by direct engagement with an externally
threaded
bottom end of the casing string 18 above the casing shoe 20. The body also
include
a generally cylindrical transverse plug 24 which is provided with fluid inlet
passages
comprising one or more circumferentially spaced fluid inlet ports 26 formed
therein.
The ports 26 form openings for respective passages 28 which extend through the
plug 24 and open in into an interior chamber 30 bound by the cylindrical wall
22, the
internal diameter of which is preferably about one-half the length of the
chamber 30.
Referring to Figure 4, the interior side of the cylindrical wall 22 may be
stepped at the axial location that defines the top of the chamber 30 once
closed off
by insertion of the plug through the internally threaded open top end of the
body.
Here, the internal diameter of the cylindrical wall 22 is reduced compared to
the
opening at the larger top end to create an angular ledge or shoulder 22a on
which
the cylindrical plug 24 is seated when installed during assembly of the
apparatus.
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The installged plug defines a transverse end wall closing off the top of the
chamber
in a plane normal to a central longitudional axis 31 of the cylindrical wall
22.
As shown in FIGS. 1 and 2, the passages 28 intersect a plane normal
to the central longitudinal axis 31 of the cylindrical wall 22 at an acute
angle, which
may be in a range of about thirty (30) to sixty (60) degrees, and preferably
forty-five
(45) degrees. The passages 28 also have respective central axes 28a
substantially
tangential to the inner cylindrical wall 33 defining the chamber 30. Four
passages 28
are illustrated in FIG. 2 although a larger or smaller number of such passages
may
be provided, including as few as one, but preferably at least two. The
diameter of the
ports 26 and the passages 28 may also be varied.
At the end of the body opposite the internally threaded end 23 of the
cylindrical wall 22, the body features a nose portion 40 with a hemispherical
outer
surface 46 sharing the same diameter as the outer surface of the cylindrical
wall 22
to form a rounded bull-nose end of the body. The cylindrical wall 22 and nose
portion 40 are preferably integral parts machined from a unitary piece of
material.
The nose portion 40 is solid, featuring a flat upper face that defines a
transverse end
wail 42 delimiting the bottom end of the chamber 30 opposite the plug 24 that
closes
the top end thereof. As shown in Figure 4, the transverse bottom end wall 42
may
intersect the cylindrical sidewall 33 of the chamber 30 at a curved inner wall
portion
44. The frusto-conical exterior surface of the nose portion 40 is intersected
by a
plurality of fluid discharge ports 48. The discharge ports 48 form the
discharge ends
of respective plural discharge passages 50 which intersect the transverse
bottom
end wall 42, at spaced apart ports 51.
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The passages 50 may be configured such that their central longitudinal
axes 50a lie in respective radial planes relative to the cylindrical wall 22
and angle
outwardly away from the cylindrical wall's central longitudinal axis 31 at an
angle
between two (2) and fifteen (15) degrees in the downward direction, for
example
approximately ten (10) degrees in the illustrated embodiment, and
approximately five
(5) degrees in other embodiments. The end wall 42 extends in a plane normal to
the cylindrical wall's axis 31. The diameter of the ports 48 and the passages
50 and
the number of same may be varied from the illustrated embodiment, where there
are
three discharges passages 50 equally spaced around the cylindrical wall's axis
31
and each having a diameter of approximately one eighth of the chamber's
overall
diameter. In the illustrated embodiment, the inlet ports of the discharge
passages
that lie at the transverse bottom end wall 42 of the chamber are located
entirely
within the first half of the radial distance from the central axis 31 of the
body to the
inner surface 30 of the cylindrical wall 22.
Fluid flowing from the passages 28 into the chamber 30, as achieved
under pressurized pumping of fluid into the top end of the body through the
casing
string, "spreads out" and flows along the cylindrical wall 33 in a spiraling,
vortical
path. This phenomenon is described and illustrated in U.S. Patent No.
