U.S. patent application number 15/844080 was filed with the patent office on 2018-06-21 for apparatus and method for dry injecting balls for wellbore operations.
The applicant listed for this patent is ISOLATION EQUOPMENT SERVICES INC.. Invention is credited to Boris (Bruce) P. CHEREWYK.
Application Number | 20180171739 15/844080 |
Document ID | / |
Family ID | 62556087 |
Filed Date | 2018-06-21 |
United States Patent
Application |
20180171739 |
Kind Code |
A1 |
CHEREWYK; Boris (Bruce) P. |
June 21, 2018 |
APPARATUS AND METHOD FOR DRY INJECTING BALLS FOR WELLBORE
OPERATIONS
Abstract
A system and method are provided for storing and dry launching
one or more balls into a wellbore having reduced ball drop height
and ball drop stages relative to existing systems and methods.
Balls are individually stored in cartridges of a ball launcher in
communication with the wellbore via an axial bore, and are isolated
from fluids and pressure in the axial bore by seals located on the
cartridge. A selected ball can be injected into the wellbore by
isolating the axial bore from the wellbore, establishing a
launching pressure in the axial bore, actuating the cartridge of
the selected ball to a launch position to stage the ball in the
axial bore, retracting the cartridge to a sealing position,
establishing a release pressure in the axial bore, and then
re-establishing communication between the axial bore and wellbore
to allow the ball to be injected.
Inventors: |
CHEREWYK; Boris (Bruce) P.;
(Calgary, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ISOLATION EQUOPMENT SERVICES INC. |
Red Deer |
|
CA |
|
|
Family ID: |
62556087 |
Appl. No.: |
15/844080 |
Filed: |
December 15, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62435082 |
Dec 16, 2016 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 43/26 20130101;
E21B 33/068 20130101; E21B 34/02 20130101 |
International
Class: |
E21B 33/068 20060101
E21B033/068; E21B 34/02 20060101 E21B034/02; E21B 43/26 20060101
E21B043/26 |
Claims
1. A method for dry launching one or more balls into a wellbore
under wellbore pressure, comprising: individually storing each of
the one or more balls in a ball launcher, each ball being sealed
from an axial bore of the ball launcher; isolating the axial bore
from the wellbore with an upper isolation valve; establishing a
launching pressure in the axial bore, the launching pressure being
less than the wellbore pressure; actuating the ball launcher to
unseal a selected ball of the stored balls and release the ball to
the axial bore and onto the upper isolation valve; pressurizing the
axial bore to a release pressure at about the wellbore pressure;
and opening the upper isolation valve to drop the selected ball
into the wellbore.
2. The method of claim 1, further comprising: closing the upper
isolation valve; selecting a subsequent selected ball; and
repeating the step establishing of the launching pressure,
actuating the ball launcher to release the subsequent selected
ball; pressurizing the axial bore and opening the upper isolation
valve to drop the subsequent selected ball.
3. The method of claim 1, wherein the pressurizing the axial bore
to the release bore comprises pumping fluids into the axial
bore.
4. The method of claim 1, wherein the establishing the launching
pressure in the axial bore comprises removing at least some fluids
from the axial bore.
5. The method of claim 1, wherein individually storing each of the
one or more balls comprises storing each of the one or more balls
in one or more corresponding cartridges, each of which is sealed
from the axial bore; and actuating the ball launcher to unseal the
selected ball comprises actuating the cartridge corresponding to
the selected ball from a sealed position to a launch position in
the axial bore.
6. The method of claim 4, wherein the establishing the launch
pressure in the axial bore comprises removing fluids from the axial
bore to a fluid level below a lowermost of the cartridges.
7. The method of claim 4, wherein the removing of fluids from the
axial bore comprises gravity draining fluids therefrom.
8. The method of claim 4, wherein the removing of fluids from the
axial bore comprises pumping fluids therefrom.
9. The method of claim 6, further comprising introducing dry gas to
the axial bore while removing fluids.
10. The method of claim 1, wherein the launching pressure is at
about atmospheric pressure.
11. The method of claim 1, wherein pressurizing the axial bore
further comprises increasing a fluid pressure in the axial bore to
about the wellbore pressure.
12. The method of claim 1, wherein opening the upper isolation
valve further comprises pumping fluid into and through the axial
bore to displace the selected ball into the wellbore.
13. A system for storing and dry launching one or more balls into a
wellbore, comprising: a ball launcher having an axial bore in fluid
communication with the wellbore, and one or more radial bores, each
radial bore having a distal end open to the axial bore for access
thereto; cartridges corresponding to at least two of the one or
more radial bores, each cartridge storing a corresponding ball of
one of the one or more balls and actuable between a sealing
position residing in the radial bore, misaligned from the axial
bore, and a launch position aligned with the axial bore through the
open bore end; an upper isolation valve for alternatively fluidly
isolating the ball launcher from the wellbore and fluidly coupling
the ball launcher and the wellbore; and an equalization port in
fluid communication with the axial bore for adjusting fluid
pressure in the axial bore.
14. The system of claim 13, wherein each cartridge is sealed to its
respective radial bore in the sealing position with one or more
cartridge seals adjacent at least a distal end of the cartridge for
fluidly isolating the stored ball from the axial bore.
15. The system of claim 13, wherein a pumper is connected to the
equalization port and operable to selectably remove fluid from the
axial bore or deliver fluid to the axial bore to adjust the fluid
pressure in the axial bore.
16. The system of claim 13, wherein each of the one or more
cartridges has a flared distal end for engaging a corresponding
flare seat at a bore interface at the open distal end of the
cartridge's radial bore.
17. The system of claim 16, wherein each cartridge's bore interface
supports the cartridge in the sealing position against wellbore
pressures.
18. The system of claim 16, wherein each cartridge's bore interface
forms a primary seal between the axial bore and the stored
ball.
19. The system of claim 18, further comprising one or more
cartridge seals adjacent at least a distal end of the cartridge to
form a secondary seal between the axial bore and the stored
ball.
