US3627045A

US3627045A - Methods for completing wells traversing earth formations

Info

Publication number: US3627045A
Application number: US15528A
Authority: US
Inventors: Maurice P Lebourg
Original assignee: Schlumberger Technology Corp
Current assignee: Schlumberger Technology Corp
Priority date: 1970-03-02
Filing date: 1970-03-02
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14

Abstract

This application discloses new and improved methods for completing wells having earth formations which are to be fractured, acidized, or treated for inhibiting the production of unconsolidated formation materials. In one manner of practicing the present invention, a tool string is arranged for suspension from a string of pipe and includes a well packer coupled to an elongated tubular member defining an enclosed chamber of a substantial volume and which is maintained at a reduced pressure by normally closed valves at the opposite ends of the chamber that are adapted to be selectively opened in succession. This tool string is then positioned in a cased well bore and the packer is set above a previously perforated interval traversing an earth formation which is to be treated. Once the packer is set to isolate the perforated interval from the well bore thereabove, the first of the two valves is selectively opened. Upon opening of the 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 valve is selectively opened for suddenly injecting pressured treating fluids from the supporting pipe string through the perforations and back into the adjacent earth formations.

Description

l 6 e 3 O 7 0 5R l2-l4-7l XR 396279045 [72] Inventor Maurice P. Lebourg Houston, Tex. [21] Appl. No. 15,528 [22] Filed Mar. 2, 1970 [45] Patented Dec. 14, 1971 [73] Assignee Schlumberger Technology Corporation New York, N.Y.

[54] METHODS FOR COMPLETING WELLS TRAVERSING EARTH FORMATIONS l3 Clalms, 8 Drawing Figs.

[52] U.S. C1 166/278, 166/285, 166/307, 166/308, 166/311 [51] Int. Cl E2lb 43/04, E2lb 43/26, E21b 43/27 [50] Field of Search 166/278, 299, 281, 286, 305, 307, 308, 249,311,312, 177, 297, 285

[ 56] References Cited UNITED STATES PATENTS 2,918,127 12/1959 Bodine,.1r. 166/177X 3,045,749 7/1962 Brandon .l 166/249 3,048,226 8/1962 Smith 166/177 X 3,062,290 11/1962 Beckett. 166/31 1 X 3,209,834 10/1965 Essary 166/311 X 3,255,820 6/1966 Brandon 166/311 X Primary Examiner-Stephen J. Novosad A!torney.rErnest R. Archambeau, .lr., Stewart F. Moore, David L. Moseley, Edward M. Roney and William R.

Sherman ABSTRACT: This application discloses new and improved methods for completing wells having earth formations which are to be fractured, acidized, or treated for inhibiting the production of unconso'lfiifiafl formation materials. in one manner of practicing the present invention, a tool string is arranged for suspension from a string of pipe and includes a well packer coupled to an elongated tubular member defining an enclosed chamber of a substantial volume and which is maintained at a reduced pressure by normally closed valves at the opposite ends ofthe chamber that are adapted to be selectively opened in succession. This tool string is then positioned in a cased well bore and the packer is set above a previously perforated interval traversing an earth formation which is to be treated. Once the packer is set to isolate the perforated interval from the well bore thereabove, the first of the two valves is selectively opened. Upon opening of the first valve, formation fluids will he 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 valve is selectively opened for suddenly injecting pressured treating fluids from the supporting pipe string through the perforations and back into the adjacent earth formations.

Patented Dec. 14, 1971 3 Shah-Shut 1 INVENTOR Maurice P Lebourg FIG.2

FIG.4

FIG. 6

3 Shoots-shalt 2 Maurice P. Lebourg INVENTOR ATTORNEY Patnted Dec. 14, 1971 Patented Dec, 14, 1971 3 Sheets-Shut 3 Q R m N a. Y 0 1 m w 2 2 5 6 5 7 5 N R a a 6 s 5 5 6 m I m H i w M I Z 4. a 5060mm. v rid m 0a 1 rt 1%: gum Y B m w 7 G I F 5 8 7 0 8 w 3 5 5 5 6 7 W m 5 M E W 2 w 7 l4 A w .P n. 5 u bofivofih Q .,\|m1:4 pa. v o H n; JQ w.|\, LM 1 L W 9 5 METHODS FOR COMPLETING WELLS TRAVERSING EARTH FORMATTONS It is, of course, the usual practice 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 may often be deposited in a perforation by a typical shaped charge. 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 I needless treating operations will ultimately be required. Ac-

cordingly, 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 affected.