5,505,262 of
Cobb, which discloses tools sharing the same layout of tangentially sloped
inlet
passages at the top of a cylindrical chamber. However, the apparatus of the
present
invention differs notably from the Cobb patent due its unique application for
cleaning
or reaming of a pre-drilled wellbore during while running in a casing string,
and a
number of features improving its suitability for such operations.
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Cobb's discharge passages open into the chamber at the intersection
of the cylindrical wall and the transverse end wall, and are angled at forty-
five
degrees. While this may be suitable or ideal for the applications described in
the
Cobb patent, such as dislodging material from plugged perforations in
previously
installed well casing (Fig. 11), this notable outward angling of the discharge
passages may cause excessive wearing away of the wellbore wall while running
in
casing. The relatively small acute angle and close positioning of the
discharge
passages 50 relative to the central axis 31 of the body in the present
invention limits
provides a narrower focus of the fluid being discharged from the apparatus,
thus
being more suitable for removing wellbore obstructions without breaking away
non-
obstructing desired-diameter portions of the wellbore wall.
The present invention also preferably employs drillable materials for
the construction of the body, for example employing aluminum, drillable alloys
or
lower grade steels, at least for the plug 24 and the nose portion 40. This
way, the
body can be drilled out after the casing string and shoe are cemented into
place by
pumping of cement down through the casing into and through the shoe, thereby
allowing a further smaller casing string to be deployed downward through the
first
after such a drilling operation.
Also, Cobb discloses use of a relatively small spherical ball-shaped
member having a radius of curvature generally matching the curved transition
between the bottom end of the chamber and the cylindrical wall thereof and a
diameter slightly larger than the discharge passages so that the ball will
roll around
the chamber at this curved transition wall under the spiral, vertical flow of
the fluid in
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the chamber to momentarily close off the inlet ports of the discharge passages
on an
individual basis, causing a pulsed flow effect through each discharge passage
under
the successive and rapid opening and closing of the ports. However, the
illustrated
embodiment of the present invention departs from such a configuration, instead
5 employing a larger diameter spherical ball-shaped member 72 to act as an
interrupter to flow through the discharge passages 50 of the chamber 30. The
diameter of the illustrated ball 72 is somewhat smaller than the diameter of
the
chamber to allow limited motion of the ball therein, yet substantially larger
than the
diameter of each discharge passage 50. In some embodiments, the ball diameter
10 may be between four (4) and ten (10) times the diameter of the discharge
passage
diameter, for example approximately seven (7) times the discharge passage
diameter in the illustrated embodiment, and may measure between eighty (80)
and
ninety (90) percent of the chamber diameter, for example measuring
approximately
eighty-five (85) percent of the chamber diameter in the illustrated
embodiment. The
action of the incoming fluid entering the chamber will cause the ball 72 to
move on
an ongoing basis, thus intermittently opening and closing different ones of
the
discharge passages, thus causing a pulsed fluid discharge from each of the
passages into the wellbore.
As the apparatus may be used on a casing string that will be cemented
into place upon reaching a desired depth in the wellbore and subsequently
drilled
out to allow deployment of an additional smaller casing string, the ball 72
may
selected to be of such material and construction so as to gradually dissolve,
disintegrate or otherwise break down over time under ongoing exposure to the
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pressurized stream of pumped fluid being conveyed through the chamber 30. This
way, the initial presence of the ball will provide the aforementioned fluid-
interruption
action to provide pulsating fluid discharge through the different discharge
ports of the
apparatus as the pumping of the fluid is initiated at low rates and volumes
and
allowed to build up. At higher pumping rates, even once the ball 72 has been
completely worn down to components sufficiently small to be removed from the
chamber 30 through the discharge ports into the wellbore, the higher flow rate
will
nonetheless be effective to provide a fluid-pulsating action as it moves
through the
chamber. The fluid is introduced under pressure and takes on a spiraling,
vertical
motion within the cavity under the effect of the tangentially sloped inlet
passages.
