A Comprehensive Review on Design, Monitoring, and Failure in Fixed Offshore Platforms

Offshore platforms have had diverse applications in the marine industry, for example, oil or gas platforms can provide facilities to store the oil and gas before transport those to refineries. Offshore wind turbines are another well-known use of the offshore platform for generating power. As platforms encounter various strong forces from water and wind currents, the materials used for these structures are mainly steel or concrete. These platforms are classified into different types, according to the depth of water and their applications. In addition, offshore platforms, as artificial reefs may be used for decades at different marine conditions. Consequently, their design and maintenance are very important, otherwise, they can cause irreparable damage to the environment. This paper presents the latest and most significant design and monitoring methods, such as the optimal probabilistic seismic demand model, multi-objective optimization, dynamic response assessment, robust fault-tolerant control, etc., under different environmental and geographical conditions. Moreover, the effective factors on the life and failure of these offshore structures are comprehensively introduced to enhance awareness of them, which can be very helpful to improve the design and construction of more reliable and durable structures.

Hitchhiking or hang gliding? Dispersal strategies of two cereal-feeding eriophyoid mite species

Dispersal shapes the dynamics of populations, their genetic structure and species distribution; therefore, knowledge of an organisms’ dispersal abilities is crucial, especially in economically important and invasive species. In this study, we investigated dispersal strategies of two phytophagous eriophyoid mite species: Aceria tosichella (wheat curl mite, WCM) and Abacarus hystrix (cereal rust mite, CRM). Both species are obligatory plant parasites that infest cereals and are of economic significance. We investigated their dispersal success using different dispersal agents: wind and vectors. We hypothesised that in both mite species the main mode of dispersal is moving via wind, whereas phoretic dispersal is rather accidental, as the majority of eriophyoid mite species do not possess clear morphological or behavioural adaptations for phoresy. Results confirmed our predictions that both species dispersed mainly with wind currents. Additionally, WCM was found to have a higher dispersal success than CRM. Thus, this study contributes to our understanding of the high invasive potential of WCM.

Research of sources and distribution of suspended matter in Omega Bay (Crimea) based on expeditional data and numerical simulation

The regularities of the suspended matter distribution in the system of wind currents from the area of bottom elevation along the Omega Bay are revealed. Observational data show that in the region of bottom elevation there is a topographic quasi-stationary eddy cell accumulating pollutants. Based on numerical modeling, it is revealed that the meridional winds of all directions contribute to the transfer of the suspended matter from the area of elevation to the western coast of the bay to the beach area, to a small coastal area with a characteristic bend of the coastline. The most significant suspended matter flows are generated by northeasterly and southeasterly winds. With a westerly wind, the main flow of suspended matter is directed to the eastern coast of the bay. The weak easterly winds, typical for Sevastopol, do not cause the removal of suspended matter from the central area of the investigated bay.

CASPIAN SEA MATHEMATICAL MODEL OF FLUID DYNAMICS CONSIDERING THE PRESENCE OF ICE ON ITS SURFACE

This article is devoted to the development and research of a mathematical model of water fluid dynamics with variable depth. This model describes the water flow movement, the thermodynamics of ice formation and melting, considers the Coriolis force, horizontal and vertical turbulence of the water environment, the complex geometry of the coastline and bottom, friction on the bottom and wind currents, evaporation, wind speed, and atmospheric density, and the deviation of the pressure field value from the hydrostatic approximation. The article describes the influence of the spatial distribution of temperature, salinity, ionic composition, and hydrostatic pressure on the processes of ice cover formation. The Caspian Sea-was chosen as the object of the simulation. The changes in the temperature and salinity distributions measured by the electrical conductivity of the water, considering the ionic composition of the Caspian Sea waters over a long-term period, are used as input data. Modeling the movement of water flow will allow you to respond to man-made threats in an accelerated time mode. The models of hydrodynamics presented in this paper can be adapted for other reservoirs using the appropriate geoinformation systems.

