Gas Accumulation Research Articles

Massive clumps in W43-main: Structure formation in an extensively shocked molecular cloud

Aims. W43-main is a massive molecular complex undergoing starburst activities, located at the interaction of the Scutum arm and the Galactic bar. We aim to investigate the gas dynamics, in particular, the prevailing shock signatures from cloud to clump scales. We also look to assess the impact of shocks on the formation of dense gas and early-stage cores in OB cluster formation processes. Methods. We carried out NOEMA and IRAM-30 m observations at 3 mm towards five molecular gas clumps in W43 main located within large-scale interacting gas components. We used CH3CCH and H2CS lines to trace the extended gas temperature and CH3OH lines to probe the volume density of the dense gas components (≳105 cm−3). We adopted multiple tracers that are sensitive to different gas density regimes to reflect the global gas motions. The density enhancements constrained by CH3OH and a population of NH2D cores are correlated (in the spatial and velocity domains) with SiO emission, which is a prominent indicator of shock processing in molecular clouds. Results. The emission of SiO (2–1) is extensive across the region (~4 pc) and it is contained within a low-velocity regime, hinting at a large-scale origin for the shocks. Position-velocity maps of multiple tracers show systematic spatio-kinematic offsets supporting the cloud-cloud collision-merging scenario. We identified an additional extended velocity component in the CCH emission, which coincides with one of the velocity components of the larger scale 13CO (2−1) emission, likely representing an outer, less-dense gas layer in the cloud merging process. We find that the ‘V-shaped’, asymmetric SiO wings are tightly correlated with localised gas density enhancements, which is direct evidence of dense gas formation and accumulation in shocks. The dense gas that is formed in this way may facilitate the accretion of the embedded, massive pre-stellar and protostellar cores. We resolved two categories of NH2D cores: those exhibiting only subsonic to transonic velocity dispersions and those with an additional supersonic velocity dispersion. The centroid velocities of the latter cores are correlated with the shock front seen via SiO. The kinematics of the ~0.1 pc NH2D cores are heavily imprinted by shock activities and may represent a population of early-stage cores forming around the shock interface.

Determining the effect of non-condensable gas on a two-phase ammonia heat transfer loop of the satellite

It is advisable to design thermal management systems for high-power stationary satellites and specific ground applications using two-phase mechanically pumped loops with ammonia as the coolant. During prolonged operation in orbit, the accumulation of non-condensable gases can occur due to radiolysis and chemical reactions. The issues related to the effect of non-condensing gas on system parameters and performance have not yet received sufficient attention. The study of the distribution of non-condensable gas in the loop was performed by calculation-theoretical and experimental methods in a heat transfer loop with a Heat-Controlled Accumulator. Part of the gas accumulates in the steamgas zone of the Heat-Controlled Accumulator and affects the pressure value at a set temperature. The other gas is dissolved in liquid ammonia. This impacts the overheating of the cooled device when the heat load is switched on, the heat transfer intensity during boiling, and the cavitation reserve at the pump inlet. Accumulation of non-condensable gas up to ~0.075 mol nitrogen/kg ammonia, concentration of dissolved gas in the liquid up to ~5.3⋅10–4 mol/mol of the mixture does not significantly impact the parameters and performance of the system. But, if the aim is to precisely ensure the boiling temperature of the coolant or the cavitation reserve, the amount of necessary correction of the control parameters is up to 2.5 K. The results of the investigation can be used in the design of two-phase heat transfer loops for satellites and other applications, in particular, for the selection of the design and location of gas traps

