Showing papers on "Submarine pipeline published in 2014"

Two-Dimensional Model for Pore Pressure Accumulations in the Vicinity of a Buried Pipeline

Abstract: In this paper, we presented an integrated numerical model for the wave-induced residual liquefaction around a buried offshore pipeline. In the present model, unlike previous investigations, two new features were added in the present model: (i) new definition of the source term for the residual pore pressure generations was proposed and extended from 1D to 2D; (ii) preconsolidation due to self-weight of the pipeline was considered. The present model was validated by comparing with the previous experimental data for the cases without a pipeline and with a buried pipeline. Based on the numerical model, first, we examined the effects of seabed, wave and pipeline characteristics on the pore pressure accumulations and residual liquefaction. The numerical results indicated a pipe with a deeper buried depth within the seabed with larger consolidation coefficient and relative density can reduce the risk of liquefaction around a pipeline. Second, we investigated the effects of a trench layer on the wave-induced seabed response. It is found that the geometry of the trench layer (thickness and width), as well as the backfill materials (permeability K and relative density Dr) have significant effect on the development of liquefaction zone around the buried pipeline. Furthermore, under certain conditions, partially backfill the trench layer up to one pipeline diameter is sufficient to protect the pipelines from the wave-induced liquefaction.

Centrifuge modelling of active slide–pipeline loading in soft clay

Abstract: Submarine slides are a significant hazard to the safe operation of pipelines in the proximity of continental slopes. This paper describes the results of a centrifuge testing programme aimed at studying the impact forces exerted by a submarine slide on an offshore pipeline. This was achieved by dragging a model pipe at varying velocities through fine-grained soil at various degrees of consolidation, hence exhibiting properties spanning from the fluid to the geotechnical domains, relevant to the state of submarine slide material. To simulate the high strain rates experienced by the soil while flowing around a pipe in the path of a submarine slide, tests were conducted at pipe–soil velocities of up to 4·2 m/s. The changing density and shear strength of the samples were back-calculated from T-bar penetrometer test results. A hybrid approach combining geotechnical and fluid-mechanics-based components of horizontal drag resistance was developed. This approach provides an improved method to link the density and ...

Ring–truss theory on offshore pipelines buckle propagation

Abstract: Buckle propagation is an essential concern in offshore pipeline design. Once the propagation occurs, it may cause unavoidable failure of an entire pipeline. With the consideration of both longitudinal and hoop deformation behavior of pipeline, a ring-truss theory was analytically established in this study. Laboratory experiments were conducted in full-scale hyperbaric chamber in order to verify the analytical equation. It was observed that the length of transition zone has great influence on determination of propagation pressure. Due to the difficulties of measurement during test process, the length of transition zone was obtained using the finite element simulation. The comparison of propagation pressure between the current study and published model shows that for small diameter to thickness ratio, the ring-truss model is the one that is closest to the actual situation.

Global lateral buckling analysis of idealized subsea pipelines

Abstract: In order to avoid the curing effects of paraffin on the transport process and reduce the transport difficulty, usually high temperature and high pressure are used in the transportation of oil and gas The differences of temperature and pressure cause additional stress along the pipeline, due to the constraint of the foundation soil, the additional stress can not release freely, when the additional stress is large enough to motivate the submarine pipelines buckle In this work, the energy method is introduced to deduce the analytical solution which is suitable for the global buckling modes of idealized subsea pipeline and analyze the relationship between the critical buckling temperature, buckling length and amplitude under different high-order global lateral buckling modes To obtain a consistent formulation of the problem, the principles of virtual displacements and the variation calculus for variable matching points are applied The finite element method based on elasto-plastic theory is used to simulate the lateral global buckling of the pipelines under high temperature and pressure The factors influencing the lateral buckling of pipelines are further studied Based upon some actual engineering projects, the finite element results are compared with the analytical ones, and then the influence of thermal stress, the section rigidity of pipeline, the soil properties and the trigging force to the high order lateral buckling are discussed The method of applying the small trigging force on pipeline is reliable in global buckling numerical analysis In practice, increasing the section rigidity of a pipeline is an effective measure to improve the ability to resist the global buckling

