Sea Depth Research Articles

Analysis of the temporal and spatial variability of whale shark (Rhincodon typus) aggregation in the South Ari Marine Protected Area, Maldives, Indian Ocean

Whale sharks are known to aggregate in coastal areas. In the South Ari Marine Protected Area (Maldives) a aggregation, mostly represented by young males with a high level of residency, has been described in the literature. Despite the worldwide interest in the natural resources of the Maldives, this population is increasingly subjected to anthropogenic pressure and major concern regards the flourishing tourist industry. In this study, data collected by the Maldives Whale Shark Research Programme between 2014 and 2017 have been used to detect both temporal and spatial patterns of occurrence. Favourable environmental conditions to visually detect whale sharks have been defined for the studied area. Accordingly, a total of 1077 shark encounters have been analysed in this study. Environmental conditions (i.e. sea surface temperature, monsoon occurrence) have been used to detect possible factors affecting the spatial and temporal variability of Rhincodon typus aggregations. A two-way ANOVA has been performed to detect temporal trends in animal occurrence, sea surface temperature pattern and to investigate the sea bottom depth variability during encounters. Significant differences in the monthly occurrence of whale sharks within the same year and among different years have been detected. Similar patterns have been observed for environmental parameters such as sea surface temperature and depth. A different spatial distribution has also been detected as a function of the Indian Monsoon reversal (north-eastern and south-western) affecting the area. During the northeast monsoon period, whale sharks appeared to concentrate in a smaller longitudinal range closer to the western-central part of the MPA, where deeper water conditions occur due to the proximity of a deep depression (submarine canyon). Results from this study provide new pieces of information for the implementation of dedicated management actions to protect the whale sharks population inhabiting the South Ari Marine Protected Area.

THE HALACARID GENUS LOHMANNELLA (HALACARIDAE, ACARI): LIST OF SPECIES, NOTES ON CHARACTERS, DISTRIBUTION, ECOLOGY AND A TABULAR KEY

Presently, 39 Lohmannella species are accepted as valid, but future examinations may prove some of them to be junior synonyms of others. This article lists the most important descriptive papers, as well as the former names for each of the 39 species. The characters of another five species, known by their adults, are outlined but not given a name. Based on the published data, short diagnoses as well as notes on the distribution and habitats are added. In addition, the poorly known female of Lohmannella bihamata is described and illustrated. This article provides a table of morphological characters that are meant to facilitate the identification of Lohmannella species. The genus Lohmannella is spread worldwide, inhabiting all water depths and all climatic zones; its representatives live in marine and fresh water. Although the majority of Lohmannella species have been found at sea, five species have been recovered from fresh or slightly brackish water. In the following sentences, the number of unnamed species is given in square brackets. Records of 33 [plus two] marine species are exclusively from the littoral and/or bathyal zone (0–1,000 m deep); records of three [plus three] species are from the deep sea (deeper than 1,000 m); and one record is from the littoral / deep sea depth range. Most species have been found in the temperate and polar areas: namely, 12 [plus two] have been recorded north of 23°N and 20 south of 23°S. The data from the tropics include a single shallow water (0–200 m deep) record, one unnamed species from the 400–520 m depth and one [plus two] species from the depth of more than 1,000 m. Most southern hemisphere shallow water species are morphologically distinct from the bathyal and abyssal species, as well as from the northern hemisphere species.

Исследование метода вычисления текущей характеристики точности в задаче навигации по картам геофизических полей

The paper studies a previously proposed method for calculating the current accuracy characteristics of a correlation-extreme search algorithm for solving the map-aided navigation problem. The proposed method is based on the analysis of the ratio of the extreme values of the functional used in the search algorithm for comparing the measured field fragment, and the fragments obtained from a reference map, and on determining the diameter of the set of the given level for this functional. The study is carried out using an example of three spatial geophysical fields: the sea depth field, the field of gravity anomalies, and the anomalous magnetic field; it is focused on their application for underwater vehicle navigation. The specific features of the information and measurement systems used in the survey of these fields, done by means of an underwater robot are described, as well as the procedure simulating the mapping process taking these features into account. The results of computer experiments on comparison of the proposed method for calculating the current accuracy and the method used in the Bayesian algorithm for solving the navigation problem are presented.

