Offshore full-processing platforms are permanently manned due to the large number of operational and maintenance tasks. Having these platforms unmanned and remotely operated would improve the field economy, reduce the personnel risk and minimize the environmental footprint. The use of subsea mindset and technology in the platform design can enable such a shift in the manning and operations regime.
Unmanned platforms have been in operation for decades in the form of simple platforms without complex process functions. The frequency of visits has however, turned out to be quite high. Further, maintaining facilities as unmanned has proved challenging when processing functions are added. To enable full-processing platforms to operate as unmanned installations, a new approach to design can be adopted. This new approach is characterized by use of design principles for complex subsea processing facilities and benefitting from the digital revolution.
A main difference when comparing subsea and topside processing facilities is the significant number of utilities, support and safety functions on a platform. For the new platform concept proposed, several of these functions are simplified or eliminated, which reduces complexity, the need for maintenance and cost. The platform concept is among others proposed without accommodation and helideck. Access by personnel and evacuation is via bridge to Service Operation Vessel.
By examining the Mean Time Between Failure for topside vs subsea equipment, it is evident that the subsea equipment has higher availability and requires less maintenance. For the topside equipment which as of today is maintenance intensive, e.g. compressors and pumps, the concept includes using subsea derived equipment. Seal-less subsea derived compressors are already proven for topside application. The maintenance need is determined based on surveillance by sensors and predictive analytics, i.e. predictive maintenance.
On a staffed facility there are cranes and trolleys for material handling and personnel are carrying out in-situ inspection and repairs, representing a significant number of offshore man-hours. For Subsea installations, the principle is plug & play replacement by use of intervention vessels. The layout of the new platform concept is arranged in a subsea derived manner adopting the replacement principle by use of vessels. Also, the platform is proposed with robotics tailored for intervention of minor items.
New technologies as drones and crawlers are developing rapidly and are used for inspection tasks replacing personnel, in addition to sensors and cameras and in combination with a digital twin. These technologies are comparable to using ROV for inspection of subsea equipment.
This paper will present the conceptual idea for the subsea derived full-processing unmanned platform in more detail, and discuss benefits compared to a conventional staffed full-processing platform.