Abstract:
An apparatus for effecting chemical treatment of a subterranean well bore comprises vertically spaced, inflatable packing elements which are run into the well on a fluid conduit, such as continuous coiled tubing, or the like. The apparatus permits circulation while being run into the well and, when positioned, effects the expansion of the two inflatable elements by pressured fluid introduced through the supporting fluid conduit. The applied pressure is trapped within the inflatable elements by axial movement of an inner body relative to an outer body, which effects the opening of fluid communication between the central fluid conduit and the well bore portion between the inflated packing elements, permitting testing of the sealing effectiveness of the packing elements, and the application of a treatment fluid. The same movement, accompanied by an increase in fluid pressure effects the opening of a fluid path to the well bore above the uppermost packing element. For deflation of the inflatable packing elements, the central body is moved downwardly by the spring, a circulation port is opened and a rupture disc is ruptured through the application of preselected higher fluid pressures. In order to compensate for a pressure variance as a result of the initation of the release sequence involved in deflating the inflatable packing elements, a pressure compensating member is provided, with the member having a cylindrical outer housing and a valve housing concentrically movable relative to and within the cylindrical housing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of co-pending application Ser. No. 345,343, filed Apr. 28, 1989, entitled &#34;Method and Apparatus for Chemical Treatment of Subterranean Well Bores&#34;, and assigned to the same assignee as the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for chemical treatment of any selected portion of a subterranean well bore by incorporation of an inflatable tool in combination with a compensating chamber valve member. 
     The invention also relates to a pressure compensating valve mechanism which may be used independent of the inflatable tool. 
     2. Summary of the Prior Art 
     Vertically spaced, inflatable packing elements have been widely used to isolate a selected portion of a well bore for chemical treatment. Prior art apparatus for achieved circulation while the treatment apparatus was being run into the well by passing the circulation fluid through the entire tool. See U.S. Pat. No. 4,708,208. Furthermore, the required manipulation of valves in prior art treatment apparatus have generally required the utilization of set down weight. This renders impractical the use of coiled tubing as the fluid supply conduit upon which the treatment apparatus is run into the well, since coiled tubing cannot apply any significant amount of set down weight. 
     It is also highly desirable that the portion of the well bore to be chemically treated not be saturated with fluids employed to effect the inflation or testing of the inflatable packing elements In prior art inflatable apparatuses, all of such setting and/or testing fluids contained in the coiled tubing were injected into the isolated well bore portion prior to the chemical treatment fluid ever reaching such portion. This, of course, is highly undesirable. 
     Lastly, prior art well treatment apparatuses embodying a pair of vertically spaced, inflatable elements have not been designed so as to permit circulation during the retrieval of the entire apparatus from the well. There is a definitive need, therefore, for a well treatment apparatus employing axially spaced, inflatable packing elements that can be run into the well on an auxiliary tool, such as coiled tubing inserted through a pre-existing tubing string and is capable of performing all of the desirable functions, such as circulation during run-in, testing of the tool&#39;s pressure integrity after inflation of the packing elements, removal of the inflation and/or testing fluid from the tubing by forcing such fluid into a well bore above the uppermost inflatable element prior to initiating the introduction of chemical treatment fluid into the isolated portion of the well bore, deflation without set down weight to permit the inflatable packing elements to be repeatedly repositioned in the well bore, and lastly, provision for circulating while retrieving the treatment apparatus from the well bore. 
     A pressure compensating chamber within a pressure compensating valving member will expand as the bias of a spring is overcome to compress the spring resulting in the expansion of the chamber corresponding to the decrease in pressure within the fluid conduit above the apparatus. The pressure compensating member comprises a cylindrical outer housing with a valve housing concentrically movable relative to and within the housing. A fluid flow passageway within the valve housing extends to the top of the well and communicates with the interior of the tool therebelow. Valve head and seat means, preferably provided in series, are carried by the valve housing for selective blocking of fluid flow in one direction through the passageway when the valve head and seat means are in a first relative position and permit fluid flow in one direction through the valve housing when the valve head and seat means are in a second relative position. A pressure chamber is within the outer housing and extends to the lowermost side of the valve head means. A biasing means is provided for biasing the valve housing to contract the pressure chamber, with a biasing means being energized by a decrease of pressure within the fluid conduit thereabove permitting the valve housing to be moved relative to the outer housing to expand the pressure chamber without movement of the valve head means relative to the valve seat means. 
     In co-pending application Ser. No. 345,343, filed Apr. 28, 1989, entitled &#34;Method and Apparatus for Chemical Treatment of Subterranean Well Bores&#34; and assigned to the same assignee as the present application, there is disclosed a unique inflatable apparatus having particular utility for chemical treatment of subterranean wells. In such device, when the inflatable elements are retracted from set position, the pressured fluid must be exhausted within the apparatus, but such exhaust procedure must be controlled to effectively activate the releasing mechanism. If a back flow valve is utilized with such apparatus, and is mounted, for example, immediately above said apparatus on the conduit carrying the inflatable apparatus, it must not respond to permit fluid flow to the top of the well as a result of the increase in pressure therebelow at any time. 
     The present invention is directed, in part, to the combination of the apparatus disclosed in that application with a pressure compensating back pressure valving mechanism which provides for an expandable pressure chamber immediately below the lowermost valve head means which may be expanded to compensate for the decrease in pressure of the fluid control conduit during initiation of &#34;deflation&#34; of the inflatable packer elements of the inflatable packer means. While the pressure compensating member of the apparatus has particular utility with that inflatable packer mechanism, the pressure compensating valving member is not necessarily limited to use therewith, and may be used alone and independent of said apparatus in a number of downhole tool applications, or combination with another auxiliary tool in the subterranean well. 
