U.S. patent application number 16/591499 was filed with the patent office on 2020-04-02 for drop balls for use with settable downhole tools.
The applicant listed for this patent is Nine Downhole Technologies, LLC. Invention is credited to Warren Lynn Frazier, Donald Roy Greenlee, Brian David Oligschlaeger.
Application Number | 20200102804 16/591499 |
Document ID | / |
Family ID | 69947233 |
Filed Date | 2020-04-02 |
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United States Patent
Application |
20200102804 |
Kind Code |
A1 |
Frazier; Warren Lynn ; et
al. |
April 2, 2020 |
Drop Balls for Use with Settable Downhole Tools
Abstract
Aspects of the present disclosed technology relate to drop balls
and covers for drop balls for use with settable downhole tools.
Aspects of the present disclosed technology also relate to methods
for using such drop balls and covers with settable downhole tools
to selectively allow fluid to pass through such downhole tools, or
to block fluid flow through the settable downhole tool.
Inventors: |
Frazier; Warren Lynn;
(Corpus Christi, TX) ; Greenlee; Donald Roy;
(Murchison, TX) ; Oligschlaeger; Brian David;
(Aledo, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nine Downhole Technologies, LLC |
Houston |
TX |
US |
|
|
Family ID: |
69947233 |
Appl. No.: |
16/591499 |
Filed: |
October 2, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62740173 |
Oct 2, 2018 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 23/0413 20200501;
E21B 33/12 20130101 |
International
Class: |
E21B 33/12 20060101
E21B033/12 |
Claims
1. A cage for use with a drop ball for a settable downhole tool,
the cage comprising: a spherical pocket surrounded by a plurality
of deformable segments of material, wherein the plurality of
deformable segments are arranged into a plurality of rings.
2. The cage of claim 1, wherein the deformable segments have a
durometer in the range of Shore A 60 to 100.
3. The cage of claim 1, wherein the spherical pocket has a diameter
between about 0.75 inches and about 4.375 inches.
4. The cage of claim 1, wherein the plurality of deformable
segments are arranged to form three mutually orthogonal rings
around the spherical pocket.
5. The cage of claim 1, wherein the plurality of deformable
segments comprise a dissolvable material.
6. A drop ball for use with a settable downhole tool, the drop ball
comprising: a spherical body surrounded by a plurality of
deformable segments of material, wherein the plurality of
deformable segments are arranged into a plurality of rings.
7. The drop ball of claim 6, wherein the deformable segments have a
durometer in the range of Shore A 60 to 100.
8. The drop ball of claim 6, wherein the spherical pocket has a
diameter between about 0.75 inches and about 4.375 inches.
9. The drop ball of claim 6, wherein the plurality of deformable
segments are arranged to form three mutually orthogonal rings
around the spherical pocket.
10. The drop ball of claim 6, wherein the spherical body is made of
a first material, the deformable segments are made of a second
material different than the first material, and the deformable
segments are overmolded on the spherical body.
11. The drop ball of claim 6, wherein the deformable segments have
a durometer in the range of Shore A 60 to 100.
12. The drop ball of claim 6, wherein the spherical body is
comprised of a polymer acid.
13. The drop ball of claim 6, wherein the spherical body is
comprised of a first dissolvable material having a first
dissolution rate, and the plurality of deformable segments are
comprised of a second dissolvable material having a second
dissolution rate.
14. The drop ball of claim 13, wherein the second dissolution rate
is faster than the first dissolution rate.
15. A method for using a drop ball with a settable downhole tool,
the method comprising: placing a drop ball on a seat located on an
inner fluid channel of a settable downhole tool in a wellbore,
wherein the drop ball comprises: a spherical body surrounded by a
plurality of deformable segments of material, wherein each of the
deformable segments have a height measured from a boundary of the
pocket to a point on the segment having a maximum radial distance
from a center of the pocket, and wherein an outer diameter of the
drop ball including the deformable segments is greater than the
seat; and pumping a fluid through a wellbore at a first flow rate,
wherein the fluid passes around the drop ball and through the inner
channel of the downhole tool; and pumping a fluid through a
wellbore at a second flow rate, wherein the second flow rate is
greater than the first flow rate, and wherein the deformable
segments of material deform and a fluid-tight seal is formed
between the seat and the drop ball, preventing a fluid flow through
the inner channel of the settable downhole tool.
