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Records with Subject: Other
Showing records 1 to 25 of 38. [First] Page: 1 2 Last
Elimination of the Inrush Current Phenomenon Associated with Single-Phase Offline UPS Systems
Syed Sabir Hussain Bukhari, Shahid Atiq, Byung-il Kwon
November 16, 2018 (v1)
Subject: Other
Keywords: current regulation, inrush currents, offline, uninterruptible power supply
Critical load applications always rely on UPS systems to uphold continuous power during abnormal grid conditions. In case of any power disruption, an offline UPS system starts powering the load to avoid blackout. However, this process can root the momentous inrush current for the transformer installed before the load. The consequences of inrush current can be the reduction of output voltage and tripping of protective devices of the UPS system. Furthermore, it can also damage the sensitive load and decrease the transformer’s lifetime. To prevent the inrush current, and to avoid its disruptive effects, this research suggests an offline UPS system based on a current regulated inverter that eliminates the inrush current while powering the transformer coupled loads. A detailed comparative analysis of the conventional and proposed topologies is presented and the experiment was performed by using a small prototype to validate the performance, and operation of the proposed topology.
Field Experiments on 10 kV Switching Shunt Capacitor Banks Using Ordinary and Phase-Controlled Vacuum Circuit Breakers
Wenxia Sima, Mi Zou, Qing Yang, Ming Yang, Licheng Li
November 16, 2018 (v1)
Subject: Other
Keywords: field tests, phase selection, shunt capacitor banks, vacuum circuit breakers (VCBs)
During the switching on/off of shunt capacitor banks in substations, vacuum circuit breakers (VCBs) are required to switch off or to switch on the capacitive current. Therefore, the VCBs have to be operated under a harsh condition to ensure the reliability of the equipment. This study presents a complete comparison study of ordinary and phase-controlled VCBs on switching 10 kV shunt capacitor banks. An analytical analysis for switching 10 kV shunt capacitor banks is presented on the basis of a reduced circuit with an ungrounded neutral. A phase selection strategy for VCBs to switch 10 kV shunt capacitor banks is proposed. Switching on current waveforms and switching off overvoltage waveforms with, and without, phase selection were measured and discussed by field experiments in a 110 kV substation in Chongqing, China. Results show that the operation of phase-controlled VCBs for 10 kV switching shunt capacitor banks is stable, and phase-controlled VCBs can be used to implement the 10 kV... [more]
Analysis of a Solar Cooling System for Climatic Conditions of Five Different Cities of Saudi Arabia
M. Mujahid Rafique, Shafiqur Rehman, Aref Lashin, Nassir Al Arifi
November 16, 2018 (v1)
Subject: Other
Keywords: clean technology, desiccant wheel, energy saving, evaporative cooling, Saudi Arabia, thermal cooling
Air high in humidity leads to uncomfortable conditions and promotes the growth of different fungi and bacteria, which may cause health problems. The control of moisture content in the air using traditional air conditioning techniques is not a suitable option due to large consumption of primary energy and hence emission of greenhouse gases. The evaporative cooling technology is a cost effective and eco-friendly alternative but can provide thermal comfort conditions only under low humidity conditions. However, the evaporative cooling method can be used effectively in conjunction with desiccant dehumidifiers for better control of humidity. Such systems can control the temperature and humidity of the air independently and can effectively utilize the low-grade thermal energy resources. In this paper, the theoretical analysis of desiccant based evaporative cooling systems is carried out for five cities in Saudi Arabia (Jeddah, Jazan, Riyadh, Hail, and Dhahran). It has been observed that the... [more]
Acknowledgement to Reviewers of Energies in 2015
Energies Editorial Office
October 23, 2018 (v1)
Subject: Other
The editors of energies would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015.
Correction: Ding, X.; Liu, G.; Du, M.; Guo, H.; Qiao, H. and Gerada, C. Development of an Axial Flux MEMS BLDC Micromotor with Increased Efficiency and Power Density. Energies 2015, 8, 6608⁻6626
Xiaofeng Ding, Guanliang Liu, Min Du, Hong Guo, Hao Qian, Christopher Gerada
October 23, 2018 (v1)
Subject: Other
We wish to make the following change to the published paper [1]. The name of the corresponding author should be “Hao Qian” instead of “Hao Qiao”. [...]
Distinguishability, Information and Useful Energies
Shu-Kun Lin
October 15, 2018 (v1)
Subject: Other
As a scientist with a long-standing research interest in thermodynamics, information theory and diversity preservation, I would like to start publishing the journal Energies (ISSN 1996-1073).[...]
