Showing papers on "Submarine pipeline published in 1999"

In situ burning

Abstract: Although there have been numerous incidents of vessel oil spills that inadvertently caught fire, the intentional ignition of oil slicks on open water has only been seriously considered since the development of fire-resistant oil containment boom beginning in the early 1980s. The development of these booms offered the possibility of conducting controlled burns in open water conditions. In situ burning operations using these booms have been conducted at three spills in the last decade: a major offshore tanker spill, a burning blowout in an inshore environment, and a pipeline spill into a river.

Numerical Model for Local Scour under Offshore Pipelines

Abstract: A numerical model, based on potential-flow theory is proposed for simulating the equilibrium scour hole formed by unidirectional flow underneath offshore pipelines. The model employs a finite-difference method to solve the Laplace equation in terms of velocity potential in a curvilinear coordinate system. A boundary adjustment technique based on the Newton-Raphson method is used to calculate the free boundary formed by the eroded seabed by means of the equilibrium of all forces acting on a sediment particle on a sloping bed. Because the solution of flow field and adjustment of the seabed topography are carried out in an iterative manner, the model takes into account the interactions between the flow, pipe, and the seabed. The comparison of the present model with empirical formulas on the prediction of the maximum scour depth indicates that the present model is useful for approximate estimation of scour depth at a pipeline on the seabed for the case of clear-water scour.

Scour under Submarine Pipelines in Waves in Shoaling Conditions

Abstract: Submarine pipelines, one of the most important subjects in coastal engineering, are widely used in coastal structures. In order to ensure these pipelines are stable and functional during their project life, attention must be paid to their design and coastal processes. In the design phase, the possibility of local scouring under submarine pipelines must be taken into consideration. If local scour occurs under the submarine pipelines, the pipelines may either vibrate due to the hydrodynamic forces or induce additional static or dynamic loads due to self-burial. Moreover, they might be destroyed partially or fully and thus be unable to perform their functions. This paper presents experimental investigations of scour depth with respect to water depth using regular waves. The investigations encompass shoaling region conditions. Results of the measurements of velocities and beach profiles are enlightening, both for understanding of the mutual interaction between the disturbed flow field around the pipe and the seabed morphology as well as in making predictions of scour depth around submarine pipelines. Based on the present experimental data, a new equation is proposed, relating the maximum equilibrium scour depth to the modified Ursell number for the live bed condition for a rigid pipe fixed initially in contact with the bed.

Lateral thermal buckling of pipelines on the sea bed

Abstract: Lateral buckling can occur in a submarine pipeline laid (without trenching) on the seabed, when the oil temperature rises. Motion of the (elastic) pipe relative to the sea bed is resisted by friction. The initial buckling is a localization phenomenon, and the first buckle lobes to form grow in amplitude most rapidly as the temperature increases. But as the temperature continues to rise, these early buckles cease growing, and growth is transferred to adjacent, newly formed lobes. The lobes first formed thus eventually become extinct, We investigate these phenomena by means of a small-scale physical model and by computer simulation. The results of many computer runs can be condensed into a few universal curves by the use of suitable dimensionless groups. Simple formulas emerge for the amplitude and wavelength of the extinct lobes, and for the maximum bending strain experienced by the pipeline, as a function of temperature.

Heat insulating device and method for insulating at least a submarine pipeline at great depth

Abstract: The invention concerns a heat insulating device for at least a submarine pipeline (1) designed to be laid on the seafloor at great depth, comprising an insulating coating enclosing it and protective sheath. The invention is characterised in that said insulating coating comprising a quasi-incompressible material (4) with liquid-solid phase change at a melting temperature T0 higher than that T2 of the medium around the pipeline (1) when it is in operation and lower than that T1 of the effluents circulating in the pipeline, and said material (4) being preferably impregnated in an absorbent matrix (2) enclosing the pipeline (1), preferably closest to its outer surface, which protective sheath (3) is resistant and deformable, and ensures confinement against and around said insulating coating.

