U.S. patent application number 13/727950 was filed with the patent office on 2013-07-18 for downhole fluid treatment tool.
This patent application is currently assigned to NCS Oilfield Services Canada Inc.. The applicant listed for this patent is NCS Oilfield Services Canada Inc.. Invention is credited to Donald Getzlaf, Robert Nipper, Marty Stromquist.
Application Number | 20130180721 13/727950 |
Document ID | / |
Family ID | 48693624 |
Filed Date | 2013-07-18 |
United States Patent
Application |
20130180721 |
Kind Code |
A1 |
Getzlaf; Donald ; et
al. |
July 18, 2013 |
Downhole Fluid Treatment Tool
Abstract
A treatment device and method for use in delivering fluid
treatment to a wellbore is described. The device includes a first
treatment housing and a second treatment housing, mounted along a
tubing string, each of the first and second housing defining a
fluid pathway which is continuous with the tubing string and each
of the first and second treatment housing defining a port for fluid
communication between the tubing string and the wellbore. Fluid
flow through the first housing may be selectively blocked by
delivery of a deformable ball to the tubing string to seal against
a ball seat disposed between the first and second housing. While
the first pathway is blocked, fluid may be selectively delivered to
the wellbore through the port on the second treatment housing. The
ball may be removed from the ball seat by application of hydraulic
pressure in excess of the deformation threshold of the ball,
forcing the ball to deform and pass through the seat, re-opening
the fluid flow through the first treatment housing and allowing for
treatment through port defined in the first housing.
Inventors: |
Getzlaf; Donald; (Calgary,
CA) ; Stromquist; Marty; (Calgary, CA) ;
Nipper; Robert; (Spring, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NCS Oilfield Services Canada Inc.; |
Calgary |
|
CA |
|
|
Assignee: |
NCS Oilfield Services Canada
Inc.
Calgary
CA
|
Family ID: |
48693624 |
Appl. No.: |
13/727950 |
Filed: |
December 27, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61580500 |
Dec 27, 2011 |
|
|
|
Current U.S.
Class: |
166/308.1 ;
166/223; 166/305.1; 166/319 |
Current CPC
Class: |
E21B 43/26 20130101;
E21B 34/14 20130101; E21B 43/25 20130101; E21B 43/114 20130101;
E21B 34/06 20130101 |
Class at
Publication: |
166/308.1 ;
166/319; 166/223; 166/305.1 |
International
Class: |
E21B 43/26 20060101
E21B043/26; E21B 43/114 20060101 E21B043/114; E21B 43/25 20060101
E21B043/25; E21B 34/06 20060101 E21B034/06 |
Claims
1. A downhole treatment assembly, the assembly comprising: a first
housing disposed on a tubing string, the first housing defining a
first fluid pathway continuous with the tubing string and including
a wall defining a first port for passage of fluid between the first
fluid pathway and the wellbore; a second housing disposed on the
tubing string above the first housing, the second housing defining
a second fluid pathway continuous with the tubing string and with
the first fluid pathway, the wall of the second housing including a
second port through which fluid can flow from the tubing string to
the wellbore; and a ball valve disposed on the tubing string
between the first port and the second port, the ball valve
comprising a ball seat at the upper end of the valve, the ball seat
configured to receive a deformable ball, and a ball trap for
preventing unseated, deformed balls from re-entering the ball
valve.
2. The assembly of claim 1, wherein the ball valve is mounted
within the first housing above the first port.
3. The assembly of claim 1, wherein the second housing comprises a
jet perforation device and the second port comprises a jet
nozzle.
4. The assembly of claim 1, wherein the ball valve is provided as a
removable insert in the first housing.
5. A system for wellbore treatment, the system comprising: a first
housing disposed on a tubing string, the first housing defining a
first fluid pathway continuous with the tubing string; a first port
defined in the first housing for lateral fluid flow from the first
fluid pathway to the wellbore; a second housing disposed on the
tubing string above the first housing, the second housing defining
a second fluid pathway continuous with the tubing string and with
the first fluid pathway; a second port defined in the second
housing for fluid communication between the second fluid pathway
into the wellbore; a ball valve disposed the tubing string between
the first port and the second flow port, the ball valve adapted to
receive a deformable ball, wherein when seated the ball prevents
fluid flow through the fluid pathway of the first housing; and a
sealing device deployed on the tubing string below the first
housing, the sealing device for sealingly engaging the wellbore and
thereby defining a wellbore interval to be treated above the
sealing device.
6. The system of claim 5, wherein the ball valve is disposed within
the first housing above the first port.
7. The system of claim 5, wherein the second housing comprises a
jet perforation device and the lateral port is a jet perforation
nozzle.