Investment Determinants in Self-Consumption Facilities: Characterization and Qualitative Analysis in Spain
José Ángel Gimeno, Eva Llera, Sabina Scarpellini
September 21, 2018 (v1)
Subject: Other
Keywords: drivers and barriers, investments, prosumers, remuneration policies, self-consumption, solar energy
Self-consumption energy facilities are presented as viable and sustainable solutions in the energy transition scenario in which many countries are immersed. However, they rely on dispersed and private investments in the territory. Given the uneven growth in the number of self-consumption facilities in Europe, the main objective of this study is to identify and measure the investment determinants in self-consumption facilities. To this end, the main influential incentives and barriers are identified through the aggregate analysis of the regulatory framework for self-consumption in several European countries, and the empirical characterization of Spanish facilities as a multiple case study, to define the common features of the investments made. The technical, economic, and financial characterization of real self-consumption facilities in climatic zones of southern Europe is a significant contribution of the present work. There are few samples of this type in the studies published to date... [more]
Magnetotelluric Imaging of the Zhangzhou Basin Geothermal Zone, Southeastern China
Chaofeng Wu, Xiangyun Hu, Guiling Wang, Yufei Xi, Wenjing Lin, Shuang Liu, Bo Yang, Jianchao Cai
September 21, 2018 (v1)
Subject: Other
Keywords: geothermal anomaly, high-conductive zone, magnetotelluric, Zhangzhou Basin
The geothermal zone of southeast China, which is one of the country’s known geothermal zones, contains significant natural geothermal resources. To understand the formation of geothermal resources, a magnetotelluric (MT) investigation with a site spacing of 1⁻2 km was carried out around the Zhangzhou Basin. The recorded MT data were processed by robust time series and remote reference processing techniques. The data analysis results revealed that two-dimensional (2-D) modeling can be used to approximately determine the electrical structure. The joint inversions of TE and TM modes have been performed after distortion decomposition. In the inversion models, a low resistivity cap of 200⁻800 m thickness was observed, which represented the blanketing sediments composed of Quaternary and volcanic rocks of the late Jurassic period. The presence of high resistivity above a depth of 20 km indicates the granites are widely developed in the upper and middle crust. MT measurements have revealed so... [more]
Real-World Fuel Consumption, Fuel Cost and Exhaust Emissions of Different Bus Powertrain Technologies
Samuel Rodman Oprešnik, Tine Seljak, Rok Vihar, Marko Gerbec, Tomaž Katrašnik
September 21, 2018 (v1)
Subject: Other
Keywords: bus powertrain technologies, instantaneous gaseous and PM10 mass emissions, real-world driving cycles
Air quality in urban areas is strongly influenced by exhaust emitted by the public transport fleet. The aim of this study was to analyze benefits in the fuel consumption, fuel costs and exhaust emissions when replacing baseline diesel fueled EURO III city buses by the compressed natural gas (CNG)-fueled EURO V buses and by hydraulic series hybrid diesel-fueled EURO V buses. Real-world measurements were performed on the regular bus route to access realistic energy consumption and exhaust emissions. Instantaneous gaseous emission (CO₂, CO, NOx and THC) were measured together with the instantaneous PM10 mass emission. Innovativeness of the presented approach thus arises from the systematic comparison of different powertrain technologies under real-world drive cycles and measuring time traces of not only gaseous but also of PM10 mass emissions. Furthermore, lumped cycle averaged emissions are interpreted and explained by typical powertrain performance parameters and exhaust emission time t... [more]
Analysis and Design of a Compound-Structure Permanent-Magnet Motor for Hybrid Electric Vehicles
Qiwei Xu, Jing Sun, Dewen Tian, Wenjuan Wang, Jianshu Huang, Shumei Cui
September 21, 2018 (v1)
Subject: Other
Keywords: compound-structure permanent-magnet motor, hybrid electric vehicles, parameters analysis and design, state equation, torque property, working mode
On the basis of the excellent driving force demand of hybrid electric vehicles (HEVs), this paper studies the torque property of the compound-structure permanent-magnet motor (CSPM motor) used for HEVs, which is influenced by magnetic field oversaturation and variable nonlinear parameters. Firstly, the system configuration of HEVs based on CSPM motor and its working mode are introduced. Next, the state equation of CSPM motor in three-phase stationary coordinate system is proposed in order to investigate its torque performance; then, the factors affecting the output torque are gained. Finite element method (FEM)-based electromagnetic parameters analysis and design is carried out, to raise the output torque and reduce the torque ripple of CSPM motor. Besides, optimized design parameters are used to establish the FEM model, and the simulation results of electromagnetic performances for the CSPM motor before and after optimization are given to verify the rationality of optimization.
