Showing papers on "Submarine pipeline published in 2015"

Key Future Directions For Research On Turbidity Currents and Their Deposits

Abstract: Turbidity currents, and other types of submarine sediment densityflow, redistribute more sediment acrossthe surface of the Earth than any other sediment flow process, yet their sediment concentration has never been measured directly in the deep ocean. The depositsof these flows are of societal importance asimperfect records of past earthquakes and tsunamogenic landslides and as the reservoir rocks for many deep-water petroleum accumulations. Key future research directions on these flows and their deposits were identified at an informal workshop in September 2013. This contribution summarizes conclusions from that workshop, and engages the wider community in this debate. International efforts are needed for an initiative to monitor and understand a series of test sites where flows occur frequently, which needs coordination to optimize sharing of equipment and interpretation of data. Direct monitoring observations should be combined with cores and seismic data to link flow and deposit character, whilst experimental and numerical models play a key role in understandingfield observations. Such an initiative may be timely and feasible, due to recent technological advances in monitoring sensors, moorings, and autonomous data recovery. This is illustrated here by recently collected data from the Squamish River delta, Monterey Canyon, Congo Canyon, and offshore SE Taiwan. A series of other key topics are then highlighted. Theoretical considerations suggest that supercritical flows may often occur on gradients of greater than , 0.6u. Trains of up-slope-migrating bedforms have recently been mapped in a wide range of marine and freshwater settings. They may result from repeated hydraulic jumps in supercritical flows, and dense (greater than approximately 10% volume) near-bed layers may need to be invoked to explain transport of heavy (25 to 1,000 kg) blocks. Future work needs to understand how sediment is transported in these bedforms, the internal structure and preservation potential of their deposits, and their use in facies prediction. Turbulence damping may be widespread and commonplace in submarine sediment density flows, particularly as flows decelerate, because it can occur at low ( , 0.1%) volume concentrations. This could have important implications for flow evolution and deposit geometries. Better quantitative constraints are needed on what controls flow capacity and competence, together with improved constraints on bed erosion and sediment resuspension. Recent advances in understanding dilute or mainly saline flows in submarine channels should be extended to explore how flow behavior changes as sediment concentrations increase. The petroleum industry requires predictive models of longer-term channel system behavior and resulting deposit architecture, and for these purposes it is important to distinguish between geomorphic and stratigraphic surfaces

Oil and Gas Pipelines : integrity and safety handbook

Abstract: A comprehensive and detailed reference guide on the integrity and safety of oil and gas pipelines, both onshore and offshore Covers a wide variety of topics, including design, pipe manufacture, pipeline welding, human factors, residual stresses, mechanical damage, fracture and corrosion, protection, inspection and monitoring, pipeline cleaning, direct assessment, repair, risk management, and abandonment Links modern and vintage practices to help integrity engineers better understand their system and apply up-to-date technology to older infrastructure Includes case histories with examples of solutions to complex problems related to pipeline integrity Includes chapters on stress-based and strain-based design, the latter being a novel type of design that has only recently been investigated by designer firms and regulators Provides information to help those who are responsible to establish procedures for ensuring pipeline integrity and safety

A condition assessment model for oil and gas pipelines using integrated simulation and analytic network process

Abstract: Even though they are safe and economical transportation means of gas and oil products around the world, pipelines can be subject to failure and degradation generating hazardous consequences and irreparable environmental damages Therefore, gas and oil pipelines need to be effectively monitored and assessed for optimal and safe operation Many models have been developed in the last decade to predict pipeline failures and conditions However, most of these models used corrosion features as the sole factor to assess the condition of pipelines Therefore, the objective of this paper was to develop a condition assessment model of oil and gas pipelines that considers several factors besides corrosion The proposed model, which uses both analytic network process and Monte Carlo simulation, considers the uncertainty of the factors affecting pipeline condition and the interdependency relationships between them The performance of the model was tested on an existing offshore gas pipeline in Qatar and was found to b

Effects of submarine groundwater discharge on the present‐day extent of relict submarine permafrost and gas hydrate stability on the Beaufort Sea continental shelf

