Energy Science & Engineering最新文献

Multi-stage hydraulic fracturing in horizontal wells is vital for stimulating unconventional reservoirs, yet uneven fracture propagation often restricts the effective communication volume of the reservoir. We constructed a field-scale Unconventional Fracturing Model that couples fluid flow, proppant transport, stress-shadow mechanics, and height growth to explore competitive propagation among multiple clusters. Parametric experiments systematically varied cluster spacing, perforation count, proppant mass, and injection rate. Simulations reproduce the characteristic stress-shadow pattern—fractures shorter near the wellbore midpoint and longer at stage edges—and quantify how perforation and injection parameters influence this imbalance. Widening cluster spacing most effectively equalizes fracture lengths and flows, reducing perforation density, lowering proppant loading, and increasing injection flow rate, further enhancing uniformity. Together, these adjustments keep the standard deviation of fracture length within design limits, improve fracture-width retention, and promote more even fluid distribution across the stage. The results offer high-level guidance for limited-entry completion design to maximize stimulated-reservoir volume in unconventional oil fields.

The pressure of the tube at the wellhead is abruptly released during the opening of a high-production gas well, causing pressure fluctuation and subjecting the tubing to extra stress. In extreme circumstances, shock load may shatter tubing, compromising the integrity of the well and safe production. Thus, the dynamic boundary conditions of the wellhead valve opening procedure and the complex operating circumstances of the gas well must be fully taken into account. To determine the changes in wellhead pressure and velocity following valve opening, a nonlinear mathematical model of transient flow during valve opening is developed, and a method of characteristics is used for numerical solution. Next, examine how wellhead pressure and velocity are affected by well opening time T_op, valve opening coefficient m, production Q_g, and holdup H_L. According to the study, wellhead pressure steadily drops from shut-in static pressure and approaches steady flow pressure during fluctuation following valve opening. Wellhead pressure and flow rate variations essentially occur at the same time. The wellhead pressure is discharged and the pressure fluctuation decays more quickly with a shorter well opening period. The pressure variation lasts longer the longer the well is opened. The wellhead opening decreases as the valve opening coefficient decreases. The pressure drops off more quickly as the flow rate rises. The fluctuation pressure first rises and then falls as output rises. The larger the production, the quicker the fluid steady flow rate, provided that the tubing's cross section stays constant. Wellhead pressure rises and the wellhead flow rate falls as the liquid holdup increases. This study is of practical significance for determining how to reduce wellbore fluctuation pressure and improve wellbore integrity.

Hydraulic fracturing technology is widely used in Enhanced Geothermal System (EGS) projects to induce fractures and enhance the permeability of thermal reservoirs. The hydraulic fracturing process of hot dry rock (HDR) is actually a multiphysics coupling process that couples the heat transfer field, seepage field, stress field, and damage. This study selected carbonate-type HDR as a research object to test its basic mechanical parameters. Then, a Thermal-Hydraulic-Mechanical-Damage (THMD) coupling model of the HDR hydraulic fracturing process based on elastic thermodynamics was developed. The model accuracy was also confirmed through experimental verification. This study investigated the impact of different in-situ stress conditions, temperature conditions, and injection parameters on the initiation and propagation of hydraulic fractures in HDR. Simulation results indicate that under high-temperature conditions, the breakdown pressure decreases and propagates, widening the existing fracture under the same condition. The variation in stress difference will reduce the microfractures, and an increase in confining stress restricts the extension of fractures and increases the breakdown pressure of the rock. The results of this study can be compared with actual EGS projects, providing guidance for parameter designs and improving EGS development efficiency.