Hydrocarbon potential in Indian deep waters

Abstract: Deep-water exploration is a natural step forward to assess and accrete hydrocarbon reserves after having accomplished this task to a certain extent along the continental shelf areas of India. In recent years Oil and Natural Gas Corporation Limited of India (ONGC) has made a gradual but steady progress in the deep-waters beyond the 200 m isobath exploring for hydrocarbons, acquiring multichannel seismic data and other geoscientific data. Hydrocarbon potential in the deep-water areas of five offshore basins viz. Kutch, Bombay, Kerala-Konkan, Cauvery and Krishna-Godavari is analysed in this paper. The evolution of these polycyclic basins was initiated as intracratonic rifts in divergent margins set up at different geological times. Later these basins acquired a pericratonic character evolving through typical syn-rift and post-rift phases. The recently acquired seismic data corroborate the extension of identified lineaments of onshore and shelf into deep-water areas, differentiating the deep-sea basinal region into segmented linear ridge-depression complexes. The sedimentary thickness in these deep-sea basins varies from 2 to 8 km, with thicker areas being near the shelf break and in areas over 2500 m water depth near the various river mouths in the basins. The hydrocarbon potential of deep-waters of India covering about 1.4 million km2 of the Indian offshore is estimated to be between 5.0-9.0 billion tons of oil and oil equivalent gas. Analysis of about 90,000 line km seismic data has helped in identifying and mapping the geological features such as submarine fans, turbidites, build-ups, wedge-outs, growth fault-related rollover anticlines and other structural features relevant to hydrocarbon prospectivity in these basins. These prospects range in area from 10 to 600 km2, in water depths from 300 to 2000 m. The average prospect size is about 200 km2 in the western offshore and about 20 km2 in the eastern offshore. Exploration of these will help in establishing a reserve base for India's future energy supply.

Floatation of Buried Pipeline Under Cyclic Loading of Water Pressure

Abstract: A dynamic response of a submarine pipeline buried in sandy seabed sediments to water loading generated by harmonically oscillating water-table vertical movements is examined experimentally and numerically. A parametric study was carried out in order to investigate the influence of depth of burial and specific gravity of pipeline on a gradual upward displacement of the pipeline. An analysis of the pipeline stability potential against floatation is presented, in which all the experimental cases tested are verified.

Wave Setup and Other Tidal Anomalies in Coastal Rivers

Abstract: The tailwater level is together with rainfall the most important input to flood modeling in coastal rivers. Thus, the needfor an ocean-river interface which can provide tailwater levels for numerical models is obvious. The state ofthe art is however not very advanced. Detailed waterlevel profiles through the Brunswick River entrance from 500m inside the breakwaters to 150m outside during a wide range of weather conditions revealed that the wave setup through the zone of wave breaking is much smaller than what is being used by practicing modelers in Australia. Barometric effects of the order lcm per hPa is only a minor part of the tidal anomalies, which range up to 0.8m 500m inside the breakwaters, and wind effects, although not modeled in detail, are estimated to be small on the fairly narrow continental shelf of South East Australia. Tidal anomalies of the order 0.5 to 0.7 metres have been observed in the absence of rainfall and strong local winds during Cyclone Roger in 1993. An offshore record indicated that a substantial fraction of this tidal anomaly (of the order 0.25m) also occurred in 25m of water offshore from the Tweed River on the border between New South Wales and Queensland. This indicates the presence of weather related oceanic forcing of a nature which is not understood in detail.

Pore pressure on a submarine pipeline in a cross-anisotropic nonhomogeneous seabed under water-wave loading

Abstract: Conventional investigations for the wave–seabed–pipe interaction problem have dealt with a uniform and isotropic seabed, despite the influences of anisotropic soil behaviour and variable soil chara...

Probabilistic Risk Prediction of Submarine Pipelines Subjected to Underwater Explosion Shock

Abstract: A simple procedure is proposed in this paper to estimate the global failure probabilities of a submarine oil pipeline subjected to underwater explosion shock wave. The deterministic response of a pipeline subjected to an underwater shock loading is first given by solving a simplified fluid-structure interaction problem. Compared with an FEM/BEM coupling model, the present method gives good results at much lower computational efforts. Then, the Monte Carlo method is used to find the global failure probabilities of the pipeline. Finally, a practical example is given.

