Offshore Part Research Articles

Assessing the overlap between fishing and chondrichthyans exposes high‐risk areas for bycatch of threatened species

AbstractChondrichthyans (sharks, rays, skates, and chimaeras) make up one of the oldest and most ecologically diverse vertebrate groups, yet they face severe threats from fishing, necessitating improved management strategies. To effectively manage these species, we need to understand their spatial interactions with fisheries. However, this understanding is often challenged by limited data on chondrichthyan catches and species identification. In such cases, assessing potential risks from fishing activities can provide valuable insights into these spatial interactions. Here, we propose a method combining geostatistical models fitted to a fishery‐independent dataset with vessel monitoring system (VMS) data to estimate the spatial overlap between chondrichthyans and fishing. Our case study focuses on the western Adriatic Sea in the Mediterranean, examining the overlap between bottom trawling (including otter bottom trawling and beam trawling) and demersal chondrichthyans. We find that the northwestern part of the basin is a hotspot where threatened chondrichthyans (classified as Vulnerable, Endangered, or Critically Endangered by the International Union for Conservation of Nature Red List) greatly overlap with bottom trawling activities. Moreover, some areas, such as the northernmost part of the Adriatic and the “area dei fondi sporchi” in the north‐central offshore part, exhibit minimal overlap between threatened chondrichthyans and bottom trawling, potentially serving as refuges. We recommend prioritizing the management of otter bottom trawling in the northwestern basin to protect these threatened species, while also paying attention to the possible impacts of beam trawling on skates and chondrichthyan habitats. Despite certain limitations, our findings demonstrate that combining geostatistical models of species distributions with VMS data is a promising method for identifying areas of concern for species vulnerable to fishing. This approach can inform targeted management measures and cost‐effective onboard monitoring programs.

Bridging the gap between Quebec and Newfoundland: new insights on the protracted and diachronic history of the Anticosti foreland basin

The offshore part of the Anticosti foreland basin between Gaspé Peninsula (Quebec) and western Newfoundland has been investigated for its petroleum potential, mainly in the 1980s, but its geometry and evolution remain poorly documented. In this study, short-wavelength magnetic markers associated with intra-sedimentary magnetic susceptibility contrasts are interpreted in conjunction with high-resolution seismic data to map the distribution of rock units. Magnetic markers associated with igneous dykes are distinguished from those associated with sedimentary units by their higher amplitude and geometry. Conjunct interpretation of magnetic and seismic datasets provides new insight on the geometry of the Anticosti Basin and indicates that: i) a relatively thick (~ 2 km) post-Llandovery (post- Jupiter Formation) sedimentary succession occurs in the core of two regional synclines where youngest preserved sediments are interpreted as correlative with the Upper Gaspé Sandstone Group - Red Island Road Formation (Emsian–Eifelian); ii) post-Eifelian (Acadian) deformation consists of a series of folds, 2–10 km in wavelength in the Honguedo Strait, north of the Gaspé Peninsula, and to a single greater wavelength fold in the Strait of Belle Isle; iii) newly recognized NW-striking faults that parallel the eastern Gaspé Peninsula shoreline exhibit significant syn- to post-Middle Mississippian movements; iv) the southern boundary of the Anticosti Basin corresponds either to the unconformity at the base of the Carboniferous–Permian Magdalen Basin or to previously poorly documented ESE to NE-striking faults; v) a series of dykes trend from N90° near Gaspé Peninsula to N170° between Anticosti and Newfoundland islands. These new findings are integrated in an evolution model that enhances the stratigraphic and tectonic along-strike variability of the Anticosti foreland basin.

