Top Tension Riser Systems provide direct access to subsea wellheads from the floating platforms for workover, completion, and drilling operations. This class of riser systems is widely used in a number of deepwater field developments with different floating platforms. The top tensioned risers are tensioned by buoyancy can riser tensioning systems which have minimum interaction with the floater or by hydraulic tensioners directly attached to the floater. This paper presents a unique closed-form analytical formulation to describe the catenary shape of the top tension riser system as a function of top tension and motions of the floating platform. The formulation is suitable for determining the relationships among the riser weight, riser tension, riser stroke with respect to hull, riser seabed angle, riser departure angle, and platform offset, heave, and pitch motions. The developed formulation quantifies the complex interplay among these key design variables, identifies the controlling design variables, and allows the designer to improve riser system design. The developed catenary equations form the basis for a systematic design methodology for top tension riser systems.
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