This process interrupts the fluids exit from the ports located on the end of
the
bullnose. The effect is a small pressure increase within the cavity as the
fluid is
interrupted upon exiting. The fluid flow through the discharge passages then
resumes and surges from the discharge ports in use. Testing with prototypes
has
revealed that a ball having a solid plastic or rubber core with a protective
outer shell
or cover can provide an effective interruption device that will break down
under
ongoing exposure to the pumped fluid, although other ball constructions are
expected to provide similar function, whether plastic or other wearable
material and
one or multiple layers, through preferably of solid form.
With the ball worn away by the fluid prior to cementing-in of the casing
string and shoe, the apparatus can be drilled out by drilling away the plug
and nose
of the body. However, being of sufficiently wearable material to be broken
down by
the pumped fluid over time, the ball 72 is also drillable, i.e. can be drilled
through
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with a conventional drill string bit. Accordingly, even if the ball hasn't
completely
broken down and been flushed from the chamber 30 by the pumped fluid by the
time
the casing has reached its desired depth, the ball can nonetheless be drilled
out with
the body to allow deployment of a further casing string through the drill-out
apparatus.
The casing shoe apparatus may be considered a low frequency
pulsating device designed to remove sloughing and debris from an open hole
during
casing liner insertion, and may be referred to as a sonic shoe. The name
"Sonic" is
derived from the characteristics of the dynamics it creates. The compression
wave
formed travels at the speed of sound in fluid. The tool operated in the
infrasonic
frequency range.
At activation, prototypes of the tool successively pulse fluid out of three
(3) ports at a rate of 16-32 times per second. As each pulse accelerates out
of the
ports, a compression wave is formed due to the abrupt acceleration and
deceleration
of the fluid, this compression wave is commonly called "water hammer. Tool
activation is achieved with fluid velocity through the tools which activates
an
interrupter or intermitter which opens and closes ports in succession to
create a
pulse or "burst" with high inertial forces. This pulse or "burst" will form a
compression
wave in the wellbore fluid and this compression wave will travel spherically
from its
point of origin through the fluid at the speed of sound.
As this compression wave contacts at or near a location of wellbore
damage or obstruction, it subjects the material first to a compressive
loading, and
then a tensional loading. With this repeated alternating loading occurring at
the
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operational frequency of the tool, the plugging material reaches its fatigue
failure
point. Low frequency generation provides power for the tool. Infar-Sonic
Frequencies (below 50 Hz) have a long wave length that can penetrate through
material rather than absorbing into it. A "Sonic Shoe" may operate in
frequency
range of 16-32 Hz (20-24 Hz usually). This frequency combined with "burst"
velocity
will generate a wave length of 167' - 200' (dependant on actual frequency).
The
forgoing numerical values are presented as examples, and are not intended to
limit
the scope of the present invention unless specified in the appended claims.
The tool or shoe may also provide benefit in the cementing process by
providing a similar pulsing action on the cement slurry being pumped down
through
the casing to the tool. That is, the tool may provide a pulsating effect on
the slurry
exiting the discharge ports into the bottom of the wellbore and filling up the
annular
space between the casing and the wellbore wall, and the resulting force
exerted by
this pulsating slurry may aid in uniform distribution of the cement slurry,
acting in an
outward manner away from the tool to force discharged slurry against
previously
discharged deposits of slurry, resulting in a tightly packed volume of slurry
to prevent
or limit the presence of voids or air bubbles in the collective deposit of
slurry, thereby
improving the uniformity of the resulting hardened cement and thus improving
the
strength and stability of the cemented-in casing installation. The high energy
of the
'bursts' or 'pulses' of cement slurry helps ensure they impact against the
wellbore
slurry deposits made by earlier slurry discharges from the tool to uniformly
build up
the deposit in the wellbore to avoid, minimize or reduce the occurrence of
gaps,
voids or air bubbles in the overall distribution of the slurry.
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Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without department from such spirit
and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
