Sedimentation Environment Research Articles

Fauna Assemblages and Depositional Environment of Recent Deposits in Al-Salhiya Island, Southeastern Part of Basrah Governorate, Southern Iraq

The present study was carried out to give a clear view of the sedimentological characteristics, and to identify the types of faunal assemblages in Al-Salhiya Island. The results showed two types of sediment texture: Sandy silt deposits and Silt deposits. Sandy silt deposits are dominant at most depths in the study area. The graphic mean size of the sediments indicated that the sediments are soft and reflect the nature of the sedimentation environment, which was calm and had a low transport capacity. Also, the statistical size parameters of the sediments indicated that the region is under the influence of marine tidal environments, shallow brackish marsh environments, and fresh marsh-fluvial environments. This study dealt with the fauna assemblages. It is revealed through the distribution and spread of these groups that the most important species identified for Foraminifera are Ammonia beccarii, Ammonia tepida, and Eliphidium inertum, whose prevailing presence together and in most of the depths indicated brackish-shallow water environment, with varying temperatures and estuarine environments. Also, the species Quinqueloculina poyana and Spirocolina laevigata are identified. One species of Ostercoda was identified: Cyprideis torosa. The presence of this type indicates a shallow, lower estuarine-marine environment. This study identified 8 species of the Gastropoda, most of which live in lower estuarine-marine environments. This indicated that the area was affected by tidal currents and marine progress due to its proximity to the coastline of the Shatt al-Arab. Also, this study showed two types of Pelecypoda that are widely distributed and common in all depths, their presence together with the Gastropod and Pelecypoda debris reflects the effectiveness of tidal currents in transporting them to the area.

Antibiotic resistance genes transfer risk: Contributions from soil erosion and sedimentation activities, agricultural cycles, and soil chemical contamination

The transfer of antibiotic resistance genes (ARGs) pose environmental risks that are influenced by soil activity and pollution. Soil erosion and sedimentation accelerate degradation and migration, thereby affecting soil distribution and contamination. This study quantified the vertical and horizontal transfer capabilities of ARGs and simulated soil environments under various scenarios, such as erosion, agricultural cycles, and chemical pollution. The results showed that slope, runoff, and sediment volume significantly affected soil erosion and ARG transfer risks. The response of environmental factors to the transfer risk of ARGs is as follows: the promotion effect of soil deposition (average: 21.41 %) is significantly greater than the inhibitory effect of soil erosion (average: −11.31 %); the planting period (average: −64.654) is greater than the harvest period (average: −56.225); the response to soil chemical pollution is: the impact of phosphate fertilizer residues, antibiotics, and pesticide pollution is more significant. This study constructed a vertical and horizontal transfer system of ARGs in soil erosion and sedimentation environments and proposed a response analysis method for the impact of factors, such as soil erosion and sedimentation activities, agricultural cycles, and soil chemical pollution, on ARGs transfer capabilities.

Detailed Late Pliocene-Quaternary sedimentation history and diagenesis processes in the eastern part of the Norwegian-Greenland Basin based on mathematical statistical methods

As a result of univariate regression analysis, quantitative parameters on the distribution of Mn/Al and Mn/Fe ratios in the sections of the studied holes of ODP Leg 151 were obtained. On the basis of correlation analysis data with Pearson matrix construction and classical factor analysis with varimax rotation, a division of rather homogeneous Upper Pliocene-Quaternary sediments was carried out with the allocation of 3 main factors that characterize the history of sedimentation and diagenesis in the Norwegian-Greenland Basin. The boundaries between lithostratigraphic subdivisions are drawn on a strict mathematical basis. It is established that the nature and degree of intensity of diagenesis processes in this region were influenced by the following main factors: sedimentation environments in the Norwegian-Greenland Basin in the Late Pliocene-Quaternary time; grain-size and chemical composition of the studied sediments; total organic carbon content in the sediments; sedimentation rates.