Siliciclastic Reservoir Geo-modeling using TGS-SIS hybrid algorithm of the Upper Cibulakan Formation, Offshore Northwest Java Basin

Abstract The Upper Cibulakan is the primary hydrocarbon-producing formation in the Offshore Northwest Jawa area, operated by PHE ONWJ (Pertamina Hulu Energy Offshore Northwest Jawa). The productive interval in this formation comprises alternating sandstone and shale up to 45 feet of thick. Geologically, this interval is a shallow marine deposit with strong influence of tidal in the Ardjuna Sub-Basin, offshore part of Northwest Jawa Basin. The good quality reservoir layer is associated with Tidal Sand Ridges (TSR) facies characterized by lenticular sedimentary structures and the occurrence of shale intercalation in sandstone. The occurrence of shale, regarding its facies association package, varies greatly and significantly determines the quality of the reservoir. The geometry and quantity of facies distribution and association will significantly affect the calculation of hydrocarbon reserves during the modelling processes. Considering this, the selection of modeling methods and algorithms must be carried out appropriately. The use of the SIS (Sequential Indicator Simulation) algorithm in describing the TSR facies distribution still has shortcomings in randomness. Correspondingly, it requires to be combined with the TGS (Truncated Gaussian Simulation) method as it plays a great impact in calculating the distribution of sandstone and reservoir geometry. Meanwhile, SIS defines shale intercalation within TSR facies. Combining these two methods produces a more precise model of TSR facies associations. Besides, the concept of reservoir deposition is easier to explain based on the outcome result from the combined methods.

Workflow overview of reservoir drilling fluids selection

The article provides overview of the drilling fluids selection as reservoir fluids, which includes mineralogy study of the production interval such as X-Ray diffraction, fluid base selection based on capillary suction test and cation exchange capacity test used to pick up appropriate mud in the East offshore part of Russia. The described principals allowed to minimize non-productive time in overall well construction process with the increased production rate per well which was achieved by the successful planning stage work and offset data. Keywords: planning stage; X-Ray diffraction; reservoir fluids; non-productive time; capillary suction test; production rate.

Utilization of abandoned oil well logs and seismic data for modeling and assessing deep geothermal energy resources: A case study

Hammam Faraun (HF) geothermal site in Egypt shows potential for addressing energy demand and fossil fuel shortages. This study utilizes abandoned oil well logs, seismic data, and surface geology to assess HF geothermal energy resources.Seismic interpretation identified a significant clysmic fault parallel to Hammam Faraun fault (HFF), named CLB fault. The two faults together create a renewable geothermal cycle through circulation of mixed formation-sea waters.Petrophysics revealed two main geothermal reservoirs: the Nubian sandstone reservoir and the Eocene Thebes carbonate reservoir with water saturation values approaching 100 %. Corrected borehole temperatures indicated reservoir temperatures around 120 °C and 140 °C for the Thebes and Nubian reservoirs, respectively.Fracture analysis and stress state provided insights into subsurface fractures. A geomechanical model demonstrated the impact of different stresses and pore pressure on geothermal fluid flow. NE-SW oriented fractures showed a higher dilation tendency due to aquathermal expansion.The integrated conceptual geothermal model suggested a magma chamber beneath HF as the heat source, related to Oligo-Miocene volcanic activity. The breached relay ramp and fault-related open fracture system serve as pathways for geothermal fluids.Evaluation of the geothermal potential utilized volumetric calculations and Monte Carlo simulation. The estimated hot water volumes were 1.72 km3, 4.242 km3, and 5.332 km3 for the Nubian reservoir in the onshore part, Thebes reservoir in the offshore part, and Nubian reservoir in the offshore part, respectively.The results indicate a medium enthalpy resource suitable for electricity generation using a Kalina geothermal power plant. The predicted geothermal power output is promising, with an average power output of 9.64 MWe, 21.38 MWe, and 43.76 MWe for the Nubian reservoir in the onshore part, Thebes reservoir in the offshore part, and Nubian reservoir in the offshore part, respectively. These outputs can potentially supply electricity to approximately 12,000, 29,000 and 53,000 households, respectively.

