Recoil Analysis for Deepwater Drilling Riser after Emergency Disconnection with Blowout Preventer

During deepwater drilling process,recoil behavior of drilling riser will occur once the lower marine riser package is quickly disconnected from the blowout preventer,which could lead to serious drilling accidents.In order to understand riser recoil behavior,the reason for riser recoil and the recoil process were analylzed,and the main factors that influence riser recoil response were determined.Based on these studies,the analysis model of the tensioner system was built to investigate the relationship between tension force and piston stroke.Drilling fluid flow model was built to work out the relationship between friction force imparted by drilling fluid on riser and time.Finally,the modeling method for main influence factors in finite element software was studied,and the recoil analysis model was built in ANSYS software.Taking the riser in 1 500 m deep water drilling as an example,riser recoil response at different points of disconnection and top tension forces were calculated and analyzed.The results showed that the riser recoiled upward quickly after being disconnected from blowout preventer under the effect of top tension,resulting in significant shortening of telescopic joint stroke.The riser recoil response was heavily dependent on the point of disconnection and top tension force.Proper timing of disconnection and top tension force could result in a sensible riser recoil response,ensuring operation safety of deepwater drilling riser.