U.S. patent application number 13/670125 was filed with the patent office on 2013-03-14 for multi-zone screened fracturing system.
This patent application is currently assigned to WEATHERFORD/LAMB, INC.. The applicant listed for this patent is WEATHERFORD/LAMB, INC.. Invention is credited to John P. Broussard, Christopher A. Hall, Ronald van Petegem.
Application Number | 20130062066 13/670125 |
Document ID | / |
Family ID | 47828789 |
Filed Date | 2013-03-14 |
United States Patent
Application |
20130062066 |
Kind Code |
A1 |
Broussard; John P. ; et
al. |
March 14, 2013 |
Multi-Zone Screened Fracturing System
Abstract
A multi-zone formation treatment assembly has sections disposed
on a tubular structure in a borehole. An isolation element disposed
on the tubular structure that isolates a borehole annulus around
the section from the other sections, and a flow valve disposed on
the tubular structure is selectively operable between opened and
closed conditions permitting and preventing fluid communication
between the through-bore and the borehole annulus. A screen
disposed on the tubular structure communicates with the borehole
annulus, and a closure disposed on the tubular structure at least
prevents fluid communication from the through-bore to the screen. A
workstring of the assembly can be manipulated in the tubular
structure relative to each section in the same trip to: open the
flow valve, position in the through-bore relative to the open flow
valve, deliver the treatment from an outlet to the section through
the open flow valve, and close the flow valve.
Inventors: |
Broussard; John P.;
(Kingwood, TX) ; van Petegem; Ronald; (Montgomery,
TX) ; Hall; Christopher A.; (Cypress, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WEATHERFORD/LAMB, INC.; |
Houston |
TX |
US |
|
|
Assignee: |
WEATHERFORD/LAMB, INC.
Houston
TX
|
Family ID: |
47828789 |
Appl. No.: |
13/670125 |
Filed: |
November 6, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13545908 |
Jul 10, 2012 |
|
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13670125 |
|
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|
61506897 |
Jul 12, 2011 |
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Current U.S.
Class: |
166/305.1 ;
166/179; 166/205 |
Current CPC
Class: |
E21B 43/26 20130101;
E21B 34/06 20130101; E21B 43/08 20130101; E21B 43/14 20130101 |
Class at
Publication: |
166/305.1 ;
166/205; 166/179 |
International
Class: |
E21B 43/00 20060101
E21B043/00; E21B 33/12 20060101 E21B033/12; E21B 43/08 20060101
E21B043/08; E21B 34/06 20060101 E21B034/06 |
Claims
1. A multi-zone formation treatment assembly for a borehole,
comprising: a tubular structure disposed in the borehole and
defining a through-bore; a plurality of sections disposed on the
tubular structure, each of the sections comprising: an isolation
element disposed on the tubular structure and isolating a borehole
annulus around the section from the other sections, a flow valve
disposed on the tubular structure and selectively operable between
opened and closed conditions permitting and preventing fluid
communication between the through-bore and the borehole annulus, a
screen disposed on the tubular structure and communicating with the
borehole annulus, and a closure disposed on the tubular structure
and at least preventing fluid communication from the through-bore
to the screen; and a workstring defining an outlet and being
manipulated in the tubular structure relative to each section in
the same trip to: open the flow valve, position in the through-bore
relative to the open flow valve, deliver the treatment from the
outlet to the section through the open flow valve, and close the
flow valve.
2. The assembly of claim 1, wherein the isolation element comprises
a swellable packer, a hydraulically-set packer, or a
mechanically-set packer.
3. The system of claim 1, wherein the flow valve comprises a sleeve
movable in the through-bore between (a) the closed condition
preventing fluid communication through at least one flow port in
the tubular structure and (b) the opened condition permitting fluid
communication through the at least one flow port.
4. The assembly of claim 1, wherein the closure is selectively
operable between (a) a closed condition preventing fluid
communication between the through-bore and the screen and (b) an
opened condition permitting fluid communication between the
through-bore and the screen.
5. The assembly of claim 4, wherein the closure comprises a sleeve
movable in the through-bore between (a) the closed condition
preventing fluid communication through at least one flow port in
the tubular structure, the at least one flow port in communication
with the screen, and (b) the open condition permitting fluid
communication through the at least one flow port.
6. The assembly of claim 1, wherein the closure comprises a one-way
valve disposed on the tubular structure and in fluid communication
between the screen and the through-bore, the one-way valve
permitting fluid communication from the screen into the
through-bore and preventing fluid communication from the
through-bore to the screen.
7. The assembly of claim 6, wherein the one-way valve comprises: a
housing disposed on the tubular structure and communicating the
screen with at least one flow port in the tubular structure; and a
check ball movably disposed in the housing, the check ball
permitting fluid communication from the screen to the at least one
flow port and preventing fluid communication from the at least one
flow port to the screen.
8. The assembly of claim 1, wherein the screen comprises first and
second screen sections disposed on the tubular structure on both
sides of at least one flow port in the tubular structure, the
screen sections communicating with the at least one flow port.
9. The assembly of claim 8, wherein the closure is selectively
operable between (a) a closed condition preventing fluid
communication through the at least one flow port between the
through-bore and the screen sections and (b) an opened condition
permitting fluid communication through the at least one flow port
between the through-bore and the screen sections.
10. The assembly of claim 9, wherein the closure comprises a sleeve
movable in the through-bore between the closed and opened
conditions.
11. The assembly of claim 8, wherein the closure comprises a
one-way valve disposed on the tubular structure and in fluid
communication between the first and second screen sections and the
at least one flow port, the one-way valve permitting fluid
communication from the first and second screen sections into the at
least one flow port and preventing fluid communication from the at
least one flow port to the first and second screen sections.
12. The assembly of claim 11, wherein the one-way valve comprises:
a housing disposed on the tubular structure and communicating the
screen sections with the at least one flow port; and first and
second check balls movably disposed in the housing, each of the
check balls permitting fluid communication from one of the screen
sections to the at least one flow port and preventing fluid
communication from the at least one flow port to the one screen
section.
13. The assembly of claim 1, wherein the workstring is manipulated
in the same trip to open the closures after treatment of all of the
sections.
14. The assembly of claim 1, wherein workstring comprises an
actuating tool operable to open and close the flow valves of the
sections in the same trip in the through-bore.
15. The assembly of claim 14, wherein the actuating tool is
hydraulically operable.
16. The assembly of claim 14, wherein the actuating tool is
operable to at least open the closures of the sections in the same
trip in the through-bore.
17. The assembly of claim 1, wherein the workstring positions
unsealed in the through-bore relative to the open flow valve.
18. A multi-zone formation treatment assembly for a borehole,
comprising: a tubular structure disposed in the borehole and
defining a through-bore; a plurality of sections disposed on the
tubular structure, each of the sections comprising: means for
isolating a borehole annulus of the section from the other
sections, means for selectively permitting and preventing fluid
communication from the through-bore to the borehole annulus through
a first flow path, means for screening fluid communication from the
borehole annulus to the through-bore through a second flow path,
and means for at least preventing fluid communication from the
through-bore to the borehole annulus through the second flow path;
and a workstring positioning in the through-bore relative to each
of the sections and having means for delivering the treatment to
each of the sections in the same trip.
19. The assembly of claim 18, wherein the workstring comprises
means for actuating the means for selectively permitting and
preventing fluid communication from the through-bore to the
borehole annulus through the first flow path.
20. The assembly of claim 18, wherein the means for selectively
permitting and preventing fluid communication from the through-bore
to the borehole annulus through the first flow path comprises means
for selectively opening and closing a first flow port in the
tubular structure communicating the through-bore with the borehole
annulus.
21. The assembly of claim 18, wherein the means for at least
preventing fluid communication from the through-bore to the
borehole annulus through the second flow path comprises means for
selectively permitting and preventing fluid communication from the
through-bore to the borehole annulus through the second flow
path.
22. The assembly of claim 21, wherein the means for selectively
permitting and preventing fluid communication from the through-bore
to the borehole annulus through the second flow path comprises
means for selectively opening and closing a second flow port in the
tubular structure.
23. The assembly of claim 22, wherein the workstring comprises
means for actuating the means for selectively opening and closing
the second flow port in the tubular structure.
24. The assembly of claim 18, wherein the means for at least
preventing fluid communication from the through-bore to the
borehole annulus through the second flow path comprises means for
exclusively permitting fluid communication of the screened fluid
into the through-bore through the second flow path.
