Note: Descriptions are shown in the official language in which they were submitted.
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COLLET BAFFLE SYSTEM AND METHOD FOR FRACKING
A HYDROCARBON FORMATION
FIELD OF THE INVENTION
The present invention relates to a baffle system and method for fracturing or
treating
a hydrocarbon formation. More particularly, the present invention relates to a
baffle system
where one or all of the baffles employed during fracking are retrievable from
a well casing.
BACKGROUND OF THE INVENTION
This background and patent documents identified below are provided for the
purpose of making known information believed by the applicant to be of
possible relevance to
the present invention, and in particular allowing the reader to understand
advantages of the
invention over devices and methods known to the inventor, but not necessarily
public. No
admission is necessarily intended, nor should be construed as admitting, that
any of the
following documents or methods known to the inventor constitute legally
citable and relevant
prior art against the present invention.
Preferably when fracking a wellbore it is usually necessary, for optimization
of
pressurized and to concentrate volumes of fluid in localized areas, particular
zones along the
wellbore are opened to the formation to allow fracking of the formation in
such area while
isolating (i.e. closing off) all other zones along the well casing during such
localized fluid
injection. Such typically results in having to isolate, by means of packers or
plug members
pumped downhole, certain segments of the wellbore which may be otherwise open
to the
formation. Alternatively, where the well casing possesses slidable sleeves
which are typically
closed during insertion of and cementing of the casing in the wellbore, only
select slidable
sleeves along the well liner are opened, to thus allow introduction of high
pressure fluid only
into a targeted zone of the formation along the wellbore while still
maintaining all sleeves in
unfracked areas along the well casing closed.
Each of the foregoing scenarios results in actuation means such as sleeves,
balls,
packers, or the like being provided down the well to achieve in some manner
the desired
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isolation to achieve fracking of a specific region of the formation.
Often such equipment or tools, while often annular and having a flow-though
passage,
are permanently left in the well, thereby substantially restricting to some
degree the flow of
produced hydrocarbons through the well casing due to resulting reduced
diameter of the
wellbore.
Alternatively, difficult and expensive reaming operations need to be conducted
to
ream out any remaining plug members or actuation sleeves used in the fracking
process to
thereby maintain full production diameter of the wellbore when the wellbore
goes to
production.
Certain published documents teach, with varying degrees of success and
complexity,
various equipment and methods for isolating segments of the wellbore for
fracking purposes
while attempting to maintain, after fracking, as unrestricted a flow passage
from the well
casing as possible.
For example, CA 2,879,044 entitled "System and Method for Injecting Fluid at
Selected Locations Along a Wellbore" teaches a system and method for
selectively actuating
(moving from closed position to open position) a plurality of sliding sleeves
in a tubing liner,
which are covering ports in the tubing liner, via one or more darts inserted
into the wellbore to
allow fracking of the wellbore in the regions of the opened ports. The
actuating daft is
preferably coupled to a retrieval tool (or is coupleable to a retrieving tool)
which upon the
retrieval tool being so coupled allows a bypass valve to be opened to thereby
assist in
withdrawing the dart from within the valve sub-members. Upward movement of the
retrieval
tool allows a wedge-shaped member to disengage the dart member from a
corresponding
actuated sleeve to allow the dart and retrieving tool to be withdrawn from the
wellbore. The
sliding sleeve nevertheless remains in the well liner.
As is apparent from the above, the invention of CA 2,879,044 is directed to
tubing
liners/well casing having pre-existing sliding sleeve members therein covering
ports in the
tubing liner. As such , this invention is directed to, and only utilizable
with, tubing liners of
such (pre-existing ) configuration, and accordingly is not directed to nor
utilizable in well
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casings which do not possess pre-existing sliding sleeves covering pre-
existing ports in such
tubing liners.
CA 2,904,470 entitled "System for Successively Uncovering Ports along a
Wellbore
to Permit Injection of a Fluid along said Wellbore" having a common inventor
with the
present invention, teaches a system for moving sleeves to successively uncover
a plurality of
contiguous ports in a tubing liner within a wellbore which are covered by such
sleeves, or for
successively uncovering individual groups of ports arranged at different
locations along the
liner, to allow successive fracking of the wellbore at such locations. Sliding
sleeves in the
tubing liner are successively moved from a closed position covering a
respective port to an
open position uncovering such port by an actuation member placed in the bore
of the tubing
liner and pumped down the tubing liner. The actuation member for moving the
sliding sleeves
to cause them to open comprises a single collet sleeve, having a dissolvable
plug retained in a
fixed position within such collet sleeve by shear pins. The collet sleeve has
radially-outwardly
biased protuberances (fingers) at a downhole end thereof, adapted to and which
matingly
engage corresponding cylindrical grooves in such sliding sleeves, based on the
width of the
protuberance. Upon the actuation member actuating all of the desired sleeves
and after having
actuated the last most downhole sleeve, the shear pin shears thereby allowing
the plug in the
collet to move downhole in the collet sleeve and thereby preventing the
protuberances
(fingers) on the collet sleeve from thereafter disengaging the cylindrical
groove of the
corresponding sliding sleeve, thereby preventing any further progress of the
collet sleeve
downhole.
