Numerical simulation of a single-well enhanced geothermal system based on thermal-hydraulic-mechanical coupling
To improve the heat extraction efficiency of deep well heat exchangers,a single-well enhanced geother-mal system(SEGS)was proposed using the development idea of hot dry rock for reference.The rock mass at the bottom of a single-well casing was reformed by small-scale fracturing;the single-well casing was changed from a closed system to an open system to improve the heat extraction performance of a single-well system.A thermal-hy-draulic-mechanical coupling three-dimensional unsteady-state numerical model was established to study the system performance of SEGS and the influence of various key parameters.Results show that compared with the traditional deep well heat exchanger,SEGS has a greatly improved heat collection performance.Under the same injection con-dition,the production temperature and heat collection power are increased by 62.21℃and 2 612.99 kW,respec-tively.In terms of a geothermal engineering cycle and optimization,it is more appropriate to control the SEGS flow at 10 kg/s.A small flow of SEGS decreases heat extraction efficiency,and a large flow shortens service life.In-creasing the wellbore spacing and reducing the thermal conductivity of the inner pipe effectively improves the heat transfer performance of the system.Herein,we provide a reference for the theoretical analysis and practical appli-cation of SEGS.
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