OSL and radiocarbon dating of core TBF-1 on the outer shelf of the East China Sea and implications for late Quaternary stratigraphic correlation

It is crucial to establish a robust chronology for understanding late Quaternary sedimentation processes and environment changes in response to sea-level fluctuation on shelves. The shelf of the East China Sea (ECS) is featured by huge terrigenous sediment input and striking land -sea interaction during the late Quaternary. However, there remains controversy in chronostratigraphic rebuilding of transgression and regression deposits during eustatic-glacial cycles, mainly due to a lack of reliable dating data. In this study, an extensive comparison of 17 optically stimulated luminescence (OSL) and 15 AMS 14C ages from core TBF-1 (upper 40 m) provides a constraint in chronostratigraphic reconstruction since Marine Isotope Stage (MIS) 5. OSL ages range from 9.5 ± 0.7 to 67.3 ± 4.8 ka at depths from 2.00 to 28.00 m, while 14C ages range from 6645 to 41435 cal a BP at depths from 0.02 to 17.52 m. Regression analysis demonstrates a high level of agreement between OSL and 14C ages, with r2 values of 0.91 and 0.90, respectively. For Holocene sediments (U1), both OSL and 14C methods are applicable in tidal sand ridges, however, it should be noted that 14C ages may exhibit a young bias of up to 3 ka. For pre-Holocene sediments (U6-U2), OSL ages are robust within saturation limitation of OSL signal (De up to ca. 166 Gy), cross-checked by feldspar post-IR IRSL (pIRIR) dating protocol. Nevertheless, the shell 14C ages (11620 and 10390 cal a BP at depths of 13.95–14.56 m) in Last Glacial Maximum (LGM) fluvial sediments of U2 are significantly underestimated, because of their susceptibility to recrystallization and overgrowth, resulting in carbon exchange with environment. While the peaty layer's14C age in deltaic deposition (17.50 m, U5) was determined to be 36420 cal a BP, coincided with OSL age of 39.6 ± 3.9 ka. The chronostratigraphy since MIS 5 for core TBF-1 exhibits a significant correlation with previously published cores SFK-1, DZQ4, and DH02, on the ECS outer shelf. Through the evaluation of those underestimated 14C ages and saturated OSL ages, we re-elucidated the primary sedimentary facies and their respective formation periods. This sedimentary stratigraphic illustration exhibits significant consistency with eustatic-glacial cycles. The renewed chronological framework for ECS shelf allows better correlation between the late Quaternary sedimentary evolution and the land-sea interaction on open shelves dominated by siliciclastic sedimentation.

Results of the study of the section of the Takata formation "Yuzhnaya Rassolnaya" in the territory of the Poludovo-Kolchimsky anticlinorium of the Western-Ural folding zone (Krasnovishersky district, Perm territory)

Relevance. Relationship with the Takata formation of diamond reservoir rocks and previously discovered deposits and the presence of prospects for discovering new ones in the zone of the forward folds of the Urals. Aim. To reconstruct the conditions of sedimentation and composition of rocks, the source of the removal of terrigenous rocks of the Takata formation based on the results of studying the "Yuzhnaya Rassolnaya" section. Objects. Terrigenous rocks of the Takata formation in the "Yuzhnaya Rassolnaya" section located in the western part of the alluvial diamond deposit "Yuzhnaya Rassolnaya" in the Krasnovishersky district of the Perm Territory. Methods. Lithofacies analysis, petrographic study of thin sections in transmitted light using crossed nicol methods, determination of the content of rock-forming oxides by X-ray fluorescence on an S8 Tiger (Bruker) spectrometer, analysis of rock-forming elements on glassy disks. Impurity and microimpurity elements (with a content of <5%) were determined using a certified method for defining elements by inductively coupled plasma mass spectrometry according to the method, STO TGU 048-2012. The analysis was performed by ICP-MS on an Agilent 7500cx quadrupole mass spectrometer (Agilent Technologies Inc., USA) using an internal (In Internal standard, Inorganic Ventures, USA) and an external standard SGD-2A (GSO 8670-2005). Results. Lithological-facial, mineralogical, petrographic, lithogeochemical studies of Takata terrigenous deposits were carried out in the "Yuzhnaya Rassolnaya" section in the area of the Polyudovo-Kolchima anticlinorium of the Western Ural folding zone, which made it possible to clarify the sources of matter and sedimentation conditions. The formation of sediments occurred in a transitional sedimentation environment. A transgressive sequence is observed from bottom to top. Terrigenous rocks of the Takata formation include rocks of the first and second sedimentation cycles. They were cut off due to the destruction of primary igneous (acidic and basic compositions) and metamorphic rocks, as well as sedimentary rocks. The totality of the material characteristics of the terrigenous rocks of the Takata formation, taking into account the published data, allowed us to assume that sedimentation of the rocks occurred on the passive continental margin, with the supply of clastic material due to the erosion of internal raised blocks of the foundation of the East European Platform. The activation of the latter occurred in the Emsian time with the manifestation of general lithospheric folding. At the same time, water flows carrying weathering products from the East European Platform eroded sedimentary rocks of the Riphean, Vendian, Ordovician and Silurian, which fragments we observe in small quantities when describing thin sections.

