Abstract:
A well completion system and method for preventing sand production into a well casing ( 38 ) having a perforated interval ( 42 ) is disclosed. The system comprises a sand control screen ( 40 ) having expandable end sections ( 60, 62 ) each of which having an attachment member ( 72, 74 ) positioned exteriorly therearound. An expander tool ( 44 ) is operably disposed within the sand control screen ( 40 ) such that when the sand control screen ( 40 ) is positioned within the well casing ( 38 ) across the perforated interval ( 42 ), the expander tool ( 44 ) radially expands the end sections ( 60, 62 ) such that the attachment members ( 72, 74 ) are placed in contact with the interior of the well casing ( 38 ), thereby creating a fluid seal and a friction grip between the end sections ( 60, 62 ) and the well casing ( 38 ).

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    This invention relates, in general, to completing a well that traverses a hydrocarbon bearing subterranean formation and, in particular, to a system and method for preventing sand production into a well casing having a perforated interval by radially expanding the end sections of a sand control screen to provide a fluid seal and a friction grip between the sand control screen and the well casing.  
         BACKGROUND OF THE INVENTION  
         [0002]    Without limiting the scope of the present invention, its background will be described with reference to producing fluid from a subterranean formation, as an example.  
           [0003]    After drilling each of the sections of a subterranean wellbore, individual lengths of relatively large diameter metal tubulars are typically secured together to form a casing string that is positioned within each section of the wellbore. This casing string is used to increase the integrity of the wellbore by preventing the wall of the hole from caving in. In addition, the casing string prevents movement of fluids from one formation to another formation. Conventionally, each section of the casing string is cemented within the wellbore before the next section of the wellbore is drilled. Accordingly, each subsequent section of the wellbore must have a diameter that is less than the previous section.  
           [0004]    For example, a first section of the wellbore may receive a conductor casing string having a 20-inch diameter. The next several sections of the wellbore may receive intermediate casing strings having 16-inch, 13⅜-inch and 9⅝-inch diameters, respectively. The final sections of the wellbore may receive production casing strings having 7-inch and 4½-inch diameters, respectively. Each of the casing strings may be hung from a casing head near the surface. Alternatively, some of the casing strings may be in the form of liner strings that extend from near the setting depth of previous section of casing. In this case, the liner string will be suspended from the previous section of casing on a liner hanger.  
           [0005]    Once this well construction process is finished, the completion process may begin. The completion process comprises numerous steps including creating hydraulic openings or perforations through the production casing string, the cement and a short distance into the desired formation or formations so that production fluids may enter the interior of the wellbore. In addition, the completion process may involve formation stimulation to enhance production, installation of sand control devices to prevent sand production and the like. The completion process also includes installing a production tubing string within the well casing. Unlike the casing string that forms a part of the wellbore itself, the production tubing string is used to produce the well by providing the conduit for formation fluids to travel from the formation depth to the surface.  
           [0006]    Typically, the production tubing string extends from the surface to the formation traversed by the well and includes a production packer. The purpose of the packer is to support the production tubing and other completion equipment, such as a sand control screen that may be placed adjacent to the producing formation, and to seal the annulus between the outside of the production tubing and the inside of the well casing to block movement of fluids through the annulus past the packer location. Accordingly, once the production tubing string, including the production packer and sand control screen are in place, all production from the formation that enters the production tubing must pass through the sand control screen.  
           [0007]    It has been found, however, that in certain deep or high-angled wellbores in which relatively small diameter production casing is used, it may be desirable to complete the well without extending the production tubing string all the way to the producing formation. While the diameter of the production tubing that is installed within a well is determined based upon a number of factors, the maximum diameter of the production tubing is limited by the various restrictions within the well including the production casing and any tools within the production casing. Use of relatively small diameter production tubing over long distances may cause a pressure drop in the formation fluids traveling therethrough that is unnecessarily large which in turn causes the rate of production from the formation to be unnecessarily constrained. Accordingly, if the production tubing string does not extend into the last section of the production casing and formation fluids are produced directly into and travel within the last section of the production casing, the pressure drop in the formation fluids may be reduced.  
           [0008]    It has been found, however, that in such deep or high-angled wellbores wherein the production tubing string is not extended all the way to the producing formation, sand control may remain a problem. Specifically, the unfiltered formation fluids that are being produced directly into and traveling within the production casing may contain abrasive particulate matter.  
