Removable and reloadable orifice for a downhole tool

Abstract

Disclosed is an apparatus and method for providing an activation pressure for a down hole too comprising a tool string having a pressure activated tool located at a distal end thereof, an opening passing through the tool string from an interior to an exterior thereof and a blocking body locatable in said opening operable to block a portion of said opening while leaving a reduced opening therethrough selected to produce a pressure within the tool string sufficient to activate the tool at a first fluid flow rate, wherein the blocking body is formed of a material operable to be dissolved by a solvent. The method comprises pumping a fluid down the tool string at a first fluid flow rate to activate the tool, pumping a solvent down the tool string operable to dissolve the blocking body, pumping the fluid down the tool string at a second fluid flow rate above the first flow rate and transporting a replacement blocking body down the tool string to the opening.

What is claimed is: 
     
         1 . An apparatus for providing an activation pressure for a down hole too comprising:
 a tool string having a pressure activated tool located at a distal end thereof, said tool string being operable to have a fluid pumped down therethrough to said tool;   an opening passing through said tool string from an interior to an exterior thereof; and   a blocking body locatable in said opening operable to block a portion of said opening while leaving a reduced opening therethrough selected to produce a pressure within said tool string at said tool sufficient to activate said tool at a first fluid flow rate through said tool string, wherein said blocking body is formed of a material operable to be dissolved by a solvent.   
     
     
         2 . The apparatus of  claim 1  wherein said opening is located at a distal end of said tool string with said tool being upstream therefrom. 
     
     
         3 . The apparatus of  claim 2  wherein said opening has a diameter selected to produce a pressure within said tool string below a pressure required to activate said tool at said first fluid flow rate. 
     
     
         4 . The apparatus of  claim 3  wherein said opening has a diameter selected to produce a pressure within said tool string below a pressure required to activate said tool at a second fluid flow rate. 
     
     
         5 . The apparatus of  claim 4  wherein said second fluid flow rate is higher than said first fluid flow rate. 
     
     
         6 . The apparatus of  claim 1  wherein said blocking body is formed of a material selected from the group consisting of biodegradable plastics, metals susceptible to dissolution, inorganic non-metals and pressed salts. 
     
     
         7 . The apparatus of  claim 1  wherein said reduced opening comprises an orifice through said blocking body. 
     
     
         8 . The apparatus of  claim 7  wherein said orifice comprises a plurality of perforations through said blocking body. 
     
     
         9 . The apparatus of  claim 1  wherein said reduced opening comprises a passage around said blocking body. 
     
     
         10 . The apparatus of  claim 9  wherein said passage around said reduced opening extends annularly around said blocking body. 
     
     
         11 . The apparatus of  claim 10  wherein said tool string includes a central support adapted to support said blocking body centrally therein with said passage located annularly between said blocking body and said tool string. 
     
     
         12 . A method for providing an activation pressure for a down hole too comprising:
 providing a tool string locatable down a well operable to have a fluid pumped down through an interior thereof;   locating a pressure activated tool at a distal end of said tool string in fluidic communication with said interior of said tool string;   providing an opening passing through said tool string from an interior to an exterior thereof; and   locating an blocking body in said opening operable to block a portion of said opening while leaving a reduced opening therethrough selected to produce a pressure within said tool string at said tool sufficient to activate said tool at a first fluid flow rate through said tool string, wherein said blocking body is formed of a material operable to be dissolved by a solvent.   
     
     
         13 . A method for providing an activation pressure for a down hole too comprising:
 pumping a fluid down a tool string having a pressure activated tool located at a distal end thereof at a first fluid flow rate to activate said tool;   pumping a solvent down said tool string operable to dissolve a blocking body located within an opening through a distal end of said tool string to remove said blocking body, said blocking body being operable to block a portion of said opening while leaving a reduced opening therethrough;   pumping said fluid down said tool string at a second fluid flow rate above said first flow rate such that said flow through said opening produces a pressure lower than said pressure required to activate said tool; and   transporting a replacement blocking body down said tool string to said opening.