Search Results (114)

Nuclear power is a low-emission and economically competitive energy source, yet the effective disposal and management of its associated radioactive waste can be challenging. Radioactive waste can be categorised as high-level waste (HLW), intermediate-level waste (ILW), and low-level waste (LLW). LLW primarily comprises materials contaminated during routine clean-up, such as mop heads, paper towels, and floor sweepings. While LLW is less radioactive compared to HLW and ILW, the management of LLW poses significant challenges due to the large volume that requires processing and disposal. The volume of LLW can be significantly reduced through sorting, which is typically performed manually in a labour-intensive way. Smart management techniques, such as computer vision (CV) and machine learning (ML), have great potential to help reduce the workload and human errors during LLW sorting. This paper provides a comprehensive review of previous research related to LLW sorting and a summative review of existing applications of CV in solid waste management. It also discusses state-of-the-art CV and ML algorithms and their potential for automating LLW sorting. This review lays a foundation for and helps facilitate the applications of CV and ML techniques in LLW sorting, paving the way for automated LLW sorting and sustainable LLW management. Full article

Reservoir heterogeneity, fluid property variations, and permeability contrasts across different geological layers result in significant disparities in water absorption capacities during oilfield development, often leading to premature water breakthrough, uneven sweep efficiency, and suboptimal waterflooding outcomes. The accurate determination of layer-specific water injection volumes is critical to addressing these challenges. This study focuses on a study area in China, employing comprehensive on-site investigations to evaluate the current state of layered water injection practices. The injection allocation strategy was optimized using a hybrid approach combining the splitting coefficient method and grey correlation analysis. Key challenges identified in the study area include severe reservoir heterogeneity, poor injection–production correspondence, rapid water cut escalation, and low recovery rates. Seven dominant influencing factors—the sedimentary microfacies coefficient, effective thickness, stimulation factor, well spacing, permeability, connectivity, and permeability range coefficient—were identified through grey correlation analysis. Field application of the proposed method across fourteen wells demonstrated significant improvements: a monthly oil production increase of 40 tons, a water production reduction of 399.24 m³/month, and a 2.45% decline in the water cut. The obtained results substantiate the method’s capability in resolving interlayer conflicts, optimizing oil recovery performance, and effectively controlling water channeling problems. Full article

In order to improve oil recovery efficiency in low-permeability reservoirs, this study developed amphiphilic Janus-SiO₂ nanoparticles to prepare polymer gel microspheres for enhanced oil recovery (EOR). Firstly, Janus-SiO₂ nanoparticles were synthesized via surface modification using (3-aminopropyl)triethoxysilane and α-bromoisobutyryl bromide. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) characterization confirmed the successful grafting of amino and styrene chains, with the particle size increasing from 23.8 nm to 32.9 nm while maintaining good dispersion stability. The Janus nanoparticles exhibited high interfacial activity, reducing the oil–water interfacial tension to 0.095 mN/m and converting the rock surface wettability from oil-wet (15.4°) to strongly water-wet (120.6°), thereby significantly enhancing the oil stripping efficiency. Then, polymer gel microspheres were prepared by reversed-phase emulsion polymerization using Janus-SiO₂ nanoparticles as emulsifiers. When the concentration range of nanoparticles was 0.1–0.5 wt%, the particle size range of polymer gel microspheres was 316.4–562.7 nm. Polymer gel microspheres prepared with a high concentration of Janus-SiO₂ nanoparticles can ensure the moderate swelling capacity of the particles under high-temperature and high-salinity conditions. At the same time, it can also improve the mechanical strength and shear resistance of the microspheres. Core displacement experiments confirmed the dual synergistic effect of this system. Polymer gel microspheres can effectively plug high-permeability zones and improve sweep volume, while Janus-SiO₂ nanoparticles enhance oil displacement efficiency. Ultimately, this system achieved an incremental oil recovery of 19.72%, exceeding that of conventional polymer microsphere systems by more than 5.96%. The proposed method provides a promising strategy for improving oil recovery in low-permeability heterogeneous reservoir development. Full article

