Showing papers on "Submarine pipeline published in 2007"

Construction of Marine and Offshore Structures

Abstract: INTRODUCTION General Geography Ecological Environment Legal Jurisdiction Offshore Construction Relationships and Sequences Typical Marine Structures and Contracts Interaction of Design and Construction PHYSICAL ENVIRONMENTAL ASPECTS OF MARINE AND OFFSHORE CONSTRUCTION General Distances and Depths Hydrostatic Pressure and Buoyancy Temperature Seawater and Sea-Air Interface Chemistry Currents Waves and Swells Winds and Storms Tides and Storm Surges Rain, Snow, Fog, Spray, Atmospheric Icing, and Lightning Sea Ice and Icebergs Seismicity, Seaquakes, and Tsunamis Floods Scour Siltation and Bed Loads Sabotage and Terrorism Ship Traffic Fire and Smoke Accidental Events Global Warming GEOTECHNICAL ASPECTS: SEAFLOOR AND MARINE SOILS General Dense Sands Liquefaction of Soils Calcareous Sands Glacial Till and Boulders on Seafloor Overconsolidated Silts Subsea Permafrost and Clathrates Weak Arctic Silts and Clays Ice Scour and Pingos Methane Gas Muds and Clays Coral and Similar Biogenic Soils Cemented Soils, Cap Rock Unconsolidated Sands Underwater Sand Dunes ("Megadunes") Bedrock Outcrops Cobbles Deep Gravel Deposits Seafloor Oozes Seafloor Instability and Slumping Turbidity Currents Scour and Erosion Concluding Remarks ECOLOGICAL AND SOCIETAL IMPACTS OF MARINE CONSTRUCTION General Oil and Petroleum Products Toxic Chemicals Contaminated Soils Construction Wastes Turbidity Sediment Transport, Scour, and Erosion Air Pollution Marine Life: Mammals and Birds, Fish, and Other Biota Aquifers Noise Highway, Rail, Barge, and Air Traffic Protection of Existing Structures Liquefaction Safety of the Public and Third-Party Vessels Archaeological Concerns MATERIALS AND FABRICATION FOR MARINE STRUCTURES General Steel Structures for the Marine Environment Structural Concrete Hybrid Steel-Concrete Structures Plastics and Synthetic Materials, Composites Titanium Rock, Sand, and Asphaltic-Bituminous Materials MARINE AND OFFSHORE CONSTRUCTION EQUIPMENT General Basic Motions in a Seaway Buoyancy, Draft, and Freeboard Stability Damage Control Barges Crane Barges Offshore Derrick Barges (Fully Revolving) Semisubmersible Barges Jack-Up Construction Barges Launch Barges Catamaran Barges Dredges Pipe-Laying Barges Supply Boats Anchor-Handling Boats Towboats Drilling Vessels Crew Boats Floating Concrete Plant Tower Cranes Specialized Equipment MARINE OPERATIONS Towing Moorings and Anchors Handling Heavy Loads at Sea Personnel Transfer at Sea Underwater Intervention, Diving, Underwater Work Systems, Remote-Operated Vehicles (ROVs), and Manipulators Underwater Concreting and Grouting Offshore Surveying, Navigation, and Seafloor Surveys Temporary Buoyancy Augmentation SEAFLOOR MODIFICATIONS AND IMPROVEMENTS General Controls for Grade and Position Seafloor Dredging, Obstruction Removal, and Leveling Dredging and Removal of Hard Material and Rock Placement of Underwater Fills Consolidation and Strengthening of Weak Soils Prevention of Liquefaction Scour Protection Concluding Remarks INSTALLATION OF PILES IN MARINE AND OFFSHORE STRUCTURE General Fabrication of Tubular Steel Piles Transportation of Piling Installing Piles Methods of Increasing Penetration Insert Piles Anchoring into Rock or Hardpan Testing High Capacity Piles Steel H Piles Enhancing Stiffness and Capacity of Piles Prestressed Concrete Cylinder Piles Handling and Positioning of Piles for Offshore Terminals Drilled and Grouted Piles Cast-in-Drilled-Hole Piles, Drilled Shafts Other Installation Experience Installation in Difficult Soils Other Methods of Improving the Capacity of Driven Piles Slurry Walls, Secant Walls, and Tangent Walls Steel Sheet Piles Vibratory Pile Hammers Micropiles HARBOR, RIVER, AND ESTUARY STRUCTURES General Harbor Structures River Structures Foundations for Overwater Bridge Piers Submerged Prefabricated Tunnels (Tubes) Storm Surge Barriers Flow-Control Structures COASTAL STRUCTURES General Ocean Outfalls and Intakes Breakwaters Offshore Terminals OFFSHORE PLATFORMS: STEEL JACKETS AND PIN PILES General Fabrication of Steel Jackets Load-Out, Tie-Down, and Transport Removal of Jacket from Transport Barge Lifting Launching Upending of Jacket Installation on the Seafloor Pile and Conductor Installation Deck Installation Examples CONCRETE OFFSHORE PLATFORMS: GRAVITY-BASE STRUCTURES General Stages of Construction Alternative Concepts for Construction Sub-Base Construction Platform Relocation Hybrid Concrete-Steel Platforms PERMANENTLY FLOATING STRUCTURES General Fabrication of Concrete Floating Structures Concrete Properties of Special Importance to Floating Structures Construction and Launching Floating Concrete Bridges Floating Tunnels Semi-Submersibles Barges Floating Airfields Structures for Permanently Floating Service Marinas Piers for Berthing Large Ships Floating Breakwaters Mating Afloat OTHER APPLICATIONS OF MARINE AND OFFSHORE CONSTRUCTION TECHNOLOGY General Single-Point Moorings Articulated Columns Seafloor Templates Underwater Oil Storage Vessels Cable Arrays, Moored Buoys, and Seafloor Deployment Ocean Thermal Energy Conversion Offshore Export and Import Terminals for Cryogenic Gas-LNG and LPG Offshore Wind-Power Foundations Wave-Power Structures Tidal Power Stations Barrier Walls Breakwaters INSTALLATION OF SUBMARINE PIPELINES General Conventional S-Lay Barge Bottom-Pull Method Reel Barge Surface Float Controlled Underwater Flotation (Controlled Subsurface Float) Controlled Above-Bottom Pull J-Tube Method from Platform J-Lay from Barge S-Curve with Collapsible Floats Bundled Pipes Directional Drilling (Horizontal Drilling) Laying Under Ice Protection of Pipelines: Burial and Covering with Rock Support of Pipelines Cryogenic Pipelines for LNG and LPG PLASTIC AND COMPOSITE PIPELINES AND CABLES Submarine Pipelines of Composite Materials and Plastics Cable Laying TOPSIDE INSTALLATION General Module Erection Hookup Giant Modules and Transfer of Complete Deck Float-Over Deck Structures REPAIRS TO MARINE STRUCTURES General Principles Governing Repairs Repairs to Steel Structures Repairs to Corroded Steel Members Repairs to Concrete Structures Repairs to Foundations Fire Damage Pipeline Repairs STRENGTHENING EXISTING STRUCTURES General Strengthening of Offshore Platforms, Terminals, Members and Assemblies Increasing Capacity of Existing Piles for Axial Loads Increasing Lateral Capacity of Piles and Structures in Soil-Structure Interaction Penetrations Through Concrete Walls Seismic Retrofit REMOVAL AND SALVAGE Removal of Offshore Platforms Removal of Piled Structures (Terminals, Trestles, Shallow-Water Platforms) Removal of Pile-Supported Steel Platforms Removal of Concrete Gravity: Base Offshore Platforms New Developments in Salvage Techniques Removal of Harbor Structures Removal of Coastal Structures CONSTRUCTIBILITY General Construction Stages for Offshore Structures Principles of Constructibility Facilities and Methods for Fabrication Launching Assembly and Jointing Afloat Material Selection and Procedures Construction Procedures Access Tolerances Survey Control Quality Control and Assurance Safety Control of Construction: Feedback and Modification Contingency Planning Manuals On-Site Instruction Sheets Risk and Reliability Evaluation CONSTRUCTION IN THE DEEP SEA General Considerations and Phenomena for Deep-Sea Operations Techniques for Deep-Sea Construction Properties of Materials for the Deep Sea Platforms in the Deep Sea: Compliant Structures Tension-Leg Platforms (TLP's) SPARS Ship-Shaped FPSOs Deep-Water Moorings Construction Operations on the Deep Seafloor Deep-Water Pipe Laying Seafloor Well Completions Deep-Water Bridge Piers ARCTIC MARINE STRUCTURES General Sea Ice and Icebergs Atmospheric Conditions Arctic Seafloor and Geotechnics Oceanographic Ecological Considerations Logistics and Operations Earthwork in the Arctic Offshore Ice Structures Steel and Concrete Structures for the Arctic Deployment of Structures in the Arctic Installation at Site Ice Condition Surveys and Ice Management Durability Constructibility Pipeline Installation Current Arctic Developments REFERENCES INDEX

