Earthquakes Induced by Hydraulic Fracturing Are Pervasive in Oklahoma

Abstract

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 ~700 HF‐induced earthquakes with M ≥ 2.0, 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.

Induced Seismicity in the Delaware Basin, Texas

“…To maintain consistency with previous work identifying HF‐induced seismicity in Oklahoma (Skoumal, Ries, et al, ), we set a threshold of ∆ EQ rate > 10 and manually inspect all 28 wells that exceed this threshold (Figure ). This threshold is above the 2σ bounds produced by the synthetic catalogs, so we have reasonable confidence that these are not spurious correlations (Figures a and b).…”

“…Cases of HF‐induced seismicity tend to spatially cluster (Skoumal et al, ; Skoumal, Ries, et al, ). A prominent example of this in the Delaware Basin is shown in Figure .…”

“…Here, we use a modified approach addressing the limitations of Skoumal, Ries, et al () to flag cases of HF‐induced seismicity defined as where d is a distance constant, D ± t , d represents the distances of earthquakes within time window t and distance d from a given HF well, and T + t , d represents the number of days an earthquake occurred following a stimulation within time window t and distance d from a given HF well. The calculations of D ± t , d and T + t , d excluded any earthquakes that occurred during the time of other HF stimulations within distance d .…”

Hydraulic Fracture Injection Strategy Influences the Probability of Earthquakes in the Eagle Ford Shale Play of South Texas

“…About a quarter of the earthquakes occurred prior to the first cataloged earthquake in March 2017, indicating the usefulness of template matching for extending the seismicity catalog prior to when TexNet recording began in January 2017. The enhanced catalog of 2,823 earthquakes showed several short‐lived, spatiotemporally clustered events (Figure a), characteristic of HF‐induced seismicity (e.g., Kozłowska et al, ; Lei et al, ; Schultz et al, ; Skoumal, Ries, et al, ). These bursts of earthquakes, which we refer to as sequences, began in June 2014 and increased in prevalence during late 2016.…”

Leakage and Increasing Fluid Pressure Detected in Oklahoma's Wastewater Disposal Reservoir

“…Injection‐induced earthquakes (Ellsworth, ) are traditionally considered to be the result of a reduction in effective normal stress through an increase in pore pressure, but in practice, this has been difficult to establish unambiguously as a causal mechanism, except in few cases (e.g., Raleigh et al, ). For example, seismicity patterns in Oklahoma are affected by the distribution of wastewater injection (Goebel et al, ) and changes in the rate of wastewater injection (Barbour et al, ) but also include a significant proportion of events induced by high‐pressure reservoir stimulation (Skoumal et al, ). So it remains of critical importance to understand how interactions between injection and reservoir response impact pore pressure diffusion, poroelastic stress changes, and flow patterns, because of the implications for fault slip at seismogenic depths (e.g., Chang & Segall, , ; Zhang et al, ), seismicity rates (Dieterich et al, ; Llenos & Michael, ; Segall & Lu, ), and, ultimately, seismic hazard (Langenbruch et al, 2018; Langenbruch & Zoback, ; Petersen et al, ; Norbeck & Rubinstein, ; Zhai & Shirzaei, ).…”