Showing papers on "Submarine pipeline published in 1998"

Submarine pipeline for transporting petroleum products

Abstract: The invention concerns a pipeline comprising conduits (21, 22) wherein circulate petroleum products and a tubular protective sheath (1) wherein the conduits (21, 22) pass. It further comprises a packing (41, 42) in heat insulating material mechanically resistant to the hydrostatic pressure of the submarine site where the pipeline is installed, said packing ensuring the buoyancy required for laying the pipeline at reduced cost. The invention is applicable to a pipeline transporting petroleum products, installed at great depth.

Numerical simulation of submarine pipelines in dynamic contact with a moving seabed

Abstract: The dynamic response of submarine pipelines to earthquake-generated vertical seabed motions is examined with the aid of a finite element model. A relaxation algorithm is adopted in order to overcome the problem of unknown dynamic seabed reaction forces. Rotational rigidity is assumed at the boundary points, which are allowed to move vertically in unison with the random seabed oscillations. For the interior nodes, the description of the kinetic energy loss, resulting from pipeline-seabed impact, is approached through the use of a restitution coefficient of 0.5, which represents an intermediate collision mode between a perfectly elastic and an inelastic one. Fundamental system frequencies are determined by the use of support positions obtained from a static analysis of the unilaterally constrained structure. The structural damping matrix is approximately evaluated according to Rayleigh's method. Response spectra to a strong motion vertical acceleration earthquake record provide an initial guideline into the pipeline stability. Peak dynamic and static bending stresses are calculated for a case study involving two submarine pipeline crossings. Complete, partial and lack of pipeline gravel cover is assumed in the analysis. A seabed profile alteration, due to probable soil liquefaction, is furthermore imposed, in order to investigate the subsequent effect upon the dynamic pipeline stresses.

Wax deposition in offshore pipeline systems

Abstract: This paper describes a model developed to predict wax deposition in wells and pipelines. The simulation model uses a standard steady state multi-phase point model to predict pressure drop and liquid hold-up along the pipeline. By integration in time, the effect of wax deposition on pressure drop and temperature is calculated. A multi-component wax model is used to continuously estimate the wax precipitation along the pipeline and the viscosity of the current composition. The wax deposition is estimated from the diffusion of wax from the bulk towards the wall as a result of temperature gradients as well as shear dispersion effects. Varying inner pipe wall friction due to wax deposition is also included. The model has been applied to a number of single phase and multi-phase wells and pipeline systems. Two such cases are discussed in this paper. Wax build-up, temperature and pressure drops over time have been simulated in each case. (author)

Flexible offshore pipeline with a bituminous thermal insulating layer

Abstract: An improved, cost-effective, insulated flexible pipeline that is insulated with a bituminous composition.

Strain-Based Pipeline Design Criteria Review

Abstract: The new Canadian limit states pipeline design standard (CSA Z662-96, Appendix C - Limit States Design) incorporates deformation or strain-based design criteria to prevent pipe rupture and or buckling and limit ovality due to bending. These criteria are different and in some instances, much more conservative than those contained in the Canadian offshore pipeline design standard (chapter 11 of CSA Z662-96) and similar standards used in other countries. This study was completed to review the ovality, buckling (including wrinkling) and rupture criteria included in current Canadian pipeline design standards (CSA Z662-96) and define its basic differences with respect to other standards.The deformation or strain based design criteria formulations in Z662 are compared with those contained in design standards, industry association recommendations and classification society rules from Norway, Britain, Germany, Australia and the USA to illustrate their differences and relative levels of conservatism. In addition, current and on-going research efforts were reviewed to identify the state-of-the-art in pipeline strain-based design, since this research could form the basis for future amendments to existing pipeline design standards.Based on the findings of this review, recommended changes to the limit states pipeline design formulation are given to better reflect the strain-based (non-linear or post-yield) design and assessment approaches included in the Canadian offshore or foreign pipeline design approaches. In addition, an analytical basis for pipeline ovality and buckling design criteria are recommended.Copyright © 1998 by ASME

