U.S. patent number 3,578,083 [Application Number 04/875,681] was granted by the patent office on 1971-05-11 for methods and apparatus for plugging well bores with hardenable fluent substances.
This patent grant is currently assigned to Schlumberger Technology Corporation. Invention is credited to Ronald A. Anderson, Nevyl G. Owens.
United States Patent |
3,578,083 |
Anderson , et al. |
May 11, 1971 |
METHODS AND APPARATUS FOR PLUGGING WELL BORES WITH HARDENABLE
FLUENT SUBSTANCES
Abstract
As a preferred embodiment of the apparatus of the present
invention disclosed herein, a tubular bag is sealingly mounted
around an elongated body and operatively arranged to be expanded
into engagement with the walls of a well bore by discharging
thereinto an initially fluent hardenable substance contained in a
selectively operable displacement assembly releasably coupled to
the body. Biasing means are operatively arranged for imposing
opposed axial forces against the expanded bag to depress the ends
of the bag toward one another. In this manner, unbalanced pressure
forces acting on the tool will only further urge the bag radially
outwardly against the walls of the well bore with an added force
for securely anchoring the tool against longitudinal movement until
the fluent substance has solidified. In practicing the methods of
the present invention, a yieldable enclosed container of a fluent
substance capable of setting up into a hardened mass is positioned
at a selected location in a well bore with the container being
peripherally engaged with the walls of the well bore. Opposed axial
forces are applied to the opposite ends of the container to form
the container into a generally toroidal configuration. Thereafter
configuration. Thereafter, unbalanced pressure differentials acting
across the container will be effective for further increasing the
pressure of the fluent substance for firmly urging the container
outwardly against the walls of the well bore with a correspondingly
increasing frictional force to secure the container in position
until the fluent material therein has hardened.
Inventors: |
Anderson; Ronald A. (Houston,
TX), Owens; Nevyl G. (Houston, TX) |
Assignee: |
Schlumberger Technology
Corporation (New York, NY)
|
Family
ID: |
25366189 |
Appl.
No.: |
04/875,681 |
Filed: |
November 12, 1969 |
Current U.S.
Class: |
166/285;
166/187 |
Current CPC
Class: |
E21B
33/127 (20130101); E21B 33/134 (20130101) |
Current International
Class: |
E21B
33/127 (20060101); E21B 33/12 (20060101); E21B
33/134 (20060101); E21B 33/13 (20060101); E21b
033/127 () |
Field of
Search: |
;166/187,285,290 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Claims
We claim:
1. A method for plugging a well bore comprising the steps of:
positioning an enclosed, yieldable container of a fluent substance
in a well bore at a selected location therein where the perimeter
of said container is engaged with the walls of the well bore;
moving the opposite ends of said container axially inwardly to form
said yieldable container into a generally toroidal configuration
for anchoring said yieldable container in said well bore against
movement by unbalanced pressure forces acting thereon; and
discharging an initially fluent hardenable substance into said well
bore above said anchored container to form a bridge of said
hardenable substance on top of said anchored container which will
be supported thereby until said hardenable substance has solidified
into a hardened mass and plugged said well bore.
2. The method of claim 1 wherein said fluent substance in said
yieldable container is also an initially fluent hardenable
substance.
3. A method for plugging a well bore comprising the steps of
positioning an enclosed, yieldable container of an initially fluent
hardenable substance in a well bore at a selected location therein
where the perimeter of said container is engaged with the walls of
the well bore; and imposing oppositely directed axial forces on the
opposite ends of said yieldable container to depress its said ends
inwardly to form said container into a generally toroidal
configuration for anchoring said yieldable container against
movement by unbalanced pressure forces until said fluent substance
confined therein has solidified into a hardened mass.
4. The method of claim 3 further including the step of: discharging
an initially fluent hardenable substance into said well bore above
said anchored container to form a bridge of said hardenable
substance on top of said anchored container which will be supported
thereby until said hardenable substances have solidified into
hardened masses and plugged said well bore.
5. A method for plugging a well bore comprising the steps of:
positioning an enclosed, yieldable tubular container at a selected
location in a well bore; filling said container with an initially
fluent hardenable substance to expand the sides of said container
radially outwardly into engagement with the walls of the well bore;
and moving the opposite ends of said container axially inwardly
toward one another to reform said expanded container into a
generally toroidal configuration for anchoring said expanded
container against movement by unbalanced pressure forces while said
fluent substance confined therein is solidifying into a hardened
mass.
6. The method of claim 5 further including the steps of:
discharging an initially fluent hardenable substance into said well
bore above said anchored container to form a bridge of said
hardenable substance on top of said anchored container which will
be supported thereby until said hardenable substances have
solidified into hardened masses and plugged said well bore.
7. Apparatus adapted for plugging a well bore and comprising: an
elongated body adapted to be suspended in a well bore; a tubular
bag of a flexible material arranged around said body; first and
second coupling means respectively secured to the opposite ends of
said bag and operatively sealed around said body for defining an
enclosed space therearound within said bag, said first coupling
means being adapted for longitudinal movement along said body
toward said second coupling means; first means including a passage
on said body communicating with said enclosed space and adapted for
admitting a fluent hardenable substance into said enclosed space to
expand said bag outwardly into contact with a well bore wall; and
second means including spring biasing means operable upon expansion
of said bag for moving said first coupling means along said body
toward said second coupling means to depress said bag ends axially
inwardly and form said expanded bag into a generally toroidal
configuration for anchoring said well bore apparatus in a well bore
against movement by unbalanced pressure forces acting thereon as a
fluent substance disposed within said expanded bag hardens into a
solidified mass.
8. The apparatus of claim 7 wherein said first means further
include means operable upon the expansion of said bag into contact
with a well bore wall for terminating further communication between
said passage and said enclosed space to confine a fluent substance
therein once said bag is fully expanded.
9. The apparatus of claim 7 wherein said second coupling means are
also adapted for longitudinal movement along said body from a first
position to a second position toward said first coupling means upon
expansion of said bag; said first means further include valve means
operable upon movement of said second coupling means for
terminating further communication between said passage and said
enclosed space to confine a fluent substance therein once said bag
is fully expanded; and said second means further include latch
means adapted for releasably securing said second coupling means in
said second position so that upon movement of said first coupling
means by said biasing means toward said second coupling means said
bag ends will be depressed axially inwardly toward one another.