8. A method of selectively treating a wellbore, the method
comprising: deploying a tool assembly on a tubing string into a
wellbore, the tool assembly comprising a first housing and a second
housing, the first and second housing being fluidically continuous
with the tubing string and the first and second housing each having
a fluid port for fluid communication from the tubing string to the
wellbore, and a ball valve between the ports of the first and
second housing, the ball valve comprising a ball seat for receiving
a deformable ball having a pressure deformation threshold;
delivering fluid to through the tubing string to the first housing
to effect a wellbore treatment through the port of the first
housing; dropping the deformable ball through the tubing string to
land on the ball seat, thereby blocking fluid flow from the tubing
string to the first housing; continuing to deliver fluid to the
tubing string while the ball remains seated in the valve seat; and
increasing the pressure differential across the ball seat to exceed
the pressure deformation threshold of the ball, thereby unseating
the ball from the ball seat so that fluid can flow through the
first housing.
9. The method of claim 8, further comprising delivering fluid to
the tubing string to effect fluid treatment through the port of the
first housing once the ball is unseated.
10. The method of claim 8, further comprising passing the ball
through a lower end of the ball valve to a region within the first
housing after the ball has been deformed.
11. The method of claim 8, further comprising delivering fluid
suitable for fracturing prior to seating the ball and delivering
fluid suitable for sand jet perforation after seating the ball.
12. The method of claim 8, further comprising sealing the tubing
string in the wellbore below the first housing prior to fluid
delivery down the tubing string.
13. A method for selective delivery of treatment fluid from tubing
string to a wellbore, the method comprising the steps of: deploying
a tool assembly within a wellbore on tubing string, the tool
assembly comprising a first housing and a second housing, the first
and second housing being fluidically continuous with the tubing
string and the first and second housing each having a fluid port
for fluid communication from the tubing string to the wellbore, and
a ball valve between the ports of the first and second housing, the
ball valve comprising a ball seat for receiving a deformable ball
having a pressure deformation threshold; delivering treatment fluid
through a tubing string to effect treatment of the wellbore through
the port of the first housing; delivering a ball to the tubing
string, the ball of suitable size to seal against the ball seat;
seating the ball against the ball seat; continuing to deliver fluid
to the tubing string to effect fluid treatment of the wellbore
through the port of the second housing; delivering fluid treatment
to the wellbore annulus at a rate suitable to reverse circulate the
ball to surface through the tubing string; and delivering fluid to
the tubing string to effect fluid treatment through the port of the
first housing.
14. The method of claim 13, wherein the second fluid treatment
housing is a jet perforation device.
15. The method of claim 13, wherein treatment through the first
treatment pathway comprises fracturing.
16. The method of claim 13, further comprising the steps of setting
a sealing device against the annulus defined between the tubing
string and the wellbore prior to delivering the ball and unsetting
the sealing device prior to reverse circulation.
Description
RELATED APPLICATIONS
[0001] This U.S. patent application claims priority to U.S.
Provisional Application 61/580,500 filed on Dec. 27, 2011, the
disclosure of which is considered part of the disclosure of this
application and is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the delivery of
treatment fluid to a geological formation intersected by a
wellbore. More particularly, the present invention relates to
tubing-enabled completions, in which treatment fluid is delivered
through tubing to a target interval of the wellbore.
BACKGROUND OF THE INVENTION
[0003] In completing a cased well, the casing may be perforated in
specific locations to provide access to the surrounding formation.
Various fluid treatments may be delivered through the perforations,
and formations fluids may ultimately be produced through the
perforations.
[0004] In some wells, the casing may incorporate pre-perforated
sleeves, in which the perforations may be opened as needed to
provide access to the formation. However, sleeve failure does
occur, requiring re-perforation of that wellbore interval.
Accordingly, multistage fluid treatment assemblies may incorporate
a perforation device, such as fluid jet perforating device, to
avoid the need for tripping in and out of the well each time
perforation, or re-perforation, is necessary.
[0005] When delivering treatment fluid to a perforated interval,
the interval of interest may be fully or partially isolated from
the remainder of the wellbore, using a bridge plug or other sealing
device. The sealing device may be conveyed downhole on wireline or
tubing string and is typically set below the interval to be
treated. Once set, treatment fluid may be delivered to the interval
by pumping fluid down the wellbore. As fluid treatment is delivered
to the wellbore, the hydraulic pressure within the wellbore
increases, ultimately forcing fluid through the perforations and
into the formation. At intervals of great depth, large volumes of
fluid are required to achieve the hydraulic pressures required to
penetrate the formation at each interval. Such excessive fluid
usage limits the economic viability of the operation. Accordingly,
at deep intervals, delivery of treatment fluid through the tubing
string would be desirable. However, when the tubing string is used
to deliver treatment fluid, the tubing string may not then be used
for other purposes such as perforation.
