U.S. patent number 3,627,049 [Application Number 05/043,068] was granted by the patent office on 1971-12-14 for methods and apparatus for completing production wells.
This patent grant is currently assigned to Schlumberger Technology Corporation. Invention is credited to David E. Young.
United States Patent |
3,627,049 |
Young |
December 14, 1971 |
METHODS AND APPARATUS FOR COMPLETING PRODUCTION WELLS
Abstract
This application discloses new and improved methods and
apparatus for completing production wells having perforations which
either are to be cleaned or penetrate earth formations which are to
be fractured, acidized, or treated such as, for example, to inhibit
the subsequent production of unconsolidated formation materials. To
practice the present invention, a new and improved production tool
is arranged for coupling into a string of production tubing and
includes a typical well packer coupled to an elongated tubular
member defining an enclosed chamber of a substantial volume and
which is initially maintained at a reduced pressure by new and
improved normally closed pressure-actuated valves arranged at the
opposite ends of the tubular member and adapted to be selectively
opened in succession. The production string and the tool are
installed in a cased well bore with the packer being set above a
previously perforated interval traversing an earth formation which
is to be subsequently produced. Once the customary wellhead
equipment is installed to provide selective communication from the
surface with the tubing and casing, the first of the two normally
closed valves is selectively opened by increasing the pressure of
the well bore fluids in the annulus above the packer. Upon opening
of this first valve, formation fluids will be suddenly exhausted
into the reduced-pressure chamber for removing contaminants that
may have previously entered the formation following the perforation
of the casing so as to leave only uncontaminated formation
materials immediately surrounding the perforations. Thereafter, the
second normally closed valve is selectively opened by injecting
selected fluids by way of the production string through the
perforations and into the adjacent earth formations.
Inventors: |
Young; David E. (Houston,
TX) |
Assignee: |
Schlumberger Technology
Corporation (New York, NY)
|
Family
ID: |
21925306 |
Appl.
No.: |
05/043,068 |
Filed: |
June 3, 1970 |
Current U.S.
Class: |
166/374; 251/347;
166/321 |
Current CPC
Class: |
E21B
43/025 (20130101); E21B 37/08 (20130101); E21B
41/00 (20130101) |
Current International
Class: |
E21B
43/02 (20060101); E21B 37/00 (20060101); E21B
41/00 (20060101); E21B 37/08 (20060101); E21b
043/00 () |
Field of
Search: |
;166/72,224,226,314,315
;251/343,344,347 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: McGlynn; Joseph H.
Claims
What is claimed is:
1. A method for preparing a well for production of connate fluids
from a well bore having a perforated interval with one or more
perforations traversing earth formations and comprising the steps
of: coupling upper and lower pressure-actuated normally closed
valves at spaced positions in a string of production piping having
a packer coupled thereto for defining an enclosed chamber in said
production string between said upper and lower valves which is
initially at a pressure less than the expected pressure of said
connate fluids so long as said upper and lower valves remain
closed; lowering said production string into said well bore and
setting said packer therein above said perforated interval for
isolating said perforated interval from the remainder of said well
bore thereabove; coupling the upper end of said production string
to a wellhead for securing said production string in said well bore
and providing selective communication from the surface into said
production string above said upper pressure-actuated valve and from
the surface into the well annulus exterior of said lower
pressure-actuated valve and above said packer; varying the pressure
in said well annulus to selectively open said lower
pressure-actuated valve and draw said connate fluids into said
chamber for expurgating said perforations; and, thereafter, varying
the pressure in said production string for selectively opening said
upper pressure-actuated valve to establish communication through
said production string between said wellhead and said perforated
interval.
2. The method of claim 1 wherein at least the last of the latter
two steps is not performed until shortly before production is to be
commenced from the well.
3. The method of claim 1 wherein said packer is dependently coupled
to said lower valve.
4. The method of claim 1 wherein said lower pressure-actuated valve
is opened by increasing the pressure in said well annulus.
5. The method of claim 4 wherein said upper pressure-actuated valve
is opened by increasing the pressure in said well annulus.
6. The method of claim 5 wherein said upper pressure-actuated valve
is not opened until production is about to be commenced from the
well.
7. The method of claim 1 wherein said upper pressure-actuated valve
is opened by increasing the pressure in said production string.
8. Apparatus adapted for producing connate fluids from earth
formations traversed by a well bore and comprising: a production
string positioned in said well bore between the surface and a
perforated interval of said well bore having one or more
perforations directed into earth formations adjacent thereto; means
adapted for supporting said production string in said well bore and
including a wellhead coupled to the upper end of said production
string and operatively arranged for selectively controlling fluid
communication from the surface with said production string as well
as with the well annulus exterior of said production string; first
normally closed valve means coupled in said production string and
operatively arranged for opening in response to changes in the
pressure therein; second normally closed valve means operatively
arranged for opening in response to changes in the pressure in said
well annulus and coupled below said first valve means in said
production string for defining an enclosed chamber therein so long
as said first and second valve means remain closed; and a well
packer coupled in said production string below said second valve
means and operatively arranged for packing-off said well bore above
said perforated interval.
9. The apparatus of claim 8 wherein said first valve means are
selectively opened only in response to increases of the pressure in
said production string thereabove to at least a predetermined
pressure.