Probing the Physics of Molecular Clouds in Spiral Galaxies NGC 5055 and NGC 3627

Although galaxies can be grouped in a few categories in terms of morphology, they have remarkably different intrinsic properties. Spiral galaxies host substantial amounts of molecular gas and have ongoing star formation activity with respect to elliptical galaxies lacking star formation. Molecular emission lines are used to probe the internal properties of molecular gas clouds where stars are born and die. Carbon monoxide (CO) is easily detectable in the interstellar medium (ISM) of galaxies. In this research, we probe the physics of the gas clouds at multiple positions in disc galaxies NGC 5055 (M63) and NGC 3627 (M66) using four CO transitions and their line ratios. 12CO(J=1-0) is the brightest across the disc of both galaxies compared to the other lines, i.e., 12CO(J=2-1, J=3-2) and 13CO(J=1-0). The CO intensities show a decrease from the center of the galaxies to the outskirts. However, NGC 3627 shows a rather irregular decrease pattern compared to NGC 5055. The CO line ratios show an increase up to a distance from the center and start to decrease. Although NGC 5055 shows a similar variation in the line ratios on each side of the disc, NGC 3627 has an opposite trend on either side. Therefore, the ISM could have different temperatures, opacity, densities, and levels of star formation in different regions of the galaxy’s disc. Our results indicate that the line ratios found at the center of both galaxies are different. The difference could be the result of the bar-driven gas accumulation in the center of NGC 3627. The line ratios in the center of NGC 5055 are within the range found for the centers of other spiral and active galaxies in the literature, but the ratios in the center of NGC 3627 are relatively lower.

A new method for layout layer optimization of long horizontal boreholes for gas extraction in overlying strata: A case study in Guhanshan coal mine, China

AbstractThe gases released by underground coal mining pose a threat to mine safety, lead to resource wastage, and contribute to environmental pollution. Employing long horizontal boreholes (LHB) for gas extraction proves to be an effective solution. However, accurately determining the LHB's position within the overlying rock strata is challenging due to complex mining and geological conditions. This study introduces a novel “zone‐position” method for identifying the optimal LHB placement, utilizing both physical simulation tests and theoretical analysis. The approach comprises two steps. Initially, it identifies the appropriate LHB layout zone within the overlying strata. It delineates four subzones within the fractured zone, among which the stable fractured subzone (SFSZ) is identified as the most favorable for LHB placement. The boundaries of the SFSZ are also defined. Subsequently, the method focuses on pinpointing the LHB's precise location within the SFSZ, proposing a criterion that considers gas accumulation, strata permeability, and LHB stability. Application of this method in engineering projects demonstrates that the gas extracted by LHBs accounts for about 60% of the total gas emission. Furthermore, the volume of gas extracted at the optimal LHB location reaches up to 5.52 m3 min−1, triple that of other locations.

Lower Limits of Petrophysical Properties Allowing Natural Gas Accumulation in Marine Sandstones: An Example from the Qiongdongnan Basin, Northern South China Sea

The lower limits of petrophysical properties for an effective reservoir are among the key parameters for assessing hydrocarbon reserves and are therefore directly related to hydrocarbon exploration and development strategies. However, the lower limits for marine sandstone gas reservoirs are still not clear and the impact factors also remain to be discussed. This study analysed the lower petrophysical property limits of an effective sandstone reservoir in the Qiongdongnan Basin using porosity, permeability and gas testing. The results showed that the lower porosity and permeability limits of effective reservoirs developed in the deltas are 8.9% and 1.2 × 10−3 μm2, respectively, and 11.3% and 4.0 × 10−3 μm2 in the submarine canyons and fans, respectively. Sedimentary facies, sediment transport distance, grain size and burial depth of sandstone significantly influence the lower physical property limits. The lower porosity and permeability limits increase with the increase in sediment transport distance as well as the decrease in sandstone grain size and burial depth. Sediment sources and sedimentary facies determine whether sandstone can become an effective reservoir in the Qiongdongnan Basin. Specifically, the sediment source dramatically influences the petrophysical properties of sandstone. The sandstone sourced from the Red River has higher porosity and permeability, followed by the sandstone sourced from the Hainan Uplift, and the sandstone sourced from the palaeo-uplift within the basin has the lowest porosity and permeability. The feldspar dissolution by CO2 and organic acid is the primary formation mechanism of the effective reservoir in the Lingshui Formation, whereas the dissolution of glauconite is more common in the sandstone reservoirs of the Sanya and Meishan formations.