Quantitative Comparisons of Six-Phase Outer-Rotor Permanent-Magnet Brushless Machines for Electric Vehicles
Yuqing Yao, Chunhua Liu, Christopher H.T. Lee
September 21, 2018 (v1)
Subject: Other
Keywords: brushless machine, electric vehicle, flux switching machine, multiphase machine, outer rotor, permanent-magnet machine, Vernier machine
Multiphase machines have some distinct merits, including the high power density, high torque density, high efficiency and low torque ripple, etc. which can be beneficial for many industrial applications. This paper presents four different types of six-phase outer-rotor permanent-magnet (PM) brushless machines for electric vehicles (EVs), which include the inserted PM (IPM) type, surface PM (SPM) type, PM flux-switching (PMFS) type, and PM vernier (PMV) type. First, the design criteria and operation principle are compared and discussed. Then, their key characteristics are addressed and analyzed by using the finite element method (FEM). The results show that the PMV type is quite suitable for the direct-drive application for EVs with its high torque density and efficiency. Also, the IPM type is suitable for the indirect-drive application for EVs with its high power density and efficiency.
An Overview of Existing Experiences with Solar-Powered E-Bikes
Georgia Apostolou, Angèle Reinders, Karst Geurs
September 21, 2018 (v1)
Subject: Other
Keywords: commuting, e-bikes, mobility, photovoltaic, solar powered, sustainable, transportation mode
Electric bicycles (e-bikes) are considered a sustainable alternative to automobile transportation today. The electric bike includes all the benefits that conventional bicycles offer, plus faster, more comfortable and longer trips, as well as less effort for the user. In this paper, we specifically focus on a new type of e-bike, the so-called ‘solar-powered e-bike’. Therefore, this review paper explores existing literature findings for the use of solar energy in transportation, and more specifically in e-bikes. This paper aims to capture the status of and experiences with the use of e-bikes; more specifically, with solar-powered e-bikes. It presents research conducted so far on e-bikes and solar-powered e-bikes, as well as the main technical features of the solar e-bike. Finally, it analyzes a sample of e-bikes’ and solar-powered e-bikes’ users, based on Dutch National Travel Survey data and an experimental field study conducted in 2017. Data showed that the main target group of (solar)... [more]
Carbon Taxes and Carbon Right Costs Analysis for the Tire Industry
Wen-Hsien Tsai
September 21, 2018 (v1)
Subject: Other
Keywords: Activity-Based Costing (ABC), carbon emissions, carbon trading, mathematical programming, tire industry
As enterprises are the major perpetrators of global climate change, concerns about global warming, climate change, and global greenhouse gas emissions continue to attract attention, and have become international concerns. The tire industry, which is a high-pollution, high-carbon emission industry, is facing pressure to reduce its carbon emissions. Thus, carbon prices and carbon trading have become issues of global importance. In order to solve this environmental problem, the purpose of this paper is to combine mathematical programming, Theory of Constraints (TOC), and Activity-Based Costing (ABC) to formulate the green production decision model with carbon taxes and carbon right costs, in order to achieve the optimal product mix decision under various constraints. This study proposes three different scenario models with carbon taxes and carbon right used to evaluate the effect on profit of changes in carbon tax rates.
