Showing papers on "Submarine pipeline published in 1971"

Method for installing double-walled pipelines

Abstract: A double-walled pipeline is installed on the bottom of a body of water by installing a riser having a large bend near its lower end or a similar member at an offshore platform or other installation from which the pipeline is to extend, installing an outer pipe string along the pipeline route between the platform or other installation and the pipeline terminus, passing a cable through the riser or similar member and the outer pipe string, and then moving an inner pipe string into position within the riser or similar member and the outer pipe string.

Submarine Pipeline Support By Marine Sediments

Abstract: An approximate method for determining the initial settlement of a submarine pipeline in cohesive marine soils was derived by use of analogy to theories developed for use with foundations on land. Equations and a graph provide upper and lower limits of the probable range of initial settlement in terms of the submerged weight of a unit length of the pipeline, soil cohesion, and the external pipe diameter. The limitations of soil sampling, the variability of soil cohesion along the route of a pipeline, and the need for experimental and field work on the determination of submarine pipeline settlement are discussed.

Method and apparatus for installation of a flow line riser on an offshore structure

Abstract: A flow line riser is installed on an offshore structure by laying a pipeline to a point on water bottom adjacent the structure and raising the offshore structure to water surface where lengths of pipe are attached perpendicularly to the pipeline to form a riser, the pipeline and riser being lowered to water bottom as the lengths of pipe are attached while longitudinally maintaining substantially constant tension on said pipeline. When the pipeline and connected riser reaches water bottom, it is then attached to the structure.

Dynamic Positioning of Vessels at Sea

Abstract: The discovery in recent years of vast mineral deposits on and below the floors of the seas and oceans has resulted in a great increase in the number of offshore mining projects. All over the world companies are engaged in the drilling of wells the laying of submarine pipelines and the recovery of valuable minerals such as diamonds and even gravel and sand from the sea-bed.

Method and apparatus for installing risers

Abstract: A riser is installed at an offshore platform where pipeline construction terminates by lowering the riser in place adjacent a guide rail mounted on the platform and thereafter clamping the riser to the guide rail by moving clamps or similar connecting members downwardly on the guide rail and riser from the surface.

Method for installation of a riser on an offshore structure

Abstract: A method is disclosed for installing a pipeline riser on an offshore structure situated in a body of water. The technique includes laying a pipeline on bottom having a free end adjacent the base of the structure, positioning a floating vessel over the pipeline, and connecting at least one tension member between the vessel and the pipeline. The free end of the pipeline is raised to a point adjacent the water surface by applying force to the pipeline through each said tension member having a magnitude and direction such that the sum of the vertical force components is sufficient to lift the free end of the pipeline and the sum of the axial components is sufficient to prevent bending stress in the unsupported suspended section from exceeding the allowable stress. A riser bend section is attached to the free end of the pipeline and the pipeline lowered to the bottom as additional sections of the riser are attached. Simultaneously, sufficient axial tension is maintained on the pipeline to prevent the suspended section from being overstressed.

Offshore pipeline installation method

Abstract: An underwater pipeline is installed by lowering it to the bottom of the water from the stern of a lay barge as the barge advances along a long preassembled pipeline section which floats near the surface of the water and is held in tension by a second vessel positioned in front of the lay barge. An additional floating section is connected in place when the lay barge reaches the end of the initial section, this additional section is held in tension by the second vessel, and laying of the line is continued as the lay barge advances.

Protection of offshore structures against underscour

Abstract: The results of several investigations of underscour, which can significantly alter the soil-structure foundation system and subsequently, endanger offshore structures, are summarized in this paper. Reproduction at model scale of an unusual pattern of scour signified by a general lowering of the sea bed under and around the whole structure, and as observed by divers, has led to improved understanding of the phenomenon. Theoretical studies predicting this type of erosion, which contrasts with the usual bridge-pier type, are cited. Conclusions based on these investigations indicate that the flow through the permeable seabed from high pressure zones under wave crests to low pressure zones under the troughs assists the local velocity in rapidly eroding the seabed and that the use of reverse filters will minimize or prevent this erosion. The author states that model tests, special severe erosion studies, and experience with offshore installations show how effective and economical protection can be obtained.