Using isotope-geochemical criteria for Olympiadinskoye gold deposit gas system genesis diagnosis

The authors studied modern gas manifestations spatially associated with the ore deposits in the Kaitbinskaya lithological-facies zone of the Yenisei Ridge. The purpose of the research is to obtain scientifically based data on the genesis of gaseous and vaporous fluids in various sampling environments of the Vostochny open-pit mine of the Olympiadinskoye gold deposit: rocks, natural waters, free-flowing gases from blastholes and air of the surface atmosphere. It has been conducted a complex of field and analytical works including degassing, gas chromatography, pyrolysis of the organic substance of lithified and metamorphosed deposits, analysis of carbon isotopic composition in carbon dioxide and methane in fluidal systems. In order to study normal gas-geochemical field (natural background) of the work area an atmospheric geochemical survey was carried out at the reference site – an “environmentally friendly” site with the minimal influence of technogenic factors. It has been determined that the surface atmosphere of the site had been formed due to the landscape and geomorphological conditions of the Kaitbinskaya lithological-facies zone as well as fluidal systems of deep horizons. The latter, due to the presence of an extensive network of disruptive disturbances and diffusion-filtration processes of mass transfer reached the zone of exploratory geochemical sounding. The conducted pyrolytic studies of rocks have proved that within the open section of the Vostochny open-pit mine the organic substance of the Kordinskaya series of the lower Riphean deposits has implemented its oil and gas generation potential and cannot serve the formation source of abnormal gas fields of the Olympiadinskoye gold deposit. The studied gas systems are polygenic in nature and, being allochthonous to the host sediments, are formed without the participation of gases from the upper generating (bio) zone. According to isotope-geochemical criteria, these are mainly endogenous and naphthidogenic fluids identical to the gas condensate accumulations of the Yurubcheno-Tokhomskaya oil and gas accumulation zone.

Tracing Oils and Gas Accumulation in Complex Petroleum Systems Based on Biomarkers, Light Hydrocarbons, and Diamondoids from Concomitant Crude Oils: A Case Study in the Shawan Sag of the Junggar Basin, NW China.

The Shawan Sag is one of the most promising blocks in the western Junggar Basin for natural gas and oil exploration. To date, the research and exploration degree here is still low, and there is limited understanding of the origin and migration of natural gas and oils, which seriously restricts future exploration and development. At least three oil charging episodes and one gas charging episode could be confirmed in the reservoirs on the western slope of the Shawan Sag based on the analysis of concentrations and ratios of hopanes and steranes, diamondoids, and light hydrocarbons. The first and second charging oils originated from the peak and late oil generation window stages of Lower Permian Fengcheng Formation (P1f) source rocks, respectively. The third charging oil originated from the late oil generation window stage of source rocks of the Middle Permian lower Wuerhe Formation (P2w). Combining the carbon isotopic compositions and the gas composition, the fourth charging gas was derived from the postmature source rocks of Carboniferous(C) and Lower Permian Jiamuhe Formation (P1j) and the high-postmature source rock of Lower Permian Fengcheng Formation (P1f). The preservation conditions of nature gas in the Mesozoic (T-K) cap rocks in the Shawan Sag, as indicated by methyladamantanes (MAs)/methyldiamantanes (MDs) ratio, are better than those in the Mahu Sag. In this study, the methyladamantane maturity parameters of oils in the reservoirs were proposed to evaluate the maturity and further determine the migration direction of late-charging natural gas. The results suggest that late postmatured natural gases were charged from the southern part to the northwest of the Shawan Sag. Therefore, the southeastern direction of Well SP1 is a favorable area for natural gas exploration in the Shawan Sag. Meanwhile the northern part of the sag is favorable for the exploration of high-mature oil generated from source rocks within the Middle Permian Lower Wuerhe Formation.

Conditions for Generation, Accumulation, and Preservation of Oil and Gas in Permian Strata, Northwestern Anabar–Khatanga Oil and Gas Region

Abstract ––Integrated seismic, drilling, and generalizing scientific research in the southeastern Anabar–Khatanga oil and gas region (OGR) since the early 1930s led to discoveries of small oil and gas occurrences and one large Central Olgino oil field. However, the petroleum potential of the northwestern part of the region remains poorly investigated and evaluated. To assess the prospects for the oil and gas potential of this territory, all seismic and geological and geochemical information was used, including four new wells drilled in the Sopochnoe uplift and the Zhuravliny swell. The scales of oil and gas formation, accumulation and destruction of hydrocarbon accumulations in the Permian deposits, which are the most promising in terms of the initial potential of the source rocks included in their composition, is given. The source rocks of the Upper Kozhevnikovo, Lower Kozhevnikovo, and Tustakh formations have been characterized in terms of thickness, contents of organic carbon and chloroform bitumen, maturity (catagenesis) of organic matter, and density of oil migration and gas generation. The maximum possible estimates of oil and gas resources that can potentially accumulate in structural traps, without migration losses, are obtained for each of the three reservoir formations by basin modeling. Judging by geological and geochemical criteria, the Upper Kozhevnikovo Formation can preserve only a minor portion of initially accumulated hydrocarbons, while the oil and gas accumulations, as well as the petroleum generation potential of organic matter in the Lower Kozhevnikovo and Tustakh formations, were destroyed by late Permian–Early Triassic trap magmatism and Mesozoic–Cenozoic tectonic activity.