Again as will be apparent, such invention like the invention disclosed in CA
2,879,044 is directed to tubing liners/well casing having pre-existing sliding
sleeve members
therein covering ports in the tubing liner. As such , this invention is
directed to, and only
utilizable with, tubing liners of such (pre-existing ) configuration, and
accordingly is not
directed to nor utilizable in well casing which does not possess pre-existing
sliding sleeves
covering pre-existing ports in such tubing liner.
US 5,398,763 entitled "Wire/inc Set Baffle and Method of Setting Thereof", in
contrast to the above two patent publications, teaches a setting tool which
may be used to
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position a baffle within a well casing, which baffle may then act as a seat
for a plug member
which is then inserted downhole to isolate downhole sections, and thereby
allow such regions
of the casing above the baffle which are perforated to be fracked. To such
extent US
5,398,763 have a number of similarities with the present invention.
However, the apparatus and method of US 5,398,763 has a number of important
differences with the system and method of the present invention, not the least
of which, in
respect of the second, third, and fourth embodiments thereof, is the need for
explosive charges
to shear shear pins or the need of actuating blasting cap on the setting tool,
which adds to the
complexity and expense of a setting tool.
Despite the above prior art teachings, a need still exists in the fracking
industry for a
simple system and method for effectively isolating certain sectors of a
wellbore for fracking,
which after completion of the fracking along a length of a wellbore
nonetheless leaves the
length of the wellbore virtually unrestricted and of maximum original diameter
to maximize
flow of hydrocarbons therethough during production.
It is further advantageous if such a system and method can further at the same
time
provide accurate perforation of the well casing, to minimize errors in depth
placement of the
perforations along the wellbore and to minimize the number of tripping in and
out of the
wellbore of various equipment if perforation and fracking operations were
otherwise
independently conducted, to speeding up perforating and fracking operations in
completing
wells for production.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide a relatively simple
system and
method for fracking which allows the desired isolation of particular
successive segments
along a wellbore, yet nonetheless after completion of fracking leaves the
wellbore virtually
unrestricted and of maximum original diameter to increase flow during
production.
It is a further object of certain embodiments of the present invention to
provide a
baffle member which may be uniquely engaged with a landing sub at a known
depth along the
wellbore, which temporarily effectively prevents flow of pressurized fracking
fluids downhole
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but which baffle member may after completion of perforation and fracking
operations be
easily removed from the well casing leaving the well casing unrestricted.
It is a further object of certain embodiments of the present invention to
provide a
method for fracking a formation, which after such operation leaves the
wellbore virtually
unrestricted and of maximum original diameter to increase flow during
production.
Accordingly, in order to overcome some of the disadvantages of the prior art
designs
and/or in order to further realize one or more of the above non-limiting
objects of the present
invention , the collet baffle system and method of the present invention
generally comprises a
number of components, having:
(i) landing subs within the well casing, each having an annular recess of a
unique
configuration (each typically being of a unique width and/or if a plurality of
annular recesses per landing sub, each of a unique width and/or spacing) ;
(ii) one or more baffle members, wherein such baffle members each possess
collet
finger protuberances thereon configured to matingly engage a unique landing
sub in
the well casing, wherein the protuberances are further provided with a
shoulder on a
downhole side thereof to prevent further passage of the baffle member
downhole, and
with a chamfer on an uphole side thereof to allow for disengagement of the
collet
finger protuberances with the landing sub and thus removal of
the baffle member
after it has served its purpose (as further explained herein);
(iii) a plug member which may be inserted or flowed down the well casing,
which
becomes seated in the baffle member and prevents pressurized fracking fluid
from
flowing past the baffle member and thereby causes such fluid to flow into the
formation via perforations in the casing located immediately above the
particular
landing sub; and
(iv) a conveying tool, which is frangibly connected to the baffle member such
as by
shear pins, which may be withdrawn from the well casing after mating
engagement of
the baffle member with the desired landing sub in the well casing.
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The landing subs are deployed in the casing install on desired depth and
spacing. Each
landing sub, in one embodiment of the invention, has its own unique landing
length for the
matching collet finger protuberances on a particular baffle member. For
example, the landing
sub at the toe of the wellbore will have the longest profile, with each
consecutive
profile/annular recess in each landing sub being of a reduced length
progressing from heel to
toe (in a deviated well) or from the base of the well upwards in a vertical
well.
Landing subs can be run in to the wellbore with a desired spacing, which may
be every
30 meters, for example, or some other unique configuration tailored to the
geology of the
formation. After the casing has been installed and cemented into place the
wireline (or coiled
tubing) and frac equipment will rig up. The baffle member is frangibly affixed
to a standard
conveying tool, such as Baker Style # 20 setting tool, such as by a shear pin
of a
selected/desired shearing force. The conveying tool may further be provided
with perforating
guns, to allow precise location of the perforations in the well casing
relative to each landing
sub.
The assembly (baffle member, conveying tool, and perforating guns) may then be
conveyed downhole via wireline or coiled tubing. Once the baffle member
forming part of
the aforementioned assembly has reached its target landing sub and the annular
recess therein,
the collet finger protuberances on the baffle member expand radially outwardly
to matingly
engage the target landing sub, thereby preventing the baffle member from any
further
downhole movement. Circumferential external seals on the baffle member provide
a seal
against the landing sub. The conveying tool is now forceably pulled uphole,
causing the shear
pins to shear allowing the conveying tool to disengage from the baffle member
and leaving
the baffle member engaged with the target landing sub. The conveying tool and
perforating
guns are now moved (if desired) to a desired perforating depth above the
landing sub, and the
perforating guns activated. The perforating guns and conveying tool are then
pulled to
surface. A
plug member, such as a dissolvable ball, it then pumped or flowed downhole
with fracturing fluid. The ball lands on a ball seat on the baffle member, and
creates a seal.