In addition to the aforementioned sand consolidating operations, so-called gravel-packs" are also alternatively employed by the industry for inhibiting the production of sand from unconsolidated or incompetent formations. To form such gravel packs, a suitable slotted or screened tubular member is positioned within the perforated interval of a cased well bore and a slurry containing selectively sized particles of either small gravel of large-diameter sand grains is pumped into the well bore and displaced into the annulus between the liner and the perforated casing. In this manner, the resulting gravel pack will serve as a permeable filter over the entrances to the perforations for blocking the entry of the fine formation particles which would otherwise flow into the well bore as the well is subsequently being produced. With a gravel pack completion, however, the partial or total blockage of one or more of the perforations by fine sand particles will at least reduce, if not significantly impair, the subsequent efficient production of the well.

Accordingly, it is an object of the present invention to provide new and improved methods for completing well bores to provide improved fluid communication between the well bore and selected earth formations traversed thereby.

This and other objects of the present invention are attained by packing-off a perforated well bore interval traversing one or more earth formations for isolating the perforated interval from the remainder of the well bore. An enclosed chamber that is initially retained at a reduced pressure is then suddenly placed into fluid communication with the isolated interval to rapidly produce a limited volume of connate fluids for flushing foreign material and contaminants from the formations surrounding the perforations. Thereafter, a clean fluid is suddenly surged back through the perforations to clear the entrances to the perforations and force the fluid under an elevated pressure into the surrounding formations. Then, the well is completed either by performing a typical acidizing, fracturing or formation-consolidation operation or by installing a typical gravel pack in the casing over the entrances to the perforations.

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 exemplary methods employing the principles of the invention as illustrated in the accompanying drawings, in which:

FIGS. 1, 3 and 5 schematically depict the successive positions of typical apparatus while practicing the methods of the present invention;

FIGS. 2, 4 and 6 respectively show a typical perforation as it may appear during the course of a typical well completion operation involving the methods of the present invention; and

FIGS. 7A-7B schematically illustrate a preferred embodiment of a well tool which is particularly adapted for practicing the present invention.

Turning now to FIG. 1, a well tool 10 adapted for practicing the present invention is illustrated as being dependently coupled from the lower end of a tubing string 11 and positioned in a well bore 12 having a casing 13 secured in position by an external sheath of cement 14. To gain communication to 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 cement 14 in the usual manner. a

As illustrated in FIG. I, the tool 10 is comprised of a selectively settable packer 17 which is dependently coupled to the lower end of a tubular body 18 of substantial length for providing an enclosed chamber 19 that is initially at a low or atmospheric pressure and is closed at its upper and lower ends by selectively operable barrier or valve means 20 and 21 which are respectively adapted to be operated independently of one another. The chamber 19 can, if desired, be filled with an inert gas that is at an elevated pressure which is below the anticipated formation pressure. Although other well packers may, of course, be employed, it is preferred that the packer 17 be the full bore packer shown in US. Pat. No. 3,399,729. As far as the upper and lower valve means 20 and 21 are concemed, as will subsequently be described in detail, any suitable arrangement of valves or barriers may be employed so long as the lower barrier or valve means can be selectively opened independently of the upper barrier or valve means so as to induce the rapid influx of connate fluids from the formation 15 into the voided chamber 19 upon opening of the lower valve means.

As will be subsequently discussed, the methods of the present invention are uniquely applicable for performing acidizing and fracturing operations as well as typical sand consolidation or gravel packing operations. However, for purposes of illustration, FIGS. 2-6 depict the practice of the present invention as it might be conducted for an otherwise typical sand consolidation or gravel packing operation. Accordingly, as depicted in FIG. 2, an enlarged view is shown of one of the perforations 16 as it may well appear where the adjacent formation 15 is substantially unconsolidated or incompetent.

It will, of course, be appreciated that when a perforating tool which typically includes one or more shaped charges (not shown) is positioned in the well bore 12 and actuated for producing the perforations 16, the perforations will initially extend into the incompetent formation 15 as generally represented in FIG. 2. It is believed, however, by those skilled in the art that the perforation 16 will quickly fill up with loose materials from the incompetent formation 15 leaving open only a passage or so-called tunnel 22 extending through the casing 13 and the adjacent cement 14.

