Casing float tool

Abstract

A rupture disc assembly and a float tool incorporating the rupture disc assembly is disclosed. The rupture disc assembly may include a rupture disc assembly comprising a rupture disc, an upper tubular portion and a lower tubular portion, and a securing mechanism for holding the rupture disc between the upper and lower tubular portions. A float tool for creating a buoyant chamber in a casing string may include the rupture disc assembly and a sealing device for sealing the lower end of the casing string, the buoyant, sealed chamber may be created there between. In operation, applied fluid pressure causes the rupture disc to move downward. The rupture disc may be shattered by contact with a surface on the lower tubular portion. Full casing internal diameter may be restored in the region where the rupture disc formerly sealed the casing.

What is claimed is: 
     
         1 . A method for installing casing in a wellbore containing a well fluid and having an upper, vertical portion, a lower, horizontal portion, and a bend portion connecting the upper and lower portions, the method comprising:
 (a) running a casing string into the wellbore, the casing string having a full casing internal diameter that defines a fluid passageway between an upper portion of the casing string and a lower portion of the casing string the upper and lower portions of the casing string separated by a chamber sealed on one end by a rupture disc assembly and on an opposing end by a lower seal with a first fluid having a first specific gravity therein   wherein the rupture disc assembly comprises (i) a tubular member having an upper end and a lower end, the upper and lower ends connected in-line with the casing string and (ii) a rupture disc configured to rupture and sealingly engaged in a region of the tubular member within the upper and lower ends and having a rupture burst pressure that is greater than a fluid pressure imposed on the rupture disc by a fluid above the rupture disc sufficient to run the casing string into the lower, horizontal portion of the wellbore and the region of the tubular member has an inner diameter substantially the same as the full casing internal diameter after the rupture disc has ruptured; and   (b) floating at least a portion of the casing string containing the sealed chamber in the well fluid in the lower, horizontal portion of the wellbore.   
     
     
         2 . The method of  claim 1 , further comprising: filling the casing string above the rupture disc assembly with a second fluid having a second specific gravity higher than the first specific gravity. 
     
     
         3 . The method of  claim 1 , wherein the first specific gravity is less than a specific gravity of the well fluid. 
     
     
         4 . The method of  claim 1 , wherein the first fluid is air. 
     
     
         5 . The method of  claim 2 , wherein the second fluid is a liquid-phase fluid. 
     
     
         6 . A float tool configured for use in positioning a casing string in a wellbore containing a well fluid, the casing string having a full casing internal diameter that defines a fluid passageway between an upper portion of the casing string and a lower portion of the casing string, the float tool comprising:
 a rupture disc assembly comprising (i) a tubular member having an upper end and a lower end, the upper and lower ends configured for connection in-line with the casing string and (ii) a rupture disc having a rupture burst pressure and in sealing engagement with a region of the tubular member within the upper and lower ends,   wherein the rupture disc is configured to disengage from sealing engagement when exposed to a pressure greater than a hydraulic pressure in the casing string after the casing string has been positioned in the wellbore and the region of the tubular member has an internal diameter not less than the full casing internal diameter upon disengagement of the rupture disc.   
     
     
         7 . The float tool recited in  claim 6  wherein the rupture disc is further configured to rupture when exposed to a rupturing force greater than the rupture burst pressure and the pressure greater than the hydraulic pressure is less than the rupture burst pressure. 
     
     
         8 . The float tool recited in  claim 6  wherein the wellbore has an upper, substantially vertical portion, a lower, substantially horizontal portion, and a bend portion connecting the upper and lower portions and the float tool is configured for use in the casing string such that, when the casing string is positioned in the wellbore for a cementing operation, the rupture disc is located in the upper, substantially vertical portion of the wellbore. 
     
     
         9 . The float tool recited in  claim 8  wherein the float tool is configured for use in the casing string such that, when the casing string is positioned in the wellbore for the cementing operation, the rupture disc is located proximate the bend portion of the wellbore. 
     
     
         10 . The float tool recited in  claim 6  further comprising:
 a shear ring sealingly engaging the rupture disc in the region of the tubular member. 
 
     
     
         11 . The float tool recited in  claim 6  wherein the rupture disc comprises a hemispherical dome of frangible material having a convex surface oriented in an up-hole direction. 
     
     
         12 . The float tool recited in  claim 11  wherein the frangible material is selected from the group consisting of carbides, ceramics, metals, plastics, glass, porcelain, alloys, and composite materials. 
     
