Methods and apparatus for completing production wells

[57] ABSTRACT

This application discloses new and improved methods and apparatus for completing production wells having perforations

Id

Γ 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 having an elongated tubular member dependently coupled therebelow and capped at its lower end for defining an enclosed chamber of a substantial volume below the packer which is initially maintained at a reduced pressure by a new and improved normally-closed pressure-actuated valve arranged at the upper end of the tubular member. 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 communication from the surface with the tubing, the normally-closed valve is selectively opened by increasing the pressure of the fluids in the production string above the packer. Upon opening of this 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, a selectivelyreleasable tubing plug in the production tool above the normally-closed valve is removed to permit selected fluids to be pumped by way of the production string through the perforations and into the adjacent earth formations.

Claims, S Drawing Figures

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/.. 11 &lt;7 ' τ 12

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PATENTEDMAY16 ran

SHEET 1 OF 2

3,662,834

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David E. Young INVENTOR

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ATTORNEY

PATENTED may ι 6 ran

3,662,834SHEET 2 OF 2

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ATTORNEY

3,662,834 and improved apparatus and exemplary methods employing the principles of the invention as illustrated in the accompanying drawings, in which:

FIGS. 1,3 and 4 schematically depict the successive steps of the methods of the present invention;

FIG. 2 shows a typical perforation as it may appear before conducting a completion operation in accordance with the methods of the present invention; and

FIG. 5 depicts a preferred embodiment of the new and improved apparatus of the present invention.

Turning now to FIG. 1, a new and improved production tool 10 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 11 and positioned in a well bore 12 having a casing 13 secured in place by an external sheath of cement 14. To gain communication with an earth formation 15 traversed by the well bore 12, one or more perforations, as at 16, have been previously produced through the casing 13 and the cement 14 in the usual manner. As is customary, the production tubing is dependently supported in the well bore 12 by a typical wellhead assembly 17 including at least a pair of valves, as at 18 and 19, for selectively controlling communication with the tubing string 11 and the casing 13.

As illustrated in FIG. 1, the tool 10 is comprised of a selectively-settable production packer 20 from which is dependently coupled an elongated tubular body 21 having its lower end capped, as at 22. To provide an enclosed chamber 23 within the tubular body 21 that is initially maintained at a low or atmospheric pressure, normally-closed valve means 24 and selectively-releasable barrier means 25 are arranged on the upper end of the body 21 and adapted to be selectively operated 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 21. The chamber 23 can, if desired, be filled with an inert gas that is at 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 20 be one of the production packers shown in either U.S. Pat. No. 3,074,484, or U.S. Pat. No. 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 11 and the wellhead 17 are in position. Accordingly, as depicted in FIG. 2, an enlarged view is shown of one of the perforations 16 as it may well appear after the adjacent formation 15 has been perforated. 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 12 and actuated for producing the perforations 16, the perforations will initially extend into the formation 15 as generally represented in

Irrespective of the nature of the formation, debris (such as at 26) will be left in the formation 15 as a result of the disinMETHODS 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 operations — are typically conducted to prepare the well for efficient production. Those skilled in the art will appreciate, however, that it is not at all uncommon for one or more of the perforations along a given perforated interval to be at least partially blocked by loose formation materials, debris, or foreign matter which is usually deposited in a perforation by typical shaped charges. A partial or total blockage of one or more of the perforations will, of course, impede or prohibit the introduction of treating fluids into those perforations and result in the inadequate treatment of at least those portions of the earth formation immediately adjacent thereto. As a result, further and otherwise needless treating operations will ultimately be required. Accordingly, unless all of the perforations along a perforated interval are capable of readily conducting fluids, subsequent treating operations as well as the production rate of the well will be significantly impaired.

Heretofore, such treating operations have had to be conducted before the drilling rig is removed from the well site so that its associated equipment and drill string could be employed. This, of course, results in needless expenses as well as additional delays before the production string and the related surface equipment can be installed to prepare the well for production.

