A novel three-dimensional transient model for subsurface heat exchange in enhanced geothermal systems

2013 ◽  
Vol 41 ◽  
pp. 57-62 ◽  
Author(s):  
Fangming Jiang ◽  
Liang Luo ◽  
Jiliang Chen
Keyword(s):  
Heat Exchange ◽  
Three Dimensional ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Transient Model

scholarly journals Deep learning for extracting micro-fracture: Pixel-level detection by convolutional neural network

2020 ◽  
Vol 205 ◽  
pp. 03007
Author(s):  
Yejin Kim ◽  
Seong Jun Ha ◽  
Tae sup Yun
Keyword(s):  
Neural Network ◽  
Deep Learning ◽  
Convolutional Neural Network ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Frequency Noise ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Hydraulic Stimulation ◽  
Roughness Analysis

Hydraulic stimulation has been a key technique in enhanced geothermal systems (EGS) and the recovery of unconventional hydrocarbon resources to artificially generate fractures in a rock formation. Previous experimental studies present that the pattern and aperture of generated fractures vary as the fracking pressure propagation. The recent development of three-dimensional X-ray computed tomography allows visualizing the fractures for further analysing the morphological features of fractures. However, the generated fracture consists of a few pixels (e.g., 1-3 pixels) so that the accurate and quantitative extract of micro-fracture is highly challenging. Also, the high-frequency noise around the fracture and the weak contrast across the fracture makes the application of conventional segmentation methods limited. In this study, we adopted an encoder-decoder network with a convolutional neural network (CNN) based on deep learning method for the fast and precise detection of micro-fractures. The conventional image processing methods fail to extract the continuous fractures and overestimate the fracture thickness and aperture values while the CNN-based approach successfully detects the barely seen fractures. The reconstruction of the 3D fracture surface and quantitative roughness analysis of fracture surfaces extracted by different methods enables comparison of sensitivity (or robustness) to noise between each method.

scholarly journals A Semi-Analytical Method for Three-Dimensional Heat Transfer in Multi-Fracture Enhanced Geothermal Systems

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1211 ◽  
Author(s):  
Dongdong Liu ◽  
Yanyong Xiang
Keyword(s):  
Analytical Method ◽  
Three Dimensional ◽  
Heat Extraction ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Rock Matrix ◽  
Multiple Fractures ◽  
One Dimensional ◽  
Production Temperature

Multiple fractures have been proposed for improving the heat extracted from an enhanced geothermal system (EGS). For calculating the production temperature of a multi-fracture EGS, previous analytical or semi-analytical methods have all been based on an infinite scale of fractures and one-dimensional conduction in the rock matrix. Here, a temporal semi-analytical method is presented in which finite-scale fractures and three-dimensional conduction in the rock matrix are both considered. Firstly, the developed model was validated by comparing it with the analytical solution, which only considers one-dimensional conduction in the rock matrix. Then, the temporal semi-analytical method was used to predict the production temperature in order to investigate the effects of fracture spacing and fracture number on the response of an EGS with a constant total injection rate. The results demonstrate that enlarging the spacing between fractures and increasing the number of fractures can both improve the heat extraction; however, the latter approach is much more effective than the former. In addition, the temporal semi-analytical method is applicable for optimizing the design of an EGS with multiple fractures located equidistantly or non-equidistantly.

Convective heat transfer of water flowing in intersected rock fractures for enhanced geothermal extraction

2021 ◽  
Author(s):  
Yuedu chen
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Production ◽  
Three Dimensional ◽  
Heat Extraction ◽  
Rock Fractures ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Dead End

<p>Numerous intersected rock fractures constitute the fracture network in enhanced geothermal systems. The complicated convective heat transfer behavior in intersected fractures is critical to the heat recovery in fractured geothermal reservoirs. A series of three-dimensional intersected fracture models are constructed to perform the flow-through heat transfer simulations. The geometries effects of dead-end fractures on the heat transfer are evaluated in terms of intersected angles, apertures, lengths, and the connectivity. The results indicate that annular streamlines appear in the rough dead-end fracture and cause an ellipsoidal distribution of the cold front. Compared to the steady flow in plate dead-end fractures, the fluid flow formed in the rough dead-end fracture enhances the heat transfer. Both the outlet water temperature T<sub>out</sub> and heat production Q present the largest when the intersected angle is 90°. A larger intersected angle and longer length extension of the intersected dead-end fracture, raising T<sub>out</sub> and Q, are beneficial to the heat production, while increasing the aperture is ineffective. Solely increasing numbers of dead-end fractures poses a little increase on T<sub>out</sub> and Q. More significant heat extraction is obtained through connecting these dead-end fractures with the main flow fracture forming the flow network.</p>

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

scholarly journals Environmentally friendly, rheoreversible, hydraulic-fracturing fluids for enhanced geothermal systems

Geothermics ◽  
2015 ◽  
Vol 58 ◽  
pp. 22-31 ◽  
Author(s):  
Hongbo Shao ◽  
Senthil Kabilan ◽  
Sean Stephens ◽  
Niraj Suresh ◽  
Anthon N. Beck ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Environmentally Friendly ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Fracturing Fluids
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