U.S. patent number 3,595,314 [Application Number 05/042,785] was granted by the patent office on 1971-07-27 for apparatus for selectively plugging portions of a perforated zone.
This patent grant is currently assigned to Cities Service Oil Company. Invention is credited to Charles Robert Garner.
United States Patent |
3,595,314 |
Garner |
July 27, 1971 |
APPARATUS FOR SELECTIVELY PLUGGING PORTIONS OF A PERFORATED
ZONE
Abstract
Wellbore apparatus having perforation ball sealers attached
thereto and properly spaced along the length of the tool is
positioned in a perforated wellbore liner. The wellbore apparatus
is positioned so that ball sealers are adjacent to the perforations
through which fluid is not desired. When fluid is pumped down the
wellbore, the ball sealers are forced to enter the desired portion
of the perforated wellbore liner. The apparatus provides a means
for selectively plugging an interval of a perforated wellbore liner
while allowing fluid to flow in other zones of the wellbore.
Inventors: |
Garner; Charles Robert (Tulsa,
OK) |
Assignee: |
Cities Service Oil Company
(N/A)
|
Family
ID: |
21923734 |
Appl.
No.: |
05/042,785 |
Filed: |
June 2, 1970 |
Current U.S.
Class: |
166/192;
166/243 |
Current CPC
Class: |
E21B
43/261 (20130101) |
Current International
Class: |
E21B
43/25 (20060101); E21B 43/26 (20060101); E21b
033/13 () |
Field of
Search: |
;166/100,169,192,193,243 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Claims
Therefore, I Claim:
1. Apparatus for selectively plugging perforated wellbore casing
comprising:
a. a housing having one or more recesses therein;
b. ball sealers contained in one or more of said recesses;
c. flexible members, one end of which is attached to said housing
and the other to said ball sealers;
d. means for containing said ball sealers within and expelling said
ball sealers from said housing; and
e. means for positioning said apparatus in said wellbore.
2. The apparatus of claim 1 in which the means for containing said
ball sealers within and expelling said ball sealers from said
housing comprises:
a. a sleeve surrounding said housing having one or more holes
larger than said ball sealers at the same intervals as the recesses
in said housing;
b. means for compressing said ball sealer in said recess; and
c. means for expelling said ball sealer from said housing.
3. The apparatus of claim 2 in which said means for compressing
said ball sealers in said recesses is a spring, positioned in each
of said recesses between said housing and said ball sealers so as
to compress the ball sealers against said sleeve.
4. The apparatus of claim 3 in which said means for positioning
said apparatus in said wellbore is a cable securely attached to the
upper portion of said sleeve.
5. The apparatus of claim 4 in which the means for expelling said
ball sealer from said housing comprises:
a. a fluid storage chamber in the upper portion of said sleeve;
b. a release chamber within said sleeve below and adjacent to said
storage chamber and above the upper portion of said housing;
c. a reversible hydraulic pump situated between said storage
chamber and said release chamber;
d. means for actuating said hydraulic pump;
e. means for sealing the sleeve from the upper portion of said
housing at a position above the uppermost recess in said housing;
and
f. releasable means for positioning said sleeve such that the holes
therein are normally not aligned with the recesses in said housing
and when said sleeve is released are aligned with the recesses in
said housing.
6. The apparatus of claim 5 in which:
a. said means for sealing the sleeve from the upper portion of said
housing is one or more pressure rings set in races in the housing
and in sealing contact with the inside of said sleeve;
b. said releasable means for positioning said sleeve is a shear pin
having one end thereof attached to the inside of said sleeve and
the opposite end introduced into said housing; and
c. said means for actuating said hydraulic pump is a two-wire line
secured to said hydraulic pump and attached to the cable from the
surface.
7. The apparatus of claim 4 in which the means for expelling said
ball sealer from said housing comprises:
a. a pressurized fluid chamber in the upper portion of said
sleeve;
b. a release chamber within said sleeve below and adjacent to said
pressurized fluid chamber and above the upper portion of said
housing;
c. an electronically activated pressure release valve situated
between said pressurized fluid chamber and said release
chamber;
d. a two-wire line secured to said electronically activated
pressure release valve and attached to the cable from the
surface;
e. means for sealing the sleeve from the upper portion of said
housing at a position above the uppermost recess in said housing;
and
f. releasable means for positioning said sleeve such that the holes
therein are normally not aligned with the recesses in said housing
and when said sleeve is released, are aligned with the recesses in
said housing.
