Patent Abstract:
The disclosure pertains to engaging a longitudinally slidable sleeve within a well. The apparatus comprises a tool string slidably locatable within said well and a shifting tool slidably locatable within said sleeve at an end of a tool string. The shifting tool has a central bore therethrough and keys operable to be extended therefrom. The apparatus further includes a reservoir in fluidic communication with said central bore of said shifting tool and being operable to contain and hold a quantity of a fluid at a predetermined pressure sufficient to actuate said shifting tool. The method comprises comprises pressurizing the reservoir, reducing said pressure in said tool string above said reservoir slidably displacing said shifting tool and sleeve valve within said well by displacing said tool string therein.

Full Description:
BACKGROUND 
       [0001]    Field 
         [0002]    The present disclosure relates to well completion in general and in particular to a method and apparatus for operating a high pressure shifting tool within a well. 
         [0003]    Description of Related Art 
         [0004]    Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore is drilled, various forms of well completion components may be installed in order to control and enhance the efficiency of producing the various fluids from the reservoir. 
         [0005]    Fracturing is used to increase permeability of subterranean formations. A fracturing fluid is injected into the wellbore passing through the subterranean formation. A propping agent (proppant) is injected into the fracture to prevent fracture closing and, thereby, to provide improved extraction of extractive fluids, such as oil, gas or water. 
         [0006]    The disclosure pertains to methods of treating an underground formation penetrated by either vertical wells or wells having a substantially horizontal section. Horizontal well in the present context may be interpreted as including a substantially horizontal portion, which may be cased or completed open hole, wherein the fracture is transversely or longitudinally oriented and thus generally vertical or sloped with respect to horizontal. The following disclosure will be described using horizontal well but the methodology is equally applicable to vertical wells. 
         [0007]    The industry has privileged, when it comes to hydraulic fracturing, what is known as being “plug-and-perf” technique. Horizontal wells may extend hundreds of meters away from the vertical section of the wellbore. Most of the horizontal section of the well passes through the producing formation and are completed in stages. The wellbore begins to deviate from vertical at the kickoff point, the beginning of the horizontal section is the heel and the farthest extremity of the well is the toe. Engineers perform the first perforating operation at the toe, followed by a fracturing treatment. Engineers then place a plug in the well that hydraulically isolates the newly fractured rock from the rest of the well. A section adjacent to the plug undergoes perforation, followed by another fracturing treatment. This sequence is repeated many times until the horizontal section is stimulated from the toe back to the heel. Finally, a milling operation removes the plugs from the well and production commences. 
         [0008]    The common practice in the art is to perforate 4-6 clusters, and push a slickwater laden fluid at or above fracture pressure to create fractures; it is estimated that 30 to 60% of these perforations do not produce due to for example screen out, geological constraint, etc., and thus for every 100 perforations in a wellbore, commonly only 30 to 70 of the conventional perforations are useful for production. 
         [0009]    To respond to that, some operations now involve what is known as pin-point fracturing, which may be defined as the operation of pumping a fluid above the fracturing pressure of the formation to be treated through a single entry. The entry may be a perforation, a valve, a sleeve, or a sliding sleeve. Generally, sliding sleeves in the closed position are fitted to the production liner. The production liner is placed in a hydrocarbon formation. An object is introduced into the wellbore from surface, and the object is transported to the target zone by the flow field or mechanically, for example using a wireline or a coiled tubing. When at the target location, the object is caught by the sliding sleeve and shifts the sleeve to the open position. A sealing device, such as a packer or cups, is positioned below the sleeve to be treated in order to isolate the lower portion of the wellbore. The sealing device is set, fluid is pumped into the fracture and then the sealing device is unset and moved below the next zone (or sleeve) to be treated. Representative examples of sleeve-based systems are disclosed in U.S. Pat. No. 7,387,165, U.S. Pat. No. 7,322,417, U.S. Pat. No. 7,377,321, US 2007/0107908, US 2007/0044958, US 2010/0209288, U.S. Pat. No. 7,387,165, US2009/0084553, U.S. Pat. No. 7,108,067, U.S. Pat. No. 7,431,091, U.S. Pat. No. 7,543,634, U.S. Pat. No. 7,134,505, U.S. Pat. No. 7,021,384, U.S. Pat. No. 7,353,878, U.S. Pat. No. 7,267,172, U.S. Pat. No. 7,681,645, U.S. Pat. No. 7,066,265, U.S. Pat. No. 7,168,494, U.S. Pat. No. 7,353,879, U.S. Pat. No. 7,093,664, and U.S. Pat. No. 7,210,533, which are hereby incorporated herein by reference. A fracturing treatment is then circulated down the wellbore to the formation adjacent the open sleeve. 