10. The apparatus of claim 8 wherein said first valve means include
a valve member movable from a first position blocking fluid
communication between said production string to a second position
opening communication therebetween, and a pressure-responsive
actuator operatively arranged for selectively moving said valve
member to its said second position upon an increase of the pressure
in said production string to at least a predetermined pressure.
11. The apparatus of claim 10 wherein said first valve means
further include latching means operatively arranged thereon for
releasably retaining said valve member in its said first position
until said pressure-responsive actuator is operated.
12. The apparatus of claim 8 wherein said second valve means are
selectively opened only in response to increases of the pressure in
said well annulus to at least a predetermined pressure.
13. The apparatus of claim 8 wherein said second valve means
include a valve member movable between a normally closed position
to an open position; and a pressure-responsive actuator operatively
arranged in relation to said valve member for selectively moving
said valve member to its said open position upon increases of the
pressure in said well annulus to at least a predetermined
pressure.
14. The apparatus of claim 13 wherein said second valve means
further include latching means operatively arranged thereon for
retaining said valve member in its said open position once said
valve member is moved thereto.
15. Apparatus adapted to be used in a well bore having at least one
perforated interval traversing earth formations from which connate
fluids are to be produced and transported to the surface through a
string of production piping supported in the well bore by a
wellhead operatively arranged at the surface for selectively
controlling communication to the production piping and the well
annulus exterior thereof, said apparatus comprising: an elongated
body having a longitudinal bore defining a chamber between the
upper and lower ends of said body; first valve means coupled to
said upper end of said body and adapted for normally blocking fluid
communication between said chamber and a string of production
piping coupled thereabove; first pressure-responsive actuating
means operatively associated with said first valve means and
adapted for opening said first valve means only upon an increase of
fluid pressure within a string of production piping coupled to said
first valve means; second valve means coupled to said lower end of
said body and adapted for normally blocking fluid communication
between said chamber and a production packer dependently coupled
therebelow; and second pressure-responsove actuating means
operatively associated with said second valve means and adapted for
opening said second valve means only upon an increase of fluid
pressure in the well annulus exterior thereof and above a
production packer therebelow.
16. Apparatus adapted to be used in a well bore having at least one
perforated interval traversing earth formations from which connate
fluids are to be produced and transported to the surface through a
string of production piping supported in the well bore by a
wellhead operatively arranged at the surface for selectively
controlling communication to the production piping and the well
annulus exterior thereof, said apparatus comprising: first valve
means including a first tubular body adapted to be dependently
coupled to the lower end of such a string of production piping, a
fluid barrier sealingly engaged within said first tubular body and
adapted for downward movement therefrom to open communication
through said first tubular body, a pressure-responsive actuator
operatively arranged on said first tubular body for movement
relative thereto between first and second positions, latching means
operatively arranged between said actuator and said fluid barrier
for retaining said fluid barrier within said first tubular body
only so long as said actuator is in its said first position, and
passage means on said first tubular body and adapted for
communicating pressure therein above said fluid barrier to said
actuator to shift said actuator to its said second position for
releasing said latch means from said fluid barrier so that said
fluid barrier can be moved downwardly from said first tubular body
upon an increase of pressure in a production string coupled to said
first tubular body; a tubular member dependently coupled to said
first tubular body and having an internal bore adapted to receive
said fluid barrier upon its release from said first tubular body;
and second valve means including a second tubular body dependently
coupled to said tubular member and adapted for coupling to a
production packer therebelow for packing-off a perforated interval
of a well bore, a transverse barrier arranged within said second
tubular body for blocking fluid communication therethrough, upper
and lower fluid ports in said second tubular body above and below
said transverse barrier, a valve member operatively arranged on
said second tubular body and adapted for movement relative thereto
between a first position blocking fluid communication between said
fluid ports and a second position establishing fluid communication
therebetween, and pressure-responsive actuating means operatively
arranged on said second tubular body for moving said valve member
to its said second position only upon an increase of the pressure
in the well annulus.
17. A valve adapted for coupling to a string of production piping
supported in a well bore traversing earth formations and
comprising: a tubular body having a longitudinal bore therethrough;
a fluid barrier sealingly arranged in said longitudinal bore and
adapted for downward movement therefrom; actuating means slidably
mounted on said tubular body and adapted for movement relative
thereto between first and second spaced positions; means on said
tubular body defining a piston chamber; piston means operatively
disposed in said piston chamber and adapted for moving said
actuating means from said first position to said second position in
response to a pressure variation in said piston chamber; latch
means operatively arranged on said tubular body between said
actuating means and said fluid barrier and adapted for releasably
securing said fluid barrier within said longitudinal bore until
said actuating means move from said first position to said second
position; and passage means arranged between said piston chamber
and said longitudinal bore above said fluid barrier and adapted for
communicating pressure variations in a string of production piping
coupled to said tubular body to said piston means.
18. The valve of claim 17 further including means operable upon
movement of said actuating means to said second position for
securing said actuating means in said second position.