25. The assembly of claim 18, wherein the workstring positions
unsealed in the through-bore relative to each section.
26. A multi-zone formation treatment method for a borehole, the
method comprising: isolating a borehole annulus of the borehole
around an assembly into a plurality of isolated zones, the assembly
in each isolated zone having a first port and a screen
communicating a through-bore of the assembly with the borehole
annulus; positioning a workstring in the through-bore of the
assembly; and treating each of the isolated zones without sealing
the workstring in the through-bore by: selectively opening the
first port in the assembly at the isolated zone with the
workstring, flowing the treatment down the workstring to the
isolated zone through the opened first port, at least preventing
fluid communication from the through-bore to the borehole annulus
through the screen on the assembly at the isolated zone, and
selectively closing the first port at the isolated zone with the
workstring after treatment.
27. The method of claim 26, wherein positioning the assembly in the
borehole comprises positioning the assembly in casing having
perforations, in an expanded liner having slots, or in an open
hole.
28. The method of claim 27, wherein isolating the borehole annulus
of the borehole around the assembly into the isolated zones
comprises engaging isolation elements on the assembly against a
wall of the casing, a wall of the expanded liner, or a wall of the
open hole.
29. The method of claim 26, wherein positioning the workstring in
the through-bore of the assembly comprises positioning the
workstring unsealed in the through-bore of the assembly.
30. The method of claim 26, wherein selectively opening the first
port in the assembly at the isolated zone with the workstring
comprises shifting a sleeve in the assembly away from the first
port with the workstring.
31. The method of claim 30, wherein flowing the treatment down the
through-bore to the isolated zone through the opened first port
comprises flowing the treatment through an outlet in the workstring
positioned with respect to the opened first port.
32. The method of claim 26, wherein at least preventing fluid
communication from the through-bore to the borehole annulus through
the screen on the assembly at the isolated zone comprises
selectively preventing fluid communication from the through-bore to
the borehole annulus.
33. The method of claim 32, further comprising preparing each of
the isolated zones for production by: selectively opening a second
port in the assembly at the isolated zone with the workstring, the
second port communicating the through-bore with the screen; and
permitting fluid communication from the borehole annulus into the
through-bore through the screen and the opened second port at the
isolated zone.
34. The method of claim 33, further comprising screening fluid from
the borehole annulus of the isolated zones into the through-bore of
the assembly through the screens and the opened second ports.
35. The method of claim 33, further comprising exclusively
preventing fluid communication from the through-bore to the
borehole annulus of the isolated zones through the screens after
selectively opening the second ports.
36. The method of claim 33, wherein selectively opening the second
port in the assembly at the isolated zone with the workstring
comprises shifting a sleeve in the assembly away from the second
port with the workstring.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part of U.S. application Ser. No.
13/545,908, filed Jul. 10, 2012, which claims priority to U.S.
Provisional Appl. 61/506,897, filed Jul. 12, 2011, which are both
incorporated herein by reference and to which priority is
claimed.
BACKGROUND
[0002] Wells in some reservoirs need to be hydraulically fractured
to stimulate the production rates and make the wells commercially
viable. For this process, the wells are fractured with a proppant
(e.g., sand or the like) to treat the formation and improve
production. In many cases, multiple fracs are performed in a single
wellbore to treat various zones of interest in the formation. In
some of these reservoirs, the wells needing fracing are in
deepwater areas where production facilities cannot handle any
produced solids, e.g., formation sand or fracturing proppant.
[0003] Currently, completions for such reservoirs use single-trip,
multi-zone systems that allow operators to frac multiple zones in a
single trip in the wellbore, and some single-trip, multi-zone frac
systems use a wellscreen to prevent proppant flowback during
operations. Unfortunately, the current single-trip, multi-zone
systems that have a wellscreen require a service crossover tool be
used for operation. The crossover tool in these systems crosses
over the fluid flow path from a workstring to the annulus outside
the wellscreen and vice versa.
[0004] Using these system and crossover tools has a number of
disadvantages. For example, the systems and crossover tools are
very complicated and difficult to install and operate. They also
offer tremendous risks because the chances of sticking in the well
are quite high.
[0005] Although few fracing operations using single-trip,
multi-zone frac systems have been done to date, there is a lot of
interest in these systems due to the potential savings in deepwater
operations. What is needed then is a single-trip, multi-zone frac
system that can overcome, or at least reduce the effects of, one or
more of the problems set forth above.
SUMMARY OF THE DISCLOSURE
[0006] A multi-zone formation treatment assembly for a borehole has
a tubular structure disposed in the borehole and defining a
through-bore. The assembly can be used for formation treatments,
such as frac operations, frac pack operation, gravel pack
operations, or other operations. Sections are disposed on the
tubular structure, and each section has an isolation element, a
flow valve, a screen, and a closure.
[0007] The isolation element, which can be a swellable packer, a
hydraulically-set packer, or a mechanically-set packer, isolates
the borehole annulus around the section from the other sections
along the borehole. If desired, a flow tube can be disposed in the
borehole annulus and can communicate through the isolation elements
between one or more of the sections. The flow tube can be used for
dehydration of fluid in the borehole annulus of the sections during
a frac pack operation, for example.
[0008] The flow valve is selectively operable between opened and
closed conditions to permit or prevent fluid communication between
the through-bore and the borehole annulus. When opened, the flow
valve is used primarily to deliver the treatment into the borehole
annulus for a section through a first flow path.
[0009] The screen disposed on the tubular structure communicates
with the borehole annulus and can communicate with the assembly's
through-bore through a second flow path. The closure at least
prevents fluid communication from the through-bore of the tubular
structure to the screen. In one condition, for example, the closure
prevents fluid communication from the through-bore to the screen.
This condition is used when performing the formation treatment.
However, in another condition, the closure allows fluid
communication from the screen to the through-bore. This condition
is used after the treatment operations so production fluid can
communicate into the through-bore from the screen.
[0010] In one arrangement, the flow valve is a sliding sleeve
having a housing and a closure element, such as an inner sleeve or
insert, movable therein relative to a flow port. The inner sleeve
can be moved between the closed and opened conditions preventing or
permitting fluid communication through the flow port.
[0011] To move the inner sleeve in some embodiments, for example, a
plug or ball can be deployed in the tubular structure to engage a
seat disposed in the inner sleeve. Then, fluid pressure applied
against the seated plug then moves the inner sleeve open to expose
the flow port.
[0012] In other embodiments to move the inner sleeve, plugs or
balls may not be used. Instead, the flow valve's inner sleeve can
be moved open and closed by a shifting tool in addition to or as an
alternative to the ball and seat arrangement. In particular, a
workstring can be run in the through-bore of the tubular structure,
and an actuating tool on the workstring can be used to open and
close the flow valve of each section.
[0013] In one arrangement, the closure can also have an inner
sleeve that can at least be opened by the shifting tool of the
workstring. Opening of the closure is performed after formation
treatment is complete so the assembly can be used for production
operations. Thus, the closure as an inner sleeve can selectively
prevent and permit fluid communication via the second flow path
from the screen to the assembly's through-bore.
[0014] To prevent fluid loss through the screen during treatment,
however, the closure preferably has a one-way or check valve placed
in fluid communication between the screen and the through-bore. The
check valve at least prevents fluid communication from the tubular
structure's through-bore to the screen. Thus, the check valve can
exclusively prevent fluid communication via the second flow path
the assembly's through-bore to the screen.
[0015] In one arrangement, the screen has first and second screen
sections disposed on the tubular structure on both sides of a flow
port in the tubular structure. The two screen sections can
communicate screened fluid from the borehole annulus to the flow
port. In this arrangement, the closure is disposed on the tubular
structure in fluid communication between the first and second
screen sections and the flow port.
[0016] In particular, an inner sleeve can be selectively opened and
closed relative to a flow port in the tubular structure that
communicates with the screen sections. Interposed between the flow
port and the screen sections, however, are check valve having check
balls and flow passages. The check balls can move to permit or
block fluid communication through the flow passages. In one
condition, for example, the check balls permit fluid communication
from the screen sections to the flow port through the flow
passages, while in another condition, the check balls prevent fluid
communication from the flow port to the screen sections through the
flow passages.