8. The apparatus of claim 4 in which the means for expelling said
ball sealer from said housing comprises:
a. a piston, slideably mounted within the upper portion of said
sleeve;
b. a circular pressure rupture disc the same cross section as the
inner area of the sleeve securely attached to the inner surfaces of
the sleeve below the piston and above the housing so as to form a
piston chamber between the piston and the pressure rupture disc and
a release chamber between the pressure rupture disc and the
housing;
c. the uppermost portion of the sleeve housing having an opening
therein whereby the fluid surrounding the sleeve is in direct
contact with the upper portion of the piston;
d. means for sealing the sleeve from the upper portion of said
housing at a position above the uppermost recess in said housing;
and
e. releasable means for positioning said sleeve such that the holes
therein are normally not aligned with the recesses in said housing
and when said sleeve is released are aligned with the recesses in
said housing.
9. The apparatus of claim 4 in which the means for expelling said
ball sealer from said housing comprises:
a. one or more shear pins positioned at the upper portion of said
housing in a position above the uppermost recess in said
housing;
b. the uppermost portion of the sleeve housing having an opening
therein whereby the fluid surrounding the sleeve is in direct
contact with the upper portion of the housing;
c. means for sealing the sleeve from the upper portion of said
housing at a position above the uppermost recess in said housing
but below the one or more shear pins; and
d. releasable means for positioning said sleeve such that the holes
therein are normally not aligned with the recesses in said housing
and when said sleeve is released are aligned with the recesses in
said housing.
10. The apparatus of claim 1 in which means for containing said
ball sealers within and expelling said ball sealers from said
housing comprises:
a. a pressurized fluid chamber in the upper portion of said
housing;
b. a channel connecting said pressurized fluid chamber and
recesses;
c. a pressure release valve positioned so as to restrict flow of
the pressurized fluid contained within said pressurized fluid
chamber and said channel;
d. means for activating said pressure release valve so is to allow
fluid to flow from said pressurized fluid chamber through said
channel; and
e. the ball sealers are slightly larger than the recesses so as to
be held firmly therein.
Description
BACKGROUND OF THE INVENTION
The present invention encompasses an apparatus for selectively
plugging portions of a perforated zone. More particularly the
apparatus of the present invention utilizes apparatus by which
certain portions of a perforated interval in a wellbore may be
selectively plugged while treatment of other unplugged perforated
intervals is enhanced.
In the treatment of production and injection wellbores such as a
stimulation treatment by acidizing or hydraulic fracturing, the
method generally used is that of forcing the liquid into the
producing formation through the wall of the well. A particular
problem is encountered when a perforated wellbore liner is attached
to the wellbore wall in that acidizing or stimulating technique
will be applied over the entire perforation interval unless
perforations in undesired zones such as a watered out zone or a gas
cap may be selectively plugged. The stimulation treatment may be
confined to the less permeable strata by use of chemical sealing
agents which temporarily seal the more permeable strata before the
acid is applied. By this technique a thin solution of a jelly or
gelatinous-type material may be forced under pump pressure into the
more permeable strata. After a given interval of time, the solution
gels into a semisolid state which seals the strata against invasion
by the stimulation fluid. Many methods have been developed for
displacing the gelatinous material from the wellbore when the given
production or injection interval is commenced. One of the methods
for removing the gelatinous material from the wellbore is to
innoculate the material before introduction with bacteria, which
after a given interval of time consumes the solid parts of the gel
so that it will then assume a liquid state and flow further into
the formation or be produced in the wellbore, whichever the case
may be. Other methods for removing the material after stimulation
involve penetration of the material with a reagent which upon
contacting the gelatinous material precipitates it so that it may
be removed from the wellbore or pushed from the wellbore into the
formation.
