Abstract:
Disclosed herein is a downhole plug protection system. The system includes, a tubular having perforations in a perforated portion, a screen in fluidic communication with the tubular, a ring in sealable communication with the tubular and attached to the screen the ring having an extended portion positioned radially outwardly of the perforated portion, and a float shoe in fluidic communication with the perforations positionable downhole of the perforated portion.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a Continuation In Part of U.S. patent application Ser. No. 12/141,224, filed Jun. 18, 2008, which claims priority to U.S. Provisional Application No. 61/052,919, filed on May 13, 2008, the entire contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   It is common to plug fluidic openings, such as, screens, perforations and flow ports, for example, formed in tubular walls of drillstring members while the tool is being run downhole. Plugging of such flow ports prevents borehole fluids from infiltrating the drillstring during the running process, thereby reducing the weight of the drillstring through the buoyancy forces generated by wellbore fluid upon the drillstring. Further, lower density fluids can be contained within the string to adjust buoyancy. These buoyancy forces can be particularly helpful when running a tool into a highly deviated or horizontal wellbore in reducing frictional forces between the tool and the wellbore by floating the tool into position. 
   However, scraping of the drillstring along at least some of the walls of a wellbore during running is unavoidable. Such scraping abrades materials used to plug flow openings often weakening such plugging to the point of failure, thereby allowing fluid to fill the drillstring, negating the buoyancy effect and benefits resulting therefrom. Consequently, systems and methods assisting the reliable running of tools would be well received in the art. 
   BRIEF DESCRIPTION OF THE INVENTION 
   Disclosed herein is a downhole plug protection system. The system includes, a tubular having perforations in a perforated portion, a screen in fluidic communication with the tubular, a ring in sealable communication with the tubular and attached to the screen the ring having an extended portion positioned radially outwardly of the perforated portion, and a float shoe in fluidic communication with the perforations positionable downhole of the perforated portion. 
   Further disclosed herein is a method of maintaining plugs in a perforated tubular while flowing fluid therethrough. The method includes, perforating a portion of a tubular, sealedly attaching a ring to a non-perforated portion of the tubular, perimetrically surrounding a perforated portion with a longitudinally extended portion of the ring, plugging the perforations, and flowing fluid through the tubular and out through a float shoe in fluidic communication with the tubular. 
   Further disclosed herein is a method of making a flowable protected and plugged perforated tubular. The method includes, perforating a portion of a tubular, sealedly attaching a ring to a non-perforated portion of the tubular, perimetrically surrounding a perforated portion with a longitudinally extended portion of the ring, plugging the perforations, and attaching a float shoe to a non-perforated portion of the tubular. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
       FIG. 1  depicts a partial cross sectional view of a plug protection system disclosed herein illustrated in a plugged condition; 
       FIG. 2  depicts a partial cross sectional view of the plug protection system of  FIG. 1  illustrated in a open and flowing condition; 
       FIG. 3  depicts a magnified view of a portion of a plug protection system disclosed herein with an alternate embodiment of the perforated tubular as depicted in  FIG. 1 : and 
       FIG. 4  depicts a plugged screen assembly with a float shoe disclosed herein. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
   Referring to  FIG. 1 , an embodiment of a plug protection system  10  disclosed herein is illustrated. The plug protection system  10  includes, a perforated tubular member  14 , shown herein as a perforated base pipe, and a screen  18 , sealedly attached to the perforated tubular member  14 , by end rings  22  on opposing longitudinal ends of the screen  18 . The perforated tubular member  14 , in this embodiment, has a wall  26  with a plurality of ports  30  extending therethrough in two perforated portions  32 . The ports  30  are openings through which fluid, such as wellbore fluid, is flowable when the ports  30  are not plugged. The ports  30  may be any of a variety of shapes, such as, round, oval, or rectangular (to form slots), for example. The ports  30  are sized to be fluidically pluggable by any of a variety of downhole degradable materials  34 , such as paraffin, and/or polymers, for example, that are used for such purposes. The degradability of the materials  34  allows the ports  30  to be opened sometime after being positioned at a desired location within a wellbore  38 . The degradable materials  34  may be degradable in response to exposure to elevated temperatures, for example, that permit a well operator to open the ports  30 , when desired, by pumping steam (or other heat source in the case of a heat degradable material) downhole to heat the perforated tubular member  14  and the degradable material  34 . Alternate degradable materials  34  include materials that degrade when exposed to acid or other chemical compositions. Acid, for example, can be pumped downhole to expose the materials  34  thereto when opening of the ports  30  is desirable. 
   Longitudinal extensions  42  of the end rings  22  extend perimetrically to surround the perforated portions  32  of the perforated tubular member  14 . As such, the longitudinal extensions  42  protect the perforated portions  32  from direct contact with walls  46  of the wellbore  38 . By preventing abrasion of the degradable material  34  against the walls  46 , seal integrity of the degradable material  34  in the ports  30  can be maintained. 
