Showing papers on "Submarine pipeline published in 1978"

Offshore pipeline electrical survey method and apparatus

Abstract: A method and apparatus for conducting offshore pipeline electrical surveys is characterized by initially locating and marking the pipeline, traversing the length of the pipeline towing a reference electrode in close proximity to the structure, providing a supply of wire having one end electrically and mechanically connected to the pipeline at a reference location, playing out the wire along the length of the pipeline through a distance measuring device while transporting the supply of wire and towing the reference electrode, and measuring and recording the potential difference between the reference electrode and pipe either continuously or at spaced test locations along the length of the structure. The method and apparatus are further characterized by alternately connecting and disconnecting an electrical power source to the pipeline at the reference location, measuring and recording the potential difference in both connected and disconnected modes at the test locations, and measuring and recording the depolarization and/or polarization times when the power source is disconnected and/or connected, respectively, to the pipeline.

Design of Marine Pipelines for Areas of Unstable Sediment

Abstract: Burial of marine pipelines is the preferred method of improving long-term performance. Embedment is achieved with a jet sled that erodes a trench of the desired depth whereby natural processes fill the trench. Specifications usually require that embedment exceed 3 ft at water depths of 200 ft or less. The objectives of burial are to isolate the line from anticipated hazards such as wave forces, fish trawl damage, and erosion. This solution assumes that the seabed provides a stable, rigid protective coating for the pipeline, an assumption that is often erroneous. Over the length of a pipeline there are many geological processes that are capable of influencing the performance of a pipeline. The processes occur at varying rates and may be intermittent or continuous in nature. Site surveys are usually performed to detect there processes. However, a brief survey may not reveal significant processes that occur over a 10-yr to 20-yr span. Nevertheless, an understanding of the mechanisms that lead to overstressing of pipelines and long-term failure can lead to improved design and instillation methodology for unstable areas. This analysis is concerned with the mechanism of sediment mass movement on the magnitude of pipeline tension.

Undulated bottom profiles and onshore-offshore transport

Abstract: Underwater bars, the characteristic features of oceans and lakes occur singly or in a series along the coast. Nearest bar to the shore, namely the break-point bar moves shoreward in summer, joins the coast and is replaced by another bar in its original place. The other seaward bars are storm bars, more or less permanent though they may shift slightly in orientation, position and shape depending upon the wave climate and state of the coastal processes. With the sediment and bottom profiles changing constantly with differing wave characteristics and beach exposure, a rigorous mathematical analysis for long range variability of profiles and therefore coastal processes in not possible. Therefore, the concept of medium depth and steepness characteristics is introduced to distinguish the profiles and their major dimensions. Onshore-offshore sediment motion is sometimes far in excess of longshore transport mostly confined in the breaker zone. When submarine bars are present, such motion is considerable mainly as a result of the hydrodynamic reaction between the rotating eddies generated over the bars and the bar surface. By means of dimensional analysis, it is possible to relate the quantity of onshore-offshore motion to the bar dimensions, wave period, water depth and transport direction by profile steepness characteristics. The above two concepts are then applied to the Nile Delta coastal processes with satisfactory results.

Float for use in laying submarine pipelines

Abstract: A float device for use in laying a submarine pipeline from a launching base, comprising one or more tubes containing a liquid less dense than water, such as a hydrocarbon, and fixed to the pipeline so as to form therealong a plurality of compartments isolated from each other and each communicating with the sea via an opening or a pipe opening towards the bottom. Means may be provided for opening in each compartment a passage opening towards the top and for recovering the less dense liquid, driven by the water, to the outlet of said passages, or even for releasing the tube or tubes from the pipeline.

Adjustment and verification of the randdelta II model

Abstract: In the mid-1950s the Netherlands government embarked on a massive construction program, called the Delta Plan. Its purpose was to enhance protection from floods caused by the North Sea in the estuaries of the Rhine, Meuse and Scheldt. According to the plan, all connections to the sea were to be closed by dams, except the New Waterway to Rotterdam and the Western Scheldt. In 1974 all dams and dikes were complete except the dam closing off the Eastern Scheldt from the sea. In view of growing opposition to a complete closure, plans were revised in 1976, and instead of the dam, a storm surge barrier will be constructed. This barrier will reduce the tidal range in the Eastern Scheldt and will be closed during storm surges. In support of engineering and environmental studies related to the construction and operation of this barrier, a large numerical model has been developed, which covers the Eastern and Western Scheldt and the adjacent offshore area. The section of the North Sea which is included in the model is about 120 km long and 30 km wide, running from Blankenberghe in Belgium to Scheveningen in the Netherlands (Fig. 1). The bathymetry of the model area varies widely. In general it slopes from the shore to about 25 m at 30 km from the coast. In certain sections of the offshore area, the bottom is relatively flat; in other areas it has offshore bars and the bottom contains underwater sand dunes with a height of several meters. In the estuaries the tidal flow has scoured deep channels. The tidal flats near the North Sea are generally sandy, but the ecologically important tidal marshes located more inland contain much finer material. The flow and the water levels in the region which is modeled are generally tide-induced. However, the influence of meteorological effects is always present and sometimes dominates water movements and water levels (storm surges). The influence of the fresh water discharges is of much less importance; generally their effects can only be noticed in the immediate vicinity of the discharge. The tides in the offshore area of the model are part of the complicated tide system in the North Sea. The semidiurnal tidal wave propagates along the coast in a northeasterly direction. During this propagation the amplitude reduces from about 1.90 m near Blankenberghe to about .85 m near Scheveningen.