     SUMMARY OF THE INVENTION 
     A primary object of this invention is to provide an apparatus capable of fulfilling all the above mentioned deficiencies of prior art apparatus. A well bore treatment apparatus embodying this invention has a central tubular body assemblage which is connectable at its upper end to a fluid supply conduit, such as coiled tubing. The lower portions of the central tubular body assemblage is surrounded by an outer tubular body assemblage which incorporates two axially spaced, inflatable packing elements formed of elastomeric material. The central tubular body assemblage defines a central fluid conduit. The outer tubular body assemblage defines a generally annular conduit in surrounding relationship to the central tubular body assemblage. A circulation control valve assembly surrounds an upper portion of the central tubular body assemblage. 
     During run-in, a radial port in the upper end of the central tubular body assemblage permits circulation of fluid down through the fluid supply conduit and outwardly through a port in the control valve assembly into the well bore. A valve seat is provided in the central conduit above such radial port for reception of a ball which is dropped when the tool has reached the approximate position in the well bore where treatment is desired. The dropping of the ball permits fluid pressure of the supplied fluid to be increased and this effects the axial shifting of an annular piston in the control valve assembly to effect a closure of the aforementioned radial port and the opening of a second radial port in the central tubular body assemblage permitting the bypassing of the ball and the check valve to supply fluid to the central conduit. 
     Appropriate ports are provided in the medial portion of the central tubular body assemblage which, in the run-in position, provide fluid communication between the central conduit and the outer conduit, and ports in the outer tubular body assemblage provide communication with the interior of the annular elastomeric elements which constitute the inflatable packing elements. A compression spring holds the outer tubular body assemblage in said run-in position relative to the central tubular body assemblage. Thus, when the pressure of the supplied fluid is increased, the inflatable elements are inflated into sealing engagement with the well bore. 
     In this connection, it should be mentioned that the term well bore is herein applied in a generic sense. It can mean either the bore of casing mounted in a cased well or the drilled bore of an uncased well Since inflatable packing elements are being employed, a sealing engagement can be achieved with either form of bore wall. Of course, with a casing installed, the chemical treatment can be applied to only those portions of the well bore where casing perforations exist to provide communication with a particular formation for which treatment is desired. 
     During the inflation of the inflatable packing elements, a radial port in the outer tubular body assemblage which is positioned intermediate the two inflatable packing elements is in communication with that portion of the well bore isolated by the inflatable packing elements and any fluid pressure developed in that bore portion by the inflation of the packing elements is diverted by the aforementioned radial port to the well bore portion above the uppermost packing element. 
     After inflation has been completed, the central tubular body assemblage is moved upwardly through the application of an upward force to the central tubular assemblage by the coiled tubing. Such upward movement compresses the aforementioned spring and is limited by a pin and slot connection between the central tubular body assemblage and the outer tubular body assemblage. The distance of such displacement is such as to bring the inflation ports in the central tubular body assemblage upwardly beyond annular seal elements disposed between the exterior of the central tubular body assemblage and the interior of the outer tubular body assemblage, thus effecting a trapping of the fluid pressure previously supplied to the inflatable packing elements and insuring that such elements will remain in their inflated condition. 
     Testing of the adequacy of the seals effected by the two inflatable packing elements can then be effected through the supply of a suitable pressured fluid to the aforementioned radial port through the central conduit. 
     The upward movement of the central tubular body assemblage also causes a radial port in the outer tubular body assemblage to move into communication with an annular valve chamber defined in the upper portions of the outer tubular body assemblage. Such valve chamber has a radial port communicating with the well bore and such port is normally isolated by a sleeve piston mounted in the chamber and shearably secured in a port isolating position. Increasing the pressure of the fluid supplied to the central conduit will produce a pressure force on the piston sufficient to effect the shearing of the shear screws holding the piston in position and causing the piston to move upwardly to provide communication between the central conduit and the well bore above the uppermost inflatable element. When this condition has been achieved, the application of a pressured treatment fluid, such as an acid, to the surface end of the supply conduit will effect the forcing of all pressurizing or testing fluid contained in the supply conduit downwardly to the tool and then outwardly into the well bore above the inflated packing elements so that such pressurizing or testing fluid does not dilute the subsequent treatment procedure by the treatment fluid. 
     In the normal operation of the apparatus, the central tubular assemblage is then permitted to move downwardly to its run-in position under the bias of the spring which opposed its upward movement. Thus, no set down weight is required to be applied through the coiled tubing. As this downward movement occurs, a plurality of circumferentially disposed, spring pressed locking segments move inwardly into engagement with a groove on the exterior of the central tubular body assemblage and provide an abutment which effectively limits any subsequent upward movements of the central tubular body assemblage to a distance which does not permit communication of the fluid within the tool with the radial port in the valving chamber. Such downward movement would, of course, effect the deflation of the inflatable packing elements, but this can be prevented by maintaining an adequate fluid pressure in the central conduit. 
     The chemical treatment of the isolated well bore portion can then proceed in conventional fashion. At the completion of the treatment, it is generally desired to move the treatment apparatus to another position in the well bore. This is conveniently accomplished merely by releasing the upward force applied to the central tubular body assemblage and permitting it to move downwardly under the influence of the compressed spring. Such downward movement effects the alignment of ports in the central tubular body assemblage and the outer tubular body assemblage so that pressured fluid within the inflatable elements can drain into the central conduit from which any fluid pressure has been removed. 
     A rupture disc is provided in the lower portions of the central tubular body assemblage to permit the rupturing thereof under the influence of a fluid pressure which is greater than any of the fluid pressures employed for inflation or treatment. Such rupturing provides a passage for fluid to drain out of the deflated packing elements to facilitate their passage upwardly through any previously installed tubing string. 