Some effects of submarine pipeline construction on the sessile zoobenthic community of Redang Island

Abstract: A submarine pipeline, constructed in 1997–1998 to provide water to Redang Island, Malaysia traverses an area covered with corals. Biological studies were conducted before and following pipeline construction to monitor the changes in the biota at selected sites. Benthic invertebrates (including corals) were used as monitoring tools. Student's t-test and one-way ANOVA macroinvertebrates in pre- and post-construction analyses revealed that there was no significant difference in total abundance of sessile periods. Student's t-test revealed that there was a significant difference in mean of live coral coverage during pre and post-construction periods. There was no apparent change in total numbers of macroinvertebrates. Our results suggest only short-term impacts and recovery of the benthic community.

Mud Hole: A Unique Warm-Water Submarine Spring, Located Offshore Southwestern Florida

Abstract: Mud Hole Submarine Spring is an unusual warm-water submarine discharge of water offshore of the southwestern Gulf Coast of Florida, located at latitude 2615'48"N longitude 8201'06"W, or about 18.5 km due south of the Sanibel Island lighthouse, Lee County, Florida. This warm-water submarine spring oftentimes has a surface appearance of discolored turbid warm-water which is very attractive to large fish, sharks, turtles, sport fisherman, and scuba divers. The spring discharges warm water from many vents in a sinkhole depression about 61 m in diameter at about 19 m below NGVD. The bottom sediment consists of gray silt and mud atop sand and limestone gravel which, when disturbed, causes clouds of mud to be thrown into suspension, giving the spring the name "Mud Hole". Warm water flowing from several orifices has a constant temperature of 35.31C, pH of 7.25, and a salinity of 34.6 ppt (averaged hourly measurements during the period May 5 through June 17,1998). The plume extends about 1.5 m around the main orifice, about 1 m long by 0.3 m wide, with a velocity estimated at 0.6 m/s and a discharge of about 0.17 m3/s (4 million gallons/day). The total discharge from the whole depression is however considerably much larger. This study mapped the spring and measured physical water quality. The results indicated that the discharge movement is fault-related to the basement Sunniland Fracture Zone, based on the geology of southern Florida. The saline-water temperature of 35.3C indicates that the water comes from a considerable depth, as the surrounding seawater only averages 21C and onshore Upper Floridan aquifer water only ranges from 26.6C to 29.4C. The temperature profile in the oil-exploration well, State Lease #224B-1, located offshore north of Sanibel Island indicates that this temperature exists only at a depth greater than 500 m, that is, in the Boulder Zone of the Lower Floridan aquifer. This study concludes that the source is saline water migrating through faults extending from the basement Sunniland Fracture Zone and moving upwards through the section, mixing with the brackish cooler Floridan Aquifer, and eventually flowing from the spring. As no lithological gradient exists from east to west in southern Florida and higher water temperatures are found near major fault zones, the geothermally-activated convective flow cell hypothesis cannot be valid. Based on the data obtained in this study, the source is not considered the surficial aquifer as reported in the literature by some researchers.

Lower costs, environmental protection drive future pipeline technologies

Abstract: Constructing oil and gas pipelines onshore and offshore in the 21st Century will reflect efforts currently underway; developing more cost-effective technologies while mitigating environmental impact during construction and operation. This article details the path that implementation of a typical pipeline project normally follows, from route selection to construction, operation, and maintenance for both onshore and offshore pipeline projects.

Stress Analysis of Damaged Submarine Pipeline Using Finite Element Method

Abstract: The objective of this paper is to assess the stress level and consequent serviceability in the vicinity of a dry buckle caused by unknown accidental loads. A case study of a severely dented submarine pipeline, whose dent profile is known apriori, is presented in this paper. A finite element model has been generated with shell elements. Elasto-plastic analysis was carried out to simulate the probable magnitude of the equivalent static load due to the impact and corresponding stress level of the pipeline. The portion of the pipeline subjected to high locked-in stress is ascertained. Analysis has been performed with two different grades of the most commonly used material, viz. API 5L X-52 and X-60, to investigate the effect of SMYS (Specified Minimum Yield Stress) on the stress level and on the magnitude of equivalent static load.