Metagenomic discovery and functional validation of L-asparaginases with anti-leukemic effect from the Caspian Sea.

SummaryBy screening 27,000 publicly available prokaryotic genomes, we recovered ca. 6300 type I and ca. 5200 type II putative L-asparaginase highlighting the vast potential of prokaryotes. Caspian water with similar salt composition to the human serum was targeted for in silico L-asparaginase screening. We screened ca. three million predicted genes of its assembled metagenomes that resulted in annotation of 87 putative L-asparaginase genes. The L-asparagine hydrolysis was experimentally confirmed by synthesizing and cloning three selected genes in E. coli. Catalytic parameters of the purified enzymes were determined to be among the most desirable reported values. Two recombinant enzymes represented remarkable anti-proliferative activity (IC50 <1IU/ml) against leukemia cell line Jurkat while no cytotoxic effect on human erythrocytes or human umbilical vein endothelial cells was detected. Similar salinity and ionic concentration of the Caspian water to the human serum highlights the potential of secretory L-asparaginases recovered from these metagenomes as potential treatment agents.

Seafloor Topography Estimation from Gravity Anomaly and Vertical Gravity Gradient Using Nonlinear Iterative Least Square Method

Currently, seafloor topography inversion based on satellite altimetry gravity data provides the principal means to predict the global seafloor topography. Researchers often use sea surface geoid height or gravity anomaly to predict sea depth in the space domain. In this paper, a comprehensive discussion on seafloor topography inversion formulas in the space domain is presented using sea surface geoid height, gravity anomaly and introduces an approach that uses vertical gravity gradient. This would be the first study to estimate seafloor topography by vertical gravity gradient in the space domain. Further, a nonlinear iterative least-square inversion process is discussed. Using the search area for the Malaysia Airlines Flight MH370 as study site, we used the DTU17 gravity anomaly model and SIO V29.1 vertical gravity gradient to generate the seafloor topography. The results of the proposed bathymetric models were analyzed and compared with the DTU18 and SIO V20.1 bathymetric models. The experimental results show that the gravity anomaly and vertical gravity gradient in the study area are strongly correlated with the seafloor topography in the 20–200 km wavelength range. The optimal initial iteration values for seafloor topography variance and correlation length are 0.6365 km2 and 10.5′, respectively. Shipborne measurements from SONAR data were used as external checkpoints to evaluate the bathymetric models. The results show that the RMS for BAT_VGG_ILS (inversion model constructed by vertical gravity gradient) is smaller than for BAT_GA_ILS (inversion model constructed by gravity anomaly) and BAT_GA_VGG_ILS (inversion model constructed by gravity anomaly and vertical gravity gradient). The relative accuracy of the DTU18 bathymetry model was 9.27%, while the relative accuracy of the proposed seafloor models was higher than 4%. Within the 200 m difference range, the proportion of checkpoints for BAT_VGG_ILS was close to 95%, about 80% for BAT_GA_ILS and BAT_GA_VGG_ILS, and less than 50% for the DTU18. The results show that the nonlinear iterative least square method in the space domain is feasible.