         [0010]    One difficulty experienced in the actuation of sleeve valves within an oil well is that the shifting tool required to open and close the sleeve relies upon a pressure being maintained within commonly used shifting tools. In particular, when such shifting tools are utilized with long tool strings, it may be difficult to provide sufficient pressure to activate such shifting tool due to the pressure losses associated with such long tool strings. Additionally, it is also undesirable to move the tool string in such a pressurized state as such pressurized states are known to cause increased stress and wear on the pipe reducing the lifespan of such components. Improvements in actuating such tools would be welcome by the industry. 
       SUMMARY 
       [0011]    In embodiments the disclosure pertains to methods for actuating a sleeve valve without requiring the tool string to remain in a pressurized state. 
         [0012]    According to embodiments there is disclosed an apparatus for selectably engaging a longitudinally slidable sleeve within a well comprising a tool string slidably locatable within the well and a shifting tool slidably locatable within the sleeve at an end of a tool string. The shifting tool has a central bore therethrough and keys operable to be extended from an outer surface of the shifting tool when the central bore is supplied with the fluid above a predetermined pressure. The keys are engagable upon the sleeve so as to permit the shifting tool to move the sleeve longitudinally within the tubular body. The apparatus further comprises a reservoir in fluidic communication with the central bore of the shifting tool and being operable to contain and hold a quantity of a fluid at a predetermined pressure sufficient to actuate the shifting tool. 
         [0013]    The apparatus may further include an isolation body adapted to retain the fluid in the reservoir after the pressure has been reduced in the tool string. The isolation body may comprise a check valve adapted to permit a flow of fluid into the reservoir in a downward direction only. The check valve may be located above the shifting tool. 
         [0014]    The reservoir may be formed between an inner mandrel and an outer housing of the tool string. The inner mandrel and outer housing may be longitudinally movable relative to each other along the tool string. The outer housing may be operably connected to the tool and wherein the inner mandrel is operably connected to a pipe extending to a ground level of the well. The reservoir may be formed between an end wall and a lead protrusion extending radially outward from the inner mandrel. The end wall may slidably seal against the outer housing. 
         [0015]    The outer housing may include a bypass protrusion extending radially inwardly therefrom at a position adapted to seal against the lead protrusion of the inner mandrel when the inner mandrel and outer housing are at a first position relative to each other. The bypass protrusion may be adapted to longitudinally disengage from the lead protrusion as the inner mandrel is slidably displaced relative to the outer housing so as to compress the reservoir. The bypass protrusion may include a bleed passage therethrough sized to permit a predetermined flow rate of fluid therethrough. 
         [0016]    According to further embodiments there is disclosed a method for selectably engaging a longitudinally slidable sleeve within a well comprising providing a tool string slidably locatable within the well and providing a shifting tool slidably locatable within the sleeve at an end of a tool string. The shifting tool has a central bore therethrough and keys operable to be extended from an outer surface of the shifting tool when the central bore is supplied with the fluid above a predetermined pressure. The keys are engagable upon the sleeve so as to permit the shifting tool to move the sleeve longitudinally within the tubular body. The method further comprises providing a reservoir in fluidic communication with the central bore of the shifting tool and being operable to contain and hold a quantity of a fluid at a predetermined pressure sufficient to actuate the shifting tool. 
         [0017]    According to further embodiments there is disclosed a method for selectably engaging a longitudinally slidable sleeve within a well comprising locating a tool string having a shifting tool therein within the well, wherein the shifting tool has a central bore therethrough and keys operable to be extended from an outer surface of the shifting tool when the central bore is supplied with the fluid above a predetermined pressure, the keys being engagable upon the sleeve so as to permit the shifting tool to move the sleeve longitudinally within the tubular body. The method further comprises pressurizing a reservoir in fluidic communication with the central bore of the shifting tool and being operable to contain and hold a quantity of a fluid at a predetermined pressure sufficient to actuate the shifting tool to extend the keys from the outer surface of the shifting tool into engagement with a sleeve valve. The method further comprises reducing the pressure in the tool string above the reservoir and slidably displacing the shifting tool and sleeve valve within the well by displacing the tool string therein. 
         [0018]    Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying drawings illustrate only the various implementations described herein and are not meant to limit the scope of various technologies described herein. The drawings show and describe various embodiments of the current disclosure. 
