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The energy efficiency of the enhanced geothermal system (EGS) measures the economic value of the heat production and electricity generation, and it is a key indicator of system production performance. Presently there is no systematic study on the influence of well layout on the system energy efficiency. In this work we numerically analyzed the main factors affecting the energy efficiency of EGS using the TOUGH2-EOS1 codes at Gonghe Basin geothermal field, Qinghai province. The results show that for the reservoirs of the same size, the electric power of the three horizontal well system is higher than that of the five vertical well system, and the electric power of the five vertical well system is higher than that of the three vertical well system. The energy efficiency of the three horizontal well system is higher than that of the five vertical well system and the three vertical well system. The reservoir impedance of the three horizontal well system is lower than that of the three vertical well system, and the reservoir impedance of the three vertical well system is lower than that of the five vertical system. The sensitivity analysis shows that well spacing has an obvious impact on the electricity production performance; decreasing well spacing will reduce the electric power, reduce the energy efficiency and only have very slight influence on the reservoir impedance. Fracture spacing has an obvious impact on the electricity production performance; increasing fracture spacing will reduce the electric power and reduce the energy efficiency. Fracture permeability has an obvious impact on the electricity production performance; increasing fracture permeability will improve the energy efficiency and reduce the reservoir impedance.
Yuchao Zeng; Fangdi Sun; Haizhen Zhai. Numerical Study on the Influence of Well Layout on Electricity Generation Performance of Enhanced Geothermal Systems. Processes 2021, 9, 1474 .
AMA StyleYuchao Zeng, Fangdi Sun, Haizhen Zhai. Numerical Study on the Influence of Well Layout on Electricity Generation Performance of Enhanced Geothermal Systems. Processes. 2021; 9 (8):1474.
Chicago/Turabian StyleYuchao Zeng; Fangdi Sun; Haizhen Zhai. 2021. "Numerical Study on the Influence of Well Layout on Electricity Generation Performance of Enhanced Geothermal Systems." Processes 9, no. 8: 1474.
The equivalent continuum method an effective approach for modeling heat transfer in fractured geothermal reservoirs. However, presently there is a lack of systematical and profound study on application conditions of the equivalent porous media (EPM) method. In this study, we numerically investigated the application conditions of the EPM method based on geological data of Yangbajing geothermal field. The results indicate that when fracture spacing is within 3–25 m, the results of the EPM method are basically in the same levels as those of the MINC method. However, when the fracture spacing is within 25–300 m, differences of the EPM method from the MINC method increase with the fracture spacing, so when the fracture spacing is within 25–300 m, it is unreasonable to adopt the EPM method to simulate the fractured reservoirs. With the fracture spacing increasing within 25–300 m, the system production temperature and electric power will gradually decrease; the injection pressure, reservoir impedance and pump power will gradually increase; and the energy efficiency will gradually decrease.
Yuchao Zeng; Fangdi Sun; Haizhen Zhai. Numerical Study on Application Conditions of Equivalent Continuum Method for Modeling Heat Transfer in Fractured Geothermal Reservoirs. Processes 2021, 9, 1020 .
AMA StyleYuchao Zeng, Fangdi Sun, Haizhen Zhai. Numerical Study on Application Conditions of Equivalent Continuum Method for Modeling Heat Transfer in Fractured Geothermal Reservoirs. Processes. 2021; 9 (6):1020.
Chicago/Turabian StyleYuchao Zeng; Fangdi Sun; Haizhen Zhai. 2021. "Numerical Study on Application Conditions of Equivalent Continuum Method for Modeling Heat Transfer in Fractured Geothermal Reservoirs." Processes 9, no. 6: 1020.
Because geologic sedimentation and hydrofracturing processes are not homogeneous, the reservoirs of enhanced geothermal systems (EGSs) are also heterogeneous; this has a significant influence on the electricity generation performance of EGS. Presently, there are a lack of systematic and profound studies on the effect of vertical permeability heterogeneity in stratified formation on the electricity generation performance of EGS. In order to uncover the effect of vertical permeability heterogeneity on electricity generation performance of EGS, in this work we analyzed the influence of vertical permeability heterogeneity on electricity generation performance of EGS through a numerical method based on geological data at the Yangbajing geothermal field. The results indicate that when the average permeability of stratified formations is constant for a homogeneous reservoir, the system attains maximum water production rate, maximum electric power, minimum reservoir impedance and maximum pump power; with the increasing of the vertical permeability heterogeneity, the water production rate gradually decreases, the electric power gradually declines, the reservoir impedance gradually increases and the pump power gradually declines. When the average permeability of stratified formations is constant, with the increasing of the vertical permeability heterogeneity, the injection pressure and energy efficiency only changes very slightly; this indicates that the vertical permeability heterogeneity is not the main factor affecting the system injection pressure and energy efficiency.
Yuchao Zeng; Fangdi Sun; Haizhen Zhai. Effect of Vertical Permeability Heterogeneity in Stratified Formation on Electricity Generation Performance of Enhanced Geothermal System. Processes 2021, 9, 744 .
AMA StyleYuchao Zeng, Fangdi Sun, Haizhen Zhai. Effect of Vertical Permeability Heterogeneity in Stratified Formation on Electricity Generation Performance of Enhanced Geothermal System. Processes. 2021; 9 (5):744.
