Creating Reservoirs from Scratch
Conventional geothermal power requires a rare geological coincidence: hot rock, natural permeability, and trapped fluids all at accessible depth. Enhanced Geothermal Systems (EGS) remove the permeability constraint by engineering it — pumping high-pressure fluid into hot, impermeable basement rock to create fracture networks that allow heat extraction. This simulator models the hydraulic stimulation process that transforms barren granite into a productive geothermal reservoir.
Fracture Mechanics
When injection pressure exceeds the minimum horizontal stress plus the rock's tensile strength, hydraulic fractures initiate and propagate outward from the wellbore. The fracture radius depends on injection rate, fluid viscosity, rock toughness, and stress state. In crystalline basement rock, stimulation often reactivates pre-existing natural fractures through shear displacement rather than creating entirely new tensile fractures — this 'hydroshearing' mechanism creates better long-term permeability.
Induced Seismicity
The injection of high-pressure fluid into stressed rock inevitably triggers microseismic events as fractures slip and open. Most events are too small to feel (Mw < 0), but occasionally larger events occur. The Basel EGS project was suspended in 2006 after inducing a Mw 3.4 earthquake. Modern projects implement traffic-light protocols: injection continues during green (low seismicity), is reduced during amber, and stopped during red conditions.
The EGS Promise
Despite challenges, EGS represents perhaps the largest untapped energy resource on Earth. Hot rock exists everywhere at sufficient depth — the MIT study estimated US EGS potential at 100+ GW electric. Advances in directional drilling, stimulation techniques, and seismic monitoring are steadily reducing costs and risks. Projects at Soultz (France), Cooper Basin (Australia), and Fervo Energy (USA) are proving that commercial EGS is achievable.