Note: Descriptions are shown in the official language in which they were submitted.
174~
BACKGROUND OF THE INVENTION
In my previous U.S. Patent No. 3,706,344, -there is
disclosed a perforating gun which is detonated by dropping a bar
down the tubing string. The bar impacts against a firing head
which detonates the shaped charges of the gun. Once the bar has
been dropped down the tubing, the system is commit-ted to proceed
with the final completion steps~
Often it is desirable to install the perforating gun
while various workover equipment is on hand, and -to complete -the
well at some subsequent date. This effects a considerable sav-
ings in money and also provides a means for isolating the hydro-
carbon containing zone so that the well can remain dormant until
the subsequent completion date arrives. During this time, there
is always a danger of some objects being accidently dropped
downhole and inadverten-tly firing the gun and completing the well
without the necessary surface equipment and technical people
being on hand. Moreover, during a long ;'nterval of time, it is
possible for debris to collect above the firing head so that
when the bar is subsequently dropped in order to attemp-t complet-
ing the well, the overlying debris prevents the bar from contact-
ing the firing head, and the perforating gun cannot be fired.
There are many highly deviated boreholes slanted
towards the horizontal to an extent which precludes -the use of
gravity induced impact for firing a perforating gun. In this
instance, some means, o-ther than a bar, must be employed for
detonating the gun. ~his is especially so in offshore rigs where
multiple boreholes are formed by slanting each of the wells away
from a single drilling platform, -thereby radially spacing the
wells respective to one another.
In my previous U. S. Patent ~os. 3,966,236 and 4,066,
282, it is pointed out that one can often foresee that a tool
string located on the lower marginal end of a tubing string must
7~B
be subsequently disconnected from the remainder of the string
and abandoned downhole in the wellbore. It is especlally im-
portant when running tool strings into expensive offshore wells
to be able to assure everyone concerned that should the string
become stuck downhole, that provisions are included for releas-
ing the stuck part of the tool string.
As pointed out in my previously issued U. S. Patent No.
3,706,344, it is advantageous to be able -to complete a wellwhile
the tubing string is open to ambient so -that a maximum pressure
differential is achieved across the production formation instan-
taneous with the perforation thereof so that the debris is im-
media-tely flushed out of the newly completed formation, thereby
avoiding any contamination of the production zone with extraneous
material.
It would be desirable to be able to circulate fluid
downhole and across the firing head of a gun in order to wash
debris therefrom. ~t would also be desirable to be able to open
the main vent assembly of the tubing simultaneously with the
actuation of the firing head. It would further be desirable to
protect the firing head of the perforating gun prior to detona~
tion thereof. Moreover, several heretofore known advantages
would be realized if one were able to increase and then decrease
the circulation rate of the lower borehole annulus, and to be
able to close off -the lower tubing string, or to open the lower
tubing string at any time prior to detonation of -the gun. It
would furthermore be desirable to be able to fire the gun while
the tubing string is vented to ambient at -the surface of the
ground.
Apparatus and me-thod Which enable the above desirable
manipulations to be performed w~hile completing a cased wellbore
is the subject of the present inven-tion.
-- 2 --
~tii7 ~15
SUMMARY OF THE INVENTION
A ball switch device and method which enables a hydro-
carbon bearing formation to be perforated and the borehole com-
pleted in a new and unobvious ~anner so that unusual and unex-
pected results are attained thereby. The apparatus of -the
present invention includes a tubing string having the lower end
thereof connected to a per~orating gun. A packer device is
interposed between the casing and tubing to divide the casing
annulus into an upper and lower annular area. The packer device
is located uphole of a releasable coupling apparatus. An annu-
lar piston is slidabl~ ~oved downhole to effect release of the
releasable coupling apparatus so that the entire lower tool
string can be abandoned downhole in the borehole. -
The gun preferably is a large casing gun having afiring head arranged to be detonated by impac-t with an object
which has been circulated downhole through the tubing string.