The fracture fluid is then pumped into the formation via the perforations
created in the well
casing at the desired depth.
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The aforementioned process may be repeated, albeit with a second baffle member
having collet finger protuberances of a different (lesser) width or spacing
than those employed
on the first baffle member, to allow earlier engagement of a landing sub
immediately uphole
from the lowermost landing sub.
The first baffle member, prior to landing of additional baffle members in
corresponding landing subs, may be removed by means of a retrieving tool.
Typically,
however, the baffle members are left in the wellbore until after perforation
and fracking.
After completion of perforating and fracking of the formation, the balls
seated therein
dissolve. Prior to initiation of production the baffle members can all be
simultaneously
retrieved by running a retrieving tool to the toe of the well, activating dogs
on the retrieving
tool, and pulling the retrieving tool uphole-the chamfer on the uphole side of
the recesses in
the landing subs and/or a chamfer on the uphole side of the collet finger
protuberances allows
release of each of the baffle members from mating engagement with their
respective landing
subs. The recovery of the baffle members to surface advantageously allows for
dramatically
increased inner diameter of the well casing for increased flow back and
production.
More particularly, in a first broad embodiment of the present invention, the
invention
comprises a baffle system for use in a well casing having a plurality of
landed subs
longitudinally spaced therealong, for progressively fracking or treating fluid
into a
hydrocarbon formation via existing or created perforations in said well
casing, said system
comprising:
-an annular baffle member, insertable within said well casing, having at a
most-uphole
end thereof a seating surface configured to provide to a plug member dropped
downhole in said well casing a seating surface against which said plug member
may
abut to thereby prevent pressurized fluid injected downhole in said well
casing from
travelling past said plug member, said baffle member further having radially
outwardly-biased collet finger protuberances thereon configured to matingly
engage a
correspondingly-dimensioned annular recess within one of said plurality of
landing
subs within said well casing;
-a conveying tool, affixed at a lowermost end thereof via frangible means to
an
upper interior portion of said annular baffle member;
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the annular recess on a downhole side edge thereof possessing a shoulder
portion
which prevents further downhole movement of said baffle member within said
well
casing upon said collet finger protuberances engaging said annular recess; and
the annular recess and/or said collet finger protuberances at an uphole side
edge
thereof possessing a chamfer such that upward force applied to said baffle
member
causes radial compression of said collet finger protuberances and
disengagement of
said collet finger protuberances with said annular recess and thus release of
said baffle
member from mating engagement with said annular recess thereby allowing said
baffle
member to be withdrawn uphole in said well casing via a retrieving tool.
In a preferred embodiment, the frangible means comprise shear pins or shear
screws
which affix the conveying tool, at a lower region thereof, to an upper portion
of the baffle
member. The conveying tool is preferably frangibly affixed to the baffle
member uphole of
the collet finger protuberances thereon.
In a further preferred embodiment, the baffle member, at an uppermost portion
about
an interior peripheral mouth thereof, has a chamfer to allow radially-
outwardly biased dogs
on a retrieving tool inserted therein to be radially compressed and thereby
allow said
retrieving tool to pass therethrough; and at a lowermost portion has a
shoulder to allow said
radially-outwardly biased dogs after having passed through said baffle member
to abut said
dogs and allow said retrieving tool , when pulled uphole, to thus pull said
baffle member
uphole.
The baffle system in preferred embodiments is provided with a plurality of
annular
recesses respectively situated within a corresponding plurality of said
landing subs,
longitudinally spaced apart from each other along said well casing, a most
downhole of said
plurality of annular recesses having the greatest annular width, with
remaining uphole annular
recesses having, when progressing uphole along said well casing, progressively
narrower
widths.
The conveying tool, and in particular a conveying head thereof, is preferably
provided
with an electrically-actuated explosive charge for perforating said well
casing.
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Preferentially, each landing sub has a respective annular recess therein,
wherein a
respective annular baffle member when matingly engaged within a landing subs
thereby
positions said explosive charge immediately above said respective landing
subs, so that said
explosive charge, when detonated, perforates the well casing immediately above
the desired
landing sub.
In one embodiment the radially outwardly-biased collet finger protuberances
are
situated approximately midpoint on said baffle member, intermediate annular
seals situated on
an outer periphery of said baffle member at mutually opposite ends thereof.
The collet finger
protuberances may alternatively, if desired, simply be situated at a distal
(downhole) end of
the baffle member, and not midpoint thereof.
Preferentially, the conveying tool has a bypass port therein to allow fluid to
flow
therethrough when lowering said conveying tool within said well casing.
