Patent ID: 9297206
Filing Date: 2016-03-29
CPC Classification: B63B,E21B

Claim Text:
1. A method for drilling with a buoyant structure comprising: a. loading drilling equipment, drilling pipes, marine risers, casings, single/dual blow out preventers onto the buoyant structure while deballasted in port, wherein the buoyant structure defines a center of gravity below a center of buoyancy, the buoyant structure comprising: b. identifying a drilling location having a subsea drilling location for destination; c. leaving port in a deballasted/transit condition for the identified drilling location; d. either mooring the buoyant structure at the location or engaging a dynamic positioning system of the buoyant structure to maintain the buoyant structure over the drilling location; e. ballasting the buoyant structure to an operation draft ensuring that the lower cylindrical portion of the buoyant structure, the lower frustoconical portion of the buoyant structure, and a portion of the upper frustoconical portion of the buoyant structure are under water filling the at least one ballast tank at least partially with a fluid to create the center of gravity lower than the center of buoyancy and contribute to maintaining at all times a positive stability curve for the buoyant structure; f. using a first tunnel extending through the lower cylindrical portion to the moon pool, wherein the first tunnel has a first tunnel side wall, a second tunnel side wall and a first tunnel top connecting the tunnel side walls for ingress and egress of water; and g. commencing drilling operations through the moon pool while the buoyant structure is centered over the drilling location.