20. The system of claim 16, wherein each of the one or more
cartridges stores its corresponding ball in a ball-receiving cup
intermediate the cartridge, the one of one or more cartridge seals
comprise a distal seal adjacent the distal end of the cartridge and
a swab seal adjacent a proximal end of the cartridge opposing the
distal end for fluidly isolating the stored ball therebetween.
21. The system of claim 14, further comprising a swab seal adjacent
a proximal end of the cartridge opposing the distal end.
22. The system of claim 13, wherein the equalization port is
located between the upper isolation valve and the lowest of the one
or more radial bores.
23. The system of claim 13, further comprising: a first bleed port
located between the upper isolation valve and the lowest of the one
or more radial bores; and a second bleed port is located above the
one or more cartridges.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent application Ser. No. 62/435,082, filed Dec. 16, 2016, the
entirety of which is incorporated herein by reference.
FIELD
[0002] Embodiments disclosed herein generally relate to a method
for injecting balls into a wellbore, such as drop balls, frac
balls, packer balls and other balls, for interacting with downhole
tools, and more particularly to an apparatus and methods for dry
launching balls into the wellbore while avoiding ball
deterioration.
BACKGROUND
[0003] It is known to conduct fracturing or other stimulation
procedures in a wellbore by isolating zones of interest (or
intervals within a zone) in the hydrocarbon-bearing locations of
the wellbore, using packers and the like, and subjecting each
isolated zone to treatment fluids, including liquids and gases, at
treatment pressures. In a typical fracturing procedure for a cased
wellbore, for example, the casing of the well is perforated or
otherwise opened to admit oil and/or gas into the wellbore and
fracturing fluid is then pumped into the wellbore and through the
openings. Such treatment forms fractures and opens and/or enlarges
drainage channels in the formation, enhancing the producing ability
of the well. For open holes that are not cased, stimulation is
carried out directly in the zones or zone intervals.
[0004] It is typically desired to stimulate multiple zones in a
single stimulation treatment, typically using onsite stimulation
fluid pumping equipment and a plurality of downhole tools,
including packers and sliding sleeves. In one technique, a series
of packers are inserted into the wellbore, each of the packers
located at intervals for isolating one zone from an adjacent zone.
Sliding sleeves can be located between packers that are selectively
actuable to open to the isolated zone. It is known to introduce a
ball into the wellbore to selectively engage one of the sleeves in
order to block fluid flow thereby whilst opening to the isolated
zone uphole from the ball for subsequent treatment or stimulation.
Once the isolated zone has been stimulated, a subsequent ball is
dropped to block off a subsequent sleeve, uphole of the previously
blocked sleeve, for isolation and stimulation thereabove. The
process is continued until all the desired zones have been
stimulated. Typically the balls range in diameter from a smallest
ball, suitable to block the most downhole sleeve, to the largest
diameter, suitable for blocking the most uphole packer.
[0005] Similarly, introduced balls can selectively engage
sequential packers in a pre-perforated wellbore in order to
stepwise block fluid flow through the wellbore, creating an
isolated zone uphole from the selected packer for subsequent
treatment or stimulation. Once the isolated zone has been
stimulated, a subsequent ball is dropped to block off a subsequent
packer, uphole of the previously blocked packer, for isolation and
stimulation thereabove. The process is continued until all the
desired zones have been stimulated.
[0006] At surface, the wellbore is fit with a wellhead including
valves and a pipeline connection block, such as a stimulation
flowhead or frac header, which provides fluid connections for
introducing stimulation fluids, including sand, gels and acid
treatments, into the wellbore. Conventionally, operators manually
introduce balls to the wellbore through an auxiliary line, coupled
through a valve, to the wellhead. The auxiliary line is fit with a
valved tee or T-configuration connecting the wellhead to a fluid
pumping source and to a ball introduction valve. The operator
closes off the valve at the wellhead to the auxiliary line,
introduces one ball and blocks the valved T-configuration. The
pumping source is pressurized to the auxiliary line and the
wellhead valve is opened to introduce the ball. This procedure is
repeated manually, one at a time, for each ball. This operation
requires personnel to work in close proximity to the treatment
lines through which fluid and balls are pumped at high pressures
and rates. The treatment fluid is typically under high pressure,
gas energized, and possibly corrosive, which is very hazardous.
[0007] Aside from being a generally hazardous practice, other
operational problems may occur, such as valves malfunctioning and
balls becoming stuck and not being pumped downhole. These problems
have resulted in failed well treatment operations and require
re-working, which is very costly and inefficient. At times
re-working or re-stimulating of a well formation following an
unsuccessful stimulation treatment may not be successful, which
results in production loss.
[0008] Other alternative methods and apparatus for the introduction
of the balls have included an array of remote valves positioned
onto a multi-port connection at the wellhead with a single ball
positioned behind each valve. Each valve requires a separate
manifold fluid pumper line and precise coordination both to ensure
the ball is deployed and to ensure each ball is deployed at the
right time in the sequence, throughout the stimulation operation.
The multi-port arrangement, although workable, has proven to be
very costly and inefficient. Further, this arrangement is dangerous
to personnel due to the multiplicity of lines under high pressure
connected to the top the wellhead during the stimulation operation.
The multiplicity of high pressure lines also logistically limits
the amount of balls that can be dropped due to wellhead design and
available ports.
[0009] Additionally, balls must be returned such as by reverse or
produced flow up the well to permit fluid flow through the
wellbore. Naturally, the time spent retrieving dropped balls from
the wellbore instead of producing is undesirable. Further, it is
not uncommon for a ball to be damaged during injection, in many
cases forcing operators to flow the damaged balls back uphole or,
in a worst case scenario, drill them out prior to dropping a
replacement ball. However, it is even less undesirable to have to
retrieve a ball mid-operation. Accordingly, the use of dissolvable
balls is becoming more prevalent in the industry.
[0010] Dissolvable balls, which typically break down upon contact
with fluids, such as fracturing or drilling fluids, have seen
increased use as they are not required to be retrieved or drilled
out, simply dissolving from exposure to wellbore fluids after
treatment and/or stimulation operations are complete. Dissolvable
balls are often preloaded in a ball injector, and premature contact
with fluids can cause deterioration thereof, compromising the
integrity of the balls.