Accordingly, it is an object of the present invention to provide 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 arranging pressure-actuated valve means in a production string and below a production packer included therewith. The valve means are initially closed to define an enclosed chamber of selected volume in a section of tubing arranged therebelow and capped at its lower end to maintain the chamber 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 valve means are selectively opened from the surface to draw formation fluids into the enclosed chamber for 50 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 formation. Thereafter, barrier means initially arranged in the tubing above the valve means are selectively removed to 55 enable fluids to be pumped 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 valve means are operatively arranged to be 60 ^te8^r3t’^on °f ^a typical shaped charge liner. Moreover, by obselectively opened in response to a predetermined change in ----- · ·· the pressure in the production string above a production packer included with the apparatus. In this manner, communication can be selectively established between the perforated _r_____________{_}__________. .,_lsla.

interval and the enclosed chamber below the valve means. 65 tively-impermeable sheath of debris will either remain subSelectively-releasable barrier means are operatively arranged in the new and improved tool above the valve means and adapted to be selectively removed therefrom by a releasing tool for establishing communication between the production _____________________________... _v,_v„_v> „„„ _{tululllumlallO}n string and the perforated interval of the well bore below the 70 between the well bore 12 and the formation 15 will be at least jp3CiC6I*. ’ · · *· ....

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 _....... _ _{ltuIWVCU uclurc ule weu TOre K} best understood by way of the following description of new 75 fully completed and production commenced.

serving test shots fired into laboratory targets, it is known that a typical shaped charge perforating jet will leave a somewhatimpermeable layer of debris (as indicated at 27) around the walls of the forward portion of the perforation 16. This relastantially in the position illustrated at 27; or, if the formation (as at 15) is incompetent, this impermeable layer will most likely be collapsed inwardly as the perforation 16 is filled with loose formation materials. In any event, flow communication retarded, if not substantially impaired, by the debris 27 and 28 deposited in the perforations 16. It is, therefore, this debris 27 and 28 which, irrespective of the competency of the formation 15, must be removed before the well bore 12 can be success4275

3,662,834

Accordingly, as illustrated in FIG. 3, after the packer 20 has been set for isolating the interval of the well bore 12 immediately adjacent to the perforations 16 from the remainder of the well bore thereabove and the wellhead 17 is in position, the valve 24 is opened. It will be appreciated, therefore, that upon opening of the valve 24, a sudden high-pressure differential is developed between the connate fluids in the formation 15 and the enclosed chamber 23 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 28, from the formation 15 through the various perforations 16 and into the empty chamber 23. These rushing fluids will, therefore, effectively wash out the debris, as at 26 and 27 (FIG. 2), along with any loose formation materials from the perforations 16. As a result, once this sudden flow ceases upon the filling of the chamber 23, the formation 15 surrounding the perforations 16 will be effectively cleaned leaving only clean formation particles adjacent to the perforations.

It is preferred to delay the removal of the barrier means 25 ^0 after opening of the valve means 24 so as to allow loose formation particles, debris and the like to settle into the lower portion of the enclosed chamber 23 as well as into the well bore 12 therebelow. Once this is believed to have occurred, the barrier means 25 are removed to establish fluid communication between the wellhead 17 and the formation 15.

The technique employed to remove the barrier means 25 will, of course, be dependent upon the particular apparatus employed therefor. For instance, in one manner of arranging the barrier means 25, a plug, such as that shown generally at “44” in my copending application Ser. No. 43,068 filed simultaneously herewith, can be releasably secured above the valve means 24 and operatively arranged for initially closing the i ' ’ . .

mechanical force or unbalanced pressure force is imposed on the plug to drive it downwardly into the enclosed chamber. Alternatively, the barrier means 25 might also be a so-called “tubing plug” which is releasably secured in position by a shear Γ-------- ....

typical wireline overshot or grapple (not shown) that is lowered through the production string 11 and coupled to an upright fishing neck as at 29. This tubing plug might well be one of those shown on Page 3,788 of the 1968-69 “Composite Catalog of Oil Field Equipment and Services”.

In any event, once the barrier means 25 have been removed, a fluid, such as at 30 in FIG. 4, is injected into the production string 11 through the wellhead valve 18. Where the formation 15 does not require a treating operation, the fluid 30 needs ________________ _______________„ _ult only to be suitable fluid such as a clean saline solution. By 50 barrier 25 is positioned therein, one or more lateral ports 37 properly selecting a saline solution of sufficient density, the ........— * resulting hydrostatic pressure of the fluid 30 will alone be effective for retaining control of the well until production is commenced.