[0017] In a multi-zone formation treatment method for a borehole,
an assembly disposes in the borehole, and an annulus of the
borehole around the assembly is isolated into a plurality of
isolated zones to treat the isolated zones. To isolate the annulus,
for example, the method can involve engaging isolation elements on
the assembly against the borehole.
[0018] A workstring is disposed in the through-bore of the
assembly. Treating each of the isolated zones with a treatment
fluid involves selectively opening a first port in the assembly at
a given isolated zone with the workstring. Then, the treatment
fluid flows down the workstring to the isolated zone through the
opened first port, while selectively preventing fluid communication
from the borehole annulus to the assembly's through-bore through a
screen on the assembly at the isolated zone.
[0019] After treatment at the isolated zone, the first port is
selectively closed with the workstring. When all treatment
operations of the various zones are complete, the assembly is set
up for production. The workstring in the same trip then opens the
closures, allowing fluid in the borehole annulus to flow through
the screen and into the assembly's through-bore. Fluid
communication from the annulus of the isolated zones can then be
screened into the through-bore of the assembly with the screens on
the assembly. However, check valves on the assembly prevent fluid
communication from the through-bore to the annulus of the isolated
zones through the screens.
[0020] The foregoing summary is not intended to summarize each
potential embodiment or every aspect of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 illustrates a multi-zone screened frac system
according to the present disclosure disposed in a cased borehole
and having sections with frac valves and flow devices.
[0022] FIG. 2A illustrates the multi-zone screened frac system of
FIG. 1 having a dehydration tube.
[0023] FIG. 2B illustrates the multi-zone screened frac system of
FIG. 1 having an expandable liner.
[0024] FIG. 3 illustrates a multi-zone screened frac system
according to the present disclosure disposed in an open borehole
and having sections with frac valves and flow devices.
[0025] FIG. 4 illustrates a multi-zone screened frac system
according to the present disclosure disposed in an uncased borehole
and using a workstring in conjunction with frac valves and flow
devices.
[0026] FIG. 5 illustrates the multi-zone screened frac system of
FIG. 4 having flow tubes.
[0027] FIG. 6A illustrates a partial cross-sectional view of a flow
device for the disclosed multi-zone screened frac systems.
[0028] FIG. 6B illustrates a detailed view of a check valve device
for the flow device of FIG. 6A.
[0029] FIG. 6C illustrates an isolated, partial cross-sectional
view of the inflow flow control device of FIG. 6A.
[0030] FIGS. 7A-7B illustrate partial cross-sectional views of a
multi-select sliding sleeve in closed and opened states for the
flow valves in the disclosed multi-zone screen frac systems.
[0031] FIGS. 8A-8B illustrate shifting tools for use on a
workstring for the disclosed system of FIGS. 4-5.
[0032] FIGS. 9A-9D illustrate another multi-zone screened frac
system according to the present disclosure disposed in a uncased
borehole and using a workstring in conjunction with frac valves and
flow devices.
[0033] FIGS. 10A-10B illustrate partial cross-sectional views of
another frac valve for the disclosed systems in closed and open
positions.
[0034] FIG. 11 illustrates a partial cross-sectional view of
another flow device for the disclosed systems.
DETAILED DESCRIPTION
[0035] Various embodiments of a multi-zone screened frac system are
disclosed. The system does not require a crossover tool as required
in the prior art. In some implementations, certain embodiments of
the systems do not even require a complete service tool. To perform
a frac operation on multiple zones in a cased or open borehole, the
system combines: (1) wellscreens with integrated one-way or check
valves, (2) frac valves, and (3) optional shunt tubes for slurry
dehydration. The system can also include fiber optic
technology.
[0036] In a first embodiment according to the present disclosure,
FIG. 1 illustrates a multi-zone screened frac system 10 disposed in
a cased borehole and having sections 28 with frac valves 30 and
flow devices 40, which include wellscreens 46 and closure element
48. The system 10 includes an upper completion or workstring 14
disposed in casing 12. This string 14 is engaged in an uphole end
24 of a production string 22 of a frac assembly 20 and can engage
the casing 12 with an optional packer 16.
[0037] Internally, the production string 22 of the frac assembly 20
has a through-bore 25 communicating along the length of the string
22 and communicating with the completion string 14. Externally, the
frac assembly 20 has isolation devices 18, such as but not limited
to a hydraulic, a mechanical, or a swellable packer, to seal the
production string 22 in the casing 12. One of the packers 18 is
disposed at the string 22's uphole end 24, while other packers 18
are disposed along the length of the production string 22.
Separated by the packers 18, the frac assembly 20 has various
sections 28 disposed at various intervals or zones of interest in
the surrounding formation. At its downhole end 26, the frac
assembly 20 has a bottom seat 50 for engaging a setting ball 54
during frac operations.
[0038] Each section 28 has a selective frac valve 30 and a flow
device 40. Each of the selective frac valves 30 and flow devices 40
in a given section 28 is separated from other sections 28 by the
packers 18, which isolate the borehole annulus 15 for the
respective sections 28. As shown, the selective frac valves 30 are
disposed uphole of the flow devices 40 in the various sections 28.
As an alternative, the selective frac valves 30 can be disposed
downhole of the flow devices 40 in the section 28.
[0039] The selective frac valves 30 have one or more ports 32 that
can be selectively opened and closed during operation with a
closure element 34 (e.g., inner sleeve). In this arrangement and as
discussed in more detail below, for example, each of the selective
frac valves 30 can be opened to communicate their ports 32 with the
surrounding annulus 15 by using frac plugs or balls 36 deployed
downhole during frac operations. As treatment is performed in the
well, these dropped plugs or balls 36 selectively open the frac
valves 30 and isolate lower sections 28 so the selective frac
valves 30 can successively divert frac treatment to adjacent zones
of interest up the frac assembly 20.
[0040] The flow device 40 for each section 28 is disposed adjacent
or near perforations 13 in the casing 12. In this and other
assemblies disclosed herein, the flow devices 40 use wellscreens 46
with integrated closure elements 48 (e.g., one-way or check valves)
to control the flow of fluid through the flow devices 40. In
particular, each flow device 40 exclusively screens fluid
communication through a first flow path (i.e., flow from the
borehole annulus 15 to the through-bore 25 of the assembly 20
through the flow device 40). At the same time, the flow device 40
exclusively prevents fluid communication from the through-bore 25
of the assembly 20 to the borehole annulus 15 along this first flow
path. Thus, the wellscreen 46 screens fluid flow along the first
flow path from the borehole annulus 15 to the through-bore 25.
However, the flow device 40 does not permit fluid flow in the
opposite direction along this same flow path, and exclusively
prevents flow from the through-bore 25 to the borehole annulus 15
through the wellscreen 46.
[0041] In particular, the flow devices 40 can each include a
wellscreen 46 and a closure device 48, which can be an inflow
control device such as a FloReg.TM. Deploy-Assist (DA) Device
available from Weatherford International. Preferably, the closure
element 48 lacks nozzles and is used in the system 10 primarily as
a check valve, but nozzles can be used in other arrangements to
create a pressure differential in produced fluid. Further details
of a suitable flow device 40 having a wellscreen 46 and a closure
element 48, which can be an inflow control device such as the
FloReg.TM. Deploy-Assist (DA) Device, are provided below in FIGS.
6A-6C. Moreover, details of a suitable inflow control device for
the closure element 48 used with a wellscreen 46 are also disclosed
in U.S. Pat. Nos. 6,371,210 and 7,828,067, which are incorporated
herein by reference in their entireties.
[0042] In this and other assemblies disclosed herein, each
selective frac valve 30 selectively permits and prevents fluid
communication through a second flow path (i.e., between the
through-bore 25 of the assembly 20 and the borehole annulus 15). In
particular, the selective frac valves 30 can be sliding sleeves,
such as a ZoneSelect.TM. MultiShift frac sliding sleeve available
from Weatherford International. The selective frac valve 30 is
designed to open when a ball 36 lands on a landing seat (not
labeled) disposed in the selective frac valve 30 and tubing
pressure is then applied to shear the selective frac valve 30 open
to expose the through-bore 25 to the surrounding annulus 15. Again,
a ball 36 for a section 28 is dropped from the surface once the
appropriate amount of proppant is pumped into the previously
treated section 28. Further details of a suitable multi-shift
sliding sleeve, such as the ZoneSelect.TM. MultiShift frac sliding
sleeve, are provided below in FIGS. 7A-7B.
