Abstract:
A method is provided for activating a downhole system arranged in an annular space formed between a radially expandable tubular element extending into a borehole formed into an earth formation and a cylindrical wall surrounding the tubular element. The downhole system is arranged so as to be activated by movement of an annular movement device along the tubular element. The method involves arranging the annular moving device around the tubular element, the moving device having an inner diameter slightly larger than the outer diameter of the tubular element in its unexpanded shape, and gradually expanding a portion of the tubular element by moving an expander through the tubular element in the direction of the moving device, whereby a transition zone of the tubular element is defined between the expanded an unexpanded portions of the tubular element. Upon contact of the transition zone with the moving device, continuing movement of the expander through the tubular element causes the moving device to move in axial direction along the tubular element whereby the moving device activates the downhole system.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a method of activating a downhole system arranged in an annular space formed between a tubular element extending into a borehole formed into an earth formation and a cylindrical wall surrounding the tubular element. The cylindrical can be, for example, the borehole wall or the wall of a casing extending into the borehole. 
   BACKGROUND OF THE INVENTION 
   For many wellbore applications, activation of such downhole system is required to perform a downhole process or to initiate such process. It has been tried to activate the downhole systems by means of hydraulic or electrical control lines extending from surface into the borehole. However, such control lines are vulnerable to damage and generally hamper construction of the well. For example, if the tubular element is a wellbore casing and electrical control lines are used at the outer surface of the casing, an electrical connector has to be applied at each connection of two adjacent casing sections. 
   SUMMARY OF THE INVENTION 
   In accordance with the invention there is provided a method of activating a downhole system arranged in an annular space formed between a radially expandable tubular element extending into a borehole formed into an earth formation and a cylindrical wall surrounding the tubular element, the downhole system being arranged so as to be activated by movement of an annular movement device along the tubular element, the method comprising:
         arranging said annular moving device around the tubular element, the moving device having an inner diameter slightly larger than the outer diameter of the tubular element in its unexpanded shape;   gradually expanding a portion of the tubular element by moving an expander through the tubular element in the direction of the moving device, whereby a transition zone of the tubular element is defined between the expanded an unexpanded portions of the tubular element;   upon contact of the transition zone with the moving device, continuing movement of the expander through the tubular element so as to move the moving device in axial direction along the tubular element whereby the moving device activates the downhole system.       

   It is thus achieved that, upon expansion of the tubular element, the downhole system is triggered by the moving device to perform a downhole process. Such triggering occurs without the requirement for control lines extending from surface into the wellbore. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described hereinafter in more detail and by way of example with reference to the accompanying drawings in which: 
       FIGS. 1A–1C  schematically show a first embodiment of a borehole system for use in the method of the invention, during various stages of use thereof; 
       FIGS. 2A–2B  schematically show a second embodiment of a borehole system for use in the method of the invention, during various stages of use thereof; 
       FIGS. 3A–3C  schematically show a third embodiment of a borehole system for use in the method of the invention, during various stages of use thereof; and 
       FIGS. 4A–4C  schematically show a fourth embodiment of a borehole system for use in the method of the invention, during various stages of use thereof. 
   

   In the Figures like reference numerals relate to like components. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1A  there is shown a borehole  1  formed into an earth formation  3  whereby the borehole wall is indicated by reference numeral  4 . A tubular member in the form of metal borehole casing  6  with longitudinal axis  7  extends substantially concentrically into the borehole  1 . Thus, an annular space  8  is formed between said cylindrical members. It is to be understood that the borehole wall  4  does not need to be perfectly cylindrical as it generally is of irregular shape due to, for example, washouts which occur during the drilling process. 
   The casing  6  is provided with a downhole system in the form of a set of three annular seal elements  10 ,  12 ,  14  arranged around the casing  6  and being mutually displaced in axial direction thereof, and with a stop device in the form of annular stopper  16  fixedly connected to the casing  6  and arranged at one side of the set of sealing elements. Furthermore, the casing is provided with a moving device in the form of metal compression sleeve  17  arranged at the other side of the set of seal elements  10 ,  12 ,  14 . The compression sleeve  17  is movable relative to the casing  6  in axial direction thereof. 