           [0020]      FIG. 1  is a cross-sectional view of a wellbore having a plurality of flow control valves according to a first embodiment of the present disclosure located therealong. 
           [0021]      FIG. 2  is a cross sectional view of a control valves of for use in the system of  FIG. 1 . 
           [0022]      FIG. 3  is a longitudinal cross-sectional view of the control valve of  FIG. 2  as taken along the line  3 - 3 . 
           [0023]      FIG. 4  is a detailed cross-sectional view of the extendable ports of the valve of  FIG. 2  in a first or retracted position. 
           [0024]      FIG. 5  is a detailed cross-sectional view of the extendable ports of the valve of  FIG. 2  in a second or extended position with the sleeve valve in an open position. 
           [0025]      FIG. 6  is a cross sectional view of the valve of  FIG. 2  as taken along the line  3 - 3  showing a shifting tool located therein. 
           [0026]      FIG. 7  is an axial cross-sectional view of the shifting tool of  FIG. 6  as taken along the line  7 - 7 . 
           [0027]      FIG. 8  a lengthwise cross sectional view of the shifting tool of  FIG. 6  taken along the line  8 - 8  in  FIG. 7  with a control valve located therein according to one embodiment with the sleeve engaging members located at a first or retracted position. 
           [0028]      FIG. 9  is a cross sectional view of the shifting tool of  FIG. 6  taken along the line  8 - 8  with a control valve located therein according to one embodiment with the sleeve engaging members located at a second or extended position 
           [0029]      FIG. 10  is a perspective view of a shifting tool according to a further embodiment. 
           [0030]      FIG. 11  is a side view of a well at a first step of engaging a sleeve valve according to the present method. 
           [0031]      FIG. 12  is a side view of a well at a second step of opening a sleeve valve according to the present method. 
           [0032]      FIG. 13  is a cross sectional view of a sleeve valve of an optional design having a reservoir formed inside according to the present disclosure at a first or initial position. 
           [0033]      FIG. 14  is a detailed cross sectional view of a portion of a sleeve valve of  FIG. 13  at a second or pressurized position. 
           [0034]      FIG. 15  is a detailed cross sectional view of a portion of a sleeve valve of  FIG. 13  at a second or pressurized position. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation—specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In addition, the composition used/disclosed herein can also comprise some components other than those cited. In the summary and this detailed description, each numerical value should be read once as modified by the term “about” (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. Also, in the summary and this detailed description, it should be understood that a concentration range listed or described as being useful, suitable, or the like, is intended that any and every concentration within the range, including the end points, is to be considered as having been stated. For example, “a range of from 1 to 10” is to be read as indicating each and every possible number along the continuum between about 1 and about 10. Thus, even if specific data points within the range, or even no data points within the range, are explicitly identified or refer to only a few specific, it is to be understood that inventors appreciate and understand that any and all data points within the range are to be considered to have been specified, and that inventors possessed knowledge of the entire range and all points within the range. 
         [0036]    The statements made herein merely provide information related to the present disclosure and may not constitute prior art, and may describe some embodiments illustrating the disclosure. 
         [0037]    In the specification and appended claims: the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via one or more elements”; and the term “set” is used to mean “one element” or “more than one element”. Further, the terms “couple”, “coupling”, “coupled”, “coupled together”, and “coupled with” are used to mean “directly coupled together” or “coupled together via one or more elements”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and “downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the disclosure. 
         [0038]    Embodiments herein relate to methods of completing an underground formation using multi-stage pin-point fracturing for treating a well without using any sealing element. 
         [0039]    Referring to  FIG. 1 , a wellbore  10  is drilled into the ground  8  to a production zone  6  by known methods. The production zone  6  may contain a horizontally extending hydrocarbon bearing rock formation or may span a plurality of hydrocarbon bearing rock formations such that the wellbore  10  has a path designed to cross or intersect each formation. As illustrated in  FIG. 1 , the wellbore includes a vertical section  12  having a valve assembly or Christmas tree  14  at a top end thereof and a bottom or production section  16  which may be horizontal or angularly oriented relative to the horizontal located within the production zone  6 . After the wellbore  10  is drilled the production tubing  20  is of the hydrocarbon well is formed of a plurality of alternating liner or casing  22  sections and in line valve bodies  24  surrounded by a layer of cement  23  between the casing and the wellbore. The valve bodies  24  are adapted to control fluid flow from the surrounding formation proximate to that valve body and may be located at predetermined locations to correspond to a desired production zone within the wellbore. In operation, between 8 and 100 valve bodies may be utilized within a wellbore although it will be appreciated that other quantities may be useful as well. 
