Deep-water Areas Research Articles

Methods to Improve the Accuracy and Robustness of Satellite-Derived Bathymetry through Processing of Optically Deep Waters

Selecting a representative optical deep-water area is crucial for accurate satellite-derived bathymetry (SDB) based on semi-theoretical and semi-empirical models. This study proposed a deep-water area selection method where potential areas were identified by integrating remote sensing imagery with existing global bathymetric data. Specifically, the effects of sun glint correction for deep-water areas on SDB estimation were investigated. The results indicated that the computed SDB had significant instabilities when different optical deep-water areas without sun glint correction were used for model training. In comparison, when sun glint correction was applied, the SDB results from different deep-water areas had greater consistency. We generated bathymetric maps for the Langhua Reef in the South China Sea and Buck Island near the U.S. Virgin Islands using Sentinel-2 multispectral images and 70% of the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) bathymetry data. Additionally, 30% of the ICESat-2 bathymetry data and NOAA NGS Topo-bathy Lidar data served as the validation data to evaluate the qualities of the computed SDB, respectively. The results showed that the average quality of the SDB significantly improved with sun glint correction application by a magnitude of 0.60 m in terms of the root mean square error (RMSE) for two study areas. Moreover, an evaluation of the SDB data computed from different deep-water areas showed more consistent results, with RMSEs of approximately 0.4 and 1.4 m over the Langhua Reef and Buck Island, respectively. These values were consistently below 9% of the maximum depth. In addition, the effects of the optical image selection on SDB inversion were investigated, and the SDB calculated from the images over different time periods demonstrated similar results after applying sun glint correction. The results showed that this approach for optical deep-water area selection and correction could be used for improving the SDB, particularly in challenging scenarios, thereby enhancing the accuracy and robustness of SDB.

Identification and prediction of hydrate–slug flow to improve safety and efficiency of deepwater hydrocarbon transportation

The vast hydrocarbon resources (oil, gas, and gas hydrate) in deepwater areas are considered one of the most significant resources of the future. However, the dangerous flow patterns and blockage accidents caused by hydrates threaten the safety and efficiency of the transportation process. A mutual interaction exists between hydrate growth and multiphase flow. In this study, hydrate formation and gas–slurry two–phase flow tests were conducted in a pure water system with a constant pressure (4 MPa) and various liquid loadings (40–80%) in a visual flow loop. It was found that the hydrate growth process in the dynamic system included bubble promotion, subcooling promotion, and mass transfer inhibition. Meanwhile, two atypical slug patterns (rapid conversion slug and deposition slug) in the vertical upward flow were determined, which corresponded to the promotion and inhibition regions. In the rapid conversion slug flow, the churn segments replaced the original Taylor bubbles when the liquid loading was less than 60%. In the deposition slug flow, slurry shedding phenomena was observed. In addition, the hydrate particle deposition behavior was found to inhibit hydrate growth and cause flow pattern shifts, but did not trigger the differential pressure surge. The gas isolation caused by the liquid plug and energy dissipation due to the collision between hydrate particles and the tube wall may be responsible for the sudden increase in pressure drop. Furthermore, the feasibility of predicting hydrate blockage using the differential pressure method was explored. The experiment results showed that this warning method was effective when the liquid loading was below 76%. And an effective warning can improve the transport capacity by approximately 34%.

Design and evaluation of an efficient high-precision ocean surface wave model with a multiscale grid system (MSG_Wav1.0)

Abstract. Ocean surface waves induced by wind forcing and topographic effects are a crucial physical process at the air–sea interface, which significantly affect typhoon development, ocean mixing, etc. Higher-resolution wave modeling can simulate more accurate wave states but requires a huge number of computational resources, making it difficult for Earth system models to include ocean waves as a fast-response physical process. Given that high-resolution Earth system models are in demand, efficient high-precision wave simulation is necessary and urgent. Based on the wave dispersion relation, we design a new wave modeling framework using a multiscale grid system. It has the fewest number of fine grids and reasonable grid spacing in deep-water areas. We compare the performance of wave simulation using different spatial propagation schemes, reveal the different reasons for wave simulation differences in the westerly zone and the active tropical cyclone region, and quantify the matching of spatial resolutions between wave models and wind forcing. A series of numerical experiments show that this new modeling framework can more precisely simulate wave states in shallow-water areas without losing accuracy in the deep ocean while costing a fraction of the price of traditional simulations with uniform fine-gridding space. With affordable computational expenses, the new ocean surface wave modeling can be implemented into high-resolution Earth system models, which may significantly improve the simulation of the atmospheric planetary boundary layer and upper-ocean mixing.