In another broad aspect of the present invention, the present invention
comprises a
method for fracking or treating a hydrocarbon formation having a well casing
located therein
and having a plurality of landing subs spaced along said well casing,
commencing with the
most distal regions of said well casing and progressing uphole along said well
casing until all
regions of said hydrocarbon formation have been fracked or treated, comprising
the steps of:
(i) inserting well casing having a plurality of landing subs spaced therealong
in a well
drilled within said hydrocarbon formation, each of said landing subs having an
annular recess therein, said annular recesses being of a progressively greater
width
progressing downhole along said well casing;
(ii) affixing to a most downhole end of a conveying tool, via frangible means,
a first
baffle member having outwardly-biased collet finger protuberances thereon of a
width adapted to matingly engage a lowermost of said annular recesses;
(iii) inserting said conveying tool and baffle member downhole in said well
casing
until said collet finger protuberances engage said lowermost of said annular
recesses;
(iv) pulling uphole on said conveying tool and causing said frangible means
thereon
to shear thereby releasing said baffle member from said conveying tool;
(v) withdrawing said conveying tool from said well casing;
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(vi) lowering or flowing a plug member into said well casing and causing said
plug
member to abut an uppermost portion of said baffle member so as to prevent
passage
of pressurized fluid downhole of said baffle member;
(vii) injecting a pressurized fluid into said well casing and flowing said
pressurized
fluid into said formation via perforations in said well casing proximate and
above
said lowermost landing sub and plug member situated therein;
(viii) causing said plug member to be removed from said well casing;
(ix) repeating steps (ii) to (viii), save in each iteration said baffle member
has collet
finger protuberances of a lesser width and in each iteration, which
respectively
engage progressively more uphole annular recesses in each of said plurality of
landing subs which such more uphole annular recesses each likewise of
correspondingly lesser width,
until said hydrocarbon formation has been
fracked or treated.
In an alternative embodiment, such method comprises the steps of:
(i) inserting well casing having a plurality of landing subs spaced therealong
in a well
drilled within said hydrocarbon formation, each of said landing subs having a
plurality of annular recesses therein, said annular recesses longitudinally
spaced
apart within said landing sub and being of a unique spacing unique to each
landing
sub;
(ii) affixing to a most downhole end of a conveying tool, via frangible means,
a first
baffle member having outwardly-biased collet finger protuberances thereon of a
spacing adapted to matingly engage said annular recesses in a lowermost of
said
landing subs;
(iii) Inserting said conveying tool and baffle member downhole in said well
casing
until said collet finger protuberances engage said annular recesses in a
lowermost of
said landing subs;
(iv) pulling uphole on said conveying tool and causing said frangible means
thereon
to shear thereby releasing said baffle member from said conveying tool;
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(v) withdrawing said conveying tool from said well casing;
(vi) lowering or flowing a plug member into said well casing and causing said
plug
member to abut an uppermost portion of said baffle member so as to prevent
passage
of pressurized fluid downhole of said baffle member;
(vii) injecting a pressurized fluid into said well casing and flowing said
pressurized
fluid into said formation via perforations in said well casing proximate and
above
said lowermost landing sub and plug member situated therein;
(viii) Causing said plug member to be removed from said well casing;
(ix) repeating steps (ii) to (viii), save in each iteration said baffle member
has collet
finger protuberances of unique spacing , which respectively engage
progressively
more uphole annular recesses in each of said plurality of landing subs, until
said
hydrocarbon formation has been fracked or treated.
In a preferred embodiment of the above two methods, the annular recesses, on
an
uphole side edge thereof and/or said collet finger protuberances, on an uphole
side thereof,
have a chamfered portion to allow withdrawal of finger protuberances
therewith.
In one refinement of the above methods, after step (viii) the following steps
may be
inserted, namely:
-lowering a retrieving tool having radially extending dogs downhole in said
well casing, such that said dogs are lowered past said baffle member;
- actuating said dogs on said retrieving tool radially outwardly; and
- pulling uphole on said retrieving tool and withdrawing said retrieving tool
and said baffle member from within said well casing.
In another alternatively refinement of the above methods, after step (ix) the
following
steps may be added, namely:
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-lowering a retrieving tool having radially extending dogs downhole in said
well casing, such that said dogs are lowered past a lowermost of said baffle
members;
- actuating said dogs on said retrieving tool radially outwardly; and
- pulling uphole on said retrieving tool and simultaneously withdrawing said
retrieving tool and all of said baffle members uphole thereof from within said
well
casing.
In a further refinement of the above method, such method further comprises the
step,
after step (iii) and after said annular baffle member has matingly engaged
within a
lowermost of said landing subs, of:
igniting an explosive charge on said conveying tool immediately above said
lowermost of said plurality of landing subs, and detonating said explosive
charge so as to
perforate the well casing immediately above said lowermost landing sub.
The above summary of the invention does not necessarily describe all features
of the
invention.
