Subsea Smart Electric Control Unit for Building Smarter and Cheaper Subsea Hardware
Authors: York Matt , Alexander Ben , Holtz Todd , Schroeder Art J. , Chitwood Jim E. , Gay Tom A. 
Published: April 2019

Subsea production systems and processes are generally conducted using hydraulic and more recently electro-hydraulic controls. These systems have become complex and expensive to deploy, especially with increasing length of tie-backs, more deepwater installations and challenging environments. Electrically powered and controlled equipment has become the standard for onshore and topsides equipment. Developing a subsea electric control unit that is modular and easily packaged is integral to leveraging the benefits of electric monitoring and control into subsea production systems and processes, as well as many other intervention applications such as subsea chemical storage and injection. In addition to simplifying and reducing costs of these systems, the unit will be able to discern an end component's health and status providing an opportunity to adjust or modify the operation in-situ, and in some instances real-time as well as provide other benefits. New analytical techniques powered by advanced analytics and artificial intelligence (AI) are being developed to examine in greater detail the controlled equipment's operational status, infer its current state of health and even predict future performance and maintenance/repair needs. As more and more data are collected and analyzed, the predictability and accuracy of the analysis and prediction improves.

Coupling the newly developed all electric subsea controller unit described in this paper with advanced data analytics will lower operator costs and risks in subsea systems. the system presented herein has been designed as a simple, rugged and reliable piece of equipment based on years of experience with API RP 17H Class 2 torque equipment and variable speed subsea pumps. It utilizes serial communications with position limiting and has a closed loop speed/position control, torque control, and real-time torque limiting. The profiling feature helps establish valve and pump status, functionality and health monitoring. The tool is ideally suited for subsea application to 10,000 fsw for any application requiring up to 250 ft.-lbs. with position and variable speed control. Leveraging learnings from the nuclear industry and their regulators, this ‘spring-less’ unit includes an option for a ‘smart battery’ (Lithium ion) back-up for specified fail-safe positioning and monitoring. Technical specifications were driven by operator customers. A full set of Functional Design Specs (FDS) were developed as well as an Inspection and Test Quality Plan (ITP). Where practical, acceptance criteria were leveraged from API, ASME and other industry guidance.

A full-scale prototype unit has been built, tested and qualified with over 1 million cycles. The unit enables collecting sensed operating data from one or more end devices and one or more control end points, calculating and performing analytics, and reporting health and status of the one or more end devices and one or more control end points. It is currently being utilized on a common industry subsea ball valve, integrated into a subsea chemical storage and injection system as well as a drive for a variable speed subsea chemical injection pump. Regulator authorities in the U.S. have been included in the qualification witnessing.