Analysis of slope failures in submarine canyon heads: An example from the Gulf of Lions

Abstract: To improve understanding of evolution of submarine canyons, a three-dimensional slope-stability model is applied to Bourcart Canyon in the western Gulf of Lions in the Mediterranean Sea. The model builds on previous work by Chen and others, and it uses the upper bound theorem of plasticity to calculate the factor of safety of a kinematically admissible failing mass. Examples of three-dimensional failure surfaces documented in the literature were used to test the model formulation. Model application to Bourcart Canyon employed the results of a detailed stratigraphic analyses based on data acquired by swath bathymetry, sub-bottom profiling, high-resolution seismic reflection surveys, and piston coring. The sediment layers were also characterized using in-situ geotechnical measurements and laboratory tests. The effects of three loading scenarios were analyzed: (1) earthquake shaking, (2) hemipelagic sedimentation, and (3) axial incision. These three mechanisms influenced the predicted volumes and shapes of slope failures along the flanks of Bourcart Canyon, and comparison of these predictions with failure geometries inferred from seafloor morphology showed that mass failures could account for the observed morphology along the canyon walls as well as a mechanism of canyon widening

Modelling offshore sand wave evolution

Abstract: We present a two-dimensional vertical (2DV) flow and morphological numerical model describing the behaviour of offshore sand waves. The model contains the 2DV shallow water equations, with a free water surface and a general bed load formula. The water movement is coupled to the sediment transport equation by a seabed evolution equation. Using this model, we investigate the evolution of sand waves in a marine environment. As a result, we find sand wave saturation for heights of 10–30% of the average water depth on a timescale of decades. The stabilization mechanism, causing sand waves to saturate, is found to be based on the balance between the shear stress at the seabed and the principle that sediment is transported more easily downhill than uphill. The migration rate of the sand waves decreases slightly during their evolution. For a unidirectional steady flow the sand waves become asymmetrical in the horizontal direction and for a unidirectional block current asymmetrical in the vertical. A sensitivity analysis showed the slope effect of the sediment transport plays an important role herein. Furthermore, the magnitude of the resistance at the seabed and the eddy viscosity influence both the timescale and height of sand waves. The order of magnitudes found of the time and spatial scales coincide with observations made in the southern bight of the North Sea, Japan and Spain.

Large-scale modelling of soil-pipe interaction during large amplitude cyclic movements of partially embedded pipelines

Abstract: As the development of offshore hydrocarbons moves into deeper water, pipelines form an increasingly significant part of the required infrastructure. High-temperature high-pressure pipelines must be designed to accommodate thermal ex- pansion and potential lateral buckling. A novel design approach is to control the formation of pre-engineered lateral buckles to relieve the expansion. The amplitude of these buckles is typically several pipe diameters. Assessment of the force-displace- ment interaction between the on-bottom pipeline and the seabed is crucial for design. A series of large-scale plane strain model tests has been conducted to measure the response of a pipe segment partially embedded in soft clay, during large ampli- tude cyclic movements, mimicking consecutive thermal expansion and contraction at a bend in a pipeline. Four key stages in the force-displacement response have been identified: (i) breakout, (ii) suction release, (iii) resistance against a steadily grow- ing active berm, and (iv) additional resistance during collection of a pre-existing dormant berm. A simple upper bound solu- tion is proposed to model the observed response. This solution captures the experimental trends including growth of the active berm and collection of dormant berms. This approach is the first attempt to quantitatively model the mechanisms underlying the response during large-displacement lateral sweeps of an on-bottom pipeline, accounting for the growth of soil berms.

Near-bottom horizontal transfer of particulate matter in the Palamós Submarine Canyon (NW Mediterranean)

Abstract: From March to November 2001, six current meters equipped with turbidimeters were moored 12 meters above the bottom inside the Palamos submarine canyon and on the adjacent slope. Horizontal particle fluxes were calculated from current and suspended sediment concentration data. This work aims to evaluate the advective sediment fluxes taking place in the Palamos canyon region, and to discern the nature and time-scales of the processes involved in the across-margin transfer of particles over the study period. Near-bottom currents inside the canyon were constrained by the local topography and displayed a high spatio-temporal variability. The net near-bottom transport of suspended matter in the canyon was largely driven by sharp increases of sediment load and current speed, most of them attributed to sediment gravity flows. These energetic events dominated over the current-driven sediment transport, which was relatively weak due to periodical up-canyon/downcanyon inversions along the canyon axis, and to complex current patterns and the presence of low sediment loads for most of the time at the other sites. During this 8-month experiment, the mid-canyon ( 1200 m depth) acted as a by-pass zone, while at the canyon head, net sediment transport was directed persistently up-canyon. These patterns were further heightened during a major storm in November 2001. However, in this particular submarine canyon, substantial sedimentary activity and offshore export of particulate matter also occur in the absence of significant external forcings (storms, river floods). Human activities (deep trawling) induced sediment gravity flows during the dry and calm season (spring-summer) and enhanced the offshore transfer of particles during this time period.

Comparison of two wave models for Gold Coast, Australia

Abstract: STRAUSS, D., MIRFERENDESK, H. and TOMLINSON, R., 2007. Comparison of two wave models for Gold Coast, Australia. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 312 – 316. Gold Coast, Australia, ISBN 0749.0208 Managing hazards associated with shoreline responses to extreme events and the provision of safe boating access is an ongoing concern for coastal authorities. The open sandy coastline of Gold Coast city is a wave dominated coast with a highly variable wave climate and a narrow continental shelf thus experiencing substantial variations in long-shore transport rates. Detailed wave transformation information is central to further investigations of sediment transport processes as complex bathymetry associated with trained river entrances and rocky headlands causes localised interruptions to the overall northward littoral drift. Temporal variations in wave energy are driven by a wide range of swell direction and size while spatial variations occur as a result of the strong refraction during particular swell events. This paper presents a comparison of two near shore wave models of the region using MIKE 21 and SWAN. The transformation of waves arriving from offshore is simulated using the models for selected time series of wave parameters. The parameterized boundary conditions are derived from NOAA Wave Watch III global wave model data. Model output is compared with observed data from existing wave recording buoys at Gold Coast Seaway and Point Lookout. The inclusion of wind in the modelling undertaken did not improve the models’ accuracy and winds in excess of 10 ms -1 led to an over-estimation of significant wave height while increasing the processing time. Sheltering of the near-shore site during southerly swell conditions was well-represented by the modelling.