[0006] While some fluid treatment assemblies have been developed in
which perforation may be accomplished by wireline, these assemblies
have a limited capacity for multiple perforation as the explosive
charges must be replaced once depleted, necessitating a return to
surface.
[0007] The use of tool assemblies for performing multiple functions
in a single trip downhole can reduce the cost of completion
operations. In tool assemblies incorporating a jet perforation
device, it is useful to incorporate means that allow for other
treatment operations, such as fracturing, in a different portion of
the tool assembly. This allows for more efficient treatment of the
wellbore, since perforation and fracturing can occur in two
different regions of the same isolated wellbore interval.
SUMMARY OF THE INVENTION
[0008] In accordance with a first aspect of the invention, there is
provided a downhole treatment assembly, the assembly comprising: a
first housing disposed on a tubing string, the first housing
defining a first fluid pathway continuous with the tubing string
and including a wall defining a first port for passage of fluid
between the first fluid pathway and the wellbore; a second housing
disposed on the tubing string above the first housing, the second
housing defining a second fluid pathway continuous with the tubing
string and with the first fluid pathway, the wall of the second
housing including a second port through which fluid can flow from
the tubing string to the wellbore; and a ball valve disposed on the
tubing string between the first and second port, the ball valve
comprising a ball seat at the upper end of the valve, the ball seat
configured to receive a deformable ball, and a ball trap for
preventing unseated, deformed balls from re-entering the ball
valve.
[0009] In accordance with one embodiment of the invention, the ball
valve is mounted within the first housing above the first port.
[0010] In accordance with another embodiment of the invention, the
second housing comprises a jet perforation device and the second
port comprises a jet nozzle.
[0011] In accordance with another embodiment of the invention, the
ball valve is provided as a removable insert in the first
housing.
[0012] In accordance with a second aspect of the invention, there
is provided a system for wellbore treatment, the system comprising:
a first housing disposed on a tubing string, the first housing
defining a first fluid pathway continuous with the tubing string; a
first port defined in the first housing for lateral fluid flow from
the first fluid pathway to the wellbore; a second housing disposed
on the tubing string above the first housing, the second housing
defining a second fluid pathway continuous with the tubing string
and with the first fluid pathway; a second port defined in the
second housing for fluid communication between the second fluid
pathway into the wellbore; a ball valve disposed the tubing string
between the first port and the second port, the ball valve adapted
to receive a deformable ball, wherein when seated the ball prevents
fluid flow through the fluid pathway of the first housing; and a
sealing device deployed on the tubing string below the first
housing, the sealing device for sealingly engaging the wellbore and
thereby defining a wellbore interval to be treated above the
sealing device.
[0013] In one embodiment, the ball valve is disposed within the
first housing above the first port.
[0014] In one embodiment, the second housing comprises a jet
perforation device and the lateral port is a jet perforation
nozzle.
[0015] In accordance with a third aspect of this invention, there
is provided a method of selectively treating a wellbore, the method
comprising: deploying a tool assembly on a tubing string into a
wellbore, the tool assembly comprising a first housing and a second
housing, the first and second housing being fluidically continuous
with the tubing string and the first and second housing each having
a fluid port for fluid communication from the tubing string to the
wellbore, and a ball valve between the ports of the first and
second housing, the ball valve comprising a ball seat for receiving
a deformable ball having a pressure deformation threshold;
delivering fluid to through the tubing string to the first housing
to effect a wellbore treatment through the port of the first
housing; dropping the deformable ball through the tubing string to
land on the ball seat, thereby blocking fluid flow from the tubing
string to the first housing; continuing to deliver fluid to the
tubing string while the ball remains seated in the valve seat;
increasing the pressure differential across the ball seat to exceed
the pressure deformation threshold of the ball, thereby unseating
the ball from the ball seat so that fluid can flow through the
first housing.
[0016] In accordance with one embodiment, the method further
includes delivering fluid to the tubing string to effect fluid
treatment through the port of the first housing once the ball is
unseated.
[0017] In accordance with another embodiment of the invention, the
method further includes passes the ball through a lower end of the
ball valve to a region within the first housing after the ball has
been deformed.
[0018] In accordance with another embodiment, the method further
comprising delivering fluid suitable for fracturing before the ball
has been seated and delivering fluid suitable for sand jet
perforation once the ball has been seated.
[0019] In accordance with another embodiment, the method further
includes sealing the tubing string in the wellbore below the first
port prior to fluid delivery down the tubing string.