Two additional spaced apart movable annular piStOIlS
are series connected in the tubing string in underlying relation-
ship respective to the releasable coupling. The perforating gun
2Q is disposed downhole of the lowermost piston, Elow ports,
formed at spaced locations along the tubing ~all, are covered by
the pistons. Each piston has an axial passageway formed there-
through. The passage~ays of the three pistons diminish in diam-
eter in a downhole direction. ~alls of selected diameters can
therefore be circulated downhole into sea-ted rela-tionship
respective to a specific piston. A large ball, for example,
will become seated on the piston of the releasable coupling
apparatus to effect release thereof, while a smaller ball can
flow axially through both of the upper piston passageways and
come to rest in sea-ted relationship on the lower piston- ~n
intermediate size ball, on the other hand, will pass through the
uppermost piston and become seated on the intermediate or
-- 3
second piston.
Circula-tion ports are proYided below the l~wermost
piston in proximity of a gun firing head. The lowermost piston
includes a shaft depending axially downhole therefrom and into
proximity of a detonator of the gun firing head, so that when
the lower piston is forced downhole, the shaft contacts the fir-
ing head which detonates the shaped charges of -the perforating
gun. This assembly of elements enables many different options
to be exercised prior to the firing of the gun.
This invention enables a small outside diameter ball
to be circulated down through the tubing string, through the
upper passageway of the upper and intermediate pistons, and into
seated position of the lowermost piston, Thereafter, fluid pres-
sure is effected within the tubing string to force the lower
piston to move in a downward direction and detonate the shaped
charges of the perforating gun.
At any time before the gun is fired, an intermediate
size ball can be circulated downhole and into seated position on
the second piston -to thereby obstruct the lower tubing string to
prevent debris from accumulating therebelow, and wherein pressure
effected above said ball and within said tubing string forces the
second piston to move in a downward direc-tion, thereby opening
the upper ports.
Should a malfunction occur, or should the lower part of
the tool string become stuck downhole, a relatiye large ball can
be circulated downhole to actuate the releasable coupling. This
enables retrieval of all of the string located above the releas-
able coupling.
Therefore, the aboYe well completion appa~atus enables
3~ the following method to be achieved.
~ 4 _
~6~'7~
An appropria-te size ball can be placed on the second
seat, thereby preventing access to the firing head of the perfo-
rating gun. Reverse circulation thereafter removes -the ball
along with any debris that may have accumula-ted about -the gun
firing head.
I~ith the ball retrieved, circula-tion can occur down
through the tubing string and through the lowermost ports, there
by forcing any debris which may have accumulated about the gun
head to be washed up the borehole annulus and to the surface of
the ground.
The above ball can be circulated downhole onto -the
second piston, and thereafter pressure effected on the tubing
interior to move the piston in a downward direction, whereupon
the upper ports are uncovered and circulation occurs through the
uppermost ports. Thereafter reverse circulation retrieves the
ball and the perforating gun can be detonated by driving the
lower piston in a downward direction with a bar in order to deto-
nate the gun if the hole is not unduly slanted.
With the second and third pistons covering their
respective ports, a relatively small o,d. ball can be circulated
downhole through the tubing, through the upper piston ? through
the second piston, where the ball lands on the seat of the lower-
most piston, thereby driving the lower piston in a downward
direction to detonate the gun and simultaneously open additional
vent or circulation ports so that production can occur back
uphole to the surface of the ground. This last port can be
eliminiated as another embodiment of this invention.
Accordingly, a primary object of the present invention
is the provision of improvements in apparatus and method for com-
3a pleting a hydrocarbon producing formation.
7 ~3
A further objec-t of this inyention is the provision of
method and apparatus which enables -the firing head of a gun to
be protected until a well is completed, and during completion of
the well, the apparatus may be used to open additional circulat-
ing ports while simultaneously detonating a perfora-ting gun.
A still further object of this invention is the provi-
sion of method and apparatus for completing slanted boreholes by
effecting fluid pressure internally of a tool string loca-ted
within -the borehole.
Still another object of -this invention is the provision
of method and apparatus by which objects may be circulated into
and out of a tool string located in a slanted borehole so as -to
complete the well and subsequently re-trieve the tubing along with
part of the tool string.