19. A valve adapted for coupling to a string of production piping
supported in a well bore traversing earth formations and
comprising: a tubular body having a longitudinal bore therethrough;
a fluid barrier arranged within said tubular body for blocking
fluid communication through said longitudinal bore; upper and lower
fluid ports in said tubular body above and below said fluid
barrier; a tubular valve member telescopically arranged on said
tubular body and adapted for movement relative thereto between a
first position blocking fluid communication between said fluid
ports and a second position establishing fluid communication
therebetween; means on said tubular body defining an annular piston
chamber around said lower fluid ports; sealing means arranged on
said valve member and operatively disposed within said piston
chamber for isolating said lower fluid ports from the exterior of
said tubular body so that pressures exterior of said tubular body
will be imposed on said valve member for urging said valve member
toward its said second position; and means releasably securing said
valve member against movement to its said second position until the
pressures imposed on said valve member exceed a predetermined
value.
20. The valve of claim 19 wherein said fluid barrier is movably
disposed in said longitudinal bore, and further including means
releasably securing said fluid barrier in said tubular body and
adapted to release said fluid barrier upon application of a
predetermined force on said fluid barrier.
21. The valve of claim 19 further including means operable upon
movement of said valve member to its said second position for
securing said valve member in its said second position.
Description
It is, of course, customary for a cased well bore to be perforated
at one or more points to provide fluid communication with selected
earth formations therearound. Once the well is perforated, various
treating operations-- such as acidizing, fracturing, or
sand-consolidating operations-- are typically conducted to prepare
the well for efficient production. Those skilled in the art will
appreciate, however, that it is not at all uncommon for one or more
of the perforations along a given perforated interval to be at
least partially blocked by loose formation materials, debris, or
foreign matter which is usually deposited in a perforation by
typical shaped charges. A partial or total blockage of one or more
of the perforations will, of course, impede or prohibit the
introduction of treating fluids into those perforations and result
in the inadequate treatment of at least those portions of the earth
formation immediately adjacent thereto. As a result, further and
otherwise needless treating operations will ultimately be required.
Accordingly, unless all of the perforations along a perforated
interval are capable of readily conducting fluids, subsequent
treating operations as well as the production rate of the well will
be significantly impaired.
Heretofore, such treating operations have had to be conducted
before the drilling rig is removed from the well site so that its
associated equipment and drill string could be employed. This, of
course, results in needless expenses as well as additional delays
before the production string and the related surface equipment can
be installed to prepare the well for production.
Accordingly, it is an object of the present invention to provide a
new and improved methods and apparatus for completing wells to
obtain improved fluid communication between the well bore and
selected earth formations traversed thereby without delaying the
installation of the production string and the associated wellhead
and surface equipment once the drilling operation is concluded.
This and other objects of the present invention are attained by
tandemly arranging upper and lower pressure-actuated valve means at
spaced intervals in a production string including a production
packer. The upper and lower valve means are initially closed to
define an enclosed chamber of selected volume in the
interconnecting tubing therebetween which is maintained at a
reduced pressure until after the packer is set and the production
string is installed and connected to the usual wellhead and surface
equipment. When the well is to be prepared for production, the
lower valve means are selectively opened from the surface to draw
formation fluids into the enclosed chamber for clearing the
perforations below the production packer of debris or contaminants
that would otherwise impair fluid communication between the
production string and the perforated earth formations. Thereafter,
the upper valve means are selectively opened for injecting fluids
from the surface into the well bore below the packer as may be
necessary to prepare the well for production.
In the preferred embodiment of the apparatus of the present
invention, the lower valve means are operatively arranged to be
selectively opened in response to a predetermined change in the
pressure in the well annulus above the production packer. In this
manner, communication can be selectively established between the
perforated interval and the enclosed chamber below the upper valve
means thereabove. Similarly, in the preferred embodiment of the
apparatus of the present invention, the upper valve means are
operatively arranged and adapted to be selectively opened in
response to a predetermined change in the pressure in the
production string above the upper valve means for establishing
communication between the production string and the perforated
interval of the well bore below the packer.
The novel features of the present invention are set forth with
particularity in the appended claims.
The invention, together with further objects and advantages
thereof, may be best understood by way of the following description
of new and improved apparatus and exemplary methods employing the
principles of the invention as illustrated in the accompanying
drawings, in which:
FIG. 1, 3 and 5 schematically depict the successive steps of the
methods of the present invention;
FIG. 2, 4 and 6 respectively show a typical perforation as it may
appear during the course of a completion operation being conducted
in accordance with the methods of the present invention; and
FIG. 7-10 depict preferred embodiments of the new and improved
apparatus of the present invention.
Turning now to FIG. 1, a new and improved production tool 20
arranged in accordance with the principles of the present invention
is schematically illustrated as being dependently coupled from the
lower end of a string of production tubing 21 and positioned in a
well bore 22 having a casing 23 secured in place by an external
sheath of cement 24. To gain communication with an earth formation
25 traversed by the well bore 22, one of more perforations, as at
26, have been previously produced through the casing 23 and cement
24 in the usual manner. As is customary, the production tubing is
dependently supported in the well bore 22 by a typical wellhead
assembly 27 including at least a pair of valves, as at 28 and 29,
for selectively controlling communication with the tubing string 21
and casing 23.
