Showing papers on "Submarine pipeline published in 2008"

Growth and collapse of the Reunion Island volcanoes

Abstract: This work presents the first exhaustive study of the entire surface of the Reunion Island volcanic system. The focus is on the submarine part, for which a compilation of all multibeam data collected during the last 20 years has been made. Different types of submarine features have been identified: a coastal shelf, debris avalanches and sedimentary deposits, erosion canyons, volcanic constructions near the coast, and seamounts offshore. Criteria have been defined to differentiate the types of surfaces and to establish their relative chronology where possible. Debris avalanche deposits are by far the most extensive and voluminous formations in the submarine domain. They have built four huge Submarine Bulges to the east, north, west, and south of the island. They form fans 20–30 km wide at the coastline and 100–150 km wide at their ends, 70–80 km offshore. They were built gradually by the superimposition and/or juxtaposition of products moved during landslide episodes, involving up to several hundred cubic kilometers of material. About 50 individual events deposits can be recognized at the surface. The landslides have recurrently dismantled Piton des Neiges, Les Alizes, and Piton de La Fournaise volcanoes since 2 Ma. About one third are interpreted as secondary landslides, affecting previously emplaced debris avalanche deposits. On land, landslide deposits are observed in the extensively eroded central area of Piton des Neiges and in its coastal areas. Analysis of the present-day topography and of geology allows us to identify presumed faults and scars of previous large landslides. The Submarine Bulges are dissected and bound by canyons up to 200 m deep and 40 km long, filled with coarse-grained sediments, and generally connected to streams onshore. A large zone of sedimentary accumulation exists to the north–east of the island. It covers a zone 20 km in width, extending up to 15 km offshore. Volcanic constructions are observed near the coast on both Piton des Neiges and Piton de la Fournaise volcanoes and are continuations of subaerial structures. Individual seamounts are present on the submarine flanks and the surrounding ocean floor. A few seem to be young volcanoes, but the majority are probably old, eroded seamounts. This study suggests a larger scale and frequency of mass-wasting events on Reunion Island compared to similar islands. The virtual absence of downward flexure of the lithosphere beneath the island probably contributes to this feature. The increased number of known flank–failure events has to be taken into consideration when assessing hazards from future landslides, in particular, the probability of landslide-generated tsunamis.

Chapter 25 The Significance of Contourites for Submarine Slope Stability

Abstract: Publisher Summary This chapter discusses the significance of contourites for submarine slope stability. It also provides an overview of environments where the stability of the slope is affected by the distribution and properties of contouritic sediments. Slope instabilities in areas of contouritic deposits are identified on continental slopes, on rises, and in ocean gateways, including some of the largest submarine landslides known. Thermohaline and geostrophic circulation affect surface-water masses, so that the continental shelf and the upper continental slope may also be influenced by the action of bottom currents, such as offshore Norway and eastern Canada. The changes in geostrophic and thermohaline currents may also induce the necessary conditions for gas–hydrate dissociation and slope instability. Contourites are deposited on the continental slope during both times of low-stand (glacials) and of high-stand (interglacials) of the sea level. The chapter also discusses the affect of contouritic sediments on the stability of submarine slopes. The submarine slope instability in muddy contourite drifts on northern, high-latitude slopes, of elongated drift mounds on southern high-latitude continental slopes and rises and in sediment drifts in areas of ocean gateways are also addressed.

Transporting the Next Generation of CO2 for Carbon, Capture and Storage: The Impact of Impurities on Supercritical CO2 Pipelines

