Abstract:
A technique for preventing mineral, mineral salt and other deposits from impeding the motion of movable components in a submerged environment. The technique allows for a movable component in a submerged environment to move freely beneath a deformable member. As the member deforms, it fractures deposition products so they do not significantly impede the path of the movable component.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to the use of movable components, either external or internal, which are utilized in completion systems that are disposed in a wellbore during operation. 
   BACKGROUND OF THE INVENTION 
   A variety of systems are used to facilitate the production of fluid from subterranean formations, tanks and other structures that compel the use of various completion systems. In a fluid production system, for example, a pump inlet may allow the production fluid entry to the production tubing for delivery of fluid to the surface. Control lines from the surface may be employed to control and regulate the function of the various subterranean components involved in fluid production. Control and regulation of these components may involve the movement of valves, levers, pistons, sleeves, or other moving parts located on the external or internal surfaces of the submerged components. 
   The aqueous or partially aqueous environment in which components are often submerged may contain various dissolved minerals representative of the subterranean environment. As chemical reactions occur within the environment, with the components, or in response to the temperature and pressure changes which occur in the vicinity of the equipment, minerals and mineral salts precipitate out of solution and form layers of deposits on the submerged components. The rock-hard layers of minerals and mineral salts may, over time, prevent the proper function of parts that move along the exposed surfaces, either internal or external, of the submerged equipment. In particular, as the layers form, moving parts may be prevented from moving in their desired range of motion, impacting the control and regulation of the system as a whole. 
   The present invention addresses these and other problems found in supporting equipment in a downhole environment. 
   SUMMARY OF THE INVENTION 
   The present technique relates generally to preventing mineral and mineral salt deposits from impeding the motion of a movable component in a submerged environment. The technique generally comprises providing a flexible or elastic sleeve under which the movable component moves. Deposition products are only formed on the sleeve and do not impede the movable component as the sleeve temporarily deforms in response to movement by the movable component. In addition, as the sleeve deforms, the layer of deposition products is potentially broken into fragments, some or all of which may fall away from the sleeve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
       FIG. 1  depicts an exemplary system deployed in a subterranean environment, according to one embodiment of the present invention; 
       FIG. 2  is a cross-sectional view of one embodiment of the present technique prior to movement by the movable component; 
       FIG. 3  is an enlarged view of the embodiment as depicted in  FIG. 2 ; 
       FIG. 4  is a cross-sectional view of an alternative embodiment of the present technique prior to movement by the movable component; 
       FIG. 5  is a cross-sectional view of the present technique subsequent to movement by the movable component; and 
       FIG. 6  is an enlarged view of the embodiment as depicted in  FIG. 5 . 
   

   DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Although the present technique is described with reference to a specific embodiment utilized in a specific environment, this description should not be construed as limiting. The technique for breaking down mineral deposits and scale can be utilized with a variety of completion systems as well as other systems that may require mechanical motion in an aqueous environment. Similarly, the technique can be used in a variety of environments other than the exemplary subterranean, wellbore environment described. The specific embodiment and environment illustrated and described is used to facilitate an understanding of the invention rather than to limit the invention. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
   Referring generally to  FIG. 1 , an exemplary completion system  10  is illustrated. The exemplary system comprises at least tubing  12  and a fluid intake  16 . 
   The production system  10  is designed for deployment in a well  18  within a geological formation  20  containing desirable production fluids, such as petroleum. In a typical application, a wellbore  22  is drilled and lined with a wellbore casing  24 . Wellbore casing  24  may comprise a plurality of openings  26 , commonly referred to as perforations, through which a production fluid  27  flows into wellbore  22  from the formation  20 . The system  10  is deployed in wellbore  22  by a deployment system  28  that may have a variety of configurations. For example, deployment system  28  may comprise tubing  12  which extends into the fluid production region. The production fluid  27  moves into the tubing  30  via the fluid intake  16  where it is then conducted to the desired location, e.g. the surface of the earth. The flow of fluid  27  into the tubing  30  and up to the surface may result from the natural fluid pressure within the formation  20  or may be enhanced by the addition of a submersible pump and pumping system to the fluid production system  10 . 
   Numerous aspects of the completion system  10  may rely on mechanical motion to change from one operating state to another or to regulate the flow of production fluids. Control lines which run from the surface may control the setting of these valves or other mechanical interfaces which regulate the operation of various components within or cooperating with the completion. For example, the control lines may induce the operation of a valve, a lever, a piston, sleeve, or some other moving component which regulates the operation of the completion system  10 , such as the intake of production fluid  27 . 
   The wellbore environment, however, is generally hostile to mechanical equipment disposed downhole. In addition to high temperature and pressure as well as corrosive conditions, the wellbore is also typically an aqueous or partially aqueous environment. This aqueous nature of the wellbore, over time, can lead to mineral and mineral salt deposits, sometimes called scale, which coat the metallic and other surfaces of the downhole equipment. The deposition of minerals may be due to a chemical reaction with the surface of the equipment, chemical reactions within the water and other fluids within the wellbore, changes in pressure or temperature, or a change in the composition of the solution surrounding the equipment. Scale may also be formed as a byproduct of corrosion. The deposition products which comprise scale typically include calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, iron sulfide, iron oxides, iron carbonate, the various silicates, phosphates, and oxides, or any of a number of compounds insoluble or only slightly soluble in water. 
