US3627049A

US3627049A - Methods and apparatus for completing production wells

Info

Publication number: US3627049A
Application number: US43068A
Authority: US
Inventors: David E Young
Original assignee: Schlumberger Technology Corp
Current assignee: Schlumberger Technology Corp
Priority date: 1970-06-03
Filing date: 1970-06-03
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14

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.

Description

United States Patent Primary Examiner-Joseph H. McGlynn Attorneys-Ernest R. Archambeau, Jr., David L. Moseley,

Edward M. Roney and William R, Sherman 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 oli'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.

Patented Dec. 14, 1971 3,627,049

4 Sheets-Sheet 1 W FIG. 2 27 FIG! Y A Y David E. Young INVENTOR ATTORNEY Patented Dec. 14, 1971 4 Sheets-Sheet 2 FIGS David E. Yo ung IN VE N TOR ATTORNEY AL Patented Dec. 14, 1971 4 Sheets-Sheet 4 FIGIO David E. Young IN VE N TOR A TTORNE Y METHODS AND APPARATUS FOR COMPLETING PRODUCTION WELLS 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 operationsare 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 ofthe 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. ll, 3 and 5 schematically depict the successive steps of the methods of the presentinvention;

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 US. 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 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 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 hgih-pressure difierential 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 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 H0. 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 pressure 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, lnc., 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 in vention 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 101014 outs 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 lower ends and suitably adapted for tandemly coupling the valve between the packer 36 and the interconnecting tubing 311. In the preferred embodiment of the valve 34, a transverse barrier 44 is arranged across the axial bore 45 of the valve body 411 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 411 to block fluid communication through the axial bore 45.

To provide selective fluid communication through the axial bore 43 when the barrier 44 is positioned therein, longitudinally spaced

lateral ports

43 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

43 and 49 being in the upper section and the lower section having an enlargeddiameter portion 53 extending upwardly around the lower ports and defining an upwardly facing annular space 54 therearound. The lower portion of the sleeve Sill 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 53 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 4]. 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 ofthe 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 ofthe 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 53 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 ll to have a uniform diameter along the exterior sealing surface 60, these upwardly acting and downwardly acting pressure forces will be independent of the 43 respectively arranged on its upper and 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 :1 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 F IG. 8 that once the pin 61 fails to allow the sleeve 30 to be moved downwardly in relation to the valve body M 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 36 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 30 is enlarged, as at 63, between the

seals

56 and 53.

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 H0. 9, a preferred embodiment of the upper valve 33 is depicted in its initial closed position as previously described with reference to FIG. ll. 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 711, for initially bloclking 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 66 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 63 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 76 of the upper valve 33. By forming a circumferential groove 76 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 876 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 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 ofthe lower valve 34.

As previously described in relation to FIG. 3, the lower valve 34 is selectively opened to induce a rapid flow of connatc 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 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 UPC" the lower valve 34. the uppcr valve 33 will not be affected since the increased pressure will only tend to urge the ballretaining 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 vnlve 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 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 inventionhas 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 inventionQ What is claimed is:

l. 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 ll 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 ll wherein said dently coupled to said lower valve.

4. The method of claim l wherein said lower pressure-actu ated valve is opened by increasing the pressure in said well annulus.

packer is depen- Jill 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 ll wherein said upper pressure-actuated valve is opened by increasing the pressure in said production string.

a. 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 coupledin 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-offsaid well bore above said perforated interval.

9. The apparatus of claim d 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 ofthe pressure in said production string to at least a predetermined pressure.

Ill. 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.

ll2. 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.

113. 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 selectivelymoving said valve member to its said open position upon increases of the pressure in said well annulus to at least a predetermined pressure.

114. 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 pressureresponsive 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 ofa 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 second position.

w it s t lUlON (H89

Claims

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 pressureactuated 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.

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.

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.