Search Results (205)

Due to the complex mineral composition, low clay content, and strong heterogeneity of the mixed sedimentary shale in the Xinjiang Salt Lake Basin, the wettability characteristics of the reservoir and their influencing factors are not yet clear, which restricts the evaluation of oil-bearing properties and the identification of sweet spots. This paper analyzed mixed sedimentary shale samples from the Lucaogou Formation of the Jimsar Sag and the Fengcheng Formation of the Mahu Sag. Methods such as petrographic thin sections, X-ray diffraction, organic matter content analysis, and argon ion polishing scanning electron microscopy were used to examine the lithological and mineralogical characteristics, geochemical characteristics, and pore space characteristics of the mixed sedimentary shale reservoir. Alternating imbibition and nuclear magnetic resonance were employed to quantitatively characterize the wettability of the reservoir and to discuss the effects of compositional factors, lamina types, and pore structure on wettability. Research findings indicate that the total porosity, measured by the alternate imbibition method, reached 72% of the core porosity volume, confirming the effectiveness of alternate imbibition in filling open pores. The Lucaogou Formation exhibits moderate to strong oil-wet wettability, with oil-wet pores predominating and well-developed storage spaces; the Fengcheng Formation has a wide range of wettability, with a higher proportion of mixed-wet pores, strong heterogeneity, and weaker oil-wet properties compared to the Lucaogou Formation. TOC content has a two-segment relationship with wettability, where oil-wet properties increase with TOC content at low TOC levels, while at high TOC levels, the influence of minerals such as carbonates dominates; carbonate content shows an “L” type response to wettability, enhancing oil-wet properties at low levels (<20%), but reducing it due to the continuous weakening effect of minerals when excessive. Lamina types in the Fengcheng Formation significantly affect wettability differentiation, with carbonate-shale laminae dominating oil pores, siliceous laminae contributing to water pores, and carbonate–feldspathic laminae forming mixed pores; the Lucaogou Formation lacks significant laminae, and wettability is controlled by the synergistic effects of minerals, organic matter, and pore structure. Increased porosity strengthens oil-wet properties, with micropores promoting oil adsorption through their high specific surface area, while macropores dominate in terms of storage capacity. Wettability is the result of the synergistic effects of multiple factors, including TOC, minerals, lamina types, and pore structure. Based on the characteristic that oil-wet pores account for up to 74% in shale reservoirs (mixed-wet 12%, water-wet 14%), a wettability-targeted regulation strategy is implemented during actual shale development. Surfactants are used to modify oil-wet pores, while the natural state of water-wet and mixed-wet pores is maintained to avoid interference and preserve spontaneous imbibition advantages. The soaking period is thus compressed from 30 days to 3–5 days, thereby enhancing matrix displacement efficiency. Full article

In tight sandstone gas reservoirs, proppant flowback severely limits stable gas production. This study uses laboratory flowback experiments and field analyses of the ShaXimiao tight sandstone in the Wenxing gas area to investigate the mechanisms controlling sand production. The experiments show that displacing fluid viscosity significantly affects the critical sand-flow velocity: with high-viscous slickwater (5 mPa·s), the critical velocity is 66% lower than with low-viscous formation water (1.15 mPa·s). The critical velocity for coated proppant is three times that of the mixed quartz sand and coated proppant. If the confining pressure is maintained, but the flow rate is further increased after the proppant flowback, a second instance of sand production can be observed. X-ray diffraction (XRD) tests were conducted for sand produced from practical wells to help find the sand production reasons. Based on experimental and field data analysis, sand production in Well X-1 primarily results from proppant detachment during rapid shut-in/open cycling operations, while in Well X-2, it originates from proppant crushing. The risk of formation sand production is low for both wells (the volumetric fraction of calcite tested from the produced sands is smaller than 0.5%). These findings highlight the importance of fluid viscosity, proppant consolidation, and pressure management in controlling sand production. Full article