10. Apparatus adapted for plugging a well bore and comprising: an
elongated body adapted to be suspended in a well bore; first and
second coupling members fluidly sealed around said body and adapted
for movement relative to one another between longitudinally spaced
positions; a tubular bag of a flexible material arranged around
said body and having its opposite ends respectively fluidly sealed
to said first and second coupling members for defining an enclosed
space therein; selectively operable fluid displacement means
coupled to said body and adapted to fill said enclosed space with
an initially fluent hardenable substance for expanding said bag
outwardly into firm frictional contact with a well bore wall and
moving said first and second coupling members relatively toward one
another to respectively form said bag ends into a generally
hemispherical configuration; and first means operatively arranged
on said body for bringing said first and second coupling members
relatively closer to one another to respectively reform said bag
ends into a generally hemitoroidal configuration so that unbalanced
pressure forces acting on either of said bag ends will urge said
bag outwardly into firmer frictional contact with a well bore wall
while a fluent substance contained therein solidifies into a
hardenable mass.
11. The apparatus of claim 10 further including a fluid bypass on
said body adapted for providing fluid communication above and below
said expanded bag until a fluent substance contained therein
solidifies into a hardened mass; and means on said body adapted for
closing said fluid bypass after a fluent substance contained in
said bag has solidified into a hardened mass.
12. The apparatus of claim 10 further including means operable for
uncoupling said fluid displacement means from said body after said
enclosed space has been filled by said fluid displacement
means.
13. The apparatus of claim 12 further including a fluid bypass on
said body adapted for providing fluid communication above and below
said expanded bag until a fluent substance contained therein
solidifies into a hardened mass; and means on said body adapted for
closing said fluid bypass after a fluent substance contained in
said bag has solidified into a hardened mass.
14. The apparatus of claim 10 wherein said first coupling member is
slidably mounted on said body; and said first means include biasing
means operatively arranged on said body for urging said first
coupling member closer to said second coupling member with an axial
force sufficient to reform the adjacent end of said bag into its
said generally hemitoroidal configuration, and latch means operable
for securing said second coupling member to said body at least
while said biasing means are urging said first coupling member
closer to said second coupling member so that said second coupling
member will impose a reaction force a axially against the other end
of said bag to reform it into its said generally hemitoroidal
configuration.
15. The apparatus of claim 14 wherein said baising means are
comprised of a compression spring having one end engaged with said
body and another end adapted for engagement with said first
coupling member.
16. Apparatus adapted for plugging a well bore and comprising: an
upper body and a lower body tandemly coupled to one another and
adapted to be supported in a well bore from a suspension cable;
upper and lower coupling members fluidly sealed around said lower
body and adapted for sliding movement relative to said lower body
between longitudinally spaced positions; a tubular bag of a
flexible material extended around said lower body and having its
upper and lower ends respectively fluidly sealed to said upper and
lower coupling members for defining an enclosed space therein;
selectively operable fluid displacement means on said upper body
and fluidly coupled to said enclosed space for filling said bag
with an initially fluent hardenable substance to expand said bag
outwardly into firm frictional contact with a well bore wall and
respectively form said bag ends into a generally hemispherical
configuration as said upper and lower coupling members move
relatively toward one another; first means responsive to upward
movement of said upper and lower bodies for uncoupling said fluid
displacement means from said enclosed space to trap a fluent
substance discharged into said enclosed space within said expanded
bag; and second means operatively arranged on said lower body for
moving said upper and lower coupling members relatively closer to
one another to respectively reform said bag ends into a generally
hemitoroidal configuration so that unbalanced pressure forces
acting on either of said bag ends will urge said bag outwardly into
firmer frictional contact with a well bore wall while a fluent
substance contained therein solidifies into a hardened mass.
17. The apparatus of claim 16 further including third means
responsive to further movement of said upper and lower bodies for
uncoupling said upper body from said lower body.
18. The apparatus of claim 16 wherein said second means include
first latch means operatively arranged between said upper coupling
member and said lower body for securing said upper coupling member
against upward movement relative to said lower body once said upper
bag end has assumed a generally hemispherical configuration, and
biasing means operatively arranged between said lower coupling
member and said lower body for urging said lower coupling member
toward said upper coupling member once it is secured by said first
latch means.
19. The apparatus of claim 18 wherein said first means include a
fluid passage between said fluid displacement means and said
enclosed space, and valve means operatively arranged between said
upper coupling member and said lower body for closing said fluid
passage once said upper coupling member is secured by said first
latch means.
20. The apparatus of claim 19 further including third means
responsive to further movement of said upper and lower bodies for
uncoupling said upper body from said lower body.
Description
In various well completion operations it is often desired to place
a fluidtight barrier or plug at a desired location in a well bore
below the lower end of a substantially smaller well pipe or tubing
string. It will, of course, be appreciated that conventional bridge
plugs that are small enough to pass through a small-diameter tubing
string are incapable of being expanded to a diameter equal to that
of the well bore which may be two to five times greater than the
tubing diameter. Accordingly, so called "through-tubing bridge
plugs" such as those shown in U.S. Pat. Nos. 3,460,618, 3,460,624
and 3,460,625 are typically employed for situations of this
nature.
As illustrated in these patents, these through-tubing bridge plugs
generally include a fluid displacement device that is supported by
a suspension cable and releasably coupled to an elongated body
member therebelow carrying an expansible tubular bag that is
initially retained in a collapsed position. Once the tool has
passed through a reduced-diameter tubing string and is in the
enlarged well bore below the lower end of the tubing string, a
fluent substance such as a hardenable plastic or cementitious
composition is selectively discharged from the displacement device
into the expansible bag so as to firmly expand the bag into sealing
contact with the walls of the well bore therearound. Thereafter,
once the hardenable substance within the expanded bag has hardened,
the well bore will be tightly plugged so as to prevent fluid or
pressure communication between the well bore intervals above and
below this barrier.
It will, of course, be appreciated that until the fluent substance
has completely hardened, the bag and at least the lower portions of
the tool carrying the expanded bag must be secured against movement
upwardly or downwardly in the well bore. Accordingly, as described
in the aforementioned patents, a fluid bypass passage is provided
through each tool for equalizing the pressures above and below the
expanded bag as well as for accommodating at least a substantial
vertical movement of any flowing well bore fluids during the time
that the fluent material is hardening. After the fluent substance
has hardened, this bypass passage is permanently closed to complete
the formation of the fluidtight well bore barrier. In some
instances, these through-tubing bridge plugs are also provided with
selectively extendible wall-engaging anchors such as those shown in
the aforementioned U.S. Pat. No. 3,460,624 and U.S. Pat. No.
3,460,625. In this manner, upon operation of the tool, these
wall-engaging anchors will securely anchor the tools against
longitudinal movement in the well bore until the fluent substance
has fully hardened.
