Repository for Oil and Gas Energy Research (ROGER)

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For tectonic earthquakes, slip rate spans a continuum from creep to supershear earthquakes, where slow slip events (SSEs) are important in releasing stress without radiating damaging seismic energy. Industrial-scale subsurface fluid injection has caused induced earthquakes, but the role of SSEs in fault activation is currently unclear. Ground-deformation observations, measured by satellite radar, show that SSEs up to magnitude 5.0 occurred during hydraulic fracturing (HF) operations in northwestern Canada, corroborated by reported deformation of the steel well casing. Although the magnitude 5.0 SSE exceeded the magnitude of the largest induced earthquake in this region (magnitude 4.55), it was undetected by seismograph networks. The observed SSEs occurred within a buried thrust belt and their magnitude and duration are consistent with scaling behavior of SSEs in unbounded natural systems, e.g. slab interfaces in subduction zones.

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Hydraulic fracturing has induced small-to-moderate-size earthquakes around the world. Identifying spatio-temporal evolution of microseismicity is important for understanding the physical processes that control hydraulic fracturing-induced seismicity. In this study, we build an enhanced earthquake catalog from continuous seismic data recorded by 1-year temporary deployment with an automatic procedure and relocate 18,663 earthquakes in the Weiyuan shale gas block in the southern Sichuan Basin, China. Our catalog, with a maximum ML of 3.5, has a completeness magnitude (Mc) of 0.4, which is ∼23 times more events than listed in the standard National Earthquake Data Center (NEDC) of China. Most earthquakes are clustered near hydraulic fracturing wells and delineate many pre-existing faults in the north-south direction. The space-time evolution of microearthquakes indicates fluid diffusion processes as the primary drivers for seismicity in this region. The fast earthquake migration patterns show that permeability within a fault zone could be affected by fault-valve behaviors and enhanced by earthquake rupture process. We find that the Gutenberg-Richter b-values increase systematically with depth, and b-values further away from hydraulic fracturing pads are generally low, especially for three strands with relatively high migration velocities. Our results confirm that earthquake clusters in Weiyuan are induced by hydraulic fracturing and the reactivated faults act as conduit networks for fluid flow, which promote triggering of earthquakes further away from the hydraulic fracturing pad. This study provides additional evidence for hydraulic fracturing-induced earthquake in the southern Sichuan Basin and advances our understanding of injection induced earthquakes.

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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, - and - values, and then calculate the annual likelihood of earthquakes greater than magnitude 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 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 ) with lower b-values and higher hazard; (b) a Western region (∼210 events ) 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.

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To date, little research has investigated how public perceptions of policies to ban or restrict fossil-fuel extraction change over time; yet this topic is of crucial importance as countries worldwide seek to transition towards ‘net zero’ economies. This study addresses this gap by focusing on public responses to the 2019 moratorium on shale gas extraction in England, using an analytical framework comprising awareness, interpretations and opinions, and a mixed-method approach combining national survey, social media and local case interviews. Findings show high levels of awareness and support for the moratorium, yet differences between coalitions of interest based on ideology, scale and demographics. Social media analyses reveal a peak in public response across several days during a general election campaign in which different parties took divergent positions on shale gas. Public support for the moratorium – and induced seismicity as the primary reason for its introduction - was evidenced by the national survey, yet coincided with scepticism about its timing, extent and motivation, as indicated by social media activity and local case interviews. For some publics, the moratorium was a ploy to ensure electoral support, embedded in public distrust. This study indicates the merits of a mixed-method approach to understand the psychological and institutional context of public responses to policy change as it unfolds over time, and discusses the longer term implications of politicised attitudes for energy transitions.

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Monitoring small magnitude induced seismicity requires a dense network of seismic stations and high-quality recordings in order to precisely determine events’ hypocentral parameters and mechanisms. However, microseismicity (e.g. swarm activity) can also occur in an area where a dense network is unavailable and recordings are limited to a few seismic stations at the surface. In this case, using advanced event detection techniques such as template matching can help to detect small magnitude shallow seismic events and give insights about the ongoing process at the subsurface giving rise to microseismicity. In this paper, we study shallow microseismic events caused by hydrofracking of the PNR-2 well near Blackpool, UK, in 2019 using recordings of a seismic network which was not designed to detect and locate such small events. By utilizing a sparse network of surface stations, small seismic events are detected using template matching technique. In addition, we apply a full-waveform moment tensor inversion to study the focal mechanisms of larger events (ML > 1) and used the double-difference location technique for events with high-quality and similar waveforms to obtain accurate relative locations. During the stimulation period, temporal changes in event detection rate were in agreement with injection times. Focal mechanisms of the events with high-quality recordings at multiple stations indicate a strike-slip mechanism, while a cross-section of 34 relocated events matches the dip angle of the active fault.

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Drawing from hazard and disaster literature, this article advances Freudenburg’s concept of recreancy and Hobfoll’s Conservation of Resources theory in response to calls for more theory development in research on hydraulic fracturing. Respectively, these theoretical frames refer to stress associated with trust in institutional failure to safeguard the wellbeing of society, as well as resource loss, threat of loss, or investment of resources without return or gain. We contribute to the expanding body of knowledge in energy and social science research by investigating risk perceptions of induced seismicity (earthquakes) associated with hydraulic fracturing processes. Using structural equation modeling, we analyze data from a 2018 household telephone survey in two regions of Oklahoma (N = 600). Findings indicate that perceptions of recreancy (β = 0.38), opinion of fracking risks (β = 0.31), and number of earthquakes (β = 0.11) directly affect perceptions of earthquake risk, while political views, economic resource loss and views of fracking benefits are indirectly related to perceptions of earthquake risk.