The above objects are attained in accordance with the
present inyention by the provision of a tubing string disposed
within a cased borehole, with a perforating gun attached at the
lower end of the tubing string, and two spaced annular pistons
located above a gun firing head of the perforating gun, with each
2Q piston covering a vent, so that a ball of a small diame-ter can
be circulated down through the tubing string -to open the lower
piston and fire the gun, or a ball of a large diameter can be
circulated downhole to open the upper piston,
These and various other objects and advantages o~ the
invention will become readily apparent -to those skilled in the
art upon reading the following detailed description and claims
and by referring to -the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagrammatical ? cross-section~l, hypothe-
tical view of a wellbore extending downhole into the ground with
7 ~
apparatus made in accordance with the present invention ~eingdisclosed in conjunction therewith;
Figure 2 is a fragmentary, enlarged, part cross-
sectional, schematical-type view of par-t of -the apparatus dis-
closed in Figure l;
Figure 3 illustrates the apparatus of Figure 2 in an-
other operative configuration;
Figure 4 illustrates the apparatus of Figure 2 in still
another operative configuration;
Figure 5 sets forth an enlarged detail of part of the
apparatus seen in the foregoing figures;
Figure 6 sets forth an enlarged de-tail of another part
of the apparatus disclosed in the foregoing figures;
Figure 7 is a broken view of the presen-t invention dis-
closed in conjunction with a slanted borehole;
Figure 8 is an enlarged view of par-t of the apparatus
disclosed in Figures 1 and 7; and,
Figure 9 is a cross-sectional view taken along line
9-9 of Figure 8.
DETAILED DESCRIPTION OF THE PREFE~RED EMBODI~ENTS
In Pigure 1, there is schema-tically illustrated a well-
head 10 located at the upper end of a borehole having a casing
11 therewithin. Packer 12 separates the upper borehole annulus
14 from a lower borehole annulus 15. Tubing 16 extends from the
wellhead, downhole -to a je-t perforating gun 18 located in proxi-
mity of a hydrocarbon bearing forma-tion 17. The well may extend
vertically downward into the ear-th as seen at 11, or the bore-
hole can be slanted as indicated at 111 in Figures 1 and 7.
The perforating gun preferably is a large casing gun
having shaped charges 19 which are detonated by a firing head 2a.
L6~
The firing head is responsive -to impact, and the de-tails -thereof
are more fully set forth in my previously issued U. S. Patent No.
3,706,344. The -tubing string includes subs 21, 22~ 24, and 26,
the details of which are more fully disclosed in other figures
of the present drawings.
As seen illustrated in ~igures 2 and 4, a lower circu-
lation port 28 of relatively small diameter is located in close
proximity of the firing head of the gun so that circulation can
be effected therethrough. This action removes debris from the
upper end of the gun firing head. As seen in Figures 1-3, the
tubing wall has a relatively large diameter upper port 30 which
..
is sealingly closed by an annular piston 21. The piston in-
cludes spaced seals, 32 and 34, circumferentially extending there-
about and sealing the interface formed between the exterior of
the piston and the interior wall surface of the -tubing. An axial
passageway 36 of a specific relative diameter extends longitu-
dinally through the piston. The piston passageway is formed into
a seat 38 at -the upper marginal end thereof against which a ball
of a specific outside diameter can be seated so that the piston
21 can be circulated or forced to move in a downward direction
in order to uncoYer the upper ports 30 in accordance with the
present invention.
Radially spaced apart ports or vents 42 are of a speci-
fic relative size respective to vents 30 and 28. The vents 42
are located below -the upper vents 30 and above the lower ve~ts
28. The middle yents are coyered by annulus piston 23, Circum-
ferentially extending seals 44 and 46 seal the interface between
the ex-terior of the lower piston and the interior o~ -the tubing
string. Axial passageway 48 termina-tes in a lower seat 50
located at the upper end of the piston 23 and sealingly recei~es
a relatively small o.d. ball 52 ~n seated relat~onship there-
against.
