Mike Brudzinski, Miami Univ. Factors Influencing Whether Hydraulic Fracturing Induces Seismicity

Mike Brudzinski

Department of Geology and Evironmental Earth Science, Miami University

Factors Influencing Whether Hydraulic Fracturing Induces Seismicity

The sharp increase in earthquakes in the Central and Eastern United States over the past decade has primarily been attributed to the large volume injection of saltwater into deep sedimentary layers. Although microseismicity with magnitude (M) < 0 is an inherent component of hydraulic fracturing (HF) to increase permeability in hydrocarbon source rocks, we have sought to investigate the degree to which HF induces larger magnitude seismicity along pre-existing faults. We utilized multi-station seismogram cross correlation to improve the completeness of seismicity catalogs and then compared them to publicly available timing and location of HF. We have identified that HF induced the larger magnitude type of seismicity more often than generally assumed and was the dominant source of earthquakes in some areas. Through coordination, collaboration, computational developments, and field deployments, we have documented cases of HF-induced seismicity in Ohio, Pennsylvania, West Virginia, Oklahoma, Arkansas, and Texas. For example, our analysis in the Eagle Ford shale play found ~200 M ≥ 2.0 earthquakes correlated with ~350 HF wells, including the May 1, 2018 M 4.0 earthquake that appears to be the largest HF-induced earthquake in the US. Wells inducing seismicity are clustered along the southern edge of the Karnes Trough, highlighting how proximity to faults can influence whether HF results in seismicity.

In the Appalachian Basin, detailed examination of the depth distribution and frequency-magnitude patterns of HF induced seismicity indicate the maturity of faults plays a role in the types of seismicity produced. In Oklahoma, we have used ~700 M ≥ 2.0 earthquakes correlated with ~300 HF wells to identify the largest earthquake in an induced sequence was more likely as injection proceeded, highlighting opportunities for real-time decision making if sufficient monitoring exists. Detailed investigations across the different study regions indicate that the effective injection rate (i.e., volume per day per area) plays a particularly important role in the probability of seismicity. For example, multiwell completion (e.g., zipper stimulation) have had 200-300% increased incidence of seismicity over other operational strategies. In addition, statistical modeling of our observations suggests the probability of HF-induced seismicity can also be influenced by the injected volume, viscosity of the injected fluid, depth of the injection, stratigraphic interval stimulated, and number of laterals on the well pad. These findings provide clues about the physical mechanisms involved, but ultimately broader integration with geomechanical, hydrological, and structural datasets will be necessary to determine the best practices for mitigating the hazard.

https://stanford.zoom.us/j/93705355898 Passcode:  083990