Abstract: In an ocean thermal energy conversion facility, a cold water riser pipe is releasably supported at its upper end by the hull of the floating facility. The pipe is substantially vertical and has its lower end far below the hull above the ocean floor. The pipe is defined essentially entirely of a material which has a modulus of elasticity substantially less than that of steel, e.g., high density polyethylene, so that the pipe is flexible and compliant to rather than resistant to applied bending moments. The position of the lower end of the pipe relative to the hull is stabilized by a weight suspended below the lower end of the pipe on a flexible line. The pipe, apart from the weight, is positively buoyant.

Abstract: Apparatus for position stabilizing the lower end of an elongate duct, which is vertically disposable in an ocean and which is supported at its upper end, is described. The apparatus includes an elongate flexible tensile member which is disposable along the interior of the duct. The tensile member is adapted to be connected at one end thereof to a duct support structure and to extend through the duct. A weight of selected mass and size is connectible to the other end of the tensile member below the lower end of the duct. Means are connectible between the tensile member and the duct, at least adjacent the lower end of the duct, for establishing and maintaining a selected position of the tensile member relative to the duct.

Abstract: A long, vertically disposed ocean water upwelling pipe, such as a cold water riser in an ocean thermal energy conversion facility, is fitted at its lower inlet end with a self-cleaning inlet screen. The screen includes a right conical frustum of loose metal netting connected at its larger upper end to the lower end of the pipe. A heavy, negatively buoyant closure is connected across the lower end of the frustum. A weight is suspended below the closure on a line which passes loosely through the closure into the interior of the screen. The line tends to stay stationary as the lower end of the pipe moves, as in response to ocean current vortex shedding and other causes, thus causing the closure to rattle on the line and to shake the netting. The included half-angle of the frustum is about 20.degree. so that, on shaking of the netting, marine life accumulated on the netting becomes loose and falls free of the netting.

Abstract: Apparatus for drilling a well at a location submerged below a body of water includes a buoyant foundation structure. The foundation structure is floatable on the surface of the body of water and is subject to vertical motion in response to waves and the like. A riser handling and tensioning mechanism is mounted to the foundation structure and is operable for moving a riser pipe along a substantially vertical line from and to the foundation into and out of connection with the submerged location. The riser handling and tensioning mechanism is also operable for applying tension to a riser pipe connected to the submerged location. The handling and tensioning mechanism includes vertically disposed hydraulic rams mounted to the foundation structure. Holding means are releasably engageable with a riser pipe adjacent its upper end and are connected to the rams for movement along the riser line by the rams.

Abstract: A large diameter duct structure is adapted for vertical disposition in an ocean. An elongate tensile core assembly is adapted to be supported at one end, as from a floating platform, and to extend downwardly a desired distance. A plurality of duct wall sections, each of selected length, are alignable in serial order to define a tubular assembly having a diameter substantially greater than that of the core. Support means are engageable with the core at selected locations along the core and with the wall sections. The support means support the wall section substantially concentrically about the core and secure the wall sections from movement relatively along the core. Seals are engageable between the ends of adjacent wall sections disposed about and along the core, and define substantially liquid-tight connections between the wall sections.

Abstract: A heavy submersible object is deployed from or retrieved to a floating vessel in rough water. The connection or release point is sufficiently far below the water surface that surface waves have little if any effect on the object. Deployment and retrieval are made to an arm which depends from the vessel and which has a variable stiffness connection, ranging from free-swinging to rigid, to the vessel. Deployment and retrieval are made with the arm free-swinging from the vessel so the arm has no motion due to pitch or roll of the vessel. In retrieval, the connection is progressively stiffened to rigid after the object has been connected to the arm, and the arm is then raised with the retrieved object.

Abstract: A single-point mooring system is provided for substantially permanently mooring a floating structure, such as an offshore natural gas treatment facility located on a shipform hull, to an anchor point. A rigid anchor structure, fixed to the bottom of the water body, defines a vertically oriented circular cylinder above the water surface. A collar is mounted circumferentially of the cylinder for movement about and along the cylinder. A pair of rigid arms extend from the floating structure in spaced relation to either side of the cylinder and are spaced equally from the roll axis of the floating structure.

Abstract: A heat transfer method for melting thick layers of ice advancing toward an object facing the ice is disclosed. Elongated grooves or corrugations are disposed in the exterior surface of the object facing the ice. A heating fluid is circulated in intimate contact with the inside of the grooved surface, and a force is maintained between the grooved surface and the advancing ice layer. The grooves increase the heat transfer rate to the ice both by increasing the surface area exposed to the ice and by providing channels for controlling the flow of the melted ice liquid to initiate and maintain a forced convection mode of heat transfer that is necessary for high ice-melting rates. A preferred application of the invention is in oil and gas exploration and production in Arctic regions where moving ice sheets must be melted to maintain a drilling platform or oil production platform positioned over a submerged well site during periods when moving ice fields overlie the well site.

Abstract: A stationary offshore platform is protected against damage from moving ice sheets by a conical shield surrounding the platform support structure and having means, such as a pneumatic biasing system, for raising or lowering the shield along the platform support. A system of mooring lines, thrustors, or the like is used to rotate the shield about the platform support. After an advancing ice sheet contacts the narrower upper portion of the shield, the shield is raised so that a wider lower portion of the shield can exert an upward force on the ice sheet to break the ice into pieces. The shield is rotated, while in its elevated position, to carry the broken ice with it to a location downstream from the advancing ice sheet. The shield is then lowered to dump back into the ocean the ice pieces broken by the upstroke of the shield. Means are provided for heating the exterior surfaces of the shield to melt ice pieces sticking to it.