     Lastly, a ball is dropped to engage a valve seat provided on a sleeve shearably secured in the extreme upper portion of the central conduit above the previously mentioned central valve. This permits a fluid pressure to be developed which operates on the sleeve to release it and move to uncover a radial port communicating with the well bore, thus permitting circulation to be accomplished during the retrieval of the testing apparatus from the well bore. 
     A pressure compensating back pressure valving mechanism provides an expandable pressure chamber immediately below the lowermost valve head means which may be expanded to compensate for the decrease in pressure of fluid in the fluid control conduit during the sequence of tool operation effected during the deflation procedure. As the deflation sequence occurs, the valving mechanism chamber expands without interfering of the seating of the valve head relative to the valve seat. 
     Further objects and advantages of the method and apparatus of this invention will be readily apparent to those skilled in the art from the following detailed description, taken in conjunction with the annexed sheets of drawings, on which is shown a preferred embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIGS. 1A, 1B, . . . 1L collectively constitute a vertical quarter sectional view of a well treatment apparatus embodying this invention. 
     FIGS. 2A, 2B and 2C collectively constitute a schematic quarter sectional view of the well treatment apparatus illustrating the position of the components in the inflation step of the process. 
     FIGS. 3A, 3B and 3C collectively constitute a vertical quarter sectional view of the well treatment apparatus showing the components in their positions required for the pressure testing step. 
     FIGS. 4A, 4B and 4C collectively and constitute a schematic vertical quarter sectional view of the well treatment apparatus with the components shown in their positions for effecting spotting of the well treatment fluid. 
     FIGS. 5A, 5B and 5C collectively constitute a schematic vertical quarter sectional view of the apparatus with the components thereof shown in their positions for effecting treatment of the well bore portion between the inflated packing elements. 
     FIGS. 6A, 6B and 6C collectively constitute a schematic vertical quarter sectional view of the well treatment apparatus illustrating the position of the components after deflation of the packing elements to permit movement to another position in the well bore. 
     FIGS. 7A, 7B and 7C collectively constitute a schematic vertical quarter sectional view of the well treatment apparatus showing the position of the components during the retrieval of the apparatus from the well while maintaining circulation. 
     FIG. 8 is a longitudinal sectional drawing showing the pressure compensating valving member with the pressure chamber biased to its retracted configuration. 
     FIG. 9 is a view similar to that of FIG. 8, and showing the pressure compensating chamber expanded during the deflation sequence. 
     FIG. 10 is a longitudinal sectional drawing showing the valve head members moved away from the valve seat members and fluid flow passing through the pressure compensating member from the top of the well, such as during chemical injection treatment through the inflatable apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1A, 1B, . . . 1L of the drawings, a formation testing apparatus embodying this invention comprises a central tubular assemblage 100 which has its lower portions surrounded by an outer tubular assemblage 200. Thus, the central tubular assemblage 100 projects beyond the outer tubular assemblage 200 at its upper end. The uppermost part of the central tubular assemblage 100 comprises a connection sub 102 which defines on its inner surface a recess or profile 102a for engagement by a running tool carried on coiled or threaded tubing (not shown). Connecting sub 102 is provided with a conventional threaded connection (not shown) to a remedial tubing string extending to the surface. Below the recess 102a, the connecting sub 102 is provided with one or more radial ports 102b communicating between the internal bore 101 of the central tubular assemblage 100 and the well bore annulus surrounding the apparatus. The lower end of the connecting sub 102 has a reduced diameter portion 102c which is provided with external threads 102d and mounts an O-ring 102e. These elements effect a threaded sealed connection with an inner valve housing 104. Inner valve housing 104 is connected by one or more shear screws 104a to a ball valve seating member 105 having an upwardly facing ball valve seat 105a. O-rings 105b and 104b straddle the shear screw 104a and thus effectively seal off any fluid flow through the shear screw 104a. Additionally, inner valve housing 104 is provided with external threads 104c for securement to the upper end of an outer valve housing 106. This connection is sealed by an O-ring 104d. 
     The lower end of the inner valve housing 104 is provided with a reduced diameter portion 104f which has external threads 104g engaging internal threads provided in a coupling sleeve 108. Sleeve 108 cooperates with the internal surface 106b of the outer valve housing 106 to define an annular fluid pressure chamber 107. Aligned radial ports 104e and 108e communicate fluid pressure chamber 107 with the bore 101 of the central tubular assemblage 100. 
     An upper valve seating sleeve 110 is sealably mounted within the interior of the coupling sleeve 108 by being clamped between the lower end of the valve housing sub 104 and a guide ring 112 which abuts an upwardly facing shoulder 108a formed on the interior of the coupling sleeve 108. Guide ring 112 has axial passages 112a formed therein. Valve seating sleeve 110 defines an upwardly facing ball valve seating surface 110a upon which a ball is gravitated or pumped after run-in. Additionally, valve seating sleeve 110 further defines a downwardly facing seating surface 110b with which a similarily shaped head portion 114a of a check valve 114 sealably cooperates. The stem portion 114b of check valve 114 is supported by guide ring 112. A spring 114d urges the check valve 114 into sealing engagement with the downwardly facing surface 111b. An O-ring 110c prevents fluid passage around the exterior of the valve seat element 110. 
     Thus, prior to the dropping of a ball onto the upwardly facing seating surface 110a, fluid flow downwardly through the central tubular body assemblage is prevented until the fluid pressure exceeds that level required to move the check valve 114 downwardly out of engagement with seating surface 110b. 
