Academic literature on the topic 'Sevan'

L'analyse de 3 sous-bassins hydrogeologique tests composant le bassin artesien de sevan aboutit aux resultats suivants: _ independance hydraulique entre les eaux de surface et les horizons aquiferes profonds du bassin ; _ faible influence sur les nappes captives de la barometrie (3-6 cm) et des marees terrestres (0. 020. 025 bars sur forages jaillissants) ; _ role fondamental du manteau neigeux dans la recharge des nappes avec des dephasages temporels importants ; _ reconstitution des relations precipitations - piezometrie a l'aide de 2 modeles : a) modele mathematique de relation precipitations - piezometrie (mmpp), b) modele statistique de relation precipitations - piezometrie (mspp) ; _ mise en evidence d'anomalies piezometriques uniquement dues a l'activite sismique locale (interieur du bloc tectonique pull-apart de sevan) ; _ l'abaissement important du lac (17 m en 2/3 de siecle) est uniquement du a une surexploitation anterieure du lac : sa recharge artificielle est donc envisageable, sous reserve que les modalites en soient precisees (hauteur, origine des apports, duree ).

As the oil price is relative high, oil companies continue their quest for oil in new areas where it was supposed impossible earlier. 25 % of the world petroleum reserves are assumed to be in Arctic areas. In these areas ice contribute to significant engineering challenges. Ice conditions, emergency response, winterization and extreme low temperatures are some of the challenges that have to be address for design and operation purpose. Ice is an interesting material for an engineer. The knowledge of ice mechanics and physics is essential for understanding how ice forces are developed and acts. The agreement in estimating of forces and development of ice loads have been over time been evaluated for the writing of new structural code. Structural layout proofs to be a significant factor in how ice is managed and therefore in reducing ice actions. However studies have showed that prediction of ice actions is hard to establish and therefore it is difficult to establish proper loading cases. For designing a FPSO in the arctic waters, the classification criteria for floating units need to be complied with. The DNV rules for offshore structure refer to the class rules for ship with additional ice strengthening class. The ISO (International Organization for Standardization) the world's largest developer and publisher of International Standards have issued a draft for a design code for Arctic offshore structures. These two rules and codes have been compared in connection with local structural arrangement. For arctic structures, two design checks ELIE and ALIE are required. These design checks are less established. ELIE ice checks have a return period of one hundred year (10-2) and ALIE one thousand year (10-4). The SEVAN-FPU ice is designed for handling level ice up to 3 m according the DNV Polar 30 Class Notation. Structures are according to the codes required to withstand the ice actions from ELIE within the elastic region. ALIE action will involve plastic damage, but the requirement is to maintain structural integrity to survive a ULIE check. The master thesis purpose is to determine ELIE and ALIE. The ELIE and ALIE are clearly depended on local field data which makes it a challenge in estimations. The ELIE design load for the Sevan FPU-ice is based on a pressure-area equation for massive ice feature. The pressure-area equation is based on empirical data measurement from several field programs. The load area for a plate design is assumed to be the whole plate area, while for the stiffener design 80% of the plate height times four stiffener spacing. The ELIE pressure is respectively 5.11 MPa and 2.37 MPa. For arctic structures, iceberg is the governing factor for ALIE. Designing for an impact of a large iceberg in 100 or 10 000 years storm may be impossible due to the massive energy involved. Sevan FPU-ice is designed with possibility of disconnecting. This may reduced the ALIE load, however the possibility of failure in disconnecting should be included in ALIE. In estimation of iceberg impact, kinetic energy is the load applied for calculations. Structural resistance for impact is measured in energy dissipated in strain before fracture. The plastic strain gives the dominating dissipated energy and elastic strain is in a small magnitude. By equating kinetic energy applied and strain energy dissipated before fracture can be seen as what the structure can withstand. ABAQUS standard has been applied for analyzing different structural layout with the intentional structural layout for SEVAN- FPU-ice as a basis. A non linear finite element analysis is preformed to investigate structural capacity and the energy dissipated in plastic strain in order to check for ELIE and ALIE. The model has been created using the ABAQUS CAE. The ELIE design loads for plate and stiffener design are applied for the ABAQUS for the intentional structural layout. Both plate and stiffener design check was applied in the elastic region. Six different models were made with different stiffener profile. Plate and stiffener spacing were hold constant with the structural layout given from Sevan. For finding the ultimate strength of the, a plate patch load was applied with three different load intensity. The load intensity was found in the using the same pressure area curve as for the ELIE design load. The loads were scaled up to an assumed strain level beyond critical strain. The result showed that a T-bar stiffener withstands the pressure loads significant better. The results from the analysis should be handled with care. In particular the boundary conditions should be evaluated further. The results should be verified by more extensive use of finite element programs.