Changes in sedimentary environments in Shihwa Lake, Korea

Shihwa Lake was an artificial freshwater lake formed in 1994 by constructing a 12.7-km-long seawall, but it became a seawater lake in 1997. The water quality of Shihwa Lake had not been recovered despite the seawater exchange through the drain gate. This may adversely affect not only the water but also the bottom sediment environment of the lake. To determine the possible reasons for the environmental deterioration, water and core samples from three points in the lake were collected. And the parameters, such as the water temperature, salinity, dissolved oxygen (DO), particle distribution, total carbon (TC) and total nitrogen (TN), C/N ratio, and radioactive strength, were measured to estimate the water and sediment quality. In addition, we investigated changes in the sedimentation environment based on heavy-metal analysis, stable-isotope analysis of the core sample, and numerical analysis of sand transport. The core-sample analysis revealed a change in the sedimentation process on a time basis (before, during, and after the construction of the seawall). As a result, the sedimentation rate was approximately 4 cm/year during the seawall construction and 2 cm/year after the construction near the center of the lake. Furthermore, we established that the trends in these calculated sedimentation rates, determined using the radioactive strength method, align consistently with the results obtained from simulations and ultrasonic-wave observations. Finally, we evaluated the effects of a tidal power plant on the exchange of seawater and sedimentation processes.

Sedimentation Environments of the Lower Cretaceous Deposits of the North Caspian

Sedimentation Environments of the Lower Cretaceous Deposits of the North Caspian

Characteristics of Soil Particle Sizes and Fractal Parameters under Different Plantation Types of Populus alba

Vegetation plays a leading role in restoring desert ecosystems and increasing productivity. In this study, we elucidate the improvement effects of different restoration areas of Populus alba on the soil particle distribution, sedimentation environment, and fractal characteristics. We selected the restoration areas of P. alba × Caragana korshinskii (YN), P. alba × Hedysarum leave (YY), and P. alba × Hedysarum scoparium (YH), which have a history of twenty-one years. We analyzed the soil nutrients, soil particle size, soil particle size parameters, soil fractal dimension (D) values, and soil multifractal parameters at soil depths of 0–80 cm. We found that the YN, YY, and YH significantly increased the soil nutrients and soil fine particles (p < 0.05) and changed the deposition pattern of the soil particles in the sandy area. The YN, YY, and YH promote soil particle refinement and reduce the sorting performance of the soil particles. The vegetation promotes extremely positive-skewed and very leptokurtic soil particle distributions. The D values in the YN, YY, and YH restoration areas increased by 7.62%–27.94%, 7.36%–26.28%, and 7.10%–17.92%, respectively, relative to those of the LS. The construction of the different restoration areas of P. alba has made the distribution of the soil particles nonuniform. Compared with the YY and YH plantations, the distribution range of the soil particles in the YN plantation is wider, and the distribution heterogeneity is greater. In addition, we found that the fractal parameters are influenced by the soil physicochemical properties, the depositional environment, and vegetation factors. Therefore, we believe that D values and multifractal parameters are necessary as additional information for desert soil texture improvement. The results of this study provide a scientific and theoretical basis for the future revegetation of deserts.