Gas-Hydrates - A Synoptic View

Abstract: Large-scale occurrence of gas-hydrates in the marine sediments of outer continental margins is by now well-known. While the methods of tracing gas-hydrate enriched zones, like identifying markers such as bottom simulating reflectors and blanking zones on seismic reflection sections, are well-established, quantification and resource assessment of gas hydrates still remain hazy. Investigations over the classical gas-hydrate enriched Blake outer ridge on the U.S. Atlantic margin have provided new insights into the environs of gas-hydrate occurrences. Deep sea drilling results in this area indicate that the estimates of gas-hydrate from geophysical measurements could be less by an order of three in comparison with those obtained from drilling. Several factors like bathymetry, sediment thickness and sedimentation rates, sea bottom temperature and total organic carbon content, which control gas-hydrate formation, indicate that the shallow sediments in the offshore regions of India could be potentially enriched in gas hydrates. National agencies like the Oil & Natural Gas Corporation, Gas Authority of India Ltd., National Geophysical Research Institute, National Institute of Oceanography and others are now actively involved in assessing the true potential of this anticipated future energy resource. The environmental aspects of gas hydrates like large-scale release of methane gas into the air and slope instabilities and submarine landslides in the continental margins resulting in catastrophic events, however, need to be kept in mind.

Wave-Induced Pore-Pressure Response on a Submarine Pipeline Buried in Seabed Sediments - Experiment and Numerical Verification -

Abstract: The response on sandy seabed sediments to a harmonically oscillating water-table, with a special consideration of the wave-induced pore-pressure oscillations around a pipeline buried in seabed sediments, is studied in the present work experimentally and numerically. The aim of the analysis was: (1) to observe a true distribution pattern of the wave-induced pore-pressure oscillations acting on the pipeline outer surface, and (2) to verify small-scale test results using numerical computations performed for a wide range of saturation conditions of seabed sediments, under the assumption of a compressible two-phase medium compound of the pore-fluid and soil skeleton, as well as a finite thickness of a permeable seabed layer.

Method for drilling bedrock using guide pole installed on offshore platform

Abstract: PROBLEM TO BE SOLVED: To accurately drill bedrock at high speed and at low cost without being effected by tidal current, in drilling submarine bedrock at a part where a pier foundation caisson is installed for a marine bridge construction project. SOLUTION: An offshore platform 1 is installed on seabed ground T, and a guide pole 4 is pressed against the submarine ground T from the offshore platform 1 through a guide pole gripping device 3 installed on the moving truck 2 of the offshore platform 1 and traversing on the moving truck 2. A twin-drum load header 11 fitted to the end of the horizontal expansion frame 8 of a horizontal frame 5 hoisted down to a predetermined depth in sea is expanded and contracted in the vertical direction and is moved by the turning movement and horizontal expansion and contraction of the horizontal frame 5 to drill the submarine ground.

Lateral thermal buckling of pipelines

Abstract: Subsea oil and gas exploration is increasingly moving into deeper water, where trenching of a pipeline for protection and to mitigate against upheaval buckling becomes increasingly impractical In addition, the exploration of new reservoirs at higher temperatures and pressures than before leaves a submarine pipeline on the seabed more susceptible to lateral thermal buckling. A novel small-scale compressible base model, with an expanded polystyrene base compressed beneath a silicone rubber strip, has been developed to represent the constrained thermal loading of a pipeline lying on the seabed. This physical model is used, in addition to a nonlinear finite-element analysis, for a case study of a real buckled pipeline. Dimensional analysis is used to provide a means of comparing the post-buckled behaviour of the model strip with that of the fullsize pipeline. There is good agreement between the results of the post-buckled behaviour for the physical and finite-element models, and these results compare well with the survey data for the buckled real pipeline. General results from the physical model are also presented for strips with differing geometric and material properties, laid both straight and on a scaled lay-away curve. A useful measure of the evolution of a buckle, the free end displacement, is introduced. This is the axial displacement of the free end of a cut pipe, constrained to remain straight while undergoing thermal loading. This measure used in a study of the parameters which affect the far-post-buckling behaviour of a beam on a frictional foundation. The phenomenon of buckle lobe extinction, when a buckle lobe stops growing, is discovered for certain combinations of beam bending stiffness, axial friction coefficient and lateral friction coefficient. When the buckle length, buckle amplitude and free end displacement are formed into non-dimensional groups with these three parameters, curves for many parameter combinations are found to fall onto a single curve. The conditions for buckle lobe extinction, in terms of these dimensionless groups, may be determined directly from this universal curve. Finally, the closely-related problem of the stability of a pipeline being built up a slope is investigated. A case study is made of a real pipeline, incorporating numerical and physical models and also a simplified analytical model These models correlate well with each other, and enable the conditions for collapse of the real pipeline to be predicted.