Mass Wasting Processes - Offshore Sumatra

Abstract: Earthquakes are a commonly cited mechanism for triggering submarine landslides that have the potential to generate locally damaging tsunamis. With measured runups of over 35 metres in northern Sumatra from the December 26th 2004 tsunami source, these runups might be expected to be due, in part, to local submarine landslides. Mapping of the convergent margin offshore of Sumatra using swath bathymetry, single channel seismic and seabed photography reveals that seabed failures are common, but mainly small-scale, and composed of blocky debris avalanches and sediment flows. These failures would have contributed little to local tsunami runups. Large landslides are usually formed where there is significant sediment input. In the instance of Sumatra, most sediment is derived from the oceanic plate, and there is little sediment entering the system from the adjacent land areas. Input from the oceanic source is limited because of the diversion of sediment entering the subduction system off of Sumatra, that is attributed to collision between the Ninetyeast ridge and the Sunda Trench at approximately 1.5 million years ago.

Characterizing earthquake recurrence parameters for offshore faults in the low-strain, compressional Kapiti-Manawatu Fault System, New Zealand

Abstract: [1] Seafloor fault scarps and near-surface deformation of late Quaternary seismic reflectors occur along the eastern margin of the Wanganui Basin, 200 km behind the active Hikurangi subduction front, southern North Island, New Zealand. The offshore scarps are associated with the low-strain, compressional Kapiti-Manawatu Fault System (KMFS), which comprises high-angle (>60°) reactivated reverse and normal faults oriented NE-SW, highly oblique to the coast. Seafloor scarps range from 10 m high) and moderate to long fault seafloor rupture lengths, and those in central parts of the fault system are characterized by low scarps ( 10,000 a, suggest that the seismic hazard of the Kapiti-Manawatu region is relatively low. Incorporation of these new geological data, however, is likely to increase slightly the expected seismic hazard in southern North Island. The method of determining the earthquake recurrence parameters of offshore faults has potentially wider applications elsewhere.

Ocean currents-induced pipeline lateral stability on sandy seabed

Abstract: Unlike previous mechanical actuator loading methods, in this study, a hydrodynamic loading method was employed in a flow flume for simulating ocean currents induced submarine pipeline stability on a sandy seabed. It has been observed that, in the process of pipeline losing lateral stability in currents, there usually exist three characteristic times: (1) onset of sand scour; (2) slight lateral displacement of pipeline; and (3) breakout of pipeline. An empirical linear relationship is established between the dimensionless submerged weight of pipeline and Froude number for describing pipeline lateral stability in currents, in which the current-pipe-soil coupling effects are reflected. Scale effects are examined with the method of "modeling of models," and the sand particle size effects on pipeline stability are also discussed. Moreover, the pipeline stability in currents is compared with that in waves, which indicates that the pipeline laid directly upon the sandy seabed is more laterally stable in currents than in waves.