Study on multiple influence mechanism of airflow-dust-gas coupling diffusion under large vortex flow technology

In response to the serious dust pollution and excessive gas concentration in fully mechanized excavation face, a multi-phase coupling diffusion model of airflow-dust-gas was established, and the influence of pressure pumping ratio and air volume on dust and gas diffusion was studied. The results showed that the dust of the traditional ventilation mode was diffused to the whole roadway, and the high-concentration gas accumulated obviously. However, after adopting the new ventilation mode of large vortex flow, a quantity of dust was controlled in the eddy field, and high-concentration gas was dissipated by strong airflow, so there was no gas accumulation. As the pressure pumping ratio decreases, the extraction effect increases, the eddy current intensity also increases, and the control effect on dust is enhanced. The pressure pumping ratio with the best dust control effect is 0.6, and there is no dust pollution and no gas accumulation in the driver's location. The fixed pressure pumping ratio is 0.6, and the diffusion of dust and gas is not significantly affected by an increase in air volume, but high-speed airflow can dilute and reduce the concentration of dust and gas. When Qb = 600.0 mg/m³, the high-speed airflow can dilute the dust concentration, accelerate the dispersion of high-concentration gas, keep the gas below the safe level, and have a good dust control effect. The increase of air volume will further reduce the dust and gas concentration. This study provides a theoretical basis for the promotion and utilization of new ventilation method on-site.

Fluid inclusion evidence for overpressure-induced self-sealing and accumulation of deep shale gas

Shale oil and gas exploration and development are extending to greater depths, and it is important to understand the accumulation mechanisms of shale oil and gas. Here we conducted a case study in the Upper Ordovician Wufeng Formation–Lower Silurian Longmaxi Formation in the Ningxi area, Sichuan Basin, southwest China, by using petrological and fluid inclusion investigation to determine the processes involved during the overpressure-induced self-sealing accumulation of deep shale gas. Results show that fibrous quartz–calcite veins in the source rocks contain abundant gas inclusions and coeval two-phase gas–liquid aqueous inclusions. The gas inclusions are relatively uniform, translucent to transparent, single-phase inclusions with a high density, indicative of a closed shale system. The gas inclusions record varying levels of fluid overpressure (115.23–169.46 MPa), with a paleo-pressure coefficient of 2.12–2.98. Fluid overpressure and self-sealing resulted in shale gas accumulation, with bedding-parallel and laminar fractures acting as important migration pathways, which improved the horizontal porosity and permeability of the shale. These processes are common and important phenomena in petroleum systems. Unconventional oil and gas development commonly requires horizontal fracturing of wells to form a fracture network, which can improve the production capacity.

Coupling of source rock gas expulsion intensity and reservoir quality in time and space-a key to determine gas accumulation in Upper Paleozoic tight sandstones of the Mugua gas field, Ordos Basin, China

