We analyze the temporal evolution of the induced seismicity related to hydraulic fracturing activities in the Duvernay Formation, near Fox Creek, Alberta, Canada. For this analysis, we estimate annual Gutenberg‐Richter parameters, a(t) $a(t)$‐ and b(t) $b(t)$‐ values, and then calculate the annual likelihood of earthquakes greater than magnitude M>4 $M > 4$ from 2014 to 2020. The seismic hazard near Fox Creek has consistently decreased since 2015, from a 95% probability of an earthquake greater than magnitude M>4 $M > 4$ in 2015 to 4% in 2019 and less than 1% probability in 2020. The induced seismicity in Fox Creek is characterized by two actively seismic regions with distinctive features: (a) an Eastern region (∼220 events M>2 $M > 2$) with lower b‐values and higher hazard; (b) a Western region (∼210 events M>2 $M > 2$) with higher b‐values and lower seismic hazard. In contrast, extensive regions where hydraulic fracturing is performed, particularly East of the seismic cluster, remain non‐seismogenic. The overall decreasing seismic hazard, which contrasts with increasing operator activity, can be associated with (a) the intensification of hydraulic fracturing operations toward areas less susceptible to induced seismicity and (b) the reduction of seismic activity in the Eastern region, which exhibits the highest seismic hazard. We also find evidence of a minimum annual injection volume required to trigger induced seismicity in both the Western and Eastern regions. The minimum injection threshold increases over the years, implying increasingly successful mitigation strategies, likely due to regulatory implementations in the area, which has led the operators to exercise precaution in regions with significant seismic hazard and adapt treatment strategies to avoid triggering moderate magnitude size events during hydraulic fracturing stimulations.

The Bowland Shale Formation is one of the most promising targets for unconventional exploration in the United Kingdom, with estimated resources large enough to supply the country's entire natural gas consumption for 50 years. However, development of the Bowland Shale has stalled due to concerns over hydraulic-fracturing induced seismicity. Only three wells have been drilled and hydraulic fractured to date in the Bowland Shale, and all three wells have produced levels of seismicity of sufficient magnitude to be felt at the surface. Susceptibility to induced seismicity will be determined by the presence of critically-stressed faults. However, such faults can go undetected in conventional interpretation of 2D or 3D seismic surveys if they are shorter that the resolution retrievable from a seismic survey, or if they have low (and in some cases even zero) vertical displacement. In such cases, the faults that cause induced seismicity may only be visible via microseismic observations once they are reactivated. To better identify fault planes from 3D seismic images, and their reactivation potential due to hydraulic fracturing, a high-resolution fault-detection attribute was tested in a 3D seismic survey that was acquired over the Preston New Road site, where two shale-gas wells were hydraulic-fractured in the Bowland Shale in 2018 and 2019, obtaining fault planes with lengths between 400 and 1500 meters. Fault slip potential was then estimated by integrating the obtained faults with the formation's stress and pore pressure conditions (with the Bowland shale also being significantly overpressured), and several critically stressed faults were identified near the previously hydraulic fractured wells. However, the faults that induced the largest seismic events in the Preston New Road site, of approximately 200 meters in length for seismic events of magnitudes below 3.0 (as imaged with a multicomponent, downhole microseismic monitoring array deployed during the hydraulic fracturing stimulations), could not be identified in the 3D seismic survey that only mapped fault planes larger than 400 meters in length.

Passive-seismic monitoring techniques were implemented for source characterization of microseismic events generated during a hydraulic-fracturing operation in a coalbed-methane (CBM) reservoir in Colombia. Hydraulic fracturing is a common stimulation technique performed to increase the permeability and productivity of conventional and unconventional reservoirs. Its use has increased in the last decade in several countries, including Colombia, and it is expected to keep rising in the following years. The success of a hydraulic-fracturing operation can be assessed in different ways, of which microseismic monitoring is the most common technique. This method can be implemented using surface or downhole seismometers and allows the characterization of microseismic events associated with the fractures generated. A workflow for passive-seismic data analysis was developed to characterize microseismic events (i.e., hypocenter location and source-mechanism analysis) from data acquired with surface stations and to obtain important parameters for a hydraulic-fracturing design such as the stimulated reservoir volume (SRV), orientation, and anisotropy of horizontal stresses and a discrete fracture network (DFN). This workflow was implemented in a case study in Colombia in which a coalbed-methane reservoir in Cesar-Ranchería Basin was stimulated by hydraulic fracturing. Surface seismometers were deployed around the wellhead to monitor the microseismicity generated and to estimate all the design parameters of the stimulation.

The development of organic-rich, low-permeability formations for hydrocarbon production requires the use of unconventional techniques such as multiwell pad drilling of horizontal wells and massive multistage hydraulic-fracturing stimulations. However, proliferation of these unconventional development methods has been linked to localized cases of fault reactivation during or shortly after hydraulic fracturing. In the Duvernay formation, located in Alberta, Canada, induced seismicity from hydraulic fracturing has occurred on nearly vertical strike-slip faults that are difficult to detect with conventional seismic exploration methods. In such cases, faults may only be discernible from seismic events with precise and accurate locations, which generally requires dense seismic monitoring arrays deployed near the stimulated wells. In this study, we introduce a new, semiautomated workflow for processing passive seismic data from a dense array and then integrate it with a 3D seismic dataset to characterize seismicity clusters related to hydraulic fracturing and pre-existing faults. The reactivated faults inferred from the distribution of the microseismic events directly overlie a system of incised, middle Devonian channels below the Duvernay formation observed in time slices extracted from the 3D seismic data. The channel system exhibits a set of lateral offsets, interpreted as ancient strike-slip fault displacements, the detection of which is further enhanced by use of a similarity attribute calculated from the 3D seismic data. Taken together, integrated interpretation of induced seismicity and 3D seismic data support a model of a regional left-lateral strike-slip fault system that was active during the middle Devonian and reactivated in a reverse sense (right-lateral strike slip) during hydraulic-fracturing operations.

The application of seismic methods for rock and soil-mass characterization has proved to be useful for engineering projects of any kind. These methods can predict the presence and geometry of low-competent subsoil materials and can define preliminary structural designs for each project. In three studies in Colombia, refraction tomography and multichannel analysis of surface waves (MASW) were applied for road tunnels and multistory building construction, respectively. In situ rock and soil types were classified based on P- and S-wave measurements, and preliminary structural designs and construction methods were recommended for each case. Both rock and soil classifications and preliminary structural designs must be refined with direct subsoil-characterization methods such as core drilling and laboratory testing.