For a complete description of the invention, reference is to further be had to
the
drawings and the detailed description of some preferred embodiments, read
together with the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Further advantages and other embodiments of the invention will now appear from
the above along with the following detailed description of the various
particular embodiments
of the invention, taken together with the accompanying drawings each of which
are intended
to be non-limiting, in which:
FIG. 1 is a side perspective view of a baffle member which forms part of the
system
of the present invention;
FIG. 2 is a cross-section of the baffle member of Fig. 1, taken along plane A-
A;
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FIG. 3 is a is a side perspective view of another baffle member for use in the
system
of the present invention;
FIG. 4 is a cross-section of the baffle member of Fig. 3;
FIG. 5 is a is a side perspective view of another baffle member for use in the
system
of the present invention;
FIG. 6 is a cross-section of the baffle member of Fig. 5 when matingly
engaging a
landing sub in accordance with another embodiment of the present invention;
FIG.'s 7-14 show successive views of the operation of the system and method of
the
present invention, wherein:
Fig. 7 depicts the conveying tool directing a first baffle member
downwardly in the well casing, the lowest two landing subs in said well
casing being shown (not to scale);
FIG. 8 is a subsequent view in the method of operation of the present
invention, wherein the conveying tool has conveyed the baffle member to the
lowest landing sub, and the collet finger protuberances on the baffle member
have engaged the annular recess of corresponding dimensions in the landing
sub;
FIG. 9 is a subsequent view in the method of operation of the present
invention, wherein an upward force has been applied to the conveying tool and
as a result the shear pins affixing the baffle member to the conveying tool
have
become sheared, and the conveying tool is being removed uphole;
FIG. 10 is a subsequent view in the method of operation of the present
invention, wherein the conveying tool has been removed from the well casing;
FIG. 11 is a subsequent view in the method of operation of the present
invention, wherein a dissolvable ball has been flowed downhole, and has
become seated in the ball seat in the baffle member, thereby now preventing
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flow of pressurized fluid downhole, and wherein such pressurized fluid may
now be caused to flow through perforations in the well casing uphole of the
ball and particular landing sub;
FIG. 12 is a subsequent view in the method of operation of the present
invention, wherein the injection of fluid into the formation via perforations
in
the casing has been completed, the ball has dissolved , and a baffle
retrieving
tool is being inserted downhole in the casing to retrieve the baffle member;
FIG. 13 is a subsequent view in the method of operation of the present
invention, wherein the retrieving tool has been positioned to allow the dogs
thereof to become extended; and
FIG. 14 is a subsequent view in the method of operation of the present
invention, wherein the retrieving tool and baffle member are being withdrawn
uphole;
FIG. 15 is an alternative configuration for the conveying tool and the method
for
directing the conveying tool to the desired landing sub, wherein the conveying
tool is
attached to threaded pipe (or alternatively coiled tubing); and
FIG. 16 is an alternative configuration for the conveying tool and method for
directing
same along the well casing, wherein the conveying tool is attached to and
conveyed by a
wireline (not shown).
DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS OF THE
INVENTION
In the following description, similar components in the various drawings are
identified with corresponding same reference numerals.
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Reference to an element in the singular, such as by use of the article "a" or
"an" is
not intended to mean "one and only one" unless specifically so stated, but
rather "one or
more".
Reference to the relative terms "upper", "uppermost" , "above" , "below",
"lowermost", or "bottom" are with reference to the position of a component
within a vertical
well casing.
"Downhole" consistently means toward the end of the well or well casing,
regardless as to whether such well or well casing is vertical, or is
horizontal or deviated as
occurs in deviated wells.
In the drawings, the following convention is adopted, namely downhole within a
wellbore or well casing is toward the bottom of the page for portrait-style
figures, and to the
right of the page for landscape-style figures.
Fig.s 7-14 show one embodiment 10 of the baffle system and the method of the
present invention, for use in a well casing 12 having a plurality of landing
subs 14a, 14b
longitudinally spaced along the well casing 12.
Specifically, Figs. 7-14 show one embodiment 10 of the baffle system of the
present
invention, in successive steps of operation and implementation.
Pre-existing perforations (not shown) may be provided in well casing 12, but
preferentially are created in well casing 12 in the manner described herein,
immediately prior
to fracking a zone of the formation along the well casing.
As may be seen, landing subs 14a, 14b threadably coupled at together 18 via
standard threaded couplings to form an integral well casing 12, are provided
at spaced
locations along well casing 12 , each landing sub 14a, 14b have at least one
annular recess
16 therein. The annular recess 16' in the lowermost of landing subs 14a is of
the greatest
length (width) "a", and successively more uphole landing subs, such as landing
sub 14b,
have a corresponding annular recesses 16" therein of a progressively lesser
width "b", as
shown in Fig. 7.
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Importantly, each annular recess 16, on a downhole side edge thereof, is
provided
with a shoulder 17, which prevents further downhole movement of a baffle
member 30 once
said baffle member has become matingly engaged, in the manner set out below,
with a
respective annular recess 16. In a preferred embodiment shoulder 17 on each
is "back-
milled", and similarly matingly engages shoulder 53 on baffle member 30 which
is similarly
"back milled, as best shown in Figs. 4, 6, and 9-11, to thereby assist in
ensuring shoulder 17
prevents baffle member 30 once protuberances 50 thereof are matingly engaged
in a
respective annular recess 16, from further passing downhole in well casing 12.
In order to commence a fracking operation, as seen from Figs. 7, a conveying
tool
(which may comprise a Baker Style # 20 setting tool) to which a conveying head
22 is
associated, firstly conveys downhole in well casing 12 a baffle member 30.
Conveying head
22 has coupled thereto the aforesaid baffle member 30, embodiments of such
baffle member
15 30 being most clearly depicted in Figs. 1-6.
In the embodiment shown in Fig. 7, conveying head 22 is threadably coupled via
threads 28 to conveying tool 20. In the embodiment shown in Fig. 8, conveying
tool 22 is
merely coupled to or forced downhole by a tubular conveying tool 20.