           [0009]    A need has therefore arisen for a system and method for preventing sand production into a wellbore even when the production tubing string is not extended all the way to the producing formation. Accordingly, a need has arisen for such a system and method that provide for placement of a sand control screen within a wellbore that do not require the sand control screen to be coupled within the production tubing string.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention disclosed herein comprises a system and method for preventing the production of sand into a wellbore even when the production tubing string is not extended all the way to the producing formation. The system and method provide for the placement of a sand control screen within a wellbore that do not require the sand control screen to be coupled within the production tubing string. Instead, the sand control screen of the present invention is placed directly within the production casing across the perforated interval such that when the end sections of the sand control screen of the present invention are expanded, a fluid seal and a friction grip are created between the sand control screen and the well casing.  
           [0011]    The well completion system of the present invention comprises a sand control screen that has expandable end sections. Each of the expandable end sections has an attachment member positioned on its exterior surface. The sand control screen may be run downhole into the well casing on a jointed tubing string, a coiled tubing string, an electric line or other similar device. The sand control screen is positioned within the well casing across the perforated interval. Thereafter, an expander tool that is operably disposed within the sand control screen may be used to expand the end sections of the sand control screen. For example, the expander tool may have two expander members such that each of the expander members is adapted to radially expand one of the end sections of the sand control screen by traveling longitudinally therethrough. Upon expansion of the end sections, the attachment members are placed in intimate contact with the interior surface of the well casing, thereby creating a fluid seal and a friction grip between the end sections of the sand control screen and the well casing.  
           [0012]    In one embodiment of the system for preventing sand production into a well casing having a perforated interval, the expansion of the two end sections of the sand control screen may take place simultaneously. In another embodiment, the expansion of the two end sections of the sand control screen may take place sequentially.  
           [0013]    In one embodiment of the system of the present invention, the expander tool may be hydraulically operated. For example, fluid pressure may be provided from the surface via a tubing string or a downhole pump may be used to provide fluid pressure from a downhole fluid source. In another embodiment, the expander tool may be electrically operated using, for example, an electric motor to drive a rotating shaft.  
           [0014]    In one embodiment of the system of the present invention, the pair of expander members of the expander tool may move toward one another to expand the end sections. In another embodiment, the pair of expander members of the expander tool may move away from one another to expand the end sections. In yet another embodiment, an expander tool having a single expander member may be used to expand both end sections. In any of these embodiments, each expander member may have a frustaconical surface that contacts an inner radial surface of the end sections to facilitate the expansion of the end sections.  
           [0015]    Broadly stated, the method of the present invention involves installing the well casing within the wellbore, disposing a sand control screen having expandable end sections within the well casing across the perforated interval and setting the sand control screen by radially expanding the end sections, thereby creating a friction grip between the end sections and the well casing.  
           [0016]    More specifically, the method of the present invention involves installing the well casing within the wellbore, disposing a sand control screen having expandable end sections within the well casing across the perforated interval and setting the sand control screen by radially expanding the end sections with an expander tool having two expander members, each of the expander members expanding one of the end sections by contacting a frustaconical surface of the expander members with an inner radial surface of the end sections and traveling longitudinally therethrough, thereby creating a fluid seal and a friction grip between the end sections and the well casing.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:  
         [0018]    [0018]FIG. 1 is a schematic illustration of an offshore oil and gas platform installing a sand control screen having expandable end sections according to the present invention;  
         [0019]    [0019]FIG. 2 is a half sectional view of a sand control screen having expandable end sections according to the present invention positioned within a casing string prior to installation within the casing string;  
         [0020]    [0020]FIG. 3 is a half sectional view of a sand control screen having expandable end sections according to the present invention positioned within a casing string after installation within the casing string;  
         [0021]    [0021]FIG. 4 is a half sectional view of a sand control screen having expandable end sections according to the present invention positioned within a casing string after installation within the casing string and after the installation of a tubing string;  
         [0022]    [0022]FIG. 5 is a half sectional view of a sand control screen having expandable end sections according to the present invention positioned within a casing string prior to installation within the casing string;  
         [0023]    [0023]FIG. 6 is a half sectional view of a sand control screen having expandable end sections according to the present invention positioned within a casing string after installation within the casing string; and  
         [0024]    [0024]FIG. 7 is a half sectional view of a sand control screen having expandable end sections according to the present invention positioned within a casing string after installation within the casing string and after the installation of a tubing string.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the present invention.  
         [0026]    Referring initially to FIG. 1, a sand control screen having expandable end sections according to the present invention is being installed from an offshore oil and gas platform that is schematically illustrated and generally designated  10 . A semi-submersible platform  12  is centered over a submerged oil and gas formation  14  located below sea floor  16 . A subsea conduit  18  extends from deck  20  of platform  12  to wellhead installation  22  including subsea blowout preventers  24 . Platform  12  has a hoisting apparatus  26  and a derrick  28  for raising and lowering pipe strings.  