This work uses the MATLAB Reservoir Simulation Toolbox (MRST) to reduce the 3D reservoir model into a 2D version in order to investigate CO₂ storage in the Aurora model using the vertical equilibrium (VE) model. For this purpose, we used an open-source reservoir simulator, MATLAB Reservoir Simulation Toolbox (MRST). MRST is an open-source reservoir simulator, with supplementary modules added to enhance its versatility in addition to a core set of procedures. A fully implicit discretization is used in the numerical formulation of MRST-co2lab enabling the integration of simulators with vertical equilibrium (VE) models to create hybrid models. This model is then compared with the Eclipse model in terms of properties and simulation results. The relative permeability of water and gas can be compared to verify that the model fits the original Eclipse model. Comparing the fluid viscosities used in MRST and Eclipse also reveals comparable tendencies. However, reservoir heterogeneity is the reason for variations in CO₂ plume morphologies. The upper layers of the Eclipse model have lower permeability than the averaged MRST model, which has a substantial impact on CO₂ transport. According to the study, after 530 years, about 17 MT of CO₂ might be stored, whereas 28 MT might escape the reservoir, since after 530 years CO₂ plume reaches completely the open northern boundary. Additionally, a sensitivity analysis study has been conducted on permeability, porosity, residual gas saturation, rock compressibility, and relative permeability curves which are the five uncertain factors in this model. Although plume migration is highly sensitive to permeability, porosity, and rock compressibility variation, it shows a slight change with residual gas saturation and relative permeability curve in this study. Full article

Based on drilling, core and seismic data, combined with the regional tectonic sedimentary evolution background, the sedimentary environment of the Triassic carbonate rocks in the Mangeshlak Basin was studied. A sedimentary facies model of this set of carbonate rocks was established. Research has shown that the Mangeshlak Basin underwent a complete large-scale marine transgression–regression sedimentary evolution process during the Triassic. During the early to middle Triassic, seawater gradually invaded the northwest region of the basin from northwest to southeast and gradually regressed in the late Middle Triassic. In the lower part of the Triassic carbonate rocks, the primary components are developed granular limestone or dolomite with oolitic structures, interspersed with a small amount of thin mudstone, which is a good reservoir; the upper part of the Triassic is mainly composed of sedimentary mudstone and mudstone, which can form good sealings. The hill-shaped reflections of the platform edge facies, along with the high-frequency, strong-amplitude, and moderately continuous reflections within the restricted platform interior, are clearly visible on the seismic profile. These features are consistent with the sedimentary environment and lithofacies characteristics revealed by drilling data along the profile. Drilling and seismic data revealed that the sedimentary environment of the early and middle Triassic in the basin is mainly composed of shallow water platform edges and restricted platforms, as well as carbonate rock slopes and open non-marine shelves in deep water areas. A sedimentary facies model of the Triassic carbonate rock segment in the basin was established, comprising restricted platforms, platform edges, carbonate rock slopes, and non-marine shelves. Unlike the modified Wilson marginal carbonate rock platform model, the carbonate rock platform edge in the Mangeshlak Basin does not develop reef facies. Instead, it is mainly composed of oolitic beach (dam) sediments, making it the most favorable sedimentary facies zone for the Triassic reservoir development in the basin. Full article

Soils serve as critical carbon reservoirs, playing an essential role in climate change mitigation and agricultural sustainability. Accurate soil property determination relies on soil spectral reflectance data from Earth observation (EO), but current vegetation models often oversimplify soil conditions. This study introduces a novel approach that combines radiative transfer models (RTMs) with open-access soil spectral libraries to address this challenge. Focusing on conditions of low soil moisture content (SMC), photosynthetic vegetation (PV), and non-photosynthetic vegetation (NPV), the coupled Marmit–Leaf–Canopy (MLC) model is used to simulate early crop growth stages. The MLC model, which integrates MARMIT and PRO4SAIL2, enables the generation of mixed soil–vegetation scenarios. A simulated EO disturbed soil spectral library (DSSL) was created, significantly expanding the EU LUCAS cropland soil spectral library. A 1D convolutional neural network (1D-CNN) was trained on this database to predict Soil Organic Carbon (SOC) content. The results demonstrated relatively high SOC prediction accuracy compared to previous approaches that rely only on RTMs and/or machine learning approaches. Incorporating soil moisture content significantly improved performance over bare soil alone, yielding an R² of 0.86 and RMSE of 4.05 g/kg, compared to R² = 0.71 and RMSE = 6.01 g/kg for bare soil. Adding PV slightly reduced accuracy (R² = 0.71, RMSE = 6.31 g/kg), while the inclusion of NPV alongside moisture led to modest improvement (R² = 0.74, RMSE = 5.84 g/kg). The most comprehensive model, incorporating bare soil, SMC, PV, and NPV, achieved a balanced performance (R² = 0.76, RMSE = 5.49 g/kg), highlighting the importance of accounting for all surface components in SOC estimation. While further validation with additional scenarios and SOC prediction methods is needed, these findings demonstrate, for the first time, using radiative-transfer simulations of mixed vegetation-soil-water environments, that an EO-DSSL approach enhances machine learning-based SOC modeling from EO data, improving SOC mapping accuracy. This innovative framework could significantly improve global-scale SOC predictions, supporting the design of next-generation EO products for more accurate carbon monitoring. Full article