[0011] There exists apparatus such as that taught in published
application US2015/0021024 to Oil States Energy Services LLC,
Houston Tex. (Oil States), that provide a dry and atmospheric
pressure storage option for dissolvable balls just prior to well
injection. The system appears to adapt the principles of hot
tapping access to a pressurized environment through a fluid or air
lock, a hydraulic ram alternately receiving a ball into a chamber
and shifting the chamber and ball through seal packs to place the
ball into the pressurized environment and in alignment with the
wellbore. The balls are stored axially offset from the wellbore,
and are each mechanically manipulated into alignment with the
wellbore via the chamber. The chamber is then returned to storage
with a bolus of pressurized fluid therein. An equalization section
reduces the pressure within the chamber before return to the ball
storage section. As described therein, frac balls can be stored in
the dry environment until they are placed into the frac ball
injection chamber to be inserted into the wellbore. Thus, a
subsequent dissolvable ball would then be stored in a wet
environment of the previously operated injection chamber, in the
intermediate apparatus between storage and wellbore, albeit at
atmospheric pressure therein, and still be at risk of premature
deterioration.
[0012] Keeping dissolvable balls dry, such as being maintained in
an air environment, until just prior to well injection also
introduces the risk of damaging balls during staging operations due
to the balls falling through air at high speeds after being
released with no viscous fluids to slow them down. Applicant notes
in particular that vertically stacked, multi-ball magazines or
launchers permit a ball to vertically drop significant distances
onto intermediate valves or other downhole equipment.
[0013] The Oil States application also notes such disadvantages
associated with increasing heights of ball-dropping assemblies and
additional structure to accommodate such configurations. One
example of ball dropping apparatus subject to ball storage and
release from greater heights includes that disclosed in US
20140360720 to Corbeil and published Dec. 11, 2014. The disclosed
ball injector is a serially stacked ball magazine, secured above a
wellhead staging assembly and bracketing valves, all of which
result in a very tall wellhead stack.
[0014] Balls dropped through air from ever increasing heights can
accelerate to substantial speeds before impact, increasing the risk
of damage to the balls. Applicant notes, however, that the solution
taught in Oil States, while providing a low wellhead profile,
results in a limit to the number of preloaded balls and requires
frequent reloading, thereby increasing demand on labor and risk of
operator error.
SUMMARY
[0015] When storing dissolvable balls for use in the treatment of
wells, it is advantageous to isolate the balls from coming into
contact with fluids, such as fracturing, drilling, or displacement
fluids, prior to injection into the wellbore, thus avoiding
premature deterioration thereof.
[0016] Dropped ball access to fluid pressurized systems, from
external or atmospheric locations, typically result in residual
fluid retained in said access passageways which pose a risk to the
integrity of stored dissolvable balls. Therefore, in one aspect,
fluids are removed from the environment before introducing a dry
ball thereto.
[0017] In another embodiment, a system and a method for dry
launching balls comprises providing one or more balls, each housed
and selectably sealed from the wellbore in a respective cartridge,
and only introduced to the wellbore and exposed to fluids when the
ball is launched. In an embodiment, the balls are preloaded in
cartridges mounted an array or stacked arrays of radial bores of a
radial ball injector or ball launcher, so as to conveniently
provide many balls or even the desired number of balls for a
downhole job.
[0018] Each ball cartridge is actuable to access an axial bore of
the ball launcher which is exposed to wellbore fluids. The axial
bore is alternately exposed to the wellbore pressure, such as
between each ball launch. Each cartridge is fit with seals to
isolate its respective ball from the axial bore of the launcher
until the cartridge is actuated from a sealed position to a launch
position. The seals aid in keeping the ball dry.
[0019] The axial bore of the launcher can be isolated from the
wellbore and wellbore pressure by an upper isolation gate. The
upper isolation valve can stage a ball thereon in the axial bore,
the pressure of the axial bore being controllably adjusted to a
release pressure about equal to wellbore pressure before being
connected to the wellbore for injecting the staged ball therein.
Between ball launches, the pressure in the axial bore can be
adjusted, and fluid accumulated therein can be removed, such as by
pump or by gravity drainage. The fluid pressure in the axial bore
can be adjusted to a launch pressure less than the wellbore
pressure, such as before actuating a cartridge to launch a ball
into the axial bore, or to increase pressure after launch to
equalize to about wellbore pressure for injecting a staged ball
into the wellbore.
[0020] Establishing a launching pressure, lower than wellbore
pressure, in the axial bore allows the cartridges and cartridge
seals to be exposed to a manageable fluid pressure between ball
launches. Further, the lower launch pressure avoids actuation of
the cartridges from the sealed to launch positions against the
large forces generated by axial bore pressures acting against the
surface area of the cartridge when the axial bore is under wellbore
pressure. After launch, and when the cartridge has been actuated to
return to the sealed position, the pressure in the axial bore can
be equalized to a release pressure, about equal to or greater than
wellbore pressure, for injection of the staged ball. This method
can then be repeated for subsequent balls to be dropped into the
wellbore.
[0021] In one broad aspect, a method for dry launching one or more
balls into a wellbore under wellbore pressure is provided,
comprising: individually storing each of the one or more balls in a
ball launcher, each ball being sealed from an axial bore of the
ball launcher; isolating the axial bore from the wellbore with an
upper isolation valve; establishing a launching pressure in the
axial bore, the launching pressure being less than the wellbore
pressure; actuating the ball launcher to unseal a selected ball of
the stored balls and release the ball to the axial bore and onto
the upper isolation valve; pressurizing the axial bore to a release
pressure at about the wellbore pressure; and opening the upper
isolation valve to drop the selected ball into the wellbore.
