Abstract:
An apparatus and method of forming a barrier to fluid flow behind a liner are provided. In one embodiment of the invention, a method includes the steps of conveying a tool to a position within a wellbore having a liner, the tool carrying a seal material, and injecting the seal material from the tool through the liner to form a barrier to fluid flow behind the liner. In another embodiment of the invention, the apparatus includes a housing having a chamber carrying a seal material, and a means for injecting the seal material through the wellbore liner.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/910,846 filed Apr. 10, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates in general to wellbore or borehole operations and more particularly to a methods and systems for creating seals in a wellbore utilizing a tool element that emits sealing material to form a seal between the tubing and the wellbore. 
       BACKGROUND 
       [0003]    As more oilfields become mature, the need for side tracking existing wells and through tubing completions to improve production from these aging wells increases. Through tubing expandables and slotted liners may be used for side tracking and through tubing completions. Typically, at some point in the well&#39;s life, it is desired to segment or compartmentalize the well for selective treatment of a zone or to prevent encroachment of an undesired fluid. Unfortunately, through tubing expandables and slotted liners make it difficult to segment or compartmentalize the wellbore. Conventional packers do not allow segmenting or compartmentalizing these wellbores without considerable expense. 
         [0004]    Therefore, it is a desire to provide a system and method for providing a seal behind a wellbore liner. 
       SUMMARY OF THE INVENTION 
       [0005]    Apparatus and methods of forming a barrier to fluid flow behind a wellbore liner are provided. In an embodiment of the invention, a method includes the steps of conveying a tool to a position within a wellbore having a liner, the tool carrying a seal material, and injecting the seal material from the tool through the liner to form a barrier to fluid flow behind the liner. 
         [0006]    In an embodiment of the invention, an apparatus includes a housing having a chamber carrying a seal material, and a means for injecting the seal material through the wellbore liner. The seal material may react to the hydrocarbons present in the wellbore to form the barrier. The seal material may be thixotropic in nature and/or a swellable material to facilitate placement through the liner while forming a suitable sealing plug where desired. 
         [0007]    The foregoing has outlined the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The foregoing and other features and aspects of the present invention will be best understood with reference to the following detailed description of a specific embodiment of the invention, when read in conjunction with the accompanying drawings, wherein: 
           [0009]      FIG. 1  is a schematic side view of an embodiment of the sealing method of the present invention; and 
           [0010]      FIG. 2  is a further view of the sealing method illustrated in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. 
         [0012]    As used herein, the terms “up” and “down”; “upper” and “lower”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point. 
         [0013]      FIG. 1  is a schematic side view of an embodiment of the sealing method of the present invention, generally denoted by the numeral  10 . A portion of a wellbore  12  is completed with a liner  14 . Liner  14  may include one or more openings or perforations  16  along its length. For clarity, liner  14  is depicted in  FIGS. 1 and 2  with multiple openings  16 . As used herein, liner  14  includes any tubing, liner or screen that has openings  16 . Openings  16  may be formed therethrough prior to hanging the tubular in the wellbore  12  or in the wellbore with punches, explosive charges, mills, drills and the like. Liner  14  may be cemented or non-cemented. Examples of liners  14  include slotted, perforated, or predrilled liners, or a screen or a pre-packed screen. An annulus  18  is formed between liner  14  and the wall  20  of wellbore  12 . 
         [0014]    It is desired to seal annulus  18  in a region  22 . In the first step of sealing method  10 , a tool  24  is positioned within liner  14  proximate region  22  via conveyance  42 . Tool  24  includes, but is not limited to, a housing  26  having a chamber  28  carrying a seal material  30 , injection mechanism  32 , and one or more ports  34  connected to chamber  28 . Tool  24  may also include locating sub  38  and sealing members  40 . Tool  24  may also include perforating guns, drilling mechanisms or cutting mechanisms suitable for creating an opening  16 . Conveyance  42  may be an electric line, coiled tubing (CT), jointed tubing, a wireline or a slickline. Injection mechanism  32  includes piston  44  in communication with chamber  28 . Injection mechanism  32  includes pressurized fluid  46  to hydraulically actuate or motivate piston  44  against chamber  28  to expel seal material  30  from chamber  28 . Sealing members  40  are positioned about the ports  34  and are actuatable or hydraulically expandable to a position engaging liner  14 . 
         [0015]    Tool  24  may be constructed for multiple tubing sizes. Before tool  24  is positioned proximate region  22 , tool  24  may need to be run through tubing  50  having bore  56  until it reaches region  52 , which has a bore  58  greater than bore  56 , where liner  14  is deployed. As tool  24  passes through tubing  50 , sealing members  40  may actuate or hydraulically expand to engage liner  14  to help position tool  24  into this larger bore region  52 . 