1997 Annual Report: Environmental Monitoring Program Louisiana Offshore Oil Port Pipeline

Abstract: The Louisiana Offshore Oil Port (LOOP) Environmental Monitoring Program includes an onshore pipeline vegetation and wildlife survey as a continuing study designed to measure the immediate and long-term impacts of LOOP-related pipeline construction and operation on surrounding wetland plant communities and associated waterfowl, wading-bird, fur bearing mammal, and alligator populations. In 1997, the authors sampled the vegetation biomass in the intermediate salinity zone of the LOOP pipeline. They then analyzed the intermediate vegetation biomass data collected from 1978 through 1997. They included controls to assess "baseline" change rates in the absence of the pipeline because any impacts of the LOOP pipeline occur within a rapidly changing wetland ecosystem. The controls were compared to areas adjacent to the pipeline to test for any pipeline effects. In the marshes surrounding the Clovelly salt dome the authors assessed plant species and cover to characterize the spatial patterns of vegetation occurrence. Because the frequency of waterfowl and wildlife censusing was reduced to once every three years, semi-annual pipeline corridor overflights by trained wetland biologists were conducted in the 1997 monitoring program.

New gulf pipeline begins feeds to louisiana processing

Abstract: A $350 million gas gathering and processing system began its start-up sequence at the end of September, flowing wet gas from Gulf of Mexico producers offshore Louisiana to processing and marketing onshore. The Discovery project marks the first major grassroots offshore gathering and processing system along the Louisiana Gulf Coast in more than a decade. The system is fed by a new 105-mile, 30-in. main line that reaches the edge of the Outer Continental Shelf at Ewing Bank 873 and brings raw gas ashore to a cryogenic gas-processing plant near Larose, La., 35 miles south of New Orleans. With ultimate capacity of 900 MMcfd and a maximum water depth of 785 ft, Discovery`s line ranks as the deepest 30-in. (or larger) line in the gulf. An expansion scheduled for 1999 will extend the pipeline system farther offshore, accessing deepwater wells (3,200 ft deep) at Green Canyon 254. The paper discusses ownership, development, the pipeline, processing, fractionation, and construction.

Offshore pipeline risk and consequence assessment

Abstract: There are several modes of transporting oil produced offshore to the processing site onshore. In doing so there are risks that oil spill might happen. In this paper offshore pipeline as a mode of transporting oil from an offshore oilfield to the landfall site is being considered. The study also concerns the impact on the environment from the sources of damage to the subsea pipeline to the landfall site. Mitigative measures in the event of oil spills are also discussed. In addition hazard that are associated with the operational phase of the project are also identified.

Non‐linear finite element simulations of highly curved submarine pipelines

Abstract: A non-linear finite element numerical procedure is adopted for predicting the bending stresses developed along highly curved submarine pipelines during the installation process from a laybarge towards an irregular sea floor. The problem of partial seabed-pipeline and stinger-pipeline contact is tackled by means of a point iterative calculation approach. The geometric non-linearity embedded in the beam flexural theory enables major deformations of the submarine line structures to be accurately modelled. Numerical calculations tend to be demanding, especially when large differences occur between the pipeline and seabed configurations. Three structural problems of practical significance provide a suitable application platform for testing the efficiency of the mathematical model. A Fortran subroutine implementing the fundamental procedures of the proposed numerical theory is included. Copyright © 1998 John Wiley & Sons, Ltd.