     Below the guide ring 112, the coupling sleeve 108 is provided with two vertically spaced sets of radial ports 108b and 108c. An annular piston 116 is mounted in the annular fluid pressure chamber 107 and is sealably engaged with the inner wall thereof by O-ring 116a and seal 116b. The lower end of piston 116 is radially enlarged and provides a mounting for seals 116b and 116c which, in the run-in position of the apparatus, are disposed in the position illustrated in FIG. 1A straddling the radial ports 108b. Thus, in the run-in position of the apparatus, fluid circulation may be maintained by pumping fluid downwardly through the bore 101 of the central tubular assemblage 100 to exit to the well annulus through radial port 108c and then through port 120a in a spring seat 120. Since the circulation fluid is pressurized, the check valve 114 will be shifted downwardly to permit the fluid flow down the central bore 101 to the radial ports 108c. 
     When a ball B1 is dropped on the upwardly facing seating surface 110a, as illustrated in FIG. 2A, fluid pressure may be applied at a higher level to the fluid pressure chamber 107 by passage through radial ports 104e in the inner valve housing 104. Such fluid pressure is increased to a level sufficient to move the piston 116 downwardly to a position, illustrated in FIG. 1B, where the re-circulation ports 108c are sealed off by the piston seals 116b and 116c straddling such ports. In this position of the piston, the ball valve B1 is effectively bypassed with the fluid flowing out through ports 104e and then back into the bore 101 of the central tubular assemblage 100 through radial ports 108b. 
     To prevent any backflow through the ports 108b, a lower check valve 115, substantially identical to check valve 114, is mounted in bore 101 immediately below radial ports 108b. Check valve 115 is held in position between a guide ring 113 and a downwardly facing shoulder 108f on inner valve housing 108. Guide ring 113 abuts the top end of an extension sleeve 126. Check valve 115 performs another function during deflation that will be decided later. 
     The downward movement of the piston 116 is opposed by a spring 118 which acts on the bottom end of the piston 116 through a spring seat 120. Spring 118 surrounds extension sleeve 126 which is secured by external threads 126a to the bottom of connecting sleeve 108. O-ring 126b seals this connection. The lower end of spring 118 is abutted by spacer rings 118a and an internally threaded abutment sleeve 122 which has relatively coarse internal threads 122a which cooperate with similarly shaped threads provided on the exterior of a coupling sub 124. The extent of threaded engagement of the abutment sleeve 122 thus determines the amount of compression applied to compression spring 118. The abutment sleeve 122 is anchored to the bottom of extension sleeve 126 forming a continuation of the central tubular body assemblage 100. The bottom end of extension sleeve 126 is threadably engaged with internal threads 124a on coupling 124 and such threads are sealed by an O-ring 124b. 
     The lower end of coupling 124 is provided with internal threads 124c which engage the threaded upper end of an elongated body sleeve 130 and are sealed by O-ring 124d. Body sleeve 130 extends into the top end of the outer tubular assemblage 200 and, at its lower end (FIG. 1E), is provided with internal threads 130a for engagement with external threads provided on the top end of a ball seating sleeve 132. Ball seating sleeve 132 defines at its upper end an upwardly facing ball seating surface 132a upon which a ball B2 is carried during run-in. Above the position of ball B2, a ball stop 134 is positioned in a recess 130b formed in the body sleeve 130. Ball stop 134 is provided with axial passages so as to permit upward fluid flow therethrough when the ball B2 is lifted off its seat 132a. Radial ports 132c and 130d are provided in the ball seat sleeve 132 and body sleeve 130 below and above ball valve B2 for a purpose to be hereinafter described. 
     The central body sleeve 130 is further provided near its upper end with an elongated, axially extending slot 130b (FIG. 1C). This slot cooperates with an inwardly projecting pin 201 which is mounted in the top sub 202 of the outer tubular housing 200 and thus limits the extent of upward movement of the central tubular assemblage 100 relative to the outer tubular assemblage 200 when such movement is required in the operation of the tool, as will be hereinafter described. Because of the many interactions between elements of the central tubular assemblage 100 and the outer tubular assemblage 200, the description of cooperating portions of these two assemblages will be made concurrently, in the interest of clarity. 
     As described in the operation of the apparatus, when the body sleeve 130 is manipulated to retain the inflation pressure in the inflatable means, the injection ports 132c and 130d. Additionally, as shown in FIG. 6A, the valving including body sleeve 130 provides means for escape of inflation fluid into the annulus exterior of the tool during deflation. 
     As stated, the outer tubular assemblage 200 has its upper end defined by a top sub 202. The lower end of top sub 202 is externally threaded at 202b and engages internal threads in an elongated lock housing sleeve 204. Lock housing sleeve 204 is provided with axially spaced vertical ports 204a and 204b and, in cooperation with the external surface 130c of the body sleeve 130, defines an annular fluid pressure chamber 50. An annular piston 206 is sealably mounted within the annular fluid pressure chamber 50 by O-rings 206a and 206b. Piston 206 is secured in its run-in position by one or more shear pins 207 which pass radially through the lock housing sleeve 204 and engage a recess 206c in an enlarged diameter portion 206d of the piston. This enlarged diameter portion is positioned intermediate the previously mentioned radial ports 204a and 204b in the run-in position of the apparatus. The piston seal 206a is bypassed in the run-in position of the apparatus by a plurality of relatively short, axially extending grooves 130d provided in the exterior of the body sleeve 130. 
     The lower end of piston 206 is provided with one or more radial ports 206f and immediately below such radial ports has a reduced diameter section 206g which functions as a retainer for lock segments 208 which are biased radially inwardly by garter springs 209. The lock segments 208 are retained by a downwardly facing shoulder 204d on lock housing sleeve 204 and the top end 210a of the next element 210 of the outer tubular assemblage 200 which is threadably secured by threads 210b to the bottom end of the lock housing sleeve 204. 