         [0040]    Turning now to  FIG. 2 , a perspective view of one valve body  24  is illustrated. The valve body  24  comprises a substantially elongate cylindrical outer casing  26  extending between first and second ends  28  and  30 , respectively and having a central passage  32  therethrough. The first end  28  of the valve body is connected to adjacent liner or casing section  22  with an internal threading in the first end  28 . The second end  30  of the valve body is connected to an adjacent casing section with external threading around the second end  30 . The valve body  24  further includes a central portion  34  having a plurality of raised sections  36  extending axially therealong with passages  37  therebetween. As illustrated in the accompanying figures, the valve body  24  has three raised sections although it will be appreciated that a different number may also be utilized. 
         [0041]    Each raised section  36  includes a radially movable body or port body  38  therein having an aperture  40  extending therethrough. The aperture  40  extends from the exterior to the interior of the valve body and is adapted to provide a fluid passage between the interior of the bottom section  16  and the wellbore  10  as will be further described below. The aperture  40  may be filled with a sealing body (not shown) when installed within a bottom section  16 . The sealing body serves to assist in sealing the aperture until the formation is to be fractured and therefore will have sufficient strength to remain within the aperture until that time and will also be sufficiently frangible so as to be fractured and removed from the aperture during the fracing process. Additionally, the port bodies  38  are radially extendable from the valve body so as to engage an outer surface thereof against the wellbore  10  so as to center the valve body  24  and thereby the production section within the wellbore. 
         [0042]    Turning now to  FIG. 3 , a cross sectional view of the valve body  24  is illustrated. The central passage  32  of the valve body includes a central portion  42  corresponding to the location of the port bodies  38 . The central portion is substantially cylindrical and contains a sliding sleeve  44  therein. The central portion  42  is defined between first or entrance and second or exit raised portions or annular shoulders,  46  and  48 , respectively. The sliding sleeve  44  is longitudinally displaceable within the central portion  42  to either be adjacent to the first or second shoulder  46  or  48 . At a location adjacent to the second shoulder, the sliding sleeve  44  sealably covers the apertures  40  so as to isolate the interior from the exterior of the bottom section  16  from each other, whereas when the sliding sleeve  44  is adjacent to the first shoulder  46 , the sliding sleeve  44   
         [0043]    The central portion  42  includes a first annular groove  50  a therein proximate to the first shoulder  46 . The sliding sleeve  44  includes a radially disposed snap ring  52  therein corresponding to the groove  50  a so as to engage therewith and retain the sliding sleeve  44  proximate to the first shoulder  46  which is an open position for the valve body  24 . The central portion  42  also includes a second annular groove  50   b  therein proximate to the aperture  40  having a similar profile to the first annular groove  50   a . The snap ring  52  of the sleeve is receivable in either the first ore second annular groove  50  a or  50  b such that the sleeve is held in either an open position as illustrated in  FIG. 5  or a closed position as illustrated in  FIG. 4 . The sliding sleeve  44  also includes annular wiper seals  54  which will be described more fully below proximate to either end thereof to maintain a fluid tight seal between the sliding sleeve and the interior of the central portion  42 . 
         [0044]    The port bodies  38  are slidably received within the valve body  24  so as to be radially extendable therefrom. As illustrated in  FIG. 3 , the port bodies are located in their retracted position such that an exterior surface  60  of the port bodies is aligned with an exterior surface  62  of the raised sections  36 . Each raised section may also include limit plates  64  located to each side of the port bodies  38  which overlap a portion of and retain pistons within the cylinders as are more fully described below. 
         [0045]    Each raised section  36  includes at least one void region or cylinder  66  disposed radially therein. Each cylinder  66  includes a piston  68  therein which is operably connected to a corresponding port body  38  forming an actuator for selectably moving the port bodies  38 . Turning now to  FIGS. 4 and 5 , detailed views of one port body  38  are illustrated at a retracted and extended position, respectively. Each port body  38  may have an opposed pair of pistons  68  associated therewith arranged to opposed longitudinal sides of the valve body  24 . It will be appreciated that other quantities of pistons  68  may also be utilized for each port body  38  as well. The pistons  68  are connected to the valve body by a top plate  70  having an exterior surface  72 . The exterior surface  72  is positioned to correspond to the exterior surface  62  of the raised sections  36  so as to present a substantially continuous surface therewith when the port bodies  38  are in their retracted positions. The exterior surface  72  also includes angled end portions  74  so as to provide a ramp or inclined surface at each end of the port body  38  when the port bodies  38  are in an extended position. This will assist in enabling the valve body to be longitudinally displaced within a wellbore  10  with the vertical section  12  under thermal expansion of the production string and thereby to minimize any shear stresses on the port body  38 . 