Although these well completion tools have met with considerable
commercial success, the problem of securing the tools while the
fluent substance hardens is still not fully solved. For instance,
those skilled in the art will appreciate that with those tools
having extendible anchors, should it subsequently become necessary
to remove the bridge, the typical drilling-out operations will be
further complicated by the presence of these anchoring members
which are usually formed of iron or steel. Similarly, should some
malfunction prevent the expansible bag from fully expanding into
sealing engagement with the walls of the well bore, the subsequent
removal of the tool will be complicated by the extended anchors. On
the other hand, with those tools that do not employ wall-engaging
anchors (such as those tools shown in U.S. Pat. No. 3,460,618 ), it
will be recognized that it is always possible that the bypass
passage through the tool will be too small to accommodate a
substantial movement of fluids in the well bore; and, as a result,
the attendant pressure differential will tend to shift the tool
before the fluent substance in the expanded bag has fully hardened.
Thus, with tools of this nature, it is often preferred to not
uncouple the fluid displacement device from the lower portion of
the tool until the fluent substance has hardened. This, of course,
will require that the surface equipment be left in position for a
considerable time if it is necessary to be certain that the tool is
not shifted from its intended location.
Accordingly, it is an object of the present invention to provide
new and improved methods and apparatus for securely anchoring an
expanded container of an initially fluent hardenable substance in a
well bore so as to prevent movement of the container by unbalanced
well pressures as the substance is hardening.
This and other objects of the present invention are attained by
positioning a yieldable, enclosed container of an initially fluent
hardenable substance at a selected location in a well bore and
applying opposed axial forces to the opposite ends of the container
while this substance is still fluent for forming the yieldable
container into a generally toroidal configuration. Alternatively,
an initially fluent hardenable substance can be dumped on top of
the expanded bag which, in this instance, is filled with a fluent
substance that may be either hardenable or nonhardenable. In either
case, unbalanced pressure forces acting on the depressed ends of
the container will be effective for urging the walls of the
container outwardly against the well bore walls with a
correspondingly increased force to frictionally retain the
container at its selected location until the hardenable substance
has had time to harden into a solidified mass.
The novel features of the present invention are set forth with
particularity in the appended claims. The invention, together wit
further objects and advantages thereof, may be best understood by
way of the following description of exemplary apparatus and methods
employing the principles of the invention as illustrated in the
accompanying drawing, in which:
FIG. 1 depicts a preferred embodiment of a well completion tool
arranged in accordance with the principles of the present invention
as the tool is being lowered through a tubing string to a desired
location in a well bore;
FIGS. 2A--2C are successive cross-sectioned elevational views of
the tool depicted in FIG. 1 illustrating the initial positions of
the various elements thereof before the tool has been actuated;
FIGS. 3--6 successively depict the tool shown in FIG. 1 as it is
being operated in accordance with the methods of the present
invention; and
FIG. 7 graphically represents the design criteria of the present
invention.
Turning now to FIG. 1, a well completion tool 10 incorporating the
principles of the present invention and dependently supported by a
suspension cable 11 is depicted as it is being lowered through a
string of tubing 12 toward a selected position below the lower end
of the tubing string within a larger diameter well bore 13 which,
in this instance, is cased as at 14. If desired, a typical casing
collar locator 15 may be incorporated with the tool 10 for
determining the depth at which the tool is to be halted. In the
preferred embodiment depicted, the well completion tool 10 includes
selectively operable fluid displacement means 16 arranged in an
upper section 17 thereof and carrying a supply of an initially
fluent hardenable material which, upon command from the surface, is
selectively displaced into an expansible tubular bag 18 carried on
an elongated body 19 detachably mounted below the housing section.
As will subsequently be explained in detail, once the tubular bag
18 has been filled with a sufficient quantity of the fluent
substance to expand it outwardly into sealing engagement with the
well casing 14, biasing means 20 carried on the body 19 are
arranged for selectively imposing opposed axial forces against the
ends of the expanded bag to form it into a toroidal shape. The
upper section 17 of the tool is then released from the lower body
and returned to the surface. Thereafter, once sufficient time has
elapsed for the fluent substance to adequately harden so as to form
an impermeable transverse barrier or bridge plugging the well
casing 14, valve means 21 mounted on the lower end of the body 19
are operatively arranged for closing a bypass passage 22 provided
through the body of the tool 10 for reducing or, hopefully,
equalizing pressure differentials acting across the inflated bag as
the fluent substance therein is hardening.
Turning now to FIGS. 2A--2C, a cross-sectioned elevational view is
shown of the well completion tool 10 as it appears before the
collapsed bag 18 carried thereon is expanded. As depicted, the
upper section 17 of the tool 10 is operatively arranged for
carrying a substantial volume of an initially fluent, hardenable
substance 23 which, upon operation of the selectively operable
fluid displacement means 16, is forcibly displaced into the tubular
bag 18 to expand it outwardly into sealing engagement with the well
casing 14. Accordingly, as depicted in FIG. 2A, the upper housing
section 17 of the tool 10 is arranged to provide an enlarged
chamber 24 in its upper portion that is joined by an axial passage
25 to an enlarged-diameter longitudinal bore 26 extending
substantially the full length of the housing section and
terminating at its lower end. The upper portion 27 of the elongated
body 19 is also enlarged and similarly provided with an
enlarged-diameter longitudinal bore 28 which extends upwardly to
the upper end of the body. The opposed ends of the housing 17 and
the body 19 are complementally fitted together and fluidly sealed
as at 29, with the two members being releasably coupled to one
another by latching means 30 to define a combined fluid chamber 31
of substantial length and volumetric capacity.
The fluid displacement means 16 further include a piston 32
operatively arranged in the fluid chamber 31 so as to be initially
positioned just above the upper surface on the initially fluent
substance 23 disposed in the intercommunicated bores 26 and 28
defining the fluid chamber. In this manner, upon downward movement
of the piston 32, the fluent substance 23 will be forcibly
displaced downwardly from the fluid chamber 31 and into the
expansible bag 18 mounted on the body 19 therebelow. It will, of
course, be appreciated that by providing lateral ports, as at 33
and 34, in the housing section 17, the well bore fluids will be
admitted into the longitudinal housing bore 26 so as to maintain
the space above the piston 32 as well as the fluent substance 23 in
the fluid chamber 31 at the hydrostatic pressure of the well bore
fluids.
