Subsea control system for all-electric Xmas trees

Abstract

When looking at a time line from the earliest days of offshore oil and gas production developments, present day development projects and field layouts have changed tremendously. Within the offshore oil and gas industry technology industry, there has been a high level of innovation with regards to many aspects. Some of the most radical differences over time have been in the design of surface facility and platforms shown in the diversity of structures. The idea for this thesis was born out of an interest in systems and their functionality. Through research into offshore and subsea production systems, common goals in research and development projects regarding these systems identified certain trends. Examples of these are • to increase automation of production systems and controls • to reduce production system components • to reduce dependency on external supply of power • to increase production system response capabilities • to increase reliability of the production system With all-electric control systems, an attempt appears to have been made to satisfy the above goals. Electric actuators could enable an overall reduction in system weight and number of components. The implications of increases in water depth and wellhead offset distances could be reduced with respect to network complexity and control capabilities. Currently, the majority of subsea production systems operate using electro-hydraulic multiplexed power and controls. Increases in hydrostatic pressure and hydraulic transmission distances require increased system complexity due to depth-compensation of hydraulics (accumulators) and control response delays. This thesis is proposed in order to establish the current state of the art level of all-electric production control systems, address their weaknesses and influencing factors and suggest system improvements.