As illustrated in FIG. 1, the tool 20 is comprised of a selectively
settable production packer 30 which is dependently coupled to the
lower end of a tubular body 31 to provide an enclosed chamber 32
that is initially maintained at a low or atmospheric pressure by
arranging normally closed valve means 33 and 34 at the upper and
lower ends of the body which are respectively adapted to be
selectively opened independently of one another. As a matter of
convenience, it is, of course, preferred to employ one or more
joints of conventional production tubing for the elongated body 31.
The chamber 32 can, if desired, be filled with an inert gas that is
at a selected pressure which is less than the anticipated formation
pressure. Although other well packers may, of course, be employed,
it is preferred that the packer 30 be one of the production packers
shown in either U.S. Pat. No. 3,074,484 or 3,352,362.
As will be subsequently discussed, the methods of the present
invention are uniquely applicable for performing acidizing and
fracturing operations as well as sand-consolidation operations
after the production string 21 and wellhead 27 are in position.
However, for purposes of illustration, FIGS. 2-6 depict the
practice of the methods of the present invention as it might be
conducted for a sand-consolidation operation. Accordingly, as
depicted in FIG. 2, an enlarged view is shown of one of the
perforations 26 as it may well appear where the adjacent formation
25 is substantially unconsolidated or incompetent.
It will, of course, be appreciated that when a perforating tool
(not shown) which typically includes one or more shaped charges is
positioned in the well bore 22 and actuated for producing the
perforations 26, the perforations will initially extend into the
incompetent formation 25 as generally represented in FIG. 2. It is
believed, however, by those skilled in the art that the perforation
26 will quickly fill up with loose materials from the incompetent
formation 25 leaving open only a passage or so-called "tunnel" 35
extending through the casing 23 and the adjacent cement sheath
24.
In any event, irrespective of the nature of the formation, debris
(such as at 36) will be left in the formation 25 as a result of the
disintegration of a typical shaped charge liner. Moreover, by
observing test shots fired into laboratory targets, it is known
that a typical shaped charge perforating jet will leave a
somewhat-impermeable layer of debris (as indicated at 37) around
the walls of the forward portion of the perforation 26. This
relatively impermeable sheath of debris will either remain
substantially in the position illustrated at 37; or, if the
formation (as at 25) is incompetent, this impermeable layer will
most likely be collapsed inwardly as the forward portion of the
perforation 26 is filled with loose formation materials. In any
event, flow communication between the entrance tunnel 35 and the
formation 25 will be at least retarded, if not substantially
impaired, by the debris 36 and 37 deposited in the formation just
outside of the tunnel. It is, therefore, this debris 36 and 37
which, irrespective of the competency of the formation 25, must be
removed before the well bore 22 can be successfully completed and
production commenced.
Accordingly, as illustrated in FIG. 3, after the packer 30 has been
set for isolating the interval of the well bore 22 immediately
adjacent to the perforations 26 from the remainder of the well bore
thereabove and the wellhead 27 is in position, the lower valve 34
is opened. It will be appreciated, therefore, that upon opening of
the lower valve 34, a sudden high-pressure differential is
developed between the connate fluids in the formation 25 and the
enclosed chamber 32 which, preferably, is initially at atmospheric
pressure. This sudden pressure differential across the perforated
well bore interval will induce a rapid, high-velocity flow of
connate fluids, as at 38, from the formation 25 through the various
entrance tunnels 35 and into the empty chamber 32. These rushing
fluids will, therefore, effectively wash out the debris, as at 36
and 37 (FIG. 2), along with a limited quantity of loose formation
materials through the several tunnels 35. As a result, as shown in
FIG. 4, once this sudden flow ceases upon the filling of the
chamber 32, the formation 25 surrounding the perforations 26 will
be effectively cleaned leaving only clean formation particles, as
at 39, partially or totally filling the tunnels 35 through the
casing 23 and cement 24.
It will be recognized, of course, that with even these clean
formation particles, as at 39, in the entrance passages 35, the
subsequent injection of consolidating agents or the production of
connate fluids from the formation 25 will be materially limited. It
is, therefore, one of the paramount objects of the present
invention to remove these loosened particles 39 from the tunnels 35
before further completion operations are conducted.
Accordingly, to accomplish this, a clean fluid, as at 40 in FIG. 5,
is admitted to the production string 21 by way of the wellhead
valve 28; and, by opening the upper valve 33, suddenly introduced
into the previously closed chamber 32 to produce a sudden shock or
transitory pressure surge in the isolated interval of the well bore
22 below the packer 30 for driving the clean sand particles 39 back
into the formation 25 and clearing the tunnels 35 as illustrated in
FIG. 6.
It will, of course, be appreciated that although the chamber 32 may
be completely filled with the connate fluids 38 upon opening of the
lower valve 34, these fluids as well as those in the isolated
portion of the well bore 22 below the packer 30 will be at a
pressure no greater than the natural formation pressure of the
earth formation 25. Accordingly, by rapidly opening the upper valve
33, the injection fluid 40 will be suddenly moved downwardly into
the chamber 32 and develop significant dynamic shock pressures
which are substantially greater than the formation pressure of the
well fluids within the isolated portion of the well bore 22 below
the packer 30. Thus, as previously noted, the sudden release of the
injection fluid 40 into the chamber 32 will be effective for
forcibly driving the sand particles 39 out of the several tunnels
35 and back into the surrounding formation 25. It will, of course,
be appreciated that once these transitory shock pressures have
subsided, the injection fluid 40 is maintained at an elevated
pressure which will be sufficient for preventing the production of
further connate fluids through the several perforations 26 so that
additional sand particles will not reenter the several tunnels
35.