Submarine mass movements and their consequences : 3rd international symposium

Abstract: Role of submarine slides in margin development.- Fractal statistics of the Storegga Slide.- Submarine Paleo-Failure Morphology On A Glaciated Continental Margin From 3d Seismic Data.- Slope Instability And Mass Transport Deposits On The Godavari River Delta, East Indian Margin From A Regional Geological Perspective.- Repeated Instability Of The Nw African Margin Related To Buried Landslide Scarps.- Along Slope Variations In Mass Failures And Relationships To Major Plio-Pleistocene Morphological Elements, Sw Labrador Sea.- Submarine Landslides Along The North Ecuador - South Colombia Convergent Margin: Possible Tectonic Control.- The Southern Flank Of The Storegga Slide: Imaging And Geomorphological Analyses Using 3d Seismic.- Submarine Mass Movements On An Active Fault System In The Central Gulf Of Corinth.- Analysis Of Multibeam Seafloor Imagery Of The Laurentian Fan And The 1929 Grand Banks Landslide Area.- Landslide And Gravity Flow Features And Processes Of The Nazare And Setubal Canyons, West Iberian Margin.- Mass waste evolution: From slump to distal turbidites.- Experimental Studies Of Subaqueous Vs. Subaerial Debris Flows - Velocity Characteristics As A function Of The Ambient Fluid.- The General Behavior Of Mass Gravity Flows In The Marine Environment.- Submarine Spreading: Dynamics And Development.- Flood-Induced Turbidites From Northern Hudson Bay And Western Hudson Strait: A Two-Pulse Record Of Lake Agassiz Final Outburst Flood?.- Underwater Rockfall Kinematics: A Preliminary Analysis.- Anthropogenic Turbidity Current Deposits In A Seismically Active Graben, The Gulf Of Corinth, Greece: A Useful Tool For Studying Turbidity Current Transport Processes.- New techniques, approaches and challenges in submarine slope instability analysis.- Probability Study On Submarine Slope Stability.- Marine Deep-Water Free-Fall Cpt Measurements For Landslide Characterisation Off Crete, Greece (Eastern Mediterranean Sea) Part 1: A New 4000M Cone Penetrometer.- Monitoring stress on submarine slopes and sediment physical properties.- Linking Geotechnical And Rheological Properties From Failure To Post-Failure: The Pointe-Du-Fort Slide, Saguenay Fjord, Quebec.- Rheological Properties Of Fine-Grained Sediments In Modeling Submarine Mass Movements: The Role Of Texture.- Marine Deep-Water Free-Fall Cpt Measurements For Landslide Characterisation Off Crete, Greece (Eastern Mediterranean Sea) Part 2: Initial Data From The Western Cretan Sea.- Recursive Failure Of The Gulf Of Mexico Continental Slope: Timing And Causes.- Geotechnical Considerations Of Submarine Canyon Formation: The Case Of Cap De Creus Canyon.- Submarine slides in coastal areas, semienclosed seas (fjords,estuaries, gulfs) and lakes.- Submarine Mass Movements In The Betsiamites Area, Lower St. Lawrence Estuary, Quebec, Canada.- Submerged Landslide Morphologies In The Albano Lake (Rome, Italy).- Dynamics Of The Deltaic Canyon Area Of The Rv. Chorokhi, Georgia.- The 1990 Submarine Slide Outside The Nidelv River Mouth, Trondheim, Norway.- Submarine Slope Failures Near Seward, Alaska, During The M9.2 1964 Earthquake.- The Ad 1881 Earthquake-Triggered Slump And Late Holocene Flood-Induced Turbidites From Proglacial Lake Bramant, Western French Alps.- Morphosedimentology Of Submarine Mass-Movements And Gravity Flows Offshore Sept-Iles, Nw Gulf Of St. Lawrence (Quebec, Canada).- Sediment Failure Processes In Active Grabens: The Western Gulf Of Corinth (Greece).- Submarine landslides in volcanic island settings.- High Frequency Sediment Failures In A Submarine Volcanic Environment: The Santorini (Thera) Basin In The Aegean Sea.- Sediment Stability Conditions West Of Milos Island, West Hellenic Volcanic Arc.- Submarine mass movements and tsunamis.- Mass Wasting Processes - Offshore Sumatra.- Slope Failures Of The Flanks Of The Southern Cape Verde Islands.- Triggering Factors And Tsunamigenic Potential Of A Large Submarine Mass Failure On The Western Nile Margin (Rosetta Area, Egypt).- Reassessment Of Seismically Induced, Tsunamigenic Submarine Slope Failures In Port Valdez, Alaska, USA.- Towards The Mitigation Of The Tsunami Risk By Submarine Mass Failures In The Gulf Of Corinth: The Xylocastro Resort Town Case Study.- Probabilistic Smf Tsunami Hazard Assessment For The Upper East Coast Of The United States.- Role Of Soil Behavior On The Initial Kinematics Of Tsunamigenic Slides.- Revisiting Submarine Mass Movements Along The U.S. Atlantic Continental Margin: Implications For Tsunami Hazards.- Tsunamigenic Landslides In The Western Corinth Gulf: Numerical Scenarios.- Tsunamis Generated By Coastal And Submarine Landslides In The Mediterranean Sea.

Revisiting Submarine Mass Movements Along The U.S. Atlantic Continental Margin: Implications For Tsunami Hazards

Abstract: Interest in the generation of tsunamis by submarine mass movements has warranted a reassessment of their distribution and the nature of submarine landslides offshore of the eastern U.S. The recent acquisition and analysis of multibeam bathymetric data over most of this continental slope and rise provides clearer view into the extent and style of mass movements on this margin. Debris flows appear to be the dominant type of mass movement, although some translational slides have also been identified. Areas affected by mass movements range in size from less than 9 km 2 to greater than 15,200 km 2 and reach measured thicknesses of up to 70 m. Failures are seen to originate on either the openslope or in submarine canyons. Slope-sourced failures are larger than canyon-sourced failures, suggesting they have a higher potential for tsunami generation although the volume of material displaced during individual failure events still needs to be refined. The slope-sourced failures are most common offshore of the northern, glaciated part of the coast, but others are found downslope of shelf-edge deltas and near salt diapirs, suggesting that several geological conditions control their distribution.

Carbon dioxide pipelines for sequestration in the UK : an engineering gap analysis

Abstract: CLIMATE CHANGE has been attributed to greenhouse gases with carbon dioxide (CO2) being the major contributor. 60-70% of CO2 emissions worldwide originate from the burning of fossil fuek. Government authorities and power companies in the UK, along with oil and gasfield operators, are proposing to capture CO2 from their power plants and either store it in depleted reservoirs or saline aquifers, or use it for enhanced oil recovery (EOR) in depleted oil and gasfields. The capture of anthropogenic CO2 will mitigate against global warming and possibly reduce the impact of climate change. The United States has over 30 years of experience in transporting CO2, mainly from naturally-occurring CO2 sources, and mostly for the purpose of EOR. Both the source and the function of the CO2 pipelines in the USA have dictated a relatively-pure CO2 stream, in comparison, the UK's proposed carbon capture and storage (CCS) projects will be focusing on anthropogenic sources from major polluters such as fossil-fuel power plants, and the CO2 transport infrastructure will involve both on- and offshore pipelines. The fossil-fuel power plants will produce CO2 with varying combinations of impurities depending on the capture technology used. CO2 pipelines have never been designed for some of the impurities released from these power plants. Other key differences between the transport of CO2 in the US and the UK relate to design codes and legislation, pipeline routes, offshore transportation and also storage. The presence of impurities has a great impact on the physical properties of the transported CO2 that consequently affects pipeline design, compressor power, recompression distance, and pipeline capacity, and could also have implications for the prevention of fracture propagation. The effects could be either negative or positive: for example, the addition of some impurities tends to reduce compressor power while others increase the power required. These effects have direct implications for both the technical and economic feasibility of developing a CO2 transport infrastructure on- and offshore. This paper discusses the key differences between the CO2 transport scenarios in the US and the potential transport infrastructure in the UK and provides an understanding of these differences and the implications for designing a CO2-compliant pipeline. It focuses on such factors as recompression distance, flow assurance, and phase equilibrium, and present results of some initial hydraulic modelling work done using proprietary software.