A temperature-sensitive polymer with thinner effect as a rheology modifier in deepwater water-based drilling fluids

The special deepwater and deep well environment in the deepwater area of the ocean puts forward higher requirements on the temperature resistance and flat rheology performance of water-based drilling fluid. In this study, the flat rheology performance of water-based drilling fluids was improved by synthesizing a temperature-sensitive polymer with thinner effect as a rheology modifier (PVNA). PVNA was characterized by infrared spectroscopy, thermogravimetric, nuclear magnetic resonance hydrogen spectroscopy, X-ray photoelectron spectroscopy and liquid gel chromatography. The results of the evaluation experiments showed that PVNA in 4 wt% bentonite mud resisted temperature up to 180°C and had good compatibility. The slope of the viscosity-temperature curve of the 4 wt% bentonite mud after aging at 180 °C/16 h was reduced from 0.84 to 0.17 after the addition of PVNA, indicating that PVNA can substantially improve the flat rheology performance of the 4 wt% bentonite mud. Turbidity analysis, particle size analysis, thixotropy analysis and transmission electron microscopy analysized the temperature-sensitive effect of PVNA. Specifically, PVNA weakens the hydration layer on the surface of bentonite through its hydrophobic properties, reducing the low-temperature aggregation effect of bentonite, and avoiding low-temperature thickening of bentonite mud to a certain extent. At the same time, the temperature-sensitive effect of PVNA after warming brings stronger intermolecular binding, which improves the internal three-dimensional network strength of the bentonite dispersion system after warming. The two effects synergistically improved the flat rheology performance of the dispersion system. PVNA has good application prospects and can be used as a good reference for developing other rheology modifiers.

Living on the Coast in Harmony with Natural Processes

The coastal zone is a fascinating place that comprises the interface between sea and land. This interface, which is both very dynamic and sensitive, has been affected by strong urban and industrial pressures, and an increase in both traffic and recreational uses, leading to the deterioration of natural habitats and the growing instability of residential areas. Added to this disruption is ongoing climate change, which will lead to rising sea levels and increased wave action. Another problem we are increasingly concerned about is ocean pollution, which has been one of the main causes of threats to deep-water coral reef areas. The main sources of pollution include oil spills and offshore oil drilling. The effects of pollution caused by oil spills can not only seriously affect the global environmental balance of our planet but can also, on a different scale, seriously affect the economy of countries whose main resources depend heavily on the sea. Wave energy has the potential to alleviate the world's dependence on depleting fossil energy resources. With regard to coastal protection, the development of ecological solutions to preserve ecosystems and address coastal processes as an alternative to traditional coastal protection structures (seawalls, groins and breakwaters) is becoming increasingly important. These structures, generally referred to as passive measures, are usually built to alter the effects of sea waves, currents and the movement of sand along the coastline, with the aim of protecting beaches, ports and harbors. The concerns outlined are critically addressed throughout this review article. All of them are highly relevant today and, as demonstrated throughout this article, are expected to grow even more and with much more pronounced consequences starting from the middle of the current century.

Assessment of Gas Production from Complex Hydrate System in Qiongdongnan Basin of South China Sea

The China Geological Survey (CGS) has carried out a large number of surveys and core drilling over the deepwater area of Qiongdongnan Basin (QDNB) in the South China Sea and discovered the natural gas hydrate system controlled by the gas chimney with a high geothermal gradient. The complex hydrate system consists of a sandy hydrate reservoir distributed around a lateral transition gas-hydrate mixed zone and a free gas zone in the middle. The hydrate and gas are distributed in the same layer, which is thin but potentially valuable for commercial exploitation. In this paper, a geological model of the target hydrate system in QDNB was established based on the results of several rounds of drilling. The method of numerical simulation was utilized to assess the production capacity of the target hydrate system and clarify the evolution of hydrate and gas saturation distribution with different well positions. The simulation results indicate that the producer well built in the center of the highly-saturated hydrate zone has a limited gas production capacity, with a cumulative production of only 7.25 × 106 m3 in 9 years. The well built at the boundary of the hydrate zone can rapidly link up the gas in the transition zone through a large production pressure differential, but it lacks control over the hydrates and its dissociated gas in the transition zone—the cumulative gas production volume from hydrate accounts for only 12.3%. As for the wells built in the transition zone and gas zone, they can directly invoke the free gas production capacity. Free gas is produced as the formation pressure reduces and hydrate is induced to dissociate, making the gas from the hydrate the subsequent production capacity. The cumulative production can exceed 6 × 108 m3 in 9 years. The stable production duration can extend to 2645 days, and the cumulative proportion of gas at the wellhead from hydrate reaches close to 30%. It is necessary to avoid the free water layer. The bottom water coning would improve the water production by 40% and shorten the stable production duration. In summary, the complex hydrate system of this type in the QDNB has the potential for industrialized exploitation. In the future, the well group can be used for the further improvement of the hydrate utilization rate.