Studies have demonstrated that heavy oil flow exhibits threshold pressure gradient (TPG) which is closely related to the permeability and viscosity of the crude oil. Also, long-term water flooding continuously alters unconsolidated sandstone reservoir permeability through water flushing. These combined effects significantly influence water flooding performance. Therefore, in this paper, a comprehensive oil–water two phase mathematical model is developed for waterflooded heavy oil unconsolidated sandstone reservoirs based on the traditional black oil model, incorporating both time-varying permeability and threshold pressure gradient. The water-flooding-dependent threshold pressure gradient is firstly proposed, accounting for time-varying permeability. Subsequently, a simulator is developed with finite volume and Newton iteration method. Good agreement is obtained with the commercial simulator based on traditional black oil model. Afterward, the influence of permeability time variation and threshold pressure gradient is analyzed in detail. Results demonstrate that the threshold pressure gradient and time-varying permeability both decrease the oil recovery. The threshold pressure gradient (TPG) reduces the oil flow region and displacement efficiency since production. The increases in permeability after long term water flooding exacerbate reservoir heterogeneity and reduce sweep efficiency. The lowest oil recovery is observed when non-Darcy flow and permeability time variation are considered simultaneously. Furthermore, the time-varying threshold pressure gradient is observed with permeability time variation. Finally, a field data history matching was successfully performed, demonstrating the practical applicability of the proposed model. This new model better aligns with reservoir development characteristics. It can provide a theoretical guide for the development of heavy oil reservoirs. Full article

The escalating thermal demands of high-power electronic devices and energy systems necessitate advanced thermal management solutions. Flow boiling in small/micro channels has emerged as a promising approach, yet its practical implementation is hindered by flow instabilities and heat transfer deterioration under high-heat fluxes. This study presents a systematic numerical investigation of subcooled boiling flow and heat transfer in a rectangular small channel under high-heat-flux conditions, employing the VOF method coupled with the Lee phase change model. The increasing heat flux accelerates bubble nucleation and coalescence while reduced mass flux promotes early local slug formation, shifting flow transitions upstream and degrading thermal performance. A local vapor volume fraction threshold of α_ν = 0.2 is identified for the bubbly-to-sweeping flow transition and α_ν = 0.4 for the sweeping-to-churn transition. Furthermore, a novel dimensionless parameter β is proposed to classify dominant flow regimes, with critical β ranges of 12–16 and 24–32 corresponding to the two transitions, respectively. These findings provide new quantitative tools for identifying flow regimes and improve the understanding and design of compact boiling-based thermal management systems under extreme heat- flux conditions. Full article

Fractured vuggy reservoirs exhibit intricate fracture networks, where large fractures impose significant shielding effects on smaller ones, posing formidable challenges for efficient exploitation. A systematic evaluation of foaming volume, drainage half-life, decay behavior, and viscosity under varying temperatures and salinities was conducted for conventional foam, polymer-enhanced foam, and gel foam. The results yield the following conclusions: Compared to conventional foam, polymer-enhanced foam exhibits markedly improved stability. In contrast, gel foam, cross-linked with chemical agents, maintains stability for over one week at elevated temperatures, albeit at the expense of reduced foaming capacity. The three-dimensional network structure formed post-gelation enables gel foam to retain a thicker liquid film, exhibiting exceptional foam stability. As salinity increases, the base liquid viscosity of conventional foam remains largely unaffected, whereas polymer foam shows marked viscosity reduction. Gel foam displays a non-monotonic viscosity response—initially increasing due to ionic cross-linking and subsequently declining from excessive charge screening. All three systems exhibit significant viscosity decreases under high-temperature conditions. Visualized plate fracture model experiments revealed distinct flow patterns and mobility control performance; narrow fractures exacerbate bubble coalescence under shear stress, leading to enlarged bubble sizes and diminished plugging efficiency. Among the three systems, gel foam exhibited superior mobility control characteristics, with uniform bubble size distribution and enhanced stability. Integrating the findings from the foam mobility control experiments in parallel fracture systems with the diversion outcomes of mobility control and flooding, distinct performance trends emerge. It can be seen that the stronger the foam stability, the stronger the mobility control ability, and the easier it is to start the shielding effect. Combined with the stability of different foam systems, understanding the mobility control ability of a foam system is the key to increasing the sweep coefficient of a complex fracture network and improve oil-washing efficiency. Full article