On the other hand, where the earth formation 15 is to be 55 fluid communication through the lateral ports and a second consolidated by typical sand-consolidating agents, it is ........

generally preferred that the fluid 30 be a so-called “pre-flush fluid ’ such as kerosene, diesel oil, or a clean saline solution.

Once the pressured pre-flush fluid 30 is pumped into the for- ___________r___..._____ ___ mation 15, one or more consolidating agents (not shown) are 60 larged, as af41, and compFe’mentally fitted in title annular successively pumped through the tubing string 11 and into the .. . .

formation to accomplish the desired consolidation.

As is typical the consolidating fluids may then be followed by a suitable after-flush agent, such as kerosene, as well as in ----------_------------_ „ _v„,_al6CU, _{aa al} ,,, _allu some instances if production is not to be commenced im- 65 a pair of longitudinally-spaced sealing members 45 and 46 are mediately, temporary plugging agents such as “Black Magic”' an oil-base mud as supplied by Oil Base, Inc., of Houston, Texas. It will be recognized that the hydrostatic pressure and the pumping pressure of these successively-injected treating fluids ----------------- _pualuuu. , _{u IclcaaaDly} will be greater than the formation pressure of the formation 15 70 secure the sleeve 38 in its elevated position depicted in FIG. 5 Rn that trip nprrnrotinnc K ___1____a -i. . . ... . F .’

As previously mentioned, the methods of the present invention are also equally applicable for acidizing or hydraulic fracturing operations after the wellhead 17 and the production string 11 are in position. Accordingly, where the formation 15 is to be either acidized or fractured, the fluid 30 will, of course, be the treating fluid or fluids which are typically employed for such operations. Otherwise, the sequence of events will be substantially as depicted in FIGS. 1-4 with the possible exception that the formation 15 may be sufficiently competent that there will be little or no elution of loose formation materials as the debris 26 and 27 is cleared from the perforations 16. 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 hydraulic fracturing operation.

Turning now to FIG. 5, a preferred embodiment is shown of the new and improved production tool 10 of the present invention. Inasmuch as the preferred tool 10 is especially adapted to utilize a commercially-available tubing plug (such as previously described) for the selectively-releasable barrier means 25 and its detailed arrangement is not within the scope of the present invention, the barrier is only schematically depicted to facilitate the description of the production tool and the valve 24. Thus, in the preferred embodiment of the production tool 10 depicted in FIG. 5, it is preferred that the barrier means 25 be a conventional tubing plug which is adapted to be selectively released from the tool and retrieved 3q to the surface by means of a typical wireline overshot or grapple (not shown).

As illustrated, the production tool 10 includes the new and improved valve 24 and the extended tubular member 21 which is dependently coupled to the valve and has the cap 22 gated tubular body 31 having threads, as at 32 and 33, respectively arranged at its upper and lower ends for tandemly coupling the valve to the packer 20 and the elongated member . - --- 21. In the preferred embodiment of the valve 24, the axial pin or typical latching fingers and adapted to be removed by a bore 34 of the body 31 is appropriately recessed, as at 35, for *·“* ~~ ·* '“ ** ' receiving the latch fingers or dogs (not shown) of the tubing plug 25 and a selected portion 36 of the axial bore below the recess is particularly sized and located for sealing engagement by the sealing members (not shown) on the tubing plug. Thus, 45 so long as the tubing plug 25 is positioned within the new and improved production tool 10, it will be appreciated that fluid communication is reliably blocked through the axial bore 34.

To provide selective fluid communication between the well bore 12 below the packer 20 and the axial bore 34 when the upper end of the chamber 23 until a downwardly-acting „ fluidly sealing its lower end. The valve 24 includes an elonare provided in the valve body 31 below the initial position of the barrier; and an elongated sleeve 38 is slidably mounted around the valve body and cooperatively arranged for longitudinal movement thereon between a first position blocking ” ...... . . ______ position in which the ports are uncovered. In the preferred embodiment of the valve 24, the body 31 includes an enlarged-diameter upper portion 39 defining a downwardly-facing annular space 40. The upper portion of the sleeve 38 is enspace 40, with inner and outer sealing members 42 and 43 cooperatively arranged thereon for fluidly sealing the enlarged portion of the sleeve in the annular space.