[0022] In another broad aspect, a system for storing and dry
launching one or more balls into a wellbore is provided,
comprising: a ball launcher having an axial bore in fluid
communication with the wellbore, and one or more radial bores, each
radial bore having a distal end open to the axial bore for allowing
access thereto; cartridges corresponding to two or more at least
two of the one or more radial bores, each cartridge storing a
corresponding ball of one of the one or more balls and actuable
between a sealing position residing in the radial bore, misaligned
from the axial bore, and a launch position aligned with the axial
bore through the open bore end; an upper isolation valve for
alternatively fluidly isolating the ball launcher from the wellbore
and fluidly coupling the ball launcher and the wellbore; and an
equalization port in fluid communication with the axial bore for
adjusting fluid pressure in the axial bore.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a cross-sectional representation of an embodiment
of a fracturing system for launching dissolvable balls in a dry
environment, depicting a ball launcher and a frac header having a
common bore in communication with a wellbore. Isolation gate valves
are provided between the launcher and the wellbore. A ball
cartridge of the launcher has been actuated to drop a ball into the
axial bore;
[0024] FIGS. 1 through 7 illustrate steps from releasing a first
ball from the cartridge according to the apparatus of FIG. 1
through removing fluids from the axial bore of the launcher in
preparation for a subsequent launcher ball launch, more
particularly:
[0025] FIG. 1 illustrates actuation of a first ball cartridge to
drop a first ball into the axial bore above the upper isolation
valve, the launcher's axial bore isolated from the frac header;
[0026] FIG. 2 illustrates retraction and sealing of the first
cartridge, the first ball shown resting on the upper isolation
valve;
[0027] FIG. 3 illustrates a pressurization of the ball launcher
above the upper isolation valve with displacement liquid, all
remaining balls sealed from the axial bore and remaining isolated
from liquid in the axial bore;
[0028] FIG. 4 illustrates opening of the upper isolation valve to
flow displacement liquid and the first ball into the live frac
header and wellbore therebelow, the pressure in the axial bore of
the launcher and the wellbore being about the same;
[0029] FIG. 5 illustrates closing of upper isolation valve;
[0030] FIG. 6 illustrates optional bleeding of the high pressure in
the launcher, depending on the capabilities of the displacement
pumper connected thereto, for reducing the pressure in the axial
bore;
[0031] FIG. 7 illustrates a drawdown of the liquid in the ball
launcher to atmospheric or a slight vacuum in preparation for
release of the next successive ball;
[0032] FIG. 8A is a ball-storing cup of a piston cartridge for the
ball launcher of FIG. 1, shown in the sealing position and fit with
seals provided about the cartridge, the distal end having a flared
interface;
[0033] FIG. 8B is an alternative embodiment of the ball-storing cup
of FIG. 8A having a square-edged flared interface;
[0034] FIG. 8C shows the ball-storing cup of FIG. 8B being actuated
to a launch position and releasing a dissolvable ball into the
axial bore of the ball launcher;
[0035] FIG. 9A shows an alternative embodiment of the ball launcher
having cartridges set back into the radial bores of the ball
launcher away from the axial bore, both of the cartridges shown in
the sealing position;
[0036] FIG. 9B shows the embodiment of FIG. 9A wherein one of the
cartridges has been actuated to the launch position and extends
partially into the radial bore of the opposing cartridge so as to
operatively align its ball-containing cup with the axial bore;
[0037] FIG. 10 is a flow diagram setting out an example process for
loading dissolvable balls into the cartridges of embodiments of a
ball launcher described herein; and
[0038] FIG. 11 is a flow diagram setting out an example process for
injecting dissolvable balls into the wellbore using embodiments of
a ball launcher described herein.
DESCRIPTION
[0039] With reference to FIG. 1, and in a first embodiment, a
fracturing system 10 is provided for dry injection of dissolvable
balls 12 in fracturing operations. The system 10 comprises a frac
header 14 fluidly connected to a wellbore W below and a ball
injector or launcher 20 thereabove, all of which share a common
bore 16. A ball launched from the launcher 20 can traverse the
common bore 16 to the wellbore W.
[0040] The frac header 14 is further configured to provide
fracturing and/or stimulation fluids F to the wellbore W, the fluid
F suitable for well stimulation operations. Herein, the terms
fracturing fluids and/or stimulation fluids are used
interchangeably and are liquids or mixtures of liquids, other
additives, and particulates used in fracturing or stimulation
operations and the like.
[0041] The ball launcher 20 stores one or more balls 12 for
selective and sequential release to the wellbore W. Herein, in an
embodiment, the balls 12 react to exposure to fluids F, such as
balls that dissolve over time after exposure to the fluid F. The
launcher 20 stores and maintains such dissolvable balls 12 isolated
from fluids F until such time as the ball 12 is to be injected into
the wellbore W.
[0042] A dissolvable ball 12, 12a is first exposed to fluid F when
it is released from the injector 20, enroute to the wellbore W. A
selected ball 12a is injected to drop to a temporary staging
position on a closed, first or upper isolation valve 18 located
adjacent and below the launcher 20. As each ball 12 is only first
exposed to fluids F contemporaneously with being launched into the
wellbore W, balls 12 are not subject to deterioration for a
prolonged period prior to being launched.
[0043] The disclosed fracturing system 10 is characterized by a low
profile launcher 20, minimizing the ball drop height relative to
prior art systems, and further implements a minimal number of drop
stages relative to prior art systems. As each drop stage puts ball
integrity at risk, the system 10 minimizes the opportunities for
balls 12 to be damaged enroute from the launcher 20 to the wellbore
W.
[0044] The low profile launcher 20 has an axial bore 22, forming
part of the common bore 16, in fluid communication with a plurality
of radial bores 24, each of which having ball-storing cartridges 30
therein. The minimum number of drop stages can be achieved through
a launching sequence implementing a single drop to the upper
isolation valve 18 and thereafter directly into the wellbore W for
delivery to a wellbore location of interest.
[0045] Cartridge seals 38 are located on each cartridge 30 to
fluidly isolate the balls 12 stored therein from fluid F in the
axial bore 22, even when axial bore 22 is at elevated wellbore
pressure P.sub.FRAC, thus preventing balls 12 from being exposed to
fluid F until shortly before injection into the wellbore W.
