Casing wiper plug system and method for operating the same

Abstract

The present casing wiper plug system and method includes a novel top wiper plug and a dissolvable blocking element. The top wiper plug includes a rupture disk and an open tail section configured and dimensioned to receive the dissolvable blocking element. The blocking element can be dissolved by a solvent and can dissolve quickly given the size or materials of the blocking element. When used in conjunction with a bottom wiper plug and a displacement fluid, the central bores of the top and bottom wiper plugs and shoe track provide an open passage to the formation allowing future injection or fracking fluid to access the formation. The blocking element is released into a seat of the open tail section to temporarily block the passage so a casing test can be performed on the casing. After the test is complete, the blocking element is dissolved to reopen the passage.

What is claimed is: 
     
         1 . A top wiper plug for well bore casing applications comprising:
 a body having one or more wiper fins extending therefrom, a central bore having entry and exit apertures, a rupture disk for initially closing off the central bore, and an open tail section that includes an interior structure that narrows from a lower, wider end to a narrower end located at a seat structure adjacent the exit aperture of the central bore, wherein the tail section is configured and dimensioned to receive therein and direct a dissolvable blocking element that is configured and dimensioned to fit in the narrower end of the structure into contact with the seat to block the exit aperture of the central bore, where the blocking element is dissolvable by a solvent.   
     
     
         2 . The top wiper plug of  claim 1 , further comprising a sealing nose configured to be connected with a bottom wiper plug that is configured to be connected with a landing collar. 
     
     
         3 . The top wiper plug of  claim 1 , wherein the interior structure has a conical structure. 
     
     
         4 . A combination comprising the top wiper plug of  claim 1  and a dissolvable blocking element that is received in the seat structure. 
     
     
         5 . The combination of  claim 4 , wherein the open tail section has a conical interior structure and wherein the dissolvable blocking element has a diameter that is larger than but no greater than about 1½ times the diameter of the central bore of the top wiper plug so that the blocking element is sufficiently large to block the central bore but sufficiently small to be dissolved readily. 
     
     
         6 . A system for conducting a mechanical integrity test to determine whether a wellbore casing can withstand fracking conditions, comprising:
 a bottom wiper plug for initial introduction into a wellbore;   a top wiper plug comprising a body having one or more wiper fins extending therefrom, a central bore having entry and exit apertures, a rupture disk for initially closing off the central bore, and an open tail section that includes an interior structure that narrows from a lower, wider end to a narrower end located at a seat structure adjacent the exit aperture of the central bore, wherein the seat structure is configured and dimensioned to receive therein and direct a dissolvable blocking element that is configured to fit in the narrower end of the structure into contact with the seat to block the exit aperture of the central bore; and   a dissolvable blocking element that is configured and dimensioned to fit in the narrower end of the interior and contact the seat structure to block the exit aperture of the central bore, where the blocking element is dissolvable by a solvent.   
     
     
         7 . The system of  claim 6 , wherein the bottom wiper plug comprises a body having one or more wiper fins extending therefrom, a central bore having entry and exit apertures, a rupture disk for initially closing off the central bore, a sealing nose configured to be connected to a landing collar, and a plug connector configured to receive a forward portion of the top wiper plug. 
     
     
         8 . The system of  claim 7 , wherein the rupture disks of the top and bottom wiper plugs are initially configured to prevent fluids from passing through the central bores of the respective plugs. 
     
     
         9 . The system of  claim 7 , wherein the rupture disks are breakable by fluids or fluid pressure at a selected burst pressure. 
     
     
         10 . The system of  claim 6 , wherein the open tail section of the top wiper plug has a conical interior structure and wherein the dissolvable blocking element has a diameter that is equal to or larger than 1½ times the diameter of the central bore of the top wiper plug so that the blocking element is sufficiently large to block the central bore but sufficiently small to be dissolved readily. 
     
     
         11 . The top wiper plug of  claim 1 , wherein the open tail section has a conical interior structure and wherein the dissolvable blocking element is a spherical element that has a diameter that is equal to or larger than about 1½ times the diameter of the central bore of the top wiper plug so that the blocking element is sufficiently large to block the central bore but sufficiently small to be dissolved readily, and wherein the dissolvable blocking element is directly received in the seat structure of the top wiper plug. 
     
     
         12 . The top wiper plug of  claim 1 , wherein the open tail section has an arcuate interior structure and wherein the dissolvable blocking element is a spherical element so that the blocking element is sufficiently large to block the central bore but sufficiently small to be dissolved readily, and wherein the dissolvable blocking element is directly received in the seat structure of the top wiper plug. 
     
     
         13 . The combination of  claim 4 , wherein the open tail section has a conical interior structure and wherein the dissolvable blocking element is a spherical element that has a diameter that is equal to or larger than about 1½ times the diameter of the central bore of the top wiper plug so that the blocking element is sufficiently large to block the central bore but sufficiently small to be dissolved readily, and wherein the dissolvable blocking element is directly received in the seat structure of the top wiper plug. 
     
     
         14 . The system of  claim 6 , wherein the open tail section has an arcuate interior structure and wherein the dissolvable blocking element is a spherical element so that the blocking element is sufficiently large to block the central bore but sufficiently small to be dissolved readily, and wherein the dissolvable blocking element is directly received in the seat structure of the top wiper plug. 
     
     
         15 . The system of  claim 6 , wherein the dissolvable blocking element comprises a controlled electrolytic metallic nano-structured material, a polymer, a biodegradable polymer, a solid acid which is optionally held together with a wax or other binder material, a polyethylene homopolymer, a paraffin wax, a polyalkylene oxide, polyalkylene glycol, or any combination thereof. 
     
     
         16 . The system of  claim 6 , wherein the dissolvable blocking element comprises sulfamic acid, trichloroacetic acid, or citric acid, optionally held together with a wax or other binder material; a polyvinyl-alcohol based polymer, a polylactide polymer or mixture with a polyglycolide polymer, a polycaprolactam polymer, a polyethylene oxide, a polyethylene glycol, or any combination thereof. 
     
     
         17 . The system of  claim 6 , wherein the dissolvable blocking element is dissolvable by contact with an aqueous solvent. 
     
     
         18 . The combination of  claim 4 , wherein the dissolvable blocking element comprises a controlled electrolytic metallic nano-structured material, a polymer, a biodegradable polymer, a solid acid which is optionally held together with a wax or other binder material, a polyethylene homopolymer, a paraffin wax, a polyalkylene oxide, polyalkylene glycol, or any combination thereof. 
     
     
         19 . The combination of  claim 4 , wherein the dissolvable blocking element comprises sulfamic acid, trichloroacetic acid, or citric acid, optionally held together with a wax or other binder material; a polyvinyl-alcohol based polymer, a polylactide polymer or mixture with a polyglycolide polymer, a polycaprolactam polymer, a polyethylene oxide, a polyethylene glycol, or any combination thereof. 
     
     
         20 . The combination of  claim 4 , wherein the dissolvable blocking element is dissolvable by contact with an aqueous solvent.