Offshore Production Research Articles

Novel peptides based on sea squirt as biocide enhancers to mitigate biocorrosion of EH36 steel.

Microbiologically influenced corrosion (MIC) affects offshore production activities severely. Although adding biocides is a simple method, it can cause environmental damage over time. Using green biocide enhancers is a viable strategy to reduce the amount of biocides. In this study, four novel peptides, named Peptide T/Tc/Ts/Tcs, were designed by a natural peptide extracted from the Arctic sea squirt to enhance the efficacy of tetrakis hydroxymethyl phosphonium sulfate (THPS) in mitigating the biocorrosion of EH36 steel caused by Desulfovibrio ferrophilus. The combination of 40ppm THPS and 100nM Peptide T/Tc/Ts/Tcs reduced the corrosion rates of EH36 steel by 68%, 71%, 86%, and 90% after the 7-d incubation, respectively. Notably, 40ppm THPS+100nM Peptide Ts/Tcs achieved similar antimicrobial and biocorrosion mitigation effects as 100ppm THPS. It suggests that optimizing the cationic and hydrophobic properties of peptides could enhance the bactericidal properties of biocides.

Simulation of a decentralized floating offshore wind hydrogen production system with hydro-pneumatic energy storage and subsea isobaric hydrogen storage

Abstract Hydrogen production using offshore wind power is a promising solution for producing clean fuels in remote areas. However, the intermittency of offshore wind power poses significant challenges to Proton exchange membrane (PEM) water electrolysis systems. Besides, there is generally an imbalance between hydrogen production and hydrogen demand. In this study, hydro-pneumatic electricity energy storage and subsea isobaric hydrogen storage are integrated into the decentralized offshore wind hydrogen production system. The hydro-pneumatic energy storage unit (HPES) is used for mitigating the intermittency and fluctuation of wind power, thereby prolonging the lifespan of PEM electrolyzers. Subsea isobaric hydrogen storage unit is used for replacing conventional isochoric hydrogen storage. In this study, simulation models of a decentralized offshore wind hydrogen production system with various configurations are established with the software Simcenter Amesim 2021.1. The results show that an 83% reduction in the on/off operation can be achieved with the help of hydro-pneumatic electricity energy storage. The isobaric and isothermal storage of compressed hydrogen can be achieved with subsea isobaric hydrogen storage, saving compression energy and facilitating thermal management. In terms of the investigated decentralized offshore wind hydrogen production system, the amount of produced hydrogen is increased by less than 1% by integrating hydro-pneumatic energy storage and subsea isobaric hydrogen storage.

Identification of Security Scenarios in offshore Oil&Gas production facilities based on past incident analysis

Offshore Oil&Gas installations may be attractive targets of intentional attacks due to their presence in socio-political sensitive areas, their economic significance, and the high impact of scenarios that can be triggered by the mismanagement of the hazardous substances handled (e.g., crude oil, natural gas, etc.). In the present study, a new dataset including 112 past security-related incidents that affected the offshore Oil&Gas sector in the last decades was developed and analyzed using Exploratory Data Analysis (EDA), Root Cause Analysis (RCA), and Attack Tree Analysis (ATA). Significant differences were found in the types of threats and attack modes, with terrorism identified as the primary threat, followed by robbery and kidnapping. The identified scenarios caused fatalities, injuries, and asset damages at the targeted facilities, underscoring their potential to cause severe impacts, comparable to the outcomes of safety-related accidents. Tables linking identified attack modes, scenarios, and consequences specific contribution to the SVA workflow proposed by the API Recommended Practices 70 and 70I were obtained. Overall, the results obtained support the application of suitable Security Vulnerability/Risk Assessment (SVA/SRA) methodologies concerning the identification and characterization of adversaries, the definition of attack modes, the evaluation of effectiveness of existing security barriers, and the assessment of consequences.