It will, of course, be appreciated that irrespective of the nature of the formation, debris, such as at 23, will be left in the formation 15 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 sheath (as indicated by the dashed lines 24) around the walls of the forward portion of the perforation 16. This relatively impermeable sheath of debris will either remain substantially in the position illustrated by the dashed lines 24; or, if the formation (as at 15) is incompetent, this impermeable sheath will most likely be collapsed inwardly as the forward portion of the perforation 16 is filled with loose formation materials. In any event, flow communication between the entrance tunnel 22 and the formation 15 will be at least retarded, if not substantially impaired, by the

debris

23 and 24 deposited in the formation just outside of the tunnel. It is, therefore, this

debris

23 and 24 which, irrespective of the competency of the formation 15, must be .removed before the well bore 12 can be successfully completed.

Accordingly, as illustrated in FIG. 3, after the packer 17 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, the lower barrier or valve means 21 are quickly opened. It will be appreciated, therefore, that upon opening of the lower valve means 21, a sudden highpressure differential is developed between the connate fluids in the formation and the enclosed chamber 19 which, preferably, is initially at atmospheric pressure. This sudden pressure differential across the perforated well bore interval will, of course, induce a rapid, high-velocity flow of connate fluids 25 from the formation 15 through the various entrance tunnels 22 and into the empty chamber 19. These rushing fluids, therefore, will effectively wash out the debris, as at 23 and 24 (FIG. 2), along with a limited quantity of loose formation materials through the several tunnels 22. As a result, as shown in FIG. 4, once this sudden flow ceases upon the filling of the chamber 19, the formation 15 surrounding the perforations will be effectively cleaned leaving only clean formation particles, as at 26, partially or totally filling the tunnels 22 through the casing 13 and cement 14.

It will be recognized, of course, that with even these clean formation particles, as at 26, in the entrance passages 22, the subsequent injection of consolidating agents of the production of connate fluids will be materially limited. It is, therefore, one of the paramount objects of the present invention to remove these loosened particles 26 from the tunnels 22 before further completion operations are conducted.

Accordingly, to accomplish this, a clean fluid, as at 27 in FIG. 5, is confined in the tubing string 11; and, by rapidly opening the upper valve 20, suddenly introduced into the previously closed chamber 19 for producing a sudden shock or transitory pressure surge in the isolated interval of the well bore 12 below the packer 17 for driving the clean sand particles 26 back into the formation 15 and clearing the tunnels 22 as illustrated in FIG. 6.

It will, of course, be appreciated that although the chamber 19 is filled with the connate fluids 25 upon opening of the lower valve means 21, these fluids as well as those in the isolated portion of the well bore below the packer 17 will be at a pressure no greater than the natural formation pressure of the earth formation 15. Accordingly, by rapidly opening the upper valve means 20, the injection fluid 27 will be suddenly moved downwardly into the chamber 19 and develop significant dynamic shock pressure which are substantially greater than the formation pressure within the isolated portion of the well bore 12 below the packer 17. Thus, as previously noted, the sudden release of the injection fluid 27 into the chamber 19 will be effective for forcibly driving the sand particles 26 out of the several tunnels 22 and back into the surrounding formation 15. It will, of course, be appreciated that once these transitory shock pressures have subsided, the injection fluid 27 is maintained at a pressure sufficient for preventing the production of further connate fluids from the several perforations 16 so that additional sand particles will not reenter the several tunnels 22.

Where the earth formation 15 is to be consolidated by typical sandconsolidating techniques, it is generally preferred that the injection fluid 27 be a so-called preflush fluid" such as kerosene, diesel oil, or a clean saline solution. Once the pressured preflush fluid is pumped into the formation 15, one or more consolidating agents (not shown) are successively pumped into the formation to accomplish the desired consolidation. As is typical, the consolidating fluids may then be followed by a suitable afterflush 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 Compton, Cal. lt 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 15 so that the tunnels 22 will remain open throughout the consolidation operation. The particular nature or type of sand consolidation agents are, of course, of

no significance to the present invention and the consolidating agents may be either poroussetting or solid-setting plastics.