Research on gas accumulation mechanisms and variations in gas saturation is limited in the newly established Mugua gas field in the Ordos Basin. Understanding these aspects is vital for reduce drilling uncertainty and exploration risk. This study employed a variety of methods, including: (1) the use of organic geochemical examinations to determine the gas expulsion intensity of hydrocarbon source rocks; (2) fluid inclusion analyses to determine the time of gas accumulation; (3) a combination of optical microscopy, scanning electron microscopy observations, pore-simulation and permeability tests, mercury-intrusion capillary pressure experiments, and nuclear magnetic resonance studies to assess the properties of the reservoir quality and identify the tight sandstone rock type; (4) wireline logging and interpretive data analyses to research the gas saturations features; and (5) establish reservoir quality evolution model to systematically study this problem. Integrating fluid inclusion homogenization temperatures with burial and thermal histories indicates that gas accumulation in the Mugua gas fields occurred throughout the Early Jurassic to Late Cretaceous period. Five diagenetic facies have been identified: dissolution, quartz-cemented, clay mineral filling, tightly compacted, and carbonate-cemented facies. The reservoir quality evolution model reveals that the five diagenetic facies experienced densification before the period of gas accumulation. Therefore, for gas accumulation in tight sandstones, it is essential that mature and gas-generating source rocks, provide sufficient expulsion forces to drive gas into the rocks. The mechanism of gas accumulation in the Mugua gas field's tight gas sandstone reservoirs involves the process occurring in sandstones that are either near or interbedded with source rocks, under high pore-fluid pressure generated by gas production. Compared to other Upper Paleozoic gas fields in the Ordos Basin, the gas expulsion intensity in the Mugua gas field is lower, ranging from 6.12–8.39 × 108 m3/km2. Due to the low gas expulsion intensity, the Shihezi 8 Member's tight sandstone reservoirs, situated away from the source rock, typically show low gas saturation. Conversely, the dissolution and quartz-cemented facies within the Benxi, Taiyuan, and Shanxi Formations, intimately interbedded with hydrocarbon source rocks, exhibit good reservoir quality. They offer ideal conditions for gas accumulation, making them prime candidates for exploration and development.

New Oil and Gas Plays in the Cis-Urals

Abstract ––The search for oil and gas in folded zones and in the foredeep of the cis-Uralian region for many decades was reduced to testing of easy-to-find closures and reefs located at shallow depths. Many important discoveries were made as a result, but the overall performance of the work remained relatively low. On the one hand, this was due to the poor subsurface imaging of the data for reliable preparation of structures in regions of complex structure. On the other hand, the peculiarities of the development of oil and gas systems in these regions were ignored during the assessment of prospecting sites. In comparison with traditional production hubs centers in the platform regions of the Volga–Ural and Timan–Pechora basins, this distinguishing feature was caused by a thicker sedimentary cover, the variability of its composition and structure, and multiple phases of structural development. Many failures were due to the formation of traps after the passage of the primary migration flow of oil and gas, low capacity of reservoirs, and their fracturing by faults. As shown by interpretation of new geodata using modern knowledge about the oil and gas potential of regions of similar structure, the cis-Uralian region contains poorly studied oil and gas accumulation zones that can contain large deposits. These include blind thrust regions, subsalt traps in development zones of dislocated diapirs, and also stratigraphic and combined traps associated with unconformities and facies changes. The utmost attention is paid to new prospecting objects in the Timan–Pechora basin in which the thickness of the Paleozoic cover has increased. The preparation of new promising objects in these zones has become possible due to new knowledge and better geophysical data.

Geological characteristics and exploration breakthroughs of coal rock gas in Carboniferous Benxi Formation, Ordos Basin, NW China

To explore the geological characteristics and exploration potential of the Carboniferous Benxi Formation coal rock gas in the Ordos Basin, this paper presents a systematic research on the coal rock distribution, coal rock reservoirs, coal rock quality, and coal rock gas features, resources and enrichment. Coal rock gas is a high-quality resource distinct from coalbed methane, and it has unique features in terms of burial depth, gas source, reservoir, gas content, and carbon isotopic composition. The Benxi Formation coal rocks cover an area of 16×104 km², with thicknesses ranging from 2 m to 25 m, primarily consisting of bright and semi-bright coals with primitive structures and low volatile and ash contents, indicating a good coal quality. The medium-to-high rank coal rocks have the total organic carbon (TOC) content ranging from 33.49% to 86.11%, averaging 75.16%. They have a high degree of thermal evolution (Ro of 1.2%–2.8%), and a high gas-generating capacity. They also have high stable carbon isotopic values (δ13C1 of –37.6‰ to –16‰; δ13C2 of –21.7‰ to –14.3‰). Deep coal rocks develop matrix pores such as gas bubble pores, organic pores, and inorganic mineral pores, which, together with cleats and fractures, form good reservoir spaces. The coal rock reservoirs exhibit the porosity of 0.54%–10.67% (averaging 5.42%) and the permeability of (0.001–14.600)×10−3 μm2 (averaging 2.32×10−3 μm2). Vertically, there are five types of coal rock gas accumulation and dissipation combinations, among which the coal rock-mudstone gas accumulation combination and the coal rock-limestone gas accumulation combination are the most important, with good sealing conditions and high peak values of total hydrocarbon in gas logging. A model of coal rock gas accumulation has been constructed, which includes widespread distribution of medium-to-high rank coal rocks continually generating gas, matrix pores and cleats/fractures in coal rocks acting as large-scale reservoir spaces, tight cap rocks providing sealing, source-reservoir integration, and five types of efficient enrichment patterns (lateral pinchout complex, lenses, low-amplitude structures, nose-like structures, and lithologically self-sealing). According to the geological characteristics of coal rock gas, the Benxi Formation is divided into 8 plays, and the estimated coal rock gas resources with a buried depth of more than 2 000 m are more than 12.33×1012 m3. The above understandings guide the deployment of risk exploration. Two wells drilled accordingly obtained an industrial gas flow, driving the further deployment of exploratory and appraisal wells. Substantial breakthroughs have been achieved, with the possible reserves over a trillion cubic meters and the proved reserves over a hundred billion cubic meters, which is of great significance for the reserves increase and efficient development of natural gas in China.

