f Subsea BOP, Secondary Intervention System

Subsea BOP Safety is the most important issue for all industry, especially for offshore operations. That’s why BOP control systems are of the utmost importance. BOP functions in the event of total loss of the primary control system, Secondary intervention systems the last line of defense in preventing and/or minimizing environmental event, human injuries and loss of lives. Subsea BOP (Blow Out Preventer) control systems are required to remotely operate blowout preventers that are located on the seafloor in floating drilling operations. The primary components of the BOP control system are the redundant control pods located on the BOP stack. These pods direct the flow of high pressure hydraulic fluid, used to operate the BOPs, from the surface to the BOPs on the seafloor. There are two primary types of control systems: Hydraulic and E/H (Electro- Hydraulic). The key difference between the two systems is the method employed to send a signal to the control pod to initiate the desired BOP function. With a hydraulic system, the signal is hydraulically transmitted from the surface to the valves in the control pod. These valves then direct the hydraulic fluid to initiate the BOP function. The signal travels this distance in 5 to 30 seconds depending on water depth and hose type. With an E/H system, electrical signals transmitted from the surface actuate solenoids within the control pods in a fraction of a second. The control pods then hydraulically activate the BOP function. Thus, the BOP function response time is a combination of the signal transmission time and the main hydraulic fluid flow time. Because the BOP function activation signal reaches the pod in an E/H system much faster than in a hydraulic system, the E/H system is particularly well suited to ultra deepwater applications. In these operations fast electrical signal response times are required to minimize the time it takes for risers to decouple and for annular and ram-type BOPs to close. Secondary intervention can be described as an alternate means to operate BOP functions in the event of total loss of the primary control system or to assist personnel during incidents of imminent equipment failure or well control problems. A secondary intervention system can be completely independent and separate or utilize components of the primary BOP control system. These systems are of the utmost importance and offer the last line of defense in preventing and/or minimizing environmental and safety incidents. An advanced knowledge of secondary intervention systems and their shortfalls could prevent an environmental event, human injuries, and/or loss of lives. Systems and practices vary considerably from rig to rig, geographic area and regulatory agency.