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Ship traffic via navigable freezing ice channels causes a gradual accumulation of small ice floes mixed with water, known as brash ice. The thickness of the brash ice layer may reach the values when ship navigation becomes difficult or even impossible. This paper introduces a computational model intended to predict ice channel evolution in winter. The model considers the thermodynamics of the ice-growing process and allows the estimation of the parameters of the cross-section of the ice channel depending on the number of freezing degree-days and the schedule of ship passages. Unlike existing models, the described scheme of channel evolution takes into account that some brash ice is pushed beneath ice channel edges by passing vessels, and therefore the obtained cross-section profile is similar to that observed in full-scale conditions.
Ship navigation in freezing waters is conducted via ice channels made in the ice cover. A channel behind the icebreaker remains but is filled with broken ice fragments. Ships may use the same ice channel time and again. Between ship passages, a fresh ice cover grows in the channel under freezing temperatures. At each ship passage, the ice cover is broken again, and ice blocks are split into smaller pieces. Frequently used channels accumulate smaller ice floes (mean size 50 cm) mixed with water (“brash ice”). The water content is defined by the porosity of the brash ice, which influences the intensity of ice accumulation in the channel.
Ship navigation in ice channels filled with brash ice involves two main issues. First, it is necessary to know the current state of the ice channel. The second issue is related to ship performance in the ice channel, including the hull resistance and the effect of brash ice on propeller operation. This study examines only the first issue, the evolution of the ice channel during the winter season.
Gas production from shale formations is growing, especially in the USA. However, the origin of shale gases remains poorly understood. The objective of this study is to interpret the origin of shale gases from around the world using recently revised gas genetic diagrams. We collected a large dataset of gas samples recovered from shale formations around the world and interpreted the origin of shale gases using recently revised gas genetic diagrams. The dataset includes >2000 gas samples from the USA, China, Canada, Saudi Arabia, Australia, Sweden, Poland, Argentina, United Kingdom and France. Both free gases collected at wellheads and desorbed gases from cores are included in the dataset. Shale gas samples come from >34 sedimentary basins and >65 different shale formations (plays) ranging in age from Proterozoic (Kyalla and Velkerri Formations, Australia) to Miocene (Monterey Formation, USA). The original data were presented in >80 publications and reports. We plotted molecular and isotopic properties of shale gases on the revised genetic diagrams and determined the origin of shale gases. Based on the distribution of shale gases within the genetic diagram of δ13C of methane (C1) versus C1/(C2+C3), most shale gases appear to have thermogenic origin. The majority of these thermogenic gases are late-mature (e.g., Marcellus Formation, USA and Wufeng-Longmaxi Formation, China) and mid-mature (associated with oil generation, e.g., Eagle Ford Formation, USA). Importantly, shales may contain early-mature thermogenic gases rarely found in conventional accumulations (e.g., T⊘yen Formation, Sweden and Colorado Formation, Canada). Some shale gases have secondary microbial origin, i.e., they originated from anaerobic biodegradation of oils. For example, gases from New Albany Formation and Antrim Formation (USA) have secondary microbial origin. Relatively few shale gases have primary microbial origin, and they often have some minor admixture of thermogenic gas (e.g., Nicolet Formation, Canada and Alum Formation, Sweden). Two other revised gas genetic plots based on δ2H and δ13C of methane and δ13C of CO2 support and enhance the above interpretation. Although shales that contain secondary microbial gas can be productive (e.g., New Albany Formation, USA), the resource-rich, highly productive and commercially successful shale plays contain thermogenic gas. Plays with late-mature thermogenic gas (e.g., Marcellus Formation, USA and Wufeng-Longmaxi Formation, China) appear to be most productive.
The extended lift operation to deliver the Wellbay module (M5) combined with the Flare Tower (M8) from the Miller Platform in the North Sea to the shore using the Semi-Submersible Crane Vessel S7000 was sensitive to the wave environment. Weather and response forecasts were used to assist go or no go decision. Responses of interest such as main hook loads, crane tip motions and clearances between the M5/M8 and vessel crane booms were forecasted and monitored. The results of the weather and response forecasts and the data from the monitored parameters are compared to identify some uncertainties in the weather and response forecasts. To reduce these uncertainties, a method using the sea states measured from the wave rider buoy (WRB) deployed in the Miller Platform Removal campaign has been developed.