Accordingly, pressure equalization can occur in the axial bore 22
of the launcher 20. Intermediate structures, including use of a
discrete staging block, are not required for isolating a selected
ball 12a in between both the launcher 20 above and the frac header
14 below, for pressure equalization.
[0046] In some embodiments, a lower isolation valve 19 can
interconnect and fluidly isolate the frac header 14 from the
wellbore W. Typically, the lower isolation valve 19 remains open to
the wellbore W during operations, being closed only during
interruptions in flow of fluid F into the wellbore, including when
maintenance work is required for the fracturing system 10.
[0047] As shown, a common style of isolation valve 18, 19 used on a
wellhead structure is a gate valve. Herein, both the terms
isolation valve and gate valve are used interchangeably. The
connections between ball launcher 20, frac header 14, upper and
lower isolation valves 18, 19, and the wellbore W can be flanged
connections, threaded connections, or other suitable connections
known in the art.
[0048] With reference to FIG. 1, and turning to the ball launcher
20 in more detail, ball launcher 20 has at least one radial ball
array 23, each array 23 having two or more radial bores 24
extending radially from, and in communication with, the axial bore
22, and into which stored bars 12 are released for injection into
wellbore W. Each radial bore 24 houses a ball cartridge 30 for
housing a respective ball 12. The basic structure of the radial
ball array is set forth in Applicant's issued U.S. Pat. No.
8,136,585 to Isolation Equipment Services Inc., the entirely of
which is incorporated herein by reference.
[0049] Other than during loading or releasing of balls 12, the
axial bore 22 remains clear, or unobstructed, regardless of the
numbers of arrays 23 of radial bores 24 are provided.
[0050] In the embodiment depicted in FIG. 1, a radial housing 21 of
launcher 20 houses two, vertically structured radial ball arrays
23, 23 of four radial bores 24 each. The radial bores are oriented
at 90 degrees to one another. For selectively manipulating a ball
12 associated with each radial bore 24, a ball cartridge 30 and an
actuator 36 are provided for each radial bore 24. The ball
cartridge 30 is axially operable between an operably aligned launch
position and an operably misaligned sealing position. The actuator
36, such as a hydraulic ram or cylinder, reciprocates the ball
cartridge 30 along its radial bore 24 between the operably aligned
and operably misaligned positions. Cartridges 30 and actuators 36
can be secured to launcher 20 using flanged or threaded
connections, or other connection means known in the art.
[0051] With reference also to FIGS. 1 and 8C, when operably aligned
in the launch position, a ball-containing cavity, such as a cup 33,
located intermediate the ball cartridge 30 is aligned with the
axial bore 22 for receiving and for releasing a ball 12. In
embodiments, the cartridge 30 extends substantially across the
axial bore 22 for receiving a ball 12 during ball loading
procedures, releasing a selected ball 12a during ball injection
operations, and preventing a ball loaded 12 from dropping past the
operably aligned ball cartridge 30 should a ball be manually loaded
from above the cartridge through the axial bore 22. In the
misaligned and sealed position, the ball cartridge 30 is retracted
into its respective radial bore 24, fully clearing the axial bore
22 and safely housing the ball 12 from fluid F and from accidental
release into the axial bore 22. In embodiments, the cavity 33 of
ball cartridge 30 is rotationally operable between an upward
receiving position for receiving balls 12 from above into cup 33
and a downward releasing position for releasing a selected ball 12a
down towards the wellbore W.
[0052] During normal fracturing operations, each ball cartridge 30
is normally retracted into the secure sealed position within the
radial bore 24 for storing the balls. Thus, an open and
unobstructed axial bore 22 allows an operator to have unhindered
access to the wellbore 30 during normal fracturing operations.
[0053] There are typically at least as many radial bores 24 and
stored balls as there are balls required for a particular wellbore
operation. A radial housing 21 of compact height can be provided
with one or more radial ball arrays 20, each having two or more
radial bores 24. In an instance of a radial housing 21 having only
one radial ball array 23, that radial ball array 23 would normally
have two or more radial bores 24 for providing two or more balls.
As shown, two radial ball arrays 23 can be housed in one radial
housing 21. More than one radial housing 21 can be provided, the
housings being affixed to one another vertically, stacked on top of
one another for providing successive radial housings 21, 21, 21 and
so on to increase the number of arrays 23 and available balls
12.
[0054] By placing two, three, four or more radial bores 24 in the
same radial ball array 23, significant height savings are achieved.
In other words, where the prior art apparatus may require vertical
stacks of ball injection apparatus for providing multiple balls,
the structure of embodiments disclosed herein need only to consume
the height of one array of radial bores 24 for enabling four or
even more balls. Despite each housing 21 having minimum physical
size constraints on height to ensure compliance with access and
pressure ratings, a comparable compact ball injector 20 can achieve
a compact height.
[0055] For example, a typical operation may require a total of
eight (8) balls 12 to be dropped. Using a launcher 20 having two
vertically spaced arrays 23 of four radial bores 24, requires only
about 20 inches in height, which is about one half the height of
the prior art apparatus that serially stack balls vertically,
including those employing a series of vertically arranged fingers
or balls. A compact height results in a lower profile of the ball
launcher 20 allowing for easier access to the launcher 20 as well
as reducing the strain applied to the entire wellhead. Moment
forces imposed on the wellhead can be considerable and thus a
shorter wellhead is stronger and safer.
[0056] In the embodiment of FIGS. 1 through 7, the structure of the
radial ball arrays 23 are modified, as described herein, to handle
balls 12 susceptible to exposure to the fluid F.
[0057] In embodiments, each cartridge 30 now includes cartridge
seals 38 for fluidly isolating its respective stored ball 12 from
fluids in the axial bore 22. Thus, the cartridge 30 can provide a
dry environment for ball storage and release operations, thereby
avoiding premature exposure of the dissolvable balls 12 to fluids F
in the fracturing system.
[0058] As best shown in the embodiments of FIGS. 8A and 8B, in the
sealed position, to isolate their respective cups 33 from the axial
bore 22, cartridges 30 are sealed therefrom by cartridge seals 38
located at least adjacent a distal or bore end 31 of the cartridge.