Where the formation 25 does not require a consolidation operation,
the injection fluid 40 needs only to be a suitable fluid such as a
clean saline solution. By properly selecting a saline solution of
sufficient density, the resulting hydrostatic pressure of the
injection fluid 40 will alone be effective for retaining control of
the well until production is commenced.
On the other hand, where the earth formation 25 is to be
consolidated by typical sand-consolidating agents, it is generally
preferred that the injection fluid 40 be a so-called "preflush
fluid" such as kerosene, diesel oil, or a clean saline solution.
This injection fluid 40 is maintained at an elevated pressure
before the upper valve 33 is opened; and once the pressured
preflush fluid 40 is pumped into the formation 25, one or more
consolidating agents (not shown) are successively pumped through
the tubing string 21 and into the formation to accomplish the
desired consolidation. As is typical, if production is not to be
commenced immediately, the consolidating fluids may then be
followed by a suitable after-flush agent, such as kerosene, as well
as in some instances, temporary plugging agents such as "Black
Magic" an oil-base mud as supplied by Oil Base, Inc., of Houston,
Tex. It will be recognized that the hydrostatic pressure and the
pumping pressure of these successively injected treating fluids
will be greater than the formation pressure of the formation 25 so
that the tunnels 35 will remain open throughout the consolidation
operation. The particular nature or type of the sand-consolidation
agents employed are, of course, of no significance to the present
invention and the consolidating agents may be either porous-setting
or solid-setting plastics.
As previously mentioned, the methods of the present invention are
also equally applicable for acidizing or hydraulic fracturing
operations after the wellhead 27 and the production string 21 are
in position. Accordingly, where the formation 25 is to be either
acidized or fractured, the treating fluid 40 will, of course, be
the fluid or fluids which are typically employed for such
operations. Otherwise, the sequence of events will be substantially
as depicted in FIGS. 1-6 with the possible exception that the
formation 25 may be sufficiently competent that there will be
little or no loose formation materials, as at 39, drawn into the
tunnels 35 as the debris 36 and 37 is cleared from the perforations
26. In either situation, however, those skilled in the art will
appreciate that the new and improved methods of the present
invention will be of significant benefit for economically
conducting either an acidizing operation or a hydraulic fracturing
operation.
Of particular significance, it should be recognized that by
employing the methods of the present invention to commence either
an acidizing operation or a fracturing operation, the dynamic shock
or surge pressures that are developed when the treating fluid 40 is
suddenly released upon opening of the upper valve 33 will be of
material benefit in commencing the operation. This sudden surge or
pressure shock will, therefore, be particularly useful in "breaking
down" the formation 25 to assure that the treating fluid 40 is
entering all of the perforations 26. As a further benefit, it has
been found that the pumping pressures required to continue movement
of the treating fluid 40 into the formation 25 will be
significantly reduced in comparison to the pumping pressures
normally required for conducting acidizing or fracturing operations
as heretofore conducted before the present invention.
It should be noted that where the methods of the present invention
are used for sand-consolidating operations, a sufficient pressure
surge or shock will usually be developed even where the chamber 32
is completely filled before the upper valve 33 is opened. On the
other hand, where an acidizing operation or fracturing operation is
being conducted in accordance with the methods of the present
invention, it has been found that greatly enhanced surge or shock
pressures will be obtained by arranging the interconnecting tubing
31 to have a volumetric capacity (i.e., the chamber 32) that is
greater than the anticipated volume of the connate fluids 38 that
will enter the chamber during the predetermined time interval
before opening the upper valve 33. In this manner, the upper
portion of the chamber 32 will be empty when the upper valve 33 is
opened; and the sudden entrance of the treating fluid 40 into the
still-empty upper portion of the chamber will produce a
corresponding substantial imploding force which in turn develops
the greatly enhanced shock forces referred to above.
Turning now to FIGS. 7 and 8, a preferred embodiment is shown of
the lower valve 34 which is particularly adapted for practicing the
methods of the present invention. As best seen in FIG. 7, the valve
34 includes a tubular body 41 having threads 42 and 43 respectively
arranged on its upper and lower ends and suitably adapted for
tandemly coupling the valve between the packer 30 and the
interconnecting tubing 31. In the preferred embodiment of the valve
34, a transverse barrier 44 is arranged across the axial bore 45 of
the valve body 41 and, for reasons that will subsequently be
explained, releasably coupled to the valve body by means such as a
lateral pin 46 having a predetermined strength. A sealing member,
such as an O-ring 47 arranged around the barrier 44, fluidly seals
the barrier in relation to the valve body 41 to block fluid
communication through the axial bore 45.
To provide selective fluid communication through the axial bore 45
when the barrier 44 is positioned therein, longitudinally spaced
lateral ports 48 and 49 are provided in the valve body 41 above and
below the barrier; and an elongated sleeve 50 is slidably mounted
around the valve body and cooperatively arranged for longitudinal
movement thereon between a first position blocking fluid
communication between the lateral ports and a second position in
which the ports are in communication with one another. In the
preferred embodiment of the valve 34, the body 41 is arranged as
upper and lower tandemly coupled sections 51 and 52, with the ports
48 and 49 being in the upper section and the lower section having
an enlarged-diameter portion 53 extending upwardly around the lower
ports and defining an upwardly facing annular space 54 therearound.