Characteristics of Stratigraphy and sedimentation of the Phu Khanh Basin and adjacent area

The Phu Khanh Sedimentary Basin is situated in the deep-water offshore area, east of the continental shelf of Central Vietnam. This area is said to have quite good oil and gas potential, but very few geological and petroleum research projects have been carried out in the past. In this article, the authors update new research results based on new seismic interpretation and well data conducted in recent years. The obtained results show that: Stratigraphy of the Phu Khanh Basin was subdivided into 5 large sequences, including: a. Eocene(?)/Oligocene unit is mainly clastic sediments of fluvial/lacustrine, delta plain and marine environments, b. Lower Miocene stratigraphy: Includes deltaic clastic sediments and shelfal carbonates; c. Middle Miocene stratigraphy: includes delta-plain, shallow marine terrigenous sediments and shelfal carbonate, d. Upper Miocene and Pliocene - Quaternary units include continental shelf and deep-sea terrigenous sediments. Each unit of stratigraphy and corresponding sedimentary environment is related to each stage of the geological and tectonic evolution of the basin. In general, the trend changes from the fluvial/lacustrine environment to the deltaic, shelfal and deep marine environments upward. Establishing the names of the formations and the presence of the Eocene sedimentary rocks in the Phu Khanh Basin is still an open issue. More detailed data, especially well data, are needed to obtain a more convincing interpretation.

The influences of sedimentary environments on carbon accumulation in lacustrine deposits: Evidences from elemental geochemistry

The carbon dynamics of lacustrine deposits play an important role in controlling the atmospheric carbon cycle. However, the influences of various sedimentary factors on carbon accumulation in lacustrine deposits are rarely known. In this study, the petrological and geochemistry analyses of organic-rich (average total organic content = 24.22 wt%) lacustrine deposits and organic-poor (average total organic content = 2.48 wt%) lacustrine deposits buried under a peatland (the Zhibian peatland) in Northeast Asia are used to explore the above issues. Results suggest that the concentrations of major oxides, trace elements and rare earth elements in the organic-poor lacustrine deposits are higher than those in the organic-rich lacustrine deposits. Furthermore, these lacustrine deposits were sourced from felsic rocks. The tectonic background was continental island arc and active continental margin. Additionally, the sedimentary models of lacustrine deposits buried under peat sequence were also concluded. Organic-poor lacustrine deposits were developed in a deep-water area, that was freshwater and oxygenic condition. This type of lacustrine deposit was influenced by the frequent input of coarse-grained terrigenous debris and low productivity. In contrast, the organic-rich lacustrine deposits were developed in a shallow-water area, that was saline and anaerobic condition. This type of lacustrine deposit was influenced by a rare input of fine-grained terrigenous debris and high productivity. These findings should assist future studies on the carbon dynamics of buried lacustrine deposits. This study would provide a representative example of carbon accumulation processes and mechanisms in buried paleolake system in Northeast China.

Evidence of new diapiric structures in the southern Adria Plate (Eastern Margin of Tethyan Ocean): Implications for Triassic paleogeography and evaporites remobilization during subduction/collision (Northern Ionian Sea, Central Mediterranean)