[0043] In this and other assemblies 10 disclosed herein, a fracing
operation uses the series of packers 18 and selective frac valves
30 to sequentially isolate and treat the different zones or
sections 28 of the downhole formation. Initially, the assembly 20
having the packers 18, selective frac valves 30, and flow devices
40 is run downhole and set up using known techniques. Eventually, a
bottom plug or ball 54 is pumped downhole to close off the flow
path through the assembly's bottom end 50.
[0044] Next, operators set the packers 18 to create the multiple
isolated sections 28 down the borehole annulus 15. How the packers
18 are set depends on the type of packers 18 used. For example,
hydraulic pressure pumped down the assembly's through-bore 25 can
be used to set the packers 18. The closed bottom end 50, the closed
frac valves 30, and the integrated closure elements 48 prevent
fluid pressure in the assembly 20 from escaping to the annulus 15
during the setting procedures. Use of different types of packers 18
would require other known procedures.
[0045] Once the packers 18 are set, operators apply a frac
treatment successively to each of the isolated sections 28 by
selectively opening the selective frac valves 30 and allowing the
treatment fluid to interact with the adjacent zones of the
formation through the opened ports 32. To open each frac valve 30,
for example, operators drop specifically sized plugs or balls 36
into the assembly 20 and land them on corresponding seats (not
shown) on the designated frac valves 30. Typically, the balls 36
increase in size up the borehole so that a smaller ball 36 can pass
through all of the seats (not shown) on the uphole frac valves 30
before engaging its designated seat further downhole. For example,
a range of plugs or balls 36 may allow fracturing up to 13, 19, and
21 sections in the borehole when 31/2 in., 41/2 in., and 51/2 in.
frac valves 30 are used, respectively. An additional section can be
added by using a toe sleeve (not shown).
[0046] Once a dropped ball 36 is seated, the ball 36 closes off the
lower section 28 just treated, and built up pressure on the seated
ball 36 forces the frac valve 30 open so frac fluid can interact
with the adjacent zone of the formation through the open flow ports
32. Operators repeat this process up the assembly 20 to treat all
of the sections 28 by successively dropping bigger balls 36 against
bigger seats (not shown) in the frac valves 30. Once the frac
treatment is complete, flow in the assembly 20 can float all the
balls 36 to the surface, or operators can mill out the balls 36 and
ball seats (not shown) from the frac valves 30. Finally, after
fracing, the system 10 may need a clean-out trip in which a fluid
wash is pumped down the assembly 10 to clear it of excess or
residual proppant and frac fluid.
[0047] The multi-zone frac system 10 of FIG. 1 can achieve higher
flow rates and can improve reservoir performance while: only
requiring one trip upper and lower completions, using standard
packers, not requiring a crossover tool, and offering less risk.
The system 10 can also have any suitable length and spacing between
sections 28. A wet-connector is not required for using fiber
optics, and the system 10 allows for monitoring while fracing using
a fiber optic based sensor system (not shown).
[0048] In a second embodiment according to the present disclosure,
the multi-zone screened frac system 10 of FIG. 2A is similar to
that of FIG. 1 so that similar components are shown with the same
reference numerals. In contrast to the previous arrangement,
however, this system 10 has a dehydration tube (i.e., slurry or
flow tube) 60 disposed along the assembly 20 running from the
optional packer 16 at the uphole end 24 to the lower most packer 18
near the downhole end 26. Although the de-hydration tube 60 may
present a barrier issue, any potential problems can be mitigated by
running a production packer (not shown) uphole in the casing
12.
[0049] The dehydration tube 60 communicates with the borehole
annulus 15 of each of the sections 28 using flow ports (not shown)
or the like. Additionally, the tube 60 passes through the packers
18 isolating the sections 28. Use of the tube 60 is beneficial when
frac pack operations are performed, which involve fracing a zone of
interest and then gravel packing the borehole annulus 15 around the
wellscreen 46. In this way, the tube 60 in the system 10 allows the
system 10 to dehydrate the annular gravel pack when performed.
[0050] After fracing operations, the system 10 in FIG. 2A may need
a clean-out trip and may require 3-4 MM in lower tertiary. The
multi-zone frac system 10 of FIG. 2A can provide higher rates and
improve reservoir performance while not requiring a crossover tool
and offering less risk. The system 10 can be any length and
spacing, may eliminate the need for a wet-connector for fiber
optics, and allows for monitoring while fracing.
[0051] As noted above in FIGS. 1 and 2A, the system 10 can be used
in cased borehole having casing 12 with perforations 13. Other
completion arrangements can be used. For example, instead of the
borehole having perforated casing 12, the borehole can have an
expandable pre-slotted or pre-perforated liner 17a as in FIG. 2B.
As is customary, such an expandable liner 17a can be suspended from
a liner hanger and packer assembly 17b disposed in casing 12. Below
the liner hanger and packer assembly 17b, the expandable liner 17a
extends into an open borehole section. The expandable liner 17a can
have slots or perforations (not shown) in those zones of the
formation to be produced. Although not shown, the expandable liner
17a can be constructed to suit the zones of the formation using
modular components, including expandable liner or sand screen
sections, blank pipe sections, and expandable zonal isolation
joints, such as are available in Weatherford's Expandable Reservoir
Completion systems.
[0052] How the liner hanger and packer assembly 17b and the
expandable liner 17a are installed in the borehole will be
appreciated by one skilled in the art with the benefit of the
present disclosure so that particular details are not provided
here. Briefly though, the liner hanger and packer assembly 17b and
expandable liner 17a are disposed downhole, and the hanger and
packer assembly 17b is set by dropping a ball and applying
pressure. Expansion of the liner 17a is then performed using liner
expansion tools. Once the liner 17a is set, frac operations can be
performed by deploying the frac assembly 20 as described
previously.
[0053] Other than a cased or lined borehole as noted above, the
multi-zone screened frac system 10 can also be used for open hole
completions. In a third embodiment according to the present
disclosure, for example, the multi-zone screened frac system 10 of
FIG. 3 is used for an open hole completion and has many of the same
components as described previously so that like reference numeral
are used for similar components. In contrast to the cased or lined
hole arrangements of FIGS. 1 and 2A-2B, open hole packers 19 are
used for this system 10 in FIG. 3. These packers 19 can be
swellable and/or hydraulic set packers for open holes.
[0054] After fracing operations, the system 10 may need a clean-out
operation. As before, the frac valves 30 are disposed uphole of the
flow devices 40, but they could be disposed downhole of the flow
devices 40 in each section 28. As another alternative, slurry
de-hydration tubes (not shown) could also be used along the
assembly 10.
[0055] The multi-zone frac system 10 of FIG. 3 provides the highest
rates and improved reservoir performance. The system 10 can be of
any length and any spacing. The system 10 does not require
perforating to be performed and offers the option to step down one
casing size in its implementation, which can give significant
savings potential. Finally, the system 10 does not need
wet-connectors for using fiber optics, and the system 10 allows for
monitoring while fracing.
[0056] In a fourth embodiment according to the present disclosure,
the multi-zone screened frac system 10 in FIG. 4 is also used for
openhole completions as with the embodiment of FIG. 3. In contrast
to previous arrangements, this system 10 has a workstring 70 that
disposes in the frac assembly 20 to open the various frac valves 30
and treat portions of the formation. As shown, the workstring 70
has external seals 76 disposed near outlet ports 72. A dropped ball
74 can seat in a distal seat of the workstring 70 to divert fluid
flow down the workstring 70, out the outlet ports 72, and to the
open ports 32 in the frac valve 30 to treat the surrounding
formation.
[0057] The frac operation for the system 10 of FIG. 4 involves
running the assembly 20 downhole and setting the packers 19 to
create the multiple isolated sections 28 down the borehole annulus
15. Once the packers 19 are set, operators apply a frac treatment
successively to each of the isolated sections 28 by selectively
opening the selective frac valves 30 with a shifting tool 78 on the
workstring 70 since dropped balls are not used.
[0058] Details about opening the frac valves 30 are provided below
with reference to FIGS. 7A-7B and 8A-8B. In general, the shifting
tool 78 can be a "B" shifting tool for shifting the inner sleeve 34
in the frac valve 30 relative to the valve's ports 32. Thus,
opening a given frac valve 30 involves engaging the shifting tool
78 in an appropriate profile of the valve's inner sleeve 34 and
moving the inner sleeve 34 with the workstring 70 to an opened
condition so that the assembly's through-bore 25 communicates with
the borehole annulus 15 via the now opened ports 32.