   A length of the longitudinal extensions  42  can be designed to match a length of the perforated portions  32 , so that none of the ports  30  are exposed to direct abrasive contact with the walls  46 . Discontinuous non-sealing standoffs  50  can be positioned between the longitudinal extensions  42  and the perforated tubular member  14  to provide structural support and centering of the longitudinal extensions  42  relative to the perforated tubular member  14 . 
   Additionally, an annular space  52  defined by the longitudinal extensions  42  and the perforated portions  32  could also be plugged with plugging material  34  to increase pressure differentials required to extrude the plugging material  34 . Having this additional volume of plugging material  34  could also increase a time exposed to elevated temperatures or acid before the plugging material  34  sufficiently degrades to be forced through the ports  30 . 
   Referring to  FIG. 2 , a flow path for wellbore fluid from the wellbore  38  to an inside of the perforated tubular  14  is illustrated in a non-plugged configuration of the plug protection system  10 . The fluid flows through the screen  18  and then axially, along arrows  62 , in an annular space  54  defined by the screen  18  and a non-perforated portion  58  of the perforated tubular member  14 . The fluid then flows longitudinally from the annular space  54  to the annular space  52 . From the annular space  52  the fluid is able to flow radially inwardly, along arrows  68 , through the ports  30  in the perforated portions  32  to the inside of the perforated tubular member  14 . Although the fluid flow path has been described herein as flowing from outside of the plug protection system  10  to the inside of the perforated tubular member  14 , it should be understood that, in other applications, the fluid could flow in directions that are the reverse of those described herein. 
   Referring to  FIG. 3 , an alternate embodiment of a perforated portion  72  of the perforated tubular member  14  is illustrated. The perforated portion  72  includes ports  76  that are designed to increase a pressure differential sufficient to force the degradable material  34  to extrude through the ports  76 . The ports  76  may have tapered walls  80  that create a larger cross sectional area  84  at the outer surface  88  of the perforated tubular member  14  than the smaller cross sectional area  92  at an inner surface  96  of the perforated tubular member  14 . This construction creates a wedging action as the pressure differential compresses the degradable material  34  as it is forced through the ports  76 . The tapering of the walls  80 , in alternate embodiments, could be tapered at angles different to those disclosed herein. The walls  80  could be tapered to narrow at locations having greater radial dimensions to increase an extrusion pressure biased in an inside to outside direction, for example. Alternately, the ports  76  could have a normal straight hole configuration wherein the walls  80  are not tapered. 
   Embodiments disclosed herein permit high pressure differentials to be maintained across the plugged perforated tubular member  14  without extrusion of the degradable materials  34  though the ports  76 . This is due to a few factors, first a large volume of degradable material  34  can be used since it can be housed in the annular space  53 , and second, degradable material  34  in the annular space  52  needs to be displaced axially as well as radially before the plugging provided by the degradable material  34  is removed. The high pressure differentials can exist across the plugged ports  30  in either direction. For example, pressure can be greater on an outside of the perforated tubular member  14  or the pressure can be greater on an inside of the perforated tubular member  14 . While floating the perforated tubular member  14  downhole the pressure is typically greater on an outside of the perforated tubular member  14 . In contrast, while pumping fluid downhole, through the perforated tubular member  14 , the pressure is typically greater on an outside of the perforated tubular member  14 . An embodiment disclosed herein wherein fluid is pumped downhole through the perforated tubular member  14  will be described in detail below. 
   Referring to  FIG. 4 , an embodiment of a drillstring  100 , having multiple perforated portions  32 , is shown positioned in the wellbore  38 . Sealingly attached to the bottom of the drillstring  100  is a float shoe  104 . The float shoe  104  includes a housing  108  and a ball seal  112 . The ball seal  112  is movable within the housing  108  such that the float shoe  100  acts like a check valve. When the ball seal  112  is moved upward relative to the housing  108 , in this embodiment, it sealingly engages with a seat  116 , thereby preventing fluid flow thereby. When the ball seal  112  is moved downward flow channels  120  permit fluid flow by the ball seal  112 . 
   The foregoing construction allows the drillstring  100  to be floated downhole by preventing wellbore fluid from entering the drillstring  100  through the float shoe  104 . Alternately, the drillstring  100  can be run downhole while flowing fluid, such as mud pumped from surface, for example, down through the drillstring  100  and out through the float shoe  104  into the wellbore  38 . Flowing fluid out through the float shoe  104  can aid in flushing away debris in the wellbore  38  that can cause problems while running the drillstring  100  if it is allowed to jam between the housing  108  or drillstring  100  and the walls  46 . Fluid pumped out of the float shoe  104  into the wellbore  38  can also act as a lubricant to further facilitate the running of the drillstring  100 . 
   While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.