Abstract: Gas Subsea Transmission System (GSTS) is a new method for transferring large quantities of natural gas between marine distances through the oceans. Its purpose is to provide a safer, faster and more financially advantageous alternative to gas transmission via LNG. The GSTS's main part is a Submersible Suspension Pressure-equaliser Pipeline (SSPP). It is a long pipe with a large diameter which has a high capacity of gas transmission. This pipe is kept submersible and suspended in deep waters by its special mooring system. It is made from steel pipe which is reinforced by internal concrete rings. The basic concept of SSPP is to cancel the internal pressure of the gas pipeline with the external hydrostatic water pressure by varying the pipe environment. These conditions lead to the possibility of a large diameter pipeline resulting in efficient, high capacity gas transmission.

Abstract: A system for starting up a flowline suitable for conveying hydrocarbons, said flowline being extended over the seabed from a wellhead and terminating at a joint end. The joint end is suitable for connection to a subsea riser extended in a catenary. The flowline is able to stretch. A lock fixes the joint end with respect to the seabed for maintaining the flowline in its stretched position, and preventing its return movement.

Abstract: A guide tube for a flexible pipe for transporting hydrocarbons comprising an internal tubular element of a substantially rectilinear section extending along an axis (A) and extended by a free section having a curvature along its length and a wall which is internal with respect to the curvature against which the flexible pipe is accommodated when frictionally carried through guides. The rectilinear section comprises eccentric guides for directing the flexible pipe away from the axis (A) and in a direction opposite to the curvature of the free section such that the pipe is deviated from the internal wall.

Abstract: A stabilization system (10) for a section of submarine pipeline (11) comprising an end restraint (15) at each end of the section of pipeline and intermediate restraints (20) between the two end restraints (15) for limiting lateral movement of the pipeline (11) at the location of the restraints (15, 20). Each end restraint (15) is adapted to be secured to the pipeline (11) to transfer axial tension generated by lateral movement of the pipeline (11) to the seabed or ground on which the end restraint is installed. Each restraint (15, 20) comprises a pair of restraint faces (21) spaced apart to define a gap (23) through which the pipeline (11) can extend. Each restraint face (21) is configured to control curvature of the pipeline (11) during lateral movement thereof. A restraint device and a method of stabilizing a submarine pipeline is also disclosed and claimed.

Abstract: An undersea pipe of the riser type providing a connection between a floating support and the sea bottom. The riser has a rigid pipe of the catenary type extending from the floating support to a point of contact with the sea bottom. The catenary riser comprises a lower pipe portion terminating at the point of contact. The apparent weight per unit length in water of the lower pipe portion being at least 25% less than that of the remainder of the pipe constituting the catenary riser.

Abstract: The present invention relates to a device for improving the fatigue strength of a metal pipe a portion of which lies on the sea bottom and one end of which is suspended from a floating support subjected to the dynamic motions of the sea which move the touchdown point (TDP) of the pipe. The device comprises stress limiting means comprising a material (13) inserted between the pipe and the ground, in the vicinity of the touchdown point, the system thus created having a lineic stiffness below 200 kN/m/m and a thickness determined in such a way that the static and cyclic deformations remain allowable.

Abstract: During recovery of an offshore pipeline, to a floating vessel for repair, for example, the pipeline is secured to a hang-off clamp. Due to the motion of the vessel, oscillating bending moments can be caused in the pipeline below the clamp. To reduce these bending moments an auxiliary member is employed which restricts “radial” movement of the pipeline below the clamp. The auxiliary member comprises an elongate element, such as a pipe, whose upper end is fixed to the vessel and whose lower end carries a member connecting it to the pipeline. Axial movement of the pipeline with respect to the connecting member is permitted. The auxiliary member is designed to have predetermined amount of flexibility, this being provided in particular by flexibility of the pipe, and it thus restricts the amount of radial movement of the pipeline which is permitted below the clamp.

Abstract: A support assembly for a flexible line comprises a hanger to suspend the flexible line from an offshore oil rig without subjecting the line to a bending stress adjacent the support assembly, a frame supporting the hanger, and a connector coupled to the frame to removeably connect the support assembly to the rig. In an embodiment, the support assembly further comprises a base that may be a plate, an open-ended box, or a plurality of beams. In another embodiment, the flexible line includes an end comprising a swivel plate that mates with the hanger.