Chemostratigraphy of the Sherbrook Supersequence – 13 wells from the offshore Otway Basin

An elemental chemostratigraphic study of the offshore Otway Basin has been undertaken as part of a collaboration between Chemostrat and Geoscience Australia, the main aim of which is to better constrain the sequence boundaries of, and within, the Sherbrook Supersequence. This study includes the elemental analysis of 1185 cuttings samples from the Sherbrook Supersequence (and overlying stratigraphy) in 13 offshore wells. Sampling of cuttings was particularly challenging as many of the targeted wells have a paucity of material available for destructive analysis. Inductively Coupled Plasma-Optical Emission Spectrometry and Mass Spectrometry (ICP-OES and MS) analysis was undertaken to establish a regional elemental chemostratigraphic framework of the Sherbrook Supersequence. The resultant framework comprises two chemostratigraphic sequences, seven chemostratigraphic packages and eighteen chemostratigraphic units. While the analysis could not clearly distinguish the base of the Sherbrook Supersequence it has provided valuable insight into correlations between wells, within the Sherbrook and overlying Wangerrip supersequences. Importantly it has confirmed that in the offshore part of the basin sedimentary processes and inputs remain unchanged from the Shipwreck to the Sherbrook (Turonian–Maastrichtian).

Lithofacies Controls on Hydrocarbon Generation Potentiality of the Syn-Rift Late Cretaceous Rakopi Deltaic Facies in the North-Eastern Offshore Part of Taranaki Basin, New Zealand

The Taranaki Basin in New Zealand presents the most promising territory for strategies of hydrocarbon exploration and development. This basin contains multiple source rock levels in its sedimentary successions formed during syn- and post-rift periods. The deepest source rocks, found in the Rakopi Formation, were deposited in deltaic to deep marine environments and consist of gas-prone coal and organic-rich mudstone lithofacies. However, questions remain about the preservation of their organic carbon. This study integrates various organic geochemical analyses (such as Rock Eval pyrolysis, kerogen petrography, and biomarkers) to assess the hydrocarbon potential of the Rakopi coal and mudstone lithofacies. The organic carbon in Rakopi coals and mudstones originated from oxygenated bottom water, but swift burial during the initial rifting phase facilitated the preservation of organic materials. Rakopi coals are less mature than the mudstone facies and contain a mixture of desmocollinite, suberinite, and resinite macerals. In contrast, the mudstone lithofacies are enriched in liptodetrinite. The maceral mixture in the coal led to its elevated hydrogen index and likely facilitated early expulsion of liquid hydrocarbon phases. Regular steranes, diasteranes, and C29 sterane isomers distribution in the coal and mudstone extracts highlighted a greater terrestrial input in the coals, whereas significant marine input is observed in the mudstone extracts. Biomarkers in the coal and mudstone extracts are similar to some nearby oils discoveries in the Taranaki Basin, thereby confirming oil generation from both coal and mudstone lithofacies in the Rakopi Formation. These findings underscore the potential of liptinite-rich coals to generate liquid hydrocarbon phases at marginal oil maturity levels.

Fatigue crack growth behavior of SS316L deposition from wire arc additive manufacturing

Wire arc additive manufacturing has shown the potential to build large metal parts with high deposition rates and low cost of production compared to other additive manufacturing techniques. Austenitic stainless steel 316L is known for corrosion resistance and weldability, which makes it a strong candidate for building and repairing marine and offshore parts, with wire arc additive manufacturing. These parts experience fluctuating loads during service, which necessitates the fatigue performance study of wire arc additively build stainless steel. This work investigates the fatigue crack propagation behavior of stainless steel 316L depositions from wire arc additive manufacturing. Single beads of stainless steel 316L were deposited layer by layer to fabricate the wall structures. From the wall structures, the specimens were prepared for the tensile and fatigue crack growth rate tests along the traverse and build directions. In conjunction with mechanical testing, electron back-scattered diffraction and scanning electron microscopy techniques were employed to characterize the microstructure. Microstructural observations showed the presence of columnar dendrites along the build direction. The electron dispersive spectroscopy revealed the elemental diffusion at the layer interfaces due to the remelting of the layers. Differences in mechanical properties were observed across the two directions. Along build directions, the ultimate tensile strength was 8 % higher and yield strength was 7 % lower than the respective strengths along the traverse direction. The build direction also exhibited 46 % higher fatigue life cycle than the traverse direction. The difference in properties across different orientations was closely associated with the microstructural variations. Overall, the mechanical performance of the wire arc additively deposited SS316L is better than the previously reported selective laser melted SS316L.