Seismic response analysis of offshore pipelines in contact with the sea-bed

Abstract: The seismic behaviour of an offshore pipeline, which may be totally or partially in contact with the sea-bed, is characterized by the confluence of structural dynamics, hydrodynamics and soil mechanics and also the possible dynamic interactions between these aspects. This paper contains a study dealing with the seismic response analysis of such a pipeline including pressure drag effects. A numerical analysis basesd on the assumption that the pipe behaves linearly elastically and that pipe deffection is elastoplastically related, without loss, to sea-bed resistance shows that pipe response in significantly attenuated by contact, as aspected, the amount of attenuation depending upon contact length and the parameters defining idealized sea-bed behaviour.

Laying submarine pipelines

Abstract: 1536896 Laying pipelines COMPAGNIE GENERALE POUR LES DEVELOPPEMENTS OPERATIONNELS DES RICHESSES SOUS-MARINE C G DORIS 26 May 1976 [30 May 1975 13 May 1976] 21748/76 Heading F2P In laying a pipeline 1 in a body of water 2 the pipeline 1 is enclosed over its whole length within a continuous ballast tube 4 and as the assembly of the pipeline and ballast tube proceeds the intermediate space 5 between the pipeline and the ballast tube is filled with a liquid less dense than water, such as a light hydrocarbon, to give the assembly of pipeline and tube a positive buoyancy while the assembly is being laid and replacing the said liquid with a medium of sufficient density, such as soft water or a grouting having a base of an hydraulic or hydrocarbon binder, to cause the assembly to rest on the bed 2a.

Connector system between loader buoy and submarine pipeline

Abstract: PURPOSE:To improve the safety of, and to facilitate the maintenence of, a connector system between a loader buoy and a submarine pipeline, by assembling the vertical portion of the system by use of a pliable hose and a pliable suspender member while supporting the other portions by a rigid supporter member incorporating a buoyancy-regulating tank.

Offshore pipeline laying - from submersible work platform with swivelling guides for pipe section welding container

Abstract: Pipelines are laid at great depths offshore by floating a container with a number of pipe lengths to site and lowering it to a work station at a safe depth (100m). The pipe sections are joined to each other by welding or mechanically and are lowered to the seabed in J-fashion at an adjustable angle. Provides a faster laying rate than the inclined ramp method,. It can be used for pipes of larger dia. than the reel method. Larger dias. and greater depths can be handled than with the flotation method and the new method is less dependent on weather conditions.

Impact of coastal processes on resource development with an example from Icy Bay, Alaska

Abstract: The coastline of Alaska is dynamic and continually readjusting to changes in the many processes that operate in the coastal zone. Because of this dynamic nature, special consideration must be made in planning for development, and caution must be exercised in site selection for facilities to be emplaced in the coastal zone. All types of coastal processes from continuously active normal processes to the low frequency-high intensity rare event must be considered. Site-specific evaluations considering the broad range of possible processes must precede initiation of development. An example of the relation between coastal processes and a proposed resource treatment facility is presented for Icy Bay, Alaska. Icy Bay is the only sheltered bay near many of the offshore tracts leased for petroleum exploration in the 1976 northern Gulf of Alaska OCS (Outer Continental Shelf) lease sale. Consequently, it has been selected as a primary onshore staging site for the support of offshore exploration and development. The environment of Icy Bay has many potentially hazardous features, including a submarine moraine at the bay mouth and actively calving glaciers at the bay's head which produce many icebergs. But most significant from the point of view of locating onshore facilities and pipeline corridors are the high rates of shoreline erosion and sediment deposition. If pipelines or any onshore staging facilities are to be placed in the coastal areas of Icy Bay, then the dynamic changes in shoreline position must be considered so that man-made structures will not be eroded away or be silted in before the completion of development-