Abstract Tanker-based floating production, storage and offloading (FPSO) systems have been in operation since August, 1977, when a single-well FPSO was put into production by Shell Espana in the Mediterranean. The overall operational experience with this system at this field will be reviewed. Special attention will be directed to the wire line Work over facilities which have proven to be very satisfactory. A subsequent evolutionary step, a FPSO accommodating multiple wells, necessitated development of a multiple-bore product swivel. A design program for this swivel was initiated in 1978, a prototype was built and full scale testing finalized in 1980. A summary of the test results will be presented. Simultaneous with the multiple-bore swivel development, detailed engineering for an eight-well FPSO was begun. This system includes gas lift and water injection capabilities. Provisions for TFL well work over can be incorporated. The detailed design will be reviewed as well as the latest development whereby the FPSO concept has been adapted to the North Sea environment. Introduction And Background Stationary offshore terminal facilities utilizing former trading tankers were employed by the oil industry as early as fifteen years ago. Initially, a tanker was simply connected to a single point mooring (CALM) by conventional hawsers where it served as a combination buffer storage vessel and mooring platform for shuttle tankers. Poor operational experience, low survival characteristics and high maintenance costs stimulated the development of the Single Buoy Storage (SBS) system employing rigid arms for permanently mooring the vessel to the buoy. The first terminal of this type became operational in 1973 and it along with half a dozen similar terminals has served efficiently for many years. In August, 1977, a further step in the evolutionary process was taken with the start-up of a tanker-based, rigid-arm-moored (SALS) floating production facility. This system incorporates conventional separation equipment on the vessel for producing from a single subsea completed well. A second similar facility also producing from a single well was installed in 1980. Recognizing the need for testing and producing independently from two or more wells and injecting into wells, a program was instigated in 1978 to develop a high pressure, multiple flow path swivel for interfacing the weathervane vessel with the non-rotating buoy or riser. In August, 1981, a facility went into operation using this new high-pressure, multiple flow path swivel producing from two subsea-completed wells. Presently, design and construction are well advanced on a floating production, storage and offloading facility that can accommodate up to eight wells. This FPSO facility is scheduled to become operational in November 1982. Table 1 provides a recap of the tanker-based floating production, storage and offloading facilities designed by SBM Inc. The Floating Unit Whereas a semi sub is usually in a fixed mooring pattern, a tanker-based floating production facility is normally designed to weathervane, thus introducing the necessity for mechanical and fluid swivels. Both types of swivels must be very carefully engineered and constructed to precise specifications.