         [0027]    Wellbore  32  extends through the various earth strata including formation  14 . A casing string  34  is cemented within wellbore  32  by cement  36 . Casing string  34  includes a production casing liner  38  at its lower end. Placed within production casing  38  is a sand control screen  40  having expandable ends that is positioned across perforations  42 . As explained in greater detail below, to install sand control screen  40  within production casing string  38  the end sections of sand control screen  40  are plastically deformed using expander tool  44  by, for example, pumping fluid down through a coiled tubing string  52  that is in fluid communication with expander tool  44 . Once sand control screen  40  has been set and coiled tubing string  52  along with expander tool  44  has been retrieved to the surface, a relatively large diameter production tubing string (not pictured) may be installed within casing string  34  to a point above production casing  38 .  
         [0028]    Referring now to FIG. 2, therein is depicted more detailed view of a sand control screen of the present invention that is designated  40 . Production casing  38  has been installed within wellbore  32 . Specifically, production casing  38  has been hung off casing string  34  at liner hanger  50  and has been cemented within wellbore  32 . In addition, perforations  42  have been made in a section of production casing  38  using a known technique such as firing a shaped charge perforating gun.  
         [0029]    As illustrated, in deep well applications, the size of production casing  38  may be relative small, such as 4½ inches in diameter. In such cases, it may be desirable to complete the well without extending the production tubing string all the way to formation  14  as long sections of relatively small diameter production tubing cause an unnecessarily large pressure drop during the production of formation fluids which in turn causes the rate of production from formation  14  to be unnecessarily constrained.  
         [0030]    To achieve the required sand control in such cases, sand control screen  40  is positioned within production casing  38 . Sand control screen  40  is initially supported by a coiled tubing string  52  that extends from the surface. In the illustrated embodiment, sand control screen  40  includes a base pipe  54  that has a plurality of openings  56  which allow the flow of production fluids therethrough. Wrapped around base pipe  54  is a screen wire  58  that forms a plurality of turns having gaps therebetween through which formation fluids flow. The number of turns and the gap between the turns are determined based upon the characteristics of formation  14 . Ribs may be provided between base pipe  54  and screen wire  58 .  
         [0031]    It should be understood by those skilled in the art that while FIG. 2 has depicted a wire wrapped sand control screen, other types of filter media could alternatively be used in conjunction with the sand control screen of the present invention, including, but not limited to, a fluid-porous, particulate restricting, sintered metal material such as a plurality of layers of a wire mesh that are sintered together to form a porous sintered wire mesh screen designed to allow fluid flow therethrough but prevent the flow of particulate materials of a predetermined size from passing therethrough.  
         [0032]    One unique feature of sand control screen  40  of the present invention is the radially expandable end sections  60 ,  62 . Radially expandable end section  60  includes a cylindrical ramp section  64  and a radially reduced section  66 . Likewise, radially expandable end section  62  includes a cylindrical ramp section  68  and a radially reduced section  70 . Disposed exteriorly of radially reduced section  66  is an attachment member  72 . Similarly, disposed exteriorly of radially reduced section  70  is an attachment member  74 .  
         [0033]    Attachment members  72 ,  74  are capable of providing both anchoring capabilities and sealing capabilities. Attachment members  72 ,  74  may be constructed from a polymeric material such as rubber or other nonmetallic materials or may be constructed from a metal such as lead or other suitable material that can expand radially when radially reduced sections  66 ,  70  are expanded and that can provide a suitable fluid seal and gripping force against the interior of production casing  38 . Attached members  72 ,  74  may additionally have slips, metal rings or other anchoring devices to improve the gripping force between sand control screen  40  and production casing  38 . Also, even though FIG. 2 has depicted single attached members  72 ,  74  on each end section  60 ,  62 , it should be understood by those skilled in the art that other numbers of attachment members could alternatively be used without departing from the principles of the present invention.  
         [0034]    Disposed within sand control screen  40  is expander tool  44 . In the illustrated embodiment, expander tool  44  has a support member  76  that is coupled to the lower end of coiled tubing string  52 . Initially, support member  76  is also coupled to the upper end of sand control screen  40  by shear pins (not pictured) or other suitable devices that hold support member  76  within sand control screen  40  but allows the release of support member  76  as required. Accordingly, sand control screen  40  may be lowered into wellbore  32  and into alignment with perforations  42  on coiled tubing string  52 .  