Other techniques previously utilized to selectively plug a
perforated wellbore liner involve the use of a plugging agent such
as a rubber covered or solid rubber ball which is pumped down the
well hole during the stimulation treatment to plug off casing
perforations which are receiving undesired amounts of fluid. By
this procedure, the fluid is then diverted to those portions or
zones of the reservoir which are least receptive to the fluid. An
inherent problem in this procedure is that no control is maintained
over which perforated interval of the wellbore liner will receive
the balls and in many instances results in undesired stimulation in
some portions of the reservoir. The balls are released from the
perforations by decreasing the differential pressure in the
wellbore and recovered from the wellbore with the produced fluid or
allowed to fall to the bottom of the well. Methods have been
proposed for recovering the balls from the perforations by
attaching wires thereto so that after the desired stimulation
technique is accomplished, the wires may be removed from the
wellbore thereby removing the attached balls with them.
Another method utilized to selectively plug perforated zones in a
perforated wellbore liner involves the use of several packing
glands which are introduced below and above the perforated zones to
be treated. By this procedure no stimulation fluid is allowed to
enter those perforations below the lowermost packer, whereas the
top packer has a tubing string attached thereto through which
treatment solution is introduced only into that portion of the
perforated zone to be stimulated. Subsequent to the stimulation
technique, the packers may be shifted to another zone in which
stimulation is desired or removed from the well for continuity of
production from or injection into the wellbore.
The problems associated with selectively plugging perforated zones
in a wellbore liner suggest that one must use considerable
equipment in order to selectively plug zones of a wellbore liner.
Generally, the methods involve more than a one-step process for the
treatment of these intervals. What is required is apparatus by
which intervals of a production or injection wellbore liner may be
selectively treated by a single step process and subsequent to the
treatment the perforated wellbore liner may again be opened for
fluid flow therethrough.
It is an object of the present invention to provide apparatus by
which certain zones of a perforated wellbore liner may be
selectively plugged.
It is another object of the present invention to provide apparatus
by which a perforated liner may be selectively plugged and the
unplugged zones of the wellbore liner treated simultaneously.
It is still a further object of the present invention to provide
apparatus by which perforated zones of a perforated wellbore liner
may be selectively treated and subsequently returned to an
unplugged state after treatment.
With these and other objects in mind, the present invention is
hereinafter set forth with reference to the following description
and drawings.
SUMMARY OF THE INVENTION
The objects of the present invention are accomplished by apparatus
comprising a housing having one or more recesses along its length.
Some of the recesses contain ball sealers which are attached to the
housing by a flexible member. The apparatus also contains means for
compressing the ball sealer in said recess. In addition, the
apparatus comprises means for expelling the ball sealers from the
housing and means for positioning said apparatus in said wellbore.
The means for retaining the ball sealers may comprise a sleeve
surrounding the housing having one or more holes larger than the
ball sealers at the same intervals as the recesses in the housing
and springs positioned in the recesses between the housing and the
ball sealers. In most instances the housing and sleeve of the
apparatus will be circular so as to conform with the wellbore into
which it is introduced. The flexible member used to connect the
ball sealer to the housing is generally a length of wire. Suitable
means for positioning the apparatus in the wellbore may comprise a
cable securely attached to the upper portion of the sleeve so that
standard logging techniques may be used to raise or lower the
housing and sleeve in the wellbore.
Appropriate means for expelling the ball sealers from the housing
may also comprise a fluid storage chamber contained in the upper
portion of the sleeve accompanied by a release chamber within the
sleeve below and adjacent to the fluid chamber and above the upper
portion of the housing, and a reversible hydraulic pump situated
between the fluid chamber and the release chamber. Also included
are means for actuating the hydraulic pump, means for sealing the
sleeve from the upper portion of the housing at a position above
the uppermost recess in the housing and flexible means for
positioning the sleeve such that the holes therein are not aligned
with the recessing in the housing.
Another embodiment of the apparatus consists of the means for
expelling the ball sealer from the housing comprising a gas storage
chamber positioned in the upper portion of the sleeve. The release
chamber within said sleeve will be positioned below and adjacent to
the gas chamber and above the upper portion of the housing. An
electronically activated pressure release valve is situated between
the fluid chamber and the release valve. The release valve is
situated between the fluid chamber and the release valve. The
release valve is attached to the cable extending from the surface
which is used to activate the valve. Also provided is a means for
sealing the sleeve from the upper portion of the housing at a
position above the uppermost recess in the housing and releasable
means for positioning the sleeve such that the holes therein are
not aligned with the recesses in the housing. The sleeve may be
eliminated by providing a channel through which fluid may pass
within the housing connected to each recess. The ball sealers are
loaded in the recesses and the means for expelling the ball sealers
provided by a fluid rapidly passed through the channel and out the
recesses.
