Various methods exist to connect a pipeline end to a platform or a subsea structure. Normally, a separate spool or jumper is used, but a direct tie-in is advantageous if this can be used. Different ways of direct subsea tie-ins exist, however the main challenges with these methods are relatively large forces on the connection and large pipeline stresses close to the connection point. This paper shows how application of residual curvature near the end of the pipeline can be utilized for direct tie-in of pipelines to subsea structures. This is done by solving the existing direct tie-in challenges with large forces on the connection and large pipeline stresses close to the connection point. Tie-in forces will be illustrated for the main variables affecting the pipeline tie-in point such as: soil friction, residual curvature parameters, tie-in and operational loads, various tie-in systems and their requirements. Effect on lay initiation and lay down will be outlined.
This paper presents a simple and cost effective method to make a pipeline conform to the seabed topography. The method is based on shaping the pipeline to the terrain by active use of the reel-ship's straightener system during installation. Shaping the pipeline to the terrain may also be performed on Slay vessels, e.g. by roller or stinger adjustment during laying. Numerical calculations are presented, illustrating the benefits in terms of suppressing free spans, achieving acceptable bending moments and reducing intervention costs.
Bottom trawling activities can potentially influence pipeline design substantially. In order to evaluate the conservatism imposed by current standards, such as DNV-RP-F111, it is of interest to further study the interaction between trawl gear and pipelines. This paper presents results from simulating the pullover interaction that takes place when clump weights interfere with subsea pipelines. The nonlinear finite element software SIMLA has been utilized for the simulations. MARINTEK performed model tests for clump weight interference with pipelines on behalf of Statoil for the Kristin field development in 2004. These model tests have been replicated in a full scale SIMLA model, and numerical results are compared with the experimental ones. In addition to simulations of these idealized model test setups, simulations have also been performed for a realistic example flowline both in free span and resting on seabed.