Regional Energy, CO₂, and Economic and Air Quality Index Performances in China: A Meta-Frontier Approach
Ying Li, Yung-Ho Chiu, Liang Chun Lu
September 21, 2018 (v1)
Subject: Other
Keywords: AQI, Carbon Dioxide, energy use efficiency, meta-frontier, Non-radial Directional Distance Function
Rapid economic development has resulted in a significant increase in energy consumption and pollution such as carbon dioxide (CO₂), particulate matter (PM2.5), particulate matter 10 (PM10), SO₂, and NO₂ emissions, which can cause cardiovascular and respiratory diseases. Therefore, to ensure a sustainable future, it is essential to improve economic efficiency and reduce emissions. Using a Meta-frontier Non-radial Directional Distance Function model, this study took energy consumption, the labor force, and fixed asset investments as the inputs, Gross domestic product (GDP) as the desirable output, and CO₂ and the Air Quality Index (AQI) scores as the undesirable outputs to assess energy efficiency and air pollutant index efficiency scores in China from 2013⁻2016 and to identify the areas in which improvements was necessary. It was found that there was a large gap between the western and eastern cities in China. A comparison of the CO₂ and AQI in 31 Chinese cities showed a significant dif... [more]
Analysis of Shallow Subsurface Geological Structures and Ground Effective Thermal Conductivity for the Evaluation of Ground-Source Heat Pump System Installation in the Aizu Basin, Northeast Japan
Takeshi Ishihara, Gaurav Shrestha, Shohei Kaneko, Youhei Uchida
September 21, 2018 (v1)
Subject: Other
Keywords: Aizu Basin, ground effective thermal conductivity, ground-source heat pump system, Quaternary geological structure
Shallow subsurface geological structure mapping combined with ground effective thermal conductivity values at the basin scale provide an appropriate method to evaluate the installation potential of ground-source heat pump systems. This study analyzed the geological structure of the Aizu Basin (Northeast Japan) using sedimentary cores and boring log and mapped the distribution of average ground effective thermal conductivity in the range from −10 m to −100 m depth calculated from cores and logs. Gravel layers dominate in alluvial fans of the northern and southern basin areas, which are found to be associated with higher average ground effective thermal conductivity values, 1.3⁻1.4 W/m/K, while central and western floodplain areas show lower values of 1.0⁻1.3 W/m/K due to the existence of thick mud layers in the shallow subsurface. The results indicate that the conventional closed-loop systems are more feasible in northern and southern basin areas than in the central and western areas. E... [more]
A New Gob-Side Entry Layout Method for Two-Entry Longwall Systems
Rui Wu, Qingyuan He, Joung Oh, Zecheng Li, Chengguo Zhang
September 21, 2018 (v1)
Subject: Other
Keywords: entry stability, gob-side entry, pillarless mining, pre-backfill
The gob-side entry layout is popular at two-entry longwall mine sites in China for the benefit of improving the coal recovery rate. Currently, two methods have been widely used to develop gob-side entries, including gob-side entry retaining and gob-side entry driving. Gob-side entry retaining maximizes the recovery rate by pillarless mining but increases the difficulty in gob-side entry support. Also, this method has limited applications in hard roof conditions. The gob-side entry driving mine site uses the rib pillar to separate the gob entry and the gob area of the previous panel, which leads to additional coal losses. The waste is more intolerable in large-cutting-height panels and longwall top coal caving panels as the Chinese government limits the minimum recovery rate of longwall panels using these mining methods. In this paper, a new gob-side entry layout method, termed gob-side pre-backfill driving, is established to overcome the shortcomings of the existing methods. The new me... [more]
A Simple Assessment of Housing Retrofit Policies for the UK: What Should Succeed the Energy Company Obligation?
Luciana Maria Miu, Natalia Wisniewska, Christoph Mazur, Jeffrey Hardy, Adam Hawkes
September 21, 2018 (v1)
Subject: Other
Keywords: barriers, Energy Company Obligation, Energy Efficiency, energy saving, Green Mortgage, housing retrofit, policy assessment, Variable Council Tax, Variable Stamp Duty Land Tax