~6~L~4~ ~
A firing rod 54 i6 axially aligned longi-tudinally with
respect to -the tubing string and includes a fixed end 56 which
is affixed to the lower end of piston 23. The firing rod down-
wardly depends from the pis-ton and terminates at a free end 58.
Passageway 48 communicates with ports 28 by means of the radial
passageways formed through the lower end of the annular piston.
Piston 23 can be forced to slide in a downward direc-
tion relative to the tubing interior, whereupon -the free end of
the firing rod impacts agains-t the trigger device 60 of the
firing head. This action moves the trigger rod 62 in a downward
direction, whereupon detona-tion of the perforating gun occurs.
The presence of intermedia-te ports 42 in Figures 1 and 2, and
the absence of these ports from Figure 4 shows that different
embodiments of the invention are illustrated herein.
In Figure 5, there is set forth the details of one of
the subs. The sub 24 is provided with threads 64 and 66 at the
opposite marginal ends thereof so that the sub can be threadedly
made-up into the tubing string, The piston as an o.d. 68 which
enables it to be slidably received in close tolerance relation-
ship within the reduced inside diameter 70 of the sub. The i.d.of the sub increases at 71 from the nominal i.d. of the lower
tubing string.
The lower end of the piston is provided with the before
mentioned radially spaced apart circulation ports 72 which are
arranged circumferentially about the longitudinal axial center-
line of the sub, and parallel to the axial centerline of the
-tubing string, with there being ample material at 74 for transfer
of loads which may be imposed upon the before mentioned firing
rod. Shear pin 76 is received within the illustra-ted groove 77
and rigidly captures the piston within the sub until sufficient
~L6~7~8
force is exerted upon the piston to shear the pins. The por-ts 42
are smaller than ports 30, or may be excluded from the apparatus.
In Figure 6, wherein the details of the sub 22 are more
fully disclosed, the axial passageway 36 of piston 21 is unre-
stricted to proyide for movement o:F the rela-tive small i.d. ball
therethrough. The sub 22 is threaded at each marginal end 78 and
80 thereof for attachment in series relationship within the -tub-
ing string. Shear pin 82 rigidly affixes the piston wi-thin the
small i.d. portion 84 of the sub.
The interface between the piston and the inside surface
84 is sealed by -the o-rings 32. The lower circumferentially ex-
tending edge 39 of the annular piston which is opposed to the
seat 38 can be engaged by a fishing tool should it ever become
necessary to move the piston in an uphole direction respective
to the sub.
I,n Figure 7, the borehole is seYerely slanted as noted
at 111. The tool string of Figure 7 is identical to the tool
string illustrated in Figures 1-6.
In Figures 8 and 9, the details of the releasable
coupling apparatus 21 is more fully disclosed. The coupling
apparatus includes a pin end 86 opposed to a box end 87, An
outer barrel 88 slidably receives an inner ~andrel 89 ln sealed,
releasable relationship therewithin.
The barrel and mandrel are released from one another
by movement of releasing annular piston 90, which is the uppe~-
most piston of the tool str~ng. The barrel has one end 91
opposed to the pin end 86.
The releasing piston has a sea-t 92 which receives a
relative large ball 93 in seated relationship thereon. A plural-
ity of radially spaced releasing balls 94 are fi-tted into annular
-- 10 --
~61~
groove 95 jointly formed within the wall of the ~andrel and
barrel.
Seal 96 prevents fluid flow between the co-acting
marginal end portions of -the mandrel and barrel, The mandrel
includes a skirt which terminates at circumferentially extending
edge portion 97, while -the releasing piston terminates at 98.
The skirt has an axial bore 90 which slidably receives piston 90,
while the piston has an axial bore 100 which is of smaller diam-
eter 101 as compared to the i.d. of the tubing string.