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Significant increases in seismic activity have been recorded since fracturing and extraction began in 2014 in the Changning shale gas development block that is located in the Southern Sichuan Basin, China (SSBC). The primary aim of this paper was to assess the hazard and risk (HR) resulting from the induced seismicity via the Entropy-Fuzzy-AHP (E-FAHP) method. The assessment used for this study was carried out for 2700 grids with a total area of 1089 km2. The results were combined to form a regional earthquake HR map. Firstly, a large amount of raw data was collected and analyzed and six core factors were selected to form the index layers of the model. The b-value and Z-value derived from seismology indicate the level of historical seismic activity, the faults and fractures that reflect the regional structural instability, as well as two human activities that may induce seismicity: hydraulic fracturing and reservoir storage. Secondly, the evaluation criteria and the membership matrix were established, and the objective weight of each grid was obtained by using the Entropy model. Meanwhile, the subjective weight of each factor was calculated under the AHP expert scoring method, and the subjective and objective weight coupling was performed. Thirdly, the fuzzy product of the weight and the membership matrix produced the final evaluation of the grid. Based on different evaluation years, the model was divided into three classifications, among which Classification 1 has a better prediction effect than Classification 2 and can predict the precise occurrence range of new earthquakes. After correcting the combination modes of the initial data of the fracturing platform factors, the Classification 2 prediction effect was greatly improved. This study shows that as long as the key factors are thoroughly understood, the HR of induced earthquake can be predicted and controlled.

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Unconventional petroleum development involving large volume fluid injection into horizontal well bores, referred to as hydraulic fracturing (HF, or fracking), began in the Montney Trend of northeast British Columbia, Canada, in 2005, quickly initiating earthquakes. Earthquake frequency increased substantially in the Montney by 2008, in relation to the number of wells fracked and the volume of injected frack water. A spatiotemporal filter was used to associate earthquakes with HF wells. A total of 439 earthquakes (M 1.0 - 4.6 (NRCAN catalogue) during 2013-2019 have close association with HF activity, of which 77% are associated with three operators. Fifteen percent of HF wells in the Montney are associated with these earthquakes, while 1.7% of HF wells are associated with M ≥ 3.0 earthquakes. There are strong linear relationships between the maximum earthquake magnitude each year and the annual volume of injected frack fluid. M ≥ 3.0 earthquakes are associated with large cumulative frack water volumes for antecedent time periods of 1 - 3 years, often with fluid injection by multiple operators. Eighty-seven percent of the Montney M ≥ 3.0 earthquakes have associated HF triggering events, but a few are sufficiently distant to be ambiguous. Distances from the induced earthquake epicentres indicate a variety of causal mechanisms are involved. It is concluded that ~60% - 70% of M ≥ 3.0 earthquakes are induced by hydraulic fracturing. HF-induced earthquakes can be considered in part related to the cumulative development density from multiple proximal operators and cumulative antecedent fluid injection over periods ranging from a few months to a few years. It is probable that induced earthquakes of M > 5 will occur in the future. There are significant public safety and infrastructure risks associated with future HF-induced earthquakes in the Peace River area. To carry out HF operations effectively and safely, potentially destructive earthquakes must be avoided or mitigated. The Traffic Light Protocol mitigation system used in British Columbia appears unlikely to prevent large magnitude earthquakes. Risk avoidance therefore becomes important and could include the establishment of frack-free zones proximal to populations and critical infrastructure.

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Objectives To evaluate the long-term (psychosomatic) health consequences of man-made earthquakes compared with a non-exposure control group. Exposure was hypothesised to have an increasingly negative impact on health outcomes over time. Setting Large-scale gas extraction in the Netherlands causing earthquakes and considerable damage. Participants A representative sample of inhabitants randomly selected from municipal population records; contacted 5 times during 21 months (T1: N=3934; T5: N=2150; mean age: 56.54; 50% men; at T5, N=846 (39.3%) had no, 459 (21.3%) once and 736 (34.2%) repeated damages). Main measures (Psychosomatic) health outcomes: self-rated health and Mental Health Inventory (both: validated; Short Form Health Survey); stress related health symptoms (shortened version of previously validated symptoms list). Independent variable: exposure to the consequences of earthquakes assessed via physical (peak ground acceleration) and personal exposure (damage to housing: none, once, repeated). Results Exposure to induced earthquakes has negative health consequences especially for those whose homes were damaged repeatedly. Compared with a no-damage control group, repeated damage was associated with lower self-rated health (OR:1.64), mental health (OR:1.83) and more stress-related health symptoms (OR:2.52). Effects increased over time: in terms of relative risk, by T5, those whose homes had repeated damage were respectively 1.60 and 2.11 times more likely to report poor health and negative mental health and 2.84 times more at risk of elevated stress related health symptoms. Results for physical exposure were comparable. Conclusion This is the first study to provide evidence that induced earthquakes can have negative health consequences for inhabitants over time. It identifies the subpopulation particularly at risk: people with repeated damages who have experienced many earthquakes. Findings can have important implications for the prevention of negative health consequences of induced earthquakes.

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Varying the stop lights Traffic light protocols can help to mitigate induced earthquakes from unconventional oil production. However, they are not geographically tuned to account for how shaking may actually translate to structural damage. Schultz et al. incorporated damage tolerance into a traffic light protocol for the Eagle Ford shale play. They found that shut-off may be necessary more quickly in populated regions, whereas sparsely populated areas of the play can take up to a magnitude 5 earthquake without issue. This risk-based strategy provides a more nuanced approach to regulating induced seismicity. Science, this issue p. 504 Risks from induced earthquakes are a growing concern that needs effective management. For hydraulic fracturing of the Eagle Ford shale in southern Texas, we developed a risk-informed strategy for choosing red-light thresholds that require immediate well shut-in. We used a combination of datasets to simulate spatially heterogeneous nuisance and damage impacts. Simulated impacts are greater in the northeast of the play and smaller in the southwest. This heterogeneity is driven by concentrations of population density. Spatially varying red-light thresholds normalized on these impacts [moment magnitude (Mw) 2.0 to 5.0] are fairer and safer than a single threshold applied over a broad area. Sensitivity tests indicate that the forecast maximum magnitude is the most influential parameter. Our method provides a guideline for traffic light protocols and managing induced seismicity risks. Accounting for risk provides a more nuanced traffic light protocol for regulating induced seismicity. Accounting for risk provides a more nuanced traffic light protocol for regulating induced seismicity.