[0059] Once a given frac valve 30 is opened, the seals 76 on the
workstring 70 can engage and seal against inner seats 38, surfaces,
seals, or the like in the frac valve 30 or elsewhere in the
assembly 20 on both the uphole and downhole sides of the opened
ports 32. The seals 76 can use elastomeric or other types of seals
disposed on the inner workstring 70, and the seats 38 can be
polished seats or surfaces inside the frac valve 30 or other parts
of the assembly 20 to engage the seals 76. Although shown with this
configuration, the reverse arrangement can be used with seals on
the inside of the frac valve 30 or assembly 20 and with seats on
the workstring 70.
[0060] Once the workstring 70 is seated, treatment fluid is flowed
down the through-bore 75 of the workstring 70 to the sealed and
opened ports 32 in the frac valve 30. The treatment fluid flows
through the outlet ports 72 in the workstring 70 and through the
opened ports 32 to the surrounding borehole annulus 15, which
allows the treatment fluid to interact with the adjacent zone of
the formation.
[0061] Once treatment is completed for the given zone, operators
manipulate the workstring 70 to engage the shifting tool 78 in the
frac valve 30 to close the ports 32. For example, the shifting tool
78 can engage another suitable profile on the inner sleeve 34 of
the frac valve 30 to move the sleeve 34 and close the ports 32. At
this point, the workstring 70 can be moved in the assembly 20 to
open another one of the frac valves 30 to perform treatment.
Operators repeat this process up the assembly 20 to treat all of
the sections 28. Once the frac treatment is complete, the system 10
may not need a clean-out trip.
[0062] The multi-zone frac system 10 of FIG. 4 can have higher
rates compared to a conventional single trip multi-zone system and
can improve reservoir performance. The system 10 can have any
suitable length and spacing, offers the option to step down one
casing size, does not require perforating, and does not require a
clean-out trip. Consideration should be given to potential sticking
the workstring 70 during operation and to annulus packing that can
occur for a particular implementation.
[0063] In a fifth embodiment, the multi-zone screened frac system
10 of FIG. 5 also has a workstring 70, as with the previous
embodiment of FIG. 4. In addition to all of the same components,
this system 10 has slurry dehydration tubes 80 disposed along the
various sections 28.
[0064] During a frac operation similar to that discussed above, the
tubes 80 help dehydrate slurry intended to gravel pack the borehole
annulus 15 of the sections 28 during a frac pack type of operation.
In addition, the tubes 80 can act as a bypass for fluid returns
during the operation. As treatment fluid flows from the workstring
70 seated in a frac valve 30, through the opened ports 32, and into
the borehole annulus 15, the wellscreen 46 screens fluid returns
from the annulus 15, and the fluid returns can flow into the
assembly 20 downhole of the engagement of the workstring 70 in the
assembly 20. The tubes 80 can, therefore, allow these fluid returns
to flow from the downhole section of the assembly 20 to the
micro-annulus between the workstring 70 and the inside of the
assembly 20 uphole of the sealed engagement of the workstring 70
with the ports 32. From this point, the fluid returns can then flow
to the surface.
[0065] The multi-zone frac system 10 of FIG. 5 can have higher
rates compared to a conventional single trip multi-zone system 10
and can improve reservoir performance. Furthermore, the system 10
can have any length and spacing, offers the option to step down one
casing size, does not require perforating, does not require a
clean-out trip, and can give good annulus packing. Consideration
should be given to potential sticking of the workstring 70 for a
particular implementation.
[0066] As noted above, the various embodiments of the multi-zone
frac system 10 in FIGS. 1-5 use flow devices 40 disposed on the
frac assembly 20, and the flow devices 40 includes wellscreens 46
and closure element 48 (i.e., one-way or check valves). Turning now
to FIGS. 6A-6B, a flow device 150 that can be used for the
disclosed systems 10 is shown in a partial cross-sectional view and
a detailed view, respectively. The flow device 150 is a screen
joint having a screen jacket 160 (i.e., wellscreen) and an inflow
control device 170 (i.e., one-way or check valve) disposed on a
basepipe 152. (FIG. 6C shows the inflow control device 170 in an
isolated view without the basepipe 152 and the screen jacket
160.)
[0067] The flow device 150 is deployed on a completion string (22:
FIGS. 1-5) with the screen jacket 160 typically mounted upstream of
the inflow control device 170, although this may not be strictly
necessary. The basepipe 152 defines a through-bore 155 and has a
coupling crossover 156 at one end for connecting to another joint
or the like. The other end 154 can connect to a crossover (not
shown) of another joint on the completion string (22). Inside the
through-bore 155, the basepipe 152 defines pipe ports 158 where the
inflow control device 170 is disposed.
[0068] As noted above, the inflow control device 170 can be similar
to a FloReg deploy-assist (DA) device available from Weatherford
International. As best shown in FIG. 6B, the inflow control device
170 has an outer sleeve 172 disposed about the basepipe 152 at the
location of the pipe ports 158. A first end-ring 174 seals to the
basepipe 152 with a seal element 175, and a second end-ring 176
attaches to the end of the screen jacket 160. Overall, the sleeve
172 defines an annular space around the basepipe 152 communicating
the pipe ports 158 with the screen jacket 160. The second end-ring
176 has flow ports 180 that separate the sleeve's annular space
into a first inner space 186 communicating with the screen 160 and
second inner space 188 communicating with the pipe ports 158.
[0069] For its part, the screen jacket 160 is disposed around the
outside of the basepipe 152. As shown, the screen jacket 160 can be
a wire wrapped screen having rods or ribs 164 arranged
longitudinally along the base pipe 152 with windings of wire 162
wrapped thereabout to form various slots. Fluid can pass from the
surrounding borehole annulus to the annular gap between the screen
jacket 160 and the basepipe 152. Although shown as a wire-wrapped
screen, the screen jacket 160 can use any other form of screen
assembly, including metal mesh screens, pre-packed screens,
protective shell screens, expandable sand screens, or screens of
other construction.
[0070] Internally, the inflow control device 170 has a number
(e.g., ten) of flow ports 180. Rather than providing a
predetermined pressure drop along the screen jacket 160 by using
multiple open or closed nozzles (not shown), the inflow control
device 170 as shown in FIGS. 6A-6C may lack the typically used
restrictive nozzles and closing pins for the internal flow ports
180. Instead, the flow ports 180 may be relatively unrestricted
flow passages and may lack the typical nozzles, although a given
implementation may use such nozzles if a pressure drop is desired
from the screen jacket 160 to the basepipe 152.
[0071] Internally, however, the inflow control device 170 does
include port isolation balls 182, which allow the device 170 to
operate as a one-way or check valve. Depending on the direction of
flow or pressure differential between the inner spaces 186 and 188,
the port isolation balls 182 can move to an open condition (to the
right in FIG. 6B) permitting fluid communication from the screen's
inner space 186 to the pipe's inner space 188 or to a closed
condition (to the left in FIG. 6B against a seat end 184 of the
flow port 180) preventing fluid communication from the pipe's inner
space 188 to the screen's inner space 186.
[0072] In general, the inflow control device 170 can facilitate
fluid circulation during deployment and well cleanup and can be
used in interventionless deployment and setting of openhole
packers. In deployment, for example, the isolation balls 182
maximize fluid circulation through the completion shoe (50: FIGS.
1-5) of the frac assembly (20) to aid efficient deployment of the
completion string (22) and assembly (20). When the housing
components (172, 174, 175, & 176) are disposed on the basepipe
150, the isolation balls 182 are retained in-place. During initial
installation and production, the isolation balls 182 can prevent
formation surging, thereby reducing damage to the formation. In
some arrangements, the isolation balls 182 within the device 170
can be configured to erode over a period of time, allowing access
to the interval for workover activity such as stimulation.
[0073] Should a pressure drop be desired from the screen jacket 160
to the basepipe 152, the flow ports 180 can include nozzles (not
shown) that restrict flow of screened fluid (i.e., inflow) from the
screen jacket 160 to the pipe's inner space 188. For example, the
inflow control device 170 can have ten nozzles, although they all
may not be open. Operators can set a number of these nozzles open
at the surface to configure the device 170 for use downhole in a
given implementation. Depending on the number of open nozzles, the
device 170 can thereby produce a configurable pressure drop along
the string of such flow devices 150.