Experimental investigation on the wave-induced pore pressure around shallowly embedded pipelines

Abstract: A series of regular wave experiments have been done in a large-scale wave flume to investigate the wave-induced pore pressure around the submarine shallowly embedded pipelines.The model pipelines are buried in three kinds of soils,including gravel,sand and silt with different burial depth.The input waves change with height and period.The results show that the amplitudes of wave-induced pore pressure increase as the wave period increase,and decay from the surface to the bottom of seabed.Higher pore pressures are recorded at the pipeline top and the lower pore pressures at the bottom,especially in the sand seabed.The normalized pressure around pipeline decreases as the relative water depth,burial depth or scattering parameters increase.For the silt seabed,the wavelet transform has been successfully used to analyze the signals of wave-induced pore pressure,and the oscillatory and residual pore pressure can be extracted by wavelet analysis.Higher oscillatory pressures are recorded at the bottom and the lower pressures at the top of the pipeline.However,higher residual pressures are recorded at the top and the lower pressures at the bottom of the pipeline.

Challenges for offshore transport of anthropogenic carbon dioxide

Abstract: Carbon Capture and Storage (CCS) is recognised as having a significant role to play in reducing carbon dioxide emissions and tackling climate change. In CCS schemes, carbon dioxide is captured from anthropogenic sources and transported to suitable sites either for EOR (Enhanced Oil Recovery) or storage. Globally, the largest source of CO2 is from power generation, therefore the initial projects proposed for CCS in the UK are from power plant. There are various technologies for capturing CO2 from power stations, however the captured CO2 can contain significant amounts of impurities. The presence of the impurities in the CO2 stream has an effect on the requirements for pipeline transportation and can change such factors as the flow properties, the decompression characteristics and the solubility of water in the mixture. Although transport of CO2 by pipeline is not new technology, and has been implemented in the USA for over 30 years, the effect of these impurities is not fully understood. The UK is in the advantageous position of having natural sinks for CO2 available offshore in the North and Irish Sea, which can be used for either EOR or storage. Therefore CCS implementation in the UK will involve transport of anthropogenic carbon dioxide from power stations to offshore sinks. All of the current experience with CO2 pipeline transport has been onshore, predominantly from near pure natural sources and therefore this is also a new challenge. This state-of the-art review paper will: • discuss the key technical factors presented by the transport of CO2 from power plant, including the effects of impurities on the design and operation of pipelines, • compare and contrast the current experience of transporting CO2 onshore with the proposed transport onshore and offshore in the UK and identify the technical and regulatory challenges, • present the results of initial modelling work to demonstrate the effects of the key variables on the development of a CO2 transport system in the UK.Copyright © 2007 by ASME

Modelling the seasonal dynamics of SPM with a simple algorithm for the buffering of fines in a sandy seabed

Abstract: This paper discusses the application of a simple algorithm for the buffering of fines in a sandy seabed. A second layer is introduced in which fines may be stored during calm weather and from which fines may be resuspended during storms. The algorithm is applied first in a one-dimensional vertical (1DV) point model at a location in the North Sea, Noordwijk 10, 10 km offshore. It is able to reproduce the observed temporal variability of suspended particulate matter satisfactorily. Apart from the second layer, also the applied first order erosion rate is an important element of the algorithm. This allows for an equilibrium sediment mass per unit area for any combination of bed shear stress climate and sediment supply. The classical Partheniades-Krone formulation with zeroth order erosion (i.e. an erosion rate that is independent from the sediment mass per unit area) does not have such equilibrium. As a next step, the algorithm is incorporated into a 3D model for suspended particulate matter (SPM) transport in the Dutch coastal zone. It is demonstrated that the model is able to reproduce the observed spatial and temporal variability reasonably well. An essential feature of the 3D mud model is that it is sufficiently fast to compute equilibrium bed composition. This implies that the results are completely independent from the applied (uniform) initial conditions. Finally, the mud model is applied to assess the impact of a large-scale release of fines in the Dutch coastal zone. The computed impact turns out to be very sensitive to the assumed buffer capacity of the seabed. However, information on transient system response (such as the dissipation of a sediment pulse in the system) from which the buffer capacity may be estimated is most often lacking. For the time being, estimates on the residence time of fines in the seabed and its mixing depth are derived from the literature. Additional field and laboratory test on the exchange mechanisms of fines between the water column and a sandy seabed are recommended.