Influence of water area depth on wind waves

A semi-empirical technique for calculating the parameters of wind waves at variable sea depths along the wind acceleration has been developed and presented. This technique allows you to determine the average values of wind wave heights, their length and period depending on the wind velocity, taking into account and without taking into account the heaping of water by wind. Within the framework of the described method, the calculations of wind wave parameters suitable for isobaths d = 20 m were performed for a specific study area of the Bistre (Novostambulske) branch of the Danube estuary, for the north-eastern and eastern wind directions. Numerical simulations were performed for the Black Sea in the location of the protection dam of the Maritime approach channel of the Danube-Black Sea deep-sea navigation. Numerical calculations of wind wave transformation in the water area near the protection dam for the most dangerous wind directions in stormy conditions were performed. For mathematical simulation, the maximum values of wind velocity and wave height were used, which were observed during the whole period of research of the Black Sea water area in the region of the dam. Within the framework of refraction theory, wave transformation calculations have been performed for the most wave-hazardous wind acceleration directions, namely, the north-eastern and eastern wind directions. It is shown that taking into account the heaping of water by wind leads to an increase in the parameters of gravitational waves. The results of numerical simulations have shown that with the increase of wind acceleration exceeding the limit values, the parameters of the waves reach constant values. These values depend on the bathymetry of the seabed, wind velocity and direction. It was found that the increase in the deviation of the free surface of the sea from the undisturbed level significantly depends on the heaping of water by wind. It was found that the relative increase in the wave parameters is observed higher in the east wind direction than in the northeast wind direction in the study area of the Black Sea.

A polyphasic approach to the study of the genus Nitzschia (Bacillariophyta): three new planktonic species from the Adriatic Sea.

The paraphyletic diatom genus Nitzschia comprises over 1000 morphologically distinct pennate taxa, known from the benthos and plankton of freshwater, brackish, and marine environments. The principal diagnostic characters for delimitation of Nitzschia species include valve shape, the position and structure of the raphe, presence/absence and shape of the proximal raphe endings and terminal raphe fissures, areola structure, and specific morphometric features such as cell size, and stria and fibula density. In this study, we isolated 12 diatom strains into culture from samples collected at the surface or greater depths of the southeastern Adriatic Sea. Morphological analyses included LM, SEM, and TEM observations, which, along with specific morphometric features, allowed us to distinguish three new Nitzschia species. These findings were congruent with the results of phylogenetic analyses performed on nuclear-encoded SSU (18S) rDNA and chloroplast-encoded rbcL and psbC genes. One of the new species (Nitzschia dalmatica sp. nov.) formed a lineage within a clade of Bacillariaceae containing members of the Nitzschia sect. Dubiae, which was sister to Psammodictyon. A second lineage was part of a novel clade that is significantly distinct from other Nitzschia species sequenced so far and includes Nitzschia adhaerens sp. nov. and N. cf. adhaerens. A further new species was found, Nitzschia inordinata sp. nov., which appeared as the sister group to the N. adhaerens clade and the conopeoid Nitzschia species in our phylogenetic trees. Our findings contribute to the overall diversity of genus Nitzschia, especially in identifying some deep branches within the Bacillariaceae, and highlight under-scoring of this genus in marine plankton.

Four Years of Continuous Seafloor Displacement Measurements in the Campi Flegrei Caldera

We present 4 years of continuous seafloor deformation measurements carried out in the Campi Flegrei caldera (Southern Italy), one of the most hazardous and populated volcanic areas in the world. The seafloor sector of the caldera has been monitored since early 2016 by the MEDUSA marine research infrastructure, consisting of four instrumented buoys installed where sea depth is less than 100 m. Each MEDUSA buoy is equipped with a cabled, seafloor module with geophysical and oceanographic sensors and a subaerial GPS station providing seafloor deformation and other environmental measures. Since April 2016, the GPS vertical displacements at the four buoys show a continuous uplift of the seafloor with cumulative measured uplift ranging between 8 and 20 cm. Despite the data being affected by environmental noise associated with sea and meteorological conditions, the horizontal GPS displacements on the buoys show a trend coherent with a radial deformation pattern. We use jointly the GPS horizontal and vertical velocities of seafloor and on-land deformations for modeling the volcanic source, finding that a spherical source fits best the GPS data. The geodetic data produced by MEDUSA has now been integrated with the data flow of other monitoring networks deployed on land at Campi Flegrei.