In the preferred manner of moving the displacement piston 32
downwardly, the fluid displacement means 16 further include a
cylindrical weight 35 initially disposed in the enlarged bore 26
immediately above the piston and releasably supported therein by
means such as two or more upwardly extending, inwardly biased latch
fingers 36 arranged on an upright rod 37 on the upper end of the
weight. As illustrated in FIG. 2A, the latch fingers 36 have
laterally opposed, outwardly enlarged heads 38 which are adapted to
be received in an enlarged portion 39 of the axial housing passage
25 immediately above the upper end of the enlarged-diameter
longitudinal bore 26. In this manner, so long as the latch fingers
36 are laterally separated, their respective enlarged heads 38 are
supported on the upwardly directed shoulder 40 defined at the lower
end of the recess 39. To retain the latch fingers 36 initially
separated from one another, an actuating piston 41 is disposed in
the enlarged chamber 24 and coupled to a depending axial rod 42
which extends through the axial passage 25 into the enlarged recess
39 so as to be interposed between the opposed enlarged heads 38 of
the latch fingers 36 so long as the actuating piston is not further
elevated by a compression spring 43 mounted within the enlarged
chamber.
To retain the actuating piston 41 in its initial position
illustrated in FIG. 2A, the upper portion of the chamber 24 is
initially filled by a relatively noncompressible fluid 44 such as
water or oil; and this fluid is retained therein so long as a
normally closed solenoid valve 45 connected to suitable electrical
conductors 46 and 47 in the cable 11 is not operated to open
communication by way of a fluid passage 48 between the enlarged
chamber and the exterior of the tool 10. If desired, a separate
fluid passage 49 may also be provided for filling the chamber 24,
with communication in the reverse direction through the filling
passage being prevented by means of a suitable valve such as a ball
check valve 50 arranged to prevent flow out of the chamber without
unduly limiting the admission of the fluid 44 thereinto.
Accordingly, it will be appreciated from FIG. 2A that once the
chamber 24 has been filled with a sufficient volume of the fluid 44
to shift the actuating piston 41 downwardly to its illustrated
position, the depending rod 42 thereon will be positioned between
the opposed enlarged heads 38 for maintaining the weighted body 35
suspended just above the displacement piston 32.
In the preferred manner of arranging the latching means 30, the
lower end of the housing section 17 is adapted to be complementally
received within the upper end of the enlarged longitudinal bore 28
in the elongated body 19. An inwardly opening circumferential
groove 51 is formed around the wall of the internal bore 28 and
adapted for receiving outwardly enlarged heads 52 on the lower ends
of two or more yieldable latch fingers 53 dependently coupled to
the lower end of the upper housing section 17. A ring 54 is
normally positioned in the longitudinal bore 28 to the rear of the
enlarged heads 52 and suitably dimensioned to retain the enlarged
heads within the circumferential groove 51 until the ring is
shifted downwardly in relation to the heads. To retain the ring or
annular latch member 54 in its depicted elevated position, an
upstanding support 55 is coupled thereto and extended upwardly into
the lower end of the housing section 17 thereabove. An annular
plate 56 is mounted around the upper end of the support 55 and
slidably arranged within an inwardly facing recess 57 within the
bore 26 and supported therein by a spring 58 which normally urges
the annular plate upwardly against the downwardly facing surface at
the top of the recess.
In this manner, so long as the annular plate 56 is elevated as
depicted in FIG. 2A, the latch ring 54 is engaged with the reverse
side of the enlarged heads 52 to reliably retain them within the
circumferential housing groove 51 and, accordingly, securely latch
the tool sections 17 and 19 together. It will be appreciated,
however, that upon downward travel of the displacement piston 32
through the enlarged housing bore 26, the piston will ultimately
contact the annular plate 56 and shift it downwardly a sufficient
distance to displace the latch ring 54 below the enlarged heads 52
so as to permit the upper tool section 17 to be uncoupled from the
elongated body 19 by simply pulling on the suspension cable 11.
To initially retain the fluent substance 23 within the fluid
chamber 31, the lower end of the enlarged longitudinal body bore 28
is normally closed by valve means 59 which, in the preferred
embodiment of the tool 10 depicted in the drawings, include an
annular valve element 60 that is slidably arranged and fluidly
sealed, as at 61, within an enlarged chamber 62 formed in the body
19 immediately below the lower end of the enlarged body bore. To
normally secure the valve member 60 in its depicted elevated
position, means such as a shearpin 63 are provided for releasably
retaining the valve member to the elongated body 19 until the fluid
pressure of the fluent substance 23 has been increased sufficiently
to break the shearpin and shift the valve member downwardly.
For reasons that will subsequently become apparent, an elongated
tubular member 64 is coaxially supported within the elongated body
bore 28 and terminated at its upper end by a fitting, such as a tee
65, having one or more lateral outlets 66 ro provide communication
between the upper end of the tubular member and the exterior of the
tool 10. By providing an enlarged-diameter portion 67 on the
tubular member 64 immediately adjacent to the normal elevated
position of the annular valve member 60 and arranging a sealing
member 68 thereon for engagement within the axial bore 69 of the
annular valve member, the fluent substance 23 thereabove cannot be
displaced from the fluid chamber 31 until the annular valve member
has moved downwardly a sufficient distance to bring its upper end
below the sealing member 68.
The intermediate tubular portion 70 of the elongated body 19 is
sufficiently reduced in diameter to accommodate a pair of
longitudinally spaced collars 71 and 72 which are respectively
slidably mounted and fluidly sealed, as at 73 and 74, around the
reduced-diameter portion of the body and secured, as by bands 75
and 76, within the opposite ends of the elongated tubular bag 18
which is preferably formed of a suitable wear-resistant, flexible
and fluid-impervious material, such as a Dacron cloth impregnated
with Neoprene, that does not readily stretch. The bag 18, is
therefore, formed with an expanded diameter corresponding generally
to that of the well casing 14; and, preferably, folded around the
intermediate body portion 70 in such a manner as to minimize its
lateral dimensions and, if desired, lightly tied in its folded or
collapsed position by string or tape. In its initially collapsed
position illustrated in FIG. 2B, the tubular bag 18 is drawn to its
full length with the slidable collars 71 and 72 at their most
widely separated positions along the body portion 70; and the upper
collar is releasably secured in its initial position by means such
as one or more upright latch fingers 77 which are inwardly biased
to retain enlarged heads 78 thereon, in a circumferential groove 79
around the body portion 70.
