A high tide velocity makes it difficult for the riser to enter the borehole during its running after the riser section is drilled. A finite?element fluid?solid coupling model of fluid (seawater) and solid (casing) interaction is built with the finite?element analysis software ADINA. The following observations can be made from the analysis. A higher velocity results in a larger lateral offset in the final equilibrium state when the riser enters the borehole.Due to the flow blocking effect of the riser, seawater near the front end of the riser produces a strong detouring flow, while a local vortex is observed in the area near the back end of the riser.Under four working conditions of different tide velocities (0.60,0.70,0.80 and 0.90 m/s), both the Reynolds number and the equivalent flow resistance coefficient are in reasonable ranges.When the borehole diameter reaches 889.0 mm after borehole enlargement, a 508.0 mm riser is run in. No obstruction is encountered when the tide velocity is less than 0.59 m/s, whereas difficult borehole entering occurs when the tide velocity is higher than 0.83 m/s. It is suggested that the riser will be run in when the tide velocity reduces to below 0.59 m/s. The simulation analysis has a great guiding significance for the running of the riser during the drilling of offshore oil fields.