Abstract: Climate change has been attributed to greenhouse gases with carbon dioxide (CO2 ) being the major contributor. Most of these CO2 emissions originate from the burning of fossil fuels (e.g. power plants). Governments and industry worldwide are now proposing to capture CO2 from their power plants and either store it in depleted reservoirs or saline aquifers (‘Carbon Capture and Storage’, CCS), or use it for ‘Enhanced Oil Recovery’ (EOR) in depleting oil and gas fields. The capture of this anthropogenic (man made sources of CO2 ) CO2 will mitigate global warming, and possibly reduce the impact of climate change. The United States has over 30 years experience with the transportation of carbon dioxide by pipeline, mainly from naturally occurring, relatively pure CO2 sources for onshore EOR. CCS projects differ significantly from this past experience as they will be focusing on anthropogenic sources from major polluters such as fossil fuel power plants, and the necessary CO2 transport infrastructure will involve both long distance onshore and offshore pipelines. Also, 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 these differing conditions; therefore, CCS will introduce a new generation of CO2 for transport. Application of current design procedures to the new generation pipelines is likely to yield an over-designed pipeline facility, with excessive investment and operating cost. In particular, the presence of impurities has a significant impact on the physical properties of the transported CO2 which affects: pipeline design; compressor/pump power; repressurisation distance; pipeline capacity. These impurities could also have implications in the fracture control of the pipeline. All these effects have direct implications for both the technical and economic feasibility of developing a carbon dioxide transport infrastructure onshore and offshore. This paper compares and contrasts the current experience of transporting CO2 onshore with the proposed transport onshore and offshore for CCS. It covers studies on the effect of physical and transport properties (hydraulics) on key technical aspects of pipeline transportation, and the implications for designing and operating a pipeline for CO2 containing impurities. The studies reported in the paper have significant implications for future CO2 transportation, and highlight a number of knowledge gaps that will have to be filled to allow for the efficient and economic design of pipelines for this ‘next’ generation of anthropogenic CO2 .Copyright © 2008 by ASME

Gumusut-Kakap Project: Geohazard Characterisation and Impact on Field Development Plans

Abstract: Shell and venture partners encountered numerous seafloor and near seafloor geohazards at the deepwater Gumusut-Kakap field on the continental slope offshore Sabah, Malaysia. The geohazards included subsurface gas hydrates, steep seafloor slopes, a history of mass transport activity, seafloor expulsion, shallow faulting, low seismicity, shallow gas and shallow water flow.

Characteristic Features of Tsunamiites

Abstract: Tsunamiite beds can provide excellent keys to stratigraphic correlations over great distances, as they can have a wide extent. On the other hand, they occur only sporadically because of the gigantic tsunami energy and due to a great variety in sedimentary settings. The cooperation of a few elements of water movement, that is (1) shuttle movement of water currents and (2) deceleration (of the run-up tsunami) and acceleration (of the backwash tsunami) caused by gravitation, fundamentally results in a variety of tsunamiite features that depend on the variable conditions of the surrounding sedimentary settings and environments. Successive layers showing opposite palaeocurrent directions and intercalated mud drapes are characteristics and common features of tsunamiites in some environments such as coastal lakes and shallow-sea basins. Single sand sheets also occur inland, depending on their distance from the sea. An erosion surface may be the only record of a tsunami over an extensive coastal area where step-form run-up tsunami waves go forward and break, and where backwash tsunami flows (currents) are markedly accelerated by gravitation. The eroded sediments, including organic material, are transported both offshore and landward, forming a surge with some density. Because of the nature of the tsunami-induced water movement, many kinds of current structures, including those that indicate high-energy regimes, are common structural components in tsunamiites. Hummocky and swaley structures occur in submarine tsunamiites of various environments. Rip-up mud clasts are also common in submarine tsunamiites, showing the special nature of tractive tsunami currents that lack internal shear stress except in the thin bottom boundary layer. Tsunamiites are lacking almost completely in modern deep-sea areas. The Mediterranean homogenites induced by the collapse of the Santorini caldera provide a rare example of tsunami-induced sediments in a deep-sea area. Deposits from extremely gigantic tsunami, such as some Cretaceous/Tertiary (K/T) boundary tsunamiites, can be found in deep-sea records of the geological history. There is not one single convenient key to distinguish tsunami-generated sediments from those generated by other events. Integrated studies including facies analysis of the background environmental sediments are indispensable for identifying and clarifying tsunamiites and their implications.

Nearshore sediment characteristics and formation of mudbanks along the Kerala coast, southwest India

Abstract: In order to gain insight into the formation dynamics of mudbanks off the Kerala coast of India, extensive surveying of the nearshore bathymetry along with sediment characterization was undertaken. The textural and geotechnical properties of the surficial sediments of a mudbank were determined during pre-monsoon, monsoon, and post-monsoon periods. The mudbank sediments were clayey silts with high water and organic carbon contents, high Atterberg limits, and low bulk density, and therefore very susceptible to entrainment. During the monsoon, the mudbank regime was characterised by enhanced turbidity and a benthic fluff layer, triggered by the increasing swell of the early monsoon period. Re-suspension exposed a more consolidated, previously sub-bottom, layer which exhibited lower water content and greater shear strength than the pre-monsoon seabed. Texturally, the monsoon seabed was similar to the pre-monsoon seabed, with the same modal grain size, but the proportions of sand and coarse silt increased nearshore, while the proportions of fine and very fine silt increased offshore. There was a seaward-fining textural gradient at all times, but this became pronounced during the monsoon period. Paradoxically, the monsoonal seabed displayed greatly reduced wet bulk density. It is hypothesized that this was due to the presence of gas, probably methane, in the sediments (while the pre-monsoon sediments were fully saturated, the monsoon sediments were only 83% saturated). We speculate that the gas was forced into the surficial sediments either by wave pumping (at the onset of the monsoon) or by seaward-flowing subbottom freshwater (derived from monsoonal rains). With the waning of the monsoon, the benthic fluid mud layer rapidly disappeared and the seabed returned to its pre-monsoon state as suspended sediments were redeposited. The mudbank regime is therefore essentially an in situ phenomenon. It is suggested that the mudbanks are palimpsest, marshy, lagoonal deposits, rich in organic matter and derived gas, that were submerged after a marine transgression. The surficial sediment is annually entrained during the monsoon, but erosion is limited by the formation of the benthic fluid mud layer, which attenuates wave generated turbulence. Although some fine sediment disperses alongshore and offshore, most is returned to the seabed as the monsoon declines.

An integrated approach to understanding the petroleum system of a frontier deep-water area, offshore Japan

Abstract: The Naoetsu Basin is one of several oil- and gas-producing provinces in Japan where thick Neogene strata are deposited, and oil and gas are produced from both onshore and offshore shelf areas. It is believed that the Naoetsu Basin extends into deep-water areas, but exploration activities were limited until 2000, except for regional 2D seismic surveys. After acquisition of a 3D seismic survey in 2001, the first two wells were drilled in 2004 in the deep-water area of the Naoetsu Basin. One well encountered an oil zone. Multi-dimensional basin modelling was conducted to understand the petroleum system in the deep-water area of the Naoetsu Basin before and after the wells were drilled. The accuracy of basin modelling depends on the accuracy of the input data as well as the calibration process. However, even after the drilling campaign, only two wells were available in the deep-water area of the Naoetsu Basin. Therefore, the integration of various kinds of data, information and different techniques, such as 3D seismic, sedimentological and geochemical data, was carried out in this study. Development of sandstone networks, as well as the presence of major and minor faults, was identified on 3D seismic data. Oil and gas migration were constrained by geochemical data, such as carbon isotope on gases collected at the sea bottom and fluid inclusion chemistry. Understanding of the petroleum system was increased significantly by this kind of integration, although the deep-water area of the Naoetsu Basin still remains a frontier area for oil and gas exploration. It was found that the petroleum system active in the deep-water area of the Naoetsu Basin is very effective. Even though maturation of the source rock has occurred only since the Pliocene, oil and gas generated and migrated very rapidly, first horizontally along sandstone networks and then vertically through faults reaching a level just below the sea bottom, with the result that the hydrocarbon trap has leaked.

Multiphase Production: Pipeline Transport, Pumping and metering

Abstract: Fluids produced from hydrocarbon fields are composed of a mixture of oil, gas and water, often with corrosive components, sometimes laden with solid particles, and are a potential source of many flow instabilities. Frequently, they are now directly exported long distances, in multiphase conditions, towards an existing processing facility or a new processing centre created to serve simultaneously several new fields. This production scheme, which is especially applied offshore, in mature basins such as in the North Sea or in the Gulf of Mexico where infrastructure exists over large areas, can also improve the economics of small or deepwater fields. Multiphase production: pipeline transport, pumping and metering. Available from: https://www.researchgate.net/publication/316214465_Multiphase_production_pipeline_transport_pumping_and_metering [accessed May 9, 2017].

Overview of the design, construction, and operation of interstate liquid petroleum pipelines.

Abstract: The U.S. liquid petroleum pipeline industry is large, diverse, and vital to the nation's economy. Comprised of approximately 200,000 miles of pipe in all fifty states, liquid petroleum pipelines carried more than 40 million barrels per day, or 4 trillion barrel-miles, of crude oil and refined products during 2001. That represents about 17% of all freight transported in the United States, yet the cost of doing so amounted to only 2% of the nation's freight bill. Approximately 66% of domestic petroleum transport (by ton-mile) occurs by pipeline, with marine movements accounting for 28% and rail and truck transport making up the balance. In 2004, the movement of crude petroleum by domestic federally regulated pipelines amounted to 599.6 billion tonmiles, while that of petroleum products amounted to 315.9 billion ton-miles (AOPL 2006). As an illustration of the low cost of pipeline transportation, the cost to move a barrel of gasoline from Houston, Texas, to New York Harbor is only 3 cents per gallon, which is a small fraction of the cost of gasoline to consumers. Pipelines may be small or large, up to 48 inches in diameter. Nearly all of the mainline pipe is buried, but other pipeline components such as pump stations are above ground. Some lines are as short as a mile, while others may extend 1,000 miles or more. Some are very simple, connecting a single source to a single destination, while others are very complex, having many sources, destinations, and interconnections. Many pipelines cross one or more state boundaries (interstate), while some are located within a single state (intrastate), and still others operate on the Outer Continental Shelf and may or may not extend into one or more states. U.S. pipelines are located in coastal plains, deserts, Arctic tundra, mountains, and more than a mile beneath the water's surface of the Gulf of Mexico (Rabinow 2004; AOPL 2006). The network of crude oil pipelines in the United States is extensive. There are approximately 55,000 miles of crude oil trunk lines (usually 8 to 24 inches in diameter) in the United States that connect regional markets. The United States also has an estimated 30,000 to 40,000 miles of small gathering lines (usually 2 to 6 inches in diameter) located primarily in Texas, Oklahoma, Louisiana, and Wyoming, with small systems in a number of other oil producing states. These small lines gather the oil from many wells, both onshore and offshore, and connect to larger trunk lines measuring 8 to 24 inches in diameter. There are approximately 95,000 miles of refined products pipelines nationwide. Refined products pipelines are found in almost every state in the United States, with the exception of some New England states. These refined product pipelines vary in size from relatively small, 8- to 12-inch-diameter lines, to up to 42 inches in diameter. The overview of pipeline design, installation, and operation provided in the following sections is only a cursory treatment. Readers interested in more detailed discussions are invited to consult the myriad engineering publications available that provide such details. The two primary publications on which the following discussions are based are: Oil and Gas Pipeline Fundamentals (Kennedy 1993) and the Pipeline Rules of Thumb Handbook (McAllister 2002). Both are recommended references for additional reading for those requiring additional details. Websites maintained by various pipeline operators also can provide much useful information, as well as links to other sources of information. In particular, the website maintained by the U.S. Department of Energy's Energy Information Administration (EIA) (http://www.eia.doe.gov) is recommended. An excellent bibliography on pipeline standards and practices, including special considerations for pipelines in Arctic climates, has been published jointly by librarians for the Alyeska Pipeline Service Company (operators of the Trans-Alaska Pipeline System [TAPS]) and the Geophysical Institute/International Arctic Research Center, both located in Fairbanks (Barboza and Trebelhorn 2001), available electronically at http://www.gi.alaska.edu/services/library/pipeline.html codes. The Association of Oil Pipe Lines (AOPL) and the American Petroleum Institute (API) jointly provide an overview covering the life cycle of design, construction, operations, maintenance, economic regulation, and deactivation of liquid pipelines (AOPL/API 2007).

A Long-Term Real Time Sea Bed Morphology Evolution System in the South Atlantic Bight

Abstract: A long-term real time sea bed morphology monitoring system has been established on the middle continental shelf in the South Atlantic Bight. This constitutes part of the Southeast Coastal Ocean Observing System (SEACOOS) and now supports a project that focuses on studying material exchange processes in permeable sediments in response to large scale atmospheric and oceanic forcing. In particular the system supports studies of advective-pore water exchanges that depend on the size and geometry of the wave-induced ripples and the strength of the overlying flows. The seabed morphology system is composed of an Imagenex Model 881 tilted-head digital rotating imaging system (2.25 MHz) connected through 1.5 km of cable to a power and controller unit housed on the R2 Naval platform utilized by the South Atlantic Bight Synoptic Offshore Observational Network (SABSOON). The system collects acoustic images of the seabed along 6 meter long radials with resolution of 0.3 degrees. Data are acquired hourly, transmitted via microwave antenna to shore and reach the laboratory via T1 land line. Raw images are rectified and processed using a 2-dimensional fast Fourier transform algorithm providing wavelength and ripple orientation values. Post-data collection image processing allows evidence of bioturbation to be identified as well. The long-term data base (since April 2007) is used for evaluation of time-dependent ripple evolution models. System design, data analysis methods and example images are presented. The long-term data are used to evaluate a recently introduce time-depended model for coarse sand ripple evolution.

Strain-Based Pipelines: Design Consideration Overview

Abstract: The need to use strain-based design is growing due to approaching pipeline projects in challenging environments including permafrost, offshore ice hazards, active seismic areas, and in high temperature/high pressure operations. This has stimulated significant research and development efforts in industry, and some of the work is making its way into design codes and industry projects. To ensure pipeline integrity and overall cost effectiveness, a strain-based design approach needs to consider all key interrelated design aspects, including strain demand, design methods, material selection, strain capacity validation, and impact on construction and operation. This paper examines some of these key considerations and recommends practices for engineering and execution of strain-based pipelines. It also includes a discussion of strategies for projects to minimize strain demand, including monitoring and mitigating high strain locations as they develop in the pipeline during operation. The paper highlights ExxonMobil’s effort in design, testing, model development, and project applications to advance and enhance the capability of strain-based pipeline applications.

Simulation method and device for detecting lateral stability of directly laid pipes on sea floor

Abstract: The invention discloses a simulation method for detecting the side direction stability of a directly paved submarine pipeline and a simulation device; the invention firstly prepares a soil sample to simulate a seabed, mounts a test pipeline, releases the pipeline to lead the pipeline to generate initial sedimentation under the action of self-gravity when the pipeline is just contacted with the seabed and simultaneously adopts a laser displacement sensor to measure the initial sedimentation amount of the pipeline in a soil body, applies an incline pull to the pipeline through a stepping motor to simulate the actions of a horizontal daggling force and a vertical lifting force of a sea flow to the pipeline, and simultaneously measures the pull of the stepping motor, a horizontal displacement and an additive sedimentation amount during the side direction destabilization process of the pipeline, a displacement field of the soil body at the lower side during the side direction destabilization process of the pipeline, and a soil pressure of the side direction. The utilization of the simulation method and the simulation device of the invention can effectively simulate a bearing soil body, the horizontal dragging force and the vertical lifting force of the single-direction sea flow to the pipeline, etc., of the directly paved submarine pipeline and can monitor the stability parameters like the limit side direction soil resistance of a pipeline foundation in real time, thereby being capable of simulating the side stability of the directly paved submarine pipeline.

Transient Heat Transfer from an Offshore Buried Pipeline during Start-up Working Conditions

Abstract: The 2D heat transfer from offshore, completely buried pipelines is studied with reference to transient working conditions. In particular, the start-up case is considered (i.e., the case of a pipeline initially at equilibrium with the surrounding soil). Two different start-up cases are investigated: the step-rising case and the smooth-rising case. (In the latter, the steady-state wall temperature is reached in a finite time.) The energy balance equation is written in a dimensionless form and solved numerically by means of a finite element method. The dimensionless temperature field in the soil and the thermal power exchanged per unit length by the pipeline with the soil are determined. A comparison with a simpler one-dimensional model of the phenomenon (“extra-soil layer” approximation) is performed.

Development of new pipeline maintenance system for repairing early-built offshore oil pipelines

Abstract: This paper introduces a set of new pipeline maintenance system for early-built long-distance offshore oil pipelines. An on-line intelligent inspection pig is developed using ultrasonic tool to detect defects in oil pipelines and the acquired data is stored for off-line analysis. Through analysing the data, defects can be found, sized, classed, and besides, the plan to locating them is made. An autonomous pipeline robot is developed to carry out the locating defects tusk, which adopts the way of detecting girth welds, combined with odometer wheels to locate the defects' position, so the problem of locating defects in early-built offshore pipelines unequipped with magnetic markers is solved. The paper introduces major components of the intelligent inspection pig and the autonomous pipeline robot and describes the process of maintaining offshore oil pipelines with the developed system.

A Discussion of the Effect of the Reeled Installation Process On Pipeline Limit States

Abstract: Pipeline reeling is a well established method for offshore installation of rigid steel pipelines and risers. The basic process of loading stalks of pipe that have been fabricated onshore onto large reels before transit to the worksite, unspooling, straightening and lay is generally well known. However, less well understood is the mechanics of the process. This occasionally leads to concerns that a reeled pipeline has somehow been degraded by the process and must be down-rated in comparison to a similar line installed by J-lay or other methods. This paper addresses these concerns by asking and answering the question; “Does the reeled installation method introduce a greater risk of failure in-service than other installation processes?” The argument is constructed by assessing each limit state, meaning the fundamental ways that a pipeline can fail (burst, collapse, fracture), and considering the possible effect that reeling may have on each during service. The paper concludes that there is no general reduction in pipeline performance as a result of the reeled installation method, provided that certain items are considered during design, procurement and fabrication process. The paper makes use of a wide range of supporting data from extensive in-house engineering and testing program, reference to relevant Joint Industry Projects (JIPs) and a large reel-lay installation track record including some of the largest or deepest reeled pipes in both the Gulf of Mexico and West of Africa.

Bendable pre-insulated pipeline assembly

Abstract: This invention relates to a pipeline assembly especially for offshore installation comprising an inner carrier pipe, a casing and at least one closed- cell and/or solid thermal insulation material layer placed in between the casing and the inner carrier pipe, and the at least one insulation layer being directly or indirectly bonded to at least the casing and the inner carrier pipe. The pipeline assembly according to the invention has improved bending properties which is achieved as the insulation material layer comprises at least one slit substantially transversely to the longitudinal direction of the pipeline assembly. The slit can e.g. be applied as a helical or circumferential cut. Hereby is obtained that the pipeline assembly can be rolled onto a reel or spool which greatly improves the installation process of the pipeline assembly. The invention further relates to a method of improving the bending properties and the use of one or more slits in the insulation material layer to increase the bending properties of such a pipeline assembly.

Mechanical properties of longitudinal submerged arc welded steel pipes used for gas pipeline of offshore oil

Abstract: Since the development of offshore oil and gas, increased submarine oil and gas pipelines were installed. All the early steel pipes of submarine pipelines depended on importing because of the strict requirements of comprehensive properties, such as, anti-corrosion, resistance to pressure and so on. To research and develop domestic steel pipes used for the submarine pipeline, the Longitudinal-seam Submerged Arc Welded (LSAW) pipes were made of steel plates cut from leveled hot rolled coils by both the JCOE and UOE (the forming process in which the plate like the letter “J”, “C”, “O” or “U” shape, then expansion) forming processes. Furthermore, the mechanical properties of the pipe base metal and weld metal were tested, and the results were in accordance with the corresponding pipe specification API SPEC 5L or DNV-OS-F101, which showed that domestic LSAW pipes could be used for submarine oil and gas pipelines.

Fatigue Life Prediction Due to Slug Flow in Extra Long Submarine Gas Pipelines

Abstract: Some offshore production fields require transporting of production fluids through very long submarines pipelines without a previous separation process. In the case of gas production, condensate will appear in the pipeline due to the pressure losses and low temperatures. For some production conditions a slug flow pattern may then develop in the pipeline, and because of the irregular sea bottom profile, there may be pipe unsupported spans of even hundreds of meters long. Therefore, slugs traveling in the pipeline will act as moving loads for the unsupported pipe, producing a dynamic response that in some cases might reduce the fatigue life of the pipeline. In this work, a finite element (FE) model of a pipeline transporting slugs has been developed and used to assess the fatigue life of a horizontal pipeline. Slug hydrodynamic characteristics have been obtained using Taitel & Barnea’s model. The structural FE model is based in Bernoulli beam elements where slugs, once they have been geometrically characterized, are input as moving loads traveling in the pipeline. The system dynamic response was calculated for different spans conditions and slugs characteristics corresponding to different gas-liquid ratios typical from gas field production conditions. Once a steady state condition was obtained in the dynamic response, mean and alternating stress levels were obtained for each analyzed case and introduced in fatigue formulae to obtain the fatigue life of the pipeline. Results show that for some production conditions and free span longitudes, fatigue life of pipeline may experience important reductions due to slug flow. These free spans are obviously most likely to happen in extra long submarines pipelines.Copyright © 2008 by ASME

Study on Interaction Relationship for Submarine Pipeline with Axial Corrosion Defects

Abstract: Corrosion is one of the main reasons to cause the operation accident of submarine oil and gas transmission pipelines. As the major corrosion pattern in submarine pipelines, the effects of corrosion clusters consisting of the adjacent corrosion defects on failure pressure are investigated through non-linear large-deformation finite element method. Typically, the failure behavior and limit strength of submarine pipeline with axial groove-groove corrosion defect pair exposed to internal pressure are analyzed. The effects of corrosion depth and axial spacing between a pair of corrosion defects on failure pressure are concluded. An interaction relationship for corrosion defects in pipelines, as well as prediction formulations for assessing the remaining strength of corroded pipelines are proposed. The expressions based on the proposed interaction relationship give more accurate results than the methods used in the existing design guidelines.

Experimental study on local scour of sandy seabed under submarine pipeline in unidirectional currents

Abstract: The similarity rules for modeling local scour of the under submarine pipeline are established by means of dimensional analytical method. The physical phenomenon of the local scour of the pipeline was modeled in a unidirectional flow flume. The experimental observation indicates that the process of the local scour around the pipeline with an initial embedment mainly includes four characteristic stages: (1) suspension of pipeline, (2) tunnel erosion, (3) lee-wake erosion and (4) equilibrium scouring stages. In the subcritical flow regime, there exists low correlativity between the equilibrium scour depth and Reynolds number. In the case of clear-water scour, the equilibrium scour depth increases with increasing Shields number, and descends linearly with increasing initial gap-diameter ratio in the examined range of initial gap-diameter ratios ( - 0.25 e0 / D 0.55).

Crossing Active Faults on the Sakhalin II Onshore Pipeline Route: Pipeline Design and Risk Analysis

Abstract: Twin oil (20 & 24 inch) and gas (20 & 48 inch) pipeline systems stretching 800 km are being constructed to connect offshore hydrocarbon deposits from the Sakhalin II concession in the North to an LNG plant and oil export terminal in the South of Sakhalin island. The onshore pipeline route follows a regional fault zone and crosses individual active faults at 19 locations. Sakhalin Energy, Design and Construction companies took significant care to ensure the integrity of the pipelines, should large seismic induced ground movements occur during the Operational life of the facilities. Complex investigations including the identification of the active faults, their precise location, their particular displacement values and assessment of the fault kinematics were carried out to provide input data for unique design solutions. Lateral and reverse offset displacements of 5.5 and 4.5 m respectively were determined as the single‐event values for the design level earthquake (DLE)—the 1000‐year return period event. Within the constraints of a pipeline route largely fixed, the underground pipeline fault crossing design was developed to define the optimum routing which would minimize stresses and strain using linepipe materials which had been ordered prior to the completion of detailed design, and to specify requirements for pipe trenching shape, materials, drainage system, etc. Detailed Design was performed with due regard to actual topography and to avoid the possibility of the trenches freezing in winter, the implementation of specific drainage solutions and thermal protection measures.