The bound growth of induced earthquakes could de-risk hydraulic fracturing

The world's energy supply depends critically on hydraulic fracturing (HF): HF operations utilize microseismicity to enhance subsurface permeability, so that hydrocarbons or geothermal heat can be extracted economically.  Unfortunately, HF also has the potential to induce larger earthquakes – with some projects being prematurely terminated because of perceived earthquake risks.  To de-risk HF, we use a suite of novel statistical tests called CAP-tests to discern if some physical process has restricted the growth of earthquake magnitudes.  We show that all stage stimulations at UK PNR-1z indicate bound fracture growth, implying a more controllable operation.  Contrastingly, stimulations at Utah FORGE and UK PNR-2 sequentially transitioned into unbound fault reactivation.  The problematic stages (that ultimately led to the termination of PNR-2) are clearly distinguishable using CAP-tests.  We postulate that our research can discriminate fracture stimulation from fault reactivation, contributing to the de-risking of HF operations worldwide.