STATIC ANALYSIS OF LAZY-WAVE STEEL RISERS

Catenary risers have been extensively used in the late years on the offshore oil industry. Its simplicity and relatively low cost are some of the main reasons. However, as submerged oil fields become deeper, lazy-wave configurations become an interesting solution. Unlike catenary, finding the best configuration of a lazy-wave is not an easy task. It requires several simulations due to the great number of parameters involved. Lazy-wave configurations include different segments, being an intermediate one provided with floaters. Not only the lengths of these segments need to be chosen but also the floaters' characteristics as well. To help solving this problem a software of parametric analysis was developed. The parameters taken into account are the lengths of the segments and, in the case of presence of floater, its diameter, length and spacing along the segment span. This work focuses on the static problem in two stages. Firstly, only the cable's own weight is considered. Platform offset and sea current loads are considered after. The selection of the feasible configurations is made based on some criteria such as top angle, tension at the top and at the touchdown point, curvature and cable's wave heights, among others. A case study using this homemade software is performed and shows how helpful is parametric analysis in obtaining the feasible lazy-wave configurations. Also, the results are highly explored to provide a better understanding about lazy-wave configurations and to choose the best among them.