Design Analysis of a Weight Added Wave Configuration of a Flexible Riser in Shallow Water

A flexible riser configuration design in shallow water, having a large variation in riser content density, can pose a real challenge and results in significant riser immersed weight alternation particularly evident in pipes with large internal diameters. In this scenario, it is extremely difficult, if not impossible, to meet the minimum clearance at both the top (to the vessel bottom or the water’s surface) and bottom (to the seabed) in an extreme environment by using a traditional wave configuration. An innovative riser configuration concept based on the traditional lazy wave, referred to as weight added wave (WAW), has been developed with a proactive self-control mechanism to ensure riser configuration compliance during excessive weight changes [1]. The self-control mechanism consists of the traditional buoyancy modules with the addition of strategically positioned weight chains. This paper presents both an advanced and a simple structural model utilized in the WAW riser configuration study. The advanced model accounts for the individual buoyancy module and weight chain in detail.