Enrichment model and major controlling factors of below-source tight oil in Lower Cretaceous Fuyu reservoirs in northern Songliao Basin, NE China

Based on the geochemical, seismic, logging and drilling data, the Fuyu reservoirs of the Lower Cretaceous Quantou Formation in northern Songliao Basin are systematically studied in terms of the geological characteristics, the tight oil enrichment model and its major controlling factors. First, the Quantou Formation is overlaid by high-quality source rocks of the Upper Cretaceous Qingshankou Formation, with the development of nose structure around sag and the broad and continuous distribution of sand bodies. The reservoirs are tight on the whole. Second, the configuration of multiple elements, such as high-quality source rocks, reservoir rocks, fault, overpressure and structure, controls the tight oil enrichment in the Fuyu reservoirs. The source-reservoir combination controls the tight oil distribution pattern. The pressure difference between source and reservoir drives the charging of tight oil. The fault-sandbody transport system determines the migration and accumulation of oil and gas. The positive structure is the favorable place for tight oil enrichment, and the fault-horst zone is the key part of syncline area for tight oil exploration. Third, based on the source-reservoir relationship, transport mode, accumulation dynamics and other elements, three tight oil enrichment models are recognized in the Fuyu reservoirs: (1) vertical or lateral migration of hydrocarbon from source rocks to adjacent reservoir rocks, that is, driven by overpressure, hydrocarbon generated is migrated vertically or laterally to and accumulates in the adjacent reservoir rocks; (2) transport of hydrocarbon through faults between separated source and reservoirs, that is, driven by overpressure, hydrocarbon migrates downward through faults to the sandbodies that are separated from the source rocks; and (3) migration of hydrocarbon through faults and sandbodies between separated source and reservoirs, that is, driven by overpressure, hydrocarbon migrates downwards through faults to the reservoir rocks that are separated from the source rocks, and then migrates laterally through sandbodies. Fourth, the differences in oil source conditions, charging drive, fault distribution, sandbody and reservoir physical properties cause the differential enrichment of tight oil in the Fuyu reservoirs. Comprehensive analysis suggests that the Fuyu reservoir in the Qijia–Gulong Sag has good conditions for tight oil enrichment and has been less explored, and it is an important new zone for tight oil exploration in the future.

Experimental study for visualizing CO2-dissolved water plume migration under hydraulic gradient conditions and implication for field monitoring data

Investigating the possible direction of a CO2-dissolved water plume migration near the potential CO2 leakage area is a significant task because it helps estimate the spatial and temporal monitoring scale to detect the signal of released CO2 from the storage. Accordingly, the Korea CO2 Storage Environmental Management (K-COSEM) research center tried to develop an intensive monitoring system and applied it to the artificial CO2 release test in the actual field. Monitoring data from the field tests depicted the horizontal movement of the CO2-dissolved water plume along the direction of the groundwater flow. However, it remains unclear how the CO2-dissolved water plume migrates vertically and how gas accumulation occurs near the capillary zone. The present study simulated the CO2 release test with a visual expression method utilizing a Hele-Shaw cell with hydraulic gradient conditions (i = 0, 0.1, and 0.01) and tried to estimate the significant influences on a diffusive-advective transport of the dissolved gas plume with the shallow aquifer condition. The visualization experiment results were intuitively verified to determine whether the theoretical principles of action related to plume flow applied in this context. The results suggest that a CO2-dissolved water plume is distributed by hydraulic gradients and density-driven CO2 convective flow. The plume shape, center, and area were analyzed using an image analyzer program; the results demonstrated that the plume characteristic evolved depending on the significant effects on the plume. When the plume was mainly affected by the hydraulic gradient, it rapidly moved from the injection point to the last boundary; in contrast, when it was influenced primarily by density-driven CO2 convective flow, it flowed diagonally downward in the shape of varied branches. The numerical model calculated the migration of the CO2-dissolved water plume affected by both factors. The laboratory experiment and numerical simulation results suggest that the migration of a CO2-dissolved water plume may be affected by the hydraulic gradient and density-driven CO2 convective transport. As such, these factors should be considered when designing and analyzing CO2 monitoring signals to detect CO2 leaks from shallow aquifer systems.