16. The method of claim 15, wherein the deformable segments have a
durometer in the range of Shore A 60 to 100.
17. The method of claim 15, wherein the spherical pocket has a
diameter between about 0.75 inches and about 4.375 inches.
18. The method of claim 15, wherein the plurality of deformable
segments are arranged to form three mutually orthogonal rings
around the spherical pocket.
19. The method of claim 15, wherein the spherical body is made of a
first material, the deformable segments are made of a second
material different than the first material, and the deformable
segments are overmolded on the spherical body.
20. The method of claim 15, wherein the first flow rate is less
than about 20 barrels per minute.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/740,173, entitled "CONFIGURED DROP BALLS FOR USE
WITH SETTABLE DOWNHOLE TOOLS", filed 2 Oct. 2018.
TECHNICAL FIELD
[0002] Aspects of the present disclosed technology relate to drop
balls and covers for drop balls for use with settable downhole
tools. Aspects of the present disclosed technology also relate to
methods for using such drop balls and covers with settable downhole
tools to selectively allow fluid to pass through such downhole
tools, or to block fluid flow through the settable downhole
tool.
BACKGROUND OF THE INVENTION
[0003] Oil well completion operations frequently involve downhole
tools with explosive elements, such as perforating guns ("perf
guns" or "frac guns"). Examples of such operations include
formation perforation prior to hydraulic fracturing, where frac
guns are used to perforate oil well casing and/or perforate the
surrounding geological formation. Perforating is typically
performed in a series of stages, where each stage is a portion of
the well that is isolated using frac plugs or similar tools. In
some forms of frac plugs, each plug has a hole through the plug,
and a seat that is capable of receiving a ball that seals the frac
plug. These plugs are set downhole, and then frac balls can be run
downhole (or released from the setting tool), which seat themselves
in the frac plug, forming a seal capable of holding pressure.
[0004] Occasionally, frac guns will fail to fire. When this occurs,
the frac guns typically have to be removed from the hole, repaired
or replaced and re-run back into the well. Running the frac guns
back down the hole often requires pumping a fluid down the
wellbore, which pushes the frac guns back down to the intended area
of the wellbore. If a ball is already seated in the plug, it can be
difficult, if not impossible, to re-run the repaired or replaced
frac guns back down the wellbore. Attempts to pump the tools down
will be hindered by the pressure seal formed by the ball seated in
the frac plug.
[0005] Accordingly, it would be advantageous to have a drop ball in
place on a settable tool which can selectively either seal the plug
against fluid flow through the plug or permit fluid to be pumped
around the ball and through the plug seat. This feature would allow
frac guns or other downhole tools to be pumped down the wellbore
even after a drop ball has been placed on the settable downhole
tool. It would also be advantageous to have the same ball, which
can selectively either seal the plug against fluid flow through the
plug or permit fluid to be pumped around the ball and through the
plug seat during pumping down of guns, adapted to seal (hold
pressure) against the set tool seat during fracking or other high
pressure/high flow operations. Aspects of the present disclosure
accomplish these purposes, among others.
[0006] Some embodiments comprise a rubber or elastomeric overmolded
composite frac ball. In these embodiments, the cover can be an
overmolded material having multiple spikes, similar to a pet or
child's rubber spiked ball. In some embodiments, the overmold can
comprise one or more deformable segments that surround the
composite frac ball, such as in rings or other similar
configurations. The rubber or elastomer can have a durometer in the
range of Shore A 60 to 100, or preferably in the range of Shore A
of 85 to 95, including in some embodiments, a Shore A about 90
durometer, that is hard enough to maintain the ball in a standoff
position from the ball seat (low psi, gun removal/insertion) except
during higher or high psi on the ball from above the tool, such as
is encountered by the ball during a fracking operation or high pump
rates. In this condition, the spikes or deformable segments in
contact with the plug's ball seat will deform, break or collapse
responsive to the downward pressure on the ball, and the downward
pressure on the ball will push it toward the seal, causing the ball
to seal against the seat, and at least partly seal the plug, so the
plug will then hold pressure in the frac zone above the plug during
a fracking operation. Thus, a system and configuration for a tool
is created such that in the event that frac guns do not fire, one
can pull the guns out of the hole and pump good guns back down at a
slower rate or psi while being able to flow around the spiked ball
and through the plug, and still have a good seal between the ball
and the plug at a higher fracking pressure or psi pump rates.