Lithological and geochemical characteristics and sedimentary environments of the Cambrian high-carbon deposits in the east of the Siberian platform (Kyulenke river basin)

Relevance. The need to study high-carbon deposits as potential sources of hydrocarbons and ore minerals that can significantly increase the mineral resource of Russia. In addition, the analysis of lithological and geochemical features and the reconstruction of the sedimentation conditions of the Kuonamka Formation make it possible to more accurately judge the nature of the Lower and Middle Cambrian paleobasin in the east of the Siberian Platform. Aim. To identify lithological and geochemical features of the composition and determine the sedimentation environment of the Kuonamka Formation. Object. High-carbon deposits of the Kuonamka Formation uncovered by exploration wells on the eastern margin of the Mun arch of the Siberian platform in the Kulenke river basin. Methods. Lithological description of core material; mineralogical and petrographic analysis; X-ray diffraction, X-ray fluorescence and microelement analysis; determination of the content of sulfur and iron forms by wet chemistry; scanning electron microscopy using X-ray spectral microprobe; analysis of petrochemical modules. Results. It was established that the Kuonamka Formation in the studied sections has a consistent structure of four well-defined lithological-stratigraphic horizons. The composition of the deposits is predominantly mixed and is determined by variations in three main mineral groups: clay, carbonate and siliceous, in addition organic matter. The paper demonstrates different forms of organic matter confirming the mixed algal-bacterial genesis of the biocenosis of the Kuonamka basin. The revealed lithological features and lithochemical data indicate the accumulation of high-carbon deposits at a considerable distance from the drift sources in the depression zone of the open sea basin with weak circulation of bottom waters in anoxic conditions. The geochemical euxinic environment was dominant in carbonate-siliceous muds. Sedimentation occurred during one major transgressive-regressive sedimentation cycle being a typical sequence of filling a uncompensated deep depression.

Relationship of lithological data with the sedimentation environment of the Upper Batian deposits of the Kogalym region

Research subject. Upper Batian deposits (formation U2) of the Eastern part of the Kogalym region, within the North Nizhnevartovsk monocline. Aim. Reconstruction of the sedimentation environment of the U2 formation in the Kogalym region. Materials and methods. The reconstruction of sedimentation environments was conducted based on a macroscopic description of core samples with identification of structural and textural features of rocks from 35 wells. The clarification of sedimentation settings was carried out based on the description of 41 thin sections and a granulometric analysis of the clastic part of the studied rocks. Results. According to the macroscopic study, the U2 layer is composed of an uneven alternation of silty-argillaceous and silty-sandy rocks with coal interlayers. The rocks are of a polyfacial nature, represented by deposits of continental, transitional, and marine genesis. The thickness of the deposits varies markedly depending on the paleorelief of the area. The optical petrographic study revealed the polymictic composition of the studied rocks, which, according to the classification by V.D. Shutova, correspond to the arkose (graywacke arkose), less often graywacke (feldspar-quartz, quartz-feldspar greywackes) group. Cement most often exhibits a carbonate-clay composition. Rocks of marine genesis are characterized by a decrease in the proportion of rock fragments and an increase in the proportion of mechanically stable accessory minerals (zircon, garnet, tourmaline). The rocks of continental genesis are characterized by the maximum content of micas and plant detritus. An increase in the content of pyrite is noted in the sediments transitional from the continent to the sea. The grain-size analysis data of reservoir rocks of the U2 formation showed that both coastal-marine and channel deposits were formed in environments with active hydrodynamics of the medium, when the dynamic processing of clastic material exceeded the intensity of its supply. Conclusions. The performed lithofacies studies made it possible to reconstruct the sedimentation environment, as well as to reveal specific features in the distribution of the silty-sandy rock components of the U2 formation.

Field monitoring of alluvium accumulation in the riverine floodplain of the Oka River, European Russia