[0020] In accordance with a fourth aspect of the invention, there
is provided a method for selective delivery of treatment fluid from
tubing string to a wellbore, the method comprising the steps of:
deploying a tool assembly within a wellbore on tubing string, the
tool assembly comprising a first housing and a second housing, the
first and second housing being fluidically continuous with the
tubing string and the first and second housing each having a fluid
port for fluid communication from the tubing string to the
wellbore, and a ball valve between the ports of the first and
second housing, the ball valve comprising a ball seat for receiving
a deformable ball having a pressure deformation threshold;
delivering treatment fluid through a tubing string to effect
treatment of the wellbore through the port of the first housing;
delivering a ball to the tubing string, the ball of suitable size
to seal against the ball seat; seating the ball against the ball
seat; continuing to deliver fluid to the tubing string to effect
fluid treatment of the wellbore through the port of the second
housing; delivering fluid treatment to the wellbore annulus at a
rate suitable to reverse circulate the ball to surface through the
tubing string; and delivering fluid to the tubing string to effect
fluid treatment through the port of the first housing.
[0021] Other aspects and features of the present invention will
become apparent to those skilled in the art upon review of the
following description of specific embodiments of the invention in
conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Embodiments of the present invention will now be described,
by way of example only, with reference to the attached Figures,
wherein:
[0023] FIG. 1 is a schematic drawing of a dual treatment device in
accordance with an embodiment of the invention.
[0024] FIG. 2a is a schematic cross sectional view of the first
treatment housing, in accordance with an embodiment of the
invention.
[0025] FIG. 2b is a sectional view taken from A-A of FIG. 2a, in
accordance with an embodiment of the invention.
[0026] FIG. 3 is a schematic perspective view of the ball valve
insert, in accordance with an embodiment of the invention.
[0027] FIG. 4 shows a schematic view of a tool assembly
incorporating the dual treatment device, according to one
embodiment of the invention.
[0028] FIG. 5 illustrates schematically the different stages of
wellbore treatment mediated by the dual treatment device, according
to an embodiment of the invention.
[0029] FIG. 6 illustrates schematically an embodiment of the dual
treatment device disposed in a casing string with a sliding sleeve,
according to an embodiment of the invention.
DETAILED DESCRIPTION
[0030] Generally, the present invention provides a device and
method for providing multiple tubing-conveyed fluid pathways
through a single tool assembly. Delivery of fluid though a first
fluid pathway effects a first fluid treatment within a wellbore
interval, while delivery of fluid through a second fluid pathway
effects a second fluid treatment within the wellbore. A ball valve
allows for diversion of fluid from the first fluid pathway to the
second fluid pathway upon delivery of a deformable ball to the ball
valve. Hydraulic pressure is applied to force the ball against the
seat and thereby build up pressure within the tool assembly and/or
tubing string above the sealed ball seat. Once treatment through
the second fluid pathway is complete, the deformed ball may be
removed, either by reverse circulation from the tool assembly to
surface, or may be forced through the seat by application of
increased hydraulic pressure so as to deform the ball. Such
deformable balls may be engineered to deform at a particular
threshold pressure, based on the range of operating pressures of
the downhole operation of interest.
[0031] Referring to the drawings, FIG. 1 shows a dual treatment
device for completion operations according to one embodiment of the
present invention. The device is generally designated by reference
10 and is intended to be incorporated into a tubing string, with
upper end 13 of dual treatment device 10 being adapted for
connection to the upper tubing string and lower end 14 of dual
treatment device being adapted for connection to the lower tubing
string. Fluid flow would occur lengthwise through the tubing
string, and thus, through the dual treatment device 10, during
wellbore operations. The fluid flow can be diverted to various
fluid ports positioned at different regions of the device by
dropping a deformable ball through the tubing string, as described
below.
[0032] Dual treatment device 10 includes a first treatment housing
15 defining a first fluid pathway 20 in the interior of the first
treatment housing, the first fluid pathway 20 being continuous with
the tubing string. Ports 25 are formed through the wall 30 of the
first treatment housing 15. The ports 25 of the first treatment
housing are also herein referred to as "first ports" to refer to
the first ports of dual treatment device 10. The first ports 25
allow for lateral fluid communication from the tubing string to the
wellbore, and more particularly, to the annulus defined between the
tubing string and the wellbore casing. Device 10 includes a second
treatment housing 35 disposed on the tubing string above first
ports 25. The second treatment housing 35 includes a fluid pathway
21, herein referred to as the second fluid pathway. Second fluid
pathway 21 is fluidically continuous with the tubing string and
with first fluid pathway 21. The second treatment housing 35
includes ports 45. The ports 45 of the second treatment housing 35
are herein referred to as "second ports". Ports 45 are fluidically
continuous with second fluid pathway 21.
