SYSTEM AND METHOD FOR SHUT-OFF VALVES CLOSING OF UNDERWATER GAS FIELD Russian patent published in 2022 - IPC E21B43/12 E21B43/13 F16L55/00 

FIELD: gas industry.

SUBSTANCE: inventions group relates to a system for shutting off an underwater gas field with shutoff valves, as well as to a method for closing the shutoff valves of an underwater gas field using such a system. The system includes a Christmas tree containing a tubular string with an annulus, a buffer cavity, and a pipeline system, which are equipped with valves and gate valves connected to the control unit. The Christmas tree contains a side branch equipped with a central valve, a side operational valve, an operational throttle valve, a pressure sensor, located in series along the flow direction. The downstream lateral outlet is connected to a pipeline leading to a cluster manifold equipped with a cluster manifold branch valve. The Christmas tree also contains a bypass line connecting the side branch of the Christmas tree, the buffer cavity and the annular space with each other, equipped with a bypass line valve, side and central annular valves. The Christmas tree also contains monoethylene glycol (MEG) and methanol supply lines connected to the side outlet of the Christmas tree and equipped with MEG and methanol injection valves, respectively; and a corrosion inhibitor injection line provided with a corrosion inhibitor injection valve. Gate valves and valves are configured to shut off the flow upon a signal from the control unit in case of deviation of the pressure value in the side outlet, measured by the pressure sensor, from the predetermined limit value provided for by the technological operating mode of the equipment when the gas-liquid mixture flow moves, and contain a means for determining the actual position of the valves and valves, configured to transmit a signal to the control unit. The control unit is configured to send signals to close valves and gate valves in the following sequence: production throttle valve, side production valve, side annular valve, central annular valve, bypass line valve, central valve, MEG injection valve, methanol injection valve, inhibitor injection valve corrosion, branch manifold valve.

EFFECT: ensuring safe closing of control and shut-off valves by eliminating the conditions for the formation of hydrates on the equipment involved in emergency shutdown, and water hammer when closing the shut-off valves.

4 cl, 1 dwg, 1 tbl