Remote control systems for the grondin subsea oil well production station

An experimental subsea oilwell production station was installed by ELF Gabon during 1976 in 200 feet of water offshore the Republic du Gabon, West Africa. The station is the first pilot operation in a research program designed to produce subsea oil fields in water depths to 2000 feet anywhere in the world. The subsea station includes three production wellhead assemblies mounted on a template. The template is equipped with manifolds, flowlines and control cables to connect the satellite station to the Grondin Field production platform. Each well on the station is equipped with two electrohydraulic remote control systems. One system is direct-wired, the other system employs electronic multiplexing. The direct-wired system operates the primary wellhead functions required to produce the well. Retrievable subsea hydraulic power units are installed on each wellhead. Electric power is supplied through individual conductors of a subsea cable to drive the motor-pump and operate the solenoid control valves. The multiplex system utilizes signal processing to send all information over two wires. This reduces the size and number of cables needed to control the many functions, but requires more complex circuitry on the ocean floor. The system employs a code comparison circuit to prevent errors in command information. The wellhead command unit operates the same functions as the direct-wired system plus several more. It also monitors the position of a production choke (flow controller), two pollution sensors, and a system to measure the corrosive electric potential of the wellhead due to electrolysis.