Practical Experience of a Diverless Electro-Hydraulic Control System for Subsea Production

ABSTRACT The GRONDIN field offshore Gabon/West Africa is producing oil for ELFAQUITAINE through subsea wellheads controlled by an electrohydraulic control system supplied by MATRA. The installation completed in June 1979 and an experimental maintenance operation of a control pod, 6 months later, have been carried out without any diver assistance. The main features of the control system are: Multiplex Electrohydraulic Control, subsea hydraulic pumps, subsea diverless electrical conductive and hydraulic connections. Due to extensive quality control and test programmes, the Field operations have been achieved without any trouble and in accordance with the Foreseen Schedule. The present paper describes the control system, the development programme and the results of this experimentation. THE GRONDIN PROGRAMME: OBJECTIVES The French Company ELF AQUITAINE has undertaken in 1975 an experimental programme on the GRONDIN field, located 30 miles offshore Gabon, West Africa. The aim of the programme was the development and experimentation of a subsea production station involving a large number of new techniques, in order to prepare the future deepwater oil exploitation. The use of a diverless control system is probably one of the most advanced among these experimentations, as it includes:–Diverless installable and retrievable control pods,–Electro-hydraulic control,–Closed hydraulic circuit using subsea pumps,–Electronic multiplex transmission. After a comprehensive inhouse test programme, including pressure tests on all equipment, the control system has been installed on site in May-June 1979following a rigorous schedule and has since been in operation for over one year without any major failure.