Pipelaying in artic offshore waters
AssigneeShell Oil Company
InventorCarl G. Langner
Life of this patent
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Abstract
The present invention provides a method and apparatus for constructing pipelines in Arctic offshore waters by a directional drilling technique, thereby minimizing exposure to ice gouging and eliminating the hazards associated with unstable permafrost. A special drilling-pipeline construction vessel is also provided which has a conical shape with reinforced outer walls to resist ice forces, which vessel includes means to install deep underground pipeline segments and means to connect and protect the pipe ends.
Claims8
A method for laying a pipeline in an offshore area wherein the seafloor is subject to ice gouging, comprising determining the depth to which ice gouging is known to historically have occurred in the offshore area, drilling a series of invert arcuate underground paths, each path extending to below the depth to which ice gouging is known historically to have occurred in the offshore area;
- placing pipeline segments along these underground paths;
- connecting adjacent ends of the pipeline segments at a location subject to ice gouging;
- and protecting the connected ends of the pipeline segments from ice gouging by an ice-resistant structure.
A drilling-pipeline construction vessel comprising a shell structure with a height greater than the deepest water in which pipelaying is to be conducted;
- said shell structure including a reinforced ice-resistant outer wall and an inner wall and partial bottom which divide the internal volume of the structure into a ballast tank and bottomless work area;
- means for ballasting down the vessel to a position on the seafloor;
- means for removing water from the bottomless work area;
- means for drilling a slanted borehole into the seafloor;
- means for inserting a pipeline segment into the borehole;
- means for connecting a pipeline segment inserted into one borehole with a pipeline segment inserted into an adjacent borehole;
- means for excavating sea bottom from around the adjacent boreholes;
- and means for pouring concrete into the excavated seabottom to form a protective cover over and about the connected ends of the pipeline segments.
A drilling-pipeline construction vessel comprising a shell structure with a height greater than the deepest water in which pipelaying is to be conducted;
- said shell structure including a reinforced ice-resistant outer wall and an inner wall and partial bottom which divide the internal volume of the structure into a ballast tank and bottomless work area;
- means for ballasting down the vessel to a position on the seafloor;
- means for removing water from the bottomless work area;
- means for drilling a slanted borehole into the seafloor;
- means for inserting a pipeline segment into the borehole;
- means for connecting a pipeline segment inserted into one borehole with a pipeline segment inserted into an adjacent borehole;
- means for excavating sea bottom from around the adjacent boreholes;
- and means to form a protective cover over and about the connected ends of the pipeline segments.
Dependencies are inferred from the claim text.