Hot　dry　rock　geothermal　energy　relies　on　optimized　fracture　networks　for　efficient　thermal　energy　extraction.　This　research　employs　the　finite　element　method　to　establish　a　discrete　fracture　network　(DFN)　model　that　integrates　fluid　mechanics　and　thermodynamics　within　a　porous　medium,　enabling　a　comprehensive　assessment　of　the　coupled　impact　of　varying　fracture　lengths　and　densities　on　production　performance.　Unlike　prior　studies　focusing　on　uniform　or　simple　fracture　networks,　our　model　simulates　fluid　flow　and　heat　transfer　under　complex　fracture　configurations,　offering　a　quantitative　framework　to　evaluate　key　physical　properties　such　as　fluid　pressure,　Darcy　velocity,　and　temperature.　Results　reveal　that　networks　with　moderate　fracture　lengths　and　densities　form　effective　flow　channels,　maintain　pressure　gradients　and　Darcy　velocity　between　wells,　and　improve　overall　flow　and　thermal　extraction　efficiencies,　thereby　extending　the　lifespan　of　geothermal　projects.　Conversely,　low　fracture　density　or　excessive　unconnected　short　fractures　hinder　fluid　movement　and　heat　exchange,　while　overly　long　fractures　lead　to　rapid　pressure　drops　and　temperature　declines,　posing　sustainability　challenges.　Optimizing　fracture　length　and　density　is　essential　to　sustaining　extraction　efficiency　and　preventing　rapid　thermal　dissipation.　These　insights　lay　groundwork　for　theoretical　optimization　of　fracture　networks　and　are　critical　for　designing　efficient,　durable　hot　dry　rock　energy　systems.　©　2024　Elsevier　Ltd