On the other hand, where the well bore 12 is to be subsequently gravel-packed, the injection fluid 27 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 27 will be effective for retaining the loose formation 15 in position as the tool 10 and the tubing string 11 are removed and appropriate tools are installed for performing a typical gravel-packing operation. Hereagain, since the particular techniques employed for setting a typical gravel pack and screen in the casing 11 around the perforations 16 are of no significance to understanding the present invention, these details have not been illustrated. it is believed that a proper gravel-packing operation will result in filling the still open tunnels 22 with the larger gravel particles so as to define adequate fluid channels through the packed tunnels and prevent the reentry of fine formation materials.

As previously mentioned, the present invention is also equally applicable for otherwise typical acidizing or hydraulic fracturing operations. Accordingly, where the formation 15 is to be either acidized or fractured, the treating fluid 27 will, of course, be the fluid which is to be injected into the several perforations 16 for such operations. The sequence of events will, of course, be substantially as depicted in FIGS. 1-6 with the possible exception that the formation 15 may be sufficiently competent that there will be little or no loose formation materials, as at 26, deposited in the tunnels 22. 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 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 27 is suddenly released upon opening of the upper barrier or valve means 20 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 15 to assure that the treating fluid 27 is entering all of the perforations. As a further benefit, it has been found that the pumping pressures required to continue movement of the treating fluid 27 into the formation 15 will be significantly reduced in comparison to the pumping pressures normally required for conducting acidizing or fracturing operations not preceded by the methods of the present invention.

It should be noted that where the methods of the present invention are used for sand consolidating operations or gravelpacking operations, a sufficient surge or shock will usually be developed even where the chamber 19 is completely filled before the upper barrier or valve means 20 are opened. On the other hand, where an acidizing operation or fracturing operation is being conducted in accordance with the present invention, it has been found that greatly enhanced surge or shock pressures will be obtained by arranging the interconnecting tubular member 18 to have a volumetric capacity (i.e., the chamber 19) that is greater than the anticipated volume of the connate fluids 26 that will enter the chamber during the predetermined time interval before opening the upper valve means 20. In this manner, the upper portion of the chamber 19 will be empty when the upper valve means 20 are opened and the sudden entrance of the treating fluid 27 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 not to FIGS. 7A-7B, a completion tool 50 incorporating the principles of the present invention is depicted in its so-called running in" position. As illustrated, the completion tool 50 is comprised of a typical full bore well packer 51 that is dependently coupled to a pair of similar or identical selectively operable

full bore tools

52 and 53 which are respectively coupled to the upper and lower ends of a tubular member 54 of selected length. In those situations where a formation consolidation operation is to be performed, the completion tool 50 may also include a typical bypass valve 55 which is tandemly coupled above the upper full bore tool 52 for providing selective communication between the well annulus and a tubing string 56 supporting the completion tool. Since it is common to employ one or more segregating pistons or plugs (not shown) for separating the several consolidation agents as they are being pumped downwardly through the tubing string 56, it is preferred that the completion tool 50 also include means for catching such segregating plugs without preventing the continued flow of the treating agents. To accomplish this, a plug catcher 57 is comprised of a tubular housing 58 suitably arranged for tandem coupling between the bypass valve 55 and the upper full bore tool 53 and a smaller tubular member 59 coaxially mounted'within the housing. One or more inwardly directed shoulders 60 are arranged on the inner tubular member 59 for catching the first of several segregating plugs (not shown) and retaining it well below a plurality of longitudinally spaced lateral ports 61 in the inner member which provide fluid communication between the upper end of the plug catcher 57 and the full bore tool 53 therebelow when one or more plugs are progressively stacked in the inner member. As previously mentioned, the packer 51 may be the full bore packer described in U.S. Pat. No. 3,399,729.

The upper and lower

full bore tools

52 and 53 are only schematically depicted in FIGS. 7A-7B since it is preferred that these tools be similar to the full bore tool disclosed in U.S. Pat. No. 3,414,061 and the particular details of construction and operation can be readily determined from that patent. In general, therefore, the lower full bore tool 52 is comprised of an inner tubular member or mandrel 62 which is telescopically arranged within an outer tubular member or housing 63 for longitudinal movement between the extended or upper positionillustrated in F 1G. 73 and a further-telescoped lower position. To corotatively secure the telescoped members 62 and 63 to one another, one or more longitudinal splines, as at 64, on the mandrel are received in complemental grooves on the upper end of the housing. The tool 52 further includes a ball valve 65 and a sleeve valve 66 which are closed so long as the mandrel is in its illustrated position and are selectively opened by downward movement of the mandrel 62 in relation to the housing 63.

