GB2081344A - Well completion apparatus - Google Patents

Abstract

A tubing string 16 extends downhole in a cased borehole to a jet perforating gun 18. A packer device 12 is located uphole of a releasable coupling apparatus 21.The coupling apparatus 21 has an annular piston therein which is moved to release the lower string. Two spaced apart movable annular pistons are series connected in the tubing string at a location below the packer 12 and above the gun 18. Flow ports 30, 42, formed in the tubing wall, are covered by the pistons. A ball of appropriate diameter can be circulated downhole and seated upon either of the pistons, thereby forcing a selected piston in a downhole direction. Circulation ports 28 are provided below the lower piston in proximity of a gun firing head. The lower piston includes a shaft depending axially 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 firing head which detonates the shaped charges of the perforating gun. This assembly of elements enables many different options to be exercised prior to firing the gun. <IMAGE>

Description

SPECIFICATION Well completion apparatus The present invention relates to completing wells.

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 committed 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 savings in money and also provides a means for isolating the hydrocarbon 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 inadvertently firing the gun and completing the well without the necessary surface equipment and technical people being on hand. Moreover, during a long interval of time, it is possible for debris to collect above the firing head so that when the bar is subsequently dropped in order to attempt completing the well, the overlying debris prevents the bar from contacting 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, other than a bar, must be employed for detonating the gun. This 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 Nos. 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 be subsequently disconnected from the remainder of the string and abandoned downhole in the wellbore. It is especially important 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 releasing 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 well while the tubing string is open to ambient so that a maximum pressure differential is achieved across the production formation instantaneous with the perforation thereof so that the debris is immediately 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. It 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 detonation 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, orto 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.

Methods and apparatus which enable the above desirable manipulations to be performed while completing-a cased well bore art specifically described hereinafter as examples of the present invention.

The present invention provides well completion apparatus for installation in a tubing string and comprising tubing containing an upper piston, an upper vent port formed in said tubing, said upper piston being movable from an upper position in which the upper vent port is closed to a lower position in which the upper vent port is open and having an axial passageway formed through said upper piston and a relatively large ball seat formed at the upper end of said upper piston; a lower piston having an axial passageway formed therethrough and a relatively small ball seat formed at the upper end of the axial passageway of said lower piston; a circulation port, which is relatively small with respect to the upper vent port, formed in the tubing below said lower piston; means connected to said lower piston for engaging and detonating a firing head to be situated below the apparatus in use when said lower piston is moved downwards the apparatus being constructed and arranged so that, a large ball can be passed down the tubing onto the seat of the upper piston to close the axial passageway therethrough so that fluid pressure may then be employed to move said piston downwards and open said upper vent port; and instead, a relatively small ball can be passed down the tubing, through the axial passageway of the upper piston, onto the seat of said lower piston, to close the axial passageway therethrough so that fluid pressure may be employed to move said lower piston downwards to engage a firing head.

Preferably an intermediate port is formed in said tubing between the upper vent port and the lower port said lower piston closing said intermediate ports when in an upper position and opening said intermediate ports in a lower position so that when said lower piston is moved down to fire the gun, the intermediate ports are simultaneously opened.

Preferably said upper and lower pistons are held in their upper positions in the tubing by shear pins; so that when downward force is applied to either of said pistons the pistons shear pins only if the force exceeds a set value.

Preferably the means connected to the lower piston for engaging and detonating a firing head is a downwardly depending shaft attached thereto in axially aligned relationship respective of said tubing.

The present invention includes a cased borehole comprising a packer device interposed between a tubing string and the casing to divide the casing annulus into an upper and a lower annular area, a perforating gun having a firing head arranged to be detonated by impact of an object circulated downhole through a borehole and well completion apparatus which includes an upper piston, upper vent ports formed in said tubing string, seal means by which said upper piston closes said upper port, an axial passageway formed through said upper piston, a large seat formed at the upper end of said upper piston; a lower piston, an axial passageway formed through said lower piston and a small seat formed at the upper end of the axial passageway of said lower piston; small circulation ports formed in proximity of said firing head and below said lower piston; means connected to said lower piston for engaging and detonating said firing heatwhen said power piston is moved downhole; so that, a large ball can be circulated downhole into seated relationship with respect to said upper piston to thereby move said piston downhole and open said upper ports; and, a relatively small ball can be circulated down the tubing string, through the axial passage way of the upper piston, into seated engagement with the seat of said lower piston, to thereby move said lower piston downhole while concurrently engaging said firing head and detonating said perforating gun, whereupon formation fluid can immediately flow from the formation, into the tubing string, and uphole to the surface of the ground.