Platform-ship collisions are fortunately rare events, but as the development of the offshore and oil industry and the gradually frequently used offloading operation, accidents become more and more frequent. The consequences of collisions are always severe, which includes loss of life, property and environmental damage. Thus It is important to predict the outcome of collision scenarios and assess the damage that may happen to the platform as well as the shuttle tanker.Collisions are always analyzed by means of the principle of the principle of energy conservation. Initial kinetic energy is dissipated by the two contact bodies as strain energy and in viscous force generation. There is also energy remained as the kinetic energy after the impact for both the striking and struck bodies, both for translational and rotational degrees of freedom. The external mechanics of the collision is easily evaluated, but the strain energy absorption can be rather difficult to evaluate in a correct way.In this thesis, A Samsung shuttle tanker and the Sevan SSP300 platform are analyzed as the striking and struck bodies, respectively. Structural configurations are described for both structures. Different impact scenarios are then discussed in the report, some of which are chosen to analyze in the thesis work. Non Linear Finite Element Analysis (NLFEA) model of the SSP300 platform is created. The shuttle tanker model is an exist one. One-sixth of the platform is modeled in detail with the correct stiffeners and other details, while for the other part, only the outer shell and the main bulkheads are modeled. For the tanker, adjustments are made in order to increase the calculation efficiency. Only the bow is remained in details. For the hull, only the outer shell is remained. For both structural models, adjustments are made to obtain the correct mass, added mass and inertial. Both models have a user defined material with the fracture criterion included. Integrated analysis is mainly performed. Then the integrated analysis is split into internal mechanics and external mechanics. Among these, integrated analysis and internal mechanics analysis are performed with finite element method, using the explicit NLFEA solver LS-DYNA. For the collision scenarios, only bow impact with different headings is considered. Two different impact velocities are chosen in both head on collision and collision with the glancing angle of 30 degrees. Energy absorption and force-displacement relationship can be obtained. Damage on the platform is also evaluated. Internal mechanics are then analyzed by changing the boundary condition and making the impact velocity constant. The purpose is to evaluate the damage with internal mechanics and then compare it with the results from integrated analysis. Liu’s method, which is based on Stronge theory, is mainly used in external mechanics as a simplified method. Herein a Matlab program is established to calculate the energy dissipation and the velocity after the impact. Two other simplified methods are utilized to calculate the dissipated energy and then compare them with the results from NLFEA analysis. One is from the DNV-RP-C204 and the other one is from T.de Jonge&L.laukeland’s report. The latter one is an optimized method compared to the one from DNV rules, which includes the effect of roll motion. Results from the simplified methods and NLFEA method show good correlation. All the simplified methods overestimate the absorbed energy, which is conservative. Among these, Liu’s method gives the best correlation with the NLFEA method. Two additional jobs are conducted in the end. Only the energy dissipation is analyzed in this section. One is changing the loading conditions of the two bodies. The energy dissipation becomes smaller after changing. The other one is changing the friction coefficient. The energy dissipated by the tanker is smaller, while by the platform is larger. But from the overall view, the energy does not show big difference with friction coefficient 0.15 and 0.4.

