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Abstract In light of the recent increasing interest in the oil and gas developmentsin the arctic region, Huisman Equipment B.V. has developed a Mobile OffshoreDrilling Unit (MODU) named JBF Arctic suited for arctic condition. The stationkeeping in ice is one of the crucial factors determining the feasibility of thedesign. As one of the first steps of the design process ice model tests wereperformed at the Krylov Shipbuilding Research Institute (KSRI) to gain insightin the ice forces acting on the unit. During the model tests the model of theJBF Arctic was retained in a fixed position while being towed through the ice. In reality the station keeping of the unit will be ensured by a mooring system, which has certain flexibility compared to the rigid constrains in the modeltests. This paper elaborates on the creation of a numerical model that canperform time-domain simulations of the dynamic interaction between the vesseland the ice-loads. Using these simulations the mooring system is optimized inorder to cope with the ice loads corresponding to unbroken level ice withthickness up to 3.1m. Several important conclusions were drawn. One is the factthat no dominating frequencies of the ice failing could be identified from themodel tests. This can be explained by a large ratio between the diameter of theunit and the ice thickness. So the ice failure mechanism has a chaoticcharacter. Another conclusion is that the unit does not exhibit significantdynamic behavior. This means that a quasi-static approach can be generally usedfor initial design of the mooring system. Introduction The JBF Arctic is a semi-submersible drilling unit designed to cater thefuture needs for year-around drilling in the arctic region (Bereznitski, 2011). In the topside of the vessel this is reflected in the fully sheltered workingareas and number of other features needed for the winterization.
- North America > United States > Texas (0.28)
- Europe (0.28)
- Asia (0.28)
Copyright 2011, Offshore Technology Conference This paper was prepared for presentation at the Arctic Technology Conference held in Houston, Texas, USA, 7-9 February 2011. This paper was selected for presentation by an ATC program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material does not necessarily reflect any position of the Offshore Technology Conference, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of OTC copyright.
- North America > Canada > Newfoundland and Labrador (0.71)
- North America > United States > Texas > Harris County > Houston (0.54)
- North America > Canada > Newfoundland and Labrador > Newfoundland > North Atlantic Ocean > Atlantic Margin Basin > Grand Banks Basin > Jeanne d'Arc Basin (0.99)
- North America > Canada > Newfoundland and Labrador > Newfoundland > North Atlantic Ocean > Grand Banks Basin (0.89)
- North America > Canada > Newfoundland and Labrador > Labrador Sea > Hopedale Basin > Bjarni Field (0.89)
Summary In this study, we investigate the accuracy of approximating constant-Q by a series of Zener or standard linear solids (SLS) mechanisms. Modeling of approximately constant-Q in a viscoacoustic medium is implemented in time domain using finite-difference (FD) approach. The accuracy of numerical solutions is evaluated by comparison with the analytical solution of the constant-Q model. We found the FD solutions using three SLS (relaxation mechanisms) as well as a single SLS mechanism are quite accurate for weak and strong attenuation. Although the RMS errors of FD simulations using the single relaxation mechanism become larger with increasing offset, especially for strong attenuation (Q=20), the results are still acceptable. The simulated synthetic data of the complex model further illustrate that the single SLS mechanism to model constant-Q is efficient and sufficiently accurate. Moreover, it benefits from less computational costs in time and memory. Therefore, we suggest that the single relaxation is a promising choice to model constant-Q for computational intensive seismic modeling and inversion.
Summary A combination of the FDTD technique and Mittet's mapping method is a powerful and fast numerical tool for solution of marine controlled source electromagnetic problems. The efficiency of this technique can be further improved by using optimized, dispersion reducing finite difference coefficients for calculation of first derivatives in Maxwell's equations. We present a method for calculating such coefficients. It is demonstrated that by utilizing dispersion reducing coefficients, the discretization mesh size can be reduced up to two times in 3D diffusive problems.