The cartridge 30 and seals 38 are sized and configured to sealingly
fit with their respective radial bore 24 for fluidly isolating the
ball cup 33 and ball 12 stored therein from the axial bore 22.
Thus, when the pressure of fluid F in the axial bore P.sub.INJ is
pressurized to achieve an injection or release pressure about equal
to or greater than the wellbore fracturing pressure P.sub.FRAC of
frac head 14 therebelow, the balls 12 housed inside cartridge's
cups 33 remain at about the original loading pressure P.sub.CUP.
The seals 38 can be lip seals, poly-seals, or O-rings or other
seals.
[0059] Typically, the launcher 20 is loaded with balls 12 at
atmospheric pressure, such that P.sub.CUP=P.sub.ATM. As best shown
in FIG. 8C, when a cartridge 30 is actuated to the launch position,
the cartridge seals 38 disengage with the radial bore 24 and its
respective cup 33 is exposed to the axial bore 22, also exposing
the selected ball 12a to the environment therein. When the
cartridge 30 is retracted to the sealing position, seals 38 once
again seal with the radial bore 24 and the cartridge cup 33 is
again sealed from the axial bore 22.
[0060] In some circumstances, high pressures in the axial bore 22,
for example in the order of 10,000 to 15,000 psi in some frac
operations, produce significant force on the bore end 31 of the
cartridges. For example, a 4.75'' diameter cartridge, exposed to
15,000 psi results in forces on the cartridge of over 200,000
pounds.
[0061] Accordingly, when P.sub.INJ=P.sub.FRAC, the cups 33 of
cartridges 30 are under significant load. If the cartridge were to
fail, the balls 12 housed therein could be exposed to fluids,
causing premature deterioration, and further, to cause the
actuating of the ball therein to fail completely. In embodiments,
to provide structural support, such as against buckling failure,
the cartridge 30 is fit with circumferential, radially extending
flares 35, located at the distal end 31 of cartridges 30 and
configured to abut respective annular flare seats 23, formed at the
bore interface between axial bore 22 and the distal ends of radial
bores 24. The flares 35 and seats 23 engage when the cartridges 30
are in the retracted position. Flares 35 can have tapered edges for
engaging with beveled flare seats 23 (FIG. 8A), or have square
edges to engage with flare seats 23 formed as annular shoulders in
radial bores 24 (FIG. 8B). When flares 35 are forcibly engaged with
flare seats 23, by pressure P.sub.INJ inside axial bore 22, a
sealing force can be generated between the two surfaces to aid in
sealing balls 12 from wellbore fluids and pressure. In embodiments,
such seal between the flares 35 and flare seats 23 comprise the
primary seal for isolating a ball 12 from the axial bore 22, while
the cartridge seals 38 act as secondary seals. In other
embodiments, if a sealing action between flares 35 and flare seats
23 is not desired, flares 35 can comprise other structural
supports.
[0062] In embodiments wherein cartridges 30 do not have flares 35,
cartridges 30 can be installed in a radial housing 21 by sliding
the cartridge into its respective radial bore 24 from the exterior
of the housing 21, and securing the cartridge 30 and actuator 36
thereto.
[0063] In embodiments having flares 35, the flares having a
diameter greater than that of the radial bores, the cartridge 30
can first be installed in radial housing 21 as described above, and
the corresponding flare 35 can be coupled to the cartridge 30 by
inserting the flare 35 into the axial bore 22, either by hand or
using a tool, and coupling the flare 35 with its respective
cartridge 30 via a threaded or other suitable engagement.
[0064] Alternatively, as shown in FIGS. 9A to 9C, cartridges 30 can
be housed in cylinders 37 each having a radial bore 24 and secured
to the radial housing 21. As shown, the diameter of the cylinders
37 is equal to or greater than the maximum diameter of the flares
35 such that cartridge-and-cylinder assembly can be installed from
the exterior of the radial housing 21. Seal seat 23 can be formed
at a distal end of the cylinder 37 for engaging with the flare 35
when a cartridge 30 is in the retracted position. A flange or other
connector 40 can be located at a proximal end of the cylinder 37
for coupling with a respective actuator 36 and mounting to the
radial housing 21. Thus, to install a flared cartridge 30 in radial
housing 21, cartridge 30 can first be inserted into the radial bore
24 of a cylinder 37 from the distal end, and cylinder 37 can
subsequently be secured to radial housing 21 with the flanged
connection. An actuator 36 can then be operatively connected to
cartridge 30 and secured to the cylinder 37. As such, the
cartridges 30 and cylinders 37 are installed from the exterior of
the radial housing 21 as opposed to requiring manipulation of the
cartridge 30 through the axial bore 22, which can be cumbersome,
time consuming, and carries the risk of objects being dropped into
the common bore 16.
[0065] As shown in FIGS. 8A to 8C, generic O-rings are provided as
cartridge seals 38. In embodiments better seen in FIGS. 8A, 9B, one
or more swab seals 39 such as a wiper seal can be located toward a
proximal or actuator end 32 of cartridges 30 for removing potential
moisture or contaminants from radial bore 24 prior to receiving and
storing a ball 12.
[0066] In embodiments wherein the size of the stored ball is large,
for example about equal to the diameter of the axial bore 22,
additional clearance may be required to allow a cartridge 30
containing such a cup 33 to extend sufficiently to operatively
align the cup 33 with the axial bore 22 in the launched position
for receiving or releasing a ball 12 therein. With reference again
to FIGS. 9A and 9B, to provide sufficient clearance for cartridges
30 to properly actuate, opposing and aligned cartridges 30a, 30b
can be set back in their respective radial bores 24a, 24b such that
cartridge 30a can extend into the radial bore 24b of opposing
cartridge 30b when actuated to the launch position, thereby
allowing the cup 33a of cartridge 30a to be operatively aligned
with the axial bore 22. In some embodiments, as shown in FIGS. 9A
and 9B, radial bore 24 can be tapered and have a larger diameter
towards the axial bore 22 to more easily receive the distal end 31d
opposing cartridge 30. In embodiments having flares 35, radial
bores 24a can have an enlarged-diameter portion 44a for permitting
flares 35 to travel unimpeded therethrough when cartridges 30 are
actuated between the launch and sealing positions.
