Conductor is the first layer of casing installed in deep-water drilling. After the conductor, and the riser and Blowout Preventers (BOPs) installation are completed, drilling operation is continued for the surface casing. During this period, external force from the bottom of riser and weight of BOPs are supported by the conductor. The bending deformation of conductor would generate due to the drift of drilling platform (ship) and the wave-current force since the conductor is installed without well cementing. If the lateral bending deformation of conductor exceeds its bearing capacity, the stability of subsea wellhead is threatened. Besides, if the vertical bearing capacity of conductor is insufficient, serious consequences, such as wellhead sinking, even the wellbore abandon, would occur. So the bearing capacity of conductor is of great significance for the wellhead stability and deep-water drilling. In this paper, two different pile soil contact interface models are considered for the calculation of the lateral bending displacement and vertical bearing capacity with finite element (FE) method in ABAQUS software. The two different models calculating lateral displacement are contact mechanics model and contact element model, and the two different models for the vertical bearing capacity are coulomb friction model and Goodman element contact model.
Analysis results show that the lateral displacement calculated by the contact element method is larger than that calculated by the contact mechanics model, and the vertical bearing capacity calculated by the Goodman model is larger than that calculated by the coulomb friction model. The influence of the load and the conductor diameter on the lateral bending displacement and the vertical ultimate bearing capacity are analyzed in detail based on the method established in this paper.
In order to improve the subsea wellhead stability, it is necessary to analyze the conductor bearing capacity with different contact models, and the method presented in this paper provides a feasible approach.