The present invention includes a method of completing a cased wellbore having a tubing string extending downhole to a perforating gun located adjacent to a hydrocarbon bearing formation, a packer means located uphole of the gun and dividing the casing annulus into an upper and lower annulus, which method comprises providing upper, intermediate, and lower ports in said tubing string so that fluid flow can occur down the tubing string and through any of the three recited ports, with the lowermost port being placed adjacent to the firing head of the perforating gun; covering the uppermost port or ports with an upper piston and covering the intermediate port or ports with a lower piston and sealing the interface between the outside of the piston and the inside of the tubing to preclude flow of fluid through said upper and intermediate ports; said upper piston having an axial passageway therethrough and lower piston having an axial passageway therethrough so that fluid flow can occurthrough said tubing string, through said upper and lower pistons, and through said lower ports, and into said lower casing annulus; each of said pistons having a ball seat and the upper piston axial passageway large in diameter respective to said lower piston axial passageway; dropping a large ball down the tubing string so that the ball comes to rest seated on the upper piston thereby preventing access to said gun firing head; circulating said large ball out of the tubing string and circulating a small ball down the tubing string, through the passageway of the upper piston, into seated position on the lower piston; and aopplying pressure to the tubing interior until the lower piston moves downward; using the downward movement of the lower piston for actuating said gun firing head to thereby perforate said casing in proximity of said hydrocarbon bearing formation while sumultaneously opening said intermediate set of ports.

The invention includes 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 piston covering a vent, so that a ball of a small diameter 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.

The invention will be illustrated readily by the following detailed description of preferred embodiments with reference to the accompanying drawings in which: Figure 1 is a diagrammatical, cross-sectional, schematic view of a wellbore extending downhole into the ground with apparatus made in accordance with the present invention being disclosed in conjunction therewith; Figure 2 is a fragmentary, enlarged, part crosssectional, schematical-type view of part of the apparatus disclosed in Figure 1; Figure 3 illustrates the apparatus of Figure 2 in another 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 detail of another part of the apparatus disclosed in the foregoing figures; Figure 7 is a broken view of the present invention disclosed in conjunction with a slanted borehole; Figure 8 is an enlarged view of part 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.

In Figure 1,there is schematically illustrated a wellhead 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 jet perforating gun 18 located in proximity of a hydrocarbon bearing formation 17.

The well may extend vertically downward into the earth as seen at 11, or the borehole 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 20. The firing head is responsive to impact, and the details 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 Figures 2 and 4, a lower circulation 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 includes spaced seals, 32 and 34, circumferentially extending thereabout 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 longitudinally 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 uncover the upper ports 30 in accordance with the present invention.

Radially spaced apart ports or vents 42 are of a specific relative size respective to vents 30 and 28.

The vents 42 are located below the upper vents 30 and above the lower vents 28. The middle vents are covered by annulus piston 23. Circumferentially extending seals 44 and 46 seal the interface between the exterior of the lower piston and the interior of the tubing string. Axial passageway 48 terminates in a lower seat 50 located at the upper end of the piston 23 and sealingly receives a relatively small o.d. ball 52 in seated relationship thereagainst.

A firing rod 54 is axially aligned longitudinally 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 downwardly depends from the piston and terminates at a free end 58. Passageway 48 com municateswith 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 direction relative to the tubing interior, whereupon the free end of the firing rod impacts against the trigger device 60 of the firing head. This action moves the trigger rod 62 in a downward direction, whereupon detonation of the perforating gun occurs. The presence of intermediate 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 relationship 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 centerline of the sub, and parallel to the axial centerline of the tubing string, with there being ampie material at 74 for transfer of loads which may be imposed upon the before mentioned firing rod. Shear pin 76 is received within the illustrated groove 77 and rigidly captures the piston within the sub until sufficient force is exerted upon the piston to shear the pins. The ports 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 unrestricted to provide for movement of the relative 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 tubing string. Shear pin 82 rigidly affixes the piston within 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 extending 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.

In Figure 7, the borehole is severely 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 mandrel 89 in sealed, releasable relationship therewithin.

The barrel and mandrel are released from one another by movement of releasing annular piston 90, which is the uppermost piston of the tool string.

The barrel has one end 91 opposed to the pin end 86.

The releasing piston has a seat 92 which receives a relative large ball 93 in seated relationship thereon.

A plurality of radially spaced releasing balls 94 are fitted into annular groove 95 jointly formed within the wall of the mandrel 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 diameter 101 as compared to the i.d. of the tubing string.

