The present invention relates to a system and method for uncovering and removing pipeline from the seafloor using a subsea trenching system using pressurized water to uncover pipe, a subsea shear carried by a barge to cut lengths of the pipeline, and a grapple carried by a barge to lift cut lengths of pipeline for placement on a pipe haul and recovery barge.

A subsea riser is installed by lowering at least one riser conduit to the seabed when piggybacked to an elongate support that comprises at least one flowline. The elongate support may be a pipeline bundle, which may be attached to one or more towheads in a towable bundle unit. The riser conduit may be in fluid communication with the flowline. At the seabed, a free end portion of the riser conduit is detached from the elongate support by releasing subsea-releasable fastenings. Then, with the elongate support and a root end of the riser remaining at the seabed, the detached free end portion of the riser conduit is lifted away from the elongate support to a riser support, such as a platform, an FPSO (floating production, storage and offloading vessel), or a buoy.

A method of installing a subsea riser comprises placing an elongate negatively-buoyant support on the seabed and, when laying the riser on the seabed, guiding a riser portion onto the support to extend along and be cradled by the support. A hogbend region of 5 the riser is then formed by conferring positive buoyancy on the support to lift the support and the riser portion away from the seabed. An element of the support comprises a riser support disposed in a longitudinally-extending open-ended gap between buoyancy volumes disposed on opposite sides of 0 the gap. Coupling formations such as hinge portions can couple the element to a like element. When so coupled, the gaps of those elements align to define an upwardly-opening, longitudinally-extending groove to receive the riser.

The present invention relates to a system and method for uncovering and removing pipeline from the seafloor using a subsea trenching system using pressurized water to uncover pipe, a subsea shear carried by a barge to cut lengths of the pipeline, and a grapple carried by a barge to lift cut lengths of pipeline for placement on a pipe haul and recovery barge.

A method of constructing a sliding subset foundation comprises embedding at least one mass of rocks in seabed soil and placing a sliding mudmat on the seabed over the or each mass of rocks. The rocks may be lowered into a cavity in the seabed by dumping the rocks into the cavity or when contained within a gabion that is inserted into the cavity. Alternatively, a gabion containing the rocks may penetrate the seabed soil, driven by self-weight or additionally by a deadweight bearing on the gabion. The gabion may be lowered toward tie seabed suspended from the deadweight. The deadweight may be removed and recovered after the gabion has been embedded in the seabed. The mass of rocks are embedded within an area of excursion of the mudmat to ensure that the mudmat will be directly above the mass of rocks at any position within the area of excursion.

A method of constructing a sliding subset foundation comprises embedding at least one mass of rocks in seabed soil and placing a sliding mudmat on the seabed over the or each mass of rocks. The rocks may be lowered into a cavity in the seabed by dumping the rocks into the cavity or when contained within a gabion that is inserted into the cavity. Alternatively, a gabion containing the rocks may penetrate the seabed soil, driven by self-weight or additionally by a deadweight bearing on the gabion. The gabion may be lowered toward tie seabed suspended from the deadweight. The deadweight may be removed and recovered after the gabion has been embedded in the seabed. The mass of rocks are embedded within an area of excursion of the mudmat to ensure that the mudmat will be directly above the mass of rocks at any position within the area of excursion.

A supporting device configured to support a pipeline on the bed of a body of water having a frame connectable in a sliding manner to a pipeline extending along a longitudinal axis between a laying vessel and the bed of a body of water; at least one floating body connected to the frame; and at least one connecting mechanism connecting the frame to the floating body and configured to define a distance between the axis of the pipeline and the floating body, so as to apply a torque to the portion of pipeline at the frame.

A connecting device for supporting an apparatus configured to couple to a pipeline and having a coupling mechanism, which has a first portion configured to couple integrally to the apparatus, and a second portion, configured to be connected to a hoisting device, and selectively releasable from the first portion in a designated or given direction as a function of the relative position of, and the force exchanged between, the apparatus and the hoisting device.

A method has the following steps: a) providing an undersea foundation arranged on the bed of a body of water; b) laying a section of pipe and of an in-line structure on the foundation and allowing the section of pipe to freely self-orient on the foundation; c) placing at least one guide on the foundation on both sides of the section of pipe; d) blocking the guide on the foundation to laterally clamp the section of pipe with respect to the foundation, while authorizing a longitudinal movement of the section of pipe with respect to the guide.

A method has the following steps: a) providing an undersea foundation arranged on the bed of a body of water; b) laying a section of pipe and of an in-line structure on the foundation and allowing the section of pipe to freely self-orient on the foundation; c) placing at least one guide on the foundation on both sides of the section of pipe; d) blocking the guide on the foundation to laterally clamp the section of pipe with respect to the foundation, while authorizing a longitudinal movement of the section of pipe with respect to the guide.