The lower portion of the sleeve 50 is enlarged, as at 55, and
complementally fitted in the annular space 54, with inner and outer
sealing members 56 and 57 cooperatively arranged thereon for
fluidly sealing the enlarged portion of the sleeve in the annular
space to block fluid communication between the lateral ports 48 and
49 so long as the enlarged sleeve portion is positioned
therebetween. The upper portion of the sleeve 50 is extended above
the upper port 48 and a sealing member 58 is cooperatively arranged
on an inwardly enlarged upper portion 59 of the sleeve for sealing
engagement with the exterior surface 60 of the upper section 51
above the upper port for isolating the port from the well bore
fluids. To releasably secure the sleeve 50 in its elevated position
depicted in FIG. 7, means are provided such as a pin 61 of a
predetermined strength for releasably coupling the sleeve to the
valve body 41.
Accordingly, so long as the valve 34 is in the position depicted in
FIG. 7, the barrier 44 will block fluid communication through the
axial bore 45 and the ports 48 and 49 bypassing the barrier will
each be isolated from one another by the sleeve 50 and the coaction
of the sealing members 56-58 with the exterior surface 60 of the
valve body 41. It will, therefore, be appreciated from FIGS. 1 and
7, that when the valve 34 is in its initial position and
operatively coupled into the tool 20 of the present invention, the
axial bore 45 above the barrier 44 will be at a reduced pressure
(i.e., whatever pressure is initially maintained in the enclosed
chamber 32) and the lower portion of the axial bore below the
barrier will be in communication with the fluids in the well bore
22 below the packer 30. Thus, to prevent the resulting upwardly
acting pressure forces imposed by the well bore fluids on the
barrier 44 from weakening or prematurely failing the pin 46, it is
preferred to provide an inwardly directed shoulder 62 in the axial
bore 45 against which the upper end of the barrier is initially
abutted. It will be recognized, of course, that the shoulder 62
will permit the pin 46 to be much weaker than would otherwise be
possible if the barrier 44 was not abutted against the
shoulder.
Those skilled in the art will, of course, appreciate that the
sleeve 50 will be subjected to a downwardly acting pressure force
imposed on the effective cross-sectional area defined between the
O-rings 57 and 58 as well as an upwardly acting pressure force
imposed on the effective cross-sectional area defined between the
O-rings 56 and 57. By arranging the upper body section 51 to have a
uniform diameter along the exterior sealing surface 60, these
upwardly acting and downwardly acting pressure forces will be
independent of the pressure in the enclosed chamber 32 so that the
net unbalanced pressure force acting at any time on the sleeve 50
will be directly related to the pressure differential across the
production packer 30 at any given time.
Accordingly, it will be appreciated that the lower valve 34 can be
selectively opened as illustrated in FIG. 3 by increasing the
pressure in the well bore 22 above the packer 30 in relation to the
pressure below the packer to impose a corresponding downwardly
acting pressure force on the sleeve 50. This is, of course, readily
accomplished from the surface by opening the wellhead valve 29 and
applying sufficient pumping pressure to the fluids in the well bore
22 above the packer 30 to cause the failure of the pin 61 retaining
the sleeve 50 in its initail elevated position as shown in FIG. 7.
It will, of course, be appreciated from FIG. 8 that once the pin 61
fails to allow the sleeve 50 to be moved downwardly in relation to
the valve body 41 by these unbalanced pressure forces, the ports 48
and 49 will be placed into communication with one another to permit
the fluids in the well bore 22 and the formation 25 below the
packer 30 to rush into the enclosed chamber 32 as previously
described in reference to FIG. 3. To facilitate fluid communication
between the ports 48 and 49, the internal bore of the sleeve 50 is
enlarged, as at 63, between the seals 56 and 58.
As illustrated in FIG. 8, to prevent the sleeve from inadvertently
returning to its initial position, latching means are provided such
as an outwardly expansible ring 64 which is initially confined in a
circumferential groove 65 around the body 41 by the upper portion
of the sleeve 50 and is operatively arranged to expand outwardly
once the sleeve is moved downwardly. In the preferred manner of
arranging the expansible ring 64, the groove 65 is formed at the
upper end of the sealing surface 60 and the adjacent internal
surface of the sleeve 50 is complementally shaped to define therein
an upwardly directed shoulder 66 adapted to abut the lower surface
of the contracted ring while the sleeve is in its elevated position
shown in FIG. 7. As a result, upwardly directed forces on the
sleeve 50 before the valve 34 is to be opened will be incapable of
inadvertently shifting the sleeve upwardly. Once, however, the
expansible ring 64 is unconfined and expands outwardly to the
position shown in FIG. 8, its lower surface will engage the
shoulder 67 defined by the upper end of the sleeve 50 to
permanently retain the sleeve in its illustrated downward
position.
