CVAR-FPSO and workover system deepwater

摘要

A new and unique Floating Production Storage and Offloading (FPSO) concept termed the CVAR-FPSO is under development by a Japan National Oil Corporation headed Joint Industry Project (JIP). The concept, using Compliant Vertical Access Risers (CVAR) and including the ability to complete and workover a well independently, offers enormous economic and operational benefits during all phases of a deepwater oil field development. The central attribute of the CVAR-FPSO is the use of CVARs. These compliant but rigid risers, fitted with syntactic buoyancy, connect wells from the seafloor to the surface Xmas trees mounted on the weathervaning vessel turret, and can compensate for vessel motion. The CVAR, being vertical access to the wells, also allows a full range of completion and workover operations to be performed from the FPSO. This paper describes the workover system of the CVARFPSO concept. The workover system consists of rig derrick, fluid transfer system and riser centering system, and the configurations of which are very sensitive to environmental conditions. operational requirements and economics. The interface among workover system, fluid transfer system, riser centering system, turret system, and mooring system is intensively studied. And the type of the rig derrick has 3 candidates Conventional rig, Hydraulic cylinder rig, and CT hybrid rig. The rig derrick is located on the turret or over the turret of the FPSO. The CVAR FPSO is a new concept, and hence the mechanism of the interface is unique and innovative. The feasibility of the interface is mainly discussed. Here well system and riser system is also explained. The oil field development concept involves the drilling and temporary abandonment of wells by a Mobile Offshore Drilling Unit (MODU). The CVAR FPSO is then moved onto location, CVAR risers are connected from subsea tiebacks to each Xmas tree in the turret, and wells are completed from the CVAR-FPSO. Re-completions, maintenance, workovers, logging are performed from the CVAR-FPSO through the life of the wells. This oilfield development strategy with the CVAR-FPSO offers economic and operational benefits. The main benefits are 1) Completion and workover capability, 2) Artificial lift options are easily installed. 3) Weathervane capability; 4) the CVAR FPSO takes over advantages of conventional FPSO, low cost, large storage, etc.