SIL rated system for blowout preventer control

A redundant control system for a subsea blowout preventer (BOP) positioned in a lower stack, the lower stack removably engaged with a lower marine riser package (LMRP), and the LMRP having first and second control pods, each in hydraulic communication with the BOP to control the BOP, the control system comprising:

• a surface logic solver positioned at or adjacent the surface of the sea that generates first command signals comprising commands for operating the subsea BOP;
• a first subsea logic solver attached to the first control pod and in communication with the surface logic solver, the first subsea logic solver in communication with the first control pod so that the first subsea logic solver is capable of receiving the first command signals from the surface logic solver and implementing the commands in the first command signals by activating the first control pod to operate the BOP;
• and
• a second subsea logic solver attached to the second control pod and in communication with the surface logic solver, the second subsea logic solver in communication with the second control pod so that the second subsea logic solver is capable of receiving second command signals comprising second commands from the surface logic solver and implementing the second commands by activating the second control pod to operate the BOP.

A method for controlling a subsea blowout preventer (BOP), the method comprising:

• generating a first command signal comprising a command by a surface logic solver located at or adjacent the surface of the sea;
• transmitting the first command signal to a first subsea logic solver attached to a lower marine riser package;
• transmitting a second command signal comprising the command to a second subsea logic solver attached to a hydraulic control unit that is connected to an accumulator and that is in a lower stack, the hydraulic control unit in communication with the subsea BOP;
• and
• operating the subsea BOP with the hydraulic control unit in accordance with the command in the second command signal.