[0074] As noted above, the various embodiments of the multi-zone
frac system 10 in FIGS. 1-5 use frac valves 30 disposed on the frac
assembly 20 that can be opened and closed to communicate ports 32
with the borehole annulus 15. Turning now to FIGS. 7A-7B, a frac
valve 210 for the disclosed multi-zone screen frac system 10 is
shown in partial cross-section in a closed state (FIG. 7A) and an
opened state (FIG. 7B). As noted above, the frac valve 210 can be a
sliding sleeve similar to Weatherford's ZoneSelect MultiShift frac
sliding sleeve and can be placed between isolation packers in the
multi-zone completion. The sliding sleeve 210 includes a housing
220 with upper and lower subs 222 and 224. A closure element 230,
such as an inner sleeve or insert, movable within the housing 220
opens or closes fluid flow through the housing's flow ports 226
based on the inner sleeve 230's position.
[0075] When initially run downhole, the inner sleeve 230 positions
in the housing 220 in a closed state (FIG. 7A). In this state, a
holder 235 holds the inner sleeve 230 toward the upper sub 222, and
a locking ring or dogs 238 fit into an annular slot within the
housing 220. Outer seals 236 on the inner sleeve 230 engage the
housing 220's inner wall both above and below the flow ports 226 to
seal them off. In addition, the flow ports 226 may be covered by a
protective sheath 227 to prevent debris from entering into the
sliding sleeve apparatus 210. Such a sheath 227 can be composed of
a destructible material, such as a composite.
[0076] As noted previously with respect to FIGS. 1-3, the sliding
sleeve 210 is designed to open when a ball 36 lands on the landing
seat 232 and tubing pressure is applied to move the inner sleeve
230 open. To open the sliding sleeve 210 in a frac operation, for
example, operators drop an appropriately sized ball 36 downhole and
pump the ball 36 until it reaches the landing seat 232 disposed in
the inner sleeve 230 as shown in FIG. 7B. The designated ball 36
for the landing seat 232 of this particular sleeve 210 is dropped
from the surface once the appropriate amount of proppant has been
pumped into the lower formation's zone.
[0077] Once the ball 36 is seated, built up pressure forces against
the inner sleeve 230 in the housing 220, thereby shearing away from
the holder 235 and freeing the dogs 238 from the housing's annular
slot to the inner sleeve 230 can slide downward. As it slides, the
inner sleeve 230 uncovers the flow ports 226. Preferably, as the
inner sleeve 230 shifts past the flow ports 226, fracturing does
not occur through the inner sleeve 230, which protects it from
erosion.
[0078] To mitigate potential damage to the sleeve 210 as the inner
sleeve 230 moves downward, a shock absorber 240 can be connected to
the inner sleeve 230's lower end. As shown in FIG. 7A, this shock
absorber 240 is initially connected in an extended position by
shear pins 242 within the inner sleeve 230. As the inner sleeve 230
moves downward during opening, the absorber's distal lip 245
engages a shoulder 225 on the housing's lower sub 224, thereby
breaking the downward energy of the moving inner sleeve 230.
[0079] After the fracturing job, the well is typically flowed clean
and the ball seat 232 and remaining ball 36 is milled out. The ball
seat 232 can be constructed from cast iron to facilitate milling,
and the balls 36 can be composed of aluminum or non-metallic
material. Once milling is complete, the inner sleeve 230 can be
closed or opened with a standard "B" shifting tool on the tool
profiles 234 and 236 in the inner sleeve 230 so the sliding sleeve
210 can then function like any conventional sliding sleeve shifting
with a "B" tool. The ability to selectively open and close the
sliding sleeve 210 with a "B" shifting tool after milling enables
operators to isolate the particular section (28: FIGS. 1-5) of the
assembly (20).
[0080] For those embodiments of the disclosed multi-zone screen
frac system 10 that do not use a ball and seat arrangement, such as
in FIGS. 4-5, the sliding sleeve 210 may lack a seat 232
altogether. Instead as noted above, the workstring (70: FIGS. 4-5)
has a shifting tool (78), such as a standard "B" shifting tool,
that can engage on the tool profiles 234 and 236 in the inner
sleeve 230 so the workstring 70 can selectively move the inner
sleeve 230 and open and close the ports 226.
[0081] Turning now to FIGS. 8A-8B, details of a shifting tools 78
for the workstring 70 of FIGS. 4-5 are discussed. As shown for the
shifting tool 78 in FIG. 8A, a mandrel 302 is disposed between
upper and lower sections of the workstring 70 and has upper and
lower shifting elements 310 and 320. Because the mandrel 302 is
part of the workstring 70, it may have a bore (not shown)
therethrough for flow of fluid.
[0082] In the present example, the upper element 310 is designed to
be a closing tool for closing a sliding sleeve (e.g., 210: FIGS.
7A-7B) by engaging the upper profile (234), jarring up of the
workstring 70, and shifting the inner sleeve (230) upward in the
sliding sleeve (210). Likewise in this example, the lower element
320 is designed to be an opening tool for opening the sliding
sleeve (210) by engaging the lower profile (236), jarring down with
the workstring 70, and shifting the inner sleeve (230) downward in
the sliding sleeve (210). A reverse arrangement could also be
used.
[0083] As shown in the detailed cutaway, the closing shifting
element 310 has a biased collet 312 that fits around the mandrel
302 and that connects at both ends to stops 314 and 316 on the
mandrel 302. The collet 312 has B-profiles 318 that include an
upward facing shoulder, an upper (shortened) cam, and a lower
(extended) cam. As discussed above, the B-profiles 318 enable the
collet 312 to engage the recessed profile (234) in the sliding
sleeve (210) in the up direction and bypass the recessed profiles
(234 and 236) in the sliding sleeve (210) in the down direction.
This type of shifting element is typically referred to as a B
shifting tool with a B-profile.
[0084] Another arrangement of the shifting tool 78 uses a two-way
shifting element 330 as shown in FIG. 8B. Here, the two-way
shifting element 330 has a biased collet 332 that fits around the
mandrel 302 and that connects at both ends to stops 334 and 336 on
the mandrel 302. The collet 332 has dual B-profiles 328 having a
downward-facing shoulder 340, an upper cam 342, an upward-facing
shoulder 345, and a lower cam 347. Depending on the configuration
of the sliding sleeve (210) and its profiles (234 and 236) and the
direction the workstring 70 is being moved, the shifting tool 330
can open/close the sliding sleeve (210) by jarring down/up.
[0085] FIGS. 9A-9D illustrate another multi-zone screened frac
system 10 according to the present disclosure used for an open hole
completion. As with some previous arrangements, the system 10 has a
workstring 70 that disposes in the frac assembly 20 to open the
various frac valves 30 and treat portions of the formation, but the
workstring 70 in this arrangement does not seal inside the assembly
20 when delivering the treatment at various points in the
formation.
[0086] As shown, a service packer 17 can be used between the
workstring 70 and the casing 12 to isolate the internal
through-bore 25 of the assembly 20. As also shown, the workstring
70 has a service tool 77 disposed above the liner packer 16. The
service tool 77 can be used for hydraulically setting the packer
16. Regardless of the configuration used, the uphole components of
the system 10 can be used for circulating, squeeze, and reverse out
operations as is known in the art.
[0087] The workstring 70 has one or more outlet ports 72 and has
hydraulically actuated shifting tools 78a-b. Both of the shifting
tools 78a-b can be actuated with applied pressure against a ball
(74: FIG. 9B) when seated in the workstring 70. One shifting tool
78b can open the frac valves 30 when the workstring 70 is run
downhole in the assembly 20, while the other shifting tool 78a can
close the frac valves 30 when the workstring 70 is run uphole in
the assembly 20. The same can be true for opening and closing the
flow devices 40 with the shifting tools 78a-b as discussed below.
Thus, one shifting tool 78b is run facing down, while the other
tool 78a is run facing up. Other arrangements can be used, and
other types of shifting tools can be used as well.
[0088] As an example, the shifting tools 78a-b can each be a
hydraulically actuated version of an industry standard B shifting
tool. When the shifting ball (74) is dropped in the workstring 70,
the application of hydraulic pressure down the workstring 70
actuates the shifting tools 78a-b so that they expose spring-loaded
keys for shifting the frac valves 30 and flow devices 40 open or
closed. The shifting tools 78a-b may be actuated together with the
same ball 74 or actuated separately with different sized balls 74
depending on the configuration.
