The decommissioning of offshore structures is a challenge due to the numerous factors influencing the decision-making process regarding the methodology to be adopted. Activity planning involves a multidisciplinary study that considers regulatory, logistical, economic, environmental, and operational issues. One of the main stages is the pull-out, which consists of disconnecting and retrieving flexible pipes. This stage is a time-consuming and costly procedure due to the need for support vessels. Consequently, there is a constant search for alternatives to optimize this activity. A simple and economical alternative is the surface cutting of the riser followed by its free fall to the seabed. Assessing the technical feasibility of this alternative requires computational simulations to determine the geometry and internal forces during the fall. It is important to note that cutting the riser leads to the sudden release of a large amount of energy, in addition to generating a compression wave that travels through the riser, which can cause the phenomenon of dynamic buckling when another compression wave returns. Thus, this work aims to develop a computational model able to simulate the surface cutting of a flexible lazy-wave riser, considering the dynamic and nonlinear aspects involved. The studied parameters include mesh discretization, the time increment of the integration algorithm, and the effect of the drag coefficient. Initially, the riser’s static configuration will be obtained to verify the loads before cutting. Subsequently, the surface cutting of the structure will be simulated, followed by a study of the riser’s configuration during the fall, as well as the envelopes of velocity, acceleration, effective tension and compression, and curvature radius, which are all essential for assessing the operation's feasibility.