Experimental and numerical investigation of wind loads on the offshore wind power hydrogen production container modules

Experimental and numerical investigation of wind loads on the offshore wind power hydrogen production container modules

The future of offshore wind power production: Wake and climate impacts

Rapid deployment of offshore wind is expected within the coming decades to help meet climate goals. With offshore wind turbine lifetimes of 25–30 years, and new offshore leases spanning 60 years, it is vital to consider long-term changes in potential wind power resource at the farm planning stage. Such changes may arise from multiple sources, including climate change, and increasing wake-induced power losses. In this work, we investigate and compare these two sources of long-term change in wind power, for a case study consisting of 21 wind farms within the German Bight. Consistent with previous studies, we find a small but significant reduction in wind resource due to climate change by the end of the 21st century under the high-emission RCP8.5 scenario, compared with a historical period, with a mean power reduction (over an ensemble of seven climate models) of 2.1%. To assess the impact of wake-induced losses due to increasingly dense farm build-out, we model wakes within the German Bight region using an engineering wake model, under various stages of (planned) build-out corresponding to the years 2010–2027. By identifying clusters of wind farms, we decompose wake effects into long-range (inter-cluster), medium-range (intra-cluster) and short-range (intra-farm) effects. Inter-cluster wake-induced losses increase from 0 for the 2010 scenario to 2.5% for the 2027 scenario, with intra-cluster losses also increasing from 0 to 4.3%. Intra-farm losses are relatively constant, at around 13%. While the evolution of wake effects therefore outweighs the climate effect, and impacts over a shorter timescale, both factors are significant. We also find evidence of an interaction between the climate and wake effects. Both climate change and evolving wake effects must therefore be considered within resource assessment and wind farm planning.

Control of Corrosion of Carbon Steel in Sea Water by Polyaniline/Epoxy-(graphene)-Based Double-Layered Smart Coatings

Carbon steel (CS) is the preferred construction material in most industries due to its cost-effectiveness and unique mechanical properties. However, CS is susceptible to corrosion, and it thus requires the application of proper corrosion control measures to lengthen its service life. With regards to the oil and gas industry, the pipelines used to transport the oil and gas from the offshore production well are exposed to two main forms of the corrosive environment: the saltwater that surrounds the pipeline's outer wall, and the acidic corrosive environment that attacks the inner pipeline wall, especially during the oil and gas reservoir service such as the acidizing procedure for enhancing oil recovery (EOR). The most common method employed to protect the pipeline's outer wall is the application of protective coatings. However, many of the currently used coatings are not effective for extended periods of service. Therefore, there is a need to develop coatings with improved anti-corrosive properties, which could have an extended service life and, if damaged/compromised, could counterbalance the damage by acting as smart coatings.To address the outer-wallcorrosion of carbon steel pipelines exposed to a simulated sea environment (3.5wt.% NaCl), two types of coatings were developed and characterized in our laboratory: (i) a composite double-layered anti-corrosive coating based on the inner electrically-conductive polyaniline (PANI) layer doped with graphene oxide (GO) synthesized electrochemically directly on the CS surface, and on the outer commercial epoxy coating, and (ii) a smart double-layered coating based on the inner PANI layer electrochemically formed on the CS surface and doped with sodium caprylate (SC) and sodium dodecyl sulphonate (SDS) as a corrosion inhibitor mixture, and the outer commercial epoxy coating.The use of the double-layer PANI/GO/epoxy coating resulted in significantly better long-term anti-corrosive properties in the protection of CS surface in 3.5 wt.% NaCl. The coating maintained its protection efficiency over two months of constant exposure to the corrosive electrolyte (Figure 1). The excellent corrosion protection properties of the coating were prescribed solely to the presence of the underlying PANI/GO layer, which represents a high barrier for the transport of hydrated corrosive ions to the CS surface, through the combined action of charge (passive oxide film formation), surface energy (hydrophobicity), and blocking mechanisms.The smart double-layered coating based on the inner PANI layer doped with SC+SDS and the outer epoxy layer yielded a hydrophobic surface and good adhesion to CS. When damaged to allow penetration of the corrosive electrolyte through it to reach the CS surface, it relatively quickly (within one day) recovered its anti-corrosive properties, as a consequence of the potential-driven release of SC+SDS from the PANI layer and its adsorption on the exposed CS surface, and it then continued to offer high corrosion protection during the remaining 29 days of exposure in aqueous 3.5 wt.% NaCl, in comparison with the undoped coating that failed rather quickly (within 4 hours), Figure 2. Figure 1

Hazard Identification of Well Test Operation in Drilling and Production Offshore Platform by HAZID