Sedimentation traps were used to assess the annual surface renewal dynamics of the low floodplain of the Oka River (a major tributary of the Volga River in central European Russia). Trap-mats and platforms made of crushed bricks were installed in positions near the meandering and relatively straight riverbed, in different sedimentation environments. Stationary research in 2014–2020 covered a section of the bottom of the Oka River valley with a length of more than 400 km along the main channel. The graphical-analytical processing of field data using Ferret's Triangles and sedimentation diagrams showed that transport and deposition of suspended sediment dominated in the accumulation of 87% of alluvium samples. The formation of ripples was not recorded, which was lithologically reflected in the horizontal layering of the new sediment. The determination of the granulometric composition of the removed sediment and their thickness on the traps showed the absence of statistically significant differences according to the Kruskal–Wallis test between the data samples from the trap-mats and trap-platforms. The reference to the daily calendar of synoptic mechanisms according to the classification of Dzerdzeevsky contributed to the identification of meteorological prerequisites for the variation of the hydrograph curve of the Oka River in its middle reaches. Prolonged floods caused by the premature arrival of spring lead to massive deposition of silt and clay particles even on sandbanks. On the other hand, short (15–35 d) March floods and abnormal high water in June, caused by Atlantic cyclone intrusions, can stabilize sand accumulation on the riverine floodplain. The thickest sediment layers on the traps were obtained in 2018 after a very cold March and a powerful April flood, and the overall distribution of alluvium thickness and its particle size distribution also depends on the morphology of the riverine relief. The siltation is caused by the accumulation of silts; the most finely dispersed sediment was deposited in those facies environments for which siltation was also characteristic in historical times.

Provenance, chemical weathering, and sedimentary environment of the aquifer sediments: Implication for arsenic enrichment in groundwater

High arsenic (As) groundwater has been widely observed in the world, but the provenance, chemical weathering, and sedimentary environment of aquifer sediments hosting high As groundwater remain poorly understood. The geochemical and isotopic characteristics of high-resolution aquifer sediments were investigated to unravel the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments. The average values of rare earth elements (REEs) showed the enrichment of light REEs and flat heavy REEs in the aquifer and the Yellow River sediments. The chemical index of alteration reflected incipient and moderate weathering (41 to 71). The δ13CSOM (−27.4‰ ± 4.3‰) and C/N values (8.1 ± 5.8) indicated aquatic environment of sedimentation. Shallow aquifer sediments mostly had relatively high ΣREEs contents and negative Eu anomalies, demonstrating that the aquifer sediments were mainly derived from the Yellow River (up to 94.3% ± 5%). Deep aquifer sediments had relatively low ΣREEs contents and positive Eu anomalies, which originated from the Yinshan Mountains (up to 72.2% ± 20.4%) principally with igneous and metamorphic rocks. Moreover, recycling of the Yellow River sediments from Northeastern Tibetan Plateau enhanced the silicate weathering and increased contents of Fe/Mn oxides and As. The δ13CSOM and C/N values evidenced that organisms of paleo-lake or paleo-Yellow River were responsible for abundant sedimentary organic matter. Concentrations of Fe, Mn, and As were high in shallow groundwater from the plain. The As enrichment in the shallow groundwater was jointly controlled by the provenance and chemical weathering of the aquifer sediments (14%), sedimentary environment (10%), reductive dissolution (35%) of Fe/Mn oxides, As desorption under elevated pH (20%), and competitive adsorption of HCO3- (21%). This study systematically reveals the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments and highlights joint contributions of geochemical processes and geochemical conditions to As enrichment in groundwater.

Composition, age, and sedimentation environment of the ore-hosting Eravna series of the Udino-Vitim zone (Western Transbaikalia, Russia)

Data on the composition, age and formation conditions of the Ulzutui and Kydzhimit strata, which are combined as part of the Eravna Series of the Eravna Subzone of the Udino-Vitim Zone, are considered. The Eravna series, at least 2400 m thick, is composed of tephroturbidites with a significant amount of lavas and tuffs of felsic and intermediate compositions, with which tectonic-gravitational mixtites are spatially and genetically related. The features of the structure and composition of the Eravna series indicate the formation of sediments in an open deepening marine basin adjacent to the zone of active volcanism. For the first time, according to the Miospores, the time of formation of the Ulzutui sequence is limited to the Late Devonian – Early Carboniferous (Late Famennian – Early Tournaisian), the Kyjimite strata is limited to the Early Carboniferous (Visean) ages. At this time, the Kyjimit volcanic zone was formed. The suprasubduction nature of the zone is evidenced by the features of volcanites (predominance of acidic varieties, belonging of basalts to the tholeiitic, and dacites and rhyodacites to the calcareous-alkaline series, the presence of high-potassium rock varieties, their belonging to the K-Na type of alkalinity, very low MgO values, low and moderate TiO2 contents, high Al2O3 and K2O, enrichment of volcanogenic rocks in large-ionic lithophilic elements relatively to highly charged elements, minimum in Nb and negative values of εNd), their spatial association with monzonites (have suprasubduction features) and tephroturbidites, as well as metallogenic specialization (Cu and Zn) of the Eravna series. We believe that the ore-hosting strata for both pyrite-polymetallic Ulzutui and Ozernoe deposits is the Upper Devonian–Lower Carboniferous Eravna series.