TAPHONOMIC ANALYSIS OF AN ARTICULATED BALEEN WHALE (CETACEA; MYSTICETI) FROM UPPER MIOCENE INNER SHELF DEPOSITS OF PENÍNSULA VALDÉS, PATAGONIA, ARGENTINA

Abstract Fieldwork at Península Valdés (Chubut, Argentina) in the Puerto Madryn Formation (Late Miocene) resulted in the discovery of a well-preserved, almost fully articulated, baleen whale (Cetacea, Mysticeti). This specimen, one of the most complete balaenid skeletons known from the Neogene of Argentina and worldwide, was the focus of a taphonomic analysis employing a multidisciplinary approach, integrating taxonomic, sedimentological, stratigraphic, and ichnological analyses, with the aim of reconstructing the taphonomic processes and the paleoenvironmental conditions that controlled preservation of the specimen. The skeleton belongs to the family Balaenidae (right whales). It displays a high degree of articulation, moderate pre-burial fragmentation, and relatively high completeness. Our results suggest that after death, the balaenid suffered a brief biostratinomic phase that can be summarized in four stages: (1) death at sea, with initial decomposition and positive buoyancy of the carcass; (2) internal accumulation of putrefaction gases, re-orientation, then gas loss; (3) sinking and deposition in a ventral-up position on the sea floor of the inner shelf; and (4) lateral re-orientation of the postcranial region due to physical and biological processes. The high degree of articulation and association of the skeletal elements, and the presence of both mandibles, indicate no lateral transport on the seabed and excludes refloating of the carcass at any stage. Finally, the data indicate a low-energy shelf environment with normal marine benthic oxygenation and salinity conditions, characterized by a soft bottom and a moderate sedimentation rate. The last, combined with high bioturbation, plus scour-induced self-burial, resulted in rapid burial of the carcass.

Methods for Quantifying Expansion in Lithium-Ion Battery Cells Resulting from Cycling: A Review

Significant efforts are being made across academia and industry to better characterize lithium ion battery cells as reliance on the technology for applications ranging from green energy storage to electric mobility increases. The measurement of short-term and long-term volume expansion in lithium-ion battery cells is relevant for several reasons. For instance, expansion provides information about the quality and homogeneity of battery cells during charge and discharge cycles. Expansion also provides information about aging over the cell’s lifetime. Expansion measurements are useful for the evaluation of new materials and the improvement of end-of-line quality tests during cell production. These measurements may also indicate the safety of battery cells by aiding in predicting the state of charge and the state of health over the lifetime of the cell. Expansion measurements can also assess inhomogeneities on the electrodes, in addition to defects such as gas accumulation and lithium plating. In this review, we first establish the mechanisms through which reversible and irreversible volume expansion occur. We then explore the current state-of-the-art for both contact and noncontact measurements of volume expansion. This review compiles the existing literature on four approaches to contact measurement and eight noncontact measurement approaches. Finally, we discuss the different considerations when selecting an appropriate measurement technique.