A Hydrodynamic and Sediment Transport Model for the Waipaoa Shelf, New Zealand: Sensitivity of Fluxes to Spatially-Varying Erodibility and Model Nesting

Abstract: Numerical models can complement observations in investigations of marine sediment transport and depositional processes. A coupled hydrodynamic and sediment transport model was implemented for the Waipaoa River continental shelf offshore of the North Island of New Zealand, to complement a 13-month field campaign that collected seabed and hydrodynamic measurements. This paper described the formulations used within the model, and analyzed the sensitivity of sediment flux estimates to model nesting and seabed erodibility. Calculations were based on the Regional Ocean Modeling System—Community Sediment Transport Modeling System (ROMS-CSTMS), a primitive equation model using a finite difference solution to the equations for momentum and water mass conservation, and transport of salinity, temperature, and multiple classes of suspended sediment. The three-dimensional model resolved the complex bathymetry, bottom boundary layer, and river plume that impact sediment dispersal on this shelf, and accounted for processes including fluvial input, winds, waves, tides, and sediment resuspension. Nesting within a larger-scale, lower resolution hydrodynamic model stabilized model behavior during river floods and allowed large-scale shelf currents to impact sediment dispersal. To better represent observations showing that sediment erodibility decreased away from the river mouth, the seabed erosion rate parameter was reduced with water depth. This allowed the model to account for the observed spatial pattern of erodibility, though the model held the critical shear stress for erosion constant. Although the model neglected consolidation and swelling processes, use of a spatially-varying erodibility parameter significantly increased export of fluvial sediment from Poverty Bay to deeper areas of the shelf.

Underground pipeline corrosion

Abstract: Underground pipelines transporting liquid petroleum products and natural gas are critical components of civil infrastructure, making corrosion prevention an essential part of asset-protection strategy. Underground Pipeline Corrosion provides a basic understanding of the problems associated with corrosion detection and mitigation, and of the state of the art in corrosion prevention. The topics covered in part one include: basic principles for corrosion in underground pipelines, AC-induced corrosion of underground pipelines, significance of corrosion in onshore oil and gas pipelines, numerical simulations for cathodic protection of pipelines, and use of corrosion inhibitors in managing corrosion in underground pipelines. The methods described in part two for detecting corrosion in underground pipelines include: magnetic flux leakage, close interval potential surveys (CIS/CIPS), Pearson surveys, in-line inspection, and use of both electrochemical and optical probes. While the emphasis is on pipelines transporting fossil fuels, the concepts apply as well to metallic pipes for delivery of water and other liquids. Underground Pipeline Corrosion is a comprehensive resource for corrosion, materials, chemical, petroleum, and civil engineers constructing or managing both onshore and offshore pipeline assets; professionals in steel and coating companies; and academic researchers and professors with an interest in corrosion and pipeline engineering.Reviews the causes and considers the detection and prevention of corrosion to underground pipesAddresses a lack of current, readily available information on the subjectCase studies demonstrate how corrosion is managed in the underground pipeline industry

Multi sensor underwater pipeline tracking with AUVs

Abstract: The exploitation of deep-water gas and oilfields is increasing. Pipelines transport the produced oil and gas onshore or transfer these between countries through the water. Underwater communication cables on the seafloor are the backbone of our intercontinental communication infrastructure. Sea cables transfer electrical energy from offshore production facilities or between countries and continents. This infrastructure of our economics and society can corrode or can get damaged. The status of these offshore pipelines and cables needs to be monitored regularly and damages need to be found and repaired quickly. This paper presents a method to guide an autonomous underwater vehicle with the information from different sensors including cameras, multibeam echo sounder (MBES), sub bottom profilers and magnetic sensors. Our online sensor fusion and tracking algorithms for underwater pipeline and cable inspection are based on probability maps which contain the location and the rating of each pipeline detection from every sensor. With these algorithms, we want to improve the regular pipeline inspection. The proposed system will be tested for its performance in simulation with different pipeline layout scenarios. Other applications for this map based fusion algorithm (beside pipeline and cable inspection) can be the mapping of toxic substances in the water column and the search of their sources.

