A novel autonomous power and control system (APAC) is being developed by Total The system is designed to replace the control umbilical on subsea producing wells. The system comprises 2 thermo-electric generators (THEGS) which are housed m flowline spools, lead acid batteries, a closed loop electro-hydraulic control system and its associated electronics and 2 hydro-acoustic communications links. Prototypes of the main elements were built and tested independently to prove their feasibility Subsequently a full scale production system has been built and tested In the final development phase, the system will be installed on a subsea well m order to prove its long term performance and reliability. This paper looks briefly at the background to the development of autonomous control systems and to some of the design considerations The APAC development process, up to the completion of performance testing, is described. Finally, economic issues, comparing the cost of autonomous versus conventional systems, are addressed.
APAC is a collaborative effort funded by Theme and FSH (Fonds de Soutien des Hydrocarbures) It represents an extension of an earlier research and development (R&D) project for Total's Hunter field (HAPAC) and incorporates technology developed within a separate project called SPARCS.
HAPAC-Hunter Autonomous Power and Control System - funded by Total, Bertin, DCN Cherbourg and Sonardyne. It involves research into a gas driven turbo-generator, a thermo-electric generator and a long range hydro-acoustic communications link W A C was to be installed on Hunter, a single gas well m the southern sector of the North Sea Originally planned for 1994, the Hunter Project has yet to be sanctioned.
SPARCS - Subsea Powered Autonomous Remote Control System - funded by Kvaerner FSSL, Enterprise Oil p 1 c and Elf Enterprise Caledonia Ltd, SPARCS has been developed over a number of years Conceptual design started m 1989 and offshore trials took place off Falmouth in early 1996 The SPARCS system comprises a turboelectric generator, a thermo-electric generator, sea water batteries, lead acid batteries, a closed loop hydraulic control system and a hydro-acoustic link.
(The figure is available in full paper). APAC has completed successful integration and performance testing at DCN Cherbourg The next stage of the development includes a field trial on a producing well The main objectives of the field trial are to.
prove the concept of autonomous well control
prove the long term viability of an autonomous subsea control system
verify the performance of thermo-electric generators
verify the performance of long range acoustic links m all environmental conditions
verify the performance of lead acid batteries
verify the performance of a closed loop subsea hydraulic power unit (HPU)
verify the performance of a buoy based radio and/or satellite communications link