Abstract
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.
Highlights
Geothermal energy is a promising and clean renewable energy resource in the world
In addition to the wide use for heating done by ground source heat pumps (GSHP) [1], it can be utilized for power generation from enhanced geothermal systems (EGS) [2]
Numerical methods have a great advantage in solving complicated problems, the increased storage memory to store the result of each time interval and the computation time to discretize the entire computational model compromise their application in practice to some extent, especially for geothermal systems with sparsely distributed fractures
Summary
Geothermal energy is a promising and clean renewable energy resource in the world. In addition to the wide use for heating done by ground source heat pumps (GSHP) [1], it can be utilized for power generation from enhanced geothermal systems (EGS) [2]. Established a mathematical model with an infinite line-shaped and of an analytical solution for temperature distribution considering the one-dimensional fracture conduction presented an analytical solution forThe temperature distribution considering theforone-dimensional rocks and convective of fracture water. The two-dimensional heat transfer model for a finite line-shaped fracture was introduced by Cheng et al [11] who formulated a Laplace transform reservoir with a finite line-shaped fracture was introduced by Cheng et al [0] who formulated a semi-analytical method. The three-dimensional heat transfer model with a fracture and its Laplace transform semi-analytical solution was proposed by Ghassemi et al [12]. Finite disc-shaped fracture and its Laplace transform semi-analytical solution was proposed by. Took into account equidistant, parallel, infinite disc-shaped fractures and its derived its Laplace transform semi-analytical solution. Model to predict the heat extracted from an EGS with multiple fractures
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