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A relatively new term for categorizing hazards is that of “techna” hazards, or seemingly natural phenomena induced by human technology or activity. The human origin of these hazards means that mitigation aimed at addressing the underlying cause of the hazard is a possibility, which is often not considered possible with traditional natural hazards. Currently, however, there is a dearth of literature regarding how perceptions of the underlying cause of the hazard influences beliefs regarding disaster risk reduction strategies for the hazard. Thus, this work examines the factors that predict beliefs regarding whether a techna hazard can be stopped or reduced, the best actions that should be taken to reduce or stop the hazard event, and whether current regulation efforts aimed at stopping or controlling the activities causing the hazard are enough. We specifically examine the case of fluid injection induced seismicity in Oklahoma and Colorado in the United States. We find that, contrary to our expectations from prior literature, exposure to the hazard is not a strong predictive factor of these beliefs. Perceptions of the underlying activity associated with the hazard, in this case hydraulic fracturing and oil and gas development, is significant, in that those with more positive views of the industry activity are more likely to believe the earthquakes cannot be stopped and favor less intense regulative efforts to address the hazard.

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Earthquakes resulting from hydraulic fracturing (HF) can have delayed triggering relative to injection commencement over a varied range of time scales, with many cases exhibiting the largest events n

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We investigate the physical mechanisms governing the activation of faults during hydraulic fracturing. Recent studies have debated the varying importance of different fault reactivation mechanisms. Pore pressure increase caused by injection is generally considered to be the primary driver of induced seismicity. However, in very tight reservoir rocks, unless a fracture network exists to act as a hydraulic conduit, the rate of diffusion may be too low to explain the spatiotemporal evolution of some microseismic sequences. Thus, poroelastic stress transfer and aseismic slip have been invoked to explain observations of events occurring beyond the expected distance of a diffusive front. In this study we use the high quality microseismic data acquired during hydraulic fracturing at the Preston New Road (PNR) wells, Lancashire, UK, to examine fault triggering mechanisms. Injection through both wells generated felt induced seismicity-an ML 1.5 during PNR-1z injection in 2018 and an ML 2.9 during PNR-2 in 2019-and the microseismic observations show that each activated a different fault. Previous studies have already shown that PNR-1z seismicity was triggered by a combination of both direct hydraulic effects and elastic stress transfer generated by tensile fracture opening. Here we perform a similar analysis of the PNR-2 seismicity, finding that the PNR-2 fault triggering was mostly likely dominated by the diffusion of increased fluid pressure through a secondary zone of hydraulic fractures. However, elastic stress transfer caused by hydraulic fracture opening would have also acted to promote slip. It is significant that no microseismicity was observed on the previously activated fault during PNR-2 operations. This dataset therefore provides a unique opportunity to estimate the minimum perturbation required to activate the fault. As it appears that there was no hydraulic connection between them during each stimulation, any perturbation caused to the PNR-1z fault by PNR-2 stimulation must be through elastic or poroelastic stress transfer. As such, by computing the stress transfer created by PNR-2 stimulation onto the PNR-1z fault, we are able to approximate the minimum bound for the required stress perturbation: in excess of 0.1 MPa, an order of magnitude larger than commonly stated estimates of a generalised triggering threshold.

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Recent seismicity in Alberta and British Columbia has been attributed to ongoing oil and gas development in the area, due to its temporal and spatial correlation. Prior to such development, the area was seismically quiescent. Here, we show evidence that latent seismicity may occur in areas where previous operations may have occurred, even during a shutdown in operations. The global pandemic of COVID-19 furnished the unique opportunity to study seismicity during a period of 5 anthropogenic quiescence. A total of 389 events were detected within the Kiskatinaw area of British Columbia from April to August 2020, which encompasses a period with no hydraulic fracturing operations during a government imposed lockdown. Apart from a reduction in seismicity rate, the general characteristics of the observed seismicity were similar to the preceding time period of active operations. During the shutdown, observed event magnitudes fell between ML -1 and ML 1.2, but lacked temporal clustering that is often characteristic of hydraulic-fracturing induced sequences. Hypocenters occurred in a corridor 10 orientated NW-SE, just as seismicity had done in previous years in the area, and locate at depths associated with the target Montney formation or shallower (<2.5 km). A maximum of 21% of the detected events during lockdown may be attributable to natural seismicity, with a further 8% being attributed to dynamic triggering of seismicity from teleseismic events. However this leaves over 70% of the seismicity detected during lockdown being unattributable to primary activation mechanisms. Since we know this seismicity cannot be the result of direct pore-pressure increases (as no direct injection was occurring at the time) and 15 we see no patterns of temporal or spatial migration in the seismicity, we suggest that this latent seismicity may be generated by aseismic slip as fluids (resulting from previous hydraulic fracturing experiments) become trapped within permeable formations at depth, keeping pore pressures in the area elevated, and consequently allowing the generation of seismicity. This is the first time that this latent seismicity has been observed in this area of British Columbia.

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During the past decade, the number of earthquakes has increased dramatically in the state of Oklahoma, largely attributed to induced seismicity from wastewater injections (hydraulic fracturing). The increased seismic disaster risk in Oklahoma has captured public attention and necessitated actions by decision makers to mediate the consequences. Geospatial modeling to identify the populations exposed to higher levels of potential risk can help prioritize locations for mitigation actions based on the underlying social vulnerability of residents. In this paper, we explore a method for integrating the spatial distribution of seismic risk (hazard exposure) with social vulnerability (hazard impact). Loss scenarios, social vulnerability metrics, and potential physical damage are combined in a geographic information system to identify the spatial vulnerability of an exposed population to the increased seismic risk, and the locations for targeting mitigation actions — areas with the greatest exposure and vulnerability. The results of induced seismicity earthquake scenarios show disproportionately higher losses for places with more minority populations (primarily African-American) and more renters when compared to the non-induced scenarios, suggesting a potential environmental justice concern.

