Dynamic behavior of subsea wellhead and shallow pipe under seismic action

The interaction between shallow pipe and soil near the subsea wellhead is an important factor in the maintenance of subsea wellhead stability. First, a seismic test was conducted. A shaking table and a shear model box were used to measure the displacement and acceleration of the model under earthquake conditions. The effects of different soil layers on the dynamic response of the pipe were compared and analyzed. Subsequently, a dynamic finite element model of shallow pipe and soil was established. The weakening effects due to earthquakes and waves were considered in the soil model. Based on Hamilton's principle, the dynamic partial differential equations for a shallow pipe were derived and discretized into finite element equations via the weighted residual method. The liquefaction process of submarine soil under seismic force and the dynamic response of shallow pipe were simulated. The simulation results were compared with those of the test, and the accuracy of the finite element model was verified. The displacement, angle, bending moment and shear force of shallow pipe were calculated and compared. The increasing process and law of soil pore pressure were analyzed. Soil liquefaction caused by earthquake has great influence on the stability of shallow pipe. •The dynamic experiment of shallow string in offshore drilling was carried out by using shear model box.•A submarine soil weakening model considering both earthquake and wave action is established.•Based on Hamilton's principle, the dynamic partial differential equations of shallow pipe are derived.