Stability calculation and verification method for conductor suction piles in deepwater drilling

In soft soil conditions of deepwater, there exist risks of sinking and tilting of surface conductors traditionally installed by jetting during the drilling process. To enhance the stability of subsea wellheads in deepwater drilling, a method of surface casing installation using conductor suction piles was proposed, and the insertion depth and stability were analyzed. Based on the pile foundation bearing theory and the generalized Winkler foundation beam model, a theoretical model for the stability of subsea suction piles at the wellhead was established. The stability characteristics and influencing factors of subsea suction piles were studied using finite element methods and finite difference methods. Based on engineering parameters of a well project in the South China Sea, theoretical calculations on the stability of the subsea suction piles were carried out, which were then compared with finite element calculations. The comparison show that the vertical ultimate bearing capacity error was 4.23%, the maximum horizontal displacement error was 6.0% and the maximum bending moment error was 2.96%, confirming the accuracy of the calculation results. Under extreme loading conditions during drilling operations, compared to traditional surface conductors, the vertical bearing capacity of subsea suction piles was increased by 43.91%, horizontal displacement was reduced by 63.21%, and the bending safety factor was 24.5 times higher. Different horizontal displacements and bending moments were applied to the subsea suction piles, showing that horizontal loads had a significant impact on lateral stability. Subsea suction piles have high vertical and lateral bearing capacities, significantly improving the stability of subsea wellheads, providing a theoretical basis for surface casing installation in soft soil conditions of deepwater.ions of deepwater.