As seen from Fig.s 7-8, conveying head 22 has bypass ports 24 therein to allow
passage of fluid therethrough when conveying head 22 is lowered in said well
casing 12.
Conveying tool 20 , comprising in one embodiment conveying head 22, may be
conveyed
downhole in well casing 12 via wireline or via coiled tubing (not shown).
As noted above, conveying head 22 is frangibly secured at a lower end thereof
to an
upper interior portion 32 of baffle member 30. Such securement (coupling) of
baffle member
to conveying head 22 of conveying tool 20 is a frangible connection, via shear
screws 26.
Other means of frangibly securing baffle member 30 to conveying head 22 will
now occur to
30 persons of skill of the art, such as using tack welding forming a
breakable/shearable weld
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joint, or by friction-fit shear pins (not shown) which are shearable, and each
of said alternative
frangible means are expressly contemplated within the scope of the invention.
Baffle member 30, as best seen from the various embodiments thereof in Figs. 1-
6, is
insertable within well casing 12. A most uphole end of baffle member 30 has an
interior
seating surface 34 configured to provide a plug member 40 (ref. Fig. 11) such
as a
dissolvable ball or dart when dropped downhole in well casing 12 with a
seating surface 34
against which plug member 40 may abut, to thereby prevent pressurized fluid
injected
downhole in well casing 12 from travelling past plug member 40 when
pressurized fluid is to
be injected in the well casing 12 to frac the formation above a baffle 30 and
respective landing
sub 14a. One or more circumferential seals 37 may be located above and/or
below
protuberances 50 on baffle member 30, to assist in preventing, when a plug
member 40 is
seated in baffle member 30, any pressurized fluid from travelling downhole
from the
respective landing sub 14 in which the respective baffle member 30 is matingly
engaged.
Baffle member 30 is provided with a plurality of radially outwardly-biased
collet
finger protuberances 50, which are preferentially located at a midpoint of
baffle member 30
(see Fig.s 1-6), but may be located at a distal (i.e. downhole) end thereof
(not shown).
Protuberances 50a of width "a" are situated about the periphery of baffle
member 30 (Fig.
1), protuberances 50b of width "b" are situated about the periphery of baffle
member 30'
(Fig. 3), and protuberances 50c and 50d of respective widths "c" and "d" are
situated about
the periphery of baffle member 30" (Fig. 5) .
Specifically, baffle member 30 shown in Fig.s 1-2 is used for engaging a
lowermost
14a of landing subs 14 and has a single set of radially outwardly-biased
collet finger
protuberances 50a about periphery of baffle member 30, each of length (width)
"a".
Protuberances 50a are adapted to matingly engage annular recess 16' of equal
or greater
corresponding width of lowermost landing sub 14a.
Baffle member 30' shown in Fig.s 3-4 which is adapted for engagement with an
annular recess 16" in a landing sub 14b situated in well casing uphole of the
landing sub 14a,
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has collet finger protuberances 50b of length (width) "b" thereon for matingly
engaging
annular recess 16" in penultimate landing sub 14b, annular recess 16" being of
lesser
length(width) than annular recess 16' in lowermost landing sub 14a, such that
first baffle
member 30 will only be engaged with lowermost annular recess 16' in lowermost
landing sub
14a. Successive uphole baffle members 30 conveyed downhole in well casing
12 are
similarly provided with protuberances 50 thereon, but each of progressively
lesser length
(width).
Fig.s 5-6 show an alternative configuration of a baffle member 30" for use in
the
present invention. In this instance baffle member 30" is provided with a pair
of groups of
flexible, radially outwardly¨biased collet finger protuberances 50c, 50d on
the periphery
thereof, which may be of varied length (width) "c", "d", and/or whose spacing
"s"
therebetween may vary, depending on the particular landing sub 14 within well
casing 12
which is desired to be engaged. Such protuberances 50c, 50d are adapted to
only matingly
engage with similarly dimensioned and spaced annular recesses 16' in a
lowermost landing
sub 14a. Additional baffle members 30, having protuberances 50 thereon of
different lengths
and separation distance -s" therebetween, when dropped in well casing 12
matingly engage
similar uniquely dimensioned annular recesses 16" in unique uphole landing
subs 14, so that
baffle members 30 may progressively be matingly engaged to successive landing
subs 14
progressing uphole in well casing 12, with each baffle member 30 providing a
seating surface
34 for a plug member 40, to allow fracking of the formation uphole of the plug
member 40 to
occur..
Each of radially outwardly-biased collet finger protuberances 50, 50a, 50b,
50c, 50d
on all baffle members 30, 30', 30", and 30"may possess a chamfer 70 at an
uphole side
edge thereof. Alternatively, or in addition, each annular recess 16', 16",
etc. may likewise
possess a similar chamfer 72 at an uphole side edge thereof.