As fully described in U.S. Pat. No. .3,4l4,06l, downward movement of the mandrel 62 will successively open the sleeve valve 66 and then, as the mandrel approaches its lowermost position in relation to the housing 63, the valve-opening mechanism shown generally at 67 will rotate the ball valve 65 to its open position so as to provide a substantially unobstructed passage between the tubular member 54 and the well bore below the packer 51. As also described in U.S. Pat. No. 3,414,06l, downward travel of the mandrel 62 in relation to the housing 63 is selectively retarded by a typical hydraulic delay mechanism 68 cooperatively arranged between the mandrel and housing as shown in detail at "63 in FIG. 2B of the patent. In general, the hydraulic-delay mechanism 68 is cooperatively arranged to require a maintained downward force of substantial magnitude on the mandrel 62 for continuing its downward movement in relation to the housing 63. Once, however, the mandrel 62 approaches its lowermost position, the hydraulic-delay mechanism 68 functions to discontinue further retardation of the mandrel so that the force being applied thereto will suddenly shift the mandrel to its final position. As a result, this sudden release of the downwardly moving mandrel 62 will quickly open the ball valve 65. Once the mandrel 62 has reached its lowermost position in relation to the housing 63, external threads 69 around the mandrel will be cooperatively engaged with a split nut 70 mounted in the housing for retaining the mandrel in its downward position and maintaining the ball valve 65 in its fully open position.

The upper full bore tool 53 is preferably identical to the lower full bore tool 52 except that the upper tool is inverted as illustrated in FIG. 7A to prevent unbalanced pressure forces from prematurely operating the upper tool as the completion tool 50 is being positioned in a well bore and its operation is further retarded with respect to the lower tool. Accordingly, it will be appreciated that it is the housing 71 of the upper tool 53 that is moved downwardly in relation tothe mandrel 72 thereof, with this downward movement being selectively retarded by a hydraulic delay mechanism 73 until the housing is quickly released and has been moved to its lowermost position in relation to the mandrel and secured by a split nut 74 on the housing and threads 75 on the mandrel. As will be discussed later, the upper hydraulic delay mechanism 73 employs a more viscous fluid than that used in the lower delay mechanism 68. The upper tool 53 also includes a sleeve valve 76 and a ball valve 77 which is opened by a valve-operating mechanism 78 as the housing 71 is moved downwardly in relation to the mandrel 72. Hereagain, once the ball valve 77 has been opened, the split nut 74 willcooperate with the external threads 75 to retain the housing in its final lower position and lock the ball valve in its open position.

Once the completion tool 50 has been properly positioned in a well bore so that the packer 51 is just above a perforated interval, the packer is set and, assuming that a formation-consolidation operation is to be performed, the bypass valve 55 closed. The pipe string 56 is then "slacked-off so as to impose a substantial downwardly directed force on the completion tool 50. lt will be appreciated, therefore, that at this point, this downwardly acting force will be-tending to simultaneously move the

full bore tools

52 and 53 toward their respective telescoped positions for opening the

ball valves

65 and 77. The rates of relative telescoping movements of the

mandrels

62 and 72 and their respective housings 66 and 7 1 will, however, be selectively regulated at different rates by the hydraulic-

delay mechanisms

68 and 73 respectively provided in the two

full bore tools

52 and 53. Accordingly, as previously mentioned, by employing a more viscous fluid in the upper hydraulie-delay mechanism 73 than that used in the lower delay mechanism 68, the lower full bore tool 52 will be selectively operated before the upper full bore tool 53 to assure that the lower sleeve valve 66 and the lower ball valve 65 will open well before their counterparts in the upper tool.

lt will be appreciated, of course, that once the

lower valves

65 and 66 are rapidly opened, connate fluids will immediately be discharged into the tubular member 54 below the stillclosed

upper valves

76 and 77. As previously explained, this will purge the perforated formations in communication with the isolated well bore interval below the set packer 51.

