Development of an Analytical Method Based on Two Failure Criteria to Study Slip Risk Related to Fluid Injection: Case Study North-Central Oklahoma, U.S.A.

Abstract

The increment in induced seismicity in North-Central Oklahoma has been related to saltwater disposal wells. Despite the many studies that have been completed to understand the main cause of the induced earthquakes related to disposal wells in the Arbuckle Formation, more studies are required to predict the areas and operational conditions where fluid injection could trigger fault slip. This study aims to identify the parameters with higher and lower impact in fault slip, and it is divided into three steps. First, we created an analytical model based on the Mohr-Coulomb criteria and the modified slip tendency, parameters that indicate the risk of slip on a fault. This model considers the stress field, the azimuth of the maximum horizontal stress, pore pressure, friction coefficient, Biot coefficient, and the geometry (orientation and dip) of the fault planes in three-dimensions. Then, we use data from previous studies in the area (Walsh and Zoback, 2016) to verify our model. Finally, with a sensibility analysis, we determine the fault reactivation potential when varying each of the parameters in our model. We conclude that the fault geometry with respect to the azimuth of maximum horizontal stress is the most important parameter that triggers fault slip. Variations in pore pressure are also important in fault slip. While in normal and strike regimens, like North-Central Oklahoma, an increase in pore pressure leads to fault slip; in reverse regimens, a decrease in pore pressure may lead to fault slip. With this study, we propose a practical analytical model to identify the relationship between the fault geometry and pore pressure needed to avoid fault reactivation in North-Central Oklahoma.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019