Summary We show that numerical support of laboratory experiments can significantly increase the understanding and interpretation of the obtained results. First we perform simulations of the Seismic Wave Attenuation Module to measure seismic attenuation of reservoir rocks. Our findings confirm the accuracy of this system. However, precision can be improved by optimizing the sensor positions. Second we model wave propagation for an ultrasonic pulse transmission experiment that is used to determine pressure- and temperature-dependent seismic velocities in the rock. Multiple waves are identified in our computer experiment, including bar waves. The metal jacket that houses the sample assembly needs to be taken into account for a proper estimation of the ultrasonic velocities. This influence is frequency-dependent.
The recent special issue of (mt) magazine deals with the importance of human factors engineering to ultimately resolve the issues associated with health, safety, the environment, and ergonomics in maritime industry (SNAME, 2012). As Spencer pointed out in the article titled "Analyzing error - Safer maritime systems demand the integration of human performance" of the special issue, approximately 80% of maritime accidents are caused by, or associated with human error. Regulations are not enough to eliminate human error because they have tended to address primarily mechanical or physical things, and the international maritime community now recognizes that the many types of safety issues have a common thread in human factors, and managing the human element is certainly an important issue. To reduce the number of serious accidents, therefore, pertinent disciplines which may be different depending on particular circumstances should be developed and used to manage human error which should become central to the entire lifecycle at all phases from engineering and design to decommissioning. In offshore oil and gas sector, the discipline of human factors engineering should aim to systematically address human-system integration issues via practical activities during the design, fabrication, construction, and decommissioning, as Robb mentioned in the article titled "Human factors meets oil and gas - A review of industry guidance in various regions" of the (mt) special issue.
- Europe > Norway (1.00)
- North America > United States (0.93)
- Europe > United Kingdom (0.67)
Pilot Study of Environmental Risk Analysis Methodology Applied to Angolan Dalia FPSO
Libre, Jean-Marie (TOTAL E&P) | Plisson-Saune, Stephan (TOTAL E&P) | Quiniou, Valérie (TOTAL E&P) | Nissen-Lie, Torild R. (DNV) | Vandenbussche, Valentin (DNV) | Brude, Odd Willy (DNV) | Rudberg, Anders (DNV) | Battut, Maïthena (DNV)
Abstract An Environmental Risk Analysis (ERA) was conducted as a pilot study on the Dalia Total FPSO (Floating Production and Storage unit) in Angola located at about 135 km off the coast with complex subsea installations at 1400m depth. The environmental damage and its frequency resulting from the drift and fate of oil depend on many physical, chemical and environmental parameters like the location and composition of the spill, oil weathering, complex and variable surface wind and current patterns, weather conditions, sensitivity of the environmental resource etc…The detailed ERA can only be done if one can estimate the probability of a given quantity of oil to reach an environmental resource and the resulting environmental damage. The possibility to use 3D oil spill drift simulation to fulfill these technical requirements and fit with the Total HSE Reference Framework and risk Matrix is tested. The TOTAL HSE Reference Framework requires that technological risk assessments are carried out for all installations. Based on the technological risk assessment of Dalia FPSO, accidental spill scenarios were compiled and aggregated to a set of most representative scenarios including one blow out case. For each spill scenario, oil drift simulations were conducted in stochastic mode with the OSCAR model developed by Sintef i.e. repeated 246 times for a period of 5 years where met-ocean data were available. Quantities of oil and associated probabilities of presence were calculated for each cell of the model. Environmental target were identified and positioned within a Geographical Information System (GIS) also used in simulations. Environmental damages were estimated based on the MIRA method. Based on these data accidental spill scenarios could be positioned on the Total risk matrix. The pilot results as well as the acceptability of the uncertainties related to this approach are discussed.
