Sea Area Research Articles

Numerical simulation of depressurization exploitation in class 1 hydrate reservoirs under different development factors in Shenhu area, South China sea

Most of the implemented marine gas hydrate test exploitation in the world adopt the depressurization method to break down the hydrate in the reservoir into natural gas and then extract it, but because the gas production results are still a certain distance away from the commercial exploitation, and it mainly stays in the stage of theoretical research and trial exploitation. Based on two trial productions in the Shenhu area of the South China Sea, this study established a model for hydrate exploitation and investigated the impact of different well types on the recovery rates of hydrates and free gas in different development layers during depressurization. For the Class 1 hydrate reservoirs, horizontal wells are the optimal solution to extract hydrate and free gas simultaneously when exploiting the hydrate three-phase layer. Meanwhile, the effect of different well spacing in vertical wells on the recovery rate of hydrate and free gas was studied. It is found that the best recovery efficiency is achieved when the spacing between two wells is 80 m. The lower the bottom flow pressure of the well, the higher the production capacity, but its influence is limited.

Mapping the main harmful algal species in the East China Sea (Yangtze River estuary) and their possible response to the main ecological status and global climate change via a global vision

The Yangtze River Estuary (YRE) is one of the areas in China most severely affected by harmful algal blooms (HABs). This study explored the distributive patterns of HABs in the YRE and how they are influenced by the El Niño-Southern Oscillation (ENSO) and other environmental factors. Quantitative real-time PCR (qPCR) was employed to detect and quantify the four predominant HAB species in the YRE, Karenia mikimotoi, Margalefidinium polykrikoides, Prorocentrum donghaiense, and Heterosigma akashiwo. Additionally, the study analyzed how turbidity, pH, salinity, and temperature influence these algae. Distribution of the four HAB species in the YRE area shows clear geographical variations: K. mikimotoi is predominantly found in the northwest and central sea areas, M. polykrikoides (East Asian Ribotype, EAR) is mainly distributed in the southeastern part, P. donghaiense is abundant in the northern regions, and H. akashiwo is especially prevalent at stations S26 and S27 in the northeastern part of the study area. HABs dominated by H. akashiwo and P. donghaiense were observed in the northeastern sea area of the YRE on July 22, 2020. Our study reveals that K. mikimotoi, M. polykrikoides (EAR), and P. donghaiense are mainly affected by turbidity, pH, and salinity, while temperature predominantly influences the blooms of H. akashiwo. Moreover, runoff in the YRE has a certain correlation with ENSO events, which may also impact the nutrient content of the region. The findings of this study illustrate the distributive patterns of the four HAB species under various ecological conditions in the YRE and emphasize the importance of establishing practical cases for future warning systems. To better understand how climate change affects HABs, exploring the link between ENSO and HABs is essential.

A Method for Predicting High-Resolution 3D Variations in Temperature and Salinity Fields Using Multi-Source Ocean Data

High-resolution three-dimensional (3D) variations in ocean temperature and salinity fields are of great significance for ocean environment monitoring. Currently, AI-based 3D temperature and salinity field predictions rely on expensive 3D data, and as the prediction period increases, the stacking of high-resolution 3D data greatly increases the difficulty of model training. This paper transforms the prediction of 3D temperature and salinity into the prediction of sea surface elements and the inversion of subsurface temperature and salinity using sea surface elements, by leveraging the relationship between sea surface factors and subsurface temperature and salinity. This method comprehensively utilizes multi-source ocean data to avoid the issue of data volume caused by stacking high-resolution historical data. Specifically, the model first utilizes 1/4° low-resolution satellite remote sensing data to construct prediction models for sea surface temperature (SST) and sea level anomaly (SLA), and then uses 1/12° high-resolution temperature and salinity data as labels to build an inversion model of subsurface temperature and salinity based on SST and SLA. The prediction model and inversion model are integrated to obtain the final high-resolution 3D temperature and salinity prediction model. Experimental results show that the 20-day prediction results in the two sea areas of the coastal waters of China and the Northwest Pacific show good performance, accurately predicting ocean temperature and salinity in the vast majority of layers, and demonstrate higher resource utilization efficiency.

