First World Congress of International Consortium on Geo-disaster Reduction (1st ICGdR World Congress)

We evaluate stress state in the northeastern Tibetan Plateau (Gonghe EGS) using anelastic strain recovery (ASR), wellbore breakouts, and moment tensor (MT) solutions. All methods confirm that the stress regime at ~1700–4000 m is strike-slip transitioning to thrust faulting and aligned with tectonic compression (NE-SW). S_Hmax magnitudes in the critically stressed reservoir are much lower than Byerlee's limit (μ=0.6–0.85) and attributed to frictionally weak chlorite infill on fractures in a critically stressed crust. Borehole breakouts confirm that S_Hmax is orientated N35°±11°E - congruent with the ongoing northeast expansion of the Tibetan Plateau and representing the first-order control on stress state. Microearthquakes generated during fluid-injection stimulation of the Gonghe EGS reservoir migrate upward, confirming the proximity of the minor principal stresses S_hmin and Sv and providing further direct evidence of the fidelity of the stress estimates.

 

Stress state; Anelastic strain recovery; Borehole damage; Fluid-injection-MT Solutions; Enhanced geothermal systems; Gonghe Basin