Supersensitive Detector of Hydrosphere Pressure Variations.

This paper presents an instrument based on an equal-arm Michelson interferometer and a frequency-stabilized helium-neon laser. It is designed to record hydrosphere pressure variations in the frequency range from 0 (conventionally) to 1000 Hz, with accuracy of 0.24 mPa at sea depths of up to 50 m. The operating range of the instrument can be increased by order of magnitude by improving the registration system speed, and accuracy can be enhanced by using larger diameter membranes and/or their smaller thickness. The paper demonstrates some experimental results obtained on the supersensitive detector of hydrosphere pressure variations, confirming its high performance in the infrasonic and sonic ranges.

Research on fluid-structure interaction for piston/cylinder tribopair of seawater hydraulic axial piston pump in deep-sea environment

Abstract Seawater hydraulic axial piston pump (SHAPP) is a critical power component in underwater operating systems. A parameterized elasto-hydrodynamic (EHD) lubrication model of the piston/cylinder tribopair in the SHAPP is originally established, which considers the elasto-hydrodynamic behavior, viscosity temperature effect and deep-sea environmental pressure. The deformation of piston bush, bearing mechanism and energy loss characteristics of the water film under different operating conditions are discussed. The results show that the deformation of piston bush made of polyetheretherketone (PEEK) is in micron-scale under water film and deep-sea pressure, which could increase the leakage and viscous friction power loss of piston/cylinder tribopair. In deep-sea environment, the leakage and viscous friction power loss calculated by EHD are always greater than those calculated by hydrodynamic (HD), and increase with the increase of working pressure, shaft speed, gap size, sea depth and piston bush thickness. Besides, the increase of sea surface temperature could increase the leakage and decrease the viscous friction power loss of the piston/cylinder tribopair, respectively. Finally, design instructions to optimize the piston/cylinder tribopair are presented, therefore the proposed methodology can be used as a designing tool for SHAPP.

“The Chiesa della Madonna dei Mali (Ferrandina, Italy) in VR”: Virtual Reality for inaccessible cultural heritage in peripheral areas

Today the VR (Virtual Reality) enable us to enter into fantasy or real other worlds to experience a growing emotional and interaction involvement. Frequently, the Virtual Reality is correlated with activities and experiences that are tricky to realize, as, for example, the discovery of the sea depths or the flying on the sky, or the discover of village and landscapes thousands of km away from us. Over the last years, VR technologies have largely applicate for a digital fruition of cultural heritage. Some examples are the observation of monumental build or virtually rebuilt archaeological sites, experiences that provide impressive and innovative virtual activities. In many cases, it is a only alternative option for discovering archeological sites in private properties or dangerous to visit and to see inaccessible cultural heritage in peripheral areas. In this work, one example of application of virtual reality is discussed: The Chiesa della Madonna dei Mali (Ferrandina, near Matera). This is a famous rural chapel localized in a country area of Ferrandina, far from the classic tourist itineraries of the city, and it contains a cycle of frescoes by Pietro Antonio Ferro, one of the most important painters of the seventeenth century in Basilicata.

Vertical distribution pattern of cbb genes and bacterial CO2 fixing potential in the South China sea

In this study, the cbb genes which encode the key enzymes in the Calvin cycle were used as functional markers to investigate the distribution pattern of CO2 fixing potential of autotrophic bacteria at different depths of the South China Sea (SCS). The results revealed that cbb gene abundance was similar between the surface and the deep layer of SCS, over two fold higher than the middle layer. The types of cbb genes showed dramatically different distributions with depths. Metagenomic amplicon sequencing revealed that Synechococcus was the main genus containing cbb genes in the surface layer, along with Rubrivivax and Limnohabitans in the middle, and unclassified Epsilonproteobacteria in the deep. Furthermore, the surface layer had the highest CO2 fixing potential due to that Synechococcus had a high CO2 fixation capacity and relatively high autotrophic growth rate. The difference in the distribution of bacterial species and therefore cbb types with depths was potentially affected by the variation in light intensity and concentration of dissolved oxygen, inorganic carbon and reducing substances.