A significant portion of energy resources has been discovered in offshore sectors, leading to a steadily increase in the volume of activities and operations. Once a well is drilled and fluid extraction begins, all the reservoir parameters, start to change. well test operation is one of the most crucial tools for engineers to comprehend the behavior and parameters of hydrocarbon reservoirs. In this study, the hazards associated with the well test operations has been identified by using HAZID technique. A total of 189 risks were identified in the initial risk assessment, with 35 categorized as low risk, 88 as medium risk, and 66 as high risk. Following the implementation of protection layers in the secondary risk assessment, the number of low risks incidents increased, while medium and high-risk incidents saw a significant reduction. Most of the identified risks are associated with loading operations and sea transportation from the port to the drilling rig. Since loading and unloading operations are critical and frequently occurring tasks in well testing, they contribute significantly to the overall risk profile.

Diagnosis of GHG Emissions in an Offshore Oil and Gas Production Facility

This work presents a diagnosis of greenhouse gas (GHG) emissions for floating production storage and offloading (FPSO) platforms for oil and gas production offshore, using calculation methodologies from the American Petroleum Institute (API) and U.S. Environmental Protection Agency (EPA). To carry out this analysis, design data of an FPSO platform is used for the GHG emissions estimation, considering operations under steady conditions and oil and gas processing system simulations in the Aspen HYSYS® software. The main direct emission sources of GHG are identified, including the main combustion processes (gas turbines for electric generation and gas turbine-driven CO2 compressors), flaring and venting, as well as fugitive emissions. The study assesses a high CO2 content in molar composition of the associated gas, an important factor that is considered in estimating fugitive emissions during the processes of primary separation and main gas compression. The resulting information indicates that, on average, 95% of total emissions are produced by combustion sources. In the latest production stages of the oil and gas field, it consumes 2 times more energy and emits 2.3 times CO2 in terms of produced hydrocarbons. This diagnosis provides a baseline and starting point for the implementation of energy efficiency measures and/or carbon capture and storage (CCS) technologies on the FPSO in order to reduce CO2 and CH4 emissions, as well as identify the major sources of emissions in the production process.

Improved severe slugging modeling and mapping

One of the common flow assurance issues in offshore production facilities is riser-based severe slugging. This phenomenon can also occur in horizontal wells, hindering oil and gas production. Severe slugging is a cyclic process that occurs in the late life of reservoirs when there is not enough energy available from the reservoir to push the liquid out of the riser. It is highly undesirable as it results in large fluctuations in pressure, oil, and gas flow rates at the outlet of the riser. To address this challenge, we propose an improved one-dimensional severe slugging modelthat enhances the blowout step of the slugging cycleand Compared to the existing one-dimensional models. For benchmarking, the performance of this proposed model has been compared with experimental data for lab-scale geometry and with the OLGA simulations for field-scale geometry and higher operating pressures. The results demonstrate moderate errors in predicting slug characteristics, affirming the model's reliability and applicability. Additionally, a severe slugging envelope prediction approach has been proposed utilizing the developed model. The proposed severe slugging envelopes modeling approach can demarcate the severe slugging flow region for a given pipeline riser geometry and predict severe slug characteristics, including slug length and slug time within that severe slug flow region. This work significantly contributes to flow assurance strategies in production, optimizing hydrocarbon extraction processes and minimizing operational disruptions.

Standardization of Turbine Design and Installation Vessels to Accelerate the Offshore Wind Industry in the United States

Offshore wind energy has gained attention as a promising renewable energy source with many benefits, including clean, sustainable, and scalable electricity production. Despite the vast potential for offshore wind production in the United States, the country lags in its development. The industry struggles with supply chain challenges related to the complex logistics around the design and construction of many component parts, installation and maintenance vessels, and shipyards that can accommodate the massive turbine components before installation. These challenges are complicated by the rapid increase in size of offshore wind turbines to achieve higher power generation, which are not easily handled by other parts of the supply chain. The US lacks access to wind turbine installation vessels (WTIVs), particularly those that can install very large turbines. To address these issues, we propose policy options to the US Bureau of Ocean Energy Management of the Department of Interior and the US Department of Energy to spearhead standardization in this sector of the economy by exploring standardization of maximum turbine size, investment in WTIVs, or allowance of unrestricted or market-driven offshore wind farm development. These options have great potential to enable growth in the offshore wind energy sector in the US and achieve the federal government's goal of 30 GW of offshore wind energy by 2030.

Mapping the Global Carbon Emissions of Marine Sectors.