Composition, Age, and Sedimentation Environment of the Ore-Hosting Eravna Series of the Uda–Vitim Zone (Western Transbaikalia, Russia)

Composition, Age, and Sedimentation Environment of the Ore-Hosting Eravna Series of the Uda–Vitim Zone (Western Transbaikalia, Russia)

ВЫЯВЛЕНИЕ ПАЛЕОГИДРОДИНАМИЧЕСКИХ ОБСТАНОВОК ОСАДКОНАКОПЛЕНИЯ ПО ДАННЫМ ГРАНУЛОМЕТРИЧЕСКОГО АНАЛИЗА ДОННЫХ ОТЛОЖЕНИЙ МАЛЫХ ОЗЕР ШОКШИНСКОЙ ГРЯДЫ (КАРЕЛИЯ)1

The paper examines the grain size distribution of bottom sediments of lakes in the Shoksha Ridge area, Karelia, to elucidate howdeglaciation and formation of the Onego Ice Lake basin proceeded. A sequence of bottom sediments of Lake Anashkino and two sediment sequences of Lake Rzhanoe were studied, and lithostratigraphy of the sediment cores was described. The grain size compositions of the 9.32-10.32m sequence from Lake Anashkino and the 2.5-6.52 m sequence from Lake Rzhanoye were analyzed. The study revealed features of the bottomsediment fractions distribution along the depth of occurrence. Paleo-hydrodynamic sedimentation environments were identified using grain sizeanalysis. Lake Anashkino bottom sediments of a 9.96–10.31 m horizon, represented by silt and fine-grained sand, were deposited under conditions of highly dynamic shallowing (decrease in the water level of Onego Ice Lake). The upper part of sediments (9.32–9.92 m), represented by clayey silt mixed with fine-grained sand, accumulated under weak flow conditions. Paleo-hydrodynamic sedimentationenvironments in Lake Rzhanoye were characterized by alternation of highflow conditions (5.36-6.23 m, 6.31-6.32 m, 6.47-6.48 m) and weak flowconditions (2.50-4.88 m, 6.28-6.29 m, 6.30-6.31 m, 6.37-6.45 m, 6.51-6.52 m). This is possibly due to the dynamics of the decrease in the waterlevel of Onego Ice Lake and the formation of small isolated lakes.In the process of the formation of bottom sediments of small lakes of the Shoksha Ridge during the period of intensive changes in thelandscapes, outlines and levels of Onego Ice Lake at the transition from the late Pleistocene to Holocene, against a shift from nival to humid climate,we note a change in sedimentation conditionsin the bottom sediments of the two studied lakes – Anashkino and Rzhanoe – from highly dynamic(flowing conditions, decrease in water level of Onego Ice Lake) to weakly flowing, in the conditions of isolation of the lakes and formation ofmodern small lakes.

Sedimentation Processes and the Holocene Evolution of the Indigirka Paleovalley (Coastal Shelf Area of the East Siberian Sea)

Problems of the paleogeographical evolution and changes in sedimentation environment within the Indigirka River paleovalley (the East Siberian Sea) are discussed. Based on the results of geophysical and geological research and a high-resolution study of sediment cores (grain size analysis, geochemistry, macro- and micropaleontology, pollen analysis, radiocarbon dating) the development of the Holocene marine transgression has been reconstructed, sedimentation rates have been calculated, and the basic principles of changes in sedimentation processes have been established.