The purpose of chamfers 70 and/or 72 on uphole side edges of protuberances 50,
50a, 50b, 50c, 50d and/or annular recesses 16, 16' respectively is so that
upon an upward
(i.e. uphole) force applied to a lowermost end of a baffle member 30, 30',
30", 30" (by a
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retrieval tool 90 has hereinafter described) such will cause the uphole side
edge of collet
finger protuberances 50, 50a, 50b, 50c, 50d thereon to "ride up" on the uphole
(chamfered)
side edge 72 of the respective annular recess(es) 16, 16', engaged by the
respective collet
finger protuberance 50, 50a, 50b, 50c, 50d, and thereby cause collet finger
protuberances
50, 50a, 50b, 50c, 50d to be radially inwardly compressed and thus become
disengaged from
mating engagement with the respective annular recesses 16, 16', and 16", so as
to allow a
respective baffle member 30, 30', 30", 30" to be then withdrawn from the
respective landing
sub 14a, 14b and further withdrawn from well casing 12.
Each of collet finger protuberances 50, 50a, 50b, 50c, 50d, on a downhole side
edge
thereof preferably possess a shoulder 53 which when said protuberances are
matingly engaged
with a respective annular recess 16', 16", prevents further downhole movement
of baffle
member 30 within well casing 12.
Baffle member 30, at an uppermost portion thereof about an interior peripheral
mouth 34 thereof has an inward chamfer 100. Inward chamber100 on baffle member
30
allows radial-outwardly extending dogs 92 on a retrieving tool 90 (see Fig.s
12-14 and as
more fully described below) to be radially compressed and thereby allow the
retrieving tool
90 to pass through baffle member 30.
A lowermost portion of baffle member 30 is provided with a shoulder 39 which
allows said radially-outwardly extending dogs 92, after having passed downhole
through
baffle member 30 and when then allowed to be radially outwardly extended, to
abut shoulder
39 to allow retrieving tool 90 when pulled uphole to additionally pull baffle
member 30
uphole also, as shown sequentially in Fig.s 12-14.
Such shoulder 30 may be bevelled, as shown most clearly for example in Fig.s
2, 4,
& 6.
In a preferred embodiment, explosive charge(s) 142 are provided on conveying
tool
20, and preferably on a downhole side of conveying head 22 thereof as shown in
Fig.'s 8, 9.
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Such explosive charge 142 provides a further advantage of the system/method of
the present
invention 10 to be realized, namely allowing for the accurate perforation of
the well casing 12
in a region and at a depth proximate to and immediately above the matingly
engaged baffle
member 30, thereby avoiding the need for further or other locator tools to
position the
explosive charge 140 along the well casing 12, and further avoiding inaccuracy
in depth
location of the perforating charge 140 along well casing 12.
In such preferred embodiment, after a baffle member 30 has been lowered and
respectively become matingly engaged to an annular recess 16 in a particular
landing sub 14,
an upward force applied to conveying head 22 via the wireline or coil tubing
to which
conveying head 22 is coupled shears the shear pins 26 and thereby decouples
conveying head
22 from baffle member 30. Thereafter coupling head 22 and explosive charge 140
thereon
may together be lifted slightly uphole in well casing 12 to a desired distance
above baffle
member 30 and corresponding landing sub 14, and explosive charge(s) 140
thereon may be
detonated to create perforations 142 in well casing 12 at such desired
location(s) along well
casing 12.
The conveying tool 20 and detonated explosive charges 140 may then be raised
from
within well casing 12.
A plug member 40 may then be lowered in well casing 12 , which plug member 40
(typically a ball member) then rests on sealing surface 34 on baffle member 30
to thereby
isolate zones of the well casing 12 below the landed baffle member 30. If
desired, a packer
member (not shown) may be lowered downhole and actuated a distance uphole from
the ball
member 40 to isolate the well casing 12 above the packer. Such packer member
is not
however necessary, as explained below. Pressurized fracking fluid may then
inject in the
well casing 12 in the region intermediate the packer member (not shown) and
the ball member
40; to thereby frac the formation in such desired location.
Fig. 15 of the drawings shows an embodiment 10' of the invention where the
baffle
member 30 is conveyed downhole to engage a particular landing sub 14 via a
conveying tool
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20 which comprises a tubing member as shown, such as coil tubing. Embodiment
10' may be
employed in deviated well casings, wherein the coil tubing can push the
conveying tool 20
and conveying head 22 to the desired region of the well casing 12 and desired
landing sub 14.
Fig. 16 of the drawings shows an embodiment 10" of the invention where the
baffle
member 30 is conveyed downhole to engage a particular landing sub 14 via a
conveying tool
20 having conveying head 22 thereon, which conveying tool 20 is simply
threadably coupled
to and suspended from a wireline. Embodiment 10" may be employed in vertical
wells,
wherein the weight of the conveying head 22 and coupled baffle member 30
allows same to
be directly vertically lowered within the well casing 12.
Operation of a Preferred Embodiment of the Invention
In order to achieve certain desired advantages of the invention, the operation
of a
preferred embodiment and method to selectively and successively perforate and
frack a
particular zone of a formation , commencing from a most distal end of a well
casing 12 in the
desired fracking zone, is described below.
Firstly, a plurality of landing subs 14 spaced along a well casing 12 is
located in a
well drilled within a hydrocarbon formation.
Each of landing subs 14 have one or more annular recesses 16 therein, being of
a
progressively lesser width progressing uphole from a most distal end of the
wellbore, A
lowermost landing sub 14 in a zone to be fracked possesses the annular recess
16 of greatest
width. Alternatively, each landed sub 14 may possess a plurality of annular
recesses 16, of
unique but varying widths and/or spacing therebetween, to allow only a single
baffle member
having similarly-configured collet finger protuberances 50, to uniquely engage
same.