The deformation energy stored in soil-like tectonic coal plays a critical role in coal and gas outbursts. Unlike hard rocks, tectonic coal exhibits pronounced stress–strain nonlinearity, invalidating traditional elastic energy models. Based on critical state theory in soil mechanics, a nonlinear deformation energy model was developed and validated through hydrostatic and triaxial loading-unloading experiments on intact and tectonic coal samples from five coal mines. Deformation energy variations were systematically analyzed using unloading curves, confirming the model's validity under hydrostatic and deviatoric stresses. The hydrostatic deformation energy model was simplified by consolidating parameters into a single term. To generalize it to all stress states, a deviatoric stress coefficient was introduced to represent the degree of stress deviation from hydrostatic conditions. Experimental results show that the deviatoric stress coefficient for intact coal is typically greater than 1, while for tectonic coal, it is often below 0.5 and can approach 0. The modified model provides a more accurate characterization of triaxial deformation energy–stress relationships compared to elastic models, as evidenced by both experimental and published data, owing to the stress-dependent variation of Poisson's ratio and elastic modulus during loading. Both intact and tectonic coal exhibit a decreasing tangent modulus of elasticity and an increasing Poisson's ratio with progressive loading. At equivalent deviatoric stress levels, tectonic coal stores significantly more deformation energy than intact coal. However, at comparable ratios of deviatoric stress to material strength, their deformation energy becomes similar. This finding enhances the understanding of the energy mechanisms driving coal and gas outbursts.

Radioactive effluents discharged by nuclear power plants (NPPs) are classified into two categories: gas and liquid effluents, based on their source and discharge pathways. During the operation of these facilities, both types of effluents are released into the environment. In Korea, the discharge of radioactive effluents is regulated according to three criteria: radioactivity concentration, radiation dose, and the total amount of radioactivity. Among the various radioactive nuclides discharged by NPPs, carbon-14 stands out due to its long half-life and significant contribution to the effective dose to the public living near these plants. The radioactive effluents discharged from Korean NPPs contain a variety of nuclides. Korea Hydro & Nuclear Power, the operator of these facilities, carefully manages effluent discharges. This study assesses the effective dose to the public caused by carbon-14 emissions from Korean NPPs over a decade. Since 2013, the monitoring of carbon-14 in gaseous effluents at Korean pressurized water reactors (PWRs) has been conducted through direct measurements. The findings indicate that while tritium constitutes a large portion of the radioactive effluents, carbon-14 has emerged as the primary contributor to public radiation exposure. The average annual effective dose from measured carbon-14 emissions was assessed at 1.06 × 10⁻² mSv for PWRs and 3.25 × 10⁻² mSv for pressurized heavy water reactors from 2013 to 2022. As a result, carbon-14 has a relatively significant radiological impact on the effective dose received by the public living near Korean NPPs.

In situ burning (ISB) is an efficient response strategy for oil spills; however, incomplete combustion and excessive smoke production hinder its wider application. In this study, the effectiveness of using ferrocene as additives to improve the thermal behaviors and kinetics of combustion of different crude oils (Hibernia, Hebron, Dilbit and Bitumen) and commercial Diesel was investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques under atmospheric air condition. The TGA and DSC results revealed that the addition of 1.0 wt% ferrocene to crude oils and Diesel lowered the combustion oxidation reaction temperature up to 80°C, indicating reduced resistance and thermodynamic demand during ISB experiments. Iso-conversional kinetic modeling using Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunose (KAS) showed a reduction in apparent activation energy (E_a) up to 35–50 kJ mol⁻¹ in Hibernia and Hebron, 87–182 kJ mol⁻¹ in Bitumen, and 12 kJ mol⁻¹ in Diesel, confirming enhanced ignition and reaction rates, whereas Dilbit exhibited a slight increase (~up to 2.6 kJ mol⁻¹). To better understand oil oxidation behavior and mechanisms during ISB, TG-FTIR (Fourier transform infrared spectroscopy) system was employed to analyze the evolved gases at various temperature stages. It was revealed that ferrocene facilitated oxygen addition, bond scission and decarboxylation reactions, resulting into enhanced breakdown of complex, high-boiling-point oxygenated hydrocarbons during ISB. Hence, ferrocene hindered the aggregation of molecular species into larger compounds, resulting in less smoke production in ISB and these findings will inform future ISB experiments in open water bodies.