Potential of the Indonesian Navy in Protecting Maritime Border Areas: Measurement through Mahan's Theory

Indonesia as an archipelagic country has open sea areas and the existence of the Indonesian Archipelagic Sea Lane (ALKI) which can create vulnerabilities to various possible maritime threats. The country of Indonesia, most of which is territorial waters, requires a strong Navy to maintain security and the country's territorial boundaries. The aim of this research is to see the potential of the Indonesian National Army Navy through Mahan's Theory. This research uses a qualitative method with a descriptive approach. The data collection technique in this research was carried out through searching secondary data obtained from books, articles, news, comments and government publications. The results of this research indicate that there must be an increase in the Indonesian Navy and modernization of Alusista must also be carried out.

Research on Foundation Scouring for Offshore Wind Turbines in the Vast Yangjiang Sea Area

Research on Foundation Scouring for Offshore Wind Turbines in the Vast Yangjiang Sea Area

Selective Leaching and Separation of Uranium from Ochre-Umm Greifat, Red Sea Coast, Central Eastern Desert, Egypt

The Ochre-Umm Greifat area is one of the Red Sea areas with high concentrations of iron and zinc, which is formed from hydrothermal solutions as a result of the structural activity that occurred in the Red Sea Zone during the Pleistocene period. These deposits are also accompanied by deposits of low- to high uranium grade. In addition to Zn, Pb, and Cu anomalies, particularly in fault zones and their branches affecting the study area, although there are numerous zinc minerals in the Ocher-Greifat area, uranium minerals are scarce, with only one mineral, compreignacite, being recorded and the majority of the uranium being present as an adsorbed element on iron and/or clay stones. In addition, uranothorite is extremely rare and occurs as fine grains embedded in rocks. A technological sample was taken from an iron-rich clay area in a fault zone and was found to assay 700-ppm uranium. The leachability of uranium from the used sample was investigated using an alkaline solution based on the chemical and mineralogical composition of the used sample. The selected ore is treated with Na2CO3 and NaHCO3 in the presence of H2O2 as oxidant. Many digestion factors are studied and optimized. Under the optimum leaching conditions, the uranium dissolution efficiency is around 84%. For the uranium separation, the pH of the leach liquor is adjusted at 10, then subjected to a solvent extraction step using 4% Aliquat®336/kerosene in the presence of isodecanol as third-phase prevention. The loaded organic solvent was then treated with NaOH/H2O2 solution as a stripping solution. Finally, the resultant solution is subjected to a precipitation step using ammonia solution.

Research on the ice-resistance performance of conical wind turbine foundation in brash ice fields

Due to the significantly higher wind energy density in high-latitude sea areas compared to other regions, the construction of offshore wind farms is shifting towards these areas. However, in high-latitude sea areas, large amounts of sea ice float on the surface during winter, making ice loads a critical factor affecting the structural safety of wind turbines. For monopile flexible wind turbines, installing an ice-breaking cone near the waterline is an effective measure to withstand the threat of sea ice. To clarify the ice resistance performance of conical wind turbine foundations in brash ice zones, this study proposes a coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM). This method is used to calculate the ice load results for a cylindrical riser, and the results were found to be in good agreement with the ice load experiment results from China University of Petroleum's wave flume (CUPWF). This validation confirms the rationality of the method. Taking a 5 MW monopile wind turbine installed with an ice-breaking cone as the research object, the time history of dynamic ice loads and the displacement response of ice-induced vibration during the interaction between the wind turbine and brash ice are simulated. Considering the water level variations caused by tides, the differences in ice resistance performance between the upright cone and the inverted cone of the ice-breaking cone are analyzed. Finally, the impact of changes in cone angle on the ice resistance performance of the wind turbine foundation is determined. The results indicate that under the impact of brash ice, the upright cone of the ice-breaking cone has a higher ice resistance capacity compared to the inverted cone. With changes in cone angle, the trends of ice loads in the horizontal and vertical directions vary oppositely. However, the overall ice resistance capacity of the wind turbine foundation decreases as the cone angle increases. This study can provide a reference for the rational design of conical wind turbines in cold regions.

