Showing papers on "Submarine pipeline published in 1980"

Geology and geologic hazards of offshore Eel River basin, northern California continental margin

Abstract: No formal abstract is given The prefaces states, " This report summarizes aspects of the offshore and onshore geology of the Eel River Basin, California, that are of importance in assessing the potential geological hazards to offshore petroleum exploration and development Although these investigations focus on the identification and characterization of potential hazards in specific offshore basins, they should be considered regional in scope They are designed to provide broad geological perspective in these areas, to be used as an adjunct to site-specific geohazards studies The geologic phenomena investigated include faulting, seismicity, seafloor instability (eg, submarine slides and flows), seafloor erosion and deposition, hydrocarbon seepage, hydrocarbon gases and hydrates in seafloor sediments, and diapirism"

Frigg Field--Large Submarine-Fan Trap in Lower Eocene Rocks of the Viking Graben, North Sea

Abstract: In the deepest, axial part of the Viking sub-basin of the North Sea, the Frigg Field, one of the world's largest offshore gas fields, straddles the border of the British and Norwegian continental shelf at 60° N lat. The discovery well was drilled in 1971 on Norwegian block 25/1 in 100 m of water. Gas was discovered at a depth of 1,850 m in a lobate submarine fan representing the ultimate phase of a thick Paleocene deposit. Sealed by middle Eocene open-marine shales, the structure is mainly submarine-fan depositional topography enhanced by draping and differential compaction of sands. The area of structural closure is underlain by a typical "flat spot" on seismic sections, and the gas column lies on a heavy oil disc. Chromatographic analysis shows that source of both the oil and gas could be the underlying Jurassic section. Recoverable gas reserves are estimated to be about 200 billion cu m (7 Tcf). Production began September 15, 1977; the gas is brought ashore at St. Fergus in Scotland by a 360-km pipeline.

Characteristics of the ground-water seepage into Great South Bay. Special Report 35

Abstract: The water quality and salinity in Great South Bay represent a balance between the amount of seawater that enters the bay through its inlets and the amount of freshwater that is supplied from Long Island. Streamflow accounts for most of the freshwater supplied to the bay. The second largest contribution is the submarine outflow of ground water across the bay floor. Direct measurements of this source are reported here. Preliminary work showed that much of the seepage occurred within 100 meters of the shore. Submarine outflow rates were as high as 150 liters/day/square meter. The outflow near the shore was typically 50 liters/day/square meter and decreased to about 30 liters/day/square meter at a distance of 100 meters offshore. Variations in the outflow rate due to tidal changes in the water level could not be detected. The flow rate did appear to be sensitive to coastal flooding and rainfall, however. In order to calculate the total submarine outflow, the data were described as decreasing exponentially with distance from shore. The typical value of the submarine outflow was calculated to be 4.1 x 10/sup 8/ liters/day. This calculation excluded measurements made near Fire Island, but they suggest that significant amounts of ground more » water may enter the bay far from shore due to sustained, upward leakage from deep aquifers. As a result, the calculated value is an underestimate. The outflow rates are relatively large and should significantly affect the pore water chemistry. « less

Support structure for offshore platforms

Abstract: A structure for use in supporting a platform above a body of water is disclosed. The structure includes a leg extending between the bed of the body of water, the seabed, and the platform. The overall cross-sectional area of the leg is greatest near the seabed and decreases moving upwardly away from the seabed.

Creep and Relaxation in Floating Platforms — an Analysis of Case Histories

Abstract: The use of the natural ice sheet in Arctic regions to support stationary, heavy loads of 500 tons or more for periods of greater than 30 days requires analysis of the flexural creep behaviour of ice. Panarctic Oils Ltd. of Calgary, Canada has, since the spring of 1974, been thickening the natural ice cover by flooding and freezing in thin layers and placing conventional land drilling rigs on these constructed platforms. By doing this offshore exploratory drilling for hydrocarbons has proceeded over a great area at relatively little cost. (Baudais, Et. Al. 1974, Baudais, Et. Al. 1976, Masterson and Kivisild, 1978). One offshore gas well was recently completed from a floating ice platform and a pipeline brought to shore. (Watts and Masterson, 1979, Palmer, Et. Al., 1979). Design and monitoring of these platforms have been carried out by FENCO CONSULTANTS LTD. of Calgary, Canada.

Regional Distribution and Characteristics of Bottom sediments in Arctic Coastal Waters of Alaska. Review of Current Literature.