     An annular groove 130e is formed in the body sleeve 130 of the central tubular assemblage 100 and it is readily apparent that when the lower end 206g of the piston 206 is moved upwardly out of engagement with the locking segments 208, such segments will contract and latch into the annular groove 130e, for a purpose to be hereinafter described. 
     Proceeding downwardly on the tool, the next element of the outer tubular assemblage 200 is a spring seat sleeve 210. Spring seat sleeve 210 has a radially inwardly thickened top portion 210a secured by internal threads 204e to the bottom end of lock housing sleeve 204 and sealed by O-ring 210f. Top portion 210a mounts a seal ring 210c for sealing engagement with the external surface 130c of the body sleeve 130. The lower end of the spring seat sleeve 210 is provided with relatively coarse external threads 210d with which the top end of a spring housing sleeve 212 is threadably engaged. Obviously, the coarse threads 210d permit a substantial range of adjustment of the position of the spring housing sleeve 212 relative to the spring seat sleeve 210. A compression spring 214 is mounted in the annulus 213 defined between the spring housing sleeve 212 and the body sleeve 130 of the central tubular body assemblage 100. The top end of compression spring 214 abuts the bottom end 210d of spring seat sleeve 210 through a selected number of washers 216. The lower end of spring 214 is abutted by a segmented ring 232 which is engaged in an annular groove 130e formed in the body sleeve 130. Thus, upward movement of the central tubular body assemblage 100 relative to the outer tubular body assemblage 200 is opposed by the spring 214. The segmented ring 232 abuts the top end of a coupling 216 which is secured to the bottom end of the spring housing 212 by internal threads 212a and these threads are sealed by an O-ring 216a. The upper end of coupling 216 mounts an annular seal element 216b which is in engagement with the external surface of the inner body sleeve 130. An inflation port 130k is provided in body sleeve 130 slightly below seal 216b. The lower end of coupling 216 is provided with a port 216d, the purpose of which will be hereinafter defined. Additionally, the lower end of coupling 216 is provided with external threads 216e which mount the top end of an external body sleeve 218. These threads are sealed by an O-ring 216f. 
     In the annulus 75 between the outer body sleeve 218 and the inner body sleeve 130, a valving sleeve 220 is mounted by being trapped in position between the lower end of the coupling 216 and a counterbored upper end 220f of an upper trapping sleeve 222. An O-ring 220f seals this abutting connection. Upper trapping sleeve 222 is provided with one or more radial ports 220b which are disposed adjacent radial ports 224c in an upper coupling 224 which is secured to the bottom of upper external body sleeve 218 by threads 224a and O-ring 224b. A lower body sleeve 219 connects to upper coupling threads 224d which are sealed by O-ring 224e. A lower coupling 225 is secured to lower body sleeve 219 by threads 225a and O-ring 225b. 
     The bottom end of upper trapping sleeve 222 abuts the top end of a lower trapping sleeve 223 and this connection is sealed by O-ring 223a. The bottom end of trapping sleeve 223 is secured by external threads 223b to lower coupling 225. These threads are sealed by an O-ring 223c. 
     Internal seals 220a and 220b are provided in the opposite ends of valving sleeve 220 and are in sealing engagement with the exterior of the inner body sleeve 130; straddling a port 130d in inner body sleeve 130. 
     There is thus defined around the exteriors of the valving sleeve 220 and the trapping sleeve 222 an annular fluid passage 75. This passage is continued through the couplings 224 and 225 by a plurality of peripherally spaced, axially extending flow passages 224c and 225c so that the entire flow passage 75 can be defined as being generally annular and in surrounding relationship to the inner tubular body assemblage 100. 
     It should be noted that the central tubular body assemblage 100 terminates at the bottom 132d of valve seating sleeve 132, hence is vertically movable relative to the outer tubular body assemblage 200 to the extent permitted by pin 201 and slot 130b. 
     Proceeding downwardly from the lower coupling 225, external threads 225d mount an anchor sleeve 226 for securing the upper end of an inflatable elastomeric packing element 230. Threads 225d are sealed by an O-ring 225e. 
     Internal threads 225f are provided on the lower end of coupling 225 for securement to the top end of a lower inner body sleeve 140 and are sealed by O-ring 225g. An annular fluid passage 235 is maintained between the exterior of the lower inner body sleeve 140 and the internal surface of the elastomeric sleeve 228 for the passage of fluid thereunder. At a midpoint on the elastomeric sleeve 228, a reinforcing layer 228a of elastomeric material is provided with which the well bore is primarily engaged when the elastomeric sleeve 228 is inflated by pressured fluid applied through the annular passage 235. 
     The lower end 228c of the annular elastomeric element 228 is conventionally secured in position by a lower anchor sleeve 230. The lower end of anchor sleeve 230 is provided with internal threads 230a for securement to the top end of an injection port sleeve 232. O-ring 232b seals these threads. Injection port sleeve 232 is provided with one or more enlarged radial ports 232c and such sleeve snugly surrounds a coupling 234. Coupling 234 is provided with O-ring seals 234a and 234b which straddle the injection port 232c. Additionally, a radial port 234f communicates between central fluid passage 101 and ports 232c. 
     The coupling 234 is further provided at its upper end with internal threads 234c for engaging the bottom end of the lower bottom inner sleeve 140 of the outer tubular body assemblage. An O-ring 140b seals this threaded connection. Internal threads 234d on coupling 234 provide securement to the top end of a bottom inner sleeve element 142 of the outer tubular assemblage 200. These threads are sealed by an O-ring 142a. 