Still Another apparatus may be used for the means for expelling the
ball sealer from the housing which comprises one or more shear pins
positioned at the upper portion of the housing in a position above
the uppermost recess in the housing. The uppermost portion of the
sleeve has an opening therein whereby the fluid surrounding the
sleeve is in direct contact with the upper portion of the housing.
There are also provided means for sealing the sleeve from the upper
portion of the housing at a position above the uppermost recess in
the housing but below the shear pins applied to the sleeve and
housing and releasable means for positioning the sleeve such that
the holes therein are not aligned with the recesses in the
housing.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is hereinafter described in further detail
with particular reference to the accompanying drawings in
which:
FIG. 1 depicts a wellbore perforation plugging apparatus activated
by a hydraulic pump:
FIG. 2 represents a piston and rupture disc activated wellbore
perforation plugging apparatus:
FIG. 3 illustrates a wellbore perforation plugging apparatus using
shear pins for means for expelling the ball sealers; and
FIG. 4 shows a wellbore perforation plugging apparatus which
utilizes a pressurized fluid to expell the ball sealers towards the
perforated liner.
DETAILED DESCRIPTION OF THE INVENTION
Many methods and apparatus have been proposed for the selective
plugging of perforations in wellbore liners. All of the methods,
however, suffer from the fact that exact perforation plugging of
different perforated intervals is difficult. Many methods merely
teach the introduction of perforation balls into the well followed
by treatment fluid. By this random introduction method the balls
seek the path of least resistance and proceed to those perforations
through which the greatest quantity of fluid is flowing. Therefore,
the ball sealers do not always selectively plug the area of the
wellbore which is desired. The present invention, however, provides
an apparatus for selectively plugging distinct perforated zones of
a wellbore and also leaves the zones for which treatment is desired
unplugged.
The perforation plugging apparatus consists of a housing having
selective recesses at intervals along its length. The housing is
circular and made somewhat smaller in diameter than the diameter of
the wellbore to be treated. Ball sealers are set in selected
recesses and loaded so that they may be released from the apparatus
when desired. The ball sealers are further attached to the
apparatus by a length of wire so that when the apparatus is removed
from the perforated zone the ball sealers are retrieved from the
perforated liner. Means are provided for expelling the ball sealers
so that the ball sealers are shot towards the wellbore liner and
seek the perforations therein.
Referring to FIG. 1, a wellbore perforation plugging apparatus is
depicted consisting of a housing 101, which is circular and of a
diameter slightly smaller than that of the wellbore. Generally, the
diameter of the housing will be 2 to 3 inches smaller than that of
the wellbore casing. The housing is of sufficient length to allow
treatment of the total perforated zone which is to be treated. The
housing 101 has recesses 102 located at intervals along its length
commonly used for perforating wellbore liners. Each of the recesses
102 may contain a ball sealer 104 which is spring loaded by a
spring 103 if plugging at that interval is desired. The recesses
have an upward indentation 105 in which a wire 106 is contained
which is attached to the ball sealer 104 and welded to the circular
housing 101 by weld 107. Therefore, when the ball sealer 104 is
released by the spring 103, it is forced out of recess 102 towards
the perforation in the wellbore but is restricted from falling to
the bottom of the well by wire 106 and also retrieved by the wire
106 when the apparatus is removed from the wellbore. The ball
sealers 104 are positioned and compressed by sleeve 108. The sleeve
108 contains holes 100 within its body slightly larger than the
recesses 102 so that as the holes 100 are positioned over the
recesses 102 the ball sealers 104 are ejected. The sleeve is
secured by shear pin 110 in a position such that the holes 100 are
slightly below each of the recesses 102 in the housing 101. The
shear pin 110 is securely attached to the inside of the sleeve 108
and penetrates into the housing 101 and is of such shear strength
that a nominal amount of pressure on the housing 101 will break the
shear pin 110 and allow the chamber 101 to move downwardly within
sleeve 108.