Assessing the national synergy potential of onshore and offshore renewable energy from the perspective of resources dynamic and complementarity

Intermittent renewable energy sources have been transformed from supplementary energy to dominant incremental alternative energy sources in the context of carbon neutrality target worldwide. For coastal countries, it is urgent to integrate abundant offshore energy into regional onshore renewable power sources economically and reliably considering the scarcity of land resources and negative environmental impacts. However, limited knowledge on the complex spatiotemporally synergy relationships between energy potential (onshore and offshore) is a barrier in making reasonable policies to promote collaborative development of onshore and offshore energies. This study presents a spatiotemporally explicit modelling framework for assessing the synergy potential characteristics of onshore and offshore renewable energy sources. The framework firstly estimates the technical potential of solar PV and wind energy across the country by using 40 years of hourly meteorological reanalysis data (1980–2020), and then investigates the long-term changes trend, stability, and complementarity of solar-wind energy potential spatiotemporally at both onshore and offshore sub-regions. We find that a considerable amount of solar PV and wind energy sources could be harnessed in China, and onshore potential across the country (178 PWh/yr) is approximate 20 times higher than offshore energy potential (8.9 PWh/yr). Overall, onshore solar-wind energy potentials exhibit statistically insignificant but slightly increasing trend over the past 40 years, while offshore wind potentials observe an opposite change trend for solar PV and wind energy production. Complementarity assessment showed the northeast and offshore parts of China present high complementarity effects for hourly and daily power production of solar-wind systems. Furthermore, inter-regional combination between offshore and onshore northwest regions also exhibits promising synergy effect for renewable energy power output. The results on resources dynamic and complementarity highlight the advantage of interregional resources cooperative configuration and electric power grid interconnections. The analysis performed in this paper could provide a global picture for the integration planning and collaborative development strategies formulation of on-/offshore renewable energy across the country.

Integrated Geological and Petrophysical Approaches for Characterizing the Pre-Cenomanian Nubian Sandstone Reservoirs in Ramadan Oil Field, Central Gulf of Suez, Egypt

The present study integrates multidisciplinary geological and petrophysical approaches to characterize and evaluate the potential of the pre-Cenomanian Nubian sandstone reservoirs in the Ramadan oil field, the central offshore part of the Gulf of Suez, Egypt. The different petrophysical parameters of the Nubian sandstone reservoirs (shale volume, porosity, water saturation as well as gross and net-pay thicknesses) were mapped, and 3D slicing models for the hydrocarbon phases saturation were constructed to understand the reservoir heterogeneity and the distribution of the best reservoir facies. The petrophysical results of the pre-Cenomanian Nubian succession highlight very good reservoir intervals in the Nubian C sandstones containing thick pay zones (> 120 m). On the other side, the Nubian A and B reservoir rocks are less prospective with pay zone horizons (< 10 m). Integrated reservoir models and wireline log analysis elucidate that clay volume is the most detrimental factor to the reservoir quality as the pay zone thickness and hydrocarbon saturation often increase where the clay volume decreases. Therefore, the presence of scattered pay zone intervals in Nubian A and B is mainly related to their elevated clay content which acts as barriers for fluids flowing within the reservoir facies. The Nubian C succession contains three different reservoir rock types (RRT) with variable compositional and petrophysical properties. RRTI and RRTII sandstones comprise quartzose sandstones with very low clay content (< 10%) and are characterized by an open pore system dominated by macropores. These sandstones are less impacted by overburden pressure and therefore can preserve their depositional porosity and permeability. On the other hand, RRTIII reservoir rocks are clay rich (> 10%) with abundant mesopores that are more prone to compressibility and hence reduction of the pore volume and pore throat. The present study highlights the significance of comprehensive integration between wireline logs, cores, and 3D reservoir models in directing exploration endeavors toward prospective reservoirs in mature basins.