Gel system profile control and flooding is a novel profile control technology designed to address the issue of inefficient and ineffective water circulation in high water cut reservoirs during their later stages, demonstrating significant development potential. This system expands on the swept volume and enhances oil displacement efficiency, ultimately improving oil recovery. In this study, a new “injection well + intermediate well” configuration was employed to conduct physical simulation experiments on core modules using the gel system (Partially Hydrolyzed Polyacrylamide + Cr³⁺ cross-linker + Stabilizer). By adjusting the gel system dosage and the location of the intermediate well (0.123 PV + midway between the injection and production wells), changes in the recovery rate, water cut, seepage field, pressure field, oil saturation field, and swept volume were observed. The experimental results indicate that under these conditions, the model achieved the highest total recovery rate, with optimal displacement of remaining oil. Additionally, the gel system exhibited strong stability after formation and was resistant to breakthrough. Compared to single-injection well profile control and flooding, the configuration increased the recovery rate by 16.7%, demonstrating promising development prospects and application potential. Full article

This study focuses on a low-permeability sandstone reservoir in the Changqing Oilfield, aiming to elucidate the formation mechanism and occurrence state of residual oil during late-stage waterflooding development, thereby providing theoretical guidance for refined residual oil recovery. By integrating scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and digital core analysis, the oil–water occurrence state and dynamic characteristics during waterflooding were systematically investigated. NMR was employed to determine fluid distribution within core pores, while CT scanning was utilized to construct a 3D digital core model, enabling the identification of microscopic residual oil displacement and occurrence states at different flooding stages. The oil displacement efficiency was further analyzed based on variations in oil–water distribution and occurrence states within the core. The results demonstrate that pore and throat size and connectivity are the primary factors governing reservoir permeability. After high-pore-volume (PV) waterflooding, microscopic residual oil predominantly exists as dispersed droplets, films, and small-scale clusters or columns. Although prolonged high-PV waterflooding effectively expands the sweep volume, localized displacement efficiency declines, and reservoir heterogeneity adversely affects sweep volume maintenance. The post-flooding residual oil characteristics are collectively determined by the core’s local connectivity, wettability, and pore–throat morphology. This research systematically analyzes the occurrence patterns and evolutionary trends of residual oil in low-permeability reservoirs during long-term waterflooding, providing critical theoretical insights and technical support for enhanced oil recovery and residual oil exploitation. Full article

This study explores the synthesis and characterization of platinum (Pt), nickel (Ni), and cobalt (Co)-based electrocatalysts using the sol–gel method. The focus is on the effect of different support materials on the catalytic performance in alkaline media. The sol–gel technique enables the production of highly uniform electrocatalysts, supported on carbon-based substrates, metal oxides, and conductive polymers. Various characterization techniques, including X-ray diffraction (XRD) and scanning electron microscopy (SEM), were used to analyze the structure of the synthesized materials, while their electrochemical properties, which are relevant to their application in unitized regenerative fuel cells (URFCs), were investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). This hydrogen energy-converting device integrates water electrolyzers and fuel cells into a single system, reducing weight, volume, and cost. However, their performance is constrained by the electrocatalyst’s oxygen bifunctional activity. To improve URFC efficiency, an ideal electrocatalyst should exhibit high oxygen evolution (OER) and oxygen reduction (ORR) activity with a low bifunctionality index (BI). The present study evaluated the prepared electrocatalysts in an alkaline medium, finding that Pt25-Co75/XC72R and Pt75-Co25/N82 demonstrated promising bifunctional activity. The results suggest that these electrocatalysts are well-suited for both electrolysis and fuel cell operation in anion exchange membrane-unitized regenerative fuel cells (AEM-URFCs), contributing to improved round-trip efficiency. Full article

As an efficient and economical method to enhance oil recovery (EOR), it is very important to explore the applicability of chemical flooding under harsh reservoir conditions, such as high temperature and high salinity. We designed microscopic visualization oil displacement experiments to comprehensively evaluate the oil displacement performance of the zwitterionic surfactant betaine (BSB), a temperature- and salinity-resistant hydrophobically modified polymer (BHR), and surfactant–polymer (SP) binary systems. Based on macroscopic properties and microscopic oil displacement effects, we confirmed that the BSB/BHR binary solution has the potential to synergistically improve oil displacement efficiency and quantified the reduction in residual oil and oil displacement efficiency within the swept range. The experimental results show that after water flooding, a large amount of residual oil remains in the porous media in the form of clusters, porous structures, and columnar formations. After water flooding, only slight emulsification occurred after the injection of BSB solution, and the residual oil could not be activated. The injection of polymer after water flooding can expand the swept range to a certain extent. However, the distribution of residual oil in the swept range is similar to that of water flooding, and the oil washing efficiency is low. The SP binary flooding process can expand sweep coverage and effectively decompose large oil clusters simultaneously. This enhances the oil washing efficiency within the swept area and can significantly improve oil recovery. Finally, we obtained the microscopic oil displacement mechanism of BSB/BHR binary system to synergistically increase the swept volume and effectively activate the residual oil after water flooding. It is the result of the combined action of low interfacial tension (IFT) and suitable bulk viscosity. These findings provide critical insights for optimizing chemical flooding strategies in high-temperature and high-salinity reservoirs, significantly advancing EOR applications in harsh environments. Full article