Abstract: We investigate the role of submarine groundwater discharge on the offshore temperature and salinity field and its effect on the present-day extent of submarine permafrost and gas hydrate stability on the North American Beaufort Shelf with a two-dimensional numerical model based on the finite volume method. This study finds that submarine groundwater discharge can play a large role in submarine permafrost evolution and gas hydrate stability, suggesting that local hydrology may control the evolution of submarine permafrost as strongly as does sea level or paleoclimatic conditions. Submarine permafrost evolution shows transient behavior over potentially long time scales (e.g., several glacial cycles) before a balance of density- and pressure-driven flows is established with the permeability variations imposed by the overlying permafrost layer. The “detectable” offshore permafrost extent is related to the quasi-stationary location of the saltwater-freshwater transition. Larger values of submarine groundwater discharge allow permafrost to extend farther offshore because fresh pore water preserves relict ice. Therefore, differences in the permafrost extent at locations that share similar paleoclimatic history may be explained in part by differences in the local hydrology. Gas hydrate stability on the North American Beaufort Shelf may be more widespread than currently thought because low-ice saturation, highly degraded submarine permafrost likely exists beyond the boundary detectable by common geophysical methods.

Landslide Impact on Submarine Pipelines: Analytical and Numerical Analysis

Abstract: The damage to pipelines from submarine landslides or debris flows has been vastly reported. In this paper, the behavior of pipelines is investigated through analytical and numerical analyses. A refined analytical method is first brought forward by improving the tension assumption. The pipeline is divided into different segments based on loading conditions, and the continuity of displacement, inclination angle, bending moment, and shear are all preserved. Then numerical analysis by vector-form intrinsic FEM is carried out by further considering the axial soil resistance at the sliding zone. The numerical analysis demonstrates that the initial negative pipeline displacement is a threat to pipeline safety because of the large increase in bending moment. The axial tension is closely related to the location of the landslide impact and the initial pipeline configuration. The variations in displacement and tension with time are also investigated in the parametric analysis.

Analysis of the mechanism of seabed liquefaction induced by waves and related seabed protection

Abstract: As one of the most serious offshore hazards, wave-induced seabed liquefaction can trigger massive landslides on the ocean floor and pose a great threat to submarine structures (e.g., coastal levees, oil platforms, drilling platforms and seabed pipelines). In view of the complexity and practicability of the problem, this study systematically analyzes the mechanism, factors and remedial measures of liquefaction. Compared with seismic liquefaction, waved-induced liquefaction varies in many respects, such as the load pattern, loading position, drainage condition and characteristics of pore water pressure, resulting in different mechanisms of seabed liquefaction under the action of waves. Both wave characteristics and soil characteristics, including the wave period, water depth, wave height, degree of saturation, seabed thickness, permeability and stress history, affect the degree of seabed liquefaction. Moreover, to ensure the sustainable development of the ocean, a series of remedial measures against liquefaction, including evaluation of the liquefaction potential, management of disaster prevention, ocean monitoring and forecasting, are proposed.

Mesh-free modeling of liquefaction around a pipeline under the influence of trench layer

Abstract: This paper reports numerical study of pore pressure evaluation and liquefaction potential around offshore buried pipelines by using the local radial basis function differential quadrature method. The current mesh-free method is a combination of differential quadrature approximation of derivatives and function approximation of MQ-radial basis function. A multilayer node distribution around a pipeline is used to obtain more accurate results in the area near the pipelines. Various physical parameters of the soil such as the permeability coefficient (k) and unit weight (γ) of the soil along with different shapes and locations of the trench layer are considered. The results are obtained in terms of liquefaction potential contours and pore pressure profiles. From the numerical aspect, the outcomes verify that the current technique is capable of solving different physical problems with complex geometries.

Study on the Lateral Soil Resistance Acting on the Buried Pipeline

Abstract: Liu, R.; Guo, S., and Yan, S., 2015. Study on the lateral soil resistance acting on the buried pipeline. Pipe-soil interaction is a crucial problem in the global buckling design of submarine pipeline under thermal stresses. Soil resistance acting on the pipelines determines the deformation shape and amplitude as the global buckling occurs. The fine sand and soft clay are distributed widely in the upper soil layer of Bohai Gulf. Therefore, these two kinds of soil were chosen as medium in the pipe-soil interaction laboratory tests. Three different diameter pipe segments were adopted to simulate the pipeline. The pipe segments lateral displacement and the corresponding suffered soil resistance were measured during the tests. The tests were carried out separately for the pipe segments with different diameters and different depth to diameter ratios. The test data showed that the lateral soil resistance acting on the pipe depends on the soil properties and pipe diameter and depth-to-diameter ratio. A n...