I`n operation, the gun is at-tached -to the end of tubing
string 16, the packer is interposed in the tubing s-tring, and the
subs 21, 22, 24, and 26 are series connected -therein. Care must
be taken that sub 26 is arranged such that the small ports 28
are located to cause any accumulated debr~s to be washed from
about the firing trigger rod 62, The location o~ sub 24 must be
such that piston 23 is positioned to cause the depending end 58
of rod 54 to contact the firing head trigger enlargement 60 when
the piston 23 is forced downhole.
The axial piston passageway~s 36, 48, and 100, and the
balls 40, 52, and 93, must be of a size whereby balls 93, 40~
and 52, respectively, are seated on top of pistons 90 ? 21, and
23, respectlvely; while ball 52 can pass through passageway 36
and become seated on -top of piston 23; and ball 4 a can pass
through passageway 100 and become seated on -top of piston 21.
The spaced distance between rod end 58 and trigger end 60 must
be selected so -that there is no question of the gun improperly
detonating when the lower piston is moyed in a downw~ard direction.
Assuming that the cased borehole extends yertically~ or
horizontally through a pay zone 17, that packer 12 is set a and
that gun 18 is properly positioned adjacent to the pay~ zone, and
~6:iL7~
that the subs 21, 22, 2~, and 26 are properly positioned wi-thin
the tubing string; those skilled in the ar-t will now appreciate
that an intermediate size ball 40, when circulated through -the
cubing string, will pass through the annular piston of the re-
leasable coupling and come to rest in the dot-dash position seen
illustrated at 40 in Figures 2 or 3, The entire system is now
in the standby configuration, ready for the gun -to be de-tona-ted,
whenever it is desired to do so; but, at the same time, the gun
firing mechanism is safe from inadYertently being Pired because
of the presence of the large ball ~0 located on seat 38. More-
over, debris which may inadvertently fall down tubing 16 is pre-
cluded from lodging about -the firing head trigger device. The
well can remain in this configuration until it is desired to
complete the well and tie the production into a gathering system
The task of completing the well at some subsequent date has been
greatly simplified, and the wellbore and production apparatus is
rendered safe during the intervenlng -time interval.
Prior to perforating casing 11, ball 40 is circulated
out of the tubing string by means of reverse circulation through
small ports 28. At this time, several options are available to
the technician as follows:
(1) Circulation down through the tubing string
may be effected to clean debris from the borehole.
(2) A small ball 52 can be dropped down the tub-
ing string. Thereafter, small ball 52 can be retrieved by re-
verse circulation; or alternatively~ the ball may beco~e seated
on piston 23, and pressure applied to the -tubing interior where-
upon the pin 76 is sheared, thereby moving piston 23 downhole to
detonate the gun, thus completing the well.
(3) ~nstead of carry~ing out (2), the large ball
~0 can again be circulated downhole, the piston 21 engaged, the
- 12 -
pins 82 sheared, and -the large ports 30 uncovered, -thereby en-
abling a very large circula-tion in either direction to occur
above the piston 21 and through the large ports 30.
t4) Af-ter the ball 40 has been dropped, and be-
fore the piston 21 has been actuated, ball 40 can be retrieved
by reverse circulation as pointed out above.
(5) Small ball 52 can be dropped onto seat 5a,
thereafter large ball 40 can be dropped onto seat 38, pressure
can be applied to the tubing interior, thereby simultaneously
moving both pistons 21 and 23 downhole, de-tonating the casing
gun, and completing the well with production simultaneously
occurring through ports 28, 42, and 30, assuming ports 42 are
selected to be formed within sub 24.
(6) Af-ter piston 21 has been moved downhole by
ball 40, it is possible to retrieve the ball by reverse circula-
tion and thereafter reposition piston 21 u~ing a ~ireline
operated fishing -tool, so that either of steps (2) or (5) can
thereafter be carried ou-t.
~ 7) Following step (3~, the gun can be detonated
by dropping a bar down through the tuking string if the borehole
is not unduly slanted.