The Potential of Wind Energy and Design Implications on Wind Farms in Saudi Arabia

Climate change and natural resource depletion are likely to affect the future economic development of a country. The generation of power from oil and gas is among the major causes of reserves depletion and global warming. However, renewable energy is also deemed a clean and green choice for power generation to promote sustainability in engineering. The coastal lines of the Kingdom of Saudi Arabia (KSA) are widely extended, and wind energy appears to be a viable alternative to traditional sources, which needs to be investigated as it is highly desirable to seek energy from renewable energy sources, for instance, wind. This paper is aimed at addressing the wind energy potential along the Red Sea coast of KSA. Afterward, a suitable wind turbine based upon careful structural analysis has been proposed, which would form a basis, especially during the machine selection and design phases. For this purpose, seven different sites located along the coastal line, namely: Al Wajh, Umluj, Yanbu, Rabigh, Jeddah, Haddad, and Gizan, were initially selected to assess the wind energy availability. After that, a suitable turbine is recommended for yielding maximum output. It has been found from the reconnaissance that Al Wajh has sufficient land availability that receives high perennial wind speed, alongside shallow offshore water depth for monopile installation. Hence, this site is recommended for the development of a wind farm. Furthermore, turbines need to be installed at the height of almost 100 m to produce maximum energy to appropriately utilize the available indigenous wind energy. It is pertinent to mention that the superstructure of the turbines is designed based on the local loading conditions (wind, currents, waves, etc.) of the Al Wajh region. Also, the monopile substructures are proposed in the selected area in accordance with the available bathymetry.

Advanced Intelligent Control Strategy in Dynamic Positioning (DP) System Applied to a Semi-Submersible Drilling Platform in the North Sea

Dynamic Positioning (DP) systems play a crucial role in oil and gas drilling and production floaters used globally for deep-water operations. Drilling operations need to maintain automatic positioning of the platform in the horizontal-plane within the safe zone. Operating DP systems typically require highly responsive control systems when encountering prevailing weather conditions. However, DP incident analysis demonstrates that control and thruster failures have been the leading causes of accidents for the past two decades, according to the International Marine Contractors Association (IMCA). In this paper, a Predictive Neural Network (PNN) strategy is proposed for thruster allocation on a platform; it has been developed by predicting the platform response and training the network to transform the required force commands from a nonlinear Proportional Integral Derivative (PID) motion controller for each thruster. The strategy is developed for increasing safety and zone keeping of DP-assisted-drilling operations in harsh weather. This is done by allowing the platform to recover the position more rapidly whilst decreasing the risk of losing the platform position and heading, which can lead to catastrophic damage. The operational performance of the DP system on a drilling platform subjected to the North Sea real environmental conditions of wind, currents and waves, is simulated with the model incorporating the PNN control algorithm, which deals with dynamic uncertainties, into the unstable conventional PID control system for a current drilling semi-submersible model. The simulation results demonstrate the improvement in DP accuracy and robustness for the semi-submersible drilling platform positioning and performance using the PNN strategy.

A Hindcast Model for Evaluation of Iceberg Management Operations

When planning oil and gas exploration and production operations off the east coast of Canada, the potential for iceberg impacts must be considered. Environmental conditions in this region can be very harsh, and iceberg trajectories are notably unpredictable. When an iceberg has the potential to impact a Floating Production, Storage, and Offloading (FPSO) platform, ice management through towing will be attempted; and if this fails, the production system will be shut down, line flushed, the mooring and riser systems disconnected, and the platform moved off site. If trajectory forecasting were highly accurate, only icebergs passing very close to the platform would require ice management and possible shutdown of the platform. Given natural variations in wind, currents, and waves, and challenges measuring and forecasting these parameters, there is considerable forecast uncertainty. This results in added expenses for extra ice management and unnecessary shutdowns. Improvements in trajectory forecasting accuracy, characterization of forecast uncertainty, and methods to account for these uncertainties in operations would all be beneficial. This paper outlines an approach for simulating large numbers of iceberg trajectories in varied and realistic environmental conditions from hindcast met-ocean data in conjunction with a forecasting uncertainty model derived from forecast validation studies. A model, named BergCast, was developed so that proposed strategies for improving ice management operations can be evaluated, and the value of reducing forecasting uncertainty quantified.