Offshore Pipeline and Riser Geotechnical Model Testing: Practice and Interpretation

Abstract: Offshore developments may typically feature a number of subsea structures for which pipelines and risers play an integral role. Especially for deepwater projects, very soft clays will be encountered at the seabed; these can be difficult to characterize by standard in-situ and laboratory testing. This means that geotechnical model tests are increasingly used to investigate the complex interaction between the seabed soils and the risers or pipelines. The prototypes for these model tests are typically at or close to the actual dimensions used by industry and often include specific coatings for the pipeline or riser section being investigated. The models may be loaded or displaced statically or cyclically in different directions to evaluate the different mechanisms involved. Although it is a challenge to recreate the undrained shear strength found at the seabed, experience and theoretical knowledge may be combined to give good agreement between the shear strength level in the test tank and on site. This may then be verified by in situ testing in the test tank and compared with high quality data from the field itself. The model test results themselves serve as input to pipeline or riser design which can incorporate geotechnical, structural and hydrodynamic effects. This paper describes the typical procedures involved in model testing and investigates the interpretation of the data using theoretical and empirical methods. The impact of results on pipeline and riser design within a project is also considered, where the focus is on very soft clays which are often encountered in offshore projects, especially in deepwater.© 2007 ASME

Multi-channel resistivity investigations of the freshwater-saltwater interface: a new tool to study an old problem.

Abstract: It has been well established that fresh or brackish groundwater can exist both near and far from shore in many coastal and marine environments. The often permeable nature of marine sediments and the underlying bedrock provides abundant pathways for submarine groundwater discharge. While submarine groundwater discharge as a coastal hydrogeological phenomenon has been widely recognized, only recent advances in both geochemical tracers and geophysical tools have enabled a realistic, systematic quantification of the scales and rates of this coastal groundwater discharge. Here we present multi-channel electrical resistivity results using both a time series, stationary cable that has 56 electrodes spaced 2 m apart, as well as a 120 m streaming resistivity cable that has two current-producing electrodes and eight potential electrodes spaced 10 m apart. As the cable position remains fixed in stationary mode, we can examine in high resolution tidal forcing on the freshwater-saltwater interface. Using a boat to conduct streaming resistivity surveys, relatively large spatial transects can be rapidly (travel speed ∼2-3 knots) acquired in shallow (∼1-20 m) waters. Sediment formation factors, used to convert resistivity values to salinity, were calculated from porewater and sediment samples collected during the installation of an offshore well in Tampa Bay, Florida, USA. Here we examine the seabed resistivity from sites within Tampa Bay using both stationary and streaming configurations and discuss their overall effectiveness as a new tool to examine the dynamic nature of the freshwater-saltwater interface.

The importance of shallow confining units to submarine groundwater flow

Abstract: In addition to variable density flow, the lateral and vertical heterogeneity of submarine sediments creates important controls on coastal aquifer systems. Submarine confining units produce semi-confined offshore aquifers that are recharged on shore. These low-permeability deposits are usually either late Pleistocene to Holocene in age, or date to the period of the last interglacial highstand. Extensive confining units consisting of peat form in tropical mangrove swamps, and in salt marshes and freshwater marshes and swamps at mid-latitudes. At higher latitudes, fine-grained glaciomarine sediments are widespread. The net effect of these shallow confining units is that groundwater from land often flows farther offshore before discharging than would normally be expected. In many settings, the presence of such confining units is critical to determining how and where pollutants from land will be discharged into coastal waters. Alternatively, these confining units may also protect fresh groundwater supplies from saltwater intrusion into coastal wells.

Gas subsea transmission system and submersible suspension pressure-equaliser pipeline

Abstract: Gas Subsea Transmission System (GSTS) is a new method for transferring large quantities of natural gas between marine distances through the oceans. Its purpose is to provide a safer, faster and more financially advantageous alternative to gas transmission via LNG. The GSTS's main part is a Submersible Suspension Pressure-equaliser Pipeline (SSPP). It is a long pipe with a large diameter which has a high capacity of gas transmission. This pipe is kept submersible and suspended in deep waters by its special mooring system. It is made from steel pipe which is reinforced by internal concrete rings. The basic concept of SSPP is to cancel the internal pressure of the gas pipeline with the external hydrostatic water pressure by varying the pipe environment. These conditions lead to the possibility of a large diameter pipeline resulting in efficient, high capacity gas transmission. SSPP mooring system is able to change the pipe level to the right depth base on the changes in gas pressure and equalise the external and internal pressures. The GSTS has offshore stations that separate the SSPP into shorter segments. The pipe can be operated, maintained, installed and inspected from these points. During normal operation, these offshore stations are capable of staying submerged under water. This design feature means that they would be protected from adverse surface conditions.