The feasibility of a European-wide integrated CO2 transport network

Abstract: The European Union's ambition to achieve near-total decarbonization by 2050 suggests a large role for carbon capture and storage (CCS), requiring the transport (mostly by pipeline) of CO2 from source facilities to appropriate sites for geological storage. Here, a network modeling approach is used to test the scale, structure, and estimated costs of an integrated European CO2 transport network for different amounts of CCS deployment. Models are optimized with the sole objective of creating the least cost pipeline network that joins all sources to sufficient storage for a 25-year period of operation, and assume no restrictions on trans-boundary transport of CO2, or due to topographical constraints. Results show that extensive CO2 pipeline networks are required to deliver the CCS contribution to decarbonization. Sufficient storage is available but is distributed such that even for low levels of CCS deployment, both offshore storage and trans-boundary transport of CO2 are needed. Scenarios are run to test pipeline infrastructure requirements should onshore CO2 storage not be permitted, giving an estimated increase in CO2 transport infrastructure cost of 10–30% (€3–7 billion). Scenarios examining the effect of removing the more speculative storage potential in the Baltic, close to central and eastern European CO2 source clusters, reinforce the need to experimentally validate theoretical storage capacity estimates especially in the Baltic and North Sea.

Pockmark development in the Petrel Sub-basin, Timor Sea, Northern Australia: Seabed habitat mapping in support of CO2 storage assessments

Abstract: The extent to which fluids may leak from sedimentary basins to the seabed is a critical issue for assessing the potential of a basin for carbon capture and storage. The Petrel Sub-basin, located beneath central and eastern Joseph Bonaparte Gulf in tropical northern Australia, was identified as potentially suitable for the geological storage of CO2 because of its geological characteristics and proximity to offshore gas and petroleum resources. In May 2012, a multidisciplinary marine survey (SOL5463) was undertaken to collect data in two targeted areas of the Petrel Sub-basin to facilitate an assessment of its CO2 storage potential. This paper focuses on Area 1 of that survey, a 471 km2 area of sediment-starved shelf (water depths of 78 to 102 m), characterised by low-gradient plains, low-lying ridges, palaeo-channels and shallow pockmarks. Three pockmark types are recognised: small shallow unit pockmarks 10–20 m in diameter (generally

Submarine oil pipeline leakage system and method based on unmanned underwater vehicle

Abstract: The invention discloses a submarine oil pipeline leakage system and method based on an unmanned underwater vehicle. The system comprises a detection subsystem based on the unmanned underwater vehicle and a detection subsystem based on an underwater robot. The detection subsystem based on the unmanned underwater vehicle comprises the unmanned underwater vehicle and a pipeline position detection module and an oil overflowing detection module which are arranged on the unmanned underwater vehicle and is used for implementing large-area fast inspection. The detection subsystem based on an underwater robot comprises the underwater robot, an umbilical cable winding and unwinding module, a precision pipeline position detection module and a precision oil overflowing detection module and is used for implementing pipeline position detection, highly precision positioning and precision detection of micro leakage, and the precision pipeline position detection module and the precision oil overflowing detection module are arranged on the underwater robot. The system is high in detection speed and low in cost, and the requirements on offshore oil production safety can be met.