Revealing the kinetic behaviors of hydrate formation on bubble surface with different pressure gradients in deep-sea methane seepage areas of the South China Sea

In the deep-sea methane seepage environment, hydrate formation on the methane bubbles is a crucial pathway for methane transformation, and plays an important role in determining whether seepage methane can enter the surface ocean. While how the pressure determines the hydrate formation process in different water depths remains unclear. In this study, we investigated the formation kinetic characteristics and microstructure evolution of methane hydrate on suspended gas bubbles within varied pressure conditions. The pressure range (4–14 MPa) was in the deep-sea methane seepage environment. The results indicated that pressure obviously affected the hydrate film formation characteristics. As pressure increased, the lateral growth rate of the hydrate film accelerated, the hydrate crystal particles became smaller, and the initial hydrate film surface became smoother. Raman spectroscopy results showed that pressure changes did not obviously alter the microporous evolution on the hydrate film surface, that the gas-phase/water-phase Raman peak area ratio exhibited similar trends. The dissolved methane concentration under different pressure conditions was not the primary factor affecting hydrate thickening, rather, it depended mainly on the driving force. This study is of great significance in revealing the characteristics of methane hydrate formation and methane transfer in the oceanic methane seepage environment.

Comparing the Environmental Influences and Community Assembly of Protist Communities in Two Anthropogenic Coastal Areas.

Anthropogenic stresses are intensively affecting the structure and function of microbial communities in coastal ecosystems. Despite being essential components of coastal ecosystems, the environmental influences and assembly processes of protist communities remain largely unknown in areas with severe disturbance. Here, we used 18S rRNA gene high-throughput sequencing to compare the composition, assembly process, and functional structure of the protist communities from the coastal areas of the Northern Yellow Sea (NYS) and the Eastern Bohai Sea (EBS). These two areas are separated by the Liaodong Peninsula and experience different anthropogenic stresses due to varying degrees of urbanization. We detected significant differences between the protist communities of the two areas. Environmental and geographic factors both influenced the composition of protist communities, with environmental factors playing a greater role. The neutral community model indicated that the assembly of protist communities was governed by deterministic processes, with stochastic processes having a stronger influence in the EBS area compared to the NYS area. The phototrophic and consumer communities, influenced by different environmental factors, differed significantly between the two areas. Our results provide insights into the biogeography and assembly of protist communities in estuaries under anthropogenic stresses, which may inform future coastal management.

PERAMALAN EKSPOR TIGA KOMODITAS UTAMA SEKTOR PERIKANAN MENGGUNAKAN METODE TIME SERIES: ARIMA

Batam City is one of the cities in Indonesia which is located in a strategic area on international shipping routes and has a sea area of 3,675 km so it has great potential for exporting fishery products, based on main commodities. Based on data from the Ministry of Maritime Affairs and Fisheries (KKP) in 2022, the performance of the export value of Indonesian fishery products during 2022 experienced positive growth of 21.63 percent compared to 2021. In 2021, the export value of Indonesian fishery products reached 1,258 million USD, increasing to 1,530 million USD in 2022. This fact shows that the marine fisheries sector still offers significant opportunities today. However, there are several obstacles that stand in the way of the export process. These obstacles include the low level of technology application, unequal infrastructure development in various fisheries centers, limitations in providing capital, low utilization of Indonesia's marine potential, and the use of fishing systems in the production process which are deemed unable to utilize Indonesia's marine potential optimally. Given this problem, it is interesting to see the forecast for fishery product exports according to the main commodities in the city of Batam. Is there an increase or a decrease? So the aim of this research is to describe the predicted results of the export value of fishery products according to 3 main commodities, namely shellfish, crab and shrimp in Batam City in the next 5 years. This research method is quantitative using the time series method: ARIMA. The research results show that the estimated export of shellfish and crab will decrease from 2023 - 2027. Meanwhile, the estimated export of shrimp will increase from 2023 - 2027