Abstract: A heat transfer system for melting thick layers of ice advancing toward an object facing the ice are disclosed. Elongated grooves or corrugations are disposed in the exterior surface of the object facing the ice. A heating fluid is circulated in intimate contact with the inside of the grooved surface, and a force is maintained between the grooved surface and the advancing ice layer. The grooves increase the heat transfer rate to the ice both by increasing the surface area exposed to the ice and by providing channels for controlling the flow of the melted ice liquid to initiate and maintain a forced convection mode of heat transfer that is necessary for high ice-melting rates. A preferred application of the invention is in oil and gas exploration and production in Arctic regions where moving ice sheets must be melted to maintain a drilling platform or oil production platform positioned over a submerged well site during periods when moving ice fields overlie the well site.

Abstract: A mooring system for a drill ship has an annular cell mounted in the bottom of the hull concentrically around the moon pool. A plurality of annular cable drums are rotatable within the cell, the drums and the cell being rotatable about a common vertical axis. Anchor cables wound on the respective drums are directed by sheaves through the bottom of the cell through an opening in the bottom of the hull to anchors on the ocean floor for anchoring the vessel over a drill site. The drums are individually driven to adjust the associated cable, while the entire cell together with the drums is rotated within the hull to change the heading of the vessel relative to the anchors.

Abstract: A ship in which a string of heavy pipe is raised or lowered vertically beneath the ship at a substantially constant velocity in spite of heaving movement of the ship. The equipment for raising and lowering the pipe string is supported by the vessel through a heave compensation mechanism that permits vertical movement of the ship relative to the pipe raising and lowering mechanism. The heave compensation mechanism is a passive damped pneumatic-hydraulic spring system for isolating the vertical movement of the ship from the pipe raising and lowering equipment. The spring system operates over a very wide range of load imposed by the raising, lowering and supporting of a very long heavy pipe string.

Abstract: A system utilizing linear hydraulic cylinders for continuously raising or lowering a pipe string. Two sets of cylinders are spaced along the length of the pipe string. The cylinders are driven reciprocally with the cylinders in one set moving out of phase with the cylinders of the second set. Each set of cylinders includes means for releasably supporting the pipe string. The supporting means are operated out of phase so that one is released while the other is supporting the pipe. Control is such that the cylinder sets alternately raise or lower the pipe by incremental amounts, providing a continuous constant motion to the pipe string.

Abstract: A ship in which a string of heavy pipe is raised or lowered vertically beneath the ship at a substantially constant velocity in spite of heaving movement of the ship. The equipment for raising and lowering the pipe string is supported by the vessel through heave compensation means that permits vertical movement of the ship relative to the pipe raising and lowering mechanism. The heave compensation means is a passive damped pneumatic-hydraulic spring system for isolating the vertical movement of the ship from the pipe raising and lowering equipment. The spring system operates over a very wide range of load imposed by the raising, lowering and supporting of a very long heavy pipe string.

Abstract: An improved vessel for use in ice-covered waters has a motion inducing tank disposed in its hull at a location spaced from the even-keel center of buoyancy of the hull. Ports communicate from the lower extent of the hull to the exterior of the hull below the hull load waterline for flow of water into and out of the tank in response to pressure in the tank being different from ambient pressure outside the hull. The tank extends vertically in the hull from a lower end located below the hull load waterline to an upper end located above the waterline substantially as far as the location of the ports below the load waterline. Airflow devices are coupled to the upper extent of the tank and are operable alternately for generating superatmospheric and subatmospheric air pressure in the tank. The airflow devices include an air pressurizing device having a suction connection and a discharge connection.

Abstract: In conventional oil field operations there are men known as roughnecks whose job it is to receive each new section of pipe from a storage rack, position it on the center line of the rig, and join it to the existing pipe string beneath the rig. The apparatus described herein accomplishes this same function automatically and is capable of handling larger pipes faster than a manned operation. The apparatus also aids in returning a pipe section to the storage area.The apparatus has a pair of parallel tracks curved in a vertical direction extending laterally from the center line of a hoisting arrangement. A trolley rides on each track with the two trolleys mechanically synchronized to be driven together along the tracks by a hydraulic motor. Each trolley has a pivoted roller jaw for guiding the lower end of the pipe as it is swung into position. The jaws are caused to pivot at the proper location and in the proper direction by cams on the track.

Abstract: A parking brake for subsea mining equipment that is raised and lowered by a pipe string from a surface vessel. The brake assembly is mounted between a pair of linear lift units that alternately grip equally spaced collars on the pipe and move the pipe string in incremental steps. The brake includes a releasable yoke for engaging one of the collars. The yoke is rotatable to permit rotation of the pipe string by the brake assembly. The position of the brake is such that either drive unit may be used to position the pipe string so that a collar is engaged by the yoke of the brake assembly.

Abstract: A method and apparatus for mooring floating vessels (e.g. ships) generally over a fixed location on the water bottom. The vessels are provided with guide means (e.g. a track) which encircle the hull of the vessel along a line which is spaced at or above the Plimsoll line and at or below the top edge of the hull. A plurality of movable carriages are carried by the guide means for separately attaching a plurality of anchor lines to the hull and for controlling the length thereof. Means are provided for selectively positioning the carriages at desired points along the track.