Method and apparatus for evaluating offshore pipeline laying operations

Abstract: Methods and apparatus for conducting evaluations of offshore pipe-line laying operations and characterized by the performance of inspection operations, in relation to submerged pipeline means, prior to the termination of a pipeline laying operation. The inspection operation is performed while a floating vessel means, effecting the pipeline laying operation, remains operable to lay and/or retrieve pipeline increment means containing a defect detected during the inspection operation.

Ekofisk goes on production

Abstract: Phillips Petroleum Co. is planning to put Ekofisk field in the North Sea off the Norwegian coast on production next month in the first phase of a 2-phase development program. Phase 1 is a temporary program to take production from the 4 wells drilled so far until additional development wells are completed. The temporary setup will use a jack-up rig as a production platform, connected by submarine flow lines to ocean-floor wellheads. Other submarine flow lines will move the crude from the platform to mooring buoys for tanker loading. Production comes from the Danian Zone, a chalky, highly fractured limestone with good porosity and medium to low matrix permeability. At a depth of 10,000 ft, the reservoir is overpressured at 7,000 psi. Oil gravity is reported at 35$ to 38$ API, with low sulfur content and low pour point. Phillips has a long-term lease on the Gulftide, a 300-ft jack-up rig of Offshore Co. design, that will serve as the production platform during the Phase 1 program. Few modifications were made on the rig, the biggest change being the removal of pipe racks to make room for production equipment. Ekofisk field was discovered with the drilling of well 1A-X inmore » Block 2/4 in Sept. 1969. Drilling of 3 additional wells confirmed the existence of a giant field. Primary reserves have been estimated conservatively at 1 billion bbl.« less

Practical considerations in placing underwater pipelines

Abstract: The greatest risk in placing underwater pipelines is the danger of buckling and subsequent failure of the pipe. To prevent this, the pipeline structure design must consider: currents which impose lift and drag forces; bottom soil characteristics; allowable weather tolerances; equipment limitations; availability of shore support facilities; and other practical factors. The importance of a close working relationship between engineering and construction is stressed. The fundamentals of underwater pipeline design and various construction methods (lay barge, reel barge, pulley floating string, and pull barge) are discussed.

Hydraulic Trenching of Submarine Pipeline

Abstract: A consortium of oil companies commissioned two firms of contractors to construct, as a joint venture, a single buoy mooring system off the South African coast. It was planned to pull the pipes out to the sea through a sleeve to be placed in a trench blasted 600-ft rocky reef in the surf zone, and to bury the pipe on the seaward side of the reed between chainages 1,705 and 8,000. The note describes the design of trenching device, the hydraulic trials, and the operation.

Offshore Distribution of Pacific Herring (Clupea pallasi) on Basis of Records from Fur Seal Stomachs

Abstract: An examination of stomachs of fur seal (Callorhinus ursinus) taken off the coast of southern British Columbia and Washington from 1958 to 1969 indicated that Pacific herring (Clupea pallasi) were confined mainly to the continental shelf. Herring were most numerous in fur seal stomachs off Barkley Sound. Few occurred north of Cape Cook or from Cape Flattery south to the Columbia River. None were found from seals taken near the Cobb Sea-mount.

Reel-type pipelaying barge

Abstract: Technique described is innovation in offshore pipelaying. With this method, pipe is welded together onshore, wound onto large-diameter reel on a floating vessel, and laid on the ocean floor at high rates. Currently pipe is welded with manual techniques, but several automatic systems are evaluated. As the pipeline is unspooled, it is straightened with a three-wheel unit that creates uniform residual stresses along the length. A "stinger" constrains the configuration so that pipeline's radius of curvature cannot exceed a minimum value. The integrity of pipe coatings has been a problem with this technique.