A lower stack assembly of a blowout preventer for a hydrocarbon extraction well comprising: - at least one safety function which can be hydraulically activated to rapidly cut off of a pipeline section; - at least one first valve; - at least one first fluidic connection which connects in permanent manner said at least one first valve and said at least one safety function, so that said at least one first valve is adapted to selectively intercept a flow of fluid directed towards said at least one safety function; - at least one port operatively connected to said at least one first valve, said at least one port being adapted to cooperate with a remotely operated vehicle to transmit a pilot signal to said at least one first valve; - at least one accumulator, adapted to house pressurized fluid; - at least one second fluidic connection between said at least one accumulator and said first valve, so that by cooperating with at least said first valve said at least one accumulator is adapted to supply pressurized fluid, by means of said second fluidic connection and said first fluidic connection, to said at least one safety function in order to activate it; characterized in that said at least one second fluidic connection is formed by at least one rigid pipeline and connects in permanent manner said at least one accumulator and said at least one first valve, so that said second fluidic connection remains operative during the entire working life of the assembly, wherein said second fluidic connection remains operative also in case of detachment of a lower marine riser package associable with said lower stack assembly, wherein said first fluidic connection comprises at least one second valve, wherein said second valve is adapted to intercept a flow of fluid coming from said at least one accumulator and/or directed towards said at least one safety function, wherein said second valve can be controlled by means of a second valve controlling device, wherein said assembly comprises at least one control panel comprising said port and said second valve control device, so that said remotely operated vehicle is adapted to cooperate both with said port and with said second valve control device to activate said at least one safety function. - at least one safety function which can be hydraulically activated to rapidly cut off of a pipeline section; - at least one first valve; - at least one first fluidic connection which connects in permanent manner said at least one first valve and said at least one safety function, so that said at least one first valve is adapted to selectively intercept a flow of fluid directed towards said at least one safety function; - at least one port operatively connected to said at least one first valve, said at least one port being adapted to cooperate with a remotely operated vehicle to transmit a pilot signal to said at least one first valve; - at least one accumulator, adapted to house pressurized fluid; - at least one second fluidic connection between said at least one accumulator and said first valve, so that by cooperating with at least said first valve said at least one accumulator is adapted to supply pressurized fluid, by means of said second fluidic connection and said first fluidic connection, to said at least one safety function in order to activate it; said at least one second fluidic connection is formed by at least one rigid pipeline and connects in permanent manner said at least one accumulator and said at least one first valve, so that said second fluidic connection remains operative during the entire working life of the assembly, wherein said second fluidic connection remains operative also in case of detachment of a lower marine riser package associable with said lower stack assembly, wherein said first fluidic connection comprises at least one second valve, wherein said second valve is adapted to intercept a flow of fluid coming from said at least one accumulator and/or directed towards said at least one safety function, wherein said second valve can be controlled by means of a second valve controlling device, wherein said assembly comprises at least one control panel comprising said port and said second valve control device, so that said remotely operated vehicle is adapted to cooperate both with said port and with said second valve control device to activate said at least one safety function.