Deep-water wells present two problems for the casing designer, casing setting depth, and environmental loading above the seabed.
Firstly, these environments have lower fracture gradients than equivalent depths for land wells, or offshore wells in shallow water. As the water depth increases, fracture gradients are significantly different, particularly in the shallow sections of the well. Selection of casing setting depths must take into account these reduced fracture gradients.
Secondly, current and wave loading can result in direct and indirect loading on the marine conductor, subsea wellhead system and foundation pile. Generated fatigue loads should be addressed in close cooperation with the Structural Engineering Department.
Since it is not desirable to cement the conductor casing-marine conductor annulus above seabed, a centralisation program will be required which also takes into account the transfer of loading between conductor casing and marine conductor. Also here the Structural Engineering Department should assist.