Chicago/Turabian StyleYuchao Zeng; Fangdi Sun; Haizhen Zhai. 2021. "Effect of Vertical Permeability Heterogeneity in Stratified Formation on Electricity Generation Performance of Enhanced Geothermal System." Processes 9, no. 5: 744.
Poyang Lake is the largest freshwater lake connecting the Yangtze River in China. It undergoes dramatic dynamics from the wet to the dry seasons. A comparison of the hydrological changes between the wet and dry seasons may be useful for understanding the water flows between Poyang Lake and Yangtze River or the river system in the watershed. Gauged measurements and remote sensing datasets were combined to reveal lake area, level and volume changes during 2000–2020, and water exchanges between Poyang Lake and Yangtze River were presented based on the water balance equation. The results showed that in the wet seasons, the lake was usually around 1301.85–3840.24 km2, with an average value of 2800.79 km2. In the dry seasons, the area was around 618.82–2498.70 km2, with an average value of 1242.03 km2. The inundations in the wet seasons were approximately quadruple those in the dry seasons. In summer months, the lake surface tended to be flat, while in winter months, it was inclined, with the angles at around 10′′–16′′. The mean water levels of the wet and dry seasons were separately 13.51 m and 9.06 m, with respective deviations of around 0–2.38 m and 0.38–2.15 m. Monthly lake volume changes were about 7.5–22.64 km3 and 1–5.80 km3 in the wet and dry seasons, respectively. In the wet seasons, the overall contributions of ground runoff, precipitation on the lake surface and lake evaporation were less than the volume flowing into Yangtze River. In the dry seasons, the three contributions decreased by 50%, 50% and 65.75%, respectively. Therefore, lake storages presented a decrease (−7.42 km3/yr) in the wet seasons and an increase (9.39 km3/yr) in the dry seasons. The monthly exchanges between Poyang Lake and Yangtze River were at around −14.22–32.86 km3. Water all flowed from the lake to the river in the wet seasons, and the chance of water flowing from Yangtze River in the dry seasons was only 5.26%.
Fangdi Sun; Ronghua Ma; Caixia Liu; Bin He. Comparison of the Hydrological Dynamics of Poyang Lake in the Wet and Dry Seasons. Remote Sensing 2021, 13, 985 .
AMA StyleFangdi Sun, Ronghua Ma, Caixia Liu, Bin He. Comparison of the Hydrological Dynamics of Poyang Lake in the Wet and Dry Seasons. Remote Sensing. 2021; 13 (5):985.
Chicago/Turabian StyleFangdi Sun; Ronghua Ma; Caixia Liu; Bin He. 2021. "Comparison of the Hydrological Dynamics of Poyang Lake in the Wet and Dry Seasons." Remote Sensing 13, no. 5: 985.
More than 1100 lakes covering an area greater than 4500 km2 are located on the Tibetan Plateau, and these lakes are important regulators of several large and famous rivers in Asia. The determination of hydrological changes that have occurred in these lakes can reflect climate change and supply scientific data to plateau environmental research. Data from high frequency (moderate-resolution imaging spectro-radiometer) MODIS images, altimetry, and the Hydroweb database collected during 2000–2015 were integrated in this study to delineate the detailed hydrological changes of 15 lakes in three basins—Inner Basin, Indus Basin, and Brahmaputra Basin—on the southern Tibetan Plateau. Seven of the 10 lakes in the Inner Basin presented increasing trends with various intensities, and the increasing rates in the area of four lakes (Nam Co, Selin Co, Zhari-namco, and Ngangze) were 1.62, 28.81, 2.27, and 3.70 km2/yr, respectively. The yearly increases in volume of the four lakes were 3.6, 9.44, 6, and 2.36 km3, respectively. A water balance equation was established for the four lakes based on lake volume changes to illustrate the contributions of precipitation, ground runoff, evaporation, and other factors. The results revealed that surface runoff was the major contributor to expansion, and lake surface evaporation was almost 2.76–3.86 times that of lake surface precipitation. The two lakes in Indus Basin, Rakshastal and Mapam Yumco, presented a slight retreat. As a representative of Brahmaputra Basin, Yamzho Yumco underwent a retreat of –3.49 km2/yr in area, –0.39 m/yr in level, and –0.19 km3/yr in volume. Decreasing precipitation, increasing evaporation, and the operation of a hydrological project were the main causes of its constant retreat.
Fangdi Sun; Ronghua Ma; Bin He; Xiaoli Zhao; Yuchao Zeng; Siyi Zhang; Shilin Tang. Changing Patterns of Lakes on The Southern Tibetan Plateau Based on Multi-Source Satellite Data. Remote Sensing 2020, 12, 3450 .
AMA StyleFangdi Sun, Ronghua Ma, Bin He, Xiaoli Zhao, Yuchao Zeng, Siyi Zhang, Shilin Tang. Changing Patterns of Lakes on The Southern Tibetan Plateau Based on Multi-Source Satellite Data. Remote Sensing. 2020; 12 (20):3450.
Chicago/Turabian StyleFangdi Sun; Ronghua Ma; Bin He; Xiaoli Zhao; Yuchao Zeng; Siyi Zhang; Shilin Tang. 2020. "Changing Patterns of Lakes on The Southern Tibetan Plateau Based on Multi-Source Satellite Data." Remote Sensing 12, no. 20: 3450.