Turning now to FIG. 9, a preferred embodiment of the upper valve 33
is depicted in its initial closed position as previously described
with reference to FIG. 1. As illustrated in FIG. 9, the upper valve
33 includes a tubular body 68 having a transverse barrier 69 that
is initially positioned in the axial bore 70 of the body and
fluidly sealed in relation thereto, as by sealing members 71, for
initially blocking fluid communication through the axial bore. In
the preferred embodiment of the upper valve 33, the barrier 69 is
releasably secured to the valve body 68 by a plurality of balls 72
which are loosely confined in lateral openings 73 formed around the
body and appropriately sized to project into the axial bore 70 so
as to be partially received in a complemental groove 74 formed
around the barrier. Thus, it will be appreciated that so long as
the balls 72 are cooperatively engaged in the circumferential
groove 74, the barrier 69 is securely retained against axial
movement in relation to the body 68.
To selectively retain the balls 72 in the circumferential groove
74, a sleeve 75 is slidably mounted around the valve body 68 and
releasably secured thereto, as by a lateral pin 76 of predetermined
strength, for initially positioning the internal surface 77 of the
sleeve over the lateral openings 73. Thus, so long as the internal
surface 77 of the sleeve 75 is covering the lateral openings 73,
the balls 72 therein cannot be withdrawn from the circumferential
groove 74 and the barrier 69 will be retained in position to block
fluid communication through the axial bore 70 of the upper valve
33. By forming a circumferential groove 78 around the internal wall
of the sleeve 75 that is spaced above the surface 77 and of
sufficient depth to enable the balls 72 to move outwardly out of
the circumferential groove 74, upon downward movement of the sleeve
to bring the groove 78 into alignment with the openings 73 the
barrier 69 will be free to move downwardly in relation to the valve
body 68.
In the preferred manner of selectively releasing the balls 72 from
the barrier 69, the upper end of the sleeve 75 is extended upwardly
into a downwardly directed annular cavity 79 formed around the body
68. In the preferred embodiment of the valve 33, the valve body 68
is comprised of tandemly coupled tubular sections 80 and 81, with
the upper body section having an enlarged-diameter portion 82
extending downwardly around the lower body section and spaced
outwardly therefrom to define the annular space 79. The upper end
of the sleeve 75 is fluidly sealed within the annular space 79 by
seals, such as O-rings 83 and 84, mounted around the inner and
outer walls of the sleeve; and a lateral port 85 is provided in the
body 68 to communicate the axial bore 70 above the barrier 69 with
the enclosed upper portion of the annular space above the O-rings
83 and 84. An expansible ring 86 is mounted in a complementary
annular groove 87 formed around the sleeve 75 and operatively
located to retain the ring in the annular space 79 so long as the
sleeve is secured in its elevated position depicted in FIG. 9 by
the shear pin 76.
It will be appreciated, therefore, that the barrier 69 will be
secured in its flow-blocking position in the axial bore 70 so long
as the sleeve 75 is cooperatively retaining the balls 72 in the
circumferential groove 74 around the barrier. Thus, so long as the
shear pin 76 maintains the sleeve 75 in its elevated position, the
barrier 69 will be securely latched to the valve body 68 by the
balls 72 and the sleeve. Accordingly, to open the upper valve 33,
the pressure in the axial bore 70 above the barrier 69 must be
increased above the pressure of the well bore fluids above the
packer 30 to impose a downwardly acting unbalanced pressure force
on the effective cross-sectional area of the sleeve 75 defined
between the O-rings 83 and 84 that is sufficient to fail the shear
pin 76. Once the sleeve 75 is freed and is moved downwardly to its
lower position (as determined by the location of an upwardly
directed shoulder 88 formed around the body section 81 and spaced
below the sleeve), the circumferential groove 78 will be aligned
with the balls 72 so that they will be cammed outwardly into the
groove by the downward movement of the barrier 69.
Referring again to FIG. 1, it will be appreciated that when the new
and improved tool 20 of the present invention is positioned in the
well bore 22, the upper and lower valves 33 and 34 will
respectively be in their normally closed positions as depicted in
FIGS. 7 and 9. The elongated body 31 will define the enclosed
chamber 32 so long as the barriers 44 and 69 remain in position and
the sleeve 50 remains in its elevated position in relation to the
body 41 of the lower valve 34.
As previously described in relation to FIG. 3, the lower valve 34
is selectively opened to induce a rapid flow of connate fluids as
at 38 into the enclosed chamber 32 for flushing the debris 36 and
37 from the perforations 26. To accomplish this, the wellhead valve
29 is opened and sufficient pumping pressure is applied from the
surface to the well bore fluids above the packer 30 to fail the
shear pin 61 and shift the sleeve 50 downwardly to its position
illustrated in FIG. 8 for establishing fluid communication (by way
of the ports 48 and 49) between the enclosed chamber 31 and the
well bore 22 below the packer. It will, or course, be appreciated
that the barrier 44 will still be retained in its depicted position
by the shear pin 46. Moreover, once the sleeve 50 moves downwardly,
the expansible ring 64 will be partially expanded out of the groove
65 so as to move outwardly over the upper end 67 of the sleeve and
permanently secure the sleeve in its lower position in relation to
the valve body 41.
