Impact of the seabed soil properties on the stability of subsea wellhead for deepwater drilling

The seabed soil plays a supportive role to the subsea wellhead and conductors, the properties of soil determines whether the stability of the subsea wellhead. Through theoretical analysis, the relationship of the seabed soil properties and the vertical and lateral stability of subsea wellhead were established. Results illustrate that the undrained shear strength and adhesive coefficient of the clay and the internal frictional angle and submerged unit weight of the sand have great effect to the vertical stability of subsea wellhead. And the character of shallow soil is the main affecting factor to the lateral stability of subsea wellhead. The undrained shear strength of clay and the internal frictional angle of sand have the maximum effect on the lateral stability of the wellhead. Selection of the spud in location with hard soil for drilling operation, acquiring the geological sample data of shallow seabed before drilling, and reasonable determination of relevant parameter value, can improve the stability of subsea wellhead.