It will be noted that by virtue of the sealing members 73 and 74 on
the slidable collars 71 and 72, the interior of the bag 18 defines
a fluidtight space 80 therein around the intermediate body portion
70. Accordingly, to provide communication into the fluidtight space
80 within the collapsed bag 18, one or more lateral ports 81 are
provided in the reduced-diameter body portion 70 at a location
between the depicted elevated position of the upper collar 71 and
the lower position to which the collar will slide downwardly when
the bag 18 is initially expanded. The lower end of the elongated
tubular member 64 is extended below the ports 81 and sealingly
engaged, as at 82, within the longitudinal bore 83 through the
tubular body portion 70. Thus, so long as the upper collar 71 is
retained in its initial elevated position by the latch fingers 77,
once the valve member 60 is shifted downwardly, the fluent
substance 23 released from the fluid chamber 31 will be directed
through the annular space 84 around the lower portion of the
tubular member 64 and into the bag 18 by way of the lateral ports
81.
It will, of course, be appreciated that once the upper collar 71
has been carried downwardly (as will subsequently be described) a
sufficient distance to position the sealing member 73 on the collar
below the lateral ports 81, the fluent substance 23 confined in the
interior space 80 within the expanded bag will be trapped therein.
For reasons that will subsequently be explained, a second
circumferential groove 85 is formed around the reduced-diameter
body portion 70 just below the lateral ports 81 so that, once the
collar 71 has shifted downwardly in relation to the ports, the
enlarged heads 78 on the latch fingers 77 will engage this lower
circumferential groove to prevent the upper collar from moving
upwardly from its lower position.
As previously mentioned, the normally open bypass passage 22 is
provided for reducing, if not altogether, equalizing pressure
differentials existing across the expanded bag 18 as the fluent
substance 23 therein is hardening. Accordingly, one or more lateral
ports 86 are formed in the tubular tool body 70 well below the
initial depicted position of the lower collar 72. In this manner,
the bypass passage 22 between the upper and lower ports 66 and 86
is defined by the tubular member 64 and the central portion of the
longitudinal body bore 83 below the lower end of the tubular
member. To selectively close this bypass passage 22, the valve
means 21 include a tubular valve member 87 having longitudinally
spaced sealing members 88 and 89 thereon which is operatively
arranged within the longitudinal body bore 83 for movement upwardly
from an initial position immediately below the lateral ports 86 to
a final elevated position (as defined by a downwardly facing
shoulder 90 in the longitudinal bore) where the valve member is
adjacent to the lateral ports with its sealing members respectively
spanning the ports and sealingly engaged with the body 70 above and
below the ports. Thus, in its initial position, fluid communication
is readily provided through the tubular member 64 and the ports 60
and 86 for accommodating at least a substantial proportion of any
well bore fluids moving upwardly or downwardly past the well
completion tool 10 during the time that the fluent substance 23 is
hardening within the expanded bag 18.
In the preferred manner of selectively closing the valve member 87,
the upper end of an elongated tension spring 91 is anchored, as by
a transverse rod 92, to the intermediate body portion 80 and the
spring extended downwardly therefrom through the longitudinal body
bore 83. The spring 91 is terminated by a long straight portion 93
which is passed through the valve member 87 and releasably secured
in an initially stretched condition by means of a hook 94 that is
coupled to a wire or cord 95 releasably secured to a geared timer
mechanism 96 enclosed in an enlarged fluid-filled chamber 97 in the
lower portion 98 of the body 19.
In one manner of arranging the timer mechanism 96, the rotational
speed of the uppermost gear 99 therein is regulated by a train of
gears that is terminated by either a typical escapement and balance
(not shown) or a paddlelike wheel member 100 that is driven by the
force of the spring 91 acting through the gear train. Thus, by
releasably coupling the cord 95 to the shaft 101 carrying the upper
gear 99 of the gear train and winding the wire or cord therearound,
the tension force of the spring 91 will be effective for slowly
rotating this uppermost gear at a speed which, by virtue of the
gear train, is regulated by the faster, but retarded, rotational
speed of the rotating paddle member 100 in the fluid-filled chamber
97. Accordingly, once the cord 95 is wound around the shaft 101 and
coupled to the hook 94 on the lower end of the spring 91, a
preselected time interval will be provided before a transverse
member, such as a washer 102, loosely mounted on the straight
portion 93 of the spring is moved upwardly to shift the tubular
valve member 87 upwardly to close the ports 86. In other words,
once the cord 95 is connected, the tension force of the spring 91
will begin slowly unwinding the cord from the shaft 101 so that,
once the gear 99 has been rotated a sufficient number of
revolutions to unwrap the cord therefrom, the lower end of the cord
will be released from the shaft and the spring will then jerk the
washer 102 upwardly to carry the valve member 87 into its final
port-closing position.
The selectively operable biasing means 20 are preferably arranged
on the elongated body 19 below the lower collar 72. As illustrated
in FIGS. 2B and 2C, in the preferred manner of arranging the
biasing means 20, an annular member 103 is slidably mounted around
the elongated body 70 and adapted to be moved upwardly thereon by a
stout compression spring 104 carried on an upwardly directed body
shoulder 105 and engaged with the lower end of the slidable annular
member. For reasons that will subsequently be explained, the spring
104 is initially retained in compression by latching means such as
one or more ball members 106 that are respectively arranged in
lateral recesses 107 spaced around the annular member 103 and sized
for partial reception in a circumferential groove 108 formed around
the intermediate body portion 70. A sleeve member 109 is coaxially
mounted around the annular member 103 and has its lower portion
formed with an internal diameter appropriately sized in relation to
the diameter of the balls 106 and the depth of the circumferential
groove 108 to prevent outward lateral movement of the balls from
the groove so long as the ball retainer sleeve remains in the
elevated position illustrated in FIG. 2B.
To permit outward movement of the balls 106 from the
circumferential groove 108, longitudinal grooves or slots 110 are
arranged in the upper portion of the ball retainer sleeve 109.
Thus, upon downward movement of the retainer sleeve 109 in relation
to the annular member 103 to bring the slots 110 respectively into
registration with the several balls 106, the upwardly directed
force of the compression spring 104 will be effective for shifting
the annular member 103 upwardly in relation to the elongated body
70 once the balls are shifted out of the circumferential groove and
into the enlarged space provided by the elongated slots. In this
manner, it will be appreciated that once the ball retainer sleeve
109 is moved downwardly against the restraint of a relatively weak
compression spring 111 mounted within an external protective sleeve
112 coaxially arranged around the annular member 103, the stout
compression spring 104 will be freed for shifting the annular
member upwardly against the lower slidable collar 72. To provide
for the actuation of the ball retainer sleeve 109, the lower
portion of the lower collar 72 is appropriately sized, as at 113,
to engage an inwardly turned lip 114 on the upper end of the ball
retainer sleeve for shifting the retainer sleeve downwardly in
relation to the annular member 103 and the external sleeve 112 for
releasing the balls 106.