Marine operations to install jackets/towers and topsides for new fixed offshore platforms or to remove them after the end of their service life are performed within allowable weather windows. These windows are conventionally based on the comparison of weather forecasts and limiting sea states. The limiting sea states for a particular operation such as topside removal from an offshore platform are found from a dynamic analysis using standard wave spectra (typically JONSWAP spectra), during an engineering phase. The uncertainty in wave spectra used in the engineering analysis can be taken into account using a risk parameter (γ) in the calculation of most probable maximum/minimum (MPM) responses to define the limiting sea states. However, the γ factor is not considered, as the inaccuracy in wave spectra is addressed through an alpha factor (α) to account for uncertainty in weather forecasts. The value of the α factor, recommended by the DNV-GL classification society may be used to de-rate the operational limits (DNV-GL AS, 2016). This approach is generally conservative.
With the increase in computational power, and improvement in numerical weather prediction (NWP) models, the general pattern of the forecast weather is quite accurate up to about three days. For 48 hour weather forecasts wind speed is within 5 m/s 94% of the time and wave height is within 0.5 m 78% of the time (Galvin, 2014). Combining forecast two-dimensional (2D) wave energy spectra output from the NWP models with vessel response amplitude operators (RAOs) has made vessel response forecasts possible (Lai, et al, 2006).
One of the most secure storage sites for CO2 injection is in depleted gas reservoirs. To ensure that the CO2 is trapped securely and will not escape to the surface, storage in such formations must be study carefully prior to injection in such formations. After the injection, the injected CO2 will undergo several trapping mechanisms; namely: hydrodynamic, solubility and mineral trapping. The extend of geochemical reactions involved depend on the composition of the injected fluid introduced in the aquifer, the composition of the initial minerals assemblage and the aquifer brine. In this paper, the importance of biological/microbial mechanisms towards the impact on the storage capacity was studied using reactive transport modelling. The results obtained shows that the presence of microbial compound such as organic matter contributes to the enhancement of mineral precipitation, resulting in secure long-term storage.
Design of offshore structures for arctic and subarctic regions requires consideration of wave, wind and ice actions. If individual actions are not mutually exclusive, then combined actions also need consideration. ISO 19906 recommends that, when possible, extreme level combined actions should be determined based on the joint probability distribution of the actions. As an alternative, ISO 19906 provides a framework where a user can determine principal and companion extreme actions independently, and sum these with calibrated combination factors applied. While the combination factors in ISO 19906 were calibrated over a range of conditions and platforms, site-specific information is not taken into account when applying the method. In this paper, a procedure is presented for determining extreme level combined actions for sea ice and waves based on site-specific sea ice and wave information, accounting for the joint probability distribution of the actions. The procedure is demonstrated for an example fixed structure on the Grand Banks off Canada's east coast. The results are compared with extreme actions determined using the ISO 19906 combination factors.
New environmental regulations have substantially reduced the permissible level of sulfur oxide emissions from ocean vessels. An economical means of meeting the regulations is through the use of a diesel exhaust scrubber. The scrubber environment includes chlorides, high temperatures, and acidic conditions and requires the use of corrosion resistant alloys. This study will build upon a previous study that compared the corrosion resistance of multiple corrosion resistant alloys in several simulated scrubber environments. The current study evaluates the effect of welding and the presence of a crevice on five alloys. The alloys include a common austenitic alloy, UNS S31603; two superaustenitic alloys, N08367 and N08031; and two Ni-Cr-Mo alloys, N10276 and N06059. These comparisons are essential for proper material selection as the demand for marine exhaust scrubbers grows to meet the new regulations.