Despite the need for large-scale retrofit of UK housing to meet emissions reduction targets, progress to date has been slow and domestic energy efficiency policies have struggled to accelerate housing retrofit processes. There is a need for housing retrofit policies that overcome key barriers within the retrofit sector while maintaining economic viability for customers, funding organizations, and effectively addressing UK emission reductions and fuel poverty targets. In this study, we use a simple assessment framework to assess three policies (the Variable Council Tax, the Variable Stamp Duty Land Tax, and Green Mortgage) proposed to replace the UK’s current major domestic retrofit programme known as the Energy Company Obligation (ECO). We show that the Variable Council Tax and Green Mortgage proposals have the greatest potential for overcoming the main barriers to retrofit policies while maintaining economic viability and contributing to high-level UK targets. We also show that, while... [more]
Spatial Environmental Assessment Tool (SEAT): A Modeling Tool to Evaluate Potential Environmental Risks Associated with Wave Energy Converter Deployments
Craig Jones, Grace Chang, Kaustubha Raghukumar, Samuel McWilliams, Ann Dallman, Jesse Roberts
September 21, 2018 (v1)
Subject: Other
Keywords: environmental effects, marine renewable energy, numerical modeling, ocean energy, risk assessment, sediment dynamics, Wave Energy, wave modeling, wave propagation
Wave energy converter (WEC) arrays deployed in coastal regions may create physical disturbances, potentially resulting in environmental stresses. Presently, limited information is available on the nature of these physical disturbance or the resultant effects. A quantitative Spatial Environmental Assessment Tool (SEAT) for evaluating the potential effects of wave energy converter (WEC) arrays on nearshore hydrodynamics and sediment transport is presented for the central Oregon coast (USA) through coupled numerical model simulations of an array of WECs. Derived climatological wave conditions were used as inputs to the model to allow for the calculation of risk metrics associated with various hydrodynamic and sediment transport variables such as maximum shear stress, bottom velocity, and change in bed elevation. The risk maps provided simple, quantitative, and spatially-resolved means of evaluating physical changes in the vicinity of a hypothetical WEC array in response to varying wave co... [more]
Experimental Investigation of Flow-Induced Motion and Energy Conversion of a T-Section Prism
Nan Shao, Jijian Lian, Guobin Xu, Fang Liu, Heng Deng, Quanchao Ren, Xiang Yan
September 21, 2018 (v1)
Subject: Other
Keywords: Energy Conversion, flow-induced motion, load resistances, section aspect ratios, sharp sections, T-section prism
Flow-induced motion (FIM) performs well in energy conversion but has been barely investigated, particularly for prisms with sharp sections. Previous studies have proven that T-section prisms that undergo galloping branches with high amplitude are beneficial to energy conversions. The FIM experimental setup designed by Tianjin University (TJU) was improved to conduct a series of FIM responses and energy conversion tests on a T-section prism. Experimental results are presented and discussed, to reveal the complete FIM responses and power generation characteristics of the T-section prism under different load resistances and section aspect ratios. The main findings are summarized as follows. (1) Hard galloping (HG), soft galloping (SG), and critical galloping (CG) can be observed by varying load resistances. When the load resistances are low, HG occurs; otherwise, SG occurs. (2) In the galloping branch, the highest amplitude and the most stable oscillation cause high-quality electrical ene... [more]
Exploring Outdoor Solar Potential in High-Density Living: Analyzing Direct Sunlight Duration for Urban Agriculture in Seoul’s Residential Complexes
Hyungkyoo Kim, Kyung Sun Lee, Jae Seung Lee, Saewon Lee
September 21, 2018 (v1)
Subject: Other
Keywords: direct solar access, DIVA-for-Rhino, high-density residential complexes, Seoul, urban agriculture
Urban agriculture has become a favored activity in many cities around the world. This study explores how urban agriculture’s potential can be maximized in Seoul, South Korea, a city characterized by high-density residential complexes. It selects six existing residential complexes with representative site typologies and diverse density levels. The study’s aim is to assess the impact of various typology and density settings on percentages of ground-level surface with direct sunlight above certain thresholds during warmer seasons when crops can grow. DIVA-for-Rhino is used for simulation. The findings suggest that parallel typologies and lower density levels offer the best performance, while other combinations show mixed results. This study could benefit citizens and policymakers to facilitate urban agriculture practices around the world by suggesting feasible solutions for high-density residential developments.