Accordingly, to prepare the well completion tool 10 of the present
invention for operation, the control chamber 24 above the
weight-releasing piston 41 is filled with a sufficient volume of
the hydraulic fluid 44 to shift the piston against the spring 43 to
a position where the depending rod 42 extends downwardly into the
recess 39. The weighted body 35 is forced upwardly, compressing a
coil spring 115 thereabove until the enlarged heads 38 of the latch
fingers 36 are within the recess 39 on opposite sides of the lower
end of the rod 42 and are supported on the shoulder 40 for
retaining the weighted body 35 in its elevated position above the
fluid displacement piston 32. The lower end of the upper housing 17
is complementally fitted into the upper end of the upper portion 27
of the elongated body 19 and the latch ring 54 is properly
positioned to retain the enlarged heads 52 in the internal
circumferential groove 51. The annular valve member 60 is secured
in its upper or closed position by the shearpin 63, and the
enclosed fluid chamber 31 is then filled with a suitable plastic or
cementitious initially fluent substance which will harden into a
solid mass that preferably expands slightly as it fully
hardens.
The annular member 103 is shifted into position on the intermediate
body portion 70 so as to position the balls 106 in the groove 108
and releasably retain the compression spring 104 in a compressed
condition. The tension spring 91 is extended and the hook 94
thereon is connected to the release cord 95 which has been wrapped
several turns around the shaft 101 of the upper gear 99 of the
timer mechanism 96. As previously mentioned, the predetermined
delay before the bypass passage 22 is closed is determined by the
number of turns or wraps of the cord 95 around the shaft 101. This
time interval is, of course, selected so that the valve member 87
will not be actuated until some time later which is calculated to
be sufficient to permit the initially fluent substance 23 to have
at least substantially hardened.
The tool 10 is then lowered downwardly into the well bore 13 by
means of the suspension cable 11. Once the well completion tool 10
has emerged from the lower end of the tubing string 12 and has
reached a selected position therebelow, an electrical signal is
sent through the cable conductors 46 and 47 to actuate the solenoid
valve 45. As previously explained, once the solenoid valve 45 is
opened, the hydraulic fluid 44 within the upper chamber 24 will be
displaced therefrom by way of the now-opened passage 48 as the
compression spring 43 forcibly shifts the weight-releasing piston
41 upwardly. It will be appreciated, of course, that by providing a
lateral port 116 in the lower portion of the chamber 24, the
weight-releasing piston 41 will be moved upwardly without restraint
from any unbalanced pressure forces that would otherwise occur upon
opening of the solenoid valve 45 to open the enclosed chamber 24 to
the well bore fluids. Once the weight-releasing piston 41 has
reached a sufficiently elevated position to withdraw the depending
rod 42 from between the opposed ends 38 of the latch fingers 36,
the weighted body 35 will be released.
Once the body 35 is released, the force of the compressed spring
115 is effective for accelerating the weighted body downwardly so
that it strikes the fluid displacement piston 32 with considerable
impact. In this manner, a substantial shock or pressure wave is
developed in the fluent substance 33 which is effective for
shifting the annular valve member 60 downwardly with sufficient
force to break the shearpin 63. Once the shearpin 63 has failed,
the valve member 60 will be moved downwardly a sufficient distance
to bring the upper end of the valve member below the seal 68 on the
enlarged-diameter portion 67 on the axial tubular member 64 to open
communication between the fluid chamber 31 and the filling ports 81
by way of the annular space 84 between the axial tubular member and
the inner wall of the intermediate portion 70 of the elongated body
19. A sealing member 117 is arranged on the lower end of the valve
member 60 for sealing engagement with the lower portion 118 of the
enlarged chamber 62 and prevent loss of the fluent substance 23
through a pressure-equalizing port 119 provided into the chamber
below the upper sealing member 61.
Once the weighted body has come to rest on top of the fluid
displacement piston 32, the weight of the body will be effective
for moving the piston on downwardly through the fluid chamber 31 to
forcibly displace the fluent substance 23 therefrom through the
filling ports 81 and into the interior space 80 within the
expansible bag 18. It will, of course, be appreciated that since
the fluent substance 23 is initially at the hydrostatic pressure of
the well bore fluids, the pressure developed by the weighted body
35 will be in addition to the hydrostatic pressure. Thus, as the
bag 18 is filling, the increased fluid pressure developed in the
fluent substance 23 by the weighted body 35 acting on the
displacement piston 32 will be effective for expanding the bag
outwardly and into contact with the walls of the well casing 14
immediately adjacent thereto. Expansion of the tubular bag 18 will,
of course, be effective for drawing the unrestrained lower slidable
collar 72 upwardly along the intermediate body portion 70 toward
the still-latched upper collar 71. It should be noted that the
latch fingers 77 are biased inwardly with sufficient force that the
expansion of the bag 18 will draw the lower collar 72 upwardly
without releasing the enlarged heads 78 from the upper
circumferential groove 79.
Accordingly, when the expansible bag 18 is fully expanded, it will
assume a position such as depicted in FIG. 3 in which its opposite
ends substantially assume a generally hemispherical configuration.
At this point, there will still be a substantial volume of the
still-fluent substance 23 remaining in the fluid chamber 31 so that
the increased fluid pressure developed in the interior space 80 by
the weight of the body 35 acting on the piston 32 will expand the
bag 18 outwardly against the well casing 14 with a moderate lateral
force It will be recognized, of course, that once the bag 18 is
fully expanded, the discharge flow of the fluent substance 23 from
the fluid chamber 31 will temporarily cease and the displacement
piston 32 and weighted body 35 will come to rest at the upper fluid
level of the fluent substance in the fluid chamber.
It will be recognized that the fluid pressure expanding the bag 18
outwardly will urge the exterior of the bag against the well casing
14 with a lateral force that is effective to frictionally secure
the bag against longitudinal movement. Therefore, as illustrated in
FIG. 4, upon upward movement of the suspension cable 11, the upper
housing section 17 and the elongated body 19 will be moved upwardly
in relation to the stationary expansible bag 18 and the upper and
lower slidable collars 71 and 72. As will subsequently be explained
in detail, this upward movement is effective for consecutively
blocking further communication to the interior space 80 in this
expanded bag 18, actuating the biasing means 20, and ultimately
freeing the housing section 17 from the elongated body 19.
