Spatiotemporal assessment of induced seismicity in Oklahoma: Foreseeable fewer earthquakes for sustainable oil and gas extraction?

Abstract

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.