     
         13 . The float tool recited in  claim 11  wherein the dome of frangible material has a pattern of grooves in an outer surface thereof, the grooves configured to provide lines of weakness to facilitate breakage of the disc into a plurality of pieces. 
     
     
         14 . The float tool recited in  claim 6  wherein the rupture disc forms an upper seal of a sealed chamber. 
     
     
         15 . The float tool recited in  claim 14  wherein the sealed chamber is configured for releasably containing a fluid having a lower specific gravity than that of the well fluid. 
     
     
         16 . The float tool recited in  claim 15  wherein the fluid having a lower specific gravity than that of the well fluid is released upon disengagement of the rupture disc. 
     
     
         17 . The float tool recited in  claim 14  wherein the sealed chamber is filled with a fluid having a lower specific gravity than that of the well fluid. 
     
     
         18 . The float tool recited in  claim 17  wherein the fluid in the sealed chamber is a gas. 
     
     
         19 . The float tool recited in  claim 18  wherein the gas is air. 
     
     
         20 . The float tool recited in  claim 14  further comprising a lower seal on the sealed chamber. 
     
     
         21 . The float tool recited in  claim 20  wherein the lower seal is within a float shoe. 
     
     
         22 . The float tool recited in  claim 20  wherein the lower seal is within a float collar. 
     
     
         23 . The float tool recited in  claim 6  further comprising:
 a debris catcher disposed on the casing string downhole of the rupture disc. 
 
     
     
         24 . The float tool recited in  claim 23  wherein the debris catcher comprises a filter configured to capture pieces of the rupture disc after the rupture disc has ruptured. 
     
     
         25 . The float tool recited in  claim 23  wherein the debris catcher comprises a base having an outside diameter approximately the same as the full casing internal diameter of the casing string, a plurality of hollow projections having tubular walls with one or more apertures formed therein said projections being substantially hollow cylinders attached to and extending upwardly from the base, each defining a central fluid passageway configured to allow fluid to flow across the debris catcher and into the lower portion of the casing string. 
     
     
         26 . The float tool recited in  claim 20  further comprising: a landing collar positioned between the rupture disc and the lower seal. 
     
     
         27 . The float tool recited in  claim 14  wherein the sealed chamber is sized such that a portion of the sealed chamber is buoyant in the well fluid. 
     
     
         28 . A method for installing casing in a wellbore containing a well fluid and having an upper vertical portion, a lower horizontal portion, and a bend portion connecting the upper and lower portions, the method comprising:
 running a casing string into the wellbore, the casing string having a full casing internal diameter that defines a fluid passageway between an upper portion of the casing string and a lower portion of the casing string, the upper and lower portions of the casing string separated by a chamber sealed on one end by a rupture disc assembly and on an opposing end by a seal, the chamber containing a first fluid having a first specific gravity   wherein the rupture disc assembly comprises (i) a tubular member having an upper end and a lower end, the upper and lower ends connected in-line with the casing string and (ii) a rupture disc having a rupture burst pressure and in sealing engagement with a region of the tubular member within the upper and lower ends,   wherein the rupture disc is configured to disengage from sealing engagement when exposed to a pressure greater than a hydraulic pressure in the casing string after the casing string has been positioned in the wellbore and the region of the tubular member has an internal diameter not less than the full casing internal diameter upon disengagement of the rupture disc; and   floating at least a portion of the casing string containing the sealed chamber in the well fluid in the lower horizontal portion of the wellbore.   
     
     
         29 . The method recited in  claim 28  further comprising:
 filling the casing string above the rupture disc assembly with a second fluid having a second specific gravity higher than the first specific gravity. 
 
     
     
         30 . The method recited in  claim 29  wherein the first specific gravity is less than a specific gravity of the well fluid. 
     
     
         31 . The method recited in  claim 28  wherein the first fluid is air. 
     
     
         32 . The method recited in  claim 28  wherein the second fluid is a liquid-phase fluid. 
     
     
         33 . The method recited in  claim 28  further comprising applying a pressure within the casing string greater than the hydraulic pressure in the casing string to disengage the rupture disc from sealing engagement. 
     
     
         34 . The method recited in  claim 33  wherein the rupture disc is further configured to rupture when exposed to a rupturing force greater than the rupture burst pressure and the pressure greater than the hydraulic pressure is less than the rupture burst pressure. 
     
     
         35 . The method recited in  claim 34  further comprising applying a rupturing force to rupture the rupture disc.