To address the challenges of water coning and early water breakthrough commonly encountered during the development of bottom-water gas reservoirs, this study establishes a fully coupled numerical simulation model integrating a horizontal wellbore, inflow control device (ICD) screens, and a zonal water control system. A novel “dual inflow performance index” method is introduced for the first time, enabling separate calculation of the pressure drops induced by gas and water phases flowing through the ICDs, thereby improving the accuracy of pressure simulations throughout the production lifecycle. The model divides the entire production system into four physically distinct subsystems, the bottom-water gas reservoir, ICD screens, production compartments, and the horizontal wellbore, which are dynamically coupled through transient interflow exchange. Based on geological parameters from the SPE10 dataset, the model simulates realistic production scenarios. The results show that the proposed model accurately captures the time-dependent increase in ICD pressure drop as fluid properties evolve during production. Moreover, the zonal water control method outperforms the single ICD-based control strategy in water control performance, achieving a 23% reduction in cumulative water production. Additionally, the water control intensity of the ICD screens increases nonlinearly with the reduction in the number of openings. In highly heterogeneous reservoirs with significant permeability contrast, effective suppression of water coning can only be achieved by setting a minimal number of openings in the high-permeability compartments, resulting in up to a 15% reduction in cumulative water production. The timing of production compartment shutdown exerts a significant influence on water control performance. The optimal strategy is to first identify the water breakthrough point through unconstrained production simulation as production with all eight ICD screen openings fully open and then shut down the high-permeability production compartment around this critical time. This approach can suppress cumulative water production by up to 27%. Overall, the proposed model offers a practical and robust tool for optimizing completion design and water control strategies in complex bottom-water gas reservoirs. Full article

Rapid rises in water levels due to heavy rainfall can lead to the accumulation of floating debris, posing significant challenges for both water quality and resource management. However, real-time monitoring of floating debris remains difficult due to the discrepancy between meteorological conditions and the timing of debris accumulation. To address this limitation, this study proposes an amplitude change detection (ACD) model based on time-series synthetic aperture radar (SAR) imagery, which is less affected by weather conditions. The model statistically distinguishes floating debris from open water based on their differing scattering characteristics. The ACD approach was applied to 18 pairs of Sentinel-1 SAR images acquired over Daecheong Reservoir from June to September 2024. A stringent type I error threshold (α < 1 × 10⁻⁸) was employed to ensure reliable detection. The results revealed a distinct cumulative effect, whereby the detected debris area increased immediately following rainfall events. A positive correlation was observed between 10-day cumulative precipitation and the debris-covered area. For instance, on 12 July, a floating debris area of 0.3828 km² was detected, which subsequently expanded to 0.4504 km² by 24 July. In contrast, on 22 August, when rainfall was negligible, no debris was detected (0 km²), indicating that precipitation was a key factor influencing the detection sensitivity. Comparative analysis with optical imagery further confirmed that floating debris tended to accumulate near artificial barriers and narrow channel regions. Overall, this study demonstrates that this spatial pattern suggests the potential to use detection results to estimate debris transport pathways and inform retrieval strategies. Full article

Glaciers, often regarded as “frozen reservoirs”, play a crucial role in replenishing numerous rivers in arid regions, contributing to ecological balance and managing river flow. Recently, the rapid shrinkage of the glaciers in the East Tianshan Mountains has affected the water quantity in the Karez system. However, studies on glacier changes in this region are limited, and recent data are scarce. This study utilizes annual Landsat composite images from 1990 to 2022 obtained via the Google Earth Engine (GEE). It utilizes a ratio threshold approach in conjunction with visual analysis to gather the glacier dataset specific to the Turpan–Hami region. The Open Global Glacier Model (OGGM) is used to model the flowlines and mass balance of around 300 glaciers. The study analyzes the glacier change trends, distribution characteristics, and responses to climate factors in the Turpan–Hami region over the past 30 years. Additionally, future glacier changes through the end of the century are projected using CMIP6 climate data. The findings indicate that the following: (1) From 1990 to 2022, glaciers in the research area underwent considerable retreat. The total glacier area decreased from 204.04 ± 0.887 km² to 133.52 ± 0.742 km², a reduction of 70.52 km², representing a retreat rate of 34.56%. The number of glaciers also decreased from 304 in 1990 to 236 in 2022. The glacier length decreased by an average of 7.54 m·a⁻¹, with the average mass balance at −0.34 m w.e.·a⁻¹, indicating a long-term loss of glacier mass. (2) Future projections to 2100 indicate that under three climate scenarios, the area covered by glaciers could diminish by 89%, or 99%, or even vanish entirely. In the SSP585 scenario, glaciers are projected to nearly disappear by 2057. (3) Rising temperatures and solar radiation are the primary factors driving glacier retreat in the Turpan–Hami area. Especially under high emission scenarios, climate warming will accelerate the glacier retreat process. Full article