This study presents a tailored nitrogen foam flooding system developed for the Mu146 block’s medium-high permeability reservoir conditions. Through systematic optimization, we establish an optimal formulation comprising 0.40% FP2398 foaming agent and 0.13% WP2366 stabilizer. The formulated foam demonstrates superior performance characteristics with a generated volume of 850 mL and extended stability duration of 1390 s, exhibiting exceptional structural integrity under oil-bearing conditions. Core flooding experiments conducted on berea cores reveal a 33.20% incremental oil recovery factor following waterflooding that achieves 53.60% primary recovery. The non-steady-state nitrogen foam huff-and-puff (NSSNFHF) field test at Well Mu146-61 shows significant reservoir response, with post-treatment analyses indicating an average chloride ion concentration increase of 540.20 mg/L and total salinity elevation of 1194.20 mg/L across five monitoring wells. These chemical signatures confirm effective volumetric sweep enhancement through the NSSNFHF field test, demonstrating a flooding-like mechanism that mobilizes bypassed oil in previously unswept zones. The field test encompassing Well Mu146-61 and four offset producers yield substantial production improvements, including a 74.55% increase in fluid production rates and a sustained oil yield of 1.80 tons per day. The validity period of the NSSNFHF field test is more than 12 months. The technology demonstrates dual functionality in conformance control and enhanced recovery, effectively improving both oil productivity and ultimate recovery factors. Full article

A sweeping jet is commonly preferred over a steady jet owing to its ability to better cool the region away from the strong core of an impinging jet. For industrial applications, it is important to study the thermal fields of oscillating jets in a multi-jet configuration to focus on the region that falls between the two consecutive fluidic oscillators and, hence, suggest a mechanism to uniformly cool the targeted flat surface. A comparative experimental study of dual sweeping jets (DSJs), double sweeping jets (DbSJs), and double circular jets (DbCJs) was conducted at different jet-to-plate spacings, various Re numbers, and three aspect ratios. The multi-circular and sweeping jets were impinged on a flat hot surface, which was heated at a constant flux of current, and thermocouples were employed to efficiently collect the time-averaged heat transfer distribution along the sweeping and transverse directions. It was determined that heat transfer, in terms of the Nusselt number, generally increased with increasing Re number and reduced the jet-to-wall spacing for the DSJ, DbSJ, and DbCJ, with some minor exceptions. The relative performance of these fluidic devices suggested that the best performance of DSJ was at small spacing and higher Re, DbSJ at moderate spacing and lower Re, and DbCJ at moderate spacing and moderate Re. The mutual comparison showed that along the sweeping motion, in the central region, DbCJ was better than both DSJ and DbSJ; in the right region, DSJ performance was far better than DbCJ and DbSJ; in the left region, DSJ was better than DbSJ when comparing the respective centers of DSJ and DbSJ. The dominance of DSJ over DbSJ at the centers of their respective bodies even extends in the transverse direction. Finally, for higher aspect ratios, the DSJ performed better in the outer regions, while the DbSJ performed well in the central region. Similarly, for both DSJ and DbSJ unanimously, the effect of changing the aspect ratio is interesting as initially, the Nu values increase for a higher aspect ratio, but by increasing the AR further, it causes a divergence of the fluidic volume from the central region to the surrounding region. Full article