[0067] With reference to FIG. 1 and after assembly of the wellhead
components of the system 10, the ball launcher 20 can be fluidly
connected to a bi-directional displacement pumper 6 configured to
deliver displacement fluid FD into axial bore 22 for aiding in
pressure adjustment before ball launch to displace a launched ball
12 into the wellbore W, or to remove fluid from axial bore 22 for
return to a depressurized and substantially dry condition between
ball launches. Displacement fluid FD can be an operation-compatible
fluid, such as frac fluid, without added proppant or particulates
such as sand.
[0068] In the depicted embodiment, displacement pumper 6 is
connected to launcher 20 via equalization port 28. Port 28 is
preferably positioned below the lowest cartridge 30 in the ball
launcher 20 such that fluids in axial bore 22 may be drained to an
elevation below stored balls 12, thereby minimizing exposure of the
cartridges 30 to fluids when balls 12 are not being launched. In
embodiments, the pumper access port 28 can further be positioned
within the radial housing 21, to form a shallow sump of residual
fluid to rest on upper isolation valve 18 when closed, which
lessens the force of impact when a ball 12 is dropped onto the
upper isolation valve 18. A depending suctioning conduit can extend
into the upper isolation valve 18, or a port in the valve 18 itself
can reduce the amount of liquid stored thereon.
[0069] In an embodiment, displacement pumper 6 comprises first pump
7 and second pump 8. First pump 7, such as a rotary gear reversible
BOWIE.TM. pump available from Bowie Pumps of Canada Ltd., is
configured to remove fluids from axial bore 22 via port
equalization 28 and direct removed fluids to a fluid storage tank
(not shown). Second pump 8, typically a positive displacement high
pressure pump such as a triplex horizontal single-action
reciprocating pump, can be configured to deliver displacement fluid
FD into launcher 20 to pressurize the axial bore 22 to at least
fracturing pressures P.sub.FRAC. First pump 7 can also be fluidly
connected to second pump 8 and configured to be able to temporarily
redirect fluids, such as from the storage tank, to primes the
second pump 8. For example, first pump 7 can be configured to
provide fluid at 100 psi to prime the second pump 8.
[0070] The frac header 14 can be fluidly connected to fracturing
fluid pumper 15 using known piping methods for delivery of large
volumes of frac fluids F at treatment pressures P.sub.FRAC into the
wellbore W. Fracturing fluids F are typically delivered independent
of ball launching procedures and the pressure environment of
launcher 20. While frac fluid F is generally laden with sand, in
instances where the displacement fluid pumper 6 is absent or out of
service, a bypass from the frac pumpers 15 could deliver additive
and particulate-free fluids to the ball launcher 20 as a substitute
source of displacement fluid FD.
[0071] One or more bleed valves can be installed on the ball
launcher 20 and be operable to permit pressure equalization between
the interior of the ball launcher 20 and atmosphere or to
pressurize the launcher 20 with a dry gas. In the depicted
embodiment, lower bleed valve 26 is fluidly connected to port 28
below cartridges 30 and top bleed valve 27 is located above the
cartridges 30 for allowing the introduction of dry gas such air or
nitrogen into launcher 20 to assist with fluid bleed-off through
valve 26 and fluid removal via port 28. In embodiments, a check
valve 29 can be located in-line with top bleed valve 27 and
configured to prevent gas from flowing out of launcher 20 while
allowing air in, for example in response to negative pressure
created in axial bore 22 by pumper 6 as it removes fluid. In such
embodiments, top bleed valve 27 would be maintained in an open
position during depressurization of launcher 20 unless check valve
29 fails and manual control of airflow into launcher 20 is
required. During pressurization of the launcher 20 to wellbore
pressures, top bleed valve 27 can be actuated to the closed
position.
[0072] In embodiments, a fluid detector can be located on launcher
20 to confirm that fluid removal from axial bore 22 is
complete.
[0073] Leakage of some fluids past upper isolation valve 18 is
inherent in gate valve design, and methods incorporated herein can
ensure leaked fluid accumulation in the axial bore 22 is minimized
through pressure management, or removed periodically, to avoid
prolonged exposure of cartridges 30 and seals 38 to fluids. As the
wellbore W is at elevated pressures P.sub.FRAC, any leakage tends
to be upward towards through the upper isolation valve 18 and into
the ball launcher 20 when pressure P.sub.INJ inside the axial bore
22 is at atmosphere P.sub.ATM or otherwise below P.sub.FRAC. As
such, pumper 6 can be continuously run in between ball launching
procedures to remove fluids that leak into axial bore 22 from frac
header 14. During ball launch procedures, P.sub.INJ is increased to
equal to or greater than P.sub.FRAC such that leakage of fluid and
particulates into axial bore 22 is reduced or ceased entirely.
Example Ball Loading Procedure
[0074] With reference to FIG. 10, an exemplary ball loading
procedure 100 is described, wherein balls 12 can be loaded in their
respective cartridges 30 by actuating upper isolation valve 18 to
the closed position (step 102) and equalizing pressure P.sub.INJ to
a launching pressure of about atmosphere P.sub.ATM by venting via
bleed valves 26, 27 and/or removing fluid from axial bore 22 by
pumping fluid out of port 28 using pumper 6 (step 104). The axial
bore 22 can further be swabbed to clear it of excess lubricant and
fluids (step 105).