         [0046]    The pistons  68  are radially moveable within the cylinders relative to a central axis of the valve body so as to be radially extendable therefrom. In the extended position illustrated in  FIG. 5 , the exterior surface  72  of the port bodies are adapted to be in contact with the wellbore  10  so as to extend the port body  38  and thereby enable the wellbore  10  to be placed in fluidic communication with the central portion  42  of the valve body  24 . The pistons  68  may have a travel distance between their retracted positions and their extended positions of between 0.10 and 0.50 inches although it will be appreciated that other distances may also be possible. In the extended position, it will be possible to frac that location without having to also fracture the concrete which will be located between the valve body  24  and the wellbore wall thereby reducing the required frac pressure. Additionally, more than one port body  38  may be utilized and radially arranged around the valve body so as to centre the valve body within the wellbore when the port bodies are extended therefrom. 
         [0047]    The pistons  68  may include seals  76  therearound so as to seal the piston within the cylinders  66 . Additionally, the port body  38  may include a port sleeve  78  extending radially inward through a corresponding port bore  81  within the valve body. A seal  80  may be located between the port sleeve  78  and the port bore  81  so as to provide a fluid tight seal therebetween. A snap ring  82  may be provided within the port bore  81  adapted to bear radially inwardly upon the port sleeve  78 . In the extended position, the snap ring  82  compresses radially inwardly to provide a shoulder upon which the port sleeve  78  may rest so as to prevent retraction of the port body  38  as illustrated in  FIG. 5 . The pistons  68  may be displaceable within the cylinders  66  by the introduction of a pressurized fluid into a bottom portion thereof. It will also be appreciated that other sleeve valves may be utilized which do not include extendable pistons as illustrated herein as are commonly known in the art. 
         [0048]    With reference to  FIG. 3 , the entrance bore  94  intersect the central passage  32  of the valve body  24 . As illustrated each entrance bore  94  may be covered by a knock-out plug  102  so as to seal the entrance bore until removed. In operation, as concrete is pumped down the bottom section  16 , it will be followed by a plug so as to provide an end to the volume of concrete. The plug is pressurized by a pumping fluid (such as water, by way of non-limiting example) so as to force the concrete down the production string and thereafter to be extruded into the annulus between the horizontal section and the wellbore. The knock-out plugs  102  are designed so as to be removed or knocked-out of the entrance bore by the concrete plug passing thereby. In such a way, once the concrete has passed the valve body  24 , the concrete plug removes the knock-out plugs  102  so as to pressurize the entrance bore  94  and fluid bore  90  and thereafter to extend the pistons  68  from the valve body  24  once the pressurizing fluid has reached a sufficient pressure. 
         [0049]    Turning now to  FIG. 6 , a shifting tool  200  is illustrated within the central passage  32  of the valve body  24 . The shifting tool  200  is adapted to engage the sliding sleeve  44  and shift it between a closed position as illustrated in  FIG. 4  and an open position in which the apertures  40  are uncovered by the sliding sleeve  44  so as to permit fluid flow between and interior and an exterior of the valve body  24  as illustrated in  FIG. 5 . The shifting tool  200  comprises a substantially cylindrical elongate tubular body  202  extending between first and second ends  204  and  206 , respectively. The shifting tool  200  includes a central bore  210  therethrough (shown in  FIGS. 7 through 9 ) to receive an actuator or to permit the passage of fluids and other tools therethrough. The shifting tool  200  includes at least one sleeve engaging member  208  radially extendable from the tubular body  202  so as to be selectably engageable with the sliding sleeve  44  of the valve body  24 . As illustrated in the accompanying figures, three sleeve engaging members  208  are illustrated although it will be appreciated that other quantities may be useful as well. 