SUMMARY OF THE INVENTION
[0007] Aspects of the present disclosed technology relate to a cage
for use with a drop ball for a settable downhole tool, the cage
comprising: a spherical pocket surrounded by a plurality of
deformable segments of material, wherein the plurality of
deformable segments are arranged into a plurality of rings. In some
embodiments, the deformable segments have a durometer in the range
of Shore A 60 to 100. In some embodiments, the spherical pocket has
a diameter between about 0.75 inches and about 4.375 inches. In
some embodiments, the plurality of deformable segments are arranged
to form three mutually orthogonal rings around the spherical
pocket. In some embodiments, the plurality of deformable segments
comprise a dissolvable material.
[0008] Aspects of the present disclosed technology also relate to a
drop ball for use with a settable downhole tool, the drop ball
comprising: a spherical body surrounded by a plurality of
deformable segments of material, wherein the plurality of
deformable segments are arranged into a plurality of rings. In some
embodiments, the deformable segments have a durometer in the range
of Shore A 60 to 100. In some embodiments, the spherical pocket has
a diameter between about 0.75 inches and about 4.375 inches. In
some embodiments, the plurality of deformable segments are arranged
to form three mutually orthogonal rings around the spherical
pocket. In some embodiments, the spherical body is made of a first
material, the deformable segments are made of a second material
different than the first material, and the deformable segments are
overmolded on the spherical body. In some embodiments, the
deformable segments have a durometer in the range of Shore A 60 to
100. In some embodiments, the spherical body comprises a polymer
acid. In some embodiments, the spherical body comprises a first
dissolvable material having a first dissolution rate, and the
plurality of deformable segments comprise a second dissolvable
material having a second dissolution rate. In some embodiments, the
second dissolution rate is faster than the first dissolution
rate.
[0009] Aspects of the present disclosed technology also relate to a
method for using a drop ball with a settable downhole tool, the
method comprising: placing a drop ball on a seat located on an
inner fluid channel of a settable downhole tool in a wellbore,
wherein the drop ball comprises: a spherical body surrounded by a
plurality of deformable segments of material, wherein each of the
deformable segments have a height measured from a boundary of the
pocket to a point on the segment having a maximum radial distance
from a center of the pocket, and, wherein an outer diameter of the
drop ball including the deformable segments is greater than the
ball seat; and pumping a fluid through a wellbore at a first flow
rate, wherein the fluid passes around the drop ball and through the
inner channel of the downhole tool; and pumping a fluid through a
wellbore at a second flow rate, wherein the second flow rate is
greater than the first flow rate, and wherein the deformable
segments of material deform and a fluid-tight seal is formed
between the seat and the drop ball, preventing a fluid flow through
the inner channel of the settable downhole tool. In some
embodiments, the deformable segments have a durometer in the range
of Shore A 60 to 100. In some embodiments, the spherical pocket has
a diameter between about 0.75 inches and about 4.375 inches. In
some embodiments, the plurality of deformable segments are arranged
to form three mutually orthogonal rings around the spherical
pocket. In some embodiments, the spherical body is made of a first
material, the deformable segments are made of a second material
different than the first material, and the deformable segments are
overmolded on the spherical body. In some embodiments, the first
flow rate is less than about 20 barrels per minute.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Included in the present specification are figures which
illustrate various embodiments of the present disclosed technology.
As will be recognized by a person of ordinary skill in the art,
actual embodiments of the disclosed technology need not incorporate
each and every component illustrated, but can omit components, add
additional components, or change the general order and placement of
components. Reference will now be made to the accompanying figures
and flow diagrams, which are not necessarily drawn to scale, and
wherein:
[0011] FIG. 1 illustrates a drop ball in accordance with an
embodiment.