The collaboratively selective uranyl adsorption of marine fungal modification biosorbent linked by the open-chain polyether terminal with amidoxime

Abstract To further improve the uranyl adsorption capacity and the selectivity adsorption ability of marine fungus ZZF51 from Zhanjiang sea area in China, its two new modification biosorbents (ZTBA/ZTDA) linked by the open-chain polyether terminal with two/one amidoxime unit(s) on mycelium were designed according to the synthesis process of etherification, sulfonylation, substitution, and amidoximation. By the reasonable characterization of Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG), and scanning electron microscopy (SEM), it was confirmed that the above target materials were successfully prepared. The relevant experiments showed that both of ZTBA and ZTDA had not only the excellent uranium (VI) adsorption performance with the maximum adsorption capacity of 525.7 mg g−1 and 465.7 mg g−1, respectively, but also the better uranyl adsorption selectivity when in the simulated wastewater containing the various ions of UO2 2+, Th4+, Ba2+, Pb2+, Fe3+, Cu2+, and Ca2+. In addition, the selectivity analysis explored the longer polyether in the middle bridge and the more number of terminal amidoxime unit could synergistically improve their uranyl adsorption capacity and selectivity performance. Surely, the adsorption isotherm/kinetics models, the Gibbs free energy analysis, and the favourable reusability of the target materials were also discussed in this study in detail.

The Albanian Diaspora in Budzhak and Priazovye: A Problem of Language and Identity

The article analyses the problem of language and identity among the Albanian diaspora – an ethnic minority living along the Black Sea coast in the Budzhak region and the Azov Sea area in the Priazovye region. The paper outlines the history of Albanian settlements in Eastern Europe and traces various strategies for self-identification and the nuances of being an Albanian during different historical periods. In the last two decades of the 21st century, the Albanian diaspora has experienced a big rise in interest in the Albanian language, culture, and traditions. This surge has brought new group initiatives, a search for connections to the historical homeland, new ways of marking ethnic identity, and efforts to preserve the native language. Based on the author's field data, the research focuses on local ethnic activism and contemporary communication and “recognition” between representatives of the Albanian diaspora and Albanians from the Balkans. Particular attention is paid to the issue of the Albanian dialect and standard Albanian, which plays a significant role in the policy of integrating the Albanians of Budzhak and Priazovye into the transnational diaspora space.

Thermo-pressure coupling model for gas hydrate depressurization exploitation in South China Sea

The sediment type in the “Shenhu” sea area of the South China Sea is mud sediment, with poor reservoir physical conditions, and the seabed is loose with a small pressure window. These conditions pose heightened safety challenges for the extraction of hydrates in this region. This study develops a multiphase flow model that accounts for the endothermic decomposition of hydrates and employs the finite difference method for its solution. Utilizing this model, the multiphase flow characteristics during depressurization extraction at a specific well in the “Shenhu” area are investigated. Building on this, the study analyses the impact of varying pump rates and geothermal gradients on multiphase flow properties, hydrate yield, and engineering safety. Based on the analytical findings, recommendations are proposed to balance hydrate production with engineering safety, effectively mitigating potential engineering accidents during depressurization extraction. The outcomes of this research offer technical guidance for the commercial exploitation of hydrates in the “Shenhu” area of the South China Sea, laying a foundation for future related studies.