         [0035]    In the illustrated embodiment, expander tool  44  has a pair of oppositely disposed expander members  78 ,  80 . Each of the expander members  78 ,  80  has a tapered cone section  82 ,  84  having a frustaconical outer surface. Expander tool  44  also includes a piston section  86 . Piston section  86  is in fluid communication with coiled tubing string  52  via support member  76 .  
         [0036]    In operation, once sand control screen  40  is positioned within production casing  38  across perforations  42 , as depicted in FIG. 2, expander tool  44  may be operated to expand the diameter of end sections  60 ,  62  of sand control screen  40 . Specifically, expander member  78  is longitudinally moved through end section  60  and expander member  80  is longitudinally moved through end section  62 , as best seen in FIG. 3. In the illustrated embodiment, this is achieved by pumping a fluid down coiled tubing string  52  and into piston section  86  to urge expander member  78  and expander member  80  away from one another. As shown, the fluid pressure urges expander member  78  upwardly such that the frustaconical surface of tapered cone section  82  of expander member  78  contacts the interior wall of cylindrical ramp section  64 . Likewise, the fluid pressure urges expander member  80  downwardly such that the frustaconical surface of tapered cone section  84  of expander member  80  contacts the interior wall of cylindrical ramp section  68 .  
         [0037]    As the fluid pressure increases, tapered cone sections  82 ,  84 , respectively apply a radially outward force to cylindrical ramp sections  64 ,  68 . When this force is sufficient to plastically deform cylindrical ramp sections  64 ,  68 , expander members  78 ,  80  begin to travel longitudinally within cylindrical ramp sections  64 ,  68  in opposite directions from one another. As the movement of expander members  78 ,  80  progresses, cylindrical ramp sections  64 ,  68  and radially reduced sections  66 ,  70  are substantially uniformly expanded from their original diameters to a diameter similar to the diameter of expander members  78 ,  80 . As this expansion occurs, attachment members  72 ,  74  expand into intimate contact with the interior surface of production casing  38 . Once attachment members  72 ,  74  are expanded, a fluid seal and a friction grip are created between sand control screen  40  and production casing  38 .  
         [0038]    It should be noted by those skilled in the art that the force necessary to plastically deform end sections  60 ,  62  of sand control screen  40  is dependent upon a variety of factors including the ramp angle of tapered cone sections  82 ,  84 , the amount of the desired expansion of end sections  60 ,  62 , the material of end sections  60 ,  62  and the like. Since only a short segment of end sections  60 ,  62  are being expanded at any one time, however, the fluid pumped through coiled tubing string  52  provides sufficient force to expander tool  44  to expand end sections  60 ,  62 . This force may be controlled by adjusting the flow rate and pressure at which the fluid is delivered through coiled tubing string  52 .  
         [0039]    Also, it should be noted by those skilled in the art that even though FIG. 2 has described expanding end sections  60 ,  62  of sand control screen  40  simultaneously, the end sections of a sand control screen of the present invention could alternatively be expanded sequentially. For example, upward movement of expander member  78  could be disallowed until the downward stroke of expander member  80  has been accomplished, or vice versa. Likewise, the ramp angle of tapered cone section  82  could be altered relative to the ramp angle of tapered cone section  84  such that the force generated by the fluid pressure preferentially urges upward movement of expander member  78  relative to downward movement of expander member  80 , or vice versa.  
         [0040]    Further, it should be apparent to those skilled in the art that the use of direction terms such as above, below, upper, lower, upward, downward and the like are used in relation to the illustrated embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward being toward the bottom of the corresponding figure. Accordingly, it should be noted that the sand control screen of the present invention and the systems and methods for setting the sand control screen of the present invention are not limited to the vertical orientation as they are equally well suited for use in inclined, deviated and horizontal wellbores.  
         [0041]    Once the expansion of end sections  60 ,  62  of sand control screen  40  is complete, expansion tool  44  may be retrieved to the surface with coiled tubing string  52 . Specifically, if support member  76  is coupled to sand control screen  40  using shear pins, upward jarring on coiled tubing string  52  may be used to break the shear pins and release expansion tool  44  from sand control screen  40  to allow retrieval. Once expansion tool  44  and coiled tubing string  52  have been retrieved, a production tubing string  88  including production packer  90  may be installed within casing  34  down to a point above the top of production casing  38 , as best seen in FIG. 4.  
         [0042]    Referring now to FIG. 5, therein is depicted a sand control screen of the present invention that is designated  140 . Production casing  138  has been installed within wellbore  132 . Specifically, production casing  138  is a slotted liner which has been hung off casing string  134  at liner hanger  150 . Casing string  134  has been cemented within wellbore  132  with cement  136  but no cement has been placed around slotted liner  138 . In addition slotted liner  138  includes a packer  148  that is used to seal the annulus between slotted liner  138  and wellbore  132 .  