[0012] FIG. 2 illustrates a cutaway view of a drop ball in
accordance with an embodiment that illustrates the interaction of
the drop ball with ball seats of various diameters.
[0013] FIG. 2A illustrates a drop ball in accordance with an
embodiment located in a seat, where the spikes of the drop ball
provide a "stand-off" space allowing fluid to flow around the ball
and through the ball seat.
[0014] FIG. 2B illustrates a drop ball in accordance with an
embodiment located in a seat, where the spikes of the drop ball are
compressed, forming a fluid seal with the ball seat.
[0015] FIG. 3 illustrates a spike on a drop ball in accordance with
an embodiment.
[0016] FIG. 4 illustrates a drop ball in accordance with an
embodiment made of a single material.
[0017] FIG. 5A illustrates a spike in accordance with an
embodiment.
[0018] FIG. 5B illustrates a spike in accordance with an
embodiment.
[0019] FIG. 5C illustrates a drop ball in accordance with an
embodiment with long spikes.
[0020] FIG. 5D illustrates a drop ball in accordance with an
embodiment with short spikes.
[0021] FIG. 5E illustrates a drop ball in accordance with an
embodiment that does not have a spherical center core.
[0022] FIG. 6A illustrates a drop ball in accordance with an
embodiment that does not have a spherical center core.
[0023] FIG. 6B illustrates a drop ball in accordance with an
embodiment having an overmolded layer over a drop ball that does
not have a spherical center core.
[0024] FIG. 7A illustrates an overmolded spike in accordance with
an embodiment.
[0025] FIG. 7B illustrates an overmolded spike in accordance with
an embodiment where the inner spike has broken.
[0026] FIG. 8 illustrates a drop ball in accordance with an
embodiment having a cage.
[0027] FIG. 9 illustrates a drop ball in accordance with an
embodiment having a cage located on a ball seat of a settable
downhole tool.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] Although example embodiments of the present disclosure are
explained in detail, it is to be understood that other embodiments
are contemplated. Accordingly, it is not intended that the present
disclosure be limited in its scope to the details of construction
and arrangement of components set forth in the following
description or illustrated in the drawings. The present disclosure
is capable of other embodiments and of being practiced or carried
out in various ways.
[0029] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one more other features, integers,
steps, operations, element components, and/or groups thereof.
[0030] By "comprising" or "containing" or "including" is meant that
at least the named compound, element, particle, or method step is
present in the composition or article or method, but does not
exclude the presence of other compounds, materials, particles,
method steps, even if the other such compounds, material,
particles, method steps have the same function as what is
named.
[0031] In describing example embodiments, terminology will be
resorted to for the sake of clarity. It is intended that each term
contemplates its broadest meaning as understood by those skilled in
the art and includes all technical equivalents that operate in a
similar manner to accomplish a similar purpose.
[0032] It is to be understood that the mention of one or more steps
of a method does not preclude the presence of additional method
steps or intervening method steps between those steps expressly
identified. Steps of a method can be performed in a different order
than those described herein. Similarly, it is also to be understood
that the mention of one or more components in a device or system
does not preclude the presence of additional components or
intervening components between those components expressly
identified.
[0033] In the following detailed description, references are made
to the accompanying drawings that form a part hereof and that show,
by way of illustration, specific embodiments or examples. In
referring to the drawings, like numerals represent like elements
throughout the several figures.
[0034] FIG. 1 illustrates a drop ball 10 in accordance with an
embodiment. In some embodiments, the drop ball 10 comprises a
spherical core 12 with a cover having one or more protrusions from
the core. For example, FIG. 1 depicts an embodiment where the drop
ball 10 has a spherical core 12 and a cover having spikes 18 which
protrude from the core 12.