As global energy demand continues to grow, the difficulty and cost of extracting oil and gas resources are gradually increasing, making enhanced oil recovery (EOR) one of the key issues in oil and gas field development. CO₂ flooding, as an effective tertiary oil recovery technique, has significant advantages in improving recovery rates due to its ability to significantly reduce crude oil viscosity, increase formation energy, and expand the swept volume. However, the effectiveness of CO₂ flooding is influenced by various factors, including flooding methods, well patterns, and formation parameters. In this study, a two-dimensional high-temperature and high-pressure simulation device was used to simulate the CO₂ flooding process under various flooding methods, including water flooding followed by continuous gas flooding, water–gas alternating flooding, and foam flooding, for two types of injection–production well patterns based on the formation oil parameters of the Hei 125 block in the Daqingzijing Oilfield. The results indicate that during the transition from water flooding to continuous gas flooding, gas breakthrough channels form rapidly, leading to a rapid increase in the produced gas–oil ratio (GOR). Alternatively, alternating injection of gas and liquid can effectively control gas mobility, reduce gas phase permeability, delay gas breakthrough time, and improve oil displacement efficiency. Water–gas alternating flooding forms water–gas slugs, allowing CO₂ to enter the tiny pores to contact crude oil, reducing resistance in the pores, and enhancing crude oil displacement efficiency. Although the foam system can expand the fluid sweep range, excessive gas injection can lead to premature gas breakthrough. Furthermore, the type of injection–production well pattern has a significant impact on the overall reservoir recovery for foam system and gas alternating flooding with a 1:1 ratio; adjusting the well pattern can increase the sweep efficiency and improve ultimate recovery. This study reveals the mechanisms by which different flooding methods and well patterns affect the effectiveness of CO₂ flooding, providing important theoretical and practical guidance for optimizing flooding strategies and improving oil recovery in oil and gas fields. It is of great significance for promoting the application of CO₂ flooding technology in oil and gas field development. Full article

The Bohai oilfield is characterized by severe heterogeneity and high average permeability, leading to a low water flooding recovery efficiency. Polymer flooding only works for a certain heterogeneous reservoir. Therefore, supplementary technologies for further enlarging the swept volume are still necessary. Based on the concept of discontinuous chemical flooding with multi slugs, three chemical systems, which were polymer gel (PG), hydrophobically associating polymer (polymer A), and conventional polymer (polymer B), were selected as the profile control and displacing agents. The optimization design of the discontinuous chemical flooding was investigated by core flooding experiments and displacement equilibrium degree calculation. The gel, polymer A, and polymer B were classified into three levels based on their profile control performance. The degree of displacement equilibrium was defined by considering the sweep conditions and oil displacement efficiency of each layer. The effectiveness of displacement equilibrium degree was validated through a three-core parallel displacement experiment. Additionally, the parallel core displacement experiment optimized the slug size, combination method, and shift timing of chemicals. Finally, a five-core parallel displacement experiment verified the enhanced oil recovery (EOR) performance of discontinuous chemical flooding. The results show that the displacement equilibrium curve exhibited a stepwise change. The efficiency of discontinuous chemical flooding became more significant with the number of layers increasing and heterogeneity intensifying. Under the combination of permeability of 5000/2000/500 mD, the optimal chemical dosage for the chemical discontinuous flooding was a 0.7 pore volume (PV). The optimal combination pattern was the alternation injection in the form of “medium-strong-weak-strong-weak”, achieving a displacement equilibrium degree of 82.3%. The optimal shift timing of chemicals occurred at a water cut of 70%, yielding a displacement equilibrium degree of 87.7%. The five-core parallel displacement experiment demonstrated that discontinuous chemical flooding could get a higher incremental oil recovery of 24.5% compared to continuous chemical flooding, which presented a significantly enhanced oil recovery potential. Full article

Background: In northern countries, spring requires the removal of large volumes of abrasive materials used in winter road maintenance. This sweeping process, crucial for safety and environmental protection, has traditionally relied on conventional mechanical brooms. Recent technological innovations, however, have introduced more efficient and environmentally friendly sweeping solutions; Methods: This study provides a comprehensive comparative analysis of the environmental and operational performance of these innovative sweeping systems versus conventional methods. Using simulation models based on real-world data and integrating fuel consumption models, the analysis replicates sweeping behaviors to assess both operational and environmental performance. A sensitivity analysis was conducted using these models, focusing on key parameters such as the collection rate, the number of trucks, the payload capacity, and the truck unloading duration; Results: The results show that the innovative sweeping system achieves an average 45% reduction in GHG emissions per kilometer compared to the conventional system, consistently demonstrating superior environmental efficiency across all resources configurations; Conclusions: These insights offer valuable guidance for service providers by identifying effective resource configurations that align with both environmental and operational objectives. The approach adopted in this study demonstrates the potential to develop decision-making support tools that balance operational and environmental pillars of sustainability, encouraging policy decision-makers to adopt greener procurement policies. Future research should explore the integration of advanced technologies such as IoT, AI-driven analytics, and digital twin systems, along with life cycle assessments, to further support sustainable logistics in road maintenance. Full article