It has long been recognized that the Adria Plate, as well as the Dinaric-Hellenic sector, contains a large volume of Triassic salt associated with diapirism, and it is well known that Triassic evaporites in the Mediterranean Sea region were deposited over epicratonic platforms surrounding the Mesozoic passive margin of Tethys Ocean. However, the real extent of these evaporites is still unknown; especially in the deep-water offshore area where publicly available seismic reflection profiles are scarce and petroleum exploration wells are missing. Several authors highlighted the presence of Triassic salt structures, mostly triggered by Meso-Cenozoic compressions and associated with fold-and-thrust belts. Both the lack of data and the later compressions contribute to hiding how a diapiric structure, formed in a passive margin and characterized by dome's geometry, is remoulded to assume a teardrop geometry typical of diapirs in fold-and-thrust belts. Two end members of diapiric structures are discussed: extensional structures formed in a passive margin, and compressional structures formed in a fold-thrust belt. The transformation of one end-member into the other is not well known. In the Northern Ionian Sea, the Apulian foreland, belonging to the southernmost termination of the Adria Plate and considered one of the largest preserved Mesozoic passive margin block of the Tethys Ocean, is a deep-water area associated with the opposing fronts of the nearby Calabrian Arc/Apennines and Dinaric-Hellenic Chains since the Cretaceous. Therefore, it represents an ideal area for investigating both the real extent of Triassic evaporites and the transformation of the diapiric structures under different regional geodynamic contexts.Based on seismic reflection profiles but no petroleum exploration wells, we present evidence of Triassic evaporites in the deep-water portion of the Apulian foreland, as indicated by the interpretation of two diapiric structures never described previously. These two new diapirs likely formed from inherited Mesozoic salt structures such as pillows and/or salt domes. The identification of halokinetic-related sequences affecting the Plio-Quaternary foreland sediments allows constraining the polyphaser evolution of the two diapirs. We suggest they are reactivated in response to the compressive stresses transmitted by the nearby Calabrian Arc/Southern Apennines and Hellenides. But, after the Middle Pleistocene, extensional tectonics, related to Adria Plate flexuring, acted again, and the diapirs were cross-cut by normal faults. These observations and findings are integrated into the geological context that controls the fundamental features of the diapirs, providing new insights on the fate of diapiric structures formed in a passive margin, later involved in a subducting and colliding plate, and before they become part of a fold-and-thrust belt. Furthermore, the study provides new constraints on the Triassic paleogeographic reconstruction of the Northern Ionian and Central Mediterranean Seas at the continental margin of the Tethys Ocean.

Structure and functional characteristics of zooplankton and food supply for nekton in the western Bering Sea

Structure and functional characteristics of zooplankton and feeding of the most abundant nekton species (pollock, herring and salmons) are analyzed using the data of ecosystem survey in the western Bering Sea in 2020 and compared with the structural indices for 2015−2019. The main patterns of composition and distribution of zooplankton and production of organic matter by zooplankton are determined. High values and turnover rate of production are noted for the non-predatory zooplankton (mainly copepods and euphausiids) in the eastern Anadyr Bay, the area at Cape Navarin, the shelf of Koryak coast, and the continental slope of Olyutorsky Bay. High production of predatory zooplankton (mainly hyperiids) is found on the slope of Karaginsky Bay, presumably because of these species transport from the southern areas with later stage of the seasonal succession. In autumn 2020, walleye pollock and pacific herring consumed from 15 to 55 % of the copepod, euphausiid and hyperiid production. This level of consumption did not affect their food supply because of very high turnover rate of these taxonomic groups of plankton. In the deep-water areas, salmons did not use more than 3 % of their food resource. Thus, the survey data indicate a good food supply for the most abundant nekton species in the western Bering Sea in the fall season.

Analysis of the world deepwater oil and gas exploration situation

The global trends in deepwater oil and gas exploration, characteristics of deepwater oil and gas discovery, and layout of deepwater oil and gas exploration business by seven major international oil companies are systematically analyzed using commercial databases (e.g. S&P Global and Rystad) and public information of oil companies. The deepwater area is currently the most important domain for global oil and gas exploration and discovery, with the most discoveries and reserves in passive continental margin basins. The deepwater discoveries have the greatest contribution to the total newly discovered oil and gas reserves in the sea areas, with an increasing number of lithological reservoirs discovered, and oil and gas discoveries mainly distributed in the Mesozoic–Cenozoic. The seven major international oil companies are widely active in various aspects of deepwater oil and gas exploration and development, and play a leading role. Based on years of theoretical understanding of global oil and gas geology and resource evaluation, it is proposed that favorable deepwater exploration areas in the future will mainly focus on three major areas: the Atlantic coast, the Indian Ocean periphery, and the Arctic Ocean periphery. Six suggestions are put forward for expanding overseas deepwater oil and gas exploration business: first, expand the sources for obtaining multi-user seismic data and improve the scientific selection of deepwater exploration areas; second, increase efforts to obtain deepwater exploration projects in key areas; third, adopt various methods to access into/exit from resource licenses flexibly; fourth, acquire licenses with large equity and operate in “dual-exploration” model; fifth, strengthen cooperation with leading international oil companies in deepwater technology; and sixth, improve business operation capabilities and gradually transform from “non-operators” to “operators”.

