Discharging flow effect on the recoil response of a deep-water drilling riser after an emergency disconnect

To account for the discharging flow effect in recoil analysis of a drilling riser during an emergency disconnection scenario, researchers have developed two notable fluid column models (i.e. “SFM, Slug force model” and “WFCM, Whole fluid column model”) which can be solved in the pre-processing of an existing global riser analysis code. It is found that the “SFM” is developed based on the dynamical equilibrium of the internal drilling mud column, whereas the “WFCM” is established by analyzing the whole drilling mud and refilled seawater column. This study devotes efforts on the discharging flow effect on the recoil behaviour of a deep-water drilling riser employing “SFM” and “WFCM”. Large deviations are observed when comparing the results adopting these two fluid models, which can be contributed to the different resultant restoring forces exerted on the inner fluid columns. Nevertheless, same conclusions are drawn on the discharging flow effect, and the drag loading, mass loss and frontal force effects have been identified. An important finding is that when considering the inner fluid follows the oscillation of the riser, the recoil response of the riser can be affected remarkably, highlighting the great significance of this coupling effect.