In operation, the gun is attached to the end of tubing string 16, the packer is interposed in the tubing string, 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 debris to be washed from about the firing trigger rod 62. The location of 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 passageways 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, respectively; while ball 52 can pass through passageway 36 and become seated on top of piston 23; and ball 40 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 moved in a downward direction.

Assuming that the cased borehole extends vertically or horizontally through a pay zone 17, that packer 12 is set, and that gun 18 is properly positioned adjacent to the pay zone, and that the subs 21,22,24, and 26 are properly positioned within the tubing string; those skilled in the art will now appreciate that an intermediate size ball 40, when circulated through the tubing string, will pass through the annular piston of the releasable 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 detonated, whenever it is desired to do so; but, at the same time, the gun firing mechanism is safe from inadvertently being fired because of the presence of the large ball 40 located on seat 38.

Moreover, debris which may inadvertently fall down tubing 16 is precluded 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 well bore and production apparatus is rendered safe during the intervening 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, severai 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) Asmall ball 52 can be dropped down the tubing string. Thereafter, small ball 52 can be retrieved by reverse circulation; or alternatively, the ball may become seated on piston 23, and pressure applied to the tubing interior whereupon the pin 76 is sheared, thereby moving piston 23 downhole to detonate the gun, thus completing the well.

(3) Instead of carrying out (2), the large ball 40 can again be circulated downhole, the piston 21 engaged, the pins 82 sheared, and the large ports 30 uncovered, thereby enabling a very large circulation in either direction to occur above the piston 21 and through the large ports 30.

(4) Afterthe ball 40 has been dropped, and before 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 50, 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, detonating 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) After piston 21 has been moved downhole by ball 40, it is possible to retrieve the ball by reverse circulation and thereafter reposition piston 21 using a wireline operated fishing tool, so that either of steps (2) or (5) can thereafter be carried out.

(7) following step (3), the gun can be detonated by dropping a bar down through the tubing 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, 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 bottom of the borehole. Hence, there is no danger of some unforeseen malfunction causing the hole to be abandoned.

The remainder of the tool string can be removed by fishing experts, if desired, or the lower formation repenetrated 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 problems associated therewith are set forth in my issued U.S. Patent Nos. 4,151,8804,040,485; 3,931,855; and 3,871,448.

Hence, the present 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 partiaily fills the lower annulus 15, with there being compressible gas located under the seated packer 12. Ball 40 is seated on piston 21 until it is desired to complete the well. At this time, the ball 40 is retrieved by reverse circulation 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. Either 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 small ball 52 is circulated or dropped downhole and becomes seated on top of piston 23, nitrogen or water 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 at the same time intermediate vent 42 is opened. This enables the hydrocarbons to rush through the newly formed perforations, into the lower borehole annulus, into vent ports 28 and 42, and uphole to the surface of the earth.

By initially conducting the formation pressure across the minimum available pressure drop, that iss 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 at a subsequent time.

Proper adjustment of the relative positions 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 detonated and the casing has been perforated, the pressure of the formation immediately flows inwardly against the gun, turns uphole and then flows into the vents 28 and 42, where the flow is conducted uphole to the surface and into a pit where the hydrocarbons are flared until the well has been cleaned up. Thereafter, the well is tied into a gathering system.

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.

The present invention enables the simultaneous firing ofthe perforating gun, and communication of the perforated formation with ambient. The hydrostatic head of the fluids present in the lower annular area can be controlled to any predetermined desired value.

The perforating gun cannot inadvertently be 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 equipment.

The present apparatus and method provides a safe, reliable and inexpensive means for completing a well in a manner which increases the well production as compared to other known well completion techniques.

The preferred embodiments of the invention described above and their operation may be summarised as follows, a ball switch device and method having been described with enables a hydrocarbon bearing formation to be perforated and the borehole completed in a new and unobvious manner so that unusual and unexpected results are attained thereby. The apparatus includes a tubing string having the lower end thereof connected to a perforating 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 annular piston is slidably moved 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 a firing head arranged to be detonated by impact with an object which has been circulated downhole through the tubing string.

Two additional spaced apart movable annular pistons are series connected in the tubing string in underlying relationship respective to the releasable coupling. The perforating gun is disposed down hole of the lowermost piston. Flow ports, formed at spaced loations along the tubing wall, are covered by the pistons. Each piston has an axial passageway formed therethrough. The passageways of the three pistons diminish in diameter in a downhole direction. Balls of selected diameters can therefore be circulated downhole into seated relationship 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 seated relationship on the lower piston.An intermediate size ball, on the other hand, will pass through the uppermost piston and become seated on the intermediate or second piston.