Towards fully autonomous floating offshore wind farm operation & maintenance

Wind energy is one of the most versatile and promising sustainable energy solutions. Wind energy can be harvested in both onshore and offshore environments. Due to the environmental and societal impacts of onshore wind farms, the focus on developing offshore wind farms has been steadily increasing. For deep-water areas, floating wind turbine solutions have been developed in the past two decades. Each wind turbine is mounted on a floating structure and connected to a mooring system. While the floating wind turbine technology enables electricity generation in water depths where fixed-foundation turbines are not feasible, operation and maintenance (O&M) have become serious issues. This paper investigates the challenges and potential enabling technologies for the development of autonomous floating offshore wind farms. In particular, the paper explores the potential utilization of information and communication technology (ICT) and robotics toward fully autonomous floating offshore wind farm O&M, aiming for cost reduction and improved operational safety. The presented solutions cover fundamental aspects in floating platform design, remote operation in the form of digital twins, autonomous underwater robots and surface vehicles, and eco-friendly energy storage.

Physical Properties of Hydrocarbon Source Reservoir in the Lucaogou Formation in Junggar Basin (China) and Its Influence on Adsorption Ability and Surface Free Energy

A physical property of a shale gas reservoir affects shale gas content, then restricts the shale gas resource potential. In this paper, lithofacies and spatial distribution of the southern margin of the Junggar Basin in Xinjiang Province are identified and occurrence strata, gas content, and reservoir properties of shale gas are studied. Based on adsorption potential theory, adsorption and surface free energy of all the sample is discussed. The conclusions are as follows. (1) All the shale samples can be divided into five lithological phases. For example, black oil shale/shale (lithology) phase and gray-black-gray/dolomite mudstone (lithology) phase are the most developed; compared with the middle and lower sections, the vertical development continuity of the upper hydrocarbon source rock is better. Lithology of this section is mainly composed of shale mixed with marlstone and dolomite interlayer. From the horizontal view of this section, the overall trend is gradually thickening from west to east and from north to south. (2) Semi-deep lake-phase is the most developed, indicating a decreasing trend of thickness from sedimentary center to surrounding strata. (3) Sedimentary period of Lucaogou Formation is a deep water area of the lake basin; then, the TOC content is affected by the sedimentary environment. As sedimentary water depth increases, TOC content will increase, which results in the highest TOC content in the area. A specific surface area is roughly positively correlated with porosity, clay mineral content, and percentage of illite/montmorillonite interlayer ratio and negatively correlated with TOC content. (4) During the adsorption process, adsorption potential decreases with an increase in equilibrium pressure, and adsorption space increases with an increase in equilibrium pressure. Maximum adsorption space of all the sample were 0.20~0.25 cm3·g−1; then, its value is larger than the maximum adsorption space of other coal samples (0.025~0.20 cm3·g−1). In the same adsorption space, the corresponding adsorption potential of the coal sample is much larger than that of other samples. The reason is that the porosity permeability of this sample is relatively larger, leading to its better physical properties.

Importance of Red Rice (Deep Water Rice) Production and Its Potential of Export from Dhemaji District of Assam

Red kernelled rice is gaining importance in recent years due to its higher nutritive content as well as health advantages. It is rich in fibre, iron, Vitamin B1 & B2, zinc and calcium. Because of its importance and a good potential for export the present study was undertaken in Dhemaji district of Assam with the objective to find out the economics of production and scope of marketing of red kernelled rice. From the investigation it was found that red kernelled rice is cultivated in deep water areas of the district and 40% of the total rice area is under red kernelled rice. The production very low with an average production of 21q/ha. The benefit cost ratio was found to be 1.29 and only two marketing channels existed in the district. A company viz. Nature Bio Foods Ltd. (NBFL) was the main company which procured all the production of red kernelled rice from the producers in Dhemaji district which has its Office at Gogamukh. About 10000tons of red rice is being exported outside the district every year to other states and even other countries like USA, UK and European countries. The price spread was found to be high though there are few intermediaries in the marketing channel. From the investigation it can be concluded that there is much scope of increasing the area, production and productivity of red kernelled rice in the district provided processing centers are set up in the district so that the farmers can get a better price for their produce.

