Monitoring induced seismicity in the Weiyuan shale gas field utilizing a dense array

Abstract

Understanding the mechanisms of induced seismicity and assessing associated hazards is crucial for risk mitigation in shale gas production regions. From August 2022 to February 2023, we maintained a dense array of 245 nodal stations with an average spacing of ∼3 km, covering the entire Weiyuan shale gas field (WSGF), an actively exploited region that has experienced induced earthquakes up to M_w 5.0. Using the LOC-FLOW, we constructed a high-resolution earthquake catalog, precisely locating 29,669 events ranging from M_L − 1.35 to M_L 3.42 with a completeness magnitude (M_c) of −0.24. Seismicity formed five distinct clusters, with those in the southern WSGF closely surrounding hydraulic fracturing wells and exhibiting migration patterns consistent with pore-pressure diffusion. In contrast, northern seismicity displayed characteristics of fault reactivation, with events aligning with pre-existing geological structures. Additionally, we observed persistent seismic activity near the epicenter of 2019 M_w 5.0 event, suggesting a long-lasting aftershock sequence. Our findings emphasize the necessity of high-resolution seismic monitoring and long-term hazard assessment in shale gas fields. The results contribute to a better understanding of injection-induced seismicity and fault activation processes, providing valuable insights for risk mitigation and sustainable resource production in tectonically sensitive regions.