A Detailed Oklahoma Stress Map for Induced Seismicity Mitigation

Abstract

We report progress on a project to create a detailed map of in situ stress orientations and relative magnitudes throughout the state of Oklahoma. Over the past 5 years, seismicity has increased remarkably in much of the state, apparently related to significant increases in waste water injection. The purpose of this project is to develop detailed knowledge of the stress field in the state to identify which pre-existing faults could be potentially active in response to injection-related pore pressure increases. Over 50 new stress orientations have been obtained, utilizing wellbore image data and shear velocity anisotropy measurements from sonic dipole data provided by the oil and gas industry. These data reveal a very uniform ENE direction of maximum compressive stress through much of the state. As earthquake focal plane mechanisms generally indicate strike-slip faulting, the stress orientation data identify which pre-existing faults are potentially active. The data are consistent with slip on the near-vertical, NE-trending fault associated with at least one of the M 5+ earthquakes in the Prague, OK sequence in 2011. If successful, it would demonstrate that combining detailed information about pre-existing faults and the current stress field could be used to guide the siting of injection wells so as to decrease the potential for injection-related seismicity.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015