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Mitigating hydraulic fracturing-induced seismicity (HF-IS) poses a challenge for shale gas companies and regulators alike. The use of Traffic Light Schemes (TLSs) is the most common way by which the hazards associated with HF-IS are mitigated. In this study, we discuss the implicit risk mitigation objectives of TLSs and explain the advantages of magnitude as the fundamental parameter to characterise induced seismic hazard. We go on to investigate some of the key assumptions on which TLSs are based, namely that magnitudes evolve relatively gradually from green to yellow to red thresholds (as opposed to larger events occurring “out-of-the-blue”), and that trailing event magnitudes do not increase substantially after injection stops. We compile HF-IS datasets from around the world, including the USA, Canada, the UK, and China, and track the temporal evolution of magnitudes in order to evaluate the extent to which magnitude jumps (i.e. sharp increases in magnitude from preceding events within a sequence) and trailing events occur. We find in the majority of cases magnitude jumps are less than 2 units. One quarter of cases experienced a post-injection magnitude increase, with the largest being 1.6. Trailing event increases generally occurred soon after injection, with most cases showing no increase in magnitude more than a few days after then end of injection. Hence, the effective operation of TLSs may require red-light thresholds to be set as much as two magnitude units below the threshold that the scheme is intended to avoid.

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Pumping oilfield wastewater into deep injection wells causes earthquakes by effective stress change and solid elastic stressing. These processes result from fluid pressure changes in the seismogenic basement, so it is generally accepted that pressure diffusion governs spatiotemporal patterns of induced earthquake sequences. However, new evidence suggests that fluid density contrasts may also drive local-scale (near-well) pressure transients to greater depths than pressure diffusion and over much longer timescales. As a consequence, the pressure, temperature, and composition (PTX) conditions of wastewater and deep crustal (basement) fluids may be fundamental to understanding and managing injection-induced seismicity. This study develops a mechanistic framework that integrates PTX-dependent fluid properties into the generally accepted conceptual model of injection-induced seismicity. Nonisothermal variable-density numerical simulation is combined with ensemble simulation methods to isolate the parametric controls on injection-induced fluid pressure transients. Results show that local-scale, density-driven pressure transients are governed by a combination of fracture permeability and PTX-dependent fluid properties, while long-range pressure diffusion is largely governed by fracture permeability. Considering this new conceptual model in the context geochemical data from oil and gas basins in the United States identifies regions that may be susceptible to persistent density-driven pressure transients.

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Hydraulic fracturing (fracking) operations, associated with horizontal drilling for oil/gas production, are known to induce earthquakes from fluid injection in disposal wells. In recent years, numerous studies have shown a close relationship between induced seismic activities and the high-pressure injection of wastewater, especially in Texas, Kansas, and Oklahoma. Detailed analysis of 17 major fracking locations across the USA has been carried out to study the impact of horizontal wells and the corresponding injected wastewater on earthquake activities. Earthquake data for the period 1998–2018 obtained from the USGS earthquake catalog shows an increase in frequency of earthquakes within a radius of 150 km at fracking locations, prominently in south-central USA. The stimulation of earthquakes depends on the amount of injected water in both horizontal and disposal injected wells, and the geology, hydrological, and geophysical settings nearby the drilling site. The observed seismicity increases with the number of horizontal wells in Texas (correlation R2 = 0.726) and Oklahoma (correlation R2 = 0.636) at the fracking locations.

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Hydraulic fracturing (HF) in the Duvernay Formation near Fox Creek, Alberta, Canada, has produced some of the most prolific clusters of induced seismicity. In this paper, we describe newly emerging clusters of events occurring in previously quiescent (and undeveloped) areas of the Duvernay Formation. In the Duvernay East Shale Basin, an industry supplemented waveform database is examined using a variety of seismological techniques. Here, strike-slip events as large as 4.18 ML have been felt in nearby cities. Temporal relationships suggest these clusters are almost certainly (>99.7% confidence) caused by nearby HF. Spatially, these earthquakes tend to occur in the strata directly overlying the Duvernay Formation and laterally near a horizontal well. One exceptional cluster clearly delineates a 1.5 km offset between its centroid and the inducing horizontal well, raising questions about the earthquake triggering mechanism. Westward in the Duvernay, two minor clusters within the Willesden Green region appear to be tenuously related to HF completions. This study also places constraints on the structural geology of faulting occurring in the Rocky Mountain House Seismogenic Zone – a region of induced seismicity related to secondary recovery in the Strachan D-3A pool. Here, our moment tensors and double difference relocations describe thrust-slip on a fault underlying the target formation. Last, the largest event (4.27 ML) in our study area was likely natural, due to its deeper hypocentral depth (~15 km) and non-correspondence with industrial operations. Overall, the newly emerging clusters are consistent with reactivation of basement rooted faults.

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Technologies such as hydraulic fracturing and wastewater injection can elicit strong and sometimes diverging reactions among the public, particularly when there is uncertainty about the associated risks. Understanding how people are weighing potential benefits in the context of these risks can help to address some of the challenges associated with people’s responses, such as community conflict and social disruption—especially when multiple risks intersect, as in the case of induced seismicity. As a relatively new phenomenon, perceived risk of induced seismicity remains an underexplored area in hazards and risk analysis research. Prior work on hydraulic fracturing has revealed that a complex variety of factors influences how the public in a given area perceives the overall impacts, risks, and value of oil and gas operations. This article focuses on findings derived from in-depth interviews and informal conversations with 36 Oklahomans as part of a larger study of social responses to induced seismicity in that state and Colorado. These findings center around participants’ reported concerns, problems, benefits, and new opportunities associated with oil and gas development, including the ways in which participants weigh the costs and benefits of oil and gas development activities—particularly hydraulic fracturing—within the context of induced seismicity.