The means for engaging the sleeve 108 consists of a two chamber
compartment located in the sleeve 108 at the top of the housing
101. A first fluid chamber 114 is located in the uppermost part of
the sleeve 108 into which hydraulic fluid is introduced. The fluid
chamber 114 is separated from the top of the housing 101 by
structural member 115 which is a circular plate welded to the walls
of the sleeve 108 so as to form a release chamber 112 above the
housing 101. Secured to the structural member 115 is a hydraulic
pump 113 which has a reversible mechanism so that fluid may be
transferred from fluid chamber 114 to the release chamber 112 and
vice versa. The hydraulic pump 113 has an electrical drive which
receives its current from two-wire electrical line 118 which is
secured to cable 116 which extends to the surface with the opposite
end attached to the hydraulic pump 112. Cable 116 is a typical
logging cable which is secured to wellbore connector 117. The
connection to wellbore connector 117 is a fluid tight connection so
that no wellbore fluid may enter the wellbore perforation plugging
apparatus. Release chamber 112 is protected from invasion of
wellbore fluids by sealing with O-ring seals 119 and 120 in their
respective races positioned in the upper portion of housing 101.
O-rings 119 and 120 are of sufficient size so as to be mounted
flush with the inside portion of the sleeve 108. Therefore, the
entire housing 101 acts as a piston within the sleeve 108.
In the operation of the wellbore perforation plugging tool the
hydraulic pump 113 is activated by introduction of electric current
through the two-wire line 118 secured to cable 116. This activation
transports hydraulic fluid from fluid chamber 114 through
structural member 115 into release chamber 112. The introduction of
fluid into release chamber 112 drives the entire housing downward
with slippage of O-rings 119 and 120 along the inside of the sleeve
108. This downward movement breaks the shear pin 110 and allows the
housing 101 to touch the bottom of the sleeve 111. In this downward
position the holes in sleeve 108 align themselves with the recesses
102 in the housing 101 to touch that the ball sealers 104 are
expelled by the compression release of spring 103 and are projected
towards the perforations 122 in the wellbore casing 121. Subsequent
to plugging of the desired perforations 122, wellbore treatment is
begun. After the formation has been treated the apparatus 110 is
removed from the wellbore and the ball sealers 104 are retrieved
from the perforations 122 as they are connected by wire 106 to the
housing 101. The apparatus 110 is brought to the surface and
reloaded by replacing ball sealers 104 in the respective recesses
102 in the housing 101 by compressing spring 103 and replacing the
sleeve 108 into its original position with the recesses closed to
the outside environment. The shear pin 110 is placed in the housing
101 and the hydraulic fluid evacuated by reversal of the hydraulic
pump 113 and retransporting of the hydraulic fluid from release
chamber 112 to fluid chamber 114. The apparatus 110 is then readied
for another introduction into the wellbore. When loading the
apparatus 110 some intervals of the wellbore casing may not be
desired to be plugged. These intervals may be left unplugged by not
loading the ball sealer 104 in the respective recesses 102 such as
depicted by recess 109 which does not contain a ball sealer.
Therefore, as the ball sealers are released the respective
intervals along the tool will not be selectively plugged and left
open for treatment.
FIG. 2 depicts wellbore perforation apparatus which utilizes the
hydrostatic pressure of a fluid introduced in the well to
manipulate the sleeve into the position such that the ball sealers
are released. The sleeve 208 is positioned in the same manner about
the housing 201 as previously discussed above. The upper portion of
the wellbore tool is sealed by O-rings 219 and 220 as in the
previous invention embodiment. No external mechanism is required to
actuate the sleeve 208 when the apparatus reaches the perforated
zone at which plugging is desired. The sleeve 208 is actuated by
movement of the piston 223 which is sealed against the inside wall
of the sleeve 208 by O-rings 224 and 225. In normal loading, the
piston 223 is positioned in the upper portion of the sleeve 208 to
form a fluid cavity 214 containing a hydraulic fluid resting upon a
rupture disc 222. This rupture disc 222 is manufactured such that
at a specified pressure it will break and allow hydraulic fluid
from fluid chamber 214 to enter release chamber 212 which is formed
by the space between the rupture disc 222 and the top of the
housing 201. There is a cavity above the piston 221 which is in
direct contact with the wellbore fluid through opening 226 in
sleeve 208.