First of all, upon upward movement of the elongated body 19, the
inwardly enlarged ends 78 of the latch fingers 77 will be cammed
outwardly by the lower surface of the upper circumferential groove
79 to release the upper collar 71 from the intermediate body
portion 70. Thus, as depicted in FIG. 4, the continued upward
travel of the elongated body 19 will be effective for moving the
fill ports 81 above the upper collar 71 and then bringing the lower
circumferential groove 85 immediately below the fill ports up to
or, perhaps, slightly above the latch fingers 77. It will, of
course, be recognized that once the lateral ports 81 pass above the
fluid seal 73 on the upper collar 71, the fluent substance within
the expanded bag 18 will be sealingly enclosed therein. Moreover,
once the lower circumferential groove 85 engages or passes above
the latch fingers 77, the upper collar 71 cannot return upwardly in
relation to the body to a position where the ports 81 are again in
communication with the interior space 80 within the bag 18.
Furthermore, as the elongated body 19 is moved upwardly, the
annular member 103 releasably coupled thereto will be carried
upwardly toward the stationary lower collar 72 so as to bring the
depending portion 113 thereof into contact with the inwardly
directed lip 114 of the ball retainer sleeve 109. Then, as the
elongated body 19 is moved further upwardly, the ball retainer
sleeve 109 will be halted and the continued movement of the annular
member 103 will carry the balls 106 upwardly into registration with
the elongated slots 110. As previously described, once the balls
106 move into registration with the elongated slots 110, they will
be free to move outwardly into the enlarged space therearound to
disengage the balls from the circumferential groove 108 around the
intermediate body portion 70.
Accordingly, once the balls 106 are disengaged from the
circumferential groove 108, the compressed biasing spring 104 will
be released for forcibly urging the annular member 103 upwardly
against the lower collar 72. Thus, as best seen in FIG. 5, once the
compression spring 104 is released, it will impose a substantial
upwardly directed axial force against the lower end of the
stationary expanded bag 18. This axial force will be effective for
further increasing the fluid pressure of the still-fluent substance
trapped within the bag 18 which (if the enlarged heads 78 are below
the groove 85) will initially move the upper collar 71 upwardly to
accommodate the corresponding inward or upward depression of the
lower end of the bag. Once, however, the upper collar 71 reaches a
position on the intermediate body portion 70 where the latch
fingers 77 are adjacent to the circumferential groove 85 just below
the filling ports 81, the enlarged ends 78 thereof will be urged
into the circumferential groove 85 to secure the upper collar from
further upward movement. Once the upper collar 71 is secured
against further movement in relation to the elongated body 19, the
upwardly directed axial force imposed on the lower end of the bag
18 by the stout compression spring 104 will be effective for
developing a downwardly directed opposing or axial reaction force
on the upper end of the bag for depressing the central portions of
the upper and lower ends of the bag inwardly so that, ultimately,
the bag will assume the generally toroidal configuration depicted
in FIG. 5.
It will be appreciated, therefore, that once the well completion
tool 10 has reached the particular stage of its operation depicted
in FIG. 5, the fluent substance trapped within the interior space
80 of the expanded bag 18 will be at a fluid pressure which is
equal to the sum of the hydrostatic pressure of the fluids in the
well bore 13, the increased pressure developed by the displacement
piston 32 once the bag was filled, and the further-increased
pressure developed therein by the opposing axial forces imposed
thereon by the released compression spring 104. The perimeter of
the bag 18 will, therefore, be urged outwardly against the wall of
the casing 14 with a total force that is proportionally related to
the total pressure of the still-fluent substance confined within
the expanded bag. Accordingly, once the bag 18 is securely anchored
in this manner, the upper housing portion 17 of the tool 10 is
separated from the elongated body 19 by simply pulling further on
the suspension cable 11 so that the latch fingers 53 will be
released from the circumferential groove 51 at the upper end of the
elongated body once the displacement piston 32 has engaged the
annular plate 56 and shifted the ring 54 below the heads 52.
It will be appreciated from FIGS. 4--6 that, once the filling ports
81 are uncovered, the weighted body 35 will continue moving the
piston 32 downwardly to displace the remainder of the fluent
substance 23 contained within the fluid chamber 31 into the well
bore annulus defined between the casing 14 and that portion of the
elongated body 19 projecting upwardly above the expanded bag 18. In
this manner, an additional quantity of the fluent substance 23 will
be deposited on top of the expanded bag 18 to further assure that
an impermeable plug or barrier will be formed in the well bore 13
once the fluent substance has ultimately expanded and hardened. In
any event, by virtue of the increased anchoring force provided by
the toroidal shape of the bag 18, the upper section 17 of the tool
10 can be released from the elongated body 19 and returned to the
surface without having to wait for the fluent substance to harden.
Then, as shown in FIG. 6, at some predetermined time thereafter,
the timer mechanism 96 will function to release the tension spring
91 so as to shift the annular valve member 87 upwardly across the
lower bypass ports 86 and permanently close the bypass passage
22.
It will, of course, be recognized that so long as the fluent
substance confined in the expanded bag 18 has not yet hardened,
once the upper section 17 of the tool 10 is released from the
elongated body 19 the only force retaining the bag and body in
position in the well bore 13 will be the frictional force between
the bag and the well casing 14. This frictional force is,
therefore, determined by:
F.sub.h =P.sub.b (.pi.DL) .mu. (Eq. 1. ) where,
F.sub.h = frictional force holding bag stationary in relation to
well casing;
P.sub.b = internal pressure of fluent substance in expanded
bag;
D = diameter of expanded bag;
L = length of expanded bag in contact with well casing; and
.mu. = coefficient of static friction between expanded bag and well
casing. Accordingly, so long as those forces tending to move the
expanded bag 18 in the well bore 13 do not exceed the above-defined
frictional force (F.sub.h) the expanded bag and elongated body 19
will remain stationary in the well bore. It will be appreciated
that the major force tending to move the expanded bag 18 and the
body 19 will be the total force acting on the cross-sectional area
of the bag as a result of any pressure differential between well
bore fluids above and below the bag. Thus, an unbalanced pressure
force tending to displace the bag 18 and body 19 will be equal
to:
where,
F.sub.p = w0420 force tending to displace bag as a of pressure
differential acting in either direction across expanded bag;
.DELTA.P = pressure differential acting across expanded bag;
and
D = diameter of the expanded bag.
