Marine production systems with vertical flexible risers

Abstract

Abstract Throughout the world floating production systems are being installed to produce rate sensitive reservoirs. Depending upon environmental conditions, reservoirs with as little as 2.8 MM barrels of recoverable oil can be economically produced. The floating production system considered in this paper uses a subsea well, a flexible riser pipe and a floating production storage and offtake barge. The flexible riser pipe provides flow paths for full stream production, hydraulic control of the subsea well and artificial lift power fluid. Routine wireline maintenance operation can also be accomplished through the flexible riser. A requirement for making wireline maintenance operations feasible is that the vertical riser configuration cannot include any abrupt curvature changes. For this reason, a flexible pipe using a minimum radius of curvature of 75 feet has been suggested. In order to achieve this configuration, riser buoyancy distribution has been carefully studied. The drilling system uses an alignment system which permits a diverless installation of the flexible riser. This is accomplished using a single line vertical pull down installation of the flexible riser, which will connect, subsea, ten high pressure hydraulic control lines and two high pressure production tubing lines. This paper discusses the major design considerations of the subsea completion, subsea christmas tree, flexible riser tie-back system, construction of the flexible pipe, vessel storage and anchoring.