ANALYSIS OF BUILDING A FACIES MODEL OF A RESERVOIR USING THE RESULTS OF INTERPRETATION OF SEISMIC DATA

Forecasting changes in the characteristics of sediment properties is an urgent task at all stages of exploration and development of deposits. Remote sensing techniques for sediment research, such as seismic surveys, are now becoming a prerequisite for a full study of the study area. The problems that need to be solved are not limited to the construction of a structural-tectonic model. It is necessary to look for opportunities to predict filtration and capacitance properties (PP) in the interwell space. This will improve the quality of forecasting reservoir development zones for complex reservoirs, which will result in optimization of production drilling and reduction in the risks of drilling unproductive wells. The deposits considered in this work are represented by terrigenous sediments. When developing oil-saturated intervals, water and gas breakthroughs are expected, which are especially typical for high-permeability intervals. The commercial characteristics of sediments depend on many factors, including formation conditions. Knowledge of the sedimentation environment greatly facilitates the task of predicting reservoir rocks at all stages of field development.The paper presents the results of constructing a facies model using the results of inversion transformations of seismic surveys and interpretation of GIS (geophysical surveys in wells). When creating a facies distribution model, a probabilistic assessment of the presence of a particular facies in the study area was used.In previous works, the facies model was accepted conceptually. Its influence on the final geological model and assessment of hydrocarbon reserves was indirect. The facies model presented in the article does not conceptually contradict the previously accepted one. That is, the concept of sediment formation has been preserved, but its influence on the geological model has changed. This allows you to more accurately display the geological structure of layers and optimize technological solutions when developing an operational facility.After the work was completed, more than thirty-five wells were drilled. Based on the results of the assessment of new wells, the percentage of confirmation of the forecast of facies distribution along the wellbore with the actual data of new drilling (facies identification according to GIS data) is more than 60–65 % for the entire study area.

Investigating the reservoir quality of the Early Triassic succession with a new perspective on diagenesis and sequence stratigraphy in the center of the Persian Gulf, South Pars

The central part of the Persian Gulf has one of the largest gas fields in the world. This field was formed during the formation of the Neo-Tethys Sea and the Permo-Triassic period. In this research, the Earlier Triassic part of this area has been studied in Well A. The Earlier Triassic gas field in the Iranian part is called the Kangan Formation and is equivalent to the upper part of the Khuff Formation in the Arabian plate. This research is based on the petrography studies, diagenesis processes, and sequence stratigraphy with the help of core analysis data and petrophysical data (full suite logs). The main goal of this research is to evaluate the reservoir quality and classify the production potential of gas reservoirs by relating the two-variable diagrams of Permeability versus porosity and their expansion in the Earlier Triassic of the region. The studies showed that the reservoir properties of the Kangan Formation were formed under the influence of various factors: Sedimentation processes, regional tectonics, diagenesis processes, and their sequence. The sedimentation processes have been created under the influence of the sedimentation environment and the transgressive-regressive of the sea in different sequences. Each environment has different reservoir properties depending on its energy, depth, salinity, oxygen and organisms. In the studied area, 12 diagenesis processes in several diagenesis areas such as meteoric vadose, marine phreatic, meteoric, and a combination of them along with eight cement and eight types of porosity with different effects on reservoir quality were identified and the limits of each were specified. In the studied area, based on petrographic studies, the third and fourth-order sequences were determined and the reservoir quality was accurately determined by the system tracts of the third and fourth-order sequences and their location were determined. Finally, the reservoir quality of the Kangan Formation was determined based on a set of reservoir potentials in diagenesis processes (porosity and permeability) and according to the sequence stratigraphy of the region. In addition, their results were compared with the results of petrophysical logs, water, and gas saturation. Then, permeable and extractable areas and impermeable and non-reservoir areas of the Kangan Formation were determined. This research showed that the Earlier Triassic sequence in the central part of the Persian Gulf could be divided into four zones, zone one and three, which have non-reservoir potential and are mostly evaporitic and mudstone. Zones two and four have reservoir potential and often have dolomite and grainstone facies in the environment of the central shoal and the active tidal zone.