Pipeline with waterproof insulation and sealant and method of repairing the pipeline

Abstract: A submarine pipeline that is insulated from the sea water by coating comprising at least one waterproof, insulating coating layer that comprises a waterproof sealant that flows under ambient pressure or thermal expansion into and seals voids or cracks in the waterproof insulating layer to prevent electrical faults in the coating.

Protecting the Sable Offshore Energy Project

Abstract: A project to develop one of the largest remaining known natural gas deposits in North America currently is underway in the Atlantic waters of Canada. The Sable Offshore Energy Project (SOEP) is a $3 billion venture to develop six major natural gas fields that lie 10 to 40 km north of the edge of the Scotian Shelf in waters 20 to 40 m deep. The project involves constructing and installing offshore platforms, drilling up to 30 wells, building onshore gas process facilities, laying 402 km (250 miles) of subsea pipeline, and providing comprehensive corrosion prevention. SOEP will produce natural gas and condensate, to be separated and processed at the Goldboro Gas Plant (Nova Scotia, Canada) into market-quality gas. The gas will then be carried by the Maritimes and Northeast Pipeline, a $1.7 billion, 1,051-km (653-mile) underground transmission pipeline, from Goldboro to markets in Nova Scotia, New Brunswick, and into the US through Maine and New Hampshire before interconnecting with the North American pipeline grid near Dracut, Massachusetts. The paper describes production, building the offshore products on platform, and corrosion concerns.

Mechanical pipeline span prop with suction anchor foundation

Abstract: A submarine pipeline freespan support, installable by special recoverable mechanical unit operated by WROV, incorporating a system of devices to enable a contiguous pile-column consisting of a hollow square section or other suitable rolled or fabricated section to be used. The pile is driven into the seabed by creating an under pressure within it by evacuation of water from it by means of a pump or by venting the water into a one atmosphere chamber. In cases where seabed soil conditions preclude this method of foundation, an articulated base can be fitted to the column which is still deployed by the same mechanical unit.

Submarine Slope Failure In a Fluid Migration Environment Offshore Gabon

Abstract: Deep exploration blocks of the Gulf of Guinea off West Africa were investigated. Survey data include swath bathymetry, deep towed high-resolution sub-bottom profiles, side-scan sonar images and Kullenberg core analysis. A slide was identified on seismic profiles. It is interpreted as a translational mass movement with a distinct failure surface at 25 m depth below the seafloor. Triggering factors were quantitatively investigated to explain the failure. However, rigorous assessment of the failure processes would require in-situ measurements as well as theoretical and experimental developments on the mechanical behavior of sediments in fluid-laden environments.

Submarine Topography and Geology around the Chubu International Airport off Tokoname City (Chita Peninsula) in Ise Bay, Central Japan