Regional significance of normal fault systems in the western Canadian Beaufort Sea (Mackenzie delta)

The Beaufort-Mackenzie fold and thrust belt in Arctic Canada corresponds to the offshore part of the Cordilleran orogen in Yukon and Alaska. Previous tectonic studies in this area focussed on contractional structures, and comparatively little attention has been paid to normal faults, even though they are ubiquitous in the shallow Beaufort Sea. Normal faults dip either seaward or landward and most faults are located on the apex of anticlines. Despite the clear spatial relationship with anticlines, normal faults initiated after fold development as the delta front migrated seaward. Accordingly, Oligocene to Pliocene extensional structures are interpreted as recording gravity-driven deformation superimposed on an existing, mainly Eocene, fold and thrust belt. Several normal faults extend downward onto one of the anticline limbs, but the control of the fold geometry on the dip of the faults (seaward or landward) remains poorly understood. Seismic amplitude anomalies suggest that normal faults acted as fluid (most probably thermogenic gas) migration pathways.

A DOM regulation model for dolomite versus calcite precipitation in the Ediacaran ocean: Implications for the “dolomite problem”

The Ediacaran Period (∼635–539 Ma) witnessed the largest negative carbonate carbon isotope (δ13Ccarb) excursion in Earth history (to −12‰ VPDB), known as the Shuram Excursion (SE), which has been attributed to oxidation of a massive dissolved organic matter (DOM) reservoir, yielding highly 13C-depleted oceanic dissolved inorganic carbon (DIC). Limestone and dolostone are intimately interbedded in the Ediacaran Doushantuo Formation (South China) as well as in coeval successions globally, suggesting frequent shifts between calcite and dolomite precipitation in the Ediacaran ocean. In this study, we compiled paired Mg/(Mg + Ca) and δ13Ccarb data for 991 well-preserved (i.e., minimally altered) carbonate-rich samples from 17 SE-associated sections with a wide global distribution. δ13Ccarb compositions vary among the dolomite-dominated (−10‰ to +7‰), calcite-dominated (mainly in −10‰ to −5‰), and mineralogically mixed samples (with a bimodal distribution of −10‰ to −5‰ or +4‰ to +8‰). Inspired by the recent DOM catalyzation hypothesis and the highly-stratified redox model as well as the large DOM reservoir hypothesis for the Ediacaran ocean, we propose a “DOM regulation model” to account for controls on the precipitation of dolomite versus calcite in the Ediacaran ocean and, thus, for observed Mg/(Mg + Ca)-δ13Ccarb patterns. In this model, calcite was precipitated under low-DOM conditions, which existed in oxic surface waters and the nearshore part of a mid-depth DOM-anaerobic oxidation zone. The former had δ13CDIC > +4‰, buffered by atmospheric CO2, whereas the latter had δ13CDIC decreasing from +4‰ to −10‰ due to increasing contributions of DOM oxidation. On the other hand, dolomite precipitation was catalyzed by high-DOM conditions, which existed in distal anoxic deep waters and the offshore part of the DOM-anaerobic oxidation zone. The former had δ13CDIC > +4‰, ultimately buffered by atmospheric CO2, whereas the latter had δ13CDIC increasing from −10‰ to +4‰ due to decreasing contributions of DOM oxidation. Our model is well supported by coexisting redox data. Our study highlights a possible link between massive dolomite formation and the existence of a large DOM reservoir in the Ediacaran ocean, providing an alternative perspective on the origin and widespread distribution of dolomite in deep-time marine systems (i.e., the “dolomite problem”).

Assessment of prospective gas resources and develop a production view of eastern foldbelt (block 18), Bangladesh using Monte Carlo simulation method

In Bangladesh, 20 gas fields out of 28 produced 709.11 billion cubic feet (Bcf) through 112 wells against a vast amount of demand in the financial year 2021–22. Therefore, more gas fields need to be explored in the most prospective offshore part of Bangladesh. In this study, we have attempted to estimate a prospecting natural gas reserve in the Eastern Fold Belt (Block 18) consisting of Teknaf, Coral Dip, and St Martin Island as well as to develop a production view for the future. Based on the prerequisite research data collected from Petrobangla, Monte Carlo simulations were used to estimate the reserve values as Gas Initially In Place (GIIP) and Recoverable Gas Initially In Place (RGIIP) by Petroleum Engineering (PE) Essential software (version 2017.4). The results show that the estimated GIIP and RGIIP are 6145.88 billion standard cubic feet (Bscf) and 4745.5 Bscf, respectively which are quite close to the previous study. The total estimated proven natural gas of the study is 2064.4 Bcf.

