Measurements of Hydraulic-Fracture-Induced Seismicity in Gas Shales

Abstract

Hydraulic fracturing is an essential technology for hydrocarbon extraction from both conventional and unconventional reservoirs. Recently, concern has developed regarding induced seismicity generated in association with multistage fracturing of horizontal wells in shale reservoirs. A review of thousands of fracture treatments that have been microseismically monitored shows that the induced seismicity associated with hydraulic fracturing is very small and not a problem under any normal circumstances. Results are presented for six major shale basins in North America.

Microseismic Imaging of Hydraulically Induced-Fractures in Gas Reservoirs: A Case Study in Barnett Shale Gas Reservoir, Texas, USA

“…[9]). In a comparison between the magnitude calculations between the two methods, Reference [11] indicated a good agreement between the Brune spectral analysis and the moment tensor inversion, despite the considerable scatter plot, with overall Brune magnitudes less than the moment tensor inversion. This is attributed to disability of spectral analysis to fully consider the radiation pattern and non-shear behavior.…”

“…[32]). Compared to earthquake seismology that successfully utilizes seismic moment tensor inversion, the good estimation of moment tensor during hydraulic fracturing operation, even with multiple monitoring wells, remain problematic [11]. For different source mechanism (strike slip, shear, and a mix strike slip-shear), Reference [33] constructed a plot of S/P amplitude ratio of high signal-to-noise ratios signals from different hydraulic fracturing projects at various sites using the azimuth relative to the trend of the main microseismic cloud.…”

“…Such information not only improves reservoir simulation but also optimizes the treatment economics [29]. However, Reference [11] indicated that while microseismic imaging is incredibly useful in revealing the fracture geometry and the way the fracture evolves but it does not provide detailed information about the fracturing process (mechanism) and seems currently with limited value for reservoir characterization. Several methods have been developed to calculate the moment of microseismic events which fall within two categories: the simple methods such as Brune moment calculation [9] and sophisticated methods that use moment tensor inversion to obtain the full moment tensor and high-quality data to get accurate information but require two monitor wells (e.g.…”

Microseismic Monitoring at the Large-scale CO2 Injection Site, Cranfield, MS, U.S.A.

“…The upper frequency range of 80 Hz corresponds to between M w 0 and M w 1 concerning the scaling law between corner frequency and moment magnitude M w [10]. The hypocentral distance and magnitude relation [11] also indicates that around M w 0 would be the minimum detectable magnitude at the hypocentral distance of about 3km. Therefore, it seems that the obtained results give reasonable value for the minimum detectable magnitudes.…”

Discrete element modeling of cyclic rate fluid injection at multiple locations in naturally fractured reservoirs

“…The M ¼5 Denver earthquake which occurred one year post-injection was not triggered by the injection and by excluding these earthquakes, the ratio of seismic radiated to hydraulic pumped-in energy is estimated to be 0.3-3% [35]. Also for reference, data point from [36] is added to Fig. 9, which is a representative data set for shale gas fracturing.…”