[0033] In the embodiment shown, the second treatment housing 35
includes a jet perforation device, and the second ports 45 are jet
perforation nozzles. The diameter of the jet perforation nozzles 45
is generally smaller than the diameter of the first ports 25, so
that during fluid delivery through the tubing string, the pressure
differential across the jet perforation nozzles 35 and the annulus
is greater than the pressure differential across the first ports 25
and the annulus. Thus, when fluid flow through the first treatment
housing 15 is unobstructed, fluid would preferentially exit the
tubing string to the wellbore through first ports 25. A ball valve
50 for receiving a deformable ball is disposed between the first
treatment housing 15 and second treatment housing 35.
[0034] Although the illustrated embodiment shows first ports 25 as
longitudinal slots extending lengthwise through the wall of the
first treatment housing 15, other port configurations are possible.
For example, the ports may be circular and may be disposed around
the circumference of the first treatment housing. While the
embodiment shown includes multiple first ports 25 disposed around
the first treatment housing 15, there may be a single port.
Similarly, variations in the nozzles 45 in the jet perforation
device 35 are possible. For example, the nozzles may be angled, and
may be disposed around the device in any manner suitable to achieve
perforation of the wellbore region of interest.
[0035] It will also be appreciated that the invention generally
relates to a device and method for performing multiple operations
within a length of tubing, the length of tubing having multiple
treatment ports, slots, apertures or other pathways through which
fluid can be delivered laterally from the tubing string to the
wellbore. Accordingly, the term "housing" is generally used to
refer to a length of tubing through which fluid flow can occur
lengthwise through the tubing string and having a fluid pathway for
lateral fluid communication from the tubing string to the wellbore.
For example, in the embodiment shown, the first treatment housing
15 is mounted as a single tubular element with associated ball
valve 50. In an alternative arrangement, the ball valve and second
treatment housing may also form a single tubular element, with the
ball valve located below the ports of the second housing. It will
be appreciated that the housings can be connected to each other
various ways, such as through adaptors or connectors or by other
means known in the art.
[0036] Referring to FIG. 2a, first treatment housing 15 is shown.
First treatment housing 15 includes a wall 30 which defines a first
fluid pathway 20, the first fluid pathway 20 being continuous with
the tubing string. Ports 25 extend longitudinally through wall 30
of first treatment housing 15. A ball valve 50 is disposed within
the upper end of first treatment housing 15 above first ports 25.
Ball valve 50 includes a body 55 defining a hollow bore 60. The
bore 60 of ball valve 50 is continuous with the tubing string, so
that when bore 60 is unobstructed, fluid can flow from the surface
of the wellbore, through the tubing string to the first fluid
pathway 20. The lower end of the bore 60 is of smaller diameter
than the diameter of the ball in the undeformed state, but is of
larger diameter than the ball in its deformed state, so that
deformed balls can pass through bore 60. The upper body 55 has a
tapered inner surface that forms the ball seat 65. The ball seat 65
has a width that is suitable for grasping a deformable ball 125
when ball 125 is launched from the surface and down the tubing
string, in such a way so as to substantially prevent fluid flow to
the first treatment housing 15. Deformable ball 125 has a threshold
pressure differential. When the threshold deformation pressure has
been exceeded, ball 125 becomes deformed and can longer engage with
ball seat 65. The ball seat 65 is arranged in body 55 in such a way
fluid flow forces deformed balls through the length of bore 60 of
ball valve 50.
[0037] In the embodiment shown, ball valve 50 is provided as an
insert, threadedly connected to the first treatment housing 15
through set screws 80, the set screws spaced 120 degrees apart, and
sealed to the first treatment housing 15 by O-rings 56. It is
possible, however, that the first treatment housing 15 could be
engineered with the ball valve 50 drilled directly into the housing
wall 30.
[0038] As shown in FIGS. 2b and 3, the bottom end of body 55 has a
plurality of fingers 66 extending downwardly, radially spaced
around the diameter of the bore 60. The tips of fingers 66 have
tapered inner surfaces 67, to assist in preventing deformed balls
from re-entering through the lower end of ball valve 50 once they
have been unseated from the ball seat 65, and more particularly, to
prevent upward movement of deformed balls that have passed through
to first treatment housing 15. Thus, the plurality of fingers act
as a ball trap or ball catcher for preventing upward movement of
deformed balls, for example, during reverse circulation through the
wellbore annulus.