Circulation ports are provided below the lowermost piston in proximity of a gun firing head. The lowermost piston includes a shaft depending axially down hole 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 firing 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.

A small outside diameter ball may 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 pressure is effected within the tubing string to force the lower piston to move in a downward direction and detonate the shaped chargesof 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 direction, thereby opening the upper ports.

Should a malfunction occur, or should the lower part of the tool string become stuck down hole, a relative large ball can be circulated downhole to actuate the releasable coupling. This enables retrieval of all of the string located above the releasable coupling.

Therefore, the above well completion apparatus enables the following method to be achieved.

An appropriate size ball can be placed on the second seat, thereby preventing access to the firing head of the perforating gun. Reverse circulation thereafter removes the ball along with any debris that may have accumulated about the gun firing head.

With the ball retrieved, circulation can occur down through the tubing string and through the lowermost ports, thereby 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 detonate the gun if the hole is not unduly slanted.

With the second and third pistons covering their respective port, 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 lowermost 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 eliminated as another embodiment of this invention.

A particular advantage of the method and apparatus specifically described above is that it is suitable for completing slanted boreholes by effecting fluid pressure internally of a tool string located within the borehole and that objects may be circulated into and out of a tool string located in a slanted borehole so as to complete the well and subsequently retrieve the tubing along with part of the tool string.

Claims (17)

1. Well completion apparatus for installation in a tubing string and comprising tubing containing an upper piston, an upper vent port formed in said tubing, said upper piston being movable from an upper position in which the upper vent port is closed to a lower position in which the upper vent port is open, and having an axial passageway formed through said upper piston and a relatively large ball seatformed atthe upper end of said upper piston; a lower piston having an axial passageway formed therethrough and a relatively small ball seat formed at the upper end of the axial passageway of said lower piston; a circulation port, which is relatively small with respect to the upper vent port, formed in the tubing below said lower piston;; means connected to said lower piston for engaging and detonating a firing head to be situated below the apparatus in use when said lower piston is moved downwards; the apparatus being constructed and arranged so that, a large ball can be passed down the tubing onto the seat of the upper piston to close the axial passageway therethrough so that fluid pressure may then be employed to move said piston downwards and open said upper vent port; and instead, a relatively small ball can be passed down the tubing through the axial passageway of the upper piston, onto the seat of said lower piston, to close the axial passageway therethrough so that fluid pressure may be employed to move said lower piston downwards to engage a firing head.

2. Apparatus as claimed in Claim 1 wherein an intermediate port is formed in said tubing between the upper vent port and the lower port, said lower piston closing said intermediate ports when in an upper position and opening said intermediate ports in a lower position so that when said lower piston is moved down to fire the gun, the intermediate ports are simultaneously opened.

3. Apparatus as claimed in Claim 1 or Claim 2 wherein said upper and lower pistons are held in their upper positions in the tubing by shear pins; so that when downward force is applied to either of said pistons, the pistons shear pins only if the force exceeds a set value.

4. Apparatus as claimed in ay one of Claims 1 to 3 wherein the means connected to the lower piston for engaging and detonating a firing head is a downwardly depending shaft attached thereto in axially aligned relationship respective to said tubing.

5. Well completion apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

6. A cased borehole comprising a packer device interposed between a tubing string and the casing to divide the casing annulus into an upper and a lower annular area, a perforating gun having a firing head - arranged to be detonated by impact of an object circulated downhole through a borehole and well completion apparatus which includes an upper piston, upper vent ports formed in said tubing string string, seal means by which said upper piston closes said upper port, an axial passageway formed through said upper piston, a large seat formed at the upper end of said upper piston; a lower piston, an axial passageway formed through said lower piston and a small seat formed at the upper end of the axial passageway of said lower piston; small circulation ports formed in proximity of said firing head and below said lower piston;; means connected to said lower piston for engaging and detonating said firing head when said lower piston is moved downhole; so that, a large ball can be circulated downhole into seated relationship with respect to said upper piston to thereby move said piston downhole and open said upper ports; and, a relatively small ball can be circulated down the tubing string, through the axial passageway of the upper piston, into seated engagement with the seat of said lower piston, to thereby move said lower piston downhole while concurrently engaging said firing head and detonating said perforating gun, whereupon formation fluid can immediately flow from the formation, into the tubing string, and uphole to the surface of the ground.

