| 摘要 |
A method for drilling with a buoyant structure having a hull, a planar keel defining a lower hull diameter, a lower cylindrical portion connected to the planar keel, a lower frustoconical portion disposed above the lower cylindrical portion with inwardly-sloping wall at a first angle, an upper frustoconical portion directly connected to the lower frustoconical portion. The method uses a ballasted chambered buoyant storage ring which is either dockside and connected to the buoyant structure for drilling at a subsea location, or the ballasted chambered buoyant storage ring is preinstalled at a subsea location and then the buoyant structure is mounted to the ballasted chambered buoyant storage ring at sea. |
| 主权项 |
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:
(i) a hull defining a vertical axis, whereby the hull has an outer hull side connected to an inner hull side, and the outer hull side is characterized by an outer hull side shape selected from the group: circular, elliptoid, and geodesic in horizontal cross sections at all elevations; and the hull has an upper hull diameter and the inner hull side characterized by a shape selected from the group: circular, elliptoid, and geodesic;(ii) a planar keel defining a lower hull diameter;(iii) a lower cylindrical portion connected to the planar keel, wherein a lower cylindrical portion diameter is identical to the lower hull diameter, and the lower hull diameter is the largest diameter of the hull, and further wherein the lower cylindrical portion diameter is from 105 percent to 130 percent of the upper hull diameter;(iv) a lower frustoconical portion disposed above the lower cylindrical portion formed with an inwardly sloping wall at a first angle ranging from 50 degrees to 70 degrees with respect to the vertical axis;(v) an upper frustoconical portion directly connected to the lower frustoconical portion, the upper frustoconical portion with an outwardly sloping wall sloping at a second angle with respect to the vertical axis ranging from 3 degrees to 45 degrees, and wherein the lower frustoconical portion inwardly sloping wall, abuts the outwardly sloping wall forming a hull neck with a hull neck diameter;(vi) a main deck connected over the upper frustoconical portion;(vii) a moon pool formed by the inner hull side characterized by a shape selected from the group: circular, elliptoid, and geodesic having a first moon pool diameter proximate the main deck which increases to a second moon pool diameter proximate the planar keel, wherein the second moon pool diameter is less than the upper hull diameter; and(viii) at least one ballast tank in communication with a control center in the hull, the ballast tank for ballasting and deballasting the hull; 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; and f. commencing drilling operations through the moon pool while the buoyant structure is centered over the drilling location. |
