Showing papers on "Submarine pipeline published in 1983"

Subsea pipeline connection

Abstract: A method and apparatus are provided for laying an offshore pipeline or flowline bundle to a deepwater subsea structure. The pipeline or flowline bundle is laid along a prescribed path, preferably U-shape, such that a pullhead at the terminus of the pipeline or flowline bundle falls just short of the subsea structure. A pull-in tool connected to the pipeline or flowline bundle by a short length of pull cable is then landed on and latched to the subsea structure, and the pipeline or flowline bundle is pulled up to the subsea structure by the pull-in tool and pull cable.

Pipeline Reliability: An Investigation of Pipeline Failure Characteristics and Analysis of Pipeline Failure Rates for Submarine and Cross-Country Pipelines

Abstract: The most significant causes of pipeline failures are external forces (third-party damage), corrosion, and mechanical failures. Failure rates are virtually independent of the type of service and the operating environment; however, the rate of failure is inversely related to the diameter of the pipeline and directly related to its age: Corrosion (predominantly external) is a more frequent cause of failure for pipelines less than 20 in. in diameter than it is for larger pipelines. The most common sources of failure in the North Sea are damage by trenching equipment and by anchoring offshore vessels; most failures occur in shallow water and near platforms.

Underwater trencher with pipelaying guide

Abstract: A process and apparatus are provided for the simultaneous trenching and installation of submarine pipelines. The apparatus is based on a single unit which includes an excavating portion, an attached ditch sidewall retention shield, and a pipeline installation guide. The excavator creates a trench of a slightly larger cross section than required, the shield prevents the trench from closing due to the collapse of the sidewalls, and the pipe guide causes the pipeline to be deflected into that portion of the trench protected by the shield. The pipeline is fabricated on the surface of the sea or on floating ice, and is supported and guided to enter the forward portion of the shield by a stinger or other means, when required.

Handling two-phase gas condensate flow in offshore pipeline systems

Abstract: Special flow problems occur in offshore pipelines transmitting gas to processing plants onshore: as the hot, freshly produced gas cools en route, the pipeline pressure falls and the heavier hydrocarbons condense To aid drilling operators in designing condensate-separation and transport facilities, the following should be considered: (1) temperature behavior and two-phase flow in offshore lines, (2) condensate handling and slug-catcher design on booster platforms, (3) onshore separation terminal operation, and (4) the testing of industrial liquid separators

Emergency control method and device for oil leakage from submarine pipeline

Abstract: PURPOSE:To reduce the leakage of oil when a leak accident occurs by blowing up a submarine pipeline for transforming the steel pipe to reduce its sectional area. CONSTITUTION:An explosive 6 is laid on the periphery of a steel pipe 1 of a submarine pipeline, and on the explosive 6, an ultrasonic-wave-receiving fuse 5 whose operation electricity is supplied by the electric corrosion-proof operation of a sacrifice positive electrode 8 is arranged. For preventing an erroneous operation, the ultrasonic-wave-receiving fuse 5 is operated by an ultrasonic-wave signal of a specific frequency and a previously-specified pattern. When an accident of an great amount of leakage such as cutting in the pipeline or the like occurs, the above-said specific signal of ultrasonic wave is transmitted from a patrol boat 3 or the like to operate the fuse 5. Then, the explosive 6 is blown up, and the steel pipe 1 is crushed for reducing the oil leakage.

Exchange Flow of Oil and Sea-Water in a Ruptured Submarine Pipeline

Abstract: The rupture of a submarine oil pipeline starts var10US mechanisms leading to an oil spill. Among these mechanisms the leakage of oil driven by the difference in specific gravities of oil and seawater is difficult to quantify. A simple mathematical model has been developed and laboratory experiments have been carried out to obtain an insight into the density-driven exchange flow in a pipeline initially completely filled with oil, and to determine the leak rate. The mathematical model is predictive and takes account of various relevant effects, such as those of friction and inclination of the pipeline. The experiments were done in a horizontal model pipeline. Theoretical and experimental results are in satisfactory agreement.

The coaxial pipe electric heating system for pipelines

Abstract: To transport highly viscous crude oil efficiently through pipelines, some electric heating systems have been conventionally used. But they include heating cables or tubes, which are troublesome in submarine pipeline construction. A new electric heating system without a cable has been developed and is applicable to longdistance submarine pipelines. This system has a coaxial steel pipe structure, using the pipes as a heater by applying AC current to this coaxial circuit. In this paper, electromagnetic analysis on this system, experimental study using a 30-m length test pipeline, and mechanical tests on the electric insulating structure of the system are described.

Stresses of Pipelines During Earthquakes

Abstract: Construction of submarine pipelines plays an important role in offshore development Japan is famous for earthquake country It is very important to estimate the earthquake proof of the submarine pipelines An oil leakage causes the contamination of ocean if the submarine pipelines are damaged by earthquakes Pipe stresses during earthquakes are closely related to the relative displacement of the ground Field observation has been carried out to know the ground deformation Steel pipe is assumed to be buried along the observation line and pipe stresses are calculated from the ground deformation obtained by the field observation The stresses calculated by seismic deformation method that has been used for earthquake resistant design in Japan and by dynamic response analysis are compared with those from the observation

Buoyancy-driven leakage of oil from a ruptured submarine pipeline

Abstract: The rupture of a submarine oil pipeline starts various mechanisms leading to an oil spill. Among these mechanisms the leakage of oil driven by the difference in specific gravities of oil and sea-water is difficult to estimate. A simple mathematical model has been developed and laboratory experiments have been carried out to obtain an insight into the buoyancy-driven exchange flow and to determine the leak rate. The mathematical model is predictive and takes account of the effects of friction, inclination of the pipeline, and inertia of the fluid. The experiments were done in a model pipeline at various angles of inclination. Theoretical and experimental results are in satisfactory agreement.