   In the production environment, the deposition of scale may occur over time on wellbore tubulars and components. Scale deposition on the production components occurs as the relative amount of water in the surrounding porous rock is affected by the changing temperature and pressure conditions near the production components. In particular, as temperature and pressure change, minerals and mineral salts may be forced out of solution, coating the surfaces of the components comprising the submersible completion  10 . Significant scale buildup may thereby create a significant restriction to the movement of parts that regulate or control the operation of the submersible equipment. For example, scale may prevent a valve, such as a flow control valve, from properly opening or closing. Likewise levers and pistons arrangements, i.e. sliding parts, may be prevented from sliding from one operational state to another if the surface over which they move is coated with scale deposits. 
   One technique by which the problems caused by scale deposition may be addressed is shown in  FIGS. 2–6 , in which a flow regulator  42 , consisting of a sleeve which slides over the fluid inlet  16 , is depicted in cross section. It is to be understood that the flow regulator  42  is merely representative of the type of moving parts which may be found on the internal and external surfaces of downhole submersible components. 
   The hydraulic regulator  42  comprises a moving component, here represented as sliding sleeve  44 , which moves along the surface of a stationary component  46 , such as the tubing  12  or some other component of the completion  10 . An elastic or flexible covering, such as a rubber sleeve  48 , is secured to the stationary component  46  by a clamp  50 . Other means may be used to secure the elastic sleeve  48  to the stationary part  46 , however, such as screws or other mechanical fasteners or chemical fasteners such as adhesives. 
   The elastic sleeve  48  covers a portion of the surface  52  of the stationary component  46  including an engagement region  54  along which the moving component  44  moves. In the embodiment depicted in  FIG. 2 , the elastic sleeve  48  also covers at least a portion of the moving component  44 . Alternately, as illustrated in  FIG. 3 , the elastic sleeve  48  may be disposed immediately adjacent to the moving component  44 . In the embodiment depicted in  FIG. 3 , when the moving component  44  translates across the engagement region  54 , it moves underneath the portion of the elastic sleeve  48  disposed over the engagement region  54 . 
   The engagement region  54  and adjacent regions of one embodiment are enlarged and depicted in  FIG. 4  to provide further detail. In particular,  FIG. 4  depicts the various seals  55  which may underlay the moving component  44  in an arrangement supporting the depicted sliding sleeve. In addition, the moving component  44  may be seen to comprise an angled leading edge  57  to facilitate movement under the elastic sleeve  48 . 
   An exemplary layer of scale  56  is illustrated on the exterior surface  58  of the elastic sleeve  48  which is exposed to the environment within the wellbore  22 . As depicted in  FIG. 5  and in  FIG. 6  which depicts the engagement region  54  in enlarged scale, when the moving component  44  traverses along the engagement region  54  of the stationary component  46 , it need not break through the layer of scale  56 . Instead, when the moving component  44  moves along the engagement region  54 , it pushes the elastic sleeve  48  up and away from the surface  52  of the region  54 . As the sleeve  48  temporarily deforms, it lifts the scale  56  out of the path of the moving component  44 , fracturing the scale  56  over the deformed region into fragments  60  (see  FIGS. 5 and 6 ). These scale fragments  60  may remain attached to the elastic sleeve  48  or may fall off into the wellbore  22 . The fragments  60  do not impede the motion of the moving component  44  their removal, however, allows unimpeded functioning of a relevant component, e.g. allowing the fluid intake  16  to be opened. 
   A scraper edge  62  may be incorporated onto the edge of the elastic sleeve  48  as depicted on side A of  FIG. 5 . In such a configuration, scale  56  built up along the exposed portion of the moving component  44  is scraped off into the wellbore  22  as the exposed portion of the moving component  44  passes the scraper edge  62 . Alternately, as depicted on side B, the elastic sleeve  48  may simply deform to accommodate the scale  56  built up on the exposed portion of the moving component  44  during operation. In this configuration, the additional deformation caused by the scale  56  on the moving component  44  may cause the remainder of the scale  56  on the elastic sleeve  48  to be fracture and removed. However, regardless of which of these, or other, configurations are employed, the portion of the moving component  44  traversing the engagement region  54  is unimpeded due to the lifting action of the elastic sleeve  48 , allowing the free motion of the moving component  44 . 
   While the moving component  44  in  FIGS. 2–6  is depicted as engaging in a sliding motion, this is only to simplify the explanation of the general technique discussed. The moving component  44  may actually be engaged in rotational motion around the stationary component  46 , a combination of sliding and rotational motion, or in other forms of motion along the engagement region  54 . In addition, though in the example depicted in  FIGS. 2–6  the elastic sleeve  48  is not secured to the moving component  44 , in an alternative configuration the elastic sleeve  48  may be so secured. In such a configuration, the elastic sleeve  48  folds or is deformed outwardly when moving component  44  operates, breaking apart the layer of scale  56  on the elastic sleeve  48 . 
   It will be understood that the foregoing description is of exemplary embodiments of this invention, and that the invention is not limited to the specific forms shown. For example, the composition of the elastic sleeve, the mechanism of securing the sleeve, and the types of motion available to the moving component may all vary from the particulars discussed above. Indeed, such changes may be necessary due to the variety of applications which employ submersible equipment submerged within various environmental fluids. However, these and other modifications may be made in the design and arrangement of the elements without departing from the scope of the invention as expressed in the appended claims.