A review of reservoir stimulation technologies for enhanced geothermal systems

Enhanced Geothermal Systems (EGS) are a critical technology for the global low-carbon energy transition, yet their widespread commercialization is hindered by the core challenge of deep reservoir stimulation. To address this, we propose a unified analytical framework centered on the “Engineering Trilemma": the conflicting objectives of ensuring effective connectivity, achieving sustainable heat extraction, and managing induced seismicity. A systematic assessment of the three primary stimulation paradigms—hydraulic, chemical, and thermal—reveals a crucial insight: no single technology can independently resolve its inherent trade-offs. While hydraulic stimulation is most potent for creating macroscopic connectivity, it poses the highest seismic and environmental risks. Chemical stimulation offers precise, micro-scale control but is constrained by a limited radius of influence and applicability to specific mineralogies. Thermal stimulation presents a less invasive, endogenous energy-driven approach, yet its efficacy is highly contingent on specific geological settings. This central insight reframes EGS engineering as the continuous management of these trade-offs and points to an inevitable paradigm shift. Future development must move beyond reliance on any single technology toward a data-driven, integrated, and adaptive reservoir management philosophy. This evolution will ultimately pave the way for a fundamental transition from speculative geological exploration to deterministic subsurface engineering.