     A plug 144 is threadably secured by external threads 144a to the bottom end of the sleeve 142. This threaded connection is sealed by an O-ring 144b and terminates the central fluid passageway 101 which extends upwardly through the entire central tubular assemblage 100. 
     The outer tubular assemblage 200 extends downwardly from the coupling 234 to provide for the connection of a second elastomeric packing element inflatable by fluid pressure supplied through the generally annular conduit which extends through the entire outer tubular body assemblage 200. It should be mentioned that the coupling 234 is provided with a plurality of peripherally spaced, longitudinally extending fluid passages 234e which effect a continuation of the generally annular fluid passageway 75 of the outer tubular body assemblage 200. 
     The lower end of the injection sleeve 232 is provided with internal threads 232b which are secured to a space-out sleeve 236. These threads are sealed by an O-ring 236a. Space-out sleeve 236 is provided with threads 236b and a seal element 236c which engage corresponding threads provided on the top end of a second space-out sleeve 238. The bottom end of second space-out sleeve 238 is provided with threads 238a which are engagable with internal threads provided on a cross-over collar 240. A seal 240a seals the threads 238a. Cross over sub 240 has a lower portion 240b provided with external threads 240c and internal threads 240d. The external threads 240c are engaged with an upper elastomeric retainer sleeve 242 and the threads are sealed by O-ring 240e. The internal threads 240d are engaged with the upper end of a lowermost body sleeve 244 which extends to the bottom of the outer tubular body assemblage 200. 
     An annular elastomeric packing element 246 identical to the upper packing element 228 previously described has its top end secured by the upper retainer sleeve 242 and its lower end secured by a lower elastomeric retainer sleeve 248. The central portions of the annular elastomeric packing element 246 have an enlarged elastomeric well bore contact portion 246a integrally bonded thereto. 
     An annular fluid passage 247 is defined between the inner surface of the annular elastomeric packing element 246 and the external surface of the lowermost body sleeve 244, thus providing a continuation of the generally annular fluid passage 75 extending through the outer tubular body assemblage 200. 
     The lower end of the lower elastomeric anchor sleeve 248 is provided with internal threads 248a which are engaged with the upper end of a fill port sub 250. O-ring 250a seals the threads 248a. 
     The fill port sub 250 is provided with a radial fill port 250b by which the internal cavities of the outer tubular assemblage 200 may be filled with clean fluid at the well surface to eliminate air pockets. A plug 252 is then inserted in the fill port 250b to seal this opening. 
     The lower end of fill port sub 250 is provided with external threads 250c which are secured to a hold down sub 254. Hold down sub 254 is provided at its lower end with an inwardly projecting ridge 254a and such ridge is rigidly secured to a ring stop 255 by a plurality of screws 254b. Ring stop 255 is provided with a counterbore 255a in its upper end and this counterbore engages a downwardly facing shoulder 244c on lowermost body sleeve 244 to secure the lower end of the lower elastomeric retainer sleeve 248 to the lowermost body sleeve 244. 
     The lowermost body sleeve 244 is additionally provided with vertically spaced ports 244a and 244b respectively underlying the top and bottom ends of the upper elastomeric anchor sleeve 242 and the lower elastomeric sleeve 248. These ports function as inflation ports, in a manner that will be subsequently described. 
     The bottom end of the lowermost body sleeve 244 is provided with external threads 244d to which is secured a rupture cap 256. Threads 244d are sealed by an O-ring 256a. The medial portion of rupture cap 256 is provided with a radial port 256b within which is mounted a conventional rupture disc 258 which has the characteristic of being rupturable at a predetermined fluid pressure, higher than any of the fluid pressures utilized in the normal operation of the tool so that the port 256b may be opened to drain any residual fluid contained within the deflated elastomeric packing elements 230 and 246 only prior to removal of the entire tool from the well. 
     The operation of the aforedescribed tool will now be described by the remaining figures of the drawings which constitute schematic quarter sectional views of the apparatus shown in detail in FIGS. 1A-1L which has been heretofore described. Many details appearing in FIGS. 1A through 1L are omitted in the schematic views and the entire apparatus has been substantially shortened in length in order to reduce the number of sheets of drawings required. 
     As previously mentioned, FIGS. 1A, 1B . . . 1L show the components of the tool in their run-in position. It will be noted that circulation may be effected by passing pressurized fluid downwardly through the central bore 101 of the central tubular assemblage 100 which then passes outwardly through port 108c in the central tubular assemblage 100 and port 120a provided in the spring seat 120 surrounding the port 120a. 
     Now referring to FIGS. 8, 9 and 10, there is shown the pressure compensating member 300 of the present invention. The member 300 has a outer housing 301 comprised of a central housing member 301-a which is secured by threads 301-a&#39; to an upper housing member 301-b which, in turn, is secured by threads, such as 301-b&#39; to a workstring, production tubing, or the like, which may take the form of threaded sections or joints of pipe, or which may be continuous coiled tubing, or the like. 
     The outer housing 301 terminates at its lowermost end in a lower housing member 301-c which is secured at 301-a&#34; to the lowermost end of the central housing member 301a. An O-ring 301-c&#39; prevents fluid communication between the lower housing member 301c and the central housing member 301a. An O-ring 317 is carried on the lower housing member 301-c, as well as threads 318 for securing the member 300 to the inflatable apparatus, or auxiliary tool, therebelow. 
     Interiorly of the outer housing 301 is the valve housing 314 which has its lowermost tip end 314-a in abutting relationship to a shoulder 301c&#34; on the uppermost face of the lower housing member 301-c, when the bias defined through a coiled spring biasing means 315 is not overcome by an increase of pressure within the pressure chamber 316 defined interiorly of the outer housing 301 at the lowermost face 313 of the lower valve head 304. The biasing means has its upper end 315a arresting on a downwardly facing shoulder of the upper housing member 301b, while the lowermost and other end of the biasing means 315, 315-b rests upon an outwardly projecting shoulder of the valve housing 314. In this manner, the bias of the member 315 is defined between the outer housing 301 and the valve housing 314. 
