Patent Publication Number: US-8118100-B2

Title: Debris protection for sliding sleeve

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of U.S. Application Ser. No. 11/683,848, filed on Mar. 8, 2007, which is incorporated by reference in its entirety, and to which priority is claimed. 
    
    
     BACKGROUND 
     Sliding sleeves are widely used in a variety of hydrocarbon production systems. A sliding sleeve typically includes a tubular outer housing having threaded connections at one or both ends for connection to a tubing string. The outer housing also includes one or more flow ports therethrough. Inside the housing, a sleeve mechanism is arranged to slide longitudinally within the outer housing. The sleeve may have one or more flow ports therethrough. The sleeve mechanism can be positioned to align the flow ports in the sleeve with the flow ports in the housing, which will allow fluid flow (either from inside out or outside in). Alternatively, the sleeve mechanism can be positioned so that the flow ports are not aligned, thereby preventing fluid flow. Many variations of this basic concept are known to those skilled in the art, and will not be discussed in detail here. For example, in some embodiments, the sleeve may not have flow ports, but may be arranged to either block the flow ports in the outer housing or not, thereby permitting flow or not. 
     In many applications, multiple sliding sleeves are used along a tubing string so that a hydrocarbon well can be segmented into a plurality of zones. By opening and/or closing various sliding sleeves, the individual zones can be isolated so that one or more zones can be produced, stimulated, etc. One example of such applications relates to multi-zone fracture systems, which are used, for example, in the Rocky Mountains of the western United States. In such an operation, a series of sliding sleeves are cemented thru as part of the well completion process. A problem with these systems is that cement can get into the inner workings of the sliding sleeves, which can cause problems with operation of the sleeves. 
     Prior art solutions to this problem have included putting grease into the sleeves to exclude the cement from the inner workings of the sleeve. However, the grease may still be displaced, for example, while the sliding sleeve is being run in or during other operations prior to cementing. Historically, there has been no solution to this problem other than to putting in what was thought to be a sufficient amount of grease and hoping for the best. Therefore, what is needed in the art is a system for preventing the displacement of grease disposed within a sliding sleeve to prevent entry of cement and/or other debris that can interfere with operation of the sliding sleeve. 
     SUMMARY 
     A variety of sliding sleeve mechanisms are disclosed herein. In some embodiments, the sliding sleeves include an outer housing with one or more flow ports and a sleeve mechanism disposed and longitudinally moveable within the outer housing. Aligning the sleeve mechanism relative to the flow ports of the outer housing can either permit or prevent fluid flow. The sliding sleeve can also include an easily destructible protective sheath that can provide debris protection by substantially blocking one or more of the flow ports. 
     The protective sheath can be formed from a variety of materials, such as composites, metal, foil, rubber, plastic, glass, ceramic, wire mesh, tape, etc. In some embodiments, the protective sheath can be a substantially cylindrical shell, which can be one or multiple pieces. The protective sheath can be retained in various ways, including, for example, recesses in the sliding sleeve or by mechanical fasteners such as screws, pins, rivets, snap rings, bands, and buckles. The protective sheath can also be disposed outside of the sliding sleeve (i.e., around the outer housing) or inside the sliding sleeve (between the sleeve mechanism and the outer housing). 
     In other embodiments, the protective sheath can be in the form of plugs disposed within the one or more flow ports. The plugs can be separate plugs formed, for example, from one or more of the materials described above. Alternatively, the plugs can be integral with the outer housing and/or the sleeve mechanism formed by perforations. In still other embodiments the protective sheath can be from tape or wire wound around the sliding sleeve. 
     The protective sheath can protect the sliding sleeve from debris either by retaining grease that has been packed into the sliding sleeve for that purpose. Alternatively, the protective sheath can positively prevent entry of debris into the sliding sleeve. The sheath can be cleared by permitting fluid flow through the sliding sleeve, which can act to destroy and/or wash away the protective sheath. 
     Additional details and information regarding the disclosed subject matter can be found in the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a sliding sleeve with a protective sheath. 
         FIG. 2  illustrates a sliding sleeve with a protective sheath retained by set screws. 
         FIG. 3  illustrates a sliding sleeve in which the protective sheath takes the form of a plug disposed within the flow ports of the outer housing. 
         FIG. 4  illustrates a sliding sleeve with a protective sheath disposed between the inner sleeve mechanism and the outer housing. 
     
    
    