Global Path Planning of Unmanned Surface Vehicle in Complex Sea Areas Based on Improved Streamline Method

In this paper, an innovative method is proposed to improve the global path planning of Unmanned Surface Vehicles (USV) in complex sea areas, combining fluid mechanic calculations with an improved A* algorithm. This method not only generates smooth paths but also ensures feasible global solutions, significantly enhancing the efficiency and safety of path planning. Firstly, in response to the water depths limitation, this study set up safe water depths, providing strong guarantees for the safe navigation of USVs in complex waters. Secondly, based on the hydrological and geographical characteristics of the study sea area, an accurate ocean environment model was constructed using Ansys Fluent software and computational fluid dynamics (CFD) technology, thus providing USVs with a feasible path solution on a global scale. Then, the local sea area with complex obstacles was converted into a grid map to facilitate detailed planning. Meanwhile, the improved A* algorithm was utilized for meticulous route optimization. Furthermore, by combining the results of local and global planning, the approach generated a comprehensive route that accounts for the complexities of the maritime environment while avoiding local optima. Finally, simulation results demonstrated that the algorithm proposed in this study shows faster pathfinding speed, shorter route distances, and higher route safety compared to other algorithms. Moreover, it remains stable and effective in real-world scenarios.

A Marine Experiment Using Dielectric Elastomer Generators and Comparative Study with Actual Measured Values and Theoretical Values

Power generators using dielectric elastomer (DE) transducers are inexpensive, highly efficient, lightweight, stackable, and also easy to install. Therefore, it is considered optimal for an eco-energy society and is attracting attention as a renewable energy device. In particular, DE wave power generators are characterized by the fact that it is not limited by the direction and size of waves, which is a problem with existing wave power generation. This paper presents an accurate method for measuring the energy generated by a DE generator (DEG) and compares it with the theory value obtained by calculation. The electrode materials actually used in this study were a variety of carbon-based materials (including muti-wall carbon nanotube (MWCNT) and singe-wall carbon nanotubes (SWCNT)), and the performance of DEs using these materials was compared. Furthermore, ocean experiments in actual sea areas using DEG were also conducted, and the energy conversion rate was calculated based on the electrical results.

Joint probability analysis and mapping of typhoon-induced wind, wave, and surge hazards along southeast China

The southeastern coastal region of China frequently faces typhoon attacks, posing significant threats to its ever-growing infrastructure. Quantifying multiple typhoon-induced hazards in terms of wind, wave, and surge would provide valuable data to support structural design, risk assessments, and disaster mitigation. This study simulated the evolution of wave and surge driven by typhoon wind fields using the SWAN + ADCIRC coupling model, generating extreme samples of wind speed, significant wave height, and surge height. Trivariate joint probability distributions were established at six typical coastal stations (Hong Kong, Xiamen, Fuzhou, Wenzhou, Zhoushan, and Shanghai) based on optimal copula functions. Using the environmental contour and conditional return period methods, appropriate combinations of design environmental loads were analyzed for a specific return period. The results revealed two reasonable combination types for the 100-year design period. One involves the combination of the 100-year dominant variable value computed using a univariate probability distribution, with two 20-year secondary variable values calculated using the second conditional return period. The second combination selects a variable group corresponding to the maximum value of the dominant variable on the environmental surface. These methods and findings were further extended to the entire computational area to develop hazard maps covering the Southeast Sea area of China. The hazard maps show that the design values of significant wave height increase with distance from the coast. In contrast, the spatial distribution of surge presents the opposite pattern. This study provides a novel perspective on structural design values subjected to multiple disasters and offers a reference for offshore engineering construction in the sea area of southeast China.