     An O-ring 301b&#39; is carried on the upper housing member 301b to prevent fluid communication between the member 301b and the central housing member 301a positioned thereacross exteriorly. 
     A fluid flow passageway 302 is provided inwardly of the outer housing 301 and within the valve housing 314 and communicates with a fluid flow passage means interiorly of the continuous coiled tubing, or the like, sealingly secured to the tool thereabove, as well as to the interior of the inflatable apparatus, or auxiliary tool, therebelow. 
     The biasing means 315 is secured exteriorly around the outer circumference 314d of the valve housing 314, with a vent passage 319 being horizontally disposed through the valve housing 314. 
     The valve housing 314 is secured at threads 314c to a valve member 314d having an O-ring 309 to prevent fluid communication between the member 314d and the central housing 301a. A similar O-ring 307 is positioned within a valve seat member 314e to prevent fluid communication between the member 314e and 314d. A torsion spring 311 is positioned relative to the member 314d and has one end urging the upper valve head 303a into sealing securement to the lower face of the member 314e, with an O-ring seal member 305 circumferentially provided for additional sealing integrity between the valve head 303a and defining a valve seat therefore. The valve housing 314 continues lowerly of the valve head 303a and is secured by threads 314b to a second valve head member 314f having seal 310 similar to seal 309 and receiving interiorly thereof a valve seat member 314g having at its lowermost end a beveled seal surface for receipt of the lower valve head 304 into sealing engagement therewith with an elastomeric O-ring 306 providing additional sealing integrity between the valve head 304 and its companion seat. A second torsion spring 312 is provided to bias the lower valve head 304 against its seat to prevent fluid from flowing upwardly thereacross. The lower face 313 of the lowermost valve head 304 defines the uppermost end of a pressure chamber 316 within the compensating member 300. 
     OPERATION 
     When the tool is positioned in the selected portion of the well bore to be chemically treated, a ball B1 is dropped to seat on the upwardly facing surface 110a of the central tubular assemblage 100 as shown in FIG. 2A, permitting a build up of fluid pressure in central bore 101 above ball B1. This produces a downward shifting of the piston 116, against the bias of the spring 118, and closes the port 108c in the central tubular assemblage 100 to prevent fluid flow outwardly into the well bore, while at the same time opening the port 108b to permit fluid flow bypassing the ball B1. Thus, pressured fluid may flow down the central passage 101 in the central tubular assemblage and, since passage 101 is blocked by ball B2, thence pass outwardly through ports 130k and 216d into the generally annular passageway 75 provided in the outer tubular body assemblage 200. Pressured fluid in this passageway effects the inflation of the upper and lower elastomeric packing elements 228 and 246 into sealing engagement with the well bore as shown in FIGS. 2B and 2C. 
     During inflation of the packing elements, well fluids may be trapped therebetween and pressurized by the expanding packing elements. This is undesirable, so a flow path is provided through testing and treatment ports 232c and 234f to the lower end of central passage 101, then outwardly through ports 132c, 222b and 224c into the well bore above the upper packing element 228, as shown by the dotted arrows in FIGS. 2A and 2B. 
     Referring now to FIGS. 3A, 3B and 3C the pressured fluid expanding the elastomeric packing elements is trapped therein by an upward movement of the inner tubular body assemblage 100 relative to the outer tubular body assemblage 200 which is now anchored to the well bore. This upward movement is limited by pin 201 and slot 130b and seals off the inflation ports 130k by the seal 216b and hence traps the fluid pressure within the expanded elastomeric packing elements 228 and 246. Spring 214 is compressed. 
     At the same time, a fluid passage is opened through the ports 130d and 132c bypassing the ball B2 which has been in position during all of the previous operations blocking downward flow in central conduit at that point. This permits pressured fluid of a level sufficient to test the integrity of the seals effected by the expanded elastomeric packing elements to be applied to the well bore portion intermediate the upper and lower elastomeric packing element through the testing and treatment ports 234f and 232c (FIG. 3C). 
     The next step in the operation, illustrated in FIGS. 4A, 4B and 4C, is to increase the fluid pressure supplied to the tool through the central conduit 101 in the central tubular body assemblage 100 to a level sufficient to shear the shear pins 207 securing the locking piston 206 in position and causing such locking piston to move upwardly. In its upward position, the seal 206b carried by the piston 206 is disposed above the radial spotting port 204b provided in the outer tubular assemblage 200, hence permitting fluid existing in the supply conduit, which is preferably coiled tubing, to drain down through the central passage 101 in the central tubular body assemblage 100 and outwardly through port 130m in the inner body sleeve 130 and the radial spotting port 204b in the outer tubular body assemblage 200. Such drainage is preferably accomplished by applying pressured treatment fluid at the surface to the upper end of the fluid supply conduit. Thus, the pressurizing fluid theretofore supplied to the tool that remains in the fluid supply conduit will be forced out of the tool into the well bore, hence eliminating the necessity of diluting the treatment fluid by pumping such excess fluid into the well bore area to be treated. Such operation is referred to as spotting of the treatment fluid. 
     The next operation of the tool is to relax the upward tension on the inner tubular body assemblage 100 and permit it to be returned by spring 214 to its deflate position, which is the same position employed for inflation. Deflation of the expanded elastomeric packing elements is, however, prevented at this stage by maintaining a suitable fluid pressure on the treatment fluid being applied to the tool. 