[0075] Cartridges 30 can then be individually loaded with balls 12
by actuating a cartridge 30 into the launch position such that cup
33 is aligned with the axial bore 22 (step 106). Cup 33 can further
be rotated by actuator 36 such that its open end 34 faces upwards
toward the top of the launcher 20. Access to the axial bore 22 from
the top of launcher 20 can be enabled for example by removing top
bleed valve 27 or other components that would provide access to
axial bore 22. A ball 12 can then be dropped into axial bore 22
from the top of launcher 20 such that it falls into cup 33 (step
108). Once a ball 12 has been received into cup 33, the cartridge
can be actuated into the sealing position to fluidly isolate and
store ball 12 until it is to be launched (step 110). Cup 33 can
then be rotated such that its open end 34 faces downhole towards
the wellbore W such that ball 12 housed therein will fall towards
the wellbore W when the cup 33 is actuated into alignment with
axial bore 22. Subsequent balls 12 can be loaded in their
respective cartridges 30 in the same manner until all cartridges 30
house balls 12 therein (step 114).
[0076] The above is provided as an exemplary ball loading
procedure, and one of skill in the art would understand that
cartridges 30 could be loaded using other methods, such as by
removing cartridges 30 from launcher 20, loading balls 12 into cups
33 directly, and reinstalling the cartridges 30.
Example of Ball Launch Procedure
[0077] In an example ball launch procedure 200, with reference to
FIG. 11, the upper isolation valve can first be actuated to the
closed position (step 202) and the axial bore 22 be depressurized
and fluid removed therefrom (step 204) using the same procedure set
out above for loading balls 12.
[0078] With reference to FIG. 1, to release a first ball 12a from
the ball launcher 20 into wellbore W, with the axial bore 22 being
isolated from the frac header 14 by upper isolation valve 18,
pumper 6 is shut off or isolated to cease draining of fluids from
axial bore 22 and configured to deliver displacement fluid FD into
axial bore 22 when required (step 205). As shown in FIG. 2,
cartridge 30a containing ball 12a is then actuated to the launching
position to align cup 33a with the axial bore 22 and drop ball 12a
therein to a temporary staging position on upper isolation valve 18
(step 206). The cartridge 30a is then actuated to retract to the
sealing position and re-seals with the wall of the radial bore 24
(step 210). During launch procedures, all of the remaining ball
cartridges 30 remain sealed and their respective balls 12 continue
to be stored in a dry condition. Optionally, successful
introduction of ball 12a into the axial bore 22 and onto upper
isolation valve 18 can be confirmed using an acoustic detector or
any other suitable device (step 208).
[0079] With reference to FIG. 2, pumper 6 then pumps displacement
fluids FD into the ball launcher 20 to increase the pressure
P.sub.INJ in the axial bore 22 to a release pressure about or
greater than wellbore pressure P.sub.FRAC (step 212). In an
embodiment, pressure P.sub.INJ is brought to a release pressure
that is greater than the wellbore pressure P.sub.FRAC, for example
7-10 MPa greater than the frac pumping pressure, and therefore
presents a positive impetus to displace the ball 12a staged in the
axial bore 22 into the frac header 14 and wellbore W below once
upper isolation valve 18 is opened. Without the sealed cartridges
30, at this stage, the dissolvable balls 12 would be at risk of
exposure to fluids due to pressure inside axial bore 22. Instead,
the sealed ball cartridges 30 maintain their respective balls 12 in
a dry condition in ball cups 32.
[0080] As shown in FIG. 3, once the fluid pressure P.sub.INJ in the
ball launcher 20 is adjusted to about fracturing pressure
P.sub.FRAC in the frac header 14 or greater, and turning to FIG. 4,
the upper isolation valve 18 can be opened to fluidly connect the
pressurized ball launcher 20 to the frac header 14 and the wellbore
W below and allow ball 12a to be injected therein (step 214).
[0081] The ball 12a is thereby injected, dropped, or otherwise
delivered into the frac head 14 and subsequently the wellbore W.
Optionally, continued introduction of displacement fluid FD into
launcher 20 provides a co-flow to displace ball 12a and ensure it
is carried into the frac fluid F stream in frac header 14, which
conveys the ball 12a into the wellbore W (step 216). The continued
flow of displacement fluid FD into launcher 20 through port 28 also
helps remove any potential blockages in the axial bore 22 such as
accumulations of hydrates and/or sand gel. In embodiments,
depending on the operational conditions of a particular wellbore,
the amount of displacement fluid FD pumped through the ball
launcher 20 into the wellbore W after opening the isolation valve
is between about 30 to 150 L.
[0082] With reference to FIG. 5, after a sufficient amount of
displacement fluid FD is pumped downhole to maximize the likelihood
of successful delivery of the ball 12a to the frac fluid flow F,
pumping of displacement fluid FD is ceased.
[0083] Thereafter, if a subsequent ball is to be injected into the
wellbore, the ball injection procedure 200 can be repeated (step
218). Otherwise, ball injection operations can be ceased and normal
fracturing operations through the frac header 14 continue.
[0084] Meanwhile, as shown in FIG. 6, the procedure of
depressurization and fluid removal from the ball launcher 20 is
commenced (step 220) in preparation for future ball injection
operations and to minimize persistent fluid stress on the ball
cartridge seals 38 and lessen the actuation force and size of the
actuator 36 needed to open the ball cartridges 30 against pressure
in the axial bore 22.
[0085] To avoid overpressuring the pumper 6, which may occur if
fluid removal by pumper 6 is initiated when P.sub.INJ is still at
or above P.sub.FRAC, lower bleed valve 26 can first be opened to
relieve pressure and drain fluid from axial bore 22. To aid in
draining, a top bleed valve 27 can be opened as necessary to allow
air into the axial bore 22. In embodiments having a check valve 29
in line with top bleed valve 27, bleed valve 27 can be left open
and check valve 29 opens to allow air into axial bore 22 in
response to negative pressure therein. With reference to FIG. 7,
once launcher pressure P.sub.INJ has been reduced by bleeding, and
to speed fluid removal from the ball launcher 20, bleed valve 27 is
closed and pumper 6 is operated to remove remaining fluids from
axial bore 22 via first port 28. Through bleed-off and pumping, the
pressure in the ball launcher axial bore 22 is reduced to
atmospheric or can be drawn down to a slight negative pressure.
[0086] Accordingly, the ball launching procedure described above
can then be repeated for subsequent, dry dissolvable balls 12
stored in the ball launcher 20.
* * * * *