Abstract: Construction of the Chubu International Airport has started off Tokoname City (Chita Peninsula) in Ise Bay. Various surveys such as bathymetry, seafloor drilling, sonic prospecting, and geologic examinations of recovered borehole core samples, have been performed to reveal soil engineering characteristics, submarine topography, and submarine geology at the airport site (Chubu Kuukou Chousakai=The Chubu International Airport Research Foundation, 1994). Many fruitful results on the submarine geology have been obtained in these surveys, as follows : (1) The submarine topography is divided into the inshore “Upper submarine terrace”, “Offshore gently sloping sea floor”, and “Submarine scarp” between the two. A submarine channel is trenched southwards on the inshore submarine terrace.(2) The bay area is underlain by the A, B, C1, C2, and T Formations, in descending order. The T Formation is Mio-Pliocene Tokoname Group, the basement of the bay area. The Tokoname Group forms a buried wave-cut platform of a peninsular shape, which extends southwards. On the east side of the peninsular wave-cut platform, a submarine buried valley stretches southwards under the submarine channel and is mostly filled with the A Formation. On the west side of the wave-cut platform runs the Ise Bay Fault, and the A, B, C1, and C2 Formations thicken offshore.(3) The A Formation, which is divided into the A1 (upper), A2 (middle), and A3 (lower) Members, consists of marine muddy strata of the present bottom surface and is correlated with the Nanyo Formation below the Nohbi Plain (north of the Ise Bay). The A Formation is 25 to 35 meters thick, and the 14C ages range from 9, 400 to 5, 200 y. B.P. of Holocene age.The A3 and A2 Member intercalates the U-Oki and K-Ah tephra, respectively, both are widespread tephra layers in Japan.(4) The B Formation, which is divided into the B1 (upper), B2 (middle), B3 (lower), and B4 (base) Members, consists of sand beds and gravelly beds. The B1, B2, and B3 Members are correlated with the Nohbi and First Gravel Formations below the Nohbi Plain, respectively. The B4 Member forms a buried terrace on the west slope of the peninsular wave-cut platform and is correlated with the Toriimatsu or Ohzone Formations, Lower Terrace Deposits in the eastern margin of the Nohbi Plain. The B Formation is of late Pleistocene age.(5) The C1 Formation consists mainly of marine clay beds about 40 meters thick. The fossil pollen composition indicates that the C1 Formation is correlated with the lower part of the Atsuta Formation in the Nohbi Plain and is of middle Pleistocene age.(6) The C2 Formation consists of sand (upper) and gravelly (lower) beds and exceeds 50 meters thick. The fossil pollen composition indicates that the C2 Formation is correlated with the Ama Formation below the Nohbi Plain and is of middle Pleistocene age.(7) The basement T Formation (Tokoname Group) consists of alternating sand and compact mud beds and intercalates two volcanic ash layers, which are correlated with the Souri (upper, Sr) and Higashitani (lower, Hg) Volcanic Ash Layers from the conformity in index of volcanic glass. The Souri and Higashitani V. A. Ls are intercalated within the upper horizon of the Tokoname Group in the Chita Peninsula.(8) The Ise Bay Fault (faults and flexure zone), trending in the NNW-SSE direction, extends in the western margin of the bay area. The Tokoname Group on the east side of the fault trends northwest and gently dips northeast. The Utsumi Fault, trending in the WNW-ESE dircction, extends in the southern margin of the peninsula.The geological relationship between the Chita Peninsula and airport site in the above-mentioned results brings the following problems for further study.

Floatation of Buried Pipehne Under Cyclic Loading of Water Pressure

Abstract: Although the leyel of effectiye shear resistance in the A dynainic response of a submarine pipeline buried in sandy seabed contributes to the global safety condition agarnst pipe seabed sedinients to water loading generated by harmonicaliy hne floatation, the most important driying force, that can oscillating water table yertical moyements is examined exper induce pipehne yertical instability, is created by the waye imentally and nunierically. A parametric study was carried induced hydrodynamic yertical force acting on the pipeline, out in order to inyestigate the influence of depth of bunal and as a natural consequence of the waye induced yertical pore

The Europipe Landfall Project

Abstract: This chapter provides an overview of the natural gas pipeline network in the North Sea and the development of the European natural gas market. In addition, a more detailed description is given of the Europipe landfall project including the project planning and construction. Over the next few years a major offshore natural gas pipeline transportation system will be completed on the Norwegian continental shelf. From the gas fields, thousands of kilometers of large-diameter pipelines bring the natural gas to the European continent. The Europipe transportation system is a part of this integrated pipeline network designed to bring large amounts of Norwegian gas to several countries in Europe. The Europipe Transport System is owned by a joint venture including the companies Statoil, Norsk Hydro, Saga Petroleum, Esso, Shell, Total, Elf, and Conoco. Statoil is the operator of this joint venture.

Comprehensive Community Model for Physical Processes in the Nearshore Ocean

Abstract: : Our goal is to develop a comprehensive, verified community model that predicts Nearshore hydrodynamics, sediment transport, and seabed morphology changes given offshore wave conditions and initial bathymetry.