Fault reactivation and earthquakes with magnitudes of up to Mw4.7 induced by shale-gas hydraulic fracturing in Sichuan Basin, China

Abstract

This paper presents a timely and detailed study of significant injection-induced seismicity recently observed in the Sichuan Basin, China, where shale-gas hydraulic fracturing has been initiated and the aggressive production of shale gas is planned for the coming years. Multiple lines of evidence, including an epidemic-type aftershock sequence model, relocated hypocenters, the mechanisms of 13 large events (M W > 3.5), and numerically calculated Coulomb failure stress results, convincingly suggest that a series of earthquakes with moment magnitudes up to M W 4.7 has been induced by “short-term” (several months at a single well pad) injections for hydraulic fracturing at depths of 2.3 to 3 km. This, in turn, supports the hypothesis that they represent examples of injection-induced fault reactivation. The geologic reasons why earthquake magnitudes associated with hydraulic fracturing operations are so high in this area are discussed. Because hydraulic fracturing operations are on the rise in the Sichuan Basin, it would be beneficial for the geoscience, gas operator, regulator, and academic communities to work collectively to elucidate the local factors governing the high level of injection-induced seismicity, with the ultimate goal of ensuring that shale gas fracking can be carried out effectively and safely.

A new numerical method for evaluating the variation of casing inner diameter after strike‐slip fault sliding during multistage fracturing in shale gas wells

“…[26][27][28][29] Engineering monitoring in this study proved this point, the maximal moment magnitude Some scholars pointed out that West Canadian reservoirs and Sichuan Basin in China experienced anomalous activity during multistage fracturing, the microseismic moment magnitude was more than 4.…”

An Extremely Shallow Mw4.1 Thrust Earthquake in the Eastern Sichuan Basin (China) Likely Triggered by Unloading During Infrastructure Construction

“…Previous studies have reported some shallow earthquakes in the southern Sichuan Basin in the vicinity of the oil and gas wells, mostly triggered by hydraulic fracturing (e.g., Lei et al, 2008Lei et al, , 2017. However, the closest oil and gas wells with associated induced seismicity are located at least 40 km away from the Dianjiang earthquake.…”

“…The basement faults are hidden in the crystal basement (>5 km) and show minor activity . Based on the Chongqing Seismic Network catalog (1990 to 2018), there was no other M > 3.5 event within 100 km of the Dianjiang earthquake, indicating a low background seismic rate, although many shallow earthquakes in the Sichuan Basin have been linked with wastewater injection (e.g., Lei et al, 2008) and hydraulic fracturing in shale gas fields (e.g., Lei et al, 2017;Figure 1a). Based on the Chongqing Seismic Network catalog (1990 to 2018), there was no other M > 3.5 event within 100 km of the Dianjiang earthquake, indicating a low background seismic rate, although many shallow earthquakes in the Sichuan Basin have been linked with wastewater injection (e.g., Lei et al, 2008) and hydraulic fracturing in shale gas fields (e.g., Lei et al, 2017;Figure 1a).…”

Earthquakes Induced by Hydraulic Fracturing Are Pervasive in Oklahoma

“…Individual case examples of HF‐induced seismicity have been now be identified in Alberta (e.g., Wang et al, ), Arkansas (Yoon et al, ), British Columbia (e.g., B.C. Oil and Gas Commission, ), California (Kanamori & Hauksson, ), China (e.g., Lei et al, ), England (Clarke et al, ), Ohio (e.g., Skoumal et al, ), Oklahoma (e.g., Holland, ), Pennsylvania (Skoumal et al, ), and West Virginia (Skoumal et al, ).…”

“…This interpretation was based on the few documented cases of HF‐induced seismicity, with the cases consistent of small‐magnitude events. Since these interpretations were made, larger‐magnitude earthquakes that have been attributed to hydraulic fracturing have occurred, including the 2015 M 4.6 earthquake in British Columbia, Canada (Atkinson et al, ; Mahani et al, ), and the 2016 M 4.7 earthquake in the Sichuan Basin, China (Lei et al, ). Additionally, while the number of cases identified prior to these studies was limited (Clarke et al, ; Darold et al, ; Friberg et al, ; Holland, ), more recent studies have found a higher prevalence of HF‐induced seismicity than would have been previously expected (Atkinson et al, ; Skoumal et al, ).…”