О возможных причинах возникновения экстремально высоких волн в Балтийском море

Possible causes of extremely high waves in the Baltic Sea / Pohil A.E. // Hydrometeorological Research and Forecasting, 2020, no. 3 (377), pp. 58-70. The atmospheric conditions accompanying the occurrence of extremely high waves in the Baltic Sea (in particular, at the entrance to the Gulf of Bothnia) in 2004 and 2017 are analyzed. Changes in wave characteristics with a sharp decrease in the sea depth are considered. It is shown that the mechanisms like interference, when two wave systems overlap when rounding the island of Gotland, a superposition of a direct wave and a wave reflected from the steep slope at the entrance to the Gulf of Bothnia could contribute to the occurrence of extreme waves. Keywords: Baltic Sea, extreme waves, satellite data, water vapor fields Fig. 8. Ref. 19.

Sensitivity analysis of cost parameters for floating offshore wind farms: an application to Italian waters

Floating offshore wind farms represent the next frontier in wind power industry. However, the development of this technology is strongly dependent on its economic feasibility. There follows that the development of economic analyses is crucial to highlight the possible greater potential of floating offshore wind farms and to support their sustainability and technical value.In this context, the purpose of this paper is to present a sensitivity analysis of the main cost parameters for floating offshore wind farms, namely the distance from the coast, the distance from the closest port and the sea depth. It can give specific information on which parameters are more important, and how much they affect the total cost.To this aim, a comprehensive life cycle cost assessment of floating offshore wind farms has been developed. In this study the cost model has been applied to the Italian waters.The results shown should provide guidance on how to preliminary assess the quality of a given site for floating offshore wind farm installation, and should be helpful for future development of decision-making procedures in the offshore wind sector.

Geological characteristics and high production control factors of shale gas reservoirs in Silurian Longmaxi Formation, southern Sichuan Basin, SW China

Abstract Marine shale gas resources have great potential in the south of the Sichuan Basin in China. At present, the high-quality shale gas resources at depth of 2000–3500 m are under effective development, and strategic breakthroughs have been made in deeper shale gas resources at depth of 3500–4500 m. To promote the effective production of shale gas in this area, this study examines key factors controlling high shale gas production and presents the next exploration direction in the southern Sichuan Basin based on summarizing the geological understandings from the Lower Silurian Longmaxi Formation shale gas exploration combined with the latest results of geological evaluation. The results show that: (1) The relative sea depth in marine shelf sedimentary environment controls the development and distribution of reservoirs. In the relatively deep water area in deep-water shelf, grade-I reservoirs with a larger continuous thickness develop. The relative depth of sea in marine shelf sedimentary environment can be determined by redox conditions. The research shows that the uranium to thorium mass ratio greater than 1.25 indicates relatively deep water in anoxic reduction environment, and the uranium to thorium mass ratio of 0.75–1.25 indicates semi-deep water in weak reduction and weak oxidation environment, and the uranium to thorium mass ratio less than 0.75 indicates relatively shallow water in strong oxidation environment. (2) The propped fractures in shale reservoirs subject to fracturing treatment are generally 10–12 m high, if grade-I reservoirs are more than 10 m in continuous thickness, then all the propped section would be high-quality reserves; in this case, the longer the continuous thickness of penetrated grade-I reservoirs, the higher the production will be. (3) The shale gas reservoirs at 3500–4500 m depth in southern Sichuan are characterized by high formation pressure, high pressure coefficient, well preserved pores, good pore structure and high proportion of free gas, making them the most favorable new field for shale gas exploration; and the pressure coefficient greater than 1.2 is a necessary condition for shale gas wells to obtain high production. (4) High production wells in the deep shale gas reservoirs are those in areas where Long11– Long13 sub-beds are more than 10 m thick, with 1500 m long horizontal section, grade-I reservoirs penetration rate of over 90%, and fractured by dense cutting + high intensity sand injection + large displacement + large liquid volume. (5) The relatively deep-water area in the deep-water shelf and the area at depth of 3500–4500 m well overlap in the southern Sichuan, and the overlapping area is the most favorable shale gas exploration and development zones in the southern Sichuan in the future. With advancement in theory and technology, annual shale gas production in the southern Sichuan is expected to reach 450×108 m3.