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We use broadband seismic data collected within 3 km of a hydraulic fracturing (HF) well in northeast British Columbia, Canada, to estimate the stress drop values of HF-induced earthquakes and their spatial variation. Applying both spectral ratio and clustered single-spectra fitting methods to 484 induced earthquakes (M-1.0 to 3.0), we find that earthquakes close to the injection well have lower stress drops than those at greater distance. Stress drop values are generally invariant within clusters either proximal ( 0.1-1 MPa) or distal ( 1-10 MPa) to the well, suggesting that dynamic ruptures in rocks with similar rheological properties tend to have relatively constant stress drop values. Clustered single spectrum fitting also suggests that the seismic quality factor (Q) is lower proximal to the well. We interpret the lower stress drop values and higher seismic attenuation proximal to the well as a result of higher fracture density and/or elevated pore pressure in the rock matrix due to hydraulic stimulation.

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Abstract The seismicity rate in the Delaware Basin, located in western Texas and southeastern New Mexico, has increased by orders of magnitude within the past ~5 years. While no seismicity was reported in the southern Delaware Basin during 1980-2014, 37 earthquakes with M > 3 occurred in this area during 2015-2018. We generated an improved catalog of ~37,000 earthquakes in this region during 2009-2018 by applying multi-station template matching at both regional and local stations using all earthquakes in the ANSS and TexNet catalogs. We found that the vast majority of the seismicity is most likely associated with wastewater disposal, while at least ~5% of the seismicity was induced directly by hydraulic fracturing. We inferred far-field effects of wastewater disposal inducing earthquakes over distances >25 km. The spatial limits of seismicity correlate with geologic structures that include the Central Platform and Grisham Fault, suggesting hydrologic compartmentalization by low-permeability boundaries. Given that the seismicity rate increased throughout the duration of the study, if industry operations continue unaltered it is likely that both the seismicity rate and number of M > 3 earthquakes may continue to increase in the future.

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Research demonstrates that opinions about global warming and induced seismicity, earthquakes caused by human activity, are influenced by political party affiliation and ideology more than by education. Republicans and conservatives typically express less concern about environmental issues. One mechanism for how these factors shape opinion is through elite cues, wherein the prominent cultural, economic, and political voices associated with the major U.S. political parties provide guideposts that laypeople may use to form their opinions, particularly for complex social issues. Using two waves (n = 2586 and n = 2581) from a statewide survey in Oklahoma (USA), we explore the effects of political party affiliation, ideology, and education on residents’ opinions about the causes of and risk associated with these phenomena using Ordinary Least Squares and binary logistic regression equations. We examine whether these factors have a larger impact on opinions about global warming or induced seismicity using seemingly unrelated regression for the OLS equations and seemingly unrelated estimation for the binary logistic equations. These methods allow a global warming model to be estimated simultaneously with an earthquake model using the same independent variables. Consistent with other research, we found strong evidence that Republicans and conservatives perceive less risk from global warming and earthquakes than Democrats and liberals. However, the moderating effect of education on these environmental beliefs was not significant. The effects of political party affiliation and ideology were stronger for the opinions about global warming, which we hypothesize may be explained by the concept of psychological distance. This is an area for further research.

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Abstract In recent years, numerous small earthquakes have occurred near the town of Pecos in West Texas; however, when this activity began and whether it was caused by increased petroleum industry activity has been uncertain because prior to 2017 there were few permanent seismograph stations in the region. We identify and locate earthquakes using data recorded since 2000 at TXAR, a sensitive 10-station seismic array situated about 240 km south of Pecos. We thus show that in 2007 one earthquake occurred near Pecos, in 2009 several more occurred, and subsequently activity has increased considerably, with more than 2000 events identified in 2017. A time-of-day and year-by-year analysis identifies geographic areas in West Texas where events are likely to be natural earthquakes and quarry blasts. However, for the Pecos events, annual seismicity rates increase along with annual volumes of petroleum production and fluid waste disposal, suggesting a causal link. Analysis of seismograms collected by the EarthScope Transportable Array indicates the 2009 earthquakes had focal depths of 4.0-5.2 km below sea level, within or just below strata where petroleum is produced and/or wastewater is injected. The largest earthquake to date had magnitude ML3.7, but the recent high activity rates suggest that greater magnitudes may be possible. For the years 2000-2017, we provide a catalog of 10,753 epicenters of seismic events recorded at TXAR.

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This paper presents the various tools and data sources in British Columbia (Canada) that can be used by environmental consultants to assess the potential of cross-contamination between shale gas formation fluids and shallow aquifers from hydraulic fracturing and related oil and gas activities. A systematic approach for evaluating the potential of cross-contamination using these data sources is applied to a specific case study at an undisclosed location in the northeastern part of the province. This approach includes defining and then evaluating the basic criteria for assessing the potential of cross-contamination. These criteria are: a leak source; a driving force such as buoyancy or head differential and a leakage pathway. This study has revealed that there is a potential of cross-contamination due to hydraulic fracturing activities and wellbore integrity issues. Wellbore integrity can be compromised by induced seismic events or by unintentional communication with offset hydraulic fractured wells. Induced seismicity is linked to the activity of hydraulic fracturing as well as to the deep disposal of wastewater.

