Drilling riser protection system

A protection system for a drilling riser, the drilling riser comprising a main drilling riser bore and a drilling riser annulus and being configured to extend from a floating installation to a location on a seafloor and to be fluidly connected to a subsea BOP stack which comprises at least two BOPs, the system comprising:

• a choke line which extends from a choke manifold on the floating installation to the subsea BOP stack below at least one BOP of the at least two BOPs in the subsea BOP stack;
• and
• a drilling riser booster line which extends from the floating installation to a port in a lower region of the drilling riser above each of the at least two BOPs in the subsea BOP stack, the drilling riser booster line being fluidly connected with the drilling riser annulus via the port in the drilling riser,
• wherein,
• the drilling riser booster line is configured to provide at least one of a rapid pressure relief and a fluid bypass which is operable to drain from the drilling riser annulus via the port and the drilling riser booster line to prevent the drilling riser from an uncontrolled pressure build-up due to an inadvertent plugging or a restriction resulting in a maximum allowable working pressure (MAWP) of the drilling riser being exceeded, if a restriction, a plug or a blockage exists in the drilling riser annulus or in riser outlets, the drilling riser booster line is fluidly connected to a mud gas separator via a pressure relief device which is configured to open when the pressure in the drilling riser booster line exceeds a predetermined value to so as to allow a flow of fluid from the drilling riser annulus to the mud gas separator via the port and the drilling riser booster line, and
• the drilling riser booster line is fluidly connected to a booster pump which is configured, in a normal use, to pump fluids down the drilling riser booster line into the drilling riser annulus via the port.

A protection system for a drilling riser, the drilling riser comprising a main drilling riser bore and a drilling riser annulus and being configured to extend from a floating installation to a location on a seafloor and to be fluidly connected to a subsea BOP stack which comprises at least two BOPs, the system comprising:

• a choke line which extends from a choke manifold on the floating installation to the subsea BOP stack below at least one BOP of the at least two BOPs in the subsea BOP stack;
• and
• a drilling riser booster line which extends from the floating installation to a port in a lower region of the drilling riser above each of the at least two BOPs in the subsea BOP stack, the drilling riser booster line being fluidly connected with the drilling riser annulus via the port in the drilling riser,
• wherein,
• the drilling riser booster line is configured to provide at least one of a rapid pressure relief and a fluid bypass which is operable to drain from the drilling riser annulus via the port and the drilling riser booster line to prevent the drilling riser from an uncontrolled pressure build-up due to an inadvertent plugging or a restriction resulting in a maximum allowable working pressure (MAWP) of the drilling riser being exceeded, if a restriction, a plug or a blockage exists in the drilling riser annulus or in riser outlets, the drilling riser booster line is fluidly connected to a booster pump and to a mud gas separator via a pressure relief device which is provided as a safety relief valve, the pressure relief device being configured to open when the pressure in the drilling riser booster line exceeds a predetermined value to so as to allow a flow of fluid from the drilling riser annulus to the mud gas separator via the drilling riser booster line and the port, and
• the booster pump is configured, in a normal use, to pump fluids down the drilling riser booster line into the lower region of the drilling riser annulus via the port.