Drilling deep subsalt wells on the shelf typically requires seven to eight casing strings run with tight tolerances and usually hard-to-get, good cement jobs. The GI 116 field has more than 10,000 ft of salt, and well depths below 22,000 ft. The first well was drilled from a jackup, followed by a delineation well drilled by the same rig. The third and fourth wells were drilled with a second-generation floater. The first well was drilled from a jackup with water-based mud. The second well was drilled with the same rig using synthetic-based mud and PDC bits. The dramatic difference is a technological breakthrough for subsalt drilling. With good knowledge of mud weights and frac gradients below salt, there was a lot of confidence to use synthetic-based muds. Drilling rates and hole stability were dramatically improved without any substantial mud losses. Wells 3 and 4 were drilled from a floater and were the fastest for the field. Well 5 was drilled from a jackup over the platform after two years of production. Some of the noticeable flat spots and one by-pass sidetrack are due to dealing with depleted sands. Differential pressure through the payzones ranged from 1,200 psi to more than 4,000 psi.
Hickory, Gulf of Mexico, Anadarko, America(North),