Abstract: : This report includes a discussion of some of the properties and characteristics of offshore marine sediments found in the U.S. Beaufort Sea that could influence aspects of offshore development. A collection of references is also included in an appendix. Perennially and seasonally frozen sediments are extremely common, with variable distribution and properties. The depth to the top of icebonded permafrost can be as little as 7 m below the seabed many kilometers from the sea coast. The subsea permafrost can contain visible ground ice similar to that observed on land, and can be anticipated to cause problems at least as great as those experienced on land. The distribution and properties of fine-grained sediments are also variable with evidence that they are commonly overconsolidated. The distribution and properties of these sediments can be important in influencing access to material suitable for construction of offshore structures, such as islands. The possible occurrence of gas hydrates and some of industry's experience with this form of natural gas are also discussed. A recent paper by Barnes and Reimnitz (1979) provides new information on redistribution of seabed sediments during periodic events. Their observations suggest that previous estimates of gouge frequency and maximum depth can be conservative, and that gouging and sediment infilling can be more dynamic than previous data may indicate. (Author)

Environmental Aspects of Oil and Gas Pipeline Landfalls in Northeast Scotland

Abstract: Oil and gas pipelines from the North Sea have reached the northeast coast of Scotland from offshore production platforms. The pipelines date from 1973 to 1976. The environmental effects of these pipelines are compared as are the relationships between engineering work, environmental impact assessment and planning procedures. There is also a discussion of methods used to protect and restore these three landfall areas.

Anchoring pipelines prevents damage

Abstract: Pinning the pipeline to the trench or seafloor by tensioned mechanical anchors is one solution to resisting water and soil forces either offshore or onshore on swampy or frequently flooded land. Furthermore, it reduces concrete-coating requirements, thus lowering the stress on pipe during laying. Anchoring also permits designing the pipe to withstand 100-year storms without excessive costs, eliminates lift and drag effects on the pipe by wave and current forces, and ensures that the line will remain where originally placed. For later maintenance, an anchored line is easier to find and less brittle than an unanchored pipe. Based on the pressure-distribution theory of mechanical anchoring, the system uses helical anchors on long anchor rods screwed into the subsoil on either side of the pipeline. Flanges at the head of the anchors engage a bracket between them that maintains tension on the pipeline, pinning it to the trench bottom. Measurements of the soil's load resistance - obtained by a portable soil-test probe - are essential to the design of an effective anchoring system.

Simultaneous wave and current forces on a pipeline

Abstract: The hydrodynamic loads on an offshore pipeline resting on the ocean bottom are a function of parameters associated with waves and currents acting near the pipeline. There have been many studies conducted to develop the criteria needed to estimate the hydrodynamic loads imposed by waves and currents. Many of these studies have investigated the effect of these phenomena individually, but to date only limited research has been directed towards evaluating the combined effect. In general, the investigations of the interaction of waves and currents and their effect on the fluid force have been directed toward vertical piles1'2'3'1*'5 and structures in a random wave field with a current present;6'7'8'9 however, the fluid force of waves in the presence of currents on pipelines has not been directly addressed. The purpose of this research was to investigate the interaction of waves and currents and its relationship to the forces on submerged pipelines. A model pipeline in a wave-flume was used to obtain experimental values which were compared to values predicted by the Morison equation in conjunction with the superposition of the waves and a current. The Morison equation10 was used to evaluate the forces on a horizontal cylinder resting on the bottom. The two major input parameters required by this equation are (1) the water particle kinematics of velocity and acceleration; and (2) the coefficients of drag and inertia. The testing program investigated the drag forces developed by the combined waves and a current. The inertia forces were assumed small when compared to the drag forces since a relatively small diameter cylinder was used in the experiments, thus the accelerations were small.

The Advent of the Autonomous Submarine Work Base

Abstract: Reasons leading up to the introduction of the commercial submarine into the offshore market place; difference between the autonomous submarine and surface supported submersibles; platform stability and power requirements; life support and payload capability. Description of the 28.5m, 168 tonne submarine AUGUSTE PICCARD with reference to geophysical investigations off the coasts of B.C. and Southern California; utilization of high resolution subbottom profiling; side scan sonar; precision echo sounding; long baseline acoustic navigation; and computer interface. Description of the second generation autonomous submarine ARGYRONETE; the subsea work base concept; manned subsea intervention to 1,000 feet; pipeline repair, wellhead, and subsea completion activity. Future developments in autonomous submarine technology during the 1980's; the BEN FRANKLIN; interface with wellhead cellars; ocean mining exploration.