Matthew Weingarten

Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection

Wastewater disposal linked to earthquakes The number of earthquakes is increasing in regions with active unconventional oil and gas wells, where water pumped at high pressure breaks open rock containing natural gas, leaving behind wastewater in need of disposing. Keranen et al. show that the steep rise in earthquakes in Oklahoma, USA, is likely caused by fluid migration from wastewater disposal wells. Twenty percent of the earthquakes in the central United States could be attributed to just four of the wells. Injected fluids in high-volume wells triggered earthquakes over 30 km away. Science, this issue p. 448 The recent surge in central U.S. seismicity is likely attributable to injection of wastewater at a small number of wells. Unconventional oil and gas production provides a rapidly growing energy source; however, high-production states in the United States, such as Oklahoma, face sharply rising numbers of earthquakes. Subsurface pressure data required to unequivocally link earthquakes to wastewater injection are rarely accessible. Here we use seismicity and hydrogeological models to show that fluid migration from high-rate disposal wells in Oklahoma is potentially responsible for the largest swarm. Earthquake hypocenters occur within disposal formations and upper basement, between 2- and 5-kilometer depth. The modeled fluid pressure perturbation propagates throughout the same depth range and tracks earthquakes to distances of 35 kilometers, with a triggering threshold of ~0.07 megapascals. Although thousands of disposal wells operate aseismically, four of the highest-rate wells are capable of inducing 20% of 2008 to 2013 central U.S. seismicity.

High-rate injection is associated with the increase in U.S. mid-continent seismicity

Making quakes depends on injection rates Wastewater injection wells induce earthquakes that garner much attention, especially in tectonically inactive regions. Weingarten et al. combined information from public injection-well databases from the eastern and central United States with the best earthquake catalog available over the past 30 years. The rate of fluid injection into a well appeared to be the most likely decisive triggering factor in regions prone to induced earthquakes. Along these lines, Walsh III and Zoback found a clear correlation between areas in Oklahoma where waste saltwater is being injected on a large scale and areas experiencing increased earthquake activity. Science, this issue p. 1336; Sci. Adv. 10.1126/sciadv.1500195 (2015). High injection rates of wastewater into deep wells increase the risk of earthquakes in regions prone to induced seismicity. An unprecedented increase in earthquakes in the U.S. mid-continent began in 2009. Many of these earthquakes have been documented as induced by wastewater injection. We examine the relationship between wastewater injection and U.S. mid-continent seismicity using a newly assembled injection well database for the central and eastern United States. We find that the entire increase in earthquake rate is associated with fluid injection wells. High-rate injection wells (>300,000 barrels per month) are much more likely to be associated with earthquakes than lower-rate wells. At the scale of our study, a well’s cumulative injected volume, monthly wellhead pressure, depth, and proximity to crystalline basement do not strongly correlate with earthquake association. Managing injection rates may be a useful tool to minimize the likelihood of induced earthquakes.

Far‐field pressurization likely caused one of the largest injection induced earthquakes by reactivating a large preexisting basement fault structure

The Mw 5.1 Fairview, Oklahoma, earthquake on 13 February 2016 and its associated seismicity produced the largest moment release in the central and eastern United States since the 2011 Mw 5.7 Prague, Oklahoma, earthquake sequence and is one of the largest earthquakes potentially linked to wastewater injection. This energetic sequence has produced five earthquakes with Mw 4.4 or larger. Almost all of these earthquakes occur in Precambrian basement on a partially unmapped 14 km long fault. Regional injection into the Arbuckle Group increased approximately sevenfold in the 36 months prior to the start of the sequence (January 2015). We suggest far-field pressurization from clustered, high-rate wells greater than 12 km from this sequence induced these earthquakes. As compared to the Fairview sequence, seismicity is diffuse near high-rate wells, where pressure changes are expected to be largest. This points to the critical role that preexisting faults play in the occurrence of large induced earthquakes.