[0039] With reference to FIG. 4, an embodiment of the invention is
shown in which dual treatment device 10 is incorporated as part of
a downhole tool assembly 75. Suitable downward tools are known in
the art. The downhole tool shown in FIG. 4 is similar to that
described in Canadian Patent No. 2,693,676 issued to Stromquist and
assigned to the assignee of the present invention and which is
herein incorporated by reference. The dual treatment device 10
shown in FIG. 1 is incorporated into the tool assembly: a first
treatment housing 15, with associated ports 25 for carrying out a
first wellbore treatment, a second treatment housing 35 (e.g. a jet
perforation device) with nozzles 45, and a ball valve disposed
between jet perforation device 35 and first ports 25 are all
present. The tool assembly 75 also includes a compressible sealing
element 95. Mechanical slips 96 may also be present to assist in
actuation of sealing element 95. An equalization valve 100 is also
present, with an equalization port 105 is defined in the wall of
equalization valve 100. A mechanical casing collar locator 111 is
present for locating tool assembly 75 in the appropriate region of
the wellbore. In downhole tool assembly 75, fluid may be delivered
down the tubing string to effect both fluid jet perforation,
through the nozzles 45 of jet perforation device 35, and
fracturing, through the first ports 25 in first treatment housing
15.
[0040] While the embodiment shown in FIG. 4 illustrates a
particular downhole tool, other arrangements are possible. For
example, the tool may incorporate any type of anchor device,
suitable for locating the tool assembly in the wellbore region of
interest. Those skilled in the art would also appreciate that other
types of sealing devices may be used. The tool may further include
additional devices, such as pump down cups, to assist in
manipulating the tool assembly, or adding functionality
thereto.
[0041] When dual treatment device 10 is in the unactuated state
(i.e. before the ball is seated on the ball seat 65), fluid
delivered from the surface through the tubing string will primarily
exit through the first ports 25. This is because first ports 25 are
generally larger in size than the nozzles 45 of the jet perforation
device 35, and thus, a larger pressure differential is required in
order to effect fluid jetting through nozzles 45. However, there
may be some fluid exiting through nozzles 45, even when fluid is
predominantly flowing through the first treatment housing 15 and
out first ports 25. When a deformable ball is delivered from the
surface with treatment fluid, the ball will travel through the
tubing string. The ball, acting under pressure of the supply of the
fluid, is engaged in the ball seat 65 and thereby blocks fluid
communication to first ports 25 of the first treatment housing 15.
Thus, when the ball 125 is dropped, and lateral fluid flow through
first ports 25 is prevented, fluid will be diverted to jet nozzles
45, regardless of the relative size of jet nozzles 45 and first
ports 25.
Operation
[0042] FIG. 5 shows, in a highly schematic manner, successive
stages 1, 2 and 3 of the use of the dual treatment device 10 and
the associated launching of a deformable ball through tubing string
110 in a cased wellbore. When the tool string is configured as
shown in the drawings the wellbore intervals will typically be
treated from the lowermost interval and proceed to further
intervals, moving sequentially uphole.
[0043] In use, downhole tool assembly 75, including dual treatment
device 10, is lowered as part of a tubing string 110 into a
wellbore to an interval to be treated. An annulus 106 is defined
between tubing string 110 and casing 120. The downhole tool
assembly 75 is generally located at the appropriate position
through mechanical collar locator 111. Sealing element 95 is then
engaged against the casing 120 (for example, through mechanical
actuation as is known in the art), thus defining a wellbore
interval to be treated above sealing element 95. Treatment fluid
may be delivered down the tubing string 110 to effect perforation,
fracturing, debris cleaning, or various actuation functions, such
as movement of a sliding sleeve.
[0044] In the first position (Stage 1), prior to the launching of
the ball, treatment fluid is directed through the tubing string
110, primarily to first ports 25. Sealing element 95 is engaged
against the casing 120 and therefore, fluid flow across the sealing
element 95 to the wellbore region below the sealing element is
largely prevented. Fluid from the tubing string 110 exits first
ports 25 of first treatment housing 15 through perforations 137 in
casing 120. The fluid may be fracturing fluid, and the wellbore
region around first ports 25 is then fractured, as is indicated by
arrows 135.
[0045] In Stage 2, the deformable ball 125 is launched while
continuing to deliver treatment fluid from surface. The pressure of
the treatment fluid causes the ball 125 to engage within ball valve
50, preventing fluid flow to the first treatment housing 15.
Treatment fluid, such as fluid suitable for sand jet perforation,
may then be delivered through the tubing string 110 to jet
perforation device 35 and such fluid exits nozzles 45. The flow of
perforating fluid (such as that suitable for sand jet perforation)
through nozzles 45 is indicated by 136. This flow of fluid results
in the creation of perforations 137 in the region of the casing
adjacent the perforation device 35.