A Transformerless Single-Phase Current Source Inverter Topology and Control for Photovoltaic Applications
Jorge Cardoso, Nimrod Vazquez, Claudia Hernandez, Joaquin Vaquero
September 21, 2018 (v1)
Subject: Other
Keywords: current source inverter, grid-tied photovoltaic systems, leakage current, renewable sources, transformerless inverter
Low power grid-tied photovoltaic (PV) generation systems increasingly use transformerless inverters. The elimination of the transformer allows smaller, lighter and cheaper systems, and improves the total efficiency. However, a leakage current may appear, flowing from the grid to the PV panels through the existing parasitic capacitance between them, since there is no galvanic isolation. As a result, electromagnetic interferences and security issues arise. This paper presents a novel transformerless single-phase Current Source Inverter (CSI) topology with a reduced inductor, compared to conventional CSIs. This topology directly connects the neutral line of the grid to the negative terminal of the PV system, referred as common mode configuration, eliminating this way, theoretically, the possibility of any leakage current through this terminal. The switches control is based on a hysteresis current controller together with a combinational logic circuitry and it is implemented in a digital p... [more]
Data Envelopment Analysis in Energy and Environmental Economics: An Overview of the State-of-the-Art and Recent Development Trends
Abbas Mardani, Dalia Streimikiene, Tomas Balezentis, Muhamad Zameri Mat Saman, Khalil Md Nor, Seyed Meysam Khoshnava
September 21, 2018 (v1)
Subject: Other
Keywords: data envelopment analysis (DEA), efficiency measures, energy economics, Energy Efficiency, environmental economics
Measurement of environmental and energy economics presents an analytical foundation for environmental decision making and policy analysis. Applications of data envelopment analysis (DEA) models in the assessment of environmental and energy economics are increasing notably. The main objective of this review paper is to provide the comprehensive overview of the application of DEA models in the fields of environmental and energy economics. In this regard, a total 145 articles published in the high-quality international journals extracted from two important databases (Web of Science and Scopus) were selected for review. The 145 selected articles are reviewed and classified based on different criteria including author(s), application scheme, different DEA models, application fields, the name of journals and year of publication. This review article provided insights into the methodological and conceptualization study in the application of DEA models in the environmental and energy economics... [more]
Design Issues for Claw Pole Machines with Soft Magnetic Composite Cores
Chengcheng Liu, Jiawei Lu, Youhua Wang, Gang Lei, Jianguo Zhu, Youguang Guo
September 21, 2018 (v1)
Subject: Other
Keywords: claw pole machine (CPM), design issues, finite element method (FEM), soft magnetic composite (SMC)
By using global ring winding, the torque coefficient of the transverse flux machine (TFM) is proportional to its number of pole pairs, and thus the TFM possesses high torque density ability when compared with other electrical machines. As a special kind of TFM, the claw pole machine (CPM) can have more torque due to its special claw pole teeth. The manufacturing of CPM or TFM with silicon steels was very difficult in the past, and is a handicap for the progress of this kind of machine. Thanks to the advent of soft magnetic composite (SMC) materials, the manufacturing process of CPM has become more and more simple. More attention has been paid to this kind of technology, and some mass production CPMs with SMC cores have appeared. However, there are few works that discuss the key design issues for this kind of machine. In this paper, a small CPM with SMC is used as as a research benchmark. Various design methods that can be adopted to improve its performance have been studied, including... [more]
From the Balancing Reactive Compensator to the Balancing Capacitive Compensator
Adrian Pană, Alexandru Băloi, Florin Molnar-Matei
September 21, 2018 (v1)
Subject: Other
Keywords: adaptive balancing capacitive compensator, Adaptive balancing reactive compensator, electrical power quality, reactive power compensator, static var compensator, symmetrical component method
Nowadays, improving the power quality at the Point of Common Coupling (PCC) between the consumers’ installations and the distribution system operators’ installations depends more and more on the use of specialized equipment, able to intervene in the network to eliminate or diminish the disturbances. The reactive power compensators remain valid solutions for applications in consumer and electricity distribution, in those situations when the criterion regarding the costs of installing and operating the equipment is more important than the ones related to the reaction speed or the control accuracy. This is also the case of the equipment for power factor improvement and load balancing in a three-phase distribution network. The two functions can be achieved simultaneously by using an unbalanced static var compensator, known as an adaptive balancing compensator, achieved by adjusting the equivalent parameters of circuits containing single-phase coils and capacitor banks. The paper presents t... [more]
Method for Visualizing Fractures Induced by Laboratory-Based Hydraulic Fracturing and Its Application to Shale Samples
Youqing Chen, Makoto Naoi, Yuto Tomonaga, Takashi Akai, Hiroyuki Tanaka, Sunao Takagi, Tsuyoshi Ishida
September 21, 2018 (v1)
Subject: Other
Keywords: fracture pattern, hydraulic fracturing, laboratory test, polarization microscope observation, shale, visualization
A better understanding of the process of stimulation by hydraulic fracturing in shale gas and oil reservoirs is necessary for improving resource productivity. However, direct observation of hydraulically stimulated regions including induced fractures has been difficult. In the present study, we develop a new approach for directly visualizing regions of shale specimens impregnated by fluid during hydraulic fracturing. The proposed laboratory method uses a thermosetting resin mixed with a fluorescent substance as a fracturing fluid. After fracturing, the resin is fixed within the specimens by heating, and the cut sections are then observed under ultraviolet light. Based on brightness, we can then distinguish induced fractures and their surrounding regions impregnated by the fluid from other regions not reached by the fluid. Polarization microscope observation clearly reveals the detailed structures of tortuous or branched fractures on the micron scale and interactions between fractures a... [more]
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