Estimation of CO2 Transport Costs in South Korea Using a Techno-Economic Model

Abstract: In this study, a techno–economic model was used to calculate the costs of CO2 transport and specify the major equipment required for transport in order to demonstrate and implement CO2 sequestration in the offshore sediments of South Korea. First, three different carbon capture and storage demonstration scenarios were set up involving the use of three CO2 capture plants and one offshore storage site. Each transport scenario considered both the pipeline transport and ship transport options. The temperature and pressure conditions of CO2 in each transport stage were determined from engineering and economic viewpoints, and the corresponding specifications and equipment costs were calculated. The transport costs for a 1 MtCO2/year transport rate were estimated to be US$33/tCO2 and US$28/tCO2 for a pipeline transport of ~530 km and ship transport of ~724 km, respectively. Through the economies of scale effect, the pipeline and ship transport costs for a transport rate of 3 MtCO2/year were reduced to approximately US$21/tCO2 and US$23/tCO2, respectively. A CO2 hub terminal did not significantly reduce the cost because of the short distance from the hub to the storage site and the small number of captured sources.

Decompression marine natural gas hydrate mining method and submarine mining system

Abstract: The invention relates to a decompression marine natural gas hydrate mining method and a submarine mining system. The submarine mining system comprises a semi-submersible offshore platform, a mining well with multiple shower holes, a wellhead gas and water acquisition tree, a gas and water mixed delivery system, a submarine gas and water separating device, a gas delivery system, a pipeline system, a power and communication system and an auxiliary device. The decompression marine natural gas hydrate mining method and the submarine mining system have the advantages that submarine natural gas hydrate reservoirs can be safely, efficiently and economically mined; the submarine mining system is complete, and various portions of the submarine mining system are high in modularization, low in manufacturing cost and short in manufacturing cycle and can be reused; most devices are positioned in submarine environments and are controlled via the offshore platform, only natural gas is delivered offshore, and accordingly the submarine mining system is low in extra energy consumption; owing to a technology for forming the multiple shower holes in the mining well, missed mining regions can be effectively reduced, and the gas yield can be effectively increased owing to multiple horizontal wells; the submarine mining system has functions of well blocking prevention, well blowout prevention, hydrate secondary generation and the like, and accordingly safety production can be guaranteed; various main devices can flexibly move and are used with one another, and accordingly movable regional production operation can be implemented.