TO THE 60TH ANNIVERSARY OF THE DEPARTMENT OF EARTH SCIENCES OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE

In the second part of the article, the main historical events in terms of dates, facts and personalities of the formation and development of the institutions of the Department of Earth and Space Sciences of the Academy of Sciences of the Ukrainian SSR from its foundation in 1963 to Ukraine’s independence in 1991 are listed in chronological order. The course of events related to name changes is given: Department of Earth and Space Sciences (1963–1972), Department of Earth Sciences (1972–1980), Department of Geology, Geophysics and Geochemistry (1980–1983) and Department of Earth Sciences (1983–1991). Considerable attention is paid to the significant contribution of the specialists of the Department of Earth Sciences of the Academy of Sciences of the Ukrainian SSR in eliminating the consequences of the largest technogenic and environmental disaster that occurred on April 26, 1986 at the Chornobyl nuclear power plant. It is considered the most important achievements of the institutions of the Department of Earth Sciences of the Academy of Sciences of the Ukrainian SSR in the period of formation and active development. In particular, scientific substantiation of the search for industrial oil and gas accumulations in the crystalline foundation of the sedimentary basins of Ukraine, volcanic and volcanogenic-sedimentary rocks of Transcarpathia and the Dnipro region, in the zones of active water exchange on the regional monoclines of Precarpathia, the Black Sea region. The doctrine of the formation of deep fault structures has been developed, and a technique has been developed for forecasting of combined traps of hydrocarbon accumulations in deep-seated Devonian and Carboniferous horizons of the Dnipro-Donetsk Basin. Significant results were obtained regarding the geological structure of the earth’s crust and the upper mantle of the lithosphere within the framework of international projects during regional seismic research within limits of Ukraine, Southeast Europe and India. The general regularities of the structure are established for various geostructures: shields, platforms, depressions, transition zones from continents to oceans, deep-sea depressions, structures of the ocean floor. The theoretical principles, methods and technical means of remote ocean research using artificial Earth satellites were developed, and the country’s first system for collecting, transmitting and processing information about the ocean’s physical fields was created. This is a kind of report of the most significant events and facts from the life of the Department of Earth Sciences of the National Academy of Sciences of Ukraine and personal information and scientific achievements of the members of the Academy elected in the considered period.

The dominant three-element model of oil and gas accumulation in basement buried hills: A discussion on new exploration frontiers in the deepwater area of the northern South China Sea

Basement buried hill reservoirs represent significant emerging prospects among the newly discovered growth poles in the deepwater areas of the northern South China Sea. Addressing the unclear key factors contributing to their formation, this study dissects successful global exploration cases of basement buried hill reservoirs and analyzes the common characteristics of basement reservoir accumulation under different basin types, structural backgrounds, basement lithologies, and oil and gas geological conditions. A three-element coupling relationship, termed “source-reservoir-cap”, is proposed as the dominant mechanism controlling basement buried hill reservoir formation. The genesis of these reservoirs requires adequate oil and gas supply, appropriately sized accumulation bodies, and effective sealing layers. The optimal configuration of the “source-reservoir-cap” relationship directly influences the efficient charging and preservation of oil and gas within basement buried hill reservoirs. Four configurations are identified, including circumstances such as the source-underlying low-positioned basement buried hill with a “source-reservoir cover docking migration type”, the source-border middle-positioned basement buried hill with a “source-reservoir lateral window docking migration type”, and the source-outside high-positioned basement buried hill with both “source-reservoir short-distance transport and migration type” and “source-reservoir long-distance transport and migration type”. The first to three models present favorable accumulation conditions. Based on the “source-reservoir-cap” three-element coupled model, this study identifies the Yunkai basement buried hill in the Pearl River Mouth Basin, the central depression in the Qiongdongnan Basin, and the northern and southern basement buried hills belts as crucial exploration targets in the deepwater areas of the northern South China Sea.

Study on gas accumulation in polymer electrolyte membrane water electrolyzer considering two-phase flow

In this study, we analyze gas accumulation in a polymer electrolyte membrane water electrolyzer by considering two-phase flows in the porous transport layer on the anode and cathode sides. First, effect of mass flow rate on gas accumulation is analyzed. The transport of liquid water occurred differently on the anode and cathode sides. While the transport of liquid water on the anode side decreased in the high current density region, that on the cathode side increased with current density. The limiting current density increased by 1.2 A/cm2 when the mass flow rate was increased. Next, we study the effect of contact angle of the porous transport layer. When the contact angle was decreased from 75° to 30°, gas saturation decreased by 0.04. The use of a hydrophilic porous layer on the cathode side, however, hindered the transport of liquid water into the channel because the porous transport layer tended to retain liquid water. Finally, we study the effect of porosity of the porous transport layer. When the porosity was 80%, the mass flow rate of liquid water into the porous layer was 0.1 g/s, and gas saturation was approximately 0.25 at 0.8 A/cm2.