The ocean serves as a vital ecosystem for sustaining life on earth and ensuring human well-being. Presently, there is a significant surge in global demand for various ocean-based economic activities, including fishing, shipping, offshore wind energy production, maritime tourism, and so on. However, this growth has also resulted in an increase in emissions from marine sectors, which have not been thoroughly evaluated or analyzed. It is therefore necessary to conduct comprehensive evaluations of the current emissions, covering marine sectors. To address this need, through this Perspective, we have globally analyzed and discussed carbon emissions linked to maritime transportation, marine capture fisheries, marine aquaculture, offshore wind, ocean renewables, and crude oil production. Additionally, we explored country-specific scales for these emissions and discussed points for future research to address the existing gaps. By gaining a better understanding of emissions over the oceans, policymakers could prioritize policy measures for achieving emission reduction goals and promote sustainable ocean development.

A legal and regulatory compliance framework for maritime operations in Nigerian oil companies

The maritime sector plays a critical role in Nigeria's oil industry, serving as the primary conduit for offshore oil exploration, production, and transportation. As the country remains heavily reliant on its oil revenues, ensuring that maritime operations comply with legal and regulatory standards is crucial for operational safety, environmental sustainability, and economic stability. This review outlines a comprehensive legal and regulatory compliance framework for maritime operations in Nigerian oil companies, focusing on the roles of key regulatory bodies such as the Department of Petroleum Resources (DPR), the Nigerian Maritime Administration and Safety Agency (NIMASA), and the National Environmental Standards and Regulations Enforcement Agency (NESREA). It explores major laws such as the Coastal and Inland Shipping (Cabotage) Act, Petroleum Industry Act (PIA), and Environmental Impact Assessment (EIA) Act, highlighting their implications for offshore drilling, oil transportation, and environmental protection. Additionally, the review discusses the compliance challenges Nigerian oil companies face, including environmental risks, maritime security threats, jurisdictional conflicts, and the technical demands of adhering to safety standards. To address these challenges, the study emphasizes the need for regular audits, technology integration, capacity building, and collaborative engagements between oil companies and regulatory authorities. Through case studies on oil spill response and the enforcement of cabotage laws, the review underscores the importance of robust regulatory enforcement to ensure safety, mitigate environmental damage, and enhance operational efficiency. This framework is essential for the future growth of Nigeria’s oil sector, balancing economic gains with legal compliance and sustainability in maritime operations.

Design considerations and preliminary hydrodynamic analysis of an offshore decentralised floating wind-hydrogen system

Despite the number of works on the techno-economics of offshore green hydrogen production, there is a lack of research on the design of floating platforms to concomitantly support hydrogen production facilities and wind power generation equipment. Indeed, previous studies on offshore decentralised configuration for hydrogen production, implicitly assume that a floating platform designed for wind power generation (FOWT) can be also suitable as a floating wind hydrogen system (FWHS). This work proposes a novel design for an offshore decentralised FWHS, and analyses the effects of the integration of the hydrogen facilities on the platform's dynamics and how this in turn affects the performances of the wind turbine and the hydrogen equipment. Our findings indicate that despite the reduction in platform's stability, the performance of the wind turbine is barely affected. Regarding the hydrogen system, our results aim at contributing to further assessment and design of this equipment for offshore conditions.

Calm Before the Storm?

