Due to rig availability and costs, operators can face significant delays in well decommissioning before plug and abandonment (P&A), during which temperature and pressure monitoring is required. If an umbilical connected to these wells fails, then it must be replaced, adding additional costs to a field with nonproducing wells. This study addresses a solution to replacing a faulty umbilical in a small field where hydraulics are already supplied to the wells, but power and communications are failing.
Ocean Power Technologies, Inc. (OPT) has developed the PB3 PowerBuoy® that converts wave energy into local electric power. The PB3 can provide power and communications for many applications, including subsea well monitoring. OPT partnered with a prominent North Sea-based subsea controls original equipment manufacturer (OEM) and engineering company to perform a preliminary front-end engineering and design study to evaluate the use of a PB3 PowerBuoy to provide power and communications for two subsea trees (XTs) located in the North Sea.
The Subsea Control Modules (SCMs) for these two XTs are powered by an umbilical from a production platform, providing power, communications, and hydraulics. Given the government regulations for well monitoring until P&A, having a plan for an independent backup power source is critical.
In this study, the PB3, umbilical cable, and OPT's subsea battery module (SSB) are added to the existing subsea infrastructure to provide power to the subsea XTs and relay data back to the production platform via a Tampnet 4G node on the PB3. These requirements have been compared with the PB3's expected power generation capabilities in this location to develop a preliminary system configuration.
As a part of this study, OPT has also completed a preliminary mooring and umbilical cable analysis. In addition, OPT worked with our partners to develop a preliminary communications plan to integrate their legacy frequency shift keying (FSK) communications into the PB3 network by use of a modified downhole interface unit (DIU) containing a terminal server to network the master control station (MCS) on the production platform to the SCMs.
This study shows that OPT's PB3 can provide power and communications to subsea wells requiring monitoring through renewable wave-powered energy. Such a development will provide proof-of-concept for using the PB3 as a remote power and well control solution on future all-electric developments.