7. A wellbore as claimed in Claim 6 wherein intermediate ports are formed in said tubing string, seal means by which said lower piston closes said intermediate ports; so that when said lower piston is moved downhole to fire the gun, the intermediate ports are simultaneously opened.

8. A wellbore as claimed in Claim 6 or Claim 7 wherein said upper and lower pistons are held in fixed relationship respective to the tubing strings by shear pins; so that when either of said pistons are forced downhole, the pins shear as the pistons are forced downhole within the tubing string.

9. A wellbore as claimed in any one of Claims 6 to 8 wherein said lower piston has a downwardly depending shaft attached thereto in axially aligned relationship respective to said tubing string; and, said firing head has an upwardly extending trigger shaft arranged along the axial centerline of the tubing string so that when said lower piston is forced in a downward direction, said shaft contacts said trigger means.

10. A wellbore su bstantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

11. A method of completing a cased well bore having a tubing string extending downhole to a perforating gun located adjacent to a hydrocarbon bearing formation, a packer means located uphole of the gun and dividing the casing annulus into an upper and lower annulus, which method comprises providing upper, intermediate, and lower ports in said tubing string so that fluid flow can occur down the tubing string and through any of the three recited ports, with the lowermost port being placed adjacent to the firing head of the perforating gun; covering the uppermost port or ports with an upper piston and covering the intermediate port or ports with a lower piston sealing the interface between the outside of the piston and the inside of the tubing to preclude flow of fluid through said upper and intermediate ports;; said upper piston having an axial passageway therethrough and lower piston having an axial passageway therethrough so that fluid flow can occurthrough said tubing string, through said upper and lower pistons, and through said lower ports, and into said lower casing annulus; each of said pistons having a ball seat and the upper piston axial passageway large in diameter respective to said lower piston axial passageway; dropping a large ball down the tubing string so that the ball comes to rest seated on the upper piston thereby preventing access to said gun firing head; circulating said large ball out of the tubing string and circulating a small ball down the tubing string, through the passageway of the upper piston, into seated position on the lower piston; and applying pressure to the tubing interior until the lower piston moves downward;; using the downward movement of the lower piston for actuating said gun firing head to thereby perforate said casing in proximity of said hydrocarbon bearing formation while simultaneously opening said intermediate set of ports.

12. A method for completing a well comprising a cased borehole having a casing gun located downhold in proximity of a hydrocarbon bearing formation with a tubing string extending from a well head and connected to said gun, wherein said gun is provided with a gun firing head which is detonatable upon impact with an object circulated downhole through the tubing strings; fluid circulating ports are provided in proximity of said gun firing head so that fluid can be circulated downhole through the ports to cleam out debris located in proximity of said gun firing head; an annular piston is slidably positioned within the tubing uphole of the circulating ports and has an axial passageway longitudinally therethrough;; which method comprises circulating a ball downhole, into sealed relationship respectively to the passageway of said piston and using internal tubing pressure to force said piston to move into engagement with said gun firing head to thereby detonate the gun and perforate the casing, and simultaneously permitting the hydrocarbons to flow from the perforations, into the circulating ports, and up through the tubing string, thereby completing the well.

13. A method as claimed in Claim 12 wherein the tubing string includes an upper port in said tubing string at a location spaced above said piston, second annular piston slidably mounted above the first recited piston and closing said upper port; an axial passageway through the last said piston larger in diameter than the recited passageway formed through the lower piston so that a relatively large ball can be seated on the uppermost piston or a relatively small ball can be circulated downhole through the upper piston passageway and into sealed relationship with respect to the lower annular piston; thereby enabling the upper piston to be moved to the open position by a relatively large ball and for the gun to be fired by a relatively small ball.

14. A method as claimed in Claim 12 or Claim 13 wherein the tubing string is releasably connected together at a location above said upper piston; uppermost annular piston is slidably positioned within the tubing string holds the tubing string in the connected configuration; an axial passageway extends the uppermost piston which is larger than the passageway formed through the upper piston located therebelow; which method comprises circulating a ball downhole into engagement with the upper piston, forcing the piston to move downhole, and using the down hole movement of the piston to release the lowertubing string at the recited location above the first recited piston.

15. A method as claimed in Claim 14, wherein the packer device is located above the location where the tubing string is releasably connected together;

16. A method on completing a well substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

17. Hydrocarbon extracted from a wellbore as claimed in any one of Claims 6 to 9, through apparatus as claimed in any one of Claims 1 to 5, or by a method as claimed in any one of Claims 11 to 16.