L’Arménie se situe dans la zone de collision entre Arabie et Eurasie et est le siège d’une déformation intracontinental active comme l’atteste les nombreux tremblements de terre historiques qui s’y sont produits. Tous ces séismes, destructeurs, attestent d’une forte activité sismique régionale, et il est par conséquent important d'évaluer l’aléa sismique associé aux structures actives qui génère cette sismicité.Le travail présenté ici, expose les résultats de l’analyse de la tectonique active au niveau des terminaisons nord-ouest et sud-est de la faille de Pambak-Sevan-Syunik (PSSF), une des failles décrochant majeure qui traverse l'Arménie du NW au SE. La quantification des déformations en termes de géométrie, cinématique, vitesse de glissement et paléosismicité, en utilisant les méthodes de datation 3He cosmogénique, OSL/IRSL et radiocarbone, révèlent des comportements différents entre les deux régions.Au niveau de la terminaison nord-ouest, dans la région d’Amassia, la faille PSSF s’incurve vers l'ouest et se subdivise en deux branches de direction WNW-ESE, et de cinématique inverse, définissant une structure en pop-up. Nous estimons une vitesse de soulèvement de 0.5 ± 0.1 mm/an et une vitesse de raccourcissement NNE-SSW de 1.4 ± 0.6 mm/an. Ces résultats suggère que l’essentiel des ~2 mm/an de mouvement dextre estimés le long de la faille de PSSF sont absorbés au niveau du pop-up d’Amassia.Au niveau de la terminaison sud-est, dans la région du volcan Tsghuk, la faille PSSF semble disparaitre. Le peu d’activité tectonique est caractérisée par des failles normales sub-méridiennes associées à une légère composante décrochant dextre. Nous déterminons une vitesse de glissement vertical de ~0,2 mm/an, une vitesse d’extension ~EW de ~0,1 mm/an associée à une composante dextre de ~0,05 mm/an. Ces résultats suggèrent que le mouvement dextre observé le long de la faille de PSSF plus au nord, a été transféré sur d'autres failles plus à l'ouest dans le Karabakh (faille Hagari ou autres structures situés encore plus au NW)<br>The territory of Armenia was located in the collision zone between Arabia and Eurasia, and is the seat of active intercontinental deformations, which was attested by the many historical earthquakes that have occurred in this region. All these destructive earthquakes show a strong regional seismic activity, and therefore it is important to evaluate the seismic hazard associated with active structures that generates this seismicity.This study presents the results of the analysis of the active tectonics within the northwestern and southeastern extensions of the Pambak-Sevan-Syunik fault (PSSF), a major right-lateral strike-slip fault cutting through Armenia (NW - SE). Quantifying the deformations in terms of geometry, kinematics, slip rates and earthquake activity, using cosmogenic 3He, OSL/IRSL and radiocarbon dating techniques, reveal different behaviors between the two regions.Within the northwestern extension, in the region of Amassia, the PSSF bends to the west and splits into two main WNW-ESE trending reverse faults defining a compressional pop-up structure. We estimate an uplift rate and a shortening rate of 0.5 ± 0.1 mm/y and 1.4 ± 0.6 mm/y, respectively. This suggests that most of the ~2 mm/y right lateral movement of the PSSF seems to be absorbed within the Amasia pop-structure.Within the southeastern extension, in the region of Tsghuk volcano, the PSSF shows signs of dying out at the southernmost tip of the Syunik graben. A very slow NS trending normal faulting associated with a slight right-lateral movement characterizes the tectonic activity in the region of Tsghuk volcano. We estimate vertical slip rates, EW stretching rate, and right-lateral slip rate of ~0.2 mm/y, ~0.1 mm/y and ~0.05 mm/y, respectively. These results lead to the conclusion that the right lateral movement observed further north along the PSSF is mainly transferred within other active faults further west within the Karabagh (Hagari fault or other structures further northwestwards)

The interest for Arctic deep water development intensifies as the worldwide demand for oil and gas continues to grow. As much as 25 % of the world&#146;s remaining hydrocarbons are assumed to be located in the Arctic area. However, the Arctic environment represents engineering challenges due to sea ice, temperature, darkness and environmental impact requirements. To meet these challenges for Arctic deep water developments to have a possibility for year-round operations, particularly for ice loading, a combination of traditional and innovative technology is the key. A buoy shaped floater with a single point detachment is suggested. The hull shape of a buoy has the advantage to reduce loading from ice features and to be loaded in all directions. The geometry of the hull in the ice action area has a significant effect on the magnitude of ice action. In this thesis, the main scope of work is to investigate and analyze ice actions subjected to a floating offshore structure with sloping hull in the ice action water line.The first section is a literature review of the different aspect of sea ice to get a better knowledge of sea ice&#146;s properties and behavior such that the Arctic engineering becomes more comprehensible. Further, a study of the Arctic areas of interest with focus on the Barents Sea has been carried out, followed by an assessment of the industry&#146;s experiences with floating platforms in ice infested waters.An assessment of ice actions, both global ice action and local ice pressure, has been performed using a Sevan Arctic Mobile Offshore Drilling Unit design as reference structure. Theoretical formulations to determine global ice action from level ice and ridge has been examined, as well as an assessment of ice actions from managed ice due to full scale experience from an identical design, the Kulluk Drilling unit. A comparative study of upward and downward sloping structure has been conducted towards geometrical parameters for the ice features, such as level ice thickness, rubble height, consolidated layer thickness and keel height. It is found that increasing level ice thickness is more severe than increasing geometrical sizes of ridges if the slope is bending ice upwards, but opposite if the slope is bending ice downwards. Local ice pressure on sloping structures has been difficult to determine due to lack of literature available. Hence, several approaches have been assessed and the most suited approach for sloping structures has been used further in the thesis to examine structural hull capacity. As a final assessment, a nonlinear static analysis has been performed in ABAQUS of a local model extracted from a Sevan Arctic Mobile Offshore Drilling Unit design which is a buoy shaped floater. ABAQUS solves the finite element method numerically. Hence, a theory part targeting ABAQUS and the element theory relevant for this thesis has been presented. Further, the footsteps necessary to perform in ABAQUS to submit a nonlinear static analysis has been presented. A study has been done with regards to the selection of element size and type by a convergence test which establishes that linear quadrilateral elements with reduced integration and global size 200mm provide conservative results. The local model was check with regards to structural capacity for uniformly distributed ice pressure. In this thesis, the structural capability has been examined for stiffeners and plates and limited by the yielding criterion given by von Mises stress. Based on the results, it has been suggested to design the scantling with higher capability in the stiffeners and reduce the capability in the hull plate to decrease this scattering in structural capability between stiffener and plate. It has also been suggested that the operational ice draft should be designed such that ice actions are loaded on the elevation of a stringer.