It will be appreciated, therefore, that by setting (F.sub.h) in
equation 1 equal to (F.sub.p) in equation 2 and combining the two
equations, the resulting equation will define the pressure
differential required to shift the frictionally anchored expanded
bag 18 and the body 19. Thus,
and
Plotting equation 3 for a given size of the expanded bag 18, a
straight line, as at 120 in FIG. 7, is obtained. Thus, as
represented there, it will be appreciated that so long as the point
of intersection of (.DELTA.P) and (P.sub.b) for a given situation
is below or to the right of the plotted line 120, the expanded bag
18 and body 19 will remain stationary in the well bore 13. On the
other hand, should the pressure differential (.DELTA.P) increase to
a level where its point of intersection with the particular bag
pressure (p.sub.b) is above or to the left of the plotted line 120,
the bag 18 and elongated body 19 will move in the well bore 13.
Accordingly in the present invention, it has been found that an
initial holding force (F.sub.h) of increased magnitude can be
developed by imposing the axially directed force of the biasing
spring 104 on one end of the expanded bag 18 and securing the other
end of the bag against movement in relation to the body 19 so as to
provide the opposing axially directed reaction force on that end of
the bag and thereby reform the bag into the generally toroidal
configuration depicted in FIGS. 5 and 6. It will be appreciated,
therefore, that upon the upward movement of the lower collar 72 by
the spring 104 toward the upper collar 71, the internal volume of
the space 80 within the expanded bag 18 will be slightly reduced as
the opposite hemispherical ends of the bag are reformed into their
respective inverted or hemitoroidal shapes depicted in FIGS. 5 and
6. Thus, inasmuch as the fluent substance is substantially
incompressible, the opposing axial forces imposed on the expanded
bag 18 by the spring 104 and upper collar 71 will develop an
increased internal pressure within the bag for producing a
correspondingly greater initial frictional holding force (F.sub.h).
Moreover, of paramount significance, it has been found that once
the bag 18 assumes the generally toroidal configuration, increasing
pressure differentials acting on the bag will further increase the
holding force (F.sub.h) at a faster rate than the rate of increase
of the pressure force (F.sub.p) tending to shift the tool 10.
To demonstrate the new and improved operation of the biasing means
20, a tubular bag 18 of a selected length and diameter that is
appropriate for typical well completion operations was mounted on
the elongated body 19. The bag 18 was disposed inside of a section
of well casing and inflated to a moderate pressure by filling the
bag with a typical fluent, cementitious substance. Once the bag 18
was filled, a pressure differential was imposed across the bag and
progressively increased until longitudinal movement of the bag and
body was noted. The results of this test are illustrated by the
curve 121 in FIG. 7, with slippage of the bag 18 occurring at the
upper end of this curve. It should be noted that during this test
the ends of the bag 18 remained generally hemispherical since there
were no concentrated axial forces being applied to the bag.
The same test was repeated by inflating the bag to the same initial
pressure but with successively increasing, concentrated spring
forces now being applied axially against one end of the expanded
bag 18 while the slidable collar 71 at the other end of the bag was
secured to the body 19. Using the data obtained from these tests,
representative curves such as those depicted at 122--124 in FIG. 7
were plotted to portray the new and improved effects of the axially
directed, opposed forces (F.sub.1, F.sub.2 and F.sub.3) provided by
the spring 104 and the secured collar 71 arranged in accordance
with the principles of the present invention. As a result, it was
discovered that, once the spring 104 was released and the ends of
the bag 18 depressed into their hemitoroidal configuration,
increases in the pressure differential across the expanded bag
progressively increased the holding force (F.sub.h) at a much
faster rate than the holding force obtained where the bag had
hemispherical ends (curve 121). Thus, as illustrated by the curves
122--124, the resulting increased holding forces provided by the
axial biasing spring 104 tend to asymptotically approach the
limiting line 120 and thereby within the limits of the bursting
strength (line 125) provides a safe margin between the resulting
holding force and the point where slippage will occur. Moreover, as
shown by the curves in FIG. 7, a stouter spring (e.g., curve 124)
will develop a correspondingly stronger holding force than a
lighter spring (e.g., curve 122) at the same pressure differential
(.DELTA.P).
It will, therefore, be appreciated that the most effective
operation of the tool 10 is achieved by selecting a spring rate for
the biasing spring 104 that will result in the internal pressure of
the expanded bag 18 approaching the rated bursting pressure of the
bag at about the point that the pressure differential across the
bag is about to cause the tool to slip in relation to the casing
14. In other words, if the spring 104 is too weak (as depicted by
the curve 122), the tool 10 will shift at a relatively low pressure
differential; and if the biasing spring is too stout, the bag 18
will burst at a low pressure differential. The selection of the
spring 104 will, of course, be dependent upon such factors as the
expanded diameter of the bag 18, the bag material, the internal bag
pressure before the biasing spring is released, etc. In any event,
routine tests such as those described above will readily establish
the optimum selection for the spring 104 for any given design of
the tool 10. Thus, as far as the present invention requires, it is
necessary only for the opposed axial forces acting on the opposite
ends of the expanded bag 18 to form the bag into a generally
toroidal configuration. The degree or extent of depression of the
opposite ends of the expanded bag 18 will govern the rate at which
the resulting holding force will increase in response to an
increase in the pressure differential acting across the bag.
Accordingly, it will be appreciated that the present invention has
provided new and improved methods and apparatus for plugging a well
bore with a fluent hardenable substance. By disposing this
substance into an enclosed yieldable container that is expanded
into contact with the walls of a well bore and, in accordance with
the methods of the present invention, imposing an axial force
thereon, upon increased pressure differentials acting across the
container the container will be secured to the well bore walls with
a force that proportionally increases at a rate sufficient to
maintain the container safely anchored against movement. With
apparatus arranged in accordance with the principles of the present
invention, a tubular bag is sealingly mounted around an elongated
body and has one end thereof adapted for longitudinal movement
along the body toward the other fixed end of the bag. Means, such
as a spring or the like, are operatively arranged on the elongated
body for imposing opposing axial forces on the opposite ends of the
bag to reform the bag into a generally toroidal shape once the bag
has been filled with a fluent hardenable substance to expand it
into sealing engagement with the walls of the well bore. In this
manner, the bag and body will be secured in position within a well
bore as the fluent substance hardens and will not be shifted by
pressure differentials acting thereon. Moreover, should the
pressure differential increase sufficiently to burst the bag before
this substance hardens, a tool arranged in accordance with the
present invention will merely fall into the well bore and can be
easily retrieved without having to drill it out as would be the
case if mechanical anchors were used.
While a particular embodiment of the present invention has been
shown and described, it is apparent that changes and modifications
may be made without departing from this invention in its broader
aspects; and, therefore, the aim in the appended claims is to cover
all such changes and modifications as fall within the true spirit
and scope of this invention.
* * * * *