Seismic and dynamic analyses for design of offshore pipelines traversing sloped bottom profiles

Abstract: Procedures are developed for determining initial failure criteria and the major flow dynamics information necessary in design of an offshore pipeline traversing sloped bottom profiles subject to both seismic activity and surface wave action. It is shown that customary two-parameter seismic specifications are not adequate to establish a unique solution for the stress and displacement history of the pipeline. Soil behavior under sustained and repeated loading and various factors influencing downslope movement of the soil are reviewed. Procedures for analysis of pore pressure generation and dissipation during loading and for analysis of instability and slope failure prior to liquefaction are discussed. The influences of total duration of load, magnitude and asymmetry of the stresses, number of load cycles, history of previous excitation and other factors are considered. Specifically, it is noted that in cohesionless soils, the proper analysis of pore pressure generation, failure and post failure downslope motions due to irregular cyclic loading depends on proper choice of at least three parameters: a design reference stress level, an appropriate corresponding anticipated number of loading cycles, and frequency of the cycles or total duration.

Pipeline shore approach analysis and design

Abstract: A rationalized method utilizing the theory of wave refraction and soil liquefaction is presented for the analysis and design of a pipeline shoreapproach. The bending of wave train due to bottom contours near shore and the liquefaction of marine soil during storm conditions are addressed as the basis of the pipeline stability analysis. Major decisions regarding pipe burial, installation method, weight coating, construction scheduling and cost effectiveness are closely related to the final design of the pipeline.

Design and construction of the Hondo sour gas pipeline

Abstract: This 6.9 mile long subsea pipeline is designed to deliver 60 MMSCFD of sour natural gas from Exxon's ''Hondo A'' platform, which stands in 850' of water in the Santa Barbara Channel, to an onshore gas processing plant in Las Flores Canyon, 20 miles west of Santa Barbara, California. This 12'' pipeline is the deepest water line from a platform to shore off the U. S. West Coast and is believed to be the third deepest line ever installed from a platform to shore. This paper covers details of the final pipeline design and also describes the installation of the offshore portion of the pipeline.

Design and Construction of a Submarine Ocean Outfall Pipeline off Ninety Mile Beach, Gippsland, Victoria

Abstract: Procedures necessary for the hydraulic and structural design of a submarine pipeline fitted with a multiport diffuser discharging saline wastewater to the ocean are presented. Elements considered include outfall location and alignment, discharge and dilution computations, ultimate dispersion, hydraulic design of diffuser ports, structural integrity to withstand wave and current forces, selection of pipe material and details of pipe support, bedding and backfill. Construction methods are outlined whereby the pipeline was laid, utilising flange jointed pipe lengths, at depths up to 7m below the seabed.

Statistical failure mode analysis of submarine pipeline accidents

Abstract: This study was conducted to investigate the appropriate exposure and system variables that affect the frequencies of submarine pipeline accidents and spills, the relationships among these variables, and the principal failure modes for individual pipeline classes. Available data on accidents, spills, pipeline inventory, and operational experience were used to compute annual and (diameter adjusted) mean accident rates, standard deviations, and confidence limits. Combined data for three dissimilar maritime regions indicate that a failure rate for oil and gas submarine pipelines of between one and ten incidents per 1,000 kilometers (km) per year probably represents a conservative estimate; however, the number of accidents in two of these regions was too small to provide statistically meaningful results. A more detailed analysis of Gulf of Mexico data recorded in the 1969-1980 period revealed that, while external factors such as severe weather and third party (man-made) activity accounted for nearly h...

Ultimate Strength of Pipes Subjected to Combined Loads (1 st Report)

Abstract: Submarine pipelines which transport oil and gas are now being installed or planed for more, and more deep waters. It was reported that planed crossing includes a Norweigian Trench crossing with depth to 350 m and trans-Mediterranean crossing with depth to 2, 000 m. Submarine pipelines to be installed at such depths will require the utmost care in engineering design.During a pipelaying operation, the pipe is subjected to the combined loads of bending, tension and external pressure. Considering the fact that bending stress during installation often reach the yield range, even though DNV Rules allow 0.2% residual longitudinal strain, it implies that this bending may become a collapse initiator. Furthermore, it should be considered that initial deformation reduce the resistance of pipeline against collapse, especially in deep water.A rigorous analytical treatment of the collapse strength of pipeline during installation is very complicated, because it is a function of loading conditions as well as D/t ratios, material properties, and initial deformation.In this paper a simplified analytical method, which was proposed by authors for evaluating the ultimate strength of stiffend plate, is extended in order to estimate the collapse strength of pipeline under the action of combined bending, axial force and external pressure, including the effect of initial out-of-roundness.The present method is compound of two parts. One is elastic analysis based on energy method, and the other is plastic analysis in which collapse mechanism is assumed. In both analysis large deformation is considerd.The following conclusions are obtained.1) Theoretical results are checked with available published data. It is confirmed that this proposed method is fairly efficient one.2) Since this proposed method is an analytical one that the complicated collapse strength of a pipe with out-of-roundness under combined loads can easily be estimated comparing with other numerical methods.3) Analytical results indicate that there exist two different collapse modes for pipelines under combined bending and external pressure. One of them is circumferential flattening of pipe cross section (circumferential collapse) and the other is so-called Brazier's type of failure (bending collapse).4) Analytical results show that both bending moment and axial tension considerably reduce the external pressure-bearing capacity.