Neogene-Quaternary evolution of the La Baja Guajira basin, Colombia: Burial and thermal history with implications on petroleum systems

The La Baja Guajira Basin is South America's northernmost part that extends from onshore Colombia into the Caribbean Sea and represents an important gas-producing region in Colombia. The dataset used in this study consists of twenty-four (24) regional 2D seismic-reflection lines integrated with information from nine (9) boreholes across the basin. We present seismic interpretations of key stratigraphic and structural features constrained by 1D basin modeling. This allows us to describe the Neogene-Quaternary evolution of the basin, and understand the possible implications for the hydrocarbon potential.We have interpreted eight (8) seismic units within the La Baja Guajira Basin (acoustic basement to U7) affected by three fault groups: 1) NW-SE-striking basement normal faults, 2) inverted normal faults, and 3) strike-slip faults. Considering the evidence, we propose four tectonic phases along the basin's evolution. The basement was affected by normal faulting as the result of extensional tectonics prior to the deposition of the sedimentary infill (Paleogene?). Another extensional interval occurred during the Early Miocene, triggering a moderate accommodation within the proximal area. Subsequently, extension migrated westwards resulting in the formation of the main La Baja Guajira Basin depocenter. In the Middle Miocene (post-extension), sedimentation was controlled by exhumation pulses in adjacent areas to the basin, which resulted in significant sediment input contemporaneous with rapid tectonic subsidence. Yet, local inversion of NW-SE-oriented basement-rooted faults affected today's offshore domain until the Late Miocene. This inversion can be associated with regional compressive deformation linked to the activity of the Oca and Cuiza faults. A second episode of rapid tectonic subsidence happened in the Early Pliocene. In the south of the basin, rocks were subjected to maximum burial and highest temperatures in recent times, conditions that might lead to hydrocarbon generation. The high Neogene to recent sedimentation rates calculated for the La Baja Guajira Basin support microbial gas generation; structural reactivation in this time supported trap formation, particularly in the offshore parts of the basin.

Temporal dynamics in zooplankton δ13C and δ15N isoscapes for the North Atlantic Ocean: Decadal cycles, seasonality, and implications for predator ecology

The limited amount of ecological data covering offshore parts of the ocean impedes our ability to understand and anticipate the impact of anthropogenic stressors on pelagic marine ecosystems. Isoscapes, i.e., spatial models of the distribution of stable isotope ratios, have been employed in the recent years to investigate spatio-temporal patterns in biogeochemical process and ecological responses. Development of isoscapes on the scale of ocean basins is hampered by access to suitable reference samples. Here we draw on archived material from long-running plankton survey initiatives, to build temporally explicit isoscape models for the North Atlantic Ocean (&amp;gt; 40°N). A total of 570 zooplankton samples were retrieved from Continuous Plankton Recorder archives and analysed for δ13C and δ15N values. Bayesian generalised additive models were developed to (1) model the relations between isotopic values and a set of predictors and (2) predict isotopic values for the whole of the study area. We produced yearly and seasonal isoscape models for the period 1998–2020. These are the first observation-based time-resolved C and N isoscapes developed at the scale of the North Atlantic Ocean. Drawing on the Stable Isotope Trajectory Analysis framework, we identify five isotopically distinct regions. We discuss the hydro-biogeochemical processes that likely explain theses modes, the differences in temporal dynamics (stability and cycles) and compare our results with previous bioregionalization efforts. Finally, we lay down the basis for using the isoscapes as a tool to define predator distributions and their interactions with the trophic environment. The isoscapes developed in this study have the potential to update our knowledge of marine predator ecology and therefore our capacity to improve their conservation in the future.