Microsatellite markers from Peronospora tabacina, the cause of blue mold of tobacco, reveal species origin, population structure, and high gene flow

Peronospora tabacina is an obligate parasite that causes blue mold of tobacco. The pathogen reproduces primarily asexually by sporangia, and sexual oospores are a rarely observed form of propagation. A collection of 122 isolates of P. tabacina was genotyped using nine microsatellites to assess the population structure of individuals from subpopulations collected from Central, Southern, and Eastern Europe, the Middle East, Central and North America, and Australia. Genetic variation among the six subpopulations accounted for about 8% of total variation with moderate levels of genetic differentiation, high gene flow among these subpopulations, and a positive correlation between geographic and genetic distance (r = 0.225; P<0.001). Evidence of linkage disequilibrium (P<0.001) showed that populations contained partially clonal subpopulations, except subpopulations from Australia and Mediterranean Europe. High genetic variation and population structure among samples could be explained by continuous gene flow across continents via infected transplant exchange and/or long-distance dispersal of sporangia via wind currents. This study analyzed the most numerous P. tabacina collection to date and allowed conclusions on the migration, mutation, and evolutionary history of this obligate biotrophic oomycete. The evidence pointed to the species origin in Australia and identified intra- and inter-continental migration patterns of this important pathogen.

Performance statistics of a real-time Pacific Ocean weather sensor network

A distributed sensor network of over one hundred free-drifting, real-time marine weather sensors was deployed in the Pacific Ocean beginning in early 2019. The Spotter buoys used in the network represent a next generation ocean weather sensor designed to measure surface waves, wind, currents, and sea surface temperature. Large distributed sensor networks like these provide much needed long-dwell sensing capabilities in open ocean regions. Despite the demand for better weather forecasts and climate data in our oceans, direct in situ measurements of marine surface weather (waves, winds, currents) remain exceedingly sparse in the open oceans. Due to the large expanse of our oceans, distributed paradigms are necessary to create sufficient data density at global scale, similar to advances in sensing on land and in space. Here we discuss initial findings from this long-dwell open ocean distributed sensor network. Through triple-collocation analysis, we determine errors in collocated satellite-derived observations and model estimates. The correlation analysis shows that the Spotter network provides wave height data with lower errors than both satellites and models. The wave spectrum was also further used to infer wind speed. Buoy drift dynamics are similar to established drogued drifters, particularly when accounting for windage. We find a windage correction factor for the Spotter buoy of approximately 1%, which is in agreement with theoretical estimates. Altogether, we present a completely new open ocean weather data set and characterize the data quality against other observations and models to demonstrate the broad value for ocean monitoring and forecasting that can be achieved using large-scale distributed sensor networks in our oceans.

Global wind patterns shape genetic differentiation, asymmetric gene flow, and genetic diversity in trees

Wind disperses the pollen and seeds of many plants, but little is known about whether and how it shapes large-scale landscape genetic patterns. We address this question by a synthesis and reanalysis of genetic data from more than 1,900 populations of 97 tree and shrub species around the world, using a newly developed framework for modeling long-term landscape connectivity by wind currents. We show that wind shapes three independent aspects of landscape genetics in plants with wind pollination or seed dispersal: populations linked by stronger winds are more genetically similar, populations linked by directionally imbalanced winds exhibit asymmetric gene flow ratios, and downwind populations have higher genetic diversity. For each of these distinct hypotheses, partial correlations between the respective wind and genetic metrics (controlling for distance and climate) are positive for a significant majority of wind-dispersed or wind-pollinated genetic data sets and increase significantly across functional groups expected to be increasingly influenced by wind. Together, these results indicate that the geography of both wind strength and wind direction play important roles in shaping large-scale genetic patterns across the world’s forests. These findings have implications for various aspects of basic plant ecology and evolution, as well as the response of biodiversity to future global change.