Systems and methods for multistage fracturing

Abstract

A downhole system for multistage fracturing a subterranean formation that includes a first cluster of valves arranged on a tubular in an initially closed position. There is a second cluster of valves downhole of the first cluster, which is also arranged on the tubular in a respective initially closed position. The system has a plugging device operably coupled with a workstring, that is moved into the tubular. The plugging device is operable to move from a run-in configuration to a set configuration.

What is claimed is: 
     
         1 . A downhole system for multistage fracturing a subterranean formation, the downhole system comprising:
 a first cluster of valves;   a second cluster of valves downhole of the first cluster; and   a plugging device comprising:
 a plug body having a distal end, a proximate end, and an outer surface; 
   wherein the plugging device does not open any valves of the first cluster of valves, but opens at least one valve of the second cluster of valves,   wherein another plugging device is used to open at least one valve of the first cluster of valves, and   wherein at least one of the first cluster of valves and the second cluster of valves comprises a frac valve having a solid sleeve configured with a profile surface.   
     
     
         2 . The downhole system for multistage fracturing a subterranean formation of  claim 1 , the downhole system further comprising a workstring, wherein the plugging device is coupled with the workstring when the plugging device is in a run-in configuration. 
     
     
         3 . The downhole system for multistage fracturing a subterranean formation of  claim 2 , wherein in the run-in configuration the plugging device is unable to open any valves of the first cluster valves or the second cluster of valves. 
     
     
         4 . The downhole system for multistage fracturing a subterranean formation of  claim 2 , the downhole system further comprising a setting tool coupled with the workstring, wherein the setting tool is operable to move the plugging device from the run-in configuration to a set configuration. 
     
     
         5 . The downhole system for multistage fracturing a subterranean formation of  claim 4 , wherein in the set configuration the plugging device is able to disconnect from the workstring, and also in the set configuration the plugging device is able to open at least one valve of the second cluster of valves. 
     
     
         6 . The downhole system for multistage fracturing a subterranean formation of  claim 5 , wherein each valve of the first cluster of valves and the second cluster of valves is initially in a respective closed position. 
     
     
         7 . The downhole system for multistage fracturing a subterranean formation of  claim 1 , wherein each of the first cluster of valves and the second cluster of valves has only one respective frac valve. 
     
     
         8 . The downhole system for multistage fracturing a subterranean formation of  claim 7 , wherein each of the first cluster of valves and the second cluster of valves has a number of flex valves in a range of at least one flex valve to no more than one hundred flex valves. 
     
     
         9 . The downhole system for multistage fracturing a subterranean formation of  claim 8 , the plugging device further comprising:
 a cone; and   a lower sleeve proximate with the cone,   wherein in a run-in configuration the cone is not engaged with the lower sleeve, but after moving the plugging device to a set configuration, the cone is engaged with the lower sleeve, and wherein in the set configuration the plugging device remains free to move or be moved to engage a profile of any valve of the second cluster of valves.   
     
     
         10 . The downhole system for multistage fracturing a subterranean formation of  claim 9 , wherein at least one component of the plugging device comprises a shear feature, wherein at least one component of the plugging device is made of a dissolvable material, and wherein the cone further comprises a ball seat formed within an inner flowbore. 
     
     
         11 . A downhole system for multistage fracturing a subterranean formation, the downhole system comprising:
 a first cluster of valves arranged on a tubular in an initially closed position;   a second cluster of valves downhole of the first cluster, and also arranged on the tubular in a respective initially closed position;   a workstring comprising a setting tool; and   a plugging device operably coupled with the setting tool, the plugging device comprising:
 a plug body having a distal end, a proximate end, and an outer surface; 
   wherein in a run-in configuration the plugging device does not open any valves of the first cluster of valves, but in a set configuration the plugging device opens at least one valve of the second cluster of valves,   wherein another plugging device is used to open at least one valve of the first cluster of valves, and   wherein each of the first cluster of valves and the second cluster of valves comprises a respective frac valve having a solid sleeve configured with a profile surface.   
     
     
         12 . The downhole system for multistage fracturing a subterranean formation of  claim 11 , wherein the plugging device is coupled with the setting tool when the plugging device is in a run-in configuration. 
     
     
         13 . The downhole system for multistage fracturing a subterranean formation of  claim 12 , wherein in the run-in configuration the plugging device is unable to open any valves of the second cluster of valves. 
     
     
         14 . The downhole system for multistage fracturing a subterranean formation of  claim 13 , wherein in the set configuration the plugging device is able to disconnect from the setting tool. 
     
     
         15 . The downhole system for multistage fracturing a subterranean formation of  claim 11 , wherein in the set configuration the plugging device is able to disconnect from the setting tool, and wherein each of the first cluster of valves and the second cluster of valves has only one respective frac valve. 
     
     
         16 . The downhole system for multistage fracturing a subterranean formation of  claim 15 , wherein each of the first cluster of valves and the second cluster of valves has a number of flex valves in a range of at least one flex valve to no more than one hundred flex valves. 
     
     
         17 . The downhole system for multistage fracturing a subterranean formation of  claim 16 , the plugging device further comprising:
 a cone; and   a lower sleeve proximate with the cone,   wherein in the run-in configuration the cone is not engaged with the lower sleeve, but in the set configuration, the cone is engaged with the lower sleeve, and wherein in the set configuration the plugging device remains free to move or be moved to engage a the profile surface of the respective frac valve of the second cluster of valves.   
     
     
         18 . The downhole system for multistage fracturing a subterranean formation of  claim 17 , wherein at least one component of the plugging device comprises a shear feature, wherein at least one component of the plugging device is made of a dissolvable material, and wherein the cone further comprises a ball seat formed within an inner flowbore. 
     
     
         19 . A downhole system for multistage fracturing a subterranean formation, the downhole system comprising:
 a first cluster of valves arranged on a tubular in an initially closed position;   a second cluster of valves downhole of the first cluster, and also arranged on the tubular in a respective initially closed position;   a workstring comprising a setting tool; and   a plugging device operably coupled with the setting tool, the plugging device comprising:
 a plug body having a distal end, a proximate end, and an outer surface; 
   wherein in a run-in configuration the plugging device does not open any valves of the first cluster of valves, but in a set configuration the plugging device opens at least one valve of the second cluster of valves,   wherein another plugging device is used to open at least one valve of the first cluster of valves,   wherein each of the first cluster of valves and the second cluster of valves comprises a respective frac valve having a solid sleeve configured with a profile surface, and   wherein each of the first cluster of valves and the second cluster of valves has a number of flex valves in a range of at least one flex valve to no more than one hundred flex valves.   
     
     
         20 . The downhole system for multistage fracturing a subterranean formation of  claim 19 , wherein the workstring is void of a perforating gun.