Although the

upper valves

76 and 77 could be opened after the

lower valves

65 and 66 are opened by continuing to maintain the downwardly acting forces on the upper tool 53 for overcoming the upper delay mechanism 73 as soon as possible, as a matter of operating technique it is preferred to further postpone the opening of the upper valves for at least 1 or 2 hours to allow loose fonnation materials and debris which have been exhausted into the tubular member 54 to settle out into the well bore below the packer 51. Accordingly, once the

lower valves

65 and 66 open, an upward strain is applied on the tubing string 56 to prevent further downward movement of the upper housing 71 in relation to the upper mandrel 72. During this waiting period, treating fluids can be pumped into the pipe string 56 where they will be in position above the upper full bore tool 53.

Once it is desired to open the

upper valves

76 and 77, a downward force is again applied to the upper full bore tool 53 for again moving the housing 71 downwardly in relation to the mandrel 72. As previously described, therefore, once the upper valves 76'and 77 open, the treating fluids confined in the pipe string 56 will be suddenly released into the completion tool 50 for imposing the dynamic shock forces to the perforations in the isolated well bore interval therebelow. Then, by continuing to pump the treating fluids through the pipe string 56, the operation will be completed in the usual manner.

The foregoing operation will, of course, be similar to that followed where the completion tool 50 is being used to prepare the well for a gravel-packing operation or for an acidizing or fracturing operation. As previously explained, however, once the injection fluid is released by opening the

upper valves

76 and 77. the completion tool 50 is withdrawn from the well bore.

Accordingly, it will be appreciated that by employing the new and improved methods of the present invention, it can be reliably assured that perforations in a well bore traversing earth formations will be well conditioned to readily accept the subsequent injection of treating agents such as acids, formation-consolidating agents, protective fluids, or other fluids which must be introduced into earth formations. By first purging the formations and perforations of foreign matter and then imposing a sudden shock or dynamic force to the perforations, the present invention assures that a complete treating operation can be realized.

While a particular illustration of the present invention has 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.

What is claimed is:

l. A method for completing a well bore having a perforated interval with one or more perforations traversing earth formations and comprising the steps of: packing off said well bore above said perforations for isolating said perforated interval from the remainder of said well bore; providing an initially enclosed chamber which is at a first pressure; suddenly opening said chamber for placing said isolated perforated interval into communication therewith and thereby rapidly withdrawing connate fluids at a second higher pressure from said formations into said chamber to expurgate foreign matter from said perforations; and, thereafter, introducing a fluid under pressure through said chamber and into said isolated perforated interval for developing dynamic surge pressures therein to forcibly inject said pressured fluid through said perforations and into said earth formations.

2. The method of claim 1 wherein said pressured fluid is suddenly introduced into said isolated perforated interval for increasing the magnitude of said dynamic surge pressures.

3. The method of claim 1 wherein said pressured fluid is a treating fluid adapted for chemically reacting within said earth formations.

4. The method of claim I wherein said pressured fluid is a fluid adapted for fracturing said earth formations and said pressured fluid is suddenly introduced into said isolated perforated interval for increasing the magnitude of said dynamic shock pressures to further promote the fracturing of said earth formations.

5. A method for completing a well bore having a perforated interval with one or more perforations traversing earth fonnations and comprising the steps of: suspending a completion tool from a string of pipe in said well bore adjacent to said perforated interval, said completion tool including a tubular body having a flow passage therethrough, first valve means on said tubular body normally blocking flow communication between the lower end of said tubular body and said flow passage, second valve means spatially disposed above said first valve means and nonnally blocking flow communication between said pipe string and said flow passage to provide an enclosed chamber between said first and second valve means so long as said first and second valve means are closed, and packer means around said tubular body; setting said packer means for isolating said perforated interval form the remainder of said well bore; opening said first valve means for withdrawing connate fluids from said earth formations to flush foreign matter therefrom and into said enclosed chamber below said second valve means; and, thereafter, opening said second valve means and simultaneously discharging a fluid under pressure through said i strin and said flow assage into said perforated interva f r dev eloping dynamic shock pressures therein to forcibly displace said pressured fluid into said perforations and back into said earth formations.