Source Rock Evaluation of Hydrocarbons in Deep-Water Offshore Areas Based on a BP Neural Network

Due to the lack of drilling data and poor quality of seismic data in deep-water offshore areas, conventional methods cannot effectively predict the total organic carbon (TOC) content. In this paper, the BP neural network method is used to predict the TOC of the strata overlying the target layer, which adds to the TOC information in the study area. Then, the highest TOC value of the strata overlying the target layer is used to select the most sensitive seismic attributes. Finally, the sensitive seismic attributes are used to evaluate the source rocks with no or few wells. A set of TOC prediction technology flows is established for TOC combined with seismic attributes under the condition of no wells and few wells in deep-water areas. The application example shows the reliability of TOC prediction by this technical process, and the study has a certain reference significance for the evaluation of hydrocarbon source rocks in offshore deep water.

Multiple sediment source infill in a low-accommodation basin: implications for the late Paleozoic sediment routing system in the southeastern Ordos Basin

AbstractLate Paleozoic strata in the southeastern Ordos Basin comprise targeted reservoirs for tight gas exploration. As a typical intracratonic basin, the Ordos Basin is characterized by low-accommodation space and a complex sediment infilling process, which attracts much attention. During the early Permian, the southeast area was fed by sediments from multiple sediment sources, which makes it difficult to identify the pinch-out of the sand bodies and reconstruct the sediment routing system. In this study, we reconstruct the paleo-topography of the late Paleozoic setting using high-resolution 2D and 3D seismic data. Thus, we identify two types of topography: the eastern block is presented as a semiclosed depression, and the western block is observed as a flat platform. Based on detrital zircon U–Pb data and heavy mineral assemblages, we reconstruct the provenance area and show that early Permian sediments originate from the northern margin of the Ordos Basin and from the northern Qinling orogenic belt in the south. By integrating the trace element contents, carbon and oxygen isotope data and sedimentary structure from core samples, we can observe the paleoenvironment and the corresponding facies associations in these blocks. The eastern block was infilled by a prograding delta; the western block was infilled by a tide-dominated delta or a wavy-dominated delta. By using stratigraphic forward modelling, we find that most sediments in the semiclosed setting are progradational and intensely interacted. In contrast, the sediments in the western block present an open setting, infilled and gently interacted. The fine-grained deposits were not easily preserved due to tidal or wave reworking processes in the shallow-water marine setting, and they were transported into deep-water areas. Furthermore, to explore the dominant factors in a pattern of fluvial–deltaic sand bodies formed in the low-accommodation basin, we rebuild the sediment routing system parameters and plot them on a bubble chart. According to the fitness between the depositional volume and the above parameters, we determine the key factors in the routing systems that formed. The results show that the sediment supply has a high relevance to the depositional volume in a semiclosed setting, such as the eastern block, while the terrain height may drive sedimentation in an open marine setting, such as the western block. We demonstrate that two different infill patterns and different sand-body stacking patterns with multiple sediment sources in a low-accommodation basin may serve as a model for similar settings.

Application of fluid modulus inversion to complex lithology reservoirs in deep-water areas

It has been a challenge to distinguish between seismic anomalies caused by complex lithology and hydrocarbon reservoirs using conventional fluid identification techniques, leading to difficulties in accurately predicting hydrocarbon-bearing properties and determining oil-water contacts in reservoirs. In this study, we built a petrophysical model tailored to the deep-water area of the Baiyun Sag in the eastern South China Sea based on seismic data and explored the feasibility of the tri-parameter direct inversion method in the fluid identification of complex lithology reservoirs, offering a more precise alternative to conventional techniques. Our research found that the fluid modulus can successfully eliminate seismic amplitude anomalies caused by lithological variations. Furthermore, the seismic data-based direct inversion for fluid modulus can remove the cumulative errors caused by indirect inversion and the influence of porosity. We discovered that traditional methods using seismic amplitude anomalies were ineffective in detecting fluids, determining gas-water contacts, or delineating high-quality reservoirs. However, the fluid factor Kf, derived from solid-liquid decoupling, proved to be sensitive to the identification of hydrocarbon-bearing properties, distinguishing between high-quality and poor-quality gas zones. Our findings confirm the value of the fluid modulus in fluid identification and demonstrate that the tri-parameter direct inversion method can significantly enhance hydrocarbon exploration in deep-water areas, reducing associated risks.

