Numerical Simulation of Subsea Wellhead Stability for Deepwater Drilling

Abstract Subsea wellhead bearings complex stress because it joint with the marine riser and casing string. According to mechanical analysis of subsea wellhead for deepwater drilling, a comprehensive stability of subsea wellhead analysis method was established. The marine environmental loading, drilling vessel drifting, riser mechanical behavior, nonlinear behavior between casing string and formation were considered. A numerical method was adopted to solve this model. Example analysis illustrates, in order to improve the condition of riser, riser top tension is ordinarily increased. The lateral displacement and bending moment of wellhead nearly linear enlarged with the mean drifting offset. The greater TTR may cause wellhead instability because of the wellhead has a limited bearing moment capacity, and then need to disconnect the LMRP and BOP connection promptly. The affection of lateral load is focus on the upper string section, more depth of casing string is almost no affecting on its lateral bearing capacity. With drilling vessel offset or TTR enlargement, the lateral displacement, bending moment, shearing force and the soil reaction along string increased obviously, and acting depth deepened gradually. The measures such as enhance the conductor bending strength, control scour depth on seabed, get geological data sampling of shallow formation can strengthen the stability performance of wellhead.