     DETAILED DESCRIPTION 
     In the disclosure that follows, in the interest of clarity, not all features of actual implementations are described. It will of course be appreciated that in the development of any such actual implementation, as in any such project, numerous engineering and technical decisions must be made to achieve the developers&#39; specific goals and sub goals (e.g., compliance with system and technical constraints), which will vary from one implementation to another. Moreover, attention will necessarily be paid to proper engineering and programming practices for the environment in question. 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 relevant fields. 
     An exemplary sliding sleeve  100  is illustrated in  FIG. 1 . Sliding sleeve  100  includes an outer housing  101  and a sleeve mechanism  102  disposed therein. A plurality of flow ports  103  are disposed in the housing  101  and the sleeve mechanism  102 . (It will be appreciated by those skilled in the art that the flow ports in sleeve mechanism  102  are not strictly necessary, depending on the design of the sliding sleeve.) As noted above, the sliding sleeve may be opened by moving sleeve mechanism  102  longitudinally within housing  101  to align flow ports  103 . Similarly, the sliding sleeve may be closed by moving sleeve mechanism  102  longitudinally within housing  101  so that the flow ports  103  are not aligned (as shown). Exemplary sliding sleeve types include the OptiSleeve™ family of sliding sleeves available from Weatherford International Ltd., although other sliding sleeve types may also be used. The sleeve mechanism  102  may be moved by a variety of techniques. In some embodiments, operation of the sleeve may be hydraulic. In such applications, hydraulic shifting tools, such as the Hydraulic Weatherford B Shifting Tools, also available from Weatherford International Ltd., may be used to open and close the sliding sleeve. 
     As noted above, many completion operations can cause cement or other debris to enter flow ports  103  in the outer housing and interfere with operation of sliding sleeve  100 . Grease within the tool has been used to prevent the entry of cement or other debris into the workings of sliding sleeve  100 . Sliding sleeve  100  also includes protective sheath  104 , which is disposed about the outer housing and retains the grease during run in or other operations. Protective sheath  104  may take a variety of forms. In one embodiment, protective sheath  104  can be a substantially cylindrical sheath disposed around sliding sleeve after the sleeve is packed with grease but before the sleeve is run in. It is not necessary for the sheath to form a tight seal, as grease can be retained within the workings of the sleeve with only minimal mechanical constraint. However, sheaths that do tightly seal may also be used. Depending on the specifics of the design, materials, etc., protective sheath  104  may have a thickness on the order of 30-50 thousandths of an inch, although other thicknesses could also be used. 
     Protective sheath  104  can be formed from a variety of materials. In some embodiments, the sheath will be removed after downhole installation by flow of fluid from within the sliding sleeve to outside the sliding sleeve. This can take place, for example, during a fracing operation. Thus, it may be desirable to form the sheath from an easily destructible material. For example, this could be a frangible or otherwise soft and/or brittle material that can be cleared by the flow of fluid through the flow ports. Examples of such materials include composite materials like those used in composite bridge plugs, thin metals, foils, rubber, plastic, glass, ceramics, etc. Alternatively, in some embodiments chemical reaction with the supplied fluid may be used to remove protective sheath  104 . For example, sleeves that will be used in conjunction with acid fracing operations could use aluminum for protective sheath  104 . 
     Protective sheaths may be used with existing sleeves with little or no modification. For example, as illustrated in  FIG. 1 , outer housing  101  has a recess (demarked by its endpoints  105 ) machined therein into which protective sheath  104  fits. In another embodiment, illustrated diagrammatically in  FIG. 2 , protective sheath  104  and outer housing  101  can be drilled so that set screws  106  can be used to retain the protective sheath. As an alternative to set screws, pins, rivets, etc. could also be used. In still other embodiments, snap rings or other mechanical fasteners could be used to retain protective sheath  104 . 
     As an alternative to a single-piece, substantially cylindrical sheath, the protective sheath could be formed from multiple semi-cylindrical segments that are affixed together or affixed to the tool. For example, two half-cylinders could be placed around the sliding sleeve and attached to each other and/or to the sliding sleeve using a variety of mechanisms, including mechanical fasteners such as metal or plastic bands, adhesives, tapes, screws, buckles, etc. In another variation, the protective sheath could be formed from a fine wire mesh or similar material that would retain the grease, but be easily cleared by the flow of fluid through the sliding sleeve. In still another variation, the protective sheath could be formed from tape (such as duct tape, metalized tape, etc.) or wire wound around the outer housing. 
     As illustrated diagrammatically in  FIG. 3 , rather than a protective sheath, flow ports  103  in outer housing  101  could be plugged with protective plugs  107 . Protective plugs  107  can be formed from a variety of materials. Such materials can include any of the sheath materials described above, such as composites, metals, foils, rubber, plastic, glass, ceramics, etc. The plugs can be held in place by various techniques, including, for example, interference fit, snap rings, various fasteners, etc. Protective plugs  107  could also be formed by perforating but not completely opening flow ports  103  during fabrication of the sliding sleeve. Once the sliding sleeve was in place down hole and cementation or other debris-causing operations were completed, the pressure of fluid supplied or perforating charges could be used to clear the plug. Fabrication techniques required would be generally known to those skilled in the art, and are illustrated, for example, in U.S. Pat. No. 5,660,232, which is incorporated by reference herein. 
     In each of the foregoing embodiments, the protective sheath or plug has been disposed outside the sliding sleeve or within the flow ports or the outer housing. However, the device could also be constructed in other configurations. For example, as illustrated in  FIG. 4 , devices could be constructed with a sheath  104  between the sleeve mechanism and the interior of the outer housing  101 . For embodiments using plugs, whether integral or separate, the plugs could also be disposed within the flow ports of the sleeve mechanism. 
     Although specific embodiments and variations 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 that may have been suggested in the present disclosure, may be made to the disclosed embodiments without departing from the scope of the invention as defined by the appended claims. For example, although described in terms of retaining grease within the sliding sleeve, the protective sheath could also be adapted to prevent entry of debris into the sliding sleeve. The foregoing description and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.