Refined Principal Stress Estimates for Induced Seismicity in Southern Kansas Based on Seismological Tools and Laboratory Experiments
Abstract
Determining stress orientations and magnitudes at storage reservoir depths is technically challenging, both vertically and laterally away from a wellbore. State-of-the-art methods of stress field estimation require direct measurements through boreholes, but these are expensive, spatially sparse, and potentially compromised simply by virtue of drilling the borehole. Here, we develop methodologies to measure the in-situ principal stress in the deep subsurface through use of multiple, independent, but complementary seismic methods (i.e. interferometry, shear wave splitting, and focal mechanism inversion), laboratory verification, and development of theoretical frameworks. As data, we use a catalog of more than 24,000 relocated earthquakes from M~0 to M4.9 induced near active fluid disposal wells in Kansas. Applying the virtual seismometer method (VSM) we obtain a refined model of the 3D earth structure directly around the microseismic events. We can also measure variation in focal mechanisms, allowing us to track changes in stress orientation. These focal mechanism solutions are also inverted for 4D estimates of the stress tensor. Preliminary results from shear wave splitting analysis of this dataset indicate that the maximum principal stress orientation in Kansas is generally aligned with the expected ENE direction. A 90° rotation in the fast direction for some shear wave splitting measurements may indicate two primary fracture orientations, consistent with observations in Oklahoma.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S13E0488K
- Keywords:
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- 7215 Earthquake source observations;
- SEISMOLOGY;
- 7223 Earthquake interaction;
- forecasting;
- and prediction;
- SEISMOLOGY;
- 7230 Seismicity and tectonics;
- SEISMOLOGY;
- 8164 Stresses: crust and lithosphere;
- TECTONOPHYSICS