Abstract: A method for laying a pipeline on the sea bed from a lay barge in order to achieve controlled thermal expansion, comprises the following steps: Feeding out of the pipeline having a radius of initial residual curvature from a pipeline reel, preferably via a stinger to a curvature device where a radius of reversal curvature is applied to the opposite side of the pipeline with respect to the radius of initial residual curvature when the pipelines is passing through the curvature device. The curvature device straightens out the pipeline to longer, mainly straight portions with length having a radius of residual curvature which is larger than a desire minimum radius of residual curvature. The curvature device exposes shorter portions of the pipeline with a length for a radius of counter curvature forming the thermal expansion loops having a radius of residual curvature which is less than a desired maximum radius of residual curvature for the thermal expansion loops.

Abstract: The present invention is a method and a vehicle-mounted apparatus (30) for laying pipelines in which adjacent pipe (17, 28) are joined by the technique of magnetically impelled arc butt welding (MIAB). A MIAB welding head (13) having a welding axis is mounted on a transportable platform (35). A pipe guide (50) capable of engaging a welded pipe string is located rearwardly of the welding head (45). The pipe guide (50) maintains alignment of the string with the welding axis. The apparatus includes pipe feed means (47, 48, 49) maintaining alignment of a next pipe to be laid with the welding axis and the pipe string (17). The platform (37) is rotatably mounted on the vehicle (30) and tilts around a horizontal axis. The vehicle (300) is provided with pivoting steerable tracks (38).

Abstract: A shell for providing impact protection to a marine drilling riser, the shell comprising a body having at least one hollow chamber defined by inner and outer faces of the shell, the body being provided with a plurality of holes allowing flooding of the chamber.

Abstract: A pipeline laying ship and an improved method of laying a pipeline in a marine environment is disclosed. The pipeline laying ship is a dynamically positioned barge or self-propelled dynamically positioned vessel with a hull having a deck area that supports a pair of reels. The reels are independently rotatable, and are position to generally port and starboard relative to one another. A pipe joint storage area is provided for containing multiple joints of pipe. One or more pipeline welding stations are provided on the deck next to the reels, the pipeline welding stations being positioned to join the joints of pipe together to form an elongated pipeline that can be wound upon a selected reel of said pair of reels. A tower is provided for guiding the elongated pipeline as it is unwound from a selected reel, the tower including at least a bend controller, a straightener and a tensioner.

Abstract: A method for laying a pipeline (1) on the sea bed from a lay barge (10) in order to achieve controlled thermal expansion, comprises the following steps: Feeding out of the pipeline (1) having a radius of initial residual curvature (RrInit) from a pipeline reel (2), preferably via a stinger (3) to a curvature means (4) where a radius of reversal curvature (Rmk) is applied to the opposite side of the pipeline with respect to the radius of initial residual curvature (RrInit) when the pipelines is passing through the curvature means (4). The curvature means (4) straightens out the pipeline to longer mainly straight portions (L) with length (LL) having a radius of residual curvature (Rr) which is larger than a desired minimum radius of residual curvature (RrMin).

Abstract: A method for launching a steel catenary riser (SCR) from the seabed to the surface comprising three stages. During the first stage, joints are continually welded to the metal pipe resting on the seabed to form the length of the steel catenary riser (SCR) in contact with the seabed. In the second stage a length of pipe previously wound onto a receiving device is welded to the free end of the last joint welded and then it is unwound and launched to form the intermediate length of the steel catenary riser (SCR). In the third stage joints are again welded to the intermediate length of the steel catenary riser (SCR) to form the top length of the said steel catenary riser (SCR).

Abstract: Method and apparatus for the maintenance of pipelines. A number of points along the pipeline (30) is selected and the pipeline is raised at these points by an amount that the height difference between these points does not exceed the international flexibility standards. The pipeline (30) is supported at these points and thereafter maintenance is performed on those segments which have been raised enough to allow performance of the maintenance procedures. The distance between two adjacent points may be 30 meters and the height difference between two adjacent points may be not more than and preferably close to 22 cm. The initial cross-section of the selected segments are allowed to rest on the beds of the trenches because of their weights.

Abstract: A system and a method for introducing a module into a pipeline during deepwater pipeline installation wherein a hang-off clamp supports a pipeline and translates from a pipeline feeding position to a module connection position wherein a module is connected to the pipeline. By-pass lines support the pipeline and module and lower them past the hang-off clamp. The hang-off clamp resumes support of the pipeline and returns to the pipeline feeding position with the pipeline and module.

Abstract: A pipe handling apparatus for laying elongate articles in deep waters includes a tiltable pipe handling structure housing a traveling clamp for holding and/or paying out under tension the elongate article and a fixed clamp. The traveling clamp is driven via an articulated rack located by a guide mechanism. The rack driven by a pinion drive mechanism and acts at a lower portion of the rack, such that the center of gravity of the apparatus is lowered, and loading in the structure is reduced.