The tool is lowered by cable 216 attached to wellbore connector
217. When the tool is positioned in the appropriate portion of the
wellbore so that the ball sealers are directly opposite those
perforations to be plugged, fluid is pumped into the wellbore at
sufficient pressure so that the fluid enters the sleeve 208 through
opening 206, fills chamber 221 and drives piston 223 downward
against hydraulic fluid 214. As the piston moves in the downward
position the hydraulic fluid 214 develops sufficient pressure so
that rupture disc 222 breaks and allows fluid to enter release
chamber 212 and thereby drives the housing 201 into the position at
which the openings in the sleeve are adjacent to the ball sealers.
The ball sealers are released so as to selectively plug the
perforations in the wellbore casing. In the use of this invention
embodiment no external apparatus is required with the wellbore
liner perforations being plugged simultaneously with fluid
injection.
FIG. 3 depicts another embodiment of the present invention in which
the housing 301 is secured and sealed from the chamber 321 and
direct contact with wellbore fluid by means of O-rings 324 and 325.
The entire housing 301 then acts as a piston slideably mounted
within sleeve 308. There is also an opening 326 in the top of
sleeve 308 through which wellbore fluid may contact chamber 321 and
the top of housing 301. The tool is similarly fastened to cable 316
at tool connector 317 and lowered into the well. As fluid is
injected into the well the O-rings 324 and 325 hold the housing 301
stationary until sufficient pressure is built up and the shear pin
310 breaks and allows housing 301 to slide downwardly. Therefore,
with a surge of wellbore fluid injection the housing 301 is driven
downward and the holes in the sleeve 308 are aligned with the ball
sealers so as to release the ball sealers and allow perforation
plugging of the wellbore liner as desired.
The sleeve may be entirely removed by use of an apparatus of the
type shown in FIG. 4. Housing 401 contains recesses 402 as
previously described and containing ball sealers 404 slightly
larger than said recesses 402 so as to be held tightly within the
recesses, connected by wire 406, welded to housing 401 by spot weld
407. The housing 401 also contains a pressurized fluid chamber 421
which contains a pressurized fluid. Channel 423 connects
pressurized fluid chamber 421 with recesses 402. An electrically
activated pressure release valve 422 is axially positioned between
pressurized fluid chamber 421 and pressurized fluid channel 423 and
activated from the surface by two-wire line 418 secured to cable
416, passing through connector 417 and connected to pressure
release valve 422. When plugging is desired and the apparatus is
properly positioned, the pressure release valve is opened by an
electric impulse through two-wire line 418. The pressurized fluid
contained within pressurized fluid chamber 421 is released through
channel 423 so as to expell ball sealers 404 from the apparatus.
The apparatus and ball sealers are retrieved as described
previously. The pressurized fluid chamber 423 is refilled through
fluid fill valve 424.
The wellbore perforation plugging apparatus may be comprised of
standard wellbore tool materials. Generally, high grade stainless
steel or other noncorrosive metals are used for the construction of
the sleeve and housing mechanisms. Standard O-rings may be used as
sealing means and generally those of the neoprene or Teflon variety
are applicable. The ball sealers most often will consist of a
rubberlike or resilient material normally consisting of butadiene
or neoprene rubber which is noncorrosive in the wellbore elements
and through which a wire generally made of stainless steel or
another noncorrosive high strength material may be attached. Normal
springs for the spring loaders may be used but should be of
sufficient material to give lasting life, resiliency and
noncorrosiveness. In the embodiment of the invention utilizing a
hydraulic pump any standard oil or hydraulic fluid may be used for
pressuring the housing and allowing the piston type motion.
Standard wellbore cables and connectors are also used for the
tool.
The present invention provides an apparatus with which perforations
in a wellbore liner may be selectively plugged so that the wellbore
may be hydraulically fractured in preferential zones, stimulated
through preferential zones, or treated in other manners such as
selective plugging, etc. and thereby allow the wellbore after
treatment to be returned to its original perforated sequence.
While the invention has been described herein with respect to
particular embodiments and thereof, it will be appreciated by those
skilled in the art that various changes and modifications may be
made, however, without departing from the scope of the
invention.
* * * * *