A first (initial) baffle member 30 is affixed to a downhole end of conveying
tool 20 via
30 frangible means such as shear pins 26. Baffle member 30 has radially-
outwardly biased collet
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finger protuberances 50 thereon, configured to matingly engage only the unique
annular
recess (es) 16 within a lowermost landing sub 14 of well casing 12 in a zone
to be fracked.
Thereafter, the conveying tool 20 and frangibly coupled first baffle member 30
are
together lowered downhole in well casing 12 until said collet finger
protuberances 50 on
baffle member 30 matingly engage annular recess(es) 16 in lowermost landing
sub 14a in a
zone of such well casing to be fracked.
Thereafter, an uphole force is applied to conveying tool 20 via the wireline
or coiled
tubing to which conveying tool 20 is coupled, thereby shearing shear pins 26
and de-coupling
baffle member 30 from conveying tool 20.
Conveying tool is then raised slightly within well casing 20 to a position
immediately
above baffle member 30, and an explosive charge 140 on the lowermost portion
of coupling
head 22 is detonated, thereby creating perforations 142 in well casing 12
immediately above
the lowermost landing sub 14.
The conveying tool is then withdrawn from the well casing 12, and a plug
member 40
is flowed down well casing 12. Plug member 40 will then be caused to sit in
sealing surface
34 on baffle member 30, thereby isolating further downhole portions of the
wellbore and
causing said plug member 40 to abut an uppermost portion of said baffle member
30 so as to
prevent passage of pressurized fluid downhole of baffle member 30.
A packer member on coil tubing may then be inserted downhole, and actuated
above
perforations 142 to thereby isolate regions of the well casing 12 above the
packer, and a
pressurized fluid injected in the coil tubing to frac the well casing 12 in
the region
intermediate the packer and the plug member 40. It
is not necessary, however, to utilize a
packer member (not shown) to isolate sections of the well casing 12 above
baffle member 30,
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since well casing 12 is not otherwise perforated above created perforations
142 therein and
loss of pressurized fluid into other uphole regions of the well casing 12 will
not thus occur.
The plug member 40 is then caused to be removed from well casing 12. This is
done
by plug member 40 preferentially being a dissolvable ball, which then
dissolves after being in
contact with such pressurized fluid, which fluid is typically acidic or acidic
fluid may then be
injected downhole to dissolve plug member 40. Alternatively, plug member 40
may merely
have been lowered on a wireline, and after completion of the fracking
operation may then be
pulled to surface.
The aforesaid steps are repeated, in each instance with second and additional
baffle
members 30. In each iteration, the baffle member 30 has collet
finger protuberances 50
thereon of a lesser width, or of a different spacing, which allow respective
engagement of
progressively more uphole annular recesses 16 in each of the plurality of
landing subs 14,
until said hydrocarbon formation has been completely fracked or treated.
At the culmination of the fracking operation, a retrieving tool 90 having
pressure
actuated radially-extending dogs 92 thereon, is lowered downhole below the
lowermost of
the baffle members 30 matingly engaged within well casing 12 to respective
landing subs 14,
as shown sequentially in Fig. 12 & 13.
Retrieving tools 90 having pressure actuated radially-outwardly extending dogs
92 are
well known to persons of skill in the art and are readily commercially
available. Accordingly,
retrieving tool 90, a particularly suitable version for these purposes being
shown in Figs. 12-
14, is not further described herein.
Upon actuation of radially outwardly extending dogs 92 on retrieving tool 90,
such
dogs 92 engage shoulder 39 on lowermost portion of the lowermost baffle member
30, as
shown in Fig. 14. Upward force exerted on retrieving tool 90 and by extension
lowermost
baffle member 30 causes "riding up" of chamfered uphole edge 70 of
protuberances 50 on
chamfered uphole edge 72 of annular recess 16', thereby causing disengagement
of
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protuberances 50 with annular recess 16' and allowing retrieving tool 90 and
lowermost baffle
member 30 to be withdrawn uphole, as shown in Fig. 14.
Additional upward force applied to retrieving tool 90 causes similar
disengagement of
successive uphhole baffle members 30 with respective landing subs 14, thereby
additionally
and advantageously allowing such additional uphole baffle member 30 to be
withdrawn from
well casing 12 at the same time, and via only a single retrieving tool 90.
Advantageously, well casing 12 has thus had removed therefrom all actuating
and
isolating tools, thereby retaining its maximum diameter and reducing to the
greatest extent
possible any flow restrictions in well casing 12 . Such elimination of flow
restrictions
thereby reduces any pressure drops along such well casing 12 and thereby, for
a given
pumping horsepower, maximizes the amount of hydrocarbons which may then be
pumped to
surface.
In such manner hydrocarbons entering the created perforations 142 in the well
casing
12 are then able to flow in a well casing 12 of maximum diameter, thereby
maximizing to the
greatest extent the flow of hydrocarbons through the well casing 12 when
producing such
hydrocarbons to surface.
The above description of some embodiments of the present invention is provided
to
enable any person skilled in the art to make or use the present invention.
For a complete definition of the invention and its intended scope, reference
is to be
made to the summary of the invention and the appended claims read together
with and
considered with the detailed description and drawings herein on a purposive
interpretation
thereof.
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