- Management > Risk Management and Decision-Making > Risk, uncertainty, and risk assessment (1.00)
- Health, Safety, Environment & Sustainability > Environment > Oil and chemical spills (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Floating production systems (1.00)
Ship Springing Analysis For Very Large Container Ship
Kim, Jung-Hyun (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Kim, Yonghwan (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Kang, Byoung-Chul (DSME R&D Institute, Daewoo Shipbuilding and Marine Engineering) | Kim, Yooil (Department of Naval Architecture and Ocean Engineering, Inha University)
This paper considers the analysis of ship springing which is based on a hybrid BEM-FEM method to couple the boundary value problems of two distinct domains: fluid and structure. A strong-coupling scheme is applied to solve fluid-structure interaction by using a fixed-point iteration scheme. This study focuses particularly on the observation of computational results for the different beam modeling of ship structure and different structural damping. Even though the same computer code is applied, the computational results can be dependent on the user and the modeling of computational parameters such as grids, beam modeling and external forces. The ship model considered in this study is a very large containership. The computed motion RAO and the load signal time-histories are compared with experimental data, and the agreement and discrepancy are described. This kind of observation may help us to understand the uncertainty level of numerical analysis in ship springing analysis. INTRODUCTION Hydroelastic hull-girder vibrations referred to as springing and whipping have come to be real engineering issues with recent strong demands for larger and faster ships than ever before. As ship size is getting larger, the occurrence probabilities of springing and whipping are getting higher in general, and consequently more potential fatigue damage can be easily predicted. The primary mechanisms of springing and whipping are basically the same, but the excitation characteristics are very different. Springing is excited by ocean waves, while whipping is the transient response of hull-structure due to impulsive slamming force. This study focuses on ship springing. If the lowest natural frequency of global ship structure is far higher than the dominant frequency range of ocean wave spectrum, springing will be negligible in ship design. However, the recent trend of building very large container ships makes springing one of significant sources of global ship vibration.
- Transportation > Marine (1.00)
- Transportation > Freight & Logistics Services > Shipping > Container Ship (0.91)
SEAM Phase I RPSEA is in the process of completing a suite of geophysical simulations on the geophysical model representative of a salt area of the deep-water Gulf of Mexico. Part of this interdisciplinary effort includes the simulation of two types of electromagnetic acquisitions over the SEAM model, one for a controlled-source electromagnetic (CSEM) and one for magnetotelluric (MT). Both CSEM and MT 3D modeling and imaging technologies are of intense interest to companies conducting exploration and reservoir development in marine environments. SEAM's goal is to provide 3D electromagnetic data that not only mimic current field acquisitions but, in most cases, far exceed them. The resulting simulation data can be used to validate and ultimately improve 3D EM forward modeling as well as subsurface imaging and characterization methods using electromagnetic data alone or when combined with other types of geophysical data.
- North America > United States (0.35)
- North America > Mexico (0.25)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Electromagnetic Surveying (0.93)
ABSTRACT Frequency responses of seismic wave propagation can be obtained either by directly solving the frequency domain wave equations or by transforming the time domain wavefields using the Fourier transform. The former approach requires solving systems of linear equations, which becomes progressively difficult to tackle for larger scale models and for higher frequency components. On the contrary, the latter approach can be efficiently implemented using explicit time integration methods in conjunction with running summations as the computation progresses. Commonly used explicit time integration methods correspond to the truncated Taylor series approximations that can cause significant errors for large time steps. The rapid expansion method (REM) uses the Chebyshev expansion and offers an optimal solution to the second-order-in-time wave equations. When applying the Fourier transform to the time domain wavefield solution computed by the REM, we can derive a frequency response modeling formula that has the same form as the original time domain REM equation but with different summation coefficients. In particular, the summation coefficients for the frequency response modeling formula corresponds to the Fourier transform of those for the time domain modeling equation. As a result, we can directly compute frequency responses from the Chebyshev expansion polynomials rather than the time domain wavefield snapshots as do other time domain frequency response modeling methods. When combined with the pseudospectral method in space, this new frequency response modeling method can produce spectrally accurate results with high efficiency.
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling (0.68)