The Lower Devonian (Ovinparmian) reservoir: Prospects in the offshore part of the Timan-Pechora petroleum basin

The offshore part of the Timan-Pechora petroleum basin is one of the most promising areas to search for new petroleum accumulations. The commercial potential of the Carboniferous-Lower Permian play has already been proven by exploratory drilling in the Dolginskoye uplift, whereas the Prirazlomnoye field has been in production since 2013. However, significant petroleum resources in this area may be confined to the Ordovician-Lower Devonian play. The purpose of the study is to evaluate the potential of the Lower Devonian (Ovinparmian) reservoirs within the Pechora Sea shelf based on new geologic and geophysical data. We identified multiple prospects within the Dolginsko-Papaninskaya structural zone and estimated its resources. The potential of the Lower Devonian within the study area is comparable with that of the Carboniferous-Lower Permian play. Based on the new 3D seismic data performed in three offshore license blocks, we identified several unconformities, where the Timanian-Sargaevian regional seal onlaps carbonate rocks of the Ovinparmian horizon (Lochkovian stage, Lower Devonian). We hypothesize that due to the Middle Devonian structural deformations, the Lower Devonian carbonate deposits have been exposed to subaerial erosion and surface and subsurface karst. Diagenetic alterations of the Ovinparmian sediments (i.e., dolomitization, dissolution, and fracturing) are favorable for the development of high-porosity reservoirs. In our study, we consider some sedimentation, diagenesis, and catagenesis models of the Ovinparmian carbonates. Furthermore, we designed an exploration program with a view to further study the Lower Devonian reservoirs.

The potential of offshore Nile Delta Basin natural gas reserves: a case study of Messinian reservoir in Baltim field

The offshore part of the Nile Delta Basin (NDB) is a prolific provenance for gas exploration. The present study aims to perform a geophysical evaluation for the Messinian Abu Madi sandstones along the Messinian paleo-valley in Baltim field as a case study. The seismic interpretation step exposed that the Abu Madi incised valley displays NNW-SSE trend with width ranges from 5 to 8 km and a length of 32 km. The petrophysical appraisal for five drilled wells (BE-2, BE-3, BE-5, BN-1 and BN-2) in Baltim Field has been performed. The findings of this assessment revealed that the most promising intervals in the studied wells have gross-thicknesses vary between 25 and 49 m; net pay thicknesses range within 15 m and 38.5 m; net/gross ratio of 0.54–0.90; effective porosity of 15–40%; shale volume is less than 20; and water saturation ranges between 25 and 50%. Such notably talented and converging values of these parameters across the examined zones reflects the relative homogeneity and lateral continuity of the Abu Madi reservoir across the inspected paleo-valley. The results of this study can help for a better understanding of the petrophysical characteristics for the Messinian reservoir over the offshore NDB. Therefore, the Messinian sandstones could exhibit possible targets for future gas exploration over the offshore NDB together with the Pliocene sandy levels, which represent the main and the recent discoveries of gas accumulations.

CTENOPHORA &lt;i&gt;MNEMIOPSIS LEIDYI&lt;/i&gt; A. AGASSIZ, 1865 POPULATION AND ITS PRESSURE ON ZOOPLANKTON IN OPEN AREAS OF THE BLACK SEA IN JULY - AUGUST 2017

The research both of the quantity and size structure of the invader Mnemiopsis leidyi (A. Agassiz 1865), as well as the mesozooplankton abundance, species diversity, the food spectrum, trophic relations, and predatory impact by M. leidyi on prey populations in the western and eastern sectors of the open Black Sea was carried out in July - August 2017. M. leidyi biomass varied from 92 to 250 g m during the period of maximum seasonal development. The food spectrum of M. leidyi was dominated by copepods Acartia spp. and Calanus euxinus (Hulsemann 1984). A clear spatial difference in the quantity of M. leidyi and zooplankton, the intensity of food consumption and predatory impact was observed. In the western offshore part of the sea, the high food ingestion rate by M. leidyi (the mean specific daily ration was 45.50±8.31% С) and intensive predatory impact on zooplankton (up to ~50% of Acartia sp. biomass) resulted in the strong decrease in mesozooplankton biomass. In contrast, in the eastern sector M. leidyi predation had no effect on zooplankton community maintaining daily grazing of ~6% Acartia spp. biomass.