Atlantic hurricane season poses an annual threat to the billions of dollars of oil and gas hardware pumping hydrocarbons from the depths of the US Gulf of Mexico (GOM). The region’s offshore production amounts to about 1.8 million B/D—roughly 14% of the total crude output in the US, according to the US Energy Information Administration, so any disruption is felt by oil markets across the globe. Prior to the 2024 hurricane season, forecasters pegged this year as primed to be particularly intense. Colorado State University (CSU), known for its storm prognostication, estimated that the basin would experience 23 named storms, with a dozen of those becoming hurricanes (winds of 74 mph or higher), and six of those strengthening to major hurricanes (winds of 111 mph or higher). Similarly, AccuWeather meteorologists expect between 20 and 25 named storms with a possibility of 30 or more. As the season enters its busy period, the basin has only experienced five named storms to date; however, many forecasters are sticking to their initial forecasts and continue to warn of an intense September/October period. “The months of September and October should be very active across the Atlantic,” said AccuWeather lead hurricane expert Alex DaSilva. “We continue to remain very concerned about rapid intensification. Sea-surface temperatures and ocean heat content are near record levels across most of the Atlantic basin. This can act like jet fuel for tropical systems. We also continue to believe that La Niña will emerge sometime in November. When water temperatures near the equator of the eastern Pacific Ocean are lower than the long-term historical averages for an extended period, La Niña is declared. Although this is a phenomenon in the Pacific, it has ramifications for weather patterns over the Atlantic Ocean. Specifically, La Niña can reduce the wind shear across the basin. When wind shear is lower, it makes it easier for tropical systems to take shape and strengthen.” The GOM has experienced one disruption in 2024 courtesy of Hurricane Beryl. Once a Category 5 storm (winds 155 mph and higher)—and the earliest-forming Category 5 storm on record—Beryl weakened as it crossed the southern Yucatán. The storm regained Category 1 strength as it crossed the far western offshore oil patch enroute to landfall near Matagorda Bay, Texas. Shell shut in production at its Perdido spar because of the storm as well as evacuated personnel from it and its Whale facility. Chevron moved all non-essential personnel off its Anchor floating production unit, which was undergoing commissioning at the time. The last major storm to cut a path straight through the heart of the US offshore oil patch was 2021’s Hurricane Ida. Ida tore through the region as a Category 4 storm before slamming into the Louisiana coast near Port Fourchon packing 150 mph winds on 29 August. The storm prompted the shut in of almost 100% of the Gulf’s oil and gas production and caused extensive damage to major hubs in the region, including the Shell-operated West Delta Block 143 complex. The facilities, which serve as the transfer station for production from Shell’s robust Mars corridor, were off line for several months.

Low-carbon energy scheduling for integrated energy systems considering offshore wind power hydrogen production and dynamic hydrogen doping strategy

This paper proposes a low-carbon energy scheduling model for integrated energy systems (IES) considering offshore wind power hydrogen production and dynamic hydrogen doping strategy. The offshore wind electrolysis system, hydrogen mixed gas turbine (HMGT), carbon capture, utilization and storage, and laddered carbon trading are introduced to reflect the values of hydrogen blending in carbon emission reduction for IES. A carbon emission and combustion model for HMGT based on the system thermodynamics and chemical reaction kinetics is presented. The dynamic hydrogen doping strategy is leveraged to consider the impact of gas composition variations on HMGT operating and gas system. Then, an energy balance-based quasi-steady-state model is proposed to deal with the different calorific value of the gas mixture. In order to effectively solve the resulting highly nonlinear and nonconvex problem arising from the varying hydrogen blending ratio, the nonlinear hydrogen production efficiency, and the convex–concave energy balance-based quasi-steady-state model, a tractable solution formulation is proposed. Numerical results illustrate the effectiveness of the proposed model.

Harnessing offshore wind for decarbonization: A geospatial study of hydrogen production and heavy industry utilization in Mexico

This study comprehensively examines the techno-economic potential of utilizing offshore wind resources for hydrogen production in Mexico. Through the integration of geospatial analysis techniques with energy generation and economic models, the research estimates hydrogen production, CO2eq emissions reduction potential, Levelized cost of electricity (LCOE), and Levelized cost of hydrogen (LCOH). The analysis highlights Mexico’s capacity to produce up to 217.33 million tons of hydrogen annually, predominantly from the Gulf of Mexico. Centralized offshore hydrogen production demonstrates significant cost advantages, being up to 0.92 USD/kg cheaper than onshore production. The study also underscores the economic benefits of repurposing existing oil and gas infrastructure, which can reduce LCOH by up to 11%. Environmental benefits are substantial, with hydrogen use in ammonia production potentially reducing CO2eq emissions by 82.5%. Additionally, the study identifies highly suitable offshore areas for hydrogen production, particularly near existing oil infrastructure, facilitating the integration of new renewable energy projects with minimal additional infrastructure development. These findings provide valuable insights for policymakers and stakeholders, emphasizing the economic viability and environmental benefits of offshore wind hydrogen production as a strategic pathway for Mexico’s energy transition and decarbonization efforts.