6. The method of claim 5 wherein said pressured fluid includes a consolidating agent adapted to bond unconsolidated materials in said earth formations together for forming a permeable mass of said formation materials around said perforations.

7. The method of claim 5 wherein said pressured fluid has a density selected to develop a hydrostatic pressure in said perforated interval greater than the natural formation pressure of said connate fluids and including the further steps of: withdrawing said pipe string and said completion tool from said well bore; while said pressured fluid is in said perforated interval, placing a screen over the entrances to said perforations; and placing particles of a selected filter media between said screen and said entrances to fill said entrances with said filter media and block the entry of unconsolidated formation materials into said perforated interval as said well is subsequently being produced.

8. The method of claim 5 wherein said second valve means are opened suddenly for increasing the magnitude of said dynamic shock pressures and enhancing the displacement of said pressured fluids into said earth formations.

9. The method of claim 5 wherein said enclosed chamber is initially at about atmospheric pressure so that, upon opening of said first valve means, said connate fluids will be suddenly withdrawn from said earth formations into said enclosed chamber for enhancing the expurgation of said foreign matter from said earth formations.

10. The method of claim 5 wherein said pressured fluid is a treating fluid adapted for chemically reacting within said earth formations.

11. The method of claim 5 wherein said pressured fluid is a fluid adapted for fracturing said earth formations and said second valve means are opened suddenly for increasing the magnitude of said dynamic shock pressures to promote the fracturing of said earth formations.

12. The method of claim 5 wherein said pressured fluid is a treating fluid and said second valve means are opened suddenly before said connate fluids have filled said chamber for increasing the magnitude of said dynamic shock pressures to promote the displacement of said treating fluid into said earth fonnations.

13. The method of claim 12 wherein said enclosed chamber is initially at about atmospheric pressure so that, upon opening of said first valve means, said connate fluids will he suddenly withdrawn from said earth formations into said enclosed chamber for enhancing the expurgation of said foreign matter from said earth formations

Claims

1. A method for completing a well bore having a perforated interval with one or more perforations traversing earth formations and comprising the steps of: packing off said well bore above said perforations for isolating said perforated interval from the remainder of said well bore; providing an initially enclosed chamber which is at a first pressure; suddenly opening said chamber for placing said isolated perforated interval into communication therewith and thereby rapidly withdrawing connate fluids at a second higher pressure from said formations into said chamber to expurgate foreign matter from said perforations; and, thereafter, introducing a fluid under pressure through said chamber and into said isolated perforated interval for developing dynamic surge pressures therein to forcibly inject said pressured fluid through said perforations and into said earth formations.

4. The method of claim 1 wherein said pressured fluid is a fluid adapted for fracturing said earth formations and said pressured fluid is suddenly introduced into said isolated perforated interval for increasing the magnitude of said dynamic shock pressures to further promote the fracturing of said earth formations.

5. A method for completing a well bore having a perforated interval with one or more perforations traversing earth formations and comprising the steps of: suspending a completion tool from a string of pipe in said well bore adjacent to said perforated interval, said completion tool including a tubular body having a flow passage therethrough, first valve means on said tubular body normally blocking flow communication between the lower end of said tubular body and said flow passage, second valve means spatially disposed above said first valve means and normally blocking flow communication between said pipe string and said flow passage to provide an enclosed chamber between said first and second valve means so long as said first and second valve means are closed, and packer means around said tubular body; setting said packer means for isolating said perforated interval form the remainder of said well bore; opening said first valve means for Withdrawing connate fluids from said earth formations to flush foreign matter therefrom and into said enclosed chamber below said second valve means; and, thereafter, opening said second valve means and simultaneously discharging a fluid under pressure through said pipe string and said flow passage into said perforated interval for developing dynamic shock pressures therein to forcibly displace said pressured fluid into said perforations and back into said earth formations.

12. The method of claim 5 wherein said pressured fluid is a treating fluid and said second valve means are opened suddenly before said connate fluids have filled said chamber for increasing the magnitude of said dynamic shock pressures to promote the displacement of said treating fluid into said earth formations.

13. The method of claim 12 wherein said enclosed chamber is initially at about atmospheric pressure so that, upon opening of said first valve means, said connate fluids will be suddenly withdrawn from said earth formations into said enclosed chamber for enhancing the expurgation of said foreign matter from said earth formations.