Risk Assessment and Management for Offshore Geohazards

Abstract: The state-of-the-art in understanding offshore geohazards has advanced significantly in the past decade. The advances have been mostly driven by the needs of the offshore petroleum industry. The pace of exploration and field development on the continental slopes and in ultra-deep waters worldwide has increased rapidly during the past decade. Activities are concentrated in areas where the sediment thickness is high and accompanied by diapirism and overpressured formations, requiring the offshore petroleum industry to understand and quantify the risk associated with various seafloor geohazards. An increasing number of observations of seabed instabilities, often on slopes with very low inclination, is of concern to the oil industry. The size of the affected areas range from small surficial slumps to enormous retrogressive slide events. The latter may affect field development areas several kilometres upslope as well as downslope of a slide initiation area. Rapid sediment deposition may generate excess pore fluid pressures, resulting in overpressured formations, and reduced sediment strength. This may lead to increased faulting, diapirism and fluid flow processes, with possible impact on local seabed inclination and seabed instability. On the continental slopes, the pore pressure distribution is a key factor in assessment of slide risk. Natural overpressured formations also represent a drilling hazard regarding shallow gas and shallow water flow. The understanding of the geological processes that create hazardous conditions, the geomechanical explanation of observed instabilities, the dating of these events and the evaluation of present and near future conditions are key elements in geohazard investigations. Likewise, human-induced changes have to be understood and evaluated with respect to their risk potential. Geohazard risk assessment is an integral part of the overall risk assessment in offshore oil and gas projects. The assessment of the risk associated with submarine mass movements is thus not just a matter related to commercial interests of oil companies. The societal and environmental consequences of such events could also be enormous for coastal communities. For instance, large submarine slides may generate tsunamis with potential for severe damage along the coastlines. Risk assessment for offshore geohazard requires a systematic search for potentially dangerous scenarios and associated consequences, followed by quantitative assessment of the likelihood of occurrence and vulnerability of the elements at risk.

Dynamic Response Interaction of Vibrating Offshore Pipeline on Moving Seabed

Abstract: The dynamic response interaction of a vibrating offshore pipeline on a moving seabed is herein investigated where the pipeline is idealized as a beam vibrating on an elastic foundation. This problem is of relevance in offshore exploration where pipelines are laid either on or buried in the seabed. When such pipes carry oil and gas, the undulating topography of the sea floor and the internal motion of the fluid subject the entire structure to vibration due to bending forces and form the subject of our study. Our analysis revealed that in general, the seabed acts either as a damper or as a spring and in particular when we have sedimentation, the seabed geology permits the geomechanical property of the sediment cover to act only as a damper. As expected, external excitation will increase the response of these pipes for which an amplification factor has been derived. For soft beds, high transverse vibrations were dampened by increasing the internal fluid velocity whereas they became amplified for hard beds. These results are of contemporary interest in the oil/gas industry where deep sea exploration is now receiving significant attention.

Morphosedimentology Of Submarine Mass-Movements And Gravity Flows Offshore Sept-Îles, Nw Gulf Of St. Lawrence (Québec, Canada)

Abstract: Recent multibeam sonar and acoustic subbottom profiler surveys and sediment coring offshore the city of Sept-Iles (NW Gulf of St. Lawrence) reveal different types of submarine mass-movements and gravity flows in glaciomarine, paraglacial and postglacial deposits. These mass-movement and gravity flow features are slumps, gullies and channel-levee systems and fans. The key results of this study include: 1) slumps involve the entire deglacial and postglacial sequence, indicating their recent triggering; 2) identification of a 57-cm thick turbidite and several sand layers in sediment cores collected in a deep and isolated basin unaffected by fluvial inputs, along with 210 Pb measurements, indicate the recent activity of mass wasting events derived from slope instabilities; 3) important volumes of sediments are being transported from the coastal to the deeper marine environment by gravity flows processes on the prodelta of the Moisie River. Hypotheses for explaining the widespread occurrence of recent mass-movements due to slope instabilities in the area possibly include their possible triggering by the AD 1663 (M~7) or another large earthquake.

Scientific ocean drilling behind the assessment of geo‐hazards from submarine slides, Barcelona, Spain, 25–27 October 2006

Abstract: Submarine slope instability represents a geo-hazard for its destructive potential on nearshore structures and life and offshore seabed structures. Submarine slides may bear a tsunamigenic potential and are capable of methane gas release into the seawater and atmosphere. A recent workshop sponsored by the European Science Foundation (ESF; http://www.esf.org), “Scientific Ocean Drilling Behind the Assessment of Geo-hazards From Submarine Slides,” held in Barcelona, Spain, 25–27 October 2006, reviewed the current state of knowledge on submarine slope failures and how scientific drilling can improve our knowledge of the process and help to mitigate the derived risks (a report with full details of participants and program can be found at http://www.geohazards.no/IGCP511/). The workshop gathered 50 scientists and representatives of private companies, mainly from the European area, representing a wide spectrum of disciplines such as geophysics, stratigraphy sedimentology paleoceanography marine geotechnology, geotechnical engineering, and tsunami modeling. During the workshop, it was agreed that scientific drilling offers the possibility of answering a number of scientific questions, among them, (1) What is the frequency of submarine slides? (2) What was the tsunamigenic potential of past submarine slides, and what is the tsunamigenic potential of unfailed submarine slopes? (3) Do precursory phenomena of slope failure exist? (4) Can we monitor sea-floor gravitational movements such as creep? (5) What makes up weak layers in midlatitude continental margins? And (6) when and under what circumstances do weak layers form? Scientific drilling also offers the possibility of testing at least two existing hypotheses on basic mechanisms of submarine slide generation and of massive releases of gas: (1) focusing of fluids and lateral transfer of stresses under variable overburden on permeable layers and (2) proving the link between methane emissions during rapid climatic changes and submarine slides.