Rubrobacter tropicus sp. nov. and Rubrobacter marinus sp. nov., isolated from deep-sea sediment of the South China Sea.

Two novel Gram-stain-positive bacteria, designated as SCSIO 52909T and SCSIO 52915T, were isolated from a deep-sea sediment sample collected at about 3448 m water depth of the South China Sea. Phenotypic, chemotaxonomic and genomic characteristics were investigated. These strains were aerobic and tested positive for catalase activity, oxidase activity and nitrate reduction. Optimal growth occurred at 28 °C, pH 7 and 3% salinity over 14 days cultivation. Its peptidoglycan structure was type A3α (l-Lys-l-Ala) and the only menaquinone was MK-8. Both strains possessed diphosphatidylglycerol, phosphatidylglycerol, an unidentified phosphoglycolipid, an unidentified glycolipid and an unidentified phospholipid. Their major fatty acids differed, but both contained iso-branched components of C16 : 0 12-methyl. Genome sequencing revealed two large genomes of 4.58 Mbp with G+C content of 67.0 mol% in SCSIO 52909T and of 4.42 Mbp with G+C content of 69.1 % in SCSIO 52915T. The two novel strains encoded genes for metabolism that are absent in most other Rubrobacter species, and possessed many more gene copy numbers of alkaline phosphatase and thioredoxin reductase. Results of gANI and 16S rRNA gene analyses suggested that the two strains represent two new species, with 74.9, 95.0 % pairwise similarity between each other, and less than 74.3 and 93.5 % to other recognized Rubrobacter species, respectively. In the phylogenetic analysis, strains SCSIO 52909T and SCSIO 52915T were separately clustered together and formed a well-separated phylogenetic branch distinct from the other known species in the genus Rubrobacter. Based on the data presented here, these two strains should be recognized as two new species in the genus Rubrobacter, for which the names Rubrobacter tropicus sp. nov., with the type strain SCSIO 52909T (=KCTC 49412T=CGMCC 1.13853T), and Rubrobacter marinus sp. nov., with the type strain SCSIO 52915T (=KCTC 49411T=CGMCC 1.13852T), are proposed.

E&amp;P Notes (September 2020)