It will, of course, be appreciated that when the pressure of the
well bore fluids above the packer 30 is increased to open the lower
valve 34, the upper valve 33 will not be affected since the
increased pressure will only tend to urge the ball-retaining sleeve
75 upwardly against the shoulder defined by the upper end of the
annular space 79. The barrier 69 will, therefore, be securely
latched in its initial position as illustrated in FIG. 9 so long as
the sleeve 75 is cooperatively retaining the balls 72 in the
barrier groove 74. Thus, the upper valve 33 may be left closed as
long as is desired after communication has been established through
the ports 48 and 49 of the lower valve 34. It will, of course, be
recalled that the barrier 44 in the lower valve 34 will still be in
position therein after the ports 48 and 49 are opened.
Accordingly, when it is desired to open the upper valve 33 for
introducing a treating fluid into the chamber 32 as previously
described in relation to FIG. 5, the wellhead valve 28 is opened
and an increased pressure is applied to the fluid 40 in the
production string 21 for urging the ball-retaining sleeve 75
downwardly with sufficient force to fail the shear pin 76. As best
seen in FIG. 10, once the sleeve 75 is shifted downwardly into
abutment with the shoulder 88, the expansible ring 86 will expand
partially out of the groove 87 and be received in a downwardly
facing groove 89 in the lower face of the enlarged body portion 82
so as to permanently latch the ball-retaining sleeve in its lower
position.
The barrier 69 will, of course, be released once the balls 72 are
shifted outwardly into the sleeve groove 78. It will be noted that
in the preferred embodiment of the upper valve 33, the barrier 69
is made somewhat smaller than the internal diameter of the axial
bore 70 and a slight inwardly enlarged shoulder 90 is formed in the
body 68 adjacent to the initial position of the barrier for sealing
engagement with the O-rings 71. In this manner, once the barrier 69
is released and passes below the shoulder 90, the barrier will be
free to move easily through the interconnecting tubing 31 to the
lower valve 34. Accordingly, although the barrier 69 could just as
well be displaced through the interconnecting tubing 31 by
maintaining a substantial pumping pressure on the treating fluid 40
in the production string 21, it is preferred to dispose a typical
separator plug, as at 91, in the production string ahead of the
treating fluid. This will, of course, minimize the pumping pressure
required to move the barrier 69 downwardly through the
interconnecting tubing 31 to the lower valve 34.
Referring again to FIG. 8, it will be recalled that the shear pin
46 and shoulder 62 retained the barrier 44 in position within the
lower valve 34 when the sleeve 50 was shifted downwardly to place
the ports 48 and 49 into communication with one another. Thus, the
barrier 44 can not be released until the pressure of the fluids now
in the chamber 32 above the barrier 44 is increased above the
pressure of the fluids therebelow for developing a sufficient
downwardly acting force on the barrier to fail the shear pin 46.
This will, of course, occur once the separating plug 91 has carried
the upper barrier 69 downwardly to the lower barrier 44. Hereagain,
it should be noted that in the preferred embodiment of the lower
valve 34, the barrier 44 is of a reduced diameter and that portion
of the axial bore 45 just below the shoulder 62 is slightly
reduced, as at 92, to provide a sealing surface for the O-ring 47.
Thus, once the shear pin 46 does fail, the two barriers 44 and 69
will be moved further downwardly by the separator plug 91 through
the packer 30 and allowed to fall on into the well bore 22
therebelow. In the preferred embodiment of the tool 20 of the
present invention, it is preferred to fabricate the barriers 44 and
69 of either a metal such as aluminum or a rigid plastic material
which will be ultimately disintegrated in time by the corrosive
action of the well bore fluids so as to minimize the debris left in
the well bore 22.
It will, of course, be appreciated that if the separating plug 91
is not employed, the lower barrier 44 could also be released from
the lower valve 34 by dropping a so-called "sinker bar" (not shown)
from the surface through the production string 21 after the upper
barrier 69 has been released from the upper valve 33.
In any event, once both of the barriers 44 and 69 have passed
through the packer 30, a continuous and substantially uninterrupted
passage is provided through the tubing string 21 and the production
tool 20 between the wellhead 27 and the well bore 22 below the
packer. Thus, any so-called "through tubing" completion or treating
operation that is typically conducted in a production well can be
readily conducted in the well bore 22 without having to remove
either the wellhead 27 or the production tool 20 and its supporting
string of production tubing 21.
Accordingly, it will be appreciated that the present invention has
provided new and improved methods and apparatus for completing
wells to obtain improved fluid communication between the well bore
and selected earth formations traversed thereby without delaying
the installation of the production string and the associated
wellhead and surface equipment once the drilling operation is
concluded. By arranging the new and improved production tool of the
present invention into an otherwise typical production string once
the formation interval below the intended position of the
production packer has been perforated, the wellhead and other
associated surface equipment can be installed in the usual manner
without further delay. Then, when the well is to be prepared for
production, the lower valve of the new and improved production tool
of the present invention is opened to clear the perforations of
debris and the like. Thereafter, a fluid is discharged into the
production string and the upper valve of the production tool is
opened to establish communication from the surface with the
formations below the packer. Where the formations require
acidizing, fracturing or consolidation treatments to prepare the
well for production, one or more treating fluids can be readily
dispatched through the now opened production string and into the
well bore below the packer.
While particular illustrations and embodiments of the present
invention have 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.
* * * * *