Mechanisms and Operational Strategies of Multi-Lateral Steam-Assisted Gravity Drainage (SAGD) for Heterogeneous Reservoirs

As the SAGD steam chamber and production performance in heavy oil reservoirs under fluvial sedimentation environment are heavily impacted by reservoir heterogeneity, an innovative strategy was proposed in this study coupling rock dilation and multi-lateral wells in SAGD projects to break the mud barriers and achieve uniform steam chamber growth. True tri-axial experiments and numerical simulation were designed to validate the feasibility of this strategy, based on which the branches of the SAGD well pairs were designed and the operational parameters were optimized for different geologic heterogeneity conditions. The tri-axial experiment results indicate that the rock formations in the heavy oil reservoirs of the F oilfield exhibit significant shear dilation effects under low confinement pressure conditions, with a volumetric dilation capacity of up to 7%. The branches should be deployed in an interleaved manner, with a horizontal displacement of 20 m and a vertical displacement of 6 m. The optimal results are achieved when the branches intersect the interbeds, allowing for enhanced steam chamber conformance and enlarged volume. Dilation zones of 3–8 m can be created above the steam-injection horizontal wells and around the branches in the reservoir during the dilation of SAGD steam chambers. The maximum volume of dilation fluid used for hydraulic dilation is suggested to be less than 2000 m3. This strategy has been validated as being successful in the pilot SAGD well pair in the F oilfield, China, with the SAGD preheating time reduced by 50% and an incremental oil rate of 4.5 tones/day, indicating encouraging potentials in similar heavy oil reservoirs.

Sulfate sources, biologic cycling, and mobility in Atacama Desert soils revealed by isotope signatures

A set of 55 surface samples from Atacama Desert gypsisols was collected along four altitude transects and analyzed for ∆17OSO4, δ18OSO4, δ34SSO4, and 87Sr/86Sr in order to identify the main depositional mechanisms and quantify the proportional contribution of sulfate sources across the desert's main topographic units – the Coastal Cordillera, the Central Depression, and the Precordillera. Sulfate deposited at any location in the Atacama Desert may derive from up to five different source and process endmembers that can principally be identified by their isotopic composition. Three aerosol sources dominate sulfate deposition and accumulation in gypsisols throughout the Atacama. These are secondary atmospheric Ca- and Na-sulfate derived from global volcanic SO2 oxidized by ozone and its derivates, and a marine sulfate aerosol that is roughly a 9:1 mixture of sea salt (primary) sulfate from evaporated sea spray, and secondary non-sea salt sulfate, i.e., dimethyl sulfide (DMS) mainly oxidized by ozone. These marine sources dominate sulfate deposition in the Coastal Cordillera. Unlike in most places on Earth, the positive mass-independent ∆17OSO4 signature of secondary atmospheric sulfate is ubiquitous in Atacama Desert soils and is never completely erased by biologic cycling. Hence, biologic cycling of the sulfate inventory – i.e., the reduction of sulfate, subsequent oxygen isotope exchange with water, and re-oxidation – is apparently not quantitative in any of the Atacama Desert environments sampled here, including the most biologically active permanent salt lakes. The preservation of highest ∆17OSO4 values (∼ 1.0‰) at altitudes of the Coastal Cordillera above the 1200 m altitude cut-off level of fog advection suggest that episodic rainfall events are insufficient for significant in situ biologic sulfate turnover. At lower altitudes and regular fog advection, moisture supply appears to be sufficient for limited in situ biologic sulfate turnover. Overall, biologically recycled sulfate constitutes a fourth major contributor to the desert's gypsisol sulfate inventory. This may comprise fluvially redeposited sulfate from older sediments, particularly on the debris fans protruding from the Precordillera into the Central Depression. In the Central Depression, Sr-isotopes may allow for a further distinction between redeposition-dominated and aerosol-dominated sedimentation environments. On the Precordillera, rainfall and run-off provide sufficient moisture for significant but still incomplete in situ biologic sulfate cycling. Hydrothermal non-evaporitic Na-sulfate – the fifth potential source – likely originates from larger outflow events or mobilization from rock veins over the course of the Atacama's geologic history may contribute locally to the sulfate inventory. The degree of bio-cycling and mobility of sulfate likely reflects a balance between overall water availability and the mixing proportion of very soluble (mobile) Na-sulfate and less soluble Ca-sulfate inherent in the various sulfate sources.