Offshore Plankton Blooms via Mesoscale and Sub‐Mesoscale Interactions With a Western Boundary Current

AbstractWe investigate mesoscale circulations in an oligotrophic western boundary current, the East Australian Current, during a sustained offshore plankton bloom. Using a series of high resolution hydrographic sections taken a few days apart, supplemented with in situ samples of nutrients, satellite and long‐term mooring measurements, we describe a dynamic situation by which the East Australian Current's velocity core and associated front, interacts with a mesoscale eddy, migrating zonally by approximately 100 km over the course of 10 days. This interaction between the boundary current and mesoscale eddy field occurred concurrently with a sustained offshore plankton bloom. Sub‐mesoscale upwelling motions on the inshore flank of the boundary current core coincides with increased nutrient and plankton concentrations in the near surface. Calculations based on the quasi‐geostrophic omega equation and finite size lyapunov exponents suggest that these vertical motion arise from the interaction of the mesoscale with the East Australian Current. Frontolysis (the destruction of horizontal buoyancy gradients) leads to a thermally indirect ageostrophic secondary circulation that has the potential to supply nutrients to the near surface ocean. Using satellite data, we investigate the mesoscale conditions associated with all offshore phytoplankton blooms identified by an automated method, finding similar mesoscale patterns to those observed during the field campaign. We conclude that the interaction between the East Australian Current and mesoscale eddies is a recurrent catalyst for the complex sub‐mesoscale dynamics we observed, and is likely a fundamental processes in driving offshore biological productivity in the region.

Digitalization of Anchor Handling Tug Supply Vessels: Enhancing Efficiency and Safety in Offshore Operations

Abstract Global demand for safety and sustainable offshore operations has led to great and dynamic changes in the maritime and offshore industry in recent years. This has made the industry to witness a rapid transformation in recent times with the digitalization of vessels, and anchor handling tug supply (AHTS) vessels are no exception. The digitalization of offshore operational vessels is expected to play an important role in the future and support the analysis of the automation and instrumentation market. The AHTS vessel is a specialized offshore support vessel used in the oil and gas industry, which serves multiple functions and roles that provide support for offshore drilling and production operations. The multi-functional purpose of AHTS vessels includes anchor handling, towing, supply and cargo transportation, oil spill clean-up response, and cable and pipe laying, among others. This requires the integration of multiple functional digitalized systems to optimize vessel operations, especially in harsh arctic environments. The current study reviews the importance and potential of AHTS vessels' digitalization and discusses its benefits, opportunities, and challenges. A systematic approach is adopted to explore the potential development and dynamics of digitalization in the maritime industry, focusing on AHTS vessels. This study finds that the extent of knowledge is evolving and requires an integrated approach to maritime digitalization to enhance operational efficiency, safety, and resilience in critical offshore operations.

Sustainability of the Model Production Sharing Contract 2023 in Bangladesh: An Historical Analysis

Abstract The significance of the Production Sharing Contract (psc) for the onshore and offshore extraction of petroleum resources from Bangladesh’s sovereign territory has grown in recent years due to maritime delimitations among its neighbouring countries. To ensure the long-term investment, social well-being, economic growth, and energy stability of the country, the Government of Bangladesh (GoB) has introduced the Model Offshore Production Sharing Contract (psc)-2023. This article aims to provide an analysis of the Model psc-2023. Through a thorough examination of the Model psc-2023, it will address any existing loopholes and provide recommendations for its improvement. This article will be instrumental in launching the future development of the offshore model offshore production sharing contract.

Freshwater spreading far offshore the Japanese coast

River discharge to the ocean influences the transport of salts and nutrients and is a source of variability in water mass distribution and the elemental cycle. Recently, using an underwater glider, we detected thick, low-salinity water offshore for the first time, probably derived from coastal waters, in the central-eastern Sea of Japan, whose primary productivity is comparable to that of the western North Pacific. Thereafter, we aimed to investigate the offshore advection and diffusion of coastal water and its variability and assess their impact. We examined the effects of river water discharge on the flow field and biological production. Numerical experiments demonstrated that low-salinity water observed by the glider in spring was discharged from the Japanese coast to offshore regions. The water is discharged offshore because of its interaction with mesoscale eddies. A relationship between the modeled low-salinity water transport to the offshore region and the observed chlorophyll-a in the offshore region was also observed, indicating the influence of river water on offshore biological production. This study contributes to understanding coastal-offshore water exchange, ocean circulation, elemental cycles, and biological production, which are frontiers in the Sea of Japan and throughout the world.