Wide shelves as discriminators between hinterland tectonic and intra-basin rifting signals

Decoding interwoven tectonic and climatic drivers in global source-to-sink systems remains a major challenge in Earth science. This study demonstrates that the very wide shelf in the northern South China Sea acted as a critical discriminator of signals related to hinterland tectonism and basin rifting. The rifting process is the main driver of variations of detrital zircon (DZ) signals in the succession of the wide shelf. DZ data show an increasing proportion of intrabasinal sediment source that is in phase with seafloor spreading and crustal extension (ca. 32–16 Ma), and then a gradual increase of extrabasinal source until the Pleistocene, in step with post-rifting thermal subsidence. These DZ variations are free of the strongest Cenozoic tectonism, the uplift of the eastern Tibet-Himalayan orogen since ca. 23 Ma, although this regional uplift dominated the DZ-signal variations in the entire deep-water basinal areas of the northern South China Sea basins fed by the Central Canyon of the Qiongdongnan Basin. Moreover, rising of global sea-level driven by the Miocene Climatic Optimum had little impact on sediment delivery in the shelf-to-basin system. The strong decoupling of DZ-variation trends between the shelf and the deep basin in this study underscores the importance of wide shelves in distinguishing different allogenic drivers in global source-to-sink systems.

Sperm and northern bottlenose whale interactions with deep-water trawlers in the western North Atlantic.

Commercial fisheries have increased in all the world's oceans with diverse unintended impacts on marine ecosystems. As a result of resource overlap, interactions between cetaceans and fisheries are a common occurrence and, in many cases, can give rise to significant conservation issues. Research on the distribution and types of such interactions is important for efficient management. In this study, we describe the behaviors of two whale species: sperm whales (Physeter macrocephalus) and northern bottlenose whales (Hyperoodon ampullatus), interacting with benthic trawlers fishing off the eastern Grand Banks of the western North Atlantic in 2007. Whale interactions were only observed when vessels were targeting Greenland halibut (Reinhardtius hippoglossoides) in deep-water fishing areas and were most common during net hauling. Sperm whales and northern bottlenose whales appeared to engage in feeding behavior close to the surface during hauling, especially during the latter stages, suggesting they targeted fish escapees rather than discards. Using photo-identification methods, seven individual sperm whales were identified with multiple resights of six individuals being recorded over an almost two month period. The maximum distance between two resights was 234 km, suggesting individual sperm whales were repeatedly targeting and even following fishing vessels over multiple days and between fishing areas. By contrast, there were no photographic resights of individual northern bottlenose whales within this study, or with substantial photo-identification catalogues from other adjacent high density areas, suggesting that individuals of this species may be less likely to follow vessels or move between areas. This study documents the earliest confirmed records of northern bottlenose whales in this remote region. These interactions and high encounter rates may indicate that adjacent populations are recovering from the previous century of commercial whaling. Our study provides new insights and details on whale-fisheries interactions, which can inform future research and help managers understand the real and perceived impacts of depredation behaviour on fisheries and whales.

First Results of Stratigraphic Drilling in the East Siberian Sea Focused on Geological Studies of the Suture Zone of the Continental Shelf’s Marginal Structures and Deep-Water Areas of the Arctic Ocean

A shallow well was drilled in the East Siberian Sea for the first time with the purpose of geological study of the suture zone of deep waters of the Arctic Ocean and marginal structures of the continental shelf. The works have been carried out at the initiative of the Federal Agency on Mineral Resources (Rosnedra) in August 2022. The well was drilled by the Russian Geological Research Institute (VSEGEI) and Rosgeologia with the assistance of Rosneft and was linked to the Rosneft’s long-term stratigraphic drilling program. Drilling was accompanied by continuous seismic-acoustic profiling and well thermometry. The maximum depth of the well was 472 m from the bottom of the sea floor; 147.5 m of core was taken to a depth of 268 m. Two sedimentary sequences were identified in the section: the Lower Jurassic–Lower Cretaceous gently deformed sequence and the Upper Neogene–Quaternary horizontally lying sequence. The sequences are separated by a thick unsampled interval with horizons of confined waters. The Jurassic–Lower Cretaceous sequence composes a northwestern-dipping monocline broken by faults and probably belongs to the complex filling the Zhokhov marginal trough of the Verkhoyansk–Chukotka orogen on the Eastern Arctic shelf.