Hydraulic stimulation strategies in enhanced geothermal systems (EGS): a review

Abstract In enhanced geothermal systems (EGS), the natural permeability of deep rocks is normally not high enough and needs to be increased. Permeability increase can achieved through various stimulation methods, such as hydraulic, chemical, thermal stimulation. Among these, hydraulic most commonly used technique both reservoir specific area for heat exchange. A comprehensive understanding underlying processes towards an optimization performance while minimizing potential unwanted induced seismicity a critical prerequisite successful development any EGS site. this paper, we review strategies that have been developed implemented EGS. We begin with description mechanisms which exchange increases are achieved. then discuss fluid injection-induced during after operation. After that, alternative strategies, namely conventional stimulation, multi-stage fracturing, cyclic soft reviewed based on current research in theoretical studies well as, laboratory, in-situ field experiments. Finally, some representative projects reviewed, focusing injection seismic responses, enhancement performance. The shows importance need (a) geological characterization fracture system including nearby fault zones stress conditions, prior site, (b) proper design arrangement, positioning production wells, (c) selection appropriate strategy at hand.