Third Party Damages of Offshore Pipeline

Abstract: Risk assessment is established to assist authorities in determining the priority of maintenance using risk which integrates both safety and failure. An efficient pipeline risk assessment should be able to characterize and calculate the risk associated with the pipeline. Unfortunately, the calculation of risk requires knowledge about the probability of failure and the consequence of failure. Both of which are difficult to estimate and in practical, the system under analysis cannot be characterized exactly. Numerical or objective data are often inadequate, highly uncertain and sometimes not available to perform calculations. To deal with this kind of situation effectively and consistently, a rigorous method of quantifying uncertainty using provided data is needed as well as to update existing information when new knowledge and data become available. In this paper, a probability analysis model of offshore pipeline failure due to third party damages is presented. The interaction between ship anchors, dropped objects and fishing gears are discussed. Bayesian networks model is proposed to determine the probability of third party damages to subsea pipelines. To generate the probabilities of different kind of nodes in a Bayesian network, a systematic probability approach is proposed with an emphasis on eliciting the conditional probability tables with multi-parents. The UK PARLOC database and DNV reports were used for the work. The paper concluded that Bayesian Network is a superior technique for risk analysis of pipeline failure. It is envisaged that the proposed approach could serve as a basis for decision making of pipeline maintenance.

Seabed characterization for the development of marine renewable energy on the Pacific margin of Canada

Abstract: An inventory of Canada's marine renewable energy resources based on numerical modeling of the potential tidal, wave and wind energy has been published that identifies areas with maximum resource potential. However, the inventory does not consider the seabed geological conditions that will control the safe development of seabed installations and cable corridors. The Geological Survey of Canada (Natural Resources Canada) has therefore undertaken an assessment of seafloor geological characteristics and physical environmental parameters that will be encountered during any extensive deployment of marine renewable energy systems for the Pacific offshore of Canada. Here we present an overview of seabed characterization for key sites for each of the three energy types. Narrow passages exiting the Salish Sea near the Canadian boundary with the United States and northwards out of the Strait of Georgia provide very promising sites for tidal generation. Here, elliptical fields of very large subaqueous dunes, from 12 to 28 m in height, present a significant challenge to site development. Along the exposed continental shelf of Vancouver Island focused wave-energy close to shore (40–60 m water depth) offers significant energy potential, but any engineering systems would have to be founded on a seafloor made up of a mobile gravel lag and an extensive boulder pavement. A large wind farm proposed for the Pacific North Coast would be built on an extensive shallow bank that has active sediment transport and a large field of sand ridges that have developed within a macrotidal environment. A significant challenge is providing for a safe seafloor cable corridor of over 100 km that crosses a large subaqueous dune field to connect to the electrical grid on the mainland. These examples show how geoscience has and will provide critical information to project proponents and regulators for the safe development of marine renewable energy.

Submarine Mass-Movements Along the Slopes of the Active Ionian Continental Margins and Their Consequences for Marine Geohazards (Mediterranean Sea)

Abstract: The Ionian margins of Calabria and Apulia (IMCA) have been affected by mass movements of varying style, scale and age. Here we present examples of seabed and subsurface features identified along more than 400 km of the IMCA from multibeam seabed imagery and subbottom profiles acquired by OGS since 2005. Four different types of mass movement phenomena are recognized with expression at seabed and in the shallow subsurface: (1) mass transport complexes (MTCs) within intra-slope basins, (2) isolated slide scars (ISS) along open slopes, (3) slope-parallel sediment undulations (SPSU) recording block-rotations linked to fluid migration, and (4) headwall and sidewall scarps (HSC) in submarine canyons. Preliminary analyses of sedimentary processes suggest that both open-slope failures capable of triggering tsunamis and retrogression of canyon headwalls within 1–3 km of the Calabrian coast represent potential geohazards for coastal populations and offshore infrastructures.

Study on dynamic response measurement of the submarine pipeline by full-term FBG sensors.