   The seal elements  10 ,  12 ,  14  are made of a flexible material such as rubber, and are optionally strengthened in axial direction by axially extending reinforcement bars (not shown) embedded in the flexible material. Seal element  10  has a tapered edge  18  adjacent seal element  12 , seal element  12  has a tapered edge  20  adjacent seal element  10  and a tapered edge  22  adjacent seal element  14 , and seal element  14  has a tapered edge  24  adjacent seal element  12  and a tapered edge  26  adjacent stopper  16 . The stopper  16  has a tapered edge  28  adjacent seal element  14 . The tapered edges  18 ,  20  are oriented such that seal element  10  is induced to slide along radial outer surface  30  of seal element  12  when seal element  10  is pushed in the direction of seal element  12 . Similarly, the tapered edges  22 ,  24  are oriented such that seal element  12  is induced to slide along radial outer surface  32  of seal element  14  when seal element  12  is pushed in the direction of seal element  14 . Furthermore, the tapered edges  26 ,  28  are oriented such that seal element  14  is induced to slide along radial outer surface  34  of stopper  16  when seal element  14  is pushed in the direction of stopper  16 . 
   The casing  6  has a radially expanded portion  40 , a radially unexpanded portion  42 , and a transition portion  44  located between the expanded and unexpanded portions  40 ,  42  and a having a diameter varying from the unexpanded diameter to the expanded diameter. 
   The stopper  16 , the seal elements  10 ,  12 ,  14 , and the compression sleeve  17  are all arranged around the unexpanded portion  42  of the casing whereby the compression sleeve  17  is arranged adjacent the transition portion  44  of the casing. 
   The compression sleeve  17  has an edge  46  adjacent the expanded portion  40  of the casing  6 , which is provided with an axial bearing which ensures low friction between the edge and the transition portion  44  of the casing  6 . The bearing can be, for example, a bronze or Teflon (Trade Mark) bushing, a thrust bearing (e.g. set of bearing balls regularly spaced along the circumference of the edge), or a hydrostatic bearing. 
   Referring to  FIGS. 2A ,  2 B there is shown a downhole system in the form of an annular injection device  51  arranged around the casing  6 , which injection device  51  upon activation thereof injects a selected fluid into the annular space  8 . The injection device includes an annular pump  52  arranged to pump the selected fluid via a conduit  54  and a plurality of circumferentially spaced annular nozzles  56  into the annular space  8  upon activation by the compression sleeve  17 . The selected fluid is, for example, a chemical activator for hardening a body of cement slurry (not shown) present in the annular space  8 , or a catalyst or chemical for triggering a chemical reaction of a body of resin (not shown) present in the annular space  8 . Several said annular injection devices  51  are arranged at selected mutual axial distances along the casing  6 , however for the sake of simplicity only one injection device  51  is shown. 
   Referring to  FIGS. 3A–3C  there is shown a downhole system in the form of a casing centraliser  60  arranged around the casing  6 , which centraliser is largely similar to a conventional bow centraliser. The centraliser  60  has spring arms  62  which bend upon axial compression of the centraliser  60  and thereby expand radially against the borehole wall. The centraliser  60  has an end part  64  (remote from the compression sleeve  17 ) which is fixedly connected to the casing  6 , and an end part  66  (adjacent the compression sleeve  17 ) which axially slideable along the casing  6 . 
   Referring to  FIGS. 4A–4C  there is shown a downhole system which includes a slideable sleeve  70  arranged around the casing  6 , the sleeve  70  having an inner diameter slightly larger than the outer diameter of the casing  6 . The wall of casing  6  is provided with a number of openings  72  which provide fluid communication between the interior and the exterior of the casing  6 . 
   During normal operation of the first embodiment, the casing  6  is installed in the borehole  1  with the stopper  16 , the seal elements  10 ,  12 ,  14 , and the compression sleeve  17  arranged around the casing  6  as shown in  FIG. 1A . An expander (not shown) is then pushed or pulled through the casing  6  to radially expand the casing  6  and thereby to form the initial expanded portion  40  thereof. A suitable expander is, for example, a conical expander or a conical expander provided with rollers along the contact surface with the casing. By the expansion process the casing  6  is plastically deformed. 
   Referring further to  FIG. 1B , the expander is moved through the casing  1  in the direction of stopper  16  thereby increasing the length of the expanded portion  40  and moving the transition portion  44  in the direction of stopper  16 . Upon contact of the transition portion  44  with the edge  46  of the compression sleeve  17 , continued movement of the transition portion  44  induces the compression sleeve to move in the direction of stopper  16 . The compression sleeve  17  thereby induces seal element  10  to move against seal element  12  and subsequently to slide along the radial outer surface  30  thereof. When seal element  10  becomes fully arranged around seal element  12 , continued movement of the transition portion  44  induces the compression sleeve  17  to move seal element  12  against seal element  14  and subsequently to slide along the radial outer surface  32  thereof. When seal elements  10 ,  12  become fully arranged around seal element  14 , continued movement of the transition portion  44  induces the compression sleeve  17  to move seal element  14  against stopper  16  and subsequently to slide along the radial outer surface  34  thereof. A set  50  of radially stacked seal elements has thus been formed. 