Petrobras Slices Time, Cost of Post-Salt Drilling Lynnmarie P. Flowers, Technology Editor Petrobras has cut in half the time and cost of drilling some wells using its patented True One Trip Ultra Slender (TOTUS) concept. The technique can be used in certain mature fields of the postsalt where geological and reservoir characteristics favor its application. With TOTUS, the firm drilled a well in 44 days in early July, compared to the historic average of 96 days, resulting in a cost reduction of approximately 50% or $30 million. The development of post-salt wells offshore Brazil has been a challenging project. Faced with water depths of 2000-plus m - and a salt layer 2000 m thick - to reach reservoirs at 7000 m below sea level, Petrobras had the need to use novel technological and procedural techniques. Canada’s Oil Production Sinks to 2016 Levels In the first half of 2020, Canada’s production declined 20% from its 2019 average of 5.5 million B/D as a result of low crude oil prices, reduced demand, and continued production curtailments imposed by the government of Alberta. Last year, when Canada was the world’s fourth-largest producer, the province accounted for more than 80% of its production. Canada produced about the same amount of petroleum and other liquids in 2019 as it did in 2018, when western Canadian select crude oil was trading at historically low prices. The government of Alberta imposed production curtailments in early 2019 to reduce associated bitumen production and reduce inventories and growing constraints on export pipeline capacity. These restrictions were extended through the end of this year. MOL Pakistan Discovers Gas and Condensate As the operator of the TAL Block in Pakistan, MOL has made a new gas and condensate discovery at the Mamikhel South-1 exploratory well. This marks the company’s thirteenth discovery in Pakistan, its tenth in the TAL Block, and the second time in 3 months to discover hydrocarbon reserves. In March, MOL Norge discovered oil and gas in the North Sea. MOL has made 13 oil, gas, and condensate discoveries in Pakistan since 2000 including over 400 million BOE hydrocarbon reserves. It is responsible for 89 million BOED gross production (as of Q1 2020) in the TAL Block, where it has an 8.4% share. DTEK To Conduct Large-Scale Green Seismic Exploration DTEK Oil &amp; Gas this year will conduct a large-scale seismic survey using green technology on a gas-and-condensate field in Ukraine. The recording of seismic data in real time will allow DTEK to assess the quality of data logged during execution, increasing the quality of geophysical information recorded during the course of work. The cordless “green seismic” technology is connected via wireless systems in lieu of cables, enabling the exploration of complex and previously inaccessible landscapes, shortening project-completion time, and reducing environmental impact. The technology does not require special heavy machinery for installation. Supreme Court Ruling on Oklahoma Tribal Land Raises Questions for Oil Industry A US Supreme Court decision recognizing about half of Oklahoma as Native American reservation land has implications for oil and gas development and raises regulatory and tax questions that could take years to settle. On 9 July, the court overturned an Oklahoma tribe member’s criminal conviction - in the McGirt v. Oklahoma decision - because the crime was com-mitted on reservation land and therefore outside the reach of state criminal law. CNOOC Starts Production From Luda Project Exploration and production independent CNOOC has produced first oil from its Luda 21-2/16-3 regional development in the Bohai Sea, offshore China. The project currently contains one central platform, three wellhead platforms, and one production platform. CNOOC expects to drill 69 development wells; peak production is expected to reach 25,600 B/D in 2022. Situated about 25 miles north of the Luda 10-1 oil field and 55 miles northwest of the Suizhong 36-1 onshore terminal, the Liaodong Bay development is operating in an average water depth of 82 ft. Cairn Sells Senegal Interest to Lukoil Russia’s Lukoil will sell its entire 40% interest in the Rufisque, Sangomar, and Sangomar Deep (RSSD) contract area to Edinburgh oil and gas producer Cairn Energy for up to $400 million. Lukoil intends to return at least $250 million to shareholders as a special dividend after the sale. The blocks of the project covering 2212 km2 are located on the deepwater shelf of the Republic of Senegal 80 km from the shore with the sea depth of 800-2175 m. The blocks include two discovered fields, Sangomar and FAN. The cash consideration payable on completion is $300 million, and up to $100 million depending on the timing of first oil and the average Brent oil price in the first 6 months of production.

ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ТЕХНОЛОГІЇ ОТРИМАННЯ ВОДНЮ ШЛЯХОМ ВИКОРИСТАННЯ РЕГЕНЕРАЦІЙНОГО КОНТУРУ З РОТОРНО-ПОРШНЕВОЮ РОЗШИРЮВАЛЬНОЮ МАШИНОЮ

