Abstract: Systems and methods for controlling movement of an elongated member providing communication between a vessel and a subsea unit are provided. The method can include connecting a positively buoyant member to an elongated member at a first location and connecting a negatively buoyant member to the elongated member at a second location, wherein at least a portion of the negatively buoyant member rests on a seabed when the elongated member is in an operational null position.

Abstract: Apparatuses including a subsea pipeline (18) extending from a first location (14) to a second location (16) and including at least one distributed buoyancy region (102) to traverse a seabed topographic feature (12) are presented. Methods including laying a subsea pipeline (218) including laying a negatively buoyant section of pipeline (218A), a distributed buoyancy section (202) of pipeline (218), and a second negatively buoyant section of pipeline (218B) from a pipelay vessel (220) to traverse an undersea topographic feature (212) are also presented.

Abstract: Apparatuses including a subsea pipeline (18) extending from a first location (14) to a second location (16) and including at least one distributed buoyancy region (102) to traverse a seabed topographic feature (12) are presented. Methods including laying a subsea pipeline (218) including laying a negatively buoyant section of pipeline (218A), a distributed buoyancy section (202) of pipeline (218), and a second negatively buoyant section of pipeline (218B) from a pipelay vessel (220) to traverse an undersea topographic feature (212) are also presented.

Abstract: The current subject matter relates to compliant variable tension risers to connect deep-water subsea wellheads to a single floating platform in wet tree or dry try systems. The variable tension risers allow several subsea wellheads, in water depths from 1220 to 3050 meters, at lateral offsets from one-tenth to twice the depth or more, to tie back to a single floating platform. Also, the current subject matter relates to methods to counter buoyancy and install variable tension risers using a weighted chain ballast line.

Abstract: Systems and methods for controlling movement of an elongated member providing communication between a vessel and a subsea unit are provided. The method can include connecting a positively buoyant member to an elongated member at a first location and connecting a negatively buoyant member to the elongated member at a second location, wherein at least a portion of the negatively buoyant member rests on a seabed when the elongated member is in an operational null position.

Abstract: Disclosed are compliant variable tension risers (106) to connect deep-water subsea wellheads (102) to a single floating platform (104). The variable tension risers (106) allow several subsea wellheads (102), in water depths from 4,000 to 10,000 feet, at lateral offsets from one-tenth to one-half of the depth, to tie back to a single floating dry tree semi-submersible platform (104).

Abstract: Disclosed are methods to counter buoyancy and install variable tension risers using a weighted chain ballast line. An example of an apparatus used in conjunction with the embodiments includes compliant variable tension risers to connect deep-water subsea wellheads to a single floating platform. The variable tension risers allow several subsea wellheads, in water depths from 4,000 to 10,000 feet, at lateral offsets from one-tenth to one-half of the depth, to tie back to a single floating dry tree semi-submersible platform.

Abstract: The current subject matter relates to compliant variable tension risers to connect deep-water subsea wellheads to a single floating platform in wet tree or dry try systems. The variable tension risers allow several subsea wellheads, in water depths from 1220 to 3050 meters, at lateral offsets from one-tenth to twice the depth or more, to tie back to a single floating platform. Also, the current subject matter relates to methods to counter buoyancy and install variable tension risers using a weighted chain ballast line.

Abstract: Disclosed are compliant variable tension risers (106) to connect deep-water subsea wellheads (102) to a single floating platform (104) in wet tree or dry try systems. The variable tension risers (106) allow several subsea wellheads (102), in water depths from 1220 to 3050 meters, at lateral offsets from one-tenth to twice the depth or more, to tie back to a single floating platform (104). Also disclosed are methods to counter buoyancy and install variable tension risers using a weighted chain ballast line (228, 230).

Abstract: Disclosed are compliant variable tension risers (106) to connect deep-water subsea wellheads (102) to a single floating platform (104). The variable tension risers (106) allow several subsea well-heads (102), in water depths from 4,000 to 10,000 feet, at lateral offsets from one-tenth to one-half of the depth, to tie back to a single floating dry tree semi-submersible platform (104). Also disclosed are methods to counter buoyancy and install variable tension risers using a weighted chain ballast line (228, 230).

Abstract: An offshore riserless drilling system drills a subsea borehole from a platform and through a cased borehole. The system comprises a lightweight drill string suspending a bottomhole assembly and extending from the platform downwardly through a depth of water into the cased borehole; a first limiter limiting the range of motion of the drill string adjacent the platform; and a second limiter limiting the range of motion of the drill string adjacent the cased borehole. The preferred methods include lowering a bottomhole assembly suspended on a lightweight drill string from a platform through a depth of water; limiting the bend radius of the drill string adjacent the platform; guiding the bottomhole assembly into a cased borehole; limiting the bend radius of the drill string adjacent the cased borehole; maintaining the bottomhole assembly in the cased borehole, and drilling the subsea borehole.

Abstract: Various apparatuses and methods to traverse an undersea topographic feature (12) with a subsea pipeline (18) are disclosed. The apparatuses and methods of the present invention accomplish this task through the use of a concentrated buoyancy scheme (10). The invention disclosed can allow more efficient and cost effective traversal of hostile terrain for subsea pipelines at great depths while minimizing the risk of rupturing the pipeline (18) or negatively impacting the surrounding undersea environment.

Abstract: An apparatus and method for offshore riserless drilling are disclosed. The preferred embodiments comprise a system for riserless drilling of a subsea borehole from a platform and through a cased borehole, the system comprising a lightweight drill string suspending a bottomhole assembly and extending from the platform downwardly through a depth of water into the cased borehole; a first limiter limiting the range of motion of the drill string adjacent the platform; and a second limiter limiting the range of motion of the drill string adjacent the cased borehole. The preferred methods include lowering a bottomhole assembly suspended on a lightweight drill string from a platform through a depth of water; limiting the bend radius of the drill string adjacent the platform; guiding the bottomhole assembly into a cased borehole; limiting the bend radius of the drill string adjacent the cased borehole; maintaining the bottomhole assembly in the cased borehole, and drilling the subsea borehole.

Abstract: A marine riser system which effectively combines rigid (e.g. steel catenary risers) with flexible flowlines. Basically, the steel catenary risers, which are merely the end portion of submerged rigid flowlines, are curved upward through the water in a gentle catenary path to a large, submerged buoy, which, in turn, is moored to the bottom by tension leg tether lines at a depth below the turbulence zone of the water. Flexible flowlines are fluidly connected to the steel catenary risers at the buoy and extend upward through the turbulence zone to the surface.