The lower portion of the sleeve 38 is enlarged, as at 44, and . . _ ___3 cooperatively arranged therein for sealing engagement with an exterior surface 47 of the body 31 above and below the ports 37 for isolating the ports from the well bore fluids so long as the sleeve is in its illustrated elevated position. To releasably means are provided such as a pin 48 of a predetermined strength for releasably coupling the sleeve to the valve body 31. Accordingly, so long as the valve 24 is in the position depicted in FIG. 5, the barrier 25 will block fluid communication 75 through the axial bore 34 and the ports 37 below the barrier pumping pressure of these successively-injected treating fluids so that the perforations 16 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.

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3,662,834 will be isolated from the well bore 12 by the sleeve 38 and the coaction of the sealing members 45 and 46 with the exterior surface 47 of the valve body 31.

It will be appreciated from FIGS. 1 and 5 that when the valve 24 is in its initial position and operatively coupled into the tool 10 of the present invention, the axial bore 34 below the barrier 25 will be at a reduced pressure (i.e., whatever pressure is initially maintained in the enclosed chamber 23) and the upper portion of the axial bore above the barrier will be in communication with the tubing string 11 above the packer 20. To permit the valve 24 to be selectively opened from the surface, one or more ports 49 are arranged in the valve body 31 to communicate the upper portion of the annular space 40 with the upper portion of the axial bore 34 above the barrier 25.

Accordingly, to selectively open the valve 24, it is necessary only to increase the fluid pressure in the production string 11 for developing a downwardly-acting pressure force on the enlarged upper end 41 of the sleeve 38 that is sufficient to fail the pin 48 retaining the sleeve and shift it downwardly in relation to the body 31. Once the sleeve 38 is shifted downwardly to a lower position as determined by an upwardly-facing shoulder 50 around the body 31, the sealing members 45 and 46 will no longer be straddling the ports 37 and one or more lateral ports 51 in the sleeve above the sealing members will be brought into registration with the body ports to establish fluid communication between the well bore 12 below the packer 20 and the enclosed chamber 23. „ . _________________________

Referring again to FIG. 1, it will be appreciated that when 30 ^more perforations traversing earth formations and comprising the new and improved tool 10 of the present invention is posi- *' * * tioned in the well bore 12, the barrier 25 will be in its initial position and the valve 24 will be in its normally-closed position as depicted in FIG. 5. The elongated body 21 will define the enclosed chamber 23 so long as the barrier 25 remains in 35 communication between the exterior and interior of said tubuposition and the sleeve 38 remains in its elevated position in relation to the body 31 of the valve 24.

As previously described in relation to FIG. 3, the valve 24 is selectively opened to induce a rapid flow of connate fluids as and 27 from the perforations 16. To accomplish this, the wellhead valve 18 is opened and sufficient pumping pressure is applied from the surface to the fluids in the production string 11 above the packer 20 to fail the shear pin 48 and shift the .- - ---------------------sleeve 38 downwardly from its position illustrated in FIG. 5 for 45 *^e“ ^bore thereabove; coupling the upper end of said producestablishing fluid communication (by way of the ports 37 and * * * «-51) between the enclosed chamber 23 and the well bore 12 below the packer. It will, of course, be appreciated that the barrier 25 will still be retained in its depicted position. 1 from the production tool 10 by typical Wireline retrieval techniques, the fluid 30 can be freely injected through the production string 11 and the now-aligned ports 37 and 51 into the well bore 12 below the packer 20 as required for the par- -. ticular completion operation. It will, of course, be appreciated ⁵' that if the cap 22 is left in position on the lower end of the extended tubular member 21, the ports 37 and 51 will tend to limit the flow communication in either direction between the production string 11 and the formation 15. Accordingly, in the preferred embodiment of the production tool 10, the cap 22 is temporarily secured to the tubing member 21, as by a relatively-weak shear pin 52, so that the cap can be easily removed 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 in a 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 valve of the new and improved production tool of the present invention is opened to clear the perforations of debris and the like. Thereafter, the barrier in the production tool is removed to establish communication from the surface with the formations below the packer. Where the formations require acidizing, fracturing or consolidation treatments to prepare the well for production, one or more treating fluids can be readily dispatched through the now-opened production string and into the well bore below the packer.

While particular illustrations and embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.