Abandoned mines represent an innovative and under-exploited resource to meet current energy challenges, particularly because of their geothermal potential. Flooded open-pits, such as those located in the Thetford Mines region (Eastern Canada), provide large, thermally stable water reservoirs, ideal for the use of geothermal cooling systems. Thermal short-circuiting that can impact the system performance affected by both free and forced convective heat transfer is hard to evaluate in these large water reservoirs subject to various heat sink and sources. Thus, this study’s objective was to evaluate the impact of natural heat transfer mechanisms on the performance of an open-loop geothermal system that could be installed in a flooded open-pit mine. Energy needs of an industrial plant using water from the flooded Carey Canadian mine were considered to develop a 3D numerical finite element model to evaluate the thermal impact associated with the operation of the system considering free and forced convection in the flooded open-pit, the natural flow of water into the pit, climatic variations at the surface and the terrestrial heat flux. The results indicate that the configuration of the proposed system meets the plant cooling needs over a period of 50 years and can provide a cooling power of approximately 2.3 MW. The simulations also demonstrated the importance of understanding the hydrological and hydrogeological systems impacting the performance of the geothermal operations expected in a flooded open-pit mine. Full article

A study was conducted concerning the perceptions of a future reservoir (4.7–8.9 square kilometres, 42.2 million cubic metres) by residents, tourists, and visitors; the location in question was the former Kotlarnia sand pit in the catchment area of the Bierawka River (tributary of the Oder River in southern Poland). Divergent concepts for the reclamation and development of the former sand pit emerged; the construction of a reservoir was initially the dominant option but was eventually abandoned despite it having the greatest acceptance among the respondents (out of the 134 respondents, 43.3% favoured the creation of a water reservoir, 29.9% favoured introducing nature protection arrangements in the area to enable spontaneous nature regeneration, and 16.4% favoured reforestation). A clear discrepancy arose between the public’s expectations related to the reclamation and development of the former sand pit in order to create a reservoir and the official position of the land user and administrator of the potential reservoir, which indicated that it no longer intended to create such a reservoir. This study indicates that in the process of developing concepts related to the reclamation and development of former mineral workings, it is essential to obtain the results of public consultation based on a diagnostic survey conducted among representatives of the local community. This is an effective tool for predicting the optimal use of sites regenerated after the damage caused by open-pit mining provided that all technical considerations related to the planned project are taken into account in advance. Full article

This paper presents a study of the thermal structure, circulation, and mixing processes in an inland water body by taking into account horizontal heterogeneity using a three-dimensional thermohydrodynamics model. The object of this study was the Rybinsk Reservoir, a large inland water body with complex morphology. Field measurement data and ERA5 reanalysis data, as well as a three-dimensional numerical model (which is a development by the authors of this article), were used in this research. The results of the numerical experiments show that three-dimensional numerical modeling, which explicitly takes into account the contribution of seiche oscillations, allows us to describe the temperature distribution in a water body with sufficient accuracy, and this plays a fundamental role in studies of inland water objects. The obtained results could be useful for a model representation of the biochemical processes occurring in lakes and reservoirs. Thus, for models of less spatial detail that are, for example, used to hlrepresent lakes in Earth system models, it is necessary to take into account seiches in the form of parameterizations. Full article

