A system for supporting multiple-well-site, offshore, hydrocarbon-bearing fields, each well-site has one or more wells. In general, the system first comprises a floating vessel that is relocatable from a first subsea well-site to a second subsea well-site. The system also comprises two separate systems: (1) an operations control system for providing subsea well-site operations such as power and communications; and (2) an intervention system for conducting intervention services to an individual subsea well such as workover services and maintenance services. The operations system may provide control to wells and other subsea equipment at either the first well-site or the second well-site, regardless of the location of the floating vessel. The intervention system may provide workover and/or maintenance to subsea equipment or individual wells at the well-site at which it is located.