         [0050]    The sleeve engaging members  208  comprise elongate members extending substantially parallel to a central axis  209  of the shifting tool between first and second ends  212  and  214 , respectively. The first and second ends  212  and  214  include first and second catches  216  and  218 , respectively for surrounding the sliding sleeve and engaging a corresponding first or second end  43  or  45 , respectively of the sliding sleeve  44  depending upon which direction the shifting tool  200  is displaced within the valve body  24 . As illustrated in  FIGS. 8 and 9 , the first and second catches  216  and  218  of the sleeve engaging member  208  each include and inclined surface  220  and  222 , respectively facing in opposed directions from each other. The inclined surfaces  220  and  222  are adapted to engage upon either the first or second annular shoulder  46  or  48  of the valve body as the shifting tool  200  is pulled or pushed there into. The first or second annular shoulders  46  or  48  press the first or second inclined surface  220  or  222  radially inwardly so as to press the sleeve engaging members  208  inwardly and thereby to disengage the sleeve engaging members  208  from the sliding sleeve  44  when the sliding sleeve  44  has been shifted to a desired position proximate to one of the annular shoulders. In an optional embodiment, one or both of the catches  216  or  218  may have an extended length as illustrated in  FIG. 10  such that the sleeve engaging members are disengaged from the sliding sleeve at a position spaced apart from one of the first or second annular shoulders  46  or  48  and thereby adapted to position the sliding sleeve at a third or central position within the valve body  24 . 
         [0051]    Turning to  FIG. 7 , the sleeve engaging members are maintained parallel to the tubular body  202  of the shifting tool  200  by a parallel shaft  230 . Each parallel shaft  230  is linked to a sleeve engaging member  208  by a pair of spaced apart linking arms  232 . The parallel shaft  230  is rotatably supported within the shifting tool tubular body  202  by bearings or the like. The linking arms  232  are fixedly attached to the parallel shaft  230  at a proximate end and are received within a blind bore  234  of the sleeve engaging members  208 . As illustrated in  FIG. 6 , the linking arms  232  are longitudinally spaced apart from each other along the parallel shaft  230  and the sleeve engaging member  208  so as to be proximate to the first and second ends  212  and  214  of the sleeve engaging member  208 . 
         [0052]    Turning now to  FIG. 8 , the tubular body  202  of the shifting tool includes a shifting bore  226  therein at a location corresponding to each sleeve engaging member. The shifting bore  226  extends from a cavity receiving the sleeve engaging member to the central bore  210  of the shifting tool  200 . Each sleeve engaging member  208  includes a piston  224  extending radially therefrom which is received within the shifting bore  226 . In operation, a fluid pressure applied to the central bore  210  of the shifting tool will be applied to the piston  224  so as to extend the piston within the shifting bore  226  and thereby to extend the sleeve engaging members  208  from a first or retracted position within the shifting tool tubular body  202  as illustrated in  FIG. 8  to a second or extended position for engagement on the sliding sleeve  44  as discussed above as illustrated in  FIG. 9 . The parallel shafts also include helical springs (not shown) thereon to bias the sleeve engaging members to the retracted position. 
         [0053]    The first end  204  of the shifting tool  200  includes an internal threading  236  therein for connection to the external threading of the end of a production string or pipe (not shown). The second end  206  of the shifting tool  200  includes external threading  238  for connection to internal threading of a downstream productions string or further tools, such as by way of non-limiting example a control valve as will be discussed below. An end cap  240  may be located over the external threading  238  when such a downstream connection is not utilized. 
         [0054]    With reference to  FIGS. 8 and 9 , a first control valve  300  according to a first embodiment located within a shifting tool  200  for use in wells having low hydrocarbon production flow rates. The low flow control valve  300  comprises a valve housing  302  having a valve passage  304  therethrough and seals  344  therearound for sealing the valve housing  302  within the shifting tool  200 . The low flow control valve  300  includes a central housing extension  306  extending axially within the valve passage  304  and a spring housing portion  320  downstream of the central portion  310 . The central housing extension  306  includes an end cap  308  separating an entrance end of the valve passage from a central portion  310  of the valve passage and an inlet bore  322  permitting a fluid to enter the central portion  310  from the valve passage  304 . 
         [0055]    The central portion  310  of the valve passage contains a valve piston rod  312  slidably located therein. The valve piston rod  312  includes leading and trailing pistons,  314  and  316 , respectively thereon in sealed sliding contact with the central portion  310  of the valve passage. The leading piston  314  forms a first chamber  313  with the end cap  308  having an inlet port  315  extending through the leading piston  314 . The valve piston rod  312  also includes a leading extension  318  having an end surface  321  extending from an upstream end thereof and extending through the end cap  308 . The valve piston rod  312  is slidable within the central portion  310  between a closed position as illustrated in  FIG. 8  and an open position as illustrated in  FIG. 9 . In the closed position, the second or trailing piston  316  is sealable against the end of the central portion  310  to close or seal the end of the central passage and thereby prevent the flow of a fluid through the control valve. In the open position as illustrated in  FIG. 9 , the trailing piston  316  is disengagable from the end of the central portion  310  so as to provide a path of flow, generally indicated at  319 , therethrough from the central passage to the spring housing. 