Insights into water level response to seismic waves: A 24 year high‐fidelity record of global seismicity at Devils Hole

We studied the 24 year record of water level responses in Devils Hole, Death Valley National Park, NV, to dynamic crustal stresses from earthquakes. The continuous water level record exhibited 219 responses from earthquakes around the world, displaying hydroseismogram and coseismic offset types of response. We found that the water level in Devils Hole is extremely sensitive to earthquakes, and the seismic energy density required to initiate both hydroseismogram and coseismic offset responses is e ~ 10−6 J/m3, 2 orders of magnitude smaller than previously documented. Multiple mechanisms at Devils Hole may be responsible for observed water level responses to distant earthquakes. The hydroseismogram-type responses are best explained by poroelastic deformation, while coseismic offset responses are likely the result of localized permeability changes. This study could have implication to studying dynamic triggering of earthquakes, as remote earthquakes can lead to pore pressure changes and consequently effective stress changes in fluid-filled fault zones.

Induced seismicity: the potential hazard from shale gas development and CO2 geologic storage

We present an overview of the current status of unconventional energy development, particularly of shale gas, and underground CO2 storage as a measure to mitigate greenhouse gas increase in the atmosphere. We review their potential to induce seismicity, which has caused debates among related energy enterprises, engineers, researchers, and environmental and public communities regarding their potential hazards. Studies show that fracking can be a problem in that it consumes abundant water, but the seismicity induced by fracking has not yet been observed to induce many felt earthquakes. However, massive wastewater injection, a part of the unconventional energy development process has caused M5.0+ earthquakes in the past as well as several recent and ongoing cases of induced seismicity. Large-scale CO2 injection as a part of carbon sequestration efforts in the near future has a high risk of inducing large earthquakes. Therefore, injection operations related to both unconventional energy development and carbon sequestration should be optimized and managed to mitigate the likelihood of an induced seismic event.

Induced Seismicity in Oklahoma Affects Shallow Groundwater

Documentation and analysis of groundwater responses to induced earthquakes are important to better understand their influence on shallow groundwater systems and hydrogeological properties and processes. Here we show that induced seismicity in Oklahoma can cause changes of groundwater level over distances >150 km from the epicenter. We test existing models for the cause of the observed responses and find that the model most consistent with observations is enhanced crustal permeability produced by seismic waves, changing aquifer recharge. Simulation suggests that the sources of this recharge are close to the responding wells and have lateral dimensions of ∼100 m. Continuous monitoring of pressure and temperature in wells, installing clustered wells to monitor multiple water levels near injection sites, and isotopic and chemical analysis of groundwater near injection sites are required to better understand and quantify the recharging sources.

Physics-based forecasting of man-made earthquake hazards in Oklahoma and Kansas

Reinjection of saltwater, co-produced with oil, triggered thousands of widely felt and several damaging earthquakes in Oklahoma and Kansas. The future seismic hazard remains uncertain. Here, we present a new methodology to forecast the probability of damaging induced earthquakes in space and time. In our hybrid physical–statistical model, seismicity is driven by the rate of injection-induced pressure increases at any given location and spatial variations in the number and stress state of preexisting basement faults affected by the pressure increase. If current injection practices continue, earthquake hazards are expected to decrease slowly. Approximately 190, 130 and 100 widely felt M ≥ 3 earthquakes are anticipated in 2018, 2019 and 2020, respectively, with corresponding probabilities of potentially damaging M ≥ 5 earthquakes of 32, 24 and 19%. We identify areas where produced-water injection is more likely to cause seismicity. Our methodology can be used to evaluate future injection scenarios intended to mitigate seismic hazards.Reinjection of saltwater, co-produced with oil, has the potential to trigger damaging earthquakes. Here, using Oklahoma and Kansas as an example, the authors present a new physics-based methodology to forecast future probabilities of potentially damaging induced-earthquakes in space and time.