Abstract: A fault-tolerant system relieves pressure of fluid flow in a drilling system. Redundant pressure relief valves can open to relieve fluid flow from a discharge outlet of a manifold when over pressurization is detected. A hydraulic arrangement operably connected to the redundant relief valves provides hydraulic motive force in redundant hydraulic circuits respectively to the redundant relief valves. The redundant circuits are cross-connected to one another. Pressure transducers distributed in the hydraulic arrangement measures operational pressures of the hydraulic arrangement. Redundant controllers can both control the hydraulic motive force provided in the redundant circuits respectively to the redundant relief valves to open and close the relief valves in response to the pressure level measurement.

Abstract: A method for drilling a wellbore includes disposing a tubular string in the wellbore, wherein the tubular string includes a drill bit disposed at a bottom and a flow sub disposed on a top; injecting drilling fluid through a bore valve in the flow sub to rotate the drill bit; moving a sleeve in the flow sub to engage and close the bore valve; moving the sleeve independently from the bore valve to expose a flow port formed through a wall of the flow sub; and injecting the drilling fluid into the flow port while adding a stand to the top of the tubular string, wherein injection of drilling fluid into the tubular string is continuously maintained between drilling and adding the stand to the tubular string.

Abstract: A flow sub for use with a drill string includes a tubular housing having a longitudinal bore therethrough and a flow port through a wall thereof and a ball. The ball is disposed in the housing above the flow port, has a bore therethrough, and is rotatable relative to the housing between an open position where the ball bore is aligned with the housing bore and a closed position where a wall of the ball blocks the housing bore. The flow sub further includes a seat disposed in the housing above the ball for sealing against the ball wall in the closed position and a sleeve disposed in the housing and movable between an open position where the flow port is exposed to the housing bore and a closed position where a wall of the sleeve is disposed between the flow port and the housing bore.

Abstract: A method for drilling a wellbore includes disposing a tubular string in the wellbore, wherein the tubular string includes a drill bit disposed at a bottom and a flow sub disposed on a top; injecting drilling fluid through a bore valve in the flow sub to rotate the drill bit; moving a sleeve in the flow sub to engage and close the bore valve; moving the sleeve independently from the bore valve to expose a flow port formed through a wall of the flow sub; and injecting the drilling fluid into the flow port while adding a stand to the top of the tubular string, wherein injection of drilling fluid into the tubular string is continuously maintained between drilling and adding the stand to the tubular string.

Abstract: A flow sub for use with a drill string includes: a tubular housing having a longitudinal bore formed therethrough and a flow port formed through a wall thereof; a bore valve operable between an open position and a closed position, wherein the bore valve allows free passage through the bore in the open position and isolates an upper portion of the bore from a lower portion of the bore in the closed position; and a sleeve disposed in the housing and movable between an open position where the flow port is exposed to the bore and a closed position where a wall of the sleeve is disposed between the flow port and the bore; and a bore valve actuator operably coupling the sleeve and the bore valve such that opening the sleeve closes the bore valve and closing the sleeve opens the bore valve.

Abstract: A flow sub for use with a drill string includes a tubular housing having a longitudinal bore therethrough and a flow port through a wall thereof and a ball. The ball is disposed in the housing above the flow port, has a bore therethrough, and is rotatable relative to the housing between an open position where the ball bore is aligned with the housing bore and a closed position where a wall of the ball blocks the housing bore. The flow sub further includes a seat disposed in the housing above the ball for sealing against the ball wall in the closed position and a sleeve disposed in the housing and movable between an open position where the flow port is exposed to the housing bore and a closed position where a wall of the sleeve is disposed between the flow port and the housing bore.

Abstract: A flow sub for use with a drill string includes: a tubular housing having a longitudinal bore formed therethrough and a flow port formed through a wall thereof; a bore valve operable between an open position and a closed position, wherein the bore valve allows free passage through the bore in the open position and isolates an upper portion of the bore from a lower portion of the bore in the closed position; and a sleeve disposed in the housing and movable between an open position where the flow port is exposed to the bore and a closed position where a wall of the sleeve is disposed between the flow port and the bore; and a bore valve actuator operably coupling the sleeve and the bore valve such that opening the sleeve closes the bore valve and closing the sleeve opens the bore valve.