[0046] To ensure ball 125 remains seated in ball seat 65 during jet
perforation, the pressure differential across the ball seat 65
should be less than the threshold ball deformation pressure.
Accordingly, the ball is selected to deform under a hydraulic
pressure differential that is greater than the pressure
differential required to carry out jet perforation at the interval
depth. Generally, the pressure for fracturing (e.g. when treatment
fluid is exiting first treatment ports 25) is greater than the
pressure for perforating (e.g. when treatment fluid is exiting jet
nozzles 45). For example, the pressure required for perforation may
be about 2000 psi. The pressure for fracturing may be about
4000-6000 psi, and the ball may be designed to deform at about 3000
psi.
[0047] In Stage 3, once perforation is complete, the pressure
differential across the ball seat 65 is increased, for example,
through increased volume of fluid delivery down the tubing string,
and because the seating of ball results in a pressure increase
across the ball seat. Once the pressure differential across the
ball seat 65 exceeds the deformation threshold of ball 125, the
ball 125 will deform sufficiently to pass through the bore 60 of
ball valve 50 to a region within the first treatment housing 15.
The deformed balls are shown schematically as dotted lines. The
region of the first treatment housing 15 for receiving deformed
balls is also referred to herein as a ball containment region.
Fingers on the ball valve 50 prevent re-entry of deformed balls
into the ball valve 50. The disengagement of ball 125 from ball
valve 50 will result in the re-opening of fluid flow through first
treatment housing 15 and through first ports 25. Once fluid flow
through the first treatment housing 15 is re-established,
additional fracturing fluid may be pumped downhole and would
primarily exit through first ports 25. As stated above, some fluid
flow may still occur through the jet nozzles 45, even when
treatment fluid predominantly exits first ports 25.
[0048] As will be readily understood, the pressure differential
across the ball seat 65 or across the jet perforation nozzles 45
may be adjusted by adjusting the rate of fluid delivery to the
tubing string 110 or to the wellbore annulus. The hydraulic
pressure in each may be monitored as is known in the field, to
determine appropriate adjustment as necessary.
[0049] It will also be appreciated that although the illustrated
embodiment includes Stage 3, whereby delivery of treatment fluid
through the first treatment housing 15 is resumed following
deformation of the ball. However, it is also possible that no
additional treatment through first ports 25 is needed, and that
fracturing fluid is delivered to perforations 137 formed in the
casing next to jet perforation device 35 immediately following sand
jet perforation in that region.
[0050] It will also be appreciated that while the illustrated
embodiment primarily relates to the dual treatments of perforating
and fracturing, delivery of other fluids through the first ports
and through the second ports is also possible using the dual
treatment device 10 of the present invention.
Ball Composition
[0051] When deformable balls are used to seal the primary fluid
pathway, custom deformable balls may be required, for example, to
correspond to the pressure seen during the downhole operation of
interest. Deformable ball sealers, of the type typically used to
temporarily seal perforations within a wellbore, are typically
formed from materials such as elastomeric substances and/or wax, or
other predictably deformable material. Balls composed of high
stiffness polymers and thermoplastics such as
polytetrafluoroethylene and polyoxymethylene have provided suitable
composition for the presently described application.
[0052] The ball should be resistant to deformation at pressures
encountered during fluid treatment through the second fluid
treatment pathway (e.g. jet perforation). However, the ball may be
deformable at pressures lower or higher than those required during
fluid treatment through the first fluid treatment pathway (e.g.
fracturing). For example, following treatment through the second
fluid pathway, the pressure differential across the valve seat is
increased until deformation and release of the ball from the ball
seat is achieved. Fluid treatment through the first treatment
pathway may be resumed. If fluid treatment through both the first
and second fluid pathways is effected at similar pressures, a ball
that deforms at significantly greater pressure differential may be
used as long as the tool assembly and tubing string can accommodate
the higher pressures required to achieve passage of the deformable
ball. Otherwise, reverse circulation of the ball to surface through
the tubing string may be considered.
[0053] In the embodiment shown in the figures, fracturing of a
wellbore segment occurs via the first treatment housing. Fracturing
of a formation through a cased and perforated wellbore may take
place at a first tubing pressure. However, fluid jet perforation
may take place at a second tubing pressure. Accordingly, a ball
would be selected that will not deform at pressures less than the
second tubing pressure. When the first tubing pressure is
significantly greater than the second tubing pressure, it may be
convenient to have the ball deformable at pressures between the
first and second tubing pressures, so the ball can deform and pass
through the seat as the pressure is increased. For example, a ball
can be dropped down the tubing string to seal against the ball seat
65 and enable perforation at a first pressure differential, after
which the pressure differential across the ball seat can be
increased by delivery of fracturing fluid to the tubing string.