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Scientific evidence suggests earthquakes occurring in Oklahoma since 2009 are not “acts of God”, but very likely triggered by wastewater injection in disposal wells by oil and gas (O&G) companies. While sustaining the O&G industry's contribution to the economy is generally important, achieving environmental and public protection may in part rely on how earthquake inducers are held liable for damage. We use a Bayesian Tobit censored model, estimated using Markov Chain Monte Carlo (MCMC) methods to determine factors that influence public preferences for how much liability O&G companies should assume for induced earthquake-related damage. Data are from a survey of Oklahomans collected in 2017 by Survey Sampling International (SSI). Results suggest people would, on average, hold O&G companies liable for 75% of the earthquake damage. We find socio-demographic, earthquake, locational, and O&G industry-related factors as the main drivers of earthquake damage liability. However, their effects on damage liability vary between respondents that have had their property damaged by earthquakes and those that in some way benefit from O&G companies through jobs and gas-leases. We provide insights by which individuals might lobby representatives to impose new liability or regulatory mechanisms on O&G companies to avoid or compensate for earthquake damage.

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Oilfield wastewater is commonly discarded by pumping it into deep geologic formations, but this process is now known to cause earthquakes. Here, he authors show that high-density oilfield wastewater may sink deeper in the Earth’s crust than previously considered possible, thus increasing fluid pressure and inducing earthquakes for years after injection rates decline.

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During the past decades, significant progress has been made in the development of induced seismicity monitoring for related human activities. Hydraulic fracturing and induced seismicity monitoring are operating procedures for safe and effective production of oil and gas from unconventional resources, particularly shales. Hydraulic fracturing can induce seismicity through fluid injection and disturbance of subsurface stress in tight reservoirs. Most seismic events associated with hydraulic fracturing exhibit magnitude of Mw ≤ 3 and are referred to as microseismicity, while a few larger-magnitude earthquakes (e.g. Mw > 3) could also be induced by reactivating pre-existing faults. Here, we review the current status of research concerning induced seismicity monitoring for shale hydraulic fracturing. Induced seismicity contains information relating to important subsurface characteristics, e.g. rock failure potential and seismogenic zones. Microseismic monitoring is essential for reservoir characterization, e.g. fracture geometry delineation and reservoir geomechanical analysis. It is carried out with advanced acquisition, processing, and interpretation techniques, while larger-magnitude earthquakes are mainly exploited for potential geohazard management and mitigation. Challenges and prospects associated with multi-disciplines for future research and applications of induced seismicity monitoring are identified, and it contributes to achieve safe and efficient unconventional (tight) oil and gas resource exploitation.

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This study presents observations using new data from a deployment of eight broadband seismometers surrounding a horizontal well pad at distances of 1-3 km for the period before, during, and after a hydraulic fracturing (HF) treatment in the Montney Basin, British Columbia, Canada. We use a multi-station matched filter detection and double-difference earthquake relocation to develop a catalog of 350 events associated with HF stimulation, with magnitudes ranging from -2.8 to 1.8 and estimated catalog completeness of -0.2. The seismicity distribution suggests a statistically significant association with injection, and event migration can be described by a hydraulic diffusivity of 0.2 m2/s. A comparison between daily seismicity rate and analytical stress evolution inferred from daily injection volumes implies that pore pressure diffusion largely controls earthquake nucleation at distances less than 1 km, whereas poroelastic stress transfer likely dominates at intermediate distances of 1-4 km at time scales shorter than diffusion. Both mechanisms likely have a limited effect on stress perturbation at distances over 5 km.

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Hydraulic fracturing induces the shear failure of natural fracture which contributes to complex fracture network. The magnitude of fracture slip potentially causes some undesirable consequences including wellbore instability, casing deformation and fault reactivation. Therefore, it is important to predict the fracture slip induced by hydraulic fracturing for a safe and efficient stimulation. In this paper, we used a 2D hydro-mechanical coupled model to predict the injection-induced slip. The hydraulic and natural fractures are embedded in formations with cohesive zone model. The fracture propagation, rock deformation and wellbore slip displacement are captured in the 2D model. The wellbore slip displacement is input into a small-scale 3D mechanical model of casing in slip rock to simulate casing behavior. Casing curvature is also introduced to assess casing integrity. Results indicate that the rock deforms asymmetrically with respect to the wellbore after the shear failure of natural fracture. Particularly, there is a shear slip along the natural fracture. The simulation result shows that the casing failure mechanism is shear deformation induced by the fracture slip during hydraulic fracturing. The curvature of deformed casing is larger than that of directional well trajectory. The predicted results are validated by the logging and operation data from the field. This work provides a novel quantitative method for predicting fracture slip and evaluating well integrity during hydraulic fracturing.

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Wastewater disposal is generally accepted to be the primary cause of the increased seismicity rate in Oklahoma within the past decade, but no statewide analysis has investigated the contribution of hydraulic fracturing (HF) to the observed seismicity or the seismic hazard. Utilizing an enhanced seismicity catalog generated with multistation template matching from 2010 to 2016 and all available hydraulic fracturing information, we identified 274 HF wells that are spatiotemporally correlated with bursts of seismicity. The majority of HF-induced seismicity cases occurred in the SCOOP/STACK plays, but we also identified prominent cases in the Arkoma Basin and some more complex potential cases along the edge of the Anadarko Platform. For HF treatments where we have access to injection parameters, modeling suggests that poroelastic stresses are likely responsible for seismicity, but we cannot rule out direct pore pressure effects as a contributing factor. In all of the 16 regions we identified, 75% of the seismicity correlated with reported HF wells. In some regions, >95% of seismicity correlated with HF wells and >50% of the HF wells correlated with seismicity. Overall, we found similar to 700 HF-induced earthquakes with M2.0, including 12 events with M 3.0-3.5. These findings suggest state regulations implemented in 2018 that require operators in the SCOOP/STACK plays to take action if a M>2 earthquake could have a significant impact on future operations.

