Abstract: A spar platform for use in the offshore drilling or production of fossil fuels includes a hull having a centerwell. An airtight and watertight barrier traverses the centerwell, forming a variable buoyancy compartment in the centerwell. In certain embodiments the centerwell is open at the bottom to the sea, while in certain other embodiments the centerwell is sealed at the bottom. At least one sleeve for accommodating a riser extends through the barrier and the variable buoyancy compartment to the bottom of the centerwell. The sleeve has an open upper end to provide a drain for water accumulating in the centerwell, and it forms an airtight and watertight seal at its juncture with the barrier. In some embodiments, two or more airtight and watertight barriers are provided across the centerwell, defining an airtight and watertight fixed buoyancy chamber between each adjacent pair of barriers.

Abstract: An apparatus for supporting a steel catenary riser (SCR) from a floating structure having a keel includes a flexible support tube or keel sleeve through which the SCR passes. The support tube or keel sleeve includes a pivot mechanism that is lockably received in a receptacle fixed to the floating structure. A method of supporting an SCR from a floating structure includes the steps of inserting a first end of the SCR into a support tube or keel sleeve; fixing the support tube or keel sleeve to the SCR; pulling the support tube or keel sleeve into a receptacle fixed to the floating structure; releasing the support tube or keel sleeve from the SCR; pulling the SCR through the support tube or keel sleeve up to an attachment point on the structure; fixing the SCR to the structure; and fixing the support tube or keel sleeve to the SCR.

Abstract: A spar-type platform includes a hull defining a centerwell extending downward to a keel. The hull includes a reduced diameter neck portion for diverting ice flow. Adjustable ballast tanks allow the hull to be moved between a ballasted down position defining an upper water line, and a ballasted up position defined by a lower water line. A riser a support buoy is disposed in the keel. Risers extend through the centerwell, each having an upper portion extending upward from the support buoy and a lower portion supported in the support buoy. A disconnect system detachably connects the support buoy to the hull and the upper portion of each riser to the lower portion thereof, whereby the hull and the upper portion of each riser are selectively detachable from the buoy and the lower portion of each riser for movement to avoid a collision with a floating object.

Abstract: A spar platform for use in the offshore drilling or production of fossil fuels includes a hull having a centerwell. An airtight and watertight barrier traverses the centerwell, forming a variable buoyancy compartment in the centerwell. In certain embodiments the centerwell is open at the bottom to the sea, while in certain other embodiments the centerwell is sealed at the bottom. At least one sleeve for accommodating a riser extends through the barrier and the variable buoyancy compartment to the bottom of the centerwell. The sleeve has an open upper end to provide a drain for water accumulating in the centerwell and it forms an airtight and watertight seal at its juncture with the barrier. In some embodiments, two or more airtight and watertight barriers are provided across the centerwell, defining an airtight and watertight fixed buoyancy chamber between each adjacent pair of barriers.

Abstract: A spar-type platform includes a hull defining a centerwell extending downward to a keel. The hull includes a reduced diameter neck portion for diverting ice flow. Adjustable ballast tanks allow the hull to be moved between a ballasted down position defining an upper water line, and a ballasted up position defined by a lower water line. A riser a support buoy is disposed in the keel. Risers extend through the centerwell, each having an upper portion extending upward from the support buoy and a lower portion supported in the support buoy. A disconnect system detachably connects the support buoy to the hull and the upper portion of each riser to the lower portion thereof, whereby the hull and the upper portion of each riser are selectively detachable from the buoy and the lower portion of each riser for movement to avoid a collision with a floating object.

Abstract: An apparatus for supporting a steel catenary riser (SCR) from a floating structure having a keel includes a flexible support tube or keel sleeve through which the SCR passes. The support tube or keel sleeve includes a pivot mechanism that is lockably received in a receptacle fixed to the floating structure. A method of supporting an SCR from a floating structure includes the steps of inserting a first end of the SCR into a support tube or keel sleeve; fixing the support tube or keel sleeve to the SCR; pulling the support tube or keel sleeve into a receptacle fixed to the floating structure; releasing the support tube or keel sleeve from the SCR; pulling the SCR through the support tube or keel sleeve up to an attachment point on the structure; fixing the SCR to the structure; and fixing the support tube or keel sleeve to the SCR.