Due to new environmental regulations, substantial growth is expected for marine diesel exhaust scrubbers. The new regulations limit the allowable sulfur content in heavy fuel oil (HFO). Marine vessels use HFO as the primary fuel. Current regulations are in effect in certain regions, referred to as Emission Control Areas (ECAs). The ECAs established under MARPOL (International Convention for the Prevention of Pollution from Ships) Annex VI for sulfur oxides are: the Baltic Sea area, the North Sea area, the North American area (covering designated coastal areas off the United States and Canada) and the United States Caribbean Sea area (around Puerto Rico and the United States Virgin Islands)1. The sulfur content in HFO in the ECAs is limited at 0.10%. In 2020, new regulations will be applied globally. Currently, outside the emission control areas, the limit for sulfur content of fuel oil is 3.50 wt.%. However, it is scheduled to be reduced to 0.50 wt.% in 2020. Available options to meet the regulations are to burn more expensive low sulfur fuel, switch to natural gas, or install an exhaust scrubber system. Because the scrubber option is not subject to fuel price fluctuations, it is becoming a preferred choice for the marine vessel industry. Therefore, understanding the corrosion behavior of available materials for reliable scrubber design is of increasing importance.
This paper shares results from three DeepStar® Phase XII efforts championed by the X800 Metocean Committee. The first project, 12801, examined marine growth profiles for the Gulf of Mexico. The profile presently used by industry is based on limited data collected nearly thirty years ago, and was shown by the study to under-represent the amount of growth that should be expected on platforms in the Gulf. In addition, flaws in the survey processes currently used to evaluate growth as part of inspections were identified and documented. The second project, 12802, evaluated the design wind speed relationships used by industry to characterize extra-tropical storms, through analysis of high-quality overwater wind measurements collected for elevations up to 100 m made at three locations in the North Sea and Baltic Sea. The evaluation demonstrated the present NORSOK relations are adequate for extra-tropical storms, and hence going forward, industry will use separate design wind speed relationships for extra-tropical storms and tropical cyclones, a revised set for the latter being developed previously under project 11802. The third and final project, 12803, sponsored the development of an updated 54-year free-running simulation of currents in the Gulf of Mexico, with refined modeling of bottom currents in areas near steep bathymetry such as the Sigsbee Escarpment, in order to better represent topographically-enhanced Rossby waves (TRWs), which are a critical design consideration for risers and tendons. The resulting database provides an excellent basis for the development of Loop Current and TRW criteria for use in deepwater Gulf of Mexico projects.
Growing commercial activities in the High North increase the possibility of unwanted incidents. The vulnerability related to human safety and environment as well as a challenging context, call for a strengthening of the maritime preparedness system, cross-border and cross-institutional collaboration. In this paper, we look into the different stressors and risk factors of the sea regions in the High North. We elaborate on emergencies where integrated operations like mass evacuation is needed. We build upon in-depth studies of two cruise ship incidents close to the Spitsbergen Islands, and full-scale exercises in the Arctic region. We claim that coordination of such operations where several institutions and management levels are included demands significant integration and communication efforts. Implications for the training of key personnel responsible for coordinating such operations are discussed.
Emergency situations are often characterized by lack of overview and uncertainty about cause, consequences and suitable safety barriers. In areas like the High North, due to limited infrastructure and the scarcity of emergency capacities, a simple emergency situation can quickly turn into a crisis involving significant risk for people, nature and vulnerable societies. The turbulent weather conditions facing emergency actors, makes rescue and relief operations a challenging and time consuming task. In this paper, we examine how the emergency management has to be configured to overcome challenges related to large-scale emergencies with limited local infrastructure, long distances and harsh weather conditions in icy waters. In addition, we consider the limited availability of emergency support systems and the time delays caused by the geographical distances.
By examining the various emergency situations we reflect on suitable composition of the infrastructure, emergency groupings, and coordination mechanism.
