This paper summarizes results and lessons learned from qualification of a full scale subsea chemical storage and injection system. It also presents compelling findings from case studies that demonstrate the system can deliver significant savings compared to host platform chemical storage and umbilical delivery. Successful deployment of this new technology will initially provide, in brownfield applications, a very attractive alternative to an umbilical replacement, particularly later in field life when production rates and percent oil tend to be much lower, where economics may all together preclude installing a new umbilical and result in pre-mature field abandonment. The need for umbilical replacement might be triggered by a number of situations such as umbilical tube plugging or damage, or changing production composition requiring additional/different chemical treatments. In greenfield applications remote chemical storage and injection will greatly facilitate development of hundreds of smaller deepwater resources and billions of barrels of oil equivalent (BOE) by enabling safe, cost-effective long distance tie-backs to existing infrastructure out of traditional reach of umbilicals. Current shallow water deployment case studies indicate that transferring chemical storage and injection equipment weight from host facility deck to subsea and eliminating the need for on-deck personnel to maintain equipment generates positive economics and help achieve industry objects of ‘de-manning’ offshore facilities.

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.

No abstract