Assessing the feasibility of suspended BOP transportation and its impact on fatigue life

The sailing of the drilling rig along with its subsea equipment, such as, the drilling riser and the blowout preventer (BOP), from one well to another using traditional methods is a time-consuming operation. Typically, this process involves lowering and retrieving the BOP after drilling, followed by moving the rig to another well to be drilled, and again lowering the BOP and subsequently retrieving it. This method becomes even more time-consuming in ultra-deep waters, where recent oil field discoveries have taken place, as the deeper the water depths, the more time is required for such operations. Considering the high costs associated with renting and operating drilling rigs, operators are looking for ways to make these processes more efficient. One promising alternative is the method of navigation with the BOP suspended at a certain distance from the seabed, eliminating the need to retrieve the entire drilling riser and BOP, resulting in significant optimization of the process of transferring the drilling rig and its subsea equipment between wells.During the navigation of the BOP, hydrodynamic and inertial forces are exerted on the suspended riser column and the subsea BOP. In this present work, analyses of fatigue resulting from the effects of waves and vortex-induced vibration resulting from current speed and navigation, will be conducted for different lengths of the riser column. The results of these analyses will be presented, and the software used to obtain these results will be Orcaflex and Shear7.