Induced Seismicity in the Dallas-Fort Worth Basin: Enhanced Seismic Catalogue, Calibration with Geodetic Measurements, and Evaluation of Fault Slip Potential

Abstract:

Significant induced seismic activity has been recorded in the Dallas-Fort Worth basin since 2008, and previous studies have shown that these events are most likely related to the injection of wastewater that is co-produced with oil and gas extraction in the region. However, these studies rely on a relatively limited catalogue of micro-earthquakes and have generally not considered the basin-scale pressure and stress changes resulting from the extracted oil and gas, which constitute a larger volume change than wastewater injection.

We present an updated catalogue of seismicity in the Dallas-Fort Worth basin from 2008 to the end of 2019 using state-of-the-art phase picking and association methods based on machine learning. We then calculate the pore pressure changes between 2000 and 2020 for the Ellenburger and Barnett formations, incorporating fluid injection/extraction histories at 104 saltwater injection and 20576 production wells respectively. These pore pressure are calculated using analytical solutions for a point source injection in a 2D axisymmetric medium and are superposed for all wells. The pressure model data are then used to calculate poroelastic stress changes in the basement, and displacements at ground elevation using analytical solutions. The surface displacements are in turn used to calibrate hydromechanical parameters by comparison with basin-scale geodetic measurements from InSAR and GPS. Finally, the calibrated pore pressure and poroelastic stress changes are used to evaluate fault slip potential in the basement. Our results suggest that the poroelastic stress changes from oil and gas extraction in the Barnett have a significant effect on the spatial distribution of induced seismicity in the region, most notably that they may explain local sub-regions that do not experience seismicity.