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In this study we present a spatiotemporal analysis of the recent seismicity and industry-related wastewater injection activity in Oklahoma. A parsimonious predictive tool was developed to estimate the lagged effect of previous month’s injection volumes on subsequent regional seismic activity. Results support the hypothesis that the recent boom in unconventional oil and gas production and either the mitigation policies or the drop in oil prices (or both) are potentially responsible for the upsurge and reduction in the state’s seismic activity between 2006–2015 and 2016–2017, respectively. A cluster analysis reveals a synchronous migration pattern between earthquake occurrences and salt water injection with a predominant northwest direction during 2006 through 2017. A lagged cross-correlation analysis allows extracting a power law between expected number of quakes and weighted average monthly injection volumes with a coefficient of determination of R2 = 0.77. Such a relation could be used to establish “sustainable water injection limits” aiming to minimize seismicity to values comparable with several historically representative averages. Results from these analyses coincide on previously found sustainable limits of 5 to 6 million m3/month but expand to operations that could attain the same number through differential monthly planning. Findings could potentially be used for model intercomparison and regulation policies.

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During December 2011, a swarm of moderate-magnitude earthquakes was induced by hydraulic fracturing (HF) near Cardston, Alberta. Despite seismological associations linking these two processes, the hydrological and tectonic mechanisms involved remain unclear. In this study, we interpret a 3D reflection-seismic survey to delve into the geological factors related to these earthquakes. First, we document a basement-rooted fault on which the earthquake rupture occurred that extends above the targeted reservoir. Second, at the reservoir’s stratigraphic level, anomalous subcircular features are recognized along the fault and are interpreted as resulting from fault-associated karst processes. These observations have implications for HF-induced seismicity, as they suggest hydraulic communication over a large (vertical) distance, reconciling the discrepancy between the culprit well trajectory and earthquake hypocenters. We speculate on how these newly identified geological factors could drive the sporadic appearance of induced seismicity and thus be utilized to avoid earthquake hazards.

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The process of hydraulic fracturing has unlocked an unprecedented amount of oil and gas in the United States. Hydrocarbons are not the only output from this process, though, as billions of barrels of “produced” water are extracted and subsequently pumped back underground. This process of injecting produced water into disposal wells has been causally linked to the rise in earthquakes. Here I show how the amount of earthquakes in Oklahoma are positively linked to the price of oil, and further find that the decrease in earthquake activity in Oklahoma is due to both the drop in oil prices and the regulatory directives of regional authorities. The estimated impact of the various shut-in policies have been small compared to the reduction in earthquakes due to the broad price decline, though. I find that the drop in oil prices that began in mid-2014 led to as large of a reduction in earthquakes as the combined effect f new policies that started in March of 2015.

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Seismic limits for hard and soft rock Induced earthquakes from oil, gas, and geothermal energy exploration projects can damage infrastructure and concern the public. However, it remains unclear how far away from an injection site an earthquake can still be triggered. Goebel and Brodsky looked at 18 different earthquake-producing injection sites around the world to address this issue. Injecting fluid into softer layers increased the range for seismic hazard, whereas harder basement rock better confined the fluid. These findings should be considered when regulating and managing projects with the potential to induce seismicity. Science, this issue p. 899 Fluid injection can cause extensive earthquake activity, sometimes at unexpectedly large distances. Appropriately mitigating associated seismic hazards requires a better understanding of the zone of influence of injection. We analyze spatial seismicity decay in a global dataset of 18 induced cases with clear association between isolated wells and earthquakes. We distinguish two populations. The first is characterized by near-well seismicity density plateaus and abrupt decay, dominated by square-root space-time migration and pressure diffusion. Injection at these sites occurs within the crystalline basement. The second population exhibits larger spatial footprints and magnitudes, as well as a power law–like, steady spatial decay over more than 10 kilometers, potentially caused by poroelastic effects. Far-reaching spatial effects during injection may increase event magnitudes and seismic hazard beyond expectations based on purely pressure-driven seismicity. The seismic hazard distance from injection wells is dependent on rock type and fault density. The seismic hazard distance from injection wells is dependent on rock type and fault density.

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More recent public discourse has taken place regarding the potential correlation between seismic activity and hydraulic fracturing in shale gas reservoirs. Public fears about the risk of seismicity stem mainly from past earthquakes induced by conventional deep injections because the two types of projects share similar mechanisms of rock failure and fault activation. Although previous earthquake risks associated with fluid injection were not serious, the situation would be far more problematic if hydraulic fracturing in a shale gas reservoir triggered a similar-sized earthquake due to potential environmental issues. In fact, almost all documented injection-induced earthquakes have been associated with long-duration and high-volume injection rather than short-term (hours) pressurization (e.g., hydraulic fracturing). In general, hydraulic fracturing operations mostly induce microseismic events through rock failure and activation of small fractures. Although shale reservoirs in tectonically active zones pose a high risk of inducing large-magnitude seismic activities, the internal geological conditions and external stimulation conditions are impossible to be satisfied simultaneously to trigger activation of an entire fault and to result in a destructive earthquake during hydraulic fracturing operations.

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Shale oil and gas exploitation by hydraulic fracturing experienced a strong development worldwide over the last years, accompanied by a substantial increase of related induced seismicity, either consequence of fracturing or wastewater injection. In Europe, unconventional hydrocarbon resources remain underdeveloped and their exploitation controversial. In UK, fracturing operations were stopped after the Mw 2.3 Blackpool induced earthquake; in Poland, operations were halted in 2017 due to adverse oil market conditions. One of the last operated well at Wysin, Poland, was monitored independently in the framework of the EU project SHEER, through a multidisciplinary system including seismic, water and air quality monitoring. The hybrid seismic network combines surface mini-arrays, broadband and shallow borehole sensors. This paper summarizes the outcomes of the seismological analysis of these data. Shallow artificial seismic noise sources were detected and located at the wellhead active during the fracturing stages. Local microseismicity was also detected, located and characterised, culminating in two events of Mw 1.0 and 0.5, occurring days after the stimulation in the vicinity of the operational well, but at very shallow depths. A sharp methane peak was detected ~19 hours after the Mw 0.5 event. No correlation was observed between injected volumes, seismicity and groundwater parameters.

