Riser Tensioning System

摘要

The ultimate goal of Project Mohole, Phase II, is the drilling of a hole approximately 35,000 feet in depth from the ocean surface at a location where the water depth will be 14,000 to 15,000 feet. The hole will be drilled from a dynamically positioned floating platform. A riser pipe will be provided from an anchored base at the ocean floor to the floating platform to guide drill pipe, bits, and other associated drilling equipment, in and out of the hole and to provide a closed circulating system for drilling fluids. Ocean currents and limited drift of the drilling platform will tend to deflect or displace the riser from the vertical axis through the drilled hole. Response of the drilling platform to environmental forces will result in a constantly changing distance from the platform to the ocean floor and consequently a constantly changing length of the riser. Such deflections and length changes must be controlled to avoid impeding the action of the drill pipe within the riser and to control riser and drill pipe stresses. A Riser Tensioning System between the platform and the lower section of the riser telescoping joint is utilized to support a portion of the riser weight, approximately 100,000 pounds, and to apply a tensioning force, approximately 100,000 pounds, to correct adverse riser curvature. (Author)