         [0016]    In the second step of method  10 , tool  24  is positioned proximate opening  16 , or, if necessary, forms an opening  16  in liner  14  using conventional means. In the third step of method  10 , sealing members  40  may actuate to a position engaging liner  14  to form a channel  54  between housing  26  and liner  14  for injecting the seal material  30  behind liner  14 . 
         [0017]    Referring now to  FIG. 2 , in the fourth step of method  10 , a signal is sent to injection mechanism  32  to actuate the injection mechanism. The signal may be an internal signal within tool  24 , a mud pulse, a wireless or wired transmission or the like. In the fifth step of method  10 , injection mechanism  32  is actuated, and pressurized fluid  46  moves piston  44  through chamber  28  to eject seal material  30  from chamber  28 . Tool  24  then expels seal material  30  via ports  34  through channel  54  to inject seal material  30  through liner  14 , as indicated by the arrows. In the sixth step of method  10 , seal material  30  reacts with hydrocarbons in annulus  18  and forms sealing plug  48  behind liner  14  within region  22 . Sealing plug  48  may be formed circumferentially about liner  14 . 
         [0018]    To form sealing plug  48 , seal material  30  must be suitable for injecting through aperture  16  and for setting into a sealing plug  48  in reaction with contact with hydrocarbons. Thus, it is desired that seal material  30  be thixotropic in nature so that it will set and become substantially “self-supporting” relatively quickly. It may further be desired for seal material  30  to be a swellable material, so as to seal openings  16  in region  22 . The swellable property further facilitates sealing between wellbore  12  and liner  14 . It may further be desired for seal material  30  to have a sufficiently high gel strength so as to remain where placed, yet allow for a degree of gravity-induced flow to the lower portion of region  22 , for example in horizontal wellbores. It is noted that seal material  30  may include one or more of the desired properties. It is further noted, and will be recognized with the above description of the method, that sealing plug  48  may be formed in stages or by one or more seal materials  30 . For example, a first seal material  30  being primarily thixotropic in nature may be injected through opening  16  into region  22  and then followed with a second swellable seal material  30 . It may also be desired to inject spacing fluids, such as water or drilling fluid, after one or more seal material injections. 
         [0019]    Examples of suitable seal material  30  include, without limitation, foamed cements; unfoamed cements containing smectic clays such as bentonite and attapulgite, unfoamed cements containing welan gum, aluminum and/or iron sulphate, and/or calcium sulfate as thixotropy agents, thermosetting polymers such as epoxy, vinylester, phenolic and polyester resins, and cross-linking polymer gels (possibly with an added thixotrope). 
         [0020]    Swellable seal material  30  swells from an unexpanded state to an expanded state when it comes into contact with or absorbs hydrocarbons. The hydrocarbons may be present naturally in wellbore  12 , or present in the formation surrounding wellbore  12  and produced into the wellbore. 
         [0021]    Examples of suitable swellable seal material  30  and their corresponding triggering fluids (listed in parenthetical) include, without limitation: liquid hydrogel (hydrocarbon); Bacel® hardfoam (hydrocarbon); ethylene-propylene-copolymer rubber (hydrocarbon oil); ethylene-propylene-diene terpolymer rubber (hydrocarbon oil); butyl rubber (hydrocarbon oil); haloginated butyl rubber (hydrocarbon oil); brominated butyl rubber (hydrocarbon oil); chlorinated butyl rubber (hydrocarbon oil); chlorinated polyethylene (hydrocarbon oil); styrene butadiene (hydrocarbon); ethylene propylene monomer rubber (hydrocarbon); natural rubber (hydrocarbon); ethylene propylene diene monomer rubber (hydrocarbon); ethylene vinyl acetate rubber (hydrocarbon); hydrogenised acrylonitrile-butadiene rubber (hydrocarbon); acrylonitrile butadiene rubber (hydrocarbon); isoprene rubber (hydrocarbon); chloroprene rubber (hydrocarbon); and polynorbornene (hydrocarbon). 
         [0022]    In the embodiment illustrated in  FIGS. 1 and 2 , tool  24  carries both seal material  30  and injection mechanism  32  to facilitate a single trip into the well to create sealing plug  48  behind liner  14 . By providing both seal material  30  and injection mechanism  32  within tool  24 , method  10  allows for the creation of sealing plug  48  without the need for separate surface devices to pump or deliver seal material  30  downhole to region  22 . Tool  24  may further include aids, such as a source of heat or radiation, to facilitate or aid the setting of sealing plug  48 . The viscosity of seal material  30  may be varied based on the desired isolation length. 
         [0023]    From the foregoing detailed description of specific embodiments of the invention, it should be apparent that a system and method for downhole packing that is novel has been disclosed. Although specific embodiments of the invention have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed embodiments without departing from the spirit and scope of the invention as defined by the appended claims which follow.