Once suitable pressure differential is achieved, the ball will
deform and fracturing will be initiated as fluid passes through the
open ball seat 65 to the ports 25 of the first treatment housing
15.
Alternative Embodiments
[0054] Casing string: The invention was described in reference to a
cased wellbore. It will be appreciated that variations in the
casing are possible. For example, the wellbore may be cased and
unperforated, cased and perforated, or cased with perforated
collars or sleeves incorporated into the casing at predetermined
intervals. When the wellbore is cased and pre-perforated (or
otherwise already contains apertures to provide access to the
formation), the secondary fluid pathway may not be used frequently.
However, should one of the perforations fail to take up fluid, or
should it be determined that additional perforations are necessary,
the primary fluid flow pathway can be temporarily blocked by
delivering a deformable ball to the ball seat. The ball can be
subsequently removed by deformation through the ball seat, or by
reverse circulation of fluid through the annulus.
[0055] Reverse circulation: The illustrated embodiment shows the
use of a deformable ball which is released from its position in the
ball seat 65 when the ball threshold deformation pressure is
exceeded. It is possible to release the ball from its seated
position by reverse circulation through the annulus. To unseat the
ball from the ball seat, fluid can be reverse circulated through
the annulus 106 (once sealing element 95 has been released from its
engagement against the casing), and upwardly into ports 25 in first
treatment housing 15. This upward force releases the ball from its
seated position. When the ball is to be reverse circulated to
surface, a lightweight, non-deformable composition may be suitable,
such as aluminum alloys, composites, and the like. Use of a heavy
material, for example, steel, may make reverse circulation to
surface difficult.
[0056] Treatment housings: The invention generally relates to a
method and system for diverting fluid flow in a downhole tool to
carry out two different treatments. Accordingly, the invention has
applicability in any downhole tool comprising a section of tubing
having suitable, longitudinally spaced-apart fluid treatment ports,
apertures, slots or other fluid pathways for performing treatment
operations between the tubing string and the wellbore. For example,
the first treatment housing may not be incorporated as an
additional tubular region, but rather may be part of the existing
tool assembly. For example, in a downhole assembly such as that
illustrated in the figures, fluid treatment may be delivered down
the tubing string and exits port 105 of equalization valve 100, the
equalization valve housing forming the first treatment fluid
housing of the tool assembly. A ball valve would then be provided
on the tubing string between the equalization port 105 and the
second fluid treatment housing 35 (which may be a jet perforation
device). In yet another embodiment, the lower mandrel of the tool
assembly may serve as the first treatment housing, with ports or
apertures located in the mandrel allowing for fluid treatment to
the wellbore. For example, there may be apertures present in the
mechanical collar locator 111 or on the tubular on which the
mechanical collar locator is disposed. Fluid can be delivered to
the wellbore through these apertures. In this embodiment, the
mechanical collar locator (or tubular on which the locator is
disposed) would form the first treatment housing, and the apertures
in the mechanical collar locator would form the first ports.
[0057] Sliding Sleeve: The dual treatment device of the present
invention may be used in conjunction with a casing string having a
sliding sleeve. A suitable sliding sleeve system is described in
Canadian Patent No. 2,738,907, issued to Getzlaf and assigned to
the present assignee and which is herein incorporated by reference.
This embodiment is schematically illustrated in FIG. 6. Casing
string 145 includes an inner sliding sleeve 150 disposed within a
ported sub, the ported subs being connected to each other along the
casing string. A downhole tool assembly 180 including dual
treatment device 10 is deployed as part of a tubing string 155.
First treatment housing 15 with first ports 25 are present, as is
jet perforation device 35 and nozzles 45. A ball valve (not shown)
is disposed between the first treatment housing 15 and jet
perforation device 35. The tool assembly 180 includes a sealing
element 95, as well as a sleeve locator 175. Optionally, a
decompression sub 180 may be present when the lowermost interval of
a wellbore is to be treated.
[0058] In use, hydraulic pressure may cause sliding sleeve 150 to
shift downward, engaging with locator 175. This downward movement
of sleeve exposes ports 160 in ported sub. Fracturing fluid can be
applied through tubing string, exiting first ports 25 present in
first treatment housing 15 and resulting in the fracturing 135 of
the region around ports 160 of ported sub. If perforation is
desired in the region of the casing string 145 above ports 160, a
ball can be dropped to prevent fluid flow down the tubing string to
the first treatment housing 15. This results in fluid diversion to
jet perforation nozzles 45.
[0059] The above-described embodiments of the present invention are
intended to be examples only. Alterations, modifications and
variations may be effected to the particular embodiments by those
of skill in the art without departing from the invention.
* * * * *