   Referring further to  FIG. 1C , movement of the expander is continued so that movement of the transition portion  44  is continued. Since the stopper  16  prevents any further axial movement of the compression sleeve  17  and the set  50  of radially stacked seal elements, continued movement of the transition portion  44  leads to radial expansion of the compression sleeve  17 , the stopper  16  and the set  50  of radially stacked seal elements. The set  50  of radially stacked seal elements thereby becomes firmly compressed between the stopper  16  and the borehole wall  4  so as to form an annular seal there between. 
   In this manner it is achieved that an annular seal is created between the casing  6  and the borehole wall  1 , whereby a relatively large annular space is initially present there between and whereby the individual components of the seal are relatively thin so that installation of the casing  6  in the borehole  1  is not hampered by the seal. 
   During normal operation of the second embodiment, the casing  6  is installed in the borehole  1  with the compression sleeve  17  and the injection device  51  arranged around it whereby injection device  51  is fixedly connected to the casing  6 . Cement slurry is then pumped into the annular space  8 , which slurry hardens upon contact with a selected chemical activator. The injection device  51  contains an amount of such chemical activator sufficient to induce hardening a portion of the cement slurry in-between the injection device and another injection device arranged at some axial distance. The expander is then pushed or pulled through the casing  6  to radially expand the casing  6  and thereby to form the initial expanded portion  40 . As shown in  FIG. 2B , the expander is moved through the casing  1  in the direction of injection device  51  thereby moving the transition portion  44  in the direction of the injection device  51 . Upon contact of the transition portion  44  with the edge  46  of the compression sleeve  17 , continued movement of the transition portion  44  induces the compression sleeve to move against the annular pump  52  of injection device  51 . Thereby the pump  52  pumps the chemical activator via conduit  54  and the nozzles  56  into the body of cement slurry present in the annular space  8 . As a result the portion of the cement slurry in-between the injection device and the other injection device hardens and thereby seals the annular space  8 . Further movement of the expander past the injection device  51  causes the injection device  51  to be flattened due to its radial expansion. It is thus achieved that hardening of the cement occurs only at those portions of the cement slurry where the casing  6  has been successfully expanded. Should the expander become stuck in the casing  6 , the unexpanded casing portion then can be retrieved to surface. Alternatively the remainder of the cement can be of a composition such that the cement will set after a prolonged period of time (i.e. in the order of days) and therefore will result into a conventionally cemented annulus. 
   During normal operation of the third embodiment, the casing  6  is installed in the borehole  1  with the compression sleeve  17  and the casing centraliser  60  provided around the casing  6 . The expander is then pushed or pulled through the casing  6  in the direction of centraliser  60  so as to radially expand the casing  6  and thereby to form the initial expanded portion  40 . As shown in  FIG. 3B , continued movement of the transition portion  44  causes the compression sleeve  17  to move against the centraliser  60  and thereby to move end part  66  in the direction of end part  64 . As a result the centraliser is compressed so that the spring arms  62  become radially expanded against the borehole wall. As shown in  FIG. 3C , further movement of the expander past the compression sleeve  17  and the centraliser  60  causes the end parts  64 ,  66  of centraliser  60  to be radially expanded. Thereby the spring arms  62  become even more compressed against the borehole wall and thus the casing  6  becomes adequately centralised in the borehole  1 . 
   During normal operation of the fourth embodiment, the casing  6  is installed in the borehole  1  with the compression sleeve  17  and the slideable sleeve  70  provided around the casing  6  whereby the openings  72  are uncovered. The openings  72  are used to pump cement from the interior of the casing  6  into the annular space  8  (which is a conventional operation). 
   Thereafter the expander is pushed or pulled through the casing  6  in the direction of sleeve  70  so as to radially expand the casing  6  and thereby to form the initial expanded portion  40 . As shown in  FIG. 4B , continued movement of the transition portion  44  causes the compression sleeve  17  to move against the sleeve  70  and thereby causes the sleeve  70  to slide over the casing portion with the openings  72  and thereby to cover the openings  72 . As shown in  FIG. 4C , further movement of the expander past the slideable sleeve  70  causes the compression sleeve  17  and the slideable sleeve  70  to be radially expanded. In this manner it is achieved that the slideable sleeve  70  adequately covers the openings  72  and seals the interior of the casing  6  from the exterior thereof. 
   While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be readily apparent to, and can be easily made by one skilled in the art without departing from the spirit of the invention. Accordingly, it is not intended that the scope of the following claims be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all features which would be treated as equivalents thereof by those skilled in the art to which this invention pertains.