[0035] FIG. 2. illustrates a cutaway view of a drop ball in
accordance with an embodiment that illustrates the interaction of
the drop ball with ball seats of various diameters. In some
embodiments, the cover 18 can be layered or molded as an overmold
member 14. In some embodiments, the cover 18 can be formed
separately from the core 12, and can be placed on, or removed from
core 12. In some embodiments, overmold member 14 can include a
spherical shell 16, having a diameter greater than the core 12 and
typically layered or adhering directly against the outer surface of
the core 12. In some embodiments, overmold member 14 can include a
multiplicity of spikes 18, extending outward from the spherical
shell 16. In some embodiments, overmolded member 14 can include a
plurality of deformable segments of material. In some embodiments,
the overmolded member 14 can be comprised of the same material as
spherical shell 16. In some embodiments, overmold member 14 can
have gaps or spaces where the core 12 is exposed to the
surroundings. FIGS. 8-9 illustrate an embodiment having gaps or
spaces 41, which form a cage 40 around core 12. In some
embodiments, such gaps 41 can allow the overmolded member 14 or a
cage 40 to be removed from the core 12, or can allow an overmolded
member 14 or a cage 40 formed separately to be placed around the
core 12. In some embodiments, the spherical shell 16 and/or the
overmolded member 14 and/or cage 40 can comprise an elastomer, such
as Nitrile, urethane rubber, TPE or rubber in some embodiments
having a durometer in the range of 60 to 100 Shore A.
[0036] In some embodiments, core 12 and/or the cover 18 can
comprise a degradable or non-degradable material or any number of
known downhole tool composites comprising a resin and a cloth. In
some embodiments, components can be comprised of a polymer acid,
which optionally can be degradable in downhole fluids. In some
embodiments, the core 12 can comprise a material that degrades at a
rate slower than the cover 18. For those embodiments, when the
cover 18 dissolves or degrades, the drop ball 10 behaves as an
ordinary spherical drop ball. In some embodiments, the polymer acid
can be selected from the group comprising polyglycolic acid or
polylactic acid. In some embodiments, core 12 can have a diameter
of D1, which can be in the range of 0.75'' to 4.375''. In some
embodiments, the core 12 can be rigid and harder than overmolded
member 14.
[0037] In some embodiments, overmold member 14 can be overmolded
onto core 12. An example of a method for overmolding in accordance
with embodiments include those described in U.S. Application
62/625,099, entitled "Molded Degradable Downhole Tool Elements,"
published as U.S. 2019/0169953 A1 on Jun. 6, 2019, which
publication is hereby incorporated by reference in its entirety as
if fully set forth herein. In some embodiments, the cover 18 can be
overmolded on a temporary core, such as a steel ball or other
tooling, and then removed for use on other cores. In some
embodiments, the overmolded member 14 can include spherical shell
16 which can have an outer diameter D2 that is greater than D1, the
diameter of the core 12, the difference between D1 and D2
representing the thickness of spherical shell 16, which can be in
the range of 0.100'' to 4.125 inches, when uncompressed. In some
embodiments, the thickness of the spherical shell can be 1/8'' to
1.0''. In some embodiments, the thickness of the spherical shell 16
can be uniform. An example of such an embodiment is shown in FIG.
5E, for example. As illustrated in FIG. 5D, in some embodiments
overmolded member 14 can include a multiplicity of spikes 18
extending from an outer surface of the spherical shell. As set
forth in FIGS. 1 and 2, spiked ball 10 can have a diameter D3
representing the greatest diameter of the spiked ball and the
diameter from the tip of a first spike 18' to the tip of a second
spike 18'' about 180.degree. opposite from the first spike. This
diameter can be in the range of 1.00 to 5.00 inches, or up to 6.00
inches, or any other suitable dimension.
[0038] FIG. 2 illustrates three possible relationships between D1
(core diameter), D2 (shell diameter), and D3 (greatest
diameter--spike tip to spike tip), and three seat diameters
(circular seat), A, B, and C. In some embodiments, seat diameter A
is equal to or less than diameter D1. In some embodiments, seat
diameter B is greater than D1 and equal to or less than D2. In some
embodiments, seat diameter C is greater than D2, but less than D3.
Testing of the various embodiments has revealed that embodiments
where seat diameter A is equal to or less than diameter D1 can seal
against the greatest pressure.