Geology of the seabed and shallow subsurface: the Irish Sea

Abstract: The British Geological Survey was commissioned by the Crown Estate to assess geological conditions in the Irish Sea in relation to the possible constraints they may place on development of offshore infrastructure. The report describes the geology between 0 m and 50 m below seabed, which is the depth most relevant to current pile foundation technology. The report reviews the best available data from a variety of sources including, BGS legacy data, map sheets, and regional reports, as well as site investigations carried out for hydrocarbon and offshore renewable industries. Additional data collected for the proposed Round 3 offshore wind farm in the Irish Sea (Celtic Array) was also included. Prof. Richard Chiverrell and Dr. Katrien Van Landeghem (of Liverpool and Bangor universities), who together have extensive experience working in the Irish Sea, provided valuable advice and guidance. The report is split into four principle sections as summarised below. Section 3 summarises seabed topography, sediments and processes. The topography of the report area is split into shallow platforms and deeper troughs. Seabed sediments are subdivided into regions of soft mud- (clay and silt) rich sediment in the eastern and western Irish Sea and a central gravel belt comprising coarse sand and gravel. Small areas of bedrock outcrop at seabed are also recognised. Currents in the Irish Sea mobilise sediment to form a collection of marine bedforms ranging from ripples to very large (up to 36 m in height) solitary sediment waves and banner banks. Predicting bedform migration speeds and pathways is difficult and requires repeat surveys. Bedform migration rates of 0 m/yr to 66 m/yr, with average values around 6 m/yr have been observed. Shallow gas is expected in some areas of the Irish Sea. Where this gas is present, pockmarks or methane derived authigenic carbonate may occur. Section 4 summarises the Quaternary history of the Irish Sea and its impact on the distribution, thickness and properties of sediment. Growth and collapse of ice sheets and associated sea level fluctuations principally determine geological properties of Quaternary sediments. The stratigraphy in the report area reflects three major glacial periods with the last one having the most pronounced influence. Very stiff diamicts (glacial ‘boulder clays’ or tills) are present across most of the report area of variable thickness. In enclosed deeps, locally sediment thickness can be >100 m. Glacial landforms are preserved at the seabed and can be used to predict sediment properties. Extensive studies onshore can provide analogues to assess potential geological properties offshore. Section 5 provides a review of bedrock distribution and properties. Where Quaternary sediment cover is <50 m, bedrock will be encountered in the shallow subsurface. The predominant bedrock lithologies in the report area are Triassic and Carboniferous sandstone and mudstone. Geotechnical properties of Triassic rocks are comparable and potentially predictable. Carboniferous rock show high lateral and vertical variability. There are a number of igneous intrusions in the report area and rock properties near to the location of these igneous bodies may differ due to alteration of the host rock during intrusion. Section 6 summarises the geological constraints identified in preceding sections with reference to engineering activities and infrastructure. The report outlines the current state of knowledge of geological conditions in the Irish Sea. It is recommended for use as a guide and should not replace a detailed site investigation.

Ultimate Load Capacity of Offshore Pipeline with Arbitrary Shape Corrosion Defects

Abstract: A set of generalized solutions are proposed for estimating ultimate load capacity of pipeline with arbitrary corrosion shapes subjected to combined internal pressure, axial force and bending moment. Isotropic and anisotropic material characteristics in longitudinal and circumferential direction of pipeline are also considered in the proposed equations. Simplified numerical method is used to solve the generalized expressions. The comparisons of numerical results based generalized solutions and full-scale experimental results are carried out. The predicted results agree reasonably well with the experiment results. Meanwhile, the effects of corrosion shapes and locations on the ultimate load capacity are studied.

Runout prediction and dynamic characteristic analysis of a potential submarine landslide in Liwan 3-1 gas field

Abstract: A large number of submarine landslides with different scales have been identified in the canyon area of the submarine pipeline route of Liwan 3-1 gas field. There is still much chance that submarine slope failures would happen, and the following mass movement would present great risk to the submarine pipeline. In view of this, a numerical prediction method based on Eulerian-Eulerian two-phase flow model is introduced to simulate the mass movement of potential submarine landslides. The sliding soil and ambient water are respectively simulated by Herschel-Bulkley rheology model and Newtonian fluid model. The turbulence is simulated using the k-e model. Compared with both the experiment data and Bing result, the two-phase flow model shows a good accuracy, and its result is more close to the actual situation; the dynamic coupling between soil and ambient water can be effectively simulated and the phenomena of hydroplaning and head detachment can be obtained. Finally, the soil movement of a potential submarine landslide is simulated as an example, according to the seismic profile in the canyon area. The result shows that the hydroplaning occurs during the movement process. The runout distance calculated by the two-phase flow model is 877 m, which is 27.1% larger than the Bing result. However, the peak front velocity of soil is relative small, with a maximum value of 8.32 m/s. The Bing program with a simple and rapid process can be used for a preliminary evaluation, while the two-phase flow model is more appropriate for an accurate assessment.

Selection of Power From Shore for an Offshore Oil and Gas Development

Abstract: With a step-out distance of 161 km and a design power of 55 MW, Martin Linge offshore gas field will be the longest ac submarine cable power supplying an entire offshore oil and gas platform from the shore. This field development comprises a platform with a jack-up rig and a floating storage offloading unit. This paper discusses the criteria that have been considered to select a power-from-shore concept instead of an offshore gas turbine power plant, which is the current practice in the offshore oil and gas industry. Since in a first approach, for such a long step-out distance, the choice of power from shore would be to select a dc transmission line, this paper discusses the design and the main technical challenges of this long step-out ac transmission development. Finally, the system approach that is required for the development of the onshore and offshore parts of the project is described.