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Permeability enhancing treatments such as hydraulic fracturing (HF) induce microseismic events with typical magnitudes in the -3.0 to -0.5 range, although significantly larger induced earthquakes up to 4.7 in moment magnitude have been reported. Diffusion of pore pressure away from the hydraulic fracture system is thought to be a primary controlling mechanism. Understanding other primary or secondary triggering mechanisms during HF is expected to furnish new insights regarding stress, strength of faults, and rupture initiation and propagation. Using novel methods from statistical seismology, we present evidence for the existence of event-event triggering cascades in microseismicity induced by HF. Although background seismicity dominates, we find that these triggering cascades exhibit features that also characterize tectonic aftershock sequences such as the empirical Omori-Utsu relation and the productivity relation. This suggests that the underlying physical earthquake-earthquake triggering mechanisms are similar in both cases, as also observed for other earthquake swarms. The presence of triggering cascades is of direct relevance for optimizing the effectiveness of the stimulation.

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The recent growth in energy technologies and the management of subsurface reservoirs has led to increased human interaction with the Earth’s crust. One consequence of this is the overall increase of anthropogenic earthquakes. To manage fluid-injection-induced seismicity, in this study, we propose to use an advanced fluid-injection scheme. First, long-term fluid-injection experiments are separated from short-term fluid-injection experiments. Of the short-term experiments, enhanced geothermal systems stimulations have shown a higher propensity to produce larger seismic events compared to hydraulic fracturing in oil and gas. Among the factors discussed for influencing the likelihood of an induced seismic event to occur are injection rate, cumulative injected volume, wellhead pressure, injection depth, stress state, rock type, and proximity to faults. We present and discuss the concept of fatigue hydraulic fracturing at different scales in geothermal applications. In contrast to the conventional hydraulic fracturing with monotonic injection of high-pressure fluids, in fatigue hydraulic fracturing, the fluid is injected in pressure cycles with increasing target pressure, separated by depressurization phases for relaxing the crack tip stresses. During pressurization phases, the target pressure level is modified by pulse hydraulic fracturing generated with a second pump system. This combination of two pumps with multiple-flow rates may allow a more complex fracture pattern to be designed, with arresting and branching fractures, forming a broader fracture process zone. Small-scale laboratory fluid-injection tests on granite cores and intermediate-scale fluid-injection experiments in a hard rock underground test site are described. At laboratory scale, cyclic fluid-injection tests with acoustic emission analysis are reported with subsequent X-ray CT fracture pattern analysis. At intermediate scale, in a controlled underground experiment at constant depth with well-known stress state in granitic rock, we test advanced fluid-injection schemes. The goal is to optimize the fracture network and mitigate larger seismic events. General findings in granitic rock, independent of scale, are summarized. First, the fracture breakdown pressure in fatigue hydraulic testing is lower than that in the conventional hydraulic fracturing. Second, compared to continuous injection, the magnitude of the largest induced seismic event seems to be systematically reduced by cyclic injection. Third, the fracture pattern in fatigue testing is different from that in the conventional injection tests at high pressures. Cyclic fracture patterns seem to result from chiefly generated low energy grain boundary cracks forming a wider process zone. Fourth, cyclic injection increases the permeability of the system. A combination of cyclic progressive and pulse pressurization leads to the best hydraulic performance of all schemes tested. One advantage of fatigue testing is the fact that this soft stimulation method can be applied in circumstances where the conventional stimulation might otherwise be abandoned based on site-specific seismic hazard estimates.

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Induced earthquakes and shallow groundwater contamination are two environmental concerns associated with the interaction between hydraulic fracturing (fracking) operations and geological faults. To reduce the risks of fault reactivation and faults acting as fluid conduits to groundwater resources, fluid injection needs to be carried out at sufficient distances away from faults. Westwood et al. (Geomechanics and geophysics for geo-energy and geo-resources, pp 1–13, 2017) suggest a maximum horizontal respect distance of 433 m to faults using numerical modelling, but its usefulness is limited by the model parameters. An alternative approach is to use microseismic data to infer the extent of fracture propagation and stress changes. Using published microseismic data from 109 fracking operations and analysis of variance, we find that the empirical risk of detecting microseismicity in shale beyond a horizontal distance of 433 m is 32% and beyond 895 m is 1%. The extent of fracture propagation and stress changes is likely a result of operational parameters, borehole orientation, local geological factors, and the regional stress state. We suggest a horizontal respect distance of 895 m between horizontal boreholes orientated perpendicular to the maximum horizontal stress direction and faults optimally orientated for failure under the regional stress state.

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The state of Oklahoma has experienced a dramatic increase in the amount of measurable seismic activities over the last decade. The needs of a petroleum-driven world have led to increased production utilizing various technologies to reach energy reserves locked in tight formations and stimulate end-of-life wells, creating significant amounts of undesirable wastewater ultimately injected underground for disposal. Using Phased Array L-band Synthetic Aperture Radar (PALSAR) data, we performed a differential Synthetic Aperture Radar Interferometry (InSAR) technique referred to as the Small BAseline Subset (SBAS)-based analysis over east central Oklahoma to identify ground surface deformation with respect to the location of wastewater injection wells for the period of December 2006 to January 2011. Our results show broad spatial correlation between SBAS-derived deformation and the locations of injection wells. We also observed significant uplift over Cushing, Oklahoma, the largest above ground crude oil storage facility in the world, and a key hub of the Keystone Pipeline. This finding has significant implications for the oil and gas industry due to its close proximity to the zones of increased seismicity attributed to wastewater injection. Results southeast of Drumright, Oklahoma represent an excellent example of the potential of InSAR, identifying a fault bordered by an area of subduction to the west and uplift to the east. This differentiated movement along the fault may help explain the lack of any seismic activity in this area, despite the large number of wells and high volume of fluid injected.