Artificial reservoirs formed by hydroelectric dams are young ecosystems requiring water quality monitoring, as they often serve local populations. Traditionally, this is performed through hydrochemical and sanitary assessments, alongside phytoplankton composition analysis. This study aimed to assess the seasonal dynamics of microbial communities—both bacterioplankton and microeukaryotes including phytoplankton—in the Irkutsk Reservoir (IR), which is fed by the cold oligotrophic waters of Southern Baikal (SB). Using parallel metabarcoding of 16S and 18S rRNA gene fragments, we analyzed community composition during the open-water season and evaluated the ecological connectivity between these two freshwater systems. We demonstrated that seasonal changes in microeukaryotic communities were closely linked between SB and IR, with the greatest divergence observed in early summer and progressive convergence by autumn. Metabarcoding confirmed microscopy-based observations while providing higher taxonomic resolution and detecting otherwise overlooked groups. Bacterioplankton communities also exhibited seasonal variation and were shaped by environmental gradients and reservoir characteristics. Cyanobacteria peaked in SB in late summer but did not dominate communities, unlike in mesotrophic lowland reservoirs. These findings demonstrate the value of metabarcoding for freshwater monitoring and provide new insights into microbial community dynamics in river–reservoir systems influenced by oligotrophic lake inflow. Full article

After hydraulic fracturing, hydraulic fractures and opened beddings are intertwined, which results in a complex fracture network in shale oil reservoirs. In addition, the migration of multi-phase fluids during fracturing and shut-in processes leads to complex flowback performance and brings difficulty to flowback strategies optimization. In this paper, taking the Daqing Gulong shale reservoir as an example, a numerical model, which considers oil–water–gas three-phase flow and the orthogonal fracture network, has been established for flowback period. The characteristics and influencing factors of flowback performance have been deeply studied, and the flowback modes of shale oil are reasonably optimized. Geological factors such as PTPG (pseudo-threshold pressure gradient), matrix permeability, and engineering factors such as opened bedding stress sensitivity, opened bedding permeability, and fracturing fluid distribution have obvious effects on the flowback performance, resulting in significant variations in production peaks, high production periods, and decline rates. Furthermore, three flowback modes distinguished by the BHP (bottom hole pressure) correspond to the three types of choke mode that have been optimized. This study reveals the main factors affecting the flowback performance. Meanwhile, the optimization method can be applied to optimize flowback strategies in Gulong and other similar shale reservoirs to obtain higher shale oil production. Full article

The accelerated expansion of urban areas has significantly increased the complexity of managing water distribution systems. Network sectorization into smaller, independently controlled areas is often highlighted as an important measure to enhance operational security and reduce water losses in networks. However, identifying the optimal sectorization strategy is challenging due to the vast number of possible combinations, and existing methods still present practical limitations. This study proposes a hybrid model for the optimal design of district-metered areas in water distribution systems. The methodology combines graph theory, the Dijkstra shortest path algorithm (DSP), and the meta-heuristic binary particle swarm optimization (BPSO) algorithm. Structuring the topology of the water distribution network using graphs allows the identification of existing connections between the network components. By DSP, the shortest paths from the reservoir to the consumption points were determined, while the proposed BPSO sought the best combination of pipe conditions (open or closed) while meeting the constraint conditions. The application of the model to three real water distribution systems in João Pessoa, in northeastern Brazil, demonstrated its efficiency in sectorization projects, providing optimal solutions that meet the imposed constraints. The results highlight the model’s potential to optimize costs and enhance decision-making in water utility projects. Full article

Sustainable water management requires integrated approaches balancing competing demands and environmental sustainability. This study introduces the Sustainable Water Optimization Tool (SUWO), an open-source, Python-based simulation-optimization framework for basin-scale surface-water-resources management. SUWO employs the water–energy–food–ecosystem (WEF-E) nexus approach, utilizing a multi-objective genetic algorithm (MOGA) to generate Pareto-optimal solutions and facilitate a trade-off analysis among water uses through simulations of reservoir operations, hydro-energy production, irrigation, and flow regulation. SUWO integrates scenario analysis with multi-criteria decision making (MCDM), enabling the evaluation of various management, climate, and environmental scenarios. The framework was applied to the Sakarya River Basin (SRB) in Türkiye, a rapidly developing region pressured by water infrastructure development, hydroelectric power plants (HEPPs), and irrigation expansion. The SUWO-SRB model showed that while Non-dominated Sorting Genetic Algorithm II (NSGA-II) generally exhibited superior performance, NSGA-III presented a competitive alternative. The optimization results were analyzed across four management scenarios under varying hydrological conditions and environmental management classes (EMCs) for the near future. The model results highlight WEF-E nexus trade-offs. Maximizing energy production often impacts irrigation and the ecosystem, while prioritizing sustainable irrigation can reduce energy output. Dry conditions reduce hydropower and irrigation capacity, emphasizing water scarcity vulnerabilities. Ecological deviation negatively correlates with anthropogenic factors. Full article