As a key component of the power industry, the rapid growth of the wire and cable industry has exposed it to the challenge of carbon emissions. However, there is still a lack of research on organizations’ carbon footprint in the wire and cable industry. To fill these research gaps, this study has quantified the carbon footprint of five wire and cable companies (A, B, C, D, and E) above a designated size in China under the greenhouse gas protocol framework and life cycle assessment method, and proposed emission reduction directions. The results revealed that the cumulative indirect carbon footprint generated by electricity consumption (Scope 2) for the five companies accounted for over 89% when the accounting boundary was within the company's control (gate-to-gate) between 2020 and 2022. Meanwhile, the direct carbon footprint caused by natural gas consumption was much greater than that of gasoline and diesel for companies with annual revenue exceeding one billion, contributing 9.53%, 1.79%, and 6.63% of the carbon footprint for companies C, D, and E, respectively. Nevertheless, when the accounting boundary not only includes the company's control (cradle-to-gate), the carbon footprint of the raw material extraction and refining stages may be a major contributor to the carbon footprint of wire and cable companies. For example, Company A's carbon footprint in this stage in 2023 was 22295.51 tCO₂e, accounting for 94% of the total carbon footprint (23828.70 tCO₂e) within and outside the company's control. Based on the above research results, wire and cable companies should focus on reducing emissions from electricity, natural gas, and raw materials.

Phase change materials (PCMs) are increasingly essential in thermal energy storage (TES) systems (TES) because of their excellent energy storage density per unit volume, particularly in low- and medium-temperature applications. This investigation focuses on the improvement of advanced composite phase change materials (CPCMs) by integrating 20 wt% carbon quantum dots (CQDs) into paraffin wax (PW) to increase thermal conductivity. The CPCMs were synthesized using the ultra-sonication technique. The microstructural morphology of the PCMs and CPCMs was characterized using scanning electron microscopy (SEM). Thermal conductivity measurements were conducted using a Heat Flow Meter, while latent heat and melting temperature were determined through differential scanning calorimetry (DSC). The findings revealed an important enhancement in thermal conductivity with the addition of CQDs mixed with PCM matrix. Specifically, the addition of 20 wt% CQDs into PW increased the thermal conductivity to 0.452 W/m K and enhanced the latent heat by 10.4%. Furthermore, the CPCMs exhibited a larger and higher melting temperature range compared to conventional PCMs, highlighting their improved thermal performance.

Nuclear magnetic resonance (NMR), as an advanced non-destructive and rapid measurement technology, has shown unique advantages in the evaluation of unconventional shale reservoirs. This paper systematically introduces the fundamental principles of NMR spectroscopy and relaxation theory in porous media and comprehensively analyzes the experimental techniques and analytical methodologies for NMR and magnetic resonance imaging (MRI) applications in shale characterization. The content aims to provide substantive reference value for researchers and practitioners engaged in shale NMR investigations. Notably, despite existing technical challenges in expository relaxation mechanisms and capturing nanoscale pore signals within shale matrices, NMR applications present novel possibilities for developing emerging research frontiers. For instance, there is significant synergy between NMR technology and emerging fields such as supercritical CO₂ enhanced recovery, carbon capture, utilization and storage (CCUS), and underground hydrogen storage. This paper methodological framework exhibits extensibility to studies of tight sandstones, hydrate-bearing sediments, and other porous media systems, thereby offering cross-disciplinary technical support for establishing carbon neutrality-oriented energy development paradigms.

Connecting independent microgrids (MGs) to multi-MGs through a reasonable topology design is beneficial for improving the operational stability and power supply capability of isolated MGs in confronting malfunctions. A bi-objective optimization model is established, taking both the total length of connection lines and the resilience index of the multi-MGs into consideration. Besides, a segmented function is established for the output power of ocean current energy generation in response to the characteristics of underwater MGs. The calculation rules for the waiting time of loads with charging demand are considered in addition to conventional operational constraints. Then, the NSGA-II algorithm is utilized to efficiently solve the problem, where the cross strategy is customized based on the characteristics of the problem. The validity and rationality of the proposed method are demonstrated through simulation experiments, and numerical results show the superior performance of the proposal.