[0039] FIG. 2A illustrates a seated, substantially non-sealed
position of a drop ball 10 in accordance with an embodiment against
the seat 31 of a settable downhole tool 30. FIG. 2B illustrates a
seated, substantially sealed position of a drop ball in accordance
with an embodiment against the seat 31 of a settable downhole tool
30. In the non-sealed position, the spikes 18 are substantially
non-deformed or only slightly deformed and allow fluid to flow 32
(see arrows) between the spiked tips 18 and the outer surface of
the spherical outer shell 16. This space that allows fluid flow 32
is referred to as the "standoff space" 33. In FIG. 2A, H1 the
height of the ball above the seat 31 at pressure P1 (for example,
pressure encountered during gun removal) is greater than H2 the
height of the ball above the seat 31 at a greater pressure P2, such
as a pressure encountered during fracking operations or, in some
embodiments, insertion of guns. The greater pressure has caused the
spikes 18 (as seen in FIG. 2B) that are in contact with the ball
seat 31 to deform and wedge or jam into the standoff space 33 that
existed or at least most of the standoff space 33 that existed
between the spikes 18 and the seat 31 at the lower pressure
illustrated in FIG. 2A. This wedging or jamming created by
deformation of the elastomeric spikes 18 is illustrated in FIG. 2B.
Note that spike axis is deformed in FIG. 2B when compared with the
spike axis in FIG. 3, a ball 10 not under pressure.
[0040] FIG. 3 illustrates a drop ball 10 in accordance with an
embodiment in an uncompressed (no pressure delta or fluid flow)
condition. It is seen that a spike 18, which is typically conical,
and can have a base 20 where the spike joins the spherical shell
16, has a spike axis 19 aligned with an axis representing a radius
of the core 12. However, under compression against the seat 31, the
spike axis 19 can shift as the spike 18 deforms from its conical
position to a jammed, collapsed or deformed position between the
seat 31 and the spherical shell 16.
[0041] FIG. 3 also illustrates that spike base 20 can have a
diameter D.sub.SPIKE BASE (D.sub.SB) and that the outer surface of
the spherical shell 16 has a multiplicity of spikes 18. In some
embodiments, the distance from all spikes 18a to all adjacent
spikes 18b can be equal to or less than the diameter of the spiked
base D.sub.SB (assuming all spikes have same dimensions). In other
embodiments, the distance between adjacent spike bases 20 can be
greater than a single D.sub.SB. Distances are measured along the
curved surface of spherical shell 16.
[0042] In some embodiments, the total area of the spike bases 20 is
50% or more of what the total spherical area of the outer surface
of the spherical shell 16 would be if it had no spikes. In other
words, in some embodiments, spikes 18 cover more than half the
surface of the outer shell 16. In other embodiments, spikes 18
cover the same or less than the surface of the outer shell 16.
[0043] In some embodiments, one, some or all of the core 12 and
spherical shell 16 and spikes 18 are made of the same material, in
some embodiments, an elastomer; in some embodiments, one, some or
all can be degradable (see FIG. 4). Degradable spikes 18, for
example, will upon degradation either seal the ball 10 to the seat
31 or permit the ball 10 to pass through the seat 31 depending on
size and configuration.
[0044] In some embodiments, the projections 18 are compressible or
crushable, and can or can not be elastomeric. Compressing or
crushing the projections 18 to an outer diameter which is less than
the inner diameter of the seat 31 permits the ball 10 to pass
through the seat 31 and fully open the seat 31. Compressing or
crushing the projections 18 to an outer diameter which is greater
than the inner diameter of the seat 31 permits the ball 10 to seal
against the seat 31 and close or seal the seat 31. In some
embodiments of the projections 18 are shearable, shearing the
projections 18, permitting the ball 10 to pass through the seat 31
and fully open the seat 31.
[0045] FIGS. 5A and 5B show non-conical spikes 18, here regular
cylindrical (FIG. 5A) and wavy cylindrical (FIG. 5B), but both,
like FIG. 3, showing spikes 18 with height greater than maximum
thickness (width). FIG. 5C shows a ball 10 with multiple "filament"
projections 18, with a height at least length several multiples of
its thickness (width). FIGS. 5D and 5E show balls with `nub" shaped
projections 18, whose thickness (width) is greater than height.
[0046] FIG. 6A illustrates a non-spherical core 12, here with
multiple core projections 22, the non-spherical core 12 overmolded
with an elastomeric outer shell 16 (here of non-uniform thickness).