[0089] As before, the frac assembly 20 has a production string 22
supported from a packer 16 in the casing 12. Along its length, the
string 22 has isolation devices 19, frac valves 30, and flow
devices 40. The isolation devices 19, which can be packers, seal
the borehole annulus 15 around the assembly 20 and separate the
annulus 15 into various zones or sections 28A-C. Each section 28A-C
has at least one of the frac valves 30 and at least one of the flow
devices 40, both of which can selectively communicate the string's
through-bore 25 with the borehole annulus 15 as detailed below. At
its downhole end, the frac assembly 20 has a bottom seat 50 for
engaging a setting ball 54 to close off the shoe 26 during frac
operations.
[0090] As shown, the selective frac valve 30 is disposed uphole of
the flow device 40 in each of the various sections 28A-C. As an
alternative, the selective frac valve 30 can be disposed downhole
of the flow device 40 in each section 28A-C. Moreover, a given
section 28A-C may have more than one frac valve 30 and/or flow
device 40.
[0091] The selective frac valves 30 have one or more ports 32 that
can be selectively opened and closed during operation. In this
arrangement as with others discussed above, each of the selective
frac valves 30 can be opened to communicate their ports 32 with the
surrounding annulus 15 by using the shifting tool 78a on the
workstring 70. As before, the frac valves 30 can be sliding sleeves
having a movable closure element 34, such as an inner sleeve or
insert, which isolates or exposes ports 32 in the sliding sleeve's
housing.
[0092] Similar to the frac valves 30, the flow devices 40 also have
one or more ports 42 that can be selectively opened and closed
during operation. Each of the flow devices 40 also includes a
closure and a screen 46. The closure in this arrangement includes a
first closure element 44 that selectively opens and closes flow
through the flow ports 42 and includes a second closure element 48
that at least prevents fluid flow from the through-bore 25 through
the screen 46.
[0093] This assembly 10 is a single trip, multi-zone frac system as
discussed in previous embodiments. Briefly, the assembly 20 is run
downhole as part of the production string 22 or liner system
deployed in the borehole, and the liner packer 16 is set
hydraulically. Frac treatments are then performed for the various
zones or sections 28A-B of the borehole annulus 15 by selectively
opening the frac valves 30.
[0094] After fracing is completed, excess proppant is cleaned out
of the assembly 20, and the frac valves 30 are closed because they
are used primarily for outlet ports for the frac treatment. To
prepare the assembly 20 for production, the flow devices 40 are
then opened in the assembly 20 with the workstring 70 in the same
trip in the wellbore by opening the first closure element 44 (e.g.,
inner sleeve) to expose the flow ports 42. Once open, the flow
devices 40 screen fluid from the borehole annulus 15 into the
string's through-bore 25. At the same time, the flow device's
second closure element 48 functions to prevent flow in the reverse
direction. As discussed in more detail below, for example, the flow
device's second closure element 48, which can use one-way or check
valve, can prevent fluid loss into the formation while pulling out
the workstring 70 from the assembly 20 and while performing
production.
[0095] With a general understanding of how the assembly 20 is used,
discussion now turns to how frac operations are performed in more
detail. Initially, all of the frac valves 30 and flow devices 40
are closed on the assembly 20 when run in the borehole. After
setting the liner packer 16 and closing off the bottom seat 50 with
the setting ball 54, operators set the packers 19 along the
assembly 20 with the appropriate procedures to create the multiple
isolated sections 28A-C down the borehole annulus 15. Once the
packers 19 are set, operators can then commence with applying frac
treatment successively to each of the isolated sections 28A-C by
selectively opening and then closing the selective frac valves 30
with the shifting tools 78a-b on the workstring 70.
[0096] As shown in FIG. 9A, for example, the selective frac valve
30 for the lower section 28A is opened, but its accompanying flow
device 40 remains closed. To open this lower frac valve 30,
operators position the workstring 70 near the frac valve 30 and
drop the shifter ball (74) to the shifting tools 78a-b on the
workstring 70. Operators then pressure up the workstring 70, and
the applied pressure in the workstring's bore 75 acts against the
seated ball (74) and actuates the shifting tools 78a-b. Using the
opening tool (e.g., 78b), operators open the frac valve 30 (e.g.,
by shifting the inner sleeve 34 in the valve 30 open). Once the
frac valve 30 is open, operators then bleed off the applied
pressure and reverse the flow so that the seated ball (74) in the
workstring 70 can be reversed out through the workstring's bore 75
to the surface.
[0097] For example, the flow device 40 can be a sliding sleeve
having a movable closure element 44, such as an inner sleeve or
insert, which isolates or exposes the ports 42 in the sliding
sleeve's housing. The flow device 40 can be opened to communicate
its ports 42 with the surrounding annulus 15 through its screen 46
by using the shifting tool 78a on the workstring 70. In this way,
the flow device 40 when closed does not communicate the string's
through-bore 25 with the borehole annulus 15 through screens 46,
but the flow device 40 when opened allows screened fluid from the
annulus 15 to pass through the screen 46 on the device 40 and into
the through-bore 25.
[0098] Now, operators position the workstring 70 uphole of the open
frac valve 30 as shown in FIG. 9A. In manipulating the workstring
70 in the assembly 20, the workstring 70 is positioned unsealed in
the assembly's through-bore 25 relative to the open ports 32 in the
frac valve 30. In other words, the workstring 70 at the section 28A
to be treated is not engaged with seals or seats inside the
assembly's through-bore 25 as in previous embodiment.
[0099] Without sealing the workstring 70 in the assembly's section
28A, operators apply the frac treatment down the workstring 70 to
treat the borehole annulus 15 for this section 28A. The fluid
leaves the ports 72 in the workstring 70 and flows along a first
flow path through the open ports 32 of the frac valve 30 and into
the formation around the open section's borehole annulus 15. To
maintain the pressure in the assembly 20 during the frac operation,
the system 10 can use a live annulus technique (if the service
packer 17 is not used or can be removed, or the system 10 can use a
pure squeeze technique with the service packer 17 in the casing
12.
[0100] At the same time as the frac treatment, the closure on the
flow device 40 at least prevents fluid flow through the ports 42
and screen 46 from the through-bore 25 to the borehole annulus 15.
Preventing the flow out of the screen 46 can be accomplished by
either the first or second closure elements 44 and 48 or by both.
Preferably, the first closure element 44 also prevents fluid flow
from the borehole annulus 15 into the through-bore 25 via the
screen 46.
[0101] Once treatment of the first section 28A is done, operators
reverse out at least some of the excess slurry from the workstring
70 so treatment can commence with the next section 28B. As then
shown in FIG. 9B, operators drop the shifter ball 74 down the
workstring 70 again, and pressure up the workstring 70 to actuate
the shifting tools 78a-b with the seated ball 74. With the tools
78a-b actuated, operators close the open frac valve 30 for the
lower section 28A with the closing tool 78a. After bleeding off the
pressure, the workstring 70 is raised to the frac valve 30 in the
next section 28B. At this point, operators then pressure up on the
seated shifter ball 74 in the workstring 70 again and open this
frac valve 30 with the actuated opening tool 78b. After bleeding
off the applied pressure in the workstring 70 and reversing out the
seated ball 74, the treatment process for this new section 28B is
then repeated as before.
[0102] Similar procedures are then repeated for all of the
subsequent sections (i.e., 28C) of the assembly 20. Once treatment
is complete for all of the sections 28A-C as then shown in FIG. 9C,
all of the frac valves 30 and flow device 40 on the assembly 20 are
closed. Operators perform a washout operation. To do this, the
workstring 70 is lowered down toward the shoe 26 of the assembly
20, and operators pump a washout fluid down the casing 12 to
reverse out any residual frac proppant or other treatment up the
workstring 70. Because all of the frac valves 30 are closed,
operators have no issues with reversing flow for the washout
operation.
[0103] When washout is complete, operators then open all of the
flow devices 40 so their ports 42 communicate with the string's
through-bore 25 to accept production. The workstring 70 positions
toward the bottom shoe 26, and operators drop the shifter ball 74
again. Pressure is applied to the seated ball 74 to actuate the
shifter tools 78a-b on the workstring 70, and operators raise the
workstring 70 and open the first closure elements 44 (e.g., inner
sleeve) of the flow devices 40 up the assembly 20 using the opening
tool 78b.