     The previously described upward movement of the piston 206 permits the spring biased locking segments 208 to be urged inwardly into engagement with the external surface of the body sleeve 130 of the central tubular body assemblage 100. Thus, when the downward movement of the central tubular body assemblage 100 occurs under the bias of the compressed spring 214, the annular recess 130e moves into axial alignment with the spring biased locking segments 208 and they snap into the annular recess 130e, as shown in FIG. 5A. This engagement has no effect on the downward movement of the central tubular body assemblage 100, but any subsequent upward movement of the central tubular body assemblage 100 is limited by the presence of the locking segments 208 to a distance which does not bring the port 130m on the central body sleeve 130 past seal 210c in the outer tubular body assemblage. Thus, there is no need for the operator to be concerned about subsequent elevations of the central tubular body assemblage effecting a drainage connection for the treatment fluid contained in the tool. 
     As shown in FIGS. 5A, 5B and 5C, the central tubular body assemblage 100 is then again moved upwardly to a lesser extent than before by virtue of the action of the locking segments 208 and this creates a fluid supply passage from the central passage 101 in the central tubular body assemblage through radial port 234f and thence through a radial port 232c in the outer tubular body assemblage in the same manner as previously described for the testing operation, and permits pressurized treatment fluid to be supplied to the well bore portion between the expanded elastomeric packing elements. 
     When the treatment of the originally selected well bore portion has been completed, pressure within the tubing (or fluid supply conduit) is reduced below the pressure required to shift the piston which carries the seals 116a and 116b thereby permitting the chamber 316 to expand. During expansion of the chamber 316 the piston carrying the seals 116a and 116b is permitted to shift longitudinally to open the deflation portions 108c. Accordingly, as the chamber 316 expands, further movement of the seal piston 116a-b will be permitted. As the seal piston 116a-b moves, the trapped pressure above the seal piston 116a-b and below the lowermost valve head means 313 will be reduced as the chamber 316 expands. Thereafter, the tension on the central tubular body assemblage is released and it is returned to its deflate position by the compressed spring 214 (FIGS. 6A-6C). This permits the inflated elastomeric packing elements to deflate and the tool can be readily moved in the well bore to another position for treatment of the well bore at the new position. 
     When the entire treatment operation has been completed, and it is desired to withdraw the treatment apparatus from the well through the previously existing tubing string, the central tubular body assemblage 100 is returned to its inflate-deflate position and then the fluid pressure is substantially increased above the inflation, testing and treatment levels to effect a rupturing of the rupture disc 258 provided in the bottom end of the outer tubular body assemblage 200. 
     If it is desired to circulate fluid during the removal of the treatment apparatus, this may be accomplished by dropping a third ball B3 to seat on the uppermost valve seat 105a provided on the central tubular body assemblage 100 and applying a fluid pressure sufficient to effect the shearing of shear screws 104a holding the valve seat sleeve 105 in position. The shearing of these screws permits the valve seal sleeve to move downwardly and thus open a path to the well bore through the ports in the same plane as the shear screws, as shown in FIGS. 7A, 7B and 7C. 
     The advantages of a tool embodying this invention will be readily apparent to those skilled in the art. In the first place, the entire treatment apparatus may be inserted in the well bore through a pre-existing tubing string, such as production tubing. Circulation may be maintained while the treatment apparatus is being inserted in the well. The elastomeric packing elements are inflated and deflated at the same position of the central tubular body assemblage 100 relative to the outer tubular body assemblage 200. A simple upward movement of the central tubular body assemblage 100 against the bias of compression spring 214 effects the trapping of the inflation fluid pressure within the expanded elastomeric packing elements. During the expansion of the elastomeric packing elements, any fluid pressure developed in the well bore between such elements is drained into the well bore above the uppermost packing element, thus avoiding any undesirable build up of fluid pressure between the two expanded elastomeric packing elements. Spotting of the treatment fluid may be accomplished by increasing the fluid pressure to a level above that required for expanding the packing elements and thus effecting the upward movement of the locking piston 206. Such upward movement provides communication between the central passage 101 in the central tubular body assemblage 100 with the well bore above the uppermost packing element and permits all pressurizing or testing fluid contained in the fluid supply conduit to be pumped into this area of the well bore by the treatment fluid. 
     Subsequent downward movement of the central tubular body assemblage 100 is accomplished by the compressed spring 214, hence eliminating the need for any set down weight, which is a practical impossibility when using coiled tubing as the fluid supply conduit. The resulting engagement of locking segments 208 limits all subsequent axial movements of the inner tubular body assemblage between two fixed positions, eliminating guess work by the operator. 
     The treatment apparatus can not only be shifted to a variety of positions in the well bore but, when removal of the apparatus from the well bore is desired, the downward shifting of the central tubular body assemblage 100 by the compressed spring 214 to the inflate-deflate position and the application of a higher fluid pressure to the central passage in the central tubular body assemblage 100 effects the rupturing of rupture disc 258 to drain any remaining fluid from the deflated elastomeric packing elements prior to their passage through a preexisting tubing string. Thus, all of the disadvantages of the prior art apparatus have been completely eliminated through the method and apparatus of the aforedescribed fluid treatment tool. 
     It will be appreciated that the apparatus is easily converted from a device containing a circulation valve to one containing a fluid control valve upon dropping of a first ball on the ball seat after the apparatus is run into the well, as described, and prior to retrieval of the apparatus from its set condition, by dropping a second ball upon a ball seat positioned above the first ball seat, also as described. 
     It will also be appreciated that the apparatus, as designed, is easily resettable within the well, without requirement of retrieval to the top of the well. 
     Although the invention has been described in terms of specified embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent to those skilled in the art in view of the disclosure. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention.