Littérature scientifique sur le sujet « Marges continentales – Asie »

La préhistoire du Sud-est asiatique se caractérise par un matériel lithique dont les chaînes opératoires restent encore peu connues ou mal décrites. Cette méconnaissance s’explique par l’éloignement géographique de ces régions tropicales vis à vis des problématiques préhistoriques occidentales développées depuis maintenant deux siècles. La préhistoire de l’Extrême-Orient est complexe, originale, surprenante parfois paradoxale car en marge des grandes lignées techniques connues ailleurs pour la période concernée, celle qui a vu l’avènement de l’Homme anatomiquement moderne. Cette préhistoire régionale d’environ 2 millions de km2 que l’on nomme l’Asie du Sud-est péninsulaire ou continentale renvoie à l’élaboration d’une science en mouvement dont la construction est toujours d’actualité. En se heurtant à la thèse classique de l’évolution comme à celle du progrès technique, le Hoabinhien bouscule les règles et les repères en préhistoire. Il se situe aux antipodes du modèle classique (Eurasiatique, Africain) de développement des outils de pierre selon l’enrichissement et l’allègement progressif de l’outillage depuis la pebble culture jusqu’au Néolithique. C’est précisément sur cette singularité que porte notre réflexion à propos d’un phénomène technique unique qui reste difficile à positionner sur l’axe évolutif des industries tel qu’il existe ailleurs dans le monde ou en Asie de l’Est (Chine, Corée, Japon). La régularité et l’homogénéité des formes d’outils façonnées sur galet dans un vaste espace et sur une durée record de près de 30 000 ans sont les caractéristiques principales de ce technocomplexe peu orthodoxe qui interroge la capacité cognitive d’Homo sapiens en écosystème tropical humide. Mais aussi, la question de la nature des liens existants entre l’homme et ses productions lithiques ou la place occupée par la technique de la pierre taillée lors du développement humain dans cette région hors d’Europe.A cette monotone pérennité d’outils sur galet se greffe l’absence d’outils lithiques pointus (pointe, extrémité apicale, outil à bords saillants convergents, etc.) tels qu’ils se rencontrent partout ailleurs chez les groupes de chasseurs-cueilleurs qu’ils soient du Paléolithique supérieur ou (sub-)actuels.C’est pourquoi la stabilité de ces outillages sur galet cacherait tout un pan de complexité inconnu du domaine technique comme l’insaisissable travail des matières dures d’origine animale mais surtout végétale non conservées à ce jour dans les niveaux archéologiques. Le cheminement du minéral vers la question du végétal renvoie à la nécessité de compléter la « boîte à outils » des artisans préhistoriques hoabinhiens par des objets pointus. Connue à ce jour qu’à travers les données de l’ethnographie, la « civilisation du végétal » conduit tout naturellement à réfléchir sur l’importance de ce matériau périssable dans le bagage outillé des derniers chasseurs-cueilleurs de la forêt tropicale d’Asie du Sud-est continentale. Autrement dit, la possibilité d’une autre existence technique en équilibre avec le milieu extérieur.Après avoir mis en avant l’originalité du phénomène culturel hoabinhien au regard de l’impact de la recherche en préhistoire et en paléoanthropologie dans les régions du Sud-est asiatique, cet article présentera d’un point de vue strictement qualitatif, les chaînes opératoires du techno-complexe hoabinhien. Faciès industriel sur galet qui caractérise la principale culture technique des chasseurs-cueilleurs du Paléolithique final d’Asie du Sud-est entre environ 30 000 et 5 000 ans BP. Plus largement des précisions seront apportées d’une part sur l’inachèvement informatif du phénomène lithique en tant que donnée archéologique et d’autre part, sur son dépassement en tant que phénomène. Il s’agira donc de repenser l’envers de la dialectique lithique-lignic c’est-à-dire les objets du végétal à jamais disparus, à la lumière des objets de pierre taillée seuls conservés comme marqueurs de temps, de technique, d'espace et d’absence.

Lagynochthonius fragilis n. sp. is described from a limestone cave in the Hong Chong karst of Kien Giang Province, southern Vietnam, which is currently threatened by quarrying activities. This is the first record of a troglomorphic species of Lagynochthonius Beier, 1951 from continental Asia. The presence of chemosensory setae on the dorsum of the chelal palm is interpreted as a synapomorphy of the tribe Tyrannochthoniini Chamberlin, 1962. The New Zealand genus Maorichthonius Chamberlin, 1925 is transferred from the Chthoniini Daday, 1888 to the Tyrannochthoniini. The genus Tyrannochthoniella Beier, 1966, also endemic to New Zealand, is assigned to the tribe Chthoniini Daday, 1888. The genus Stygiochthonius Carabajal Márquez, García Carrillo & Rodríguez Fernández, 2001, from southern Spain, is synonymized with Paraliochthonius Beier, 1956 (n. subj. syn.). Five new combinations are proposed: Lagynochthonius ovatus Vitali-di Castri, 1984 (ex Tyrannochthonius); Paraliochthonius barrancoi (Carabajal Márquez, García Carrillo & Rodríguez Fernández, 2001) (ex Stygiochthonius); P. curvidigitatus (Mahnert, 1997) (ex Lagynochthonius); P. setiger (Mahnert, 1997) (ex Tyrannochthonius); and P. superstes (Mahnert, 1986) (ex Tyrannochthonius). A key is given to the genera of the Tyrannochthoniini. The parallel evolution in several groups of pseudoscorpions of a characteristic chelal morphology, here termed lagyniform, is discussed. New designations are proposed for the spot-sensilla of the chelal fingers. The so-called ‘sensorium’ near the tip of the fixed chelal finger of Lagynochthonius species is shown to be a modified tooth that has migrated dorsally from the dental margin. The new term rallum is introduced as a replacement for the inappropriate term ‘flagellum’, as applied to the cheliceral blades of pseudoscorpions. The term bothridial vestibulum is introduced for the internal cuticular sheath at the base of the bothridia of the trichobothria.Lagynochthonius fragilis n. sp. est décrit d’une grotte calcaire de la province de Kien Giang, au sud du Vietnam, actuellement menacée par une exploitation de carrière. Elle est la première espèce troglomorphe du genre Lagynochthonius Beier, 1951 connue de l’Asie continentale. La présence des soies chemosensorielles sur la main de la pince est interprétée comme une synapomorphie de la tribu des Tyrannochthoniini Chamberlin, 1962. Le genre néo-zélandais Maorichthonius Chamberlin, 1925 est transféré des Chthoniini Daday à la tribu des Tyrannochthoniini. Le genre Tyrannochthoniella Beier, 1966, également endémique de la Nouvelle Zélande, est attribué à la tribu des Chthoniini Daday, 1888. Le genre Stygiochthonius Carabajal Márquez, García Carrillo & Rodríguez Fernández, 2001, du sud de l’Espagne, est mis en synonymie avec Paraliochthonius Beier, 1956 (n. syn. subj.). Cinq combinaisons nouvelles sont proposées : Lagynochthonius ovatus Vitali-di Castri, 1984 (ex Tyrannochthonius) ; Paraliochthonius barrancoi (Carabajal Márquez, García Carrillo & Rodríguez Fernández, 2001) (ex Stygiochthonius) ; P. curvidigitatus (Mahnert, 1997) (ex Lagynochthonius) ; P. setiger (Mahnert, 1997) (ex Tyrannochthonius) ; et P. superstes (Mahnert, 1986) (ex Tyrannochthonius). Une clé de détermination des genres de Tyrannochthoniini est fournite. L’évolution parallèle des facies caractéristiques de la pince, ici qualifié de “ lagyniforme ”, est évoquée chez plusieurs groupes de pseudoscorpions. Desnouveaux sigles sont proposés pour les sensilles punctiformes des doigts de la pince. Il est démontré que le “ sensorium ” à l’extrémité du doigt fixe de la pince des espèces de Lagynochthonius est une dent modifiée qui a migré dorsalement dès la marge dentale. Le terme inapproprié de “ flagelle ”, dans le sens de son application aux lames chélicèriennes des pseudoscorpions, est remplacé par rallum. Le terme nouveau vestibule trichobothriale est introduit pour la gaine cuticulaire à la base des bothridies des trichobothries.

We propose a concept for a geodynamic model of East Asia, taking into account the mechanism of the interaction between the stable part of the regional continental lithosphere and the active continental margin along the Kuril-Kamchatka and Japan island arcs. The concept involves upper mantle convection combined with keyboard-block mechanism explaining seismic cycle patterns in the active continental margin and provides grounds to resolve the paradoxes of the present-day velocity field observed by satellite geodesy methods. These paradoxes are associated with enormous variation in the velocity field, such as sometimes contradict directions of surface motions in the adjacent portions of the earth’s surface. We propose a model that attribute the observed motion pattern to the superposition of the long-term subduction-driven convection regime beneath the continent causing the ocean-ward lithosphere extension and the shorter-term cyclic motion of seismogenic blocks with alternating directions. The model contributes to the development of the physically-based theoretical concepts of modern plate tectonics and eliminates the contradictions between the observed data and classical plate tectonics in East Asia region.

AbstractAimThe continental island system comprising Sakhalin, Hokkaido and the southern Kuril Islands (SHSK) in northeastern Asia serves as one of the southernmost habitats for many boreal and arctic organisms, with colonization via land bridges formed during glacial periods. To understand the impacts of past land‐bridge formation under Quaternary climate changes across SHSK, we investigated the demographic history of forest‐dwelling marten species.LocationSakhalin, Hokkaido and the southern Kuril Islands in northeastern Asia.TaxonSable, Martes zibellina (Carnivora, Mustelidae).MethodsWe employed multiplexed inter‐simple sequence repeat genotyping by sequencing (MIG‐seq) to obtain genome‐wide single nucleotide polymorphisms (SNPs). We tested possible scenarios of colonization and diversification for SHSK sables using several population genetics approaches including clustering analysis, population tree estimation and approximate Bayesian computation modelling. We also examined haplotype diversity for the mitochondrial ND2 gene.ResultsThe genetic diversity of the island populations and their affinity for continental populations were found to be higher in the order Sakhalin > Hokkaido > Iturup in both nuclear SNP and mitochondrial DNA analyses. Demographic analyses indicated that the sable migrated repeatedly from the continent, particularly to the neighbouring Sakhalin Island. However, only an earlier colonized lineage has persisted on marginal Iturup Island since the Middle Pleistocene. The stronger effects of repeated migrations and/or isolation influenced by the distance to the continent have shaped the contemporary genetic diversity and differentiation of sable populations in SHSK.Main ConclusionsGenome‐wide and comprehensive sampling approaches demonstrated that the forest‐dwelling sable had long‐term persistence with partial admixture of multiple lineages in SHSK, suggesting the existence of forest corridors and refugia on the islands during the last several glacial periods. The SHSK system of continental islands is valuable for understanding the impacts of Quaternary climate changes on the genetic diversity and evolutionary histories of boreal organisms.

Le plateau de la Sonde, qui fait partie du sud de la mer de Chine méridionale (SCS), est situé dans une région tropicale caractérisée par une tectonique stable depuis le Quaternaire. Elle a examiné des échantillons de sédiments fluviaux dans des régions sources potentielles, des sédiments du fond marin et des carottes du plateau de la Sonde (ST13) et du talus (18288-2), à l'aide d'analyses élémentaires et isotopiques. Elle a analysé l'évolution des sources de sédiments depuis la dernière déglaciation et les changements induits sur le cycle du carbone par plateau de la Sonde pendant les périodes de haut et de bas niveau de la mer. En particulier, elle a exploré les changements relatifs de l'intensité de l'altération des silicates entre les périodes glaciaires et interglaciaires dans le sud de la SCS. Elle a également calculé le taux de consommation de CO₂ atmosphérique par l'altération des silicates depuis la dernière déglaciation et identifié les facteurs contrôlant ce taux. Les principales observation et conclusions de ce travail sont les suivantes : Les grandes rivières dominent les sources actuelles de sédiments marins. La composition isotopique Sr-Nd des sédiments du plateau continental de la Sonde et du sud du SCS ressemble étroitement à celle des sédiments des grandes rivières du nord (Mékong, Fleuve Rouge), ce qui indique que les sédiments marins actuels sont principalement contrôlés par de grandes rivières à fort flux de sédiments. Les changements du niveau de la mer ont imposé des changements dans les transferts et la nature des sédiments dans le sud du SCS depuis la fin du dernier maximum glacière (LGM). Les valeurs ⁸⁷Sr/⁸⁶Sr et ɛNd des sédiments du stade I (0-12.5 Ka) de 18288-2 et les sédiments de ST13 sont dans la gamme de celles du golfe de Beibuwan, du plateau de la Sonde et des sédiments au large de la péninsule indochinoise. Les valeurs ⁸⁷Sr/⁸⁶Sr et ɛNd des sédiments du stade II (12.5-16.5 Ka) de 18288-2 sont assez proches de celles des sédiments au large de la péninsule indochinoise. La composition isotopique des sédiments du stade III (16.5-18.5 Ka) de 18288-2 est proche de la gamme de distribution isotopique des sédiments offshore de Bornéo. Quatre facteurs suivants contrôlent les changements de provenance des sédiments des niveaux marins élevés et bas : le changements du niveau de la mer, les flux fluviaux et distance de transport, les courants océaniques, et les changements climatiques. Les changements d'intensité d'altération enregistrés par les sédiments des carottes ST13 et 18288-2 sur les différentes périodes géologiques nécessitent la détermination des contributions de diverses sources par l'analyse de provenance. Les différences de consommation de CO₂ par l'altération des silicates au cours de la période glaciaire et de l'Holocène ont été calculées quantitativement sur la base des différences d'intensité d'altération et relative à la consommation de CO₂ entre le stade I (fin de la LGM à début de la déglaciation), le stade II (fin de la déglaciation) et le stade III (Holocène) pour les sédiments de la carotte 18288-2. Les changements entre le stade I et le stade III sont minimes. Pour le stade II, la consommation de CO₂ était comprise entre - 44 et 14 × 10⁹ mol/an, selon la présence ou non de matériel de Bornéo dans la source. En supposant un taux moyen de consommation de CO₂ de 191 × 10³ mol/km²/an pendant l'Holocène (stade III) basé sur des données publiées précédemment sur les taux d'altération terrestre autour du SCS, avec une superficie moyenne de terres altérables de 1,76 × 10⁶ km² dans la zone d'étude, nous avons estimé la consommation moyenne de CO₂ pendant l'Holocène à 336 × 10⁹ mol/an. La consommation de CO₂ pendant les stades I et II a été calculée à 300-350 × 10⁹ mol/an, ce qui suggère que la consommation de CO₂ par l'altération des silicates dans le sud du SCS est restée relativement constante depuis la fin du LGM
The Sunda Shelf, as part of southern South China Sea (SCS), is in a low-latitude tropical region, with stable tectonics since the Quaternary. During glacial lowstand, the Sunda Shelf was exposed and connected to surrounding land, forming the Sunda Continent, which is the most important geographical change in the low-latitude regions during the Quaternary. How did the exposure of the shelf during glacial-interglacial cycles alter the sediment "source-sink" processes in the southern SCS? Did the increased land available for weathering reactions due to shelf exposure affect atmospheric CO₂ concentrations? Research on these questions remains limited. This study focuses on the Sunda Shelf of southern SCS and surrounding lands. It examined samples both from the land and marine with geochemical methods. analyzed the evolution of sediment sources in the southern SCS since the last deglaciation and the changes in the "source-sink" role of the Sunda Shelf during of high and low sea levels periods. Explored the relative changes in silicate weathering intensity between glacial and interglacial periods in the southern SCS. It also calculated the atmospheric CO₂ consumption rate by silicate weathering since the last deglaciation and identified the factors controlling this rate. The main findings and conclusions are as follows:(1) Large rivers dominate the present-day marine sediment sources on the southern Sunda shelf of the southern SCS. The Sr-Nd isotopic composition of sediments from the Sunda Shelf and southern SCS closely resembles that of sediments from northern large rivers, indicating that present-day marine sediments are mainly controlled by large rivers with high sediment flux. (2) Sea level changes controlled the shifts in sediment source-to-sink processes in the southern SCS since late LGM. During the glaciation, low sea levels exposed the shelf, with large paleo-river systems. Sediments were directly transported to the slope through these paleo-channels. As sea levels rose, the shelf was gradually submerged, reducing material from southern small island rivers while increasing input from major rivers in the northern shelf. During the Holocene highstand, the Mekong River became the primary sediment source for the Sunda Shelf. It is indicated that sea level changes dictated shifts in source areas and sedimentary centers, while climate, ocean currents, and sediment flux jointly influenced sediment provenance in the southern SCS. (3）The (²³⁴U/²³⁸U) ratio revealed the ongoing active erosion of equatorial tropical islands during glacial periods. It was found that tropical islands near the equator experienced slightly weaker precipitation compared to the Holocene. Materials that had undergone early erosion or had been retained for extended periods were shallowly eroded and remobilized to the slope via paleo-rivers. This indicated that the tropical islands in the southern SCS remained actively eroded during glacial periods.（4）Shelf exposure during glacial periods compensated for the reduced CO₂ consumption rates by silicate weathering due to decreased precipitation, thereby maintaining the overall balance of CO₂ consumption flux since the LGM. Calculations of major elements in core sediments indicated that atmospheric CO₂ consumption flux in the southern SCS has remained nearly constant since the LGM, although silicate weathering rates during glacial periods were only half of those in the Holocene. The increased area available for weathering reactions during glacial periods compensated for the reduced silicate chemical weathering rates, thus controlling the long-term balance of atmospheric CO₂ consumption flux. It was revealed that changes in precipitation are the primary factor controlling variations in silicate weathering and CO₂ consumption rates, while the roles of temperature and lithology require further evidence

La péninsule d'hengchun correspond a l'émergence de la zone de collision active. Un ensemble des dernières nouvelles ont été interprétées afin de proposer un schéma structural et un modèle d'évolution de la subduction manilaise a la collision taiwanaise. On considère. 1. La mise en évidence du matériel ophiolitique oligo-miocène, 2. Une déformation majeure d'âge miocène, 3. Un système d'obduction-collision nettement séparé dans le temps, 4. Un dispositif structural avec des phases de structuration. Dans les nombreuses questions restées en suspens, celle relative a la grande chaine centrale est la plus importante

Abstract The exact definition of ophiolite was formalized by Anonymous (1972) and has generally been followed since. Ophiolite is a distinctive assemblage of mafic to ultramafic rocks. In a completely developed ophiolite the rock types occur in the following sequence: The most common occurrence of ophiolite is along the margins of marginal basins, where the obducted ophio1ite has not yet been compressed into an orogenic sumre zone. Notable examples occur in the Philippines, eastern Indonesia and Sabah. Within the continental sector of SE Asia known as Sundaland, ophiolites are more restricted, more dismembered and incomplete (Hutchison. 1975) and confined to narrow suture zones between different continental lithospheric terrains.

Abstract In this book a distinction has been made between Early Mesozoic (Triassic and Jurassic) and Late Mesozoic (Cretaceous) because of the very different global geographies of these times. As already indicated, Pangaea had become established as a coherent supercontinent at the beginning of the era and did not disintegrate significantly until the Cretaceous. Although uncertainties remain, especially in Asia, knowledge of the relative positions of continental areas in the Mesozoic is considerably better than for the Palaeozoic. A prime reason for this is the existence for the first time, from the Mid Jurassic onwards, of a deep sea record, with magnetic anomalies, preserved on the present ocean floor. Reconstructions have been made starting from the present and removing successively older areas of oceanic crust. This is done by matching sets of magnetic anomalies and following traces of fracture zones on the ocean floor. As for the Palaeozoic, palaeomagnetic data from the continents provide latitudinal control. The early set of reconstructions of Smith and Briden (1977) are still valuable as first-order approximations of reasonable accuracy (Figs 7.1 and 7.2) except for Asia and parts of the Pacific margins, where a series of terranes was accreted. Furthermore, the continental fits are unduly tight, having failed to allow for the fact that there can be significant continental extension before breakup.

The opening of the European market for freight and passenger services has initiated the need for cross-border locomotives which fulfill the specific requirements of each country and comply with new European standards. The TRAXX locomotive platform addresses this new market with four locomotive types. Each type is configured with standard building blocks. The TRAXX platform covers both electric and diesel 4-axle locomotives. A high level of standardization allows manufacturing of all types in a single assembly line, thus also reducing manufacturing costs for small production lots. The key to the TRAXX platform is a high level of system integration. Important innovations are in the traction chain, carbody, air supply, in the development of automatic train protection (ATP) systems based on the future European standard ETCS (European Train Control System) and in system integration. Today, the TRAXX platform covers all major mainline traction needs in continental Europe with more than 1′200 locomotives so far sold. Further developments are needed to optimize the ATP systems for new and important cross-border freight corridors and to streamline the homologation procedures throughout Europe.

Abstract This paper studies the investment planning of a decarbonised Norwegian continental shelf energy system considering the connection and interfaces with the European energy system. A multi-horizon stochastic mixed-integer linear programming model is developed for such a problem. We consider short-term uncertainties, including wind and solar capacity factors, energy load, platform production profiles, and hydro power production limits. Hydrogen based energy hubs are considered both onshore and offshore for potential renewable power generation, distribution and storage. Future hydrogen market or demand is not included in the model. The results of multi-period planning towards 2050 show that: (a) offshore energy hubs are essentially wind power generation, conversion and distribution hubs, (b) a combination of offshore wind and power from shore may be a cost-efficient pathway for cutting emissions from the Norwegian continental shelf, (c) a total of 1.6 GW offshore wind may be needed to achieve a near zero emission Norwegian continental shelf energy system, 80% of which may be added in the first investment period and (d) offshore grid design is important for decarbonisation by distributing wind power efficiently; all five offshore platform clusters are connected to at least three other clusters by 2040, and they are fully connected by 2050.

The performance characteristics of new heat pumps are usually evaluated under standard test conditions in certified test laboratories prior to their market release. While this data allows potential customers an opportunity to compare different heat pumps under the same conditions it is difficult to assess how variations in operating conditions, particularly around horizontally oriented ground collectors impact on heat pump Coefficient Of Performance (COP). Indeed, harsh winter conditions of continental climates dictate that horizontal collectors are buried sufficiently deep enough to operate in a thermally stable environment, independent of the weather, but this is not as critical in milder maritime climates and shallower collectors that may be influenced by climate are used. This review paper therefore seeks to identify the key climate variables that have been shown to influence the efficiency of horizontal collector heat pump systems. The literature highlights the significant impact of soil moisture content on COP, but the extended relationship between climate, moisture content and COP has not been established. Historical climate data from both a continental and maritime climate is presented and key aspects of their respective weather patterns are compared to assess their capacity to influence soil condition and COP. A series of empirical models linking changes in soil moisture content to fluctuations in soil thermal conductivity, diffusivity and resistance are also presented so that the impact of climate on soil thermal energy content and heat transfer characteristics might be assessed. However, since no one study has experimentally determined the complex relationship between climate, soil heat transfer characteristics and heat pump performance, this paper concludes with an overview of an experimental test facility that allows this relationship to be established for horizontal collector heat pumps in maritime climates.

Abstract The advent of Direct Broadcast Satellites requires the associated development of origination facilities supporting hundreds of viewer channels. Such facilities use highly automated, fault tolerant control systems to facilitate cost-effective staffing levels and the flexibility to support services that are only now evolving. We summarize the capabilities and architecture of two such facilities that are among the largest in the world: the more than 175 channel DIRECTV® Castle Rock Broadcast Center (CRBC) servicing the continental United States from Colorado, and the 72 channel DIRECTV International Inc. California Broadcast Center in Long Beach servicing Latin America and the Caribbean. For program transmission, these services use the latest, high-powered Hughes Kuband communication satellites. For program playback, each plant uses relatively conventional digital tape-based technology. Two factors make the program playout operations unique. First, their extreme size and scope. Second, all the resources in the plant are sharable and schedulable among different viewer channels to assure the plant can adapt to the services demanded by their evolving market. Some “lessons learned” are then discussed as suggestions to aid future product and facility developments.

Abstract A mathematical model is presented to predict the formation of gas hydrates in porous media under various boundary conditions. The new mathematical modeling framework is based on coupling the analytical pore network approach (APNA) and equation proposed by De La Fuente et al. [1]. Further, we also integrate thermodynamic models to capture the phase boundary at which the formation of gas hydrates takes place. The proposed analytical framework is a set of equations that are computationally inexpensive to solve, allowing us to predict the formation of gas hydrates in complex porous media. Complete governing equations are provided, and the method is described in detail to permit readers to replicate all results. To demonstrate the formation of hydrates in porous media, we analyzed the saturation of hydrates in porous media with different properties. Our model shows that the hydrate formation rate is positively related to the porous media's pore size. The hydrates were found to be preferably formed in the porous media composed of relatively larger pores, which could be attributed to the weak capillary forces resisting the formation of hydrates in porous media. The novelty of the new analytical model is the ability to predict the gas hydrates formation in porous media in a reasonable time using standard engineering computers. Furthermore, the model can aid in the estimation of natural gas hydrate reservoirs, which offer the avenue for effective methane recovery from the vast natural gas hydrate reserves in continental margins.

Abstract Subsea technology often enables the low-cost development of small marginal fields with short production lifetimes and low profit margins. However, ensuring high levels of reliability and low maintenance requirements for these subsea systems is critical for success and can be difficult to achieve. The goal of this research is to use numerical programming and optimization as a decision-support tool for the design of subsea production systems, while taking reliability and maintenance into account. The optimization was designed to determine the most suitable subsea equipment and production strategy while considering production constraints, system downtime, lost revenue from production losses, and operational expenses. The reliability and maintenance model was integrated in the optimization model to provide the best solution possible, avoiding the problem of using two separate models that may only provide suboptimal results. This paper also discusses some of the difficulties in offshore reliability and maintenance modelling, as well as the uncertainties, constraints, and calculations used to improve the model’s accuracy. The method was tested on a synthetic field study case in the Norwegian Continental Shelf. When reliability and maintenance parameters were included in the model, a different optimal solution was discovered. When the two solutions were compared, the new optimal design had an increase in NPV of 11 million USD over the previous one. The methodology presented advances modelling and automated decision-making in subsea production system design.

A simplified reliability assessment is carried out for a generic jacket at 200m water depth. The purpose is to indicate the sensitivity of the annual failure probability to the selected airgap and current design profile. Two example cases are considered. For one case the required airgap is defined by the 10−4 wave crest height, while for the other the required airgap is defined from the 10−2 wave crest height plus an uncertainty margin taken to be 10% of the crest height. For both cases, the required minimum design base shear capacities are determined both using the 10-year current profile (earlier practice at the Norwegian Continental Shelf) and the associated current profile (i.e. the current profile which when used in combination with the n-year wave height yields the n-year load). The investigation shown herein clearly demonstrates that the chosen airgap is a crucial parameter regarding the annual probability of structural failure. It is, furthermore, demonstrated that if a wave-deck impact is required in order to fail the structure (which will be the case for most jackets), the current modeling is not very important. However, if the structure is designed such that failure may occur for wave heights not reaching deck level (either due to a highly utilized design or a very generous initial airgap), the current modeling (both in terms of selected design profile and joint description of wave height and current speed) may be far more important.