The article discusses a promising technology for the production and safe accumulation of hydrogen from the Black Sea hydrogen sulfide, which includes the following processes: production of hydrogen sulfide from the depths of the Black Sea; separation of hydrogen sulfide and seawater; destruction of hydrogen sulfide to produce a hydrogen-containing gas; separation of hydrogen from a hydrogen-containing gas; safe hydrogen storage; safe transportation of hydrogen. It is proposed to use the regeneration circuit to increase the efficiency of this technology, which includes: an expansion machine for high-pressure hydrogen sulfide, a seawater hydraulic turbine, and a heat pump installation. It is proposed to evaluate the efficiency of the application of the technology for the production and safe accumulation of hydrogen from the Black Sea hydrogen sulfide by effective capacity, which includes: thermal power of hydrogen, power of the regeneration circuit; the power needed to carry out hydrogen production processes. It is proposed to use the 20RPD-4.4/1.75 rotary piston engine as a hydrogen sulfide expansion machine that will satisfy all the requirements. Rational operating modes and limiting values of the efficiency of using the technology for obtaining and safe accumulation of hydrogen from the Black Sea hydrogen sulfide for daily hydrogen production of 200 kg/day were determined depending on the degree of hydrogen sulfide conversion during destruction, the gas content of hydrogen sulfide in seawater and the depth of immersion of the lifting pipeline using the regeneration circuit. The minimum permissible degrees of conversion at which the efficiency of using the technology for obtaining and safe accumulation of hydrogen from the Black Sea hydrogen sulfide for a gas content of hydrogen sulfide of 2.5 m3/m3 at a depth of immersion of the lifting pipeline of 250...1000 m is 0.427 ... 0.413, for 5 m3/m3 – 0.375...0.363, for 7.5 m3/m3 – 0.363...0.350, for 10 m3/m3 – 0.356...0.343. The use of the regeneration circuit allowed us to reduce the minimum permissible degrees of conversion for the gas content of hydrogen sulfide of 2.5...10 m3/m3 at a depth of immersion of the lifting pipeline of 250...1000 m by 0.136 ... 0.069.

Study on three-phase flow characteristics of natural gas hydrate pipeline transmission

Based on the basic principles of thermodynamics and fluid mechanics, the temperature and pressure model of natural gas hydrate hydraulic lifting pipeline, the hydrate decomposition mass transfer model and the mathematical model of pipeline multiphase flow are established. The relationship between the back pressure of the pipeline outlet, the decomposition surface and the depth of the seawater was analyzed. On this basis, the numerical simulation and experimental verification of natural gas hydrate pipeline transmission were carried out. The effects of pipe diameter, inlet velocity and solid phase parameters on the three-phase flow of natural gas hydrate pipelines were analyzed. The result shows that with the outlet pressure increasing, the position at which the hydrate begins to decompose moves up and the decomposition rate slows down. As the depth of mining increases, the rate of hydrate decomposition slows and the position at which decomposition begins to move up. In deep sea mining below 1500 m, the increase of mining depth has little effect on the decomposition rate of hydrate, and the decomposition starting position is always near 510 m in sea depth. The pipe pressure loss gradient decreases as the pipe diameter increases. After the pipe diameter is larger than 300 mm, the pressure loss gradient decreases slowly, and the pressure loss gradient drops sharply at 450 mm, and eventually stabilizes after 500 mm. When the inlet velocity of the pipe is low, the fluid flow in the pipe is unstable and reflow occurs. The pipe pressure loss gradient first decreases and then increases as the fluid flow rate increases, and there is an optimal flow rate value that minimizes the pressure loss gradient.

Synthesis of group compressed-air sources for marine seismics

The improvement of geological efficiency of marine seismic survey implies continuous improvement of the entire technological complex used in water areas. This is typically accomplished by using complex linear or spatial non-uniform compressed-air groups. In the development of such sources, in addition to solving a number of purely technical problems related to their placement on board the ship and safe operation, one of the most difficult tasks is to determine the initial requirements for selection of the main parameters of the group, such as the volumes of working chambers sources and geometry of their grouping, as well as other factors determining amplitude, time and frequency of emitted acoustic signals. This study considers the main principles of grouping the compressed-air sources for marine seismic survey. It is shown that the most important factors determining the choice of source parameters and specific research technology include the nature of geological tasks and seismic conditions, which primarily depend on the sea depth in the study area. A simple method of calculating the configuration of linear subgroups with fluctuation suppression is described, as well as examples of building linear and spatial groups based on them with pronounced directional properties are considered.