         [0056]    A spring  324  is located within the spring housing  320  and extends from the valve piston rod  312  to an orifice plate  326  at a downstream end of the spring housing  320 . The spring  324  biases the valve piston rod  312  towards the closed position as illustrated in  FIG. 8 . Shims or the like may be provided between the spring  324  and the orifice plate  326  so as to adjust the force exerted by the spring upon the valve piston rod  312 . In other embodiments, the orifice plate may be axially moveable within the valve body by threading or the like to adjust the force exerted by the spring. In operation, fluid pumped down the production string to the valve passage  304  passes through the inlet bore and into the central portion  310 . The pressure of the fluid within the central portion  310  is balanced upon the opposed faces of leading and trailing pistons  314  and  316  such that the net pressure exerted upon the valve piston rod  312  is provided by the pressure exerted on the end surface  321  of the leading extension  318  and on the leading piston  314  from within the first chamber  313 . The resulting force exerted upon the end surface  321  is resisted by the biasing force provided by the spring  324  as described above. 
         [0057]    Additionally, the orifice plate  326  includes an orifice  328  therethrough selected to provide a pressure differential thereacross under a desired fluid flow rate. In this way, when the fluid is flowing through the central portion  310  and the spring housing  320 , the spring housing  320  will have a pressure developed therein due to the orifice plate. This pressure developed within the spring housing  320  will be transmitted through apertures  330  within the spring housing to a sealed region  332  around the spring housing proximate to the shifting bore  226  of the shifting tool  200 . This pressure serves to extend the pistons  224  within the shifting bores  226  and thereby to extend the sleeve engaging members  208  from the shifting tool. The pressure developed within the spring housing  320  also resists the opening of the valve piston rod  312  such that in order for the valve to open and remain open, the pressure applied to the entrance of the valve passage  304  is required to overcome both the biasing force of the spring  324  and the pressure created within the spring housing  320  by the orifice  328 . 
         [0058]    The valve  300  may be closed by reducing the pressure of the supplied fluid to below the pressure required to overcome the spring  324  and the pressured created by the orifice  328  such that the spring is permitted to close the valve  300  by returning the valve piston rod  312  to the closed position as illustrate in  11  as well as permitting the springs on the parallel shaft  230  to retract the sleeve engaging members  208  as the pressure within the spring housing  320  is reduced. Seals  336  as further described below may also be utilized to seal the contact between the spring housing  320  and the interior of the central bore  210  of the shifting tool  200 . 
         [0059]    A shear sleeve  340  may be secured to the outer surface of the valve housing  302  by shear screws  342  or the like. The sheer sleeve  340  is sized and selected to be retained between a pipe threaded into the internal threading  236  of the shifting tool  200  and the remainder of the shifting tool body. In such a way, should the valve be required to be retrieved, a spherical object  334 , such as a steel ball, such as are commonly known in the art may be dropped down the production string so as to obstruct the valve passage  304  of the valve  300 . Obstructing the flow of a fluid through the valve passage  304  will cause a pressure to develop above the valve so as to shear the shear screws  342  and force the valve through the shifting tool. The strength of the sheer screws  342  may be selected so as to prevent their being sheered during normal operation of the valve  300  such as for pressures of between 1000 and 3000 psi inlet fluid pressure. The valve illustrated in  FIGS. 8 and 9  is adapted for use in a low hydrocarbon flow rate well. In such well types, the flow of fluids such as hydrocarbons or other fluids is low enough that the fluid pumped down the well to pressurize the central portion  310  is sufficient to overcome the flow of the fluids up the well so as to pass through the orifice  328 . It will be appreciated that for wells of higher well pressure or flow rates, such a valve will be limited in its application. 
         [0060]    Turning now to  FIGS. 11 and 12 , a system for pressurizing the shifting tool  200  is illustrated within the production tubing  20 . In operation, as will be described further below, the shifting tool may be formed with a reservoir  500  operable to contain a fluid above the activation pressure of the shifting tool. The tool string  510  may include an isolation element  502  operable to selectably retain a fluid pressure within the reservoir  500  after it has been reduced within the tool string  510  such that the tool string may be moved in a lower pressure state thereby reducing wear and stress thereon. In particular as illustrated in  FIG. 11 , the reservoir may be initially pressurized to extend the shifting keys on the shifting tool. Thereafter the pressure above the reservoir  500  may be reduced while maintaining the pressure within the reservoir by the isolation element  502  and moved as illustrated in  FIG. 12 . Thereafter, the pressure within the reservoir  500  may be released by a release element  504  downstream of the shifting tool  200 . 