Unlike previous embodiments, here the outer shell projections 18
are the result of overmolding an elastomeric shell 16 over core
projections 22. D.sub.max and D.sub.min, in some embodiments, are
sized such that D.sub.max is greater than the seat diameter and
D.sub.min is less than the seat diameter. FIG. 6B shows the core of
FIG. 6A with overmolded elastomeric outer shell 16 (speckled
layer).
[0047] FIGS. 7A and 7B show a non-spherical core 22 with multiple
spiked projections 18 overmolded with elastomeric outer shell 16.
FIG. 7B shows how the spike 18, being rigid and thin, can break
under high pressure forcing the ball 10 against the seat 31 and
helping "wedge" or "jam" the elastomeric material against the seat
31 for a good seal.
[0048] FIG. 8 illustrates an embodiment where the cover 18 is a
"cage" 40. In the embodiment illustrated in FIG. 8, the cage 40
comprises a plurality of deformable segments 42 of material
arranged in three rings, each of which is perpendicular to the
other two. These mutually perpendicular rings or deformable
segments 42 serve to provide a "stand-off" distance 33 when seated
on the seat of a settable downhole tool, as with other embodiments.
FIG. 9 illustrates the embodiment of FIG. 8 when placed on an
example seat 31 of a downhole tool 30. As can be seen, the cage 40
provides a standoff distance 33 from the seat, allowing fluid to
pass around the drop ball 10 and through the settable downhole tool
30. When sufficient flow rate is applied to the drop ball 10, the
deformable segments 42 will deform, and create a fluid seal on the
seat 31 between the deformable segments 42, the core 12, and the
seat 31 of the downhole tool 30. This fluid seal can then hold high
pressure, such as the pressures required to perform hydraulic
fracturing.
[0049] In some embodiments, the cover 18 can provide sufficient
standoff distance 33 to allow fluid to pass around the drop ball 10
and through the settable downhole tool 30 at fluid rates of up to
10 or up to 20 barrels per minute. As would be recognized by a
person of ordinary skill in the art, the cover 18 configuration can
be adjusted, either by changing the material (such as to use a
material with a different durometer rating), or the shape of the
cover (such as spike size, length, or the use of cages,
non-spherical cores, etc.), to adjust the maximum flow rate capable
of being pumped around the downhole tool 30. Harder materials, and
larger standoff distances 33 will result in higher possible flow
rates before a seal is formed.
[0050] In some embodiments, the core 12 can also be made of a
dissolvable material, such as an elastomer, which can after a
period of time, or predetermined period of time, dissolve, leaving
a through path for the oil, gas or fluid to flow through set plugs.
In some embodiments, the cover 18 can also be made of a dissolvable
material, such as an elastomer, which can, after a period of time,
or a predetermined period of time, dissolve. In some embodiments,
the cover 18 can be made of a dissolvable material that dissolves
more quickly than the dissolvable material of the core 12. In such
embodiments, after the cover 18 dissolves, the remaining core 12 is
substantially equivalent to a standard drop ball 10. In some
embodiments, the drop ball 10 can withstand higher pressures after
the cover has been removed. Nevertheless, testing has shown that
embodiments can hold pressures suitable for hydraulic fracturing
operations, including pressures of at least up to 10,000 psi,
including with the cover 18 configuration shown in FIG. 7, without
needing to dissolve the cover 18.
[0051] The corresponding structures, materials, acts, and
equivalents of all means or step plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. The description of the present
invention has been presented for purposes of illustration and
description, but is not intended to be exhaustive or limited to the
invention in the form disclosed. Many modifications and variations
will be apparent to those of ordinary skill in the art without
departing from the scope and spirit of the invention. The
embodiment was chosen and described in order to best explain the
principles of the invention and the practical application, and to
enable others of ordinary skill in the art to understand the
invention for various embodiments with various modifications as are
suited to the particular use contemplated.
[0052] While the preferred embodiment to the invention had been
described, it will be understood that those skilled in the art,
both now and in the future, can make various improvements and
enhancements which fall within the scope of the claims which
follow. These claims should be construed to maintain the proper
protection for the invention first described.
* * * * *