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The Thermal-Hydraulic-Mechanical Coupling Effects on Heat Extraction of Enhanced Geothermal Systems
Received date: 2015-09-18
Revised date: 2015-10-12
Online published: 2015-12-30
During heat extraction in enhanced geothermal systems (EGS), the reservoir porosity and permeability can be greatly affected by the multi-physical coupling of Thermal (T), Hydraulic (H), and Mechanical (M) actions. In the present work we develop a three-dimensional transient model coupling the subsurface THM behaviors during EGS heat extraction process. The local thermal non-equilibrium is assumed when describing the heat exchange between the rock matrix and heat transmission fluid. Case studies with respect to an imaginary quintuplet EGS reveal the involved mechanisms of inter-couplings in-between T-H-M actions, and the results indicate significant mechanical effects on EGS heat extraction performance. The stress of the rock matrix is largely influenced by the pore pressure and the temperature distributions. The stress triggered by fluid pressure is found to be compressive and confined in the very vicinity region of the injection well; the thermal stress is tensile and to some extent also concentrates around the injection well, but its distribution region expands toward the production well with the proceeding of heat extraction process. The temperature difference between rock matrix and heat transmission fluid is not only the driving force of heat extraction from heat reservoir but also significantly affects the formation of thermal stress in the reservoir.
CAO Wen-jiong , HUANG Wen-bo , JIANG Fang-ming . The Thermal-Hydraulic-Mechanical Coupling Effects on Heat Extraction of Enhanced Geothermal Systems[J]. Advances in New and Renewable Energy, 2015 , 3(6) : 444 -451 . DOI: 10.3969/j.issn.2095-560X.2015.06.006
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