At any time, should it become necessary to do so, the
largest ball 93 can be circulated downhole onto seat 92 of piston
90, to force the annular piston downhole causing the releasing
balls 94 to fall from the annular ball receiving groove 95, This
action enables the mandrel to slidably part from the barrel,
whereupon the tubing string and part of the tool string can be
removed from the borehole, leaving the lower end of the tool
string in the bo-ttom of the boreholet ~ence~ there is no danger
of some unforeseen malfunction causing the hole to be abandoned.
- 13 -
L748
The remainder of the -tool string can be removed by fishing e~-
perts, if desired, or the lower forma-tion repene-trated using a
whipstock.
Further details of apparatus similar to the releasable
coupling 21 are found in my issued Patent Nos. 4,078,611; 4,066,
282; 3,990,507; 3,966,236; and 3,912,013 to which reference is
made.
Further details of other vent assemblies and the pro-
blems associated therewith are set forth in my issued U.S. Patent
Nos. 4,151,880; 4,040,485; 3,~31,855; and 3,871,448.
Hence, the presen-t combination of elements enables a
number of choices of downhole manipulations to be carried out in
a low cost manner during the well completion operation,
In the preferred method of completing a well, clean,
clear water par*ially fills the lower annulus 15, wi-th there
being compressible gas loca-ted under the seated packer 12, Ball
40 is seated on piston 21 unt~l it is desired to complete the
well. At this time, the ball 40 is retrieved by reverse circu-
la-tion after unlatching packer 12 so that fluid flow can occur
in a reverse direction through small ports 28, thereby carrying
ball 40 back to the surface and cleaning any debris from about
the firing head of the gun. Ei-ther liquid or gas can be used
for this operation. The packer 12 is reset, fresh water is
pumped down tubing 16 to provide a hydrostatic head on the gun ?
and gas is again compressed under -the packer. The s~mall ball 52
is circulated or dropped downhole and becomes seated on top of
piston 23, nitrogen or wa-ter is then pumped into tubing 16,
causing shear pin 76 to fail, whereupon piston 23 moves downhole,
engages and moves -the detonator rod 60~ 62; and a-t the same time
intermediate ven-t 42 is opened. This enables the hydrocarbons to
- 14 -
748 ~
rush through the newly formed perfora~tions, into the lower bore-
hole annulus, into vent por-ts 28 and 42, and uphole to the sur-
face of -the ear-th.
By initially conducting the formation pressure across
the minimum available pressure drop, that is, by flowing the new
pay zone directly to ambient~ the perforations are cleaned up
and all contaminants removed from the pay zone. This provides a
superior production formation which is more economical to produce
and which is subject to less remedial action a-t a subsequent time.
Proper adjustment of the relative posi-tions of the vent
ports 42, piston 23, rod end 58, and trigger rod 60 will render
the system such that it is impossible to fire -the gun until
after the piston has commenced to move, with -these two actions
occurring substantially simultaneously respective to one another.
In an extreme instance when a large circulation must
be employed to clean out the borehole, the upper large vent 30
can be opened, and thereafter a bar used to force the piston 23
or both pistons 21 and 23 downward to detonate the gun.
After the shaped charges of the casing gun are deto-
nated and the casing has been perforated, the pressure of the
formation immediately flows inwardly against the gun, turns up-
hole and then flows into the vents 28 and 42, where the flow is
conducted uphole to the surface and into a pit where the hydro-
carbons are flared until the well has been cleaned up. There-
after, the well is tied into a gathering syst-em.
In the above examples, at any -time before the pins of
-the lower piston have been sheared, any of the above recited
options can be exercised, rather than going ahead and completing
-the well by movement of -the lower piston.
3a The present ~nyentIon enables the simultaneo~s firing
of the perforating gun, and communication of -the perfora-ted
4~
formation with ambien-t. The hydrostatic head o~ the fluids
present in the lower annular area can be controlled to any pre-
determined desired value.
The perforating ~un cannot inadvertently ~e fired by
employing the present method, nor can debris accumulate above
the firing head, thereby making the firing head inaccessible and
necessitating the expensive employment of pulling equipmen-t.
The present apparatus and method provides a safe, re-
liable and inexpensive means for completing a well in a manner
which increases the well production as compared to other known
well completion techniques.