Emergency Management and Emergency Response Pattern
High levels of uncertainty combined with a need for fast and reliable action are the main characteristic of emergencies (Kyng, Nielsen, and Kristensen 2006). Major incidents like shootouts and terror action, or cruise ship groundings with mass rescue operations (MRO) are categorized by lack of sufficient resources to meet the emergency situation. These situations are often chaotic and stressful with a large number of causalities, and a mix of SAR capacities. Thus, obtaining and maintaining an overview for such an incident become extremely hard for the coordinators and the different levels of command.
Wang, Guanxue (Huazhong University of Science and Technology) | Xu, Guohua (Huazhong University of Science and Technology) | Shen, Xiong (Wuhan Second Ship Design and Research Institute) | Xu, Han (Huazhong University of Science and Technology) | Liu, Chang (VTT Technical Research Centre of Finland) | Wang, Wenjin (Huazhong University of Science and Technology)
This paper focuses on design and experiment of an abdominal operation ROV. Firstly, overall design for system of abdominal operation ROV which consists of surface unit, power module, umbilical cable and ROV body is introduced. Secondly, the design of ROV body is described in detail to give a further study on body frame, buoyancy, thrusters, locking mechanism, underwater camera, lamps, navigation sensor and control cabin. Thirdly, research on control system which is the key part of ROV is presented. Finally, based on designed ROV a number of experiments are conducted to verify and test the functions and performances of abdominal operation ROV.
With the increasing attention of human beings to marine resources, ROV has been growing as a major vehicle in ocean exploration. Due to the complex and uncertain underwater environment, ROV need to be equipped with operating system, power system, observation system and control system to complete a series of missions. It`s significant to design and manufacture new type of ROV to adapt different working conditions while realizing various functions and high performances.
The shape and the appearance of the ROV proposed in this paper is shown in Fig. 1. It weighs 52.25kg in air. Main dimensions are 700mm in length, 550mm in width and 425mm in height. The velocity is up to 4kn and it is capable of dividing to the depth of 300m under water. ROV is open frame equipped with thrusters, a linear actuator, an underwater camera, lamps and a navigation sensor. It is able to complete 3-DOF motion maneuvers: along axes X and Y, as well as rotate around Z by sending commands from the surface unit to the underwater main controller. To execute docking tasks, ROV will hover in order to search for the rod which is the object to be docked. When the rod came into the view of camera, ROV approaches to it and tilts its camera to identify the relative position between them. At the same time, ROV adjusts its attitude to let the rod insert into its abdominal operation mechanism with the help of the guidance conic. At last, the linear actuator extends out to lock the rod which means rigid connection between the ROV and the rod is completed, that is to say, docking tasks are achieved.
ABSTRACT: Samples of anisotropic gneiss oriented at 0, 30, 60 and 90 degrees to the maximum loading stress were tested in a true-triaxial deformation cell. The loading path was designed to simulate the in situ stresses that rock would be exposed to during the excavation, heating and cooling of canister holes created for the proposed containment of radioactive waste. The results show that the deformation response would not be replicated with a traditional triaxial test were the intermediate and minimum stress are assumed to be equal. In two situations the loading history induced failure when the intermediate stress was reduced. Acoustic emission and velocity data are used to characterize the damage and the sensitivity of the velocity data provide a future method to link laboratory to in situ observations.
Understanding damage around boreholes and tunnels in rock is significant to numerous engineering applications. Borehole breakout and spalling, where the preferential orientation of stresses can induce failure, is a classic manifestation of this damage. Ever since the early work of Kirsch over a century ago we have endeavored to understand the complex interactions of stress and geometry on failure. More recently rock mechanics experimental testing and discrete particle numerical models have been used to deconvolve the complex fracture processes that lead to crack coalescence and the various modes of failure in rock materials (Hoek & Martin 2014). One application, which requires an understanding of failure around underground openings, is the concept of deep geological disposal of radioactive waste. Several countries have proposed schemes that involve the placement of spent fuel in canisters that will be placed in large diameter boreholes in tunnel complexes that are between 300 m and 500 m below the surface. Three such countries include Canada, Sweden and Finland where extensive investigations have been undertaken in crystalline rock to create a design that will be safe for the long term management, storage and disposal of radioactive waste.