Seismic sequence stratigraphy and depositional evolution of the Cretaceous-Paleogene sedimentary successions in the offshore Taranaki Basin, New Zealand: implications for hydrocarbon exploration

The seismic stratigraphy and sedimentary facies of the Cretaceous and Paleogene sedimentary successions in north-eastern offshore part of Taranaki Basin, New Zealand have been investigated in order to unravel their depositional evolution and identify the potential hydrocarbon plays. Interpretation of regional seismic lines covering the entire shelf-slope and deepwater regions as well as integrating seismic and sedimentary facies allows the identification of several seismic-stratigraphic sequences within the studied successions. Early Cretaceous syn-rift successions (C1 sequence) were deposited in the structural lows near the present-day slope as swamp and marsh facies changing basinwards into turbidites and marine shales. The post-rift Cretaceous sequences (C2, C3 sequences) started with the progradation of the Taranaki delta (C2A-C2D units) followed by sedimentation of the transgressive C3A-E facies accumulated in response to thermal subsidence and high-rates of clastic supply. Extensive shelf conditions prevailed during the deposition of C2 and C3 Cretaceous sequences continued during the Paleogene with deposition of uniform marine shales throughout the basin. Rates of sediment supply substantially decreased during Oligocene prompting the deposition of marine micrite-rich carbonate. Variation in fossil content confirms the occurrence of several cycles of sea level fluctuations and episodic variations in terrigenous input. Organic-rich facies could be associated with the prograding clinoforms of the C2B unit and probably contain, basinward, large amount of gas and oil prone kerogen. The transgressive facies of C2D unit may also contain organic-rich shales basinward and coal near the present day Taranaki shelf. Potential reservoirs are hosted on the C3 transgressive estuarine sandstones. Paleogene mudstones are excellent regional seals for the hydrocarbons generated and trapped in the underlying Late Cretaceous facies.

Quantitative reconstruction of Holocene ground displacements in the offshore part of the Campi Flegrei caldera (southern Italy): Perspectives from seismo-stratigraphic and archaeological data

Analysis of high-resolution seismic profiles integrated with archaeological data along the coast has allowed quantifying the last ∼10 ka BP displacements in the offshore part of the Campi Flegrei resurgent caldera, one of the world's highest-risk volcanic areas. Previous onland studies revealed that, following the Neapolitan Yellow Tuff (NYT) eruption at 15 ka, post-caldera evolution was associated with rapid ground uplift and subsidence cycles. In this paper, we use the stacking pattern of Prograding Wedges (PWs) and Aggrading Fills (AF) to reconstruct relative sea-level changes and estimate the amount of vertical deformation in the Pozzuoli Bay, the submerged part of the caldera. We document five generations of prograding wedges (PW1 to PW5), associated with as many periods of relative ground stability between uplift and subsidence. Instead, deposition of aggrading fills above prograding wedges underpins the subsidence that typically follows volcanic unrest and uplift. The older wedges PW1 and PW2 are larger and likely indicate whole-caldera uplift events. In particular, the development of PW2 starting from ∼5.2 ka is related to the rapid growth of a resurgent dome in the central part of the caldera. After ∼3.7 ka, subsidence prevailed in the caldera leading to deposition of an aggrading fill (AF2). However, subsidence was interrupted by short-term uplift episodes in historical times at (100 BCE-100 CE, 600–700 CE, 1430–1538 CE) that led to the growth of comparatively minor-sized wedges PW1 to PW3, respectively. Displacement of coastal infrastructures of the Roman age (∼2 ka BP) is consistent with the vertical motion retrieved by the seismostratigraphic analysis, and further indicates the existence of two deformation signals. A short-wavelength signal confined to the Pozzuoli Bay reflects the contribution of an intra-caldera source. This signal is superposed to a long-wavelength regional subsidence increasing between Naples and Procida Island from 1.5 to 2 mm/a, respectively. The east-to-west enhancing subsidence likely reflects the transition between the uplifting Apennines and the foundered Tyrrhenian back-arc basin.