         [0061]    Turning now to  FIG. 13 , a cross sectional view of the shifting tool and reservoir assembly is illustrated. The tool string is formed with an inner mandrel  520  and an outer housing  530  forming a cavity  522  therebetween. The cavity  522  spans the shifting tool  200  and is adapted to retain the outer housing at an extended position relative to the inner mandrel under pressure of a fluid contained therein and be released therefrom at a controlled rate to release the outer housing  530  relative to the inner mandrel thereby releasing the pressure applied to the shifting tool  200 . In such a manner the shifting tool  200  may be maintained at a pressurized while the tool string state is allowed to reduce to a lower pressure for movement thereof. 
         [0062]    Turning now to  FIGS. 14 and 15  the inner mandrel  520  includes an end wall  524  extending therefrom into engagement with the outer housing  530 . The inner mandrel  530  also includes a lead protrusion  526  extending annularly outward therefrom wherein the cavity  522  is formed between the lead protrusion  526  and the end wall  524 . The outer housing  530  includes a bypass protrusion  532  extending radially inward therefrom at a position adapted to engage against the end protrusion  526  extending from the inner mandrel. As illustrated one or both of the bypass protrusion  532  or end protrusion  526  may include a seal  534  for sealing the contact between the bypass protrusion  532  and end protrusion  526 . Similarly, the end wall  524  includes a seal  528  at a position therein adapted to engage upon and seal the end wall against the outer housing. The bypass protrusion  532  includes at least one bypass passage  540  extending therethrough to permit fluid to flow therethrough into and out of the cavity  522 . 
         [0063]    At a first or closed position as illustrated in  FIG. 14 , the bypass protrusion  532  and lead protrusion  526  are aligned so as to enclose the cavity  522  therebehind. As illustrated in  FIG. 15 , the inner mandrel is longitudinally movable relative to the outer housing in a direction indicated at  550  to a second position to disengage the bypass protrusion  532  from the lead protrusion  526  such that fluid is permitted to flow out of the cavity  522  in a direction generally indicated at  552 . 
         [0064]    In operation, the shifting tool  200  may be located at the desired location. Thereafter, the inner mandrel  520  may be positioned relative to the outer hosing  530  at the initial position as illustrated in  FIG. 14  with the bypass protrusion  532  and lead protrusion  526  aligned. Thereafter, the cavity  522  may be pressurized with the fluid so as to engage the shifting tool as set out above. Optionally, the cavity  522  may be pressurized before the bypass protrusion  532  and lead protrusion  526  are aligned to seal the cavity  522 . In this position, the shifting tool will be engaged upon a sleeve valve permitting the sleeve to be opened or closed as desired by an operator. For such movement, the annulus, generally indicated at  560  as the annual region between the inner mandrel  520  and the outer housing  530  above the may be depressurized so as to depressurize the tool string for such movement in a depressurized state. It will be appreciated that such depressurized state will reduce wear and damage to the tool string during such movement. 
         [0065]    After the annulus  560  of the tool string has been depressurized, the fluid within the cavity  522  will be permitted to escape therefrom through the bypass passage  540 . The size of the bypass passage  540  will be selected such that the rate of fluid escape therefrom will be low so as to retain a sufficient volume of fluid within the cavity  522  to keep the cavity  522  at a pressure to keep the shifting tool activated as well as to prevent the volume of the cavity  522  from significantly decreasing. During this period, the inner mandrel  520  may be pulled in a direction generally indicated at  562  such that the pressure within the cavity  522  will maintain the relative positions between the inner mandrel  520  and outer housing  530 . While the inner mandrel is pulled in the direction  560 , fluid within the cavity will, as set out above maintain the positions between the inner mandrel and outer hosing. During this movement, after the pressure within the annulus  560  is reduced the fluid within the cavity  522  escapes from the cavity  522  through the pyass passage  540  at a controlled rate thereby reducing the pressure within the cavity. When the pressure within the cavity  522  reaches a predetermined level, the bypass protrusion  532  will be permitted to move relative to the lead protrusion  526  to an amount sufficient to disengage the two protrusions from each other as illustrated in  FIG. 15  whereupon the remaining fluid may escape from the cavity  522  in a direction generally indicated at  552 . After this remaining fluid has escaped the shifting tool will be disengaged. It will be appreciated that the size of the bypass passage  540  will be selected to provide a desired time delay to keep the shifting tool activated. 
         [0066]    While the present disclosure has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations there from. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the disclosure.

Technology Classification (CPC): 4