[0104] As the flow devices 40 are opened, fluid from the borehole
annulus 15 can flow along a second flow path through the screens
46, closure elements 48, and opened ports 42. As the flow devices
40 are opened up the assembly 20, the second closure elements 48
(e.g., one-way or check valves) of the flow devices 40 prevent
fluid loss from the string's through-bore 25 to the annulus 15
during this process. As shown in FIG. 9D, once all of the flow
devices 40 are open, the workstring 70 is removed from the assembly
20. At this point, the assembly 20 is prepared to receive
production through the screens 46, closure elements 48, and opened
ports 42 via the second flow path.
[0105] As can be seen, operation of this system 10 can reduce the
time and risk involved in performing the treatment because no
service tool needs to seal in the assembly 20. Moreover, pickup and
operations time are reduced. Essentially, the workstring 70 can be
run in during the liner setting trip so that no added runs are
needed. Cleanout and opening/closing of the ports 32 and 42 in the
frac valves 30 and flow devices 40 are all done in the same
trip.
[0106] The present example of the system 10 is described for an
open hole, but the system 10 for a cased hole would be the same
except that the isolation packers 19 may be different. Because the
system 10 does not use dropped balls in the assembly 20 to open the
frac valve 30 or flow devices 40, the number of stages that can be
deployed downhole is not limited by the required step-down sizes in
balls and seats. Moreover, no balls or seats are left in the
assembly 20 after treatment operations so the operation does not
need a separate milling operation, which can be time consuming and
can encounter its own issues. In essence, the wellbore is ready to
receive production tubing after the frac operation is
completed.
[0107] As discussed above, the frac devices 30 in FIGS. 9A-9D have
one or more ports 32 that can be selectively opened/closed to
allow/prevent fluid communication from the borehole annulus 15 into
the string's through-bore 25. FIGS. 10A-10B show a multi-shift
sliding sleeve 210 for use as a frac valve (30) in the disclosed
system (10). Similar to the previous sliding sleeve disclosed above
actuated by a seated ball, the sliding sleeve 210 includes a
housing 220 with upper and lower subs 222 and 224. A first closure
element 230, which is an inner sleeve or insert, is movable within
the housing 220 and opens or closes fluid flow through the
housing's flow ports 226 based on the inner sleeve 230's position.
Rather than using a ball and seat to move the inner sleeve 230, the
inner sleeve has profiles 234 and 236 for engaging shifting tools
(78a-b) on the workstring (70). As noted above, these profiles 234
and 236 can be standard B-profiles, although other possible
configurations can be used.
[0108] As discussed above, the flow devices 40 in FIGS. 9A-9D also
have one or more ports 42 that can be selectively opened/closed
with the first closure elements 44 (e.g., inner sleeve) to
allow/prevent fluid communication from the borehole annulus 15 into
the string's through-bore 25 through the flow devices' screens 46.
Additionally, the flow devices' second closure elements 48 (e.g.,
check valves) prevent loss of fluid flow in the through-bore 25 to
the borehole annulus 15 during the opening process. FIG. 11
illustrates a flow device 400 for use in the system 10 of FIGS.
9A-9D.
[0109] The flow device 400 fits onto the producing string (22) of
the system (10) and has a basepipe 410 with a bore 415 that
communicates with the string's through-bore (25). Disposed on both
ends of the basepipe 410, the device 400 has wellscreen 420A-B. In
general, the wellscreens 420A-B can use any form of screen assembly
used for sand control, including wire-wrapped screens, metal mesh
screens, pre-packed screens, protective shell screens, expandable
sand screens, or screens of other construction.
[0110] As shown in this embodiment, the wellscreens 420A-B are
wire-wrapped screens having wires 422 wrapped on longitudinal rods
424 that run along the outside length of the basepipe 410. Far ends
(not shown) of the wellscreens 420A-B can having end rings (not
shown) so that screened fluid flows towards the central area of the
device 400 between the wellscreens 420A-B.
[0111] Between the two wellscreens 420A-B, the device 400 has a
central housing 430 that receives the screened flow from the
wellsceens 420A-B. The housing 430 has end rings 432 at each end
with a central sleeve 434 connected between them. Flow from the
wellscreens 420A-B can pass through flow passages in the end rings
432 and can enter a plenum 435 in the housing 430 around the
basepipe 410.
[0112] To control the flow of fluid into the basepipe's bore 415
through its inlet ports 412 (and eventually into the assembly's
through-bore) through the second flow path through the device 400,
the basepipe 410 has a first closure element 440, which is an inner
sleeve or insert, disposed in the bore 415 and movable relative to
the inlet ports 412. In a closed position (not shown in FIG. 11),
the inner sleeve 440 is moved so the sleeve's openings 442 do not
align with the inlet ports 412. With the sleeve 440 closed, flow in
the housing's plenum 435 cannot pass into the basepipe's bore 415.
Seals (not labeled) are provided between the interface of the
sleeve 440 and the basepipe's bore 415 to seal off the inlet ports
412.
[0113] When the sleeve 440 is shifted to an open position shown in
FIG. 11, however, the sleeve 440 is moved so the sleeve's openings
442 align with the inlet ports 412. Flow in the housing's plenum
435 can now pass into the basepipe's bore 415. Other configurations
can be used for the inner sleeve 440 that can lack the openings 442
and may instead move fully away from the ports 412 to expose them
to the bore 415.
[0114] To prevent loss of fluid in the basepipe's bore 415 to the
borehole annulus outside the device 400 during operations as noted
above, the housing 430 has a second closure element, such as
one-way or check valves, that prevents back flow from the housing's
plenum 435 to the wellscreens 420A-B. In the arrangement shown,
these closure elements include seats 450 formed inside the flow
passages of the housing 430 between the end rings 432 and the
plenum 435 and include check balls 455 movably disposed in the
housing's plenum 435.
[0115] When regular flow occurs along the second flow path from the
wellscreens 420A-B to the inlet ports 412, the check balls 455 move
away from the seats 450 allowing the screened fluid to pass, but
the check balls 455 remain held in the plenum 435. When reverse
flow occurs from the plenum 435 towards the wellscreens 420A-B, by
contrast, the check balls 455 engage in the seats 450 and block the
flow in this reverse direction. Although the balls 455 are shown
entirely free floating in the plenum 435, additional features can
restrict the balls' movements to areas close to the seats 450.
[0116] As can be seen, the device 400 can be closed to flow in
either direction when the inner sleeve 440 is closed to seal the
ports 412. With the inner sleeve 440 opened, flow is allowed in
only one direction into the bore 415 due to the check valves (balls
455 and seats 450). Meanwhile, the wellscreens 420A-B prevent the
production of solids from the formation into the bore 415.
Likewise, the wellscreens 420A-B can prevent frac or gravel pack
proppant from flowing into the bore 415 during treatment
operations.
[0117] Finally, the seats 450 in the device 400 can be constructed
with flow restrictive ports or nozzles to create a pressure drop if
desired. When the device 400 is opened, the restrictions allow the
device 400 to be used as an inflow control device. Although two
wellscreens or sections 420A-B are shown in FIG. 11, a comparable
flow device 400 can have all of the same components, but may have
only one wellscreen and one check ball and seat arrangement on one
side of the device's flow ports 412.
[0118] The foregoing description of preferred and other embodiments
is not intended to limit or restrict the scope or applicability of
the inventive concepts conceived of by the Applicants. It will be
appreciated with the benefit of the present disclosure that
features described above in accordance with any embodiment or
aspect of the disclosed subject matter can be utilized, either
alone or in combination, with any other described feature, in any
other embodiment or aspect of the disclosed subject matter.
[0119] Moreover, the systems have been described herein as single
trip, multi-zone frac systems. As will be appreciated, in addition
to frac treatment, certain embodiments of the disclosed systems can
be configured and used for other types of formation treatments,
such as acidizing treatments and the like, and can be used for
gravel pack and frac pack operations when configured to handle
fluid returns from the borehole annulus 15 with one or more flow
tubes or other features as disclosed herein.
[0120] In exchange for disclosing the inventive concepts contained
herein, the Applicants desire all patent rights afforded by the
appended claims. Therefore, it is intended that the appended claims
include all modifications and alterations to the full extent that
they come within the scope of the following claims or the
equivalents thereof.
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