Spatial Structure and Vulnerability of Container Shipping Networks: A Case Study in the Beibu Gulf Sea Area

Ports play an important role in maintaining the effectiveness of maritime logistics. When ports encounter congestion, strikes, or natural disasters, the maritime container transportation network might be significantly affected. The Beibu Gulf sea area is a key channel to supporting China’s participation in international economic cooperation in the western region. It is highly susceptible to the influence of the political and economic instability. This study introduces a dual-component framework to analyze the inherent structure and potential vulnerabilities of the container transportation network in the Beibu Gulf Sea areas. The findings show that the core layer of the network exhibited circular solidification characteristics. The entire network heavily relies on some core ports, such as Haiphong Port, Ho Chi Minh Port, and Qinzhou Port, and it highlights the potential increases in vulnerability. The finding shows that deliberate attacks have a greater impact than random attacks on the normal operations of maritime networks. If ports with high intermediary centrality are attacked, the connectivity and transportation efficiency of the Beibu Gulf maritime network will be significantly affected. However, under such circumstances, redistributing cargo transportation through route adjustments can deal with the transmission of cascading failures and maintain the network’s resilience. Based on the existing knowledge and the data collected in a case study, this research stands out as the first to provide a critical examination of the spatial structure and vulnerability of container shipping networks in the Beibu Gulf sea.

From Water to Desert: Evolution of Transportation Systems in The Aral Sea Area

From Water to Desert: Evolution of Transportation Systems in The Aral Sea Area

Numerical experimental study on combined support of bolt-arch in circular roadway

The deep soft rock roadway is in high stress environment, and the surrounding rock is prone to large deformation. Appropriate roadway cross-section form and high-strength support are effective control methods for surrounding rock deformation. Circular roadway is widely used in mine engineering because of its uniform stress and deformation, which gives full play to the characteristics of rock compression and non-tension. With the advantages of high strength, high cost performance and stability, the application of arch frame in deep soft rock roadway is increasing day by day. Based on this, based on the engineering background of deep roadway in extremely soft rock in sea area, numerical experiments were carried out using the FLAC3D bolt-arch fine numerical simulation platform. The progressive failure characteristics of bolt-arch combined support in soft rock roadway are revealed. The influence law of roadway section form, geostress grade and lateral pressure coefficient on support effect is clarified. The results show that: (1) Under the condition of deep soft rock, the surrounding rock deformation of circular roadway is uniform. Compared with the straight wall semi-circular roadway, the deformation is reduced by about 86% at most. (2) The failure of arch frame in circular roadway has a significant influence on the final control effect of surrounding rock. When the ground stress exceeds 15 MPa, the loss of bearing capacity of arch frame is instantaneous, and the deformation of surrounding rock increases suddenly. (3) When the support of circular roadway in deep soft rock fails, the axial force of bolt is very small, and it basically does not play a supporting role. According to the research results, the support optimization design is carried out, and the field verification is obtained.

Investigation on the effect of ship emissions on the air quality, A case study in Hainan Island, China

This paper presents an air quality simulation model that incorporates shipping activities and weather conditions, with a case study of Hainan Island to examine the impact of ship emissions on air quality. The findings reveal that the density of automatic identification system (AIS) signals is particularly high in the southern coastal regions. The results showed that the annual ship emissions recorded the highest density of 896.7 tons/0.01°, 49.8 tons/0.01°, 1139.7 tons/0.01°, and 122000 tons/0.01° for sulfur oxides (SOx), particulate matter (PM), nitrogen oxides (NOx), and carbon dioxide (CO2), respectively. Furthermore, the partial distributions of these emissions were not significantly affected by the seasons. Ships within twelve nautical miles of Hainan coastlines emit approximately 2817.7 tons of SOx, 14686.4 tons of NOx, 630.4 tons of PM2.5, and 416.9 tons of hydrocarbons (HC) annually. These emissions are primarily concentrated in the sea areas surrounding the ports of Haikou, Yangpu, Basuo, and Sanya. Ships manufactured between 2000 and 2010 have contributed significantly to air pollution, with SOx and HC emissions accounting for approximately 51% and 56% of total emissions, respectively. However, for ships manufactured after 2016, these proportions have dropped to approximately 10%. In terms of air pollutants from ship emissions in Hainan Island, the spatial distribution of their contributions is significantly uneven. The impact of PM2.5 differs significantly depending on the season, with the concentrations being substantially higher during Spring. However, the proportions of O3 and other pollutants do not vary significantly, except during Spring.