Optimised float-out of concrete offshore platforms towards increasing construction potential in Australia

Abstract: With the increasing number of significant oil and gas discoveries in Western Australia and the Northern Territory, there is a predicted demand for a range of concrete gravity structures (CGSs) from the Carnarvon to the Browse Basins and the Timor Sea. Shallow founded CGSs may be installed in soft or hard seabed conditions, with the softer conditions typically found in deeper water and requiring protruding skirt structures to penetrate the seabed to improve stability and provide scour resistance. Such open bottom structures are floated by displacing water inside the skirted compartments with compressed air. Where construction and float-out are done in shallow water, small underkeel clearance (UKC) is likely. Wave induced motions of both the structure and the water plug inside the skirted compartments have to be accommodated to ensure that the structure does not touch the seabed and that the water plug motions do not promote the escape of air from compartments. Pilot research into the dynamics of CGSs with small UKC has been completed and this has identified some very important parameters for inclusion in the design loop of CGSs. The research also identified parameters worthy of more thorough research and with the potential to advance the knowledge base in this area and thus provide local industry with a competitive advantage.

Baldpate lands in the limelight

Abstract: The construction and installation of the Baldpate-compliant tower is described in this paper. This new form of deepwater offshore structure, the world`s tallest free-standing structure will be located in the Gulf of Mexico. Water depth limits for the new tower exceed those possible with the traditional steel jacket, and it is ballasted to make it storm-safe. A pipeline to the Poseidon system, 17 miles away is used to export the oil produced. (UK)

Loop Marine and Estuarine Monitoring Program, 1978–95: Volume 2: Water Chemistry

Abstract: This is Volume 2, Water Chemistry, of a six volume set that includes: Volume 1: Executive Summary; Volume 2: Water Chemistry; Volume 3: Physical Hydrography; Volume 4. Zooplankton and Ichthyoplankton; Volume 5: Demersal Nekton; and Volume 6. Sediment Quality. The Louisiana Offshore Oil Port (LOOP) facilities in coastal Louisiana provide the United States with the country's only Superport for off-loading deep draft tankers. The three single-point mooring (SPM) structures connected by pipelines to a platform mounted pumping station are located west of the Mississippi River delta, 30 kilometers southeast of Belle Pass in the Gulf of Mexico, in 36 meters of water, where the offshore depth contours fold landward. Pumping stations offshore and at the land-based Fourchon Booster Station move the off-loaded crude via subsurface pipeline to a storage facility located in the intermediate marsh zone of the northern Barataria Bay watershed. The proposed construction and use of these facilities in an environmentally sensitive area led to questions about various consequential environmental impacts. A water quality environmental sampling program was established by the state of Louisiana to monitor the inshore and offshore area potentially impacted by the project. This water chemistry analysis is part of the water quality monitoring program.

Breccia hazards in the South Caspian Basin

Abstract: Ejection of breccia from mud volcanoes for the onshore and offshore South Caspian Basin provides hazards for rigs, pipeline, and subsea completion equipment. Here we investigate the lateral ranges of ejected rock fragments for aeolian and submarine conditions. In addition, the consequences are considered of emission from a raised or depressed crater, with or without a surrounding crater wall. Also investigated is aeolian transport to an ocean surface, and subsea motion thereafter. Rough rules of thumb for aeolian hazards from breccia would indicate that seconds to tens of seconds after breccia emission is the onset time of hazard, with hazard distances typically of order a few hundred meters, but occasionally reaching about a kilometer or so for fairly large (5 kg) rocks emitted at high (∼500 m/s) speeds, with impact speeds of order 10-100 m/s. Submarine hazards yield 0.1-4 m/s impact speeds on the ocean floor for water depths in excess of about 2 m. For shallower water depths the aeolian impact speed is a good approximation. The hazard potential to equipment from breccia is one of concern, with a worst case distance estimate of about 1 km from the ejection point.

Tomographic Imaging of the Shear Wave Velocity Structure of the Shallow Seabed of the New Jersey Continental Shelf

Abstract: : The long term goals of this project are to map the three-dimensional, shear-wave velocity structure of the upper 50-100 m of the seabed, to correlate these measurements with geological structure, and to use the spatial variability in shear-wave structure to understand the depositional and erosional processes responsible for the measured structure. The objective of this work is to carry out a three-dimensional refraction/interface-wave tomography experiment on the continental shelf offshore New Jersey in an area that has been extensively surveyed with high-resolution, seismic reflection imaging techniques. The motivation is our belief that, in many geological settings, the internal structure and geometry of sedimentary facies are sufficiently complex that they can be determined only by carrying out a three-dimensional experiment. Mapping the geometry of these sedimentary facies is an essential component to any study that aims to provide physical constraints on the processes governing sediment deposition and erosion and their evolution over time.