Bell nipple with annular preventers and coolant injection

Abstract

A bell nipple assembly is attached to an upper end of a blowout preventer stack and has a central passageway fluidically connected to a central bore of the blowout preventer stack. The bell nipple assembly includes upper and lower nipple annular preventers. Closure of the nipple annular preventers forms a closed volume within the central passageway between the upper and lower nipple annular preventers. A coolant injection system selectively injects coolant through a coolant conduit positioned within the closed volume.

1 . A system for drilling a wellbore into a subterranean zone, comprising:
 a drill string suspended from a drilling rig;   a blow-out preventer stack comprising a central bore through which the drill string passes as the drill string is raised or lowered within the wellbore, and further comprising a plurality of preventers configured to selectively prevent a flow of fluids through the central bore;   a bell nipple assembly comprising a central passageway fluidically connected to the central bore and configured to receive the drill string, wherein a lower end of the bell nipple assembly is attached to an upper end of the blow-out preventer stack and an upper end of the bell nipple assembly is positioned below a rig floor of the drilling rig, and wherein the bell nipple assembly further comprises:
 a lower nipple annular preventer positioned above the lower end of the bell nipple assembly and configured to selectively prevent a flow of fluids from below the lower nipple annular preventer through the central passageway; and 
 an upper nipple annular preventer positioned above the lower nipple annular preventer and below the upper end of the bell nipple assembly and configured to selectively prevent a flow of fluid from above the lower nipple annular preventer through the central passageway, wherein a closure of the lower nipple annular preventer and of the upper nipple annular preventer forms a closed volume between the lower nipple annular preventer and the upper nipple annular preventer; 
   a coolant conduit positioned within the closed volume; and   a coolant injection system configured to selectively inject coolant into the coolant conduit within the closed volume.   
     
     
         2 . The system of  claim 1 , wherein the closed volume comprises an annular volume defined by a packing element of the upper nipple annular preventer, an exterior surface of the drill string, an inner wall of the central passageway, and a packing element of the lower nipple annular preventer. 
     
     
         3 . The system of  claim 1 , wherein the coolant injection system comprises a check valve for selectively allowing coolant to flow through the coolant conduit. 
     
     
         4 . The system of  claim 1 , further comprising a coolant tank that is external to the bell nipple assembly. 
     
     
         5 . The system of  claim 1 , further comprising a coolant tank that is a component of the bell nipple assembly. 
     
     
         6 . The system of  claim 1 , wherein the system is configured to close the upper nipple annular preventer and the lower nipple annular preventer simultaneously. 
     
     
         7 . The system of  claim 1 , wherein the coolant injection system is configured to inject the coolant into the closed volume after closure of the upper nipple annular preventer and of the lower nipple annular preventer. 
     
     
         8 . The system of  claim 1 , wherein the system is configured to close the lower nipple annular preventer and the upper nipple annular preventer in response to a detection of an indication of a partial or complete failure of one or more of the preventers of the blow-out preventer stack. 
     
     
         9 . The system of  claim 1 , wherein the coolant conduit is a helical coil. 
     
     
         10 . The system of  claim 9 , wherein an inner diameter of the helical coil is greater than an outside diameter of the drill string. 
     
     
         11 . The system of  claim 1 , wherein the coolant is liquid nitrogen. 
     
     
         12 . The system of  claim 1 , wherein the coolant conduit isolates the coolant from other fluids within the central passageway. 
     
     
         13 . A method, comprising:
 drilling, with a drill string suspended from a drilling rig, a wellbore into a subterranean zone, the drilling rig comprising:
 a blow-out preventer stack comprising a central bore through which the drill string passes as the drill string is raised or lowered within the wellbore, and further comprising a plurality of preventers configured to selectively prevent a flow of fluids through the central bore; 
 a bell nipple assembly comprising a central passageway fluidically connected to the central bore and configured to receive the drill string, wherein a lower end of the bell nipple assembly is attached to an upper end of the blow-out preventer stack and an upper end of the bell nipple assembly is positioned below a rig floor of the drilling rig, and wherein the bell nipple assembly further comprises:
 a lower nipple annular preventer positioned above the lower end of the bell nipple assembly and configured to selectively prevent a flow of fluids from below the lower nipple annular preventer through the central passageway; 
 an upper nipple annular preventer positioned above the lower nipple annular preventer and below the upper end of the bell nipple assembly and configured to selectively prevent a flow of fluids from above the lower nipple annular preventer through the central passageway, wherein a closure of the lower nipple annular preventer and of the upper nipple annular preventer forms a closed volume between the lower nipple annular preventer and the upper nipple annular preventer; and 
 a coolant conduit positioned within the closed volume; 
 
   closing the lower nipple annular preventer and the upper nipple annular preventer; and   injecting, after the closing of the lower nipple annular preventer and the upper nipple annular preventer, coolant into the coolant conduit.   
     
     
         14 . The method of  claim 13 , wherein the closed volume comprises an annular volume defined by a packing element of the upper nipple annular preventer, an exterior surface of the drill string, an inner wall of the central passageway, and a packing element of the lower nipple annular preventer. 
     
     
         15 . The method of  claim 13 , wherein the lower nipple annular preventer and the upper nipple annular preventer are closed simultaneously. 
     
     
         16 . The method of  claim 13 , the closing the lower nipple annular preventer and the upper nipple annular preventer is in response to a detection of an indication of a partial or complete failure of one or more of the preventers of the blow-out preventer stack. 
     
     
         17 . The method of  claim 13 , wherein the coolant conduit is a helical coil. 
     
     
         18 . The method of  claim 13 , wherein an inner diameter of the helical coil is greater than an outside diameter of the drill string. 
     
     
         19 . The method of  claim 13 , wherein the coolant is liquid nitrogen. 
     
     
         20 . The method of  claim 13 , wherein the coolant conduit isolates the coolant from other fluids within the central passageway.