Abstract: The field of structural health monitoring is concerned with accurately and reliably assessing the integrity of a given structure to reduce ownership costs, increase operational lifetime, and improve safety. In structural health monitoring systems, fiber Bragg grating (FBG) is a promising measurement technology for its superior ability of explosion proof, immunity to electromagnetic interference, and high accuracy. This paper is a study on the dynamic characteristics of fiber Bragg grating (FBG) sensors applied to a submarine pipeline, as well as an experimental investigation on a laboratory model of the pipeline. The dynamic response of a submarine pipeline under seismic excitation is a coupled vibration of liquid and solid interaction. FBG sensors and strain gauges are used to monitor the dynamic response of a submarine pipeline model under a variety of dynamic loading conditions and the maximum working frequency of an FBG strain sensor is calculated according to its dynamic strain responses. Based on the theoretical and experimental results, it can be concluded that FBG sensor is superior to strain gauge and satisfies the demand of dynamic strain measurement.

Seabed friction on carbonate soils: Physical modelling of axial pipe-soil friction

Abstract: This paper is concerned with the 'friction' and 'sliding resistance' that can be mobilised on the unusual carbonate sediments prevalent across many parts of the world, including Offshore Australia. Physical centrifuge model testing was conducted to evaluate the axial pipe-soil resistance on a soil obtained from the North West Shelf, offshore Australia. Tests were performed at a range of speeds, spanning drained/undrained conditions, interspersed with consolidation periods. The resulting axial friction factors are generally higher than is often assumed in conventional design practice for pipeline end expansion or buckling and walking analysis, which is consistent with the high friction angles and dilatancy of these angular carbonate soils. In addition, the results demonstrate the effect that soil drainage response and history of pipeline sliding movements can have on the axial-pipe friction. Overall, the results highlight the importance of making site-specific assessments of seabed sliding resistance, rather than rely on non-sitespecific results (particularly from different regions) that may display a very different soil response. Lastly, recommendations are made for design assessments of the sliding resistance of carbonate soils.

Probabilistic seismic hazard analysis at a strategic site in the Bay of Bengal

Abstract: Probabilistic seismic hazard analysis (PSHA) along the route of an offshore pipeline for the transport of oil in the Bay of Bengal has been performed, in order to set up design parameters and identify possible geohazards. The complexity of geological and seismotectonic setting of the region where the pipeline is planned to be installed is the result of the interaction of the Indian, Eurasian and Burmese tectonic plates. In order to properly account for the intricate way by which these plates interact, a large area extending 450 km from the pipeline route has been considered for the compilation of a compre- hensive earthquake catalogue, spanning the period 1663-2012 AD. Differently from earlier PSHA analyses conducted in the region based on assuming two-dimensional polygons as seismogenic provinces, this study adopted a seismotectonic source model which also includes for the first time a linear tectonic lineament representing the northward extension of the Sunda mega thrust, responsible for the large Sumatra-Andaman earthquake of 26 December 2004. Hazard computations have been performed over a grid of sites spaced 0.045 covering a rectangular area which contains the pipeline. Epistemic uncertainty in the hazard computations has been taken into account by a logic tree framework, incor- porating different seismotectonic source models, maximum cut-off magnitude and ground- motion prediction equations. Horizontal median uniform hazard spectra and median uni- form hazard spectra plus and minus one sigma on stiff ground have been calculated at the selected sites for different return periods. Peak ground acceleration with 10 % probability of exceedance in 50 years has been compared with values from previous hazard studies available for Bangladesh.

Submarine pipeline detection device based on ROV platform

Abstract: The invention discloses a submarine pipeline detection device based on an ROV platform. The submarine pipeline detection device comprises a deck unit and an underwater detection device. The underwater detection device integrates a set of multi-beam sonar, a set of single-beam sonar, an optical imaging system, an illumination system, a CTD, an electronic compass, an acoustic beacon and an electrical system on the ROV platform. The multi-beam sonar is arranged in front of the ROV platform. The single-beam sonar is arranged below the ROV platform. By arranging two sets of two-dimensional foresight sonar, the resolution ratio of three-dimensional information including the distance, the angle and the depth can be obtained; abnormal points of a submarine pipeline can be accurately positioned through combination with data of the GPS, an ultra-short base line positioning system, the electronic compass and the CTD and through data calculation and analysis.