         [0043]    As illustrated, in deep well applications, the size of slotted liner  138  may be relative small such that it may be desirable to complete the well without extending the production tubing string all the way to formation  114 . Accordingly, to achieve the required sand control, sand control screen  140  is positioned within slotted liner  138 . Sand control screen  140  is initially supported by an electric line  152  that extends from the surface. In the illustrated embodiment, sand control screen  140  includes a base pipe  154  that has a plurality of openings  156  which allow the flow of production fluids therethrough with a screen wire  158  wrapped therearound.  
         [0044]    One unique feature of sand control screen  140  of the present invention is the radially expandable end sections  160 ,  162 . Radially expandable end section  160  includes a cylindrical ramp section  164  and a radially reduced section  166 . Likewise, radially expandable end section  162  includes a cylindrical ramp section  168  and a radially reduced section  170 . Disposed exteriorly of radially reduced section  166  is an attachment member  172 . Similarly, disposed exteriorly of radially reduced section  170  is an attachment member  174 .  
         [0045]    Disposed within sand control screen  140  is expander tool  144 . In the illustrated embodiment, expander tool  144  has a support member  176  that is coupled to the lower end of electric line  152 . Initially, support member  176  is also coupled to the upper end of sand control screen  140  by shear pins (not pictured) or other suitable devices that hold support member  176  within sand control screen  140  but allows the release of support member  176  as required. Accordingly, sand control screen  140  may be lowered into wellbore  132  and into alignment with opening  142  of slotted liner  138  on electric line  152 .  
         [0046]    In the illustrated embodiment, expander tool  144  has a pair of oppositely disposed expander members  178 ,  180 . Each of the expander members  178 ,  180  has a tapered cone section  182 ,  184  having a frustaconical outer surface. Expander tool  144  also includes a piston section  186 .  
         [0047]    In operation, once sand control screen  140  is positioned across openings  142  of slotted liner  138 , as depicted in FIG. 5, expander tool  144  may be operated to expand the diameter of end sections  160 ,  162  of sand control screen  140 . Specifically, expander member  178  is longitudinally moved through end section  160  and expander member  180  is longitudinally moved through end section  162 , as best seen in FIG. 6. In the illustrated embodiment, this may be achieved by operating a downhole power unit disposed within support member  176 . Electricity for the downhole power unit is provided via electric line  152 . The downhole power unit may be used to rotate a threaded member within piston section  186  which urges expander member  178  and expander member  180  toward one another. Alternatively, the downhole power unit may be used to pump fluid from a downhole hydraulic fluid source disposed with support member  176  into piston section  186  to urges expander member  178  and expander member  180  toward one another. In either case, expander member  176  is downwardly urged such that the frustaconical surface of tapered cone section  182  of expander member  176  contacts the interior wall of cylindrical ramp section  164 . Likewise, expander member  180  is upwardly urged such that the frustaconical surface of tapered cone section  184  of expander member  180  contacts the interior wall of cylindrical ramp section  168 .  
         [0048]    Tapered cone sections  182 ,  184 , respectively apply a radially outward force to cylindrical ramp sections  164 ,  168 . When this force is sufficient to plastically deform cylindrical ramp sections  164 ,  168 , expander members  178 ,  180  begin to travel longitudinally within cylindrical ramp sections  164 ,  168  in opposite directions toward one another. As the movement of expander members  178 ,  180  progresses, cylindrical ramp sections  164 ,  168  and radially reduced sections  166 ,  170  are substantially uniformly expanded from their original diameters to a diameter similar to the diameter of expander members  178 ,  180 . As this expansion occurs, attachment elements  172 ,  174  expand into intimate contact with slotted liner  138 . Once attachment elements  172 ,  174  are expanded, a fluid seal and a friction grip are created between sand control screen  140  and slotted liner  138 .  
         [0049]    Once the expansion of end sections  160 ,  162  of sand control screen  140  is complete, expansion tool  144  may be retrieved to the surface with electric line  152 . Specifically, if support member  176  is coupled to sand control screen  140  using shear pins, upward jarring on electric line  152  may be used to break the shear pins and release expansion tool  144  from sand control screen  140  to allow retrieval. Once expansion tool  144  and electric line  152  have been retrieved, a production tubing string  188  including production packer  190  may be installed within casing  134  down to a point above the top of slotted liner  138 , as best seen in FIG. 7.  
         [0050]    While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.