Abstract: A pipe lay vessel with a reel for carrying a length of pipe and first drive part for controlling rotation of the reel. A substantially vertical guide structure includes at its upper end a deflection member for deflecting the pipe from a first trajectory extending between the reel and the guide structure to a second, substantially vertical trajectory. A clamping member carries the vertical pipe section and has second drive for feeding the pipe along the vertical trajectory. A movable tension compensator (7) is provided at the first pipe trajectory for lengthening or shortening the first pipe trajectory to maintain a substantially constant tension of the pipe along the first trajectory during unwinding of the reel.

Abstract: A method of abandoning a pipeline (2) being laid by a vessel having an A/R system, wherein a sealine (2, 11, 13) is initially held by a pipe laying and tensioning arrangement. The method includes a step of reducing tension at sea level of the sealine (2, 11, 13), by connecting one or more buoyant members (13) to the end of the pipeline (2). The members (13) are then lowered into the sea, using a line (16). At least one member (13) is connected to the pipeline (2) through a connection (12) which allows pivoting of the member (13) so that the end of the member (13) at the end of the pipeline (2) projects upwardly from the seabed (3).

Abstract: Method for preparing an elongated object (22) having a relatively high bending stiffness, such as an elongated tube or cable, before storing and/or transporting object, wherein a) the elongated object is provided with sufficient buoyancy capacity to enable the object to float on a liquid (14) with a predetermined specific gravity and that b) the elongated object (22), while floating on the liquid and carried thereby, is spirally wound into a flat monolayer spiral (36), the inner radius of which is preferably in the order of the diameter of the elongated body divided by the yield point (ratio) or larger of the most fracture critical material in the elongated object.

Abstract: A system for laying a pipeline from a floating vessel onto the ocean floor in relatively deep ocean water which provides guidance, bend restricting, and stabilizing means for the pipe sections while the connection by welding processes are being done and for providing means to remove the guidance, bend restricting, and stabilizing means from the central area of the stinger when passing objects of a larger diameter than the pipeline.

Abstract: An apparatus for deploying pipe string is disclosed. The apparatus comprises a mast; an articulated stationary table to which the mast is affixed; a stinger affixed to the stationary table to articulate with the mast; and a pipe erector operatively connected to the mast.

Abstract: An apparatus for deploying pipe string is disclosed. The apparatus comprises a mast; an articulated stationary table to which the mast is affixed; a stinger affixed to the stationary table to articulate with the mast; and a pipe erector operatively connected to the mast.

Abstract: A diverless process of tapping a pressurized subsea pipeline without removing the pipeline from service. The process includes the steps of lowering and landing a measurement tool onto the pipeline in order to check ovality and straightness of the pipeline. Pipe lift frames are lowered and landed onto the pipeline spaced from a chosen location. The pipeline is lifted by hydraulic actuators or mechanical screws on the lift frames. A hot tap machine and accompanying orientation frame are lowered from the surface and landed on the pipeline between the pipe lift frames. A fitting clamp is secured to the pipeline. A hot tap machine is lowered onto the hot tap fitting and orientation frame. The pipeline is then tapped with the hot tap machine.

Abstract: A riser system connecting a oil or gas well head and a surface vessel comprises a first riser section maintained substantially vertically under tension, attached for example by a tension cable to a constant load tensioner means mounted on the vessel, and a flexible second riser section arranged above the first riser, the second riser being able to flex to accommodate movements in the surface vessel. The second riser section includes a curvature limiter, achieved for example by making the riser from a material of variable stiffness along the riser's length. An emergency disconnect valve is provided between the lower riser section and the upper flexible section. An alternative curvature limiter comprises a plurality of discrete collars which are connected together and surround the outer diameter of the second riser.

Abstract: A subsea steep wave lock and guide mechanism (1) for elongated articles (2) such as cables, pipes and umbilicals provides a substantially horizontal inlet (6) for the article at seabed level and a substantially vertical flexible article outlet (4) leading to the steep wave. The lock and guide mechanism (1) includes a number of lockable/releasable gates (20-24) for restricting and defining allowable movements of the article in the horizontal as well as in the vertical direction.

Abstract: An apparatus for deploying an underwater pipe string includes a mast, an articulated table, a stinger, and a pipe erector. The mast is affixed to the articulated table and extends above the articulated table. The stinger is affixed to the articulated table and depends below the articulated table. The pipe erector is connected to the mast for loading pipe joints up to the mast. A pipe joint loaded in the mast is welded to the pipe string, which depends from the articulated table and through the stinger toward a seabed. The stationary table is articulated for tilting of the table, the mast, and the stinger azimuthally and angularly for a preferred direction and lay angle of the pipe string being deployed.