Indicator Diagram for Underground Fluid Injection Induced Seismicity

Abstract

Pressure build-up induced by geological carbon sequestration (GCS) will decrease the effective stresses in the storage formation, and geomechanical effects of overpressure may affect fault stability, possibly resulting in felt induced seismicity. Predicting the geomechanical stability of faults is of crucial importance for the safety of GCS. In this paper, we applied a numerical approach to evaluate the potential magnitude of fault slippage for a specific stress regime. Next, we focused on the geometry and structures of fault zones through comprehensive analyses of the thickness of the overburden (H), the fault dip (Φ), and the distance between the fault and the injection well (D). Based on the relationships of D, H, and Φ with the corresponding fault behavior, we obtained a traffic light indicator diagram to assess the risk of induced seismicity at a specific level of each factor. Further, to overcome the complicated relationship between factor variations and the corresponding fault slippage, we introduced a danger surface in the traffic light indicator diagram with a security threshold of inducing moderate to strong seismicity to distinguish the danger zone. This approach provides physically sound outcomes for prioritizing the well location to avoid the risk of inducing strong seismicity.